International Journal of Power Electronics and Drive Systems (IJPEDS)
Vol. 12, No. 3, September 2021, pp. 1673~1686
ISSN: 2088-8694, DOI: 10.11591/ijpeds.v12.i3.pp1673-1686  1673
Journal homepage: http://ijpeds.iaescore.com
Asymmetrical four-wire cascaded h-bridge multi-level inverter
based shunt active power filter supplied by a photovoltaic
source
Kamel Saleh, Omar Mahmoud
Electrical Engineering Department, An-Najah National University, Nablus-West Bank, Palestine
Article Info ABSTRACT
Article history:
Received Apr 27, 2021
Revised Jun 6, 2021
Accepted Jul 25, 2021
This paper presents a novel shunt active power filter (SAPF). The power
converter that is used in this SAPF is constructed from a four-leg asymmetric
multi-level cascaded H-bridge (CHB) inverter that is fed from a photovoltaic
source. A three-dimensional space vector modulation (3D-SVPWM)
technique is adopted in this work. The multi-level inverter can generate 27-
level output with harmonic content is almost zero. In addition to the
capability to inject reactive power and mitigating the harmonics, the
proposed SAPF has also, the ability to inject real power as it is fed from a PV
source. Moreover, it has a fault-tolerant capability that makes the SAPF
maintaining its operation under a loss of one leg of the multi-level inverter
due to an open-circuit fault without any degradation in the performance. The
proposed SAPF is designed and simulated in MATLAB SIMULINK using a
single nonlinear load and the results have shown a significant reduction in
total harmonics distortion (THD) of the source current under the normal
operating condition and post a failure in one phase of the SAPF. Also, similar
results are obtained when IEEE 15 bus network is used.
Keywords:
Fault-tolerant
Multi-level inverter
PV system
SAPF
This is an open access article under the CC BY-SA license.
Corresponding Author:
Kamel Saleh
Electrical Engineering Department
An-Najah National University
Nablus-West Bank, Palestine
Email: kamel.saleh@najah.edu
1. INTRODUCTION
Recently, the research on active power filters (APFs) fed from renewable energy sources has
witnessed a significant increase due to the ability of such filters to solve many power quality issues [1].
However, the performance of these filters will be dramatically degraded if a failure in one leg of the inverter
is introduced to the SAPFs. Hence, many techniques have been proposed in the literature to enhance the
reliability of the inverter and to maintain the performance of the SAPF post a failure. Most of these
techniques are based on the use of some kind of redundancies that exist in the 2-level inverters [2]. This
redundancy can be inherited in the structure of the 2-level inverter [3] or it is introduced intentionally to the
2-level inverter to make it fault-tolerant [4]. This is done by adding a fourth leg to the conventional 2-level
inverter as reported in [5], [6].
Multi-level inverters have many advantages over the 2-level inverters in terms of the low THD in
the output, less dv/dt, and higher output voltages. These characteristics have encouraged the researcher to use
the multi-level inverters in many applications especially in APFs [7]-[11]. A fault-tolerant multi-level
inverter can be achieved through different techniques including neutral-shift, DC-bus voltage
reconfiguration, and redundant modules installation is employed [12]-[14]. Various pulse width modulation
 ISSN: 2088-8694
Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686
1674
(PWM) and control techniques have been reported and discussed in the literature [15]. These techniques aim
to control the currents of the inverter that is used in the APFs and to convert the output voltage of the
controllers to a digital signal that will be used to gate the inverter. One example of these control techniques is
the Hysteresis control. Hysteresis control has many advantages such as it is simple and has a fast dynamic
response. But on the other hand, it has a variable switching frequency and produces relatively large current
ripples in the system [16]. Another example is the predictive control which has a lower current ripple and
constant frequency [16]. Many modulation techniques were proposed to convert the output voltage signals of
the control to digital pulses to switch the multi-level inverter such as selective harmonics, multi-level PWM,
and multi-level SVPWM [17]. Among these modulation techniques, SVPWM can be considered as an ideal
solution to be used in APFs. This is related to the ability to implement it in 3 and 4-wire systems. In addition
to its ability to reduce the switching losses, minimize the capacitor balancing problem, and reduce the total
harmonic content in the output [18]. In a 3-wire system, 2D-SVPWM can be used [19] while 3D-SVPWM is
used in a 4-wire system to control the neutral current [20].
In this paper, a SAPF using the 3-phase 4-wire (leg) asymmetric CHB 27-level inverter system is
implemented with the 3D-SVM algorithm. The 3-phase 4-leg multi-level inverter is powered from a PV
system to have better reliability and control. The SAPF can maintain the operation pre and post a non-healthy
operating condition for both the load such as asymmetry and the SAPF such as the failure in one leg of the
SAPF.
2. RESEARCH METHOD
2.1. Shunt active filter
The structure of the SAPF that is proposed in this paper is shown in Figure 1. The SAPF is
consisting of the CHB inverter. The multi-level inverter has an extra leg that is connected permanently to the
neutral of the load or the power system. Moreover, it is supplied from batteries that are fed from
photovoltaic arrays. P&O maximum power point (MPPT) technique is used to get maximum possible power
from the solar energy [21]. The controller is using 3D-SVPWM to generate the pulses that trigger the multi-
level inverter. A brief view in each part of the SAPF is introduced:
Figure 1. the structure of the proposed SAPF
2.1.1. Fault-tolerant 27-level inverter
Each leg of the multi-level inverter is composed of three H-Bridges connected in series. Each H-
Bridge is fed from seperate battery. The voltage levels of the three batteries in each leg will be 36 V, 108 V,
and 324 V which means that the ratio is 1:3:9 [14], [22]. This ratio makes it is possible to connect the SAPF
to the PCC directly without the need for any transformer. Moreover, it makes the multi-level inverter
Int J Pow Elec & Dri Syst ISSN: 2088-8694 
Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh)
1675
generates the maximum number of levels (27-level) while using only three H-Bridges per leg. This is quite
important to minimize the harmonic content of the output voltage of the multi-level inverter and produce a
sinusoidal output which helps to eliminate the need for any kind of filtering at the output of the multi-level
inverter. The output of each H-Bridge and the output of one leg of the 27-level inverter are shown in Figure
2. The H-Bridge that is interfaced to the 324 V battery will generate 69% of the total power generated by the
multi-level inverter. Also, The H-bridge that is connected to the 108 V battery will be responsible for
generating about 23.1% of the total power while the H-Bridge interfaced with the 36 V battery will generate
about 7.7 % of the total power. the switching frequency of each bridge varies from 50 Hz which is the
switching frequency of the H-Bridge interfaced with the 324V battery to reach 5 kHz which is the frequency
of the H-Bridge connected to the 36 V battery and the switching frequency of the multi-level inverter too.
This low switching frequency especially for the high power H-Bridges helps to enhance the efficiency of the
multi-level inverter by reducing the switching losses.
In addition to the previously mentioned features of the proposed multi-level inverter, it has another
important feature which is the fourth leg connected to the neutral of the electrical system. The use of the
added leg besides using 3D-SVPWM will enable the SAPF to work under unhealthy operating conditions
such as load asymmetry and a failure on one leg of the SAPF due to the open-circuit fault. This will help in
enhancing the reliability of the SAPF and maintains its performance post a failure in one leg of the multi-
level inverter.
Figure 2. output voltage waveforms of the 27- level 4-leg inverter
2.1.2. PV system design
A 125 W polycrystalline PV modules (BP 3125S photovoltaic module) were used to design all PV
arrays. The specifications of these modules are given in Table 1.
Table 1. Specification of BP 3125S photovoltaic module
Maximum power 125 watt
Maximum power voltage 17.6 V
Maximum power current 7.1 A
Open circuit voltage 22.1 V
Short circuit current 7.54 A
According to the load current of the grid, a 30Kwp, 48.3 A, 400 V, and 50 Hz PV source is needed, the
design of the PV system will be as:
No. pv =
Ppv
Pmpp
=
30000
125
= 244 module (1)
The number of modules connected in series Ns can be obtained as:
Ns =
needed voltage
Vmpp for module
=
300
17.6
≈ 17 (2)
 ISSN: 2088-8694
Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686
1676
The number of strings connected in parallel can be calculated as:
Number of strings =
total power
string power
=
30000
17∗125
≈ 14 (3)
The Boost converter should receive DC voltage from PV which varies between 0 to 299 volts and fixed the
output voltage to 324 V (DC). The specifications of the boost converter are given in Table 2.
Table 2. Specification of the boost converter
Specification Detail
Input voltage 0-299
Output voltage 324
2.1.3. 3D–SVPWM
The proposed 3D-SVPWM technique that is adopted in this work is presented in [20]. This
technique is very simple and based on geometrical consideration. Moreover, it is independent of the number
of levels of the multi-level inverter. And more importantly, can be used under healthy conditions such as load
asymmetry and failure in one phase of the SAPF without modifications. The reference voltage will be
pointing to a sub-cube. This sub–cube can be identified using the components (a, b, c) which are the integer
values of the reference voltage (V_ref). This cube can be decomposed into six tetrahedrons. These
tetrahedrons and the associated PWM waveforms are shown in Figure 3.
Figure 3. Switching sequence and timing diagram of type 3 used in SVPWM for the multi-level converter
2.2. Control structure of the SAPF
The performance of the SAPF especially in the harmonics mitigation process depends on the
harmonic extraction method. Many techniques were proposed in the literature to extract the harmonic signal.
These techniques can be divided into two categories. The first one works in the frequency domain [21] while
the second one is base on the time domain [23]. In the frequency domain techniques, a transformation from
the time domain to frequency domain using fast fourier transform (FFT) is needed while in the time-domain
technique, an instantaneous estimation is done without the need for any frequency transformation. The time-
Int J Pow Elec & Dri Syst ISSN: 2088-8694 
Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh)
1677
domain method is simpler and needs less calculation compared to the frequency domain so the result will be
faster [23].
2.2.1. Harmonic extraction using d-q method
d-q Harmonic extraction method was adopted in this research to calculate the current reference for
the SAPF filter [24], [25]. The illustration of the principle of operation of this technique is shown in Figure 4.
The voltages (Vabc) and the currents (IL abc) of the non-linear loads are measured firstly. Then, the load
currents (IL abc) are transformed to a synchronous frame oriented to voltages of the nonlinear load (VL abc).
This step is achieved with the help of the phase locked loop (PLL). The currents of the nonlinear loads (IL
abc) become IdL, and IqL at this stage. The d-component of the current of the nonlinear load will be in the
direction of the voltage of the nonlinear load (VL abc) and so it will present the real power of the nonlinear
load while the q-component of the current of the nonlinear load will be perpendicular to the voltage of the
nonlinear load (VL abc) and so it will present the reactive power of the nonlinear load. Due to the presence of
the harmonics in the nonlinear load currents (IL abc), then, the nonlinear load power component (IdL) and
reactive power component (IqL) that is obtained from the transformation to the synchronous frame will have
components as shown in equations (4-5).
IdL=IdL
̃ + IdL
̅̅̅̅ (4)
IqL=iqL
̃ + IqL
̅̅̅̅ (5)
The DC components (𝑖dL
̅̅̅, iqL
̅̅̅) represent the fundamental component of the non-linear load real and
reactive power. While the oscillating components (idL,
̃ iqL
̃ ) represent the harmonics in the non-linear load
currents. The d-q components of the currents of the nonlinear load will be processed further to obtain the
reference signals idL _ref and iqL _ref according to the task of the SAPF as follows:
− If the SAPF is wanted to mitigate harmonics only, then the DC components (𝑖dL
̅̅̅, iqL
̅̅̅) are filtered out
using s high pass filter.
− If the SAPF is wanted to mitigate harmonics and inject reactive power, then the DC component (idL
̅̅̅) is
filtered out using a high pass filter.
− If the SAPF is wanted to mitigate harmonics, inject reactive power, and inject real power, then the DC
component (idL
̅̅̅) is filtered out using a high pass filter and then an offset DC value is added to idL_ref.
Phase locked
loop
VL abc
Ɵ
IL abc
idL_ref
abc
dq
High pass
filtter
iqL_ref
Real power
injection
+
+
idL
iqL
Figure 4. d-q harmonic extraction technique
2.2.2. Modelling and controlling the SAPF
Assuming that the SAPF is connected to the PCC through cable that has a small resistance and
inductance as shown in Figure 5. The (6)-(8) hold true:
𝑣𝑎𝑛𝑖𝑛𝑣 = 𝑖𝑎𝑖𝑛𝑣 ∗ 𝑟 + 𝐿
𝑑𝑖𝑎𝑖𝑛𝑣
𝑑𝑡
+ 𝑣𝑎𝑛𝑝𝑐𝑐 (6)
𝑣𝑏𝑛𝑖𝑛𝑣 = 𝑖𝑏𝑖𝑛𝑣 ∗ 𝑟 + 𝐿
𝑑𝑖𝑏𝑖𝑛𝑣
𝑑𝑡
+ 𝑣𝑏𝑛𝑝𝑐𝑐 (7)
𝑣𝑐𝑛𝑖𝑛𝑣 = 𝑖𝑐𝑖𝑛𝑣 ∗ 𝑟 + 𝐿
𝑑𝑖𝑐𝑖𝑛𝑣
𝑑𝑡
+ 𝑣𝑐𝑛𝑝𝑐𝑐 (8)
The (6)(8) are transformed into the load voltage-oriented frame (d-q-0) frame as:
 ISSN: 2088-8694
Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686
1678
𝐿
𝑑𝑖𝑑𝑖𝑛𝑣
𝑑𝑡
= −𝑖𝑑𝑖𝑛𝑣 ∗ 𝑅 + (𝑉𝑑𝑖𝑛𝑣 − 𝑉𝑑𝑝𝑐𝑐) − 𝜔 ∗ 𝐿 ∗ 𝑖𝑞𝑖𝑛𝑣 (9)
𝐿
𝑑𝑖𝑞𝑖𝑛𝑣
𝑑𝑡
= −𝑖𝑞𝑖𝑛𝑣 ∗ 𝑅 + (𝑉𝑞𝑖𝑛𝑣 − 𝑉𝑞𝑝𝑐𝑐) + 𝜔 ∗ 𝐿 ∗ 𝑖𝑑𝑖𝑛𝑣 (10)
𝐿
𝑑𝑖𝑜
𝑑𝑡
= −𝑖𝑜 ∗ 𝑅 + +Vo (11)
The (9)-(11) can be rewritten as:
𝑣𝑑 = 𝑖𝑑𝑖𝑛𝑣 ∗ 𝑅 + 𝐿
𝑑𝑖𝑑𝑖𝑛𝑣
𝑑𝑡
(12)
𝑣𝑞 = 𝑖𝑞𝑖𝑛𝑣 ∗ 𝑅 + 𝐿
𝑑𝑖𝑞𝑖𝑛𝑣
𝑑𝑡
(13)
𝑣𝑜 = 𝑖𝑜𝑖𝑛𝑣 ∗ 𝑅 + 𝐿
𝑑𝑖𝑜𝑖𝑛𝑣
𝑑𝑡
(14)
where
𝑣𝑑 = (𝑉𝑑𝑖𝑛𝑣 − 𝑉𝑑𝑝𝑐𝑐) − 𝜔 ∗ 𝐿 ∗ 𝑖𝑞𝑖𝑛𝑣 (15)
𝑣𝑞 = (𝑉𝑞𝑖𝑛𝑣 − 𝑉𝑞𝑝𝑐𝑐) + 𝜔 ∗ 𝐿 ∗ 𝑖𝑑𝑖𝑛𝑣 (16)
Figure 6 shows the closed-loop through which the controllers can be designed. In this work three
proportional-integral (PI) controllers are designed to regulated the currents of the multi-level inverter
(𝑖𝑑𝑞0𝑖𝑛𝑣) to make the SAPF capable of mitigating harmonics, injecting reactive power, and injecting real
power-based on the reference currents (idq0L_ref.) obtained from the dq-harmonic extraction technique. The
outputs of the controllers (Vdq0_ref) are then transformed to digital pulses using 3D-SVPWM technique as
illustrated in Figure 7.
Phase locked
loop
VL abc
Ɵ
IL abc
idL_ref
abc
dq
High pass
filtter
iqL_ref
Real power
injection
+
+
idL
iqL
Figure 5. Dynamic modelling of the shunt active filter
PI
Controller
1
R+Ls
idq0 L_ref Vdq0_ref idq0inv
+
-
Figure 6. SAPF controller design
Int J Pow Elec & Dri Syst ISSN: 2088-8694 
Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh)
1679
Figure 7. The control structure of active filter
3. RESULTS AND DISCUSSION
The proposed SAPF is simulated in MATLAB/Simulink environment to check its performance and
reliability. Many scenarios have been considered as:
− The first scenario was about testing the performance of the proposed SAPF when the load is a single
nonlinear load.
− The second scenario was about investigating the functionality of the proposed SAPF on the IEEE fifteen
bus system where the load at bus 5 was made nonlinear. In this case, the SAPF was put near the source
(i.e the harmonics inside the network are out of scope).
− The third scenario was about investigating the effect of the SAPF on the loesses and harmonics of the
whole IEEE fifteen bus system when the SAPF was put near to the bus that has the nonlinear load (bus 5).
3.1. Fist scenario
The structure of the whole electrical system during this test is shown in Figure 8. There are two
objectives of this test:
− The first objective is to check the ability of the SAPF to inject the reactive power, real power, and to
mitigate the harmonics
− The second objective is to check the fault-tolerant capability of the SAPF in the case of a loss of one
− phase during operation
The results obtained from the above test under healthy operating conditions and in the cases of an
open circuit in phase ‘c’ of the SAPF are given in Figure 9 and Figure 10 respectively. Figure 9 demonstrates
the effectiveness of the system in mitigating the harmonics, injecting reactive power, and injecting real power
under healthy operating conditions. The SAPF was disabled till t= 0.2s. after that, at t=0.2s, the SAPF was
commanded to mitigate the harmonics only. It can be noticed that the source currents became almost pure
sinusoidal as the Total Harmonic Distortion was reduced from 20.86% before the use of the SAPF to 2.43%
after using it. Then at t= 0.4s, the APF was commanded to inject reactive power in addition to the mitigating
of the harmonics. The results of reactive power measurements of the source in Figure 9 show that the APF
was responded to this command properly. It can be noticed from the results that the reactive power that
comes from the source at this time became zero which means that all the reactive power needed by the load
no was generated from the SAPF and the p.f at the source became 1. Finally, at t=0.6s, a command was sent
to the SAPF to inject a real power in addition to the mitigating of the harmonics, and the injection of the
reactive power. The results show that the SAPF at that time started to inject real power. The evidence of that
can be obtained from two things: the first one is the reduction of the source current which means that part of
the real power consumed by the load was generated by the SAPF. The second one is the reduction of the
measurements of the source real power due to the same reason mentioned previously.
Figure 10 demonstrates the enhancement of the reliability of the SAPF obtained by adding a fourth
leg connected permanently to the neural and using a 3D-VPWM technique. Before t= 0.8s, the SAPF was
running under healthy operating conditions. Also, it was used to inject real and reactive power in addition to
mitigating the harmonics. After that, at t=0.8s, an open-circuit fault on phase ‘c’ was introduced to the SAPF
without enabling the fourth leg. It can be noticed from the results that the SAPF was no longer able to
 ISSN: 2088-8694
Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686
1680
mitigate harmonics in the failure leg. At t, 1s the fourth leg was enabled and the SAPF returned to work as
before the failure and could maintain the system performance.
Figure 8. Four-leg 27-level inverter APF supplying nonlinear load
Figure 9. Results of the APF with single nonlinear load under healthy operating condition
Int J Pow Elec & Dri Syst ISSN: 2088-8694 
Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh)
1681
Figure 10. Results of the APF with single nonlinear load under a failure in phase ‘c’
3.2. Second scenario
In this test, the IEEE 15 bus network was utilized with the nominal voltage of 400 V as shown in
Figure 11. The load at the bus no 5 was made nonlinear. The SAPF was connected to bus no 1 and the whole
network is treated as a single load. The current waveform of the source currents at Bus no 1 was measured
and the THD was calculated as shown in Figure 12. The current waveforms in addition to the Fast Fourier
Transform (FFT) show a significant reduction in the harmonic content of the source currents which became
near sinusoidal. The above-mentioned results also were confirmed from the calculated values of the THD of
the source currents. The THD was reduced from 13% before using the SAPF to 4.5% after using it.
Figure 11. SAPF connected to bus no 1 of the IEEE 15 bus network
 ISSN: 2088-8694
Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686
1682
Figure 12. Source current when APF connected to bus no 1 of the IEEE 15 bus network
To investigate the effect of the SAPF on the THD in the whole network in this case, the currents
waveforms were measured at buses 7,9,11, and 15. The results are given in Figure 13. Figure 13 shows that
there is a slight improvement in the current waveforms at these buses which means that the total harmonic
distortion inside the network is still high. Figure 14 shows the calculation of the THD at these buses before
and after using the SAPF. The results confirm that the SAPF at this place is inefficient in reducing the THD
in the network since it is far away from the place of the nonlinear load at bus 5.
Figure 13. Currents waveforms at buses 7, 9, 11, 15 when APF connected to bus no 1
Int J Pow Elec & Dri Syst ISSN: 2088-8694 
Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh)
1683
Figure 14. Currents waveforms at buses 7,9,11,15 when APF connected to bus no 1
3.3. Third Scenario
The results obtained from the previous scenario (i.e connecting the SAPF at bus no 1 and far from
the nonlinear load) shows an improvement in the THD of the source currents but the currents in the network
still distorted and the THD of these currents is still high which will cause many power quality issues to the
network. In this scenario, the SAPF was connected at bus no 5 near the nonlinear load as shown in Figure 15.
The current waveform of the source currents at Bus no 1 was measured and the THD was calculated
as shown in Figure 16. The current waveforms in addition to the fast fourier transform (FFT) show a
significant reduction in the harmonic content of the source currents which became near sinusoidal. The
above-mentioned results were also confirmed from the calculated values of the THD of the source currents.
The THD was reduced from 13% before using the SAPF to 2.79 % after using it. These results of the source
current are even better than the results obtained by connecting the SAPF at bus 1.
To investigate the effect of the APF on the THD in the whole network in this case, the currents
waveforms were measured again at buses 7,9,11, and 15. The results are given in Figure 17. Figure 17 shows
that there is a significant improvement in the current waveforms at these buses which means that the total
harmonic distortion inside the network is very low. Figure 18 shows the calculation of the THD at these
buses before and after using the SAPF. The results confirm that the SAPF at this place is efficient in reducing
the THD in the network since it is near the place of the nonlinear load at bus 5.
Figure 15. SAPF connected to bus no 5 of the IEEE 15 bus network
29.43
41.5
30.8
35
18.47
28.6
23
27
7 9 11 15
THD
%
BUS NO
T HD A T D IFFEREN T B U SES
without APF with APF
 ISSN: 2088-8694
Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686
1684
Figure 16 source current when APF connected to bus no 5 of the IEEE 15 bus network
Figure 17. Currents waveforms at buses 7,9,11,15 when APF connected to bus no 5
Figure 18. Currents waveforms at buses 7,9,11,15 when APF connected to bus no 5
29.43
41.5
30.8
35
7.41
11.2
8.2
9.2
7 9 11 15
THD
%
BUS NO
T HD % A T D IFFEREN T B U SES
without APF with APF
Int J Pow Elec & Dri Syst ISSN: 2088-8694 
Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh)
1685
4. CONCLUSION
This paper has presented a four-leg 27-level SAPF that can maintain operation in the cases of
asymmetric nonlinear loads and even in the case of a loss in one phase of the APF due to the open circuit
fault. This enhancement in the reliability of the APF is achieved through two things; the first one is the
addition of the fourth leg to the multi-level inverter which is connected to the neutral permanently. The
second one is the use of the 3D-SVPWM technique instead of the 2D-SVPWM. The proposed SAPF can do
many tasks under healthy operating conditions and post and open circuit fault. It can mitigate harmonics in
the power system, improve power factor in the system by injecting reactive power, and inject real power to
the system. The proposed SAPF can be used if the load just a single nonlinear load and if the load is a
complete power system network. In the case that the network is a power system network, the best place of
the SAPF is near the load to improve the whole network.
REFERENCES
[1] S. Devassy and B. Singh, “Implementation of solar photovoltaic system with universal active filtering capability,”
in IEEE Transactions on Industry Applications, vol. 55, no. 4, pp. 3926-3934, July-Aug. 2019, doi:
10.1109/TIA.2019.2906297.
[2] W. Zhang, D. Xu, P. N. Enjeti, H. Li, J. T. Hawke, and H. S. Krishnamoorthy, “Survey on fault-tolerant
techniques for power electronic converters,” IEEE Transactions on Power Electronics, vol. 29, no. 12, pp. 6319-
6331, Dec. 2014, doi: 10.1109/TPEL.2014.2304561.
[3] M. A. Rodriguez, A. Claudio, D. Theilliol, L. G. Vela, and L. Hernandez, “A strategy to replace the damaged
element for fault-tolerant induction motor drive,” in 5th International Conference on Electrical Engineering,
Computing Science and Automatic Control, 2008, pp. 51-55, doi: 10.1109/ICEEE.2008.4723458.
[4] J.-R. Fu, and T. A. Lipo, “Disturbance-free operation of a multiphase current-regulated motor drive with an
opened phase,” IEEE Transactions on Industry Applications, vol. 30, no. 5, pp. 1267-1274, Sept.-Oct. 1994, doi:
10.1109/28.315238.
[5] P. Verdelho, and G. D. Marques, “Four-wire current-regulated PWM voltage converter,” IEEE Transactions on
Industrial Electronics, vol. 45, no. 5, pp. 761-770, Oct. 1998, doi: 10.1109/41.720333.
[6] X. Yuan, G. Orglmeister, and W. Merk, “Managing the DC link neutral potential of the three-phase-four-wire
neutral-point-clamped (NPC) inverter in FACTS application,” in IECON'99. Conference Proceedings. 25th
Annual Conference of the IEEE Industrial Electronics Society (Cat. No.99CH37029), 1999, pp. 571-576 vol.2,
doi: 10.1109/IECON.1999.816446.
[7] J. Rodriguez, J.-S. Lai, and F. Z. Peng, “Multilevel inverters: a survey of topologies, controls, and applications,”
IEEE Transactions on Industrial Electronics, vol. 49, no. 4, pp. 724-738, Aug. 2002, doi:
10.1109/TIE.2002.801052.
[8] A. Mohammadpour, S. Sadeghi, and L. Parsa, “A generalized fault-tolerant control strategy for five-phase pm
motor drives considering star, pentagon, and pentacle connections of stator windings,” IEEE Transactions on
Industrial Electronics, vol. 61, no. 1, pp. 63-75, Jan. 2014, doi: 10.1109/TIE.2013.2247011.
[9] K. Saleh, and N. Hantouli, “A photovoltaic integrated unified power quality conditioner with a 27-level inverter,”
TELKOMNIKA Telecommunication, Computing, Electronics and Control, vol. 17, no. 6, pp. 3232-3248, 2019,
doi: 10.12928/TELKOMNIKA.v17i6.13224.
[10] M. Tounsi, A. Allali, H. Boulouiha, and M. Denaï, “ANFIS control of a shunt active filter based with a five-level
NPC inverter to improve power quality,” International Journal of Electrical and Computer Engineering (IJECE),
vol. 11, no. 3, pp. 1886-1893, 2021, doi: 10.11591/ijece.v11i3.pp1886-1893.
[11] M. Lada, M. Radzi, J. Jasni, H. Hizam, A. Jidin, and S. Mohamad, “Performance of three-phase three-wire
cascaded H-bridge multilevel inverter-based shunt active power filter,” International Journal of Power
Electronics and Drives (IJPEDS), vol. 11, no. 3, pp. 1430-1440, 2020, doi: 10.11591/ijpeds.v11.i3.pp1430-1440.
[12] A. Yousfi, T. Allaoui, and A. Chaker, “A new approach to extract reference currents for multilevel shunt active
filter in three phase systems,” International Journal of Power Electronics and Drives (IJPEDS), vol. 11, no. 3,
pp. 1459-1467, 2020.
[13] P. Lezana, J. Pou, T. A. Meynard, J. Rodriguez, S. Ceballos, and F. Richardeau, “Survey on fault operation on
multilevel inverters,” IEEE Transactions on Industrial Electronics, vol. 57, no. 7, pp. 2207-2218, July 2010, doi:
10.1109/TIE.2009.2032194.
[14] K. Saleh, and A. Madi, “A fault-tolerant photovoltaic integrated shunt active power filter with a 27-level
inverter,” International Journal of Electrical and Computer Engineering (IJECE), vol. 11, no. 2, pp. 1166-1177,
2021, doi: 10.11591/ijece.v11i2.pp1166-1177.
[15] R. Mienski, R. Pawelek, and I. Waisak, “Shunt compensation for power quality improvement using a STATCOM
controller: Modelling and simulation,” in IEEE Proceedings Generation Transmission Distribution, vol. 151, no.
2, 2004, pp. 274-280, doi: 10.1049/ip-gtd:20040053.
[16] N. Mittal, B. Singh, S. P. Singh, R. Dixit, and D. Kumar, “Multilevel inverters: A literature survey on topologies
and control strategies,” 2nd International Conference on Power, Control and Embedded Systems, 2012, pp. 1-11,
doi: 10.1109/ICPCES.2012.6508041.
[17] N.-Y. Dai, M.-C. Wong, Y.-D. Han, “Controlling trilevel center-split power quality compensator by 3-
dimensional space vector modulation,” in The Fifth International Conference on Power Electronics and Drive
Systems, vol. 2, 2003, pp. 1692-1697, doi: 10.1109/PEDS.2003.1283246.
 ISSN: 2088-8694
Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686
1686
[18] J. Rodriguez, J.-S. Lai, and F. Z. Peng, “Multilevel inverters: a survey of topologies, controls, and applications,”
IEEE Transactions on Industrial Electronics, vol. 49, no. 4, pp. 724-738, Aug. 2002, doi:
10.1109/TIE.2002.801052.
[19] M. M. Prats, L. G. Franquelo, R. Portillo, J. I. Leon, E. Galvan, and J. M. Carrasco, “A 3-D space vector
modulation generalized algorithm for multilevel converters,” IEEE Power Electronics Letters, vol. 1, no. 4, pp.
110-114, Dec. 2003, doi: 10.1109/LPEL.2004.825561.
[20] L. G. Franquelo et al., “Three-dimensional space-vector modulation algorithm for four-leg multilevel converters
using abc coordinates,” IEEE Transactions on Industrial Electronics, vol. 53, no. 2, pp. 458-466, April 2006, doi:
10.1109/TIE.2006.870884.
[21] A. K. Gupta, and R. Saxena, “Review on widely-used MPPT techniques for PV applications,” International
Conference on Innovation and Challenges in Cyber Security ICICCS-INBUSH, 2016, pp. 270-273, doi:
10.1109/ICICCS.2016.7542321.
[22] P. Flores, J. Dixon, M. Ortuzar, R. Carmi, P. Barriuso, and L. Moran, “Static var compensator and active power
filter with power injection capability, using 27-level inverters and photovoltaic cells,” IEEE Transactions on
Industrial Electronics, vol. 56, no. 1, pp. 130-138, Jan. 2009, doi: 10.1109/TIE.2008.927229.
[23] S. Chandrasekaran, and K. Ragavan, “Sliding DFT assisted instantaneous symmetrical components method for
estimating reference current to Active Power Filter,” in IEEE 55th International Midwest Symposium on Circuits
and Systems MWSCAS, 2012, pp. 1168-1171, doi: 10.1109/MWSCAS.2012.6292233.
[24] H. Akagi, Y. Kanazawa, and A. Nabae, “Generalized theory of the instantaneous reactive power in three-phase
circuits,” in International Power Electronics Conference, Japan, 1983, pp. 1375-1386.
[25] D. M. Soomro, S. Alswed, M. N. Abdullah, N. H. Radzi, and M. H. Baloch, “Optimal design of a single-phase
APF based on PQ theory,” International Journal of Power Electronics and Drives (IJPEDS), vol. 11, no. 3, pp.
1360-1367, 2020, doi: 10.11591/ijpeds.v11.i3.pp1360-1367.

More Related Content

PDF
A modified bridge-type nonsuperconducting fault current limiter for distribut...
PDF
In-depth perception of dynamic inductive wireless power transfer development:...
PDF
Reduction of total harmonic distortion of three-phase inverter using alternat...
PDF
Using Y-source network as a connector between turbine and network in the stru...
PDF
Comparison of electronic load using linear regulator and boost converter
PDF
Modeling and design of an adaptive control for VSC-HVDC system under paramete...
PDF
Short and open circuit faults study in the PV system inverter
PDF
Improved 25-level inverter topology with reduced part count for PV grid-tie a...
A modified bridge-type nonsuperconducting fault current limiter for distribut...
In-depth perception of dynamic inductive wireless power transfer development:...
Reduction of total harmonic distortion of three-phase inverter using alternat...
Using Y-source network as a connector between turbine and network in the stru...
Comparison of electronic load using linear regulator and boost converter
Modeling and design of an adaptive control for VSC-HVDC system under paramete...
Short and open circuit faults study in the PV system inverter
Improved 25-level inverter topology with reduced part count for PV grid-tie a...

What's hot (19)

PDF
A comprehensive review of distributed power system architecture for telecom a...
PDF
The new approach minimizes harmonics in a single-phase three-level NPC 400 Hz...
PDF
Modeling of static var compensator-high voltage direct current to provide pow...
PDF
An efficient dynamic power management model for a stand-alone DC Microgrid us...
PDF
Design and Development of Grid-connected Quasi-Z-Source PV Inverter
PDF
LCL filter design for grid-connected single-phase flyback microinverter: a st...
PDF
Stability analysis of photovoltaic system under grid faults
PDF
Electrical and environmental parameters of the performance of polymer solar c...
PDF
Real time emulator for parallel connected dual-PMSM sensorless control
PDF
A1103030111
PDF
Droop control approach for power sharing in AC microgrid
PDF
J1103035766
PDF
Impact of hybrid FACTS devices on the stability of the Kenyan power system
PDF
J010417781
PDF
Improvement of Power Quality using Fuzzy Logic Controller in Grid Connected P...
PDF
IRJET- Power Quality Improvement in Solar by using Fuzzy Logic Controller
PDF
I010416376
PDF
N01041106112
PDF
M0104198105
A comprehensive review of distributed power system architecture for telecom a...
The new approach minimizes harmonics in a single-phase three-level NPC 400 Hz...
Modeling of static var compensator-high voltage direct current to provide pow...
An efficient dynamic power management model for a stand-alone DC Microgrid us...
Design and Development of Grid-connected Quasi-Z-Source PV Inverter
LCL filter design for grid-connected single-phase flyback microinverter: a st...
Stability analysis of photovoltaic system under grid faults
Electrical and environmental parameters of the performance of polymer solar c...
Real time emulator for parallel connected dual-PMSM sensorless control
A1103030111
Droop control approach for power sharing in AC microgrid
J1103035766
Impact of hybrid FACTS devices on the stability of the Kenyan power system
J010417781
Improvement of Power Quality using Fuzzy Logic Controller in Grid Connected P...
IRJET- Power Quality Improvement in Solar by using Fuzzy Logic Controller
I010416376
N01041106112
M0104198105
Ad

Similar to Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active power filter supplied by a photovoltaic source (20)

PDF
A fault-tolerant photovoltaic integrated shunt active power filter with a 27-...
PDF
Study of the performance of fault-tolerant multi-level inverter included in s...
PDF
A New Multilevel Active Power Filter Using Switches Meticulously Controlled
PDF
Gl3112351241
PDF
Power Quality Analysis Using Active NPC Multilevel inverter in PV sourced sta...
PDF
Power Quality Analysis Using Active NPC Multilevel inverter in PV sourced sta...
PDF
Dt4301719726
PDF
A photovoltaic integrated unified power quality conditioner with a 27-level i...
PPT
Switched Capacitor Based Multilevel Inverter With Reduced Device Counts For E...
PDF
Application of Backstepping to the Virtual Flux Direct Power Control of Five-...
PPT
Forharsha basha
PDF
Starting torque and torque ripple reduction using SVPWM based vector control ...
PDF
A Single-Phase Dual-Stage PV-Grid System with Active Filtering
PPTX
Photovoltaic based three phase three-wire saf for significant energy conserva...
PDF
Multilevel Inverter using SPWM Technique for AC Power Supply
PPTX
Fault Tolerant.pptx
PDF
Modified T-type topology of three-phase multi-level inverter for photovoltaic...
PDF
Ch32524527
PDF
Ch32524527
A fault-tolerant photovoltaic integrated shunt active power filter with a 27-...
Study of the performance of fault-tolerant multi-level inverter included in s...
A New Multilevel Active Power Filter Using Switches Meticulously Controlled
Gl3112351241
Power Quality Analysis Using Active NPC Multilevel inverter in PV sourced sta...
Power Quality Analysis Using Active NPC Multilevel inverter in PV sourced sta...
Dt4301719726
A photovoltaic integrated unified power quality conditioner with a 27-level i...
Switched Capacitor Based Multilevel Inverter With Reduced Device Counts For E...
Application of Backstepping to the Virtual Flux Direct Power Control of Five-...
Forharsha basha
Starting torque and torque ripple reduction using SVPWM based vector control ...
A Single-Phase Dual-Stage PV-Grid System with Active Filtering
Photovoltaic based three phase three-wire saf for significant energy conserva...
Multilevel Inverter using SPWM Technique for AC Power Supply
Fault Tolerant.pptx
Modified T-type topology of three-phase multi-level inverter for photovoltaic...
Ch32524527
Ch32524527
Ad

More from International Journal of Power Electronics and Drive Systems (20)

PDF
Adaptive backstepping controller design based on neural network for PMSM spee...
PDF
Classification and direction discrimination of faults in transmission lines u...
PDF
Integration of artificial neural networks for multi-source energy management ...
PDF
Rotating blade faults classification of a rotor-disk-blade system using artif...
PDF
Artificial bee colony algorithm applied to optimal power flow solution incorp...
PDF
Soft computing and IoT based solar tracker
PDF
Comparison of roughness index for Kitka and Koznica wind farms
PDF
Primary frequency control of large-scale PV-connected multi-machine power sys...
PDF
Performance of solar modules integrated with reflector
PDF
Generator and grid side converter control for wind energy conversion system
PDF
Wind speed modeling based on measurement data to predict future wind speed wi...
PDF
Comparison of PV panels MPPT techniques applied to solar water pumping system
PDF
Prospect of renewable energy resources in Bangladesh
PDF
A novel optimization of the particle swarm based maximum power point tracking...
PDF
Voltage stability enhancement for large scale squirrel cage induction generat...
PDF
Simplified cascade multiphase DC-DC buck power converter for low voltage larg...
PDF
Modeling and control of a hybrid DC/DC/AC converter to transfer power under d...
PDF
Two-level inverter and three-level neutral point diode clamped inverter for t...
PDF
Implementation on the dSPACE 1104 of VOC-SVM based anti-windup PI Controller ...
PDF
Newly fault-tolerant indirect vector control for traction inverter
Adaptive backstepping controller design based on neural network for PMSM spee...
Classification and direction discrimination of faults in transmission lines u...
Integration of artificial neural networks for multi-source energy management ...
Rotating blade faults classification of a rotor-disk-blade system using artif...
Artificial bee colony algorithm applied to optimal power flow solution incorp...
Soft computing and IoT based solar tracker
Comparison of roughness index for Kitka and Koznica wind farms
Primary frequency control of large-scale PV-connected multi-machine power sys...
Performance of solar modules integrated with reflector
Generator and grid side converter control for wind energy conversion system
Wind speed modeling based on measurement data to predict future wind speed wi...
Comparison of PV panels MPPT techniques applied to solar water pumping system
Prospect of renewable energy resources in Bangladesh
A novel optimization of the particle swarm based maximum power point tracking...
Voltage stability enhancement for large scale squirrel cage induction generat...
Simplified cascade multiphase DC-DC buck power converter for low voltage larg...
Modeling and control of a hybrid DC/DC/AC converter to transfer power under d...
Two-level inverter and three-level neutral point diode clamped inverter for t...
Implementation on the dSPACE 1104 of VOC-SVM based anti-windup PI Controller ...
Newly fault-tolerant indirect vector control for traction inverter

Recently uploaded (20)

PDF
Cryptography and Network Security-Module-I.pdf
PPT
Programmable Logic Controller PLC and Industrial Automation
PPTX
CS6006 - CLOUD COMPUTING - Module - 1.pptx
PDF
VTU IOT LAB MANUAL (BCS701) Computer science and Engineering
PPTX
Software-Development-Life-Cycle-SDLC.pptx
PDF
[jvmmeetup] next-gen integration with apache camel and quarkus.pdf
PPTX
Module1.pptxrjkeieuekwkwoowkemehehehrjrjrj
PDF
Software defined netwoks is useful to learn NFV and virtual Lans
PDF
Using Technology to Foster Innovative Teaching Practices (www.kiu.ac.ug)
PPTX
Design ,Art Across Digital Realities and eXtended Reality
PPTX
CNS - Unit 1 (Introduction To Computer Networks) - PPT (2).pptx
PDF
IAE-V2500 Engine for Airbus Family 319/320
PDF
AIGA 012_04 Cleaning of equipment for oxygen service_reformat Jan 12.pdf
PDF
Mechanics of materials week 2 rajeshwari
PDF
Principles of operation, construction, theory, advantages and disadvantages, ...
PPTX
AI-Reporting for Emerging Technologies(BS Computer Engineering)
PDF
IAE-V2500 Engine Airbus Family A319/320
PDF
CELDAS DE COMBUSTIBLE TIPO MEMBRANA DE INTERCAMBIO PROTÓNICO.pdf
PDF
Lesson 3 .pdf
PDF
MLpara ingenieira CIVIL, meca Y AMBIENTAL
Cryptography and Network Security-Module-I.pdf
Programmable Logic Controller PLC and Industrial Automation
CS6006 - CLOUD COMPUTING - Module - 1.pptx
VTU IOT LAB MANUAL (BCS701) Computer science and Engineering
Software-Development-Life-Cycle-SDLC.pptx
[jvmmeetup] next-gen integration with apache camel and quarkus.pdf
Module1.pptxrjkeieuekwkwoowkemehehehrjrjrj
Software defined netwoks is useful to learn NFV and virtual Lans
Using Technology to Foster Innovative Teaching Practices (www.kiu.ac.ug)
Design ,Art Across Digital Realities and eXtended Reality
CNS - Unit 1 (Introduction To Computer Networks) - PPT (2).pptx
IAE-V2500 Engine for Airbus Family 319/320
AIGA 012_04 Cleaning of equipment for oxygen service_reformat Jan 12.pdf
Mechanics of materials week 2 rajeshwari
Principles of operation, construction, theory, advantages and disadvantages, ...
AI-Reporting for Emerging Technologies(BS Computer Engineering)
IAE-V2500 Engine Airbus Family A319/320
CELDAS DE COMBUSTIBLE TIPO MEMBRANA DE INTERCAMBIO PROTÓNICO.pdf
Lesson 3 .pdf
MLpara ingenieira CIVIL, meca Y AMBIENTAL

Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active power filter supplied by a photovoltaic source

  • 1. International Journal of Power Electronics and Drive Systems (IJPEDS) Vol. 12, No. 3, September 2021, pp. 1673~1686 ISSN: 2088-8694, DOI: 10.11591/ijpeds.v12.i3.pp1673-1686  1673 Journal homepage: http://ijpeds.iaescore.com Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active power filter supplied by a photovoltaic source Kamel Saleh, Omar Mahmoud Electrical Engineering Department, An-Najah National University, Nablus-West Bank, Palestine Article Info ABSTRACT Article history: Received Apr 27, 2021 Revised Jun 6, 2021 Accepted Jul 25, 2021 This paper presents a novel shunt active power filter (SAPF). The power converter that is used in this SAPF is constructed from a four-leg asymmetric multi-level cascaded H-bridge (CHB) inverter that is fed from a photovoltaic source. A three-dimensional space vector modulation (3D-SVPWM) technique is adopted in this work. The multi-level inverter can generate 27- level output with harmonic content is almost zero. In addition to the capability to inject reactive power and mitigating the harmonics, the proposed SAPF has also, the ability to inject real power as it is fed from a PV source. Moreover, it has a fault-tolerant capability that makes the SAPF maintaining its operation under a loss of one leg of the multi-level inverter due to an open-circuit fault without any degradation in the performance. The proposed SAPF is designed and simulated in MATLAB SIMULINK using a single nonlinear load and the results have shown a significant reduction in total harmonics distortion (THD) of the source current under the normal operating condition and post a failure in one phase of the SAPF. Also, similar results are obtained when IEEE 15 bus network is used. Keywords: Fault-tolerant Multi-level inverter PV system SAPF This is an open access article under the CC BY-SA license. Corresponding Author: Kamel Saleh Electrical Engineering Department An-Najah National University Nablus-West Bank, Palestine Email: [email protected] 1. INTRODUCTION Recently, the research on active power filters (APFs) fed from renewable energy sources has witnessed a significant increase due to the ability of such filters to solve many power quality issues [1]. However, the performance of these filters will be dramatically degraded if a failure in one leg of the inverter is introduced to the SAPFs. Hence, many techniques have been proposed in the literature to enhance the reliability of the inverter and to maintain the performance of the SAPF post a failure. Most of these techniques are based on the use of some kind of redundancies that exist in the 2-level inverters [2]. This redundancy can be inherited in the structure of the 2-level inverter [3] or it is introduced intentionally to the 2-level inverter to make it fault-tolerant [4]. This is done by adding a fourth leg to the conventional 2-level inverter as reported in [5], [6]. Multi-level inverters have many advantages over the 2-level inverters in terms of the low THD in the output, less dv/dt, and higher output voltages. These characteristics have encouraged the researcher to use the multi-level inverters in many applications especially in APFs [7]-[11]. A fault-tolerant multi-level inverter can be achieved through different techniques including neutral-shift, DC-bus voltage reconfiguration, and redundant modules installation is employed [12]-[14]. Various pulse width modulation
  • 2.  ISSN: 2088-8694 Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686 1674 (PWM) and control techniques have been reported and discussed in the literature [15]. These techniques aim to control the currents of the inverter that is used in the APFs and to convert the output voltage of the controllers to a digital signal that will be used to gate the inverter. One example of these control techniques is the Hysteresis control. Hysteresis control has many advantages such as it is simple and has a fast dynamic response. But on the other hand, it has a variable switching frequency and produces relatively large current ripples in the system [16]. Another example is the predictive control which has a lower current ripple and constant frequency [16]. Many modulation techniques were proposed to convert the output voltage signals of the control to digital pulses to switch the multi-level inverter such as selective harmonics, multi-level PWM, and multi-level SVPWM [17]. Among these modulation techniques, SVPWM can be considered as an ideal solution to be used in APFs. This is related to the ability to implement it in 3 and 4-wire systems. In addition to its ability to reduce the switching losses, minimize the capacitor balancing problem, and reduce the total harmonic content in the output [18]. In a 3-wire system, 2D-SVPWM can be used [19] while 3D-SVPWM is used in a 4-wire system to control the neutral current [20]. In this paper, a SAPF using the 3-phase 4-wire (leg) asymmetric CHB 27-level inverter system is implemented with the 3D-SVM algorithm. The 3-phase 4-leg multi-level inverter is powered from a PV system to have better reliability and control. The SAPF can maintain the operation pre and post a non-healthy operating condition for both the load such as asymmetry and the SAPF such as the failure in one leg of the SAPF. 2. RESEARCH METHOD 2.1. Shunt active filter The structure of the SAPF that is proposed in this paper is shown in Figure 1. The SAPF is consisting of the CHB inverter. The multi-level inverter has an extra leg that is connected permanently to the neutral of the load or the power system. Moreover, it is supplied from batteries that are fed from photovoltaic arrays. P&O maximum power point (MPPT) technique is used to get maximum possible power from the solar energy [21]. The controller is using 3D-SVPWM to generate the pulses that trigger the multi- level inverter. A brief view in each part of the SAPF is introduced: Figure 1. the structure of the proposed SAPF 2.1.1. Fault-tolerant 27-level inverter Each leg of the multi-level inverter is composed of three H-Bridges connected in series. Each H- Bridge is fed from seperate battery. The voltage levels of the three batteries in each leg will be 36 V, 108 V, and 324 V which means that the ratio is 1:3:9 [14], [22]. This ratio makes it is possible to connect the SAPF to the PCC directly without the need for any transformer. Moreover, it makes the multi-level inverter
  • 3. Int J Pow Elec & Dri Syst ISSN: 2088-8694  Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh) 1675 generates the maximum number of levels (27-level) while using only three H-Bridges per leg. This is quite important to minimize the harmonic content of the output voltage of the multi-level inverter and produce a sinusoidal output which helps to eliminate the need for any kind of filtering at the output of the multi-level inverter. The output of each H-Bridge and the output of one leg of the 27-level inverter are shown in Figure 2. The H-Bridge that is interfaced to the 324 V battery will generate 69% of the total power generated by the multi-level inverter. Also, The H-bridge that is connected to the 108 V battery will be responsible for generating about 23.1% of the total power while the H-Bridge interfaced with the 36 V battery will generate about 7.7 % of the total power. the switching frequency of each bridge varies from 50 Hz which is the switching frequency of the H-Bridge interfaced with the 324V battery to reach 5 kHz which is the frequency of the H-Bridge connected to the 36 V battery and the switching frequency of the multi-level inverter too. This low switching frequency especially for the high power H-Bridges helps to enhance the efficiency of the multi-level inverter by reducing the switching losses. In addition to the previously mentioned features of the proposed multi-level inverter, it has another important feature which is the fourth leg connected to the neutral of the electrical system. The use of the added leg besides using 3D-SVPWM will enable the SAPF to work under unhealthy operating conditions such as load asymmetry and a failure on one leg of the SAPF due to the open-circuit fault. This will help in enhancing the reliability of the SAPF and maintains its performance post a failure in one leg of the multi- level inverter. Figure 2. output voltage waveforms of the 27- level 4-leg inverter 2.1.2. PV system design A 125 W polycrystalline PV modules (BP 3125S photovoltaic module) were used to design all PV arrays. The specifications of these modules are given in Table 1. Table 1. Specification of BP 3125S photovoltaic module Maximum power 125 watt Maximum power voltage 17.6 V Maximum power current 7.1 A Open circuit voltage 22.1 V Short circuit current 7.54 A According to the load current of the grid, a 30Kwp, 48.3 A, 400 V, and 50 Hz PV source is needed, the design of the PV system will be as: No. pv = Ppv Pmpp = 30000 125 = 244 module (1) The number of modules connected in series Ns can be obtained as: Ns = needed voltage Vmpp for module = 300 17.6 ≈ 17 (2)
  • 4.  ISSN: 2088-8694 Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686 1676 The number of strings connected in parallel can be calculated as: Number of strings = total power string power = 30000 17∗125 ≈ 14 (3) The Boost converter should receive DC voltage from PV which varies between 0 to 299 volts and fixed the output voltage to 324 V (DC). The specifications of the boost converter are given in Table 2. Table 2. Specification of the boost converter Specification Detail Input voltage 0-299 Output voltage 324 2.1.3. 3D–SVPWM The proposed 3D-SVPWM technique that is adopted in this work is presented in [20]. This technique is very simple and based on geometrical consideration. Moreover, it is independent of the number of levels of the multi-level inverter. And more importantly, can be used under healthy conditions such as load asymmetry and failure in one phase of the SAPF without modifications. The reference voltage will be pointing to a sub-cube. This sub–cube can be identified using the components (a, b, c) which are the integer values of the reference voltage (V_ref). This cube can be decomposed into six tetrahedrons. These tetrahedrons and the associated PWM waveforms are shown in Figure 3. Figure 3. Switching sequence and timing diagram of type 3 used in SVPWM for the multi-level converter 2.2. Control structure of the SAPF The performance of the SAPF especially in the harmonics mitigation process depends on the harmonic extraction method. Many techniques were proposed in the literature to extract the harmonic signal. These techniques can be divided into two categories. The first one works in the frequency domain [21] while the second one is base on the time domain [23]. In the frequency domain techniques, a transformation from the time domain to frequency domain using fast fourier transform (FFT) is needed while in the time-domain technique, an instantaneous estimation is done without the need for any frequency transformation. The time-
  • 5. Int J Pow Elec & Dri Syst ISSN: 2088-8694  Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh) 1677 domain method is simpler and needs less calculation compared to the frequency domain so the result will be faster [23]. 2.2.1. Harmonic extraction using d-q method d-q Harmonic extraction method was adopted in this research to calculate the current reference for the SAPF filter [24], [25]. The illustration of the principle of operation of this technique is shown in Figure 4. The voltages (Vabc) and the currents (IL abc) of the non-linear loads are measured firstly. Then, the load currents (IL abc) are transformed to a synchronous frame oriented to voltages of the nonlinear load (VL abc). This step is achieved with the help of the phase locked loop (PLL). The currents of the nonlinear loads (IL abc) become IdL, and IqL at this stage. The d-component of the current of the nonlinear load will be in the direction of the voltage of the nonlinear load (VL abc) and so it will present the real power of the nonlinear load while the q-component of the current of the nonlinear load will be perpendicular to the voltage of the nonlinear load (VL abc) and so it will present the reactive power of the nonlinear load. Due to the presence of the harmonics in the nonlinear load currents (IL abc), then, the nonlinear load power component (IdL) and reactive power component (IqL) that is obtained from the transformation to the synchronous frame will have components as shown in equations (4-5). IdL=IdL ̃ + IdL ̅̅̅̅ (4) IqL=iqL ̃ + IqL ̅̅̅̅ (5) The DC components (𝑖dL ̅̅̅, iqL ̅̅̅) represent the fundamental component of the non-linear load real and reactive power. While the oscillating components (idL, ̃ iqL ̃ ) represent the harmonics in the non-linear load currents. The d-q components of the currents of the nonlinear load will be processed further to obtain the reference signals idL _ref and iqL _ref according to the task of the SAPF as follows: − If the SAPF is wanted to mitigate harmonics only, then the DC components (𝑖dL ̅̅̅, iqL ̅̅̅) are filtered out using s high pass filter. − If the SAPF is wanted to mitigate harmonics and inject reactive power, then the DC component (idL ̅̅̅) is filtered out using a high pass filter. − If the SAPF is wanted to mitigate harmonics, inject reactive power, and inject real power, then the DC component (idL ̅̅̅) is filtered out using a high pass filter and then an offset DC value is added to idL_ref. Phase locked loop VL abc Ɵ IL abc idL_ref abc dq High pass filtter iqL_ref Real power injection + + idL iqL Figure 4. d-q harmonic extraction technique 2.2.2. Modelling and controlling the SAPF Assuming that the SAPF is connected to the PCC through cable that has a small resistance and inductance as shown in Figure 5. The (6)-(8) hold true: 𝑣𝑎𝑛𝑖𝑛𝑣 = 𝑖𝑎𝑖𝑛𝑣 ∗ 𝑟 + 𝐿 𝑑𝑖𝑎𝑖𝑛𝑣 𝑑𝑡 + 𝑣𝑎𝑛𝑝𝑐𝑐 (6) 𝑣𝑏𝑛𝑖𝑛𝑣 = 𝑖𝑏𝑖𝑛𝑣 ∗ 𝑟 + 𝐿 𝑑𝑖𝑏𝑖𝑛𝑣 𝑑𝑡 + 𝑣𝑏𝑛𝑝𝑐𝑐 (7) 𝑣𝑐𝑛𝑖𝑛𝑣 = 𝑖𝑐𝑖𝑛𝑣 ∗ 𝑟 + 𝐿 𝑑𝑖𝑐𝑖𝑛𝑣 𝑑𝑡 + 𝑣𝑐𝑛𝑝𝑐𝑐 (8) The (6)(8) are transformed into the load voltage-oriented frame (d-q-0) frame as:
  • 6.  ISSN: 2088-8694 Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686 1678 𝐿 𝑑𝑖𝑑𝑖𝑛𝑣 𝑑𝑡 = −𝑖𝑑𝑖𝑛𝑣 ∗ 𝑅 + (𝑉𝑑𝑖𝑛𝑣 − 𝑉𝑑𝑝𝑐𝑐) − 𝜔 ∗ 𝐿 ∗ 𝑖𝑞𝑖𝑛𝑣 (9) 𝐿 𝑑𝑖𝑞𝑖𝑛𝑣 𝑑𝑡 = −𝑖𝑞𝑖𝑛𝑣 ∗ 𝑅 + (𝑉𝑞𝑖𝑛𝑣 − 𝑉𝑞𝑝𝑐𝑐) + 𝜔 ∗ 𝐿 ∗ 𝑖𝑑𝑖𝑛𝑣 (10) 𝐿 𝑑𝑖𝑜 𝑑𝑡 = −𝑖𝑜 ∗ 𝑅 + +Vo (11) The (9)-(11) can be rewritten as: 𝑣𝑑 = 𝑖𝑑𝑖𝑛𝑣 ∗ 𝑅 + 𝐿 𝑑𝑖𝑑𝑖𝑛𝑣 𝑑𝑡 (12) 𝑣𝑞 = 𝑖𝑞𝑖𝑛𝑣 ∗ 𝑅 + 𝐿 𝑑𝑖𝑞𝑖𝑛𝑣 𝑑𝑡 (13) 𝑣𝑜 = 𝑖𝑜𝑖𝑛𝑣 ∗ 𝑅 + 𝐿 𝑑𝑖𝑜𝑖𝑛𝑣 𝑑𝑡 (14) where 𝑣𝑑 = (𝑉𝑑𝑖𝑛𝑣 − 𝑉𝑑𝑝𝑐𝑐) − 𝜔 ∗ 𝐿 ∗ 𝑖𝑞𝑖𝑛𝑣 (15) 𝑣𝑞 = (𝑉𝑞𝑖𝑛𝑣 − 𝑉𝑞𝑝𝑐𝑐) + 𝜔 ∗ 𝐿 ∗ 𝑖𝑑𝑖𝑛𝑣 (16) Figure 6 shows the closed-loop through which the controllers can be designed. In this work three proportional-integral (PI) controllers are designed to regulated the currents of the multi-level inverter (𝑖𝑑𝑞0𝑖𝑛𝑣) to make the SAPF capable of mitigating harmonics, injecting reactive power, and injecting real power-based on the reference currents (idq0L_ref.) obtained from the dq-harmonic extraction technique. The outputs of the controllers (Vdq0_ref) are then transformed to digital pulses using 3D-SVPWM technique as illustrated in Figure 7. Phase locked loop VL abc Ɵ IL abc idL_ref abc dq High pass filtter iqL_ref Real power injection + + idL iqL Figure 5. Dynamic modelling of the shunt active filter PI Controller 1 R+Ls idq0 L_ref Vdq0_ref idq0inv + - Figure 6. SAPF controller design
  • 7. Int J Pow Elec & Dri Syst ISSN: 2088-8694  Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh) 1679 Figure 7. The control structure of active filter 3. RESULTS AND DISCUSSION The proposed SAPF is simulated in MATLAB/Simulink environment to check its performance and reliability. Many scenarios have been considered as: − The first scenario was about testing the performance of the proposed SAPF when the load is a single nonlinear load. − The second scenario was about investigating the functionality of the proposed SAPF on the IEEE fifteen bus system where the load at bus 5 was made nonlinear. In this case, the SAPF was put near the source (i.e the harmonics inside the network are out of scope). − The third scenario was about investigating the effect of the SAPF on the loesses and harmonics of the whole IEEE fifteen bus system when the SAPF was put near to the bus that has the nonlinear load (bus 5). 3.1. Fist scenario The structure of the whole electrical system during this test is shown in Figure 8. There are two objectives of this test: − The first objective is to check the ability of the SAPF to inject the reactive power, real power, and to mitigate the harmonics − The second objective is to check the fault-tolerant capability of the SAPF in the case of a loss of one − phase during operation The results obtained from the above test under healthy operating conditions and in the cases of an open circuit in phase ‘c’ of the SAPF are given in Figure 9 and Figure 10 respectively. Figure 9 demonstrates the effectiveness of the system in mitigating the harmonics, injecting reactive power, and injecting real power under healthy operating conditions. The SAPF was disabled till t= 0.2s. after that, at t=0.2s, the SAPF was commanded to mitigate the harmonics only. It can be noticed that the source currents became almost pure sinusoidal as the Total Harmonic Distortion was reduced from 20.86% before the use of the SAPF to 2.43% after using it. Then at t= 0.4s, the APF was commanded to inject reactive power in addition to the mitigating of the harmonics. The results of reactive power measurements of the source in Figure 9 show that the APF was responded to this command properly. It can be noticed from the results that the reactive power that comes from the source at this time became zero which means that all the reactive power needed by the load no was generated from the SAPF and the p.f at the source became 1. Finally, at t=0.6s, a command was sent to the SAPF to inject a real power in addition to the mitigating of the harmonics, and the injection of the reactive power. The results show that the SAPF at that time started to inject real power. The evidence of that can be obtained from two things: the first one is the reduction of the source current which means that part of the real power consumed by the load was generated by the SAPF. The second one is the reduction of the measurements of the source real power due to the same reason mentioned previously. Figure 10 demonstrates the enhancement of the reliability of the SAPF obtained by adding a fourth leg connected permanently to the neural and using a 3D-VPWM technique. Before t= 0.8s, the SAPF was running under healthy operating conditions. Also, it was used to inject real and reactive power in addition to mitigating the harmonics. After that, at t=0.8s, an open-circuit fault on phase ‘c’ was introduced to the SAPF without enabling the fourth leg. It can be noticed from the results that the SAPF was no longer able to
  • 8.  ISSN: 2088-8694 Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686 1680 mitigate harmonics in the failure leg. At t, 1s the fourth leg was enabled and the SAPF returned to work as before the failure and could maintain the system performance. Figure 8. Four-leg 27-level inverter APF supplying nonlinear load Figure 9. Results of the APF with single nonlinear load under healthy operating condition
  • 9. Int J Pow Elec & Dri Syst ISSN: 2088-8694  Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh) 1681 Figure 10. Results of the APF with single nonlinear load under a failure in phase ‘c’ 3.2. Second scenario In this test, the IEEE 15 bus network was utilized with the nominal voltage of 400 V as shown in Figure 11. The load at the bus no 5 was made nonlinear. The SAPF was connected to bus no 1 and the whole network is treated as a single load. The current waveform of the source currents at Bus no 1 was measured and the THD was calculated as shown in Figure 12. The current waveforms in addition to the Fast Fourier Transform (FFT) show a significant reduction in the harmonic content of the source currents which became near sinusoidal. The above-mentioned results also were confirmed from the calculated values of the THD of the source currents. The THD was reduced from 13% before using the SAPF to 4.5% after using it. Figure 11. SAPF connected to bus no 1 of the IEEE 15 bus network
  • 10.  ISSN: 2088-8694 Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686 1682 Figure 12. Source current when APF connected to bus no 1 of the IEEE 15 bus network To investigate the effect of the SAPF on the THD in the whole network in this case, the currents waveforms were measured at buses 7,9,11, and 15. The results are given in Figure 13. Figure 13 shows that there is a slight improvement in the current waveforms at these buses which means that the total harmonic distortion inside the network is still high. Figure 14 shows the calculation of the THD at these buses before and after using the SAPF. The results confirm that the SAPF at this place is inefficient in reducing the THD in the network since it is far away from the place of the nonlinear load at bus 5. Figure 13. Currents waveforms at buses 7, 9, 11, 15 when APF connected to bus no 1
  • 11. Int J Pow Elec & Dri Syst ISSN: 2088-8694  Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh) 1683 Figure 14. Currents waveforms at buses 7,9,11,15 when APF connected to bus no 1 3.3. Third Scenario The results obtained from the previous scenario (i.e connecting the SAPF at bus no 1 and far from the nonlinear load) shows an improvement in the THD of the source currents but the currents in the network still distorted and the THD of these currents is still high which will cause many power quality issues to the network. In this scenario, the SAPF was connected at bus no 5 near the nonlinear load as shown in Figure 15. The current waveform of the source currents at Bus no 1 was measured and the THD was calculated as shown in Figure 16. The current waveforms in addition to the fast fourier transform (FFT) show a significant reduction in the harmonic content of the source currents which became near sinusoidal. The above-mentioned results were also confirmed from the calculated values of the THD of the source currents. The THD was reduced from 13% before using the SAPF to 2.79 % after using it. These results of the source current are even better than the results obtained by connecting the SAPF at bus 1. To investigate the effect of the APF on the THD in the whole network in this case, the currents waveforms were measured again at buses 7,9,11, and 15. The results are given in Figure 17. Figure 17 shows that there is a significant improvement in the current waveforms at these buses which means that the total harmonic distortion inside the network is very low. Figure 18 shows the calculation of the THD at these buses before and after using the SAPF. The results confirm that the SAPF at this place is efficient in reducing the THD in the network since it is near the place of the nonlinear load at bus 5. Figure 15. SAPF connected to bus no 5 of the IEEE 15 bus network 29.43 41.5 30.8 35 18.47 28.6 23 27 7 9 11 15 THD % BUS NO T HD A T D IFFEREN T B U SES without APF with APF
  • 12.  ISSN: 2088-8694 Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686 1684 Figure 16 source current when APF connected to bus no 5 of the IEEE 15 bus network Figure 17. Currents waveforms at buses 7,9,11,15 when APF connected to bus no 5 Figure 18. Currents waveforms at buses 7,9,11,15 when APF connected to bus no 5 29.43 41.5 30.8 35 7.41 11.2 8.2 9.2 7 9 11 15 THD % BUS NO T HD % A T D IFFEREN T B U SES without APF with APF
  • 13. Int J Pow Elec & Dri Syst ISSN: 2088-8694  Asymmetrical four-wire cascaded h-bridge multi-level inverter based shunt active ... (Kamel Saleh) 1685 4. CONCLUSION This paper has presented a four-leg 27-level SAPF that can maintain operation in the cases of asymmetric nonlinear loads and even in the case of a loss in one phase of the APF due to the open circuit fault. This enhancement in the reliability of the APF is achieved through two things; the first one is the addition of the fourth leg to the multi-level inverter which is connected to the neutral permanently. The second one is the use of the 3D-SVPWM technique instead of the 2D-SVPWM. The proposed SAPF can do many tasks under healthy operating conditions and post and open circuit fault. It can mitigate harmonics in the power system, improve power factor in the system by injecting reactive power, and inject real power to the system. The proposed SAPF can be used if the load just a single nonlinear load and if the load is a complete power system network. In the case that the network is a power system network, the best place of the SAPF is near the load to improve the whole network. REFERENCES [1] S. Devassy and B. Singh, “Implementation of solar photovoltaic system with universal active filtering capability,” in IEEE Transactions on Industry Applications, vol. 55, no. 4, pp. 3926-3934, July-Aug. 2019, doi: 10.1109/TIA.2019.2906297. [2] W. Zhang, D. Xu, P. N. Enjeti, H. Li, J. T. Hawke, and H. S. Krishnamoorthy, “Survey on fault-tolerant techniques for power electronic converters,” IEEE Transactions on Power Electronics, vol. 29, no. 12, pp. 6319- 6331, Dec. 2014, doi: 10.1109/TPEL.2014.2304561. [3] M. A. Rodriguez, A. Claudio, D. Theilliol, L. G. Vela, and L. Hernandez, “A strategy to replace the damaged element for fault-tolerant induction motor drive,” in 5th International Conference on Electrical Engineering, Computing Science and Automatic Control, 2008, pp. 51-55, doi: 10.1109/ICEEE.2008.4723458. [4] J.-R. Fu, and T. A. Lipo, “Disturbance-free operation of a multiphase current-regulated motor drive with an opened phase,” IEEE Transactions on Industry Applications, vol. 30, no. 5, pp. 1267-1274, Sept.-Oct. 1994, doi: 10.1109/28.315238. [5] P. Verdelho, and G. D. Marques, “Four-wire current-regulated PWM voltage converter,” IEEE Transactions on Industrial Electronics, vol. 45, no. 5, pp. 761-770, Oct. 1998, doi: 10.1109/41.720333. [6] X. Yuan, G. Orglmeister, and W. Merk, “Managing the DC link neutral potential of the three-phase-four-wire neutral-point-clamped (NPC) inverter in FACTS application,” in IECON'99. Conference Proceedings. 25th Annual Conference of the IEEE Industrial Electronics Society (Cat. No.99CH37029), 1999, pp. 571-576 vol.2, doi: 10.1109/IECON.1999.816446. [7] J. Rodriguez, J.-S. Lai, and F. Z. Peng, “Multilevel inverters: a survey of topologies, controls, and applications,” IEEE Transactions on Industrial Electronics, vol. 49, no. 4, pp. 724-738, Aug. 2002, doi: 10.1109/TIE.2002.801052. [8] A. Mohammadpour, S. Sadeghi, and L. Parsa, “A generalized fault-tolerant control strategy for five-phase pm motor drives considering star, pentagon, and pentacle connections of stator windings,” IEEE Transactions on Industrial Electronics, vol. 61, no. 1, pp. 63-75, Jan. 2014, doi: 10.1109/TIE.2013.2247011. [9] K. Saleh, and N. Hantouli, “A photovoltaic integrated unified power quality conditioner with a 27-level inverter,” TELKOMNIKA Telecommunication, Computing, Electronics and Control, vol. 17, no. 6, pp. 3232-3248, 2019, doi: 10.12928/TELKOMNIKA.v17i6.13224. [10] M. Tounsi, A. Allali, H. Boulouiha, and M. Denaï, “ANFIS control of a shunt active filter based with a five-level NPC inverter to improve power quality,” International Journal of Electrical and Computer Engineering (IJECE), vol. 11, no. 3, pp. 1886-1893, 2021, doi: 10.11591/ijece.v11i3.pp1886-1893. [11] M. Lada, M. Radzi, J. Jasni, H. Hizam, A. Jidin, and S. Mohamad, “Performance of three-phase three-wire cascaded H-bridge multilevel inverter-based shunt active power filter,” International Journal of Power Electronics and Drives (IJPEDS), vol. 11, no. 3, pp. 1430-1440, 2020, doi: 10.11591/ijpeds.v11.i3.pp1430-1440. [12] A. Yousfi, T. Allaoui, and A. Chaker, “A new approach to extract reference currents for multilevel shunt active filter in three phase systems,” International Journal of Power Electronics and Drives (IJPEDS), vol. 11, no. 3, pp. 1459-1467, 2020. [13] P. Lezana, J. Pou, T. A. Meynard, J. Rodriguez, S. Ceballos, and F. Richardeau, “Survey on fault operation on multilevel inverters,” IEEE Transactions on Industrial Electronics, vol. 57, no. 7, pp. 2207-2218, July 2010, doi: 10.1109/TIE.2009.2032194. [14] K. Saleh, and A. Madi, “A fault-tolerant photovoltaic integrated shunt active power filter with a 27-level inverter,” International Journal of Electrical and Computer Engineering (IJECE), vol. 11, no. 2, pp. 1166-1177, 2021, doi: 10.11591/ijece.v11i2.pp1166-1177. [15] R. Mienski, R. Pawelek, and I. Waisak, “Shunt compensation for power quality improvement using a STATCOM controller: Modelling and simulation,” in IEEE Proceedings Generation Transmission Distribution, vol. 151, no. 2, 2004, pp. 274-280, doi: 10.1049/ip-gtd:20040053. [16] N. Mittal, B. Singh, S. P. Singh, R. Dixit, and D. Kumar, “Multilevel inverters: A literature survey on topologies and control strategies,” 2nd International Conference on Power, Control and Embedded Systems, 2012, pp. 1-11, doi: 10.1109/ICPCES.2012.6508041. [17] N.-Y. Dai, M.-C. Wong, Y.-D. Han, “Controlling trilevel center-split power quality compensator by 3- dimensional space vector modulation,” in The Fifth International Conference on Power Electronics and Drive Systems, vol. 2, 2003, pp. 1692-1697, doi: 10.1109/PEDS.2003.1283246.
  • 14.  ISSN: 2088-8694 Int J Pow Elec & Dri Syst, Vol. 12, No. 3, September 2021 : 1673 – 1686 1686 [18] J. Rodriguez, J.-S. Lai, and F. Z. Peng, “Multilevel inverters: a survey of topologies, controls, and applications,” IEEE Transactions on Industrial Electronics, vol. 49, no. 4, pp. 724-738, Aug. 2002, doi: 10.1109/TIE.2002.801052. [19] M. M. Prats, L. G. Franquelo, R. Portillo, J. I. Leon, E. Galvan, and J. M. Carrasco, “A 3-D space vector modulation generalized algorithm for multilevel converters,” IEEE Power Electronics Letters, vol. 1, no. 4, pp. 110-114, Dec. 2003, doi: 10.1109/LPEL.2004.825561. [20] L. G. Franquelo et al., “Three-dimensional space-vector modulation algorithm for four-leg multilevel converters using abc coordinates,” IEEE Transactions on Industrial Electronics, vol. 53, no. 2, pp. 458-466, April 2006, doi: 10.1109/TIE.2006.870884. [21] A. K. Gupta, and R. Saxena, “Review on widely-used MPPT techniques for PV applications,” International Conference on Innovation and Challenges in Cyber Security ICICCS-INBUSH, 2016, pp. 270-273, doi: 10.1109/ICICCS.2016.7542321. [22] P. Flores, J. Dixon, M. Ortuzar, R. Carmi, P. Barriuso, and L. Moran, “Static var compensator and active power filter with power injection capability, using 27-level inverters and photovoltaic cells,” IEEE Transactions on Industrial Electronics, vol. 56, no. 1, pp. 130-138, Jan. 2009, doi: 10.1109/TIE.2008.927229. [23] S. Chandrasekaran, and K. Ragavan, “Sliding DFT assisted instantaneous symmetrical components method for estimating reference current to Active Power Filter,” in IEEE 55th International Midwest Symposium on Circuits and Systems MWSCAS, 2012, pp. 1168-1171, doi: 10.1109/MWSCAS.2012.6292233. [24] H. Akagi, Y. Kanazawa, and A. Nabae, “Generalized theory of the instantaneous reactive power in three-phase circuits,” in International Power Electronics Conference, Japan, 1983, pp. 1375-1386. [25] D. M. Soomro, S. Alswed, M. N. Abdullah, N. H. Radzi, and M. H. Baloch, “Optimal design of a single-phase APF based on PQ theory,” International Journal of Power Electronics and Drives (IJPEDS), vol. 11, no. 3, pp. 1360-1367, 2020, doi: 10.11591/ijpeds.v11.i3.pp1360-1367.