Space Vector Pulse Width Modulation Schemes for Two-Level Voltage Source Inverter

ACEEE Int. J. on Control System and Instrumentation, Vol. 02, No. 03, October 2011

Space Vector Pulse Width Modulation Schemes for
Two-Level Voltage Source Inverter
P.Tripura1, Y.S.Kishore Babu2, Y.R.Tagore2
1
Vignan’s Nirula Institute of Technology & Science for Women,EEE Dept.,Guntur,A.P.,INDIA
Email: tripura.pidikiti@gmail.com
2
Vignan University, Vadlamudi, School of Electrical Engineering, A.P, INDIA
Email: yskbabu@gmail.com,yrtagore@yahoo.com

Abstract—Space Vector Pulse Width Modulation (SVPWM) is presented.
method is an advanced, computation intensive PWM method
and possibly the best among all the PWM techniques for II. PRINCIPLES OF SVPWM
variable frequency drive applications. The SVPWM is an
alternative method for the determination of switching pulse SVPWM is based on the fact that there are only two
width and their position. The major advantage of SVPWM independent variables in a three-phase voltage system. We
stem from the fact that, there is a degree of freedom of space can use orthogonal coordinates to represent the 3-phase
vector placement in a switching cycle. This feature improves voltage in the phasor diagram. A three-phase voltage vector
the harmonic performance of this method. This method has
may be represented as
been finding widespread application in recent years because
of the easier digital realization and better dc bus utilization.
In this paper, three SVPWM schemes, called 7-segment space
V  2 1
1 1  V A0 
   VB 0 
vector modulation (SVM), 7-segment SVM with even-order
V    2 2
harmonic elimination and 5-segment (discontinuous) SVM
   3 0   (1)
are studied in detail. The theoretical analysis, design,  3 2  3 2 VC 0 
 
switching sequence and SIMULINK implementation of these
three SVM schemes is presented in step-by-step manner. In the SVPWM scheme, the three phase output voltage is
represented by a reference vector, which, rotates at an angular
Index Terms—SVPWM, 7-Segment SVM, 5-Segment SVM, speed of  =2f. The task of SVM is to use the combinations
Two -Level Inverter, SIMULINK of switching states to approximate the locus of Vref , the eight
possible switching states of the inverter are represented as
I. INTRODUCTION two null vector vectors and six active vectors as listed in the
In recent years, Space Vector Pulse Width Modulation Table 1.
(SVPWM) technology gradually obtains widespread TABLE I. SWITCHING STATES OF THE TWO LEVEL INVERTER
applications in the power electronics and the electrical drives.
It reduces motor axis pulsation and current waveform
distortion, moreover, its DC voltage utilization ratio has been
enhanced very much which is 70.7% of the DC link voltage
(compared to the conventional Sine-Pulse width
Modulation’s 61.2%), in the linear modulation range and it is
also easier to realize digitally [3].
There are three different algorithms for using SVPWM to
modulate the inverter. Many SVPWM schemes have been
investigated extensively in the literature [5-7]. The goal in
each modulation strategy is to lower the switching losses, These vectors (V1~V6) can be used to frame the vector plane,
maximize the bus utilization, reduce harmonic content and which is illustrated in Fig: 1. The rotating reference vector
still achieve precise control. So, the performance of a SVPWM can be approximated in each switching cycle by switching
scheme is usually judged based on the following criteria: between the adjacent active vectors and the zero vectors. In
total harmonic distortion (THD) of the output voltages, order to maintain the effective switching frequency at a
switching losses of the inverter and the maximum output minimal value, the sequence of the toggling between these
voltage. vectors is organized in such a way that only one leg is affected
In this paper three Space Vector Modulation (SVM) in every step. For a given magnitude and position Vref, can be
schemes called 7-segment space vector modulation (SVM), synthesized by three nearby stationary vectors, based on
7-segment SVM with even-order harmonic elimination and 5- which, the switching states of the inverter can be selected
segment (discontinuous) SVM are studied in detail and and gate signals for the active switches can be generated.
SIMULINK implementation of these three SVM techniques When Vref, passes through sectors one by one, different sets
© 2011 ACEEE 34
DOI: 01.IJCSI.02.03.517


of switches will be turned on and off .As a result, when Vref, vector determines the SVM scheme. There are a few options:
rotates one revolution in space, the inverter output voltage the null vector V0 only, the null vector V7 only, or a combination
varies one cycle over time. of the null vectors. A popular SVM technique is to alternate
the null vector in each cycle and to reverse the sequence
after each null vector. This will be referred to as the symmetric
7-segment technique. Fig. 3 shows conventional 7-segment
switching sequences of sector I. It is shown that the se-
quence V0-V1-V2-V0 is used in the first Ts/2, and the sequence
V0-V2-V2-V0 is used in the second Ts/2. The sequences are
symmetrical. The switching frequency is the same as sam-
pling frequency of the inverter.

Fig.1. Switching vectors hexagon
Three stationary vectors can synthesize the reference Vref.
The dwell time for the stationary vectors essentially
represents the duty-cycle time (on-state or off-state time) of
the chosen switches during a sampling period Ts of the
modulation scheme. The dwell time calculation is based on
‘volt-second balancing’ principle, that is, the product of the
reference voltage Vref and sampling period Ts equals the sum
of the voltage multiplied by the time interval of chosen space
vectors. For example, when Vref falls into sector I as shown in Fig.3. 7-Segment Switching Sequence for Vref in sector I
Fig: 2, it can be synthesized by V1, V2 and V0.The volt second The SIMULINK Implementation of the system has been
balance equation is carried out in the following sequence:
Calculation of 3 phase voltages (MATLAB Fcn is used)
Vref Ts  V1T0  V2Tb  V0T0  Calculation of V alpha and V bheta (3 phase to 2 phase
(2) transformation block is used)
TS  Ta  Tb  Tc Calculation Vref and alpha (Polar to Rectangle block is used.
The inputs to this block are Valpha and Vbheta and outputs of
this block are Vref and alpha.)
Calculation of Ta, Tb, T0 (Sub-system is shown in Fig.9)
Calculation of sector value
Calculation cumulative sum of Ta, Tb, T0 (Sub-system is
shown in Fig. 10)
Calculation of Tn (Sub-system is shown in Fig. 11)
Determination of switching states (look-up table is used
Realization of switching states (multi-port switch is used)
Derivation of 6 individual gate pulses to two level inverter
Fig.2. Vref synthesized by V1, V2 and V0
For linear modulation range, the dwell times can be IV. 7 SEGMENT SVM WITH EVEN ORDER HARMONIC ELIMINATION
calculated as:
From the results of 7 segment SVM, it is clear that, the
3TsV ref line-to-line voltage waveform contains even order harmonics.
 
Ta  sin     Since, most IEEE standards have more stringent requirements
Vd 3  on even-order harmonics than odd-order harmonics; this
3TsVref section presents a modified SVM scheme with even-order
 harmonic elimination. To investigate the mechanism of even
Tb  sin( ),0    (3)
Vd 3 order harmonic elimination two switching sequences for the
T0  Ts  Ta  Tb Vref falls into sector IV are shown in Fig: 4. & Fig: 5. Space
vector diagram is shown in Fig: 6.

II. 7 SEGMENT SPACE VECTRO MODULATION
The sector judgment and application time of active vector
for all SVM strategies are the same. The choice of the null
© 2011 ACEEE 35
DOI: 01.IJCSI.02.03.517


Realization of switching states (same as in the 7 segment
model)
Derivation of 6 individual gate pulses to two level inverter

V. FIVE SEGMENT SVM
The switching sequence design is not unique for a given
set of stationary vectors and dwell times. Fig: 7 shows two
five-segment switching sequences and generated inverter
terminal voltages for Vref in sector I. For type-A sequence,
Fig.4. Type A Switching Sequence for Vref in sector IV [start and the zero switching sate [OOO] is assigned for V0 while type-
ends with (0,0,0)] B sequence utilizes [PPP] for V0.
In the five-segment sequence, one of the three inverter
output terminals is clamped to either the positive or negative
dc bus without any switching’s during the sampling period
Ts. Furthermore, the switching sequence can be arranged
such that the switching in an inverter leg is continuously
suppressed for a period of 2*pi/3 per cycle of the fundamental
frequency.

Fig.5. Type B Switching Sequence for Vref in sector IV [start and
ends with (P,P,P)]
To make the three-phase line-to-line voltage half-wave
symmetrical, Type-A and Type-B switching sequences can
be alternatively used. In addition, each sector in the space
vector diagram is divided into two regions as shown in Fig. 6.
Type-A sequence is used in the non-shaded regions, while
type-B sequence is employed in the shaded regions.

Fig.7. Five Segment switching sequence
The SIMULINK Implementation of the system has been
carried out in the following sequence
Calculation of 3 phase voltages (same as in the 7 segment
model)
Calculation of Valpha and Vbheta (same as in the 7 segment
model)
Fig.6. Space vector diagram for even order harmonic elimination Calculation Vref and alpha (same as in the 7 segment model)
The SIMULINK Implementation of the system has been Calculation of Ta, Tb, T0 (same as in the 7 segment model)
carried out in the following sequence: Calculation of sector value (same as in the 7 segment model)
Calculation of 3 phase voltages (same as in the 7 segment Calculation cumulative sum of Ta, Tb, T0 (Sub-system is
model) shown in Fig.14)
Calculation of Valpha and Vbheta (same as in the 7 segment Calculation of Tn (Sub-system is shown in Fig.15)
model) Determination of switching states (look-up table is used)
 Calculation Vref and alpha (same as in the 7 segment model) Realization of switching states (different from 7 segment
Calculation of Ta, Tb, T0 (same as in the 7 segment model) model)
 Calculation of sector value (This step is different from Derivation of 6 individual gate pulses to two level inverter
previous model. Here 12 sectors are calculated each with 30o)
Calculation cumulative sum of Ta, Tb, T0 (same as in the 7 VI. MATLAB/SIMULINK MODELS OF THREE SVM SCHEMES
segment model) This section details the step-by-step development of
Calculation of Tn (same as in the 7 segment model) MATLAB/SIMULINK models of the three SVM schemes.
Determination of switching states (look-up table is used)

© 2011 ACEEE 36
DOI: 01.IJCSI.02.03.517


A. Simulink model of 7-Segment SVM B. Simulink model of 7-Segment SVM with even order
harmonic elimination

Fig.12. SIMULINK model of 7-Segment SVM with even order
harmonic elimination

C. Simulink model of 5-Segment SVM
Fig.8. SIMULINK model of 7-Segment SVM

Fig.13. SIMULINK model of 5-Segment SVM

Fig.9. SIMULINK model of Ta, T b, T 0 calculator

Fig.14. SIMULINK model of Cumulative sum calculator for 5-
Segment SVM
Fig.10. SIMULINK model of cumulative some calculator

Fig.15. SIMULINK model of T n block for 5-Segment SVM

Fig.11. SIMULINK model of T n block

© 2011 ACEEE 37
DOI: 01.IJCSI.02.03.517


VII. SIMULATION RESULTS VIII. CONCLUSIONS
Simulink models for the three SVM schemes were built SVM is a popular choice in the inverter control. Three
respectively and the models were run according to the SVM schemes are presented and analyzed through
following data: DC Link Voltage Vd=5883 V, output line voltage simulation. The comparison study shows that all the three
line voltage frequency=60Hz, R=16.4, L=14.2 mH. The SVM schemes can obtain the same output voltage in linear
simulation results were presented for ma=0.8, f1=60 Hz, and modulation region. It was observed from the harmonic
Ts=1/720 sec. for all the three schemes. spectrum of three schemes, the 7-segment SVM scheme
performs better in terms of THD of the output line voltage. It
is also observed that the THD of the 5-segment SVM lies
between the THD of 7-segment SVM and &7-segment SVM
with even order harmonic elimination.

REFERENCES
[1] Bin Wu, High-Power Converters and AC Drives. IEEE Press,
2006.
[2] M.Rashid, Power Electronics Pearson Prentice Hall,3/e 2007.
[3] B. K. Bose, Power Electronics and AC Drives. Pearson Prentice
Hall, 2006.
[4] Ned Mohan, Undeland and Robbins, Power Electronics. Wiley-
edition, 2007.
Fig. 16. Waveform and FFT analysis of Vab for ma=0.8, f1=60 Hz,
[5] Atif Iqbal, Adoum Lamine, Imtiaz Asharf and Mohibullah,
and T s =1/720 sec 7-segment svm “MATLAB/SIMULINK model of space vector pwm for three-
phase voltage source inverter,” in Proc UPEC, 2006, p. 1096-1100.
[6] Wei-Feng Zhang and Yue-HuiYu, “Comparison of Three
SVPWM Schemes,” in Proc of Journal of Electronic Science and
Technology fo China, Vol.5, No.3 September 2007 p.283-287
[7] Xiang Shaobang and Hhao Ke-You, “Research on a Novel
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[8] Baohua Lang, Miao miao, Weiguo Liu and Guangzhao Luo
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onElectronic Measurement & Instruments-ICEMI’2009 pg.1-408-
1-412.
Fig. 17. Waveform and FFT analysis of Vab for ma=0.8, f1=60 Hz, [9] H. W. van der Broeck, H.-C. Skudelny, and G. V. Stanke,
and T s =1/720 sec 7-segment SVM with even order harmonic “Analysis and realization of a pulse width modulator based on
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[10] C. Attaianese, V. Nardi, and G. Tomasso, “A novel SVM
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[11] A. M. Trzynadlowski, R. L. Kirlin, and S. F. Legowski, “Space
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[12] B. Hariram and N. S. Marimuthu, “Space vector switching
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Kong, 2005, pp. 1444-1449.

Fig. 18. Waveform and FFT analysis of Vab for ma=0.8, f1=60 Hz,
and T s=1/720 sec 5-segment SVM

© 2011 ACEEE 38
DOI: 01.IJCSI.02.03.517

Space Vector Pulse Width Modulation Schemes for Two-Level Voltage Source Inverter

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Space Vector Pulse Width Modulation Schemes for Two-Level Voltage Source Inverter