Cascaded multilevel converter for Photovoltaic applications
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This document summarizes a cascaded multilevel converter system for photovoltaic applications. It discusses different PV system configurations and topologies before focusing on a cascaded H-bridge converter. The key features of this converter include its ability to generate low distortion output voltage with multiple levels using fewer components than other topologies. It also describes the control system used, including voltage control loops for each module, power control loops, phase locked loops, and maximum power point tracking algorithms. The conclusions discuss the specific 11-level cascaded converter system used along with its control strategy, and future work is proposed to further implement and optimize the system.
Cascaded multilevel converter for Photovoltaic applications
- 1. Cascaded Multilevel Converter and Their Applications in photovoltaic SystemsSugengWidodo
- 5. Conclusions
- 6. Future WorksPV Systems - OverviewSystemDifferent power configurations
- 7. Different topologies for power converter
- 9. Current control (THD limits)
- 11. MPPT
- 12. PLL
- 13. Ancillary functions (Future)PV Cells Configurations
- 14. Power configuration for PV systemsPV Cells ConfigurationCentral Inverter10 kW -250 kW, 3 phase several string in parallelHigh efficiency, low cost, low reliability, not optimal MPPTUsed for power plantString inverters1.5 – 5 kW, typical residential applicationsEach string has its own inverter enabling better MPPTThe strings can have different orientationsThree phase inverter for power < 5 kWModule inverters50 – 180 W, each panel has its own inverterLower efficiency, difficult maintenanceHigher cost / kW p
- 15. Power Configurations for PV SystemsWithout boost /with boost of dc voltageGalvanic isolation necessary some placesLF/HF transformer (Cost-Volume issue)The optimal topology is not matured yet as for drivesTransformer less topologies having higher efficiency are emerging
- 16. Equivalent circuit for a PV cellVpv : PV array output voltage (V)Ipv : PV array output current (A)Ns : number of cells connected in seriesnp : number of strings connected in parallelq: charge of electronk : BoltzmanconstantA :pnjunction ideality factors (2.15)T : Cell temperatureIrs : Cell reverse saturation currentIscr : cell short circuit current at reference temperature and radiationki: short circuit current temperature coefficients : solar radiation Using this PV array model it is possible to simulate the dynamic performance of the power and control systems and MPPT strategy in response to the radiation and temperature step changes
- 17. V-I characteristic under different irradiance conditionsBehavior of system under different irradiance value, bigger irradiance value the bigger value of V-I
- 18. Generic Single Phase H-bridges Convertera. Generic single phase string converterb. Generic single phase H-bridges converter
- 19. Cascaded Multilevel Inverter Featurescan generate output voltage with extremely low distortion and lower dv/dt.circuit layout has more flexibility.compared to other multi level topologies, CMC requires least number of components, because there is no need for clamping diodes and flying capacitors.The number of output voltage levels can be easily adjusted by adding or removing the H-Bridges cells.
- 20. Cascaded Multilevel inverter System Overview
- 21. Inverter topology and carrier shifting control scheme
- 22. Switching Pattern of 11-level cascade inverter
- 23. PWM Control featuresprosTo balance power sharing between the modules, this switching scheme gives a very balanced averaged power sharing between all modules.ConsIn reality, inter cycle difference of power still exists in each module.
- 24. General control methodology of ConverterShows the block diagram of generalized voltage control for any k-thmodule.
- 25. Voltage Control Loop of Each moduleDescribe how to generated DC voltage of each module of PV module. The corresponding digital filtered voltages Vdckare sent to next stage where the power control is carried out.
- 26. Power Control LoopPower Control loop output is Vht, whose Vht that must be synthesized by the converter.
- 27. Phase locked loop (PLL) configurationTypical PLL algorithms include inverse park-based PLL, hilbert transformer-based PLL, and transport delay-based PLL
- 28. Simplified output circuit and unitary factor power operation Power flow controlled according to
- 29. MPPT algorithmsInstead of sensing the individual panel voltages (depend on temperature and irradiance), MPPT algorithms determines the optimal point of operation of the panel by calculating the output power and phase angle variation.It monitor output voltage and current parameters by making small changes on phase angle and looking at the power variationIn this PV configuration a perturbation and observation (P&O) algorithms has been used.
- 30. ConclusionsThis project uses string or multi string array configuration, and multilevel converter without DC-DC converter and without isolation (transformer less).This project uses 11-level PWM H-bridge cascade PV converter, which uses PLL and MPPT with separate solar DC panel DC source to enable grid interaction.Each PV array will have its specific MPP. And MPPT algorithms using P&O algorithms.Present new control strategy for CMC to gain the best performance of the systems under all environmental conditions.
- 31. Future WorksImplementation of MPPT algorithms each solar array.Implementation Of PWM control.Finding best filter configuration for inverter output.Implementation Of PLL to inverter.Making general controls methodology working properly.
- 32. Thank you for your attention