Power Control Algorithm Of Single-phase Cascaded H-bridge Inverter

With the development of power electronics technology,medium and high voltage,high power,and large capacity converters with multilevel topologies have gradually become hotspots in the field of power electronics.At present,the topology of multilevel converters includes neutral point-clamped,flying capacitor,cascaded H-bridges,and so on.Based on the advantages of high modularity,less power electronic switching device usage with the same level number of output voltage,and simple layout,the topology of cascaded H-bridges is widely used in the fields of electric traction,new energy generation,and energy storage.Taking a single-phase cascaded H-bridge inverter as the research object,the research of the power control algorithm adopted to single-phase cascaded H-bridge inverters used for the combined power supply device of the new ground phase-splitting system and the large-scale photovoltaic power generation system.Firstly,based on the characteristic of low voltage’s phase difference between the two ends of the existing line section and the power capacity of ground phase-splitting system is large,a combined power supply device based series connected transformer at output side of single-phase cascaded H-bridge inverter is presented.In this paper,after analyzing the operation principles of the ground phase-splitting system composed of the combined power supply device,the mathematical model corresponding to the system is established.According to the idea of traditional direct power control algorithm,a direct power control algorithm for the single-phase cascaded H-bridge inverter of the combined power supply device is presented.The effectiveness of the control algorithm is verified through computer simulation based on Matlab / Simulink.Secondly,for the single-phase cascaded H-bridge photovoltaic inverter in a large-scale photovoltaic power generation system,a DC-side capacitor voltage reconstruction algorithm used for single-phase cascaded H-bridge inverters is presented to simplify the system structure.At the meanwhile,adopting serial calculation mode,embedding the DC-side capacitor voltage balance algorithm into the cost function,a model predictive power control algorithm for dc-side sensor-less single-phase cascaded H-bridge photovoltaic inverters is proposed.The correctness and effectiveness of the proposed algorithm are verified through computer simulation based on Matlab / Simulink.Finally,a ground phase-splitting system based on the combined power supply device and a dc-side sensor-less single-phase cascaded H-bridge photovoltaic inverter are built in the hardware-in-loop experimental platform based on RT-Lab.Then,the control algorithm and the modulation scheme are implemented based on DSP and FPGA.The correctness and effectiveness of the proposed control algorithm are furtherly verified,by comparing hardware-in-loop experimental results and simulation results.