Single Source Cascaded Switched-capacitor Multilevel Inverter And SHEPWM Modulation Based On Hybrid Particle Swarm Optimization Algorithm

With the rapid development of photovoltaic(PV)energy,it is more and more important to study how to improve the output power quality of PV inverter.Multilevel inverter(MLI)is widely used in PV generation system as its low switch stress,sinusoidal output voltage waveform and low switching frequency.Compared with the previous research of MLI,MLI based on switched capacitor(SC)has the advantages of simple structure,self-balancing capacitor voltage and self-boosting.Therefore,the research of SCMLI with good performance can effectively save the cost of inverter system.At the same time,SHEPWM can not only reduce the switching loss of the device,but also reduce harmonic contents of the inverter output voltage,so as to effectively improve the power quality of the inverter output.Therefore,this paper presents two novel SCMLI topologies,and then applies SHEPWM technology to the proposed inverters,and verifies whether the inverter output power is improved through theoretical derivation and experimental analysis.Firstly,the traditional MLI structure is complex,the capacitor voltage can’t be self-balanced,and there is no independent boost capability.In this paper,two new types of MLI were proposed by combining SC module and cascaded H-bridge.The proposed inverter can generate more output levels with fewer devices.In addition,all capacitors are charged by single DC voltage source many times in one output voltage cycle,so that their voltages can be balanced automatically.This paper analyzes the working principle and related parameters of the proposed inverter circuit structure,and verifies it by building simulation model and experimental platform,the results prove the feasibility of the proposed inverter and correctness of theoretical analysis.Secondly,to overcome the difficulty of SHEPWM technology in the process of solving nonlinear harmonic elimination equations,this paper proposes a hybrid particle swarm optimization algorithm to further improve SHEPWM technology.Based on particle swarm optimization,the elitist retention strategy and the operator of genetic algorithm are introduced in the proposed algorithm,which can improve the optimization ability and accelerate the convergence.In order to verify the performance of the proposed hybrid particle swarm optimization algorithm,this paper used SHEPWM technology to modulate the proposed MLIs.By comparing the voltage harmonic content of the iterative results of genetic algorithm,particle swarm optimization algorithm and the proposed hybrid particle swarm optimization algorithm,it is found that the proposed hybrid particle swarm optimization algorithm has better harmonic suppression effect,and the effectiveness of solving nonlinear harmonic elimination equations is also verified.Finally,the inverter system based on SHEPWM technology was built.The experimental results show that the proposed algorithm can effectively improve SHEPWM technology.