Research On A New Single-phase Five Level Photovoltaic-storage Inverter

Photovoltaic(PV)power generation as the representative of the new energy power generation on the converter efficiency and power quality put forward higher requirements.While the multi-level inverter in raising the voltage level and reducing the output current ripple has obvious advantages.At the same time,the introduction of energy storage link in the inverter can effectively solve the problem of photovoltaic power generation volatility and discontinuity,so as to ensure continuous and reliable power output.Therefore,the multi-level inverter with energy storage function has a wide application prospect in photovoltaic power generation system.In recent years,the research of optical storage and power generation system has been focused on the structure of photovoltaic and energy storage independently,while there is little research on the integration of energy storage in photovoltaic inverter topology.This paper focuses on this research,hoping to find a new idea of optical energy storage system design,the main contents include:(1)Based on the active neutral-point clamped five-level topology structure and working principle,an optical storage inverter system with energy storage is designed,and the modulation of the inverter is realized by carrier stacking and carrier phase shifting,and finally selected for the hardware control system carrier phase modulation method.(2)The control method for the inverter topology is proposed,and the method of solving the potential balance of the DC side capacitor and the control method of the charge and discharge of the energy storage link are put forward by using the weight of the DC side capacitor.The basic control strategy such as DC side neutral potential balance strategy,super capacitor charge and discharge strategy,super capacitor voltage control strategy and precharge strategy are simulated by MATLAB-Simulink simulation software.(3)The hardware main circuit and the control system are designed.The main functions and implementation methods of the main controller DSP and the auxiliary controller CPLD are studied.The control strategy of the system off-grid operation is put forward.(4)A single-phase five-level optical storage inverter prototype is built.The experimental scheme is used to verify the modulation strategy and the basic control strategy.The experimental waveforms are given under the off-grid condition,and verify the feasibility of the inverter case.