Research On A Novel Distributed Photovoltaic Grid-connected Inverter

With the continuous consumption of energy and pollution continues to intensify,the use of new energy for grid-connected power generation technology has become the focus of scientific and technological work.PV grid-connected inverter is an important device for connecting distributed photovoltaic power generation system and power grid.It is the core of distributed photovoltaic grid-connected power generation system and plays a key role in the stable operation of the whole power generation system.Therefore,the study of photovoltaic grid-connected inverter is of great significance.This paper briefly introduces the various circuit topology of grid-connected inverter,and studies the topology of low-cost inverter circuit for small distributed generation system,that is,Three-switch single-stage buckboost grid-connected inverter,The inverter uses a small number of switches,the topology is simple,the output efficiency is high and the advantages of a wide range of buck.The PID controller parameters of the closed-loop SPWM method are optimized when the inverter is operated in the inductor current intermittent mode.In this paper,we design a comprehensive index J,which can reflect the robustness of the system and the integral performance of the system.We use the method of full space recursive search to find the optimal J value,and finally get the PID controller optimized parameters.Simulation and experimental study show that the output current of the inverter can be stabilized when the input voltage changes greatly,and the THD is lower in synchronization with the grid voltage.In this paper,an energy modulation based inverter modulation method is analyzed: pulse energy modulation(PEM).The Lyapunov stability theorem is used to analyze the stability of PEM inverters.This modulation technique is based on energy control and calculates the pulse width by calculating the magnitude of the energy demand for each switching cycle to achieve inverter control.The energy requirements are calculated from the output voltage and the reference current,and the degree of modulation of the inverter is calculated based on the instantaneous energy requirements.And also build a small signal equivalent model of PEM inverter,compared with the PWM inverter,PEM step-up and down the performance of the inverter has been greatly improved.The simulation results show that the PEM method can provide a more stable sinusoidal output,has a lower THD value,and can be applied to a wider DC input voltage and a wider output power range.