Research On A Single-phase Current Source Grid-connected Inverter Based On Critical Voltage Control

The grid-connected inverter is the core part of photovoltaic power generation system.Compared with the voltage source inverter,the current source inverter has the advantages of single-stage boost,no electrolytic capacitor and no short-circuit protection,which makes it a greater potential for development in the field of small and medium power photovoltaic power generation.However,using the traditional SPWM modulation method,the current source inverter is hard switching and the DC-side inductance value is large.The current source inverter is not conducive to meeting the requirements of high frequency,low loss,and lightweight of small and medium power inverters.The soft-switching technology and the lightweight of DC-side inductance of a single-phase current source grid-connected inverter have important theoretical research significance and engineering realization value.Firstly,this paper summarizes the existing research results of soft switching.It converts the boundary current control method in controlled-type soft switching technology into the critical voltage control through duality,which is applied to the single-phase current source inverter.Through analyzing the working principle,it is concluded that the high-frequency switches can achieve zero current switching(ZCS).Secondly,the mathematical relationship between the DC-side inductance current and the output current of the single-phase current source inverter based on critical voltage control is quantitatively analyzed.It is found that using critical voltage control can not only achieve ZCS of high-frequency switches,but also reduce the value of the DC-side inductance.Thus,this paper established a mathematical model of single-phase current source inverter under passive load,and designed the closed-loop and grid connected control system based on critical voltage control.Simulation results show that the inverter has good closed-loop performance.Based on theoretical analysis and simulation research,the software and hardware of the system were designed in this paper.Besides,a 300 W experimental prototype based on critical voltage control was built.According to the experimental results,the correctness and feasibility of the theoretical analysis and simulation results were verified.