Single Phase Full Bridge Buck Inverter With Input Current Low Frequency Ripple Suppression

With the increasing demand for energy,new energy power generation technologies,such as fuel cells and photovoltaic power generation,have become the research hotspots.Inverter is an essential part of new energy power generation technology for AC power supply.In the case of small and medium power,inverters are usually single-phase structure.Because of pulsating power at output side of the inverter,low-frequency current ripple is produced at the input side.The current ripple reduces the efficiency of new energy utilization,and affects the steady-state and dynamic response characteristics of power generation system.In this paper,the generation mechanism of low frequency ripple of input current in single-phase inverter is analyzed,and an active power decoupling scheme and modulation strategy is proposed.The circuit structure based on a single-phase full bridge inverter structure is added by two power switches.The two output filter capacitor,as power decoupling capacitor,is superimposed by the same fundamental voltage.The output pulsating power can be limited at the AC output side of inverter,low frequency ripple of input current is effectively inhibited.The output voltage of the inverter is the difference between the two output filter capacitor voltages,and the fumdamental voltage superimposed on the capacitor does not affect the output voltage.In order to reduce the input voltage of the inverter,a part of the fundamental voltage is supplied by the inverter control bridge arm,and the other part is supplied by the additional bridge arm.The output voltage of the inverter is controlled by the closed loop of voltage and current,and the active power decoupling circuit is controlled by voltage closed loop.In order to ensure the amplitude and phase of the fundamental voltage meet the requirements,the controller selects the quasi proportional-resonant controller which can track the AC reference signal without static error.According to the steady-state working principle of the inverter,the steady-state mathematical model of the single-phase full-bridge Buck inverter is obtained through the state-space averaging method.The inverter is modeled with small signal to verify the dynamic response characteristics to meet the requirements.The steady-state and dynamic simulation results of single phase full bridge Buck inverter with low frequency ripple suppression function are given.Steady state simulation results show that the output voltage of the inverter meets the requirements the effect of low frequency input current ripple suppression is good,the low frequency ripple suppression scheme can be applied to a wide range of load;dynamic simulation results show that the inverter has good dynamic performance and high stability.The experimental prototype of 1kVA single-phase full bridge Buck inverter is built.The experimental results verify the feasibility of the input current low frequency ripple suppression scheme.