Input Current Low Frequency Ripple Reduction In High Gain Differential Boost DC-DC Converter Mode Inverter

Traditional fossil fuels,such as coal,natural gas and oil,have been mined extensively and their storage capacity has been depleted,and new energy sources such as solar,wind and fuel cells have become mainstream in the future due to their cleanliness and renewable nature.The inverters,including single stage inverters,quasi single stage inverters and two stage inverters,are the core part of the new energy power generation system.Among them,single-phase inverter is mainly used in small and medium power generation system,occupying a large number of market share.Whatever kind of single-phase inverter,due to the time-varying characteristics of the utput power,the inverter input current contains a large number of second harmonic,resulting in the increase of the current stress of the component parts,the decrease of fuel cell utilization,and the instability of the maximum power points of the photovoltaic power system and so on.The main contents include:This paper summarizes and analyzes the current research and development of low frequency current ripple suppression technique,and discusses their advantages and disadvantages.Based on that,a control scheme is proposed to suppress the input current low frequency ripple of high gain differential Boost DC-DC converter mode inverter,which injecting a same second harmonic into the two output filter capacitor voltage of the inverter.In this method,the output filter capacitor is used as the power decoupling capacitor to provide the secondary pulsating power on the load.The circuit topology,steady state characteristic and the input current low frequency ripple suppression principle are analyzed.The influence of capacitance values deviation,parasitic resistances and sampling error on the secondary current ripple suppression and the fundamental principle of generating fourth current ripple are analyzed.Based on the mathematical model of the inverter,the double closed loop control strategy of capacitor voltage and inductance current is analyzed.The input current closed loop control is proposed to eliminate the secondary current ripple caused by capacitance values deviation,parasitic resistances and sampling error and the fourth current ripple caused by the second harmonic voltage injection.The inverter has a strong capability on input current low frequency ripple suppression.The flow path of each ripple current in the inverter is analyzed,which comes to the conclusion that the secondary current ripple flow path is shifted from the low voltage side to the high voltage side and the internal resistance loss caused by the secondary current ripple is reduced after adding input current low frequency ripple suppression.The design method of the key circuit parameters such as power circuit,control circuit and auxiliary circuit of the inverter are deduced.The simulations and experiments of lkVA 60VDC/220V50HzAC high gain differential Boost DC-DC converter mode inverter are completed.The simulation and experimental waveforms of the inverter under different control strategies and different load characteristics are compared and analysed to verify the correctness and feasibility of the proposed method.