Voltage Clamping And Control Of Single-stage HFL DC/AC Converter

With the development of power electronics technology,it has become a trend to study the converter with high efficiency and high power density.The single-stage high frequency link DC/AC converter studied in this paper adopts high frequency transformer to transmit energy,which can not only solve the problems of large volume and high cost of the traditional power frequency converter,but also realize the bidirectional flow of energy and the soft switching of the main circuit switch,and improve the conversion efficiency of the system.The main work of this paper includes the following aspects:(1)This paper introduces the research background,significance and current situation of high frequency converter,classifies and summarizes the circuit structure of high frequency converter,and discusses the problems of single-stage high frequency converter at present stage.(2)Aiming at the circuit topology of single-stage high frequency link DC/AC converter,the working principle and control strategy in off-grid mode were analyzed,and the implementation scheme was designed based on synchronous modulation strategy,and the simulation was carried out.(3)The equivalent resonance circuit model of transformer leakage inductance and parasitic capacitor of switch was established.The resonance mechanism and the cause of overvoltage in the circuit are analyzed in detail.Two solutions of passive absorption and active clamping were given,their working principles are analyzed in detail,the resistancecapacitance parameters in passive absorption circuit are designed,the control method of active clamping switch is studied,and the selection of clamping capacitor was given.(4)The relationship between the soft switching characteristics of the main circuit and voltage clamp circuit was analyzed and summarized,and the realization conditions of the soft switching of the main circuit under different conditions were deduced.(5)A 150 W single-stage high frequency link DC/AC converter prototype was built,and the selection method of transformer,inductor and main circuit switch was given.Using DSP+CPLD as the joint controller can effectively avoid the problem caused by the timing disorder of the switch drive signal in the circuit.Finally,the correctness of the theoretical analysis was verified by simulation and experimental results.