Modulation Strategy And Control Based On Push-pull Forward High Frequency Link Matrix Inverter

The push-pull forward converter has received the attention of the most scholars in recent years,mainly because it combines the push-pull converter with the forward converter skillfully by a capacitor,and overcomes the magnetic reset problem of the push-pull converter and the problem of magnetic bias in forward converter,having both advantages of them.The push-pull forward high-frequency link matrix inverter is a new type of power converter combining the matrix converter and the push-pull forward converter,which consists of a front-stage push-pull forward inverter circuit,a high-frequency transformer,matrix converter circuit,output filter network and load,through the DC-HFAC-LFAC energy conversion to achieve the two levels of power conversion with light weight,small size,low noise and other characteristics of the high-frequency link inverter.Based on this topology,the paper presents a single-phase de-re-coupling sine wave modulation strategy and a single-phase de-re-coupling sine modulating square wave trigger method in order to provide a safe freewheeling path for leakage inductance current of the transformer secondary and realize the soft switching of the matrix converter,and carrying on the principle analysis as well as the simulation and the experimental verification.Firstly,based on the push-pull forward high-frequency link matrix inverter topology,this paper introduces an existing single-phase de-re-coupling bipolar modulation strategy,and analyzes its operating modes and modulation principles.The safety commutation problem is described in detail,and the causes of over-voltage of the power switch are summarized.Secondly,in order to solve the above problems,a single-phase de-re-coupling sine modulating square wave trigger method for push-pull forward high-frequency link matrix inverters is proposed,and the modulation method is expounded and the working mode analysis is carried out.This strategy realises the safe commutation of the leakage current of the transformer,and reduces the voltage peak of the power switch,and realises the soft switch of the matrix converter switch.Compared with the single-phase de-re-coupling bipolar modulation method,the efficiency of the converter is obviously improved.Then a simple comparison is made between the proposed single-phase de-re-coupling sine wave modulation strategy and the single-phase de-re-coupling sine modulating square wave trigger method,which can also realize leakage current safe continuation of the transformer secondary,and realize zero voltage switch of the power switch of the matrix converter.Then the closed-loop control of the push-pull forward high-frequency link matrix inverter is studied.The mathematical model of the inverter is established according to the single-phase de-re-coupling sine modulating square wave trigger method.The double closed loop control include of the current inner loop is PI control and the external voltage loop is quasi PR control,and the control system can suppress disturbances and quickly follow given.Finally,the whole circuit system is simulated.On the basis of the hardware and software design,the joint control circuit is made up of DSP and CPLD,and the push-pull forward high frequency link matrix inverter platform is built,and the feasibility and effectiveness of the proposed method are verified by simulation and experiment.