A Three-phase AC/DC PWM Converter Based On Single-phase Module

With the rapid development of switching power supplies.the power capacity continues to improve,Three-phase PWM rectifier is commonly used as the pre-converter of high-power electrical equipment.But the harmonic current injected into the grid from the equipment could be a problem. Power Factor Correction(PFC) technology can reduce the Total Harmonic Distortion (THD). A three-phase AC/DC PWM converter based on single-phase module has following advantages:First, this modular development approach of different power levels can shorten the research and design costs and cycle; Second, the structure of single-phase module is simple, so easy-to-scale production can reduce manufacturing costs; mature single phase PFC technology can be appleid on three-phase rectifier; single-phase module can use low-voltage power devices,so there may be some advantages. on cost and conversion efficiency.In the first chapter,several kinds of three-phase PWM rectifier topology are reviewd, A variety of current sharing strategy is discussed and analysed, the master-slave strategy in which modules share the voltage outer loop can be a good choice.The second chapter focuses on the design of the double-loop control strategy in the single-phase module.Experiments show that the control parameters of PI regulator are reasonable.The third chapter describes the three-phase PWM rectifier current sharing strategy:Master-slave strategy through the CAN bus communication..Mathematical models of the common voltage outer loop is proposed based on small signal modeling. Because the three-phase rectifier output voltage ripple is smaller than single-phase module, the bandwidth of the common voltage loop can be improved. Boost circuits consisting of three-phase PWM rectifier require soft start to precharge the bus capacitor, on the basis of the single-phase module soft-start program, a simple and effective three-phase rectifier soft-start strategy is proposed, experiments verify the feasibility of the program. Experiments show that the THD of three-phase current of three-phase PWM rectifier is low and current sharing in steady state and transient state is achieved.The fourth chapter details the CAN bus protocol software design. In order to meet the the modular requirements,the automatic established master program is put forward, CAN communication baud rate of the CAN bus communication is selected on theory analysis to achieve current sharing of transient state..