基于基本矢量钳位策略的过调制算法研究

Research on Over-modulation Algorithm Based on Basic Bus Clamping Strategy

低开关频率大功率牵引变流器为了充分利用直流电压,往往要过渡到方波工作模式,传统双模式过调制算法采用异步方式实现过渡,很难保证输出电流的对称性,且存在较多的寄生谐波和转矩脉动。本文基于基本矢量钳位策略BBCS(Basic Bus Clamping Strategy)对传统过调制算法进行了改进,在每个扇区固定位置通过特定矢量作用顺序进行调制,保证了低开关频率下较好的谐波特性,有效抑制了转矩脉动,且能平滑过渡到方波。仿真和实验验证了所提方案的可行性和有效性。

The traction converter of rail vehicles is characterized by great power and low-switching frequencies , and in order to make full use of DC bus voltages , transition to operation of square-waves is needed .Since the traditional over-modulation algorithm uses the asynchronous mode , the output current is hard to achieve sym-metry under a relatively low switching frequency and it also contains more parasitic harmonics and torque rip-ples . For this reason , this paper put forward a synchronous over-modulation algorithm based on the Basic Bus Clamping Strategy （BBCS） . The conventional over-modulation algorithm was improved to guarantee genera-tion of good harmonic characteristics under low switching frequencies and to guarantee effective suppression of torque ripples and a smooth transition to square waves . The simulation and experiment results show the feasi-bility and validity of the proposed scheme . The scheme is significant to promote R＆amp;D of high-power low switc-hing frequency traction systems for urban rail vehicles and also their applications .