基于PAM＋PWM级联多电平逆变器的SVG的研究

Research of cascade SVG based on PAM+PWM inverter

为了使级联SVG降低开关损耗、减小谐波含量,提出了PAM(Pulse Amplitude Modulation)+PWM(Pulse Width Modulation)调制策略。四个H桥级联构成PAM单元,各H桥都工作于基频开关频率下,开关损耗较低。第五个H桥构成PWM单元,PWM单元对PAM单元输出阶梯波中的谐波分量进行补偿,极大地降低了电压电流畸变率,提高装置输出电流的质量。PAM单元直流侧采用脉冲轮换策略,有效地抑制了直流侧电压的不平衡。PWM单元采用电流直接控制策略,响应速度快,控制精度高。最后在Matlab/Simulink中建立级联SVG仿真模型,验证了所提方法的有效性。

In order to lower the switching losses and reduce the harmonic content of the cascade SVG the method of PAM＋PWM is introduced. Four H bridges constitute the PAM unit, every H bridge works under the fundamental frequency, so the switching losses are low. One H bridge constitutes the PWM unit, the PWM unit can compensate the harmonic content of the output step waveform of the PAM unit, it can greatly reduce the voltage and current distortion factor and improve the power quality. The pulse cycle transposition is used on the DC side, it can effectively solve the problem of the DC capacitors voltage unbalance of the PAM unit. The PWM unit outputs the reactive current by the current direct control method, it can improve control accuracy and response speed of the device. The model of SVG with chain inverter is built in Matlab/Simulink, the result proves the validity of the method.