级联型多电平逆变器线电压谐波优化的SVPWM策略

A SVPWM Strategy with Optimal Line-to-Line Voltage Harmonic Spectrum for Cascaded Multilevel Inverters

级联型多电平逆变器采用载波移相控制可以自然实现各H桥单元功率均衡,开关管开关次数保持一致,而采用同相层叠控制可得到谐波含量更小的线电压,但各H桥单元功率不均衡,开关次数也不一致。本文提出一种结合同相层叠控制和载波移相控制二者优点且实现简单的空间矢量调制策略。通过对电压矢量进行重新组合划分,可以将多电平空间矢量控制算法简化为多个两电平空间矢量的移相叠加。对载波进行重构,可以实现输出线电压谐波更小,同时各H桥单元功率自然实现均衡,开关管开关次数达到一致。搭建了一台三相4.5kW的级联型五电平逆变器,对所提出的SVPWM策略进行了实验验证,实验结果表明所提出的空间矢量调制策略的有效性。

As for cascaded multilevel inverter, carrier phase shift(CPS) can naturally achieve power balance between each H-bridge, and the number of switching transitions of all the switching transistors trends to be equivalent. However, for three phase systems, CPS is suboptimal compared with phase disposition(PD) in terms of the spectrum of line-line voltage. Firstly, this paper discusses a simplified SVPWM algorithm for cascaded multilevel inverter. The SVPWM algorithm for multilevel inverter can be simplified to the summation of traditional SVPWM algorithm for two-level inverter. By way of reconstructing the carrier waveforms, the optimal harmonic spectrum of the output line-to-line voltage can be achieved. At the same time, power balance and the same switching number can be naturally achieved. The algorithm based on state machine is discussed in this paper, and a 4.5kW prototype is built in the lab. The experimental results verify the proposed SVPWM.