不平衡负载情况下矩阵变换器的拓扑改进及控制策略

针对3×3矩阵变换器(matrix converter，MC)不能带不平衡负载问题，提出一种新型的3×4MC，新增加的中线桥臂连接到负载中性点。建立其交-直-交的等效模型，并通过在等效模型上对3×4MC带不平衡负载的分析可知，获得三相对称输出电压的关键是对负载中性点电位的控制。继承3×3MC的空间矢量调制(space vector pulse width modu- lation，SVPWM)方法，并根据其调制特点，分析SVPWM与正弦脉宽调制(sinusoida pulse width modulation，SPWM)的内在关系：SVPWM实质上是在三相正弦调制波中注入了零序分量的改进SPWM。对中线桥臂单独采用SPWM方法，控制负载中性点的电压为相应的零序电压，使输出为三相对称电压。采用开关函数法对网侧的输入电流进行谐波分析，得出输入电流中低次谐波的表达式。最后针对所提出的3×4MC用Matlab/Simulink进行仿真，仿真结果验证了其可行性。

Improvement of Matrix Converter's Topology and Study on It's Control Strategy Under Unbalance Load

This paper proposed a novel 3×4 matrix converter (MC) for the problem that 3×3 MC can't carry the unbalance load. The added midline bridge connects the neutral point of load. The equivalent AC/DC/AC model is founded and the instance of 3×4 MC with unbalance load is analyzed. The fact that the key of obtained three phases symmetrical output voltage is to control the voltage of neutral point is achieved. Space vector pulse width modulation (SVPWM) of 3×3 MC is inherited and the relationship of SVPWM and space pulse width modulation (SPWM) is analyzed: the SVPWM is an improved space pulse width modulation (SPWM) of adding zero-sequence component to sinusoidal modulation wave. The midline bridge is modulated by SPWM method and the voltage of load's neutral point is controlled to be fitting zero-sequence voltage, which can make output voltage symmetry. The input current is analyzed by switching function method and the expression of lower harmonic current is given. Simulation results are given to verify the feasibility of 3×4 MC.