三电平容错拓扑分析及预测控制研究

A new fault tolerant three-level inverter and FCS-MPC research

三电平逆变器系统具有输出电压谐波含量少和电压变化率低等优点,但随着开关元器件的增加,系统的可靠性将会下降,同时传统三电平电路拓扑存在中点电位不平衡的问题。基于此,提出一种改进的三电平逆变器拓扑。该电路的主要优点是采用串联的两电平对称结构,在任一桥臂的器件故障后通过并联到对称支路上,实现两电平的工作方式,同时引入第四桥臂对中点电位进行独立控制。在此基础上,采用模型预测控制对电路进行控制,针对其对模型依赖性较强的特点,对新型电路进行混杂系统建模,提高模型的精确性。实验结果验证了该电路拓扑和控制方法的正确性和可行性。

Three-level inverters could achieve more levels of output voltages with lower total harmonic distortion （THD）. However, increasing of semiconductors would decrease the reliability of the inverter, what＇s more, the topology causes a low frequency oscillation of the neutral-point voltage. This paper establishes an improved three-level inverter topology, it has better fault-tolerant ability to work as a two-level inverter by its asymmetry topology, when a break occurred in any of devices. In addition, the improved topology adding assistant leg to control neutral-point voltage independently. On the basis of the improved topology, a more accurate mixed logic dynamic model （MLD） is established for the inverter, then the MLD model is taken as prediction model to research the finite control set model predictive control （FCS-MPC） for the inverter. The paper explicitly researches the solving algorithm and realization procedure of the inverter, its feasibility and validity is verified by the simulation and experiment. This work is supported by National Basic Research Program of China （973 Program） （No. 2015CB755800）.