单相三电平并网逆变器多状态模型预测控制研究

Research on multi-state model predictive control for a single-phase three-level grid-tied inverter

单相三电平逆变系统中,传统有限控制集模型预测控制在较低的采样频率下无法保证输出电能质量。针对这一问题,提出一种多状态虚拟矢量模型预测控制方法。在单个控制周期内,输出多个开关状态,以提高并网电流的电能质量。建立了逆变器预测模型,根据预测矢量初步筛选一组开关状态,每个开关状态的作用时间由所设计的电流代价函数确定。为有效平衡直流母线电压,设计均压代价函数,进一步调整开关状态,得到最终输出到逆变器的开关状态序列。搭建仿真系统并进行了仿真分析,结果验证了所提控制策略的有效性,并网电能质量得到有效提高,直流母线电压波动小。

In a single-phase three-level inverter system,the classic finite control set model predictive control cannot guarantee the output power quality at a lower sampling frequency.To solve this problem,a multi-state virtual-vector model predictive control method is proposed.In a single control period,multiple switch states are output to improve the power quality of the grid current.The inverter predictive model is established,and a set of switch states are initially selected according to the predicted vector,and the work time of each state is determined by the designed current cost function.To effectively balance the voltage of the DC bus,a voltage balancing cost function is designed,and the switch state is further adjusted to obtain the final switch state sequence output to the inverter.A simulation is built and the analysis is carried out.The results verify the effectiveness of the proposed control strategy,the grid-connected power quality is effectively improved,and the voltage fluctuation of the DC bus is small.