三电平中性点钳位整流器模型预测电流控制算法

Model Predictive Current Control Method for Three-level Neutral Point-clamped Rectifier

将三电平中性点钳位整流器作为研究对象,以维持单位功率因数运行、减小网侧电流谐波、补偿计算时间延迟和保持直流侧电容电压平衡为研究目标,提出了一种基于在线简化的模型预测电流控制策略。该方法通过坐标变换构建α-β静止坐标系下三电平中性点钳位整流器的预测模型,结合电压空间矢量等效变换的原理,求出三电平中性点钳位整流器的参考输出电压矢量,判断其所在扇区,从而选择该扇区最优电压矢量所对应的开关状态直接作用于整流器。同时,针对该算法在实际应用中容易产生计算时间延迟现象,引入拉格朗日外推法,得到具有延时补偿的控制策略。最后,仿真结果证明了该方法的正确性和有效性。

In this paper,a three-level neutral point-clamped(NPC) rectifier is taken as the research object.To maintain the unit power factor operation,reduce the grid-side current harmonics,compensate the delay in calculation time and maintain the DC-side capacitor voltage balance,an online simplified model predictive current control strategy is proposed.The prediction model of the three-level NPC rectifier is established in α-β stationary reference frame by means of coordinate transform.Combined with the principle for voltage space vector equivalent transform,the reference output voltage vectors of the three-level NPC rectifier are obtained,and the sectors where they are located are determined.In this way,the switching state corresponding to the optimal voltage vector in the sector is selected and directly applied to the rectifier.Meanwhile,considering that the delay in calculation time is easily encountered in practical applications,Lagrange extrapolation method is introduced,thus forming the control strategy with time delay compensation.Finally,simulation results show that the proposed method is correct and effective.