电容均压三相四开关整流器多矢量模型预测控制

三相四开关整流器因其交流侧某一相直接连接在直流侧两电容中性点之间,存在着电容电压不平衡问题。为了保证电容电压平衡,且进一步提高三相四开关整流器控制系统的稳态性能,提出了一种电容均压的多矢量模型预测控制(multi-vector model predictive control, MVMPC)策略。针对三相四开关整流器无零矢量问题,建立等效零矢量模型;为保证直流电压的稳定,采用参考功率补偿策略来平衡直流侧电容电压;多矢量模型预测控制方面,每个采样周期选取两个基本电压矢量和一个等效零矢量,这使得等效合成矢量方向幅值均可调,扩大了等效合成矢量的作用范围,提高了系统的控制精度。仿真结果表明,电容均压多矢量模型预测控制策略能使三相四开关整流器可靠稳定地运行,对功率、网侧电流、直流侧电容电压等有着良好的控制效果;与传统的模型预测控制策略(conventional model predictive control, CMPC)相比,所提控制策略具有更小的功率脉动以及更低的电流谐波含量,且开关频率恒定,谐波电流分布规律。

Multi-Vector Model Predictive Control for Three-Phase Four-Switch Rectifier with Capacitor Voltage Balancing

Three-phase four-switch rectifier has the problem of unbalanced capacitor voltage because one phase of its AC side is directly connected between two capacitor neutral points on the DC side. In order to ensure the capacitor voltage balance and further enhance the steady-state performance of the three-phase four-switch rectifier control system, a multi-vector model predictive control (MVMPC) strategy for capacitor voltage balance is proposed. Since no zero voltage vector for three-phase four-switch rectifier, the equivalent zero vector model is derived to implement the proposed control strategy. To ensure the stability of the DC voltage, it is proposed to power compensation strategy to balance the DC-link capacitor voltage. In multi-vector model predictive control, two basic voltage vectors and one equivalent zero vector are selected for each sampling period, which makes the amplitude of the equivalent synthetic vector direction adjustable, as a result of expanding the range of the equivalent synthetic vector and improving the system's control precision. The simulation results show that the multi-vector model predictive control with capacitor voltage balancing strategy can make the three-phase four-switch rectifier operate reliably and stably, with great control effects on power, grid side current, DC side capacitor voltage. Compared with the conventional model predictive control (CMPC) strategy, the proposed control strategy has less power ripple and lower current harmonic content with a constant switching frequency.