改进虚拟磁链观测器在PWM整流器中的应用

Application of Improved Virtual Flux Observer for PWM Rectifiers

采用虚拟电网磁链矢量作为电压型脉宽调制(PWM)整流器直接功率控制(DPC)中的控制量可达到省去交流侧电网电压传感器、降低硬件成本、提高系统稳定性的目的,因此如何在电网电压发生突变时准确快速地观测虚拟电网磁链及如何实现开关频率的恒定就成为PWM整流器无电网电压传感器运行的关键。通过深入分析虚拟磁链特点,结合预测控制技术,提出一种基于虚拟磁链的预测直接功率控制(VF-P-DPC)方法,同时提出采用四阶级联型低通滤波器取代传统纯积分器来构造新型磁链观测器。实验表明所提方法不仅在稳态时具有优良的控制效果,且在电网电压突变时动态响应速度快,过渡过程中直流侧电压、有功、无功功率波动小。

A virtual line-flux-linkage vector can be constructed, which may serve as the oriented vector in the direct power control （DPC） of the pulse width modulation （PWM） rectifier instead of the line voltage vector to eliminate the line voltage sensors, reduce the cost of the equipment and improve the stability of the system.The key points of the virtual line-flux-linkage vector oriented control of the PWM rectifier without line voltage sensors is to observe the virtual line-flux-linkage accurately and to keep the switching frequency constant when the grid voltage mutates.To solve the mentioned problem, a virtual fox oriented predictive direct power control（VF-P-DPC） strategy is proposed by analyzing the characteristic of virtual flux and combining the advantage of the predictive direct power control and a new virtual flux observer formed by cascaded four-order filters instead of traditional filters.Experimental results show that the proposed method can get good control results at steady state, and achieve fast dynamic response, small fluctuations of DC voltage, active and reactive power under grid voltage mutation.