无电网电压传感器三相PWM整流器虚拟电网磁链定向矢量控制研究

电压型三相PWM整流器与变频器供电三相交流电机的定子电路有很大的相似性,采用类似于交流电机磁链观测的方法构造出虚拟的电网磁链矢量,作为PWM整流器矢量控制中的定向矢量,可以达到取消交流侧电网电压传感器、降低PWM整流器硬件成本的目的.准确观测虚拟电网磁链是PWM整流器虚拟电网磁链定向无电压传感器运行的关键.与同步电机磁链观测相似,虚拟电网磁链的观测也存在初始值的问题.不带初始磁链估计的观测器会导致PWM整流器在起动过程中产生很大电流冲击甚至无法起动.为了解决这一问题,该文通过深入分析虚拟电网磁链的特点,提出了一种新的带初值估计的虚拟电网磁链的观测方法.仿真和实验结果验证了所提出观测方法的有效性和无电网电压传感器条件下,三相电压型PWM整流器虚拟电网磁链定向矢量控制运行的良好动、静态特性.

VIRTUAL LINE-FLUX-LINKAGE ORIENTED VECTOR CONTROL OF THREE-PHASE VOLTAGE SOURCE PWM RECTIFIER WITHOUT LINE VOLTAGE SENSORS

There is a great similarity between the circuit of three-phase voltage-source PWM rectifier and the stator of an inverter-fed AC motor. Therefore a virtual line-flux-linkage vector can be constructed similarly to the observation of AC motor flux linkage, which may serve as the oriented vector in the vector control of the PWM rectifier instead of the line voltage vector. As a result, the line voltage sensors will be eliminated and the costs of PWM rectifier can be reduced. The key problem 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. However, there are initial problems in the observation of the virtual line-flux-linkage, similarly to the synchronous motors, should be solved. The observer without initial value estimation will lead to a large current rush, which sometimes could even cause the rectifier hard to start up. To solve the problem, the characteristics of the virtual line-flux-linkage were analyzed in this paper and a novel virtual line-flux-linkage observer with estimation of the initial value was suggested. The validity of the observer has been proved and the good dynamic and static performance of the PWM rectifier under the virtual line flux linkage vector oriented control without line voltage sensors have been showed by both simulation and experiment.