电网故障时电力电子变流器的直接解耦同步法

Direct Decoupled Synchronization Method for Power Electronic Converters Under Unbalanced and Distorted Operation Conditions

现代电网出现短路、断线等故障时,临近故障点的各电网节点及并网变流器将运行于三相不平衡、电压闪变等异常状况下。通过对故障电网电压各序分量、谐波分量的分析,提出一种基于正、负序解耦的电网故障状态下并网电力电子变流器的直接解耦同步法(direct decoupled synchronization method,DDSM)。确切地说,通过克拉克变换,然后对参考电压uα、uβ中的基波正负序分量进行解耦,即得到三相电压的正负序基波分量。正负序分量的解耦是利用现有的一些单向锁相环(phase-locked loop,PLL)模块来实现的,这些模块可以理解为一种频率跟随的滤波器,能够滤得基波及其正交分量。对于电网存在较严重低次谐波的情况,还介绍对该解耦方法的简便扩展方案。相对于现有的一些三相电网同步方法,直接解耦同步法能够处理正负序基波频率不同的情况,其扩展方案可有效节省系统工作量。对直接解耦同步法及其扩展方案的频谱响应和运行特性进行分析和比较,并通过基于DSPACE半实物仿真平台的实验进行验证。

During short-circuit or broken-line faults in modem grids, Three-phase grid-connected power converters neighboring fault points usually operate under three-phase unbalanced and distorted operation conditions. This paper proposed a direct decoupled synchronization method （DDSM） based on direct decoupling of fundamental symmetrical components. Specifically, after Clarke transformation, a decoupling scheme of positive and negative components form reference voltage ua and u/~ was operated, which exploits some existing advanced single phase phase-locked loop （PLL） modules. These modules can be regarded as frequency adaptive filters, generating the in-phase and quadrature-phase waveforms of input signals. The decoupling scheme can also be easily expanded while dealing with low-order harmonics. The proposed schemes facilitate programming and can deal with the situation while positive fundamental frequency differs from negative one. Frequency response and operation properties of the proposed synchronization schemes were analyzed and conclusions were verified by experimental results.