面向柔性互联配电网的变换器稳定控制策略

Stabilization Control Strategy for Converter in the Flexible Interconnected Distribution Network

针对新能源变换器与柔性互联配电网交互产生谐波振荡等问题,此处建立了旋转d,q坐标系下变换器的输出阻抗模型,基于广义奈奎斯特判据揭示电网强度、锁相环控制带宽等参数对变换器小信号稳定性的影响规律。在此基础上,提出一种谐波虚拟电阻(HVR)控制策略,并给出HVR增益、控制时间常数的设计方法。接下来,进一步验证加入HVR控制后变换器的小信号稳定性,研究结果表明,所提HVR控制器能够有选择地增加潜在振荡频率处的电气阻尼,并提高新能源变换器与电网的交互稳定性。基于PSCAD/EMTDC搭建了仿真模型,验证了理论分析的正确性以及所提HVR控制方法的可行性。最后,搭建了实验样机,进一步验证了HVR控制策略的有效性。

Aiming at harmonic oscillation caused by the interaction between the renewable energy converter and the flexible interconnected distribution network,the converter's output impedance model in the rotated d,q frame is es-tablished,and the influence of parameters such as grid strength and phase-locked loop's control bandwidth on the converter's small-signal stability is revealed based on the generalized Nyquist criterion.On this basis,a harmonic virt-ual resistance(HVR)control strategy is proposed,and the designing method of HVR's gain and control time constant is provided.Then,the converter's small-signal stability after adding HVR controller is further verified.The analysis re-sults indicate that the proposed HVR controller can selectively increase the electrical damping at the potential oscilla-tion frequency,thus improving interaction stability between the converter and the grid.A simulation model is built based on PSCAD/EMTDC to verify the correctness of the theoretical analysis and the feasibility of the proposed HVR control strategy.Finally,an experimental prototype is built to further verify the effectiveness of HVR control strategy.