双馈直驱风机混合接入MMC-HVDC送端系统的次同步振荡特性分析与抑制

Sub-synchronous Oscillation Characteristics Analysis and Suppression of DFIGs and PMSGs Mixed Access to MMC-HVDC Sending-end System

双馈/直驱风机混合接入模块化多电平高压直流输电(modular multi-level converter based HVDC,MMC-HVDC)的次同步振荡事件频繁发生,已有双馈或直驱某一种风机与MMC-HVDC交互产生振荡的研究,但鲜有针对双馈/直驱风机混合接入MMC-HVDC的次同步振荡分析与抑制措施研究。该文首先阐述并分析了某双馈/直驱风机混合接入MMC-HVDC后发生次同步振荡实际事件的特征与原因,通过阻抗相量方法研究了双馈/直驱风机频域阻抗的交互影响方式。研究表明,在双馈或直驱风机单独接入MMC-HVDC不存在振荡风险的条件下,双馈和直驱风机并联接入后依然可能存在振荡风险。最后,根据电网调度运行的实际要求,提出了考虑机组启停数量调配的临时抑制振荡策略。

Sub-synchronous oscillations frequently occur when the doubly-fed induction generator(DFIG)-based wind turbine and the direct-driven permanent magnetic synchronous generator(PMSG)-based wind turbine are connected mixedly to the modular multilevel converter-based HVDC(MMC-HVDC).The previous studies have already investigated the oscillations that occur when either the DFIGs or the PMSGs incorporates into the MMC-HVDC independently,while the subsynchronous oscillations caused by the mixed connection of these two are rarely considered.This paper first describes and analyzes the characteristics and causes of the actual sub-synchronous oscillation events when a mixture of the DFIGs and the PMSGs are integrated into the MMC-HVDC.Then using the phasor method,the interactions between these two types of turbines are revealed.The study shows that even though it is safe for either a DFIG or a PMSG is connected to the MMC-HVDC,there may still be an oscillation risk after integrating them in simultaneously.Finally,based on the practical requirements of the grid scheduling and operation,a temporary oscillation suppression strategy is proposed that considers the allocation of the number of unit start-ups and shutdowns.