双馈风机下垂控制对系统小扰动功角稳定的影响机理分析

Mechanism Analysis of Droop Control of DFIG Influence on System Small-Signal Dynamic Stability Based on Damping Torque Analysis

附加下垂控制可以改善双馈风机响应系统频率变化的特性,但同时将改变其与系统同步机动态特性间的耦合关系,进而影响系统小扰动功角稳定特性。针对该问题,文章用阻尼转矩分析法研究了双馈风机下垂控制对系统小扰动功角稳定的影响机理。首先从双馈风机下垂控制的基本原理出发,针对扩展两机系统,分析了风电接入点频率与系统同步机频率间的关系,进而采用阻尼转矩分析法揭示了双馈风机下垂控制影响系统小扰动功角稳定的机理。在此基础上,分析了下垂控制增益对系统小扰动功角振荡模式阻尼的影响特性及其与风机接入位置、同步机惯性时间常数的关系。最后,利用模态分析法验证了理论分析的正确性。分析结果表明,双馈风机附加下垂控制对系统振荡模式阻尼的影响性质和程度与双馈风机接入位置和系统同步机惯性时间常数的分布相关。

Droop control can improve frequency response characteristics of doubly-fed induction generators（DFIGs）. It also affects coupling between dynamic characteristics of DFIGs and synchronous generators, influencing system small-signal dynamic stability. In this paper, influence mechanism of DFIG droop control on system small-signal dynamic stability was studied based on damping torque analysis（DTA） method. Firstly, basic principle of droop control was presented. Then, based on an extended two machines system, relationship between frequencies of DFIG access point and synchronous generators were derived. Mechanism of DFIG droop control affecting small-signal stability was revealed with DTA. On this basis, effects of droop control gain on system oscillation mode and its relationship with DFIG location and synchronous machine inertias were analyzed. Finally, effectiveness of the theoretic analysis was verified based on modal analysis method. Analysis results show that droop control nature and extent influencing system oscillation mode are related to DFIG location and system inertia distribution.