换相失败下STATCOM助增暂态过电压机理与优化策略

Mechanism of STATCOM Assisting Transient Voltage under Commutation Failure at Weak Sending End System and Its Optimization Strategy

随着新能源发电的大规模接入,交直流输电系统“强直弱交”特点日益突出。当直流输电系统发生换相失败时,弱送端系统会产生暂态过电压。静止同步补偿器(static synchronous compensator,STATCOM)响应电网电压的变化时,其控制环节的滞后性会导致STATCOM对暂态过电压产生助增作用。针对该现象,文章首先分析了换相失败下弱送端系统暂态过电压的产生机理,接着通过分析频率响应特性,对STATCOM响应滞后时间给出了理论推导,最后针对STATCOM响应滞后特性提出了一种基于阻尼投切的优化策略,以抑制STATCOM对过电压的助增作用,并通过仿真验证了优化策略的有效性。

With the large-scale access of new energy,the power grid presents the characteristics of strong DC system and weak AC system.When commutation failure occurs in HVDC transmission system,transient overvoltage will appear in weak sending end system.Since STATCOM responds to the change of grid voltage through the command of control link,the lag of its control link will lead to the enhancement of transient overvoltage by STATCOM.Firstly,in view of this phenomenon,this paper analyzes the generation mechanism of AC transient overvoltage in weak sending end system under commutation failure.Secondly,by analyzing the frequency response characteristics,theoretical derivation of STATCOM response delay time is given.Finally,an optimization strategy based on damped switching is proposed to suppress STATCOM’s increasing effect on overvoltage response,and the effectiveness of the optimization strategy is verified by simulation.