基于直流电流控制的特高压直流分层接入系统协调控制策略

Coordinated control strategy for a UHVDC hierarchical connection system based on DC current control

为解决特高压直流分层接入系统中传统换相失败预防方法的失效问题,提出一种基于直流电流控制的协调控制策略。该策略在深入分析换相失败发生的主次要因素的基础上,通过检测交流系统故障,根据故障层换相失败预防控制的输出,提前触发非故障层换相失败预防控制。同时根据交流母线电压的跌落程度自适应地降低故障初期的直流电流,增大非故障层的换相失败免疫能力,改善故障层的后续换相失败。在PSCAD/EMTDC中搭建特高压直流分层接入系统。仿真结果表明,该策略能够有效抑制非故障层的换相失败和缓解故障层的后续换相失败,大幅度提升故障时期直流功率的传输,有利于电力系统安全稳定运行。

To solve a problem of failure of the traditional commutation failure prevention method for a UHVDC hierarchical access system,a coordinated control strategy based on DC current control is proposed.Based on the in-depth analysis of the primary and secondary factors of the commutation failure,the strategy detects the AC system failure and triggers the non-fault layer commutation failure prevention control in advance according to the output of the failure layer commutation failure prevention control.At the same time,it instantaneously reduces the DC current at the initial stage of the failure,which increases the immunity to commutation failure of the non-faulty layer,and improves the subsequent commutation failure of the faulty layer.The UHVDC hierarchical access system is built in PSCAD/EMTDC.Simulations show that this strategy can effectively suppress the commutation failure of the non-faulty layer and the subsequent commutation failure of the faulty layer.This greatly improves DC power transmission during the fault period and is conducive to the safe and stable operation of the power system.