特高压混合三端直流输电系统换流站电流转移抑制策略

Transfer current suppression strategies for hybrid three-terminal UHVDC transmission system converter station

特高压混合多端直流输电系统需要具备有效的换流站电流转移抑制策略,尤其针对阀组投退过程,应避免因过流而触发暂时性闭锁。基于特高压混合三端直流输电系统,提出了2种采用受端直流电流作为控制量的电流转移抑制策略:基于直流电流-直流电压偏差量的电流转移抑制策略控制对象为阀组的直流电压;基于直流电流-直流功率偏差量的电流转移抑制策略控制对象为交流有功功率。然后基于PSCAD/EMTDC搭建了特高压混合三端直流输电系统的仿真模型,通过对比采用策略前、后系统的动态特性验证了所提抑制策略的有效性,并对比了2种电流转移抑制策略性能的优劣。仿真结果表明,投阀时基于直流电流-直流电压偏差量策略的抑制过流性能更为优越,退阀时基于直流电流-直流功率偏差量策略的抑制效果更为优越。

An effective transfer current suppression strategy for converter station is necessary in hybrid multi-terminal UHVDC system,especially aiming at the process of valve group entry/exit,and temporary blocking due to overcurrent should be avoided.Based on the hybrid three-terminal UHVDC system,two transfer current suppression strategies using the DC current of receiving end as control quantity are proposed.The control object of the transfer current suppression strategy based on the deviation of DC current and DC voltage is the DC voltage of the valve group,while the control object of the transfer current suppression strategy based on the deviation of DC current and DC power is the AC active power.Then,based on PSCAD/EMTDC,a simulation model of the hybrid three-terminal UHVDC system is built.The effectiveness of the proposed strategies is verified by comparing the dynamic characteristics of the system before and after applying the strategies,and the performance of the two transfer current suppression strategies is compared.The simulative results show that the strategy based on the deviation of DC current and the DC voltage is better for overcurrent suppression during valve entry,while the strategy based on the deviation of DC current and DC power is better during valve exit.