柔性直流输电的动态电流限幅控制

Transition Current Limitation Control of VSC-HVDC Power Transmission

研究了对电压源变流器型高压直流输电系统(voltage source converter-high voltage direct current,VSC-HVDC)的电压和电流的限幅控制。通过建立VSC-HVDC的离散化状态方程,分析电压、电流的稳态限幅控制和电流的动态限幅控制的关系,设计了电流可工作范围的预测方法。建立了VSC-HVDC的串级控制系统,用外环控制功率目标,内环控制电流,在两环间加入动态限幅环节。对VSC-HVDC系统的启动状态和接收电网发生接地故障进行仿真,仿真显示动态电流限幅措施可以大大减小系统的波动和恢复时间,说明动态电流限幅对提高控制系统动态响应速度有明显效果。

The voltage and current limitation for voltage source converter-high voltage direct current （VSC-HVDC） power transmission system, is researched in detail. By means of diseretizing the state equation of VSC-HVDC power transmission system, the relation between steady state limitation control of current and voltage and transition limitation control of current is obtained and analyzed, and a method to predict the operationable range of current is designed. A cascade control system for VSC-HVDC power transmission system is built, and the power of the transmission system is controlled by outer loop and the current of transmission system is controlled by inner loop in corporate with the transition current limitation. The starting state of VSC-HVDC transmission system and the grounding fault occurred in receiving power network are simulated, and simulation results show that the transition limitation measures can mitigate the post-fault oscillation effectively and the time for the recovery of the transmission system is evidently shortened, so it is proved that the transition current limitation can obviously improve the dynamic response of control system.