柔性直流换流站供电无源交流线路电压单环控制策略研究

Control Strategy of Flexible HVDC Station Supplying Passive AC Line Under Single Voltage Control Loop

高比例新能源经柔性直流并网送出时无源交流线路空载加压是必不可少的环节,换流站闭环运行控制存在谐振失稳风险。针对该应用场景,提出了一种具备故障限压限流和谐振抑制能力的电压单环控制策略。首先,在考虑换流站链路延时的基础上,采用常规电压单环控制方式,分析了该场景下诱发谐振失稳的关键因素。其次,考虑故障限压限流和谐振抑制需求,提出了电压前馈和电流前馈补偿控制策略,推导了故障电流与电压单环控制器限幅和电流前馈补偿等效直流增益之间的数学关系。再次,以抑制谐振为目标,从不同频率段实现了前馈补偿器参数选择范围的解析计算和优化设计。最后,采用电磁暂态仿真模型验证所给控制策略和参数解析计算与优化设计的有效性。

It is an essential operation part of the flexible high voltage direct current transmission system when supplying the passive AC lines for a high proportion of new energy power plant without power transferred,which may lead to a high risk of resonances in the closed-loop operation control.For this scenario,a single voltage control loop with voltage and current limitation and resonance suppression abilities is proposed.The key factors causing resonance under the traditional single voltage control method are analyzed based on the consideration of time delay.Secondly,considering the requirements of fault voltage and current limiting and resonance suppression,a compensation control strategy with voltage and current feeding forward is proposed.The fault current relating with the output limitation of voltage controller and the equivalent DC gain of current feed forward compensator are derived.Thirdly,the analytic calculation and optimal design of the parameter’s selection ranges of the feed forward compensator are presented to suppress resonance from different frequency bands.Finally,simulation models are used to verify the effectiveness of proposed strategy and the method of parameters calculation and optimization design.