VSC-HVDC互联系统的改进前馈控制策略

An improved feedforward control strategy for interconnected VSC-HVDC transmission system

为了提高柔性直流(VSC-HVDC)输电系统中系统的动态响应速度及与目标值具有更好的跟随性能,在传统直接电流控制中采用双闭环解耦控制策略基础上,针对系统中定有功功率和定直流电压控制方式,分别提出了对应的改进前馈控制策略。整流侧的定有功控制中,在其电压外环基础上增加一个预测信号输入到电流内环,以加快系统的响应速度,补偿了反馈信号的滞后性;逆变侧的定直流电压控制中,为了增加直流电压对外界的抗干扰性,把系统电压和直流电流的信号引入到该前馈控制中。最后,在PSCAD/EMTDC中搭建了一个2端的柔性直流输电系统模型,对系统处于不同运行状态下进行了仿真分析,结果表明,改进的前馈控制策略和目标值有较好的契合度,鲁棒性好,对外界的干扰具有一定的刚性。

In order to improve the dynamic response speed and its tracing performance with the target value in the VSC-HVDC transmission system,aimed at the constant DC voltage control method and constant active power of the system,this paper proposes the corresponding improved feedforward control strategy on the basis of the traditional direct current control controlled by the double closed loop decoupling control strategy.In the constant active power control of rectifier side,a predictive signal is added to the inner current loop on the basis of the outer voltage loop to enhance the response speed of the system and compensate the hysteresis nature of the feedback signal.In the DC voltage control of inverter side,in order to increase the anti interference performance of the DC voltage to the outside,an improved feedforward control strategy adopts the system voltage and DC current signal is introduced so that the DC voltage has a strong resistance to the external disturbance.Finally,a two terminal VSC-HVDC model is built in PSACD/EMTDC,simulations and analyses are carried out in the system under different operating conditions.The results show that the improved feedforward control strategy has a good value that fits to the target value,and the good robustness and rigidity of DC voltage also have obtained to the external disturbance.