针对柔性直流电网中某换流站交流侧发生不对称故障时产生负序电流，引起瞬时功率和直流侧电压、电流较大波动继而影响系统稳定运行的问题，提出了一种基于线性自抗扰控制(linear active disturbance rejection control，LADRC)的柔性直流电网换流站级控制策略。该策略采用比例积分(proportional-integral，PI)控制器和二阶LADRC控制器分别进行外环控制和内环电流控制，并以模块化多电平换流器(modular multilevel converter，MMC)为被控对象，针对二阶LADRC控制器进行频域分析，确定控制器参数的合理取值。最后，利用PSCAD/EMTDC平台搭建了四端柔性直流电网模型进行算例分析。结果表明:相比于传统PI控制，所提控制策略有效抑制了负序电流，大幅减小了有功、无功功率和直流侧电压的二倍频波动，提高了系统的故障穿越能力和动态响应速度。
Flexible DC grids control strategy based on second-order linear active disturbance rejection
To solve the problem of negative sequence current generated when an asymmetric fault occurs on the AC side of a converter station in a flexible DC grid,which causes large fluctuations in instantaneous power and DC side voltage and current,thereby affecting the stable operation of the system,a converter station level control strategy for flexible DC grids based on linear active disturbance rejection control(LADRC)was proposed.This strategy uses a proportional-integral(PI)controller and a second-order LADRC controller to control the outer loop and inner loop current,respectively.Taking the modular multilevel converter(MMC)as the controlled object,frequency domain analysis was conducted on the second-order LADRC controller to determine the reasonable values of the controller parameters.Finally,a four-terminal flexible DC grid model was built based on the PSCAD/EMTDC platform for example analysis.The results indicate that compared with traditional PI control,the proposed control strategy effectively suppresses negative sequence current,significantly reduces the second harmonic fluctuations of active and reactive power and DC side voltage,and improves the system's fault ride-through capability and dynamic response speed.
flexible DC gridsasymmetric faultlinear active disturbance rejection control(LADRC)negative sequence current suppression
万方数据
维普
