基于勒让德多项式的MMC自适应反步控制策略

Adaptive Back-stepping Stability Control Strategy for MMC Based on Legendre Polynomial

针对柔性直流输电中模块化多电平换流器在运行过程中因严重信号干扰或器件温度上升等因素造成的系统动态模型结构中参数变化,使得系统的稳定控制效果不佳,引起系统安全运行事故等问题,提出了一种基于勒让德多项式的自适应反步法稳定控制策略。该方法在静态abc坐标系下建立动态模型,利用勒让德多项式去逼近补偿模块化多电平换流器中因参数改变引起的误差值,从而消除对动态模型的影响,然后采用反步控制理论选取状态变量,构造Lyapunov函数,求得满足Lyapunov稳定性要求作为稳定控制的变量。最后,通过PSCAD/EMTDC仿真模型和实验平台的验证表明,所提出的控制策略与工程中常用的PI控制策略相比拥有更好的控制性能和鲁棒性。

In view of the poor stability control performance and frequent operation faults of the flexible HVDC transmission system due to the parameter changes of system dynamic model structure caused by serious signal interference or device temperature rise during the operation of the modular multilevel converter(MMC),an adaptive back-stepping stability control strategy is proposed based on Legendre polynomial.Firstly a dynamic model is established in a static a-b-c coordinate system,and the Legendre polynomial,which has advantages of simple structure and no modeling,is used to approximately compensate for the error value caused by the parameter changes in MMC,thus eliminating its effects on dynamic model.Then,the back-stepping control theory is used to select the state variables,construct the Lyapunov function,and obtain the control variables that meet the requirements of Lyapunov stability.Finally,simulation verification is carried out through PSCAD/EMTDC,which shows that the control strategy proposed in this paper has better control ability and robustness than the conventional PI control strategy.