电网电压不平衡条件下MMC的基于Lyapunov函数非线性控制策略

Nonlinear Control Strategy Based on Lyapunov Function for MMC Under Grid Voltage Unbalance Condition

当电网电压发生不平衡时,采用模块化多电平变流器(modular multilevel converter,MMC)实现的高压直流输电系统会发生交流侧电流不对称、有功/无功功率产生二次脉动等问题。为了解决这些问题,根据MMC的拓扑结构建立了电网不平衡条件下MMC的数学模型,在此基础上建立MMC的Lyapunov模型,制定出了基于Lyapunov函数的非线性控制理论的控制策略,并讨论了关于控制不精确问题及参数选择范围。通过在Matlab/Simulink平台上对所提出的Lyapunov函数控制策略与传统PI控制方法的控制效果进行了对比,表明了所提出的控制方法的有效性和优越性,并在硬件平台上做了进一步实验验证。

For a high voltage DC(HVDC)transmission system using modular multilevel converter(MMC),there exist problems such as asymmetry of the AC current and secondary ripple of the active/reactive power when the grid voltage imbalance occurs.To solve the problems,we put forward a Lyapunov-function-based control strategy for MMC under grid voltage unbalance conditions by establishing a mathematical model of MMC under the condition of grid imbalance based on the topology of MMC.On the basis of the established Lyapunov model of MMC,we developed a control strategy of nonlinear control theory based on the Lyapunov function and discussed control inaccuracy and the choice of parameters.By comparing the control effect of the Lyapunov function control strategy proposed in this paper with that of the traditional PI control method on Matlab/Simulink platform,the effectiveness and superiority of the proposed control method could be demonstrated.Moreover,further experiments were carried out on the hardware platform.And the experimental verification was carried out on the hardware platform.