模块化多电平变流器HVDC系统的模型预测控制

随着电压源变换器型高压直流(Voltage-Sourced Converter-Based High-Voltage Direct Current,VSC-HVDC)输电需求的持续增加,模块化多电平变换器(Modular Multilevel Converter,MMC)成为柔性直流输电的研究热点。环流的抑制和子模块电容电压的平衡是MMC控制的研究重点之一。推导了模块化多电平变换器高压直流(Modular Multilevel Converter based HVDC,MMC-HVDC)输电系统的离散数学模型,在此基础上针对五电平MMC的控制目标提出一种改进的具有工程应用价值的模型预测控制策略(Model Predictive Control,MPC)。通过引入误差因子减小了子模块电压波动范围,同时通过MPC与电压排序算法相结合减小了传统MPC的计算量,并实现了HVDC系统传输功率的控制、MMC环流的抑制和MMC子模块中电容电压的平衡。仿真结果验证了所提出的控制策略的有效性。

Model predictive control of modular multilevel converter for HVDC system

With the continuously growing demand of the voltage-sourced converter-based high-voltage direct current (VSC- HVDC) transmission, modular multilevel converter (MMC) achieves great attentions in VSC-HVDC system. Circulating current eliminating and sub-module capacitor voltage balancing is one of the main technical challenges associated with the control of MMC. The discret mathematic model of the modular multilevel converter based HVDC (MMC-HVDC) system is derived, and an improved model predictive control (MPC) strategy with engineering value is proposed for five-level MMC. The sub-module voltage ripple is reduced by introducing the error factor. Furthermore, the combination of MPC and voltage sequencing algorithm reduces the computation burden, and realizes the transmission power control in MMC-HVDC system, circulating current eliminating, sub-module capacitor voltage balancing. Simulation results validate the proposed control strategy.