不平衡电网下CCS-MPC在STATCOM中的应用

Application of CCS-MPC in STATCOM Under Unbalanced Grid

基于连续控制状态集模型预测控制(CCS-MPC)具有滤波器设计简单、开关频率固定等优点,在星形级联H桥静止同步补偿器(STATCOM)中得到广泛应用。然而,星形级联H桥STATCOM的模块较多,数学模型复杂,导致CCS-MPC的鲁棒性变差。首先建立关于三相电流的目标函数,获得不含零序分量的最优调制波,使得CCS-MPC具备优化目标结果的能力,改善补偿电流的动态性能。为了使得星形级联H桥STATCOM能够在不平衡电网下正常工作,此处提出一种相间零序分量预测均压控制算法快速选取最优的零序调制分量,并叠加到上述最优调制波中实现三相直流侧电压均衡。通过仿真与实验验证了上述方案的可行性与正确性。

The continuous state control set of model predictive control(CCS-MPC) has a simple filter and fixed switching frequency which is widely used in the star-connected cascaded H-bridge static synchronous compensator(STATCOM).However,the modules of star-connected cascaded H-bridge STATCOM is so complicated that its mathematical model gets difficult to derive.As a result,the robustness of CCS-MPC becomes worse.Firstly,the objective function about three-phase current is built and the optimal modulating waves without zero-sequence component can be obtained by analyzing the function.Hence,CCS-MPC achieves the ability to optimize the object which enhances the dynamic performance of compensating current.In order to make the star-connected cascaded H-bridge STATCOM work normally under unbalanced grid,a prediction algorithm has been presented to select the optimal zero-sequence component which is superimposed in the above optimal modulating waves.Therefore,three-phase cluster direct current voltage will keep balanced.The proposed control method is verified by simulation and a scaled-down prototype in the laboratory.