三相电压不平衡下级联STATCOM的控制方法

针对三相电压不平衡下级联静止同步补偿器(STATCOM)的控制问题,分析了级联STATCOM在三相电压不平衡时的工作特性,指出可以通过让级联STATCOM输出负序电压的办法来保证接入点的电压平衡。详细推导了系统在正序和负序环境下的解耦控制方程,提出一种新的正序—负序解耦脉宽调制的控制方法,分析了其两种工作模式:无功功率补偿模式和电压控制模式。级联STATCOM上层采用正序—负序解耦控制;下层采用能量平衡的控制策略保证各模块直流侧电容电压平衡。仿真和实验表明,该方法可以有效地解决级联STATCOM在三相电压不平衡下的安全运行问题,使得其在抵御一定的不平衡电压的同时具有较快的无功功率补偿特性,实现其最大化利用。

Control Method of Cascade STATCOM in Three-phase Voltage Imbalance Condition

Aimed at the control problem of cascade static synchronous compensator (STATCOM) in three-phase voltage imbalance condition, this paper analyzes the operating characteristics of the cascade STATCOM in three-phase voltage imbalance condition, and points out that the cascade STATCOM output negative sequence voltage can be made to ensure access point voltage balance. The decoupled control equation of the system is derived in detail in the positive and negative sequence environment, a new control method of positive-negative sequence decoupling pulse-width modulation (PWM) is put forward, and the two kinds of work mode within the method are analyzed, namely the reactive power compensation mode and voltage control mode. At the upper layer, the positive-negative sequence decoupling control is adopted; at the lower layer, the energy balance control strategy is adopted to ensure capacitor voltage at direct current side of each module is balanced. Simulation and experiment results show that this method can effectively solve the problem of the cascade STATCOM safe operation in unbalanced conditions. While coping with definite unbalanced voltage, it has fast reactive compensating features, and achieves maximum utilization.