三电平逆变器直接功率控制的拓展算法

Improve ment of Direct Power Control in Three-Level Inverter

阐述了多电平逆变器的控制策略和拓扑结构,并具体分析了三电平逆变器的工作原理。提出了一种基于直接功率控制的算法,协调控制系统的有功功率、无功功率和中点电压。该算法通过3个滞环控制器实现,并分析各个逆变器电压矢量作用后产生的有功、无功、中点电压的变化,从而选择合适的逆变器电压矢量,控制各个IGBT的关断。仿真结果表明:基于该算法的三电平逆变器输出电压与电流波形良好,直流侧电压稳定,同时中点电压滞环控制器抑制了中点电压的波动。

The control strategy and topology of multilevel inverters,as well as the work principle of three-level inverter,are firstly analyzed.And then,a three-level direct power-based control algorithm is proposed,which can coordinately control the active power,reactive power and midpoint voltage.The proposed algorithm is implemented by three hysteretic controllers.By analyzing the change of active power,reactive power and midpoint voltage after applying every inverter voltage vector,the appropriate inverter voltage vector can be chosen to control the on-off of every IGBT.It is shown from the simulation results that both the output voltage and waveform of three-level inverter based on direct power control are in good shape,D C voltage is stable,and the midpoint voltage hysteresis control can inhibit the fluctuation of midpoint voltage.