电网不对称时四桥臂整流器的控制方法研究

Research on control strategy for four-leg rectifier under asymmetry grid voltage condition

电网不对称时,四桥臂整流器的直流侧电压含有二次谐波。分析四桥臂整流器的功率关系后,得出四桥臂整流器输入功率含有二次脉动功率,二次脉动功率是导致整流器直流侧电压含有二次谐波分量的根本原因。为了抑制直流侧电压的二次谐波,提出了四桥臂整流器的直接功率控制策略。在控制策略上,将产生脉动功率的功率指令值设为0,根据功率指令值算出内环的指令电流,零序电流指令值也设为0。为了实现整流器单位功率因数运行,无功功率指令设为0。根据仿真模型研究了两种工况下四桥臂整流器的特性,仿真实验结果表明采用控制算法能有效地抑制直流侧电压的二次谐波。

Four-leg rectifier operating in asymmetry grid voltage condition, its DC side voltage comprises the second harmonic component. Four-leg rectifier＇s power relation between AC side＇s power and DC side＇s power was analyzed. There is the second order pulse power in input power, which led to generate the second order harmonic voltage in DC side. To suppress the second harmonic voltage, a direct power control method was presented for four-leg rectifier, and then the second order pulse power reference values and zero sequence current reference values were set to zero. The current reference values were calculated in terms of power values. In order to operate in unit power factor condition, reactive power reference value was set to zero, too. Finally, the four-leg rectifier system simulation model was setup. The performances of the four-leg rectifier operating under two work conditions were investigated. The second harmonic component in DC side voltage was suppressed by the proposed control method, which was verified through simulation experimental results.