三相双Buck逆变器过零畸变问题与解决方法

Zero-crossing Distortion and Solution of Three-phase Dual-buck Inverters

双Buck拓扑克服了传统桥式拓扑上下桥臂的直通问题,将其应用于三相并网逆变器,能够避免驱动信号死区引入的低次谐波,从而降低进网电流谐波含量,且外接快恢复二极管续流,减小了反向恢复损耗。然而,为消除电感的偏置电流以及提高逆变器效率,双Buck逆变器需采用半周期控制策略,导致了进网电流的过零畸变。针对带LCL滤波器的三相双Buck逆变器,分析半周期控制所导致过零畸变的原因,提出带纹波电流负反馈的半周期空间矢量脉宽调制(space vector pulse width modulation,SVPWM)控制方法,通过在过零点处改变空间电压矢量的基准,有效地消除了进网电流过零畸变,并讨论新型控制算法对系统稳定性的影响,通过仿真和实验验证理论分析。

The dual-buck topology overcomes the straight-through problem of the traditional bridge topology. Its applications in three-phase grid-connected inverters can avoid low frequency harmonics caused by the dead-time and reduce the grid current harmonic. External fast recovery diodes can reduce the reverse recovery loss. However, to eliminate the bias current of the inductor and improve the efficiency, the driving signal could only exist in a half grid-cycle, which may lead to zero-crossing distortion. This paper analyzed the cause of zero-crossing distortion of the half-cycle controlled three-phase dual-buck inverter with the LCL filter. A new control strategy with ripple current negative feedback is proposed, with which the zero-crossing distortion can be inhibited by changing the reference voltage space vector in the zero-crossing points. What＇s more, the influence on the stability of the system with the new control method is discussed. Finally, the simulation and experimental results verified the theoretical analysis.