模块化UPS采用虚拟阻抗的瞬时均流控制方法

Instantaneous Current-sharing Control Strategy for Modular UPS Using Virtual Impedance

多逆变器并联系统中大多采用基于相量的均流控制策略,这种均流方式由于精度低,且缺乏对瞬时环流冲击的抑制能力,已逐渐被瞬时均流方式所取代。针对逆变器并联系统建立瞬时环流模型,提出一种在瞬时环流的反馈通路中引入虚拟阻抗的瞬时均流方法。通过合理配置该虚拟阻抗值可获得简洁的动态环流调节方程,从而实现良好的瞬时均流调节特性。分析表明,引入虚拟阻抗的瞬时均流方法具有很好的均流效果,且虚拟阻抗的引入并不影响并联系统的稳定性及输出特性。仿真与实验结果验证了所提出方法的优越性。

The current-sharing control strategies based on phasors are commonly used in parallel inverters. However, they have been replacing by instantaneous control methods because of their low regulation speed, low accuracy and incapable of restraining the instantaneous circulating currents. In this paper, the transient model of circulating currents between parallel inverters was discussed, and an instantaneous current sharing control method was proposed based on virtual impedance, which is realized in the instantaneous circulating currents feedback routine. The concise equation of instantaneous current sharing control can be derived by properly configuring the virtual impedance, and it achieves good load sharing. Analyses show that this virtual impedances based method achieves excellent stability and current sharing effect. Furthermore, the virtual impedances do not influence the output characteristic of the whole parallel system. Simulation and experiment results validate the advantage of the proposed method.