基于柔性接地技术的配电网三相不平衡过电压抑制方法

Suppressing Method of Three-phase Unbalanced Overvoltage Based on Distribution Networks Flexible Grounding Control

配电网三相对地参数不平衡会产生三相不平衡电压,一般采用投切电容器或电抗器补偿三相不平衡参数,抑制不平衡电压,但该方法补偿的精度和速度有限,难以彻底而迅速地实现三相不平衡过电压抑制。因此,在前期发明的柔性接地技术(专利201110006701.2)基础上,提出配电网三相不平衡过电压抑制新方法。通过PWM有源逆变向配电网注入零序电流补偿三相对地不平衡电流,实现对零序电压的控制,从而抑制三相不平衡过电压。仿真分析结果表明,所提方法可有效抑制三相不平衡过电压,能够将中性点位移电压限制为零。

Unbalanced three-phase parameters to ground can result in the three-phase unbalanced voltage in distribution networks. Generally switched capacitors and reactors are applied in the compensation of three-phase unbalanced parameters to limit the unbalanced voltage. Whereas, the compensation method has limited precision and speed, it is difficult to satisfy the requirement of the three-phase unbalanced voltage suppressing thoroughly and rapidly. In order to improve it, a new method based on the invention patent of flexible grounding technique （Patent number 201110006701.2） was presented in this paper. The three-phase unbalanced current to ground was compensated by the injecting zero sequence current to distribution network through pulse width modulation （PWM） inverter. The zero sequence voltage was controlled and the three-phase unbalanced overvoltage was thus suppressed. Simulation results showed that the proposed method limited the unbalanced overvoltage effectively, and the neutral displacement voltage could be limited to zero.