Energy buffer systems to improve power network stability

Abstract

Power electronics has seen increasing use in industries, to handle issues such as power quality and load management. Collectively, these loads will often present themselves as constant power load. De-stabilizing effects of the constant power loads, should a disturbance occurs, will pose a challenge to power network operators, and has lead to various researches into ways to mitigate the effects. One such research has recommended the method of using Power Buffers, which are front-end convertors connected upstream of the network, to switch these loads between constant power and constant impedance. A stability study of such a method was therefore conducted in this project.

Using PSCAD, a simple two-machine power network was modeled. Connected loads were designed to be switchable between constant power and constant impedance modes. Simulation result shows that by switching the loads, enhanced stability of the power system is achieved. Further simulation shows that the critical clearing time of the power system can be increased significantly as compared to when the buffers are absent.