POWER FLOW REDISTRIBUTION BETWEEN POWER GRID SECTIONS BY SERIES COMPENSATORS BASED ON VOLTAGE SOURCE CONVERTERS

Abstract

Power transmitted through a power transmission line is limited by the current-carrying capacity, which determines line heating. Increasing the current lines capacity is becoming imperative due to the expensiveness of constructing new PTLs. The most cost-effective solution is to increase the power transmitted through the transmission lines up to the thermal limit by using a variety of devices, which includes fully controlled power electronics. One such device is a series compensator based on voltage source converter (VSC) that can distribute power flows between parallel power grid sections. In particular, it can prevent the one line from being overloaded by redistributing the load to other lines. Series compensators based on VSC can have both stationary and portable design. Smaller devices are increasingly popular in Russia and abroad. The paper analyzes the specifics of controlling a power grid and dwells upon its normal and postemergency operation, with evidence sampled from the IEEE 14 Bus Test Case (steady-state models for parts of 110 kV and 220 kV American Electric Power, AEP). It finds that disconnecting a PTL effectively triggers a worst-case post-emergency scenario, whereby the operating parameters go beyond the permitted current limits for the thermal resistance of the conductor. The paper proves portable series compensators capable of minimizing the power losses in normal operation. In turn, stationary series compensators can unload the overloaded PTLs without a need to reinforce the existing PTLs or construct new ones.