EXPERIMENTAL INVESTIGATION AND PROPOSAL OF A SOLUTION FOR MITIGATING OVERVOLTAGE OF THE DC BUS IN THE DC POWER SYSTEM OF POWER TRANSFORMER SUBSTATIONS

Abstract

The requirement of the internal DC load of power transformer substations is to be supplied from the DC bus with a stable voltage around the rated value. However, for the efficient boost charging of the battery system connected to this bus, the step-up charge voltage should usually be 10% higher and in excess of the rated value. Furthermore, during the charging operation, the voltage could be even higher than above-mentioned value if there is a breakdown battery in the system. Therefore, it is essential to restrain the overvoltage of the load DC bus in different operating modes. The paper presents an experimental investigation and a solution to mitigate the overvoltage of the DC bus by splitting it into the battery charging section and the load section. Following this, selection of power elements and control diagram with PLC application is introduced to a DC power system of power substation. The control algorithm is then verified in a low-voltage experimental model that shows satisfied response to validate the control diagram. The proposed solution is highly effective, simple and low-cost.