Design, simulation and testing of semiconductor assisted OLTC for a grid voltage regulator

Integration of higher shares of solar and other renewable sources as well as use of heavy domestic loads in the distribution network and growing consumer acceptance of electric vehicles results in frequent voltage fluctuations in the grid leading to an increasing need for voltage regulation. An effective solution for voltage regulation in the distribution grid is the utilization of On-Load Tap Changers (OLTCs) with hybrid switches. Combination of semiconductor switches and no-load mechanical switches form a hybrid switch which can achieve arc free tap changing while the steady state power loss is kept at minimum. This paper describes the design, analysis and testing of semiconductor assisted OLTC used in the low voltage distribution network for series voltage regulation. Details of high current (1000A) hybrid switch using parallel connected low power MOSFETs and its related issues such as current sharing are discussed.