A SSSC protection scheme based on thyristor integrate with phase change material

Abstract

With the development of the economy and society, the power of distribution network increases and the demand for power quality is higher and higher. At the same time, with the rapid development of renewable energy such as photovoltaic power generation, wind power generation and etc, more and more distributed energy systems are connected to medium-voltage networks. Nevertheless the existing distribution networks have limited capacity. Static synchronous series compensator (SSSC) is one of the solutions for these issues. Since SSSC is connected to the power grid in series, it is a great challenge to protect the SSSC especially when a short-circuit fault occurs in the power grid. In this paper, a parallel connection of metal–oxide varistors (MOV) and the thyristors with SSSC is proposed to protect SSSC in case of transmission system failure. In the protection process, MOV only works for about 1ms, providing the time of fault detection and thyristor conduction. The thyristors are turned on to bypass the SSSC, and the short-circuit current flows through the thyristors. Furthermore, it is inevitable that the junction temperature of the thyristors rise sharply and even causes damage to the thyristors, when the surge current passes through the thyristors. In order to restrain the junction temperature of the thyristors from rising too fast and improve the current surge handing capability, this paper proposes to integrate phase change materials (PCMs) into the thyristors. During the current surge, PCMs absorb a large amount of heat for phase change while its temperature remains constant, which can reduce the temperature rise rate of the chip, and ensure that the thyristors work properly. The protection scheme proposed in this paper is simulated in MATLAB/ Simulink and implemented experimentally in the laboratory. The thermal simulation model of thyristors is built in COMSOL. The finite element simulation results show that PCMs can reduce the junction temperature of the thyristors during current surges.