Electromagnetic Transient Efficient Modelling Of Power Electronic Device Based On H-Bridge

Because there has long been active and reactive power balance, voltage loss, power transmission capacity and system stability issue in China grid, smart grid technology has been proposed. As one of the most popular field in smart grid, Flexible AC Transmission System(FACTS) has been widely applied to the grid with the development of smart grid. Representative technology of FATCS are usually high-voltage and high-power power electronic devices, which consists of a large number of H-bridge and power electronic switches. The analysis and design of these devices is usually conducted by Offline electromagnetic transient simulation. Due to the large number of H-bridge and power electronic switches, the simulation efficiency is very low and time is very long, which brought great inconvenience to researchers. So it is necessary to study the causes and solutions of this problem.This thesis analyzed the cause of low efficiency in electromagnetic transient simulation and characteristics of most FACTS devices and carried out the efficient modeling of FACTS devices based on H-bridge. The thesis proposed an equivalent model of H-bridge based on the principle of electromagnetic transient simulation and Thevenin’s theorem. Then the simulation was conducted in PSCAD, which showed that the equivalent model has good accuracy. As cascaded multilevel Static Synchronous Compensator(STATCOM) and Electronic Power Transformer(EPT) is two kinds of typical device in FACTS, the efficient model of cascaded multilevel STATCOM and EPT was built based on the equivalent model of H-bridge. Theoretical analysis showed that the efficient model can reduce node numbers and partition the network into small sub-nework, which can reduce the simulation calculation quantity drastically. Simulation comparison between efficient model, traditional model and node splitting model(only STATCOM) was conducted in PSCAD under different simulation step and condition to validate the accuracy and acceleration effect of efficient model. The simulation results showed most waveform of efficient model is the same with traditional model and efficient model can reduce simulation time drastically. Besides the acceleration effect of efficient model is better than node splitting model, which is more obvious when the number of cascaded H-bridge increases.The research result showed that efficient model proposed by this thesis is of great significance and wide application prospect. It can applied to the electromagnetic transient simulation of high voltage and high capacity FACTS devices to reduce simulation time.