Development of Cascade H Bridge SVG

Recent years have witnessed a rapid development of Electrified railway. A large amount of reactive power can be generated when the electric locomotive is too much on the traction network, It Cause a serious decline in power quality, Harmonics and reactive power has negative impacts on stability and security of locomotive running. Traditional reactive power compensation technologies are difficult to meet system requirements due to the switching frequency and voltage limit. In order to overcome the contradiction between the switching frequency of power device and power capacity in the traditional SVG, the principle and topology of H-Bridge SVG were studied, Control strategy adopts Carrier phase-shifted SPWM which is applicable to Cascade H-Bridge Multi-level Converter. The SVG designed adopt the control strategy based on instantaneous reactive power voltage and two closed loop, which can quickly follow the voltage changes controlling the output of SVG..MATLAB simulation results prove the validity of the control method and the performance of cascade H-bridge SVG for reactive power compensation.