Simulation Research On The Function Of SSSC Based On H-bridge Cascaded Synchronous Paralleling Device

With the continuous expansion of China's power system scale,the interconnection of power grid has become an inevitable trend' of China's power grid development..The development of FACTS technology provides technical support for power grid interconnection,and the static synchronous series compensator(SSSC).which is a new generation of series-compensated FACTS equipment has broad application prospects and development-space.It can effectively improve the transmission capacity of transmission lines without changing the structure of the power grid,which is of great significance to improve the stability of the power grid.In view of the current high voltage level and large transmission capacity of transmission lines,it is necessary to use a larger capacity facts device to meet the development requirements of the power grid,and generally adopt a method of increasing the capacity of the main circuit of converters.Since the H-bridge cascaded multi-level architecture has advantages in realizing modu.larization and expansion,this paper analyzes the synchronous paralleling device based on H-bridge cascade structure,clarifies the conversion process of synch ronous paralleling device and SSSC,and describes the three-level integrated control including system level,equipment level and device level to achieve multiple functions of the composite device.The selection principle of the main equipments in the composite device is analyzed in detail,and the main parameters are calculated.Based on the working principle of SSSC,the function of adjusting power flow and limiting fault current of SSSC are emphatically analyzed.The good implementation of the composite device's function mainly depends on the control effect of the controller.Aiming at the disadvantage of PI control which can not achieve no static error regulation,an impedance compensation control strategy based on PR is proposed to improve the accuracy of the control and ensure the power quality of the system.The equivalent simulation model of SSSC with cascade H-bridge which is built in PSCAD verifies the power flow regulation and current limiting function of SSSC.By comparing and analyzing the control effects of two impedance compensation control strategies based on PI and PR,SSSC based on PR impedance compensation control strategy can make impedance compensation more accurate.