Research On Modeling And Simulation Of AC/DC Power System Including STATCOM Based On RTDS

With the rapid development of modern power systems, many new power electronic devices such as HVDC links and FACTS devices have been widely applied in system operations and control,which make it gradually formed complex power systems with the parallel operation of AC-DC transmission and multiple FACTS devices, especially in South China Power Grid(CSG).STATCOM serving as one of the key technologies of FACTS system is widely applied in power system in recent years.By 2013, CSG has installed four sets of STATCOM. The effects of the multi-STATCOMs connection on CSG AC&DC parallel grid are highly concerned. Therefore, the study of STATCOM and its impacts on power system with detailed electromagnetic transient modeling of STATCOM and the AC&DC power system is necessary.The paper firstly analyzed the main circuit structure and control strategy of the chain STATCOM. To meet the requirements of exactly simulating the properties of STATCOM which is rapidly triggered by VSC(Voltage Source Converter) composed of IEGT, the RTDS digital simulation models of VSC chain group and its triggering unit of STATCOM is builed, by using the small step simulation technology in RTDS.The control protection system of STATCOM combine the real devices and RTDS digital models that are consistent with the actual hardware control protection features.To build the high-realistic RTDS model of the large-scale AC-DC interconnected power grid, the paper proposed a technique route that combine FDNE(Frequency Dependent Network Equivalent) and the DFS(Depth-First-Search) algorithm. On the one hand, the method optimizes the simulation resources, which make it possible to accurately complete the RTDS model of a large-scale grid on the limited RTDS resources. On the other hand, aiming at the defects of time-consuming and error-prone brought by human modeling, it innovatively applies the DFS algorithm to the modeling process, especially load-modeling process, which helps to build the simulation platform quickly and efficiently. According to the superiority of connecting the real control and protection devices to RTDS, the AC-DC power network for voltages of 220 k V and above which has interfaced multiple real HVDC and STATCOM control and protection devices is modeled.This paper developed a series of simulation studies is based the simulation system. One real faults have been successfully simulated and the simulation results are compared against the actual fault record data, which further proved the precision and reliability of the simulation model. Also, the paper analyzed the operating characteristics of STATCOM when faults occur in the external AC-DC system, especially the faults near HVDC inverter stations which will cause voltage fluctuation of the inverter bus. Finally, it studied the influence of STATCOM on the AC-DC system, by analyzing and comparing the difference of HVDC response such as power and voltage recovery and HVDC commutation faults in the case of multi-STATCOMs are connected to the grid or not.