Stability Analysis Of AC/DC Hybrid System With Flexible HVDC

With the global energy Internet and the new requirements of the "two alternative", the rapid development of interconnected power grid will have more and more access to new energy power generation, flexible HVDC can be smooth access to a wide variety of clean energy, and further adapt to the needs of all kinds of distributed power supply, and in the future, the new urban power grid construction and other aspects have a higher value. In this paper, through the analysis of the three level control system and its control principle of VSC-HVDC, the model is decoupled by Park transform and the mathematical model of VSC-HVDC system is obtained by d-q system, and the active and reactive power decoupling control and SPWM modulation principle are analyzed, and in the PSCAD/EMTDC environment, a three phase two level VSC-HVDC transmission system with 230kV AC tie line is set up, based on the design of the main circuit parameters and control system of the internal and external control system, based on the design of the main circuit parameters and control system of internal and external control system, the main circuit parameters and the control system, based on this, the main circuit parameters are designed. The main circuit parameters and the control system are established. The main circuit parameters are designed, the step and the flip can be quickly restored to stable operation The stability and effectiveness of the system are verified by the state. Under the condition of fault operation, the VSC-HVDC system has no more limited impact on the AC side, and the VSC-HVDC system can quickly restore stability, which reflects the timeliness and effectiveness of the system. The system responds quickly, without impact, and can quickly restore stability in the VSC-HVDC rectifier side (delivery). And the region of Xiamen power grid N-1, N-2 fault, DC fault, AC tie line three-phase short circuit fault analysis results show that the settlement column, AC and DC transmission lines are controlled by N-1 and N-2 can impact fault, fault of line breaking form the island in exchange, take flexible DC active power load or promotion measures, island the grid can maintain the stable trend. The failure mode of the potential risk of AC/DC system is found to provide a basis for its protection and defense.