Study On Frequency Stability Control For Sending-End Power System With Large-Scale Wind Powers

In recent years, the integration of large-scale wind power bring challenges to the frequency control of the power system. Unlike distributed wind power generation in Europe and the United States, wind power is adopted by centralized and large-scale development patterns in China, such as large-scale regional wind power base in Gansu and Xinjiang. When wind power penetration rate is over 20%, it will be difficult for power system to meet the frequency modulation needs of wind power extreme output. In the meantime, limited transmission lines dealing with a large demand of power output, the sending-end power grid may lead itself to disconnected from the main power grid. Hence, the frequency stability of the sending-end system has been a severe challenge. Therefore, the research of this thesis on frequency stability control for sending-end power system with large-scale wind powers is important significance and practical value.The main contributions of this thesis are summarized below:(1) In this thesis, the frequency dynamic response characteristics of sending-end power system with large-scale wind powers are studied. The equivalent model is proposed to analysis frequency emergency control for sending-end power system with high wind power penetration rate. When the offset of initial frequency is large, this equivalent model will be more accurate than full-state simulation model. (2) By considering high frequency protection of wind power and traditional transient frequency assessment index, a modified transient frequency assessment index is proposed for sending-end power system with high wind power penetration rate. The test of different frequency response curves verifies this index to be valid and accurate. On this basis, this thesis has extended application of this index. (3) Currently, the study on high frequency generator scheme trip involved wind power is quite limited. In this thesis, based on the frequency dynamic response model and the modified transient frequency assessment index, a new high frequency generator trip scheme with wind power is proposed for sending-end power system. Furthermore, by sorting generator unit according to the sensitivity index, the suggested scheme is optimized. Simulations are performed on a practical power grid using PSASP. Simulation results show that the optimized high frequency generator trip scheme can adapt to different operation mode.