Frequency stability analysis and control for thermal-wind generation with HVDC islanded sending

After explaining the scenario of large-scale thermal-wind generation with HVDC islanded sending in Northern China, this paper points out the frequency analysis and control is one of the key issues for the islanded sending system. Based on the frequency modeling of thermal power unit, wind turbine and DC transmission system, the fundamental frequency behavior of HVDC islanded sending was studied. To improving the frequency regulation of the rectifier side, a frequency composite control strategy of DC transmission based on the idea of Load-Frequency Control (LFC) is employed. The important basis of this composite control strategy is the analysis of droop stability of thermal power unit and the implementation of HVDC coordinating control. This paper also analyzed the stability of the control system on the fluctuation of wind power output. The paper takes the Ha-Zheng HVDC sending as an example to illustrate the effectiveness of the control strategy for thermal-wind generation with HVDC islanded sending.