Design Of Underfrequency Load Shedding Scheme With The Integration Of Large-Scale Wind Power

Because of the increasing severity of energy and environment problems, renewable energy is developed all over the world. Wind energy, which is environmental friendly, proved technique, high reliability and low cost, becomes the fastest developing renewable energy.In resent years, with the increasing share of the installed capacity of wind energy in the power system, the impacts of the integration of wind power are increasingly evident. After the integration of large-scale wind power, there are several new problems in the original underfrequency load shedding scheme (UFLS). On the one hand, wind power has a characteristic of fluctuation, the original load shedding amount may not be enough to restore the frequency. On the other hand, while UFLS devices are shedding loads, wind turbines may exit the system due to low frequency protection, which leads to greater power shortage. The original load shedding scheme may not meet the design requirements. In addition, the traditional single machine with centralized load model doesn't consider the difference between different generation units and the impacts of wind turbine units. So the accuracy of UFLS scheme is low.In this paper, the impacts of integration of large-scale wind power on design of UFLS scheme are studied. Analysis shows that the decrease of wind power output is much smaller than the load shedding amount, there is no impacts of fluctuating wind power on the UFLS scheme. The design of UFLS scheme must be compatible with the low frequency protection setting value for wind turbine generatorsThe frequency response characteristics of different wind turbine generators are analyzed and compared. Extra active power support is adopted in variable speed wind turbine. Thus, the variable speed wind turbine can support the grid frequency, and reduce the decline of frequency.The system model for checking underfrequency load shedding scheme is studied. The analysis shows that it's necessary to improve the traditional single machine model into multiple machines model. The impacts of main simulation parameters on system frequency response are analyzed. By considering the impact of wind turbines on the system model, a method of modifying the model parameters is proposed. Finally, the underfrequency load shedding scheme under large-scale wind power integration is designed based on initial scheme. And compare the improvement scheme with the initial scheme by using multiple machines system model. The final simulation results show that the improvement scheme can meet the design requirements very well, and the effect of frequency recovery is much better.