Frequency response of full-power converter wind turbines: impacts on grid frequency stability

Introduction: Power generation based on fossil fuels has increasingly presented significant challenges due to its detrimental impact on the environment. Consequently, the transition toward more environmentally sustainable power generation methods has become essential. Moreover, the growing penetration of renewable energy sources and the continuous expansion of power systems introduce additional stability challenges. In this context, system inertia emerges as a critical factor in maintaining and ensuring overall power system stability. The ability to predict and respond to the variations of grid frequency is vital for maintaining a reliable power supply. This paper attempts to address this issue by establishing a combined model that couples the wind turbine system to the power grid to assess how renewable energy generation influences power system frequency stability.

Materials and methods: A conventional power generation of 10 GW incorporated with load frequency and automatic generation control, coupled with a 2 MW full-power converter wind turbine system, is presented. Simulations of the model’s response to 1 GW loss of power generation on a 10 GW power system, are conducted to validate the results.

Results and discussion: The variable-speed wind turbines with full-power conversion (FPC) demonstrate a positive impact on frequency stability by reducing the initial frequency nadir by up to 66% compared to the case without wind support. However, the fast-acting supplementary frequency control introduces low-frequency oscillations and increases the transient settling time by up to 158% before the system reaches steady state.

Conclusions: It has been concluded that utilising load frequency control alone is insufficient to restore a nominal 50 Hz system frequency, necessitating the need for automatic generation control to fully restore the system to 50 Hz. The variable-speed wind turbines with full-power conversion (FPC) have a positive impact on power grid stability, and their ability to release power promptly in critical moments helps to reduce the initial dip in frequency. Despite the relatively limited capacity of the wind turbines with respect to the total grid capacity, its contribution is not intended to stabilise the entire system, but rather to demonstrate the capability of full-power converter wind turbines to provide fast frequency response and virtual inertia, thereby mitigating the rate of change of frequency following a disturbance.