The advancement and capacity allocation of variable-speed hydropower units (VSHUs) for suppressing wind power fluctuations are studied. First, a wind–hydropower generation system model, comprising the doubly fed VSHU (DFVSHU) and full-size power VSHU (FSVSHU) is established. Then, three typical operating conditions, namely the wind speed step-up, wind speed sudden drop, and wind gust, are selected to quantify the advantages of the VSHU in suppressing wind power fluctuations using the power range, power standard deviation, and power fluctuation time. Finally, a VSHU capacity allocation scheme in which some FSHUs are transformed into VSHUs for the same total capacity of hydropower units is proposed. A VSHU capacity allocation formula based on this scheme is also proposed. Simulations and comparisons reveal that the VSHU can effectively suppress wind power fluctuations over short time scales, and its effectiveness is 90% higher than that of the FSHU. In addition, the simulation based on the measured wind speed data verifies the effectiveness of the capacity allocation formula. This study provides a new method for suppressing wind power fluctuations over short time scales and provides theoretical guidance for the application of VSHUs through capacity allocation.

Introduction

Carbon peaking and neutrality in the power industry are essential for guaranteeing the “double carbon target.” Clean energy, especially wind power generation, must be incorporated into the power grid on a large scale to achieve this target (Han et al., 2021). According to the Global Wind Energy Council (GWEC), the global wind power installed capacity increased by 93.6 GW in 2021, with China experiencing an increase of 47.6 GW (Global Wind Energy Council, 2022). By the end of 2021, the installed capacity of wind power in China reached 3300 GW, accounting for 13.87% of the total installed capacity in the nation (Yao, 2022). However, the fluctuation, randomness, and intermittence of wind power create power fluctuations that considerably affect the power grid’s stability and quality (Barra et al., 2021).

According to the different time scales, wind power fluctuations can be divided into short time scales (within 1 min), medium time scales (several minutes to tens of minutes), and long time scales (above 1 h), and the measures to suppress the wind power fluctuation are different (Wang and Jiang, 2014). The measures used to suppress wind power fluctuation over short time scales must have sufficient response speeds and power densities, whereas those used to suppress wind power fluctuation over medium time scales must have sufficient energy densities. Those for suppressing wind power fluctuation over long time scales must have sufficient