Short-term scheduling strategies for hydro-wind-solar-storage considering variable-speed unit of pumped storage

A pumped storage hydropower plant (PSHP) effectively counteracts the inadequate regulation of traditional hydro-wind-solar complementary systems because of its unique bidirectional regulating capacity. However, the uncertainty of clean energy, the defects of traditional fixed-speed units, and the neglect of unit commitment pose considerable challenges to the efficient operation of PSHPs. To overcome these challenges, a short-term co-scheduling model for hydro-wind-solar-PSHP hybrid energy system (SHWSSCMM) considering the variable-speed unit (VSU) strategy and the principle of minimum number of units started for the PSHP is constructed. First, the objective of minimizing the number of units started is proposed, which, together with minimizing the peak-valley difference and maximizing the power generation revenue, forms the multi-objective of the SHWSSCMM while pursuing the peak shaving effect and preserving certain available units to respond to emergency grid requirements. Second, based on the VSU characteristics, the strategy of real-time adjusting the pumping power based on load fluctuations is formulated and mathematized into a constraint of the SHWSSCMM, significantly improving the flexibility of the PHSP. Finally, to capture the uncertainty of renewable energy, the combination of virtual plant strategy, Latin hypercube sampling and backward reduction algorithms are absorbed into the SHWSSCMM to generate deterministic scenarios conforming with historical characteristics as input factors. The practical case of the provincial power grid shows that SHWSSCMM can effectively reduce the large peak-valley difference in the day-ahead load, increase the load rate by an average of 11 % and scale back the number of units started by 3, guaranteeing the safe and stable operation of the transmission system operators (TSO).