Optimal operation of cascade hydro-wind-photovoltaic complementary generation system with vibration avoidance strategy

Abstract

The cascade hydro-wind-photovoltaic complementary generation system is considered to be an effective approach to solve the output fluctuation of renewable energy. However, for hydropower units, grid-connected operation results in frequent power adjustments and increases the risk of operating in vibration zones, which may lead to the low generation efficiency and hidden danger for the power plant. This study proposes a vibration avoidance strategy based on the unit commitment while considering multiple vibration factors. Multi-objective optimization is performed to minimize the water consumption, the number of times crossing the vibration zone and the number of units involved in regulation. Results for a case study located in the Southwest China, indicate that the proposed strategy avoids hydropower units operating in the vibration zone (the vibration rates decrease from 7.6%, 6.7%, 6.3% to 0 under three initial water levels). Comparing 9 scenarios with different meteorological conditions, indicates that photovoltaic power enables less hydropower units to complete the peak load regulation and to cross the vibration zone less frequently due to PV daily generation profile fitting better the load curve, unlike wind power. Finally, the operation schemes of cascade hydropower station in different periods are proposed. The suggested models are beneficial in reducing the impact of the vibration on hydropower units in hybrid power system and provide operation strategy for cascade hydropower station.