Short-term Optimization Of Cascade Hydropower Station Under Large-scale Wind And Solar Power Integrating The Power Grid

Accelerating the development of renewable energy is an important way to achieve the carbon peaking and carbon neutrality goals and to transform the energy structure.However,large-scale renewable energy power is highly uncertain and volatile.Grid-connected operation will lead to severe load fluctuation of the power system.With large installed capacity,mature technology and flexible operation,cascade hydropower station can suppress the power fluctuation of wind and photoelectric power.However,the frequent switching of working conditions leads to the operation of the hydroelectric unit in the biased working condition and the frequent crossing of the vibration zone.Therefore,reducing the vibration impact of renewable energy system on hydropower system is an important content to expand the proportion of renewable energy.The complex operation,large number of units,large scale and close connection between upstream and downstream hydraulic systems of cascade hydropower stations not only aggravate the vibration of units,but also increase the difficulty of model construction and solution.Therefore,from the perspective of vibration avoidance optimization operation of cascade hydropower station,this paper studies the stable operation of the cascade hydro-wind-photovoltaic complementary generation system,and makes the following main achievements:(1)To solve the vibration problem caused by load regulation during the operation of cascade hydropower station,this paper comprehensively considers the factors of multiple units and vibration zones and hydraulic connection of cascade hydropower station,and proposes a vibration avoidance strategy suitable for cascade hydropower station based on the concept of mathematical set.The optimization takes the minimum times of crossing vibration zone and the minimum number of units involved in regulation as the objective function.On the basis of power balance,the negative vibration effects of the units are reduced as much as possible.Finally,the effectiveness of the vibration avoidance model is verified by taking a cascade hydropower station in southwest China as an example.The results show that the proposed model can avoid the hydropower units operating in the vibration zone all day long,but will increase the number of units involved in regulation greatly.(2)To explore the impact of the power station operation mode on the cascade hydro-wind-photovoltaic complementary generation system,the overall optimization and independent optimization methods are adopted for the cascade hydropower system to analyze its impact on the economy and stability of the system.As for the operation mode of the complementary system,this paper makes a comparative analysis of the joint complementary operation and independent operation networking mode of each sub-power station.Among them,the comprehensive benefit maximizes the power generation benefit as far as possible in terms of economic benefit,and reduces the fluctuation influence on the power grid load as far as possible in terms of operation risk,as well as the negative impact on the vibration of the cascade hydropower station units.The system load supply deficit,power generation benefit,power change coefficient and other indicators were evaluated and calculated.Finally,the results were applied to actual engineering cases to verify the reliability and effectiveness of the model and evaluation indicators.(3)To explore the influence of meteorological factors such as wind speed,light intensity and reservoir inflow on the complementary power generation system,especially on the unit in the peak regulating process of cascade hydropower system,In this paper,the cascade hydro-wind-photovoltaic complementary generation system model is divided into photovoltaic power system,wind power system,cascade hydropower station considering upstream and downstream hydraulic connection,control center and power grid and other subsystems for modular modeling,and the model containing the cascade vibration avoidance strategy is nested in the complementary system.After the establishment of hydraulic and electric constraints,the coupling subsystem model is the cascade water-wind complementary power generation system model.The third generation of non-dominated sorting genetic algorithm was used to optimize and calculate the water consumption of the unit,the frequency of passing through the vibration zone and the number of units involved in regulation under different wind speed,solar intensity and water resources richness.Suggestions were put forward for the operation mode of the cascade hydropower system under the corresponding scenario,and a reference basis was provided for the planning of renewable energy.