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The natural hydraulic connections between cascade hydropower may make hydraulic and electric connections mismatch after the market clears. Aiming at relieving the contradiction between water surplus and water shortage after market clearing, this paper proposes a new market clearing method considering the coupling relationship between water and electricity. And the method is verified by the simulation of a virtual spot market consisting of eight stations in Sichuan Province, China. The main contributions of this paper lay on three aspects: firstly, a new index called water-electricity coupling degree (WCD) and its calculation method are proposed to measure the overall situation of water shortage and water abandonment in the clearing results. Secondly, a multi-objective clearing model for cascade hydropower stations is established with the goal of minimizing power purchase cost and maximizing WCD. Thirdly, a solution method combined with the characteristics of the clearing model is developed. The case results demonstrate that the built model increases the WCD value by 1.57 % and reduces the insufficient output and surplus water by 45.18 % without increasing the power purchase cost of the power grid; The proposed solution strategy lowers the complexity of the model and improves the solution efficiency, where the search space reduction and time period merging strategies can reduce the calculation time by about 3 % and 8 % respectively. The new clearing method provides a new idea for solving the uncoupling problem of water-electricity-price in the cascade hydropower spot market. • Propose a new index called water-electricity coupling degree (WCD). • Establish a multi-objective clearing model for cascade hydropower market. • Develop a model dimensionality reduction strategy for model solution. [ABSTRACT FROM AUTHOR]

The stochasticity of photovoltaic (PV) generation output makes it necessary to smooth the output using other flexible power sources to realize the scale development of PV power. Small cascade hydropower stations (SCHSs) are also widely distributed in space, like PV generation. Therefore, it is proposed to utilize the regulation capability of SCHSs to complement PV generation. Targeting the maximization of the utilization rate of outgoing lines (utilization rate for short) of the system, the minimization of the curtailment rate, and the maximization of the minimum output within a time frame, a model for exploring the capability of SCHSs for regulating PV generation was established and solved by a hierarchical optimization method. By taking two small hydropower stations (the Mupo and Yangjiawan stations) on the Fabian River with a total installed capacity of 105 MW and the surrounding PV power source in China's Sichuan Province as examples, it was found that SCHSs can regulate a certain level of PV generation through the combined operation of cascade reservoirs and reduce the fluctuations and stochasticity of the PV generation output. The results have far-reaching significance on the large-scale development of PV generation. [ABSTRACT FROM AUTHOR]

China may require a long time to transition its power system from a planned one to a completely competitive market. Priority power generation (PPG), as a special type of power in the transitional period, is of great importance to incentivise power generation entities to participate in the market and promote power system reforms. However, the allocation of PPG currently relies excessively on the subjective decisions and experience of staff and lacks scientific basis and reasonable methods. Considering the case of Sichuan Province in China, this study proposed a PPG allocation method for reservoir power stations (RPSs) based on the principles of fairness, justice, and openness. First, RPSs were divided into categories based on the clustering results of many variable indicators that reflect the contribution and cost in aspects such as power generation, flood control, water supply, irrigation, emission reduction, grid peak shaving. Second, the random forest method was adopted to select the key indicators affecting the classification results. Then, the key indicators were weighted to obtain the priority index, and the PPG allocation was performed based on the priority index. Finally, the proposed method was used to allocate the PPG of RPSs in Sichuan in 2019. The results indicated that the allocation method based on the priority index is more conducive to increasing the market participation of RPSs than the original plan. In addition, it can save approximately 73 million yuan in electricity purchase costs for the grid. • Propose a priority power generation allocation method for reservoir power stations. • The allocation method is based on the priority index. • Cluster and random forest algorithms are used to calculate the priority index. [ABSTRACT FROM AUTHOR]