A review and study on the joint optimization of wind generation units and storage pumps in the electricity market

One of the fundamental problems in power system operation is maintaining the balance between generation and consumption. The disruption of this balance entails frequency oscillations, voltage fluctuations, and in the worst-case scenario, it can jeopardize the power system stability and lead to partial or complete blackouts. Maintaining the balance between generation and consumption is especially challenging during peak hours. As a consequence of the constant growth in the number of consumers, the peak load in the system is also growing, so the peak load management problem is becoming more and more important. The commonly used approach in addressing this problem lays in the use of gas and diesel engine power plants, however, these units are characterized by high operating costs and they are not in compliance with modern environmental protection aspirations. On the other hand, the presented issue may be treated through peak load shaving, sometimes referred to as load leveling. Namely, peak load shaving represents the process of eliminating the peaks and the valleys from the daily load profile making it as close as possible to the average daily load. The benefits of peak load shaving, both for the grid operator and for the end-users, are various and have been elaborated in a large number of studies. Thus, different strategies for peak load shaving are being developed and a large number of these strategies are currently in use. One of the main characteristics of wind power is the inherent variability and unpredictability of the generation source, even in the short-term. To cope with this drawback, hydro pumped-storage units have been proposed in the literature as a good complement to wind generation for their ability of managing the positive and negative energy imbalances along the time. This paper investigates the combined optimization of a wind farm and a pumped-storage facility in a market environment, where some decisions must be taken before the uncertainty is unveiled. The optimization model is formulated as a two-stage stochastic programming problem considering two random parameters: market prices and wind generation. The optimal bids for the day-ahead spot market are the “here and now” decisions while the optimal operation of the facilities are the recourse variables. Two different joint configurations are modeled and compared with the reference case of the uncoordinated operation. A realistic example case is presented where the different developed models are tested with satisfactory results.

Keywords:

Wind power , energy storage , optimization , dayahead electricity markets , profit maximization.