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Analysis of offering continuous level of power to electricity market from wind plants and back-up plant –– what flexibility should have the NPP?

Wind power varies over time and variations occur on all time scales. Understanding these variations and their predictability is of key importance for the integration and optimal utilization of wind in the power system. Due to the variability and uncertainty, wind plants cannot offer a continuous level of power to electricity market. The main motivation for this analysis is to investigate possibilities to participate in the electricity market by offering continuous guaranteed power from wind plants by a backup plant. If NPPs and RESs want to become ‘friends’, it is necessary to determine which minimum characteristics of feasibility the NPPs should have. A model of electricity production from wind farms and a backup plant was developed based on real hourly and minute by minute electricity production from wind plants. For the calculation, the following parameters are necessary: ramp up and down rate, time of start time reduction, fuel mass flow during start, electricity production during start, variable cost of the startup process, cost and charges for lifetime consumption for each start and start type, remuneration during startup time regarding expected or unexpected starts and the cost and revenue for balancing energy. In the analysis, because all needed parameters for the NPP are not known, a backup plant was selected to be a Combined Cycle Gas Turbine (CCGT) plant with input data and all characteristics on hourly and minute by minute timescales. Hourly analysis showed that there was no problem with delivery of the defined power, but the minute by minute resolution analysis showed that the backup plant could not always cover rapid changes in response to actual changes in wind power production. The analysis has shown that with the same wind variability with shorter time resolution, realistic technical limitations of the backup power plant come to light, especially in terms of output speeds and output power drops. The one minute resolution results in significantly higher requirements on the backup facility, which confirms the need to adjust the time resolution of input data based on stochastic modelling of wind power plants, and time resolution (intervals) of optimization. The paper describes problem that was analysed in the study [15] Analysis of the possibilities of work and assessment of the corresponding costs of the new CCGT type 3 + 1 plant in Croatian Power System. Descriptions of models, scenarios, results and discussion are taken over from that study. From the results of the analysis, it is possible to determine which minimum characteristics of flexibility the NPP should have for a required production in conjunction with real wind power plants.

Electricity market ; wind plants ; nuclear power plant ; combine cycle gas plant

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