| In recent years, with the economy develops continuously and the environmental pollution get serious, traditional fossil fuels power generation has been unable to meet the environment needs. In order to relieve the pressure of conventional power mode on environmental protection, it is necessary to develop greatly solar energy which is the representative of renewable energy sources. Photovoltaic(PV) power generation is not controllable power, so this dissertation conducted a study on the controllability of PV power generation systems output.Firstly, characteristics of PV power generation were analyzed. Because the uncertainties of PV output made an impact on power quality, the energy storage device applied to the power system will decrease the power fluctuation, thus increasing the power quality. So energy storage technology applied to PV power generation was analyzed. Secondly according to the working principle of PV power generation system, expected output of system need to be determined to realize the controllability of output in PV power system. Due to the load must be provided stable electricity under stand-alone PV system mode, the expected output is a fixed constant, while the expected output can be obtained by the model of economic operation system under grid-connected PV system mode, which not only can improve the economic benefit of PV power generation system, but also can achieve the effect of reducing peak and filling valley on the distribution network. Then for the PV power generation with energy storage device, with the aim for the lowest comprehensive cost consisting of operating cost per day and battery cost, an economy operating model in controllability of system output had been established. Because the system economy operation is concerned only with battery capacity, under stand-alone PV system mode, after observing traditional calculation methods about energy storage capacity, a better minimum capacity selection method had been proposed, guaranteeing the battery work continuously. Under grid-connected PV power system mode, the comprehensive cost of PV power generation under different capacity of battery were figured out by using particle swarm optimization algorithm, then determining the optimal battery capacity. At last, when the optimal capacity of the battery had been fixed, on the basis of PV power hourly generation forecasts, the output distribution, the expected value of system output each moment, corresponding to the lowest comprehensive cost is presented, realizing system stable output and economic operation by controlling battery charging and discharging.Simulating calculation and analysis show that in the stand-alone PV power system, the improved minimum battery capacity selection principle meets the demand of energy conversion, and increases the system reliability. While in the grid-connected PV power system, the application of energy storage device controls the system output to a certain degree, and a reasonable choice of energy storage capacity not only improves the economical efficiency of the system operation, but also has the effect of peak load shifting. |
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