Modeling of the combined operation of a solar photovoltaic power plant and a system of electric energy storage

Abstract

In view of the dependence of power generation at photovoltaic solar power plants on the level of intensity of solar radiation and cloud cover, their operation creates a number of problems in the power system. This article describes the problems of operation of such power plants of non-guaranteed capacity during their parallel operation as a part of the Unified Energy System of Ukraine. One of the measures of stabilizing the operation of power plants of non-guaranteed capacity is the use of systems of electric energy storage. The article describes the conditions of electrical connection, which ensure the possibility of combined operation of a system of electric energy storage and a photovoltaic solar power plant. The article presents the developed mathematical model of the combined operation of a photovoltaic solar power plant (PSPP) and a system of electric energy storage. We consider the daily mode of recharging from a PSPP and discharging batteries into the power system in order to preserve the excess of generated electricity at the PSPP, which earlier was lost due to the restriction on inverters caused by the overload with photovoltaic power. The model enables one to identify the key parameters of batteries – power and capacity, taking into account the physical and technical features of the operation of battery storage as to the conversion efficiency, the number of working cycles and the depth of possible discharge depending on the structure of PSPP equipment and solar radiation intensity. Using the developed model, we determined the values of power, charging and discharging capacities of a lithium-ion system for storing electrical energy, when it works together with a 10 MWAC photovoltaic solar power plant at different overload factors. The article presents some results of technical and economic assessment of the combined operation of a PSPP and a lithium-ion system for storing electrical energy. The results showed an increase in the power and capacity of a storage device with increase in the overload factor of PSPP, which leads to the growth of cost of electrical energy at their combined work. At the same time, the amounts and quality of electricity supplied increase. Keywords: mathematical model, photovoltaic solar power plant, system of electric energy storage, cost of electricity, power system