Study On Lead-acid Battery Energy Storage System With Power Quality Control

New energy power generation technology has developed rapidly,but due to the volatility and intermittent nature,energy storage systems are used to increase energy efficiency and grid stability with the “peak-cut and valley-fill” function.With the access of a large number of new energy generation and energy storage systems,the problems of harmonics,three-phase voltage unbalance,reactive power and voltage have become increasingly prominent.Because the energy storage system inverter and power quality controller have the same topology,therefore,it is necessary to research energy storage systems that have power quality control functions.First of all,in order to better optimize the the energy storage system operating characteristics,a new battery power estimation method was proposed.Firstly,according to the battery charge and discharge requirements,and propose the battery charge and discharge strategy,that is,select the constant current-constant voltage-constant voltage three-phase charging method and constant current discharge method to charge and discharge the battery.Secondly,under this strategy and the problem that the traditional battery estimation methods of the energy storage system battery has a large error and is affected by the aging of the battery,this paper presents a kind of multi-factor staged capacity estimation method considering electromotive force,resistance and terminal voltage weighted combination with ampere-hour correction,when the capacith is high,electromotive force,resistance and terminal voltage weighted combination with ampere-hour correction method is used,when the capacity is low,electromotive force,resistance and terminal voltage weighted combination is used.For harmonics problems under the active distribution networks/micro-grids,according to the principle of harmonic damping,a fast Fourier transform is performed on the grid voltage and the output current to obtain each harmonic voltages and harmonic currents,and the energy storage system is equivalent to each harmonic resistance,the simulation results show that the harmonic damping technology based on the energy storage system can reduce the background harmonic voltage by absorbing harmonic currents.To solve the three-phase voltage unbalance,reactive power and voltage problems existing in the grid point of traditional energy storage systems,three-phase voltage unbalance,reactive voltage control technologies based on energy storage systems were proposed and verified through simulation.In order to verify the theoretical research,based on the the NP80-12 lead-acid battery to build the experimental the energy storage system platform,and introduce the specific implementation method of the system overall structure,main circuit,control circuit and system software design.And developed a 10 kW energy storage inverter prototype with power quality control function,the experimental results verify the theoretical and simulation research.