Research On Direct Power Control Of Battery Storage System

With the continuous consuming of fossil fuels and the demand of electrical energyincreasing, the energy storage technology has become a hot topic of human research. Theenergy storage system plays an important role in regulating power peak, stabilizingelectricity networks and efficiently using of renewable energy. Battery energy storagesystem is more mature than others, it will have characters of high frequency, high efficiencyand small volume. In this paper battery charging and discharging system is presented, andthe control strategy is applied in an500kVA energy storage system.First, the development status of energy storage technology is described, and for thebattery storage system, many charge and discharge devices are listed, nowsilicon-controlled rectifiers (SCR) are widely used, but SCR system has low power factor ingrid side and causes severe harmonic pollution. In this paper, voltage-source PWMRectifier is presented.Secondly, this paper introduces the principle of voltage-source PWM Rectifier, selectsthree-phase voltage-controlled inverter which is composed by three single full-phaseinverters as the main circuit., and establishes mathematical models of three-phase inverterin ABC, αβ and dq reference frame.Thirdly, a variety of control strategies are analyzed and studied. In the discharge mode,the mathematic model of rectifier for DPC is analyzed and the corresponding control chemeis developed. The estimating equation for instance active and reactive power is derived. Theway to achieve the constant switching frequency for DPC is introduced. Then the impact ofcurrent when the PWM Rectifier starts is analyzed, and the control strategy is improved. Inthe charge mode, the mathematic model of rectifier for DPC in dq reference frame and PIcontrol in ABC reference frame are analyzed and the corresponding control schemes aredeveloped, and the reactive current generation is introduced.Finally, The simulation models of rectified in charge and discharge modes onMatlab/Simulink environments are established. The simulation results verify the DPC forthe system. these control strategies are carried out on an500kVA battery storage system,and from the experimental results, the feasibility of the proposed approach is showed.