Research On Statcom With Battery Energy Storage

Static synchronous compensator (STATCOM) is an important reactive powercompensation device, compared with other type of devices, it has characteristic ofpowerful function, excellent performance and high cost performance, it can solvepower quality problems in the grid comprehensively like voltage fluctuation andflicker, current distortion, three-phase voltage unbalance and so on, thus gainspopularity in distribution network, becomes development direction of current gridreactive power compensation and power quality control. When power system needsactive power compensation such as damping system active vibration or prolongingsupport time in accidental state, simple STATCOM can’t meet the demands at thistime. If storage battery is paralleled with DC side, then it can not only compensatereactive power, but also proceed active power flow, realize work mode of the fourquadrants, has great meaning in power grid. So in this paper, static synchronousreactive power compensator with battery energy storage system (STATCOM/BESS)is studied in detail.Battery energy storage is linked to STATCOM dc-link through DC/DCbidirectional converter in the paper. Bi-directional DC/DC converter takes on tasksof battery energy and DC/AC inverter bidirectional transport of energy. In order tocontrol the active and reactive power accurately, the whole system needs to bemodeled. The dq coordinate based on linear decoupling small signal dynamic modelis established through analysis of holistic large signal model, realizing decouplingcontrol of DC/DC side and STATCOM side. Based on this model, STATCOM sidecurrent-voltage double-loop and power feed-forward term combination controller isrealized for better control of DC link capacitor voltage stable output. DC/DC sideadopts closed loop control of inductive current, realizing tracking control ofSTATCOM/BESS charge/discharge active power. Design correctness is validated byMatlab/Simulink simulation and experiment.In this paper, an LCL filter is proposed to replace L-type filter in a dc/dcconverter for battery charging and discharging applications. In this way, it not onlycan reduce inductor value and cost, but also get low ripple of charging anddischarging current so as to improve the battery lifetime. The parameters of LCL aredesigned based on the requirements of the ripple of charging and dischargingcurrent, storage battery side current is taken as control object and the controlstrategy with the capacitor voltage differential feedback was proposed in this paperto control the battery side current, which can eliminate resonance and improvesystem stability. The simulation and experiment results proved that LCL filter can inhibit high frequency harmonic better and the strategy proposed is correct.In the end, STATCOM/BESS is used for wind power plant, because theshortcomings of wind power generation such as intermittency and uncontrollability,STATCOM/BESS has the effect of inhibit power fluctuation. The result ofSTATCOM/BESS inhibiting wind power plant power fluctuation is analyzedthrough simulation. Experimental platform is set up to further verify theeffectiveness of control strategy proposed in the paper.