The Research Of Control Strategy Of Photovoltaic And Energy-storage Generation System Based On LCL Filter

In recent years, distribution generation techniques have drawn increasingattention to alleviate shortage of energy and pollution of environment. Thanks tothe environmental friend and high reliability of photovoltaic power generation,it develops very fast. Photovoltaic power output, influenced by illuminationintensity and temperature, is characterized by volatility and randomness, whichis detrimental to power quality. Energy storage technology can well cope withthese problems. LCL filter has good filtering characteristics and is widely usedwhen high electric power injecting in grids. However necessary controllingmethods should be applied to LCL to inhibition its resonance when working atstatic condition. This paper have combined photovoltaic power generation withstrategy energy storage technology and proposed a LCL controlling strategy,which allows for high power injection with proper power factor, improvingharmonic distortion rate and provide efficient scheme to put large scale solarenergy in practice. Major contributions of this paper are:（1）This paper gives a simulation model that is suited for practicalengineering based on analysis of fundamental working principles of photovoltaic power generation devices and lithium battery energy storage unit.Proposed model and control algorithm are proved validity via building boostcircuit, designing DC/DC converter, controlling MPPT with disturbanceobservation method and establish Matlab/Simulink simulation model.（2）This paper also analyses the filter character of LCL filter. Themathematical model of three-phase grid inverter based on LCL filter underthree-phase static coordinate system, two-phase static coordinate system andtwo-phase rotating coordinate system is presented and analyzed, itsfeed-forward decoupling control strategy is proposed, too. By studying eachconstraint of electric parameters, a LCL filter parameter design methodcompatible with all constraint condition is presented.（3）The mechanism of resonance and methods to inhibition of resonance inLCL filter are analyzed, passive and active damping method are studied indetails especially: passive damping method is used to select installation positionof resistor and determine damping resistance with satisfied inhibition results ofresonance and fewer energy loss. Inverter output current feedback control,capacitive current splitting method and the double closed loop control with gridcurrent at outer ring and capacitive current at inner ring are compared with eachother. Their stability and harmonic suppression effect are also analyzed. Bothpassive and active damping method are realized on Matlab/Simulink platform,and both of them have the ability suppressing resonance efficiently, allowing forhigh power injection with proper power factor, and satisfy the requirement of power quality.（4）This paper have designed experimental platform of three-phase opticalinverter system with storage-generation function based on LCL filter by usingthe environment of controller development on dSPACE. Details of componentsselection and hardware circuit establishment are presented in our work.Sampling circuit drive circuit and protection circuit are designed, convertor hasbeen control in real-time in Control Desk. Steady and dynamic inverterexperiments of optical storage-generation unit entering the system were doneunder low voltage using LCL filter. Results show that proposed hardware circuitand control strategy can well suited for system steady operation, power qualityand required dynamic property.