Research On Low Voltage Ride Through Technology Of Photovoltaic System

The photovoltaic grid-connected inverter becomes more and more important inthe photovoltaic plant applications when the grid failure occurs. According to therelated grid directive, the inverter is required to maintain the running status even thegrid voltage drops and needs to have the capability to contribute towards the stabilityof the grid voltage and to support the grid voltage ride through. The technology of lowvoltage ride through of photovoltaic power generation system is researched when thegrid voltage falling based on materials of solar cells and maximum power pointtracking, in this paper, the stability and the ability to cope with failure of the system isimproved, and the simulation tool is MATLAB.In this paper the mathematical model of photovoltaic grid connected inverter inABC three-phase static coordinate system, two-phase stationary coordinate and dqcoordinate is set up.By studying the topological structure and work principle of thegrid-connected photovoltaic inverter,and the traditional control strategy ofphotovoltaic grid connected inverter is analyzed, the PI current control method is usedin this paper. The feed-forward decoupling control method is used in the synchronousrotating coordinate, the control of the AC side current is realized by the fixedswitching frequency. The structure of the control strategy is simple and the design ofthe parameter is easy, and the closed loop control of the public node grid current canbe realized. The mathematical model of the photovoltaic grid connected inverter basedon the low voltage ride through technology is built, the grid negative sequence currentinner loop control is increased based on the traditional voltage outer loop, currentinner loop double loop control strategy.The adaptability of inverter is improvedwhen the grid power three-phase is unbalance,combined with the DC-DC controlthe low voltage ride through of photovoltaic power generation system is realized.A method of using the super capacitor energy storage of the low voltage ridethrough is offered. The output of photovoltaic array is kept when the grid voltagefalling.The redundant power of inverter DC side is stored in the super capacitor.Thegenerating capacity of the photovoltaic grid connected power system is kept and thelow voltage ride through is realized. The simulation model of the photovoltaic gridconnected inverter based on the low voltage ride through technology based on theMatlab/Simulink platform has been built, and the corresponding simulationexperiment is carried out. The simulation results show that the method has high speed of current recovery, and the system response is fast, and the redundant power of DCside can be stored. In photovoltaic inverter, the parallel operation can be kept duringthe voltage dip. A certain amount of reactive power can be output to meet the need ofthe grid, the voltage of grid-connected point is supported. When it breaking awayform the grid the suddenly, the adverse effect of the photovoltaic inverter for the gridis reduced.The experiments cooperate with related enterprises are carried out to verifythe correctness of simulation model of the low voltage ride through technical at theend,and the feasibility of the low voltage ride through technology is indicated in theexperimental results.