Design And Control Strategy For Grid-connected Inverter With LCL Filter

In today’s world energy tense situation grim, renewable energy sources such as windpower and solar energy is more and more attention. And the use of power converters isvery important in maximizing the power transfer from renewable energy sources such aswind, solar,even a hydrogen-based fuel cell to the utility grid. A LCL filter is often used tointerconnect an inverter to the utility grid in order to filter the harmonics produced by theinverter.Even though there is an extensive amount of literature available describing the desingof LCL filters, there has rarely papers in providing a systematic design method. This paperdescribes a design method of a LCL filter for grid-interconnected inverters, presenting theconstraint of designing Component parameters and the process of systematic design.Themethod can design a matching LCL grid filter according to the inverter rated parameters.On the basis of the completion of the LCL filter parameter design,The following and main step is to design the control structure and the parameters ofcontrolle for the grid inverter mathematical model which has been build. As for singlephase inverter adopts double closed loop control, When designing inner closed loopdesign, comparing the improvement damping situation of different inner feedbackvariables, Select capacitance current as inner feedback variables. And as for outer closedloop design, Using typical Ⅱ type system parameter setting method to design thecontroller parameters. Compare advantages and disadvantages of three controllers:Proportional Integral, Proportional Resonance, and Proportional Resonance+Harmoniccompensation.and Obtain grid current waveform by simulink simulation. Three-phasegrid-connected inverters use the same bicyclic control structure:outer net current and innercapacitor current. build PR control under α β axis and PI control under dq axisespectively. Analysis of the links and differences between the two two controller equationsunder different coordinate systems. Finally,at case of grid voltage waveform distortion.Contrast control and simulation waveforms of PR+HC under αβ axis with the twocontrol before, indicates harmonic compensator has a strong inhibitory effect insuppressing specified harmonic interference.