Research On Harmonic Suppression And Power Control Of High-power Pv Grid-connected Inverter

This paper focuses on PV grid-connected inverter, researches the design offilter, the algorithm of active damping, the repetitive controller and so on.Propose a MPPT method basing on changing PV curves, through loss analysis ofPerturbation and Observation method. On the other hand, this paper also doessome research on reactive compensation of PV grid-connected inverter.Occasions in the high-power, it is difficult for the single-inductor filter tomeet the filtering requirements, and thus, this paper researches the LCL filter.This filter owns better filtering characteristic, even with small inductor, w hichreduces the filter’s cost. However, the computation of the filter parameter isdifficult, as well as the resonant problem. Considering the resonant frequency,the filter cost and harmonic current decay rate, this paper proposes a newcalculation method of the grid side inductance. In addition, resonance problemof the LCL filter is effectively suppressed with the introduction of the capacitorcurrent feedback, further more, the shortcomings of the traditional passivedamping such as fever is also overcome.In order to meet the requirements of the grid standards, a composite controlalgorithm of the PI controller and the repetitive controller is studied. Therepetitive controller can suppress periodic harmonics contained by the grid andcaused by the dead time effect. This composite controller owns both gooddynamic response and good inhibition of periodic harmonics. Further more,considering the impact to the coefficient N, the feature of the coordinatetransformation, as well as periodic harmonics, a modified repetitive controllerwith only even-order harmonics suppression is proposed, which further improvesthe output characteristic.In this paper, P&O method is analyzed from the perspective of solar energyutilization. To better inhibition of the misjudge problem, analyze the reason ofmisjudge and propose a modified P&O method basing on the changing PVcurves. Furthermore, the variable step problem is also researched. Nowadays,the new grid standards require the grid-connected inverters with certain amount of reactive power compensation. So this paper does some research on thereactive power compensation for grid-connected inverter.