| Currently,people are committed to developing and applying renewable energy.Energy storage systems have become a hot topic in social research because of their ability to regulate the uncertainty of renewable energy and instability.Energy storage converter as energy transmission channel for energy storage battery and power grid in energy storage system,one of the important indicators is the harmonic distortion rate of the grid.In this paper,the three-phase voltage-type energy storage converter is taken as the research object,and the harmonic suppression of grid-connected is studied.The topology and working principle of the energy storage converter are introduced.A new type of LLCCL filter is proposed for the switching frequency sub-high harmonics introduced by Sine Pulse-Width Modulation(SPWM)technology.The passive damping and active damping methods are analyzed to suppress the resonance peak of the LLCCL type filter.The simulation of matlab/simulink verified that the LLCCL filter has a good suppression of the switching frequency harmonics,and the addition of damping can suppress the harmonic distortion rate caused by the resonance peak.A mathematical model of three-phase energy storage converter under three-phase static(abc),two-phase static(αβ),two-phase rotation(dq)coordinate system is established.In order to avoid the complex decoupling in the dq coordinate system,a double closed-loop controller of the branch current and the incoming current in the αβ coordinate system is designed.Aiming at the low-order harmonics caused by grid voltage disturbance,a proportional resonance(PR)and grid voltage feedback control strategy are proposed.The simulation verifies the effectiveness of the control strategy to suppress low-order harmonics.In this paper,the control circuit,power circuit and other hardware circuits and software programs are designed.An experimental prototype was built and a grid-connected experiment was performed. |
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