In order to improve the stability of the photovoltaic (PV) grid-connected multi-inverter parallel system with widely varying grid impedance
a multi-functional PV grid-connected inverter with active damper function based on energy-stored quasi-Z-source inverter is proposed
which simultaneously achieves grid-connected power generation and resonance suppression. Firstly
the circuit parameter design criteria for the multi-functional grid-connected inverter are presented. Then
an overall control strategy based on inverter side current feedback
considering the influence of the phase-locked loop (PLL)
and the corresponding control parameter design method are provided. In the control strategy
the phase margin of the original port impedance is increased to improve the system stability by employing phase lag compensation in the capacitor current feedback loop. Additionally
the virtual impedance satisfying the damping target resonance frequency band is constructed at the output end of the multi-functional inverter to achieve resonance suppression in the multi-inverter parallel system. Finally
the feasibility and effectiveness of the proposed multi-functional PV grid-connected inverter are verified through experiments.
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references
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