Modeling and analysis of DC-link voltage for three-phase four-wire two-stage micro-inverter

DC-link voltage control plays a key role for two-stage micro-inverter application. Modeling &analysis of dc-link voltage is investigated in this paper. The first-stage circuit employs transient maximum power point tracking method to realize fast MPP tracking without causing output distortion and dc-link variation. In order to keep dc-link voltage constant, injecting current to grid varies with the output of a positive feedback of dc-link voltage regulator at steady situation. Two disturbances to cause dc-link constant are investigated and small signal model of dc-link voltage is also built while considering dynamic response. Followed by the small signal model of dc-link voltage, the dc-link capacitance is also calculated. The performance of dc-link voltage control is verified by experimental results based on a 400 watt two-stage three-phase four-wire prototype with grid-connected, the input voltage from 35V to 60V, dc-link voltage 400Vdc and AC output voltage 110V RMS.