CONTROL METHOD AND SYSTEM FOR THREE-PHASE GRID-CONNECTED INVERTER, AND THREE-PHASE GRID-CONNECTED INVERTER

摘要

A control method and control system for a three-phase grid-connected inverter, and a three-phase grid-connected inverter. The control method is applied to a three-phase three-bridge grid-connected inverter. By improving the structure of the three-phase three-bridge grid-connected inverter, filter capacitors (C1, C2, C3) are connected to the negative pole of a direct-current input bus to form a harmonic bypass channel so as to improve the ability to suppress harmonics, thereby achieving a high-quality grid-connected current at low power, such that there is no need to increase the inductance of inductors (L1, L2, L3), and accordingly, parallel inverter devices in a system can operate stably, thus facilitating the present application to photovoltaic micro-inverters. Moreover, the three-phase three-bridge grid-connected inverter works in a mode with discontinuous inductor currents (iL1, iL2, iL3), that is, when power switches (Q1, Q2, Q3, Q4, Q5, Q6) on bridges are turned on, the inductor currents (iL1, iL2, iL3) drop to zero, so that the switching loss of power switch tubes (Q1, Q2, Q3, Q4, Q5, Q6) is reduced, thereby improving the conversion efficiency of the inverter.