Voltage Balance Control Based Aalborg Inverter with Single Source in Photovoltaic System

The Aalborg inverter was proposed in recent years, where it has a lot of advantages. For example, its input voltage can be varied in a wide range, the minimum voltage drop on filtering inductors can be realized, the minimum switching power losses can be achieved, and therefore the efficiency of the inverter is high. However, it's in essence a 'half-bridge' inverter using two input sources. Note that in practical PV applications, the output voltage of each PV array is not always the same. For a conventional Aalborg inverter, to maintain the current to be injected into the power grid without DC component, part of input DC energies may have to be discarded, which will reduce the efficiency of whole system. In this paper, the circuit configuration of modified Aalborg inverter with single source and its voltage balance control method are presented. Different from the conventional Aalborg inverter, this configuration can avoid the situation of the energy unbalance of two input DC sources and has higher maximum power point tracking efficiency, in addition to its already excited advantages. An 800W/110V/50Hz prototype has been built to verify the feasibility of the proposed inverter together with the new control strategy.