A new control allocation method for power converters and its application to the four-leg two-level inverter

The deployment of renewable energies requires power electronic converters to produce sinusoidal voltages of appropriate magnitude and frequency. In the case of isolated microgrids, unbalanced loads can result in off-nominal voltages on the loads. A solution to this problem consists in replacing the conventional three-leg converter by a four-leg converter with neutral wire. Four-leg converters have not been studied as extensively as three-leg converters, and existing approaches to control them are based on geometric properties that become difficult to extend to converters with a higher number of levels/switches. The objective of the paper is to show that an approach developed in the context of flight control can be applied to this problem with great advantages. Specifically, control allocation methods are shown to be applicable to a four-leg two-level three-phase inverter. The method offers a single generic control scheme regardless on the number of switches. In addition, the approach may offer the incorporation of interesting converter properties, such as the minimization of switching (or conduction) losses, or the reconfiguration of the inverter in the event of a fault detected on a switch, if redundancies allow it.