Sunday, 11 August 2013

Asymmetric Control of DC-Link Voltages for Separate MPPTs in Three-Level Inverters

Abstract—It is important to improve the overall efficiency of a photovoltaic (PV) inverter when it is connected to the grid. Fundamentally, the conversion efficiency from dc to ac power of an inverter is important. However, in the presence of partial shading, maximum power point tracking (MPPT) on PV modules is more important than the conversion efficiency. In this paper, a new control method for a three-level inverter is proposed.With the proposed method, each dc-link voltage of the three-level inverter can be asymmetrically regulated. When PV modules are split into two and each split module is connected to the respective dc-link capacitors of the inverter, the asymmetric control can be helpful because separateMPPTs are possible. The effectiveness of the proposed method was examined through experiments with a T-type three-level inverter, where each dc-link capacitor was supplied by a PVsimulator emulating two separate PVmodules under different shading conditions.


(Index Terms—Asymmetric voltage control, grid-connected inverter, maximum power point tracking (MPPT), photovoltaic (PV), three-level inverter.)

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