Abstract :
This paper presents the control of a three-level Neutral Point Clamped (NPC) voltage source inverter for grid connected photovoltaic
(PV) systems. The control method used is the Extended Direct Power Control (EDPC), which is a generic approach for Direct Power
Control (DPC) of multilevel inverters based on geometrical considerations. Maximum Power Point Tracking (MPPT) algorithms, that
allow maximal power conversion into the grid, have been included. These methods are capable of extracting maximum power from each
of the independent PV arrays connected to each DC link voltage level. The first one is a conventional MPPT which outputs DC link
voltage references to EDPC. The second one is based on DPC concept. This new MPPT outputs power increment references to EDPC,
thus avoiding the use of a DC link voltage regulator. The whole control system has been tested on a three-level NPC voltage source
inverter connected to the grid and results confirm the validity of the method.
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