Current-Fed Single-Stage Converter with MPPT and Auto-Voltage-Sharing
Integrated for MVDC Grids
Abstract
Summary - This paper proposes a current-fed
single-stage input-parallel-output-series (IPOS) modular converter for a
large-scale photovoltaic (PV) generation connected to MVDC grids, which
can realize maximum power point tracking and auto-voltage-sharing by
only sampling the PV voltage and current. The submodule (SM) is
integrated by an interleaved parallel boost unit and a full-bridge LC
series resonant unit. The simple pulse width modulation is adopted,
while the drivers of different SMs are interleaved but with the same
duty cycle set. Since the full-bridge LC series resonant unit operates
as a DC transformer (DCX) with zero-current switching realized for all
rectifier diodes, the voltage gain of SM is only related to the duty
cycle of the interleaved parallel boost unit for the boost inductor
current is continuous. Hence, without any SM output voltage nor input
current sensors, the SMs can automatically share the output voltage by
using the same duty cycle set for each SM. Moreover, the
zero-voltage-switching can be realized for switches. A 1.5 kW prototype
with three SMs is built to verify the converter characteristics and
control strategy.
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