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High Step-Up DC-AC Inverter Suitable for ACModule Applications
Abstract:
In this paper a novel grid-connected high step-up inverter is proposed. The
topology is composed of two stages. First stage is a single switch high step-up DCDC converter with bipolar outputs and the second stage is a conventional halfbridge DC-AC grid-connected inverter. Negative grounding of the PV-Module has
resulted in elimination of unwanted ground leakage currents in PV system. Simple
structure, employing few semiconductor switches, simple control and high
efficiency are features of the proposed topology. Theoretical analysis and principal
operation of the circuit are discussed. An experimental prototype is implemented to
verify the performance of the proposed inverter. The experimental results confirm
the aforementioned features and the theoretical analysis of the converter operation.
Existing system:
The newest breakthrough in PV technology is AC-module. AC-module is an
innovative pre-assembled module consisting of a micro inverter and one or two
PV-modules. AC-module system maximizes energy production by individual
Maximum Power Point Tracking (MPPT) for each PV module. The performance
issues within traditional PV systems technologies caused by clouds, partial shade
from trees or roof obstructions as well as module mismatches, are resolved in ACModule technology. Although, higher cost for AC-modules is expected, but due to
the modularity there is opportunity for massive production and hence reduction in
overall system price. AC-module yields more energy and lower design and
installation cost
Proposed system:
In this paper a novel DC-AC grid-connected inverter with high boost ratio for
eliminating of ground leakage current is presented. The proposed inverter consists
of two stages in which the first stage is a high step up DC-DC converter with
bipolar outputs and the second stage is a conventional half bridge inverter.
Simultaneous grounding of PV module and grid in this topology is provided by the
same strategy applied in. Higher voltage gain, using fewer MOSFET switches and
soft switching are the main advantages of the proposed topology.
Block diagram:
Advantages:
 Generating bipolar outputs with only one low voltage rated MOSFET
switch, which results in lower switching losses and easier control and
MPPT.
 Extended voltage gain by using coupled inductors and switched capacitors,
which makes it suitable for AC-module application in which a high boost
ratio is required to amplify the low DC voltage of PV module to adequate
DC level for grid-connected inverter.
 Recycling the leakage inductance energy and absorbing the voltage ringing
on the boost switch by using a passive regenerative clamp circuit.
Reference:
[1] Yaosuo Xue; Liuchen Chang; Sren Baekhj Kjaer; Bordonau, J.; Shimizu, T.,
"Topologies of single-phase inverters for small distributed power generators: an
overview," IEEE Trans. Power Electron. , vol.19, no.5, pp.1305,1314, Sept. 2004.
[2] Soeren B. Kjaer, John K. Pedersen and Frede Blaabjerg, “A review of singlephase grid-connected inverters for photovoltaic modules”, IEEE Trans. Ind.
Electron. , vol. 41, No. 5, Sep. 2005.