ABSTRACT:
This
paper presents a novel single-stage soft switched high frequency link
three-phase DC-AC converter topology. The topology supports unidirectional DC
to AC power flow and is targeted for applications like grid integration of photovoltaic
sources, fuel cell etc. The high frequency magnetic isolation results in
reduction of system volume, weight and cost. Sine-wave pulse width modulation
is implemented in DC side converter. Though high frequency switched, DC side
converter is soft-switched for most part of the line cycle. The AC side converter
active switches are line frequency switched incurring negligible switching
loss. The line frequency switching of AC side converter facilitates use of high
voltage blocking inherently slow semiconductor devices to generate high voltage
AC output. In addition, a cascaded multilevel structure is presented in this
paper for direct medium voltage AC grid integration. A detailed circuit analysis
considering non-idealities like transformer leakage and switch capacitances, is
presented in this paper. A 6kW three phase laboratory prototype is build. The
presented simulation and experimental results verify the operation of proposed
topologies.
KEYWORDS:
1. Zero-voltage
switching (ZVS)
2. Pulse
width modulation
3. DC-AC
converter
4. High-frequency
transformer (HFT)
5. Cascaded
multilevel inverter
6. Single-stage
7. Rectifier-type
HFL
SOFTWARE:
MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig.
1. Proposed 3φ single stage HFL topology
Fig.
2. Proposed 3φ cascaded multilevel HFL topology
EXPERIMENTAL RESULTS:
Fig.
3. Output phase voltages- (a) simulation, (b) experimental: [CH1] c phase
voltage (100V/div.), [CH2] a phase voltage (100V/div.), [CH3] b phase voltage
(100V/div.). Time scale 4ms/div. Output current waveforms- (c) simulation, (d)
experimental: [CH1] c phase current (10A/div.), [CH2] a phase current (10A/div.),
[CH3] b phase current (10A/div.). Time scale 4ms/div.
CONCLUSION:
In
this paper, a single-stage unidirectional 3φ high frequency link inverter
topology along with its multilevel configuration is proposed. Proposed
topologies have following features. 1) The DC side converter is soft switched
(ZVS) for most part of the line cycle without additional snubber circuit. 2) High frequency magnetic isolation improves
the system power density and reduces weight and cost. 3) The AC side active switches
are line frequency switched incurring negligible switching loss. 4) High
voltage blocking slow switches can be used in line frequency switched AC side
converter to generate high voltage AC output. 5) The cascaded structure
proposed in this paper is targeted for direct medium voltage grid integration and
6) in this scheme the grid end line filter will have high voltage and low
current rating resulting in smaller size with reduced conduction loss. The
circuit operation of the proposed converters are discussed in detail
considering non-idealities like transformer leakage inductance and device
capacitances. The presented simulation and experimental results at verify the operation
principle and advantages of the proposed converter topologies. The proposed
topologies support unidirectional DC to AC power flow and primarily targeted
for grid integration of utility scale photovoltaic sources.
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