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Derivation of Boost-Buck Converter Based High-Efficiency PV InverterZheng Zhao, Jih-Sheng Lai and Younghoon Cho
Future Energy Electronics Center, Virginia Tech, Blacksburg, VA 24060 USA
Boost-Buck Converter Based High-Efficiency Robust PV Inverter
Each mode operates separately based on instantaneous grid voltage.
A universal control could be realized for both modes.
PROPOSED PV INVERTER
MODELING of BUCK MODE
EXPERIMENTAL RESULTS
PV LightingBIPV
OPERATION MODES
Boost Mode Transfer FunctionDouble-pole position Q
Buck Mode Transfer FunctionDouble-pole position Double-zero position Q
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Experiment Results of PWM Signals
Photograph of Prototype
Small L1 leads to high frequency double-pole, high gain and small Q, which are all critical to controller design.
Interleaved boost is proposed for smaller inductance of L1 to achieve the same current ripple.
Efficiency of the Boost-Buck Stage
PWM MODULATOR
An offset of the sawtooth ramp right on the top of the buck mode PWM modulator
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MODELING of BOOST MODE
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INDUCTANCE’S IMPACT ON BOOST MODEExperiment Results
SUMMARY Efficiency peaks at 98.5%. High efficiency is achieved because of single-
stage PWM operation. Ultra high control loop bandwidth with a
multiphase interleaved boost stage, which allows a high resonant pole frequency.
The proposed circuit along with its controller has been designed, simulated, and tested with a hardware prototype.
Buckmode
BoostMode
VPV(t)
Vgrid(t)BoostMode
Buckmode
Buckmode
0
Rated power: 2.5 kWInput voltage: 200 – 500 VOutput voltage: 208/240 VrmsOutput frequency: 60 Hz
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