ABSTRACT:
In this paper, a soft-switching single-inductor
push– pull converter is proposed. A push–pull converter is suitable for low-voltage
photovoltaic ac module systems, because the step-up ratio of the high-frequency
transformer is high, and the number of primary-side switches is relatively
small. However, the conventional push–pull converter does not have high
efficiency because of high-switching losses due to hard switching and
transformer losses (copper and iron losses) as a result of the high turn ratio
of the transformer. In the proposed converter, primary-side switches are turned
ON at the zero-voltage switching condition and turned OFF at the zero-current
switching condition through parallel resonance between the secondary leakage
inductance of the transformer and a resonant capacitor. The proposed push–pull
converter decreases the switching loss using soft switching of the primary
switches. In addition, the turn ratio of the transformer can be reduced by half
using a voltage-doubler of secondary side. The theoretical analysis of the
proposed converter is verified by simulation and experimental results.
KEYWORDS:
1.
Current-fed
push–pull converter
2.
Photovoltaic
(PV) ac module
3.
Soft-switching
SOFTWARE: MATLAB/SIMULINK
CONTROL BLOCK DIAGRAM:
Fig.
1. Control block diagram of the dc–dc converter and dc–ac inverter using a
microcontroller.
EXPECTED SIMULATION RESULTS:
Fig.
2. (a) Carriers and a reference for PWM. (b) Waveforms of primary
switch
S1 . (c) Waveforms of primary switch S2 .
Fig.
3. (a) Boost inductor current iLbst . (b) Resonant capacitor voltage vC
r .
Fig.
4. (a) Waveforms of tracking the MPP. (b) PWM according to MPPT. (c) Start flag
of MPPT.
Fig.
5. Current and voltage waveforms of switch S1 according to ZVS and ZCS.
Fig. 6. Waveforms of resonant capacitor
voltage and boost inductor current.
CONCLUSION:
In
this paper, the soft-switching single-inductor push–pull converter for PV ac
module applications is proposed. Soft switching was confirmed at each part, and
MPPT is performed for extracting the maximum power from the PV module. Switches
of the primary side operate in the ZVS condition at turn-off and in the ZCS
condition at turn-on. The proposed converter maintains a Vo of 400 V to
provide ac 220 Vrms for dc–ac inverters. The maximum efficiency is 96.6%. These
results were confirmed by simulation and verified by a 250-W experimental setup.
REFERENCES:
[1]
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[2]
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[3]
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