This paper presents a fuzzy logic controller (FLC)-based single-ended primary-inductor converter (SEPIC) for maximum power point tracking (MPPT) operation of a photovoltaic (PV) system. The FLC proposed presents that the convergent distribution of the membership function offers faster response than the symmetrically distributed membership functions. The fuzzy controller for the SEPIC MPPT scheme shows high precision in current transition and keeps the voltage without any changes, in the variable-load case, represented in small steady-state error and small overshoot. The proposed scheme ensures optimal use of PV array and proves its efficacy in variable load conditions, unity, and lagging power factor at the inverter output (load) side. The real-time implementation of the MPPT SEPIC converter is done by a digital signal processor (DSP), i.e., TMS320F28335. The performance of the converter is tested in both simulation and experiment at different operating conditions. The performance of the proposed FLC-based MPPT operation of SEPIC converter is compared to that of the conventional proportional–integral (PI)-based SEPIC converter. The results show that the proposed FLC-based MPPT scheme for SEPIC can accurately track the reference signal and transfer power around 4.8% more than the conventional PI-based system.

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Fuzzy-Logic-Controller-Based SEPIC Converter for
Maximum Power Point Tracking
ABSTRACT:
This paper presents a fuzzy logic controller (FLC)-based single-ended primary-inductor
converter (SEPIC) for maximum power point tracking (MPPT) operation of a photovoltaic (PV)
system. The FLC proposed presents that the convergent distribution of the membership function
offers faster response than the symmetrically distributed membership functions. The fuzzy
controller for the SEPIC MPPT scheme shows high precision in current transition and keeps the
voltage without any changes, in the variable-load case, represented in small steady-state error
and small overshoot. The proposed scheme ensures optimal use of PV array and proves its
efficacy in variable load conditions, unity, and lagging power factor at the inverter output (load)
side. The real-time implementation of the MPPT SEPIC converter is done by a digital signal
processor (DSP), i.e., TMS320F28335. The performance of the converter is tested in both
simulation and experiment at different operating conditions. The performance of the proposed
FLC-based MPPT operation of SEPIC converter is compared to that of the conventional
proportional–integral (PI)-based SEPIC converter. The results show that the proposed FLC-based
MPPT scheme for SEPIC can accurately track the reference signal and transfer power
around 4.8% more than the conventional PI-based system.
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KEYWORDS:
1. DC–DC power converters
2. Fuzzy control
3. Photovoltaic (PV) cells
4. Proportional–integral (PI) controller

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5. Real-time system
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig.1.Circuit diagram of the SEPIC converter for the FLC-based MPPT scheme.
CONTROL SCHEME:
Fig.2.Overall control scheme for the proposed FLC-based MPPT scheme for the SEPIC
converter.

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EXPECTED SIMULATION RESULTS:
Fig.3. Output (top) voltage and (bottom) current waveforms of the SEPIC converter with the
proposed FLC-based MPPT scheme.
Fig. 4. Error signal (difference between Vreal and Vref ) of the proposed FLC-based SEPIC
converter.
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Fig. 5. Variable-load inverter current, voltage, and voltage error signals.
Fig.6. Inverter current, voltage, and voltage error signals with lagging power factor load for the
proposed FLC-based SEPIC and inverter system.
Fig.7. FLC-based SEPIC’s output voltage.
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Fig. 8. Comparison of the power output for the proposed FLC- and PI-based SEPIC converters.
Fig. 9. Experimental results for Vinv and Iinv with unity power factor load.
Fig. 10. Experimental results for Vinv and Iinv with 0.766 lagging power factor load.
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Fig. 11. Harmonic analysis of the current waveform in Fig. 19.
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CONCLUSION:
An FLC-based MPPT scheme for the SEPIC converter and inverter system for PV power
applications has been presented in this paper. A prototype SEPIC converter-based PV inverter
system has also been built in the laboratory. The DSP board TMS320F28335 is used for real-time
implementation of the proposed FLC and MPPT control algorithms. The performance of the
proposed controller has been found better than that of the conventional PI-based converters.
Furthermore, as compared to the conventional multilevel inverter, experimental results indicated
that the proposed FLC scheme can provide a better THD level at the inverter output. Thus, it
reduces the cost of the inverter and the associated complexity in control algorithms. Therefore,
the proposed FLC-based MPPT scheme for the SEPIC converter could be a potential candidate
for real-time PV inverter applications under variable load conditions.

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[5] M. Hongbo, L. Jih-Sheng, F. Quanyuan, Y. Wensong, Z. Cong, and Z. Zheng, “A novel
valley-fill SEPIC-derived power supply without electrolytic capacitor for LED lighting
application,” IEEE Trans. Power Electron., vol. 27, no. 6, pp. 3057–3071, Jun. 2012.