New Fast MPPT Method Based on a Power Slope Detector for Single Phase PV Inverters

Jose Miguel Espi and Jaime Castello
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Jose Miguel Espi: Department of Electrical Engineering, University of Valencia, Avd. Universitat S/N, 46100 Burjassot-Valencia, Spain
Jaime Castello: Department of Electrical Engineering, University of Valencia, Avd. Universitat S/N, 46100 Burjassot-Valencia, Spain

Energies, 2019, vol. 12, issue 22, 1-20

Abstract: This article presents a novel MPPT method for two stage PV inverters with a single phase connection to the power grid. The method takes advantage of the 100 Hz/120 Hz harmonic present on the DC-bus voltage to guide the MPP search. It consists of detecting the slope of the P-V curve and integrating it to obtain the duty-cycle. The power slope detector (PSD) is able to calculate the P-V slope to command the MPPT even at very low powers, where the amplitude of the oscillations is barely perceptible. Design equations are provided, both of the gain of the PSD and of the gain of the MPPT integrator. It also shows how this PSD-MPPT strategy can be combined with the power control, allowing regulation of powers lower than those of the MPP. The power control loop is analyzed, and its stability is related to a single gain to be designed. The PSD-MPPT is tested in a two stage PV inverter, where the step-up DC-DC converter consists of three parallel boost converters. The results show that the PSD-MPPT method can work without the measurement of the current in the boost converters, which implies a cost reduction. A PV efficiency of about 99.8% is obtained with a usual ripple in the DC-bus of 4% peak-peak. In addition, the PSD-MPPT method is characterized as being extremely fast, both in the MPP search and in the power control, with response times around 50 ms. The PSD-MPPT is a simple algorithm of constant parameters that can be solved in a low cost microcontroller at a sampling frequency of about 2 kHz, requiring only the voltage and current of the PV array.

Keywords: photovoltaic (PV); two stage single phase PV inverter; power slope detector MPPT (PSD-MPPT); interleaved boost converter (IBC) (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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