Abstract
This paper presents the implementation of a maximum power point tracking (MPPT) algorithm in a multilevel three-phase photovoltaic (PV) system using the ripple correlation control (RCC) method. Basically, RCC adopts the inherent oscillations of PV current and voltage as perturbation, and it has been predominantly used for single-phase configurations, where the oscillations correspond to the 2nd order harmonics. The implementation of an RCC-MPPT algorithm in a three-phase system has not been presented yet in the literature. In this paper, the considered three-phase three-level converter is a three-level flying capacitor (FC) inverter. The proffered RCC method uses the 3rd harmonic components of PV current and voltage for the estimation of the voltage derivative of the power dPpv/dVpv (or current, dIpv/dVpv), compelling the PV array to operate at or very close to the maximum power point. The analysis and calculation of the low-frequency PV current and voltage ripple harmonic components in the three-phase flying capacitor inverter is presented first, with reference to centered carrier-based three-level PWM. The whole grid-connected PV generation scheme has been implemented by MATLAB/Simulink, and detailed numerical simulations verified the effectiveness of the control method in both steady-state and dynamic conditions, emulating different sun irradiance transients.
Highlights
To fulfill the constantly increasing worldwide energy demand, renewable energy sources such as photovoltaic (PV), wind, geothermal, and biomass, are being explored
Among the different methods known in the literature, the most popular and effective are perturb and observe (P&O) [1] and incremental conductance [2]
This paper presents an ripple correlation control (RCC)-maximum power point tracking (MPPT) algorithm for a grid-connected three-phase three-level flying capacitor (FC) inverter (Figure 1) with reference to centered level-shifted (LS) carrier-based pulse with modulation (PWM) modulation
Summary
To fulfill the constantly increasing worldwide energy demand, renewable energy sources such as photovoltaic (PV), wind, geothermal, and biomass, are being explored. In case of three-phase two-level (2L) inverters, the RCC algorithm cannot be applied due to the inexistence of inherent (natural) low-order harmonic oscillations on the PV side of the inverter. Adopting a multilevel inverter introduces different low-order voltage and current harmonics on the dc-link side compared to the case of a single-phase H-bridge inverter where only the. In order to maximize the resolution, the proposed solution makes reference to the highest amplitude harmonic, leading to a more effective estimation of dPpv /dVpv. Though numerous RCC-MPPT algorithms for single-phase grid-connected PV systems have been developed, no analysis of RCC-MPPT in case of three-phase multilevel inverters has been reported. This paper presents an RCC-MPPT algorithm for a grid-connected three-phase three-level FC inverter (Figure 1) with reference to centered level-shifted (LS) carrier-based PWM modulation.
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