Abstract
When a photovoltaic (PV) system is exposed to physical objects and cloud coverage and connected to bypass diodes, a partial shading condition (PSC) occurs, which causes a global maximum power point (GMPP) and numerous local maximum power points (LMPPs) on the power-voltage (P-V) curve. Unlike conventional MPPT techniques that search for multiple LMPPs on the P-V curve, it is possible to track GMPP straightaway by designing a simple but robust MPPT technique that results in faster tracking speed and low power oscillations. Hence, in this study, an improved proportional-integral (PI) coordinated Maximum Power Point Tracking (MPPT) algorithm is designed to enhance the conversion efficiency of a PV system under PSC with fast-tracking speed and reduced power oscillations. Here, PI controllers are used to mitigating the steady-state errors of output voltage and current of PV system that later on passed through an incremental conductance (INC) algorithm to regulate the duty cycle of a dc–dc boost converter in order to ensure fast MPPT process. The PV system is integrated with the grid through an H-bridge inverter, which is controlled by a synchronous reference frame (SRF) controller. Tracking speed and steady-state oscillations of the proposed MPPT are evaluated in the MATLAB/Simulink environment and validated via a laboratory experimental setup using Agilent solar simulator and dSPACE (DS1104) controller. Results show that the proposed MPPT technique reduces the power fluctuations of PV array significantly and the tracking speed of the proposed method is 13% and 11% faster than the conventional INC and perturb and observe (P&O) methods respectively under PSCs.
Highlights
A model of the PV panel has been developed under several patterns of solar insolation Isc : to Short-circuit current conditions compute the actual power of the PV system and robust Maximum Power Point Tracking (MPPT) schemes [23]
A fluctuation of 0.02 in the duty cycle step size is found in the conventional HC MPPT algorithms, whereas the constant duty cycle is operated in the proposed scheme under steady-state condition (SSC)
Experimental and simulation results demonstrate that the coordinated PI-MPPT algorithm tracks the GMPPr, GMPPm, and GMPPlfaster and is more reliable for the three shade-oriented patterns than conventional MPPT techniques in terms of the tracking of a correct maximum power points (MPPs) region and identifying the true global maximum power point (GMPP) faster
Summary
An operating point at the steady-state condition of the conventional perturb and observe (P&O), and incremental conductance (INC) MPPT techniques under PSCs revolves around a GMPP or LMPP, and generates low tracking speed, resulting in continuous power oscillations equal to changes in a predetermined perturbation size [11]. Power oscillations can be extreme since the conventional algorithms continue to search for the operating point on the P-V curve at steady-state condition (SSC), the MPP is tracked earlier [13]. A P&O-based voltage regulation loop is designed with a PID controller to increase the tracking speed of the MPP and regulate the output reference voltage faster than the conventional P&O algorithm [15]. To prove the effectiveness of the proposed MPPT technique, its performance is compared with conventional INC and perturb and observe (P&O) methods
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