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This review covers global maximum power point tracking (GMPPT) methods for photovoltaic (PV) systems under partial shading conditions. Unlike the previous review works that primarily focused on soft computing and hybrid GMPPT, this study gives exclusive attention to the improvement achieved by the conventional MPPT (perturb and observe, hill climbing, and incremental conductance). The improved methods include the popular 0.8 × V oc model and, more recently, the skipping algorithms. In addition to providing qualitative descriptions of the available techniques, this work also attempts to provide a fair evaluation of GMPPT to determine their comparative performances. The competing algorithms, which are selected to represent every category (conventional and soft computing and hybrid MPPT), are benchmarked under carefully selected operating conditions and shading scenarios. The evaluation is focused on four main criteria: tracking accuracy, convergence time, length of voltage fluctuations, and transient efficiency during the search for the global maximum power point. The results obtained from this study can become a basis for researchers and designers to select the best MPPT technique for their respective applications.

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The direct and indirect control methods are commonly used for maximum power point tracker (MPPT) of photovoltaic (PV) systems. Due to the absence of the literature that assess their performance in a comprehensive way, this work attempts to analyze the effectiveness of both control methods for the perturb and observe (P&O) MPPT algorithm. The MATLAB/Simulink simulation is verified experimentally using a PV array simulator and the dSPACE DS1104 DSP board driving a buck-boost converter. The results show that the indirect method exhibits lower steady-state oscillation and is less sensitive to rapid irradiance change and load variations. It increases the steady-state efficiency by 1.6%. Furthermore, under irradiance and load step changes, the transient efficiency increases by 29% and 30%, respectively. Based on these findings, it is envisaged that the indirect method is more suitable to be used as the controller in conjunction with the MPPT algorithm. K E Y W O R D S direct control, indirect control, maximum power point tracking, perturb and observe, photovoltaic system LIST OF SYMBOLS AND ABBREVIATIONS: Φ D , duty cycle perturbation; Φ V , voltage perturbation; D, duty cycle; D MPP , optimum duty cycle; D ref , reference duty cycle; G, irradiance; PV, photovoltaic; P&O, perturb and observe; P act , actual measured output power; P act , actual measured voltage; P pre , previous value for power; MPPT, maximum power point tracking; MPP, maximum power point; V PV , photovoltaic voltage; V ref , reference voltage; V pre , previous value for voltage.

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