In practical photovoltaic (PV) installations the operating conditions of the panels the PV array is made of are different owing to different factors. Such irregular conditions are known as 'mismatching conditions' and produce multiple maxima in the power-voltage curves of any PV array. The traditional maximum power point tracking (MPPT) techniques are able to track one of those maxima, but they cannot guarantee the extraction of the maximum power the PV array would be able to deliver. To overcome this problem, many techniques have been presented in the literature: they use one converter for the entire array (centralised MPPT), one converter for each part of the array (distributed MPPT) or they reconfigure the PV array (RMPPT). This paper presents the general architectures used by 61 different MPPT techniques, by discussing their main advantages and disadvantages, in order to give to the reader a comprehensive view of both the control strategies and the architectures for extracting the maximum power from a mismatched PV field. Moreover, the widely adopted techniques for each hardware structure are presented in a structured and compact way, thus providing to the reader some guidelines regarding the technique's operation principle and hardware requirements.

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Photovoltaic (PV) arrays can be connected following regular or irregular connection patterns to form regular configurations (e.g., series-parallel, total cross-tied, bridge-linked, etc.) or irregular configurations, respectively. Several reported works propose models for a single configuration; hence, making the evaluation of arrays with different configuration is a considerable time-consuming task. Moreover, if the PV array adopts an irregular configuration, the classical models cannot be used for its analysis. This paper proposes a modeling procedure for PV arrays connected in any configuration and operating under uniform or partial shading conditions. The procedure divides the array into smaller arrays, named sub-arrays, which can be independently solved. The modeling procedure selects the mesh current solution or the node voltage solution depending on the topology of each sub-array. Therefore, the proposed approach analyzes the PV array using the least number of nonlinear equations. The proposed solution is validated through simulation and experimental results, which demonstrate the proposed model capacity to reproduce the electrical behavior of PV arrays connected in any configuration.

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In Photovoltaic (PV) systems with Distributed Maximum Power Point Tracking (DMPPT) architecture each panel is connected to a DC/DC converter, whose outputs are connected in series to feed a grid-connected inverter. The series-connection forces the output voltage of those converters to be proportional to the converter’ output power; therefore, under mismatched conditions, the output voltage of a highly-irradiated converter may exceed the rating (safe) value, causing an overvoltage condition that could damage the converter. This paper proposes a sliding-mode controller (SMC) acting on each converter to regulate both the input and output voltages, hence avoiding the overvoltage condition under partial shading. The proposed control strategy has two operation modes: maximum power point tracking (MPPT) and Protection. In MPPT mode the SMC imposes to the PV panel the voltage reference defined by an MPPT technique. The Protection mode is activated when the output voltage reaches the safety limit, and the SMC regulates the converter’ output voltage to avoid overvoltage condition. The SMC has a bilinear sliding surface designed to provide a soft transition between both MPPT and Protection modes. The SMC analysis, parameters design and implementation are presented in detail. Moreover, simulation and experimental results illustrate the performance and applicability of the proposed solution.