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A novel model-based technique is presented for maximum power point tracking (MPPT) of photovoltaic (PV) systems. In this paper, an exact single-diode circuit model without any simplification or approximation is considered. Using datasheet information, an adaptive identification technique is utilized to find the electrical parameters uniquely and precisely. After this offline identification scheme, an estimation of solar irradiation is achieved from real-time measurements of PV voltage and current. In the next step, the gradient function of power with respect to voltage is represented from strongly concave mapping between power and voltage. Since the nonlinear gradient consists the complex Lambert W-function, a mathematical formulation is derived to approximate it with conventional logarithmic functions. Finally, a gradient update law is derived to find the unknown optimal voltage value, which results in maximum power generation for any environmental condition. The proposed approach guarantees exponential convergence with highly accurate steady-state performance. [ABSTRACT FROM AUTHOR]

Islanding detection in power systems poses a challenge that can result in technical problems and safety hazards. This study examines a new passive islanding detection method for photovoltaic-based distributed generation (DG) units. The modal signal of the three-phase current and its envelope are calculated for a targeted DG unit. Variance in the autocorrelation of the modal current envelope (VAMCE) is used as an islanding detection criterion in the proposed method. The proposed method employs autocorrelation function (ACF) of modal current envelope (derived by Hilbert-transform-based approach) to extract the transient content. Then, the variance of the ACF is calculated, called criterion VAMCE to distinguish between islanded and normal operating conditions. The main advantage of the proposed technique is more relevant to its more accuracy and smaller non-detection zone in comparison with the other similar passive techniques. Since the VAMCE has significant variation during islanding conditions and negligible change in normal conditions, it can be used for detection of islanding condition effectively. The method was evaluated through several simulations under different islanded and normal operating conditions. The results confirm that the proposed method has better accuracy and speed compared to other similar methods. [ABSTRACT FROM AUTHOR]

Reliable operation of dc–dc converters is vital for many applications. An appropriate converter monitoring scheme is required for fault detection and adoption of effective remedial strategies. Switch faults and degradation of electrolytic capacitor account for a considerable portion of the converter failures. Although rate of diode failures is not remarkable, power switch may be damaged in case of diode fault occurrence. Furthermore, for applications in which a redundant switch is employed as a remedy, it will be also endangered by diode failures if diode fault detection has not been considered in the monitoring scheme. Therefore, diode condition monitoring improves reliability of the converter monitoring approaches. This paper presents a simple diagnosis technique for open-circuit and short-circuit faults of the switch and diode in nonisolated dc–dc converters. The technique only employs diode voltage as the detection signature. The diode voltage and gate driver signal are processed in a simple logic circuit to generate some indicators for switch and diode fault diagnosis. Basis of the technique is discussed in detail. Several experiments have been carried out on buck, boost, and buck–boost converters. The results confirm the technique capability for switch and diode fault diagnosis in less than one switching cycle. [ABSTRACT FROM PUBLISHER]

This study presents an optimisation method to find the best switch set (SWS) topology for reconfiguration of photovoltaic (PV) panels. An approach based on particle swarm optimisation is used to find the optimised topology. In the optimisation, an objective function is defined, in which a minimum number of switches and maximum capability for realising different desired configurations are taken into account. Although the result is a SWS with the capability of reconfiguring PV panels in different series–parallel configurations, the algorithm can be extended for deriving different SWSs aimed to realise other configurations. Some experiments were carried out to validate the proposed approach. The results confirm that the optimised SWS not only can implement different desirable configurations with a minimum number of switches but also able to overcome different abnormal conditions by a suitable switching. [ABSTRACT FROM AUTHOR]