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Dynamic reconfiguration, the monitoring of power production, and the fault diagnosis of photovoltaic arrays, among other applications, require fast and accurate models of photovoltaic arrays. In the literature, some models use the Lambert-W function to represent each module of the array, which increases the calculation time. Other models that use implicit equations to avoid the Lambert-W function do not use the inflection voltages to simplify the system of nonlinear equations that represent the array, increasing the computational burden. Therefore, this paper proposes mathematical models for series-parallel (SP) and total-cross-tied (TCT) photovoltaic arrays based on the implicit equations of the single-diode model and the inflection points of the current–voltage curves. These models decrease the calculation time by reducing the complexity of the nonlinear equation systems that represent each string of SP arrays and the whole TCT. Consequently, the calculation process that solves the model speeds up in comparison with processes that solve traditional explicit models based on the Lambert-W function. The results of several simulation scenarios using the proposed SP model with different array sizes show a reduction in the computation time by 82.97 % in contrast with the traditional solution. Additionally, when the proposed TCT model for arrays larger than 2 × 2 is used, the reduction in the computation time is between 47.71 % and 92.28 % . In dynamic reconfiguration, the results demonstrate that the proposed SP model provides the same optimal configuration but 7 times faster than traditional solutions, and the TCT model is solved at least 4 times faster than classical solutions. [ABSTRACT FROM AUTHOR]

This paper proposes a proton exchange membrane fuel cell control strategy to produce the power requested by an electrical load, minimizing the fuel consumption and also providing a regulated dc bus voltage to the load. The power system consists of a hybrid fuel cell/capacitor topology, and the control objective is to follow the minimum fuel consumption points for a given load power profile. This is done by controlling the air pump voltage and regulating the fuel cell current through a dc/dc switching converter. Moreover, the design and control parameters of the output dc bus are discussed, and the calculations are adjusted to a Ballard 1.2-kW Nexa power module. Finally, the control results, fuel consumption, and fuel cell protection against oxygen starvation phenomenon are analyzed and experimentally validated, contrasting its performance with the Nexa power module internal control system. Index Terms--Efficiency, fuel optimal control, optimization, oxygen excess ratio control, power control, proton exchange membrane (PEM) fuel cell.

The maximum power point tracking (MPPT) of photovoltaic systems must be as fast and accurate as possible to increase the power production, which eventually increases the PV system profitability. This paper proposes and mathematically analyses a sliding-mode controller to provide a fast and accurate maximum power point tracking in grid-connected photovoltaic systems using a single control stage. This approach avoids the circular dependency in the design of classical cascade controllers used to optimize the photovoltaic system operation, and at the same time, it reduces the number of controllers and avoids the use of linearized models to provide global stability in all the operation range. Such a compact solution also reduces the system cost and implementation complexity. To ensure the stability of the proposed solution, detailed mathematical analyses are performed to demonstrate the fulfillment of the transversality, reachability and equivalent control conditions. Finally, the performance of the proposed solution is validated using detailed simulations, executed in the power electronics simulator PSIM, accounting for both environmental and load perturbations. [ABSTRACT FROM AUTHOR]