In this paper, a design method for a photovoltaic system based on a dual active bridge converter and a photovoltaic module is proposed. The method is supported by analytical results and theoretical predictions, which are confirmed with circuital simulations. The analytical development, the theoretical predictions, and the validation through circuital simulations, are the main contributions of the paper. The dual active bridge converter is selected due to its high efficiency, high input and output voltages range, and high voltage-conversion ratio, which enables the interface of low-voltage photovoltaic modules with a high-voltage dc bus, such as the input of a micro-inverter. To propose the design method, the circuital analysis of the dual active bridge converter is performed to describe the general waveforms derived from the circuit behavior. Then, the analysis of the dual active bridge converter, interacting with a photovoltaic module driven by a maximum power point tracking algorithm, is used to establish the mathematical expressions for the leakage inductor current, the photovoltaic current, and the range of operation for the phase shift. The design method also provides analytical equations for both the high-frequency transformer equivalent leakage inductor and the photovoltaic side capacitor. The design method is validated through detailed circuital simulations of the whole photovoltaic system, which confirm that the maximum power of the photovoltaic module can be extracted with a correct design of the dual active bridge converter. Also, the theoretical restrictions of the photovoltaic system, such as the photovoltaic voltage and power ripples, are fulfilled with errors lower than 2% with respect to the circuital simulations. Finally, the simulation results also demonstrate that the maximum power point for different environmental conditions is reached, optimizing the phase shift factor with a maximum power point tracking algorithm.

This paper presents a mathematical procedure for modeling rectangular (N rows with M modules each) and non-rectangular photovoltaic (PV) arrays in Total Cross-Tied (TCT) configuration operating in uniform and mismatching conditions. The proposed model uses the simple single diode representation for each PV module; then each row of the TCT array is represented as an equivalent non-linear PV circuit with a bypass diode, which allows to represent the TCT array as one string of equivalent PV circuits. The inflection voltages (array voltages that turn off the bypass diodes) of the string are calculated in order to solve only the non-linear equation system related to the active equivalent PV circuits for calculating the array current for a given voltage. Such a strategy reduces the computational burden and improves calculation speed. A TCT array of 4×2 with deep mismatching conditions was implemented in PSIM software to validate the proposed model, obtaining a correlation between model predicted data and the circuital simulation. The accuracy and improved calculation speed of the proposed model allow its use altogether with reconfiguration techniques as well as to reduce the time of energetic evaluations of TCT arrays for PV planning.

An active bypass structure that was initially proposed as a solution to minimize the reduction in produced power caused by mismatch of photovoltaic modules is compared in terms of efficiency with single and distributed maximum power point solutions based in more conventional dc-dc structures. The analysis and simulations performed under simplified losses assumptions demonstrate that the bypass structure is very competitive with respect to boost, buck or buck-boost based solutions in terms of efficiency.