T. Ahmadzadeh, E. Babaei, M. Sabahi, T. Abedinzadeh,
Volume 16, Issue 4 (12-2020)
Abstract
The main purposes of a transformerless grid-connected photovoltaic (PV) system consist of the reduction of leakage current, extraction of maximum power point (MPP), tracking of MPP (MPPT), controlling the active and reactive powers, and having the unity power factor. To achieve the above-mentioned aims, the following actions have been performed in this paper. First of all, a brief analysis of the transformerless PV system has been done by using the conventional full-bridge (FB) topologies with two bipolar and unipolar PWM techniques. Then, an effective solution has been also introduced to significantly reduce the leakage current in the conventional H5 FB topology. Moreover, a proper control method has been proposed by using the combination of the fractional open-circuit voltage (FOCV) and the model predictive control (MPC) strategies to extract the MPP from PV panels, control the injection of the reactive power to the gird and have the unity power factor. At last, the simulation results performed in PSCAD software will be used to prove the correct performance of the proposed control method in the improved H5 FB topology.
Milad Babalou, Hossein Torkaman, Edris Pouresmaeil, Nazanin Pourmoradi,
Volume 20, Issue 2 (6-2024)
Abstract
In this paper, a dual-active bridge converter based on the utilization of two transformers is presented. The principles of operation, switching strategy, and transmission power characteristics of the proposed converter under normal operation are discussed, comprehensively. Moreover, the RMS current of two transformers with different values of inductances of the inductors that are in series with the transformers; is discussed. The operation of the proposed dual active bridge (DAB) converter under the open-circuit failure of transformers is studied. In addition, the loss distribution of the proposed converter in different powers is investigated. The proposed dual-transformer-based dual-active bridge converter is compared with the presented converters. Finally, the proposed converter with a low-voltage side (VL= 300 V), the switching frequency of power MOSFETs (fs= 50 kHz), and an accurate model of the electric battery at a high-voltage side (VH= 450 V) are simulated to verify the way of charging and discharging the electrical battery with the proposed converter under normal and open-circuit fault of transformers.
