Distributed energy resources have been broadly developed in recent years for supporting DC and AC microgrids. Unfortunately, most of them produce low output DC or AC voltages, and interfacing converters are required. These are implemented either in single‐stage or dual‐stage configurations. Step‐up converters are the essential section in dual‐stage designs, which their producing gain is important. Improving the boost factor and efficiency as well as decreasing the number of required components and electrical stresses on power components are the most critical challenges in designing such topologies. Continuing past efforts, this paper proposes a new non‐isolated step‐up DC/DC converter that can be used in low‐voltage distributed power systems and many other applications requiring step‐up DC/DC conversion. The topology requires only one power switch located on the converter's low voltage (LV) side. Hence, it can be easily selected from LV ratings, low on‐resistance power semiconductors. Besides, the converter operates with a continuous input current, which is a valuable feature in connection with current‐sensitive voltage resources. Compared with the recently proposed topologies, the topology provides better conversion gain and efficiency. In this article, the operating principle of the introduced converter is comprehensively investigated. Also, in order to examine the converter performance, experimental results will be presented and analyzed. For this purpose, a 400 V/400 W prototype has been designed and built. Results confirm the above claims and show that the converter efficiency equals 96.1%, and it produces high output voltage gain about 12 times.
This paper proposes a nonisolated high step‐up dc‐dc converter, which optimally integrates coupled inductor, and diode‐capacitor and provides superior features such as high gain, high efficiency, and low voltage stresses on power switches. Moreover, the common ground between the input and output of the proposed converter makes it appropriate for photovoltaic systems. It consists of two power switches, one inductor, one coupled inductor (CI), four diodes, and four capacitors. The power switches are exposed to low voltage stresses and are selected from low voltage ratings and low on‐resistance semiconductors. The topology, operating principle, complete steady‐state and ac small‐signal models, loss model, and design criterion are presented and described in detail. Also, the proposed topology is compared with other previous topologies. In order to evaluate the performance of the proposed converter, a 400 V/400 W experimental prototype has been designed and built. Experimental results validate the theory and show the converter produces high gain (14.25 times in the full‐load condition tested) and operates with high efficiency (94.9% in the full‐load condition).
Here, a new two‐input step‐up DC–DC converter for electric vehicles (EVs) and renewable energy systems (RESs) is proposed. It requires few components and provides high step‐up voltage gain and high efficiency. The topology includes two input channels connected to two energy sources based on the “switch‐mode coupling” method. Sources supply the load via the proposed converter. Each source can charge another if it is rechargeable. The regenerative output side energy is also transmitted to the rechargeable source thanks to the bidirectional power transferring capability. Current sensitive resources can be employed as the converter operates with the continuous input current. The topology comprises only one main power switch located on the low‐voltage side; therefore, it is exposed to low voltage stress and can be readily picked up from low voltage rating semiconductors with small on‐resistance. Thanks to this feature, the conduction loss decreases considerably. The input and output terminals have a common ground. This paper demonstrates the theory and operating principle of the proposed topology. Experimental results are also presented and examined to verify the converter. For this purpose, a 48/400 V/1 kW prototype has been designed and built. Results confirm the converter and its operation.
This paper proposes a new single‐phase direct step‐up ac–ac converter by modifying the p‐type impedance source. It provides a high boost factor as well as high efficiency, while only six parts are required to design it, involving just two bidirectional power switches. A safe commutation method has been applied to power switches to make the converter snubber‐free and high efficient. Input and output harmonic filters are no longer required since input and output currents variate continuously with small ripple and low total harmonic distortion (THD). The proposed topology only modulates the output voltage amplitude, not the phase and frequency, so the output frequency is identical to the input frequency and constant. Thus, it can be utilized in step‐up conversion applications, like inductive power transmission from low ac voltage sources. Input and output have the same ground, which is a good protective feature. In this paper, the operating principle of the converter is demonstrated. Experimental results have been represented to evaluate the performance of the converter. For this purpose, an experimental prototype has been fabricated. Results are investigated and compared with other previous step‐up ac–ac converters. Results confirm the theory, operating principle, and performance of the converter.
Bidirectional synchronized transfer (BST) in variable frequency drive (VFD) systems implies automatic synchronization with seamless transfer of the motor to the grid or take‐over of the motor from the grid. This feature is realized if the magnitude, frequency, and phase angle of the VFD voltage and the grid voltage are synchronized. So, an accurate synchronization algorithm is necessary. This paper proposes a new BST method based on the discrete Fourier transformation (DFT) that obtains the magnitude, frequency and phase angle of VFD and grid voltages precisely through determining the fundamental components. This new BST coordinates the output voltage of the VFD with the grid using two error amplifiers. Also, additional decoupling reactors or transformers are no longer required by using this method due to exact estimation and synchronization. Furthermore, the algorithm can be integrated into any motor control strategy. This paper presents the principle of the proposed BST comprehensively and evaluates it by experimental results. The algorithm is tested on an induction motor via a 13‐level cascaded H‐bridge (CHB) inverter and the V/Hz constant control. The effect of BST on the motor voltage and current, the inverter current and dc‐link voltage is also examined. Results confirm the proposed strategy.
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