A switched-capacitor (SC)-based dual-switch dc-dc converter with a high-boost voltage gain is proposed in this paper. The proposed converter can obtain a high-voltage gain with a small duty cycle, which decreases the voltage stress and the conduction loss on the power switches. This paper presents the key waveforms, the operating principles at the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM), and the parameter design. Moreover, a comparison between the proposed converter and other non-isolated converters has been completed. To verify the operating principle, a 200 W prototype is constructed with an input voltage of 25 V to 50 V and an output voltage of 200 V. The simulation and experiment results are shown.

In this paper, two switched-capacitor quasi-switched boost inverters (qSBIs) are proposed. By adding one capacitor and one diode to the qSBIs, the proposed inverters achieve high voltage gain with low voltage stress on active switches, capacitors, and diodes. The proposed inverters can extend to n-cell for voltage gain improvement. The operating principle, steady-state analysis, and impedance parameter selections of the proposed inverter are presented. A full comparison between the proposed inverter and other impedance-source inverters is addressed. A 500-W prototype is built to verify the operating theory of the proposed inverter in both the standalone mode and the grid-connected mode. Simulation and experimental results validate the theoretical analysis.

Two high voltage gain quasi-switched boost inverters (HG-qSBIs) are introduced in this paper. The proposed HG-qSBIs has the following characteristics: 1) continuous input current with low ripple; 2) reduced voltage stress on the capacitor, switch and diodes; 3) shoot-through immunity; 4) achieved high voltage gain with single-stage conversion; and 5) improve the output voltage capability with using high modulation index. A novel PWM control technique is proposed for the introduced HG-qSBI. Operating principle, circuit analysis, and passive component design guideline of the HG-qSBI are addressed. Comparison analysis between the introduced HG-qSBI and other Z-source-based high voltage gain inverters is presented. A prototype is made to test the introduced HG-qSBI. Simulation and experimental verifications are shown to prove the accuracy of the theoretical analysis.

Fault-tolerant methods have been recognized for improving the reliability of multiphase bidirectional dc–dc converters, including current-fed and voltage-fed dual active bridge converters. Fault-tolerant research for voltage-fed dual active bridge converters has caught much attention recently. In this article, a new fault-tolerant method for current-fed dual active bridge (CF-DAB) converters with blocking capacitors is proposed. The operation of the CF-DAB converter when an open-circuit fault occurs is comprehensively presented and analyzed. A frozen-phase fault-tolerant method with additional blocking capacitors on both sides of the transformer is proposed. The aim of the use of blocking capacitors is to block the dc current component of the high-frequency transformer, which could avoid the core saturation of the transformer. Also, the dc blocking capacitors help isolate the faulty phase when a frozen-phase fault-tolerant method is applied. The proposed method is shown to be a practical, simple, low loss, and effective solution for not only open-circuit fault isolation but also for shedding capability of the multiphase converter. The proposed concept could be applied for general multiphase current-fed converters. The experiment of a 6-kW prototype is implemented to confirm the proposed concept.

In this paper, a modified three-phase two-level voltage source inverter is proposed. By combining the conventional three-phase H-bridge inverter with a switched-capacitor-voltage-doubler network, the DC-link voltage of the proposed inverter is double with respect to the input DC voltage. As a result, the output voltage of the proposed inverter can be higher than the input DC voltage. Furthermore, a common-mode voltage (CMV) of the proposed inverter can be reduced through controlling the two additional switches based on the space vector pulse-width modulation. Compared to the existing modulations and topologies, the variation in CMV can only be up to 16.6% of DC-link voltage. Furthermore, the voltage stress across additional switches and diodes is equal to half of DC-link voltage. Mathematical analysis, operating principles, and comparison of the proposed three-phase two-level voltage source inverter with the conventional three-phase voltage source inverters are presented. The simulation results based on PLECS software verify a good performance of the proposed inverter. Finally, a laboratory prototype based on a TMS320F280049 DSP is developed and experimental tests are carried out to validate the effectiveness of the proposed three-phase inverter topology

In grid-connected photovoltaic (PV) systems, a transformer is needed to achieve the galvanic isolation and voltage ratio transformations. Nevertheless, these traditional configurations of transformers increase the weight, size, and cost of the inverter while decreasing the efficiency and power density. The transformerless topologies have become a good solution. However, the problem is that commode-mode voltage and leakage current can occur via the stray capacitors between the PV array and the ground of the inverter. Various transformerless inverters have been introduced with different techniques, such as reducing the common-mode voltage or eliminating the leakage current. Furthermore, to introduce the development of transformerless PV inverters, especially in three-phase two-level inverter systems, this paper provides a comprehensive review of various common-mode voltage reduction three-phase two-level inverters.