This article presents a novel control method for a multilevel dc–dc flying capacitor converter for applications in medium voltage range. Quasi-two-level modulation provides the possibility to obtain low flying capacitance even below 1 μF, whereas the triangular current mode controller part enables to achieve zero voltage switching at turn- on for a wide operating range, lowering power losses, and providing the possibility to operate at higher frequencies. The proposed novel control converges the advantages of these both methods leading to very high efficiency with high power density. Performance of the flying capacitor converter with the proposed control method is illustrated with a model-based Saber simulation at first, and then, an experimental model operating at wide frequency range (40 ÷ 250 kHz) and in medium voltage range was designed and constructed. A series of laboratory tests at up to 1.5 kV dc and 10 kW confirmed the noteworthy characteristics of the converter. The voltage between the power devices is balanced and the efficiency achieved reached as high as 99.1%. Therefore, the proposed converter can be competitively employed against classical two-level, as well as three-level and series connection-based counterparts.

High power density, high voltage gain soft-switching PWM DC-DC converter with a tapped inductor is proposed in this paper as a front-end for low-voltage sources in energy generation systems. The leakage inductance is incorporated into the resonant tank, decreasing the component count. The use of the boost capacitor connected in series with the secondary windings of the tapped inductor causes high voltage gain at the low turn ratio of the coupled inductor. By incorporating a resonant passive clamp circuit, not only the voltage spikes on the transistor are restrained, but zero-voltage switching of the transistor and zero-current turning-off of the diodes are obtained. The resonant operation results in low power losses in the switches, providing high efficiency in a wide output power range. Owing to soft-switching operation, the transistor can be driven with a high switching frequency, providing a consolidated design of the high power density converter. The principles of operation of the converter were also analyzed theoretically. Finally, the converter is validated through a laboratory model with a power rating of 300 W and a switching frequency of 200 kHz.

The paper proposes and investigates an alternative coupled inductor configuration in a three-level interleaved dc-dc converter. The new common-leg coupled inductor structure is introduced, and possible modulation methods are studied and theoretically analyzed, focusing on the impact on current ripples, power losses, and common-mode noise. The concept is validated using an MV-rated, SiC-based bidirectional converter dedicated to battery storage application in a bipolar EV charging station, tested up to 1 kV and 10 kW. Furthermore, the comparative study shows that the suggested method exhibits a smaller volume when compared to the conventional approach with several single inductors, comparable performance but with a more straightforward inductor design than the tapped inductor solution, and full section current controllability, unlike the single-inductor option. Finally, using the proposed technique, common-mode noise can be entirely limited, allowing the minimization of excess filtering. Overall, the proposed inductor configuration can be effectively and competitively used in modern SiC-based threelevel dc-dc converters.

Boost DC/DC converters are widely used in renewable energy systems. With growing demand for high efficiency and high voltage gain, many new topologies have been published. This paper proposes a novel zero current switching (ZCS) boost converter with a tapped inductor and active edge-resonant cell (AERC). To achieve high voltage gain, the tapped inductor was implemented in the structure of the converter, and by employing an AERC, zero current switching (ZCS) of transistors was attained. Subsequently, by employing a resonant operation current, overshoots by leakage inductance were eliminated. This article presents an analysis, mathematical derivations and laboratory test results. Finally, a (30—50) V input, 380 V output and 750 W output power laboratory model operating with (45—100) kHz switching frequency was built and tested. The maximum reported efficiency was 96.6%. Soft switching of semiconductors was achieved in the whole output power range.

This work is focused on the design and experimental validation of the all-SiC active neutral-point clamped (ANPC) submodule for an advanced electric vehicle (EV) charging station. The topology of the station is based on a three-wire bipolar DC bus (±750 V) connecting an ac grid converter, isolated DC-DC converters, and a non-isolated DC-DC converter with a battery energy storage. Thus, in all types of power converters, the same three-level submodule may be applied. In this paper, a submodule rated at 1/3 of the nominal power of the grid converter (20 kVA) is discussed. In particular, four different modulation strategies for the 1.5 kV ANPC submodule, exclusively employing fast silicon carbide (SiC) MOSFETs, are considered, and their impact on the submodule performance is analyzed. Moreover, the simulation study is included. Finally, the laboratory prototype is described and experimentally verified at a switching frequency of 64 kHz. It is shown that the system can operate with all of the modulations, while techniques PWM2 and PWM3 emerge as the most efficient, and alternating between them, depending on the load, should be considered to maximize the efficiency. Furthermore, the results showcase that the impact of the different PWM techniques on switching oscillations, including overvoltages, can be nearly fully omitted for a parasitic inductance optimized circuit, and the choice of modulation should be based on power loss and/or other factors.

This paper investigates the soft-switching quasi-square-wave (QSW) technique in DC/DC SiC-based flying capacitor converter with quasi-two-level (Q2L) control establishing design guidelines for constructing high-efficiency soft-switched bidirectional converters with low-voltage power transistors. The general idea behind the soft-switching in the proposed system is based on near-CRM (critical conduction mode) operation using TCM (triangular current mode) and Q2L control with the addition of auxiliary transistor capacitances. The soft-switching process is based on a resonance between the capacitances in parallel to each transistor, and the main inductor - ZVS at turn-on is ensured through proper modulation pattern according to TCM-Q2L control, and the turn-off soft-switching mechanism is assured through the novelty in the form of adding auxiliary capacitance in parallel to each of the SiC power MOSFETs according to QSW operation. Thus, the converter can reach very high efficiency (peak at 99.5%), maintaining soft-switching for a wide operating range, using only small auxiliary SMD capacitors and a low-volume flying capacitor, leading to high power density. The presented study is based on experimental tests using a 1.5 kV model at up to 15 kW and includes the impact of various auxiliary capacitance values and optimal capacitor value selection for maximizing the converter efficiency.