J Jordi Everts

A 80-kW Isolated DC–DC Converter for Railway Applications

This paper provides an analysis of a three-phase dual active bridge (DAB) topology used as high-power-density dc-dc converter for railway applications. The three-phase DAB is analyzed concerning the current intervals, the output power, and softswitching region, including the impact of zero-voltage switching capacitors. Furthermore, two measures are proposed to achieve soft-switching in the entire operating range, being auxiliary inductors and a straightforward switching strategy called the burst mode. Optimal component values are calculated to minimize losses in the complete operating range and to assess which measure is best suited. A prototype with the specifications acquired from the application has been built, yielding an efficiency of 95.6% at a nominal output power of 80 kW.

Performance Evaluation of a Three-Phase Dual Active Bridge DC–DC Converter With Different Transformer Winding Configurations

This paper investigates the impact of three transformer winding configurations, i.e., the Y-Y, the Y-Δ, and the Δ-Δ configuration, on the performance of a three-phase dual active bridge (DAB) dc-dc converter. For each configuration, equations for the phase currents, power flow, and zero-voltage switching (ZVS) boundaries are derived for all possible switching modes of the three-phase DAB. Thereafter, a comparison is made of the stress on the switches, the transformer, and the filter capacitors for the selected winding configurations. The comparison reveals that the Y-Y and Δ-Δ configuration perform equally regarding above aspects, with the only difference of a lower winding current for the Δ-Δ configuration. The Y-Δ configuration shows a constant commutation current for phase-shifts from 0 to 30 degrees. Therefore, this configuration features a wider ZVS region for low output powers. Overall, the Y-Δ configuration performs best for power levels between 50% and 80%, regarding the stress on the switches, the transformer, and the filter capacitors. The theoretical analysis is supported with measurements obtained from a high-power experimental setup.

Using fourier series to derive optimal soft-switching modulation schemes for dual active bridge converters

A generic, Fourier-based method for the derivation of optimal, full-operating-range zero voltage switching (ZVS) modulation schemes for dual active bridge (DAB) converters is presented. Thereby, the AC-link voltages and currents, and the DABs input current and power flow, are described using trigonometric Fourier series. Furthermore, the amount of charge that is available in the bridge currents to charge the nonlinear parasitic output capacitances of the switches during commutation is deduced from the respective Fourier current coefficients. This yields ZVS constraints that are more accurate than the energy-based ZVS constraints proposed in literature. Subsequently, it is shown that by combing the equation for the DABs input current with the ZVS constraints in a numerical optimization algorithm, an optimal, ZVS modulation scheme can easily be derived with higher flexibility, lower calculation time, and lower implementation effort compared to the traditional piecewise-linear modeling approach. Although applicable to any DAB implementation, the procedure is demonstrated for a full-bridge full-bridge DAB as core part of a single-phase, single-stage, bidirectional, isolated AC-DC converter. The modulation scheme outputted by the presented Fourier-based method is compared with the modulation scheme calculated using a previously published piecewise-linear modeling approach, showing a negligible deviation.

ZVS modulation strategy for a 3 - 5 level bidirectional Dual Active Bridge DC - DC converter

This paper presents a Zero Voltage Switching (ZVS) modulation strategy for the 3 Level - 5 Level (3-5L) Dual Active Bridge (DAB) DC-DC converter. The DAB accommodates a full bridge in the primary side and two 3-level T-Type bridge legs in the secondary side, linked by a high-frequency transformer and an inductor. A ZVS modulation strategy is presented, in which commutation inductances are utilized to extend the ZVS region to the entire operating range of the converter. The configuration of the secondary-side bridge allows further flexibility, compared to a full bridge configuration, to minimize the RMS current in the inductor. The nominal power of the converter is 2.8 kW with input voltage range from 8 V to 16 V, and output voltage range from 175 V to 450 V. The RMS currents of the 3-5L DAB are compared with those of a typical 3-3L full bridge - full bridge DAB, by applying the proposed modulation strategy in the 3-5L DAB, and a strategy proposed in literature in the 3-3L DAB.

Charge-based ZVS modulation of a 3–5 level bidirectional dual active bridge DC-DC converter

This paper presents a charge-based Zero Voltage Switching (ZVS) modulation strategy for the 3 Level–5 Level (3–5L) Dual Active Bridge (DAB) DC-DC converter. The DAB combines a primary-side full bridge and a secondary-side mixed bridge (i.e. a 3-level T-type leg with a half-bridge leg), linked by a high-frequency transformer and an inductor. A ZVS modulation strategy is presented, in which a charge-based model of the non-linear parasitic output capacitances of the switches is used to accurately describe the ZVS constraints. Moreover, commutation inductances are included to extend the ZVS region to the entire operating range. The configuration of the secondary-side bridge facilitates increased flexibility compared to a full bridge configuration, in order to reduce the RMS current in the switches, inductor, and transformer. The nominal power of the investigated converter is 2.8 kW with input voltage range from 8 V to 16 V and output voltage range from 175 V to 450 V. The RMS currents of the 3–5L DAB are compared with those of a typical 3–3L DAB, applying the proposed modulation strategy in the 3–5L DAB, and a similar strategy previously proposed in literature in the 3–3L DAB.

Overview of the requirements and implementations of bidirectional isolated AC-DC converters for automotive battery charging applications

This paper is divided into three main parts. In the first part, i.e. Section II, a general outline of the system level aspects regarding battery chargers (power converters) for plug-in electric vehicles (PEVs) is given. Thereby, the different charging modes of the converters, the corresponding power levels, and the infrastructural facilities are discussed. Moreover, Vehicle-to-Grid (V2G) operation by means of grid-forming, grid-feeding, and grid-supporting converter functionality is briefly explained, and the input power quality and electromagnetic compatibility requirements are summarized. In the second part, i.e. Section III, the mutually coupled indices that determine the overall performance of the system, such as power losses (efficiency), volume (power density), weight (specific power), failure rate (reliability), and costs (relative cost), are outlined. In this context, the role that wide band-gap power semiconductors (e.g. SiC, GaN) can play in order to further improve the system performance is highlighted. In the third part, i.e. Section IV, a concise overview of the possible topological implementations for the mentioned power converters is provided. The focus is on conductive, isolated AC-DC converter topologies with high AC input power quality in terms of power factor correction (PFC) and harmonic distortion, and with bidirectional power flow capability in order to facilitate V2G operation.

ZVS modulation strategy for a three-phase dual active bridge DC-DC converter with three-level phase-legs

This paper analyzes a three-phase Dual Active Bridge (DAB) dc-dc converter with three-level phase-legs, showing a significant increase in the soft-switching region compared to two-level operation. A strategy is presented that results in a Zero Voltage Switching (ZVS) modulation scheme that relies on analytical equations, uses a small amount of switching modes, and obtains close-to-minimal rms currents.

Evaluation of a high-power three-phase dual active bridge DC-DC converter with three-level phase-legs

A three-phase dual active bridge (DAB) converter with three-level phase-legs is analyzed, showing an increased soft-switching region and a reduction in rms current in the ac-link for unequal input and output voltages compared to the conventional two-level circuit. Furthermore, a comparison of the semiconductor losses is carried out for different three-level inverter implementations using commercially available silicon (Si) and silicon-carbide (SiC) power modules. The lowest losses are found for the T-type implementation with a combination of SiC and Si power modules. Experimental results, obtained from a high-power prototype, are included to support the evaluation of the three-level three-phase DAB.

Comparative Evaluation of Bidirectional Dual Active Bridge DC-DC Converter Variants

For the realization of DC-DC converters in automotive industry, the Dual Active Bridge (DAB) converter seems to be a promising choice because of its soft-switching and high-power-density capability. Contrary to the traditional 3 level - 3 level (3-3L) DAB, a 3 level - 5 level (3-5L) DAB can operate under soft-switching and lower RMS inductor current. For this reason, a fair comparison is needed among the 3-3L DAB and two possible implementations of the 3-5L DAB, which utilize a T-Type bridge leg (3-5L-T DAB) or an NPC bridge leg (3-5L-NPC DAB) in the secondary bridge. In this paper, a comparative evaluation of the aforementioned Dual Active Bridge DC-DC converter variants is presented. The advantages and drawbacks of each concept are discussed in detail, focusing on the semiconductor chip area utilization and the impact on the converter efficiency. Furthermore, the analytical models allow a power density comparison, by correlating the component losses with their volume.

Charge-based Zero-Voltage Switching of a Flying Capacitor Resonant Pole Inverter with trapezoidal filter current

An advanced charge-based Zero-Voltage Switching (ZVS) modulation strategy for a Flying Capacitor Resonant Pole Inverter (FC RPI) with trapezoidal filter current is presented, resulting in full operating range ZVS, decreased rms value of the circulating filter current, and increased switching frequency. A charge-based model that correctly incorporates the nonlinear parasitic output capacitances of the switches is used to ensure ZVS. Increased efficiency of the multilevel RPI configuration is achieved due to minimized rms and peak value of the circulating filter current. Interleaving of multiple switching cells using simple phase control to increase the apparent switching frequency and lower the stress on filter components is investigated. The presented modulation strategy is verified using simulations from which proper operation is concluded.