Cryogenic step-down dc-dc converters for supplying high-temperature superconducting magnets operate from low dc input voltages in the order of 1 V and provide high output/magnet currents. The proposed three-switch T-type (3STT) bridge-leg utilizes the (limited) reverse-blocking capability of standard gallium nitride (GaN) transistors to provide the same functionality (bipolar output voltage) as a conventional full-bridge (FB) topology. Advantageously, the 3STT features only a single transistor in the load current path (instead of two for the FB), reducing conduction losses by at least 50%. Loss measurements of a 25 A 3STT phase module demonstrator operating at 77 K (immersed in liquid nitrogen) verify the concept.

This letter presents a comparative life cycle assessment of two ultralightweight, bidirectional, nonisolated buck-boost DC-DC converters for hybrid (fuel cell and battery) powertrains of electric vertical takeoff and landing aircraft: A two-level (2 L) SiC design and a three-level (3 L) GaN flying-capacitor design. Embodied and use-phase carbon footprints are evaluated for representative urban and regional mission profiles. Whereas the specific 3 L design shows nearly twice the gravimetric power density and slightly lower embodied emissions, its lower conversion efficiency consistently results in higher overall life cycle carbon footprints compared to the selected 2 L design. The results demonstrate that despite aggressive weight reduction, efficiency remains the dominant factor governing the environmental performance of airborne DC-DC converters.

The clean energy transition and the emergence of an all-electric society critically depend on power electronics and digitalization, both of which require substantial amounts of (critical) raw materials with limited availability due to physical, economic, and geopolitical constraints. However, the total material demand—especially considering the necessary expansion of transmission and distribution infrastructure—remains insufficiently quantified, posing challenges for achieving netzero CO₂ emissions and zero end-of-life waste within a circular economy. While power conversion efficiency remains relevant, its importance is expected to diminish in increasingly renewable electricity systems, shifting focus toward embodied carbon emissions and material efficiency during manufacturing. This work highlights the need to integrate environmental impact indicators beyond carbon footprint into multiobjective design optimization of power electronic systems. A major barrier is the lack of standardized, transparent environmental data for components, calling for improved data availability, harmonized assessment methodologies, and enabling tools such as digital datasheets. Furthermore, life-cycle strategies—including durability, repairability, reuse, and recycling—are assessed, emphasizing that recycling should follow efforts to extend product lifetime and utility while preserving material quality. The paper also discusses emerging business models and underscores the importance of transdisciplinary research and education to equip engineers with life-cycle thinking for sustainable system design.

Integration is a fundamental innovation vector and features prominently among the X-Concepts of power electronics (modularization, decentralization, digitalization, hybridization, and integration) that facilitate x-times performance improvements, utilizing basic scaling laws. After briefly introducing these X-Concepts, the paper takes a holistic perspective on integration in power electronics and highlights the various aspects beyond the typical focus on maximizing power density of components and building blocks by means of advanced packaging and manufacturing methods: Integration concepts exist on all hierarchical levels of power electronics functional elements and units (materials, component, building blocks, converters, systems, and systems of systems), and encompasses not only the hardware, but also the software/control domains, especially on the higher hierarchical levels. Salient examples for integration on all levels are provided. Moreover, we discuss benefits and barriers of integration in power electronics, and challenges and opportunities for academic research. There is an immediate need for research to drive integration on all levels in combination with the other X-Concepts. Thereby, new tools for the multidomain design of highly integrated systems are necessary, which should also inform DTs of hardware realizations to enable augmented-reality experimental analysis, i.e., enhancing measured terminal waveforms by estimates of nonaccessible inner quantities, possibly using AI and/or machine learning. Finally, we consider power electronics integration in the wider context, i.e., complementing technological by economical and environmental aspects, which leads to the "Integration Trilemma" representing the three key competing requirements in the context of integration: ultra-compact realizations of units with specific functionality, low costs/economies of scale through standardization, and, importantly, the dismantlability at the end of life, which is crucial for facilitating repair, refurbishment, and recycling, i.e., compatibility with a future circular economy: Power Electronics 5.0, which refers to the general next step of power electronics development where X-Concepts etc. are implemented in an environmentally compatible form.

The rapid growth of AI datacenters and the transition toward megawatt scale power consumption of single server racks demand a fundamental redesign of datacenter power distribution architectures. Conventional low voltage ac (LVac) systems face increasing limitations in efficiency, scalability, and material usage. Solid state transformers (SSTs) offer a pathway to compact medium voltage ac to low voltage dc (MVac LVdc) conversion, enabling MVac distribution directly to the server racks. However, today’s industrial fully modular SST demonstra-tors show limited power density of roughly 0.2 MW/m3, which is insufficient for supporting the targeted high compute densities. This paper surveys emerging single-stage and quasi single-stage SST topologies with the potential for breaking through the power density barrier and achieving 1 MW/m3 at 99% efficiency. Alternatives based on low-frequency transformers for near term adoption of LVdc distribution are also discussed. The paper highlights the need for a holistic comparative benchmarking of the different distribution architectures together with protection methods and SST concepts, especially including future MVdc distribution and MVdc-LVdc SSTs close to the server racks.

Variable speed drives (VSDs) operating from a threephase mains are typically realized as ac-ac voltage dc-link/source converters (VSCs). Compact VSCs using wide-bandgap (WBG) semiconductors often require LC output filters to protect the motor from high dv/dt of the switched voltage. Ac-ac current dclink/source converters (CSCs) featuring a back-to-back connection of a current-source rectifier (CSR) and current-source inverter (CSI) by a shared dc-link inductor inherently provide continuous motor voltages. This paper introduces the loss-optimal operating mode of ac-ac CSCs: using the minimum possible and hence time-varying dc-link current (the maximum absolute value of the CSR and CSI phase currents) minimizes the conduction losses and either the CSR or the CSI operates with 2/3-PWM (one phase terminal clamped to the dc-link inductor while only the remaining two phase currents are synthesized with PWM), reducing switching losses. The respective other stage employs PWM in all three phases (3/3-PWM) and shapes the dc-link current. A proposed synergetic control method realizes loss-optimal operation for the entire output voltage and current range of the ac-ac CSC, with motor voltages lower and higher than the grid voltage, and ensures smooth transitions between operating points. Experimental results of a 1.4 kW, 200 V (line-to-line rms) ac-ac CSC demonstrator using first-generation 600 V, 140 mm Omega monolithic bidirectional GaN transistors, grid-side and motor-side EMI filters, and a switching frequency of 72 kHz confirm the loss optimal operation (measured nominal ac-ac efficiency increases by 0.3% to 97% compared to conventional operation; part-load efficiency gains of up to 1% are observed) and seamless transitions between operating points.

Grid-variable speed drives (VSDs) are ac-ac converters that ideally provide smooth sinusoidal output voltages for compatibility with standard motors, avoiding over-voltage and/or EMI issues if long motor cables are used. Such ac-ac VSDs are either realized as a voltage-source converter (VSC) with an output filter or as a current-source converter (CSC), which inherently provides smooth motor voltages. CSCs require switching devices with bipolar voltage blocking capability, leading to a significant disadvantage regarding chip area usage compared to VSCs. The recent availability of 600 V GaN monolithic bidirectional power transistors removes this disadvantage and therefore motivates an in-depth comparison of a VSC and a CSC with identical system specifications (1.4kW, 200 V line-to-line-rms, 97% nominal efficiency, conducted EMI limits on grid and motor side) and roughly equal chip area usage as the CSC employs first-generation 140 m Omega GaN monolithic bidirectional switches (M-BDSs). The presented 600V-GaN-based ac-ac VSC and the CSC demonstrators achieve similar power densities of 1.7 and 1.8 kW/dm(3), respectively, and almost equal nominal efficiencies of 97%. The CSC shows generally higher part-load efficiency, which is reflected in weighted efficiencies of 95.7% for the VSC and 96.6% for the CSC, considering the NEMA Power Index mission profile for variable-speed centrifugal systems like pumps, fans, or compressors. EMI pre-compliance tests confirm that both demonstrators meet the same conducted EMI limits, and radiated EMI pre-compliance testing of the CSC indicates the effectiveness of the motor-side EMI filter even with inexpensive unshielded motor cables.

Voltage-source inverters (VSIs) provide dc-ac conversion in three-phase motor drives, e.g., operating from a common dc-bus in industry or from a battery in electric vehicles. To comply with electromagnetic interference (EMI) regulations, dc-side passive filters are needed, which can contribute up to 30% of the total converter weight/volume. Consequently, active filters (AFs) are of interest: Even though the AF effectiveness becomes limited at higher frequencies, the cutoff frequency of the remaining passive filter can be increased and its size thus substantially reduced. This paper proposes a common-mode (CM) AF for six-switch three-phase VSIs operated with standard SPWM or SVM. The AF only requires two low-voltage half bridges and a capacitive injection network. The operating principle, sensitivities, and design aspects are presented, and detailed circuit simulations of an industrial motor drive ($\mathbf{4 0 0 ~ V ~ d c, ~} \mathbf{2. 5 ~ k W}$, IEC $\mathbf{6 1 8 0 0 - 3 ~ E M I}$ limits, 24 V AF supply) and an EV traction inverter (800 V dc, 125 kW, CISPR 25 EMI limits, 48 V AF supply) verify the concept, indicating a reduction of the required CM filter inductance by a factor of 2 (EV) to 6 (industrial) compared to a passive filter.

Conventionally, high-voltage batteries are interfaced to ac systems (e.g., motors or the mains) via three-phase dc-ac inverters. Recently, battery-integrated multilevel inverters (BIMIs) have attracted interest by distributing the power electronics within the battery: each battery cell (or group of battery cells) is equipped with a low-voltage switching stage, and the resulting modules are cascaded into one string per phase. A first variant uses fullbridge (FB) switching modules with four switches each, whereas a second option termed “BM3” requires only three instead of four switches per module, which restricts the string output voltage to positive values and hence doubles the number of modules compared to the FB-BIMI (for equal ac output voltage capability), but facilitates paralleling of battery cells for lower instantaneous string output voltages. This paper first derives the optimal BM3BIMI configurations for a given number of modules, minimizing conduction losses. Then, for equal total silicon (Si) chip area, an FB-BIMI still exhibits $\mathbf{1 0 - 3 0 \%}$ lower conduction losses (depending on the modulation index) than a BM3-BIMI. To compare systems with different semiconductor materials, i.e., a two-level (2L) silicon carbide (SiC) inverter and BIMIs with Si switches, a possible characteristic is the embodied energy per semiconductor die area, which is closely related to the embodied carbon footprint and also related to cost. Targeting equal total embodied carbon footprint of the power semiconductors, a BIMI can thus use 3.25 times more Si chip area than a 2 L SiC inverter $(225 \mathrm{~kW}, 800 \mathrm{~V}$ dc) with a dc-side battery, which then achieves almost a factor of five lower total losses-even when including switching losses-than an FB-BIMI at nominal current. Furthermore, due to their phasemodular nature, BIMIs introduce strong low-frequency pulsations in the battery power flow, leading to approximately twice the battery losses compared to a $\mathbf{2 L}$-based system using the same number of battery cells.

Variable speed drives (VSDs) operating from the mains can be realized either with a voltage dc-link/voltage-source converter (VSC) or, alternatively, with a current dc-link/current-source converter (CSC), which has received renewed interest recently due to the availability of monolithic bidirectional (M-BDS) GaN power transistors. Considering equally rated ac-ac VSC and CSC systems with sinusoidal output voltages (additional LC filter for the VSC, inherently present filter capacitors for the CSC), this article first derives equivalent dc-dc converter models that accurately capture the dynamic behavior of the ac-ac converters and thus advantageously allow for a straightforward design and analysis of the converter control systems. Detailed experimental results obtained with realized ac-ac VSC and CSC prototypes (1.4 kW, 200 V line-to-line rms, and 600-V GaN monolithic bidirectional power transistors in the CSC) show very close matching of the open-loop and the closed-loop behavior with that predicted by the dc-dc equivalent circuits. Therefore, these circuits are then utilized to compare the small-signal and large-signal output voltage control performance of the VSC and the CSC, indicating certain advantages for the CSC regarding small-signal bandwidth (5 kHz versus 1.8 kHz for 72-kHz switching frequency, identical for both systems) and, in case of the CSC, highlighting the trade-off between control dynamics (dc-link current kept at the nominal value) and efficiency (dc-link current adapted to the load). Finally, a case study considering the time until nominal current is reached in an exemplary motor at standstill finds mixed comparative large-signal performance of VSC and CSC; a CSC variant with the output capacitor selected for equal high-frequency ripple as the VSC is slower than the VSC (by around 45% for the considered converter's specifications) whereas a CSC variant with the output capacitor selected for equal fundamental-frequency reactive power consumption as the VSC is faster (by around 40% for the considered converter's specifications).

The three-/single-phase ac input single-stage isolated eXtended-functionality rectifier (X-Rectifier) EV on-board charger (OBC) employs 650V GaN monolithic bidirectional power transistors (M-BDS) in the input stage, provides sinusoidal input currents and bidirectional operation in three-phase and split/singlephase grids without power derating, operates from asymmetrical three-phase mains, provides reactive power if needed, and supports extremely asymmetric phase loading in islanding/standalone mode. This paper first presents an improved X-Rectifier standard modulation method (M#1) with significantly lower current stresses compared to a previously published proof-of-concept method while being applicable for all operating modes discussed above. Next, the optimization of M#1 regarding semiconductor losses is discussed and the implementation of near-optimum secondary-side duty-cycle calculation (named M#2) without requiring high-dimensional look-up-tables is introduced. Considering a 6.6kW X-Rectifier and a typical charging process, simulation results indicate an improvement of the average semiconductor efficiency from 98.6% for M#1 to 98.9% for M#2, i.e., a semiconductor loss reduction of about 20%.

Remotely operated underwater vehicles (ROVs) are crucially important in deep-sea exploration. Today, ROVs are typically supplied from a surface vessel via a medium-voltage (MV) 50 Hz/60 Hz ac umbilical. The thus bulky and heavy step-down transformer aboard the ROV complicates achieving neutral buoyancy of the ROV. Further, for a given diameter, dc cables offer lower losses and/or higher power transfer capability than ac cables. Therefore, this paper conceptualizes an MVdc power supply system, which is based on using identical modular dc-transformer (DCX) converters in input-parallel output-series (IPOS) configuration aboard the vessel and in input-series output-parallel (ISOP) configuration aboard the ROV. The DCX concept ensures natural voltage sharing among the series-connected converter modules, full soft-switching operation of the 900V and 1200V SiC power transistors of the converter modules, and does not require any closed-loop control. A detailed analysis of the dynamic behavior of this open-loop DCX ROV power supply, including the MVdc umbilical, is conducted and safe operation in the presence of sudden load changes can be assured. Further, the performance limits of the converter system and the umbilical cable are systematically assessed by means of multi-objective Pareto optimization. A higher MVdc transmission voltage benefits the umbilical design and efficiency, but lowers the IPOS/ISOP DCX converter efficiency and/or power density. Hence, an MVdc level of 4 kV is identified as a system-level sweet spot for a 50kW DCX work-class ROV power supply with a 4000m umbilical, achieving an overall system efficiency (DCX-umbilical-DCX) of around 97%. Finally, two industrial prototypes of 50kW, 600 V/4 kV DCX IPOS/ISOP converters are realized and successfully tested in a back-to-back configuration, indicating a rated-power efficiency of around 99% per DCX converter stage.

Nonisolated three-phase ac/dc electric vehicle (EV) chargers show improved efficiency and power density compared with their counterparts with a galvanic isolation stage, but residual current devices (RCDs) are mandatory to ensure electrical safety. However, RCDs are prone to nuisance tripping caused by low-frequency (LF) common-mode (CM) leakage currents through the ground, which therefore must be suppressed. Therefore, first, modulation schemes that do not result in LF CM voltages (i.e., do not use third-harmonic voltage injection) that could drive LF CM currents through parasitic capacitors from the dc output to ground must be used. Second, closed-loop ground current control (GCC) ensures near-zero LF CM leakage currents even with a direct connection of the charger dc output midpoint to protective earth (PE). Considering a voltage DC-link power-factor-correction (PFC) rectifier system that consists of a boost-type three-level T-type (Vienna) ac/dc-stage and a dc/dc-stage with two stacked buck converters, this article proposes a new modulation scheme for buck-mode operation at low dc output voltages: the dc/dc-stage then shapes the DC-link voltage such that only one of the ac/dc-stage's three bridge-legs operates with high-frequency (HF) switching [1/3-pulse-width modulation (PWM)] at any given time, and, different from previous methods, does not require third-harmonic injection to do so. Furthermore, a synergetic GCC is proposed, which operates the two converter stages in the loss-optimum mode for any output dc voltage (buck-mode and boost-mode) and regulates the LF CM ground current to near zero. The proposed concepts are verified using a 10-kW hardware demonstrator with a wide output voltage range (200-800V) and a direct connection of the dc output midpoint to PE, considering terra-terra (TT) and terra-neutral (TN) grid grounding systems, whereby the proposed GCC results in LF CM leakage currents below 7mA, i.e., far below typical RCD trip limits (30mA). The test voltages obtained with the human-body impedance model from UL 2202 are below 120mV, i.e., below 50% of even the most stringent limit of 250mV of the standard.

DC loads or sources like motor drives, batteries, and strings of photovoltaic (PV) panels with power levels up to the lower single-digit kilowatt range are typically connected to the single-phase mains using bidirectional ac-dc converters providing power factor correction (PFC) functionality. Often, a dc output voltage range spanning from values lower than to values greater than the grid voltage amplitude is required, and hence, the ac-dc converter must provide buck-boost capability. As an alternative to conventionally used two-stage systems, single-stage converters promise lower realization effort and, in particular, fewer active components like power transistors. This article, therefore, analyzes a new bidirectional single-stage single-phase ac-dc buck-boost converter with only three power transistors, whose topology is identified using a systematic approach that is briefly summarized. Advantageously, the new ac-dc converter's negative dc output terminal is connected to the mains neutral, i.e., there is no common-mode (CM) voltage at the dc output. The operating principle is explained in detail, and a new advanced modulation method is proposed, which reduces the switching losses by more than 33% and lowers the component stresses. A 3.3-kW proof-of-concept (non-optimized) demonstrator is developed, which connects to the single-phase European ac mains (230 V rms, line-to-neutral) and provides a wide dc output voltage range of 300-450 V. Both the conventional and the proposed advanced modulation method are experimentally verified, confirming an improvement of the peak efficiency from 95.9% to 96.7% (300 V dc output, 2.5 kW output power) for the advanced modulation method.

Single-phase-supplied variable-speed drive (VSD) systems are widely used in industrial applications, typically following a two-stage design with a boost-type power factor correction (PFC) rectifier at the input and a three-phase voltage source inverter (VSI) at the output. However, the reliance on large electrolytic DC-link capacitors, required to buffer power pulsations at twice the grid frequency, together with the boost inductor, introduces drawbacks in terms of reliability, volume, cost, and complexity. To address these limitations, a dualinverter topology with a three-phase open-end winding (OEW) machine and the motor power pulsation buffer (MPPB) concept is employed. In this approach, power pulsations are absorbed by the total drive system’s inertia, drastically reducing the required DClink capacitance and thereby eliminating the need for electrolytic capacitors, which enables a more compact, reliable, and longlifespan drive system. This paper presents hardware verification of the dual-inverter MPPB system. A custom-built 1.8 kW demonstrator, supplied from a single-phase $230 \mathrm{~V}_{\text {rms }} \mathrm{AC}$ grid and driving a threephase OEW motor, is developed and experimentally tested. The measured waveforms confirm that power pulsations are buffered in the mechanical inertia rather than in capacitors, while maintaining PFC operation, regulating the secondary DClink voltage, and ensuring stable speed control. These results validate the effectiveness of the dual-inverter MPPB concept.

Medium-voltage (MV) ac to low-voltage (LV) dc conversion for, e.g., high-power EV charging can be realized either with a low-frequency transformer (LFT) and a downstream LV ac-dc converter, or, alternatively, as a modular solid-state transformer (SST) that employs high-frequency (HF) transformers to provide galvanic isolation. Both solutions achieve similar power conversion efficiencies in the order of 98% but differ significantly regarding complexity and the types and amounts of employed components and materials. Thus, this paper compares the two approaches regarding the embodied carbon footprint and the material usage, on the basis of industrial 400 kW first-generation and 1200 kW second-generation SST demonstrators, highlighting the potential of SST technology to benefit from improvements in power electronics whereas the LFT-based solutions remain constrained by high material usage for the transformer. Specifically, the 1200 kW second-generation SST demonstrator features only about 40% of the mass (2 kg/kW) and about 2/3 of the embodied carbon footprint (13.7 kg CO2eq/kW) of an equally rated LFT-based solution.

Solid-state transformers (SSTs) are considered for interfacing a medium-voltage (MV) ac grid to a low-voltage (LV) dc load in applications like high-power EV charging. This paper provides the first detailed analysis of a new modularized bridge rectifier (mBR) SST, which essentially consists of a three-phase diode rectifier with isolated dc-dc converters connected in parallel to the diodes, explains the operating principle, proposes a control method, and verifies the theoretical considerations with comprehensive circuit simulations. Finally, considering a 10kV ac mains input, an 800V dc output and a rated power of 1MW, a comparative evaluation of the mBR SST against a state-of-the-art modular integrated-active-filter rectifier (mIAFR) SST indicates lower utilization of the mBR’s dc-dc converters but practical advantages like the absence of direct series connections of transistors and the need for only a single type of power electronic building block (PEBB).

Fast charging of electric vehicles (EVs) requires isolated AC/DC converters with a wide output voltage range of 200V to 1000V. Combining a three-level Vienna Rectifier (VR) with four isolated Dual-Active-Bridge DC/DC Converter (DABC) modules and latest-generation 600V GaN technology enables very high switching frequencies of 560 kHz for the VR and up to 330 kHz for the DABCs. Hence, in this paper an ultra-compact realization of a 10 kW EV charger module with a power density of 9 kW/dm 3 (about 150 W/in 3 ), not including the coldplate, is presented. In this context, a simplified DABC modulation method and straightforward yet accurate (confirmed by experiments) loss models for the DABCs and the VR are introduced, which facilitate a thorough investigation of the optimum synergetic operation of the two stages: For the considered converter, changing the VR operating mode from conventional 3/3-PWM (where the two stages operate rather independently and hence all three VR bridge-legs operate with PWM) to 1/3-PWM (where the DABCs shape the voltage of the shared intermediate DC-link such that always only one of the VR’s three bridge-legs must operate with PWM) results in an advantageous efficiency improvement of up to about 2% over a large part of the output voltage and power range, and in a peak efficiency of more than 97%. Further, the synergetic operation of the two-stage system (VR and DABCs) is experimentally verified for the first time, confirming the modeling results and the efficiency advantage of 1/3-PWM (i.e., 95.4% vs. 95.1% at the rated load of 10 kW and with 500V output voltage). Conducted EMI pre-compliance measurements indicate that the change of the operating strategy from 3/3-PWM to 1/3-PWM only requires minor changes of the EMI filter design.

The trend toward urbanization intensifies road congestion and thus increases interest in research on urban air mobility. Electric motors enable lightweight distributed propulsion in all-electric vertical take-off and landing (eVTOL) aircraft which combine the advantages of helicopters (low-operating space requirement for take-off and landing) and fixed-wing planes (efficient cruising). When aiming at ranges beyond 300 km, a hybrid power supply architecture leveraging the advantages of fuel-cells (FCs; with high-gravimetric energy density) and batteries (with high-gravimetric power density) is required, as weight is a key performance metric in airborne applications. To regulate the power flow between the two energy sources with their respective dc terminal voltages varying in a wide range, a buck-boost (BB) dc-dc converter is required. Such BB dc-dc converters are, however, understudied in the literature and gravimetric power densities today are limited to 20 kW/kg, whereas a goal of 80 kW/kg is stated for 2040. This article systematically identifies the optimal BB dc-dc converter realization among a set of topologies with respect to weight and mission profile efficiency, considering cutting edge component technology, e.g., SiC power semiconductors and 3-D printed complex geometry liquid-cooled aluminum heatsinks. Two 15-kW demonstrator systems with wide bandgap power semiconductors are built and extensively tested, i.e., an all-SiC two-level four-switch BB dc-dc converter with 44 kW/kg and an all-GaN three-level eight-switch BB dc-dc converter with 86 kW/kg, thus complying with the 2040 power density target and exceeding state-of-the-art BB dc-dc converter systems by a factor of four with respect to the gravimetric power density.

Solid-state transformers (SSTs) enable the interfacing of medium-voltage (MV) ac grids to low-voltage (LV) dc loads with high power density and advanced power flow control over traditional approaches based on low-frequency transformers (LFTs). The modularized bridge rectifier (mBR) is a promising, yet understudied, topology which has been recently proposed for highpower electric vehicle (EV) charging applications. The mBR is essentially composed of a three-phase diode rectifier with isolated dc-dc converters connected in parallel to the series-connected diodes, thus forming six branches; the LV outputs of the isolated dc-dc converters are connected in parallel to the LVdc port. In this paper, the mBR SST and its operating principle are first recalled along with an in-depth analysis of the state-of-the-art branch-oriented current control method, which, however, cannot adequately handle the inherent coupling between the branches. Thus, a novel ΣΔ-Vector modeling and control method is proposed, which is based on the Clarke transform and a subsequent ΣΔ decoupling to treat the sums (Σ) and differences (Δ) of the branch quantities separately. The two corresponding equivalent circuits contain only the four effectively available degrees of freedom the mBR topology offers, and hence facilitate a clear analysis and a straightforward, decoupled controller design. Finally, the novel ΣΔ-Vector control method is validated by means of circuit simulations of a 1-MW, 10-kV case study system, and found to show better dynamic performance and robustness than the conventional branch-oriented control method.