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ZVS modulation strategy for a 3–5 level bidirectional Dual Active Bridge DC-DC converter
... It can output three output voltage levels V dc1 /2, 0, and −V dc1 /2, which are denoted as V P , V O , and V N in the article, respectively. At present, several types of 3L circuits have been applied to DAB, including flying capacitor 3L circuit [7], T-type 3L circuit [8]- [10], diode neutral-point-clamped (DNPC) 3L circuit [11]- [17], active neutral-point-clamped (ANPC) 3L circuit [12], [13], and hybrid clamped 3L circuit [18]- [23]. ...
Multi-level circuits can achieve high voltage level, power density, and performance. This paper considers a dual active bridge (DAB) based on the active neutral-point-clamped (ANPC) three-level circuit (ANPC-DAB). The soft-switching characteristics of the ANPC circuit during the switching process between switching states are analyzed, and the conditions for enabling all 12 switching devices to achieve zero-voltage switching (ZVS) on all the turn-on switching transitions are obtained. Based on this, the distribution of hard-switching turn-off and conduction losses of power devices is further analyzed, and an optimized switching strategy that can balance the loss distribution of power devices is proposed by the evaluation of all zero states and analysis of a switching-state sequence. Moreover, this paper examines the effect of the proposed switching strategy by analyzing the loss distribution of power devices and efficiency of the ANPC-DAB. Finally, experiments are conducted using a 1-kW prototype. The simulation and experimental results show that the proposed switching strategy can effectively improve the loss distribution of power devices while all the power devices realize ZVS. 1
A new control method for the bidirectional series-resonant converter is presented that optimizes dynamic behavior. The series-resonant converter is a frequently used converter type due to its inherent zero-voltage switching property for switching frequencies above the resonance frequency. However, a method to control the series-resonant converter dynamically while facilitating bidirectional power flow and zero-voltage switching of all switches is not yet presented. This article presents bidirectional charge control, a control method that realizes dynamic, bidirectional operation of the series-resonant converter. It targets a net amount of charge displacement through the controlled port between two consecutive zero-current crossings, by describing all switching events as a function of the charge difference across the resonant capacitor. As a result, bidirectional charge control facilitates ZVS operation of all switches, regardless of the operating conditions, while minimizing the reactive currents through the connected voltage sources. This article describes the theoretical analysis regarding bidirectional charge control as well as an experimental verification, including nonidealities and the corresponding implementation to guarantee the desired control of the series-resonant converter. Bidirectional charge control realizes dynamic, bidirectional operation of the series-resonant converter while guaranteeing zero-voltage switching of all switches.
This paper proposes a bi-directional isolated DC/DC converter for the battery charger and discharger of Electric Vehicle to reduce the power loss under light loads. The proposed DC/DC converter consists of two full-bridge inverters, an isolated transformer, and a boost reactor, and provides bi-directional transmission, buck-boost conversion, zero-voltage-switching and reactive power suppression. Two power semiconductors of the inverter in the rectification side are turned off to block a reactive current, which increases the power loss under light loads. The phase shift amount in the two full bridge inverters are controlled continuously and simultaneously seamless power transmission. The 400V–3.5kW experimental system exhibits stable bi-directional buck-boost conversion and seamless transition between the charging and discharging modes, while suppressing the reactive power. Moreover, the proposed DC/DC converter reduces power loss by 67.5W under light loads (240 W), compared with the conventional control.
This paper proposes a bi-directional isolated DC/DC converter for the battery charger and discharger of Electric Vehicle to reduce the power loss under light load condition. The proposed DC/DC converter consists of two full-bridge inverters, an isolated transformer, and a boost reactor, and provides bi-directional transmission, buck-boost conversion, zero - voltage - switching and reactive power suppression. Two power semiconductors of the inverter in the rectification side are turned off to block a reverse current, which increases the power loss under light load condition. The amount of phase shift in the two full bridge inverters are controlled continuously and simultaneously seamless power transmission. The 400V-3.5kW experimental system exhibits stable bi-directional buck-boost conversion and seamless transition between the charging and discharging modes, while suppressing the reactive power. Moreover, the proposed DC/DC converter reduces power loss by 67.5W under light load (240W) condition, compared with the conventional control.
This paper gives a comprehensive comparison of multilevel high-frequency-link (HFL) dc transformer (abbreviated MDCT) based on modular multilevel converter (MMC) and multilevel-dc-link dc transformer (abbreviated ADCT) based on dual-active-bridge (DAB) for medium-voltage dc (MVDC) application. The topology, operation, HFL voltage and current, active and circulating power, characteristic currents, switching behaviors, and power loss are analyzed in detail. Both MDCT and ADCT have fault treatment ability for MVDC application. However, the installation and commissioning of ADCT are more flexible and simpler. In addition, the MDCT needs more switches and high-frequency inductors than ADCT in MVDC side with the same voltage level, but the number of high-frequency transformer can be reduced. Compared with MDCT, the ADCT has higher power transfer ability and lower circulating power, then it has lower HFL voltage, and current RMS and peak values with the same transmission power in MVDC side. However, the arm RMS and average currents of MDCT are lower than those of ADCT in MVDC side. The switching performance of MDCT deteriorates when the MVDC voltage fluctuates, but the switching behaviors of half-bridges are added to ADCT. The loss of ADCT almost keep the same when the MVDC voltage fluctuates, but the loss of MDCT changes a lot. Finally, a small scale prototype platform with 1kW/450V/150V is built and experimental results verify the correctness and effectiveness of the theoretical analysis.
Design of high performance, low cost and clean propulsion systems requires multiple disciplines such as physics, mathematics, electrical engineering, mechanical engineering and specialisms like control engineering and safety. This paper details the program of EU FP7 Multi-ITN project ADvanced Electric Powertrain Technology (ADEPT) and presents a review of current research achievements of the recruited fellows. The ADEPT programme will provide a virtual research lab community from labs of European universities and industries. After finishing the ADEPT project, the know-how and expertise will also be opened to other research organizations or industry beyond those involved in the project. Special attention in this paper is given to ADEPT Virtual Library - collection of component level, sub-system level and system level components produced and maintained by the ADEPT Consortium. Functional Mock-up Interface (FMI) standard for model exchange and simulation is described and its connection with the ADEPT project is established.
This paper presents a converter consisting of a dual active bridge built upon three-level neutral-point-clamped legs in order to synthesize a five-level medium- or high- frequency stepped waveform on each side of the transformer. Thanks to the modulation extra degrees of freedom, the transformer current harmonic content can be reduced (less magnetic losses) and the fundamental component of the transformer primary and secondary voltages can be adjusted to minimize the reactive power (less conduction losses). A modulation strategy and control scheme to regulate the dc-link capacitor voltage balance is proposed. The topology, modulation, and balancing control are validated through simulations.
This paper details efficiency optimized operation and design of a bi-directional and isolated five-level Dual Active Bridge (5LDAB) converter for an application that requires ultra-wide voltage and power ranges. The rated power of the considered converter is 7.5kW, the specified input voltage range is 150V ≤ Vdc1 ≤ 800V and the output voltage is constant, Vdc2 = 700V. In order to achieve high efficiency levels in a wide operating range, a modulation scheme is proposed to minimize the transformer rms current. Results of transformer rms currents and of efficiencies are presented for the 5LDAB and compared with the results obtained for an efficiency optimized conventional Dual Active Bridge (DAB) converter. Compared with the DAB topology, the 5LDAB converter can achieve an overall reduction of transformer rms currents and of conduction losses in the higher voltage regime of the operating range.
A novel converter configuration that allows for high frequency transformer integration and high voltage distribution is proposed for large scale grid-connected photovoltaic (PV) system. The proposed configuration has in the front-end of the solar panel, dual-active bridge dc-dc converter with three-level neutral-point clamped secondary and a high-step-up ratio high frequency transformer. The output of the dual-active bridge converter may be connected to a high voltage inverter to achieve high ac voltage to allow for direct interconnection with the utility ac grid at distribution voltage level. The proposed configuration has advantages of high frequency transformer, high efficiency and high voltage operation. Phase-shift modulation technique along with Maximum Power Point Tracking is proposed for the three-level dual-active bridge converter and the overall converter performance is verified in simulation.
Dual Active Bridge (DAB) dc-dc converter finds applications in the intermediate high frequency link power conversion stage of a high-power solid state transformer. In this paper, a multilevel DAB dc-dc converter is proposed. A three-level neutral point clamped (NPC) inverter topology has been used in the high voltage bridge which enables semiconductor switches to be operated in higher voltage range without using cascaded bridges and multiple DAB converters. Modulation strategy to control power flow between the active bridges with one of the bridges switching at multi-level is proposed in this paper. Steady-state analysis of the converter with the proposed modulation scheme is presented along with simulation results to augment the analysis.
A comprehensive procedure for the derivation of optimal, full-operating-range zero voltage switching (ZVS) modulation schemes for single-phase, single-stage, bidirectional and isolated dual active bridge (DAB) ac–dc converters is presented. The converter topology consists of a DAB dc–dc converter, receiving a rectified ac line voltage via a synchronous rectifier. The DAB comprises primary and secondary side full bridges, linked by a high-frequency isolation transformer and a series inductor. ZVS modulation schemes previously proposed in the literature are either based on current-based or energy-based ZVS analyses. The procedure outlined in this paper for the calculation of optimal DAB modulation schemes (i.e., combined phase-shift, duty-cycle, and switching frequency modulation) relies on a novel, more accurate, current-dependent charge-based ZVS analysis, taking into account the amount of charge that is required to charge the nonlinear parasitic output capacitances of the switches during commutation. Thereby, the concept of “commutation inductance(s)” is shown to be an essential element in achieving full-operating-range ZVS. The proposed methods are applied to a 3.7 kW, bidirectional, and unity power factor electric vehicle battery charger which interfaces a 400 dc-bus with the , 50-Hz utility grid. Experimental results obtained from a high-power-density, high-efficiency converter prototype are given to validate the theoretical analysis and practical feasibility of the proposed strategy.
An optimal modulation scheme that enables minimum conduction and copper losses is presented for a bidirectional dual active bridge (DAB) dc-dc converter. The considered converter system is employed for an automotive application and comprises of a high voltage (HV) port with port voltage V1, 240V ≤ V1 ≤ 450 V, and a low voltage (LV) port with port voltage V2, 11 V ≤ V2 ≤ 16 V; the rated output power is 2 kW. The closed-form expressions for the optimal control parameters are derived and implementation details are presented in order to facilitate the direct application to a given DAB converter. The paper further details the properties of the presented modulation scheme with respect to switching losses. Experimental results confirm a considerable increase of the converter efficiency achieved with the proposed optimal modulation scheme, compared to the efficiency obtained with conventional phase shift modulation. The efficiency increase is most distinct at V1=450V and V2 = 11V with an increase from 78.6% to 90.6% at 1 kW output power and from 85.9% to 90.7% at rated output power as compared to conventional phase shift modulation.
A new Dual Active Bridge (DAB) topology is proposed with a 15-kV SiC-IGBT based three-level inverter at the high-voltage side and 1200-V SiC-MOSFET based paralleled two-level inverter at the low-voltage side. The proposed DAB is an integral part of a solid state transformer which connects a 13.8-kV distribution grid and a 480-V utility grid. The three-level inverter connected at the high-voltage side and a pair of two-level inverters connected at the low-voltage sides (in Y/Δ) of the high frequency link transformer help to reduce dominant harmonic currents. Thus harmonic-free currents in the high frequency link transformer are achieved without pulse-width modulation. A simple control is proposed and validated with simulation results.
For realizing bidirectional and isolated AC/DC converters, soft-switching techniques/topologies seem to be a favourable choice as they enable a further loss and volume reduction of the system. Contrary to the traditional dual-stage approach, using a power factor corrector (PFC) stage in series with a DC/DC isolation stage, we showed recently that the same functionality can be achieved under full soft-switching operation using a single-stage dual active bridge (DAB) AC/DC converter. This paper investigates the performance of this single-stage approach by comparing it with a state-of-the-art conventional dual-stage concept (both soft-switching converters), where a bidirectional interleaved triangular current mode (TCM) PFC rectifier was chosen in combination with a DAB DC/DC converter. The advantages and drawbacks of each concept are discussed in detail, focusing on the impact of the utilized semiconductor technology and silicon area on the converter efficiency. Furthermore, a comprehensive comparison of power density is allowed by the analytical models that correlate the component losses with their respective volume.
A switching control strategy to enable Zero-Voltage-Switching (ZVS) over the entire input-voltage interval and the full power range of a single-stage Dual Active Bridge (DAB) AC/DC converter is proposed. The converter topology consists of a DAB DC/DC converter, receiving a rectified AC line voltage via a synchronous rectifier. The DAB comprises primary and secondary side full bridges, linked by a high-frequency isolation transformer and inductor. Using conventional control strategies, the soft-switching boundary conditions are exceeded at the higher voltage conversion ratios of the AC input interval. Recently we presented a novel pulse-width-modulation strategy to fully eliminate these boundaries, using a half bridge — full bridge DAB configuration. In this papers the analysis is extended towards a full bridge — full bridge DAB setup, providing more flexibility to minimize the component RMS currents and allowing increased performance (in terms of efficiency and volume). Experimental results are given to validate the theoretical analysis and practical feasibility of the proposed strategy.
An efficiency-optimized modulation scheme and an efficiency-optimized design method are developed for an existing hardware prototype of a bidirectional Dual Active Bridge (DAB) DC/DC converter. The DAB being considered is used for an automotive application and is made up of a High Voltage (HV) port with port voltage V1, 240V V1 450V, and a Low Voltage (LV) port with port voltage V2, 11V V2 16V; the rated output power is 2 kW. A much increased converter efficiency is achieved with the methods detailed in this paper: the average efficiency, calculated for different voltages V1 and V2, different power levels, and both directions of power transfer, rises from 89.6% (conventional phase shift modulation) to 93.5% (proposed modulation scheme). Measured efficiency values, obtained from the DAB hardware prototype, are used to verify the theoretical results.
A new modulation strategy that allows operating the dual active bridge (DAB) dc-dc converter under soft switching in the whole operating range is proposed. This strategy is ruled by imposing a certain modulation index in one of the two bridges and a phase shift between the transformer primary and secondary voltages. Moreover, the proposed algorithm reduces the reactive power and thus reducing the converter conduction losses. An experimental prototype was implemented and some experimental results are presented to validate the theoretical analysis. The experimental results reveal that the overall efficiency of the DAB topology can be improved up to 20% by implementing the proposed modulation strategy instead of the conventional one.
The authors present three DC/DC converter topologies suitable for high-power-density high-power applications. All three circuits operate in a soft-switched manner, making possible a reduction in device switching losses and an increase in switching frequency. The three-phase dual-bridge converter proposed is seen to have the most favorable characteristics. This converter consists of two three-phase inverter stages operating in a high frequency six-step mode. In contrast to existing single-phase AC-link DC/DC converters, low RMS current ratings are obtained for both the input and output filter capacitors. This is in addition to smaller filter element values due to the higher-frequency content of the input and output waveforms. The use of a three-phase symmetrical transformer instead of single-phase transformers and a better utilization of the available apparent power of the transformer (as a consequence of the controlled output inverter) significantly increase the power density attainable
The performance of a high-power, high-power-density DC-to-DC
converter based on the single-phase dual active bridge (DAB) topology is
described. The dual active bridge converter has been shown to have very
attractive features in terms of low device and component stresses, small
filter components, low switching losses, high power density and high
efficiency, bidirectional power flow, buck-boost operation, and low
sensitivity to system parasitics. For high output voltages, on the order
of kilovolts, a cascaded output structure is considered. The effects of
snubber capacitance and magnetizing inductance on the soft switching
region of control are discussed. Various control schemes are outlined.
Coaxial transformer design techniques have been utilized to carefully
control leakage inductance. The layout and experimental performance of a
prototype 50 kW 50 kHz unit operating with an input voltage of 200 V DC
and an output voltage of 1600 V DC are presented
Three DC/DC converter topologies suitable for high-power-density
high-power applications are presented. All three circuits operate in a
soft-switched manner, making possible a reduction in device switching
losses and an increase in switching frequency. The three-phase
dual-bridge converter proposed is shown to have the most favorable
characteristics. This converter consists of two three-phase inverter
stages operating in a high-frequency six-step mode. In contrast to
existing single-phase AC-link DC/DC converters, lower turn-off peak
currents in the power devices and lower RMS current ratings for both the
input and output filter capacitors are obtained. This is in addition to
smaller filter element values due to the higher-frequency content of the
input and output waveforms. Furthermore, the use of a three-phase
symmetrical transformer instead of single-phase transformers and a
better utilization of the available apparent power of the transformer
(as a consequence of the controlled output inverter) significantly
increase the power density attainable
Elektrischer Leistungswandler zur DC/DC-Wandlung mit Dualen Aktiven Briicken
- J Everts
- J W Kolar
Researchers within the EU funded Marie Curie ITN project ADEPT, grant number 607361
- A Stefanskyi
- A Dziechciarz
- F Chauvicourt
- G E Sfakianakis
- K Ramakrishnan
- K Niyomsatian
- M Curti
- N Djukic
- P Romanazzi
- S Ayat
- S Wiedemann
- W Peng
- A Tamas
- S Stipetic