Abstract

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. View Full-Text

Keywords: ANPC converter; EV charging; multilevel converter; PWM methods; SiC MOSFETs

Authors: Rafał Kopacz,Michał Harasimczuk,Bartosz Lasek,Rafał Miśkiewicz and Jacek Rąbkowski 

Date of publication: 6 September 2021

Abstract

This paper presents a three-level ANPC AC/DC converter designed as an input stage on the grid side for an EV fast-charging This paper investigates an advanced electric vehicle fast-charging system with a bipolar DC-link rated at
+/- 750 V. The bipolar dc grid concept is known to provide lower on-state loss and much higher flexibility compared to conventional unipolar systems. However, multilevel structure  also requires a proper balancing mechanism. The system described in the article contains three types of bidirectional three-level converters based on 1200 V SiC power devices: active-neutral-point-clamped (ANPC) grid converter, non-isolated DC/DC converter for battery energy storage, and isolated dual active-bridge as interface with electric vehicles. All of the converters use the same submodule. The crucial part of the infrastructure is energy storage which enables managing power flow across the converters, thus providing more independence from the grid, such as exceeding maximal charging power from the grid or providing standalone work in case of grid failure. Moreover, bidirectional converters also enable to operate as grid backup energy storage or return energy from the vehicle batteries in vehicle-to-grid (V2G) operation. The study is focused on the various operation modes of the presented fast-charging station, grounded on the theoretical and simulation-based analysis.

Authors: Jacek Rąbkowski, Dimosthenis Peftitsis,  Radosław Sobieski, Michał Harasimczuk, Rafał Miśkiewicz, Kaushik Naresh Kumar, Rafał Kopacz, Krzysztof Kalinowski, Przemysław Trochimiuk

Date of Conference: 27.06 – 01.07 2022

Abstract

This paper presents a three-level ANPC AC/DC converter designed as an input stage on the grid side for an EV fast-charging This paper investigates an advanced electric vehicle fast-charging system with a bipolar DC-link rated at
+/- 750 V. The bipolar dc grid concept is known to provide lower on-state loss and much higher flexibility compared to conventional unipolar systems. However, multilevel structure  also requires a proper balancing mechanism. The system described in the article contains three types of bidirectional three-level converters based on 1200 V SiC power devices: active-neutral-point-clamped (ANPC) grid converter, non-isolated DC/DC converter for battery energy storage, and isolated dual active-bridge as interface with electric vehicles. All of the converters use the same submodule. The crucial part of the infrastructure is energy storage which enables managing power flow across the converters, thus providing more independence from the grid, such as exceeding maximal charging power from the grid or providing standalone work in case of grid failure. Moreover, bidirectional converters also enable to operate as grid backup energy storage or return energy from the vehicle batteries in vehicle-to-grid (V2G) operation. The study is focused on the various operation modes of the presented fast-charging station, grounded on the theoretical and simulation-based analysis.

Authors: Jacek Rąbkowski, Dimosthenis Peftitsis,  Radosław Sobieski, Michał Harasimczuk, Rafał Miśkiewicz, Kaushik Naresh Kumar, Rafał Kopacz, Krzysztof Kalinowski, Przemysław Trochimiuk

Date of Conference: 27.06 – 01.07 2022

Abstract

In this paper, six 10 kW DC/DC isolated and bidirectional dual active bridge topologies, supplied by +750/0/-750V three-wire DC bus, are evaluated based on efficiency, loss distribution, volt-ampere semiconductors ratings and normalized cost of SiC MOSFETs for electric vehicle charging applications. The selected topologies are evaluated under the same voltage and power conditions, through electrothermal simulations and experiments. The simulation results were verified through experiments conducted on 5 kW prototypes of four of the considered topologies. The advantages and disadvantages of the topologies are discussed and analyzed based on the chosen performance metrics. It has been shown that series-resonant input-series output-parallel full-bridge DAB topology exhibits the highest efficiency while the active neutral point clamped (ANPC) DAB topology can be designed with the lowest cost. However, considering a fair trade-off between all the performance metrics, series-resonant ANPC DAB topology is shown to be the best design choice for the considered evaluation conditions.

Authors: Kaushik Naresh Kumar, Rafał Miśkiewicz, Przemysław Trochimiuk, Jacek Rąbkowski, Dimosthenis Peftitsis

Date of Conference: 5-9 September 2022

Abstract

This study presents a three-level, interleaved, non-isolated DC/DC converter designed as a battery interface for an EV fast-charging system with a bipolar +/- 750 V DC-link. A 20 kW prototype is exhibited based on a universal All-SiC MOSFET submodule for each leg. The core of the paper is the design of the experimental model, along with the description of the system’s control, as well as validation in simulation and in introductory experiments. It is shown that such a converter employing modularized power modules can properly operate as the DC/DC interface.

Authors: Rafał Kopacz, Michał Harasimczuk, Radosław Sobieski, Jacek Rąbkowski

Date of Conference: 23-25 November 2022

Abstract

This paper presents the experimental validation of a 10 kW isolated DC-DC converter for off-board EV charging applications with a bipolar DC bus operating in the medium voltage (MV) range. The Series-Resonant Dual-Active-Bridge (SRDAB) structure was proposed in conjunction with silicon carbide (SiC) semiconductors to achieve high power conversion efficiency. Additionally, the minimum current trajec-tory (MCT) algorithm was applied to extend the range of operation with high efficiency for different power and battery voltage levels corresponding to the battery charging process. On the primary side, Active-Neutral-Point-Clamped (ANPC) topology was proposed to convert voltages as high as 1.5 kV. On the battery side, full-bridge (FB) topology was used. It is shown that using MCT control enables operation with high efficiency in wide power and voltage range as opposed to simple phase shift (PS) control.

Authors: Przemysław Trochimiuk, Rafał Miśkiewicz, Jacek Rąbkowski, Kaushik Naresh Kumar

Date of Conference: 09-11 May 2023

Abstract

This study presents a three-level, interleaved, non-isolated DC/DC converter designed as a battery interface for an EV fast-charging system with a bipolar +/- 750 V DC-link. A 20 kW prototype is exhibited based on a universal All-SiC MOSFET submodule for each leg. The core of the paper is the design of the experimental model, along with the description of the system’s control, as well as validation in simulation and in introductory experiments. It is shown that such a converter employing modularized power modules can properly operate as the DC/DC interface.

Authors: Rafał Kopacz, Michał Harasimczuk, Radosław Sobieski, Jacek Rąbkowski,

Date of publication: May 2023

Abstract

In this paper, six 10 kW DC/DC isolated and bidirectional dual active bridge topologies, supplied by +750/0/-750V three-wire DC bus, are evaluated based on efficiency, loss distribution, volt-ampere semiconductors ratings and normalized cost of SiC MOSFETs for electric vehicle charging applications. The selected topologies are evaluated under the same voltage and power conditions, through electrothermal simulations and experiments. The simulation results were verified through experiments conducted on 5 kW prototypes of four of the considered topologies. The advantages and disadvantages of the topologies are discussed and analyzed based on the chosen performance metrics. It has been shown that series-resonant input-series output-parallel full-bridge DAB topology exhibits the highest efficiency while the active neutral point clamped (ANPC) DAB topology can be designed with the lowest cost. However, considering a fair trade-off between all the performance metrics, series-resonant ANPC DAB topology is shown to be the best design choice for the considered evaluation conditions.

Authors: Kaushik Naresh Kumar, Rafał Miśkiewicz, Przemysław Trochimiuk, Jacek Rąbkowski, Dimosthenis Peftitsis

Date of Conference: 5-9 September 2022

Abstract

This article presents a concept of the control algorithm for an advanced fast charging system for electric vehicles with battery energy storage. Such a system consists of an AC/DC grid converter, isolated DC/DC converters for slow and fast vehicle charging, and a non-isolated DC/DC converter ensuring bi-directional energy flow between the storage and other converters of the system. All the components are connected via a bidirectional DC bus. They have to be controlled by the main unit due to the complex structure of the system.
Several possible operating modes and control signals are analyzed, ensuring the safe and correct operation of the system, and the following converters are proposed. In addition to the analysis, simulation results are presented in the study to confirm the proper system operation.

Authors: Krzysztof Kalinowski, Jacek Rąbkowski, Rafał Miśkiewicz, Radosław Sobieski, Dimosthenis Peftitsis

Date of Conference: 14-16 June 2023

Abstract

This paper presents an investigation on a nonisolated, three-level DC/DC converter; more specifically, on the possible combinations of inductor configurations and modulation techniques directly affecting the performance of the converter. The many state-of-the-art and conventional solutions are compared theoretically, as well as based on experimental considerations founded on a medium voltage SiC-based DC/DC converter to be applied as an energy storage interfacing system in a fast charging station. The study focuses on the effects of the configurations on the output ripples of the converter, which is crucial for battery-oriented systems. The tests were performed at 1 kV and up to nearly 10 kW of power, successfully validating the use of each configuration. It is shown that for a system to operate in a wide output range, the current ripple criterion is not enough for choosing the optimal configuration, and other factors, e.g., efficiency, must be considered.

Authors: Rafał Kopacz, Michał Harasimczuk, Jacek Rąbkowski, Radosław Sobieski

Date of Conference: 14-16 June 2023

Abstract

This paper compares two topologies of Series-Resonant Dual-Active-Bridge (SRDAB) converters with three-level input applied for EV charging from medium voltage (MV) bipolar DC-link. To convert such a voltage with the utilization of low-voltage silicon carbide (SiC) transistors Active-Neutral-Point-Clamped (ANPC) and series-connected half-bridges (SHB) legs from the DC-link side were examined. Additionally, to increase the efficiency of energy conversion in a wide operating range minimum current trajectory (MCT) control algorithm was applied in each converter. To make a fair comparison between both solutions dedicated laboratory setup was designed and built where ANPC and SHB submodules could be interchanged. Conducted simulation and experimental research confirmed that both configurations could be successfully employed as an isolated DC/DC stage in EV charging systems. The measured peak efficiencies, in either case, were close to 99%, and the performance of both solutions was satisfactory in the entire operating range. However, in applications with a broader input and output voltage range, the SHB leg could be more beneficial.

Authors: Przemysław Trochimiuk, Rafał Miśkiewicz, Jacek Rąbkowski, Kaushik Naresh Kumar, Dimosthenis Peftitsis

Date of Conference: 14-16 June 2023