Energies – MDPI
All-SiC ANPC Submodule for an Advanced 1.5 kV EV Charging System under Various Modulation Methods
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
Date of publication: 6 September 2021
Battery Charging System with Three-level ANPC Converter Operating at Variable Bipolar DC-link
Three-level converters are an interesting solution for the input stage of EV charging systems as a number of advantages over two-level counterparts can be found, only to mention the better quality of the processed energy (lower harmonic distortion and EMI level). On the other hand, higher element count and power loss may be recognized as disadvantages. In such systems switching losses represent a significant part of the overall losses even if modern SiC power devices are applied. To resolve this issue, this paper focuses on the single-phase (1/3 PWM) modulation of the three-level Active Neutral-Point-Clamped (ANPC) converter. The system also contains a three-level DC/DC converter connected to the energy storage, which delivers variable DC-link voltage. A simulation study compares variable DC-link approach to other PWM strategies: carrier-based sinusoidal with 3 rd harmonic component and two-phase discontinuous modulation. For the investigated 20 kW charging system with the 1/3 modulation the semiconductor losses of the ANPC converter drop by 184 W (0,92% of nominal power). Operating conditions of the DC/DC converter are challenging due to required variable DC-link voltage but with a lower average value. This also leads to decreased switching loss. All in all, the total loss in selected SiC MOSFETs (C3M0015065K) semiconductors are reduced by 0,96% of nominal power.
Date of Conference: 13-16 October 2021