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.
Highlights
There is no doubt that available fast charging infrastructure is a necessary condition in the further expansion of electric vehicles (EVs) beyond current numbers, even in the most developed countries [1,2]
Fast charging stations may offer a reduction in time from the range of hours to tens of minutes [3]
According to the literature, the impact of commutation path lengths is a crucial matter, determining the proper PWM method for a specific application as well. This is especially relevant when systems with silicon carbide (SiC) power devices are considered, as wide-band-gap semiconductors are capable of high-speed switching, and are more prone to ringing and overvoltages compared to its Si counterparts
Summary
There is no doubt that available fast charging infrastructure is a necessary condition in the further expansion of electric vehicles (EVs) beyond current numbers, even in the most developed countries [1,2]. According to the literature, the impact of commutation path lengths is a crucial matter, determining the proper PWM method for a specific application as well This is especially relevant when systems with SiC power devices are considered, as wide-band-gap semiconductors are capable of high-speed switching, and are more prone to ringing and overvoltages compared to its Si counterparts. In this paper, except for validating the constructed low-volume prototype of the all-SiC ANPC single leg rated at 1500 V DC and 6.67 kVA power (1/3 of three-phase 20 kVA system), it is shown that when enough care and focus is put into the design process of the converter and the commutation path lengths are vastly minimized, the variances between different modulation techniques in this regard are not as apparent and the choice may be limited to other factors, namely in this case, efficiency. A system with six SiC MOSFETs per leg is justified and interesting for further studies, especially including the impact of various modulation techniques
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