论文分享：High Voltage Side DC-Bus Capacitor Voltage Balancing Control of a 350 kW Multiport EV Charging System
标题：High Voltage Side DC-Bus Capacitor Voltage Balancing Control of a 350 kW Multiport EV Charging System
作者：Abhijit Choudhury, Yuichi Mabuchi, Kimihisha Furukawa, Nawaz Husain
单位：株式会社 日立製作所
本文发表于2022 IEEE Energy Conversion Congress and Exposition (ECCE)。
阅读全文：https://ieeexplore.ieee.org/document/9947794
摘要
“目前，基于固态变压器（SST）的功率变换器在高功率电动汽车充电应用中受到广泛关注，与传统的低频解决方案相比，整体尺寸降低。每一个变换器模块单元都连接到同一个公共直流母线，再通过DC/DC变换器连接到电动汽车。尽管这种拓扑结构作为电动汽车充电解决方案来看非常简单方便，但输出侧DC/DC变换器的数量与连接的电动汽车数量成正比。因此，整体系统成本很高，并且由于含有多个串联连接的变换器单元，整体系统效率也较低。为了克服这个限制，本文中提出了一种基于矩阵开关的充电解决方案。在这种拓扑结构中，变换器模块单元的输出连接到一个矩阵开关（而不是将它们连接在一起），这能够提供三个单独的快速充电口（分别为100kW、100kW、150kW）。然而，该策略在提供负载功率不等的情况下，存在直流母线电压不平衡问题。为了解决这个问题，本文提出了一个直流母线电压平衡策略，该策略可以在为连接的电动汽车提供不等的充电功率时，保持高电压侧直流母线电压平衡。本文通过进行详细的仿真研究和实验，验证了6.6 kV和350 kW系统的控制方案。”
“Solid state transformer (SST) based power converter is now days very popular for high power EV charging, while keeping a reduced overall footprint size as compared to the conventional low frequency-based solutions. The output from all cell converter units are connected together to form a common DC-bus, which can be then connected to EVs with the help of additional DC/DC converters. Although, this topology is quite simple and convenient as an EV charging solution, the numbers of the output side DC/DC converters are proportional to the connected EVs. Hence, the overall system cost is high, and the overall system efficiency is also lower due to the multiple series connected converter units. To overcome this limitation a matrix switch-based charging solution is proposed in this research work. In this topology the output from the cell converter units are connected to a matrix switch in place of connecting them together, which helps to provide three separate fast charging ports (100 kW, 100 kW, 150 kW respectively). However, this strategy has a common problem of the DC bus voltage balancing, while serving inequal load power. Hence, to solve this issue a DC-Bus voltage balancing strategy is proposed which can keep the high voltage side DC-bus voltages balanced, while even feeding inequal charging power to the connected EVs. Detailed simulation studies and experimental verification is presented to verify the control scheme for a 6.6 kV and 350 kW system.”
使用DSIM进行“大规模变换器系统仿真”
本文采用DSIM对6.6 kV、350 kW系统的控制方案进行了验证（该系统包含21个单元，252个开关）。“DSIM的使用是由于在大规模变换器系统仿真中无法使用传统的仿真软件进行研究。”通过DSIM仿真可以验证平衡以及不平衡负载条件下的系统性能。DSIM仿真结果表明：
（1）当“电动汽车2的充电功率从额定功率的90 kW降低到70 kW（减少了23%）”，“所有三相的所有高压电容电压都稳定在1050 V”。“单元2的调制信号（Vam_up2）低于单元1和单元3，显示出该系统的可控性”。
（2）当“电动汽车2充电功率从额定90 kW进一步降低到45 kW（减少50%），所有的高压电容器电压都稳定在参考值”，从而验证了作者提出的控制方案的稳定性。
“DSIM is used due to the large numbers of converter system simulation, which would not be possible to study using the conventional simulation software.”
“EV2 output power is reduced to 70 kW from rated 90 kW (23% reduction).”
“All the HV capacitor voltages are stable at 1050 V for all the three phases.”
“The modulation signals for unit 2 (Vam_up2) is lower than the unit 1 and unit 3.”
“It shows the controllability of the proposed system.”
“EV2 output power is reduced further to 45 kW from rated 90 kW (50% reduction). From the simulation results it can be seen that, all the HV capacitor voltages are stable at the reference value.”
