A Simple and Cost-effective Precharge Method for Modular Multilevel Converters by Using a Low-Voltage DC Source
A Simple and Cost-effective Precharge Method for Modular Multilevel Converters by Using a Low-Voltage DC Source
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DOI：
10.1109/tpel.2015.2484222
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发表时间：
2016-07
影响因子：
6.7
通讯作者：
K. Tian;Bin Wu;Sixing Du;D. Xu;Zhongyuan Cheng;N. Zargari
中科院分区：
文献类型：
--
作者：
K. Tian;Bin Wu;Sixing Du;D. Xu;Zhongyuan Cheng;N. Zargari
提出了一种使用低压直流电源对模块化多电平变流器(MMC)进行预充电的简单而经济的方法。MMC中的子模块(SM)电容器在启动时需要预充电到其额定电压值，以确保MMC正常工作。传统方法通过使用昂贵的高压旁路断路器、充电电阻器或高压直流电源来通过网侧或直流侧执行预充电。高压直流电源的电压必须等于SM电容电压，并且可以高达数千伏。相比之下，该方法通过串联阻断二极管在直流母线上使用一个极低电压的直流电源，并且不需要充电电阻和旁路断路器。它充分利用MMC中已有的功率器件、ARM电感和SM电容，配置成Boost电路进行预充电。该方法简单易行，成本低。此外，Boost电路的特点使所提出的方法更加灵活。例如，直流源的电压选择是灵活的，不限于固定值。SM电容器可以在不同的组中充电。此外，该方法还适用于不同的MMC SM，包括具有不同电容电压的SM。通过仿真和实验验证了该方法的有效性。
A simple and cost-effective precharge method for modular multilevel converter (MMC) by using a low-voltage direct current (dc) source is proposed in this paper. The submodule (SM) capacitors in MMC are required to be precharged to their nominal voltage values at start-up to ensure MMC work normally. Conventional methods perform the precharging either through grid side or dc side by using costly high-voltage bypass breakers, charging resistors or a high-voltage dc source. Voltage of the high-voltage dc source must be equal to SM capacitor voltage and could be as high as thousands of volts. By contrast, the proposed method employs a very low voltage dc source on dc bus through a series-connected blocking diode, and requires no charging resistor and bypass breakers. It takes advantages of the existing power devices, arm inductors, and SM capacitors in MMC, and configures them into boost circuit for the precharging. The proposed method is simple and cost-effective. Moreover, the characteristics of the boost circuit render the proposed method flexible. For instance, the voltage selection of the dc source is flexible and not restricted to a fixed value. The SM capacitors can be charged in different groups. In addition, the method is applicable to different MMC SMs, including SM with different capacitor voltages. The effectiveness of the proposed method is verified through simulation and experiment.