Precharge circuit of modular multilevel converter and charge method of precharge circuit

Abstract

The invention discloses a precharge circuit of a modular multilevel converter and a charge method of the precharge circuit. According to a few of existing methods, submodules of a modular multilevel converter cannot be charged to the condition that capacitor voltage is close to a theoretical operating voltage value, operation is complicated and the charging time is relatively long. The precharge circuit comprises a DC voltage source, a diode, a current-limiting resistor, a first switch, a second switch and a current feed resistor, wherein a positive electrode of the DC voltage source is connected with the positive electrode of the diode through the first switch; a negative electrode of the diode is connected with one end of the current feed resistor and one end of the current-limiting resistor at the same time; the other end of the current feed resistor is connected with the negative electrode of the DC voltage source and a DC bus at the negative electrode of the modular multilevel converter at the same time; the other end of the current-limiting resistor is connected with a DC bus at the positive electrode of the modular multilevel converter; and the second switch is connected with the current-limiting resistor in parallel. According to the precharge circuit and the charge method thereof, the submodules can be directly charged to the condition that capacitor voltage values areclose to a rated operating value in a precharge state, so that the charge method is simple and fast.

Description

technical field [0001] The invention relates to the field of precharging of modular multilevel converters, in particular to a precharging circuit applied to modular multilevel converters and a charging method thereof. Background technique [0002] With the progress and rapid development of society, people's demand for medium and high voltage high power transmission equipment is increasing day by day. In recent years, due to the development of power electronics technology, the manufacturing process of power switching devices has been further improved, and its voltage and current resistance level has been further improved, thus making it possible for power switching devices to be used in medium-high voltage and high-power applications. However, at higher power levels, the increase in the switching frequency of power switching devices is limited. Under the premise that the traditional two-level voltage source converter cannot meet the requirements of high-voltage and high-powe...

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Problems solved by technology

[0006] The purpose of the present invention is to overcome the characteristics of relatively low efficiency and complicated operation of the pre-charging mode of the existing modular multi-level converter, and provide a modular multi-level converter with reasonable design, low cost and high reliability. current converter pre-charge circuit

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