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Pre-charging system and method for modular multilevel inverter

A modular multi-level, pre-charging technology, applied to electrical components, output power conversion devices, AC power input conversion to DC power output, etc., can solve the problems of complex grouping, increased control complexity, etc., to improve the system Safety factor, reduced pre-charge time, simple control effects

Inactive Publication Date: 2013-08-14
CHINA UNIV OF MINING & TECH
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Problems solved by technology

However, this method still continuously detects the capacitor voltage of the sub-modules, which increases the complexity of the control, and its grouping is also more complicated. After the pre-charging is completed, the sum of the capacitor voltages of all sub-modules of each phase bridge arm is equal to the peak voltage of the AC side, which is less than the normal MMC Rated voltage U at work dc

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  • Pre-charging system and method for modular multilevel inverter
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  • Pre-charging system and method for modular multilevel inverter

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Embodiment Construction

[0030] The present invention will be further described below in conjunction with accompanying drawing:

[0031] Such as figure 1 As shown, the three-phase MMC is composed of six bridge arms, and each bridge arm is composed of N submodules and a reactor L connected in series.

[0032] The structure of the submodule is as follows figure 2 As shown, each sub-module is composed of two switch tubes VT1, VT2 and a capacitor, wherein the switch tubes are connected in antiparallel with diodes, and the capacitors are connected in parallel at both ends of the series switch tubes.

[0033] When precharging, the precharge equivalent circuit such as image 3 shown, which is the current limiting resistor R 1 The equivalent capacitance C after being connected in series and parallel with the bridge arm eq In a typical first-order circuit composed of the bridge arm, the impedance of the series reactance in the bridge arm is very small compared with the impedance of the equivalent capacita...

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Abstract

The invention discloses a pre-charging system and method for a modular multilevel inverter, the common DC bus of the modular multilevel inverter is connected with every phase bridge arm of the modular multilevel converter through a current-limiting resistance R1 and a pre-charging initial contactor KM2 in sequence, a pre-charging finishing contactor KM1 is connected with a current-limiting resistance R1 in parallel, and the purpose of pre-charging is achieved by controlling the switch tube of the contactor and the modular neutron multilevel inverter module; according to the method provided by the invention, during the process of pre-charging, the current direction and the sub-module capacitance voltage value of the bridge arm are beyond testing, the workload of the controller is decreased; as the sub-module capacitance voltage value can achieve the rated value in normal operation after pre-charging, the decreasing of the wave form in the initial time when the system operates normally is avoided; and full-automatic pre-charging can be realized by switching on and off the circuit by the contactor, and the safety factor of the system is improved.

Description

technical field [0001] The invention relates to a floating capacitor precharging system and method, in particular to a floating capacitor precharging system and method in a sub-module of a modular multilevel inverter. Background technique [0002] Modular Multilevel Converter (MMC) is a new type of voltage source inverter. MMC adopts a strict modular design to achieve high voltage and high power by connecting sub-modules in series to avoid It solves the problem of dynamic voltage equalization that exists in the traditional two-level through the direct series-parallel connection of a large number of switching devices, and can reach a very high number of levels, and its output waveform is very close to a sine wave, which simplifies the design of the output filter. High-power transmissions and other inverter applications that need to output energy from the public DC bus to the AC side have attracted much attention. [0003] MMC topology such as figure 1 As shown, the three-ph...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/483H02M7/5387
Inventor 戴鹏郭全军梁改革公铮赵霞高超绪戴华夏宗晓
Owner CHINA UNIV OF MINING & TECH
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