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Closed-loop charging method of modular multilevel converter

A modular multi-level, charging method technology, applied in the direction of electrical components, output power conversion devices, etc., can solve the problem of increasing the impact current during the start-up and unlocking process of the converter, and achieve the effect of simple operation process

Active Publication Date: 2018-08-24
XIAN XJ POWER ELECTRONICS TECH
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AI Technical Summary

Problems solved by technology

With the development of multi-terminal flexible DC transmission and flexible DC grid, the working conditions faced by the converter charging process are becoming more and more complex, and there will be a certain deviation between the AC and DC voltage relative to the rated value. There is a deviation, which increases the inrush current of the converter to start the unlocking process

Method used

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  • Closed-loop charging method of modular multilevel converter

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Embodiment Construction

[0012] The present invention will be described in further detail below in conjunction with the accompanying drawings.

[0013] see figure 1 , in the charging method of the present invention, the converter monitors the voltage state of the sub-module in real time, and controls the voltage of the sub-module within the rated voltage value or the rated voltage operating range by adjusting the number of cut-off sub-modules.

[0014] With this charging method, the converter does not need to receive system information (whether the constant DC voltage station is unlocked, the island operation of the converter station or network operation, etc.) under different start-up modes of the converter station. Different phases of different start-up processes can stabilize the sub-module voltage at the rated voltage or within the rated voltage operating range.

[0015] When using the closed-loop charging startup method, attention should be paid to the fact that bridge arm overcurrent or submodu...

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Abstract

Disclosed is a closed-loop charging method of a modular multilevel converter. The closed-loop charging method comprises the following steps of firstly, determining a sub module voltage control targetand target range; then, according to a sub module average voltage sampling value, calculating a deviation value between the sub module average voltage sampling value and the control target; and finally, performing adjustment on the removal number of sub modules according to a condition that whether the deviation value exceeds the target range or not, wherein in the adjustment process, the sub modules are divided into an overvoltage condition and an undervoltage condition, and two different gain values are set; in the overvoltage condition, the relatively high gain value is selected to accelerate adjustment; in the undervoltage condition, the relatively low gain value is selected to prevent overcurrent of a bridge arm; and finally, the sub module average voltage is stabilized to be the control target value. The closed-loop charging method is simple in operation flow, and by performing sub module voltage control, a condition of sudden increasing of the charging voltage does not occur.

Description

technical field [0001] The invention relates to power electronics technology, in particular to a closed-loop charging method for a modular multilevel converter. Background technique [0002] Compared with the conventional DC transmission system, the flexible DC transmission system can achieve power flow reversal by reversing the current direction without changing the voltage polarity. The most notable feature of the flexible DC transmission and flexible DC grid system with high reliability is that it can realize multi-source power supply and multi-drop power reception, providing a more flexible and efficient power transmission method for the power system. [0003] Modular multilevel converter (MMC) is suitable for flexible DC transmission, flexible DC grid and DC distribution network field. The successful completion of the start-up process is the premise and basis for the normal operation of the flexible DC transmission and distribution system. A suitable start-up strategy...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M1/36H02M1/32
CPCH02M1/32H02M1/36
Inventor 张浩王先为杨美娟马焕吴金龙
Owner XIAN XJ POWER ELECTRONICS TECH
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