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Starting method of modular multi-level flexible direct-current transmission converter

A flexible DC power transmission, modular multi-level technology, applied in output power conversion devices, electrical components, etc., can solve the problem of intensifying the internal dependence of valve control system hardware, high control system resource consumption, and poor operability, etc. problems, to achieve the effect of simplifying the starting method, reducing requirements, and ensuring consistency

Active Publication Date: 2013-03-13
XJ ELECTRIC +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0010] Among the charging methods of the above two sub-modules, the first charging method is to charge each sub-module one by one, the charging time is long, and if the sub-module control circuit takes power from both ends of the DC capacitor of the sub-module, it will cause the sub-module that completes charging first The voltage will complete the discharge process within a certain period of time. For the actual system, this method is not very operable; one of the defects of the second charging method is that it does not consider the difference in circuit parameters of the sub-module itself and the difference in the DC power load of the sub-module. For the sub-module The influence of natural charging uneven voltage; the second defect is that the voltage equalization strategy adopted for sub-module charging after the soft start enters stability is selected with one phase unit (two bridge arms) as the control object. For a huge system, If the number of bridge arm sub-modules is large, the amount of calculation for sorting the voltages of the two bridge arm sub-modules will greatly increase, so the consumption of control system resources is relatively high. In addition, the modular multi-level valve control system is generally controlled by the bridge arm The controller is a unit, and the phase unit is used as a whole to carry out voltage equalization control, which will inevitably bring about huge communication requirements between the controllers of each phase bridge arm, which intensifies the internal dependence of the valve control system hardware.

Method used

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  • Starting method of modular multi-level flexible direct-current transmission converter
  • Starting method of modular multi-level flexible direct-current transmission converter
  • Starting method of modular multi-level flexible direct-current transmission converter

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Embodiment Construction

[0025] The specific implementation manners of the present invention will be further introduced below.

[0026] The basic topology of the modular multilevel flexible HVDC converter is as follows: figure 1 as shown, figure 2 It is a schematic diagram of the sub-module structure. The modular multi-level flexible DC transmission converter is composed of three-phase six bridges. Each phase bridge is composed of two bridge arms. Each bridge arm is cascaded by bridge arm reactors and several sub-modules. made. The number of submodules contained in a single bridge arm is represented by Nsm. The sub-module is the basic unit of the converter, and the topology of the sub-module is as follows: figure 2 As shown, it includes a DC capacitor, an upper IGBT connected in series with the DC capacitor, and a lower IGBT connected in parallel with the DC capacitor. There are diodes in the upper and lower IGBT tubes connected in antiphase and parallel with them, and the sub-module also...

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Abstract

The invention relates to a starting method of a modular multi-level flexible direct-current transmission converter. The method comprises the following steps: realizing switch between soft start and a normal operating circuit through on-off of a circuit breaker and a line contactor; in the soft start process, cutting off the highest direct current voltage of a sub module at a certain frequency to ensure even charge of a bridge arm sub module; and ensuring that the voltage of the bridge arm sub module reaches a system operational rated value by selecting the cutting number of the sub modules so as to create condition for the system for smooth switch from the soft start process to the control mode. A single bridge arm in the control stage is used as a unit control unit, and even charge control of the sub module is carried out for each bridge arm at the same time. Thus, charging is easier to realize without detecting the current of the bridge arm. The soft start process is remarkably shortened, and the even charging degree of the sub modules is very high.

Description

technical field [0001] The invention belongs to the technical fields of flexible power transmission and distribution of electric power systems, power electronics and user electric power, and relates to a starting method of a modularized multi-level flexible direct current transmission converter. Background technique [0002] Flexible DC transmission technology is based on power electronic devices that can be shut down and voltage source converter stations (VSC), mostly in BtB topology, and uses underground cables and submarine cables as transmission media to realize power transmission. Among them, the voltage source converter (VSC) is the basic unit of the transmission system. Modular multilevel converter (MMC) is a multilevel converter topology that has attracted much attention in recent years. In the modular multilevel converter, each bridge arm is composed of several submodules (SM) connected in series. By controlling the input and disconnection states of each submodule,...

Claims

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Application Information

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IPC IPC(8): H02M1/36
Inventor 姚为正吴金龙何青连梁燕韩坤刘普
Owner XJ ELECTRIC
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