CN-122021522-A - Nine-bridge arm modularized multi-level converter absorption resistance parameter design method, system, equipment and medium

Abstract

The invention relates to the technical field of flexible direct current transmission of power systems, and discloses a method, a system, equipment and a medium for designing absorption resistance parameters of a nine-bridge arm modularized multi-level converter, wherein the method comprises the steps of establishing a charging equivalent model according to transient overvoltage requirements in a switching-off process of a switch to obtain a first limiting condition based on voltage stress; according to the over-current level requirement of superposition of the discharging current of the absorption circuit and the bridge arm current, analyzing and cutting off two discharging working conditions to obtain a second limiting condition based on current stress and discharging time, establishing a loss model according to the system loss requirement to obtain a third limiting condition, and determining the final value of the absorption resistor meeting all design requirements by integrating the limiting conditions. The invention can realize balance among suppression of overvoltage, control of current stress and optimization of system loss, and remarkably improves the reliability, economy and operation safety of the state control switch of the nine-bridge arm modularized multi-level converter.

Inventors

• XU YUTAO
• LI XINZHUO
• ZHANG HOUYI
• XIONG NAN
• Dai Qiji
• GAO YUAN
• ZHANG YUANYUAN
• XING DENGJIANG
• LIU ZONGSHENG
• ZHANG ZHENXING
• TAN ZHUKUI
• CHEN DUNHUI
• FENG QIHUI
• LV QIANSU
• LIN CHENGHUI
• QI XUEWEN
• LI SHAOSHUAI
• GAO JIPU

Assignees

• 贵州电网有限责任公司

Dates

Publication Date

20260512

Application Date

20251231

Claims (10)

1. 1. A nine-bridge arm modularized multi-level converter absorption resistance parameter design method is characterized by comprising the following steps of, Calculating the value range of the absorption resistor according to the transient overvoltage requirement in the turn-off process of the state control switch to obtain a first limiting condition; Calculating the value range of the absorption resistor according to the overcurrent level requirement generated when the discharge current of the absorption circuit flows through the bridge arm, so as to obtain a second limiting condition; Calculating the value range of the absorption resistor according to the loss requirement in the charge and discharge process of the absorption circuit to obtain a third limiting condition; And combining the first limiting condition, the second limiting condition and the third limiting condition to determine the final value of the absorption resistor.
2. 2. The method for designing absorption resistance parameters of the nine-bridge arm modularized multi-level converter of claim 1, wherein said obtaining a first constraint condition comprises analyzing the action process of the state control switch under four switching conditions, and determining the condition in which transient overvoltage is generated; aiming at the working condition that transient overvoltage can be generated, a charging equivalent circuit of the absorption circuit in the switching-off process of the switch is established; And obtaining the value range of the absorption resistor through circuit analysis based on the charging equivalent circuit, the maximum port voltage born by the state control switch, the rated voltage of the switching device and the action delay time thereof, and taking the value range as the first limiting condition.
3. 3. The method for designing absorption resistance parameters of the nine-bridge arm modularized multi-level converter of claim 2, wherein said obtaining second constraint comprises analyzing discharge loops of the absorption circuit at different switching stages of the state control switch; respectively establishing a discharge equivalent circuit of the absorption circuit in the process of putting the third bridge arm into the sub-module and in the process of cutting off all the sub-modules of the third bridge arm; based on the bridge arm current peak value constraint and the time requirement that the discharging process needs to be completed in a specific section of the system modulation wave, the value range of the absorption resistor is obtained through circuit analysis and is used as a second limiting condition.
4. 4. The method for designing absorption resistance parameters of the nine-bridge arm modularized multi-level converter of claim 3, wherein said obtaining third constraint comprises analyzing a charge-discharge process of the absorption circuit along with a third bridge arm port voltage change; Establishing a loss calculation model in the charge and discharge process of the absorption circuit; And determining a value interval of the absorption resistance based on the loss calculation model and the allowable loss level of the system, and taking the value interval as a third limiting condition.
5. 5. The method for designing absorption resistance parameters of the nine-bridge arm modularized multi-level converter according to claim 4, wherein when the charging equivalent circuit is established, a loop formed by a single insulated gate bipolar transistor IGBT, an absorption capacitor and an absorption resistor connected in parallel is equivalent to a resistance-capacitance RC charging circuit, and a charging voltage source is the maximum voltage of the third bridge arm port.
6. 6. The method for designing absorption resistance parameters of the nine-bridge arm modularized multi-level converter of claim 5, wherein the absorption circuit comprises two types, wherein the first type is generated after the working state of the state control switch is switched and when the third bridge arm starts to be put into the submodule, the discharge current flows through the conducted IGBT; the second type occurs after all sub-modules of the third leg are cut off, before or after the state control switch completes switching, and the discharge current flows through the diode or IGBT.
7. 7. The method for designing absorption resistance parameters of the nine-bridge arm modular multilevel converter of claim 6, wherein determining the final value of the absorption resistance comprises determining that the resistance value is less than an upper limit value determined by the first constraint condition; The resistance value needs to be larger than the larger of the two lower limit values determined by the second constraint.
8. 8. The absorption resistance parameter design system of the nine-bridge arm modularized multi-level converter is characterized by comprising a voltage constraint analysis module, a current constraint analysis module, a loss constraint analysis module and a parameter comprehensive determination module, wherein the method for designing the absorption resistance parameter of the nine-bridge arm modularized multi-level converter is applied to any one of claims 1-7; the voltage constraint analysis module is used for calculating the value range of the absorption resistor according to the transient overvoltage requirement in the switching-off process of the state control switch to obtain a first limiting condition; the current constraint analysis module is used for calculating the value range of the absorption resistor according to the overcurrent level requirement generated when the discharge current of the absorption circuit flows through the bridge arm, so as to obtain a second limiting condition; The loss constraint analysis module is used for calculating the value range of the absorption resistor according to the loss requirement in the charging and discharging process of the absorption circuit to obtain a third constraint condition; And the parameter comprehensive determination module is used for integrating the first limiting condition, the second limiting condition and the third limiting condition to determine the final value of the absorption resistor.
9. 9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the steps of a nine-leg modular multilevel converter absorption resistance parameter design method according to any one of claims 1 to 7.
10. 10. A computer-readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements the steps of a nine-leg modular multilevel converter absorption resistance parameter design method according to any one of claims 1 to 7.

Description

Nine-bridge arm modularized multi-level converter absorption resistance parameter design method, system, equipment and medium Technical Field The invention relates to the technical field of flexible direct current transmission of power systems, in particular to a method, a system, equipment and a medium for designing absorption resistance parameters of a nine-bridge arm modularized multi-level converter. Background The conventional modularized multi-level converter module has high integration level, the submodule structure is simple, the structure of half/full-bridge submodule cascade connection is adopted, the AC output level number and the equivalent switching frequency are improved, AC harmonic waves and DC side ripple waves are reduced, the transmission of active power and reactive power can be independently regulated, and the modularized multi-level converter has wide application prospects in the aspects of DC power transmission, power generation grid connection of renewable energy sources and the like. However, the conventional modularized multi-level converter has the disadvantages of more submodules, high cost and large occupied area, and restricts the development of the flexible direct current transmission technology. The scholars propose a nine-bridge arm modularized multi-level converter structure, and the utilization rate of the submodules is improved by configuring the third bridge arm, so that the number of the submodules in each phase is reduced, and the light converter is effectively realized. The nine-bridge arm modularized multi-level converter comprises nine bridge arms and six state control switches, the number of sub-modules of each bridge arm is smaller than that of the conventional modularized multi-level converter, six state control switches are required to act to realize the same function of the conventional modularized multi-level converter, the state control switches are formed by connecting IGBTs in series, and when the IGBTs are in series operation, the phenomenon of unbalanced partial pressure on each IGBT device in series can be caused due to the fact that individual parameter differences and peripheral circuit parameters are inconsistent. When the IGBT is in an on-off state, although the voltages at two ends of each IGBT device in the power electronic series valve bank basically keep stable, static uneven voltage is caused by different volt-ampere characteristics and temperature changes of the series IGBT devices, and when the IGBT is in an on-off transient state, abrupt voltage changes at two ends of each IGBT device in the series valve bank are caused by differences of parameters of the IGBT and inconsistent parameters of peripheral circuits. For series static voltage equalizing, a method of parallel static voltage equalizing resistance is generally adopted, for series dynamic voltage equalizing, a passive buffer method is selected, and a parallel absorption resistance-capacitance circuit is adopted to slow down the rising speed of anode voltage during turn-off, so that dynamic pressure difference is reduced, and the resistance-capacitance absorption circuit has the advantages of simple structure, easiness in realization, high reliability and the like. Disclosure of Invention In view of the existing problems, the invention provides a method, a system, equipment and a medium for designing absorption resistance parameters of a nine-bridge arm modularized multi-level converter. Therefore, the technical problem solved by the invention is that aiming at the dynamic voltage equalizing requirement of the state control switch series IGBT in the nine-bridge arm modularized multi-level converter, the prior art lacks a systematic absorption resistance parameter design method, so that the optimal value of the absorption resistance cannot be rapidly and accurately determined under a plurality of constraint conditions of inhibiting transient overvoltage, limiting bridge arm overcurrent, controlling system loss and the like, thereby influencing the reliability, economy and safety of the operation of the converter. The invention provides a nine-bridge arm modularized multi-level converter absorption resistance parameter design method, which comprises the steps of calculating a value range of an absorption resistance according to transient overvoltage requirements in a state control switch turn-off process to obtain a first limiting condition, calculating a value range of the absorption resistance according to overcurrent level requirements generated when discharge current of an absorption circuit flows through a bridge arm to obtain a second limiting condition, calculating a value range of the absorption resistance according to loss requirements in an absorption circuit charge-discharge process to obtain a third limiting condition, and determining a final value of the absorption resistance by integrating the first limiting condition, the second limiting condition and the third limiting con