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CN-122026545-A - Configuration method of voltage flexible proportioning cascading type converter system

CN122026545ACN 122026545 ACN122026545 ACN 122026545ACN-122026545-A

Abstract

The invention discloses a configuration method of a voltage flexible proportioning cascading type converter system, which comprises the steps of firstly constructing a voltage flexible proportioning cascading type converter topological structure, then establishing an initial distribution relation between voltage grade selection and transmission power of a cascading type converter, determining rated voltage division ratio of each station according to the planning requirement of a network frame at a receiving end, next determining a constraint relation between the running range of full-half-bridge mixed MMC direct-current voltage and the proportion of full-bridge submodules, and finally establishing a corresponding relation between the flexible power distribution adjusting range and the configuration proportion of the full-bridge submodules in the running process of the cascading type converter, and realizing flexible mutual adjustment of active power among different converter stations by cooperatively adjusting the direct-current voltage proportions of two stations. The invention not only realizes the differential proportioning of the power of the receiving end in the planning stage, but also realizes the flexible power dispatching across the power grid in the running stage, and obviously improves the dispatching activity and engineering applicability of the cascading direct current power transmission system.

Inventors

  • WANG GUOTENG
  • HUANG YING
  • HOU TIAN

Assignees

  • 浙江大学

Dates

Publication Date
20260512
Application Date
20260414

Claims (10)

  1. 1. The configuration method of the voltage flexible proportioning cascading type converter system is characterized by comprising the following steps of: (1) The method comprises the steps of constructing a voltage flexible proportion cascading type current conversion topological structure, wherein the topological structure consists of a power supply at a transmitting end and a cascading station at a receiving end, the cascading station at the receiving end comprises two converters A1 and A2, and the direct current sides of the converters A1 and A2 are connected in series, one end of the direct current sides of the converters A1 and A2 are connected with the power supply at the transmitting end, and the other ends of the direct current sides of the converters A1 and A2 are grounded; (2) Establishing an initial distribution relation between voltage class selection and transmission power of a receiving-end cascade station, and determining rated direct current voltage ratio of converters A1 and A2 according to active planning requirements of receiving-end alternating current power grids AC1 and AC 2; (3) Determining a modulation boundary of the converter in the voltage regulation process according to the constraint relation between the direct-current voltage operation range of the converter and the proportion of the full-bridge submodule; (4) And establishing a corresponding relation between a flexible power distribution adjusting range and a full-bridge submodule configuration proportion in the operation process of the receiving end cascade station, and further cooperatively adjusting direct-current voltage proportion of the converters A1 and A2 to realize flexible mutual compensation of active power between the two converters.
  2. 2. The method for configuring the voltage flexible proportioning cascading type current converting system according to claim 1, wherein the current converters A1 and A2 adopt MMC, and each bridge arm cascading submodule adopts a full-bridge submodule and half-bridge submodule mixed proportioning design.
  3. 3. The method of claim 1, wherein the direct current of the converters A1 and A2 is exactly equal, i.e., I dc =I dcA1 =I dcA2 , during steady state operation, and the direct current of the receiving end cascade station is U dc =U dcA1 +U dcA2 , wherein I dcA1 and I dcA2 are the direct current of the converters A1 and A2, respectively, and are collectively denoted as I dc ,U dcA1 and U dcA2 are the direct current of the converters A1 and A2, respectively.
  4. 4. The method of claim 3, wherein the initial allocation in the step (2) satisfies the following relationship: ; Wherein, P dcA1 and P dcA2 are active power transmitted by the converters A1 and A2 respectively.
  5. 5. The method of claim 1, wherein in the step (2), if the active power ratio of the AC1 and AC2 of the receiving end is N1, the number of sub-modules in the converters A1 and A2 is configured and the transformation ratio of the converter transformer is adjusted so that the rated dc voltage ratio of A1 to A2 is N1 and N is a positive real number.
  6. 6. The method of claim 1, wherein in the step (3), for any one of the converters A1 and A2, the modulation boundary of the converter needs to satisfy the following relation: ; wherein M ac is the alternating current modulation ratio of the converter, M dc is the direct current voltage modulation ratio of the converter, and K FB is the number ratio of Quan Qiaozi modules in a single bridge arm of the converter.
  7. 7. The method of claim 1, wherein in the step (4), on the premise that the direct current voltage U dc of the receiving end cascade station is kept constant, the dynamic mutual compensation of active power between two converters is realized by increasing the direct current voltage command value of one converter and decreasing the direct current voltage command value of the other converter, and for the step-down converters, the number duty ratio K FB of Quan Qiaozi modules in a single bridge arm of the step-down converter monotonically increases along with the decrease of the active power duty ratio of the converter.
  8. 8. The method of claim 5, wherein the power allocation flexible adjustment range in the step (4) and the full-bridge submodule configuration ratio correspond to each other as follows: Under the rated state, the active power ratio of the converters A1 and A2 is N1, and at the moment, K FBA1 =K FBA2 =0%; Under the mutual-compensation operation scene, the active power ratio of the converters A1 and A2 is adjusted to be M1, and if M is less than N, then K FBA2 =0%; if M > N, K FBA1 =0%, ; When the active power ratio of the converter A2 is 100%, then K FBA1 =50%,K FBA2 =0%; when the active power ratio of the converter A1 is 100%, then K FBA1 =0%,K FBA2 =50%; Wherein K FBA1 is the number ratio of Quan Qiaozi modules in a single bridge arm of the converter A1, and K FBA2 is the number ratio of Quan Qiaozi modules in a single bridge arm of the converter A2.
  9. 9. The computer equipment comprises a memory and a processor, wherein the memory stores a computer program, and the computer program is characterized in that the processor is used for executing the computer program to realize the voltage flexible proportioning cascade type converter system configuration method according to any one of claims 1-8.
  10. 10. A computer readable storage medium storing a computer program, wherein the computer program is executed by a processor to implement the voltage flexible ratio cascading commutation system configuration method according to any one of claims 1-8.

Description

Configuration method of voltage flexible proportioning cascading type converter system Technical Field The invention belongs to the technical field of power systems, and particularly relates to a configuration method of a voltage flexible proportioning cascading type converter system. Background Because the new energy resource distribution and the load center are obviously mismatched in space, the flexible direct current transmission technology is adopted to carry out large-capacity and long-distance transmission, and the method becomes a main technical means. Under the background, in order to improve the capacity of a receiving-end power grid for absorbing large-scale new energy current and reduce the safety risk of a single access point, a cascaded modularized multi-level converter (MMC) topology is gradually paid attention to, and by connecting two or more converters in series on a direct current side, a large amount of power at a transmitting end can be respectively injected into different area alternating current systems at the receiving end, so that the dispersed absorption of loads is realized. The application research of the LCC-VSC hybrid cascading DC technology in Jiangsu power grid is carried out in the literature [ Wang Zhiwei, zheng Jianhua, mo Zhen ], the global energy Internet is 2025, 8 (1): 3-12] adopts a structure that a high-end LCC (grid commutation converter) is connected in series with a low-end multi-group VSC (voltage source converter) so as to improve the safety and stability level and reactive support capability of a receiving-end power grid. Literature [ Zhou Baorong, li Xuanping, li Shoutao ] is a high-low voltage valve bank voltage-equalizing control strategy of an LCC-MMC ultra-high voltage hybrid direct current transmission system, south power grid technology, 2022, 16 (8): 79-85] aims at the problem of voltage distribution in a cascade system, and voltage deviation among all valve banks in cascade is adjusted by designing a voltage-equalizing controller so as to realize the balanced distribution of direct current side voltage. However, in the research and engineering practice of these existing cascaded dc power transmission systems, the following key problems to be solved still remain: Firstly, the power grid in the receiving end region has obvious difference in the capacity of absorbing, and after large-scale new energy is sent to the receiving end, the single-region alternating current system often cannot completely absorb the issued power due to insufficient grid strength and limited load level. Although the cascade topology provides two access points, the conventional design of the high-low voltage valve group generally follows the principle of symmetry, namely, two cascaded MMC converter stations are designed to have the same direct current voltage level, and as the direct current is equal everywhere in the cascade structure, the output power of the two receiving end converter stations is forcedly fixed (generally 1:1 distribution) due to the uniformity of the voltage level, and the differential proportioning design according to the actual consumption capacity of different receiving end power grids cannot be performed in the planning stage. Secondly, the load demand of the alternating current system has dynamic property, and in the running process of the system, the power consumption load of the alternating current 1 area and the alternating current 2 area periodically fluctuates, or the receiving end absorption pressure changes in real time due to the randomness of the new energy output. The existing cascade topology lacks flexible power scheduling means in the operation process, and because of direct current receiving ends or total voltage control coupling, if the power distribution between two cascade stations is changed, the voltage distribution proportion of the two cascade stations must be adjusted. However, when the conventional half-bridge submodule structure converter is regulated under the direct-current partial voltage, the direct-current voltage is lower than the voltage peak value at the alternating-current side, so that the direct-current voltage is easy to enter an overmodulation zone, and the harmonic wave of the system is increased rapidly, and even is out of control and collapses. In summary, the existing cascading flexible-direct technology has a double bottleneck of "power proportional locking in planning stage" and "power mutual restriction in running stage" when the existing cascading flexible-direct technology is used for meeting the multi-point consumption requirement of new energy. Therefore, the research design can realize flexible power proportioning at the design stage and can dynamically adjust the direct-current voltage division relation according to the alternating-current power grid demand at the operation stage, so that the cascade topology and the control method of optimal power distribution and dynamic mutual utilization are realized, a