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KR-102962140-B1 - Zero-sequence current suppression method and device, converter and wind power generation set

KR102962140B1KR 102962140 B1KR102962140 B1KR 102962140B1KR-102962140-B1

Abstract

The present disclosure provides a zero-sequence current suppression method and device, a converter, and a wind power generation set. The converter comprises N converter units connected in parallel, where N is a positive integer greater than or equal to 2. The zero-sequence current suppression method comprises: acquiring zero-sequence currents of N-1 converter units among the N converter units; synchronizing PWM control signals of all rectifiers on the N converter units and synchronizing PWM control signals of all inverters to suppress high-frequency components of the zero-sequence currents of the N converter units; and performing PI control using zero-sequence currents of N-1 converter units and zero-sequence current reference values of the N-1 converter units to suppress low-frequency components of the zero-sequence currents of the N converter units. According to the zero-sequence current suppression method provided by embodiments of the present disclosure, high-frequency and low-frequency components of the zero-sequence currents of the converters can be suppressed simultaneously.

Inventors

  • 왕 진펑

Assignees

  • 골드윈드 사이언스 앤 테크놀로지 컴퍼니 리미티드

Dates

Publication Date
20260508
Application Date
20220629
Priority Date
20211229

Claims (10)

  1. A zero-sequence current suppression method for a converter, wherein the converter comprises N converter units connected in parallel, N is a positive integer greater than or equal to 2, and the method comprises: To suppress high-frequency components of zero-sequence currents in the N converter units, the step of synchronizing pulse width modulation (PWM) control signals of all rectifiers in the N converter units and synchronizing PWM control signals of all inverters in the N converter units; A step of obtaining a zero-sequence current at each of N-1 converter units among the above N converter units - for each of the above N-1 converter units, the zero-sequence current is obtained by calculating from the input current of the rectifier of the converter unit -; and A step of performing PI adjustment using the zero-sequence currents of the N-1 converter units and the zero-sequence current reference values of the N-1 converter units to suppress low-frequency components of the zero-sequence currents in the N converter units. A zero-sequence current suppression method for a converter comprising
  2. In claim 1, the step of performing PI adjustment using the zero-sequence currents of the N-1 converter units and the zero-sequence current reference values of the N-1 converter units to suppress the low-frequency components of the zero-sequence currents in the N converter units comprises: A step of performing PI adjustment using zero-sequence currents of the N-1 converter units and zero-sequence current reference values of the N-1 converter units to obtain voltage control components for controllers within each of the N-1 converter units; and A step of controlling the PWM controllers of the inverters in each of the above converter units based on the voltage control components to suppress the low-frequency components of the zero-sequence currents in the above N converter units. A zero-sequence current suppression method for a converter comprising
  3. A zero-sequence current suppression method for a converter, wherein, in claim 1, the DC buses in each of the N converter units are independent of each other.
  4. delete
  5. In paragraph 1, Among the above N converter units, The PWM controllers of the rectifiers within adjacent converter units among the above converter units communicate with each other via optical fiber connections, and A zero-sequence current suppression method for a converter, wherein the PWM controllers of inverters within adjacent converter units among the above converter units communicate with each other via a fiber optic connection.
  6. A zero-sequence current suppression method for a converter according to claim 5, wherein the PWM control signals of all rectifiers in the N converter units are synchronized through clock synchronization, and the PWM control signals of all inverters in the N converter units are synchronized through clock synchronization.
  7. A computer-readable storage medium, wherein the computer-readable storage medium stores instructions or programs, and when the instructions or programs are executed by a processor, implements a zero-sequence current suppression method according to any one of claims 1 to 3, 5 and 6.
  8. As a zero-sequence current suppression device, A carrier synchronization unit configured to synchronize PWM control signals of all rectifiers within the N converter units and synchronize PWM control signals of all inverters within the N converter units in order to suppress high-frequency components of zero-sequence currents in the N converter units; A current sampling unit configured to obtain a zero-sequence current at each of N-1 converter units among the above N converter units—for each of the above N-1 converter units, the zero-sequence current is obtained by calculating from the input current of the rectifier of the converter unit—; and A PI control unit configured to perform PI control using the zero-sequence currents of N-1 converter units and zero-sequence current reference values of N-1 converter units to suppress low-frequency components of the zero-sequence currents in the N converter units. A zero-sequence current suppression device comprising
  9. As a converter, A computer-readable storage medium pursuant to paragraph 7, or As a zero-sequence current suppression device, A carrier synchronization unit configured to synchronize PWM control signals of all rectifiers within the N converter units and synchronize PWM control signals of all inverters within the N converter units in order to suppress high-frequency components of zero-sequence currents in the N converter units; and A current sampling unit configured to obtain a zero-sequence current at each of N-1 converter units among N converter units—for each of the N-1 converter units, the zero-sequence current is obtained by calculating from the input current of the rectifier of the converter unit—; A zero-sequence current suppression device comprising a PI control unit configured to perform PI control using the zero-sequence currents of N-1 converter units and zero-sequence current reference values of the N-1 converter units to suppress low-frequency components of the zero-sequence currents in the N converter units. A converter including
  10. A wind turbine comprising a converter according to paragraph 9, as a wind turbine.

Description

Zero-sequence current suppression method and device, converter and wind power generation set This application claims priority to Chinese patent application No. 202111632947.0, filed with the China National Intellectual Property Administration (CNIPA) on December 29, 2021, the title of the invention "ZERO-SEQUENCE CURRENT SUPPRESSION METHOD AND DEVICE, CONVERTER, MEDIUM AND WIND GENERATING SET," the entirety of which is incorporated herein by reference. Technology field The present disclosure generally relates to the field of converters, and in particular to zero-sequence current suppression methods and apparatus, converters, and wind turbines. In a converter, the parallel connection of converter cabinets or converter units can not only increase the capacity of the converter system but also improve conversion efficiency and enhance the stability and reliability of the system. However, due to incomplete matching of hardware parameters between parallel-connected converter cabinets or converter units, the operation of switching devices within the converter may not be fully synchronized, which can result in differing output voltages of the converter units or cabinets. Consequently, zero-sequence voltages are generated. Additionally, structural differences among modules within the converter, sampling, control parameters, and fiber delay can also cause discrepancies in the output voltages of the converter units or cabinets. When zero-sequence voltages act on the equivalent resistance between wind power converters, zero-sequence currents or zero-sequence cycles are formed. Zero-sequence circulating current increases the degradation of switching devices, reduces system efficiency, increases the probability of failure and shutdown of wind power converters, and in severe cases, can destroy the entire converter system. Currently, there are no effective countermeasures to suppress zero-sequence circulating current in converters. Conventionally, due to capacity limitations, the parallel connection of converter cabinets or converter units is not common in wind power converters. However, with the continuous increase in the overall power levels of wind turbines, topologies of parallel-connected converter cabinets are becoming a trend. Nevertheless, conventional technologies for controlling wind power converters lack solutions to suppress zero-sequence circulating currents in parallel connections. Additionally, in the case of a solution that reduces the zero-sequence voltage difference by increasing resistance, more resistors need to be added as the number of wind converter cabinets or converter units increases, which also leads to increased costs and losses. The above content is presented for background information only to aid in understanding the relevant technical content. The disclosure of the above content does not imply that it constitutes prior art. The object of the present disclosure is to provide a zero-sequence current suppression method and a zero-sequence current suppression apparatus capable of zero-sequence current suppression. Another object of the present disclosure is to provide a zero-sequence current suppression method and a zero-sequence current suppression apparatus capable of suppressing both the high-frequency and low-frequency components of the zero-sequence current. According to a first aspect of the present disclosure, a method for suppressing zero-sequence current for a converter is provided. The converter comprises N converter units connected in parallel, wherein N is a positive integer greater than or equal to 2. The method for suppressing zero-sequence current comprises: obtaining zero-sequence currents in each of N-1 converter units among the N converter units; synchronizing PWM control signals of all rectifiers in the N converter units and synchronizing PWM control signals of all inverters in the N converter units to suppress high-frequency components of zero-sequence currents in the N converter units; and performing PI control using zero-sequence currents of N-1 converter units and zero-sequence current reference values of N-1 converter units to suppress low-frequency components of zero-sequence currents in the N converter units. According to a second aspect of the present disclosure, a computer-readable storage medium storing instructions or a program is provided. A zero-sequence current suppression method is implemented when a processor executes the instructions or the program. According to a third aspect of the present disclosure, a zero-sequence current suppression device for a converter is provided. The device comprises: a current sampling unit configured to acquire zero-sequence currents in each of N-1 converter units among N converter units; a carrier synchronization unit configured to synchronize PWM control signals of all rectifiers in N converter units and PWM control signals of all inverters in N converter units to suppress high-frequency components of zero-sequence currents in N