CN-121983919-A - Frequency converter differential protection method, device, equipment and storage medium

CN121983919ACN 121983919 ACN121983919 ACN 121983919ACN-121983919-A

Abstract

The application discloses a differential protection method, device and equipment for a frequency converter and a storage medium, and relates to the technical field of fault protection. The frequency converter differential protection method comprises the steps of collecting three-phase current instantaneous values of valve bank units in a static frequency converter in a preset sampling period, calculating an arithmetic average value of the three-phase current instantaneous values in a preset sliding film window, dividing a bridge and a bridge valve bank of the static frequency converter into at least two valve bank units, determining differential currents and action currents of the valve bank units according to the arithmetic average value, constructing a ratio brake curve according to the action currents, wherein the ratio brake curve is used for representing whether the running state of the valve bank units is a fault state or not, and triggering the valve bank units to start differential overcurrent protection under the condition that the differential currents are in an action region of the ratio brake curve. And combining sliding filtering and a ratio braking curve, balancing protection sensitivity and anti-interference performance, avoiding false triggering of instantaneous values, and realizing differential protection under the condition of inconsistent frequencies at the bridge side and the network bridge side.

Inventors

WANG XIAOYUAN
LI FENG
WANG XING
WANG LICHUN
CUI YUJIE
CHAN DONGHUI
PAN YANSHENG

Assignees

特变电工科技投资有限公司

Dates

Publication Date: 20260505
Application Date: 20260206

Claims (10)

1. The differential protection method for the frequency converter is characterized by being applied to a static frequency converter, and comprises the following steps of: Collecting three-phase current instantaneous values of valve bank units in the static frequency converter in a preset sampling period, and calculating an arithmetic average value of the three-phase current instantaneous values in a preset sliding film window; Determining differential current and action current of the valve group unit according to the arithmetic average value; constructing a ratio brake curve according to the action current, wherein the ratio brake curve is used for representing whether the running state of the valve group unit is a fault state or not; And triggering the valve group unit to start differential over-current protection under the condition that the differential current is in an action zone of the ratio brake curve.
2. The method of claim 1, wherein the arithmetic mean comprises a positive current mean and a negative current mean; The step of collecting three-phase current instantaneous values of a valve group unit in the static frequency converter in a preset sampling period and calculating an arithmetic average value of the three-phase current instantaneous values in a preset synovial window comprises the following steps: Calculating a three-phase positive current accumulated value and a three-phase negative current accumulated value of the valve group unit in the preset sampling period based on the acquired three-phase current instantaneous value; acquiring the sampling times of the valve group unit according to the preset sliding film window and the preset sampling period; and calculating the positive current average value of the valve group unit according to the sampling times and the three-phase positive current accumulated value, and calculating the negative current average value of the valve group unit according to the sampling times and the three-phase positive current accumulated value.
3. The method of differential protection of a frequency converter according to claim 2, wherein the step of calculating a three-phase positive current integrated value and a three-phase negative current integrated value of the valve group unit within the preset sampling period based on the acquired three-phase current instantaneous values includes: comparing the three-phase current instantaneous value acquired in the preset sampling period with zero potential; Determining three-phase positive current and three-phase negative current of the valve group unit in the preset sampling period according to the comparison result of the three-phase current instantaneous value and zero potential; And accumulating the three-phase positive currents of the valve bank units to obtain three-phase positive current accumulated values, and accumulating the three-phase negative currents of the valve bank units to obtain three-phase negative current accumulated values.
4. The method of claim 3, wherein the stationary frequency converter comprises at least two six-pulse rectifying units, each of the six-pulse rectifying units comprising an upper bridge arm and a lower bridge arm; based on the upper bridge arm and/or the lower bridge arm of the adjacent six-pulse rectifying units connected by one current loop, the bridge and the bridge valve bank of the static frequency converter are divided into one valve bank unit, and the number of the valve bank units is the same as that of the six-pulse rectifying units.
5. The method of claim 4, wherein the stationary frequency converter is a twelve-pulse-six-pulse stationary frequency converter, and wherein the step of collecting three-phase current instantaneous values of a first valve bank unit in the stationary frequency converter and calculating an arithmetic average of the three-phase current instantaneous values within a predetermined synovial window during a predetermined sampling period further comprises: Dividing a bridge of the static frequency converter into a first valve group unit and a second valve group unit, and dividing a bridge valve group of the static frequency converter into a third valve group unit; The step of determining the differential current and the action current of the first valve group unit according to the arithmetic average value comprises the following steps: Obtaining differential current and action current of the first valve bank unit according to the arithmetic average value of the first valve bank unit and the arithmetic average value of the third valve bank unit; the differential current and the action current of the first valve group unit are obtained according to the arithmetic average value of the second valve group unit and the arithmetic average value of the third valve group unit; and obtaining differential current and action current of a third valve group unit according to the arithmetic average value of the first valve group unit and the arithmetic average value of the second valve group unit.
6. The method of claim 1, wherein the step of constructing a ratio brake curve from the operating current comprises: Calculating the braking current of the valve group unit according to the action current; And constructing a ratio brake curve of the valve group unit based on the starting current of the static frequency converter and the brake current.
7. The method of claim 6, wherein the step of triggering the valve block unit to initiate differential over-current protection when the differential current is in the operating region of the ratio brake curve further comprises: collecting three-phase current instantaneous values of the valve group unit in the static frequency converter in the next period based on the preset sampling period; and recalculating an arithmetic average value of the three-phase current instantaneous value in a preset synovial window according to the sampling times.
8. A differential protection device for a frequency converter, the device comprising: The sliding film filter module is used for collecting three-phase current instantaneous values of valve bank units in the static frequency converter and calculating an arithmetic average value of the three-phase current instantaneous values in a preset sliding film window; the current calculation module is used for determining differential current and action current of the valve group unit according to the arithmetic average value; the curve construction module is used for constructing a ratio brake curve according to the action current, wherein the ratio brake curve is used for representing whether the running state of the valve group unit is a fault state or not; And the fault protection module is used for triggering the valve group unit to start differential overcurrent protection under the condition that the differential current is in the action zone of the ratio brake curve.
9. A differential protection device for a frequency converter, characterized in that the device comprises a memory, a processor and a computer program stored on the memory and executable on the processor, the computer program being configured to implement the steps of the differential protection method for a frequency converter according to any one of claims 1 to 7.
10. A storage medium, characterized in that the storage medium is a computer-readable storage medium, on which a computer program is stored, which computer program, when being executed by a processor, realizes the steps of the method for differential protection of a frequency converter according to any one of claims 1 to 7.

Description

Frequency converter differential protection method, device, equipment and storage medium Technical Field The present application relates to the field of fault protection technologies, and in particular, to a method, an apparatus, a device, and a storage medium for protecting a frequency converter differential. Background The frequency converter is a power control device which controls the alternating current motor by changing the frequency of a working power supply of the motor by applying a frequency conversion technology and a microelectronic technology. The device mainly comprises modules such as rectification (alternating current to direct current), filtering, inversion (direct current to alternating current), a braking unit, a driving unit, a detection unit, a micro-processing unit and the like. The frequency converter adjusts the voltage and frequency of the output power supply by switching on and off an internal switching device, and provides the required power supply voltage according to the actual requirement of the motor, thereby achieving the purposes of energy saving and speed regulation. The normal operation of the high-power frequency converter is related to the economical efficiency and the stability of the power system, and the normal operation of the unit can be influenced to different degrees when any equipment is abnormal or fails. The pumped storage static frequency converter (Static Frequency Converter) is used as a typical application of a high-power frequency converter, and the working principle is that a network bridge side is directly connected to a power frequency power grid (the frequency is fixed to be 50 Hz), the machine bridge side is required to generate variable-frequency three-phase alternating current through rectification and inversion according to the spatial position of a motor rotor, and the generated stator magnetic field and the rotor magnetic field interact to form electromagnetic torque so as to gradually drag the motor to the rated rotation speed. Therefore, the frequency of the bridge side electric quantity gradually increases from 0 to 50 Hz. The bridge side current of the static frequency converter is a power frequency current, and the bridge side current is a current ranging from 0 to 50 Hz. The significant difference of the current frequencies at the two sides makes the differential protection method based on vector operation not directly applicable. Disclosure of Invention The application mainly aims to provide a differential protection method, device and equipment for a frequency converter and a storage medium, and aims to solve the technical problem that effective differential protection cannot be carried out under the condition that bridge current and bridge current frequency of the frequency converter are inconsistent in the prior art. In order to achieve the above objective, the present application provides a differential protection method for a frequency converter, which includes: Collecting three-phase current instantaneous values of valve bank units in the static frequency converter in a preset sampling period, and calculating an arithmetic average value of the three-phase current instantaneous values in a preset sliding film window; Determining differential current and action current of the valve group unit according to the arithmetic average value; constructing a ratio brake curve according to the action current, wherein the ratio brake curve is used for representing whether the running state of the valve group unit is a fault state or not; And triggering the valve group unit to start differential over-current protection under the condition that the differential current is in an action zone of the ratio brake curve. In one embodiment, the arithmetic mean comprises a positive current mean and a negative current mean; The step of collecting three-phase current instantaneous values of a valve group unit in the static frequency converter in a preset sampling period and calculating an arithmetic average value of the three-phase current instantaneous values in a preset synovial window comprises the following steps: Calculating a three-phase positive current accumulated value and a three-phase negative current accumulated value of the valve group unit in the preset sampling period based on the acquired three-phase current instantaneous value; acquiring the sampling times of the valve group unit according to the preset sliding film window and the preset sampling period; and calculating the positive current average value of the valve group unit according to the sampling times and the three-phase positive current accumulated value, and calculating the negative current average value of the valve group unit according to the sampling times and the three-phase positive current accumulated value. In an embodiment, the step of calculating the three-phase positive current integrated value and the three-phase negative current integrated value of the valve group unit