CN-122000837-A - Double-fed motor rotor winding inverse time limit overload protection method and device

CN122000837ACN 122000837 ACN122000837 ACN 122000837ACN-122000837-A

Abstract

The application discloses a doubly fed motor rotor winding inverse time limit overload protection method and device, wherein the method comprises the steps of collecting three-phase current of a doubly fed motor rotor winding; rectifying the three-phase current signal of the rotor winding, converting the three-phase current signal into a six-pulse waveform rectified current signal, converting overload reference current, calculating a heat accumulation value in real time by adopting an inverse time limit heat accumulation equation based on the overload reference current and the rectified current, judging whether the heat accumulation value is greater than or equal to a heat accumulation threshold value, and sending a tripping signal by a protection system if the heat accumulation value is greater than or equal to the heat accumulation threshold value. According to the technical scheme, the three-phase alternating current signal is rectified, and the overload heat accumulation value calculation and judgment are carried out on the rectified output signal by adopting the converted overload reference current, so that the problem that the conventional inverse time limit protection method cannot meet the accuracy and timeliness requirements when processing the extremely low-frequency rotor current is solved, and the accurate and timely inverse time limit overload protection is ensured to be provided for the doubly fed motor.

Inventors

CHEN DAIFAN
WANG KAI
ZHANG QIXUE
WANG GUANG
XU TIANLE
LI HUAZHONG
JI YAOYAO
SHU JIAMING

Assignees

南京南瑞继保电气有限公司
南京南瑞继保工程技术有限公司

Dates

Publication Date: 20260508
Application Date: 20241108

Claims (12)

1. A method of double-fed motor rotor winding inverse time-limited overload protection, comprising: collecting three-phase current of a rotor winding of the doubly-fed motor; rectifying the three-phase current signal of the rotor winding, and converting the three-phase current signal into a six-pulse waveform rectified current signal; Calculating a heat accumulation value in real time by adopting an inverse time limit heat accumulation equation based on the overload reference current and the rectification current; And judging whether the heat accumulation value is larger than or equal to a heat accumulation threshold value, and if so, sending a tripping signal by the protection system.
2. A method of doubly fed motor rotor winding inverse time-limited overload protection as claimed in claim 1 wherein: the three-phase current signals of the rotor winding are rectified and converted into six-pulse waveform rectified current signals, and the six-pulse waveform rectified current signals are realized by a hardware method or a software method.
3.A method of protecting a doubly fed motor rotor winding against inverse time-limited overload in accordance with claim 2, The hardware method comprises the steps of converting a three-phase current signal of a rotor winding into a voltage signal through a conversion circuit, inputting the voltage signal into a three-phase bridge rectifier circuit for rectification, and obtaining rectification current output by the three-phase bridge rectifier circuit.
4.A method of protecting a doubly fed motor rotor winding against inverse time-limited overload in accordance with claim 2, The calculation formula for rectifying by the software method is as follows: i t ＝max[abs(i ab ),abs(i bc ),abs(i ca )] wherein t represents time, i t is a rectifying current at t, i ab 、i bc and i ac are line currents between AB phases, BC phases and AC phases of the doubly-fed motor respectively, ABs is an absolute value function, and max is a maximum value function.
5. The method for protecting inverse time limit overload of rotor winding of doubly-fed machine according to claim 1, wherein the specific method for converting overload reference current is as follows: I base ＝λI ezd Wherein I base is the overload reference current of the rotor, lambda is an equivalent coefficient, and I ezd is the rated current secondary value of the doubly fed motor rotor.
6. The method for protecting inverse time limit overload of doubly-fed motor rotor windings according to claim 5, wherein the equivalent coefficient is 1.5-3.
7. A method for protecting rotor windings of doubly-fed machine against inverse time-lapse overload as set forth in claim 1, wherein said inverse time-lapse thermal accumulation equation is defined as follows: Wherein A represents a heat accumulation value in a period from an initial time to a time T, I t represents a rectifying current at the time T, I base represents a rotor overload reference current, k srzd represents a heat dissipation effect coefficient, T represents time, T 0 represents an inverse time limit protection starting time, and T represents a current time.
8. The method for protecting rotor windings of doubly-fed machine against overload in inverse time limit as set forth in claim 7, wherein said inverse time limit starting time is a time when any one of three phases of currents of rotor windings of doubly-fed machine is greater than a setting value of overload protection current.
9. The method for protecting inverse time limit overload of rotor winding of doubly-fed machine as claimed in claim 7, wherein the value range of the heat dissipation effect coefficient is 1.02-1.05.
10. The anti-time limit overload protection device for the doubly fed motor rotor winding is characterized by comprising an electric quantity acquisition unit, a rectifying unit, an overload protection calculation unit and an overload protection control unit, wherein: The electric quantity acquisition unit is used for acquiring three-phase current of the rotor winding of the doubly-fed motor; the rectification unit rectifies the three-phase current signals of the rotor winding and converts the three-phase current signals into rectified current signals with six-pulse waveforms; The overload protection calculation unit is used for converting overload reference current and calculating a heat accumulation value in real time by adopting an inverse time limit heat accumulation equation based on the overload reference current and the rectification current; and the overload protection control unit is used for judging whether the heat accumulation value is greater than or equal to a heat accumulation threshold value, and if so, sending a tripping signal.
11. An electronic device comprising a processor and a memory, the memory having stored thereon a program capable of being loaded by the processor for performing the method according to any of claims 1-9.
12. A computer readable storage medium storing a computer program, which when executed by a processor performs the method of any one of claims 1-9.

Description

Double-fed motor rotor winding inverse time limit overload protection method and device Technical Field The invention belongs to the field of power systems, and particularly relates to a doubly-fed motor rotor winding inverse time limit overload protection method and device. Background With the rapid development of the economy in China, the power demand continuously rises, the peak-valley difference of the load is increased, the large-scale grid connection proportion of new energy sources such as wind energy, photovoltaic power generation and the like is obviously increased, and the power fluctuation forms challenges for the safe and stable operation of the power grid. In this context, the role of pumped-storage power stations is increasingly prominent. Compared with a constant-speed unit, the variable-speed pumped storage unit improves the flexibility and reliability of a power system by flexibly adjusting the amplitude, the phase and the frequency of alternating-current exciting current. The inverse time limit overload protection is particularly important in the application of the pumped storage unit motor, a set heat accumulation model can be adopted, the heat accumulation state of a motor winding can be calculated in real time according to the current overload degree, and the motor is cut off before overheat, so that the motor is effectively prevented from being damaged. Therefore, it is particularly important to perform accurate inverse time-limited overload protection on the motor. The current traditional inverse time limit overload protection method mainly depends on monitoring and protecting motor current. When the current exceeds the lower limit setting, the inverse time limit protection starts and begins accumulating the calculated heat. Once the heat accumulation value exceeds the set heat accumulation constant value, the protection device sends out a tripping signal, so that the motor power supply is cut off to prevent damage. However, this method is not applicable to a doubly-fed motor. The doubly-fed motor is a motor which can still keep the frequency of a power grid constant when the rotating speed changes, a rotor winding of the doubly-fed motor is powered by a frequency converter, and the frequency of exciting current output by the frequency converter is related to the rotating speed of the rotor, and the doubly-fed motor is characterized by extremely-low frequency three-phase current which changes in the range of 0-5 Hz. The conventional inverse time limit overload protection method is difficult to accurately calculate the heat accumulation state of the winding, so that the overload protection accuracy and timeliness requirements of the doubly-fed motor cannot be met. Therefore, the doubly fed machine needs to introduce a new anti-time-limit overload protection method. Disclosure of Invention The application aims to provide a doubly-fed motor rotor winding inverse time limit overload protection method, which is used for solving the problem that the extremely low frequency rotor current in a doubly-fed motor cannot adopt the conventional inverse time limit protection method. In order to achieve the above purpose, the technical scheme adopted by the application is as follows: according to a first aspect of the present application, there is provided a doubly-fed motor rotor winding inverse time-limited overload protection method, comprising: collecting three-phase current of a rotor winding of the doubly-fed motor; rectifying the three-phase current signal of the rotor winding, and converting the three-phase current signal into a six-pulse waveform rectified current signal; Calculating a heat accumulation value in real time by adopting an inverse time limit heat accumulation equation based on the overload reference current and the rectification current; And judging whether the heat accumulation value is larger than or equal to a heat accumulation threshold value, and if so, sending a tripping signal by the protection system. According to some embodiments, the rectifying the three-phase current signal of the rotor winding is converted into a six-pulse waveform rectified current signal, and the rectifying is implemented by a hardware method or a software method. According to some embodiments, the hardware method comprises the steps of converting the three-phase current signals of the rotor winding into voltage signals through a conversion circuit, inputting the voltage signals into a three-phase bridge rectifier circuit for rectification, and obtaining rectification currents output by the three-phase bridge rectifier circuit. According to some embodiments, the software method performs rectification according to the following calculation formula: it＝max[abs(iab),abs(ibc),abs(ica)] wherein t represents time, i t is a rectifying current at t, i ab、ibc and i ac are line currents between AB phases, BC phases and AC phases of the doubly-fed motor respectively, ABs is an absolute value function, and m