CN-121980824-A - Determination method and system for short circuit demagnetization checking scene of permanent magnet wind driven generator

CN121980824ACN 121980824 ACN121980824 ACN 121980824ACN-121980824-A

Abstract

The invention discloses a method and a system for determining a short-circuit demagnetizing check scene of a permanent magnet wind driven generator, and relates to the technical field of permanent magnet wind driven generators; the method comprises the steps of determining a plurality of candidate checking scenes according to a joint probability density function, respectively calculating output power of a permanent magnet wind driven generator after short circuit faults occur in each candidate checking scene, constructing an expected value equation based on the joint probability density function and the output power, solving the expected value equation, and determining the candidate checking scenes corresponding to wind speed values and environment temperature values meeting the equation as final short circuit demagnetization checking scenes. The method solves the problems of over conservation of the permanent magnet wind power generator design and restriction of power density improvement caused by adopting a very small probability scene as a checking reference in the prior art, and can effectively improve the power density of the permanent magnet wind power generator on the premise of ensuring the overall output reliability.

Inventors

ZHANG YUNHAI
DU YIDONG
XIAO YANG
CHEN LIANG
XU LIWEN
ZHUANG PEI
ZHANG ZHIHAN

Assignees

苏州大学

Dates

Publication Date: 20260505
Application Date: 20260407

Claims (10)

1. A method for determining a short-circuit demagnetizing check scene of a permanent magnet wind driven generator is characterized by comprising the following steps: acquiring a joint probability density function of wind speed and ambient temperature of a target wind field; Determining a plurality of candidate checking scenes according to the joint probability density function, wherein each candidate checking scene corresponds to a group of wind speed values and environment temperature values; respectively calculating the output power of the permanent magnet wind driven generator after short circuit faults occur in each candidate checking scene; Constructing an expected value equation for representing the overall output level of the permanent magnet wind driven generator based on the joint probability density function and the output power; And solving the expected value equation, and determining candidate checking scenes corresponding to the wind speed value and the environment temperature value which meet the expected value equation as final short circuit demagnetizing checking scenes.
2. The method for determining a short-circuit demagnetization checking scene of a permanent magnet wind generator according to claim 1, wherein the obtaining a joint probability density function of a wind speed of a target wind field and an ambient temperature specifically comprises: Collecting historical wind speed data and historical environmental temperature data of a target wind field; respectively determining a probability distribution model of wind speed and a probability distribution model of ambient temperature; And constructing the joint probability density function by considering the relevance between the wind speed and the ambient temperature based on the probability distribution model of the wind speed and the probability distribution model of the ambient temperature.
3. The method for determining a short-circuit demagnetizing check scene of a permanent magnet wind power generator according to claim 1, wherein the calculating the output power of the permanent magnet wind power generator after the occurrence of the short-circuit fault in each candidate check scene comprises: simulating a three-phase short-circuit process of the permanent magnet wind driven generator in each candidate checking scene, and calculating irreversible demagnetization degree of the permanent magnet caused by short-circuit current; based on the demagnetizing degree, a demagnetized permanent magnet wind driven generator model is established; under a preset rated operation condition, rated current is introduced into the demagnetized permanent magnet wind driven generator model, and the output electromagnetic power and stator side loss are calculated; and calculating to obtain the output power of the permanent magnet wind driven generator after short circuit demagnetization occurs in the candidate checking scene according to the electromagnetic power and the stator side loss.
4. The method for determining a short-circuit demagnetization checking scene of a permanent magnet wind generator according to claim 3, wherein the preset rated operation conditions specifically comprise a preset maximum wind speed value and a preset maximum environment temperature value.
5. The method for determining a short circuit demagnetization checking scenario of a permanent magnet wind power generator according to claim 3, wherein the demagnetization degree is characterized by a torque loss percentage, and the torque loss percentage is a ratio of a difference value between an average value of electromagnetic torque before demagnetization and an average value of electromagnetic torque before demagnetization at the same stator current.
6. The method for determining a short circuit demagnetizing check scene of a permanent magnet wind power generator according to claim 1, wherein the expected value equation is a weighted sum of output powers corresponding to all candidate check scenes and occurrence probabilities thereof, and the weighted sum is equal to the output power corresponding to the finally determined check scene; wherein the probability of occurrence of each candidate check scene is determined by the joint probability density function.
7. The method for determining a short circuit demagnetization check scenario of a permanent magnet wind turbine according to claim 6, wherein the expected value equation is specifically expressed as: ; Wherein, the To the point of Is that The output power corresponding to each candidate check scene, To the point of Is that The occurrence probabilities corresponding to the candidate check scenes, Check scene for final determination The corresponding output power.
8. A system for determining a short-circuit demagnetization check scene of a permanent magnet wind power generator, which is characterized in that the system is used for realizing the method for determining the short-circuit demagnetization check scene of the permanent magnet wind power generator according to any one of claims 1 to 7, and specifically comprises the following steps: the joint probability density acquisition module is used for acquiring a joint probability density function of the wind speed and the ambient temperature of the target wind field; the candidate scene determining module is used for determining a plurality of candidate checking scenes according to the joint probability density function, and each candidate checking scene corresponds to a group of wind speed values and environment temperature values; The output power calculation module is used for calculating the output power of the permanent magnet wind driven generator after the short circuit fault occurs in each candidate checking scene; the expected value equation construction module is used for constructing an expected value equation for representing the integral output level of the permanent magnet wind driven generator based on the joint probability density function and the output power; and the check scene selection module is used for solving the expected value equation and determining candidate check scenes corresponding to the wind speed value and the environment temperature value which meet the expected value equation as final short circuit demagnetizing check scenes.
9. An electronic device, characterized in that the electronic device comprises a processor, a memory and a bus system, wherein the processor and the memory are connected through the bus system, the memory is used for storing instructions, and the processor is used for executing the instructions stored in the memory so as to realize the method for determining the short-circuit demagnetization checking scene of the permanent magnet wind power generator according to any of claims 1 to 7.
10. A computer storage medium, wherein the computer storage medium stores a computer software product comprising instructions for causing a computer device to perform the method for determining a short circuit demagnetization check scenario of a permanent magnet wind turbine according to any of claims 1 to 7.

Description

Determination method and system for short circuit demagnetization checking scene of permanent magnet wind driven generator Technical Field The invention relates to the technical field of permanent magnet wind power generators, in particular to a method and a system for determining a short circuit demagnetization checking scene of a permanent magnet wind power generator. Background Wind energy plays a key role in global energy structure transformation as an important clean energy source. Permanent magnet wind power generators (hereinafter referred to as "generators") have become the mainstream model of wind power generator sets at present because of their advantages of high efficiency, high power density, high reliability, and the like. However, the permanent magnetic material in the generator is at risk of irreversible demagnetization (hereinafter referred to as "demagnetization") under specific working conditions, which directly affects the performance, safety and service life of the generator, and is a key problem that must be considered when designing the generator. The main factors that lead to demagnetization of permanent magnets can be categorized into two points, namely, an excessively high temperature and a strong reverse demagnetizing field. Short-circuit faults, in particular three-phase short-circuits, are typical conditions for generating strong demagnetizing fields. Short circuit occurs under severe conditions that the generator is fully loaded and the environment temperature is highest, the stator current can reach 4-5 times of rated current, and the generated reverse magnetic field is extremely easy to cause irreversible demagnetization of the permanent magnet. Therefore, in the conventional design theory of the generator, in order to ensure absolute safety and reliability, a most severe check standard is generally adopted, wherein when the generator is required to be short-circuited under the worst condition of full load and highest environmental temperature, no demagnetization can be ensured. If the design cannot meet the criterion, the temperature of the windings and the permanent magnets must be limited by reducing the stator current and the like so as to improve the anti-demagnetizing capability. Aiming at checking of short circuit demagnetization, the existing research focuses on simulating an extreme current working condition. For example, the Romania pedicel Mi Shenwa university of Las A. Popa professor team verifies that the generator is demagnetized at 2 times rated current. The t.m. Jahns professor team, university of madison, america, checked at a d-axis current of 3 times the rated current amplitude to simulate the characteristics of a short circuit current. These studies all attempt to cover all possible short-circuit risks by setting a current condition that is sufficiently severe, essentially in line with the proof-reading of the "worst case scenario". However, such conventional design criteria have significant limitations. It uses a very small probability of event as a boundary condition of design, while absolute safety is theoretically guaranteed, the result is that the design of the generator is too conservative, and further improvement of the power density and the torque density of the generator is severely restricted. In practice, the wind speed and the ambient temperature in the wind farm are not constant values, but follow a certain probability distribution (as the wind speed is often described by a weibull distribution, the ambient temperature can be fitted with a normal distribution), and there is a correlation between the two. This means that the scenario "generator is fully loaded and ambient temperature is highest" has a very low probability of occurring in actual operation. From the perspective of a plurality of generators and a full life cycle of the whole wind power plant, most of the generators can not suffer from short circuit faults in the extreme scene in the service period, and even if short circuit occurs, the current wind speed and the current temperature are low, so that demagnetization is not caused, or the degree of demagnetization is very slight. In summary, the prior art mainly has the following disadvantages: 1. The design criterion is too conservative, namely an extreme scene of minimum probability of full load of the generator and highest environmental temperature is adopted as a checking reference of short circuit demagnetization, and the reliability is guaranteed in a theoretical level, but the design redundancy of the generator is directly caused to be too large, the improvement of the power density and the torque density is severely restricted, and the optimal utilization of the material performance cannot be realized. 2. The probability characteristics of the operation condition are ignored, namely the prior art fails to take the actual probability distribution characteristics of key factors such as wind speed, ambient temperature and the lik