Method for determining stator phase causing three-phase voltage unbalance of doubly-fed wind generator

Abstract

The invention discloses a method for determining a stator phase causing three-phase voltage unbalance of a doubly-fed wind generator. Vibration signals, voltage signals and current signals which are collected from the doubly-fed wind generator are analyzed, the analysis results are combined to diagnose the stator phase causing three-phase voltage unbalance of the doubly-fed wind generator, and the stator phase causing three-phase unbalance is determined by using the phase angle extracted from the vibration signals, the fault stator phase determined from the voltage signals, and the 120-degree deviation value of current and phase difference among three phases and the three-phase stator current effective value extracted from the current signals. Vibration factors, voltage factors and current factors are introduced, the factor values corresponding to all the phases are added, three probability values of a three-phase stator causing three-phase unbalance of the generator are obtained, then, the three probability values are ranked, so that the priority of the three stator phases causing three-phase unbalance of the generator is determined, and a key stator phase causing three-phase unbalance of the generator is determined according to the priority. According to the method, the analysis result of the vibration signals, the analysis result of the voltage signals and the analysis result of the current signals are combined, and therefore fault analysis errors caused by a certain signal merely are reduced.

Description

technical field [0001] The invention relates to the technical field of doubly-fed wind power generators, in particular to a method for determining stator phases that cause unbalanced three-phase voltages of doubly-fed wind power generators. Background technique [0002] At present, there are mainly two methods for diagnosing the unbalanced voltage of the three-phase stator of the generator: one is to diagnose through the voltage signal, which is the most direct method. In comparison, if the effective value of the voltage corresponding to the stator of a certain phase differs greatly from the effective value of the voltage corresponding to the stators of the other two phases, it can be considered that the stator of this phase has caused the three-phase voltage imbalance of the generator. The second method is: the current negative sequence component method. This method collects the three-phase current signal of the generator through the current sensor, compares the negative se...

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Problems solved by technology

[0003] At present, there are many ways to monitor the vibration of the generator through vibration sensors, but this method is rarely used to diagnose the three-phase unbalanced stator phase of the generator.

[0004] The monitoring and signal analysis of electrical signals such as voltage, current and power of generators with high-frequency components are still in the research stage at home and abroad. For generator three-phase voltage unbalance faults, most studies are limited to a single electrical signal. The single electrical signal (current, voltage signal) method for diagnosing the three-phase voltage unbalance fault of the generator, due to the influence of electromagnetic interference, measurement error and other factors, will reduce the measurement accuracy. For the slight three-phase voltage unbalance fault of the generator, It is difficult to extract effective feature information from electrical signals to identify faults

[0005] In addition, for the currently existing method of detecting the three-phase voltage to determine the unbalanced stator phase of the three-phase voltage of the doubly-fed generator, when the grid voltage is unbalanced or the load is unbalanced, it will also cause the three-phase stator voltage of the generator to be measured. In this case, it is impossible to judge whether the three-phase voltage imbalance of the doubly-fed generator is caused by the fault of the generator stator

[0006] The current negative sequence component method is used to diagnose the three-phase unbalanced stator phase of the generator. The working principle of the commonly used current sensor is the inductance principle. Due to the influence of electromagnetic interference, measurement error and other factors, the measurement accuracy will be reduced, especially for For doubly-fed wind turbines, because the control cabinet, converter, etc. are very close to the generator, the current sensor will be more affected by electromagnetic interference, so it is difficult to judge the initial fault of the stator through the current signal

[0007] When the three-phase voltage of the generator is unbalanced, it will cause the vibration of the generator. By monitoring the vibration of the generator, combining the vibration signal with the electrical signal (current, voltage signal) to diagnose the unbalanced fault of the three-phase voltage of the wind turbine can overcome the above-mentioned problems. Disadvantages, the ability of vibration sensors to resist electromagnetic interference is stronger than that of current sensors, but the measurement accuracy of vibration sensors is usually not as high as that of current sensors. Based on this background, this patent provides a combination of vibration signals, current and voltage signals to diagnose power generation The method of the three-phase unbalanced stator phase of the machine, which not only utilizes the advantages of various methods, but also fully considers their respective shortcomings

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