Abstract
As a new type of generator, an asynchronized high-voltage generator has the characteristics of an asynchronous generator and high voltage generator. The effect of the loss of an excitation fault for an asynchronized high-voltage generator and its fault diagnosis technique are still in the research stage. Firstly, a finite element model of the asynchronized high-voltage generator considering the field-circuit-movement coupling is established. Secondly, the three phase short-circuit loss of excitation fault, three phase open-circuit loss of excitation fault, and three phase short-circuit fault on the stator side are analyzed by the simulation method that is applied abroad at present. The fault phenomenon under the stator three phase short-circuit fault is similar to that under the three phase short-circuit loss of excitation. Then, a symmetrical loss of the excitation fault diagnosis system based on wavelet packet analysis and the Back Propagation neural network (BP neural network) is established. At last, we confirm that this system can eliminate the interference of the stator three phase short-circuit fault, accurately diagnose the symmetrical loss of the excitation fault, and judge the type of symmetrical loss of the excitation fault. It saves time to find the fault cause and improves the stability of system operation.
Highlights
One of the most common faults in the excitation circuit of a generator is that they sometimes lose a part or all of the excitation suddenly
If we focus on the changes of electrical quantities after a loss of excitation for asynchronized high-voltage generators and adopt an effective loss of excitation fault diagnosis technique, the loss of excitation fault can be accurately determined and remedied in time to ensure the safe and stable operation of the power system
We introduce a logical unit to the fault diagnosis system based on the loose combination method of wavelet packet analysis and BP neural network, which can effectively diagnose the type of symmetrical loss of the excitation fault and improve the accuracy of fault diagnosis results
Summary
One of the most common faults in the excitation circuit of a generator is that they sometimes lose a part or all of the excitation suddenly. If we focus on the changes of electrical quantities after a loss of excitation for asynchronized high-voltage generators and adopt an effective loss of excitation fault diagnosis technique, the loss of excitation fault can be accurately determined and remedied in time to ensure the safe and stable operation of the power system. The field-circuit-movement coupling method needs to solve the electromagnetic field equations, winding circuit equations, and mechanical equations of the generator simultaneously [20] This method analyses the loss of excitation faults from a magnetic field and electrical quantity, and simulates the actual running state of the generators. The large generator mentioned in this paper cannot do a loss of excitation test on the grid-connected mode, so the field-circuit-movement coupling method is more suitable for the analysis of the asynchronized high-voltage generator. We establish the finite element model and external circuit of the asynchronized high-voltage generator
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