Research On Phase Selection Technology Based On Hilbert Transformation

The low voltage circuit breaker pertains protective type electrical apparatus, and its reliability is related to the safety of power system and people. Many domestic factory production of circuit breakers often appear mistaken and malfunction phenomenon in the reliability test, therefore it is necessary to study on the circuit breaker instantaneous validation. Phase selection can eliminate the non periodic component in the circuit, and to ensure the accuracy of instantaneous check current and to prevent mistaken and malfunction occurs. Based on this, and in this thesis to study the technology of phase selection based on Hilbert transformation.The traditional phase selection device is based on the FFT method calculation of phase selection coefficient, and through in-depth analysis of this method find This algorithm is sensitive to the signal frequency, and the frequency resolution and initial phase calculation presenting interdependent relationship, and is not conducive to get precise switching coefficient. Therefore proposed the method of calculate periodic signal phase selection parameters based on the adding-window Hilbert transformation, and by writing Hilbert transformation procedures in Matlab and MCU, through the comparison of the simulation test, found that Hilbert transformation can realize the dynamic measurement of phase selection of parameters compared with FFT algorithm. Through the windowed signal pretreatment tests found, and the calculation accuracy is almost not affected by the signal frequency、amplitude fluctuation of the power grid of this method, and the calculated results of phase selection parameters amplitude smooth、 accurate, and is advantageous to improve the accuracy of calculation.For the design of phase selection device, first elaborated the phase selection device hardware design flow, then design of main control circuit and the external circuit; The software adopts modular design, and describes the key problems like the implementation of Hilbert algorithm of this.The phase selection parameters test results show that design calculation method has higher accuracy of measurement in the frequency fluctuation; Simulation load experiments show that the phase selection device overall execution effect is good in phase selection test; Instantaneous calibration test description the device has higher accuracy of phase selection in conjunction with the circuit breaker instantaneous calibration equipment.