Acoustic Emission Signal Analysis Of Power Devices In Inverter And Chopper Circuits

With the development of science and technology,power electronics technology has been widely used.As the core component of power electronic technology,the reliability of power electronic devices affects the operation of the whole system.The traditional detection or monitoring methods of power electronic power devices include electrical parameter detection,magnetic field parameter detection and temperature parameter detection.In order to realize fast,real-time and non-invasive nondestructive testing,acoustic emission testing technology has been widely used in nondestructive testing.Acoustic emission detection technology can not only achieve excellent performance in equipment defect location and equipment fault detection,but also has a good performance in the condition monitoring of power electronic power devices.This thesis studies the power electronic power devices in the circuit by using acoustic emission detection technology,introduces the acoustic emission detection principle and system composition,and analyzes the acoustic emission signals under three different tests.Firstly,the principle of the sensor in the acoustic emission detection technology is explained.The piezoelectric acoustic emission sensor can convert the vibration signal into electrical signal by using the piezoelectric effect,and use this sensor to collect the acoustic emission signal inside the power electronic power device.Three kinds of experimental circuits are introduced: square wave inverter experimental circuit,sine wave inverter experimental circuit and boost chopper experimental circuit.The time domain and frequency domain of acoustic emission signal under the condition of air coupling and solid coupling agent coupling are compared,and the corresponding frequency range of stress wave is found.For the square wave inversion experiment,the extracted stress wave is analyzed in time domain peak,energy,rise time,frequency domain peak and peak frequency.This analysis of extracting stress wave based on acoustic emission signal is called the classical analysis method of acoustic emission signal of power electronic power devices.For the sine wave inversion experiment,it is explained that the superposition of aperiodic acoustic emission signals caused by SPWM modulation is caused by the switching speed of power devices and the switching time interval is not fixed,and the classical analysis is carried out in the aspects of time domain peak,energy,frequency domain peak and peak frequency.In addition,wavelet decomposition and empirical mode decomposition are used to analyze the root mean square of the decomposed signal as the eigenvalue.For the boost chopper circuit,the superposition of periodic signals caused by too fast switching speed of power devices is explained,and the superposition signal is approximately sine wave.Similarly,the classical analysis of the collected data is carried out to find the variation trend of the stress wave in time domain peak,energy,frequency domain peak and peak frequency,and the root mean square of the decomposed signal is analyzed as the eigenvalue by using wavelet transform and empirical mode decomposition.By analyzing the acoustic emission signal of power devices in inverter circuit and boost chopper circuit,this thesis obtains the relationship between the eigenvalue of acoustic emission signal and the circuit under different working conditions,which provides a new method and new idea for the condition monitoring of power electronic power devices.