Research On Electric Signal Detection And Signal Processing In Motor Control

With the development of modern high-tech industry,the motor technology has been gradually mature.As a mechanical and electrical energy conversion device,it is widely used in all fields of national economy and people's daily life.The future motor will develop towards high efficiency,high power density,high reliability,low noise,good controllability and replaceability.In addition,the motor control is also in the direction of intelligent,intelligent control is applied in many fields,so the demand for power quality under the control of motor is getting higher and higher.Due to the large use of nonlinear loads and power electronic components,serious harmonic pollution will be generated,so harmonic control is particularly important.This requires a good algorithm to detect harmonics.Therefore,FFT is used to analyze the harmonic of the motor.The paper first introduces the sampling principle of electrical signals and three sampling methods and implementation methods of hardware synchronous sampling,synchronous sampling and asynchronous sampling.According to the mathematical model of voltage and current detection,the frequency band characteristics of voltage and current signal are obtained by Fourier transform,and the characteristics of each frequency voltage and current signal are calculated(including frequency,amplitude,phase and effective value).In order to solve the problems of fast fourier transform algorithm,such as fence effect,spectrum aliasing and truncation effect,the FFT algorithm is improved,and a FFT algorithm with Hanning window is proposed.At the same time,aiming at the algorithm,the harmonic content of MATLAB orthogonal frequency converter model is analyzed to verify the reasonableness of the algorithm.It is concluded that the algorithm greatly improves the accuracy of measurement,especially improves the accuracy of phase calculation.Then the principle and similarities of analog and digital filters are introduced in detail,and the two order Butterworth low pass analog filter and FIR digital filter are designed and the amplitude frequency and phase frequency response of the filter is analyzed by MATLAB.At the same time,using MATLAB design example,the filter performance of two order Butterworth filter is tested by SPWM inverter circuit.The harmonic content of the filter is analyzed by FFT,and the filtered waveform is a sine wave.The voltage THD is reduced from 64.39% to 1.47%,and the filtering performance is good.Finally,the selected part of this experiment is 750 W permanent magnet synchronous motor.The hardware design part uses DSP28335 as the main control chip.The main design modules include the design of the signal detection circuit,the design of the A/D conversion circuit and the peripheral circuit,the design of the phase locked loop,and so on.The software part is mainly based on the CCS software programming to control the related hardware circuit so as to achieve the order of the signal detection and processing of the signal.