Detection And System Design Of Transient Voltage Quality

In recent years, due to the extensive use of power electronic, devices and nonlinear devices, distortion of grid voltage and current waveform becomes more and more serious, which results in the deterioration of power quality. The traditional analysis method of voltage quality such as Fourier transform, is not suitable for handling non-stationary power quality signal. Therefore, a new analysis method, the right of transient power quality testing, analysis and evaluation is very necessary.From the power quality of the definition and current situation of domestic and international power quality, this thesis analyzes the reasons of current transient power quality problems in the details. In addition, the thesis makes a deep study on the transient voltage disturbance location, the classification of transient disturbance signal and the design problem of detection system. Main results are as follows:A new method of transient voltage disturbance localization is proposed. This method is based on an improved S transform. From the extraction of characteristics of transient voltage disturbance signal, the method can detect the start and end time, duration, amplitude changes of the disturbance signal accurately. Simulation results show that the method is simple, real-time, and can accurately locate the transient power quality disturbances. Thus, this method provides the basis for the disturbance signal analysis.A new classification method of disturbance signal is provided in this thesis, which is based on the use of S transform and image processing technology. The analysis method shows that the disturbance signal after S transform can be expressed as an image, and the characteristics of each disturbed image is very obvious. Therefore, using image-matching technology, we can achieve automatic classification of disturbance. Simulation results show the effectiveness of the disturbance signal classification in this way.Based on the above methods, a detection and analysis system of transient voltage quality is designed. The core of the system is DSP, using PC+DSP structure. DSP is responsible for the voltage signal processing, and PC’s function is storing voltage data, displaying curve etc. A/D connected DSP via FIFO, and this design allows faster data transfer. Experimental results show that the system fully meets the design requirements.