The Research On Detection And Restriction Scheme Of Harmonics For Oilfield Power Supply System

In the oilfield, frequency converter, rectifier, and mechanical equipments whose impacting property is heavy and frequent are usually applied, the pollution of harmonics is quite heavy, and recently there is no scheme for harmonics detection and restriction which is mature and can be applied widely, which not only brings much electricity loss, but also affects and even heavily interfere the normal practice of power supply system and the electric equipment in the oilfield. For the power supply system of oilfield, how to detect and restrict harmonics effectively is of much importance in reality.On the basis of understanding the principle of harmonic production, the state of home and overseas for this subject and development, and problems existing in the recent harmonics detection system, an effective harmonics detection unit is designed, and wavelet transform and DSP technology are applied to improve the real time and accuracy in the process of signal detection and procession.Several parts are introduced and researched as following in this thesis.Firstly, on the basis of understanding wavelet transform basic theory, the harmonic signal is simulated by multi-resolution analysis theory, and the Mallat algorithm is introduced and applied to harmonic detection on the basis of multi-resolution analysis, the real time is improved. Decomposing the detail signal further in Mallat algorithm, the improved wavelet transform algorithm is achieved, the simulation results show that the improved wavelet algorithm is of not only being simple algorithm, less calculation and more real-time, but also being sensitive to the detail signal especially singular signal, tracking the change of harmonics real-timely, capturing the appearing and disappearing time of singular signal accurately, so it's quite suit to extract break signal, which is what traditional Fourier transform and wavelet transform lack.Secondly, on the side of hardware, the data sampling circuit is designed, and the data sampling circuit is connected with TI DSP develop system to process the harmonic signal further, the signal processed is to control converse main circuit to produce compensating signal to compensate power supply system by the control unitof Active Power Filter.Thirdly, on the side of software, Mallat algorithm is programmed by Assembly language, simulation is done after the hardware and software design, the simulation results show that the signal detection unit designed and the adopted software procession method is effective in all.