Study On Detection And Treatment Of Power System Harmonic

In power system, the power quality is declined because of the role of non-linear load which cause the voltage and current waveform distortion and generate a lot of high-order harmonics to the power grids. With the various types of the non-linear loads, power system harmonics become more and more serious and it has been a threat to the safe operation and economic operation of the power system.First of all, this paper introduced the basic concepts of the harmonic, the production of the harmonic and the effect of the harmonics to the power system, then this paper introduced several methods for harmonics detection and focus on the fast Fourier transform (FFT) to detect the harmonics in power gird, simulated the FFT with C language and introduced problems appeared in practical engineering applications when used the FFT. Harmonic source detection is a very important part of harmonics detection. This paper introduced several methods of harmonic source detection, and compared the advantages and disadvantages of these methods. Power direction method is widely used in harmonic source detection. The author analyzed this method and pointed out the location of power direction method used in harmonic source detection though a simulation. Harmonic magnification is one of the most serious problems in the power system. This paper analyzed the causes of the harmonic magnification and introduced the methods to reduce the effect of the harmonic magnification to the substation. From one substation in power system, this thesis analyzed the faults in the substation and gave the harmonics analysis equivalent electric circuit of paralleling condenser. After calculated the voltage and current of the paralleling condenser this thesis gave the harmonic frequencies that can cause the harmonic magnification. Then through the calculation, we can see that after adding in series reactance, the harmonic frequency was decreased and the harmonic magnification was reduced.Finally, the paper introduced the passive power filter and the active power filter and the advantages and disadvantages of each briefly. Based on the passive power filter , flexible passive power filter design for eliminating harmonics was presented including the structure and the control method .The simulation of the flexible passive power filter with MATLAB showed that it was capable of filtering harmonics.