Research On The Methods Of Power System Harmonic Detection And Suppression

There are a large number of the power consuming equipments which have nonlinear impedance properties in power system, the resulting harmonic pollution is increasingly serious, the existence of the harmonic not only can reduce the power quality, but also can shorten the service life of the electrical equipments, moreover malfunction or burn can occur. So detecting and depressing the harmonic rapidly and accurately in power system is of great significance to improve the power quality and enhance the stability of power grid.Firstly, the research status of the power system harmonic detection and suppression methods is overviewed, the principles and advantages and disadvantages of the common methods of harmonic detection and suppression in power system are analyzed in the thesis.Then, the principle and the main parameters’ selection strategy of the extended Prony algorithm are described detailedly in the thesis. Because the actual signals contain random noise and impulse noise, and the extend Prony algorithm is more sensitive to noise, at the same time, now the denoising methods can’t remove random noise and impulse noise very well, thus the de-noising method which combines tunable Q-factor wavelet transform and basis pursuit is applied in the thesis. The denoising effect of the method is confirmed superior to the ensemble empirical mode decomposition denoising and wavelet denoising through the simulation experiments. It can greatly reduce the noise in the signal after denoising and then the denoising signal is analyzed by using the extended Prony algorithm. The detecting results show that the method can detect the amplitude, frequency and phase of the harmonic and inter-harmonic more accurately and can improve the detection accuracy of the harmonic and inter-harmonic.Secondly, in view of the limitations of the harmonic detection method based on instantaneous reactive power theory applied in three-phase four-wire circuit, the tunable Q-factor wavelet transform is used to filter the zero sequence harmonic component and inter-harmonic component of the phase voltage and phase current, and then the total amount of harmonic component is detected combining with the instantaneous reactive power theory, which is verified feasible through simulation experiments.Finally, the active power filter is applied to restrain harmonic in power system. The simulation model of three-phase four-wire active power filter is established through MATLAB/SIMULINK, the extended Prony algorithm and the method which combines tunable Q-factor wavelet transform with instantaneous reactive power theory are applied in the harmonic detection module of active power filter, the corresponding simulation parameters are set, and the harmonic suppression effect of the active power filter is analyzed according to the simulation results.