| With the rapid development of new energy,more and more new energy power generation system into the power grid.The development and utilization of new energy in the power grid has led to the deterioration of the power quality indicators,which has caused great harm to the safe and stable operation of the power grid.Power quality not only affects the stable and reliable operation of the power system,but also related to the safe operation of the user,especially the distributed power supply that mainly based on photovoltaic power generation and wind power generation accessing power grid,which bring more power quality problems to the power system,has become a research hotspot in the world.At the same time,the electronic technology of contemporary society and other applications of the high-end electrical equipment,its operation on the power quality put forward higher requirements.The main circuit of photovoltaic power generation system,its working principle is turning the power electronic switch components on and off for energy conversion,the sources of power generation system will produce a large number of harmonics.Therefore,after the new energy accessing to the grid,it will lead further deterioration to the power quality,so the research work of the power quality is imminent.The research on the analysis,detection、classification and recognition of power quality perturbation is the premise to improve the quality of power,which is also one of the important work of further improve the power quality detection system.Based on the research status quo of power quality at home and abroad,this paper analysis characteristic the Various problems of power quality in the background of PV system.This paper has research in detail on the method of power quality detection and classification,the algorithm Four-level Third-order Nuttall Window Four-peak Interpolation FFT has been proposed to detection photovoltaic grid-connected power harmonic,using MATLAB to simulate the harmonic signal,According to the test results,it can be seen that the absolute error of the algorithm is less than 6.92×10-8,the relative error is less than 4.29×10-6%,the phase absolute error is less than 7.42×10-6%,the relative error of phase is less than 5.7×10-3%,which is superior to Hanning window bimodal interpolation and Blackman-harris window tristimulus interpolation in detection amplitude and phase.By using the Hilbert-Huang transform algorithm to detect the power quality perturbation,five kinds of single perturbed power quality simulation models and two kinds of compound disturbance power quality simulation models are analyzed by using the HHT method.The simulation results show that Application of HHT method to the power quality of the disturbance detection is feasible and accurate.Based on the analysis and research of traditional detection and classification methods,a method of power quality disturbance detection and classification based on HHT and PSO-BP neural network is proposed.Use Matlab platform,based on the HHT and PSO-BP neural network method,seven kinds of disturbance signals are simulated and analyzed.Based on the simulation results,tThe method proposed in this paper has the characteristics that it is fast and accurate to extract features and classify the power quality disturbance signal.The classification and recognition method based on HHT and PSO-BP neural network is very ideal for single-disturbance signal classification.The results of classification tests are all more than 90%,and some of the signals can reach 100%.For the classification effects of multi-perturbation,although there is not as ideal as single disturbance is,from the test results can be found that the accuracy rate is still high.In the signal which containing various signal-to-noise ratios,it can identify the type of power quality disturbance in the signal very accurately as well,which verifies that the verifies method verifies in this paper has the advantages of high speed,simple mode,high accuracy of detection and classification. |
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