Research And Realization Of High Precision On Harmonics And Inter-harmonics Detection Methods

The heavy uses of nonlinear loads and fluctuating loads are the main cause of harmonics and inter-harmonics in the power system.Harmonics and inter-harmonics pollute the power system and seriously affect the quality of the power system.Nowadays,controlling harmonics and inter-harmonics are becoming more and more important,and high-accurate harmonics and inter-harmonics detection methods are the key process of harmonics and inter-harmonics control,it is significant to maintain the safe,stable and efficient operation of the power system.At present,the windowing and interpolating FFT method is widely used in current studies of harmonics and inter-harmonics detection,this method improves the spectrum leakage and fence effect.The selection of window functions has a decisive effect on the precision of this method,how to select window functions is a problem that worth to attention.In addition,there are still some shortcomings in this method,such as the complexity of calculation,the incomplete detection of harmonics and inter-harmonics and the failure to ensure the accurate detection of harmonics and inter-harmonics.Thus,this paper has carried out these following researches:(1)Firstly,welch method based on power spectrum estimation is used to select the most appropriate window function under the current situation,which alleviates the spectrum leakage problem to the greatest extent.The feasibility of this method is verified by simulation experiments.(2)Secondly,a harmonics and inter-harmonics detection method based on self-increasing frequency is deduced from the frequency correction formula,a harmonics and inter-harmonics detection method based on zeroing spectrum amplitude is deduced from the analysis of the discrete spectrum of signals,which are both different from the common harmonics and inter-harmonics detection method.The simulation results show that two harmonics and inter-harmonics detection methods are both high-accurate,stable under the condition of fundamental frequency fluctuation and anti-interference under the condition of white noise.(3)Thirdly,the harmonics and inter-harmonics detection method based on zeroing spectrum amplitude and the harmonics and inter-harmonics detection method based on self-increasing frequency are used to detect the voltage signal and electricity current signal which are caused by the EAST experiment,and the validity of the two methods for real power grid signals is verified.(4)Finally,the harmonics and inter-harmonics detection methods based on zeroing spectrum amplitude and the harmonics and inter-harmonics detection method based on self-increasing frequency are programmed on the DSP platform,the detection results show that the two harmonics and inter-harmonics detection methods can both adapt to the embedded development platform and have the engineering feasibility.