Research On Single-phase Voltage Drop Detection Technology Of Intelligent Swift Emergency Power System

In recent years,with the rapid development of smart grid,more and more advanced power electronic equipments and microprocessors have been put into the grid.These advanced equipments not only improve the efficiency of the grid,but also bring some hidden dangers.These advanced equipments are vulnerable to interference,and increasingly demanding the reliability of power supply and power quality.Intelligent Swift Emergency Power System(ISPS),which is characterized by energy saving and environmental protection,is a new standby power supply after UPS and EPS.It combines the advantages of UPS and EPS,that is,it works in off-line mode and can realize fast power switching.Fast and accurate detection of voltage drop is the first step for ISPS to realize fast switching.Based on this,this paper focuses on how to realize fast and accurate detection of voltage sags.the common voltage sag detection algorithms are studied and analyzed,and the working principle of the algorithm is described.These methods are simulated and validated in MATLAB/Simulink by using ideal and noise-disturbed voltage sag waveforms respectively.The above algorithms are compared and analyzed according to the detection delay,algorithm accuracy,calculation amount and other indicators.Finally,the above algorithms are summarized.Self-advantages and disadvantages.In view of the small detection delay and the simplicity and easy implementation of the algorithm,the comprehensive advantages of the above-mentioned algorithm are obvious,but the anti-interference ability is not strong enough,and the corresponding filters need to be used,while the traditional filters have obvious delay and low accuracy.Therefore,a composite morphological filter based on mathematical morphology is used in this paper.The composite morphological filter consists of different shapes.Composite elements make full use of the filtering characteristics of different shape and structure elements,and can filter all kinds of complex noise to the greatest extent.The working principle of the composite morphological filter is discussed in detail.The influence of the length and shape of the structural elements on the performance of the filter is analyzed.The method to find the optimal parameters of the composite morphological filter is described.The optimal parameters of the composite morphological filter are found when the sampling frequency is 12.8kHz.A novel voltage sag detection method based on delayed small-angle method and composite morphological filter is proposed.First,the collected voltage signal is filtered by the composite morphological filter for the first time,which can filter most of the noise.Then,the virtual three-phase voltage is constructed by the method of delayed small-angle for the filtered voltage.Finally,the traditional linear morphological filter is used to change the voltage after Park transformation.After the replacement,the DC component is filtered again to detect the voltage sag.In order to verify the feasibility of the proposed algorithm,Simulink is used to simulate ideal and harmonic and noise disturbed voltage drop data,and the algorithm is used to detect them.After that,the related hardware circuit is designed,and a practical hardware model of voltage sag is built.The algorithm is simulated and validated by using three sets of data collected from experiments with different depth of voltage sag.The simulation results show that the algorithm solves the problem of inadequate precision of the small angle delay method when disturbed by harmonics and noise.Compared with the traditional voltage sag detection method,the proposed algorithm solves the problem of inaccurate precision when disturbed by harmonics.and noise.The comprehensive performance of the algorithm is improved obviously,and it can meet the requirement of fast detection of intelligent swift emergency power system ISPS.