Research On Power Quality Detection Technology Based On Synchronous Clock

With the improvement of industrial production level and the development of social living conditions,a large number of nonlinear loads and distributed power sources are connected to the distribution network system,which causes the two-way flow of power flow,the pollution of electric energy increases,and when serious,it exceeds the allowable limit.The quality of electric energy will affect people's production and life.High quality electric energy is helpful to ensure the safe and stable operation of power grid and electrical equipment,to improve the quality of product production,and to ensure the normal life of the people.In order to systematically analyze and study power quality,improve power quality,find out the problems that lead to power quality,and take corresponding measures to solve these problems,it is necessary to measure and analyze the power quality parameters.At present,most of the data acquisition of the power quality detection system is a local single point measurement,and the results of the measurement only reflect the running state of the local system,but the measured data have no unified time mark and connection,and lack of accuracy.A method based on GPS synchronous sampling is proposed to realize the synchronous measurement and analysis of power quality parameters in different locations.A GPS based synchronous sampling method is proposed in order to realize synchronous sampling at different locations.That is to say,using the GPS high precision second pulse PPS signal to start the external interrupt of the main control chip,trigger the sampling device at different locations,and synchronize the sampling of the three-phase voltage and current signal.At the same time,the ADC converter converts the sampled analog data into digital signal,and then labels the data to record the world clock to realize the synchronous sampling and measurement of the equipment.In the process of synchronous sampling,the analog signal is converted into digital signal to obtain the effective value of voltage and current,and then the phase of voltage and current is obtained by Fourier transform,so as to obtain the voltage and current vector accurately.For the design and implementation of the power quality detection device,the detection algorithm of the power quality parameters is first explained,and the detection method of the steady-state power index is mainly introduced,in which the flash detection adopts the existing IEC square flash detection method.For harmonic detection,because of the high computational efficiency of FFT,it can be easily implemented in embeddedsystem DSP,so we propose a multi-spectral line interpolation FFT improved algorithm based on 4 items(Rife-Vincent,RV)window on the proposed algorithm.The calculation expressions of frequency,amplitude and phase of harmonics are calculated,and the simple and practical interpolation correction expressions are derived by curve fitting function.Then the weak signal and complex harmonic signal are simulated and compared with several typical cosine window function FFT algorithms,it is found that the accuracy of the four RV(?) window function FFT algorithm in calculating harmonic parameters is good,and the long range leakage caused by non-cycle sampling can be well suppressed,while the modified algorithm FFT multispectral interpolation can effectively correct the short range leakage.Based on the synchronous sampling of GPS clock signal and each power quality measurement algorithm,the hardware and software of the ADC+DSP+MCU hardware architecture system are designed according to the idea of modularization,and the source of measurement error is analyzed.