Research And Design Of Power Quality Detection Device In Power Grid

Electric energy is the basis of normal production and life in modern society.Most equipment work directly with electric energy.At present,wind energy has become the most potential renewable clean energy.Wind power is more changeable than water power.Water flow can be controlled by height difference and valves,while wind energy can only be roughly predicted by meteorology.The working state of wind turbine generator is unstable due to the fluctuation of wind energy.In order to improve the power quality of wind power generation,it is necessary to develop a set of fast and accurate frequency measurement device to give feedback error in real time and adjust the energy in closed loop with the help of feedback.This paper analyzes the research methods and ideas of frequency measurement devices at home and abroad,comprehensively compares the common measurement methods,solves the problems of poor real-time and high price of common methods,and develops a device suitable for wind power quality detection.The flyback converter is used to adapt the system to different working voltages and isolate them.The electric energy signal is sampled through a series of converters and compensation circuits.In order to reduce spectrum leakage,periodic sampling is needed.A phase-locked frequency doubling circuit is designed to obtain the sampling frequency,and the high-precision ADC chip is used for conversion.A filter circuit is built to filter and deconstruct the signal,so as to set appropriate sampling parameters for different frequency components,simplify the algorithm and improve the real-time performance.At the same time,the ECAP unit of DSP is used for hardware measurement to capture the square wave output by the voltage comparison circuit,and the frequency is calculated through the measurement cycle.Spectrum studies signals from the perspective of frequency,which can clearly show the frequency components of electric energy signals.Spectrum analysis has great advantages in the analysis of signals with complex frequency components^[1,2].The frequency domain result of Fourier transform is concise and clear for detection,which is very suitable for the detection requirements of power grid.In view of the lack of traditional steady-state analysis method Fourier transform for time-varying signal analysis,short-time Fourier transform increases the parameter evaluation and display of signal time domain,uses the Fourier transform of short-time local signal to represent the instantaneous spectrum characteristics^[3],and describes the changes of non-stationary signal in two dimensions of time and frequency.Its advantage is that its physical meaning is very clear,and it can realize three-dimensional characterization of signal change characteristics^[4].Compared with wavelet transform,it greatly reduces the difficulty of implementation on real-time embedded hardware platform,and can detect power quality well.Build the above hardware system to realize the time-frequency characteristic analysis of the combination of hardware measurement and short-time Fourier transform.The measurement and operation parameters are sent to the Lab VIEW host computer through the communication module,and the graphic program is written for visual display.Compared with the specific implementation effect of wavelet transform,it has the advantages of simple algorithm,easy implementation and stable measurement.