Research On The Electric Energy Measurement Of Nonlinear Loads Algorithm Based On Wavelet Packet Transform

With the social progress and the industrial development,the capacity of the electric power grid is quickly expand,the number of non-linear loads is increasing,such as the electrified railways,rolling mills,grid-connected photovoltaic system,power electronics products and so on have become an important part of the power grid load.Due to a large number of nonlinear loads access to the power grid and field load fluctuate frequently,the current of electro-load is changed with time,and even led to high volatility in a short time.These nonlinear loads would also lead into harmonics,which make the waveform of voltage and current distortion,especially the current.Thus lead to the power quality is declining in power network.Smart meter is one of the authorized measurement instruments.The existing energy meter is based on the traditional sinusoidal steady state power theory to measure the electric energy.It's difficult to fulfill the accurate measuring of energy under the condition of nonlinear load.Because of less change of measuring accuracy will bring considerable economic benefit,come true the power accurate measurement of the nonlinear load can not be ignored.This paper mainly studies the application of the wavelet packet transform in the nonlinear load electric energy measurement.This paper first introduces the development of the electric energy measurement of nonlinear loads.Developed a rolling mills,electrified railways,grid-connected photovoltaic system,power electronics products site voltage,current data collection program.According to the collected data analyzes the harmonics and inter harmonics existence situation.Then this paper gives a description of the existing power measurement algorithm,namely,dot product and electric energy measurement,FFT electric energy measurement,two-line spectroscopy interpolating windowed FFT electric energy measurement.And completes Matlab simulation.On this basis,analysis of the above methods existed problem.For the instances of that nonlinear load have a large number of harmonics and Inter harmonics,this paper brings forward a new method of electric energy measurement based on wavelet packet transform.According to the measurement standard IEEE1459-2000 for the non-linear load electric energy measurement,the paper gives the concrete electric energy measurement steps and the calculation formula deduced process.The new method is simulated through Matlab.Through three aspect of Matlab simulate,the electric energy calculated by the collected data and algorithm complexity in comparison with the existing methods.The simulation and the calculation of the field data results show that compared with the existing power measurement methods the wavelet packet power algorithm can improve the accuracy of the nonlinear load electric energy measurement.The proposed algorithm has reference value for the nonlinear load electric energy measurement.