Nonlinear Harmonic Energy Measurement Technology And Its Application

With the development of industrial modernization, the amount of nonlinear loads like electrification railway, electric locomotives in grid are increasing. However, due to the nonlinear load will inject a lot of harmonics into the grid, resulting that the voltage and current waveform in grid become distorted. Harmonic not only endanger the supply network and electrical equipment, but also affect the accuracy of the measurement of the energy metering meter, leading to economic losses in power supply enterprises and users.According to China’s Current energy metering policies and energy metering meter in use, once the utility grid containing harmonics, the problem like harmonic impact of energy metering meter, and how to measure harmonic energy are still to be resolved. Therefore, the harmonic power energy meter was put forward to measure the harmonic energy which can distinguish between the fundamental harmonic energy and harmonic power, it helps to improve the monitoring level of non-linear user power usage. Monitoring data can be used as the basic sources to be analyzed, and provide basic analysis data for assessing the rationality of harmonic energy charges.This paper describes the harmonic harm to the grid, mainly discussing the technical aspects related to energy metering under influence of non-linear loads, such as harmonic detection methods, detection devices, etc. The paper analyzed the fast Fourier transform algorithm and its corresponding correction windowed interpolation algorithm, and put forward a new interpolate algorithm which is very suitable to apply to the embedded hardware. The algorithm put forward has important reference value in harmonic analysis.The research has finished the harmonic energy monitoring device development. The hardware framework is based on ADC+ARM, using 16 bit ADC to sample signal and calculating data with the ARM chip featuring floating point unit. The harmonic analysis result will be obtained by calculating the fundamental and harmonic energy, and be displayed on the LCD screen. The hardware test shows that the windowed interpolation algorithm discussed above is highly efficient.Finally, a non-linear circuit is set up to test the designed harmonic energy metering meter, and the measured data is compared with the 0.2% accuracy power quality analyzer. According to the test result, the accuracy of the fundamental power and harmonic content attained from the circuit are equivalent to those of the control device, in line with GB/T GB/T14595-93 class A precision measuring instruments. The subject of the research, such as windowed interpolation algorithm, energy metering hardware framework, are good references for the harmonic energy measurement.