A simple and low cost measuring method for harmonics in the power system

Various harmonics in power systems are measured typically by the heterodyne receiver in analog techniques or the FFT (fast Fourier transform) analyzer in digital methods. Using these methods, the harmonics can be analyzed over a wide range of frequency. However, circuit configurations using such methods become very complicated and the devices become too expensive. This paper presents a harmonic analyzing meter using a PLL (phase locked loop) circuit. By means of the PLL circuit, the reference sinusoidal wave is locked on to the input signal with the harmonics for measurement, and hence the harmonic component in the input signal is easily detected. The usefulness of the proposed analyzing meter is confirmed by experiments.