A simple harmonic meter using phase locked loop

Abstract

Various harmonics in the power system are measured typically by the heterodyne receiver in analog methods or the FFT (fast Fourier transform) in digital methods. By means of these methods, the harmonics can be analyzed over a wide range of frequency. However, since circuit configurations of such methods become very complicated, the equipment becomes too expensive. This paper presents a harmonic meter using a PLL (phase locked loop) circuit. By means of the feedback loop for phase, 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 harmonic meter is confirmed by experiment.