A new current injection method for impedance measurement using superposed modulated square pulse

Harmonic impedance measurement is very important in Micro-grid because of the close relationship between impedance and stability. This paper presents a new current injection method for impedance measurement. Sinusoidal amplitude modulation is a method to shift signals to different frequency bands. A signal with large frequency bandwidth and small amplitude attenuation can be obtained by superposing square pulse signals with sinusoidal amplitude modulation. When the superposed signal is injected to the system as a current source, impedance information in the frequency range of interest can be calculated with short time cost and high accuracy. The simulation results demonstrate the effectiveness of this method.