Design Method of Multi-Sine Signal for Broadband Impedance Measurement Considering Frequency Coupling Characteristic

Impedance measurement is an effective method to obtain the impedance characteristic of renewable power generation equipment (RPGE) for stability analysis. Frequency-coupling characteristic of RPGE will bring about the difficulty to measuring the impedance in a wide frequency band based on broadband signals. In order to guarantee the accuracy of the broadband impedance measurement considering the frequency–coupling characteristic, this article explores the method to accurately measure the frequency–coupling characteristic of the RPGE. The signal-to-noise ratio (SNR) issue in view of the measurement of the frequency–coupling characteristic is also investigated. Accordingly, an evaluation method for measurement accuracy is proposed. The evaluation results will be adopted to guide the design for the perturbation amplitudes. The redesigned multi-sine signal will be used in another group of measurements so as to achieve a targeted accuracy level. Finally, experiments based on the Typhoon control-hardware-in-loop (CHIL) platform are carried out to verify the reliability of the proposed evaluation method and the effectiveness of the proposed design method for the perturbation amplitudes.