Accuracy Evaluation and Enhancement Method for Measuring Frequency Coupling Characteristics Based on Generalized Signal-to-Noise Ratio Index

Impedance measurement is an effective method to obtain the dynamic characteristics of a renewable energy generator. Signal-to-noise ratio (SNR) is an important index to analyze the noise resistance of measurement and to ensure measurement accuracy. Existing research on SNR primarily focuses on single-input single-output impedance models. Frequency coupling characteristics make the impedance multiple-input multiple-output models. Measuring frequency coupling characteristics involves the intertwinement of eight measurement signals. As a result, solely relying on the SNR of each individual measurement signal cannot accurately reflect measurement accuracy, nor can it provide a theoretical basis for improving measurement accuracy. In this article, considering the intertwinement of eight measurement signals and frequency coupling characteristics, a generalized-SNR (GSNR) index is proposed to evaluate the accuracy and depicted as error bars in Bode diagram. Moreover, a GSNR-based accuracy enhancement method, including quantitative design of perturbation amplitudes and overlap extraction of multiple error bars, are proposed to realize the broadband accurate measurement. Finally, control-hardware-in-loop experiments are carried out to verify the effectiveness of the proposed method.