Perturbation Amplitudes Design Method Based on Confidence Interval Evaluation for Impedance Measurement

Due to the growing demand for broadband impedance modeling and stability analysis of renewable power generation equipment, extensive research has been conducted on impedance measurement techniques. While using wideband signals in the impedance measurement, accuracy evaluation methods and perturbation amplitudes design are crucial to the accurate measurement. To achieve wideband accurate measurement, in this article, we establish the mathematical relationship between measurement error and perturbation components considering frequency-coupling characteristic and noise interference. Next, based on the uncertainty characterization of the noise, a confidence interval evaluation method is proposed to quantify the measurement accuracy. Furthermore, by simplifying the mathematical relationship, the article explores the inversely proportional relationship between accuracy and perturbation amplitudes. Accordingly, the amplitude design method of each component in the multisine signal is proposed in this article. Finally, experiments based on the Typhoon control-hardware-in-loop platform are carried out to verify the reliability of the proposed method. According to the experimental results, the measurement error is within the range of confidence interval, which verifies the reliability of calculated confidence intervals. Moreover, the perturbation amplitudes can be designed according to the estimation of inversely proportional function, leading to the accurate measurement of the whole frequency span.