Adaptive Frequency Adjustment Method for Impedance Measurement

Impedance measurement is an effective method to obtain the impedance model of the renewable power generation equipment (RPGE). On the basis of the measurement points, the impedance characteristic curves of the RPGE can be obtained. The distribution of the measurement points will influence the accuracy of the obtained curves. In order to obtain accurate impedance curves effectively, adaptively adjusted frequency intervals could be used which can reduce the required number of the measurement frequencies and improve the measurement efficiency. Moreover, the existing work can still be further enhanced by implementing a fitting algorithm while adaptively adjusting the measurement frequencies. In this article, an improved adaptive adjustment method for the measurement frequencies in the impedance measurement based on a vector fitting algorithm is proposed. By implementing a fitting algorithm, the impedance characteristic at unmeasured frequencies can be predicted, which can further raise the measurement efficiency and meanwhile obtain the accurate impedance curves. The measurement frequencies will be adjusted adaptively according to the measurement points and fitting curves. The experiments based on control-hardware-in-loop (CHIL) are conducted to verify the effectiveness of proposed adaptive frequency adjustment method.