Design Method of Multisine Signal for Broadband Impedance Measurement

With the increasing penetration of renewable energy, it is important to analyze the impedance characteristic of renewable energy grid-connected system (REGS) to implement the stability analysis of the grid connection operation. In order to further improve the accuracy of the broadband impedance measurement, this article proposes a design method for the multisine signal considering both the signal-to-noise ratios (SNRs) of the perturbation signal and the response signal in the impedance measurement. By quantitatively analyzing the mathematical relationship between the SNRs and the measurement error, the principle to select the minimum SNR requirement of the perturbation and response signal can be obtained so as to guide the amplitude design of the perturbation signal, which can further improve the broadband impedance measurement accuracy. The multisine signal is adopted in this article to realize the proposed design method. In the application of the multisine signal, in order to limit the peak value of the multisine signal to avoid overmodulation, an improved phase design method for the multisine signal based on crest factor reduction algorithm is proposed. Finally, experiments based on the Typhoon control-hardware-in-loop (CHIL) platform are carried out to verify the effectiveness of the proposed design method for the multisine signal in the impedance measurement.