A Magnetic-Sensing-Based Wide-Bandwidth Grid Impedance Measurement Technique With Small Perturbation Injection

Grid impedance is an important parameter in the impedance-based stability analysis method for analyzing the interaction between the power electronic inverters and the power grid. However, the existing measurement technique is deteriorated by narrow-bandwidth sensors, large perturbation injections, and inaccurate response components extraction based on the Fast Fourier transform (FFT) algorithm. To overcome these problems, a magnetic-sensing-based wide-bandwidth grid impedance measurement technique with a small perturbation injection is proposed in this paper. A novel impedance extraction algorithm based on the quadrature delay estimator (QDE) is developed to overcome the spectral leakages and frequency aliasing effect of the existing FFT-based impedance extraction algorithm. The proposed grid impedance measurement technique is implemented on a digitally controlled inverter system, and its effectiveness is verified through the experimental results.