A method for in-situ measurement of grid impedance and load impedance at 2 k–150 kHz

A new approach to measure the grid and load impedance of converters in-situ at frequency range 2k-150 kHz has been developed. It is called three-probe approach. This approach allows impedance measurements of power supplies and electric appliances without interrupting their normal operations. The measurement accuracy is improved by proper Fast Fourier Transform (FFT) process to obtain both amplitude and phase information in the measurement. With the proposed setup, the equivalent model consisting of both resistive and reactive components can be derived to represent the grid and load in this frequency range. Grid impedance at different locations and load impedance of various solid state lamps and a SMPS are measured and the results are shown in the paper.