On-line Measurement of Inward and Outward Impedances for Stability Assessment

The paper presents an alternative on-line stability monitoring method, where by performing internal perturbation, converter itself can measure source output impedance and load input admittance simultaneously. Using these measurements, and combining them with converter's un-terminated transfer functions, equivalent system output impedance (and admittance) can be calculated out, offering a great opportunity to observe stability at both, input and output side of the converter. Additionally, using all terminal impedances, Nyquist plots for both sides can also be plotted offering better insight into system stability margins.