Wide bandwidth system identification of AC system impedances by applying pertubations to an existing converter

A new approach is developed using an existing single-phase power electronics inverter to make a wideband impedance measurement at its interface using a pseudo-random binary sequence (PRBS) voltage perturbation and digital network analyzer techniques. Since the PRBS is an approximation to white noise, all frequencies of interest can be excited simultaneously. The perturbation at the interface is measured and cross-correlation techniques are applied to construct the wideband impedance of the system under test. Online monitoring of interface impedances is a key enabler for a number of smart-grid related capabilities, such as grid health monitoring, active filter re-tuning, identifying system interaction, and adaptive control of grid-connected switching converters. Knowledge of the converter´s surroundings enables smarter control actions, which lead to improved stability, performance and reliability of the smart grid.