Wide bandwidth three-phase impedance identification using existing power electronics inverter

In smart grid applications knowing system impedances over a wide frequency range makes it possible to perform useful diagnostic and prognostic activities related to a number of grid related issues, such as: predicting harmonic propagation, identifying resonances, detecting high impedance faults, identifying voltage distortion, and identifying harmonic polluters. The proposed online monitoring technique leverages wideband impedance identification to enable a number of smart-grid related capabilities, such as health monitoring, active filter re-tuning, and adaptive control of grid-connected switching converters, all of which lead to the improved stability, performance and reliability of smart grid systems. In this paper, a new approach is developed using a power converter to make a wideband three-phase impedance measurement at its interface in addition to providing power generation capability. A small signal white noise injection via a pseudo-random binary sequence (PRBS) is added to the converter´s PWM, eliciting a small signal wideband impedance disturbance. Using cross-correlation techniques, the output impedances seen by the converter are constructed.