Online network impedance identification with wave-package and inter-harmonic signals

In power system analysis the main supply at a point of common coupling (PCC) is often presented by its Thévenin or Norton equivalent. In most cases these models adequately define the electrical characteristics of a PCC and are commonly used for power flow evaluations, fault estimations, as well as stability and power quality assessments. To determine the equivalent impedance of a PCC through analytical calculation or simulation precisely may be challenging due to the complexity and time varying nature of power supply systems. Especially in medium- and low-voltage distribution networks with a high share of fluctuating consumers and generators a measurement may be required to exactly capture the equivalent impedance over time. This contribution presents a method, which can be used to identify varying equivalent parameters of an AC power system with high accuracy and time resolution. To identify the network impedance the system is excited with short sequences of current signals while measuring the corresponding voltage and current characteristics. The method is evaluated in a simulation model. Further on, impedance measurements on the low-voltage level are presented and discussed.