Non-invasive power system impedance monitoring for improved power quality

The use of power quality equipment such as active filters requires a knowledge of power system impedance back to source for stable control design. Impedance measurement is usually invasive and presents a noticeable disturbance to the system. To reduce the number of disturbances, a non-invasive measurement technique is presented, which monitors the switching frequency components of an active filter, to detect changes in power system impedance. Only when a change is detected is the invasive technique triggered to obtain an accurate measure.