Estimating the Effect on Harmonic Impedance in a Low Voltage Network Due to Different FACTS Controllers

Harmonic impedance is the equivalent spectral impedance of the power system which characterizes the frequency response characteristics of the particular system. This paper presents different considerations on harmonic impedance due to different FACTS devices in an effective and easy to implement method. This method uses a different FACTS device to create a controlled short circuit at the measurement point. The short circuit produces a pulse current and a voltage distortion, which are then used to estimate the system impedance. The strength of current pulse is controlled through the thyristor firing angle so that enough signal energy available for precise measurement and yet the disturbance is small enough not to cause any power quality problems. This method uses DFT analysis to extract the harmonic voltage caused by the FACTS devices.