Modeling and active damping of harmonic propagation on electric distribution systems

This work presents a control algorithm for an active resonance damper. This kind of equipment must act as a harmonic impedance in order to damp harmonic propagation throughout a distribution feeder. This harmonic resistance must be equal to the characteristic impedance of the distribution feeder in order to achieve optimized compensating currents. As the analytical calculation of this impedance is a non-trivial (and maybe, impossible) task, it is proposed an ARIMAX least-squares based parameters estimator to determine, on line, the optimal value for the harmonic resistance. A detailed modeling of the system is presented. The system is modeled in a way that allows the feeder´s characteristic impedance to be estimated based only on the installation site voltage (i.e., no voltage/current sensors are required on other parts of the feeder) independently on the number of buses or non-linear loads attached to them and important properties are derived from the equations. A sliding-Goertzel algorithm is used to extract the harmonic content of the installation site voltage (thus, no PLL or d-q transforms are necessary, making the algorithm suitable for single phase systems).