Voltage quality enhancement with minimum power injection

This work proposes the usage of a repetitive-based control to dynamically restore the voltage applied to sensitive and critical loads of power systems. Besides, sag and voltage swells, the proposed control can intrinsically mitigate harmonic distortions. Furthermore, the filter is able to work out on sinusoid references and, thus, avoids the need of employing the dq transform. A recursive least-squares is also included to the control system in order to assure the synchronization of the injected voltages to be restored. The design of the control parameters along with the system stability are discussed throughout the paper. Also, this work aims to analyze two different types of voltage insertion into the grid through the series compensator. In the first one, the voltage injection is in synchronization with the pre-faulted grid voltage, while the second injects the voltage in a manner that the compensator spends a minimum of active power. Both types produce reference voltages that are used by the repetitive control. Additionally, simulated and experimental results are presented and corroborate the method efficacy.