Compensation of Voltage Sags Through DVR Under Distorted Grid Voltages

This work proposes a type of voltage insertion into the grid through a dynamic voltage restorer (DVR) to compensate sagged and distorted voltage applied to sensitive load. The control to dynamically restore voltages applied to sensitive loads generates only voltage with the fundamental frequency. The proposed method has the advantage of generates a simple waveform to compensate only the sag, this allows a longer battery life of the DVR. As a consequence, restoration of the fundamental voltage, besides recomposing it to its nominal value, also attenuates the level of THD in the load. Thus, this method also improves the power quality of the system. A recursive least-squares is included to the control system to estimate the harmonic components that compose the distorted voltage to be restored, rather than using filtering on the waveform. In addition, the RLS does not contain delays, common to filters, which improves the performance of the control system used. It is important to highlight these harmonic components are not compensated by the restorer device. Their estimation has the function of reconstituting the distorted voltage digitally in the DSP. Simulation and experimental results are presented.