Abstract
The dynamic voltage restorer (DVR) is a power electronics based solution for mitigation of voltage sags and voltage swells effects on sensitive loads that injects voltages in series with the grid. Typically, the controller structure for a DVR comprises an inner current loop and an outer voltage loop. Usually, a proportional controller or a proportional integral controller is used for the current loop, and a resonant controller is used for the voltage loop. This paper presents the design of a robust controller for the voltage tracking loop of a DVR that guarantees robust stability against load parameter variation. Moreover, the proposed controller ensures the tracking of a sinusoidal voltage waveform as well the rejection of the nonlinear load current influence, both with a prespecified error. The voltage controller design is based on the H∞ parameter specification approach. All performance and robustness requirements are specified and analyzed on the basis of the frequency response plot of the closed loop transfer function. The proposed controller performance is validated by simulation and by experiments carried out on a low-scale DVR prototype.
