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.
The Dynamic Voltage Restorer (DVR) is a power electronics based solution for mitigation of voltage sags and swells effects on sensitive loads, which basically injects voltages in series with the grid. Typically the controller structure for a DVR is composed by an inner current loop and an outer voltage loop. Usually a proportional 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 guaranties the robust stability against load parameters variation. Moreover, the proposed controller assures the tracking of a sinusoidal voltage waveform, as well the rejection of the non linear load current influence, both with a pre specified error. The voltage controller design is based on H∞ mix-sensitivity parameter specification approach. All the performance and robustness requirements are specified and analyzed based on the frequency response plot of closed loop transfer function (sensitivity and complementary sensitivity functions). The proposed controller performance is validated by simulation and by experiments carried out on a low scale DVR prototype.
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