An Intelligent Two-Level Control of Solar Photovoltaic Power Plant for Electromechanical Oscillation Damping in Power Systems

The design and integration of a novel two-level supervisory active power control scheme for solar photovoltaic (PV) power plants is described in this paper. The scheme maintains active power reserves by operating the PV below its maximum power point (MPP) to damp electromechanical oscillations in power systems. An intelligently designed fuzzy logic controller (FLC) with a locally generated frequency deviation signal as its input constitutes the supervisory controller. The FLC sets a suitable power set-point for the PV plant's inner control scheme to ensure that power system oscillations are suppressed. To guarantee that the PV power plant follows this power set-point, a voltage tracking mechanism (inner control) has been devised to guarantee the instant transformation of an active power set-point into a corresponding voltage set-point for the converter interface. The inner control regime dynamically self-adapts to any given PV operational conditions, guaranteeing that the scheme may be readily translated to any PV operating environment. In addition, the proposed method estimates the PV plant's MPP quantities in real-time without the use of an irradiance sensor. Modal analysis and extensive nonlinear time-domain simulation studies reveal that the proposed control strategy successfully damps electromechanical oscillations on a well-known two-area, four-machine power system. Such functionalities are projected to be included in future power systems with high PV penetration in order to compensate for the reduced system inertia and enhance system stability.