A photovoltaic (PV) plant model is presented. It is based on a detailed electrothermal description of the panels forming strings that, in turn, form the power plant. It accounts for environmental working conditions, such as temperature and wind speed, and specific plant configuration, such as plant topology and power losses due to interconnections. The input variables of the model are the ambient temperature, irradiance, and wind speed. The model derives the working temperature of the panel taking into account also the power conversion performed by the panel; the electrical operating point is determined by simulating the actions done by the maximum power point tracker that operates at plant level. This model has been tested using a large database of experimental data from industrial PV plants characterized by power levels ranging from 250 kW to 1 MW. As shown, the model is capable to predict power production when “fed” by forecast irradiance, ambient temperature, and wind speed data.

This work presents a technique to estimate on-line the inertia of a power system based on ambient measurements. The proposed technique utilizes the covariance matrix of these measurements and solves an optimization problem that fits such measurements to the synchronous machine classical model. We show that the proposed technique is adequate to accurately estimate the actual inertia of synchronous machines and also the virtual inertia provided by the controllers of converter-interfaced generators that emulate the behavior of synchronous machines. We also show that the proposed approach is able to estimate the equivalent damping of the classical synchronous machine model. This feature is exploited to estimate the droop of grid-following converters, which has a similar effect of the swing equation equivalent damping. The technique is comprehensively tested on a modified version of the IEEE 39-bus system as well as on a dynamic 1479-bus model of the all-island Irish transmission system.

Circuit simulation is seen by some people as a well established discipline, where there remains little or no space for improvement. Yet, no steady state and stability analysis methods are available for circuits described by a combination of analog, digital and behavioral parts. Recently, the theory necessary for development of such simulators was proposed and a circuit simulator incorporating these theoretical developments has been presented. It manages analog, digital and behavioral components, while retaining all the classical "spice-like" features. This was possible by importing some mathematical concepts from the hybrid dynamical systems realm. Such tools represent the interface between the conventional analog world and the more contemporary digital/behavioral one. The reviewed simulation framework is appealing not only for people interested in circuit analysis and design, but for all researches and engineers working in the wider field of system simulation where the analog mixed signal concept is absolutely pervasive.

Steady state simulation and noise analysis are two essential tools for circuit designers. The algorithms currently available in commonly used simulators are basically limited to the analysis of analog circuits that can be modeled by Lipschitz continuous functions. This is a strong restriction, since current applications are often naturally described by mixed analog-digital models; these models are only piece-wise continuous and Lipschitz condition is not satisfied in the breakpoints. In this paper we propose a method to overcome this limitation by showing how circuits in this class, and, in general, circuits showing discontinuities, can be modeled as hybrid systems. Conventional steady state and noise analysis methods are then extended to this class of circuits. A method to identify the discontinuity points, that, in general, are not known a priori in circuit analysis, is also proposed. With this last addition the method is fully automated and does not require any user intervention.

This letter studies the impact of the dead-band in the input signal of Power System Stabilizers (PSSs) on the transient response of power systems. The letter provides a taxonomy of the dynamic behaviour of the system in various scenarios: no PSS, PSS without dead- band, and PSS with dead-band. For the latter, the dead-band stability margin and the interaction of the PSS with the system loading level as well as primary and secondary frequency regulators are discussed. The oscillatory behavior of the system is rigorously studied through the monodromy matrix and limit cycles are characterized by means of Floquet multipliers. The IEEE 14-bus system serves to illustrate the aforementioned scenarios.