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

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 paper considers the formulation of the variational model (VM) of autonomous circuits (oscillators) working in periodic steady-state conditions. The shooting method, which is largely used to compute the solution in the time domain when the VM is forced by a small-signal perturbation, is studied. The proposed analytical approach can be exploited to improve accuracy in the simulation of the effects of noise sources. In particular, we justify from an analytical standpoint the adoption of a suitable periodicity constraint in the shooting method. We exploit the properties of block circulant matrices that naturally arise in the description of the problem. We prove that the frequency of the small-signal perturbation must be different from that of the unperturbed oscillator to avoid inaccuracy of the shooting method due to the existence of singularities in the VM formulation, and derive a method that allows us to get closer to the singularity

Accurate phase noise simulation of circuits for radio frequency applications is of great importance during the design and development of wireless communication systems. In this paper, we present an approach based on the Floquet theory for the analysis and numerical computation of phase noise that solves some drawbacks implicitly present in previously proposed algo- rithms. In particular, we present an approach that computes the perturbation projection vector directly from the Jacobian matrix of the shooting method adopted to compute the steady-state solution. Further, we address some problems that arise when dealing with circuits whose modeling equations do not satisfy the Lipschitz condition at least from the numerical point of view. Fre- quency-domain aspects of phase noise analysis are also considered and, finally, simulation results for some benchmark circuits are presented

SUMMARYIn this paper it is shown that a numerical method largely adopted for the simulation of noise in autonomous circuits is affected by singularities that manifest when the frequency at which the noise analysis is carried out approaches a harmonic of the autonomous circuit. The resulting noise power spectral density (PSD) is thus characterized by spurious spikes. The presence of these singularities is for the first time justified from an analytical standpoint and their effects are shown by simulating some oscillators, employed as benchmarks. Furthermore, the presented approach justifies the 1/( f s − f ) 2 shape of the PSD of noise at the output when the f s frequency approaches the f fundamental of a stable oscillator and the 1/| f s − f | 3 shape when the effects of flicker noise are manifest.