Horia Andrei

PV Module Parameter Characterization From the Transient Charge of an External Capacitor

In the classical model of the photovoltaic (PV) cell/module, based on the single-exponential or double-exponential representation of PV cell/module behavior, parasitic parameters are ignored. Their presence, however, has multiple effects, such as the maximum power point tracking on the current-voltage curve, the switching ON/OFF of the inverters for grid connection, and the electrical safety of persons against indirect contact due to ground leakage currents and lightning phenomena. The effects of parasitic parameters can be visualized in the experimental results gathered through the transient charge of an external capacitor connected to the PV generator terminals. The impact of the parasitic components is different when considering a single PV module or a PV array composed of several PV modules. At the module scale, an oscillation occurs in the initial part of the current waveform, which indicates the presence of some inductive components. At the array scale, the inductive phenomena are overdamped, and parasitic capacitive effects become predominant. This paper shows how to determine the parameters of an extended model of PV modules embedding the parasitic parameter effects. It starts from the experimental results obtained from the fast-sampled voltage and current waveforms during the transient charge of an external capacitor. Numerical examples taken from real cases with different PV technologies are provided.

Identification of the Radial Configurations Extracted From the Weakly Meshed Structures of Electrical Distribution Systems

The electrical distribution systems are typically structured as weakly meshed networks with multiple supply points, but they are operated with radial configurations by opening the redundant branches. The nonregular composition of the meshed structure and the constraints imposed by the number and location of the supply points complicate the problem of determining all of the possible radial configurations that can be extracted out of a given structure. This paper illustrates a novel procedure, based on the creation of a reduced network structure, to determine the number of possible radial configurations and the set of open branches corresponding to each radial configuration. The proposed approach is presented and applied to five test distribution systems commonly available in the literature, providing for the first time the information about the number and the layout of the possible radial configurations obtainable for these systems.

Curve fitting method for modeling and analysis of photovoltaic cells characteristics

This paper deals with the mathematical model to assess the performances of photovoltaic (PV) cells. The PV system characteristics are modeled and analyzed by using the curve fitting method referred to the different connections of PV cells and different solar irradiance. The results are compared with those resulting from measured data in a real case. Specific LabVIEW™ and Matlab™ software applications are implemented to prove the theoretical methods.

Contributions Regarding the Principles of the Minimum Dissipated Power in Stationary Regime

The use of the power and energy functional in the analysis of the electric circuits makes it possible to appreciate the energetic equilibrium state attained in the circuit at a certain moment. In the present work, a power functional is built and its limit is determined. It is shown that the equilibrium state is one of a minimum energetic state

The Modelling of the Power Factor in Steady State Non Sinusoidal Regime with Mathcad Techniques

The paper presents the results of a new mathematical method to calculate the power factor in the electroenergetical circuits. The relative values which characterize the voltage and current harmonics have been used. The MathCAD example will prove, comparatively, the efficiency and the application of this method

Modeling and simulation of dynamic voltage restorer for voltage sags mitigation in medium voltage networks with secondary distribution configuration

This paper discusses the performance of a dynamic voltage restorer (DVR) used for improving the voltage quality in medium voltage distribution networks with secondary distribution configuration. The DVR compensator is analyzed as a voltage controller. Modeling of DVR and his control scheme are proposed. Validation of control scheme and DVR model is carried out through simulations by using SimPowerSystem module of Matlab/Simulink. The obtained results demonstrate the performances and the benefits of dynamic voltage restorer use in power network with secondary distribution structure.

Dynamic voltage restorer response analysis for voltage sags mitigation in MV networks with secondary distribution configuration

This paper investigates the performance of the DVR for enhancing voltage dips in medium voltage (MV) distribution networks with secondary distribution configuration. The DVR compensator is analyzed as a rectifier & inverter based voltage controller. Matlab/Simulink modeling of DVR and his control strategy are presented. The DVR performances are compared for different grid connection of the DVR rectifier. The obtained results demonstrate the performances and the benefits of dynamic voltage restorer use in power networks with secondary distribution structure, and help us to choose the proper supply configuration for the DVR rectifier.

Evaluation of hilbert space techniques and lagrange's method for the analysis of dissipated power in DC circuits

The basic circuit laws of DC circuits are interpreted in this paper by defining suitable functionals in terms of dissipated power. It is then shown that the minimum of dissipated power determined by taking the derivative of these functionals verifies the first Kirchhoffs law. This allows interpreting the circuit equations by using the second Kirchhoffs law and the minimum power principles. In order to estimate the extreme values of dissipated power for DC circuits with modifiable parameters, and the relation between the variation in one or all the resistances of the networks and the variation of dissipated power we use the Lagranges method. Numerical examples obtained with Mathematica are provided to show the practical applications and comparison between of two proposed principles of DC circuits.

Systematic analysis of the electric power and magnetic energy for linear electric and magnetic circuits with modifiable parameters

The paper presents a new systematic analysis method in order to estimate the total absorbed power and energy in linear electric and magnetic circuits with modifiable parameters. The relation between the variation in one or all the resistances and reluctances of the networks and the variation of total absorbed power and energy are discussed using the Lagranges method. For the considered applications the results are obtained with Mathematica and Maple useful for establishing the variation limits of absorbed power and energy.

The systematic analysis of the absorbed power in D.C. Networks with modifiable parameters using a new mathematic algorithm

The paper presents a new systematic analysis method in order to calculate the absorbed power in D.C. networks with modifiable parameters. The relation between the change in one or all the resistances of the networks, and the variation of total absorbed power are discussed using the Lagrangepsilas multipliers, and the bilinear theorem. The results obtained with the dedicated software Mathematica 6.0 are useful for establishing the variation limits of absorbed power.