Andrés Julián Saavedra-Montes

Reconfiguration analysis of photovoltaic arrays based on parameters estimation

Abstract A method to determine the photovoltaic (PV) series–parallel array configuration that provides the highest Global Maximum Power Point (GMPP) is proposed in this paper. Such a procedure was designed to only require measurements of voltage and current of each string, which avoids to perform experiments in each module. The ideal single-diode model parameters of each module in the string are obtained from the analysis of the voltage vs. current characteristics of the string. Using the estimated parameters, all feasible PV array configurations are evaluated to determine the array configuration that provides the highest GMPP. Finally, the proposed solution is validated using simulations and experimental data.

PV field distributed maximum power point tracking by means of an active bypass converter

An active bypass structure that was initially proposed as a solution to minimize the reduction in produced power caused by mismatch of photovoltaic modules is compared in terms of efficiency with single and distributed maximum power point solutions based in more conventional dc-dc structures. The analysis and simulations performed under simplified losses assumptions demonstrate that the bypass structure is very competitive with respect to boost, buck or buck-boost based solutions in terms of efficiency.

Mathematical model of total cross-tied photovoltaic arrays in mismatching conditions

This paper presents a mathematical procedure for modeling rectangular (N rows with M modules each) and non-rectangular photovoltaic (PV) arrays in Total Cross-Tied (TCT) configuration operating in uniform and mismatching conditions. The proposed model uses the simple single diode representation for each PV module; then each row of the TCT array is represented as an equivalent non-linear PV circuit with a bypass diode, which allows to represent the TCT array as one string of equivalent PV circuits. The inflection voltages (array voltages that turn off the bypass diodes) of the string are calculated in order to solve only the non-linear equation system related to the active equivalent PV circuits for calculating the array current for a given voltage. Such a strategy reduces the computational burden and improves calculation speed. A TCT array of 4×2 with deep mismatching conditions was implemented in PSIM software to validate the proposed model, obtaining a correlation between model predicted data and the circuital simulation. The accuracy and improved calculation speed of the proposed model allow its use altogether with reconfiguration techniques as well as to reduce the time of energetic evaluations of TCT arrays for PV planning.

Modeling and control of grid-connected photovoltaic systems for 100 Hz oscillations mitigation

In grid-connected Photovoltaic (PV) applications, DC-links based on large electrolytic capacitors are used to attenuate voltage oscillations caused by the sinusoidal power injection into the grid, where the electrolytic capacitors introduce reliability problems. This paper proposes the unified modeling of the complete PV system in typical grid-connected operation conditions to design control strategies that mitigate the DC-link voltage oscillations as well as irradiance disturbances caused by environmental perturbations, it making feasible the use of non-electrolytic capacitors. The developed control strategy has been associated with a maximum power point tracking technique to maximize the power produced by the PV panel, evaluating the system performance using analytical and simulation results.

Analysis of harmonic pollution caused by typical loads in offices

An analysis of the harmonic pollution produced by different load scenarios in an office is presented in this paper. An experiment was carried out, in which typical load scenarios in office environments were reproduced. The devices used in the experiment were selected based on the characterization of the consumption groups in office environments in several countries. The analysis shows that THDi and TDD were different for each load scenarios, so the scenario of highest consumption was not the most polluted. Moreover, it was concluded that scenarios, which include plug-load devices, has the highest harmonic pollution.

Maximum power point tracking in wind farms by means of a multivariable algorithm

A maximum power point tracking strategy based on a multivariable perturb and observe algorithm aimed at maximizes the power generated in wind farms, reducing the requirements in terms of current sensors and control units is presented in this paper. Such a solution increases the economical viability of wind power systems, since the same power is extracted in comparison with classical wind farms, but a reduced number of components are required. Comparison of the power extracted from a generalized wind farm using the algorithm proposed vs a traditional MPPT algorithm is presented. Simulation results confirm that the proposed solution extracts the maximum power but only using one current sensor and one control unit.

Dynamic model validation via error indexes

An error index to support the validation stage of dynamic models is proposed in this paper. The result of the index quantifies the percentage of the relative difference between an experimental signal and an estimated signal. The index is calculated for several test signals, which are selected and designed to exhibit controlled differences in contrast with a reference signal. Also, other seven indexes are calculated and compared with the proposed one. The results of the proposed index are the same controlled differences in the test signals, allowing an accurate interpretation of the results in a validation stage of a dynamic model. Additionally, experimental data taken from an excitation system for a synchronous generator are used to evaluate and validate the proposed index.

Parameter calculation of a small wind turbine model cálculo de parámetros del modelo de una turbina eólica (160 w)

A method to estimate the model parameters of a small wind turbine is proposed in this paper. The method highlights an experiment in which the wind speed, the generator angular speed and the real power consuming by the load are registered. A fifth order polynomial to represent the ratio between the power coefficient and the tip speed ratio is obtained from the registered data. The proposed method does not require a wind tunnel and can be carried out in the location of the wind generator.

Experimental characterization of compact fluorescent lamps for harmonic analysis of power distribution systems

The modeling of a compact fluorescent lamp for harmonic analysis under terminal voltage variation is presented in this paper. The compact fluorescent lamp is represented with the diode bridge rectifier model, which is commonly used for harmonic analysis. The set of parameters is estimated for different values of the terminal voltage applied to the lamp. The equations to estimate the parameters and the required measurements to calculate them are presented. To characterize the lamp an experiment is carried out varying the RMS terminal voltage from 10 V to 131.6 V and for each terminal voltage value the apparent, real and reactive powers, the power factor, the current and the applied voltage are registered. To validate the model in the range of the terminal voltage, the total harmonic distortion of current calculated with the experimental signal and the total harmonic distortion of current calculated with simulation software are compared. The results show that the compact fluorescent lamp can be represented for one set of parameters in the operation range of the terminal voltage suggested by the manufacture.

Análisis de factibilidad técnico-económico de microrredes que integran celdas de combustible en zonas no interconectadas de Colombia

La necesidad de proveer soluciones energeticas sostenibles para las zonas no interconectadas de Colombia, dependiendo de los recursos renovables disponibles en cada zona, supone un desafio respecto al analisis de viabilidad tecnico-economica de las alternativas de solucion a traves de las microrredes. Este documento tiene como objetivo analizar el impacto tecnico-economico de introducir celdas de combustible en la reduccion de costos a lo largo del tiempo de vida de una microrred para zonas no interconectadas, empleando el software HOMER. Dicho impacto se evalua tanto en el diseno tecnico de la microrred como en el Valor Presente Neto y en el Costo nivelado de Energia (