Carlos A. Ramos-Paja

Improving the perturb and observe Maximum Power Point Tracking by using Sliding Mode control

In this paper the Sliding Mode (SM) control, used to reject the 100Hz oscillation of the voltage of the photovoltaic field in a grid connected system, is discussed. With respect to the classical linear voltage control the SM gives rise to a wider regulation band but, unfortunately, in presence of a fast irradiance variation the SM conditions could be violated producing a divergence of the operating point with respect to the desired one. In order to prevent such a drawback, an appropriate voltage compensation loop is used to interface the Sliding Mode with the Maximum Power Point Tracking algorithm. Simulation results confirm the goodness of the proposed algorithm. The proposed approach is currently patent pending.

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.

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 (

Cargador de baterías fotovoltaico con control por modos deslizantes y limitación de la derivada de corriente de carga

/kWh). El analisis se realiza a partir de la cuantificacion de la demanda de un poblado prototipo, el dimensionamiento y costo de las tecnologias que conforman la microrred para atender la demanda, y la disponibilidad de los recursos renovables solar y eolico de dos zonas localizadas en diferentes latitudes no interconectadas de Colombia. Adicionalmente, se analiza el efecto de introducir las celdas de combustible en el mix energetico, resaltando las ventajas obtenidas al comparar cada caso frente a una generacion tradicional basada en consumo de Diesel.

Análisis de la estabilidad de alto orden de un convertidor buck entrelazado basado en el método de Filippov

In stand-alone photovoltaic (PV) systems, battery chargers are important to guaranteethe energy supply when sunlight is not available. Such chargers need to track the maximumpower point (MPPT) and limit the derivative of the batteries’ charging current to extendtheir lifetime. This paper proposes a battery charging system composed of a Buck converter,a cascade control of the battery current and the PV panel voltage, and the Perturb andObserve (P&O) MPPT technique. P&O generates the reference of the panel voltage for theexternal loop of the cascade control implemented with a P regulator, whose control action isthe reference of the batteries’ charging current. Such current reference passes through aderivative limiter before reaching the internal current control loop, which is implementedby a sliding-mode controller (SMC). This paper includes transversality and reachabilityanalyses of the SMC, as well as the procedure to design the P regulator. The proposedsystem is validated by simulations in PSIM software to show its capacity to perform MPPTand limit the battery’s charging current derivative at the same time.

Reconfiguración de paneles fotovoltaicos para reducción del consumo de hidrógeno en las celdas de combustible de sistemas híbridos

espanolEl diseno de convertidores conmutados en gran parte de la literatura cientifica esta realizado desde el modelo promediado, debido a la facilidad de obtener las funciones de transferencia lineales. Asimismo, la conmutacion en los convertidores de potencia causa un rizado en las variables de estado que no es considerado en el modelo promediado. El componente de frecuencia de una de las variables de estado esta compuesto por un espectro de potencia con un unico pico de nivel DC (valor promedio), un unico pico a la frecuencia de conmutacion (componente de rizado) y en un numero finito de picos en cada sub-armonico (inestabilidades). El metodo de Filippov es utilizado para la prediccion de inestabilidades debidas a las dinamicas rapidas, este metodo predice el rango de los parametros que evitan la primera bifurcacion en las dinamicas rapidas. En el presente articulo se presenta una prediccion de un espacio de parametros estables para el controlador PI (), estimados por el metodo de Filippov para un convertidor buck de dos fases con regulacion de voltaje. Finalmente, los resultados presentados son validados mediante simulaciones de Matlab y Psim. EnglishIn many papers, the averaged model of power switching converters is used to design the control system due to its simple manipulation, which can be approximated by linear transfer functions. Therefore, the power converter commutation causes a state variable ripple that is not considered on the averaged model. The component frequency of the state variables is composed by a power spectrum with a unique peak at the DC level (average variable), a unique peak at the switching frequency (ripple component) and a finite number of peaks in each sub-harmonic (instabilities). The Filippov method is used for instability predictions due to fast dynamics, this method predicts the parameters range that avoids the first bifurcation of the fast dynamics. In this paper a stable space of parameters (Kp, Ti) for a PI controller is presented, it estimated with the Filippov method, for a buck converter with voltage regulation. Finally, the presented results are validated using both Matlab and Psim simulations.

Real Time Simulation of Mismatched PV Arrays

Hybrid generation combines advantages from fuel cell systems with non-predictable generation approaches, such as photovoltaic and wind generators. In such hybrid systems, it is desirable to minimize as much as possible the fuel consumption, for the sake of reducing costs and increasing the system autonomy. This paper proposes an optimization algorithm, referred to as population-based incremental learning, in order to maximize the produced power of a photovoltaic generator. This maximization reduces the fuel consumption in the hybrid aggregation. Moreover, the algorithms speed enables the real-time computation of the best configuration for the photovoltaic system, which also optimizes the fuel consumption in the complementary fuel cell system. Finally, a system experimental validation is presented considering 6 photovoltaic modules and a NEXA 1.2KW fuel cell. Such a validation demonstrates the effectiveness of the proposed algorithm to reduce the hydrogen consumption in these hybrid systems.