Johanna Salazar

Predictive control of a renewable energy microgrid with operational cost optimization

A proposal for optimal control of a microgrid powered by solar energy with mixed temporary storage based on a battery bank and hydrogen is presented and evaluated here by means of simulations. The proposal is based on a Predictive Controller that optimizes the operational costs by taking into account the value of the energy generated, the cost of locally storing energy, the aging of the components and the operational constraints. The Constrained Mixed-Integer Predictive Control problem obtained is then solved using a formulation based on the duration of the states, which simplifies the numerical solution. Some simulation results are presented to show the validity of the proposed approach.

Control for a Variable Speed Wind Turbine Equipped with a Permanent Magnet Synchronous Generator (PMSG)

In wind turbine systems, one of the operational problems is the unpredictable factor of wind. This leads the quality of produced energy becomes an important problem in the system. Several control techniques have been applied to improve the quality of power generated from wind turbines. Pitch control is the most efficient and popular power control method, especially for variable-speed wind turbines. In this paper, a traditional PI controller is developed. Simulations were carried out to validate the proposed control design when realistic data of wind speed collected in Borj Cedria, Tunissia, are taken into account.

Operation of Medium-size Reverse Osmosis Plants with Optimal Energy Consumption

Abstract This paper deals with the optimal operational strategy of a reverse osmosis (RO) plant for remote sites. The electricity supply to these plants comes usually from renewable energies (wind and solar), when they are not temporarily available, they are complemented by a diesel generator and batteries. The water demand of small settlements in arid regions suffers strong variations along a day. As the higher demand of water usually occurs when solar energy is more available, the operational expenses can be reduced by considering the RO plant as an active load. A good control strategy, will implement a variable operation point, taking into account the predictions of water demand, the expected variation of the available energy sources and the scheduling of cleaning operations in the RO plant, in order to optimize the energy use. In this paper a hybrid predictive control is proposed to implement this task. Simulations of a specific plant show that an adequate operation reduces the diesel energy consumption, while satisfying the variable water demand.

A Microgrid Library in a General Simulation Language

Abstract A library in the EcosimPro environment, developed with the objective of providing the tools needed to integrate MicroGrids into multi-domain simulations is presented. Thus, practical simulated components of renewable energy sources (photovoltaic arrays, wind turbines), diesel generators, power electronic interfaces (DC/AC or AC/DC/AC), energy storage devices (batteries) are developed, in order to integrate them with the existing libraries of loads (such as electrical systems, hydraulic systems, chemical engineering process, etc). Components in the library are designed so they can be parametrized from data sheet information by general engineers, and then graphically connected to simulate under variable conditions specific real-life Microgrids. With this, different configurations and control strategies for Microgrids can be tested when operating on the real process. After presenting the main ideas behind the dynamic modelling of the components, the application to a case study is presented.

Initial validation of a reverse osmosis simulator

Reverse Osmosis (RO) is the most common technique to produce drinkable water in arid regions. The desalination plants are usually designed for a short number of constant operation points. A dynamic strategy of control would help to decrease the operation expense and the equipments cost. However, the lack of dynamic simulation tools for this kind of plants, avoids the optimal design, which would use a continuously changeable operation point. For this, a new dynamic simulation library of RO plants was presented elsewhere. Now, the present paper deals with the validation of that library, using experimental data from a real RO plant.

Modelling for dynamic simulation of pretreatment in Reverse Osmosis plants

The development of mathematical dynamical models of the pretreatment process in reverse osmosis plants is presented. The objective is to use the models for testing and comparison of control strategies in reverse osmosis plants. Thus, these models have been developed to implement them using off-the-shelf software (EcoSimPro), so that advanced control algorithms can be easily tested. During modeling, the parameters are selected to be simple to obtain from available plant measurements.

Scheduling of the membrane module rotation in RO desalination plants

Abstract This work deals with the optimization, in reverse osmosis desalination plants, of the scheduling of membrane cleanings and rotation of the membrane modules inside each pressure vessel. Each pressure vessel consists of several membrane modules (typically around seven) in series. The modules closer to the feed inlet are prone to be damaged by biofouling and solids, while the modules closer to the reject outlet are prone to be damaged by scaling due to increased salt concentration. Besides, the permeate flux varies for different modules along the pressure vessel. In order to increase the life of the membrane modules, it is a good practice to rotate the modules, thus spreading the difference effects in each module. The topic of this work is to suggest a way to calculate the number and time instants for the rotations, and the optimal operation scheduling. This depends on several factors, such as the time instant for cleanings, the percentage of replacements, the quality of the feed water, etc. Due to ...

Modeling of MicroSource for Microgrid during Island Operation

This paper describes the control strategies to be adopted for the operation of a MicroGrid when it operates isolated from the main grid (that is, in Islanded Operation). The MicroGrids studied here comprise a variety of inverter-interfaced distributed energy sources (typically, photovoltaic arrays, wind turbines and diesel generators), together with energy storage devices (batteries) and controllable loads. Some simulation results obtained with the presented control scheme are presented.