Ionut Ciocan

Modeling and simulation of supercapacitors

In this paper we present some models for supercapacitors. The supercapacitors are used more and more in high level industries such as: traction systems, automotive industry, aerospace industry, telecommunications etc. Understanding supercapacitors operation mode is necessary so we can be able to determine the applications which require these components, and to be able to choose between supercapacitors and other energy storage devices. In this paper were used some models for the implementation of supercapacitors, and the simulations made in Orcad 9.2 to determine their operation, are in time and frequency domain. Also, the models were implemented in Simulink 7.5 and the simulation results prove the models accuracy. Two test measurements on the ECOND Pscap350 supercapacitor were realized and using the measurement data, two methods to compute the parameters are presented.

An improvement on empirical modelling of photovoltaic cells

The photovoltaic (PV) cells convert solar radiation directly into electricity. An operating point of a photovoltaic module will move by the variation of the solar radiation, cell temperature, cell surface and values of the load connected to the system. In this paper four models for photovoltaic cells were analyzed, and two improved empirical models were implemented. The empirical models were developed using Mathcad and were validated by comparison of the obtained characteristics with the ones given by the manufacturers of the PV panels.

Single-stage low cost grid connected inverter in photovoltaic energy applications

Due to the rising fuel costs and growing worldwide demand for electricity, renewable energy sources become a necessity rather than a luxury. This paper presents an original control strategy for a buck-boost based converter used as a low cost inverter in a photovoltaic (PV) system. The main objective of the inverter is to harvest maximum power from the PV module and to inject it into the grid. The design of the converter is detailed and, together with the control method, a macro-model for the inverter is proposed. The macro-model is developed in order to have shorter simulation times and test various maximum power point tracking (MPPT) algorithms. Simulations and experimental results validate the proposed PV system.

An improvement on empirical modelling of the batteries

Batteries are devices that convert chemical energy contained in its active materials into electric energy throughout electrochemical red-ox reactions. Theoretically, the energy provided by a battery depends only on its active substances. Practically, just a part of a batterys capacity can be used, due to the nonreactive substances that add up to the process and which influence the magnitude of the charge-transfer reaction, diffusion rates and energy losses. In this paper five methods for modeling the batteries were presented, and one improved empirical model was implemented. The empirical model was built using Mathcad and was validated through the comparison of the experimental obtained characteristics with the ones given by the producer.

SCADA development for an islanded microgrid

The aim of this paper is to describe a SCADA tool for an intelligent microgrid. This application provides control over a smart microgrid that contains inverters, batteries and generators with power meters. In this system, the energy is generated by solar panels, a geothermal generator, a biomass generator and stored in batteries. The data is collected and represented on a PC Interface. The communication between the components and the application is accomplished through different protocols and standards. The connected devices can be detected, the inverters and power meter values, such as power and voltage, are read through the software application. These values, such as power, voltage, the speed of generators, can also be modified through this interface.

Modeling Transfer Function for Buck Power Converter

Switching regulators offer two main advantages compared to the linear regulators. First, switching efficiency is much better than linear. Second, because less energy is lost in the transfer, smaller components and less thermal management are required. A switching power supply has to assure the stability between input and output voltage, the stability between load and output voltage, and a good transient response between different disturbances signals. The paper will outline a mathematical method for modeling the transfer function for switching power supplies. That model will be implemented in Simulink and after that, the result will compared with PSpice. This model can be used to design a best control for power converters.

Weekly electronic pills dispenser with circular containers

This paper proposes the improvement of the process of health recovery by using a programmable medication dispenser. We designed and realized an electronic pills dispenser with seven circular containers. The dispenser is realized around PIC18F458 microcontroller which controls all the function of the dispenser. Using a keyboard and an LCD, the user can easily set the hour when the pills will be supplied on a plate. When the time for medication is arrived, a dose of medication is released and an audio alarm is generated. If the patient does not take the dose prescribed by the doctor, an SMS is sent to a phone number.

Comparison between fixed and solar oriented PV modules' energy production using a simplified PSIM model

This paper presents a simplified Powersim (PSIM) model for simulating and estimating the power losses due to the change in the relative position of the sun to a fixed south oriented solar panel. The proposed equation used for describing the difference between the sun-tracking system and the fixed system is validated by testing a solar panel guidance system based on data provided by Stellarium software. The results obtained when using a fixed, a single-axis and a dual-axis tracking system are compared for different energy test reports. For example, in summer time (Cluj-Napoca), when using Stellarium indications, if only the azimuth is respected, the energy production can be increased by almost 31%, and by about 35% if the elevation is respected as well. This is compared to a fixed south oriented solar panel tilted at 45 degrees.

A new forward based converter with power factor correction

The paper presents a forward converter with power factor correction. The novelty of the paper consists in a combination between a forward converter and a valley fill circuit. The auxiliary winding of forward converter is included in valley fill converter. The new converter has a high power factor. The paper will present the design, simulations and experimental results of the proposed circuit. Another important advantage of the proposed circuit is a reduced stress of the power transistor.

Thermal modeling and analysis of a power device heat sinks

This paper presents a study about thermal behavior of heat sink - power device assembly. The power device (power transistor, triac, thyristor etc) and the heat sink were modeled in SolidWorks. These models have been used in simulations. We take into consideration different power devices packages, different heat sinks and different thermally conductive pastes. A thermal analysis has been performed by position of heat sink on PCB. In our study, we have taken into consideration the influence of the holes from heat sink in heat dissipations. The results of simulations and experimental measurements realized with a temperature data logger are presented in the paper.