Kostas Kalaitzakis

Development of a microcontroller-based, photovoltaic maximum power point tracking control system

Maximum power point tracking (MPPT) is used in photovoltaic (PV) systems to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions and of the load electrical characteristics. A new MPPT system has been developed, consisting of a buck-type DC/DC converter, which is controlled by a microcontroller-based unit. The main difference between the method used in the proposed MPPT system and other techniques used in the past is that the PV array output power is used to directly control the DC/DC converter, thus reducing the complexity of the system. The resulting system has high-efficiency, lower-cost and can be easily modified to handle more energy sources (e.g., wind-generators). The experimental results show that the use of the proposed MPPT control increases the PV output power by as much as 15% compared to the case where the DC/DC converter duty cycle is set such that the PV array produces the maximum power at 1 kW/m/sup 2/ and 25/spl deg/C.

Design of a maximum power tracking system for wind-energy-conversion applications

A wind-generator (WG) maximum-power-point-tracking (MPPT) system is presented, consisting of a high-efficiency buck-type dc/dc converter and a microcontroller-based control unit running the MPPT function. The advantages of the proposed MPPT method are that no knowledge of the WG optimal power characteristic or measurement of the wind speed is required and the WG operates at a variable speed. Thus, the system features higher reliability, lower complexity and cost, and less mechanical stress of the WG. Experimental results of the proposed system indicate near-optimal WG output power, increased by 11%-50% compared to a WG directly connected via a rectifier to the battery bank. Thus, better exploitation of the available wind energy is achieved, especially under low wind speeds.

A survey of video processing techniques for traffic applications

Video sensors become particularly important in traffic applications mainly due to their fast response, easy installation, operation and maintenance, and their ability to monitor wide areas. Research in several fields of traffic applications has resulted in a wealth of video processing and analysis methods. Two of the most demanding and widely studied applications relate to traffic monitoring and automatic vehicle guidance. In general, systems developed for these areas must integrate, amongst their other tasks, the analysis of their static environment (automatic lane finding) and the detection of static or moving obstacles (object detection) within their space of interest. In this paper we present an overview of image processing and analysis tools used in these applications and we relate these tools with complete systems developed for specific traffic applications. More specifically, we categorize processing methods based on the intrinsic organization of their input data (feature-driven, area-driven, or model-based) and the domain of processing (spatial/frame or temporal/video). Furthermore, we discriminate between the cases of static and mobile camera. Based on this categorization of processing tools, we present representative systems that have been deployed for operation. Thus, the purpose of the paper is threefold. First, to classify image-processing methods used in traffic applications. Second, to provide the advantages and disadvantages of these algorithms. Third, from this integrated consideration, to attempt an evaluation of shortcomings and general needs in this field of active research.

Designing a new generalized battery management system

Battery management systems (BMSs) are used in many battery-operated industrial and commercial systems to make the battery operation more efficient and the estimation of battery state nondestructive. The existing BMS techniques are examined in this paper and a new design methodology for a generalized reliable BMS is proposed. The main advantage of the proposed BMS compared to the existing systems is that it provides a fault-tolerant capability and battery protection. The proposed BMS consists of a number of smart battery modules (SBMs) each of which provides battery equalization, monitoring, and battery protection to a string of battery cells. An evaluation SBM was developed and tested in the laboratory and experimental results verify the theoretical expectations.

Advanced fuzzy logic controllers design and evaluation for buildings’ occupants thermal–visual comfort and indoor air quality satisfaction

The aim of this paper is to present and evaluate control strategies for adjustment and preservation of air quality, thermal and visual comfort for buildings’ occupants while, simultaneously, energy consumption reduction is achieved. Fuzzy PID, fuzzy PD and adaptive fuzzy PD control methods are applied. The inputs to any controller are: the PMV index affecting thermal comfort, the CO2 concentration affecting indoor air quality and the illuminance level affecting visual comfort. The adaptive fuzzy PD controller adapts the inputs and outputs scaling factors and is based on a second order reference model. More specifically, the scaling factors are modified according to a sigmoid type function, in such a way that the measured variable to be as closer as possible to the reference model. The adaptive fuzzy PD controller is compared to a non-adaptive fuzzy PD and to an ON–OFF one. The comparison criteria are the energy required and the controlled variables response. Both, energy consumption and variables responses are improved if the adaptive fuzzy PD type controller is used. The buildings’ response to the control signals has been simulated using MATLAB/SIMULINK.

Development of an integrated data-acquisition system for renewable energy sources systems monitoring

Data-acquisition systems are widely used in renewable energy source (RES) applications in order to collect data regarding the installed system performance, for evaluation purposes. In this paper, the development of a computer-based system for RES systems monitoring is described. The proposed system consists of a set of sensors for measuring both meteorological (e.g. temperature, humidity etc.) and electrical parameters (photovoltaics voltage and current etc.). The collected data are first conditioned using precision electronic circuits and then interfaced to a PC using a data-acquisition card. The LABVIEW program is used to further process, display and store the collected data in the PC disk. The proposed architecture permits the rapid system development and has the advantage of flexibility in the case of changes, while it can be easily extended for controlling the RES system operation.

A Hybrid Photovoltaic Simulator for Utility Interactive Studies

An analog-digital photovoltaic (PV) array simulator is considered. The analog section is designed on the basis of an equivalent solar cell model while the digital section is constructed realizing the mathematical representation of the array. Fast time responses achieved by the analog section make this part suitable for the study of transient phenomena associated with the interconnected operation of PVs and the utility grid. Its digital counterpart is more appropriate for long-term experimental investigations due to its inherent accuracy and reliability. The combined hybrid simulator offers a versatile and flexible piece of apparatus capable of simulating the performance of any PV array under a variety of operating conditions. The device can be constructed with low-cost components in a compact arrangement offering transportability and ease of operation. Experimental results derived from a laboratory constructed prototype match closely the theoretically computed characteristics.

Decision support methodologies on the energy efficiency and energy management in buildings

Abstract The aim of the present chapter is to analyse the decision support processes towards energy efficiency and improvement of the environmental quality in buildings. The main criteria in the decision analysis of buildings are categorized. The decision alternatives which may formulate specific actions, or group of actions (strategies) for buildings’ sustainability are analysed. The decision methodologies presented are separated to online (based on real-time operation of buildings) and offline decision approaches. Both approaches are supported by simulation, multi-objective programming optimization techniques, multi-criteria decision analysis techniques and their combinations in order to reach optimum solution, rank alternatives or provide trade-offs between the criteria. The advantages and drawbacks of the various methods are discussed and analysed.

Genetic algorithms optimized fuzzy controller for the indoor environmental management in buildings implemented using PLC and local operating networks

Abstract In this paper, an optimized fuzzy controller is presented for the control of the environmental parameters at the building zone level. The occupants’ preferences are monitored via a smart card unit. Genetic algorithm optimization techniques are applied to shift properly the membership functions of the fuzzy controller in order to satisfy the occupants’ preferences while minimizing energy consumption. The implementation of the system integrates a smart card unit, sensors, actuators, interfaces, a programmable logic controller (PLC), local operating network (LON) modules and devices, and a central PC which monitors the performance of the system. The communication of the PLC with the smart card unit is performed using an RS 485 port, while the PLC-PC communication is performed via the LON network. The integrated system is installed and tested in the building of the Laboratory of Electronics of the Technical University of Crete.

High-frequency pulse width modulation implementation using FPGA and CPLD ICs

Pulse width modulation (PWM) has been widely used in power converter control. Most high power level converters operate at switching frequencies up to 500 kHz, while operating frequencies in excess of 1 MHz at high power levels can be achieved using the planar transformer technology. The contribution of this paper is the development of a high-frequency PWM generator architecture for power converter control using FPGA and CPLD ICs. The resulting PWM frequency depends on the target FPGA or CPLD device speed grade and the duty cycle resolution requirements. The post-layout timing simulation results are presented, showing that PWM frequencies up to 3.985 MHz can be produced with a duty cycle resolution of 1.56%. Additionally, experimental results are also presented for low cost functional verification of the proposed architecture.