Emmanuel S. Karapidakis

On-Line Preventive Dynamic Security of Isolated Power Systems Using Decision Trees

In this paper the application of decision trees for on-line preventive dynamic security of isolated power systems is presented. Decision trees provide the necessary computational speed for on-line performance and the flexibility of providing preventive control. Emphasis is placed on the on-line use of the decision trees to test the dynamic security of each generation dispatch scenario and thus to provide corrective advice via generation redispatch. Moreover, the algorithm implemented provides the flexibility of displaying the cost of each redispatch. In this way, the method can help in objective decision making. Results from the application of the system on actual load series from the island of Crete, where the proposed system is in trial operation, are presented.

Energy efficiency and environmental impact of biogas utilization in landfills

This study investigates the utilization of landfill biogas as a fuel for electrical power generation. Landfills can be regarded as conversion biogas plants to electricity, not only covering internal consumptions of the facility but contributing in the power grid as well. A landfill gas plant consists of a recovery and a production system. The recovery of landfill gas is an area of vital interest since it combines both alternative energy production and reduction of environmental impact through reduction of methane and carbon dioxide, two of the main greenhouse gases emissions. This study follows two main objectives. First, to determine whether active extraction of landfill gas in the examined municipal solid waste sites would produce adequate electric power for utilisation and grid connection and second, to estimate the reduction of sequential greenhouse gases emissions. However, in order to optimize the designing of a plant fed by biogas, it is necessary to quantify biogas production over several years. The investigation results of energy efficiency and environmental impact of biogas utilization in landfills are considering satisfactory enough both in electric energy production and in contribution to greenhouse gases mitigation.

Genetic algorithm solution to optimal sizing problem of small autonomous hybrid power systems

The optimal sizing of a small autonomous hybrid power system can be a very challenging task, due to the large number of design settings and the uncertainty in key parameters This problem belongs to the category of combinatorial optimization, and its solution based on the traditional method of exhaustive enumeration can be proved extremely time-consuming This paper proposes a binary genetic algorithm in order to solve the optimal sizing problem Genetic algorithms are popular optimization metaheuristic techniques based on the principles of genetics and natural selection and evolution, and can be applied to discrete or continuous solution space problems The obtained results prove the performance of the proposed methodology in terms of solution quality and computational time.

Generation Expansion Planning of Crete Power System for High Penetration of Renewable Energy Sources

In this paper the Crete’s Island power system, which is the largest isolated power system in Greece, is analyzed in two long term scenarios in order to estimate the corresponding costs and benefits associated with a significant high electricity production from renewable energy sources (RES) technologies in the period 2009-2020. In the first scenario, a 20% RES energy penetration in year 2020 is assumed, while in the second scenario the final RES energy penetration is increased to 50%, and it is achieved with the installation of hydro pumped storage systems. Long-range Energy Alternatives Planning (LEAP) software is used to develop the electricity demand model, as well as to estimate the gross electricity generation in Crete and the annual CO2 equivalent emissions for the considered scenarios. This study demonstrates that substantial RES production till 2020 is technically feasible, and provides benefits in the forms of carbon emission reductions, energy adequacy and dependency.

Wireless Monitoring and Remote Control of PV Systems Based on the ZigBee Protocol

Systems that convert the sunlight into electrical energy like photovoltaics (PV) have been becoming widespread worldwide. The prospect of using the promising technology of wireless sensor networks (WSN) in the field of PV plant supervising and monitoring is studied here. The knowledge of the status and good working condition of each PV module separately as well as of any PV system component will lead in a more efficient way for power management. The nature of the wireless sensor networks (WSN) offers several advantages on monitoring and controlling applications over other traditional technologies including self-healing, self-organization and flexibility. The versatility, ease of use and reliability of a mesh network topology offered by the ZigBee technology that is based on the IEEE 802.15.4 standard, is used here to offer its maximum advantages on a system that is capable for real time measurements and event alerts.

Identification of synchronous machine parameters using constrained optimization

In order to investigate transient performance problems in isolated power systems an accurate system dynamic model is required. Real measurements, under specific system operational conditions, have been used for the identification of the conventional generator unknown parameters. Frequency and power variations, resulting from the formulation model using the estimated parameters, are compared with the frequency and power deviations, measured during the corresponding real operational conditions in order to demonstrate the successful performance of the proposed methodology.

Techno-Economic and Environmental Evaluation of Large Scale PV Integration in Greece

This paper evaluates the current status of renewable energy sources integration and future trends, especially of the photovoltaics, in the interconnected power system of Greece and the power system of Crete Island, which is the largest isolated power system in Greece. Focusing on the ongoing developments and prospects, the paper investigates the impacts of the expected sufficient photovoltaic installations on the energy market and the greenhouse gas emissions, as well as the reduction in CO2 emissions costs due to the installation of photovoltaics and other renewable energy technologies.

Impact of Increased RES Generation on Power Systems Dynamic Performance

In this paper, the impact of high wind power and photovoltaics penetration on the dynamic behavior of an island power system like one operates in Crete is investigated. Several simulations were performed leading to the fact that it is possible to achieve higher level of renewable energy sources penetration without significant dynamic security problems, if power units spinning reserve exists and the corresponding control systems have a sufficiently fast response.

Wind Power Impact on Power System Dynamic Performance

It is well known that wind power is one of the major sources of renewable energy with a remarkable contribution to the installed capacity of electrical power systems. In this chapter, the impact of large scale wind power generation on the dynamic performance especially of weak and/or islands power systems are presented. Weak or Autonomous power systems, like the ones operating in idiomorphic areas or in islands, face increased problems related to their operation and control, [Hatziargyriou, N. & Papadopoulos, M. (1997)]. In most of these systems, the real cost of electricity production is much higher than in interconnected systems due to the high operating costs of their thermal generating units, mainly diesel and gas turbines, and the import and transportation costs of the fuel used. Security is also a major concern, since mismatches in generation and load and/or unstable system frequency control might lead to system failures, easier than in interconnected systems, [Hatziargyriou, N. et al. (1997)]. Although under ongoing energy policies wind power exploitation appear particularly attractive, the integration of a substantial amount of wind power in isolated electrical systems needs careful consideration, so as to maintain a high degree of reliability and security of the system operation. The main problems identified concern operational scheduling (mainly unit commitment) due to high production forecasting uncertainties, as well as steady state and dynamic operation disorder, [Dialynas, E. et al. (1998)]. These problems may considerably limit the amount of wind generation that can be connected to the power systems, increasing the complexity of their operation. Thus, next to the more common angle and voltage stability concerns, frequency stability must be ensured, [Hatziargyriou, N. et al. (1998)]. This depends on the ability of the system to restore balance between generation and load in case of a severe system upset with minimum loss of load. Dynamic simulation studies are the first step in determining the level of wind power penetration in power systems. Analytical studies are required in order to derive security rules and guidelines for the optimal operation of each system [Arrilaga, J. & Arnold, C.P. (1993)]. Simulations of a power system dynamic performance mainly cover voltage and frequency calculations under several abnormal operating conditions, start-up or sudden disconnection of wind generation, wind fluctuations and short circuits on the transmission and distribution network. In order to ensure the maximum exploitation of the available renewable power sources and to operate systems with increased wind power penetration in

Analytical Assessment of DC Components Generated by Renewable Energy Resources with Inverter-Based Interconnection System due to Even Harmonics

This paper deals with the assessment of DC components generated by renewable energy resources with inverter-based interconnection system to the electric grid. DC injection is a critical issue related to power quality of distribution network systems with high penetration of inverter-based interconnection systems. This type of interface systems may improve the performance of the electric generation unit and affect positively or negatively the power quality of the distribution network depending on the proper or improper designation. The investigation of the various causes of DC components and the analytical assessment of their maximum levels are crucial for the proper operation of inverter-based interface systems and the limitation of DC injection. A method based on analytical calculations using a computer software has been implemented for the assessment of DC components contained on an inverters output voltage when even harmonics are present on the network voltage. Moreover, a simulation package was used to demonstrate the existence of DC components under various conditions. It was proved by the current analysis that the amounts of DC components generated when even harmonics are present on the network voltage can be high under abnormalities on the power grid but they are not considerable under normal operating conditions.