Semra Ozturk

Eigenvalues obtained with two simulation packages (SIMPOW and PSAT) and effects of machine parameters on eigenvalues

Eigenvalues of a power system can explain the system stability in its operating point. In this paper the linear analysis capabilities of two software packages are evaluated and compared. The paper also illustrates the impact of the models of the power system components (like generators) on the location of the eigenvalues. Eigenvalue analysis are not only dependent on the properties of the investigated system, but also on the software package which is used, as well as on how the components of the power system are modeled. Therefore, conclusions can differ when studying the same power system with different software packages.

Turkey's long-term generation expansion planning with the inclusion of renewable-energy sources

A long-term generation expansion planning that use the renewable energy was made.Optimization of generation expansion planning was realized with genetic algorithm.The ratio of renewable sources to total installed power was determined as 8.08%.The ratio of costs of renewable sources to total costs was determined as 12%. According to the Turkeys energy supply policy, the main target on electricity generation is to increase the share of renewable-energy usage to above 30% by the year 2023. However, the steps taken to achieve this goal are being realized away from a long-term generation planning. The aim of this study is to examine the situation of renewable-energy sources, considering the Turkeys generation planning and determine its contribution to overall generation together with its electrical and economic consequences. In the study, optimization of generation expansion planning (GEP), which covers the 2012-2027 planning horizon, was performed by using genetic algorithm (GA). The share of renewable sources to be installed for all source types was determined as 8.08%. Furthermore, the effects of reserve capacity level and rate of constraints on sources were investigated. The share of these sources can be increased by encouragements like tax deductions, mandatory quota application or carbon emission trade.

A simple and efficient implemantation of interleaved boost converter

Recently, DC-DC boost converters are usually required in many applications which has low output voltage, such as renewable energy sources. The interleaved boost converters consists of several identical boost converters connected in parallel and controlled by the interleaved method which has the same switching frequency and phase shift. The advantages of interleaved boost converters include increased efficiency, reduced size and improved reliability. This paper presents, simple design and implementation of a two phase interleaved boost converter.

New phenemenon on power transformers and fault identification using artificial neural networks

In this paper voltage recovery after voltage dip that cause magnetizing inrush current which is a new phenomenon in power transformers are discussed and a new technique is proposed to distinquish internal fault conditions from no-fault conditions that is also containing these new phenomenons. The proposed differential algorithm is based on Artificial Neural Network (ANN). The training and testing data sets are obtained using SIMPOW-STRI power system simulation program and laboratory transformer. A novel neural network is designed and trained using back-propagation algorithm. It is seen that the proposed network is well trained and able to discriminate no-fault examples from fault examples with high accuracy.

Generation expansion planning scenarios to reduce natural gas dependency of Turkey

Turkey relies heavily on natural gas in electricity generation and imports almost all of its natural gas needs. The country’s natural gas import bill currently comprises a large proportion of the country’s total energy bill, and the government of Turkey wants to reduce the weight of natural gas in the energy mix to reduce dependency in its energy policy. In this study, three different scenarios were considered to explore whether renewable energy sources or nuclear energy can be alternatives to natural gas to reduce energy dependency. The economic and technical analyses and comparisons of these scenarios have also been carried out. First, electricity generation expansion planning of Turkey for the 2015–2030 planning horizon was realized by using a genetic algorithm. In the first scenario, besides all conventional energy sources, renewable energy sources were included in the model as an input. In the second scenario, the first scenario was repeated without natural gas. In the third scenario, all conventional energy sources are included in the first scenario, except natural gas and renewable energy source. It was concluded from these calculations that nuclear energy is not likely to have a significant place in Turkey’s future energy policy since it has a high investment cost and leads to dependence on foreign resources. Additionally, it is argued that renewable energy source cannot be an alternative to natural gas or other energy sources considering the low capacity factor and high investment costs.

Performance of an over/under voltage relay at non-sinusoidal conditions

The effects of non-sinusoidal voltages on the performance of an over/under voltage relay were experimentally studied. The frequency and amplitude of individual harmonics were adjusted with a programmable power source and the operating times of the relay are examined. The relation between the harmonic voltages and relay behavior is determined. The measurements show that the relay may operate slower or faster than expected when distorted voltages have third harmonic component

Influence of Phase-Angle Jump on Inrush Currents of Transformers

In power systems, the transients caused by the energization of the power transformers and the voltage sags are some of the more common problems. The voltage recovery after voltage sag can saturate the transformer and this saturation can produce an inrush current, which is similar to that of the energizing. In this paper transformer inrush currents resulting from voltage sags with and without phase jumps are experimentally analyzed. The analysis of the test results reveal that the peak value of the inrush current strictly depends on the phase jumps which are occurred during the voltage sags