Browsing by Author "Demirok, Erhan"

Now showing 1 - 6 of 6

Citation - WoS: 14
Citation - Scopus: 18
Adaptive Controller Based on Grid Impedance Estimation for Stable Operation of Grid-Connected Inverters Under Weak Grid Conditions
(Inst Engineering Technology-Iet, 2020) Temiz, Hakan; Keysan, Ozan; Demirok, Erhan
An electric grid having high impedance seen from the connection point is considered as a weak grid and it adversely affects the system stability of grid-tied voltage source inverters in renewable power devices. In this study, an adaptive controller is proposed by configuring the settling time of the phase-locked loop based on the estimated grid impedance. Pseudorandom binary sequence injection and Fourier techniques are carried out for grid impedance estimation. Impedance-based stability analysis is performed for a predetermined steady-state operation point. The proposed method is verified by a 300-kVA inverter prototype for wide-range grid impedance varying from 0.3 to 3 mH.
Citation - WoS: 2
Citation - Scopus: 5
Decimal States Smart Grid Operations Concept: Technical Solution and Benefit for Renewable Energy Integration
(IEEE, 2022) Ouedraogo, Kiswendsida Elias; Ekim, Pinar Oguz; Demirok, Erhan
The energy transition is a global challenge that retains the attention of a wide range of stakeholders including engineers, regulators, consumers, investors, and academicians. With higher intermittent renewable energy penetration, electrification of mobility, and intensification of air conditioning demand, important stress on the power grid, resulting in overloading of distribution network infrastructures and grid stability issues may arise in near future. Various solutions such as smart metering, demand response, and energy storage have been explored, however, their cost-to-benefit ratio is still not satisfying. This paper explores a new grid operation concept named "Decimal State" grid which dynamically throttles the subscribed power to match the grid supply capability without a direct load control. A simple yet effective communication method has been built and tested to support the implementation of the decimal state grid. Also, simulations showed that decimal state grid operation can avoid power outages in both fossil fuel or fully solar powered grid with a power deficit. Further, the simulation revealed that a decimal state grid can significantly reduce the size of long-duration energy storage.
Citation - WoS: 17
Citation - Scopus: 38
Feasibility of Low-Cost Energy Management System Using Embedded Optimization for Pv and Battery Storage Assisted Residential Buildings
(Pergamon-Elsevier Science Ltd, 2023) Ouedraogo, Kiswendsida Elias; Oğuz Ekim, Pınar; Demirok, Erhan
In this study, an energy management system (EMS) focusing on low-cost hardware and embedded optimization has been built. A benchmark consisting of a residential photovoltaic (PV) and battery connected to the grid but without feed in power has been considered. The proposed EMS accepts input variables as building electrical load data, PV output data, the electricity time of use rates. The master EMS ensures the optimization of the battery charge-discharge profile to reach the lowest possible energy bill. Sensitivity analysis demonstrates that the presence of optimization systems leads to a more stable energy cost even though power demand and PV pro-duction vary during the day. In the cases studied, the bill reduction is 32% up to 50% depending on load or solar PV generation variations. By comparison, in the literature where more complex optimization in MATLAB environment were used, a bill reduction of 24%-34% was realized. The system cost is estimated to be around 30$ which is much lower than the typical 100$-600$ price for similar products. The system can be practically in-tegrated in applications such as EMS of schools, residential or public buildings by inserting it through the power distribution panel where all protection devices are located.
Citation - Scopus: 1
Flexible Reactive Power Capacity of Full Converter Wind Turbines
(Institute of Electrical and Electronics Engineers Inc., 2021) Alisar I.; Demirok, Erhan
This study proposes a control system for parallel connected back-to-back converters of FC (full converter) wind turbines in order to increase the total reactive power capacity. A sample wind turbine was chosen to use the power curve and different wind profiles. Various grid voltage values have been utilized to examine the effectiveness of the proposed method. The enhancement of reactive power capacity has been showed for each wind speed and each collector grid voltage level with the proposed method. The increase of reactive power capability of the sample wind turbine was obtained and demonstrated using MATLAB. © 2021 Chamber of Turkish Electrical Engineers.
A System Level Lifetime Enhancement Method for Power Converters of Type-4 Wind Turbines
(IEEE, 2024) Alisar, Ibrahim; Demirok, Erhan; Akan, Aydin
This study proposes a new system level lifetime enhancement method for back-to-back connected power converters of Type-4 wind turbines. The method is based on swapping both the position and roles of MSC (machine side converter) and GSC (grid side converter) periodically at ultra low frequency with additional mechanical switches so that the lifetime consumption of electrical switches (IGBTs and diodes) is shared by the inverter and rectifier operating modes. Moreover, the aging effect of the semiconductors have been considered and tested as an additional evaluation. The proposed method is tested with PSCAD (for the simulation of wind turbine and converter system) and MATLAB (for the development of thermal models, loss calculation and lifetime calculations) tools. The results show the effectiveness of the proposed method with significantly increased lifetime values.
Citation - WoS: 1
Tracking neighborhood closed-loop pumped hydro storage potential
(IEEE Computer Society, 2023) Ouedraogo, Kiswendsida Elias; Oğuz Ekim, Pınar; Demirok, Erhan
Worldwide, energy is at the center of the socio-economical, geopolitical, and climate crises. For this reason, governments, businesses, and communities are promoting green energy to boost their energy resilience and energy independence sustainably. However, the bottleneck of replacing fossil fuel power plants entirely with intermittent renewable energy remains the high cost of energy storage systems. The study explored the existence of megawatt-hours scale closed-loop pumped hydro storage reservoirs near communities' centers. A MATLAB algorithm has been developed to detect pairs of reservoirs with one, four, and nine hectares each, and a head of one to three hundred meters, corresponding to an energy capacity of 20 to 540 megawatt hours per pair. For the three cities studied, (Banfora / Burkina, Syracuse / New York, Manisa / Turkey) the results revealed the existence of more than 10.000 megawatt-hours storage capacity in each city which meets or exceeds the need of the communities. Therefore, a 100% renewable energy power grid that is resilient, and reliable, can be achieved faster by adopting distributed closed-loop pumped hydro storage which is likely to attract a large number of smaller investors. © 2023 IEEE.