Yazar "Ucar, Mehmet" seçeneğine göre listele

Listeleniyor 1 - 3 / 3
  • Küçük Resim Yok
    Öğe
    Analysis of a Soft Switching High Voltage Gain DC/DC Boost Converter for PV Systems
    (İstanbul Gelişim Üniversitesi, 2018) Al-hajm, Sarah; Ucar, Mehmet
    This paper presents an analysis of a non-isolated soft switching high voltage gain DC/DC boost converter by using a coupling inductor, voltage quadrupler and active clamp circuit for Photovoltaic (PV) systems. The main advantage of this converter, coupled inductor with voltage quadrupler circuit is used to decrease voltage stress in semiconductor switches and providing high voltage gain. Therefore, low voltage valued and low on-resistance MOSFETs can be used to decrease on-state losses. The reverse recovery and high frequency turn off losses is reduced for achieving Zero-Current Switching (ZCS) in all diodes. Voltage spike caused by leakage inductance of the coupled inductor is minimized by means of the active clamp circuit. Thus, Zero-Voltage Switching (ZVS) turn on of all MOSFET switches are achieved. The Perturb and Observe (P&O) method is utilized in this study to obtain maximum power from the PV system. In order to show the effectiveness of the converter, PSIM simulations are realized under various irradiance cases. The conversion efficiency is obtained about 95.97% at full load from the simulation results.
  • Küçük Resim
    Öğe
    Dual-Mode Operation of 3-Level 4-Leg AT-NPC Inverter for Microgrids
    (Ieee, 2019) Avci, Emre; Ucar, Mehmet
    This study presents dual-mode operation and seamless transfer of 3-level 4-leg Advanced T-type Neutral Point Clamped (AT-NPC) inverter for low voltage microgrids. The proposed control technique is designed with Proportional Resonant (PR) based current controlled in grid-connected operation and with Proportional Multi Resonant (PMR) based voltage controlled in islanded operation. In order to ensure smooth transition between these operating modes, combined seamless transfer method is proposed. The proposed 3-phase 4-leg inverter system can supply both 1-phase and unbalanced 3-phase load groups in islanded mode. A laboratory prototype is installed for the experimental testing of the 3-phase 4-leg AT-NPC 3-level inverter system. The proposed system is simulated via PSIM software and the model-based embedded codes are generated with PSIM/SimCoder software. Real-time control algorithm of the inverter system is carried out with TMS320F28335 digital signal controller board. Finally, the operation performance of the inverter system is investigated both in the islanded/grid-connected mode and the seamless transfer process between these two operating modes.
  • Küçük Resim
    Öğe
    Proportional multi-resonant-based controller design method enhanced with a lead compensator for stand-alone mode three-level three-phase four-leg advanced T-NPC inverter system
    (Inst Engineering Technology-Iet, 2020) Avci, Emre; Ucar, Mehmet
    This study presents an inverter current sampled double-loop proportional multi-resonant (PMR)-based control technique for three-level (3L) three-phase four-leg (3P4L) advanced T-type neutral point clamped (AT-NPC) stand-alone mode inverter. Apart from the conventional linear controller the PMR controller has the ability to track a sinusoidal reference and does not require any axis transformation. Therefore, the main advantage of the proposed control technique for a 3P4L inverter is to independently control the output phase voltages when feeding a single phase and/or three phase loads. This is achieved by the inverter current sampled double-loop controller with a lead compensator in order to increase the control system phase margin unlike the capacitor current sampled controller. Thus, the harmonic compensation capability of the controller is increased which strengthens the controller against highly non-linear load types. The design procedures of the controller for the system are analytically explained. Then, the steady-state and dynamic performance of the controller is tested in a 3L 3P4L AT-NPC inverter system through many simulations and experimental studies. The results verify the fast-dynamic performance and the achievement of the low total harmonic distortion with a maximum of 2.89% for the 3L 3P4L AT-NPC inverter system even under serious non-linear load type.