Yazar "Subramaniam, Umashankar" seçeneğine göre listele

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    A Demand Side Management Controller Configuration for Interleaved DC-DC Converters Applicable for Renewable Energy Sources
    (Wiley, 2021) Ertekin, Davut; Bayrak, Gökay; Subramaniam, Umashankar
    In Micro-grid applications, accuracy and sensitivity of the Demand Side Management (DSM) process decrease when the load impedance changes. In this study, the impact of the DSM is analyzed and the interleaved structure is presented for DC-DC converter blocks equipped with adaptive PI controllers. This approach reinforces a same voltage source that can be a serial and parallel connection of Photovoltaic (PV) panels in different power rates as the input voltage source to enhance the voltage to the micro-grid DC level and is modeling the power transmission in Renewable Energy Sources (RESs) that they produce limited amounts of power. For the voltage droop problem, the Power-Voltage (P-V) approach is selected. Since the resistive loads are considered in this study, this approach can control DC currents based and depending on the DC voltages in DC micro-grid applications. For per controller block, different values of the gain coefficients are tested and the optimal droop coefficients are presented. All simulations have been done in MATLAB/SIMULINK and a prototype by power around 1kW is tested. The results of the hardware implementation confirm the theoretical and simulation outcomes.
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    Influence of a Proposed Switching Method on Reliability and Total Harmonic Distortion of the Quasi Z-Source Inverters
    (Ieee-Inst Electrical Electronics Engineers Inc, 2020) Hang, Liu; Subramaniam, Umashankar; Bayrak, Gökay; Moayedi, Hossein; Ghaderi, Davood; Minaz, Mehmet Recep
    An Improved Sinusoidal Pulse Width Modulation (ISPWM) technique carried out to obtain pure sine waves for voltage and current signals in Quasi Z-Sourc Inverters (QZSIs) in the load side is given in this study. This switching method can be examined to two and multi-phase approaches simply through the addition of the same controller structure to per phase. This is the main advantage of the proposed converter to obtain higher voltage gains at the output ends of this inverter. The idea is to generate a positive rectified voltage at the output point of the QZSI and positive and negative rectified voltages at the output terminals of the QZSI in two-phase approaches to improve the quality of the output voltage of the F-Bridge Inverter (FBI). These rectified voltages are applied to the Full-Bridge Inverter (FBI) block and pure sine waves to obtain the load current and voltages. 1.34% of the Total Harmonic Distortion (THD) for the output voltage has been reported in the one-phase system while 0.88% of THD has been obtained in the two-phase approach. Besides, the reliability of the QZSI was tested through the Mean Time to Failure (MTTF) analysis with the values of the proposed components. The calculations show a very good result for the long-life of the converter. All experimental and simulations steps have been obtained for the same values of the components to support and confirm the accuracy and correctness of the proposed IMSPW. For the states of single-phase and two-phase converters, a 50 Hz sine-wave with 220 V and 440 V peak to peak amplitude has been acquired. Evaluations of the quality of the voltage and current waveforms related to different active (Resistive, P) and reactive (combination of Resistance and Inductance, QL) loads have been carried out. Experimental results show confirmation for all simulation and mathematical results.
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    Investigation of the Thermal Loading and Random Vibration Influences on Fatigue Life of the Solder Joints for a Metal-Oxide-Semiconductor-Field-Effect Transistor in a DC-DC Power Boost Converter
    (Ieee-Inst Electrical Electronics Engineers Inc, 2020) Li, Songgang; Subramaniam, Umashankar; Yang, Guobiao; Ghaderi, Davood; Rajabiyoun, Niloufar
    This study presents the effects of the vibration and thermal cycling on the fatigue life of a power Metal Oxide Semiconductor Field Effect Transistor (MOSFET) in a power converter circuit. The fatigue mechanism in per loading mode was investigated separately and based on the overlap approach, the synchronous effects were analyzed. The solder creeps & x2019; attitudes are depended on the fatigue life for the thermal loops. The success of the deposited strain per thermal loop is in direct relation with the fatigue lifetime. The main source of the stress in the packaging process is the differences between the components & x2019; thermal coefficients. To evaluate the effects of the vibration on the fatigue life for the solder layers, the RMS value of the peeling stress was considered. According to the results, the maximum stress and main affected points realized at the corners of the layers. It has been identified that the assembling of the thermal effects and mechanical loads are quickened the failure rate at the solder joints for this device. The Finite Element Method (FEM) is used for the simulation and the results confirm the estimated crack formation places in the layers.
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    Leakage current repression and real-time spectrum analysis with chirp Z-transform for a novel high-efficiency PV-based inverter applicable in micro-grids
    (Springer, 2020) Bayrak, Gökay; Ghaderi, Davood; Subramaniam, Umashankar
    One of the most critical elements in the connection of photovoltaic (PV)-based systems used to generate electricity from solar energy is the inverter. The harmonic effects of the inverters to be connected to the grid should be as low as possible, and the total harmonic distortion (THD) should be less than 10%. A high THD value will distort the power quality on the grid side. For this reason, the THD value of the inverters in the grid connection approaches must be determined by spectral analysis to ensure that the necessary protection and improvements are made technically. In this study, a novel inverter topology, including six power switches and two power diodes, is presented, and the voltage data obtained from a grid-connected inverter are acquired in real time, and spectrum analysis is performed with the software developed with LabVIEW. The power efficiency of the proposed inverter is compared with conventional inverter types such as HERIC, H5, and H6 inverters. One of the novelty aspects of the proposed inverter topology is forming a proper freewheeling path including switches and diodes in the inverter branches that can provide a separate DC and ac components, and as a result, this prevents the following the PV side leakage currents to the ac grid side. In the spectrum analysis, the chirp Z-transformation (CZT) was used along the contours of the Z-transformation outside the unit circle. Using CZT, the z-transform was calculated for the inverter output voltage along the spiral lines in the z-plane. Besides, spectrum analysis was performed with fast Fourier transform (FFT) and compared with CZT. The results show that the CZT transformation is more efficient than the FFT algorithm and is useful in calculating a subset of FFT for a sequence. The performance of the proposed inverter is compared with conventional topologies. Hardware implementation and the output signals and the leakage current waveforms are also presented.