Faculty Publications

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    A novel fifteen level inverter for photovoltaic power supply system
    (2004) Beig, A.R.; Udaya Kumar, R.Y.; Ranganathan, V.T.
    A novel dc to ac inverter for photovoltaic power supply system is presented in this paper. The objective is to develop a low cost, reliable and efficient photovoltaic power supply unit for domestic applications. A fifteen level cascaded H-Bridge configuration using low voltage MOSFETs as switching devices is used. This configuration results in sinusoidal output voltages with step modulation and fundamental frequency switching. The proposed configuration has reduced conduction loss and switching loss. Simple gate drive circuit is designed using commonly available integrated circuit components. The simulation results are presented.
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    A novel technique for control of Cascaded multilevel inverter for photovoltaic power supplies
    (IEEE Computer Society, 2005) Naik, R.L.; Udaya Kumar, R.Y.
    Multilevel voltage source inverters offer several advantages compared to their conventional counterparts. By synthesizing the AC output terminal voltage from several levels of voltages, staircase wave forms can produced, which approach the sinusoidal wave form with low harmonic distortion, thus reducing filter requirements. The need of several sources on the DC side of the converter makes multilevel technology attractive for photovoltaic applications. The basic modulation techniques enable harmonic elimination by predetermination of the switching angles. This is determined according to a previously calculated and stored pulse width modulated waveform. It has the advantage of operating at fundamental frequency switching. However, this technique is seriously limited as the number of levels increases because of the increased complexity and the reduced accuracy of the non-linear solutions. This paper proposes a novel Multilevel PWM technique (phase-shifted sinusoidal PWM) to over come all these limitations while maintaining switching at fundamental frequency, found better THD. Simulation results are presented in the paper.
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    Transformer-Based seven-level inverter with single-dc supply for renewable energy applications
    (IEEE Computer Society help@computer.org, 2016) Behara, S.; Sandeep, N.; Yaragatti, R.Y.
    This paper puts forward a single-DC source based seven-level inverter for harvesting energy from renewable sources. Three single-phase transformers with cascaded outputs are powered from the switching power circuit resulting in then generation of multilevel at the output of the inverter. The proposed configuration can generate output voltage having levels of magnitude (-3VDC, -2VDC, -VDC, 0, VDC, 2VDC, 3VDC) from the DC supply (VDC). Structurally this topology exhibits the advantage of fewer power devices in comparison to conventional inverter for the generation of same number of output voltage levels. Simple logic gate based gating pulse generation scheme is suggested obviating the need for complex pulsewidth-modulation (PWM) scheme. Simulation results confirming the viability and effectiveness of the proposed inverter are presented. © 2016 IEEE.
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    A new nine-level single-DC source-based inverter topology for distributed generation
    (Institute of Electrical and Electronics Engineers Inc., 2017) Sandeep, N.; Yaragatti, U.R.
    Multilevel inverter enables to completely remove the passive filtering requirement at the grid interfacing end, resulting in improved efficiency and reduced cost. These features have led to increasing attention towards their application to medium and high-power arena. In this paper, investigation of a hybrid 9-level inverter topology for grid integration of renewable energy sources is presented. The structural details, operating principle, capacitor voltage balancing control and the main features of the proposed inverter are presented. The proposed topology is compared with other similar 9-level converters to emphasize its superior characteristics and performance. Simulation results demonstrating the grid connected operation of the converter for two test cases are presented. The results affirm the effectiveness of the capacitor voltage balancing control in maintaining capacitor voltages at set values, under steady state and transient operation of the converter. © 2016 IEEE.
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    A Single Stage Switched-Capacitor Hexad Boost Multilevel Inverter Featuring Boost Ability
    (Institute of Electrical and Electronics Engineers Inc., 2020) Shiva Naik, B.S.; Yellasiri, Y.; Venkataramanaiah, J.
    Nowadays, curtailment in the number of dc sources, circuit component count along with the boosting gain property of the output voltage are considered as the essential topological features for the new multilevel inverter (MLI) structures. Considering the above, a novel 13-level single-stage switched-capacitor hexad boost (S3 CHB) inverter featuring boosting gain and self-balancing ability is proposed in this paper. Each phase of the proposed \mathrm{S}^{3} CHB-MLI is designed with only 14 semiconductor switches and three electrolytic capacitors. Here, the capacitors' voltages are balanced automatically by utilizing the series-parallel technique effectively. An absence of H-bridge at the back-end makes the circuit to extend for higher levels. Capacitors' voltage ripple are analyzed in detail. Further, a cost comparison is conducted among the state-of-art MLIs to highlight the superiority of the proposed configuration. Finally, the effectiveness of the proposed \mathrm{S}^{3} CHB circuit is experimentally demonstrated. Results at different load conditions are captured to prove the inductive load capability. © 2020 IEEE.
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    A review on symmetric, asymmetric, hybrid and single DC sources based multilevel inverter topologies
    (Elsevier Ltd, 2017) Venkataramanaiah, J.; Yellasiri, Y.; Panda, A.K.
    In recent past, multilevel inverters(MLIs) are treated as sophisticated power conversion systems demanded for high power medium voltage applications. The aim of this article is to review on recent examined multilevel inverter topologies which can be classified into four groups according to the DC voltage supplied to each fundamental unit and/or arrangement of non-identical fundamental units in an one configuration: Symmetric, Asymmetric, Hybrid and Single DC source topologies. In each group, several new versions have been constructed for last few decades. In this study the position (design and functionality) of each and every topology and also every group are reviewed. Further, a special attention is focused on Single DC source MLIs. Finally at the end of the review, merits, limitations and adequate applications are clearly mentioned. Thus, present review provides complete overview among newly developed multilevel inverters. © 2017 Elsevier Ltd
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    Cascade multilevel inverter using sub multi-cells
    (Praise Worthy Prize S.r.l, 2016) Pakala, P.; Yellasiri, Y.
    Multilevel inverters (MLI) are one of the selected areas in the industry for medium and high power application. The real challenge of MLI is to generate more voltage levels utilizing less voltage sources and power semiconductor switches. This paper presents a new topology of cascaded multilevel inverter with sub multi-cells. This new structure is optimized based on number of powers witches, voltage sources. Moreover the topology enhancement of this cascaded multilevel inverter considering various factors such as the number of power semiconductor devices, the voltage levels of output and the switch standing voltage is given. Since the proposed topology is generalized, the traditional cascaded multilevel inverters can be derived from the proposed multilevel inverter and it offers a provision to propose the desired cascaded multilevel inverter. In addition to that, some facts related to the proposed topologies are proved mathematically. It has the capacity to produce increased output voltage levels with less sources voltages and switches. The proposed topology will generate twenty five output voltage levels with twelve numbers of switches. Further, to figure out the value of voltage sources, an algorithm is presented. To check the operation and execution of the proposed structure, MATLAB/Simulink is used for the simulation and to validate these results a hardware prototype is developed and results are presented. © 2016 Praise Worthy Prize S.r.l. - All rights reserved.
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    Investigation on stacked cascade multilevel inverter by employing single-phase transformers
    (Elsevier B.V., 2016) Yellasiri, Y.; Panda, A.K.
    In the present paper a new version of multilevel inverter is investigated. This new version is based on hybrid association of commutation cells with H-bridge cells. The association allows a significant reduction of the volume of the capacitors. In fact, presented topology allows us to work on higher input voltage levels with the same power switches. This new version is generally called as SCMI (stacked cascade multilevel inverter). The proposed inverter has potential to generate high quality waveforms, reduction in switching frequency, capable to operate at higher voltage levels and finally utilizes minimum number of switching components. The presented version of SCMI is simulated in Matlab-simulink and further, experimental validation is carried out in the laboratory with prototype setup. © 2016 Karabuk University
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    Operation and Control of an Improved Hybrid Nine-Level Inverter
    (Institute of Electrical and Electronics Engineers Inc., 2017) Sandeep, N.; Yaragatti, R.Y.
    This paper proposes a new nine-level inverter for medium- and high-power applications. The proposed topology comprises of a three-level (3L) active neutral-point-clamped (ANPC) inverter connected in series with a floating capacitor (FC) fed H-bridge. Besides, two additional switches operating at line frequency are appended across the dc link of the 3L ANPC structure. Compared with conventional hybrid cascaded inverters, the primary advantage of this addition is doubling of the resulting root mean square output voltage. This amelioration is achieved while preserving the standard 3L ANPC and H-bridge structures with minimum topological modification. A simple logic-gate-based voltage balancing scheme is developed to regulate the FC voltage. The proposed voltage balancing method is independent of load power factor, inverter modulation index, and can balance the voltage across FC instantaneously. The step-by-step formulation of logical expressions for the generation of gating pulses is deliberated in detail and can be generalized for any n-level inverter. Further, simulation results as well as the experimental measurements obtained from the laboratory prototype are presented to validate the effectiveness and practicability of the proposed configuration. Finally, the notable merits of the proposed inverter over the prior art topologies is established through a comprehensive comparative study. © 1972-2012 IEEE.
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    Design and implementation of active neutralpoint-clamped nine-level reduced device count inverter: An application to grid integrated renewable energy sources
    (Institution of Engineering and Technology journals@theiet.org, 2018) Sandeep, N.; Yaragatti, U.R.
    Multilevel inverters are one of the preferred choices in medium-voltage and high-power applications in the recent past. Active neutral-point-clamped (ANPC) inverter is the most popular topology, especially in the class of five-level (5L) inverters. In this study, a nine-level topology with improved output waveform quality is proposed based on ameliorating the 5L ANPC inverter with least modifications. The addition of only two switches operating at line frequency to the conventional 5L ANPC inverter while maintaining an identical precursor part count is the proposed modification. A logic form equation-based active voltage balancing scheme that is independent of load current and power factor is developed to regulate the flying capacitor voltage at the reference value. The operating principle, salient features, and the developed control scheme are comprehensively detailed. The operation of the proposed inverter considering a grid integrated case is simulated in MATLAB/ Simulink, and the results corresponding to steady-state and dynamic conditions are presented. The benefits of the proposed topology are elucidated by comparing it with other classic topologies considering various prominent viewpoints. This comparison has illustrated the proposed topology's distinctive characteristics and profound advantages. The performance validation, feasibility, and practicability of the proposed inverter are established through the experimental results obtained from a laboratory-scale prototype. © The Institution of Engineering and Technology 2017.