Faculty Publications

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Author: search.filters.author.Reddivari, R.

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    Differential mode gamma source inverter with reduced switching stresses
    (IEEE Computer Society, 2017) Reddivari, R.; Jena, D.
    Impedance source inverters are covered with entire spectrum of power conversion process (dc-dc, dc-ac, ac-dc, and ac-ac). The traditional impedance source inverter suffers from high switching stresses and poor efficiency during high boost requirements. Compared to traditional impedance source inverters, the transformer based impedance source inverters are able to boost the output voltage gain and modulation index simultaneously with reduced passive components. The applications of transformer based gamma source impedance inverters are limited due to the difficulty in maintaining tight coupling, high instantaneous currents, increasing turn's ratio, high cost and large size. However, the gamma source inverter increases voltage gain by reducing turns ratio. This paper presents the operational modes of gamma source inverter in electric and magnetic domains, which helps the researchers to understand effects of transformer coupling in converter performance. In addition, the differential mode gamma source inverter is proposed that reduces the switching stresses. The operating principles of the proposed converter have been analyzed mathematically. Finally the theoretical analysis of proposed impedance inverter is validated by using MATLAB/SIMULINK. © 2017 IEEE.
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    A detailed model of Z-source converter considering parasitic parameters
    (Institute of Electrical and Electronics Engineers Inc., 2018) Reddivari, R.; Jena, D.
    This paper contributes towards the small-signal analysis of Z-Source converter considering all the losses introduced by non-ideal inductors, capacitor and semiconductor switches. The mathematical model is formulated using state-space averaging method under continuous conduction mode (CCM). The system dynamics are analyzed through computer simulation and reported using frequency response plots and pole-zero plots. The optimum values of the ZSC parameters i.e. the value of inductors and capacitors under CCM operating condition are determined. The effects of equivalent series resistance values (ESR) on the efficiency and boost capability of ZSC are analyzed mathematically, validated with MATLAB/SIMULINK and also with help laboratory proto-type model. © 2018 IEEE.
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    Practical limitations of embedded Z-source DC-DC converters in PV applications
    (Institute of Electrical and Electronics Engineers Inc., 2018) Reddivari, R.; Jena, D.
    This paper presents a detailed mathematical model for embedded Z-source converters (EZSC) by using a state-space averaging technique. In addition, the steady-state operational limits are derived concerning the internal voltage drops and parasitic parameters. Z-source converters exhibit non-minimum phase behavior, which is due to the presence of right-hand plane (RHP) zero. Thus, control of such a converter is a challenge, that slowdowns the transient response of traditional linear controllers. The paper investigates the impedance matching, the position of maximum power point (MPP) in EZSC for both active and shoot-through operational modes, and the effect of RHP zero in the placement of MPP. The steady state solution is derived for dc-link voltage to analyze the impact of non-ideal passive components like capacitors, inductors, diode, and switches. The expression for critical shoot-through duty ratio (STDR) for which the dc-link voltage is maximal is derived. Through critical analysis, the paper provides a valuable insight into the behavior of the embedded topologies and its steady state operational limits under photovoltaic (PV) applications. The paper presents a detailed comparison between positive embedded Z-source converter (PEZSC) and negative embedded Z-source converter (NEZSC). Simulation results are obtained using Matlab/Simulink™ and compared with the experimental results obtained using a laboratory prototype. © 2018 IEEE.
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    Differential Mode Y-Source DC-DC Converter for Better Performance with Loosely Coupled Inductors
    (Institute of Electrical and Electronics Engineers Inc., 2018) Reddivari, R.; Jena, D.; Goutham, T.N.
    Magnetically coupled inductor based impedance source dc-dc boost converters are capable of producing high voltage boost with reduced components and low shoot-through duty ratios (STDR). A Y-source converter (YSC) is one of the prominent topologies in the family of magnetically coupled impedance networks, which offers the highest degree (three degrees) of freedom to the controller to maintain constant output voltage compared to the former magnetically coupled Z-source topologies. However, YSC requires tight coupling (nearly unity) among three coupled windings to generate high voltage boosting. But, the continuation of tight coupling is quite difficult in the design of offline YSC when it involves high switching frequency operations. The leakage inductances are common in the design of any magnetically coupled topologies under high operational frequencies. High voltage overshoots, voltage boost degradations are the consequences of the leakage inductance with loosely coupled inductors. This paper attempts to analyse the effect of leakage inductances mathematically with detailed circuit representation of coupled inductors. In addition, a differential mode Y-source converter (DYSC) is proposed which is derived from the former Y-source network by changing the winding orientation. The performance of the proposed DYSC is analyzed using Matlab/SimulationsTM and also compared with YSC. The hardware results are presented to validate the theoretical simulations of both YSC and DYSC topologies. © 2018 IEEE.
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    Comparative Overview of Internal Model Control Based PID, State Feedback Integral, and Sliding Mode Controllers for Buck Converter
    (Institute of Electrical and Electronics Engineers Inc., 2019) Shankar, K.G.; Jena, D.; Reddivari, R.
    The controller plays a key role in the performance of switched mode power supplies (SMPS). Various control techniques have been proposed in the literature to improve the performance of SMPS. However, each and every controller has its own merits as well as demerits. This paper used three different kinds of control schemes such as IMC-PID control, state feedback integral control, and sliding mode control, applied to the traditional buck converter to show their effectiveness. Firstly, a detailed small-signal model of a buck converter is developed. The small signal transfer function derived from the small signal model is used to calculate the control parameters. The working principle and control parameter tuning of above-mentioned control schemes are clearly shown with mathematical expressions. Finally, the effectiveness of the given controllers is validated by using MATLAB/SIMULINK software platform. © 2019 IEEE.
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    Design Implementation of High Boost Embedded Semi Quasi-ZSI for Photovoltaic System Applications
    (Institute of Electrical and Electronics Engineers Inc., 2019) Gautham, T.N.; Reddivari, R.; Jena, D.
    The semi Z-source inverter (SZSI) is a well suitable non-isolated converter for grid-connected PV systems, because of its low cost and doubly grounded features. In addition, an SZSI produces a sinusoidal output voltage without using any additional low pass filter circuit. However, the limited output voltage range, the operating region of the duty cycle is restricted to 0.666, discontinuous input currents are the main concerns of SZSI. In order to overcome the above limitations, an embedded semi quasi Z-source inverter (ESqZSI) topology is proposed, that is constructed with two semi quasi ZSIs. Further, a quasi Z-source converter (qZSC) is interfaced as front-end DC-DC converter to implement Perturb and Observe (P and O) MPPT method. The symmetrical and asymmetrical output voltage control methods are presented to improve the voltage profile. The component design specifications and its sizing are clearly discussed for qZSC and ESqZSI. Comparing with H-bridge inverter, the proposed EZSI topology has lower converter ratings, low stress on the system and reduced leakage currents. Finally, the performance of the proposed system is verified through MATLAB/SIMULINK. © 2019 IEEE.
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    Component level reliability evaluation of boost converter, Z-Source, and improved gamma type ysource inverters
    (Institute of Electrical and Electronics Engineers Inc., 2020) Kumbale, S.; Pius, J.; Reddivari, R.; Jena, D.
    A power electronic converter should support high efficiency and high reliability to improve renewable energy connected to grid applications. Notably, low power photovoltaic (PV) applications use module-level DC-DC and DC-AC converters, where the minimum and maximum operating voltage ranges of the power conversion system is decided by DC-DC converter topology. These DC-DC converters highly suffer in the process of maximum power point tracking under extreme weather conditions and are installed with limited maintenance in remote locations. These cumulative factors make the power converters vulnerable and likely to fail early in the photovoltaic system, though the lifetime of the PV panels is about 25-30 years. To ensure longetivity, the power electronic converter must satisfy high efficiency and high-reliability demands even at extreme weather and loading conditions. Taking these constraints into account, this paper introduces a simple algorithm for understanding the component level reliability of power electronic converters under various input voltage, load, and ambient temperature conditions. The suggested algorithm can be modified depending on the topology of the converter The process involves defining critical components, assessing failure prognosis, and establishing a criterion to estimate failure time. The reliability evaluation of a conventional boost converter, Z-source inverter, and improved gamma type-YSI is presented in this paper as examples of the proposed algorithm. The electro-thermal circuit simulation in PLECS is used to validate the effectiveness of the proposed reliability algorithm. © 2020 IEEE.
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    A Correlative Investigation of Impedance Source Networks: A Comprehensive Review
    (Taylor and Francis Ltd., 2022) Reddivari, R.; Jena, D.
    In recent times, impedance networks have been developed to overcome the limitations and problems of traditional VSI / CSI and various traditional dc-dc converter networks. From then on, impedance source converters replace the entire range of power electronic converters: dc-dc (converters), dc-ac (inverters), ac-dc (rectifiers), ac-ac frequency regulators (matrix converters). In addition, the impedance source networks are used in a wide range of applications like PV-Grid tied systems, wind energy systems, distributed generations, adjustable speed drives, UPS systems, battery/supercapacitor/flywheel energy storage systems, electric vehicles, electronic loads, and dc circuit breakers, etc. Several topological changes have occurred to improve the performance of conventional ZSIs. This paper provides a concise review of the state-of-the-art impedance source topologies. This paper categorized the impedance topologies based on their functionality, performance improvements, and switching configuration employed. This paper also demonstrates the fundamental structural similarities, advantages, and disadvantages of each topology, which helps the end-users in topology selection. © 2022 IETE.
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    A critical analysis of Z-source converters considering the effects of internal resistances
    (Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2018) Reddivari, R.; Jena, D.
    Nowadays Z-source networks are the most promising power converter networks that cover almost all electric power conversion (dc–dc, dc–ac, ac–dc and ac–ac) applications. However, the controller design is critical for Z-source converter (ZSC) due to the presence right-half-plane zero (RHPZ) in the control-to-capacitor-voltage transfer function. This RHPZ exhibits non-minimum phase undershoot in the capacitor voltage and also in the dc-link voltage waveforms. A perfect small-signal model is required to predict locations of the RHP zero and its dynamics. This paper contributes towards the small-signal analysis of ZSC under continuous conduction mode considering the parasitic resistance of the inductor, equivalent series resistance of the capacitor, internal resistances of active switch and forward voltage drop of the diode. The maximum allowable value of shoot-through duty ratio (STDR) and voltage gain for different values of the internal resistance and load resistance are discussed in this paper. The accuracy of the developed small-signal average model is compared with detailed circuit model in MATLAB/SIMULINK. Finally, the steady-state simulation results of ZSC are validated with hardware results. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.
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    Novel active clamped Y-source network for improved voltage boosting
    (Institution of Engineering and Technology JBristow@theiet.org, 2019) Reddivari, R.; Jena, D.
    Y-source impedance networks are one of the prominent two-port networks for DC–DC and DC–AC applications with the higher boosting ability and reduced stress across the switching elements. However, the boosting ability of the Y-source converter needs better magnetic coupling between the windings. The loosely coupled inductors cause high-voltage spikes and poor voltage regulation. Use of highly rated switches or incorporation of the proper clamping circuit is essential to improve the performance Y-source converter. It is always better to go with clamping/absorbing circuits instead of the selection of highly rated devices. Various passive and active clamping/absorbing circuits are introduced in literature to suppress the voltage spikes at the expense of higher component count. This article proposes a novel active clamped Y-source impedance network and its family by adding one additional clamping diode to the existing type-I improved Y-source network. Compared to other Y-source networks, the proposed networks absorb the voltage spikes with reduced passive component count and re-utilise the absorbed energy to enhance the voltage gain in the presence of leakage inductance and winding equivalent series resistance. Finally, one of the proposed impedance networks, i.e. an active clamped Y-source DC–DC converter, has been verified experimentally using a ferrite core. © The Institution of Engineering and Technology 2019.