Faculty Publications
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Item Analysis of RCD snubber based non-ideal Z-source inverter using average modelling approaches(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2020) Reddivari, R.; Jena, D.Z-Source inverters (ZSIs) are one of the most promising single-stage power converters in modern industrial applications. However, these ZSIs exhibit non-minimum phase behaviour as a result of right half-plane (RHP) zero in the converter transfer functions and impose a constraint on the controller design. A detailed mathematical model of the converter plays a crucial role in the design of an efficient control strategy. This paper presents a detailed mathematical model of non-ideal ZSI using averaged modelling approaches and its comparisons are summarised. The pole-zero and step response plots reveals the impact of parasitic elements and parameter variations on system steady-state and dynamic performance. Finally, the effects are outlined, which gives a basic guideline to the designers in the converter performance optimisation such as the feedback control bandwidth, damping factor, resonant frequency, and overshoot/undershoot in the desired output. The sensitivity function is defined for a voltage gain of ZSI with respect to system parasitic elements and snubber parameters. In order to validate the theoretical analysis of converter dynamics, a laboratory prototype model of 50 watts ZSI is developed. Further, a hardware implimentation of PID-based capacitor voltage control is shown to check the effectiveness of the derived transfer functions on closed-loop performance. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.Item A Negative Embedded Differential Mode ?-Source Inverter with Reduced Switching Spikes(Institute of Electrical and Electronics Engineers Inc., 2020) Reddivari, R.; Jena, D.Magnetically coupled impedance source networks (MCIS) are capable of producing higher voltage gains at the expense of high switching voltage spikes due to the presence of leakage inductance. These voltage spikes decorate the converter efficiency and life expectancy of switches. Therefore, to reduce the voltage spikes, a negative embedded differential mode gamma source inverter (NEDM ${{\Gamma }}$ ZSI) is presented in this brief. The proposed inverter can achieve higher voltage gains with reduced switching voltage spikes and low capacitor voltage stresses compared to other MCIS networks. Also, the proposed inverter draws continuous input current from the dc mains, having a common ground, and uses the minimum number of component in a circuit. The operating principle of the proposed NEDM ${{\Gamma }}$ ZSI is analyzed in electrical and magnetic domains. The ability of the proposed impedance network, in terms of voltage spike suppression has been verified experimentally using DC-DC converter configuration. Finally, the performance of a NEDM ${{\Gamma }}$ ZSI is validated with simulation and experimental verification using a single-phase inverter configuration. © 2004-2012 IEEE.Item A cost-effective single-phase semi flipped gamma type magnetically coupled impedance source inverters(John Wiley and Sons Ltd, 2021) Gautham, T.N.; Reddivari, R.; Jena, D.This paper presents a new two winding coupled inductor architecture for a semi magnetically coupled impedance source (SMCIS) inverter by connecting the coupled inductor windings in flipped gamma fashion. The proposed topology is derived from the conventional MCIS inverters. It can produce sinusoidal output voltage/current without using any shoot-through operation and output LC filter, which improves the system reliability. Further, a doubly grounded feature, no start-up inrush current, reduced component count, low input current ripple, continuous output currents, and small leakage currents are the major advantages of the proposed inverter. However, the proposed semi flipped gamma MCIS inverters still suffer from limited output voltage gain problem. The voltage-boosting feature is added to the proposed inverter by connecting two converter modules in differential boost configuration through the embedded structure. The voltage-boosting ability is the major advantage of this differential boost embedded configuration. It has flexibility in choosing a wide range of duty cycle operation from zero to one (whereas, the duty cycle was limited to 0.666 in case of semi-Z-source inverter [ZSI]). The modes of operation, design procedure, and feature comparisons of proposed inverters are discussed in this paper. Finally, the effectiveness of proposed inverters is validated through simulation and experimental results in terms of component count, voltage gain, and feature comparison. © 2020 John Wiley & Sons, Ltd.Item A low voltage harvesting in photovoltaic generation systems using negative embedded Z-source inverter(John Wiley and Sons Ltd, 2021) Reddivari, R.; Jena, D.Commercial two-stage grid-connected photovoltaic (PV) inverters suffer from a narrow band maximum power point (MPP) voltage operation. If the voltage falls outside this narrow band, the inverter switches its operation from MPP to power limitation mode. At the same time, these inverters need high start-up voltages to turn them ON again. The evolutionary algorithms are widely used to track the global MPP at wide input (PV) voltage range. However, the global MPP at low PV voltages cannot be boosted to grid voltage level due to the limited duty ratio of conventional DC-DC converters that restricts the inverter MPP voltage range. This paper summarizes the potential challenges of narrow range MPP voltage solar inverters under partial shading scenarios. Also, demonstrates a proposed single-stage negative embedded Z-source single-stage inverter (NEZSI) to extend the MPP voltage range. The proposed topology wakes up the inverter at lower threshold voltages that enables it to extract energy from low PV string voltages. In addition, the proposed inverter tracks the MPP at a faster rate with low input current ripple, inrush current, and device stresses. Further in this paper, qualitative and quantitative comparisons between state-of-the-art topologies are provided to highlight the superiority of the proposed inverter. Simulation and experimental validation of the proposed inverter are demonstrated with traditional perturb and observe (P&O) and variable step P&O algorithms. © 2021 John Wiley & Sons Ltd.Item A Comparative Study of Different Capacitor Voltage Control Design Strategies for Z-Source Inverter(Taylor and Francis Ltd., 2022) Kumar, K.V.; Reddivari, R.; Jena, D.The Z-source inverter (ZSI) is a prominent single-stage power conversion topology compared to traditional voltage source inverter (VSI)/ current source inverter (CSI). It adds the additional buck–boost capability to input voltage with improved reliability. However, the non-minimum phase (NMP) behavior is the major disadvantage of ZSI due to the existence of the right half plane (RHP) zero in the converter transfer functions. The existences of RHP zero destabilize the wideband feedback loops, which imply high gain instability and introduce the constraints on controller design. This paper presents different types of controllers and its design to maintain the required capacitor voltage with better transient response for non-minimum phase ZSI. Different tuning algorithms have been considered for both proportional–integral (PI), and integral–proportional (IP) control schemes. Also, the unified control algorithm has been implemented with both simple boost pulse width modulation (SBPWM) and a modified space vector pulse width modulation (MSVPWM) schemes to obtain the required capacitor voltage. The converter performance is comprehensively analyzed for different controllers and observations are tabulated. The complete analysis has been carried out using the MATLAB/Simulink environment for the proposed models. © 2022 IETE.Item Improved Gamma type Y-source inverter for rooftop PV based V-G applications(Elsevier Ltd, 2022) Reddivari, R.; Jena, D.Renewable energy generation is inherently unpredictable and may contain unacceptably significant variations. In particular, high solar photovoltaic (PV) penetration makes it difficult for utility companies to coordinate production and consumption on the grid. PV generation with an energy storage element flattens the duck curve and eliminates the PV curtailment during the mid-day hours. This paper proposes a novel improved Gamma (Γ-) type Y-source inverter for rooftop photovoltaic (PV)-grid applications with battery storage ability. The proposed inverter can maintain high voltage gain even under partial shading conditions, where the PV voltage at the maximum power point is far away from the open circuit PV voltage. The proposed inverter allows plant owners to charge the battery from PV source during low-peak loading hours and can reduce power import during high-peak loading hours (or) export the excess power to the distribution grid, which increases the return on investment. The operation of the proposed inverter is analysed in three modes (a) stand-alone operational mode without battery, (b) stand-alone operational mode with battery, and (c) stand-alone operational mode with PV and battery. A scaled-down laboratory prototype of 70 W is created to test the functionality of the proposed inverter and validate the simulation results. Experiments show that the proposed Improved Gamma type YSI can generate a boosted ac voltage using independent PV and battery sources, as well as their combination. © 2022 Elsevier LtdItem Semi-λ Type Single Phase Differential Boost Inverter With High Voltage Gain(Institute of Electrical and Electronics Engineers Inc., 2023) Gautham, T.N.; Reddivari, R.; Jena, D.The conventional differential boost inverters have limited voltage gain due to the inductor's parasitic resistance, which limits the output voltage ranges as the duty cycle approaches unity and causes a narrow input voltage range. Moreover, it is also vulnerable to shoot-through problems and a dc-offset problem that leads to high voltage stress across capacitors. The proposed two winding magnetically coupled semi Γ-type structures produce high voltage boosting with decreasing turns ratio (1 < K < 2). The modified PWM scheme is implemented to operate the proposed inverter to overcome the dc-offset problem in output capacitors, which further reduces the voltage stress on the system. Furthermore, provides step-up sinusoidal output voltage/current without LC-filter, dead time, and shoot-through operation. The designed prototype is analyzed for Silicon and silicon carbide (SiC) switch using PSIM thermal module. The features of the proposed inverter are comprehensively compared with state-of-the-art topologies. Finally, the simulation and experimental findings verify the proposed topology. © 2004-2012 IEEE.