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 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.