Faculty Publications
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Item A Fault Diagnosis and Postfault Reconfiguration Scheme for Interleaved Boost Converter in PV-Based System(Institute of Electrical and Electronics Engineers Inc., 2021) Ahmad, M.W.; Brahmendra Yadav Gorla, N.B.Y.; Malik, H.; Panda, S.K.To utilize the solar photovoltaic (PV) energy efficiently, dc-dc converters are widely used in both grid-connected and stand-alone systems. Among the various topologies, interleaved dc-dc boost converter offers the benefit of modularity, high power density, and high efficiency along with reduced input current ripple to the PV panel, thereby improving its power extraction efficiency. Open-circuit faults in any of the semiconductor switches of interleaved boost converter could lead to unequal loading on the healthy phases and increase in ripple current that reduces the extraction efficiency of the PV system. To address this issue, a new fault detection and localization scheme is proposed in this article. The proposed scheme utilizes the switching-frequency-based harmonic component for fault detection and localization. Once the fault is localized, a postfault restoration and control strategy is also proposed to ensure equal current sharing among the remaining healthy modules within their maximum current rating and minimize the input current ripple in the PV panel. Detailed simulations are carried out to show the effectiveness of the proposed approach. A laboratory prototype of the interleaved converter is built to validate the proposed approach and experimental test results are provided. © 1986-2012 IEEE.Item Noninvasive Model-Based Open-Circuit Switch Fault Detection of AC-Bypass Leg Switches in Transformerless PV Inverter(Institute of Electrical and Electronics Engineers Inc., 2021) Ahmad, M.W.; Brahmendra Yadav Gorla, N.B.Y.; Malik, H.; Panda, S.K.Transformerless inverters are being used for integrating photovoltaic (PV) sources into the grid. Highly efficient and reliable inverter concept (HERIC) inverter is one such topology, which is derived from an H-bridge by adding a bypass leg on the ac side using two back-to-back insulated gate bipolar transistors (IGBTs). Open-circuit fault in the bypass leg would result in conduction of current through antiparallel diodes of the main switches of the inverter, effectively making the inverter operate in bipolar mode. As a result of the fault, there would not be an issue of leakage current, and the operation would continue at the expense of increased conduction losses and dc-offset in the grid current. This article proposes an online noninvasive model-based technique to detect switch faults in the bypass leg of the HERIC inverter. The grid current at the peak of the carrier signal is predicted based on the measured grid current at the start of the zero states. By comparing the estimated and measured grid currents at the peak of the carrier signal, the faulty switch in the bypass leg is localized. Once the fault is localized, the inverter's modulation scheme is changed to conventional bipolar mode to improve the performance of the converter during the post-fault stage. A detailed simulation study is carried out to verify the effectiveness of the proposed approach. Experimental tests on the prototype converter show that the proposed algorithm can reliably detect the open-circuit fault in switches of the bypass leg, and once a fault is detected, the algorithm would change the modulation scheme to bipolar mode to minimize the inverter loss and dc-offset in the grid current. © 2013 IEEE.Item A Robust Open Circuit Fault Detection and Localization Scheme for HERIC PV Inverter(Institute of Electrical and Electronics Engineers Inc., 2025) Muhammed Ramees, M.M.K.P.; Ahmad, M.W.Transformerless inverters are widely used to integrate the photovoltaic (PV) source into the distributed generation system. Within the converter, an open-circuit (OC) switch fault may lead to the partial or total failure of the converter. To address this issue, a new technique for detecting and localizing OC switch faults based on pole-to-pole voltage (voltage measured across the inverter output terminals) is proposed. The proposed variables for fault detection and localization (FDL) are continuously generated with every sampled pole-to-pole voltage and are compared with threshold values which are immune to parameter variation. As a result, OC is detected and located within a switching cycle for the ac side bypass switches. For localizing the OC fault in the H-bridge, the converter is reconfigured once the fault in the H-bridge switch is detected using pole-topole voltage. The input voltage required for the maximum power point tracking (MPPT) is estimated from the voltage measured with the new sensor arrangement for pole-to-pole voltage measurement. This makes the number of sensors the same as in a conventional converter. The viability and effectiveness of this approach are demonstrated through simulation studies on the highly efficient and reliable inverter concept (HERIC) inverter, a popular transformerless inverter topology. Additionally, a laboratory prototype is developed to validate the practical applicability of the method. © 1982-2012 IEEE.