Date of Award
Doctor of Philosophy
Daniel Costinett, Leon Tolbert, Hua Bai, Thomas McDermott
Renewable energy, such as wind and solar are becoming an integral part of world energy production. Photovoltaic (PV) systems are projected to constitute a large portion of the energy generation portfolio. Achieving a low-cost residential PV system will enable the wide adoption of solar energy throughout the USA. Although innovation in several areas is required to achieve this goal of a low-cost residential PV system, inverter reliability innovation is one key area that is essential. Present string inverters' lifetime is less than 15 years. Increasing their lifetime to 50 years will reduce the cost of operation and maintenance, increase energy yield, and drive down the levelized cost of energy (LCOE) for residential PV systems. Present-day solutions for increasing the inverter reliability focus on topologies that use the more-reliable film capacitors instead of electrolytic. However, following the elimination of electrolytic capacitors, further improvement of inverter lifetime requires consideration of the overall system architecture including power devices.
In this dissertation, a new topological and control scheme that allows dynamic hardware allocation (DHA) has been developed to address this challenge. In the proposed architecture, a common set of modules consisting of a pool of identical hardware resources dynamically shifts operation between active power filtering (APF) and line frequency inverter operation. Each module is used either as a buck type APF (with embedded energy storage) or a ZVS inverter phase leg, in each case controlled through a low-frequency current reference.
The benefit of this approach is multifold. First, inverter lifetime and reliability are increased because the pooled hardware resources are re-assigned in the event of a single failure of any element. Second, the modular nature of the system facilitates the use of high-reliability components, and allows for simple repair or maintenance through the replacement of individual modules instead of requiring a complete inverter replacement. Third, the cycle-by-cycle operation of the DHA allows the use of a smaller total semiconductor area in the power stage compared to a traditional system.
Sabi, Kamal, "Reducing The Levelized Cost of Energy of Residential PV Inverters Through Dynamic Hardware Allocation. " PhD diss., University of Tennessee, 2023.