Development of new power decoupling and pulse energy modulation technologies for single-phase distributed generation inverters

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Distributed generation (DG) systems using renewable energy are increasingly penetrating into mainstream power systems. Many small distributed generation systems are connected to single-phase grids. These small DG systems (PV, wind systems etc.) all require single-phase grid-connected inverters. For single-phase systems, there is a mismatch between the desired constant power drawn from distributed energy resources (PV, wind), and the required pulsating instantaneous power feeding to the single-phase grid. The mechanism which provides the difference between the constant source power and the pulsating grid instantaneous power is referred to as “power decoupling”. Innovative power decoupling technologies are needed to replace traditional large and unreliable electrolytic capacitors with film capacitors with a comparable life-span with DG systems. This project proposes to develop a new power decoupling topology using small film capacitors and active semiconductor devices, and to advance a new modulation concept called “pulse energy modulation (PEM)” for single-phase grid-connected inverters. The developed technologies will lead to the replacement of traditional large electrolytic capacitors in inverter dc link with small film capacitors actively controlled by power semiconductor devices, and lead to advanced pulse modulation methodologies for inverters with enhanced immunity to dc voltage variations and grid harmonics. This will result in increased reliability and enhanced power quality of single-phase grid-connected DG inverters. The project will have four tasks: (1) Develop Power Decoupling Theory and Operating Principles for the New Inverter; (2) Develop PEM Algorithm for Bridge Inverters; (3) Verification of the Proposed Inverter Topology and PEM Control; and (4) Performance Evaluation of the Proposed Inverter Topology and PEM Control. Opportunities for patent filing and technology transfer will be exploited at the latter stage of the project. The project will provide hands on training for two PhD students and one postdoctoral fellow (PDF).