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ECE PhD Defense: "Photovoltaic Nanogrid: Parallel Operating Inverters and Energy Management Flow," Su Sheng


013 Snell Library

March 22, 2017 10:00 am
March 22, 2017 10:00 am

This thesis first presents the design of a lightweight, compact and high reliability modified sine wave inverter. The inverter is integrated with foldable photovoltaic (PV) panel, maximum power point tracking (MPPT) charger and rechargeable battery to construct a portable PV nanogrid that can supply both DC and AC loads, for campers, hikers and especially soldiers on the move.

The designed modified sine wave inverters are able to operate in parallel to achieve higher power rating and higher system reliability. However, existing current sharing methods used to parallel either pure sine wave inverters or DC-DC converters cannot be applied directly to modified sine wave inverters because of possible circulating currents. This dissertation proposes methods to safely parallel the modified sine wave inverters without adding filtering inductors or capacitors. The methods merge approaches used to parallel pure sine wave inverters with methods sometimes used to parallel DC-DC converters. The developed approaches are then extended to parallel cascaded H-bridge multilevel inverters.

For a even higher power movable nanogrid, such as those that may include a solar tents, battery storage and a diesel generator, it is not feasible to parallel too many designed inverters for energy management. For such system, the research proposes optimal power management approaches to reduce operating costs by managing the power flows in a PV-diesel generator hybrid nanogrid with batteries. The proposed algorithms utilize dynamic programming (DP) technique to optimize the power flows in the system to meet the load demand, achieve maximum utilization of the solar energy available, minimize fuel consumption and increase battery life cycle, simultaneously. The optimization algorithm also deals with the uncertainty of the PV power.

  • Prof. Brad Lehman (Advisor)
  • Prof. Bahram Shafai
  • Dr. Peng Li