Bidirectional inverter with improved light load efficiency for integration in a hybrid AC/DC distribution system in buildings
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Date
2023-03-28Embargo Date
2024-04-30
Author
Alshammari, Meshari
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Abstract
Increasingly more research is being done on DC distribution systems with the aim of
increasing system efficiency for power delivery between DC power sources, loads,
and energy storage equipment as compared to AC distribution. When compared to a
traditional AC system in such circumstances, the DC distribution system is preferable
for residential use since it offers inherent benefits over the latter. These include
increased efficiency and dependability, as well as the simplicity of integrating
batteries and renewable energy sources. Residential building energy efficiency must
be improved to optimize solar PV energy utilization since PVs and energy storage
may not be available in winter and autumn months, when residential load demand is
high. In such cases, grid power is necessary to meet electricity demand. Thus, a
bidirectional inverter is introduced to interface between the DC distribution system
and the utility grid and deliver energy to meet demands and sell surplus PV power.
However, it is found that the low operating power of a bidirectional inverter causes
significant losses when grid power is provided. Therefore, energy savings are
possible for the DC distribution system, particularly under light-load conditions. Its
efficiency at light-load is notably low, which has received considerable attention since
it ultimately recovers the initial investment in the DC distributed system and reduces
the cost of grid power. Therefore, this thesis demonstrates a light-load-efficient
solution to the challenges that limit the efficiency of bidirectional inverters in DC
distribution systems. Particularly, the design of the bidirectional inverter solution is
focused on light-load with power levels of 5 kW and voltages of 380 V.
The proposed solution (bidirectional synchronous H6) topology permits AC-DC
converters to operate efficiently at low power with a high DC bus voltage distribution
system and integrate with the utility grid. The synchronous H6 inverter could
increase the efficiency of DC distribution systems. This bidirectional synchronous H6
inverter is also applicable for low-power applications.