Grid-Interactive DC-Link PV Charging Station
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PROBLEM Photovoltaics supply variable energy and electric vehicles add unpredictable load; both can impact grid stability.
PROJECT Satcon Technology Corporation is developing an inverter to efficiently charge vehicles using direct DC solar power as well as smooth solar power for a better interface with the electricity grid on Lanai.
AWARD $890,864 (HREDV 66%, private 34%)
LOCATION Lana’i City, Lana’i
PARTNERS
- Castle & Cooke Resorts
- SunPower
- University of Colorado
SUMMARY
Satcon’s PowerGate Plus photovoltaic (PV) systems, in partnership with SunPower and Castle & Cooke, have been deployed in the 1.2 MW La Ola PV farm on the island of Lanai. Satcon’s cutting-edge inverter and control technologies, as practically demonstrated in the Lanai PV farm, enable a number of advanced PV grid integration features. With these features, a PV farm in many respects approaches capabilities of a dispatchable power plant. However, grid integration remains a challenge for distributed PV in key areas:
- Curtailment-related capacity factor reductions
- Effects of rapid, wide-swing variations in PV system power output
- Communication latency complicating closed-loop system controls
These challenges could be addressed through effective integration of energy storage in PV systems. In addition to wider utilization of renewable sources, the Hawaii goals depend on reduction of oil usage in transportation. To this end, together with shifting electricity generation from oil to renewable sources, a much wider penetration of electric-drive vehicles including plug-in hybrids (PHEVs) and pure electric vehicles (EVs) is envisioned. Grid integration of PHEVs and EVs presents additional challenges including the load presented to the electric power grid, and the need for charging infrastructure. Furthermore
, in Hawaii, transportation electrification makes sense only if oil-based electricity generation is replaced with renewable sources.
The Grid-Interactive DC-Link PV Charging Station is a candidate solution addressing challenges in grid integration of both renewable sources and electric-drive vehicles. The existing Satcon PV inverter will be extended to include bidirectional DC-to-AC functionality, and bidirectional charge-control DC-DC converters providing battery recharge services to a number of electric-drive vehicles. The vehicle batteries can also serve as auxiliary energy storage for the PV system.
With support from Castle & Cooke Resort, LLC, the system will be evaluated on the island of Lanai, the Hawaiian island with largest percentage penetration of renewable energy on a microgrid. The project goal is to bring the prototype system to Technology Readiness Level 6 based on engineering modifications of an existing, commercially available Satcon Solstice system. Specifically, project objectives are:
- Design, develop, implement and test extensions of the Satcon DC-AC inverter to enable bidirectional power flow capability
- Design, develop, implement and test a bidirectional DC-DC power converter to serve as the DC-DC battery charge/discharge unit in the system
- Design, develop, implement and test prototype system control functions
- Integrate a prototype system (TRL5 for the complete system)
- Deploy and evaluate the prototype system (TRL6) at Castle & Cooke Resorts LLC, Lanai City Hawaii