ACEP Hybrid Applications Testbed
At a glance:
• ACEP operates an isolated micro grid laboratory at similar scale as rural Alaskan power systems.
• The grid consists of a 320 kWe diesel genset, a 100 kW wind turbine simulator, and a 250 kW load bank.
• The system is setup for 480 VAC operation.
ACEP has developed a Hybrid Applications Testbed with the aim to emulate typical rural Alaskan Wind-Diesel systems up to power levels of 500 kW. The philosophy of the testbed is to be able to test technologies meant to increase power plant efficiency, as measure by the amount of diesel burned per unit of energy produced, in a controlled setting which is readily accessible by road. Through this, the risk of acquiring sub-optimal equipment for rural Alaskan utilities is to be reduced.
The testbed setup utilized for the test of a particular piece of equipment can be adjusted depending on the equipments typical and rated power levels, or based on the power levels of a given rural power plant.
For the test regiment described here the testbed was configured with a 320kWe Caterpillar diesel genset, a 100 kWe wind turbine simulator and a 250 kW/187.5 kvar variable load bank. The nominal grid voltage is 480 VAC, three-phase.
The wind turbine simulator, a product of Sustainable Power Systems LLC, consists of two mechanically coupled induction machines, the motor and the generator. The motor is controlled by a variable frequency drive (VFD) and its output torque can be controlled via torque, power, or wind speed and wind turbine power curve time series, or set point inputs. The generator connects directly to the main grid bus. The power output is not conditioned.
The 250 kW/187.5 kvar variable load bank is a product of Load Technology, Inc. Load can be controlled in 5 kW and 3.5 kvar steps, independently of each other. The nominal voltage of the load bank is three phase 208 VAC, and it is connected to the grid through a Delta-Wye-connected transformer (Delta on 480VAC, Wye on 208 VAC, 300 kVA). The lab setup for this test is illustrated below:
Figure above: The configuration of the Hybrid Testbed can be varied to meet the needs of particular projects. The configuration shown was utilized in the test of Sustainable Power Systems’ GRIDFORM Inverter. Shown here: single line drawing of hybrid applications testbed setup for the GFI test. The GFI is shown in green, connected to the battery and the isolation transformer (T2). The components of the Wind turbine simulator (WTS) are shown on gray background. The induction motor (IM) drives the induction generator (IG) based on control signals transmitted to the variable frequency drive (VFD). Only the IG of the WTS is electrically connected to the hybrid grid, the VFD and IM receive external grid power. The main load bank (L1) is connected to the hybrid grid through a voltage transformer (T1). The load bank (L2) was used to simulate slight phase imbalances. The load bank connection and the connection to the synchronous generator (SG, diesel genset) were instrumented with WattsOn meters (blue dots). A Fluke 435 II Power Quality and Energy Analyzer (red dot) was connected to the load bank transformer for most test. The exception is the inverter efficiency test, where the Fluke 435 II was connected to the grid side of the isolation transformer and the DC link of the GFI.