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Value-Added SolutionsP

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er ABB Constructs World’s Largest

Battery Energy Storage Systemin Fairbanks, Alaska

w w w . a b b . c o m / m o t o r s & d r i v e s

OverviewGolden Valley Electric Association inFairbanks signed a contract with ABB toconstruct a Battery Energy StorageSystem (BESS.) The BESS will automati-cally pick up 26 megawatts of load for15 minutes (or 40 MW for 7 minutes) inthe event of power plant or transmissionline equipment failure. Fifteen minutesis long enough to start up and bringlocal generation online. The switch frompower line to battery and back to powerline is seamless and goes unnoticed bythe customers. So the prime function ofthe BESS is to provide spinning reserve.At the end of the spinning reservesequence, the BESS will automaticallyre-establish the operation mode, whichwas active prior to the event.

Power Conversion System(PCS)The two primary subsystems in the BESSare the IGCT converter and the Ni-Cdbattery. The battery is the energy storagemedium. The IGCT converter is theinterface between the DC batteryvoltage and the 60 Hz AC GVEA systemvoltage. The converter transformersmatch the converter output to the138 kV system voltage.

Converter TransformerThere are three single-phase transform-ers, each rating 14.9 MVA. The fourprimary windings of each unit areconnected in series. The secondarywindings are connected to the con-verter. On the AC-side the single unitsare star connected.

Ni-Cd BatteriesThere are four battery strings. Eachstring consists of 344 series connectedbattery modules. The batteries aremonitored with a battery monitoringsystem (BMS.)

ConverterOn the AC line side the IGCT powerconverter consists of four paralleled twinconnected three-phase units (total of24 converter phases). On the DC side

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the battery is connected to theconverter’s DC link with an aluminumbusbar system. Due to the power andthe high number of phases, the con-verter is built of two converter frames(half converters). One of these convert-ers includes a Voltage Limiting Unit (VLU.)

DC-Filter CircuitsThe purpose of the High Pass Filters isto balance the DC link voltage and toreduce the voltage ripple. The tunedFilters (60, 120 Hz) are designed inorder to eliminate parallel resonancesand to protect the batteries from har-monic current injection.

Cooling SystemThe challenging environmental condi-tions of Fairbanks have been givensignificant consideration. The IGCTconverter is cooled with a closed-watercooling system. This design has twowater loops. De-ionized water is used forcooling of the converter. A raw-water/glycol solution, which circulates in asecondary loop, removes the waste heatvia outdoor radiators.

ControlThe BESS system is controlled by aPentium PC based control platform, thePSR II (Programmable High SpeedController). The PSR II is programmedto provide all required control modes. Inaddition, the PSR II provides the BESSsystem protection. In addition it inter-faces with the GVEA SCADA system andhas a local graphical human machineinterface (HMI.) Following operationmodes are programmed:

Spinning Reserve, Automatic Schedul-ing, Support for Scheduled Load In-crease, Automatic Generation Control,Var Support, Power System Stabilizer,Charging, Discharge Test Main TechnicalData Plant: BESS GVEA, Fairbanks,Alaska, USA.

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