ABB Review Special Report - ABB - ABB Group
ABB Review Special Report - ABB - ABB Group
ABB Review Special Report - ABB - ABB Group
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2From the rectifier station at Kollsnes, subsea HVDC cables transmit power to the Troll A Platform, where the inverter station andMotorformer are located. Two identical systems are to be installed.KollsnesSubseacableTroll A platform132-kV switchboardRectifier stationHVDC LightcableInverter stationMotorformerPrecompressorPowertransformerHVDC Lightrectifier70 kmHVDC Lightinverter40 MW56 kVGearused together with an advanced modelof the machine’s electromagnetic parametersto calculate converter switchingpulses in much the same way as forsmaller industrial variable-speed drives(ACS 600/ACS 1000/ACS 6000). Unitypower factor and low harmonics areassured, along with a sufficiently highdynamic response, over the motor’sentire operating range. Protection andmonitoring of the converters and synchronousmachines, as well as controlof the excitation converter feeding thelatters’ field winding, are handled by<strong>ABB</strong>’s well-proven Industrial IT HVDCControl, MACH 2.HVDC LightIn the past, high-voltage DC links have beenused almost exclusively to transmit very highpowers over long distances. HVDC Light [1]is a new transmission technology based onvoltage source converters that extends theeconomical power range of HVDC transmissiondown to just a few megawatts.HVDC Light also offers power qualityimprovements, for example reactive powercompensation and harmonic/flicker compensation.Thanks to fast vector control,active and reactive power can be controlledindependently, with harmonics kept low,even in weak grids.Overall control of the rectifier station atKollsnes is also handled by the MACH 2.There is no need for communication betweenthe rectifier control system onland and the motor control system onthe platform; the only quantity that canbe detected at each end of the transmissionsystem is the DC link voltage. Asthe DC link cannot store much energy,the motor control system is designed tofollow even rapid changes in powerflow at the opposite end without disturbingmotor operation. Nuisance trippingis generally kept to a minimum.The HVDC Light converter for Troll isbased on a two-level bridge withgrounded midpoint. Only extremely lowground currents are induced duringsteady state and dynamic operation, thisfeature being one of the main reasonsfor using HVDC for the power supply.No cathode protection of any kind hasto be provided for this installation.HVDC Light cable – the power carrierThe HVDC Light concept includes a furtherinnovation: the HVDC Light extrudedpolymer cable. The shift in high-voltageAC technology from paper-insulatedto extruded polymer cable was the incentivefor <strong>ABB</strong> to develop and producean extruded cable offering the samebenefits – flexibility and cost-effectiveness– for HVDC transmission.Troll A’s importance as a major gas producercalled for an extremely reliabletransmission link. The actual cable hasa 300-mm 2 copper conductor surroundedby a very strong and robust polymericinsulating material 3 . Wateringress is prevented by a seamless layerof extruded lead, over which there aretwo layers of armor – steel wire wovenin counter helix – to provide the requiredmechanical properties. This designensures that the cable has thestrength and flexibility necessary forlaying in the North Sea. The two electricdrive systems require an HVDCLight cable system with two cable pairsMotorformerMotorformer [2] features conventional rotor,exciter, control and protection technologies.Most of the stator technology is also conventional– the exception is the winding, which ismade of XLPE-insulated cable. The stator’scable slots are designed for low electricallosses, high-strength cable clamping,efficient cooling and simple installation.The first Motorformer to go into commercialoperation, at the AGA plant in Sweden,has verified the many benefits of using HVcable technology in large electric motors.Motorformer is suitable for most applicationswhere conventional technology is used today.<strong>Special</strong> <strong>Report</strong><strong>ABB</strong> <strong>Review</strong>55