Josco C.P. Kester (MSc) ECN Intelligent Energy Grids (kester@ecn.nl)

IntroductionTNO connects people and knowledge to create innovations that boost the sustainable competitive strength of industry and well-being of societypublic / privateindependentindustrial innovationinformation societyICTenergymobilityresearch and developmentThe Netherlandsturnover 600Mapplied physicsmeasurements & controltechnologyhikingEnergie Delflandelectric power systemsconsultancyresearch & developmentECN2

power electronic technologyKomen vanuit KPN research (ICT in adviserende rol)Titel van de presentatie16-4-2012 17:092Smart Substation

A 10/0.4 kVdistribution substationthat supports LV grids withdistributed generation and demand peaks

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IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl3

How will our energy supply look in 2050?4

Power grid operators face new requirementsIOP-EMVT 06101 intelligent distributie station#kester@ecn.nl4Smart Substation

RequirementsFunctional DesignDetailed DesignPrototype AssemblyLaboratory testsField demonstration(May 2007- December 2010)5

IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl5

Inside the prototypeLV Cabinet6MV CabinetIOP-EMVT 06101 intelligent distributie station#kester@ecn.nl6

LV cabinet73. Monitoring and control2. Sensors1. Electric energy storageIOP-EMVT 06101 intelligent distributie station#kester@ecn.nl7

MV cabinet

8Switchgear indicatorsSmart Trafo - trafoSmart Trafo control unitIOP-EMVT 06101 intelligent distributie station#kester@ecn.nl8Smart Substation

by improvingload profilereliabilitypower quality

A 10/0.4 kV distribution substationthat supports LV grids with distributed generation and demand peaks9

IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl9Lab tests in FPG-LabMay 2009 February 2010

10IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl10Smart SubstationTransport Services for the Distribution Grid Operator

Josco C.P. Kester josco.kester@tno.nlLoad profilePeak load: - 30% (simulation)PowerMatcherSupply Demand Matching

12IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl12Reliability

Decrease peak loadsCoordination of local supply*Intentional islanding*

* not yet fully tested13IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl13FPG-Lab: islandingESI System operating in islanding mode after removal of MV supply(passive resistive load of 20kW applied)

14IOP-EMVT 06101 intelligent distributie station#kester@ecn.nlPower QualityResonances: - 70% (simulation)

Harmonic Compensation

with

Virtual Resistive Harmonic Dampening (VRHD)15IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl15Smart Substation: results field demonstrationTested in an operational grid (easy circumstances) stable operation harmonic compensation voltage stability flicker reduction

Not yet tested controlling microCHPs active power control (in preparation) rough conditions

Duration testongoing

16IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl

Field demo: Reference harmonics (wk20)THD 3rd 5th 7th 11th 13thAll PQ characteristics within limits17very goodsufficientvery badIOP-EMVT 06101 intelligent distributie station#kester@ecn.nl

Field demo: THD (May - October 2010)THD3rd 5th 7th 11th 13th17-19 prep 20 ref

21-26 V

29 harm

30 ref

35-36 V

42-43 flicker

18IOP-EMVT 06101 intelligent distributie station#kester@ecn.nlField demo: Harmonic Compensation (THD)Off On

THD reduced by 15%

2.52.50.00.019IOP-EMVT 06101 intelligent distributie station#kester@ecn.nlField demo: Harmonic Compensation (5th)Off On

5th harmonic reduced by 20% 20

2.50.02.50.0IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl

Field demo: Reference PQ (wk20)V (dips) Dfreq flicker THD unbalanceNot applicableConnection.error21very goodsufficientvery badIOP-EMVT 06101 intelligent distributie station#kester@ecn.nl

Field demo: PQ (May - October 2010)V(dips)Dfreq. Flicker THD Unb.17-19 prep 20 ref

21-26 V

29 harm

30 ref

35-39 V

42-43 flicker

22Not applicableConnection.errorIOP-EMVT 06101 intelligent distributie station#kester@ecn.nlField demonstration: Flicker reductionOffOn

Flicker reduced from max 0.4 to max 0.2

231.00.01.00.0IOP-EMVT 06101 intelligent distributie station#kester@ecn.nlField demonstration: Voltage stabilityOffOn

Voltage excursions reduced from +/- 4 V to +/- 0.8 V

24IOP-EMVT 06101 intelligent distributie station#kester@ecn.nlSmart Trafo

Voltage distribution at input

Voltage distribution at output

25IOP-EMVT 06101 intelligent distributie station#kester@ecn.nlIntroductionThe Smart Trafo consists of an adapted distribution transformer and an electronic control unit. The system adapts the transformer winding ratio in order to keep the secondary voltage at a constant level, independent of 10 kV voltage variations or transformer load current. This requirement is restricted to the tapping range of the transformer. As a standard for distribution transformers a range of +/- 5% is commonly used. Within this voltage range the SmartTrafo will stabilise the load to 400 V (or any other level). Outside this tapping range the system operates as a normal transformer with a fixed winding ratio, but at the end of its tapping range, so as near to the voltage as required.

IGBT semiconductor switches instead of traditional off-load tap changerTo keep the LV grid stabilised at a varying 10 kV voltage, the off-load tap changer has been changed into an on-load continuous tap changer. This is realized by implementing IGBT semiconductor switches on the primary side of the transformer in order to avoid the high currents that would have to be controlled on the secondary side. In order to comply with the requirements for harmonics and cos , the IGBT quasi Graetz bridge topology with controlled duty cycle (PWM) has been chosen.

LV voltage regulation by duty-cycle controlThe PWM switching topology chosen will allow for secondary voltages with a high level of stability, independent of the 10 kV voltage variation and independent of load current. The switching concept can be explained in the following way:If switch 1 is continuously switched-on, the highest transformer winding ratio is chosen, resulting in the lowest transformer secondary voltage. If switch 2 is continuously switched-on, the secondary voltage will be correspond with the highest transformer winding ratio, but lowered by 2.5 %. The step from closing switch 1 to closing switch 2 is a relatively large voltage step of 2.5 % upwards. The tap windings are chosen for this design as 4 steps of 2.5 % each.

By applying PWM control of IGBTs, is it not necessary to select the fixed secondary voltage level corresponding to switch 1 or switch 2, but with the PMW techniques the secondary voltage can be controlled gradually in between these two levels. Moreover, operating in this stabilised regulation mode, any secondary voltage level in the range between the outer tapping switches 1 and 4 can be set.

Other featuresA thyristor crowbar has been added to enable start-up when no power is available for the electronics, and to ensure operation in fault conditions. This important feature makes a smart trafo as reliable as an ordinary distribution transformer and reduces installation cost.The SmartTrafo furthermore withstands a 75 kV impulse voltage in accordance with the requirements of IEC 60076-3 for a conventional distribution transformer. Detailed simulations and measurements have been carried out and have resulted in a new transformer design that minimises the imposed voltages on the IGBTs to within rated levels. At the same time the new tap winding design was combined with the requirements for a short- circuit proof tap winding design.

ResultsIn the first graph the distribution of the primary voltage during the day has been depicted, in intervals of 20V between 5750V and 6100 V (line to neutral). As can be seen from the second graph the secondary voltage is kept exactly at the desired voltage. The secondary voltage is stabilized with an accuracy of 0.2%.

2526Flex Power Grid Lab (FPGLab)offers services for development and testing of SmartGrids and power electronicsfor industrial high voltage (24kV), power up to 1MVAby offering a predefined bad grid or loadindependent laboratory, operated by KEMA, Arnhem (Netherlands)www.flexpowergridlab.com

Applications

IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl16 April 20122627Key figures make test facility uniqueVoltage level up to 24 kVDC to 75 Hz frequency rangeContinuous power up to 1 MVAUp to >25th harmonics4 Quadrant operationSynchronization with other sourceControllable power exchangeAdjustable loads (0.5MW, 1MVAr)

A freely programmable nightmare grid1 MVA2.4 kHz24 kV1 MVA

IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl16 April 201227Spin-offAlfen: ESIImtech: Smart Trafo 2.0KEMA: FPG-LabAlliander: test environmentTNO: PowerMatcherEaton: equipment for sustainable electricity supply, home automation

28IOP-EMVT 06101 intelligent distributie station#kester@ecn.nlRecommendations Continue monitoring Test active power control Perform test including microCHPs Demonstrations take more time than one expects even when one takes that into account Significant cost reduction possible Significant volume reduction possible Consider mobile applications29IOP-EMVT 06101 intelligent distributie station#kester@ecn.nlConclusions Lab tests anti-islanding and islanding tested and approved specifications tested and documented approved for field operation

Field demonstration tests with microCHPs not possible active power control not yet working smart substation has operated without incidents since June 2010 voltage stability improved THD improved flicker improvedInternational interest in Smart Substation30Questions?josco.kester@tno.nl+31-88-866 7392IOP-EMVT 06101 intelligent distributie station#kester@ecn.nl