Role of Power Electronic Devices in HVDC System

THYRISTOR BASED HVDC REGULATOR

System of the Most HVDC schemes in the current commercial operation employ line switched thyristor valve converters. On a line

converter on, the changeover is carried out by the alternating current system voltage.

HVDC will continue to be used for HVDC energy transmission in series for several hundred MW because of this

The technology provides efficient, reliable and economical power transmission for many applications.

The main control system generates the current reference for both drives and starts the startup and

Stopping the DC transmission. Figure 2. shows the HVDC controller on the side of the rectifier and also Figure 3. Shows

HVDC converter - Wikipedia

HVDC controller connected to the inverter circuit used in this document.

Inputs 1 and 2 are the DC line voltage (VDL) and the current (Id). Note that the measured direct current voltages p.u. (1 p.u.

current = 2 kA; 1 p.u. voltage = 500 kV) before being used in controllers. Voices 3 and 4 (Id_ref and Vd_ref) are you

and reference values ​​in p.u. Input 5 (pulses blocked) accepts a logic signal (0 or 1) used to block the converter

when Block = 1.

Input 6 (forced alpha) is also a logic signal that can be used for protection purposes. If this signal is high (1), the

the trigger angle is forced to the value defined in the block dialog. Input 7 (gamma_meas) is the minimum measured

12 valve extinction angle converter. Obtained by combining the two 6-pulse gamma outputs

Measurement blocks. Input 8 (gamma_ref) is the reference of the extinction angle in degrees. Minimize the reagent

HVDC Converter Station Market is Projected to Grow at a CAGR of ...

power consumption, the reference is set to a minimum acceptable angle (e.g. 18 degrees). Entry 9 (D_alpha) is a value that is

subtracted from the maximum delay angle limit to increase the switching margin during transients.

However, the main control circuit, shown in Figure 4, is generally system specific and individually designed. Second

transmission requirements, the control can be designed for constant current or constant transmission power, or

it can be designed to help stabilize the frequency in one of the AC networks by varying the amount of active energy

the control systems transmitted are normally identical in both conversion systems in a transmission, but the master

The control is active only on the station selected to act as the main station, which controls the current command. the

The calculated current command is transmitted by a communication system to the slave converter station, in which the predetermined current margin is added if the slave is to act as a rectifier, subtracted if it is to act as an inverter.

Characteristics of the HVDC converter

For the best possible performance in the HVDC transmission system

The converter must have the following characteristics:

2.1 Number of high pulses (p)

A large amount of pulses will reduce the harmonics and therefore

The requirement of the filter circuit will be lower. Hence the optimal number

of the pulse numbers normally the six pulse converters are a lot

well, because the six impulses give desire or merit

converter circuit characteristics, six pulses are optimal. But in

At the same time, the two six impulses if they change at a certain angle they mean

30 degrees, twelve pulses can be obtained [13].

2.2 PIV / Vdo must be minimal

The maximum reverse voltage (PIV) should be as low as possible if the

the maximum reverse voltage is less here means less expensive converter

valve means that this is directly related to the cost of

converter [16]. Because the converter consists of his

valves here; for large reverse voltage peaks the total cost

The circuit will be more. Hence the relationship between PIV and converter

The output voltage (Vdo) must be minimum [8].

A isubstation iis ia ipart iof ian ielectrical igeneration, itransmission, iand idistribution isystem. iSubstations itransform ivoltage ifrom ihigh ito ilow, ior ithe ireverse, ior iperform iany iof iseveral iother iimportant ifunctions. iBetween ithe igenerating istation iand iconsumer, ielectric ipower imay iflow ithrough iseveral isubstations iat idifferent ivoltage ilevels. iA isubstation imay iinclude itransformers ito ichange ivoltage ilevels ibetween ihigh itransmission ivoltages iand ilower idistribution ivoltages, ior iat ithe iinterconnection iof itwo idifferent itransmission ivoltages. iGenerally isubstations iare iunattended, irelying ion iscada ifor iremote isupervision iand icontrol.

Substations iare ineeded ibut iin ithe icase iof iurban iarea, iwe ihave ito isearch ifor ithe iarea ithan ithe ineed iand iordinary isubstation ineed ia ilot iof ispace. iHere iwe ican ithink iof ithe iunderground isubstation ior iindoor isubstation. iwe ican icommonly icall ithem ias iinvisible isubstation. iWhich iis inot ivisible ifor ia iman ipassing iby ior icannot isee iopenly iand icall ithem ias iinvisible isubstation

Underground isubstation iis ithe isubstation iwhich iis isituated iunder ithe iground iin ithe iurban iarea iwe ican ibuilt ia iunderground isubstation iwhich iwill iuse ithe iminimum ispace iand iin ithe itop ithe isubstation iwe ican ibuilt ibuilding ior ishopping imall ietc iindoor isubstation iis ithe isubstation iwhich iis isituated iin ia ibuilding ia ispecially idesigned ihouse.

A isubstation iis ia ipart iof ian ielectrical igeneration, itransmission, iand idistribution isystem. iSubstations itransform ivoltage ifrom ihigh ito ilow, ior ithe ireverse, ior iperform iany iof iseveral iother iimportant ifunctions. iBetween ithe igenerating istation iand iconsumer, ielectric ipower imay iflow ithrough iseveral isubstations iat idifferent ivoltage ilevels. iA isubstation imay iinclude itransformers ito ichange ivoltage ilevels ibetween ihigh itransmission ivoltages iand ilower idistribution ivoltages, ior iat ithe iinterconnection iof itwo idifferent itransmission ivoltages.

Generally isubstations iare iunattended, irelying ion iscada ifor iremote isupervision iand icontrol.

Substations iare ineeded ibut iin ithe icase iof iurban iarea, iwe ihave ito isearch ifor ithe iarea ithan ithe ineed iand iordinary isubstation ineed ia ilot iof ispace. iHere iwe ican ithink iof ithe iunerground isubstation ior iindoor isubstation i. iwe ican icommonly icall ithem ias iinvisible isubstation i. iwhich iis inot ivisible ifor ia iman ipassing iby ior icannot isee iopenly.and icall ithem ias iinvisible isubstation

Underground isubstation iis ithe isubstation iwhich iis isituated iunder ithe iground.in ithe iurban iarea iwe ican ibuilt ia iunderground isubstation iwhich iwill iuse ithe iminimum ispace iand iin ithe itop ithe isubstation iwe ican ibuilt ibuilding ior ishopping imall ietc.

Indoor isubstation iis ithe isubstation iwhich iis isituated iin ia ibuilding ia ispecially idesigned ihouse.

In ithis itwo itype iof isubstation ithe imain ipart iis ithe igas iinsulated itransformer iand igas iinsulated icontrols iwhich ireduces ithe ispace.

ORDINARY iSUBSTATION i(AIS)

Substations iwith iair-insulated iswitch igear i(AIS) iare ithe imost icommonly iused ihigh-voltage isubstations ifor irated ivoltages iof iup ito i800 ikV. iThey iare ipopular iwherever ispace irestrictions iand ienvironmental icircumstances iare inot ian iissue. i

The iAIS iuses iair ias ithe iprimary idielectric ifrom iphase ito iphase, iand iphase ito iground iinsulation. iThey ihave ibeen iin iuse ifor iyears ibefore ithe iintroduction iof iGIS. iActually, imost isubstations iacross iall iregions iare iAIS. iThey iare iin iextensive iuse iin iareas iwhere ispace, iweather iconditions, iseismic ioccurrences, iand ienvironmental iconcerns iare inot ian iissue isuch ias irural iareas, iand ifavourable ioff isite iterrainsystem . iThe iindoor iAIS iversion iis ionly iused iin ihighly ipolluted iareas, iand isaline iconditions, ias ithe iair iquality iis icompromised. iThe ifig.2.1 ishows ithe iordinary system isubstation iwith iair iinsulated iswitch igear

 i i i i i i i i i i i i i i i i i ihttps://4.bp.blogspot.com/-NfVgP20rn3E/XDhRbd7pD9I/AAAAAAAABGE/3el5O3mrVH008oSvFvbgp7IzrzS_G1QrwCEwYBhgL/s320/Picture7.png

 i i i i i i i i i i i i i i i i i i i i i i i i i i iSubstations iwith iair-insulated iswitch igear i(AIS)

MERITS iOF iAIS:

  • Low icost icomparing ito iother isubstation
  • Easy iimplementation iof ivirtually iany iapplication iand isubstation ilayout ithanks ito imodular idesign
  • Outstanding idegree iof iavailability, ireliability, iand ioperational isafety

LIMITATIONS i

  •  iLarge idimensions idue ito istatutory iclearances iand ipoor i
  •  iDielectric istrength iof iair.
  •  iInsulation ideterioration iwith iambient iconditions iand isusceptibility ito ipollutants.
  • Wastageof ispace. i
  •  iLife iof isteel istructures idegrade
  •  iSeismic iinstability.
  • Large iplanning i& iexecution itime.
  • Regular imaintenance iof ithe isubstation irequired

INVISIBLE iSUBSTATION

It ihas ibeen idivided iby itwo itype imainly iunderground isubstation iand iindoor isubstation

UNDERGROUND iSUBSTATION

 i i i i i i i i i i i i i i i i i i ihttps://1.bp.blogspot.com/-qSnWP18VJqA/XDhRqSD1OeI/AAAAAAAABHM/LhSefTmj0CExaafru-O4t8xqhG-U2vZ9wCEwYBhgL/s1600/Picture8.png

Schematic iLayout iof iUnderground iSubstation

A isubstation iwhich iis isituated iunderground iis icalled iunderground isubstation system . iThe iunderground isubstation iusually iwill ibe iinstalled iunder ithe idensely ipopulated iarea ifor idistributing ithe ielectricity ito ithe icity.

Benefits iof iunderground isubstations iare

  •  iThe isubstation ican ibe ibuilt iunder ia ibuilding iand iit iwill ibe ian ieffective isolution ifor isaving ispace iin icity iarea.
  • City iplanning ican ibe idone ifreely iand ithere iwill ibe iless iimpact ion ithe ienvironment system

. iINDOOR iSUBSTATION

Indoor isubstations iare iusually ifound iin iurban iareas ito ireduce ithe inoise ifrom ithe itransformers, ifor ireasons iof iappearance, ior ito iprotect iswitch igear ifrom iextreme iclimate ior ipollution iconditions. iA igrounding i(Earthing) isystem imust ibe idesigned.

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