IOP call discussions:

In today’s call we answered some questions. I marked these with green further down.

In addition some classes will be renamed to fit with IEC 62747.

The association between ConverterACside and ConverterDCSide is only added to make the validation based on UML possible. Because of this it is required that the cardinality is 1 to 1. There is no point to have flexibility on this.

The planning is as follows:

1.       By 15-16 May: Lars-Ola to update the UML and xls (and the doc) with the changes we agreed and also align to the current draft of the IEC 62747 on VSC

2.       15 May: WG13 has 2h call – discussion on HVDC and SSH is expected. Lars-Ola will need input from WG13 in order to update the UML accordingly

3.       By 20 May: Chavdar to make a version for the profile (on the basis of the updated HVDC xls by Lars-Ola) in which HVDC will be split  - EQ, TP, SV, SSH (steady state hypothesis former OH)

4.       By 20 May: Chavdar to make a version of the profile which includes last changes related to the SSH

5.       By 27 May: IOP participants to review all

The next call is on 20 May: The task is to discuss other open issues we have in the xls. This may result in another version of the profile.

Outcome from the last call on HVDC:

a.       The current modelling covers CSC and VSC with the whole structure from one AC end of the interconnection to the other AC end (transformers, converters, DC line, etc.).

b.      There are ways of representing: detailed way (in which you model all main equipment) which vendors seem to support; bus-branch kind of model which maybe applicable for HVDC grid but because no vendors (or almost all) support HVDC grid modelling and how power flow would be performed in an HVDC grid this kind of modelling is more as an option for future extension rather than for primary use.

c.       The current model does not cover short circuit and dynamics modelling

[Chavdar Ivanov] Comments IOP call 13 May 2013

1)     VSC

a)    It should be interesting to add a “PowerFactor” possibility as qPccControl in order to control the cos q

[Chavdar Ivanov] Lars –Ola will check this and correct. We have the mode but not the target value

b)    directQcontrol seems to be redundant with qPccControl[Chavdar Ivanov]  - directQcontrol to be deleted

2)    CSC

a)    We don’t see the Commutation Reactance (switching resistance ?) of the converter[Chavdar Ivanov]  - given on the AC side

b)    A absolute value is probably missing in the poleLossP formula :

  poleLossP = idleLossFactor + switchLossFactor* |Idc| + resitiveLossFactor*Idc^2[Chavdar Ivanov]  Lars-Ola will correct

c)     The qPccControl seems to be missing.

Two possibilities should be available in this mode :

-       The Voltage target in AC grid (Pcc= Point of Common Coupling) => targetUpcc

-       The Angle target => alphaTarget or gammaTarget

[Chavdar Ivanov] i.e. control parameter is missing; choice between angle control and voltage control is necessary. Lars-Ola will fix

Currently identified TSO needs on HVDC model

a.       Support a common model for operation and planning [Chavdar Ivanov]  OK. Covered in the current proposal

b.      Able to exchange the model with DC partner (other TSO) [Chavdar Ivanov]  Xnodes discussion needed. Chavdar made a proposal that should be reviewed

c.       Connect measurements to a model that can be used for load flow calculation (and need to handle both side of the connection – a simple load cannot do that on its own) [Chavdar Ivanov]  OK. Covered in the current proposal

d.      Allocate schedules that can be used for load flow ahead of time or when signal is lost [Chavdar Ivanov]  now missing for the DC side; additional things as extensions to the current model

e.      Can be used for controlling ramping [Chavdar Ivanov]  related to the dynamics

f.        Support both CSC and VSC (or be possible to be extended to VSC without too much changes) [Chavdar Ivanov] OK. Covered in the current proposal. Now we have CSC and VSC

g.       Short-circuit calculation – or be possible to be extended to support it without too much changes [Chavdar Ivanov]  to be extended without changes on existing classes/attributes; need to check the progress on the IEC 60909 or related HVDC std for Short Circuit

h.      Outage management – identify and tag equipment that is taken out for maintenance [Chavdar Ivanov]  not at this stage; needs discussions as a part of the discussions of the outage management topic

i.         Training simulation – slow dynamic [Chavdar Ivanov]  not included in the proposal

j.        Dynamic modelling – or be possible to be extended to support full dynamic modelling [Chavdar Ivanov]  how to fit dynamic models? One point or different points in the HVDC system. The group tend to agree that the dynamics models will be associated with the elements in the equipment to the level of detail they are represented now, i.e. vendors that are having HVDC dynamic model that is associated with complete HVDC system should be split on pieces.

k.       Support of all TSO HVDC models [do we have difference in load flow parts or this is only on dynamics parts][Chavdar Ivanov]  This was not discussed

l.         Support for DC equipment inside the same Synchronous area [Chavdar Ivanov]  ok in the current proposal

Steady State (Load Flow): [to be checked item by item against current proposal][Chavdar Ivanov]  some of the items were checked. The rest should be double checked

The model should have the capability to control power flows with regards to the power flow situation in the AC system. Therefore input signals for the power flow control of the HVDC system according the AC system state should be foreseen:

-       Angle difference between connection points

-       Contingencies in the AC system

-       …

Reactive power capability and control modes should be included.[Chavdar Ivanov]  covered. There is a VsCapabilityCurve associated with VSC

Reference to HVDC preliminary scope:

• Reactive power capability
• Reactive power compensation
• Reactive power control mode
• Priority to active or reactive power

Dynamic Models:[not yet; also see above; the approach should be extendable to cover these][Chavdar Ivanov]  Items listed below should be allowed at the moment dynamics models for HVDC are added. Now the issue is to prepare the UML so that dynamics package is easily extendable.

Dynamic models should have the capability to react on faults in the AC and in the DC grid. Fault clearing and active power recovery after fault clearing on the AC and DC side should be covered. In addition POD with SSTI controller and AC voltage control as well a grid controller in case of multi terminal or tapped multi terminal systems.

Reference to HVDC preliminary scope:

• Converter synchronisation/disconnection
• Power oscillation damping
• Subsynchronous torsional interaction damping
• Operability at minimum short circuit power
• Grid controller

For the dynamic model both AC and DC system should be included physically in the model.[Chavdar Ivanov] This is the current intention as we have equipment for DC and AC network.  A black box model for the DC circuit is not preferable.

The best option would be to have a standard model for one converter type. Then a DC system could be designed individually by setting the converter controller and the grid controller. [Chavdar Ivanov] This goes in line with the discussion we had to not have dynamic model that covers the complete HVDC system, but rather on pieces.