Differences in Steady State Power Data Definitions Data Structure Differences.pdf · switched shunts on the bus (or buses connected by low impedance branches) that regulate the same

Differences in Steady State Power Data Definitions

WECC SRWG Meeting November 4, 2015

Presented by: Jamie Weber, Ph.D. Director of Software Development [email protected] 217 384 6330 ext 13

©2015 PowerWorld Corporation

Summary

• Presentation concentrates on the differences in the data definitions in software tools

• This is clearly Step #1 for any tool that coordinates input data between tools

• Obviously the file format is related

• This is a rough draft of the differences and some differences may be missing still


Bus Differences • Name

– PSS/E and PSLF limit to 12 characters – Simulator has no specific character limit

• When writing out to PSS/E or PSLF, Simulator will truncate names in a way that ensures unique names remain unique

• BonnevillePowerDam Bonneville~1 • BonnevillePowerSub Bonneville~2 • BonnevillePowerTap Bonneville~3

• Voltage Schedules – PSS/E and Simulator

typically specify the voltage setpoint with the control device

– PSLF specifies the specific voltage setpoint with a Bus record • Except for transformers

Device Type PowerWorld Simulator

PTI PSS/E GE PSLF

Generator Generator Setpoint

Generator Setpoint

Bus Setpoint

Shunt Shunt Setpoints

Shunt Setpoints

Bus Setpoint and Shunt VBAND

Transformer Transformer Vmin and Vmax

Transformer Vmin and Vmax

Transformer Vmax and Vmin

VSC DC Line VSC DC Line Setpoint

VSC DC Line Setpoint

VSC DC Line Setpoint


Bus “Types”

Device Type PowerWorld Simulator

GE PSLF

PTI PSS/E

PQ Bus Automatically Determined based on devices

Type = 1 (If any generators are at this bus, Simulator changes this to a 2)

IDE = 1 If an closed generator is at such a bus then it will be ignored, so Simulator will open it

Allow a PV Bus Automatically Determined based on devices and Generators with AVR = YES

Type = 2

IDE = 2

Slack Bus Slack = YES Type = 0 IDE = 3

Disconnected Automatically Determined based on topology

Presumably this is auto determined because Type = 0 at disconnected buses

IDE = 4 After reading file if you find that a bus is actually connected to online generation through closed branches, then if the Type = 4 Simulator will go back through and open all branches connected to the bus to isolate it.

Special unlimited Mvar

Change Min/Max Vars

Type = – 2 Change Min/Max Vars


Generator Differences

• Reactive Capability Curves – Simulator and PSLF both specify the capability curve

explicitly, though many users do not populate this data – PSS/E has a separate input file called “GCAP” which

specifies the capability. (Simulator is able to read this file) • GE Baseload Flag

– Extra flag used by PSLF in transient simulation only (user-written EPCL code might also use this)

– Simulator allows you to interpret this field as a Post-Contingency AGC status (Simulator has a separate field for Transient simulation use)

• Owners – PSLF support up to 8 owners – PSS/E support 4 owners – Simulator Version 19 supports 8 owner (previously was 4)


Generator Differences

• AVR status – Simulator has a AVR flag that is set to YES or NO – PSS/E you would change Qmax and Qmin – PSLF uses (Qmax – Qmin) to determine. By default ranges at 2.0

Mvar or less are considered AVR = NO. • Remote Regulation Percentages

– PSS/E uses RMPCT that is the same for all generators at same bus – PSLF allows different “prf” values at the same bus – Other software (EMS system) handle this yet a 3rd way – PowerWorld Simulator has an option to choose between 3

choices • Line Drop Compensation with Generator

– PowerWorld Simulator allows the specification of a Rcomp and Xcomp with a generator record in the Power Flow Solution

– PSLF has input data. Not sure if it’s used. – PSS/E does not have this


Generator Difference

• “Unit type” field is available in PowerWorld and PSLF. – String shown below in Simulator, Integer in PSLF

• Field not in PSS/E

UN (Unknown) = 0 CA (Combined Cycle Steam Part) = 2 CC (Combined Cycle Generic) = 4 CE (Compressed Air Storage) = 15 CS (Combined Cycle Single Shaft) = 13 CT (Combined Cycle Combustion Turbine Part) = 3 DC (represents DC ties) = 40 FC (Fuel Cell) = 15 GT (Gas Turbine) = 11 HY (Hydro) = 5 IC (Internal Combustion) = 6 IT (Internal Combustion Turbo Charged) = 7

JE (Jet Engine) = 12 MP (Motor/Pump) = 41 NB (ST - Boiling Water Nuclear Reactor) = 15 NG (ST - Graphite Nuclear Reactor) = 15 NH (ST - High Temperature Gas Nuclear Reactor) = 15 NP (ST - Pressurized Water Nuclear Reactor) =15 OT (Other) = 15 PS (Hydro Pumped Storage) =15 PV (Photovoltaic) = 31 SC (Synchronous Condenser) = 14 ST (Steam Turbine) = 1 WT (Wind Turbine) = 21

PowerWorld String = PSLF Integer


General Extra Fields In Software Data Definitions

• Several other additional fields are available in PSLF and PowerWorld data structures which do not appear to be used extensively in WECC – PSLF has In Service Data, Project ID, Dispatch Flag, AGC Flag,

and so on – PowerWorld adds extra fields to track fields like this – PowerWorld has entire set of Custom integers, floats,

string, memos user can populate (this available • PSS/E data definitions do not include these, though

Base Case Coordination system did add additional structures to store these

• For purposes of this rough draft presentation, we’ll put this in the parking lot for future discussion


Shunts • PSLF support up to 4 owners • PSS/E ownership is inherited from terminal bus • PowerWorld Version 19 supports up to 4 owners (previously it was inherited from bus)

GE PSLF PTI PSS/E PowerWorld Simulator

Controllable Shunt

SVD (Multiple allowed per bus)

Switched Shunt (Only one allowed per bus)

Switched Shunt Control Mode = Fixed, Discrete, or Continuous Multiple allowed per bus (coordinated in version 16)

Fixed Bus Shunt SHUNT (Multiple allowed per bus)

Fixed Bus Shunt (multiple allowed per bus)

Switched Shunt Control Mode = Bus Shunt (multiple allowed per bus)

Fixed Line Shunt SHUNT Assigned to a line. IDs must start with an f or t

No special record. Fields with AC Line GI, BI, GJ, BJ specify the total at each end

Line Shunt Each end of a line can have multiple shunts. IDs assigned for multiple shunts.

G and B for equiv None None Bus fields Nom G Shunt and Nom B Shunt


Coordinated Switched Shunt Control

• Starting in Simulator Version 16 in 2010, PowerWorld has supported having multiple switched shunts on the bus (or buses connected by low impedance branches) that regulate the same point in the electrical network – This occurs automatically when shunts share the same

regulated bus (or buses in a group of buses connected by low impedance branches)

– Requires extra parameter with shunt (RegFactor) • PowerWorld has forwarded information on how

this works to WECC staff who has forwarded this to the PSLF software team

• PSS/E does not allow multiple controllable shunts at the same bus at all


Load Distribution Equivalent and Load Characteristic

• PSLF merges these 2 concepts in one string the “LongID”

• PowerWorld has two separate fields – Load Model Group

• Each load can be assigned to one of these as a container to which it’s transient stability model is assigned

– Distribution Equivalent • Specifies the distribution equivalent independently

• PSS/E does not have this concept


Branch Differences (both AC lines and transformers) • Branch Ratings

– PSLF allows 8 line MVA ratings – PSS/E allows 12 line MVA ratings – PowerWorld allows 15 line MVA ratings

• This starts to get silly… • Owners

– PSLF allows 8 owners – PSS/E allows 4 owners – Simulator Version 19 allows 8 owners (previously 4)

• Status/ByPass – PSLF has a Status flag (0 = OPEN, 1 = CLOSED, 2 = BYPASSED) – PSS/E has only a Status flag (0 or 1)

• To allow bypass you either change impedance of branch • Or put in another branch in parallel (I would recommend)

– Simulator has 2 flags • Status = OPEN or CLOSED • Bypassed = Bypassed or Not Bypassed


Transformer Differences

• Fixed Taps – PSS/E does not support a fixed tap definition on the same

side as the variable tap (FROM), thus Fixed tap is always assumed as 1.00 • The fixed tap is just added to the variable tap, so having a fixed tap

on the side with a variable tap is not completely necessary • Intermediate Star Bus of 3-winding transformer

– PSS/E does not specify this bus explicitly. The voltage and angle at this point are part of the transformer record.

– PSLF and Simulator specify this point explicitly in Bus table • 3-winding transformer without the tertiary

– PSS/E does not allow the tertiary to be excluded – PSLF allows a tertiary bus number of zero (0) – Simulator supports both, but we do not consider excluding

the tertiary to be good practice • When writing to a RAW file, if the tertiary is missing, then we

write the transformer as two 2-winding transformers.


Transformer Differences

• Magnetizing Impedance – In PSLF this is split equally between the From and

To bus of the transformer – In PSS/E and PowerWorld this is all placed on the

From Bus of the transformer • Line Drop Compensation

– In PowerWorld Simulator Rcomp and Xcomp can be specified with a transformer to use line drop compensation which is then used in the power flow solution

– PSLF has this input data. Not sure if it’s used. – PSS/E RAW file does not have this input data


Multi-Section Lines

• Generally, a multi-section line must be strictly a series of AC branches – Intended to represent breaker configurations that require

all branches to go out-of-service together – Helps with modeling series capacitors and reactors

• Intermediate buses – In PSLF, intermediate buses are not defined in the EPC

format and thus loads, generators, and shunts at these points are not allowed

– In Simulator and PSS/E, the intermediate buses are specifically identified and thus loads, generators, and switched shunts can be connected at these points • In Simulator when writing out to an EPC file, the multi-section

line record is ignored if intermediate buses have objects • This is actually very common in ERCOT


What is a “Line” and what is a “Multi-Section Line”?

• PSLF calls this entire thing “line” • PSLF calls the pieces a “section”

• PowerWorld and PSS/E call these lines

• A separate “multi-section line” aggregation is made

Loads

• Intermediate Buses are included in the bus table

• Gens, Loads, and Shunts at intermediate buses is allowed

• Intermediate Buses are NOT in the bus table

• Gens, Loads, and Shunts at intermediate buses is NOT allowed

Definitions Implications


Area/Zones for Shunt Objects

• PSLF and Simulator allow Generators, Loads, and Switched Shunts to have a different area or zone than the terminal bus. PSS/E only allows this for Loads. – These objects are then treated as tie-lines in area and

zone interchange calculations – PSS/E has a special solution option to specify whether

to include the interchange as “LINES ONLY” or “LINES AND LOADS”. Simulator and PSLF always use Lines and Loads.

• PSLF also allows area and zone designations for specific branches and transformers – Simulator reads this into special EPC file fields but does

not use them for anything


BalancingAuthority

• Balancing Authorities are something new in PSLF and PowerWorld Simulator Version 19 – Functionality is identical to an Area – It’s essentially an alternate set of Area

designations


Area MW Transactions

• In Simulator two settings specify the scheduled export for each area with the scheduled export being the SUM of all of these. – MW transaction records (bilateral transactions) – Area record’s Unspecified MW Interchange

• Tables showing Transactions are included in both the PSLF EPC and PSS/E RAW file formats – Scheduled values in those tables are informational only – Both PSLF and PSS/E do NOT use these MW Transactions in

their power flow solutions – Instead, each program has a net MW export with each area – Simulator handles this when reading from those formats

and the Unspecified MW Interchange in Simulator is assigned as the “left-over” which isn’t included in the transactions table.


DC Lines

• In PSS/E and Simulator, there are distinct container objects for both a two-terminal DC line and a multi-terminal DC line (MTDC) – Within a particular MTDC there are then DC Buses, AC/DC

Converter and DC Line objects • In PSLF, there are only definitions of the DC Buses,

AC/DC Converter and DC Line objects – The groupings are then determined by the topology of the

DC line links • File format issue

– PSS/E requires that all DC buses of a particular MTDC grouping be numbered from 1 to the number of DC buses

– PSLF requires that all DC buses throughout the entire model have a unique DC bus number

– Simulator must support this when reading/writing


What is a Multi-Terminal DC Line? “Device” or “Network”

• It’s a very special “Device” connected to the AC system – This is how PSS/E looks at it – PowerWorld has some flavor of this as well as we

require you to assign each MTDC Bus, Converter and Line to a particular “MTDCRecord”

• It’s just additional parts of the model with objects DC Bus, DC Converter and DC Line – This is how PSLF looks at it – PowerWorld has some flavor of this as well as we

maintain the DC Bus, Converter and Line as separate objects in the data structure


Interfaces

• PSLF supports the definition of an interface as a group of AC lines (or Multi-Section lines)

• Simulator supports numerous interface elements – AC Branch, Multi-Section Line, Area-To-Area, Zone-To-Zone,

DC Line, Injection Group, Generator, Load, or another interface

– Simulator also supports “contingent interfaces” which include a specific line outage or insertion

• PSS/E has a monitor functionality (MON file) which allows definition of an interface which includes AC branches and Line Open or Close contingent elements

• The term “Flowgate” is often used, especially in relation to contingent-interfaces in the Eastern United States


Injection Groups

• Simulator supports the definition of an injection group which represents a group of generators, loads, or switched shunts – Can be used for summary calculations, sensitivity-based

calculations, or as a source and sink for a transfer (think PV curve)

– Injection group can also contain another injection group – Used extensively in Contingency Actions that are used for

model RAS • PSS/E has a concept called a “subsystem” which you

may find in a SUB file which is somewhat similar • In PSLF a user-written EPCL would be required

– PSLF is being paid by WECC to implement this feature as part of their contract to model RAS


Substations

• In Simulator, each bus can be optionally assigned to a substation – Feature was added in May 2000 – Useful in one-line diagram creation – Needed to support EMS-based full-topology

models – Specify a latitude/longitude with each substation – By default the substation is unassigned

• PSLF and PSS/E latest versions have begun to support substations – Necessary for GIC modeling


Super Areas

• In Simulator, Super Area objects can be created and each area can be assigned to one super area – Useful in studying groups of areas that are

dispatched together (Electricity Markets)

• PSLF and PSS/E do not support


Nomograms

• In Simulator, Nomogram objects can be created which specify two interfaces and then a two-dimensional limit region – Nomogram limit violations can then be

monitored or enforced in Contingency Analysis, ATC, OPF and SCOPF studies

• PSLF and PSS/E do not support

Documents

Differences in Steady State Power Data Definitions Data Structure Differences.pdf · switched shunts on the bus (or buses connected by low impedance branches) that regulate the same