A generator EMT model, checked against site measurements.
For a synchronous generation plant we built the full PSCAD model: generator, excitation system, stabiliser and protection. Then we checked it against measurements from the real machines and against the system operator’s EMT model checklist.
- No.
- 02
- Client
- Confidential generation operator
- Plant
- Synchronous generators
- Scope
- EMT model, validation and compliance evidence
- Tools
- PSCAD/EMTDC, PowerFactory
- Standard
- System operator EMT model checklist
- Result
- 7 of 7 basic checks met
Every part that shapes the transient response.
The machine data came from the operator’s PowerFactory model. The excitation system, stabiliser and protection had no equivalent there, so we built them in PSCAD from the manufacturer’s data sheets. Pick a part to see where it sits in the model.
Swipe to see it all
Synchronous machine
Each unit’s electrical and mechanical behaviour: voltages, currents, flux, inertia and damping, with saturation from the magnetising curve. The parameters came from the operator’s PowerFactory model, so the two models agree.
- Electrical and mechanical
- Inertia and damping
- Saturation on
- Multi-mass ready
Excitation system (AVR)
Built from the manufacturer’s control diagram, including the inner field-current loop and the field-voltage limits. The gains match the supplied controller data, and they decide how fast terminal voltage recovers after a disturbance.
- Voltage regulator
- Field-current loop
- Field-current limiter
- Tuned per machine
Power system stabiliser
A dual-input stabiliser using speed and electrical power, with washout, filter and lead-lag stages. It only switches on above a set MW output, and it damps electromechanical oscillations.
- Speed and power inputs
- Lead-lag
- Output limits
- MW threshold
Excitation limiters
Under- and over-excitation limiters cap what the AVR can ask of the field. They sit inside the regulator logic and pull field voltage back whenever a limit is reached.
- UEL
- OEL
- Inside the AVR
Protection
A protection module we wrote in PSCAD: two stages each of over- and under-voltage and over- and under-frequency, plus over-flux (V/Hz). Each stage has its own threshold and delay and trips the breaker, so the model trips when the real relay would.
- OV and UV, 2 stages
- OF and UF, 2 stages
- V/Hz
- Settable delays
Transformers and grid
Two-winding step-up transformers with their vector group, impedance and saturation, which the checklist asks for. The grid is a Thévenin source, run at both weak and strong settings.
- Saturation on
- Thévenin source
- Weak and strong grid
Connection point and FFCI
A measurement block at the point of interconnection works out P, Q, V, f and the positive-sequence currents. It also plots the reactive current that shows fast fault current injection (FFCI).
- P · Q · V · f
- Positive-sequence currents
- FFCI plot
Two checks. The second one against the real machines.
- 01
PSCAD against PowerFactory
With the controls switched off, we applied a 100 ms three-phase fault on the transformer HV side in both tools. Matching responses show the machine model is right before any controls go on top.
Machine model matches - 02
PSCAD against site measurements
With the controls on, we laid terminal voltage, field current, field voltage, P and Q from the model over recordings from the real units at several operating points.
Model follows the plant
Pick a test to see the response.
All seven basic checks met.
The system operator’s EMT model checklist has seven basic checks. This is how the model meets each one.
FFCI is shown by the connection-point measurement block. The detailed checks follow once the basic checks are accepted, and the model is set up so a governor can be added later for frequency-response work.
- 01Met
Recognised EMT software
Delivered in PSCAD/EMTDC v5, the tool the system operator specifies, ready to open and run.
- 02Met
Plant, controls and protection
Generator, AVR, stabiliser, limiters and protection for every unit, not just the machine.
- 03Met
Three-phase EMT model
All three machines and their step-up transformers, in full three-phase detail.
- 04Met
Transformer saturation on
The step-up transformers are modelled with saturation enabled.
- 05Met
Runs at a 10 µs time step
The time step can be set anywhere from 10 to 50 µs.
- 06Met
Initialises on its own
It starts from the user’s terminal conditions, well inside the required time.
- 07Met
Model, guide and report
A runnable model, a user guide to the control blocks, and a report covering both validation stages.