Disturbances

Disturbances define the sequence of events during a dynamic simulation. Disturbances need to have a continuity. All disturbance commands follow the format:

time(s) COMMAND parameters

Continue Solver

Defines solver settings. Must be the first line of the disturbance file:

time(s) CONTINUE SOLVER disc_meth max_h(s) min_h(s) latency(pu) upd_over

Discretization method (disc_meth):

• TR: Trapezoidal
• BE: Backward Euler
• BD: BDF2

Jacobian update override (upd_over):

• ALL: Force a full Jacobian refactorisation
• NET: Force a refactorisation of the network Jacobian
• ABL: Force an update of the injector Jacobian at every bus
• IBL: Force nothing in addition, but keep the bus Jacobian updates already requested by the other disturbances applied at this time instant
• NOT: Override, discarding even those; the bus Jacobian flags are restored to their values on entry

Example:

0.000 CONTINUE SOLVER BD 0.0200 0.001 0. ALL

Continue Display

Changes the sampling time step used for the output of observed variables from that point of the simulation onwards:

time(s) CONTINUE DISPLAY new_plot_step(s)

Example, reducing the output sampling to one point per second after $t = 20$ s:

20.000 CONTINUE DISPLAY 1.0

Stop

Signals the end of the simulation. Must be the last line:

time(s) STOP

Example:

100.000 STOP

Trip Line (BREAKER BRANCH)

Open or close breakers of a line:

time(s) BREAKER BRANCH name_of_line orig_break(0/1) extrem_break(0/1)

Example, opening both ends of a line at $t = 10$ s:

10.000 BREAKER BRANCH 1044-4032 0 0

Trip Machine / Injector

Open or close the breaker of a synchronous machine or injector:

time(s) BREAKER SYNC_MACH name_of_machine breaker(0/1)
time(s) BREAKER INJ name_of_injector breaker(0/1)

Example:

10.000 BREAKER INJ L_11 0

Trip Two-Port

Disconnect a two-port component (e.g. an HVDC link) at both ends. Only opening is supported, so the breaker status must be 0:

time(s) BREAKER TWOP name_of_twoport 0

Example:

10.000 BREAKER TWOP hvdc1 0

Three-Phase Short-Circuit (Impedance)

Apply a three-phase fault with specified impedance to ground. This requires two commands, one to apply the fault and one to clear it.

time(s) FAULT BUS name_of_bus rfault [xfault]
time(s) CLEAR BUS name_of_bus

The fault has an impedance of rfault + j*xfault to ground:

• rfault and xfault are in Ω
• If xfault is omitted, a fully resistive fault is assumed

Example, 100 ms bolted fault:

10.000 FAULT BUS 1044 0. 0.
10.100 CLEAR BUS 1044

Three-Phase Short-Circuit (Voltage)

Apply a fault where the post-fault voltage is specified. Internally, RAMSES creates a temporary shunt admittance $B_{fault}$ at the faulted bus and iteratively adjusts it using a secant method until the bus voltage matches the target value to within $\pm 0.5\%$. The injected currents are $i_x = B_{fault}\, v_x$ and $i_y = -B_{fault}\, v_y$. Up to 10 correction steps are attempted; if convergence is not reached, the simulation halts with an error message.

time(s) VFAULT BUS name_of_bus Voltage_after_fault(pu)
time(s) CLEAR BUS name_of_bus

Example, 100 ms fault with 0.5 pu residual voltage:

10.000 VFAULT BUS 1044 0.5
10.100 CLEAR BUS 1044

Note

Supported from version 3.13 onwards.

Change Parameters (CHGPRM)

Modify model parameters during the simulation.

Branch Parameters

time(s) CHGPRM BRANCH name_of_line MAGN/PHAN ±increment

Shunt Parameters

time(s) CHGPRM SHUNT name_of_shunt QNOM ±increment

The increment is in MVAr and is per-unitized internally by RAMSES.

Exciter Parameters

time(s) CHGPRM EXC name_of_equipment name_of_parameter ±increment [MVAr/%] duration(s)

Units: No unit = absolute, MVAr = per-unitized by $S_{nom}$, % = percentage of original.

Duration: 0 = step change, > 0 = ramp over given duration.

Example, ramp voltage setpoint by +10% over 10 seconds:

10.000 CHGPRM EXC g1 V0 +10 % 10

This means the parameter V0 of the exciter of synchronous machine g1 is ramped by +10% between 10 and 20 seconds.

Torque Controller Parameters

time(s) CHGPRM TOR name_of_equipment name_of_parameter ±increment [MW/%] duration(s)

Units: No unit = absolute, MW = per-unitized by $P_{nom}$ of the machine, % = percentage of original value.

Duration: 0 = step change, > 0 = ramp over given duration.

Example, ramp active power setpoint by +1 MW over 10 seconds:

10.000 CHGPRM TOR g1 P0 +1 MW 10

This means the parameter P0 of the torque controller of synchronous machine g1 is ramped by +1 MW between 10 and 20 seconds.

Injector / Two-Port / Discrete Controller Parameters

time(s) CHGPRM INJ/TWOP/DCTL name_of_equipment name_of_parameter ±increment [MW/MVAr/%/SETP] duration(s)

Units: No unit = absolute, MW or MVAr = per-unitized using the system’s $S_{base}$, % = percentage of original value, SETP = the increment is the new setpoint value.

Duration: 0 = step change, > 0 = ramp over given duration.

Example, load increase of 50% active and 30% reactive over 60 seconds:

10.000 CHGPRM INJ L_11 P0 +50 % 60
10.000 CHGPRM INJ L_11 Q0 +30 % 60

This means the parameter P0 (resp. Q0) of the injector L_11 is ramped by +50% (resp. 30%) between 10 and 70 seconds. If L_11 is a load model, this simulates a load increase.

Export Jacobian Matrix

time(s) JAC 'name_of_filename'

Required solver settings:

$OMEGA_REF SYN ;
$SCHEME IN ;

Export Load Flow Snapshot

Takes a snapshot and exports the load flow at a specific time:

time(s) LFRESV 'name_of_filename'

Next Steps

• Solver Settings, Configure time steps, tolerances, and parallelism
• PyRAMSES Examples. See complete simulation workflows in Python