Custom Governor Models

This page documents the custom turbine-governor (tor_) models in RAMSES. These models are implemented in Fortran using the legacy multi-subroutine API and cover a wide range of prime-mover types: thermal (steam), gas turbine, hydraulic, nuclear, and simplified equivalents.

Governor/torque models in RAMSES are defined as sub-records within a SYNC_MACH block using the TOR keyword, followed by the model name and its parameters. They are not standalone records. The TOR line appears after the EXC (exciter) line, and the ; at the end closes the entire SYNC_MACH block.

SYNC_MACH name bus FP FQ P Q SNOM Pnom H D IBRATIO
                    XT  Xl  Xd  X'd  X"d  Xq  X'q  X"q  m  n  Ra  T'do  T"do  T'qo  T"qo
              EXC model_name  param1  param2  ...
              TOR model_name  param1  param2  ... ;

tor_constant

Scientific Description

The tor_constant model provides a constant mechanical torque source. The mechanical torque is fixed at its initialisation value and does not respond to speed deviations or load changes:

T_m(t) = T_{m0} \quad \forall t

The single algebraic state satisfies:

f(1) = x(1) - T_{m0} = 0

The observable output is mechanical power:

P_m = T_m \cdot \omega

Implementation details:

nbxvar = 1, nbzvar = 0, nbdata = 0
One additional parameter: prm(1) = Tm0 (set at initialisation from load-flow)
Observable: Pm = x(1) * omega

Parameters

Parameter	Description
(none)	No user-supplied parameters. $T_{m0}$ is taken from the load-flow initialisation.

SYNC_MACH g6  g6  1. 1.  0.  0.   400. 360. 6. 0. 2.05
                    XT   0.15  2.2  0.3    0.2   2.   0.4  0.2  0.1  6.0257  0.  7.00  0.05  1.5  0.05
              EXC GENERIC1   3.0618 -0.1  1.  0.  100. -1. -20.0  10.  120. 5.  12.5 0.1  0.  5.
                                1     75.   15.    0.22    0.012     0.22    0.012    -0.1    0.1
              TOR CONSTANT ;

Useful for machines operating at fixed setpoint, for testing generator models in isolation, or as a placeholder.
The mechanical power observable $P_m = T_m \cdot \omega$ will vary slightly with speed changes.
TOR CONSTANT takes no parameters — $T_{m0}$ is set automatically from the load-flow initialisation.

tor_1storder

Scientific Description

The tor_1storder model is a first-order speed governor with droop and a two-mass (HP/LP) turbine representation. It captures the primary frequency response through a proportional-droop speed controller with a first-order lag.

Speed controller with droop $R$ :

The mechanical torque setpoint is:

T_{set} = T_{m0} - \frac{\omega - 1}{R}

The HP torque tracks $T_{set}$ through a first-order lag with time constant $T_2$ :

\frac{d x_1}{dt} = \frac{1}{T_2}\left(T_{set} - x_1\right)

The LP (shaft) torque is a weighted combination:

x_2 = (1 - F_{HP}) \cdot x_1 + F_{HP} \cdot T_{set}

where $F_{HP}$ is the fraction of power generated in the HP stage.

From the Fortran equations:

f(1) = (-x(1) + (prm(4) - (omega-1.d0)/prm(3))) / prm(2)
f(2) = (1.d0-prm(1))*x(1) + prm(1)*(prm(4)-(omega-1.d0)/prm(3)) - x(2)

i.e.:

prm(1) = FHP (HP fraction), prm(2) = T2 (time constant), prm(3) = R (droop)
prm(4) = Tm0 (setpoint, set at init)

Implementation details:

nbxvar = 2, nbzvar = 0, nbdata = 3
State 1 = HP torque x(1), State 2 = LP torque x(2)
Observables: HP torque, LP torque

Parameters

Parameter	Description
`FHP`	Fraction of torque produced by the HP turbine stage (0–1)
`T2`	Governor/HP turbine time constant (s)
`R`	Speed droop (pu/pu)

Usage Example

RAMSES Data File
Notes

SYNC_MACH g1  g1  1. 1.  0.  0.   800. 760. 3. 0. 0.95
                    XT   0.15  1.1  0.25   0.2   0.7   *   0.2  0.1  6.0257  0.  5.00  0.05  *  0.1
              EXC GENERIC1   1.8991 -0.1  0.  1.  100. -1. -11  10.  70.  10.  20. 0.1  0.  4.
                                1     75.   15.    0.2    0.01     0.2    0.01    -0.1    0.1
              TOR 1STORDER  0.30  0.50  0.05 ;  ! FHP  T2  R

FHP = 0 makes the model a pure first-order lag on the total torque.
FHP = 1 bypasses the HP lag entirely; the torque instantly tracks the droop setpoint.
Typical primary-frequency response studies use R = 0.04–0.05.

tor_thermal_generic1

Scientific Description

The tor_thermal_generic1 model is a generic multi-stage steam turbine governor, suitable for both single-shaft and cross-compound units. It includes a speed controller with rate-limiting, a three-section steam chest/reheater, and separate HP, MP, and LP turbine stages.

Speed governor:

A speed measurement with time constant $T_{mes}$ feeds a droop-based error:

e_{gov} = P_0 - P_{meas} \cdot \sigma + (1 - \omega)

where $\sigma$ is the droop coefficient.

The gate/valve demand is computed by an integrator with rate limits $[zdot_{min},\, zdot_{max}]$ and position limits $[z_{min},\, z_{max}]$ , filtered through a servo time constant $T_{sm}$ .

Turbine power stages:

The steam chest dynamics drive three stages with power fractions $F_{hp}$ , $F_{mp}$ , $(1-F_{hp}-F_{mp})$ :

\frac{d T_{mHP}}{dt} = \frac{1}{T_{hp}}(F_{hp} \cdot z - T_{mHP})

\frac{d T_{mMP}}{dt} = \frac{1}{T_r}(F_{mp} \cdot T_{mHP}/F_{hp} - T_{mMP})

\frac{d T_{mLP}}{dt} = \frac{1}{T_{lp}}((1-F_{hp}-F_{mp}) \cdot T_{mMP}/F_{mp} - T_{mLP})

Total mechanical power:

P_m = T_{mHP} + T_{mMP} + T_{mLP}

Parameters from Fortran associate block:

Parameter	Index	Description
`sigma`	1	Speed droop (pu/pu)
`Tmes`	2	Speed measurement time constant (s)
`Tsm`	3	Servo/gate time constant (s)
`zdotmin`	4	Minimum gate rate (pu/s) — also additional parameter
`zdotmax`	5	Maximum gate rate (pu/s)
`zmin`	6	Minimum gate opening (pu)
`zmax`	7	Maximum gate opening (pu)
`Thp`	8	HP turbine time constant (s)
`Fhp`	9	HP power fraction
`Tr`	10	Reheater / MP time constant (s)
`Fmp`	11	MP power fraction
`Tlp`	12	LP turbine time constant (s)

Implementation details:

nbxvar = 10, nbzvar = 2, nbdata = 12, nbaddpar = 2
Additional: prm(13) = P0 (initial power), prm(14) = ivo (initial valve opening)
Observables: z, PmHP, PmMP, PmLP, Pm

Usage Example

RAMSES Data File
Notes

SYNC_MACH g1  g1  1. 1.  0.  0.   800. 760. 3. 0. 0.95
                    XT   0.15  1.1  0.25   0.2   0.7   *   0.2  0.1  6.0257  0.  5.00  0.05  *  0.1
              EXC GENERIC1   1.8991 -0.1  0.  1.  100. -1. -11  10.  70.  10.  20. 0.1  0.  4.
                                1     75.   15.    0.2    0.01     0.2    0.01    -0.1    0.1
              TOR THERMAL_GENERIC1  0.05  0.02  0.20  -0.10  0.10  0.0  1.05  0.30  0.30  7.0  0.40  0.50 ;
              !                     sigma Tmes  Tsm  zdotmin zdotmax zmin zmax  Thp   Fhp   Tr   Fmp   Tlp

The LP fraction is 1 - Fhp - Fmp; ensure Fhp + Fmp ≤ 1.
Set Tmes = 0 to bypass the speed measurement filter (instantaneous speed sensing).
Rate limits zdotmin/zdotmax are critical for AGC studies.

tor_hydro_generic1

Scientific Description

The tor_hydro_generic1 model is a generic hydraulic turbine governor with a penstock (water column) and PI controller. It implements the standard hydraulic governor structure following IEEE Std 1110 conventions.

PI speed governor:

The speed error with droop $\sigma$ :

e = (P_0 - P_{meas}) \cdot \sigma + (1 - \omega)

A PI controller with gains $K_P$ and $K_I$ drives the gate demand:

\dot{x}_{I} = K_I \cdot e

z_{demand} = K_P \cdot e + x_I

The gate is rate-limited by $LIM_{\dot{z}}$ and position-limited by $[0, 1]$ , with a servo time constant $T_{sm}$ .

Water column (penstock):

The flow $Q$ and head $H$ are related by the water-starting time $T_W$ :

T_W \cdot \frac{dQ}{dt} = H - 1

The head is:

H = \left(\frac{Q_{v} + T_m (1 - Q_v)}{z}\right)^2

where $Q_v$ is the no-load flow fraction.

Turbine mechanical torque:

T_m = \sqrt{H} \cdot (Q - Q_v \cdot \sqrt{H})

P_m = T_m \cdot \omega

Parameters from Fortran associate block:

Parameter	Index	Description
`SIGMA`	1	Speed droop (pu/pu)
`Tmes`	2	Speed measurement time constant (s)
`Qv`	3	No-load water flow fraction (pu)
`KP`	4	PI proportional gain
`KI`	5	PI integral gain
`TSM`	6	Gate servo time constant (s)
`LIMZDOT`	7	Gate velocity limit (pu/s)
`TW`	8	Water starting time (s)

Implementation details:

nbxvar = 6, nbzvar = 2, nbdata = 8, nbaddpar = 1
Additional: prm(9) = P0 (initial electrical power)
Observables: z, Q, H, Pm

Usage Example

RAMSES Data File
Notes

SYNC_MACH g1  g1  1. 1.  0.  0.   800. 760. 3. 0. 0.95
                    XT   0.15  1.1  0.25   0.2   0.7   *   0.2  0.1  6.0257  0.  5.00  0.05  *  0.1
              EXC GENERIC1   1.8991 -0.1  0.  1.  100. -1. -11  10.  70.  10.  20. 0.1  0.  4.
                                1     75.   15.    0.2    0.01     0.2    0.01    -0.1    0.1
              TOR HYDRO_GENERIC1  0.04  2.0  0.  2.00  0.40  0.2  0.1  1.0 ;
              !                   SIGMA  TP  Qv   KP    KI   TSM LIMZDOT TW

TW (water-starting time) is the most influential parameter; typical values are 0.5–3 s.
Increase KP / KI carefully: large values can cause governor instability with high TW.
Qv = 0 assumes no no-load losses.
Parameters follow the order in dyn_A.txt: SIGMA TP Qv KP KI TSM LIMZDOT TW.

tor_gasturbm

Scientific Description

The tor_gasturbm model is a gas turbine governor following a multi-stage combustion model. It captures the compressor, fuel system, combustion chamber delay, and turbine torque characteristic. The name suffix m indicates a modified version.

Speed governor:

The governor error drives a PI controller producing a fuel demand signal. The speed governor uses:

e_{gov} = (\omega_{ref} - \omega) / TDSP - STAT \cdot P_{elec}

with saturation limits $[MIN,\, MAX]$ .

Fuel system and combustion:

The fuel valve position g1 is driven through:

A speed governor with gain $ZZ$ and lead–lag time constants determined by $XX$ , $YY$
A fuel flow path through first-order lag $TVALVE$
Combustion chamber lag $TGAZ$

Turbine output:

The turbine mechanical power follows:

P_m = BF2 \cdot g_{comb} + AF2

where $g_{comb}$ is the combustion output through lag $TCD$ .

Additional thermodynamic correction terms involve $TF$ (flame lag) and $ECR$ (exhaust correction ratio).

Parameters from Fortran source (prm array):

Index	Name	Description
1	`TDSP`	Speed droop time constant (s)
2	`STAT`	Steady-state gain
3	`ZZ`	Governor proportional gain
4	`XX`	Lead numerator factor
5	`YY`	Lag denominator factor
6	`SACC`	Acceleration constant
7	`MIN`	Minimum fuel valve position (pu)
8	`MAX`	Maximum fuel valve position (pu)
9	`TVALVE`	Fuel valve time constant (s)
10	`TGAZ`	Combustion chamber time constant (s)
11	`TF`	Flame lag time constant (s)
12	`ECR`	Exhaust correction ratio
13	`TCD`	Compressor discharge time constant (s)
14	`BF2`	Turbine power output slope
15	`AF2`	Turbine power output intercept (pu)

Implementation details:

nbxvar = 10, nbzvar = 4, nbdata = 15, nbaddpar = 1
Additional: prm(16) = SETPOINT (initialised from load-flow power)
Observables: g2, x4, g1

Usage Example

RAMSES Data File

SYNC_MACH g1  g1  1. 1.  0.  0.   800. 760. 3. 0. 0.95
                    XT   0.15  1.1  0.25   0.2   0.7   *   0.2  0.1  6.0257  0.  5.00  0.05  *  0.1
              EXC GENERIC1   1.8991 -0.1  0.  1.  100. -1. -11  10.  70.  10.  20. 0.1  0.  4.
                                1     75.   15.    0.2    0.01     0.2    0.01    -0.1    0.1
              TOR GASTURBM  0.05  1.0  25.0  0.50  1.0  1.0  0.0  1.0  0.05  0.40  0.01  0.0  0.20  1.0  0.0 ;
              !              TDSP STAT  ZZ    XX   YY  SACC MIN  MAX TVALVE TGAZ   TF   ECR   TCD  BF2  AF2

tor_govclasm

Scientific Description

The tor_govclasm model is a classical thermal governor with a composite control law including deadband, droop, integral control, and combustion dynamics. The name stands for “governor classical model”.

Speed governor with deadband and droop:

The speed error passes through a deadband $[DBON, DEADB]$ before entering a proportional–integral controller. The integral path has saturation at $MAXINT$ and gain $ALPHA$ . The reset time $TRES$ determines the integration rate.

Valve and combustion dynamics:

The valve demand passes through:

A governor with static gain $V0$ and fuel-flow limit $VFN$
A first-order lag $TFV$ (valve actuator)
A rate limiter $[PVARMIN,\, PVARMAX]$ (with gain $GPVAR$ ) representing fuel response
A combustion/steam chest lag $KCR$ , $TCR$ producing fuel flow
Lower bound: $MINFUEL$
Transport delay $TDELAY$ (approximated)
Turbine output through lag $TCH$ with limits $[PMIN,\, PMAX]$

Parameters from Fortran source (prm array):

Index	Name	Description
1	`STAT`	Governor static characteristic selector
2	`DEADB`	Deadband half-width (pu)
3	`DBON`	Deadband onset (pu)
4	`TSM`	Speed measurement / filter time constant (s)
5	`V0`	Governor voltage reference (pu)
6	`VFN`	Fuel-flow nominal (pu)
7	`TFV`	Valve actuator time constant (s)
8	`VFR`	Fuel flow rate limit (pu/s)
9	`MAXINT`	Maximum integral output (pu)
10	`ALPHA`	Integral controller gain
11	`TRES`	Integral reset time (s)
12	`GOMP`	Governor proportional gain
13	`PVARMAX`	Maximum power variation rate (pu)
14	`PVARMIN`	Minimum power variation rate (pu)
15	`GPVAR`	Power variation gain
16	`KCR`	Combustion gain
17	`TCR`	Combustion time constant (s)
18	`MINFUEL`	Minimum fuel flow (pu)
19	`TDELAY`	Combustion transport delay (s)
20	`PMAX`	Maximum turbine output (pu)
21	`TCH`	Steam chest / turbine lag (s)
22	`PMIN`	Minimum turbine output (pu)

Implementation details:

nbxvar = 6, nbzvar = 10, nbdata = 22, nbaddpar = 1
Additional: prm(23) = P0 (initialised from load-flow power)
Observables: x2, b3, b4

Usage Example

RAMSES Data File

SYNC_MACH g1  g1  1. 1.  0.  0.   800. 760. 3. 0. 0.95
                    XT   0.15  1.1  0.25   0.2   0.7   *   0.2  0.1  6.0257  0.  5.00  0.05  *  0.1
              EXC GENERIC1   1.8991 -0.1  0.  1.  100. -1. -11  10.  70.  10.  20. 0.1  0.  4.
                                1     75.   15.    0.2    0.01     0.2    0.01    -0.1    0.1
              TOR GOVCLASM  1.0  0.003  0.001  0.10  1.0  1.0  0.30  0.5  1.0  1.0  5.0  25.0  0.10  -0.10  0.05  1.0  0.20  0.05  0.30  1.05  0.30  0.05 ;
              !              STAT DEADB  DBON   TSM   V0  VFN   TFV  VFR MAXINT ALPHA TRES  GOMP PVARMAX PVARMIN GPVAR KCR  TCR MINFUEL TDELAY PMAX  TCH  PMIN

tor_govhydr

Scientific Description

The tor_govhydr model is a simplified hydraulic governor with PI control and a non-linear penstock. It differs from tor_hydro_generic1 in its simplified turbine characteristic and simpler water-column formulation.

PI governor:

\dot{x}_2 = K_I \cdot e, \quad x_2 \in [0, 1]

z_{demand} = K_P \cdot e + x_2

where the speed error $e = P_0/\omega - T_m - \omega \cdot STAT + \ldots$ accounts for the droop and steady-state bias.

Penstock (two-lag water column):

T_{CE1} \cdot \frac{dx_3}{dt} = P - x_3(1 + T_{CE2}/T_{CE1})

The turbine mechanical power is computed via an empirical quadratic:

P_m = 1.35 \cdot z - 0.7 z^2

derived from the non-linear head-flow curve approximated at initialisation.

Parameters from Fortran source:

Index	Name	Description
1	`STAT`	Steady-state gain selector
2	`KP`	Proportional gain
3	`KI`	Integral gain
4	`TC`	Governor/servo time constant (s)
5	`V0`	Reference voltage (pu)
6	`VF`	Flow gain
7	`TCE2`	Second penstock time constant (s)
8	`TCE1`	First penstock time constant (s)

Implementation details:

nbxvar = 4, nbzvar = 4, nbdata = 8, nbaddpar = 1
Additional: prm(9) = P0 (initialised from load-flow power)
No observables defined (nbobs = 0)

Usage Example

RAMSES Data File
Notes

SYNC_MACH g1  g1  1. 1.  0.  0.   800. 760. 3. 0. 0.95
                    XT   0.15  1.1  0.25   0.2   0.7   *   0.2  0.1  6.0257  0.  5.00  0.05  *  0.1
              EXC GENERIC1   1.8991 -0.1  0.  1.  100. -1. -11  10.  70.  10.  20. 0.1  0.  4.
                                1     75.   15.    0.2    0.01     0.2    0.01    -0.1    0.1
              TOR GOVHYDR  1.0  2.0  0.5  0.10  1.0  1.0  1.0  5.0 ;
              !             STAT  KP   KI   TC   V0   VF  TCE2 TCE1

TCE1 corresponds roughly to the water-starting time $T_W$ .
TCE2/TCE1 sets the ratio of the two penstock lags.

tor_govnuc

Scientific Description

The tor_govnuc model is a nuclear plant governor with deadband, droop, integral control, and a non-linear turbine characteristic via GOMP (the gain of the output multiplier). It is structurally similar to tor_govclasm but tailored for the slower, tightly-regulated dynamics of nuclear steam supply systems.

Speed governor:

The speed error passes through a deadband $[DBON, DEADB]$ :

e = \text{deadband}(\omega_{ref} - \omega) - STAT \cdot (P - P_0)

The error enters an integrator with rate limits $[GRADMIN, GRADMAX]$ (pu/s) filtered through a ramp time $TGRAD$ . The integrator output $x_I$ passes through a servo $TSM$ .

Turbine characteristic with GOMP:

The turbine output is non-linearly mapped through a gain $GOMP$ :

P_m = \min\!\left(\frac{x_I}{GOMP},\, 1\right) \cdot f(x_I)

where the limiter prevents over-power and $f$ is a piecewise-linear characteristic.

The fuel valve dynamics use time constants $TFV$ (valve), $V0$ (reference), and $VFR$ (flow rate), then go through lag $TRES$ (reset) and $GOMP$ to produce the final torque.

Parameters from Fortran source:

Index	Name	Description
1	`STAT`	Governor static characteristic selector
2	`DEADB`	Deadband half-width (pu)
3	`DBON`	Deadband onset (pu)
4	`GRADMAX`	Maximum load gradient (pu/s)
5	`GRADMIN`	Minimum load gradient / unloading rate (pu/s)
6	`TGRAD`	Ramp filter time constant (s)
7	`TSM`	Servo time constant (s)
8	`V0`	Governor reference (pu)
9	`VFN`	Nominal valve position (pu)
10	`TFV`	Valve actuator time constant (s)
11	`VFR`	Valve rate limit (pu/s)
12	`ALPHA`	Integral gain
13	`TRES`	Reset time constant (s)
14	`GOMP`	Output power gain

Implementation details:

nbxvar = 4, nbzvar = 8, nbdata = 14, nbaddpar = 1
Additional: prm(15) = P0 (initialised from load-flow power)
Observable: TM

Usage Example

RAMSES Data File
Notes

SYNC_MACH g1  g1  1. 1.  0.  0.   800. 760. 3. 0. 0.95
                    XT   0.15  1.1  0.25   0.2   0.7   *   0.2  0.1  6.0257  0.  5.00  0.05  *  0.1
              EXC GENERIC1   1.8991 -0.1  0.  1.  100. -1. -11  10.  70.  10.  20. 0.1  0.  4.
                                1     75.   15.    0.2    0.01     0.2    0.01    -0.1    0.1
              TOR GOVNUC  1.0  0.005  0.002  0.02  -0.02  10.0  5.0  1.0  1.0  0.50  0.10  1.0  20.0  1.0 ;
              !            STAT DEADB   DBON GRADMAX GRADMIN TGRAD TSM  V0  VFN   TFV   VFR ALPHA  TRES  GOMP

Nuclear plants typically have slow load-following characteristics: GRADMAX is typically 0.005–0.02 pu/s.
The DEADB is important to prevent hunting around the setpoint.
GOMP scales the turbine output; set to 1.0 for standard normalisation.