Turbine-Governor (GGOV1)

GGOV1 general-purpose turbine-governor (IEEE PES-TR1). A speed-governing prime mover for the synchronous machine: it senses rotor speed ω and electrical power Pe and drives the machine's mechanical-torque input Tm. The full model includes a PID speed governor with selectable droop feedback (electrical power, valve stroke, governor output, or isochronous), a fuel-valve actuator with rate and position limits, a turbine with gain Kturb, lead-lag (1+sTc)/(1+sTb) and an optional transport delay Teng, plus two supervisory limiters — an acceleration limiter and a load (fuel-flow) limiter — combined with the governor through a low-value select so the most restrictive fuel command wins. Optional supervisory MW set-point control adjusts the load reference. Mechanical power Pmech = Kturb·(Wf − Wfnl) is converted to torque Tm = Pmech/ω at the output. Pairs with the synchronous machine for bumpless load-flow initialization: wire ω from the machine's speed output and Pe from its electrical-power output, and Tm back to the machine's Tm input. The right-edge ω / Pe (in) and Tm (out) ports line up with the machine's left-edge speed / Pe (out) and Tm (in) ports for a direct connection.

Category: Control / Governor

Overview

The GGOV1 general-purpose turbine-governor (IEEE PES-TR1, Dynamic Models for Turbine-Governors in Power System Studies) is the prime mover for a synchronous machine. It senses the rotor speed ω (and, for electrical-power droop, the machine's electrical-power output Pe) and drives the machine's mechanical-torque input Tm so the unit shares load and regulates frequency the way a real governed turbine does.

GGOV1 is deliberately broad: with one parameter set it represents a gas turbine, and with others a diesel or a simple steam unit. It pairs a PID speed governor (with selectable droop feedback) and a fuel-valve actuator with two supervisory limiters — an acceleration limiter and a load (fuel-flow) limiter — combined through a low-value select so the most restrictive fuel command always wins. With the optional load-flow auto-initialization (below) the whole speed-governor → turbine loop starts on its operating point, so a study begins in steady state with no torque transient.

Block diagram

Signal flow, block by block (per-unit, $s=\mathrm{d}/\mathrm{d}t$):

1. Speed error — the governor compares the load reference to the droop feedback and the speed deviation, with a deadband and error limits,

$$e=\mathrm{clamp}(P_{\text{ref}}-R{P}_{fb}-\mathrm{dbd}(\omega -1),e_{min},e_{max}),$$

where $P_{fb}$ is the droop feedback selected by Rselect (see below), $R$ is the permanent droop, and $\mathrm{dbd}$ is the optional ±db/2 deadband.

2. Governor PID — the fuel request from a parallel proportional-integral-derivative law,

$$f_{srn}=K_{pgov}e+\frac{K_{igov}}{s}e+\frac{s{K}_{dgov}}{1+s{T}_{dgov}}e.$$

Leave $K_{dgov}=0$ for the usual PI governor.

3. Acceleration limiter — an integrator that drives the fuel down when the rotor accelerates faster than aset,

$${\dot{f}}_{sra}=K_a(a_{set}-\frac{1}{1+s{T}_a}\dot{\omega }).$$

4. Load (fuel-flow) limiter — a PI loop holding the measured fuel flow at or below Ldref,

$$f_{srt}=K_{pload}\epsilon +\frac{K_{iload}}{s}\epsilon ,\epsilon =L_{dref}-\frac{1}{1+s{T}_{fload}}{W}_f.$$

5. Low-value select — the governor competes with the two limiters; the most restrictive wins,

$$f_{sr}=min(f_{srn},f_{sra},f_{srt}).$$

6. Fuel-valve actuator — a first-order lag with a rate limit $[R_{close},R_{open}]$ and a position limit $[V_{min},V_{max}]$,

$$\text{valve}=\mathrm{clamp}(\frac{1}{1+s{T}_{act}}{f}_{sr};\text{rate}\in [R_{close},R_{open}];\text{pos}\in [V_{min},V_{max}]).$$

7. Turbine — the fuel flow $W_f$ ( $=\text{valve}\cdot \omega$ when Flag = 1, else just the valve) drives the mechanical power through a gain, a lead-lag and an optional transport delay,

$$P_{mech}=e^{-s{T}_{eng}}\frac{1+s{T}_c}{1+s{T}_b}{K}_{turb}(W_f-W_{fnl})-D_m(\omega -1).$$

8. Output — mechanical power is delivered to the machine as torque,

$$T_m=\frac{P_{mech}}{\omega }.$$

Droop feedback (Rselect)

The permanent-droop feedback signal $P_{fb}$ is selectable, which sets how the unit shares load with others on the same network:

Rselect	Feedback $P_{fb}$	Use
Electrical power (Pe)	the transduced electrical power $\frac{1}{1+s{T}_{pelec}}{P}_e$	the usual choice — exposes the Pe input port
Valve stroke	the valve position	droop on actuator position
Governor output	the post-governor fuel request	droop on fuel demand
Isochronous (none)	$0$	a single unit holding system frequency (R has no effect)

With droop, the steady speed falls by $R$ (per-unit) from no-load to full-load, so $N$ parallel units share a load change in inverse proportion to their droops. An isochronous unit carries the whole frequency-regulation duty alone and must be the only governed unit on an island.

Acceleration and load limiters

Both supervisory limiters feed the low-value select, so they only act when they would command less fuel than the governor:

• The acceleration limiter caps the rate of rotor acceleration to aset — it protects the prime mover during a large under-frequency event by refusing to dump fuel in faster than the shaft can safely accelerate. Raise aset well above any expected acceleration to make it inactive.
• The load limiter is the temperature / fuel-flow ceiling of a gas turbine: it holds the measured fuel flow at or below Ldref. Raise Ldref above the operating fuel flow to keep it inactive.

Each limiter's integrator uses back-calculated anti-windup so it tracks the achievable fuel command instead of winding past it while the low-value select holds another path.

Per-unit convention

All power quantities — Pe, the mechanical power $P_{mech}$, the fuel flow $W_f$, the valve position and the limits — are per-unit on the machine's MVA base (the paired machine's S rated). $T_m=1.0$ pu is rated torque at synchronous speed. The machine's Tm input and Pe output use the same base, so the governor and machine plug together without any scaling. The speed ω and the deadband / droop are per-unit of synchronous speed.

Load-flow auto-initialization

The governor participates in the project's controller auto-initialization so a run starts bumpless. After the load-flow solves, the apply pass back-calculates the load reference and the integrator seeds so every derivative in the block diagram is zero at $t=0$:

• Pairing is wire-traced. The governor declares that its Tm output drives a machine shaft; the initializer follows that wire (through GoTo/From labels) to the unique synchronous machine whose Tm it feeds. If the output fans out to more than one machine, or an intermediate block sits in the path, initialization is skipped with a warning rather than guessing.

• The mechanical power matches the machine. $P_{mech}(0)$ is set to the same mechanical torque the paired machine derives from its load-flow operating point (shared back-calculation), and $P_e(0)$ to the machine's terminal real-power output.

• The fuel chain is inverted. From the steady turbine ($P_{mech0}=K_{turb}(W_{f0}-W_{fnl})$) the operating fuel flow, valve position and governor-output set-point are

$$W_{f0}=\frac{P_{mech0}}{K_{turb}}+W_{fnl},f_{sr0}=W_{f0},P_{\text{ref}}=R{P}_{fb0},$$

where $P_{fb0}$ is the operating-point droop feedback for the selected Rselect. The governor PI integrator, the valve, the turbine lead-lag, the transport-delay buffer and both limiter tracking states are seeded from these so the speed error is exactly zero and $T_m(0)=P_{mech0}$.

These quantities populate Pref, Pmech(0) and Pe(0) on the Initialization tab. You normally never type them by hand; set them only when using the governor standalone (driven by a constant speed), in which case choose them to start flat.

Wiring

• speed (ω) ← the synchronous machine's speed output (pu).
• Pe ← the synchronous machine's Pe output (electrical power, pu). Present only when Rselect = Electrical power.
• Tm → the synchronous machine's Tm input (mechanical torque, pu).

The governor sits to the left of the machine: its right-edge ω / Pe (in) and Tm (out) ports line up with the machine's left-edge speed / Pe (out) and Tm (in) ports, so the three wires draw straight across. Enable Monitor Pmech / valve / fuel request / measured power on the Monitoring tab to record those signals as named channels for plotting.

When to use something else

• A fixed mechanical drive (no speed governing): leave the machine's Tm unwired and use its constant tm0 fallback instead of a governor — appropriate when you only study the electrical / excitation side and the prime mover is assumed stiff.
• Detailed multi-shaft / hydro / boiler dynamics: GGOV1 is a general single-shaft model; a turbine with significant penstock-water-column (hydro), boiler-pressure or cross-compound dynamics needs a model tailored to that plant. GGOV1 covers the gas / diesel / simple-steam cases that dominate frequency-stability studies.

Ports

Name	Direction	Value type	Notes
speed	input	double
Pe	input	double	Visible when Rselect == 1
Tm	output	double

Parameters

Governor

Name	Label	Type	Default	Units	Description
Rselect	Droop feedback	enum (Electrical power (Pe) / Valve stroke / Governor output / Isochronous (none))	1	—	Signal fed back through the permanent droop R to form the speed-governing characteristic. Electrical power uses the machine's Pe output (the Pe input port appears); valve stroke and governor output use internal signals; isochronous removes the droop feedback (R has no effect) for a single unit holding frequency.
R	R (droop)	double	0.04	—	Permanent speed droop (pu). The steady speed/load characteristic: a 0.04 (4%) droop drops speed 4% from no-load to full-load. Ignored when the droop feedback is Isochronous.
Tpelec	Tpelec	double	1	s (s, ms)	Electrical-power transducer time constant 1/(1+sTpelec) on the Pe input (used for the electrical-power droop feedback).
Kpgov	Kpgov	double	10	—	Governor proportional gain.
Kigov	Kigov	double	2	—	Governor integral gain. The integral term removes steady speed error (within the droop characteristic).
Kdgov	Kdgov	double	0	—	Governor derivative gain. Set 0 to disable the derivative term (PI control).
Tdgov	Tdgov	double	1	s (s, ms)	Governor derivative-filter time constant of the sKdgov/(1+sTdgov) term.
maxerr	maxerr	double	0.05	—	Upper limit on the governor speed error (pu) entering the PID.
minerr	minerr	double	-0.05	—	Lower limit on the governor speed error (pu) entering the PID.
db	Deadband	double	0	—	Speed-error deadband (pu, total width). The governor ignores speed errors within ±db/2. Set 0 for no deadband.

Actuator & Turbine

Name	Label	Type	Default	Units	Description
Tact	Tact	double	0.5	s (s, ms)	Fuel-valve actuator time constant 1/(1+sTact).
Vmax	Vmax	double	1	—	Maximum valve position (pu).
Vmin	Vmin	double	0.15	—	Minimum valve position (pu).
Ropen	Ropen	double	0.1	—	Maximum valve opening rate (pu/s). Positive.
Rclose	Rclose	double	-0.1	—	Maximum valve closing rate (pu/s). Negative.
Kturb	Kturb	double	1.5	—	Turbine gain. Mechanical power Pmech = Kturb·(Wf − Wfnl).
Wfnl	Wfnl	double	0.187	—	No-load fuel flow (pu). The fuel needed to run the unloaded turbine at synchronous speed.
Tb	Tb	double	0.5	s (s, ms)	Turbine lag (denominator) time constant of the (1+sTc)/(1+sTb) block.
Tc	Tc	double	0	s (s, ms)	Turbine lead (numerator) time constant of the (1+sTc)/(1+sTb) block. Leave Tc = 0 (with Tb the dominant turbine lag) for a simple first-order turbine.
Teng	Teng	double	0	s (s, ms)	Transport delay (s) of the turbine, e^(−sTeng). Used for reciprocating (diesel) engines; leave 0 for gas / steam turbines (no delay).
Flag	Fuel vs speed	enum (Proportional to speed / Independent of speed)	1	—	Whether the fuel flow depends on speed. 'Proportional to speed' (Flag = 1) sets Wf = valve·ω (the usual gas-turbine case); 'Independent of speed' sets Wf = valve.
Dm	Dm	double	0	—	Mechanical damping / speed-sensitivity of the turbine power: Pmech is reduced by Dm·(ω − 1). Set 0 to disable.

Load Limiter

Name	Label	Type	Default	Units	Description
Ldref	Ldref	double	1	—	Load limiter reference (pu fuel flow). The load limiter holds the fuel flow at or below this value; raise it well above the operating fuel flow to keep the limiter inactive.
Kpload	Kpload	double	2	—	Load limiter proportional gain.
Kiload	Kiload	double	0.67	—	Load limiter integral gain.
Tfload	Tfload	double	3	s (s, ms)	Fuel-flow measurement lag 1/(1+sTfload) feeding the load limiter.

Acceleration Limiter

Name	Label	Type	Default	Units	Description
aset	aset	double	0.01	—	Acceleration limiter set-point (pu/s). When the rotor acceleration dω/dt exceeds aset the limiter reduces fuel through the low-value select; raise aset to effectively disable it.
Ka	Ka	double	10	—	Acceleration limiter integrator gain.
Ta	Ta	double	0.1	s (s, ms)	Acceleration measurement (derivative-filter) time constant.

Supervisory (MW)

Name	Label	Type	Default	Units	Description
Kimw	Kimw	double	0	—	Supervisory MW-controller integral gain. When non-zero, a slow outer loop adjusts the load reference Pref to hold the electrical power at Pmwset. Set 0 to disable (the load reference stays at its initialized value).
Pmwset	Pmwset	double	0	—	Supervisory MW set-point (pu on the machine base). Used only when Kimw ≠ 0.

Monitoring

Name	Label	Type	Default	Units	Description
measure_pmech	Monitor Pmech	enum (Off / On)	0	—	Record the mechanical power Pmech (pu) as a named observable.
measure_valve	Monitor valve	enum (Off / On)	0	—	Record the fuel-valve position (pu) as a named observable.
measure_fsr	Monitor fuel request	enum (Off / On)	0	—	Record the post-low-value-select fuel request fsr (pu) as a named observable.
measure_pmeas	Monitor measured power	enum (Off / On)	0	—	Record the transduced electrical power Pmeas (pu) as a named observable.

Signal Names

Name	Label	Type	Default	Units	Description
pmech_name	Pmech name	string	(empty)	—	Observable name for the mechanical power Pmech. Blank = skip.
valve_name	Valve name	string	(empty)	—	Observable name for the valve position. Blank = skip.
fsr_name	fsr name	string	(empty)	—	Observable name for the fuel request fsr. Blank = skip.
pmeas_name	Pmeas name	string	(empty)	—	Observable name for the measured electrical power. Blank = skip.

Initialization

Name	Label	Type	Default	Units	Description
pref0	Pref	double	0	—	Load reference (pu). Normally computed by the load-flow auto-initialization (Pref = R·Pfb at the operating point) so the governor starts in balance; set manually only for standalone use.
pmech0	Pmech(0)	double	0	—	Initial mechanical power at t = 0 (pu, = the machine's mechanical torque at synchronous speed). Seeds the turbine, valve and governor integrator. Normally set by the load-flow auto-initialization from the paired machine's operating point.
pe0	Pe(0)	double	0	—	Initial electrical power at t = 0 (pu on the machine base). Seeds the power transducer. Normally set by the load-flow auto-initialization to the machine's terminal real-power output.

Observables

Signal	Type	Default name	Enable	Description
pmech	signal	from pmech_name	measure_pmech	Turbine mechanical power Pmech (pu) = Kturb·(Wf − Wfnl) after the turbine lead-lag and transport delay, less Dm·(ω − 1).
valve	signal	from valve_name	measure_valve	Fuel-valve position (pu) after the actuator rate and position limits.
fsr	signal	from fsr_name	measure_fsr	Fuel set request fsr (pu) — the low-value select of the governor, acceleration-limiter and load-limiter outputs that drives the actuator.
pmeas	signal	from pmeas_name	measure_pmeas	Transduced electrical power Pmeas (pu) after the 1/(1+sTpelec) power transducer (the droop feedback when Rselect = electrical power).