Turbine-Governor (TGOV1)

TGOV1 simple steam turbine-governor (IEEE PES-TR1). The classic minimal speed-governing prime mover for the synchronous machine: it senses rotor speed ω and drives the machine's mechanical-torque input Tm. The model is a permanent speed droop 1/R on the speed deviation, a single first-order governor/valve lag 1/(1+sT1) with non-windup valve position limits [Vmin, Vmax], a turbine lead-lag (1+sT2)/(1+sT3) that represents the reheat (T2 < T3), and a turbine damping term Dt·Δω. Mechanical power Pmech is delivered as 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 Tm back to the machine's Tm input. There is no electrical-power feedback (droop acts on speed only); for the richer gas/diesel model with load and acceleration limiters use GGOV1. The right-edge ω (in) and Tm (out) ports line up with the machine's left-edge speed (out) and Tm (in) ports for a direct connection.

Category: Control / Governor

Overview

The TGOV1 turbine-governor is the classic minimal steam-unit speed governor (IEEE PES-TR1). It is the model to reach for when you want a synchronous machine to participate in frequency regulation with the fewest parameters: a permanent speed droop, a single governor/valve lag, a turbine lead-lag for reheat, and an optional damping term.

It senses the machine rotor speed ω and outputs the mechanical torque Tm that drives the machine. With the optional load-flow auto-initialization (below) the governor starts on its operating point, so a study begins in steady state with no torque transient.

For a richer prime mover with electrical-power droop, a PID governor, fuel-valve rate limits, and load / acceleration limiters, use GGOV1 instead.

Block diagram

Signal flow, block by block (all per-unit on the machine base, $s=\mathrm{d}/\mathrm{d}t$, speed deviation $\mathrm{\Delta }\omega =\omega -1$):

1. Permanent droop and summing junction — the valve command is the load reference less the droop feedback,

$$P_{\text{in}}=P_{\text{ref}}-\frac{\mathrm{\Delta }\omega }{R}.$$

A droop of $R=0.05$ (5%) means a 5% speed rise backs the valve all the way off. $R$ must be non-zero (a zero value disables the droop term, giving an isochronous valve command).

2. Governor / valve lag — a first-order actuator with a non-windup position limit,

$$P_{\text{valve}}=\mathrm{clamp}(\frac{1}{1+s{T}_1}{P}_{\text{in}},V_{min},V_{max}).$$

While the valve is pinned at a rail the lag state is held there (anti-windup).

3. Turbine lead-lag (reheat) — the $(1+s{T}_2)/(1+s{T}_3)$ block. With $T_2<T_3$ it represents the reheater: $T_2/T_3$ is the fraction of total power the high-pressure stage develops promptly, the rest building up with the $T_3$ lag. Its DC gain is $1$, so it does not change the steady power. Set $T_2=T_3$ for a turbine with no reheat dynamics.

4. Turbine damping — the mechanical power is reduced by the speed-sensitivity term,

$$P_{\text{mech}}=\frac{1+s{T}_2}{1+s{T}_3}{P}_{\text{valve}}-D_t\mathrm{\Delta }\omega .$$

5. Output — the mechanical power is delivered as torque,

$$T_m=\frac{P_{\text{mech}}}{\omega },$$

which equals $P_{\text{mech}}$ at synchronous speed.

Load reference convention

This model takes Pref as the scheduled mechanical power directly: at synchronous speed ($\mathrm{\Delta }\omega =0$) the valve command is $P_{\text{in}}=P_{\text{ref}}$, so the steady mechanical power equals $P_{\text{ref}}$. That makes the load reference read in the same per-unit power as the machine output — Pref = 0.8 means "schedule 0.8 pu" — and is what the auto-initialization writes.

Load-flow auto-initialization

The governor participates in the project's controller auto-initialization so a run starts bumpless:

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

• The mechanical power matches the machine. $P_{\text{mech}}(0)$ is set to the machine's mechanical torque $t_{m0}$ derived from the load-flow operating point (shared back-calculation), and the governor lag and turbine lead-lag states are seeded to it.

• The load reference balances the loop. Because $\mathrm{\Delta }\omega =0$ at the operating point,

$$P_{\text{ref}}=P_{\text{mech}}(0).$$

These quantities populate Pref and Pmech(0) on the Initialization tab. You normally never type them by hand; set them only when using the governor standalone (in which case choose $P_{\text{ref}}=P_{\text{mech}}(0)$ to start flat).

Wiring

• speed ← the synchronous machine's speed output (ω, pu).
• Tm → the synchronous machine's Tm input (mechanical torque, pu).

Enable Monitor Pmech / valve on the Monitoring tab to record the mechanical power and valve position as named signals for plotting.

When to use something else

• GGOV1 — a general-purpose governor with electrical-power droop, a PID, fuel-valve rate limits, and load / acceleration limiters. Use it for gas / diesel units or when you need the supervisory limiters.
• A fixed prime mover (no governor): leave the machine's Tm unwired and use its constant tm0 fallback instead of a governor.

Ports

Name	Direction	Value type	Notes
speed	input	double
Tm	output	double

Parameters

Governor

Name	Label	Type	Default	Units	Description
R	R (droop)	double	0.05	—	Permanent speed droop (pu). The steady speed/load characteristic: a 0.05 (5%) droop drops speed 5% from no-load to full-load. The speed deviation enters the governor as Δω/R. Must be non-zero; set a small value for a stiff governor (a value of 0 disables the droop term).
T1	T1	double	0.5	s (s, ms)	Governor / valve actuator time constant of the 1/(1+sT1) lag. The dominant control-valve response.
Vmax	Vmax	double	1	—	Maximum valve / gate position (pu). Non-windup upper limit on the governor lag state — caps the deliverable mechanical power.
Vmin	Vmin	double	0	—	Minimum valve / gate position (pu). Non-windup lower limit on the governor lag state.

Turbine

Name	Label	Type	Default	Units	Description
T2	T2	double	2.1	s (s, ms)	Turbine lead (numerator) time constant of the (1+sT2)/(1+sT3) block. With T2 < T3 the block models reheat; T2/T3 is the fraction of total power developed promptly by the high-pressure stage. Set T2 = T3 (or both 0) for a turbine with no reheat dynamics (pass-through).
T3	T3	double	7	s (s, ms)	Turbine lag (denominator) time constant of the (1+sT2)/(1+sT3) block (the reheater / steam-chest lag). T3 = 0 makes the block a pure lead 1+sT2 — usually keep T3 > 0.
Dt	Dt	double	0	—	Turbine damping coefficient (pu). Mechanical power is reduced by Dt·(ω − 1), modeling the speed-sensitivity of the turbine. Set 0 to disable.

Monitoring

Name	Label	Type	Default	Units	Description
measure_pmech	Monitor Pmech	enum (Off / On)	0	—	Record the turbine mechanical power Pmech (pu) as a named observable.
measure_valve	Monitor valve	enum (Off / On)	0	—	Record the governor / valve position (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.

Initialization

Name	Label	Type	Default	Units	Description
pref0	Pref	double	0	—	Load reference (pu) = the scheduled mechanical power. Normally computed by the load-flow auto-initialization (Pref = Pmech0 at synchronous speed) 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 governor lag and turbine lead-lag states. Normally set by the load-flow auto-initialization from the paired machine's operating point.

Observables

Signal	Type	Default name	Enable	Description
pmech	signal	from pmech_name	measure_pmech	Turbine mechanical power Pmech (pu) after the (1+sT2)/(1+sT3) lead-lag, less Dt·(ω − 1).
valve	signal	from valve_name	measure_valve	Governor / valve position (pu) after the 1/(1+sT1) lag and the [Vmin, Vmax] limit.