Turbine-Governor (IEEEG1)

IEEEG1 IEEE Type 1 speed-governing model for steam turbines (IEEE PES-TR1), the steam governor PES-TR1 recommends. It senses rotor speed ω and drives the synchronous machine's mechanical-torque input Tm. The speed deviation passes a speed relay K(1+sT2)/(1+sT1), where K is the reciprocal of the droop; the valve servo integrates (Pref − relay output − GV)/T3 within the valve rate limits [Uc, Uo] and the position limits [PMIN, PMAX]; and the valve position GV feeds four cascaded turbine stages 1/(1+sT4) … 1/(1+sT7) whose outputs, weighted by the high-pressure power fractions K1, K3, K5 and K7, sum to the mechanical power Pm, delivered as torque Tm = Pm/ω. The model drives a single shaft: K2, K4, K6 and K8, the low-pressure fractions of a cross-compound unit's second shaft, are kept for data exchange but not used. Pairs with the synchronous machine for bumpless load-flow initialization. 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 IEEEG1 turbine-governor is the IEEE Type 1 speed-governing model for steam units, the one IEEE PES-TR1 recommends for steam turbines in grid studies. Compared with the minimal TGOV1 it adds valve rate limits, a speed relay with lead-lag shaping, and four turbine stages (steam chest, reheater, crossover and a second reheater), each contributing its own fraction of the shaft power.

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

IEEEG1 assumes constant steam pressure and temperature. It suits frequency deviations of a few tenths of a percent; boiler dynamics and coordinated plant controls are outside its scope.

Block diagram

Signal flow, block by block (all quantities per-unit on the machine rating, $s=\mathrm{d}/\mathrm{d}t$):

1. Speed relay —

$$y=K\frac{1+s{T}_2}{1+s{T}_1}(\omega -1),$$

where $K$ is the reciprocal of the permanent droop ($K=20$ is a 5% droop). With $T_1=T_2=0$ the relay is the pure gain $K$.

2. Valve servo — the valve position $GV$ is the integral of

$$\frac{dGV}{dt}=\mathrm{clamp}(\frac{P_{\text{ref}}-y-GV}{T_3},U_c,U_o),$$

held inside $[P_{min},P_{max}]$ by a non-windup limit, so the valve leaves a limit as soon as its command turns back. $U_o$ caps the opening rate and $U_c$ (negative) the closing rate.

3. Turbine stages — four cascaded lags

$$x_1=\frac{GV}{1+s{T}_4},x_2=\frac{x_1}{1+s{T}_5},x_3=\frac{x_2}{1+s{T}_6},x_4=\frac{x_3}{1+s{T}_7},$$

for the steam chest, the reheater, the crossover and a second reheater. A zero time constant bypasses its stage; a single-reheat unit leaves $T_7=K_7=0$.

4. Mechanical power and torque —

$$P_m=K_1{x}_1+K_3{x}_2+K_5{x}_3+K_7{x}_4,T_m=\frac{P_m}{\omega }.$$

Normally $K_1+K_3+K_5+K_7=1$, so the steady mechanical power equals the valve position.

In steady state a speed change $\mathrm{\Delta }\omega$ moves the mechanical power by

$$\mathrm{\Delta }{P}_m=-K(K_1+K_3+K_5+K_7)\mathrm{\Delta }\omega ,$$

as long as the valve stays inside its position limits.

One shaft: the low-pressure fractions

The standard model can drive a cross-compound unit, whose high- and low-pressure turbines spin two separate generators: $K_1$, $K_3$, $K_5$, $K_7$ set the power on the first shaft and $K_2$, $K_4$, $K_6$, $K_8$ the power on the second.

This component drives one shaft, the usual tandem-compound unit. $K_2$, $K_4$, $K_6$ and $K_8$ are kept so imported data round-trips, but the model does not use them: the model's notes say they are ignored for a tandem-compound turbine. If your data puts low-pressure power there for a single machine, move it into $K_1$, $K_3$, $K_5$ and $K_7$. The load-flow initialization warns when any of the four is set.

A PSS/E IEEEG1 record whose JBUS names a second machine is a cross-compound unit; the import lists it as unsupported.

Rate limits and sign convention

$U_c$ is a closing rate and should be negative. A positive $U_c$ is read as its negative (and $U_o$ as its magnitude), so data written with either convention behaves the same. With $T_3=0$ the valve follows its command as fast as the rate limits allow.

Load-flow auto-initialization

After the load flow solves, the apply pass back-calculates the load reference and the valve seed so every derivative in the diagram is zero at $t=0$:

• Pairing is wire-traced. The initializer follows the Tm wire (through GoTo/From labels) to the unique synchronous machine whose Tm it feeds. Fan-out to several machines skips initialization with a warning.
• The valve holds the machine's power. At synchronous speed the relay is at rest and every stage passes $GV$ at unity gain, so

$$GV(0)=\frac{P_{m0}}{K_1+K_3+K_5+K_7},P_{\text{ref}}=GV(0),$$

with $P_{m0}$ the mechanical power of the paired machine at its operating point.

A warning is raised, and the seed still proposed, when $GV(0)$ lies outside $[P_{min},P_{max}]$ or when a low-pressure fraction is set. The initialization is skipped when $K_1+K_3+K_5+K_7=0$. When the paired machine has a multi-mass shaft, the governor is initialized on the machine's total mechanical torque, with a warning.

These quantities populate Pref and GV(0) on the Initialization tab. On the first time step the model uses $\omega =1$ in place of the not-yet-available speed signal.

Wiring

• ω ← the synchronous machine's speed output.
• Tm → the synchronous machine's Tm input.

Enable Monitor Pm / valve on the Monitoring tab to record the mechanical power and the valve position.

When to use something else

• The fewest parameters: use TGOV1, one valve lag and one reheat lead-lag.
• A gas turbine or a governor with load and acceleration limiters: use GGOV1.
• A hydro unit: use HYGOV, whose water column produces the initial power dip a steam model cannot.

Ports

Name	Direction	Value type	Notes
speed	input	double
Tm	output	double

Parameters

Governor

Name	Label	Type	Default	Units	Description
K	K (gain)	double	20	—	Governor gain, the reciprocal of the permanent droop (pu/pu). K = 20 is a 5% droop: in steady state a speed drop Δω raises mechanical power by K·(K1 + K3 + K5 + K7)·Δω. K = 0 removes the speed feedback, so the valve holds Pref.
T1	T1	double	0	s (s, ms)	Speed-relay lag time constant, the denominator of K(1+sT2)/(1+sT1). With T1 = T2 = 0 the relay is the pure gain K.
T2	T2	double	0	s (s, ms)	Speed-relay lead time constant, the numerator of K(1+sT2)/(1+sT1).
T3	T3	double	0.1	s (s, ms)	Valve servo time constant: the valve moves at (Pref − relay output − GV)/T3, within the rate limits. T3 = 0 makes the valve follow its command as fast as the rate limits allow.
Uo	Uo	double	0.1	—	Maximum valve opening rate (pu/s).
Uc	Uc	double	-0.1	—	Maximum valve closing rate (pu/s), negative. A positive value is read as its negative, so the magnitude convention works too.
PMAX	PMAX	double	1	—	Maximum valve position (pu on the machine rating). Non-windup upper limit on the valve integrator; with K1 + K3 + K5 + K7 = 1 it caps the steady mechanical power.
PMIN	PMIN	double	0	—	Minimum valve position (pu on the machine rating). Non-windup lower limit on the valve integrator.

Turbine

Name	Label	Type	Default	Units	Description
T4	T4	double	0.3	s (s, ms)	First turbine stage time constant: steam chest and inlet piping. 0 bypasses the stage.
K1	K1	double	0.3	—	Fraction of the shaft power developed after the first stage (high-pressure turbine).
K2	K2	double	0	—	Fraction of a cross-compound unit's second (low-pressure) shaft power after the first stage. Not used: this model drives one shaft.
T5	T5	double	7	s (s, ms)	Second turbine stage time constant: the reheater. 0 bypasses the stage.
K3	K3	double	0.4	—	Fraction of the shaft power developed after the second stage (intermediate-pressure turbine).
K4	K4	double	0	—	Second-shaft (low-pressure) fraction after the second stage. Not used: this model drives one shaft.
T6	T6	double	0.5	s (s, ms)	Third turbine stage time constant: the crossover piping. 0 bypasses the stage.
K5	K5	double	0.3	—	Fraction of the shaft power developed after the third stage (low-pressure turbine).
K6	K6	double	0	—	Second-shaft (low-pressure) fraction after the third stage. Not used: this model drives one shaft.
T7	T7	double	0	s (s, ms)	Fourth turbine stage time constant: a second reheater. 0 bypasses the stage, as on a single-reheat unit.
K7	K7	double	0	—	Fraction of the shaft power developed after the fourth stage. Normally K1 + K3 + K5 + K7 = 1.
K8	K8	double	0	—	Second-shaft (low-pressure) fraction after the fourth stage. Not used: this model drives one shaft.

Monitoring

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

Signal Names

Name	Label	Type	Default	Units	Description
pmech_name	Pm name	string	(empty)	—	Observable name for the mechanical power Pm. Blank = skip.
valve_name	Valve name	string	(empty)	—	Observable name for the valve position GV. Blank = skip.

Initialization

Name	Label	Type	Default	Units	Description
pref0	Pref	double	0	—	Load reference (pu): the valve position the governor holds at synchronous speed. Normally computed by the load-flow auto-initialization (Pref = GV(0)) so the governor starts in balance; set manually only for standalone use.
gv0	GV(0)	double	0	—	Initial valve position at t = 0 (pu), Pm(0)/(K1 + K3 + K5 + K7). Seeds the valve integrator and all four turbine stages. 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 Pm (pu): K1·x1 + K3·x2 + K5·x3 + K7·x4 over the four turbine stages.
valve	signal	from valve_name	measure_valve	Valve position GV (pu) after the rate limits and the [PMIN, PMAX] limit.

Used in samples

• Governor Island Load Step