GB/T 7409.2-2020 PDF in English
GB/T 7409.2-2020 (GB/T7409.2-2020, GBT 7409.2-2020, GBT7409.2-2020)
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Excitation systems for synchronous machines--Part 2: Models for power system studies
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Standards related to: GB/T 7409.2-2020
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GB/T 7409.2-2020: PDF in English (GBT 7409.2-2020) GB/T 7409.2-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.160.20
K 21
Replacing GB/T 7409.2-2008
Excitation Systems for Synchronous Machines - Part 2:
Models for Power System Studies
ISSUED ON: JUNE 2, 2020
IMPLEMENTED ON: DECEMBER 1, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 4
Introduction ... 6
1 Scope ... 8
2 Normative References ... 8
3 Terms and Definitions ... 8
4 Classification of Exciters - Graphical Method and Mathematical Model for Stability
Studies ... 9
4.1 DC Exciters ... 9
4.2 AC Exciters ... 10
4.3 Potential Source Static Exciter ... 15
4.4 Compound Source Static Exciter ... 16
5 Mathematical Models of Control Functions ... 17
5.1 Voltage Measurement and Load Current Compensation Link Model ... 17
5.2 Proportional-integral-derivative (PID) Correction Link Model ... 19
5.3 Excitation Feedback Link Model ... 20
5.4 Amplitude Limiting Link ... 21
5.5 Power System Stabilizer Model ... 21
5.6 General Structure of Main Voltage Control ... 22
5.7 Auxiliary Limiter Model ... 23
5.8 Mode of Auxiliary Limiter’s Intervention in Main Voltage Control ... 27
6 Excitation System Models ... 28
6.1 Overview ... 28
6.2 Excitation System Models for AC Exciters ... 28
6.3 Excitation System Models for DC Exciters ... 31
6.4 Static Excitation System Model ... 31
7 Terminology ... 33
7.1 Parameters ... 33
7.2 Variables ... 36
Appendix A (informative) Transformer High-voltage Side Voltage Control Model ... 39
Appendix B (normative) Amplitude Limiting Expression Method ... 40
Appendix C (informative) Multi-band Power System Stabilizer Model ... 44
Appendix D (normative) Inverse Time Characteristic Calculation ... 46
Appendix E (informative) UEL Model Table Lookup Function... 48
Appendix F (informative) Integral Reset Representation ... 49
Appendix G (normative) Saturation Function ... 50
Appendix H (normative) Rectifier Regulation Characteristics ... 51
Appendix I (informative) Estimation of Over Excitation Limiter (OEL) Reference
Value ... 53
Appendix J (normative) Per-unit System ... 60
Bibliography ... 61
Excitation Systems for Synchronous Machines - Part 2:
Models for Power System Studies
1 Scope
This Part of GB/T 7409 specifies the simulation diagram of the excitation system, the
mathematical model of the exciter and control functions, and the terminology definitions of its
related parameters and variables.
This Part is applicable to the excitation system models of steam (gas) turbine generators,
hydroelectric generators, pumped storage power generators / motors and nuclear power units
used in the power system studies and analysis.
2 Normative References
The following documents are indispensable to the application of this document. In terms of
references with a specified date, only versions with a specified date are applicable to this
document. In terms of references without a specified date, the latest version (including all the
modifications) is applicable to this document.
GB/T 7409.1 Excitation Systems for Synchronous Electrical Machines - Definitions
3 Terms and Definitions
The terms and definitions defined in GB/T 7409.1, and the following are applicable to this
document.
3.1 main voltage control
The link of comparing the actual measured value of the synchronous generator terminal voltage
with the given value and adjusting the excitation output with appropriate control rules in
accordance with its deviation.
NOTE: its main functions also include load current compensation, excitation feedback link and
power system stabilizer (PSS) functions.
3.2 auxiliary limiters
The limiting link in the excitation regulator other than the main voltage control.
NOTE: it includes V/Hz limiter, over excitation limiter, maximum current limiter, stator current
limiter and under excitation limiter, etc.
3.3 maximum current limiter
Under any operating conditions, the output current of the excitation system is instantaneously
limited to not exceed the specified maximum value.
3.4 volts per hertz limiter; VEL
An additional unit or function in a voltage regulator that prevents the voltage-to-frequency ratio
of a synchronous machine or its connected transformer from exceeding an allowable range.
3.5 over excitation limiter; OEL
An additional unit or function in a voltage regulator that limits the output current of the
excitation system to an allowable value.
3.6 stator current limiter; SCL
An additional unit or function in a voltage regulator that limits the stator current within an
allowable value by adjusting the reactive component of the stator current of the synchronous
generator during over excitation or under excitation.
3.7 under excitation limiter; UEL
An additional unit or function in a voltage regulator that limits the reactive power of the
synchronous generator to no less than a specified value under different active loads.
4 Classification of Exciters - Graphical Method and
Mathematical Model for Stability Studies
4.1 DC Exciters
In recent years, although DC exciters have been rarely used in new units, some synchronous
machines are still equipped with such exciters. Figure 2 is a schematic diagram of an DC exciter
using separately excited windings, and Figure 3 demonstrates the model of the exciter. In the
model, the constant KE of the self-excited magnetic field of the AC and DC exciters is used to
describe the characteristics of the exciter with self-excited components. Please be noted that
when adopting the separately excited exciters, KE = 1.
XE---rectifier load factor, which is proportional to the commutation reactance of the voltage
source and current source, or the combined equivalent commutation reactance of the voltage
and current source, see Appendix H.
Fe---commutation pressure drop coefficient, see Appendix H.
X---commutation reactance.
KI---current loop input constant.
KP---voltage loop input constant.
Uf max, Uf min---maximum and minimum voltage output by the excitation system.
Ur max, Ur min---maximum and minimum output of the regulator
UFE max---exciter magnetic field current limiting parameter.
UP+, UP---at the rated voltage of the generator, the maximum and minimum no-load output
voltage of the potential source exciter.
KG---feedback gain of the inner loop magnetic field regulator.
KR---gain of voltage measurement link.
KZ---static difference compensation coefficient of the control link, which is generally set to the
reciprocal of the proportional gain KS of the control link.
TR---time constant of terminal voltage converter and load current compensator.
XP---rectifier load factor of potential source converter, see Appendix H.
KMAX---proportional gain constant coefficient, which is generally set to 1,000,000.
KA, KA1, KFF, KV, KAP, KAD, KAI, KB, KBP, KBI---voltage regulator gain constant.
KF, KH---gain constant of excitation feedback link.
TB1, TB2, TC1, TC2, TA, TB, TAD, TG---voltage regulator time constant.
TF---time constant of excitation feedback link.
XC, RC---current and power compensator gain constants.
UA max, UA min, UA1 max, UA1 min, UA2 max, UA2 min, UB max, UB min, UD max, UD min, UI max, UI min---voltage
regulator amplitude limiting values.
KL1---over excitation instantaneous limit gain.
UL1R---over excitation instantaneous setting value.
KPSS, KS1, KS2, KS3---power system stabilizer gain.
TS1, TS2---time constant of power system stabilizer signal measurement link.
TW1, TW2, TW3, TW4---time constant of DC blocking link of power system stabilizer.
TP1, TP2, TP3, TP4, TP5, TP6, TP7, TP10, TP11---power system stabilizer time constant.
A1, A2, M, N, TP8, TP9---power system stabilizer filter parameters.
USS max, USS min---power system stabilizer output amplitude limiting values.
USI1 max, USI1 min, USI2 max, USI2 min---power system stabilizer input amplitude limiting values.
UfB, IfB, RfB UefB, IefB, RefB---respectively: generator magnetic field voltage, field current and
field winding resistance reference value, exciter field voltage, field current and field winding
resistance reference value.
UVF_REF---fixed value amplitude limiting value (expressed by the per-unit value of the rated
value).
Kinv, Kcool---heat accumulation and heat dissipation integral coefficient.
KexpVEL---inverse time characteristic exponential coefficient of V/Hz limiter.
UVFL_th---inverse time timing start setting value of V/Hz limiter (expressed by the per-unit value
of the rated value).
UVFL_rth---action return fixed value of V/Hz limiter (expressed by the per-unit value of the rated
value).
UREF max---output maximum setting value of V/Hz limiter (expressed by the per-unit value of
the rated value).
KexpOEL---inverse time characteristic exponential coefficient of OEL limiter.
Ifth---inverse time limit timing start setting value of OEL limiter (expressed by the per-unit value
of the rated value, and the setting value setting can be found in Appendix I).
Ifn---heat accumulation rotor current reference value of OEL limiter (expressed by the per-unit
value of the rated value, and the setting value setting can be found in Appendix I).
Ifrth---inverse time limit setting value of OEL (expressed by the per-unit value of the rated value,
and the setting value setting can be found in Appendix I).
If max---maximum magnetic field current setting value allowed by OEL (expressed by the per-
unit value of the rated value, and the setting value setting can be found in Appendix I).
C---upper amplitude limiting value of heat accumulation integral.
P, Q---active power and reactive power of the generator (expressed by the per-unit value of the
apparent rated value).
IP, IQ---active current and reactive current of the generator (expressed by the per-unit value of
the apparent rated value).
---generator power angle.
Ue---exciter voltage after commutation reactance (expressed by the per-unit value of the
generator air gap magnetic field voltage).
UREF---voltage regulator setting value (determined in accordance with the initial conditions).
Upss---output of power system stabilizer.
Upss1, Upss2, Upss3---outputs of the power system stabilizer intervening in the main voltage control
at different positions.
UERR---deviation signal of the voltage control channel.
Uess---output of excitation feedback link.
Uie---a signal proportional to the exciter magnetic field current.
UC---voltage measurement and compensator output.
UA---output of voltage correction link.
USI1, USI2---input signals of power system stabilizer.
fG---generator frequency (expressed by the per-unit value of power frequency 50 Hz).
UVF_REF---fixed value output of V/Hz limiter.
UVFL---output of V/Hz limiter.
UVFL1, UVFL2, UVFL3---outputs of V/Hz limiter intervening in the main voltage control at different
positions.
SOEL---OEL action flag bit (expressed by 0 and 1).
UOEL---inverse time limit output of OEL limiter.
UOEL1, UOEL2, UOEL3, UOEL4, UOEL5---outputs of OEL limiter intervening in the main voltage
control at different positions.
USCL1, USCL2---outputs of SCL limiter adopting the superposition mode to intervene in the main
voltage control at different positions.
USCLind, USCLcap---SCL delayed phase side limit output and advanced phase side limit output.
Appendix J
(normative)
Per-unit System
In power system studies, the voltage and current of the generator and exciter, as well as the
input and output quantities of the regulator are expressed by per-unit values. The per-unit
system shall be established in accordance with the following requirements:
a) The per-unit value is equal to the actual value divided by the reference value.
b) The reference value of the generator voltage is the generator rated voltage. The
reference value of the generator current is the generator rated current. The reference
value of the generator power is the rated apparent power of the generator. The
reference value of the generator frequency is the generator rated frequency.
c) The reference value IfB of the generator magnetic field current is the magnetic field
current required to generate the rated voltage on the generator’s no-load characteristic
air gap curve. The reference value RfB of the generator magnetic field winding
resistance is the generator’s rated magnetic field voltage divided by the generator’s
rated magnetic field current. Under certain circumstances, the influence of the loop
resistance needs to be considered. The reference value UfB of the generator magnetic
field voltage is the reference value of the magnetic field current multiplied by the
reference value of the magnetic field winding resistance.
d) The reference values of the output current and voltage of the exciter are respectively
the reference values of the generator magnetic field current and voltage.
e) The reference value IefB of the exciter magnetic field current is the exciter magnetic
field current value required to generate a per-unit value of generator magnetic field
voltage on the air gap curve of the exciter no-load characteristic curve. The reference
value RefB of the exciter magnetic field winding resistance is the resistance of the
excitation circuit of the exciter under the rated operating conditions of the generator.
The reference value UefB of the exciter magnetic field voltage is the reference value
of the exciter magnetic field current multiplied by the reference value of the exciter
magnetic field winding resistance.
f) The reference values of the input voltage, current and power of the regulator are equal
to the reference values of the generator voltage, current and power. When controlling
the generator magnetic field voltage, the reference value of the regulator output
voltage is equal to the reference value of the generator magnetic field voltage. When
controlling the exciter magnetic field voltage, the reference value of the regulator
output voltage is equal to the reference value of the exciter magnetic field voltage.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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