CC BY
6
© A. Alzakkar, N.P. Mestnikov, Y.O. Samofalov УДК 621.31
ESTIMATION OF LOAD ANGLE OF SYNCHRONOUS TURBO-GENERATOR
MODEL TGH-32
A. Alzakkar1,2, N. P. Mestnikov3,4, Y. O. Samofalov1
1Kazan State Power Engineering University, Kazan Russia 2Al-Baath University, Homs, Syrian Arab Republic 3North-Eastern Federal University named M.K. Ammosov, Russia 4Institute of Physical and Technical Problems of the North named V.P. Larionov
SB Russia
https://orcid.org/0000-0002-8355-189X, [email protected]
Abstract: More than 98% of the electrical power in the world is generated using the synchronous machine, it is the most used for converting mechanical power into electrical. The reason for calling it synchronicity is due to the exact correspondence between the rotation speed of the magnetic field and the rotor. PURPOSE. The purpose of this article is measurement load angle in excitation control systems of synchronous generator type TGH -32 which used in many Syrian power stations (Taiym, Jander, Der Ali, Tishreen, etc.) with the help of load angle sensor to prevent the generator from out of synchronization. METHODS The program used in the study are: (MATLAB) for simulation of power system which consists of synchronous generator, external power system and angle sensor. RESULTS. The presented graphs testify to the high accuracy of the indirect measurement of the load angle by currents and voltages in the stator circuits of a synchronous generator and in its excitation winding. CONCLUSION. From results of simulation was found that the results are almost identical between the theoretical calculation method and the readings of the load angle sensor; taking into account the fact that the application of such methods does not require expensive sensors and any intervention in the internal structure of the machine, it can be concluded that it is advisable to use sensors with indirect determination of the load angle during the operation of synchronous machines.
Keywords: sensor; generator; load angle; excitation current.
Acknowledgements: Work by results of which article is executed is executed together with the research supervisor I.M. Valeev, the Dr.Sci.Tech., professor of IEPE KSPEU, research laboratories on the basis of KSPEU and the University of Al Baath.
For citation: Alzakkar A, Mestnikov N.P., Samofalov Y.O. Estimation of load angle of synchronous turbo-generator model TGH-32. KAZAN STATE POWER ENGINEERING UNIVERSITY BULLETIN. 2022;14;2(54):40-47.
РАСЧЕТ УГЛА НАГРУЗКИ СИНХРОННОГО ТУРБОГЕНЕРАТОРА ТИПА
ТВС-32
А. Альзаккар12, Н. П. Местников3,4, Ю. О. Самофалов1
казанский государственный энергетический университет, Казань Россия 2Университет Аль-Баас, г. Хомс, Сирийская Арабская Республика 3Северо-Восточный федеральный университет им. М.К. Аммосова, г. Якутск,
Россия
4Институт физико-технических проблем Севера имени В.П. Ларионова СО
РАН, Якутск, Россия
https://orcid.org/0000-0002-8355-189X, [email protected]
Резюме: Более 98% электроэнергии в мире вырабатывается с помощью синхронной машины, она наиболее часто используется для преобразования механической энергии в электрическую. ЦЕЛЬ. Целью данной статьи является измерение угла нагрузки в системах управления возбуждением синхронного генератора типа ТВС-32, который используется на многих сирийских электростанциях (Тайым, Джандер, Дер Али, Тишрин и др.) с помощью датчика угла нагрузки для предотвращения генератор от рассинхронизации. МЕТОДЫ. В исследовании использовались следующие программы: (MATLAB) для моделирования энергосистемы, состоящей из синхронного генератора, внешней энергосистемы и датчика
Вестник КГЭУ, 2022, том 14, № 2 (54)
угла. РЕЗУЛЬТАТЫ. Представленные графики свидетельствуют о высокой точности косвенного измерения угла нагрузки по токам и напряжениям в цепях статора синхронного генератора и в его обмотке возбуждения. ЗАКЛЮЧЕНИЕ. По результатам моделирования было установлено, что результаты практически идентичны между теоретическим методом расчета и показаниями датчика угла нагрузки; с учетом того, что применение таких методов не требует дорогостоящих датчиков и какого-либо вмешательства во внутреннюю структуру машины, можно сделать вывод о целесообразности применения датчиков с косвенным определением угла нагрузки при работе синхронных машины.
Ключевые слова: датчик; генератор; угол нагрузки; ток возбуждения.
Благодарности: Работа, по результатам которой выполнена статья, выполнена совместно с научным руководителем И.М. Валеевым, д.т.н., профессор ИЭЭ КГЭУ, научно-исследовательскими лабораториями на базе КГЭУ и Университета Аль-Баас.
Для цитирования: Альзаккар А., Местников. Н.П., Самофалов Ю.О. Расчет угла нагрузки синхронного турбогенератора типа ТВС-32 // Вестник Казанского государственного энергетического университета. 2022. Т. 14. №2 (54). С. 40-47.
Introduction
The angle (б) between EMF vectors (or the direction of the transverse axis q) and the network voltage Un (Fig.6) is called the load angle of the synchronous machine.
To determine the value of this angle, we can use following methods [1, 2]:
1. The angle measuring machine: is a synchronous generator operating in idle mode, the geometric dimensions of which are similar to the machine under test. Both machines are connected mechanically so that their geometric axes coincide, for which holes of the corresponding configuration are provided in the coupling. When rotating in the armature winding of the angle measuring machine, an EMF is induced, which coincides in space with the idling EMF vector of the synchronous machine under test. Thus, the angle measuring machine is a sensor of the transverse axis of the synchronous machine. The linear voltage of the network and the corresponding linear EMF of the measuring machine are fed to the phase meter, which determines the values of the load angle.
2. The measuring winding: is placed in the grooves of the armature under the slot wedge.
It is made of a thin wire with a diametrical pitch and its axis coincides with the axis of one of the phase armature windings of the tested SM. The load angle, as in the previous case, can be measured using a phase meter. Since the phase voltage is removed from the measuring winding, the line-to-line voltage of the network must be rotated through an angle of 30 electrical degrees to obtain correct results.
3. The Hall sensor: is glued to the tooth of the armature magnetic circuit in the middle of the package and its output signal is proportional to the magnetic field induction at the place of its installation, i.e. the maximum signal coincides with the moment of passage of the longitudinal axis d, zero (minimum) - the q axis.
4. Angle sensors: at present, a large number of contact and non-contact angular position sensors have been developed, in particular, using synchros in transformer operation, tachometers that implement frequency measurement methods, and photoelectric sensors. The essence of the measurements is that the signal (pulse) from the angular position sensor corresponds to the passage through zero or the maximum idle EMF of the tested synchronous machine. The vector of this EMF is rigidly connected with the position of the rotor (with the direction of the q axis).
The authors Yu.A. Makarichev and V.N. Ovsyannikov [3] describe detailed explanation of the structure, working principle and types of synchronous generators. The authors A.Yu. Stogov, A.N. Belyaev [4] present method for improving the transient stability of autonomous power system on basis of wide area control system. The authors T. Idzotic, G. Erceg, D. Sumina [5] presents method for estimation of load angle for synchronous generator. The author A. E. Vagnov [6] in his book speaks about transient processes in AC machines. The authors M. P. Kostenko and L. M. Piotrovsky [7] present a comprehensive book about electrical machines. The authors M. Islam, M. Reza, M. Hossain [8] focused on Accurate Estimation of Phase Angle for Three-Phase Systems in Presence of Unbalances and Distortions. The authors M. Kutija, D. Sumina, I. Colovic, T. Idzotic, M. Hossain [9] describe the rotor flux estimation method for squirrel-cage induction generators (SCIGs) used in wind power applications. The authors K. Kondo, Koken Kim [10] study a q-axis inductance compensation method to improve the stability of the PMSM rotor angle sensorless control system using the induced voltage. The authors M. Kumar, S. Affijulla [11]
present a methodology for estimation of alternator rotor angle by using empirical modelled reactance, voltage and current phasors measured from phasor measurement units (PMUs). The authors Kh. N. Rasulzoda, J. B. Rahimov, M. Kh. Safaraliev [12] present the results of the study and comparison of mode parameters on the example of the Nurek HPP with a capacity of 3000 MW.
At this stage, the phenomenon out of sync is frequent in Syrian power plants. This phenomenon brings the power loss due to frequency drop, voltage swing and load angle deviation. The above methods are confirmation of the practical and scientific significance of this study.
Materials and methods
Load angle equation.
The load angle sensor of synchronous machines must calculate the value of the load angle according to easily measurable indicators of a synchronous machine, such as: field current If, field voltage Uf, active and reactive stator currents [13].Proceeding from the fact that the initial value of the flux linkage of the excitation winding W(0) is known from the equations corresponding to the steady state operation of the synchronous machine, then the flux linkage W in the transient mode is determined from the excitation voltage Uf and the excitation current If according to the equation [14, 15]:
t
Tf =J(«/ - iff )dr + Vf (0) (1)
0
The flux linkage of the field winding W and the flux linkage of the stator ¥sd along the longitudinal axis are related to the currents in the machine circuits by the following equations:
T . = i l + i L + i l (2)
sd sd ad f ad sq aq v y
% = i X , + ifLf + i L (3)
f sd ad f f sq aq v/
Longitudinal stator current isd, included in equations (2) and (3), can be determined only for known values of the load angle 5, active and reactive stator current. If the isx current corresponds to the stator reactive current and is oriented along the stator flux linkage vector ¥s = ¥sd + j¥sq, and the isy current corresponds to the active stator current and coincides with the stator voltage vector Us = Usd + jUsq, then the load angle 5 is the load angle between the coordinate axes dq and xy:
'X = isx + J'sy = (isd + J sq )e (4)
isx = Re.iX = Re.id eJ = isd cos (J) +isq sin (J) (5)
iy = Im.i:y = Im.id e J = isq cos(J)+i^ sin (J) (6)
From equations (4), (5), (6) you can get the stator longitudinal current:
isd = 'x COs (J)-isy sin (J) (7)
The magnitude of the flux linkage ¥sd from equation (2) depends on the stator voltage Us and the load angle 5, since the projection of the stator flux linkage vector onto the d axis is determined by the following equation:
Tsd =Ts cos (S) = 0-1us cos (J) (8)
As a result of combining equations (1), (2), (3) and (7), (8), we obtain that the flux linkage of the excitation winding is expressed by the equation:
Tf = m-lus cos(J)-^ (ix cos(J)-isy sin(J)) + ifL„f (9)
Equation (9) can be transformed to the form:
-i*La)cos{S) + (ixyL^)sin(^-(Y, -ifLf ) = 0
Equation (10) has several solutions for the angle 5:
S = + arccos
9 = arctg
Y f ifLaf
fa— 1us-ixL.)2+0^)'
2nn+9
i xyL a
Where, based on physical considerations, the correct root is:
S = + arccos
Ç-
Y f ifLaf
fa— '«s -ixL*)2 + (ixyLa)
i L
xy a
a —u — i L
s s sx a
(10)
(11)
(12)
To calculate the load angle using the formula (12), the stator voltage Us and the excitation current if are measured directly, and the flux linkage W is calculated using equation (1).
Active isy and reactive isx stator currents are calculated through phase currents and stator voltages in physical coordinates.
Simulation of load angle equation.
According to this block diagram in the MATLAB Simulink environment, a block diagram
was drawn up, shown in Fig.3:
Fig. 3. Simulation ofpower system consists of (synchronous generator, external power system, angle sensor). From Fig.3. the block diagram compiled uses:
1. The transformation coordinate system from (A", "B", "C") to ("d", "q").
2. The transformation coordinate system from ("d", "q") to ("x","y").
3. The transformation coordinate system from (A", "B", "C") to ("V", "3").
4. The transformation coordinate system from ("V", "3") to ("x","y").
To obtain the angular characteristics of a synchronous generator, it is necessary to carry out a series of experiments with different external loads.
A", "B", "C": The original system of stationary phase axes of the stator windings. "d", "q": Two mutually perpendicular axes connected with the rotor. "x","y": Cartesian coordinate system. "V", "3": Fixed coordinate system.
Structure of load angle sensor system of a synchronous machine.
According to formulas (1), (9), (12), a block diagram of a synchronous machine with a load angle sensor [16] was drawn up, consisting of:
Synchronous machine (SM); Drive Motor (DM); Stator Voltage Sensor (SVS); Stator Current Sensor (SIS); Excitation Current Sensor (ECS); Active-Reactive Power Converter (ARPC).
The control system with the load angle identifier is shown in the block diagram (Fig. 4):
Fig 4. Block diagram of load angle sensor
The excitation current regulator compensates for the time constant of the excitation winding and provides the required speed in the excitation current control circuit. The reactive current regulator is necessary to ensure an economical mode of operation of the generator. In cases where the load node does not experience a shortage of reactive power, the optimal mode of operation is the SM, with cos(^) close to 0.9, providing a minimum of electrical losses and favorable thermal conditions of the generator. Voltage regulator provides voltage stabilization in the load node by changing the amount of reactive power consumed or generated in the network.
The SM rotor vibration damping unit is designed to limit the amplitude of the rotor vibrations, reduce swings of the active and reactive power of the SM. This increases the stability and reliability of the engine during shock application of the load. The regulation of the excitation current in order to dampen the oscillations of the rotor is carried out according to the load angle (5) and its derivative, which are parameters that directly determine the stability of the generator. The load angle (5) and its derivative are calculated by the load angle identifier.
Results and Discussions
In this section, the results of the programs (Matlab) and equation (12) will be obtained and compared for identification of the load angle of TGH-32.
Fig. 5. Identification of the load angle: 1- Theoretical calculation method; 2- Readings of the load angle sensor.
During the experiments, a model of a salient-pole synchronous generator TGH- 32 (turbine generator - hydrogen cooling-32MW) located in the Syrian Tishreen plant was used. After processing the results of a series of experiments, it is possible to build a graph of the dependence of the active power of the synchronous generator on the readings of the load angle sensor [17]. This dependence is shown in Fig.6:
Fig. 6. Plot of the impact of the generator output power on the load angle.
The characteristic of the simulated synchronous generator can be obtained only in the area of stable operation [18, 19], without falling out of synchronism (5 <5crit).
From Equations (1; 9; 12), due to the application of the transformation of the coordinate system ("d", "q") to axis of windings ("x","y") oriented along the phase A, for using load angle sensors in practice, it is necessary to know:
1. The instantaneous values of the voltages and currents of each phase of the stator.
2. The instantaneous values of the current and voltage of the excitation circuit.
It is required to establish theoretical angular characteristics in order to examine the performance and applicability of this load angle sensor.
The active power of a synchronous machine is determined by the equation:
Pj = m-Ui cos^ (13)
Using the vector diagram, Fig.7, it is possible to transform the formula (13) to the dependence PI = f (5):
Fig. 7. Vector diagram of a synchronous generator.
m.Ui E
mU,2
P=" ''"^"sin (5) + mu 1 X ^
_'___1_
sin (25)
(14)
In Fig.8, the comparative angular characteristics, calculated theoretically and obtained experimentally, are shown:
Pi.MVNj I...... .....
1 -
—7»"
20
/ A \ \ S, deg
•íííf
Fig. 8. Angular characteristics of a synchronous generator. 45
The presented graphs testify to the high accuracy of the indirect measurement of the load angle by currents and voltages in the stator circuits of a synchronous generator and in its excitation winding.
Conclusion
In the course of the research, the authors of the article formulated the following conclusions:
1. From Fig.4 (results of simulation), it was found that the results are almost identical between the theoretical calculation method and the readings of the load angle sensor;
2. The load angle sensor can be used for other types of turbogenerators in Syria, for example: air-cooled synchronous turbogenerators; synchronous turbogenerators with hydrogen-water cooling; synchronous turbogenerators with full water cooling;
3. References (in the introduction) The question of calculating the loading angle for synchronous turbo-generators, especially type TGH-32, has not been studied in sufficient depth;
4. Taking into account the fact that the application of such methods does not require expensive sensors and any intervention in the internal structure of the machine, it can be concluded that it is advisable to use sensors with indirect determination of the load angle during the operation of synchronous machines.
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Вестник КГЭУ, 2022, том 14, № 2 (54)
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Authors of the publication
Ahmad Alzakkar - Institute of Electric Power Industry of Kazan State Power Engineering University, Al-Baath University. E-mail: [email protected].
Nikolai Mestnikov Petrovich - North-Eastern Federal University named after M.K. Ammosov, North-Eastern Federal University named after M.K. Ammosov, Institute of Physical and Technical Problems of the North named V.P. Larionov SB RAS.
Yuri Samofalov Olegovych - Senior Lecturer, graduate student of the Institute of Electric Power Engineering of Kazan State Power Engineering University.
Получено 10.05.2022г.
Отредактировано 25.05.2022г.
Принято 25.05.2022г.
