Thyristor Excitation Research Articles

Linear Active Disturbance Rejection Control for Flexible Excitation System of Pumped Storage Units

The role of pumped storage in global energy structure transformation is becoming increasingly prominent. This article introduces a flexible excitation system based on fully controlled device converters into pumped storage units (PSUs). It can address the issues of insufficient excitation capacity and limited stability associated with traditional thyristor excitation systems. The study focuses on linear active disturbance rejection control (LADRC) for the flexible excitation control system of pumped storage units and utilizes intelligent optimization algorithms to optimize the controller parameters. This addresses the inherent problem of traditional PID controllers, which are unable to alleviate the trade-off between response speed and overshoot. At the same time, the robustness and anti-interference of the control system are improved, effectively enhancing the performance of the pumped storage flexible excitation control system. Simulation verifies the feasibility and superiority of the proposed method.

Patent Analysis of the Digital Synchronous Motor Excitation Regulator

A significant part of the devices at enterprises has been in operation since the eighties of the last century. A thyristor exciter is a system designed to control and stabilize the operating processes of engines that are part of devices operating at high speed. The efficiency of operation of such machines as compressors, fans, pumps directly depend on how high-quality exciters are installed in their design. Thyristor exciters are also designed for the generation of low-power hydro and turbo generators, synchronous motors and compensators. In order to increase reliability and ensure uninterrupted operation of a synchronous electric drive with optimal electrical performance, it is necessary to use high speed thyristor exciters, in our case, the digital excitation regulator of a synchronous motor — ANICRON. In comparison with electric machine exciters, thyristor ones require three times less maintenance costs. The improvement of the technical and economic indicators of a synchronous electric drive is carried out by reducing losses in power lines, increasing the reliability of the power electric drive, and additional capabilities of a thyristor-exciter device. To date, the effectiveness of such pathogens has been evaluated by enterprises in the sugar, chemical, energy and other industrial fields. Thyristors are widely used not only in the Russian Federation, but also abroad.

Emulation of IEEE STD 421.5/Industrial Excitation Systems Using a Micro-Alternator's Exciter

Micro-alternators, having similar parameters as turbo-alternators, play a significant role in the experimental evaluation of power system dynamics. Early thyristor excitation systems of micro-alternators have limited re-configurable options. Three possible control structures, two closed-loop control structures proposed in the literature and one open-loop control structure proposed in this paper, including a time constant regulator to mimic large machine time constants, are evaluated to emulate any IEEE 421.5 standard excitation system model or interface an industrial excitation system controller hardware in the loop (CHIL). It is shown that the communication delay introduced in CHIL does not impact the closed-loop stability within the bandwidth requirements of the excitation systems. One of the closed-loop structures, which is more generalized, and the open-loop structure performances are compared for emulating IEEE AC4C, DC1C, and ST1C excitation systems on a laboratory micro-machine based single machine infinite bus test system with buck exciter and H-bridge chopper (HBC) exciter using EMTP simulations under small and large disturbances. HBC exciter is used in the experimental validation with both the closed-loop and the open-loop control structures. The proposed open-loop structure is easy to implement and performs better than the closed-loop structure.

IMPROVEMENT OF THE ENERGY PERFORMANCE OF ASYMMETRIC EXCITORS OF SYNCHRONOUS MACHINES IN VOLTAGE FORCING MODES

The main mode of operation of synchronous machines in electric drives of industrial plants is the mode in which a static load moment close to the nominal is applied to the shaft. If the synchronous machine works as a generator, when consumers of comparable power are connected to the stator to stabilize the output voltage of the generator, forcing of the excitation voltage is applied by influencing the control angles of the thyristors of the controlled rectifier. In the nominal mode, the control angles of the thyristors of the exciter are significant, which makes it possible to ensure a sufficient multiplicity of the voltage during forcing. But with significant thyristor opening angles, the controlled rectifier consumes significant reactive power, which reduces the power factor of the rectifier bridge. In addition, forcing the excitation voltage is necessary for synchronous motors when a significant load is applied to the shaft and when voltage drops in the power supply network.
 It is widely used to connect capacitors in parallel to the windings of the power transformer, or to use two zero diodes that are connected in series and connected to the output of the exciter to improve its energy performance. A significant improvement in the power factor can be achieved by using forced capacitive switching nodes. However, the improvement of energy indicators by turning on zero diodes and capacitors leads to a significant change in the harmonic composition of the excitation voltage. In the work, a research of the harmonic composition of the excitation voltage of synchronous machines with asymmetric bridge rectifiers using artificial commutation circuits was carried out. 
 To research the harmonic composition, experimentally obtained dependences of the forced excitation voltage, which are decomposed into a trigonometric series, are used. Calculated amplitude spectra of the excitation voltage during natural and forced switching of thyristors. The above calculations show that the coefficient of ripples of the output voltage of the thyristor exciter when using a rectifier with forced commutation is more than two times less (5.4 %) than the coefficient of ripples of the output voltage of a rectifier with natural commutation (11.2 %). The conducted experiments and the results of their analysis proved the expediency of using the developed exciter with forced capacitive commutation.

EXPERIMENTAL STUDY OF STATIC CHARACTERISTICS ASYNCHRONOUS MACHINE IN DYNAMIC BRAKING MODE WITH INDUCTION RESISTANCE IN THE ROTOR WINDING

The article discusses the results of a study of the static electromechanical characteristics of an asynchronous machine (AM) when prototypes of induction resistances (IR) with improved parameters are included in its rotor circuits. The dynamic braking (DB) of asynchronous machines, which is widespread in practice, provides for the dissipation of the kinetic energy of the rotating parts in the resistance boxes included in the rotor winding. In the process of stopping, to maintain a constant average braking torque AM, a bulky relay-contactor circuit for shunting rotor resistances is used. However, it is not possible to eliminate significant fluctuations in the electromagnetic torque in this way. To optimize the DB AM process, it is proposed to include a three-phase IR in the rotor winding instead of resistance boxes, the value of which automatically decreases along with the rotor current frequency. This approach allows you to abandon contact equipment and ensure smooth braking of the machine with fluctuations in the electromagnetic moment in narrower limits. The known IR designs are designed for starting modes of induction motors with a wound rotor, but they cannot ensure the constancy of the torque on the AM shaft in the DB mode. Therefore, the purpose of the study is to develop and experimentally confirm the effectiveness of simple control circuits of an induction machine in the specified mode with improved contactless induction rheostats in the rotor. The paper presents a diagram of a pilot plant and a figure explaining the design features of the IR. The studies were carried out for an asynchronous machine of the MTB-412-8 type, equipped with a thyristor exciter and a tachogenerator. The three phases of the AM rotor included ICs connected by a "star". The experiments were carried out in the direction of obtaining the necessary braking characteristics of the AM by varying the switching circuit of the stator phases and the value of the current supplying them. The figures show the mechanical characteristics of AM, obtained in the process of studying the influence on them of three typical circuits for switching on the phases of the stator winding and two values ​​of the fixed supply current. The research results show that the desired form of the mentioned AM characteristics is achieved only when using the stator phase switching in a function of the rotor speed and a constant supply current value.

EXPERIMENTAL STUDY OF THE STATIC CHARACTERISTICS OF THE SYNCHRONOUS MACHINE IN THE MODE OF DYNAMIC BRAKING WITH INDUCTION RESISTANCE IN THE WINDING OF THE STATOR

The article discusses the results of a study of the static electromechanical characteristics of a synchronous machine (SM) when prototypes of induction resistances (IR) with improved parameters are included in its stator circuits.
 Widespread in practice, dynamic braking (DB) of synchronous machines provides for the dissipation of the kinetic energy of the rotor in the resistance boxes included in the stator winding. In the process of stopping, to maintain the constancy of the average braking torque of the SM, a bulky relay-contactor shunt circuit for stator resistances is used. At low speeds, regulation of the excitation current of the SM or its forcing can also be applied. However, it is not possible to eliminate significant fluctuations in the electromagnetic moment in this way.
 To optimize the SM DB process, instead of resistance boxes, it was proposed to include a three-phase induction resistance in the stator winding, the value of which automatically decreases along with the stator current frequency. This approach allows you to drastically reduce the number of contact equipment and ensure smooth braking of the machine with electromagnetic moment fluctuations within narrow limits. Known IR designs are designed for asynchronous motors with a phase rotor and satisfy the requirements of the given quality factor of their starting characteristics, but cannot ensure the constancy of the torque on the SM shaft in the DB mode.
 Therefore, the objective of the work is to improve the design of the IR and obtain the necessary inhibitory mechanical characteristics of the SM using experimental studies.
 The work provides a pilot plant diagram and a drawing explaining the design features of the IR.
 The studies were performed for a synchronous machine, type МСА-72 / 4А, equipped with a thyristor exciter and a speed sensor. In three phases of the SM stator, IRs connected by a "star" were turned on. The experiments were carried out in the direction of obtaining the necessary braking characteristics of the SM by varying the design of the internal elements of the IR.
 The figures show the mechanical characteristics of the SM obtained in the process of studying the effect on them of the thickness of the inner steel rings and massive ferromagnetic disks at three values of the fixed excitation current.
 The research results show that the desired form of the mentioned characteristics of the SM is achieved only when using massive internal elements in the design of the IR. A separate figure shows the curves of changes in some values of the SM load, which will facilitate the development of methods for calculating the DB mode of the machine for the optimal design of the IR.

A study of the system “thyristor exciter - synchronous motor of a pump unit” in the conditions of a deep voltage drop

A mathematical model of the system “synchronous motor of a pump unit - thyristor exciter” was developed. The operation of the system model was investigated in the MatLab environment. The situation of a deep voltage drop in the power supply network was investigated. Graphs of changes in the currents of the stator and rotor windings during a voltage drop in the supply network were obtained and their analysis was performed.

The use of drive turbine cooling systems based on renewable energy sources

The mechanical energy of the turbine is converted into electric energy by means of a rotating magnetic field of the rotor in the stator. The voltage and current in the rotor windings create a thyristor excitation system. The generator on the shaft of the central turbine usually has problems with cooling the turbine. The progress of turbine construction mainly depends on the success in solving this problem today. The article describes the main scientific idea of improving the efficiency of electric generators, namely the possibility of using renewable energy sources. For the first time, data on the possibility of using cooling systems based on renewable energy are presented.

Analysis of the Trip of a High-Power Turbine-Generator of a Nuclear Power Plant Upon Damage of the Stator Winding Insulation According to Data of Monitoring and Modeling

The operating conditions of a turbine-generator with the stator winding short-circuited to the frame are analyzed. The features of the shape of the zero-sequence voltage during arcing in the damaged gap are described. The operation of the relay protection in these conditions is analyzed. The real oscillograms of the subsequent suppression of the rotor field are theoretically justified. It is shown that improving the thyristor excitation system is necessary and possible.

Turboset shaft voltage

The paper presents an analyses of shaft voltage and bearing current phenomena in electrical machines. An overview of the causes of these voltages and currents and their possible consequences is also given. The influence of the thyristor excitation system on the level of shaft voltages is examined, followed by the proposal of a measuring method and the preventive measures for shaft voltage reduction. Finally the paper reports the experimental measurements of shaft voltages on a turbo set that is a part of the Electric Power Industry of Serbia.

Оценка быстродействия энергоблоков «синхронный генератор – ОРПМ» при регулировании напряжения в схемах выдачи мощности электростанций

The main method of voltage and reactive power control is to change the excitation current of synchronous generators. This method requires a complex excitation system that can provide a necessary control range. In addition, response performance of such control is constrained by a long time constant of the excitation circuit. One of the alternative control methods is the use of power units including synchronous generators with a non-controlled excitation system and unified power flow controllers (UPFC). The MATLAB Simulink software package enabled research of mode control performance of such power units and comparison with the thyristor excitation systems. Furthermore, a real voltage change was analyzed at short-circuit in the power system. The synchronous generator - UPFC power units are proved to implement a high-speed voltage control, which can significantly increase flexibility and adaptability of mode control in the power distribution circuits of the power plants.

Analysis and assessment of VSC excitation system for power system stability enhancement

The voltage source converter (VSC) excitation system is a novel excitation system based on pulse-width modulation (PWM) voltage source converter, which is proposed as improved alternatives to the conventional thyristor excitation systems. This paper aims to provide theoretical confirmation of power system stability enhancement by the VSC excitation system. The reactive current injected to generator terminals by the VSC excitation system can be controlled flexibly. Its capability of enhancing power system stability is investigated in this paper. The simplified model of VSC excitation system suitable for use in system stability studies is developed. An extended Philips–Heffron model of a single-machine infinite bus (SMIB) system with VSC excitation system is established and applied to analyze the damping torque contribution of the injected reactive current to the power system. This paper also gives a brief explanation on why the VSC excitation system can enhance the transient stability in light of equal area criterion. The results of calculations and simulations show that the injected reactive current of VSC excitation system contributes to system damping significantly and has a great effect on the transient stability. When compared with conventional thyristor excitation systems, the VSC excitation system can not only improve the small-signal performance of the power system, but also can improve the system transient stability limit.

Output voltage control of synchronous generator using diode and thyristor excitation structures combined with multivariable H ∞ controllers

In this study, the authors present a comparison between two excitation structures. The first one consists of a diode bridge rectifier connected to a wound field synchronous machine. In the second structure, the diode bridge is replaced by a thyristor one. A multi-input single-output (MISO) H∞ voltage controller is designed for each structure. The proposed controllers take into account the modeling of each structure and permit to guarantee the system stability during the sudden variation of the load connected to the terminal of the main synchronous machine. The performance of each structure is evaluated by experimental tests in the presence of unknown variations of the power system operating conditions. The results show the great efficiency of the thyristor excitation structure combined with the MISO H∞ controller as regards the response time, the voltage drop and the voltage overshoot.

A Hamiltonian Model of Generator With AVR and PSS Parameters*

Take the typical thyristor excitation system including the automatic voltage regulator (AVR) and the power system stabilizer (PSS) as an example, the supply rate of AVR and PSS branch are selected as the energy function of controller, and that is added to the Hamiltonian function of the generator to compose the total energy function. By proper transformation, the standard form of the Hamiltonian model of the generator including AVR and PSS is derived. The structure matrix and damping matrix of the model include feature parameters of AVR and PSS, which gives a foundation to study the interaction mechanism of parameters between AVR, PSS and the generator. Finally, the structural relationships and interactions of the system model are studied, the results show that the relationship of structure and damping characteristic reflected by model consistent with practical system.

Comparison of intelligent fuzzy based AGC coordinated PID controlled and PSS controlled AVR system

This paper attempts to investigate the performance of intelligent fuzzy based coordinated control of the Automatic Generation Control (AGC) loop and the excitation loop equipped with Proportional Integral Derivative (PID) controlled Automatic Voltage Regulator (AVR) system and Power System Stabilizer (PSS) controlled AVR system. The work establishes that PSS controlled AVR system is much more robust in dynamic performance of the system over a wide range of system operating configurations. Thus, it is revealed that PSS equipped AVR is much more superior than PID equipped AVR in damping the oscillation resulting in improved transient response. The paper utilizes a novel class of Particle Swarm Optimization (PSO) termed as Craziness based Particle Swarm Optimization (CRPSO) as optimizing tool to get optimal tuning of PSS parameters as well as the gains of PID controllers. For on-line, off-nominal operating conditions Takagi Sugeno Fuzzy Logic (TSFL) has been applied to obtain the off-nominal optimal gains of PID controllers and parameters of PSS. Implementation of TSFL helps to achieve very fast dynamic response. Fourth order model of generator with AVR and high gain thyristor excitation system is considered for PSS controlled system while normal gain exciter is considered for PID controlled system. Simulation study also reveals that with high gain exciter, PID control is not at all effective. Transient responses are achieved by using modal analysis.

Practical Application of Fiber-Optic Current Sensor in Power System Harmonic Measurement

This paper presents a portable fiber-optic current sensor (FOCS), modified for current harmonic measurement in high-voltage electric power systems. The details of the sensing head redesign are illustrated. Also, both electronic processing block and harmonic analysis algorithm have been illustrated. The practical application of the so-redesigned device has been successfully verified experimentally at a thermal power plant. The measurements have been made for the operation of a 6-kV induction motor with different load conditions and the thyristor excitation of a 15-kV alternating current generator. The experimentally determined current waveforms, the corresponding relative harmonic content computed by discrete Fourier transform, and total harmonic current distortion for various measuring points have been displayed. Important requirements for accurate harmonic measurements have been discussed. The results clearly verified the applicability of the FOCS for monitoring electric power quality as suggested in this paper

Experience in the commercial operation of the pilot asynchronized turbogenerator T3FA-110 at cogeneration plant-22 (TÉTs-22) of the Mosénergo Company

Results of commercial operation of a world pioneer asynchronized turbogenerator T3FA-110 with a capacity of 11 MW and full air cooling at a cogeneration plant are presented. The turbogenerator developed jointly by the Electric Power Research Institute and the Elektrosila Company differs from traditional synchronous generators by the presence on the rotor of two mutually orthogonal windings, a two-channel reverse thyristor excitation system, and a special control system. The special features of design and control allow such generators to operate in the modes of both production and high consumption of reactive power at normal static and dynamic stability. This widens the range of regulation of the voltage level in the connected electric network and makes it possible to bring parallel-connected synchronous generators to optimum operation conditions. The generator can work without excitation for a long time at 70% load. Commercial operation of the pilot T3FA-110 turbogenerator started in December 2003 at TETs-22 of the Mosenergo Company and has proved its full correspondence to the design engineering parameters. A program of wide use of such turbogenerators in the United Power System of Russia (RAO “EES Rossii” Co.) has been developed.

New Equipment for Excitation Systems and Operating Experience

Principles of redundancy of the equipment of excitation systems of powerful synchronous generators are considered and examples of realization of these principles in new high-speed nonbrush field excitation systems, static thyristor excitation systems, and kits for control systems (KOSUR) for reconstruction of excitation systems with high-frequency, nonbrush, and commutator exciters are discussed.

Improvement of power system stability using multivariable excitation control

AbstractImprovement of power system stability is the most important issue of generator excitation control. The combination of thyristor excitation with ΔP‐PSS is usually applied to recently installed very large turbogenerators. This power system generator (PSS) is not always effective for wide‐range operation of generators or for various changes of power system line impedance. The application of the optimal control theory, especially the multifeedback signal resulting from the Riccati equation has been studied and reported in many papers. These papers, however, do not clearly describe how to set performance index values and the studies reported in them also use inadequate signals. This paper presents a method to set the performance index values to make adequate feedback signals for selecting actual control on the application of the Riccati equation. Further, the developed PSS using multifeedback signals is applied to actual very large turbogenerators after confirming the performance of effective damping for power oscillation.

Introduction of dynamic braking systems for increasing the operating reliability of high-lift pump units

1. The use of dynamic braking on high-lift units with excitation of the synchronous motor from an electrical machine exciter considerably reduces the maximum reverse speed (1.5–1.7 times). Thyristor excitation with an AER by deflection of the stator voltage of the motor additionally reduces the reverse speed by 20% in comparison with electrical machine excitation. 2. The factors affecting braking effectiveness are the time of delivering the exciting voltage to the motor's rotor, duration and magnitude of the rotor's current, and magnitude of the Bethel resistors in the stator circuit. 3. Dynamic braking reduces the level of vibration of individual components of the unit by 2.5–4 times in comparison with the regime of stopping the unit in free running down, which substantially increases the operating reliability of the unit.