Automatic Excitation Regulators Research Articles

STUDY OF STATIC STABILITY OF COMPLEX ELECTRICAL SYSTEMS

An analysis of the currently used algorithms and programs for assessing the static stability reserve of electric power systems (EPS) is carried out, which make it possible to build the boundaries of stability and calculate the sensitivity coefficient of all generators of the power system, which speeds up the process of selecting the settings of automatic excitation regulators (AER) and increases the visibility of the calculation results. On the example of the well-known in the theory of automatic regulation "Butterworth's rule", a qualitative analysis of the transient process in the control system in the presence of optimal stochastic AER is given and it is proved that the method of synthesis of optimal stochastic systems allows, under conditions of real limitations, to more accurately and qualitatively build regulators that provide the necessary stabilization accuracy. Keywords: static stability, electric power system, transient process, vibrational stability, constant voltage, aperiodic stability, automatic excitation regulator.

Features of practical application of electric power system’s stability estimation methods

Timeliness of the topic is conditioned by the need to keep up ample of static and transient stability margins in modern electrical power systems. Object of an article is to give a determination of present methods of evaluating damping of systems with synchronous machines, in the context of their effectiveness. And also to estimate the effectiveness of these methods in the performance of the task concerned with selecting of best settings of automatic excitation regulators of synchronous generators. This analysis led us to the conclusions, in particular, about possibility to apply the root locus methods in estimating stability of electrical power systems, and also about genericity of the matrix method with the use of QR-algorithm, which is widely used in practice of calculating stability.

Сильное регулирование возбуждения и стабилизация режимов в многомашинной энергосистеме

In the previously published papers: «Features of Strong Excitation Control of Synchronous Generators in a Complex Power System» (magazine Electric Power Plants, 2019, No. 7) and «Improving Power System Stabilization in Response to Grid Disturbances» (magazine Electricity, 2020, No. 5 ) the author, on the basis of experimental data, showed that the standard method of stabilizing modes in the case of disturbances in a modern complex power system, adopted in the Unified Energy System of Russia, is not always effective. Automatic excitation regulators (AER) rely on the deviation and derivative of the voltage frequency at the terminals of the generators. In oscillatory transient modes, these signals differ significantly in phase from the deviation and derivative of the generator rotation frequency. Instead of reducing the resulting vibrations, this can cause vibration amplitude and duration increase. The author suggested an alternative method based on comparing frequency of rotation of generator to frequency on the busbars of the power plant along with derivative of the difference. Results of full-scale tests, confirming effectiveness of the proposed method, were presented. Effectiveness of the proposed method was also verified in the discussion in the Electric Power Plants magazine, after the publication of the above articles. This publication offers physical perspective of the difference between the proposed method of stabilization versus the standard method, and illuminates why it’s effective in modern complex power systems. Previously unpublished oscillograms of transient processes are also presented.

Estimation of Damage Rotor Shaft of Turbogenerators with a Diode Brushless Excitation System

The damage to the rotor shafts of high-power turbo generators is estimated as a result of the resonant in-teraction between the generator and the exciter caused by the operation of the automatic excitation regulator (AER) by mathematical modeling. The analysis covers turbo generators with a capacity of 300 to 1000 MW with a diode brushless excitation system (DBES). The simulated circuit includes a turbo generator with a block transformer, a power transmission line, an exciter in the form of a reversed synchronous generator with a rotat-ing rectifier diode converter unit, a static thyristor converter, and a sub-exciter in the form of a synchronous machine with permanent magnets. When modeling the electrical part, an approach is used from the positions of its own coordinates, which ensures maximum methodological consistency of the models of the listed devices and allows directly reproducing resonant phenomena at torsional vibration frequencies with the determination of instantaneous values of currents, voltages and electromagnetic moments of the turbo generator and exciter. The mechanical system is presented taking into account the exciter and sub-exciter as a seven-mass system. AER is introduced into the mathematical model by means of transfer functions with corresponding coefficients and time constants. The control system of the thyristor converter is represented in the model by a generator of line-arly increasing signals, a body for comparing these signals with the signal from the AER and a control pulse generator. To assess the damage rate, the deformation criterion for soft and hard loads in the zone of low-cycle fatigue and the force criterion in the zone of multi-cycle fatigue were used. A comparative quantitative assess-ment of the damage in the neck of the G-E shaft line in the resonant interaction between the exciter and the generator with different automatic excitation control systems is given. The influence of attenuation of electro-magnetic transients and damping of torsional vibrations on the damage values is analyzed. The results ob-tained can be used to analyze the functioning and determine the settings of the AER.

Modeling a gas-turbine unit with prognostic regulators of voltage and speed

Object. The article presents the results of computer research, the purpose of which was to develop dynamic models of low-power twin-shaft gas turbine units (GTU) equipped with automatic excitation and speed regulators with predictive links. Methods. Setting up the regulators of the commissioned gas turbine requires complex calculations. The use of algorithms that make it possible to improve the classical regulators with minimal costs allows us to effectively solve the problems of their settings. These include prognostic algorithms that allow you to configure the automatic control system using one parameter - forecast time. The models presented in the article are implemented using the Simulink package of the MATLAB system. Results. The influence of prognostic algorithms on the quality of controlling the voltage and rotor speed of a gas turbine generator in the modes of connecting and dumping loads is studied. Studies have shown that increasing the coefficient of the amplifier of the auto-predictive speed regulator can significantly reduce overshoot and the transition process, and also has a positive effect on voltage regulation. Conclusions. The results made it possible to formulate the following conclusions: the use of prognostic regulators when connecting an additional load to the gas turbine allows you to remove the oscillation, reduce voltage dips, reduce the transient time by 2.5 s; with a sharp load shedding due to the use of prognostic algorithms, it is possible to completely remove the oscillation, reduce the overshoot of the rotor speed and overvoltage at the generator terminals, and also significantly reduce the transient time for speed compared to classical regulators; the use of prognostic algorithms allows us to obtain acceptable quality indicators of transients without the use of complex regulator tuning procedures.

A control method of an additional damper for hydro turbine speed governor system in hydro-dominant power system

With the rapid development of the national inter-connected power grid, the fast automatic excitation regulators and fast turbine governor have been widely used. In the current system, some power plants adjust the response of turbine governor system to a very sensitive level to meet the primary frequency regulation assessment index, which, however, brings the negative damping intensively. Under the circumstances, the ultralow frequency oscillation (ULFO) phenomenon emerged in hydro-dominant power system. In order to solve the problem of ULFO, the hydro-turbine Governor Additional Damper (GAD) based on the phase compensation which adapt to the ULFO is developed. It is improved on the basis of traditional PSS and the design of the control system is relatively simple. As phase compensation based on the field testing and modeling of turbine governor, GAD can provide the power system with the positive damping, which contributes to improving the stability and security of the system. According to the impact of the mechanism of turbine governor on the dynamic stability of the power system and the research of modeling and parametric test, the proposed method not only supports positive damping, but also eliminates the negative damping of the speed governing system, which can significantly suppress the ultralow frequency oscillation and make it feasible to configure the GAD parameters accoraing to field test.

Determination of Frequency Characteristics of a Power System in the Course of Commissioning Operations Performed on the Excitation System of the TG5 Turbogenerator of the Beloyarskaya Nuclear Power Plant

A method of determining the amplitude-frequency characteristics and phase-frequency characteristics of a power system by the exposure of the output adder of an automatic excitation regulator to a white noise signal containing a spectrum of the frequency range of the electromechanical oscillations for different tuning parameters of the regulator is presented. The safety of the method and the possibility of using it for verification of physical and digital models of power systems are demonstrated.

Особенности практического применения методов оценки устойчивости электроэнергетической системы

Timeliness of the topic is conditioned by the need to keep up ample of static and transient stability margins in modern electrical power systems. The article object is to give a determination of present methods of evaluating damping of systems with synchronous machines, in the context of their effectiveness. And also to estimate the effectiveness of these methods in the performance of the task concerned with selecting best settings of automatic excitation regulators of synchronous generators. This analysis led us to the conclusions, in particular, about possibility to apply the root locus methods in estimating stability of electrical power systems, and also about genericity of the matrix method with the use of QR-algorithm, which is widely used in practice of calculating stability

Torsional Oscillations and Damageability of the Rotor Shaft of the Turbogenerators Fitted with Automatic Regulated Excitation

The assessment of damage to the rotor shaft of the turbine-generator due to resonant interaction between generator and exciter, due to automatic excitation regulator (ARV) by mathematical modeling. The thyristor system of independent excitation is used in the work. The simulated circuit includes a turbogenerator with a block transformer, a power line, a synchronous generator and a gate-controlled exciter Converter. When modeling the electrical part, an approach is used from the position of its own coordinates, which provides maximum methodological consistency of the models of the listed devices and allows directly reproducing resonant phenomena at frequencies of torsional vibrations with the determination of instantaneous values of currents, voltages and electromagnetic moments of the turbo generator and exciter. The mechanical system is presented taking into account the exciter as a six-mass system. ARV is introduced into the mathematical model by means of transfer functions with corresponding coefficients and time constants. The control system of the gate Converter of the exciter is represented in the model by a generator of linearly increasing signals, a body for comparing these signals with the signal from the ARV and a control pulse generator. The deformation criterion for soft and hard loads in the zone of low-cycle fatigue and the force criterion in the zone of multi-cycle fatigue were used to assess the damage. A comparative quantitative assessment of the damage to the generator rotor shaft under resonant interaction at all subsynchronous frequencies of torsional vibrations and in near-resonant modes is given. The influence of attenuation of electromagnetic transients and damping of torsional vibrations on the damage values is analyzed.

ANALYSIS OF TRANSITION PROCESSES IN POWER SYSTEMS WITH HYDROENERGETIC ISTALLATIONS

This article is presented an overview of hydro mechanical and electromechanical processes. Little attention was paid to the study of these two areas at the same time. The two directions above are the results of a simultaneous study. A joint study of these components of a single process received little attention. In conclusion, conclusions are drawn on the effect of AER (automatic excitation regulator) on the damped operational parameters and ensuring the stable operation of hydropower plants. The results can be used in the reconstruction of existing and designing new pumping stations, so transients are considered for a certain range of variation of these parameters. One of the difficult modes is to reduce the voltage on the tare of the station,especially on the system buses. The analysis shows that a decrease in voltage on the system buses by more than 8% leads to the output of the LED out of synchronism, if during this period for some reason the ARV of the machine is turned off. The characteristics of transients with a decrease in voltage on the system tires by 2% are given.

Implementing the System Functions of the Automatic Proportional-Derivative Excitation Control of Synchronous Generators

Subsystems of Russian automatic excitation regulators that ensure the maximum dynamic stability and effective damping of oscillations in an electric power system are described. They are compared to stabilizers included in international and national standards of other countries. It is shown that the Russian system stabilizer PSS2RU is effective in oscillation damping in various circuits and modes.

Some problems related to using automatic control of voltage of synchronous generators in case of frequency change

Considered is the possibility of using a proportional type automatic excitation regulation implemented in the form of compounding devices with an electromagnetic voltage corrector changing excitation depending on the frequency and voltage at the generator terminals in particular power supply systems. It is demonstrated that the suggested solution is more efficient compared to automatic excitation regulators having no frequency control. Graphs are provided showing changes in consumption of active and reactive power by an equivalent load characteristic of industrial customers, depending on frequency, and depending on voltage. Analysis of the evaluation results shows that implementation of the proposed solution reduces the active power imbalance from 6.5% to 3.5% (with a 10% frequency decrease). Proportional type automatic excitation controls with frequency control may find application in in-house power supplies of companies with a continuous operation process, where high quality of power supply is achieved by using a second independent power supply generated on a standalone basis, with no connection to the power grid. As the record of operation of such enterprises shows, the effectiveness of such a solution is quite high due to minimization of damage from voltage dips that occur in the external power supply system due to damage and abnormal conditions in 110 and 220 kV networks. As recommendations, features are assessed of the proposed automatic excitation regulator with frequency control in an embodiment providing for generators of the companies’ own power supplies operating in parallel with the external power grid, as well as in cases of some disruptions of static stability.

Software and Hardware Complex for Setting of Automatic Excitation Regulators of Turbogenerators

The motivation of the presented research is based on the needs for development of new methods and tools for research setting problem of automatic excitation regulators of turbogenerators. Simulation tools must meet the requirements of reproduction processes reliability in all elements of electric power system. The developed block diagram of the adequate mathematical model of automatic excitation regulator is presented. The simulation results of electric power system scheme confirm the adequacy of the reproduction processes of functioning of automatic excitation regulator and a generator.

Certification Testing of Home- and Foreign-Made Automatic Excitation Regulators Using the STC-UPS Electrodynamic Simulator

The experience and brief results of the qualification and certification testing of automatic PD excitation regulators of synchronous generators conducted on the STC UPS electrodynamic simulator are described.

System for Monitoring Automatic Excitation Regulators of Synchronous Generators with Brushless Excitation Systems

An algorithm for a monitoring system for automatic excitation regulators in synchronous generators is described. It takes the features of brushless excitation systems into account and provides effective monitoring of their operation. Results from a test of a prototype of the system on a digital-analog physical test stand at the Scientific and Technical Center of the United Power System are also reported.

Method of determining the optimal settings of automatic excitation regulators of synchronous machines in EPS

The stability of the electric power system can be improved by forming of the correct settings of automatic exciting regulators. Currently, there is no unified methodology of automatic exciting regulators, so analysis of their impact is still an urgent task. The article describes the approach to solving above-mentioned problem, which combines several methods. Research based on Hybrid Real Time Simulator of EPS developed in Tomsk Polytechnic University.

Research on DSP-Based Automatic Excitation Regulator in Small Rural Hydropower Station

Excitation regulator has played an important role to ensure that generator run safely and stably. However, in some remote areas, the rural small generator excitation control system is very backward, and it has hindered the development of Chinese agriculture and the pace of new countryside construction. This paper introduced a kind of structure and basic principle of DSP-based automatic excitation regulator, which was applied to rural small generator. We chose TMS320LF2407A chip as the core of regulator control system; the regulator adjusted PWM based on PID control strategy to control the exciting current. The theoretical analysis showed that the regulator had the characteristics of simplicity and reliability, well dynamic and static characteristics, and it could also adjust its own state quickly. The result was applicable to small rural hydropower station.

Automatic excitation control of synchronous generators as an effective means to ensure the reliable parallel operation of generation equipment and the united power system as a whole

The reliability of the parallel operation of generation equipment and the functioning of the power system as a whole depends on the effectiveness of automatic excitation regulators (AER) and excitation systems (ES) of synchronous generators at power plants. The SO-UPS elaborated, approved, and enforced the standard Requirements to Excitation Systems and Automatic PD Excitation Regulators of Synchronous Generators, which extends and supplements the requirements to ESs and AERs established by the technical regulations currently in force. A system regulators monitoring system is being developed.

The excitation control system of the ASK-100-4 asynchronous compensator

The excitation regulation system of the ASK-100-4 asynchronous compensator is described. The main modes of operation of the compensators in the Beskudnikovo substation of the “Mosenergo” JSC are considered. The results of an investigation of an actual sample of an AER-ASC automatic excitation regulator on a computer bench, operating in real time, are presented.

A computer test bench for checking and adjusting the automatic regulators of generator excitation systems

A computer test bench for testing and debugging natural samples of the automatic excitation regulation systems of generators, the protection units and the power part of the excitation system is described. The bench includes a personal computer with specialized input-output circuit boards for analog and digital signals, and enables the time and cost involved in developing and checking control systems to be reduced considerably. The program employed operates in real time and enables the automatic excitation regulators of synchronous generators and generators with longitudinal-transverse excitation in a specific power system to be adjusted.