RU2339144C1 - Method for improving dynamic stability and damping oscillations of electric-power systems and device for its realisation - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention is attributed to the field of electric engineering and can be used for improving dynamic stability of electric-power systems and for damping electromechanical vibrations of generator rotor. In the method for improving dynamic stability and vibrations damping, alternating current synchronous generator rotor speed is monitored and synchronous generator rotor speed is lowered after insertion disturbance into system up to the rotation rate of magnetic field by means of mechanical deceleration of mentioned generator rotor. Electromagnetic brake is mechanically linked with generator rotor and prime mover rotor via clutches, voltage on generator terminals and generator stator current is continuously measured by which parameters the generator electromagnetic power is determined. This power is compared with electromagnetic power value which existed before insertion of disturbance. When result of power comparison exceeds predefined value, control signal for electromagnetic brake switching on is generated. The value of decelerating torque is determined by difference between values of the measured electromagnetic power and the electromagnetic power which existed before disturbance insertion, and duration of decelerating torque application is determined by change in generator rotor speed. To do this the generator rotor speed after disturbance insertion is determined and compared with the value which existed before disturbance insertion. Electromagnetic brake is switched off when equality of current rotor speed and rotor speed in mode before disturbance is reached and when measured power is equal to the power which existed before disturbance insertion.

EFFECT: dynamic stability of electric-power system improvement and providing damping of electric-power system electromechanical vibrations.

11 cl, 9 dwg

Description

FIELD OF THE INVENTION

The present invention relates to electric power, and more specifically to a method for improving the dynamic stability and damping of electromechanical vibrations of electric power systems and a device for implementing this method.

The invention can be used to improve the dynamic stability of electric power systems (EES), as well as to damp the electromechanical vibrations of the generator rotor. Dynamic stability is understood to mean the property of the system to return to normal operation and close to it after large disturbances, such as a short circuit, open circuit, disconnection of electric generators, a large amount of load power change. Electromechanical vibrations arise due to disturbances in the system or are the result of the work of inconsistently tuned systems of automatic control of EPS elements: synchronous generator, controlled reactive power sources and other devices.

State of the art

Electric power systems are designed to economically and reliably provide consumers with electric energy in the required volumes and of proper quality. EES include primary engines (steam, hydraulic and gas turbines, piston engines using liquid and gaseous fuels) and synchronous generators for generating electric energy, which are called generating units (GA), raising and lowering power transformers to change the voltage and current electricity, power lines for transmitting electricity over a distance, switching equipment, including switches and disconnectors for changing the configuration of the network and switching and current circuits. Electricity is generated by the GA, then converted into transformers, while the voltage increases and the current decreases without changing the power and is transmitted through power lines to places of electricity consumption. As a rule, power lines are connected to an electrical network. Then the electricity through step-down transformers, through which the voltage decreases and the current increases, is supplied to the consumers of electricity. In addition to these devices, the EPS also contains equipment for measuring parameters, i.e. frequency, voltage, current, power, and regulation of the EES mode.

The main mode in which the EPS operates is the normal mode, characterized by an economical and reliable supply of electrical energy to consumers. In addition to the normal mode, the EPS can operate in a weighted, emergency, post-emergency and normal transition mode. The emergency mode is short-term, as a rule, its duration is determined by the response time of the relay protection and automation of the EPS and switching equipment. Then the system goes into emergency mode. The transition from emergency to post-emergency is called a transient. In the transition process, there are two processes - electromagnetic and electromechanical. The electromagnetic transition process occurs quickly in the electrical part of the EPS (milliseconds), the electromechanical transition occurs in both the mechanical and electrical parts and is associated with the movement of the rotors of the generating units and proceeds from fractions to several seconds. If the system after applying a large disturbance, for example, as a result of a short circuit, shutdown / inclusion of a large load volume, emergency shutdown of generating capacities, returns to the state before the disturbance or close to it, then we can say that the system has dynamic stability.

We can talk about improving the conditions of dynamic stability of the EPS, if it is possible during the electromechanical transition process to control the electromagnetic and / or mechanical moment on the shaft of the generating unit. To improve the conditions of the dynamic stability of the EPS, a device for forcing the excitation of the generator, a device for compensating the inductive resistance of the power line, and an electric braking device for the rotor of the synchronous generator are used.

The device (figure 1) forcing the excitation of the generator increases the voltage several times over the winding 10 (1) of the excitation of the synchronous generator 10 when a slip of the rotor of the synchronous generator occurs or when the voltage at the terminals of the generator decreases below 85% of the nominal value (operating condition). The generator excitation forcing device consists of a comparison device (slip or voltage, or both) and a voltage source. When the triggering conditions are met, a voltage signal is supplied from the voltage source to the excitation system of the synchronous generator, which leads to an increase in the voltage at the terminals of the field winding to a value that exceeds its nominal value by a number of times equal to the frequency of excitation forcing. In turn, the current in the field coil begins to increase exponentially with the time constant of the field coil, which for generators of various types and power ranges from 2.7 to 13 seconds. For the most common turbogenerators, this value is about 7 seconds.

The principle of operation of the excitation forcing is to increase the excitation current of the generator and, therefore, to increase the electromagnetic moment, which in certain cases allows the generator to maintain synchronous stability after the application of a disturbing effect, for example, a short circuit.

When using automatic excitation control (ARV) 10 (2) with accelerated excitation to improve the conditions of dynamic stability, the rate of increase of the electromagnetic moment of the generator is significantly limited, moreover, the time constant of the excitation winding and, to a lesser extent, the time constant of the pathogen, which limits the possibilities of this method improving the conditions of dynamic stability. In addition, the magnitude of the electromagnetic moment is inversely proportional to the electrical resistance between the generator attachment node and the receiving system node, and after short circuits it is possible to increase this resistance by disconnecting the power line circuits as a result of correct or false triggering of relay protection and EES automation. Thus, the effectiveness of the use of ARV with forced excitation decreases when disconnecting the power line circuits.

In general, the effectiveness of the use of ARV with forced excitation depends on the time constants of the generator, the current state of the electric network and its mode, which does not allow efficient control of the balance of moments on the GA shaft in all states.

The use of a device forcing excitation has the following disadvantages:

it is impossible to quickly increase the electromagnetic moment of the generator due to the relatively large time constant of the excitation winding of the synchronous generator (about 7 seconds);

a strong dependence of the electromagnetic moment of the generator on the circuit and the EES mode after removing the disturbance.

The device (figure 2) for compensating the reactance of the line is used to increase the electromagnetic moment on the generator shaft. Compensation of the reactance of the line is carried out by including capacitive resistance in the line, for example, capacitor banks, the value of which is determined by the degree of compensation of the line. When compensating for part of the line resistance, the electromagnetic moment of the generator increases, all other things being equal, and this improves the conditions of dynamic stability, and in certain cases allows the generator to maintain synchronous stability after application of a disturbing effect, for example, a short circuit.

When using a compensation device for the inductive resistance of a power line, an increase in the electromagnetic moment depends, among other things, on the voltage at the ends of the power line, which decreases during transients in the EPS, which reduces the effectiveness of this method.

In general, the efficiency of compensating the reactance of a power transmission line largely depends on the current state of the electric network and its mode, which does not allow you to effectively manage the balance of moments on the GA shaft.

The closest technical solution is the method of electric braking (ET) of the rotor of a synchronous generator, carried out using an electric braking device.

Electrical braking is carried out by connecting the brake generator of resistance to the tires of the generator (Fig. 3). When resistance is turned on, an additional electromagnetic moment is created on the GA shaft, which leads to braking. To connect the braking active resistance 10 (4), use a mechanical power switch 10 (3) or a key based on power semiconductor electronics.

When braking resistance is turned on, the electromagnetic moment on the GA shaft substantially depends on the voltage value at the point of attachment of this resistance. To switch the braking active resistance, you need a high-speed high-voltage switch, which has a relatively small resource, or an electronic switch, which is performed in a high-voltage version and for high switching currents, which is quite expensive. The inclusion of braking active resistance leads to a decrease in voltage at the point of attachment. When the voltage decreases, the electromagnetic moment of the generator decreases, which worsens the conditions of electrical braking of the GA shaft and reduces the effectiveness of this method. To eliminate the voltage drop, in addition to the braking resistance, it is necessary to install a reactive power compensator, which has a high cost and, in addition, will stand idle waiting for the use of electric braking, although it could be used to regulate the voltage in other nodes of the electric network.

The disadvantages of this method of using electric braking include:

a strong dependence of the created braking torque on the GA shaft on the voltage level at the point of attachment of the braking active resistance, which reduces the efficiency of applying electrical braking when the voltage is reduced;

a decrease in voltage at the point of attachment of the braking active resistance, which can cause a deterioration in the conditions of the dynamic stability of the EPS as a whole;

the need to allocate space for the construction of inhibitory resistances.

SUMMARY OF THE INVENTION

The technical task of the present invention is to provide a method for improving the dynamic stability of an electric power system, which would eliminate the dependence of the generated braking torque on the shaft of the generating unit (HA) on the line resistance and voltage levels on the power transmission connecting the generating unit and the receiving system, eliminating the need for additional high-voltage switches , semiconductor switches and other equipment, eliminate the need to allocate space th for the construction of braking active resistances.

Another objective of the present invention is to provide a method for damping electromechanical vibrations of an electric power system.

Another objective of the present invention is to provide a device for improving the dynamic stability of an electric power system, the constructive implementation of which would eliminate the dependence of the generated braking torque on the GA shaft on the voltage level at the connection point of the device.

Another objective of the present invention is to provide a device for damping electromechanical vibrations of an electric power system.

The problem is solved by creating a way to improve the dynamic stability of the electric power system, containing many primary motors and synchronous alternators, power transformers, power lines, switching equipment and load, which consists in monitoring the rotational speed of the rotor of the synchronous alternator, reduce the speed rotor rotation of the synchronous generator after applying a disturbance to the system up to the magnetic I stator, this method is characterized by the fact that the rotation speed of the generator rotor is reduced by mechanical braking of the specified generator rotor, for which the electromagnetic brake is mounted coaxially with the generator shaft and the primary engine shaft, with the generator rotor and the primary engine rotor by means of couplings, continuously measure the voltage at the terminals of the generator and the current of the stator of the generator, which determine the electromagnetic power of the generator, comparing t the obtained value of the electromagnetic power of the generator with the value of electromagnetic power before the perturbation is applied, if the comparison value exceeds the specified value, a control signal is generated to activate the electromagnetic brake, and the braking torque is determined by the difference between the values of the measured electromagnetic power and electromagnetic power before the perturbation is applied , and the duration of application of the braking torque is determined by the change in the speed of rotation of the rotor of the generator, for which redelyayut generator rotor speed applications after a disturbance and compared with the value before the perturbation application, the electromagnetic brake is switched off on reaching equal current rotor speed and rotor speed for prior to the disturbance, and with equal power and the measured power to the disturbance application.

It is advisable that when making a mechanical connection, the electromagnetic brake is placed in a position selected from the group consisting of: from the generator side, from the primary engine side, between the generator and the primary engine.

In an alternative embodiment, the task is solved by creating a way to improve the dynamic stability of the electric power system, containing many primary motors and synchronous alternators, power transformers, power lines, switching equipment and load, which consists in monitoring the rotational speed of the rotor of the synchronous alternator current, reduce the rotor speed of the synchronous generator after applying a disturbance to the system up to the rotational speed of the magnetic field of the stator, this method is characterized in that the rotor speed of the generator rotor is reduced by mechanical braking of the specified rotor of the generator, for which the electromagnetic brake is placed mechanically, connected coaxially with the generator shaft and the primary motor shaft, with the generator rotor and rotor the primary engine through the couplings, continuously measure the voltage at the terminals of the generator, compare the obtained value of the voltage at the terminals of the gene an actuator with a predetermined voltage value that is in the range from 65% to 95% of the nominal voltage value, in case the comparison value is lower than the preset value, a control signal is generated to activate the electromagnetic brake, while the generator stator current is additionally continuously measured, the electromagnetic voltage is determined generator power according to the measured values of voltage and current, compare the obtained value of the electromagnetic power of the generator with the value of electromagnetic power before disturbance , the magnitude of the braking torque is determined by the difference between the values of the measured electromagnetic power and the electromagnetic power before the disturbance is applied, the duration of the braking torque is determined by the change in the rotation speed of the generator rotor, for which the rotation speed of the generator rotor after the disturbance is determined and compared with the value before the disturbance is applied, turn off electromagnetic brake when the current rotor speed is equal to the rotor speed in the pre-disturbance mode, etc. equality of the measured power and the power to the disturbance application.

It is useful that when making a mechanical connection, the electromagnetic brake is placed in a position selected from the group consisting of: from the generator side, from the primary engine side, between the generator and the primary engine.

In an alternative embodiment, the task is solved by creating a way to improve the dynamic stability of the electric power system, containing many primary motors and synchronous alternators, power transformers, power lines, switching equipment and load, which consists in monitoring the rotational speed of the rotor of the synchronous alternator current, reduce the rotor speed of the synchronous generator after applying a disturbance to the system up to the rotational speed of the magnetic field of the stator, this method is characterized in that the rotor speed of the generator rotor is reduced by mechanical braking of the specified rotor of the generator, for which the electromagnetic brake is placed mechanically, connected coaxially with the generator shaft and the primary motor shaft, with the generator rotor and rotor the primary engine by means of couplings, detect the presence of a deviation in the rotor speed of the generator rotor as a result of the application of disturbances to the system We then determine the difference in the rotational speeds between the measured speed and the rotational speed before applying a disturbance, compare the obtained difference with the set value, if the comparison value is higher than the set value, generate a control signal to activate the electromagnetic brake, while continuously measuring the voltage across the terminals of the generator and the stator current of the generator, which determine the electromagnetic power of the generator, determine the braking torque from the difference in the values of the measured electromagnetic power and electromagnetic power before the perturbation is applied, the duration of application of the braking torque is determined by the change in the rotation speed of the generator rotor, for which the rotor speed of the generator is determined after the perturbation is applied and compared with the value before the perturbation is applied, the electromagnetic brake is disabled when the current rotor speed is equal and rotor speed in the pre-disturbance mode and when the measured power and power are equal before the disturbance is applied.

It is advisable that when making a mechanical connection, the electromagnetic brake is placed in a position selected from the group consisting of: from the generator side, from the primary engine side, between the generator and the primary engine.

The problem is also solved by creating a method of damping the electromechanical vibrations of the electric power system, which consists in monitoring the rotor speed of the synchronous alternator, voltage and stator current, continuously measuring the voltage at the terminals of the generator and the current of the generator stator, which determine the electromagnetic power of the generator , determine the time derivative of the voltage across the terminals of the generator, determine the derivative of the generator stator current in time, the deviation of the measured rotor speed from the rotational speed in steady state is determined, the derivative of the measured rotor speed in time is determined, the derived derivatives of voltage, current, the deviation of the rotor speed of the generator and the deviation of the rotational speed are summed, and a control electric signal is obtained, which is fed to a voltage converter for damping oscillations.

The problem is also solved by creating a way to improve the dynamic stability and damping of the electromechanical vibrations of the electric power system, containing many primary motors and synchronous alternators, power transformers, power lines, switching equipment and electrical loads, which consists in monitoring the speed of rotation of the synchronous rotor alternator, reduce the rotational speed of the rotor of the synchronous gene after applying a disturbance to the system to the rotational speed of the stator magnetic field, according to the invention, the rotor speed of the generator rotor is reduced by mechanical braking of the specified rotor of the generator, for which the electromagnetic brake is placed coaxially with the generator shaft and the primary motor shaft, and the generator rotor and the rotor of the prime mover by means of couplings, continuously measure the voltage at the terminals of the generator and the current of the generator stator, which m determine the electromagnetic power of the generator, compare the obtained value of the electromagnetic power of the generator with the value of the electromagnetic power before disturbance is applied, if the comparison value exceeds a predetermined value, a control signal is generated to activate the electromagnetic brake, while the magnitude of the braking torque is determined by the difference in the measured electromagnetic power and values of electromagnetic power before the perturbation is applied, and the duration of application of the braking torque determines by changing the rotor speed of the generator rotor, for which the rotor speed of the generator is determined after the perturbation is applied and compared with the value before the perturbation is applied, then the electromechanical vibrations of the electric power system are damped, for which the time derivative of the voltage at the generator terminals is determined, the current derivative is determined the stator of the generator in time, determine the deviation of the measured rotor speed from the rotational speed in the steady state, determined yayut derivative of the measured rotor speed with respect to time, the received signals are summed derivatives voltage, current and deviation generator rotor speed and the magnitude of the rotation speed deviation is obtained and the control electrical signal which is fed to a voltage converter for damping vibrations.

The problem was also solved by creating a system for improving the dynamic stability and damping of electromechanical vibrations of an electric power system, containing many primary motors and synchronous alternators, power transformers, power lines, switching equipment and electrical loads, this system contains a generator rotor speed sensor, a means of reducing generator rotor speed after application of disturbance to the system up to the stator magnetic field, made in the form of an electromagnetic brake containing a brake disk, an electromagnetic system formed by a magnetic circuit and an inductor, the disk is placed in the gap of the magnetic circuit, according to the invention, the electromagnetic brake is placed coaxially with the generator shaft and the shaft of the primary engine and is mechanically connected with the generator rotor and the rotor of the prime mover by means of couplings, wherein the system comprises a control unit for generating electric control signals an electromagnetic brake and comprising a unit for determining the electromagnetic power of the generator, a unit for comparing the value of the electromagnetic power of the generator after applying the perturbation to the value of the electromagnetic power before applying the perturbation, a unit for generating a control signal for activating the electromagnetic brake if the comparison value exceeds a predetermined value, the system also the voltage sensor at the generator terminals and the current sensor of the generator stator connected to the control unit, to which Also connected is a generator of the rotor speed of the generator rotor, a converter of the magnitude of the braking torque and the duration of the braking torque, the input connected to the output of the control unit, and the output to the coil of the electromagnetic brake, a power source electrically connected to the converter.

Preferably, for the mechanical connection, the electromagnetic brake is placed in a position selected from the group consisting of: from the generator side, from the primary engine side, between the generator and the primary engine.

Brief Description of the Drawings

The invention is further explained in the description of the preferred embodiments with reference to the accompanying drawings, in which:

Figure 1 depicts a diagram of a device for forcing the excitation of a generator according to the prior art.

Figure 2 - diagram of a device for compensating the reactance of a line, according to the prior art.

Figure 3 - diagram of the electrical braking according to the prior art.

4 is a diagram of a system for improving dynamic stability in which an electromagnetic brake is connected between a prime mover and a generator according to the invention.

5 is a diagram of an electromagnetic brake control system according to the invention.

6 is a diagram of a system for improving dynamic stability in which an electromagnetic brake is connected to a generator according to the invention.

7 is a diagram of a system for improving dynamic stability in which an electromagnetic brake is connected to a prime mover according to the invention.

Fig. 8 is a diagram showing the installation of inductance coils of a magnetic system circumferentially in an axial direction to a brake disk, according to the invention.

Fig.9 is a diagram of a combined system for improving dynamic stability and damping of electromechanical vibrations according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The system for improving the dynamic stability of an electric power system comprising a plurality of primary engines and synchronous alternators, power transformers, power lines, switching equipment and load, comprises a sensor 1 (Fig. 4) of a rotor speed of a generator and a means 2 for reducing the rotor speed of the generator during and after the perturbation is applied to the system up to the rotation speed of the stator magnetic field. The tool 2 is made in the form of an electromagnetic brake 3 containing a brake disk 4, an electromagnetic system formed by a magnetic circuit 5 and an inductor 6, and the brake disk 4 is placed in the gap 7 of the magnetic circuit 5.

The shaft 8 of the electromagnetic brake 3 is placed coaxially with the shaft 9 of the generator 10 and the shaft 11 of the prime mover 12 and is mechanically connected to the shaft 9 of the generator and the shaft 11 of the prime mover via clutches 13, 14, respectively.

The system also contains a control unit 15 for generating control signals of the electromagnetic brake 3. The control unit 15 contains a generator unit 16 (Fig. 5) for determining the electromagnetic power of the generator, a unit 17 for storing the value of the electromagnetic power of the generator prior to application of the disturbance, and a unit 18 for comparing the value of the electromagnetic power of the generator after the application of the perturbation with the value of electromagnetic power to the application of the perturbation and the block 19 of the formation of the control signal to turn on the electromagnetic brake when the comparison value exceeds a predetermined value. The output of block 16 is connected to the input of block 17 and the first input of block 19, and the output of block 17 is connected to the second input of block 19. The specified output of block 17 is also connected to one input of block 18, the output of block 16 is connected to the other input of it.

The system also includes a voltage sensor 20 (Fig. 4) at the generator terminals and a voltage converter 21 (Fig. 5), a generator stator current sensor 22 (Fig. 4) and a generator stator current converter 23 (Fig. 5). Blocks 20 and 22 are connected by outputs to the inputs of blocks 21, 23, respectively, of control unit 15.

To the input 24 of the block 15 is connected to the sensor 1 of the rotor speed of the rotor of the generator through the Converter 25 of the rotation speed. Block 27 is connected to the input 26 of block 18, which stores the value of the rotation speed of the generator rotor in the mode before disturbance is applied. To this end, the output of block 25 is connected to the input 28 of block 27, and the output of comparison unit 30 is connected to input 29 of block 27. In the control unit 15, a channel for protecting the brake disk 4 from overheating is formed, for this a temperature sensor of the brake disk (not shown) is connected to the input 31 of the block 18 through a temperature converter 32.

The control unit 15 is connected to the system controller 33 (Fig. 4), which is a top-level controller, and the logic of its operation, as well as the structure, are determined by the requirements for EPS.

The system contains a converter 34 of the magnitude of the braking torque and the duration of the braking torque, the input connected to the output 35 of the control unit 15, and the output 36 to the coil 6 of the electromagnetic brake 3.

The system also contains a power source 37 (Fig.6) power connected to the Converter 34.

To create a braking torque on the shaft of the generating unit, an electromagnetic brake 3 can be used, and for a mechanical connection, the electromagnetic brake 3 can be placed in one of three positions: either from the generator side (Fig. 6) or from the side of the prime mover (Fig. 7 ), or between the generator and the prime mover (Fig. 4).

The electromagnetic brake 3 comprises a shaft 8 (FIG. 4), on which a brake disk 4 of a material with a high electrical conductivity is placed, and an electromagnet that creates a magnetic field in the axial direction to the disk. The electromagnetic system consists of an electromagnet (coil with core) (the core and magnetic core functions are combined) and a brake disc.

Another version of the magnetic system is the installation of inductors with cores around the circumference in the axial direction to the brake disk (Fig. 8). The number of coils is even, and their poles alternate when circumambulating. In both versions, the brake disc has channels for cooling, i.e. It is designed to create a forced circulation of the cooling medium.

The magnitude of the current in the winding of the electromagnet is controlled by the automatic control unit 15 (Fig. 7). The power of the electromagnet winding is provided from a power source 37 through a converter 34 of a braking torque value and a braking torque duration. The specified Converter 34 is a managed voltage (current) Converter. The source 37 of power is the auxiliary system of the system or the operational current of the power plant (AC or DC). The parameters by which the current is regulated are the rotational speed of the GA shaft, the voltage at the terminals of the generator and the current of the generator. In addition, block 15 receives control signals from the system controller 33, which is a higher control level. The control signal is supplied from block 15 to the converter 34, which in turn directly controls the current in the electromagnet winding.

Figure 9 presents a diagram of a joint system for improving dynamic stability and damping of electromechanical vibrations. The system comprises an electromagnetic brake 3 and a control unit 15. The sensor 38 of the temperature of the brake disc through the Converter 32 temperature is connected to the block 18 of the comparison.

The control unit 15 further comprises a summing unit 39, to the input 40 of which a time differentiation unit 41 is connected, a deviation creation unit 43 is connected to the input 42, a time differentiation unit 45 is connected to the input 44, a deviation creation unit 47 is connected to the input 46, to the input 48, a time differentiation unit 49 is connected. The input of block 41 is connected to the output of block 21, the input of block 43 is connected to the output of block 23, which is also connected to the input of block 45, the input of block 47 is connected to the output of block 25, which is also connected to the input of block 49.

The output 50 of block 39 is connected to the input 51 of block 18.

The input 52 of the block 18 is supplied with a threshold value of the temperature of the disk.

In addition, EMT can be performed in conjunction with the generator 10. In this case, EMT can be installed inside the generator housing (not shown). A possible embodiment of the power source 37 in the form of a direct or alternating current generator located on the shaft 8 of the electromagnetic brake 3.

The system is as follows.

The electric power system (EES) consists of generating, transmitting and consuming electricity (EE) equipment. Generating equipment is mainly synchronous turbo and hydro generators, transmission equipment is transformers and power lines.

The state of the EPS at a given moment or time interval is called a mode. The mode is determined by the composition of the included elements of the EPS and their loading. The values of voltages, capacities and currents of system elements, as well as frequencies that determine the process of production, transmission, distribution and consumption of electricity, are called the parameters of the EES mode.

During the operation of the EPS, various kinds of disturbances of the mode arise, caused by short circuits, breaks in the network, switching of a large load, improper operation of relay protection and automation devices, etc. Due to the unbalance of the mechanical and electromagnetic moments, the oscillation of its rotor occurs on the shaft of the generating unit. The rotor of the generator oscillates relative to the magnetic field of the stator, while the parameters of the mode, in particular the voltage, change, which leads to unstable modes of power consumption and is the cause of the swinging of other generating units of EPS and load nodes. Swings are of various amplitudes and can lead to disruption of the synchronous operation of the generator and subsequent asynchronous operation, which is an extremely undesirable mode of the power system. In addition, in modern automatically controlled EPS, low-frequency intersystem oscillations occur.

GA rotor motion is described by the equation

- угловая скорость вращения ротора генератора в установившемся режиме, как правило

- номинальная угловая скорость вращения генератора;

- крутящий момент первичного двигателя;

- электромагнитный момент генератора (момент первичного двигателя и генератора в уравнении фигурируют в относительных единицах и численно равны мощности первичного двигателя и электромагнитной мощности генератора, соответственно).where ω is the angular velocity of rotation of the rotor of the generator (or GA);

- the angular velocity of rotation of the rotor of the generator in steady state, as a rule

- nominal angular speed of rotation of the generator;

- torque of the prime mover;

- electromagnetic moment of the generator (the moment of the primary engine and the generator in the equation appear in relative units and are numerically equal to the power of the primary engine and the electromagnetic power of the generator, respectively).

на валу, генератор - тормозящий

. В нормальном режиме выработки электроэнергии моменты, создаваемые первичным двигателем и генератором, равны по модулю и противоположны по направлению. Таким образом, в нормальном режиме скорость вала ГА не изменяется во времени

When the power plant operates, the turbine creates an accelerating moment

on the shaft, the generator is braking

. In the normal mode of power generation, the moments created by the primary engine and the generator are equal in magnitude and opposite in direction. Thus, in normal mode, the speed of the shaft GA does not change in time

, который связан с угловой скоростьюThe position of the rotor of the generator is characterized by an angle

which is related to angular velocity

, которому соответствует определенная выдаваемая мощность при рабочем напряжении на зажимах генератора. Вообще, можно говорить о сохранении динамической устойчивости, если после снятия возмущения ротор генератора, достигнув некоторого значения угла, меньшего 180°, возвращается к значению угла в доаварийном режиме, если не произошло изменения мощности первичного двигателя, конфигурации и режима работы сети ЭЭС, или же к другому значению, которое определяется условиями установившегося послеаварийного режима.In steady state, the generator operates with a certain angle

which corresponds to a specific power output at an operating voltage at the terminals of the generator. In general, one can talk about maintaining dynamic stability if, after removing the disturbance, the generator rotor, having reached a certain angle value less than 180 °, returns to the angle value in the pre-emergency mode, if there has not been a change in the primary engine power, configuration and operating mode of the EPS system, or to another value, which is determined by the conditions of the established post-emergency mode.

и возникает небаланс моментов на валу генератора, что приводит, как правило, к возникновению ускорения и изменению скорости вращения ротора генератора, и соответственно, качаниям. А в некоторых случаях возникает асинхронный ход генератора.In the case of application of a disturbance to the EPS,

and there is an imbalance of moments on the shaft of the generator, which leads, as a rule, to the occurrence of acceleration and a change in the speed of rotation of the rotor of the generator, and accordingly, to swings. And in some cases, an asynchronous generator stroke occurs.

механического и электромагнитного моментов на валу генерирующего агрегата

Now, if an electromagnetic brake is connected to the shaft of the primary engine-generator unit, then it becomes possible, regardless of the parameters of the current EES mode, to influence the balance of moments on the shaft of the generating unit. Since EMT creates only braking torque, the use of a braking device is required only with a positive speed difference

mechanical and electromagnetic moments on the shaft of the generating unit

- момент, создаваемый ЭМТ.Where

- the moment created by EMT.

можно добиться сохранения синхронной работы генератора при больших возмущениях, а также демпфирования электромеханических колебаний генерирующего агрегата и демпфирования межсистемных колебаний.Thus, with the appropriate parameters of EMT and control

it is possible to maintain synchronous operation of the generator with large disturbances, as well as damping the electromechanical vibrations of the generating unit and damping the intersystem vibrations.

When current is passed through the winding of the electromagnet, a magnetic field is created that closes through the core of the coil, the magnetic circuit and the body of the rotating brake disc, in which currents interact with the magnetic field of the electromagnet. As a result of the interaction of currents with a magnetic field, a braking moment arises. The value of the braking torque can be adjusted by changing the current value in the windings of the electromagnet of the magnetic EMT system.

When disturbances are applied to the system, the shaft of the generating unit (GA) begins to accelerate. The rotor GA rotational speed signal from the sensor 1 is supplied to block 15 (Fig. 7) and the change in the rotor speed of the GA generator is estimated. When the following conditions are met: acceleration of the GA shaft and voltage drop on the generator tires relative to the voltage of the previous steady state (or decrease in the generator electric power), a signal is generated in the system to increase the current in the EMT winding and transmitted to the controlled voltage (current) converter, which increases the voltage on the winding electromagnet, and braking moment is created. As soon as the shaft rotation speed becomes equal to the speed of the stator electromagnetic field and the measured generator power becomes equal to the power value before the disturbance is applied, the EMT is turned off (the current of its windings is brought to zero). Or, as soon as the speed of rotation of the shaft of the generating unit becomes equal to the speed of rotation of the electromagnetic field of the stator, and the measured electromagnetic power of the generator becomes equal to the mechanical power of the turbine, EMT is turned off. Next, synchronous swings begin and, with the correct settings of the automatic regulators, the GA switches to the steady state operation mode.

For damping the electromechanical vibrations of the electric power system, a signal from the output of block 21 is sent to the time differentiation block 41 (Fig. 9), a signal from the output of the block 23 is sent to the deviation creating block 43, a signal from the output of the block 23 is sent to the time differentiation block 45, the deviation creating unit 47 receives a signal from the output of the block 25, a signal from the output of the block 25 is supplied to the time differentiation unit 49.

Since EMT creates a moment of only one sign (braking), but of a variable value, then to improve the conditions of the dynamic stability of the electric system, it can be switched on once or repeatedly, depending on the specific mode of EPS. Since the magnitude of the braking torque is regulated over a wide range, it is possible to damp the synchronous oscillations of the generators using EMT.

EMT can be used for emergency speed reduction in case of various damage to the generating unit (oil pressure drop in the lubrication circuit, destruction of the primary engine (turbine) or generator).

EMT can be used to damp electromechanical vibrations of a synchronous compensator. In this case, the synchronous compensator and EMT are structurally combined in one housing.

A method for improving the dynamic stability of an electric power system is as follows.

The rotor speed of the generator rotor is reduced by mechanical braking of the specified generator rotor, for which purpose the electromagnetic brake is placed mechanically connected coaxially with the generator shaft and the primary engine shaft, with the generator rotor and the primary engine rotor by means of couplings.

Continuously measure the voltage U _G at the terminals of the generator and the current I _{G of the} generator stator, which determine the electromagnetic power of the generator.

The obtained value of the electromagnetic power of the generator is compared with the value of the electromagnetic power before the disturbance is applied.

In case the comparison value exceeds a predetermined value, a control signal is generated to activate the electromagnetic brake, while

the magnitude of the braking torque is determined by the difference between the values of the measured electromagnetic power and electromagnetic power before the disturbance is applied, and

the duration of application of the braking torque is determined by the change in the rotation speed of the generator rotor, for which the rotation speed of the generator rotor is determined after the perturbation is applied and compared with the value before the perturbation is applied.

The electromagnetic brake is switched off when the current rotor speed and the rotor speed are equal in the pre-disturbance mode and when the measured electromagnetic power of the generator and the power are equal before the disturbance is applied.

Or, they turn off the electromagnetic brake when the current rotor speed of the generating unit is equal to its speed before the disturbance is applied and if the measured electromagnetic power of the generator and the mechanical power of the turbine are equal.

When making a mechanical connection, an electromagnetic brake is placed either on the side of the generator, or on the side of the prime mover, or between the generator and the prime mover.

According to a second embodiment of the proposed method for improving the dynamic stability of an electric power system:

continuously measure the voltage at the terminals of the generator,

comparing the obtained voltage value at the terminals of the generator with a predetermined voltage value, which is in the range from 65% to 95% of the nominal voltage value,

in case the comparison value is below a predetermined value, a control signal is generated to activate the electromagnetic brake, while

additionally continuously measure the stator current of the generator,

determine the electromagnetic power of the generator from the measured values of voltage and current,

comparing the obtained value of the electromagnetic power of the generator with the value of the electromagnetic power before the disturbance is applied,

determine the magnitude of the braking torque from the difference between the values of the measured electromagnetic power and electromagnetic power before the disturbance is applied.

In this case, the duration of application of the braking torque is determined by the change in the rotation speed of the generator rotor, for which the rotation speed of the generator rotor is determined after the perturbation is applied and compared with the value before the perturbation is applied,

they release the electromagnetic brake when the current rotor speed and the rotor speed are equal in the pre-disturbance mode and when the measured power and the power are equal before the disturbance is applied.

Or, they turn off the electromagnetic brake when the current rotor speed of the generating unit is equal to its speed before the disturbance is applied and if the measured electromagnetic power of the generator and the mechanical power of the turbine are equal.

According to a third embodiment of the proposed method for improving the dynamic stability of an electric power system:

detect the presence of a deviation in the rotor speed of the generator rotor as a result of the application of the disturbance to the system and determine the difference in the rotation speeds between the measured speed and the rotation speed before applying the disturbance,

compare the resulting difference with a given value.

In case the comparison value is higher than the set value, a control signal is generated to activate the electromagnetic brake, while

continuously measure the voltage at the terminals of the generator and the current of the stator of the generator, which determine the electromagnetic power of the generator,

determine the magnitude of the braking torque from the difference between the values of the measured electromagnetic power and electromagnetic power before the disturbance is applied.

The duration of application of the braking torque is determined by the change in the rotation speed of the generator rotor, for which the rotation speed of the generator rotor is determined after the perturbation is applied and compared with the value before the perturbation is applied,

they release the electromagnetic brake when the current rotor speed and the rotor speed are equal in the pre-disturbance mode and when the measured power and the power are equal before the disturbance is applied.

According to the invention, in addition to the three options for implementing the inventive method, it is possible to damp the electromechanical vibrations of the electric power system.

Monitor the rotor speed of the synchronous alternator, voltage and stator current,

continuously measure the voltage at the terminals of the generator and the current of the stator of the generator, which determine the electromagnetic power of the generator,

determine the derivative of the voltage at the terminals of the generator in time,

determine the time derivative of the generator stator current,

determine the deviation of the measured rotor speed from the speed of rotation in steady state,

determine the derivative of the measured rotor speed over time.

Then, the obtained signals of the derivatives of voltage, current, deviation of the rotor speed of the generator rotor and the magnitude of the deviation of the rotational speed are summarized, and a control electric signal is obtained, which is supplied to the voltage converter to damp electromechanical vibrations.

The technical effect of the claimed invention is a direct effect on the balance of torques on the shaft of the generating unit. The EMT device has a small time constant, which allows you to adjust the balance of moments almost inertialess.

The advantages of using an electromagnetic brake device to improve the dynamic stability of EPSs compared to the above methods and devices are:

almost zero-energy regulation of the balance of moments on the shaft of the generating unit;

the effectiveness of the use of this device does not depend on the voltage level, state and mode of the EPS network;

control the duration and magnitude of the braking torque;

the ability to quickly reduce speed and stop in case of emergency on the GA;

damping of the electromechanical vibrations of the generator rotor is carried out directly by controlling the power balance on the GA shaft, and the damping process does not affect the electric mode of the EPS.

Claims (11)

1. A method of improving the dynamic stability of an electric power system containing a variety of primary motors and synchronous alternators, power transformers, power lines, switching equipment and load, which consists in monitoring the rotational speed of the rotor of the synchronous alternator, reduce the rotational speed of the synchronous rotor generator after applying a disturbance to the system to the rotation speed of the stator magnetic field, characterized in that the decrease the rotor speed of the generator rotor is carried out by mechanical braking of the specified rotor of the generator, for which a mechanical connection of the electromagnetic brake, placed coaxially with the shaft of the generator and the shaft of the primary engine, is carried out with the rotor of the generator and the rotor of the primary engine by means of couplings, continuously measure the voltage at the terminals of the generator and the current of the generator stator which determine the electromagnetic power of the generator, compare the obtained value of the electromagnetic power of the generator with the electromagnetic power value before the perturbation is applied, if the comparison value exceeds a predetermined value, a control signal is generated to activate the electromagnetic brake, and the braking torque is determined by the difference between the measured electromagnetic power and electromagnetic power before the perturbation is applied, and the duration of the application of the braking torque is determined by the change in the rotor speed of the generator rotor, for which they determine the speed of rotation of the rotor of the generator after application ozmuscheniya and compared with the value before the perturbation application, the electromagnetic brake is switched off on reaching equal current rotor speed and rotor speed to the perturbations in mode and at equal measured electromagnetic power generator and power generator to the disturbance application. 2. The method according to claim 1, characterized in that when the mechanical connection is made, the electromagnetic brake is placed in one of three positions: either from the generator side, or from the primary engine, or between the generator and the primary engine. 3. A method for improving the dynamic stability of an electric power system comprising a plurality of primary engines and synchronous alternators, power transformers, power lines, switching equipment and load, which consists in monitoring the rotational speed of the rotor of the synchronous alternator, and reduce the rotational speed of the synchronous rotor generator after applying a disturbance to the system to the rotation speed of the stator magnetic field, characterized in that the decrease the rotor speed of the generator rotor is carried out by mechanical braking of the specified generator rotor, for which the electromagnetic brake is placed coaxially with the generator shaft and the primary engine shaft, with the generator rotor and the primary engine rotor by means of couplings, the voltage across the generator terminals is continuously measured, and the obtained value is compared voltage at the terminals of the generator with a given voltage value, which is in the range from 65 to 95% of the nominal value voltage, in case the comparison value is lower than the set value, a control signal is generated to activate the electromagnetic brake, while the generator stator current is additionally continuously measured, the generator electromagnetic power is determined from the measured voltage and current values, the obtained value of the generator electromagnetic power is compared with the electromagnetic value power before the perturbation is applied, the braking torque is determined from the difference in the values of the measured electromagnetic power and electromagnetic power before the perturbation is applied, the duration of application of the braking torque is determined by the change in the rotation speed of the generator rotor, for which the rotor speed of the generator is determined after the perturbation is applied and compared with the value before the perturbation is applied, the electromagnetic brake is turned off when the current rotor speed and rotor speed are equal in the pre-disturbance mode and when the measured electromagnetic power of the generator and the generator power are equal before the application scheniya. 4. The method according to claim 3, characterized in that when the mechanical connection is made, the electromagnetic brake is placed in one of three positions: either from the side of the generator, or from the side of the primary engine, or between the generator and the primary engine. 5. A method for improving the dynamic stability of an electric power system comprising a plurality of primary motors and synchronous alternators, power transformers, power lines, switching equipment and load, which consists in monitoring the rotational speed of a rotor of a synchronous alternator, reducing the rotational speed of a synchronous rotor generator after applying a disturbance to the system to the rotation speed of the stator magnetic field, characterized in that the decrease the rotor speed of the generator rotor is carried out by mechanical braking of the specified rotor of the generator, for which a mechanical coupling of the electromagnetic brake placed coaxially with the shaft of the generator and the shaft of the primary engine, with the rotor of the generator and the rotor of the primary engine by means of couplings is carried out, the presence of a deviation of the rotation speed of the generator rotor is detected as a result of application disturbances to the system and determine the difference in rotational speeds between the measured speed and the rotational speed before Perturbations, compare the resulting difference with a given value, in case the comparison value is higher than a given value, a control signal is generated to activate the electromagnetic brake, while the voltage across the generator terminals and the generator stator current are continuously measured, which determine the electromagnetic power of the generator, determine the value the braking torque according to the difference between the values of the measured electromagnetic power and the electromagnetic power before the disturbance is applied, the duration of application of the brake m The moment is determined by the change in the rotor speed of the generator, for which the rotor speed of the generator is determined after the disturbance is applied and compared with the value before the disturbance is applied, the electromagnetic brake is switched off when the current rotor speed and the rotor speed are equal in the pre-disturbance mode and when the measured electromagnetic generator power and generator power before disturbance is applied. 6. The method according to claim 5, characterized in that when the mechanical connection is made, the electromagnetic brake is placed in one of three positions: either from the side of the generator, or from the side of the primary engine, or between the generator and the primary engine. 7. A method for improving the dynamic stability of an electric power system containing a plurality of primary motors and synchronous alternators, power transformers, power lines, switching equipment and load, which consists in monitoring the rotational speed of a rotor of a synchronous alternator, reducing the rotational speed of a synchronous rotor generator after applying a disturbance to the system to the rotation speed of the stator magnetic field, characterized in that the decrease the rotor speed of the generator rotor is carried out by mechanical braking of the specified rotor of the generator, for which a mechanical connection of the electromagnetic brake, placed coaxially with the shaft of the generator and the shaft of the primary engine, is carried out with the rotor of the generator and the rotor of the primary engine by means of couplings, continuously measure the voltage at the terminals of the generator and the current of the generator stator which determine the electromagnetic power of the generator, compare the obtained value of the electromagnetic power of the generator with the electromagnetic power value before the perturbation is applied, if the comparison value exceeds a predetermined value, a control signal is generated to activate the electromagnetic brake, and the braking torque is determined by the difference between the measured electromagnetic power and electromagnetic power before the perturbation is applied, and the duration of the application of the braking torque is determined by changing the speed of rotation of the rotor of the generator, for which determine the speed of rotation of the rotor of the generator after application perturbations and compare it with the value before the perturbation is applied, the electromagnetic brake is disabled when the current rotor speed of the generating unit is equal to its speed before the perturbation is applied and when the measured electromagnetic power of the generator and the mechanical power of the turbine are equal. 8. The method of damping electromechanical vibrations of the electric power system, which consists in monitoring the rotor speed of the synchronous alternator, voltage and stator current, continuously measuring the voltage at the terminals of the generator and the current of the generator stator, which determine the electromagnetic power of the generator, and determine the derivative of voltage at the terminals of the generator in time, determine the derivative of the current of the stator of the generator in time, determine the deviation of the measured speed the rotor rotation growth versus the rotation speed in the steady state, the derivative of the measured rotor rotation speed with respect to time is determined, the obtained derivatives of voltage, current, deviation of the rotor speed of the generator and the deviation of the rotational speed are summed up and a control electric signal is received, which is fed to the voltage converter for damping of electromechanical vibrations. 9. A method for improving the dynamic stability and damping of electromechanical vibrations of an electric power system comprising a plurality of primary motors and synchronous alternating current generators, power transformers, power lines, switching equipment and electrical loads, the method comprising monitoring the rotational speed of a rotor of a synchronous alternating current generator, reduce the rotational speed of the rotor of the synchronous generator after applying a disturbance to the system d rotation speed of the stator magnetic field, characterized in that the rotation speed of the rotor of the generator is reduced by mechanical braking of the specified rotor of the generator, for which a mechanical connection is made of the electromagnetic brake, placed coaxially with the shaft of the generator and the shaft of the primary engine, with the rotor of the generator and the rotor of the primary engine by means of couplings continuously measure the voltage at the terminals of the generator and the current of the stator of the generator, which determine the electromagnetic power of the generator RA, compare the obtained value of the electromagnetic power of the generator with the value of electromagnetic power before the disturbance is applied, if the comparison value exceeds a predetermined value, a control signal is generated to activate the electromagnetic brake, and the magnitude of the braking torque is determined by the difference between the measured electromagnetic power and the value of electromagnetic power up to disturbance applications, and the duration of application of the braking torque is determined by the change in the rotor speed of the generator a, for which the rotation speed of the generator rotor is determined after the perturbation is applied and compared with the value before the perturbation is applied, then the electromechanical vibrations of the electric power system are damped, for which the derivative of voltage at the generator terminals is determined, the derivative of the generator stator current is determined, the deviation of the measured rotor speed is determined derivative of the rotational speed in the steady state, determine the derivative of the measured rotor speed in time, total the received signals are derived voltage, current and deviation generator rotor speed and the magnitude of the rotation speed deviation is obtained and the control electrical signal which is fed to a voltage converter for damping electromechanical oscillations. 10. A system for improving the dynamic stability and damping of electromechanical vibrations of an electric power system containing a plurality of primary motors and synchronous alternators, power transformers, power lines, switching equipment and electrical loads, comprising a generator rotor speed sensor, a means for reducing the generator rotor speed after application disturbances to the system up to the rotation speed of the stator magnetic field, made in the form of an electromagnet a brake comprising a brake disk, an electromagnetic system formed by a magnetic circuit and an inductor, the disk being placed in the gap of the magnetic circuit, characterized in that the electromagnetic brake is placed coaxially with the generator shaft and the primary motor shaft and is mechanically connected to the generator rotor and the primary motor rotor by means of clutches wherein the system comprises a control unit for generating electromagnetic brake control signals and comprising an electromagnetic detection unit total generator power, a unit for comparing the generator’s electromagnetic power after applying compensation to the electromagnetic power before the disturbance is applied, a control signal generating unit for applying the electromagnetic brake if the comparison value exceeds a predetermined value, while the system also contains a voltage sensor at the generator terminals and a generator stator current sensor connected to a control unit to which a generator rotor speed sensor is also connected, pre the creator of the magnitude of the braking torque and the duration of the braking torque, the input connected to the output of the control unit, and the output to the coils of the electromagnetic brake, a power source electrically connected to the Converter. 11. The system of claim 10, characterized in that for the mechanical connection of the electromagnetic brake is placed in one of three positions: either from the side of the generator, or from the side of the primary engine, or between the generator and the primary engine.

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