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Method for increasing dynamic stability of synchronous electric machines

IPC classes for russian patent Method for increasing dynamic stability of synchronous electric machines (RU 2295817):

H02P9/10 - Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load

H02J3/24 - Arrangements for preventing or reducing oscillations of power in networks (by control effected upon a single generator H02P0009000000)

Another patents in same IPC classes:

Method for control of generator (modifications) / 2256272
The method provides for control of insulation resistance of the rotor winding. At a reduction of this value below the set point a short-time boosting of the rotor current is conducted. As a result of boosting, shacking-off of the conducting bridges occurs between the winding conductors and the rotor steel. Such bridges are formed by adhering dust. In other modifications of the invention provision is made for disconnection of the generator from the network before such a boosting.

Method for increasing dynamic stability of synchronous electric machines / 2295817
Method for increasing dynamic stability of synchronous electric machines includes additional acceleration or braking of synchronous electric machines, performed by shifting of resulting magnetic flow of rotor simultaneously with mechanical turning of stator towards relative deviation of rotor in case of perturbation.

Method for detecting asynchronous mode in power system / 2316098
Proposed method includes calculation of impedance vector as voltage-to-current vector ratio in point under check. Impedance vector projection onto axis turned in complex plane of impedances relative to imaginary axis through angle supplementing rated angle of equivalent power transmission impedance to 90 deg. is calculated. Resistance up to electrical center of oscillations is found by projection. Disposition of center of oscillations on line section under check is recorded when projection value occurs within specified range. Vector of voltage being measured onto axis turned in complex plane relative to power transmission current vector through same additional angle is calculated. Power transmission angle is calculated by voltage projection using simple trigonometric function. Asynchronous mode onset is detected by coincidence between signs of power transmission angle and those of its first and second time derivatives. Asynchronous mode hazard is recognized by excess of first derivative above admissible value calculated with aid of "angle-slip" boundary phase functions and parameters of original modes.

Method of finding and liquidation of async mode in electric power by automatic control system / 2316099
Method can be used in aids of anti-alarm automatics of electric-power system. According to method, full resistance Z , calculated from local information (current and voltage in unit to be controlled) due to reduction its angle for correcting angle. Correcting angle is found during process through relation of increased reactive and active components of full resistance. Resistance is fixed till electric center of oscillations by using reactive component of transformed resistance Z. Active component of transformed resistance, which component is multiplied by electric transmission current, allows finding voltage Um in center. On base of voltage Um, angle δ_m of electric transmission is calculated on base trigonometric transform. From specified range of modeled voltage, range of angles of electric transmission is fixed beyond limits of working mode, in which mode the calculated angle more precisely corresponds to real one and async mode is revealed. By using angle of electric transmission and its derivatives and by defining location of center of oscillations in relation to unit to be controlled, threat, moment and fact of arise of async mode is fixed to form optimal action of automatic system.

Method of finding and liquidating of asynchronous mode in power system by automatic device / 2316100
Projection of total resistance onto axis is calculated, which projection is turned in complex plane of resistances for estimated angle relatively axis of coordinates. Projection of measured voltage to axis is calculated, which is turned in complex plane relatively current vector for the same estimated angle. First and second time derivatives are calculated from projection of voltage vector. Moment, when asynchronous mode origins, is registered on base of non-coincidence of sign of voltage vector with signs of its first and corrected second derivatives. Starting from that moment, time is measured and half-period of asynchronous mode is calculated through first derivative of projection of voltage vector. In case measured time exceeds time of half-period of async mode, reduced by preset value, availability of async mode is fixed to form effect of automatics for liquidation of the mode at favorable value of angle of electricity transmission.

Method of revealing an asynchronous regime of electricity transmission / 2316101
The method allows calculate the coordinates of the end of the of impedance in vector in the system of coordinates received by turning in the complex plane of resistances on the calculated angle and transferring along the axes of real numbers on a prescribed value. Voltage in the electrical center of rocking is modeled and the diapason of the values of this voltage corresponding to the diapason of the angles of electric transmission substantially different from zero and including the value of 180^o is controlled. The asynchronous regime is fixed at the output of the value of modeled voltage out of the set diapason if the symbol of voltage differs from the symbol of this voltage at the input into the prescribed diapason and the duration of passing through the established diapason prevails the prescribed value. The position of the electrical center of rocking is defined at the moment of changing of the symbol of the modeled voltage according to the outfit of the value of the coordinates of the end of the vector of impedance along the coordinate axis to one of the three prescribed diapasons. The number of cycles of the asynchronous mode is additionally calculated according to the moments of changing of the symbol of modeled voltage in the established diapason of values and operation of automatic equipment is formed at prevailing the number of the cycles of the prescribed setting.

Method for improving dynamic stability and damping oscillations of electric-power systems and device for its realisation / 2339144
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.

Method and device for electrical transmission system / 2406207
Device is designed to reduce subsynchronous resonance in electrical transmission systems and includes facilities (16), (17) to define voltage components from the side of stator windings in generator (9) with one or more discrete frequencies and calculation means taking into account the results of the said calculations, voltage to be added to the specified voltage of stator windings to reduce subsyncronous resonance in electrical system and a circuit (20) configured so that calculated voltage can be added to the specified voltage of stator windings.

Emergency control method of power of turbine generator of modular thermal power station (versions) / 2412512
As per the first version of the method there measured is output current and output voltage of turbine generator, active power is determined according to them, controlled and compared with reduction speed set points of active power and output voltage, and emergency imbalance of active power is calculated and compared to the set point. As per the second version of the method, the rotor speed is measured, rotor slip is determined relative to synchronous rotation speed and exceedance is controlled with the slide of the specified positive set point. As per the first and the second versions of the method, when set points are exceeded, there formed is pulse control impact on the turbine off-loading. As per the third version of the method, frequency of output voltage, rotor speed and flow of live steam before turbine is measured; negative rotor slip is determined relative to synchronous rotation speed, current power reserve of turbine is determined, exceedance is fixed with current turbine power reserve and with absolute value of rotor slip of the appropriate set points, and when frequency of output voltage is decreased to its set point, there formed is control impact on additional loading (forcing) of turbine, which is proportional to current reserve of its power.

Thyristor-controlled series capacitor damping subsynchronous resonances / 2433517
Control unit (17) for a thyristor-controlled series capacitor connected to a electric power transmission line (12) comprises a control unit integrating a thyristor start control (18) and a generator of required voltage of the capacitor passing through zero depending on line current and voltage of the capacitor in response on a command signal, and a command control (19) which is used to generate the command signal for the thyristor start control, and accommodates a command damping control (24) comprising a damping unit at least on one discrete frequency.

Method for fast-acting control of active-power flow / 2449446
During regulation of active-power flow between power system parts connected with power line (1), unbalance of active power on shaft (11) of generating unit is monitored, active-power flow over line (1) is changed by adjusting phase angle between voltage vectors in its end-points on buses (2) and (3) by means of controlled phase-slue device (12) included in line (1). Limited time interval is allocated, within which unbalance of active power is compensated by means of transferring electric energy accumulator (7) into discharging or charging mode when there is deficiency or excess of active power respectively, and power balance is restored by corresponding changing power generated by unit.

Electromechanical device / 2453033
Output of DC source is connected through rheostat to the first input of automatic release mechanism having the second input connected to output of three-phase rectifier with stabiliser the inputs of which are connected to outputs of synchronous generator. Output of automatic release mechanism is connected to input of DC motor rigidly attached to synchronous generator with exciter. Automatic release mechanism is actuated at equality of voltages. Potentiometer is installed between the second input of automatic release mechanism and output of three-phase rectifier with stabiliser. At that, rheostat output is connected to input of DC motor.

Device to control excitation of synchronous generator / 2465716
Device to control excitation of a synchronous generator comprises a metre of rotor current, a metre of stator current and voltage, a unit of feedback by excitation current, a metre of active power, a sensor of generator voltage frequency, a unit of analog-to-digital conversion, an operational unit, a unit of digital-to-analog conversion and a unit of parameters adaptation. The operational unit and the unit of parameters adaptation are arranged as specified in the application materials.

Automatic voltage controller of synchronous generator / 2465717
Invention may be used both for automation of equipment commissioning process and in a functional mode in devices for control of electric generators in order to get the required value of output parameters, in particular, to control generator excitation in order to weaken hazardous effect of overloads or transition processes, for instance, in case of spontaneous connection, removal or variation of a load. The automatic voltage controller of the synchronous generator comprises a voltage metre, the first summator, a PID controller, the second summator, an amplifier, a generator of initiating pulses, a set point generator, an analog to digital converter, a signal energy calculator, a delay unit, a control parameters calculator, an averaging unit. The control parameters calculator is arranged in the form of a processor device operating in accordance with the logic of ultra-fast annealing.

Method for control of synchronous generator excitation / 2498494
In method for control of synchronous generator excitation amplification coefficients are set against derivative of excitation winding current, deviations and voltage derivatives of stator winding and generator frequency; excitation is measured and regulated against deviations of the specified values and their derivatives. During transient period pairs of training support vectors that consist of discreet samples of electric generator signals and discreet samples of these signals delayed per one sampling period; learning set is added with the above training support vectors and included N transient processes. Three-layer neuron net is taught with sequential presentation of pairs of training support vectors till minimum mean-root error of training is reached: against weight coefficients of trained neuron net by means of the preset multidimensional array amplification coefficients are determined with deviations and derivatives of voltage and frequency and amplification coefficient with current derivative of generator excitation winding; thereafter coefficients are averaged against N transient processes and set as regulating parameters where N is depth-averaging of regulating parameters.

Method for parameters setting for exciting regulator of asynchronous generator / 2498495
Parameters of exciting regulator are set against deviation of setup of one of its output signals; initial value of parameters optimisation criterion for regulator is E₀, a new value of parameters optimisation criterion for the regulator is calculated in compliance with formula; setup of the regulated output signal is changed by constant value for fixed time; scale and duration of transient process for the generator output signal is measured against the specified changed setup, new value of parameters optimisation criterion for the regulator E is calculated in compliance with formula and value E₀ and value of the parameter are set so that conditions E<E₀ is met or the following conditions are met: E≥E₀ and (E-E₀)/c>β_i set E₀=E and the parameter is not changed. Otherwise the parameter is set to initial value. The above operations are repeated for other parameters subjected to regulation till average rate of E₀ values is changed up to the preset value, where β_i is a random value distributed evenly within the range [0.1], c is a positive permanent value that determines rate of optimisation for the regulator parameters.

FIELD: electric engineering, possible use in electro-energetic systems and in electric supply systems.

SUBSTANCE: method for increasing dynamic stability of synchronous electric machines includes additional acceleration or braking of synchronous electric machines, performed by shifting of resulting magnetic flow of rotor simultaneously with mechanical turning of stator towards relative deviation of rotor in case of perturbation.

EFFECT: increased speed of operation of electromagnetic effect on rotor of synchronous electric machine.

The present invention relates to the field of electricity and can be used in power systems and power supply systems to more effectively improve the dynamic stability of synchronous electrical machines (synchronous generators, synchronous compensators and synchronous motors).

This may be viewed as another kind of ways "flexible links", are under active consideration at the present time. The known method (A.S. USSR №176624, CL H 02 J 3/24, 1964), in which the improvement of dynamic stability is achieved by the additional braking generators, consisting in the application of three-phase automatic reclosing (AR) with an abrupt change of the phase voltage by receiving part of the system, implemented by the change of a group of transformers connection.

However, this method has poor efficiency due to the use of discrete control and complete disconnection of the generator from the system during pause when switching.

In addition, there is a method of increasing the dynamic stability of synchronous electric machines, of which the prototype is based on the electrical offset of the resulting magnetic flux of the rotor of a synchronous electric machine carried out by regulating the currents in predolin the th and transverse excitation windings. For example, Lukashov AS, Gamma B.Z., Ptuskin G.S. Improvement of dynamic stability of power transmission through the use of cross-field winding of the synchronous generator. News of the Siberian branch of the USSR Academy of Sciences, series of technical Sciences, No. 13, issue 3, Novosibirsk, 1976.

However, this method has poor performance due to the considerable inertia of electromagnetic transients in the windings of the rotor.

The task of the invention is to improve the performance of electromagnetic influence on the rotor of a synchronous electric machine.

This object is achieved in that in the method of improving the dynamic stability of synchronous electric machines, consisting in additional electrical braking or acceleration performed by the offset of the resultant magnetic flux of the rotor simultaneously with the specified offset carry out mechanical rotation of the stator of a synchronous electric machine in the direction of relative deviation of the rotor when the outrage.

The method is as follows. When the perturbation in the electric power system or power supply system (short circuit, disconnection of power lines, the power loss in the load nodes and other) regulation of the current in the two windings of the excitation shift resultyou is the overall magnetic flux of the rotor and simultaneously carry out mechanical rotation of the stator of the synchronous machine in the direction of deflection of the rotor when the outrage.

The rotation of the stator relative to the axis of the machine may be implemented, for example, installation of the stator on the rollers located on the arc of a circle along its axis, and rotate it using senatorsanders worm gear mechanism with a special actuator, or by removing the fixation of the stator on the frame when the perturbation and the imposition of fixation after appropriate and necessary rotation.

We offer mechanical rotation of the stator can be carried out both during the disturbances, and in a pause period during automatic re-enabling or automatic activation of a backup power supply. After saving sustainability (synchronism) and transition in the post-accident mode, the return of the stator to its original position, the gradual mechanical rotation in the opposite direction.

When the turns of the stator appropriate design solutions should be ensured integrity of electrical circuits connecting the windings of the stator of a synchronous electric machine to the external network. For example, it can be sliding contacts or flexible connection.

Thus, the proposed method has better performance.

A method of improving the dynamic stability of synchronous electric machines, consisting in additional electrical braking or acceleration, carried out with what emeniem result of the magnetic flux of the rotor, characterized in that simultaneously with the specified offset carry out mechanical rotation of the stator in the direction of deflection of the rotor when the outrage.