RU2662728C2 - Method of emergency control of the mode of parallel operation of synchronous generators in electrical networks - Google Patents

Abstract

FIELD: electric power engineering.

SUBSTANCE: use: in electric power engineering. Method consists in determining the cross sections of the network for division in the normal mode. When an emergency disturbance occurs, the network is divided. In the after-failure mode with the separation of the network at an increased frequency in the low-power part of the network, the output power of the generators is reduced, and part of the load is cut off at a reduced frequency. Voltage and output power of the remaining generators are regulated, the separated low- and high-power parts of the network are synchronized and switched to parallel operation. Normal mode is restored. In this case, two fixed cross-sections are used to divide the network into high- and low-power parts. First one – for normal modes with power output by a low-power part of the network, the second – with power consumption. In normal mode with the power output by a low-power part of the network, one or more generators are loaded up to the value of the output power in the first cross-section. Upon a sudden deep voltage drop with the anticipation of short circuit clearing, the first-section switches and the generators of the low-power part of the network loaded up to the value of the output power in the first cross-section are disconnected. In the normal mode of power consumption, the low-power part of the network is loaded by its generators to a zero active-power flow in the second cross-section. Upon the fact of a sudden deep voltage drop with the anticipation of short circuit clearing, the switches of the second section are disconnected.

EFFECT: prevention of the occurrence of unacceptable dynamic moments on the shafts of synchronous generators and asynchronous modes with their parallel operation, reduction of cutoff short-circuit currents, decrease in the values of the powers of disconnected loads, generators, reduction of the need for telemetric information.

1 cl, 4 dwg

Description

The proposed invention relates to the field of electric power and can be used in electric power systems, electric networks to control the operating modes of synchronous electric generators and the electric network to reduce disconnected short-circuit currents, prevent unacceptable dynamic moments on the shafts of synchronous generators and asynchronous modes, reduce the power values of disconnected loads, generators.

THE METHOD OF EMERGENCY CONTROL CONTROL OF THE PARALLEL OPERATION MODE OF SYNCHRONOUS GENERATORS IN ELECTRIC NETWORKS (STO _59012820.29.240.001-2011. Organization standard (OPEN JOINT STOCK COMPANY “SYSTEM OPERATOR SYSTEM. Conditions for the creation of the facility. Norms and requirements. Official publication. P. 19-23) in which, in the event of emergency power imbalances to prevent stability disturbances with the emergence of asynchronous modes, reduce power consumption in the scarce part of the network, as a rule, by disconnecting the load, and generating in the excess part of the network, as a rule, by disconnecting part of the generators or impulse unloading of the turbines. After attenuation of the transient electromechanical process, the power supply to disconnected consumers is restored and normal network mode.

HOWEVER THE SPECIFIED METHOD has the following disadvantages:

- The method is ineffective with low inertia of the rotors of the generators, characteristic of parts of a low power network, because at a high rate of change in the mutual movement of the rotors of the generators of the high and low power network parts, the inevitable delays in introducing control actions on the power change in the scarce and excess parts of the network do not allow for the stability of their parallel operation.

- With a strong connection between the network parts on the shafts of the rotors of the generators of the low-power network part in the dynamic process, unacceptable moments arise, many times exceeding their nominal values and capable of damaging power units.

- In the event of short circuits in the electric network, parallel operation of parts of the low and high power network leads to a significant increase in disconnected short circuit currents in the part of the low power electric network, which increases the requirements for its switching devices.

In addition, the METHOD FOR EMERGENCY CONTROL OF THE PARALLEL OPERATION MODE OF SYNCHRONOUS GENERATORS IN ELECTRIC NETWORKS (STO _59012820.29.240.001-2011. Organization standard (OPEN JOINT STOCK COMPANY SYSTEM SYSTEM. The conditions of the organization of the process. The conditions for the creation of the object. Norms and requirements. Official publication. P. 17-18), which is the prototype of the invention, in which occurrence of emergency power imbalances to prevent stability disturbances with the occurrence of asynchronous modes, in the pre-emergency mode, the network cross section is determined for dividing from the number of technologically possible according to the criterion of the minimum power unbalance in the subsystems in the pre-emergency mode. When an emergency disturbance occurs, the network is divided by a predetermined cross-section by turning off the circuit breakers included in it. If there are significant power imbalances in the separated parts, the separated parts are balanced by disconnecting the load in the deficient part of the network, impulse unloading of the turbines or disconnecting part of the generators in the excess part of the network. After restoring the conditions for synchronization of the separated parts, they include disconnected communications, restore power to disconnected consumers and normal network mode.

HOWEVER THE SPECIFIED METHOD has the following disadvantages:

- The division of the network occurs after the short circuit is disconnected, which, due to the feeding of the short circuit location in the low-power network part from the high-power network, leads to a significant increase in the disconnected short-circuit currents.

- Often an unacceptable dynamic moment arises on the shafts of the generators of a low-power network part due to their significant relative run-out during short circuits and getting to the maximum angular power characteristic when the short circuit is turned off.

- A limited set of possible cross-sections for dividing does not allow for accurate balancing of the shared parts of the network, which leads to disconnection of loads, generators to limit an unacceptable decrease or increase in frequency.

- A significant amount of telemetric information and technological capabilities for dividing the network into variable sections is necessary, because the desired section is random in nature, which complicates the management and reduces its reliability.

- Restored normal network mode, because synchronization of the separated parts in a section not prepared for this is impossible.

THE PROBLEM (TECHNICAL RESULT) OF THE PROPOSED INVENTION IS to prevent the occurrence of unacceptable dynamic moments on the shafts of synchronous generators and asynchronous modes during their parallel operation, to reduce disconnected short-circuit currents, to reduce the power of disconnected loads, generators, and to reduce the need for telemetry information.

The posed problem is solved at the expense of the fact that in the KNOWN METHOD, division is carried out accelerated (before disconnecting short-circuit places) along one of two fixed sections. One for power delivery modes as part of a low power network, the other for power consumption.

At the same time, in normal mode, with the power being supplied by a part of a low-power network, one or more of its generators are loaded to the power transmitted over the cross-section of the power, and, in the event of an emergency unbalance, they are turned off simultaneously with the cross-section switches. If the emergency unbalance was of a passing nature, then after separation by the specified method in the post-emergency mode, the network parts remain balanced, and their parallel operation and normal mode are quickly restored. If the emergency unbalance was of a non-passing nature and arose in part of the low-power network, then after its separation, the resulting unbalance is detected by the change in frequency and is eliminated by balancing changes in generation and load in the separated part of the network.

For the mode of power consumption by a part of a low-power network, a dividing section is formed inside it so that after dividing, a part of the load equal to the power transmitted over the cross-section is connected to a large part of the network.

In FIG. 1 shows an example of a circuit of a fixed-section electric network for dividing, comprising parts of a high power network (ES1) and low power (ES2), representing the implementation of the proposed method;

In FIG. 2 shows a block diagram of an emergency control device for a parallel operation mode that implements the proposed method;

In FIG. 3 shows the angular characteristic of the power of the generators of the low-power network part;

In FIG. 4 shows the transition process corresponding to the proposed control method.

DIAGRAM OF THE ELECTRIC NETWORK WITH FIXED SECTIONS (S1, S2) FOR DIVISION (FIG. 1) contains a transformer (1) with switches (2, 3), switches of the outgoing feeders (4, 5) of the substation connecting ES2 to ES1, switches (6, 7) electric communication lines (8) of the network parts, switches of the outgoing feeders of the load of the distribution point (9, 10, 11, 12), switches of the electric communication lines of the power station with the distribution point (13, 14), switches of the load feeders of the electric station (15, 16 ), generator switches (17, 18), power generating units s power plant (19, 20).

The emergency control device of the parallel operation mode (FIG. 2) contains a measuring device for collecting and processing data (21), a decisive unit (22), and a unit for issuing control actions (23).

THE METHOD IS CARRIED OUT AS FOLLOWS.

Consider the mode of power output by a part of a low power network to a high power network.

In the normal (pre-emergency) mode, the G1 generator (19) is loaded to the transmitted power (Rvyd) of section 1, i.e. through the switch 7. The value of the transmitted power Rvyd is fixed as the setting in the Emergency Control Device for the parallel operation mode, which, when the transmitted power deviates from the setting, acts on the power output by the G2 generator to maintain the constancy of the given transmitted power.

In the event of an emergency disturbance in a high-power network (for example, a short circuit (short circuit) at the load feeder (5), the USOD (21) immediately detects the occurrence of an emergency power imbalance on the basis of a pulse voltage drop (U7, U13) on the distribution point bus (RP), the decisive unit (22) generates a command, and the HC output unit (23) issues a command to turn off the first section switch (7) and generator G1 (17). Disconnecting the switch (7) removes the short-circuit feed current from the generators of the network part low power, h The low-power network is separated with the active power balance, which maintains its normal mode of operation.After disconnecting the damaged feeder (5) by relay protection, the conditions are restored for the parallel operation of the divided parts of the network to resume, the decision unit (22) and the HC output unit (23) act to the generator G2 mode (20), ensuring that the conditions for accurate synchronization of the subsystems are met, and turn on the switch (7). Then, the G1 generator (19) is synchronized with the network with the same automation and its initial load is restored.

In the event of an emergency disturbance in the part of the low-power network (for example, short circuit on the load feeder (9)), the USOD (21) immediately detects the occurrence of emergency power unbalance by the sign of a voltage drop (U7, U13) on the distribution point bus, which decides the unit (22) generates, and the HC output unit (23) issues a command to turn off the switch of the first section (7) and the generator G1 (17). Opening the circuit breaker (7) removes the short-circuit feeding current from the generators of the high-power network part, the relay protection opens the circuit-breaker (9), part of the low-power network is separated with unbalance in active power in the emergency mode, equal to the power of the disconnected load feeder. The resulting imbalance, depending on its magnitude, is eliminated by the regulators of the rotor speed of the generators and the frequency in the low-power system, as well as, if necessary, by standard automation to limit the frequency reduction. After eliminating the unbalance that has arisen, the conditions are restored for the parallel operation of the subsystems to resume, the decisive unit (22) and the HC output unit (23) act on the G2 generator mode (20), ensuring that the conditions for accurate synchronization of network parts are met, and turn on the switch (9). Further, the G1 generator (19) is synchronized with the network by the same automation and its initial load is restored.

Consider the mode of power consumption by a part of a low-power network from a part of a high-power network.

In the normal mode, the generators G1, G2 (19, 20) are loaded so that the transmitted power of section 2 (Rvyd), i.e. through switch 13, was close to zero. The value of the transmitted power (Rvyd) is fixed as the setting in the Emergency Control Device for the parallel operation mode, which, when the transmitted power deviates from the setting, affects the power output by the G2 generator to maintain the constancy of the given transmitted power.

In the event of an emergency disturbance in a part of a high-power network (for example, a short circuit on the load feeder (5), the USOD (21) immediately detects the occurrence of an emergency power unbalance based on the pulse voltage reduction on the RP bus (U7, U13), the deciding unit (22) generates a command, and the output unit HC (23) issues a command to turn off the circuit breaker of the second section (13). Turning off the circuit breaker (13) removes the short-circuit feed current from part of the low-power network, separates part of the low-power network with an active power balance that with It preserves its normal mode of operation.After disconnecting the damaged feeder (5) by relay protection, the conditions are restored for the parallel operation of the divided parts of the network to resume, the decisive unit (22) and the HC output unit (23) affect the mode of generators G1, G2 (19, 20), trying to fulfill the conditions for accurate synchronization of subsystems, and turn on the switch (13).

In the event of an emergency disturbance in the part of the low-power network (for example, short circuit on the load feeder (9), the USOD (21) immediately detects the occurrence of emergency power unbalance based on the pulse voltage reduction on the RP bus (U7, U13), the decisive unit ( 22) generates a command, and the HC output unit (23) issues a command to turn off the circuit breaker of the second section (13) .Turning off the circuit breaker (13) removes the short-circuit feed current from part of the low power network, separates part of the low power network with active power balance, what save After switching off the damaged feeder (9) by relay protection, the conditions for resuming parallel operation of the subsystems are restored, the decisive unit (22) and the output unit У В (23) act on the mode of generators G1, G2 (19, 20), achieving fulfilling the conditions for accurate synchronization of subsystems, and turn on the switch (13).

In the event of an emergency disturbance in the part of the low-power network up to section S2 (for example, short circuit on the load feeder (15)), the USOD (21) immediately detects the occurrence of emergency power unbalance on the basis of a pulse voltage drop on the RP bus (U7, U13) , the decisive unit (22) generates, and the issuing unit HC (23) issues a command to open the circuit breaker of the second section (13). Opening the circuit breaker (13) removes the short-circuit feeding current from part of the high-power network, relay protection opens the circuit-breaker (15), part of the low-power network is separated with unbalance in active power in the emergency mode, equal to the power of the disconnected load feeder. The resulting imbalance, depending on its magnitude, is eliminated by the regulators of the rotor speed of the generators and the frequency in the separated part of the low power network, as well as, if necessary, by standard automation to limit the increase in frequency. After eliminating the unbalance that has arisen, the conditions are restored for the parallel operation of the subsystems to resume, the decisive unit (22) and the HC output unit (23) act on the mode of the generators G1, G2 (19, 20), ensuring that the conditions for accurate synchronization of network parts are met, and turn on the switch (13 ) Further, by the same automation, the divided parts of the network are synchronized, the switch 13 is turned on, and the generators G1, G2 (19, 20) are loaded to the level of zero power flow over section 2.

In FIG. 3, it can be seen that in order to exclude the occurrence of a shock moment on the shafts of synchronous generators of a part of a low-power network, it is necessary to divide the network provided by the proposed method before disconnecting a short circuit, i.e. implementation of leading division. Its use removes the supply of short circuit places from one of the shared parts of the network and, thus, reduces disconnected short circuit currents.

In FIG. 4 presents graphs of the transition process when managing the proposed method. You can see the achievement of the objectives of the proposed method, because the change of operating parameters in the post-emergency mode is not emergency, the frequency change is caused by the occurrence of a short-term dynamic power imbalance on the generator shaft and is eliminated by the work of the standard power unit speed controller.

Thus, in contrast to the prototype, the proposed method (leading balanced division of the network into parts by fixed sections) reduces disconnected short-circuit currents, eliminates the risk of unacceptable moments on the shafts of synchronous generators of a low-power network, prevents the occurrence of asynchronous modes, eliminates the need for or reduces load shedding to prevent accidents.

Claims (1)

A method of emergency control of the parallel operation mode of synchronous generators in electric networks, which consists in the fact that in normal mode the network cross sections are determined for dividing from the number of technologically possible ones, in the event of an emergency disturbance, the network is divided according to a predetermined section by turning off the breakers included in it, in the after-emergency mode with network separation at high frequency in part of the low-power network reduce the output power of the generators, and at a lower frequency They take away part of the load, adjust the voltage and the power output of the remaining generators to fulfill the conditions for accurate synchronization of the small and high power network parts according to the cross-section used for dividing, and turn on its switches to restore parallel operation of the network parts, restore the network to normal mode by turning on all disconnected loads and generators and with their respective loading, characterized in that in order to prevent the occurrence of unacceptable dynamic moments on the shafts of synchronous generator in and asynchronous modes during their parallel operation, reducing disconnected short-circuit currents, decreasing the power of disconnected loads, generators in the electric network fix two constant sections for dividing in the event of emergency unbalances, the first for normal modes with power output, the second with consumption of part of the network low power, in normal mode with power output, one or more generators of a part of the low power network is loaded to the amount of power output in the first section, in fact at a sudden deep voltage drop ahead of a short circuit disconnect, the first section and generators of the low-power network part are turned off, loaded to the amount of output power in the first section, in the normal mode of power consumption by a part of the low-power network, their generators are loaded to zero active power flow in the second cross-section, upon the fact of a sudden deep decrease in voltage ahead of the short circuit disconnection, the circuit breakers of the second section are disconnected.

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