RU2790322C1 - Frequency control method in electric power systems - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to the field of electrical engineering and can be used in electric power systems, electric networks with distributed generation to automatically maintain the balance of the normal mode in terms of active power during changes in load and power output by power plants. The method for frequency and power control in electric power systems consists in the fact that in case of frequency deviation, the power regulators of the primary engines of power plants carry out static control of the speed of rotation of the generator rotors with a given time for introducing the primary control reserve. The regulator of the power plant allocated for secondary frequency control performs astatic frequency control with a given time for introducing a secondary regulation reserve that exceeds the time for introducing primary regulation reserves, power correctors of generators not participating in secondary astatic regulation, if the secondary regulation power reserve is insufficient, change their power in the opposite direction in relation to the frequency deviation to restore the reserve of secondary regulation with the time of input of its reserve, equal to the time of input of the reserve of secondary regulation. Equal time intervals of a given multiplicity are formed synchronized with the external signal of the satellites in relation to the time of entering the secondary regulation reserve to allocate a secondary frequency regulation power plant, the participation of other power plants in restoring the secondary regulation reserve by correcting their output power, permitting changes in the planned load, at each power plant in the control system. For all power plants of the power system, uniform rules for participation in frequency regulation and changes in the output power, priority for participation in secondary frequency regulation are established once. At each time interval at all power plants, the process controllers, according to the specified rules, identify the compliance of the process with the state class of the frequency and power control system and, depending on the identified state class and their sequence, each controller independently decides on the nature of its participation in frequency control and power balance change in the electric power system without disturbing the power balance in the power system.

EFFECT: simplification of the frequency and power control system in power systems, increasing the reliability of its operation.

1 cl, 2 dwg

Description

The present invention relates to the field of electric power industry and can be used in electric power systems, electric networks with distributed generation to automatically maintain the balance of the normal mode in terms of active power with changes in load and power output by power plants.

A known method of frequency control in power systems (Operation hand book UCTE / UCTE OH - Policy 1: Load - Frequency Control - Final version (approved by SC jn 19 March 2009) B. Secondary Control) in which several control areas are allocated in the power system. Primary (static) frequency control with the required droop and the time of input of the primary control reserve is carried out by speed controllers at all power plants of the power system, and secondary astatic control of the balance of flows through external connections is carried out within each of the control areas included in the power system, and balance (frequency) control inside the control area, a power plant is involved only if the balance deviation is caused by a change in the load in itself. The method is based on the following property of power systems.

If in any area of regulation the load has changed, then in it a decrease in frequency is accompanied by a decrease in the balance of flows through external connections, while in other areas a decrease in frequency is accompanied by an increase in the balance of power flows through external connections. This is explained by the fact that all power units of the power system, having static regulation at power plants, in an effort to maintain the frequency, increase the output power.

Thus, for the control area in which the load change occurred, the sign of the frequency deviation and the sign of the deviation of the balance of power flows through external connections from the value preceding the change are the same, and in other areas these signs are opposite.

In each region, one control station is allocated, at which astatic regulation of frequency or exchange power is implemented, and a blocking of this regulation is created, which is triggered when the signs of frequency deviations and exchange power flow from the previous value change coincide.

If the power balance is disturbed in any area of regulation, the signs of the change in frequency and exchange power coincide, the secondary regulation is not blocked, and under the action of the astatic frequency controller, the load on the units of the regulating power plant increases or decreases. In other areas of regulation, the signs of the change in frequency and exchange power are opposite, and therefore astatic regulation is blocked.

However, this method has the following disadvantages:

For regulation in this way, in each of the areas of regulation, the presence of TV channels is required for data transmission between substations, from which external communication lines depart, and the station that regulates the frequency or power exchange flow.

In case of violations in the frequency control system of the leading power plant or the depletion of power reserves necessary to increase or decrease the load of the power plant, astatic regulation is not carried out, which violates the normal modes of the power system and reduces the quality of electricity in terms of frequency.

Also known is a method of frequency control in power systems (GOST R 55890-2013 National standard of the Russian Federation. Unified power system and isolated power systems. Operational dispatch control. Frequency control and active power flows. Norms and requirements) which is a prototype of the present invention, in which the primary (static) regulation of frequency with the required droop and input time of the primary regulation reserve is carried out by speed controllers at all power plants of the power system, secondary (astatic) regulation is carried out by one power plant designated by a single control center (leading in frequency) with the input time of the required secondary regulation reserve significantly exceeding the time input of reserves of primary regulation. To increase the reserves of secondary regulation at the frequency-leading power plant, a single control center additionally assigns one or more power plants for secondary regulation according to the method of share participation in the power of the frequency-leading power plant. When the reserve of secondary regulation at the power plant leading in frequency (to reduce or increase frequency) is exhausted, taking into account its increase due to power regulation of power plants with shared participation, a single control center corrects the power tasks for one or more power plants not participating in secondary regulation, for loading or unloading power plants that carry out secondary regulation.

When assigning the leading power plant in terms of frequency and power plants that help it in the regulation according to the equity method, adjusting power targets to other power plants to restore reserves of secondary regulation for loading or unloading, a single control center receives information about the capabilities of power plants to change their operating modes, and also transmits commands to their change through technological channels of data teletransmission.

However, this method has the following disadvantages:

The need for a single control center does not allow the use of this method in the absence of such a center in power systems and electrical networks with distributed small generation.

In case of violations of data transmission over communication channels between the frequency-leading power plant and power plants participating in the regulation according to the equity method, their participation in the regulation becomes impossible.

In case of violations of data transmission over communication channels between a single control center and power plants participating in the restoration of secondary regulation reserves, their use for frequency regulation becomes impossible.

The objective (technical result) of the invention is to simplify the frequency and power control system in power systems, to increase the reliability of its operation.

The problem is solved due to the fact that in the known method, decisions on participation in the implementation of secondary regulation, power correction to restore secondary regulation reserves and permission to change the power of the power plant are taken by the control device (controller) located directly at the power plant itself. At the same time, for the operation of this device, fixed in time and synchronized for all such devices at power plants of the power system, time cycles of double duration are created on it with respect to the time of input of secondary regulation reserves. At each time step, the controller, by the nature of the frequency change in the power system, identifies the state class of the frequency control system from a given set, using the conditions for belonging to a particular class, taking into account the current and previous classes, and independently makes decisions about the nature of participation in frequency control based on general for all power plants rules.

Figure 1 shows an example of an electrical network diagram of a power system with three power plants and controllers, representing the implementation of the proposed method.

Figure 2 shows a graph of the change in frequency in the power system under the influence of disturbances in the form of violations of the balance of active power and reactions to these changes in the frequency and power control system.

The scheme of the electrical network of the power system with three power plants and controllers (Fig. 1), representing the implementation of the proposed method, contains: generators of power units of power plants 1, 2, 3, power lines 4, 5, 6, forming an electrical network, loads in the nodes of the electrical network 7, 8, 9, intelligent controllers for controlling the power of power units of power plants 10, 11, 12, channels for measuring the frequency and power output by generators of power units 13, 14, 15, channels for influencing controllers on power output by generators of power units 16, 17, 18.

On the graph of frequency changes in the power system under the influence of disturbances in the form of active power balance disturbances and reactions to these changes in the frequency and power control system (Fig. 2), the numbers of clock time intervals 19-27 synchronized for all controllers (10-12 Fig.1) are shown , graph of frequency change in the power system 28, upper 29 and lower 30 limits of effective frequency retention in the EPS by secondary regulation, state classes of the frequency and power control system in the power system B (with modifications), indicator of the frequency control participant on the time step and the nature of his participation A ( with modifications).

The method is carried out as follows:

Before the automatic frequency control system is put into operation on the controllers (10-12, Fig.1), the priority of their use for secondary frequency control is set, and the following parameters are introduced: the same for all the duration of the time cycles synchronized by the satellites, the input times of the reserves of the primary, secondary regulation, power correction to restore reserves of secondary regulation.

From the generator buses (1, 2, 3) through the measurement channels (13, 14, 15) the measured frequency values are constantly received by the intelligent power control controllers of power generating units (10, 11, 12). Intelligent controllers for power control of power units of power plants (10, 11, 12) on the basis of specified conditions identify the class of state of the frequency control system and, according to specified rules, decide on the nature of their participation in frequency control, switching to astatic control, blocking astatic control, correcting the output power to restore reserves of secondary regulation in the power system or proceed to change its planned output power.

To do this, algorithms are launched for identifying the state classes of the frequency control system within the clock cycle and making decisions on the established unified rules for the participation of power plants in maintaining the power balance in the EPS and permissions to change their load.

When making decisions about the participation of power plants in regulating the frequency and output power, the controllers use the following classes of the state of the frequency and power control system, as well as the conditions for their identification:

1. Efficient operation of the secondary regulation in the current tact of time (B)

In this state, the balance of active power for most of the duration of the time cycle is maintained by the frequency-leading power plant, i.e. the frequency is in the range of values of its effective maintenance by secondary regulation with a total duration of 0.5 - 1.0 of the duration of the time cycle:

fуставки

Δfдоп. втор. рег., ∆f

fsettings

Δfadm. sec. reg.,

where fset is the secondary frequency control setting,

Δfadm. sec. reg - permissible error of frequency recovery by secondary regulation,

Δf - current frequency value.

)Inefficient operation of the secondary control in the current time step (

)

In this state, the balance of active power by the frequency-leading power plant is not maintained for most of the duration of the time cycle, i.e. the condition for state class B is not met.

)2. Inefficient operation of the secondary regulation in the current tact of time with a shortage of active power (

)

This class of state corresponds to a failure of the secondary regulation or the depletion of the reserve for increasing the frequency in the event of a power shortage in the EPS

0∆f

0

with a total duration of more than 0.5 of the duration of the clock cycle.

)3. Inefficient operation of the secondary regulation in the current cycle of time with an excess of active power (

)

This class of state corresponds to a failure of the secondary regulation or the depletion of the reserve for frequency reduction in case of excess power in the EPS

∆f

with a total duration of more than 0.5 of the duration of the clock cycle.

4. The need to block the secondary regulation at the leading station with its subsequent introduction to the second power plant in the priority list ( C + 1 )

This class of state corresponds to a failure of the secondary control with the need to block at the power plant that performed it earlier and put it into operation at the next power plant in priority.

5. The need to block secondary regulation at the second leading station with its subsequent introduction at the third power plant in the priority list (C + 2)

This class of condition corresponds to a failure of the secondary control with the need for blocking at the previously performing power plant of the second priority

6. Permission of commands from external systems to change the power output of the power plant by external systems (D)

)7. Permission of commands from external systems to increase the power output by the power plant (

)

)8. Permission of commands from external systems to reduce the power output by the power plant (

)

)9. Request for an increase in the power output of the power plant to restore the reserve of secondary regulation (

)

)10. Request to reduce the power output of the power plant to restore the reserve of secondary regulation (

)

To control power plants in the implementation of frequency and power regulation in EPS, as well as to allow changes in their planned load, controllers use the following general rules:

1. All generators participate in primary regulation.

2. For astatic (secondary) regulation, power plants are used with a predetermined priority for their participation in regulation.

3. If the inefficiency of the secondary regulation with a duration of more than 2 cycles is revealed, the secondary regulation at the power plant is terminated.

4. If the inefficiency of secondary regulation is detected within a time interval of a given time tact for generators included in the ranked list of their involvement in secondary regulation, secondary regulation is introduced at the corresponding power plant from this list.

5. In case of a unilateral frequency deviation at a full time step, at power plants that are not included in the list for participation in secondary regulation, a power correction is launched aimed at eliminating the mode imbalance that has arisen, with a duration not exceeding the duration of the time step. The value of power change before frequency recovery is fixed, and an additional change in the specified multiplicity is made in relation to the frequency entered before frequency recovery to restore the power reserve at the frequency-leading power plant.

6. Changing the load of power plants, in addition to impacts for frequency control, is allowed in two cases and with a working time of no more than the duration of the clock interval:

After detecting the hang of the frequency deviation from the setpoint, it is allowed to change the load in the direction of reducing this deviation.

After confirming the effectiveness of the secondary regulation at the previous time step.

After synchronization of power plants and their inclusion in parallel operation, the frequency and power control system is put into operation.

), в коридоре эффективности вторичного регулирования, т.е. более половины такта времени, даже несмотря на то, что во втором такте возникло нарушение баланса мощности (класс

). На этих тактах времени контроллерами электростанций 2,3 разрешено изменение загрузки электростанций для такта 21 (при условиях сохранения эффективности вторичного регулирования), однако на такте 21 условие эффективности не выполнилось.On the first and second time steps of the graph (19.20 Fig. 2), the frequency is held by the power plant 1, leading the frequency (class

), in the secondary regulation efficiency corridor, i.e. more than half of the clock cycle, even though there was a power imbalance in the second cycle (class

). At these time cycles, power plant controllers 2,3 allowed changing the load of power plants for cycle 21 (under conditions of maintaining the efficiency of secondary regulation), however, at cycle 21, the efficiency condition was not met.

). Электростанциям 2,3 на четвертом такте времени (22) дается задание на коррекцию мощности для восстановления резерва вторичного регулирования на электростанции 1. Увеличение загрузки этими электростанциями производится с фиксацией введенной мощности до восстановления номинальной частоты с последующей дополнительной загрузкой на величину с заданной кратностью по отношению к введенной (

,

). После восстановления резерва вторичного регулирования на электростанции 1 частота в ЭЭС на четвертом такте времени (22) восстановилась (частота суммарно находится в коридоре эффективности вторичного регулирования более половины такта времени).At the third time step (21), the controllers revealed the inefficiency of secondary regulation with a shortage of active power in the EPS (class

). At the fourth time step (22), power plants 2,3 are given the task of adjusting the power to restore the secondary regulation reserve at power plant 1. The increase in load by these power plants is carried out with fixing the input power until the nominal frequency is restored, followed by additional load by a value with a given multiplicity with respect to entered (

,

). After the restoration of the secondary regulation reserve at power plant 1, the frequency in the EPS was restored at the fourth time step (22) (the frequency in total is in the secondary regulation efficiency corridor for more than half of the time step).

). Электростанциям 2,3 на 6 такте времени (24) дается задание на коррекцию мощности для восстановления резерва вторичного регулирования на электростанции 1, а также разрешается снижение мощности. При этом, допустим, что на 3-ей электростанции возникло отсутствие возможности снижения мощности, а на второй стало предпочтительным снижение загрузки электростанции (класс

).At the 5th time step (23), the controllers revealed the inefficiency of secondary regulation with excess active power in the EPS (class

). Power plants 2,3 at the 6th time step (24) are given the task of power correction to restore the reserve of secondary regulation at power plant 1, and power reduction is also allowed. In this case, let us assume that at the 3rd power plant there was no possibility of reducing the power, and at the second it became preferable to reduce the load of the power plant (class

).

).Reducing the load of power plant 2 at the 6th time step (24) leads to the restoration of the reserve of secondary regulation at power plant 1 and the efficiency of secondary regulation (class

).

), при этом на контроллере электростанции 1 вторичное регулирование выводится, а на следующей по приоритетности для вторичного регулирования электростанции 2 вводится (

).At the 7th (25) and 8th time steps (26) (two in a row), controllers at power plants detect a long-term secondary regulation inefficiency (

), while at the controller of power plant 1 secondary control is output, and at the next priority for secondary control of power plant 2 it is entered (

).

) в энергосистеме электростанций 2 (

).At the 9th time step (27), the controllers identify effective secondary regulation (

) in the power system of power plants 2 (

).

Thus, in contrast to the prototype, in the proposed frequency control method, the assignment and change of the frequency-leading power plant, maintaining its reserves of secondary control power, permitting and implementing changes in the planned power at the power plants of the power system are carried out without centralized control and the use of technological data transmission channels, which simplifies frequency control system and increases its reliability.

Claims (1)

A method for regulating frequency and power in electric power systems, which consists in the fact that in case of frequency deviation, the power regulators of the primary engines of power plants carry out static regulation of the speed of rotation of the generator rotors with a given time for introducing the primary regulation reserve, the regulator of the power plant allocated for secondary frequency regulation performs astatic frequency regulation with a given time for introducing the secondary regulation reserve exceeding the time for introducing the primary regulation reserves, correctors the power of generators not participating in the secondary astatic regulation, in case of insufficient secondary regulation power reserve, change their power in the opposite direction with respect to the frequency deviation to restore the secondary regulation reserve with the time of entering their reserve equal to the time of introducing the secondary regulation reserve, characterized in that to allocate a power plant of secondary frequency regulation, participation of other power plants in restoring the reserve of secondary regulation by correcting its output power, permitting changes in the planned load, at each power plant in the control system, the same time intervals of a given multiplicity are formed synchronized with an external satellite signal in relation to the time of introducing a secondary regulation reserve, for all power plants of the power system, uniform rules for participation in frequency regulation and change output power, the priority of participation in the secondary frequency control, at each time interval at all power plants, the process controllers identify, according to the specified rules, the compliance of the process with the state class of the frequency and power control system and, depending on the identified state class and their sequence, each controller independently decides on the nature of their participation in frequency regulation and change in the power balance in the electric power system, namely, the transition to astatic frequency regulation, the adjustment of output available capacity to restore the secondary regulation reserve at the power plant performing secondary regulation, or to change its planned load without disturbing the power balance in the power system.

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