RU2723544C1 - Automatic emergency load control system in isolated power system - Google Patents

Abstract

FIELD: electrical engineering.SUBSTANCE: invention relates to electrical engineering, in particular to systems for automatic prevention of instability and automatic systems for limiting frequency reduction in isolated power systems.EFFECT: technical result consists in improvement of accuracy of selection of control actions at disconnection of power units of power plants in isolated power system and is achieved by the fact that invention contains a control element of previous mode, unit for comparing current loads of generators (power units) by active power, unit for implementing control actions, actuating and launching elements, is supplemented with a unit for calculating optimum control actions, which performs calculation of control actions in accordance with the proposed algorithm.1 cl, 2 dwg

Description

Technical field

The invention relates to the field of electric power and can be used to optimize the operation of automatic stability control systems and automatic systems to limit frequency reduction in isolated energy systems.

State of the art

According to STO 59012820.29.020.004-2018 "Standard of JSC" SO UES ". Relay protection and automation. Automatic emergency control of power system modes. Emergency Automation. Standards and requirements "automatic emergency control is designed to identify, prevent the development and liquidation of the emergency power system, which is implemented by means of emergency control devices (PA).

Conventionally, all existing PA systems can be divided into local subsystems that implement the volume of control actions (HC), obtained on the basis of previously performed calculations for the group of the most difficult circuit-mode situations, and centralized emergency control systems (CSPA), which calculate and implement the HC based on data on the current operating mode of the energy system obtained in real time.

In general, PA devices can perform the following functions:

- prevention of instability in the parallel operation of power plant generators;

- preventing the occurrence of unacceptable current overloads of equipment;

- elimination of asynchronous modes of generating equipment;

- limiting the reduction or increase in the frequency of alternating voltage in the electric power system (EPS);

- limiting the reduction or increase in voltage in the nodes of the electric network.

Currently, local PA devices are used to solve all of the above problems in the emergency control structure, and centralized devices are used only to prevent instability in the parallel operation of power plant generators, to limit voltage drop in the nodes of the electric network and to prevent unacceptable current overloads of equipment.

An analysis of the principles of development of modern energy systems shows that in recent decades there has been a tendency around the world to increase the participation of gas turbine (gas turbine) and combined cycle plants (CCGT), as well as alternative sources of electricity (AIE), in the overall energy balance of individual power plants. First of all, this circumstance is due to the environmental friendliness and energy efficiency of the use of these power plants.

From the point of view of the influence of gas turbines, combined cycle plants and nuclear power plants on the course of emergency processes in power systems, these power plants have a negative feature associated with the inability to carry out long-term (and in some cases short-term) operation under conditions of a reduced frequency of alternating voltage. In many cases, this circumstance leads to their disconnection from technological protections or automation even before the operation of local PA devices that limit the decrease in frequency in the EPS (including automatic frequency unloading devices (AFR)), increase the initial deficit of active power in the power system and develop cascade accident with uncontrolled disconnection of consumers during its course.

Due to the fact that, compared with large power systems, isolated power plants are more sensitive to the occurrence of emergency active power deficits, which lead to a change in the frequency of the alternating voltage beyond the permissible limits, as well as the tendency to the widespread introduction of gas turbines, combined cycle plants and nuclear power sources, it becomes relevant to use energy systems of intelligent PA systems that optimally compensate for emergency shortages of active power and ensure the stability of power plant generators under the condition of preventing their shutdown by technological protections and automation.

The most common way to compensate for emergency imbalances in active power arising in isolated power plants is currently the use of additional automatic unloading (DAR) devices or automatic unloading devices when the generator or power unit (AROG or AROB) is turned off, which relate to local PA devices.

According to STO 59012820.29.020.004-2018, DAR devices should be used to eliminate large local deficiencies in active power (more than 45% of consumption) with a frequency reduction rate of more than 1.8-2.0 Hz / s, while the implementation of control actions by these PA devices should be aimed at increasing the efficiency of work or providing the possibility of triggering of AChR devices. The purpose of the AROB (AROG) devices in isolated power plants is not strictly regulated and, as a rule, it is similar to the purpose of the DAR devices (for example, the AROB and AROG devices of the Kaliningrad power system).

As a prototype, automatic unloading was selected when the generator was turned off (AROG) [Gurevich Yu.E., Libova L.E., Okin A.A. Calculations of stability and emergency automation in power systems. - M .: Energoatomizdat, 1990].

The specified automation includes:

- starting bodies fixing emergency shutdowns of generators (power units);

- the control body of the previous mode, the task of which is to receive and process information about the current load of generators (power units) by active power;

- a unit for comparing current loads of generators (power units) in terms of active power with previously prepared response settings;

- a block for the implementation of control actions, which, in the event of an alarm signal about turning off the generators (power units) of power plants and exceeding the setpoints of operation, generates a command for implementing control actions (load disconnection) according to the previously prepared table of control actions;

- executive bodies implementing control actions (load shedding);

- communication channels and transmitters and receivers of television information and executive teams.

Automation measures the generator power preceding the shutdown and the total previous transmitted power in a controlled section and, when the emergency shutdown of the generator (power unit) is detected, it performs a metered effect depending on these values.

The settings and actions are selected on the condition of ensuring static stability with a standard margin in the emergency mode, caused by the shutdown of the controlled generator and the surge of power in the section.

Due to the fact that DAR and AROB (AROG) devices do not use information about the current operating mode of the energy system in their algorithms, then:

- the volume of control actions implemented by these devices, in most cases are redundant. This circumstance leads to an unjustified disconnection of electricity consumers;

- in those cases when the load of the generator (power unit) of the power plant is less than the predefined setpoint for the operation of the DAR or AROB (AROG) devices, situations may arise when the frequency of the alternating voltage is outside the permissible limits, and the HC is not realized.

A disadvantage is the impossibility of taking into account the nature of the transition process (PP) after the implementation of control actions in the DAR, AROB (AROG) algorithms and, as a result, the determination of their redundancy or insufficiency to prevent the operation of AChR devices and technological protections of gas turbines, gas-fired power plants and nuclear power generators.

SUMMARY OF THE INVENTION

EFFECT: creation of an automatic emergency load control system in an isolated operating energy system with increased accuracy of selection (optimization of the required volume) of HC when power units of a power plant are turned off, which ensures that conditions for triggering of automatic frequency unloading devices and technological protection of gas turbines, gas turbine units, and nuclear power generators are prevented, and also maintaining the frequency level in the emergency mode according to the requirements of GOST 32144-2013 “Electric energy. Electromagnetic compatibility. Quality standards for electric energy in general-purpose power supply systems ”using information on the current operating mode of an isolated EPS.

The specified technical result is achieved by the fact that the device AROB or AROG containing:

- start-up bodies that record emergency shutdowns of generators (power units), the signals of which are triggered via communication channels enter the block for the implementation of control actions;

- the control body of the previous mode, the input of which receives information about the current load of generators (power units) by active power and the output of which is connected with the first input of the unit for comparing the current load of generators (power units) by active power with operation settings;

- a unit for comparing current loads of generators (power units) by active power with the operation settings, the output of which is connected to the first input of the control actions implementation block;

- a block for the implementation of control actions, transmitting emergency commands to disconnect the load through communication channels to executive bodies that implement control actions (load disconnection);

- executive bodies implementing control actions (load shedding),

It is supplemented by a block for calculating optimal control actions, the first output of which is connected to the second input of the unit for comparing current loads of generators (power units) with the settings for operating and implementing control actions, and the second output is connected to the second input of the block for implementing control actions. As source data, the specified block uses information about:

1) the composition of generators (power units) of power plants operating in the network (TS _gene );

2) loading on the active power of power units of power plants operating in the network ( P _gene );

3) the current outside temperature at power plants (TNV);

4) the current value of the frequency of the alternating voltage in the EPS ( f _tech );

5) the current capacity of consumers that are disabled by the action of PA devices ( R _SAON );

6) the current consumption of active power in the EPS ( R _consumption ).

Brief Description of the Drawings

In FIG. 1 shows a general diagram of an automatic emergency load control system in an isolated operating energy system, which contains: a control unit 1 of the previous mode, a unit 2 for comparing current loads of generators (power units) with operation settings, a unit 3 for implementing control actions, start-up bodies 4 (fixing devices emergency shutdowns of generators (power units), executive bodies 5 (devices that realize load shedding), block 6 for calculating the optimal volumes of control actions.

In FIG. 2 presents an algorithm for calculating control actions implemented in block 6.

The implementation of the invention

The control body 1 of the previous mode receives and processes telemetric information about the load of generators of power plants by active power, which is transmitted to block 2 comparing the current load of generators (power units) with the operation settings. In block 2, the pre-emergency loading of generators is compared with the operation settings calculated by block 6 for calculating the optimal volumes of control actions, and if they are exceeded, block 2 transmits information about the excess of the set point to control actions implementation block 3. In block 3, information is stored on cases of exceeding the operation settings and, in the case of an alarm from unit 4 about turning off the generator (power unit), the power of which exceeded the operation setting, block 3 generates a control action calculated by unit 6 for calculating the optimal HC volumes, which is implemented by executive bodies 5.

Information on the composition of the generators (power units) of power plants operating in the network, the load by active power of the power units of power plants operating in the network, the current temperature of the outside air in power plants, the current value of the frequency of the alternating voltage in the power system, the current power of consumers disconnected by the action of PA devices and the current the consumption of active power in the energy system comes through communication channels from the operational measuring complex (DEC) to block 6. In block 6:

- calculates the value of the maximum allowable imbalance of active power for the current circuit-mode situation, leading to an unacceptable change in the frequency of the alternating voltage according to the expression (1):

, (1)

, (1)

where R _{NB max} - the maximum allowable imbalance of active power for the current circuit-mode situation, MW;

f _tech - the current value of the frequency of the alternating voltage in an isolated EPS (according to the OIC), Hz;

f _nom - nominal value of the frequency of the alternating voltage in an isolated EPS, Hz (50 Hz);

D _ƒ - permissible frequency change in the emergency mode, p.u. (set by the technologist, the permissible frequency deviation of ± 0.4 Hz in the emergency mode corresponds to a value of D _f equal to 0.008);

K _{g f} - the regulatory effect of frequency generation (set by the technologist varies within a fairly wide range (from 0 to 25 or more), depends on the composition of the generators of power plants, the circuit-balance situation, the availability of a rotating reserve, the position of the operating point of the speed controllers in the dead band, etc. );

K _{n f} - the regulatory effect of the load in frequency (set by the technologist, defaults to 1.0);

P _{so . i} - rated poweriof the 1st power unit involved in the primary frequency regulation, MW (set by the technologist, while for the CCGT and GTU power units it is necessary to indicate the rated power of the power units at a temperature of + 15 ° C. The indicated parameter is automatically corrected in block 6 depending on the high-voltage pump at power plants with CCGT and GTU according to the data from the OIC);

s _i - state of the power unit (0 - the power unit is disconnected from the network, 1 - the power unit is connected to the network, is automatically adjusted in block 6 according to the data from the DEC);

P _consumption - total consumption of EPS (according to OIC), MW.

tables (column vectors) of the minimum required hydrocarbon volumes for each launching organ (POR) are formed, according to expression (2):

, (2)

, (2)

where HC _POR is the minimum required volume of HC, MW;

R _gene.Por - the current value of the generator power, the shutdown of which is POR according to the data from the DEC, MW;

R _s.n. - active auxiliary power of the disconnected power unit, according to data from the DEC, MW;

P _{NB max} - the maximum allowable imbalance of active power for the current circuit-mode situation, calculated in block 6, MW.

- a table is formed (a column vector) available for the Automatic Emergency Load Management System in an isolated working energy system of OH volumes (HC _add );

- for each launching organ, a table (column vector) of control actions (TUV) is formed, according to the algorithm presented in FIG. 2.

After processing the information in block 6, the settings are transferred to block 2, and the generated control action table is transmitted to block 3.

The proposed system was tested during testing in May 2019 in the power system of the Kaliningrad region. The test results showed that the use of the device in EES allows not only to optimize and reduce the volume of disconnection of consumers due to the “quick” implementation of HC, but also to prevent the operation of technological automation of generating equipment, taking into account factors of reduction or speed of frequency reduction in EES, and the further development of frequency accidents .

The inventive system of automatic emergency load control in an isolated operating energy system provides the required technical result associated with increased accuracy of selection (optimization of the required volume) of HC when power units are turned off, as well as ensuring that conditions are not triggered for automatic frequency unloading devices and technological protection of gas turbines, CCPP and AIE, and maintaining the frequency level in the emergency mode according to the requirements of GOST 32144-2013 “Electric energy. Electromagnetic compatibility. Quality standards for electric energy in general-purpose power supply systems ”using information on the current operating mode of an isolated EPS.

Claims (1)

An automatic emergency load control system in an isolated operating energy system containing a control unit of the previous mode, the input of which receives information about the current load of generators (power units) by active power, associated with the unit for comparing current loads of generators (power units) by active power with operation settings, associated with the control actions implementation unit transmitting emergency commands to disconnect the load to the executive bodies implementing control actions; and start-up bodies that record emergency shutdowns of generators (power units), the triggering signals of which are sent to the control actions implementation unit, characterized in that it additionally contains an optimal control actions calculation unit using information about the composition of generators (power units) of power plants operating in the network, on loading the active power of generators (power units) of power plants operating in the network; current outdoor temperature at power plants; the current value of the frequency of the alternating voltage in the energy system; the current power of consumers, which are switched off by the operation of emergency control devices, the current consumption of active power in the energy system, and transmitting the calculated settings and the generated control actions table to the unit for comparing current generators (power units) loads with the operation settings and the control actions implementation unit, respectively.

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