RU2671659C1 - Method and system of automatic regulation of the ccgt unit with forcing impact on the control valves of high and medium pressure of the steam turbine - Google Patents

Abstract

FIELD: power engineering.SUBSTANCE: invention relates to power engineering. Method and system for automatic power control (SAPC) of a combined cycle gas turbine unit (CCGT), including at least one gas turbine unit (GTU), corresponding number of waste-heat boilers (WB) connected to their gas exhausts and in parallel a steam-turbine installation (STI) connected to the last in a couple. When the frequency of the electrical network deviates from the nominal value, the power change reference signal is distributed to the control systems of the CCGT and steam turbine, and in the steam turbine control system, the corresponding reference signal is passed through the boost elements. Specified reference signal of the steam turbine control system is additionally distributed to the reference signals of the control of high and medium pressure valves of the specified steam turbine. On the cover of these valves restrictions are set, and the movement of the regulating bodies of the medium pressure valves towards their cover is carried out upon reaching a predetermined threshold level of deviation from the nominal value of the electrical frequency of the network, which requires the highest possible speed of the control system.EFFECT: invention allows to increase the speed and accuracy of power control, as well as the efficiency of the CCGT in maneuverable modes of its operation.2 cl, 4 dwg

Description

Technical field

The group of inventions relates to a power system and can be used to automatically control the power of combined cycle plants (CCGT).

State of the art

A modern CCGT unit usually includes one or two gas turbine units (GTU), each of which serves as a drive for its own electric generator, the corresponding number of waste heat boilers connected to the GTU gas exhaust, and connected in parallel to the waste heat boilers using a steam turbine mixing manifold installation (vocational school). In accordance with industry requirements (Unified energy system and isolated energy systems. Operative-dispatch control. Regulation of frequency and active power flows. Norms and requirements / GOST R 55890-2013. Approved by order of Rosstandart No. 2164 - st dated 05.12.2013. // [1]) the following types of restoration of the unbalance between the generated power system and the active electric power required by consumers are established: primary regulation carried out in order to limit frequency deviations from the nominal value cheniya for the safe operation of power plants and minimize the risk of disconnection of power plants electricity consumers emergency control actions; secondary regulation, performing the functions of maintaining the nominal value of the network frequency during energy flows between networks; tertiary regulation - automatic regulation of active power to restore the reserve of secondary regulation.

With a planned (seasonal or daily) load change, a corresponding change in CCGT power is usually carried out only at the expense of GTU regulatory bodies by supplying fuel and air to its combustion chamber with fully open control valves for supplying steam to the PTU steam turbine, which is most preferable from an economic point of view.

At the same time, CCGT, as well as other generating units operating as part of the power system, must necessarily provide a change in power when the network frequency changes with certain specified characteristics regulated by state and industry standards ([1] and Organization Standard of JSC SO UES STO 59012820.27.100.004-2016 “Norms for participation of combined cycle gas and gas turbine plants in the normalized primary frequency regulation and automatic secondary regulation of the frequency and active power flows” [2]). The requirements for these characteristics are quite stringent in terms of accuracy and dynamics of power change: for 15 seconds. CCGT installed capacity should change by no less than 2.5% in 30 seconds. - not less than 5% and in 2 minutes - not less than 10% when the resulting power value deviates from the set value - not more than 1% of the CCGT rated power. Given that the rate of change of gas turbine power is limited by the conditions of its reliable operation, these characteristics cannot be realized only by influencing the regulatory bodies of gas turbines.

A known method of automatically controlling the power of a combined cycle gas turbine unit containing at least one gas turbine unit with its own electric generator, the corresponding number of utilized boiler units connected to the gas exhausts and a steam turbine unit with a steam turbine connected in parallel to the last ones, is known and its electric generator, which consists in the fact that when deviating from the nominal value of the frequency of the electric eti reference signal power change partitioned by regulatory systems of a gas turbine plant and a steam turbine, and a steam turbine control system corresponding to the reference signal is passed through a forcing elements (RU 61349, F01K 13/02, 2007 [3]).

From the same source [3], there is also known a system for automatically controlling the power of a combined cycle plant, which includes at least one gas turbine unit with its own electric generator, the corresponding number of these waste heat boiler units connected to the gas exhaust, and a steam turbine unit connected in parallel to the last ones a steam turbine and its own electric generator, comprising a driver for changing the power of the combined cycle plant in primary, secondary and tertiary regulation, the signal distributor of the specified task for the control systems of the gas turbine unit and the steam turbine and the power regulator of the gas turbine unit connected to the specified distributor and equipped with the means for forcing the corresponding signal, the power regulator of the steam turbine unit.

The main disadvantage [3] is the loss of efficiency due to the need for deep shuttering of the valves of the high pressure cylinders (high pressure valves) of the steam turbine, which leads to partial throttling of the steam with some corresponding loss of its initial enthalpy. Another disadvantage can be considered limited speed and accuracy, due to the need for deep shut-off of the high-pressure valve to ensure these indicators.

Disclosure of inventions

The task to which the inventions of the patented group are directed is to ensure effective CCGT maneuverability in a wide range of load changes while maintaining the frequency of the electrical network, and the technical results achieved are to increase the speed and accuracy of power control, as well as the cost of CCGT in the maneuverable modes of its operation .

The solution of this problem by achieving the specified technical results in relation to the 1st patentable invention is ensured by the fact that when implementing the method of automatically controlling the power of a combined cycle plant containing at least one gas turbine unit with its own electric generator, the corresponding number of said waste heat boiler units connected to the gas exhausts and in parallel connected to the last steam turbine unit with a steam turbine and its own electric generator ohm, consisting in that the deviation from the nominal value of the mains frequency reference signal power change partitioned by regulatory systems of a gas turbine plant and a steam turbine, and a steam turbine control system corresponding to the reference signal is passed through a forcing elements,

according to the 1st invention of the patented group

the specified reference signal to the steam turbine control system is additionally distributed to the control signals of the high and medium pressure cylinder valves of the specified steam turbine, and restrictions are set to cover these valves, and the regulating bodies of the medium pressure cylinder valves are moved towards their cover when the specified threshold level of deviation is reached from the nominal value of the electric frequency of the network, requiring the highest possible speed of the control system education.

In relation to the 2nd patentable invention, the solution of this problem by achieving the specified technical results is ensured by the fact that in the automatic power control system of a combined cycle plant, which includes at least one gas turbine unit with its own electric generator, the corresponding number of boilers connected to gas exhausts is heat recovery units and a steam turbine unit with a steam turbine and its own electric generator connected in parallel to the last in pairs, contains the shaper of the task for changing the power of the combined cycle plant for primary, secondary and tertiary regulation, the signal distributor of the specified task in the control systems of the gas turbine unit and the steam turbine and the power regulator of the gas turbine unit connected to the indicated distributor and equipped with the means for forcing the corresponding signal the power regulator of the steam turbine unit the invention of this group

the steam turbine power regulator is additionally equipped with a distributor of the incoming task signal to the control valves of the high and medium pressure cylinders of the steam turbine and customizable adjusters for restricting the movement of the regulating bodies of these valves to the side of their cover, and this means of forcing is made in the form of two autonomous forcing devices installed on the transmission lines signal to control valves of high and medium pressure steam cylinders, respectively urbines, and the specified distributor for covering the indicated 2 groups of valves of the steam turbine is made in the form of an element with a dead zone installed on the signal transmission line to the valves of the medium pressure cylinder with a predetermined threshold for the deviation from the nominal value of the frequency of the electric network, which requires the maximum possible speed of the control system.

A causal relationship between the totality of the essential features of these inventions and the technical results achieved is that the distribution of the control signals for the valve control of the high and medium pressure cylinders of the specified steam turbine with the setting of a restriction on the closing of these valves leads to an increase in speed due to the introduction of instead one of two groups of valves, which speeds up the process of changing the power and improves the accuracy of regulation as a result of reducing the degree nor inertia of the process. Moreover, during regulation, the regulation becomes more economical by reducing the necessary degree of steam throttling in each valve group.

Legend

GT - gas turbine;

GTU - gas turbine installation;

K is an element of statism;

COMP - compressor;

KS - combustion chamber;

KU - waste heat boiler;

KCH GT - frequency corrector of a gas turbine;

КЧ ПТ - frequency corrector of a steam turbine;

MP - non-linear element with a deadband ("dead band")

CCP - combined-cycle plant;

PTU - steam turbine installation;

PT - steam turbine;

RAS VD / SD - task distributor for regulating valves VD and SD;

RAS GTU / PT - job dispenser between GTU and PT;

RK VD - control valve CVP;

RK SD - control valve ЦСД;

PKT - fuel control valve;

RM - power regulator;

RNA - regulatory guiding apparatus;

PC VD - servo controller of the high pressure control valve;

PC SD - servo controller for medium pressure control valve;

SUM - adder;

ФЗ - shaper of a task for changing the CCGT power;

FU - forcing device;

CVP - high pressure cylinder;

Low pressure cylinder - low pressure cylinder;

CSD - medium pressure cylinder;

EG is an electric generator.

Brief Description of the Drawings

In FIG. 1 shows a simplified flow diagram of a CCGT unit equipped with an automatic power control system according to patentable inventions; in FIG. 2 is a schematic structural diagram of a CCGT automatic power control system according to the 2nd invention of the patented group; in FIG. 3 - graphs of changes in the CCGT active power with an abrupt change in the power task by ± 12.5% of the CCGT rated power, obtained as a result of model studies of 420 MW CCGT equipped with an automatic power control system according to the patented method; in FIG. 4 - obtained as a result of the same study, graphs of changes in the position of the regulating bodies of the valves of the high and medium pressure cylinders of a steam turbine.

List of drawing items

10, 20 - GTU; 11, 21 - KU; 111, 211 - boiler steam pipelines; 12, 22 - COMP; 121, 221 - PHA; 13, 23 - KS; 131, 231 - fuel supply lines; 14, 24 - GT; 15, 25, 32 - EG GTU and vocational school; 30 - vocational schools, 31 - Fri; 311 - CVP; 312 - DAC; 313 - LPC; 314 - turbine steam line; 40 - mixing manifold; RK VD - 315; RK SD - 316; 40 - mixing manifold; 50 - ФЗ ПГУ; 51, 52 - SUM; 60 - RAS GTU / PT; 70 - RM GTU; 71, 72 - RKT; 80 - RM vocational schools; 81 - RAS VD / SD; 811 - MP; 82 - PC VD; 83 - PC LED; 84 - FU VD; 85 - FU SD; 86, 87, 88, 89 - SUM; 90 - CC GTU; 91 - To _kchgtu ; 92 - MP _KCHGTU ; 100 - KKCH PT; 110 - _{CZK Fri} ; 120 - MP _{KCH PT} .

List of Symbols and Indexes

N _{gas turbine} - the actual value of the power of gas turbine;

N _{vocational schools} - the actual value of the power of vocational schools;

N _ass - the set value of the CCGT power;

N _nom - nominal (installed) value of the CCGT power;

N _{health, pl} - tasks on the planned (tertiary) component of power;

N _{, W} - tasks for secondary power;

- заданное значение перемещения регулирующих органов клапанов высокого давления паровой турбины

- setpoint displacement of the regulating bodies of the high pressure valves of the steam turbine

- текущее значение перемещения регулирующих органов клапанов высокого давления паровой турбины

- the current value of the movement of the regulatory bodies of the high pressure valves of the steam turbine

- заданное значение перемещения регулирующих органов клапанов среднего давления паровой турбины

- setpoint displacement of regulating bodies of medium pressure valves of a steam turbine

- текущее значение перемещения регулирующих органов клапанов среднего давления паровой турбины

- the current value of the movement of the regulatory bodies of the valves of the medium pressure of the steam turbine

Δn is the difference between the nominal and actual rotational speeds of the rotors of the respective turbines

The implementation of the invention

Presented in FIG. 1 CCGT contains two gas turbine units GTU 10 and GTU 20, waste heat recovery boilers KU 11 and KU 21, respectively, and a steam turbine unit PTU 30. Each gas turbine unit includes a compressor KOMP 12 and KOMP 22, respectively, a combustion chamber KS 13 and КС 23 with a fuel supply line 131 and 231, a gas turbine ГТ 14 and ГТ 24, and an electric generator EG 15 and EG 25. ПТУ 30 contains a steam turbine ПТ 31 with high-pressure cylinders CVP 311, medium pressure ЦСД 312 and low pressure ЦНД 313, and an electric generator EG 32. In this case, Fri 31 is connected to KU 11 and KU 21 according to in parallel with the help of boiler steam pipelines 111 and 211, combined by a mixing manifold 40 and a common turbine steam pipe 314.

The automatic power control system (CAPM) of a given CCGT according to patentable inventions is presented in the most general form in FIG. 1, and in more detail in FIG. 2 (to simplify the CAPM scheme in Fig. 2 compared with Fig. 1, only one gas turbine is shown). Patented CARM contains a shaper of a task for changing the power of a CCGT (ФЗ ПГУ) 50 (Fig. 2), a signal distributor of the specified task for the control systems of gas turbines and gas turbines (PAC GTU / PT) 60 (Fig. 1), a power regulator for gas turbines (RM gas turbines) 70 and the power regulator PT (PM PT) 80 (Fig. 1, 2).

To take into account the component of deviations from the nominal value of the frequency of the electric network in accordance with the regulatory document [1], current measurements of the mechanical rotational speed of the rotors of the gas and steam turbines are used using frequency correctors (CC), respectively: CC GTU 90 and CC PT 100, at the input of which the difference Δn between the nominal and actual rotational speeds of the rotors of the respective turbines. KCH PT 100 includes an element of statism K _kchpkh 110 and an element of the dead zone, which acts as a distributor of PAC GTU / PT 60 (Fig. 1), MP _{kch Fri} 120.

The KCH GTU 90 includes elements of statism _Kchtu 91 and dead zones MP _kchtu 92.

The output of each power regulator RM GTU 70 is connected to its executive bodies, which are fuel control valves RKT 71 and RKT 72, installed on the fuel lines 131 and 231, respectively, to the combustion chambers KS 13 and KS 23, and the regulating air-guiding apparatus RIA 121 and 221, installed at the inputs of the KOMP 12 and KOMP 22 compressors.

и

заданных и текущих значений положения регулирующих органов соответственно РК ВД 315 и РК СД 316. Кроме того, каждый из указанных PC ВД 82 и PC СД 83 оборудован не показанными настраиваемыми задатчиками ограничения перемещения регулирующих органов указанных клапанов в сторону их прикрытия.The power regulator PM ПТ 80 is equipped with a distributor of the incoming signal of the reference РАС ВД / СД 81 to the control valves of the high pressure cylinder (high pressure control valves) of the VD 315 and the control valves of the medium pressure cylinder (the control valves of medium pressure) of the SD 316 steam turbine ПТ 31 through servo regulators, respectively, PC VD 82 and PC SD 83, respectively, valves RK VD 315 and RK SD 316. On the signal transmission lines to the regulators of servo drives of control valves, two autonomous boosters are installed three FU VD 84 and FU SD 85, respectively, in the form of not shown differentiating and integro-differentiating links, as well as adders SUM 86, SUM 88 and SUM 87, SUM 89 generating output control signals to eliminate the imbalance

and

preset and current values of the position of the regulatory bodies, respectively, RK VD 315 and RK SD 316. In addition, each of the specified PC VD 82 and PC SD 83 is equipped with not shown adjustable adjusters restricting the movement of the regulatory bodies of these valves towards their cover.

The composition of the task shaper PSU FZ PGU 50 includes:

preliminary adder (SUM) 51 for changing the CCGT power, including tasks for the planned (tertiary) power component Nzd, pl, tasks for the secondary power Nzd, W, the resulting adder SUM 52 for changing the power of the gas turbine, including the task from the output of the preliminary SUM 51, data at actual power values GTP (N _STU) and a power PTU (N _PTU) and the data from CN 90 GTU unbalance frequency. The output of the specified adder SUM 52, which receives the reference signal proportional to the algebraic sum of all the above data is connected to the input of the RM GTU 70.

The CARM CCGT operation in the maneuverable mode according to the patented inventions is carried out as follows: with a planned change in the loads without a significant change in the frequency of the electric network, the task generator ФЗ ПГУ 50 produces only the main control signal coming through the adders СУМ 51 and СУМ 52 to the RM GTU 70. valves RK VD 315 and RK SD 316 of a steam turbine are maintained in a fully open position with a change in power of the PT 31 at a sliding vapor pressure, which corresponds to the most economical operation of the CCGT unit.

In maneuverable operating modes that require an increase in CAPM speed, a threshold (50 MHz) is fulfilled that acts as a distributor of RAS ГТУ / ПТ 60 dead zones of the MP _{kh pt} 120. At the same time, a signal passes through the SUM 86 and the SUM 86 adder taking into account the KP PT 100 adder and distributor RAS VD / SD 81, forcing device ФУ ВД 84 to the servo controller PC VD 82, which moves the regulating bodies of the valves of the RK VD 315 towards their cover. When the network frequency deviates by an amount that requires the maximum possible speed of the CAPM (over 200 MHz), the leading signal, overcoming the dead zone MP 811, is additionally fed to the servo controller PC SD 83, which moves towards the cover of the regulating organs of the valves of the Republic of Kazakhstan SD 316. Adders SUM 86 and SUM 87 generate control signals for the controllers of the servo drives of high PC VD 82 and medium pressure PC SD 83 by summing the forcing signals from the forcing devices and the unbalances in the position of the regulators control valves of high and medium pressure, respectively, formed in the adders SUM 88 and SUM 89. When the valve cover limits RK VD 315 and RK SD 316 set with the help of customizable adjusters are reached, the corresponding actuator controllers PC VD 82 and PC SD 83 disable further movement of these valves .

Example.

As an example, the research data on the CARM PGU-420 mathematical model performed in accordance with the patented inventions are given below. In FIG. Figure 3 shows the graphs of changes in the CCGT active power with an abrupt change in the power task by ± 12.5% of the CCGT nominal power and automatic control without and with the participation of control valves of high and medium pressure cylinders of a steam turbine. In FIG. 4 shows graphs of the corresponding changes in the position of the regulatory bodies of these valves. On the graphs of both of these figures, the numbers indicate the curves: 1 - power control of a CCGT unit without the participation of a transformer; 2 - CCGT power control with the participation of PT without restriction on the VD valves; 3 - CCGT power control with the participation of PT with a restriction on the cover of VD control valves equal to 20% of the full bore; 4 - CCGT power control with the additional participation of SD control valves when opening them by 17%, and VD valves - by 20% of the full bore (with a restriction on the cover of VD control valves of 20% of the full bore); 5 - (N back - 1% Nnom); 6 - (Nad + 1% Nnom), where Nadd is the set value of the CCGT power, Nnom is the nominal (set) value of the CCGT power.

An analysis of the above results allows us to draw the following conclusions: the implementation of the impact on the control valves of a steam turbine ensures the fulfillment of the energy system requirements of primary regulation [1, 2] for the dynamics of transients; in the case of the additional effect on the medium pressure control valves, the energy system requirements of the primary regulation [1, 2] for the dynamics of transients are met even if there are restrictions on the degree of opening / closing of high pressure control valves up to 20% of the full bore. Moreover, calculations have shown that the cost-effectiveness of automatic control of CCGT power in maneuverable mode when using high and medium pressure control valves compared to using only high pressure steam turbine control valves increases by 0.15%, speed increases by 10%, and the control accuracy decreases (improves) from 0.9 to 0.7%.

Industrial applicability

The claimed group of inventions meets the condition of "industrial applicability". The essence of technical solutions is disclosed in the formula, description and figures of the drawing quite clearly, and the tools used are simple and affordable for industrial implementation in the field of heat power.

Claims (6)

1. A method for automatically controlling the power of a combined cycle plant containing at least one gas turbine unit with its own electric generator, the corresponding number of waste heat boiler units connected to the gas exhausts and parallel to the last steam turbine unit with a steam turbine and its own electric generator, which consists in that when deviating from the nominal value of the frequency of the electric network, the task signal for changing the power is distributed among the control systems gas turbine installation and steam turbine, and in the control system of the steam turbine, the corresponding reference signal is passed through the boost elements, characterized in that the specified reference signal to the steam turbine control system is additionally distributed to the control signals of the high and medium pressure cylinder valves of the specified steam turbine, and restrictions are set to cover these valves, and the regulating bodies of the medium pressure cylinder valves are moved towards their cover when the specified threshold level of deviation is reached from the nominal value of the electric frequency of the network, requiring the highest possible speed of the control system education. 2. A system for automatically controlling the power of a combined cycle gas turbine unit including at least one gas turbine unit with its own electric generator, a corresponding number of waste heat boiler units connected to the gas exhausts and parallel to the last steam turbine unit with a steam turbine and its own electric generator, comprising shaper of the task for changing the power of the combined cycle plant for primary, secondary and tertiary regulation, signal distributor the specified task for the control systems of a gas turbine installation and a steam turbine and a power regulator of a gas turbine installation connected to a specified distributor and equipped with means for forcing a corresponding signal, a power regulator of a steam turbine installation, characterized in that the steam turbine power regulator is additionally equipped with a distributor of the incoming task signal to the control valves of the high and medium pressure cylinders of the steam turbine and customizable adjusters for restricting the movement of the regulating bodies of these valves to the side of their cover, and this means of forcing is made in the form of two autonomous forcing devices installed on the transmission lines signal to control valves of high and medium pressure steam cylinders, respectively urbines, and the specified distributor for covering the indicated 2 groups of valves of the steam turbine is made in the form of an element with a dead zone installed on the signal transmission line to the valves of the medium pressure cylinder with a predetermined threshold for the deviation from the nominal value of the frequency of the electric network, which requires the maximum possible speed of the control system.

Images