CN214887553U - Gas-steam combined cycle unit provided with two stages of gas superchargers at gas turbine inlet - Google Patents

Abstract

The embodiment of the utility model provides a gas-steam combined cycle unit provided with a two-stage gas supercharger at a gas turbine inlet, wherein one end of a TCA system is connected with the water outlet end of a high-pressure feed pump set, and the other end of the TCA system is connected with the water outlet end of a high-pressure economizer; the gas outlet end of the FGH system is communicated with the gas inlet end of the gas turbine; one end of the natural gas conveying pipeline is communicated with a natural gas source, and the other end of the natural gas conveying pipeline is connected with the gas inlet end of the FGH system; the natural gas supercharger is arranged on the natural gas conveying pipeline; the natural gas conveyed by the natural gas conveying pipeline enters the natural gas booster through the inlet valve, is subjected to secondary compression and boosting through the primary cylinder and the secondary cylinder in sequence and then is output out of the natural gas booster through the outlet valve; the IGV is arranged between the inlet valve and the outlet valve and used for adjusting the outlet pressure and the natural gas flow of the natural gas supercharger; the recirculation control valve is disposed between the IGV and the outlet valve, and regulates the outlet pressure of the natural gas booster and the flow of natural gas through the natural gas booster.

Description

Gas-steam combined cycle unit provided with two stages of gas superchargers at gas turbine inlet

Technical Field

The utility model relates to a gas-steam combined cycle unit technical field particularly, relates to a gas-steam combined cycle unit with gas turbine entry two-stage gas booster compressor.

Background

In a thermal power plant, in order to achieve the purposes of stable combustion of a combustion engine, backfire prevention, and the like, it is necessary to maintain the gas supply pressure within a certain range and provide low gas pressure protection. However, gas supply pressures of gas companies are currently subject to fluctuations within certain limits. Therefore, in order to maintain the inlet gas pressure of the combustion engine stable and ensure the safe operation of the combustion engine, a gas supercharger is usually arranged in front of the combustion engine to realize the supercharging and pressure stabilization of the gas. The outlet pressure of the gas booster is typically regulated, among other things, by the booster inlet IGV and the recirculation control valve. For IGV control, when the actual pressure at the outlet of the supercharger is greater than the set pressure, the IGV is turned off and is turned on, otherwise; the IGV has a minimum opening limit for preventing surging when the supercharger operates; when the current of the motor of the supercharger exceeds the maximum limiting current, the ICV is closed. For the recirculation control valve, setting forward bias according to an IGV control value, and when the actual pressure at the outlet of the supercharger is greater than the set pressure and the forward bias is added, opening the recirculation valve greatly, otherwise closing the recirculation valve small; according to the requirement of anti-surge control of the supercharger, the lowest flow limit of the outlet of the supercharger is generally adopted, and when the anti-surge control value is smaller than a set value, the recirculation valve is opened greatly, otherwise, the recirculation valve is closed slightly.

According to the control mode, when the gas consumption on the load side is small or the gas pressure at the inlet of the supercharger is high, the IGV is closed to the minimum opening degree, and the recirculation control valve is opened to adjust the pressure at the outlet of the supercharger; when the gas consumption on the load side is small, and the gas pressure at the inlet of the supercharger is low, the IGV is opened to increase the pressure at the outlet of the supercharger, and the recirculation control valve is also opened to ensure the minimum flow required for preventing the surge of the supercharger. In addition, once the gas booster compressor breaks down, the gas that the combustion engine needs will be supplied absolutely in the twinkling of an eye, leads to the combustion engine system can't normally operate the electricity generation, causes the unit to not stop, and the fail safe nature of system can not obtain the guarantee.

SUMMERY OF THE UTILITY MODEL

The present description provides a combined gas-steam cycle unit provided with a two-stage gas booster at the inlet of a combustion engine, in order to overcome at least one of the technical problems of the prior art.

According to an embodiment of the present specification, there is provided a gas-steam combined cycle unit provided with a two-stage gas supercharger at an inlet of a combustion engine, the gas-steam combined cycle unit including: the system comprises two sets of boiler systems, two sets of gas turbine systems, a steam turbine system, a condenser system and a bypass system, wherein the two sets of gas turbine systems correspond to the two sets of boiler systems one by one;

each set of boiler system respectively comprises a waste heat boiler, a low-pressure steam pocket, a low-pressure economizer, a low-pressure evaporator, a low-pressure superheater, a medium-pressure water feed pump set, a medium-pressure steam pocket, a medium-pressure economizer, a medium-pressure evaporator, a medium-pressure superheater, a primary reheater, a secondary reheater, a high-pressure water feed pump set, a high-pressure steam pocket, a high-pressure economizer, a high-pressure evaporator, a high-pressure superheater, a heat supply network water pump and a heat supply network water heat exchanger; the low-pressure economizer, the low-pressure evaporator, the low-pressure superheater, the medium-pressure economizer, the medium-pressure evaporator, the medium-pressure superheater, the primary reheater, the secondary reheater, the high-pressure economizer, the high-pressure evaporator and the high-pressure superheater are arranged in the waste heat boiler; the water inlet end of the low-pressure steam pocket is connected with the water outlet end of the low-pressure economizer; two ends of the low-pressure evaporator are respectively communicated with the low-pressure steam pocket; the steam inlet end of the low-pressure superheater is communicated with the low-pressure steam drum; the water inlet end of the medium-pressure economizer is communicated with the low-pressure steam drum through the medium-pressure water feed pump unit, and the water outlet end of the medium-pressure economizer is communicated with the medium-pressure steam drum; two ends of the medium-pressure evaporator are respectively communicated with the medium-pressure steam pocket; the steam inlet end of the medium-pressure superheater is communicated with the medium-pressure steam drum, and the steam outlet end of the medium-pressure superheater is connected with the steam inlet end of the primary reheater; the steam inlet end of the secondary reheater is connected with the steam outlet end of the primary reheater; the water inlet end of the high-pressure economizer is communicated with the low-pressure steam drum through the high-pressure water feed pump set, and the water outlet end of the high-pressure economizer is communicated with the high-pressure steam drum; two ends of the high-pressure evaporator are respectively communicated with the high-pressure steam pocket; the steam inlet end of the high-pressure superheater is communicated with the high-pressure steam drum; the water inlet end of the heat supply network water pump is communicated with the heat supply network water heat exchanger, and the water outlet end of the heat supply network water pump is communicated with the water inlet end of the low-pressure economizer; the water inlet end of the heat supply network water heat exchanger is communicated with the water outlet end of the low-pressure economizer;

each set of the combustion engine system respectively comprises a gas turbine, a TCA system, an FGH system and a natural gas conveying system; the gas outlet end of the gas turbine is communicated with the waste heat boiler; one end of the TCA system is connected with the water outlet end of the high-pressure water feed pump set, and the other end of the TCA system is connected with the water outlet end of the high-pressure economizer; the gas outlet end of the FGH system is communicated with the gas inlet end of the gas turbine; the natural gas conveying system comprises a natural gas conveying pipeline, a natural gas supercharger, a natural gas bypass pipeline, a first check valve, a pneumatic quick opening and closing valve, an opening and closing control valve and a gas source supply system; one end of the natural gas conveying pipeline is communicated with a natural gas source, and the other end of the natural gas conveying pipeline is connected with the gas inlet end of the FGH system; the natural gas booster is arranged on the natural gas conveying pipeline; the natural gas supercharger comprises a variable frequency motor, an inlet valve, an outlet valve, an adjustable air inlet guide vane IGV, a primary air cylinder, a secondary air cylinder and a recirculation control valve; the natural gas conveyed by the natural gas conveying pipeline enters the natural gas booster through the inlet valve, is subjected to secondary compression and pressure boosting through the primary cylinder and the secondary cylinder in sequence and then is output out of the natural gas booster through the outlet valve; the IGV is arranged between the inlet valve and the outlet valve and used for adjusting the outlet pressure and the natural gas flow of the natural gas supercharger; the recirculation control valve is arranged between the IGV and the outlet valve and is used for adjusting the outlet pressure of the natural gas booster and the flow of the natural gas flowing through the natural gas booster; the natural gas supercharger is connected with the first check valve and the pneumatic quick opening and closing valve in parallel through the natural gas bypass pipeline; the air source supply system is communicated with the pneumatic quick opening and closing valve; the opening and closing control valve is arranged between the air source supply system and the pneumatic quick opening and closing valve;

the steam turbine system comprises a high-intermediate pressure cylinder and a low-pressure cylinder which are coaxially connected; the condenser system comprises a condenser and a condensed water pump set; the water outlet end of the condenser is communicated with the water inlet end of the condensed water pump set;

the bypass system comprises a communicating pipe, a low-pressure steam conveying pipeline, a medium-pressure superheated steam conveying pipeline, a reheated steam conveying pipeline, a high-pressure steam exhaust main pipe, a high-pressure steam exhaust branch pipe, a condensed water conveying pipeline, a low-pressure bypass and a medium-pressure bypass; the medium-pressure steam outlet end of the high and medium-pressure cylinder is communicated with the steam inlet end of the low-pressure cylinder through the communicating pipe; the steam outlet end of the low-pressure superheater of each set of the boiler system is respectively connected with one low-pressure steam conveying pipeline; a low-pressure steam combining valve is arranged on the low-pressure steam conveying pipeline; the two low-pressure steam delivery pipelines are converged and then are connected to the communicating pipe together; the medium-pressure superheater and the primary reheater of each set of the boiler system are respectively communicated through the medium-pressure superheated steam conveying pipeline; the steam outlet end of the secondary reheater of each set of the boiler system is respectively connected with one reheat steam conveying pipeline; a medium-pressure parallel valve is arranged on the reheating steam conveying pipeline; the two reheat steam delivery pipelines are converged and then are connected to the medium-pressure steam inlet end of the high and medium-pressure cylinder together; the steam outlet end of the high-pressure superheater of each set of the boiler system is respectively connected with one high-pressure steam conveying pipeline; a high-pressure steam combining valve is arranged on the high-pressure steam conveying pipeline; the two high-pressure steam conveying pipelines are converged and then are connected to a high-pressure steam inlet end of the high-intermediate pressure cylinder; the high-pressure steam outlet end of the high and medium pressure cylinder is connected with the high-pressure steam exhaust main pipe; two paths of high-pressure steam exhaust branch pipes led out from the high-pressure steam exhaust main pipe are respectively connected with the two medium-pressure superheated steam conveying pipelines; the condensed water conveying pipeline is connected with the water outlet end of the condensed water pump set and is communicated with the low-pressure coal economizer in the two sets of boiler systems; a low-pressure bypass connected with the condenser is led out from the low-pressure steam conveying pipeline; a low-pressure bypass pressure regulating valve is arranged on the low-pressure bypass; a middle-pressure bypass connected with the condenser is led out from the reheating steam conveying pipeline; a medium-pressure bypass pressure regulating valve is arranged on the medium-pressure bypass; and a high-pressure bypass pressure regulating valve is arranged between the high-pressure steam conveying pipeline and the high-pressure steam exhaust branch pipe.

Optionally, the gas-steam combined cycle unit further comprises an electric motor system;

the motor system comprises two gas turbine generators and a steam turbine generator; the two gas turbine generators are respectively and coaxially connected with the gas turbines of the two gas turbine systems; the steam wheel generator is coaxially connected with the high and medium pressure cylinder.

Optionally, the combustion engine system further comprises a second check valve; and the water outlet end of the FGH system is communicated with the water inlet end of the low-pressure economizer through the second check valve.

Optionally, the combustion engine system further comprises an air heat exchanger; and the air inlet end of the gas turbine is connected with the air heat exchanger.

Optionally, a third check valve is mounted on the medium pressure superheated steam delivery line.

Optionally, a fourth check valve is mounted on the high-pressure exhaust branch pipe.

Further optionally, the second check valve, the third check valve and the fourth check valve are all manual valves.

Optionally, the low-pressure parallel valve, the medium-pressure parallel valve and the high-pressure parallel valve are all electrically operated valves.

Optionally, the first check valve is a flap check valve.

Optionally, the inlet valve and the outlet valve are both pneumatic valves.

The beneficial effects of the embodiment of the specification are as follows:

the natural gas booster compressor adopts inverter motor, introduce frequency conversion control through inverter motor, when satisfying natural gas booster compressor export pressure control and natural gas booster compressor and prevent breathing heavily the control requirement, reduced or even eliminated natural gas booster compressor IGV not fully open, the not complete throttle loss and the recirculation loss that causes of recirculation control valve for can guarantee the safe operation of natural gas booster compressor under the operating mode that changes, when load side gas consumption is less, the station service power is used in the great saving, the economic benefits of power plant has been improved greatly.

Meanwhile, the mode of connecting a bypass device in parallel at the natural gas booster is adopted, and the safety and reliability of the natural gas system are improved. The quick opening and closing valve in the bypass device is opened and closed according to the real-time states of starting, stopping and the like of the natural gas supercharger, so that the investment cost of the natural gas supercharger is not increased, the natural gas of the gas turbine cannot be supplied instantly when the natural gas supercharger breaks down, the gas turbine can be guaranteed to be in load shedding and normal stopping, and the non-stop of a unit is avoided. Meanwhile, when the gas supply of a gas company can directly meet the use requirement of the gas turbine, the natural gas booster compressor can be stopped to directly supply natural gas through the bypass device, so that the natural gas is prevented from forming pressure drop through the booster compressor, and the economic benefit of a power plant is improved.

The innovation points of the embodiment of the specification comprise:

1. in the embodiment, the natural gas supercharger adopts the variable frequency motor, the variable frequency control is introduced through the variable frequency motor, the throttling loss and the recycling loss caused by the fact that the IGV of the natural gas supercharger is not fully opened and the recycling control valve is not fully closed are reduced or even eliminated while the requirements of outlet pressure control of the natural gas supercharger and anti-surge control of the natural gas supercharger are met, the safe operation of the natural gas supercharger can be ensured under the changing working condition, when the gas consumption on the load side is small, the auxiliary power is greatly saved, the economic benefit of a power plant is greatly improved, and the variable frequency control method is one of the innovation points of the embodiment of the specification.

2. In this embodiment, the mode of connecting a bypass device in parallel at the natural gas booster compressor is adopted, and the safe reliability of the natural gas system is improved. The quick opening and closing valve in the bypass device is opened and closed according to the real-time states of starting, stopping and the like of the natural gas supercharger, so that the investment cost of the natural gas supercharger is not increased, the natural gas of the gas turbine cannot be supplied instantly when the natural gas supercharger breaks down, the gas turbine can be guaranteed to be in load shedding and normal stopping, and the non-stop of a unit is avoided. Meanwhile, when the gas supply of a gas company can directly meet the use requirement of the gas turbine, the natural gas booster compressor can be stopped to be operated, the natural gas is directly supplied through the bypass device, the natural gas is prevented from forming pressure drop through the booster compressor, the economic benefit of a power plant is improved, and the natural gas booster compressor is one of the innovation points of the embodiment of the specification.

Drawings

In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present disclosure, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a gas-steam combined cycle unit provided with a two-stage gas supercharger at an inlet of a combustion engine according to an embodiment of the present disclosure;

FIG. 2 is a schematic structural diagram of a natural gas booster of a gas-steam combined cycle unit provided with a two-stage gas booster at the inlet of a combustion engine according to an embodiment of the present disclosure;

FIG. 3 is a schematic flow chart of a control process of a natural gas booster of a gas-steam combined cycle unit provided with a two-stage gas booster at an inlet of a combustion engine according to an embodiment of the present disclosure;

FIG. 4 is a schematic diagram illustrating the relationship between the inlet pressure of the natural gas supercharger and the variable frequency rotating speed of the gas-steam combined cycle unit provided with the two-stage gas supercharger at the inlet of the gas turbine according to the embodiment of the present disclosure;

FIG. 5 is a schematic view of a surge control line of a combined gas-steam cycle plant provided with a two-stage gas booster at the inlet of a combustion engine according to an embodiment of the present disclosure;

in the figure, 1 is a waste heat boiler, 2 is a low-pressure steam pocket, 3 is a low-pressure economizer, 4 is a low-pressure evaporator, 5 is a low-pressure superheater, 6 is a medium-pressure water feed pump group, 7 is a medium-pressure steam pocket, 8 is a medium-pressure economizer, 9 is a medium-pressure evaporator, 10 is a medium-pressure superheater, 11 is a primary reheater, 12 is a secondary reheater, 13 is a high-pressure water feed pump group, 14 is a high-pressure steam pocket, 15 is a high-pressure economizer, 16 is a high-pressure evaporator, 17 is a high-pressure superheater, 18 is a heat network water pump, 19 is a heat network water heat exchanger, 20 is a TCA system, 21 is an FGH system, 22 is a gas turbine, 23 is a natural gas conveying pipeline, 24 is a natural gas booster, 25 is a natural gas bypass pipeline, 26 is a first check valve, 27 is a pneumatic quick on-off valve, 28 is an on-off control valve, 29 is a gas source supply system, 30 is a variable frequency motor, 31 is an inlet valve, 32 is an outlet valve, and a high-pressure gas supply system is connected with a high-pressure pump, 33 is IGV, 34 is a first-stage cylinder, 35 is a second-stage cylinder, 36 is a recirculation control valve, 37 is a high-intermediate cylinder, 38 is a low-intermediate cylinder, 39 is a condenser, 40 is a condensed water pump set, 41 is a communicating pipe, 42 is a low-pressure steam conveying pipeline, 43 is a medium-pressure superheated steam conveying pipeline, 44 is a reheat steam conveying pipeline, 45 is a high-pressure steam conveying pipeline, 46 is a high-pressure exhaust main pipe, 47 is a high-pressure exhaust branch pipe, 48 is a condensate delivery line, 49 is a low pressure bypass, 50 is an intermediate pressure bypass, 51 is a low pressure combination valve, 52 is an intermediate pressure combination valve, 53 is a high pressure combination valve, 54 is a low pressure bypass pressure regulating valve, 55 is an intermediate pressure bypass pressure regulating valve, 56 is a high pressure bypass pressure regulating valve, 57 is a gas turbine generator, 58 is a steam turbine generator, 59 is a second check valve, 60 is an air heat exchanger, 61 is a third check valve, and 62 is a fourth check valve.

Detailed Description

The technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are only some embodiments of the present disclosure, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without any creative effort belong to the protection scope of the present invention.

It should be noted that the terms "including" and "having" and any variations thereof in the embodiments of the present specification and the drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

The embodiment of the specification discloses a gas-steam combined cycle unit provided with a two-stage gas supercharger at an inlet of a gas turbine. The following are detailed below.

The embodiment of the utility model provides an in gas-steam combined cycle unit be two and drag a combustion engine combined cycle unit, including two sets of boiler system, two sets of combustion engine systems, the steam turbine system, the condenser system, bypass system and motor system, wherein, two sets of combustion engine systems and two sets of boiler system one-to-ones, the exhaust high-temperature gas of combustion engine system is carried to corresponding boiler system in, heat into steam among the boiler system and promote the steam turbine system work, two gas turbine generator 57 of motor system respectively with the gas turbine 22 coaxial coupling of two sets of combustion engine systems, steam turbine generator 58 and high intermediate pressure jar 37 coaxial coupling, drive gas turbine generator 57 respectively by combustion engine system and steam turbine system, steam turbine generator 58 generates electricity, with the waste of reducing heat energy as far as possible, improve the economic benefits of power plant.

Fig. 1 and 2 show a combined gas-steam cycle unit provided with a two-stage gas supercharger at an inlet of a combustion engine according to an embodiment of the present description. As shown in fig. 1, a low-pressure economizer 3, a low-pressure evaporator 4, a low-pressure superheater 5, a medium-pressure economizer 8, a medium-pressure evaporator 9, a medium-pressure superheater 10, a primary reheater 11, a secondary reheater 12, a high-pressure economizer 15, a high-pressure evaporator 16 and a high-pressure superheater 17 in each set of boiler system are arranged in the waste heat boiler 1; the water outlet end of a condenser 39 in the condenser system is communicated with the water inlet end of a condensed water pump unit 40; the condensed water conveying pipeline 48 is connected with the water outlet end of the condensed water pump set 40 and is communicated with the low-pressure coal economizer 3 in the two sets of boiler systems. The condensed water in the condenser 39 is delivered into the low-pressure economizer 3 through the condensed water pump unit 40, and is delivered in the low-pressure evaporator 4, the low-pressure superheater 5, the medium-pressure economizer 8, the medium-pressure evaporator 9, the medium-pressure superheater 10, the primary reheater 11, the secondary reheater 12, the high-pressure economizer 15, the high-pressure evaporator 16 and the high-pressure superheater 17 in the waste heat boiler 1, and then the water in the high-pressure evaporator is heated by the high-temperature gas discharged by the combustion engine system to generate steam to drive the high-medium pressure cylinder 37 and the low-pressure cylinder 38 which are coaxially connected in the steam turbine system to rotate.

Wherein, the medium pressure steam outlet end of the high and medium pressure cylinder 37 is communicated with the steam inlet end of the low pressure cylinder 38 through a communicating pipe 41; the water inlet end of the low-pressure steam pocket 2 is connected with the water outlet end of the low-pressure economizer 3; two ends of the low-pressure evaporator 4 are respectively communicated with the low-pressure steam drum 2; the steam inlet end of the low-pressure superheater 5 is communicated with the low-pressure steam drum 2; the steam outlet end of the low-pressure superheater 5 of each set of boiler system is respectively connected with a low-pressure steam conveying pipeline 42 of a bypass system; the low-pressure steam delivery pipeline 42 is provided with a low-pressure parallel valve 51, and preferably, the low-pressure parallel valve 51 is an electric valve, so that the automation is strong and the control is more sensitive; the two low-pressure steam delivery pipes 42 are joined together and then connected to the communicating pipe 41. In a specific embodiment, the condensed water delivered by the condensed water pump set 40 is preheated by the low-pressure economizer 3 and then delivered into the low-pressure steam drum 2, the low-pressure steam drum 2 is communicated with the low-pressure evaporator 4, the condensed water is heated in the low-pressure evaporator 4 into saturated steam which rises into the low-pressure steam drum 2, the saturated steam is delivered from the low-pressure steam drum 2 and then heated by the low-pressure superheater 5 to generate low-pressure superheated steam, the two paths of low-pressure superheated steam are merged and then mixed with the medium-pressure steam outlet end of the high and medium pressure cylinder 37 and then delivered into the low pressure cylinder 38 together, so that the low pressure cylinder 38 is driven to rotate to apply work, and the steam wheel generator 58 is driven to generate electricity.

The high-pressure steam outlet end of the high and medium pressure cylinder 37 is connected with a high-pressure steam exhaust manifold 46; two high-pressure steam exhaust branch pipes 47 led out from the high-pressure steam exhaust main pipe 46 are respectively connected with the two medium-pressure superheated steam conveying pipelines 43; the water inlet end of the medium-pressure economizer 8 is communicated with the low-pressure steam drum 2 through a medium-pressure water feed pump unit 6, and the water outlet end is communicated with a medium-pressure steam drum 7; two ends of the medium-pressure evaporator 9 are respectively communicated with the medium-pressure steam drum 7; the steam inlet end of the medium-pressure superheater 10 is communicated with the medium-pressure steam drum 7, and the steam outlet end of the medium-pressure superheater is connected with the steam inlet end of the primary reheater 11; the steam inlet end of the secondary reheater 12 is connected with the steam outlet end of the primary reheater 11; the medium-pressure superheater 10 and the primary reheater 11 of each set of boiler system are respectively communicated through a medium-pressure superheated steam conveying pipeline 43; the steam outlet end of the secondary reheater 12 of each set of boiler system is respectively connected with a reheat steam conveying pipeline 44; the reheat steam delivery pipe 44 is provided with a medium-pressure parallel valve 52, and preferably, the medium-pressure parallel valve 52 is an electric valve, so that the automation is strong and the control is more sensitive; two reheat steam delivery lines 44 are joined and commonly connected to the intermediate pressure steam inlet end of high intermediate pressure cylinder 37. The water output by the low-pressure steam drum 2 is injected into the medium-pressure economizer 8 by the medium-pressure water feed pump unit 6 to be continuously heated, then enters the medium-pressure steam drum 7, is heated into saturated steam in the medium-pressure evaporator 9, and rises into the medium-pressure steam drum 7. Saturated steam output from the medium-pressure steam drum 7 is heated by the medium-pressure superheater 10, mixed with high-pressure steam outlet end exhaust steam of the high-and medium-pressure cylinder 37, and then heated by the primary reheater 11 and the secondary reheater 12 in sequence to generate medium-pressure reheated steam, and the two paths of medium-pressure reheated steam are converged and then conveyed to the medium-pressure cylinder part of the high-and medium-pressure cylinder 37 together to drive the high-and medium-pressure cylinder 37 to rotate to do work and drive the steam wheel generator 58 to generate power.

The water inlet end of the high-pressure economizer 15 is communicated with the low-pressure steam drum 2 through a high-pressure water feed pump set 13, and the water outlet end is communicated with the high-pressure steam drum 14; two ends of the high-pressure evaporator 16 are respectively communicated with the high-pressure steam drum 14; the steam inlet end of the high-pressure superheater 17 is communicated with the high-pressure steam drum 14; the steam outlet end of the high-pressure superheater 17 of each set of boiler system is respectively connected with a high-pressure steam conveying pipeline 45; the high-pressure steam conveying pipeline 45 is provided with a high-pressure parallel valve 53, and preferably, the high-pressure parallel valve 53 is an electric valve, so that the automation is strong, and the control is more sensitive; the two high-pressure steam delivery pipes 45 are merged and then are jointly connected to the high-pressure steam inlet end of the high-intermediate pressure cylinder 37. Water output by the low-pressure steam pocket 2 is injected into the high-pressure economizer 15 through the high-pressure water feed pump unit 13 to be continuously heated, and then enters the high-pressure steam pocket 14, because the high-pressure evaporator 16 is communicated below the high-pressure steam pocket 14, the water input into the high-pressure steam pocket 14 is heated into saturated steam in the high-pressure evaporator 16 and rises into the high-pressure steam pocket 14, the saturated steam output from the high-pressure steam pocket 14 is heated through the high-pressure superheater 17 to generate high-pressure superheated steam, the two paths of high-pressure superheated steam are converged and then jointly conveyed to the high-pressure cylinder part of the high-intermediate pressure cylinder 37 to drive the high-intermediate pressure cylinder 37 to rotate and do work, and the steam wheel generator 58 is driven to generate electricity.

In addition, in order to further improve the utilization rate of heat energy, the water inlet end of the heat supply network water pump 18 is communicated with the heat supply network water heat exchanger 19, and the water outlet end is communicated with the water inlet end of the low-pressure economizer 3; the water inlet end of the heat supply network water heat exchanger 19 is communicated with the water outlet end of the low-pressure economizer 3. The water preheated by the low-pressure economizer 3 is used for water heat exchange in the heat supply network water heat exchanger 19, and the water cooled by the heat exchange is conveyed to the low-pressure economizer 3 again for heating, so that a heat source is supplied to the urban heat supply network.

Meanwhile, in order to ensure the operation safety of the unit and the normal delivery of the steam in the pipeline, a low-pressure bypass 49 connected with the condenser 39 is led out from the low-pressure steam delivery pipeline 42, a low-pressure bypass pressure regulating valve 54 is installed on the low-pressure bypass 49, and the steam in the low-pressure steam delivery pipeline 42 is discharged into the condenser 39 through the low-pressure bypass 49 by controlling the low-pressure bypass pressure regulating valve 54, so that the overhigh pressure of the low-pressure steam delivery pipeline 42 when the unit fails is avoided. A middle-pressure bypass 50 connected with the condenser 39 is led out from the reheat steam conveying pipeline 44, a middle-pressure bypass pressure regulating valve 55 is installed on the middle-pressure bypass 50, and steam in the reheat steam conveying pipeline 44 is conveyed into the condenser 39 through the middle-pressure bypass 50 by controlling the middle-pressure bypass pressure regulating valve 55, so that the phenomenon that the pressure in the reheat steam conveying pipeline 44 is overhigh when a unit fails is avoided. A high-pressure bypass pressure regulating valve 56 is arranged between the high-pressure steam conveying pipeline 45 and the high-pressure steam exhaust branch pipe 47, steam in the high-pressure steam conveying pipeline 45 is conveyed to the high-pressure steam exhaust branch pipe 47 through the high-pressure bypass pressure regulating valve 56, and then the steam is discharged into the condenser 39 through the medium-pressure bypass 50, so that the situation that the pressure in the high-pressure steam conveying pipeline 45 is too high when a unit fails is avoided.

Furthermore, in order to improve the safety of the boiler system, the third check valve 61 is installed on the medium-pressure superheated steam delivery pipe 43, the fourth check valve 62 is installed on the high-pressure exhaust branch pipe 47, preferably, both the third check valve 61 and the fourth check valve 62 are manual valves, and the third check valve 61 and the fourth check valve 62 prevent the backflow of steam or condensed water in the pipes, thereby ensuring the safety of the system and improving the stability of the system.

The embodiment of the utility model provides an in TCA system 20's of combustion engine system one end link to each other with the play water end of high pressure feed water pump package 13, high-pressure economizer 15's play water end is connected to the other end, FGH system 21's the end of giving vent to anger communicates with gas turbine 22's inlet end mutually, the one end intercommunication natural gas air supply of natural gas transmission pipeline 23, FGH system 21's inlet end is connected to the other end, natural gas booster compressor 24 installs on natural gas transmission pipeline 23, utilize TCA system 20 to provide service for combustion engine system's turbine environmental control, supply with gas turbine 22 after the temperature that heats the needs with the natural gas through FGH system 21, the natural gas after preheating helps the improvement of the burning of fuel and average endothermic temperature, thereby can raise the efficiency.

Wherein, in the present specification, the TCA system refers to a Turbine Cooling Air system (TCA); the FGH system refers to a Fuel performance Heater system (FGH).

In order to avoid non-stop of the unit when the natural gas booster 24 of the natural gas conveying system fails and improve the safety and stability of the natural gas conveying system, a bypass device is connected in parallel with the natural gas booster 24, specifically, the natural gas booster 24 is connected in parallel with a first check valve 26 and a pneumatic quick opening and closing valve 27 through a natural gas bypass pipeline 25, and preferably, the first check valve 26 is a flap type check valve; the air source supply system 29 is communicated with the pneumatic quick opening and closing valve 27, provides a driving air source for opening and closing the pneumatic quick opening and closing valve 27, and controls the opening of the pneumatic quick opening and closing valve 27, wherein the driving air source supplied by the air source supply system 29 can be a factory compressed air main pipe so as to ensure that the pressure of the adopted driving air source is about 0.8 MPa; the on-off control valve 28 is arranged between the air source supply system 29 and the pneumatic quick on-off valve 27; the water outlet side of the FGH system 21 is in communication with the water inlet side of the low pressure economizer 3 through a second check valve 59, the second check valve 59 preferably being a manual valve. Meanwhile, an air heat exchanger 60 is connected to an air inlet end of the gas turbine 22, and the air heat exchanger 60 exchanges heat with air entering a compressor of the gas turbine 22, so as to improve the working efficiency of the gas turbine 22.

When the gas supply pressure of the upstream gas group can directly meet the use requirement of the gas turbine 22, the natural gas can be conveyed into the gas turbine 22 for combustion even without passing through the natural gas supercharger 24, so that the natural gas is prevented from forming pressure drop through the natural gas supercharger 24, the natural gas supercharger 24 is stopped, then the natural gas is supplied to a driving gas source for opening and closing the pneumatic quick opening and closing valve 27 by the gas source supply system 29, the pneumatic quick opening and closing valve 27 is opened, the natural gas is directly conveyed through the natural gas bypass pipeline 25, the transmission speed is improved, and unnecessary energy waste can be reduced; when the gas supply pressure of the upstream gas group cannot meet the use requirement of the gas turbine 22, the pneumatic quick opening and closing valve 27 is closed, and the natural gas supercharger 24 operates normally to provide natural gas meeting the use requirement for the gas turbine 22; when the natural gas supercharger 24 breaks down and stops running in the running process, the pneumatic quick opening and closing valve 27 is opened, natural gas is conveyed by the natural gas bypass pipeline 25, so that natural gas required by the gas turbine 22 cannot be supplied instantly, normal shutdown of the gas turbine 22 by load shedding can be guaranteed, and non-shutdown of a unit is avoided.

In the present embodiment, as shown in fig. 2, the natural gas booster 24 includes a variable frequency motor 30, an inlet valve 31, an outlet valve 32, an adjustable inlet guide vane IGV33, a primary cylinder 34, a secondary cylinder 35, and a recirculation control valve 36; the inlet valve 31 and the outlet valve 32 are preferably pneumatic valves; the natural gas conveyed by the natural gas conveying pipeline 23 enters the natural gas supercharger 24 through the inlet valve 31, is subjected to secondary compression and pressure boosting through the primary cylinder 34 and the secondary cylinder 35 in sequence, and is output out of the natural gas supercharger 24 through the outlet valve 32; the IGV33 is disposed between the inlet valve 31 and the outlet valve 32, and regulates the outlet pressure of the natural gas supercharger 24 and the natural gas flow rate; the recirculation control valve 36 is disposed between the IGV33 and the outlet valve 32, and regulates the outlet pressure of the natural gas booster 24 and the natural gas flow through the natural gas booster 24.

The utility model provides a natural gas booster compressor 24 adopts inverter motor 30, introduces frequency conversion control through inverter motor 30, when satisfying 24 export pressure control of natural gas booster compressor and 24 anti-surge control requirements of natural gas booster compressor, has reduced or even eliminated in the natural gas booster compressor 24 IGV33 not fully open, the not complete throttle loss and the recirculation loss that cause of closing of recirculation control valve 36.

In a specific embodiment, the minimum rotation speed and the minimum opening degree of the IGV33 for the frequency conversion operation of the natural gas supercharger 24 are determined according to the critical rotation speed of the two-stage bearing of the natural gas supercharger 24 and the requirements of the supercharger manufacturer and the frequency converter manufacturer. After the natural gas booster 24 is started, the IGV33 is kept at the minimum opening degree, the recirculation control valve 36 is fully opened, and the frequency conversion is rapidly added to the minimum rotating speed, which is the lowest output point of the frequency conversion operation of the natural gas booster 24. When the natural gas booster 24 outlet pressure set value is greater than the outlet pressure actual value, the recirculation control valve 36 is first gradually closed to reduce recirculation to increase the outlet pressure. After the recirculation control valve 36 is fully closed, if the set outlet pressure of the natural gas booster 24 is still greater than the actual outlet pressure, the IGV33 is gradually opened to increase the outlet pressure. After the IGV33 is fully opened, if the set value of the outlet pressure of the natural gas supercharger 24 is still larger than the actual value of the outlet pressure, the frequency conversion is gradually increased to increase the outlet pressure until the frequency conversion is full, and the set value is the highest output point of the frequency conversion operation of the natural gas supercharger 24. When the set value of the outlet pressure of the natural gas booster 24 is smaller than the actual value of the outlet pressure, the variable frequency is gradually reduced to reduce the outlet pressure. When the frequency conversion is reduced to the lowest rotating speed of the natural gas supercharger 24, if the set value of the outlet pressure of the natural gas supercharger 24 is still smaller than the actual value of the outlet pressure, the IGV33 is closed to reduce the outlet pressure. When IGV33 is closed to the minimum opening, if the set outlet pressure value of natural gas booster 24 is still less than the actual outlet pressure value, recirculation control valve 36 is gradually opened to reduce the outlet pressure until recirculation control valve 36 is fully opened and natural gas booster 24 returns to the lowest outlet point for variable frequency operation.

All the operating conditions of normal operation have been satisfied by the above-described variable frequency regulation and IGV regulation, and the recirculation control valve 36 is normally kept fully closed, as a backup regulation means only in an emergency, and its control flow chart is shown in fig. 3, and in addition, in the case where the set value of the outlet pressure is constant and the flow rate of the fuel gas on the load side is constant, the control relationship between the inlet pressure of the natural gas turbocharger 24 and the variable frequency rotation speed is shown in fig. 4. The IGV33 control set value is the outlet pressure of the natural gas supercharger 24, the recirculation control valve 36 control set value is the outlet pressure of the natural gas supercharger 24 plus the forward bias, and the frequency conversion control set value is the same as IGV 33; in addition, the dwell frequency is increased when the IGV33 command is less than maximum and the dwell IGV33 is decreased when the frequency command is less than minimum speed setting. The overload protection circuit of the electric variable frequency motor 30 acts on the variable frequency rotating speed control circuit under the variable frequency operation of the natural gas supercharger 24, and when the current of the variable frequency motor 30 exceeds a set maximum value, a variable frequency instruction is reduced; the overload protection circuit of the variable frequency motor 30 acts on the IGV33 control circuit under the power frequency operation of the natural gas supercharger 24, and when the current of the variable frequency motor 30 exceeds a set maximum value, the opening degree of the IGV33 is reduced. The IGV33 should set a minimum opening limit when the natural gas booster 24 is operating and the recirculation control valve 36 should be provided with a surge-proof control loop.

The two-stage natural gas booster 24 has a surge point calculated as follows:

at start up, the natural gas booster 24 begins to produce flow, as shown in fig. 5, and the operating point will follow the horizontal axis until the process begins to produce back pressure. The operating curve varies according to the IGV settings and process requirements, while the operating point moves up with the operating curve. The curve shown in fig. 5 shows that as the pressure increases, the flow rate decreases accordingly. If left uncontrolled, the pressure will increase and the flow will decrease until the natural gas booster 24 surges. The points in fig. 5 represent points at which surge is likely to occur in the natural gas booster 24. The final surge walk graph is located by four points. As can be seen from fig. 5, the upper left region of the graph is the surge generation region, and the lower right region is the normal operation region of the natural gas turbocharger 24.

Surging of natural gas booster 24 occurs because at a given pressure, the flow through natural gas booster 24 is too low. To prevent this, a recirculation control valve 36 is added. When the process demand drops below the surge flow rate, the recirculation control valve 36 is adjusted open to prevent the occurrence of surge. This will increase the flow through the natural gas booster 24 while maintaining the desired process flow to prevent surge.

The surge point (Q/n) of the flow and rotational speed required by the natural gas booster 24 is obtained from an aerodynamic parameter table of the natural gas booster 24. The actual surge point (Q/n) is first calculated by converting the mass flow of the natural gas booster 24 to the volume flow of the second stage. The second stage volumetric flow is compensated by the inlet temperature and pressure of the stage. The volume flow is calculated from the mass flow using the formula:

in the above formula, Q is a volume flow rate (m)³/hr)；

Mass flow rate (kg/hr); t is the secondary inlet temperature (K); r_μIs a gas constant of 0.083144 Lbar/Kmol; z is a calculated value of the compression factor, dependent on temperature; p is the secondary inlet pressure (bar); m is the molar weight (constant M17.048). The optimal linear equation can be obtained by the relation curve chart of T (K) and Z.

Once the Q value is found, the ratio of Q/n must be taken. "N" is the rotational speed of the stage. The gear ratio is involved to obtain the exact pinion rotational speed from the rotational speed of the motor/gear wheel.

Considering that a certain safety buffer is required to be reserved for the surge control Q/n value, wherein the minimum Q/n is as follows:

surge point Q/nx (1+ safety buffer percentage)

The recirculation control valve 36 performs surge prevention control according to a minimum surge point (Q/n).

To sum up, this specification discloses a gas-steam combined cycle unit with gas turbine entry two-stage gas booster compressor, and the natural gas booster compressor adopts inverter motor, introduces frequency conversion control through inverter motor, when satisfying natural gas booster compressor export pressure control and natural gas booster compressor and prevent breathing heavily the control requirement, has reduced or even eliminated the throttle loss and the recirculation loss that natural gas booster compressor IGV did not fully open, recirculation control valve did not fully close and arouse for can guarantee the safe operation of natural gas booster compressor under the operating mode that changes, when load side gas consumption is less, the large scale station service power saving has improved the economic benefits of power plant greatly.

Meanwhile, the mode of connecting a bypass device in parallel at the natural gas booster is adopted, and the safety and reliability of the natural gas system are improved. The quick opening and closing valve in the bypass device is opened and closed according to the real-time states of starting, stopping and the like of the natural gas supercharger, so that the investment cost of the natural gas supercharger is not increased, the natural gas of the gas turbine cannot be supplied instantly when the natural gas supercharger breaks down, the gas turbine can be guaranteed to be in load shedding and normal stopping, and the non-stop of a unit is avoided. Meanwhile, when the gas supply of a gas company can directly meet the use requirement of the gas turbine, the natural gas booster compressor can be stopped to directly supply natural gas through the bypass device, so that the natural gas is prevented from forming pressure drop through the booster compressor, and the economic benefit of a power plant is improved.

Those of ordinary skill in the art will understand that: the figures are schematic representations of one embodiment, and the blocks or processes in the figures are not necessarily required to practice the present invention.

Those of ordinary skill in the art will understand that: modules in the devices in the embodiments may be distributed in the devices in the embodiments according to the description of the embodiments, or may be located in one or more devices different from the embodiments with corresponding changes. The modules of the above embodiments may be combined into one module, or further split into multiple sub-modules.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the embodiments of the present invention.

Claims (10)

1. A gas-steam combined cycle unit provided with a two-stage gas booster at the inlet of a gas turbine, characterized in that it comprises: the system comprises two sets of boiler systems, two sets of gas turbine systems, a steam turbine system, a condenser system and a bypass system, wherein the two sets of gas turbine systems correspond to the two sets of boiler systems one by one;

each set of boiler system respectively comprises a waste heat boiler, a low-pressure steam pocket, a low-pressure economizer, a low-pressure evaporator, a low-pressure superheater, a medium-pressure water feed pump set, a medium-pressure steam pocket, a medium-pressure economizer, a medium-pressure evaporator, a medium-pressure superheater, a primary reheater, a secondary reheater, a high-pressure water feed pump set, a high-pressure steam pocket, a high-pressure economizer, a high-pressure evaporator, a high-pressure superheater, a heat supply network water pump and a heat supply network water heat exchanger; the low-pressure economizer, the low-pressure evaporator, the low-pressure superheater, the medium-pressure economizer, the medium-pressure evaporator, the medium-pressure superheater, the primary reheater, the secondary reheater, the high-pressure economizer, the high-pressure evaporator and the high-pressure superheater are arranged in the waste heat boiler; the water inlet end of the low-pressure steam pocket is connected with the water outlet end of the low-pressure economizer; two ends of the low-pressure evaporator are respectively communicated with the low-pressure steam pocket; the steam inlet end of the low-pressure superheater is communicated with the low-pressure steam drum; the water inlet end of the medium-pressure economizer is communicated with the low-pressure steam drum through the medium-pressure water feed pump unit, and the water outlet end of the medium-pressure economizer is communicated with the medium-pressure steam drum; two ends of the medium-pressure evaporator are respectively communicated with the medium-pressure steam pocket; the steam inlet end of the medium-pressure superheater is communicated with the medium-pressure steam drum, and the steam outlet end of the medium-pressure superheater is connected with the steam inlet end of the primary reheater; the steam inlet end of the secondary reheater is connected with the steam outlet end of the primary reheater; the water inlet end of the high-pressure economizer is communicated with the low-pressure steam drum through the high-pressure water feed pump set, and the water outlet end of the high-pressure economizer is communicated with the high-pressure steam drum; two ends of the high-pressure evaporator are respectively communicated with the high-pressure steam pocket; the steam inlet end of the high-pressure superheater is communicated with the high-pressure steam drum; the water inlet end of the heat supply network water pump is communicated with the heat supply network water heat exchanger, and the water outlet end of the heat supply network water pump is communicated with the water inlet end of the low-pressure economizer; the water inlet end of the heat supply network water heat exchanger is communicated with the water outlet end of the low-pressure economizer;

each set of the combustion engine system respectively comprises a gas turbine, a TCA system, an FGH system and a natural gas conveying system; the gas outlet end of the gas turbine is communicated with the waste heat boiler; one end of the TCA system is connected with the water outlet end of the high-pressure water feed pump set, and the other end of the TCA system is connected with the water outlet end of the high-pressure economizer; the gas outlet end of the FGH system is communicated with the gas inlet end of the gas turbine; the natural gas conveying system comprises a natural gas conveying pipeline, a natural gas supercharger, a natural gas bypass pipeline, a first check valve, a pneumatic quick opening and closing valve, an opening and closing control valve and a gas source supply system; one end of the natural gas conveying pipeline is communicated with a natural gas source, and the other end of the natural gas conveying pipeline is connected with the gas inlet end of the FGH system; the natural gas booster is arranged on the natural gas conveying pipeline; the natural gas supercharger comprises a variable frequency motor, an inlet valve, an outlet valve, an adjustable air inlet guide vane IGV, a primary air cylinder, a secondary air cylinder and a recirculation control valve; the natural gas conveyed by the natural gas conveying pipeline enters the natural gas booster through the inlet valve, is subjected to secondary compression and pressure boosting through the primary cylinder and the secondary cylinder in sequence and then is output out of the natural gas booster through the outlet valve; the IGV is arranged between the inlet valve and the outlet valve and used for adjusting the outlet pressure and the natural gas flow of the natural gas supercharger; the recirculation control valve is arranged between the IGV and the outlet valve and is used for adjusting the outlet pressure of the natural gas booster and the flow of the natural gas flowing through the natural gas booster; the natural gas supercharger is connected with the first check valve and the pneumatic quick opening and closing valve in parallel through the natural gas bypass pipeline; the air source supply system is communicated with the pneumatic quick opening and closing valve; the opening and closing control valve is arranged between the air source supply system and the pneumatic quick opening and closing valve;

the steam turbine system comprises a high-intermediate pressure cylinder and a low-pressure cylinder which are coaxially connected; the condenser system comprises a condenser and a condensed water pump set; the water outlet end of the condenser is communicated with the water inlet end of the condensed water pump set;

the bypass system comprises a communicating pipe, a low-pressure steam conveying pipeline, a medium-pressure superheated steam conveying pipeline, a reheated steam conveying pipeline, a high-pressure steam exhaust main pipe, a high-pressure steam exhaust branch pipe, a condensed water conveying pipeline, a low-pressure bypass and a medium-pressure bypass; the medium-pressure steam outlet end of the high and medium-pressure cylinder is communicated with the steam inlet end of the low-pressure cylinder through the communicating pipe; the steam outlet end of the low-pressure superheater of each set of the boiler system is respectively connected with one low-pressure steam conveying pipeline; a low-pressure steam combining valve is arranged on the low-pressure steam conveying pipeline; the two low-pressure steam delivery pipelines are converged and then are connected to the communicating pipe together; the medium-pressure superheater and the primary reheater of each set of the boiler system are respectively communicated through the medium-pressure superheated steam conveying pipeline; the steam outlet end of the secondary reheater of each set of the boiler system is respectively connected with one reheat steam conveying pipeline; a medium-pressure parallel valve is arranged on the reheating steam conveying pipeline; the two reheat steam delivery pipelines are converged and then are connected to the medium-pressure steam inlet end of the high and medium-pressure cylinder together; the steam outlet end of the high-pressure superheater of each set of the boiler system is respectively connected with one high-pressure steam conveying pipeline; a high-pressure steam combining valve is arranged on the high-pressure steam conveying pipeline; the two high-pressure steam conveying pipelines are converged and then are connected to a high-pressure steam inlet end of the high-intermediate pressure cylinder; the high-pressure steam outlet end of the high and medium pressure cylinder is connected with the high-pressure steam exhaust main pipe; two paths of high-pressure steam exhaust branch pipes led out from the high-pressure steam exhaust main pipe are respectively connected with the two medium-pressure superheated steam conveying pipelines; the condensed water conveying pipeline is connected with the water outlet end of the condensed water pump set and is communicated with the low-pressure coal economizer in the two sets of boiler systems; a low-pressure bypass connected with the condenser is led out from the low-pressure steam conveying pipeline; a low-pressure bypass pressure regulating valve is arranged on the low-pressure bypass; a middle-pressure bypass connected with the condenser is led out from the reheating steam conveying pipeline; a medium-pressure bypass pressure regulating valve is arranged on the medium-pressure bypass; and a high-pressure bypass pressure regulating valve is arranged between the high-pressure steam conveying pipeline and the high-pressure steam exhaust branch pipe.

2. The gas-steam combined cycle unit provided with a gas turbine inlet two-stage gas supercharger according to claim 1, characterized in that the gas-steam combined cycle unit further comprises an electric motor system;

the motor system comprises two gas turbine generators and a steam turbine generator; the two gas turbine generators are respectively and coaxially connected with the gas turbines of the two gas turbine systems; the steam wheel generator is coaxially connected with the high and medium pressure cylinder.

3. The gas-steam combined cycle unit provided with a gas turbine inlet two-stage gas supercharger according to claim 1, wherein the gas turbine system further comprises a second check valve; and the water outlet end of the FGH system is communicated with the water inlet end of the low-pressure economizer through the second check valve.

4. The gas-steam combined cycle unit provided with a gas turbine inlet two-stage gas supercharger according to claim 1, wherein the gas turbine system further comprises an air heat exchanger; and the air inlet end of the gas turbine is connected with the air heat exchanger.

5. The gas-steam combined cycle unit provided with a gas turbine inlet two-stage gas supercharger according to claim 3, wherein a third check valve is installed on the medium-pressure superheated steam delivery pipe.

6. The gas-steam combined cycle unit provided with a gas turbine inlet two-stage gas supercharger according to claim 5, wherein a fourth check valve is installed on the high-pressure exhaust branch pipe.

7. The gas-steam combined cycle unit provided with a gas turbine inlet two-stage gas supercharger according to claim 6, wherein the second check valve, the third check valve and the fourth check valve are all manual valves.

8. The gas-steam combined cycle unit provided with a gas turbine inlet two-stage gas supercharger according to claim 1, wherein the low-pressure combining valve, the intermediate-pressure combining valve and the high-pressure combining valve are all electrically operated valves.

9. The gas-steam combined cycle unit provided with a gas turbine inlet two-stage gas supercharger according to claim 1, wherein the first check valve is a flap type check valve.

10. The gas-steam combined cycle unit provided with a two-stage gas supercharger at the inlet of a gas turbine according to claim 1, wherein the inlet valve and the outlet valve are pneumatic valves.

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