Patent Description:
A combined power generation system is a power generation system that combines a gas turbine and a steam turbine to achieve high efficiency by guiding high-temperature exhaust gas from the gas turbine to a heat recovery steam generator (HRSG) and generating steam using thermal energy retained in the exhaust gas. This steam enables power generation by the steam turbine and can be combined with the power generated by the gas turbine to improve higher thermal efficiency leveraging the thermal energy retained in the exhaust gas. This improvement is in contrast to the autonomous power production solely through the gas turbine.

A gas turbine is a power engine that mixes compressed air compressed by a compressor and fuel, burns an air-fuel mixture, and rotates a turbine with high-temperature combustion gas. Gas turbines are used to drive generators, aircrafts, ships, trains, and the like.

A combustor and a turbine section of a gas turbine are heated by combustion gases and need to be cooled, and compressed air from a compressor is used to cool the combustor or turbine section. However, the compressed air for cooling is also heated during the compression process and needs to be cooled by a refrigerator before being supplied to a heat source.

The refrigerator cools the compressed air by performing heat exchange between the feedwater supplied from the HRSG and the compressed air. However, when the compressed air for cooling does not undergo sufficient cooling within the refrigerator, there may be a problem that the gas turbine is overheated.

Traditionally, compressed air for turbine cooling is cooled by a separate external heat exchanger such as a kettle boiler.

However, the use of an external heat exchanger requires piping between the HRSG and the heat exchanger, requires an additional construction site, and cannot utilize water during a sub cycle as a cooling source when the turbine section is started.

<CIT> and <CIT> give examples of combined cycle power generation with cooling of compressed air as known in the art.

Accordingly, the present disclosure has been made keeping in mind the above problems occurring in the related art, and an objective of the present disclosure is to provide a combined power generation system in which a plurality of heat exchangers is provided inside a heat recovery steam generator (HRSG) so that exhaust gases are utilized as a cooling source to shorten startup time and there is no need to provide a separate construction site for a cooling system, and an operation control method thereof.

In an aspect of the present invention, which is defined by the features of the independent apparatus claim, there is provided a combined power generation system including: a gas turbine including a compressor configured to compress air, a combustor configured to mix the compressed air from the compressor and fuel and combust a mixture of the compressed air and fuel, and a turbine section configued to rotate a turbine with combustion gases generated by the combustor and discharge exhaust gases; a heat recovery steam generator (HRSG) in which steam is generated by heat of the exhaust gases from the gas turbine; and a steam turbine driven by the steam generated by the HRSG, wherein the HRSG includes a plurality of heat exchangers provided to cool the compressed air by performing heat exchange between the compressed air and the exhaust gases.

In the combined power generation system, the plurality of heat exchangers supplies cooled compressed air to the turbine section.

The plurality of heat exchangers may include: a medium-pressure heat exchanger disposed upstream of a medium-pressure evaporator; and a low-pressure heat exchanger disposed upstream of a low-pressure evaporator to re-cool the compressed air having been cooled by the medium-pressure heat exchanger.

The combined power generation system may further include: a compressed air flow path that flows the compressed air from the compressor to the plurality of heat exchangers; a cooling air flow path that flows the cooled compressed air from the plurality of heat exchangers to the turbine section; a bypass flow path that flows the compressed air from the compressed air flow path to the cooling air flow path; a main valve installed in the compressed air flow path; and a bypass valve installed in the bypass flow path.

The combined power generation system may further include a plurality of temperature sensors installed in the cooling air flow path to measure the temperature of the cooled compressed air entering the turbine section.

The plurality of temperature sensors may include a first temperature sensor installed near an inlet of the turbine section in the cooling air flow path; and a second temperature sensor installed at a point in the cooling air flow path before the cooling air flow path is joined by the bypass flow path.

The HRSG may sequentially include a high-pressure superheater, a second medium-pressure superheater, a high-pressure evaporator disposed below a high-pressure drum, a high-pressure economizer, a first medium-pressure superheater, a medium-pressure evaporator disposed below a medium-pressure drum, a second low-pressure superheater, a medium-pressure economizer, a first low-pressure superheater, a low-pressure evaporator disposed below a low-pressure drum, and a low-pressure economizer, according to a flow direction of the exhaust gases, wherein the medium-pressure heat exchanger is disposed between the first medium-pressure superheater and the medium-pressure evaporator, and the low-pressure heat exchanger is disposed between the first low-pressure superheater and the low-pressure evaporator according to a flow direction of the exhaust gases.

The combined power generation system may further include a controller configured to regulate opening degrees of the main valve and the bypass valve, wherein the controller is configured to increase the opening degree of the bypass valve when the measured temperature of the cooled compressed air by the temperature sensor is lower than a target value, and decrease the opening degree of the bypass valve when the measured temperature of the cooled compressed air by the temperature sensor is higher than the target value.

The combined power generation system may further include a controller configured to regulate opening degrees of the main valve and the bypass valve, wherein the controller is configured to regulate the opening degree of the main valve when the temperature control by the bypass valve fails, and when the temperature control by the bypass valve does not fail, increase the opening degree of the bypass valve when the measured temperature of the cooled compressed air by the temperature sensor is less than the target value, and decrease the opening degree of the bypass valve when the measured temperature of the cooled compressed air by the temperature sensor is greater than the target value.

In a combined power generation system according to another embodiment of the present disclosure, the plurality of heat exchangers may include a high-pressure heat exchanger disposed downstream of a high-pressure evaporator, a medium-pressure heat exchanger disposed upstream of a medium-pressure evaporator to re-cool the compressed air that has been cooled by the high-pressure heat exchanger, and a low-pressure heat exchanger disposed upstream of a low-pressure evaporator to re-cool the compressed air having been cooled by the medium-pressure heat exchanger.

The combined power generation system may further include: a compressed air flow path from the compressor to the plurality of heat exchangers; a cooling air flow path from the plurality of heat exchangers to the turbine section; a bypass flow path from the compressed air flow path to the cooling air flow path; a main valve installed in the compressed air flow path; and a bypass valve installed in the bypass flow path.

The plurality of temperature sensors may include a first temperature sensor installed near an inlet of the turbine section in the cooling air flow path; and a second temperature sensor installed at a point in the cooling air flow path before the cooling air flow path joins the bypass flow path.

The HRSG may sequentially include a high-pressure superheater, a second medium-pressure superheater, a high-pressure evaporator disposed below a high-pressure drum, a high-pressure economizer, a first medium-pressure superheater, a medium-pressure evaporator disposed below a medium-pressure drum, a second low-pressure superheater, a medium-pressure economizer, a first low-pressure superheater, a low-pressure evaporator disposed below a low-pressure drum, and a low-pressure economizer, according to a flow direction of the exhaust gases, wherein the high-pressure heat exchanger is disposed between the high-pressure evaporator and the high-pressure economizer, the medium-pressure heat exchanger is disposed between the first medium-pressure superheater and the medium-pressure evaporator, and the low-pressure heat exchanger is disposed between the first low-pressure superheater and the low-pressure evaporator according to a flow direction of the exhaust gases.

In another aspect of the present disclosure, there is provided an operation control method of a combined power generation system including: a gas turbine including a compressor, a combustor, and a turbine section; a heat recovery steam generator (HRSG); a steam turbine, and a plurality of heat exchangers provided in the HRSG to cool compressed air by heat exchange between the compressed air and exhaust gases, the method including: determining whether the temperature measured by a temperature sensor installed in a cooling air flow path connecting, and flowing the cooled compressed air, from the heat exchangers to the turbine section is within a target range; when the measured temperature is not within the target range and is lower than a target value, increasing an opening degree of a bypass valve installed in a bypass flow path connecting, and flowing the compressed air, from a compressed air flow path to the cooling air flow path; when the measured temperature is not within the target range and is higher than the target value, decreasing the opening degree of the bypass valve; and, when the measured temperature is within the target range, completing the adjustment of the opening degree of the bypass valve.

The compressed air flow path may connect, and flow the compressed air, from the compressor to the plurality of heat exchangers and the cooling air flow path may connect, and flow the cooled compressed air, from the heat exchangers to the turbine section.

The plurality of heat exchangers may further include a high-pressure heat exchanger disposed downstream of a high-pressure evaporator.

In a further aspect of the present invention, which is defined by the features of the independent method claim, there is provided an operation control method of a combined power generation system including: a gas turbine including a compressor, a combustor, and a turbine section; a heat recovery steam generator (HRSG); a steam turbine, and a plurality of heat exchangers provided in the HRSG to cool compressed air by performing heat exchange between the compressed air and exhaust gases and supply cooled compressed air, the method including: determining whether the temperature measured by a temperature sensor installed in a cooling air flow path connecting, and flowing the cooled compressed air, from the heat exchangers to the turbine section is within a target range; determining whether temperature control by a bypass valve installed in a bypass flow path connecting, and flowing the compressed air, from a compressed air flow path to the cooling air flow path has failed, the compressed air flow path connecting, and flowing the compressed air, from the compressor to the plurality of heat exchangers; when the temperature control by the bypass valve is determined to fail, adjusting an opening degree of a main valve installed in the compressed air flow path; when the temperature control by the bypass valve is determined to not fail, determining whether the measured temperature is lower than a target value; when the measured temperature is lower than the target value, increasing an opening degree of the bypass valve installed in the bypass flow path; when the measured temperature is higher than the target value, decreasing the opening degree of the bypass valve; and, when the measured temperature is within the target range, completing the adjustment of the opening degree of the bypass valve.

According to the combined power generation system and the operation control method thereof, the plurality of heat exchangers is provided inside the HRSG so that exhaust gases are utilized as a cooling source to shorten startup time and there is no need to provide a separate construction site for a cooling system.

Terms used herein are used to merely describe specific embodiments, and are not intended to limit the present disclosure. As used herein, an element expressed as a singular form includes a plurality of elements, unless the context clearly indicates otherwise. Further, it will be understood that the term "comprising" or "including" specifies the presence of stated features, numbers, steps, operations, elements, parts, or combinations thereof, but does not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, parts, or combinations thereof.

Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. It is noted that like elements are denoted in the drawings by like reference symbols whenever possible. Further, the detailed description of known functions and configurations that may obscure the gist of the present disclosure will be omitted. For the same reason, some of the elements in the drawings are exaggerated, omitted, or schematically illustrated.

<FIG> is a block diagram illustrating a combined power generation system according to an embodiment of the present disclosure.

The combined power generation system <NUM> of the present disclosure includes: a gas turbine <NUM> including a compressor <NUM> that compresses air, a combustor <NUM> that combusts a mixture of the compressed air compressed by the compressor and fuel, and a turbine section <NUM> that obtains rotational power by the combustion gases generated by the combustor; a heat recovery steam generator (HRSG) <NUM> in which steam is generated by heat of exhaust gases from the gas turbine; and a steam turbine <NUM> driven by the steam generated by the HRSG.

The compressor <NUM> sucks and compresses ambient air. The compressor <NUM> is connected to the turbine section <NUM> by a rotary shaft so that the compressor can rotate with the rotation of the turbine section <NUM>. The compressor <NUM> has a plurality of blades and vanes in multiple stages to compress the incoming air.

The combustor <NUM> may combust a mixture of fuel and compressed air compressed by the.

The rotary shaft of the turbine section <NUM> may be rotated by the combustion gases generated by the combustor <NUM>. The turbine section <NUM> has the plurality of blades and vanes arranged in multiple stages so that the rotary shaft is rotated by the combustion gases.

The HRSG <NUM> may also be referred to as a heat recovery boiler. The HRSG <NUM> may recover heat from the high-temperature exhaust gases from the gas turbine. This heat is utilized to heat water, ultimately resulting in generation of steam. The generated steam can be piped to drive the steam turbine <NUM>.

A central rotary shaft of the steam turbine <NUM> may be rotated by the steam generated in the HRSG <NUM>. The steam turbine <NUM> may include a high-pressure turbine section <NUM>, a medium-pressure turbine section <NUM>, and a low-pressure turbine section <NUM>, with a rotary shaft connected therebetween. The high-pressure turbine section <NUM>, the medium-pressure turbine section <NUM>, and the low-pressure turbine section <NUM> may be supplied with high-pressure steam, medium-pressure steam, and low-pressure steam, respectively, from the steam generated by the HRSG <NUM>.

The HRSG <NUM> may generate steam using exhaust gases from the steam turbine <NUM>. The HRSG <NUM> may have a plurality of superheaters, economizers, reheaters, and evaporators sequentially arranged according to steam pressure to heat exchange with the exhaust gases. The HRSG <NUM> according to the present disclosure may include a plurality of heat exchangers <NUM>, <NUM> to cool the compressed air by performing a heat exchange process between a portion of the compressed air from the compressor <NUM> and the exhaust gases from the turbine section <NUM>. In a normal state operation of the gas turbine <NUM>, the temperature of the exhaust gases remains lower than the temperature of the compressed air. This temperature difference allows the exhaust gases to serve as cooling fluid for lowering the temperature of the compressed air. This cooling action may facilitate to maintain the optimal operating temperature of the internal components within the turbine section <NUM>.

The HRSG <NUM> sequentially includes a high-pressure superheater <NUM>, a second medium-pressure superheater 138B, a high-pressure evaporator <NUM> disposed below a high-pressure drum <NUM>, a high-pressure economizer <NUM>, a first medium-pressure superheater 138A, and a medium-pressure evaporator <NUM> disposed below a medium-pressure drum <NUM>, a second low-pressure superheater 139B, a medium-pressure economizer <NUM>, a first low-pressure superheater 139A, a low-pressure evaporator <NUM> disposed below a low-pressure drum <NUM>, and a low-pressure economizer <NUM>, according to a flow direction of the exhaust gas.

The superheaters <NUM>, 138A, 138B, 139A, 139B may heat the saturated steam generated in the drums <NUM>, <NUM>, <NUM>, to generate superheated steam with a higher temperature. The superheated steam generated by the high-pressure superheater <NUM> may be supplied to the high-pressure turbine section <NUM>. A high-pressure valve <NUM> may be installed in a high-pressure superheated steam flow path between the high-pressure superheater <NUM> and the high-pressure turbine section <NUM> to regulate a flow rate of superheated steam.

The superheated steam generated by the first medium-pressure superheater 138A and the second medium-pressure superheater 138B may be supplied to the medium-pressure turbine section <NUM>. A medium-pressure valve <NUM> may be installed in a medium-pressure superheated steam flow path between the first/second medium-pressure superheater 138A, 138B and the medium-pressure turbine section <NUM> to regulate a flow rate of superheated steam.

According to an embodiment, the first medium-pressure superheater 138A may be configured as a reheater. The reheater may reheat the steam that has dropped in temperature after working in the high-pressure turbine section <NUM> to increase the superheat degree.

The superheated steam generated by the first low-pressure superheater 139A and the second low-pressure superheater 139B may be supplied to the low-pressure turbine section <NUM>. A low-pressure valve <NUM> may be installed in a low-pressure superheated steam flow path between the first/second low-pressure super heater 139A, 139B and the low-pressure turbine section <NUM> to regulate a flow rate of superheated steam.

The evaporator evaporates water supplied to the HRSG <NUM> to generate steam. The high-pressure evaporator <NUM> may be disposed below the high-pressure drum <NUM>, the medium-pressure evaporator <NUM> may be disposed below the medium-pressure drum <NUM>, and the low-pressure evaporator <NUM> may be disposed below the low-pressure drum <NUM>. The feedwater may flow sequentially through the low-pressure evaporator <NUM>, the medium-pressure evaporator <NUM>, and the high-pressure evaporator <NUM>, in which the feedwater is evaporated by the exhaust gases to generate steam.

The economizers, <NUM>, <NUM>, <NUM>, also known as a feedwater preheater, use heat from the exhaust gases to raise the feedwater temperature to recover lost heat, increase boiler efficiency, and save fuel.

When upstream/downstream directions are defined based on the flow direction of the exhaust gas, the high-pressure economizer <NUM> may be disposed downstream of the high-pressure evaporator <NUM> to preheat the feedwater. The medium-pressure economizer <NUM> may be disposed downstream of the medium-pressure evaporator <NUM> to preheat the feedwater. The low-pressure economizer <NUM> may be disposed downstream of the low-pressure evaporator <NUM> to preheat the feedwater.

The exhaust gases may enter the HRSG <NUM> and pass from the high-pressure superheater <NUM> to the low-pressure economizer <NUM> for heat exchange before being discharged to an exhaust stack <NUM>.

The HRSG <NUM> may further include a medium-pressure heat exchanger <NUM> and a low-pressure heat exchanger <NUM>. The medium-pressure heat exchanger <NUM> may be disposed upstream of the medium-pressure evaporator <NUM> and cools the compressed air by heat exchange between the compressed air and the exhaust gas. The low-pressure heat exchanger <NUM> may be disposed upstream of the low-pressure evaporator <NUM> to re-cool the compressed air that has been cooled by the medium-pressure heat exchanger <NUM>.

The medium-pressure heat exchanger <NUM> may be disposed nearby the upstream side of the medium-pressure evaporator <NUM> to perform heat exchange between the compressed air and the exhaust gases to cool the compressed air. Specifically, the medium-pressure heat exchanger <NUM> may be disposed between the first medium-pressure superheater 138A and the medium-pressure evaporator <NUM>.

The low-pressure heat exchanger <NUM> may be disposed nearby the upstream side of the low-pressure evaporator <NUM> to perform heat exchange between the compressed air and the exhaust gases to further cool the compressed air. Specifically, the low-pressure heat exchanger <NUM> may be disposed between the first low-pressure superheater 139A and the low-pressure evaporator <NUM>.

The combined power generation system <NUM> may further include a compressed air flow path <NUM> connecting, and flowing (i.e., delivering) the compressed air, from the compressor <NUM> to the plurality of heat exchangers <NUM>, <NUM>, a cooling air flow path <NUM> connecting, and flowing (i.e., delivering) the cooled compressed air, from the plurality of heat exchangers <NUM>, <NUM> to the turbine section <NUM>. The combined power generation system <NUM> may further include a bypass flow path <NUM> connecting, flow (i.e., delivering) the compressed air from the compressed air flow path to the cooling air flow path.

According to an embodiment, the compressed air flow path <NUM> may branch off from a flow path from the compressor <NUM> to the combustor <NUM> (the "compressor-combustor path") and connect to the medium-pressure heat exchanger <NUM>, and connect from the medium-pressure heat exchanger <NUM> to the low-pressure heat exchanger <NUM>. In other words, an upstream part of the compressed air flow path <NUM> may be disposed between and connecting the compressor-combustor path and the medium-pressure heat exchanger <NUM> and a downstream part of the compressed air flow path <NUM> may be disposed between and connecting the medium-pressure heat changer <NUM> and the low-pressure heat exchanger <NUM>.

The cooling air flow path <NUM> may connect from the low-pressure heat exchanger <NUM> to a cooling air inlet of the turbine section <NUM>.

According to an embodiment, the bypass flow path <NUM> may connect from an upstream midpoint of the compressed air flow path <NUM> to a downstream midpoint of the cooling air flow path <NUM>. The downstream midpoint of the cooling air flow path <NUM> where the bypass flow path <NUM> joins may be referred to as a bypass flow joint point. Accordingly, the portion of the compressed air introduced into the compressed air flow path <NUM> may flow through the bypass flow path <NUM> directly into the turbine section <NUM> without flowing through the plurality of heat exchangers <NUM> and <NUM>.

According to an embodiment a main valve <NUM> may be installed in the compressed air flow path <NUM> to regulate the air flow rate in the compressed air flow path <NUM>. In addition, a bypass valve <NUM> may be installed in the bypass flow path <NUM> to regulate the air flow rate in the bypass flow path <NUM>.

The combined power generation system <NUM> of the present disclosure may further include a plurality of temperature sensors including temperature sensors <NUM>, <NUM> installed in the cooling air flow path <NUM> to measure the temperature of the cooling air (i.e., "the cooled compressed air" throughout the specification) entering the turbine section <NUM>.

The first temperature sensor <NUM> may be installed near the cooling air inlet of the turbine section <NUM> in the cooling air flow path <NUM> between the cooling air inlet of the turbine section <NUM> and the bypass flow joint point. The second temperature sensor <NUM> may be installed in the cooling air flow path <NUM> at a point before the bypass flow j oint point (i.e., at a point upstream than the bypass flow joint point based on the flow direction of the cooled compressed air).

The first temperature sensor <NUM> may measure the temperature of the cooling air within the cooling air flow path <NUM> immediately before the cooling air enters the turbine section <NUM>. Thus, the first temperature sensor <NUM> may measure the temperature of a mixture of two airs: the cooled compressed air that has been cooled by passing through the plurality of heat exchangers <NUM> and <NUM> and the compressed air that has flowed through the bypass flow path <NUM>.

The second temperature sensor <NUM> may be installed in the middle of the cooling air flow path <NUM> before the cooling air flow path meets the bypass flow path <NUM>. The second temperature sensor <NUM> may measure the temperature of the cooling air (i.e., the cooled compressed air) that has been cooled through flowing through the plurality of heat exchangers <NUM> and <NUM>.

The combined power generation system <NUM> of the present disclosure may further include a controller <NUM> that regulates the opening degree of the main valve <NUM> and the bypass valve <NUM>.

As illustrated in <FIG>, the controller <NUM> may be configured to increase the opening degree of the bypass valve <NUM> when the measured temperature of the cooling air from the temperature sensor <NUM> is lower than a target value, and to decrease the opening degree of the bypass valve <NUM> when the measured temperature of the cooling air from the temperature sensor <NUM> is higher than the target value.

The controller <NUM> may receive a temperature measurement signal of the cooling air from the first temperature sensor <NUM> to control the main valve <NUM> and the bypass valve <NUM> depending on the temperature of the cooling air.

First, the controller determines whether the measured temperature of the cooling air is within a target range, i.e., a set temperature range (S10). When the measured temperature of the cooling air is within the target range, the controller <NUM> may keep the opening degree of the main valve <NUM> and the bypass valve <NUM> unchanged.

When the measured temperature of the cooling air is out of the target range, the controller <NUM> determines whether the measured temperature is lower than the target range (S20).

When the measured temperature is lower than the target value, the controller may increase the opening degree of the bypass valve <NUM> (S30) to allow more of the compressed air to flow through the bypass flow path <NUM> without passing through the plurality of heat exchangers <NUM> and <NUM>, thereby further increasing the temperature of the cooling air.

Conversely, when the measured temperature is higher than the target value, the controller may decrease the opening degree of the bypass valve <NUM> (S40) to allow more of the compressed air to pass through the plurality of heat exchangers <NUM> and <NUM>, thereby further lowering the temperature of the cooling air.

<FIG> is a flowchart illustrating a method of controlling an operation of the combined power generation system according to another embodiment of the present disclosure.

The controller <NUM> may be configured to controls the temperature of the cooling air by regulating the opening degree of the main valve <NUM> when it is determined that the temperature control by the bypass valve <NUM> fails (i.e., being not operable), and controls the temperature of the cooling air by regulating the opening degree of the bypass value <NUM> when it is determined that the temperature control by the bypass valve <NUM> is operable.

Specifically, first, the controller <NUM> may determine whether the measured temperature of the cooling air from the temperature sensor <NUM> is within a target range, i.e., a set temperature range (S110). When the measured temperature of the cooling air by the temperature sensor <NUM> is within the target range, the controller <NUM> may keep the opening degree of the main valve <NUM> and the bypass valve <NUM> unchanged.

When the measured temperature of the cooling air measured by the temperature sensor <NUM> is out of the target range, the controller determines whether the temperature control by the bypass valve <NUM> has failed (S120). When the temperature of the cooling air cannot be regulated by the bypass valve <NUM> due to a failure of the bypass valve <NUM> or the like, the controller <NUM> may attempt to regulate the temperature of the cooling air by adjusting the opening degree of the main valve <NUM> only (S130).

Next, when the temperature control by the bypass valve <NUM> has not failed, i.e., when the temperature control by the bypass valve <NUM> is possible, the controller determines whether the measured temperature of the cooling air is lower than the target range (S140).

When the measured temperature is lower than the target value, the controller may increase the opening degree of the bypass valve <NUM> (S150) to allow more of the compressed air to flow through the bypass flow path <NUM> without passing through the plurality of heat exchangers <NUM> and <NUM>, thereby further increasing the temperature of the cooling air.

Conversely, when the measured temperature is higher than the target value, the controller may decrease the opening degree of the bypass valve <NUM> (S160) to allow more of the compressed air to pass through the plurality of heat exchangers <NUM> and <NUM>, thereby further lowering the temperature of the cooling air.

<FIG> is a diagram illustrating a combined power generation system according to another embodiment of the present disclosure.

In this combined power generation system <NUM>, the plurality of heat exchangers may further include a high-pressure heat exchanger <NUM> disposed downstream of the high-pressure evaporator <NUM>.

The high-pressure heat exchanger <NUM> may be disposed between the high-pressure evaporator <NUM> and the high-pressure economizer <NUM> in the HRSG <NUM>.

The compressed air flow path <NUM> may connect from the compressor <NUM> to the high-pressure heat exchanger <NUM>, connect from the high-pressure heat exchanger <NUM> to the medium-pressure heat exchanger <NUM>, and then connect from the medium-pressure heat exchanger <NUM> to the low-pressure heat exchanger <NUM>. In other words, an upstream portion of the compressed air flow path <NUM> may be disposed between and connecting the compressor <NUM> and the high-pressure heat exchanger <NUM>, a middle portion of the compressed air flow path <NUM> may be disposed between and connecting the high-pressure heat exchanger <NUM> and the medium-pressure heat exchanger <NUM>, and a downstream portion of the compressed air flow path <NUM> may be disposed between and connecting the medium-pressure heat changer <NUM> and the low-pressure heat exchanger <NUM>.

The cooling air flow path <NUM> may connect from the low-pressure heat exchanger <NUM> to the compressor <NUM>, as in the embodiment described above. In addition, the bypass flow path <NUM> may connect from the middle of the compressed air flow path <NUM> to the middle of the cooling air flow path <NUM>.

According to this embodiment, the combined power generation system <NUM> may be further equipped with an additional heat exchanger to perform heat exchange between the compressed air and the exhaust gases to further cool the compressed air using the exhaust gases.

Since the operation control method of the combined power generation system <NUM> of the present embodiment is as described in the above embodiment, a redundant description will be omitted.

According to the combined power generation system and the operation control method thereof, the plurality of heat exchangers is provided inside the HRSG so that exhaust gases are additionally utilized as a cooling source to cool the compressed air, thereby shortening startup time. Furthermore, no separate construction site is necessary for the cooling system to cool the compressed air.

Claim 1:
A combined power generation system (<NUM>) comprising:
a gas turbine (<NUM>) including a compressor (<NUM>) configured to compress air, a combustor (<NUM>) configured to combust a mixture of the compressed air and fuel and generate combustion gases, and a turbine section (<NUM>) configured to rotate a turbine with the combustion gases and discharge exhaust gases;
a heat recovery steam generator HRSG (<NUM>) in which steam is generated by heat of the exhaust gases from the gas turbine (<NUM>); and
a steam turbine (<NUM>) driven by the steam generated by the HRSG (<NUM>),
characterized in that
the HRSG (<NUM>) includes a plurality of heat exchangers provided to cool the compressed air by performing heat exchange between the compressed air and the exhaust gases.