An external heat storage and heat transfer working medium heat island system for retrofitting an existing steam turbine generator unit and an operation method thereof

Abstract

This invention belongs to the field of thermal power plant retrofitting and energy storage application technology. Addressing the issue of ensuring the safe connection of existing steam turbine generator units to an external thermal energy storage source and stable power generation after the removal of the original boiler heating surface, this invention proposes an external thermal energy storage heat transfer working fluid heat island system and its operation method for retrofitting existing steam turbine generator units. The system includes an external thermal energy storage device, a closed-loop heat transfer working fluid loop, a heat transfer working fluid-water / steam heat exchange network, and an external interface unit for the turbine island. It connects to the existing loop through the external interface unit, retaining core equipment and achieving working fluid isolation. A high-temperature bypass and mixing device are used to regulate the heat exchange terminal temperature difference. The circulation power of the closed-loop heat transfer working fluid loop is provided by a fluid circulation drive device, and the heating of medium- and low-temperature feedwater is undertaken by existing steam extraction and regeneration equipment. During operation, multi-parameter coordinated adjustment optimizes the heat-to-work conversion efficiency.

Description

Technical Field

[0001] This invention belongs to the field of thermal power plant retrofitting and energy storage application technology, specifically relating to an external heat storage and heat transfer working fluid heat island system and its operation method for retrofitting existing steam turbine generator sets. Background Technology

[0002] With the increasing demand for large-scale grid connection of new energy sources and long-term energy storage, existing steam turbine generator units need to be decommissioned and their original turbine islands reused after being disconnected from the original boiler heating surface and water / steam power generation circuit. Utilizing an external thermal energy storage device to provide a heat source and supplying heat to the existing water / steam power generation circuit through a closed-loop heat transfer medium circuit is a feasible retrofitting approach.

[0003] This type of modification needs to address at least the following issues:

[0004] First, when an external heat source is directly coupled to a high-pressure water / steam power generation circuit, it is easy to expand the pressure boundary and generate the risk of cross-contamination of the working fluid.

[0005] Second, existing units typically include multiple heat absorption sections such as main heat absorption, main steam superheating, and reheating. If the heat source state of the heat transfer medium entering the main heat absorption heat exchanger cannot be adjusted, insufficient minimum heat exchange terminal difference is likely to occur.

[0006] Third, if the heat transfer medium is used as the power cycle medium in the power turbine, it will increase the system complexity and reduce the reuse value of the existing turbine island.

[0007] Fourth, significantly altering the cylinder pressure boundary or rotor flow path structure of an existing steam turbine will substantially increase the difficulty of modification and engineering risks.

[0008] Therefore, there is a need for a system and method that allows an external heat storage and heat transfer working fluid heat island to be connected to the existing turbine island after the original boiler heating surface is taken out of operation, while taking into account working fluid isolation, terminal differential control and equipment reuse. Summary of the Invention

[0009] To address the issue of how to safely connect existing steam turbine generator sets to an external thermal storage heat source and ensure stable power generation after the original boiler heating surface is taken out of service, this invention provides an external thermal storage heat transfer working fluid heat island system and its operation method for retrofitting existing steam turbine generator sets.

[0010] To address the aforementioned technical problems, this invention provides an external heat storage and heat transfer working fluid heat island system for retrofitting existing steam turbine generator sets. The system includes an external thermal energy storage device, a closed-loop heat transfer working fluid circuit, a water / steam heat exchange network, and an external interface unit for the turbine island. The system is suitable for ultra-high pressure, subcritical, supercritical, and ultra-supercritical operating conditions. The water / steam heat exchange network includes a main absorber heat exchanger and a main steam superheater, and, depending on the applicable operating conditions, can be selectively configured as a reheat-free system without a reheater, or a reheat system with at least one stage of reheater. The external interface unit for the turbine island connects the heat exchanger to the existing water / steam power generation circuit. In an embodiment including two stages of reheating, the reheater includes a first-stage reheater and a second-stage reheater.

[0011] The external thermal energy storage device is located outside the pressure boundary of the existing water / steam power generation circuit and exchanges heat with the closed heat transfer medium circuit; water or steam does not enter the external thermal energy storage device, and the heat transfer medium does not enter the water / steam power generation circuit.

[0012] The original boiler heating surface includes at least one of the original main steam heating surface, the original reheat heating surface, and the original feedwater heating surface; the original boiler heating surface is disconnected from the water / steam power generation circuit and is taken out of operation, and the external heat storage and heat transfer working medium heat island serves as the main heat source in the water / steam power generation circuit that replaces the original boiler heating surface.

[0013] The external interface unit of the turbine island is located outside the pressure boundary of the turbine body, and connects the main heat exchanger, the main steam superheater, and the reheater (if the system includes a reheater) to the corresponding pipelines of the existing water / steam power generation circuit, without changing the cylinder pressure boundary and rotor flow structure of the existing turbine. In an embodiment including two-stage reheat, the reheat pipeline includes a primary reheat pipeline and a secondary reheat pipeline.

[0014] At least one of the following components is retained: steam turbine, generator, condenser, feedwater pump, steam extraction and regeneration equipment, shaft sealing system, vacuum system, and grid connection system, and operates in conjunction with the external heat storage and heat transfer working fluid heat island.

[0015] The closed-loop heat transfer medium circuit includes a fluid circulation drive device, a high-temperature working medium diversion device, a main steam superheating branch, a reheating branch when the system includes a reheater, a high-temperature bypass, and a heat transfer medium mixing device. The closed-loop heat transfer medium circuit does not include a power turbine located in the main heat transfer circulation path for expanding the heat transfer medium and outputting shaft work or electrical work. The main steam superheating branch is connected to the main steam superheater, the reheating branch is connected to the reheater, and the high-temperature bypass bypasses at least one of the main steam superheater and the reheater.

[0016] The outlet of the fluid circulation drive device and the external thermal energy storage device are configured to form a direct or indirect heat exchange path, so that the heat transfer medium in the closed heat transfer medium loop obtains heat from the external thermal energy storage device and forms a high-temperature heat transfer medium. The output end of the high-temperature heat transfer medium is fluidly connected to the high-temperature diversion device. Further, when a direct heat exchange path is used, the outlet of the fluid circulation drive device is fluidly connected to the inlet of the external thermal energy storage device, and the heat transfer medium flows directly through and absorbs heat. When an indirect heat exchange path is used, an intermediate heat exchanger and a second heat transfer medium circulation loop are configured. After the second heat transfer medium obtains heat from the external thermal energy storage device, it indirectly transfers the heat to the heat transfer medium in the closed heat transfer medium loop in the intermediate heat exchanger.

[0017] The high-temperature working fluid distribution device distributes the high-temperature heat transfer working fluid to the main steam superheating branch, the reheating branch when the system includes a reheater, and the high-temperature bypass. In an embodiment including two-stage reheating, the reheating branch includes a first-stage reheating branch connected to the first-stage reheater and a second-stage reheating branch connected to the second-stage reheater.

[0018] The closed-loop heat transfer medium circuit includes a heat transfer medium mixing device installed before the inlet of the main heat absorber; the heat transfer medium mixing device mixes the heat transfer medium after the main steam superheated branch releases heat with the heat transfer medium in the high-temperature bypass before entering the main heat absorber; when the system includes a reheater, the heat transfer medium after the reheated branch releases heat also enters the mixing device to participate in the mixing.

[0019] The heat transfer medium at the outlet of the main heat absorber is connected to the inlet of the fluid circulation drive device to obtain heat again from the external thermal energy storage device through the direct or indirect heat exchange path. The system is used to provide main heat absorption and reheat heat (when the system includes a reheater) to the existing water / steam power generation circuit after the original boiler heating surface is taken out of operation. The minimum heat exchange terminal difference of the main heat absorber is maintained within a preset range by adjusting at least one of the high-temperature bypass flow rate, the main steam superheated branch flow rate, the reheat branch flow rate, and the total circulating flow rate of the heat transfer medium. In an embodiment including two-stage reheat, the reheat branch flow rate includes the first-stage reheat branch flow rate and the second-stage reheat branch flow rate.

[0020] Furthermore, the direct or indirect heat exchange path specifically includes: when a direct heat exchange path is used, the outlet of the fluid circulation drive device is fluidly connected to the inlet of the external thermal energy storage device, and the heat transfer medium flows directly through and absorbs heat; when an indirect heat exchange path is used, an intermediate heat exchanger and a second heat transfer medium circulation loop are configured, and after the second heat transfer medium obtains heat from the external thermal energy storage device, it indirectly transfers the heat to the heat transfer medium in the closed heat transfer medium loop in the intermediate heat exchanger.

[0021] The existing water / steam power generation circuit's extraction and reheat equipment is used to heat condensate, low-pressure feedwater, or high-pressure feedwater, so that the heat released from the closed heat transfer working fluid circuit is mainly used for main heat absorption, main steam superheating, and reheating.

[0022] The circulating power of the heat transfer medium in the closed heat transfer medium loop is provided by the fluid circulation drive device; the fluid circulation drive device is used to compensate for the flow pressure drop in the closed heat transfer medium loop and maintain the circulation flow rate.

[0023] Furthermore, the heat transfer medium is selected from pure nitrogen, argon, air, carbon dioxide or a mixture thereof; the heat transfer medium is in a pure gaseous state, near-critical state, dense phase or supercritical state in the closed heat transfer medium loop; the overall operating pressure range of the closed heat transfer medium loop is 0.5 MPa to 40 MPa.

[0024] In one embodiment, the heat transfer medium is pure carbon dioxide or a mixed medium with carbon dioxide as the main heat transfer component, and the circulation power of the closed heat transfer medium loop is provided by a carbon dioxide reflux compressor.

[0025] In another embodiment, when the external thermal energy storage device uses a carbon-based or graphite thermal storage medium with a maximum operating temperature of not less than 1000°C, the heat transfer medium is pure nitrogen or argon, and the circulation power of the closed heat transfer medium loop is provided by a high-temperature resistant circulating fan.

[0026] Furthermore, the closed-loop heat transfer medium circuit is equipped with an online moisture monitoring and active explosion-proof isolation system; the isolation system includes a high-frequency trace moisture detector installed on the inlet pipe of the external thermal energy storage device, and quick-cut-off isolation valves installed on the inlet and outlet main pipes of the external thermal energy storage device. When the water vapor concentration in the heat transfer medium exceeds a set threshold, the quick-cut-off isolation valve closes.

[0027] Furthermore, high-pressure water, steam, or a mixture of steam and water circulates inside the tubes of the main heat exchanger, main steam superheater, and reheater, while the outside of the tubes is scourned by the heat transfer medium, so that the highest temperature of the metal tube wall of the heat exchanger is kept within a preset safety threshold under the convective heat transfer effect on the water side inside the tube.

[0028] This invention also provides a method for retrofitting and operating an external heat storage and heat transfer working fluid heat island in an existing steam turbine generator set, including:

[0029] S1. Remove the original boiler heating surface from operation;

[0030] S2. An external thermal energy storage device, a closed heat transfer medium loop, and a heat transfer medium-water / steam heat exchange network are installed outside the turbine island.

[0031] S3. Connect the main heat exchanger to the existing feedwater or main heat absorption section pipeline through the external interface unit of the turbine island, connect the main steam superheater to the existing main steam pipeline, and connect zero, one, or multiple reheaters according to the reheat configuration of the existing unit, without changing the cylinder pressure boundary and rotor flow structure of the existing turbine; S4. Make the heat transfer medium absorb the heat released by the second heat transfer medium by directly flowing through the external heat storage device or indirectly absorbing the heat through the intermediate heat exchanger to form a high-temperature heat transfer medium; S5. Make the high-temperature heat transfer medium... S6. Distribute the heat transfer medium to the main steam superheating branch, the high-temperature bypass, and one or more reheating branches when a reheater is installed; S7. Mix the heat transfer medium after heat release in each high-temperature heat exchange branch with the heat transfer medium in the high-temperature bypass in the mixing device before entering the main heat absorption heat exchanger; S8. Based on the main steam temperature, the reheat steam temperature corresponding to the reheat system configuration, the minimum heat exchange terminal difference of the main heat absorption heat exchanger, and the operating boundary of the fluid circulation drive device, coordinate and adjust the total circulation flow rate, the flow rate of each high-temperature heat exchange branch, and the flow rate of the high-temperature bypass.

[0032] During operation, based on at least one of the following: the main steam temperature, and for conditions including a reheater, the reheat steam temperature, the minimum heat exchange terminal difference of the main heat exchanger, and the inlet heat transfer medium temperature of the external thermal energy storage device, the flow rate of the high-temperature bypass, the flow rate of the main steam superheated branch, the flow rate of the reheat branch, the total circulating flow rate of the heat transfer medium, the feedwater flow rate, and the extraction steam regeneration ratio, the flow rate is adjusted according to at least one of the following: the main steam temperature, and for conditions including a reheater, the reheat steam temperature, the minimum heat exchange terminal difference of the main heat exchanger, and the inlet heat transfer medium temperature of the external thermal energy storage device. In embodiments including two-stage reheat, the reheat steam temperature includes the primary reheat steam temperature and the secondary reheat steam temperature, and the reheat branch flow rate includes the first-stage reheat branch flow rate and the second-stage reheat branch flow rate.

[0033] After the main steam temperature, the reheat steam temperature corresponding to the reheat system configuration, the minimum heat exchange terminal difference of the main heat exchanger, and the safety boundary of the fluid circulation drive device meet preset conditions, optimized control is performed with the goal of increasing the ratio of the turbine's net output power to the heat release power of the external thermal energy storage device. In the embodiment including two-stage reheat, the reheat steam temperature includes the primary reheat steam temperature and the secondary reheat steam temperature.

[0034] In this invention, the safety boundary of the fluid circulation drive device includes at least one of the following boundary conditions: inlet pressure, inlet temperature, outlet pressure, outlet temperature, pressure ratio, rotational speed, mass flow rate, surge margin, and drive power; the preset condition is a normal operating threshold range pre-set for each of the above parameters.

[0035] The net output power of the steam turbine is the power of the generator output power minus the power consumption of the fluid circulation drive device, feedwater pump and other auxiliary equipment; the heat release power of the external thermal energy storage device is determined based on the temperature, pressure, mass flow rate and enthalpy difference of the heat transfer medium at the inlet and outlet of the external thermal energy storage device.

[0036] Compared with existing technologies, the present invention has at least the following advantages: First, the external thermal energy storage device is located outside the pressure boundary of the water / steam power generation loop, reducing the risk of pressure leakage and working fluid crosstalk; second, the heat exchange network is connected outside the pressure boundary of the turbine body, which facilitates the retention of existing turbines, generators, condensers, feedwater pumps, and extraction steam regeneration equipment; third, the state of the heat transfer working fluid entering the main heat exchanger is regulated by the high-temperature bypass and heat transfer working fluid mixing device, which helps to maintain the minimum heat exchange end difference; fourth, the closed heat transfer working fluid loop does not have a heat transfer working fluid power turbine, and the fluid circulation drive device mainly compensates for the flow pressure drop, resulting in a simple system structure; fifth, the heating of low-temperature and medium-temperature feedwater is undertaken by the existing extraction steam regeneration equipment, which helps to make the closed heat transfer working fluid loop mainly serve medium and high-temperature heating. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the overall process of connecting an external heat storage and heat transfer working fluid heat island to an existing steam turbine generator set according to an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram illustrating the non-intrusive connection relationship between the external heat storage and heat transfer working fluid heat island and the existing steam turbine island in an embodiment of the present invention.

[0039] Explanation of reference numerals in the attached figures:

[0040] TES is an external thermal energy storage device; CC is a fluid circulation drive device; DIV1 is a high-temperature working fluid diversion device; DIV2 is a first-stage turbine outlet diversion device; DIV3 is a second-stage turbine outlet diversion device; DIV4 is a subsequent turbine stage outlet diversion device; MIX1 is a heat transfer working fluid mixing device; MIX2 is an open feedwater regenerative mixer; MIX3 is a low-pressure exhaust / regenerative return mixer; HX-SH is the main steam superheater; HX-RH1 is the first-stage reheater; HX-RH2 is the second-stage reheater; HX-EV is the main heat absorption heat exchanger; HX-EC is the high-pressure regenerative heater; HX-DO is the low-pressure regenerative heater; WP1 is the low-pressure feedwater pump; WP2 is the high-pressure feedwater pump; AC is the condenser; T1 is the first-stage turbine; T2 is the second-stage turbine; T3A is the subsequent turbine stage A; T3B is the subsequent turbine stage B. C1B-V is a high-temperature bypass regulating valve; V1 is a high-pressure regenerative heater outlet throttle valve; V2 is a low-pressure regenerative heater outlet throttle valve; IF is an external interface unit for the turbine island; V-Q1 is an inlet quick-cut-off isolation valve for the external thermal energy storage device; V-Q2 is an outlet quick-cut-off isolation valve for the external thermal energy storage device; MT is a high-frequency trace moisture detector.

[0041] C1 is the main high-temperature heat transfer fluid stream from the external thermal energy storage device outlet (TES outlet to DIV1 inlet); C1A is the main steam superheater branch stream (DIV1 outlet to HX-SH inlet); C1C is the first-stage reheat branch stream (DIV1 outlet to HX-RH1 inlet); C1D is the second-stage reheat branch stream (DIV1 outlet to HX-RH2 inlet); C1B is the high-temperature bypass stream (DIV1 outlet to C1B-V inlet); C1B-2 is the regulated high-temperature bypass stream (C1B-V outlet to MIX1 inlet); C2A is the main steam superheater outlet heat transfer fluid stream (…). (HX-SH outlet to MIX1 inlet); C2C is the heat transfer fluid stream from the outlet of the first-stage reheater (HX-RH1 outlet to MIX1 inlet); C2D is the heat transfer fluid stream from the outlet of the second-stage reheater (HX-RH2 outlet to MIX1 inlet); C2 is the mixed medium-high temperature heat transfer fluid stream before entering the main heat exchanger (MIX1 outlet to HX-EV inlet); C3 is the heat transfer fluid stream from the outlet of the main heat exchanger (HX-EV outlet to CC inlet); C4 is the return heat transfer fluid stream from the outlet of the fluid circulation drive device to the external thermal energy storage device (CC outlet to TES inlet).

[0042] W1 is the condensate outlet stream (from AC outlet to WP1 inlet); W2 is the low-pressure feedwater pump outlet stream (from WP1 outlet to HX-DO inlet); W3 is the low-pressure regenerative heater outlet stream (from HX-DO outlet to MIX2 inlet); W4 is the open feedwater regenerative mixer outlet stream (from MIX2 outlet to WP2 inlet); W5 is the high-pressure feedwater pump outlet stream (from WP2 outlet to HX-EC inlet); W6 is the high-pressure regenerative heater outlet stream (from HX-EC outlet to HX-EV inlet); W7 is the main heat exchanger outlet stream (from HX-EV outlet to HX-SH inlet). W8 is the main steam stream from the main superheater outlet (HX-SH outlet to T1 inlet); W9 is the first-stage turbine outlet stream (T1 outlet to DIV2 inlet); W9A is the primary cold / reheat steam stream entering the first-stage reheater (DIV2 outlet to HX-RH1 inlet); W9B is the extraction steam stream entering the high-pressure regenerative heater (DIV2 outlet to HX-EC heating side inlet); W10 is the primary hot / reheat steam stream from the first-stage reheater outlet (HX-RH1 outlet to T2 inlet); W11 is the second-stage turbine outlet stream (T2 outlet to DIV3 inlet); W11A is the secondary cold / reheat steam stream entering the second-stage reheater (DIV3 outlet to HX-RH2 inlet); W11B is the extraction steam stream entering the open feedwater regenerative mixer (DIV3 outlet to MIX2 inlet); W12 is the secondary hot / reheat steam stream from the second-stage reheater outlet. (HX-RH2 outlet to T3A inlet); W13 is the intermediate exhaust or extraction steam stream of the subsequent turbine stage (T3A outlet to DIV4 inlet); W13A is the final stage power branch stream entering the subsequent turbine stage B (DIV4 outlet to T3B inlet); W13B is the extraction steam stream entering the low-pressure regenerative heater (DIV4 outlet to HX-DO heating side inlet); W14 is the exhaust steam stream of the final stage turbine (T3B outlet to MIX3 inlet); W15 is the heating side outlet stream of the high-pressure regenerative heater (HX-EC outlet to V1 inlet); W16 is the high-pressure regenerative return stream (V1 outlet to MIX2 inlet); W17 is the heating side outlet stream of the low-pressure regenerative heater (HX-DO outlet to V2 inlet); W18 is the low-pressure regenerative return stream (V2 outlet to MIX3 inlet); W19 is the low-pressure exhaust / regenerative mixed stream (MIX3 outlet to AC inlet). Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0044] The external heat storage and heat transfer working fluid heat island system provided by this invention can be configured with a heat exchange network according to the parameter level of the existing steam turbine generator set. For ultra-high pressure conditions, the original unit usually does not have a reheater, and the system is configured as a reheat-free system. In this case, the heat transfer working fluid-water / steam heat exchange network only includes the main heat absorber and the main steam superheater. The closed heat transfer working fluid loop does not need to be equipped with a reheat branch, and the high-temperature bypass only needs to bypass the main steam superheater. For subcritical, supercritical, and ultra-supercritical conditions, the system is configured as a reheat-equipped system with at least one reheater, and its specific structure is described in subsequent embodiments.

[0045] This invention proposes an external thermal storage and heat transfer working medium heat island system for retrofitting existing steam turbine generator sets. Its core architecture involves constructing an independent "closed-loop heat transfer working medium loop" as an intermediate decoupling layer, physically isolating the external thermal energy storage device from the existing water / steam power generation loop and enabling indirect heat exchange. For thermal storage media with different operating temperature ranges and chemical properties, the closed-loop heat transfer working medium loop can flexibly select pure carbon dioxide, pure nitrogen, argon, or mixtures thereof as the heat transfer medium, and the overall operating pressure range of the loop is controlled within the range of 0.5 MPa to 40 MPa. Depending on the phase characteristics of the selected working medium and the specific pipeline operating pressure, the system is correspondingly matched with a compressor or a high-temperature resistant circulating fan as the fluid circulation drive device. Regardless of the specific working medium and drive equipment used, all embodiments of this invention rely on a general thermodynamic system and active control logic for heat exchange terminal difference. To ensure the safety of the medium under extreme high-temperature conditions, the general system structure of this invention may optionally be equipped with an online moisture monitoring and active explosion-proof isolation system. The following sections will detail the modification scheme of the present invention using typical application scenarios with carbon dioxide and pure nitrogen as heat transfer media.

[0046] In this invention, the external heat storage and heat transfer working medium heat island refers to a heating system that includes an external thermal energy storage device (TES), a closed heat transfer working medium loop, a heat transfer working medium-water / steam heat exchange network, and an external interface unit (IF) of the turbine island.

[0047] The main heat exchanger (HX-EV) is a heat exchanger used for main heat absorption, evaporation, or heating of high-pressure feedwater or water / steam working fluid.

[0048] High-temperature bypass refers to a heat transfer fluid flow path that bypasses at least one of the main steam superheater and reheater and enters the heat transfer fluid mixing device; in an embodiment including two-stage reheating, the reheater includes a first-stage reheater (HX-RH1) and a second-stage reheater (HX-RH2).

[0049] The external interface unit (IF) of the turbine island refers to the combination of pipes, valves, connectors, measuring points or control interfaces set outside the pressure boundary of the existing turbine body for connecting the heat transfer medium—water / steam heat exchange network—to the existing water / steam power generation circuit.

[0050] Example 1: External thermal island system based on carbon dioxide working fluid

[0051] (1) Overall system architecture and boundaries of existing unit modification

[0052] like Figure 2 As shown, this embodiment provides an external thermal energy storage carbon dioxide heat island system for retrofitting existing steam turbine generator sets, which has a non-intrusive connection to the existing turbine island. The system includes an external thermal energy storage device (TES), a closed carbon dioxide heat transfer loop, a carbon dioxide-water / steam heat exchange network, and an external interface unit (IF) for the turbine island.

[0053] like Figure 1 As shown, this embodiment takes a reheat system with two reheaters as an example. This system is used to provide main heat absorption, main steam superheat and reheat heat to the existing water / steam power generation circuit after the original boiler heating surface is taken out of operation. Figure 1 A two-stage reheat implementation is shown, including a first-stage reheater (HX-RH1) and a second-stage reheater (HX-RH2); for ultra-high pressure units without reheat, refer to the simplified configuration in Example 4. In existing units with only one reheat cycle, the reheaters and reheat branches can be configured as a single stage. The original boiler heating surface includes at least one of the original main steam heating surface, the original reheat heating surface, and the original feedwater heating surface.

[0054] The external interface unit (IF) of the turbine island is located outside the pressure boundary of the turbine body and is connected to at least one of the existing feedwater pipeline, main steam pipeline, and reheat pipeline. In the embodiment including two-stage reheat, the reheat pipeline includes a primary reheat pipeline and a secondary reheat pipeline. The modification does not change the cylinder pressure boundary and rotor flow structure of the existing turbine, and at least one of the existing turbine, generator, condenser (AC), feedwater pump, extraction steam regeneration equipment, shaft sealing system, vacuum system, and grid connection system is retained.

[0055] In one optional generator set retrofit implementation, for scenarios where the heat storage medium inside the external thermal energy storage device (TES) is highly corrosive, prone to leakage, or has physical limitations that make direct high-flux heat exchange with the main heat transfer medium unsuitable, the direct or indirect heat exchange path adopts an indirect dual heat exchange path. Under this architecture, the system adds a second heat transfer medium loop and an intermediate heat exchanger. During operation, the second heat transfer medium is heated to a high temperature by the external thermal energy storage device (TES), then enters the hot side of the intermediate heat exchanger to release heat, and subsequently returns to the external thermal energy storage device (TES). The main heat transfer medium in the closed-loop heat transfer medium loop, after being output by the fluid circulation drive device (CC), enters the cold side of the intermediate heat exchanger, absorbs the high-grade heat released by the second heat transfer medium, forms a high-temperature heat transfer medium, and then enters the high-temperature working fluid diversion device (DIV1). The subsequent multi-stage superheat / reheat branch diversion, independent high-temperature bypass mixing and regulation, and thermodynamic matching logic of the main heat exchanger (HX-EV) are all consistent with the direct heat exchange path. This indirect dual heat exchange structure effectively isolates the heat storage medium from the heat island of the power generation circuit, further improving the operational safety of the core dynamic equipment.

[0056] (2) External thermal energy storage device (TES) and closed carbon dioxide heat island

[0057] The external thermal energy storage device (TES) is independently installed outside the pressure boundary of the existing water / steam power generation circuit and exchanges heat with the closed carbon dioxide heat transfer circuit. Water or steam does not enter the external thermal energy storage device (TES), and the carbon dioxide heat transfer medium does not enter the water / steam power generation circuit.

[0058] In this embodiment, a direct heat exchange path is used between the fluid circulation drive device (CC) and the external thermal energy storage device (TES). During operation, the heat transfer medium stream C3 at the outlet of the main heat absorber (HX-EV) is connected to the inlet of the fluid circulation drive device (CC) to form a return heat transfer medium stream C4. After absorbing heat in the external thermal energy storage device (TES), it forms a high-temperature heat transfer medium stream C1 and then enters the high-temperature carbon dioxide diversion device (DIV1).

[0059] (3) Access method of carbon dioxide-water / steam heat exchange network

[0060] The carbon dioxide-water / steam heat exchange network includes a main absorber heat exchanger (HX-EV), a main steam superheater (HX-SH), and a reheater. The main absorber heat exchanger (HX-EV) is connected to the existing feedwater or main absorber section piping; the main steam superheater (HX-SH) is connected to the existing main steam piping; and the reheater is connected to the existing reheat piping. Figure 1In the two-stage reheat implementation shown, the reheater includes a first-stage reheater (HX-RH1) and a second-stage reheater (HX-RH2). The first-stage reheater (HX-RH1) is connected to the first-stage reheat pipeline, and the second-stage reheater (HX-RH2) is connected to the second-stage reheat pipeline.

[0061] (4) Water / steam side power generation loop cycle working process

[0062] On the existing water / steam side, the condensate stream W1 from the condenser (AC) outlet is pressurized by the low-pressure feedwater pump (WP1) to form stream W2, which enters the low-pressure regenerative heater (HX-DO) to absorb heat. The heated stream W3 enters the open feedwater regenerative mixer (MIX2). The mixed stream W4 is pressurized by the high-pressure feedwater pump (WP2) to form stream W5, which enters the high-pressure regenerative heater (HX-EC) to absorb heat, and then forms the high-pressure regenerative heater outlet stream W6, which enters the main heat exchanger (HX-EV) to absorb heat and evaporate.

[0063] exist Figure 1 In the two-stage reheat implementation shown, the stream W7 from the outlet of the main absorber heat exchanger (HX-EV) enters the main steam superheater (HX-SH) for superheating, forming the main steam stream W8 at the outlet of the main steam superheater, which then enters the first-stage turbine (T1) to expand and perform work. The stream W9 from the outlet of the first-stage turbine (T1) is divided into two paths by the first-stage turbine outlet splitter (DIV2): one path is the extraction steam stream W9B, which enters the heating side of the high-pressure regenerative heater (HX-EC); the other path is the primary cold reheat steam stream W9A, which enters the first-stage reheater (HX-RH1) for heating and forms the primary hot reheat steam stream W10, which then enters the second-stage turbine (T2) to perform work.

[0064] In this two-stage reheat implementation, the outlet steam stream W11 of the second-stage turbine (T2) is divided by the second-stage turbine outlet splitter (DIV3) into an extraction steam stream W11B that enters the open feedwater regenerative mixer (MIX2), and a secondary cold reheat steam stream W11A that enters the second-stage reheater (HX-RH2). After heating, the secondary hot reheat steam stream W12 at the outlet of the second-stage reheater (HX-RH2) enters the subsequent turbine stage A (T3A) to perform work. The intermediate exhaust or extraction steam stream W13 at the outlet of the subsequent turbine stage A (T3A) is divided by the subsequent turbine stage outlet splitter (DIV4) into an extraction steam stream W13B that enters the heating side of the low-pressure regenerative heater (HX-DO), and a final-stage power branch stream W13A that enters the subsequent turbine stage B (T3B). The final exhaust steam stream W14 from the subsequent turbine stage B (T3B) enters the low-pressure exhaust / regenerative return mixer (MIX3).

[0065] On the regenerative side, the outlet stream W15 of the high-pressure regenerative heater (HX-EC) is depressurized by the high-pressure regenerative heater outlet throttle valve (V1) to form a return stream W16, which is connected to the open feedwater regenerative mixer (MIX2); the outlet stream W17 of the low-pressure regenerative heater (HX-DO) is depressurized by the low-pressure regenerative heater outlet throttle valve (V2) to form a return stream W18, which is connected to the low-pressure exhaust / regenerative return mixer (MIX3) and mixed with stream W14 to form stream W19, which is finally discharged into the condenser (AC) to complete the water / steam closed loop.

[0066] (5) High-temperature carbon dioxide diversion and bypass mixing mechanism

[0067] The high-temperature carbon dioxide diversion device (DIV1) distributes the total high-temperature carbon dioxide flow C1 into three branches: the main steam superheater branch C1A, the reheater branch C1A, and the high-temperature bypass C1B. The main steam superheater branch C1A enters the main steam superheater (HX-SH), the reheater branch C1A enters the reheater, and the high-temperature bypass C1B, via the high-temperature bypass regulating valve (C1B-V), forms the regulated high-temperature bypass C1B-2. Figure 1 In the two-stage reheat implementation shown, the reheat branch stream includes a first-stage reheat branch stream C1C entering the first-stage reheater (HX-RH1) and a second-stage reheat branch stream C1D entering the second-stage reheater (HX-RH2).

[0068] The carbon dioxide stream C2A from the main steam superheater (HX-SH) outlet, the carbon dioxide stream from the reheater outlet, and the regulated high-temperature bypass stream C1B-2 enter the carbon dioxide mixing unit (MIX1) for mixing, forming a mixed high-temperature carbon dioxide stream C2, which then enters the main heat exchanger (HX-EV). By adjusting the high-temperature bypass flow rate, the main steam superheater branch flow rate, the reheater branch flow rate, or the total carbon dioxide circulation flow rate, the minimum heat exchange terminal difference of the main heat exchanger (HX-EV) can be maintained within a preset range. Figure 1 In the two-stage reheat implementation shown, the carbon dioxide stream at the reheater outlet includes stream C2C ​​and stream C2D, and the reheat branch flow rate includes the first-stage reheat branch flow rate and the second-stage reheat branch flow rate.

[0069] (6) Carbon dioxide non-powered circulation and high reflux temperature operation

[0070] The working fluid circulation power of the closed carbon dioxide heat transfer loop is provided by a carbon dioxide reflux compressor (CC); the carbon dioxide reflux compressor (CC) is used to compensate for the flow pressure drop of the closed carbon dioxide heat transfer loop and maintain the circulation flow rate.

[0071] The carbon dioxide stream C3 from the outlet of the main heat exchanger (HX-EV) returns to the external thermal energy storage unit (TES) via the return pipeline and the carbon dioxide return compressor (CC).

[0072] The existing steam extraction and reheat equipment of the water / steam power generation circuit is used to heat condensate, low-pressure feedwater or high-pressure feedwater, so that the heat released by the closed carbon dioxide heat transfer circuit is mainly used for main heat absorption, main steam superheating and reheating.

[0073] Example 2: Ultra-high temperature external thermal island system based on pure nitrogen working fluid

[0074] This embodiment is a unit retrofit scheme adapted to ultra-high temperature all-carbon-based thermal storage media. The system flow field topology, high-temperature bypass setting, and anti-pinch temperature control logic of this embodiment are completely consistent with Embodiment 1. The main difference is:

[0075] When the external thermal energy storage device uses pure graphite or other carbon-based thermal storage media, and the maximum operating temperature reaches or exceeds 1000℃, in order to prevent the strong carbothermic reduction reaction between the conventional working fluid and the carbon-based material, this embodiment uses pure nitrogen, which is chemically inert to carbon-based materials, as the heat transfer medium in a closed loop. Accordingly, since there is no need for gas compression phase change, the fluid circulation drive device (CC) is replaced by a high-temperature resistant circulating fan, providing low-pressure head circulation power to overcome pipeline resistance.

[0076] Furthermore, to address the high-temperature safety constraints of carbon-based materials, this embodiment incorporates an online moisture monitoring and active explosion-proof isolation system. This protection system includes a high-frequency trace moisture detector (MT) and quick-shutdown isolation valves (V-Q1, V-Q2) installed on the inlet and outlet main pipelines of the external thermal energy storage device. When the detector detects that the water vapor concentration in the heat transfer medium exceeds a preset threshold, the control unit triggers the quick-shutdown isolation valves to close urgently, physically cutting off and blocking the fluid connection between the external thermal energy storage device and the front-end heat exchange area, preventing a water-gas combustion explosion.

[0077] Example 3: Modification and Operation Method of External Thermal Island Based on Carbon Dioxide Working Fluid

[0078] Based on the system described in Embodiment 1, this embodiment also provides a method for retrofitting and operating an existing steam turbine generator set with an external thermal storage carbon dioxide heat island, including the following steps:

[0079] S1. Remove the original boiler heating surface from operation;

[0080] S2. An external thermal energy storage device (TES), a closed carbon dioxide heat transfer loop, and a carbon dioxide-water / steam heat exchange network are installed outside the turbine island.

[0081] S3. Connect the main heat exchanger to the existing feedwater or main heat absorption section pipeline through the external interface unit of the turbine island, connect the main steam superheater to the existing main steam pipeline, and connect zero, one, or multiple reheaters according to the reheat configuration of the existing unit, without changing the cylinder pressure boundary and rotor flow structure of the existing turbine; S4. Make the heat transfer medium absorb the heat released by the second heat transfer medium by directly flowing through the external heat storage device or indirectly absorbing the heat through the intermediate heat exchanger to form a high-temperature heat transfer medium; S5. Make the high-temperature heat transfer medium... S6. Distribute the heat transfer medium to the main steam superheating branch, the high-temperature bypass, and one or more reheating branches when a reheater is installed; S7. Mix the heat transfer medium after heat release in each high-temperature heat exchange branch with the heat transfer medium in the high-temperature bypass in the mixing device before entering the main heat absorption heat exchanger; S8. Based on the main steam temperature, the reheat steam temperature corresponding to the reheat system configuration, the minimum heat exchange terminal difference of the main heat absorption heat exchanger, and the operating boundary of the fluid circulation drive device, coordinate and adjust the total circulation flow rate, the flow rate of each high-temperature heat exchange branch, and the flow rate of the high-temperature bypass.

[0082] During operation control, based on at least one of the following: main steam temperature, reheat steam temperature, minimum heat exchange terminal difference of the main heat exchanger (HX-EV), and inlet carbon dioxide temperature of the external thermal energy storage device (TES), at least one of the following is adjusted: high-temperature bypass flow rate, main steam superheated branch flow rate, reheat branch flow rate, total carbon dioxide circulation flow rate, feedwater flow rate, and extraction steam regeneration ratio. Figure 1 In the two-stage reheat implementation shown, the reheat steam temperature includes the primary reheat steam temperature and the secondary reheat steam temperature, and the reheat branch flow rate includes the first-stage reheat branch flow rate and the second-stage reheat branch flow rate.

[0083] After the main steam temperature, reheat steam temperature, minimum heat exchange terminal difference of the main heat exchanger (HX-EV), and safety boundary of the carbon dioxide reflux compressor (CC) meet preset conditions, optimized control is performed with the goal of increasing the ratio of the turbine's net output power to the heat release power of the external thermal energy storage device (TES). Figure 1 In the two-stage reheat implementation shown, the reheat steam temperature includes the primary reheat steam temperature and the secondary reheat steam temperature.

[0084] It should be noted that the control logic of the modification and operation method of the ultra-high temperature external thermal island system based on pure nitrogen working medium described in Example 2 above is basically the same as that in this example. The only difference is that when executing steps S2 to S7 and subsequent coordinated control, the circulating medium in the system is replaced with pure nitrogen, the execution device that provides the power for medium circulation is replaced with a high temperature resistant circulating fan, and during operation, the system synchronously performs active explosion-proof isolation monitoring based on a high-frequency trace moisture detector (MT) and fast shut-off isolation valves (V-Q1, V-Q2).

[0085] Example 4: External carbon dioxide thermal storage island system for ultra-high pressure reheatless units

[0086] This embodiment focuses on an ultra-high pressure steam turbine generator set designed without a reheater. The system structure is basically the same as in Embodiment 1, with the following differences:

[0087] The heat transfer medium—water / steam heat exchange network consists only of the main heat absorber (HX-EV) and the main steam superheater (HX-SH), without a reheater.

[0088] In the closed carbon dioxide heat transfer loop, the working fluid high-temperature diversion device (DIV1) only distributes the high-temperature carbon dioxide stream C1 to the main steam superheating branch C1A and the high-temperature bypass C1B, without setting up a reheating branch.

[0089] The high-temperature bypass C1B bypasses the main steam superheater (HX-SH), and after being regulated by the high-temperature bypass regulating valve (C1B-V), it mixes with the carbon dioxide stream C2A at the outlet of the main steam superheater in the heat transfer working fluid mixing device (MIX1) to regulate the temperature of the medium entering the main heat exchanger (HX-EV).

[0090] In this water / steam side process, the main steam stream W8 from the outlet of the main steam superheater (HX-SH) directly enters each stage of the steam turbine to perform work, without a reheat step. The carbon dioxide-water / steam heat exchange network includes the main absorber heat exchanger (HX-EV) and the main steam superheater (HX-SH). The main absorber heat exchanger (HX-EV) is connected to the existing feedwater or main absorber section pipeline; the main steam superheater (HX-SH) is connected to the existing main steam pipeline.

Claims

1. An external heat storage and heat transfer working fluid heat island system for retrofitting existing steam turbine generator sets, characterized in that, It includes an external thermal energy storage device, a closed heat transfer medium loop, a heat transfer medium-water / steam heat exchange network, and an external interface unit for the turbine island. The heat transfer medium-water / steam heat exchange network includes a main heat absorber and a main steam superheater. The system is applicable to ultra-high pressure, subcritical, supercritical and ultra-supercritical operating conditions; the heat transfer medium-water / steam heat exchange network is selectively configured as a non-reheating system without a reheater or a reheating system with at least one stage reheater, depending on its applicable operating conditions. The external interface unit of the turbine island is located outside the pressure boundary of the turbine body. It is used to connect the main heat exchanger, the main steam superheater, and the reheater (when the system includes a reheater) to the corresponding pipelines of the existing water / steam power generation circuit without changing the cylinder pressure boundary and rotor flow structure of the existing turbine. The closed heat transfer working fluid circuit includes a fluid circulation drive device, a working fluid high-temperature diversion device, a main steam superheating branch, a reheating branch when the system includes a reheater, a high-temperature bypass, and a heat transfer working fluid mixing device. The closed heat transfer working fluid circuit does not include a power turbine set in the main heat transfer circulation path for expanding the heat transfer working fluid and outputting shaft work or electrical work to the outside. The heat transfer medium in the closed heat transfer medium loop is powered by the fluid circulation drive device and obtains heat from the external heat storage device through direct or indirect heat exchange to form a high-temperature heat transfer medium; the output end of the high-temperature heat transfer medium is fluidly connected to the high-temperature diversion device of the medium. The high-temperature working fluid distribution device distributes the high-temperature heat transfer working fluid to the main steam superheating branch, the reheating branch when the system includes a reheater, and the high-temperature bypass; the high-temperature bypass bypasses at least one of the main steam superheater and the reheater. The heat transfer medium mixing device mixes the heat transfer medium after the main steam superheating branch releases heat with the heat transfer medium in the high-temperature bypass before entering the main heat exchanger. When the system includes a reheater, the heat transfer medium after the reheating branch releases heat also enters the mixing device to participate in the mixing. The high-temperature bypass is used to actively adjust the temperature and flow rate of the mixed heat transfer medium so that the main heat exchanger maintains a preset minimum heat exchange terminal difference. The heat transfer medium at the outlet of the main heat exchanger is connected to the inlet of the fluid circulation drive device to obtain heat again from the external thermal energy storage device through the direct or indirect heat exchange path; the system is used to provide main heat absorption, main steam superheating, and reheat heat when the system includes a reheater to the existing water / steam power generation circuit after the original boiler heating surface is taken out of operation.

2. The system according to claim 1, characterized in that: The heat transfer medium is selected from pure nitrogen, argon, air, carbon dioxide or a mixture thereof; the heat transfer medium is in a pure gaseous state, near-critical state, dense phase or supercritical state in the closed heat transfer medium loop.

3. The system according to claim 2, characterized in that: The heat transfer medium is pure carbon dioxide or a mixed medium with carbon dioxide as the main heat transfer component, and the circulation power of the closed heat transfer medium loop is provided by a carbon dioxide reflux compressor.

4. The system according to claim 1, characterized in that: When the external thermal energy storage device uses a graphite-containing carbon-based thermal storage medium with a maximum operating temperature of not less than 1000℃, the heat transfer medium is pure nitrogen or argon, and the circulation power of the closed heat transfer medium loop is provided by a high-temperature resistant circulating fan.

5. The system according to claim 4, characterized in that, The closed-loop heat transfer medium circuit is equipped with an online moisture monitoring and active explosion-proof isolation system. The isolation system includes a high-frequency trace moisture detector installed on the inlet pipe of the external thermal energy storage device, and a quick-cut-off isolation valve installed on the inlet and outlet main pipes of the external thermal energy storage device. When the moisture detector detects that the water vapor concentration in the heat transfer medium instantaneously exceeds a set threshold, the quick-cut-off isolation valve closes, cutting off the fluid connection between the external thermal energy storage device and the heat transfer medium-water / steam heat exchange network.

6. The system according to claim 1, characterized in that, The closed-loop heat transfer medium circuit and the existing water / steam power generation circuit exchange heat indirectly in the main heat exchanger, the main steam superheater, and the reheater when the system includes a reheater, without any other intermediate transition fluid circuits. High-pressure water, steam, or a steam-water mixture flows inside the tubes of the main heat exchanger, the main steam superheater, and the reheater when the system includes a reheater. The outside of the tubes is scourned by the heat transfer medium, so that the highest temperature of the metal tube wall of each heat exchanger is kept within a preset safety threshold under the action of convective heat transfer on the water side inside the tube.

7. The system according to claim 1, characterized in that, The indirect heat exchange method is an indirect dual heat exchange path; the heat extraction section of the heat transfer medium is the cold side flow channel of the intermediate heat exchanger, which is located between the outlet of the fluid circulation drive device and the high-temperature diversion device of the working medium; the system also includes a second heat transfer medium loop, which flows through the external heat storage device to obtain heat, and transfers the heat to the heat transfer medium in the closed heat transfer medium loop through the intermediate heat exchanger.

8. The system according to claim 1, characterized in that, The external thermal energy storage device is located outside the pressure boundary of the existing water / steam power generation circuit; the external thermal energy storage device exchanges heat with the closed heat transfer medium circuit, and water or steam does not enter the external thermal energy storage device, and the heat transfer medium does not enter the water / steam power generation circuit.

9. The system according to claim 1, characterized in that, The original boiler heating surface includes at least one of the original main steam heating surface, the original reheat heating surface, and the original feedwater heating surface; the original boiler heating surface is disconnected from the water / steam power generation circuit and is taken out of operation, and the external heat storage and heat transfer working medium heat island serves as the main heat source in the water / steam power generation circuit that replaces the original boiler heating surface.

10. The system according to claim 1, characterized in that, The external interface unit of the turbine island includes a feedwater interface, a main steam interface, and a reheat interface when the system includes a reheater; the feedwater interface connects the existing feedwater pipeline to the main heat exchanger, the main steam interface connects the main steam superheater to the existing main steam pipeline, and the reheat interface connects the reheater to the existing reheat pipeline; the external interface unit of the turbine island also includes at least one of an isolation valve, a check valve, a bypass valve, a temperature, pressure and flow measurement interface, and a control and communication interface.

11. The system according to claim 1, characterized in that, At least one of the following components is retained: steam turbine, generator, condenser, feedwater pump, steam extraction and regeneration equipment, shaft sealing system, vacuum system, and grid connection system, and operates in conjunction with the external heat storage and heat transfer working fluid heat island.

12. The system according to claim 1, characterized in that, When the system includes a reheater, the reheater includes a first-stage reheater and a second-stage reheater, and the reheat branch includes a first-stage reheat branch connected to the first-stage reheater and a second-stage reheat branch connected to the second-stage reheater; the minimum heat exchange terminal difference of the main heat exchanger is maintained within a preset range by adjusting at least one of the high-temperature bypass flow rate, the main steam superheat branch flow rate, the first-stage reheat branch flow rate, the second-stage reheat branch flow rate, and the total circulating flow rate of the heat transfer medium.

13. The system according to claim 12, characterized in that, The existing steam extraction and regeneration equipment undertakes at least part of the heating of condensate, low-pressure feedwater or high-pressure feedwater; the closed heat transfer working fluid loop is connected to the main heat absorber, the main steam superheater, the first-stage reheater and the second-stage reheater for heat exchange.

14. The system according to claim 1, characterized in that, The operating pressure of the heat transfer medium in the closed heat transfer medium loop is from 0.5 MPa to 40 MPa.

15. A method for retrofitting and operating an external heat storage and heat transfer working fluid heat island in an existing steam turbine generator set, characterized in that, include: S1. Remove the original boiler heating surface from operation; S2. An external thermal energy storage device, a closed heat transfer medium loop, and a heat transfer medium-water / steam heat exchange network are installed outside the turbine island. S3. Connect the main heat exchanger to the existing feedwater or main heat absorption section pipeline through the external interface unit of the turbine island, connect the main steam superheater to the existing main steam pipeline, and connect one, one or more reheaters according to the reheat configuration of the existing unit, without changing the cylinder pressure boundary and rotor flow structure of the existing turbine; S4. Make the heat transfer medium absorb the heat released by the second heat transfer medium by directly flowing through the external heat storage device or indirectly absorbing the heat through the intermediate heat exchanger to form a high-temperature heat transfer medium; S5. Make the high-temperature heat transfer medium... S6. Distribute the heat transfer medium to the main steam superheating branch, the high-temperature bypass, and one or more reheating branches when a reheater is installed; S7. Mix the heat transfer medium after heat release in each high-temperature heat exchange branch with the heat transfer medium in the high-temperature bypass in the mixing device before entering the main heat absorption heat exchanger; S8. Based on the main steam temperature, the reheat steam temperature corresponding to the reheat system configuration, the minimum heat exchange terminal difference of the main heat absorption heat exchanger, and the operating boundary of the fluid circulation drive device, coordinate and adjust the total circulation flow rate, the flow rate of each high-temperature heat exchange branch, and the flow rate of the high-temperature bypass.

16. The method according to claim 15, characterized in that, For operating conditions including a reheater, the reheater includes a first-stage reheater and a second-stage reheater, and the reheat branch includes a first-stage reheat branch connected to the first-stage reheater and a second-stage reheat branch connected to the second-stage reheater; based on at least one of the main steam temperature, primary reheat steam temperature, secondary reheat steam temperature, minimum heat exchange terminal difference of the main heat exchanger, and inlet heat transfer medium temperature of the external heat storage device, at least one of the following is adjusted: high-temperature bypass flow rate, main steam superheated branch flow rate, first-stage reheat branch flow rate, second-stage reheat branch flow rate, total circulating flow rate of heat transfer medium, feedwater flow rate, and extraction steam regeneration ratio.

17. The method according to claim 16, characterized in that, For operating conditions including reheaters, after the main steam temperature, primary reheat steam temperature, secondary reheat steam temperature, minimum heat exchange end difference of the main heat exchanger, and safety boundary of the fluid circulation drive device meet the preset conditions, the optimization control is carried out with the goal of increasing the ratio of the net output power of the steam turbine to the heat release power of the external thermal energy storage device.

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