Control System and Method for a Coal-Fired Power Unit with Steam Energy Storage Coupled with Molten Salt Thermal Energy Storage

Abstract

The present invention relates to a control system and method for a coal-fired unit coupled with molten salt heat storage using steam energy storage. This method constructs start / stop instructions for the molten salt system's heat storage process, then proposes a method for calculating the coal feedforward amount during the heat storage process, designs a feedforward compensation method for the boiler master control, and then proposes a control and switching method for the steam extraction valve. Finally, a corresponding interlocked start / shutdown method is designed for the molten salt pump. This control method proposes a logical switching and control configuration design method for heat storage / non-heat storage conditions, which improves the energy balance of the coupled molten salt coal-fired unit during the steam heat storage process, reduces large fluctuations in main steam pressure and unit load, and thereby enhances the safety of unit operation.

Description

Technical Field

[0001] The present invention relates to the technical field of molten salt thermal energy storage control, and particularly relates to a control system and method for a coal-fired power unit that utilizes steam energy storage to couple with molten salt thermal energy storage. Background Art

[0002] In recent years, the penetration rate of new energy sources such as wind power in the power system has been continuously increasing. However, the randomness and intermittency of new energy power generation such as wind power and solar energy are significantly different from those of traditional synchronous generators, posing a great threat to the stability and security of the power system frequency. At the same time, the capacity ratio of conventional units such as thermal power plants is gradually decreasing, resulting in a weakened system peak shaving and frequency modulation ability. Against this background, it is urgent for coal-fired power units in China to improve their own operation flexibility to support the consumption of a high proportion of new energy and maintain the safe and stable operation of the power system.

[0003] At present, coal-fired power units in China are innovating different flexible and intelligent operation technical means to improve the rapid load change and deep peak shaving operation capabilities of the units through flexibility transformation methods. Installing a molten salt thermal energy storage system is an important technical means proposed in recent years. Currently, research on the deep coupling of molten salt thermal energy storage systems and coal-fired power units generally focuses on the optimized design of the molten salt system structure, the heat transfer mechanism of the molten salt system, and the heat loss problems faced during the operation of high-temperature molten salt systems, as shown in the following references:

[0004] [1] Mao Cuiji, Yu Xiongjiang, Xu Jinliang, etc. Research progress on key technologies of a flexible peak shaving system for a thermal power unit coupled with molten salt energy storage [J]. Thermal Power Generation, 2023, 52(02): 10-22.

[0005] [2] Zou Xiaogang, Liu Ming, Xiao Haifeng, etc. Design and performance analysis of a deep peak shaving system for a thermal power unit coupled with molten salt energy storage [J]. Thermal Power Generation, 2023, 52(02): 146-153.

[0006] Currently, there is little research on the optimization of the operation control of the deep coupling of molten salt thermal energy storage systems and coal-fired power units. When the existing molten salt system stores heat, high-temperature and high-pressure steam is extracted from the unit, and the heat is transferred to the molten salt system through a heat exchanger and then enters the unit's thermal cycle. The molten salt system absorbs the heat released by the steam and changes from cold salt to hot salt to complete heat storage. In this process, a part of the energy in the boiler needs to be allocated to the molten salt system. However, the energy of the boiler comes from coal combustion, and there is a certain buffer time from the coal feeding amount to the main steam pressure. Currently, the molten salt system only relies on the feedback regulation of the boiler main controller during heat storage, and situations such as excessive deviation of the main steam pressure and deviation of the unit load from the set value often occur. In severe cases, the unit may even shut down. Therefore, in response to this situation, it is necessary to optimize the operation control program for the deep coupling of molten salt thermal energy storage and coal-fired power units to reduce / counteract the occurrence of the above situations, maintain the energy balance of the boiler and steam turbine, and protect the safety of the unit. Summary of the Invention

[0007] To overcome the deficiencies of the above-mentioned prior art, the present invention provides a control system and method for a coal-fired power unit coupled with molten salt heat storage using steam energy storage, specifically adopting the following technical solutions for a coal-fired power unit coupled with molten salt heat storage using steam energy storage:

[0008] A control system for a coal-fired power unit coupled with molten salt heat storage using steam energy storage, which includes a boiler, a steam turbine unit, a main steam pipeline, a branch steam pipeline, a heat exchanger, and a molten salt heat storage unit. The main steam pipeline connects the boiler and the steam turbine unit, and a steam extraction valve is provided on the main steam pipeline. One end of the branch steam pipeline is connected to the steam extraction valve, and the other end is connected to the feedwater heating system of the boiler. The heat exchanger is located on the branch steam pipeline, and the molten salt heat storage unit is connected to the heat exchanger. The heat of the branch steam pipeline is exchanged to the molten salt heat storage unit through the heat exchanger.

[0009] Optionally: The boiler is provided with a main controller, and a feedforward compensator is provided in the main controller. The feedforward compensator includes a compensated coal quantity signal line, and the compensated coal quantity signal line is used to control the main controller to output a compensated coal quantity during the heat storage stage.

[0010] The present invention also discloses a control method for a coal-fired power unit coupled with molten salt heat storage using steam energy storage, which is implemented using the above control system. The method includes the following steps:

[0011] S1. Generate a heat storage action instruction according to the heat storage control signal, the unit load state, and the liquid level state. The heat storage control signal includes a heat storage start control signal and a heat storage stop control signal, and the heat storage action instruction includes a heat storage start instruction and a heat storage stop instruction.

[0012] S2. Generate a coal feeding control signal according to the heat storage action instruction, and calculate the boiler compensated coal quantity according to a preset steam extraction flow rate.

[0013] S3. Perform feedforward compensation on the boiler main controller to generate a coal feeding execution signal, and control the boiler to perform the coal feeding action by the coal feeding execution signal.

[0014] S4. The heat storage action instruction is input into the first delay algorithm to generate a switching control signal, and a steam extraction valve opening signal is generated based on the switching control signal.

[0015] S5. The heat storage action instruction is input into the second delay algorithm to generate a molten salt pump interlock control signal, and the molten salt pump interlock control signal includes a molten salt pump interlock start signal and a molten salt pump interlock stop signal.

[0016] Optionally: The step of generating a heat storage action instruction according to the heat storage control signal, the unit load state, and the liquid level state includes:

[0017] Collect the current heat storage control signal, the load status of the coal-fired unit, and the liquid level information of the molten salt hot tank;

[0018] Judge that the heat storage control signal is a heat storage start control signal, the coal-fired unit is not in the load increasing state, and the liquid level of the molten salt hot tank is within the safe range, output a heat storage start command, and the heat storage process starts;

[0019] Judge that the heat storage control signal is a heat storage stop control signal, the coal-fired unit is in the load increasing state or the liquid level of the molten salt hot tank is higher than the preset upper threshold, output a heat storage stop command, and the heat storage process stops.

[0020] Optionally: The step of calculating the boiler compensation coal quantity according to the preset extraction steam flow rate includes:

[0021] Calculate the conversion efficiency of coal quantity and production capacity under the current working condition:

[0022] η = D st h st / u B ;

[0023] Where η is the conversion efficiency; D st is the main steam flow rate; h st is the main steam enthalpy value, obtained from the characteristics of water and steam; h st = f1(P st , T st ), f1 is the steam enthalpy value calculation function, P st is the measured value of the main steam pressure, T st is the measured value of the main steam temperature; u B is the current coal feeding quantity of the unit;

[0024] Calculate the set value of the extraction steam flow rate:

[0025] D sin = f2(N)

[0026] Where D sin is the extraction steam flow rate; f2 is the calculation function of the extraction steam flow rate; N is the current unit load;

[0027] Calculate the boiler compensation coal quantity Δu during heat storage according to the conversion efficiency and extraction steam flow rate calculation under the current working condition:

[0028] Δu = D sin h st / η.

[0029] Optionally: The step of performing feedforward compensation on the boiler main controller includes:

[0030] Add a compensation coal quantity signal line to the feedforward compensator of the boiler main controller;

[0031] The output u of the compensation coal quantity signal line selection module forms u / (Ts + 1) through an inertia link, where T is the inertia time constant and s is the Laplace operator;

[0032] The selection module includes an output channel u, a first input channel Δu, a second input channel 0, and a switching condition D;

[0033] When the switching condition D = 1, that is, the heat storage action instruction is a heat storage start instruction, the output channel u of the selection module outputs the value of the first input channel Δu, and at this time, the boiler main controller outputs a coal feeding execution signal;

[0034] When the switching condition D = 0, that is, the heat storage action instruction is a heat storage stop instruction, the output channel u of the selection module outputs the value of the second input channel 0, and at this time, the boiler main controller does not output a coal feeding execution signal.

[0035] Optionally: The steps of performing feedforward compensation on the boiler main controller include:

[0036] Add a compensation coal quantity signal line to the feedforward compensator of the boiler main controller;

[0037] The output u of the compensation coal quantity signal line selection module forms u / (Ts + 1) through an inertia link, where T is the inertia time constant and s is the Laplace operator;

[0038] The selection module includes an output channel u, a first input channel Δu, a second input channel 0, and a switching condition D;

[0039] When the switching condition D = 1, that is, the heat storage action instruction is a heat storage start instruction, the output channel u of the selection module outputs the value of the first input channel Δu, and at this time, the boiler main controller outputs a coal feeding execution signal;

[0040] When the switching condition D = 0, that is, the heat storage action instruction is a heat storage stop instruction, the output channel u of the selection module outputs the value of the second input channel 0, and at this time, the boiler main controller does not output a coal feeding execution signal.

[0041] Optionally: The steps of inputting the heat storage action instruction into the first delay algorithm to generate a switching control signal and generating a steam extraction valve opening signal based on the switching control signal include:

[0042] The heat storage action instruction is input into the first delay algorithm to generate a switching control signal:

[0043] D(t - τ);

[0044] Where t is time and τ is the lag time of the coal pulverizing system and the combustion process, which is determined by the coal pulverizing system and the fuel combustion characteristics of the current boiler;

[0045] When the switching control signal changes from 0 to 1, the heat storage starts, and the extraction steam valve opening signal changes from 0 to the output value of the PID based on the extraction steam flow control, where the input quantities of the PID based on the extraction steam flow control are the extraction steam flow set value and the measured extraction steam flow value respectively;

[0046] When the switching control signal changes from 1 to 0, the heat storage shuts down, and the extraction steam valve opening signal changes from the output value of the PID based on the extraction steam flow control to 0, where the input quantities of the PID based on the extraction steam flow control are the extraction steam flow set value and the measured extraction steam flow value respectively.

[0047] Optionally: The step of generating the molten salt pump interlock control signal by inputting the heat storage action instruction into the second delay algorithm includes:

[0048] When the heat storage process starts, the heat storage start instruction generates the molten salt pump interlock control signal after a delay time γ:

[0049] Molten salt pump interlock control signal = D(t - γ);

[0050] Where D is the heat storage start control signal; γ is the delay time of the molten salt pump interlock control signal, γ = τ - δ, τ is the lag time of the coal pulverizing system and the combustion process, and δ is an empirically set constant value;

[0051] When the heat storage process shuts down, the heat storage stop instruction generates the molten salt pump interlock control signal after a delay time γ:

[0052] Molten salt pump interlock control signal = NOT[D(t - γ)];

[0053] Where NOT is the logical NOT calculation; D is the heat storage start control signal; γ is the delay time of the molten salt pump interlock control signal, γ = τ - δ, τ is the lag time of the coal pulverizing system and the combustion process, and δ is an empirically set constant value.

[0054] Furthermore, the present invention also discloses a non - volatile storage medium, and the non - volatile storage medium includes a stored program, wherein when the program runs, it controls the device where the non - volatile storage medium is located to execute the above - mentioned control method.

[0055] In addition, the present invention also discloses a device including a processor and a memory; computer - readable instructions are stored in the memory, and the processor is used to run the computer - readable instructions, wherein when the computer - readable instructions run, they execute the above - mentioned control method.

[0056] Beneficial Effects

[0057] The technical solution of the present invention has obtained the following beneficial effects:

[0058] In the control method of the present invention, during the molten salt heat storage process, with the issuance of the heat storage instruction, the compensated coal quantity can be calculated and added. After the compensated coal quantity burns and releases heat sufficiently, the branch steam pipeline is opened for heat storage. This method enables the boiler to maintain sufficient energy before steam extraction during the molten salt heat storage process, reduces the energy mismatch during the steam extraction stage, and thereby reduces the fluctuations of the main steam pressure and the unit load, effectively improving the operating stability and safety of the unit. Description of the Drawings

[0059] Figure 1 It is a schematic structural diagram of the control system of a coal-fired power unit using steam energy storage to couple molten salt heat storage according to the present invention;

[0060] Figure 2 It is a schematic structural diagram of the boiler main controller of a common existing unit;

[0061] Figure 3 It is a simplified schematic control structure diagram of the steam extraction valve of a common existing unit;

[0062] Figure 4 It is a composition diagram of the interlock start / stop processing logic structure of the molten salt pump of a common existing unit;

[0063] Figure 5 It is a schematic diagram of the optimized structure of the boiler main control according to the embodiment of the present invention, where the dotted box is the added compensated coal quantity signal line;

[0064] Figure 6 It is a schematic diagram of the optimized control structure of the steam extraction valve according to the embodiment of the present invention;

[0065] Figure 7 It is a composition diagram of the interlock start / stop processing logic structure according to the embodiment of the present invention;

[0066] Figure 8 It is a command signal curve diagram when the molten salt system stores heat according to the embodiment of the present invention;

[0067] Figure 9 It is a feed-forward curve diagram of coal feeding during the heat storage process of the molten salt system according to the embodiment of the present invention;

[0068] Figure 10 It is a signal curve diagram of the steam extraction valve opening instruction when the molten salt system stores heat according to the embodiment of the present invention, with a 100s delay;

[0069] Figure 11 It is a signal curve diagram of the steam extraction valve opening instruction when the molten salt system stores heat according to the embodiment of the present invention. Detailed Embodiment

[0070] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and cannot be used to limit the protection scope of the present invention. It should be noted that the following detailed description is exemplary and is intended to provide further description of the present application.

[0071] Currently, the boiler master control mode of conventional coal-fired units is as Figure 2 shown. The boiler master controller is composed of two parts superimposed. One part is the feedforward signal line for unit load calculation, and the other part is the output line of the PID controller. The inputs of the PID controller are the main steam pressure set value and the measured value respectively. The existing coal-fired units' extraction steam valve control logic during the extraction steam heat storage process is as Figure 3 shown. When the extraction steam process starts, the extraction steam valve opening command switches from 0 opening to extraction steam flow control. The extraction steam flow uses a PID controller, and the input quantities are the extraction steam flow set value and the measured value respectively. Similarly, the start and stop conditions of the molten salt pump are as Figure 4 shown. When the flag bit D changes from 0 to 1, the interlock start condition of the molten salt pump is synchronously generated, and the molten salt pump starts to open. When the flag bit D changes from 1 to 0, the interlock stop condition of the molten salt pump is synchronously generated, and the molten salt pump starts to close. However, when the existing equipment coupling molten salt heat storage and coal-fired units uses steam for heat storage, it does not consider the energy loss of the boiler during heat storage in advance and cannot supplement it in time, resulting in the bad consequences of untimely adjustment of the boiler coal feeding amount and large fluctuations in the main steam pressure.

[0072] In view of this phenomenon, the present invention optimizes the coal feeding feedforward control process during the molten salt heat storage process. After the molten salt heat storage instruction is issued, first, according to the heat loss of the main steam pipeline (i.e., the heat transferred to the molten salt heat storage), the coal feeding amount is preferentially added to the boiler. After the newly added coal enters the furnace and burns to release heat, then the extraction steam heat storage is carried out, which can effectively reduce the large fluctuations in the boiler energy during the heat storage process and plays an important role in maintaining the stable operation of the unit.

[0073] The control system of the coal-fired unit coupling steam energy storage and molten salt heat storage of the present invention is as Figure 1 shown. The system includes a boiler, a steam turbine unit, a main steam pipeline, a branch steam pipeline, a heat exchanger, and a molten salt heat storage unit. The main steam pipeline connects the boiler and the steam turbine unit, and a steam extraction valve is provided on the main steam pipeline; one end of the branch steam pipeline is connected to the steam extraction valve, and the other end is connected to the feedwater heating system of the boiler; the heat exchanger is located on the branch steam pipeline, and the molten salt heat storage unit is connected to the heat exchanger, and the heat of the branch steam pipeline is exchanged to the molten salt heat storage unit through the heat exchanger. This structure is transformed on the original coal-fired unit boiler-steam turbine system. An additional branch steam pipeline is externally connected to the main steam pipeline or other steam pipelines, and the steam extraction flow is controlled by the opening of the steam extraction valve. The opening of the steam valve is u t , and a steam extraction flow measuring point D is set sin, and temperature measurement point T is set st and pressure measurement point P st . The steam in the branch steam pipeline enters the regenerative system after releasing heat through the heat exchanger to complete the cycle. On the molten salt side, the cold salt in the molten salt cold tank is pumped out by the molten salt pump, enters the molten salt hot tank after absorbing heat through the heat exchanger, and completes the heat storage of the molten salt system.

[0074] In addition, the boiler described in the present invention is provided with a main controller, and a feedforward compensator is provided in the main controller. The feedforward compensator includes a compensated coal quantity signal line, and the compensated coal quantity signal line is used to control the main controller to output a compensated coal quantity during the heat storage stage.

[0075] Furthermore, the present invention also discloses a control method for a coal-fired unit using steam energy storage coupled with molten salt heat storage, which is implemented by using the above control system. The method includes the following steps:

[0076] S1. Generate a heat storage action instruction according to the heat storage control signal, the unit load state, and the liquid level state; the heat storage control signal includes a heat storage start control signal and a heat storage stop control signal, and the heat storage action instruction includes a heat storage start instruction and a heat storage stop instruction;

[0077] Specifically, the specific process of generating the heat storage action instruction in this embodiment is as follows:

[0078] Collect the current heat storage control signal, the load state of the coal-fired unit, and the liquid level information of the molten salt hot tank;

[0079] Judge that the heat storage control signal is a heat storage start control signal, the coal-fired unit is not in the load increasing state, and the liquid level of the molten salt hot tank is within the safe range, that is, when the above conditions are all met, output a heat storage start instruction, and the heat storage process starts. At this time, the flag bit D is set to 1; as Figure 8 shown, the control system of this embodiment officially forms a heat storage start instruction signal at time 0.

[0080] Judge that the heat storage control signal is a heat storage stop control signal, the coal-fired unit is in the load increasing state or the liquid level of the molten salt hot tank is higher than the preset upper threshold, that is, when any of the above conditions is met, output a heat storage stop instruction, and the heat storage process stops. At this time, the flag bit D is set to 0.

[0081] S2. Generate a coal feeding control signal according to the heat storage action instruction, and calculate the boiler compensated coal quantity according to the preset extraction steam flow rate;

[0082] Specifically, the specific process of calculating the boiler compensated coal quantity according to the preset extraction steam flow rate includes:

[0083] Calculate the conversion efficiency of coal quantity and production capacity under the current working condition:

[0084] η = D st h st / u B ;

[0085] where η is the conversion efficiency; D st is the main steam flow rate; h st is the main steam enthalpy value, obtained from the properties of water and steam; h st = f1(P st , T st ), f1 is the steam enthalpy value calculation function, P st is the measured value of the main steam pressure, T st is the measured value of the main steam temperature; u B is the current coal feeding amount of the unit;

[0086] Calculate the set value of the extraction steam flow rate:

[0087] D sin = f2(N)

[0088] where D sin is the extraction steam flow rate; f2 is the calculation function of the extraction steam flow rate; N is the current unit load;

[0089] Calculate the boiler compensation coal amount Δu according to the conversion efficiency and the extraction steam flow rate calculation under the current working condition:

[0090] Δu = D sin h st / η.

[0091] S3. Perform feed-forward compensation on the boiler main controller to generate a coal feeding execution signal, and control the boiler to perform the coal feeding action by the coal feeding execution signal;

[0092] Specifically, the specific steps of the above feed-forward compensation for the boiler main controller include:

[0093] As Figure 5 shown, add a compensation coal amount signal line to the feed-forward compensator of the boiler main controller; the existing feed-forward compensator of the boiler main controller currently includes a load command calculation signal line and a main steam pressure signal line. In this embodiment, a compensation coal amount signal line is added to realize the control of the boiler coal feeding action.

[0094] The compensation coal amount signal line forms u / (Ts + 1) from the output u of the selection module through an inertia link, where T is the inertia time constant and s is the Laplace operator;

[0095] The selection module includes an output channel u, a first input channel Δu, a second input channel 0, and a switching condition D;

[0096] When the switching condition D = 1, that is, the heat storage action instruction is a heat storage start instruction, the output channel u of the selection module outputs the value of the first input channel Δu. At this time, the boiler main controller outputs a coal feeding execution signal, such as Figure 9 shown, to realize the coal feeding action of the boiler;

[0097] When the switching condition D = 0, that is, the heat storage action instruction is a heat storage stop instruction, the output channel u of the selection module outputs the value of the second input channel 0. At this time, the boiler main controller does not output a coal feeding execution signal, indicating that the heat storage process is over.

[0098] S4. The heat storage action instruction is input into the first delay algorithm to generate a switching control signal, and a steam extraction valve opening signal is generated based on the switching control signal;

[0099] Specifically, as Figure 6 shown, in this embodiment, when starting heat storage, the steam extraction process will be started after a certain delay. The steam extraction valve opening instruction is switched from the 0 opening to the steam extraction flow control. The steam extraction flow uses a PID controller, and the input quantities are the steam extraction flow set value and the measured value respectively. Further, the steps of inputting the heat storage action instruction into the first delay algorithm to generate a switching control signal and generating a steam extraction valve opening signal based on the switching control signal include:

[0100] The heat storage action instruction D is input into the first delay algorithm to generate a switching control signal:

[0101] D(t - τ);

[0102] where t is time and τ is the lag time of the coal pulverizing system and the combustion process, which is determined by the coal pulverizing system and the fuel combustion characteristics of the current boiler, generally about 90 - 270 s;

[0103] When the switching control signal changes from 0 to 1, heat storage starts, and the steam extraction valve opening signal changes from 0 to the output value of the PID based on the steam extraction flow control. The input quantities of the PID based on the steam extraction flow control are the steam extraction flow set value and the measured steam extraction flow value respectively; based on the above control process, this embodiment can control the unit to first compensate the coal quantity to the boiler and fully burn for a certain time after the heat storage start instruction is issued, and then start the steam extraction process to ensure the stability of the boiler and the main steam flow.

[0104] For example, in this embodiment, the lag time is set to 100 s, and the result is as Figure 10 shown. Then, after the heat storage start instruction is issued, the steam extraction valve opening instruction is generated only at the 100th second. At this time, the steam extraction valve opening signal is switched from 0 to the output value of the PID based on the steam extraction flow control. During this stage, the steam extraction valve opening will be controlled by the steam extraction flow. The input quantities of this PID are the steam extraction flow set value D sin and the measured steam extraction flow value, and the result of this PID controller is as Figure 11As shown, after receiving the opening instruction at the 100th second, after a certain degree of fluctuation, the extraction valve opening finally stabilizes at a certain value, ensuring that the actual extraction flow rate is equal to the set value D of the extraction flow rate. sin ;

[0105] When the switching control signal changes from 1 to 0, the heat storage is closed, and the extraction valve opening signal changes from the output value of the PID based on the extraction flow rate control to 0, where the input quantities of the PID based on the extraction flow rate control are the set value of the extraction flow rate and the measured value of the extraction flow rate respectively.

[0106] S5. The heat storage action instruction is input into the second delay algorithm to generate the molten salt pump interlock control signal, and the molten salt pump interlock control signal includes the molten salt pump interlock start signal and the molten salt pump interlock stop signal.

[0107] Specifically, the specific process of the above-mentioned heat storage action instruction input into the second delay algorithm to generate the molten salt pump interlock control signal includes:

[0108] When the heat storage process starts, the heat storage start instruction generates the molten salt pump interlock control signal after a delay time γ:

[0109] Molten salt pump interlock control signal = D(t - γ);

[0110] Where D is the heat storage start control signal; γ is the delay time of the molten salt pump interlock control signal, γ = τ - δ, τ is the lag time of the coal pulverizing system and the combustion process, and δ is an empirically set constant value, generally set between 30 - 60 s;

[0111] When the heat storage process is closed, the heat storage stop instruction generates the molten salt pump interlock control signal after a delay time γ:

[0112] Molten salt pump interlock control signal = NOT[D(t - γ)];

[0113] Where NOT is the logical NOT calculation; D is the heat storage start control signal; γ is the delay time of the molten salt pump interlock control signal, γ = τ - δ, τ is the lag time of the coal pulverizing system and the combustion process, and δ is an empirically set constant value, generally set between 30 - 60 s.

[0114] Combined with Figure 7 As shown, in this embodiment, when the heat storage process starts, the flag bit D changes from 0 to 1. At this time, after calculation by the delay algorithm, the molten salt pump interlock start condition will be generated after a certain time, and the molten salt pump starts to open; when the heat storage process stops, the flag bit D changes from 1 to 0. At this time, the logical NOT calculation is performed, and the molten salt pump interlock stop condition is immediately generated, and the molten salt pump closes.

[0115] Further, the present invention also discloses a non-volatile storage medium, which includes a stored program. When the program runs, it controls the device where the non-volatile storage medium is located to execute the above control method.

[0116] In addition, the present invention also discloses a device including a processor and a memory; computer-readable instructions are stored in the memory, and the processor is used to run the computer-readable instructions. When the computer-readable instructions run, they execute the above control method.

[0117] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable non-transitory storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program code.

[0118] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices, and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0119] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured product including an instruction device, and the instruction device implements the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0120] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide for implementing the functions specified in Figure 1 one process or multiple processes and / or blocks Figure 1Steps of the functions specified in one or more boxes.

[0121] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A control method for a coal-fired power unit using steam energy storage coupled with molten salt heat storage, characterized in that, It includes the following steps: S1. Generate a thermal energy storage action instruction according to the thermal energy storage control signal, the unit load status, and the liquid level status; the thermal energy storage control signal includes a thermal energy storage start control signal and a thermal energy storage stop control signal, and the thermal energy storage action instruction includes a thermal energy storage start instruction and a thermal energy storage stop instruction; S2. Generate a coal feeding control signal according to the thermal energy storage action instruction, and calculate the boiler compensation coal quantity according to the preset extraction steam flow rate: Calculate the conversion efficiency of coal quantity and production capacity under the current working condition: η = D st h st / u B ; where η is the conversion efficiency; D st is the main steam flow rate; h st is the main steam enthalpy value, obtained from the properties of water and steam; h st = f1(P st , T st ), f1 is the steam enthalpy value calculation function, P st is the measured value of the main steam pressure, T st is the measured value of the main steam temperature; u B is the current coal feeding amount of the unit; Calculate the set value of the extraction steam flow rate: D sin = f2(N); Among which D sin is the extraction steam flow rate; f2 is the calculation function of the extraction steam flow rate; N is the current unit load; Calculate the boiler compensation coal quantity Δu during thermal energy storage according to the conversion efficiency and the extraction steam flow rate under the current working condition: Δu = D sin h st / η; Calculate the boiler compensation coal quantity during thermal energy storage according to the conversion efficiency and the extraction steam flow rate under the current working condition; S3. Perform feedforward compensation on the boiler main controller to generate a coal feeding execution signal, and control the boiler to perform the coal feeding action by the coal feeding execution signal; Among them, the step of performing feedforward compensation on the boiler main controller includes: Add a compensation coal quantity signal line to the feedforward compensator of the boiler main controller; The compensation coal quantity signal line forms u / (Ts + 1) from the output u of the selection module through an inertia link, where T is the inertia time constant and s is the Laplace operator; The selection module includes an output channel u, a first input channel Δu, a second input channel 0, and a switching condition D; When the switching condition D = 1, that is, the thermal energy storage action instruction is a thermal energy storage start instruction, the output channel u of the selection module outputs the value of the first input channel Δu, and at this time, the boiler main controller outputs a coal feeding execution signal; When the switching condition D = 0, that is, the thermal energy storage action instruction is a thermal energy storage stop instruction, the output channel u of the selection module outputs the value of the second input channel 0, and at this time, the boiler main controller does not output a coal feeding execution signal; S4. The thermal energy storage action instruction is input into a first delay algorithm to generate a switching control signal, and a steam extraction valve opening signal is generated based on the switching control signal: The thermal energy storage action instruction is input into a first delay algorithm to generate a switching control signal: D(t - τ); Where t is time and τ is the lag time of the coal pulverizing system and the combustion process, which is determined by the coal pulverizing system and the fuel combustion characteristics of the current boiler; When the switching control signal changes from 0 to 1, thermal energy storage starts, and the steam extraction valve opening signal changes from 0 to the output value of the PID based on the extraction steam flow control, where the input quantities of the PID based on the extraction steam flow control are the set value of the extraction steam flow rate and the measured value of the extraction steam flow rate respectively; When the switching control signal changes from 1 to 0, thermal energy storage is closed, and the steam extraction valve opening signal changes from the output value of the PID based on the extraction steam flow control to 0, where the input quantities of the PID based on the extraction steam flow control are the set value of the extraction steam flow rate and the measured value of the extraction steam flow rate respectively; S5. The thermal energy storage action instruction is input into a second delay algorithm to generate a molten salt pump interlock control signal, and the molten salt pump interlock control signal includes a molten salt pump interlock start signal and a molten salt pump interlock stop signal: When the thermal energy storage process starts, the thermal energy storage start instruction generates a molten salt pump interlock control signal after a delay time γ: Molten salt pump interlock control signal = D(t - γ); Where D is the thermal energy storage start control signal; γ is the delay time of the molten salt pump interlock control signal, γ = τ - δ, τ is the lag time of the coal pulverizing system and the combustion process, and δ is an empirically set constant value; When the heat storage process is shut down, a heat storage stop instruction generates a molten salt pump interlock control signal after a delay time γ: Molten salt pump interlock control signal = NOT[D(t - γ)]; where NOT is a logical NOT calculation; D is a heat storage start control signal; γ is the delay time of the molten salt pump interlock control signal, γ = τ - δ, τ is the lag time of the coal pulverizing system and the combustion process, and δ is an empirically set constant value.

2. The control method according to claim 1, wherein The step of generating a heat storage action instruction according to the heat storage control signal, the unit load status, and the liquid level status includes: Collect the current heat storage control signal, the load status of the coal-fired unit, and the liquid level information of the molten salt hot tank; Judge that the heat storage control signal is a heat storage start control signal, the coal-fired unit is not in a load increasing state, and the liquid level of the molten salt hot tank is within the safe range, and output a heat storage start instruction, and the heat storage process starts; Judge that the heat storage control signal is a heat storage stop control signal, the coal-fired unit is in a load increasing state or the liquid level of the molten salt hot tank is higher than the preset upper threshold, and output a heat storage stop instruction, and the heat storage process stops.

3. A control system for a coal-fired power unit that utilizes steam energy storage coupled with molten salt heat storage, characterized in that, The control system operates according to the control method described in claim 1 or 2. The control system includes a boiler, a steam turbine unit, a main steam pipeline, a branch steam pipeline, a heat exchanger, and a molten salt heat storage unit. The main steam pipeline connects the boiler and the steam turbine unit, and a steam extraction valve is provided on the main steam pipeline; one end of the branch steam pipeline is connected to the steam extraction valve, and the other end is connected to the feedwater heating system of the boiler; the heat exchanger is located on the branch steam pipeline, and the molten salt heat storage unit is connected to the heat exchanger, and the heat of the branch steam pipeline is exchanged to the molten salt heat storage unit through the heat exchanger.

4. The control system according to claim 3, characterized in that The boiler is provided with a main controller, and a feedforward compensator is provided in the main controller. The feedforward compensator includes a compensated coal quantity signal line, and the compensated coal quantity signal line is used to control the main controller to output a compensated coal quantity during the heat storage stage.

5. A non-volatile storage medium, characterized in that, The non-volatile storage medium includes a stored program. When the program runs, it controls the device where the non-volatile storage medium is located to execute the control method described in claim 1 or 2.

6. An electronic device, characterized in that, It includes a processor and a memory; computer-readable instructions are stored in the memory, and the processor is used to run the computer-readable instructions. When the computer-readable instructions run, they execute the control method described in claim 1 or 2.

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