Thermal power generating unit isolated network electrified and thermal load operation method under participation of heat storage device

Abstract

The invention discloses a thermal power generating unit isolated network electrified and thermal load operation method with participation of a heat storage device, and belongs to the technical field of thermal power generating unit safe operation. On the basis of a combined system model, the electric heating load balance relation of the system after the electric boiler is added is established by analyzing the condition of the electric heating load of the power generation thermal power generating unit during isolated network operation and the operation characteristics of the electric boiler with continuous power change, and finally the thermal power generating unit isolated network electrified and thermal load operation method under the participation of the electric boiler is designed. According to the method, from the perspective of economy, the scheduling method that the electric boiler participates in power grid adjustment under different scheduling requirements is provided, and the dual potential that the electric boiler serves as an electric load to participate in heat supply is brought into full play. The method can practically improve the power and heat preservation capability of the thermal power generating unit-electric boiler combined system when the power grid breaks down, and has great practical significance for solving the practical problems that the power grid in the alpine region is insufficient in extreme weather disaster resistance and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of safe operation of thermal power units, and in particular relates to an isolated grid energized and heat load operation method for a thermal power unit with the participation of a heat storage device. Background Art

[0002] Extreme weather is prone to occur in high-cold areas. The probability of power grid accidents increases under extreme weather. After an accident occurs, the thermal power units in the faulty circuit will be disconnected from the power grid. However, due to the large demand for heating in residents in high-cold areas, there are many cogeneration thermal power units that undertake heating tasks. These thermal power units have thermal-electric coupling. Once a power grid failure occurs, it may even cause large-scale power outages and heating. Therefore, it is an urgent problem to ensure the stable operation of the cogeneration thermal power units in the isolated grid when the power grid fails. As an electric-driven load, electric boilers can not only serve as the electric load of the isolated grid, but also cooperate with steam turbines to provide heat to meet the heat load demand. They have great application prospects in coordinating the power and heat load of the isolated grid of thermal power units. They can effectively ensure the stable operation of the power grid and meet the heating needs of residents. It is an extremely economical regulation strategy.

[0003] Regarding the control technology of thermal power unit isolated grid operation, the most classic one is the fast load shedding technology (FCB technology) of thermal power unit. FCB technology can make the thermal power unit enter the isolated operation state after being disconnected from the grid when the grid fails. In response to this, domestic and foreign scholars have made a lot of research. Regarding the control of thermal power units themselves, some scholars have proved that some large-capacity thermal power units have the ability to achieve FCB operation under rated load; and some researchers have realized the FCB function in 1000MW thermal power units, verifying the effectiveness of the technology; Regarding how to better operate the components of thermal power units, some scholars have designed a sudden load shedding multi-actuator coordinated control strategy to achieve stable speed control; Regarding OPC control in the FCB process, some researchers used the actual operation failure of a certain power generation thermal power unit to analyze the impact of the OPC overspeed protection setting value on the operation of the grid, and gave fault resolution measures. For the application of electric boilers, some researchers have proposed an optimized operation strategy for the cogeneration system with the participation of electric boilers. The objective function is selected as the minimum operating cost of the system, and an optimization scheduling model is established based on this, verifying that the addition of electric boilers does reduce the effectiveness of the degree of thermal-electric coupling.

[0004] In summary, the current research on emergency process control technology for thermal power units, both at home and abroad, is mainly based on FCB technology. However, both at home and abroad, the research on FCB technology is still mainly limited to the traditional thermal power units themselves, studying how to change their structure or how the components of the thermal power units operate, such as studying the shutdown sequence of the coal mill, etc., and the ability to solve the thermal-electric coupling problem of the cogeneration thermal power units is limited. The addition of auxiliary equipment such as electric boilers can reduce the degree of thermal-electric coupling and effectively improve the stability of the power grid operation. However, there are currently few studies on how to coordinate the operation of the thermal power units with isolated grids and thermal loads after the addition of auxiliary equipment such as electric boilers, and how to control various systems during operation. The research on the control strategy of thermal power units with the participation of auxiliary equipment is still in a relatively early stage.

[0005] Therefore, a new technical solution is urgently needed in the prior art to solve this problem. Summary of the invention

[0006] The technical problem to be solved by the present invention is: to provide a method for operating a thermal power unit in an isolated grid with power on and under heat load with the participation of a heat storage device, so as to solve the current technical problems of how to coordinate the operation of the thermal power unit in an isolated grid with power on and under heat load with the addition of auxiliary equipment, how to control each system during operation, and the control strategy of the thermal power unit with the participation of auxiliary equipment.

[0007] The method for operating a thermal power unit in an isolated grid with power and heat load under the participation of a heat storage device comprises the following steps, which are performed in sequence:

[0008] Step 1: Establish a joint system model including the thermal power unit model and the simplified power model of the electric boiler

[0009] The thermal power unit model includes a main steam turbine, a drum boiler and a corresponding speed regulating system; wherein the output power of the main steam turbine is obtained in two ways: one is that under the condition of a certain main steam pressure of the main steam turbine, the output power of the steam turbine is proportional to the valve opening of the regulating steam valve in front of the high-pressure cylinder; the other is that the main steam turbine obtains the output power by adding the output powers of the high-, medium- and low-pressure cylinders of the steam turbine;

[0010] The drum boiler includes a combustion chamber model, a boiler pressure model and a burner swing angle model;

[0011] The speed regulation system includes primary frequency modulation, secondary frequency modulation and peak regulation; the primary frequency modulation uses the frequency difference as a feedback signal; the secondary frequency modulation and peak regulation use the automatic generation control AGC command issued by the dispatching center as a control signal; the primary frequency modulation, secondary frequency modulation and peak regulation together form a comprehensive valve position command to achieve speed regulation;

[0012] The simplified power model of electric boiler adopts the power model of jet electrode electric boiler;

[0013] Step 2: Obtain the balance relationship between the electric load and the heat load of the joint system model after the electric boiler is added

[0014] The balance relationship of electric load is that the load carried by the thermal power unit is equal to the difference between the actual output power of the steam turbine and the power consumption of the electric boiler. The balance relationship of electric load is shown in the following formula:

[0015] P dfh =P qljgl -P dglgl

[0016] Where P dfh P is the load of the thermal power unit; qljgl is the actual output power of the steam turbine; P dglgl P is the power consumption of electric boiler; dfh , P qljgl and P dglgl All are values ​​​​normalized to the corresponding parameters under rated heating conditions;

[0017] The actual output power of the steam turbine is related to the operating power of the thermal power unit and the opening of the steam extraction valve, as shown in the following formula:

[0018] P qljgl =P hd +P hd (1-F cq )K rd

[0019] In the formula, F cq P is the per unit opening value of the extraction valve; hd is the operating power of the thermal power unit; K rd is the thermoelectric conversion coefficient;

[0020] The heat load balance relationship is that the heat load of the thermal power unit is equal to the sum of the unit's steam extraction heating, electric boiler heating and heat storage tank heat exchange, where heat storage is positive and heat release is negative. The heat load balance relationship is shown in the following formula:

[0021] P rfh =P cq +P dglgr -P xrggr

[0022] Where P rfh P is the heat load of the thermal power unit; cq Extract steam to supply heat for heating; P dglgr Provide heat for electric boiler; P xrggr Provide heat for the heat storage tank; P cq , P dglgr and P xrggr All are values ​​​​normalized to the corresponding parameters under rated heating conditions;

[0023] Among them, the heating steam heat supply P cq The operating power P of the thermal power unit hd And the extraction valve opening is calculated and obtained as shown in the following formula:

[0024] P cq =P hd F cq

[0025] Electric boiler power consumption P dglgl Heat supply from electric boiler P dglgr The relationship is as follows:

[0026] P dglgr =P dglgl λk by

[0027] Where, λ is the efficiency of the electric boiler; k by It is the coefficient used for per unit, which is related to the rated extraction steam heating capacity;

[0028] Step 3: For the case where the electric power of the electric boiler is continuously adjustable, set the isolated grid stable operation strategy when it cooperates with the thermal power unit

[0029] For the case where the electric power is continuously adjustable, the following operating methods are set:

[0030] Taking the electrical load and thermal load of the thermal power unit as input, after judgment and execution, the final output is the set operating power of the unit, the input power of the electric boiler and the opening of the steam extraction valve under different conditions. Among them, the conversion relationship between the thermal load and the electrical load is connected through the conversion coefficient of the two processes;

[0031] The judgment and execution process is as follows:

[0032] The loads carried by thermal power units under isolated grid operation conditions mainly fall into the following three situations:

[0033] Case 1: The electrical load and thermal load of the thermal power unit are very small, both lower than the minimum operating load limit of the boiler;

[0034] Case 2: The electrical load of the thermal power unit is greater than or equal to the minimum electrical load required to meet the thermal load;

[0035] Case 3: The electrical load of the thermal power unit is less than the minimum electrical load required to meet the thermal load;

[0036] Condition 1 is used to determine whether the load of the thermal power unit meets condition 1. Condition 1 is expressed as follows:

[0037] P dfh ≤P min

[0038] ∧P rfh ≤-K dr P dfh +(1+K dr ) min

[0039] ∨P min ≤P dfh ≤P min (1+K rd )

[0040]

[0041] In the formula, P min is the minimum load power of the electric boiler, take 0.3; K dr is the electric heat conversion coefficient, which is taken as 0.9 here; K rd is the thermoelectric conversion coefficient, which is taken as 0.1263 here; ∧ means and, ∨ means or;

[0042] If condition 1 is met, the electric boiler is put into operation. By adjusting the power of the electric boiler, the thermal power unit can operate at the lowest load. As an electrical device, the electric boiler is both the electrical load of the thermal power unit and a heating device. It can meet the heat load demand together with the thermal power unit. Adjustment is performed according to execution 1 as shown below:

[0043] P hd =P min

[0044] P dgl =P hd -P dfh

[0045]

[0046] In the formula, P dgl is the operating power of the electric boiler, F cq is the opening of the extraction valve;

[0047] If the condition 1 is not met, the unit operating power is temporarily set to the minimum power required to meet the electrical load, and is adjusted by executing 2. Execution 2 is as follows:

[0048] P hd =P dfh

[0049] Then, through condition 2, it is determined whether the load condition of the thermal power unit belongs to condition 2 or condition 3. Condition 2 is expressed as follows:

[0050] P rfh ≤P hd

[0051] If condition 2 is met, it is determined to belong to situation 2. Adjustment is performed by executing 3, that is, the electric boiler does not need to be put into use, and the opening of the steam extraction valve is adjusted to reduce the main steam flow of the thermal power unit and the heating steam extraction at the same time, but the output power is increased externally until the thermal power unit operates at the minimum power required to meet the electricity and heat loads. Execution 3 is expressed as follows:

[0052]

[0053] P dgl =0

[0054]

[0055] If condition 2 is not met, it is judged as situation 3. Adjustment is made by executing 4, that is, the electric boiler is put into operation, the opening of the steam extraction valve is kept at the maximum, and the sum of the heating supply of the electric boiler plus the heating supply increment of the unit power meets the heating load demand. In order to be economical, the unit needs to operate at the lowest power under the premise of ensuring the heat load. Execution 4 is expressed as follows:

[0056]

[0057] P dgl =P hd -P dfh

[0058] F cq =1

[0059] Among them, P min Take 0.3; K dr Take 0.9; K rd Take 0.1263.

[0060] In the combustion chamber model of step 1, under ideal conditions, the combustion heat release process is a first-order inertia link with a delay, and the combustion chamber model is expressed as follows:

[0061]

[0062] In the formula, S G (s) is the heat output of the combustion chamber; μ r (s) is the actual fuel quantity; s is the differential operator; T F is the combustion chamber time constant, and S G (s), μ r (s) and T F All are per unit values.

[0063] In the pressure calculation model in step 1, the main steam flow rate entering the steam turbine and the drum pressure satisfy the following relationship:

[0064]

[0065] Where P d is the drum pressure; P T is the main steam pressure; K sh is the drag coefficient; S F is the main steam flow rate; and P d , P T , S F and K sh All are per unit values.

[0066] The swing angle instruction μ in the burner swing angle model in step 1 P The actual angle A p There is an inertial link with a delay, which is expressed as follows:

[0067] S Y =K y μ r

[0068] Q z =f1(A p )S Y

[0069] Q g =f2(A p )S Y

[0070] In the formula, μ r K is the fuel instruction; y is the proportionality coefficient; f1 is the mapping relationship between the actual angle and the proportion of reheat steam heat exchange to the total heat; f2 is the mapping relationship between the actual angle and the proportion of superheat steam heat exchange to the total heat; S Y is the total heat of the boiler; Q z It is the heat exchange between reheat steam and flue gas; Q g is the heat exchange between superheated steam and flue gas, and μ r , S Y , Q z and Q g All are per unit values.

[0071] Through the above design scheme, the present invention can bring the following beneficial effects:

[0072] The present invention is based on an accurate joint system model. By analyzing the electric and thermal loads of thermal power generating units during isolated grid operation and the operating characteristics of electric boilers with continuously changing power, the electric and thermal load balance relationship of the system after the electric boiler is added is established, and finally a method for thermal power generating units to operate with power and thermal loads in an isolated grid with the participation of electric boilers is designed. From the perspective of economy, this method proposes a dispatching method for electric boilers to participate in grid regulation under different dispatching requirements, giving full play to the dual potential of electric boilers as electric loads to participate in heating, and verifies that the coordination of electric boilers can ensure that the joint system is at the lowest operating power when carrying different thermal and electric loads in an isolated grid. The present invention can effectively improve the power and heat preservation capabilities of the thermal power generating unit-electric boiler joint system when a grid failure occurs, and has great practical significance for solving practical problems such as the insufficient ability of grids in high-cold areas to resist extreme weather disasters. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The present invention is further described below with reference to the accompanying drawings and specific embodiments:

[0074] Figure 1 The present invention is a flowchart of a method for operating a thermal power unit in an isolated grid with power and heat load with the participation of a heat storage device.

[0075] Figure 2 The present invention is a schematic structural diagram of a main steam turbine in an embodiment of a method for operating a thermal power unit in an isolated grid with power and heat load with the participation of a heat storage device.

[0076] Figure 3 The present invention is a schematic structural diagram of a speed regulating system in an embodiment of a method for operating a thermal power unit in an isolated grid with power and heat load in the presence of a heat storage device.

[0077] Figure 4 The present invention is a schematic structural diagram of a speed regulating system in an embodiment of a method for operating a thermal power unit in an isolated grid with power and heat load in the presence of a heat storage device.

[0078] Figure 5 The present invention is a flow chart of an isolated grid operation strategy when the power of an electric boiler is continuously adjustable in an embodiment of a method for operating a thermal power unit in an isolated grid with power and heat load in the presence of a heat storage device.

[0079] Figure 6 The present invention is a flowchart of judging and executing when the power of an electric boiler is continuously adjustable in an embodiment of a method for operating a thermal power unit in an isolated grid with power and heat load under the participation of a heat storage device.

[0080] Figure 7 The present invention is a power setting module instruction diagram when the heat load changes in an embodiment of a method for operating a thermal power unit in an isolated grid with power on and heat load with the participation of a heat storage device.

[0081] Figure 8The present invention is a power setting module instruction diagram when the electric load changes in an embodiment of a method for operating a thermal power unit in an isolated grid with power and heat load in the presence of a heat storage device.

[0082] Fig. 9 The invention discloses an operating power diagram for a thermal power unit in an embodiment of a method for operating a thermal power unit in an isolated grid with power supply and heat load under the participation of a heat storage device.

[0083] Fig.10 The invention discloses an electric boiler input power setting diagram in an embodiment of a method for operating a thermal power unit in an isolated grid with power on and heat load with the participation of a heat storage device.

[0084] Fig.11 The invention discloses a diagram for setting the opening degree of the extraction valve in an embodiment of a method for operating a thermal power unit in an isolated grid with power supply and heat load under the participation of a heat storage device. DETAILED DESCRIPTION

[0085] In response to the need to enhance the power and heat preservation capabilities of cogeneration thermal power units in high-cold areas when power grid failures occur, the present invention designs a method for thermal power units to operate in an isolated grid with power and heat loads with the participation of a heat storage device. First, the actual process is reasonably simplified to establish a thermal power unit model, a simplified power model of an electric boiler, and a joint system model formed by the two; secondly, several operating states of the heating thermal power unit under isolated grid conditions are analyzed, and the balance relationship between the thermal power unit and the electric boiler in terms of electricity and heat after the participation of the electric boiler is constructed; finally, combined with the operating characteristics of the electric boiler with continuously adjustable power, the stable operation strategy of the isolated grid when it cooperates with the thermal power unit is designed on the premise of meeting the electricity and heat loads. It has been verified that the method proposed by the present invention can ensure that the joint system is at the lowest operating power when carrying different heat and electricity loads under isolated grid conditions, and enhance the power and heat preservation capabilities of the joint system when power grid failures occur.

[0086] The design flow chart of the scheduling method proposed by the present invention is as follows: Figure 1 As shown, specifically comprising the following steps:

[0087] Step 1:

[0088] The model of a thermal power unit includes the main steam turbine, drum boiler and speed regulation system.

[0089] Main steam turbine: Figure 2 As shown in the figure, the modeling requirements for the steam turbine side are mainly reflected in the output power. When the main steam pressure is constant, the output power of the steam turbine is mainly affected by the opening of the regulating steam valve in front of the high-pressure cylinder.

[0090] Steam volume link model: The steam volume model is used to describe the main dynamic characteristics of the high, medium and low pressure cylinders and reheater of the steam turbine. In actual calculations, for a specific steam turbine, the output power of each cylinder can be obtained through the power share:

[0091] P T =P TH +P TM +P TL (1)

[0092] Where P TH is the output power of the high-pressure cylinder, in W; P TM is the output power of the medium pressure cylinder, in W; P TL is the output power of the low-pressure cylinder, in W.

[0093] Drum boiler: There are three main modeling units required for a drum boiler: combustion chamber model, boiler pressure model, and burner swing angle model.

[0094] Combustion chamber model: Ideally, the combustion heat release process can be considered as a first-order inertia link with a delay:

[0095]

[0096] In the formula, S G (s) is the heat output of the combustion chamber; μ r (s) is the actual fuel quantity; T F is the combustion chamber time constant, which is related to the combustion chamber structure; s is the differential operator.

[0097] Pressure calculation model: The main steam flow rate entering the steam turbine and the drum pressure satisfy the following relationship:

[0098]

[0099] Where P d is the drum pressure; P T is the main steam pressure; K sh is the drag coefficient; S F Main steam flow.

[0100] Burner swing angle model: swing angle command μ P The actual angle A p There is an inertial link with a delay:

[0101] S Y =K y μ r (4)

[0102] Q z =f1(A p )SY (5)

[0103] Q g =f2(A p )S Y (6)

[0104] In the formula, μ r K is the fuel instruction; y is the proportional coefficient; f1 is the mapping relationship between the actual angle and the proportion of reheat steam heat exchange to the total heat; f2 is the mapping relationship between the actual angle and the proportion of superheat steam heat exchange to the total heat; S Y is the total heat of the boiler; Q z It is the heat exchange between reheat steam and flue gas; Q g Exchange heat between superheated steam and flue gas.

[0105] Speed ​​regulation system: Figure 3 As shown in the figure, speed regulation includes primary frequency modulation, secondary frequency modulation and peak modulation. Primary frequency modulation uses the frequency difference as feedback signal to perform power-frequency conversion according to the speed inequality rate. Secondary frequency modulation and peak modulation use the AGC command issued by the dispatching center as control signal. Together, they form a comprehensive valve position command to achieve speed regulation. Figure 3 The actual power here refers to the actual output power.

[0106] Power model of jet electrode electric boiler: The structure of jet electrode electric boiler is as follows: Figure 4 As shown in the figure, the power of the jet electric boiler is controlled by the flow rate of water sprayed onto the electrode plate A. The flow rate can be changed by adjusting the opening of the row nozzle B, thereby realizing stepless regulation of the electric boiler power. Considering the dynamic power model of the row nozzle B, the row nozzle B opening instruction μ is used as the input signal, and the nozzle flow rate G is used as the output signal. The nozzle flow rate is consistent with the power of the jet electric boiler, and the relationship between the flow rate and the nozzle opening instruction is obtained:

[0107]

[0108] Where T is the nozzle time constant, which is related to the geometric dimensions of the row nozzle.

[0109] The thermal power unit model and the electric boiler model are aggregated into a joint system, providing an accurate mathematical model for the subsequent scheduling plan design.

[0110] Step 2:

[0111] Establish a balanced relationship between thermal power units and electric boilers in terms of electricity and heat

[0112] Electric load balance: The electric load of the thermal power unit is equal to the difference between the actual output power of the steam turbine and the input power of the electric boiler, as shown in the following formula:

[0113] P dfh =P qljgl -P dglgl (8)

[0114] Where P dfh P is the load of the thermal power unit; qljgl is the actual output power of the steam turbine; P dglgl P is the power consumption of electric boiler; dfh , P qljgl and P dglgl All are values ​​​​normalized to the corresponding parameters under rated heating conditions;

[0115] The actual output power of the steam turbine is related to the operating power of the thermal power unit and the opening of the steam extraction valve, as shown in the following formula:

[0116] P qljgl =P hd +P hd (1-F cq )K rd (9)

[0117] In the formula, F cq P is the per unit opening value of the extraction valve; hd is the operating power of the thermal power unit; K rd is the thermoelectric conversion coefficient.

[0118] Thermal load balance: The thermal load of the thermal power unit is equal to the sum of the thermal power unit's steam extraction heating, electric boiler heating and heat exchange with the heat storage tank (heat storage is positive, heat release is negative), as shown in the following formula:

[0119] P rfh =P cq +P dglgr -P xrggr (10)

[0120] Where P rfh P is the heat load of the thermal power unit; cq Extract steam to supply heat for heating; P dglgr Provide heat for electric boiler; P xrggr Provide heat for the heat storage tank; all parameters under rated heating conditions are standardized.

[0121] The heating steam supply can be calculated based on the operating power of the thermal power unit and the opening of the steam extraction valve, as shown in the following formula:

[0122] P cq =P hd F cq (11)

[0123] The relationship between electric boiler power consumption and heat supply is as follows:

[0124] P dglgr =P dglgl λk by (12)

[0125] Where, λ is the efficiency of the electric boiler; k by It is the coefficient used for per unit, which is related to the rated extraction steam heating capacity.

[0126] Step 3:

[0127] For the case where the electric power is continuously adjustable, the following operation strategies are set, such as Figure 5 As shown. Taking the electrical load and thermal load of the thermal power unit as input, after judgment and execution, the final output is the set operating power of the thermal power unit under different conditions, the input power of the electric boiler and the opening of the steam extraction valve. Among them, the conversion relationship between heat and electricity is connected through the conversion coefficient of the two processes. The judgment and execution process is as follows Figure 6 shown.

[0128] When only thermal power units are operating in isolated grid, the load they carry will mainly fall into three situations:

[0129] Case 1: The electric and thermal loads of the thermal power units are very small, lower than the minimum operating load limit of the boiler;

[0130] Case 2: The electrical load of the thermal power unit is greater than or equal to the minimum electrical load required to meet the thermal load;

[0131] Case 3: The electrical load of the thermal power unit is less than the minimum electrical load required to meet the thermal load.

[0132] Condition 1 is used to determine whether the load of the thermal power unit meets Condition 1:

[0133] P dfh ≤P min

[0134] ∧P rfh ≤-K dr P dfh +(1+K dr ) min

[0135] ∨P min ≤P dfh ≤P min (1+K rd )

[0136]

[0137] If condition 1 is met, the electric boiler needs to be put into operation. By adjusting the power of the electric boiler, the thermal power unit can operate at the lowest load. As an electrical device, the electric boiler is both the electrical load of the thermal power unit and a heating device. It can meet the heat load demand together with the thermal power unit. This can be achieved by executing 1:

[0138] P hd =P min

[0139] P dgl =P hd -P dfh

[0140]

[0141] If condition 1 is not met, the operating power of the thermal power unit is temporarily set to the minimum power required to meet the electrical load, which can be achieved by executing 2:

[0142] P hd =P dfh (15)

[0143] At this time, condition 2 is used to determine whether the load condition of the thermal power unit belongs to condition 2 or condition 3:

[0144] P rfh ≤P hd (16)

[0145] If the second condition is met, the electric boiler does not need to be put into use. At this time, the operating power of the thermal power unit can be appropriately reduced, and the opening of the steam extraction valve can be adjusted so that the operating power (main steam flow) of the thermal power unit is reduced at the same time as the heating steam extraction volume, but it is reflected externally as an increase in output power until the thermal power unit operates at the minimum power required to meet the electrical and thermal loads. This process is achieved by executing 3:

[0146]

[0147] P dgl =0

[0148]

[0149] If condition 3 is met, the electric boiler must be put into operation, the extraction valve opening is kept at the maximum, and the sum of the heating capacity of the electric boiler plus the incremental heating capacity of the thermal power unit power should meet the heating load demand. In order to be economical, the thermal power unit needs to be operated at the lowest power under the premise of ensuring the heat load. This process is achieved by executing 4:

[0150]

[0151] P dgl =P hd -Pdfh

[0152] F cq =1 (18)

[0153] In equations (1) to (13), all physical quantities are per unit values, P rfh P is the heat load of the thermal power unit; dfh P is the load of the thermal power unit; hd P is the operating power of the thermal power unit; dgl F is the operating power of the electric boiler; cq is the opening of the extraction valve; P min is the minimum load of the boiler, take 0.3; K dr is the electric heat conversion coefficient, which is taken as 0.9; K rd is the thermoelectric conversion coefficient, which is taken as 0.1263.

[0154] Step 4:

[0155] Verify the effectiveness of the scheduling strategy

[0156] Applying the above scheduling strategy to the system model, we can obtain the power setting module instructions when the electric load is constant (for example, 10%, 20%, 30%) and the thermal load changes, and the power setting module instructions when the thermal load is constant (for example, 60%, 70%, 80%) and the electric load changes, such as Figure 7 , Figure 8 As shown in the figure, when the power and heat load of the thermal power unit change, the corresponding set operating power of the thermal power unit, the set input power of the electric boiler and the set valve opening of the steam extraction are as follows: Fig. 9 , Fig.10 , Fig.11 shown.

[0157] As can be seen from the figure, after the electric boiler with continuously variable power is added, for each group of thermal power units with electric heat load input, there are corresponding thermal power unit set power, electric boiler set input power and extraction valve set opening output, which verifies the effectiveness of the scheduling model. The addition of electric boilers not only acts as an electric load, but also participates in heat supply, which can indeed reduce the degree of thermal-electric coupling and effectively improve the stability of power grid operation.

Claims

1. A method for operating a thermal power unit in an isolated grid with power and heat load under the participation of a heat storage device, characterized in that: The process includes the following steps, which are performed in sequence: Step 1: Establish a joint system model including the thermal power unit model and the simplified power model of the electric boiler The thermal power unit model includes a main steam turbine, a drum boiler and a corresponding speed regulating system; wherein the output power of the main steam turbine is obtained in two ways: one is that under the condition of a certain main steam pressure of the main steam turbine, the output power of the steam turbine is proportional to the valve opening of the regulating steam valve in front of the high-pressure cylinder; the other is that the main steam turbine obtains the output power by adding the output powers of the high-, medium- and low-pressure cylinders of the steam turbine; The drum boiler includes a combustion chamber model, a boiler pressure model and a burner swing angle model; The speed regulation system includes primary frequency modulation, secondary frequency modulation and peak regulation; the primary frequency modulation uses the frequency difference as a feedback signal; the secondary frequency modulation and peak regulation use the automatic generation control AGC command issued by the dispatching center as a control signal; the primary frequency modulation, secondary frequency modulation and peak regulation together form a comprehensive valve position command to achieve speed regulation; The simplified power model of electric boiler adopts the power model of jet electrode electric boiler; Step 2: Obtain the balance relationship between the electric load and the heat load of the joint system model after the electric boiler is added The balance relationship of electric load is that the load carried by the thermal power unit is equal to the difference between the actual output power of the steam turbine and the power consumption of the electric boiler. The balance relationship of electric load is shown in the following formula: P dfh =P qljgl -P dglgl Where P dfh P is the load of the thermal power unit; qljgl is the actual output power of the steam turbine; P dglgl P is the power consumption of electric boiler; dfh , P qljgl and P dglgl All are values ​​​​normalized to the corresponding parameters under rated heating conditions; The actual output power of the steam turbine is related to the operating power of the thermal power unit and the opening of the steam extraction valve, as shown in the following formula: P qljgl =P hd +P hd (1-F cq )K rd In the formula, F cq P is the per unit opening value of the extraction valve; hd is the operating power of the thermal power unit; K rd is the thermoelectric conversion coefficient; The heat load balance relationship is that the heat load of the thermal power unit is equal to the sum of the unit's steam extraction heating, electric boiler heating and heat storage tank heat exchange, where heat storage is positive and heat release is negative. The heat load balance relationship is shown in the following formula: P rfh =P cq +P dglgr -P xrggr Where P rfh P is the heat load of the thermal power unit; cq Extract steam to supply heat for heating; P dglgr Provide heat for electric boiler; P xrggr Provide heat for the heat storage tank; P cq , P dglgr and P xrggr All are values ​​​​normalized to the corresponding parameters under rated heating conditions; Among them, the heating steam heat supply P cq The operating power P of the thermal power unit hd And the extraction valve opening is calculated and obtained as shown in the following formula: P cq =P hd F cq Electric boiler power consumption P dglgl Heat supply from electric boiler P dglgr The relationship is as follows: P dglgr =P dglgl λk by Where, λ is the efficiency of the electric boiler; k by It is the coefficient used for per unit, which is related to the rated extraction steam heating capacity; Step 3: For the case where the electric power of the electric boiler is continuously adjustable, set the isolated grid stable operation strategy when it cooperates with the thermal power unit For the case where the electric power is continuously adjustable, the following operating methods are set: Taking the electrical load and thermal load of the thermal power unit as input, after judgment and execution, the final output is the set operating power of the unit, the input power of the electric boiler and the opening of the steam extraction valve under different conditions. Among them, the conversion relationship between the thermal load and the electrical load is connected through the conversion coefficient of the two processes; The judgment and execution process is as follows: The loads carried by thermal power units under isolated grid operation conditions mainly fall into the following three situations: Case 1: The electrical load and thermal load of the thermal power unit are very small, both lower than the minimum operating load limit of the boiler; Case 2: The electrical load of the thermal power unit is greater than or equal to the minimum electrical load required to meet the thermal load; Case 3: The electrical load of the thermal power unit is less than the minimum electrical load required to meet the thermal load; Condition 1 is used to determine whether the load of the thermal power unit meets condition 1. Condition 1 is expressed as follows: P dfh ≤P min ∧P rfh ≤-K dr P dfh +(1+K dr )P min ∨P min ≤P dfh ≤P min (1+K rd ) In the formula, P min is the minimum load power of the electric boiler, take 0.3; K dr is the electric heat conversion coefficient, which is taken as 0.9 here; K rd is the thermoelectric conversion coefficient, which is taken as 0.1263 here; ∧ means and, ∨ means or; If condition 1 is met, the electric boiler is put into operation. By adjusting the power of the electric boiler, the thermal power unit can operate at the lowest load. As an electrical device, the electric boiler is both the electrical load of the thermal power unit and a heating device. It can meet the heat load demand together with the thermal power unit. Adjustment is performed according to execution 1 as shown below: P hd =P min P dgl =P hd -P dfh In the formula, P dgl is the operating power of the electric boiler, F cq is the opening of the extraction valve; If the condition 1 is not met, the unit operating power is temporarily set to the minimum power required to meet the electrical load, and is adjusted by executing 2. Execution 2 is as follows: P hd =P dfh Then, through condition 2, it is determined whether the load condition of the thermal power unit belongs to condition 2 or condition 3. Condition 2 is expressed as follows: P rfh ≤P hd If condition 2 is met, it is determined to belong to situation 2. Adjustment is performed by executing 3, that is, the electric boiler does not need to be put into use, and the opening of the steam extraction valve is adjusted to reduce the main steam flow of the thermal power unit and the heating steam extraction at the same time, but the output power is increased externally until the thermal power unit operates at the minimum power required to meet the electricity and heat loads. Execution 3 is expressed as follows: P dgl ＝0 If condition 2 is not met, it is judged as situation 3. Adjustment is made by executing 4, that is, the electric boiler is put into operation, the opening of the steam extraction valve is kept at the maximum, and the sum of the heating supply of the electric boiler plus the heating supply increment of the unit power meets the heating load demand. In order to be economical, the unit needs to operate at the lowest power under the premise of ensuring the heat load. Execution 4 is expressed as follows: P dgl =P hd -P dfh F cq ＝1 Among them, P min Take 0.3; K dr Take 0.9; K rd Take 0.1263.

2. The method for operating a thermal power unit in an isolated grid with power and heat load under the participation of a heat storage device according to claim 1 is characterized in that: In the combustion chamber model of step 1, under ideal conditions, the combustion heat release process is a first-order inertia link with a delay, and the combustion chamber model is expressed as follows: In the formula, S G (s) is the heat output of the combustion chamber; μ r (s) is the actual fuel quantity; s is the differential operator; T F is the combustion chamber time constant, and S G (s), μ r (s) and T F All are per unit values.

3. The method for operating a thermal power unit in an isolated grid with power and heat load under the participation of a heat storage device according to claim 1 is characterized by: In the pressure calculation model in step 1, the main steam flow rate entering the steam turbine and the drum pressure satisfy the following relationship: Where P d is the drum pressure; P T is the main steam pressure; K sh is the drag coefficient; S F is the main steam flow rate; and P d , P T , S F and K sh All are per unit values.

4. The method for operating a thermal power unit in an isolated grid with power and heat load under the participation of a heat storage device according to claim 1 is characterized in that: The swing angle instruction μ in the burner swing angle model in step 1 P The actual angle A p There is an inertial link with a delay, which is expressed as follows: S Y =K y m r Q z =f1(A p )S Y Q g =f2(A p )S Y In the formula, μ r K is the fuel instruction; y is the proportionality coefficient; f1 is the mapping relationship between the actual angle and the proportion of reheat steam heat exchange to the total heat; f2 is the mapping relationship between the actual angle and the proportion of superheat steam heat exchange to the total heat; S Y is the total heat of the boiler; Q z It is the heat exchange between reheat steam and flue gas; Q g is the heat exchange between superheated steam and flue gas, and μ r , S Y , Q z and Q g All are per unit values.

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