Fused salt energy storage control method and device for assisting thermal power generating unit in frequency modulation and medium

Abstract

The invention discloses a fused salt energy storage control method and device for assisting frequency modulation of a thermal power generating unit and a medium, and relates to the field of power grid frequency modulation.The method comprises the steps that an automatic power generation control instruction is analyzed, the load change condition is determined, and whether a fused salt energy storage system has the adjusting capacity or not and whether the capacity of the fused salt energy storage system is sufficient or not are determined; different fused salt energy storage control strategies are adopted for different conditions (1) the fused salt energy storage system independently executes a load increasing task; (2) the thermal power generating unit and the fused salt energy storage system cooperatively execute a load increasing task; (3) independently executing a load increasing task by the thermal power generating unit, and maintaining the capacity of the hot molten salt tank; (4) independently executing a load reduction task by the fused salt energy storage system; (5) the thermal power generating unit and the fused salt energy storage system cooperatively execute a load reduction task; and (6) independently executing a load reduction task by the thermal power generating unit, and simultaneously executing capacity maintenance of the cold molten salt tank. The method can guarantee the power balance of the power grid, and avoids the operation fluctuation caused by the overlarge adjustment amplitude of the thermal power generating unit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power grid frequency modulation, and in particular to a molten salt energy storage control method and device for assisting the frequency modulation of a thermal power unit, and a medium. BACKGROUND

[0002] In the process of the current power system transforming towards the "double carbon" goal, the penetration rate of new energy power generation such as wind power and photovoltaic power continues to rise, and the strong volatility and intermittency of the output thereof pose a serious challenge to the frequency stability of the power grid. As the main force of power grid frequency modulation, the traditional thermal power unit is limited by its large thermal inertia, delayed response of the turbine governor, limited single adjustment range and other characteristics, and it is difficult to meet the requirements of "fast response, accurate tracking and continuous adjustment" of the frequency modulation resources of the high-proportion new energy power grid. Frequent adjustment will also lead to increased coal consumption and intensified equipment wear and tear. SUMMARY

[0003] The purpose of the present application is to provide a molten salt energy storage control method and device for assisting the frequency modulation of a thermal power unit, which can realize the deep coupling of stable operation of the thermal power unit and flexible adjustment of the molten salt, improve the accuracy and sustainability of the collaborative frequency modulation of the thermal power unit and the molten salt energy storage, and both guarantee the power balance of the power grid and avoid excessive adjustment range of the thermal power unit leading to operation fluctuation.

[0004] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0005] In a first aspect, the present application provides a molten salt energy storage control method for assisting the frequency modulation of a thermal power unit, comprising:

[0006] When the automatic generation control instruction changes, the automatic generation control instruction is analyzed to determine the load change condition; the load change condition includes load increase and load decrease;

[0007] The adjustment capacity condition of the molten salt energy storage system is determined based on the total capacity of the molten salt energy storage system; the adjustment capacity condition of the molten salt energy storage system includes that the molten salt energy storage system has adjustment capacity and that the molten salt energy storage system does not have adjustment capacity;

[0008] The molten salt energy storage system capacity condition is determined based on the load increase energy and the current effective heat storage capacity of the molten salt tank; the molten salt energy storage system capacity condition includes that the molten salt energy storage system capacity is sufficient and that the molten salt energy storage system capacity is insufficient;

[0009] Different molten salt energy storage control strategies are adopted based on the load change condition, the adjustment capacity condition of the molten salt energy storage system and the molten salt energy storage system capacity condition to control the molten salt energy storage;

[0010] The molten salt energy storage control strategy includes: the molten salt energy storage system independently performing an increase load task; the thermal power unit and the molten salt energy storage system cooperatively performing the increase load task; the thermal power unit independently performing the increase load task while performing hot molten salt tank capacity maintenance; the molten salt energy storage system independently performing a decrease load task; the thermal power unit and the molten salt energy storage system cooperatively performing the decrease load task; and the thermal power unit independently performing the decrease load task while performing cold molten salt tank capacity maintenance.

[0011] In a second aspect, the present application provides a computer device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor executes the computer program to implement the molten salt energy storage control method for assisting frequency modulation of a thermal power unit.

[0012] In a third aspect, the present application provides a computer readable storage medium, having a computer program stored thereon, and the computer program is executed by a processor to implement the molten salt energy storage control method for assisting frequency modulation of a thermal power unit.

[0013] According to the specific embodiments provided by the present application, the present application has the following technical effects:

[0014] The present application provides a molten salt energy storage control method, device, and medium for assisting frequency modulation of a thermal power unit. To adapt to the demand of the thermal power unit and the molten salt energy storage system participating in the frequency modulation of the power grid, the present application integrates the molten salt energy storage state discrimination on the basis of the original automatic generation control (AGC) instruction response logic, and realizes the deep coupling of the stable operation of the thermal power unit and the flexible adjustment of the molten salt energy storage system under the driving of the AGC instruction, improves the accuracy and sustainability of the collaborative frequency modulation of the thermal power unit and the molten salt energy storage system, and not only guarantees the power balance of the power grid, but also avoids the large adjustment range of the thermal power unit leading to operation fluctuation. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0016] Figure 1 A schematic diagram of the molten salt energy storage system coupled with the thermal power unit;

[0017] Figure 2 A flowchart of the molten salt energy storage control method for assisting frequency modulation of a thermal power unit provided by an embodiment of the present application;

[0018] Figure 3An embodiment of the present application provides a detailed flowchart of a molten salt energy storage control method for assisting frequency modulation of a thermal power unit. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0020] To make up for the insufficient frequency modulation capacity of the thermal power unit, energy storage technology becomes a key solution. Among them, the molten salt energy storage system has unique potential in the field of collaborative frequency modulation with the thermal power unit due to its large heat storage capacity, high operating temperature, long cycle life, and relatively low cost: on the one hand, it can absorb the redundant heat (such as the flue gas waste heat during the low load period) of the thermal power unit through heat storage-heat release cycle, or release heat to supplement power during the high load period, to smooth the unit output fluctuation; on the other hand, the mechanical response speed of the molten salt pump, heat exchanger and other devices is faster than the thermal response of the thermal power unit, which can fill the response gap in the initial stage of frequency modulation.

[0021] According to the calculation rules of the molten salt energy storage system state and the frequency modulation index, the present application designs a molten salt energy storage control strategy for assisting frequency modulation of the thermal power unit, realizes deep coupling of stable operation of the thermal power and flexible adjustment of the molten salt, improves the accuracy and sustainability of collaborative frequency modulation of the thermal power unit and the molten salt energy storage, guarantees power balance of the power grid, and avoids excessive adjustment range of the thermal power unit leading to operation fluctuation.

[0022] As shown in FIG. 1, the molten salt energy storage system coupled with the thermal power unit includes a steam turbine and a steam extraction subsystem, a high-pressure heater and a steam extraction and drainage subsystem, a low-pressure heater and a steam extraction and drainage subsystem, a molten salt heat storage subsystem, a molten salt heat release subsystem, and a hot and cold molten salt tank capacity maintenance subsystem. The red line represents a steam pipeline, the blue line represents a water pipeline, and the gray line represents a molten salt pipeline. The purple line represents a heat storage process, and the green line represents a heat release process. Figure 1 As shown in FIG. 1, the molten salt energy storage system coupled with the thermal power unit includes a steam turbine and a steam extraction subsystem, a high-pressure heater and a steam extraction and drainage subsystem, a low-pressure heater and a steam extraction and drainage subsystem, a molten salt heat storage subsystem, a molten salt heat release subsystem, and a hot and cold molten salt tank capacity maintenance subsystem. The red line represents a steam pipeline, the blue line represents a water pipeline, and the gray line represents a molten salt pipeline. The purple line represents a heat storage process, and the green line represents a heat release process.

[0023] In the molten salt system side, in the heat storage working condition, the low-temperature molten salt in the molten salt heat storage subsystem flows out from the molten salt cold tank and is divided into two paths, one of which passes through the steam-molten salt heat exchanger to exchange heat with the extracted main steam, the main steam is cooled by releasing heat and then enters the condenser to condense and enter the steam-water circulation of the unit, and the molten salt absorbing heat is stored in the molten salt hot tank; the other path passes through the flue gas-molten salt heat exchanger and the electric heater in turn, and whether the electric heater works or not depends on whether there is a wind / photovoltaic curtailment signal: if there is, the molten salt absorbs the waste heat of the boiler tail flue gas through the flue gas-molten salt heat exchanger, is heated by the electric heater, and is then stored in the molten salt hot tank; if not, the molten salt only utilizes the flue gas waste heat. In the heat release working condition, the high-temperature molten salt in the molten salt heat release subsystem flows out from the molten salt hot tank and is divided into two paths, one of which enters the evaporator and the superheater to heat the extracted boiler feed water to generate superheated steam, which is sent to the high-pressure cylinder to do work, and the molten salt releasing heat is cooled to a certain temperature by the cooler and then stored in the molten salt cold tank; the other path enters the steam-molten salt heat exchanger to exchange heat with the extracted cold reheat steam, the exchanged steam enters the intermediate-pressure cylinder to do work, and the low-temperature molten salt after heat release flows back to the molten salt cold tank, realizing the deep coupling of the molten salt energy storage and the thermal system of the thermal power unit and the bidirectional flow of energy.

[0024] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below in combination with the drawings and specific embodiments.

[0025] In one exemplary embodiment, as shown in Figures 2-3 a molten salt energy storage control method for assisting frequency modulation of a thermal power unit is provided, including the following steps S1 to S7.

[0026] S1: When the automatic generation control instruction changes, the automatic generation control instruction is analyzed to determine the load change condition; the load change condition includes load increase and load decrease. Specifically, if the automatic generation control instruction is greater than the current actual output value of the joint system, it is determined that the load increases; the joint system includes a thermal power unit and a molten salt energy storage system; if the automatic generation control instruction is less than the current actual output value of the joint system, it is determined that the load decreases.

[0027] Specifically, the maximum of the minimum adjustment range of the thermal power unit and the minimum response power of the molten salt energy storage system is set as a threshold value. When the deviation of the collected AGC instruction and the current joint output exceeds the threshold value, it is determined that the instruction changes; if the deviation is within the threshold value, it is determined that there is no change, the current joint operation state is maintained, and continuous monitoring is continued.

[0028] When the instruction changes, the instruction is analyzed: according to the current AGC instruction collected in real time and the current actual output value of the joint system, the "load increase" or "load decrease" is distinguished:

[0029] 1) If AGC command value > actual output value: it indicates that the power grid requires the system to increase the overall output, and it is determined as "load increase".

[0030] 2) If AGC command value < actual output value: it indicates that the power grid requires the system to increase the overall output, and it is determined as "load decrease".

[0031] S2: Determine whether the molten salt energy storage system has the adjustment capability based on the total capacity of the capacitor of the molten salt energy storage system. The adjustment capability of the molten salt energy storage system includes that the molten salt energy storage system has the adjustment capability and that the molten salt energy storage system does not have the adjustment capability.

[0032] Specifically, whether the load increases or decreases, the state of the molten salt energy storage system is determined first.

[0033] (1) Effective adjustment interval definition:

[0034] 1) Priority adjustment interval: based on the design parameters, the effective heat storage capacity of the molten salt energy storage system is set to 20%-80% of the total capacity, and the device has no fatal failure (such as normal operation of the molten salt pump).

[0035] 2) Limited adjustment interval definition:

[0036] <1> Total capacity < 20% (close to the freezing point): only short-term heat release (≤10 minutes) of less than 50% of the rated power is allowed;

[0037] <2> Total capacity > 80% (close to the upper limit of the temperature): only short-term heat storage (≤15 minutes) of less than 30% of the rated power is allowed;

[0038] 3) Invalid interval: fatal failure of the device (such as shutdown of the molten salt pump) or capacity exceeding the limited adjustment interval range;

[0039] (2) State determination

[0040] 1) Priority adjustment interval: if the molten salt energy storage system is in this interval, it is determined as "having the adjustment capability";

[0041] 2) Invalid interval: the "maintain the current state of energy storage" strategy is executed, and the capacity data is recorded to provide a basis for peak shaving.

[0042] S3: Determine the capacity situation of the molten salt energy storage system based on the load increase energy and the current effective heat storage capacity of the molten salt tank; the capacity situation of the molten salt energy storage system includes that the capacity of the molten salt energy storage system is sufficient and that the capacity of the molten salt energy storage system is insufficient.

[0043] Specifically, when the effective heat release capacity of the molten salt tank in the molten salt energy storage system is greater than or equal to the load increase energy, the molten salt energy storage system capacity is sufficient; when the effective heat release capacity of the molten salt tank in the molten salt energy storage system is less than the load increase energy, the molten salt energy storage system capacity is insufficient.

[0044] S4: Different molten salt energy storage control strategies are adopted for controlling the molten salt energy storage based on the load change condition, the molten salt energy storage system adjustment capability condition and the molten salt energy storage system capacity condition. Specifically as follows:

[0045] (1) When the load increases, the molten salt energy storage system has adjustment capability, and the molten salt energy storage system capacity is sufficient, the molten salt energy storage system independently performs the load increase task; the molten salt energy storage system capacity is sufficient, which means that the effective heat release capacity of the molten salt tank in the molten salt energy storage system is greater than or equal to the load increase energy.

[0046] (2) When the load increases, the molten salt energy storage system has adjustment capability, and the molten salt energy storage system capacity is insufficient, the thermal power generating unit and the molten salt energy storage system cooperatively perform the load increase task; the molten salt energy storage system capacity is sufficient, which means that the effective heat release capacity of the molten salt tank in the molten salt energy storage system is less than the load increase energy.

[0047] Specifically, when the AGC instruction requires load increase, the molten salt energy storage system has adjustment capability, and the molten salt energy storage system capacity is insufficient, the thermal power generating unit is taken as the basic adjustment subject, and the molten salt energy storage system provides dynamic power compensation to avoid the single adjustment amplitude of the thermal power generating unit being too large. The cooperative control strategy is as follows:

[0048] 1) Thermal power basic response:

[0049] The burner output and the turbine valve opening degree of the thermal power generating unit are finely adjusted to bear the basic load increase of the AGC instruction.

[0050] 2) Molten salt energy storage system response:

[0051] Medium-pressure cylinder cooperation: part of the cold reheat steam and the molten salt heat release are extracted, the generated high-temperature steam enters the medium-pressure cylinder to do work, and the power generation power is rapidly increased;

[0052] High-pressure cylinder cooperation: the boiler feed water sequentially passes through the evaporator and the superheater to absorb the heat released by the molten salt, and the superheated steam enters the high-pressure cylinder to further supplement the power generation capacity.

[0053] 3) Molten salt circulation management:

[0054] The low-temperature molten salt after heat release flows back to the cold tank for storage to reserve medium for subsequent heat storage process.

[0055] (3) When the load increases and the molten salt energy storage system does not have adjustment capability, the thermal power generating unit independently performs the load increase task, and simultaneously performs the hot molten salt tank capacity maintenance.

[0056] The molten salt heat tank liquid level is too low to release heat, and the thermal power unit needs to complete the load increase alone. Specifically, the waste heat is used to heat the molten salt, the flue gas waste heat enters the flue gas-molten salt heat exchanger to heat the low-temperature molten salt; if there is a wind / light signal, the electric heater is started synchronously, and is connected in series with the flue gas-molten salt heat exchanger to accelerate the heating of the molten salt and raise the liquid level of the hot molten salt tank.

[0057] (4) When the load decreases, the molten salt energy storage system has adjustment capability, and the molten salt energy storage system capacity is sufficient, the molten salt energy storage system independently performs the load reduction task; the molten salt energy storage system capacity is sufficient, which means that the effective heat storage capacity of the molten salt tank in the molten salt energy storage system is greater than or equal to the load reduction energy.

[0058] (5) When the load decreases, the molten salt energy storage system has adjustment capability, and the molten salt energy storage system capacity is insufficient, the thermal power unit and the molten salt energy storage system cooperatively perform the load reduction task; the molten salt energy storage system capacity is insufficient, which means that the effective heat storage capacity of the molten salt tank in the molten salt energy storage system is less than the load reduction energy.

[0059] Specifically, when the AGC instruction requires load reduction and the molten salt energy storage has adjustment capability, flexible adjustment of "heat storage priority, thermal power slow load reduction" is realized. Capacity insufficient scenario: if there is a wind or light signal, and the unit waste heat is used, the low-temperature molten salt is heated in turn through the flue gas-molten salt heat exchanger and the electric heater; if there is no wind or light signal, the main steam is extracted and reversely exchanged with the molten salt to convert the steam heat energy into molten salt sensible heat storage, and the exchanged steam is reduced in pressure by a pressure reducing valve and enters the condenser, and the thermal power unit synchronously and gently reduces the load.

[0060] (6) When the load decreases and the molten salt energy storage system does not have adjustment capability, the thermal power unit independently performs the load reduction task, and simultaneously performs the cold molten salt tank capacity maintenance.

[0061] The cold tank molten salt liquid level is too low to store heat, and the thermal power unit needs to complete the load reduction alone. Specifically, the hot molten salt pump is started, part of the cold reheat steam is extracted and exchanged with the hot molten salt, and then the steam enters the intermediate pressure cylinder, while the hot molten salt flows into the cold tank to raise the liquid level of the cold tank, and when the liquid level recovers to 50%, the molten salt pump is closed and the heat release is stopped.

[0062] In this embodiment, whether the load increases or decreases, as long as the molten salt energy storage system participates in adjustment, or the thermal power unit independently performs the frequency modulation task, the hierarchical control strategy is executed, that is:

[0063] When the thermal power unit and the molten salt energy storage system cooperatively perform the load increase task, or the thermal power unit and the molten salt energy storage system cooperatively perform the load reduction task, the thermal power unit and the molten salt energy storage system are adjusted according to the sub-instruction sequence.

[0064] When the molten salt energy storage system independently performs a load increase task or an independent load decrease task, the molten salt energy storage system is adjusted according to the sub-instruction sequence.

[0065] When a thermal power unit independently performs a load increase task or a load decrease task, the molten salt energy storage system is adjusted according to the sub-instruction sequence.

[0066] The sub-instruction sequence is obtained by decomposing the automatic generation control command using a model predictive control algorithm; the sub-instruction sequence includes response time control sub-instruction, response rate control sub-instruction, response accuracy control sub-instruction, molten salt heat storage and release efficiency control sub-instruction, and molten salt capacity recovery control sub-instruction.

[0067] Specifically, the Model Predictive Control (MPC) algorithm is adopted to apply AGC commands (including frequency correction R) to... f (t) and power ramp-up R r The combined instruction of (t), that is, R(t) = R f (t)+R r (t) is decomposed into a sequence of sub-instructions: "response time control, response rate control, response accuracy control, molten salt heat storage and release efficiency control, and molten salt capacity recovery control".

[0068] (1) The control objectives of each sub-instruction are as follows:

[0069] 1) Response time control sub-instruction U t (t): Focusing on "response delay", the goal is to minimize the time difference between the issuance of the command and the start of the actual power output response (such as the delay from command triggering to power deviation from the initial value).

[0070] 2) Response rate control sub-instruction U r (t): Focusing on "the rate of power change", the goal is to control the rate of change of power output (such as the power increment per unit time) so that it tracks the desired rate.

[0071] 3) Response precision control sub-instruction U z (t): Focusing on "dynamic tracking accuracy", the goal is to reduce deviations (such as overshoot and oscillation) in the transient process and achieve fast and error-free tracking of instructions.

[0072] 4) Molten salt heat storage and release efficiency control sub-instruction U s (t): Focusing on "energy conversion efficiency", the goal is to optimize the heat exchange process between molten salt and steam / flue gas, ensuring sufficient heat absorption during heat storage and efficient heat release during heat release, thereby reducing energy loss.

[0073] 5) Molten salt capacity recovery control sub-instruction U c(t): Focus on "system sustainability", target is to push the hot / cold tank level back to the safe range by adjusting the heat recovery intensity, electric heating power or molten salt circulation amount when the molten salt level or heat storage capacity deviates from the target range, to ensure the stability of subsequent heat storage capacity.

[0074] (2) Frequency component separation:

[0075] The two components of AGC instructions (frequency correction, power ramping) have obvious differences in time scale, which need to be separated by filtering first, and the target is allocated for sub-instructions:

[0076] 1) High-pass filter R(t), extract high-frequency component R f (t), mainly tracked by response time control sub-instructions (reduce start-up delay, ensure fast trigger response) and response accuracy control sub-instructions (improve dynamic tracking accuracy, reduce transient deviation).

[0077] 2) Low-pass filter R(t), extract low-frequency component R r (t), mainly tracked by response time control sub-instructions (reduce start-up delay, ensure fast trigger response) and response accuracy control sub-instructions (improve dynamic tracking accuracy, reduce transient deviation).

[0078] (3) Sub-instruction decomposition logic under MPC framework

[0079] 1) Objective function

[0080] The objective function is based on model predictive control, which is used to realize the optimization control of "response time, response rate, response speed" in the process of molten salt energy storage system and thermal power unit coordinated frequency modulation, and also takes into account the balance of molten salt heat storage capacity. The specific is as follows:

[0081] <1> Sub-instruction control target design

[0082] Design independent optimization target for each sub-instruction, and construct the total objective function J of MPC by weighted summation, to ensure that the sub-instructions track the composite instruction cooperatively.

[0083]

[0084] Where, k represents the current control time; i represents the step number in the prediction time domain; N represents the prediction time domain length; τ salt (k+i) represents the response delay of the molten salt energy storage system at the k time step i; τ unit(k+i) represents the response delay of the i-th step of the thermal power unit at time k; a1 represents the start-up time penalty weight of the molten salt energy storage system; a2 represents the start-up time penalty weight of the thermal power unit; if a1 » a2, the molten salt energy storage system alone undertakes the load increase task, and the molten salt energy storage system is preferentially ensured to start up quickly; if a1 « a2, the thermal power unit alone undertakes the load increase task, and the thermal power unit is preferentially ensured to start up quickly.

[0085] 2> Objective function J of the response rate control sub-instruction r :

[0086]

[0087] wherein, represents the total power change rate of the i-th step at time k; represents the target rate of the automatic generation control instruction of the i-th step at time k; represents the power change rate contributed by the molten salt energy storage system of the i-th step at time k; represents the maximum safe power change rate of the molten salt energy storage system of the i-th step at time k, which is calculated based on the liquid level of the hot molten salt tank; represents the power change rate contributed by the thermal power unit of the i-th step at time k; represents the maximum safe power change rate of the thermal power unit of the i-th step at time k; b1 and b2 represent weight coefficients, respectively.

[0088] 3> Objective function J of the response speed control sub-instruction z :

[0089]

[0090] wherein, P(k+i) represents the actual power of the i-th step at time k; P ref (k+i) represents the target power of the i-th step at time k; m represents the temperature weight; H hot (k+i) represents the liquid level of the hot molten salt tank of the i-th step at time k; H hot,min (k+i) represents the minimum safe liquid level of the hot tank molten salt; I low represents a liquid level indication function, which is 1 if the liquid level is lower than the minimum safe liquid level, and 0 otherwise;

[0091] 4> Objective function J of the molten salt heat storage efficiency control sub-instruction s :

[0092]

[0093] wherein, Q salt (k+i) represents the heat storage amount of the molten salt of the i-th step at time k; Q target (k+i) represents the target heat storage amount of the i-th step at time k; Tsalt,out (k+i) represents the outlet temperature of the i-th step of the molten salt heat exchanger at time k; T design represents the design temperature; δ1, δ2 represent the weight coefficients, respectively.

[0094] 5> Objective function J of the molten salt capacity recovery control sub-instruction c :

[0095]

[0096] wherein, L hot,target , L cold,target represent the target liquid levels of the hot and cold molten salt tanks, respectively; I hot,low , I cold,low represent the liquid level indication functions of the hot and cold molten salt tanks, respectively, which are 1 when the liquid level is lower than the target, otherwise; ε1, ε2 represent the weight coefficients, respectively.

[0097] <2> The expression of the total objective function is:

[0098] J = ω t J t + ω r J r + ω z J z + ω s J s + ω c J c

[0099] wherein, ω t , ω r , ω z , ω s , ω c represent the response time control weight, the response rate control weight, the response precision control weight, the molten salt heat storage efficiency control weight, and the molten salt capacity recovery control weight, respectively. The above weights are dynamically adjusted according to the molten salt capacity state and the load scenario. The specific adjustment rules are as follows:

[0100] If the molten salt energy storage system independently performs the load increasing task, the proportion of the molten salt energy storage system in the response time control weight and the response rate control weight is 90%, the molten salt response is preferentially guaranteed; the value of the molten salt heat storage efficiency control weight is moderate, to avoid excessive consumption of heat storage. According to the sub-instruction sequence, the thermal power unit and the molten salt energy storage system are adjusted: on the one hand, in the molten salt system, the "high-temperature molten salt main pump" on the molten salt side is opened, and the heat salt is sent to the high-pressure cylinder side evaporator, superheater and medium-pressure cylinder side heat exchanger. The "cold reheat steam regulating valve" on the steam-water side is opened, the cold reheat steam is heated with the molten salt, and the high-temperature steam generated is introduced into the medium-pressure cylinder through the medium-pressure joint steam valve. The "feedwater regulating valve" is opened, and part of the feedwater is extracted, passes through the evaporator and the superheater, and then enters the high-pressure cylinder through the high-pressure main steam valve. At the same time, the hot tank liquid level is monitored in real time, and if it is lower than the safety value, the molten salt flow is gradually reduced. On the other hand, the thermal power unit keeps the current fuel quantity and the turbine regulating valve opening unchanged, and only maintains the basic load.

[0101] If the thermal power unit and the molten salt energy storage system cooperatively perform the load increasing task, the response rate control weight is distributed according to the molten salt energy storage system:thermal power unit = 2:3, and the value of the response speed control weight is the highest, to ensure that the total power accurately meets the standard. According to the sub-instruction sequence, the thermal power unit and the molten salt energy storage system are adjusted: on the one hand, in the molten salt system, the molten salt flow operates according to the "maximum safety value". On the other hand, on the thermal power unit side, the fuel quantity, feedwater quantity and the like of the boiler system respond to the changes, the high-pressure regulating valve and the medium-pressure regulating valve of the turbine system are controlled, the steam quantity growth is matched, and the main steam pressure is ensured to be stable.

[0102] If the thermal power unit independently performs the load increasing task, and simultaneously performs the hot molten salt tank capacity maintenance, the value of the molten salt capacity recovery control weight is relatively high (to recover the hot tank liquid level), and the proportion of the thermal power unit in the response rate control weight is 100%. According to the sub-instruction sequence, the thermal power unit and the molten salt energy storage system are adjusted: on the one hand, the fuel quantity of the thermal power unit is increased, the main steam valve opening is increased, and the "flue gas-molten salt heat exchanger bypass valve" is changed, so that more flue gas heat is used to heat the molten salt. On the other hand, in the molten salt system, the "molten salt heat release valve" is closed to stop heat release; the "low-temperature molten salt pump" is opened to extract the salt from the cold tank; if there is a wind / photovoltaic power curtailment signal: the low-temperature molten salt is first heated by the flue gas-molten salt heat exchanger, then by the electric heater, and then sent to the hot tank to raise the liquid level; if there is no wind curtailment signal: only the flue gas-molten salt heat exchanger is used to heat the low-temperature molten salt and send it to the hot tank to slowly supplement the energy.

[0103] If the molten salt energy storage system independently performs the load reduction task, the proportion of the molten salt energy storage system in the response rate control weight is 90%, and the value of the molten salt heat storage and release efficiency control weight is the highest, and the heat storage effect is preferentially ensured. According to the sub-instruction sequence, the thermal power generating unit and the molten salt energy storage system are adjusted: on the one hand, in the molten salt system, the "low-temperature molten salt pump" is opened to extract the salt from the cold tank; if there is a wind / photovoltaic curtailment signal, the molten salt first passes through the flue gas-molten salt heat exchanger, and then passes through the electric heater to enter the hot tank; if there is no wind curtailment signal, the "main steam extraction valve" is opened to exchange heat with the molten salt in the opposite direction, and the steam after heat exchange enters the condenser through the pressure reducing valve. On the other hand, the thermal power generating unit keeps the fuel quantity and the valve opening degree unchanged.

[0104] If the thermal power generating unit and the molten salt energy storage system cooperatively perform the load reduction task, the response rate control weight is distributed according to the molten salt energy storage system:thermal power generating unit = 3:5, and the value of the response speed control weight is the highest, to ensure that the total power accurately meets the standard. According to the sub-instruction sequence, the thermal power generating unit and the molten salt energy storage system are adjusted: on the one hand, the molten salt system operates according to the maximum energy storage capacity. On the other hand, the fuel quantity of the thermal power generating unit decreases, and the opening degree of the main steam valve decreases.

[0105] If the thermal power generating unit independently performs the load reduction task, and simultaneously performs the cold molten salt tank capacity maintenance, the value of the molten salt capacity recovery weight is relatively high (to recover the cold tank liquid level), and the weight proportion of the unit item of the response rate control sub-instruction is 100%. The cold tank liquid level is guaranteed to be recovered. According to the sub-instruction sequence, the thermal power generating unit and the molten salt energy storage system are adjusted: on the one hand, the fuel quantity of the thermal power generating unit decreases, and the main steam valve is synchronously closed. On the other hand, in the molten salt system, the "high-temperature molten salt pump" is opened, and the molten salt after heat release flows into the cold tank to increase the cold tank liquid level. When the liquid level is recovered to 50%, the heat release is stopped, and the next heat storage instruction is waited for.

[0106] 2) Constraint conditions

[0107] <1> Response time control sub-instruction constraint:

[0108] 1> Molten salt start-up delay constraint: τ salt (k+i)≤τ salt,max .

[0109] 2> Unit start-up delay constraint: τ unit (k+i)≤τ unit,max .

[0110] <2> Response rate control sub-instruction constraint:

[0111] 1> Total rate upper and lower limit constraint: limit the safety range of the total power change rate to avoid exceeding the rate interval allowed by the power grid AGC,

[0112] 2> Molten salt rate limit constraint: the maximum heat release / storage rate is determined by the molten salt flow and temperature, and when the molten salt is charging time

[0113] 3) Unit rate limit constraint: limit the power regulation rate of the unit itself,

[0114] <3) Response accuracy control sub-instruction constraint:

[0115] 1) Power deviation allowable range constraint: |P(k+i)-P ref (k+i)|≤ΔP max .

[0116] Thermal storage capacity constraint (through all sub-instructions): the thermal storage amount Q salt (t) directly limits the charging and discharging duration, and the hot molten salt tank is avoided from being overfilled or overheated during charging, and the temperature T salt is lower than the freezing point during discharging, so it needs to be added as a hard constraint to the MPC optimization:

[0117] Q salt,charge ≤Q salt,max

[0118] Q salt,discharge ≥Q salt,min

[0119] In the formula, Q salt,charge represents the change in thermal storage, Q salt,max represents the maximum thermal storage, and Q salt,min represents the minimum thermal storage.

[0120] 3) Rolling optimization execution: the MPC solves the sub-instruction sequence through "rolling optimization": at each time k, based on the current system state (such as the current power P(k) and the delay τ(k)), the power output in the future N steps (prediction horizon) is predicted, the sub-instruction sequence in the future M steps (control horizon) is obtained through optimization of the objective function, only the first step is executed, and then the rolling is repeated at time k+1.

[0121] (4) Hierarchical control

[0122] If the AGC instruction is a combination of multiple single instructions (such as continuous power ramping + frequency correction), the "instruction decomposition-hierarchical control" process is executed in a loop, the latest instruction covers the old instruction, the prediction horizon is automatically adjusted to the remaining regulation time, and the regulation process is ensured to be disturbance-free and the target is conflict-free.

[0123] 1) Response time control:

[0124] <1) Utilizing the faster mechanical response of the molten salt pump, high-temperature molten salt is preferentially dispatched into the steam generator to fill the initial response gap of the thermal power unit (steam turbine governor delay time).

[0125] <2> Preheat prediction: When the load increase command is given for the third time in a row, start the molten salt pump at low speed in advance, and shorten the start-up delay to within 5 minutes.

[0126] 2) Response rate control:

[0127] By dynamically adjusting the molten salt circulation flow rate, the heat exchange capacity of the steam generator is controlled, and thus the power change rate of the thermal power generating unit is stabilized. When T salt ≤T salt,min , the power is forced to be reduced to 50% of the rated power.

[0128] 3) Response accuracy control:

[0129] In coordination with the action of the steam turbine regulating valve of the thermal power generating unit, the molten salt energy storage power is dynamically adjusted based on the MPC algorithm to make the combined output quickly converge to the AGC command target value, thereby ensuring the accuracy of frequency modulation.

[0130] In this embodiment, the cold and hot molten salt tank capacities of the molten salt energy storage system are maintained in a balanced mode. Specifically:

[0131] (1) Dynamic evaluation period

[0132] 1) Combined with the load prediction and frequency modulation demand of the power grid: If there is a continuous frequency modulation command (such as load fluctuation > 5% rated power) in the next 1 hour, the evaluation period is shortened to 10 minutes; if there is no significant frequency modulation demand, the original period (5 minutes in the valley and 30 minutes in the peak) is executed.

[0133] 2) Capacity trend prediction: The capacity state in the next 2 hours is predicted through the capacity change rate in the last 1 hour, and a warning is triggered 1 hour in advance (such as predicted to be reduced to 15%, start the preparation for storage in advance).

[0134] (2) When the effective heat storage capacity < 20% or > 80%, it is determined that the capacity is deviated, and the balanced mode is triggered; if it is within a reasonable range, it is determined that it is not deviated, the adjustment process is ended, and the monitoring is maintained.

[0135] The balanced mode is as follows:

[0136] 1) Low capacity scenario (<20%)

[0137] <1> When the power grid is in the valley and there is no power waste, the redundant heat (flue gas waste heat) of the thermal power generating unit at low load is used to heat the molten salt.

[0138] <2> When there is power waste, in addition to using the flue gas waste heat, the molten salt is heated by an electric heater.

[0139] ​<3>Supplemental storage rate control: according to the future frequency modulation demand prediction, if there is no significant load increase instruction within 1 hour, the supplemental storage rate is set to 80% of the rated power (fast recovery); if there is potential frequency modulation demand, it is limited to 50% (reserve part of the response ability).

[0140] 2) High capacity scenario (> 80%)

[0141] <1> Safe energy release: a small amount of molten salt (flow is only 10%-20% of the rated heat storage flow) is drawn from the high-temperature molten salt tank and exchanged with cold reheat steam to generate steam introduced into the intermediate pressure cylinder of the steam turbine. Under the premise of not interfering with the operation of the thermal power unit, the redundant heat storage capacity is slowly consumed to avoid the risk of equipment caused by over-temperature or over-full heat storage of molten salt;

[0142] <2> Heat storage suspension threshold: when the capacity is > 90%, all heat storage operations (including abandoned heating) are forced to suspend to prioritize equipment safety.

[0143] The bidirectional collaborative optimization proposed in the application realizes the deep complementation of thermal power and molten salt by the auxiliary thermal power unit frequency modulation control strategy of molten salt "increasing load heat release and reducing load heat storage", reduces the adjustment pressure of the thermal power unit, applies the hierarchical regulation and control and multi-instruction processing logic to all frequency modulation scenarios to improve the adjustment accuracy under complex working conditions, strengthens the capacity balancing mechanism to ensure that the molten salt energy storage system can be used for a long time, and guarantees that the system can continuously participate in grid frequency modulation, and through unified evaluation and hierarchical regulation of the molten salt energy storage system state, the system reliability is improved.

[0144] In an exemplary embodiment, a computer device is provided, including a memory and a processor, the memory storing a computer program, and the processor implementing the steps in the above-mentioned method embodiments when executing the computer program. The computer device can be a server or a terminal. The computer device includes a processor, a memory, an input / output interface (Input / Output, I / O for short), and a communication interface. The processor, the memory, and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store to-be-processed data. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals through a network connection. The computer program is executed by the processor to implement a molten salt energy storage control method for assisting frequency modulation of a thermal power unit.

[0145] In an exemplary embodiment, a computer readable storage medium storing a computer program is provided, the computer program, when executed by a processor, implements the steps of any of the above method embodiments.

[0146] In an exemplary embodiment, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements the steps of any of the above method embodiments.

[0147] It should be noted that the user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the present application are all information and data authorized by the user or authorized by all parties, and the collection, use and processing of related data need to comply with relevant regulations.

[0148] It can be understood by those skilled in the art that all or part of the processes in the above-mentioned embodiments can be completed by a computer program instructing related hardware, and the computer program can be stored in a non-volatile computer readable storage medium. When the computer program is executed, it can include the processes of the above-mentioned embodiments. Any reference to memory, database or other medium used in the embodiments provided by the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (Read-Only Memory, ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive memory (ReRAM), magnetoresistive memory (Magnetoresistive Random Access Memory, MRAM), ferroelectric memory (Ferroelectric Random Access Memory, FRAM), phase change memory (Phase Change Memory, PCM), graphene memory, etc. Volatile memory can include random access memory (Random Access Memory, RAM) or external cache memory, etc. As an illustration but not limitation, RAM can be in various forms, such as static random access memory (Static Random Access Memory, SRAM) or dynamic random access memory (Dynamic Random Access Memory, DRAM), etc.

[0149] The database involved in each of the embodiments provided in the present application can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a blockchain, and the like, without being limited thereto. The processor involved in each of the embodiments provided in the present application can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, and the like, without being limited thereto.

[0150] The technical features of the above embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above embodiments are not described, but it should be considered that any combination of the technical features is within the scope of the present disclosure, as long as there is no contradiction.

[0151] The principles and implementation modes of the present application are described by applying specific examples herein, and the above embodiments are only used to help understand the method of the present application and its core idea. Meanwhile, for those skilled in the art, the specific implementation modes and application ranges will be changed according to the idea of the present application. In summary, the content of the present description should not be understood as a limitation of the present application.

Claims

1. A molten salt energy storage control method for assisting frequency regulation of thermal power units, characterized in that, include: When the automatic power generation control command changes, the command is parsed to determine the load change; the load change includes load increase and load decrease. The regulation capability of the molten salt energy storage system is determined based on its total capacity; the regulation capability of the molten salt energy storage system includes whether the molten salt energy storage system has regulation capability and whether the molten salt energy storage system does not have regulation capability. The capacity of the molten salt energy storage system is determined based on the energy required to increase the load and the current effective thermal storage capacity of the molten salt tank; the capacity of the molten salt energy storage system includes whether the molten salt energy storage system has sufficient capacity or insufficient capacity; Different molten salt energy storage control strategies are adopted to control molten salt energy storage based on load changes, the regulation capacity of the molten salt energy storage system, and the capacity of the molten salt energy storage system. The molten salt energy storage control strategy includes: the molten salt energy storage system independently performs load increase tasks; the thermal power unit and the molten salt energy storage system jointly perform load increase tasks; the thermal power unit independently performs load increase tasks while simultaneously performing hot molten salt tank capacity maintenance; the molten salt energy storage system independently performs load reduction tasks; the thermal power unit and the molten salt energy storage system jointly perform load reduction tasks; and the thermal power unit independently performs load reduction tasks while simultaneously performing cold molten salt tank capacity maintenance.

2. The molten salt energy storage control method for assisting frequency regulation of thermal power units according to claim 1, characterized in that, When the automatic generation control command changes, the automatic generation control command is parsed to determine the load change, specifically including: If the automatic power generation control command is greater than the current actual output of the combined system, the load is determined to increase; the combined system includes thermal power units and molten salt energy storage system. If the automatic generation control command is less than the current actual output of the combined system, the load reduction is determined.

3. The molten salt energy storage control method for assisting frequency regulation of thermal power units according to claim 1, characterized in that, Different molten salt energy storage control strategies are adopted to control molten salt energy storage based on load changes, the regulation capacity of the molten salt energy storage system, and the system capacity. Specifically, these strategies include: When the load increases, the molten salt energy storage system has the ability to regulate and its capacity is sufficient. The molten salt energy storage system can independently perform the load increase task. The sufficient capacity of the molten salt energy storage system means that the effective heat release capacity of the molten salt tank in the molten salt energy storage system is greater than or equal to the energy of the load increase. When the load increases, the molten salt energy storage system has the ability to regulate, but the capacity of the molten salt energy storage system is insufficient. The thermal power unit and the molten salt energy storage system work together to perform the load increase task. The insufficient capacity of the molten salt energy storage system means that the effective heat release capacity of the molten salt tank in the molten salt energy storage system is less than the energy required to increase the load. When the load increases and the molten salt energy storage system does not have the ability to regulate, the thermal power unit independently performs the load increase task and performs hot molten salt tank capacity maintenance. When the load decreases, the molten salt energy storage system has the ability to regulate, and the molten salt energy storage system has sufficient capacity, the molten salt energy storage system can independently perform the load reduction task; the sufficient capacity of the molten salt energy storage system means that the effective heat storage capacity of the molten salt tank in the molten salt energy storage system is greater than or equal to the energy of load reduction. When the load decreases, the molten salt energy storage system has the ability to regulate, and when the capacity of the molten salt energy storage system is insufficient, the thermal power unit and the molten salt energy storage system work together to perform the load reduction task; the insufficient capacity of the molten salt energy storage system means that the effective heat storage capacity of the molten salt tank in the molten salt energy storage system is less than the energy of load reduction. When the load decreases and the molten salt energy storage system lacks the ability to regulate, the thermal power unit independently performs the load reduction task while simultaneously performing cold molten salt tank capacity maintenance.

4. The molten salt energy storage control method for assisting frequency regulation of thermal power units according to claim 1, characterized in that, When thermal power units and molten salt energy storage systems work together to increase load, or when thermal power units and molten salt energy storage systems work together to decrease load, the thermal power units and molten salt energy storage systems are adjusted according to the sub-instruction sequence. When the molten salt energy storage system independently performs a load increase task or an independent load decrease task, the molten salt energy storage system is adjusted according to the sub-instruction sequence; When a thermal power unit independently performs a load increase task or a load decrease task, the molten salt energy storage system is adjusted according to the sub-instruction sequence. The sub-instruction sequence is obtained by decomposing the automatic generation control instruction using a model predictive control algorithm; the sub-instruction sequence includes response time control sub-instruction, response rate control sub-instruction, response accuracy control sub-instruction, molten salt heat storage and release efficiency control sub-instruction, and molten salt capacity recovery control sub-instruction.

5. The molten salt energy storage control method for assisting frequency regulation of thermal power units according to claim 4, characterized in that, The automatic generation control command is decomposed using a model predictive control algorithm, specifically including: Construct the target functions for each sub-instruction; Construct the overall objective function based on the objective functions of each instruction; For any molten salt energy storage control strategy, a model predictive control algorithm is adopted to solve the total objective function under the current molten salt energy storage control strategy through rolling optimization, and the sub-instruction sequence is obtained.

6. The molten salt energy storage control method for assisting frequency regulation of thermal power units according to claim 5, characterized in that, The target functions of each sub-instruction include: The objective function J of the response time control sub-instruction t : Where k represents the current control time; i represents the number of steps in the prediction time domain; N represents the length of the prediction time domain; τ salt (k+i) represents the response delay of the molten salt energy storage system at step i starting from time k; τ unit (k+i) represents the response delay of the i-th thermal power unit starting from time k; α1 represents the start-up time penalty weight of the molten salt energy storage system; α2 represents the start-up time penalty weight of the thermal power unit; if α1 >> α2, it means that the molten salt energy storage system undertakes the load increase task alone; if α1 << α2, it means that the thermal power unit undertakes the load increase task alone. The objective function J of the response rate control sub-instruction r : in, This represents the rate of change of total power at step i starting from time k; This represents the target rate of the i-th automatic power generation control command starting from time k. This represents the rate of change in power contributed by the molten salt energy storage system at step i starting from time k; This represents the maximum safe power change rate of the molten salt energy storage system at step i starting from time k; This represents the rate of change in power contribution from the thermal power unit at time k in the i-th step. β1 and β2 represent the maximum safe power change rate of the thermal power unit at step i starting from time k; β1 and β2 represent the weighting coefficients, respectively. The objective function J of the response precision control sub-instruction z : Where P(k+i) represents the actual power at step i starting from time k; P ref (k+i) represents the target power at step i starting from time k; μ represents the temperature weight; H hot (k+i) represents the molten salt tank level at step i starting from time k; H hot,min (k+i) represents the minimum safe level of molten salt in the hot tank; I low This represents the liquid level indication function, which is 1 when the liquid level is below the minimum safe level and 0 otherwise. The objective function J of the molten salt heat storage and release efficiency control sub-instruction s : Among them, Q salt (k+i) represents the heat storage capacity of the molten salt at step i starting from time k; Q target (k+i) represents the target heat storage at step i starting from time k; T salt,out (k+i) represents the molten salt heat exchanger outlet temperature at step i starting from time k; T design This represents the design temperature; δ1 and δ2 represent the weighting coefficients, respectively. The objective function J of the molten salt capacity recovery sub-control instruction c : Among them, L hot,target L cold,target These represent the target liquid levels in the hot molten salt tank and the cold molten salt tank, respectively; I hot,low I cold,low ε1 and ε2 represent the liquid level indication functions for the hot molten salt tank and the cold molten salt tank, respectively. ε1 is 1 when the liquid level is lower than the target liquid level, and 0 otherwise. ε2 represents the weighting coefficients. The expression for the overall objective function is: J=ω t J t +oh r J r +oh z J z +oh s J s +oh c J c Where, ω t ω r ω z ω s ω c These represent the control weights for response time, response rate, response accuracy, molten salt heat storage and release efficiency, and molten salt capacity recovery, respectively.

7. The molten salt energy storage control method for auxiliary frequency regulation of thermal power units according to claim 6, characterized in that, When the molten salt energy storage system independently performs load increase tasks, ω t and ω r Molten salt energy storage systems account for 90%; When thermal power units and molten salt energy storage systems work together to perform load increase tasks, ω r The molten salt energy storage system is allocated to thermal power units at a ratio of 2:3; When a thermal power unit performs a load increase task alone, and the hot molten salt tank is undergoing capacity maintenance, ω r The proportion of medium-density thermal power units is 100%.

8. The molten salt energy storage control method for auxiliary frequency regulation of thermal power units according to claim 6, characterized in that, When the molten salt energy storage system performs load reduction tasks independently, ω t Molten salt energy storage systems account for 90%; When thermal power units and molten salt energy storage systems work together to perform load reduction tasks, ω r The molten salt energy storage system is allocated to thermal power units at a ratio of 3:5; When a thermal power unit independently performs load reduction tasks while simultaneously performing cold molten salt tank capacity maintenance, ω r The proportion of medium-density thermal power units is 100%.

9. A computer device, comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the computer program to implement the molten salt energy storage control method for frequency regulation of auxiliary thermal power units as described in any one of claims 1-8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the molten salt energy storage control method for frequency regulation of auxiliary thermal power units as described in any one of claims 1-8.

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