Method for improving frequency modulation technology through electric heating linkage of thermal power plant

Abstract

The invention relates to the technical field of power system frequency modulation control, in particular to a method for improving the frequency modulation technology through electric heating linkage of a thermal power plant. According to the technical scheme, the method for improving the frequency modulation technology through electric heating linkage of the thermal power plant comprises the following steps that S1, a multi-input first-order inertial transfer function model of dynamic response of a heat supply network is established through a heat source side step test and a system identification method; s2, constructing a multivariable cooperative control model, including an energy correlation model of a thermal load and a steam extraction amount, a linear relation model of the steam extraction amount and an electrical load, and a control model of the electrical load and a valve opening degree; and S3, implementing an electric heating linkage frequency modulation control strategy, triggering dynamic feed-forward compensation according to a homodromous judgment result of the AGC instruction and the power grid frequency deviation, performing hierarchical response control based on the rotating speed deviation, linking a heat supply network quick-closing valve, and generating a weighted heat supply correction instruction. Deep cooperation of heat supply network energy storage and power frequency modulation is achieved, and the frequency modulation performance of the unit is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency modulation control in power systems, and particularly to a method for improving frequency modulation technology through electro-thermal linkage in thermal power plants. Background Art

[0002] With the transformation of the global energy structure, the proportion of new energy power generation (such as wind power and photovoltaic power) in the power system is increasing continuously. However, the intermittency and volatility of new energy power generation pose severe challenges to the stability and frequency modulation ability of the power grid. In this context, traditional thermal power units, especially cogeneration units, need to undertake more peak shaving and frequency modulation tasks to ensure the stable operation of the power grid.

[0003] Cogeneration units have high energy utilization efficiency by providing both electricity and heat simultaneously. However, due to the strong coupling characteristics between heat supply and power generation, traditional cogeneration units face the following main problems during the frequency modulation process:

[0004] "Power determined by heat" constraint: The electrical load and heat load of cogeneration units are closely coupled. When frequency modulating, it is necessary to meet the heat load demand simultaneously, resulting in a slow frequency modulation response speed and low regulation accuracy.

[0005] Thermal network time-delay characteristic: The thermal network system has significant time-delay characteristics, which causes a delay when the unit responds to the power grid frequency modulation command and affects the frequency modulation performance.

[0006] Lack of coordinated control mechanism: In the existing technology, the coordinated control mechanism between thermal network energy storage and power frequency modulation is imperfect, and it is difficult to make full use of the heat storage capacity of the thermal network to improve the frequency modulation response speed and accuracy.

[0007] Frequency modulation assessment pressure: The assessment indicators of the power grid for frequency modulation performance (such as response rate and regulation accuracy) are becoming increasingly strict. Traditional cogeneration units are difficult to meet these requirements and face greater economic assessment pressure.

[0008] The existing technology is difficult to fully exert the potential of cogeneration units when dealing with the frequency modulation requirements brought about by the access of new energy. Summary of the Invention

[0009] The present invention proposes a method for improving frequency modulation technology through electro-thermal linkage in thermal power plants, which solves the problems of slow frequency modulation response, low accuracy, and poor economy of traditional cogeneration units in the existing technology due to the "power determined by heat" constraint, thermal network time-delay characteristics, and lack of coordinated control mechanism.

[0010] To solve the above technical problems, the technical solution adopted by the present invention is:

[0011] A method for improving frequency modulation technology through electro-thermal linkage in thermal power plants, comprising the following steps:

[0012] Step S1, establishing a multi-input first-order inertia transfer function model of the dynamic response of the heating network through a step test on the heat source side and a system identification method;

[0013] Step S2, constructing a multivariable collaborative control model, including an energy correlation model between heat load and steam extraction, a linear relationship model between steam extraction and electrical load, and a control model between electrical load and valve opening;

[0014] Step S3, implement the electric-heat linkage frequency modulation control strategy, trigger the dynamic feedforward compensation according to the same direction judgment result of the AGC instruction and the grid frequency deviation, perform graded response control based on the speed deviation, link the heat network fast closing valve and generate a weighted heating correction instruction;

[0015] Step S4, integrating grid assessment and economic evaluation: freezing the adjustment of heating target value within a frequency regulation assessment cycle, calculating the peak regulation compensation income and evaluating the investment payback period.

[0016] Furthermore, the form of the multi-input first-order inertia transfer function in step S1 is Where K is the steady-state gain, T is the time constant, and τ is the pure lag time, which is determined by fitting the step response data of the inlet and outlet water temperatures of the heating network using the least squares method.

[0017] Furthermore, the energy correlation model of the heat load and the steam extraction amount in step S2 is expressed by the formula

[0018] Q=D·c·(T out -T in ) / 3.6 Calculate the heat load of the heating network, and calculate the extraction volume D based on the difference between the extraction enthalpy and the drainage enthalpy s .

[0019] Furthermore, the steam extraction amount D s The linear relationship between the unit power change ΔP and ΔP=K·ΔD s , where K is the steam extraction-electric load conversion coefficient.

[0020] Furthermore, the isotropic determination function in step S3 is dir=sign(P AGC (t)-P AGC (t-Δt))∑sign(Δf), where dir represents the judgment result, sign() represents the symbolic function in mathematics, and P AGC (t) represents the power command of the automatic generation control AGC system at time t, P AGC (t-Δt) represents the AGC power command at time t-Δt, Δf represents the grid frequency deviation, and when the same direction occurs, the feedforward compensation is triggered, and the compensation amount is

[0021] Further, the condition for hierarchical response control in step S3 is that when the rotational speed deviation |Δn| > 2.5 r / min, the heat network quick closing valve is linked, the weighted heat supply correction instruction satisfies w1 + w2 = 1, and the weight coefficient is dynamically adjusted according to the heat supply scenario.

[0022] Further, the calculation formula for peak shaving compensation income in step S4 is where the compensation unit price λ is determined according to the real-time situation of the power grid.

[0023] Further, the investment payback period model in step S4 is where T is the investment payback period, C is the total project investment, and R is the average annual peak shaving compensation income.

[0024] Further, the multivariable coordinated control model and the frequency modulation control strategy are integrated into the DCS system to realize the real-time closed-loop control of unit parameters.

[0025] Further, in step S4, the adjustment of the heat supply target value is frozen within the assessment period: where T set is the heat supply target value, which can be the heat network supply water temperature or the set value of the heat supply load, is the change rate of the heat supply target value.

[0026] The positive effects of the present invention are as follows: The present invention realizes the deep coordination of heat network energy storage and power frequency modulation, significantly improves the frequency modulation performance of the unit, and key indicators such as the AGC instruction response time, the qualified rate of primary frequency modulation actions, and the peak shaving compensation income are greatly optimized, providing an efficient solution for improving the frequency modulation ability and economic optimization of cogeneration units under the background of new energy consumption.

[0027] By obtaining a multi-input first-order inertial transfer function to quantify the time-delay characteristics of the heat network, constructing a relationship model between heat load - extraction steam volume - electric load - valve opening, realizing the accurate mapping of thermoelectric parameters; designing an AGC dynamic feedforward control and a primary frequency modulation hierarchical response mechanism, balancing the heat supply stability and the power grid frequency modulation requirements through a co-directionality judgment function and a weighted heat supply correction instruction; obtaining a heat load compensation mechanism according to the heat network delay characteristics and the relationship model between heat load - extraction steam volume - electric load - valve opening; according to the assessment mechanism of each regional power grid, by measuring the improvement of the frequency modulation income for each electro-thermal linkage, combining the peak shaving compensation income and the investment payback period model to quantify the project economy.

[0028] Breaking the "electricity determined by heat" constraint, realizing the parametric expression of the heat network delay characteristics, enabling the unit to predict in advance the impact of heat load changes on electric load regulation.

[0029] Form a closed-loop control link for the thermoelectric coupling system to enable real-time linkage between the energy storage state of the heat network and the electric load regulation command, and improve the response accuracy of the unit.

[0030] According to the heat network delay characteristics and the relationship model of heat load - extraction steam volume - electric load - valve opening, obtain a heat load compensation mechanism to realize the judgment of the adjustment of the heating valve opening and the influence of heat users; realize the "two-way coordination of heat network energy storage - electric load regulation", greatly shorten the AGC response time, and improve the passing rate of primary frequency modulation actions; break through the singularity of the control of traditional cogeneration units, and construct an integrated framework of "model prediction - intelligent control - economic evaluation" to provide a replicable technical path for the transformation of similar units. Brief Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the technical route of the method for improving the frequency modulation technology by the electro-thermal linkage of the thermal power plant of the present invention;

[0032] Figure 2 It is a schematic diagram of the frequency modulation adjustment heat load compensation in the embodiment of the present invention;

[0033] Figure 3 It is a schematic diagram of the flow of the frequency modulation, delay characteristics, and heat load compensation adjustment method in the embodiment of the present invention. Detailed Embodiments

[0034] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0035] Embodiment 1

[0036] A method for improving the frequency modulation technology by the electro-thermal linkage of a thermal power plant includes the following steps:

[0037] Step S1: Establish a multi-input first-order inertial transfer function model of the dynamic response of the heat network through the step test on the heat source side and the system identification method;

[0038] Step S2: Construct a multivariable coordinated control model, including an energy correlation model of heat load and extraction steam volume, a linear relationship model of extraction steam volume and electric load, and a control model of electric load and valve opening;

[0039] Step S3: Implement the electro-thermal linkage frequency modulation control strategy. According to the judgment result of the same direction of the AGC command and the grid frequency deviation, trigger dynamic feedforward compensation, perform hierarchical response control based on the speed deviation, link the heat network quick-closing valve, and generate a weighted heating correction command;

[0040] Step S4, Integrating Grid Assessment and Economic Evaluation: Freeze the adjustment of the heating target value within the primary frequency regulation assessment period, calculate the peak shaving compensation revenue, and evaluate the payback period, as Figure 1 shown.

[0041] In Step S1, the form of the multi-input first-order inertial transfer function is where K is the steady-state gain, T is the time constant, and τ is the pure dead time, which are determined by fitting the step response data of the water temperatures at the inlet and outlet of the heat network using the least squares method.

[0042] The water in the heat network serves as the heat-carrying medium, and its temperature change requires absorption / release of energy. The water temperature at the inlet of the heat conduction user lags behind the change on the heat source side. Obtain the dynamic response characteristics of the heat network to solve the thermal-electric coupling delay problem during the response to AGC commands.

[0043] Multi-input first-order inertial transfer function:

[0044]

[0045] K: Steady-state gain (K = ΔT out / ΔT in ).

[0046] T: Time constant (unit: min), determined by the heat capacity and heat dissipation of the heat network.

[0047] τ: Pure dead time (unit: min), determined by the pipe length and flow velocity.

[0048] D: Heat network circulating water flow rate (unit: t / h).

[0049] Step response characteristic curve: Pure dead time stage (0 - τ): The water temperature at the inlet of the heat user remains unchanged. Inertial response stage (τ - τ + T): The water temperature at the inlet of the heat user approaches the steady-state value according to an exponential law.

[0050] The input step signal is the water temperature at the inlet of the heat network ΔT_in(t) = A·u(t), and the water temperature at the inlet of the heat user T out (t):

[0051]

[0052] A is the step change amount of the water supply temperature on the heat source side, with the unit of °C.

[0053] In the energy correlation model between the heat load and the extraction steam volume in Step S2, the heat load of the heat network is calculated through the formula

[0054] Q = D·c·(T out -T in ) / 3.6, and the extraction steam volume D is calculated based on the difference between the extraction steam enthalpy and the drain enthalpy s .

[0055] Calculation of Heat Load of Heat Network

[0056] According to the inlet and outlet temperatures of the heat source and the heat network flow rate, the calculation formula for the heat load Q of the heat network is:

[0057] Q = D·c·(T out - T in ) / 3.6 (3)

[0058] Q: Heat load of the heat network, unit kW; D: Heat network flow rate, unit t / h; c: Specific heat capacity of water, unit kJ / (kg·°C); T in : Inlet temperature of the heat source, unit °C; T out : Outlet temperature of the heat source, unit °C.

[0059] Calculation of Extraction Steam Flow Rate of Steam Turbine

[0060] Based on the law of conservation of energy, the extraction steam flow rate D is calculated through the enthalpy values of the extraction steam and the drain water s :

[0061]

[0062] D s : Extraction steam flow rate for heating, t / h; h cn : Specific enthalpy of extraction steam of the steam turbine, unit kJ / kg, obtained by looking up the enthalpy-entropy table of steam according to the extraction steam pressure and temperature; h ss : Specific enthalpy of drain water of the heat network heater, unit kJ / kg, obtained by looking up the enthalpy value table according to the heater pressure and drain water temperature.

[0063] Relationship between Extraction Steam Flow Rate and Electrical Load

[0064] Assume that the unit responds to the change in extraction steam flow rate for frequency modulation ΔD s , the change in unit power ΔP can be expressed as:

[0065] ΔP = K·ΔD s (5)

[0066] is the conversion coefficient between extraction steam flow rate and electrical load, unit MW / (t / h), where h n is the enthalpy of turbine exhaust steam, unit kJ / kg.

[0067] Relationship between Extraction Steam Flow Rate and Valve Opening

[0068] The regulation of heat network load mainly involves the EV valve (quick closing valve for extraction steam for heating), LV valve (valve for connecting the middle and low pressure cylinders) and industrial extraction steam regulating valve. Through the flow-opening characteristic curves of each valve under the heating condition, the relationship between the valve and the flow rate after the change in extraction steam flow rate can be obtained as:

[0069] Ds = a0 + a1μ + a2μ 2 + ………… + a m μ m (6)

[0070] μ: Valve opening, unit: %; a0, a1, a2, ······, a m are polynomial coefficients, and m is the highest degree of the polynomial.

[0071] Electric load - valve opening relationship

[0072] During the frequency modulation process of the thermal power unit, the change in electric load and the valve opening need to be precisely matched to achieve fast and stable power regulation. The electric load - valve characteristic function is used to quantify this relationship, and the formula is:

[0073]

[0074] μ: Valve opening, μ max is the maximum valve opening limit, unit: %;

[0075] ΔP: Change in the electric load of the unit, unit: MW. After the frequency modulation command is issued, ΔP can be obtained.

[0076] K v : Valve flow coefficient, unit: MW / min, indicating the change in electric load corresponding to a 1% change in opening.

[0077] ΔP rated : Rated load change, unit: MW, referring to the maximum load change range allowed under the rated operating conditions of the unit.

[0078] By the ratio of ΔP to K v ·ΔP rated , determine the proportion of the electric load change in the rated regulation capacity, and then multiply by μ max , to obtain the valve opening μ.

[0079] Extraction steam flow D s and the change in unit power ΔP satisfy a linear relationship ΔP = K·ΔD s , where K is the extraction steam - electric load conversion coefficient.

[0080] The co - directionality judgment function in step S3 is dir = sign(P AGC (t) - P AGC (t - Δt))·sign(Δf), where dir represents the judgment result, sign() represents the sign function in mathematics, P AGC (t) represents the power command of the automatic generation control AGC system at time t, P AGC(t - Δt) represents the AGC power command at time t - Δt, and Δf represents the power grid frequency deviation. When they are in the same direction, feed-forward compensation is triggered, and the compensation amount is

[0081] To ensure that the feed-forward compensation is only enabled when it helps to balance the power-frequency of the power grid, the co-direction judgment function can avoid ineffective or reverse regulation.

[0082] dir = sign(P AGC (t) - P AGC (t - Δt))·sign(Δf) (8)

[0083] dir represents the judgment result, and finally outputs the logical attribute of "in the same direction" or "in the opposite direction" through symbolic operations. sign() represents the sign function in mathematics, which judges the change direction of physical quantities. If the input value is positive, it outputs 1; if the input value is negative, it outputs -1; if the input value is 0, it outputs 0. P AGC (t) represents the power command of the automatic generation control (AGC) system at time t, with the unit of MW. P AGC (t - Δt) represents the AGC power command at time t - Δt. Where Δt is the set time interval, used to compare the changes of AGC commands at different times and judge its increase or decrease trend. Δf represents the power grid frequency deviation, that is, the difference between the actual frequency and the rated frequency, with the unit of Hz.

[0084] AGC command change direction: P AGC (t) - P AGC (t - Δt) calculates the change of the AGC command within Δt, and the sign function outputs its direction (1 for increasing power, -1 for decreasing power).

[0085] Power grid frequency difference direction: Δf is the frequency deviation, and sign(Δf) outputs the adjustment direction (1 for reducing power, -1 for increasing power).

[0086] Final direction judgment: Multiply the two signs of the AGC command change direction and the power grid frequency difference direction. If the result is 1, the AGC command is consistent with the frequency difference adjustment direction, and feed-forward compensation is triggered (same-direction action). If the result is -1 or 0: the directions are inconsistent, and compensation is not triggered (opposite-direction action).

[0087] Utilize the prediction characteristic of feed-forward control to adjust the unit power in advance when the AGC command changes. When the AGC requires rapid power increase and meets the co-direction condition, the feed-forward compensation can accelerate the response and reduce the lag of traditional control.

[0088]

[0089] ΔP feed is the feed-forward compensation power. When the system judges as "same-direction action", through the differential coefficient Kd The product of the AGC instruction change rate quickly generates the compensation power to respond to the grid demand in advance; if it is "reverse action", the compensation is not triggered (ΔP feed = 0).

[0090] K d determines the feed-forward compensation intensity, generally taking 0.8 min. The AGC instruction change rate is larger and in the same direction, K d makes ΔP feed increase synchronously, accelerating the response. It is necessary to reasonably set K d to balance the response speed and system stability and avoid over-compensation.

[0091] Through equations (3)-(6), the electric load change is accurately converted into the valve opening, extraction steam flow rate and heat load change, improving the response accuracy of the unit to the AGC instruction and primary frequency regulation demand. With the help of μ max ensure that the valve opening is within the safe range, avoiding the imbalance of the heat network pressure and abnormal operation of the unit. Provide a quantitative basis for the coordinated control of heat network energy storage and electric load regulation, optimize the dynamic performance of the system, and make the valve action closely cooperate with the unit frequency regulation strategy.

[0092] The condition for the hierarchical response control in step S3 is: when the rotational speed deviation |Δn| > 2.5 r / min, the heat network quick closing valve is linked, the weighted heating correction instruction satisfies w1 + w2 = 1, and the weight coefficient is dynamically adjusted according to the heating scenario.

[0093] During the primary frequency regulation process, in order to balance the heating stability and the grid frequency regulation demand, a weighted heating correction load instruction is introduced:

[0094] P adj = w1·P heat + w2·P fm (10)

[0095] P adj is the corrected comprehensive load instruction, which is used to guide the unit to consider the heating demand during frequency regulation. P heat is the load reference value related to heating, which reflects the basic demand of the heat network for the unit load. P fm is the load adjustment amount required for primary frequency regulation, which is calculated based on the grid frequency deviation. w1 is the weight of heating steam supply. During the winter heating period, it is necessary to give priority to ensuring the heating of residents, so a higher weight is given to ensure the stability of heating steam supply. w2 is the weight of industrial steam supply. The flexibility of industrial steam supply is relatively high, and a low weight is default; if industrial steam supply is the core business and allows adjustment, w1 + w2 = 1.

[0096] The trigger condition for optimizing the frequency difference driving strategy is adopted as the rotational speed deviation Δn = 3000·Δf, and the response is graded according to the deviation magnitude:

[0097] Small deviation (|Δn| < 2.5 r / min): Only the steam turbine governing valve responds; avoid frequent operation of the heat network quick closing valve, reduce the interference to heating, and maintain stable heating.

[0098] Large deviation (|Δn| > 2.5 r / min): Link the heat network quick closing valve, and the response delay ≤ 10 seconds. When the frequency deviation is large, relying solely on the steam turbine governing valve is insufficient, and the heat network quick closing valve is required to cooperate.

[0099] Through hierarchical response, primary frequency modulation realizes precise control under different frequency deviations, which not only ensures the stability of the power grid frequency, but also reduces the disturbance to the heating system and improves the comprehensive operation performance of the cogeneration unit.

[0100] The calculation formula for the peak shaving compensation income in step S4 is where the compensation unit price λ is determined according to the real-time situation of the power grid.

[0101] The investment payback period model in step S4 is where T is the investment payback period, C is the total project investment, and R is the average annual peak shaving compensation income.

[0102] The multivariable coordinated control model and the frequency modulation control strategy are integrated into the DCS system to realize real-time closed-loop control of the unit parameters.

[0103] In step S4, freeze the adjustment of the heating target value during the assessment period: where T set is the heating target value, which can be the heat network supply water temperature or the heating load set value, is the change rate of the heating target value.

[0104] Guarantee of primary frequency modulation priority:

[0105] In the operation of the power grid, primary frequency modulation is crucial for maintaining frequency stability, so its priority needs to be guaranteed. The specific measures are: within the assessment period (usually set to 5 minutes), freeze the adjustment of the heating target value, that is:

[0106] Freeze the adjustment of the heating target value within the assessment period (5 minutes):

[0107]

[0108] T set : The heating target value, which can be the heat network supply water temperature or the heating load set value. : The change rate of the heating target value, set to 0 means that the heating target value remains unchanged within the assessment period and does not actively adjust.

[0109] During the assessment period, if the heating target value is adjusted and primary frequency modulation is carried out simultaneously, the frequency modulation effect may be affected due to control logic conflicts. Freezing the heating target value can ensure that the unit responds to primary frequency modulation first, meeting the grid's assessment requirements for frequency regulation. For example, during the peak heating period in winter, if the grid frequency drops suddenly, the unit immediately adjusts the frequency through the steam turbine control valve, while the heating temperature set value remains unchanged, avoiding heating regulation interfering with the frequency modulation response.

[0110] AGC compensation logic:

[0111] To balance AGC regulation and heating demand, combined with the time-delay characteristic (τ) of the heat network, the heating system is compensated in advance by predicting the change of the AGC command, reducing heating fluctuations, and realizing the coordination of power generation and heating. The AGC compensation logic is designed as follows:

[0112] P heat (t) = P AGC (t + τ) - P AGC (t) (12)

[0113] P heat (t): The power that needs to be compensated for the heating system at time t, used to adjust the heat storage release or storage of the heat network. P AGC (t): The power generation command of AGC at time t. P AGC (t + τ): The predicted value of the AGC power command at a future time considering the heat network time-delay τ. The heating compensation amount is calculated through the difference to achieve advanced regulation.

[0114] If the AGC command requires the unit to increase power after τ time in the future, calculate P heat (t) and adjust the heat storage of the heat network in advance to ensure that the heating system has been adapted when the unit executes the AGC power increase command.

[0115] Thermal load compensation in response to frequency modulation

[0116] Assume that at time t1, the unit receives a frequency modulation command. To improve the frequency modulation response speed, the opening of the heating valve is adjusted from μ to μ1, and the frequency modulation adjustment is completed at time t2. Since the heating load decreases to improve the frequency modulation response, therefore, to make up for this part of the heating load, after the frequency modulation adjustment is completed, the valve opening is adjusted to μ2 and lasts until time t3 to complete the response compensation of the entire frequency modulation.

[0117] Before time t1, the extraction steam flow rate for heating is D s , according to the AGC command, the required ΔP for the response can be obtained, and the opening of the control valve corresponding to the frequency modulation command can be obtained from formula (7). The extraction steam volume ΔD required for frequency modulation can be obtained according to formula (5) s .

[0118] Starting from t2, the extraction steam volume is D s +ΔD s, according to formula (6), the valve opening μ2 required for heat load compensation can be obtained, and the compensation duration is default equal to the adjustment duration. After reaching time t3, the valve supplies heat at the normal opening, specifically as Figure 2 shown.

[0119] Based on the delay time obtained from formula (1), if the frequency modulation completion time is less than the delay time, seamless regulation for heat users can be achieved through heat load compensation. If the frequency modulation completion time is greater than the delay time, there will be fluctuations in heat users in the short term after heat load compensation.

[0120] Economic evaluation module

[0121] The peak shaving compensation revenue is used to quantify the economic return of the unit participating in the power grid peak shaving and frequency modulation services. The calculation formula is:

[0122]

[0123] R: Total peak shaving compensation revenue (yuan), reflecting the economic value of the unit's peak shaving. N: Total number of peak shaving events, reflecting the frequency of participating in peak shaving. ΔP i : Power adjustment amount (MW) for the i-th peak shaving, representing the contribution of a single peak shaving. λ: Peak shaving compensation unit price (yuan / (MWh)), determined by the power grid policy or market mechanism. t i : Duration (h) of the i-th peak shaving, i.e., the service duration.

[0124] The payback period is used to evaluate the economy of unit transformation or new technology application. The model is:

[0125]

[0126] T: Payback period (years), reflecting the cost recovery speed. C: Total project investment (yuan), covering equipment procurement, installation and commissioning, technology research and development, etc. R: Annual average peak shaving compensation revenue (yuan / year), taking the annual average value of the peak shaving compensation revenue.

[0127] The payback period model helps enterprises judge the economy of projects such as frequency modulation technology upgrade and heat network energy storage transformation.

[0128] Example 2

[0129] Based on Example 1, this example discloses a method for improving the frequency modulation technology of a thermal power plant through electro-thermal linkage, aiming to solve the problems of slow frequency modulation response, low accuracy, and poor economy caused by the "power generation determined by heat supply" constraint, heat network time-delay characteristics, and lack of coordinated control mechanism in traditional combined heat and power units.

[0130] A method for improving the frequency modulation technology of a thermal power plant through electro-thermal linkage includes the following steps:

[0131] The time-delay characteristics of the heating network are quantitatively modeled using a multi-input first-order inertia transfer function Describe the dynamic response of the heating network by applying a step signal on the heat source side, measuring the water temperature changes at the inlet and outlet of the heating network, and using the system identification method to determine the steady-state gain K, time constant T and pure lag time τ;

[0132] Construct a multivariable collaborative control model, including:

[0133] According to the heat source inlet and outlet temperature T out , T in And the heat network flow D, through the formula Q = D·c·(T out -T out ) / 3.6 Calculate the heat load Q of the heating network;

[0134] According to the heat load Q, using the formula Calculate the steam extraction capacity D of the steam turbine s , where h cn is the extraction enthalpy, h ss is the hydrophobic enthalpy;

[0135] Establish the relationship between extraction steam change and unit power ΔP=K·ΔD s , where ΔD s is the change in extraction steam, ΔP is the change in unit power;

[0136] By valve characteristic function Determine the corresponding relationship between electrical load and valve opening, where K v is the valve characteristic coefficient, ΔP rated is the rated power change, μ max is the maximum opening of the valve;

[0137] The electric-heat linkage frequency regulation control strategy is adopted, including:

[0138] AGC dynamic feedforward control: through the same direction judgment function dir = sign (P AGC (t)-P AGC (t-Δt))·sign(Δf) determines the AGC command power change ΔP text The same direction as the grid frequency deviation Δf, when the same direction, triggers the differential feedforward compensation Where K d is the differential feedforward coefficient;

[0139] Primary frequency modulation hierarchical response: hierarchical control is performed according to the speed deviation Δn=3000·Δf. When |Δn|<2.5r / min, the power is adjusted only by the turbine regulating valve; when |Δn|≥2.5r / min, the heat network fast closing valve is linked, and the weighted heating correction instruction P is introduced. adj= w1·P heat + w2·P fm , where w1 and w2 are weighting coefficients, and P heat is the heating load, and P fm is the primary frequency regulation load;

[0140] According to the heat network delay characteristics and the heat load - extraction steam volume - electric load - valve opening relationship model, a heat load compensation mechanism is obtained to realize the adjustment of the heating valve opening and the judgment of the influence on heat users, as Figure 3 shown.

[0141] Integrate the power grid assessment mechanism and economic evaluation:

[0142] Within the primary frequency regulation assessment period (5 minutes), let the adjustment of the heating target value T text be frozen, and through the AGC compensation logic P text (t) = P text (t + τ) - P text (t) to adapt to the heat storage of the heat network in advance;

[0143] Calculate the peak shaving compensation benefit through the peak shaving compensation benefit formula R = ∑ΔP i ·λ·t i , where ΔP i is the single - time peak shaving adjustment amount, λ is the compensation unit price, and t i is the duration, and evaluate the project economy through the payback period model with the requirement that T ≤ 8 years, where C is the total investment cost.

[0144] In the quantitative modeling of the heat network time - delay characteristics, the system identification method is the least - squares method, and K, T, and τ are determined by fitting the measured water temperature change data at the inlet and outlet of the heat network; in the multivariable coordinated control model, the specific heat capacity c takes the value of 4.186 kJ / (kg·°C).

[0145] In the AGC dynamic feed - forward control, the differential feed - forward coefficient K d is optimized and adjusted according to the unit characteristics and historical operation data.

[0146] In the primary frequency regulation hierarchical response, the weighting coefficients w1 and w2 are dynamically adjusted according to different heating demand scenarios (such as winter heating period, industrial steam supply - dominated scenario), and w1 + w2 = 1.

[0147] In the integration of the power grid assessment mechanism and economic evaluation, the compensation unit price λ is determined according to the relevant power grid policies and market conditions.

[0148] Integrate the models and algorithms involved in the above steps into the DCS system, and realize the real - time control and monitoring of the unit through the DCS system.

[0149] The above-described embodiments are described in relatively detailed and specific terms, expressing the preferred embodiments of the present invention. They are only used to illustrate the technical idea and characteristics of the present invention. The purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. However, it is not limited to the present invention alone. The patent scope of the present invention cannot be limited only by this embodiment. That is, any equivalent changes or modifications made in accordance with the spirit disclosed by the present invention, for researchers or technicians in the field, within the structure of the present invention, local improvements within the system and changes and transformations between subsystems are still within the patent scope of the present invention.

Claims

1. A method for improving the frequency regulation technology through electro-thermal linkage in a thermal power plant, characterized in that, The following steps are involved: Step S1, establishing a multi-input first-order inertia transfer function model of the dynamic response of the heating network through a step test on the heat source side and a system identification method; Step S2, constructing a multivariable collaborative control model, including an energy correlation model between heat load and steam extraction, a linear relationship model between steam extraction and electrical load, and a control model between electrical load and valve opening; Step S3, implement the electric-heat linkage frequency modulation control strategy, trigger the dynamic feedforward compensation according to the same direction judgment result of the AGC instruction and the grid frequency deviation, perform graded response control based on the speed deviation, link the heat network fast closing valve and generate a weighted heating correction instruction; Step S4, integrating grid assessment and economic evaluation: freezing the adjustment of heating target value within a frequency regulation assessment cycle, calculating the peak regulation compensation income and evaluating the investment payback period.

2. The method for the electro-thermal linkage frequency regulation technology improvement in a thermal power plant according to claim 1, characterized in that, In the step S1, the form of the multi-input first-order inertia transfer function is where K is the steady-state gain, T is the time constant, and τ is the pure dead time, which are determined by fitting the step response data of the water temperatures at the inlet and outlet of the heat network using the least squares method.

3. A method for improving the frequency modulation technology by electro-thermal linkage in a thermal power plant according to claim 1, characterized in that, The energy correlation model of the heat load and the steam extraction amount in step S2 is expressed by the formula Q = D·c·(T out - T in ) / 3.6 to calculate the heat load of the heat network, and calculate the extraction steam flow rate D based on the difference between the extraction steam enthalpy and the drain enthalpy s .

4. A method for improving the frequency modulation technology by electro-thermal linkage in a thermal power plant according to claim 3, characterized in that, The extracted steam flow rate D s and the change in unit power ΔP satisfy a linear relationship ΔP = K·ΔD s , where K is the steam extraction - electrical load conversion coefficient.

5. A method for improving the frequency modulation technology by electro-thermal linkage in a thermal power plant according to claim 3, characterized in that, In step S3, the co-directionality judgment function is dir = sign(P AGC (t) - P AGC (t - Δt))·sign(Δf), where dir represents the judgment result, sign() represents the sign function in mathematics, P AGC (t) represents the power command of the automatic generation control (AGC) system at time t, P AGC (t - Δt) represents the AGC power command at time t - Δt, and Δf represents the power grid frequency deviation. When they are co-directional, feed-forward compensation is triggered, and the compensation amount is 6. The method for the electro-thermal linkage frequency modulation technology improvement in a thermal power plant according to claim 1, wherein The condition of the graded response control in step S3 is: when the speed deviation |Δn|>2.5r / min, the heating network fast closing valve is linked, the weighted heating correction instruction satisfies w1+w2=1, and the weight coefficient is dynamically adjusted according to the heating scenario.

7. A method for improving the frequency modulation technology by electro-thermal linkage in a thermal power plant according to claim 1, characterized in that, The calculation formula for the peak shaving compensation benefit in step S4 is where the compensation unit price λ is determined according to the real-time situation of the power grid.

8. A method for improving the frequency modulation technology by electro-thermal linkage in a thermal power plant according to claim 1, characterized in that, In step S4, the payback period model is where T is the payback period, C is the total project investment, and R is the average annual peak shaving compensation income.

9. A method for improving the frequency modulation technology by electro-thermal linkage in a thermal power plant according to claim 1, characterized in that, The multivariable collaborative control model and frequency modulation control strategy are integrated into the DCS system to achieve real-time closed-loop control of unit parameters.

10. A method for improving the frequency modulation technology by electro-thermal linkage in a thermal power plant according to claim 1, characterized in that, In step S4, the adjustment of the heating target value is frozen within the assessment period: where T set is the heating target value, which can be the hot water supply temperature of the heat network or the set value of the heating load, is the change rate of the heating target value.

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