An operating control strategy for an electrofused magnesia load to provide fast frequency response services

Abstract

The present invention relates to an operation control strategy for an electrofused magnesia load to provide fast frequency response services, including Step 1: Divide the fast frequency response into a response stage, a continuous stage, a deactivation stage, and a recovery stage, and summarize the technical requirements for fast frequency response in the four stages; Step 2: Establish a frequency response model for the electrofused magnesia load, and clarify that the technical indicators of the electrofused magnesia load are control mode, response time, duration, deactivation stage, recovery stage, service time, and service flexibility; Step 3: Adopt different operation control strategies for the electrofused magnesia load according to short duration and long duration; formulate an implementation of a coordinated fast frequency response control strategy for electrofused magnesia furnaces, implement active frequency response control for the power grid, effectively improve the overall frequency response control ability of the system, introduce the fuzzy evaluation theory, realize the intelligent centralized control of the furnaces, and achieve the fast frequency response of electrofused magnesia furnaces under large disturbances.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid frequency stability control, and particularly to an operation control strategy for an electrofused magnesia load to provide fast frequency response services. Background Art

[0002] The primary frequency regulation process is a crucial stage for preventing under-frequency load shedding in the power system under large power deficits and maintaining system stability. In a traditional power system dominated by thermal power, the primary frequency regulation ability is strong, and the demand for fast frequency response reserve capacity is small. However, with the large-scale grid connection of renewable energy units, the high degree of power electronics in power system control, and the gradual formation of a UHV AC / DC hybrid power grid, the proportion of conventional unit capacity in the power system has decreased, the grid moment of inertia has decreased, the primary frequency regulation ability has weakened, the risk of large power loss faults has increased, and the system frequency safety and stability situation has become increasingly severe. Therefore, in the new situation, in order to maintain the frequency safety and stability of the system, the power system has an increasing demand for fast frequency response reserve capacity. It is necessary to achieve fast frequency response of the system from the load side to solve the increasingly severe frequency stability problem.

[0003] The electrofused magnesia smelting process has the characteristic of adjustable power, which provides the possibility for power control and thus participation in the fast frequency response control of the power grid. Therefore, for the power grid, an electrofused magnesia furnace with certain interruptible operation characteristics can be used as a load-side resource to participate in fast frequency response control.

[0004] Chinese Patent with Publication No. CN 111682559 B discloses a fast frequency response control method and control system for a wind turbine under all operating conditions, specifically: collecting wind speed, and switching to different frequency response control strategies according to different wind speed conditions, a low wind speed frequency response control strategy; saving a large amount of operation and maintenance costs for power generation enterprises without incurring penalties due to insufficient primary frequency regulation; however, this patent is applicable to wind turbines under all operating conditions and is not applicable to the fast frequency response of electrofused magnesia loads.

[0005] A Chinese patent with the publication number CN 113078662 B discloses a new energy rapid frequency response system and method. By means of a frequency modulation control response device to forward the active voltage control instruction of the power grid dispatching master station, the daily active power output control and steady-state voltage control of each new energy generating unit can be carried out, reducing the use and operation and maintenance of other equipment, and improving the reliability of the power grid operation of the new energy power station. When the power grid frequency is abnormal, the locking control of the active power control instruction of the power grid dispatching master station is carried out, so that the frequency modulation control response device can independently carry out frequency modulation without superimposing the control value in the active power control instruction issued by the power grid dispatching master station, improving the accuracy of rapid frequency modulation. When the frequency modulation control operation ends or times out, the locking control of the active power control instruction of the power grid dispatching master station is released, so that the power grid dispatching master station and the frequency modulation control response device work in coordination, ensuring the stable operation of the power grid of the new energy power station; however, this method is applicable to starting from the control side and cannot achieve a good rapid frequency response effect from the load side when applied to the electrofused magnesia load. Summary of the Invention

[0006] The present invention provides an operation control strategy for an electrofused magnesia load to provide rapid frequency response services, formulates an implementation strategy for coordinated rapid frequency response control of electrofused magnesia furnaces, implements active frequency response control for the power grid, effectively improves the overall frequency response control ability of the system, introduces the fuzzy evaluation theory, realizes the intelligent centralized control of the furnaces, and realizes the rapid frequency response of electrofused magnesia furnaces under large disturbances.

[0007] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0008] An operation control strategy for an electrofused magnesia load to provide rapid frequency response services, comprising the following steps:

[0009] Step 1: Divide the rapid frequency response into a response stage, a continuous stage, a deactivation stage, and a recovery stage, and summarize the technical requirements for rapid frequency response in the four stages;

[0010] Step 2: Establish a frequency response model for the electrofused magnesia load, and clarify that the technical indicators of the electrofused magnesia load are control mode, response time, duration, deactivation stage, recovery stage, service time, and service flexibility;

[0011] Step 3: Adopt different operation control strategies for the electrofused magnesia load according to short duration and long duration.

[0012] Further, the technical requirements for rapid frequency response in the four stages in Step 1 are as follows:

[0013] 1) Response stage: 0.25 seconds to 2 seconds;

[0014] 2) Continuous stage: 5 seconds to 20 minutes;

[0015] 3) Deactivation stage: The power decline rate per second is 0 to 20% of the winning bid capacity under short duration;

[0016] 4) Recovery stage: The power action amplitude is 0 to 25% of the installed capacity;

[0017] 5) The entire process from activation to recovery is 0 to 15 minutes;

[0018] 6) Minimum capacity: 0.1 MW to 1 MW.

[0019] Furthermore, in step two, it is determined whether to input fast frequency response according to the electrofused magnesia load frequency response model. The model is as follows:

[0020]

[0021] Where, ΔP G is the additional power of electrofused magnesia participating in fast frequency response, ΔP is the accident-triggered disturbance value, P k is the declared capacity, ΔP L is the fast frequency response trigger power, t is the trigger time point, and ε is the step function.

[0022] Furthermore, the technical index requirements of the electrofused magnesia load in step two are as follows:

[0023] 1) Control mode: Fixed trajectory control;

[0024] 2) Response time: 1.5 seconds;

[0025] 3) Duration: Short duration is 30 seconds, long duration is 10 minutes;

[0026] 4) Deactivation stage: The power decline rate per second is 0 to 20% of the winning bid capacity under short duration;

[0027] 5) Recovery stage: The power action amplitude is 0 to 10% of the installed capacity;

[0028] 6) Service time: From May to April of the following year, a total of 4608 hours at night on weekdays and on weekends;

[0029] 7) Service flexibility: Real-time demand on weekdays is 1000 hours.

[0030] Furthermore, the different electrofused magnesia load operation control strategies for short duration and long duration in step three are as follows:

[0031] (1) The operation control strategy of electrofused magnesia load under short duration;

[0032] 1) In the response stage, the electrofused magnesia load receives the task requirements and senses the online operation status of the electrofused magnesia cluster furnaces;

[0033] (2) Directly perform furnace shutdown control according to the fast frequency response requirements and the pre-declared response capacity as needed.

[0034] (3) After the completion of the short-duration task, the fused magnesia load needs to withdraw from the response according to the "stop-one-start-two" control strategy, specifically: for every one fused magnesia furnace stopped, two fused magnesia furnaces are restarted.

[0035] (2) The operation control strategy for the fused magnesia load under long duration is a method of load combination. Using the idea of fuzzy mathematics, evaluate the adjustment potential of each furnace, and select the furnaces with higher scores to participate in the adjustment.

[0036] Furthermore, in the fast frequency response service with short duration, the duration can be increased or decreased, but it needs to be controlled within 1 minute.

[0037] Furthermore, in the fast frequency response service with long duration, the duration can be increased or decreased, but it needs to be controlled within 15 minutes.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) Formulate and implement the coordinated fast frequency response control strategy for the fused magnesia group furnaces according to the frequency safety task requirements.

[0040] (2) Implement active frequency response control for the power grid, provide sufficient adjustment capacity within the specified time, effectively improve the overall frequency response control ability of the system, and thus improve the tense situation of system frequency stability under large disturbances.

[0041] (3) Introduce the fuzzy evaluation theory, intelligently refine the frequency modulation ability of each fused magnesia group furnace, realize the intelligent centralized control of the group furnaces, and achieve the fast frequency response of the fused magnesia group furnaces under large disturbances. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is the flow schematic diagram of the present invention.

[0043] Figure 2 is the operating state curve of a single fused magnesia furnace described in the present invention.

[0044] Figure 3 is the operating power curve of a single fused magnesia furnace described in the present invention.

[0045] Figure 4 is the fast frequency response service scenario described in the present invention.

[0046] Figure 5 is the schematic diagram of the operating control strategy for the fused magnesia load under short duration described in the present invention.

[0047] Figure 6 It is a schematic diagram of the operation control strategy for the electrofused magnesia load under long-duration conditions in the present invention. Detailed implementation manners

[0048] The following further explains the detailed implementation manners of the present invention with reference to the accompanying drawings:

[0049] See Figure 1 , which is a schematic flowchart of the present invention. An operation control strategy for an electrofused magnesia load to provide fast frequency response service in the present invention includes the following steps:

[0050] Step 1: Divide the fast frequency response into a response stage, a continuous stage, a deactivation stage, and a recovery stage, and summarize the technical requirements for fast frequency response in the four stages;

[0051] Step 2: Establish a frequency response model for the electrofused magnesia load, and clarify that the technical indicators of the electrofused magnesia load are control mode, response time, continuous time, deactivation stage, recovery stage, service time, and service flexibility;

[0052] Step 3: Adopt different operation control strategies for the electrofused magnesia load according to short-duration and long-duration conditions.

[0053] Furthermore, in the power system, when a large-power disturbance occurs in the system, synchronous inertia response, primary frequency modulation, and secondary frequency modulation are successively used to provide power support. Before primary frequency modulation, the frequency drop caused by the disturbance will cross the action threshold of the under-frequency load shedding device. Therefore, to make up for the insufficient synchronous inertia and primary frequency modulation reserve capacity, the rate of frequency decline is limited by injecting active power quickly before the primary frequency modulation response to avoid under-frequency load shedding, and fast frequency response products emerge as the times require. Fast frequency response needs to act before primary frequency modulation. Classified by input signals, its control methods can be divided into 3 types: rate of change of frequency control, frequency deviation control, and fixed trajectory control. The technical requirements for fast frequency response in the four stages in Step 1 are as follows:

[0054] 1) Response stage: 0.25 seconds to 2 seconds;

[0055] 2) Continuous stage: 5 seconds to 20 minutes;

[0056] 3) Deactivation stage: The power decline rate per second under short-duration conditions is 0 to 20% of the winning bid capacity;

[0057] 4) Recovery stage: The power action amplitude is 0 to 25% of the installed capacity;

[0058] 5) The entire process from activation to recovery is 0 to 15 minutes;

[0059] 6) Minimum capacity: 0.1 MW to 1 MW.

[0060] Further, in the second step, it is determined whether to input the fast frequency response according to the electrofused magnesia load frequency response model. The model is as follows:

[0061]

[0062] where, ΔP G is the additional power for the electrofused magnesia to participate in the fast frequency response, ΔP is the accident-triggered disturbance value, P k is the declared capacity, ΔP L is the fast frequency response trigger power, t is the trigger time point, and ε is the step function;

[0063] When the fast frequency response trigger power ΔP L is greater than or equal to the accident-triggered disturbance value ΔP, the electrofused magnesia load needs to achieve a response, and then the corresponding additional power of the fast frequency response is input according to formula (1).

[0064] Further, the technical index requirements for the electrofused magnesia load in the second step are as follows:

[0065] 1) Control mode: fixed trajectory control;

[0066] 2) Response time: 1.5 seconds;

[0067] 3) Duration: short duration of 30 seconds, long duration of 10 minutes;

[0068] 4) Deactivation stage: the power decline rate per second in the short duration is 0 to 20% of the winning bid capacity;

[0069] 5) Recovery stage: the power action amplitude is 0 to 10% of the installed capacity;

[0070] 6) Service time: from May to April of the following year, a total of 4608 hours at night on weekdays and on weekends;

[0071] 7) Service flexibility: 1000 hours of real-time demand on weekdays.

[0072] Further, in the third step, the fast frequency response needs to require the supplier to provide product services with different time scales according to different frequency deviation levels. Therefore, as the electrofused magnesia load of the supplier, different control strategies need to be adopted according to different time scales to avoid affecting its own production process. The different operation control strategies for the electrofused magnesia load in the short duration and the long duration are as follows:

[0073] (1) Operating control strategy for fused magnesia load under short durations: A single fused magnesia furnace can be shut down for 30 seconds to one minute. Therefore, for fast frequency response services under short durations, the fused magnesia load can adopt a direct control strategy on demand. Since short durations have strict power reduction requirements for the deactivation phase, an "off-one-on-two" operating control strategy is designed;

[0074] 1) During the response phase, the fused magnesia load receives the task requirements and senses the online operating status of the fused magnesia furnace group;

[0075] 2) According to the fast frequency response demand and the pre-declared response capacity, directly conduct shutdown control on demand;

[0076] 3) After the task under short durations is completed, the fused magnesia load needs to withdraw from the response according to the "off-one-on-two" control strategy. Specifically: for every one fused magnesia furnace shut down, two fused magnesia furnaces are restored;

[0077] (2) Under long durations, it is impossible for the fused magnesia load to complete the task with just one shutdown. Therefore, a method of load combination is needed to conduct staged combined shutdowns to achieve fast frequency response tasks under long durations. Since the fused magnesia furnaces are restricted by the number of regulations and regulation time, their regulation potentials are different. Therefore, the idea of fuzzy mathematics can be used to evaluate the regulation potential of each furnace, and select the furnaces with high scores to participate in the regulation. There are 4 decision variables for the regulation ability of the fused magnesia furnace, including: operating condition, number of times already regulated, remaining adjustable time, and real-time power. Since the four variables do not affect each other, the four decision variables can be analyzed separately to form membership functions under each decision variable, and conduct weighted summation;

[0078] 1) Operating condition

[0079] The fused magnesia load has 5 operating conditions, including: main melting condition, feeding condition, exhaust condition, furnace starting condition, and shutdown condition. When the fused magnesia is in the feeding condition, exhaust condition, furnace starting condition, and shutdown condition, the power cannot be adjusted. Therefore, to simplify the operation, the decision variable operating condition is set as x, with a value of "1" under the main melting condition and a value of "0" under other operating conditions.

[0080] 2) Number of times already regulated

[0081] According to the control principle, the smaller the number of times already regulated, the greater the probability of adoption. Therefore, a smaller normal type membership function is adopted. Let y be the number of times already regulated, and k y is a mapping of y used to represent the score of y. Specifically:

[0082]

[0083] Among them, is the average value of y, and σy is the standard deviation of y, and N is the number of fused magnesia furnaces, specifically:

[0084]

[0085] 3) Adjustable time

[0086] According to the control principle, the greater the adjustable time, the greater the probability of adoption. Therefore, a larger normal membership function is adopted. Let z be the number of adjustments, and k z is a mapping of z used to characterize the score of z, specifically:

[0087]

[0088] where is the average value of z, and σ z is the standard deviation of z, and N is the number of fused magnesia furnaces, specifically:

[0089]

[0090] 4) Real-time power

[0091] According to the control principle, the greater the adjustable time, the greater the probability of adoption. Therefore, a larger normal membership function is adopted. Let p be the number of adjustments, and k p is a mapping of p used to characterize the score of p, specifically:

[0092]

[0093] where is the average value of p, and σ p is the standard deviation of p, and N is the number of fused magnesia furnaces, specifically:

[0094]

[0095] Based on formulas (3)-(11), an evaluation model for the regulation ability of fused magnesia furnaces is established. Since the furnace condition is a 0-1 variable, decoupling calculation can be performed on it, so the weight it occupies is no longer considered. Assume the weights of each factor are:

[0096] λ = (λ y , λ z , λ p ) (12)

[0097] Therefore, the score matrix A can be expressed as:

[0098] A = x × (λ ο k) (13)

[0099] where the process matrix B is:

[0100]

[0101] The operator calculation in matrix B can be expressed as:

[0102]

[0103] Using the following operator can take all factors into consideration according to their weights, which is more reasonable in a comprehensive way.

[0104] Operator: That is, use the real number multiplication · to replace Use To replace

[0105] Therefore, the score matrix A is:

[0106]

[0107] Based on the above analysis, for long-duration, a running control strategy for fused magnesia load is implemented using the idea of fuzzy mathematics as follows:

[0108] 1) In the response stage, the fused magnesia load receives the task requirements and senses the online operation status of the fused magnesia furnace group.

[0109] 2) In the long-duration stage, after obtaining the score matrix of the current period online, sort it, and select the regulated fused magnesia furnaces in descending order until the task requirements are completed. Take one minute as a regulation period, change its operation status to the shutdown state online, and modify the power matrix of the next period.

[0110] 3) After the long-duration task is completed, it can be restored in groups as needed or directly fully restored according to the actual power grid requirements.

[0111] 4) When determining the regulated fused magnesia furnace group, to ensure the quality of fused magnesia products, if a fused magnesia furnace is scheduled within the current scheduling period, it will not participate in the scheduling in the next time.

[0112] Furthermore, in the fast frequency response service with short duration, the duration can be increased or decreased, but it needs to be controlled within 1 minute.

[0113] Furthermore, in the fast frequency response service with long duration, the duration can be increased or decreased, but it needs to be controlled within 15 minutes.

[0114] Furthermore, under the task of large power shortage, the fused magnesia load completes the frequency regulation task issued by the power grid to achieve the effect of curbing the frequency drop, which can effectively relieve the frequency regulation pressure on the grid side.

[0115] The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The methods used in the following embodiments are all conventional methods unless otherwise specified.

[0116]

Embodiment

[0117] To verify the effectiveness of the control strategy, 20 electric fused magnesia furnaces are provided. The single-ton energy consumption value of each furnace is between 2,600 kWh and 3,600 kWh, the declared capacity is 263.33 kW, the start-up time of the furnace is between 1.5 hours and 2 hours, the total smelting time is between 10 hours and 12 hours, among which the normal smelting working condition time is between 6 minutes and 7 minutes, the feeding working condition time is between 1 minute and 2 minutes, the exhaust working condition time is between 1 minute and 2 minutes, and the furnace shutdown working condition time is random. Through the random production simulation method, the working states of 20 electric fused magnesia furnaces are simulated. Among them, the start-up state of electric fused magnesia is represented by "0", the feeding state is represented by "1", the smelting state is represented by "2", the exhaust state is represented by "3", and the furnace shutdown state is represented by "4"; then the operation state curve of a single electric fused magnesia is as Figure 2 shown, and the operation power curve is as Figure 3 shown.

[0118] Based on the above simulation conditions, a fast frequency response service scenario as Figure 4 shown is set. Its service time point is at 522 minutes, and the power magnitude is: 266.402 kW. According to the operation control strategy proposed by the present invention, for this scenario, the result of the operation control strategy under short duration is as Figure 5 shown. In the actual operation process, the coordinated control of the electric fused magnesia furnace group can be realized accordingly on a short time scale; in the case of long duration, affected by product quality, it is required that the electric fused magnesia furnace group cannot be started and stopped frequently. If blindly controlled, it will surely lead to industrial accidents. Therefore, according to the operation control strategy proposed by the present invention, on the premise of ensuring product quality, the electric fused magnesia furnace group is coordinated to provide fast frequency response service. For the Figure 4 shown service scenario, the operation control strategy of 20 electric fused magnesia furnaces under long duration is simulated, and the result is as Figure 6 shown; as shown in Figures 2 - 6 shown, in different dispatching time periods, the method proposed by the present invention can effectively coordinate and control the electric fused magnesia furnace group, ensure that each electric fused magnesia furnace participates in the service, and realize the fast frequency response of the system from the load side, which not only ensures product quality but also ensures the stability of the service.

Claims

1. An operating control strategy for an electrofused magnesia load to provide fast frequency response services, characterized in that, It includes the following steps: Step 1: Divide the fast frequency response into a response stage, a sustained stage, a deactivation stage, and a recovery stage, and summarize the technical requirements of the fast frequency response technology in the four stages; Step 2: Establish an electrofused magnesia load frequency response model, and clarify that the technical indicators of the electrofused magnesia load are control mode, response time, duration, deactivation stage, recovery stage, service time, and service flexibility; Decide whether to engage in fast frequency response according to the electrofused magnesia load frequency response model. The model is as follows: Among them, ΔP G is the additional power for the electrofused magnesia to participate in the fast frequency response. ΔP is the accident-triggered disturbance value, and P k is the declared capacity. ΔP L is the fast frequency response trigger power, t is the trigger time point, and ε is the step function; Step 3: Adopt different operation control strategies for the electrofused magnesia load according to short duration and long duration; The different operation control strategies for the electrofused magnesia load adopted for short duration and long duration are as follows: (1) The operation control strategy for the electrofused magnesia load under short duration; 1) In the response stage, the electrofused magnesia load receives a task requirement and senses the online operation status of the electrofused magnesia cluster furnaces; 2) According to the fast frequency response demand and the pre-declared response capacity, directly perform furnace shutdown control as needed; 3) After the task of short duration is completed, the electrofused magnesia load needs to withdraw from the response according to the "stop-one-start-two" control strategy. Specifically: for every one electrofused magnesia furnace stopped, two electrofused magnesia furnaces are restarted; (2) The operation control strategy for the electrofused magnesia load under long duration is a method of load combination. Using the idea of fuzzy mathematics, evaluate the adjustment potential of each furnace, and select the furnaces with higher scores to participate in the adjustment.

2. The operation control strategy for an electrofused magnesia load to provide fast frequency response service according to claim 1, characterized in that, The technical requirements of the fast frequency response technology in the four stages in the above Step 1 are as follows: 1) Response stage: 0.25 seconds to 2 seconds; 2) Sustained stage: 5 seconds to 20 minutes; 3) Deactivation stage: The power decline rate per second under short duration is 0 to 20% of the winning bid capacity; 4) Recovery stage: The power action amplitude is 0 to 25% of the installed capacity; 5) The entire process from activation to recovery completion is 0 to 15 minutes; 6) Minimum capacity: 0.1 MW to 1 MW.

3. The operating control strategy for an electrofused magnesia load to provide fast frequency response services according to claim 1, characterized in that, The technical indicator requirements of the electrofused magnesia load in the above Step 2 are as follows: 1) Control mode: Fixed trajectory control; 2) Response time: 1.5 seconds; 3) Duration: 30 seconds for short duration and 10 minutes for long duration; 4) Deactivation stage: The power decline rate per second under short duration is 0 to 20% of the winning bid capacity; 5) Recovery stage: The power action amplitude is 0 to 10% of the installed capacity; 6) Service time: From May to April of the following year, a total of 4608 hours at night on weekdays and on weekends; 7) Service flexibility: 1000 hours of real-time demand on weekdays.

4. The operation control strategy for an electrofused magnesia load to provide fast frequency response service according to claim 1, characterized in that, In the fast frequency response service of short duration, the duration can be increased or decreased, but it needs to be controlled within 1 minute.

5. The operation control strategy for an electrofused magnesia load to provide fast frequency response services according to claim 1, wherein In the fast frequency response service of long duration, the duration can be increased or decreased, but it needs to be controlled within 15 minutes.

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