Frequency control method, device, equipment and medium based on interruptible load

Abstract

The present invention discloses a frequency control method, device, equipment, and medium based on an interruptible load, which is used to achieve rapid adjustment of frequency drops. The present invention includes: when a power shortage fault occurs in the power system, obtaining the frequency change rate in real time; determining the current protection layer currently triggered based on the frequency change rate and the starting frequency change rate of the preset protection layer; determining the current interruptible load of the current protection layer, and calculating the response delay and current interruptible capacity of the current interruptible load; obtaining the low-frequency load shedding starting frequency; determining the target interruptible load based on the frequency change rate, the response delay, and the current interruptible capacity; and interrupting the target interruptible load to perform frequency control.

Description

Technical Field

[0001] The present invention relates to the field of frequency control technology, and in particular to a frequency control method, device, equipment and medium based on an interruptible load. Background Art

[0002] When a severe power imbalance within the system causes a frequency collapse, the process unfolds rapidly, perhaps lasting only tens or even seconds. Underfrequency load shedding is the power system's third and final line of defense, effectively suppressing frequency drops. To this day, underfrequency load shedding remains a key emergency frequency control measure.

[0003] Underfrequency load shedding protection uses frequency deviation as a triggering criterion and controls the circuit breaker via an underfrequency relay. When a system experiences a severe power shortage, causing the frequency to drop too far, the circuit breaker, under protective control, quickly trips the corresponding load, preventing a significant drop in system frequency and halting the escalation of the incident. Underfrequency load shedding protection in my country's power system consists of both basic and special protection. The basic protection is designed to operate quickly, suppressing frequency drops as quickly as possible without excessive load shedding. It is typically pre-classified by frequency trigger values ​​and divided into three to six cycles, with each cycle shedding a fixed amount of load. To prevent false tripping, a delay of 0.2 to 0.5 seconds is applied after the frequency exceeds the trigger value. Special protection is designed to prevent the frequency from remaining below the minimum allowable value for an extended period or slowly decreasing after the basic protection has terminated. It is typically classified by time and has a longer delay of 10 to 30 seconds. However, underfrequency load shedding protection is only triggered passively when the frequency drops too far, serving only as an emergency measure and failing to fully utilize the load's ability to actively regulate grid frequency stability. Summary of the Invention

[0004] The present invention provides a frequency control method, device, equipment and medium based on an interruptible load, which are used to achieve rapid regulation of frequency drops.

[0005] The present invention provides a frequency control method based on an interruptible load, comprising:

[0006] When a power shortage fault occurs in the power system, the frequency change rate is obtained in real time;

[0007] Determining a currently triggered protection layer according to the frequency change rate and a preset starting frequency change rate of the protection layer;

[0008] Determining a current interruptible load of the current protection layer, and calculating a response delay and a current interruptible capacity of the current interruptible load;

[0009] Get the low-frequency load shedding starting frequency;

[0010] determining a target interruptible load according to the underfrequency load shedding starting frequency, the frequency change rate, the response delay, and the current interruptible capacity;

[0011] Interrupting the target may interrupt the load for frequency control.

[0012] Optionally, before the step of determining the currently triggered current protection layer according to the frequency change rate and the preset starting frequency change rate of the protection layer, the method further includes:

[0013] Establish system frequency response model;

[0014] According to the system frequency response model, obtaining the starting criticality of the power system in a protection starting criticality scenario; the starting criticality includes a first critical unbalanced power and a first critical maximum frequency change rate;

[0015] According to the system frequency response model, obtaining the failure criticality of the power system in a protection failure critical scenario; the failure criticality includes a second critical unbalanced power, a second critical maximum frequency change rate, and a maximum frequency drop time;

[0016] Get the number of protection layers;

[0017] Calculating a protection interval according to the starting criticality, the failure criticality and the number of protection layers;

[0018] Determining a starting frequency change rate of each protection layer according to the protection interval;

[0019] Obtaining an initial interruptible capacity of each interruptible load in the protection layer;

[0020] Under a preset disturbance, the initial interruptible capacity is adjusted according to the low-frequency load shedding starting frequency to obtain the adjusted interruptible capacity as the current interruptible capacity of the protection layer.

[0021] Optionally, the step of adjusting the initial interruptible capacity according to the low-frequency load shedding starting frequency under a preset disturbance to obtain the adjusted interruptible capacity as the current interruptible capacity of the protection layer includes:

[0022] Calculate the lowest value of the system frequency drop after the first j interruptible loads are interrupted under a preset disturbance based on the initial interruptible capacity;

[0023] When the lowest value of the system frequency drop is greater than the low-frequency load shedding starting frequency, reducing the interruption capacity of the j-th interruptible load, and returning to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under the preset disturbance;

[0024] When the lowest value of the system frequency drop is less than the low-frequency load shedding starting frequency, set j=j+1, and return to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under the preset disturbance;

[0025] When the lowest value of the system frequency drop is equal to the low-frequency load shedding starting frequency, the adjusted interruptible capacity of each interruptible load is output as the current interruptible capacity of the protection layer.

[0026] Optionally, the step of calculating the protection interval according to the starting threshold, the failure threshold, and the number of protection layers includes:

[0027] Calculating a first protection range according to the first critical maximum frequency change rate and the second critical maximum frequency change rate;

[0028] Calculating a second protection range according to the first critical unbalanced power and the second critical unbalanced power;

[0029] Calculating a first protection interval according to the first protection range and the number of protection layers;

[0030] A second protection interval is calculated according to the second protection range and the number of protection layers.

[0031] The present invention also provides a frequency control device based on an interruptible load, comprising:

[0032] The frequency change rate acquisition module is used to obtain the frequency change rate in real time when a power shortage fault occurs in the power system;

[0033] a current protection layer determining module, configured to determine a currently triggered current protection layer according to the frequency change rate and a preset starting frequency change rate of the protection layer;

[0034] a response delay and current interruptible capacity calculation module, configured to determine a current interruptible load of the current protection layer, and calculate a response delay and a current interruptible capacity of the current interruptible load;

[0035] Low-frequency load shedding starting frequency acquisition module, used to obtain low-frequency load shedding starting frequency;

[0036] a target interruptible load determination module, configured to determine a target interruptible load according to the underfrequency load shedding starting frequency, the frequency change rate, the response delay, and the current interruptible capacity;

[0037] The frequency control module is used to interrupt the target interruptible load to perform frequency control.

[0038] Optionally, it also includes:

[0039] System frequency response model building module, used to build a system frequency response model;

[0040] A starting criticality acquisition module is used to obtain the starting criticality of the power system in a protection starting criticality scenario according to the system frequency response model; the starting criticality includes a first critical unbalanced power and a first critical maximum frequency change rate;

[0041] A failure criticality acquisition module is used to obtain the failure criticality of the power system in a protection failure criticality scenario according to the system frequency response model; the failure criticality includes a second critical unbalanced power, a second critical maximum frequency change rate, and a maximum frequency drop time;

[0042] A protection layer number acquisition module is used to obtain the number of protection layers;

[0043] A protection interval calculation module, configured to calculate a protection interval according to the starting criticality, the failure criticality and the number of protection layers;

[0044] a starting frequency change rate determination module, configured to determine the starting frequency change rate of each protection layer according to the protection interval;

[0045] An initial interruptible capacity acquisition module, configured to acquire an initial interruptible capacity of each interruptible load in the protection layer;

[0046] The adjustment module is used to adjust the initial interruptible capacity according to the low-frequency load reduction starting frequency under a preset disturbance, and obtain the adjusted interruptible capacity as the current interruptible capacity of the protection layer.

[0047] Optionally, the adjustment module includes:

[0048] A system frequency drop minimum value calculation submodule, configured to calculate, based on the initial interruptible capacity, the system frequency drop minimum value after the first j interruptible loads are interrupted under a preset disturbance;

[0049] A first return submodule is configured to reduce the interruption capacity of the jth interruptible load when the lowest value of the system frequency drop is greater than the low-frequency load shedding starting frequency, and return to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under a preset disturbance;

[0050] The second return submodule is configured to, when the lowest value of the system frequency drop is less than the low-frequency load shedding starting frequency, set j=j+1 and return to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under a preset disturbance;

[0051] The interruptible capacity adjustment output submodule is configured to output the adjusted interruptible capacity of each interruptible load as the current interruptible capacity of the protection layer when the system frequency drops to a minimum value equal to the low-frequency load shedding starting frequency.

[0052] Optionally, the guard interval calculation module includes:

[0053] A first protection range calculation submodule, configured to calculate a first protection range according to the first critical maximum frequency change rate and the second critical maximum frequency change rate;

[0054] A second protection range calculation submodule, configured to calculate a second protection range according to the first critical unbalanced power and the second critical unbalanced power;

[0055] A first protection interval calculation submodule, configured to calculate a first protection interval according to the first protection range and the number of protection layers;

[0056] The second protection interval calculation submodule is configured to calculate a second protection interval according to the second protection range and the number of protection layers.

[0057] The present invention further provides an electronic device, comprising a processor and a memory:

[0058] The memory is used to store program code and transmit the program code to the processor;

[0059] The processor is configured to execute any one of the above frequency control methods based on an interruptible load according to instructions in the program code.

[0060] The present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium is used to store program code, and the program code is used to execute the frequency control method based on interruptible load as described in any one of the above items.

[0061] It can be seen from the above technical solutions that the present invention has the following advantages: The present invention discloses a frequency control method based on interruptible loads, which obtains the frequency change rate in real time when a power shortage fault occurs in the power system; determines the current protection layer currently triggered according to the frequency change rate and the starting frequency change rate of the preset protection layer; determines the current interruptible load of the current protection layer, and calculates the response delay and current interruptible capacity of the current interruptible load; obtains the low-frequency load reduction starting frequency; determines the target interruptible load according to the frequency change rate, the response delay and the current interruptible capacity; and interrupts the target interruptible load to perform frequency control. The present invention responds to interruptible loads in layers according to the frequency change rates of different depths corresponding to different degrees of severity of the power shortage fault, following the load priority interruption criterion with fast response speed, and realizes efficient utilization of interruptible loads and rapid adjustment of frequency drops. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0063] Figure 1 A flowchart of a frequency control method based on an interruptible load provided by an embodiment of the present invention;

[0064] Figure 2 The figure is a schematic diagram of the interruptible load hierarchical control process based on RoCoF;

[0065] Figure 3 It is a schematic diagram of the system frequency response process after the interruptible load control strategy is activated;

[0066] Figure 4 A flow chart of the steps of a parameter setting method for an interruptible load control strategy provided by an embodiment of the present invention;

[0067] Figure 5 A schematic diagram of a system frequency response model provided by an embodiment of the present invention;

[0068] Figure 6 A flow chart of control strategy parameter setting provided by an embodiment of the present invention;

[0069] Figure 7 This is the grid structure topology diagram of the example system;

[0070] Figure 8 This is a schematic diagram of the frequency response model of a conventional thermal power unit;

[0071] Figure 9 This is a schematic diagram of the frequency response model of new energy units;

[0072] Figure 10 Schematic diagram of the average frequency response of the system under two operating scenarios;

[0073] Figure 11 This is a structural block diagram of a frequency control device based on an interruptible load provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0074] Embodiments of the present invention provide a frequency control method, apparatus, device, and medium based on an interruptible load, for achieving rapid regulation of frequency drops.

[0075] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0076] See also Figure 1 , Figure 1 A flow chart of the steps of a frequency control method based on an interruptible load provided in an embodiment of the present invention.

[0077] The present invention provides a frequency control method based on an interruptible load, which may specifically include the following steps:

[0078] Step 101, when a power shortage fault occurs in the power system, obtain the frequency change rate in real time;

[0079] The rate of change of frequency (RoCoF) can be used as a trigger for interruptible load frequency control.

[0080] In this embodiment of the present invention, a frequency control strategy for hierarchical active shutdown of interruptible loads is proposed, drawing on an underfrequency load shedding protection scheme based on passive load shedding. This strategy first categorizes different interruptible loads and then implements hierarchical protection based on the frequency change rate obtained in real time during a power shortage fault.

[0081] Step 102, determining the currently triggered protection layer according to the frequency change rate and the preset starting frequency change rate of the protection layer;

[0082] After obtaining the frequency change rate when a power shortage fault occurs in the power system, the currently triggered protection layer can be determined according to the frequency change rate and the starting frequency change rate of each protection layer.

[0083] It should be noted that when a power shortage fault occurs, the frequency changes continuously in a short period of time. During the frequency change process, the power change rate may meet the starting frequency change rate of different protection layers at different stages, thereby triggering frequency adjustment of different protection layers.

[0084] Step 103: determine the current interruptible load of the current protection layer, and calculate the response delay and current interruptible capacity of the current interruptible load;

[0085] In an embodiment of the present invention, each protection layer can contain multiple different interruptible loads. The interruptible loads can be classified based on response latency, with interruptible loads meeting the same response latency requirements being categorized into the same protection layer. When the current protection layer requiring interruptible load adjustment is determined, the response latency and current interruptible capacity of each interruptible load in the current protection layer can be obtained to facilitate the subsequent determination of the interruption order for each interruptible load based on actual needs.

[0086] Step 104, obtaining the low-frequency load shedding starting frequency;

[0087] Step 105 , determining a target interruptible load according to the underfrequency load shedding starting frequency, the frequency change rate, the response delay, and the current interruptible capacity;

[0088] Step 106: interrupt the target load to perform frequency control.

[0089] In practical applications, in order to avoid conflict with under-frequency load reduction protection, all interruptible loads need to be completely interrupted before under-frequency load reduction action.

[0090] Therefore, after determining the response delay and current interruptible capacity of each interruptible load, the target interruptible load that actually needs to be interrupted can be determined in combination with the low-frequency load reduction starting frequency, and the frequency control and adjustment of the power system can be performed by interrupting the target interruptible load.

[0091] Figure 2 The interruptible load hierarchical control process based on RoCoF is given. Figure 3 The system frequency response process after the interruptible load control strategy is activated is given.

[0092] like Figure 2 As shown in the figure, when the power system encounters a power shortage fault, when the frequency change rate df / dt is greater than the starting frequency change rate (df / dt)1 of the first protection layer, the interruption of the interruptable load ΔP L1 =ΔP L1,t1u(t-t1)+ΔP L1,t2u(t-t2) +...+ΔP L1,tju(t-tj) When the frequency change rate df / dt is greater than the starting frequency change rate (df / dt)2 of the second protection layer, the interruption of the interruptible load ΔP L2 =ΔP L2,t1u(t-t1) +ΔP L2,t2u(t-t2) +...+ΔP L2,tju(t-tj) , when the frequency change rate df / dt is greater than the starting frequency change rate (df / dt) of the i-th protection layer i When interruption occurs, the interruptible load ΔP Li =ΔP Li,t1u(t-t1) +ΔP Li,t2u(t-t2) +...+ΔP Li,tju(t-tj) .

[0093] like Figure 3 As shown in the figure, taking the frequency change rate df / dt triggering the starting frequency change rate of the i-th protection layer as an example, the power system encounters a power shortage fault, resulting in the frequency change rate df / dt triggering the starting frequency change rate (df / dt) of the i-th protection layer. i After the response delay t1, the load ILt1 can be interrupted.

[0094] When the frequency change rate df / dt triggers the starting frequency of the i-th layer protection action (df / dt) i When the load IL is disconnected after the response delay t1 t1 Load ΔP L1,t1 After the response delay t2, the interruptable load IL is disconnected t2 Load ΔP L1,t2 , to prevent the lowest frequency fnadir from exceeding the low-frequency load reduction starting frequency f UFSL .

[0095] When a power shortage fault occurs in the power system, the frequency change rate is obtained in real time; the current protection layer currently triggered is determined based on the frequency change rate and the starting frequency change rate of the preset protection layer; the current interruptible load of the current protection layer is determined, and the response delay and current interruptible capacity of the current interruptible load are calculated; the low-frequency load shedding starting frequency is obtained; the target interruptible load is determined based on the frequency change rate, response delay and current interruptible capacity; and the target interruptible load is interrupted to perform frequency control. The present invention responds to interruptible loads in layers according to the frequency change rates of different depths corresponding to different degrees of power shortage fault severity, following the principle of prioritizing interruption of loads with fast response speed, thereby achieving efficient utilization of interruptible loads and rapid regulation of frequency drops.

[0096] It should be noted that, in the embodiment of the present invention, when performing layered protection on the power system, the parameters of the interruptible load control strategy can be adjusted first. Figure 4 , based on the above embodiment, Figure 4 This is a flowchart of a parameter setting method for an interruptible load control strategy provided by an embodiment of the present invention. Specifically, the following steps may be included:

[0097] Step 401, establishing a system frequency response model;

[0098] In an embodiment of the present invention, parameter setting of the interruptible load control strategy may be performed by establishing a system frequency response model.

[0099] In this embodiment of the present invention, the interruptible load control strategy's action priority should be lower than source-side frequency regulation, such as the synchronous inertia response of synchronous power supplies and the rapid frequency response of asynchronous power supplies, but higher than underfrequency load shedding protection, as a supplement to the rapid frequency response on the load side. Therefore, when tuning the control strategy's parameters, the frequency response characteristics of each frequency-regulated power supply within the system should be fully considered.

[0100] In the specific implementation, based on the ASF modeling method, after ignoring the dynamic changes of system voltage, grid topology, synchronous machine power angle stability and spatial distribution of frequency, the rotor swing equations of all synchronous units are aggregated to obtain the system equivalent rotor swing equation, but the independent responses of various frequency-modulated power sources with different characteristics and their frequency control are retained, and the sum of their output powers is used as the input of the system equivalent rotor swing equation to establish a system frequency response model such as Figure 5 shown.

[0101] Among them, Δω Ref and Δω ref is the frequency deviation and its reference value; ΔP Imbalance is the magnitude of the unbalanced disturbance power; ΔP i It is the output frequency modulation power of various frequency modulation power supplies.

[0102] The system frequency response model can simulate the frequency response of the system to be evaluated under different operating scenarios. The simulation is based on the actual scenario of the system to be evaluated and is achieved by adjusting three characteristic parameters: the capacity ratio of the frequency-regulated power source, the load frequency regulation effect coefficient, and the equivalent inertia. Therefore, the model can fully reflect the frequency response characteristics of each frequency-regulated power source in the system. Among them:

[0103] 1) Coefficient K i It is the capacity ratio of various frequency regulating power sources participating in frequency regulation, that is, the frequency regulating capacity of various frequency regulating power sources and the capacity base value S B The ratio of

[0104] 2) Coefficient D is the load frequency regulation effect coefficient, that is, the percentage of system active load reduction (increase) when the system frequency decreases (increases) by 1%. The typical value is between 1 and 3;

[0105] 3) Coefficient H sys is the equivalent inertia time constant of the power system, representing the aggregation of the equivalent inertia of all running synchronous machines in the system. Its calculation expression is:

[0106]

[0107] Among them, H sys is the equivalent inertia time constant of the power system, S G,i is the rated capacity of the i-th (i=1,2,...,N) synchronous generator, H i is the inertia time constant of the i-th (i=1,2,...,N) synchronous generator, S B It is the base value of system capacity.

[0108] In the present invention, for a specific power system to be protected, the system's maximum power shortage fault condition after the load interruption protection at different levels can be determined by numerically calculating the system frequency response model. Based on this, the parameters of the RoCoF-based interruptible load control strategy can be adjusted. The adjustment strategy is: based on RoCoF measurements, according to the response capability of the interruptible load (response delay and interruptible capacity), the capacity of the interruptible load participating in the response at different levels is set to meet the total interruptible load capacity requirements at each level.

[0109] When performing numerical calculations on the power system to be protected, it is first necessary to classify the interruptible loads, determine the system inertia of the power system to be protected, the load frequency regulation effect coefficient, and the control and frequency regulation capacity of various frequency-regulated power sources, and establish a frequency response model that takes into account the characteristics of the frequency-regulated power source. At the same time, according to the response delay t j Classify the interruptible load and determine the capacity P of the interruptible load IL .

[0110] Step 402: Obtaining the starting criticality of the power system in a protection starting criticality scenario based on the system frequency response model; the starting criticality includes a first critical unbalanced power and a first critical maximum frequency change rate;

[0111] After completing the classification of the interruptible loads of the power system to be protected, the protection range of the power system can be calculated. In an embodiment of the present invention, the boundaries of the protection range of the power system to be protected can be defined as a protection start-up critical scenario and a protection failure critical scenario, respectively. In the protection start-up critical scenario, the power system is in a state where it is just unable to prevent the low-frequency load reduction action from starting after the synchronous inertia response and the power supply side frequency regulation response. At this time, the system's first critical unbalanced power and the first critical maximum frequency change rate are ΔP start and (df / dt) start .

[0112] Step 403: Obtain the failure criticality of the power system in a protection failure critical scenario according to the system frequency response model; the failure criticality includes the second critical unbalanced power, the second critical maximum frequency change rate, and the maximum frequency drop time;

[0113] In the critical protection failure scenario, the power system is in a state where all interruptible loads are disconnected and the low-frequency load reduction startup cannot be prevented. At this time, the second critical unbalanced power, the second critical maximum frequency change rate and the maximum frequency drop time of the system are ΔP stop 、(df / dt) stop , t nadir Among them, the effective interruptible load is the response delay less than t nadir interruptible load.

[0114] Step 404, obtaining the number of protection layers;

[0115] Step 405, calculating the protection interval according to the starting criticality, the failure criticality and the number of protection layers;

[0116] In one example, step 405 may include the following sub-steps:

[0117] S51, calculating a first protection range according to the first critical maximum frequency change rate and the second critical maximum frequency change rate;

[0118] S52, calculating a second protection range according to the first critical unbalanced power and the second critical unbalanced power;

[0119] S53, calculating a first protection interval according to the first protection range and the number of protection layers;

[0120] S54: Calculate a second protection interval according to the second protection range and the number of protection layers.

[0121] In the embodiment of the present invention, the same hierarchical starting method as the under-frequency load reduction protection is used to change the protection range (df / dt) of the interruptible load active frequency control strategy to start ~(df / dt) stop (Second protection range) and ΔP start ~ΔP stop The (first protection range) is divided into N protection layers at equal intervals, with each layer separated by Δ(df / dt) (second protection interval) and ΔP (first protection interval). Therefore, the protection range of each layer is (df / dt) start +(i-1)×Δ(df / dt)~(df / dt) start +i×Δ(df / dt) and ΔP start +(i-1)×ΔP~ΔP start+i×ΔP. When the frequency drop speed exceeds the i-th protection layer, the starting frequency change rate (df / dt) i When the interruption load of the interruptible load is exited, the interruption load capacity ΔP Li .

[0122] Step 406, determining the starting frequency change rate of each protection layer according to the protection interval;

[0123] In the embodiment of the present invention, the starting frequency change rate (df / dt) of the i-th protection layer is i The setting principle is: directly select the minimum value (df / dt) of the protection range of the i-th protection layer start +(i-1)×Δ(df / dt) as the starting frequency change rate (df / dt) of the i-th protection layer i .

[0124] Step 407, obtaining the initial interruptible capacity of each interruptible load in the protection layer;

[0125] Step 408 : Under the preset disturbance, the initial interruptible capacity is adjusted according to the low-frequency load shedding starting frequency to obtain the adjusted interruptible capacity as the current interruptible capacity of the protection layer.

[0126] In the embodiment of the present invention, the interruption load ΔP of the i-th protection layer Li The setting principle is: assuming that after the protection of the i-th protection layer is activated, the subsequent actions are not activated and the system does not have a new power shortage. Based on the principle that the interruptible load with fast response speed is exited first, after considering the frequency deviation constraint, the highest unbalanced power ΔP that the i-th protection layer may encounter is start +i×ΔP condition, by calculating the different response delays t of the system frequency response model j Critical exit quantity ΔP of interruptible load Li,tj , as the adjustment of the i-th protection layer can interrupt the load.

[0127] In one example, under a preset disturbance, adjusting the initial interruptible capacity according to the low-frequency load shedding starting frequency to obtain the step of adjusting the interruptible capacity may include the following sub-steps:

[0128] S81, calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under a preset disturbance based on the initial interruptible capacity;

[0129] S82, when the lowest value of the system frequency drop is greater than the low-frequency load shedding starting frequency, reducing the interruption capacity of the j-th interruptible load, and returning to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under the preset disturbance;

[0130] S83, when the lowest value of the system frequency drop is less than the low-frequency load shedding starting frequency, set j = j + 1, and return to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under the preset disturbance;

[0131] S84, when the lowest value of the system frequency drop is equal to the low-frequency load shedding starting frequency, the adjusted interruptible capacity of each interruptible load is output as the current interruptible capacity of the protection layer.

[0132] In the specific implementation, in ΔP start Under +i×ΔP unbalanced power disturbance, the delayed interruption IL ti ~IL tj After that, calculate the lowest value of system frequency drop f nadir , when the system frequency drops to the lowest value f nadir Greater than the low-frequency load reduction starting frequency f UFSL When the system frequency drops to the lowest value f nadir Less than low-frequency load reduction starting frequency f UFSL When the frequency is

[0133] For easier understanding, see Figure 6 , Figure 6 The control strategy parameter setting flow chart provided in the embodiment of the present invention is as follows:

[0134] 1. Establish a system frequency response model;

[0135] 2. Get the low-frequency load reduction starting frequency f UFSL ;

[0136] 3. Calculate the time delay t of the interruptible load s With capacity P IL ;

[0137] 4. Calculate the starting critical value: ΔP start 、(df / dt) start ;

[0138] 5. Calculate failure threshold: ΔP stop 、(df / dt) stop , t nadir ;

[0139] 6. Determine the effective IL(t s <t stop ) and its interruptible capacity IL t1 , IL t2 ,...,IL tM (t1 <t2<...<t M );

[0140] 7. Determine N layers of protection;

[0141] 8. Calculate the guard interval Δ(df / dt) and ΔP;

[0142] 9. Let i = 1, j = 1;

[0143] 10. Determine the starting frequency change rate of the i-th protection layer (df / dt) i =(df / dt) start +(i-1)×Δ(df / dt);

[0144] 11. In ΔP start Under +i×ΔP unbalanced power disturbance, the delayed interruption IL t1 ~IL tj After that, calculate the lowest value of system frequency drop f nadir ;

[0145] 12. Compare f nadir With f UFSL The size of f nadir >f UFSL When IL is reduced tj The interruption capacity and return to step 11; when f nadir <f UFSL When f nadir =f UFSL When IL of the i-th protection layer is determined t1 ~IL tM interruption capacity;

[0146] 13. Determine whether i is equal to N; if not, set i=i+1 and return to step 10; if so, summarize the parameters of the active frequency control strategy based on interruptible loads.

[0147] In order to verify the effectiveness of the frequency control method based on interruptible loads provided by the embodiment of the present invention, a time domain simulation verification is carried out on an IEEE39 node system containing new energy equipment in combination with a calculation example system.

[0148] Figure 7 The grid structure topology of the example system is given. The grid structure topology refers to the IEEE 39-node classic power system model, and the specific line parameters are shown in Table 1.

[0149] Conventional power sources G1 to G10 are connected to nodes 30 to 39, and all units are thermal synchronous units. New energy equipment No. 1 to 10 are connected to the high-voltage grid connection points of the step-up transformers of units G1 to G10, respectively. By proportionally replacing the grid connection capacity and active power output of the synchronous units at the same grid connection point, the process of increasing renewable energy penetration in the power grid is simulated. The total grid connection capacity of the system units is 7563MW, and the total active load is 3781.5MW. Figure 8 and Figure 9 The frequency response models of conventional thermal power units and new energy units are given respectively. Tables 2, 3 and 4 respectively give the grid-connected parameters of thermal power units and new energy equipment, the parameters of each load and the key frequency regulation parameters of conventional thermal power units and new energy units.

[0150] Table 1: IEEE 39-bus system line parameters including new energy equipment

[0151]

[0152]

[0153] Table 2: Grid-connected parameters of thermal power units and new energy equipment

[0154]

[0155]

[0156] Table 3: Load parameters of a 39-node system including new energy equipment

[0157]

[0158] Table 4: Key frequency regulation parameters for thermal power units and new energy units in the IEEE 39-node system including new energy equipment

[0159]

[0160]

[0161] Among them, the proportion of new energy in the example system is 30%. New energy equipment No. 1 to 10 adopts grid-following additional frequency regulation control (Kd=3, Kf=5), which has fast frequency response capability. The low-frequency load reduction starting frequency fUFSL of the example system is 48.8Hz, the load frequency regulation effect coefficient D is 1, and the system equivalent inertia time constant Tsys is 8.2s.

[0162] Step 1: Classification of interruptible loads. Assume that the node loads at nodes 16, 18, 20, 21, and 23 in the example system have interruptible loads with different response delays, as shown in Table 5.

[0163] Table 5: Node location, response delay and interruptible capacity of interruptible load

[0164]

[0165] Step 2: Calculate the protection scope.

[0166] The results of the critical protection start-up scenario are calculated. Through numerical calculations of the system frequency response model, it is found that when the interruptible load does not operate, the system frequency will drop to the low-frequency load shedding start frequency of 48.8Hz under an unbalanced power disturbance of 0.255pu, and the maximum frequency change rate at this time is 1.52Hz / s.

[0167] Results for the critical protection failure scenario were calculated. When all interruptible loads are correctly actuated, the unbalanced power required to drop the system frequency to 48.8Hz is 0.305 pu, corresponding to a maximum frequency change rate of 1.81 Hz / s. The frequency minimum occurs 1.48 seconds after the disturbance occurs. Therefore, only the interruptible loads IL0.1s, IL0.5s, and IL1.0s are considered effective interruptible loads, and the control strategy only needs to consider interrupting these three loads.

[0168] In summary, the power disturbance protection range of the control strategy is ΔP start ~ΔP stop =0.255pu~0.305pu, the frequency change rate protection range is (df / dt) start ~(df / dt) stop =1.52Hz / s~1.81Hz / s. In a given operating scenario, the active frequency control strategy based on interruptible loads can increase the maximum disturbance power that the example system can withstand by 0.05pu.

[0169] Step 3: Setting Layered Protection Parameters. Assuming three protection layers, the starting frequency change rate interval Δ(df / dt) is (1.81-1.52) / 3 = 0.097 Hz / s, and the power disturbance interval ΔP is (0.305-0.255) / 3 = 0.0167 pu. The starting frequency rates for the three protection layers are 1.52 Hz / s, 1.617 Hz / s, and 1.714 Hz / s, respectively.

[0170] Calculate the interruption load ΔP of the first layer of protection L1 When the system encounters a power disturbance of 0.255+0.0167=0.2717pu, all 0.02pu ILs are interrupted first. 0.1s After that, the system frequency dropped to 48.81Hz (>48.80Hz). 0.1sWhen the frequency drops to 48.80Hz, it is at the critical starting point of low-frequency load shedding. Therefore, the interruption load of the first layer of protection is ΔP L1 IL of 0.0175pu 0.1s .

[0171] Calculate the interruption load ΔP of the second layer protection L2 When the system encounters a power disturbance of 0.255+0.0167×2=0.2884pu, all 0.02pu ILs are interrupted. 0.1s After that, the frequency drops to 48.73Hz (<48.80Hz). 0.1s With IL 0.5s When the IL of 0.02pu is interrupted, the frequency drops to 48.82Hz (>48.80Hz). 0.1s With an IL of 0.0155pu 0.5s When the frequency drops to 48.80Hz, it is at the critical starting point of low-frequency load shedding. Therefore, the interruption load of the second layer protection is ΔP L2 IL of 0.02pu 0.1s With an IL of 0.0155pu 0.5s .

[0172] The third layer of protection is the last layer of protection, which interrupts the load ΔP L3 Should be the total effective interruptible load, i.e. IL of 0.02pu 0.1s , IL of 0.02pu 0.5s With IL of 0.02pu 1.0s When the system encounters a power disturbance of 0.305 pu, the frequency drops to a minimum of 48.80 Hz, which is at the critical starting point for low-frequency load shedding.

[0173] The parameters of each protection layer of the summary control strategy are shown in Table 6.

[0174] Table 6: Layered protection parameters

[0175]

[0176]

[0177] In the PSCAD / EMTDC electromagnetic transient simulation environment, an interruptible load control strategy was deployed in the example system according to the setting parameters in Table 2, implementing interruption control for the interruptible loads within nodes 16, 18, and 20 at intervals of 0.1s, 0.5s, and 0s, respectively. To verify the effectiveness of the interruptible load-based active frequency control strategy and its impact on improving the grid's renewable energy carrying capacity, the dynamic response characteristics of the system frequency were compared under two operating scenarios: with and without the interruptible load control strategy, when the example system encountered a 0.3pu power disturbance.

[0178] In the time domain simulation, at t = 10s, the system encounters a 0.3pu power disturbance in the form of a sudden load increase at node 16. The average frequency response of the system under the two operating scenarios is compared. The results are as follows: Figure 10 shown.

[0179] Comparing the results of the two operating scenarios, it can be seen that when the interruptible load control strategy is involved in the system frequency control, the system frequency characteristics are effectively improved, and the system frequency, which originally dropped to 48.56Hz at the lowest point, is increased to 48.82Hz. If the low-frequency load reduction protection (f UFSL =48.8Hz). Without the interruptible load control strategy, the system would have already activated underfrequency load shedding protection, potentially removing loads that require high power reliability. The deployment of the interruptible load control strategy mitigated this risk to a certain extent, validating the effectiveness of the control strategy.

[0180] See also Figure 11 , Figure 11 This is a structural block diagram of a frequency control device based on an interruptible load provided by an embodiment of the present invention.

[0181] An embodiment of the present invention provides a frequency control device based on an interruptible load, comprising:

[0182] The frequency change rate acquisition module 1101 is used to acquire the frequency change rate in real time when a power shortage fault occurs in the power system;

[0183] The current protection layer determining module 1102 is configured to determine the currently triggered current protection layer according to the frequency change rate and the preset starting frequency change rate of the protection layer;

[0184] The response delay and current interruptible capacity calculation module 1103 is used to determine the current interruptible load of the current protection layer and calculate the response delay and current interruptible capacity of the current interruptible load;

[0185] An under-frequency load shedding starting frequency acquisition module 1104 is used to acquire the under-frequency load shedding starting frequency;

[0186] A target interruptible load determination module 1105 is configured to determine a target interruptible load according to the underfrequency load shedding starting frequency, the frequency change rate, the response delay, and the current interruptible capacity;

[0187] The frequency control module 1106 is used to interrupt the target interruptible load to perform frequency control.

[0188] In an embodiment of the present invention, the following further comprises:

[0189] System frequency response model building module, used to build a system frequency response model;

[0190] A starting criticality acquisition module is used to obtain the starting criticality of the power system in a protection starting criticality scenario based on a system frequency response model; the starting criticality includes a first critical unbalanced power and a first critical maximum frequency change rate;

[0191] A failure criticality acquisition module is used to obtain the failure criticality of the power system in a protection failure criticality scenario based on a system frequency response model; the failure criticality includes the second critical unbalanced power, the second critical maximum frequency change rate, and the maximum frequency drop time;

[0192] A protection layer number acquisition module is used to obtain the number of protection layers;

[0193] A protection interval calculation module is used to calculate the protection interval based on the starting criticality, failure criticality and the number of protection layers;

[0194] A starting frequency change rate determination module, used to determine the starting frequency change rate of each protection layer according to the protection interval;

[0195] An initial interruptible capacity acquisition module is used to obtain the initial interruptible capacity of each interruptible load in the protection layer;

[0196] The adjustment module is used to adjust the initial interruptible capacity according to the low-frequency load reduction starting frequency under a preset disturbance, and obtain the adjusted interruptible capacity as the current interruptible capacity of the protection layer.

[0197] In an embodiment of the present invention, the adjustment module includes:

[0198] The system frequency drop minimum value calculation submodule is used to calculate the system frequency drop minimum value after the first j interruptible loads are interrupted under the preset disturbance based on the initial interruptible capacity;

[0199] The first return submodule is configured to reduce the interruption capacity of the jth interruptible load when the lowest value of the system frequency drop is greater than the low-frequency load shedding starting frequency, and return to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under a preset disturbance;

[0200] The second return submodule is used to set j = j + 1 when the lowest value of the system frequency drop is less than the low-frequency load reduction starting frequency, and return to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under the preset disturbance;

[0201] The interruptible capacity adjustment output submodule is used to output the adjusted interruptible capacity of each interruptible load as the current interruptible capacity of the protection layer when the system frequency drops to a minimum value equal to the low-frequency load reduction starting frequency.

[0202] In an embodiment of the present invention, the guard interval calculation module includes:

[0203] A first protection range calculation submodule, configured to calculate a first protection range according to a first critical maximum frequency change rate and a second critical maximum frequency change rate;

[0204] A second protection range calculation submodule, configured to calculate a second protection range according to the first critical unbalanced power and the second critical unbalanced power;

[0205] A first protection interval calculation submodule, configured to calculate a first protection interval according to the first protection range and the number of protection layers;

[0206] The second protection interval calculation submodule is configured to calculate the second protection interval according to the second protection range and the number of protection layers.

[0207] An embodiment of the present invention further provides an electronic device, the device including a processor and a memory:

[0208] The memory is used to store program codes and transmit the program codes to the processor;

[0209] The processor is configured to execute the frequency control method based on the interruptible load according to the instructions in the program code.

[0210] An embodiment of the present invention further provides a computer-readable storage medium, which is used to store program code, and the program code is used to execute the frequency control method based on interruptible load according to an embodiment of the present invention.

[0211] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0212] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0213] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, apparatus, or computer program products. Thus, embodiments of the present invention may take the form of a fully hardware embodiment, a fully software embodiment, or an embodiment combining software and hardware. Furthermore, embodiments of the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0214] The embodiments of the present invention are described with reference to the flowcharts and / or block diagrams of the methods, terminal devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing terminal device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device generate instructions for implementing the process in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0215] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing terminal device to operate in a specific manner, so that the instructions stored in the computer readable memory produce a manufactured product including an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0216] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal device so that a series of operating steps are executed on the computer or other programmable terminal device to produce a computer-implemented process, thereby providing instructions for executing on the computer or other programmable terminal device to implement the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0217] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0218] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or terminal device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or terminal device that includes the element.

[0219] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency control method based on interruptible load, characterized in that: include: When a power shortage fault occurs in the power system, the frequency change rate is obtained in real time; Determining a currently triggered protection layer according to the frequency change rate and a preset starting frequency change rate of the protection layer; Determining a current interruptible load of the current protection layer, and calculating a response delay and a current interruptible capacity of the current interruptible load; Get the low-frequency load shedding starting frequency; determining a target interruptible load according to the underfrequency load shedding starting frequency, the frequency change rate, the response delay, and the current interruptible capacity; Interrupting the target may interrupt the load for frequency control.

2. The method according to claim 1, characterized in that Before the step of determining the currently triggered current protection layer according to the frequency change rate and the preset starting frequency change rate of the protection layer, the method further includes: Establish system frequency response model; According to the system frequency response model, obtaining the starting criticality of the power system in a protection starting criticality scenario; the starting criticality includes a first critical unbalanced power and a first critical maximum frequency change rate; According to the system frequency response model, obtaining the failure criticality of the power system in a protection failure critical scenario; the failure criticality includes a second critical unbalanced power, a second critical maximum frequency change rate, and a maximum frequency drop time; Get the number of protection layers; Calculating a protection interval according to the starting criticality, the failure criticality and the number of protection layers; Determining a starting frequency change rate of each protection layer according to the protection interval; Obtaining an initial interruptible capacity of each interruptible load in the protection layer; Under a preset disturbance, the initial interruptible capacity is adjusted according to the low-frequency load shedding starting frequency to obtain the adjusted interruptible capacity as the current interruptible capacity of the protection layer.

3. The method according to claim 2, characterized in that The step of adjusting the initial interruptible capacity according to the low-frequency load shedding starting frequency under a preset disturbance to obtain the adjusted interruptible capacity as the current interruptible capacity of the protection layer includes: Calculate the lowest value of the system frequency drop after the first j interruptible loads are interrupted under a preset disturbance based on the initial interruptible capacity; When the lowest value of the system frequency drop is greater than the low-frequency load shedding starting frequency, reducing the interruption capacity of the j-th interruptible load, and returning to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under the preset disturbance; When the lowest value of the system frequency drop is less than the low-frequency load shedding starting frequency, set j=j+1, and return to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under the preset disturbance; When the lowest value of the system frequency drop is equal to the low-frequency load shedding starting frequency, the adjusted interruptible capacity of each interruptible load is output as the current interruptible capacity of the protection layer.

4. The method according to claim 2, characterized in that The step of calculating the protection interval according to the starting threshold, the failure threshold, and the number of protection layers includes: Calculating a first protection range according to the first critical maximum frequency change rate and the second critical maximum frequency change rate; Calculating a second protection range according to the first critical unbalanced power and the second critical unbalanced power; Calculating a first protection interval according to the first protection range and the number of protection layers; A second protection interval is calculated according to the second protection range and the number of protection layers.

5. A frequency control device based on an interruptible load, characterized in that: include: The frequency change rate acquisition module is used to obtain the frequency change rate in real time when a power shortage fault occurs in the power system; a current protection layer determining module, configured to determine a currently triggered current protection layer according to the frequency change rate and a preset starting frequency change rate of the protection layer; a response delay and current interruptible capacity calculation module, configured to determine a current interruptible load of the current protection layer, and calculate a response delay and a current interruptible capacity of the current interruptible load; Low-frequency load shedding starting frequency acquisition module, used to obtain low-frequency load shedding starting frequency; a target interruptible load determination module, configured to determine a target interruptible load according to the underfrequency load shedding starting frequency, the frequency change rate, the response delay, and the current interruptible capacity; The frequency control module is used to interrupt the target interruptible load to perform frequency control.

6. The device according to claim 5, characterized in that Also includes: System frequency response model building module, used to build a system frequency response model; A starting criticality acquisition module is used to obtain the starting criticality of the power system in a protection starting criticality scenario according to the system frequency response model; the starting criticality includes a first critical unbalanced power and a first critical maximum frequency change rate; A failure criticality acquisition module is used to obtain the failure criticality of the power system in a protection failure criticality scenario according to the system frequency response model; the failure criticality includes a second critical unbalanced power, a second critical maximum frequency change rate, and a maximum frequency drop time; A protection layer number acquisition module is used to obtain the number of protection layers; A protection interval calculation module, configured to calculate a protection interval according to the starting criticality, the failure criticality and the number of protection layers; a starting frequency change rate determination module, configured to determine the starting frequency change rate of each protection layer according to the protection interval; An initial interruptible capacity acquisition module, configured to acquire an initial interruptible capacity of each interruptible load in the protection layer; The adjustment module is used to adjust the initial interruptible capacity according to the low-frequency load reduction starting frequency under a preset disturbance, and obtain the adjusted interruptible capacity as the current interruptible capacity of the protection layer.

7. The device according to claim 6, characterized in that The adjustment module includes: A system frequency drop minimum value calculation submodule, configured to calculate, based on the initial interruptible capacity, the system frequency drop minimum value after the first j interruptible loads are interrupted under a preset disturbance; A first return submodule is configured to reduce the interruption capacity of the jth interruptible load when the lowest value of the system frequency drop is greater than the low-frequency load shedding starting frequency, and return to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under a preset disturbance; The second return submodule is configured to, when the lowest value of the system frequency drop is less than the low-frequency load shedding starting frequency, set j=j+1 and return to the step of calculating the lowest value of the system frequency drop after the first j interruptible loads are interrupted under a preset disturbance; The interruptible capacity adjustment output submodule is configured to output the adjusted interruptible capacity of each interruptible load as the current interruptible capacity of the protection layer when the system frequency drops to a minimum value equal to the low-frequency load shedding starting frequency.

8. The device according to claim 6, characterized in that The guard interval calculation module includes: A first protection range calculation submodule, configured to calculate a first protection range according to the first critical maximum frequency change rate and the second critical maximum frequency change rate; A second protection range calculation submodule, configured to calculate a second protection range according to the first critical unbalanced power and the second critical unbalanced power; A first protection interval calculation submodule, configured to calculate a first protection interval according to the first protection range and the number of protection layers; The second protection interval calculation submodule is configured to calculate a second protection interval according to the second protection range and the number of protection layers.

9. An electronic device, characterized in that: The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the interruptible load-based frequency control method according to any one of claims 1 to 4 according to instructions in the program code.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium is used to store program codes, and the program codes are used to execute the frequency control method based on interruptible loads according to any one of claims 1 to 4.

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