Power system inertia evaluation method considering direct current FLC influence

Abstract

The invention discloses an electric power system inertia evaluation method considering direct current FLC influence, which comprises the following steps of: firstly, calculating the center frequency of a sending end system according to collected frequency data of a bus at a grid-connected part of a generator set before and after large power disturbance, and then carrying out per-unit processing; secondly, according to the collected active power data on the alternating current tie line of the sending end system, carrying out mean value removal and per-unit processing to obtain the per-unit data of the active power variation of the tie line of the sending end system; according to the collected alternating current side frequency data of the rectifier station, direct current power output after the action of the direct current FLC controller is obtained, and per-unit processing is carried out on the direct current power; thirdly, according to the center frequency fluctuation data of the sending end system, the disturbance occurrence moment is identified; finally, selecting a preset time period after the disturbance occurrence moment as a to-be-solved time period; and calculating a first equivalent inertia time constant of the asynchronous sending-end power system by using a sliding data window method in a to-be-solved time period, and on the basis, averaging all the calculated first equivalent inertia time constants to obtain a final equivalent inertia time constant of the asynchronous sending-end power system. According to the method, the inertia evaluation problem of the asynchronous sending end power system under the action of the direct current FLC can be effectively solved.

Description

Technical Field

[0001] The invention relates to an inertia evaluation method for a power system taking into account the influence of a direct current FLC, and belongs to the field of frequency stability analysis of a power system. Background Art

[0002] The asynchronous operation of large power grids is an important measure to solve the problem of safe and stable operation of large interconnected power systems. The asynchronous operation of power grids can effectively solve the problem of power angle stability of AC interconnected power systems, but it will also increase the risk of frequency stability operation, especially for asynchronous sending-end power systems. The frequency stability problem is more prominent. In addition, with the development of new power systems, the proportion of new energy in the system is increasing. Since the mechanical inertia of wind power and photovoltaics is very small, even close to zero, the overall inertia level of the system has decreased, further exacerbating the problem of frequency stability of the power system. Under the same power disturbance conditions, the lower the system inertia level, the larger the range of system frequency fluctuations and the higher the risk of frequency instability. Therefore, the inertia assessment of the power system has become an important link in ensuring the reliability of power supply.

[0003] In order to improve the frequency stability capability of the asynchronous sending-end power system, the asynchronous sending-end power system is usually equipped with a DC FLC controller. The DC FLC controller is an auxiliary control link of the DC power control on the AC side of the rectifier station. It can provide fast power support for the forward and reverse power shortages of the sending-end power system, thereby achieving the purpose of improving the frequency stability of the sending-end system. However, when the system suffers from a large power disturbance, the frequency response process of the DC FLC is strongly coupled with the inertia response and primary frequency modulation response of the synchronous generator set, and they jointly participate in the system frequency modulation, resulting in the existing inertia evaluation method being difficult to effectively evaluate the system inertia level. Therefore, for the inertia evaluation of the asynchronous sending-end power system, it is necessary to develop an inertia evaluation method that solves the inertia evaluation under the interference conditions of the DC FLC. This method is crucial to ensure the safe and stable operation of the asynchronous sending-end power system involving the DC FLC. Due to the uniqueness of the inertia evaluation of the sending-end power system, few of the existing inertia evaluation methods involve effective evaluation methods in the context of this research. Summary of the invention

[0004] The present invention provides a method for evaluating the inertia of a power system taking into account the influence of a DC FLC, so as to evaluate the inertia of an asynchronous sending-end power system involving a DC FLC.

[0005] The technical solution of the present invention is:

[0006] According to a first aspect of the present invention, there is provided a method for evaluating inertia of a power system taking into account the influence of DC FLC, comprising the following steps:

[0007] Step 1: Under a large disturbance of the asynchronous sending-end power system, frequency data of the busbars at the grid-connected locations of all generator sets in the asynchronous sending-end power system are collected, and active power data on the AC interconnection lines of the sending-end system of the asynchronous sending-end power system are synchronously collected;

[0008] Step 2: Perform per-unit processing on the frequency data of the busbar at the grid-connected generator set to obtain per-unit frequency data, and calculate the per-unit data of the center frequency of the sending-end system based on the obtained per-unit frequency data; perform de-averaging and per-unit processing on the collected active power data on the AC interconnection line of the sending-end system to obtain the per-unit data of the active power change of the sending-end system;

[0009] Step 3, collect the frequency data of the AC side of the rectifier station, remove the mean value of the collected frequency data of the AC side of the rectifier station, and obtain the frequency change data of the AC side of the rectifier station; calculate the output DC power after the DC FLC controller is activated according to the frequency dead zone parameter of the DC FLC controller, the proportional link gain coefficient, the integral link gain coefficient, the positive / negative power output limit value and the frequency change data of the AC side of the rectifier station; and obtain the active power of the DC FLC controller acting on the asynchronous sending-end power system according to the conversion efficiency and the output DC power after the DC FLC controller is activated, and perform standardization processing on it;

[0010] Step 4: Identify the instant when the disturbance occurs based on the normalized data of the center frequency of the sending end system;

[0011] Step 5, taking the instantaneous moment of the disturbance determined in step 4 as the demarcation point; selecting a preset time period after the demarcation point as the time period to be sought, and fixing the data window length in the time period, and using the sliding data window method to traverse the time period to be sought with the same step length; according to the frequency and power data in the time period to be sought obtained in steps 1 to 3, calculating the first equivalent inertia time constant of the asynchronous sending-end power system in each data window in the time period to be sought; averaging the first equivalent inertia time constants of the asynchronous sending-end power system calculated in all data windows to obtain the final equivalent inertia time constant of the asynchronous sending-end power system.

[0012] Furthermore, assuming that the frequency dead zone of the DC FLC controller is [Δf - ,Δf + ], the active power ΔP acting on the asynchronous sending-end power system by the DC FLC controller FLC As shown below:

[0013]

[0014] ΔP FLC =ηΔP DC ;

[0015] Among them, ΔPDC is the output DC power after the DC FLC controller is activated; ΔP up The DC power boost value; ΔP down is the DC power reduction; ΔP FLC is the active power of the DC FLC controller acting on the asynchronous sending-end power system; η is the conversion efficiency; Δf is the frequency change data on the AC side of the rectifier station.

[0016] Furthermore, the step 4 is specifically as follows:

[0017] The EWMA algorithm is designed for the center frequency normalized data of the sending system to detect the data disturbance point through the following discriminant. If the discriminant is satisfied, the moment can be considered as the disturbance point. The first disturbance point is the instant when the disturbance occurs:

[0018] res t >alpha·sig

[0019] Where: res t is the residual of the data at time t; alpha is the significance level; sig represents the standard deviation of the residual sequence.

[0020] Furthermore, with i as the order, the calculation expression for the first equivalent inertia time constant is:

[0021]

[0022] Among them, H aream-i is the ith calculated value of the first equivalent inertia time constant of the asynchronous sending-end power system; t i,0 Indicates the starting time of the calculation of the i-th first equivalent inertia time constant, t i,1 represents the end time of the calculation of the i-th first equivalent inertia time constant; P s is the per-unit value of the disturbance power; ΔP m ΔP' is the normalized data of the active power change of the sending end system; FLC represents the per unit value of active power acting on the asynchronous sending-end power system by the DC FLC controller; f COI It is the normalized data of the center frequency of the sending system.

[0023] According to a second aspect of the present invention, there is provided an asynchronous sending-end power system inertia assessment system taking into account DC FLC, comprising: one or more processors; a memory for storing operable instructions, wherein when the instructions are executed by the one or more processors, the one or more processors perform operations, wherein the operations include the steps of any one of the methods described above.

[0024] The beneficial effects of the present invention are as follows: for the inertia assessment problem of the asynchronous sending-end power system involving DC FLC, when the system is subjected to a large disturbance, the previous inertia assessment method cannot assess the inertia problem of the asynchronous sending-end power system involving DC FLC, while the present invention can effectively assess the inertia level of the asynchronous sending-end system under the influence of the DC FLC action based on the acquired normalized data of the active power change of the asynchronous sending-end system, the normalized data of the active power output of the DC power acting on the asynchronous sending-end power system after the DC FLC controller is actuated, and the center frequency of the sending-end system, and verification shows that the inertia level of the asynchronous sending-end system is smaller than the actual inertia time constant error. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flow chart of the present invention;

[0026] Figure 2 It is a four-machine two-area DC interconnected distribution system with DC FLC used in the evaluation example of the present invention;

[0027] Figure 3 is the DC FLC controller model used in the evaluation example of the present invention;

[0028] Figure 4 is the center frequency fluctuation data of the sending end system obtained by calculation in the present invention;

[0029] Figure 5 It is the normalized data of active power variation of asynchronous sending end system after preprocessing;

[0030] Figure 6 The DC power output by the DC FLC controller after the controller is actuated is obtained by calculation in the present invention;

[0031] Figure 7 It is a schematic diagram of the EWMA algorithm designed by the present invention to detect the disturbance occurrence time. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. 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. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other arbitrarily without conflict.

[0033] Example 1: Figure 1-7 As shown, according to a first aspect of an embodiment of the present invention, a method for evaluating inertia of a power system taking into account the influence of DC FLC is provided, comprising the following steps:

[0034] Step 1: Under the condition of large disturbance of the asynchronous sending-end power system, the frequency data of the busbars at the grid connection point of all generator sets in the asynchronous sending-end power system are collected, and the active power data on the AC interconnection line of the asynchronous sending-end power system is synchronously collected; generally, the large disturbance condition of the asynchronous sending-end power system is that the large disturbance causes the active power on the DC interconnection to fluctuate, causing the maximum frequency fluctuation value of the asynchronous sending-end power system to be greater than the dead zone value of the DC FLC;

[0035] Step 2: Perform per-unit processing on the frequency data of the busbar at the grid-connected generator set to obtain per-unit frequency data, and calculate the per-unit data of the center frequency of the sending-end system based on the obtained per-unit frequency data; perform de-averaging and per-unit processing on the collected active power data on the AC interconnection line of the sending-end system to obtain the per-unit data of the active power change of the asynchronous sending-end system;

[0036] For each sampling point, the following formula is used to calculate the center frequency normalized data of the sending end system:

[0037]

[0038] In the formula, f COI Indicates the per-unit value of the center frequency of the sending end system; f k is the normalized frequency data of the kth generator set; H k is the inertia time constant of the kth generator set; S k is the rated capacity of the kth generator set.

[0039] Step 3, obtain the topological structure and control parameters of the DC FLC controller on the AC side of the rectifier station; synchronously collect the frequency data of the AC side of the rectifier station, remove the mean value of the collected frequency data of the AC side of the rectifier station, and obtain the frequency change data of the AC side of the rectifier station; calculate the output DC power of the DC FLC controller after the action according to the control parameters of the DC FLC controller and the frequency change data of the AC side of the rectifier station; and obtain the active power of the DC FLC controller acting on the asynchronous sending-end power system according to the conversion efficiency and the output DC power of the DC FLC controller after the action, and perform standardization processing on it;

[0040] The details are as follows:

[0041] Assume that the frequency dead zone of the DC FLC controller is [Δf - ,Δf + ], the active power ΔP acting on the asynchronous sending-end power system by the DC FLC controller FLC As shown below:

[0042]

[0043] ΔP FLC =ηΔPDC ;

[0044]

[0045] Among them, ΔP DC ΔP is the DC power output after the DC FLC controller is activated; up The DC power boost value; ΔP down is the DC power reduction; ΔP FLC is the active power of the DC FLC controller acting on the asynchronous sending-end power system; ΔP' FLC Indicates ΔP FLC Per unit value, P base It represents the reference value of active power; η is the conversion efficiency, which depends on the conversion rate of DC power into active power, and the reference range of the value is 0.9~1; Δf is the frequency change data of the AC side of the rectifier station.

[0046] The DC boost power value and DC drop power value are expressed as:

[0047]

[0048] In the formula, K p , K I They are the proportional link gain coefficient and the integral link gain coefficient respectively;

[0049] And the constraints must be met:

[0050]

[0051] In the formula, ΔP up.max Indicates the forward power output limit value; ΔP down.min Indicates the negative power output limit value;

[0052] For example, the DC FLC controller adopts a reverse frequency difference reset type FLC controller, and the topology and parameters of the reverse frequency difference reset type FLC controller are as follows: Figure 3 As shown, the specific parameters include frequency dead zone parameters, proportional link gain coefficient, integral link gain coefficient, and positive / negative power output power limit value.

[0053] Step 4: Use the EWMA algorithm to detect the fluctuation of the center frequency of the sending end system and identify the instant when the disturbance occurs;

[0054] The step 4 is specifically as follows:

[0055] The EWMA algorithm is designed for the center frequency fluctuation data of the sending system. The expression is as follows:

[0056] v t =β·x t-1+(1-β)·θ t

[0057] Where: The exponentially weighted moving average v at time t is denoted by v t ;x t-1 is the center frequency of the sending end system at time t-1; θ t is the value of the variable v at time t-1; β is the attenuation weight, which is 0.2;

[0058] Recursively extrapolate the above formula to obtain:

[0059] θ t =v t-1 =β·x t-2 +(1-β)·θ t-1 ;

[0060] Combining the above two equations, we can get:

[0061] v t =β·x t-1 +(1-β)·(β·x t-2 +(1-β)·θ t-1 );

[0062] Calculate the residual sequence and calculate the standard deviation of the residual sequence:

[0063] res t =v t -x t ;

[0064]

[0065] The data disturbance point can be detected by the following discriminant:

[0066] res t >alpha·sig;

[0067] Where: res t is the residual of the data at time t; alpha is the significance level, which is 0.02; sig represents the standard deviation of the residual sequence; if the discriminant is satisfied, the moment can be considered as the moment when the disturbance occurs, that is, the disturbance point; the first disturbance point is the instant when the disturbance occurs.

[0068] Step 5, take the instantaneous moment of the disturbance determined in step 4 as the demarcation point; select the preset time period after the demarcation point as the time period to be sought, and fix the data window length in this time period, and use the sliding data window method to traverse the time period to be sought with the same step length; according to the frequency and power data in the time period to be sought obtained in steps 1 to 3, calculate the first equivalent inertia time constant of the asynchronous sending power system in each data window in the time period to be sought; average the first equivalent inertia time constants of the asynchronous sending power system calculated in all data windows to obtain the final equivalent inertia time constant of the asynchronous sending power system. Exemplarily, assuming that the instantaneous moment of the disturbance identified in step 4 is 15s, [15.1,16] is taken as the time period to be sought; in this time period, the first equivalent inertia time constant is calculated every 0.1s, and the average of the 9 first equivalent inertia time constants calculated after 15.1s is taken as the final equivalent inertia time constant of the asynchronous sending power system. It should be noted that the starting and ending times of each time period to be sought are sampling points.

[0069] Taking i as the order, the calculation expression of the first equivalent inertia time constant is given as follows:

[0070]

[0071] Among them, H aream-i is the ith calculated value of the first equivalent inertia time constant of the asynchronous sending-end power system; t i,0 Indicates the starting time of the calculation of the i-th first equivalent inertia time constant, t i,1 represents the end time of the calculation of the i-th first equivalent inertia time constant; P s is the per-unit value of the disturbance power; ΔP m ΔP' is the normalized data of the active power change of the sending end system; FLC represents the per unit value of active power acting on the asynchronous sending-end power system by the DC FLC controller; f COI is the center frequency normalized data of the sending end system, f COI (t i,0 ) indicates t i,0 The center frequency of the sending end system at the time is normalized data, f COI (t i,1 ) indicates t i,1 The normalized data of the sending system center frequency at time.

[0072] According to a second aspect of the present invention, there is provided a power system inertia assessment system taking into account the influence of DC FLC, comprising: one or more processors; a memory for storing operable instructions, wherein when the instructions are executed by the one or more processors, the one or more processors perform operations, wherein the operations include the steps of any one of the methods described above.

[0073] Obviously, it should be understood by those skilled in the art that the above steps of the present invention can be implemented by a general-purpose computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than herein, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0074] Example 2: Combination Figure 1-7 As shown, an optional method for evaluating the inertia of an asynchronous power system sending end taking into account the DC FLC of the present invention is given, which is specifically described as follows: a DC FLC controller is added to the rectifier station of a four-machine two-area system of high-voltage direct current transmission (LCC-HVDC), such as Figure 2 As shown, the DC FLC controller topology and parameters are as follows Figure 3 As shown. Figure 2 For reference, a power disturbance event of shedding 120MW load is set at bus 7, and the load shedding duration is 1s. The sampling rate is set to 100Hz, and the frequency data of the bus at the grid connection of the generator set before and after the large power disturbance, the active power data on the AC tie line of the regional sending end system, and the frequency data on the AC side of the rectifier station are collected through the PMU device.

[0075] Step 1: Under the condition of large disturbance in the asynchronous power sending system, the frequency data of the buses at the grid connection points of all generator sets in the asynchronous power sending system are collected through the PMU device, and the active power data on the AC interconnection lines of the asynchronous power sending system are collected synchronously; generally, the frequency disturbance exceeding 0.15Hz is regarded as a large disturbance. Figure 7 In the example shown, a given disturbance causes the system frequency to change by about 0.3 Hz.

[0076] Step 2: The collected frequency data of the busbar at the grid-connected generator set are sequentially normalized to obtain normalized frequency data, and the normalized data of the center frequency of the sending-end system is calculated based on the obtained normalized frequency data; the collected active power data on the AC interconnection line of the sending-end system is de-averaged and normalized to obtain the normalized data of the active power variation of the asynchronous sending-end system; illustratively, Figure 4 What is shown is the center frequency variation curve of the sending end system under the sampling time of 1-40s; Figure 5 What is shown is the normalized data of the active power change of the asynchronous sending end system under the sampling time of 1-40s.

[0077] Step 3, obtain the topological structure and control parameters of the DC FLC controller; synchronously collect the frequency data of the AC side of the rectifier station, remove the mean value of the collected frequency data of the AC side of the rectifier station, and obtain the frequency change data of the AC side of the rectifier station; calculate the output DC power of the DC FLC controller after the action according to the control parameters of the DC FLC controller and the frequency change data of the AC side of the rectifier station; and according to the conversion efficiency and the output DC power of the DC FLC controller after the action, obtain the active power of the DC FLC controller on the asynchronous sending-end power system, and perform standardization processing on it; Figure 6 The figure shows the DC power output ΔP after the DC FLC controller is activated. DC .

[0078] S4, using the EWMA algorithm to detect the fluctuation of the center frequency of the sending end system and identify the instant when the disturbance occurs; Figure 7 As shown, the instantaneous moment of the identified disturbance is 15.01s;

[0079] S5. The instantaneous moment of the disturbance identified in step 4 is 15.01s, and [15.1,16] is used as the time period to be calculated; the sliding data window length is 0.1s, and the sliding step is 0.1s; in this time period, the first equivalent inertia time constant is calculated every 0.1s, and the average value of the 9 first equivalent inertia time constants calculated after 15.1s is taken as the final equivalent inertia time constant of the asynchronous sending-end power system. The calculated first equivalent inertia time constant of the asynchronous sending-end system is shown in Table 1:

[0080] Table 1 Calculated values ​​of equivalent inertia time constant of asynchronous sending end system in different time periods

[0081]

[0082]

[0083] From Table 1, we can see that the final equivalent inertia time constant H is calculated. aream The other variables in the power system model remain unchanged, only the operation state of the DC FLC controller is changed, the DC FLC controller is decommissioned, and the disturbance method is used to obtain the final equivalent inertia time constant of the asynchronous sending-end power system when the DC FLC controller is decommissioned, which is used as the real inertia time constant of the system. The real inertia time constant of the system is 4.67s, and the deviation between the method proposed in the present invention and the real inertia time constant of the sending-end system is only -1.28%, which shows that the method proposed in the present invention can perform accurate inertia evaluation in the asynchronous sending-end power system taking into account the DC FLC.

[0084] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for evaluating the inertia of a power system taking into account the influence of DC FLC, characterized in that: The following steps are involved: Step 1: Under a large disturbance of the asynchronous sending-end power system, frequency data of the busbars at the grid-connected locations of all generator sets in the asynchronous sending-end power system are collected, and active power data on the AC interconnection lines of the sending-end system of the asynchronous sending-end power system are synchronously collected; Step 2: Perform per-unit processing on the frequency data of the busbar at the grid-connected generator set to obtain per-unit frequency data, and calculate the per-unit data of the center frequency of the sending-end system based on the obtained per-unit frequency data; perform de-averaging and per-unit processing on the collected active power data on the AC interconnection line of the sending-end system to obtain the per-unit data of the active power change of the sending-end system; Step 3, collect the frequency data of the AC side of the rectifier station, remove the mean value of the collected frequency data of the AC side of the rectifier station, and obtain the frequency change data of the AC side of the rectifier station; calculate the output DC power after the DC FLC controller is activated according to the frequency dead zone parameter of the DC FLC controller, the proportional link gain coefficient, the integral link gain coefficient, the positive / negative power output limit value and the frequency change data of the AC side of the rectifier station; and obtain the active power of the DC FLC controller acting on the asynchronous sending-end power system according to the conversion efficiency and the output DC power after the DC FLC controller is activated, and perform standardization processing on it; Step 4: Identify the instant when the disturbance occurs based on the normalized data of the center frequency of the sending end system; Step 5, taking the instantaneous moment of the disturbance determined in step 4 as the demarcation point; selecting a preset time period after the demarcation point as the time period to be sought, and fixing the data window length in the time period, and using the sliding data window method to traverse the time period to be sought with the same step length; according to the frequency and power data in the time period to be sought obtained in steps 1 to 3, calculating the first equivalent inertia time constant of the asynchronous sending-end power system in each data window in the time period to be sought; averaging the first equivalent inertia time constants of the asynchronous sending-end power system calculated in all data windows to obtain the final equivalent inertia time constant of the asynchronous sending-end power system.

2. The method for evaluating the inertia of a power system taking into account the influence of DC FLC according to claim 1, characterized in that: Assume that the frequency dead zone of the DC FLC controller is [Δf - ,Δf + ], the active power ΔP acting on the asynchronous sending-end power system by the DC FLC controller FLC As shown below: ΔP FLC =ηΔP DC ; Among them, ΔP DC is the output DC power after the DC FLC controller is activated; ΔP up The DC power boost value; ΔP down is the DC power reduction; ΔP FLC is the active power of the DC FLC controller acting on the asynchronous sending-end power system; η is the conversion efficiency; Δf is the frequency change data on the AC side of the rectifier station.

3. The method for evaluating the inertia of a power system taking into account the influence of DC FLC according to claim 1, characterized in that: The step 4 is specifically as follows: The EWMA algorithm is designed for the center frequency normalized data of the sending system to detect the data disturbance point through the following discriminant. If the discriminant is satisfied, the moment can be considered as the disturbance point. The first disturbance point is the instant when the disturbance occurs: travel t >alpha·say Where: res t is the residual of the data at time t; alpha is the significance level; sig represents the standard deviation of the residual sequence.

4. The method for evaluating the inertia of a power system taking into account the influence of DC FLC according to claim 1, characterized in that: Taking i as the order, the calculation expression for the first equivalent inertia time constant is: Among them, H aream-i is the ith calculated value of the first equivalent inertia time constant of the asynchronous sending-end power system; t i,0 Indicates the starting time of the calculation of the i-th first equivalent inertia time constant, t i,1 represents the end time of the calculation of the i-th first equivalent inertia time constant; P s is the per-unit value of the disturbance power; ΔP m ΔP' is the normalized data of the active power change of the sending end system; FLC represents the per unit value of active power acting on the asynchronous sending-end power system by the DC FLC controller; f COI It is the normalized data of the center frequency of the sending system.

5. A method system for evaluating inertia of a power system taking into account the influence of DC FLC, characterized in that: include: one or more processors; A memory for storing operable instructions, wherein when the instructions are executed by the one or more processors, the one or more processors are caused to perform operations, wherein the operations include the steps of the method according to any one of claims 1 to 4.

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