Active and reactive coordination control strategy method and device for wind turbine generator

Abstract

The invention discloses a wind turbine generator active and reactive coordination control strategy method and device, and the method comprises the steps: obtaining a grid-connected point frequency value and a grid-connected point voltage value of a wind turbine generator; determining whether the grid-connected point frequency value and the grid-connected point voltage value meet a coordination control strategy condition or not; if the grid-connected point frequency value and the grid-connected point voltage value meet a coordination control strategy condition, determining a target active power compensation amount and a target reactive power compensation amount based on an optimal compensation amount model; and regulating and controlling the frequency and the voltage of the power grid based on the target active power compensation amount and the target reactive power compensation amount. Therefore, the target active power compensation amount and the target reactive power compensation amount are determined based on the optimal compensation amount model, and the frequency and the voltage of the power grid are regulated and controlled based on the target active power compensation amount and the target reactive power compensation amount, so that active and reactive power support is performed on the power grid, and a power system is enabled to operate safely and stably.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine control, and in particular to a wind turbine active and reactive power coordinated control strategy method and device. Background Art

[0002] At present, the voltage characteristics of the power grid will change after wind power is connected to the grid. Since the power electronic equipment of the wind turbine is connected to the grid, it is sensitive to the fluctuation of the frequency and voltage of the grid. Based on this, the power system needs to regulate large-scale grid-connected wind power to ensure the safe and stable operation of the power system.

[0003] In the prior art, the power system regulates the grid-connected wind power through active power, ignoring the reactive power of the grid-connected voltage, which causes fluctuations in the wind turbine generator set when connected to the grid, thereby affecting the power generation effect. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0005] To this end, the present invention proposes a wind turbine active and reactive coordinated control strategy method, which can determine the target active power compensation and reactive power compensation based on the optimal compensation model, and based on the target active power compensation and reactive power compensation, regulate the frequency and voltage of the power grid, thereby providing active and reactive power support to the power grid, so that the power system can operate safely and stably.

[0006] Another object of the present invention is to provide a wind turbine active and reactive power coordinated control strategy device.

[0007] To achieve the above object, the present invention proposes a wind turbine active and reactive power coordinated control strategy method, the method comprising:

[0008] Obtain the grid connection point frequency value and grid connection point voltage value of the wind turbine generator set;

[0009] Determining whether the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions;

[0010] If the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions, then based on the optimal compensation amount model, determine the target active power compensation amount and the target reactive power compensation amount;

[0011] Based on the target active power compensation amount and the target reactive power compensation amount, the frequency and voltage of the power grid are regulated.

[0012] The wind turbine active and reactive power coordinated control strategy method according to the embodiment of the present invention may also have the following additional technical features:

[0013] In one embodiment of the present invention, the determining whether the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions includes:

[0014] Determining whether the grid connection point frequency value and / or the grid connection point voltage value exceeds corresponding preset thresholds;

[0015] If the grid connection point frequency value and / or the grid connection point voltage value exceeds the corresponding preset threshold value, it is determined that the grid connection point frequency value and the grid connection point voltage value meet the coordination control strategy conditions.

[0016] In one embodiment of the present invention, determining the target active power compensation amount and the target reactive power compensation amount based on the optimal compensation amount model includes:

[0017] Determining active power and reactive power objective functions of the optimal compensation model;

[0018] Determining a plurality of constraints corresponding to the active power and reactive power objective functions;

[0019] The active power and reactive power objective functions and the plurality of constraints are optimized and calculated by using the grey wolf algorithm to obtain a target active power compensation amount and a target reactive power compensation amount.

[0020] In one embodiment of the present invention, the plurality of constraints include: voltage constraints, active power constraints, reactive power constraints, frequency deviation constraints, stability constraints and weight coefficient constraints.

[0021] In one embodiment of the present invention, the determining of the multiple constraints corresponding to the active power and reactive power objective functions includes:

[0022] Determine the stability value of the current power system;

[0023] Based on the stability value, stability constraints corresponding to the active power and reactive power objective functions are determined.

[0024] In one embodiment of the present invention, determining the stability value of the power system includes:

[0025] Establishing a frequency and voltage regulation model for the power system;

[0026] Determining a state matrix based on the power system frequency and voltage regulation model;

[0027] Based on the state matrix, a stability value of the power system is determined.

[0028] To achieve the above object, the present invention provides, on the other hand, a wind turbine active and reactive power coordinated control strategy device, the device comprising:

[0029] An acquisition module is used to obtain the grid connection point frequency value and grid connection point voltage value of the wind turbine generator set;

[0030] A first determination module is used to determine whether the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions;

[0031] A second determination module is used to determine a target active power compensation amount and a target reactive power compensation amount based on an optimal compensation amount model if the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions;

[0032] The control module is used to control the frequency and voltage of the power grid based on the target active power compensation amount and the target reactive power compensation amount.

[0033] In one embodiment of the present invention, the first determining module is specifically configured to:

[0034] Determining whether the grid connection point frequency value and / or the grid connection point voltage value exceeds corresponding preset thresholds;

[0035] If the grid connection point frequency value and / or the grid connection point voltage value exceeds the corresponding preset threshold value, it is determined that the grid connection point frequency value and the grid connection point voltage value meet the coordination control strategy conditions.

[0036] Another object of the present invention is to provide an electronic device, comprising:

[0037] at least one processor; and

[0038] a memory communicatively connected to the at least one processor; wherein,

[0039] The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform any one of the methods described in the above aspect.

[0040] Another object of the present invention is to provide a computer storage medium, wherein the computer storage medium stores computer executable instructions; after the computer executable instructions are executed by a processor, the computer executes any one of the methods described in the above aspect.

[0041] The active and reactive power coordinated control strategy method and device of the wind turbine set in the embodiment of the present invention can determine the target active power compensation and reactive power compensation based on the optimal compensation model, and based on the target active power compensation and reactive power compensation, regulate the frequency and voltage of the power grid, thereby providing active and reactive power support to the power grid, so that the power system can operate safely and stably.

[0042] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0044] Figure 1 is a flow chart of a wind turbine active and reactive power coordinated control strategy method according to an embodiment of the present invention;

[0045] Figure 2 4 is a structural diagram of a wind turbine active and reactive coordinated control strategy device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0047] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme 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 described embodiments 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 creative work should fall within the scope of protection of the present invention.

[0048] The following describes a wind turbine active and reactive power coordinated control strategy method and device according to an embodiment of the present invention with reference to the accompanying drawings.

[0049] Figure 1 The present invention is a flowchart of a wind turbine active and reactive power coordinated control strategy method according to an embodiment of the present invention.

[0050] like Figure 1 As shown, the method includes:

[0051] S1, obtaining the grid connection point frequency value and grid connection point voltage value of the wind turbine generator;

[0052] In one embodiment of the present invention, the grid connection point frequency value and the grid connection point voltage value of the wind turbine generator system may be acquired based on the sensor of the grid connection point.

[0053] S2, determining whether the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions;

[0054] In one embodiment of the present invention, after obtaining the grid connection point frequency value and the grid connection point voltage value through the above steps, it can be determined whether the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions based on the grid connection point frequency value and the grid connection point voltage value to determine whether to perform coordinated control.

[0055] Specifically, in one embodiment of the present invention, the method for determining whether the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions may include: determining whether the grid connection point frequency value and / or the grid connection point voltage value exceed the corresponding preset threshold value; if the grid connection point frequency value and / or the grid connection point voltage value exceed the corresponding preset threshold value, then determining that the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions; if both the grid connection point frequency value and the grid connection point voltage value do not exceed the corresponding preset threshold value, then determining that the grid connection point frequency value and the grid connection point voltage value do not meet the coordinated control strategy conditions, and no control is required.

[0056] S3, if the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions, then determine the target active power compensation amount and the target reactive power compensation amount based on the optimal compensation amount model;

[0057] In one embodiment of the present invention, if the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions, the target active power compensation amount and the target reactive power compensation amount can be determined based on the optimal compensation amount model, thereby realizing the wind turbine's active support for the frequency and voltage of the power grid.

[0058] In one embodiment of the present invention, based on the optimal compensation amount model, the method for determining the target active power compensation amount and the target reactive power compensation amount may include the following steps:

[0059] S31, determining the active power and reactive power objective functions of the optimal compensation model;

[0060] S32, determining multiple constraints corresponding to the active power and reactive power objective functions;

[0061] S33, optimizing and calculating the active power and reactive power objective functions and multiple constraints by using the Grey Wolf Algorithm to obtain target active and reactive power compensation amounts.

[0062] In one embodiment of the present invention, the active power and reactive power target functions can be determined by taking the maximum value of the active power compensation amount and the reactive power compensation amount as the goal. Specifically, in one embodiment of the present invention, the above-mentioned target functions active power and reactive power target functions can be:

[0063] fitness=max(w1P sup +w2Q sup )

[0064] Among them, P sup is the active power compensation, Q sup is the reactive power compensation amount, w1 is the weight coefficient of the active power compensation amount, and w2 is the weight coefficient of the active power compensation amount.

[0065] And, in one embodiment of the present invention, the above-mentioned multiple constraints may include: voltage constraints, active power constraints, reactive power constraints, frequency deviation constraints, stability constraints and weight coefficient constraints.

[0066] In one embodiment of the present invention, the voltage constraint condition, the active power constraint condition and the reactive power constraint condition among the multiple constraints can be determined based on the maximum voltage, the maximum active power and the maximum reactive power in the power system.

[0067] Specifically, in one embodiment of the present invention, the voltage constraint condition is: U sup ≤U max , where U sup is the voltage compensation value required for reactive power compensation, U max is the maximum voltage value.

[0068] In one embodiment of the present invention, the above active power constraint condition is: (P sup +P s )≤P w_max , where P sup is the active power compensation, P s is the active power value, P w_max is the maximum active power.

[0069] In one embodiment of the present invention, the above reactive power constraint condition is: (Q sup +Q s )≤Q w_max , where Q sup is the reactive power compensation, Q s is the reactive power value, Q w_max is the maximum reactive power.

[0070] In one embodiment of the present invention, the frequency deviation constraint condition is: |Δf|<±0.05, which means that the amplitude of the frequency deviation of the wind turbine grid connection point is less than or equal to 0.05 Hz.

[0071] In one embodiment of the present invention, the above weight coefficient constraint condition is: w1+w2=1.

[0072] In one embodiment of the present invention, the method for determining multiple constraints corresponding to the active power and reactive power objective functions may include: determining stability constraints of the active power and reactive power objective functions. In one embodiment of the present invention, the method for determining stability constraints of the active power and reactive power objective functions may include: determining a stability value of the current power system, and determining stability constraints corresponding to the active power and reactive power objective functions based on the stability value.

[0073] In one embodiment of the present invention, the method for determining the stability value of the current power system may include the following steps:

[0074] Step a, establishing a frequency and voltage regulation model for the power system;

[0075] Step b: determining a state matrix based on a frequency and voltage regulation model of a power system;

[0076] Step c: Based on the state matrix, determine the stability value of the power system.

[0077] In one embodiment of the present invention, the above-mentioned power system frequency regulation and voltage regulation model may be:

[0078]

[0079] in, represents the differential of the power system state variable x, A represents the state matrix of the power system, B represents the input matrix, C represents the output matrix, D represents the direct transfer matrix, and y represents the output.

[0080] Furthermore, in one embodiment of the present invention, by calculating the above-mentioned frequency regulation and voltage regulation model of the power system, the state matrix A of the power system can be determined.

[0081] Further, in one embodiment of the present invention, after determining the state matrix A through the above steps, the stability value of the power system can be determined based on the state matrix. In one embodiment of the present invention, the stability value of the power system can be determined by a stability formula, wherein the stability formula is:

[0082] λ=eig(A)

[0083] Among them, λ is the stability value of the power system and eig is.

[0084] Further, in one embodiment of the present invention, after determining the stability value of the current power system through the above steps, the stability constraint conditions corresponding to the active power and reactive power objective functions can be determined according to the stability value as follows:

[0085] |ζ(λ sys)|≥0.15

[0086] Among them, λ sys =λ=σ±jω is the characteristic root of the system, is the damping ratio.

[0087] Furthermore, in one embodiment of the present invention, after determining the active power and reactive power objective functions and the corresponding multiple constraints of the optimal compensation model through the above steps, the active power and reactive power objective functions and the multiple constraints can be optimized by the gray wolf algorithm to obtain the target active power compensation and the target reactive power compensation.

[0088] Specifically, in one embodiment of the present invention, the update expression of the individual position of the gray wolf in the optimization solution is set as shown in the following equation:

[0089]

[0090] Where t represents the current iteration number; is the current distance between the gray wolf and its prey; and is the step coefficient vector; is the position vector of the prey, is the active power and reactive power objective function of the optimization problem; is the position vector of the gray wolf itself. And, the coefficient vector and The calculation is done by the following formula:

[0091]

[0092] in, is the convergence factor, which decreases linearly from 2 to 0 during the iteration process; is a random vector in [0, 1]. And the model of gray wolf tracking prey position update is shown in the following formula:

[0093]

[0094] in, and Respectively represent the distances between a, b, c and other gray wolf individuals; Indicates the current position of a, b, and c; is a random vector; is the current position of the gray wolf.

[0095]

[0096]

[0097] in, Indicates the position of the bottom wolf d approaching a, b, and c. Represents the final position of the individual gray wolf d.

[0098] And, in one embodiment of the present invention, through the above configuration, the method of optimizing the active power and reactive power objective functions and multiple constraints using the gray wolf algorithm to obtain the target active power compensation amount and the target reactive power compensation amount may include the following steps:

[0099] Step 1: According to the upper and lower bounds of the optimization variable, the initial variables are randomly generated, and the frequency modulation active output is calculated;

[0100] Step 2: Establish gray wolf individuals and populations;

[0101] Step 3, initialize the gray wolf algorithm parameters and population;

[0102] Step 4: Determine whether the current gray wolf meets the constraints. If yes, continue. If not, update the gray wolf according to the corresponding constraints.

[0103] Step 5: Calculate the fitness value of each individual gray wolf by the active power and reactive power objective functions, and find and save the top three gray wolves in fitness;

[0104] Step 6: Update the convergence factor and coefficient vector according to the current number of iterations;

[0105] Step 7: Update the distance between the gray wolf and the prey and the current position of the gray wolf according to the gray wolf algorithm introduced in the previous section and the updated coefficient vector;

[0106] Step 8: Update the top three best gray wolves;

[0107] Step 9, determine whether the current iterative optimization has reached the maximum number of iterations. If so, end the loop and obtain the target active power compensation amount and the target reactive power compensation amount; if not, return to step 5 and repeat the above steps until the loop ends and the target active power compensation amount and the target reactive power compensation amount are obtained.

[0108] S4, regulating the frequency and voltage of the power grid based on the target active power compensation amount and the target reactive power compensation amount.

[0109] In one embodiment of the present invention, after obtaining the target active power compensation amount and the target reactive power compensation amount through the above steps, the active and reactive power can be adjusted based on the target active power compensation amount and the target reactive power compensation amount, thereby controlling the current on the rotor side of the wind turbine, thereby achieving active support of the frequency and voltage of the power grid by the wind turbine.

[0110] In one embodiment of the present invention, the grid connection point frequency value and grid connection point voltage value of the wind turbine are obtained; it is determined whether the grid connection point frequency value and grid connection point voltage value meet the coordinated control strategy conditions; if the grid connection point frequency value and grid connection point voltage value meet the coordinated control strategy conditions, the target active power compensation amount and the target reactive power compensation amount are determined based on the optimal compensation amount model; based on the target active power compensation amount and the target reactive power compensation amount, the frequency and voltage of the power grid are regulated. Thus, the target active power compensation amount and reactive power compensation amount can be determined based on the optimal compensation amount model, and the frequency and voltage of the power grid can be regulated based on the target active power compensation amount and reactive power compensation amount, so as to provide active and reactive power support to the power grid, so that the power system can operate safely and stably.

[0111] In order to implement the above embodiment, Figure 2 As shown, this embodiment also provides a wind turbine active and reactive coordinated control strategy device 10, which includes an acquisition module 201, a first determination module 202, a second determination module 203 and a control module 204;

[0112] An acquisition module 201 is used to acquire a grid connection point frequency value and a grid connection point voltage value of a wind turbine generator system;

[0113] The first determination module 202 is used to determine whether the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions;

[0114] The second determination module 203 is used to determine the target active power compensation amount and the target reactive power compensation amount based on the optimal compensation amount model if the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions;

[0115] The control module 204 is used to control the frequency and voltage of the power grid based on the target active power compensation amount and the target reactive power compensation amount.

[0116] In the embodiment of the present disclosure, the first determining module 202 is specifically used to:

[0117] Determine whether the grid connection point frequency value and / or the grid connection point voltage value exceeds the corresponding preset threshold value;

[0118] If the grid connection point frequency value and / or the grid connection point voltage value exceeds the corresponding preset threshold value, it is determined that the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions.

[0119] Furthermore, the second determining module 203 is specifically configured to:

[0120] Determine the active power and reactive power objective functions of the optimal compensation model;

[0121] Determine multiple constraints corresponding to active power and reactive power objective functions;

[0122] The active power and reactive power objective functions and multiple constraints are optimized and calculated using the Grey Wolf Algorithm to obtain the target active power compensation amount and the target reactive power compensation amount.

[0123] Furthermore, the above-mentioned multiple constraints include: voltage constraints, active power constraints, reactive power constraints, frequency deviation constraints, stability constraints and weight coefficient constraints.

[0124] Furthermore, the second determining module 203 is further configured to:

[0125] Determine the stability value of the current power system;

[0126] Based on the stability value, the stability constraints corresponding to the active power and reactive power objective functions are determined.

[0127] Furthermore, the second determining module 203 is further configured to:

[0128] Establish frequency and voltage regulation models for power systems;

[0129] Determine the state matrix based on the power system frequency and voltage regulation model;

[0130] Based on the state matrix, the stability value of the power system is determined.

[0131] According to the active and reactive coordinated control strategy device of a wind turbine set in an embodiment of the present invention, the device can determine the target active power compensation amount and reactive power compensation amount based on the optimal compensation amount model, and based on the target active power compensation amount and reactive power compensation amount, regulate the frequency and voltage of the power grid, thereby providing active and reactive power support to the power grid, so that the power system can operate safely and stably.

[0132] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0133] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

Claims

1. A wind turbine active and reactive power coordinated control strategy method, characterized in that: The method comprises: Obtain the grid connection point frequency value and grid connection point voltage value of the wind turbine generator set; Determining whether the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions; If the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions, then based on the optimal compensation amount model, determine the target active power compensation amount and the target reactive power compensation amount; Based on the target active power compensation amount and the target reactive power compensation amount, the frequency and voltage of the power grid are regulated.

2. The method according to claim 1, characterized in that The determining whether the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions includes: Determining whether the grid connection point frequency value and / or the grid connection point voltage value exceeds corresponding preset thresholds; If the grid connection point frequency value and / or the grid connection point voltage value exceeds the corresponding preset threshold value, it is determined that the grid connection point frequency value and the grid connection point voltage value meet the coordination control strategy conditions.

3. The method according to claim 1, characterized in that The step of determining a target active power compensation amount and a target reactive power compensation amount based on the optimal compensation amount model includes: Determining active power and reactive power objective functions of the optimal compensation model; Determining a plurality of constraints corresponding to the active power and reactive power objective functions; The active power and reactive power objective functions and the plurality of constraints are optimized and calculated by using the grey wolf algorithm to obtain a target active power compensation amount and a target reactive power compensation amount.

4. The method according to claim 3, characterized in that The multiple constraints include: voltage constraints, active power constraints, reactive power constraints, frequency deviation constraints, stability constraints and weight coefficient constraints.

5. The method according to claim 4, characterized in that The determining of the multiple constraints corresponding to the active power and reactive power objective functions includes: Determine the stability value of the current power system; Based on the stability value, stability constraints corresponding to the active power and reactive power objective functions are determined.

6. The method according to claim 5, characterized in that Determining the stability value of the current power system includes: Establishing a frequency and voltage regulation model for the power system; Determining a state matrix based on the power system frequency and voltage regulation model; Based on the state matrix, a stability value of the power system is determined.

7. A wind turbine active and reactive power coordinated control strategy device, characterized in that: The device comprises: An acquisition module is used to obtain the grid connection point frequency value and grid connection point voltage value of the wind turbine generator set; A first determination module is used to determine whether the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions; A second determination module is used to determine a target active power compensation amount and a target reactive power compensation amount based on an optimal compensation amount model if the grid connection point frequency value and the grid connection point voltage value meet the coordinated control strategy conditions; The control module is used to control the frequency and voltage of the power grid based on the target active power compensation amount and the target reactive power compensation amount.

8. The device according to claim 7, characterized in that The first determining module is specifically configured to: Determining whether the grid connection point frequency value and / or the grid connection point voltage value exceeds corresponding preset thresholds; If the grid connection point frequency value and / or the grid connection point voltage value exceeds the corresponding preset threshold value, it is determined that the grid connection point frequency value and the grid connection point voltage value meet the coordination control strategy conditions.

9. An electronic device comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1 to 6.

10. A computer storage medium, wherein: The computer storage medium stores computer executable instructions; after the computer executable instructions are executed by the processor, the method according to any one of claims 1 to 6 can be implemented.

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