Power station voltage oscillation judgment method and device and storage medium

Abstract

The invention discloses a power station voltage oscillation judgment method and device and a storage medium. The method comprises the following steps: monitoring bus voltage in real time, and accumulating oscillation time accumulated values; determining whether to reset the oscillation accumulation times and the oscillation time accumulation value or not according to the oscillation time accumulation value; acquiring the oscillation amplitude of the bus voltage, and determining the oscillation accumulation times according to the oscillation amplitude of the bus voltage; and judging whether to lock the AVC substation or not according to the oscillation accumulation times. The method effectively solves the problem of abnormal oscillation of the power station voltage caused by voltage regulation between the new energy power stations near the new energy gathering area, and guarantees the bus voltage of the power station and the operation safety of equipment.

Description

Technical Field

[0001] The present invention belongs to the field of power system control and protection, and in particular relates to a method, a device and a storage medium for determining voltage oscillation in a power station. Background Art

[0002] All regions are actively promoting large-scale new energy bases with multiple energy types to enter the large-scale construction stage. Multiple new energy power stations send out clean energy continuously through new energy collection stations, which is conducive to the large-scale and centralized development of new energy. Taking into account the realistic factors such as project cost and distribution of new energy resources, the distance between new energy power stations in some new energy collection areas is only 3-10 kilometers, the electrical distance is short, and there is no unified power station coordination device in the upper new energy collection station. Therefore, when the operation mode is changed in the new energy collection station, the short-circuit capacity of the connected new energy power station changes greatly. The adjustment process of the automatic voltage control device (AVC) substation of the new energy power station is very dependent on this value, but it actually fails to adapt to the changes in the short-circuit capacity of the system. At the same time, when adjusting the bus voltage of the new energy power station, it is very easy to be affected by the action of the AVC substation of the adjacent station, and there is a reactive overshoot, which causes the bus voltage oscillation of the power station. However, there is currently little research on the judgment of bus voltage oscillation in power stations. Summary of the invention

[0003] The present invention provides a method, device and storage medium for determining voltage oscillation in a power station, so as to solve the problem of abnormal voltage oscillation in the power station and ensure the safety of bus voltage and equipment operation in the power station.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] According to the first aspect of the present application, a method for determining voltage oscillation in a power station is proposed, comprising:

[0006] Monitor the bus voltage in real time and accumulate the accumulated value of oscillation time;

[0007] Determine whether to clear the accumulated oscillation times and the accumulated oscillation time value according to the accumulated oscillation time value;

[0008] Obtaining the oscillation amplitude of the bus voltage, and determining the number of oscillation accumulations according to the oscillation amplitude of the bus voltage;

[0009] Determine whether to lock the AVC substation based on the accumulated number of oscillations.

[0010] According to some embodiments, the oscillation amplitude is the difference between a maximum value of the oscillation record and a minimum value of the voltage oscillation record.

[0011] According to some embodiments, if the oscillation amplitude exceeds the allowable voltage oscillation amplitude, it is determined that one oscillation has occurred and the number of accumulated oscillations is increased by one.

[0012] According to some embodiments, if the oscillation time accumulated value exceeds the oscillation determination period, the accumulated number of oscillations and the oscillation time accumulated value are cleared.

[0013] According to some embodiments, if the accumulated number of oscillations exceeds the maximum number of oscillations allowed, the AVC substation is locked and an alarm is issued.

[0014] According to some embodiments, the method specifically comprises:

[0015] Step 100: monitor the bus voltage in real time, record the real-time voltage value, dynamically update the maximum value and the minimum value of the voltage oscillation record, and accumulate the oscillation time cumulative value; enter step 200;

[0016] Step 200: Determine whether the accumulated oscillation time value exceeds the oscillation determination period; if yes, clear the accumulated oscillation times and the accumulated oscillation time value, and return to step 100; otherwise, proceed to step 300;

[0017] Step 300: Obtain the oscillation amplitude according to the difference between the maximum value and the minimum value of the voltage oscillation record, and determine whether the oscillation amplitude exceeds the allowable voltage oscillation amplitude; if yes, it is determined that one oscillation occurs, the oscillation accumulation number is increased by 1, and the maximum value and the minimum value of the voltage oscillation record are reset as the real-time voltage value, and then go to step 400; otherwise, return to step 100;

[0018] Step 400: Determine whether the accumulated number of oscillations exceeds the maximum number of oscillations allowed; if yes, lock the AVC substation, issue an alarm, and clear the accumulated number of oscillations and the accumulated value of oscillation time; otherwise, return to step 100.

[0019] According to some embodiments, the dynamic update of the maximum value and the minimum value of the voltage oscillation record is specifically as follows: the larger value between the real-time voltage value and the maximum value of the voltage oscillation record is assigned to the maximum value of the voltage oscillation record, and the smaller value between the real-time voltage value and the minimum value of the voltage oscillation record is assigned to the minimum value of the voltage oscillation record.

[0020] According to some embodiments, the oscillation determination period is set to 3 to 5 times the in-station regulation period.

[0021] According to some embodiments, the allowable voltage oscillation amplitude is set to 3 to 5 times the single voltage adjustment amount within the station.

[0022] According to some embodiments, the maximum number of allowed oscillations is set to 3 to 6 times.

[0023] According to the second aspect of the present application, a power station voltage oscillation judgment device is proposed, the device comprising: a collection unit, an oscillation time judgment unit, an oscillation amplitude judgment unit and an oscillation number judgment unit; wherein

[0024] The acquisition unit is used to monitor the bus voltage in real time and accumulate the oscillation time cumulative value;

[0025] The oscillation time determination unit is used to determine whether to clear the accumulated number of oscillations and the accumulated value of the oscillation time according to the accumulated value of the oscillation time;

[0026] The oscillation amplitude determination unit is used to obtain the oscillation amplitude of the bus voltage and determine the number of oscillation accumulations according to the oscillation amplitude of the bus voltage;

[0027] The oscillation number determination unit is used to determine whether to lock the AVC substation according to the accumulated number of oscillations.

[0028] According to some embodiments, the oscillation amplitude is the difference between the maximum oscillation record and the minimum voltage oscillation record; if the oscillation amplitude exceeds the allowable voltage oscillation amplitude, it is determined that one oscillation has occurred and the accumulated oscillation times are increased by 1; if the accumulated oscillation time exceeds the oscillation judgment period, the accumulated oscillation times and the accumulated oscillation time are cleared; if the accumulated oscillation times exceed the maximum allowable oscillation times, the AVC substation is locked and an alarm is issued.

[0029] According to some embodiments, the acquisition unit of the device specifically includes: a unit for real-time monitoring of bus voltage, recording a real-time value of voltage, dynamically updating a maximum value and a minimum value of voltage oscillation record, and accumulating an accumulated value of oscillation time;

[0030] The oscillation time determination unit specifically includes: determining whether the oscillation time cumulative value exceeds the oscillation determination period; if so, clearing the oscillation cumulative number and the oscillation time cumulative value;

[0031] The oscillation amplitude determination unit specifically includes: obtaining the oscillation amplitude according to the difference between the maximum value of the voltage oscillation record and the minimum value of the voltage oscillation record, judging whether the oscillation amplitude exceeds the allowable voltage oscillation amplitude; if yes, judging that one oscillation occurs, increasing the number of oscillation accumulation by 1, and resetting the maximum value of the voltage oscillation record and the minimum value of the voltage oscillation record as the real-time voltage value;

[0032] The oscillation number determination unit specifically includes: determining whether the accumulated oscillation number exceeds the maximum allowed oscillation number; if yes, locking the AVC substation, giving an alarm, and clearing the accumulated oscillation number and the accumulated oscillation time.

[0033] According to a third aspect of the present application, a computer-readable storage medium storing one or more programs is proposed, wherein the one or more programs include instructions, and when the instructions are executed by a computing device, the computing device executes a power plant voltage oscillation judgment method described above.

[0034] The beneficial effects achieved by the present invention are as follows: the present invention accumulates the oscillation time cumulative value based on real-time monitoring of the bus side voltage; determines whether to clear the oscillation cumulative times and the oscillation time cumulative value based on the oscillation time cumulative value; obtains the bus voltage oscillation amplitude, determines the oscillation cumulative times based on the bus voltage oscillation amplitude; determines whether to lock the AVC substation based on the oscillation cumulative times to avoid aggravating the voltage oscillation degree. The present invention effectively solves the problem of abnormal power station voltage oscillation caused by voltage regulation between new energy power stations near new energy convergence areas, which is currently widespread, and ensures the safety of power station bus voltage and equipment operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic flow chart of a method for determining power station voltage oscillation provided by an embodiment of the present invention;

[0036] Figure 2 It is a schematic flow chart of another method for determining power station voltage oscillation provided by an embodiment of the present invention;

[0037] Figure 3 It is a schematic diagram of a power station voltage oscillation judgment device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be further described below in conjunction with the accompanying drawings.

[0039] After the new energy collection station changes its operation mode, the short-circuit capacity of the connected new energy power station changes greatly. The adjustment process of the AVC substation is very dependent on this value, but it is actually unable to adapt to the change of the system short-circuit capacity. At the same time, when adjusting the bus voltage of the new energy power station, it is very easy to be affected by the action of the adjacent AVC substation, and there is a reactive overshoot, which causes the bus voltage of the power station to oscillate. Based on this, the embodiment of the present application provides a method for judging the voltage oscillation of the power station, such as Figure 1 The steps shown include:

[0040] S1: Monitor the bus voltage in real time and accumulate the accumulated value of the oscillation time.

[0041] The bus voltage is monitored in real time, the real-time voltage value is recorded, and the maximum voltage oscillation record and the minimum voltage oscillation record are dynamically updated according to the real-time voltage value. At the same time, the oscillation time cumulative value is accumulated.

[0042] S2: Determine whether to clear the accumulated number of oscillations and the accumulated value of oscillation time according to the accumulated value of oscillation time.

[0043] If the accumulated oscillation time exceeds the oscillation judgment period, it is considered that the system has not oscillated for a long time and is in a stable state, and the accumulated oscillation times and accumulated oscillation time are cleared.

[0044] In some embodiments, the oscillation determination period is set to 3 to 5 times the in-station regulation period.

[0045] S3: Obtain the oscillation amplitude of the bus voltage, and determine the number of oscillation accumulations according to the oscillation amplitude of the bus voltage.

[0046] When a power station oscillates, the voltage and current will change dramatically, and the voltage oscillation amplitude will be large. Therefore, the oscillation amplitude can be used to determine whether the power station oscillates. The oscillation amplitude algorithm is the difference between the maximum oscillation record and the minimum voltage oscillation record. If the oscillation amplitude exceeds the allowable voltage oscillation amplitude, it is determined that one oscillation has occurred and the oscillation accumulation number is increased by 1.

[0047] In some embodiments, the voltage oscillation amplitude is allowed to be set to 3 to 5 times the single voltage adjustment amount within the station.

[0048] S4: Determine whether to lock the AVC substation based on the accumulated number of oscillations.

[0049] If the accumulated number of oscillations exceeds the maximum allowed number of oscillations, the AVC substation will be locked and an alarm will be issued.

[0050] In some embodiments, the maximum number of allowed oscillations is set to 3 to 6 times.

[0051] The above method can solve the problem of abnormal voltage oscillation of power stations caused by voltage regulation between new energy power stations near new energy gathering areas by real-time monitoring of bus voltage, and ensure the safety of power station bus voltage and equipment operation. This method is also applicable to the judgment of bus voltage oscillation of conventional substations and has wide adaptability.

[0052] like Figure 2 The flowchart of another method for determining power station voltage oscillation provided by an embodiment of the present application is shown, and includes the following steps:

[0053] S100: monitor the bus voltage in real time, record the real-time voltage value, dynamically update the maximum voltage oscillation record and the minimum voltage oscillation record, and accumulate the oscillation time cumulative value; enter step S200.

[0054] Monitor the bus voltage in real time and record the real-time voltage value. Dynamically update the maximum value of the voltage oscillation record and the minimum value of the voltage oscillation record according to the real-time voltage value and the maximum value of the voltage oscillation record and the minimum value of the voltage oscillation record. The specific updating method is: assign the larger value between the real-time voltage value and the maximum value of the voltage oscillation record to the maximum value of the voltage oscillation record, and assign the smaller value between the real-time voltage value and the minimum value of the voltage oscillation record to the minimum value of the voltage oscillation record.

[0055] S200: Determine whether the accumulated oscillation time value exceeds the oscillation determination period; if so, clear the accumulated oscillation times and the accumulated oscillation time value, and return to step S100; otherwise, enter step S300.

[0056] If the accumulated oscillation time exceeds the oscillation judgment period, it is considered that the system has not oscillated for a long time and is in a stable state, then the accumulated oscillation times and accumulated oscillation time are cleared and a new round of oscillation time monitoring begins.

[0057] In some embodiments, the oscillation determination period is set to 3 to 5 times the in-station regulation period.

[0058] S300: Obtain the oscillation amplitude according to the difference between the maximum value and the minimum value of the voltage oscillation record, and determine whether the oscillation amplitude exceeds the allowable voltage oscillation amplitude; if so, determine that one oscillation has occurred, increase the cumulative number of oscillations by 1, and reset the maximum value and the minimum value of the voltage oscillation record to the real-time voltage value, and proceed to step S400; otherwise, return to step S100.

[0059] Because when the power station oscillates, the voltage and current will change dramatically, and the voltage oscillation amplitude is large, so the oscillation amplitude can be used to determine whether the power station oscillates. When the oscillation amplitude exceeds the allowable voltage oscillation amplitude, it is determined that one oscillation has occurred and the oscillation accumulation number is increased by 1. At the same time, the maximum and minimum voltage oscillation records are reset to prepare for a new round of oscillation amplitude monitoring.

[0060] In some embodiments, the voltage oscillation amplitude is allowed to be set to 3 to 5 times the single voltage adjustment amount within the station.

[0061] S400: Determine whether the accumulated number of oscillations exceeds the maximum number of oscillations allowed; if yes, lock the AVC substation, issue an alarm, and clear the accumulated number of oscillations and the accumulated value of oscillation time; otherwise, return to step S100.

[0062] In some embodiments, the maximum number of allowed oscillations is set to 3 to 6 times.

[0063] Figure 3 The present invention provides a power station voltage oscillation judgment device 500, which includes: a collection unit 501, an oscillation time judgment unit 502, an oscillation amplitude judgment unit 503, and an oscillation number judgment unit 504.

[0064] The acquisition unit 501 is used to monitor the bus voltage in real time and accumulate the oscillation time accumulated value.

[0065] The oscillation time determination unit 502 is used to determine whether to clear the oscillation accumulation times and the oscillation time accumulation value according to the oscillation time accumulation value.

[0066] The oscillation amplitude determination unit 503 is used to obtain the oscillation amplitude of the bus voltage and determine the number of oscillation accumulations according to the oscillation amplitude of the bus voltage.

[0067] The oscillation number determination unit 504 is used to determine whether to block the AVC substation according to the accumulated number of oscillations.

[0068] In some embodiments, the oscillation amplitude in the oscillation amplitude determination unit 503 is the difference between the maximum oscillation record and the minimum voltage oscillation record. If the oscillation amplitude exceeds the allowable voltage oscillation amplitude, it is determined that one oscillation has occurred and the number of oscillation accumulations is increased by one.

[0069] In the oscillation time determination unit 502, if the oscillation time cumulative value exceeds the oscillation determination period, the oscillation accumulation times and the oscillation time cumulative value are cleared.

[0070] In the oscillation number determination unit 504, if the accumulated number of oscillations exceeds the maximum number of oscillations allowed, the AVC substation is locked and an alarm is issued.

[0071] In some embodiments, the acquisition unit 501 specifically includes: being used to monitor the bus voltage in real time, record the real-time value of the voltage, dynamically update the maximum value and the minimum value of the voltage oscillation record, and accumulate the oscillation time cumulative value.

[0072] The oscillation time determination unit 502 specifically includes: determining whether the oscillation time cumulative value exceeds the oscillation determination period; if yes, clearing the oscillation accumulation times and the oscillation time cumulative value.

[0073] The oscillation amplitude determination unit 503 specifically includes: obtaining the oscillation amplitude according to the difference between the maximum value and the minimum value of the voltage oscillation record, and judging whether the oscillation amplitude exceeds the allowable voltage oscillation amplitude; if so, judging that one oscillation occurs, increasing the number of oscillation accumulation times by 1, and resetting the maximum value and the minimum value of the voltage oscillation record as the real-time voltage value.

[0074] The oscillation number determination unit 504 specifically includes: determining whether the accumulated oscillation number exceeds the maximum allowed oscillation number; if yes, blocking the AVC substation, giving an alarm, and clearing the accumulated oscillation number and the accumulated oscillation time.

[0075] A power station voltage oscillation judgment device 500 in the present application performs functions similar to the aforementioned method. For details, please refer to the previous description, which will not be repeated here.

[0076] Based on the same technical solution, the present invention also discloses a computer-readable storage medium storing one or more programs, wherein the one or more programs include instructions, and when the instructions are executed by a computing device, the computing device executes a reactive voltage control method.

[0077] Based on the same technical solution, the present invention also discloses a computing device, comprising one or more processors, one or more memories and one or more programs, wherein the one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing a reactive voltage control method.

[0078] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, 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 disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0079] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to 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 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 device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes 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.

[0080] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0081] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0082] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A method for determining voltage oscillation in a power station, characterized in that: include: Monitor the bus voltage in real time and accumulate the accumulated value of oscillation time; Determine whether to clear the accumulated oscillation times and the accumulated oscillation time value according to the accumulated oscillation time value; Obtaining the oscillation amplitude of the bus voltage, and determining the number of oscillation accumulations according to the oscillation amplitude of the bus voltage; Determine whether to lock the AVC substation based on the accumulated number of oscillations.

2. The method according to claim 1, characterized in that: The oscillation amplitude is the difference between the maximum oscillation record and the minimum voltage oscillation record.

3. The method according to claim 2, characterized in that If the oscillation amplitude exceeds the allowable voltage oscillation amplitude, it is determined that one oscillation has occurred and the number of oscillation accumulations is increased by 1.

4. The method according to claim 1, characterized in that If the oscillation time accumulated value exceeds the oscillation determination period, the oscillation accumulation times and the oscillation time accumulated value are cleared.

5. The method according to claim 1, characterized in that If the accumulated number of oscillations exceeds the maximum number of oscillations allowed, the AVC substation is locked and an alarm is issued.

6. The method according to claim 1, characterized in that Specifically include: Step 100: monitor the bus voltage in real time, record the real-time voltage value, dynamically update the maximum value and the minimum value of the voltage oscillation record, and accumulate the oscillation time cumulative value; Enter step 200; Step 200: determine whether the accumulated oscillation time value exceeds the oscillation determination period; if yes, clear the accumulated oscillation times and the accumulated oscillation time value, and return to step 100; Otherwise, proceed to step 300; Step 300: Obtain the oscillation amplitude according to the difference between the maximum value and the minimum value of the voltage oscillation record, and determine whether the oscillation amplitude exceeds the allowable voltage oscillation amplitude; if yes, it is determined that one oscillation occurs, the oscillation accumulation number is increased by 1, and the maximum value and the minimum value of the voltage oscillation record are reset as the real-time voltage value, and then go to step 400; otherwise, return to step 100; Step 400: Determine whether the accumulated number of oscillations exceeds the maximum number of oscillations allowed; if yes, lock the AVC substation, issue an alarm, and clear the accumulated number of oscillations and the accumulated value of oscillation time; otherwise, return to step 100.

7. The method according to claim 6, characterized in that The dynamic updating of the maximum value and the minimum value of the voltage oscillation record is specifically as follows: the larger value between the real-time voltage value and the maximum value of the voltage oscillation record is assigned to the maximum value of the voltage oscillation record, and the smaller value between the real-time voltage value and the minimum value of the voltage oscillation record is assigned to the minimum value of the voltage oscillation record.

8. The method according to claim 4 or 6, characterized in that: The oscillation determination period is set to be 3 to 5 times of the station regulation period.

9. The method according to claim 3 or 6, characterized in that: The allowable voltage oscillation amplitude is set to 3 to 5 times the single voltage adjustment amount in the station.

10. The method according to claim 5 or 6, characterized in that: The maximum number of allowed oscillations is set to 3 to 6 times.

11. A power station voltage oscillation judgment device, characterized in that: The device comprises: a collection unit, an oscillation time determination unit, an oscillation amplitude determination unit and an oscillation number determination unit; wherein The acquisition unit is used to monitor the bus voltage in real time and accumulate the oscillation time cumulative value; The oscillation time determination unit is used to determine whether to clear the accumulated number of oscillations and the accumulated value of the oscillation time according to the accumulated value of the oscillation time; The oscillation amplitude determination unit is used to obtain the oscillation amplitude of the bus voltage and determine the number of oscillation accumulations according to the oscillation amplitude of the bus voltage; The oscillation number determination unit is used to determine whether to lock the AVC substation according to the accumulated number of oscillations.

12. The device according to claim 11, characterized in that The oscillation amplitude is the difference between the maximum value of the oscillation record and the minimum value of the voltage oscillation record; If the oscillation amplitude exceeds the allowable voltage oscillation amplitude, it is determined that one oscillation has occurred and the oscillation accumulation number is increased by 1; If the oscillation time cumulative value exceeds the oscillation determination period, the oscillation cumulative times and the oscillation time cumulative value are cleared; If the accumulated number of oscillations exceeds the maximum number of oscillations allowed, the AVC substation is locked and an alarm is issued.

13. The device according to claim 11, characterized in that The acquisition unit specifically includes: for real-time monitoring of bus voltage, recording the real-time value of voltage, dynamically updating the maximum value and the minimum value of voltage oscillation record, and accumulating the oscillation time cumulative value; The oscillation time determination unit specifically includes: determining whether the oscillation time cumulative value exceeds the oscillation determination period; if so, clearing the oscillation cumulative number and the oscillation time cumulative value; The oscillation amplitude determination unit specifically includes: obtaining the oscillation amplitude according to the difference between the maximum value of the voltage oscillation record and the minimum value of the voltage oscillation record, judging whether the oscillation amplitude exceeds the allowable voltage oscillation amplitude; if yes, judging that one oscillation occurs, increasing the number of oscillation accumulation by 1, and resetting the maximum value of the voltage oscillation record and the minimum value of the voltage oscillation record as the real-time voltage value; The oscillation number determination unit specifically includes: determining whether the accumulated oscillation number exceeds the maximum allowed oscillation number; if yes, locking the AVC substation, giving an alarm, and clearing the accumulated oscillation number and the accumulated oscillation time.

14. A computer-readable storage medium storing one or more programs, characterized in that: The one or more programs include instructions which, when executed by a computing device, cause the computing device to perform any one of the methods according to claims 1 to 10 .

Images