Electric power system power supply planning method and device based on electric pinch point analysis

Abstract

The invention relates to an electric power system power supply planning method and device based on electric pinch point analysis, and the method comprises the steps: S1, putting forward a power value and a risk degree as key indexes for reflecting the power flow and the power quality in the electric pinch point analysis, and considering the time sequence characteristics of new energy output and load for describing the matching relation of new energy and load; and S2, constructing a power supply planning model for electric pinch point analysis, respectively giving tabular and graphical calculation steps, and solving an analytical solution of a planning scheme. And S3, reasonably planning a power supply structure and determining a flexible thermal power installation scale on the basis of the electric pinch point analysis model made in the step S2 on the premise of ensuring that the regional abandoned power is minimum. According to the method, a new solution idea and reference are provided for planning and research of a novel power system, and the model solving speed is increased.

Description

Technical Field

[0001] The present invention relates to the field of power system power supply planning, and in particular to a power system power supply planning method and device based on electrical pinch point analysis. Background Art

[0002] The temporal fluctuations of renewable energy sources pose a significant challenge in the development of new power systems. The high uncertainty and volatility of renewable energy sources, as well as their spatial and temporal mismatch with loads, have led to the problem of renewable energy curtailment. While improvements have been made, the problem remains unresolved. While renewable energy installed capacity and power generation are growing rapidly in Northwest China, local consumption capacity is limited and the development of transmission channels is lagging. These challenges hinder the development of new power systems. As the proportion of renewable energy continues to increase and its scalability remains limited, power generation planning that considers the fluctuating nature of renewable energy is crucial for ensuring energy security. Existing methods for incorporating renewable energy volatility into planning have varying degrees of impact on planning results, primarily manifesting in miscalculation of flexibility needs and insufficient capacity. While pinch point technology has been applied in many fields, its application in long-term power generation planning with an annual resolution is limited. Therefore, a new power generation planning method is urgently needed to address these issues. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a method and device for power system power planning based on electrical pinch analysis. This method introduces risk and power value to characterize the time series fluctuation characteristics of new energy and load, establishes a mapping relationship network that describes the source-load energy balance, and constructs an electrical pinch analysis model that combines tabular and graphical representations. It can simply, intuitively and quickly give power planning results and flexibility resource demand scales based on the consideration of new energy fluctuation characteristics. The present invention provides a new solution and reference for new power system planning research, improves the model solving speed, and is of great significance for balancing the "energy triangle" and ensuring the safe and reliable operation of the system.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A power system power planning method based on electrical pinch analysis includes the following steps:

[0006] Step S1: Power value and risk degree are proposed as key indicators reflecting power flow and power quality in power pinch analysis, taking into account the timing characteristics of renewable energy output and load, to describe the matching relationship between renewable energy and load.

[0007] Step S2: Construct a power planning model for electrical pinch point analysis, provide tabular and graphical calculation steps, and obtain an analytical solution for the planning scheme.

[0008] Step S3: Based on the power pinch analysis model made in step S2, rationally plan the power structure and determine the scale of flexible thermal power installed capacity while ensuring that regional power curtailment is minimized.

[0009] The present invention also provides a power system power planning device based on electrical pinch point analysis, comprising the following modules:

[0010] The description module proposes power value and risk as key indicators reflecting power flow and power quality in power pinch analysis. It considers the timing characteristics of renewable energy output and load to describe the matching relationship between renewable energy and load.

[0011] Obtain analytical solution module, build power planning model for electrical pinch point analysis, provide tabular and graphical calculation steps, and obtain analytical solution of planning model.

[0012] The scale determination module, based on the constructed power planning model of electrical pinch point analysis, rationally plans the power structure and determines the scale of flexible thermal power installed capacity while ensuring the minimum regional power curtailment.

[0013] The present invention also provides an electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the above-mentioned method for power system power planning based on electrical pinch point analysis are implemented.

[0014] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the above-mentioned method for power system power planning based on electrical pinch point analysis are implemented.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. Through electrical pinch analysis, this invention converts the original time series of renewable energy and load into risk and power values for description, characterizing the time series characteristics of renewable energy and load. While ensuring the goal of energy completeness, it also minimizes power curtailment in the region, makes the planned power structure more reasonable, and determines the demand scale of flexible thermal power units.

[0017] 2. The present invention adopts a graphical method to achieve rapid solution of the planning model and intuitive display of planning results. Compared with traditional power system planning methods, it greatly improves the model solution speed.

[0018] 3. This invention clarifies that under the fixed constraint of renewable energy installed capacity, the proportion of wind power installed capacity and photovoltaic installed capacity will affect the amount of power curtailment and regulation demand of the power system, providing a more targeted reference for power supply planning. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of a method for power system power planning based on electrical pinch point analysis according to an embodiment of the present invention;

[0020] Figure 2 Schematic diagram of source-load supply-demand relationship mapping network in an embodiment of the present invention;

[0021] Figure 3 Schematic diagram of the combined curve of electric pinch analysis in an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the interval selection process in an embodiment of the present invention;

[0023] Figure 5 Schematic diagram of the power pinch planning process in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The present invention provides a power system power planning method based on electrical pinch analysis, which can effectively address power planning issues caused by renewable energy fluctuations in new power systems. It offers significant advantages in ensuring energy security and increasing renewable energy absorption rates. To further clarify the objectives, technical solutions, and advantages of the present invention, the present invention is further described below through specific implementations and in conjunction with the accompanying drawings.

[0025] Example 1

[0026] like Figure 1 As shown, an embodiment of the present invention provides a power system power planning method based on electrical pinch analysis, comprising the following steps:

[0027] Step S1: Power value and risk degree are proposed as key indicators reflecting power flow and power quality in power pinch analysis, taking into account the timing characteristics of renewable energy output and load, to describe the matching relationship between renewable energy and load.

[0028] Step S2: Construct a power planning model for electrical pinch point analysis, provide tabular and graphical calculation steps, and obtain an analytical solution to the planning model.

[0029] Step S3: Based on the power planning model of the electric pinch point analysis constructed in step S2, the power structure is rationally planned and the scale of flexible thermal power installed capacity is determined while minimizing regional power curtailment.

[0030] In one embodiment, in the above step S1, the power supply-load supply-demand relationship mapping network (the network is only used to represent one supply-demand relationship between power supply and load, that is, each source can supply multiple loads, and each load can be satisfied by multiple power supplies) is as follows. Figure 2 In the mapping network shown, 、 Indicates the power value and risk level corresponding to power source n, 、 Indicates the power value and risk degree corresponding to load m, 、 Indicates the power value and risk level of the power source to be planned. Some new energy output systems with time and space mismatch cannot be absorbed and utilized, and the wasted power is . Indicates the power value corresponding to power supply n, Indicates the power value corresponding to load m, Indicates the power value corresponding to the power source to be planned; in actual operation, there is a possibility that only part of the internal source abandons power and the external source only supplements part of the internal source. The step S1 specifically includes:

[0031] Step S1.1. Characterize the relationship between power and risk and electrical pinch points, including:

[0032] Step S1.1.1: Convert the new energy output curve to power difference The interval is divided into N intervals, with the power lower limit is the starting point, the risk of the nth interval The expression is as follows:

[0033] ;

[0034] in, Represents the letter t and its subscript, representing 1 The time interval; n is the number of intervals, the number of intervals n <N。

[0035] Step S1.1.2: The number of intervals n can be maximized for:

[0036] ;

[0037] The wind power output in the system is , photovoltaic output is , new energy output is , whose upper and lower limits are and .

[0038] Step S1.1.3: Take the middle value in the interval as the power value of the corresponding risk level, and the risk level of the nth interval Corresponding power value as follows:

[0039] ;

[0040] Step S1.2. Source-load supply and demand relationship mapping, including:

[0041] Step S1.2.1: Divide the new energy into N internal sources with one-to-one correspondence between power values and risk levels;

[0042] Step S1.2.2: Divide the load into M internal loads with one-to-one correspondence between power values and risk levels;

[0043] Step S1.2.3: Satisfy power balance, achieve complete energy balance, and ensure that the total energy on both sides of the source-load supply and demand relationship mapping network is equal:

[0044] ;

[0045] Where: Indicates the power value corresponding to power supply n, Indicates the power value corresponding to load m, Indicates the power value corresponding to the power supply to be planned. Indicates the amount of wasted electricity.

[0046] Step S1.2.4: Based on the power difference Determine whether an external source needs to be added and the power value of the external source:

[0047] ;

[0048] In one embodiment, the above step S2 specifically includes:

[0049] Step S2.1. Power planning model for electrical pinch analysis, including:

[0050] Step S2.1.1: The first column is the risk level. The risk levels of all new energy sources and loads are combined and sorted in descending order from high to low (the same risk factor is listed only once) to form an ordered supply-demand matching risk set. Renewable energy sources are divided into N internal sources with corresponding power values and risk levels. Similarly, loads are divided into M internal loads with corresponding power values and risk levels. K represents the total number of internal sources and loads divided, and qK represents the corresponding risk level. , this set determines the supply and demand matching principle of power supply and load, namely: ;

[0051] Step S2.1.2: The second column is the power flow, which represents the power value corresponding to the risk level. The power flow of renewable energy is positive, and the power flow of load is negative. The power flow corresponding to the risk level is the sum of the power values of renewable energy and load with the same risk level.

[0052] Step S2.1.3: The third column is the cumulative power flow, which represents the sum of the power flows in the corresponding risk level and the last row is the power difference. ;

[0053] Step S2.1.4: The fourth column is the risk power flow, which represents the supply and demand risk of each interval. It is calculated by multiplying the difference in risk between adjacent intervals by the cumulative power flow. The first row is always 0, and the second row and above are , the calculation formula is as follows:

[0054] ;

[0055] Where K represents the total number of all divided internal sources and internal charges, k represents the kth divided internal source or internal charge, q k represents the risk of the kth divided internal source or internal load, P k Represents the power flow of the kth divided internal source or internal load.

[0056] Step S2.1.5: The fifth column is the cumulative risk power flow, which is obtained by adding up all the previous risk energies. The first row is always 0, and the second row and above are , let the value of the last row be ;

[0057] ;

[0058] Step S2.1.6: The minimum amount of curtailed power corresponding to each risk level can be estimated based on the risk power flow and the cumulative risk power flow. The calculation method is as follows:

[0059] ;

[0060] Among them, W k Represents the minimum amount of abandoned current corresponding to each risk level, q K represents the risk of the Kth internal source or internal load that is divided. The remaining parameters have been mentioned in step S2.1.5.

[0061] Step S2.2. Graphical electrical pinch analysis model, such as Figure 3 Shown, including:

[0062] Step S2.2.1: Ensure the minimum amount of abandoned electricity and select the minimum risk level that meets the energy demand as the risk level of the external source, that is, , where q out Represents the risk level from external sources.

[0063] Step S2.2.2: Draw a source combination curve with the cumulative risk power flow as the horizontal axis and the risk degree as the vertical axis. , the vertical axis range is (0, 1), and the dotted line is the minimum current abandonment curve.

[0064] Step S2.2.3: Based on the source combination curve, As the fulcrum, the abandoned current flow curve is rotated upward, and the first intersection with the source combination curve is regarded as the pinch point. At this time, the slope of the dotted line is the minimum abandoned current flow.

[0065] ;

[0066] Among them, △Q is the cumulative risk power flow, W is Figure 3 The dotted line slope is q, and the other parameters are mentioned above.

[0067] Step S2.3. New energy interval interval load interval division, such as Figure 4 As shown in the figure, the new energy and load data are put into the power planning model of the electric pinch point analysis, and then the minimum interval △P between the new energy and load is determined. new,min , △P load,min And calculate the minimum abandoned current W under the interval min Then, the new energy interval is taken as △P new,min +50i, the load interval is △P load,min +50j uses step S2 to calculate the minimum energy rejection flow W11, if W min >W ij , then W ij Assign to W min Otherwise, let △P new,min +50i<△P new,max , △P load,min +50j<△P load,max If W min The minimum amount of abandoned current is calculated, and the abandoned power and basic power capacity are calculated. Otherwise, let i+1,j+1 return to the new energy interval and take △P new,min +50i, the load interval is △P load,min +50j iterations, including:

[0068] Step S2.3.1: Use a combination of fixed step size and sensitivity analysis to determine the interval step size to be 50.

[0069] Step S2.3.2: Determine by simulation comparison The minimum value of , that is:

[0070] ;

[0071] Where: The interval for new energy is , load interval The minimum curtailed current is calculated when . i and j represent the subscripts of the intervals of new energy and load at different iteration times.

[0072] Step S2.3.3: Calculate the minimum amount of power abandonment based on the risk level corresponding to the minimum amount of power abandonment. ,Right now:

[0073] .

[0074] in, is the risk level corresponding to the minimum amount of abandoned power.

[0075] In one embodiment, the above step S3 specifically includes:

[0076] like Figure 5 As shown, first, the historical data of renewable energy and load in the planned area are put into the power planning model of the electric pinch analysis with the minimum power curtailment, and then the model is verified on the data from 2018 to 2022. If the model is passed, the development plan of renewable energy installed capacity in the planned area is carried out, and the proportion of wind and solar installed capacity in different situations (under resource reserves and current planning) is put into the power planning model of the electric pinch analysis to obtain the flexible thermal power installed capacity and power generation under different wind-solar ratios. With the complete energy target as the constraint, combined with the power planning model of the electric pinch analysis, under the premise of known renewable energy installed capacity planning, with the goal of minimizing the curtailment, the flexible thermal power installed capacity and power generation of the power system are determined, that is, the power value of the external source in the electric pinch analysis model is determined.

[0077] The present invention also provides a power system power planning device based on electrical pinch point analysis, comprising the following modules:

[0078] The description module proposes power value and risk as key indicators reflecting power flow and power quality in power pinch analysis. It considers the timing characteristics of renewable energy output and load to describe the matching relationship between renewable energy and load.

[0079] Obtain analytical solution module, build power planning model for electrical pinch point analysis, provide tabular and graphical calculation steps, and obtain analytical solution of planning model.

[0080] The scale determination module, based on the power planning model constructed for electrical pinch point analysis, rationally plans the power structure and determines the scale of flexible thermal power installed capacity while ensuring that regional power curtailment is minimized.

[0081] The present invention also provides an electronic device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the above-mentioned method for power system power planning based on electrical pinch point analysis are implemented.

[0082] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the above-mentioned method for power system power planning based on electrical pinch point analysis are implemented.

[0083] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, 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 drives, CD-ROMs, optical storage devices, etc.) containing computer-usable program code. The solutions in the embodiments of the present invention may be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0084] 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 flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, 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 flowcharts and / or block diagrams. 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.

[0085] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work 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 The function specified in one or more boxes.

[0086] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0087] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0088] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A power system power planning method based on electrical pinch analysis, characterized in that: The steps include: Step S1: Power value and risk degree are proposed as key indicators reflecting power flow and power quality in power pinch analysis. The timing characteristics of renewable energy output and load are considered to describe the matching relationship between renewable energy and load. Step S2: Construct a power planning model for electrical pinch point analysis, provide tabular and graphical calculation steps, and obtain an analytical solution to the planning model; Step S3: Based on the power planning model of the electric pinch point analysis constructed in step S2, the power structure is rationally planned and the scale of flexible thermal power installed capacity is determined while minimizing regional power curtailment.

2. The method for power system power planning based on electrical pinch analysis according to claim 1, characterized in that: In step S1, power is a measure of the rate of electric energy transfer, which can reflect the transmission situation on both sides of the electric energy supply and demand. The output of new energy in a fixed area has the characteristics of volatility, intermittency and periodic change. The risk degree is used as an indicator to describe the power quality. The higher the risk degree, the worse the power quality. The power value and risk degree are also applicable to conventional power sources and loads. The electric pinch point analysis can ensure the balance of supply and demand energy and consider the impact of the operating characteristics of new energy. In terms of the source-load supply and demand relationship mapping network, the new energy is divided into N internal sources and the load is divided into M internal loads. The conventional power source is used as an external source to supplement the power. There is power abandonment. The source-load supply and demand relationship mapping network is given, indicating that each source can supply multiple loads and each load can be satisfied by multiple power sources.

3. The method for power system power planning based on electrical pinch analysis according to claim 2, characterized in that: The step S1 comprises: Assume that the wind power output in the system is , photovoltaic output is , new energy output is , whose upper and lower limits are and ; Propose risk level As an indicator describing power quality in electrical pinch analysis, the higher the risk, the worse the corresponding power quality. Considering the intrinsic relationship between power and risk, and considering that the amount of abandoned power reflects the flexibility and adaptability of the system, the amount of abandoned power is used as an attribute indicator to evaluate the overall performance of the system, that is, the new energy absorption rate.

4. The method for power system power planning based on electrical pinch analysis according to claim 3, characterized in that: The step S1 comprises: Step S1.

1. Characterize the relationship between power and risk and the electrical pinch point, including: Step S1.1.1: Convert the new energy output curve to The interval is divided into N intervals, with the power lower limit is the starting point, the risk of the nth interval The expression is as follows: ； Step S1.1.2: The maximum value that the number of intervals n can take for: ； Step S1.1.3: Take the middle value in the interval as the power value of the corresponding risk level, and the risk level of the nth interval Corresponding power value as follows: ； Step S1.

2. Mapping the source-load supply and demand relationship, including: Step S1.2.1: Divide the new energy into N internal sources with one-to-one correspondence between power values and risk levels; Step S1.2.2: Divide the load into M internal loads with one-to-one correspondence between power values and risk levels; Step S1.2.3: Satisfy power balance, achieve complete energy balance, and ensure that the total energy on both sides of the source-load supply and demand relationship mapping network is equal: ； Where: Indicates the power value corresponding to power supply n, Indicates the power value corresponding to load m, Indicates the power value corresponding to the power supply to be planned. Indicates the amount of waste electricity; Step S1.2.4: Based on the power difference Determine whether an external source needs to be added and the power value of the external source: 。 5. The method for power system power planning based on electrical pinch analysis according to claim 1, characterized in that: The step S2 comprises: Step S2.

1. Tabulate the electrical pinch analysis model, including: Step S2.1.1: The first column is the risk level. Collect the risk levels of all new energy sources and loads and arrange them in descending order from high to low. The same risk factor is listed only once to form an orderly supply and demand matching risk set. , this set determines the supply and demand matching principle of power supply and load, namely: ; Step S2.1.2: The second column is the power flow, which represents the power value corresponding to the risk level. The power flow of renewable energy is positive, and the power flow of load is negative. The power flow corresponding to the risk level is the sum of the power values of renewable energy and load with the same risk level. Step S2.1.3: The third column is the cumulative power flow, which represents the sum of the power flows in the corresponding risk level and the last row is the power difference. ; Step S2.1.4: The fourth column is the risk power flow, which represents the supply and demand risk of each interval. It is calculated by multiplying the difference in risk between adjacent intervals by the cumulative power flow. The first row is always 0, and the second row and above are , the calculation formula is as follows: ； Step S2.1.5: The fifth column is the cumulative risk power flow, which is obtained by adding up all the previous risk energies. The first row is always 0, and the second row and above are , let the value of the last row be ; ； Step S2.1.6: The minimum amount of curtailed power corresponding to each risk level can be estimated based on the risk power flow and the cumulative risk power flow. The calculation method is as follows: ； Step S2.

2. Graphical electrical pinch analysis model, including: Step S2.2.1: Ensure the minimum amount of abandoned electricity and select the minimum risk level that meets the energy demand as the risk level of the external source, that is, ; Step S2.2.2: Draw a source combination curve with the cumulative risk power flow as the horizontal axis and the risk degree as the vertical axis. , the vertical axis range is (0, 1), and the dotted line is the minimum curtailment flow curve; Step S2.2.3: Based on the source combination curve, As a fulcrum, the abandoned power flow curve is rotated upward, and the first intersection with the source combination curve is regarded as a pinch point. At this time, the slope of the dotted line is the minimum abandoned power flow: 。 6. The method for power system power planning based on electrical pinch analysis according to claim 5, characterized in that: The step S2 further includes: Step S2.

3. Divide the new energy interval into load intervals, including: Step S2.3.1: Use a combination of fixed step size and sensitivity analysis to determine the interval step size to be 50; Step S2.3.2: Determine by simulation comparison The minimum value of , that is: ； Where: The interval for new energy is , load interval The minimum abandoned current amount calculated when Step S2.3.3: Calculate the minimum amount of power abandoned based on the risk level corresponding to the minimum amount of power abandoned ,Right now: 。 7. The method for power system power planning based on electrical pinch analysis according to claim 6, characterized in that: The step S3 specifically includes: taking the complete energy target as a constraint, combining the electrical pinch analysis model, under the premise of known new energy installed capacity planning, and taking minimizing the amount of curtailed current as the goal, determining the flexible thermal power unit size and power generation of the power system, that is, determining the power value of the external source in the electrical pinch analysis model. Through this method, the real-time power balance of the power system is converted into a match of power values under risk, thereby ensuring the reliability of the system energy supply.

8. A power system power planning device based on electrical pinch point analysis, characterized in that: Includes the following modules: The description module proposes power value and risk as key indicators reflecting power flow and power quality in power pinch analysis. It considers the timing characteristics of renewable energy output and load to describe the matching relationship between renewable energy and load. The analytical solution module builds a power planning model for electrical pinch point analysis, provides tabular and graphical calculation steps, and obtains the analytical solution of the planning model; The scale determination module, based on the constructed power planning model of electrical pinch point analysis, rationally plans the power structure and determines the scale of flexible thermal power installed capacity while ensuring the minimum regional power curtailment.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the steps of the power system power planning method based on electrical pinch analysis according to any one of claims 1 to 7 are implemented.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the power system power planning method based on electrical pinch point analysis as claimed in any one of claims 1 to 7 are implemented.

Images