Electrical automation power supply method and system

Abstract

The present invention relates to the technical field of regional power supply planning, and specifically discloses an electrical automation power supply method and system, comprising the following steps: obtaining a power supply plan for a target area; obtaining the operation status of a new energy station corresponding to the target area; setting a correction period T, obtaining a curve of the output power Ps of each power generation node over time in the previous correction period T, and calculating a stable output interval; predicting the average output power of each power generation node in the next correction period; calculating the theoretical output difference; calculating the operation score coefficient of each power generation node; according to the operation score of each power generation node, selecting n power generation nodes from low to high and marking them as dormant periods, and stopping power generation. The present invention not only saves a part of the maintenance cost, but also slows down the aging speed of equipment and avoids the waste of electric energy.

Description

Technical Field

[0001] The present invention relates to the technical field of regional power supply planning, and in particular to an electrical automation power supply method and system. Background Art

[0002] Electrical automation is a discipline covering multiple fields such as power electronics technology, computer technology, motor and electrical technology, information and network control technology, and mechatronics technology. It aims to cultivate senior professional and technical personnel who are suitable for modern large and medium-sized power plants and power systems.

[0003] With the acceleration of the construction of new power systems, the proportion of new energy represented by wind power and photovoltaics in the energy system structure continues to increase, but its volatility, intermittent and random characteristics also bring challenges to the stable operation of the power grid. With the rapid growth of new energy such as wind power and photovoltaics in the power grid, the uncertainty of their output increases the difficulty of power supply. In the existing technology, the distribution of electricity in various regions is usually planned in advance, and usually includes a part of new energy electricity. However, due to the uncertainty of new energy output, there is often a gap between its actual output and planned output; when the actual output is lower than the plan, it can be compensated by grid mobilization; but when the actual output is greater than the plan, because the difficulty of new energy grid connection is high and there are losses, the excess new energy electricity is connected to the grid, and the benefits are small, which is not worth the loss; taking wind power as an example, when the wind is strong, in addition to the planned supply of wind turbine power capacity, a considerable part of the power capacity will be released due to energy storage limits, resulting in energy waste.

[0004] In the prior art, a Chinese patent with patent application number CN2023110818237 discloses a wind power supply method and device. In its scheme, historical data is used to predict the wind power production capacity in the future, so that a plan is made according to the predicted wind power production capacity. Although this method can make the formulated plan more in line with the actual wind power production capacity, there is still a gap between the actual production capacity and the predicted production capacity during operation. Summary of the invention

[0005] The purpose of the present invention is to provide an electrical automation power supply method and system to solve the above technical problems.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] An electrical automation power supply method comprises the following steps:

[0008] Obtain a power supply plan for the target area, and obtain a planned output power P corresponding to the new energy power supply from the power supply plan;

[0009] Acquire the operation status of the new energy station corresponding to the target area, wherein the operation status includes the number N of power generation nodes in the new energy station, the output power Ps of each power generation node and the position coordinates of each power generation node;

[0010] Set the correction period T, obtain the output power Ps of each power generation node in the previous correction period T over time curve P(t), t'∈(0, T), and calculate the stable output interval (t1, T), where t1 satisfies the following constraints:

[0011] |P(T)-P(t')|≤ΔP,t'∈(t1,T);

[0012] Wherein ΔP represents the preset power error value;

[0013] The average output power Ps' of each power generation node in the next correction period is predicted to be:

[0014] ;

[0015] Obtain the sum of the average output powers P' of all power generation nodes in the new energy station in the next correction cycle. When the sum of the average output powers P' is greater than the planned processing power P, calculate the theoretical output difference Ph=P'-P;

[0016] Calculate the operation score coefficient K of each power generation node, and the calculation method is:

[0017] ;

[0018] in, l Indicates the preset scale factor, l ∈(0,1);S represents the total number of power generation nodes in the circular area divided by the preset maintenance radius r with the power generation node as the center;

[0019] According to the operation score K of each power generation node, n power generation nodes are selected from low to high and marked as dormant, and power generation is stopped; where n satisfies the following constraints:

[0020] Psn'≤Ph;

[0021] Ps(n+1)'>Ph;

[0022] Among them, Psn' represents the sum of the average output powers of n power generation nodes selected from low to high; Ps(n+1)' represents the sum of the average output powers of (n+1) power generation nodes selected from low to high.

[0023] As a further solution of the present invention: when the sum of the average output power P' is less than the planned output power P, and there are power generation nodes in a dormant period, the following steps are performed:

[0024] Obtain the position coordinates of the power generation node in the dormant period, and obtain the average value of the average output power Ps' of the other power generation nodes in the circular area divided by the preset maintenance radius r with the power generation node as the center as the average output power of the power generation node in the next correction cycle, and mark the power generation node as the operating period;

[0025] Recalculate the sum P' of the average output power of all power generation nodes in the new energy station in the next correction cycle.

[0026] As a further solution of the present invention: when the sum of the average output power P' is less than the planned output power P, and there is no power generation node in a dormant period, the energy storage system matched with the new energy station is used to supplement the power, and the specific method includes:

[0027] Obtain the energy storage capacity E of the energy storage system supporting the new energy station;

[0028] Calculate the output deviation Px = (P-Ps'), and the operating time t2 = (eE) / Px of the energy storage system when the output deviation is met, where e represents the preset minimum reserved power;

[0029] Determine the relationship between the running time t2 and the correction period T. When t2 ≥ T, at the beginning of the next correction period T, the energy storage system uses Px as the output power.

[0030] When t2<T, at the beginning of the next correction period T, the output power of the energy storage system is (eE) / T.

[0031] As a further solution of the present invention, it also includes real-time output correction, and the real-time output correction includes the following steps:

[0032] Obtain the sum of the real-time output power Ps' of all power generation nodes in the new energy station within the current correction period;

[0033] Calculate the output deviation Px=(P-Ps'). When the output deviation Px>0, charge the energy storage system matched with the new energy station, the charging power is equal to the output deviation Px, and release the excess power generation when the energy storage system is fully charged;

[0034] When the output deviation Px is less than 0, the energy storage system is used to make up for the power, and its output power is equal to the output deviation Px;

[0035] When the output deviation Px=0, no response is given.

[0036] As a further solution of the present invention: when the power generation node in the dormant period does not have other power generation nodes in the circular area divided by a preset maintenance radius r with the power generation node as the center, the average output power of the power generation node closest to it is used as the average output power of the power generation node, and the power generation node is marked as in the operating period.

[0037] As a further solution of the present invention: when the time interval ΔT=T-t1 in the stable output interval (t1, T) is less than the preset minimum interval value, t1 is recalculated, wherein t1 satisfies the following constraints:

[0038] |P(T)-P(t')|≤1.2ΔP,t'∈(t1,T).

[0039] As a further solution of the present invention, it also includes the correction of the sum of average output power P', and the specific steps are as follows:

[0040] Obtain the real-time processing correction data in the previous correction cycle and calculate the predicted error power X;

[0041] The predicted error power X=Er+Es-Ec, where Er is the charge capacity of the energy storage system, Ec is the output capacity of the energy storage system, and Es represents the reactive power released by the system when the energy storage system is fully charged;

[0042] Let P'=P'+X / T to complete the correction process.

[0043] An electrical automation power supply system, comprising:

[0044] Data acquisition module: obtains the power supply plan of the target area, and obtains the planned output power P corresponding to the new energy power supply from the power supply plan;

[0045] Acquire the operation status of the new energy station corresponding to the target area, wherein the operation status includes the number N of power generation nodes in the new energy station, the output power Ps of each power generation node and the position coordinates of each power generation node;

[0046] Output prediction module: Set the correction period T, obtain the output power Ps of each power generation node in the previous correction period T over time curve P(t), t'∈(0, T), calculate the stable output interval (t1, T), where t1 satisfies the following constraints:

[0047] |P(T)-P(t')|≤ΔP,t'∈(t1,T);

[0048] Wherein ΔP represents the preset power error value;

[0049] The average output power Ps' of each power generation node in the next correction period is predicted to be:

[0050] ;

[0051] Power generation node scheduling module: obtain the sum of average output powers P' of all power generation nodes in the new energy station in the next correction cycle, and when the sum of average output powers P' is greater than the planned processing power P, calculate the theoretical output difference Ph=P'-P;

[0052] Calculate the operation score coefficient K of each power generation node, and the calculation method is:

[0053] ;

[0054] in, l Indicates the preset scaling factor, l ∈(0,1);S represents the total number of power generation nodes in the circular area divided by the preset maintenance radius r with the power generation node as the center;

[0055] According to the operation score K of each power generation node, n power generation nodes are selected from low to high and marked as dormant, and power generation is stopped; where n satisfies the following constraints:

[0056] Psn'≤Ph;

[0057] Ps(n+1)'>Ph;

[0058] Among them, Psn' represents the sum of the average output powers of n power generation nodes selected from low to high; Ps(n+1)' represents the sum of the average output powers of (n+1) power generation nodes selected from low to high.

[0059] Beneficial effects of the present invention: In the present application, the long-term prediction often used in the prior art is changed to a short-term prediction, that is, the correction period T in the present application, and the capacity of the supporting energy storage system of the new energy station is used as the correction. The predicted production capacity is adjusted in a series of correction periods, and the prediction error is corrected by the capacity of the energy storage system, so that the entire new energy station can output at a relatively stable output power. In the process of adjustment and correction, some power generation nodes are arranged to sleep and start according to the actual meteorological conditions (wind power and sunshine, etc.). Therefore, under relatively good meteorological conditions, only some power generation nodes need to be started to meet the planned power supply needs, and the redundant power generation nodes are in a dormant state, which not only saves part of the maintenance costs, but also slows down the aging of equipment and avoids the waste of electricity. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The present invention will be further described below in conjunction with the accompanying drawings.

[0061] Figure 1It is a flow chart of an electrical automation power supply method of the present invention. DETAILED DESCRIPTION

[0062] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 are within the scope of protection of the present invention.

[0063] See also Figure 1 As shown, the present invention is an electrical automation power supply method, comprising the following steps:

[0064] Obtain a power supply plan for the target area, and obtain a planned output power P corresponding to the new energy power supply from the power supply plan;

[0065] Acquire the operation status of the new energy station corresponding to the target area, wherein the operation status includes the number N of power generation nodes in the new energy station, the output power Ps of each power generation node and the position coordinates of each power generation node;

[0066] Set the correction period T, obtain the output power Ps of each power generation node in the previous correction period T over time curve P(t), t'∈(0, T), and calculate the stable output interval (t1, T), where t1 satisfies the following constraints:

[0067] |P(T)-P(t')|≤ΔP,t'∈(t1,T);

[0068] Wherein ΔP represents the preset power error value;

[0069] The average output power Ps' of each power generation node in the next correction period is predicted to be:

[0070] ;

[0071] Obtain the sum of the average output powers P' of all power generation nodes in the new energy station in the next correction cycle. When the sum of the average output powers P' is greater than the planned processing power P, calculate the theoretical output difference Ph=P'-P;

[0072] Calculate the operation score coefficient K of each power generation node, and the calculation method is:

[0073] ;

[0074] in, l Indicates the preset scaling factor, l∈(0,1);S represents the total number of power generation nodes in the circular area divided by the preset maintenance radius r with the power generation node as the center;

[0075] According to the operation score K of each power generation node, n power generation nodes are selected from low to high and marked as dormant, and power generation is stopped; where n satisfies the following constraints:

[0076] Psn'≤Ph;

[0077] Ps(n+1)'>Ph;

[0078] Among them, Psn' represents the sum of the average output powers of n power generation nodes selected from low to high; Ps(n+1)' represents the sum of the average output powers of (n+1) power generation nodes selected from low to high.

[0079] It is not difficult to understand from common knowledge that the power generation node in the present invention refers to the power generation unit in wind power or photovoltaic power, which can be calculated by group or by individual. For example, for wind power, the distribution of wind turbines is relatively scattered, so a single wind turbine can be used as a power generation node, while the distribution of photovoltaic power is relatively dense, so a group of several photovoltaic panels can be used as a power generation node;

[0080] Another thing we can easily understand is that both wind power and photovoltaic power require considerable maintenance costs during daily operation. This part of the cost is worthwhile for power generation, but in the case of overcapacity, it increases the financial burden. The excess capacity can only be released in vain due to the difficulty of temporary grid connection of new energy and the possible interference with power supply plans, which undoubtedly causes corresponding losses.

[0081] Therefore, in the present application, the long-term prediction often used in the prior art is changed to a short-term prediction, that is, the correction period T in the present application, and the capacity of the supporting energy storage system of the new energy station is used as the correction. The predicted production capacity is adjusted in a series of correction periods, and the prediction error is corrected by the capacity of the energy storage system, so that the entire new energy station can output at a relatively stable output power. In the process of adjustment and correction, some power generation nodes are arranged to sleep and start according to the actual meteorological conditions (wind power and sunshine, etc.). Therefore, under relatively good meteorological conditions, only some power generation nodes need to be started to meet the planned power supply needs, and the redundant power generation nodes are in a dormant state, which not only saves part of the maintenance costs, but also slows down the aging of equipment and avoids the waste of electricity.

[0082] It is worth noting that new energy stations are generally built in areas with relatively stable meteorological conditions, that is, short-term changes are not large (the energy storage system can meet the errors caused by fluctuations in environmental factors). Therefore, for the corresponding application scenarios, when using this solution, there will be no phenomenon of frequent start and stop of a certain power generation node in multiple consecutive correction cycles;

[0083] It is also worth noting that the supporting energy storage system is an important component of real-time correction. When there is a continuous power shortage for multiple correction cycles, it is necessary to increase a part of the original planned output power to charge the energy storage system.

[0084] In a preferred embodiment of the present invention, when the sum of the average output powers P' is less than the planned output power P, and there are power generation nodes in a dormant period, the following steps are performed:

[0085] Obtain the position coordinates of the power generation node in the dormant period, and obtain the average value of the average output power Ps' of the other power generation nodes in the circular area divided by the preset maintenance radius r with the power generation node as the center as the average output power of the power generation node in the next correction cycle, and mark the power generation node as the operating period;

[0086] Recalculate the sum P' of the average output power of all power generation nodes in the new energy station in the next correction cycle.

[0087] In a preferred embodiment of the present invention, when the sum of the average output power P' is less than the planned output power P, and there is no power generation node in a dormant period, the energy storage system supporting the new energy station is used to supplement the power, and the specific method includes:

[0088] Obtain the energy storage capacity E of the energy storage system supporting the new energy station;

[0089] Calculate the output deviation Px = (P-Ps'), and the operating time t2 = (eE) / Px of the energy storage system when the output deviation is met, where e represents the preset minimum reserved power;

[0090] Determine the relationship between the running time t2 and the correction period T. When t2 ≥ T, at the beginning of the next correction period T, the energy storage system uses Px as the output power.

[0091] When t2<T, at the beginning of the next correction period T, the output power of the energy storage system is (eE) / T.

[0092] In a preferred embodiment of the present invention, it also includes real-time output correction, and the real-time output correction includes the following steps:

[0093] Obtain the sum of the real-time output power Ps' of all power generation nodes in the new energy station within the current correction period;

[0094] Calculate the output deviation Px=(P-Ps'). When the output deviation Px>0, charge the energy storage system matched with the new energy station, the charging power is equal to the output deviation Px, and release the excess power generation when the energy storage system is fully charged;

[0095] When the output deviation Px is less than 0, the energy storage system is used to make up for the power, and its output power is equal to the output deviation Px;

[0096] When the output deviation Px=0, no response is given.

[0097] In a preferred embodiment of the present invention, when the power generation node is in a dormant period and there are no other power generation nodes in the circular area divided by a preset maintenance radius r with the power generation node as the center, the average output power of the power generation node closest to it is used as the average output power of the power generation node, and the power generation node is marked as in the operating period.

[0098] In a preferred embodiment of the present invention, when the time interval ΔT=T-t1 in the stable output interval (t1, T) is less than the preset minimum interval value, t1 is recalculated, wherein t1 satisfies the following constraints:

[0099] |P(T)-P(t')|≤1.2ΔP,t'∈(t1,T).

[0100] In a preferred embodiment of the present invention, the correction of the sum of average output power P' is also included, and the specific steps are as follows:

[0101] Obtain the real-time processing correction data in the previous correction cycle and calculate the predicted error power X;

[0102] The predicted error power X=Er+Es-Ec, where Er is the charge capacity of the energy storage system, Ec is the output capacity of the energy storage system, and Es represents the reactive power released by the system when the energy storage system is fully charged;

[0103] Let P'=P'+X / T to complete the correction process.

[0104] An electrical automation power supply system, comprising:

[0105] Data acquisition module: obtains the power supply plan of the target area, and obtains the planned output power P corresponding to the new energy power supply from the power supply plan;

[0106] Acquire the operation status of the new energy station corresponding to the target area, wherein the operation status includes the number N of power generation nodes in the new energy station, the output power Ps of each power generation node and the position coordinates of each power generation node;

[0107] Output prediction module: Set the correction period T, obtain the output power Ps of each power generation node in the previous correction period T over time curve P(t), t'∈(0, T), calculate the stable output interval (t1, T), where t1 satisfies the following constraints:

[0108] |P(T)-P(t')|≤ΔP,t'∈(t1,T);

[0109] Wherein ΔP represents the preset power error value;

[0110] The average output power Ps' of each power generation node in the next correction period is predicted to be:

[0111] ;

[0112] Power generation node scheduling module: obtain the sum of average output powers P' of all power generation nodes in the new energy station in the next correction cycle, and when the sum of average output powers P' is greater than the planned processing power P, calculate the theoretical output difference Ph=P'-P;

[0113] Calculate the operation score coefficient K of each power generation node, and the calculation method is:

[0114] ;

[0115] in, l Indicates the preset scale factor, l ∈(0,1);S represents the total number of power generation nodes in the circular area divided by the preset maintenance radius r with the power generation node as the center;

[0116] According to the operation score K of each power generation node, n power generation nodes are selected from low to high and marked as dormant, and power generation is stopped; where n satisfies the following constraints:

[0117] Psn'≤Ph;

[0118] Ps(n+1)'>Ph;

[0119] Among them, Psn' represents the sum of the average output powers of n power generation nodes selected from low to high; Ps(n+1)' represents the sum of the average output powers of (n+1) power generation nodes selected from low to high.

[0120] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. An electrical automation power supply method, characterized in that: The following steps are involved: Obtain a power supply plan for the target area, and obtain a planned output power P corresponding to the new energy power supply from the power supply plan; Acquire the operation status of the new energy station corresponding to the target area, wherein the operation status includes the number N of power generation nodes in the new energy station, the output power Ps of each power generation node and the position coordinates of each power generation node; Set the correction period T, obtain the output power Ps of each power generation node in the previous correction period T over time curve P(t), t'∈(0, T), and calculate the stable output interval (t1, T), where t1 satisfies the following constraints: |P(T)-P(t')|≤ΔP,t'∈(t1,T); Wherein ΔP represents the preset power error value; The average output power Ps' of each power generation node in the next correction period is predicted to be: ； Obtain the sum of the average output powers P' of all power generation nodes in the new energy station in the next correction cycle. When the sum of the average output powers P' is greater than the planned output power P, calculate the theoretical output difference Ph=P'-P; Calculate the operation score coefficient K of each power generation node, and the calculation method is: ； in, λ Indicates the preset scaling factor, λ ∈(0,1);S represents the total number of power generation nodes in the circular area divided by the preset maintenance radius r with the power generation node as the center; According to the operation score K of each power generation node, n power generation nodes are selected from low to high and marked as dormant, and power generation is stopped; where n satisfies the following constraints: Psn'≤Ph; Ps(n+1)'>Ph; Among them, Psn' represents the sum of the average output powers of n power generation nodes selected from low to high; Ps(n+1)' represents the sum of the average output powers of (n+1) power generation nodes selected from low to high.

2. An electrical automation power supply method according to claim 1, characterized in that: When the sum of the average output powers P' is less than the planned output power P, and there are power generation nodes in a dormant period, the following steps are performed: Obtain the position coordinates of the power generation node in the dormant period, and obtain the average value of the average output power Ps' of the other power generation nodes in the circular area divided by the preset maintenance radius r with the power generation node as the center as the average output power of the power generation node in the next correction cycle, and mark the power generation node as the operating period; Recalculate the sum P' of the average output power of all power generation nodes in the new energy station in the next correction cycle.

3. An electrical automation power supply method according to claim 2, characterized in that: When the sum of the average output power P' is less than the planned output power P, and there is no power generation node in a dormant period, the energy storage system supporting the new energy station is used to supplement the power, and the specific method includes: Obtain the energy storage capacity E of the energy storage system supporting the new energy station; Calculate the output deviation Px = (P-Ps'), and the operating time t2 = (eE) / Px of the energy storage system when the output deviation is met, where e represents the preset minimum reserved power; Determine the relationship between the running time t2 and the correction period T. When t2 ≥ T, at the beginning of the next correction period T, the energy storage system uses Px as the output power. When t2<T, at the beginning of the next correction period T, the output power of the energy storage system is (eE) / T.

4. An electrical automation power supply method according to claim 3, characterized in that: The invention also includes real-time output correction, wherein the real-time output correction includes the following steps: Obtain the sum of the real-time output power Ps' of all power generation nodes in the new energy station within the current correction period; Calculate the output deviation Px=(P-Ps'). When the output deviation Px>0, charge the energy storage system matched with the new energy station, the charging power is equal to the output deviation Px, and release the excess power generation when the energy storage system is fully charged; When the output deviation Px is less than 0, the energy storage system is used to make up for the power, and its output power is equal to the output deviation Px; When the output deviation Px=0, no response is given.

5. The electrical automation power supply method according to claim 2, characterized in that: When the power generation node in the dormant period does not have any other power generation nodes in the circular area divided by the preset maintenance radius r with it as the center, the average output power of the power generation node closest to it is used as the average output power of the power generation node, and the power generation node is marked as in the operating period.

6. The electrical automation power supply method according to claim 1, characterized in that: When the time interval ΔT=T-t1 in the stable output interval (t1, T) is less than the preset minimum interval value, t1 is recalculated, where t1 satisfies the following constraints: |P(T)-P(t')|≤1.2ΔP,t'∈(t1,T).

7. The electrical automation power supply method according to claim 4, characterized in that: It also includes the correction of the sum of average output power P', and the specific steps are as follows: Obtain the real-time processing correction data in the previous correction cycle and calculate the predicted error power X; The predicted error power X=Er+Es-Ec, where Er is the charge capacity of the energy storage system, Ec is the output capacity of the energy storage system, and Es represents the reactive power released by the system when the energy storage system is fully charged; Let P'=P'+X / T to complete the correction process.

8. An electrical automation power supply system, characterized in that: include: Data acquisition module: obtains the power supply plan of the target area, and obtains the planned output power P corresponding to the new energy power supply from the power supply plan; Acquire the operation status of the new energy station corresponding to the target area, wherein the operation status includes the number N of power generation nodes in the new energy station, the output power Ps of each power generation node and the position coordinates of each power generation node; Output prediction module: Set the correction period T, obtain the output power Ps of each power generation node in the previous correction period T over time curve P(t), t'∈(0, T), calculate the stable output interval (t1, T), where t1 satisfies the following constraints: |P(T)-P(t')|≤ΔP,t'∈(t1,T); Wherein ΔP represents the preset power error value; The average output power Ps' of each power generation node in the next correction period is predicted to be: ； Power generation node scheduling module: obtain the sum of the average output powers P' of all power generation nodes in the new energy station in the next correction cycle, and when the sum of the average output powers P' is greater than the planned output power P, calculate the theoretical output difference Ph=P'-P; Calculate the operation score coefficient K of each power generation node, and the calculation method is: ； in, λ Indicates the preset scaling factor, λ ∈(0,1);S represents the total number of power generation nodes in the circular area divided by the preset maintenance radius r with the power generation node as the center; According to the operation score K of each power generation node, n power generation nodes are selected from low to high and marked as dormant, and power generation is stopped; where n satisfies the following constraints: Psn'≤Ph; Ps(n+1)'>Ph; Among them, Psn' represents the sum of the average output powers of n power generation nodes selected from low to high; Ps(n+1)' represents the sum of the average output powers of (n+1) power generation nodes selected from low to high.

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