A power sensor positioning method suitable for cable trench scenarios

Abstract

This invention discloses a power sensor positioning method applicable to cable trench scenarios, belonging to the field of wireless sensor monitoring technology for power systems. Cable trenches are home to numerous transmission cables and power sensors. This invention, based on traditional BeiDou satellite positioning technology, combines wireless sensor ranging technology and employs a BeiDou-based power sensor positioning method to solve the problem of locating power sensors within cable trenches. This method uses the power cover terminal located by the BeiDou system as a reference node. By introducing a transformation matrix and a compensation matrix, the positional relationship between the BeiDou satellite and the sensors within the cable trench is established. The least squares method is used to directly calculate the position coordinates of the power sensors within the cable trench. Simulation results show that the proposed BeiDou-based joint positioning algorithm can accurately locate the position coordinates of power sensors within the cable trench, with a positioning coordinate error within 0.1m. This achieves accurate positioning of sensors within cable trenches.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless sensor monitoring of power systems, and in particular relates to a power sensor positioning method suitable for cable trench scenarios. Background Art

[0002] With the rapid advancement of my country's construction of urban smart grids, the coverage rate of urban cables has continued to increase, and with it comes the increase of a series of potential risks such as cable damage and loss of power covers. Therefore, more and more sensors are installed in cable trenches to monitor the status of power transmission cables in the cable trenches in real time. In actual engineering applications, the sensors under the cable trenches send the collected power transmission cable status information to the smart power cover terminal in real time. The power cover terminal calculates and analyzes the temperature, humidity and other conditions of the transmission cable at the location of the sensor. When a transmission cable fails, the sensor that transmits this information can determine the exact location of the transmission cable fault. However, due to the lack of wireless sensor positioning methods suitable for cable trench scenarios, when a transmission cable fails in a cable trench, it is impossible to locate the fault location of the transmission cable in a timely and accurate manner. After arriving at the site, maintenance personnel need to spend a lot of time to inspect the entire transmission cable, resulting in untimely maintenance and increased maintenance difficulty and cost. Therefore, in order to further promote the construction of urban smart grids, it is imperative to strengthen the management and control of sensors in urban cable trenches. How to accurately locate the position of sensors in cable trenches has become an urgent problem to be solved in the current smart grid field.

[0003] In order to solve the problem of sensor positioning in special scenarios such as cable trenches, Ge Ribo et al. proposed a method for wireless sensor positioning in coal mines based on ultra-wideband technology. The method uses a communication protocol based on ultra-wideband technology to collect signal strength information from each sensor, establishes an underground ultra-wideband path loss model, and calculates the distance between each sensor and the reference sensor in the mine by the maximum likelihood estimation method to locate the sensor, thereby improving the accuracy of target positioning in the mine. Zhang Yanpeng et al. combined visible light communication technology with received signal strength monitoring technology to locate trains in subway stations, and verified the feasibility and effectiveness of this method based on the operation data of Chengdu Metro Line 1 trains. Zhou Su et al. proposed a method for autonomous vehicle positioning based on laser radar to solve the problem that vehicle positioning sensors cannot be positioned in parking lots due to limited signals. This method can accurately locate vehicles in parking lots and other scenarios without GPS signals, and the positioning accuracy is within 10 cm.

[0004] In the fields of power and smart grid construction, the importance of the Beidou satellite positioning system is also increasing day by day. In my country's power system, many power businesses are currently using the Beidou satellite positioning system to locate power equipment. [1-2]For example, in the inspection of power lines, Beidou satellite positioning equipment can be installed on drones or inspection vehicles to inspect the transmission circuits, which can quickly and accurately locate the fault part of the line, greatly reducing the difficulty and time of fault location. [3] Jiang Chen et al. proposed a method for monitoring substation workers based on the Beidou positioning system. They used laser scanning technology to build a three-dimensional model of the substation scene, combined ultra-wideband technology with Beidou positioning technology, located the workers indoors and outdoors of the substation, and connected the smart bracelet to the Beidou system terminal to achieve safety and health monitoring of substation workers. In the literature [4], the authors installed fault indicators on the smart distribution network lines, uploaded the line fault information to the Beidou data center, and used the Beidou satellite navigation system to locate the fault location, thereby narrowing the scope of fault investigation and achieving real-time fault monitoring of smart distribution network lines.

[0005] When positioning sensors in urban cable trenches, since the cable trenches are buried under the urban surface, the Beidou satellite ranging signal will be blocked by the ground and urban surface buildings. The Beidou positioning system alone cannot accurately locate the position of the sensors in the cable trenches. [5-6] . To solve this problem, this paper combines Beidou satellite positioning technology with wireless sensor ranging technology based on signal reception strength, and proposes a power sensor positioning method suitable for cable trench scenarios. This method uses the Beidou positioning system to locate power cover terminals at two different locations on the urban cable trench, regards the two located power cover terminals as reference nodes, and uses wireless sensor ranging technology based on signal reception strength to obtain the position relationship between the sensor under the cable trench and the power cover terminal, thereby realizing the positioning of the sensor in the cable trench. Summary of the invention

[0006] The object of the present invention is to provide a power sensor positioning method suitable for cable trench scenarios, which is characterized by comprising:

[0007] 1. Establish the Beidou positioning system model,

[0008] (1) Cable trench scenario model: a large number of transmission cables are laid in the cable trench, multiple power sensors are arranged at intervals on the transmission cables, power covers and power sensors are fixed on the wellhead of the cable trench, and a ground user control center is set up; the position of the ground user control center in the Beidou positioning system is recorded as "point O", point O is taken as the origin, the plane where the cable trench is located is the xoy plane, and a spatial coordinate system o-xyz is established; in this coordinate system o-xyz, the coordinates of the four Beidou satellites are (x'1, y'1, z'1), (x'2, y'2, z'2), (x'3, y'3, z'3), (x'4, y'4, z'4); the position coordinates of the two power covers are (x1, y1, z1), (x2, y2, z2); the required sensor position coordinates are (x, y, z);

[0009] Beidou satellites transmit ranging signals to the power cover terminal on the cable trench. The ground control center synchronizes its clock with the Beidou satellite and collects the transmission time taken for the ranging signal sent by each Beidou satellite to reach the power cover terminal. Sensors under the cable trench collect temperature, humidity and position status information of the transmission cable, and then send the collected data to the power cover terminal. The power cover terminal processes the received data and reports the transmission cable status information to the ground control center.

[0010] (2) The distance between the Beidou satellite and the power cover terminal is measured based on the pseudo-range positioning principle. The distance between the Beidou satellite and the power cover terminal is calculated by the time difference between the transmitted and received ranging signals, which can be expressed as:

[0011]

[0012] In formula (1), c is the propagation speed of the Beidou satellite ranging signal, and the propagation speed is; c = 2.998 × 10 8 m / s; t e (t) is the time when the power cover terminal receiver receives the ranging signal, t b (t - τ) is the time when the Beidou satellite transmits the ranging signal; τ is the actual propagation time from the ranging signal sent by the Beidou satellite to the time when it is received by the power cover terminal receiver; R' is used to represent the pseudorange between the power cover terminal and the Beidou satellite. Because there is a clock difference Δt between the power cover terminal receiver and the Beidou satellite, the obtained distance is not the actual geometric distance between the two, so the measured distance is called pseudorange.

[0013] The pseudo-range between the power cover terminal and the Beidou satellite, and the distance between the two power cover terminals and the four Beidou satellites are:

[0014] R' ij =[(x' i -xj ) 2 +(y' i -y j ) 2 +(z' i -z j ) 2 ] 1 / 2 +cΔt (2)

[0015] In formula (2), [x' i ,y' i ,z' i ] represents the Beidou satellite coordinate information, i = 1, 2, 3, 4; [x j ,y j ,z j ] represents the position information of the power cover, j = 1, 2; R' ij represents the pseudorange from the i-th BeiDou satellite to the j-th power cover; c is the propagation speed of the signal in a vacuum, i.e., the speed of light c = 2.998×10 8 m / s; Δt is the clock difference between the Beidou satellite clock and the power cover terminal receiver clock. For the convenience of calculation, R ij =R' ij -cΔt is used to represent the distance between the Beidou satellite and the power cover terminal. Therefore, the positional relationship between the Beidou satellite and the power cover terminal can be expressed by formula (3):

[0016]

[0017] The position coordinates of the two power cover terminals can be obtained by the above formula (3). Then, the located power cover terminals are used as reference nodes, and the sensors are positioned according to the positional relationship between the power cover terminals and the sensors under the cable trench. Due to the special geometric structure of the cable trench, the sensors under the cable trench and the power cover terminals have a linear positional relationship. Therefore, only the two power cover terminals need to be located to realize the positioning of the sensors under the cable trench. j represents the distance from the sensor under the cable trench to the power cover, and the positional relationship between the two can be expressed as:

[0018] d j =[(x j -x) 2 +(y j -y) 2 +(z j -z) 2 ] 1 / 2 (4)

[0019] By solving formula (3) and formula (4) together, the position coordinates (x, y, z) of the sensor are obtained.

[0020] (3) Analysis of positioning error of pseudo-range. In the actual positioning process, if the two positioning processes are solved separately, that is, the positioning coordinates of the power cover are solved first, and then the positioning coordinates of the sensor are solved, a large positioning error will be generated. Because when the Beidou satellite locates the power cover terminal, the ranging signal is affected by the ionosphere and troposphere when passing through the atmosphere, which will cause errors in the positioning results; at the same time, when the power cover terminal is used as a reference node to locate the sensor, the signal is interfered by the electromagnetic environment in the cable trench, which will also cause positioning errors; in addition, since the sensor position coordinates are solved based on the position information of the power cover terminal, in the above two positioning projects, the positioning error of the power cover terminal in the first stage will aggravate the positioning error of the sensor in the second stage. To this end, this paper proposes a joint positioning algorithm based on Beidou positioning. According to the Beidou satellite position information collected by the ground control center and the position relationship between the power cover terminal and the sensor under the cable trench, the direct position relationship between the Beidou satellite and the sensor is established to achieve accurate positioning of the sensor under the cable trench.

[0021] 2. The distance between the power cover terminal and the sensor is determined by a distance measurement method based on signal reception strength: the electromagnetic environment in the cable trench is very complex. When the sensor sends data to the power cover terminal, the signal strength decreases as the signal transmission distance increases. The distance between the power cover terminal and the sensor is calculated based on the received signal strength and the existing wireless signal attenuation model. The relationship between signal strength and signal transmission distance can be expressed as:

[0022]

[0023] where [p(d)] dbm is the signal strength received by the signal receiver on the power cover terminal from the sensor; [p(d o )] dbm is the reference signal strength of the sensor at a distance d0 from the power cover terminal, where d0 is the reference distance; d is the transmission distance of the signal between the sensor and the power cover terminal; X dbm is a Gaussian random variable, which is used to represent the Gaussian white noise generated by the environment in the cable trench during signal transmission; n is the path loss index in the cable trench scenario;

[0024] Considering that the signal is easily interfered by the electromagnetic environment in the cable trench, in order to reduce the positioning error and improve the positioning accuracy, the power cover terminal is used to measure the received signal strength value from the same sensor multiple times to obtain multiple groups of measurement values. The weighted mean model is used to process the collected multiple groups of received signal strength values. Suppose the received signal strength value p k Total occurrences w k times, that is, w kis the weight value, w1+w2+…+w k =f, then the weighted average of the received signal strength can be expressed as:

[0025] p=(p1w1+p2w2+…+p k w k ) / f (6)

[0026] In order to simplify formula (6), the reference distance is set to 1m, that is, d o =1m; use p, p o They represent the signal receiving strength at the actual transmission distance and the reference distance respectively; ignoring the influence of noise during signal transmission, the distance from the sensor to the power cover terminal can be obtained as:

[0027]

[0028] Under the condition that the path loss index of the cable trench environment is known, the distance between the sensor and the two power covers can be calculated according to formula (7), which are represented by d1 and d2 respectively.

[0029] 3. Establish the positional relationship between Beidou satellite and the sensor in the cable trench, and use the transformation matrix and compensation matrix to improve the positioning accuracy of Beidou satellite for the sensor in the cable trench.

[0030] During the positioning process, since the sensor is installed in the cable trench and is blocked by the ground, the Beidou satellite cannot directly locate it. It is necessary to first locate the power cover terminal on the cable trench, and then use the located power cover terminal to locate the sensor in the cable trench. In this process, the positioning error of the power cover terminal will increase the positioning error of the sensor. In order to reduce the influence of the positioning error of the power cover terminal on the positioning of the sensor under the cable trench, the position relationship between the Beidou satellite and the sensor under the cable trench is established based on the Beidou satellite position information collected by the ground control center and the distance from the sensor under the cable trench to the power cover terminal, using the transformation matrix and compensation matrix. Then, the sensor under the cable trench is directly located using the position relationship between the Beidou satellite and the sensor under the cable trench, so as to improve the positioning accuracy of the sensor in the cable trench;

[0031] To set up the appropriate transformation matrix and compensation matrix, firstly, subtract the fourth term from the first three terms of the equation system in formula (3), and we can get:

[0032]

[0033] Formula (8) can be solved to obtain:

[0034] X e =A -1 B (9), Formula (9) is expressed in matrix form, where

[0035]

[0036]

[0037] Similarly, in order to express the positional relationship between the power cover terminal and the sensor under the cable trench in the form of a matrix, formula (4) is expanded as follows:

[0038]

[0039] Subtract the second term from the first term in the equation system in formula (11), and we get:

[0040]

[0041] Convert formula (12) into matrix form CX s =D, where

[0042] C=2[x1-x2 y1-y2 z1-z2],

[0043]

[0044] D=[x1 2 +y1 2 +z1 2 -x2 2 -y2 2 -z2 2 -d1 2 +d2 2 ], (13),

[0045] In order to reduce the influence of the positioning error of the power cover terminal on the positioning error of the sensor in the cable trench during the solution, according to the positional relationship between the Beidou satellite and the power cover terminal and between the power cover terminal and the sensor, the compensation matrix V, transformation matrix P and Q are set as follows:

[0046] V=[d2 2 -d1 2 ] (14),

[0047]

[0048] Q=||A -1 B|| -2 P -1 (DV) (16)

[0049] Then the position relationship between the Beidou satellite and the sensor under the cable trench can be expressed by a matrix:

[0050]

[0051]

[0052] Among them, matrix A and matrix B are obtained by collecting satellite data from the ground control center in the Beidou satellite positioning system.

[0053] In the actual positioning process, due to the influence of environmental noise, when solving the position coordinates of the sensor under the cable trench, the positioning error of the system often leads to no solution or multiple solutions. In order to calculate the position coordinates of the sensor more accurately, the least squares method is used to obtain formula (17) and formula (18):

[0054] The optimal approximate solution of , where the error square sum function S is introduced:

[0055] S(X S )=||CX S -D|| 2 (19)

[0056] Set When , the error square sum function S takes the minimum value, and the positioning error is the smallest at this time, which is recorded as:

[0057]

[0058] In order to obtain the minimum value of the error square sum function, the formula (20) is differentiated and its derivative value is set to 0, and we can get:

[0059] C T CX s =C T D (21),

[0060] From this, the optimal solution of the sensor position coordinates can be deduced as:

[0061]

[0062] The beneficial effect of the present invention is that the method combines Beidou satellite positioning technology and wireless sensor positioning technology based on signal reception strength. The power cover terminal on the cable trench in the urban environment is first positioned by Beidou satellite positioning technology. After determining the position coordinates of the power cover terminal, the power cover terminal is regarded as a reference node, and the power sensor in the trench is positioned by wireless sensor positioning technology based on signal reception strength. And a joint positioning algorithm of Beidou positioning is adopted. Through simulation experiments, it is confirmed that this algorithm can realize the positioning of sensors in urban cable trenches, with a small positioning error, and effectively reduces the influence of the positioning error of the power cover terminal on the positioning error of the sensor, thereby realizing the precise positioning of sensors in cable trenches. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 Beidou positioning system model diagram

[0064] Figure 2 Power sensor positioning flow chart

[0065] Figure 3 Positioning error value comparison chart DETAILED DESCRIPTION

[0066] The present invention provides a method for locating a power sensor suitable for a cable trench scenario, the method comprising:

[0067] A Beidou positioning system model is established, the distance between the power cover terminal and the sensor is measured using a ranging method based on signal reception strength, and the positional relationship between the Beidou satellite and the sensor under the cable trench is established. The transformation matrix and compensation matrix are used to improve the positioning accuracy of the Beidou satellite for the sensor in the cable trench. The present invention is further explained below in conjunction with the accompanying drawings and simulation embodiments.

[0068] like Figure 1 As shown in the Beidou positioning system model diagram, a large number of transmission cables are laid in the cable trench, multiple power sensors are arranged at intervals on the transmission cables, a power cover terminal is fixed on the inner wall of the cable trench wellhead, and a ground user control center is set up; the position of the ground user control center in the Beidou positioning system is recorded as "point O", point O is taken as the origin, the plane where the cable trench is located is the xoy plane, and a spatial coordinate system o-xyz is established; in this coordinate system o-xyz, the coordinates of the four Beidou satellites are (x'1, y'1, z'1), (x'2, y'2, z'2), (x'3, y'3, z'3), (x'4, y'4, z'4); the position coordinates of the two power cover plates are (x1, y1, z1), (x2, y2, z2); the required sensor position coordinates are (x, y, z); as Figure 2 The positioning flow chart of the power sensor shown in the figure, the method includes:

[0069] 1. Establish the Beidou positioning system model,

[0070] (1) Beidou satellites transmit ranging signals to the power cover terminal on the cable trench. The ground control center synchronizes the clock with the Beidou satellite and collects the transmission time taken for the ranging signal sent by each Beidou satellite to reach the power cover terminal. The sensors under the cable trench collect the temperature, humidity and position status information of the transmission cable, and then send the collected data to the power cover terminal. The power cover terminal processes the received data and reports the transmission cable status information to the ground control center.

[0071] (2) The distance between the Beidou satellite and the power cover terminal is solved by the joint positioning algorithm. The distance between the Beidou satellite and the power cover terminal is measured based on the pseudo-range positioning principle. The distance between the Beidou satellite and the power cover terminal is calculated by the time difference between the transmitted and received ranging signals, which can be expressed as formula (1):

[0072]

[0073] In formula (1), c is the propagation speed of the Beidou satellite ranging signal, and the propagation speed is; c = 2.998 × 10 8 m / s; t e (t) is the time when the power cover terminal receiver receives the ranging signal, t b (t-τ) is the time when the Beidou satellite transmits the ranging signal; τ is the actual propagation time from the ranging signal sent by the Beidou satellite to the signal received by the power cover terminal receiver; R' is used to represent the pseudorange between the power cover terminal and the Beidou satellite. Because there is a clock difference Δt between the power cover terminal receiver and the Beidou satellite, the obtained distance is not the actual geometric distance between the two, so the measured distance is called pseudorange.

[0074] The pseudo-range between the power cover terminal and the Beidou satellite, and the distance between the two power cover terminals and the four Beidou satellites are:

[0075] R' ij =[(x' i -x j ) 2 +(y' i -y j ) 2 +(z' i -z j ) 2 ] 1 / 2 +cΔt (2)

[0076] In formula (2), [x' i ,y' i ,z' i ] represents the Beidou satellite coordinate information, i = 1, 2, 3, 4; [x j ,y j ,z j ] represents the position information of the power cover, j = 1, 2; R' ij represents the pseudorange from the i-th BeiDou satellite to the j-th power cover; c is the propagation speed of the signal in a vacuum, i.e., the speed of light c = 2.998×10 8 m / s; Δt is the clock difference between the Beidou satellite clock and the power cover terminal receiver clock. For the convenience of calculation, R ij =R' ij-cΔt is used to represent the distance between the Beidou satellite and the power cover terminal. Therefore, the positional relationship between the Beidou satellite and the power cover terminal can be expressed by formula (3):

[0077]

[0078] The position coordinates of the two power cover terminals can be obtained by the above formula (3). Then, the located power cover terminals are used as reference nodes, and the sensors are positioned according to the positional relationship between the power cover terminals and the sensors under the cable trench. Due to the special geometric structure of the cable trench, the sensors under the cable trench and the power cover terminals have a linear positional relationship. Therefore, only the two power cover terminals need to be located to realize the positioning of the sensors under the cable trench. j represents the distance from the sensor under the cable trench to the power cover, and the positional relationship between the two can be expressed as:

[0079] d j =[(x j -x) 2 +(y j -y) 2 +(z j -z) 2 ] 1 / 2 (4)

[0080] By solving formula (3) and formula (4) together, the position coordinates (x, y, z) of the sensor are obtained.

[0081] (3) Analysis of positioning error of pseudo-range. In the actual positioning process, if the two positioning processes are solved separately, that is, the positioning coordinates of the power cover are solved first, and then the positioning coordinates of the sensor are solved, a large positioning error will be generated. Because when the Beidou satellite locates the power cover terminal, the ranging signal is affected by the ionosphere and troposphere when passing through the atmosphere, which will cause errors in the positioning results; at the same time, when the power cover terminal is used as a reference node to locate the sensor, the signal is interfered by the electromagnetic environment in the cable trench, which will also cause positioning errors; in addition, since the sensor position coordinates are solved based on the position information of the power cover terminal, in the above two positioning projects, the positioning error of the power cover terminal in the first stage will aggravate the positioning error of the sensor in the second stage. To this end, this paper proposes a joint positioning algorithm based on Beidou positioning. According to the Beidou satellite position information collected by the ground control center and the position relationship between the power cover terminal and the sensor under the cable trench, the direct position relationship between the Beidou satellite and the sensor is established to achieve accurate positioning of the sensor under the cable trench.

[0082] 2. The distance between the power cover terminal and the sensor is determined by a distance measurement method based on signal reception strength: the electromagnetic environment in the cable trench is very complex. When the sensor sends data to the power cover terminal, the signal strength decreases as the signal transmission distance increases. The distance between the power cover terminal and the sensor is calculated based on the received signal strength and the existing wireless signal attenuation model. The relationship between signal strength and signal transmission distance can be expressed as:

[0083]

[0084] where [p(d)] dbm is the signal strength received by the signal receiver on the power cover terminal from the sensor; [p(d o )] dbm is the reference signal strength of the sensor at a distance d0 from the power cover terminal, where d0 is the reference distance; d is the transmission distance of the signal between the sensor and the power cover terminal; X dbm is a Gaussian random variable, which is used to represent the Gaussian white noise generated by the environment in the cable trench during signal transmission; n is the path loss index in the cable trench scenario;

[0085] Considering that the signal is easily interfered by the electromagnetic environment in the cable trench, in order to reduce the positioning error and improve the positioning accuracy, the power cover terminal is used to measure the received signal strength value from the same sensor multiple times to obtain multiple groups of measurement values. The weighted mean model is used to process the collected multiple groups of received signal strength values. Suppose the received signal strength value p k Total occurrences w k times, that is, w k is the weight value, w1+w2+…+w k =f, then the weighted average of the received signal strength can be expressed as:

[0086] p=(p1w1+p2w2+…+p k w k ) / f (6)

[0087] In order to simplify formula (6), the reference distance is set to 1m, that is, d o =1m; use p, p o They represent the signal receiving strength at the actual transmission distance and the reference distance respectively; ignoring the influence of noise during signal transmission, the distance from the sensor to the power cover terminal can be obtained as:

[0088]

[0089] Under the condition that the path loss index of the cable trench environment is known, the distance between the sensor and the two power covers can be calculated according to formula (7), which are represented by d1 and d2 respectively.

[0090] 3. Establish the positional relationship between Beidou satellite and the sensor in the cable trench, and use the transformation matrix and compensation matrix to improve the positioning accuracy of Beidou satellite for the sensor in the cable trench.

[0091] During the positioning process, since the sensor is installed in the cable trench and is blocked by the ground, the Beidou satellite cannot directly locate it. It is necessary to first locate the power cover terminal on the cable trench, and then use the located power cover terminal to locate the sensor in the cable trench. In this process, the positioning error of the power cover terminal will increase the positioning error of the sensor. In order to reduce the influence of the positioning error of the power cover terminal on the positioning of the sensor under the cable trench, the position relationship between the Beidou satellite and the sensor under the cable trench is established based on the Beidou satellite position information collected by the ground control center and the distance from the sensor under the cable trench to the power cover terminal, using the transformation matrix and compensation matrix. Then, the sensor under the cable trench is directly located using the position relationship between the Beidou satellite and the sensor under the cable trench, so as to improve the positioning accuracy of the sensor in the cable trench;

[0092] To set up the appropriate transformation matrix and compensation matrix, firstly, subtract the fourth term from the first three terms of the equation system in formula (3), and we can get:

[0093]

[0094] Formula (8) can be solved to obtain:

[0095] X e =A -1 B(9), express equation (9) in matrix form, where

[0096]

[0097]

[0098] Similarly, in order to express the positional relationship between the power cover terminal and the sensor under the cable trench in the form of a matrix, formula (4) is expanded as follows:

[0099]

[0100] Subtract the second term from the first term in the equation system in formula (11), and we get:

[0101]

[0102] Convert formula (12) into matrix form CX s =D, where

[0103] C=2[x1-x2 y1-y2 z1-z2],

[0104]

[0105] D=[x1 2 +y1 2 +z1 2 -x2 2 -y2 2 -z2 2 -d1 2 +d2 2 ], (13),

[0106] In order to reduce the influence of the positioning error of the power cover terminal on the positioning error of the sensor in the cable trench during the solution, according to the positional relationship between the Beidou satellite and the power cover terminal and between the power cover terminal and the sensor, the compensation matrix V, transformation matrix P and Q are set as follows:

[0107] V=[d2 2 -d1 2 ] (14),

[0108]

[0109] Q=||A -1 B|| -2 P -1 (DV) (16)

[0110] Then the position relationship between the Beidou satellite and the sensor under the cable trench can be expressed by a matrix:

[0111]

[0112]

[0113] Among them, matrix A and matrix B are obtained by collecting satellite data from the ground control center in the Beidou satellite positioning system.

[0114] In the actual positioning process, due to the influence of environmental noise, when solving the position coordinates of the sensor under the cable trench, the positioning error of the system often leads to no solution or multiple solutions. In order to calculate the position coordinates of the sensor more accurately, the least squares method is used to obtain formula (17) and formula (18):

[0115] The optimal approximate solution of , where the error square sum function S is introduced:

[0116] S(X S )=||CX S -D|| 2 (19)

[0117] Set When , the error square sum function S takes the minimum value, and the positioning error is the smallest at this time, which is recorded as:

[0118]

[0119] In order to obtain the minimum value of the error square sum function, the formula (20) is differentiated and its derivative value is set to 0, and we can get:

[0120] C T CX s =C T D (21),

[0121] From this, the optimal solution of the sensor position coordinates can be deduced as:

[0122]

[0123] Simulation Example

[0124] The above-mentioned method was simulated and the position coordinates of the two power cover terminals were set to (10m, 10m) and (50m, 50m), respectively. A power sensor was placed at the middle position (25m, 25m) between the two power cover terminals. The signal strength from the sensor was measured by the power cover terminal signal receiver. The distance from the sensor to the power cover terminal was calculated using the mean model. The two power cover terminals were located by four Beidou satellites. The two power cover terminals were then used as reference nodes to solve the position coordinates of the sensor under the cable trench. Due to the particularity of the cable trench scene, only the horizontal and vertical coordinates need to be considered when locating it. From the simulation results, it can be obtained that the positioning coordinates of the two power cover terminals are (10.0499m, 9.9490m) and (50.0971m, 49.9328m), respectively, and the positioning coordinates of the sensor are (25.0414m, 24.9575m). It can be seen that the position of the sensor under the cable trench can be accurately located through the joint positioning algorithm based on the Beidou system. A relatively small error will occur during the positioning process. The positioning error is mainly caused by the Beidou signal being affected by the ionosphere and troposphere when it propagates to the power cover plate through the atmosphere; and when the signal is directly transmitted between the power cover plate and the power sensor, the complex electromagnetic environment under the cable trench affects the signal reception strength, which will also cause positioning errors. In order to compare the positioning error, the positioning error value is defined as E. Assuming that the actual coordinates of the sensor under the cable trench are (x0, y0), and the sensor coordinates calculated by the Beidou-based joint positioning algorithm are (x, y), then:

[0125]

[0126] According to formula (23), the coordinate errors of the two power covers and the sensor are calculated to be 0.0720m, 0.1349m and 0.0593m respectively. The error generated by the positioning sensor is smaller than the positioning error of the positioning power cover.

[0127] In order to further prove that the joint positioning algorithm based on the Beidou system can reduce the influence of the positioning error of the power cover on the positioning error of the sensor when positioning the sensor, the positions of the two power covers are fixed at (10m, 10m) and (50m, 50m), and a power sensor is placed every 4m in the middle of the two power covers. The 9 power sensors in the middle of the two power covers are positioned. s1 ,y s1 ) represents the sensor coordinates obtained using the joint positioning algorithm based on the Beidou system, and E1 represents its positioning error value; (x s2 ,y s2 ) represents the sensor coordinates obtained by first positioning the power cover terminal and then positioning the sensor, E2 represents its positioning error value, and the simulation results are shown in Table 1.

[0128] 1 Table 1 Sensor positioning coordinates and error values

[0129]

[0130] like Figure 3 As shown in the figure, if the power cover terminal is positioned first, and then the sensor is positioned with the power cover terminal as the reference node, the positioning error value of the sensor is greater than the positioning error value of the two power cover terminals. This shows that in the positioning process, the positioning error of the power cover terminal will increase the error of sensor positioning; the sensor positioning error value generated by the joint positioning algorithm based on Beidou positioning is smaller than the positioning error value of the two power cover terminals. This method can effectively reduce the influence of the power cover terminal positioning error on the sensor positioning and improve the positioning accuracy of the sensor under the cable trench. It can be proved that the joint algorithm based on Beidou positioning can realize the positioning of the sensor in the cable trench, and can solve the problem of increased sensor positioning error caused by the positioning error of the power cover terminal.

[0131] References

[0132] [1]ZHOU H,FU N,MA,et al.Application of beidou satellite navigationsystem in tower monitoring system[J].Digital Communication World,2018(5):212-213,268.

[0133] [2]ZHANG B, ZHANG Y, LIU Z, et al. Construction scheme and application of BDS ground-based augmentation system of State Grid Shandong Electric Power[J]. Power System Protection and Control, 2020, 48(3): 70-76.

[0134] [3] Li Zhe, Liu Haoyu, She Zuochao. Exploration of the application of Beidou system in disaster prevention monitoring of transmission lines [J]. Sichuan Electric Power Technology, 2020(12): 71-74.

[0135] [4] Fan Yong. Research on comprehensive monitoring system of intelligent distribution network lines based on Beidou navigation system[D]. North China Electric Power University, 2017.

[0136] [5]LIU S,WANG Z,ZHU X,et al.The Design and application of beidousatellite navigation system in power distribution terminal conditionmonitoring[J].Electric Power Information and Communication Technology,2016,14(12):90-94..

[0137] [6]ZHANG B, ZHANG Y, LIU Z, et al. Construction scheme and application of BDS ground-based augmentation system of State Grid Shandong Electric Power[J]. Power System Protection and Control, 2020, 48(3): 70-76.

Claims

1. A power sensor positioning method suitable for cable trench scenarios, characterized in that: include: Step 1. Establish the Beidou positioning system model. Cable trench scenario model, a large number of transmission cables are laid in the cable trench, multiple power sensors are arranged at intervals on the transmission cables, the power cover terminal is fixed on the inner wall of the cable trench wellhead, and a ground user control center is set up; the position of the ground user control center in the Beidou positioning system is recorded as "point O", point O is taken as the origin, the plane where the cable trench is located is the xoy plane, and the spatial coordinate system o-xyz is established; in this coordinate system o-xyz, the coordinates of the four Beidou satellites are (x1', y1', z1'), (x'2, y'2, z'2), (x'3, y'3, z'3), (x'4, y'4, z'4); the position coordinates of the two power cover plates are (x1, y1, z1), (x2, y2, z2); the required sensor position coordinates are (x, y, z); Beidou satellites transmit ranging signals to the power cover terminal on the cable trench. The ground control center synchronizes the clock with the Beidou satellite to collect the transmission time taken for the ranging signal sent by each Beidou satellite to reach the power cover terminal. The sensors under the cable trench collect the temperature, humidity and position status information of the transmission cable, and then send the collected data to the power cover terminal. The power cover terminal processes the received data and reports the transmission cable status information to the ground control center. Step 2. Determination of the distance between the power cover terminal and the sensor, using a distance measurement method based on signal reception strength: The electromagnetic environment in the cable trench is very complex. When the sensor sends data to the power cover terminal, the signal strength decreases as the signal transmission distance increases. The distance between the power cover terminal and the sensor is calculated based on the received signal strength and the existing wireless signal attenuation model. The relationship between signal strength and signal transmission distance can be expressed as: where [p(d)] dbm is the signal strength received by the signal receiver on the power cover terminal from the sensor; [p(d o )] dbm The reference signal strength of the sensor at a distance d0 from the power cover terminal is measured by the power cover terminal, where d0 is the reference distance; d is the transmission distance of the signal between the sensor and the power cover terminal; X dbm is a Gaussian random variable, which is used to represent the Gaussian white noise generated by the environment in the cable trench during signal transmission; n is the path loss index in the cable trench scenario; Considering that the signal is easily interfered by the electromagnetic environment in the cable trench, in order to reduce the positioning error and improve the positioning accuracy, the power cover terminal is used to measure the received signal strength value from the same sensor multiple times to obtain multiple groups of measurement values. The weighted mean model is used to process the collected multiple groups of received signal strength values. Suppose the received signal strength value p k Total occurrences w k times, that is, w k is the weight value, w1+w2+···+w k =f, then the weighted average of the received signal strength can be expressed as: p=(p1w1+p2w2+···+p k w k ) / f (6) Step 3. Establish the positional relationship between the Beidou satellite and the sensor in the cable trench, and use the transformation matrix and compensation matrix to improve the positioning accuracy of the Beidou satellite for the sensor in the cable trench; During the positioning process, since the sensor is installed in the cable trench and is blocked by the ground, the Beidou satellite cannot directly locate it. It is necessary to first locate the power cover terminal on the cable trench, and then use the located power cover terminal to locate the sensor in the cable trench. In this process, the positioning error of the power cover terminal will increase the positioning error of the sensor. In order to reduce the influence of the positioning error of the power cover terminal on the positioning of the sensor under the cable trench, the position relationship between the Beidou satellite and the sensor under the cable trench is established based on the Beidou satellite position information collected by the ground control center and the distance from the sensor under the cable trench to the power cover terminal, the transformation matrix and compensation matrix are used to establish the position relationship between the Beidou satellite and the sensor under the cable trench; then the sensor under the cable trench is directly located using the position relationship between the Beidou satellite and the sensor under the cable trench, so as to improve the positioning accuracy of the sensor in the cable trench.

2. The power sensor positioning method applicable to the cable trench scene according to claim 1 is characterized in that: In step 1, in order to simplify formula (6), the reference distance is set to 1m, that is, d o =1m; use p, p o They represent the signal receiving strength at the actual transmission distance and the reference distance respectively; ignoring the influence of noise during signal transmission, the distance from the sensor to the power cover terminal can be obtained as: Under the condition that the path loss index of the cable trench environment is known, the distance between the sensor and the two power covers can be calculated according to formula (7), which are represented by d1 and d2 respectively.

3. The power sensor positioning method applicable to the cable trench scene according to claim 1 is characterized in that: The distance between the Beidou satellite and the power cover terminal is measured based on the pseudo-range positioning principle. The distance between the Beidou satellite and the power cover terminal is calculated by the time difference between the transmitted and received ranging signals, which can be expressed as formula (1): In formula (1), c is the propagation speed of the Beidou satellite ranging signal, and the propagation speed is; c = 2.998 × 10 8 m / s; t e (t) is the time when the power cover terminal receiver receives the ranging signal, t b (t-τ) is the time when the Beidou satellite transmits the ranging signal; τ is the actual propagation time from the ranging signal sent by the Beidou satellite to the signal received by the power cover terminal receiver; R' is used to represent the pseudorange between the power cover terminal and the Beidou satellite. Because there is a clock difference Δt between the power cover terminal receiver and the Beidou satellite, the obtained distance is not the actual geometric distance between the two, so the measured distance is called pseudorange.

4. The power sensor positioning method applicable to the cable trench scene according to claim 3 is characterized in that: The pseudo-range between the power cover terminal and the Beidou satellite, and the distance between the two power cover terminals and the four Beidou satellites are: R i ' j =[(x i '-x j ) 2 +(y i '-y j ) 2 +(z i '-z j ) 2 ] 1 / 2 +cΔt (2) In formula (2), [x i ',y i ',z i '] represents the Beidou satellite coordinate information, i = 1, 2, 3, 4; [x j ,y j ,z j ] represents the position information of the power cover, j = 1, 2; R i ' j represents the pseudorange from the i-th BeiDou satellite to the j-th power cover; c is the propagation speed of the signal in a vacuum, i.e., the speed of light c = 2.998×10 8 m / s; Δt is the clock difference between the Beidou satellite clock and the power cover terminal receiver clock. For the convenience of calculation, R ij =R i ' j -cΔt is used to represent the distance between the Beidou satellite and the power cover terminal. Therefore, the positional relationship between the Beidou satellite and the power cover terminal can be expressed by formula (3): The position coordinates of the two power cover terminals can be obtained by the above formula (3). Then, the located power cover terminals are used as reference nodes, and the sensors are positioned according to the positional relationship between the power cover terminals and the sensors under the cable trench. Due to the special geometric structure of the cable trench, the sensors under the cable trench and the power cover terminals have a linear positional relationship. Therefore, only the two power cover terminals need to be located to realize the positioning of the sensors under the cable trench. j represents the distance from the sensor under the cable trench to the power cover, and the positional relationship between the two can be expressed as: d j =[(x j -x) 2 +(y j -y) 2 +(z j -z) 2 ] 1 / 2 (4) By solving formula (3) and formula (4) together, the position coordinates (x, y, z) of the sensor are obtained.

5. The power sensor positioning method applicable to the cable trench scene according to claim 3 is characterized in that: The positioning error analysis of the pseudorange shows that in the actual positioning process, if the two positioning processes are solved separately, that is, the power cover positioning coordinates are solved first, and then the sensor positioning coordinates are solved, a large positioning error will be generated; because when the Beidou satellite is locating the power cover terminal, the ranging signal is affected by the ionosphere and troposphere when passing through the atmosphere, which will cause errors in the positioning results; at the same time, when the power cover terminal is used as a reference node to locate the sensor, the signal is interfered by the electromagnetic environment in the cable trench, which will also cause positioning errors; in addition, since the sensor position coordinates are solved based on the power cover terminal position information, in the above two positioning processes, the positioning error of the power cover terminal in the first stage will aggravate the positioning error of the sensor in the second stage.

6. The power sensor positioning method applicable to the cable trench scene according to claim 1 is characterized in that: The positional relationship between the Beidou satellite and the sensor under the cable trench is used to directly locate the sensor under the cable trench, thereby improving the positioning accuracy of the sensor in the cable trench; setting a suitable transformation matrix and compensation matrix, firstly subtracting the fourth term from the first three terms of the equation group in formula (3), and obtaining: Formula (8) can be solved as follows: X e =A -1 B (9), Formula (9) is expressed in matrix form, where Similarly, in order to express the positional relationship between the power cover terminal and the sensor under the cable trench in the form of a matrix, formula (4) is expanded as follows: Subtract the second term from the first term in the equation system in formula (11), and we get: Convert formula (12) into matrix form CX s =D, where C=2[x1-x2 y1-y2 z1-z2], <h2 style=";text-align:left;direction:ltr">D=[x1<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +y1<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +z1<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> -x2<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> -y2<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> -z2<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> -d1<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +d2<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> ], (13), In order to reduce the influence of the positioning error of the power cover terminal on the positioning error of the sensor in the cable trench during the solution, according to the positional relationship between the Beidou satellite and the power cover terminal and between the power cover terminal and the sensor, the compensation matrix V, transformation matrix P and Q are set as follows: V=[d2 2 -d1 2 ] (14), Q=||A -1 B|| -2 P -1 (D-V) (16) Then the position relationship between the Beidou satellite and the sensor under the cable trench can be expressed by a matrix: Among them, matrix A and matrix B are obtained by collecting satellite data from the ground control center in the Beidou satellite positioning system; In the actual positioning process, due to the influence of environmental noise, when solving the position coordinates of the sensor under the cable trench, the positioning error of the system will cause the solution result to be no solution or multiple solutions. In order to calculate the position coordinates of the sensor more accurately, the least squares method is used to obtain the optimal approximate solution of formula (17) and formula (18), and the error square sum function S is introduced here: S(X S )=||CX S -D|| 2 (19), Set When , the error square sum function S takes the minimum value, and the positioning error is the smallest at this time, which is recorded as: In order to obtain the minimum value of the error square sum function, the formula (20) is differentiated and its derivative value is set to 0, and we can get: C T CX s =C T D (21), From this, the optimal solution of the sensor position coordinates can be deduced as:

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