Design calculation method and system of urban rail transit AC3kV traction power supply system

Abstract

The invention discloses a design and calculation method and system for an AC3kV traction power supply system of urban rail transit. The method comprises the following steps: establishing a mathematical model of the traction power supply system; determining a basic assumed condition; dividing the traction network into N + b-1 branches according to the traction substation and the train position point, and calculating the resistance of each branch; each traction substation is expressed by an ideal voltage source and an equivalent resistor RS; treating the current taking train as a current source; establishing a matrix relationship through a Kirchhoff's current law and a Kirchhoff's voltage law, and solving each branch current and network point voltage; solving of the electrical parameters is completed; and determining a calculation principle and calculation content of the traction transformer, and determining the power of the traction substation and the capacity of the traction transformer through a calculation formula. A solid theoretical support is established for system calculation, and the problem that no reliable basis exists in electrical parameter calculation is effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of traction power supply for urban rail transit, and particularly to a design calculation method for an AC 3 kV traction power supply system for urban rail transit. Background Art

[0002] At present, the traction power supply systems for urban rail transit in China are mainly divided into DC systems and AC systems. Among them, the DC systems include DC 1500 V and DC 750 V, and the AC system is mainly AC 25 kV. These traditional traction power supply systems have played an important role in the long-term operation of urban rail transit, but there are also certain limitations. For example, the power supply distance of the DC system is relatively short, and more traction substations need to be added when applied to long lines, resulting in an increase in construction costs; although the AC 25 kV AC system has a long power supply distance, it has serious harmonic pollution and great interference to the communication system.

[0003] As a new type of traction power supply system pioneered at home and abroad, the AC 3 kV traction power supply system exhibits unique advantages and application potential. Its three-phase AC bilateral power supply method can effectively reduce line losses, improve power supply efficiency, and to a certain extent reduce harmonic effects, with better power supply stability and reliability. However, since it is a completely new power supply system, there is currently no systematic design calculation method corresponding to the AC 3 kV traction power supply system. The existing DC 1500 V and DC 750 V traction power supply systems adopt a DC bilateral power supply method, and adjacent two traction substations jointly supply power to the traction network in this section; while the existing AC 25 kV traction power supply system adopts an AC, single-phase unilateral power supply method. The AC 3 kV traction power supply system adopts an AC, three-phase bilateral power supply method, and its power supply method and electrical characteristics are significantly different from traditional systems, resulting in the inability of existing design calculation methods to be applicable to the design of the AC 3 kV traction power supply system.

[0004] In the absence of a targeted design calculation method, the design of the AC 3 kV traction power supply system lacks a reliable theoretical basis, is unable to accurately select electrical technical parameters, and is also difficult to select traction substations reasonably. This not only restricts the popularization and application of the AC 3 kV traction power supply system, but also may affect the safe and stable operation of urban rail transit. For example, improper selection of electrical parameters may lead to unstable train power supply, problems such as excessive voltage fluctuations and power supply interruptions. Therefore, there is an urgent need for a design calculation method applicable to the AC 3 kV traction power supply system to fill this technical gap and provide solid technical support for the engineering application of this new type of traction power supply system. Summary of the Invention

[0005] The present invention aims to provide a design calculation method specifically applicable to the AC 3 kV traction power supply system of urban rail transit. By establishing a scientific and comprehensive mathematical model of the traction power supply system, precisely considering various complex calculation conditions such as lines, train operations, trains, traction networks, and voltages, and applying unique calculation principles, accurate calculation of electrical parameters is achieved.

[0006] In view of the above defects or improvement requirements of the prior art, according to the first aspect of the present invention, the present invention provides a design calculation method for an AC 3 kV traction power supply system of urban rail transit, including:

[0007] S1. Collect line data, train operation data, train data, traction network data, and voltage parameters;

[0008] Determine the calculation time interval and the number of required moments. On the operation diagram within the calculation period, according to the number of required moments, obtain the corresponding number of instantaneous load diagrams, and calculate the corresponding instantaneous values of electrical parameters;

[0009] S2. Establish a calculation method for the traction power supply system, specifically as follows:

[0010] Determine the basic assumption conditions;

[0011] Divide the traction network into N + b - 1 branches according to the traction substation and train position points, where N represents the number of traction substations and b represents the number of trains; then calculate the resistance of each branch according to the known conditions;

[0012] Represent each traction substation with an ideal voltage source plus an equivalent resistance R S to represent;

[0013] Treat the current-taking trains as current sources;

[0014] Establish a matrix relationship through Kirchhoff's current law and Kirchhoff's voltage law, and solve the branch currents and node voltages;

[0015] Obtain the instantaneous current of the upfeed line based on the branch currents of the upfeed traction network; obtain the voltage at non-node locations by interpolation according to the node voltages; obtain the instantaneous power of the upfeed traction transformer from the instantaneous current of the feeder and the bus voltage; integrate the instantaneous current curve of the feeder to obtain the average current; integrate its square to obtain the effective current; obtain the effective current of the traction transformer according to the variance law;

[0016] S3. Determine the calculation principles and calculation contents of the traction transformer, and then determine the power of the traction substation and the capacity of the traction transformer through calculation formulas.

[0017] Furthermore, it is characterized in that the calculation formula for the instantaneous value of the electrical parameter in S1 is as follows: the instantaneous current i of the feeder gThe calculation formula is as follows:

[0018]

[0019] In the formula, i1, i2, …, i n represent the instantaneous current values of each train powered by the feeder at a certain moment;

[0020] The average current I of the feeder g The calculation formula is as follows:

[0021]

[0022] In the formula, i gj represents the instantaneous current of the feeder at the j-th moment; n represents the number of trains at the selected moments.

[0023] Furthermore, the basic assumption conditions in S2 are as follows:

[0024] It is assumed that the AC side voltages of all traction substations along the line are the same and stable, that is, the influence of the AC system change on the calculation is not considered;

[0025] It is assumed that the transformers of all traction substations along the line are regarded as voltage source branches with internal resistance;

[0026] It is assumed that the traction network system is a uniform and symmetric structure, and the whole traction network system has a consistent resistance per unit length;

[0027] The coordinates of the traction network feeding point are used as the position coordinates of the traction substation, and it is considered that the traction network feeding point and the return point are at the same coordinate position;

[0028] The trains running on the line are regarded as "ideal current sources" and move on the line according to the description of the operation diagram;

[0029] It is assumed that there are b trains, N traction substations in the traction power supply network, and at the starting moment, multiple trains are taking current in the up direction.

[0030] Furthermore, the method for calculating the resistance of each branch in S2 according to the known conditions is as follows:

[0031] Let R1, R2, R3, …, R N+b－1 be the traction network resistances of the 1st branch, the 2nd branch, the 3rd branch, …, the (N + b - 1)-th branch respectively; since the positions of the current-taking trains are given, the positions of each traction substation are determined, and the traction network resistance is uniform and symmetric, the above resistances R1, R2, R3, …, R N+b－1 can be calculated according to the formula:

[0032] R i = L i r

[0033] where \(i = 1, 2, \cdots, N + b - 1, L\) i is the distance between points, \(R\) i represents the traction network resistance of each branch, and \(r\) is the resistance per unit length of the traction network.

[0034] Furthermore, the method for solving the branch currents and substation voltages in S2 is as follows:

[0035] Let the currents of each traction network branch be \([I_1, I_2, I_3, \cdots, I\) N+b－1 , and the currents of each traction substation branch be \([I\) N+b , \(I\) N+b+1 , \(\cdots, I\) 2N+b－1 ; where \(I_1, I_2, I_3, \cdots, I\) N+b－1 are the traction network currents of the 1st branch, 2nd branch, 3rd branch, \(\cdots\), \((N + b - 1)\)th branch respectively; \(I\) N+b , \(I\) N+b+1 , \(\cdots, I\) 2N+b－1 are the currents of the \((N + b)\)th traction substation branch, \((N + b + 1)\)th traction substation branch, \(\cdots\), \((N + b - 1)\)th traction substation branch respectively;

[0036] Let \(I = [I_1, I_2, I_3, \cdots, I\) N+b－1 , \(I\) N+b , \(I\) N+b+1 , \(\cdots, I\) 2N+b－1 T ; \(B = [I\) a1 , \(I\) a2 , \(I\) a3 , \(\cdots, I\) ab , 0, 0, \(\cdots, 0] T ; where \(b\) represents the number of trains in the traction power supply network, \(I\) a1 represents the current value of the first train in the \(a\)th branch, \(I\) a2 represents the current value of the second train in the \(a\)th branch, and so on, \(I\) ab represents the current value of the \(b\)th train in the \(a\)th branch; the array \(B\) contains \(b + 2N - 1\) elements, and the number of elements with a value of 0 is \(2N - 1\).

[0037] Let \(A\) be a \((b + 2N - 1)×(b + 2N - 1)\) matrix, where the first \(b\) rows are established according to Kirchhoff's current law at each train position point, the \((b + 1)\)th to \((b + N)\)th rows are established according to Kirchhoff's current law at each traction substation position point, and from the \((b + N + 1)\)th to \((b + 2N - 1)\)th rows are established successively according to Kirchhoff's voltage law between the positive equal - potential points of two adjacent traction substations.

[0038] The matrix equation of the up - line traction power supply network is: ​

[0039] I = A -1 B

[0040] Wherein, I is an array of current values of the traction network branch and the traction substation branch to be solved; A is a current-voltage matrix established according to Kirchhoff's current law and Kirchhoff's voltage law; B is an array composed of all train vehicles and zero elements in all branches; the current I can be obtained by using this equation, and after obtaining the branch currents, the branch currents and the voltages of each network point can be calculated:

[0041]

[0042] Wherein, R S represents the equivalent resistance of the power supply provided by the traction network, and R1, R2, R3,..., R N+b－1 are the traction network resistances of the first branch, the second branch, the third branch,..., the (N + b - 1)th branch respectively; U1, U2, U3,..., U N+b－1 are the traction network voltages of the first branch, the second branch, the third branch,..., the (N + b - 1)th branch respectively; I1, I2, I3,..., I N+b－1 are the traction network currents of the first branch, the second branch, the third branch,..., the (N + b - 1)th branch respectively.

[0043] Furthermore, the S2 further includes:

[0044] The mathematical model under the abnormal bilateral power supply mode is considered as follows:

[0045] When the end traction substation is disconnected from the grid, between the end traction substation and the secondary end traction substation for power supply, which was originally bilateral power supply, will be changed to unilateral power supply by the secondary end traction substation. At this time, the equivalent network can be established by removing the faulty end traction substation;

[0046] When the intermediate traction substation is disconnected from the grid, it is divided into two cases:

[0047] Case 1: The corresponding power supply section adopts the "large bilateral power supply mode", and at this time, the equivalent network can be established by removing the faulty intermediate substation;

[0048] Case 2: The corresponding power supply section adopts the unilateral power supply mode, and at this time, the original equivalent network can be divided into two independent equivalent networks on the left and right to establish.

[0049] Furthermore, it is characterized in that the calculation principle in the S3 is as follows:

[0050] Meet the requirements of the long-term peak-hour traffic volume: the load factor of the traction unit during the peak hour is between 90% and 100%;

[0051] Under normal circumstances, two traction transformers operate in parallel to jointly bear the traction load of this substation;

[0052] When any traction substation fails and is disconnected from the grid, relying on the overload capacity of adjacent traction substations, the ability to transport passengers is not reduced, enabling the normal operation of urban rail transit;

[0053] Overload capacity of traction transformers: continuous operation at 100% In; operation for 2 h at 150% In; operation for 1 min at 300% In; In represents the rated current;

[0054] When one traction transformer in the traction substation fails or is taken out of service for maintenance, the other set of traction transformers continues to operate when the overload capacity and harmonic conditions are met.

[0055] Furthermore, the calculation content in S3 is as follows:

[0056] Under the normal double-sided operation mode, the traction load borne by the traction transformer groups of each traction substation;

[0057] When any intermediate traction substation is disconnected from the grid, the traction load borne by the traction transformers of adjacent traction substations that form the large double-sided power supply mode;

[0058] When the terminal traction substation is disconnected from the grid, the traction load borne by the traction transformer of the sub-terminal traction substation;

[0059] When a set of traction transformers in a traction substation is taken out of service, the traction load borne by the other set of traction transformers in this substation.

[0060] As the second aspect of the present invention, the present invention provides a design calculation system for an urban rail transit AC 3 kV traction power supply system, which is characterized by including:

[0061] A traction power supply system mathematical model unit, which is used to collect line data, train operation data, train data, traction network data, and voltage parameters; within the calculation period, n instantaneous load diagrams are obtained by taking n moments according to the train operation diagram of the power supply section, and n sets of instantaneous values of electrical parameters are obtained through calculation;

[0062] A calculation unit of the traction power supply system, which is used to implement the following processes:

[0063] Determine the basic assumption conditions;

[0064] According to the positions of traction substations and train points, the traction network is divided into N + b - 1 branches, and then the resistance of each branch is calculated according to the known conditions;

[0065] Each traction substation is represented by an ideal voltage source plus an equivalent resistance;

[0066] The current-taking trains are regarded as current sources;

[0067] Establish matrix relationships through Kirchhoff's current law and Kirchhoff's voltage law to solve the currents of each branch and the voltages of network nodes.

[0068] Obtain the instantaneous current of the upfeed line based on the currents of each branch of the up-traction network; obtain the voltage at non-node positions according to the node voltages through interpolation; obtain the instantaneous power of the up-traction transformer from the instantaneous current of the feeder and the bus voltage; integrate the instantaneous current curve of the feeder to obtain the average current; integrate the square of the instantaneous current to obtain the effective current; obtain the effective current of the traction transformer according to the variance law.

[0069] The traction transformer capacity calculation unit is used to determine the calculation principles and calculation contents of the traction transformer, and then determine the power of the traction substation and the capacity of the traction transformer through calculation formulas.

[0070] As the third aspect of the present invention, the present invention also provides a computer-readable storage medium, on which a computer program is stored, and the computer program is executed by a processor to perform any step of the above-mentioned design calculation method for the urban rail transit AC 3 kV traction power supply system.

[0071] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the following beneficial effects can be achieved:

[0072] 1. The design calculation method for the urban rail transit AC 3 kV traction power supply system of the present invention, by creating a mathematical model under the condition of three-phase traction power supply for the first time, precisely considering various complex calculation conditions such as lines, train operations, trains, traction networks, and voltages, and applying a unique calculation principle, builds a solid theoretical support for system calculation, and effectively solves the problem of no reliable basis for calculating electrical parameters.

[0073] 2. The design calculation method for the urban rail transit AC 3 kV traction power supply system of the present invention, by constructing a complete set of calculation methods, covering basic assumptions, mathematical model construction, electrical parameter solution, and model consideration under different operation modes, provides a comprehensive and systematic theoretical basis for the selection of various electrical technical parameters and the selection of traction substations, ensuring the stable operation of the traction power supply system under various working conditions.

[0074] 3. The design calculation method for the urban rail transit AC 3 kV traction power supply system of the present invention, by establishing a targeted traction transformer capacity calculation method, clarifying the calculation principles and contents, accurately determining the transformer capacity, meeting the requirements of the long-term peak-hour traffic volume, and ensuring that the urban rail transit can still operate safely, stably, and efficiently under different operation scenarios, such as when the traction substation fails and is disconnected, which strongly promotes the wide application of the AC 3 kV traction power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 Flow chart of the design calculation method for the urban rail transit AC 3 kV traction power supply system according to an embodiment of the present invention;

[0076] Figure 2 Power supply system diagram corresponding to the calculation method according to an embodiment of the present invention;

[0077] Figure 3 Schematic diagram of the train operation diagram and train current curve for the power supply section ABC according to an embodiment of the present invention;

[0078] Figure 4 Schematic diagram of the mathematical model of the up - line traction power supply network according to an embodiment of the present invention;

[0079] Figure 5 Schematic diagram of the system unit according to an embodiment of the present invention. Detailed implementation manners

[0080] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0081] Embodiment 1

[0082] Please refer to Figure 1 , Embodiment 1 of the present invention provides a design calculation method for an urban rail transit AC 3 kV traction power supply system, including:

[0083] S1. Establish a mathematical model of the traction power supply system

[0084] Please refer to Figure 2 , Figure 2 is the AC 3 kV power supply system diagram, where the components within the dashed box are the composition of the traction power supply system. Embodiment 1 of the present invention proposes a corresponding design calculation method for the traction power supply system, and the process of establishing its mathematical model is as follows:

[0085] 1.1 Calculation conditions

[0086] Collect line data, train operation data, train data, traction network data, and voltage parameters; among them, the line data includes: line length, gradient, number of stations, station spacing, etc.; the train operation data includes: operation route, vehicle formation, number of departures per peak hour, departure time, stop time, etc.; the train data includes: train current curve, train speed curve, and train time curve, etc.; the traction network data includes: unit impedance of the traction network and running rails, etc.; the voltage parameters include: no - load voltage of the traction substation, rated voltage of the traction network, etc.;

[0087] 1.2 Calculation principle

[0088] Determine the calculation time interval and the number of required moments. On the operation diagram within the calculation period, according to the number of required moments, obtain the corresponding number of instantaneous load diagrams and calculate the corresponding instantaneous values of electrical parameters; the specific details are as follows:

[0089] In the traction power supply system targeted in this embodiment, the uplink line is taken as an example for illustration here, and the calculation method for the downlink line is also applicable to this method. Please refer to Figure 3 , Figure 3 is the train operation diagram for the ABC power supply section. The abscissa represents time (t), and the ordinate represents distance (l). The traction substations are located at Station A and Station C. There are a total of four trains operating in the power supply section (within the time period of 6:00 - 8:00). Trains 1 and 3 are downlink trains, and trains 2 and 4 are uplink trains. The current consumption situation of the downlink trains (i.e., the i = f(l) curve) is plotted on the left side of the figure, with the abscissa being the current value i and the ordinate being the running distance l. The current consumption situation of the uplink trains is plotted on the right side of the figure, and the axis representation method is the same as that on the left side.

[0090] At any moment on the operation diagram, such as the t1 - t1 line, its intersection points a and b with the train operation time curve t = f(l) indicate that there are trains 1 and 2 operating in this section at this moment. The current consumed by the downlink train 1 at this time can be found from point a on the downlink train current curve on the left side to obtain the i1 value. Similarly, the current consumed by the uplink train 2 at this time can be found from point b on the right side to obtain the i2 value. In this way, the number of trains operating in the power supply section at the t1 - t1 moment, the current values consumed by each of them, and the positions of the trains can be obtained. As Figure 2 shown, such a diagram is called the "instantaneous load" diagram of the power supply section. According to the circuit calculation method for this instantaneous load diagram, the instantaneous values of the electrical parameters we need at this moment can be calculated, such as the feeder current, train voltage drop, traction network voltage loss, etc.

[0091] Take n moments (t1, t2,..., t n ) on the operation diagram within the calculation period (such as 2h), and the interval between them is calculated in minutes or seconds. In this way, n instantaneous load diagrams can be obtained, and n sets of instantaneous values of electrical parameters can be obtained. Taking the calculation of the average current value of the feeder in the double - sided power supply section as an example for illustration.

[0092] The instantaneous current i of the feeder g The calculation formula is as follows:

[0093]

[0094] In the formula, i1, i2,..., i n represent the instantaneous current values of each train supplied by the feeder at a certain moment;

[0095] Average current I of the feeder g The calculation formula is as follows:

[0096]

[0097] In the formula, i gj represents the instantaneous current of the feeder at the j-th moment; n represents the number of trains at the selected moments.

[0098] S2. Establish a calculation method for the traction power supply system as follows:

[0099] 2.1 Basic assumption conditions

[0100] Determine the basic assumption conditions as follows:

[0101] Assume that the AC-side voltages of all traction substations along the line are the same and stable, that is, the influence of the AC system change on the calculation is not considered;

[0102] Assume that the transformers of all traction substations along the line are regarded as voltage source branches with internal resistance;

[0103] Assume that the traction network system is a uniform and symmetric structure, and the whole traction network system has a consistent resistance per unit length;

[0104] Take the coordinates of the traction network feeding point as the coordinates of the traction substation location, and consider that the traction network feeding point and the return point are at the same coordinate position;

[0105] Regard the trains running on the line as "ideal current sources" and move along the line according to the description of the operation diagram;

[0106] Assume that there are b trains, N traction substations (N>2) in the traction power supply network, and at the starting moment, multiple trains are taking current in the up direction.

[0107] 2.2 Construction of the mathematical model

[0108] Please refer to Figure 4 , taking the up-line as an example, establish a mathematical model.

[0109] Now, the mathematical model of the up-line traction power supply network is described as follows:

[0110] In the equivalent circuit, the position points of the traction substations and the train position points divide the traction network into N + b - 1 branches.

[0111] R1, R2, R3,..., R N+b－1They are the traction network resistances of the 1st branch, 2nd branch, 3rd branch, …, (N + b - 1)th branch respectively. Since the positions of the current-taking trains are given, the positions of each traction substation are determined, and the traction network resistance is uniformly symmetric, the above resistances R1, R2, R3, …, R N+b－1 can be calculated according to R1 = L1r (i = 1, 2, …, N + b - 1), where L1 is the distance between each point and r is the resistance per unit length of the traction network.

[0112] Each traction substation is represented by an ideal voltage source in series with an equivalent resistance R S . R S is the equivalent resistance that provides power for the traction network.

[0113] The trains taking current from the traction network can be treated as current sources. Let the currents of each traction network branch be [I1, I2, I3, …, I N+b－1 , and the currents of each traction substation branch be [I N+b , I N+b+1 , …, I 2N+b－1 ; among them, I1, I2, I3, …, I N+b－1 are the traction network currents of the 1st branch, 2nd branch, 3rd branch, …, (N + b - 1)th branch respectively; I N+b , I N+b+1 , …, I 2N+b－1 are the currents of the (N + b)th traction substation branch, (N + b + 1)th traction substation branch, …, (N + b - 1)th traction substation branch respectively;

[0114] Let I = [I1, I2, I3, …, I N+b－1 , I N+b , I N+b+1 , …, I 2N+b－1 T ; B = [I a1 , I a2 , I a3 , …, I ab , 0, 0, …, 0] T ; where b represents the number of trains in the traction power supply network, I a1 represents the current value of the first train in the ath branch, I a2 represents the current value of the second train in the ath branch, and so on, I ab represents the current value of the bth train in the ath branch; the array B contains b + 2N - 1 elements, and the number of elements with a value of 0 is 2N - 1.

[0115] ​Let A be a (b + 2N - 1)×(b + 2N - 1) matrix. Among them, the first b rows are established according to Kirchhoff's current law by each train position point, the (b + 1)-th row to the (b + N)-th row are established according to Kirchhoff's current law by each traction substation position point, and from the (b + N + 1)-th row to the (b + 2N - 1)-th row are successively established according to Kirchhoff's voltage law between the positive equal-potential points of two adjacent traction substations.

[0116] The matrix equation of the up-traction power supply network is:

[0117] I = A -1 B

[0118] In the formula, I is the array of the current values of the traction network branches and the traction substation branches to be solved; A is the current-voltage matrix established according to Kirchhoff's current law and Kirchhoff's voltage law; B is the array composed of all train vehicles and 0 elements in all branches; the current I can be obtained by using this equation. After obtaining the currents of each branch, the currents of each branch and the voltages of each network node can be calculated:

[0119]

[0120] In the formula, R S represents the equivalent resistance of the power supply provided by the traction network, and R1, R2, R3,..., R N+b－1 are the traction network resistances of the first branch, the second branch, the third branch,..., the (N + b - 1)-th branch respectively; U1, U2, U3,..., U N+b－1 are the traction network voltages of the first branch, the second branch, the third branch,..., the (N + b - 1)-th branch respectively; I1, I2, I3,..., I N+b－1 are the traction network currents of the first branch, the second branch, the third branch,..., the (N + b - 1)-th branch respectively.

[0121] 2.3 Solution of Electrical Parameters

[0122] According to the currents of each branch of the up-traction network that have been obtained, the instantaneous current of the up-feed line of the traction substation can be obtained;

[0123] According to the voltages of each node of the up-traction network that have been obtained, the voltage at any non-node position of the up-traction network can be obtained by using the interpolation method;

[0124] According to the instantaneous current of each feed line and the bus voltage, the instantaneous power of the up-traction transformer can be obtained;

[0125] Integrate the instantaneous current curve of the feed line f(t) = I(t) to obtain the average current of the up-line feed line;

[0126] Integrate the square of the instantaneous current curve of the feed line f(t) = I(t) to obtain the effective current of the up-line feed line;

[0127] According to the variance law, the effective current of the corresponding traction transformer can be obtained.

[0128] 2.4 Mathematical Models of Other Operating Modes

[0129] The mathematical model under the normal double-sided power supply mode is described above. The mathematical models under other operating modes can be considered as follows:

[0130] When the terminal traction substation is disconnected from the grid, between the terminal traction substation and the power supply to the next terminal traction substation, which was originally double-sided power supply, it will be changed to single-sided power supply by the next terminal traction substation. At this time, the equivalent network can be established by removing the faulty terminal traction substation.

[0131] When the intermediate traction substation is disconnected from the grid, there are two cases.

[0132] Case 1: The corresponding power supply section adopts the "large double-sided power supply mode". At this time, the equivalent network can be established by removing the faulty intermediate substation.

[0133] Case 2: The corresponding power supply section adopts the single-sided power supply mode. At this time, the original equivalent network can be divided into two independent equivalent networks on the left and right to establish.

[0134] S3. Establishing the Calculation Method for the Capacity of Traction Transformers

[0135] Determine the calculation principles and calculation contents of the traction transformer, and then determine the power of the traction substation and the capacity of the traction transformer through the calculation formula. The specific content is as follows:

[0136] 3.1 Calculation Principles of Traction Transformers

[0137] It should meet the requirements of the long-term peak-hour traffic volume: the load factor of the traction unit during peak hours should be preferably between 90% and 100%.

[0138] Under normal circumstances, two traction transformers operate in parallel to jointly bear the traction load of this substation.

[0139] When any traction substation fails and is disconnected from the grid, relying on the overload capacity (150% In, 2h) of the adjacent traction substation, the ability to transport passengers is not reduced, so that the urban rail transit operates normally.

[0140] Overload capacity of traction transformers: continuous operation at 100% In; operation at 150% In for 2h; operation at 300% In for 1min;

[0141] When one of the traction transformers in the traction substation fails or is taken out of operation for maintenance, the other set of traction transformers can continue to operate when the overload capacity and harmonic conditions are met.

[0142] 3.2 Calculation Contents of Traction Transformer

[0143] Under the normal double - line operation mode, the traction loads borne by the traction transformer groups of each traction substation

[0144] When any intermediate traction substation is disconnected from the grid, the traction loads borne by the traction transformers of the adjacent traction substations that form the large double - line power supply mode

[0145] When the end traction substation is disconnected from the grid, the traction loads borne by the traction transformers of the sub - end traction substations

[0146] When one set of traction transformers in a traction substation is taken out of operation, the traction loads borne by the other set of traction transformers in this substation

[0147] 3.3 Calculation Methods of Traction Transformer

[0148] Power of traction substation:

[0149] P Σ =k c k δ U c I xΣ

[0150] In the formula, P Σ represents the power of the traction substation; K c represents the coefficient for increasing traction network losses; K δ represents the coefficient for increasing train power consumption; U c represents the rated voltage of the traction network (kV); I X∑ represents the total effective current of the traction substation (A);

[0151] Capacity of traction transformer:

[0152] S Σ ≥1.1P Σ

[0153] In the formula, S Σ represents the capacity of the traction transformer, and P Σ represents the power of the traction substation;

[0154] Thus, the capacity S of the traction transformer is determined Σ .

[0155] Example 2

[0156] Please refer to Figure 5 , this Example 2 provides a design calculation system for the urban rail transit AC 3kV traction power supply system, including:

[0157] The traction power supply system mathematical model unit is used to collect line data, train operation data, train data, traction network data, and voltage parameters; within the calculation period, n instantaneous load diagrams are obtained at n moments according to the train operation diagram of the power supply section, and n sets of instantaneous electrical parameter values are obtained through calculation.

[0158] The calculation unit of the traction power supply system is used to implement the following processes:

[0159] Determine the basic assumptions.

[0160] The traction network is divided into N + b - 1 branches according to the traction substation and train position points, and then the resistance of each branch is calculated according to the known conditions.

[0161] Each traction substation is represented by an ideal voltage source plus an equivalent resistance.

[0162] The current-taking train is regarded as a current source.

[0163] Matrix relationships are established through Kirchhoff's current law and Kirchhoff's voltage law to solve the current of each branch and the node voltage.

[0164] Based on the current of each branch of the up-line traction network, the instantaneous current of the up-line feeder is obtained; the voltage at non-node points is obtained by interpolation according to the node voltage; the instantaneous power of the up-line traction transformer is obtained from the instantaneous current of the feeder and the bus voltage; the average current is obtained by integrating the instantaneous current curve of the feeder; the effective current is obtained by integrating its square; the effective current of the traction transformer is obtained according to the variance law.

[0165] The traction transformer capacity calculation unit is used to determine the calculation principles and calculation contents of the traction transformer, and then determine the power of the traction substation and the capacity of the traction transformer through calculation formulas.

[0166] Embodiment 3

[0167] Embodiment 3 of the present application also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, any step of the design calculation method of the urban rail transit AC 3 kV traction power supply system can be realized.

[0168] The computer-readable storage medium may include: various media such as USB flash drives, mobile hard disks, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical discs that can store program codes.

[0169] For the introduction of the computer-readable storage medium provided in the present application, please refer to the above method embodiments, and the present application will not elaborate here.

[0170] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A design calculation method for an urban rail transit AC 3 kV traction power supply system, characterized in that, Including: S1. Collect line data, train operation data, train data, traction network data, and voltage parameters; Determine the calculation time interval and the number of required moments. On the train operation diagram within the calculation period, obtain the corresponding number of instantaneous load diagrams according to the number of required moments, and calculate the corresponding instantaneous values of electrical parameters; S2. Establish a calculation method for the traction power supply system as follows: Determine the basic assumptions; Divide the traction network into N + b - 1 branches according to the traction substation and train position points, where N represents the number of traction substations and b represents the number of trains; then calculate the resistance of each branch according to the known conditions; Each traction substation is represented by an ideal voltage source in series with an equivalent resistance R S ; Treat the current-taking trains as current sources; Establish a matrix relationship through Kirchhoff's current law and Kirchhoff's voltage law to solve the current of each branch and the node voltage; Obtain the instantaneous current of the upfeed line based on the current of each branch of the up-traction network; obtain the voltage at non-node points by interpolation according to the node voltage; obtain the instantaneous power of the up-traction transformer from the instantaneous current of the feeder and the bus voltage; integrate the instantaneous current curve of the feeder to obtain the average current; integrate its square to obtain the effective current; obtain the effective current of the traction transformer according to the variance law; S3. Determine the calculation principles and calculation content of the traction transformer, and then determine the power of the traction substation and the capacity of the traction transformer through calculation formulas.

2. The design calculation method of an urban rail transit AC 3 kV traction power supply system according to claim 1, characterized in that, The calculation formula for the instantaneous value of the electrical parameter in S1 is as follows: The instantaneous current i of the feeder g The calculation formula is as follows: where i1, i2, …, i n represent the instantaneous current values of each train powered by the feeder line at a certain instant; Average current I of the feeder g The calculation formula is as follows: Where, i gj represents the instantaneous current of the feeder at the j-th moment; n represents the number of trains at the selected moments.

3. The design calculation method of an urban rail transit AC 3 kV traction power supply system according to claim 1, characterized in that, The basic assumptions in S2 are as follows: Assume that the AC-side voltages of all traction substations along the line are the same and stable, that is, the influence of AC system changes on the calculation is not considered; Assume that the transformers of all traction substations along the line are regarded as voltage source branches with internal resistance; Assume that the traction network system is a uniform and symmetric structure, and the whole traction network system has a consistent resistance per unit length; Take the coordinates of the traction network feeding point as the position coordinates of the traction substation, and consider that the traction network feeding point and the return point are at the same coordinate position; Regard the trains running on the line as "ideal current sources" and move along the line according to the description of the train operation diagram; Assume that there are b trains, N traction substations, and a starting moment in the traction power supply network, and multiple trains are taking current in the up direction.

4. The design calculation method of an urban rail transit AC 3 kV traction power supply system according to claim 1, characterized in that, The method for calculating the resistance of each branch according to the known conditions in S2 is: Let R1, R2, R3, …, R N+b－1 be the traction network resistances of the 1st branch, 2nd branch, 3rd branch, …, (N + b - 1)th branch respectively; since the positions of the current-taking trains are given, the positions of the traction substations are determined, and the traction network resistance is uniformly symmetric, the above resistances R1, R2, R3, …, R can be calculated according to the formula N+b－1 as follows: R i = L i r where \(i = 1, 2, \ldots, N + b - 1, L\) i is the distance between each point, \(R\) i represents the traction network resistance of each branch, and \(r\) is the resistance per unit length of the traction network.

5. The design calculation method of an urban rail transit AC 3 kV traction power supply system according to claim 1, characterized in that, The method for solving the current of each branch and the node voltage in S2 is: Let the currents of each traction network branch be [I1, I2, I3, …, I N+b－1 , and the currents of each traction substation branch be [I N+b , I N+b+1 , …, I 2N+b－1 ; among them, I1, I2, I3, …, I N+b－1 are the traction network currents of the 1st branch, 2nd branch, 3rd branch, …, (N + b - 1)th branch respectively; I N+b , I N+b+1 , …, I 2N+b－1 are the currents of the (N + b)th traction substation branch, (N + b + 1)th traction substation branch, …, (N + b - 1)th traction substation branch respectively; Let \(I = [I_1, I_2, I_3, \ldots, I N+b－1 , I N+b , I N+b+1 , \ldots, I 2N+b－1 T ; \(B = [I a1 , I a2 , I a3 , \ldots, I ab , 0, 0, \ldots, 0] T ; where \(b\) represents the number of trains in the traction power supply network, \(I a1 represents the current value of the first vehicle in the \(a\)-th branch, \(I a2 represents the current value of the second vehicle in the \(a\)-th branch, and so on. \(I ab represents the current value of the \(b\)-th vehicle in the \(a\)-th branch; the array \(B\) contains \(b + 2N - 1\) elements, and the number of elements with a value of 0 is \(2N - 1\).​ Let A be a (b + 2N - 1) × (b + 2N - 1) matrix, where the first b rows are established according to Kirchhoff's current law by each train position point, the b + 1th to b + Nth rows are established according to Kirchhoff's current law by each traction substation position point, and from the b + N + 1th to b + 2N - 1th rows are successively established according to Kirchhoff's voltage law between the positive equal-potential points of adjacent two traction substations; The matrix equation of the up-traction power supply network is: I = A -1 B In the formula, I is the array of current values of the traction network branches and traction substation branches to be solved; A is the current-voltage matrix established according to Kirchhoff's current law and Kirchhoff's voltage law; B is the array composed of all trains and 0 elements in all branches; the current I can be obtained by using this equation, and after obtaining the current of each branch, the current of each branch and the node voltage can be calculated: Wherein, R S represents the equivalent resistance of the traction network for providing power, and R1, R2, R3, …, R N+b－1 are respectively the traction network resistances of the first branch, the second branch, the third branch, …, the (N + b - 1)-th branch; U1, U2, U3, …, U N+b－1 are respectively the traction network voltages of the first branch, the second branch, the third branch, …, the (N + b - 1)-th branch; I1, I2, I3, …, I N+b－1 are respectively the traction network currents of the first branch, the second branch, the third branch, …, the (N + b - 1)-th branch.

6. The design calculation method of an urban rail transit AC 3 kV traction power supply system according to claim 1, characterized in that The content in S2 also includes: The mathematical model under the abnormal bilateral power supply mode is considered as follows: When the end traction substation is disconnected from the grid, between the end traction substation and the power supply to the next-end traction substation, which was originally bilateral power supply, will be changed to unilateral power supply by the next-end traction substation. At this time, the equivalent network can be established by removing the faulty end traction substation; When the intermediate traction substation is disconnected from the grid, there are two cases: Case 1: The corresponding power supply section adopts the "large bilateral power supply mode". At this time, the equivalent network can be established by removing the faulty intermediate substation; Case 2: The corresponding power supply section adopts the unilateral power supply mode. At this time, the original equivalent network can be divided into two independent equivalent networks on the left and right to establish.

7. The design calculation method of an urban rail transit AC 3 kV traction power supply system according to claim 1, characterized in that The calculation principle in S3 is as follows: Meet the requirements of the peak-hour traffic volume in the long term: The load factor of the traction units during the peak hour is between 90% and 100%; Under normal circumstances, two traction transformers operate in parallel to jointly bear the traction load of this substation; When any traction substation fails and is disconnected from the grid, relying on the overload capacity of the adjacent traction substation, the ability to transport passengers is not reduced, so that the urban rail transit operates normally; The overload capacity of the traction transformer: continuous operation at 100% In; operation for 2 h at 150% In; operation for 1 min at 300% In; In represents the rated current; When one of the traction transformers in the traction substation fails or is taken out of operation for maintenance, the other set of traction transformers continues to operate when the overload capacity and harmonic conditions are met.

8. The design calculation method of an urban rail transit AC 3 kV traction power supply system according to claim 1, characterized in that, The calculation content in S3 is: Under the normal bilateral operation mode, the traction load borne by each traction transformer group in the traction substation; When any intermediate traction substation is disconnected from the grid, the traction load borne by the traction transformers of the adjacent traction substations that form the large bilateral power supply mode; When the end traction substation is disconnected from the grid, the traction load borne by the traction transformer of the next-end traction substation; When a set of traction transformers in the traction substation is taken out of operation, the traction load borne by the other set of traction transformers in this substation.

9. A design calculation system for an urban rail transit AC 3 kV traction power supply system, characterized in that, It includes: The traction power supply system mathematical model unit is used to collect line data, train operation data, train data, traction network data, and voltage parameters; within the calculation period, n instantaneous load diagrams are obtained by taking n moments according to the train operation diagram of the power supply section, and n sets of instantaneous electrical parameter values are obtained through calculation; The calculation unit of the traction power supply system is used to implement the following processes: Determine the basic assumption conditions; According to the positions of the traction substations and the train points, the traction network is divided into N + b - 1 branches, and then the resistance of each branch is calculated according to the known conditions; Each traction substation is represented by an ideal voltage source plus an equivalent resistance; The current-taking train is regarded as a current source; Establish a matrix relationship through Kirchhoff's current law and Kirchhoff's voltage law to solve the current of each branch and the node voltage; Based on the current of each branch in the up-line traction network, the instantaneous current of the up-line feeder is obtained; the voltage at non-node positions is obtained by interpolation according to the node voltage; the instantaneous power of the up-line traction transformer is obtained from the instantaneous current of the feeder and the bus voltage; the average current is obtained by integrating the instantaneous current curve of the feeder; Integrate its square to obtain the effective current; the effective current of the traction transformer is obtained according to the variance law; The traction transformer capacity calculation unit is used to determine the calculation principles and calculation contents of the traction transformer, and then determine the power of the traction substation and the capacity of the traction transformer through calculation formulas.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, The computer program is executed by a processor to perform the design calculation method of the urban rail transit AC 3 kV traction power supply system according to any one of claims 1-8.

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