Traction power supply system power flow calculation method and system

Abstract

The present invention discloses a method and system for calculating the power flow of a traction power supply system. Firstly, a holomorphic embedded power flow model of the traction power supply system is constructed, including constructing a holomorphic power flow model of the traction substation balance section and the locomotive load section nodes; secondly, the node voltage and current power series are approximately solved; finally, the power flow results are tested, so as to quickly and accurately obtain the power flow distribution of the traction power supply system.

Description

Technical Field

[0001] The invention relates to the technical field of electrified railway traction power supply, and in particular to a traction power supply system power flow calculation method and system. Background Art

[0002] The traction power supply system is the only power source for electric locomotives. The locomotive obtains electricity from the traction network through the pantograph. Too high or too low traction network voltage will affect the traction power of the locomotive, and thus affect the safe operation of the locomotive. In view of the phenomenon that the network voltage deviation on some lines affects the normal operation of the locomotive, it is necessary to analyze the quality of the locomotive operation network voltage. The analysis of the quality of locomotive operation network voltage lies in accurately obtaining the locomotive voltage. It is an effective method to obtain the corresponding voltage during the locomotive operation process by means of power flow calculation.

[0003] Many scholars at home and abroad have done a lot of research on system modeling and model solving for the calculation of traction power supply system flow. In terms of system modeling, the mathematical model of the traction power supply system is mainly constructed based on the chain circuit model. This method can retain the details of the traction power supply system to the greatest extent. The modeling of locomotive load is mainly divided into two types: current source and power source. In terms of model solving, many literatures use the Newton-Raphson method, improved PQ method, continuous linear power flow method, etc. to apply to the calculation of traction power supply system flow, but the above iterative methods are sensitive to the initial values, and it is difficult to ensure that the selected initial values ​​can make the flow solution converge to a feasible solution, which also increases the calculation time and is difficult to apply to real-time calculations.

[0004] In terms of constructing a fully pure embedded model, from the perspective of node type and load type, both the traditional three-phase power flow algorithm and the transient stability network equation algorithm divide the nodes in the network into balance nodes, PV nodes and PQ nodes. In the traction power supply system, it is divided into a traction substation balance section and a locomotive load section according to the multi-conductor chain network model. A node in each section corresponds to a voltage and a current. Moreover, the load node in the power system, namely the PQ node, is different from the locomotive load PQ section in the traction power supply system. One end of the power system PQ node is connected to the grid and the other end is grounded, while the locomotive load is not grounded.

[0005] In solving the holomorphic embedded model, since the constant power locomotive load in the locomotive load section of the traction power supply system is not grounded, there is coupling between the voltage and current of the contact line T node and the voltage and current of the rail R node in the locomotive load section. In the traditional three-phase power flow algorithm and the transient stability network equation algorithm, additional auxiliary holomorphic functions are constructed to solve the problem that the denominator in the equation needs to be Taylor expanded. This method is computationally complex. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a traction power supply system power flow calculation method and system in view of the shortcomings of the existing technology, so as to solve the problem that the traditional three-phase power flow algorithm and the transient stability network equation algorithm need to additionally construct auxiliary holomorphic functions, the denominator in the equation needs Taylor expansion, and the Taylor coefficient is not easy to obtain, resulting in calculation difficulties.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for calculating the power flow of a traction power supply system, comprising the following steps:

[0008] S1. Construct a holomorphic embedding model of the locomotive load section: Among them, U q,T× (α), U q,R× (α) represents the voltage holomorphic function of nodes T and R on the slice q, S q,× is the injection power of the slice q, I q,T× (α), I q,R× (α) represents the current holomorphic function of the T and R nodes on the slice q, × represents a single line or a complex line, α represents an embedded real variable, For I q,T× The conjugate function of (α), W PQ Represents the PQ slice set of the traction power supply system;

[0009] S2. Calculate the voltage of each node Current The N-order Taylor expansion coefficients, where N is the maximum order of the node voltage and current expansions;

[0010] S3, use approximate functions to approximate the voltage and current power series, and make any node voltage The approximate value of is expressed as m represents the power series order. If the difference between the two largest consecutive approximate values ​​of any node voltage is less than the preset iteration error, the iteration is stopped and the approximate result is output; if the difference between the two largest consecutive approximate values ​​of any node current is less than the preset iteration error, the iteration is stopped and the approximate result is output; u q,i [m] is the m-th order voltage power series coefficient of the ith node of slice q.

[0011] In the traditional three-phase power flow algorithm and transient stability network equation algorithm, auxiliary variables need to be constructed to replace the fractions in the equations, and the Taylor expansion coefficients are not easy to obtain. To solve this difficult problem, the present invention constructs the holomorphic functions of voltage and current at the same time. There are no fractions in the holomorphic model, which simplifies the calculation. In the traditional three-phase power flow calculation, the current vector is represented by the voltage vector, and UI*=S exists. There is a denominator in the model, and the inverse of the voltage function needs to be replaced by another variable. In this solution, the voltage and current are directly expressed as holomorphic functions at the same time, and the inverse of the voltage function will not appear. Finally, the voltage and current results can also be directly output, which greatly simplifies the calculation process.

[0012] After step S3, the method further includes:

[0013] Let α = 1, and substitute the first N-order and first N-1-order voltage Taylor expansion into the calculation

[0014] like If the value of is less than the preset tolerance, it is determined that the power flow solution meets the requirements, that is, the approximate result meets the requirements, and the process ends; otherwise, the value of m is increased by 1, and the process returns to step S2; if m is greater than the preset order m max ,Finish.

[0015] In step S1, the holomorphic embedding model of the locomotive load section satisfies the following current constraints:

[0016]

[0017] Among them, Y TPSS,ij is the admittance between node i and node j in the traction power supply system, U j (α) is the voltage function of node j, and K represents the total number of nodes in the traction power supply system.

[0018] In step S2, the node voltage is obtained by calculating the following equations: Current The Taylor expansion coefficients of are:

[0019]

[0020] Among them, Y tpss represents the matrix related to the node admittance matrix of the traction power supply system; A1 and A2 are constant matrices composed of 0 and 1; X u [m], X v [m] represents the unknown vector of the m-order power series coefficients; B1[m-1] and B2[m-1] are known vectors calculated from the m-1-order power series coefficients.

[0021] B1[m-1]=0, δ mk

[0022] represents a pulse variable, that is, S q Inject the power vector into slice q, is the conjugate of the mkth order current power series coefficient of the T node on the section q, "*" is the conjugate operation, "×" represents a single line or a double line, u q,T× [0] is the initial voltage value of node T on slice q, u q,R× [0] is the initial voltage value of the R node on the slice q.

[0023] As an inventive concept, the present invention also provides a traction power supply system flow calculation system, including a memory, a processor and a computer program stored in the memory; the processor executes the computer program to implement the steps of the above method.

[0024] As an inventive concept, the present invention also provides a computer-readable storage medium having a computer program / instruction stored thereon; the computer program / instruction implements the steps of the above method when executed by a processor.

[0025] As an inventive concept, the present invention also provides a computer program product, including a computer program / instruction; when the computer program / instruction is executed by a processor, the steps of the above method are implemented.

[0026] Compared with the prior art, the present invention has the following beneficial effects: the present invention constructs a holomorphic embedded model of the traction power supply system, so that it does not need to perform iterative operations when performing power flow calculations, thereby improving the calculation efficiency. The present invention also constructs the holomorphic functions of the voltage and current of the nodes, avoiding the problem of additional construction of auxiliary holomorphic functions in the traditional three-phase power flow algorithm and transient stability network equation algorithm to solve the problem that the denominator in the equation needs Taylor expansion, resulting in complex calculations, and can simultaneously output the approximate solutions of the node voltage and current of the traction power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of a traction power supply system in an embodiment of the present invention;

[0028] Figure 2 The figure is a flow chart of a method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] like Figure 2 As shown, an embodiment of the present invention provides a method for calculating power flow of a traction power supply system based on a holomorphic embedding method, comprising the following steps:

[0032] S1. Establish the node admittance matrix Y of the traction power supply system-locomotive coupling model TPSS , Y TPSS Including the establishment of the node admittance matrix Y of the external power supply and the three-phase transmission line S and Y TL , the node admittance matrix Y of the traction transformer and traction network TT , Y q ; Construct the voltage vector U of the traction power supply system-locomotive TPSS , locomotive load power vector S TPSS ;

[0033] S2. The process of establishing a pure embedded power flow model for the traction power supply system is as follows:

[0034] The holomorphic embedding model for constructing the balanced section of the traction substation is:

[0035]

[0036] In the formula, α represents the embedded real variable; Indicates the voltage amplitude set at the balanced section of the traction substation; U w,i (α) represents the voltage holomorphic function of the balanced section of the traction substation; represents the initial value of the balanced section of the traction substation, W slack Represents a balanced facet set.

[0037] According to the characteristics that the locomotive load current flows in from the contact wire T node and flows out from the rail R node, the holomorphic embedded model of the locomotive section load is constructed as follows:

[0038]

[0039] Where U q,T× (α), U q,R× (α) represents the voltage holomorphic function of the T and R nodes on the slice q respectively; S q,× is the injected power of the slice q; I q,T× (α), I q,R× (α) represents the current holomorphic function of the T and R nodes on the section q; × represents a single line or a multi-line, For I q,T× The conjugate function of (α); W PQ Represents a PQ facet set.

[0040] In addition, the node injection current constraint must be met during power flow calculation, and its full-pure embedded model is:

[0041]

[0042] Where Y TPSS is the node admittance matrix of the traction power supply system, K represents the total number of nodes in the traction power supply system; U j (α) is the voltage function of node j.

[0043] S3. Calculate the holomorphic function of voltage and current at each node

[0044] (1) Based on the equality of the power series of the same order on both sides of the equation, solve the voltage of each node Current The Taylor expansion coefficients of are:

[0045] Holomorphic function of voltage at each node U q,i (α) and the injected current I q,i The initial solution of (α) is taken as the no-load state of the traction power supply system:

[0046]

[0047] Through the power series α of the same order on both sides of the equation m The coefficients of are equal, so we can deduce that:

[0048]

[0049] In the formula, δ mk represents a pulse variable, that is,

[0050] After obtaining the recursive formula of the power series coefficients of the holomorphic function, we can obtain it by solving the following system of equations: and The coefficient of:

[0051]

[0052] Where Y tpss represents the matrix related to the node admittance matrix of the traction power supply system; A1 and A2 are constant matrices composed of 0 and 1; X u [m], X v [m] represents the unknown vector of the coefficients of the power series of order m; B1[m-1] and B2[m-1] are known vectors calculated for the coefficients of the power series of order not greater than m-1.

[0053] (2) Based on the Nth-order Taylor expansion of the known node voltage and current, an approximate function is used to obtain the approximate solution of the power series:

[0054] The voltage and current power series are approximated by using approximate functions. The approximate value of can be expressed as Then, whether to continue the iteration is determined based on whether the difference between the two largest consecutive approximations is less than the preset iteration error δ; Similarly, if the difference between the largest two consecutive approximations is less than the iteration error, the approximate result is output.

[0055] S4. Convergence conditions

[0056] First, let α = 1, N = m and substitute the first N-order and first N-1-order voltage Taylor expansion into the calculation Secondly, when the maximum voltage difference of the node is lower than the preset tolerance ε, the power flow solution is considered to meet the requirements and the output The calculation is finished; otherwise, set m to m+1, recalculate the coefficients of the higher-order terms, and repeat operation S3; if the holomorphic function The highest term order N=m is greater than the preset order m max If the upper limit value is exceeded, the output is "Exceeded the maximum order upper limit" and the calculation ends.

[0057] Example 2

[0058] Embodiment 2 of the present invention provides a terminal device corresponding to the above-mentioned embodiment 1. The terminal device may be a processing device for a client, such as a mobile phone, a laptop computer, a tablet computer, a desktop computer, etc., to execute the method of the above-mentioned embodiment.

[0059] The terminal device of this embodiment includes a memory, a processor, and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method in the above-mentioned embodiment 1.

[0060] In some implementations, the memory may be a high-speed random access memory (RAM), and may also include a non-volatile memory, such as at least one disk memory.

[0061] In some other implementations, the processor may be a central processing unit (CPU), a digital signal processor (DSP), or other general-purpose processors of various types, which are not limited herein.

[0062] Example 3

[0063] Embodiment 3 of the present invention provides a computer-readable storage medium corresponding to the above embodiment 1, on which a computer program / instruction is stored. When the computer program / instruction is executed by a processor, the steps of the method of the above embodiment 1 are implemented.

[0064] Computer readable storage media can be tangible devices that hold and store instructions used by instruction execution devices. Computer readable storage media can be, for example, but not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any combination thereof.

[0065] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0066] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0067] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0068] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0069] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for calculating power flow of a traction power supply system, characterized in that: The following steps are involved: S1. Construct a holomorphic embedding model of the locomotive load section: q∈W PQ ; Among them, U q,T× (α), U q,R× (α) represents the voltage holomorphic function of nodes T and R on the slice q, S q,× is the injection power of the slice q, I q,T× (α), I q,R× (α) represents the current holomorphic function of the T and R nodes on the section q, × represents a single line or a multi-line, α represents an embedded real variable, For I q,T× The conjugate function of (α), W PQ Represents the PQ slice set of the traction power supply system; S2. Calculate the voltage of each node Current The N-order Taylor expansion coefficients, where N is the maximum order of the node voltage and current expansions; S3, use approximate functions to approximate the voltage and current power series, and make any node voltage The approximate value of m represents the power series order. If the difference between the two largest consecutive approximate values ​​of any node voltage is less than the preset iteration error, the iteration is stopped and the approximate result is output; if the difference between the two largest consecutive approximate values ​​of any node current is less than the preset iteration error, the iteration is stopped and the approximate result is output; u q,i [m] is the m-order voltage power series coefficient of the ith node of slice q.

2. The method for calculating power flow of a traction power supply system according to claim 1, characterized in that: After step S3, the method further includes: Let α = 1, and substitute the first N-order and first N-1-order voltage Taylor expansion into the calculation like If the value of is less than the preset tolerance, it is determined that the power flow solution meets the requirements, that is, the approximate result meets the requirements, and the process ends; otherwise, the value of m is increased by 1, and the process returns to step S2; if m is greater than the preset order m max ,Finish.

3. The method for calculating power flow of a traction power supply system according to claim 1, characterized in that: In step S1, the holomorphic embedding model of the locomotive load section satisfies the following current constraints: Among them, Y TPSS,ij is the admittance between node i and node j in the traction power supply system, U j (α) is the voltage function of node j, and K represents the total number of nodes in the traction power supply system.

4. The method for calculating power flow of a traction power supply system according to claim 1, characterized in that: In step S2, the node voltage is obtained by calculating the following equations: Current The Taylor expansion coefficients of are: Among them, Y tpss represents the matrix related to the node admittance matrix of the traction power supply system; A1 and A2 are constant matrices composed of 0 and 1; X u [m], X v [m] represents the unknown vector of the m-order power series coefficients; B1[m-1] and B2[m-1] are known vectors calculated from the m-1-order power series coefficients.

5. The method for calculating power flow of a traction power supply system according to claim 4, characterized in that: B1[m-1]=0, δ mk surface represents a pulse variable, that is, S q Inject the power vector into slice q, is the conjugate of the mkth order current power series coefficient of the T node on the slice q, "*" is the conjugate operation, "×" Indicates single or double line, u q,T× [0] is the initial voltage value of node T on slice q, u q,R× [0] is the initial voltage value of the R node on the slice q.

6. A traction power supply system power flow calculation system, comprising a memory, a processor and a computer program stored in the memory; characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 5.

7. A computer-readable storage medium having a computer program / instruction stored thereon; characterized in that: When the computer program / instructions are executed by a processor, the steps of the method described in any one of claims 1 to 5 are implemented.

8. A computer program product comprising a computer program / instructions; characterized in that: When the computer program / instructions are executed by a processor, the steps of the method of any one of claims 1 to 5 are implemented.

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