Electrified railway traction power supply capability boundary evaluation method and storage medium

Abstract

The invention discloses an electrified railway traction power supply capability boundary evaluation method. The method comprises a parameter input module; an electrical modeling module; the load flow calculation module is used for calculating the traction network load flow of the vehicle-network electrical interactive coupling system in consideration of load network voltage iterative calculation under various operation conditions; and the power supply evaluation module is used for solving the electrical quantity of power supply equipment based on a non-planar graph load flow calculation result, comparing and analyzing a theoretical calculation result and a national standard specified value, and uniformly reducing the line transportation capacities under different driving organizations to form a system maximum power supply capacity boundary evaluation system with the line maximum transportation capacity as a representation. The power supply capability evaluation time domain is wider, the evaluation process is more convenient, and the precision is higher. The method is wider in power supply capability evaluation time domain, more convenient in evaluation process and higher in precision, and is suitable for power supply capability evaluation of lines such as existing non-plain map driving organizations, combined transportation of multiple different types of electric locomotive groups, large and small intersection line planning and the like.

Description

Technical Field

[0001] The invention relates to a boundary evaluation method for traction power supply capacity of an electrified railway, and in particular to a boundary evaluation method for maximum traction power supply capacity of an AC traction power supply system under non-flat line operation organization and combined operation of multiple types of electric locomotive groups. Background Art

[0002] The traction power supply system is an important part of the electrified railway and is the necessary power for the high-speed, safe and stable operation of electric locomotives. The insufficient capacity of the traction power supply system will directly lead to the unstable operation of the entire vehicle-grid coupling system. With the rapid development of electrified railways, the number of electric locomotives running on the same line has gradually increased, making the number of trains running on the same line on the line saturated. The transportation plan of long-formation or double-connected EMUs can improve the transportation capacity but puts forward higher requirements on the power supply capacity. In addition, the traction power of electric locomotives is gradually increasing. It is necessary to study the maximum power supply boundary of the traction power supply system to guide the operation organization planning and ensure the safe, stable and efficient operation of the vehicle-grid coupling system.

[0003] At present, the research on traction power supply capacity boundary assessment is mainly divided into two methods: based on field measured data and modeling simulation analysis.

[0004] Based on the field measured data, by measuring the voltage at the end of the line power supply arm, the substation feeder current and other data, and then combining analysis and calculation to study the factors affecting the power supply capacity of each power supply section, this method requires a lot of manpower and material resources and cannot provide guidance for the traffic organization planning of the lines under construction.

[0005] Modeling and simulation analysis Through the study of the traction power supply system, an electrical simulation model of the traction power supply system was built based on Matlab / Simulink, PSCAD and other software to study the electrical quantities such as feeder voltage and current under normal and fault conditions, the impact of the external short-circuit capacity of the power grid on the terminal voltage of the traction network, and the power quality data such as the harmonic characteristics and power factor of the system under different operating conditions of the train. The simulation analysis method is more convenient than the test data, but it does not comprehensively consider the constraints of the reliable operation of other power supply facilities, and the simulation conditions are relatively single and lack versatility. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiency that the power supply capacity assessment method of the lines under construction and reconstruction cannot comprehensively take into account the dynamic driving organization planning and the electrical quantity problem of the traction transformer, and provide a traction power supply boundary assessment method based on non-flat diagram flow calculation, which takes the traction power supply system flow calculation as the data solution platform, takes the traction network voltage, traction transformer capacity, transformer winding current, and power factor as indicator constraints, and uniformly calculates the transportation volume index for different types of trains, and assesses the power supply capacity boundary characterized by the maximum transportation capacity of the line. The present invention can realize the power supply capacity assessment of different types of electric locomotive groups and uneven departure interval timetables under the constraints of the safe and stable operation index of the power supply equipment in the electrified railway.

[0007] The specific technical solutions of the present invention are as follows:

[0008] The invention discloses an electrified railway traction power supply capacity boundary assessment method. The method calculates the traction network voltage, traction transformer capacity and power factor based on the node flow of the power supply system, reduces the line transportation capacity, evaluates the traction power supply capacity, and finds the maximum transportation capacity of the electric locomotive group to characterize the maximum power supply capacity boundary of the line. The method comprises: a parameter input module for inputting system specification parameters, train mechanical parameters, line slope parameters and operation diagram driving organization parameters; an electrical modeling module for completing the modeling of the external power supply impedance of the power system, the modeling of the power supply equipment of the traction power supply system, the modeling of the train load electrical parameter considering the mechanical characteristics of the electric locomotive, and the modeling of the multi-car load process of different departure intervals and multiple trains running on the same line; a flow calculation module for calculating the traction network flow of the vehicle-grid electrical interactive coupling system considering the iterative calculation of the load network voltage under multiple operating conditions; and a power supply assessment module for solving the electrical quantity of the power supply equipment based on the non-flat diagram flow calculation results, and comparing and analyzing the theoretical calculation results with the national standard values, uniformly reducing the line transportation capacity under different driving organizations, and forming a system maximum power supply capacity boundary assessment system characterized by the maximum transportation capacity of the line. The power supply capacity evaluation of the present invention has a wider time domain, a more convenient evaluation process, and a higher accuracy, and is suitable for power supply capacity evaluation of existing non-flat traffic organization, combined operation of multiple types of electric locomotive groups, and large and small intersection line planning.

[0009] The main features and basic principles of the method of the present invention include:

[0010] (1) Based on the calculation of the electrical interaction and coupling power flow between the traction power supply system and multiple electric locomotives, the coupling system mainly considers the coupling of "vehicle-grid-diagram" such as three-phase power system short circuit, traction transformer, traction network, electric locomotive, and operation diagram;

[0011] (2) Considering the co-operation of different types of electric locomotives and applicable to the calculation of the current on the traction network side of the traction power supply system under the actual non-uniform departure interval operation diagram. The traction transformer in the traction substation and the equivalent impedance on the three-phase power system side are comprehensively considered and modeled, and then converted to the traction network side as the impedance admittance matrix of the traction substation traction network side; considering the situation that electric locomotives have different formations and different traction powers but the same operating line, a solution model for the train dynamic line operation electrical parameters (active power, reactive power, speed, position, time, traction force, etc.) is established based on the spatial dimension and the electric locomotive's own parameters;

[0012] (3) Considering the multi-car load process with uneven departure intervals and different electric locomotives running on the same line, the electrical parameters of the same position on the same line are assumed to be the same for the same type of trains, and the corresponding types of electric locomotives are arranged according to the departure intervals. The multi-car load process considering electrical characteristics is coupled with the power supply system flow calculation to model and complete the traction network flow calculation. The electrical quantity of the power supply equipment inside the power supply system is calculated based on the traction network flow results, and a comparative analysis is performed based on the allowable values ​​specified in the national standard. The line transportation capacity under different driving organizations is uniformly calculated, thereby completing the power supply capacity evaluation of this "car-grid-map" electrified railway;

[0013] (4) Taking the maximum power supply capacity boundary of the traction power supply system (i.e. the worst case) as a prerequisite, based on the multi-car load process, the tracking interval of the train group is continuously reduced, and the number of high-power locomotives put into operation is continuously increased to make the electrical quantity of the power supply equipment close to the national standard limit to the greatest extent, forming a traction power supply capacity boundary assessment method characterized by the maximum transportation capacity of the line under non-flat load process.

[0014] Furthermore, the power flow calculation model of the vehicle-grid electrical interaction system under non-flat multi-vehicle co-line operation is an analysis and solution tool for the electrified railway traction power supply boundary assessment method proposed in the present invention, which is mainly composed of a three-phase power system, a traction substation, a traction network, a single electric locomotive electrical parameter model, and a non-flat multi-vehicle dynamic load process.

[0015] Furthermore, the three-phase power system and traction substation are uniformly converted to the traction grid side to obtain the equivalent circuit of the traction grid side. As the core equipment, the traction transformer is connected to the three-phase power system on the primary side to take power and convert it to 27.5kV single-phase AC power to the secondary side traction grid side. According to the voltage and current transformation relationship between the primary and secondary sides of the traction transformer and the wiring form of the traction transformer, the voltage and current transformation matrix R is obtained. U , R I ; Based on the voltage and current transformation matrix combined with the impedance Z of the high-voltage transmission line of the three-phase power system GRID With the power system impedance Z SYS Obtain the equivalent impedance of the traction grid side of the three-phase power system; Based on the leakage reactance Z equivalent to the secondary side of the traction transformer T-T, the equivalent circuit of the three-phase power system and the traction grid side of the traction substation is obtained and the impedance values ​​are solved.

[0016] Furthermore, the traction network is studied and modeled. The traction network is a collection of conductors in the traction power supply system, including contact wires, feeders, rails, etc. The traction network of any traction power supply system can be summarized as a multi-conductor parallel transmission power line. Therefore, the impedance and admittance of the traction network are modeled using the multi-conductor transmission line theory in the power system. First, the unit length impedance of each conductor is obtained based on the parameter model of each conductor itself, and multiple parallel conductors are combined based on the Carson formula to solve the unit length impedance matrix Z of the multi-conductor. m , according to the electrostatic field theory, solve the multi-conductor parallel admittance matrix Y m The traction network is a composite chain circuit in terms of its skeleton. The entire traction network is divided into sections using longitudinal parallel elements such as substations, substations, and electric locomotives. The Π-type equivalent circuit of this section of the traction network is solved using the sections between each other.

[0017] Furthermore, the traction calculation of the electrical characteristics of the electric locomotive is completed in both time and space dimensions. The traction calculation solves the active power and reactive power of a single electric locomotive under different operating conditions. The force analysis of the electric locomotive shows that the train forces include its own traction / braking force, basic resistance, additional resistance of the line slope, curve friction resistance and air resistance in the tunnel. Combined with the basic parameters such as the train weight, load, traction and braking force, the line is discretized, and the candidate speed level discrete points corresponding to the train are set at the discrete points of the line. Based on the conditions of satisfying the train's own operating constraints and the driving strategy comfort of the line train, the train speed level is calculated. Solve the acceleration of the train at each discrete segment at the speed level at both ends, and solve the resultant force F under each operating condition of the train based on the vehicle weight. loco . Then according to P=F loco v and power factor to complete the solution of the electrical characteristics of each section of electric locomotive. Finally, the feasibility is judged based on whether the train travel time meets the actual constraints. The data of the departure interval is extracted from the local line operation diagram to obtain the departure interval between trains, and a blank data matrix of preset size is established. According to the actual number of departures n in the required power flow calculation time period, n data matrices are established for storage. The dimension of the data matrix corresponds to the number of electrical parameters obtained from the single train traction calculation. The blank row at the front of each data matrix represents the time difference between the train and the start time of the simulation. The electrical information of each data matrix (i.e., representing each train) is read in sequence according to the simulation time and substituted into the traction network power supply calculation to complete the multi-vehicle load process.

[0018] Furthermore, the power flow calculation on the traction network side is completed based on the continuous power flow algorithm. The node voltage and current matrix are initialized, and according to the electrical characteristics of the traction transformer and the electric locomotive, they are regarded as current sources and injected into the current matrix. The voltage of each node is solved according to YI=U, and the voltage is repeatedly solved iteratively until the voltage error of each electric locomotive meets the convergence accuracy, and the voltage and current of each node on the traction network side are output.

[0019] Furthermore, a traction power supply boundary assessment method based on traction network flow calculation and considering the multi-vehicle load process of the operation diagram is proposed. According to the traction calculation results of the electric locomotive combined with the power supply range of the existing power supply mode, the traction condition, cruising condition, idling condition and braking condition of the electric locomotive are divided into time dimensions and described as a series of time points, such as T t ={T t1 ,T t2 ,T t3 ...,T tn} represents the starting time point set of each traction working condition of the electric locomotive, T c ={T c1 ,T c2 ,T c3 ...,T cn} is the set of time points when traction ends and cruising begins, T l ={T l1 ,T l2 ,T l3 ...,T ln} is the set of braking start time points, T b ={T b1 ,T b2 ,T b3 ...,T bn} is a set of braking end time points. The present invention aims to explore the worst case of the maximum capacity boundary of traction power supply, and in combination with the traffic organization planning, adjust the departure interval between two trains within the allowable range of the departure interval to maximize the overlap of multi-vehicle traction conditions or multi-vehicle braking conditions in the time dimension. This is the worst case for the power supply system. When a series of departure intervals are determined, the traction network voltage deviation, traction transformer capacity, traction transformer winding current and traction transformer power factor are further calculated based on the traction network flow calculation results, and compared with the allowable values ​​specified in the national standard, the departure interval is continuously changed to adjust the traffic density and multi-vehicle operating conditions, and then the traction load is adjusted until one of the above electrical parameters is close to the upper and lower limits of the allowable values ​​specified in the national standard. At this point, the transportation volume under the traffic organization is output as the maximum capacity boundary of the traction power supply of this line, characterized by the maximum transportation capacity.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) In view of the fact that the existing methods cannot comprehensively consider the dynamic process of multi-car loads in the actual operation diagram and the frequent electrical interactions of the system power supply equipment, the present invention designs a multi-car load dynamic traction calculation process that takes into account different departure intervals and co-line operation of different trains, and discusses the maximum power supply capacity boundary based on the calculation results of the vehicle-grid diagram coupling flow, iteratively solves the grid voltage of each electric locomotive in different time and space dimensions until convergence. Compared with the early researchers based on Simulink and simulation, the accuracy is higher, the power supply capacity evaluation time domain is wider, and the evaluation process is more convenient;

[0022] (2) The present invention can realize system power flow analysis and power supply capacity evaluation for multiple trains running on the same line under non-uniform departure intervals, and is applicable to existing lines and lines in the design and construction stages, and outputs power supply capacity boundary evaluation results for reference by the traffic organization and planning department;

[0023] (3) In the past, the evaluation of traction power supply capacity was limited to the traction grid voltage. The present invention takes into account the transformer capacity, winding current, power factor and other electrical equipment stable operation and power quality multi-dimensional indicators. The evaluation system is more comprehensive and the evaluation results are more in line with actual needs.

[0024] (4) The present invention is applicable to the evaluation of line power supply capacity under conditions of co-operation of a variety of electric locomotives and non-uniform departure intervals, and is more universal and more accurate than the existing flat-map power flow calculation evaluation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The following drawings are used to help further understand the technical solution of the present invention:

[0026] Figure 1 is a flow chart of the traction power supply capability boundary assessment method of the present invention;

[0027] Figure 2 is a schematic diagram of a traction power supply boundary assessment process according to an embodiment of the present invention;

[0028] Figure 3 is an electrical wiring diagram of an external power supply and a traction transformer according to an embodiment of the present invention;

[0029] Figure 4 is an equivalent circuit diagram of the system traction network side of an embodiment of the present invention;

[0030] Figure 5 This is a diagram of a chain network model of a traction network according to an embodiment of the present invention;

[0031] Figure 6 is a Π-type equivalent circuit diagram of a traction network according to an embodiment of the present invention;

[0032] Figure 7 Schematic diagram of a method for calculating electric locomotive traction at a distance discrete scale according to an embodiment of the present invention;

[0033] Figure 8 It is a schematic diagram of the simultaneous traction and braking conditions of multiple vehicles in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to make the research purpose, technical principle and evaluation method of the present invention clearer and easier to understand, the following describes the principle, evaluation process and results of the present invention in detail in combination with the embodiments and drawings.

[0035] The technical process of the present invention is further described below in conjunction with a specific domestic line.

[0036] See also Figure 1 and Figure 2 , a method for evaluating the boundary of traction power supply capacity of electrified railways, comprising:

[0037] Step 1: The voltage level of the three-phase power system outside the line is 220kV, the short-circuit capacity is 2000MVA, the traction transformer adopts the Vv connection form, and the electrical connection between the traction transformer and the three-phase power system is as follows: Figure 3 The conversion formula of voltage and current on the grid side and traction grid side is: The transformation ratios of the traction transformers in the left and right power supply arms of the traction substation are k α =k β = k, we can get the current conversion matrix Voltage conversion matrix According to the voltage level E and short-circuit capacity S of the external power grid GRID 、Impedance per unit length of high voltage transmission line z sl and length L, find the total impedance The equivalent impedance of the traction grid side of the three-phase power system is further obtained.

[0038] Step 2: According to the short-circuit voltage percentage U of the local traction transformer k %, rated capacity S N And the rated voltage U of the traction network 2N , calculate the secondary equivalent leakage reactance of the traction transformer

[0039] Step 3: Substitute the system secondary equivalent impedance and the traction transformer secondary equivalent leakage reactance into Figure 4 Among them, The equivalent impedance of the three-phase power system and the traction substation uniformly converted to the traction network is obtained.

[0040] Step 4: Establish an equivalent model of the traction network (contact network, feeder, rail, return line, reinforcement line (if any)) based on the parallel multi-conductor transmission line theory. For the unit series impedance of the multi-conductor transmission line, let the number of multi-conductors in the traction network be m, and solve according to the Carson theory, the unit self-impedance of conductor i is Unit mutual impedance between wire i and wire j f is the current frequency, μ0=4π×10 -4 is the vacuum permeability, D g To replace the equivalent depth of the conductor in the ground to replace the influence of the earth, d ij is the distance between wire i and wire j, R εi —Equivalent radius of conductor i.

[0041] For the unit parallel admittance of a multi-conductor transmission line, according to the electrostatic field calculation, the voltage U of each conductor i to the ground i Its linear charge density Q i The relationship is shown in the following formula:

[0042]

[0043] is the self-potential coefficient of conductor i, is the mutual potential coefficient between conductors i and j, U i is the potential of conductor i to ground, Q i is the linear charge density of wire i, ε0 is the space dielectric constant, h i is the height of conductor i above the ground, D ij is the mirror distance between wire i and wire j, d ij is the distance between wire i and wire j.

[0044] That is, Q = P -1 U=CU

[0045]

[0046] The P matrix is ​​the potential coefficient matrix, and the C matrix is ​​the capacitance coefficient matrix. The C matrix can be obtained by inverting the P matrix. According to the basic principle of electromagnetic field, the charge vector Q in the multi-conductor of the traction network changes with time to form the longitudinal current vector I of the multi-conductor of the traction network. Since the present invention considers the steady-state electrical process, the conductivity of all conductors to the ground can be calculated without calculation, and the frequency domain equation of the multi-conductor of the traction network can be obtained. The parallel admittance matrix of multiple conductors can be obtained as follows:

[0047]

[0048] Step 5: The electrical interaction between the entire multi-vehicle and traction power supply system can be regarded as a composite chain network on the traction grid side. The chain network model is as follows: Figure 5 As shown in the figure, each longitudinal parallel element such as traction transformer, electric locomotive, substation, etc. is regarded as a section, that is, each power supply arm needs to be divided according to the section, and the impedance and admittance matrix of each section segment multi-conductor is solved separately, Z k For the traction network impedance slice segment between slice k and slice k+1, write the node voltage equation:

[0049]

[0050] The left side is the system node admittance matrix Y, which is obtained by the staggered superposition of the admittance matrices of the longitudinal parallel elements and the transverse series elements in a single power supply arm. When the length L between each section segment is known, each section segment can be equivalent to a Π-type equivalent circuit based on the unit length multi-conductor impedance matrix Z' and the admittance matrix Y', as shown in Figure 6 As shown, the calculation method is as follows:

[0051]

[0052] Step 6: The electrical parameters of the electric locomotive are calculated based on the train parameters and line parameters. The traction calculation method is as follows: Figure 7 First, the entire line is discretized according to a fixed step size Δs to obtain a series of discrete points {s1, s2, ..., s k ...,s n}, taking the line speed limit as the upper speed limit, we can get the optional speed range [0,v lim ], the speed interval at each discrete point is divided with Δv as a fixed step size, and the complete vs speed curve can be obtained by determining the speed point combination at each discrete point. The actual electric locomotive has its own maximum traction force F tm , maximum acceleration a max , Maximum braking force F bm , stipulated travel time T tot Therefore, it is necessary to determine whether the train trajectory is feasible. The feasibility is mainly determined by calculating and comparing various parameters based on the speed between two discrete points. For the traction force solution, assuming v k-1 <v k <v k+1 , If F t (v k )>F tm Then these two candidate speeds are unattainable, and the same is true for the braking force; solve for the train acceleration, If a k >a max After satisfying the above constraints, the total travel time T is calculated based on the trajectory. If the specified travel time T is met totIf the allowable error is less than 0, the trajectory is feasible, otherwise the candidate speeds are re-screened. After obtaining the feasible trajectory, according to P = F·v and Solve the active power and reactive power of the electric locomotive, where F is the resultant force on the electric locomotive and cosa is the power factor of the train itself. The formula for calculating the train resultant force is F=Ma, where M is the weight of the electric locomotive. Then, the time, position, speed, active power, reactive power and other data of the train at each discrete point can be obtained. In order to facilitate the calculation of the flow uniformly distributed in the time domain, the linear interpolation method is used to convert the train traction calculation results into the traction calculation results uniformly distributed in the time domain with 1 second as the unit.

[0053] Step 7: Establish the multi-vehicle load process under non-uniform departure interval based on the line traffic organization planning. The data matrix s_p_loco of the electric locomotive traction calculation result in step 6, the behavior time, is listed as the corresponding parameter. According to the operation diagram, the departure intervals between the up and down trains are counted to obtain the data vector D up , D down , remember D up ={D up (1),D up (2),...,D up (K)},D do ={D do (1),D do (2),...,D do (K)}, the data vector represents the running difference between two adjacent electric locomotives with the same running direction. The up and down lines are separated by their respective time differences to arrange multiple vehicles in time and space dimensions, that is, the time and space relative translation properties are formed according to the time difference but the movement process of the same electric locomotive is not changed. The corresponding traction calculation results are called for different types of electric locomotives.

[0054] Step 8: Calculate the power flow of the multi-vehicle loads and the traction grid electrical interaction of the traction power supply system in units of 1 second. The power flow calculation process is as follows: Figure 2 As shown in the figure. Each time the power flow is calculated, that is, every second, the position of the online electric locomotive is determined, and each power supply arm is divided into sections according to the substation, substation, and electric locomotive position, and then the node admittance matrix Y between the two sections is calculated. The node current vector I is updated with the electrical parameters of the traction transformer and the electric locomotive. Assuming that the grid voltage of all electric locomotives is 27.5kV, that is, the rated voltage of the traction network, the current vector and voltage vector are updated through U=YI until the difference between the two adjacent node voltage vectors meets the convergence accuracy, stop the calculation and save the results.

[0055] Step 9, the maximum boundary evaluation method for traction power supply capacity of multiple electric locomotives running on the same line under non-uniform departure intervals proposed by the present invention is based on the calculation results of the traction network power flow, which belongs to the worst case. The worst case in the electrified railway is mainly that multiple vehicles are in traction or braking conditions at the same time, which directly leads to severe fluctuations in network voltage. The schematic diagram of multiple vehicles traction braking at the same time is as follows Figure 8 As shown. According to the operating conditions of the electric locomotive, the departure interval is adjusted in combination with the departure interval of the actual line, and the minimum departure interval is found as the boundary of the maximum power supply capacity. When a series of departure intervals are determined, the maximum power supply capacity is determined by comparing the allowable values ​​specified in the national standard. For the traction network voltage, the national standard stipulates that the upper limit of the overhead line and electric locomotive network voltage is 29kV and the lower limit is 20kV. When the system is in a fault or maintenance, the lower limit is 19kV. Therefore, the node voltage vector value is extracted to determine whether it is within the allowable range. If it exceeds the range, it is judged that the power supply capacity is insufficient; for the traction transformer winding current and capacity, taking the α power supply arm as an example, the transformer T winding current I T 、F winding current I F The calculation formula is as follows:

[0056]

[0057] In the formula, are the impedance values ​​of the primary winding, tertiary winding and secondary winding converted to the primary winding. The capacity of the traction transformer is S α =|U TN I T |+|U FN I F |, if the overload current exceeds 1.5 times the rated current of the transformer winding or the transformer capacity exceeds 1.5 times the rated capacity, it means that the power supply capacity is insufficient; for the power factor, the power industry department stipulates that the monthly average power factor of the traction load on the high-voltage side of the traction substation cannot be lower than 0.9, so for the α power supply arm traction transformer, according to its active output P α And the corresponding capacity S α Solving for Power Factor If λ<0.9, the power supply capacity is insufficient.

[0058] Step 10: If the grid voltage, transformer winding current, capacity and power factor are not close to the national standard limit, continue to reduce the departure interval, increase the number of departures, increase the traction load, adjust the departure interval to make the traction braking conditions of multiple vehicles overlap, and repeat the evaluation process until the evaluation result is close to the national standard limit. For different types of trains and uneven departure intervals, uniformly calculate them into the transportation capacity index for comparison, and output the maximum transportation capacity as the maximum capacity boundary of traction power supply.

Claims

1. A method for evaluating the boundary of traction power supply capacity of electrified railways. It is characterized in that The method includes: Step 1: Modeling the external power source impedance of the power system; Step 2: Modeling of power supply equipment of traction power supply system; Step 3, modeling the train load electrical parameters considering the mechanical characteristics of the electric locomotive; Step 4: Modeling the multi-vehicle load process with different departure intervals and multiple trains running on the same line, including: (a) Based on the calculation results of electric locomotive traction and the power supply range of the existing power supply mode, the traction condition, cruising condition, coasting condition and braking condition of the electric locomotive are divided into time dimensions, and a series of time points are used to describe the start time point set of each traction condition of the electric locomotive, the end of traction (i.e., the start of cruising time point set), the start braking time point set and the end braking time point set; (b) The maximum capacity boundary of traction power supply is the worst case. Combined with the traffic organization planning, the departure interval between two trains is adjusted within the range allowed by the departure interval regulations to maximize the overlap of multi-vehicle traction conditions or multi-vehicle braking conditions in the time dimension. This is the worst case for the power supply system. Step 5: traction network power flow calculation modeling of the vehicle-grid electrical interactive coupling system considering multiple operating conditions, load and grid voltage iterative calculation; Step 6: Calculate the electrical quantity of the power supply equipment based on the power flow calculation results, compare and analyze the theoretical calculation results with the national standard values, and evaluate the maximum power supply capacity boundary of the system, including: When a series of departure intervals are determined, the traction network voltage deviation, traction transformer capacity, traction transformer winding current and traction transformer power factor are further calculated based on the traction network flow calculation results. By comparing with the allowable values ​​specified in the national standard, the departure interval is continuously changed to adjust the traffic density and multi-vehicle operating conditions, and then the traction load is adjusted until one of the above electrical parameters is close to the upper and lower limits of the allowable values ​​specified in the national standard. At this point, the traffic organization is output as the maximum capacity boundary of the traction power supply for this line, represented by the minimum departure interval.

2. The method for evaluating the boundary of traction power supply capacity of an electrified railway according to claim 1, It is characterized in that In step 5: The power flow calculation modeling includes three-phase power system, traction substation, traction network and single electric locomotive electrical parameter model and non-flat multi-vehicle dynamic load process.

3. The method for evaluating the boundary of traction power supply capacity of an electrified railway according to claim 2, Features: The three-phase power system and the traction substation are uniformly converted to the traction grid side to obtain the traction grid side equivalent circuit; As the core equipment, the traction transformer is connected to the three-phase power system on the primary side to take power and convert it to 27.5kV single-phase AC power to the secondary traction grid side. According to the voltage and current transformation relationship between the primary and secondary sides of the traction transformer and the connection form of the traction transformer, the voltage and current transformation matrix R is obtained. U , R I ; Based on the voltage and current transformation matrix combined with the impedance Z of the high-voltage transmission line of the three-phase power system GRID With the power system impedance Z SYS Obtain the equivalent impedance of the traction grid side of the three-phase power system; Based on the leakage reactance Z equivalent to the secondary side of the traction transformer T-T , the equivalent circuit of the three-phase power system and the traction grid side of the traction substation is obtained and the impedance values ​​are solved.

4. The method for evaluating the boundary of traction power supply capacity of an electrified railway according to claim 1, It is characterized in that In step 1: The conductors of the traction power supply system include contact wires, feeder wires and rails; First, the unit length impedance of each conductor is obtained based on the parameter model of each conductor itself, and multiple parallel conductors are combined based on the Carson formula to solve the unit length impedance matrix Z of the multi-conductor m , according to the electrostatic field theory, solve the multi-conductor parallel admittance matrix Y m The traction network is a composite chain circuit in terms of its skeleton. The entire traction network is divided into sections consisting of substations, substations and longitudinal parallel elements of electric locomotives. The Π-type equivalent circuit of this section of the traction network is solved in units of two sections.

5. The method for evaluating the boundary of traction power supply capacity of an electrified railway according to claim 1, It is characterized in that Step 2 includes: The traction calculation solves the active power and reactive power of a single electric locomotive under different operating conditions. The forces on the electric locomotive include its own traction / braking force, basic resistance, additional resistance of the line slope, curve friction resistance and air resistance in the tunnel. Combined with the train weight, load and traction braking force, the line is discretized, and the candidate speed level discrete points corresponding to the train are set at the discrete points of the line. Under the condition of satisfying the train's own operating constraints and the driving strategy comfort of the line train, the speed level of the train is calculated. Solve the acceleration of the train at each discrete segment at the speed level at both ends, and solve the resultant force F under each operating condition of the train based on the vehicle weight. loco ; And then according to P = F loco v and power factor to complete the solution of the electrical characteristics of each section of the electric locomotive; finally, the feasibility is judged based on whether the train travel time meets the actual constraints.

6. The method for evaluating the boundary of traction power supply capacity of an electrified railway according to claim 5, It is characterized in that Also includes: The departure interval data of the local line operation diagram is extracted to obtain the departure interval between trains, and a blank data matrix of preset size is established. According to the actual number of departures n in the required power flow calculation time period, n data matrices are established for storage. The dimension of the data matrix corresponds to the number of electrical parameters obtained from the traction calculation of a single train. The blank row at the front of each data matrix represents the time difference between the train and the start time of the simulation. The data matrices representing each train are read in sequence according to the simulation time, and the electrical information is substituted into the traction network power supply calculation to complete the multi-vehicle load process.

7. The method for evaluating the boundary of traction power supply capacity of an electrified railway according to claim 1, It is characterized in that The step 6 also includes: The traction network side power flow calculation is completed based on the continuous power flow algorithm; the node voltage and current matrix are initialized, and according to the electrical characteristics of the traction transformer and electric locomotive, they are regarded as current sources and injected into the current matrix. The voltage of each node is solved according to YI=U, and the voltage is repeatedly solved iteratively until the ground voltage error of each electric locomotive meets the convergence accuracy, and the voltage and current of each node on the traction network side are output.

8. A method for evaluating the boundary of traction power supply capacity of electrified railways. It is characterized in that The following steps are involved: Step 1: The voltage level of the three-phase power system outside the line is 220kV, the short-circuit capacity is 2000MVA, and the traction transformer adopts the Vv connection form. The conversion formula of the voltage and current on the grid side and the traction network side is: The transformation ratios of the traction transformers in the left and right power supply arms of the traction substation are k α =k β = k, and the current conversion matrix is ​​obtained Voltage conversion matrix According to the voltage level E and short-circuit capacity S of the external power grid GRID 、Impedance per unit length of high voltage transmission line z sl and length L, find the total impedance The equivalent impedance of the traction grid side of the three-phase power system is further obtained. Step 2: According to the short-circuit voltage percentage U of the local traction transformer k %, rated capacity S N And the rated voltage U of the traction network 2N , calculate the secondary equivalent leakage reactance of the traction transformer Step 3: Substitute the system secondary equivalent impedance and the traction transformer secondary equivalent leakage reactance into the equivalent circuit, where: Obtain the equivalent impedance of the three-phase power system and the traction substation uniformly converted to the traction network; Step 4: Establish an equivalent model of the traction network based on the parallel multi-conductor transmission line theory; for the unit series impedance of the multi-conductor transmission line, assume that the number of multi-conductors in the traction network is m, and solve according to the Carson theory, the unit self-impedance of conductor i is Unit mutual impedance between wire i and wire j f is the current frequency, μ 0 =4π×10 -4 is the vacuum permeability, D g To replace the equivalent depth of the conductor in the ground to replace the influence of the earth, d ij is the distance between wire i and wire j, R εi —equivalent radius of conductor i; For the unit parallel admittance of a multi-conductor transmission line, according to the electrostatic field calculation, the voltage U of each conductor i to the ground i Its linear charge density Q i The relationship is shown in the following formula: is the self-potential coefficient of conductor i, is the mutual potential coefficient between conductors i and j, U i is the potential of conductor i to ground, Q i is the linear charge density of wire i, ε 0 is the space dielectric constant, h i is the height of conductor i above the ground, D ij is the mirror distance between wire i and wire j, d ij is the distance between wire i and wire j; That is, Q = P -1 U = CU The P matrix is ​​the potential coefficient matrix, and the C matrix is ​​the capacitance coefficient matrix. The C matrix is ​​obtained by inverting the P matrix. According to the basic principle of electromagnetic field, the charge vector Q in the multi-conductor of the traction network will form the longitudinal current vector I of the multi-conductor of the traction network as it changes with time. The frequency domain equation of the traction network multi-conductor is obtained The multi-conductor parallel admittance matrix is ​​obtained as: Step 5: The electrical interaction between the entire multi-vehicle and traction power supply system is regarded as a composite chain network on the traction grid side, and each longitudinal parallel element is regarded as a section. The longitudinal parallel element includes a traction transformer, an electric locomotive, and a substation. Each power supply arm needs to be divided according to the section, and the impedance-admittance matrix of each section segment multi-conductor is solved separately, Z k For the traction network impedance slice segment between slice k and slice k+1, write the node voltage equation: The left side is the system node admittance matrix Y, which is obtained by the staggered superposition of the admittance matrices of the longitudinal parallel elements and the transverse series elements in a single power supply arm; when the length L between each section segment is known, each section segment is equivalent to a Π-type equivalent circuit according to the unit length multi-conductor impedance matrix Z' and the admittance matrix Y', and the calculation method is as follows: Step 6: The traction calculation of the electric locomotive's electrical parameters is based on the train's own parameters and the line parameters. The traction calculation method includes: first, discretizing the entire line according to a fixed step size Δs to obtain a series of discrete points {s 1 ,s 2 ,...,s k ...,s n }, taking the line speed limit as the upper speed limit, we can get the optional speed range [0,v lim ], the speed interval at each discrete point is divided with Δv as a fixed step size, and the complete vs speed curve is obtained by determining the speed point combination at each discrete point; the actual electric locomotive includes its own maximum traction force F tm , maximum acceleration a max , Maximum braking force F bm and the prescribed travel time T tot Limitation, determine whether the train trajectory is feasible; the feasibility is mainly based on the speed between two discrete points to calculate and compare various parameters, solve for traction, assuming v k-1 <v k <v k+1 , If F t (v k )>F tm Then these two candidate speeds are unattainable, and the same is true for the braking force; solve for the train acceleration, If a k =a max Then the two speed points are unreachable; after satisfying the above constraints, the total travel time T is calculated based on the trajectory. If the specified travel time T is met tot If the error is allowed, the trajectory is feasible, otherwise the candidate speeds are re-screened; after obtaining the feasible trajectory, according to P = F·v and Solve the active power and reactive power of the electric locomotive, where F is the resultant force on the electric locomotive and cosα is the power factor of the train itself; the formula for calculating the resultant force of the train is F=Ma, where M is the weight of the electric locomotive, and then obtain the time, position, speed, active power and reactive power of the train at each discrete point in distance, and use linear interpolation to convert the train traction calculation results into traction calculation results uniformly distributed in the time domain with 1 second as the unit; Step 7: Establish a multi-vehicle load process under non-uniform departure intervals based on the line traffic organization planning; the data matrix s_p_loco of the electric locomotive traction calculation result in step 6, the behavior time, is listed as the corresponding parameter; according to the operation diagram, the departure intervals between the up and down trains are counted respectively to obtain the data vector D up , D down , remember D up ={D up (1),D up (2),...,D up (K)},D do ={D do (1),D do (2),...,D do (K)}, the data vector represents the running difference between two adjacent electric locomotives with the same running direction, and the multiple locomotives are arranged in time and space dimensions according to their respective time differences for up and down directions, that is, the time and space relative translation properties are formed according to the time difference, but the movement process of the same electric locomotive is not changed, and the corresponding traction calculation results are called for different electric locomotives; Step 8, perform flow calculation on the electrical interaction between multi-vehicle loads and the traction grid side of the traction power supply system in units of 1 second. For each flow calculation, that is, every second, determine the position of the online electric locomotive, divide each power supply arm into sections according to the substation, substation, and electric locomotive position, and then calculate the node admittance matrix Y between the two sections; update the node current vector I with the electrical parameters of the traction transformer and the electric locomotive, assuming that the grid voltage of all electric locomotives is 27.5kV, that is, the rated voltage of the traction grid, and update the current vector and voltage vector through U=YI until the difference between two adjacent node voltage vectors meets the convergence accuracy, stop the calculation and save the result; Step 9, according to the operating conditions of the electric locomotive, combined with the departure interval of the actual line, the departure interval is adjusted to find the maximum transportation capacity of the line as the maximum power supply capacity boundary; Step 10: If the grid voltage, transformer winding current, capacity and power factor are not close to the national standard limit, continue to reduce the departure interval, increase the number of departures, increase the traction load, adjust the departure interval to make the traction braking conditions of multiple vehicles overlap, and repeat the evaluation process of steps 6 to 9 until the evaluation result is close to the national standard limit. Calculate the traffic organization into the transport volume, and use the maximum transport capacity of the output line as the maximum capacity boundary of the traction power supply.

9. The method for evaluating the boundary of traction power supply capacity of an electrified railway according to claim 8, It is characterized in that Step 9 also includes: When a series of departure intervals are determined, the maximum power supply capacity is determined by comparing the allowable values ​​specified in the national standard. For the traction network voltage, the national standard stipulates that the upper limit of the overhead line and electric locomotive network voltage is 29kV and the lower limit is 20kV. When the system is in a fault or under maintenance, the lower limit is 19kV. Therefore, the node voltage vector value is extracted to determine whether it is within the allowable range. If it exceeds the range, it is determined that the power supply capacity is insufficient. For the winding current and capacity of the traction transformer, taking the α power supply arm as an example, the transformer T winding current I T 、F winding current I F The calculation formula is as follows: In the formula, Z 1 , are the impedance values ​​of the primary winding, tertiary winding and secondary winding converted to the primary winding; the capacity of the traction transformer is S α =|U TN I T |+|U FN I F |, if the overload current exceeds 1.5 times the rated current of the transformer winding or the transformer capacity exceeds 1.5 times the rated capacity, it means that the power supply capacity is insufficient; for the power factor, for the α power supply arm traction transformer, according to its active output P α And the corresponding capacity S α Solving for Power Factor If λ<0.9, the power supply capacity is insufficient.

10. A computer-readable storage medium having a computer program stored thereon, It is characterized in that The computer program is executed by a processor to implement the steps of the method for evaluating the boundary of traction power supply capacity of an electrified railway as described in any one of claims 1-9.

Images