A modeling method for calculating an arc reignition model during a lowering of a pantograph of a motor train set based on PSCAD

Abstract

The application discloses a modeling method for calculating an arc reignition model during a pantograph lowering process of a motor train unit based on PSCAD, considers an overvoltage factor, finds that the arc generated during the pantograph lowering process can cause a high overvoltage result, and establishes a simulation model for the situation. The simulation model modeling method proposed in the scheme is different from the prior art, and aims to propose a modeling method for simulating the arc reignition development and change process and the overvoltage evolution process during the pantograph lowering process of the motor train unit. The main function is to judge the arc reignition extinction condition in real time and calculate the arc resistance in real time according to the pantograph-catenary distance change and the voltage difference change on both sides of the pantograph, to assign the equivalent value of the calculated arc resistance RDF in the variable RLC module, and finally to simulate the pantograph-catenary arc development and change process and the overvoltage evolution process during the pantograph lowering process in the form of a series nonlinear resistance in the circuit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of high-speed motor train pantograph simulation, more particularly, to a modeling method for calculating a pantograph arc reignition model during pantograph lowering based on PSCAD. BACKGROUND

[0002] In recent years, China's railway industry has developed rapidly. However, China's high-speed railway will encounter various problems in the process of rapid development, among which the train operation safety is the most important. In order to avoid the influence of external natural environment such as snow, rain, haze, etc., more and more trains integrate the high-voltage equipment on the roof into the network side cabinet. There are many devices in the network side cabinet, and when overvoltage occurs, the equipment in the box may flash over. Therefore, the electric field simulation of the train network side cabinet equipment is crucial to the safe and stable current collection of the train.

[0003] The consequences of overvoltage are as follows:

[0004] Because the arc resistance has a nonlinear characteristic, a certain bow net distance corresponds to a certain breakdown voltage value. During the process of raising the pantograph, as the bow net distance decreases, when the actual voltage is less than the breakdown voltage, it shows a large resistance characteristic; continue to raise the pantograph for a distance, when the actual voltage is greater than the breakdown voltage, an arc is generated. This phenomenon will cause pantograph failure and other problems.

[0005] During the lowering of the train, arc reignition phenomenon occurs: at a certain time before the arc current zero, the arc voltage is lower than the arc ignition voltage at this time, the arc is extinguished, and at this time, the gas containing positive and negative ions is left in the air, and the gap voltage of the gas is recorded as U b . After the alternating current crosses zero, during the process of lowering the pantograph, the voltage measured by the power supply changes according to the sine law, while the voltage on the train side of the pantograph is basically unchanged, and the voltage difference (gap voltage) between the two sides of the pantograph gradually increases. When the voltage difference (gap voltage) between the two sides of the pantograph increases to more than the gap breakdown voltage U b , the arc reignites; then it is extinguished at the zero crossing of the alternating current. If the lowering process is slow, the above process will be repeated and multiple arc reignition and extinction will occur. During the arc reignition process, a high overvoltage is generated, which causes strong impact on the insulation equipment and even damages it.

[0006] The existing arc resistance simulation technologies mainly include: combination modeling based on EMTP software to simulate the arc dynamic characteristics before and after the tripping of a circuit breaker, and to obtain the dynamic parameter change waveform; simulation of the working process of a DC circuit breaker based on ANSOFT software, to study the influence of the selection of internal devices of the DC circuit breaker on the arc process; improvement of mayr and cassie arc simulation based on a simulink toolbox; and simulation of the physical field of an AC arc based on COMSOL software. In the modeling of the arc model, it is found that many scholars do not consider the arc reignition and the change of the pantograph-catenary distance when modeling the pantograph-catenary drop-out overvoltage.

[0007] The simulation model modeling method provided in the scheme is different from the prior art, and aims to provide a modeling method for simulating the arc reignition development change process and the overvoltage evolution process in the pantograph drop process. The main function is to determine the arc reignition extinction condition in real time according to the change of the pantograph-catenary distance and the voltage difference on both sides of the pantograph, and to calculate the arc resistance in real time. The equivalent value of the calculated arc resistance RDF is assigned in the variable RLC module, and finally the pantograph-catenary arc development change process and the overvoltage evolution process in the pantograph drop process are simulated in the form of a series nonlinear resistor in the circuit. SUMMARY

[0008] Therefore, the present application provides a modeling method for calculating an arc reignition model in a pantograph drop process based on PSCAD. The pantograph drop speed and the pantograph-catenary distance are set as needed. The present application simulates the overvoltage value caused by the arc reignition process in the pantograph drop process, simulates the arc resistance after the time interval breakdown of the pantograph by building a pantograph-catenary module, and thus achieves the purpose of providing a new basis for the insulation selection of equipment.

[0009] A modeling method for calculating an arc reignition model in a pantograph drop process based on PSCAD, comprising:

[0010] A pantograph simulation model, a pantograph-catenary arc simulation model, a gap breakdown process simulation model, a pantograph-catenary distance simulation model, an arc variable capacitance simulation model, and a current zero-crossing detection model;

[0011] The implementation steps are as follows:

[0012] Step 1): output the distance between the pantograph and the catenary in the pantograph drop process according to the pantograph-catenary distance simulation model;

[0013] Step 2): output the time of the gap breakdown between the pantograph and the catenary in the pantograph drop process according to the gap breakdown process simulation model;

[0014] Step 3): output the time of the current zero-crossing according to the current zero-crossing detection model;

[0015] Step 4): The pantograph-catenary arc is output according to the pantograph-catenary arc simulation model;

[0016] Step 5): The equivalent variable capacitance between the arcs is output according to the arc variable capacitance simulation model;

[0017] Step 6): The vehicle-side voltage waveform diagram output in the EMU simulation model can be used to determine the overvoltage at arc breakdown and the number of arc reignitions by comparing the numerical mutation and shape changes of the vehicle-side voltage at different times.

[0018] Preferably, the step 1): The pantograph-catenary distance simulation model is used to simulate the change of the pantograph-catenary distance with time, L is the pantograph-catenary distance, C1 is a logic signal for determining whether the pantograph and catenary are in reliable contact, C1 is 1 when not in contact and 0 when in reliable contact, and the mathematical model is:

[0019] L = vt (0≤L≤0.5m)

[0020]

[0021] Where v represents the pantograph lowering speed.

[0022] Preferably, in the step 2): Gap breakdown process simulation model, L is the pantograph-catenary distance obtained in step 1), E a The voltage between the pantograph and the contact wire, and C2 is a signal for determining whether the arc is broken down, C2 is 0 when not broken down and 1 when broken down, and the mathematical model is:

[0023]

[0024]

[0025] Where U represents the breakdown voltage between the pantograph and the catenary, and a certain pantograph-catenary distance corresponds to a certain breakdown voltage value.

[0026] Preferably, in the step 3): Current zero-crossing detection model, I1 is the current between the catenary and the EMU, and C3 is the I1 zero-crossing signal, and the mathematical model is:

[0027]

[0028] Where C3 = 1 represents the current zero-crossing.

[0029] Preferably, in the step 4) : pantograph-catenary electric arc simulation model, L is the pantograph-catenary distance obtained in step 1), and RDF is the electric arc resistance, which is determined based on C1, C2 and C3 obtained in steps 1), 2) and 3) to determine whether the electric arc is ignited, i.e. when the distance L increases to a certain extent, the voltage between the pantograph and the catenary is greater than the breakdown voltage, at this time the electric arc is reignited, at the zero-crossing point of the alternating current, the electric arc is extinguished, and when the distance L continues to increase to a certain extent, the voltage between the pantograph and the catenary is again greater than the breakdown voltage, at this time the second electric arc is ignited. Wherein the electric arc resistance is a very small value when the electric arc is ignited, and is infinite when the electric arc is extinguished, and the equivalent value of the final output RDF is assigned to the inherent variable RLC module in PSCAD, and finally the electric arc between the pantograph and the catenary when the pantograph is lowered is simulated in the form of a series nonlinear resistor in the circuit. The mathematical model is:

[0030]

[0031] Wherein g represents the electric arc conductance, k1, k2 and β are electric arc parameters, and the value of β ranges from -3 to 0.

[0032] Preferably, in the step 5) : electric arc variable capacitance simulation model, L is the pantograph-catenary distance obtained in step 1), and C is the numerical value of the variable capacitance, with the unit of pF, and the equivalent value of the final output C is assigned to the inherent variable RLC module in PSCAD, and finally the variable capacitance between the pantograph and the catenary when the pantograph is lowered is simulated in the form of a parallel nonlinear resistor with the electric arc resistance in the circuit. The mathematical model is:

[0033]

[0034] Wherein, the electric arc capacitance when completely disconnected is represented by 10 6

[0035] Preferably, in the step 6) : EMU simulation model, a 27.5kV power supply is used to replace the catenary, and the overvoltage and the number of reignitions of the electric arc when the electric arc is broken down are determined by comparing the amplitude mutation and the number of amplitude mutations of the vehicle-side voltage at different times in the vehicle-side voltage waveform diagram output by the model, wherein the vehicle-side voltage is represented by E1. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is the pantograph-catenary distance simulation model of the present application.

[0037] Figure 2 It is the gap breakdown process simulation model of the present application.

[0038] Figure 3 It is the pantograph-catenary electric arc simulation model of the present application.

[0039] Figure 4 ​Arc variable capacitance simulation model for the present application.

[0040] Figure 5 Design for four models.

[0041] In the figure, L is the pantograph-catenary distance, C1 is the logical signal for judging whether the pantograph and catenary are in reliable contact (C1 is 1 when not in contact, and C1 is 0 when in reliable contact), E1 is the voltage value between the pantograph and the catenary, C2 is the logical signal for judging whether the pantograph and catenary are in breakdown (C2 outputs 1 when in air breakdown, and C2 outputs 0 when not in breakdown), C3 is the logical signal for judging whether the current is over the zero point (C3 is 1 when over the zero point, and C3 is 0 when not over the zero point), C is the variable capacitance of the arc between the pantograph and the catenary, k1, k2 and β are arc parameters, and RDF is the arc resistance. DETAILED DESCRIPTION

[0042] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0043] The present application provides a simulation model of pantograph-catenary overvoltage for a motor train unit, and an arc will be generated between the pantograph and the catenary as the distance between the pantograph head and the catenary increases during the process of lowering the pantograph. Figure 1 As shown in the figure, a simulation model of pantograph-catenary distance is built in PSCAD. The time of lowering and raising the pantograph is generally about 5-10 s, and the working height is about 2 m. When the pantograph-catenary distance is less than 10 m, it is considered that the pantograph and the catenary are in reliable contact, and the arc disappears. -6 The output L in the figure is the pantograph-catenary distance, and C1 is the logical signal for judging whether the pantograph and the catenary are in reliable contact.

[0044] As the pantograph is lowered, when the pantograph-catenary distance increases to a certain value, the air will be broken down and an arc will be generated. Under standard atmospheric pressure, the empirical formula of the breakdown voltage of the gap and the distance is as follows:

[0045]

[0046] In the formula, U is the air breakdown voltage, with the unit of kV, and l is the distance between the pantograph and the catenary, with the unit of cm. As shown in the figure, a simulation model of the process of gap breakdown is built according to formula (1), and E1 is the voltage value between the pantograph and the catenary. C2 outputs 1 when in air breakdown, and C2 outputs 0 when not in breakdown. Figure 2

[0047] After the air gap between the pantograph and the catenary is broken down, an arc between the pantograph and the catenary will be generated. Assuming that the arc radius is constant, the arc column temperature is uniformly distributed along the radial direction, the electrical conductivity is a function of temperature, and the arc column plasma of the arc does not have space charge, the derivation of the arc conductance g model is as follows:

[0048] ​g = F(Q) = F[∫(P - P0)dt] (2)

[0049]

[0050] where P is the input power of the arc, P0 is the output power of the arc, and Q is the energy accumulated in the arc formation. Both P and P0 are functions of the arc conductance g, and the specific relationship is shown as follows:

[0051]

[0052] P0 = k1g -β L (5)

[0053] where i is the arc current, L is the arc length, and k1 and β are constants.

[0054] The above relationship is rearranged as follows:

[0055]

[0056] The total arc energy Q and the arc conductance g are:

[0057] Q = qπr 2 L (7)

[0058]

[0059] According to the gas molecule motion theory, the energy q accumulated per unit volume of the arc is:

[0060]

[0061] where p is the atmospheric pressure, T1 is the ambient temperature, and T0 is the temperature of the generated arc. Assuming that the atmospheric pressure p and the constant pressure specific heat capacity are constants, the arc conductivity σ is derived from the Saha formula of the arc theory as:

[0062]

[0063] where σ0 is the arc conductance per unit length, and m is a coefficient.

[0064] It can be seen that both the total arc energy Q and the arc conductance g are functions of the arc temperature T0. From the above series of formulas, it can be derived that:

[0065]

[0066] Substituting formula (11) into formula (6) gives:

[0067]

[0068] The formula (12) is the final arc model, k1, k2 and β are arc parameters, and the value range of β is -3<β<0 according to the description in the literature and the analysis of arc mechanism. The arc simulation model of catenary is built in PSCAD according to the formula (12) as shown in the formula (13), and RDF is the arc resistance. Figure 3

[0069] With the increase of the pantograph-catenary distance, there is a variable capacitance between the pantograph and the catenary related to the pantograph-catenary distance. The variable capacitance simulation model of arc is built in PSCAD as shown in the formula (14), and the formula of the model is as shown in the formula (15). Figure 4

[0070]

[0071] When the pantograph is completely lowered, the capacitance between the pantograph and the catenary is approximately 0.5 pF, and the variable capacitance is 1×10 6 pF when the pantograph and the catenary are completely separated (the pantograph-catenary distance L<0.1 mm).

[0072] According to the above pantograph-catenary distance, gap breakdown process, pantograph-catenary arc and variable capacitance four models, they are created in PSCAD software. The final output arc resistance RDF of the pantograph-catenary arc simulation model is given in the inherent variable RLC module in PSCAD, and the pantograph-catenary arc when the pantograph rises and falls is simulated in the form of a series nonlinear resistance in the circuit. The overvoltage and arc reignition times when the arc breaks down can be judged by comparing the amplitude mutation of the vehicle side voltage and the amplitude mutation times in the vehicle side voltage waveform diagram output by the model.

[0073] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, and all equivalent changes or modifications made according to the patent application scope of the present application are within the scope of the present application.​​

Claims

1. A modeling method based on PSCAD for calculating the arc reignition model during pantograph lowering of a high-speed train, characterized in that, include: Simulation models for high-speed trains, pantograph-catenary arc, gap breakdown process, pantograph-catenary spacing, variable capacitor arc, and current zero-crossing detection. The implementation steps are as follows: Step 1): Output the distance between the pantograph and the contact wire when lowering the pantograph based on the pantograph-contact wire spacing simulation model; Step 2): Obtain the moment of bow-net penetration during bow lowering based on the output of the simulation model of the gap penetration process; Step 3): Obtain the time of the current zero-crossing point based on the output of the current zero-crossing detection model; Step 4): Obtain the pantograph-catenary arc during pantograph descent based on the output of the pantograph-catenary arc simulation model; In the pantograph-catenary arc simulation model, L The distance between the pantograph and the catenary obtained in step 1) is given by RDF, which is the arc resistance. This arc resistance is used to determine whether an arc has occurred based on C1, C2, and C3 obtained in steps 1), 2), and 3). C1 is the logic signal for reliable pantograph-catenary contact, C2 is the signal for arc breakdown, and C3 is the current zero-crossing signal. When lowering the pantograph, the distance... L When the voltage between the pantograph and the catenary increases to exceed the breakdown voltage, the arc reignites. At this point, the alternating current crosses zero, and the arc extinguishes. L When the voltage between the pantograph and the catenary is increased again to exceed the breakdown voltage, a secondary arc occurs. During arcing, the arc resistance is very small, and when the arc is extinguished, it is infinite. The equivalent value of the RDF output from the pantograph-catenary arc model is assigned to the inherent variable RLC module in PSCAD. Finally, the pantograph-catenary arc during pantograph descent is simulated by connecting a nonlinear resistor in series in the circuit. The RDF can be calculated using the following mathematical model: in g Represents arc conductivity; , as well as β Here are the arc parameters, where β The value range is -3< β <0; Step 5): Obtain the equivalent variable capacitance between arcs based on the output of the arc variable capacitance simulation model; In the arc variable capacitance simulation model, C represents the magnitude of the variable capacitance in pF. The equivalent value of C output from the final arc variable capacitance simulation model is assigned to the inherent variable RLC module in PSCAD. Ultimately, the variable capacitance between the pantograph and the catenary during pantograph descent is simulated by connecting a nonlinear resistor in parallel with the arc resistance in the circuit. The mathematical model of C is: Among them, C=10 6 pF represents the arc capacitance when the circuit is completely disconnected. Step 6): In the train simulation model, the overvoltage and the number of arc reignitions during arc breakdown are determined by comparing the amplitude changes and the number of amplitude changes of the train side voltage at different times.

2. The modeling method for calculating the arc reignition model during pantograph lowering of a high-speed train based on PSCAD according to claim 1, characterized in that, In step 1): In the pantograph-catenary spacing simulation model, C1 is 1 when there is no contact and 0 when there is reliable contact. The mathematical model of C1 is: in v This represents the bow lowering speed.

3. The modeling method for calculating the arc reignition model during pantograph lowering of a high-speed train based on PSCAD according to claim 1, characterized in that, In step 2): the gap breakdown process simulation model, input... Ea The voltage between the pantograph and the contact wire is 0 when there is no breakdown and 1 when there is a breakdown. The mathematical model for C2 is: in U This represents the breakdown voltage between the bow and the catenary; a certain bow-catenary distance corresponds to a certain breakdown voltage value.

4. The modeling method for calculating the arc reignition model during pantograph lowering of a high-speed train based on PSCAD according to claim 1, characterized in that, In step 3): the current zero-crossing detection model For the current between the overhead contact line and the train, the mathematical model for C3 is: Where C3=1 represents the point where the current crosses zero.

5. The modeling method for calculating the arc reignition model during pantograph lowering of a high-speed train based on PSCAD according to claim 1, characterized in that, Step 6): In the train simulation model, the vehicle-side voltage waveform is compared with the amplitude changes and the number of amplitude changes at different times to determine the overvoltage and the number of arc reignitions during arc breakdown. The vehicle-side voltage is used as... express.

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