CN108363831A - A kind of DC series fault electric arc model emulation method - Google Patents

Abstract

The invention relates to a simulation method for a DC series fault arc model, belonging to the technical field of electrical engineering. The method includes the following steps: S1: build a DC series fault arc test platform, and conduct a test, measure and record the power supply voltage, arc distance, arc voltage, and arc current; S2: calculate the arc resistance according to the measured and recorded arc voltage and arc current, and analyze The relationship between the arc resistance, the power supply voltage and the arc distance is fitted by the formula; S3: According to the formula obtained by the fitting, the simulation model of the DC fault arc is established through Matlab/Simulink; S4: Set the simulation parameters, run the simulation model, and output the simulation results , and compared with the experimental results. The simulation method of the invention is based on real test data, comprehensively considers the influence of the power supply voltage and the arc distance on the arc, and has high simulation accuracy and strong universality.

Description

A Simulation Method of DC Series Fault Arc Model

technical field

The invention belongs to the technical field of electrical engineering and relates to a simulation method for a DC series fault arc model.

Background technique

With the continuous development of social economy, high-power power electronic devices have been widely used. What followed was the rapid popularization of DC systems in aerospace, solar power generation, and large-scale power grid energy storage. In a DC system, loose metal connectors, animal bites, and damage to insulation layers such as transmission lines may cause DC arcs. Due to the great difference between the DC fault arc and the AC arc, it cannot be detected by the existing protection devices such as fuses and circuit breakers, and the high temperature generated by the DC fault arc can easily burn the device and ignite the surrounding flammable and explosive products, eventually causing fire. Therefore, perfecting the DC fault arc model will help us to understand the combustion process of the arc more comprehensively, and provide more basis for the detection and protection of the DC fault arc.

At present, the more arc models used in engineering are mainly the Cassie model and the Mayr model, but the Cassie model is only suitable for the arc in the low resistance state before the current crosses zero, and the Mayr model is only suitable for the arc in the high resistance state, so the two The versatility is not high, and the parameter setting of the model is relatively difficult, which is inconvenient for users to use. In addition, the traditional static resistance model and time-varying resistance model have fewer considerations in the modeling process, and it is difficult to combine the simulation results with reality. Moreover, the above-mentioned several arc models do not consider the influence of the power supply voltage and the arc distance on the arc at the same time.

Contents of the invention

In view of this, the purpose of the present invention is to provide a DC series fault arc model simulation method to obtain a DC series fault arc model with high simulation accuracy, strong versatility, and comprehensive consideration of power supply voltage and arc spacing.

To achieve the above object, the present invention provides the following technical solutions:

A DC series fault arc model simulation method, the method includes the following steps:

S1: Build a DC series fault arc test platform and conduct tests to measure and record the power supply voltage, arc distance, arc voltage, and arc current;

S2: Calculate the arc resistance based on the measured arc voltage and arc current, analyze the relationship between the arc resistance, the power supply voltage and the arc distance, and perform formula fitting;

S3: According to the formula obtained by fitting, establish a simulation model of DC fault arc through Matlab/Simulink;

S4: Set the simulation parameters, run the simulation model, output the simulation results, and compare with the measured results.

Further, the DC series fault arc test platform in step S1 includes an arc generating device, and the arc generating device includes two insulating fixtures, one end of one insulating fixture is fixed on a fixed base, the other end clamps a stationary electrode, and the other One end of the insulating fixture is fixed on the sliding block, and the other end clamps the movable electrode. The fixed base is provided with a scale, and the sliding block is slid and adjusted on the fixed base through a side regulator. To DC regulated power supply;

Step S1 specifically includes the following steps:

S11: Set the output voltage of the DC stabilized power supply, adjust the side regulator so that the stationary electrodes are in full contact with the movable electrodes, close the entire test circuit, and start the test;

S12: record the voltage and current waveforms at both ends of the arc generating device under normal conditions through an oscilloscope;

S13: Slowly adjust the side regulator to make the distance between the movable electrode and the stationary electrode until the distance is just enough to make the arc extinguish naturally, and record the output voltage and the maximum arcing distance at this time;

S14: Change the output voltage of the DC stabilized power supply, and repeat step S13 to record the maximum arcing distance under different voltages;

S15: Disconnect the test circuit, reset the output voltage of the DC stabilized power supply, and adjust the side regulator so that the stationary electrode is in full contact with the movable electrode, so that the entire test circuit is closed, and the test is started;

S16: Adjust the side regulator to make the distance between the movable electrode and the stationary electrode reach the set value, and record the arc voltage and arc current of the arc at this distance through the oscilloscope;

S17: Change the output voltage of the DC stabilized power supply, repeat step S16, and record the arc voltage and arc current at the same distance and at different voltages.

Further, the DC stabilized power supply is connected to the arc generating device through a current limiting resistor.

Further, the adjustment method of the side adjuster includes rough adjustment of the knob and fine adjustment of the stepping motor.

Further, the step S2 is specifically:

S21: According to the measured arc voltage and arc current, respectively calculate the average value of the arc voltage and arc current, and obtain the arc resistance;

S22: The mathematical model for fitting the arc resistance, power supply voltage, and arc spacing is,

R＝C ₁ +C ₂ ·U+C ₃ ·D+C ₄ ·U·D

Among them, C ₁ , C ₂ , C ₃ , and C ₄ are calculation coefficients, U is the power supply voltage, and D is the arc distance.

Further, step S3 is specifically: according to the obtained mathematical model, establish a simulation model of DC fault arc in Matlab/Simulink, and add white noise to the arc voltage and arc current output by the simulation model according to the actual situation.

The beneficial effects of the present invention are:

1. High simulation accuracy and strong versatility. Compared with the Cassie model, the Mayr model, the static resistance model, and the time-varying resistance model, the simulation results of the present invention on the arc voltage and arc current are closer to the actual arc data.

2. The influence of power supply voltage and arc spacing on arc is considered comprehensively. The input parameters of the simulation model include power supply voltage and arc distance, and the simulation results are affected by these two factors, which are consistent with the actual situation.

3. The present invention is based on the DC series fault arc model established by Matlab/Simulink, and the data all come from experiments, which is highly convincing. And it provides a simulation platform for the research of DC series fault arc.

Description of drawings

In order to make the purpose, technical scheme and beneficial effect of the present invention clearer, the present invention provides the following drawings for illustration:

Fig. 1 is the circuit diagram of the DC series fault arc system used in the test of the embodiment of the present invention;

Fig. 2 is a structural diagram of an arc generating device according to an embodiment of the present invention;

Fig. 3 is a three-dimensional discrete point diagram of arc resistance, power supply voltage, and arc spacing;

Fig. 4 is a three-dimensional discrete point diagram of arc resistance, power supply voltage, and arc spacing;

Fig. 5 is a simulation model diagram of a DC series fault arc;

Fig. 6 is a simulation result figure;

Figure 7 is a graph of the measured results.

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The present invention provides a DC series fault arc model simulation method, which first needs to collect real test data,

The embodiment of the present invention adopts the series circuit shown in FIG. 1 . The power supply used is a DC stabilized power supply. The output voltage of the power supply is adjustable from 0-1000V, and the output current is adjustable from 0-3A; the current-limiting resistor adopts a 1000W/200Ω variable resistor, which acts as a current-limiting function to avoid excessive circuit current. Damage to DC power supply and oscilloscope.

As shown in Figure 2, the arc generating device includes a stationary electrode 6, a movable electrode 7 and a sliding block 9, the sliding block 9 is provided with a side adjuster 10, and the stationary electrode 6 and the movable electrode 7 are fixed on a fixed surface by an insulating clamp 8. On the base 11, both the stationary electrode 6 and the movable electrode 7 are 10mm ² multi-core copper wires, and the side regulator 10 can adjust the movable electrode 7 to adjust the arc distance. The side regulator 10 has two adjustment methods. Coarse adjustment, there is a scale on the guide rail of the fixed base 11, and the moving distance can be seen; the second type is to precisely control the movement of the sliding block 9 by a stepping motor, and the moving distance can be directly displayed. Before the test, the two electrodes were in contact, and the distance between the arcs was the moving distance of the sliding block 9 . The oscilloscope collects arc voltage and arc current.

Arcing method: first make the two electrodes fully contact through the side regulator, so that the entire circuit is closed, and record the voltage and current waveforms under normal conditions with an oscilloscope and other equipment after power on. Then move the moving electrode slowly through the side regulator, and when the two electrodes are separated, an arc is generated. To keep the arc burning stably, the oscilloscope records the waveform of the voltage and current in the arc state. And when the distance between the two electrodes is too large, the arc is extinguished.

experiment procedure:

1. Study the maximum arcing distance of different voltages

①Set the output voltage of the DC stabilized power supply in advance. In this embodiment, a total of 5 levels are set, which are 250V, 290V, 330V, 370V, and 410V; ③Continue to slowly adjust the side regulator until the arc is naturally extinguished when the distance is too large, and record the distance that the moving electrode moves at this time. The distance can be read from the scale on the guide rail or directly from the stepper motor, that is, is the maximum arcing distance under this voltage condition, and the results are shown in Table 1.

Table 1

voltage 250V 290V 330V 370V 410V Maximum distance for arc stable combustion 7mm 8mm 10mm 12mm 13mm

2. Study the arc characteristics under different voltages and different distances

①Set the output voltage of the DC stabilized power supply in advance. In this embodiment, a total of 5 levels are set, which are 250V, 290V, 330V, 370V, and 410V; Fixed spacing (2mm, 3mm, 4mm, 5mm, etc. until the maximum spacing that can stably burn or the maximum spacing that can stably burn under different voltages has been known in the previous experiment), stable combustion; ③ The oscilloscope records in detail the arc voltage, Variations in arc current.

Considering that the generation process of the arc is not higher than 1ms, the arc quickly enters a stable combustion state. Therefore, only the average value of the arc voltage and the average value of the arc current are calculated when the arc burns stably, and the voltages of each power supply and each arc are calculated according to Ohm's law. Arc resistance at pitch.

Figure 3 and Figure 4 are three-dimensional discrete point diagrams of arc resistance, power supply voltage, and arc distance. The x-axis represents the power supply voltage, the y-axis represents the arc distance, and the z-axis represents the arc resistance. It decreases with the increase of the power supply voltage; when the power supply voltage is constant, the arc resistance increases with the increase of the arc distance.

In the actual implementation process of the present invention, it is found that the arc resistance is greatly affected by the power supply voltage and the arc distance, and the functional relationship between the arc resistance, the power supply voltage and the arc distance is fitted according to the experimental data. Using crossover (interaction) regression, the expression is as follows:

R＝C ₁ +C ₂ U+C ₃ D+C ₄ U D (1)

In the above formula, R is the arc resistance, the unit is Ω; U is the power supply voltage, the unit is V, 250V≤U≤410V; D is the arc distance, the unit is mm. C ₁ ~ C ₄ are coefficients obtained by calculation, which are related to the electrode materials used in the test. When 10mm ² multi-core copper wire is used in this embodiment, the obtained coefficients are as follows:

C ₁ =48.4803, C ₂ =-0.1294, C ₃ =18.9024, C ₄ =-0.0331 (3)

Furthermore, the power supply voltage is different, and the maximum arc distance that can maintain stable combustion is different, as shown in Table 2.

Table 2

voltage 250V 290V 330V 370V 410V Maximum distance for arc stable combustion 7mm 8mm 10mm 12mm 13mm

The relationship between the power supply voltage and the maximum distance for stable burning of the arc is as follows:

_Dmax ＝0.04U-3.2 (3)

In the above formula, D _max is the maximum distance for the arc to burn stably, and U is the power supply voltage.

To sum up, the mathematical model of the series fault arc is shown in formula (4), where, 250V≤U≤410V, the maximum stable arcing distance D _max under a certain power supply voltage U is 0.04U-3.2, 0<D≤D _max .

R＝48.4803-0.1294U+18.9024D-0.0331UD (4)

Fig. 5 is the mathematical model of the series arc fault established according to the present invention, and the series arc fault model built in Matlab/Simulink software. 1 and 2 in the model are input terminals, input power supply voltage and arc spacing respectively, 4 is the calculation module of the series fault arc mathematical model established by the present invention, and 5 is an output processing module, and it is practical to add the arc voltage and arc current of output 3 is an oscilloscope showing the final simulation results of arc voltage and arc current.

According to the built series fault arc model, input the power supply voltage and arc distance, and then the arc voltage and arc current waveform can be simulated. Figure 6 shows the simulation results when the input power supply voltage is 250V and the arc spacing is 2mm, and Figure 7 shows the actual measurement results. Comparing the simulation results with the measured results, the simulation results of arc voltage and arc current are very close to the actual arc data.

Finally, it is noted that the above preferred embodiments are only used to illustrate the technical solutions of the invention and not limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that it may be possible in form and details. Various changes can be made to it without departing from the scope defined by the claims of the present invention.

Claims (6)

1. a kind of DC series fault electric arc model emulation method, it is characterised in that：This method comprises the following steps：

S1：DC series fault electric arc test platform is built, and is tested, recording power voltage, electric arc spacing and electricity are measured Arc voltage, arc current；

S2：Arc resistance is calculated according to the arc voltage and arc current that measure record, analyzes arc resistance and supply voltage, electricity The relationship of arc spacing carries out formula fitting；

S3：According to the formula that fitting obtains, the simulation model of DC Line Fault electric arc is established by Matlab/Simulink；

S4：Simulation parameter is set, simulation model is run, exports simulation result, and compared with the result of actual measurement.

2. a kind of DC series fault electric arc model emulation method according to claim 1, it is characterised in that：In step S1 The DC series fault electric arc test platform includes arc generating device, and the arc generating device includes two insulating blanked clampers Tool, one end of one of dielectric holder are fixed on firm banking, and the other end clamps stationary electrode, another dielectric holder One end is fixed on sliding shoe, and the other end clamps float electrode, and scale is provided on the firm banking, and the sliding shoe passes through Side adjuster realizes that sliding shoe slidable adjustment on firm banking, the arc generating device are connected to D.C. regulated power supply；

Step S1 is specifically comprised the following steps：

S11：The output voltage of D.C. regulated power supply is set, adjusts side adjuster so that stationary electrode is complete with float electrode Contact allows entire test loop to be closed, starts to test；

S12：Pass through the voltage current waveform at oscillograph recording arc generating device both ends under normal circumstances；

S13：Slowly adjusting side adjuster makes the distance between float electrode and stationary electrode, until distance is just so that electric arc Naturally extinguish, record output voltage at this time and maximum arcing distance；

S14：Change the output voltage of D.C. regulated power supply, repeats step S13 and record the maximum arcing distance under different voltages；

S15：Disjunction hookup, resets the output voltage of D.C. regulated power supply, and adjusts side adjuster so that stationary electrode It is completely attached to float electrode, allows entire test loop to be closed, start to test；

S16：So that the distance between float electrode and stationary electrode is reached setting value by adjusting side adjuster, passes through oscillograph Record arc voltage and arc current of the electric arc under the distance；

S17：Change the output voltage of D.C. regulated power supply, repeats step S16, the electricity being recorded under same distance and different voltages Arc voltage and arc current.

3. a kind of DC series fault electric arc model emulation method according to claim 2, it is characterised in that：The direct current Regulated power supply is connected to the arc generating device by current-limiting resistance.

4. a kind of DC series fault electric arc model emulation method according to claim 2, it is characterised in that：The side The regulative mode of adjuster includes knob coarse adjustment and stepper motor accurate adjustment.

5. a kind of DC series fault electric arc model emulation method according to claim 2, it is characterised in that：The step S2 is specially：

S21：According to arc voltage and arc current that measurement obtains, the average value of arc voltage and arc current is calculated separately, Seek arc resistance；

S22：The mathematical model for fitting arc resistance and supply voltage, electric arc spacing is,

R=C₁+C₂·U+C₃·D+C₄·U·D

Wherein, C₁、C₂、C₃、C₄For design factor, U is supply voltage, and D is electric arc spacing.

6. a kind of DC series fault electric arc model emulation method according to claim 5, it is characterised in that：Step S3 tools Body is：According to the mathematical model of acquisition, the simulation model of DC Line Fault electric arc is established in Matlab/Simulink, and according to Arc voltage that actual conditions export simulation model, arc current add white noise.