In-phase traction network fault current online detection device based on dynamic compensation

Abstract

The utility model relates to the technical field of railway in-phase traction power supply, in particular to an in-phase traction network fault current online detection device based on dynamic compensation, which comprises an analog differential sampling circuit, a signal conditioning filter circuit and a threshold comparison output circuit. And a photoelectric isolation output interface, a shielding metal shell and a bipolar auxiliary power supply module are also arranged. The analog differential sampling circuit is connected in parallel to two ends of the direct current bus capacitor, converts voltage fluctuation into analog voltage signals, inputs the analog voltage signals into the threshold comparison output circuit to be compared with reference voltage after clutter and direct current components are filtered out through the signal conditioning filter circuit, and outputs signals to the converter controller fault interruption interface through the photoelectric isolation output interface. The shielding metal shell guarantees the anti-interference performance, and the bipolar auxiliary power supply module provides stable power supply. According to the device, fault current online detection is realized through a hardware circuit, the problem of software algorithm delay is effectively avoided, and the real-time performance and reliability of in-phase traction network fault identification are remarkably improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to railway same phase traction power supply technical field, concretely relates to a same phase traction network fault current on -line detection device based on dynamic compensation. BACKGROUND

[0002] In the same phase traction power supply system of modern electrified railway, the dynamic compensation device (such as SVG or same phase power supply current controller) based on voltage source type converter is widely used, and AC-DC-AC conversion structure is used to realize negative sequence treatment and reactive power compensation. In the core architecture of this kind of device, the DC bus capacitor as the energy buffer unit is connected between the rectifier side and the inverter side, and plays a key role in supporting DC voltage stability and instantaneous power exchange. The current traction network fault detection technology mainly follows the traditional relay protection idea. For example, the technical scheme disclosed in patent CN214011411U needs to install a special high-voltage current transformer and a voltage transformer on the 27.5kV high-voltage side feeder, collect the real-time power frequency electrical quantities of the power supply arm, and calculate the impedance or current increment through a digital microcomputer protection device to identify the short-circuit fault.

[0003] The above-mentioned existing technology based on high-voltage side direct sampling has the following specific hardware and architecture defects in actual engineering application: 1. High insulation cost and difficult installation and maintenance of high-voltage side sensor. The existing scheme must obtain signals in a high-voltage environment, which requires that the matching current / voltage transformer must have a very high insulation voltage level. This not only greatly increases the volume and manufacturing cost of the device, but also the high-voltage side sensor is usually installed in an outdoor switchyard, and the signal needs to be transmitted through a long cable to an indoor control cabinet. Long-line transmission is easily disturbed by a strong electromagnetic environment, resulting in distortion of the sampling signal and affecting the detection accuracy. 2. There is inherent calculation delay and algorithm burden in digital algorithm. The existing technology relies on DSP (digital signal processor) for complex mathematical operations. This software algorithm-based processing method is limited by the sampling window width and has a natural calculation delay, which is difficult to meet the real-time requirements of microsecond-level fast cutting or locking pulses for transient fault currents, and occupies valuable algorithm resources of the controller. UTILITY MODEL CONTENTS

[0004] The utility model aims at solving the technical problems of high insulation cost, difficult installation and maintenance and large processing delay of traditional digital algorithm caused by the dependence of the existing traction network fault detection technology on high-voltage side transformers.

[0005] To solve the above technical problems, the utility model adopts the following technical scheme:

[0006] Analog differential sampling circuit, signal conditioning filter circuit and threshold value comparison output circuit.

[0007] The input end of the analog differential sampling circuit is connected in parallel to the two ends of the DC bus capacitor of the phase-shifting power converter, and is used to convert the fluctuation of the DC bus voltage into an analog voltage signal; the output end of the analog differential sampling circuit is electrically connected to the input end of the signal conditioning filter circuit, and is used to filter out high-frequency noise and DC components in the analog voltage signal;

[0008] The output end of the signal conditioning filter circuit is electrically connected to the signal input end of the threshold comparison output circuit.

[0009] The output end of the threshold comparison output circuit is connected to the fault interruption interface of the converter controller.

[0010] In the above technical solution, the analog differential sampling circuit comprises a DC blocking high-voltage capacitor, an input resistor, a first operational amplifier and a feedback resistor; one end of the DC blocking high-voltage capacitor is connected to the positive electrode of the DC bus capacitor, and the other end is connected to the inverting input end of the first operational amplifier through the input resistor; the feedback resistor is connected between the inverting input end and the output end of the first operational amplifier; the non-inverting input end of the first operational amplifier is grounded, and the output end thereof serves as the output end of the analog differential sampling circuit.

[0011] In the above technical solution, the analog differential sampling circuit further comprises a set of bidirectional limiting diodes; the set of bidirectional limiting diodes is connected in parallel between the inverting input end and the non-inverting input end of the first operational amplifier, and is used to clamp the input voltage amplitude.

[0012] In the above technical solution, the signal conditioning filter circuit comprises a second operational amplifier, a first filter capacitor, a second filter capacitor, a first filter resistor and a second filter resistor; the first filter resistor and the second filter resistor are connected in series between the input end and the inverting input end of the second operational amplifier; the first filter capacitor is connected between the common connection point of the first filter resistor and the second filter resistor and the output end of the second operational amplifier.

[0013] In the above technical solution, the passband frequency range of the signal conditioning filter circuit is set by an RC constant network hardware composed of the parameter values of the first filter capacitor, the second filter capacitor, the first filter resistor and the second filter resistor.

[0014] In the above technical solution, the threshold comparison output circuit comprises a voltage comparator, a reference voltage generation branch and a positive feedback hysteresis branch; the non-inverting input end of the voltage comparator receives a signal from the signal conditioning filter circuit, and the inverting input end thereof is connected to the reference voltage generation branch; the positive feedback hysteresis branch is connected between the output end and the non-inverting input end of the voltage comparator.

[0015] Adopting the technical scheme, the reference voltage generating branch includes a pull-up resistor and an adjustable potentiometer connected in series between the auxiliary power supply and the ground; and the sliding contact of the adjustable potentiometer is connected to the inverting input terminal of the voltage comparator.

[0016] Adopting the technical scheme, the detection device further includes a photoelectric isolation output interface; the input side light emitting diode of the photoelectric isolation output interface is connected to the output terminal of the threshold value comparison output circuit, and the output side photosensitive triode is connected to the fault interruption interface of the converter controller.

[0017] Adopting the technical scheme, the detection device further includes a shielded metal shell; the analog differential sampling circuit, the signal conditioning filter circuit and the threshold value comparison output circuit are all installed inside the shielded metal shell; and a grounding terminal is arranged on the surface of the shielded metal shell.

[0018] Adopting the technical scheme, the detection device is configured with a bipolar auxiliary power supply module; and the output terminals of the bipolar auxiliary power supply module are respectively connected to the positive power supply terminal and the negative power supply terminal of the operational amplifier in the analog differential sampling circuit and the signal conditioning filter circuit.

[0019] Due to the adoption of the above technical scheme, the present application has the following technical progress compared with the prior art:

[0020] By connecting the input terminal of the analog differential sampling circuit in parallel to both ends of the DC bus capacitor of the phase power supply converter, the correlation between the DC bus voltage fluctuation and the fault occurrence is utilized to directly obtain the fault characteristic analog voltage signal on the DC side of the converter; the change of the analog voltage signal detection position in the present application makes the device not need to install high-voltage level voltage or current transformers on the high-voltage AC feeder side of the traction network, thereby effectively solving the problems of high insulation cost, large size and difficult outdoor installation and maintenance of the high-voltage side sensor in the prior art.

[0021] The analog voltage signal is continuously filtered and compared by the hardware processing architecture formed by the analog differential sampling circuit, the signal conditioning filter circuit and the threshold value comparison output circuit in sequence, and the result is directly output to the fault interruption interface of the converter controller; the pure hardware signal processing mode of the present application avoids the sampling and holding delay of the analog-to-digital conversion and the calculation delay caused by the complex algorithm operation of the digital processor in the traditional microcomputer protection device, significantly improves the response speed of the fault detection, and meets the protection demand of the phase power supply converter system for fast response to faults. BRIEF DESCRIPTION OF DRAWINGS

[0022] The present application will be further described below with reference to the drawings.

[0023] Figure 1The utility model discloses a kind of based on dynamic compensation's in-phase traction network fault current on-line detection device's overall principle schematic diagram;

[0024] Figure 2 It is the principle schematic diagram of the analog differential sampling circuit of the utility model;

[0025] Figure 3 It is the principle schematic diagram of the signal conditioning filter circuit of the utility model;

[0026] Figure 4 It is the principle schematic diagram of the threshold value comparison output circuit of the utility model.

[0027] In the drawing: 1, analog differential sampling circuit;2, signal conditioning filter circuit;3, threshold value comparison output circuit;4, opto-isolator output interface;5, bipolar auxiliary power module;6, shielded metal enclosure. DETAILED DESCRIPTION

[0028] The utility model is further explained in detail in connection with embodiment as follows:

[0029] Example 1

[0030] As Figures 1-4 The utility model discloses a kind of based on dynamic compensation's in-phase traction network fault current on-line detection device, including analog differential sampling circuit 1, signal conditioning filter circuit 2 and threshold value comparison output circuit 3, and is equipped with opto-isolator output interface 4, shielded metal enclosure 6 and bipolar auxiliary power module 5 in matching arrangement.The device is installed in the interior of inverter cabinet, and the rapid detection and fault discrimination to DC bus voltage fluctuation are realized by analog circuit mode.

[0031] The shielding shell of aluminium alloy material is installed on the circuit board periphery of the detection device, the shell size is 150mm long, 100mm wide, 40mm high, and the shell thickness is 2mm.The surface of shell is silver gray after anodizing treatment, four sides are provided with cooling groove, and the top surface is provided with the grounding bolt of M4 specification, the bolt is reliably connected with the inverter cabinet ground row by braided copper band.The bottom of shell is fixed to the mounting hole position of the four corners of circuit board by four M3 screws, to realize the integrated installation of circuit board and shielding shell.

[0032] Analog differential sampling circuit 1 includes direct-current isolation high-voltage capacitor, input resistor, first operational amplifier, feedback resistor and bidirectional limiting diode group.The input interface of the circuit adopts two wiring terminals with a spacing of 10mm, and the terminal rated current is 10 amperes.The left terminal is connected to the positive terminal of inverter DC bus capacitor by red high-voltage wire with a cross-sectional area of 2.5 square mm, and the right terminal is connected to the negative terminal of bus capacitor by black wire of the same specification, and the length of the wire is 300mm, and OT type cold pressure terminal is pressure connected at both ends.

[0033] The direct-current blocking high-voltage capacitor is selected from a B32774 series of metallized polypropylene film capacitors, and has a capacitance of 100 nF and a withstand voltage of DC 2000 V. The capacitor is installed in a vertical manner, and two pins have a spacing of 27.5 mm. One pin is welded to a positive input terminal through a via hole in the circuit board, and the other pin extends downward by 15 mm and is welded to a trace on an inner layer of the circuit board. The capacitor is packaged with blue flame-retardant resin, and a white parameter mark is printed on the top.

[0034] The input resistor is selected from a PR02 series of metal film resistors, has a resistance of 100 kΩ, a power rating of 2 W, and an accuracy of 1%. One end of the resistor is welded to a downstream pin of the direct-current blocking capacitor, and the other end extends by 20 mm and is welded to an inverting input pin of the operational amplifier chip. The resistor has a color ring of brown, black, gold and red, and clearly indicates the parameter value.

[0035] The first operational amplifier is selected from an OPA2277 type of dual operational amplifier chip, and eight pins of the chip have a spacing of 2.54 mm and are arranged in two rows. The chip uses an internal A channel operational amplifier unit, a second pin is an inverting input terminal, a third pin is a non-inverting input terminal, and a first pin is an output terminal. An eighth pin of the chip is connected to a positive 12 V power supply rail, and a fourth pin is connected to a negative 12 V power supply rail. Each of the power supply pins is connected in parallel with a 100 nF MLCC surface mount capacitor as a decoupling capacitor.

[0036] The feedback resistor is also selected from a PR02 series of metal film resistors, and has a resistance of 10 kΩ and a power of 2 W. One end of the resistor is welded to the second pin of the operational amplifier, and the other end is connected across the first pin to form a negative feedback path of the inverting amplifier. According to the virtual short and virtual open principle, the ratio of the input resistor to the feedback resistor determines the gain coefficient of the differential circuit.

[0037] The bidirectional limiting diode group is composed of two Schottky diodes connected in reverse series, and is selected from a BAT54S type of Schottky diode of On Semiconductor. The forward voltage drop of a single diode is about 0.3 V. The cathodes of the two diodes are connected to the second pin of the inverting input terminal, and the anodes of the two diodes are connected to the third pin of the non-inverting input terminal. The third pin is directly connected to the ground layer of the circuit board. When the input voltage exceeds ±0.6 V, the diodes are turned on to clamp and protect the input stage of the operational amplifier.

[0038] The signal conditioning filter circuit 2 comprises a second operational amplifier, a first filter capacitor, a second filter capacitor, a first filter resistor and a second filter resistor. The signal conditioning filter circuit 2 is arranged adjacent to the differential sampling circuit. The second operational amplifier adopts a B channel operational amplifier unit of the same type OPA2277 chip, which shares the same power supply rail with the first operational amplifier. The first filter resistor is selected from a metal film resistor with a resistance of 20kΩ and an accuracy of 1%, and the second filter resistor is selected from a resistor of the same series with a resistance of 30kΩ and an accuracy of 1%, both of which are 2-watt power level. The starting end of the first filter resistor is welded to the output end pin of the first operational amplifier, and the end is connected in series with the second filter resistor through a copper foil wire of 8mm long, and the terminal of the second filter resistor is welded to the sixth pin of the second operational amplifier.

[0039] The first filter capacitor is selected from a solid-state electrolytic capacitor with a capacitance of 4.7μF, and the positive electrode of the capacitor is welded to the intermediate connection node of the two filter resistors, and the negative electrode is connected to the seventh pin of the second operational amplifier through a wire of 15mm long, and is connected in parallel with the feedback resistor to form an integral element. The second filter capacitor has a capacitance of 10nF and is a CBB capacitor, and the two pins are welded between the output end and the inverting input end of the second operational amplifier, and together with the first filter capacitor form a second-order low-pass filter network. According to RC parameter calculation, the cutoff frequency of the filter circuit is about 350Hz, which has good attenuation effect on high-frequency switching noise.

[0040] The threshold comparison output circuit 3 comprises a voltage comparator, a reference voltage generation branch and a positive feedback hysteresis branch. The voltage comparator selects a LM393 dual-channel comparator chip, and uses one of the comparator units. The fifth pin of the chip is the A channel same-phase input end, which is directly connected to the output end of the second operational amplifier to receive the filtered and conditioned signal. The fourth pin is the A channel inverting input end, which is connected to the reference voltage generation branch. The first pin is the A channel open set output end, which is connected to the positive electrode of the 5V auxiliary power supply through a pull-up resistor with a resistance of 4.7kΩ.

[0041] The reference voltage generation branch is composed of a pull-up resistor and a adjustable potentiometer in series. The pull-up resistor is selected from a metal film resistor with a resistance of 10kΩ, one end of which is welded to the positive copper foil of the 12V auxiliary power supply, and the other end is connected to the first pin of the adjustable potentiometer. The potentiometer selects a multi-turn precision potentiometer of the 3296W series of the BOURNS company, with a total resistance of 20kΩ and 25 turns of adjustment. The potentiometer is welded by surface mounting, and the three pads are located at the bottom. The middle sliding end pin is connected to the fourth pin of the comparator through a copper foil wire with a width of 0.3mm. The third pin of the potentiometer is welded to the ground layer of the circuit board. A one-slot adjustment hole is provided at the top, and a special adjustment tool can be used to accurately set the reference voltage value, and the typical setting range is 1V to 5V.

[0042] The positive feedback hysteresis branch is formed by a 100kΩ resistor, one end of which is welded to the first foot output end of the comparator, and the other end is welded to the fifth foot in-phase input end, forming a positive feedback loop. When the output state flips, the positive feedback causes the in-phase input end voltage to have an additional bias, forming a hysteresis voltage window of about 200mV, effectively suppressing the frequent flipping of the output end caused by the jitter of the input signal.

[0043] The photoelectric isolation output interface 4 uses a TLP521-1 type optical coupler, which contains an infrared light-emitting diode and a photosensitive transistor inside the chip. The anode of the light-emitting diode is connected to the 5V auxiliary power supply through a current-limiting resistor with a resistance of 470Ω and a power of 1 / 4W, ensuring that the operating current of the light-emitting diode is about 8mA. The cathode of the light-emitting diode is connected to the first foot of the open set output end of the comparator. The collector of the photosensitive transistor is led out through the edge pin connector of the circuit board and connected to the GPIO interrupt pin of the inverter controller, and the emitter is connected to the ground of the inverter controller through another pin.

[0044] The bipolar auxiliary power module 5 is installed on the back of the circuit board, and a VRB2412LD-6WR3 type isolated DC-DC module is selected. The module has an input voltage range of 9V to 36V, and outputs positive and negative 12V dual power with a total power of 6W. The positive input pin of the module is connected to the 24V auxiliary power input terminal on the front through the PCB via hole, and the negative input and ground pins are connected to the ground copper foil together. The positive 12V output pin of the module is connected to the positive power rail on the front circuit through the hole, which is a 3mm wide copper foil trace extending along the long edge of the circuit board, and is connected in series with multiple 100μF electrolytic capacitors and 0.1μF ceramic capacitors for filtering. The negative 12V output pin is also connected to the negative power rail through the via hole. Decoupling capacitors are welded near the power pins of each operational amplifier and comparator chip to ensure that the power supply ripple is less than 10mV.

[0045] The working process of the device is as follows:

[0046] After the device is powered on, the independent power supply module first provides stable bipolar operating voltage for the operational amplifiers and comparators at all levels, and the analog differential sampling circuit 1 starts to monitor the voltage state of the in-phase power supply inverter DC bus capacitor in real time. During normal operation of the railway traction network, the DC bus voltage only contains a small power frequency ripple, and the DC high voltage is blocked by the high-voltage blocking capacitor in the analog differential sampling circuit 1, allowing only a weak ripple current to pass through, so the voltage signal amplitude of the first operational amplifier output is very low, and the subsequent circuit is in standby state.

[0047] When the traction network fails to cause transient fluctuation of the DC bus voltage, the working process enters the signal capture stage. The analog differential sampling circuit 1 connected in parallel on the DC bus uses the physical characteristic that the capacitor current is proportional to the voltage change rate, and through the high-voltage isolation capacitor, the voltage is instantaneously sensed to the sharp drop, and the input resistor and the feedback resistor are matched, and the first operational amplifier directly converts the voltage change rate into an analog voltage spike signal with a certain amplitude. In order to ensure the purity of the signal, the analog signal is immediately sent to the signal conditioning filter circuit 2, and the second operational amplifier in the circuit is matched with the second-order active band-pass filter network composed of resistors and capacitors to frequency discriminate the signal, filter out the high-frequency noise generated by the IGBT switch and the residual DC component, and only let the specific frequency band signal representing the fault characteristics pass through without loss.

[0048] The pure fault signal after conditioning then enters the decision-making link, and is transmitted to the voltage comparator of the threshold comparison output circuit 3. The voltage comparator compares the amplitude of the received signal with the preset voltage threshold set by the reference voltage source at the anti-phase input end in real time. Once the amplitude of the fault signal instantaneously exceeds the threshold, the output end state of the voltage comparator rapidly reverses, and the hysteresis feedback resistor connected between the output end and the input end is used to lock this state to prevent signal jitter at the threshold critical point. Finally, the high-level signal after the flip drives the light-emitting diode in the opto-isolated output interface 4 to conduct, and through the photoelectric triode, the analog detection result on the strong current side is converted into a digital interrupt signal electrically isolated from the main circuit, and is directly sent to the protection interface of the converter controller, thereby triggering the fault blocking and protection action of the system.

[0049] The above has made a detailed description of the general utility model, but some modifications or improvements can be made on the basis of the utility model, which is obvious to those skilled in the art. Therefore, without departing from the modification or improvement of the spirit of the utility model, it is within the protection scope of the utility model.

Claims

1. A device for on-line detection of fault current in a traction network in phase based on dynamic compensation, characterized in that, The detection device is applied to a same-phase power supply converter system comprising a direct-current bus capacitor, and comprises an analog differential sampling circuit (1), a signal conditioning filter circuit (2) and a threshold value comparison output circuit (3). The input end of the analog differential sampling circuit (1) is arranged in parallel across the direct-current bus capacitor of the same-phase power supply converter, and is used for converting the fluctuation of the direct-current bus voltage into an analog voltage signal; the output end of the analog differential sampling circuit (1) is electrically connected with the input end of the signal conditioning filter circuit (2), and is used for filtering out high-frequency noise and direct-current components in the analog voltage signal. The output end of the signal conditioning filter circuit (2) is electrically connected with the signal input end of the threshold value comparison output circuit (3). The output end of the threshold value comparison output circuit (3) is connected to a fault interruption interface of a converter controller.

2. The device for online detection of fault current in the same phase traction network based on dynamic compensation according to claim 1, characterized in that: The analog differential sampling circuit (1) comprises a direct-current isolation high-voltage capacitor, an input resistor, a first operational amplifier and a feedback resistor; one end of the direct-current isolation high-voltage capacitor is connected to the positive pole of the direct-current bus capacitor, the other end is connected to the inverting input end of the first operational amplifier through the input resistor; the feedback resistor is connected across the inverting input end and the output end of the first operational amplifier; the non-inverting input end of the first operational amplifier is grounded, and the output end thereof serves as the output end of the analog differential sampling circuit (1).

3. The device for online detection of fault current in the same phase traction network based on dynamic compensation according to claim 2, characterized in that: The analog differential sampling circuit (1) further comprises a set of bidirectional limiting diodes; the set of bidirectional limiting diodes is arranged in parallel between the inverting input end and the non-inverting input end of the first operational amplifier, and is used for clamping the input voltage amplitude.

4. The device for online detection of fault current in the same phase traction network based on dynamic compensation according to claim 1, characterized in that: The signal conditioning filter circuit (2) comprises a second operational amplifier, a first filter capacitor, a second filter capacitor, a first filter resistor and a second filter resistor; the first filter resistor and the second filter resistor are connected in series between the input end and the inverting input end of the second operational amplifier; the first filter capacitor is connected between the common connection point of the first filter resistor and the second filter resistor and the output end of the second operational amplifier.

5. The device for online detection of fault current in the same phase traction network based on dynamic compensation according to claim 4, characterized in that: The passband frequency range of the signal conditioning filter circuit (2) is set by an RC constant network hardware composed of the parameter values of the first filter capacitor, the second filter capacitor, the first filter resistor and the second filter resistor.

6. The device for online detection of fault current in the same phase traction network based on dynamic compensation according to claim 1, characterized in that: The threshold value comparison output circuit (3) comprises a voltage comparator, a reference voltage generation branch and a positive feedback hysteresis branch; the non-inverting input end of the voltage comparator receives a signal from the signal conditioning filter circuit (2), and the inverting input end thereof is connected to the reference voltage generation branch; the positive feedback hysteresis branch is connected between the output end and the non-inverting input end of the voltage comparator.

7. The device for online detection of fault current in the same phase traction network based on dynamic compensation according to claim 6, characterized in that: The reference voltage generation branch comprises a pull-up resistor and an adjustable potentiometer connected in series between an auxiliary power supply and the ground; the sliding contact of the adjustable potentiometer is connected to the inverting input end of the voltage comparator.

8. The device for online detection of fault current in the same phase traction network based on dynamic compensation according to claim 1, characterized in that: The detection device further comprises an opto-isolating output interface (4); the input side light-emitting diode of the opto-isolating output interface (4) is connected to the output end of the threshold value comparison output circuit (3), and the output side photo-sensitive triode thereof is connected to the fault interruption interface of the converter controller.

9. The device for online detection of fault current in the same phase traction network based on dynamic compensation according to claim 1, characterized in that: The detection device further comprises a shielded metal shell (6); the analog differential sampling circuit (1), the signal conditioning filter circuit (2) and the threshold comparison output circuit (3) are all installed inside the shielded metal shell (6); and a grounding terminal is arranged on the surface of the shielded metal shell (6).

10. The device for online detection of fault current in the same phase traction network based on dynamic compensation according to claim 1, characterized in that: The detection device is configured with a bipolar auxiliary power module (5); and the output ends of the bipolar auxiliary power module (5) are respectively connected to the positive power supply end and the negative power supply end of the operational amplifier in the analog differential sampling circuit (1) and the signal conditioning filter circuit (2).

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