Active injection type feeder protection system

Abstract

The utility model discloses an active injection type feeder protection system, and belongs to the technical field of traction network feeder protection. The protection system comprises a ground energy storage and characteristic signal injection system, an incoming line current sensor, a wavelet energy calculation device, a feeder line protection device and an incoming line switch, a characteristic signal injection device is introduced on a direct current bus, and characteristic signals can be actively injected into the direct current bus. Meanwhile, a wavelet energy calculation device is introduced to calculate and judge wavelet energy values before and after characteristic signals are injected, so that subway locomotive starting and far-end short-circuit faults can be distinguished according to the wavelet energy ratio, and finally, a feeder protection device is controlled to act according to a judgment result. Therefore, the active protection of the subway direct current traction network can be realized, and compared with the existing urban rail transit direct current traction system, the starting accuracy and reliability of the protection device are effectively improved, and the occurrence probability of misoperation is reduced.

Description

Technical Field

[0001] The utility model relates to an active injection type feeder protection system, belonging to the technical field of traction network feeder protection. Background Technique

[0002] With the rapid development of cities and the sharp increase of population in China, the pressure of urban traffic is also increasing day by day. The subway has a large passenger volume and high density, which can greatly relieve the traffic pressure. However, the subway has a high operating power and consumes a large amount of electric energy, so it is imperative to implement energy conservation and emission reduction. When the subway train is working normally, it will brake frequently, and the electric energy consumption generated by braking accounts for about 40% of the whole traction process. The use of energy storage devices to recover the braking energy of locomotives is applied in more and more urban rail transits due to its high recovery efficiency and environmental superiority. Therefore, the energy storage type subway traction system is selected as the research object of the utility model.

[0003] In the urban rail transit DC traction power supply system, the subway DC feeder protection mainly adopts overcurrent tripping protection, rate of change of current and current increment (DDL) protection, etc. The feeder current will rise rapidly both at the moment of locomotive starting and at the moment of short-circuit fault. There is a certain similarity between the starting current of the locomotive in amplitude and rate of change and the remote fault current, so there is a possibility of misoperation in DDL protection. The existing solution is to delay for a period of time, but this method has a slow action speed and is difficult to meet the protection requirements of the energy storage type subway traction system. Content of the Utility Model

[0004] In order to improve the accuracy and reliability of the feeder protection of the rail transit DC traction network and prevent misoperation, the utility model provides an active injection type feeder protection system, and the technical solution is as follows.

[0005] An active injection type feeder protection system for the urban rail transit DC traction network, the active injection type feeder protection system includes: a ground energy storage and characteristic signal injection system, an incoming line current sensor, a wavelet energy calculation device, a feeder protection device, and an incoming line switch;

[0006] The input end of the incoming line current sensor is connected to the traction substation, and the output end is connected to the input end of the wavelet energy calculation device; the output end of the wavelet energy calculation device is connected to the input end of the feeder protection device; the output end of the feeder protection device is connected to the control end of the incoming line switch;

[0007] The ground energy storage and characteristic signal injection system is connected to the DC bus of the traction network, and includes: a supercapacitor, a bidirectional DC / DC converter, and a characteristic signal injection device. The supercapacitor is connected in parallel to the supercapacitor side of the bidirectional DC / DC converter; the characteristic signal injection device includes a signal generating device and a coupling circuit. The signal generating device is connected to one side of the bidirectional DC / DC converter connected to the DC bus through the coupling circuit;

[0008] The wavelet energy calculation device includes: a specific harmonic filter and a wavelet calculation and determination unit. The output end of the specific harmonic filter is connected to the input end of the wavelet calculation and determination unit. The input end of the specific harmonic filter is the input end of the wavelet energy calculation device, and the output end of the wavelet calculation and determination unit is the output end of the wavelet energy calculation device.

[0009] In one embodiment, the traction network includes: a DC bus, a catenary, a running rail, and a return line;

[0010] The DC bus is connected to the catenary, the catenary is connected to the pantograph of the subway locomotive, the running rail is connected to the subway locomotive and is connected to the traction substation through the return line.

[0011] In one embodiment, the incoming line switch is a unidirectional high-current trip switch.

[0012] In one embodiment, the positive and negative poles of the first diode 35 of the bidirectional DC / DC converter are connected in parallel across the source and drain of the first IGBT 33, and the positive and negative poles of the second diode 36 are connected in parallel across the source and drain of the second IGBT 34; the first IGBT 33 and the second IGBT 34 are connected in series across the DC bus voltage;

[0013] The supercapacitor 39 of the bidirectional DC / DC converter is connected in series with a resistor 40 and then connected in parallel with an intermediate capacitor 38; one end of the intermediate capacitor 38 is connected to one end of a filter inductor 37, and the other end is connected to one end of the DC bus;

[0014] The other end of the filter inductor 37 is connected to the source electrode of the first IGBT 33, and the filter capacitor 32 of the bidirectional DC / DC converter is connected in series across the DC bus voltage.

[0015] Advantages of the present utility model:

[0016] The active injection type feeder protection system for the DC traction network of urban rail transit of the present utility model introduces a characteristic signal injection device on the DC bus, which can actively inject characteristic signals into the DC bus. At the same time, a wavelet energy calculation device is introduced to calculate and judge the wavelet energy values before and after the injection of characteristic signals. Thus, the starting of subway locomotives and remote short-circuit faults can be distinguished by the magnitude of the wavelet energy ratio, that is, the action of the feeder protection device is controlled by the signal output by the wavelet energy calculation device. Therefore, the present utility model can achieve the active protection of the subway DC traction network. Compared with the existing DC traction system of urban rail transit, it effectively improves the accuracy and reliability of the starting of the protection device and reduces the occurrence probability of misoperation.

[0017] In addition, the characteristic signal injection device of the present utility model can be integrated into the ground energy storage system, realizing channel multiplexing and reducing certain costs. Brief Description of the Drawings

[0018] Figure 1 It is a structural diagram of the energy storage type DC traction system for urban rail transit of the present utility model.

[0019] Figure 2 It is a structural diagram of the subway energy storage and characteristic signal injection system of the present utility model.

[0020] Figure 3 It is a working principle diagram of the active injection type feeder protection system for the DC traction network of urban rail transit of the present utility model.

[0021] In the figure: 1 - First traction substation; 2 - Second traction substation; 3 - First incoming line current sensor; 4 - Second incoming line current sensor; 5 - First wavelet energy calculation device WC1; 6 - Second wavelet energy calculation device WC2; 7 - First specific harmonic filter; 8 - Second specific harmonic filter; 9 - First wavelet calculation discriminator; 10 - Second wavelet calculation discriminator; 11 - First feeder protection device PT1; 12 - Second feeder protection device PT2; 13 - First incoming line switch; 14 - Second incoming line switch; 15 - First supercapacitor SC1; 16 - Second supercapacitor SC2; 17 - First bidirectional DC / DC converter; 18 - Second bidirectional DC / DC converter; 19 - First characteristic signal injection device; 20 - Second characteristic signal injection device; 21 - First subway energy storage and characteristic signal injection system; 22 - Second subway energy storage and characteristic signal injection system; 23 - Positive DC bus; 24 - Negative DC bus; 25 - Upward catenary; 26 - Downward catenary; 27 - Running rail; 28 - Return line; 29 - First coupling inductor; 30 - Second coupling inductor; 31 - Magnetic core; 32 - Filter capacitor; 33 - First IGBT; 34 - Second IGBT; 35 - First diode; 36 - Second diode; 37 - Filter inductor; 38 - Intermediate capacitor; 39 - Supercapacitor; 40 - Resistor.

[0022] Figure 3 In: E di / dt is the set protection startup setting value. Specific implementation mode

[0023] The following is a specific description of the present invention.

[0024] Embodiment 1:

[0025] This embodiment provides an active injection type feeder protection system for the DC traction network of urban rail transit, including: a ground energy storage and characteristic signal injection system, an incoming line current sensor, a wavelet energy calculation device, a feeder protection device, and an incoming line switch.

[0026] The input end of the incoming line current sensor is connected to the traction substation, and the output end is connected to the input end of the wavelet energy calculation device; the output end of the wavelet energy calculation device is connected to the input end of the feeder protection device; the output end of the feeder protection device is connected to the control end of the incoming line switch.

[0027] The ground energy storage and characteristic signal injection system is connected to the DC bus of the traction network, including: a supercapacitor, a bidirectional DC / DC converter, and a characteristic signal injection device. The supercapacitor is connected in parallel on the supercapacitor side of the bidirectional DC / DC converter; the characteristic signal injection device includes a signal generating device and a coupling circuit, and the signal generating device is connected to one side of the bidirectional DC / DC converter connected to the DC bus through the coupling circuit.

[0028] In this embodiment, the characteristic signal injection device can adopt a function / arbitrary waveform generator, such as the DG800 series of RIGOL Technologies, the AFG1000 series of TEKTRONIX, etc.

[0029] The wavelet energy calculation device includes: a specific sub-harmonic filter and a wavelet calculation and determination device. The output end of the specific sub-harmonic filter is connected to the input end of the wavelet calculation and determination device. The input end of the specific sub-harmonic filter is the input end of the wavelet energy calculation device, and the output end of the wavelet calculation and determination device is the output end of the wavelet energy calculation device.

[0030] In this embodiment, the wavelet calculation and determination device can be implemented by using wavelet analysis software on the PC side (such as the Wavelet Toolbox in MATLAB, the PyWavelets library in Python).

[0031] Among them, the subway traction network includes: a DC bus, a catenary, a running rail, and a return line; the DC bus is connected to the catenary, the catenary is connected to the pantograph of the subway locomotive, the running rail is connected to the subway locomotive and is connected to the traction substation through the return line.

[0032] The incoming line switch in this embodiment is a unidirectional high-current trip switch.

[0033] The structure of the ground energy storage and characteristic signal injection system in this embodiment is as Figure 2 shown. The positive and negative poles of the first diode 35 of the bidirectional DC / DC converter are connected in parallel across the source and drain terminals of the first IGBT 33, and the positive and negative poles of the second diode 36 are connected in parallel across the source and drain terminals of the second IGBT 34; the first IGBT 33 and the second IGBT 34 are connected in series across the DC bus voltage terminals.

[0034] The super capacitor 39 of the bidirectional DC / DC converter is connected in series with the resistor 40 and then connected in parallel with the intermediate capacitor 38; one end of the intermediate capacitor 38 is connected to one end of the filter inductor 37, and the other end is connected to one end of the DC bus.

[0035] The other end of the filter inductor 37 is connected to the source electrode of the first IGBT 33, and the filter capacitor 32 of the bidirectional DC / DC converter is connected in series across the DC bus voltage terminals.

[0036] Embodiment 2:

[0037] This embodiment provides an energy storage type urban rail DC traction system, which uses the active injection type feeder protection system described in Embodiment 1 to realize the protection of the DC bus. The system structure is as Figure 1As shown in the figure, it includes: the first traction substation 1, the second traction substation 2, the first incoming line current sensor 3, the second incoming line current sensor 4, the first wavelet energy calculation device 5, the second wavelet energy calculation device 6, the first feeder protection device 11, the second feeder protection device 12, the first incoming line switch 13, the second incoming line switch 14, the first subway energy storage and characteristic signal injection system 21, and the second subway energy storage and characteristic signal injection system 22.

[0038] The subway traction network includes: a DC bus, a catenary, a running rail, and a return line. The DC bus is connected to the catenary, the catenary is connected to the pantograph of the subway locomotive, the running rail is connected to the subway locomotive and is connected to the traction substation through the return line.

[0039] Among them, one end of the first traction substation 1 is connected to the 35 kV AC power grid, and the other end is connected to the positive DC bus 23 through the first incoming line switch 13. The input end of the first incoming line current sensor 3 is connected to the outgoing line of the first traction substation 1, and the output end is connected to the input end of the first wavelet energy calculation device 5. The first wavelet energy calculation device 5 is connected to the input end of the first feeder protection device 11, and the output end of the first feeder protection device 11 is connected to the control end of the first incoming line switch 13.

[0040] The first wavelet energy calculation device 5 includes a first specific harmonic filter 7 and a first wavelet calculation and determination device 9.

[0041] As Figure 1 shown, the connection method of the second traction substation 2 with each component is the same as that of the first traction substation 1.

[0042] In this embodiment, the subway energy storage and characteristic signal injection system is composed of a super capacitor, a bidirectional DC / DC converter, and a characteristic signal injection device. Taking the connection at one end of the left first traction substation 1 as an example, it includes: the first super capacitor 15, the first bidirectional DC / DC converter 17, and the first characteristic signal injection device 19. The connection method is as Figure 2 shown. The first characteristic signal injection device 19 is connected to the DC bus side of the first bidirectional DC / DC converter 17 in the way of coupled inductor - magnetic core - coupled inductor. The positive and negative poles of the first diode 35 are connected in parallel across the source and drain ends of the first IGBT 33, and the positive and negative poles of the second diode 36 are connected in parallel across the source and drain ends of the second IGBT 34. The first IGBT 33 and the second IGBT 34 are connected in series across the DC bus voltage. The super capacitor 39 is connected in series with the resistor 40 and then connected in parallel with the intermediate capacitor 38, and is connected in series with the filter inductor 37. The filter capacitor 32 is connected in series across the DC bus voltage.

[0043] The working principle of the present utility model:

[0044] Taking the first traction substation on the left as an example for illustration, the first incoming line current sensor 3 transmits the feeder current data to the first wavelet energy calculation device 5, and the first wavelet energy calculation device 5 sets different setting values. When the DC current change rate di / dt is greater than the set value, the first characteristic signal injection device 19 is activated, and a specific harmonic is injected into the DC bus through the coupling inductor. After filtering the fault current, the first wavelet energy calculation device 5 calculates the wavelet energy values E0 and E1 of the specific harmonic within 0.1 s before and after injection, takes D = E1 / E0, and compares the calculated wavelet energy value ratio D with the setting value (taking 11 - 13). For example, taking the setting value as 12, if it is determined that the locomotive starts (D ≤ 12), the first feeder protection device 11 does not operate; if it is judged as a short - circuit fault (D > 12), the first feeder protection device 11 operates.

[0045] The working flow chart of the whole system is as Figure 3 shown, and the specific process is as follows:

[0046] (1) Taking the DC current change rate di / dt being greater than the setting value as the starting criterion for the characteristic signal injection device;

[0047] (2) After the characteristic signal injection device is activated, calculate the n - th characteristic harmonic current energies E0 and E1 within 0.1 s before and after the injection of the specific harmonic respectively, and calculate their ratio D (E1 / E0);

[0048] (3) Judge the type of this abnormal operation (locomotive start, short - circuit fault) through the magnitude of D;

[0049] (4) If it is a locomotive start, the process ends; if it is a short - circuit fault, the feeder protection device operates.

[0050] Embodiment 3: Illustrate the effectiveness of the active injection type DC traction network feeder protection system of the present utility model by way of example.

[0051] The locomotive start position is 0.5 km away from the first traction substation, and the fault positions are 0.5 km, 1.5 km, and 2.5 km respectively. Assume that the locomotive starts at 0.1 s and a fault occurs at 1 s.

[0052] The wavelet energy values within 0 - 0.1 s are 30.34, 30.42, and 31.75 respectively. The wavelet energy values within 0.1 - 0.2 s are 294.91, 294.07, and 293.87 respectively. The wavelet energy values within 0.9 - 1.0 s are 3.0796, 3.08, and 3.08 respectively. The wavelet energy values within 1.0 - 1.1 s are 113.56, 49.95, and 44.46 respectively. Then the wavelet energy ratios within 0.1 s before and after the locomotive starts are 9.72, 9.677, and 9.2 respectively. The wavelet energy value ratios within 0.1 s before and after the short - circuit fault are 36.8, 16.2, and 14.4 respectively. Based on the above ratios, the short - circuit fault and the locomotive start can be distinguished.

[0053] Embodiment 4: Illustrate the effectiveness of the active - injection type DC traction network feeder protection system for urban rail transit of the present utility model by way of example.

[0054] The locomotive start position is 1.5 km away from the first traction substation. The fault positions are 0.5 km, 1.5 km, and 2.5 km respectively. It is assumed that the locomotive starts at 0.1 s and a fault occurs at 1 s.

[0055] The wavelet energy values within 0 - 0.1 s are 15.12, 15.2, and 15.12 respectively. The wavelet energy values within 0.1 - 0.2 s are 28.54, 29, and 28.55 respectively. The wavelet energy values within 0.9 - 1.0 s are 0.2789, 0.2790, and 0.279 respectively. The wavelet energy values within 1.0 - 1.1 s are 266.52, 9.85, and 3.74 respectively. Then the wavelet energy ratios within 0.1 s before and after the locomotive starts are 1.89, 1.90, and 1.89 respectively. The wavelet energy value ratios within 0.1 s before and after the short - circuit fault are 955.63, 35.33, and 13.41 respectively. Based on the above ratios, the short - circuit fault and the locomotive start can be distinguished.

[0056] Although the present utility model has been disclosed above with preferred embodiments, it is not intended to limit the present utility model. Anyone familiar with this technology can make various modifications and decorations without departing from the spirit and scope of the present utility model. Therefore, the protection scope of the present utility model should be defined by the claims.

Claims

1. An active injection feeder protection system for urban rail transit DC traction network, characterized in that: The active injection feeder protection system comprises: a ground energy storage and characteristic signal injection system, an incoming current sensor, a wavelet energy calculation device, a feeder protection device, and an incoming switch; The input end of the incoming current sensor is connected to the traction substation, and the output end is connected to the input end of the wavelet energy calculation device; the output end of the wavelet energy calculation device is connected to the input end of the feeder protection device; the output end of the feeder protection device is connected to the control end of the incoming switch; The ground energy storage and characteristic signal injection system is connected to the DC bus of the traction network, and includes: a supercapacitor, a bidirectional DC / DC converter and a characteristic signal injection device, wherein the supercapacitor is connected in parallel to the supercapacitor side of the bidirectional DC / DC converter; the characteristic signal injection device includes a signal generating device and a coupling circuit, and the signal generating device is connected to the side of the bidirectional DC / DC converter connected to the DC bus through the coupling circuit; The wavelet energy calculation device includes: a specific subharmonic filter and a wavelet calculation determiner, the output end of the specific subharmonic filter is connected to the input end of the wavelet calculation determiner, the input end of the specific subharmonic filter is the input end of the wavelet energy calculation device, and the output end of the wavelet calculation determiner is the output end of the wavelet energy calculation device.

2. The active injection feeder protection system according to claim 1, characterized in that: The traction network includes: a DC bus, a contact network, a running rail and a return line; The DC bus is connected to the overhead contact network, the overhead contact network is connected to the pantograph of the subway locomotive, the running rail is connected to the subway locomotive and is connected to the traction substation through the return line.

3. The active injection feeder protection system according to claim 1, characterized in that: The incoming line switch is a unidirectional high current tripping switch.

4. The active injection feeder protection system according to claim 1, characterized in that: The positive and negative electrodes of the first diode (35) of the bidirectional DC / DC converter are connected in parallel to the source and drain of the first IGBT (33), and the positive and negative electrodes of the second diode (36) are connected in parallel to the source and drain of the second IGBT (34); the first IGBT (33) and the second IGBT (34) are connected in series to the two ends of the DC bus voltage; The super capacitor (39) and the resistor (40) of the bidirectional DC / DC converter are connected in series and then connected in parallel with the intermediate capacitor (38); one end of the intermediate capacitor (38) is connected to one end of the filter inductor (37), and the other end is connected to one end of the DC bus; The other end of the filter inductor (37) is connected to the source of the first IGBT (33), and the filter capacitor (32) of the bidirectional DC / DC converter is connected in series to both ends of the DC bus voltage.

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