Current detection circuit in bidirectional conversion process of urban subway rail transit

Abstract

The invention discloses a current detection circuit in a bidirectional conversion process of urban subway rail transit, which relates to the field of current detection and comprises a direct-current sampling control module, a direct-current sampling control module, a direct-current sampling control module, a direct-current sampling control module, a direct-current sampling control module, a direct-current sampling control module and a direct-current sampling control module, if the DC voltage value is greater than the upper threshold or less than the lower threshold, the AC sampling module is driven to work; the alternating current sampling module is used for detecting alternating current of a power grid and providing working signals for the zero crossing point closing module and the zero crossing point disconnecting module when the alternating current crosses a zero point; compared with the prior art, the beneficial effects are that through cooperation of the DC sampling control module, the AC sampling module, the zero crossing point closing module and the zero crossing point disconnection module, the moment of connection or disconnection of the AC-DC conversion device is controlled to be the moment of AC zero crossing of the commercial power; the current at the moment of connection or disconnection of the AC-DC conversion device is small, and the service life of the bidirectional converter device is prolonged.

Description

Technical Field

[0001] The invention relates to the field of current detection, in particular to a current detection circuit in a bidirectional current conversion process of urban subway rail transit. Background Art

[0002] The specific bidirectional conversion process of urban subway rail transit is as follows: Traction state: When it is determined that the train is in the traction state and the DC network voltage is lower than the set value, the bidirectional converter immediately starts the traction voltage stabilization power supply function to convert AC power into DC traction power for train traction. Braking state: When it is determined that the train is in the braking state and the DC network voltage is higher than the set value, the bidirectional converter immediately starts the energy feedback function to feed the braking energy back to the power grid. In this process, the device uses high-power inverter feedback technology to quickly invert the DC energy generated by the train's regenerative braking and feed it back to the AC power grid. This not only greatly improves energy utilization efficiency, but also effectively reduces carbon emissions.

[0003] It should be noted that during the voltage conversion process, the current size based on the grid alternating current changes. If the bidirectional converter is closed when the current is large, the instantaneous high current will be relatively large, which may easily damage the bidirectional converter and needs to be improved. Summary of the invention

[0004] The object of the present invention is to provide a current detection circuit in a bidirectional current conversion process of urban subway rail transit to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A current detection circuit in a bidirectional current conversion process of urban subway rail transit, comprising:

[0007] The DC sampling control module is used to detect the DC voltage value of the train. If the DC voltage value is greater than the upper threshold or less than the lower threshold, the AC sampling module is driven to work;

[0008] The AC sampling module is used to detect the AC power of the power grid and provide working signals for the zero-crossing closing module and the zero-crossing disconnecting module when the AC power passes through the zero point;

[0009] The delay driving module is used to provide a trigger signal to the zero-crossing closing module after the AC sampling module works and after a delay;

[0010] The zero-crossing closing module is used to receive a trigger signal, and then receive a working signal to start working. After a delay in starting working, the switch of the bidirectional converter is controlled to close. The delay time is a cycle time of the AC mains.

[0011] The zero-crossing disconnection module is used when the DC voltage value of the train is between the upper threshold and the lower threshold. When receiving the working signal, it drives the DC sampling control module to delay and control the bidirectional converter switch to disconnect after a delay. The delay time is one cycle time of the AC mains.

[0012] The first output end of the DC sampling control module is connected to the input end of the AC sampling module, the second output end of the DC sampling control module is connected to the first input end of the zero-crossing disconnection module, the first output end of the AC sampling module is connected to the input end of the delay driving module, the second output end of the AC sampling module is connected to the second input end of the zero-crossing closing module and the second input end of the zero-crossing disconnection module, the output end of the delay driving module is connected to the first input end of the zero-crossing closing module, and the output end of the zero-crossing disconnection module is connected to the input end of the DC sampling control module.

[0013] As a further solution of the present invention: the DC sampling control module includes:

[0014] A DC sampling unit is used to sample the DC voltage value of the train, obtain the sampled voltage, and output it to the lower limit detection control unit and the upper limit detection control unit;

[0015] A lower limit detection control unit is used to compare the sampling voltage with the first reference voltage. When the sampling voltage is lower than the first reference voltage (corresponding to the lower limit threshold), the first switch, the second switch and the third switch are controlled to close, so as to drive the AC sampling module to work;

[0016] An upper limit detection control unit is used to compare the sampling voltage with the second reference voltage. When the sampling voltage is greater than the second reference voltage (corresponding to the upper limit threshold), the fourth switch, the fifth switch and the sixth switch are controlled to close, so as to drive the AC sampling module to work;

[0017] The output end of the DC sampling unit is connected to the first input end of the lower limit detection control unit and the first input end of the upper limit detection control unit, the first output end of the lower limit detection control unit is connected to the input end of the AC sampling module (the first relay controls the second switch and the third switch), the second output end of the lower limit detection control unit is connected to the first input end (common point A1 and common point A2) of the zero-crossing disconnection module, the first output end of the upper limit detection control unit is connected to the input end of the AC sampling module (the fourth relay controls the fifth switch and the sixth switch), the second output end of the upper limit detection control unit is connected to the first input end (common point B1 and common point B2) of the zero-crossing disconnection module, and the output end of the zero-crossing disconnection module is connected to the second input end (common point A3) of the lower limit detection control unit and the second input end (common point B3) of the upper limit detection control unit.

[0018] As a further solution of the present invention: the DC sampling unit includes a seventh resistor and an eighth resistor, one end of the seventh resistor is connected to the DC voltage value of the train, the other end of the seventh resistor is connected to one end of the eighth resistor, the first input end of the lower limit detection control unit, and the first input end of the upper limit detection control unit, and the other end of the eighth resistor is grounded.

[0019] As a further solution of the present invention: the lower limit detection control unit includes a fifth amplifier, a sixth amplifier, a fourth MOS tube, a fifth MOS tube, and a first relay. The non-inverting end of the fifth amplifier is connected to the first reference voltage, the inverting end of the fifth amplifier is connected to the non-inverting end of the sixth amplifier and the output end of the DC sampling unit, the inverting end of the sixth amplifier is connected to the output end of the fifth amplifier and one end of the ninth resistor, the output end of the sixth amplifier is connected to the common point A1, the other end of the ninth resistor is connected to the control electrode of the second thyristor, the positive electrode of the second thyristor is connected to the S electrode of the fourth MOS tube, the D electrode of the fourth MOS tube is connected to the power supply voltage and one end of the tenth resistor, the other end of the tenth resistor is connected to the G electrode of the fourth MOS tube and the D electrode of the fifth MOS tube, the S electrode of the fifth MOS tube is grounded, the G electrode of the fifth MOS tube is connected to the common point A3, the negative electrode of the second thyristor is connected to the common point A2 and one end of the eleventh resistor, the other end of the eleventh resistor is connected to the negative electrode of the eighth diode and one end of the first relay, the other end of the first relay is grounded, and the positive electrode of the eighth diode is grounded.

[0020] As a further solution of the present invention: the AC sampling module includes an AC optocoupler and a second amplifier. The first end of the AC optocoupler is connected to the twenty-first resistor, the second end of the AC optocoupler is connected to the twenty-second resistor, the third end of the AC optocoupler is connected to one end of the twenty-third resistor and the in-phase end of the second amplifier, the other end of the twenty-third resistor is connected to the power supply voltage, the fourth end of the AC optocoupler is grounded, the inverting end of the second amplifier is connected to the third reference voltage, the output end of the second amplifier is connected to the second input end of the zero-crossing closing module and the second input end of the zero-crossing disconnecting module, the other end of the twenty-first resistor is connected to one end of the second switch and one end of the fifth switch, the other end of the second switch is connected to the other end of the fifth switch and the live wire, the other end of the twenty-second resistor is connected to one end of the third switch, one end of the sixth switch, and the input end of the delay driving module, and the other end of the third switch is connected to the other end of the sixth switch and the neutral wire.

[0021] As a further solution of the present invention: the delay driving module includes a first diode, a first capacitor, a first resistor, a second diode, a second capacitor, and a third diode. The positive electrode of the first diode is connected to the first output end of the AC sampling module, the negative electrode of the first diode is connected to one end of the first capacitor and one end of the first resistor, the other end of the first capacitor is grounded, the other end of the first resistor is connected to the negative electrode of the second diode, one end of the second capacitor, and the positive electrode of the third diode, the positive electrode of the second diode is grounded, the other end of the second capacitor is grounded, and the negative electrode of the third diode is connected to the first input end of the zero-crossing closing module.

[0022] As a further solution of the present invention: the zero-crossing closing module includes a first MOS tube, a first thyristor, and a seventh relay. The D pole of the first MOS tube is connected to the power supply voltage, the G pole of the first MOS tube is connected to the output end of the delay driving module, the S pole of the first MOS tube is connected to one end of the fourth resistor, the other end of the fourth resistor is connected to the positive pole of the first thyristor, the control pole of the first thyristor is connected to the second output end of the AC sampling module through the second resistor, the negative pole of the first thyristor is connected to one end of the first potentiometer, the other end of the first potentiometer is connected to one end of the third capacitor and the negative pole of the fourth diode, the other end of the third capacitor is grounded, the positive pole of the fourth diode is connected to one end of the third resistor, the other end of the third resistor is connected to one end of the seventh relay and the negative pole of the fifth diode, the other end of the seventh relay is grounded, and the positive pole of the fifth diode is grounded.

[0023] As a further solution of the present invention: the zero-crossing disconnection module includes two zero-crossing disconnection units, the zero-crossing disconnection unit includes a third AND gate, a second MOS tube, a fourth thyristor, the D pole of the second MOS tube is connected to the second output end of the AC sampling module, the G pole of the second MOS tube is connected to the output end of the third AND gate, the two input ends of the third AND gate are respectively connected to the common point A1 and the common point A2, the S pole of the second MOS tube is connected to the control pole of the fourth thyristor, the positive pole of the fourth thyristor is connected to the power supply voltage, the negative pole of the fourth thyristor is connected to one end of the second potentiometer through the fifth resistor, the other end of the second potentiometer is connected to the negative pole of the sixth diode and one end of the fourth capacitor, the other end of the fourth capacitor is grounded, and the positive pole of the sixth diode is connected to the common point A3.

[0024] Compared with the prior art, the beneficial effect of the present invention is that the present invention controls the instant when the AC / DC conversion device is turned on or off to be when the AC power crosses the zero point through the cooperation of the DC sampling control module, the AC sampling module, the zero-crossing closing module and the zero-crossing disconnecting module, so that the instant current when the AC / DC conversion device is turned on or off is small, thereby increasing the service life of the bidirectional converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1The schematic diagram is a current detection circuit in the bidirectional current conversion process of urban subway rail transit.

[0026] Figure 2 This is the circuit diagram of the DC sampling control module.

[0027] Figure 3 It is a circuit diagram of an AC sampling module, a delay driving module, a zero-crossing closing module and a zero-crossing disconnecting module.

[0028] Figure 4 Schematic diagram of a bidirectional converter. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] See also Figure 1 , a current detection circuit in a bidirectional current conversion process of urban subway rail transit, comprising:

[0031] The DC sampling control module 1 is used to detect the DC voltage value VDD of the train. If the DC voltage value is greater than the upper threshold or less than the lower threshold, the AC sampling module 2 is driven to work;

[0032] The AC sampling module 2 is used to detect the AC power of the power grid (live line L, neutral line N), and provide a working signal to the zero-crossing closing module 4 and the zero-crossing disconnecting module 5 when the AC power passes through the zero point;

[0033] The delay driving module 3 is used to provide a trigger signal to the zero-crossing closing module 4 after a delay after the AC sampling module 2 works;

[0034] The zero-crossing closing module 4 is used to receive a trigger signal, and then receive a working signal to start working. After a delay in starting working, the switch of the bidirectional converter is controlled to close. The delay time is a cycle time of the AC mains;

[0035] The zero-crossing disconnection module 5 is used for receiving a working signal when the DC voltage value VDD of the train is between the upper threshold and the lower threshold, and after a delay, drives the DC sampling control module 1 to delay the control of the bidirectional converter switch to disconnect, and the delay time is a cycle time of the AC mains;

[0036] The first output end of the DC sampling control module 1 is connected to the input end of the AC sampling module 2, the second output end of the DC sampling control module 1 is connected to the first input end of the zero-crossing disconnection module 5, the first output end of the AC sampling module 2 is connected to the input end of the delay driving module 3, the second output end of the AC sampling module 2 is connected to the second input end of the zero-crossing closing module 4 and the second input end of the zero-crossing disconnection module 5, the output end of the delay driving module 3 is connected to the first input end of the zero-crossing closing module 4, and the output end of the zero-crossing disconnection module 5 is connected to the input end of the DC sampling control module 1.

[0037] In this example: See Figure 2 , the DC sampling control module 1 includes:

[0038] A DC sampling unit is used to sample the DC voltage value VDD of the train, obtain the sampled voltage, and output it to the lower limit detection control unit and the upper limit detection control unit;

[0039] A lower limit detection control unit is used to compare the sampling voltage with the first reference voltage VREF1. When the sampling voltage is lower than the first reference voltage VREF1 (corresponding to the lower limit threshold), the first switch S1, the second switch S2, and the third switch S3 are controlled to close, so as to drive the AC sampling module 2 to work;

[0040] The upper limit detection control unit is used to compare the sampling voltage and the second reference voltage VREF2. When the sampling voltage is greater than the second reference voltage VREF2 (corresponding to the upper limit threshold), the fourth switch S4, the fifth switch S5 and the sixth switch S6 are controlled to be closed, so as to drive the AC sampling module 2 to work;

[0041] The output end of the DC sampling unit is connected to the first input end of the lower limit detection control unit and the first input end of the upper limit detection control unit, the first output end of the lower limit detection control unit is connected to the input end of the AC sampling module 2 (the first relay J1 controls the second switch S2 and the third switch S3), the second output end of the lower limit detection control unit is connected to the first input end (common point A1 and common point A2) of the zero-crossing disconnection module 5, the first output end of the upper limit detection control unit is connected to the input end of the AC sampling module 2 (the fourth relay controls the fifth switch S5 and the sixth switch S6), the second output end of the upper limit detection control unit is connected to the first input end (common point B1 and common point B2) of the zero-crossing disconnection module 5, and the output end of the zero-crossing disconnection module 5 is connected to the second input end (common point A3) of the lower limit detection control unit and the second input end (common point B3) of the upper limit detection control unit.

[0042] In this example: See Figure 2The DC sampling unit includes a seventh resistor R7 and an eighth resistor R8. One end of the seventh resistor R7 is connected to the DC voltage value VDD of the train, and the other end of the seventh resistor R7 is connected to one end of the eighth resistor R8, the first input end of the lower limit detection control unit, and the first input end of the upper limit detection control unit. The other end of the eighth resistor R8 is grounded.

[0043] The DC voltage value VDD of the train is divided by the seventh resistor R7 and the eighth resistor R8. The voltage on the eighth resistor R8 is the sampling voltage, which is output to the lower limit detection control unit and the upper limit detection control unit.

[0044] In another embodiment: the seventh resistor R7 can be replaced with a potentiometer to facilitate adjustment of the proportion of the eighth resistor R8 in the DC voltage value VDD of the train.

[0045] In this example: See Figure 2 and Figure 4 The lower limit detection control unit includes a fifth amplifier U5, a sixth amplifier U6, a fourth MOS tube V4, a fifth MOS tube V5, and a first relay J1. The in-phase end of the fifth amplifier U5 is connected to the first reference voltage VREF1, the inverting end of the fifth amplifier U5 is connected to the in-phase end of the sixth amplifier U6 and the output end of the DC sampling unit, the inverting end of the sixth amplifier U6 is connected to the output end of the fifth amplifier U5 and one end of the ninth resistor R9, the output end of the sixth amplifier U6 is connected to the common point A1, the other end of the ninth resistor R9 is connected to the control electrode of the second thyristor Z2, and the positive electrode of the second thyristor Z2 is connected to the first The S pole of the fourth MOS tube V4 and the D pole of the fourth MOS tube V4 are connected to the power supply voltage VCC and one end of the tenth resistor R10, the other end of the tenth resistor R10 is connected to the G pole of the fourth MOS tube V4 and the D pole of the fifth MOS tube V5, the S pole of the fifth MOS tube V5 is grounded, the G pole of the fifth MOS tube V5 is connected to the common point A3, the cathode of the second thyristor Z2 is connected to the common point A2 and one end of the eleventh resistor R11, the other end of the eleventh resistor R11 is connected to the cathode of the eighth diode D8 and one end of the first relay J1, the other end of the first relay J1 is grounded, and the anode of the eighth diode D8 is grounded.

[0046] When the DC voltage value VDD of the train is less than the lower threshold, the sampling voltage is too small, so that the first reference voltage VREF1 is greater than the sampling voltage, and the fifth amplifier U5 outputs a high level, driving the second thyristor Z2 to turn on, and the power supply voltage VCC drives the first relay J1 to work through the fourth MOS tube V4, the second thyristor Z2, and the eleventh resistor R11, and controls the first switch S1, the second switch S2, and the third switch S3 to close; the AC sampling module 2 works;

[0047] The structure of the upper limit detection control unit is similar to that of the lower limit detection control unit. Figure 2As shown, when the DC voltage value VDD of the train is greater than the upper threshold, the sampling voltage is too large, so that the second reference voltage VREF2 is less than the sampling voltage, and the seventh amplifier U7 outputs a high level, driving the third thyristor Z3 to turn on, and the power supply voltage VCC drives the fourth relay J4 to work through the sixth MOS tube V6, the third thyristor Z3, and the thirteenth resistor R13, and controls the fourth switch S4, the fifth switch S5, and the sixth switch S6 to be closed; the AC sampling module 2 works.

[0048] In another embodiment, the eleventh resistor R11 may be omitted. The eleventh resistor R11 is provided here to avoid mismatch between the power supply voltage VCC and the voltage of the first relay J1, so as to reduce the circuit current and avoid damage to components.

[0049] In this example: See Figure 3 The AC sampling module 2 includes an AC optocoupler U1 and a second amplifier U2. The first end of the AC optocoupler U1 is connected to the twenty-first resistor R21, the second end of the AC optocoupler U1 is connected to the twenty-second resistor R22, the third end of the AC optocoupler U1 is connected to one end of the twenty-third resistor R23 and the in-phase end of the second amplifier U2, the other end of the twenty-third resistor R23 is connected to the power supply voltage VCC, the fourth end of the AC optocoupler U1 is grounded, the inverting end of the second amplifier U2 is connected to the third reference voltage VREF3, the output end of the second amplifier U2 is connected to the second input end of the zero-crossing closing module 4 and the second input end of the zero-crossing disconnecting module 5, the other end of the twenty-first resistor R21 is connected to one end of the second switch S2 and one end of the fifth switch S5, the other end of the second switch S2 is connected to the other end of the fifth switch S5 and the live wire L, the other end of the twenty-second resistor R22 is connected to one end of the third switch S3, one end of the sixth switch S6, and the input end of the delay driving module 3, and the other end of the third switch S3 is connected to the other end of the sixth switch S6 and the zero line N.

[0050] After the second switch S2 and the third switch S3 are closed (or the fifth switch S5 and the sixth switch S6 are closed), the voltage signals of the live line L and the neutral line N are input to the AC optocoupler U1. Two photosensitive diodes are provided inside the AC optocoupler U1, and the two photosensitive diodes are in opposite directions, so that when the input voltage is positive or negative, as long as the voltage is sufficient, there is always a photosensitive diode that emits light, so that the in-phase end of the second amplifier U2 is a low level. Only when the AC mains passes through the zero point (or is close to the zero point), it is not enough to turn on the photosensitive diode inside the AC optocoupler U1. At this time, the in-phase end of the second amplifier U2 is a high level, and the second amplifier U2 outputs a high level signal to indicate the zero point.

[0051] In another embodiment, the second amplifier U2 can be replaced with a triode, which also outputs a voltage signal to the zero-crossing closing module 4 and the zero-crossing disconnecting module 5 when receiving a high level.

[0052] In this example: See Figure 3 The delay driving module 3 includes a first diode D1, a first capacitor C1, a first resistor R1, a second diode D2, a second capacitor C2, and a third diode D3. The positive electrode of the first diode D1 is connected to the first output end of the AC sampling module 2, the negative electrode of the first diode D1 is connected to one end of the first capacitor C1 and one end of the first resistor R1, the other end of the first capacitor C1 is grounded, the other end of the first resistor R1 is connected to the negative electrode of the second diode D2, one end of the second capacitor C2, and the positive electrode of the third diode D3, the positive electrode of the second diode D2 is grounded, the other end of the second capacitor C2 is grounded, and the negative electrode of the third diode D3 is connected to the first input end of the zero-crossing closing module 4.

[0053] After the second switch S2 and the third switch S3 are closed (or the fifth switch S5 and the sixth switch S6 are closed), the voltage charges the first capacitor C1 through the first diode D1, and the voltage on the first capacitor C1 is clamped by the second diode D2 (voltage regulator diode) through the first resistor R1, providing a stable voltage for the zero-crossing closing module 4.

[0054] In another embodiment, the third diode D3 can be omitted. The third diode D3 is a light emitting diode and serves as an indicator.

[0055] In this example: See Figure 3 and Figure 4 The zero-crossing closing module 4 includes a first MOS tube V1, a first thyristor Z1, and a seventh relay J7. The D pole of the first MOS tube V1 is connected to the power supply voltage VCC, the G pole of the first MOS tube V1 is connected to the output end of the delay driving module 3, the S pole of the first MOS tube V1 is connected to one end of the fourth resistor R4, the other end of the fourth resistor R4 is connected to the positive pole of the first thyristor Z1, the control pole of the first thyristor Z1 is connected to the second output end of the AC sampling module 2 through the second resistor R2, the negative pole of the first thyristor Z1 is connected to one end of the first potentiometer RP1, the other end of the first potentiometer RP1 is connected to one end of the third capacitor C3 and the negative pole of the fourth diode D4, the other end of the third capacitor C3 is grounded, the positive pole of the fourth diode D4 is connected to one end of the third resistor R3, the other end of the third resistor R3 is connected to one end of the seventh relay J7 and the negative pole of the fifth diode D5, the other end of the seventh relay J7 is grounded, and the positive pole of the fifth diode D5 is grounded.

[0056] After the output voltage of the delay driving module 3 drives the first MOS tube V1 to turn on, when the alternating current passes through the zero point, the second amplifier U2 outputs a high level, so that the first thyristor Z1 is turned on, and the power supply voltage VCC passes through the first MOS tube V1, the fourth resistor R4, the first thyristor Z1, the first potentiometer RP1, the third capacitor C3, the fourth diode D4, and the third resistor R3 to control the seventh relay J7 to work, and control the seventh switch S7 and the eighth switch S8 to be closed. Previously, the first relay J1 (or the fourth relay) worked, and the first switch S1 (or the fourth switch S4) was closed. The AC power generates a DC voltage through the AC to DC circuit to increase the DC voltage value VDD of the train (or the DC voltage value VDD of the train generates AC power through the DC to AC circuit to feed the braking energy back to the power grid); the bidirectional converter is a common technology and will not be described in detail here.

[0057] Because there is a delay in the closing or opening of the relay control switch, a high level is output to the first thyristor Z1 when the AC power passes through zero. The time when the seventh relay J7 controls the seventh switch S7 and the eighth switch S8 to close is not the time when the AC power passes through zero. Therefore, the charging time of the third capacitor C3 is changed by adjusting the resistance value of the first potentiometer RP1, so that after the second amplifier U2 outputs a high level, the seventh switch S7 and the eighth switch S8 are closed after a cycle of AC power (including the time when the third capacitor C3 is charged to turn on the fourth diode D4 and the time when the seventh relay J7 controls the switch).

[0058] In another embodiment, the supply voltage VCC can be converted from AC power of the city power, or can be obtained by converting the DC voltage value VDD of the train.

[0059] In this example: See Figure 2 , Figure 3 and Figure 4 The zero-crossing disconnection module 5 includes two zero-crossing disconnection units, and the zero-crossing disconnection unit includes a third AND gate U3, a second MOS tube V2, a fourth thyristor Z4, and the D pole of the second MOS tube V2 is connected to the second output end of the AC sampling module 2, the G pole of the second MOS tube V2 is connected to the output end of the third AND gate U3, and the two input ends of the third AND gate U3 are respectively connected to the common point A1 and the common point A2, the S pole of the second MOS tube V2 is connected to the control pole of the fourth thyristor Z4, the positive pole of the fourth thyristor Z4 is connected to the power supply voltage VCC, the negative pole of the fourth thyristor Z4 is connected to one end of the second potentiometer RP2 through the fifth resistor R5, the other end of the second potentiometer RP2 is connected to the negative pole of the sixth diode D6 and one end of the fourth capacitor C4, the other end of the fourth capacitor C4 is grounded, and the positive pole of the sixth diode D6 is connected to the common point A3.

[0060] After the seventh relay J7 works, the DC voltage value VDD of the train gradually increases through the AC power supply of the mains to reach the lower limit threshold. At this time, the output of the fifth amplifier U5 changes from a high level to a low level, and the output terminal A1 of the sixth amplifier U6 changes from a low level to a high level. At the same time, based on the conduction of the second thyristor Z2, the common point A2 is also at a high level, so that the input terminals of the third AND gate U3 are all high levels, the third AND gate U3 outputs a high level, and the second MOS tube V2 is turned on. When the AC power of the mains passes through the zero point, the second amplifier U2 outputs a high level through the second MOS tube V2 to trigger the fourth thyristor Z4 to turn on, and the power supply is The voltage VCC passes through the fourth thyristor Z4, the fifth resistor R5, the second potentiometer RP2, the fourth capacitor C4, and the sixth diode D6 to make the common point A3 become a high level, the fifth MOS tube V5 is grounded, the fourth MOS tube V4 is turned off, the first relay J1 stops working, the first switch S1, the second switch S2, and the third switch S3 are disconnected, and the bidirectional converter stops working; here, by adjusting the resistance value of the second potentiometer RP2, the second amplifier U2 outputs a high level until the first switch S1 is disconnected, which is a cycle of the AC mains, and the first switch S1 is disconnected when the AC mains passes through zero next time.

[0061] Similarly, after the seventh relay J7 works, the DC voltage value VDD of the train is fed back to the AC power through discharge and gradually decreases to the upper limit threshold. The working principles at the common points B1, B2, and B3 are similar to those at the common points A1, A2, and A3, so that the second switch S2 is disconnected when the AC power passes through zero next time.

[0062] After the first switch S1 (or the second switch S2) is disconnected, the delay driving module 3 has no voltage input at this time. Based on the storage voltage of the first capacitor C1 and the second capacitor C2, the first MOS tube V1 is disconnected after a delay. Similarly, based on the storage voltage of the third capacitor C3, the seventh relay J7 is disconnected after a delay, so that after the first switch S1 (or the second switch S2) is disconnected, the seventh switch S7 and the eighth switch S8 are disconnected after a delay. The switches of the bidirectional converter device are disconnected twice and restored to the initial state, waiting for the next operation of the bidirectional converter device.

[0063] In another embodiment, the third AND gate U3 can be replaced by two switch tubes in series.

[0064] The working principle of the present invention is as follows: a DC sampling control module 1 is used to detect a DC voltage value VDD of a train, and if the DC voltage value is greater than an upper threshold value or less than a lower threshold value, an AC sampling module 2 is driven to work; the AC sampling module 2 is used to detect the AC power of the power grid, and when the AC power passes through zero, a working signal is provided to a zero-crossing closing module 4 and a zero-crossing disconnecting module 5; a delay driving module 3 is used to provide a trigger signal to the zero-crossing closing module 4 after a delay after the AC sampling module 2 works; the zero-crossing closing module 4 is used to receive a trigger signal, and then receive a working signal to start working, and control the switch of the bidirectional converter to close after a delay when the work starts, and the delay time is a cycle time of the AC mains; the zero-crossing disconnecting module 5 is used to receive a working signal when the DC voltage value VDD of the train is between an upper threshold value and a lower threshold value, and drive the DC sampling control module 1 to delay and control the switch of the bidirectional converter to disconnect after a delay, and the delay time is a cycle time of the AC mains.

[0065] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered as exemplary and non-restrictive in all respects.

[0066] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A current detection circuit in the bidirectional current conversion process of urban subway rail transit, characterized in that: The current detection circuit in the bidirectional current conversion process of the urban subway rail transit includes: The DC sampling control module is used to detect the DC voltage value of the train. If the DC voltage value is greater than the upper threshold or less than the lower threshold, the AC sampling module is driven to work; The AC sampling module is used to detect the AC power of the power grid and provide working signals for the zero-crossing closing module and the zero-crossing disconnecting module when the AC power passes through the zero point; The delay driving module is used to provide a trigger signal to the zero-crossing closing module after the AC sampling module works and after a delay; The zero-crossing closing module is used to receive a trigger signal, and then receive a working signal to start working. After a delay in starting working, the switch of the bidirectional converter is controlled to close. The delay time is a cycle time of the AC mains. The zero-crossing disconnection module is used when the DC voltage value of the train is between the upper threshold and the lower threshold. When receiving the working signal, it drives the DC sampling control module to delay and control the bidirectional converter switch to disconnect after a delay. The delay time is one cycle time of the AC mains. The first output end of the DC sampling control module is connected to the input end of the AC sampling module, the second output end of the DC sampling control module is connected to the first input end of the zero-crossing disconnection module, the first output end of the AC sampling module is connected to the input end of the delay driving module, the second output end of the AC sampling module is connected to the second input end of the zero-crossing closing module and the second input end of the zero-crossing disconnection module, the output end of the delay driving module is connected to the first input end of the zero-crossing closing module, and the output end of the zero-crossing disconnection module is connected to the input end of the DC sampling control module.

2. The current detection circuit in the bidirectional current conversion process of urban subway rail transit according to claim 1 is characterized in that: The DC sampling control module includes: A DC sampling unit is used to sample the DC voltage value of the train, obtain the sampled voltage, and output it to the lower limit detection control unit and the upper limit detection control unit; A lower limit detection control unit is used to compare the sampling voltage with the first reference voltage, and when the sampling voltage is lower than the first reference voltage, control the first switch, the second switch, and the third switch to close, so as to drive the AC sampling module to work; An upper limit detection control unit is used to compare the sampling voltage with the second reference voltage, and when the sampling voltage is greater than the second reference voltage, control the fourth switch, the fifth switch, and the sixth switch to close, so as to drive the AC sampling module to work; The output end of the DC sampling unit is connected to the first input end of the lower limit detection control unit and the first input end of the upper limit detection control unit, the first output end of the lower limit detection control unit is connected to the input end of the AC sampling module, the second output end of the lower limit detection control unit is connected to the first input end of the zero-crossing disconnection module, the first output end of the upper limit detection control unit is connected to the input end of the AC sampling module, the second output end of the upper limit detection control unit is connected to the first input end of the zero-crossing disconnection module, and the output end of the zero-crossing disconnection module is connected to the second input end of the lower limit detection control unit and the second input end of the upper limit detection control unit.

3. The current detection circuit in the bidirectional current conversion process of urban subway rail transit according to claim 2 is characterized in that: The DC sampling unit includes a seventh resistor and an eighth resistor. One end of the seventh resistor is connected to the DC voltage value of the train, the other end of the seventh resistor is connected to one end of the eighth resistor, the first input end of the lower limit detection control unit, and the first input end of the upper limit detection control unit, and the other end of the eighth resistor is grounded.

4. The current detection circuit in the bidirectional current conversion process of urban subway rail transit according to claim 2 is characterized in that: The lower limit detection control unit includes a fifth amplifier, a sixth amplifier, a fourth MOS tube, a fifth MOS tube, and a first relay. The in-phase end of the fifth amplifier is connected to the first reference voltage, the inverting end of the fifth amplifier is connected to the in-phase end of the sixth amplifier and the output end of the DC sampling unit, the inverting end of the sixth amplifier is connected to the output end of the fifth amplifier and one end of the ninth resistor, the output end of the sixth amplifier is connected to the common point A1, the other end of the ninth resistor is connected to the control electrode of the second thyristor, the positive electrode of the second thyristor is connected to the S electrode of the fourth MOS tube, the D electrode of the fourth MOS tube is connected to the power supply voltage and one end of the tenth resistor, the other end of the tenth resistor is connected to the G electrode of the fourth MOS tube and the D electrode of the fifth MOS tube, the S electrode of the fifth MOS tube is grounded, the G electrode of the fifth MOS tube is connected to the common point A3, the negative electrode of the second thyristor is connected to the common point A2 and one end of the eleventh resistor, the other end of the eleventh resistor is connected to the negative electrode of the eighth diode and one end of the first relay, the other end of the first relay is grounded, and the positive electrode of the eighth diode is grounded.

5. The current detection circuit in the bidirectional current conversion process of urban subway rail transit according to any one of claims 1 to 4, characterized in that: The AC sampling module includes an AC optocoupler and a second amplifier. The first end of the AC optocoupler is connected to the twenty-first resistor, the second end of the AC optocoupler is connected to the twenty-second resistor, the third end of the AC optocoupler is connected to one end of the twenty-third resistor and the in-phase end of the second amplifier, the other end of the twenty-third resistor is connected to the power supply voltage, the fourth end of the AC optocoupler is grounded, the inverting end of the second amplifier is connected to the third reference voltage, the output end of the second amplifier is connected to the second input end of the zero-crossing closing module and the second input end of the zero-crossing disconnecting module, the other end of the twenty-first resistor is connected to one end of the second switch and one end of the fifth switch, the other end of the second switch is connected to the other end of the fifth switch and the live wire, the other end of the twenty-second resistor is connected to one end of the third switch, one end of the sixth switch, and the input end of the delay driving module, and the other end of the third switch is connected to the other end of the sixth switch and the zero line.

6. The current detection circuit in the bidirectional current conversion process of urban subway rail transit according to claim 1 is characterized in that: The delay driving module includes a first diode, a first capacitor, a first resistor, a second diode, a second capacitor, and a third diode. The positive electrode of the first diode is connected to the first output end of the AC sampling module, the negative electrode of the first diode is connected to one end of the first capacitor and one end of the first resistor, the other end of the first capacitor is grounded, the other end of the first resistor is connected to the negative electrode of the second diode, one end of the second capacitor, and the positive electrode of the third diode, the positive electrode of the second diode is grounded, the other end of the second capacitor is grounded, and the negative electrode of the third diode is connected to the first input end of the zero-crossing closing module.

7. The current detection circuit in the bidirectional current conversion process of urban subway rail transit according to claim 5, characterized in that: The zero-crossing closing module includes a first MOS tube, a first thyristor, and a seventh relay. The D pole of the first MOS tube is connected to the power supply voltage, the G pole of the first MOS tube is connected to the output end of the delay driving module, the S pole of the first MOS tube is connected to one end of the fourth resistor, the other end of the fourth resistor is connected to the positive pole of the first thyristor, the control pole of the first thyristor is connected to the second output end of the AC sampling module through the second resistor, the negative pole of the first thyristor is connected to one end of the first potentiometer, the other end of the first potentiometer is connected to one end of the third capacitor and the negative pole of the fourth diode, the other end of the third capacitor is grounded, the positive pole of the fourth diode is connected to one end of the third resistor, the other end of the third resistor is connected to one end of the seventh relay and the negative pole of the fifth diode, the other end of the seventh relay is grounded, and the positive pole of the fifth diode is grounded.

8. The current detection circuit in the bidirectional current conversion process of urban subway rail transit according to claim 5 is characterized in that: The zero-crossing disconnection module includes two zero-crossing disconnection units, and the zero-crossing disconnection unit includes a third AND gate, a second MOS tube, a fourth thyristor, and the D pole of the second MOS tube is connected to the second output end of the AC sampling module, the G pole of the second MOS tube is connected to the output end of the third AND gate, the two input ends of the third AND gate are respectively connected to a common point A1 and a common point A2, the S pole of the second MOS tube is connected to the control pole of the fourth thyristor, the positive pole of the fourth thyristor is connected to the power supply voltage, the negative pole of the fourth thyristor is connected to one end of the second potentiometer through a fifth resistor, the other end of the second potentiometer is connected to the negative pole of the sixth diode and one end of the fourth capacitor, the other end of the fourth capacitor is grounded, and the positive pole of the sixth diode is connected to the common point A3.

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