A short-circuit protection test circuit and method for AC charging piles based on quantitative analysis

Abstract

A short-circuit protection test circuit and method for AC charging piles based on quantitative analysis is disclosed. The circuit includes: a current transformer (1), a short-circuit resistor array (2), a DSP processing unit (4), a human-machine interaction unit (5), a thyristor drive circuit (6), and a sampling module. The primary side of the current transformer (1) is connected to the neutral line, and the secondary side is connected to the input terminal of the sampling module. One end of the short-circuit resistor array (2) is connected to the neutral line, and the other end is connected to the live line. The short-circuit resistor array (2) includes multiple parallel short-circuit resistor branches, each including a short-circuit resistor and a controllable switch connected in series. The DSP processing unit (4) is connected to the output terminal of the sampling module, the human-machine interaction unit (5), and the thyristor drive circuit (6) to calculate I. 2 t, receives input from the human-machine interaction unit (5), outputs test results to the human-machine interaction unit (5), and determines the number of short-circuit resistance branches to be put into short-circuit protection test.

Description

Technical Field

[0001] This invention belongs to the field of instrumentation technology, and more specifically, relates to a short-circuit protection test circuit and method for AC charging piles based on quantitative analysis. Background Technology

[0002] AC charging piles currently account for a very high percentage of the charging pile market. According to Section 7.7.1 of "NB / T 33002-2018 Technical Conditions for AC Charging Piles for Electric Vehicles", charging piles should have short-circuit protection function. Section 5.4.1 of "NB / T33008.2-2018 Inspection and Testing Specifications for Electric Vehicle Charging Equipment Part 2: AC Charging Piles" requires short-circuit protection testing for AC charging piles. Currently, the conventional short-circuit test is to directly short-circuit through a switch or by short-circuiting through a switch connected in series with a resistor. This test method is destructive due to the large short-circuit current.

[0003] 1. Due to the low short-circuit impedance, the short-circuit current is large, which reduces the service life of the switch;

[0004] 2. Because the short-circuit impedance is small and the short-circuit current is large, if the circuit impedance is insufficient, it can easily cause accidents such as fires.

[0005] 3. Due to the small short-circuit impedance and large short-circuit current, a larger power supply capacity is required to conduct the test; otherwise, the power grid switch will trip frequently.

[0006] 4. Unable to perform thermal analysis on the short-circuit protection of AC charging piles. Quantitative analysis;

[0007] 5. According to GB / T 18487.1-2015_Electric Vehicle Conductive Charging System Part 1: General Requirements, when a short circuit is detected in the charging cable, the vehicle plug of the Mode 3 (Mode C) power supply equipment... The value should not Quantitative analysis and judgment cannot be made using the direct short-circuit method. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a short-circuit protection test circuit and method for AC charging piles based on quantitative analysis, which can perform short-circuit protection tests on charging piles without causing damage to the charging piles or impacting the power grid.

[0009] The present invention adopts the following technical solution. A short-circuit protection test circuit for AC charging piles based on quantitative analysis includes: a current transformer, a short-circuit resistor array, a DSP processing unit, a human-machine interface unit, a thyristor drive circuit, and a sampling module. The primary side of the current transformer is connected to the neutral line, and the secondary side is connected to the input terminal of the sampling module. One end of the short-circuit resistor array is connected to the neutral line, and the other end is connected to the live wire. The short-circuit resistor array includes multiple parallel short-circuit resistor branches, each including a short-circuit resistor and a controllable switch connected in series. The DSP processing unit is connected to the output terminal of the sampling module, the human-machine interface unit, and the thyristor drive circuit, and is used to calculate the thermal energy value. It receives input from the human-machine interface unit, outputs test results to the human-machine interface unit, and determines the number of short-circuit resistance branches to be put into short-circuit protection test.

[0010] Preferably, the sampling module includes: an IV feedback resistor, an operational amplifier, and an A / D converter. One end of the IV feedback resistor is connected to the second output terminal of the secondary side of the current transformer, and the other end is connected to the output terminal of the operational amplifier. The output terminal of the operational amplifier is connected to the input terminal of the A / D converter.

[0011] Preferably, the short-circuit resistor array includes: a first resistor, a second resistor, a third resistor, and a fourth resistor connected in parallel; a first bidirectional thyristor connected in series with the first resistor; a second bidirectional thyristor connected in series with the second resistor; a third bidirectional thyristor connected in series with the third resistor; and a fourth bidirectional thyristor connected in series with the fourth resistor.

[0012] Preferably, the AC charging pile short-circuit protection test circuit further includes: a switching power supply, the input terminal of which is connected to an external 220V AC power supply, and the output terminal providing... Operating power supply.

[0013] Preferably, the DSP processing unit includes SPI1, an IO output module, and a data acquisition and calculation module. It includes a control output module and a control management module. SPI1 is connected to the A / D converter for communication, sending data to the acquisition and calculation module for thermal energy values. and control output module, to collect and calculate thermal energy values The control output module is also connected to the IO output module and the control management module respectively. The IO output module is also connected to the thyristor drive circuit. Here, SPI refers to the serial peripheral interface.

[0014] Preferably, the human-computer interaction unit is connected to the control and management module of the DSP processing unit, and the human-computer interaction unit includes a display device and an input device.

[0015] Preferably, the thyristor driving circuit includes: a first 5V to 5V isolated power supply (65a), a second 5V to 5V isolated power supply, a third 5V to 5V isolated power supply and a fourth 5V to 5V isolated power supply (65d), each 5V to 5V isolated power supply including: a driving resistor Rin, an optocoupler, an output pull-up resistor Rout and a tracking driving amplifier.

[0016] Preferably, the operational amplifier is an OPA343 with harmonic distortion plus noise of less than 0.0007%.

[0017] Preferably, the A / D converter is a 32-bit SAR type A / D converter LTC2500, with a sampling rate set to 1MSPS, where MSPS refers to millions of samples per second.

[0018] The present invention also provides a test method based on the short-circuit protection test circuit of the AC charging pile, characterized by comprising the following steps:

[0019] Step 1: Set the rated current value of the AC charging pile through the human-machine interaction unit. .

[0020] Step 2: The thyristor driver circuit drives the short-circuit resistor array to short-circuit at the zero-crossing point of the voltage signal. The DSP processing unit starts and calculates the thermal energy value using the following formula. ,

[0021]

[0022] In the formula:

[0023] Indicates the number of sampling points.

[0024] This represents the instantaneous value of the current at the sampling point.

[0025] This indicates the sampling rate of A / D converter 9.

[0026] Indicates the length of time;

[0027] Step 3, the DSP processing unit determines the rated current value according to the settings. The number of short-circuit circuits to be activated is determined within a set time period;

[0028] Step 4: Set the delay time, and the DSP processing unit 4 determines whether to trip based on the short-circuit current;

[0029] Step 5: If no trip occurs, it indicates that the short-circuit protection failed to operate, which does not meet the requirements; if a trip occurs, the human-machine interface unit displays the thermal energy value. If the value is [value], then determine the thermal energy value. Does it exceed the threshold? If it does, the short-circuit protection trips at the thermal energy value. If the requirements are not met, such as not exceeding the threshold, the short-circuit protection trips due to thermal energy. Meets the requirements;

[0030] Step 6: Display the test results through the human-computer interaction unit.

[0031] The beneficial effects of this invention are that, compared with the prior art, this invention uses short-circuit resistors of different capacities (different short-circuit currents) for AC charging piles with different capacities (rated currents), reducing damage to the charging pile switches and lines. Furthermore, by controlling the zero-crossing switching of the short-circuit resistors with thyristors, it further reduces damage to the charging piles and the impact on the power grid. Simultaneously, it utilizes DSP calculations... The value represents the thermal energy value of a short circuit in an AC charging pile. Perform quantitative analysis. Attached Figure Description

[0032] Figure 1 This invention provides a short-circuit protection test circuit for AC charging piles based on quantitative analysis.

[0033] Figure 2 This is a schematic diagram of a thyristor drive circuit;

[0034] Figure 3 This is a schematic diagram of a DSP processing unit;

[0035] Figure 4 The flowchart of a short-circuit protection test method for AC charging piles based on quantitative analysis is provided for this invention.

[0036] In the picture:

[0037] 1- Current transformer;

[0038] 2-Short-circuit resistor array, R1-First resistor, R2-Second resistor, R3-Third resistor, R4-Fourth resistor, G1-First bidirectional thyristor, G2-Second bidirectional thyristor, G3-Third bidirectional thyristor, G4-Fourth bidirectional thyristor;

[0039] 3- Switching power supply;

[0040] 4-DSP processing unit, 41-SPI1, 43-IO output module, 44-Acquisition and calculation and control output module, 46-control management module;

[0041] 5-Human-Computer Interaction Unit;

[0042] 6-SCR driver circuit, 61-Drive resistor Rin, 62-Optical isolation, 63-Output pull-up resistor Rout, 64-Tracking driver amplifier, 65a-First 5V to 5V isolation power supply, 65d-Fourth 5V to 5V isolation power supply;

[0043] 7-IV feedback resistor Rf;

[0044] 8-Operational amplifier;

[0045] 9-A / D converter. Detailed Implementation

[0046] The present application will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and should not be construed as limiting the scope of protection of the present application.

[0047] Example 1: A short-circuit protection test circuit for AC charging piles based on quantitative analysis

[0048] like Figure 1 As shown, this invention provides a short-circuit protection test circuit for AC charging piles based on quantitative analysis, comprising: a current transformer 1, a short-circuit resistor array 2, a switching power supply 3, a DSP processing unit 4, a human-machine interface unit 5, a thyristor drive circuit 6, and a sampling module. The sampling module includes: an IV feedback resistor 7, an operational amplifier 8, and an A / D converter 9.

[0049] The primary side of current transformer 1 is connected to the neutral line N, and the first output terminal S1 and the second output terminal S2 of the secondary side are connected to the input terminal of operational amplifier 8. A preferred but non-limiting embodiment is to use a 0.01 class zero flux current transformer to ensure measurement accuracy.

[0050] One end of the short-circuit resistor array 2 is connected to the neutral wire N, and the other end is connected to the live wire. The short-circuit resistor array 2 includes a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4 connected in parallel. A preferred but non-limiting embodiment is as follows: The short-circuit resistor array 2 further includes: a first bidirectional thyristor G1 connected in series with the first resistor R1, a second bidirectional thyristor G2 connected in series with the second resistor R2, a third bidirectional thyristor G3 connected in series with the third resistor R3, and a fourth bidirectional thyristor G4 connected in series with the fourth resistor R4. The bidirectional thyristors can achieve rapid turn-off and rapid turn-on at zero crossings. A preferred but non-limiting embodiment is to achieve 10... It features rapid turn-off and rapid turn-on. The bidirectional thyristor experiences minimal short-circuit impact, and the thermal energy value can be accurately calculated via A / D converter 9. A preferred, but not limiting, implementation is as follows: the bidirectional thyristor is selected with a rated current of 100A, and the normal short-circuit current of each bidirectional thyristor is... =27.5A.

[0051] The input terminal of switching power supply 3 is connected to an external 220V AC power supply, and the output terminal provides power for the chip to operate. Operating power supply.

[0052] DSP processing unit 4, such as Figure 3 As shown, it includes: SPI1 41 (SPI, or Serial Peripheral interface), IO output module 43, and a module for collecting and calculating thermal energy values. The system includes a control output module 44 and a control management module 46. In a preferred but non-limiting embodiment, the DSP processing unit 4 uses an ADSP BF609 chip. The ADSP BF609 chip has very rich on-chip resources; this preferred embodiment only samples a portion of these resources. SPI1 41 is connected to the A / D converter 9 for communication, sending data to the acquisition and calculation unit for thermal energy values. and control output module 44, which collects and calculates thermal energy values. The control output module 44 is also connected to the IO output module 43 and the control management module 46, respectively. The IO output module 43 is also connected to the thyristor drive circuit 6.

[0053] The human-computer interaction unit 5 is connected to the control and management module 46 of the DSP processing unit 4. In a preferred but non-limiting embodiment, the human-computer interaction unit 5 includes a display device and an input device.

[0054] Thyristor drive circuit 6, such as Figure 2 As shown, it includes: a first 5V to 5V isolated power supply 65a, a second 5V to 5V isolated power supply, a third 5V to 5V isolated power supply, and a fourth 5V to 5V isolated power supply 65d, a drive resistor Rin 61, an optocoupler 62, an output pull-up resistor Rout 63, and a tracking driver amplifier. The 5V to 5V isolated power supply is used to achieve 5V to 5V isolated output with an output current of 1A. A preferred but non-limiting embodiment is that the drive resistor Rin 61 and the output pull-up resistor Rout 63 are... The chip resistors, optocoupler 62 uses a 10MHz 6N137, and the tracking driver amplifier 64 is a rail-to-rail operational amplifier with a current of 50mA or more. The tracking driver amplifier 64 is used to increase the drive current and reliably control the thyristors. Simultaneously, four general-purpose control circuits are distributed to control the first bidirectional thyristor G1, the second bidirectional thyristor G2, the third bidirectional thyristor G3, and the fourth bidirectional thyristor G4 in the short-circuit resistor array 2.

[0055] One end of the IV feedback resistor 7 is connected to the second output terminal S2 on the secondary side of the current transformer 1, and the other end is connected to the output terminal of the operational amplifier 8. A preferred but non-limiting embodiment is to use a precision resistor with a temperature drift of 1 ppm (parts per million) and an initial accuracy of 0.01% to ensure measurement accuracy.

[0056] The output of operational amplifier 8 is connected to the input of A / D converter 9. A preferred, but non-limiting, implementation is that operational amplifier 8 uses an OPA343, with harmonic distortion plus noise less than 0.0007%, ensuring measurement accuracy.

[0057] The output of A / D converter 9 is connected to SPI1 of DSP processing unit 4. A preferred but non-limiting implementation is that A / D converter 9 uses a 32-bit SAR type A / D converter LTC2500 to ensure high accuracy, while the sampling rate is set to 1MSPS (Million Samples per Second).

[0058] Example 2: A short-circuit protection test method for AC charging piles based on quantitative analysis

[0059] like Figure 4 As shown, the present invention also provides a test method based on the AC charging pile short-circuit protection test circuit described in Embodiment 1, comprising the following steps:

[0060] Step 1: Set the rated current value of the AC charging pile through the human-machine interaction unit 5. .

[0061] Step 2: The thyristor drive circuit 6 drives the short-circuit resistor array 2 to short-circuit at the zero-crossing point of the voltage signal, further reducing the current surge. The short-circuit current is selected based on the charging pile's capacity, thus achieving the purpose of short-circuit testing without causing excessive destructive short-circuit current. The DSP processing unit 4 starts calculating the thermal energy value using the following formula: thermal energy value... ,

[0062]

[0063] In the formula:

[0064] Indicates the number of sampling points.

[0065] This represents the instantaneous value of the current at the sampling point.

[0066] The sampling rate of the A / D converter 9 is indicated by a preferred, but not limiting, implementation. That is, sampling one million times per second, with a cumulative time of ,

[0067] Indicating the duration, a preferred but non-limiting implementation is that the duration is 2 seconds after the DSP processing unit 4 starts up. .

[0068] Thermal energy value The accuracy is determined by the current transformer 1 and the IV feedback resistor 7. The calculation accuracy can reach 0.02%, and the A / D converter 9 is a 32-bit high-speed A / D with a linearity of up to 1ppm, which is negligible.

[0069] The operational amplifier's 8th harmonic distortion plus noise is less than 0.0007%, and its impact is negligible.

[0070] Step 3, the DSP processing unit 4 processes the current according to the set rated current value. Within a set time period, preferably, but not limited to, within 100 The internal system determines the number of short-circuit circuits to be deployed.

[0071] The judgment is shown in the table below.

[0072]

[0073] Step 4: After a one-second delay, DSP processing unit 4 determines whether to trip based on the short-circuit current. Generally, the tripping time of a charging pile is less than 100 seconds. Delay 1 This ensures that a judgment is made after the circuit breaker trips.

[0074] Step 5: If no trip occurs, it indicates that the short-circuit protection failed to operate, which does not meet the requirements; if a trip occurs, the human-machine interface unit 5 displays the thermal energy value. If the value is [value], then determine the thermal energy value. To determine whether a threshold is exceeded, a preferred but non-limiting implementation is to determine the thermal energy value of the vehicle plug of the power supply equipment in Mode 3 (Mode C) when a short circuit protection is detected in the charging cable according to GB / T 18487.1-2015_Electric Vehicle Conductive Charging System Part 1: General Requirements. It should not exceed If the threshold is exceeded, the short-circuit protection trips due to thermal energy. If the requirements are not met, such as not exceeding the threshold, the short-circuit protection trips due to thermal energy. Meets the requirements.

[0075] Step 6: Display the test results through the human-computer interaction unit 5.

[0076] The beneficial effects of this invention are that, compared with the prior art, this invention uses short-circuit resistors of different capacities (different short-circuit currents) for AC charging piles with different capacities (rated currents), reducing damage to the charging pile switches and lines. Furthermore, by controlling the zero-crossing switching of the short-circuit resistors with thyristors, it further reduces damage to the charging piles and the impact on the power grid. Simultaneously, it utilizes DSP calculations... The value represents the thermal energy value of a short circuit in an AC charging pile. Perform quantitative analysis.

[0077] The applicant of this invention has provided a detailed description of the embodiments of the invention in conjunction with the accompanying drawings. However, those skilled in the art should understand that the above embodiments are merely preferred embodiments of the invention. The detailed description is only intended to help readers better understand the spirit of the invention and is not intended to limit the scope of protection of the invention. On the contrary, any improvements or modifications made based on the inventive spirit of the invention should fall within the scope of protection of the invention.

Claims

1. A short-circuit protection test circuit for AC charging piles based on quantitative analysis, comprising: The system comprises a current transformer (1), a short-circuit resistor array (2), a DSP processing unit (4), a human-machine interface unit (5), a thyristor drive circuit (6), and a sampling module, characterized in that... The primary side of the current transformer (1) is connected to the neutral line, and the secondary side is connected to the input terminal of the sampling module. The sampling module includes: IV feedback resistor (7), operational amplifier (8) and A / D converter (9). One end of IV feedback resistor (7) is connected to the second output terminal (S2) of the secondary side of the current transformer (1), and the other end is connected to the output terminal of operational amplifier (8). The output terminal of operational amplifier (8) is connected to the input terminal of A / D converter (9). One end of the short-circuit resistor array (2) is connected to the neutral wire, and the other end is connected to the live wire. The short-circuit resistor array (2) includes multiple parallel short-circuit resistor branches. Each short-circuit resistor branch includes a short-circuit resistor and a controllable switch connected in series. The short-circuit resistor array (2) includes: a first resistor (R1), a second resistor (R2), a third resistor (R3), and a fourth resistor (R4) connected in parallel; a first bidirectional thyristor (G1) connected in series with the first resistor (R1); a second bidirectional thyristor (G2) connected in series with the second resistor (R2); a third bidirectional thyristor (G3) connected in series with the third resistor (R3); and a fourth bidirectional thyristor (G4) connected in series with the fourth resistor (R4). The DSP processing unit (4) is connected to the output of the sampling module, the human-machine interaction unit (5) and the thyristor drive circuit (6). It is used to calculate the thermal energy value, receive the input of the human-machine interaction unit (5), output the test results to the human-machine interaction unit (5), and determine the number of short-circuit resistor branches to be put into short-circuit protection test. Different capacity short-circuit resistors are put into AC charging piles of different capacities.

2. The AC charging pile short-circuit protection test circuit based on quantitative analysis according to claim 1, characterized in that: The AC charging pile short-circuit protection test circuit also includes: a switching power supply (3), the input terminal of which is connected to an external 220V AC power supply, and the output terminal provides... Operating power supply.

3. The AC charging pile short-circuit protection test circuit based on quantitative analysis according to claim 1, characterized in that: The DSP processing unit (4) includes SPI1 (41), IO output module (43), thermal energy acquisition and control output module (44), and control management module (46). SPI1 (41) is connected to the A / D converter (9) for communication and sends data to the thermal energy acquisition and control output module (44). The thermal energy acquisition and control output module (44) is also connected to the IO output module (43) and the control management module (46) respectively. The IO output module (43) is also connected to the thyristor drive circuit (6). SPI stands for Serial Peripheral Interface.

4. The AC charging pile short-circuit protection test circuit based on quantitative analysis according to claim 3, characterized in that: The human-computer interaction unit (5) is connected to the control and management module (46) of the DSP processing unit (4). The human-computer interaction unit (5) includes a display device and an input device.

5. The AC charging pile short-circuit protection test circuit based on quantitative analysis according to claim 1, characterized in that: The thyristor drive circuit (6) includes: a first 5V to 5V isolated power supply (65a), a second 5V to 5V isolated power supply, a third 5V to 5V isolated power supply and a fourth 5V to 5V isolated power supply (65d). Each 5V to 5V isolated power supply includes: a drive resistor Rin (61), an optical isolator (62), an output pull-up resistor Rout (63) and a tracking drive amplifier (64).

6. The AC charging pile short-circuit protection test circuit based on quantitative analysis according to claim 1, characterized in that: The operational amplifier (8) uses OPA343, with harmonic distortion + noise less than 0.0007%.

7. The AC charging pile short-circuit protection test circuit based on quantitative analysis according to claim 1, characterized in that: The A / D converter (9) uses a 32-bit SAR type A / D converter LTC2500 with a sampling rate set to 1MSPS, where MSPS means millions of samples per second.

8. A test method based on the short-circuit protection test circuit of an AC charging pile according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Set the rated current value of the AC charging pile through the human-machine interaction unit (5). ; Step 2, the thyristor drive circuit (6) drives the short-circuit resistor array (2) to short-circuit at the zero crossing of the voltage signal, and the DSP processing unit (4) starts to calculate the thermal energy value using the following formula. , In the formula: Indicates the number of sampling points. This represents the instantaneous value of the current at the sampling point. This indicates the sampling rate of A / D converter 9. Indicates the length of time; Step 3, the DSP processing unit (4) processes the current according to the set rated current value. The number of short-circuit circuits to be activated is determined within a set time period; Step 4: Set the delay time, and the DSP processing unit 4 determines whether to trip based on the short-circuit current; Step 5: If no trip occurs, it indicates that the short-circuit protection failed to operate, which does not meet the requirements; if a trip occurs, the human-machine interface unit (5) displays the thermal energy value. If the value is [value], then determine the thermal energy value. Does it exceed the threshold? If it does, the short-circuit protection trips at the thermal energy value. If the requirements are not met, such as not exceeding the threshold, the short-circuit protection trips due to thermal energy. Meets the requirements; Step 6: Display the test results through the human-computer interaction unit (5).

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