Direct current charging pile active electric energy detection device

Abstract

The invention belongs to the technical field of charging piles, and particularly relates to an active electric energy detection device for a direct-current charging pile. Comprising a control module, a current acquisition module and a voltage acquisition module used for acquiring the voltage of a charging pile DC output bus, the current acquisition module comprises a current transformer, the current acquisition module is used for acquiring the current of the charging pile DC output bus through the current transformer, and the control module is used for acquiring the impedance of a charging pile gun head connecting line. The charging pile gun head output voltage is obtained according to the impedance of the charging pile gun head connecting line and the voltage of the charging pile direct-current output bus, and the active electric energy in the charging process of the charging pile is calculated according to the charging pile gun head voltage and the current of the charging pile direct-current output bus. The error caused by the impedance of the gun head connecting line is considered, and the error is corrected, so that the accuracy of the active electric energy detection of the charging pile is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of charging piles, and particularly relates to a DC charging pile active power detection device. Background Art

[0002] With the wide application of new energy vehicles, the number of public charging piles is increasing. Public charging piles usually charge according to the active power consumed during the charging process of the vehicle. Therefore, higher requirements are put forward for the measurement accuracy of the active power of the charging pile. In order to calibrate the measurement accuracy of the active power of the DC charging pile, in the prior art, a detection device is usually used to detect the active power of the charging pile, and the active power measured by the charging pile is calibrated according to the detection result. The detection device often carries a high-power load, and calibrates the refining accuracy of the charging pile during the process of the high-power load consuming low energy. However, this detection method not only consumes a large amount of electricity, but also the high-power load is not convenient to carry due to its volume and weight.

[0003] In order to solve the technical problem of large power consumption of the high-power load causing waste of electric energy, a technical solution has been proposed in the prior art that does not require a high-power load and directly uses an electric vehicle as a load to calibrate the active power of the charging pile during the charging process of the electric vehicle. However, in this solution, due to the high current and voltage of the calibration device and high power consumption, the device generates a large amount of heat, and a liquid cooling device needs to be equipped to cool the detection device. The liquid cooling device makes the entire calibration device still large in volume, heavy in weight, not easy to carry and costly.

[0004] In order to solve the technical problems of large volume, not easy to carry and high cost of the calibration device, the Chinese patent application with the application publication number CN109061291A proposes a technical solution that reduces the DC output bus current of the charging pile collected by the detection device through a current transformer, thereby reducing the energy consumption and heat generation of the detection device, eliminating the liquid cooling device, and reducing the volume and cost of the detection device. However, since there is still a certain distance (the length of the charging gun connecting wire of the charging pile) between the sampling point of its detection device and the charging gun, the voltage collected by the detection device is not the voltage output by the charging gun, resulting in a certain error in the active power detection result of the detection device. Summary of the Invention

[0005] The purpose of the present invention is to provide a DC charging pile active power detection device to solve the technical problem that the voltage collected by the charging pile power calibration device in the prior art is not the voltage output by the charging gun, resulting in a certain error in the active power detection result of the detection device.

[0006] To solve the above technical problems, the present invention provides a DC charging pile active power detection device, which includes a control module, a current acquisition module, and a voltage acquisition module for acquiring the DC output bus voltage of the charging pile. The current acquisition module includes a current transformer, and the current acquisition module is used to acquire the current of the DC output bus of the charging pile through the current transformer. The control module is used to obtain the impedance of the charging pile gun head connection line, and obtain the charging pile gun head output voltage according to the impedance of the charging pile gun head connection line and the voltage of the DC output bus of the charging pile, and calculate the active power during the charging process of the charging pile according to the charging pile gun head voltage and the current of the DC output bus of the charging pile.

[0007] Further, the method for obtaining the charging pile gun head output voltage according to the impedance of the charging pile gun head connection line and the voltage of the DC output bus of the charging pile is as follows:

[0008] Vb = V - I * Rz

[0009] In the formula, Vb is the charging pile gun head output voltage, V is the voltage of the DC output bus of the charging pile, I is the current of the DC output bus of the charging pile, and Rz is the impedance of the charging pile gun head connection line.

[0010] Further, the impedance of the charging pile gun head connection line is calculated according to the length and resistivity of the charging pile gun head connection line.

[0011] Further, the DC charging pile active power detection device further includes a communication module, and the communication module is used to communicate with the detection device control device to obtain the impedance of the charging pile gun head connection line.

[0012] Further, the control module is a DSP chip. Correspondingly, the DC charging pile active power detection device further includes an analog-to-digital conversion circuit for converting the analog signals output by the voltage acquisition module and the current acquisition module into digital signals and inputting them into the DSP chip.

[0013] Further, the current acquisition module further includes a voltage amplification module and a shunt. The shunt is connected in series with the secondary side of the current transformer, and both sides of the shunt are connected to the input end of the voltage amplification module; the output end of the voltage amplification module is used to connect to the control module, and the voltage amplification module is used to convert the current signal after the current transformer ratio into a voltage form and amplify it to the range that the control module can process.

[0014] Further, the voltage acquisition module includes a voltage division module and a voltage tracking module. The voltage division module includes a first voltage division resistor and a second voltage division resistor connected in series. The series connection point of the two voltage division resistors is connected to the voltage tracking module, and the voltage division ratio of the two voltage division resistors is equal to the ratio of the current transformer.

[0015] Further, the communication module is a Bluetooth communication module.

[0016] The present invention is an improved invention, and its beneficial effects are as follows: The active power detection device for the DC charging pile of the present invention uses a DC current transformer in the current acquisition module to reduce the current of the DC output bus of the charging pile and then collect it, thereby reducing power consumption and heat generation, saving the volume and cost of the liquid cooling equipment, obtaining the impedance of the charging pile gun head connecting wire, calculating the output voltage of the charging pile gun head according to the impedance of the charging pile gun head connecting wire, and then calculating the active power of the charging pile according to the output voltage of the charging pile gun head and the current of the DC output bus of the charging pile, making the final detection result of the active power of the charging pile more accurate. Brief Description of the Drawings

[0017] Figure 1 It is a structural diagram of the detection device of the embodiment of the active power detection device for the DC charging pile of the present invention;

[0018] Figure 2 It is a structural diagram of the voltage amplification module of the embodiment of the active power detection device for the DC charging pile of the present invention;

[0019] Figure 3 It is a structural diagram of the voltage tracking module of the embodiment of the active power detection device for the DC charging pile of the present invention;

[0020] Figure 4 It is a flowchart of the use of the detection device of the embodiment of the active power detection device for the DC charging pile of the present invention;

[0021] Figure 5 It is a flowchart executed by the mobile phone in the embodiment of the active power detection device for the DC charging pile of the present invention.

[0022] The reference numerals are as follows: 1. Current sensor flexible wire; 2. Power supply module; 3. Current transformer; 4. First voltage dividing resistor; 5. Second voltage dividing resistor; 6. Positive soft wire of voltage sensor; 7. Voltage tracking module; 8. DSP chip; 9. Bluetooth communication module; 10. Negative soft wire of voltage sensor; 11. 3.3V power converter; 12. 1.8V power converter; 13. Power bank; 14. Reference voltage module; 15. Analog-to-digital conversion module; 16. Voltage amplification module; 17. Shunt; 18. Mobile phone. Detailed Description of the Invention

[0023] The active power energy detection device for a DC charging pile of the present invention uses a DC current transformer in the current acquisition module to reduce the current of the DC output bus of the charging pile and then collect it, thereby reducing power consumption and heat generation, saving the volume and cost of liquid cooling equipment, obtaining the impedance of the charging gun connection wire of the charging pile, calculating the output voltage of the charging gun of the charging pile according to the impedance of the charging gun connection wire of the charging pile, and then calculating the active power energy of the charging pile according to the output voltage of the charging gun of the charging pile and the current of the DC output bus of the charging pile, making the final detection result of the active power energy of the charging pile more accurate.

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0025] Embodiment of the active power energy detection device for a DC charging pile:

[0026] The active power energy detection device for a DC charging pile of the present invention has a structure as Figure 1 shown, including a power supply module, a current acquisition module, a voltage acquisition module, an analog-to-digital conversion module and a control module. The control module is connected to the output ends of the current acquisition module and the voltage acquisition module to obtain the current and voltage of the internal bus of the DC charging pile.

[0027] The current acquisition module is used to collect the current of the DC output bus inside the charging pile. In the detection device of the present invention, the current acquisition module includes a current transformer 3. The primary side of the current transformer 3 is used to collect the current of the internal bus of the DC charging pile, and convert the current inside the charging pile through a turns ratio and transformation into a smaller voltage signal, which is input into the analog-to-digital conversion module 15. The analog-to-digital conversion module 15 converts the voltage signal into a digital signal and then inputs it into the control module. The heat generation of the detection device is reduced, and there is no need to install a liquid cooling device, thereby reducing the volume of the detection device and reducing the cost.

[0028] In this embodiment, the current transformer 3 is a through-hole DC current transformer, which does not need to change the charging line of the charging pile and can be directly connected to the DC bus inside the DC charging pile in a through-hole and non-contact manner, having the effect of convenient and fast installation. At the same time, it can also electrically isolate the charging pile and the detection device of the present invention, thereby avoiding an increase in the energy consumption of the detection device. In this embodiment, the current acquisition module further includes: a shunt resistor 17 and a voltage amplification module 16. The through-hole DC current transformer 3 is connected to the DC bus inside the DC charging pile in a through-hole and non-contact manner, and the secondary side of the through-hole DC current transformer 3 is connected in series with the shunt resistor 17 of the current detection module. The resistance R0 value of the shunt resistor 17 is 2 Ω, and a voltage amplification module 16 is connected to both ends of the shunt resistor 17, which is used to adjust the voltage at both ends of the shunt resistor 17 to the range allowed by the analog-to-digital conversion module 15. In this embodiment, the amplification factor of the voltage amplification module 16 is 2 times. The structure of the voltage amplification module 16 is asFigure 2 As shown, it consists of AD620U2 and gain resistor Rg. The calculation formula for the amplification factor of programmable gain amplification is as follows:

[0029]

[0030] In the formula, G is the amplification factor of the voltage discharge module, and Rg is the resistance of the gain resistor Rg.

[0031] Assume that the DC bus output current of the charging pile is I dc , and the output voltage of the voltage amplification module 16 is I 2dc , then the relationship between the two is as follows:

[0032]

[0033] In this embodiment, the through-type DC current transformer uses CIT600A of Shenzhen Aviation Technology, with a maximum input current of 600A, and the turns ratio of the 600A:400mA current transformer is 1500:1.

[0034] In summary, for the current acquisition module of the present invention, when the DC current output by the charging pile is 600A, the secondary side current of the current transformer is 0.4A. After being converted by the shunt resistor 17 and the voltage amplification module 16, it is converted into a voltage signal of 0.4A * 2Ω * 2 = 1.6V. This voltage signal passes through the analog-to-digital conversion module 15, is converted from an analog signal to a digital signal, and then input into the control module. The control module calculates the DC current output by the charging pile based on the direction of this voltage signal.

[0035] The voltage acquisition module is used to acquire the DC output bus voltage inside the charging pile. In this embodiment, the voltage acquisition module includes: the first voltage-dividing resistor 4 with a resistance value of R1, the second voltage-dividing resistor 5 with a resistance value of R2, and the voltage tracking module 7. The voltage acquisition module is connected to the DC bus inside the DC charging pile through the alligator clips of the positive voltage sensor wire 6 and the negative voltage sensor wire 10. The voltage division ratio of the first voltage-dividing resistor 4 and the second voltage-dividing resistor 5 is equal to the turns ratio of the current transformer. The structure of the voltage tracking module 7 is as Figure 3 shown. The voltage tracking module 7 is mainly composed of the OPA2277 operational amplifier U7. In this embodiment, the voltage division ratio of the first voltage-dividing resistor 4 and the second voltage-dividing resistor 5 is also 1500:1, which is convenient for the controller to restore the voltage and current of the DC bus inside the charging pile according to the signals input by the voltage acquisition module and the current acquisition module. Specifically, in this embodiment, the resistance value R1 of the first voltage-dividing resistor 4 = 1499k, and the resistance value R2 of the second voltage-dividing resistor 5 = 1k. After voltage division, when the DC output bus voltage of the charging pile is 1500V, after transformation, the voltage input to the analog-to-digital conversion module 15 is 1V.

[0036] Assume that the DC output bus voltage of the charging pile is U dc , and the output voltage of the voltage tracking module 7 is U 2dc , then the relationship between the two is as follows:

[0037]

[0038] As another implementation, the turns ratio of the current transformer and the voltage division ratio of the voltage dividing resistors in the voltage acquisition module can also be different.

[0039] The analog-to-digital conversion module 15 is used to convert the analog signals input by the voltage acquisition module and the current acquisition module into digital signals and input them into the control module. In this embodiment, the analog-to-digital conversion module 15 uses an 8-channel, 24-bit, strictly synchronous sigma-delta AD converter ADS1278. The typical value of the integration error is: ±0.0003%, the maximum sampling rate is 128KSPS, and the allowable input voltage signal range is -2.5V to +2.5V. The signals output by the voltage acquisition module and the current acquisition module are both within this range. The reference voltage of this analog-to-digital conversion module 15 is 2.5V provided by the reference power supply module 14, the digital-to-analog power supply voltage is 3.3V provided by the 3.3V power converter, and the internal digital power supply voltage is 1.8V provided by the 1.8V power converter.

[0040] The control module restores the voltage and current of the DC output bus inside the charging pile according to the digital signals input by the analog-to-digital conversion module 15. In this embodiment, the control module is the DSP chip 8, specifically the BF609 chip of ADI Company. The chip is built-in with a large number of peripherals, including 1 SPI interface, 1 UART interface, 16 general-purpose IO ports, AMC interface (asynchronous storage interface), etc., 256MBYTE DRAM, and is used to calculate the error of the active electric energy of the charging pile according to the voltage and current of the DC output bus inside the charging pile.

[0041] The power supply module 2 is used to supply power to each module. In this embodiment, the power supply module 2 is powered by the power bank 13. The power supply module 2 is used to adjust the output voltage of the power bank 13 into 5V and 15V voltages to supply power to other modules. The power bank 13 uses a Xiaomi 10000mAh power bank. The power bank 13 is connected to the power supply module 2. The power supply module 2 uses a customized switching power supply with + / -15V and 5V outputs, which can provide 15V power for the voltage amplification module 16 and the voltage tracking module 7, provide 5V power for the power converter, with a current output of 2A and an input of 5V. The power bank 13 is charged by connecting to a charger.

[0042] In this embodiment, the active power detection device of the DC charging pile further includes a communication module, which is used to enable communication connection between the detection device and a control device (hereinafter referred to as the control device for short). The control device is used to send a charging start instruction and a charging stop instruction to the calibration device, so that the calibration device can calculate the active power charged by the charging pile to the electric vehicle during the process from charging start to charging stop.

[0043] In this embodiment, the communication module is a Bluetooth communication module 9, which uses the DX-BT23 5.0 Bluetooth module of Shenzhen Daxia Longque Technology Co., Ltd. The DX-BT23 module supports the BT5.0 BLE protocol at the same time and has the function of directly connecting to BLE Bluetooth-enabled devices, and can directly perform transparent transmission through the serial port (UART). As other implementation manners, it can also be other communication modules with communication functions, such as a wireless network communication module or a wired network communication module.

[0044] In this embodiment, for the detection device control device, the control device includes a communication module the same as that of the detection device to realize communication between the control device and the detection device. For example, if the communication module of the detection device is a Bluetooth communication module, the communication module of the control device should also be a Bluetooth communication module. In this embodiment, in order to reduce costs, the control device uses a mobile phone 18 that includes a Bluetooth communication module and installs a corresponding APP. As other implementation manners, it can also be a computer or other processors with execution and communication functions. The process executed by the mobile phone is as Figure 5 shown, and the process executed by the detection device is as Figure 4 shown.

[0045] In summary, for the active power detection device of the DC charging pile of the present invention, after the current transformer ratio is changed, the current of the actual detection device is reduced, which has the advantages of small power and small heat generation. And the primary side of the current transformer is connected to the DC bus inside the charging pile, and the liquid cooling system in the charging pile can be used for cooling, without the need to set up a liquid cooling system. At the same time, the electric vehicle is used as a high-power load, and there is no need to set up a high-power load, avoiding power waste. Since there is no need to set up a high-power load and a liquid cooling system, the active power detection device of the DC charging pile of the present invention has the advantages of small volume, small weight, low cost and convenient carrying.

[0046] Furthermore, the present invention uses an independent control device, such as a mobile phone, as an interactive interface for information input and output, reducing the cost and volume of the detection device.

[0047] Further, since the actual sampling points of the current acquisition module and the voltage acquisition module in the active power detection device of the DC charging pile of the present invention are both on the DC bus inside the DC charging pile, rather than at the charging gun head position of the charging pile, it is necessary to consider the impedance of the cable between the gun head and the DC bus inside the DC charging pile, correct the voltage detected by the voltage acquisition module, and use the corrected voltage to represent the voltage of the charging gun head of the charging pile, so as to make the verification result more accurate.

[0048] For the convenience of description, the following will be described in chronological order in combination with the process executed by the detection device and the mobile phone. The specific voltage correction, the calculation of the power error after voltage correction, and the usage method of the active power detection device of the DC charging pile of the present invention are as follows:

[0049] Step 1: Connect the detection device to the charging pile.

[0050] Open the door of the DC charging pile, connect to the DC voltage bus through the alligator clip of the voltage sensor flexible wire, and connect to the bus current through the current sensor flexible wire 1 and the DC split-core current transformer. The charging pile software shields the door opening protection or directly presses the access control switch to avoid triggering the door opening protection.

[0051] Step 2: Set the specifications and length of the charging gun head connection wire on the control device of the detection device. The control device of the detection device calculates the impedance of the charging gun head connection wire according to the length of the charging gun head connection wire and sends it to the detection device.

[0052] In this embodiment, the charging gun head connection wire is exemplified by a GB / T3956 cable with a length of 7m and a cross-sectional area of 25cm 2 . By looking up the conductor table, the resistance of 1km of this cable can be obtained as 0.75Ω, that is, the resistivity of this cable is 0.75Ω. Substituting these data into the calculation formula of the cable resistance value can obtain the impedance of the charging gun head connection wire. The calculation formula of the cable resistance value is as follows:

[0053] Rz = p * L / 1000 (4)

[0054] In the formula, Rz is the impedance of the charging gun head connection wire, p is the resistivity of the charging gun head connection wire, and L is the length of the charging gun head connection wire. The length of the charging gun head connection wire refers to the length of the connection wire between the charging gun head and the charging pile body.

[0055] Step 3: The control module of the inspection equipment determines whether it has received the impedance of the charging gun head connection wire sent by the control device of the detection device. If it has received it, it sends a confirmation message to the control device to enable the control device to enter the next step; otherwise, it does not send a confirmation message.

[0056] Step 4: After receiving the confirmation information sent by the detection device, the control device sends a charging start command to the detection device.

[0057] Step 5: After receiving the start command sent by the control device, the control module in the detection device calculates the corrected voltage according to the current information collected by the current acquisition module, the voltage information collected by the voltage acquisition module, and the impedance of the charging pile connection line sent by the control device, and calculates the cumulative charging electric energy of the charging pile according to the corrected voltage. The specific calculation method is as follows:

[0058] Vb = V - I * Rz (5)

[0059] P = Vb * I (6)

[0060]

[0061] In the formula, Vb is the voltage of the charging pile gun head connection line, V is the DC bus voltage inside the charging pile, I is the DC bus current inside the charging pile, Rz is the impedance of the charging pile connection line, P is the active power of the charging pile, Pi is the active power of the charging pile at time i, Eb is the active electric energy of the charging pile from time 0 to time n, TS is the sampling time, which is 0.1 us in this embodiment.

[0062] Step 6: At the end of charging, the control device sends a charging end instruction to the detection device.

[0063] Step 7: The detection device determines whether it has received the charging end instruction sent by the control device. If it has received it, it ends Step 4 and sends the active electric energy value Eb of this charging to the control device. Otherwise, it continues to execute Step 5 and waits for the charging end instruction.

[0064] Step 8: The control device calculates the measurement error of the active electric energy of the charging pile according to the received active electric energy value of this charging and the active electric energy value measured by the charging pile. The specific calculation formula is as follows:

[0065]

[0066] In the formula, e is the error of the active electric energy of the charging pile, and Ex is the active electric energy measured by the charging pile.

[0067] In summary, the present invention also obtains the impedance of the charging pile gun head connection line, combines the voltage of the DC output bus of the charging pile, calculates the output voltage of the charging pile gun head, and then calculates the active electric energy during the charging process of the charging pile according to the output voltage of the charging pile gun head, avoiding errors and making the final detection result more accurate.

Claims

1. A DC charging pile active power detection device, comprising a control module, a current acquisition module and a voltage acquisition module for acquiring the voltage of the DC output bus of the charging pile, wherein the current acquisition module comprises a current transformer, and the current acquisition module is used to acquire the current of the DC output bus of the charging pile through the current transformer, characterized in that; The control module is used to obtain the impedance of the charging pile gun head connecting line, and obtain the charging pile gun head output voltage according to the impedance of the charging pile gun head connecting line and the voltage of the charging pile DC output bus, and calculate the active electric energy of the charging pile during the charging process according to the charging pile gun head voltage and the current of the charging pile DC output bus.

2. The DC charging pile active power detection device according to claim 1, characterized in that: The method for obtaining the output voltage of the charging pile gun head according to the impedance of the charging pile gun head connection line and the voltage of the charging pile DC output bus is: Vb=VI*Rz Where Vb is the output voltage of the charging pile gun head, V is the DC output bus voltage of the charging pile, I is the DC output bus current of the charging pile, and Rz is the impedance of the charging pile gun head connecting line.

3. The DC charging pile active power detection device according to claim 1, characterized in that: The impedance of the charging pile gun head connection line is calculated based on the length and resistivity of the charging pile gun head connection line.

4. The split type DC charging pile active power detection device according to claim 1, characterized in that: The DC charging pile active power detection device also includes a communication module, which is used to communicate with the detection device control device to obtain the impedance of the charging pile gun head connection line.

5. The DC charging pile active power detection device according to claim 1, characterized in that: The control module is a DSP chip. Correspondingly, the DC charging pile active power detection device also includes an analog-to-digital conversion circuit for converting analog signals output by the voltage acquisition module and the current acquisition module into digital signals and inputting them into the DSP chip.

6. The DC charging pile active power detection device according to any one of claims 1 to 5, characterized in that: The current acquisition module also includes a voltage amplifier module and a shunt. The shunt is connected in series with the secondary side of the current transformer, and both sides of the shunt are connected to the input end of the voltage amplifier module. The output end of the voltage amplifier module is used to connect to the control module. The voltage amplifier module is used to convert the current signal after the current transformer is transformed into a voltage form and amplify it to a range that the control module can handle.

7. The DC charging pile active power detection device according to any one of claims 1 to 5, characterized in that: The voltage acquisition module includes a voltage dividing module and a voltage tracking module. The voltage dividing module includes a first voltage dividing resistor and a second voltage dividing resistor connected in series. The series connection point of the two voltage dividing resistors is connected to the voltage tracking module. The voltage dividing ratio of the two voltage dividing resistors is equal to the transformation ratio of the current transformer.

8. The DC charging pile active power detection device according to claim 4, characterized in that: The communication module is a Bluetooth communication module.

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