A method to reduce the deviation of CC resistance acquisition value

Abstract

This invention discloses a method for reducing the deviation of the CC resistance acquisition value, comprising: determining whether both the main positive relay and the main negative relay are closed; if so, then U c +U0 is used to calculate the voltage of the CC resistor. If not, then U... c The voltage used to calculate the CC resistance acquisition value is used. Additionally, the grounding method is changed so that the BMS grounding wire L3 and the AC socket's PE grounding wire L4 are grounded separately. Using this invention reduces costs and simplifies control.

Description

Technical Field

[0001] This invention belongs to the field of vehicle charging, and specifically relates to a method for reducing the deviation of CC resistance acquisition values. Background Technology

[0002] During the charging process of an electric vehicle, the BMS (Battery Management System) calculates the CC resistance value based on the voltage obtained from the CC sampling port, then identifies the type of AC gun (i.e., AC gun, including charging gun and discharging gun) based on the CC resistance value (different types of AC guns have different corresponding CC resistance values, see Table 1), and finally executes the corresponding charging and discharging strategy according to the type of AC gun.

[0003] Table 1 (Corresponding data of AC gun types and CC resistance values ​​specified in the standard)

[0004]

[0005] To accurately identify the type of AC charging gun and achieve the corresponding charging and discharging functions, it is necessary to ensure the accuracy of the calculated CC resistance value and minimize the deviation of the CC resistance value. In practical applications, ground offset between the BMS reference ground and the CC acquisition reference ground, as well as high voltage on the vehicle, can affect the accuracy of the CC resistance value, leading to significant deviations. A detailed analysis follows:

[0006] (1) As Figure 1 As shown, one end of the fixed resistor R2 (3.3KΩ) is connected to the 5V power supply, and the other end of the fixed resistor R2 is connected to one end of the current-limiting resistor R1 at point D. The other end of the current-limiting resistor R1 is connected to the CC sampling port of the MCU. After the gun is inserted, the CC resistor R4 of the AC gun is connected to point D. The CC resistor R4, the fixed resistor R2, and the 5V power supply form a loop. The voltage across the CC resistor R4 is limited by the current-limiting resistor R1 and then input to the CC sampling port. The MCU's sampling reference point for the CC resistor R4 is GND (i.e., BMS reference ground), while the BMS reference ground (i.e., ... Figure 1 GND) and CC acquisition reference location (i.e. Figure 1 The chassis ground (in the vehicle) needs to be grounded before normal data acquisition can be performed. After the vehicle is powered by high voltage, the BMS reference ground and the CC acquisition reference ground are on the same line. Since there is a resistor R3 between the BMS reference ground and the CC acquisition reference ground, when the main positive and main negative relays are enabled, the current on the BMS reference ground increases. The current flows through R3, which will generate a voltage drop between the BMS reference ground and the CC acquisition reference ground, causing a ground bias between the BMS reference ground and the CC acquisition reference ground, resulting in a lower CC resistance acquisition value.

[0007] (2) Figure 2As shown, because the BMS ground wire L3, the wiper controller ground wire L1, and the water pump controller ground wire L2 are connected together in the fuse box before being connected to the BMS grounding point in the front engine compartment, when the air conditioning and wipers are turned on, the low-voltage operating current of the water pump controller and wiper controller will form a loop, causing the BMS reference ground (i.e., Figure 2 The B-point of the BMS and the CC acquisition reference location (i.e., Figure 2 The grounding at point A of the AC socket causes a deviation in the measured value of the CC resistor.

[0008] (3) Because the OBC (on-board charger) integrates a DC-DC converter, the CC collects reference ground (i.e., Figure 2 Point A of the AC socket will be connected to the vehicle ground (i.e., connected to the DC-DC grounding point on the vehicle body) after passing through the OBC and DC-DC common line. Since the BMS reference ground and CC acquisition reference ground need to be grounded together before normal acquisition can be performed, and the CC acquisition reference ground needs to pass through the OBC and DC-DC before being grounded with the BMS reference ground; when the DC-DC is working (maximum current reaches 70A~100A), an equivalent potential to the vehicle ground will be formed at the common grounding point. This potential is equal to the product of the low voltage current of the DC-DC and the grounding wire resistance, which will cause the BMS reference ground and CC acquisition reference ground to be grounded, resulting in a deviation in the CC resistance acquisition value.

[0009] Therefore, how to reduce the deviation of the CC resistance acquisition value in order to accurately identify the type of AC gun is an urgent problem to be solved.

[0010] CN218824485U discloses a charging CC resistance detection device, which reduces the influence of ground bias on the CC resistance acquisition value by changing the hardware detection circuit of the charging CC resistance. However, it is costly and complex to control. Summary of the Invention

[0011] The purpose of this invention is to provide a method for reducing the deviation of CC resistor acquisition values, thereby reducing costs and simplifying control.

[0012] The method for reducing the deviation of the CC resistance acquisition value according to the present invention includes: determining whether both the main positive relay and the main negative relay are closed; if so (indicating high voltage on the entire vehicle), then U... c +U0 is the voltage used to calculate the CC resistance value (i.e., U... c +U0 is the voltage corresponding to the CC resistor value. If not (indicating the vehicle is not connected to high voltage), then U... c This is the voltage used to calculate the CC resistance acquisition value. Where, U c U0 represents the voltage value obtained from the CC sampling port, and U0 represents the preset compensation voltage, where U0 > 0.

[0013] Preferably, the preset compensation voltage U0 ranges from 17mV to 22mV.

[0014] Preferably, the preset compensation voltage U0 is 20mV.

[0015] Preferably, the preset compensation voltage U0 is obtained by calibration using the following method:

[0016] Step 1: Select n AC guns with known CC resistance values.

[0017] Step 2: Insert the i-th AC gun into the vehicle charging port. With the main positive relay and main negative relay not closed, obtain the sampling voltage U of the lower high voltage CC resistor. i_1 Then close the main positive relay and the main negative relay to obtain the sampling voltage U of the high voltage CC resistor at this time. i_2 ; where i takes any integer from 1 to n.

[0018] Step 3: Using the formula: △U i =U i_1 -U i_2 The CC resistance sampling voltage deviation ΔU of the i-th AC gun is calculated. i .

[0019] Step 4: Average the voltage deviation of the CC resistor sampling at the n AC guns to obtain the average value ΔU of the CC resistor sampling voltage deviation. avg .

[0020] Step 5: Average the voltage deviation ΔU from the CC resistor sampling. avg The preset compensation voltage U0 is used.

[0021] Preferably, to avoid the low-voltage operating current of the water pump controller and wiper controller forming a loop when the air conditioner and wipers are turned on, thus causing ground offset between the BMS reference ground and the CC acquisition reference ground, this invention provides three methods to solve this problem, specifically:

[0022] The first method involves connecting the grounding wire L1 of the wiper controller and the grounding wire L2 of the water pump controller to the PEU grounding point in the front engine compartment; and connecting the grounding wire L3 of the BMS to the BMS grounding point in the front engine compartment separately. With the BMS grounding wire L3 connected separately to the BMS grounding point in the front engine compartment, the low-voltage operating current of the water pump controller and wiper controller will not cause grounding bias in the BMS reference ground and the CC acquisition reference ground, thereby reducing the deviation in the CC resistance acquisition value.

[0023] The second method involves connecting the grounding wire L1 of the wiper controller and the grounding wire L2 of the water pump controller to the BMS grounding point in the front engine compartment; and connecting the BMS grounding wire L3 separately to the OBC grounding point at the rear of the vehicle. With the BMS grounding wire L3 connected separately to the OBC grounding point at the rear of the vehicle, the low-voltage operating current of the water pump controller and wiper controller will not cause grounding bias in the BMS reference ground and the CC acquisition reference ground, thus not affecting the CC resistance acquisition value and reducing the deviation of the CC resistance acquisition value.

[0024] The third method involves connecting the grounding wire L1 of the wiper controller and the grounding wire L2 of the water pump controller to the BMS grounding point in the front engine compartment; then removing the BMS grounding wire, allowing the BMS to be grounded through its own casing (i.e., disconnecting the BMS grounding wire from the BMS grounding point). With the BMS grounded through its own casing, the low-voltage operating current of the water pump controller and wiper controller will not cause grounding bias in the BMS reference ground and the CC acquisition reference ground, thus not affecting the CC resistance acquisition value and reducing the deviation in the CC resistance acquisition value.

[0025] Preferably, the BMS grounding point is located at the left end of the longitudinal beam in the forward engine compartment.

[0026] Preferably, to avoid the formation of an equivalent potential to the vehicle body ground at the common grounding point when the DC-DC converter is operating, which could cause ground bias in the BMS reference ground and CC acquisition reference ground, this invention connects the PE grounding wire L4 of the AC socket separately to the rear right side panel of the vehicle body, and connects the grounding wires of the OBC and DC-DC converters to the DC-DC grounding point on the vehicle body. With the AC socket and DC-DC converter grounded separately, the low-voltage operating current of the DC-DC converter will not cause ground bias in the BMS reference ground and CC acquisition reference ground, and will not affect the CC resistance acquisition value, thereby reducing the deviation of the CC resistance acquisition value.

[0027] Preferably, the DC-DC grounding point is located on the left side panel of the rear of the vehicle body.

[0028] Because applying high voltage to the entire vehicle can cause the CC resistance measurement value to be too low, a preset compensation voltage U0 is used to adjust the voltage value U obtained from the CC sampling port. c Compensation is performed, and the compensated voltage U c +U0 is used as the voltage for calculating the CC resistance acquisition value, thereby reducing the influence of the high voltage on the CC resistance acquisition value of the whole vehicle, reducing the deviation of the CC resistance acquisition value, and without changing the CC resistance detection circuit, reducing costs. Only a compensation voltage needs to be added to the voltage value obtained from the CC sampling port, making control simpler. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the circuit for acquiring the CC resistor.

[0030] Figure 2 This is a grounding diagram of the various electrified components in the existing vehicle architecture.

[0031] Figure 3 This is a flowchart of voltage compensation in Example 1.

[0032] Figure 4 The flowchart shows the calibration method for the preset compensation voltage U0.

[0033] Figure 5 This is a grounding diagram of each electrified component in the vehicle architecture of Example 1.

[0034] Figure 6 This is a grounding diagram of each electrified component in the vehicle architecture of Example 2.

[0035] Figure 7 This is a grounding diagram of each electrified component in the vehicle architecture of Example 3. Detailed Implementation

[0036] Example 1: As Figure 3 , Figure 4 , Figure 5 As shown, the method for reducing the deviation of the CC resistor acquisition value in this embodiment has been optimized from both hardware grounding method and software aspects.

[0037] Among them, the optimization of hardware grounding method (see...) Figure 5 The following steps are taken: Connect the wiper controller's ground wire L1 and the water pump controller's ground wire L2 to the PEU grounding point in the front engine compartment; connect the BMS ground wire L3 separately to the BMS grounding point in the front engine compartment; the PEU grounding point is located in the middle of the front engine compartment longitudinal beam, and the BMS grounding point is located at the left end of the front engine compartment longitudinal beam. Connect the AC socket's PE ground wire L4 separately to the rear right side panel of the vehicle body; connect the OBC ground wire and the DC-DC ground wire to the DC-DC grounding point on the vehicle body; the DC-DC grounding point is located on the rear left side panel of the vehicle body. With the BMS ground wire L3 separately connected to the BMS grounding point in the front engine compartment, the low-voltage operating current of the water pump controller and wiper controller will not cause ground bias in the BMS reference ground and CC acquisition reference ground. After the AC socket and DC-DC are grounded separately, the low-voltage operating current of the DC-DC will not cause ground bias in the BMS reference ground and CC acquisition reference ground, and will not affect the CC resistance acquisition value, thus reducing the deviation of the CC resistance acquisition value.

[0038] The software optimization involves the MCU performing the following steps (see...). Figure 3 ):

[0039] Step 1: Determine if both the main positive relay and the main negative relay are closed. If yes (indicating high voltage is applied to the vehicle), proceed to Step 2; otherwise (indicating high voltage is not applied to the vehicle), proceed to Step 3.

[0040] Step 2, U c +U0 is the voltage used to calculate the CC resistance value (i.e., U... c +U0 is the voltage corresponding to the CC resistor value, and then the process ends. Where U... c U0 represents the voltage value obtained from the CC sampling port, and U0 represents the preset compensation voltage. U0 > 0. In this embodiment, U0 = 20mV.

[0041] Step 3, put U c The voltage used to calculate the CC resistance value is then used to end the calculation.

[0042] The preset compensation voltage U0 is obtained through the following method (see...). Figure 4 The calibration yielded:

[0043] Step 1: Select n AC guns with known CC resistance values. Referring to Tables 1 and 2, this embodiment selects 4 (i.e., n=4) AC guns with known CC resistance values. The CC resistance (standard) values ​​of the 4 AC guns are: 50Ω (corresponding to a 16A discharge gun), 220Ω (corresponding to a 32A charging gun), 680Ω (corresponding to a 16A charging gun), and 2000Ω (corresponding to a 16A discharge gun).

[0044] Step 2: Insert the i-th AC gun into the vehicle charging port. With the main positive relay and main negative relay not closed, obtain the sampling voltage U of the lower high voltage CC resistor. i_1 Then close the main positive relay and the main negative relay to obtain the sampling voltage U of the high voltage CC resistor at this time. i_2 Where i takes all integers from 1 to n. See Table 2; in this embodiment, U... 1_1 =0.076096688V, U 1_2 =0.055439017V, U 2_1 =0.313831298V, U 2_2 =0.296465222V, U 3_1 =0.849271357V, U 3_2 =0.82706574V, U 4_1 =1.886792453V, U 4_2 =1.866691986V.

[0045] Step 3: Using the formula: ΔU i =U i_1 -U i_2The CC resistance sampling voltage deviation ΔU of the i-th AC gun is calculated. i Referring to Table 2, in this embodiment, ΔU1 = 0.02065767V, ΔU2 = 0.017366076V, ΔU3 = 0.022205617V, and ΔU4 = 0.020100467V.

[0046] Step 4: Average the voltage deviation of the CC resistor sampling at the n AC guns to obtain the average value ΔU of the CC resistor sampling voltage deviation. avg Referring to Table 2, in this embodiment, ΔU avg =0.02008244V≈20mV.

[0047] Step 5: Average the voltage deviation ΔU from the CC resistor sampling. avg The preset compensation voltage is U0 (i.e., U0 = 20mV).

[0048] Table 2 (Relevant data on CC resistance under high voltage conditions obtained from actual vehicle testing)

[0049] CC resistance (Ω) Under high voltage condition (Ω) High voltage state (Ω) High voltage sampling voltage (V) High voltage sampling voltage (V) Voltage difference (V) 50 51 37 0.076096688 0.055439017 0.02065767 220 221 208 0.313831298 0.296465222 0.017366076 680 680 655 0.849271357 0.82706574 0.022205617 2000 2000 1966 1.886792453 1.866691986 0.020100467

[0050] After optimization in both hardware grounding and software, real-vehicle testing showed that even when the air conditioning, windshield wipers, and / or DC-DC converter were on, and a 32A charging gun (see Table 1, its standard CC resistance value is 220Ω) was used for charging, the detected CC resistance value remained at 220±1Ω, demonstrating a significant optimization effect.

[0051] Example 2: As Figure 6 As shown, the method for reducing the deviation of the CC resistor acquisition value in this embodiment is optimized from both hardware grounding and software aspects. The software optimization method is the same as in Embodiment 1. The optimization of the hardware grounding method (see...) Figure 6 The following steps are taken: Connect the grounding wire L1 of the wiper controller and the grounding wire L2 of the water pump controller to the BMS grounding point in the front engine compartment; connect the BMS grounding wire L3 separately to the OBC grounding point at the rear of the vehicle; the BMS grounding point is located at the left end of the longitudinal beam in the front engine compartment. Connect the PE grounding wire L4 of the AC socket separately to the right side panel of the rear of the vehicle; connect the OBC grounding wire and the DC-DC grounding wire to the DC-DC grounding point on the vehicle body; the DC-DC grounding point is located on the left side panel of the rear of the vehicle. With the BMS grounding wire L3 separately connected to the OBC grounding point at the rear of the vehicle, the low-voltage operating current of the water pump controller and wiper controller will not cause ground bias in the BMS reference ground and CC acquisition reference ground. After the AC socket and DC-DC are grounded separately, the low-voltage operating current of the DC-DC will not cause ground bias in the BMS reference ground and CC acquisition reference ground, and will not affect the CC resistance acquisition value, thereby reducing the deviation of the CC resistance acquisition value.

[0052] Example 3: As Figure 7 As shown, the method for reducing the deviation of the CC resistor acquisition value in this embodiment is optimized from both hardware grounding and software aspects. The software optimization method is the same as in Embodiment 1. The optimization of the hardware grounding method (see...) Figure 7 The steps are as follows: Connect the grounding wire L1 of the wiper controller and the grounding wire L2 of the water pump controller to the BMS grounding point in the front engine compartment; disconnect the BMS grounding wire, and ground the BMS through its own housing (i.e., disconnect the BMS grounding wire from the BMS grounding point); the BMS grounding point is located at the left end of the longitudinal beam in the front engine compartment. Connect the PE grounding wire L4 of the AC socket separately to the right rear panel of the vehicle body; connect the grounding wires of the OBC and DC-DC to the DC-DC grounding point on the vehicle body; the DC-DC grounding point is located on the left rear panel of the vehicle body. With the BMS grounded through its own housing, the low-voltage operating current of the water pump controller and wiper controller will not cause ground bias in the BMS reference ground and CC acquisition reference ground. After the AC socket and DC-DC are grounded separately, the low-voltage operating current of the DC-DC will not cause ground bias in the BMS reference ground and CC acquisition reference ground, and will not affect the CC resistance acquisition value, thus reducing the deviation of the CC resistance acquisition value.

Claims

1. A method of reducing the deviation of CC resistance collection values, characterized in that, The application relates to a method for reducing the deviation of CC resistance acquisition value. determines whether the main positive relay and the main negative relay are both closed, if yes, U c +U0 is taken as the voltage for calculating the CC resistance collection value, if no, U c is taken as the voltage for calculating the CC resistance collection value; wherein, U c represents the voltage value obtained from the CC sampling port, U0 represents a preset compensation voltage, U0>0; The preset compensation voltage U0 is calibrated by the following method: First, select n AC guns with known CC resistance values; Second step, the i-th AC gun is inserted into the vehicle charging port, and the main positive relay and the main negative relay are not closed, and the lower high-voltage CC resistance sampling voltage U is obtained i_1 Then the main positive relay and the main negative relay are closed, and the upper high-voltage CC resistance sampling voltage U is obtained at this time i_2 ; wherein i takes all integers from 1 to n in turn; Third step, using the formula: △U i =U i_1 -U i_2 , the calculation of the i-th AC gun CC resistance sampling voltage deviation △U i ; Fourth step, average the CC resistance sampling voltage deviation of n AC guns, get the CC resistance sampling voltage deviation average value ΔU avg ; Fifth step, the CC resistance sampling voltage deviation average value ΔU avg As the preset compensation voltage U0.

2. The method of claim 1, wherein: The preset compensation voltage U0 ranges from 17 mV to 22 mV.

3. The method of claim 1, wherein: The preset compensation voltage U0 is 20 mV.

4. The method for reducing the deviation of CC resistance acquisition value according to claim 1, wherein: After the ground wire L1 of the wiper controller and the ground wire L2 of the water pump controller are collinear, the ground wire L1 is connected to the PEU grounding point in the front cabin; The ground wire L3 of the BMS is separately connected to the BMS grounding point in the front cabin.

5. The method for reducing the deviation of CC resistance acquisition value according to claim 1, wherein: After the ground wire L1 of the wiper controller and the ground wire L2 of the water pump controller are collinear, the ground wire L1 is connected to the BMS grounding point in the front cabin; The ground wire L3 of the BMS is separately connected to the OBC grounding point at the tail of the vehicle.

6. The method for reducing the deviation of CC resistance acquisition value according to claim 1, wherein: After the ground wire L1 of the wiper controller and the ground wire L2 of the water pump controller are collinear, the ground wire L1 is connected to the BMS grounding point in the front cabin; The ground wire of the BMS is cancelled, and the BMS is grounded through the shell.

7. The method of reducing the deviation of the collected value of the CC resistance according to any one of claims 4 to 6, characterized in that: The BMS grounding point is located at the left end of the front cabin longitudinal beam.

8. The method for reducing the deviation of CC resistance acquisition value according to any one of claims 4 to 6, wherein: The PE ground wire L4 of the AC socket is separately connected to the right side surrounding sheet metal at the rear of the vehicle body; The ground wire of the OBC and the ground wire of the DCDC are connected to the DCDC grounding point on the vehicle body.

9. The method of claim 8, wherein: The DCDC grounding point is located on the left side surrounding sheet metal at the rear of the vehicle body.

Images