An insulation detection system and detection method for a ship power battery pack

Abstract

The present invention discloses an insulation detection system and detection method for a ship power battery pack. The device comprises a DC system, a detection circuit and a sampling circuit, an AD conversion circuit and a single-chip microcomputer MCU connected in sequence. The method performs real-time insulation detection on the ship power battery pack, records data and judges the fault level at the same time, and explores the factors affecting the insulation detection resistance measurement, namely the bridge arm resistance. R , bridge arm resistance R 1 , voltage and actual positive and negative insulation resistance, and obtain an approximate relationship by summarizing the value rules of the test group, and design a set of optimal bridge resistance matching design schemes based on the approximate relationship. This device has low cost and simple circuit structure. This method is easy to operate, short in measurement time, and easy to realize digital measurement.

Description

Technical Field

[0001] The present invention relates to ship power battery technology, in particular to an insulation detection system and a detection method for a ship power battery pack. Background Art

[0002] As energy and environmental issues become increasingly prominent, electric ships are becoming more and more popular. To ensure the safety of drivers and passengers, safe and reliable operation of electric ships is crucial. The DC voltage of the battery pack of the electric ship energy storage system is high when working, far exceeding the safe voltage. In addition, the working environment is relatively harsh and the battery insulation performance changes dramatically. If it is not detected and handled in time, it may cause safety accidents and casualties.

[0003] At present, the commonly used insulation detection methods are signal high voltage injection method and bridge method. The high voltage injection method is that when the battery is disconnected from the high voltage system, high voltage is injected externally to monitor the leakage current, and then the insulation resistance is calculated. This monitoring method can realize the insulation resistance monitoring when the battery is not working, but the design circuit is complex and the cost is high; the balanced bridge method can detect the insulation resistance in a simple circuit, but when the positive and negative insulation resistance values ​​drop at the same time, it is easy to cause false monitoring and low reliability. Based on the above research, the traditional measurement method has problems such as low accuracy, long time, and poor reliability. The Chinese patent publication number CN201410604060.4, the invention name of which is "A charger insulation detection device and insulation detection method", discloses a charger insulation detection device and insulation detection method. This method uses the balanced branch-unbalanced branch method to detect the insulation resistance. By switching the two arm resistances of the unbalanced bridge, the bridge does not have a fixed balance point, and the equivalent insulation resistance of the positive and negative DC bus to the ground can be calculated. In this method, there are many branch circuits of the insulation detection circuit, the design circuit is complex, the cost is high, and the corresponding test resistors on each branch do not consider the insulation resistance test error.

[0004] In recent years, insulation alarms have occurred frequently in electric ships. The main reason is insulation failure of the power battery. Therefore, real-time and accurate detection of the insulation status of the power battery pack is of great significance to the safety of electric ships. Summary of the invention

[0005] The purpose of the present invention is to provide an insulation detection system and detection method for ship power battery packs in view of the shortcomings of the prior art. The device has low cost and simple circuit structure, and the method is easy to operate, short in measurement time, and easy to realize digital measurement.

[0006] The technical solution for achieving the purpose of the present invention is:

[0007] An insulation detection system for a ship power battery pack includes a DC system, a detection circuit and a sampling circuit, an AD conversion circuit and a single-chip microcomputer MCU connected in sequence, wherein:

[0008] The DC system is provided with a power battery pack V B , positive electrode insulation resistance Rp and negative electrode insulation resistance Rn, wherein one end of the positive electrode insulation resistance Rp is connected to the power battery pack V B The positive electrode is connected to the ground, and the other end is grounded. One end of the negative insulation resistor Rn is connected to the power battery pack V B The negative pole of the resistor is connected and the other end is grounded;

[0009] The detection circuit in the detection circuit and the sampling circuit is provided with two first bridge arm resistors R, a second bridge arm resistor R1, a third bridge arm resistor R3, and a relay switch S, wherein one end of the first bridge arm resistor R is connected to the positive electrode insulation resistor Rp and the other end is grounded, one end of the second bridge arm resistor R1 is connected to the negative electrode insulation resistor Rn and the other end is grounded, one end of the third bridge arm resistor R3 is connected to the switch S and the other end is grounded, and the other end of the switch S is connected to the power battery pack V B The negative connection of

[0010] The sampling circuit in the detection circuit and the sampling circuit is provided with a diode VD, a capacitor C, and a resistor R2 connected in parallel, wherein one end of the resistor R2 is connected to the third bridge arm resistor R3, and the other end is connected to the parallel circuit of the diode VD and the capacitor C;

[0011] In the detection circuit and sampling circuit, the positive electrode is the power battery pack V B The positive busbar is the voltage to ground, and the negative busbar is the power battery pack V B Negative bus voltage to ground, when the system is powered on, the power battery pack V B The detection circuit is composed of the internal resistance, and the insulation resistance is calculated by collecting the voltage values ​​of each part. The sampling points corresponding to the positive electrode-to-ground voltage and the negative electrode-to-ground voltage are located at the connection of the positive electrode insulation resistance Rp and the negative electrode insulation resistance Rn. The sampling circuit collects the voltage on the corresponding branch as the sampling voltage. The process is: close the switch S on the branch and sample the power battery pack V on the corresponding branch. B Positive pole to ground voltage, power battery pack V B Negative pole to ground voltage; disconnect the switch S on the branch and sample the power battery pack V on the corresponding branch B Positive pole to ground voltage, power battery pack V B Negative pole voltage to ground;

[0012] The AD conversion circuit and the single-chip microcomputer MCU are composed of an AD chip or a battery sampling analog front-end chip with AD sampling and a single-chip microcomputer.

[0013] The first bridge arm resistor R, the second bridge arm resistor R1 and the third bridge arm resistor R3 are all precision resistors with a power of 2W and an accuracy of 1%, wherein the first bridge arm resistor R and the third bridge arm resistor R3 have the same resistance value.

[0014] The relay switch S is a HFD4 / 5-S relay, and the closing and opening of the relay is controlled by a single-chip microcomputer MCU.

[0015] The diode VD is a LESD3Z5.0CMT1G electrostatic protection diode.

[0016] The capacitance of the capacitor C is 1 nf.

[0017] When the switch S is open, the voltage between the ship chassis and the positive electrode of the power battery pack is V1, and the voltage between the ship chassis and the negative electrode of the power battery pack is V2. When the switch S is closed, the voltage between the ship chassis and the positive electrode of the power battery is V3, and the voltage between the ship chassis and the negative electrode of the power battery is V4. The sum of the voltages V1 and V2 is the total voltage V across the high-voltage system. B .

[0018] The positive electrode insulation resistance Rp and the negative electrode insulation resistance Rn are calculated based on Hoff's voltage law and the switch S as shown in formula (1) and formula (2):

[0019]

[0020]

[0021] According to the general requirements for ship insulation, the insulation resistance of electric ships must reach 500Ω / V or above, which means that the insulation performance is good. This technical solution sets an alarm threshold. When the positive and negative insulation resistance is 200Ω / V~500Ω / V, the first-level alarm is activated. When the positive and negative insulation resistance is between 100Ω / V and 200Ω / V, the second-level alarm is activated. When the positive and negative insulation resistance is lower than 100Ω / V, the third-level alarm is activated and the relay S is disconnected.

[0022] A detection method for an insulation detection system for a ship power battery pack, comprising the above-mentioned insulation detection system for a ship power battery pack, the method comprising the following steps:

[0023] S1: According to the general requirements of ships, the insulation requirements of the power resistor group of electric ships must reach 500Ω / V or above to consider that the insulation performance of the ship is good, and the error of ship insulation detection must also be <5% to meet the actual application. First, the voltage value of the power battery group of the electric ship is actually measured. According to the voltage value V of the power battery group and the insulation resistance value that should meet the condition of >500Ω / V, the values ​​of various parameters in the single-arm unbalanced bridge can be preliminarily set. The parameters include: actual positive insulation resistance Rp, negative insulation resistance Rn and bridge arm resistance R, R1, that is, assuming that the insulation requirement is X and the voltage is Y, the values ​​of insulation resistance Rp and Rn = XY, and the values ​​of bridge arm resistance R, R1 = 2XY;

[0024] S2: Set the values ​​of the parameters initially set: bridge arm resistance R 0 , bridge arm resistance R1 0 , Positive insulation resistance Rp 0 , Negative insulation resistance Rn 0 And the voltage value of the power battery pack V 0 , substituting into the positive and negative insulation resistance formula (1) and formula (2), the result is calculated as follows:

[0025]

[0026]

[0027] Measured value Actual Rp 0 and Actual Rn 0 Insulation resistance Rp with reference 0 , Rn 0 By comparison, we can get the error formula E x =(Actual Rp x -Rp x ) / Rp x *100%, E x is the measurement error, and the variance formula is is the average of the measurement errors, S 2 Variance, determine whether the absolute value of the error is less than 5% and whether the variance is less than 0.3. If the relative error is <5% and the variance is <0.3, the values ​​of the parameters initially set meet the requirements. If the relative error is >5% or the variance is >0.3, the values ​​of the parameters initially set do not meet the requirements and need to be reset until they meet the actual application requirements.

[0028] S3: According to the insulation resistance calculation formula (1) and formula (2), there are four factors that affect the insulation resistance measurement. When considering their influence, the order is bridge arm resistance R, bridge arm resistance R1, Rp, Rn, power battery pack voltage V. According to the values ​​of the parameters initially set, R 0 、R1 0 , Rp 0 and Rn 0 、V 0 ,Four groups of comparative experiments were set up to explore the influence of single factors on insulation resistance measurement;

[0029] S4: The first group of experiments: Based on the initial setting of the bridge arm resistance R 0 , set a set of experimental variables R x , respectively: R 1 , R 2 , R 3 , R 4 , R 5 , R6 ...R x , where R x =yR 0 According to the range of error and variance, the value range of y is determined to be 1 / 5 to 5 times, and different R x Under V1, V2, V3, V4, get x groups of experimental results, substitute them into the calculation formula (1) and formula (2) of the positive and negative insulation resistance respectively, and get the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 , Rp 6 ,...Rp x and Actual Rn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ...Rn x , substitute the experimental results into the measurement error formula: E x =(Actual Rn x -Rn x ) / Rn x *100%, get different R x The insulation measurement error results under different bridge arm resistance R x The relative error diagram of the insulation resistance value measurement. The horizontal axis in the relative error diagram is the different bridge arm resistance R x , the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different R x The variance under different bridge arm resistance R x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is the different bridge arm resistance R x , the ordinate is the corresponding S x 2 , the intersection of the horizontal and vertical coordinates, that is, the variance of the insulation resistance value measurement;

[0030] S5: The second group of experiments: Based on the initial setting of the bridge arm resistance R1 0 , set a set of experimental variables R1 x , respectively: R1 1 、R1 2 、R1 3 、R1 4 、R15 、R1 6 ...R x , where R1 x =y1R1 0 According to the range of error and variance, the value range of y1 is determined to be 1 / 5 to 5 times, and different R1 values ​​in the circuit are measured in turn. x The experimental results of x groups are obtained by substituting V1, V2, V3, and V4 under the condition of positive electrode insulation resistance into the calculation formula (1) and formula (2) respectively to obtain the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 , Rp 6 ..Rp x and Actual Rn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ..Rn x , substitute the experimental results into the measurement error formula: E x =(ActualRn x -Rn x ) / Rn x *100%, get different R1 x The insulation measurement error results under different bridge arm resistance R1 x The relative error diagram of the insulation resistance value measurement. The horizontal axis in the relative error diagram is the different bridge arm resistance R1 x , the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different R1 x Under the variance, make different bridge arm resistance R1 x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is the different bridge arm resistance R1 x , the ordinate is the corresponding S x 2 , the intersection of the horizontal and vertical coordinates, that is, the variance of the insulation resistance value measurement;

[0031] S6: The third group of experiments: According to the preliminary setting of Rp 0 and Rn 0 , set a set of experimental variables R n x (Here Rn 0 For example), they are: Rn1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ...R x , where Rn x =y2Rn 0 According to the range of error and variance, the value range of y2 is determined to be 1 / 4 to 5 times, and different R n x The experimental results of x groups are obtained by substituting V1, V2, V3, and V4 under the condition of positive electrode insulation resistance into the calculation formula (1) and formula (2) respectively to obtain the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 , Rp 6 ...Rp x and Actual Rn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ...Rn x , substitute the experimental results into the measurement error formula: E x =(Actual Rn x -Rn x ) / Rn x *100%, get different R n x The insulation measurement error results under different insulation resistance R n x The measured value error diagram, the horizontal axis of the measured value error diagram is the different negative electrode insulation resistance Rn x , the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different Rn x The variance under different bridge arm resistance Rn x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is the different negative insulation resistance Rn x , the ordinate is the corresponding S x 2 , the intersection of the horizontal and vertical coordinates, that is, the variance of the insulation resistance value measurement;

[0032] S7: The fourth group of experiments: According to the initial setting of V 0 , set a set of experimental variables V x (Here Rn 0 For example), they are: V 1 、V 2 、V 3 、V 4 、V 5 ...R x , where V x =y3V 0 According to the range of error and variance, the value range of y3 is determined to be 1 to 5 times, and different V x The experimental results of x groups are obtained by substituting V1, V2, V3, and V4 under the condition of positive electrode insulation resistance into the calculation formula (1) and formula (2) respectively to obtain the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 ..Rp x and Actual Rn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 ..Rn x , substitute the experimental results into the measurement error formula: E x =(Actual Rn x -Rn x ) / Rn x *100%, get different V x The insulation measurement error results under different V x The measured value error diagram, the horizontal axis of the measured value error diagram is different V x , the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different V x The variance under different V x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is different V x , the ordinate is the corresponding S x 2 , the intersection of the horizontal and vertical coordinates, that is, the variance of the insulation resistance value measurement;

[0033] S8: Analyze the above four groups of comparative experiments, the variance and relative error of each factor on the insulation resistance measurement, and find the test group that satisfies the relative error of the insulation resistance value measurement <5% and the variance <0.3. By summarizing the value rules of this test group, a set of approximate relationships can be obtained, namely y i The value range of , according to which a set of optimal bridge resistance matching design schemes can be designed.

[0034] This technical solution connects a monitoring bridge resistor between the positive and negative electrodes of the hull, calculates the positive and negative insulation resistances according to the insulation status of the DC system and the branch, and finally quantifies the measurement results to study the influence of different resistance values ​​in the circuit on the insulation resistance test error.

[0035] This device has low cost and simple circuit structure; this method is easy to operate, short measuring time and easy to realize digital measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the circuit structure of the embodiment;

[0037] Figure 2 It is a flow chart of the insulation monitoring system in the embodiment;

[0038] Figure 3 Schematic diagram of the bridge arm resistance optimization process in the embodiment. DETAILED DESCRIPTION

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited thereto.

[0040] Reference Figure 1 , an insulation detection system for a ship power battery pack, comprising a DC system, a detection circuit and a sampling circuit, an AD conversion circuit and a single-chip microcomputer MCU connected in sequence, wherein,

[0041] The DC system is provided with a power battery pack V B , positive electrode insulation resistance Rp and negative electrode insulation resistance Rn, wherein one end of the positive electrode insulation resistance Rp is connected to the power battery pack V B The positive electrode is connected to the ground, and the other end is grounded. One end of the negative insulation resistor Rn is connected to the power battery pack V B The negative pole of the resistor is connected and the other end is grounded;

[0042] The detection circuit in the detection circuit and the sampling circuit is provided with two first bridge arm resistors R, a second bridge arm resistor R1, a third bridge arm resistor R3, and a relay switch S, wherein one end of the first bridge arm resistor R is connected to the positive electrode insulation resistor Rp and the other end is grounded, one end of the second bridge arm resistor R1 is connected to the negative electrode insulation resistor Rn and the other end is grounded, one end of the third bridge arm resistor R3 is connected to the switch S and the other end is grounded, and the other end of the switch S is connected to the power battery pack V B The negative connection of

[0043] The sampling circuit in the detection circuit and the sampling circuit is provided with a diode VD, a capacitor C, and a resistor R2 connected in parallel, wherein one end of the resistor R2 is connected to the third bridge arm resistor R3, and the other end is connected to the parallel circuit of the diode VD and the capacitor C;

[0044] In the detection circuit and sampling circuit, the positive electrode is the power battery pack V B The positive busbar is the voltage to ground, and the negative busbar is the power battery pack V B Negative bus voltage to ground, when the system is powered on, the power battery pack V B The detection circuit is composed of the internal resistance, and the insulation resistance is calculated by collecting the voltage values ​​of each part. The sampling points corresponding to the positive electrode-to-ground voltage and the negative electrode-to-ground voltage are located at the connection of the positive electrode insulation resistance Rp and the negative electrode insulation resistance Rn. The sampling circuit collects the voltage on the corresponding branch as the sampling voltage. The process is: close the switch S on the branch and sample the power battery pack V on the corresponding branch. B Positive pole to ground voltage, power battery pack V B Negative pole to ground voltage; disconnect the switch S on the branch and sample the power battery pack V on the corresponding branch B Positive pole to ground voltage, power battery pack V B Negative pole voltage to ground;

[0045] The AD conversion circuit and the single-chip microcomputer MCU are composed of an AD chip or a battery sampling analog front-end chip with AD sampling and a single-chip microcomputer. In this example, the AD sampling circuit and the single-chip microcomputer are composed of AN49503 and STM32F105VCT6 chips.

[0046] In this example, the first bridge arm resistor R, the second bridge arm resistor R1, and the third bridge arm resistor R3 are all precision resistors with a power of 2W and an accuracy of 1%, wherein the first bridge arm resistor R and the third bridge arm resistor R3 are the same in size.

[0047] In this example, the relay switch S is a HFD4 / 5-S relay, and the closing and opening of the relay is controlled by the microcontroller MCU.

[0048] The diode VD in this example is a LESD3Z5.0CMT1G electrostatic protection diode.

[0049] In this example, the capacitance of capacitor C is 1nf.

[0050] In this example, when the switch S is open, the voltage between the ship chassis and the positive electrode of the power battery pack is V1, and the voltage between the ship chassis and the negative electrode of the power battery pack is V2. When the switch S is closed, the voltage between the ship chassis and the positive electrode of the power battery is V3, and the voltage between the ship chassis and the negative electrode of the power battery is V4. The sum of the voltages V1 and V2 is the total voltage V across the high-voltage system. B .

[0051] In this example, the positive electrode insulation resistance Rp and the negative electrode insulation resistance Rn are calculated based on Hoff's voltage law and the switch S as shown in formula (1) and formula (2):

[0052]

[0053]

[0054] The monitoring process of the insulation detection system for ship power battery packs is as follows: Figure 2 As shown, according to the general requirements for ship insulation, the insulation resistance of electric ships must reach 500Ω / V or above, that is, the insulation performance is good. In this example, the alarm threshold is set. When the positive and negative insulation resistance values ​​are 200Ω / V~500Ω / V, the first-level alarm is activated. When the positive and negative insulation resistance values ​​are between 100Ω / V and 200Ω / V, the second-level alarm is activated. When the positive and negative insulation resistance values ​​are lower than 100Ω / V, the third-level alarm is activated and the relay S is disconnected.

[0055] like Figure 3 As shown, a detection method for an insulation detection system for a ship power battery pack includes the above-mentioned insulation detection system for a ship power battery pack, and the method includes the following steps:

[0056] S1: According to the general requirements of ships, the insulation requirements of the power resistor group of electric ships must reach 500Ω / V or above to be considered that the insulation performance of the ship is good, and the error of ship insulation detection must also be <5% to meet the actual application. First, the voltage value of the power battery group of the electric ship is actually measured. According to the voltage value V and insulation resistance of the power battery group, which should meet the condition of >500Ω / V, the values ​​of various parameters in the single-arm unbalanced bridge can be preliminarily set. The parameters include: actual positive insulation resistance Rp, negative insulation resistance Rn and bridge arm resistance R, R1, that is, assuming that the insulation requirement is X and the voltage is Y, the values ​​of insulation resistance Rp and Rn = XY, and the values ​​of bridge arm resistance R, R1 = 2XY. In this example, the experimental data is sent by RS485, and the insulation detection system records it automatically or as required. The 102.4V / 300Ah lithium iron phosphate battery tests the positive and negative insulation resistances of 198.95kΩ and 197.9kΩ, where the single-arm unbalanced bridge arm resistances R and R1 are 620kΩ and 575kΩ respectively;

[0057] S2: Set the values ​​of the parameters initially set: bridge arm resistance R 0 , bridge arm resistance R1 0 , Positive insulation resistance Rp 0 , Negative insulation resistance Rn 0 And the voltage value of the power battery pack V 0 , substituting into the positive and negative insulation resistance formula (1) and formula (2), the result is calculated as follows:

[0058]

[0059]

[0060] Measured value Actual Rp 0 and Actual Rn 0 Insulation resistance Rp with reference 0 , Rn 0 By comparison, we can get the error formula E x =(Actual Rp x -Rp x ) / Rp x *100%, E x is the measurement error, and the variance formula is is the average of the measurement errors, S 2 Variance, determine whether the absolute value of the error is less than 5% and whether the variance is less than 0.3. If the relative error is <5% and the variance is <0.3, the values ​​of the parameters initially set meet the requirements. If the relative error is >5% or the variance is >0.3, the values ​​of the parameters initially set do not meet the requirements and need to be reset until they meet the actual application requirements.

[0061] S3: According to the insulation resistance calculation formula (1) and formula (2), there are four factors that affect the insulation resistance measurement. When considering their influence, the order is bridge arm resistance R, bridge arm resistance R1, Rp, Rn, power battery pack voltage V. According to the values ​​of the parameters initially set, R 0 、R1 0 , Rp 0 and Rn 0 、V 0 ,Four groups of comparative experiments were set up to explore the influence of single factors on insulation resistance measurement;

[0062] S4: The first group of experiments: Based on the initial setting of the bridge arm resistance R 0 , set a set of experimental variables R x , respectively: R 1 , R 2 , R 3 , R 4 , R5 , R 6 ...R x , where R x =yR 0 According to the range of error and variance, the value range of y is determined to be 1 / 5 to 5 times, and different R x The experimental results of x groups are obtained by substituting V1, V2, V3, and V4 under the condition of positive electrode insulation resistance into the calculation formula (1) and formula (2) respectively to obtain the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 , Rp 6 ,..Rp x and Actual Rn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ...Rn x , substitute the experimental results into the measurement error formula: E x =(Actual Rn x -Rn x ) / Rn x *100%, get different R x The insulation measurement error results under different bridge arm resistance R x The relative error diagram of the insulation resistance value measurement. The horizontal axis in the relative error diagram is the different bridge arm resistance R x , the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different R x The variance under different bridge arm resistance R x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is the different bridge arm resistance R x , the ordinate is the corresponding S x 2 , the intersection of the horizontal and vertical coordinates, that is, the variance of the insulation resistance value measurement. In this example, the bridge arm resistance R xThe values ​​of are: 61.8KΩ, 122KΩ, 181.5KΩ, 241.5KΩ, 301KΩ, 362KΩ, 432KΩ, 510KΩ, among which, when R is greater than 301KΩ, the measurement errors of positive and negative insulation resistance are small, less than 2.8%, when R is 61.8kΩ, the maximum variance is about 1.45, and the variance gradually decreases with the increase of R. When R is greater than 301kΩ, the variance is slightly smaller, about 0.079. It is concluded that when the ratio of the single-arm unbalanced bridge arm resistance R to the reference insulation resistance is greater than 1.5 times, the bridge arm resistance R has little effect on the insulation measurement, otherwise, it has a greater impact on the insulation measurement.

[0063] S5: The second group of experiments: Based on the initial setting of the bridge arm resistance R1 0 , set a set of experimental variables R1 x , respectively: R1 1 、R1 2 、R1 3 、R1 4 、R1 5 、R1 6 ...R x , where R1 x =y1R1 0 According to the range of error and variance, the value range of y1 is determined to be 1 / 5 to 5 times, and different R1 values ​​in the circuit are measured in turn. x Under V1, V2, V3, V4, get x groups of experimental results, substitute them into the calculation formula (1) and formula (2) of the positive and negative insulation resistance respectively, and get the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 , Rp 6 ..Rp x and Actual Rn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ..Rn x , substitute the experimental results into the measurement error formula: E x =(ActualRn x -Rn x ) / Rn x *100%, get different R1 x The insulation measurement error results under different bridge arm resistance R1 x The relative error diagram of the insulation resistance value measurement. The horizontal axis in the relative error diagram is the different bridge arm resistance R1 x, the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different R1 x Under the variance, make different bridge arm resistance R1 x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is the different bridge arm resistance R1 x , the ordinate is the corresponding S x 2 , the intersection of the horizontal and vertical coordinates, that is, the variance of the insulation resistance value measurement. In this example, the bridge arm resistance R1 x The values ​​are: 61.8KΩ, 120.8KΩ, 181KΩ, 240.5KΩ, 299.5KΩ, 361KΩ, 431KΩ, 473.5KΩ, among which the measurement errors and variances of positive and negative insulation resistances are basically unchanged. It is concluded that the bridge arm resistance R1 has almost no effect on the measurement of insulation resistance; however, according to experimental experience, if the value of the bridge arm resistance R1 is less than 61.8kΩ or greater than 473.5kΩ, it will cause the resistance to heat up and burn out. It is recommended that the ratio of the bridge arm resistance R1 to the negative insulation resistance Rn be between 1-2.5 times;

[0064] S6: The third group of experiments: According to the preliminary setting of Rp 0 and Rn 0 , set a set of experimental variables R n x In this example, Rn 0 For example, they are: Rn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ...R x , where Rn x =y2Rn 0 According to the range of error and variance, the value range of y2 is determined to be 1 / 4 to 5 times, and different R n x Under V1, V2, V3, V4, get x groups of experimental results, substitute them into the calculation formula (1) and formula (2) of the positive and negative insulation resistance respectively, and get the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 , Rp 6 ...Rp x and Actual Rn1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ...Rn x , substitute the experimental results into the measurement error formula: E x =(Actual Rn x -Rn x ) / Rn x *100%, get different R n x The insulation measurement error results under different insulation resistance R n x The measured value error diagram, the horizontal axis of the measured value error diagram is the different negative electrode insulation resistance Rn x , the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different Rn x The variance under different bridge arm resistance Rn x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is the different negative insulation resistance Rn x , the ordinate is the corresponding S x 2 The intersection of the horizontal and vertical axes is the variance of the insulation resistance value. In this example, the negative insulation resistance Rn x The values ​​are 61.45KΩ, 120.8KΩ, 180.6KΩ, 240KΩ, 299KΩ, 360.5KΩ, 430KΩ, and 507KΩ, respectively. As the actual negative electrode insulation resistance value increases, the measurement error gradually increases. When the negative electrode insulation resistance value is greater than 299KΩ, the insulation measurement error is greater than 3%, and the variance also gradually increases with the increase of the negative electrode insulation resistance value. It is concluded that when the ratio of the bridge arm resistance R to the negative electrode insulation resistance Rn is greater than 2 times, the influence on the insulation measurement is small, otherwise, the influence on the insulation measurement is large.

[0065] S7: The fourth group of experiments: According to the initial setting of V 0 , set a set of experimental variables V x In this example, Rn 0 For example, they are: V 1 、V 2 、V 3 、V 4 、V 5 ...R x , where V x =y3V0 According to the range of error and variance, the value range of y3 is determined to be 1 to 5 times, and different V x Under V1, V2, V3, V4, get x groups of experimental results, substitute them into the calculation formula (1) and formula (2) of the positive and negative insulation resistance respectively, and get the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 ..Rp x and Actual Rn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 ..Rn x , substitute the experimental results into the measurement error formula: E x =(Actual Rn x -Rn x ) / Rn x *100%, get different V x The insulation measurement error results under different V x The measured value error diagram, the horizontal axis of the measured value error diagram is different V x , the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different V x The variance under different V x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is different V x , the ordinate is the corresponding S x 2 , the intersection of the horizontal and vertical coordinates, that is, the variance of the insulation resistance value measurement. In this example, the battery pack voltage values ​​are: 100v, 200v, 300v, 400v, 500v, among which, when the voltage increases from 100v to 500v, the measurement error increases from 1.43% to 3.14%. When the voltage is 500v high voltage, the error increases rapidly. The reason is that the battery voltage is too large and the internal resistance of the resistor increases, which causes the resistor to heat up and burn out. Therefore, the rule is that the battery pack voltage should be less than or equal to 400V, which is more reasonable. At the same time, according to the insulation test standard of electric ships, when designing the bridge, the ratio of voltage to negative insulation resistance Rn must reach 500Ω / V or more;

[0066] S8: Analyze the above four groups of comparative experiments, the variance and relative error of each factor on the insulation resistance measurement, and find the test group that satisfies the relative error of the insulation resistance value measurement <5% and the variance <0.3. By summarizing the value rules of this test group, a set of approximate relationships can be obtained, namely y i The value range of , according to this approximate relationship, a set of optimal bridge resistance matching design schemes can be designed as shown below:

[0067] R=xRn,(x≥2)

[0068] R1=yRn,(1≤y≤2.5)

[0069] Rn / V≥500Ω / V

[0070] Where Rn is the negative electrode insulation resistance, R and R1 are the bridge arm resistances, and V is the voltage of the ship's power battery pack.

Claims

1. A detection method for an insulation detection system for a ship power battery pack, the insulation detection system for a ship power battery pack comprising a DC system, a detection circuit and a sampling circuit, an AD conversion circuit and a single-chip microcomputer MCU connected in sequence, wherein: The DC system is provided with a power battery pack V B , positive electrode insulation resistance Rp and negative electrode insulation resistance Rn, wherein one end of the positive electrode insulation resistance Rp is connected to the power battery pack V B The positive electrode is connected to the ground, and the other end is grounded. One end of the negative insulation resistor Rn is connected to the power battery pack V B The negative pole of the resistor is connected and the other end is grounded; The detection circuit in the detection circuit and the sampling circuit is provided with a first bridge arm resistor R, a second bridge arm resistor R1, a third bridge arm resistor R3, and a relay switch S, wherein one end of the first bridge arm resistor R is connected to the positive electrode insulation resistor Rp and the other end is grounded, one end of the second bridge arm resistor R1 is connected to the negative electrode insulation resistor Rn through the relay switch S and the other end is grounded, one end of the third bridge arm resistor R3 is connected to the switch S and the other end is grounded, and one end of the switch S is connected to the power battery pack V B The negative connection of The sampling circuit in the detection circuit and the sampling circuit is provided with a diode VD, a capacitor C, and a resistor R2 connected in parallel, wherein one end of the resistor R2 is connected to the third bridge arm resistor R3, and the other end is connected to the parallel circuit of the diode VD and the capacitor C; In the detection circuit and sampling circuit, the positive electrode is the power battery pack V B The positive busbar is the voltage to ground, and the negative busbar is the power battery pack V B Negative bus voltage to ground, when the system is powered on, the power battery pack V B The detection circuit is composed of the internal resistance, and the insulation resistance is calculated by collecting the voltage values ​​of each part. The sampling points corresponding to the positive electrode-to-ground voltage and the negative electrode-to-ground voltage are located at the connection of the positive electrode insulation resistance Rp and the negative electrode insulation resistance Rn. The sampling circuit collects the voltage on the corresponding branch as the sampling voltage. The process is: close the switch S on the branch and sample the power battery pack V on the corresponding branch. B Positive pole to ground voltage, power battery pack V B Negative pole to ground voltage; disconnect the switch S on the branch and sample the power battery pack V on the corresponding branch B Positive pole to ground voltage, power battery pack V B Negative pole voltage to ground; The AD conversion circuit and the single-chip microcomputer MCU are composed of an AD chip or a battery sampling analog front-end chip with AD sampling and a single-chip microcomputer; The first bridge arm resistor R, the second bridge arm resistor R1, and the third bridge arm resistor R3 are all precision resistors with a power of 2W and an accuracy of 1%, wherein the first bridge arm resistor R and the third bridge arm resistor R3 have the same resistance value; The relay switch S is a HFD4 / 5-S relay, and the closing and opening of the relay is controlled by a single-chip microcomputer MCU; The capacitance of the capacitor C is 1nf; The diode VD is a LESD3Z5.0CMT1G electrostatic protection diode; The positive electrode insulation resistance Rp and the negative electrode insulation resistance Rn are calculated based on Hoff's voltage law and the switch S as shown in formula (1) and formula (2): Characterized in that the method comprises the following steps: S1: Preliminary setting of the values ​​of various parameters in the single-arm unbalanced bridge, including: actual positive insulation resistance Rp, negative insulation resistance Rn and bridge arm resistance R, R1, that is, assuming that the insulation requirement is X and the voltage is Y, then the values ​​of insulation resistance Rp and Rn = XY, and the values ​​of bridge arm resistance R, R1 = 2XY; S2: Set the values ​​of the parameters initially set: bridge arm resistance R 0 , bridge arm resistance R1 0 , Positive insulation resistance Rp 0 , Negative insulation resistance Rn 0 And the voltage value of the power battery pack V 0 , substituting into the positive and negative insulation resistance formula (3) and formula (4), the result is calculated as follows: Measure the calculated value ActualRp 0 and ActualRn 0 Insulation resistance Rp with reference 0 , Rn 0 For comparison, according to the error formula E x =(Actual Rp x -Rp x ) / Rp x *100%, E x is the measurement error, and the variance formula is is the average of the measurement errors, S 2 Variance, determine whether the absolute value of the error is less than 5% and whether the variance is less than 0.

3. If the relative error is <5% and the variance is <0.3, the values ​​of the parameters initially set meet the requirements. If the relative error is >5% or the variance is >0.3, the values ​​of the parameters initially set do not meet the requirements and need to be reset until they meet the actual application requirements. S3: According to the insulation resistance calculation formula (3) and formula (4), there are four factors that affect the insulation resistance measurement, namely the bridge arm resistance R, bridge arm resistance R1, Rp, Rn, and power battery pack voltage V. According to the values ​​of the parameters initially set, R 0 、R1 0 , Rp 0 and Rn 0 、V 0 ,Four groups of comparative experiments were set up to explore the influence of single factors on insulation resistance measurement; S4: The first group of experiments: Based on the initial setting of the bridge arm resistance R 0 , set a set of experimental variables R x , respectively: R 1 , R 2 , R 3 , R 4 , R 5 , R 6 ...R x , where R x =yR 0 According to the range of error and variance, the value range of y is determined to be 1 / 5 to 5 times, and different R x Under V1, V2, V3, V4, get x groups of experimental results, substitute them into the calculation formula (3) and formula (4) of the positive and negative insulation resistance respectively, and get the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 , Rp 6 ,..Rp x and ActualRn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ...Rn x , substitute the experimental results into the measurement error formula: E x =(Actual Rn x -Rn x ) / Rn x *100%, get different R x The insulation measurement error results under different bridge arm resistance R x The relative error diagram of the insulation resistance value measurement. The horizontal axis in the relative error diagram is the different bridge arm resistance R x , the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different R x The variance under different bridge arm resistance R x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is the different bridge arm resistance R x , the ordinate is the corresponding S x 2 , the intersection of the horizontal and vertical coordinates, that is, the variance of the insulation resistance value measurement; S5: The second group of experiments: Based on the initial setting of the bridge arm resistance R1 0 , set a set of experimental variables R1 x , respectively: R1 1 、R1 2 、R1 3 、R1 4 、R1 5 、R1 6 ...R x , where R1 x =y1R1 0 According to the range of error and variance, the value range of y1 is determined to be 1 / 5 to 5 times, and different R1 values ​​in the circuit are measured in turn. x Under V1, V2, V3, V4, get x groups of experimental results, substitute them into the calculation formula (3) and formula (4) of the positive and negative insulation resistance respectively, and get the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 , Rp 6 ..Rp x and ActualRn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ..Rn x , substitute the experimental results into the measurement error formula: E x =(Actual Rn x -Rn x ) / Rn x *100%, get different R1 x The insulation measurement error results under different bridge arm resistance R1 x The relative error diagram of the insulation resistance value measurement. The horizontal axis in the relative error diagram is the different bridge arm resistance R1 x , the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different R1 x Under the variance, make different bridge arm resistance R1 x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is the different bridge arm resistance R1 x , the ordinate is the corresponding S x 2 , the intersection of the horizontal and vertical coordinates, that is, the variance of the insulation resistance value measurement; S6: The third group of experiments: According to the preliminary setting of Rp 0 and Rn 0 , set a set of experimental variables R n x , respectively: Rn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ...R x , where Rn x =y2Rn 0 According to the range of error and variance, the value range of y2 is determined to be 1 / 4 to 5 times, and different R n x Under V1, V2, V3, V4, get x groups of experimental results, substitute them into the calculation formula (3) and formula (4) of the positive and negative insulation resistance respectively, and get the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 , Rp 6 ...Rp x and ActualRn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 , Rn 6 ...Rn x , substitute the experimental results into the measurement error formula: E x =(Actual Rn x -Rn x ) / Rn x *100%, get different R n x The insulation measurement error results under different insulation resistance R n x The measured value error diagram, the horizontal axis of the measured value error diagram is the different negative electrode insulation resistance Rn x , the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different Rn x The variance under different bridge arm resistance Rn x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is the different negative insulation resistance Rn x , the ordinate is the corresponding S x 2 , the intersection of the horizontal and vertical coordinates, that is, the variance of the insulation resistance value measurement; S7: The fourth group of experiments: According to the initial setting of V 0 , set a set of experimental variables V x , respectively: V 1 、V 2 、V 3 、V 4 、V 5 ...R x , where V x =y3V 0 According to the range of error and variance, the value range of y3 is determined to be 1 to 5 times, and different V x Under V1, V2, V3, V4, get x groups of experimental results, substitute them into the calculation formula (3) and formula (4) of the positive and negative insulation resistance respectively, and get the experimental result Actual Rp 1 , Rp 2 , Rp 3 , Rp 4 , Rp 5 ...Rp x and Actual Rn 1 , Rn 2 , Rn 3 , Rn 4 , Rn 5 ...Rn x , substitute the experimental results into the measurement error formula: E x =(ActualRn x -Rn x ) / Rn x *100%, get different V x The insulation measurement error results under different V x The measured value error diagram, the horizontal axis of the measured value error diagram is different V x , the ordinate is the corresponding E x The absolute value of |E x |, the intersection of the horizontal and vertical coordinates, that is, the relative error of the insulation resistance value measurement, and then substitute the experimental results into the variance formula in turn Get different V x The variance under different V x The variance diagram of the insulation resistance measurement, the horizontal axis of the variance diagram is different V x , the ordinate is the corresponding S x 2 , the intersection of the horizontal and vertical coordinates, that is, the variance of the insulation resistance value measurement; S8: Analyze the above four groups of comparative experiments, the variance and relative error of each factor on the insulation resistance measurement, find the test group that satisfies the relative error of insulation resistance measurement <5% and variance <0.3, and obtain a set of approximate relationships by summarizing the value rules of the test group, that is, y i A set of optimal bridge resistance matching design schemes are designed based on the approximate relationship. Among them, V1 is the voltage between the ship chassis and the positive electrode of the power battery pack when the switch S is open, and the voltage between the ship chassis and the negative electrode of the power battery pack is V2. When the switch S is closed, the voltage between the ship chassis and the positive electrode of the power battery is V3, and the voltage between the ship chassis and the negative electrode of the power battery is V4. The sum of the voltages V1 and V2 is the total voltage V across the high-voltage system. B .

Images