A high voltage battery management system insulation resistance detection circuit and method

Abstract

The present invention discloses a high-voltage battery management system insulation resistance detection circuit and method, including a DC bus, the high-voltage positive pole of the DC bus is electrically connected to the earth, one end of a first resistor and one end of a second resistor, and the high-voltage negative pole of the DC bus is electrically connected to the earth, one end of a fourth resistor and one end of a fifth resistor. The present invention can accurately measure the insulation resistance value of the positive pole of the DC bus to the earth and the insulation resistance value of the negative pole to the earth. The insulation resistance value of the positive pole and the insulation resistance value of the negative pole may not be equal, including insulation resistance in any state, and the stability is very high. The application field range is very wide, including insulation protection detection of battery busbars in the automotive new energy industry, photovoltaic new energy industry, industrial storage new energy industry, etc.

Description

Technical Field

[0001] The present invention relates to the field of electricity, and in particular to an insulation resistance detection circuit and method for a high-voltage battery management system. Background Art

[0002] The working voltage of the DC bus is usually a high DC voltage ranging from several hundred volts to more than one thousand volts. The insulation resistance detection of the high DC voltage in the low-voltage energy storage box is very important. If the insulation resistance of the DC bus is too low, the leakage current will be too large, causing destructive damage to most equipment, and in severe cases, it will cause a fire. The energy storage box of the new energy storage system is composed of three modules: the BMU module is for the detection and management of single cells at the PACK level; the BCU module is for the detection and protection management of cluster-level battery packs; and the BAU module is for the detection and protection management of stack-level battery stacks. In the series-parallel combination energy storage circuit of each level of modules, the number of module access circuit nodes increases, and the circuit resistance will change. The existing balanced insulation resistance detection technology cannot accurately measure the resistance value of the DC bus positive electrode to the earth and the resistance value of the negative electrode to the earth. It cannot measure the balanced resistance of the high-voltage positive and negative electrodes of the DC bus. The fluctuation range is very large, which is easy to cause misoperation of the safety protection function.

[0003] Voltage division theorem: that is, voltage division formula, source voltage U, resistance value R1 of resistor 1, resistance value R2 of resistor 2. Total current I = U / (R1+R2); voltage division on resistor 1 U1 = IR1 = UR1 / (R1+R2). Voltage division on resistor 2 U2 = IR2 = UR2 / (R1+R2). Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a high-voltage battery management system insulation resistance detection circuit and method.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A high-voltage battery management system insulation resistance detection circuit, characterized in that it includes a DC bus, the high-voltage positive electrode of the DC bus is electrically connected to the earth (PE), one end of a first resistor (R1) and one end of a second resistor (R2), and the high-voltage negative electrode of the DC bus is electrically connected to the earth (PE), one end of a fourth resistor (R4) and one end of a fifth resistor (R5); the resistance between the high-voltage positive electrode of the DC bus and the earth (PE) is a first resistor to be measured (Rp), and the resistance between the negative electrode and the earth (PE) is a second resistor to be measured (Rn); the other end of the second resistor (R2) is electrically connected to one end of a first bidirectional switch (Q1), and the other end of the first resistor (R1) is electrically connected to one end of the first bidirectional switch (Q1). The first resistor (R1) is electrically connected to one end of the third resistor (R3), the other end of the third resistor (R3) is electrically connected to the other end of the first bidirectional switch (Q1), one end of the second bidirectional switch (Q2), one end of the third bidirectional switch (Q3) and one end of the sixth resistor (R6); the other end of the second bidirectional switch (Q2) is electrically connected to the ground (PE), the other end of the fourth resistor (R4) is electrically connected to the other end of the third bidirectional switch (Q3), and the other end of the fifth resistor (R5) is electrically connected to the other end of the sixth resistor (R6); the resistance value of the first resistor (R1) is equal to the resistance value of the fourth resistor (R4), and the resistance value of the third resistor (R3) is equal to the resistance value of the sixth resistor (R6).

[0007] As a further improvement, the first resistor (R1) includes a resistor seven (R7), a resistor eight (R8), a resistor nine (R9), a resistor ten (R10), a resistor eleven (R11) and a resistor twelve (R12) connected in series in sequence, and the resistor twelve (R12) is electrically connected to one end of the third resistor (R3) and one end of the second capacitor (C2).

[0008] As a further improvement, the first bidirectional switch (Q1) includes a first chip (U1), a sixth pin of the first chip (U1) is electrically connected to the other end of the second resistor (R2), and a fourth pin of the first chip (U1) and the other end of the third resistor (R3) and the other end of the second capacitor (C2) are all electrically connected to a reference ground (GND).

[0009] As a further improvement, the model of the first chip (U1) is AQV258H5.

[0010] As a further improvement, the second resistor includes resistor one (R1-1), resistor two (R1-2), resistor three (R1-3), resistor four (R1-4) and resistor five (R1-5) connected in series in sequence, and resistor five (R1-5) is electrically connected to the sixth pin of the first chip (U1).

[0011] As a further improvement, the fifth resistor (R5) includes resistor twenty-six (R26), resistor twenty-seven (R27), resistor twenty-eight (R28), resistor twenty-nine (R29), resistor thirty (R30) and resistor thirty-one (R31) connected in series in sequence, and resistor thirty-one (R31) is electrically connected to the other end of the sixth resistor (R6) and one end of the fifth capacitor.

[0012] As a further improvement, the third bidirectional switch (Q3) includes a third chip (U1), a sixth pin of the third chip (U1) is electrically connected to the other end of the fourth resistor (R6), and a fourth pin of the third chip (U1) is electrically connected to a reference ground (GND) with one end of the sixth resistor (R6) and the other end of the fifth capacitor.

[0013] As a further improvement, the fourth resistor (R6) includes resistor nineteen (R19), resistor twenty (R20), resistor twenty-one (R21), resistor twenty-two (R22) and resistor twenty-three (R23) connected in series in sequence, and resistor twenty-three (R23) is electrically connected to the sixth pin of the third chip (U1).

[0014] As a further improvement, the second bidirectional switch (Q2) comprises a fifth chip (U5), a sixth pin of the fifth chip (U5) is electrically connected to the earth (PE), and a fourth pin is electrically connected to a reference ground (GND).

[0015] A method for detecting insulation resistance of a high-voltage battery management system, the detection method adopts any of the above-mentioned circuits, and specifically includes the following:

[0016] Step 1: disconnect the first bidirectional switch (Q1), the second bidirectional switch (Q2) and the third bidirectional switch (Q3), and detect the voltage U between the positive and negative electrodes of the DC bus;

[0017] Then, the second bidirectional switch (Q2) is turned on, and the first bidirectional switch (Q1) and the third bidirectional switch (Q3) are turned off. At this time, the first resistor (R1) and the third resistor (R3) are connected in series and then connected in parallel with the Rp resistor between the high-voltage positive pole of the DC bus and the earth (PE). The equivalent resistance Rp1 is:

[0018]

[0019] Wherein: Rp is the resistance value of the resistor between the high voltage positive electrode of the DC bus and the earth, R1' is the resistance value of the first resistor (R1), and R3' is the resistance value of the third resistor (R3);

[0020] At this time, assuming that the resistance between the high-voltage negative pole of the DC bus and the earth (PE) is Rn, then:

[0021]

[0022] Rn1 is the resistance value of the equivalent resistance after the fifth resistor (R5) and the sixth resistor (R5) are connected in series and then connected in parallel with the resistance between the high-voltage negative electrode of the DC bus and the earth (PE), R5' is the resistance value of the fifth resistor (R5), and R6' is the resistance value of the sixth resistor (R5);

[0023] The voltage U1 between the high voltage positive pole of the DC bus and the earth (PE) is calculated as:

[0024]

[0025] Then calculate the voltage between the high-voltage negative pole of the DC bus and the earth (PE) as U2:

[0026]

[0027] The voltage across the third resistor (R3) is calculated to be Vp1:

[0028]

[0029] It is calculated that the voltage across the sixth resistor when the second bidirectional switch (Q2) is turned on and the first bidirectional switch (Q1) and the third bidirectional switch (Q3) are turned off is Vn1:

[0030]

[0031] Then we have:

[0032]

[0033] Then the first bidirectional switch (Q1) and the second bidirectional switch (Q2) are turned on, and the third bidirectional switch (Q3) is turned on.

[0034] Cut-off;

[0035] At this time, the resistance value of the resistor between the high voltage positive pole of the DC bus and the earth (PE) is Rp. Assuming that the resistance between the high voltage positive pole of the DC bus and the earth (PE) is connected in parallel with the second resistor (R2) and the equivalent resistance value of the first resistor (R1) and the second resistor (R2) in series is Rp11, then

[0036]

[0037] R2' is the resistance value of the second resistor (R2);

[0038] The resistance value of the resistor between the high-voltage negative pole of the DC bus and the earth (PE) is Rn, and the resistance value Rn11 of the equivalent resistor after the resistor between the high-voltage negative pole of the DC bus and the earth (PE) is connected in parallel with the fifth resistor (R5) and the sixth resistor (R6) connected in series is as follows:

[0039]

[0040] Calculate the voltage U12 between the high voltage positive pole of the DC bus and the earth (PE):

[0041]

[0042] Calculate the voltage U22 between the high-voltage negative pole of the DC bus and the earth (PE):

[0043]

[0044] Calculate the voltage across the third resistor to be Vp2:

[0045]

[0046] The voltage across the sixth resistor is calculated to be Vn2:

[0047]

[0048] Then we have:

[0049]

[0050] Among them, it is known that R1'=R5'=8MΩ; R3'=R6'=0.013MΩ; R2'=R4'=2.55MΩ, then:

[0051] The calculation formula of the insulation resistance Rp of the high voltage positive pole of the DC bus to the earth is:

[0052] Rp=-(136221*(Vn1*Vp2-Vp1*Vn2)) / (20*(3521*Vn1*Vp2-850*Vp1*Vn2))

[0053] The calculation formula for the insulation resistance of the high-voltage negative pole of the DC bus to the earth is:

[0054] Rn=-(136221*(Vn1*Vp2-Vp1*Vn2)) / (20*(2671*Vp1*Vp2+850*Vn1*Vp2-850*Vp1*Vn2)).

[0055] The beneficial effects of the present invention are:

[0056] The present invention can accurately measure the insulation resistance value of the DC bus positive electrode to the earth and the insulation resistance value of the negative electrode to the earth. The insulation resistance value of the positive electrode and the insulation resistance value of the negative electrode can be unequal, including the insulation resistance in any state, and the stability is very high. The application field range is very wide, including the insulation protection detection of battery busbars in the automotive new energy industry, photovoltaic new energy industry, industrial storage new energy industry, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The present invention is further described with reference to the accompanying drawings, but the contents in the accompanying drawings do not constitute any limitation to the present invention.

[0058] Figure 1 This is the schematic diagram of the insulation resistance detection circuit of the high-voltage battery management system;

[0059] Figure 2 Detailed circuit diagram of the second resistor R2, the fourth resistor R6 and the second bidirectional switch Q2.

[0060] Figure 3 is a circuit diagram of the first resistor R1 and the fifth resistor R5. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solutions and advantages of the invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.

[0062] Example 1

[0063] According to the voltage division ratio, the battery voltages of V1 and V2 can be calculated independently. Let the voltage between the batteries be U.

[0064] (1) Q2 is turned on, Q1 and Q3 are turned off.

[0065] 1a. At this time, the high voltage positive electrode to PE resistor Rp, from the circuit diagram, we can see that Rp is connected in parallel with R1 and R3, and the series resistance is set to Rp1, so

[0066]

[0067] 1b. At this time, the resistance from the high voltage negative electrode to PE is Rn. From the circuit diagram, we can see that the series resistance of Rn in parallel with R5 and R6 is set to Rn1, so

[0068]

[0069] 1c. According to the voltage division theorem, the voltage between the high voltage positive electrode and PE is calculated to be U1. From the circuit diagram, we can see

[0070]

[0071] 1d. According to the voltage division theorem, the voltage between the high voltage negative electrode and PE is calculated to be U2. From the circuit diagram, we can see

[0072]

[0073] 1e. According to the voltage division theorem, the voltage at the high voltage positive electrode measurement point can be calculated to be V1. From the circuit diagram, we can see

[0074]

[0075] 1f. According to the voltage division theorem, the voltage at the high voltage negative electrode measurement point can be calculated to be V2. From the circuit diagram, we can see

[0076]

[0077] 1g. From the above calculation data, we know:

[0078]

[0079] (2) Q1 and Q2 are turned on, and Q3 is turned off;

[0080] 2a. At this time, the resistance from the high voltage positive electrode to PE is Rp. From the circuit diagram, we can see that the series resistance of Rp in parallel with R2, R1 and R3 in parallel is Rp11, so

[0081]

[0082] 2b. The resistance from the high voltage negative electrode to PE is Rn. From the circuit diagram, we can see that the series resistance of Rn in parallel with R4 and R6 is set to Rn11, so

[0083]

[0084] 2c. According to the voltage division theorem, the voltage between the high voltage positive electrode and PE can be calculated to be U12. From the circuit diagram, we can know that

[0085]

[0086] 2d. According to the voltage division theorem, the voltage between the high voltage negative electrode and PE can be calculated to be U22. From the circuit diagram, we can know that

[0087]

[0088] 2e. According to the voltage division theorem, the voltage at the high voltage positive electrode measurement point can be calculated to be V1. From the circuit diagram, we can see

[0089]

[0090] 2f. According to the voltage division theorem, the voltage at the high voltage negative electrode measurement point can be calculated to be V2. From the circuit diagram, we can see

[0091]

[0092] 2g. According to the above calculation formula, we can get:

[0093]

[0094] 2. The insulation resistance calculation formula of the DC bus high voltage positive pole to the earth and the insulation resistance calculation formula of the DC bus high voltage positive pole to the earth

[0095] (1) Given R1 = R5 = 8MΩ; R3 = R6 = 0.013MΩ; R2 = R4 = 2.55MΩ, we can substitute the above formula to get:

[0096] a. Calculation formula for the insulation resistance of the high voltage positive electrode to the earth:

[0097] Rp=-(136221*(Vn1*Vp2-Vp1*Vn2)) / (20*(3521*Vn1*Vp2-850*Vp1*Vn2))

[0098] b. Calculation formula for the insulation resistance of the high voltage negative electrode to the earth:

[0099] Rn=-(136221*(Vn1*Vp2-Vp1*Vn2)) / (20*(2671*Vp1*Vp2+

[0100] 850*Vn1*Vp2-850*Vp1*Vn2))

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for detecting insulation resistance of a high-voltage battery management system, characterized in that: A high-voltage battery management system insulation resistance detection circuit is used, the high-voltage battery management system insulation resistance detection circuit comprises a DC bus, the high-voltage positive pole of the DC bus is electrically connected to the earth (PE), one end of a first resistor (R1) and one end of a second resistor (R2), the high-voltage negative pole of the DC bus is electrically connected to the earth (PE), one end of a fourth resistor (R4) and one end of a fifth resistor (R5); the resistance between the high-voltage positive pole of the DC bus and the earth (PE) is a first resistor to be measured (Rp), and the resistance between the negative pole and the earth (PE) is a second resistor to be measured (Rn); the other end of the second resistor (R2) is electrically connected to one end of a first bidirectional switch (Q1), and the other end of the first resistor (R1) is electrically connected to the third resistor (R3). one end of the first two-way switch (Q1), one end of the second two-way switch (Q2), one end of the third two-way switch (Q3) and one end of the sixth resistor (R6); the other end of the second two-way switch (Q2) is electrically connected to the ground (PE); the other end of the fourth resistor (R4) is electrically connected to the other end of the third two-way switch (Q3); the other end of the fifth resistor (R5) is electrically connected to the other end of the sixth resistor (R6); the resistance value of the first resistor (R1) is equal to the resistance value of the fourth resistor (R4); the resistance value of the third resistor (R3) is equal to the resistance value of the sixth resistor (R6); the first resistor (R1) includes a resistor seven (R7), a resistor eight (R8), a resistor nine (R9) connected in series in sequence R9), a resistor ten (R10), a resistor eleven (R11) and a resistor twelve (R12), wherein the resistor twelve (R12) is electrically connected to one end of the third resistor (R3) and one end of the second capacitor (C2); the first bidirectional switch (Q1) comprises a first chip (U1), a sixth pin of the first chip (U1) is electrically connected to the other end of the second resistor (R2), and a fourth pin of the first chip (U1) and the other end of the third resistor (R3) and the other end of the second capacitor (C2) are all electrically connected to a reference ground (GND); the model of the first chip (U1) is AQV258H5; the second resistor comprises a resistor one (R1-1), a resistor two (R1-2), a resistor three (R1-3), and a resistor four (R1-4) which are connected in series in sequence. 1-4) and resistor five (R1-5), the resistor five (R1-5) is electrically connected to the sixth pin of the first chip (U1); the fifth resistor (R5) includes resistor twenty-six (R26), resistor twenty-seven (R27), resistor twenty-eight (R28), resistor twenty-nine (R29), resistor thirty (R30) and resistor thirty-one (R31) connected in series in sequence, and resistor thirty-one (R31) is electrically connected to the other end of the sixth resistor (R6) and one end of the fifth capacitor; the third bidirectional switch (Q3) includes a third chip, the sixth pin of the third chip is electrically connected to the other end of the fourth resistor (R4), and the fourth pin of the third chip is electrically connected to a reference ground (GND) with one end of the sixth resistor (R6) and the other end of the fifth capacitor;The fourth resistor (R4) comprises a resistor 19 (R19), a resistor 20 (R20), a resistor 21 (R21), a resistor 22 (R22) and a resistor 23 (R23) which are sequentially connected in series, and the resistor 23 (R23) is electrically connected to the sixth pin of the third chip; the second bidirectional switch (Q2) comprises a fifth chip (U5), the sixth pin of the fifth chip (U5) is electrically connected to the earth (PE), and the fourth pin is electrically connected to the reference ground (GND); The detection method specifically includes the following: Step 1: disconnect the first bidirectional switch (Q1), the second bidirectional switch (Q2) and the third bidirectional switch (Q3), and detect the voltage U between the positive and negative electrodes of the DC bus; Then, the second bidirectional switch (Q2) is turned on, and the first bidirectional switch (Q1) and the third bidirectional switch (Q3) are turned off. At this time, the first resistor (R1) and the third resistor (R3) are connected in series and then connected in parallel with the Rp resistor between the high-voltage positive pole of the DC bus and the earth (PE). The equivalent resistance Rp1 is: Wherein: Rp is the resistance value of the resistor between the high voltage positive electrode of the DC bus and the earth, R1' is the resistance value of the first resistor (R1), and R3' is the resistance value of the third resistor (R3); At this time, assuming that the resistance between the high-voltage negative pole of the DC bus and the earth (PE) is Rn, then: Rn1 is the resistance value of the equivalent resistance after the fifth resistor (R5) and the sixth resistor (R6) are connected in series and then connected in parallel with the resistance between the high-voltage negative electrode of the DC bus and the earth (PE), R5' is the resistance value of the fifth resistor (R5), and R6' is the resistance value of the sixth resistor (R6); The voltage U1 between the high voltage positive pole of the DC bus and the earth (PE) is calculated as: Then calculate the voltage between the high-voltage negative pole of the DC bus and the earth (PE) as U2: The voltage across the third resistor (R3) is calculated to be Vp1: It is calculated that the voltage across the sixth resistor when the second bidirectional switch (Q2) is turned on and the first bidirectional switch (Q1) and the third bidirectional switch (Q3) are turned off is Vn1: Then we have: Then, the first bidirectional switch (Q1) and the second bidirectional switch (Q2) are turned on, and the third bidirectional switch (Q3) is turned off; At this time, the resistance value of the resistor between the high voltage positive pole of the DC bus and the earth (PE) is Rp. Assuming that the resistance between the high voltage positive pole of the DC bus and the earth (PE) is connected in parallel with the second resistor (R2) and the equivalent resistance value of the first resistor (R1) and the second resistor (R2) in series is Rp11, then R2' is the resistance value of the second resistor (R2); The resistance value of the resistor between the high-voltage negative pole of the DC bus and the earth (PE) is Rn, and the resistance value Rn11 of the equivalent resistor after the resistor between the high-voltage negative pole of the DC bus and the earth (PE) is connected in parallel with the fifth resistor (R5) and the sixth resistor (R6) connected in series is as follows: Calculate the voltage U12 between the high voltage positive pole of the DC bus and the earth (PE): Calculate the voltage U22 between the high-voltage negative pole of the DC bus and the earth (PE): Calculate the voltage across the third resistor to be Vp2: The voltage across the sixth resistor is calculated to be Vn2: Then we have: Among them, it is known that R1'=R5'=8MΩ; R3'=R6'=0.013MΩ; R2'=R4'=2.55MΩ, then: The calculation formula of the insulation resistance Rp of the high voltage positive pole of the DC bus to the earth is: Rp=-(136221*(Vn1*Vp2-Vp1*Vn2)) / (20*(3521*Vn1*Vp2-850*Vp1*Vn2)) The insulation resistance calculation formula of the high voltage negative pole of the DC bus to the earth is: Rn=-(136221*(Vn1*Vp2-Vp1*Vn2)) / (20*(2671*Vp1*Vp2+850*Vn1*Vp2-850*Vp1*Vn2))。

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