TWI762235B - Insulation resistance detection system for electric vehicle and method of detecting the same in insulation resistance - Google Patents

Abstract

An insulation resistance detection system for an electric vehicle is used to detect a positive insulation resistance between a positive electrode of a battery and an equipment grounding point of the electric vehicle, and a negative insulation resistance between a negative electrode and the equipment grounding point. The insulation resistance detection system includes a negative end detection circuit, a positive end detection circuit, and a control unit. The control unit controls the negative end detection circuit to becharged to generate a first capacitor voltage, and controls the positive end detection circuit to be charged to generate a second capacitor voltage. The control unit determines whether the negative insulation resistance is abnormal according to the first capacitor voltage and a battery voltage of the battery, and determines whether the positive insulation resistance is abnormal according to the second capacitor voltage and the battery voltage.

Description

Insulation resistance detection system for electric vehicle and insulation resistance detection method thereof

The invention relates to an insulation resistance detection system and an insulation resistance detection method thereof, in particular to an insulation resistance detection system for an electric vehicle and an insulation resistance detection method thereof.

As electric vehicles powered by electricity are becoming more and more popular nowadays, the research and application of electric vehicles are getting more and more attention. Especially in the application of batteries and electric vehicles, it is usually necessary to ensure that the accommodating space in which the batteries are installed in the electric vehicles is well insulated, so as to avoid battery leakage and cause electric shock to personnel or continuous consumption of battery power. Therefore, it is necessary to use a specific instrument or circuit to measure the insulation resistance of the electric vehicle to determine the leakage.

However, the current insulation detection method of electric vehicles usually only uses resistance measurement or capacitance measurement voltage at the detection point, and then inversely deduces the insulation resistance value from the formula. The disadvantage is that the fluctuation of the charging voltage on the capacitor caused by the fluctuation of the battery voltage during the use of the electric vehicle is not considered. This fluctuation will affect the calculation accuracy of the insulation resistance and cause the system to make a misjudgment. Moreover, because the calculation method requires the microprocessor to calculate the insulation resistance, the impedance value can be obtained. Therefore, the calculation method is more complicated and the protection action of the system is slow, which cannot timely prevent circuit damage and protect personnel safety. In addition, if the detection process needs to use the main power supply, the frequent operation will affect the mileage of the electric vehicle.

Therefore, how to design an insulation resistance detection system for electric vehicles and its insulation resistance detection method to detect the insulation condition between the positive electrode of the battery and the grounding point of the equipment, and the path between the negative electrode of the battery and the grounding point of the equipment. Insulation condition, fast detection process and energy saving are a major subject that the author of this project intends to study.

In order to solve the above problems, the present invention provides an insulation resistance detection system for an electric vehicle to overcome the problems of the prior art. The insulation resistance detection system is used to detect the positive insulation resistance between the positive pole of the battery of the electric vehicle and the grounding point of the equipment, and the negative insulation resistance between the negative pole of the battery and the grounding point of the equipment. The insulation resistance detection system includes a negative pole detection circuit, Positive detection circuit and control unit. The negative electrode detection circuit is connected in parallel with the battery, and includes a first charging and discharging circuit and a first current limiting resistor. The first current limiting resistor is coupled between the ground point of the device and the negative electrode, and the first charging and discharging circuit includes a first charging circuit and a first discharging circuit. The first charging circuit includes a first capacitor and a first switch. The first capacitor is coupled between the positive electrode and the ground point of the device, the first switch is coupled between the positive electrode and the first capacitor, and the first discharge circuit is connected in parallel with the first capacitor. The positive electrode detection circuit is connected in parallel with the battery, and includes a second charging and discharging circuit and a second current limiting resistor. The second current limiting resistor is coupled between the ground point of the device and the positive electrode, and the second charging and discharging circuit includes a second charging circuit and a second discharging circuit. The second charging circuit includes a second capacitor and a second switch. The second capacitor is coupled between the negative electrode and the device ground point, the second switch is coupled between the negative electrode and the second capacitor, and the second discharge circuit is connected in parallel with the second capacitor. The control unit periodically turns on the first charging circuit to charge the first capacitor, periodically turns on the first discharge circuit to discharge the first capacitor, periodically turns on the second charging circuit to charge the second capacitor, and periodically turns on the first capacitor. Two discharge circuits discharge the second capacitor. The first capacitor voltage is generated when the first capacitor is charged, and the second capacitor voltage is generated when the second capacitor is charged. The first charging circuit and the second discharging circuit are turned on at the same time, the second charging circuit and the first discharging circuit are turned on at the same time, and the first charging circuit and the second charging circuit are not turned on at the same time. The control unit judges whether the negative electrode insulation resistance is abnormal according to the first capacitor voltage and the battery voltage of the battery, and judges whether the positive electrode insulation resistance is abnormal according to the second capacitor voltage and the battery voltage.

In order to solve the above problems, the present invention provides an insulation resistance detection method for an electric vehicle to overcome the problems of the prior art. The insulation resistance detection method uses an insulation resistance detection system to detect the positive insulation resistance from the positive pole of the battery of the electric vehicle to the grounding point of the equipment, and detects the negative insulation resistance from the negative pole of the battery to the grounding point of the equipment. The insulation resistance detection system includes a negative pole detection circuit and a positive pole. A detection circuit; the negative detection circuit includes a first capacitor, and the positive detection circuit includes a second capacitor. The insulation resistance detection method includes: measuring the battery voltage of the battery; periodically charging and discharging the first capacitor, and obtaining the first capacitor voltage when the first capacitor is charged; periodically charging and discharging the second capacitor, and obtaining The second capacitor voltage when the second capacitor is charged; wherein the steps of periodically charging and discharging the first capacitor and periodically charging and discharging the second capacitor include: when charging the first capacitor, simultaneously charging the second capacitor The capacitor discharges; and when the first capacitor is discharged, the second capacitor is charged at the same time; wherein the charging and discharging time are the same; calculating the negative electrode insulation resistance according to the first capacitor voltage and the battery voltage is less than the first predetermined resistance range, and judging that the negative electrode insulation resistance The resistance is abnormal; and the positive insulation resistance calculated according to the second capacitor voltage and the battery voltage is less than the second predetermined resistance range, and it is determined that the positive insulation resistance is abnormal.

The main purpose and effect of the present invention is that the insulation resistance detection system can detect the insulation condition between the positive electrode and the negative electrode of the battery and the path from the negative electrode to the grounding point of the device by periodically charging and discharging the negative electrode detection circuit and the positive electrode detection circuit, so as to prevent the battery from leaking. It can cause electric shocks to people, avoid continuous detection that consumes battery power and affect the mileage of electric vehicles, and the detection process is fast and timely, which can improve the efficacy of safety.

In order to further understand the technology, means and effect adopted by the present invention to achieve the predetermined purpose, please refer to the following detailed description and accompanying drawings of the present invention. For specific understanding, however, the accompanying drawings are only provided for reference and description, and are not intended to limit the present invention.

Hereby, the technical content and detailed description of the present invention are described as follows in conjunction with the drawings:

Please refer to FIG. 1 , which is a schematic block diagram of an insulation resistance detection system for an electric vehicle according to the present invention. The insulation resistance detection system 1 is used to detect the positive insulation resistance RP between the positive pole 200+ of the battery 200 and the equipment grounding point GND of the electric vehicle 300 , and also detect the equipment from the negative pole 200 of the battery 200 - to the electric vehicle 300 Negative insulation resistance RN between ground points GND. The electric vehicle 300 may be a mobile device powered by a battery (eg, but not limited to, an electric boat, an electric vehicle, etc.). Specifically, the battery 200 is usually installed in an accommodating space of the electric vehicle 300 , such as a battery slot. Since the path between the battery slot and the device ground point GND may cause poor insulation due to environmental or time factors, the power of the battery 200 after the battery 200 is installed may cause a risk of leakage through this path. Therefore, the insulation resistance detection system 1 is used to detect the insulation condition between the battery 200 and the ground point GND of the equipment (usually to detect the impedance from the chassis of the electric vehicle 300 to the ground point GND of the equipment), so as to prevent the power of the battery 200 from being damaged due to poor insulation of the equipment. A situation that causes leakage of electricity to endanger personnel and system safety.

Referring back to FIG. 1 , the insulation resistance detection system 1 includes a negative electrode detection circuit 10 , a positive electrode detection circuit 20 and a control unit 30 . The negative electrode detection circuit 10 is connected in parallel with the battery 200 , and includes a first charging and discharging circuit 12 and a first current limiting resistor REN. The first current limiting resistor REN is coupled between the device ground GND and the negative electrode 200-. The positive electrode detection circuit 20 is connected in parallel with the battery 200, and includes a second charging and discharging circuit 22 and a second current limiting resistor RPE. The second current limiting resistor RPE is coupled between the device ground GND and the positive electrode 200+. The control unit 30 is coupled to the battery 200 , the first charging and discharging circuit 12 and the second charging and discharging circuit 22 . Both the first charging and discharging circuit 12 and the second charging and discharging circuit 22 have built-in capacitors. The control unit 30 controls the first charging and discharging circuit 12 to charge and discharge periodically, so that the first charging and discharging circuit 12 generates a first capacitor voltage VC1 when charging. , and control the second charging and discharging circuit 22 to periodically charge and discharge, so that the second charging and discharging circuit 22 generates a second capacitor voltage VC2 when charging.

The control unit 30 determines whether the equivalent negative insulation resistance RN (hereinafter referred to as negative insulation resistance RN) of the path between the negative pole 200 and the equipment ground point GND is abnormal according to the first capacitor voltage VC1 and the battery voltage VPN, and according to the second capacitance voltage VC2 Determine whether the equivalent positive insulation resistance RP (hereinafter referred to as positive insulation resistance RP) of the path between the positive pole 200+ and the equipment ground point GND is abnormal with the battery voltage VPN. When the negative electrode insulation resistance RN is abnormal, it means that the path between the negative electrode 200 of the battery 200 and the equipment grounding point GND is poorly insulated, resulting in a leakage current. When the positive electrode insulation resistance RP is abnormal, it means that the path between the positive electrode 200+ of the battery 200 and the equipment grounding point GND is poorly insulated, resulting in a leakage current.

The insulation resistance detection system 1 further includes a battery detection circuit 40 , a first detection circuit 42 and a second detection circuit 44 . The battery detection circuit 40 is coupled to the battery 200 and the control unit 30, and is used to detect the battery voltage VPN and accordingly provide the battery voltage signal Sbv to the control unit 30, so that the control unit 30 can know the magnitude of the battery voltage VPN according to the battery voltage signal Sbv. The first detection circuit 42 is coupled to the first charging and discharging circuit 12, and is used for detecting the first capacitor voltage VC1 and correspondingly providing the first voltage signal Sv1 to the control unit 30, so that the control unit 30 can know the first voltage signal Sv1 according to the first voltage signal Sv1. The size of a capacitor voltage VC1. The second detection circuit 44 is coupled to the second charging and discharging circuit 22, and is used to detect the second capacitor voltage VC2 and accordingly provide the second voltage signal Sv2 to the control unit 30, so that the control unit 30 can know the second voltage signal Sv2 according to the second voltage signal Sv2. The size of the two capacitor voltage VC2. The battery detection circuit 40 , the first detection circuit 42 and the second detection circuit 44 may be coupled to the battery 200 in series or in parallel.

The insulation resistance detection system 1 further includes at least one circuit breaker unit 50, and the circuit breaker unit 50 is coupled on the path between the battery 200 and the electric vehicle 300, and can be coupled on the path from the positive electrode 200+ to the electric vehicle 300 or the negative electrode 200- On the path to the electric vehicle 300, or both (as shown in FIG. 1). The control unit 30 provides the protection signal Sp to the corresponding circuit breaker unit 50 according to the abnormality of the negative electrode insulation resistance RN or the abnormality of the positive electrode insulation resistance RP, so as to form a circuit breaker between the battery 200 and the electric vehicle 300 by turning off the circuit breaker unit 50, thereby providing The function of leakage protection. When the insulation resistance detection system 1 determines that both the negative insulation resistance RN and the positive insulation resistance RP are normal, the control unit 30 turns on the disconnecting unit 50 so that the battery voltage VPN can be supplied to the electric vehicle 300 .

Please refer to FIG. 2 , which is a schematic block diagram of a preferred embodiment of the insulation resistance detection system of the present invention, and refer to FIG. 1 in combination. The first charging and discharging circuit 12 includes a first charging circuit 121 and a first discharging circuit 122, and the first charging circuit 121 includes a first switch S1 and a first capacitor C1. The first switch S1 is coupled to the positive electrode 200+ and the first capacitor C1, and the first capacitor C1 is coupled to the first switch S1 and the device ground GND. The positions of the first capacitor C1 and the first switch S1 can be replaced with each other, and the first discharge circuit 122 and the first detection circuit 42 are connected in parallel with the first capacitor C1 . The second charging and discharging circuit 22 includes a second charging circuit 221 and a second discharging circuit 222, and the second charging circuit 221 includes a second switch S2 and a second capacitor C2. The second switch S2 is coupled to the negative electrode 200- and the second capacitor C2, and the second capacitor C2 is coupled to the second switch S2 and the device ground GND. Similarly, the positions of the second capacitor C2 and the second switch S2 can also be interchanged, and the second discharge circuit 222 and the second detection circuit 44 are connected in parallel with the second capacitor C2.

A preferred implementation of the first discharge circuit 122 and the second discharge circuit 222 is that the first discharge circuit 122 includes a third switch S3 and a first discharge resistor R1, and the second discharge circuit 222 includes a fourth switch S4 and a second discharge Resistor R2. The third switch S3 is coupled to one end of the first capacitor C1, the first discharge resistor R1 is connected in series with the third switch S3, and the first discharge resistor R1 is coupled to the other end of the first capacitor C1. The fourth switch S4 is coupled to one end of the second capacitor C2, the second discharge resistor R2 is connected in series with the fourth switch S4, and the second discharge resistor R2 is coupled to the other end of the second capacitor C2. The positions of the third switch S3 and the first discharge resistor R1 can be replaced with each other, and the positions of the fourth switch S4 and the second discharge resistor R2 can be replaced with each other.

The control unit 30 provides the first control signal Sc1 to control the first switch S1 to be turned on or off, provides the second control signal Sc2 to control the second switch S2 to be turned on or off, and provides the third control signal Sc3 to control the third switch S3 to be turned on or off, and the fourth control signal Sc4 is provided to control the fourth switch S4 to be turned on or off. The first control signal Sc1 and the third control signal Sc3 are complementary control signals, so that the first capacitor C1 is charged and discharged respectively. The second control signal Sc2 and the fourth control signal Sc4 are complementary control signals, so that the second capacitor C2 is charged and discharged respectively. The first control signal Sc1 and the second control signal Sc2 may be complementary control signals. That is, the control unit 30 simultaneously provides the first control signal Sc1 and the fourth control signal Sc4 to control the first charging circuit 121 and the second discharging circuit 222 to be turned on at the same time. The control unit 30 simultaneously provides a second control signal Sc2 complementary to the fourth control signal Sc4 and a third control signal Sc3 complementary to the first control signal Sc1 to control the second charging circuit 221 and the first discharging circuit 122 to be turned on at the same time. The first charging circuit 121 and the second charging circuit 221 are not turned on at the same time, and it is preferable to make the second capacitor C2 discharge when the first capacitor C1 is charged, and vice versa. The advantage is that the first capacitor C1 and the second capacitor C2 can be charged and discharged alternately (ie, when one is being charged, the other is being discharged). Thereby, the efficiency of the detection speed of the insulation resistance detection system 1 can be improved to simplify the process and reduce the energy consumption of the system, especially the above-mentioned embodiment in which the battery 200 is directly used as the power supply device. In addition, the control signals Sc1 to Sc4 may have a fixed time period, so that the control unit 30 can periodically detect. Since the control signals Sc1 ˜ Sc4 can have a fixed time period, the charging and discharging time of the first capacitor C1 is the same as the charging and discharging time of the second capacitor C2 .

Referring back to FIG. 2 , when the control unit 30 controls the first switch S1 to be turned on and the third switch S3 to be turned off, the battery voltage VPN will charge the first capacitor C1 to generate the first charging path Lc1 . The first charging path Lc1 is a closed path formed by the battery 200 , the first switch S1 , the first capacitor C1 and the first current limiting resistor REN. Among them, since the first current limiting resistor REN is designed to be much smaller than the resistance value of the negative electrode insulation resistance RN (in normal state), the current flowing through the negative electrode insulation resistance RN is negligible, and equivalently, there is no current path. When the control unit 30 controls the first switch S1 to be turned off, and controls the third switch S3 to be turned on, the first capacitor C1 will discharge to generate the first discharge path Ld1. The first discharge path Ld1 is a closed path 3 formed by the first capacitor C1 , the first discharge resistor R1 and the third switch S. Wherein, the control unit 30 of the insulation resistance detection system 1 controls the turn-on or turn-off of the second switch S2 and the fourth switch S4 to generate the control method and path structure of the second charging path Lc2 and the second discharging path Ld2, which are similar. The first charging path Lc1 and the first discharging path Ld1 described above will not be repeated here.

Further, in order to prevent the battery voltage VPN from being consumed too much in the detection process of the insulation resistance detection system 1, the endurance of the electric vehicle 300 will be greatly reduced. Therefore, the design of the first current limiting resistor REN must be maintained at a relatively large resistance value to reduce the current flowing through the first charging path Lc1 during detection. However, in order to avoid that the charging speed of the first capacitor voltage VC1 is too slow or the charging amount is too small, making it difficult for the control unit 30 to determine whether the negative electrode insulation resistance RN is abnormal according to the first capacitor voltage VC1, the resistance value of the first current limiting resistor REN is designed to be It should not be too large, so the preferred embodiment is to set the resistance value at the MΩ level. In addition, since the resistance value of the first discharge resistor R1 is designed with respect to the discharge speed of the first capacitor C1, that is, the smaller the first discharge resistor R1 is (even if the first discharge resistor R1 is not installed), the faster the discharge speed of the first capacitor C1 is. Fast, ideally, it can be completely discharged within a predetermined time, so that the charging of the first capacitor C1 in the next detection period starts from 0 potential, which increases the detection accuracy of the insulation resistance detection system 1 . However, when the resistance value of the first discharge resistor R1 is too small, the current flowing through the first discharge path Ld1 will be too large, so it is necessary to improve the current withstand specification of the third switch S3, which increases the circuit cost. Therefore, the first discharge resistor R1 The design of the resistance value should not be too small, so the preferred embodiment is to set the resistance value of the KΩ level. The design of the resistance values of the second current limiting resistor RPE and the second discharging resistor R2 is also considered in the same way, that is, the second current limiting resistor RPE is preferably set to a resistance value of MΩ level, and the second discharging resistor R2 is relatively In the preferred embodiment, the resistance value is set to the KΩ level, which will not be repeated here.

Please refer to FIG. 3 for a flowchart of the method for detecting the insulation resistance of an electric vehicle according to the present invention, and refer to FIGS. 1 to 2 in combination. The insulation resistance detection method includes measuring the battery voltage VPN of the battery 200 disposed in the electric vehicle 300 ( S100 ). The control unit 30 obtains the magnitude of the battery voltage VPN through the battery voltage signal Sbv measured and obtained by the battery detection circuit 40 . Then, the first capacitor C1 is periodically charged and discharged, and the first capacitor voltage VC1 when the first capacitor C1 is charged is obtained ( S120 ). The control unit 30 periodically controls the turn-on and turn-off of the first switch S1 and the third switch S3, so that the first capacitor C1 is periodically charged and discharged to generate a first capacitor voltage VC1 during charging, and the first capacitor C1 is charged and discharged through the first capacitor C1. The magnitude of the first capacitor voltage VC1 is known from the first voltage signal Sv1 measured by the detection circuit 42 . Then, the second capacitor C2 is periodically charged and discharged, and the second capacitor voltage VC2 when the second capacitor C2 is charged is obtained ( S140 ). The control unit 30 periodically controls the turn-on and turn-off of the second switch S2 and the fourth switch S4, so that the second capacitor C2 is periodically charged and discharged to generate the second capacitor voltage VC2 during charging, and the second capacitor C2 is charged and discharged through the second capacitor C2. The magnitude of the second capacitor voltage VC2 is known from the second voltage signal Sv2 measured by the detection circuit 44 .

Then, according to the first capacitor voltage VC1 and the battery voltage VPN, it is determined whether the negative electrode insulation resistance RN is abnormal (S160). The control unit 30 determines whether the negative electrode insulation resistance RN of the path between the negative electrode 200 and the device grounding point GND is abnormal according to the first capacitor voltage VC1 and the battery voltage VPN. When the negative electrode insulation resistance RN is abnormal, it means that the path between the negative electrode 200 of the battery 200 and the equipment grounding point GND is poorly insulated, resulting in a leakage current. Then, according to the second capacitor voltage VC2 and the battery voltage VPN, it is determined whether the positive electrode insulation resistance RP is abnormal (S180). The control unit 30 determines whether the positive insulation resistance RP of the path between the positive electrode 200+ and the equipment ground point GND is abnormal according to the second capacitor voltage VC2 and the battery voltage VPN. When the positive electrode insulation resistance RP is abnormal, it means that the path between the positive electrode 200+ of the battery 200 and the equipment ground point GND is poorly insulated, resulting in a leakage current. Finally, the battery 200 and the electric vehicle 300 are controlled to be disconnected according to the abnormality of the negative electrode insulation resistance RN or the abnormality of the positive electrode insulation resistance RP ( S200 ). When the insulation resistance detection system 1 determines that the negative insulation resistance RN and the positive insulation resistance RP are normal, the control unit 30 turns on the circuit breaker unit 50 so that the battery voltage VPN can be supplied to the electric vehicle 300 . On the contrary, the corresponding circuit breaking unit 50 is turned off to provide the function of leakage protection.

Please refer to FIG. 4A , which is a method flowchart of the first embodiment of the insulation resistance detection method of the present invention, and refer to FIGS. 1 to 3 in combination. Using the first capacitor voltage VC1 and the second capacitor voltage VC2 to determine whether the insulation resistance is abnormal can include three determination methods. The process shown in FIG. 4A is the first determination method. The steps include: measuring the battery voltage VPN of the battery 200 (S300). Then, the first switch S1 and the fourth switch S4 are turned on, and the second switch S2 and the third switch S3 are turned off (S320). When the control unit 30 controls the first switch S1 and the fourth switch S4 to be turned on, the first capacitor C1 is charged and the second capacitor C2 is discharged. Then, the first capacitor voltage VC1 is measured (S340). Then, the second switch S2 and the third switch S3 are turned on, and the first switch S1 and the fourth switch S4 are turned off (S360). When the control unit 30 controls the second switch S2 and the third switch S3 to be turned on, the second capacitor C2 is charged and the first capacitor C1 is discharged. Then, the second capacitor voltage VC2 is measured (S380). Finally, it returns to step (S300) to perform the detection of the next cycle.

When the step (S340) is completed, the negative electrode insulation resistance RN can be recalculated (S400). The control unit 30 uses the first capacitor voltage VC1 and the battery voltage VPN to calculate the current negative electrode insulation resistance RN, and the negative electrode insulation resistance RN can be calculated by the formula of capacitor charge and discharge or obtained by searching a pre-made first capacitor voltage and battery voltage correspondence table. . When the step (S380) is completed, the anode insulation resistance RP may be recalculated (S420). The control unit 30 uses the second capacitor voltage VC2 and the battery voltage VPN to calculate the current positive electrode insulation resistance RP, and the positive electrode insulation resistance RP can be calculated by the formula of capacitor charge and discharge or obtained by searching a pre-made corresponding table between the second capacitor voltage and the battery voltage. . Then, it is judged whether the insulation resistance RN or RP is within a predetermined resistance range (S440). The control unit 30 obtains the current negative electrode insulation resistance RN by calculation in step ( S400 ), and determines whether the resistance value of the current negative electrode insulation resistance RN is within a preset first predetermined resistance range. When the current resistance value of the negative electrode insulation resistance RN is not within the preset first predetermined resistance range, a protection action is performed (S460). Wherein, when the insulation resistance detection system 1 determines that the current resistance value of the negative insulation resistance RN is not within the preset first predetermined resistance range, the control unit 30 turns off the circuit breaking unit 50 to provide a leakage protection function. Wherein, in step (S420), the control unit 30 obtains the current resistance value of the positive insulation resistance RP by calculation, and can also judge whether the resistance value is within the preset second predetermined resistance range, and the judgment method adopted is also the same. This will not be repeated here.

It is worth mentioning that the setting of the first predetermined resistance range and the second predetermined resistance range may be the resistance values of the negative insulation resistance RN and the positive insulation resistance RP measured in advance under the condition of good insulation of the electric vehicle 300, The resistance value is added with positive and negative percentages to make a preset range. Alternatively, the specified resistance values of the negative electrode insulation resistance RN and the positive electrode insulation resistance RP are obtained from the specification table of the electric vehicle 300 , and then the resistance values are added with positive and negative percentages to form a preset range.

Please refer to FIG. 4B for a method flowchart of the second embodiment of the insulation resistance detection method of the present invention, and refer to FIGS. 1 to 4A in combination. The step of FIG. 4B includes measuring the battery voltage VPN of the battery 200 ( S500 ). Then, the first switch S1 and the fourth switch S4 are turned on, and the second switch S2 and the third switch S3 are turned off (S520). When the control unit 30 controls the first switch S1 and the fourth switch S4 to be turned on, and controls the second switch S2 and the third switch S3 to be turned off, the first capacitor C1 is charged and the second capacitor C2 is discharged. Then, the first capacitor voltage VC1 is measured (S540). Then, it is determined whether the negative electrode insulation resistance RN is abnormal according to the threshold voltage Vth and the first capacitor voltage VC1 (S560). Wherein, in step (S500), the battery voltage VPN is scaled down to calculate the threshold voltage Vth (S580), and the threshold voltage Vth is provided to the step (S560) for use, that is, the control unit 30 proportionally scales the battery voltage VPN The threshold voltage Vth is calculated by scaling down, and then the threshold voltage Vth is compared with the first capacitor voltage VC1 to determine whether the negative electrode insulation resistance RN is abnormal. Then, when the control unit 30 determines that the negative electrode insulation resistance RN is abnormal, a protection operation is performed (S600). When the insulation resistance detection system 1 determines that the negative insulation resistance RN is abnormal, the control unit 30 turns off the circuit breaking unit 50 to provide the function of leakage protection. Among them, the above-mentioned "scale reduction" is a preferred embodiment, but not limited thereto, and it can be scaled up or down according to actual needs.

Further, the determination method of FIG. 4B is to determine whether the leakage of the insulation resistance is determined by using whether the charging amount of the fixed charging time is sufficient to charge the capacitor voltage to the threshold voltage. The control unit 30 sets the period from the first switch S1 to the first predetermined time as the first charging period, and determines the negative electrode according to whether the first capacitor C1 can be charged to the threshold voltage Vth during the first charging period Whether the insulation resistance RN is abnormal. When the first capacitor C1 can be charged to reach or exceed the threshold voltage Vth during the first charging period, it means that the negative electrode insulation resistance RN is abnormal, and the process proceeds to step ( S600 ). Otherwise, go to step (S620). Among them, when the negative electrode insulation resistance RN is abnormal, its resistance value becomes too small, so that the power of the battery 200 bypasses the first charging path Lc1 formed by the first current limiting resistor REN, and the battery 200, the first switch S1, The other charging paths of the first capacitor C1 and the negative electrode insulation resistance RN make the first capacitor C1 charge faster than expected. It is worth mentioning that the methods of detecting and judging the abnormality of the positive insulation resistance RP shown in other steps ( S620 ) to ( S660 ) in FIG. 4B are similar to those of steps ( S520 ) to ( S560 ), which are not described here. In addition, steps ( S620 ) to ( S660 ) and steps ( S520 ) to ( S560 ) can be reversed in two groups, that is, the positive insulation resistance RP is detected first, and then the negative insulation resistance RN is detected.

Please refer to FIG. 4C for a method flowchart of the third embodiment of the insulation resistance detection method of the present invention, and refer to FIGS. 1 to 4B in combination. The step of FIG. 4C includes measuring the battery voltage VPN of the battery 200 ( S700 ). Then, the first switch S1 and the fourth switch S4 are turned on, and the second switch S2 and the third switch S3 are turned off (S720). When the control unit 30 controls the first switch S1 and the fourth switch S4 to be turned on, and controls the second switch S2 and the third switch S3 to be turned off, the first capacitor C1 is charged and the second capacitor C2 is discharged. Then, measure the first capacitor voltage VC1 (S740). Then, the second switch S2 and the third switch S3 are turned on, and the first switch S1 and the fourth switch S4 are turned off (S760). When the control unit 30 controls the second switch S2 and the third switch S3 to be turned on, and controls the first switch S1 and the fourth switch S4 to be turned off, the second capacitor C2 is charged and the first capacitor C1 is discharged. Then, the second capacitor voltage VC2 is measured (S780).

Then, take the larger of the first capacitor voltage VC1 and the second capacitor voltage VC2 and compare the threshold voltage Vth ( S800 ). The control unit 30 compares the voltage peak value of the first capacitor voltage VC1 and the voltage peak value of the second capacitor voltage VC2, and selects the relatively higher one of the two voltage peak values for comparison with the threshold voltage Vth. Since the voltage peak value of the capacitor voltage is larger, it means that the resistance value of the corresponding insulation resistance RN or RP is smaller, so the situation of poor insulation is more likely to occur. In step ( S700 ), the battery voltage is scaled down to calculate the threshold voltage Vth ( S820 ), and the threshold voltage Vth is provided to the step ( S800 ) for use. Then, according to the comparison result of the comparison step (S800), it is determined whether at least one of the insulation resistances is abnormal (S840). When the judgment result is "Yes", the protection action is performed (S860); when the judgment result is "No", the process returns to step (S700) to perform the next cycle of detection. For example, but not limited to, the control unit 30 selects the corresponding first capacitor voltage VC1 to compare the threshold voltage Vth according to the voltage peak value of the first capacitor voltage VC1 is greater than the voltage peak value of the second capacitor voltage VC2, and when the first capacitor voltage VC1 is greater than the threshold value When the voltage is Vth, it is judged that the negative electrode insulation resistance RN is abnormal, and the process proceeds to step (S860); otherwise, the process proceeds to step (S700).

It is worth mentioning that in FIGS. 4A to 4C , since the battery 200 is being consumed during detection, the battery voltage VPN will gradually decrease. Therefore, the battery voltage VPN and the threshold voltage Vth are not fixed values, and the threshold voltage Vth The size will vary with the size of the battery voltage VPN. In addition, since the charging of the capacitor is an exponential curve. When the capacitor is nearly fully charged, the change of the capacitor voltage is small, which is less conducive to the control unit 30 to determine the insulation resistance. Therefore, it is a better embodiment to set the threshold voltage Vth at 60%-70% of the battery voltage VPN.

However, the above descriptions are only the detailed descriptions and drawings of the preferred embodiments of the present invention, but the features of the present invention are not limited thereto, and are not intended to limit the present invention. The scope of the patent shall prevail, and all embodiments that are consistent with the spirit of the scope of the patent application of the present invention and similar variations thereof shall be included in the scope of the present invention. Anyone who is familiar with the art in the field of the present invention can easily think Changes or modifications can be covered by the following patent scope of the present case.

1: Insulation resistance detection system

10: Negative detection circuit

12: The first charge and discharge circuit

121: The first charging circuit

S1: The first switch

C1: first capacitor

122: The first discharge circuit

S3: The third switch

R1: The first discharge resistor

REN: The first current limiting resistor

20: Positive detection circuit

22: Second charge and discharge circuit

221: Second charging circuit

S2: Second switch

C2: second capacitor

222: Second discharge circuit

S4: Fourth switch

R2: Second discharge resistor

RPE: Second current limiting resistor

30: Control unit

40: Battery detection circuit

42: The first detection circuit

44: Second detection circuit

50: Circuit breaker unit

200: battery

200+: positive

200-: negative pole

VPN: battery voltage

300: Electric Vehicle

GND: device ground point

RN: Negative Insulation Resistance

RP: positive insulation resistance

VC1: The first capacitor voltage

VC2: The second capacitor voltage

Sbv: battery voltage signal

Sv1: the first voltage signal

Sv2: the second voltage signal

Sp: protection signal

Sc1: The first control signal

Sc2: The second control signal

Sc3: The third control signal

Sc4: Fourth control signal

Lc1: The first charging path

Ld1: The first discharge path

Lc2: The second charging path

Ld2: Second discharge path

Vth: threshold voltage

1 is a schematic block diagram of an insulation resistance detection system for an electric vehicle according to the present invention;

2 is a schematic block diagram of a preferred embodiment of the insulation resistance detection system of the present invention;

3 is a flow chart of the method for detecting the insulation resistance of an electric vehicle according to the present invention;

4A is a flow chart of the method of the first embodiment of the insulation resistance detection method of the present invention;

4B is a method flow chart of the second embodiment of the insulation resistance detection method of the present invention; and

FIG. 4C is a flow chart of the method of the third embodiment of the insulation resistance detection method of the present invention.

1: Insulation resistance detection system

10: Negative detection circuit

12: The first charge and discharge circuit

REN: The first current limiting resistor

20: Positive detection circuit

22: Second charge and discharge circuit

RPE: Second current limiting resistor

30: Control unit

40: Battery detection circuit

42: The first detection circuit

44: Second detection circuit

50: Circuit breaker unit

200: battery

200+: positive

200-: negative pole

VPN: battery voltage

300: Electric Vehicle

GND: device ground point

RN: Negative Insulation Resistance

RP: positive insulation resistance

VC1: The first capacitor voltage

VC2: The second capacitor voltage

Sbv: battery voltage signal

Sv1: the first voltage signal

Sv2: the second voltage signal

Sp: protection signal

Claims (10)

An insulation resistance detection system for an electric vehicle is used to detect a positive insulation resistance between a positive pole of a battery of an electric vehicle and a grounding point of an equipment, and detect a negative pole of the battery to the grounding point of the equipment Between a negative insulation resistance, the insulation resistance detection system includes: A negative electrode detection circuit is connected in parallel with the battery, and includes a first charging and discharging circuit and a first current limiting resistor; the first current limiting resistor is coupled between the ground point of the device and the negative electrode, and the first charging and discharging circuit is The circuit includes: A first charging circuit, comprising: a first capacitor coupled between the positive electrode and the device ground; and a first switch coupled between the positive electrode and the first capacitor; and a first discharge circuit, connected in parallel with the first capacitor; A positive electrode detection circuit is connected in parallel with the battery, and includes a second charge and discharge circuit and a second current limiting resistor; the second current limiting resistor is coupled between the ground point of the device and the positive electrode, and the second charge and discharge circuit The circuit includes: A second charging circuit, comprising: a second capacitor coupled between the negative electrode and the device ground; and a second switch coupled between the negative electrode and the second capacitor; and a second discharge circuit in parallel with the second capacitor; and a control unit for periodically turning on the first charging circuit to charge the first capacitor, periodically turning on the first discharging circuit to discharge the first capacitor, and periodically turning on the second charging circuit to charge the second capacitor charging, and periodically turning on the second discharge circuit to discharge the second capacitor; Wherein, a first capacitor voltage is generated when the first capacitor is charged, and a second capacitor voltage is generated when the second capacitor is charged; Wherein, the first charging circuit and the second discharging circuit are turned on at the same time, the second charging circuit and the first discharging circuit are turned on at the same time, and the first charging circuit and the second charging circuit are not turned on at the same time; The control unit judges whether the negative electrode insulation resistance is abnormal according to the first capacitor voltage and a battery voltage of the battery, and judges whether the positive electrode insulation resistance is abnormal according to the second capacitor voltage and the battery voltage. The insulation resistance detection system of claim 1, wherein the first discharge circuit comprises: a third switch; and a first discharge resistor connected in series with the third switch; Wherein, the battery, the first switch, the first capacitor and the first current limiting resistor form a first charging path for charging the first capacitor when the first switch is turned on and the third switch is turned off, and The first capacitor, the third switch and the first discharge resistor form a first discharge path for discharging the first capacitor when the third switch is turned on and the first switch is turned off; and Wherein, the second discharge circuit includes: a fourth switch; and a second discharge resistor connected in series with the fourth switch; Wherein, the battery, the second switch, the second capacitor and the second current limiting resistor form a second charging path for charging the second capacitor when the second switch is turned on and the fourth switch is turned off, and The second capacitor, the fourth switch and the second discharge resistor form a second discharge path for discharging the second capacitor when the fourth switch is turned on and the second switch is turned off. The insulation resistance detection system according to claim 2, wherein the resistance value of the first current limiting resistor is set to the MΩ level, and the resistance value of the first discharge resistor is set to the KΩ level, so that the discharge speed of the first capacitor is greater than charging speed; and The resistance value of the second current limiting resistor is set to MΩ level, and the resistance value of the second discharge resistor is set to KΩ level, so that the discharge speed of the second capacitor is faster than the charging speed. The insulation resistance detection system of claim 1, wherein the control unit provides a first control signal to control the first switch to be turned on or off, provides a second control signal to control the second switch to be turned on or off, and provides A third control signal complementary to the first control signal controls the first discharge circuit to be turned on or off, and a fourth control signal complementary to the second control signal is provided to control the second discharge circuit to be turned on or off, Wherein, the first control signal and the second control signal are complementary signals, and the turn-on or turn-off times of the switches are the same. The insulation resistance detection system as claimed in claim 1, further comprising: a circuit breaker unit, coupled to the battery and the electric vehicle; Wherein, the control unit turns off the circuit breaking unit according to the abnormality of the negative electrode insulation resistance or the abnormality of the positive electrode insulation resistance, so as to disconnect the battery from the electric vehicle. An insulation resistance detection method for an electric vehicle, using an insulation resistance detection system to detect a positive pole insulation resistance of a battery of an electric vehicle to a ground point of a device, and to detect a negative pole of the battery to the equipment A negative electrode insulation resistance at the ground point, the insulation resistance detection system includes a negative electrode detection circuit and a positive electrode detection circuit, the negative electrode detection circuit includes a first capacitor, the positive electrode detection circuit includes a second capacitor, and the insulation resistance detection method includes : measuring a battery voltage of the battery; Periodically charge and discharge the first capacitor, and obtain a first capacitor voltage when the first capacitor is charged; Periodically charge and discharge the second capacitor, and obtain a second capacitor voltage when the second capacitor is charged; The steps of periodically charging and discharging the first capacitor and periodically charging and discharging the second capacitor include: When the first capacitor is charged, the second capacitor is simultaneously discharged; and When discharging the first capacitor, simultaneously charging the second capacitor; The charging and discharging time are the same; According to the first capacitor voltage and the battery voltage, it is calculated that the negative electrode insulation resistance is less than a first predetermined resistance range, and it is determined that the negative electrode insulation resistance is abnormal; and According to the second capacitor voltage and the battery voltage, it is calculated that the positive electrode insulation resistance is less than a second predetermined resistance range, and it is determined that the positive electrode insulation resistance is abnormal. The method for detecting insulation resistance according to claim 6, further comprising: calculating a threshold voltage from the battery voltage in a ratio; According to the first capacitor voltage reaching the threshold voltage, it is determined that the negative electrode insulation resistance is less than the first predetermined resistance range, and then it is determined that the negative electrode insulation resistance is abnormal; and According to the second capacitor voltage reaching the threshold voltage, it is determined that the positive electrode insulation resistance is smaller than the second predetermined resistance range, and then it is determined that the positive electrode insulation resistance is abnormal. The method for detecting insulation resistance according to claim 7, further comprising: judging that the negative electrode insulation resistance is abnormal according to the charging of the first capacitor to the threshold voltage within a first charging period; and It is determined that the positive electrode insulation resistance is abnormal according to the second capacitor being charged to reach the threshold voltage within a second charging period. The method for detecting insulation resistance according to claim 7, further comprising: selecting a larger one to compare with the threshold voltage according to the voltage peak value of the first capacitor voltage and the voltage peak value of the second capacitor voltage; and According to the capacitor voltage corresponding to the larger voltage peak value being greater than the threshold voltage, it is determined that at least one of the negative electrode insulation resistance and the positive electrode insulation resistance is abnormal, and a protection action is performed. The method for detecting insulation resistance according to claim 6, wherein the ratio is 60% to 70%.

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