CN111398856A - Quick accurate insulation detection circuit - Google Patents
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- CN111398856A CN111398856A CN202010302419.8A CN202010302419A CN111398856A CN 111398856 A CN111398856 A CN 111398856A CN 202010302419 A CN202010302419 A CN 202010302419A CN 111398856 A CN111398856 A CN 111398856A
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
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Abstract
The invention relates to the technical field of motor controllers and photovoltaic inverters for new energy vehicles, in particular to a quick and accurate insulation detection circuit which comprises a positive insulation resistor, a negative insulation resistor, a first-stage bus differential amplification circuit, a first-stage half bus differential amplification circuit, a second-stage bus differential amplification circuit and a second-stage half bus differential amplification circuit, wherein the positive insulation resistor, the negative insulation resistor, the first-stage bus differential discharge circuit and the first-stage half bus differential amplification circuit are connected, the first-stage bus differential discharge circuit is connected with the second-stage bus differential discharge circuit, and the first-stage half bus differential amplification circuit is connected with the second-stage half bus differential amplification circuit. According to the invention, the short circuit and the insulation abnormity of the PE by the equipment can be rapidly and accurately detected by detecting the bus voltage and the half bus voltage of the equipment in real time and a corresponding software control strategy.
Description
Technical Field
The invention relates to the technical field of motor controllers and photovoltaic inverters for new energy vehicles, in particular to a quick and accurate insulation detection circuit.
Background
With the popularization of new energy vehicles and the popularization of renewable energy photovoltaic power generation, the three-phase inverter is fully applied in the two industries, the motor controller for the new energy vehicle and the front-stage power supply of the photovoltaic inverter for photovoltaic power generation are matched with the battery, and the battery has the possibility of liquid leakage; the output cable of the motor controller and the corresponding motor load also have the problems of skin breaking and abnormal insulation of the winding to the ground, so that the inverter is applied to the two fields, and insulation detection is necessary to be matched. At present, the battery end of the whole vehicle can be matched with an insulation detector, as shown in fig. 1, the detection is limited by the limitation of detection topology, the real-time performance of detection is difficult to guarantee, the response time is basically about 10s, particularly, in order to solve the problem of EMI, a Y capacitor for PE is added at the input end of a bus, and the capacitance value of the Y capacitor added at the moment influences the detection precision and the response time of the insulation resistance value to different degrees. However, due to the existence of the Y capacitor of the inverter, when the bus or the output is abnormal to ground, we need fast and accurate protection, otherwise, when a single-end or multi-end short circuit to ground occurs, a loop can be formed through the Y capacitor, because the magnitude of the loop current is determined by the loop impedance, when the short circuit to ground occurs and the insulation resistance value is very low, the loop current value will be very large, at this time, the fault may be enlarged, if the fault is not responded in time, more serious accidents such as fire may be caused, and therefore, it is imperative to fast detect the insulation abnormality.
Disclosure of Invention
The present invention is directed to a fast and accurate insulation detection circuit to solve the above problems in the prior art.
In order to achieve the purpose, the invention provides the following technical scheme:
the utility model provides a quick accurate insulation detection circuit, includes positive and negative insulation resistance, first level bus differential amplifier circuit, first level half bus differential amplifier circuit, second level bus differential amplifier circuit and second level half bus differential amplifier circuit, wherein, positive and negative insulation resistance is connected with first level bus differential discharge circuit, first level half bus differential amplifier circuit, first level bus differential discharge circuit is connected with second level bus differential discharge circuit, first level half bus differential amplifier circuit is connected with second level half bus differential amplifier circuit.
Preferably, the first-stage bus differential amplification circuit comprises a PE line and a current-limiting bleeder resistor thereof, a positive bus and a current-limiting bleeder resistor thereof, the positive and negative insulation resistors comprise resistors RPE, the resistors RPE are respectively connected to the input ends of the PE line and the positive bus, the PE line is connected with the second-stage bus differential amplification circuit through a back-stage circuit, and the current-limiting bleeder resistor of the positive bus is connected with a capacitor resistor connected in parallel.
Preferably, the first-stage half-bus differential amplification circuit comprises a negative bus and a current-limiting voltage-dividing resistor thereof, the positive and negative insulation resistors comprise resistors RNE, the resistors RNE are respectively connected to the input ends of the PE line and the negative bus, the post-stage circuit comprises a first operational amplifier and a resistor thereof, a second operational amplifier and a resistor thereof, the negative input and the output ends of the first operational amplifier are connected in parallel to the PE line, the negative input and the output ends of the second operational amplifier are connected in parallel to the negative bus, and the positive inputs of the first operational amplifier and the second operational amplifier are connected with the positive bus after being connected.
Preferably, the second-stage bus differential amplification circuit comprises a third operational amplifier, a positive input of the third operational amplifier is connected with an output end of the first operational amplifier in parallel through a resistor, a positive input of the third operational amplifier is connected with a grounded capacitor and a resistor which are connected in parallel, a negative input of the third operational amplifier is connected with a resistor, a negative input and an output of the third operational amplifier are connected with a capacitor resistor which is connected in parallel, and an output of the third operational amplifier is connected with an RC filter circuit through a resistor.
Preferably, the second-stage half-bus differential amplification circuit comprises a fourth operational amplifier, the positive input of the fourth operational amplifier is connected with the output end of the second operational amplifier in parallel through a resistor, the positive input of the fourth operational amplifier is connected with a grounded capacitor and a resistor which are connected in parallel, the negative input of the fourth operational amplifier is connected with a resistor, the negative input and the output of the fourth operational amplifier are connected with a capacitor resistor which is connected in parallel, and the output of the fourth operational amplifier is connected with a grounded capacitor through a resistor.
Preferably, the device further comprises an input clamping diode connected in parallel to the output ends of the PE line, the positive bus and the negative bus.
Preferably, the output clamping diode is connected to the output of the third operational amplifier and the output of the fourth operational amplifier.
Compared with the prior art, the invention has the beneficial effects that:
the invention comprises a first-stage bus voltage difference amplifying circuit and a second-stage bus voltage difference amplifying circuit: the device comprises a PE wire, a current-limiting bleeder resistor of the PE wire, a positive current-limiting bleeder resistor of the bus, a negative current-limiting bleeder resistor of the bus, a first-stage half-bus voltage difference amplifying circuit, a second-stage half-bus voltage difference amplifying circuit and an RC filter circuit corresponding to bus detection voltage and half-bus detection voltage. Where RPE and RNE are schematic indications of the positive and negative bus to PE resistance values. The invention can quickly and accurately detect the PE short circuit and the insulation abnormity of the equipment by detecting the bus voltage and the half bus voltage of the equipment in real time and corresponding software control strategies.
Drawings
FIG. 1 is a prior art insulation detection circuit;
FIG. 2 is a circuit diagram of a first embodiment of a rapid accurate insulation detection circuit arrangement of the present invention;
FIG. 3 is a circuit diagram of a second embodiment of the rapid accurate insulation detection circuit arrangement of the present invention;
FIG. 4 is a circuit diagram of a third embodiment of the rapid accurate insulation detection circuit arrangement of the present invention;
fig. 5 is a flow chart of a method for detecting the insulation detection circuit scheme of the invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 2 to 5, the present invention provides a technical solution:
the utility model provides a quick accurate insulation detection circuit, constructs two sets of voltage detection circuit and detects equipment direct current busbar voltage and half busbar voltage respectively (can be just to PE's voltage, also can be PE to negative voltage), including PE line and current-limiting bleeder resistor R21, positive bus and current-limiting bleeder resistor R1 ~ R10, negative bus and current-limiting bleeder resistor R11 ~ R20, still include first order half busbar voltage difference partial amplification circuit and second level half busbar voltage difference partial amplification circuit and correspond busbar detected voltage and half busbar detected voltage's RC filter circuit: the capacitor C2, the resistors R22 and R23, the capacitor C240 and the resistor R34, and the capacitor R238 and the capacitor R29. Where RPE and RNE are schematic indications of the resistance of the positive and negative pairs of bus lines PE.
Fig. 2 is a circuit diagram of a first embodiment of the rapid and accurate insulation detection circuit scheme of the present invention. The two groups of voltage detection circuits are in mirror symmetry. Firstly, a sampling period is required to be appointed, the sampling period of the bus voltage and the half bus voltage is related to the switching period of the inverter bridge, the sampling period is set to be 1/2 of the switching period, namely, the bus voltage and the half bus voltage are sampled twice in one switching period, and thus, the sampling judgment can be carried out for tens of times in the millisecond time period.
Under normal conditions, half busbar voltage is about half of busbar voltage, can do real-time judgement, accurate quick through busbar voltage and half busbar voltage that real-time detection this moment.
In the abnormal condition:
first, a bus insulation abnormality is described, when an insulation abnormality or even a short circuit occurs to a positive bus or a negative bus, a detection value of a bus voltage UDC _ AD is not affected, but a value of HA L F _ UDC _ AD is far deviated from a half of the bus voltage, as shown in a circuit diagram corresponding to the first embodiment of fig. 2, when the insulation abnormality occurs to the bus, a sampling value twice in each switching period of HA L F _ UDC _ AD is very low or even 0, and when the insulation abnormality or short circuit occurs to the bus negatively, a sampling value twice in each switching period of HA L F _ UDC _ AD is very close to the bus voltage.
After the U-phase insulation abnormality occurs, it can be estimated that the detected value of the bus voltage UDC _ AD is still not affected, but the value of HA L F _ UDC _ AD changes along with the on-off of the switching tube corresponding to the U-phase inversion bridge, the sampled value of HA L F _ UDC _ AD is very close to the bus voltage when the U-phase is turned off, and the sampled value of HA L F _ UDC _ AD is very low or even 0 when the U-phase is turned on, namely the sampled value of two times in one switching period is abnormal, one time is close to the bus voltage, and the other time is close to zero.
According to the difference of the HA L F _ UDC _ AD sampling values under the two insulation abnormal conditions and the corresponding working conditions, a positive insulation abnormal counter, a negative insulation abnormal counter and an output insulation abnormal counter are respectively set, threshold values in the counters can be set according to practical application scenes and experimental conditions, filtering is achieved through the threshold values, and false alarm is avoided.
When the HA L F _ UDC _ AD sampling value is close to half of the bus voltage all the time, the sampling value is normal, namely no insulation abnormity occurs;
when two sampling values in a switching period of HA L F _ UDC _ AD are always smaller than a low value set in software, the count of the positive insulation abnormity counter is increased by 1, and positive insulation abnormity is reported when the count is accumulated to a corresponding count threshold value;
when two sampling values in a switching period of HA L F _ UDC _ AD are always larger than the bus voltage minus a low value set in software, the count of the negative insulation abnormity counter is increased by 1, and negative insulation abnormity is reported when the count is accumulated to a corresponding count threshold value;
when the sampling value of one time in a switching period of HA L F _ UDC _ AD is smaller than a low value set in the software, and the sampling value of the other time is larger than the bus voltage minus a low value set in the software, the count of the output insulation abnormity counter is increased by 1, and output insulation abnormity is reported when the count is accumulated to a corresponding count threshold value;
therefore, the insulation abnormity can be accurately and quickly reported, and whether the insulation abnormity of the positive bus and the negative bus or the output insulation abnormity can be identified. See the detection flow chart of the corresponding method in detail in fig. 5.
Fig. 3 is a circuit diagram of a second embodiment of the fast and accurate insulation detection circuit scheme of the present invention, which adds the first diode D1, the second diode D2, and the third diode D3 as input clamping diodes, and the first diode D1, the second diode D2, and the third diode D3 are used for clamping protection of the post-stage circuit U1.
Fig. 4 is a circuit diagram of a third embodiment of the rapid and accurate insulation detection scheme of the present invention, which adds a fourth diode D4 and a fifth diode D5 as output clamping diodes, and the fourth diode D4 and the fifth diode D5 are used for protecting a sampling IC of a subsequent circuit, compared with the second embodiment.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (7)
1. A quick accurate insulation detection circuit characterized in that: the differential amplification circuit comprises positive and negative insulation resistors, a first-stage bus differential amplification circuit, a first-stage half bus differential amplification circuit, a second-stage bus differential amplification circuit and a second-stage half bus differential amplification circuit, wherein the positive and negative insulation resistors are connected with the first-stage bus differential discharge circuit and the first-stage half bus differential amplification circuit, the first-stage bus differential discharge circuit is connected with the second-stage bus differential discharge circuit, and the first-stage half bus differential amplification circuit is connected with the second-stage half bus differential amplification circuit.
2. A fast and accurate insulation detection circuit as claimed in claim 1, wherein: the first-stage bus differential amplification circuit comprises a PE wire and a current-limiting bleeder resistor thereof, a positive bus and a current-limiting bleeder resistor thereof, the positive and negative insulation resistors comprise resistors RPE, the resistors RPE are respectively connected to the input ends of the PE wire and the positive bus, the PE wire is connected with the second-stage bus differential amplification circuit through a post-stage circuit, and the current-limiting bleeder resistor of the positive bus is connected with a capacitor resistor connected in parallel.
3. A fast and accurate insulation detection circuit according to claim 2, wherein: the first-stage half-bus differential amplification circuit comprises a negative bus and a current-limiting divider resistor thereof, the positive and negative insulation resistors comprise resistors RNE, the resistors RNE are respectively connected to the input ends of a PE (polyethylene) line and the negative bus, the post-stage circuit comprises a first operational amplifier and a resistor thereof, a second operational amplifier and a resistor thereof, the negative input and the output ends of the first operational amplifier are connected to the PE line in parallel, the negative input and the output ends of the second operational amplifier are connected to the negative bus in parallel, and the positive inputs of the first operational amplifier and the second operational amplifier are connected with the positive bus after being connected.
4. A fast and accurate insulation detection circuit according to claim 3, wherein: the second-stage bus differential amplification circuit comprises a third operational amplifier, the positive input of the third operational amplifier is connected with the output end of the first operational amplifier in parallel through a resistor, the positive input of the third operational amplifier is connected with a grounded capacitor and a resistor which are connected in parallel, the negative input of the third operational amplifier is connected with a resistor, the negative input and the output of the third operational amplifier are connected with a capacitor resistor which is connected in parallel, and the output of the third operational amplifier is connected with an RC filter circuit through a resistor.
5. A fast and accurate insulation detection circuit according to claim 4, characterized in that: the second-stage half-bus differential amplification circuit comprises a fourth operational amplifier, wherein the positive input of the fourth operational amplifier is connected with the output end of the second operational amplifier in parallel through a resistor, the positive input of the fourth operational amplifier is connected with a grounded capacitor and a resistor which are connected in parallel, the negative input of the fourth operational amplifier is connected with a resistor, the negative input and the output of the fourth operational amplifier are connected with a capacitor resistor which is connected in parallel, and the output of the fourth operational amplifier is connected with a grounded capacitor through a resistor.
6. A fast and accurate insulation detection circuit according to any of claims 5, characterized in that: an input clamping diode is also included and is connected in parallel to the output ends of the PE wire, the positive bus and the negative bus.
7. A fast and accurate insulation detection circuit according to claim 6, wherein: and the output clamping diode is respectively connected to the output of the third operational amplifier and the output of the fourth operational amplifier.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010302419.8A CN111398856A (en) | 2020-04-17 | 2020-04-17 | Quick accurate insulation detection circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010302419.8A CN111398856A (en) | 2020-04-17 | 2020-04-17 | Quick accurate insulation detection circuit |
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| CN111398856A true CN111398856A (en) | 2020-07-10 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115932514A (en) * | 2022-12-27 | 2023-04-07 | 江苏吉泰科电气有限责任公司 | Insulation detection method and circuit |
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Application publication date: 20200710 |