Insulation impedance detection device for off-board chargers

Abstract

The present application relates to an insulation impedance detection device for non-vehicle chargers, and relates to the field of insulation detection. By combining the test principles of a balanced bridge and an unbalanced bridge, the problem that the balanced bridge cannot detect insulation impedance when the positive and negative busbars are grounded at the same time is solved, and the insulation impedance measurement between the DC busbar and the ground is realized. The solution can accurately measure insulation impedance within the voltage range of DC100V to DC1500V, and the detection range is 100Ω to 10MΩ, providing reliable protection for insulation detection.

Description

Technical Field

[0001] The present application relates to the field of insulation detection, and in particular to an insulation impedance detection device applied to a non-vehicle charger. Background Art

[0002] The current insulation impedance detection method generally supports a voltage range of DC200V to DC1000V, while the latest national standard requires a maximum voltage of DC1250V, so it is difficult for existing detection methods to detect insulation impedance under high voltage. Existing detection methods are usually offline detection, which cannot monitor the change trend of insulation impedance in real time, and it is difficult to detect potential problems of insulation performance degradation in time. In addition, in the presence of DC-to-ground capacitance (such as Y capacitance, parasitic capacitance, etc.), the existing detection method has weak adaptive ability, which can easily lead to inaccurate detection results and unstable performance. Summary of the invention

[0003] Based on this, it is necessary to provide an insulation impedance detection device for non-vehicle chargers to address the above technical issues, which can detect insulation impedance under high voltage and improve the accuracy of insulation detection results.

[0004] In the first aspect, the present application provides an insulation impedance detection device for a non-vehicle charger. The device comprises: an upper bridge arm resistance module, a lower bridge arm resistance module, a relay module and an MCU (Microcontroller Unit); wherein the relay module comprises a first relay, a second relay and a third relay;

[0005] Two ends of the upper bridge arm resistance module are respectively connected to the first insulation impedance to be measured and the second relay; two ends of the lower bridge arm resistance module are respectively connected to the second insulation impedance to be measured and the third relay; the other end of the first insulation impedance to be measured is connected to the second insulation impedance to be measured;

[0006] The first relay is connected to the connection line between the first insulation impedance to be measured and the second insulation impedance to be measured through the protective ground wire PE; the positive pole of the DC bus is connected to the connection line between the upper bridge arm resistance module and the first insulation impedance to be measured; the negative pole of the DC bus is connected to the connection line between the lower bridge arm resistance module and the second insulation impedance to be measured;

[0007] The micro control unit MCU is respectively connected to one end of the first relay, the second relay and the third relay;

[0008] The microcontroller unit MCU is used to provide a high level or a low level for the first relay, the second relay and the third relay, control the attraction or release of the first relay, the second relay and the third relay, so that the relay module is in different working states, and collects the positive sampling voltage and the negative sampling voltage;

[0009] The microcontroller unit MCU is further used to determine the absolute value ratio of the positive electrode sampling voltage to the negative electrode sampling voltage when the relay module is in different working states; according to the voltage division theorem, the absolute value ratio of the positive electrode sampling voltage to the negative electrode sampling voltage is represented by the resistance value of the upper bridge arm resistance module, the resistance value of the lower bridge arm resistance module, the resistance value of the first insulation impedance to be measured, and the resistance value of the second insulation impedance to be measured;

[0010] The microcontroller unit MCU is further used to determine the resistance values ​​of the first insulation impedance to be measured and the second insulation impedance to be measured according to the absolute value ratio of the positive electrode sampling voltage to the negative electrode sampling voltage when the relay module is in different working states.

[0011] In one embodiment, the upper bridge arm resistance module includes a first series circuit and a second series circuit, and the first series circuit is connected in parallel with the second series circuit; the lower bridge arm resistance module includes a third series circuit and a fourth series circuit, and the third series circuit is connected in parallel with the fourth series circuit.

[0012] In one embodiment, the total resistance of the first series circuit is the same as the total resistance of the third series circuit; the total resistance of the second series circuit is the same as the total resistance of the fourth series circuit.

[0013] In one embodiment, the positive sampling voltage is connected to the fourth pin of the metering chip in the micro control unit MCU, and the negative sampling voltage is connected to the sixth pin of the metering chip in the micro control unit MCU.

[0014] In one embodiment, the micro control unit MCU controls the first relay to be attracted, the second relay to be attracted, and the third relay to be released, so as to obtain a first state absolute value ratio of the positive electrode sampling voltage and the negative electrode sampling voltage;

[0015] The microcontroller unit MCU controls the first relay to be attracted, the second relay to be released, and the third relay to be attracted, so as to obtain a second state absolute value ratio of the positive electrode sampling voltage and the negative electrode sampling voltage;

[0016] The micro control unit MCU controls the first relay to be pulled in, the second relay to be pulled in, and the third relay to be pulled in, so as to obtain a third state absolute value ratio of the positive electrode sampling voltage and the negative electrode sampling voltage;

[0017] The micro control unit MCU determines the resistance values ​​of the first insulation impedance to be measured and the second insulation impedance to be measured based on the absolute value ratio of the first state, the absolute value ratio of the second state and the absolute value ratio of the third state.

[0018] In one embodiment, the first insulation impedance to be measured is the impedance to be measured between the positive pole of the DC output bus and the ground, and the second insulation impedance to be measured is the impedance to be measured between the negative pole of the DC output bus and the ground.

[0019] In one embodiment, the positive voltage range of the DC bus is a DC voltage of [100V, 1500V]; the negative voltage range of the DC bus is a DC voltage of [-100V, -1500V].

[0020] In one embodiment, the resistance range of the first insulation impedance to be measured and the second insulation impedance to be measured are both [100Ω, 10MΩ].

[0021] In one of the embodiments, the microcontroller unit MCU supports reading the positive electrode sampling voltage, the negative electrode sampling voltage, the resistance value of the first insulation impedance to be measured, and the resistance value of the second insulation impedance to be measured through a 485 communication interface.

[0022] In one embodiment, the first relay, the second relay and the third relay are all high-insulation signal relays.

[0023] The above-mentioned insulation impedance detection device for the off-board charger solves the problem that the insulation impedance cannot be detected when the positive and negative busbars of the balanced bridge are grounded at the same time by combining the test principles of the balanced bridge and the unbalanced bridge, and realizes the insulation impedance measurement between the DC bus and the ground. This solution can accurately measure the insulation impedance within the voltage range of DC100V to DC1500V, and the detection range is 100Ω to 10MΩ, providing reliable protection for the detection of the insulation status of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a structural block diagram of an insulation impedance detection device applied to a non-vehicle charger in one embodiment;

[0025] Figure 2 is a structural block diagram of an insulation impedance detection device applied to a non-vehicle charger in one embodiment;

[0026] Figure 3 FIG. 4 is a structural block diagram of a microcontroller unit MCU in an embodiment. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0028] In one embodiment, Figure 1 As shown, an insulation impedance detection device 100 applied to a non-vehicle charger is provided. The device includes: an upper bridge arm resistance module 110, a lower bridge arm resistance module 120, a relay module 130 and a micro control unit MCU140; wherein the relay module 130 includes a first relay 131, a second relay 132 and a third relay 133;

[0029] The two ends of the upper bridge arm resistance module 110 are respectively connected to the first insulation impedance to be measured 150 and the second relay 131; the two ends of the lower bridge arm resistance module 120 are respectively connected to the second insulation impedance to be measured 160 and the third relay 133; the other end of the first insulation impedance to be measured 150 is connected to the second insulation impedance to be measured 160;

[0030] The first relay 131 is connected to the connection line of the first insulation impedance to be measured 150 and the second insulation impedance to be measured 160 through the protective ground line PE; the positive pole of the DC bus is connected to the connection line of the upper bridge arm resistance module 110 and the first insulation impedance to be measured 150; the negative pole of the DC bus is connected to the connection line of the lower bridge arm resistance module 120 and the second insulation impedance to be measured 160;

[0031] The micro control unit MCU140 is connected to one end of the first relay 131, the second relay 132 and the third relay 133 respectively;

[0032] The microcontroller unit MCU140 is used to provide a high level or a low level for the first relay 131, the second relay 132 and the third relay 133, and control the first relay 131, the second relay 132 and the third relay 133 to be attracted or released, so that the relay module 130 is in different working states, and the positive electrode sampling voltage and the negative electrode sampling voltage are collected;

[0033] The microcontroller unit MCU140 is further used to determine the absolute value ratio of the positive sampling voltage to the negative sampling voltage when the relay module 130 is in different working states; according to the voltage division theorem, the absolute value ratio of the positive sampling voltage to the negative sampling voltage is represented by the resistance value of the upper bridge arm resistor module 110, the resistance value of the lower bridge arm resistor module 120, the resistance value of the first insulation impedance to be measured 150, and the resistance value of the second insulation impedance to be measured 160;

[0034] The microcontroller unit MCU140 is further used to determine the resistance values ​​of the first insulation impedance 150 to be measured and the second insulation impedance 160 to be measured according to the absolute value ratio of the positive sampling voltage and the negative sampling voltage of the relay module 130 in different working states.

[0035] In one embodiment, the upper bridge arm resistance module 110 includes a first series circuit and a second series circuit, and the first series circuit is connected in parallel with the second series circuit; the lower bridge arm resistance module 120 includes a third series circuit and a fourth series circuit, and the third series circuit is connected in parallel with the fourth series circuit.

[0036] In one embodiment, the total resistance of the first series circuit is the same as the total resistance of the third series circuit; the total resistance of the second series circuit is the same as the total resistance of the fourth series circuit.

[0037] In one embodiment, the positive sampling voltage is connected to the fourth pin of the metering chip in the micro control unit MCU140 , and the negative sampling voltage is connected to the sixth pin of the metering chip in the micro control unit MCU140 .

[0038] In one embodiment, the microcontroller unit MCU140 controls the first relay 131 to be energized, the second relay 132 to be energized, and the third relay 133 to be released, so as to obtain a first state absolute value ratio of the positive electrode sampling voltage and the negative electrode sampling voltage;

[0039] The microcontroller unit MCU140 controls the first relay 131 to be pulled in, the second relay 132 to be released, and the third relay 133 to be pulled in, so as to obtain a second state absolute value ratio of the positive electrode sampling voltage and the negative electrode sampling voltage;

[0040] The microcontroller unit MCU140 controls the first relay 131 to be energized, the second relay 132 to be energized, and the third relay 133 to be energized, so as to obtain a third state absolute value ratio of the positive electrode sampling voltage and the negative electrode sampling voltage;

[0041] The micro control unit MCU140 determines the resistance values ​​of the first insulation impedance to be measured 150 and the second insulation impedance to be measured 160 based on the absolute value ratio of the first state, the absolute value ratio of the second state, and the absolute value ratio of the third state.

[0042] In one embodiment, the first insulation impedance to be measured 150 is the impedance to be measured between the positive electrode of the DC output bus and the ground, and the second insulation impedance to be measured 160 is the impedance to be measured between the negative electrode of the DC output bus and the ground.

[0043] In one embodiment, the positive voltage range of the DC bus is a DC voltage of [100 V, 1500 V]; the negative voltage range of the DC bus is a DC voltage of [-100 V, -1500 V].

[0044] In one embodiment, the resistance ranges of the first insulation impedance to be measured 150 and the second insulation impedance to be measured 160 are both [100Ω, 10MΩ].

[0045] In one embodiment, the microcontroller unit MCU140 supports reading the positive electrode sampling voltage, the negative electrode sampling voltage, the resistance value of the first insulation resistor 150 to be measured, and the resistance value of the second insulation resistor 160 to be measured through the 485 communication interface.

[0046] In one embodiment, the first relay, the second relay and the third relay are all high-insulation signal relays, wherein the high-insulation signal relay is a relay that can maintain high insulation performance under high voltage environment, is mainly used for signal transmission and circuit control, and has the capabilities of high voltage switching, high power switching, high insulation, etc.

[0047] For example, Figure 2 As shown:

[0048] Upper bridge arm resistance: One end of resistor R26 is connected to the DC+ output terminal of the off-board charger, and the other end is connected in series with R26, R27, R28, R29, R30, R31, R32, and R33 in sequence. The other end of R33 (sampling resistor) is connected to GND;

[0049] Lower bridge arm resistance: one end of the resistor R40 is connected to the DC- output terminal of the off-board charger, and the other end is connected in series with R40, R41, R42, R43, R44, R45, R46, and R50 in sequence. The other end of R50 (sampling resistor) is connected to GND;

[0050] One end of resistor R21 is connected to the DC+ output terminal of the off-board charger, and the other end is connected in series with R22, R23, R24, and R25 in sequence. The other end of R25 is connected to pin 7 of the main contact of relay K2, and pin 6 of the main contact of the relay is connected to GND.

[0051] One end of resistor R35 is connected to the DC- output terminal of the off-board charger, and the other end is connected in series with R36, R37, R38, and R39 in sequence. The other end of R39 is connected to the 6th pin of the main contact of relay K2, and the 7th pin of the main contact of the relay is connected to GND.

[0052] like Figure 3 As shown, the positive voltage sampling is performed by connecting V1P_DC+ to the 4th pin of the metering chip U2, and the negative voltage sampling is performed by connecting V2P_DC- to the 6th pin of the metering chip U2.

[0053] R8 / C48, R9 / C49, and R10 / C12 are used for anti-aliasing filtering;

[0054] K1, K2, and K3 are ultra-small high-insulation signal relays, which are driven to close or release by MCU. When the insulation monitoring function is turned off, the positive and negative terminal relays K1, K2, and K3 are disconnected, and DC voltage and insulation resistance monitoring will not be provided at this time. When it is necessary to start insulation detection, the MCU drives the corresponding IO ports in sequence to realize Relay_Driver high level, PWM1 high level, and PWM2 high level, and then controls the closure of K1, K2, and K3 relays, and then performs DC voltage acquisition and insulation monitoring resistance calculation. The corresponding DC voltage and insulation resistance value and whether the voltage is reversed can be read through the 485 communication interface.

[0055] The voltage values ​​under different combinations collected by V1P_DC+ and V2P_DC- are processed by the main control MCU through some delay, filtering and other processing, and the insulation impedance Rt1 and Rt1 to be measured are inferred through some algorithms.

[0056] Take an example to illustrate the insulation resistance calculation process:

[0057] For the upper arm resistor:

[0058] ∑R1=R26+R27+R28+R29+R30+R31+R32+R33=3000KΩ;

[0059] ∑R2=R21+R22+R23+R24+R25=750KΩ;

[0060] ∑R1&2=∑R1 / / ∑R2=600KΩ;

[0061] The impedance to be measured between the positive electrode and the ground: Rt1 (unit: KΩ).

[0062] For the lower bridge arm resistor:

[0063] ∑R3=R40+R41+R42+R43+R44+R45+R46+R47=3000KΩ;

[0064] ∑R4=R35+R36+R37+R38+R39=750KΩ;

[0065] ∑R3&4=∑R3 / / ∑R4=600KΩ;

[0066] The impedance to be measured between the negative electrode and the ground: Rt2 (unit: KΩ).

[0067] When K1 is on, K2 is on, and K3 is released:

[0068] Total resistance of upper bridge arm:

[0069] Total resistance of lower bridge arm:

[0070] Assume that the absolute value ratio of the positive sampling voltage V1P_DC+ to the negative sampling voltage V2P_DC- is equal to a. According to the voltage division theorem, we can get

[0071] When K1 is on, K2 is released, and K3 is on:

[0072] Total resistance of upper bridge arm:

[0073] Total resistance of lower bridge arm:

[0074] Assume that the absolute value ratio of the positive sampling voltage V1P_DC+ to the negative sampling voltage V2P_DC- is equal to b. According to the voltage division theorem, we can get

[0075] When K1, K2 and K3 are closed:

[0076] Total resistance of upper bridge arm:

[0077] Total resistance of lower bridge arm:

[0078] Assume that the absolute value ratio of the positive sampling voltage V1P_DC+ to the negative sampling voltage V2P_DC- is equal to c. According to the voltage division theorem, we can get

[0079] Method 1: Further use → Substituting equation (10) into equations (3), (6), and (9) respectively, three groups of Rt1 can be obtained (the results are averaged) to improve the accuracy of insulation resistance measurement.

[0080] Method 2: Further use → Substituting equation (11) into equations (3), (6), and (9) will yield three groups of Rt2 (the results are averaged) to improve the accuracy of insulation resistance measurement.

[0081] After filtering, delay and other processing in the MCU program, the Rt1 and Rt2 results calculated by the above two methods are averaged again to further improve the detection accuracy and stability.

[0082] In summary, the insulation impedance detection device for non-vehicle chargers provided in this application has the following effects:

[0083] 1) The test principle of combining balanced bridge and unbalanced bridge is adopted to avoid the problem that the balanced bridge cannot be detected when the positive and negative busbars are grounded at the same time. The insulation impedance between the DC busbar and the ground can be measured within the voltage range of DC100V to DC1500V, and the insulation impedance detection range is 100Ω to 10MΩ.

[0084] 2) Supports online real-time monitoring, periodic detection, and can also exit detection after the detection is completed (floating work).

[0085] 3) It has the function of detecting reverse connection of DC voltage.

[0086] 4) Monitor the voltage of the DC output circuit bus DC+ to PE (protective ground wire: conducts leakage current to the ground to prevent electric shock accidents) and DC- to PE in real time. When it is detected that the voltage exceeds its possible DC voltage range [-15V, 15V], a fault alarm is triggered within 1s.

[0087] 5) In the case of DC output bus (DC+, DC-) ground capacitance, the module can realize adaptive detection of ground capacitance below 2.2uF (positive and negative pole ground capacitance is below 2.2uF respectively). When ground capacitance exists, the maximum detection time does not exceed 2s.

[0088] 6) It has 485 communication function, which is convenient for data interaction with other main control modules.

[0089] It should be understood that, although the steps in the flowcharts involved in the above embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0090] Each module in the above insulation impedance detection device for non-vehicle charger can be implemented in whole or in part by software, hardware and their combination. Each module can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to each module above.

[0091] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0092] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. An insulation impedance detection device for a non-vehicle charger, characterized in that: The device comprises: an upper bridge arm resistance module, a lower bridge arm resistance module, a relay module and a micro control unit MCU; wherein the relay module comprises a first relay, a second relay and a third relay; Two ends of the upper bridge arm resistance module are respectively connected to the first insulation impedance to be measured and the second relay; two ends of the lower bridge arm resistance module are respectively connected to the second insulation impedance to be measured and the third relay; the other end of the first insulation impedance to be measured is connected to the second insulation impedance to be measured; The first relay is connected to the connection line between the first insulation impedance to be measured and the second insulation impedance to be measured through the protective ground wire PE; the positive pole of the DC bus is connected to the connection line between the upper bridge arm resistance module and the first insulation impedance to be measured; the negative pole of the DC bus is connected to the connection line between the lower bridge arm resistance module and the second insulation impedance to be measured; The micro control unit MCU is respectively connected to one end of the first relay, the second relay and the third relay; The microcontroller unit MCU is used to provide a high level or a low level for the first relay, the second relay and the third relay, control the attraction or release of the first relay, the second relay and the third relay, so that the relay module is in different working states, and collects the positive sampling voltage and the negative sampling voltage; The microcontroller unit MCU is further used to determine the absolute value ratio of the positive electrode sampling voltage to the negative electrode sampling voltage when the relay module is in different working states; according to the voltage division theorem, the absolute value ratio of the positive electrode sampling voltage to the negative electrode sampling voltage is represented by the resistance value of the upper bridge arm resistance module, the resistance value of the lower bridge arm resistance module, the resistance value of the first insulation impedance to be measured, and the resistance value of the second insulation impedance to be measured; The microcontroller unit MCU is further used to determine the resistance values ​​of the first insulation impedance to be measured and the second insulation impedance to be measured according to the absolute value ratio of the positive electrode sampling voltage to the negative electrode sampling voltage when the relay module is in different working states.

2. The device according to claim 1, characterized in that The upper bridge arm resistance module includes a first series circuit and a second series circuit, and the first series circuit is connected in parallel with the second series circuit; the lower bridge arm resistance module includes a third series circuit and a fourth series circuit, and the third series circuit is connected in parallel with the fourth series circuit.

3. The device according to claim 2, characterized in that The total resistance of the first series circuit is the same as the total resistance of the third series circuit; the total resistance of the second series circuit is the same as the total resistance of the fourth series circuit.

4. The device according to claim 1, characterized in that The positive sampling voltage is connected to the fourth pin of the metering chip in the micro control unit MCU, and the negative sampling voltage is connected to the sixth pin of the metering chip in the micro control unit MCU.

5. The device according to claim 1, characterized in that The micro control unit MCU controls the first relay to be attracted, the second relay to be attracted, and the third relay to be released, so as to obtain a first state absolute value ratio of the positive electrode sampling voltage and the negative electrode sampling voltage; The microcontroller unit MCU controls the first relay to be attracted, the second relay to be released, and the third relay to be attracted, so as to obtain a second state absolute value ratio of the positive electrode sampling voltage and the negative electrode sampling voltage; The micro control unit MCU controls the first relay to be pulled in, the second relay to be pulled in, and the third relay to be pulled in, so as to obtain a third state absolute value ratio of the positive electrode sampling voltage and the negative electrode sampling voltage; The micro control unit MCU determines the resistance values ​​of the first insulation impedance to be measured and the second insulation impedance to be measured based on the absolute value ratio of the first state, the absolute value ratio of the second state and the absolute value ratio of the third state.

6. The device according to claim 1, characterized in that The first insulation impedance to be measured is the impedance to be measured between the positive pole of the DC output bus and the ground, and the second insulation impedance to be measured is the impedance to be measured between the negative pole of the DC output bus and the ground.

7. The device according to claim 1, characterized in that The positive voltage range of the DC bus is a DC voltage of [100V, 1500V]; The negative pole voltage range of the DC bus is a DC voltage of [-100V, -1500V].

8. The device according to claim 1, characterized in that The resistance range of the first insulation impedance to be measured and the second insulation impedance to be measured are both [100Ω, 10MΩ].

9. The device according to claim 1, characterized in that The microcontroller unit MCU supports reading the positive electrode sampling voltage, the negative electrode sampling voltage, the resistance value of the first insulation impedance to be measured, and the resistance value of the second insulation impedance to be measured through a 485 communication interface.

10. The device according to claim 1, characterized in that The first relay, the second relay and the third relay are all high-insulation signal relays.

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