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CN-122003338-A - Method for monitoring the insulation of an on-board charger for detecting insulation faults between a primary circuit and a secondary circuit of a power conversion stage of the charger

CN122003338ACN 122003338 ACN122003338 ACN 122003338ACN-122003338-A

Abstract

The invention relates to a method for monitoring insulation between a primary circuit and a secondary circuit of a power conversion stage, which method is implemented in an on-board charger on a vehicle, which charger comprises-a controller, -a phase line, a neutral line and a ground line, -an insulation monitoring device comprising a DC voltage source, a voltage divider and a stage for filtering out AC voltage components, which method for monitoring insulation comprises the steps of-determining a charging mode of the charger (E1), -injecting a DC current into the voltage divider (E3), -receiving a voltage signal supplied at an output of the filtering stage (E4), -comparing said received voltage value with a threshold voltage value (E5).

Inventors

  • Sebastian Delepfe
  • Roman Guyenne
  • Ali Ben Zela

Assignees

  • 舍弗勒技术股份两合公司

Dates

Publication Date
20260508
Application Date
20241213
Priority Date
20231219

Claims (7)

  1. 1. A method for monitoring insulation between a primary circuit (P1) and a secondary circuit (P2) of a power conversion stage (CV), the method being implemented in an on-board charger (OBC) on a vehicle, the charger (OBC) comprising: -the power conversion stage (CV); -a controller (C) connected to the power conversion stage (CV); -a phase line (L), a neutral line (N) and a ground line (PE), the phase line (L) and the neutral line (N) being connected to a primary circuit (P1) of the power conversion stage (CV); -an Insulation Monitoring Device (IMD) connected in circuit to the phase line (L), the neutral line (N), the ground line (PE) and the controller (C) and comprising a DC voltage source (12), a voltage divider (14) with an input (14A) connected to the DC voltage source (12) and one of the phase line (L) or the neutral line (N), and a stage (16) for filtering out AC voltage components, said stage (16) for filtering out AC voltage components being connected between an output (14B) of the voltage divider (14) and an input (CO 1) of the controller (C); The method for monitoring insulation comprises the steps of: -a first step (E1) of determining a charging mode of the charger (OBC); -if the charging mode is a vehicle-to-load (V2L) mode: -a step (E3) of injecting a DC current into the voltage divider (14) by the DC voltage source (12), the DC current then flowing into the stage (16) for filtering out AC voltage components; -a step (E4) of receiving, by the controller (C), a voltage signal (V1) supplied at the output of the stage (16) for filtering out AC voltage components; A step (E5) of comparing, by the controller (C), the received voltage value (V1) with a threshold voltage value, and A step (E8) of transmitting, by the controller (C), a signal for deactivating the power conversion stage (CV) if said received voltage value (V1) is greater than the threshold voltage value for a predetermined time interval.
  2. 2. The method for monitoring insulation according to claim 1, characterized in that if the charging mode is a vehicle-to-load (V2L) mode and if said received voltage value (V1) is greater than the threshold voltage value within the predetermined time interval, the method further comprises a first intermediate step (E6) of transmitting by the controller (C) a signal for deactivating the DC voltage source (12), a second intermediate step (E7) of transmitting by the controller (C) a signal for reactivating the DC voltage source (12), then re-implementing said step (E3) of injecting DC current, said step (E4) of receiving the voltage signal, and said step (E5) of comparing the received voltage value (V1) with a threshold voltage value, the step (8) of transmitting the signal for deactivating the power conversion stage (CV) being implemented if and only if, in said last comparing step (E5), the received voltage value (V1) is still greater than the threshold voltage value within the predetermined time interval.
  3. 3. A charger (OBC) intended to be onboard a vehicle, the charger comprising: -a power conversion stage (CV) provided with a primary circuit (P1) and a secondary circuit (P2); -a controller (C) connected to the power conversion stage (CV); -a phase line (L), a neutral line (N) and a ground line (PE), the phase line (L) and the neutral line (N) being connected to a primary circuit (P1) of the power conversion stage (CV); -an Insulation Monitoring Device (IMD) connected in circuit to the phase line (L), the neutral line (N), the ground line (PE) and the controller (C) and comprising a DC voltage source (12), a voltage divider (14) with an input (14A) connected to the DC voltage source (12) and one of the phase line (L) or the neutral line (N), and a stage (16) for filtering out AC voltage components, said stage (16) for filtering out AC voltage components being connected between an output (14B) of the voltage divider (14) and an input (CO 1) of the controller (C); characterized in that the charger (OBC) is configured to implement the steps of the method for monitoring insulation according to claim 1 or 2.
  4. 4. A charger (OBC) according to claim 3, characterized in that the DC voltage source (12) comprises a boost converter (22) and a current injection resistor (R inj_L ) connected between the boost converter (22) and the input (14A) of the voltage divider (14).
  5. 5. The charger (OBC) of claim 4, wherein the current injection resistor (R inj_L ) has a resistance value substantially equal to 600 k Ω.
  6. 6. Charger (OBC) according to any of claims 3 to 5, characterized in that the voltage divider (14) is a voltage divider bridge provided with two resistors (R1, R2) connected in series, the two resistors (R1, R2) being such that the voltage divider bridge (14) has a voltage division ratio between 8 and 12, preferably substantially equal to 10.
  7. 7. A charger (OBC) according to any of claims 3 to 6, characterized in that the stage (16) for filtering out the AC voltage component comprises a current measuring resistor (R3), the current measuring resistor (R3) having a resistance value substantially equal to 1.2M Ω.

Description

Method for monitoring the insulation of an on-board charger for detecting insulation faults between a primary circuit and a secondary circuit of a power conversion stage of the charger Technical Field The present invention relates to the field of vehicle chargers for electric motor vehicles. The invention more particularly relates to monitoring insulation in such AC chargers. Background An Insulation Monitoring Device (IMD) is typically provided in the on-board charger illustrated in fig. 1. It is a hardware module that is connected between phase line L, neutral line N and ground line PE. The hardware communicates with the microcontroller C via digital and analog signals. The microcontroller C is configured to be able to disconnect the insulation monitoring device IMD from the ground PE. For electrical and electronic facilities there is already monitoring insulation between the AC voltage part and the protective earth conductor, but these solutions are dedicated to stationary facilities (e.g. in houses, buildings). New functions such as vehicle-based charging are being developed for electric vehicles, and these functions also require insulation monitoring. The on-board charger may operate in a variety of modes of operation in the electric vehicle, including: -grid to vehicle (or G2V); -vehicle to grid (or V2G); -vehicle to home (or V2H); vehicle to load (or V2L). The new vehicle-to-load (or V2L) function that is about to be released would require such monitoring, but V2G, G V or V2H would not. In particular, the insulation monitoring device IMD may interfere with the network in some configurations (e.g., V2G, G V or V2H) and not in other configurations (e.g., V2L). In V2L mode, the supply of AC current (typically 230V single phases) is typically achieved by drawing electrical energy from the high-voltage battery of the vehicle (a battery having a nominal voltage of 400V or 800V) and converting it into AC current (using a power conversion stage CV present in the charger). An external electrical device may then be connected to the vehicle to supply AC current to the device. The power conversion stage conventionally comprises a primary circuit P1, which is arranged on the AC current side and is connected to the phase line L and the neutral line N, and a secondary circuit P2, which is arranged on the high-voltage battery side of the vehicle. Furthermore, in V2L mode, since the charger is no longer connected to the household grid, it is necessary to guarantee an electrically insulating coordination between the primary circuit P1 and the secondary circuit P2 (corresponding to the AC domain and the DC domain, respectively) of the power conversion stage CV. In particular, in the event of an electrical insulation fault between the primary circuit P1 and the secondary circuit P2 of the power conversion stage CV, a current loop may be formed, introducing into the loop a load of parasitic capacitances which in themselves are liable to cause electric shock and injury to the user of the vehicle. To this end, the new standard requires the charger to achieve a protective separation between primary and secondary in the circuit, or to employ a simple separation in combination with a mechanism aimed at detecting any failure or malfunction of the electrical insulation, and to allow the microcontroller C to be able to deactivate the transfer of electrical energy from the vehicle to the load if necessary. However, in the latter case of "simple separation", the separation must be galvanic isolation. Thus, there is a need to detect any insulation failure in such galvanic isolation without introducing a non-galvanically connected insulation monitoring circuit. Disclosure of Invention The object of the present invention is to remedy the deficiencies of the prior art and in particular to propose a solution for protecting against electrical insulation faults which are liable to occur between the primary circuit and the secondary circuit of the power conversion stage of a vehicle charger in the V2L mode of the vehicle charger (thus when the vehicle is no longer connected to the household electrical network), which solution makes it possible to meet the requirements imposed by the new standard and in particular which makes it possible to detect electrical insulation faults accurately and reliably and to monitor the insulation while maintaining galvanic isolation between the primary circuit and the secondary circuit. In order to achieve this object, the invention proposes, in its broadest sense, a method for monitoring insulation between a primary circuit and a secondary circuit of a power conversion stage, the method being implemented in an on-board charger on a vehicle, the charger comprising: -said power conversion stage; -a controller connected to the power conversion stage; -a phase line, a neutral line and a ground line, the phase line and the neutral line being connected to a primary circuit of the power conversion stage; -an Insu