Device for estimating and compensating for the leakage current of a battery charger, vehicle provided with such a device and embodiments of the device

Abstract

A device for estimating and compensating for leakage current of a battery charger of an electric or hybrid motor vehicle, the device comprising: current measurement means configured to measure, during charging, the differential residual current between the charger and the power supply network of the charger; first comparison means (15) configured to compare the measured residual current with a tripping threshold; and processing means (16) configured to determine a charging setpoint as a function of a predetermined charging profile. The processing means are configured to determine, when the residual current is higher than the tripping threshold, the charging setpoint to comprise a safety charging setpoint configured to limit the value of the leakage current within a leakage current allowed value to prevent interruption of the charging.

Description

Technical Field

[0001] This invention relates to chargers and embodiments of chargers in electric or hybrid motor vehicles.

[0002] More specifically, the present invention relates to a device for estimating and compensating for leakage current in a battery charger, and embodiments thereof. Background Technology

[0003] Typically, hybrid or electric vehicles include a charger for recharging the battery that powers the vehicle's traction motor.

[0004] The charger can be non-isolated, making it easier to integrate into the vehicle than an isolated charger.

[0005] However, components of non-isolated chargers are exposed to various electrical interferences from the outside of the charger, especially interferences generated by the charging infrastructure that powers the charger (including charging stations and the power supply networks that power the charging stations).

[0006] During charging, power converters, including transistors, generate leakage current. This leakage current is filtered by the common-mode capacitor of the charger on one hand, and flows to ground on the other.

[0007] The leakage current flowing to ground is circulated back through the power supply network and generates electrical interference in the network, especially due to the interaction with the charger and other connected devices (“bidirectional” or cyclic interaction), which can produce overvoltages and overcurrents that can degrade the charger.

[0008] To prevent charger degradation, the charger may include a differential circuit breaker that disconnects the charger when the differential current measured at the charger input exceeds a safety threshold.

[0009] However, the charging was interrupted.

[0010] "Bidirectional" or cyclic interactions are difficult to quantify because they depend in particular on the topology of the charging system's power circuitry, vehicle parasitic capacitances associated with the vehicle configuration, algorithms driving the onboard power components (especially charging control), and upstream connections to the charging station.

[0011] Document US 9,696,743 proposes a method for compensating leakage current by measuring the leakage current flowing to the grounding point and then injecting a current of the opposite value to counteract the effect of the leakage current.

[0012] However, this method is difficult to implement for complex devices with multiple interfaces between the device and the ground, such as chargers.

[0013] document:

[0014] -(S. Haghbin, S. Lundmark, M. Alaküla and O. Carlson - Grid-Connected Integrated Battery Chargers in Vehicle Applications: Review and New Solution, IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL.60, NO.2, FEBRUARY 2013)

[0015] -(I. Subotic, N. Bodo, E. Levi, B. Dumnic, D. Milicevic, V. Katic - Overview of fast on-board integrated battery chargers for electric vehicles based on multiphase machines and power electronics, IET Electric Power Applications, ISSN 1751-8660)

[0016] -(Yilmaz and PTKrein - Review of Battery Charger Topologies, Charging Power Levels, and Infrastructure for Plug-In Electric and Hybrid Vehicles, IEEE Transactions on Power Electronics, Vol. 28, No. 5, May 2013)

[0017] -(Y. Zhang et al. - Leakage Current Issue of Non-Isolated Integrated Chargers for Electric Vehicles, Proceedings of the 2018 IEEE Energy Conversion Congress and Exposition (ECCE), Portland, OR, USA, 23-27 Sept. 2018) proposed adding components to the power conversion system or reconfiguring the electrical connections of the motor to improve electrical isolation, thereby minimizing leakage current.

[0018] However, these modifications lead to increased complexity in charging control, increased magnetic current in the core of the motor stator, and decreased charging efficiency, and enable power to be supplied to the motor rotor during charging.

[0019] The methods proposed in the prior art attempt to minimize the flow of leakage current and do not provide suppression of the occurrence of overvoltage in the charger. Summary of the Invention

[0020] The purpose of this invention is to overcome all or some of these disadvantages.

[0021] In view of the foregoing, the present invention proposes a method for estimating and compensating for leakage current of a battery charger for an electric or hybrid motor vehicle, the method comprising: measuring a differential residual current between the charger and the charger's power supply network during charging, comparing the differential residual current with a tripping threshold, and determining a charging setpoint based on the comparison result according to a predetermined charging curve.

[0022] When the differential residual current is higher than the trip threshold, the charging setpoint includes a safe charging setpoint configured to limit the leakage current value within the maximum allowable leakage current so as not to interrupt charging. The safe charging setpoint is determined based on the difference between the measured differential residual current and the trip threshold, which is amplified by an amplifier with variable gain and then injected into the input of a filter implementing a dynamic model. This amplifier depends on the current determined according to the charging curve. The output of the dynamic model is added to the current determined according to the charging curve to provide the safe charging setpoint.

[0023] According to one characteristic, the method includes identifying the type of power supply network that powers the charger, and determining the tripping threshold and the maximum allowable leakage current based on the identified type of power supply network.

[0024] Preferably, the dynamic model includes a first-order transfer function, the parameters of which are determined by frequency domain identification of the charging infrastructure.

[0025] Advantageously, this variable gain depends on a polynomial function.

[0026] According to another property, the coefficients of this polynomial function are determined empirically.

[0027] Another subject of the present invention is an apparatus for estimating and compensating for leakage current in a battery charger of an electric or hybrid motor vehicle, the apparatus comprising: a current measuring device configured to measure a differential residual current between the charger and the charger's power supply network during charging; a first comparison device configured to compare the measured differential residual current with a tripping threshold; and a processing device configured to determine a charging setpoint according to a predetermined charging curve.

[0028] The processing device is configured to determine a charging setpoint, including a safe charging setpoint, when the differential residual current is higher than the trip threshold. The safe charging setpoint is configured to limit the leakage current value within the maximum allowable leakage current so as not to interrupt charging. The processing device includes a variable gain amplifier for the difference between the measured differential residual current and the trip threshold. The variable gain amplifier depends on the current determined according to the charging curve and is connected to the input of a filter implementing a dynamic model. The output of the filter is connected to an adder that adds the output of the filter to the current determined according to the charging curve to provide the safe charging setpoint.

[0029] According to one feature, the device includes an identification device configured to identify the type of power supply network used for the charger, and the identification device is further configured to determine the tripping threshold and the maximum allowable leakage current based on the identified type of power supply network.

[0030] Preferably, the dynamic model is configured to approximate the dynamic behavior of the charging infrastructure connected to the power supply network of the charger and these leakage currents.

[0031] Advantageously, the dynamic model includes a first-order transfer function.

[0032] Another subject of the invention is an electric or hybrid motor vehicle comprising a battery charger having a charging controller and means for estimating and compensating for leakage current of the battery charger of the electric or hybrid motor vehicle as previously defined, said means driving the charging controller. Attached Figure Description

[0033] Other objects, features, and advantages of the invention will become apparent from the following description, which is given by way of non-limiting example only and with reference to the accompanying drawings, in which:

[0034] [ Figure 1 An example of an electric or hybrid motor vehicle according to the present invention is shown;

[0035] [ Figure 2 An example embodiment of the processing module according to the present invention is shown;

[0036] [ Figure 3 An example embodiment of a device for estimating and compensating leakage current according to the present invention is shown; and

[0037] [ Figure 4 This illustrates an example of how the differential current changes over time based on the activation state of a device used to estimate and compensate for leakage current, according to the present invention. Detailed Implementation

[0038] refer to Figure 1 The figure shows an electric or hybrid motor vehicle 1 connected to a charging infrastructure 2, which includes a charging station 3 and a power supply network R that supplies power to the charging station 3.

[0039] Vehicle 1 includes a battery charger 4 connected to a charging station 3 and a battery 5 connected to the charger 4, such that when the power supply network R charges the battery 5, the current I... BATT It flows at the terminal of battery 5.

[0040] The power supply network R provides single-phase AC voltage, such as 230V, or three-phase AC voltage, such as 380V.

[0041] Charger 4 includes a filter stage 6, a buck and rectifier stage 7, and a three-phase traction motor 8. The filter stage includes an input connected to station 3 and is configured to prevent electrical interference, particularly generated by power conversion operations within charger 4, from being output to the power supply network R. The buck and rectifier stage includes an input connected in common-mode to the output of filter stage 6. The three-phase traction motor includes a star-connected stator winding, with its neutral point N connected to the output of buck and rectifier stage 7, and a neutral current I. N It flows between stage 7 and motor 8.

[0042] The buck and rectifier stage 7 bucks and rectifies the AC voltage delivered by the power supply network R, and includes a buck power converter and at least one smoothing inductor to smooth the DC current generated after the buck and rectification operation.

[0043] The stator windings of motor 8 are also used to smooth DC current, allowing the inductors in stage 7 to have a reduced size.

[0044] Additionally, the charger 4 includes a boost stage 9, which includes inputs each connected to a different phase of the motor 8, and a fourth input connected to a second output of a buck and rectifier stage. The output of stage 9 is connected to the battery 5.

[0045] The boost stage 9 increases the voltage and includes a boost power converter.

[0046] Charger 4 includes a charging controller 10, a device 11 for estimating and compensating for leakage current, and a charging setpoint module 12. The charging controller is configured to adjust the charging setpoint current I based on the leakage current. C This device drives the buck and rectifier stage 7 and the boost stage 9, and is connected to the controller 10 to generate the charging setpoint current I. C The charging setpoint module is configured to generate a current I1 when the battery 5 is being charged, and this current I1 is based on the charging curve P stored in module 12. R The neutral line current I during charging is determined. N It follows the change in current I1.

[0047] Charging curve P R For example, it is based on the current I when battery 5 is being charged. BATT It is determined by changes over time.

[0048] The device 11 for estimating and compensating for leakage current is configured to generate a safety charging setpoint current I. CS The safe charging setpoint is configured to limit the leakage current value within a safe threshold so as to control the differential residual current I between the charger 4 and the charger's power supply network R. diff Charging will not be interrupted when the circuit breaker threshold Se1 is exceeded.

[0049] Device 11 includes a current measuring device 13 and a processing module 14. The current measuring device is configured to measure the differential residual current between the charger and the charger's power supply network. The processing module includes a first input E1 connected to the measuring device 13, a second input E2 receiving current I1, and an output S1 connected to the controller 10. The charging setpoint current I1 is... C It flows on this output.

[0050] Differential residual current I diffThe leakage current is particularly related to the following relationships, which include the equivalent impedance of the common-mode filter present in charger 4, the impedance of parasitic capacitance, and the equivalent impedance of network R, which are difficult to quantify.

[0051] Therefore, processing module 14 includes using the residual differential current I diff The value of the parasitic effect is estimated by a partial model using the operating point of the charging controller 10 given by module 12 and the value of the parasitic effect. The estimator is based on the differential residual current I. diff The dynamics of the common-mode filter stage 6 and its parasitic capacitance are determined in real time, and the differential residual current I is... diff It is considered an image of the parasitic currents in the earth.

[0052] Estimate the leakage current or parasitic current in the ground and use it to compensate for their impact on charging control in order to minimize their propagation and amplification.

[0053] Seeking to suppress the occurrence of overvoltage in chargers.

[0054] The measuring device 13 is made, for example, of a magnetic core with windings.

[0055] Figure 2 An example embodiment of the processing module 14 is shown.

[0056] Processing module 14 includes a first comparison device 15 and a processing device 16, the first comparison device being configured to process the differential residual current I received at the first input E1. diff The value is compared with the trip threshold Se1, and the processing device is configured to adjust the value according to the charging curve P. R Determine including the charging setpoint current I C The charging setting point.

[0057] Processing device 16 is configured to operate in differential residual current I diff When the current exceeds the trip threshold Se1, the charging setpoint is determined, including the safe charging setpoint current I. CS The safe charging setpoint current is configured to limit the leakage current value to the maximum allowable leakage current I. diffmax So that charging is not interrupted.

[0058] Additionally, module 14 includes an identification device 17 configured to identify the type of power supply network R and further configured to determine a tripping threshold Se1 based on the identified type of power supply network R and a sensitivity coefficient β varying between 0 and 1.

[0059] The tripping threshold Se1 is equal to:

[0060] Se1 = β.I diffmax (1)

[0061] For example, if the identification device 17 detects that the power supply network R is single-phase and less than 12.5 amps, then the maximum allowable leakage current I... diffmax It equals 70mA, while in other cases, the maximum allowable leakage current I diffmax It equals 171mA.

[0062] The coefficient β is determined based on the sensitivity of charger 4 to changes in leakage current, and is, for example, equal to 0.75.

[0063] The identification device 17 includes, for example, storing the maximum allowable leakage current I. diffmax The device includes a memory MEM for the coefficient β, a communication module COM for communicating with station 3 to determine the type of power supply network R, and a processing unit UT configured to select, calculate, and transmit the trip threshold Se1 to the first device 15.

[0064] The first device 15 calculates the differential residual current I. diff The weighted difference E15 between the trip threshold Se1 and the trip threshold Se1:

[0065]

[0066] E15 = 0, others

[0067] The processing device 16 includes a variable gain amplifier 18, a filter 19, and an adder 20. The variable gain amplifier is configured to be driven by a current I1 and receive a difference E15 as input. The filter implements a first-order dynamic model, which is configured to approximate the dynamic behavior of the charging infrastructure 2 and the leakage current based on the difference E15 amplified by the amplifier 18. The adder is configured to add the output of the filter 19 to the current I1.

[0068] The first comparator 15 and the amplifier 18 are made, for example, using an operational amplifier.

[0069] Amplifier 18 transmits signal S18 as its output, such that:

[0070] S18=(I Nmax -I1).F(E15) (3)

[0071] Among them, I Nmax It is the maximum neutral line current I authorized by Charger 4. N And F is a cubic polynomial function:

[0072] F(X) = a0 + a1X + a2X 2 +a3X 3 (8)

[0073] The coefficients a0, a1, a2, and a3 are adjustment parameters, the determination of which is disclosed below.

[0074] Dynamic models include first-order transfer functions H of the following types:

[0075]

[0076] Where s is the Laplace operator, and the coefficients n1, n2, d1, and d2 are adjustment parameters, the determination of which is disclosed below.

[0077] The dynamic model generates signal S19 as output.

[0078] Adder 20 delivers a charge setpoint current I. C The charging setpoint makes:

[0079] I C =I1+S19 (5)

[0080] Figure 3 An example implementation of the device 11 for estimating and compensating leakage current is shown.

[0081] Before using device 11, the values ​​of the coefficients n1, n2, d1 and d2 of the first-order transfer function H, the sensitivity coefficient β, and the coefficients a0, a1, a2 and a3 of the polynomial function F must be determined.

[0082] In calibration step 30, the coefficients n1, n2, d1, and d2 of the first-order transfer function H are determined based on values ​​appearing in, for example, the prior art, and especially depending on the characteristics of the charger 4 equivalent to an RLC circuit, the estimated values ​​of the network R and the parasitic capacitance.

[0083] Of course, device 11 can be used to estimate and compensate for the leakage current of any type of charger, dynamic model, and maximum allowable leakage current I. diffmax The model should be adapted to the type of charger and the system it drives. Dynamic models, in particular, can include functions of order greater than one.

[0084] The amplification function can also be adapted to the type of charger, especially since the maximum neutral current setpoint is replaced with a maximum current setpoint controlled according to the circuit type in the other charger topology. Amplification functions other than function F can also be used.

[0085] Another method for determining the coefficients n1, n2, d1, and d2 can be based on frequency domain identification, for example, that of charger 4.

[0086] During this step, the value of the sensitivity coefficient β is determined.

[0087] Then, once the coefficients n1, n2, d1, d2 and β have been determined, the coefficients a0, a1, a2 and a3 of the polynomial function F are determined empirically so that the weighted difference E15 is zero in the static scenario.

[0088] The coefficients n1, n2, d1, d2 and β fix the amplification value of the instantaneous state difference E15.

[0089] This amplification value is determined by testing the charger's response to each operating point.

[0090] Every operation point is taken into consideration.

[0091] Of course, the order of function F can be lower than or higher than the third order.

[0092] Then, in step 31, when the charger 4 is connected to the charging infrastructure 2, the identification device 17 determines the type of the power supply network R and the maximum allowable leakage current I. diffmax And the tripping threshold Se1.

[0093] In step 32, the measuring device 13 measures the differential residual current I. diff .

[0094] If the differential residual current I diff If the value exceeds the trip threshold Se1 (step 33), the charging setpoint includes a safe charging setpoint, which includes a safe charging current I. CS The safe charging current is configured to limit the leakage current value to the maximum allowable leakage current I. diffmax To ensure uninterrupted charging, the safe charging current I... CS equal:

[0095] I CS =I1+S19 (6)

[0096] If the differential residual current I diff If the current is below the trip threshold Se1 (step 34), then the charging current setpoint I is included. C The charging setpoint is equal to:

[0097] IC = I1 (7)

[0098] Figure 4 This indicates that the differential residual current I is based on the activation state of device 11. diff Examples of changes over time.

[0099] Between time 0 and time T1, device 11 is in state "0", i.e., out of service. Differential residual current I diff Exceeding the maximum allowable leakage current I diffmax This causes the charging of battery 5 to be cut off in order to protect charger 4 and the user.

[0100] Starting from time T1, device 11 is activated (“1”). Differential residual current I diff Less than or equal to the maximum allowable leakage current I diffmax This ensures that charging will not be interrupted.

[0101] Since existing electric and hybrid vehicles typically include a measuring device 13, the device 11 only needs to add a module 14 that includes a calculation algorithm.

[0102] Since device 11 does not require hardware modifications, its implementation will not cause electromagnetic interference to the components of charger 4.

[0103] Furthermore, due to the differential residual current I diff When the circuit breaker threshold Se1 is exceeded, device 11 trips, so the charging performance of battery 4 will be temporarily reduced, and charging will not be interrupted until battery 4 is fully charged.

Claims

1. A method for estimating and compensating for leakage current in a battery charger (4) of an electric or hybrid motor vehicle (1), the method comprising: During charging, measure the differential residual current (I) between the charger and its power supply network (R). diff The differential residual current is compared with the trip threshold (Se1), and based on the result of this comparison, a predetermined charging curve (P) is used. R Determine the charging setpoint (I) C The feature is that when the differential residual current is higher than the trip threshold, the charging setpoint includes a safe charging setpoint (I). CS The safe charging setpoint is configured to limit the leakage current value to the maximum allowable leakage current (I0). diffmax To ensure uninterrupted charging, the safe charging setpoint (I) is located within the safe charging setpoint. CS Based on the measured differential residual current (I) diff The difference between the current (I1) and the trip threshold (Se1) is determined, the difference is amplified by an amplifier with variable gain and then injected into the input of a filter (19) that implements a dynamic model, the amplifier depending on the current (I1) determined according to the charging curve, the output of the dynamic model is added to the current determined according to the charging curve to provide the safe charging setpoint.

2. The method of claim 1, further comprising identifying the type of power supply network (R) supplying power to the charger, and determining the tripping threshold (Se1) and the maximum allowable leakage current (I) based on the identified type of power supply network. diffmax ).

3. The method as described in claim 1 or 2, wherein, The dynamic model includes a first-order transfer function (H), the parameters of which are determined by frequency domain identification of the charging infrastructure.

4. The method as described in claim 1 or 2, wherein, The variable gain depends on the polynomial function (F).

5. The method of claim 4, wherein, The coefficients of the polynomial function (F) are determined empirically.

6. A device (11) for estimating and compensating for leakage current of a battery charger (4) of an electric or hybrid motor vehicle (1), the device comprising: A current measuring device (13) configured to measure the differential residual current (Io) between the charger and its power supply network (R) during charging. diff The first comparison device (15) is configured to compare the measured differential residual current with a trip threshold (Se1); and the processing device (16) is configured to process the measured differential residual current according to a predetermined charging curve (P). R The processing device is configured to determine a charging setpoint, wherein when the differential residual current is higher than the trip threshold, the charging setpoint includes a safe charging setpoint (I). CS The safe charging setpoint is configured to limit the leakage current value to the maximum allowable leakage current (I0). diffmax To ensure uninterrupted charging, the processing device includes a differential residual current (I0) measured within the measured differential residual current (I0). diff A variable gain amplifier is used to measure the difference between the current (I1) and the trip threshold (Se1), the variable gain amplifier depending on the current (I1) determined according to the charging curve and connected to the input of a filter (19) that implements a dynamic model, the output of the filter being connected to an adder (20) that adds the output of the filter to the current determined according to the charging curve to provide the safe charging setpoint.

7. The device of claim 6, further comprising an identification device (17) configured to identify the type of power supply network (R) for the charger, the identification device being further configured to determine the tripping threshold (Se1) and the maximum allowable leakage current (I) based on the identified type of power supply network. diffmax ).

8. The device as claimed in claim 6 or 7, wherein, The dynamic model is configured to approximate the charging infrastructure, including the power supply network connected to the charger, and the dynamic behavior of these leakage currents.

9. The device as claimed in claim 8, wherein, The dynamic model includes a first-order transfer function (H).

10. An electric or hybrid motor vehicle (1) comprising a battery charger (4) having a charging controller (10) and a device (11) as claimed in any one of claims 6 to 9, said device driving the charging controller.

Images