METHOD FOR CALIBRATING A VOLTAGE CONVERSION DEVICE

Abstract

The present invention relates to a method for calibrating a voltage conversion device (1) comprising a power circuit (2) comprising a resonant circuit determining a nominal resonant frequency and a controller capable of delimiting, in a first calibration state, an operating frequency interval of the conversion device (1) by a lower limit frequency (FLB) and an upper limit frequency (FLH) around a theoretical value of the resonant frequency, the method comprising the following steps of measuring the actual value (FRR) of the resonant frequency, calibrating a second calibration state so as to configure the lower limit frequency (FLB) and the upper limit frequency (FLH) of the operating frequency interval around the actual value (FRR) of the resonant frequency according to at least one predetermined frequency deviation. The invention finds an application for electrified vehicles.Figure 1.

Description

Title of the invention: METHOD FOR CALIBRATING A VOLTAGE CONVERSION DEVICE

[0001] The field of the invention relates to a method for calibrating a voltage conversion device comprising a resonant circuit.

[0002] Electrified vehicles include electronic power systems providing the AC / DC and / or DC / DC voltage conversion function; this is the case, for example, of motor vehicles including an on-board charger whose function is to convert the alternating voltage of an electrical network external to the vehicle into a DC charging voltage suitable for the battery system. For example, on-board chargers for electrified vehicles are designed to convert an alternating voltage of the 220 volt type into a DC voltage of between 350 volts and 450 volts. Generally, on-board chargers are equipped with more than one conversion device allowing the conversion of a bus voltage, for example around 400 volts, to an on-board network voltage operating at 12 volts.

[0003] Conventionally, a voltage conversion device comprises a resonant circuit comprising inductors and a capacitor determining the resonant frequency of the conversion device. In addition, such a device generally cooperates with a controller whose function is, in particular, to delimit a nominal operating range around a nominal frequency theoretically determined by the electrical characteristics of the components of the resonant circuit. In reality, the actual components supplied by manufacturers have up to 10% deviation from the nominal value, which induces a deviation of the actual resonant frequency from the nominal frequency of approximately 11%.

[0004] However, this frequency is extremely important because depending on the control laws, for example of the ZVS type for "Zero Voltage Switching" in English, driving at a frequency significantly offset from the nominal resonant frequency is likely to damage the circuits, in particular for frequencies lower than the resonant frequency where the tolerances can be tiny, of the order of a few kilohertz. A problem for these circuits is therefore to guarantee a sufficient level of reliability of the operating frequency of a power converter with a resonant circuit.

[0005] Document US-A1-20140268904 is known from the state of the art, describing a method for calibrating a power converter comprising a resonant circuit. In particular, it provides a controller implementing a control method comprising the calculation of the optimal input voltage using the voltage output voltage, the load current and the tolerances of the components of the conversion device, namely the resonant inductor and the resonant capacitor. Then, the conversion device is started in open loop mode at a nominal resonant frequency. In parallel, the output voltage of the conversion device is measured and compared to the calculated input voltage. The controller function is configured by an input voltage calibration parameter whose value depends on the difference between the expected nominal voltage value and the voltage value measured in real conditions. This control method makes it possible to optimize the energy efficiency of the conversion device thanks to the control function with regard to a solution using tables stored in memory.

[0006] An objective of the invention is to propose a calibration solution making it possible to reinforce the reliability of a voltage conversion device due to manufacturing dispersions of the actual electrical characteristics of the electronic components. In particular, an objective of the invention is to guarantee the operation of the power electronics controller in the nominal frequency ranges of the electronic components. An objective of the invention aims to meet the highest requirements of the safety integrity levels expected for the vital equipment of electrified vehicles, in particular the power systems for the voltage conversion of the electrical systems.

[0007] More specifically, the invention relates to a method for calibrating a voltage conversion device comprising a power circuit comprising a resonant circuit determining a nominal resonant frequency and a controller capable of delimiting, in a first calibration state, an operating frequency interval of the conversion device by a low limit frequency and an upper limit frequency around a theoretical value of the resonant frequency. According to the invention, the method comprises the following steps of measuring the actual value of the resonant frequency, and calibrating a second calibration state so as to configure the low limit frequency and the upper limit frequency of the operating frequency interval around the actual value of the resonant frequency according to at least one predetermined frequency deviation.

[0008] The method according to the invention may include the following additional characteristics, alone or in combination:

[0009] - The low limit frequency is calibrated according to a first frequency deviation by relative to the actual resonant frequency and the upper limit frequency is calibrated according to a second frequency deviation from the actual value of the resonant frequency.

[0010] - The measurement of the actual value of the resonant frequency and the calibration are performed periodically during an expected life cycle of the conversion device tension.

[0011] - The measurement and calibration steps are performed during a recharging phase of a battery system powered by the conversion device.

[0012] The invention further provides a voltage conversion device comprising a power circuit comprising a resonant circuit determining a nominal resonant frequency and a controller capable of delimiting, in a first calibration state, an operating frequency interval of the conversion device by a low limit frequency and a high limit frequency around a theoretical value of the resonant frequency according to at least one predetermined frequency deviation, in which the controller is configured to measure the actual value of the resonant frequency, and to calibrate a second calibration state so as to configure the low limit frequency and the high limit frequency of the operating frequency interval around the actual value of the resonant frequency according to at least said predetermined frequency deviation.

[0013] According to one variant, the controller is configured to periodically perform the measurement and calibration during an expected life cycle of the voltage conversion device.

[0014] The invention further provides an electrified vehicle comprising a voltage conversion device and a control unit configured to implement the calibration method according to any one of the preceding embodiments.

[0015] Further provided is a computer program comprising instructions which, when the program is executed by a control unit of a voltage conversion device, cause the latter to implement the calibration method according to any one of the preceding embodiments.

[0016] Further provided is a computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to implement the calibration method according to any one of the preceding embodiments.

[0017] The invention allows better management of the lifespan of the electronic components of a voltage conversion device in order to increase their lifespan as well as the optimal operation of the converter.

[0018] Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows, comprising embodiments of the invention given as non-limiting examples and illustrated by the appended drawings, in which:

[0019] [Fig. 1] schematically represents by a functional block diagram a voltage conversion device provided for the implementation of the calibration method according to the invention.

[0020] [Fig.2] schematically represents by a functional block diagram the calibration method according to the invention.

[0021] [Fig.3] schematically represents an example of application of the calibration method for an electrified vehicle.

[0022] The invention applies to power electronic systems comprising a resonant circuit, for example a power voltage conversion device of the AC / DC or DC / DC type. The invention applies to the fields of electrified vehicles, i.e. comprising an electric motor machine and power electronics, 100% electric or hybrid, preferably motor vehicles, but not only such as aircraft, tractors, bicycles, ships. More generally, the invention applies to any autonomous electrical system such as drones, robots or portable devices, computers, tablets, mobile phones, consoles, cameras, scanners, which are cited as a non-exhaustive list of application examples.

[0023] [Fig.l] schematically represents a voltage conversion device 1 comprising a first power circuit 2 comprising at least one resonant circuit. Typically, the first power circuit 2 of a voltage conversion device, for example of the AC / DC type, comprising a circuit of switches, for example of the MOSFET type, provided to be controlled at a switching frequency controlled by a second control circuit 3, designated by the term controller. Furthermore, the resonant circuit consists of at least one capacitor and inductor whose electrical characteristics determine a nominal operating resonant frequency. For this type of application, compliance with the operation of the switch circuit in the operating frequency range is essential and is particularly critical.

[0024] The controller 3 of the conversion device 1 is an integrated circuit comprising at least one computer and memories and electrical means provided for measuring the input and output voltages of the conversion device 1, as well as the operating frequency of the first switch circuit. For example, the controller 3 may be a DSP (Digital Signal Processor) type circuit. In addition, the controller 3 implements at least one function 4 for controlling the operating frequency of the conversion device 1. More precisely, the controller 3 delimits an authorized operating frequency interval delimited by a first low limit frequency FLB and a second high limit frequency FLH.In a first calibration state, upstream of the design and manufacturing process, function 4 is calibrated so that the low limit frequency FLB and the high limit frequency FLH frame the theoretical value FRT of the nominal resonant frequency. This theoretical value is established in design from the electrical characteristics of the resonant circuit, in particular, established in the specifications. However, the function . 4 is provided for the dynamic calibration of the values of the low limit frequency FLB, the high limit frequency FLH, as well as the FRR value of the resonant frequency of the operating interval. These values are recorded in the memory of the controller 3 for the implementation of an operating program of the conversion device 1 during a voltage conversion, in particular for a program for scheduling the opening and closing states of the switches of the first power circuit 2.

[0025] The control of the resonant frequency is carried out by defining the external conditions, in particular an input voltage and an output load. A resonant frequency is measured by carrying out several previously chosen operating points corresponding to real load points of the conversion device. In this way, a calibration is operable under real operating conditions of the conversion device and is regularly reproducible.

[0026] For this purpose, the invention further provides a calibration method for dynamically calibrating the characteristic values of the operating frequency interval of the actual electronic components obtained from the supplier(s). The calibration is implemented by the controller 3.

[0027] In [Fig.2], the calibration method is schematically described by a functional block diagram. In a first calibration step 21, the controller of the conversion device is calibrated so that the interval of the authorized operating frequency is framed by a first lower limit frequency and a second upper limit frequency around the theoretical value FRT of the resonant frequency.

[0028] The method comprises a second step 22 of measuring the actual resonant frequency. The second step is implemented by the controller from, for example, a diagnostic program configuring the conversion device so as to detect the actual resonant frequency characteristic of the device. This type of diagnostic program is known to those skilled in the art. The actual resonant frequency FRR may vary significantly from the characteristics expected in the specifications. The diagnostic program is executed, for example, upon first commissioning of the conversion device. The actual resonant frequency FRR is determined in accordance with the calibration method according to the invention, preferably periodically from the start of the life cycle of a conversion device until the end of life.

[0029] During a complete or partial charging operation of a battery system by the voltage conversion device, the resonant frequency will adapt as the charge of the battery system evolves. A charging operation of a battery system, in particular of an electrified vehicle, is a process rela tively slow, which has the advantage of allowing the comparison of the real frequency with a theoretical curve determining the predetermined deviations and of making a recalibration.

[0030] Then, the calibration method comprises a third step 23 of calibrating a second calibration state of the low limit frequency FLB and the high limit frequency FLH of the operating frequency interval around the actual value FRR of the resonant frequency according to at least one predetermined frequency deviation. The low limit frequency FLB is calibrated according to a first frequency deviation ECF1 relative to the actual resonant frequency FRR and the high limit frequency FLH is calibrated according to a second frequency deviation ECF2 relative to the actual resonant frequency. The first deviation and the second deviation may be of distinct or equal value and are determined from a theoretical curve recorded in the memory of the control unit.

[0031] As a non-limiting example, when the theoretical value of the resonant frequency is equal to 100khz, in the first calibration state the operating interval is between 95khz and 300khz. When implementing the second measurement step 22, the diagnostic program detects that the actual value of the resonant frequency is equal to 97khz. The third calibration step 23 configures the low limit frequency FLB to 93khz according to the same first deviation ECF1 and the high limit frequency FLH of the operating frequency interval to the value of 297khz according to the same second deviation ECF2, around the actual value FRR of the resonant frequency.

[0032] The measurement 22 and calibration 23 steps may be repeated periodically during the life cycle of the conversion device. Indeed, during aging, the electrical characteristics of the components, in particular of the resonant circuit, are likely to evolve and modify the resonant frequency. The calibration method makes it possible to dynamically adapt the interval of the operating frequency.

[0033] Some or all of the functions of the conversion device are controlled by the controller. The controller may include at least one processor that executes instructions stored in a computer-readable medium such as non-volatile memory. The controller may also be multiple computing devices that control individual components or subsystems of the conversion device in a distributed manner. The processor may be any conventional processor, such as a commercially available central processing unit. Alternatively, the processor may be a dedicated device such as an application-specific integrated circuit (ASIC) or other hardware processor such as a DSP.

[0034] In [Fig.3], a preferred application of the calibration method has been described according to the invention for an electrified vehicle 30 comprising a voltage conversion device 31. The vehicle 30 may be a hybrid or fully electric vehicle. The vehicle 30 comprises an electric prime mover intended to move the vehicle and powered by a traction battery system 33. Some or all of the functions of the vehicle 30 are controlled by a control unit 35. The voltage conversion device 31 comprises a control unit comprising a computer and memories configured for implementing the calibration method according to the invention. In particular, the memories have a recorded program comprising instructions which, when the program is executed by the voltage conversion device control unit, cause the latter to implement any one of the embodiments of the calibration method.The voltage conversion device 31 is provided for converting the voltage of a direct voltage bus, operating at 400 volts for example, delivered by the battery system 33 into a voltage 34 of the on-board network of the vehicle, operating at 12 volts. The conversion device 31 is also provided for converting the alternating voltage delivered by an external source 38 to the vehicle 30, for example by a charging station 37 into a direct voltage 32 provided for recharging the battery system 33 through a charging interface 36.

[0035] The calibration method is preferably designed to operate during a charging operation of the battery system 33, in particular during charging from a source external to the vehicle. More precisely, the measurement and calibration steps of the calibration method are carried out during a recharging phase of the traction battery system 33 when it is powered by the conversion device.

[0036] This life phase has the advantage of allowing the comparison of the actual frequency with a theoretical curve recorded in the memory of the control unit and of carrying out a recalibration to delimit the operating frequency interval.

[0037] The invention is described in the above by way of example. It is understood that the person skilled in the art is able to produce different variant embodiments of the invention by associating, for example, the different characteristics above taken alone or in combination, without departing from the scope of the invention.

Claims

Claims

1. Method for calibrating a voltage conversion device (1) comprising a power circuit (2) comprising a resonant circuit determining a nominal resonant frequency and a controller capable of delimiting, in a first calibration state, an operating frequency interval of the conversion device (1) by a lower limit frequency (FLB) and an upper limit frequency (FLH) around a theoretical value of the resonant frequency, the method being characterized in that it comprises the following steps: - measuring (22) the actual value (FRR) of the resonant frequency, - calibrating (23) a second calibration state so as to configure the lower limit frequency (FLB) and the upper limit frequency (FLH) of the operating frequency interval around the actual value (FRR) of the resonant frequency according to at least one predetermined frequency deviation.

2. A calibration method according to claim 1, wherein the lower limit frequency (FLB) is calibrated according to a first frequency deviation from the actual resonant frequency (FRR) and the upper limit frequency (FLH) is calibrated according to a second frequency deviation from the actual value of the resonant frequency (FRR).

3. A calibration method according to claim 1 or 2, wherein the measurement (21) of the actual value (FRR) of the resonant frequency and the calibration (23) are performed periodically during an expected life cycle of the voltage conversion device (1).

4. Calibration method according to any one of claims 1 to 3, in which the measuring (22) and calibrating (23) steps are carried out during a recharging phase of a battery system powered by the conversion device (1).

5. Voltage conversion device (1) comprising a power circuit (2) comprising a resonant circuit determining a nominal resonant frequency and a controller (3) capable of delimiting, in a first calibration state, an operating frequency interval of the conversion device by a lower limit frequency (FLB) and an upper limit frequency (FLH) around a theoretical value of the resonant frequency according to at least one predetermined frequency deviation, characterized in that the controller (3) is configured to: - measuring the actual value (FRR) of the resonant frequency, - calibrating a second calibration state so as to configure the low limit frequency (FLB) and the high limit frequency (FLH) of the operating frequency interval around the actual value (FRR) of the resonant frequency according to at least said predetermined frequency deviation.

6. A device according to claim 5, wherein the controller (3) is configured to periodically perform the measurement and calibration during an expected life cycle of the voltage conversion device (1).

7. An electrified vehicle (30) comprising a voltage conversion device (31), a traction battery system (33) and a control unit configured to implement the calibration method according to any one of claims 1 to 4.

8. A computer program comprising instructions which, when the program is executed by a control unit of a voltage conversion device, cause the latter to implement the calibration method according to any one of claims 1 to 4.

9. A computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to implement the calibration method according to any one of claims 1 to 4.

Images