Method, controller and circuit for operating converter in operating range

Abstract

The present application relates to a method of operating a converter (12) within an operating range, the converter being included in a circuit (10) for a vehicle (50), the circuit (10) comprising at least one load (16) and at least one battery pack (18), the method comprising the steps of: determining the operating range by determining a relationship between an output current of the converter (12) and a fast current drop in the circuit (10), the fast current drop is based on parameters from the at least one load (16) and the at least one battery pack (18); and regulating the voltage from the converter (12) for controlling the output current within the determined operating range.

Description

Technical Field

[0001] The present application relates to electric and hybrid vehicles provided with a service battery and loads powered by a converter. Background Art

[0002] A conventional electrically propelled vehicle is provided with an electrical system comprising at least one converter, several loads and at least one service battery. The electrical system may be provided with electrical energy from a propulsion battery system of the vehicle. The converter is arranged to convert a high voltage from the propulsion battery system into a lower voltage for use, for example, in energizing the loads and charging the service battery.

[0003] The converter is provided with an overvoltage protection circuit to prevent the converter from outputting a high voltage in the event of an internal catastrophic fault. Since the converter input energy is supplied by the propulsion battery system, the overvoltage protection circuit is a precautionary measure. However, the overvoltage circuit cannot distinguish between a high voltage caused by an internal fault or a high voltage caused by a rapid change in current in a low-voltage power system.

[0004] The latter situation can occur if a load or maintenance battery in the power system is suddenly disconnected (commonly known as a load dump), resulting in high voltage transients. If the maintenance batteries remain connected during a load dump, they will generally provide a voltage stabilizing effect, thereby reducing the voltage transient. However, if the maintenance battery is suddenly disconnected, such as due to a fault or corrosion-related interruption of the battery cable terminals, there is no stabilizing effect on the voltage transient. If battery loss occurs at high battery charging currents, the voltage transient can trip the converter's overvoltage protection circuit.

[0005] On the other hand, if the maintenance battery is disconnected without causing very high voltage transients, the large reduction in load current may also cause high voltage transients that may trigger the overvoltage protection circuit. In addition, the large kickback current from the load may trigger the overvoltage protection circuit. In this regard, the problem is that if the battery is disconnected and the overvoltage protection circuit is tripped, all power to the load is lost, and thus the vehicle has no power to perform vehicle electrical functions.

[0006] One such critical function could be the electric servo system to the vehicle's steering system, rendering the vehicle uncontrollable. One possible solution to avoid such critical situations is to have redundancy in the power system, in particular to have several maintenance batteries that are independently connected in the system to ensure that power is maintained in the event of a failure of one of the batteries. The disadvantages of such a system are increased battery costs and increased space requirements as well as increased weight. Summary of the invention

[0007] The object of the present application is to remedy the disadvantages of the prior art regarding the operation of a converter in an electrically propelled vehicle. This object is achieved by a method according to the independent patent claim. Preferred solutions form the subject matter of the dependent patent claims.

[0008] According to one aspect, a method of operating a converter within an operating range is provided, the converter being included in a circuit for a vehicle, the circuit including at least one load and at least one battery. The method may include the steps of determining the operating range by determining a relationship between an output current from the converter and a rapid current drop in the circuit, the rapid current drop being based on parameters from the at least one load and at least one battery; and adjusting a voltage from the converter for controlling the output current within the determined operating range.

[0009] The term "rapid current drop in a circuit" refers in this context to a current drop in a circuit due to a current drop caused by a behavior of at least one load and / or at least one battery, whereby the current drop occurs very quickly or rapidly, i.e. within a short time. The behavior may for example be a disconnection, a malfunction or a failure of one or more loads and / or batteries in the circuit.

[0010] The relationship between the output current from the converter and the rapid current drop in the circuit may define a boundary or line that delimits at least a portion of the operating range or region of the converter. This will be explained in more detail below.

[0011] Therefore, in other words, a method of operating a converter within an operating range is provided, the converter being included in an electrical circuit for a vehicle, the electrical circuit comprising at least one load and at least one battery pack. The method comprises the steps of: determining the operating range by determining a relationship between an output current from the converter and a rapid current drop in the electrical circuit, wherein the rapid current drop is caused by a disconnection, fault or failure of at least one load and / or at least one battery; and regulating an output voltage from the converter for controlling the output current from the converter within the determined operating range.

[0012] With this solution, the converter will operate within an operating range in which the risk of the converter's overvoltage protection switch being triggered by sudden voltage transients will not exist if a load or battery pack in the circuit is suddenly disconnected or its function is suddenly interrupted. In this regard, the parameters mentioned in the above paragraphs include normal functional parameters, such as the behavior of different loads during normal operation, as well as abnormal parameters, such as failure or malfunction of the load and battery pack, or even disconnection, such as disconnection of a battery connection from a battery electrode. The term "battery pack" refers in this document to any battery cell, device or apparatus, such as one or several so-called low-voltage batteries (12V), which will be explained in more detail below. Therefore, in the present disclosure, battery packs will be interchangeably referred to as "battery pack(s)", "battery", "batteries" or "maintenance batteries".

[0013] According to another aspect, the method may include a further step of measuring the current through at least one battery for operating the converter. This data may then be used so that if the converter is operating outside of a determined operating range, the voltage is reduced. Thus, when adjusting the voltage of the converter, data representing the measured current through at least one battery is used in order to control the output current from the converter. By measuring the current through at least one battery, it can be determined how much current the battery uses. From this, it can be determined what percentage of the total current in the circuit that the battery is using. By knowing this, it can be determined how much current would be lost if the battery were disconnected or failed. If the amount of current used by the battery is large, a large current drop may occur, which may indicate that the converter voltage should be reduced, and vice versa. Therefore, an advantage of this embodiment is that the converter voltage can be controlled so that the risk of the overvoltage switch being triggered is even further reduced.

[0014] According to one aspect, the determination of the operating range may be primarily based on a sudden disconnection or failure of at least one battery pack. This is because if a battery is disconnected, it is generally more severe than if one or more loads are disconnected or failed, because the battery is able to reduce the adverse effects of sudden high voltage transients if a sudden current drop occurs.

[0015] When operating a vehicle, the method may include the following steps: when the vehicle is started, setting a low output voltage of the converter (also referred to herein as a charging voltage on the circuit), measuring the output current from the converter and the current through at least one battery, comparing the measured data with a determined operating range, and adjusting the voltage on the circuit, wherein if it is within the determined operating range, the voltage is increased, and if it is outside the determined operating range, the voltage is reduced.

[0016] Even though the battery may require a higher charging current, such as if the battery is discharged or low on charge, the low voltage at vehicle start-up provides a low charging current well within the determined operating range. The voltage is then increased as long as the converter operates within the operating range, but once the converter operates outside the operating range, the voltage is reduced in order to return to the permitted operating range. In this regard, voltage increases may be performed in steps of 1% to 5%, and voltage decreases may be performed in steps of 2% to 10%.

[0017] According to the present application, it may also include a computer program product including instructions, which, when the computer program product is executed by a computer, causes the computer to implement the method of operating the converter; and a computer-readable storage medium including instructions, which, when executed by a computer, causes the computer to implement the method.

[0018] Furthermore, according to the present application, it may include a controller connected to a converter in a circuit, the circuit including at least one load and at least one battery, the controller including data within a determined operating range, wherein the controller is configured to perform the method. The controller may further be included in a circuit for a vehicle, the circuit including a converter, at least one load and at least one battery, a sensor for measuring a current through at least one battery, a sensor for measuring an output current from the converter, and a sensor for measuring a voltage on the circuit, wherein the controller is connected to the sensor and the converter. The circuit may then be arranged in a vehicle.

[0019] These and other aspects and advantages of the present invention will become apparent from the following detailed description of the invention and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the following detailed description of the present invention, reference will be made to the accompanying drawings, in which

[0021] Figure 1 is a schematic diagram of an electric circuit included in a vehicle, in particular an electric propulsion vehicle,

[0022] Figure 2 is a diagram showing the relationship between the relative converter output current and the relative change of the converter output current,

[0023] Figure 3 is a diagram showing an example of the relationship between the relative battery voltage and the relative charging current,

[0024] Figure 4 Schematically shows a setup for determining the operating range of the converter,

[0025] Figure 5 A flow chart showing an example of operating a converter during operation of a vehicle, and

[0026] Figure 6 A schematic diagram of a vehicle provided with a circuit according to the present application is shown. DETAILED DESCRIPTION

[0027] Figure 1 Schematically illustrated is an electric power system 10 included in an electric propulsion vehicle. The power system 10 in turn includes a converter 12 electrically connected to a propulsion battery pack 14 of the vehicle, a plurality of loads 16, and a service battery 18. The converter 12 is designed to convert a high voltage (e.g., 500V and above) from the propulsion battery system into a low voltage (e.g., 12-48V) for the loads and the service battery.

[0028] The converter is provided with an overvoltage protection circuit to prevent high voltage from the converter in the event of a serious internal fault. The load 16 can be many different types of electric equipment required for the vehicle function, some of which are critical, such as, for example, a power steering servo. Regarding the service battery 18 (also referred to as the service battery pack 18), it can typically be one or two 12V batteries, in the latter case typically connected in series to obtain 24V. The output current from the converter 12 is preferably measured by a sensor 34, and the charging current through the battery 18 is preferably measured by a sensor 30. In addition, the voltage on the circuit can be measured by a sensor 36. The data from the sensor can be provided to the controller 32 for controlling the operation of the converter 12.

[0029] Energy from the converter 12 via the propulsion battery system 14 is thus provided for operating the different loads 16 and for charging the service battery 18. In order to determine in particular the loads 16 (and more in particular the critical loads), it is important that these loads 16 are always provided with power. Typically, the required energy is provided by the converter.

[0030] However, if there is a disturbance in the power system, and in particular if the service battery 18 is suddenly disconnected, the current drop may be significant, which in turn may result in very high voltage transients. This in turn may cause the overvoltage protection of the converter 12 to trip, so that the energy from the converter 12 is cut off. If both the battery 18 and the converter 12 are lost, the load 16 is no longer provided with power, which may result in a dangerous driving situation if, for example, the vehicle is provided with an electric steering servo. It is then no longer possible to steer the vehicle. In this regard, there may be other components and functions that are critical or at least very important for the functioning of the vehicle for which the loss of power may be critical.

[0031] In this context, the object of the present application is to ensure that as much as possible the functionality of the converter 12 is maintained. It is then important that the converter 12 operates within a current range where the overvoltage protection is unlikely to trip if a sudden current drop should occur.

[0032] Figure 2 A diagram illustrating different operating ranges is shown. The X-axis shows the output current from the converter to the power system as a percentage of the maximum converter output current, and the Y-axis shows the magnitude of the current drop or the percentage change in the maximum converter output current, where 100% represents a drop from, for example, 180A to 0A, and 50% represents a drop from, for example, 180A to 90A. In summary, a small drop is likely to eliminate the risk of the converter's overvoltage protection tripping. It should be understood that 180A is considered to be an example only, and the actual converter 12 used may have a lower or higher maximum current output.

[0033] Figure 3 An example of the relationship between battery voltage and battery current is shown. As shown, as the charging voltage increases, the charging current increases. Another battery characteristic is that if the battery is discharged, the voltage drops. The more current is discharged from the battery, the lower the battery voltage becomes. The exact relationship between battery voltage and battery current varies greatly under different conditions. Battery temperature, battery charge level, and dynamics (current changes) are just three of the influencing factors that make it difficult to give a quantitative relationship.

[0034] Depending on the application, it is important to determine and plot in a diagram the operating region, zone or range in which the converter 12 can safely operate without the risk of tripping and thus disconnecting. One possible example of performing such a determination is Figure 4 . In this case, the setup is a controlled laboratory test system. The converter 12 is connected to at least two adjustable loads 16', 16" of known properties and at least one maintenance battery 18. The output current from the converter is measured by sensor 34 and the current through at least one battery is measured by sensor 30. The voltage across the converter 12 is also measured by sensor 36.

[0035] When performing the test, the system is started with medium voltage and load. Then, the battery 18 is disconnected by the switch 40. Then, the load 16', 16" is adjusted to the desired output current, and Figure 4The disconnection of the load 16" in the converter 12 also provides the desired sudden current drop. That is, the loads 16', 16" are also adjusted so that when the load 16" is disconnected, a desired rapid or sudden current drop is achieved in the circuit. The load 16" is then disconnected by the switch 42 to produce the desired sudden current drop, and it is noted whether the overvoltage switch in the converter 12 is tripped. This operation is then performed for different output currents and sudden current drops of different magnitudes to determine the operating range or zone ( Figure 2 In the region 1 in the operating range or region, the converter 12 continues to operate without tripping the overvoltage switch. A boundary line R1 is also determined, where the region above the boundary R1 ( Figure 2 Zone 2 in (A) is an operating area where the overvoltage switch may trip and is to be avoided during operation of a vehicle with a converter 12 of this type. Therefore, the boundary line R1 is determined empirically by the above method and describes the relationship or association between the output current from the converter and the rapid current drop in the circuit. In other words, the relationship or association between the output current from the converter and the rapid current drop in the circuit defines the boundary line R1. Therefore, the operating range (zone 1) is also defined. Through this test, a second boundary line R2 and a zone 3 above the second boundary line R2 can also be found, in which the overvoltage switch is likely to trip. Zone 3 can even define a zone where the overvoltage switch will always trip when the converter 12 experiences a rapid current drop. If the vehicle is in an operating state where no danger occurs in the event of a power loss, such as when the vehicle is stationary, operation in zone 2 or even in zone 3 may be allowed.

[0036] As described above, the relationship between the output current from the converter and the rapid current drop in the circuit can define a boundary or line that defines at least a portion of the operating range or region of the converter. In addition, several lines can be defined so that more regions or operating ranges are defined. These lines are Figure 2 The operating range or area is represented by R1 and R2. Figure 2 In the region 1 and below R1. Figure 2 In FIG. 1 , the operating range or region (Region 1) is contained in a two-dimensional space spanned by the possible output currents of the converter and possible changes (e.g., decreases) in the output current of the converter. Figure 2As shown, the entire operating range or zone is bounded by three lines. The first line is a line defined by the relationship or association between the output current from the converter and the rapid current drop in the circuit. The second line is a vertical line of the converter 12 at 100% output current. Finally, the third line is a 45-degree line that defines the maximum current drop possible at a specific converter output current (for obvious reasons, the current drop will never exceed the output current). The second and third lines do not need to be drawn empirically as they follow mathematical laws. The purpose is to keep the converter 12 operating in this zone 1 unless a higher risk of tripping the overvoltage switch is acceptable, such as in a stationary state. By mapping out the operating range in this manner, a robust and reliable way of determining whether the converter 12 is operating in an operating zone or operating range with an increased risk of tripping the overvoltage switch can be achieved. It should be understood that Figure 2 The illustrated association applies in particular to rapid current drops, i.e. current drops caused by, for example, disconnection, fault failure of one or more loads and / or batteries in the circuit. If the current drops very slowly, the risk of the overvoltage switch tripping is lower. Of course, the operating area or range zone 1 will still define an area where the risk of the overvoltage switch tripping is eliminated.

[0037] Another way to determine the operating range is to perform tests on a production vehicle equipped with a converter, a service battery pack, and a number of actual loads that the vehicle is equipped with. Then, different loads are activated to obtain specific output currents from the converter, where the output current is continuously measured, and a physical disconnection of the service battery pack is performed to provide a sudden current drop in the circuit. As with the above test, for different output currents and sudden current drops of different magnitudes, an operating range is obtained and determined within which the converter will continue to operate without tripping the overvoltage switch.

[0038] Figure 5 An operation vehicle 50 ( Figure 6 ) is a flow chart of an example of a vehicle having a converter 12 having an operating range determined as described above. At vehicle start-up, the converter is controlled to output a low relative charging voltage, and as from Figure 3 As can be seen, the diagram shows an example of the relationship between the relative charging voltage and the relative charging current of a battery, with a low current being fed to the battery. This is done even if, for example, the maintenance battery pack 18 is considerably discharged and can be fed with a larger charging current. The battery charging current is determined by the battery sensor 30 ( Figure 1) is continuously measured and processed by a suitable controller 32 (also referred to as control means 32), which is connected to the converter 12 and controls and regulates the converter. In this regard, the output current from the converter 12 and the voltage on the circuit (also referred to herein as the voltage on the converter 12) are also continuously measured by the sensor 34. The measurement data are transmitted to the controller 32. The controller 32 is also provided with stored data about the previously determined permissible operating range (zone 1). If the measured current data indicates that the converter is operating in zone 1, the controller will adjust the voltage on the circuit, thereby increasing the charging current through the maintenance battery 18. Merely as an example, the voltage increase may be 1% within 1 second. If the measured data indicates that the converter is still in zone 1, the voltage increase may continue. However, if the measured data indicates that the converter is operating on or above the permissible zone, i.e., operating in zone 2, the voltage on the converter 12 is reduced, which may be 1% within 1 second, for example. In addition, if the converter is above zone 2, operating in zone 3, the controller immediately reduces the voltage so as to set the converter within the permissible operating range.

[0039] By actively controlling the converter to operate within the permitted, safe operating range, the risk of the converter disconnecting from the circuit is greatly reduced. Figure 1 Although described as a separate unit in FIG, it may also be integrated in an electronic unit that handles several functions of the vehicle. Alternatively, the controller may be an integrated part of the converter.

[0040] The control device 32 includes a control circuit to perform a method according to any of the steps, examples or embodiments described herein. The control device 32 may include one or more electronic control units (ECUs) connected to a controller area network (CAN). For example, the control device 32 may be an electronic control unit ECU of an ACC.

[0041] In more detail, the control device 32 includes one or more computers and memories. The computer includes any hardware or hardware / firmware device implemented using processing circuits, such as but not limited to a processor, a central processing unit (CPU), a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a system on a chip (SoC), a programmable logic unit, a microprocessor, an application-specific integrated circuit, or any other device capable of electronically performing operations in a defined manner.

[0042] In some embodiments, the computer readable medium can be a non-transitory computer readable medium, such as a tangible electronic, magnetic, optical, infrared, electromagnetic and / or semiconductor system, device and / or equipment. The computer readable memory is, for example, one or more memories in the memory in the control device 32. Therefore, the proposed method can be implemented as a computer program. Then, the computer program includes instructions that, when executed by a computer, cause the computer to implement a method according to any one of the aspects, embodiments or examples as described herein.

[0043] In further embodiments, the control device 32 is configured to perform a method according to any of the embodiments described above.

[0044] Although the above embodiments have been described mainly for electric vehicles, it should be understood that the solution according to the present application can also be used for hybrid vehicles provided with an electric motor for propulsion and another type of propulsion engine powered by, for example, diesel, gasoline, natural gas, to name a few. Furthermore, the solution has been described in conjunction with a converter. In this context, the converter is considered to be a universal power source, which may include other types of components capable of converting voltage levels, as well as a generator capable of providing voltage and current to a circuit including a battery.

[0045] It is to be understood that the embodiments described above and shown in the drawings are to be regarded only as non-limiting examples and that the solution can be modified in several ways within the scope of the patent claims.

Claims

1. A method of operating a converter (12) within an operating range, the converter being included in a circuit (10) for a vehicle (50), the circuit (10) including at least one load (16) and at least one battery pack (18), the method comprising the following steps: - determining the operating range by determining a relationship between an output current from the converter (12) and a rapid current drop in the circuit (10), the rapid current drop being based on parameters from the at least one load (16) and the at least one battery pack (18), and - regulating the voltage from the converter (12) for controlling the output current within a determined operating range.

2. The method of claim 1, further comprising the step of measuring a current through the at least one battery pack (18) for operating the converter (12).

3. A method according to claim 1 or 2, wherein the voltage is reduced if the converter (12) operates outside the determined operating range.

4. The method according to any of the preceding claims, wherein the determination of the operating range is primarily based on a sudden disconnection or failure of the at least one battery pack (18).

5. The method according to any one of the preceding claims, comprising the steps of: When the vehicle (50) is started, a low charging voltage is set on the circuit (10), the output current from the converter and the current through the at least one battery pack (18) are measured, The measured data is compared with the determined operating range and the voltage on the circuit (10) is adjusted, wherein If within the determined operating range, the voltage is increased, and If outside the determined operating range, the voltage is reduced. The method according to claim 5 , wherein the voltage increase is performed in steps of 1% to 5%.

7. The method according to claim 5 or 6, wherein the voltage reduction is performed in steps of 2% to 10%.

8. A computer program product comprising instructions which, when the computer program product is executed by a computer, cause the computer to perform the method according to any one of claims 1 to 7.

9. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to implement the method according to any one of claims 1 to 7.

10. A controller (32) connected to a converter (12) in a circuit (10), the circuit comprising at least one load (16) and at least one battery pack (18), the controller (32) comprising data within a determined operating range, wherein the controller (32) is configured to perform the method according to any one of claims 1 to 7.

11. A circuit (10) configured for use in a vehicle (50), the circuit comprising a converter (12), at least one load (16) and at least one battery pack (18), a sensor (30) for measuring a current through the at least one battery pack (18), a sensor (34) for measuring an output current from the converter (12) and a sensor for measuring a voltage across the circuit, and a controller (32) according to claim 10 connected to the sensors (30, 34) and the converter (12).

12. A vehicle provided with the circuit according to claim 11.

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