Dynamic control method for controlling the charging current of an electrical energy storage device of a motor vehicle

Abstract

The present invention relates to a dynamic control method for controlling the current of an electrical energy storage device (B) of a motor vehicle, the motor vehicle being equipped with at least one electrical energy generator (G), characterized in that the dynamic control method comprises: a first operation (1) for estimating the no-load voltage OCV of the storage device (B); a second operation (2) for measuring the available recharging current reserve A for recharging the storage device according to the energy generation capacity of the generator (G); a third operation (3) for determining the maximum charging current Amax authorized for the storage device; and a fourth operation (4) for determining the maximum voltage Vmax authorized for the storage device (B).

Description

Technical Field

[0001] The present invention claims the priority of French application N°1914275 filed on December 12, 2019, the contents (text, drawings and claims) of which are incorporated herein by reference.

[0002] The invention finds application in the field of electrical energy management in motor vehicles.

[0003] More precisely, the invention relates to a dynamic control method for controlling the charging current of an electrical energy storage device or of a storage device of a hybrid or electric motor vehicle having a thermodynamic powertrain. Background Art

[0004] In motor vehicles, components for providing electrical energy to various equipment include electrical energy storage devices or "reservoirs" (particularly 12V batteries which play an important role).

[0005] In order to simultaneously ensure a permanent balance between the supply of all equipment of the vehicle's onboard electrical system (which operates at 12 V), the generation of electrical energy and the charging of the storage devices, it is necessary to permanently regulate the current flowing in one or more storage devices of the vehicle in order to recharge the one or more storage devices when necessary. This adaptive measure is particularly important for lithium-ion type batteries, whose charging currents can be particularly high if not controlled.

[0006] In this context, it is therefore necessary to control the charging current that can flow in the storage device in accordance with the capabilities of the on-board system for ensuring the supply of electrical energy.

[0007] Management methods already exist for ensuring management of the charging current for lithium batteries of motor vehicles.

[0008] Thus, patent US10442373 describes a method for managing a lithium battery of a vehicle, the method being used to avoid overcharging or discharging of the battery, in order to protect the battery in complete safety and under various conditions, in particular when the battery is used as a low-voltage battery in the vehicle. The method is implemented with the aid of a system comprising a relay and a switch, the relay electrically connecting and disconnecting various equipment powered by the battery, the switch determining the connection state according to the manipulation of the user and generating activation and deactivation signals for activating and deactivating the relay according to the connection state. The system also comprises a controller for activating and deactivating the relay according to the connection state of the reconnection switch.

[0009] Some battery charging methods are also known from documents US2018134168A1 and 2016193940A1.

[0010] However, the known method is not able to dynamically control the charging current that can flow in the battery according to the electric energy generation capacity via the generator loaded in the vehicle. Summary of the invention

[0011] In this context, the present invention aims to provide a technical solution capable of continuously adapting the charging current circulating in the storage device, more specifically in the lithium-ion battery, according to the amount of current available and / or that can be generated by the electrical generator of the vehicle.

[0012] Furthermore, the solution needs to maintain a balance between the electrical energy that can be generated on the one hand and the electrical energy that can be provided to the storage and all electrical equipment of the onboard network on the other hand.

[0013] This object is achieved by means of a dynamic control method for controlling the current of a low-voltage electrical energy storage of a motor vehicle, the motor vehicle being equipped with at least one electrical energy generator to provide charging energy for charging the storage, characterized in that the dynamic control method comprises: a first operation for estimating the no-load voltage of the storage, the estimation being performed based on measured values ​​of the temperature, current and voltage of the storage; a second operation for measuring the available charging current reserve for recharging the storage according to the energy generation capacity of the generator; a third operation for determining the maximum charging current authorized for the storage; and a fourth operation for determining the maximum voltage authorized for the storage.

[0014] According to an advantageous characteristic of the method, the first operation enables estimation of the resistance of the memory.

[0015] According to a first embodiment variant of the method, the measured values ​​are provided by a monitoring box for monitoring the state of the storage device.

[0016] According to a further embodiment variant of the method, the measured values ​​are obtained with the aid of a mapping of the internal resistance of the accumulator which is formed as a function of the temperature of the accumulator.

[0017] According to another feature, the second operation is performed based on the switching-on cycle of the generator and on the temperature of the generator.

[0018] Preferably, the current reserve is determined by calculating the difference between the current switching duty cycle of the generator on the one hand and the limiting load ratio of the generator on the other hand.

[0019] According to yet another feature, the third operation is performed based on a state of charge of the memory, a current of the memory, a temperature, and the available current reserve.

[0020] According to a variant implementation of the method, the limiting current of the memory is predetermined based on the temperature of the memory and the charge state of the memory, and then the sum of the current and the available current reserve is compared with the limiting current so that when the sum of the current and the reserve is less than or equal to the limiting current, the authorized maximum charging current is equal to the sum, and when the sum is greater than the limiting current, the authorized maximum charging current is equal to the limiting current.

[0021] According to other features, the fourth operation is performed based on the no-load voltage of the memory, the estimated resistance of the memory and the authorized maximum current, so that the authorized maximum voltage is obtained by adding the product of the internal resistance of the memory and the authorized maximum current of the memory to the no-load voltage of the memory.

[0022] Another object of the invention is to provide a motor vehicle equipped with an on-board computer and software capable of and intended to implement the dynamic control method for controlling the current of a 12V storage as defined above.

[0023] The method of the invention is very generally applicable to controlling the charging current of conventional lead-acid batteries as well as the charging current of lithium-ion batteries equipped on motor vehicles with thermal, hybrid or electric powertrains.

[0024] The invention in particular provides a solution to the problems caused by the impending obsolescence of lead batteries on board vehicles in Europe.

[0025] The method of the present invention is able to manage the size and cost of on-board electrical energy generators that may be affected by the transition to lithium-ion technology, and provide a vehicle 12V energy management system that is compatible with this new technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features and advantages of the present invention will become more apparent from the following detailed description of the present invention and the accompanying drawings, in which:

[0027] Figure 1 A preferred operating example of a dynamic control method for controlling a charging current of an electrical energy storage device according to the invention is schematically shown. DETAILED DESCRIPTION

[0028] For greater clarity, the same or similar elements are denoted by the same reference numerals in the specification and drawings.

[0029] Naturally, the embodiments of the method of the invention shown in the above-mentioned figures and described in the following are given only as non-limiting examples. It is expressly provided that different examples can be provided and that different examples can be combined with each other to provide further examples.

[0030] The invention relates to the field of management of electrical energy used in motor vehicles equipped with a low-voltage electrical storage device (for example a 12V battery) and whose powertrain is thermal or hybrid or even electric.

[0031] More specifically, the present invention relates to a method for dynamically adapting the current of a low-voltage electrical storage device (hereinafter referred to as B in the figure, more specifically a 12V lithium-ion battery) in an adaptation system, the system comprising at least one electrical energy generator (hereinafter referred to as G in the figure, such as a DC / DC voltage converter) equipped on a hybrid or electric vehicle or a vehicle AC generator with a combustion engine (the vehicle AC generator is used to provide electrical energy to charge the electrical storage device).

[0032] The method according to the invention serves to control and regulate the voltage to be applied to the terminals of a 12V accumulator simultaneously as a function of the available current reserve and the amount of current that can be generated by the vehicle electrical generator in order to permanently adapt the charging current flowing in the accumulator.

[0033] The method is carried out continuously without causing a disruption in the balance between the electrical energy that can be generated and the electrical energy to be provided to the storage device and thus to all electrical equipment of the onboard power system.

[0034] In particular, the control of the charging current flowing in the storage device is a particularly critical and delicate operation in on-board electrical systems equipped with lithium-ion technology batteries, since these storage devices can incur very high charging currents (greater than 100 A).

[0035] In fact, this type of storage requires either an overdimensioning of the electrical generator, which in particular entails significant additional costs, or the implementation of adaptive control and limitation methods for controlling and limiting these high charging currents, such as provided by the present invention.

[0036] like Figure 1 As shown, in order to ensure dynamic control of the charging current of the 12V storage B, the method of the present invention includes the following operations controlled by an on-board computer with appropriate software.

[0037] A first operation 1 consists in estimating the no-load voltage (OCV, also called open circuit voltage) of the storage B. This operation is followed by a second operation 2 for measuring the available charging current reserve A for recharging the storage B according to the energy generating capacity of the generator G. A third operation 3 ensures the determination of the maximum charging current Amax authorized for the storage B and is continued by a fourth operation 4 aimed at determining the maximum voltage Vmax authorized for the storage B. Each of these operations will be described in detail in the description hereinafter.

[0038] A first operation 1 is performed based on measurements of temperature T, current C and voltage V of the storage device B and also enables estimation of the internal resistance R of said storage device. These measurements are preferably provided by a monitoring box (not shown) for monitoring the state of said 12V storage device, which optionally integrates this functionality.

[0039] However, according to a variant of the method according to the invention, it is possible to provide that these measured values ​​are obtained with the aid of a mapping of the internal resistance of the storage device B which is constructed as a function of the temperature T of the storage device.

[0040] The no-load voltage OCV of the memory B thus corresponds to the formula; OCV=V-[A×R]. If necessary, filtering of the acquired signal may prove advisable in order to have noise-free information. A first-order low-pass filter is thus adapted.

[0041] The second operation 2 is aimed at determining the charging current reserve (that is to say the current quantity A which the generator G can supply to the 12 V storage device (B), in particular for recharging the latter).

[0042] This second operation is performed based on the opening duty cycle RCO or the load ratio and the temperature of the generator G. The current reserve A is determined by calculating the difference between the current opening duty cycle RCO of the generator G on the one hand and the limiting load ratio RCOm of said generator on the other hand.

[0043] For this purpose, the current load ratio RCO of the generator G (which is an image of the amount of energy produced and therefore of the amount of energy consumed at each moment by the vehicle's onboard network and the storage B) is compared with a limit load ratio RCOm (which is determined as a static or dynamic parameter). This limit load ratio can be determined, for example, to be 90%.

[0044] The deviation between these two values ​​of the utilization rate of the generator G is subsequently used to determine the available current reserve A in terms of the generating capacity at the location of the generator G used as a function of its temperature Tg by means of a mapping of its generating capacity.

[0045] The available current reserve A is thus given by function f according to the formula; A=f(T,RCO-RCOm), where f is a mapping function of the reserve current that can be generated by the generator G of the electrical energy supply system of the vehicle, while respecting the scenario balance: energy produced / energy consumed.

[0046] The purpose of the third operation 3 is to determine the maximum charging current Amax or the optimal charging current that can be used for recharging the memory B. This operation enables the recharging of said memory to be ensured while controlling the associated current, which is necessary on systems using 12V lithium-ion memories that tend to receive strong charging currents.

[0047] In fact, in the absence of control, these charging currents could compromise the balance between electrical generation, supply of the onboard network of the vehicle and recharging of the storage device B, for example by saturating the storage device.

[0048] This third operation 3 is performed based on the state of charge SOC of the storage device, the current C of the storage device, the temperature T of the storage device and the available current reserve A obtained during the second operation 2 .

[0049] For this purpose, the limiting current Cm that can flow in the storage device B is determined in advance as a function of the temperature T and the state of charge SOC of the storage device, and the sum of the current C and the available current reserve A is then compared with the limiting current Cm. The limiting current can be determined by using a mapping as a function of the state of charge and temperature using the characteristic specifications of the 12 V storage device (delivered by its manufacturer or supplier).

[0050] The maximum current Amax authorized for memory B is determined by:

[0051] - When C+A is less than or equal to Cm, then Amax=C+A, and,

[0052] -When C+A is greater than Cm, then Amax=Cm.

[0053] For the purpose of carrying out a dynamic regulation of the current that can be drawn by the storage B (particularly when using lithium-ion batteries), the fourth operation 4 aims at determining the maximum set voltage Vmax that can be applied to the terminals of the storage B without the risk of exceeding the maximum charging current that takes into account the generating capacity of the electrical generator or generators of the vehicle. This operation thus makes it possible to permanently adapt the current drawn by the storage B according to the amount of energy that can be generated by the electrical generator G.

[0054] This fourth operation 4 is thus performed based on the no-load voltage OCV of the memory, the estimated internal resistance R of the memory and the authorized maximum current Amax by applying the formula Vmax=OCV+[R×Amax].

Claims

1. A dynamic control method for controlling the current of a low-voltage electrical energy storage device (B) of a motor vehicle, the motor vehicle being equipped with at least one electrical energy generator (G) for providing charging energy for charging the low-voltage electrical energy storage device (B), characterized in that The dynamic control method includes: a first operation (1), the first operation is used to estimate the no-load voltage OCV and resistance R of the low-voltage electric energy storage (B), and the estimation is performed based on the measured values ​​of the temperature T, current C and voltage V of the low-voltage electric energy storage (B); a second operation (2), the second operation is used to measure the available charging current reserve A for recharging the low-voltage electric energy storage (B) according to the energy generation capacity of the electric energy generator (G); a third operation (3), the third operation is used to determine the maximum charging current Amax authorized for the low-voltage electric energy storage based on the charge state SOC, current C, temperature T and the available charging current reserve A of the low-voltage electric energy storage (B); and a fourth operation (4), the fourth operation is used to determine the maximum voltage Vmax authorized for the low-voltage electric energy storage.

2. The dynamic control method according to claim 1, characterized in that: The measured values ​​are provided by a monitoring box for monitoring the state of the low-voltage electrical energy store.

3. The dynamic control method according to claim 1, characterized in that: The measured value is obtained with the aid of a mapping of the internal resistance of the low-voltage electrical energy store (B) which is constructed as a function of the temperature T of the low-voltage electrical energy store.

4. The dynamic control method according to any one of the above claims, characterized in that: The second operation (2) is performed based on the on duty ratio RCO of the electric energy generator (G) and the temperature of the electric energy generator.

5. The dynamic control method according to claim 4, characterized in that: The available charging current reserve A is determined by calculating the difference between, on the one hand, the instantaneous on-time duty cycle RCO of the electrical energy generator (G) and, on the other hand, the limiting load ratio RCOm of the electrical energy generator.

6. The dynamic control method according to any one of claims 1 to 3 and 5, characterized in that: The limiting current Cm of the low-voltage electric energy storage (B) is determined in advance according to the temperature T of the low-voltage electric energy storage and the state of charge SOC of the low-voltage electric energy storage, and then the sum of the current C and the available charging current reserve A is compared with the limiting current Cm so that when C+A is less than or equal to Cm, Amax=C+A, and when C+A is greater than Cm, Amax=Cm.

7. The dynamic control method according to any one of claims 1 to 3 and 5, characterized in that: The fourth operation (4) is performed by applying the formula Vmax=OCV+R×Amax based on the no-load voltage OCV of the low-voltage electric energy storage (B), the estimated resistance R of the low-voltage electric energy storage and the authorized maximum current Amax.

8. A motor vehicle equipped with an on-board computer and software which is capable of and is used to implement the dynamic control method for controlling the current of a low-voltage electrical energy store (B) according to any of the preceding claims.

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