Description:FIELD OF THE INVENTION

The disclosure relates to a control unit of a Battery Management System (BMS), and more particularly, a control unit for determining a current limit for charging/discharging of an electric vehicle.

BACKGROUND

Electric Vehicle (EV) is a category of vehicle that uses electric energy to power the vehicle. The EV has a battery pack that powers a prime mover of the EV and is charged using an electric charger. The EV also includes a battery management system (BMS) that operates the battery pack to provide electric current to the prime mover. In addition, the BMS enables charging of the battery pack from an EV charging point at an EV charging station. Additionally, the BMS enables charging of the battery pack by means of regenerative braking, in which, the prime mover acts as a generator to generate electric current. The BMS is configured to regulate a State of Charge (SoC) of the battery pack while supplying requested electric current to power the EV and/or receiving current during charging of the battery pack (charging by EV charging point or charging by regenerative braking). Other components of the EV include a motor controller that draws electric current supplied by the BMS from the battery pack to power the prime mover of the EV.

Conventionally, both the motor controller and the BMS are configured to prioritize their respective associated parameters. For instance, the BMS is configured to prioritize limiting the electric current drawn to ensure that excess current is not drawn from the battery pack whereas the motor controller is configured to prioritize the torque to be delivered by the prime mover so that the EV’s performance is maintained. There may be scenarios where the motor controller may draw more current from the battery than a safe operating current associated with the battery pack, the safe operating electric current being a maximum current that is safely drawn from the battery without causing damage, such as thermal runaway, to the battery pack. In such a scenario, the BMS may determine and send the current limit for supply of electric current based on which the motor controller draws the current, thereby limiting the performance of the EV. In case the BMS is not able to limit the drawn current, drawing excess electric current may damage the battery thereby shortening the operational life of the battery.

SUMMARY

This summary is provided to introduce a selection of concepts, in a simplified format, which is further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention and nor is it intended for determining the scope of the invention.

The present disclosure relates to a control unit that determines a current limit for charging/discharging operations associated with an electric vehicle. The control unit sets a current limit on the value of the charging/discharging current.

In an embodiment, a control unit for determining a current limit for charging/discharging operation associated with an electric vehicle is disclosed. The control unit includes a processing module adapted to receive a voltage value, a current value, and a temperature value at a predefined interval associated with an operational state of a battery pack of the electric vehicle. In addition, the processing module is adapted to determine a State of Charge (SoC) value by processing the received voltage value and the current value using a state estimation technique. Further, the processing module is adapted to determine a first safe operating current value associated with the determined SoC value and determine a second safe operating current value associated with the received temperature value. The processing module is further configured to compare the first safe operating current value and the second safe operating current value to determine a lower value therebetween. The processing module is further configured to assign the lower value as the current limit to execute the charging/discharging operation.

In another embodiment, a method for determining a current limit for charging/discharging operations associated with an electric vehicle is disclosed. The method comprises receiving, by a control unit, a voltage value, a current value, and a temperature value at a predefined interval associated with an operational state of a battery pack of the electric vehicle. The method also comprises determining a State of Charge (SoC) by processing the received voltage value and the current value using a state estimation technique. The method also comprises determining, by the control unit, a first safe operating current value associated with the determined SoC value and determining, by the control unit, a second safe operating current value associated with the received temperature value. The method also comprises comparing, by the control unit, the first safe operating current value and the second safe operating current value to determine a lower value therebetween and assigning, by the control unit, the lower value as the current limit to execute the charging/discharging operation.

According to the present disclosure, the control unit sets the current limit as per the SoC and a safe operating temperature of the battery pack that other components of the EV can request or supply. The current limit thus acts as a maximum current that the components of the EV may either request from the BMS for executing operations on the EV or to supply electric current for recharging the battery pack. Further, the control unit determines the current limit in real-time and can update as the SoC and temperature of the battery pack change thereby ensuring that the battery pack operates within safe operating conditions.

To further clarify the advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Figure 1A illustrates an Electric Vehicle (EV), according to an embodiment of the disclosure;
Figure 1B illustrates a block diagram of an Electronic Control Unit (ECU) of the EV, in accordance with an embodiment of the present disclosure;
Figure 2 illustrates a block diagram showing a Battery Management System (BMS) having a control unit interacting with a Body Control Module (BCM), and a motor controller, according to an embodiment of the disclosure;
Figure 3 shows a block diagram of the control unit, according to an embodiment of the present disclosure;
Figure 4 illustrates a block diagram of an Extended Kalman Filter (EKF) architecture of the control unit, according to an embodiment of the present disclosure;
Figure 5 illustrates a block diagram showing an overall process executed by a processing module of the control unit to determine the current limit, according to an embodiment of the disclosure;
Figure 6 illustrates a set of graphs showing a variation in discharge current limit as per Voltage(V), Temperature(deg), and current SoC, according to an embodiment of the present disclosure;
Figure 7 illustrates a set of graphs showing a variation in the charging current limit as per Voltage(V), Temperature(deg), current(I), and SoC, according to an embodiment of the present disclosure;
Figure 8 illustrates a block diagram showing an operation executed by the motor controller in response to receiving the current limit, according to an embodiment of the present disclosure;
Figure 9 illustrates a set of graphs showing a temporal variation of discharge current with respect to an electric motor speed and the torque, according to an embodiment of the present disclosure; and
Figure 10 illustrates a method for determining a current limit for an operation associated with the charging/discharging of the EV, according to an embodiment of the disclosure.

Further, skilled artisans will appreciate those elements in the drawings are illustrated for simplicity and may not have necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present invention. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

DETAILED DESCRIPTION OF FIGURES

For the purpose of promoting an understanding of the principles of the present disclosure, reference will now be made to the various embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the present disclosure is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the present disclosure as illustrated therein being contemplated as would normally occur to one skilled in the art to which the present disclosure relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the present disclosure and are not intended to be restrictive thereof.

Whether or not a certain feature or element was limited to being used only once, it may still be referred to as “one or more features” or “one or more elements” or “at least one feature” or “at least one element.” Furthermore, the use of the terms “one or more” or “at least one” feature or element do not preclude there being none of that feature or element, unless otherwise specified by limiting language including, but not limited to, “there needs to be one or more…” or “one or more elements is required.”

Reference is made herein to some “embodiments.” It should be understood that an embodiment is an example of a possible implementation of any features and/or elements of the present disclosure. Some embodiments have been described for the purpose of explaining one or more of the potential ways in which the specific features and/or elements of the proposed disclosure fulfil the requirements of uniqueness, utility, and non-obviousness.

Use of the phrases and/or terms including, but not limited to, “a first embodiment,” “a further embodiment,” “an alternate embodiment,” “one embodiment,” “an embodiment,” “multiple embodiments,” “some embodiments,” “other embodiments,” “further embodiment”, “furthermore embodiment”, “additional embodiment” or other variants thereof do not necessarily refer to the same embodiments. Unless otherwise specified, one or more particular features and/or elements described in connection with one or more embodiments may be found in one embodiment, or may be found in more than one embodiment, or may be found in all embodiments, or may be found in no embodiments. Although one or more features and/or elements may be described herein in the context of only a single embodiment, or in the context of more than one embodiment, or in the context of all embodiments, the features and/or elements may instead be provided separately or in any appropriate combination or not at all. Conversely, any features and/or elements described in the context of separate embodiments may alternatively be realized as existing together in the context of a single embodiment.

Any particular and all details set forth herein are used in the context of some embodiments and therefore should not necessarily be taken as limiting factors to the proposed disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by “comprises... a” does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

Embodiments of the present disclosure will be described below in detail with reference to the accompanying drawings.

For the sake of clarity, the first digit of a reference numeral of each component of the present disclosure is indicative of the Figure number, in which the corresponding component is shown. For example, reference numerals starting with digit “1” are shown at least in Figure 1. Similarly, reference numerals starting with digit “2” are shown at least in Figure 2.

An Electric Vehicle (EV) or a battery-powered vehicle including, but not limited to two-wheelers such as scooters, mopeds, motorbikes/motorcycles; three-wheelers such as auto-rickshaws, four-wheelers such as cars and other Light Commercial Vehicles (LCVs) and Heavy Commercial Vehicles (HCVs) primarily work on the principle of driving an electric motor using the power from the batteries provided in the EV. Furthermore, the electric vehicle may have at least one wheel which is electrically powered to traverse such a vehicle. The term ‘wheel’ may refer to any ground-engaging member that allows traversal of the electric vehicle over a path. The types of EVs include a Battery Electric Vehicle (BEV), a Hybrid Electric Vehicle (HEV), and a Range Extended Electric Vehicle. However, the subsequent paragraphs pertain to the different elements of the BEV.

Referring to Figure 1A, an EV (100) typically comprises a battery or battery pack (102) enclosed within a battery casing and includes a Battery Management System (BMS), an onboard charger (104), a motor controller, an electric motor (106) and an electric transmission system (108). The primary function of the above-mentioned elements is detailed in the subsequent paragraphs: The battery of the EV (100) (also known as Electric Vehicle Battery (EVB) or traction battery) is re-chargeable in nature and is the primary source of energy required for the operation of the EV, wherein the battery (102) is typically charged using the electric current taken from the power grid through a charging infrastructure (120), such as an EV charger. The battery may be charged using Alternating Current (AC) or Direct Current (DC), wherein in case of AC input, the onboard charger (104) converts the AC signal to a DC signal after which the DC signal is transmitted to the battery pack (102) via the BMS. However, in the case of DC charging, the onboard charger (104) is bypassed, and the current is transmitted directly to the battery pack (102) via the BMS.

The battery pack (102) is made up of a plurality of cells which are grouped into a plurality of modules in a manner in which the temperature difference between the cells does not exceed 5 degrees Celsius. The terms “battery”, “cell”, and “battery cell” may be used interchangeably and may refer to any of a variety of different rechargeable cell compositions and configurations including, but not limited to, lithium-ion (e.g., lithium iron phosphate, lithium cobalt oxide, other lithium metal oxides, etc.), lithium-ion polymer, nickel metal hydride, nickel cadmium, nickel hydrogen, nickel-zinc, silver zinc, or other battery type/configuration. The term “battery pack” as used herein may be referred to as multiple individual batteries enclosed within a single structure or multi-piece structure. The individual batteries may be electrically interconnected to achieve a desired voltage and capacity for a desired application. The Battery Management System (BMS) is an electronic system whose primary function is to ensure that the battery (102) is operating safely and efficiently. The BMS continuously monitors different parameters of the battery such as temperature, voltage, current, and so on, and communicates battery charge/discharge limits to an Electronic Control Unit (ECU) and the motor controller in the EV (100) using a plurality of protocols including and not limited to a Controller Area Network (CAN) bus protocol which facilitates the communication between the ECU/motor controller and other peripheral elements of the EV (100) without the requirement of a host computer.

The motor controller primarily controls/regulates the operation of the electric motor (106) based on the signal transmitted from the vehicle battery, wherein the primary functions of the motor controller include starting the electric motor (106), stopping the electric motor (106), controlling the speed of the electric motor (106), enabling the vehicle to move in the reverse direction and protect the electric motor (106) from premature wear and tear. The primary function of the electric motor (106) is to convert electrical energy into mechanical energy, wherein the converted mechanical energy is subsequently transferred to the transmission system (108) of the EV (100) to facilitate the movement of the EV (100). Additionally, the electric motor (106) also acts as a generator during regenerative braking (i.e., kinetic energy generated during vehicle braking/deceleration is converted into potential energy and stored in the battery of the EV (100). The types of motors generally employed in EVs include, but are not limited to a DC series motor, a Brushless DC motor (also known as BLDC motors), a Permanent Magnet Synchronous Motor (PMSM), a Three Phase AC Induction Motor, and a Switched Reluctance Motors (SRM).

The transmission system (108) of the EV (100) facilitates the transfer of the generated mechanical energy by the electric motor (106) to the wheels (22a,22b) of the EV. Generally, the transmission systems (108) used in EVs include a single-speed transmission system and a multi-speed (i.e., two-speed) transmission system, wherein the single-speed transmission system comprises a single gear pair whereby the EV is maintained at a constant speed. However, the multi-speed/two-speed transmission system comprises a compound planetary gear system with a double-pinion planetary gear set and a single-pinion planetary gear set thereby resulting in two different gear ratios which facilitates higher torque and vehicle speed.

In one embodiment, all data pertaining to the EV (100) and/or charging infrastructure (120) are collected and processed using a remote server (124). In an embodiment, the remote server (124) may be a cloud server in communication with the EV via a communication network. The processed data is indicated to the rider/driver of the EV (100) through a display unit present in the dashboard (126) of the EV (100). In an embodiment, the display unit may be an interactive display unit. In another embodiment, the display unit may be a non-interactive display unit.

Figure 1B illustrates a block diagram of an embodiment of an Electronic Control Unit (ECU) (150) of the EV (100), in accordance with an embodiment of the present disclosure. The ECU (150) of the vehicle is responsible for managing all the operations of the EV (100), wherein the key elements of the ECU (150) typically include (i) a microcontroller core (or processor unit) (152); (ii) a memory unit (154); (iii) a plurality of input (156) and output modules (158) and (iv) communication protocols including, but not limited to the CAN protocol, a Serial Communication Interface (SCI) protocol, and so on. The sequence of programmed instructions and data associated therewith can be stored in a non-transitory computer-readable medium such as a memory unit or a storage device which may be any suitable memory apparatus such as, but not limited to a read-only memory (ROM), a programmable read-only memory (PROM), an electrically erasable programmable read-only memory (EEPROM), a random-access memory (RAM), a flash memory, a disk drive, and the like. In one or more embodiments of the disclosed subject matter, non-transitory computer-readable storage media can be embodied with a sequence of programmed instructions for monitoring and controlling the operation of different components of the EV (100).

The processor may include any computing system that includes but is not limited to, a Central Processing Unit (CPU), an Application Processor (AP), a Graphics Processing Unit (GPU), a Visual Processing Unit (VPU), and/or an AI-dedicated processor such as a Neural Processing Unit (NPU). In an embodiment, the processor can be a single processing unit or several units, all of which could include multiple computing units. The processor may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and/or any devices that manipulate signals based on operational instructions. Among other capabilities, the processor is configured to fetch and execute computer-readable instructions and data stored in the memory. The instructions can be compiled from source code instructions provided in accordance with a programming language such as Java, C++, C#.net, or the like. The instructions can also comprise code and data objects provided in accordance with, for example, the Visual Basic™ language, LabVIEW, or another structured or object-oriented programming language. The one or a plurality of processors control the processing of the input data in accordance with a predefined operating rule or artificial intelligence (AI) model stored in the non-volatile memory and the volatile memory. The predefined operating rule or artificial intelligence model is provided through training or learning algorithms which include, but are not limited to, supervised learning, unsupervised learning, semi-supervised learning, or reinforcement learning.

Furthermore, the modules, processes, systems, and devices can be implemented as a single processor or as a distributed processor. Also, the processes, modules, and sub-modules described in the various figures of and for embodiments herein may be distributed across multiple computers or systems or may be co-located in a single processor or system. Further, the modules can be implemented in hardware, instructions executed by a processing unit, or by a combination thereof. The processing unit can comprise a computer, a processor, such as the processor, a state machine, a logic array, or any other suitable devices capable of processing instructions. The processing unit can be a general-purpose processor which executes instructions to cause the general-purpose processor to perform the required tasks or, the processing unit can be dedicated to performing the required functions. In another embodiment of the present disclosure, the modules may be machine-readable instructions (software) that, when executed by a processor/processing unit, perform any of the described functionalities. In an embodiment, the modules may include a receiving module, a generating module, a comparing module, a pairing module, and a transmitting module. The receiving module, the generating module, the comparing module, the pairing module, and the transmitting module may be in communication with each other. The data serves, amongst other things, as a repository for storing data processed, received, and generated by one or more of the modules. Exemplary structural embodiment alternatives suitable for implementing the modules, sections, systems, means, or processes described herein are provided below.

Figure 2 illustrates a block diagram (200) showing a Battery Management System (BMS) (202) having a control unit (204) in communication with a Body Control Module (BCM) (206) and a motor controller (208), according to an embodiment of the present disclosure. The BMS (202), as described previously, is configured to regulate the charging and discharging of the battery pack (102). In an embodiment, the BMS (202) comprises the control unit (204) that determines a current limit associated with a charging and a discharging operation associated with the EV (100). The charging operation, in one embodiment, may include a process of charging via an EV charging point whereas, in another embodiment, the charging operation may include a process of charging via regenerative braking. Further, the discharging operation may include a process of drawing current from the battery pack (102) to power the electric motor (106) and/or to power an accessory coupled to the EV (100). For both the charging and the discharging operations, the control unit (204) is configured to determine the current limits so that the charging and discharging operations may be executed without causing an overburden on the battery pack (102) to ensure safe operation and longer operational life thereof. Further, the control unit (204) communicates the current limits to the BCM (206). In one instance, the control unit (204) may communicate the current limit as a discharge current limit to the BCM (206) and the BCM (206) communicates the same to the motor controller (208) to execute the discharging operation of the battery pack (102) and in another instance, the control unit (204) may communicate the current limit as a charge current limit to the BCM (206) so that the BCM (206) may communicate the charge current limit to the EV charger (120) to execute the charging operation of the battery pack (102).

The control unit (204) is configured to determine the current limit in real-time based on a State of Charge (SoC) of the battery pack (102). Further, the control unit (204) is configured to repeatedly determine the current limit at predetermined time intervals during the charging and/or discharging operations of the EV (100). Based on the determined SoC, the control unit (204) may determine a safe operating current value and compare the same with another safe operating current corresponding to an instantaneous temperature of the battery pack (102) to determine the current limit(s). A manner in which the control unit (204) determines the current limit(s) is explained in subsequent embodiments.

As shown in Figure 2, the BMS (202) may be communicably coupled to the BCM (206), the BCM (206) being configured to perform operations associated with the working of the EV (100). The BCM (206), in one embodiment, may include the ECU (150) that controls the EV (100). The BCM (206) may communicate the charging current limit to the EV charger (120) in order to receive the charging current equal to or less than the charging current limit. The BCM (206) may be communicably coupled to various sensors that relay information, such as vehicle states (214) and/or ride modes (216) to the BCM (206). The vehicle state (214) may include REGEN, CRUISE, or CRAWL whereas the ride mode (216) may include ECO, SPORT, or WARP. The BCM (206) may be configured to receive the current limit from the control unit (204) and may be configured to further optimize the current limit for the charging/discharging/regenerative braking of the battery pack (102). In one embodiment, the BCM (206) may process the current limit against parameters, such as regenerative braking limits corresponding to the maximum regenerative current limit that is generated for a predefined torque and mode limits corresponding to the amount of current needed to execute the aforementioned ride mode (216). Based on the processing, the BCM (206) may send an optimized discharge and Regen limits to the motor controller (208). This ensures uniformity in the operation of the motor controller (208) and the motor controller (208) is configured to control the working thereof based on current limits instead of looking at multiple ECUs’ constraints.

In one embodiment, the motor controller (208) may also be communicably coupled to the BMS (202) to receive the current limit from the control unit (204). The current limit received by the motor controller (208), in one embodiment, is either the discharge current limit or the regenerative current limit. The discharging current limit may correspond to a maximum DC current drawn by the motor controller (208) to power the electric motor (106) whereas the regenerative current limit may correspond to the maximum DC current generated during the regenerative braking. The motor controller (208) of the present disclosure may be configured to receive a throttle input (218) from a throttle on a handlebar of the EV (100). The motor controller (208) may also include a processor (not shown) that processes the received current limit and determines one or more of a power torque for moving the vehicle or regenerative torque for regenerative braking based on the current limit. The motor controller (208) may include a controller, such as a Proportional Integral (PI) controller (210) that may regulate the current flow between the motor controller (208) and the electric motor (106). In one embodiment, the motor controller (208) may also include other types of controllers, such as a Proportional-Integral-Derivative (PID) controller.

Figure 3 shows a detailed schematic of the control unit (204), according to an embodiment of the present disclosure. The control unit (204) may include but is not limited to, a processor (302), a memory (304), a module, and a database (308). The module and the memory (304) may be coupled to the processor (302). The processor (302) may be a single processing unit or a number of units, all of which could include multiple computing units. In one embodiment, the control unit (204) may be a part of the ECU (150), without departing from the scope of the present disclosure.

The processor (302) may be configured to communicate with the memory 304 to execute programmable instructions stored in the memory (304). The programmable instructions, when executed by the processor (302), cause the processor (302) to provide the functionalities of the first control device 212 as discussed in the disclosure. In one or more embodiments, the processor (302) may be one or more microprocessor(s) or microcontroller(s). The processor (302) may include one or a plurality of processors, which may further include one or more general-purpose processors, such as a central processing unit (CPU), an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and/or an Artificial intelligence (AI) dedicated processor such as a neural processing unit (NPU).

In some embodiments, the memory (304) may store data and instructions executable by the processor(s) 302 to perform the method steps for controlling the operation of the control unit (204), as discussed herein throughout the disclosure. The memory (304) may further include, but is not limited to, a non-transitory computer-readable storage media such as various types of volatile and non-volatile storage media, including but not limited to, random access memory, read-only memory, programmable read-only memory, electrically programmable read-only memory, electrically erasable read-only memory, flash memory, magnetic tape or disk, optical media and the like. Further, the non-transitory computer-readable storage media of memory (304) may include executable instructions in the form of modules and a database to store data.

In an implementation, the module(s) may include a processing module (306). The database (308) serves, amongst other things, as a repository for storing data processed, received, and generated by the processing module (306). In one example, the database (308) may store information regarding a safe operating current value with respect to the SoC. In addition, the database (308) may store information regarding a safe operating current value with respect to an instantaneous temperature of the battery pack (102).

In an embodiment of the present disclosure, the module may be implemented as part of the processor (302). In another embodiment of the present disclosure, the module may be external to the processor (302). In yet another embodiment of the present disclosure, the module may be part of the memory (304). In another embodiment of the present disclosure, the module may be part of the hardware, separate from the processor (302).

The processing module (306), in one embodiment, may be configured to receive operational status-related parameters, such as a current value, a voltage value, and a temperature value from the battery pack (102) at a predefined interval. Based on the received parameters, the processing module (306) may determine the SoC using a state estimation technique. The state estimation technique may include, but is not limited to, an Extended Kalman Filter (EKF) technique, Unscented Kalman Filter (UKF), and Particle Filters (PF). An exemplary embodiment of the architecture of the EKF is explained with respect to Figure 4.

Figure 4 illustrates a block diagram of the EKF architecture (400) of the control unit (204), according to an embodiment of the present disclosure. In the present embodiment, the control unit (204) may receive a current value (402) and a voltage value (404) that corresponds to an instantaneous current and terminal voltage of the battery pack (102). In one embodiment, the current value (402) and the voltage value (404) are provided in the form of a matrix. The EKF architecture (400) also includes a prediction model (406), also referred to as the ‘plant model’ that includes predicting conditions/equations that generate a predicted voltage (408). Further, the control unit (204) may compare the predicted voltage (408) with the voltage value (404) to determine an error (410). The error (410) is then processed via a gain ‘K’ (412) and provided back to the prediction model (406). The value ‘K’ is a standard gain and is referred to as ’Kalman gain'. Further, processing of the current value (402) and the voltage value (404) is done on the basis of parameters, such as Q (Process Noise Covariance matrix) and R (Measurement Noise Covariance matrix). The Q and R matrix values are tuned in a way to give best estimation and performance which reflects in change in K value, since ‘K’ depends on matrix values ‘Q’ and ‘R’. The processing module (306) of the control unit (204) may process the current value (402) and the voltage value (404) to minimize the error (410) to determine the SoC. The determined SoC may then be used to determine the current limit, as described in detail below.

Reference is now made to Figure 5 which illustrates a block diagram (500) showing an overall process executed by the processing module (306) to determine the current limit, according to an embodiment of the disclosure. Initially, the processing module (306) (shown in Figure 5) may receive the temperature value (502), the current value (402), and the voltage value (404) from the battery pack (102). In one embodiment, each of the temperature value (502), the current value (402), and the voltage value (404) are communicated in the form of matrices. Out of the three values, the current value (402) and the voltage value (404) are processed by the processing module (306) using the EKF architecture (400) (as explained above with respect to Figure 4) and determines an SoC matrix (504) that includes the predicted voltage (408) values and the SoC. The determined SoC may then be processed by the processing module (306) to determine a first safe operating current value. The first safe operating current value may correspond to a current value that the battery pack (102) can either supply or receive to keep the battery pack (102) in safe operating condition.

The determined SoC matrix (504) may be processed further by the processing module (306) to determine either a safe operating charging current limit and/or a safe operating discharging/derating current limit. Considering the charging scenario, the processing module (306) may process the reference charging current matrix (506) and the charging current gain matrix (508). The processing module (306), in one embodiment, may perform vector multiplication (510) to determine the safe charging current value. In one embodiment, the vector multiplication (510) may be represented by the following configuration:
I = [K_1 K_2 K_3 ] [0 0 SOCmax ] -[V ^_1 V ^_2 SO ^C ]

where ‘I’ represents the first safe operating current value
K1, K2, K3 are gains found using pole placement, LQR (Linear Quadratic Regulator), or other similar methods,
[¦] represent state matrix having V1 = V2 = 0, SOCmax is 1 since the current limit is to be determined which will result in an increase of SoC to 100% SoC (soc = 1),
[() ^_1 () ^_2 () ^ ] represent a state matrix that has the present state values of V1, V2 and SOC, and
V1 is predicted cell dynamics voltage 1 and V2 is predicted cell dynamics voltage 2.
Simultaneously, the processing module (202) may perform the vector multiplication (512) between the temperature value (502) and a reference temperature value (530) to determine a second safe operating current value which corresponds to a maximum safe current supplied at a safe operating temperature of the battery pack (102) during a charging operation of the battery pack (102). In one embodiment, in order to compute the second safe operating current value, the processing module (202) may also perform the vector multiplication between the voltage value (404) and a reference voltage value corresponding to the temperature value (502). The second safe operating current values determined using the voltage value (404) and the temperature value (502) are compared to select a lower value therebetween. Finally, the processing module (306) may compare both the values, i.e., the first safe current value and the second current value to determine a lower value (514) by the processing module (306). The lower value (514) may then be assigned as the current limit (516). The processing module (202) may communicate the current limit (516) to either the BCM (206) or the motor controller (208) to perform the normal charging and the regenerative braking charging respectively.

In one embodiment, the BCM (208) may compare the current limit (516, 528) with an instantaneous charge current value (804) to determine a lower charging value. Based on the comparison, the BCM (208) may communicate the lower charging value to the EV charger (120) to receive the electric current of the lower charging value to execute the charging operation.

The processing module (306) may also determines the safe discharging current value as the first safe operating current value. Considering the discharging scenario, the processing module (306) may process the reference discharging current matrix (518) and the discharging current gain matrix (520). The processing module (306), in one embodiment, may perform vector multiplication (522) to determine a safe discharging current value. In one embodiment, the vector multiplication (522) may be represented by the following equation:

I = [K_1 K_2 K_3 ] [0 0 SOCmin ] -[V ^_1 V ^_2 SO ^C ]
where ‘I’ represents the first safe operating current value.
K1, K2, K3 are gains found using pole placement using LQR (Linear Quadratic Regulator), or other similar methods.
[¦] represent a state matrix having V1 = V2 = 0, SOCmin is 1 since the current limit is to be determined which will result in reduction of SoC to 0% SOC (soc = 0).
[() ^_1 () ^_2 () ^ ] represent a state matrix that has the present state values of V1, V2 and SOC
V1 is predicted cell dynamics voltage 1, V2 is predicted cell dynamics voltage 2.

Simultaneously, the processing module (202) may perform the vector multiplication (524) to determine the second safe operating current value, the second safe operating current indicating a maximum current drawn at a safe operating temperature of the battery pack (102) during a discharging operation of the battery pack (102). Further, the processing module (202) may compare the first and the second safe operating current values to determine a lower value (526) therebetween which is assigned as the discharge current limit (528) and later communicated to the motor controller (208).

Figure 6 illustrates a set of graphs (600) showing variation in discharge current limit varied as per Voltage(V), Temperature(deg), current(I), and SoC, according to an embodiment of the present disclosure. Specifically, graph (602) shows variation in the discharge current limit whereas graph (604) shows variation in the temperature of the battery pack (102). Further, graph (606) shows variation in the voltage value of the battery pack (102) and graph (608) shows variation in the SoC from maximum, i.e., ‘1’ to minimum, i.e., ‘0’. Initially, both the SoC and the voltage values are at their respective maximum values. Thereafter, the control unit (204) computes the discharge current limit in a manner explained above and based on the current limit, the motor controller (208) may request the battery pack (102) to supply the electric current as per the discharge current limit. For instance, the motor controller (208), after computing the phase voltages, passes the same to a rectifier associated with the battery pack (102), and the received current is directly applied at the motor terminals of the motor (106).

The supply of electric current may cause the temperature value to increase towards a maximum safe operating temperature Tmax of the battery pack (102). As a result, the temperature approaches Tmax, and the control unit (204) reduces the discharge current limit to keep the temperature of the battery pack (102) under Tmax. At one point, a difference between the temperature Tmax and the temperature value increases as the SoC approaches ‘0’. As may be deduced from the set of graphs (600), the control unit (204) ensures that the temperature does not exceed Tmax thereby ensuring safe operation of the battery pack (102).

Figure 7 illustrates a set of graphs (700) showing variation in the charging current limit as per Voltage(V), Temperature(deg), current(I), and SOC, according to an embodiment of the present disclosure. Specifically, graph (702) shows variation in the discharge current limit whereas graph (704) shows variation in the temperature of the battery pack (102). Further, graph (706) shows variation in the voltage value of the battery pack (102) and graph (708) shows variation in the SoC from maximum, i.e., ‘1’ to minimum, i.e., ‘0’. In this case, the control unit (204) initially sets a higher discharge current limit thereby allowing a greater amount of current to be supplied for charging the battery pack (102).

As the battery charges, the SoC starts to increment from ‘0’ towards the value ‘1’. At the same time, the temperature value increases and approaches the Tmax, the control unit (204) reduces the charging current limit sharply to ensure that the temperature does not exceed Tmax. The control unit (204) further reduces the charging current limit in a more gradual manner to allow the temperature to also reduce gradually. This operation is repeated until the SoC reaches the maximum value of ‘1’.

Figure 8 illustrates a block diagram (800) showing an operation executed by the motor controller (208) in response to receiving the current limit from the control unit (204), according to an embodiment of the present disclosure. The motor controller (208) may receive parameters, such as the discharge current limit (802) from the processing module (202), an instantaneous discharge current value (804) indicating current flowing through the electric motor (106), and a reference torque (806) indicative of the torque output needed to be delivered. The motor controller (208) may process the parameters using the PI control module (808). The PI control module (808) compares the instantaneous discharge current value (804) with the discharge current limit (802). In addition, the PI control module (808) changes the instantaneous discharge current value (804) to reduce a difference between the instantaneous discharge current value (804) and the discharge current limit (802) to obtain the maximum output in terms of delivering power torque (810).

The PI control module (808), while comparing, checks if the current limit is less than the safe discharging current value. Accordingly, the PI control module (808) determines that the power torque (810) is greater than the reference torque (806) and accordingly, the PI control module (808) may perform current saturation (812) so that the output torque does not exceed the reference torque (806). If, at any point, the discharge current limit (802) becomes less than the instantaneous discharge current value (804) before the power torque (810) can reach the reference torque (806), the PI control module (808) limits the power torque (810) so that the power torque does not increase any further because of the current limit.

A similar approach is applied during the regenerative braking operation. In this embodiment, the PI control module (808) may compare the regenerative current limit (802) with an instantaneous regenerative current value (814) and reduce the difference between the instantaneous regenerative current value (814) and the regenerative current limit (816) to an output regenerative torque (818). Hereto, in case the instantaneous regenerative current value (814) is saturated when the instantaneous regenerative current value tends to exceed the regenerative current limit (816), the PI control module (808) reduces the regenerative torque (818) to match with the reference torque (806).

Figure 9 illustrates a set of graphs (900) showing a temporal variation of discharge current with respect to the electric motor (106) speed and the torque, according to an embodiment of the present disclosure. Specifically, graph (902) shows variation between the discharge current limit (802) (shown in Figure 8) and the instantaneous discharge current value (804) (shown in Figure 8) whereas graph (904) shows variation between instantaneous motor speed and reference motor speed. Further, graph (906) indicates a change in the torque. Initially, in order to deliver the reference torque shown in graph (906), the instantaneous current value rises and just after the lapse of time 2.5 seconds, the instantaneous current value has reached its limit as shown by the flattening of the curve (908) and can't be increase beyond this limit. After this point, motor torque can't increase up to the desired torque because the instantaneous current value remains constant.

Referring to Figure 10, the present disclosure also relates to a method (1000) for determining a current limit for an operation associated with charging/discharging of the EV (100), according to an embodiment of the disclosure. The order in which the method steps are described below is not intended to be construed as a limitation, and any number of the described method steps may be combined in any appropriate order to execute the method or an alternative method. Additionally, individual steps may be deleted from the method without departing from the scope of the subject matter described herein.

Furthermore, embodiments of the disclosed methods, processes, modules, devices, systems, and computer program products may be readily implemented, fully or partially, in software using, for example, object or object-oriented software development environments that provide portable source code that can be used on a variety of computer platforms. Alternatively, embodiments of the disclosed methods, processes, modules, devices, systems, and computer program products can be implemented partially or fully in hardware using, for example, standard logic circuits or a very-large-scale integration (VLSI) design. Other hardware or software can be used to implement embodiments depending on the speed and/or efficiency requirements of the systems, the particular function, and/or particular software or hardware system, microprocessor, or microcomputer being utilized.

The method (1000) may be explained in conjunction with Figure 6 and begins at step (1002) at which the control unit (204) receives a voltage value, a current value, and a temperature value at a predefined interval associated with an operational state of the battery pack (102) of the electric vehicle. Thereafter, at step, (1004), the control unit (204) may determine the State of Charge (SoC) by processing the received voltage value and the current value using the state estimation technique. Once the SoC is determined, the control unit (204), at step (1006), determines the first safe operating current value associated with the determined SoC value. At step (1008), the control unit (204) determines a second safe operating current value associated with the received temperature value. Once both the values are determined, the control unit (204), at step (1010) compares the first safe operating current value and the second safe operating current value to determine a lower value therebetween. Finally, at step (1012), the control unit (204) assigns the lower value as the current limit to execute the charging/discharging operation.

While the above steps of figure 10 is shown and described in a particular sequence, the steps may occur in variations to the sequence in accordance with various embodiments of the disclosure. Further, a detailed description related to the various steps of figure 10 is already covered in the description related to figures 2 to 5 and is omitted herein for the sake of brevity.

According to the present disclosure, the control unit (204) determines the SoC in real-time to determine the current limit that is communicated internally to the BCM (206) and the motor controller (208) through the BCM (206) so that none of the components draw current or supply current that can damage the battery pack (102).

It will be appreciated that the modules, processes, systems, and devices described above can be implemented in hardware, hardware programmed by software, software instruction stored on a non-transitory computer-readable medium, or a combination of the above. Embodiments of the methods, processes, modules, devices, and systems (or their sub-components or modules), may be implemented on a general-purpose computer, a special-purpose computer, a programmed microprocessor or microcontroller, and peripheral integrated circuit element, an ASIC or other integrated circuit, a digital signal processor, a hardwired electronic or logic circuit such as a discrete element circuit, a programmed logic circuit such as a programmable logic device (PLD), programmable logic array (PLA), field-programmable gate array (FPGA), programmable array logic (PAL) device, or the like. In general, any process capable of implementing the functions or steps described herein can be used to implement embodiments of the methods, systems, or computer program products (software programs stored on a non-transitory computer-readable medium).

Furthermore, embodiments of the disclosed methods, processes, modules, devices, systems, and computer program products may be readily implemented, fully or partially, in software using, for example, object or object-oriented software development environments that provide portable source code that can be used on a variety of computer platforms. Alternatively, embodiments of the disclosed methods, processes, modules, devices, systems, and computer program products can be implemented partially or fully in hardware using, for example, standard logic circuits or a very-large-scale integration (VLSI) design. Other hardware or software can be used to implement embodiments depending on the speed and/or efficiency requirements of the systems, the particular function, and/or the particular software or hardware system, microprocessor, or microcomputer being utilized.

In this application, unless specifically stated otherwise, the use of the singular includes the plural, and the use of “or” means “and/or.” Furthermore, the use of the terms “including” or “having” is not limiting. Any range described herein will be understood to include the endpoints and all values between the endpoints. Features of the disclosed embodiments may be combined, rearranged, omitted, etc., within the scope of the invention to produce additional embodiments. Furthermore, certain features may sometimes be used to advantage without a corresponding use of other features.

While specific language has been used to describe the present subject matter, any limitations arising on account thereto, are not intended. As would be apparent to a person in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein. The drawings and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment.
, Claims:1. A control unit (204) for determining a current limit for charging/discharging operation associated with an electric vehicle (100), the control unit (204) comprising:
a processing module (306) adapted to:
receive a voltage value (404), a current value (402), and a temperature value (502) at a predefined interval associated with an operational state of a battery pack (102) of the electric vehicle (100);
determine a State of Charge (SoC) value by processing the received voltage value (404) and the current value (402) using a state estimation technique;
determine a first safe operating current value associated with the determined SoC value;
determine a second safe operating current value associated with the received temperature value (502);
compare the first safe operating current value and the second safe operating current value;
assign the lower value as the current limit (516, 528) to execute the charging/discharging operation.

2. The control unit (204) as claimed in claim 1, wherein the first safe operating current value is a safe charging current value, and the processing module (306) is adapted to compare the safe charging current value with the second safe operating current value to determine the current limit (516, 528) as a charging current limit (516).

3. The control unit (204) as claimed in claim 1, wherein the first safe operating current value is a safe discharging current value, and the processing module (306) is adapted to compare the safe discharging current value with the second safe operating current value to determine the current limit (516, 528) as a discharge current limit (528).

4. The control unit (204) as claimed in claim 1, wherein the processing module (306) is further adapted to communicate the current limit (516, 528) to a Body Control Module (206), wherein the Body Control Module (206) is adapted to:
optimize the current limits (516, 528) based on vehicle states and transmit the charging limit to the charger (120), and discharge and regen limits to a Motor Controller (208).

5. The control unit (204) as claimed in claim 1, wherein the processing module (306) is further adapted to communicate the current limit (516, 528) to a motor controller (208) via a Body Control Module (206), wherein the motor controller (208) is adapted to:
compare the current limit (516, 528) with an instantaneous discharge current value (804) to check if the current limit (516, 528) is less than the instantaneous discharge current value (804); and
limit a power torque (810) based on the current limit (516, 528) when the current limit (516, 528) is less than the instantaneous discharge current value (804).

6. The control unit (204) as claimed in claim 1, wherein the processing module (306) is further adapted to communicate the current limit (516, 528) to a motor controller (208) via a Body Control Module (206), wherein the motor controller (208) is adapted to:
compare the current limit (516, 528) with an instantaneous regenerative current value (814) to determine if the current limit (516, 528) is less than the instantaneous regenerative current value (814); and
limit a regenerative torque (818) based on the current limit (516, 528) when the current limit is less than the instantaneous regenerative current value (814).

7. The control unit (204) as claimed in claim 1, wherein the processing module (306) is integrated to a battery management system (202).

8. The control unit (204) as claimed in claim 1, wherein the state estimation technique is one of an Extended Kalman Filter technique, Unscented Kalman Filter, and Particle Filters.

9. The control unit (204) as claimed in claim 1, wherein the second safe operating current value is a maximum safe current drawn at a safe operating temperature of the battery pack (102) during a discharge mode of the battery pack (102).

10. The control unit (204) as claimed in claim 1, wherein the second safe operating current value is a maximum safe current supplied at a safe operating temperature of the battery pack (102) during a charge mode of the battery pack (102).

11. A method for determining a current limit (516, 528) for charging/discharging operation associated with an electric vehicle (100), the method comprising:
receiving, by a control unit (204), a voltage value (404), a current value, and a temperature value (502) at a predefined interval associated with an operational state of a battery pack (102) of the electric vehicle (100);
determining, by the control unit (204), a State of Charge (SoC) by processing the received voltage value (404) and the current value using a state estimation technique;
determining, by the control unit (204), a first safe operating current value associated with the determined SoC value;
determining, by the control unit (204), a second safe operating current value associated with the received temperature value (502);
comparing, by the control unit (204), the first safe operating current value and the second safe operating current value to determine a lower value therebetween; and
assigning, by the control unit (204), the lower value as the current limit (516, 528) to execute the charging/discharging operation.

12. The method as claimed in claim 11, wherein the first safe operating current value is a charging current value, and comparing, by the control unit (204), comprises comparing the charging current value with the second safe operating current value to determine the current limit (516, 528) as a charging current limit (516, 528).

13. The method as claimed in claim 11, wherein the first safe operating current value is a discharging current, and comparing, by the control unit (204), comprises comparing the discharging current value with the second safe operating current value to determine the current limit (516, 528) as a discharge current limit (516, 528).

14. The method as claimed in claim 11, wherein the processing module (306) is further adapted to communicate the current limit (516, 528) to a Body Control Module (206), wherein the Body Control Module (206) is adapted to:
optimize the current limits (516, 528) based on vehicle states and transmit the charging limit to the charger (120), and discharge and regen limits to a Motor Controller (208).

15. The method as claimed in claim 11, comprising communicating, by the control unit (204), the current limit (516, 528) to a motor controller (208) via a Body Control Module (206), wherein the motor controller (208) is adapted to:
compare the current limit (516, 528) with an instantaneous discharge current value (804) to determine if the current limit (516, 528) is less than the instantaneous discharge current value (804); and
limit a power torque (810) based on the current limit (516, 528) when the current limit is less than the safe discharging current value.

16. The method as claimed in claim 11, comprising communicating, by the control unit (204), the current limit (516, 528) to a motor controller via a Body Control Module (206), wherein the motor controller (208) is adapted to:
compare the current limit (516, 528) with an instantaneous regenerative current value (814) to determine if the current limit (516, 528) is less than the instantaneous regenerative current value (814); and
limit a regenerative torque (818) based on the current limit (516, 528) when the current limit is less than the instantaneous regenerative current value (814).

17. The method as claimed in claim 11, wherein the control unit (204) is integrated to a battery management system.

18. The method as claimed in claim 11, wherein the state estimation technique is one of an Extended Kalman Filter technique, Unscented Kalman Filter, and Particle Filters.

19. The method as claimed in claim 11, wherein the first safe operating current is a maximum safe current drawn at a safe operating temperature of the battery pack (102) during a discharge mode of the battery pack (102).

20. The method as claimed in claim 11, wherein the first safe operating current is a maximum safe current drawn at a safe operating temperature of the battery pack (102) during a charge mode of the battery pack (102).