Method and system for controlling a battery state of charge of a hybrid vehicle

Abstract

A method for controlling a battery state of charge (SOC) of a hybrid vehicle, comprising: Determining, by a control device, a driving load of the hybrid vehicle based on driving modes for respective speeds of the hybrid vehicle and on an inclination of a roadway of the hybrid vehicle, Determining, by the controller, a calibration value based on the driving load and a main battery charge state, and Setting, by the control device, an auxiliary battery charge state according to two driving load modes based on the calibration value, the two driving load modes comprising a high-load mode and a low-load mode, wherein setting the auxiliary battery charge level state comprises: Determining by the control device, when the calibration value is equal to or greater than a predetermined reference value, that the driving load of the hybrid vehicle is in the high-load mode, and variably setting, by the controller, a low-voltage direct current (DC-DC) converter (LDC) output voltage using an LDC output voltage instruction table associated with the high-load mode to maintain the auxiliary battery state of charge at a high level, or wherein setting the auxiliary battery charge level state comprises: Determining, by the controller, when the calibration value is equal to or less than a predetermined reference value, that the driving load of the hybrid vehicle is in the low-load mode, entering the low-load mode and setting the auxiliary battery charge level by dividing the low-load mode into three areas, where the three areas include a discharge area, a weak discharge area and a charge / discharge area.

Description

Background(a) Technical field

[0001] The present invention relates to a method and a system for controlling a battery state of charge (Battery SOC) of a hybrid vehicle and, more particularly, to a method for controlling a battery state of charge of a hybrid vehicle (e.g., a hybrid motor vehicle) for improving fuel efficiency in an urban area with a differentiated (e.g., different) strategy for controlling an auxiliary battery state of charge balance. (b) Background technology

[0002] A low-voltage direct current (DC-DC) converter (LDC) (e.g., a low-voltage DC-DC converter) mounted in a hybrid vehicle is generally configured to charge an auxiliary battery (e.g., an auxiliary battery) by converting a high DC voltage output from a main battery into a low DC voltage, and to monitor the electric field load quantity of the vehicle to supply electricity to each electric field load (e.g., the electrical loads) based on the voltage used by each electric field load.

[0003] In an urban area where there is congestion compared to a highway area (e.g., traffic is slow / congested) and the road gradient (or road gradient) varies frequently, the average vehicle speed is very low (e.g., compared to an area with no traffic congestion) and LDC energy consumption (or consumption) is high. The influence of LDC energy consumption on fuel efficiency is therefore unfavorable. If the conventional control method is used to adjust (e.g., adapt) the LDC output voltage in a driving situation with variable driving load (or driving load) due to conditions such as the average vehicle speed and the road gradient, as described above, fuel efficiency is reduced in urban areas.Consequently, there is a need to improve fuel efficiency in urban areas using a differentiated control method.

[0004] The above information disclosed in this section is provided only to enhance the understanding of the background of the invention and may therefore contain information that does not constitute prior art as already known to those skilled in the art.

[0005] Furthermore, DE 699 32 487 T2 discloses a method for controlling a battery state of charge (Battery SOC) of a hybrid vehicle, comprising: determining, by a controller, a driving load of the vehicle based on driving modes for respective speeds of the vehicle and on an inclination of the vehicle, determining, by the controller, a calibration value based on the driving load and a main battery state of charge state, and setting, by the controller, an auxiliary battery state of charge state according to two driving load modes based on the calibration value, wherein the two driving load modes comprise a high load mode and a low load mode.

[0006] Further methods and devices for controlling a battery state of charge (battery SOC) of a hybrid vehicle as well as relevant technologies are known from DE 10 2013 222 748 A1, DE 10 2013 217 274 A1, US 6 314 346 B1 and KR 10 2009 0 059 175 A. Explanation

[0007] It is an object of the present invention to provide a method and a system for controlling a battery state of charge (SOC) of a hybrid vehicle to improve fuel efficiency in urban areas with a differentiated strategy of controlling a state of charge balance of an auxiliary battery, taking into account that the degree of influence of the electric field load consumption (SOC) on the fuel efficiency varies according to the LDC voltage in the hybrid vehicle based on a driving mode and a road gradient.

[0008] The problem is solved by the features of the independent patent claims. Advantageous developments are described in the dependent claims.

[0009] The present invention therefore provides a method for controlling a battery state of charge (or a battery SOC) of a hybrid vehicle (e.g., a hybrid motor vehicle) according to claim 1 and a system for controlling a battery state of charge (battery SOC) of a hybrid vehicle according to claim 8. Advantageous further developments are described in the dependent claims and may be as follows. In an exemplary embodiment, the determination of the driving load may comprise: dividing speeds of the vehicle by means of steps from a low speed to a high speed based on an average speed, and determining the driving mode for each speed, dividing an inclination (or a gradient) of roadways / a roadway by means of steps and determining an inclination of a road having the vehicle thereon, and dividing the driving load of the vehicle into (e.g., at least) a high level and (e.g.,at least) a low level (e.g. into high and low levels) based on the determined driving mode and the determined inclination and determining the same (or the driving load), whereby the levels are represented (e.g. represented) by relative numerical values.

[0010] The dividing of the speeds and the determination of the driving mode may further comprise: dividing the speeds of the vehicle into six modes, ranging from an extreme congestion mode (e.g., an extreme traffic congestion mode or an extremely congested traffic mode) to a high-speed mode (e.g., a highest speed mode), and determining the driving mode; and the dividing and the determination of the incline may comprise: dividing the incline into five levels, ranging from a downward incline to a sharp upward incline (e.g., a steep upward incline), and determining the incline of the road.

[0011] In a further exemplary embodiment, the determination of the calibration value may include: determining the driving load of the vehicle and the main battery state of charge by classifying (e.g., ranking / ranking) the driving load of the vehicle and the main battery state of charge into high and low levels, which are represented (e.g., represented) by a plurality of relative numerical values, and determining that the calibration value is one (e.g., a single one) of the relative numerical values ​​based on the determined driving load and the determined main battery state of charge. Furthermore, the calibration value may be determined by a calibration value derivation table (e.g., a calibration value derivation map), wherein the calibration value is variably (e.g., differently) set (e.g.,adjusted).

[0012] An auxiliary battery state of charge value may be compared to a transition threshold, and it may be determined whether a transition of the auxiliary battery state of charge condition occurs. The transition threshold may be determined as a sum of the calibration value and a reference value, where the reference value is set to a constant for a transition of the auxiliary battery state of charge condition. Short description of the drawings

[0013] The above and other features of the present invention will now be described in detail with reference to exemplary embodiments thereof shown in the accompanying drawings, which are given below by way of illustration only and are therefore not limitative of the invention, and in which: Fig. 1 illustrates a process of determining an output voltage of a conventional low-voltage DC-DC converter (LDC) according to the prior art, Fig. 2 illustrates an energy flow according to an LDC output for efficient control in a regenerative braking mode of a conventional hybrid vehicle according to the prior art, Fig. 3 illustrates a process of determining whether regeneration efficiency control for efficient LDC output control is performed in the regenerative braking mode of the conventional hybrid vehicle according to the prior art, Fig. 4 illustrates a process of determining a calibration value related to a method for controlling a battery state of charge of a hybrid vehicle according to an exemplary embodiment of the present invention, Fig. 5 illustrates a change in an auxiliary battery state of charge relating to a method for controlling a battery state of charge of a hybrid vehicle according to an exemplary embodiment of the present invention, and Fig. 6 shows a comparison between the present invention and the conventional art.

[0014] It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features for the purpose of illustrating the basic principles of the invention. The specific design features of the present invention, including, for example, specific dimensions, directions, positions, and shapes disclosed herein, will be dictated in part by the particular intended application and usage environment. In the figures, reference numerals refer to like or equivalent components of the present invention throughout several figures of the drawing. Detailed description

[0015] It is to be understood that the terms "vehicle" or "vehicle-..." or any similar term used herein includes motor vehicles in general, such as passenger vehicles, including so-called sport utility vehicles (SUVs), buses, trucks, numerous commercial vehicles, watercraft, including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid vehicles, hydrogen-powered vehicles, and other alternative fuel vehicles (e.g., fuels produced from resources other than petroleum). A hybrid vehicle, as referred to herein, is a vehicle that has two or more power sources, e.g., vehicles that run on both gasoline and electricity.

[0016] Although example embodiments are described as utilizing a plurality of units to perform the example operations, it is to be understood that the example operations may also be performed by one or more modules. Additionally, it is to be understood that the term controller / controller refers to a hardware device including a memory and a processor. The memory is configured to store the modules, and the processor is specifically configured to execute the modules to perform one or more operations described below.

[0017] Furthermore, control logic of the present invention may be embodied as a non-transitory, computer-readable medium on a computer-readable medium containing executable program instructions executed by a processor, controller, or the like. Examples of the computer-readable medium include, but are not limited to, ROM, RAM, compact disk (CD)-ROMs, magnetic tapes, floppy disks, flash memory, memory cards, and optical data storage devices. The computer-readable recording medium may also be distributed in network-connected computer systems such that the computer-readable medium is stored and executed in a distributed manner, e.g., by means of a telematics server or a controller area network (CAN).

[0018] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms "a," "an," and "the," "which," as used herein, are intended to include the plural forms, unless the context clearly indicates otherwise. Further, it is to be understood that the terms "comprising" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, acts, elements, and / or components, but do not preclude the presence or addition of one or more additional features, integers, steps, acts, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated enumerated items.

[0019] The present invention will now be described in more detail with reference to the accompanying drawings in which exemplary embodiments of the present invention are shown.

[0020] Variable voltage control is conventionally performed using an efficient voltage control method for an LDC. The charging voltage or the discharging voltage of the LDC is thus determined and output based on a distinguished driving mode. Since adjustment (e.g., adjustment) of the LDC charging voltage for charging an auxiliary battery is mainly performed when the vehicle is traveling in the regenerative braking mode (or the regenerative braking mode, e.g., a mode in which electrical energy is recovered by means of generator operation of the electric motor during braking), it is important to set (e.g., determine and set) a criterion for determining switching to and triggering / releasing the regenerative braking mode.The vehicle driving modes used for voltage control of the conventional LDC can be broadly divided into three modes, including an engine charging mode (e.g., a mode in which battery charging is performed by operating the engine), a regenerative braking mode, and an electric vehicle (EV) mode. A voltage control method for the conventional LDC is described below.

[0021] Fig. 1 illustrates a process of determining an output voltage of a conventional LDC according to the prior art. Specifically, voltage adjustment (e.g., voltage adjustment) of the LDC is performed such that a hybrid control unit (HCU), which is installed in a vehicle as a control device, is configured to output a voltage instruction (e.g., a voltage command) to the LDC.

[0022] As in Fig. 1, the HCU is configured to first determine a driving mode of the vehicle from the EV mode, the engine charging mode, and the regenerative braking mode based on a shift lever (e.g., a shift lever position), the presence or absence of fuel injection, a vehicle speed, an electric motor output, and the operation value of an accelerator pedal (e.g., the pressure value applied to the pedal). The HCU is further configured to select an instruction table for an LDC voltage instruction based on the determined driving mode, the obtained auxiliary battery state of charge information(s), and the auxiliary battery temperature information(s), and to determine and set (e.g., adjust) the LDC output voltage (e.g., target voltage) based on the selected instruction table.

[0023] The HCU is in particular configured to select an instruction table for an LDC voltage instruction based on a driving mode and auxiliary battery state of charge information (e.g., auxiliary battery state of charge information). The instruction table is formed (or constructed) based on the auxiliary battery state of charge and temperature information(s) and stored (or stored) in the HCU. The instruction table is also based on the driving mode and the auxiliary battery state of charge and temperature information(s), taking into account a minimum LDC output (or a minimum LDC output, e.g., a minimum LDC output voltage), a minimum LDC target voltage for charging, an optimal efficiency for maintaining the battery state of charge (or battery SOC), an optimal LDC target voltage for charging, or a maximization of the recovery of regenerative braking energy (ora maximization of the recuperated energy).

[0024] For example, when the auxiliary battery state of charge is high (e.g., greater than a predetermined level), a minimum voltage output control (e.g., a minimum voltage output control) of the LDC for minimizing the charging rate of the auxiliary battery may be considered in the instruction table in the EV mode and the engine charging mode. When the auxiliary battery state of charge is low (e.g., lower than a predetermined level), an (LDC) voltage control for the LDC for charging the auxiliary battery may be considered in the EV mode and the engine charging mode, and an LDC voltage control for maximizing energy recovery may be considered in the regenerative braking mode.For the LDC output voltage control described above, the LDC may be configured to output a charging voltage for charging the auxiliary battery even when the auxiliary battery charge level is sufficient in the regenerative braking mode.

[0025] Fig. 2 illustrates an energy flow according to an LDC output (or an LDC output) for efficient control in regenerative braking mode of a conventional hybrid vehicle of the prior art, and Fig. 3 illustrates a process of determining whether regeneration efficiency control (e.g., so-called regen efficiency control) for efficient LDC output control is performed in the regenerative braking mode of the conventional hybrid vehicle according to the related art.

[0026] As in Fig. 2, it may not be necessary to charge the auxiliary battery when the auxiliary battery charge level is sufficient. Consequently, when the LDC output voltage is reduced, unnecessary charging of the auxiliary battery in the regenerative braking mode, which causes LDC output loss (e.g., LDC output loss), can be prevented, and regenerative braking energy corresponding to the LDC output loss (e.g., a loss due to driving an electric field load of the vehicle and charging the auxiliary battery) caused by unnecessary LDC output (e.g., unnecessary LDC output) can be used to charge the main battery.

[0027] As in Fig. As shown in Figure 3, performing regeneration efficiency control for efficient LDC output control in the regenerative braking mode is determined based on the auxiliary battery state of charge and the electric motor power, and the operation mode to be used for LDC output voltage control is determined. The LDC output voltage is thus adjusted (e.g., adjusted) by determining an LDC output value for variable voltage control based on the operation mode.

[0028] Furthermore, power consumption (e.g., power input, energy consumption) of an electric field load (e.g., an electrical load) of the vehicle varies based on the setting of the LDC output voltage, and the degree of influence on fuel efficiency based on the power consumption of the electric field load varies depending on the vehicle driving condition (e.g., (road) gradient, vehicle speed, deceleration, etc.). In other words, when the LDC output voltage is adjusted using the conventional variable-voltage control method, the power consumption of an electric field load varies based on the set value of the LDC output voltage, and the degree of influence on fuel efficiency varies according to the power consumption of the electric field load based on the vehicle driving condition.

[0029] When the conventional variable voltage control method, which does not consider driving modes based on vehicle speed and gradient (or incline level), is used to adjust the LDC output voltage in an urban area where traffic congestion and inclines (or road gradients) are more frequently encountered than on a highway, an influence degree on fuel efficiency based on the power consumption (or energy consumption) of the electric field load deteriorates, and consequently, fuel efficiency in the urban area is deteriorated. The present invention therefore attempts to improve fuel efficiency in urban areas by using a differentiated auxiliary battery state of charge balance control strategy, which considers that the influence of the power consumption based on the LDC voltage control (e.g.,-setting / adjustment) of a hybrid vehicle based power consumption (or energy consumption) of the electric field load on the fuel efficiency varies based on the driving mode for a vehicle speed and the gradient.

[0030] In particular, if the instantaneous LDC voltage control strategy is improved to improve the main range of the auxiliary battery state of charge (or auxiliary battery state) used under the condition of medium / high speed and high load driving, the fuel efficiency can be optimized when the vehicle traveling under driving conditions such as medium / high speed and high load, e.g., on a highway (e.g., generally on a rural road), enters (or enters) an urban area.

[0031] A description will be given below so that a person skilled in the art can easily implement the present invention. The method described hereinafter can be understood to be carried out by a control device comprising a processor and a memory. In particular, the present invention provides a method for optimizing an auxiliary battery state of charge balance resulting from a change in the influence of electric field load power consumption (or electric field load energy consumption) on fuel efficiency according to driving modes for respective speeds by adding a driving state of a vehicle to an input factor (e.g., an input variable) of a conventional LDC voltage, which can enable improvement in fuel efficiency on an actual road. In order to use driving modes for respective speeds as an input variable (orinput variable), an average vehicle speed can be calculated to classify (e.g., rank / categorize) driving modes for respective vehicle speeds, ranging from an extreme stop mode, which indicates a lowest average vehicle speed, to a highest speed mode, which indicates a highest average vehicle speed.

[0032] Referring to Fig. 5, the driving modes for respective vehicle speeds can be divided into six modes, including an extreme congestion mode (e.g., an extreme traffic congestion mode or an extreme slow-moving traffic mode (e.g., a mode for extremely slow and / or congested traffic)), a congestion mode (e.g., a traffic congestion mode or a slow-moving traffic mode (e.g., a mode for slow-moving traffic)), an urban area mode, a route mode (e.g., a route mode), a high-speed mode, and a maximum-speed mode (or a maximum-speed mode). The driving modes can be divided based on the average vehicle speeds, and the average vehicle speed can gradually increase from the extreme congestion mode to the maximum-speed mode.For example, the average vehicle speeds are equal to or less than 10 km / h in the extreme congestion mode, 10 to 30 km / h in the congestion mode, 30 to 60 km / h in the urban area mode, 60 to 90 km / h in the route mode, 90 to 120 km / h in the high speed mode and equal to or greater than 120 km / h in the highest speed mode.

[0033] The electric field load power consumption (or electric field load energy consumption) gradually increases from the extreme congestion mode to the highest speed mode. The (speed) modes can be divided into a high load mode and a low load mode based on the electric field load power consumption. Regarding the electric field load power consumption, the modes from the extreme congestion mode to the urban area mode can be set to the low load mode, and the modes from the route mode to the highest speed mode can be set to the high load mode.

[0034] In order to further consider a vehicle gradient as an input variable, a vehicle inclination or the road gradient may be classified (e.g., graded / classified) based on a specific reference point (e.g., a starting point from which the gradient is calculated) into stages ranging from a downward incline stage, at which a lowest driving load may be applied to the vehicle, to a steep upward incline, at which a highest driving load may be applied to the vehicle. With reference to Fig. 5, the inclination of the vehicle may be divided into five stages, including a downward slope stage (e.g., a stage of a descending slope), a flat area stage (e.g., a flat terrain stage), a slight upward slope stage (e.g., a stage of a gently rising slope), a moderate upward slope stage (e.g., a stage of a moderately rising slope), and a steep upward slope stage (e.g., a stage of a steep or steep rising slope). The respective stages may be divided based on the inclination of the vehicle, and the load of the vehicle gradually increases from the downward slope stage to the steep upward slope stage.

[0035] A table (e.g., a map) for deriving (e.g., calculating) a two-dimensional driving load level can thus be generated based on driving modes for respective average vehicle speeds and on a vehicle inclination. The table can be pre-generated (or previously generated) and stored in a memory of a vehicle control device. The vehicle control device can be configured to determine the driving mode for each vehicle speed and each vehicle inclination as internal variables or quantities (e.g., as input quantities) and to determine a relative output value from the driving load level derivation table based on the detected values ​​of the internal variables (e.g., the input quantities) as a driving load level value.

[0036] A main battery state of charge, which indicates a change in the state of charge based on a change in the LDC output voltage, may be taken into account. The main battery state of charge may be divided into three levels or states (e.g., main battery state of charge states) (0, 1, and 2), and switching between the levels may be set and implemented by means of hysteresis. A state of charge (SOC) equal to or less than a first threshold, which may be set relatively low, may be classified (e.g., ranked) into a level 0 (or Low); a state of charge (SOC) equal to or less than a second threshold, which is set to be greater than the first threshold, may be classified (e.g., ranked) into a level 2 (or High); and a state of charge (SOC) equal to or less than a second threshold, which is set to be greater than the first threshold, may be classified (e.g., ranked) into a level 3 (or High).SOC which is greater than the first threshold and less than the second threshold may be classified (e.g., rated) as Level 1 (or Normal).

[0037] A calibration value derivation table (e.g., a calibration value derivation map) for determining a calibration value based on the driving load level and the main battery state of charge, which are determined as above, namely a two-dimensional (2D) calibration value derivation table based on an input (e.g., dependent on input variables) of the driving load level information and the main battery state of charge information, can be created and stored in the vehicle control device. Using the created calibration value derivation table, a calibration value that takes into account / reflects the vehicle driving load state and the main battery state of charge can be determined as a relative value, as in Fig. 4 shown.

[0038] In order to differentiate the control process based on the input variables (e.g., perform it differently), the LDC output voltage can also be set (e.g., adjusted) based on the high driving load mode (or high load mode) or the low driving load mode (or low load mode). The auxiliary battery state of charge balance can therefore be optimized. When driving in the high load mode, the auxiliary battery state of charge can be set (e.g., adjusted) so that it increases to a certain level and remains there. When driving in the low load mode, the LDC output voltage can be set (e.g., adjusted) to decrease from the increased level of the auxiliary battery state of charge (e.g., decrease the increased level of the auxiliary battery state of charge) in order to reduce and maintain the auxiliary battery state of charge level (or state). The electric field load power consumption (orThe electric field load power consumption can therefore be reduced.

[0039] This power control strategy can be applied when the vehicle enters an urban area congestion section (e.g., a section in the urban area with high traffic volume (e.g., with congested and / or tailback traffic)) from a high-speed driving section, such as a highway, on which the vehicle is driving in the high-load mode, and is driving in a low-load mode, as in Fig. 5 (and Fig. 4). If a calibration value determined based on the calibration value derivation table using the driving load level information and the main battery state of charge information as input variables is equal to or greater than a reference value set for determining that the driving load is in the high-load mode, then an LDC output voltage instruction table associated with the high-load mode can be used to control the LDC output voltage.

[0040] The LDC output voltage instruction table, which is a 2D-type instruction table (or a two-dimensional instruction table) for determining an LDC output voltage based on an input of the auxiliary battery state of charge information (e.g., the auxiliary battery state of charge information) and the auxiliary battery temperature information, can be generated to determine an LDC output voltage for maintaining a high level of the auxiliary battery state of charge. When the vehicle is in the high-load mode in a section such as the high-speed section of Fig. 4, the LDC output voltage can be adjusted (e.g., adjusted) using the LDC output voltage instruction table associated with the high load mode. Consequently, the auxiliary battery charge level can be maintained at a high level, and the auxiliary battery charge level can be maintained at the high level (or high level).

[0041] When the vehicle is traveling in the high-load mode, the auxiliary battery charge level can be maintained at the high level (or the high level) by repeatedly charging and discharging the battery. When the vehicle traveling in the high-load mode enters an urban area congestion section (e.g., an urban area traffic congestion section) and travels in the low-load mode, the auxiliary battery charge level can be changed (e.g., switched) from the high level to the normal level (or from the high level to the normal level) and can then be maintained at the normal level (or normal level). The congestion section can thus be changed into a discharging section (section I of Fig. 4), a weak discharge area (Section II of Fig. 4) and a loading / unloading area (Section III of Fig. 4) be divided to adjust (e.g. adjust) the LDC output voltage.

[0042] When the vehicle enters the low-load mode and travels in the low-load mode, the discharge region may be reached first. In the discharge region, the LDC output voltage is reduced compared to the output voltage for traveling in the high-load mode. Since only one discharge is performed in the discharge region, the auxiliary battery state of charge, which is set to the high state during traveling in the high-load mode, can be reduced along with the gradual discharge.

[0043] In the discharge range, the LDC output voltage can be set (e.g., adjusted) so that it is maintained in a burst mode (e.g., a burst discharge mode / rapid discharge mode (so-called burst mode)) for conducting a discharge of the auxiliary battery or so that it is maintained at a minimum voltage for driving an electric field load. When the LDC output voltage is set (e.g., adjusted) in the burst mode, the instruction voltage of the LDC can be set (e.g., adjusted) so that it is lower than the voltage (e.g., the potential) of the auxiliary battery, and the LDC output can be (e.g., subsequently) turned off (e.g., disconnected) (which, for example, no longer causes the auxiliary battery to be charged by the LDC and, at the same time, causes loads to consume energy from the auxiliary battery). Consequently, the auxiliary battery can be discharged.

[0044] Once the auxiliary battery state of charge, which has decreased in the discharge region, reaches a transition threshold, the auxiliary battery state of charge may enter (or transition into) the weak discharge region. The calibration value can be used to determine whether the auxiliary battery state of charge enters (or should enter) the weak discharge region from the discharge region, i.e., to determine a transition of the auxiliary battery state of charge and transition conditions.

[0045] In conventional cases, three auxiliary battery state of charge states, including low, normal, and high, were set as transition thresholds of the target state of charge values ​​(constants). In contrast, in the present invention, sums of the target state of charge values ​​(e.g., constants) and the calibration value can be set as the transition threshold. In other words, by setting the transition thresholds for determining whether an auxiliary battery state of charge state has transitioned or changed to values ​​that include the calibration value, the transition thresholds can be calibrated and determined as variables / quantities that can be variably set (e.g., adjusted) in contrast to fixed constants. The range(s) of the high level (or high levels) and the normal level (or normal levels) of the auxiliary battery state of charge state can thus be changed (e.g., expanded).

[0046] If, based on the transition values ​​calibrated by the calibration value, it is determined that the auxiliary battery state of charge enters the weak discharge range corresponding to the normal level (or normal level), the auxiliary battery state of charge can be limited by triggering / releasing regeneration efficiency control. Regeneration efficiency control is a control method for preventing the auxiliary battery from being charged and causing the main battery to continue charging by reducing the LDC output voltage when the vehicle enters regenerative braking mode and charging the auxiliary battery is not necessary because the auxiliary battery state of charge is sufficient.

[0047] Conventional conditions for determining whether to perform and trigger / release the regeneration efficiency control include the auxiliary battery charge level, the electric motor power, and the like. When the auxiliary battery charge level satisfies a hysteresis, that is, the auxiliary battery charge level is equal to or less than a threshold value set to determine that charging of the auxiliary battery charge level is required, and the electric motor power satisfies the hysteresis, that is, the electric motor power is equal to or greater than a threshold value set to determine that the electric motor power is in the deceleration state for generating regenerative braking energy (e.g.Regenerative braking energy), the conditions for performing regeneration efficiency control are determined to be met, and consequently, it is determined that the LDC operation mode is set to EV mode as opposed to transitioning to regenerative braking mode (e.g., consequently, the LDC operation mode is determined / determined to be set to EV mode as opposed to transitioning to regenerative braking mode). Consequently, the LDC is configured to output a corresponding, relatively low voltage.

[0048] In the present invention, sums of conventional constants and the calibration value can be determined and used as threshold values ​​for the auxiliary battery state of charge for determining whether to perform and trigger / release regeneration efficiency control. Therefore, threshold values ​​for the auxiliary battery state of charge, which are one of the conditions for determining whether to perform and trigger / release regeneration efficiency control, can be used as variables that vary based on the calibration value.

[0049] By using the calibration value to calibrate (e.g., set / adjust) the threshold values ​​for determining whether regeneration efficiency control is being performed (e.g., should be performed), power consumption (e.g., power consumption) in the electric field loads (e.g., electrical loads) can be reduced by reducing the LDC output voltage. In the weak discharge region, the condition for performing regeneration efficiency control, that is, the condition having the threshold values ​​calibrated by the calibration value, is not met, and thus, the execution may be restricted.

[0050] In the charge / discharge range, the condition for performing the regeneration efficiency control may be met, and thus the LDC output voltage may be variably adjusted (e.g., adjusted) using the regeneration efficiency control. If the auxiliary battery state of charge is sufficient and thus charging is not necessary, the LDC output voltage may be reduced. In the charge / discharge range, the auxiliary battery may be repeatedly charged and discharged to maintain the state of charge (SOC) at the normal level, and the conventional LDC output voltage control method is used to control the LDC output voltage, as shown in Fig. 5 shown.

[0051] In other words, in the charge / discharge range, a value determined by the LDC output voltage instruction table generated based on the auxiliary battery charge level and the auxiliary battery temperature information based on the LDC operation mode and the auxiliary battery charge level state may be set as the LDC output voltage (see Fig. 2). When the vehicle changes from the Low Load Mode back to the High Load Mode in the loading / unloading area (see section C of Fig. 4), then a high level of the LDC output voltage can be set to be output for auxiliary battery state-of-charge charging. The LDC output voltage instruction table associated with the high-load mode can therefore be used to variably adjust (e.g., adjust) the LDC output voltage.

[0052] With reference to Section C of Fig. 4, the auxiliary battery charge level gradually increases from the normal level to the high level by performing charging. After the auxiliary battery charge level reaches the high level (see section A of Fig. 4), the LDC output voltage can be set (e.g., adjusted) to be an output value (or assume an output value) determined based on the LDC output voltage instruction table associated with the high load mode to maintain the state of charge at the high level (or high level).

[0053] Fig. 6 illustrates a comparison between the auxiliary battery state of charge control strategy of the present invention and the conventional art. As shown in the figure, in conventional cases, when a vehicle traveling in the high-speed mode (high-load mode) enters the congestion mode (low-load mode), fuel efficiency in urban areas in the congestion mode is reduced, and an auxiliary battery state of charge balance changes from the normal level (or normal level) to the high level (or high level), so that the LDC energy consumption is increased and the influence of the LDC energy consumption on the fuel efficiency is increased.

[0054] How to continue in Fig.As shown in FIG. 6, in the present invention, fuel efficiency in urban areas can be improved in the congestion mode, where the auxiliary battery state of charge balance changes from a high level to a low level, and thus LDC power consumption can be reduced and an influence thereof on fuel efficiency can be improved. In an urban area where traffic congestion frequently occurs, the auxiliary battery state of charge can be changed to a low state to reduce LDC power consumption to reduce electric field load power consumption. Fuel efficiency can thus be improved.

[0055] As apparent from the above description, the present invention provides the following effects.

[0056] Fuel efficiency in urban areas can be improved by differentiating a state of charge balance control strategy for the auxiliary battery.

[0057] Consequently, fuel efficiency can be optimized when a vehicle traveling on a road, such as a highway, with a high average speed and a high load enters an area, such as an urban area, where the average speed and load of the vehicle are reduced. Improving fuel efficiency can also lead to an increase in the market value of the vehicle.

Claims

[1] A method for controlling a battery state of charge (SOC) of a hybrid vehicle, comprising: Determining, by a control device, a driving load of the hybrid vehicle based on driving modes for respective speeds of the hybrid vehicle and on an inclination of a roadway of the hybrid vehicle, Determining, by the controller, a calibration value based on the driving load and a main battery charge state, and Setting, by the control device, an auxiliary battery charge level according to two driving load modes based on the calibration value, the two driving load modes comprising a high-load mode and a low-load mode, wherein setting the auxiliary battery charge level state comprises: Determining by the control device, when the calibration value is equal to or greater than a predetermined reference value, that the driving load of the hybrid vehicle is in the high-load mode, and variably setting, by the controller, a low-voltage direct current (DC-DC) converter (LDC) output voltage using an LDC output voltage instruction table associated with the high load mode to maintain the auxiliary battery state of charge at a high level, or wherein setting the auxiliary battery charge level state comprises: Determining by the control device, when the calibration value is equal to or less than a predetermined reference value, that the driving load of the hybrid vehicle is in the low-load mode, entering the low-load mode and setting the auxiliary battery charge level by dividing the low-load mode into three areas, where the three areas include a discharge area, a weak discharge area and a charge / discharge area. [2] The method of claim 1, wherein determining the driving load comprises: Dividing, by the control device, speeds of the hybrid vehicle by means of stages from a low speed to a high speed based on an average speed of the hybrid vehicle and determining the driving mode for each speed, Dividing, by the control device, the inclination of the roadways into a plurality of stages and determining the inclination of a road on which the hybrid vehicle is traveling, and Dividing, by the control device, the driving load of the hybrid vehicle into a high and a low level based on the determined driving mode and the determined inclination. [3] The method of claim 2, wherein dividing the speed and determining the driving mode comprises: Dividing, by the control device, the speeds of the hybrid vehicle into six modes ranging from an extreme stall mode to a highest speed mode, and determining the driving mode. [4] The method according to claim 2 or 3, wherein said dividing and determining the inclination comprises: Dividing, by the control device, the gradient into five stages, ranging from a downward slope to a steep upward slope, and determining the gradient of the road. [5] The method according to any one of claims 1 to 4, wherein determining the calibration value comprises: Determining, by the control device, the driving load of the hybrid vehicle and the main battery charge level by classifying the driving load of the hybrid vehicle and the main battery charge level into high and low levels, and Determining, by the controller, the calibration value based on the determined driving load and the determined main battery state of charge. [6] The method according to any one of claims 1 to 5, wherein the calibration value is determined by a calibration value derivation table and the calibration value derivation table is generated, the calibration value being variably set based on information about the driving load of the hybrid vehicle and the main battery state of charge condition. [7] The method according to any one of claims 1 to 6, wherein setting the auxiliary battery state of charge comprises: Comparing, by the controller, an auxiliary battery state of charge value with a transition threshold and determining whether a transition of the auxiliary battery state of charge occurs, wherein the transition threshold is set as a sum of the calibration value and a reference value, the reference value being set to a constant for a transition of the auxiliary battery state of charge condition. [8] A system for controlling a battery state of charge (SOC) of a hybrid vehicle, comprising: a memory configured to store program instructions, and a processor configured to execute the program instructions, wherein the program instructions, when executed, are configured to: to determine a driving load of a hybrid vehicle based on driving modes for respective speeds of the hybrid vehicle and on an inclination of a road surface of the hybrid vehicle, to determine a calibration value based on the driving load and a main battery charge state, and set an auxiliary battery charge level according to two driving load modes based on the calibration value, the two driving load modes comprising a high-load mode and a low-load mode, wherein the program instructions for setting the auxiliary battery charge level state, when executed, are further configured to: to determine, when the calibration value is equal to or greater than a predetermined reference value, that the driving load of the hybrid vehicle is in the high-load mode, and variably adjust a low-voltage direct current (DC-DC) converter (LDC) output voltage using an LDC output voltage instruction table associated with the high-load mode to maintain the auxiliary battery state of charge at a high level, or wherein the program instructions for setting the auxiliary battery charge level state, when executed, are further configured to: to determine, when the calibration value is equal to or less than a predetermined reference value, that the driving load of the hybrid vehicle is in the low-load mode, to enter the low-load mode and to adjust the auxiliary battery charge state by dividing the low-load mode into three areas, where the three areas include a discharge area, a weak discharge area and a charge / discharge area. [9] The system of claim 8, wherein the program instructions for determining the driving load, when executed, are further configured to: To divide the speeds of the hybrid vehicle into stages from a low speed to a high speed based on an average speed of the hybrid vehicle and to determine the driving mode for each speed, to divide the gradient of the roadways into a plurality of levels and to determine the gradient of a road on which the hybrid vehicle is traveling, and to divide the driving load of the hybrid vehicle into a high level and a low level based on the determined driving mode and the determined inclination. [10] The system of claim 9, wherein the program instructions, when executed, are further configured to: to divide the speeds of the hybrid vehicle into six modes, ranging from an extreme slowdown mode to a maximum speed mode, and to determine the driving mode. [11] The system of claim 9 or 10, wherein the program instructions, when executed, are further configured to: to divide the gradient into five levels, ranging from a downward slope to a steep upward slope, and to determine the gradient of the road. [12] The system according to any one of claims 8 to 11, wherein the program instructions for determining the calibration value, when executed, are further arranged to: to determine the driving load of the hybrid vehicle and the main battery state of charge by classifying the driving load of the hybrid vehicle and the main battery state of charge into high and low levels, and to determine the calibration value based on the determined driving load of the hybrid vehicle and the determined main battery state of charge. [13] The system according to claim 8, wherein the calibration value is determined by a calibration value derivation table and the calibration value derivation table is generated, the calibration value being variably set based on information about the driving load of the hybrid vehicle and the main battery state of charge condition. [14] The system of claim 8, wherein the program instructions for setting the auxiliary battery charge level state, when executed, are further configured to: compare an auxiliary battery state of charge value with a transition threshold and determine whether a transition of the auxiliary battery state of charge occurs, wherein the transition threshold is set as a sum of the calibration value and a reference value, the reference value being set to a constant for a transition of the auxiliary battery state of charge condition.

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