Electric system for vehicle

Abstract

This electric system for a vehicle comprises: a battery for traveling that is used as a power source for a motor provided as a driving source of wheels in the vehicle; an inverter that drives the motor with power stored in the battery for traveling; a capacitor that is connected in parallel with the inverter; an auxiliary machinery battery that is provided as a power source for auxiliary machinery of the vehicle; a boosting circuit that boosts an output voltage of the auxiliary machinery battery; and a control unit that performs control to charge the capacitor by using the voltage boosted by the boosting circuit. The control unit controls the boosting rate of the boosting circuit on the basis of a detection result of the state of the auxiliary machinery battery during charging of the capacitor using the boosted voltage.

Description

Vehicle Electrical Systems

[0001] The present invention relates to a vehicle electrical system, and more particularly to a technique for precharging a capacitor connected in parallel to an inverter in an electric vehicle.

[0002] In electric vehicles equipped with a motor as a drive source for the wheels, a capacitor that functions as a noise filter is sometimes connected in parallel to the inverter that drives the motor. In such electric vehicles equipped with a capacitor, when the traction battery used as the power source for the motor is electrically connected to the inverter, the capacitor is precharged to prevent inrush current from flowing into the inverter.

[0003] The pre-charging can be achieved by supplying power from the driving battery to the capacitor via a path separate from the path via a relay inserted between the driving battery and the inverter before turning on the relay. Alternatively, pre-charging can be performed using power from an auxiliary battery provided separately from the driving battery (see, for example, Patent Documents 1 to 3 listed below).

[0004] JP 2016-114584 A JP 2007-302129 A JP 2017-085869 A

[0005] An object of the present invention is to improve the stability of the operation of precharging a capacitor connected in parallel to an inverter in an electric vehicle.

[0006] One embodiment of the vehicle electrical system of the present invention comprises a traction battery used as a power source for a motor provided as a drive source for wheels in a vehicle, an inverter that drives the motor based on power stored in the traction battery, a capacitor connected in parallel to the inverter, an auxiliary battery provided as a power source for auxiliary equipment of the vehicle, a boost circuit that boosts the output voltage of the auxiliary battery, and a control unit that controls the charging of the capacitor using the boosted voltage from the boost circuit, wherein the control unit controls the boost speed of the boost circuit based on the detection result of the state of the auxiliary battery when charging the capacitor using the boosted voltage.

[0007] According to the present invention, it is possible to improve the stability of the operation of precharging a capacitor connected in parallel to an inverter in an electric vehicle.

[0008] It is a diagram showing an example of a schematic internal configuration of a vehicle equipped with a vehicle electrical system as an embodiment. It is a diagram showing an example of a conventional precharge configuration. It is a diagram for explaining an example of the configuration of a vehicle electrical system as an embodiment. It is a flowchart showing an example of processing by a control unit provided in a vehicle electrical system as an embodiment. It is a diagram showing an example of boost control information in an embodiment.

[0009] An embodiment of the present invention will be described below with reference to the accompanying drawings. Fig. 1 is a diagram showing an example of a schematic internal configuration of a vehicle equipped with a vehicle electrical system 1 according to an embodiment. Note that Fig. 1 shows only the components according to the present invention among the various components of the vehicle according to the embodiment.

[0010] The vehicle of this embodiment is configured as a hybrid electric vehicle (HEV) equipped with an engine 2 and a motor generator (MG) 3, and is also equipped with a high-voltage battery 4 (driving battery) used as a power source for the MG 3. In a vehicle that is an HEV, the engine 2 may be used as a drive source for the wheels, or as a power source for generating power to drive the MG 3 and to charge the high-voltage battery 4.

[0011] In this example, the vehicle is assumed to be a four-wheeled vehicle, but the vehicle according to the embodiment may be any vehicle having at least two or more wheels.

[0012] The vehicle is provided with an inverter 5 for the MG 3. When the MG 3 is powered, the inverter 5 outputs a drive voltage generated based on the input voltage from the high-voltage battery 4 to the MG 3, and when regenerating power, the inverter 5 charges the high-voltage battery 4 using the regenerated power from the MG 3.

[0013] A relay 6 is provided between the inverter 5 and the high-voltage battery 4 to electrically isolate the high-voltage battery 4. When the relay 6 is in the off state, the high-voltage battery 4 is electrically isolated, and when the relay 6 is in the on state, the high-voltage battery 4 is electrically connected to the inverter 5, allowing power to be supplied from the high-voltage battery 4 to the inverter 5.

[0014] The vehicle is also provided with a cruise control ECU (Electric Control Unit) 7 that controls the operation of the MG 3. The cruise control ECU 7 controls the operation of the MG 3 by controlling the inverter 5. For example, the cruise control ECU 7 controls the inverter 5 so that the operation of the MG 3 corresponds to various driving operations by the driver, such as accelerator operation and brake operation.

[0015] As shown in the figure, a noise filter Fn is connected in parallel to the inverter 5. The noise filter Fn is configured with a capacitor and removes high-frequency noise in the inverter 5. Although not shown in FIG. 1 , the capacitor included in the noise filter Fn will hereinafter be referred to as a "capacitor Cn."

[0016] The vehicle of the embodiment is equipped with accessories 3. The accessories 3 broadly include various electronic components, such as a fuel injector and an electronic throttle, for operating the engine 2, various ECUs (Electronic Control Units) for controlling various vehicle operations, such as controlling the engine 2 and MG 3, and on-board electronic devices, such as meters, navigation equipment, and audio equipment. Here, the above-mentioned cruise control ECU 7 is also included in the accessories 3, but for convenience of illustration, the accessories 3 and the cruise control ECU 7 are shown as separate entities in FIG. 1.

[0017] The vehicle is provided with an auxiliary battery unit 9 for supplying power to the above-described auxiliary devices 3. The auxiliary battery unit 9 has an auxiliary battery 9a provided as a power source for the auxiliary devices 3. In this example, the rated output voltage of the auxiliary battery 9a is 12 V. However, the rated output voltage of the auxiliary battery 9a is not limited to 12 V and may be, for example, 24 V. The rated output voltage of the auxiliary battery 9a is lower than the rated output voltage of the high-voltage battery 4 (for example, 400 V).

[0018] In this example, a lithium-ion battery is used as the auxiliary battery 9a, rather than a lead battery. Lithium-ion batteries can be made smaller and lighter in weight and size than lead batteries, and have advantages in terms of reducing vehicle weight and installation space. Note that using a lithium-ion battery as the auxiliary battery 9a is merely an example for illustrative purposes, and other batteries, such as lead batteries, can also be used.

[0019] Although not shown, the auxiliary battery unit 9 includes the auxiliary battery 9a and a unit controller that performs various processes related to the auxiliary battery 9a. This unit controller is configured with a microcomputer having, for example, a central processing unit (CPU), a read-only memory (ROM), and a random access memory (RAM). The CPU executes various processes according to programs stored in the ROM, thereby performing various processes related to the auxiliary battery 9a. The unit controller's functions include a state monitoring function for the auxiliary battery 9a. Specifically, the unit controller is capable of detecting the output voltage, output current, battery temperature, etc. of the auxiliary battery 9a and calculating the SOC (State of Charge) and SOH (State of Health).

[0020] In the vehicle of the embodiment, the auxiliary battery 9a can be charged by the high-voltage battery 4. In order to enable the auxiliary battery 9a to be charged by the high-voltage battery 4, a DC / DC converter 10 is provided in the vehicle.

[0021] The DC / DC converter 10 has a step-down function for the input voltage from the high-voltage battery 4 via the relay 6, and steps down the input voltage from the high-voltage battery 4 to a predetermined voltage value, specifically, to DC 12 V in this example. By outputting this stepped-down voltage from the DC / DC converter 10 to the auxiliary battery unit 9, the auxiliary battery 9a can be charged by the high-voltage battery 4.

[0022] As shown in FIG. 1, the vehicle electrical system 1 according to the embodiment includes a high-voltage battery 4, an inverter 5, a relay 6, a noise filter Fn (capacitor Cn), an auxiliary battery unit 9, and a DC / DC converter 10.

[0023] In the vehicle shown in FIG. 1, when the high-voltage battery 4 is used as a power source for running the vehicle, the relay 6 is turned on, and the high-voltage battery 4 and the inverter 5 are electrically connected.

[0024] However, at this time, there is a risk that an inrush current may flow from the high-voltage battery 4 into the inverter 5, and in order to prevent this, the capacitor Cn in the noise filter Fn is precharged.

[0025] 2 shows an example of a conventional precharge configuration. As shown in the figure, conventionally, to achieve precharge, a series-connected circuit of a precharge relay 100 and a precharge resistor 101 is provided in parallel with the relay 6. In this case, precharge is achieved by turning on the precharge relay 100 before turning on the relay 6. Because the precharge resistor 101 is present in the current supply path from the high-voltage battery 4 to the parallel-connected circuit of the inverter 5 and capacitor Cn, the amount of current from the high-voltage battery 4 is suppressed, making it possible to prevent inrush current from flowing in.

[0026] However, in the conventional configuration as shown in FIG. 2, it is necessary to prepare components capable of withstanding high loads such as the precharge relay 100 and the precharge resistor 101, which leads to an increase in costs.

[0027] Therefore, in this embodiment, the method of using the bypass path including the precharge relay 100 and the precharge resistor 101 is not adopted, but a method of precharging the capacitor Cn from the auxiliary battery 9a is adopted.

[0028] Fig. 3 is a diagram for explaining an example of the configuration of the vehicle electrical system 1 according to the embodiment. Note that Fig. 2 also shows the driving control ECU 7 shown in Fig. 1 together with the example of the configuration of the vehicle electrical system 1.

[0029] To enable precharging of capacitor Cn from auxiliary battery 9a, DC / DC converter 10 is provided with step-down circuit 11, which performs the step-down function described above, as well as step-up circuit 12. DC / DC converter 10 is also provided with switches SW1 and SW2 for controlling inputs and outputs of step-down circuit 11 and step-up circuit 12, as well as with control unit 13, which controls the step-down operation by step-down circuit 11 and the step-up operation by step-up circuit 12, and controls switching between switches SW1 and SW2.

[0030] The control unit 13 is configured with, for example, a microcomputer having a CPU, ROM, and RAM, and the CPU executes various processes in accordance with programs stored in the ROM, thereby performing overall control of the DC / DC converter 10, such as controlling the above-mentioned switches SW1 and SW2, the step-down circuit 11, and the step-up circuit 12.

[0031] In the DC / DC converter 10, the switches SW1 and SW2 are each configured as a switch having three terminals, namely, terminals t1, t2, and t3. The terminal t1 of the switch SW1 is connected to the connection point between the capacitor Cn and the inverter 5, the terminal t2 is connected to the step-down circuit 11, and the terminal t3 is connected to the step-up circuit 12. The terminal t1 of the switch SW2 is connected to the auxiliary battery 9a (connected to the positive output terminal), the terminal t2 is connected to the step-down circuit 11, and the terminal t3 is connected to the step-up circuit 12. When the terminal t2 of the switches SW1 and SW2 is selected, the auxiliary battery 9a can be charged from the high-voltage battery 4. Specifically, the input voltage from the high-voltage battery 4 can be stepped down by the step-down circuit 11 to charge the auxiliary battery 9a. On the other hand, if the terminal t3 is selected by the switches SW1 and SW2, the output voltage of the auxiliary battery 9a can be supplied to the capacitor Cn via the boost circuit 12, thereby precharging the capacitor Cn. That is, in this example, the 12V output voltage from the auxiliary battery 9a can be boosted by the boost circuit 12 to a voltage value required for precharging, thereby charging the capacitor Cn.

[0032] In the DC / DC converter 10, the control unit 13 controls the boost rate of the boost circuit 12 based on the state detection results of the auxiliary battery 9a when precharging the capacitor Cn as described above, i.e., when charging the capacitor Cn using the boosted voltage from the boost circuit 12. Specifically, the control unit 13 controls the boost rate of the boost circuit 12 based on the state detection results of the auxiliary battery 9a, which are the temperature, SOC, SOH, output current value, and output voltage value of the auxiliary battery 9a. For these temperature, SOC, SOH, output current value, and output voltage value, values ​​detected (calculated) by the unit controller of the auxiliary battery unit 9 can be used.

[0033] For clarity, the "boost speed" refers to the rate of voltage increase during the boost operation, and can be expressed as the voltage increase value per unit time. In the boost circuit 12, the boost speed can be adjusted by, for example, adjusting the switching frequency of the switching element used in the boost operation (DC / DC conversion).

[0034] When the high-voltage side capacitor Cn is precharged using a relatively low output voltage from the auxiliary battery 9a, the amount of power drawn from the auxiliary battery 9a may become excessive, causing the output voltage to drop excessively, which may cause the boost circuit 12 to stop operating. In other words, there is a risk that the precharge may be unintentionally stopped. By controlling the boost rate of the boost circuit 12 based on the status detection results of the auxiliary battery 9a as described above, it is possible to prevent the amount of power drawn from the auxiliary battery 9a from becoming excessive, thereby improving the stability of the boost operation during precharge. Therefore, the stability of the operation of the precharge of the capacitor Cn can be improved.

[0035] In this example, the control unit 13 determines the initial value of the boost rate based on at least one of the temperature, SOC, and SOH of the auxiliary battery 9a, and after starting the boost operation using the initial value, performs a process to correct the boost rate based on at least one of the output current value and output voltage value of the auxiliary battery 9a.

[0036] By performing the processing in this manner by the control unit 13, the initial value of the boost rate is determined based on battery state indicators that hardly fluctuate during precharging, such as temperature, SOC, and SOH, and after the start of precharging, the boost rate is corrected based on battery state indicators that may fluctuate relatively greatly, such as the output current value and output voltage value. Therefore, the boost rate by the boost circuit 12 can be controlled based on battery state indicators that are appropriate for both the start and end of precharging, and the precharging of the capacitor Cn can be performed appropriately.

[0037] In this example, the control unit 13 determines the above initial value based on the temperature, SOC, and SOH of the auxiliary battery 9a. At this time, the control unit 13 determines a slower initial boost rate as the temperature of the auxiliary battery 9a is lower. Also, the control unit 13 determines a slower initial boost rate as the SOC value is lower. Furthermore, the control unit 13 determines a slower initial boost rate as the SOC value is lower.

[0038] At low temperatures, low SOC, and low SOH, the output characteristics of the auxiliary battery 9a deteriorate. Therefore, by determining a slow boost rate as described above, the stability of the boost operation can be improved, and the stability of the operation of precharging the capacitor Cn can be improved.

[0039] In this example, the control unit 13 corrects the boost speed after starting the boost operation based on the initial value based on both the output current value and the output voltage value of the auxiliary battery 9a, and corrects the boost speed to be slower as the output current value increases, and also corrects the boost speed to be slower as the output voltage value decreases. This prevents excessive current from being output from the auxiliary battery 9a during precharge, stabilizes the boost operation, and improves the stability of the precharge operation of the capacitor Cn.

[0040] A specific example of the processing procedure of the control unit 13 will be described with reference to the flowchart of Fig. 4. In this example, the processing shown in Fig. 4 is executed by the CPU of the control unit 13 based on a program stored in a storage device such as a ROM.

[0041] First, in step S101, the control unit 13 waits for a pre-charge start notification. In this example, the driving control ECU 7 is configured to notify the control unit 13 of the pre-charge start at the start of pre-charge, and the control unit 13 waits for the pre-charge start notification in step S101. As will be understood from the above description of FIG. 2, during pre-charge, the relay 6 is turned off.

[0042] If it is determined in step S101 that a precharge start notification has been received, the control unit 13 executes a switch control process in step S102, that is, causes the switches SW1 and SW2 to select the terminal t2 so as to enable charging of the capacitor Cn from the auxiliary battery 9a.

[0043] In step S103 following step S102, the control unit 13 determines an initial boost rate based on the temperature, SOC, and SOH of the auxiliary battery. In this example, the initial boost rate is determined based on boost control information Ic (see FIG. 3) set in the control unit 13 (for example, stored in advance in the ROM).

[0044] FIG. 5 shows an example of the boost control information Ic, and FIG. 5A shows examples of first initial value table information Ic1 and second initial value table information Ic2 used to determine the initial boost speed. The first initial value table information Ic1 is table information for determining an initial value based on temperature and SOC, and the second initial value table information Ic2 is table information for determining an initial value based on SOH. Specifically, the first initial value table information Ic1 is table information in which a boost speed value is associated with each combination of temperature and SOC. The second initial value table information Ic2 is table information in which a boost speed correction coefficient is associated with each SOH. As shown in the figure, the first initial value table information Ic1 associates a slower boost speed with a smaller temperature value and a smaller SOC value, while the second initial value table information Ic2 sets a correction coefficient such that the boost speed is slower with a smaller SOH value.

[0045] In the determination process of step S103, the control unit 13 first acquires the temperature, SOC, and SOH of the auxiliary battery 9a from the auxiliary battery unit 9 (unit controller), and acquires the boost rate value corresponding to the acquired combination of temperature and SOC from the first initial value table information Ic1. Then, the control unit 13 acquires a boost rate correction coefficient corresponding to the acquired SOH from the second initial value table information Ic2, corrects the boost rate value acquired from the first initial value table information Ic1 using the correction coefficient, and sets the corrected value as the initial value of the boost rate.

[0046] In the first initial value table information Ic1, the temperature and SOC values ​​represent representative values ​​within a range. For example, temperature = "25°C," "0°C," and "-30°C" indicate a range of 25°C or higher, a range of less than 25°C and -30°C or higher, and a range of less than -30°C, respectively. For example, SOC = "80%," "50%," and "10%" indicate a range of 80% or higher, a range of less than 80% and 10% or higher, and a range of less than 10%, respectively. The same applies to the notation of SOH in the second initial value table information Ic2. The representative values ​​are merely examples and are not limited to the illustrated values. Furthermore, the boost rates and correction coefficients shown in FIG. 5A are merely examples and are not limited to the illustrated values.

[0047] In step S104 following step S103, the control unit 13 issues a command to start boosting at the initial boost speed, i.e., starts the boosting operation of the booster circuit 12 at the boost speed as the initial value obtained in the determination process of step S103.

[0048] In step S105 following step S104, the control unit 13 determines whether a speed correction condition is satisfied. That is, the control unit 13 determines whether the correction condition for the boost speed set as an initial value is satisfied. The speed correction condition here is an increase in the output current value of the auxiliary battery 9a and a decrease in the output voltage value. Specifically, the control unit 13 determines whether the speed correction condition is satisfied based on whether either the condition that the rate of increase in the output current value is equal to or greater than a predetermined threshold value THi or the condition that the rate of decrease in the output voltage value is equal to or greater than a predetermined threshold value THv is satisfied. As an example, the above-mentioned increase rate and decrease rate are assumed to be increase rates per second (A / sec) and decrease rates per second (V / sec), respectively, and the threshold value THi is set to 5 A / sec and the threshold value THv is set to 1 V / sec.

[0049] After issuing the command to start boosting in step S104, the control unit 13 calculates the output current increase rate and output voltage decrease rate of the auxiliary battery 9a, for example, every 1 second, and for each calculation, determines whether the speed correction condition is met using the above-mentioned threshold values ​​THi and THv.

[0050] If it is determined in step S105 that the output current increase rate is not equal to or greater than the threshold THi and the output voltage decrease rate is not equal to or greater than the threshold THv, and the speed correction condition is not satisfied, the control unit 13 proceeds to step S106 and determines whether or not a pre-charge end notification has been issued. In this example, the cruise control ECU 7 is configured to issue a pre-charge end notification to the control unit 13 at the end of pre-charge, and the control unit 13 determines whether or not the pre-charge end notification has been issued in step S106.

[0051] If it is determined in step S106 that the precharge end notification has not been received, the control unit 13 returns to step S105. That is, the control unit 13 waits for either the establishment of the speed correction condition or the reception of the precharge end notification through the processes of steps S105 and S106.

[0052] In step S105, if it is determined that either the condition that the output current increase rate is equal to or greater than the threshold value THi or the condition that the output voltage decrease rate is equal to or greater than the threshold value THv is met and the speed correction condition is met, the control unit 13 proceeds to step S107 and determines a correction coefficient for the boost speed based on the output current and output voltage.

[0053] In this example, the determination process of step S107 uses the current correction table information Ic3 and the voltage correction table information Ic4 shown in FIG. 5B . These current correction table information Ic3 and voltage correction table information Ic4 are also information set in the control unit 13 as the above-mentioned boost control information Ic. As shown in the figure, the current correction table information Ic3 is information in which a correction coefficient for the boost speed is associated with each output current increase rate of the auxiliary battery 9a, and the voltage correction table information Ic4 is information in which a correction coefficient for the boost speed is associated with each output voltage decrease rate of the auxiliary battery 9a. As shown in the figure, the current correction table information Ic3 and the voltage correction table information Ic4 have correction coefficients set so that the boost speed becomes slower as the output current increase rate and output voltage decrease rate become higher.

[0054] In the determination process of step S107 in this example, the following method is adopted: when only the speed correction condition related to the output current is satisfied, the correction coefficient is determined based only on the current correction table information Ic3; when only the speed correction condition related to the output voltage is satisfied, the correction coefficient is determined based only on the voltage correction table information Ic4; and when the speed correction conditions for both the output current and the output voltage are satisfied, the correction coefficient is determined based on both the current correction table information Ic3 and the voltage correction table information Ic4.

[0055] Specifically, if the only condition satisfied in step S105 is that the output current increase rate is equal to or greater than the threshold THi, the control unit 13 obtains a correction coefficient corresponding to the most recently calculated value of the output current increase rate from the current correction table information Ic3, and sets this as the correction coefficient to be used for correcting the voltage step-up speed. If the only condition satisfied in step S105 is that the output voltage decrease rate is equal to or greater than the threshold THv, the control unit 13 obtains a correction coefficient corresponding to the most recently calculated value of the output voltage decrease rate from the voltage correction table information Ic4, and sets this as the correction coefficient to be used for correcting the voltage step-up speed. If the both conditions satisfied in step S105 are that the output current increase rate is equal to or greater than the threshold THi and that the output voltage decrease rate is equal to or greater than the threshold THv, the control unit 13 obtains a correction coefficient corresponding to the most recently calculated value of the output current increase rate from the current correction table information Ic3 and a correction coefficient corresponding to the most recently calculated value of the output voltage decrease rate from the voltage correction table information Ic4, calculates a combined value (e.g., a multiplication value) of these correction coefficients, and sets this calculated value as the correction coefficient to be used for correcting the voltage step-up speed.

[0056] In the current correction table information Ic3 and the voltage correction table information Ic4, the numerical values ​​of the current rise rate and voltage drop rate represent representative values ​​of the range. For example, current rise rate = "5 A / sec," "10 A / sec," and "50 A / sec" indicate the ranges of 5 A / sec or more and less than 10 A / sec, 10 A / sec or more and less than 50 A / sec, and 50 A / sec or more, respectively. Regarding the voltage drop rate, for example, voltage drop rate = "1 V / sec," "3 V / sec," and "5 V / sec" indicate the ranges of 1 V / sec or more and less than 3 V / sec, 3 V / sec or more and less than 5 V / sec, and 5 V / sec or more, respectively. Note that the numerical values ​​of the representative values ​​are merely examples and are not limited to the illustrated numerical values. Furthermore, the correction coefficients shown in FIG. 5B are merely examples and are not limited to the indicated numerical values.

[0057] In response to the determination of the correction coefficient in step S107, the control unit 13 performs a process of correcting the boost speed based on the correction coefficient in step S108. That is, the boost speed of the boost circuit 12 is corrected by the correction coefficient determined in step S107.

[0058] After the process of step S108 is completed, the control unit 13 returns to step S105. As a result, after the precharge is started, the boost speed is corrected according to the output current and output voltage of the auxiliary battery 9a each time the speed correction condition is satisfied.

[0059] If it is determined in step S106 that the precharge end notification has been received, the control unit 13 ends the series of processes shown in FIG.

[0060] In the above, an example has been given in which the correction coefficient for the voltage step-up speed is determined based on the current correction table information Ic3 and the voltage correction table information Ic4 when the speed correction conditions for both the output current and the output voltage are met. However, when the speed correction conditions for both the output current and the output voltage are met, it is also possible to adopt a method in which the correction coefficient is determined using only the table information for the output current increase rate or the output voltage decrease rate, whichever is larger.

[0061] Alternatively, instead of dividing the table information into different output current increase rates and output voltage decrease rates, it is also possible to use a method in which table information is created in which a correction coefficient is associated with each combination of output current increase rate and output voltage decrease rate, and a correction coefficient corresponding to the calculated combination of output current increase rate and output voltage decrease rate is obtained from the table information and used to correct the boost speed.

[0062] In the above example, the step-up speed is corrected based on the output current increase rate and output voltage decrease rate of the auxiliary battery 9a, but the step-up speed may also be corrected based on the output current value and output voltage value of the auxiliary battery 9a itself. For example, table information may be prepared that stores correction coefficients corresponding to output voltage ranges defined as 10V or more, less than 10V, 5V or more, and 5V or less, and the correction coefficient corresponding to the output voltage value of the auxiliary battery 9a may be determined from the table information.

[0063] Note that this embodiment is not limited to the specific example described above, and various modified configurations are possible. For example, although the above example illustrates an example in which the initial value of the boost rate is determined based on the temperature, SOC, and SOH of the auxiliary battery 9a, the initial value of the boost rate may be determined based on at least one of the temperature, SOC, and SOH. Furthermore, the correction of the boost rate after the start of precharging is not limited to being based on both the output current value and the output voltage value of the auxiliary battery 9a, but may be based on at least one of the output current value and the output voltage value. Furthermore, although the above example illustrates an example in which the boost rate is corrected from the initial value after precharging, such correction of the boost rate is not essential.

[0064] In the above example, the control unit 13 provided in the DC / DC converter 10 is used to control the boost rate of the boost circuit 12 during precharging, but the control unit for the boost rate is not limited to being provided in the DC / DC converter 10. For example, a configuration in which the aforementioned unit controller or the driving control ECU 7 in the auxiliary battery unit 9 is used to control the boost rate may be considered.

[0065] Furthermore, although the above example illustrates the application of the present invention to an HEV, the present invention can also be suitably applied to vehicles such as BEVs (Battery Electric Vehicles) that do not have an engine, or to engine vehicles that do not have a traction motor and use an engine as a drive source for the wheels.

[0066] As described above, a vehicle electrical system (1) according to an embodiment of the present invention includes a traction battery (high-voltage battery 4) used as a power source for a motor provided to drive the vehicle's wheels, an inverter (5) that drives the motor using power stored in the traction battery, a capacitor (Cn) connected in parallel to the inverter, an auxiliary battery (9a) provided as a power source for the vehicle's accessories, a boost circuit (12) that boosts the output voltage of the auxiliary battery, and a control unit (13) that controls charging of the capacitor using the boosted voltage from the boost circuit. The control unit controls the boost rate of the boost circuit based on the auxiliary battery status detection result when charging the capacitor using the boosted voltage. By controlling the boost rate of the boost circuit based on the auxiliary battery status detection result when charging the capacitor as described above, the stability of the boost operation during pre-charging can be improved. Therefore, the stability of the pre-charging operation of the capacitor connected in parallel to the inverter can be improved.

[0067] In the embodiment, an example has been shown in which the processing of the "controller" is realized by software processing, but in this case, the "controller" can be rephrased as having the following configuration: That is, the control unit includes one or more processors (e.g., CPUs), and one or more storage media (e.g., ROMs) in which programs executed by the one or more processors are stored, the programs including one or more instructions, and the instructions cause the one or more processors to execute processing to control the boost speed of the boost circuit based on the detection result of the auxiliary battery state when the capacitor is charged using the boost voltage.

[0068] The processing by the "control unit" can also be realized as hardware processing using, for example, a digital logic circuit, etc. For example, a configuration in which the temperature of the auxiliary battery is input and a boosting speed instruction value based on the temperature is instructed to the boost circuit can be sufficiently realized by hardware processing.

[0069] In the vehicle electrical system according to the embodiment, the control unit detects the auxiliary battery's state by detecting any one of its temperature, SOC, SOH, output current, and output voltage. The battery's temperature, SOC, SOH, output current, and output voltage are suitable indicators for estimating the battery's output characteristics. This allows appropriate detection to be performed as the state detection related to the boost rate control, thereby improving the stability of the capacitor precharge.

[0070] Furthermore, in the vehicle electrical system according to the embodiment, the control unit determines an initial value of the boost rate based on at least one of the auxiliary battery's temperature, SOC, and SOH, and, after starting the boost operation based on the initial value, corrects the boost rate based on at least one of the auxiliary battery's output current and output voltage. This allows the initial value of the boost rate to be determined based on battery state indicators that hardly fluctuate during precharge, such as temperature, SOC, and SOH, and after precharge starts, corrects the boost rate based on battery state indicators that may fluctuate relatively greatly, such as the output current and output voltage. Therefore, the boost rate of the boost circuit can be controlled based on battery state indicators appropriate for both the start and end of precharge, ensuring appropriate precharging of the capacitor.

[0071] Furthermore, in the vehicle electrical system according to the embodiment, the control unit performs a process of determining a slower boost rate as an initial value the lower the temperature of the auxiliary battery, or a process of determining a slower boost rate as an initial value the lower the SOC value, or a process of determining a slower boost rate as an initial value the lower the SOC value. Since the output characteristics of the battery deteriorate at low temperatures, low SOC, or low SOH, determining a slow boost rate as described above can improve the stability of the boost operation and can also improve the stability of the capacitor pre-charge operation.

[0072] In the vehicle electrical system according to the embodiment, the control unit corrects the boost rate to slow down in response to an increase in the output current value or a decrease in the output voltage value, thereby preventing excessive current from being output from the auxiliary battery during pre-charging, stabilizing the boost operation, and improving the stability of the capacitor pre-charging operation.

[0073] REFERENCE SIGNS LIST 1 Vehicle electrical system 2 Engine 3 MG (motor generator) 4 High-voltage battery 5 Inverter 6 Relay 7 Travel control ECU 8 Auxiliary equipment 9 Auxiliary battery unit 9a Auxiliary battery 10 DC / DC converter Fn Noise filter Cn Capacitor 11 Step-down circuit 12 Step-up circuit 13 Control unit SW1, SW2 Switch Ic Step-up control information Ic1 First initial value table information Ic2 Second initial value table information Ic3 Current correction table information Ic4 Voltage correction table information

Claims

1. A vehicle electrical system comprising: a traction battery used as a power source for a motor provided as a drive source for wheels of a vehicle; an inverter that drives the motor based on power stored in the traction battery; a capacitor connected in parallel to the inverter; an auxiliary battery provided as a power source for auxiliary equipment of the vehicle; a boost circuit that boosts the output voltage of the auxiliary battery; and a control unit that controls charging of the capacitor using the boosted voltage from the boost circuit, wherein the control unit controls the boost speed of the boost circuit based on the detection result of the state of the auxiliary battery when the capacitor is charged using the boosted voltage.

2. The vehicle electrical system according to claim 1, wherein the control unit detects one of the temperature, SOC, SOH, output current value, and output voltage value of the auxiliary battery as the detected state.

3. The vehicle electrical system according to claim 1, wherein the control unit determines an initial value of the boost rate based on at least one of the temperature, SOC, and SOH of the auxiliary battery, and after starting the boost operation based on the initial value, performs processing to correct the boost rate based on at least one of the output current value and output voltage value of the auxiliary battery.

4. The vehicle electrical system according to claim 3, wherein the control unit performs a process of determining a slower boost rate as the initial value the lower the temperature of the auxiliary battery, or a process of determining a slower boost rate as the initial value the lower the value of the SOC, or a process of determining a slower boost rate as the initial value the lower the value of the SOC.

5. A vehicle electrical system according to claim 3 or claim 4, wherein the control unit performs a process of correcting the boost rate to be slower in response to an increase in the output current value, or a process of correcting the boost rate to be slower in response to a decrease in the output voltage value.

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