Power supply system and method for determining state of relay in power supply system

Abstract

To properly determine a state of a contact type relay included in a power supply system.SOLUTION: A power supply system includes: a power storage device; a power control device including a capacitor precharged with power from a power supply other than the power storage device; a contact type relay electrically connecting the power storage device and the power control device and releasing the connection of both; and a control device. The control device sets target voltage of precharge of the capacitor in response to a request of system startup, outputs a closing command of the relay in response to completion of the precharge, sets the target voltage before or after the output of the closing command to a value different from voltage of the power storage device, and determines a state of the relay based on voltage of the capacitor after the output of the closing command.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a power supply system including a relay and a method for determining the state of a relay in a power supply system. [Background technology]

[0002] Conventionally, a mobile body is known that includes a storage battery, a power supply device that converts DC power from the storage battery into AC power and supplies it to a motor, two contacts to which a charging device that outputs DC power for charging the storage battery is connected, and a charging control device (for example, see Patent Document 1). In this mobile body, the storage battery and the power supply device are electrically connected via two power lines each including a system main relay, and the storage battery and the two contacts are electrically connected via two charging lines each including a charging relay. Furthermore, when charging the storage battery with DC power from the charging control device, the charging control device controls the charging device so that a capacitor of the power supply device is pre-charged with the two system main relays opened prior to charging the storage battery. Furthermore, the charging control device opens at least one of the two charging relays to put at least one of the two charging lines into an open state, and then controls the charging device so that the capacitor is pre-charged, and if the voltage of the capacitor is equal to or higher than a threshold value, determines that an abnormality exists in the opened charging relay. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-112000 Summary of the Invention [Problem to be solved by the invention]

[0004] In the mobile body as described above, a contact type (mechanical or hybrid type) relay including a movable contact and a fixed contact is generally adopted as a system main relay or the like. However, when the surrounding environment of such a contact type relay is humid and below freezing point, moisture may freeze between the movable contact and the fixed contact. When such freezing occurs in the relay, even if the relay starts to be energized, the movable contact and the fixed contact cannot be electrically connected. In addition, in the contact type relay, the conductive state between the movable contact and the fixed contact may be disabled due to the inclusion of a foreign object. When the relay is not normally closed due to freezing or the like, it becomes impossible to supply power from the storage battery or the like to the power supply device, and the fault diagnosis function may erroneously diagnose that a fault has occurred in the power supply device. For this reason, in order to suppress erroneous diagnosis by the fault diagnosis function, it is required to properly determine the state of the contact type relay included in the power supply system.

[0005] Therefore, a primary object of the present disclosure is to appropriately determine the state of a contact-type relay included in a power supply system. [Means for solving the problem]

[0006] The power supply system of the present disclosure includes a power storage device, a power control device including a capacitor precharged with power from a power source other than the power storage device, and a contact-type relay that electrically connects the power storage device and the power control device and disconnects the two, and includes a control device that sets a target voltage for precharging the capacitor in response to a request for system startup, outputs a closing command for the relay in response to completion of the precharging, sets the target voltage to a value different from the voltage of the power storage device before or after output of the closing command, and determines the state of the relay based on the voltage of the capacitor after output of the closing command.

[0007] In addition, the method for determining the state of a relay in a power supply system disclosed herein is a method for determining the state of a relay in a power supply system including a power storage device, a power control device including a capacitor precharged with power from a power source other than the power storage device, and a contact-type relay that electrically connects the power storage device and the power control device and disconnects the two, the method including: setting a target voltage for precharging the capacitor in response to a request for system startup; outputting a closing command for the relay in response to completion of the precharging; setting the target voltage to a value different from the voltage of the power storage device before or after output of the closing command; and determining the state of the relay based on the voltage of the capacitor after output of the closing command. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram showing a vehicle including a power supply system according to the present disclosure. [Diagram 2] 4 is a flowchart illustrating an example of a routine executed by a control device of the power supply system of the present disclosure. [Diagram 3] 3 is a time chart illustrating an example of time variations of a precharge target voltage, a voltage of a capacitor of a power control device, and the like while the routine of FIG. 2 is being executed; [Figure 4] 10 is a flowchart showing another example of a routine executed by the control device of the power supply system of the present disclosure. [Diagram 5] 5 is a time chart illustrating an example of time variations of a precharge target voltage, a voltage of a capacitor of a power control device, and the like while the routine of FIG. 4 is being executed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Next, an embodiment of the present disclosure will be described with reference to the drawings.

[0010] 1 is a schematic diagram showing a hybrid vehicle V as a vehicle including a power supply system 1 of the present disclosure. In addition to the power supply system 1, the hybrid vehicle V shown in the figure includes an engine EG, a single-pinion planetary gear PG, motor generators MG1 and MG2 that exchange power with the power supply system 1, and a hybrid electronic control unit (hereinafter referred to as "HVECU") 10 that controls the entire vehicle. The power supply system 1 also includes a high-voltage battery (electricity storage device) 2, a power control device (hereinafter referred to as "PCU") 3 that exchanges power with the high-voltage battery 2 to drive the motor generators MG1 and MG2, a positive-side system main relay SMRB (hereinafter referred to as "positive-side relay SMRB") and a negative-side system main relay SMRG (hereinafter referred to as "negative-side relay SMRG"), a low-voltage battery (second electricity storage device) 4 that has a lower voltage than the high-voltage battery 2, and a bidirectional DC / DC converter (voltage conversion device) 5.

[0011] The engine EG is an internal combustion engine that generates power by explosive combustion of a mixture of air and a hydrocarbon fuel such as gasoline, diesel, or LPG, and is controlled by an engine electronic control unit (not shown). The planetary gear PG includes a sun gear connected to the motor generator MG1 (rotor), a ring gear connected to the output shaft and connected to the motor generator MG2 (rotor), and a planetary carrier that rotatably supports a plurality of pinion gears and is connected to the crankshaft of the engine EG. The output shaft is connected to the left and right drive wheels DW via a differential gear DF ​​and a drive shaft DS.

[0012] Both motor generators MG1 and MG2 are synchronous generator motors (three-phase AC motors). Motor generator MG1 mainly operates as a generator that is driven by engine EG operated under load to generate electric power. Motor generator MG2 mainly operates as an electric motor that is driven by at least one of electric power from high-voltage battery 2 and electric power from motor generator MG1 to generate drive torque, and outputs regenerative braking torque when braking hybrid vehicle V. Furthermore, motor generators MG1 and MG2 exchange electric power with high-voltage battery 2 via PCU3, and can exchange electric power with each other via PCU3.

[0013] The HVECU10 includes a microcomputer having a CPU, ROM, RAM, input / output interfaces, etc. (not shown), various drive circuits, various logic ICs, etc. The HVECU10 is connected to an engine electronic control unit, etc. via a communication line such as a CAN, and is also connected to various sensors, etc., such as a start switch SS, an accelerator pedal position sensor, a shift position sensor, and a vehicle speed sensor. When the hybrid vehicle V runs, the HVECU10 sets a required torque required for running based on the accelerator opening and the vehicle speed, and also sets a required power and target rotation speed for the engine EG, a torque command value for the motor generators MG1, MG2, etc.

[0014] The high-voltage battery 2 of the power supply system 1 is, for example, a lithium-ion secondary battery or a nickel-hydrogen secondary battery having a rated output voltage of 200 to 400 V. A positive power line PL is connected to a positive terminal of the high-voltage battery 2 via a positive relay SMRB, and a negative power line NL is connected to a negative terminal of the high-voltage battery 2 via a negative relay SMRG. The high-voltage battery 2 also includes a voltage sensor 21 that detects a terminal voltage VB of the high-voltage battery 2, and a current sensor 22 that detects a current (charge / discharge current) IB flowing through the high-voltage battery 2. The terminal voltage VB of the high-voltage battery 2 detected by the voltage sensor 21 and the current IB detected by the current sensor 22 are transmitted to the HVECU 10 directly via a signal line (not shown) or by a power supply management electronic control device (not shown) that manages the high-voltage battery 2.

[0015] The positive relay SMRB and the negative relay SMRG are contact-type (mechanical) relays including coils, movable contacts, and fixed contacts (not shown), and are normally open relays that are closed when an excitation current is supplied to the coils. In this embodiment, the positive and negative relays SMRB, SMRG are controlled to be opened and closed by the HVECU10. That is, when the driver turns on the start switch SS to request system startup of the hybrid vehicle V, the HVECU10 outputs a closing command for both relays SMRB, SMRG so that an excitation current is supplied to the coils (not shown) of the positive and negative relays SMRB, SMRG. Then, when each coil is excited and the positive and negative relays SMRB, SMRG are normally closed (when the movable contacts and the fixed contacts come into contact), the high-voltage battery 2 and the PCU3 are electrically connected.

[0016] Furthermore, when the driver turns off the start switch SS to request a system stop of the hybrid vehicle V, the HVECU10 outputs an open command to the positive and negative relays SMRB, SMRG so that the supply of excitation current to the relays SMRB, SMRG is cut off. As a result, when the excitation of each coil is released and the positive and negative relays SMRB, SMRG are opened (when the movable contact and the fixed contact are separated), the electrical connection between the high-voltage battery 2 and the PCU3 is released. The positive relay SMRB and the negative relay SMRG may be a contact-type hybrid relay that does not have a coil.

[0017] The PCU3 of the power supply system 1 includes a first inverter 31 that drives the motor generator MG1, a second inverter 32 that drives the motor generator MG2, a step-up / step-down converter (voltage conversion device) 33 that can step-up the power from the high-voltage battery 2 and step-down the voltage from the motor generators MG1 and MG2, and a motor electronic control unit (hereinafter referred to as "MGECU") 30 that controls the first and second inverters 31, 32 and the step-up / step-down converter 33.

[0018] The first and second inverters 31 and 32 each include six transistors (e.g., insulated gate bipolar transistors (IGBTs)) (not shown) and six diodes (not shown) connected in parallel in the reverse direction to each transistor. The six transistors are paired in pairs, two of them being on the source side and the sink side with respect to the high voltage power line HPL and the negative power line NL. The three-phase coils (U phase, V phase, W phase) of the motor generators MG1 and MG2 are electrically connected to each of the connection points between the paired transistors. The step-up / step-down converter 33 includes two transistors (e.g., insulated gate bipolar transistors) Tra and Trb, two diodes Da and Db connected in parallel in the reverse direction to each of the transistors Tra and Trb, and a reactor L. One end of the reactor L is electrically connected to the positive power line PL, and the other end of the reactor L is electrically connected to the emitter of one transistor (upper arm element) Tra and the collector of the other transistor (lower arm element) Trb. The collector of the one transistor Tra is electrically connected to the high voltage power line HPL, and the emitter of the other transistor Trb is electrically connected to the negative power line NL.

[0019] The PCU 3 further includes a filter capacitor (first capacitor) 34, a smoothing capacitor (second capacitor) 35, and voltage sensors 36 and 37. The positive terminal of the filter capacitor 34 is electrically connected to the positive power line PL (one end of the reactor L) between the positive relay SMRB and the step-up / step-down converter 33. The negative terminal of the filter capacitor 34 is electrically connected to the negative power line NL between the negative relay SMRG and the step-up / step-down converter 33. In this way, the filter capacitor 34 smoothes the voltage on the high-voltage battery 2 side of the step-up / step-down converter 33. The voltage sensor 36 detects the terminal voltage (pre-step-up voltage) VL of the filter capacitor 34.

[0020] The positive terminal of the smoothing capacitor 35 is electrically connected to the high voltage power line HPL (collector of the transistor Tra of the step-up / step-down converter 33) between the step-up / step-down converter 33 and the first and second inverters 31 and 32. The negative terminal of the smoothing capacitor 35 is electrically connected to the negative power line NL and the emitter of the transistor Trb of the step-up / step-down converter 33 between the step-up / step-down converter 33 and the first and second inverters 31 and 32. In this way, the smoothing capacitor 35 smoothes the voltage on the motor generators MG1 and MG2 side of the step-up / step-down converter 33. The voltage sensor 37 detects the terminal voltage VH (boosted voltage) of the smoothing capacitor 35. The terminal voltage VL of the filter capacitor 34 detected by the voltage sensor 36 and the terminal voltage VH of the smoothing capacitor 35 detected by the voltage sensor 37 are transmitted to the MGECU 30 and are also transmitted to the HVECU 10 directly or by the MGECU 30 via a signal line not shown.

[0021] The MGECU 30 includes a microcomputer having a CPU, ROM, RAM, input / output interface, etc. (not shown), various drive circuits, various logic ICs, etc., and is connected to the HVECU 10, etc. via a communication line such as a CAN. The MGECU 30 also acquires command signals from the HVECU 10, detection values ​​of a resolver (not shown) that detects the rotational position of the rotor of the motor generator MG1, detection values ​​of a resolver that detects the rotational position of the rotor of the motor generator MG2, current values ​​from a current sensor (not shown) of the step-up / step-down converter 33, terminal voltages VL, VH from voltage sensors 36, 37, phase currents applied to the motor generators MG1, MG2 detected by a current sensor (not shown), etc. Based on these signals, the MGECU 30 generates gate signals (switching control signals) to the first and second inverters 31, 32 and the step-up / step-down converter 33, and controls the switching of these.

[0022] The low-voltage battery 4 of the power supply system 1 is, for example, a lead-acid battery having a rated output voltage of about 12V, and is connected to a plurality of auxiliaries (low-voltage auxiliaries) via a low-voltage power line. A bidirectional DC / DC converter (DDC) 5 is connected to a positive-side power line PL between a positive-side relay SMRB and the PCU 3, and is also connected to a negative-side power line NL between a negative-side relay SMRG and the PCU 3. The bidirectional DC / DC converter 5 is also connected to the low-voltage battery 4 and a plurality of auxiliaries via the low-voltage power line. In addition to the bidirectional DC / DC converter 5, high-voltage auxiliaries such as a compressor (inverter compressor) of an air conditioner and a converter to AC 100V are connected to the positive-side power line PL and the negative-side power line NL.

[0023] The bidirectional DC / DC converter 5 of the power supply system 1 can step down the power on the positive power line PL side, i.e., the side of the high-voltage battery 2 and PCU 3 (step-up / step-down converter 33), and supply it to the low-voltage power line side, i.e., various auxiliaries and the low-voltage battery 4, and can also step up the power from the low-voltage battery 4 and supply it to the positive power line PL side, i.e., the high-voltage battery 2 and PCU 3. In this embodiment, the bidirectional DC / DC converter 5 includes a voltage conversion circuit 50, a voltage sensor 51 that detects the voltage on the high-voltage battery 2 and PCU 3 sides of the voltage conversion circuit 50, a voltage sensor (not shown) that detects the voltage on the low-voltage battery 4 side of the voltage conversion circuit 50, and a control circuit 55 that feedback-controls the voltage conversion circuit 50 so that the detection value of the voltage sensor 51 becomes a required value.

[0024] In this embodiment, when the driver turns on the start switch SS to request system startup of the hybrid vehicle V, the bidirectional DC / DC converter 5 (voltage conversion circuit 50) boosts the power from the low-voltage battery 4 as a power source and supplies it to the PCU 3 before closing the positive and negative relays SMRB and SMRG. That is, the HVECU 10 transmits a target voltage Vtag as a requested value of the voltage output from the voltage conversion circuit 50 in response to the request for system startup to the control circuit 55, and the control circuit 55 feedback-controls the voltage conversion circuit 50 so that the detection value of the voltage sensor 51 becomes the target value. As a result, the filter capacitor 34 and the smoothing capacitor 35 of the PCU 3 are precharged (recharged) before closing the positive and negative relays SMRB and SMRG, making it possible to suppress a large inrush current from flowing to the positive power line PL or the PCU 3 when the positive and negative relays SMRB and SMRG are closed.

[0025] Next, a control procedure of the power supply system 1 when the driver turns on the start switch SS to start up the system of the hybrid vehicle V will be described with reference to Figures 2 and 3. Figure 2 is a flowchart showing an example of a routine executed by the HVECU 10 when the start switch SS is turned on to request system startup of the hybrid vehicle V. Figure 3 is a time chart showing an example of time changes in the target voltage Vtag and the inter-terminal voltage VL of the filter capacitor 34 of the PCU 3 while the routine of Figure 2 is being executed.

[0026] As shown in Fig. 2, when the driver turns on the start switch SS (time t1 in Fig. 3), the HVECU10 (CPU) acquires the inter-terminal voltage VB of the high-voltage battery 2 detected by the voltage sensor 21 (step S100). Furthermore, in step S100, the HVECU10 sets the acquired inter-terminal voltage VB as the target voltage Vtag of the filter capacitor 34 and the smoothing capacitor 35 (precharge) of the PCU 3, and transmits the set target voltage Vtag to the control circuit 55 of the bidirectional DC / DC converter 5. The control circuit 55, which has received the target voltage Vtag from the HVECU10, starts feedback control of the voltage conversion circuit 50 so that the detection value of the voltage sensor 51 becomes the target voltage Vtag with the positive and negative relays SMRB and SMRG open, and when the detection value of the voltage sensor 51 becomes the target voltage Vtag, feedback controls the voltage conversion circuit 50 so that the detection value is maintained at the target voltage Vtag.

[0027] After transmitting the target voltage Vtag to the control circuit 55 of the bidirectional DC / DC converter 5, the HVECU 10 acquires the terminal voltage VB of the high-voltage battery 2 detected by the voltage sensor 21 and the terminal voltage VL of the filter capacitor 34 detected by the voltage sensor 36, and determines whether precharging of the filter capacitor 34 and the like has been completed normally based on the absolute value |VB-VL| of the difference between the terminal voltage VB and the terminal voltage VL (step S110). In step S110, the HVECU 10 determines, for example, whether a state in which the absolute value |VB-VL| of the difference is equal to or smaller than a predetermined threshold value ΔV0 continues for a predetermined time tref0 (step S110). The threshold value ΔV0 used in step S110 is a relatively small positive value (for example, about 30 V).

[0028] If the absolute value |VB-VL| of the difference does not remain equal to or less than the threshold value ΔV0 for a predetermined time tref0, or if the absolute value |VB-VL| exceeds the threshold value ΔV0 even after a predetermined time has elapsed since the transmission of the target voltage Vtag, the HVECU10 determines that the precharging of the filter capacitor 34 and the like using the bidirectional DC / DC converter 5 has not been completed normally due to an abnormality or disconnection in the voltage conversion circuit 50 or the control circuit 55 (step S120: NO). In this case, the HVECU10 transmits a command to stop the precharging to the control circuit 55, turns on a predetermined warning light provided on an instrument panel (not shown), and further prohibits the operation of the power supply system 1, the transition to a READY-ON state (driving permitted state) in which the hybrid vehicle V is permitted to run, and the operation of the bidirectional DC / DC converter 5 (step S125), and ends the routine of FIG.

[0029] Furthermore, when it is determined that the precharging of the filter capacitor 34, etc. using the bidirectional DC / DC converter 5 has been completed normally (step S120: YES), the HVECU10 outputs a close command to the positive and negative relays SMRB, SMRG so that an excitation current is supplied to the coils of both relays SMRB, SMRG (step S130, time t2 in FIG. 3). Furthermore, the HVECU10 obtains detection voltages from two voltage sensors (not shown) that detect the voltages applied to the coils of the positive and negative relays SMRB, SMRG, respectively, and determines whether the coils of both relays SMRB, SMRG are excited (whether a voltage is applied) based on the obtained detection voltages (step S140).

[0030] When at least one of the detected voltages of the two voltage sensors is less than a predetermined voltage threshold, the HVECU10 determines that at least one of the coils of the positive and negative relays SMRB, SMRG is not normally excited due to an abnormality in the wiring of the positive and negative relays SMRB, SMRG (step S150: NO). In this case, the HVECU10 transmits a command to stop precharging to the control circuit 55, turns on a predetermined warning light provided on an instrument panel (not shown), and further prohibits transition to the READY-ON state (step S155), and ends the routine of FIG.

[0031] On the other hand, when it is determined that both of the detected voltages of the two voltage sensors are equal to or higher than the predetermined voltage threshold value and that both of the coils of the positive and negative relays SMRB and SMRG are normally excited (step S150: YES), the HVECU10 sets the pre-charge target voltage Vtag to a value different from the value (terminal voltage VB) set in step S100, and transmits the set target voltage Vtag to the control circuit 55 of the bidirectional DC / DC converter 5 (step S160, time t3 in FIG. 3). In step S150, the HVECU10 acquires the terminal voltage VB of the high-voltage battery 2 detected by the voltage sensor 21, and sets the sum of the acquired terminal voltage VB and a predetermined value α (for example, about 5 V) to the pre-charge target voltage Vtag. The control circuit 55, which has received the target voltage Vtag from the HVECU10, feedback controls the voltage conversion circuit 50 so that the detection value of the voltage sensor 51 becomes the new target voltage Vtag.

[0032] After the process of step S160, the HVECU10 acquires the terminal voltage VL of the filter capacitor 34 detected by the voltage sensor 36, and determines whether the terminal voltage VL has changed (followed) in accordance with the change in the target voltage Vtag (step S170). In step S170, the HVECU10 determines, for example, whether a state in which the absolute value |Vtag-VL| of the difference between the target voltage Vtag transmitted in step S160 and the terminal voltage VL of the filter capacitor 34 is equal to or smaller than a predetermined comparatively small threshold value ΔV1 continues for a predetermined time tref1.

[0033] Here, when both the positive and negative relays SMRB, SMRG are normally closed in response to a closing command from the HVECU 10 after completion of precharging, even if the precharging target voltage Vtag and the terminal voltage VB of the high-voltage battery 2 are different, the terminal voltage VL of the filter capacitor 34 after the closing command is output will roughly match the terminal voltage VB of the high-voltage battery 2, as shown by the dashed line in Fig. 3. In other words, the increase (value α) of the target voltage Vtag set in step S160 relative to the terminal voltage VB of the high-voltage battery 2 is not used to charge the filter capacitor 34, but is used to charge the high-voltage battery 2.

[0034] Therefore, if the state in which the absolute value of the difference |Vtag-VL| is equal to or less than the threshold value ΔV1 does not continue for the time tref1 after the target voltage Vtag is changed in step S160, the HVECU10 determines that the terminal voltage VL of the filter capacitor 34 is approximately equal to the terminal voltage VB of the high-voltage battery 2, and that both the positive and negative relays SMRB and SMRG are normally closed (step S180: NO). Then, the HVECU10 transmits a command to stop precharging to the control circuit 55 and permits transition to the READY-ON state (step S210, time t4 in FIG. 3), and ends the routine in FIG. 2. This enables the hybrid vehicle V to travel on the condition that other predetermined READY-ON permission conditions are satisfied.

[0035] On the other hand, if ice has formed in at least one of the positive and negative relays SMRB, SMRG, or if a foreign object is present between the movable contact and the fixed contact, at least one of the positive and negative relays SMRB, SMRG will not be closed normally even if a close command is output from the HVECU 10 after the completion of precharging. In such a case, the high-voltage battery 2 and the PCU 3 are not electrically connected, so that the terminal voltage VL of the filter capacitor 34 after the output of the close command follows a target voltage Vtag (=VB+α) different from the terminal voltage VB of the high-voltage battery 2, as shown by the two-dot chain line in FIG.

[0036] Therefore, if the state in which the absolute value of the difference |Vtag-VL| is equal to or less than the threshold value ΔV1 continues for a time tref1 after the target voltage Vtag is changed in step S160, the HVECU10 determines that the terminal voltage VL of the filter capacitor 34 fluctuates following the changed target voltage Vtag, and that both the positive and negative relays SMRB and SMRG are not normally closed (step S180: YES, time t4 in FIG. 3). In this case, the HVECU10 increments a counter C indicating the number of times that it has been determined that both the positive and negative relays SMRB and SMRG are not normally closed (step S190), and determines whether the counter C is equal to or more than a predetermined threshold value Cref (step S200). The threshold value Cref used in step S200 is an integer equal to or more than "2" (for example, 3 to 5 times).

[0037] When the HVECU10 determines that the counter C is less than the threshold value Cref (step S200: NO), the HVECU10 transmits a pre-charge stop command to the control circuit 55 and prohibits the transition to the READY-ON state (operation of the power supply system 1) (step S215, time t4 in FIG. 3), and ends the routine in FIG. 2. As a result, after the process of step S215 is executed, the hybrid vehicle V is in the system-off state, and the driver of the hybrid vehicle V turns on the start switch SS again to execute the routine in FIG. 2. When the routine in FIG. 2 is executed multiple times and the counter C is determined to be equal to or greater than the threshold value Cref (step S200: YES), the HVECU10 transmits a pre-charge stop command to the control circuit 55 and permits the transition to the READY-ON state (step S210), and ends the routine in FIG. 2. In step S215, a message prompting the driver to operate the start switch SS again may be displayed on a display unit provided on an instrument panel (not shown) or the like.

[0038] As described above, the HVECU10 as the control device of the power supply system 1 sets the precharge target voltage Vtag of the filter capacitor 34 and the like included in the PCU3 in response to a request for system startup via the start switch SS (step S100). In addition, the HVECU10 outputs a closing command for the positive and negative relays SMRB, SMRG to electrically connect the high-voltage battery 2 and the PCU3 in response to the completion of the precharge (steps S110-S130 in FIG. 2). Furthermore, after outputting the closing command, the HVECU10 sets a value (VB+α) different from the inter-terminal voltage VB of the high-voltage battery 2 to the target voltage Vtag (step S160), and determines the state of the positive and negative relays SMRB, SMRG, i.e., whether or not both relays SMRB, SMRG are normally closed based on the inter-terminal voltage VL of the filter capacitor 34 after outputting the closing command (steps S170, S180).

[0039] That is, when the positive and negative relays SMRB, SMRG are normally closed in response to a closing command by the HVECU10 after the completion of precharging, even if the target voltage Vtag of precharging differs from the inter-terminal voltage VB of the high-voltage battery 2, the inter-terminal voltages VL, etc. of the filter capacitor 34, etc. after the output of the closing command generally coincide with the inter-terminal voltage VB of the high-voltage battery 2. In contrast, when the positive and negative relays SMRB, SMRG are not normally closed due to icing or the like despite the output of a closing command by the HVECU10 after the completion of precharging, the inter-terminal voltages VL, etc. of the filter capacitor 34, etc. after the output of the closing command follow the target voltage Vtag (=VB+α) which is different from the inter-terminal voltage VB of the high-voltage battery 2. Therefore, in the power supply system 1, it is possible to accurately determine whether the positive and negative relays SMRB, SMRG are normally closed from the fluctuation state of the voltage of the filter capacitor 34 after the output of the closing command of the positive and negative relays SMRB, SMRG. As a result, the states of the contact-type positive and negative relays SMRB, SMRG included in the power supply system 1 can be determined appropriately.

[0040] Furthermore, if the terminal voltage VL of the filter capacitor 34 fluctuates following the target voltage Vtag after the output of the closing command (step S180: YES), the HVECU10 determines that the positive and negative relays SMRB, SMRG are not normally closed, and prohibits the transition to the READY-ON state, i.e., the operation of the main functions of the hybrid vehicle V and the power supply system 1 (steps S190, S200, S215). On the other hand, if the voltage of the filter capacitor 34 does not follow the target voltage Vtag after the output of the closing command (step S180: NO), the HVECU10 determines that the positive and negative relays SMRB, SMRG are normally closed, and permits the transition to the READY-ON state (step S210). In this way, by prohibiting the transition to the READY-ON state when the positive and negative relays SMRB, SMRG are not normally closed due to icing or the like, it is possible to prevent the fault diagnosis function of the hybrid vehicle V from erroneously diagnosing that a fault has occurred in the power supply system 1 including the PCU 3 and the like.

[0041] Furthermore, when the HVECU10 determines that the positive and negative relays SMRB, SMRG are not normally closed after the output of the closing command (step S180: YES), and the counter C indicating the number of times that the positive and negative relays SMRB, SMRG are not normally closed is less than a threshold value Cref (predetermined number of times) equal to or greater than 2 (step S200: NO), the HVECU10 prohibits the hybrid vehicle V from transitioning to a READY-ON state (traveling permitted state) (step S215). When the HVECU10 determines that the positive and negative relays SMRB, SMRG are normally closed (step S180: NO), and when the HVECU10 determines that the positive and negative relays SMRB, SMRG are not normally closed after the output of the closing command (step S180: YES), and the counter C is equal to or greater than the threshold value Cref (step S200: YES), the HVECU10 permits the hybrid vehicle V to transition to the READY-ON state (step S210).

[0042] That is, when ice is generated in at least one of the positive and negative relays SMRB and SMRG, the coils of both relays SMRB and SMRG are excited multiple times, so that the ice between the movable contacts and the fixed contacts is likely to be broken and removed. Therefore, if the hybrid vehicle V is permitted to transition to the READY-ON state on the condition that the counter C is equal to or greater than the threshold value Cref, even if ice is generated in at least one of the positive and negative relays SMRB and SMRG, the hybrid vehicle V can be transitioned to the READY-ON state after the ice is removed by performing the closing of both relays SMRB and SMRG multiple times. In addition, when the counter C is equal to or greater than the threshold value Cref, the hybrid vehicle V is transitioned to the READY-ON state and the execution of a fault diagnosis is permitted, so that the cause of the positive and negative relays SMRB and SMRG not being normally closed can be diagnosed.

[0043] In addition, the HVECU10 acquires the terminal voltage VB of the high-voltage battery 2 in response to a request for system startup via the start switch SS, and sets the acquired voltage Vtag to the target voltage Vtag (step S100). After outputting the closing command and confirming that the coils of the positive and negative relays SMRB and SMRG are excited, the HVECU10 changes the target voltage Vtag to a value (VB+α) different from the terminal voltage VB of the high-voltage battery 2 acquired again (steps S130-S160). Then, the HVECU10 determines whether the terminal voltage VL of the filter capacitor 34 fluctuates following the changed target voltage Vtag (steps S170, S180). This makes it possible to appropriately precharge the filter capacitor 34 of the PCU3 and the like, while appropriately determining the state of the positive and negative relays SMRB and SMRG.

[0044] 2, the terminal voltage VB of the high-voltage battery 2 may be regarded as not changing substantially for a while after the system startup request is made, and the sum of the target voltage Vtag set in step S100 and the value α may be set as the new target voltage Vtag. Also, in step S160, the target voltage Vtag may be set to a value obtained by subtracting the value α from the terminal voltage VB of the high-voltage battery 2 or the target voltage Vtag set in step S100. Furthermore, the determination process in step S170 may be such that, when a state in which the absolute value |VB-VL| of the difference between the terminal voltage VB of the high-voltage battery 2 and the terminal voltage VL of the filter capacitor 34 remains equal to or lower than a predetermined threshold value for a predetermined time period, it is determined that both the positive and negative relays SMRB and SMRG are normally closed. In addition, the judgment process of step S170 may be one that determines whether or not both the terminal voltage VL of the filter capacitor 34 and the terminal voltage VH of the smoothing capacitor 35 have fluctuated in accordance with the target voltage Vtag, or may be one that determines whether or not the terminal voltage VH of the smoothing capacitor 35 has fluctuated in accordance with the target voltage Vtag.

[0045] Furthermore, in the power supply system 1, the filter capacitor 34 and the like are precharged by power from the bidirectional DC / DC converter 5 that boosts the power from the low-voltage battery 4 to the target voltage Vtag in response to a request to start the system, but the filter capacitor 34 and the like may be precharged by power from a power source other than the low-voltage battery 4 and the bidirectional DC / DC converter 5. That is, when the high-voltage battery 2 of the power supply system 1 can be charged by power from an external charging device such as a charger connected to a household power source or a quick charger installed at a station, the filter capacitor 34 and the like may be precharged by adjusting the power from the external charging device to the target voltage Vtag. In this case, the power supply system 1 may include a power receiving connector to which the external charging device is connected, and the power receiving connector may be connected to the positive power line PL between the positive relay SMRB and the PCU3 via a positive charging relay (not shown), and may be connected to the negative power line NL between the negative relay SMRG and the PCU3 via a negative charging relay (not shown).

[0046] Furthermore, the vehicle including the above-mentioned power supply system 1 is not limited to a two-motor (series-parallel) hybrid vehicle V having a planetary gear PG for power distribution. That is, the vehicle on which the power supply system 1 is mounted may be a one-motor hybrid vehicle, a series hybrid vehicle, a parallel hybrid vehicle, a plug-in hybrid vehicle (PHV), or an electric vehicle (BEV). Furthermore, the PCU 3 may include two or more step-up / step-down converters.

[0047] Fig. 4 is a flowchart showing another example of a routine executed by the HVECU 10 when the start switch SS is turned on to request system startup of the hybrid vehicle V. Fig. 5 is a time chart showing an example of time variations in the target voltage Vtag and the inter-terminal voltage VL of the filter capacitor 34 of the PCU 3 while the routine of Fig. 4 is being executed. Note that, among the processes of the routine shown in Fig. 4, the same processes as those in the routine shown in Fig. 2 are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0048] As shown in Fig. 4, when the driver turns on the start switch SS (time t10 in Fig. 5), the HVECU10 (CPU) acquires the inter-terminal voltage VB of the high-voltage battery 2 detected by the voltage sensor 21 (step S100B). Furthermore, in step S100B, the HVECU10 sets the sum of the acquired inter-terminal voltage VB and a predetermined value α (for example, about 5V) as the pre-charge target voltage Vtag, and transmits the set target voltage Vtag to the control circuit 55 of the bidirectional DC / DC converter 5. The control circuit 55, which has received the target voltage Vtag from the HVECU10, controls the voltage conversion circuit 50 so that the detection value of the voltage sensor 51 becomes the target voltage Vtag from the HVECU10 with the positive and negative relays SMRB, SMRG open. Furthermore, if the HVECU10 determines that the coils of both the positive and negative relays SMRB, SMRG are normally excited after executing the processing of steps S110-S140 (step S150: YES), it acquires the terminal-to-terminal voltage VL of the filter capacitor 34 detected by the voltage sensor 36 without changing the target voltage Vtag, and determines whether the terminal-to-terminal voltage VL generally coincides with the target voltage Vtag (presence or absence of fluctuation) (steps S170B, S180B).

[0049] That is, in response to a request for system startup via the start switch SS, the pre-charge target voltage Vtag is set to a value (VB+α) different from the terminal voltage VB of the high-voltage battery 2, and after completion of pre-charge, when the positive and negative relays SMRB, SMRG are normally closed in response to a closing command from the HVECU10 (time t20 in FIG. 5), the terminal voltage VL of the filter capacitor 34 after the output of the closing command no longer follows the target voltage Vtag, as shown by the dashed line in FIG. 5, and converges to the terminal voltage VB of the high-voltage battery 2. In contrast, if the target voltage Vtag is set to a value (VB+α) different from the terminal voltage VB of the high-voltage battery 2 in response to a request for system startup, and at least one of the positive and negative relays SMRB, SMRG is not normally closed due to icing or the like even though a closing command is output by the HVECU10 after completion of pre-charging, the terminal voltage VL of the filter capacitor 34 after the closing command is output follows the target voltage Vtag (=VB+α) different from the terminal voltage VB of the high-voltage battery 2, as shown by the two-dot chain line in Figure 5, and does not substantially fluctuate.

[0050] Therefore, even if the routine of Fig. 4 is executed in the power supply system 1 instead of the routine of Fig. 2, it is possible to accurately determine whether the positive and negative relays SMRB, SMRG are normally closed from the fluctuation state of the voltage of the filter capacitor 34 after the output of a command to close the positive and negative relays SMRB, SMRG. As a result, the routine of Fig. 4 also makes it possible to properly determine the state of the positive and negative relays SMRB, SMRG while properly precharging the filter capacitor 34 of the PCU 3. Note that the determination process in step S170B of Fig. 4 may be a process for determining whether the absolute value |Vtag-VL| of the difference between the target voltage Vtag transmitted in step S100B and the inter-terminal voltage VL of the filter capacitor 34 continues to be equal to or less than a predetermined threshold value for a predetermined time. In addition, the judgment process in step S170B of FIG. 4 may be such that, when the absolute value |VB-VL| of the difference between the terminal voltage VB of the high-voltage battery 2 and the terminal voltage VL of the filter capacitor 34 remains below a predetermined threshold for a predetermined period of time, it is judged that both the positive and negative relays SMRB, SMRG are normally closed.

[0051] As described above, the power supply system of the present disclosure is a power supply system (1) including a power storage device (2), a power control device (3) including a capacitor (34, 35) precharged with power from a power source (4) other than the power storage device (2), and contact-type relays (SMRB, SMRG) that electrically connect the power storage device (2) and the power control device (3) and disconnect the connection between them, the power storage device (2) and the power control device (3) are configured to set a target voltage (Vtag) for precharging the capacitor in response to a request for system startup (S100, and a control device (10) that outputs a command to close the relays (SMRB, SMRG) in response to completion of the precharge (S130), sets the target voltage (Vtag) to a value different from the voltage (VB) of the power storage device (2) before or after the output of the closing command (S160, S100B), and determines a state of the relays (SMRB, SMRG) based on the voltage (VL) of the capacitor (34) after the output of the closing command (S170, S180, S170B, S180B).

[0052] The control device of the power supply system of the present disclosure sets a target voltage for precharging the capacitor included in the power control device in response to a request for starting the system, and outputs a command to close the relay to electrically connect the power storage device and the power control device in response to completion of the precharging. Furthermore, the control device sets the target voltage to a value different from the voltage of the power storage device before or after outputting the closing command, and determines the state of the relay based on the voltage of the capacitor after outputting the closing command. That is, if the relay is normally closed in response to the closing command after completion of the precharging, even if the target voltage of precharging and the voltage of the power storage device are different, the voltage of the capacitor after outputting the closing command roughly matches the voltage of the power storage device. In contrast, if the relay is not normally closed due to freezing or the like despite the output of the closing command after completion of the precharging, the voltage of the capacitor after outputting the closing command follows a target voltage different from the voltage of the power storage device. Therefore, in the power supply system of the present disclosure, it is possible to accurately determine whether the relay is normally closed or not from the fluctuation state of the voltage of the capacitor after outputting the closing command of the relay. As a result, it is possible to properly determine the state of the contact type relay included in the power supply system.

[0053] In addition, if the voltage (VL) of the capacitor (34) follows the target voltage (Vtag) after output of the closing command (S180: YES, S180B: YES), the control device (10) may determine that the relay (SMRB, SMRG) is not closed normally and prohibit operation of the power supply system (1), and if the voltage (VL) of the capacitor (34) does not follow the target voltage (Vtag) after output of the closing command (S180: NO, S180B: NO), the control device (10) may determine that the relay (SMRB, SMRG) is closed normally and permit operation of the power supply system (1).

[0054] In this way, when the relay is not closed normally due to icing or the like, operation of the power supply system can be prohibited, thereby preventing the fault diagnosis function from erroneously diagnosing that a fault has occurred in the power supply system.

[0055] Furthermore, the power control device (3) may drive electric motors (MG1, MG2) mounted on a vehicle (V), and when the control device (10) determines that the relays (SMRB, SMRG) are not normally closed after the output of the close command (S180: YES, S180B: YES) and the number of times (C) that the relays (SMRB, SMRG) are not normally closed is less than a predetermined number (Cref) of 2 or more (S200: NO), the control device (10) ) from transitioning to a driving permitted state, and transitioning the vehicle (V) to a driving permitted state when it is determined that the relays (SMRB, SMRG) are normally closed (S180: NO, S180B: NO), and when it is determined that the relays (SMRB, SMRG) are not normally closed after the output of the closing command (S180: YES, S180B: YES), and when the number of determinations (C) is equal to or greater than the predetermined number of times (Cref) (S200: YES).

[0056] As a result, even if ice has formed on the relay, the relay is closed multiple times to break up and remove the ice formed on the relay, and then the vehicle can be transitioned to a traveling permitted state. In addition, if the number of times that it is determined that the relay is not normally closed is equal to or greater than a predetermined number, the vehicle can be transitioned to a traveling permitted state and a fault diagnosis can be permitted to be performed, thereby diagnosing the cause of the relay not being normally closed.

[0057] In addition, the control device (10) may obtain the voltage (VB) of the power storage device (2) in response to a request for system startup and set the voltage (Vtag) as the target voltage (Vtag) (S100), and after outputting the closing command, change the target voltage (Vtag) to a value (VB+α) different from the voltage (VB) of the power storage device (2) (S160), and determine whether the voltage (VL) of the capacitor (34) fluctuates in accordance with the changed target voltage (Vtag) (S170, S180).

[0058] This makes it possible to properly judge the state of the relay while properly precharge the capacitor of the power control device.

[0059] Furthermore, the control device (10) may acquire the voltage (VB) of the power storage device (2) in response to a request for system startup, and set a value (VB+α) different from the acquired voltage (VB) to the target voltage (Vtag) (S100B), and determine whether or not the voltage (VL) of the capacitor (34) fluctuates after output of the closing command (S170B, S180B).

[0060] In such a power supply system, it is possible to properly judge the state of the relay while properly precharge the capacitors of the power control device.

[0061] The power source may include a second power storage device (4) having a lower voltage than the power storage device (2), and a voltage conversion device (5) that steps down the power from the power storage device (2) and the power control device (3) to supply it to the second power storage device (4), and that boosts the power from the second power storage device (4) to the target voltage (Vtag) in response to a request for system startup to precharge the capacitors (34, 35). However, the power source for precharging the capacitor of the power control device is not limited to the second power storage device and the voltage conversion device, and may be a so-called external charging device, etc.

[0062] The method for determining the state of a relay in a power supply system disclosed herein is a method for determining the state of a relay in a power supply system (1) including a power storage device (2), a power control device (3) including a capacitor (34, 35) precharged with power from a power source (4) other than the power storage device (2), and a contact-type relay (SMRB, SMRG) that electrically connects the power storage device (2) and the power control device (3) and disconnects the connection between them, the method comprising the steps of: determining a target voltage (Vtag) for precharging the capacitor in response to a request for system startup; (S100, S100B), and in response to completion of the precharge, a close command for the relays (SMRB, SMRG) is output (S130). Before or after the output of the close command, the target voltage (Vtag) is set to a value different from the voltage (VB) of the power storage device (2) (S160, S100B). The state of the relays (SMRB, SMRG) is determined based on the voltage (VL) of the capacitor (34) after the output of the close command (S170, S180, S170B, S180B).

[0063] According to this method, it is possible to properly determine the state of the contact type relay included in the power supply system.

[0064] The present disclosure is not limited to the above embodiment, and various modifications can be made within the scope of the present disclosure. Furthermore, the above embodiment is merely a specific form of the invention described in the Summary of the Invention, and does not limit the elements of the invention described in the Summary of the Invention. [Industrial Applicability]

[0065] The invention of the present disclosure can be used in the manufacturing industry of power systems, etc. [Explanation of symbols]

[0066] 1 power supply system, 2 high-voltage battery (energy storage device), 21, 36, 37, 51 voltage sensor, 3 power control device (PCU), 34 filter capacitor, 35 smoothing capacitor, 4 low-voltage battery (second energy storage device), 5 bidirectional DC / DC converter (voltage conversion device), 50 voltage conversion circuit, 55 control circuit, 10 hybrid electronic control device (HVECU), MG1, MG2 motor generator, SMRB positive system main relay, SMRG negative system main relay, SS start switch, V vehicle.

Claims

1. A power supply system including a power storage device, a power control device including a capacitor precharged with power from a power source other than the power storage device, and a contact relay electrically connecting the power storage device and the power control device and disconnecting the connection between them, a control device that acquires a voltage of the power storage device in response to a request for system startup, sets the voltage to a target voltage for precharging the capacitor, and outputs a command to close the relay in response to completion of the precharging, changes the target voltage to a value different from the voltage of the power storage device after the command to close is output, and determines whether the voltage of the capacitor after the command to close fluctuates to follow the changed target voltage; The control device, when the voltage of the capacitor follows the target voltage after the output of the closing command, determines that the relay is not closed normally and prohibits operation of the power supply system, and when the voltage of the capacitor does not follow the target voltage after the output of the closing command, determines that the relay is closed normally and allows operation of the power supply system.

2. 2. The power supply system according to claim 1, The power control device drives an electric motor mounted on a vehicle, The control device prohibits the vehicle from transitioning to a traveling-permitted state when it determines that the relay is not closed normally after the output of the closing command and the number of times that it has been determined that the relay is not closed normally is less than a predetermined number of times that is two or more, and transitions the vehicle to a traveling-permitted state when it determines that the relay is closed normally, and when it determines that the relay is not closed normally after the output of the closing command and the number of times that it has been determined is equal to or greater than the predetermined number.

3. 3. The power supply system according to claim 1, The power supply system includes a second storage device having a lower voltage than the storage device, and a voltage conversion device that reduces the voltage of power from the storage device and the power control device and supplies it to the second storage device, and that boosts the power from the second storage device to the target voltage in response to a request to start up the system, thereby precharging the capacitor.

4. A method for determining a state of a relay in a power supply system including a power storage device, a power control device including a capacitor precharged with power from a power source other than the power storage device, and a contact relay electrically connecting the power storage device and the power control device and disconnecting the connection between them, comprising: acquiring a voltage of the power storage device in response to a request for system startup and setting the voltage as a target voltage for precharging the capacitor, and outputting a command to close the relay in response to completion of the precharging, changing the target voltage to a value different from the voltage of the power storage device after outputting the command to close, and determining whether the voltage of the capacitor after outputting the command to close fluctuates in accordance with the changed target voltage; if the voltage of the capacitor follows the target voltage after the output of the close command, it is determined that the relay is not normally closed and operation of the power supply system is prohibited, and if the voltage of the capacitor does not follow the target voltage after the output of the close command, it is determined that the relay is normally closed and operation of the power supply system is permitted. A method for determining the state of a relay in a power system.

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