Patent Publication Number: US-2022238944-A1

Title: Power supply system and method of power supply

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Priority is claimed on Japanese Patent Application No. 2021-011084, filed Jan. 27, 2021, the content of which is incorporated herein by reference. 
     BACKGROUND 
     Field of the Invention 
     The present invention relates to a power supply system and a method of power supply. 
     Description of Related Art 
     Conventionally, a technology for supplying power from a fuel cell system mounted on a vehicle to vehicle auxiliary devices is known (for example, Japanese Unexamined Patent Application, First Publication No. 2004-222376, Japanese Unexamined Patent Application, First Publication No. 2005-251674, and Japanese Unexamined Patent Application, First Publication No. 2007-335151). 
     SUMMARY 
     However, there is a likelihood that a voltage that can be generated in a fuel cell may change significantly due to an influence of a sweep current, an influence of a situation of power generation, or the like. Therefore, when power is directly supplied from a fuel cell to an auxiliary device, it is necessary to provide a function of adjustment according to fluctuation of power on the auxiliary device side, and this may cause an increase in costs of the auxiliary device or the like. 
     One aspect of the present invention has been made in consideration of such circumstances, and one objective thereof is to provide a power supply system capable of supplying appropriate power to an auxiliary device while increase in cost of the auxiliary device is curbed, and a method of power supply. 
     The power supply system and the method of power supply according to one aspect of the present invention employs the following configuration. 
     (1): A power supply system according to one aspect of the present invention includes a fuel cell which is able to generate power, a power storage device which stores the power generated by the fuel cell, a converter which converts power from the fuel cell or the power storage device and switches between supply of power from the fuel cell to an auxiliary device and supply of power from the power storage device to the auxiliary device, and a controller which controls at least the switching of the converter. 
     (2): In the above-described aspect (1), the controller acquires a state of the fuel cell and a state of the power storage device, selects one of the fuel cell and the power storage device to supply power to the auxiliary device on the basis of the acquired states, and controls the converter so that power from the selected one is supplied to the auxiliary device. 
     (3): In the above-described aspect (1), the converter includes a first terminal connected to the fuel cell, a second terminal connected to the power storage device, and a third terminal connected to the auxiliary device, and switches supply of the power to the auxiliary device by switching between a conductive state and an open state for the first terminal and the third terminal or for the second terminal and the third terminal on the basis of the control of the controller. 
     (4): In the above-described aspect (3), when the controller determines that the power storage device needs to be charged on the basis of a state of charge of the power storage device, the controller controls the converter so that at least the first terminal and the second terminal are in a conductive state. 
     (5): In the above-described aspect (4), the controller converts power from the fuel cell to have a voltage value which is equal to or lower than an upper limit value of an allowable voltage of the auxiliary device to which the power is supplied and is higher than a voltage value of the power storage device. 
     (6): In the above-described aspect (1), the controller controls the converter so that power from the power storage device is used as power for starting the fuel cell. 
     (7): A method of power supply according to another aspect of the present invention includes a controller of a power supply system which is configured to acquire a state of a fuel cell which is able to generate power and a state of a power storage device which stores the power generated by the fuel cell, select one of the fuel cell and the power storage device to supply power to an auxiliary device on the basis of the acquired states, and control a converter which converts power from the fuel cell or the power storage device and switches between supply of power from the fuel cell to the auxiliary device and supply of power from the power storage device to the auxiliary device so that power from the selected one is supplied to the auxiliary device. 
     According to any of the above-described aspects (1) to (7), appropriate power can be supplied to the auxiliary device while increase in cost of the auxiliary device connected to the power supply system is curbed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing an example of a schematic configuration of a power supply system according to an embodiment. 
         FIG. 2  is a diagram showing an example of a configuration of an energy ECU of the embodiment. 
         FIG. 3  is a diagram showing an example of a configuration of a DC-DC converter according to the embodiment. 
         FIG. 4  is a flowchart showing an example of a processing flow executed by the power supply system of the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of a power supply system and a method of power supply of the present invention will be described with reference to the drawings. In the following, a power supply system mounted on a vehicle will be mainly described. The vehicle is an electric vehicle that uses, for example, power generated by a fuel cell to be described later or power stored in a power storage device as power for traveling or power for operating in-vehicle devices (auxiliary devices). The vehicle is an automobile such as, for example, a two-wheeled vehicle, a three-wheeled vehicle, or a four-wheeled vehicle. 
       FIG. 1  is a diagram showing an example of a schematic configuration of a power supply system  1  of an embodiment. The power supply system  1  includes, for example, a fuel cell  100 , a battery  200 , a DC-DC converter  300 , and an energy electronic control unit (ECU)  400 . The battery  200  is an example of a “power storage device.” The energy ECU  400  is an example of a “controller.” A main output device  120  and one or more auxiliary devices  500 - 1 ,  500 - 2 , . . . ,  500 - n  are connected to the power supply system  1 . The main output device  120  and the auxiliary devices  500  are examples of a “load.” In the following, when the auxiliary devices  500 - 1 ,  500 - 2 , . . . , and  500 - n  are referred to without distinguishing them from each other, they are simply collectively referred to as the “auxiliary device  500 .” 
     The fuel cell  100  is a battery capable of generating power by reacting, for example, hydrogen contained in a fuel gas with oxygen contained in air. The fuel cell  100  performs power generation under control of, for example, the energy ECU. For example, the fuel cell  100  outputs the generated power to the main output device  120  or outputs the generated power to the DC-DC converter  300  via a DC link or the like. The main output device  120  is a motor that outputs a driving force used for traveling of the vehicle to drive wheels using, for example, power from the fuel cell  100 . The main output device  120  may be other devices (for example, a brake device, and the like) for traveling of or stopping the vehicle. The main output device  120  may be connected to the fuel cell  100  via a converter or the like. 
     The fuel cell  100  may include, for example, a fuel cell sensor that detects presence or absence of power generation, an amount of generated power, a temperature, and the like of the fuel cell  100 . A detection result of the fuel cell sensor is output to, for example, the energy ECU  400 . 
     The battery  200  is a secondary battery that can be repeatedly charged and discharged such as, for example, a lithium ion battery, a nickel-hydride battery, or a lead battery. The battery  200  may be, for example, a battery having a lower voltage (for example, 12 [V] or 48 [V]) than that of the power generated by the fuel cell  100 . The battery  200  may be a battery unit in which a plurality of battery cells are connected. For example, the battery  200  may store (be charged with) the power generated by the fuel cell  100  and converted by the DC-DC converter  300  or supply (discharge) the power stored in the battery  200  to the auxiliary device  500  or the like. 
     The battery  200  may include a battery sensor (a current sensor, a voltage sensor, and a temperature sensor) that detects, for example, a current value, a voltage value, a temperature, and the like of the battery  200 . A detection result of the battery sensor is output to, for example, the energy ECU  400 . 
     The DC-DC converter  300  converts DC power from the fuel cell  100  or the battery  200  to supply the converted DC power to the auxiliary device  500  or the like. For example, the DC-DC converter  300  boosts or lowers DC power from the fuel cell  100  or the battery  200  to a predetermined power value required by the auxiliary device  500  under control of the energy ECU  400 . The DC-DC converter  300  switches between supply of DC power (hereinafter, simply referred to as “power”) from the fuel cell  100  to the auxiliary device  500  and supply of power from the battery  200  to the auxiliary device  500  under the control of the energy ECU  400 . The DC-DC converter  300  may convert power from the fuel cell  100  and supply it to the battery  200  under the control of the energy ECU  400 . 
     The energy ECU  400  performs control for supplying power to the main output device  120  and the auxiliary device  500 . For example, the energy ECU  400  controls at least switching between supply of power from the fuel cell  100  to the auxiliary device  500  and supply of power from the battery  200  to the auxiliary device  500  in the DC-DC converter  300 . Details of a function of the energy ECU  400  will be described later. 
     The auxiliary device  500  is, for example, a device that uses power supplied from the fuel cell  100  or the battery  200  via the DC-DC converter  300  as power for operation. The auxiliary device  500  may be an electric device other than the main output device  120  mounted on the vehicle. The auxiliary device  500  may be, for example, a vehicle sensor, a display device, a light device, a navigation device, a communication device, a drive recorder, a human machine interface (HMI), other in-vehicle devices, or the like. 
     &lt;Energy ECU&gt; 
     Next, details of a function of the energy ECU  400  will be described.  FIG. 2  is a diagram showing an example of a configuration of the energy ECU  400  of the embodiment. The energy ECU  400  includes, for example, a state acquirer  420 , a supply controller  440 , a switching controller  460 , and a power controller  480 . The state acquirer  420 , the supply controller  440 , the switching controller  460 , and the power controller  480  are each realized by a hardware processor such as, for example, a central processing unit (CPU) executing a program (software). Some or all of these components may be realized by hardware (including circuitry) such as a large scale integration (LSI), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a graphics processing unit (GPU), or may be realized by software and hardware in cooperation. 
     The state acquirer  420  acquires a power request, an operation status, and the like for each of one or more auxiliary devices  500 - 1  to  500 - n  connected to the DC-DC converter  300 . For example, when the state acquirer  420  receives that an ignition switch of the vehicle has entered an ON state or receives an operation of an occupant from the HMI or the like, the state acquirer  420  acquires a power request from an auxiliary device associated with the received contents. The state acquirer  420  acquires an operation status of the auxiliary device  500  by communicating with the auxiliary device  500  during its starting (during its operation) at predetermined time intervals or at predetermined timings, or by receiving an operation signal (for example, a normal signal or an abnormal signal) from the auxiliary device  500 . The state acquirer  420  may acquire a state (for example, information detected by a vehicle sensor) or the like of the vehicle on which the power supply system  1  is mounted. 
     The state acquirer  420  acquires a state of the fuel cell  100  and a state of the battery  200  on the basis of, for example, detection results of sensors (a fuel cell sensor and a battery sensor) provided in the fuel cell  100  and the battery  200 . The state of the fuel cell  100  includes information such as, for example, whether or not the fuel cell  100  is generating power, a power generation status when power is being generated (for example, an amount of power generated in a predetermined time), a degree of deterioration, and whether or not an abnormality has occurred. The state of the battery  200  includes information such as, for example, whether or not the battery  200  is being charged or discharged, a state of charge (SOC) of the battery  200 , a degree of deterioration, and whether or not an abnormality has occurred. 
     The supply controller  440  selects one of the fuel cell  100  and the battery  200  to supply power to the auxiliary device  500  on the basis of a power request from the auxiliary device  500 , states of the fuel cell  100  and the battery  200 , and the like acquired by the state acquirer  420 . For example, the supply controller  440  calculates a required amount of power for the power request from the auxiliary device  500 . For example, the supply controller  440  calculates a torque to be output by the motor on the basis of an accelerator opening degree of the vehicle and a speed of the vehicle, and calculates the required amount of power by summing a drive shaft load power obtained from the torque and a rotation speed of the motor, and the power required by at least one of the plurality of auxiliary devices. The supply controller  440  may calculate the required amount of power by storing a required amount of power for each auxiliary device during operation in advance and referring to the stored required amount of power. When there are power requests from a plurality of auxiliary devices, the supply controller  440  calculates a total value of required amounts of power from these auxiliary devices. Then, the supply controller  440  compares the calculated required amount of power with the SOC or the like of the battery  200 , selects the battery  200  when it is determined that the required amount of power can be supplied by the battery  200 , and selects the fuel cell  100  when it is determined that the required amount of power cannot be supplied by the battery  200 . 
     For example, the supply controller  440  may select the battery  200  when the fuel cell  100  is not started or when the fuel cell  100  is caused to be started, and may select the fuel cell  100  when the fuel cell  100  is started (operating). In this case, the supply controller  440  controls the DC-DC converter  300  so that power from the battery  200  is used as power for starting the fuel cell  100 . 
     The supply controller  440  may select the fuel cell  100  or the battery  200  according to types and the number of the auxiliary devices  500  from which power is requested. For example, in a case of an auxiliary device that needs to be started immediately, the supply controller  440  may select the battery  200  that can immediately supply the stored power. The supply controller  440  may select the battery  200  when the number of the auxiliary devices  500  to which power is to be supplied is less than a predetermined number, and select the fuel cell  100  when the number is equal to or more than the predetermined number because the power of the battery  200  would be immediately consumed. 
     The supply controller  440  may select the battery  200  when an abnormality has occurred in the fuel cell  100  and may select the fuel cell  100  when an abnormality has occurred in the battery  200 . The supply controller  440  may select the battery  200  when a degree of deterioration of the fuel cell  100  is equal to or higher than a reference value, and may select the fuel cell  100  when a degree of deterioration of the battery  200  is equal to or higher than a reference value. The supply controller  440  may select the fuel cell  100  or the battery  200  on the basis of an instruction from a user (for example, an occupant of the vehicle on which the power supply system  1  is mounted or a system administrator) or the like. 
     The switching controller  460  controls a switch (to be described later) included in the DC-DC converter  300  so that power from the fuel cell  100  or the battery  200  selected by the supply controller  440  is supplied to the auxiliary device  500  or the like. 
     The power controller  480  performs control of power generation of the fuel cell  100 , control of charging or discharging the battery  200 , or the like on the basis of states of the fuel cell  100  and the battery  200  acquired by the state acquirer  420 , a supply status of power to the main output device  120  and the auxiliary device  500 , or the like. For example, the power controller  480  determines that the battery  200  needs to be charged when the SOC calculated on the basis of an output of the battery sensor included in the battery  200  is less than a threshold value, and executes control (charging control) for charging the battery  200  using power generation by the fuel cell  100 . When the SOC of the battery  200  is equal to or higher than the threshold value, the power controller  480  determines that charging of the battery  200  is not necessary, and executes control to stop the charging control. For example, when there is surplus power generated by the fuel cell  100 , the power controller  480  may perform control for charging the battery  200 , causing the auxiliary device  500  or the like to consume it, or the like. 
     &lt;Switching Control in DC-DC Converter&gt; 
     Next, contents of the switching control in the DC-DC converter  300  will be specifically described.  FIG. 3  is a diagram showing an example of a configuration of the DC-DC converter  300  of the embodiment. The DC-DC converter  300  includes, for example, a converter  320  and a switch  340 . 
     The converter  320  lowers or boosts power supplied from the fuel cell  100  or the battery  200  according to a required amount of power of the auxiliary device  500  of a supply destination that has requested power. 
     The switch  340  switches between supply of power from the fuel cell  100  to the auxiliary device  500  and supply of power from the battery  200  to the auxiliary device  500  under the control of the switching controller  460 . The switch  340  is, for example, a switch swing circuit or a switching element such as an electromagnetic switch. For example, as shown in  FIG. 3 , the switch  340  includes at least a first terminal  360 - 1  connected to the fuel cell  100 , a second terminal  360 - 2  connected to the battery  200 , and a third terminal  360 - 3  connected to the auxiliary device  500 . The first terminal  360 - 1  connected to the fuel cell  100  includes not only a case in which the fuel cell  100  and the first terminal  360 - 1  are directly connected, but also a case in which they are connected via an electric line (electrically conductive line) or the like. The same applies to the second terminal  360 - 2  connected to the battery  200  and the third terminal  360 - 3  connected to the auxiliary device  500 . When there are a plurality of auxiliary devices  500 - 1  to  500 - n  in the power supply system  1 , the third terminal  360 - 3  may be provided for each auxiliary devices to be connected. 
     The switch  340  switches between a conductive state or an open state for the terminals of the first terminal  360 - 1 , the second terminal  360 - 2 , and the third terminal  360 - 3 , for example, on the basis of the control of the switching controller  460 . For example, when the supply controller  440  selects to supply power from the fuel cell  100  to the auxiliary device  500 , the switching controller  460  outputs a control signal for making the first terminal  360 - 1  and the third terminal  360 - 3  conductive and making the second terminal  360 - 2  and the third terminal  360 - 3  open to the switch  340 . When the supply controller  440  selects to supply power from the battery  200  to the auxiliary device  500 , the switching controller  460  outputs a control signal for making the second terminal  360 - 2  and the third terminal  360 - 3  conductive and making the first terminal  360 - 1  and the third terminal  360 - 3  open to the switch  340 . 
     When a control of charging the battery  200  is performed by a control of the power controller  480 , the switching controller  460  outputs a control signal for making at least the first terminal  360 - 1  and the second terminal  360 - 2  conductive to the switch  340 . When the battery  200  is charged, the first terminal  360 - 1  and the third terminal  360 - 3  may be in an open state or may be in a conductive state. In this case, when the power controller  480  causes the converter  320  to convert power from the fuel cell  100 , the power is converted into a voltage value that is equal to or lower than an upper limit value of an allowable voltage of the auxiliary device  500  to which the power is supplied and is higher than a voltage value of the battery  200 . Thereby, since the voltage value of the battery  200  is lower than the converted voltage value, the power can be caused to flow to the battery  200  side to charge the battery  200  even in a conductive state. When power from the fuel cell  100  is supplied to the battery  200 , the power controller  480  may cause the converter  320  to perform power conversion to approach an upper limit value of the allowable voltage of the auxiliary device  500  within a range not exceeding the upper limit value thereof. 
     When supply of power from the fuel cell  100  to the battery  200  or the auxiliary device  500  is not performed, the switching controller  460  may output a control signal for making the first terminal  360 - 1  and the second terminal  360 - 2  open and making the first terminal  360 - 1  and the third terminal  360 - 3  open to the switch  340 . 
     The switch  340  performs switching control of states between the terminals on the basis of a control signal of the switching controller  460 . Thereby, power from the fuel cell  100  and power from the battery  200  can be adjusted to a predetermined voltage by the DC-DC converter  300  and can be supplied to all the auxiliary devices  500 - 1  to  500 - n . Therefore, a function for adjusting power fluctuation is not necessary to be provided in the auxiliary device  500 , and thereby costs of the auxiliary device  500  can be reduced. 
     [Processing Flow] 
       FIG. 4  is a flowchart showing an example of a processing flow executed by the power supply system  1  of the embodiment. In the example of  FIG. 4 , the state acquirer  420  determines whether or not a power request from the auxiliary device  500  has been received (step S 100 ). When it is determined that the power request from the auxiliary device  500  has been received, the state acquirer  420  acquires states of the fuel cell and the battery  200  (step S 102 ). Next, the supply controller  440  selects one of the fuel cell  100  and the battery  200  to supply power to the auxiliary device  500  on the basis of the states acquired by the state acquirer  420  (step S 104 ). Next, the switching controller  460  controls the DC-DC converter  300  so that power from the selected one is supplied to the auxiliary device  500 , and switches between a conductive state or an open state for the terminals (the first terminal  360 - 1 , the second terminal  360 - 2 , and the third terminal  360 - 3 ) (step S 106 ). The power controller  480  causes the DC-DC converter  300  to convert power on the basis of the power request from the auxiliary device  500  (step S 108 ), and supplies the converted power to the auxiliary device (step S 110 ). 
     Next, the supply controller  440  determines whether or not the battery  200  needs to be charged on the basis of a state of charge (for example, SOC) of the battery  200  (step S 112 ). When it is determined that the battery needs to be charged, the switching controller  460  controls the DC-DC converter  300  so that power from the fuel cell  100  is supplied to the battery  200  (step S 114 ). In the processing of step S 114 , the DC-DC converter  300  switches so that the first terminal  360 - 1  and the second terminal  360 - 2  are in a conductive state on the basis of, for example, the control from the switching controller  460 . The power controller  480  causes the fuel cell  100  to generate power and supplies it to the battery  200  via the DC-DC converter  300  (step S 116 ). The battery  200  is charged by the processing of step S 116 . Thereby, processing of the present flowchart ends. When it is determined in the processing of step S 100  that the power request from the auxiliary device  500  has not been received, or when it is determined in the processing of step S 112  that the battery does not need to be charged, the present flowchart ends. When it is no longer necessary to supply power to the auxiliary device  500  after the processing of step S 110  shown in  FIG. 4  is executed, the switching controller  460  may perform processing of switching between a conductive state or an open state for the terminals (the first terminal  360 - 1 , the second terminal  360 - 2 , and the third terminal  360 - 3 ) of the DC-DC converter  300  so that power from the fuel cell  100  or the battery  200  is not supplied to the auxiliary device  500 . When it is no longer necessary to supply power to the battery  200  after the processing of step S 116  is executed (for example, when the SOC is equal to or higher than a threshold value), the switching controller  460  may perform a control for switching the first terminal  360 - 1  and the second terminal  360 - 2  of the DC-DC converter  300  to an open state so that power from the fuel cell  100  is not supplied to the battery  200 . 
     In the processing shown in  FIG. 4 , the processing of steps S 100  to S 110  (hereinafter referred to as first processing) and the processing of steps S 112  to S 116  (hereinafter referred to as second processing) may be executed separately. In this case, the energy ECU  400  may control so that, when one of the first processing and the second processing is being executed, the other processing is not executed (waits until one processing is completed), or may execute the first processing and the second processing in parallel while dividing them in a time-division manner or the like. The energy ECU  400  may execute the first processing in preference to the second processing, or may execute the second processing when the first processing is not executed. 
     According to the embodiment described above, the power supply system  1  includes the fuel cell  100  capable of generating power, the battery (an example of a power storage device)  200  that stores the power generated by the fuel cell  100 , the DC-DC converter (an example of a converter)  300  that converts power from the fuel cell  100  or the battery  200  and switches between supply of power from the fuel cell  100  to the auxiliary device  500  and supply of power from the battery  200  to the auxiliary device  500 , and the energy ECU (an example of a controller)  400  that controls at least the switching in the DC-DC converter  300 , and thereby appropriate power can be supplied to the auxiliary device while increase in cost of the auxiliary device connected to the power supply system is curbed. 
     Specifically, in the power supply system  1  of the embodiment, for example, the DC-DC converter  300  is provided between the fuel cell  100  and the auxiliary device  500 , and the battery  200  having a voltage (for example, 12 [V] or 48 [V]) lower than that of the fuel cell  100  is connected to the DC-DC converter  300 . Then, the DC-DC converter  300  boosts or lowers power from the fuel cell  100  and power from the battery  200  to supply a stable voltage (for example, a constant voltage) to the auxiliary device  500 . Therefore, even when it is assumed that power generated by the fuel cell  100  fluctuates or is connected to the fuel cell  100  or the battery  200  having different voltage values, a function of adjusting voltage fluctuation or the like on the auxiliary device side becomes unnecessary, and as a result, costs of the auxiliary device  500  can be suppressed, and versatility in use of the auxiliary device  500  can be improved. 
     According to the embodiment, the DC-DC converter  300  includes the first terminal  360 - 1  connected to the fuel cell  100 , the second terminal  360 - 2  connected to the battery  200 , and the third terminal  360 - 3  connected to the auxiliary device  500  and switches between a conductive state or an open state for the terminals according to a supply source and a supply destination of power, and thereby not only power of the fuel cell  100  or the battery  200  can be supplied to the auxiliary device  500  but also power of the fuel cell  100  can be supplied to the battery  200  to charge the battery  200 . 
     In the fuel cell  100  of the embodiment, a battery that generates power by reacting hydrogen and oxygen has been used as an example, but other fuel cells of various types may also be applied. A part or all of the functions included in the energy ECU  400  of the embodiment may be provided in the DC-DC converter  300 . The power supply system  1  of the above-described embodiment may be mounted on an electric device (for example, a ship, a flight vehicle, or a robot) other than a vehicle in addition to (or instead of) a vehicle, and may be mounted on a fuel cell system of a stationary type. 
     While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description and is only limited by the scope of the appended claims.