Work machine power control device

Abstract

To enable power to be supplied from a fuel cell and a capacitor to an electric motor with an appropriate distribution that can suppress deterioration of the fuel cell and the capacitor.SOLUTION: An electric motor 77 is configured to be supplied with power from a fuel cell 51 and a capacitor 61. A controller 90 determines a power share amount between the fuel cell 51 and the capacitor 61 on the basis of power supplied to the electric motor 77, an actual voltage of the capacitor 61, and a limit value of a fluctuation amount of power output from the fuel cell 51. The controller 90 instructs a fuel cell converter 53 to control the power output from the fuel cell 51, and instructs a capacitor converter 63 to control the power for charging and discharging of the capacitor 61 in accordance with the determined power share amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a work machine power control device that controls the power for operating a work machine. [Background technology]

[0002] For example, Patent Document 1 describes a technique for supplying power from a fuel cell and a capacitor to an electric motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-61212 Summary of the Invention [Problem to be solved by the invention]

[0004] If the fluctuation in the power output by the fuel cell is too large, the fuel cell may deteriorate. If the voltage of the capacitor is too high, the capacitor may deteriorate. Therefore, it is desirable to be able to suppress the deterioration of the fuel cell and capacitor and to be able to appropriately supply power from the fuel cell and capacitor to the electric motor.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a power control device that can supply power from a fuel cell and a capacitor to an electric motor in an appropriate distribution that can suppress deterioration of the fuel cell and the capacitor. [Means for solving the problem]

[0006] The work machine power control device includes a fuel cell, a fuel cell converter, a capacitor, a capacitor converter, an electric motor, and a controller. The fuel cell converter controls the power output by the fuel cell. The capacitor converter controls the charging and discharging power of the capacitor. The electric motor is configured to be able to supply power from the fuel cell and the capacitor. The electric motor is for driving the work machine. The controller calculates the power sharing amount between the fuel cell and the capacitor based on the power supplied to the electric motor, the actual voltage of the capacitor, and a limit value for the amount of fluctuation in the power output by the fuel cell. The controller instructs the fuel cell converter on the power to be output by the fuel cell and the capacitor converter on the power to be charged and discharged to the capacitor based on the calculated power sharing amount. [Effects of the Invention]

[0007] The above-described power control device makes it possible to supply power from the fuel cell and the capacitor to the electric motor in an appropriate distribution that can suppress deterioration of the fuel cell and the capacitor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a side view of the work machine 10. [Figure 2] FIG. 2 is a circuit diagram of the power control device 40 shown in FIG. [Figure 3] FIG. 3 is a block diagram of calculation of the maximum capacitor charging power PW41 by the controller 90 shown in FIG. 2. [Figure 4] FIG. 3 is a block diagram of calculation of the capacitor maximum discharge power PW51 by the controller 90 shown in FIG. 2. [Figure 5] 3 is a block diagram of calculation of capacitor required charge / discharge power PW2b by controller 90 shown in FIG. 2. FIG. [Figure 6] 3 is a flowchart showing calculation of FC output target power PW12 by the controller 90 shown in FIG. 2. [Figure 7]3 is a flowchart of calculation of a capacitor command power PW31, an FC output command power PW43, etc. by the controller 90 shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] A work machine 10 equipped with a power control device 40 (work machine power control device) will be described with reference to FIGS. 1 to 7.

[0010] As shown in Figure 1, the work machine 10 is a machine that performs work. The work machine 10 may be a construction machine that performs construction work, or a loading and unloading machine that performs loading and unloading work. The work machine 10 may be, for example, a shovel or a crane. The work machine 10 may be a bulldozer or a wheel loader. The work machine 10 is powered by power output from a fuel cell 51 (see Figure 2). The work machine 10 is, for example, a fuel cell shovel. The following description will mainly focus on the case where the work machine 10 is a shovel. The work machine 10 comprises a machine body 10a, an attachment 15, a hydraulic circuit 20 shown in Figure 2, and a power control device 40.

[0011] As shown in FIG. 1, the machine body 10a is the main body of the work machine 10. The machine body 10a includes a lower body 11 and an upper rotating body 13. The lower body 11 supports the upper rotating body 13 so that it can rotate. The lower body 11 may be a lower running body that can run on a running surface (such as the ground). If the lower body 11 is runnable, the lower body 11 may be equipped with crawlers or wheels. The upper rotating body 13 is mounted on the lower body 11 so that it can rotate.

[0012] The attachment 15 is the part that performs work. The attachment 15 is attached to the machine body 10a (more specifically, to the upper rotating body 13). For example, the attachment 15 includes a boom 15a, an arm 15b, and a tip attachment 15c. The boom 15a is rotatably attached to the upper rotating body 13 (capable of rotating in the front-to-back and up-down directions). The arm 15b is rotatably attached to the boom 15a (capable of rotating in the front-to-back and up-down directions). The tip attachment 15c is provided at the tip of the attachment 15. The tip attachment 15c is rotatably attached to the arm 15b (capable of rotating in the front-to-back and up-down directions). The tip attachment 15c may be a bucket that can be used to scoop up work objects and perform excavation, etc. The tip attachment 15c may be equipped with a device for clamping the work object (grapple, nibbler, rotating fork, etc.), a device for crushing the work object (breaker, etc.), or a magnet for attracting metal work objects.

[0013] 2, the hydraulic circuit 20 is a circuit for operating the hydraulic actuator 30. The hydraulic circuit 20 includes a hydraulic pump 21 and the hydraulic actuator 30.

[0014] The hydraulic pump 21 draws hydraulic oil from a tank. The hydraulic pump 21 supplies hydraulic oil to the hydraulic actuator 30. The hydraulic pump 21 is driven (rotationally driven) by an electric motor 77. Only one hydraulic pump 21 may be provided, or multiple hydraulic pumps 21 may be provided. The capacity of the hydraulic pump 21 is variable.

[0015] The hydraulic actuator 30 is a device that moves the work machine 10. The hydraulic actuator 30 is hydraulically driven by hydraulic oil supplied from the hydraulic pump 21. The hydraulic actuator 30 may be equipped with a hydraulic motor for rotational drive, or may be equipped with a hydraulic cylinder (telescopic cylinder) for telescopic drive. As shown in FIG. 1 , the hydraulic actuator 30 is equipped with a travel motor 31, a swing motor 33, a boom cylinder 35a, an arm cylinder 35b, and a tip attachment cylinder 35c. The travel motor 31 drives the lower body 11 to travel. The travel motor 31 is a hydraulic motor (as is the swing motor 33). The swing motor 33 drives the upper swing body 13 to swing relative to the lower body 11. The boom cylinder 35a drives (raise and lower) the boom 15a relative to the upper swing body 13. The boom cylinder 35a is a hydraulic cylinder (as are the arm cylinder 35b and the tip attachment cylinder 35c). The arm cylinder 35b rotates the arm 15b relative to the boom 15a. The tip attachment cylinder 35c rotates the tip attachment 15c relative to the arm 15b. If the tip attachment 15c itself is drivable, for example, as a device for clamping an object, a hydraulic actuator 30 may be provided to drive the tip attachment 15c.

[0016] The power control device 40 (work machine power control device) is a device (power control system) that controls the power used to operate the work machine 10. The power control device 40 controls the power (power system) used to operate the work machine 10. The power control device 40 may also control the power used to operate auxiliary equipment (for example, a computer, a cooling fan, etc.). The power control device 40 is mounted on the machine main body 10a (specifically, the upper rotating body 13) (see FIG. 1).

[0017] As shown in FIG. 2, this power control device 40 includes a fuel cell 51 and a capacitor 61 (a hybrid system of the fuel cell 51 and the capacitor 61). The drive source of the work machine 10 (see FIG. 1) is the fuel cell 51 and the capacitor 61. Therefore, compared to when the drive source of the work machine 10 is an engine (motor) alone, it is possible to reduce or eliminate carbon dioxide emissions from the work machine 10. The power control device 40 is a fuel cell control system that controls the output of the fuel cell 51, and a capacitor control system that controls the output of the capacitor 61. The power control device 40 includes a fuel cell 51, a fuel cell converter 53, a capacitor 61, and a capacitor converter 63. Furthermore, the power control device 40 includes a motor inverter 71, a high-voltage DC unit 73, an AC unit 75, an electric motor 77, a sensor 80, and a controller 90.

[0018] A fuel cell 51 (FC) is a device that generates electrical energy through a chemical reaction between a fuel and an oxidant. The fuel of the fuel cell 51 may be hydrogen or alcohol (e.g., methanol, ethanol, etc.). The oxidant of the fuel cell 51 is, for example, oxygen.

[0019] The fuel cell converter 53 is a device that controls the power output by the fuel cell 51. The fuel cell converter 53 is a device (power conversion device) that converts the power output by the fuel cell 51. The fuel cell converter 53 is connected to the fuel cell 51. "Connected" means electrically connected (the same applies to "connected" below). The fuel cell converter 53 is connected to the high-voltage DC unit 73. The fuel cell converter 53 controls the voltage (output voltage) output by the fuel cell converter 53 to a specific voltage (set voltage). The fuel cell converter 53 is a step-up converter that increases the voltage output by the fuel cell 51 and outputs it to the high-voltage DC unit 73. The fuel cell converter 53 may also be a step-down converter that decreases the voltage output by the fuel cell 51 and outputs it to the high-voltage DC unit 73.

[0020] The capacitor 61 is a power storage device that stores electric power. The capacitor 61 is an electric double layer capacitor (electric double layer condenser). Compared to secondary batteries (lead-acid batteries, lithium-ion batteries, etc.), the capacitor 61 has a faster charge / discharge response and is capable of instantaneous charging and discharging (inputting and outputting) of electric power. For this reason, the capacitor 61 is more suitable than a secondary battery as a power storage device that stores electric power for operating the work machine 10 (see FIG. 1) (for example, to drive the electric motor 77). More specifically, the work machine 10 shown in FIG. 1 may be subjected to sudden operations or may come into contact with a work target (such as soil). For this reason, the load acting on the work machine 10 fluctuates more drastically (for example, the load time constant is on the order of approximately 0.1 seconds) than, for example, an automobile. This causes a sudden change in the pressure of the hydraulic oil discharged by the hydraulic pump 21 shown in FIG. 2. This causes a sudden change in the load (required electric power) on the electric motor 77 that drives the hydraulic pump 21. This requires instantaneous charging and discharging (releasing and absorbing) of power, so a capacitor 61 is more suitable than a secondary battery as a power storage device for storing power to operate the work machine 10 (see FIG. 1).

[0021] The capacitor converter 63 is a device that controls the charging and discharging power of the capacitor 61. The capacitor converter 63 is a device (power conversion device) that converts the charging and discharging power of the capacitor 61. The capacitor converter 63 is connected to the capacitor 61. The capacitor converter 63 is connected to the high-voltage DC unit 73. The capacitor converter 63 is configured to be able to both charge and discharge the capacitor 61. The capacitor converter 63 is a bidirectional (step-up / step-down) converter. More specifically, when the capacitor 61 is discharging, the capacitor converter 63 functions as a step-up converter that increases the voltage of the high-voltage DC unit 73 relative to the voltage of the capacitor 61. When the capacitor 61 is charging, the capacitor converter 63 functions as a step-down converter that decreases the voltage of the high-voltage DC unit 73 relative to the voltage of the capacitor 61 (increases the voltage of the capacitor 61 relative to the voltage of the high-voltage DC unit 73). The configuration (circuit configuration, etc.) of the capacitor converter 63 can be set in various ways. 2, the capacitor converter 63 includes a switch element 63a, a capacitor 63c, and a reactor 63e. Two switch elements 63a are provided. The switch elements 63a are semiconductor elements (power elements). In the example shown in FIG. 2, the switch elements 63a are insulated gate bipolar transistors (IGBTs).

[0022] The motor inverter 71 is a device (motor drive device) that drives the motor 77. The motor inverter 71 is configured to be able to receive power from the fuel cell 51 and the capacitor 61. The motor inverter 71 converts the power received from the fuel cell 51 and the capacitor 61 and supplies the power to the motor 77. More specifically, the motor inverter 71 converts a direct current input from the high-voltage DC unit 73 into an alternating current. The motor inverter 71 outputs the alternating current to the motor 77 via the AC unit 75.

[0023] The high voltage DC section 73 (DC; Direct Current) is a section configured to be able to supply power from the fuel cell 51 and the capacitor 61 to the motor inverter 71. The high voltage DC section 73 is a section through which a direct current flows.

[0024] The AC section 75 (AC: Alternating Current) is a section between the motor inverter 71 and the motor 77, through which an alternating current flows.

[0025] The electric motor 77 is a load (electric load) that consumes the electric power output by the fuel cell 51 and the capacitor 61. The electric motor 77 is driven by the electric power output by the fuel cell 51 and the capacitor 61. The electric motor 77 is driven by the electric motor inverter 71. The electric motor 77 is used to drive the work machine 10 (see FIG. 1). Specifically, the electric motor 77 drives the hydraulic pump 21. When the hydraulic pump 21 is driven, the hydraulic pump 21 discharges hydraulic oil, which is supplied to the hydraulic actuator 30, which moves the hydraulic actuator 30, thereby moving the work machine 10. Note that an electric motor 77 that moves something other than the hydraulic pump 21 may also be provided. For example, the electric motor 77 may move the work machine 10 without going through the hydraulic circuit 20. Specifically, the electric motor 77 may be the swing motor 33 that rotates the upper swing body 13 relative to the lower body 11 shown in FIG. 1. Only one electric motor 77 shown in FIG. 2 may be provided, or multiple electric motors 77 may be provided.

[0026] (Other loads (auxiliary equipment)) The load (electrical power load) that consumes the power output by the fuel cell 51 and the capacitor 61 may include equipment other than the electric motor 77 (main engine). The load may include auxiliary equipment. For example, the auxiliary equipment may include a computer (such as the controller 90) or a cooling fan (such as a fan that cools the electric motor 77). Note that the work machine 1 may be equipped with equipment that does not use the power of the fuel cell 51 and the capacitor 61, but operates only on power supplied from a battery, for example. Equipment that is not powered by the fuel cell 51 and the capacitor 61 is not included in the "auxiliary equipment" below.

[0027] The sensors 80 detect various types of information. The sensors 80 detect information used for processing (such as control) by the controller 90. The sensors 80 output the detected information (signals) to the controller 90. The sensors 80 include, for example, an element input / output current sensor 83i, a high-voltage DC voltage sensor 83v, a capacitor temperature sensor 86t, a capacitor voltage sensor 86v, an inverter input current sensor 87i, and an inverter input voltage sensor 87v. Note that sensors 80 other than these may also be provided.

[0028] The element input / output current sensor 83i detects the current input / output to / from the capacitor converter 63. The element input / output current sensor 83i detects the current input / output to / from the switch element 63a. The high-voltage DC voltage sensor 83v detects the voltage (voltage between the positive and negative poles) of the high-voltage DC unit 73. The capacitor temperature sensor 86t detects the temperature of the capacitor 61. The capacitor voltage sensor 86v detects the voltage (voltage between the positive and negative poles) of the capacitor 61. The inverter input current sensor 87i detects the current input to the motor inverter 71 (current at the inverter high-voltage input section). The inverter input voltage sensor 87v detects the voltage (voltage between the positive and negative poles) (voltage at the inverter high-voltage input section) input to the motor inverter 71. In the example shown in FIG. 2, the inverter input voltage sensor 87v detects the voltage of the high-voltage DC unit 73.

[0029] The controller 90 is a computer that inputs and outputs signals, performs calculations (processing), stores information, etc. The functions of the controller 90 are realized by the execution of a program stored in the memory unit of the controller 90 by the calculation unit of the controller 90. The controller 90 may be connected to other devices via wireless communication or wired communication. For example, information is input to the controller 90 from the sensor 80. For example, the controller 90 controls the power output by the fuel cell 51 and the power charged and discharged by the capacitor 61. For example, the controller 90 outputs commands to the fuel cell converter 53 and the capacitor converter 63 (described later). The controller 90 (the functions of the controller 90) includes a high-voltage DC voltage control means 91 and a power distribution control means 93.

[0030] The high-voltage DC voltage control means 91 controls the voltage of the high-voltage DC unit 73. The high-voltage DC voltage control means 91 controls (stabilizes) the voltage of the high-voltage DC unit 73 so that it remains constant (at a specific voltage). The high-voltage DC voltage control means 91 is a capacitor converter control means that controls the capacitor converter 63 and controls the charging and discharging of the capacitor 61. Specifically, the high-voltage DC voltage control means 91 outputs a command to the switch element 63a (specifically, a command to turn the switch on and off).

[0031] The power distribution control means 93 determines the distribution of the power output by the fuel cell 51 (also referred to as output power) and the power output by the capacitor 61 (details will be described later). The power distribution control means 93 is a fuel cell converter control means that controls the fuel cell converter 53 and controls the power output by the fuel cell 51. Specifically, for example, the power distribution control means 93 instructs the fuel cell converter 53 on power (outputs a power command). For example, it controls the current output by the fuel cell converter 53 (output current) so that the power output by the fuel cell converter 53 becomes the power instructed by the power distribution control means 93. The power distribution control means 93 outputs a switching signal (a command to turn a switch on or off) to the power element of the fuel cell converter 53.

[0032] (Activation) Work machine 10 (see FIG. 1) is configured to operate as follows.

[0033] As described above, the electric motor 77 is driven to rotate by the power output from the fuel cell 51 and the capacitor 61. The electric motor 77 is controlled by the controller 90. More specifically, the controller 90 outputs a command to the electric motor inverter 71, and the electric motor inverter 71 drives the electric motor 77 in accordance with the command. The electric motor 77 is controlled (speed controlled) by the controller 90 so as to be driven to rotate at a speed set in the controller 90. The electric motor 77 drives the hydraulic pump 21.

[0034] The hydraulic pump 21 draws hydraulic oil from a tank, discharges the hydraulic oil, and supplies the hydraulic oil to the hydraulic actuator 30. The power (work) of the hydraulic pump 21 is controlled by the controller 90. The power of the hydraulic pump 21 is controlled (limited) so that it is equal to or less than a set power (a hydraulic maximum power PW71 (see FIG. 7) described below). For example, in the hydraulic pump 21, control of the discharge flow rate of the hydraulic pump 21 (PQ control) is performed in accordance with the discharge pressure of the hydraulic pump 21. The flow rate of the hydraulic pump 21 is proportional to the product of the rotation speed and capacity of the hydraulic pump 21, and the flow rate of the hydraulic pump 21 is controlled by controlling the capacity of the hydraulic pump 21.

[0035] A control valve (not shown) controls the flow rate and direction of hydraulic oil supplied from the hydraulic pump 21 to the hydraulic actuator 30. The hydraulic actuator 30 moves (drives) when hydraulic oil is supplied from the hydraulic pump 21. When the hydraulic actuator 30 moves, the work machine 10 (see FIG. 1) moves.

[0036] Similar to the electric motor 77, loads other than the electric motor 77 (for example, auxiliary machines) are also operated by the electric power output from the fuel cell 51 and the capacitor 61.

[0037] (power control) The controller 90 determines the amount of power shared between the fuel cell 51 and the capacitor 61 (performs FC-capacitor power distribution control). Specifically, the controller 90 determines the power output by the fuel cell 51 (FC output command power PW43 (see FIG. 7) described later) and the power output by the capacitor 61 (capacitor command power PW31 (see FIG. 7) described later).

[0038] The controller 90 calculates the power share based on the power supplied to the load (including the electric motor 77), the actual voltage of the capacitor 61, and the limit value of the fluctuation amount of the power output by the fuel cell 51.

[0039] (Regarding the power being supplied to the load) The controller 90 calculates the power share based on the power supplied to the load (including the electric motor 77). An example of the reason for this is as follows: The power consumed by the load (load required power PW1 (see FIG. 6) described later) varies depending on the load condition. Specifically, the power consumed by the electric motor 77 varies due to fluctuations in the pressure of the hydraulic oil in the hydraulic circuit 20. More specifically, when the force acting on the hydraulic actuator 30 varies, the pressure of the hydraulic oil fluctuates, and the power (work) of the hydraulic pump 21 varies. This causes the power (electricity) consumed by the electric motor 77 to vary. Furthermore, the power consumed by the load (load required power PW1 (see FIG. 6) described later) also varies depending on the condition of the auxiliary equipment. Therefore, the controller 90 calculates the power share based on the power consumed by the load.

[0040] The controller 90 determines the power share based on at least the power consumed by the electric motor 77. The controller 90 may calculate the power consumed by the electric motor 77 from the power supplied to the electric motor inverter 71. Specifically, the controller 90 calculates the power supplied to the electric motor inverter 71 from the product of the current detected by the inverter input current sensor 87i and the voltage detected by the inverter input voltage sensor 87v. The controller 90 may calculate the power consumed by the electric motor 77 from the power (work) of the hydraulic pump 21. Specifically, the controller 90 may calculate the power of the hydraulic pump 21 from the product of the flow rate and pressure of the hydraulic oil discharged by the hydraulic pump 21. In this case, a sensor 80 may be provided that detects the pressure of the hydraulic oil discharged by the hydraulic pump 21. The flow rate of the hydraulic oil discharged by the hydraulic pump 21 may be calculated from the rotation speed and capacity of the hydraulic pump 21, or may be detected by the sensor 80.

[0041] The controller 90 may obtain or calculate the power consumed by the auxiliary devices from information detected by the sensor 80. The power consumed by the auxiliary devices may be set in the controller 90 in advance.

[0042] The controller 90 determines the power allocation amount so that the power required by the load (required by the load and appropriate for the load) can be supplied to the load. Therefore, the load (e.g., electric motor 77) operates appropriately. For example, the electric motor 77 operates appropriately. For example, limitations on the drive of the electric motor 77 (e.g., torque limitations) due to insufficient power supplied to the electric motor 77 are suppressed. Therefore, the hydraulic pump 21 operates appropriately. For example, limitations on the power of the hydraulic pump 21 (e.g., power limitations due to PQ control) due to insufficient power supplied to the electric motor 77 can be suppressed. As a result, the hydraulic actuator 30 operates appropriately, and the work machine 10 (see FIG. 1) operates appropriately. Therefore, the workability (e.g., excavation performance, etc.) of the work machine 10 can be ensured. Hereinafter, "power" refers to electric power unless otherwise specified.

[0043] (Regarding the actual voltage of capacitor 61) The controller 90 determines the power allocation based on the actual voltage of the capacitor 61. An example of the reason for this is as follows: If the voltage of the capacitor 61 is too high (overcharge) or too low (overdischarge), the capacitor 61 may deteriorate (including damage (the same applies below)). Furthermore, a target voltage (described later) may be set for the capacitor 61. Therefore, the controller 90 determines the power allocation based on the actual voltage of the capacitor 61. The actual voltage of the capacitor 61 is the voltage detected by the capacitor voltage sensor 86v. Since the actual voltage of the capacitor 61 indicates the state of charge (SOC) of the capacitor 61, it can also be said that the controller 90 determines the power allocation based on the SOC of the capacitor 61. Specifically, the controller 90 determines the power allocation so that the charge / discharge amount of the capacitor 61 becomes an appropriate value (so as to prevent overcharging or overdischarging). Furthermore, the controller 90 determines the power allocation so that the voltage of the capacitor 61 becomes (approaches) the target voltage (a specific example will be described later).

[0044] (Limit value of fluctuation in power output by fuel cell 51) If the power output by the fuel cell 51 fluctuates excessively (suddenly, rapidly), there is a risk that the fuel cell 51 will rapidly deteriorate (including damage (the same applies hereinafter)). For this reason, it is preferable to limit (dull or slow down) the fluctuations in the power output by the fuel cell 51. Therefore, the controller 90 calculates the power allocation based on a limit value of the amount of fluctuation in the power output by the fuel cell 51. This limit value is set in advance in the controller 90 (before the power allocation is calculated). This limit value is, for example, a limit value (rate limiter) of the amount of change (rate of change) in power per unit time, such as the FC output power rate PWr (see FIG. 6 ), which will be described later. The controller 90 limits the amount of fluctuation in the power output by the fuel cell 51, and as a result, limits the power allocation of the fuel cell 51.

[0045] (Outline of how to calculate the power share) The controller 90 calculates the power allocation amount, for example, as follows. The controller 90 determines the power to be output by the fuel cell 51. At this time, the controller 90 determines the output power of the fuel cell 51 after limiting the amount of fluctuation in the output of the fuel cell 51. The controller 90 determines the charge / discharge power of the capacitor 61 so that the excess or deficiency of the power output by the fuel cell 51 relative to the power required by the load (such as the electric motor 77) is compensated for by the charging / discharging of the capacitor 61. If the power output by the fuel cell 51 is insufficient relative to the power required by the load, the controller 90 determines the power allocation amount so that the capacitor 61 discharges and supplies power to the load. If the power output by the fuel cell 51 is in excess of the power required by the load, the controller 90 determines the power allocation amount so that the power output by the fuel cell 51 is charged to the capacitor 61. The controller 90 determines the power allocation amount (charge / discharge power) of the capacitor 61 so that the actual voltage of the capacitor 61 is an appropriate value. Specifically, the controller 90 determines the power allocation amount of the capacitor 61 within a range in which the capacitor 61 is not overcharged or overdischarged, and so that the actual voltage of the capacitor 61 becomes the target voltage of the capacitor 61. A specific example of how to determine the power allocation amount will be described later.

[0046] Based on the power allocation amount calculated by the controller 90, the controller 90 instructs the fuel cell converter 53 on the power to be output by the fuel cell 51, and instructs the capacitor converter 63 on the power to be charged and discharged by the capacitor 61.

[0047] (Example of power control) A specific example of power control by the controller 90 is as follows. The controller 90 performs high-voltage DC voltage stabilization control, calculates the capacitor maximum charging power PW41 (see FIG. 3), calculates the capacitor maximum discharging power PW51 (see FIG. 4), and calculates the capacitor required charging / discharging power PW2b (see FIG. 5). Then, the controller 90 performs processing to determine the power allocation amount (see FIGS. 6 and 7).

[0048] (High voltage DC voltage constant control) The controller 90 (more specifically, high-voltage DC voltage control means 91) controls the capacitor converter 63 so that the voltage of the high-voltage DC unit 73 is constant. The controller 90 controls the capacitor converter 63 so that the voltage input to the motor inverter 71 is constant. Note that the voltage of the high-voltage DC unit 73 only needs to be approximately constant, and does not need to be strictly constant, as long as fluctuations in the voltage of the high-voltage DC unit 73 are suppressed. By the controller 90 performing control so that the voltage of the high-voltage DC unit 73 is constant, it is possible to stabilize the control in the power control device 40. Specifically, it is possible to stabilize the control of the power supplied to the load (for example, the electric motor 77), and it is possible to stabilize the control of the electric motor 77.

[0049] A specific example of high-voltage DC voltage stabilization control is as follows: The controller 90 (high-voltage DC voltage control means 91) stabilizes the voltage of the high-voltage DC unit 73 through feedback control. Specifically, a target voltage of the high-voltage DC unit 73 is set in the controller 90. The controller 90 also acquires the actual voltage of the high-voltage DC unit 73 detected by the high-voltage DC voltage sensor 83v (or the inverter input unit voltage sensor 87v). The controller 90 calculates the deviation of the actual voltage of the high-voltage DC unit 73 from the target voltage. The controller 90 then controls the capacitor converter 63 so that this deviation becomes zero. The controller 90 changes the command to be output to the capacitor converter 63 (specifically, to the switch element 63a) according to this deviation. The controller 90 stabilizes the voltage of the high-voltage DC unit 73, for example, by controlling the switch element 63a using PWM (Pulse Width Modulation).

[0050] (Calculation of maximum capacitor charge / discharge power (PW41, PW51)) In order to suppress deterioration of the capacitor 61, it is necessary to suppress over-discharging and over-charging of the capacitor 61. Therefore, the controller 90 (for example, a power distribution control means 93) limits the charging and discharging power of the capacitor 61. The controller 90 limits the charging and discharging power of the capacitor 61 based on the actual voltage of the capacitor 61, as well as the capacitor upper limit voltage and the capacitor lower limit voltage. Below, each component of the power control device 40 (fuel cell 51, capacitor 61, controller 90, etc.) will be described with reference to FIG. 2.

[0051] 3, the controller 90 calculates the capacitor maximum charging power PW41 based on the actual voltage of the capacitor 61 and the capacitor upper limit voltage. The capacitor upper limit voltage is set in advance in the controller 90 (before calculating the capacitor maximum charging power PW41). The capacitor upper limit voltage is the highest voltage when the capacitor 61 is charged, and is the upper limit voltage that can suppress deterioration of the capacitor 61. The capacitor maximum charging power PW41 is a limit value for the charging power of the capacitor 61. The magnitude of the charging power of the capacitor 61 is limited to be equal to or less than the magnitude of the capacitor maximum charging power PW41. The charging power (negative value) of the capacitor 61 is limited to be equal to or greater than the capacitor maximum charging power PW41 (negative value). Further specific examples of the calculation of the capacitor maximum charging power PW41 will be described later.

[0052] As shown in Fig. 4, the controller 90 calculates the capacitor maximum discharge power PW51 based on the actual voltage of the capacitor 61 and the capacitor lower limit voltage. The capacitor lower limit voltage is set in advance in the controller 90 (before calculating the capacitor maximum discharge power PW51). The capacitor lower limit voltage is the lowest voltage during discharge of the capacitor 61, and is the lower limit voltage that can suppress deterioration of the capacitor 61. The capacitor maximum discharge power PW51 is a limit value for the discharge power of the capacitor 61. The discharge power (positive value) of the capacitor 61 is limited to be equal to or less than the capacitor maximum discharge power PW51 (positive value). Further specific examples of calculation of the capacitor maximum discharge power PW51 will be described later.

[0053] (Limiting the maximum charge and discharge current of capacitor 61 according to temperature) 2, the upper limit of the current (charging / discharging current) that can be passed through the capacitor 61 during charging / discharging varies depending on the temperature of the capacitor 61. Therefore, the controller 90 (for example, the power distribution control means 93) limits the charging / discharging current of the capacitor 61 based on the temperature of the capacitor 61. The controller 90 acquires the temperature of the capacitor 61 from the capacitor temperature sensor 86t.

[0054] Specifically, for example, as shown in FIG. 3, the controller 90 limits the maximum charging current (described later) calculated to calculate the capacitor maximum charging power PW41 based on the temperature of the capacitor 61. Also, for example, as shown in FIG. 4, the controller 90 limits the maximum discharging current (described later) calculated to calculate the capacitor maximum discharging power PW51 based on the temperature of the capacitor 61. The controller 90 determines the upper limit of the maximum charging current and the upper limit of the maximum discharging current based on the temperature of the capacitor 61 (these upper limit values ​​are changed depending on the temperature of the capacitor 61). As a result, the controller 90 limits the capacitor maximum charging power PW41 (see FIG. 3) and the capacitor maximum discharging power PW51 (see FIG. 4) based on the temperature of the capacitor 61 (further specific examples will be described later).

[0055] (Example of calculating the maximum capacitor charging power PW41) A specific example of calculation of the capacitor maximum charging power PW41 shown in FIG. 3 will be described. The controller 90 calculates the deviation between the capacitor upper limit voltage set in advance in the controller 90 (before calculating the capacitor maximum charging power PW41) and the actual voltage of the capacitor 61 detected by the capacitor voltage sensor 86v. The controller 90 calculates a value (product) by multiplying this deviation by a charging gain (Kccc). This product is defined as the "maximum charging current A11 without considering the current limit." The charging gain is a coefficient that represents the relationship between this deviation and the maximum charging current. The charging gain is set in advance in the controller 90.

[0056] The controller 90 is preset with a "capacitor temperature-maximum charging current characteristic," which is the relationship between the temperature of the capacitor 61 (also referred to as the capacitor temperature) and the maximum charging current. The "maximum charging current" is the maximum value of the charging current of the capacitor 61 that can suppress deterioration of the capacitor 61. The controller 90 acquires the temperature of the capacitor 61 detected by the capacitor temperature sensor 86t. The controller 90 calculates a "maximum charging current A12 that takes capacitor temperature into account" based on the temperature of the capacitor 61 and the "capacitor temperature-maximum charging current characteristic." Specifically, the controller 90 calculates the maximum charging current corresponding to the acquired (current, detected) capacitor temperature based on the "capacitor temperature-maximum charging current characteristic." Then, if the "maximum charging current A11 without considering the current limit" exceeds the "maximum charging current corresponding to the capacitor temperature," the controller 90 sets the "maximum charging current corresponding to the capacitor temperature" to the "maximum charging current A12 that takes capacitor temperature into account." Furthermore, if the "maximum charging current A11 without considering the current limit" does not exceed the "maximum charging current corresponding to the capacitor temperature," the controller 90 sets the "maximum charging current A11 without considering the current limit" as the "maximum charging current A12 considering the capacitor temperature."

[0057] The controller 90 is preset with a "maximum current limit due to electrical circuit constraints." The "maximum current limit due to electrical circuit constraints" may include a current limit (the upper limit of the current that can flow) of the capacitor converter 63, and may also include, for example, a current limit of the switch element 63a. The controller 90 calculates the "maximum charging current" based on the "maximum charging current A12 taking into account capacitor temperature" and the "maximum current limit due to electrical circuit constraints." Specifically, if the "maximum charging current A12 taking into account capacitor temperature" exceeds the "maximum current limit due to electrical circuit constraints," the controller 90 sets the "maximum current limit due to electrical circuit constraints" to the "maximum charging current A13 taking into account temperature and circuit constraints." Furthermore, if the "maximum charging current A12 taking into account capacitor temperature" does not exceed the "maximum current limit due to electrical circuit constraints," the controller 90 sets the "maximum charging current A12 taking into account capacitor temperature" as the "maximum charging current A13 taking into account temperature and circuit constraints."

[0058] The controller 90 calculates the capacitor maximum charging power PW41 from the product of the "maximum charging current A13 taking into account temperature and circuit constraints" and the actual voltage of the capacitor 61. Note that the charging power of the capacitor 61, such as the capacitor maximum charging power PW41, is a negative value.

[0059] (Example of calculating the capacitor maximum discharge power PW51) The specific example of calculation of the capacitor maximum discharge power PW51 shown in Fig. 4 is almost the same as the specific example of calculation of the capacitor maximum charge power PW41 (see Fig. 3). The specific example of calculation of the capacitor maximum discharge power PW51 can be calculated by replacing "charge" with "discharge" and "upper limit" with "lower limit" in the explanation of calculation of the capacitor maximum charge power PW41. The specific example of calculation of the capacitor maximum discharge power PW51 will be mainly explained with respect to the differences from the specific example of calculation of the capacitor maximum charge power PW41.

[0060] The controller 90 (e.g., power distribution control means 93) calculates the deviation between the actual voltage of the capacitor 61 and the capacitor lower limit voltage. The controller 90 calculates the product (maximum discharge current A21 without considering capacitor temperature) of this deviation multiplied by a discharge gain (Kcdc). The controller 90 calculates the "maximum discharge current A22 taking capacitor temperature into consideration" based on the temperature of the capacitor 61 and the "capacitor temperature-maximum discharge current characteristics." The controller 90 calculates the "maximum discharge current A23 taking temperature and circuit constraints into consideration" based on the "maximum discharge current A22 taking capacitor temperature into consideration" and the "maximum current limit due to electrical circuit constraints." The controller 90 calculates the capacitor maximum discharge power PW51 from the product of the "maximum discharge current A23 taking temperature and circuit constraints into consideration" and the actual voltage of the capacitor 61. Note that the discharge power of the capacitor 61, such as the capacitor maximum discharge power PW51, is a positive value.

[0061] (Calculation of capacitor required charge / discharge power PW2b) A target voltage (target charge amount) of the capacitor 61 is set in the controller 90 so that the capacitor 61 can appropriately charge and discharge in accordance with fluctuations in the power required by the load (e.g., the electric motor 77) shown in Fig. 2. Then, the controller 90 (e.g., power distribution control means 93) controls the capacitor converter 63 so that the actual voltage of the capacitor 61 becomes the target voltage of the capacitor 61. Specifically, the controller 90 calculates a capacitor required charge / discharge power PW2b (see Fig. 5) which is the charge / discharge power of the capacitor 61 so that the actual voltage of the capacitor 61 becomes the target voltage of the capacitor 61.

[0062] (target voltage of capacitor 61) The controller 90 sets a voltage lower than the upper limit voltage of the capacitor 61 as the target voltage of the capacitor 61. This "upper limit voltage of the capacitor 61" is set in advance in the controller 90 (before the capacitor required charge / discharge power PW2b (see FIG. 5) is calculated). This "upper limit voltage of the capacitor 61" is a voltage that can suppress deterioration of the capacitor 61. This "upper limit voltage of the capacitor 61" may be the same value as the "capacitor upper limit voltage" used in calculating the above-mentioned capacitor maximum charge power PW41 (see FIG. 3).

[0063] The reason why the target voltage of capacitor 61 is set to a voltage lower than the upper limit voltage of capacitor 61 is as follows. It is assumed that the power required by a load (e.g., electric motor 77) suddenly drops while fuel cell 51 is outputting power. In this case, fuel cell 51 cannot suddenly reduce its output. If fuel cell 51 suddenly reduces its output, there is a risk that fuel cell 51 will deteriorate. Therefore, capacitor 61 needs to absorb the power output by fuel cell 51. In this situation, if the voltage of capacitor 61 has already reached the upper limit voltage, capacitor 61 cannot absorb (charge) power. Therefore, the target voltage of capacitor 61 is set to a voltage lower than the upper limit voltage of capacitor 61. Controller 90 determines the power allocation amount with the goal of reducing the voltage of capacitor 61 to a voltage lower than the upper limit voltage. Therefore, even if the power required by the load suddenly drops and capacitor 61 suddenly needs to absorb power, capacitor 61 can absorb the power.

[0064] The controller 90 sets a voltage higher than the lower limit voltage of the capacitor 61 as the target voltage of the capacitor 61. This "lower limit voltage of the capacitor 61" is set in advance in the controller 90 (before the capacitor required charge / discharge power PW2b (see FIG. 5) is calculated). This "lower limit voltage of the capacitor 61" is a voltage that can suppress deterioration of the capacitor 61. This "lower limit voltage of the capacitor 61" may be the same value as the "capacitor lower limit voltage" used in calculating the above-mentioned capacitor maximum discharge power PW51 (see FIG. 4).

[0065] The reason why the target voltage of capacitor 61 is set to a voltage higher than the lower limit voltage of capacitor 61 is as follows. It is assumed that the power required by the load (for example, electric motor 77) will suddenly increase. In this case, fuel cell 51 cannot suddenly increase its output. If fuel cell 51 suddenly increases its output, there is a risk that fuel cell 51 will deteriorate. Therefore, capacitor 61 needs to supply the power to be supplied to the load. In this situation, if the voltage of capacitor 61 has already reached the lower limit voltage, capacitor 61 will not be able to supply (discharge) power to the load. Therefore, the target voltage of capacitor 61 is set to a voltage higher than the lower limit voltage of capacitor 61. Controller 90 determines the power allocation amount with the goal of raising the voltage of capacitor 61 to a voltage higher than the lower limit voltage. Therefore, even if the power required by the load suddenly increases and capacitor 61 suddenly needs to release power, capacitor 61 can release the power.

[0066] Specifically, the target voltage of capacitor 61 may be a value equal to or less than 95% or equal to 90% of the upper limit voltage of capacitor 61. The target voltage of capacitor 61 may be a value equal to or more than 70% or equal to or more than 80% of the upper limit voltage of capacitor 61. Note that the above target voltage values ​​are merely examples, and the target voltage of capacitor 61 does not have to be within these ranges.

[0067] (Limiting the charge / discharge current of capacitor 61 according to temperature) As described above, the controller 90 (for example, the power distribution control means 93) limits the charge / discharge current of the capacitor 61 based on the temperature of the capacitor 61. Specifically, the controller 90 limits the charge / discharge current (described later) calculated to calculate the capacitor required charge / discharge power PW2b based on the temperature of the capacitor 61 (a specific example will be described later).

[0068] (Specific example of calculation of capacitor required charge / discharge power PW2b) A specific example of calculation of the capacitor required charge / discharge power PW2b shown in FIG. 5 will be described. The controller 90 acquires the target voltage of the capacitor 61 and the actual voltage of the capacitor 61. The controller 90 calculates the deviation between the target voltage and the actual voltage of the capacitor 61. The controller 90 calculates a value (product) by multiplying this deviation by a charge / discharge gain (Kcqc). This product is set as the "required charge / discharge current A31 without considering the current limit." The charge / discharge gain is a coefficient that represents the relationship between this deviation and the charge / discharge current. The charge / discharge gain is set in advance in the controller 90 (before calculating the capacitor required charge / discharge power PW2b).

[0069] The controller 90 aims to discharge the capacitor 61 when the actual voltage of the capacitor 61 is higher than the target voltage of the capacitor 61 (when the deviation and the "requested charge / discharge current A31 without considering the current limit" are positive values). The controller 90 aims to charge the capacitor 61 when the actual voltage of the capacitor 61 is lower than the target voltage of the capacitor 61 (when the deviation and the "requested charge / discharge current A31 without considering the current limit" are negative values).

[0070] The controller 90 acquires the temperature of the capacitor 61 detected by the capacitor temperature sensor 86t. When the controller 90 aims to discharge the capacitor 61, it calculates a "discharge current A32a taking into account the capacitor temperature" based on the temperature of the capacitor 61 and the "capacitor temperature-maximum discharge current characteristics." A specific example of this calculation is similar to the calculation of the "maximum discharge current A22 taking into account the capacitor temperature" in the specific example of calculation of the capacitor maximum discharge power PW51 shown in FIG. 4. Furthermore, as shown in FIG. 5, when the controller 90 aims to charge the capacitor 61, it calculates a "charge current A32b taking into account the capacitor temperature" based on the temperature of the capacitor 61 and the "capacitor temperature-maximum charge current characteristics." A specific example of this calculation is similar to the calculation of the "maximum charge current A12 taking into account the capacitor temperature" in the specific example of calculation of the capacitor maximum charge power PW41 shown in FIG.

[0071] As shown in FIG. 5, the controller 90 calculates the "charge / discharge current A33 taking into account temperature and circuit constraints." Specifically, when the target is to discharge the capacitor 61, the controller 90 calculates the "charge / discharge current A33 taking into account temperature and circuit constraints" based on the "discharge current A32a taking into account capacitor temperature" and the "maximum current limit due to electrical circuit constraints." When the target is to charge the capacitor 61, the controller 90 calculates the "charge / discharge current A33 taking into account temperature and circuit constraints" based on the "charge current A32b taking into account capacitor temperature" and the "maximum current limit due to electrical circuit constraints." These calculations are similar to the calculation of the "maximum charge current A13 taking into account temperature and circuit constraints" based on the "maximum current limit due to electrical circuit constraints" in the calculation of the capacitor maximum charge power PW41 shown in FIG. 3.

[0072] The controller 90 calculates the capacitor required charging / discharging power PW2b from the product of the "charge / discharge current A33 taking into account temperature and circuit constraints" and the actual voltage of the capacitor 61. The capacitor required charging / discharging power PW2b is a negative value in the case of charging and a positive value in the case of discharging.

[0073] (Example of calculation of power share) As described above, the controller 90 shown in FIG. 2 determines the power sharing amount between the fuel cell 51 and the capacitor 61 (performs FC-capacitor power distribution control). Specifically, as shown in FIG. 7, the controller 90 determines the capacitor command power PW31, which is the power sharing amount of the capacitor 61 (see steps S42, S52, and the case where NO is returned in step S51). The controller 90 determines the FC output command power PW43, which is the power sharing amount of the fuel cell 51 (see steps S43, S53, and S63). The controller 90 determines the power sharing amount using the capacitor maximum charging power PW41 (see FIG. 3), capacitor maximum discharging power PW51 (see FIG. 4), and capacitor requested charging / discharging power PW2b (see FIG. 5), which are calculated by the controller 90.

[0074] A specific example of calculation of the power allocation amount by the controller 90 will be described with reference to the flowcharts shown in Figures 6 and 7. Unless otherwise specified, the following description will be given in the order of processing. Note that the order of processing can be changed in various ways.

[0075] As shown in FIG. 6, in step S1, the controller 90 calculates the load required power PW1. The load required power PW1 is the power that the fuel cell 51 and the capacitor 61 need to supply to the load. The load required power PW1 is the sum of the hydraulic required power PW1a and the auxiliary required power PW1b. The hydraulic required power PW1a is the power required to drive the electric motor 77 that drives the hydraulic pump 21. The auxiliary required power PW1b is the power required to operate the auxiliary.

[0076] In step S2, the controller 90 calculates the FC output required power PW2. The FC output required power PW2 is the value of the output power of the fuel cell 51, calculated in order to calculate the final FC output command power PW43 (see FIG. 7). The FC output required power PW2 is the value obtained by subtracting the capacitor required charge / discharge power PW2b (see FIG. 5) from the load required power PW1 (see step S1).

[0077] In step S11, the controller 90 determines a change in the output (FC output) of the fuel cell 51. The controller 90 determines whether the output of the fuel cell 51 is to be increased or decreased. Specifically, the controller 90 determines whether the FC output required power PW2 (see step S2) is equal to or greater than the FC output power PW11. The FC output power PW11 is the previous value of the final FC output command power PW43 (see FIG. 7). Here, the controller 90 repeatedly performs a series of processes (processing from start in FIG. 6 to return in FIG. 7). With respect to the current series of processes including the processing of step S11, the series of processes performed one time before is considered to be the "previous" series of processes. The "previous value" is the value in the "previous" series of processes. If the FC output required power PW2 is equal to or greater than the FC output power PW11 (YES in step S11), the output of the fuel cell 51 is to be increased or not changed. In this case, the controller 90 causes the processing flow to proceed to step S12. If the FC output power requirement PW2 is less than the FC output power PW11 (NO in step S11), the situation is one in which the output of the fuel cell 51 needs to be reduced. In this case, the controller 90 advances the process flow to step S22.

[0078] In step S12, controller 90 calculates FC output target power PW12 when increasing (or not changing) the output of fuel cell 51. FC output target power PW12 is a value obtained by adding a limit value of the amount of fluctuation in the output power of fuel cell 51 to FC output power PW11 (previous value) (a value obtained by subtracting it when the output of fuel cell 51 is to be reduced (see step S22)). FC output target power PW12 is an upper limit value of FC output power requirement PW2 (a lower limit value when the output of fuel cell 51 is to be reduced) that takes into account the limit value of the amount of fluctuation in the output power of fuel cell 51.

[0079] Specifically, the controller 90 calculates the product (PWr×Ts) of the FC output power rate PWr and the control period Ts. The FC output power rate PWr is a limit value for the amount of fluctuation in the output power of the fuel cell 51 per unit time (e.g., one second). The unit of the FC output power rate PWr is, for example, W / s (watts per second). The control period Ts is a period during which the controller 90 performs the above-mentioned "series of processes." The unit of the control period Ts is, for example, seconds. The controller 90 calculates the product (PWr×Ts) of the FC output power rate PWr and the control period Ts (a limit value for the amount of fluctuation in the output power of the fuel cell 51 per control period). The controller 90 calculates the sum of this product (PWr×Ts) and the FC output power PW11 (previous value) (see step S11) as the FC output target power PW12. Then, the controller 90 causes the flow to proceed to step S13.

[0080] In step S13, the controller 90 determines whether the FC output power requirement PW2 (see step S2) is equal to or less than the FC output target power PW12 (see step S12). That is, the controller 90 determines whether the amount of variation in the FC output power requirement PW2 (current target value) relative to the FC output power PW11 (previous value) is equal to or less than the limit value (PWr×Ts) of the amount of variation.

[0081] The case where FC output power requirement PW2 (see step S2) exceeds FC output target power PW12 (see step S12) (NO in step S13) will be described. If step S13 is NO, the amount of fluctuation in FC output power requirement PW2 (current target value) relative to FC output power PW11 (previous value) exceeds the fluctuation amount limit value (PWr × Ts). In this case, FC output power requirement PW2 needs to be limited by the fluctuation amount limit value (PWr × Ts). In this case, the controller 90 sets the FC output target power PW12 calculated in step S12, taking into account the FC output power rate PWr, as the FC output target power PW12 without any change. The controller 90 then proceeds to step S31 (see FIG. 7).

[0082] If the FC output power requirement PW2 (see step S2) is equal to or less than the FC output target power PW12 (see step S12) (YES in step S13), the controller 90 advances the process flow to step S13y.

[0083] Step S13y is a process that is performed if the result of step S13 is YES. If the result of step S13 is YES, the FC output power requirement PW2 (see step S2) is equal to or less than the FC output target power PW12 (see step S12). In this case, the amount of fluctuation in the FC output power requirement PW2 (current target value) relative to the FC output power PW11 (previous value) is equal to or less than the limit value (PWr×Ts) for the amount of fluctuation. In this case, it is not necessary to limit the FC output power requirement PW2 (current target value) by the limit value (PWr×Ts) for the amount of fluctuation in the output power of the fuel cell 51. Therefore, the controller 90 sets the FC output power requirement PW2 (see step S2) as the new FC output target power PW12. In other words, the controller 90 sets the FC output target power PW12 to the FC output power requirement PW2 calculated in step S2, rather than the FC output target power PW12 calculated in step S12 taking into account the FC output power rate PWr. Then, the controller 90 advances the process flow to step S31 (see FIG. 7).

[0084] Step S22 is a process that is performed when the output of the fuel cell 51 is to be reduced (when the answer is NO in step S11). In step S22, the controller 90 calculates the FC output target power PW12 in substantially the same manner as in step S12. The process of this step S22 will be described mainly with respect to the differences from the process of step S12. The controller 90 calculates the product (PWr×Ts) of the FC output power rate PWr and the control period Ts (similar to step S12). When the output of the fuel cell 51 is to be reduced, the FC output target power PW12 (current target value) becomes smaller than the FC output power PW11 (previous value). Therefore, the controller 90 sets the value (difference) obtained by subtracting the above product (PWr×Ts) from the FC output power PW11 (see step S11) as the FC output target power PW12. Then, the controller 90 causes the process flow to proceed to step S23.

[0085] In step S23, the controller 90 determines whether the FC output power requirement PW2 (see step S2) is equal to or greater than the FC output target power PW12 (see step S12). That is, the controller 90 determines whether the amount of fluctuation (negative value) of the FC output power requirement PW2 (present target value) relative to the FC output power PW11 (previous value) is equal to or greater than the limit value of the amount of fluctuation (-PWr x Ts). The controller 90 determines whether the magnitude (absolute value) of the amount of fluctuation of the FC output power requirement PW2 (present target value) relative to the FC output power PW11 (previous value) is equal to or less than the magnitude of the limit value of the amount of fluctuation (|-PWr x Ts|).

[0086] The case where FC output power requirement PW2 (see S2) is less than FC output target power PW12 (see S12) (NO in step S23) will be described. If step S23 is NO, the amount of fluctuation (negative value) of FC output power requirement PW2 (current target value) relative to FC output power PW11 (previous value) is less than the limit value (-PWr x Ts) (negative value) of the amount of fluctuation. In this case, FC output power requirement PW2 needs to be limited by the limit value (-PWr x Ts) of the amount of fluctuation. In this case, the controller 90 sets the FC output target power PW12 calculated in step S12, taking into account the FC output power rate PWr, as the FC output target power PW12 without any change. The controller 90 then causes the process flow to proceed to step S31.

[0087] If the FC output power requirement PW2 (see S2) is equal to or greater than the FC output target power PW12 (see S12) (YES in step S23), the controller 90 advances the process flow to step S23y.

[0088] Step S23y is a process that is performed if the answer is YES in step S23. If the answer is YES in step S23, required FC output power PW2 (see step S2) is equal to or greater than FC output target power PW12 (see step S12). In this case, the amount of fluctuation (negative value) of required FC output power PW2 (present target value) relative to FC output power PW11 (previous value) is equal to or greater than the limit value (-PWr x Ts) (negative value) of the amount of fluctuation. In this case, it is not necessary to limit required FC output power PW2 (present target value) by the limit value (-PWr x Ts) of the amount of fluctuation in the output power of fuel cell 51. Therefore, controller 90 sets required FC output power PW2 (see step S2) as new FC output target power PW12 (similar to step S13y). Then, controller 90 causes the process flow to proceed to step S31 (see FIG. 7).

[0089] In the process shown in FIG. 7, the controller 90 calculates the final capacitor command power PW31 (steps S31, S42, and S52) and the final FC output command power PW43 (steps S43, S53, and S63).

[0090] In step S31, the controller 90 calculates a capacitor command power PW31. The capacitor command power PW31 calculated in step S31 is a value that may become the final output of the capacitor 61 (if NO in step S41 and NO in step S51). The capacitor command power PW31 is a power that the controller 90 commands to the capacitor converter 63. The capacitor command power PW31 calculated in step S31 is a value that may be limited by the capacitor maximum charge / discharge power (PW41, PW51) (see steps S42 and S52 described later). The controller 90 determines the value (difference) obtained by subtracting the FC output target power PW12 (see FIG. 6) from the load required power PW1 (see step S1 in FIG. 6) as the capacitor command power PW31.

[0091] In step S41, the controller 90 compares the capacitor command power PW31 (see step S31) with the capacitor maximum charging power PW41 (see FIG. 3). Specifically, the controller 90 determines whether the capacitor command power PW31 is less than the capacitor maximum charging power PW41 (negative value). If the capacitor command power PW31 is less than the capacitor maximum charging power PW41 (YES in step S41), the controller 90 advances the process flow to step S42. If the capacitor command power PW31 is equal to or greater than the capacitor maximum charging power PW41 (NO in step S41), the controller 90 advances the process flow to step S51.

[0092] Step S42 is a process that is performed when the capacitor command power PW31 (see step S31) is less than the capacitor maximum charging power PW41 (negative value) (see FIG. 3) (YES in step S41). This process is performed when the magnitude (absolute value) of the capacitor command power PW31 exceeds the magnitude (absolute value) of the capacitor maximum charging power PW41. If the capacitor 61 is charged with this capacitor command power PW31, there is a risk that the capacitor 61 will deteriorate. Therefore, the controller 90 limits the capacitor command power PW31 to the capacitor maximum charging power PW41. Specifically, the controller 90 sets the capacitor maximum charging power PW41 as the new capacitor command power PW31. Then, the controller 90 causes the process flow to proceed to step S43.

[0093] In step S43, the controller 90 calculates the FC output command power PW43. The FC output command power PW43 is a value that will ultimately be output to the fuel cell 51. The FC output command power PW43 is the electric power that the controller 90 commands the fuel cell converter 53. The controller 90 determines the value (difference) obtained by subtracting the capacitor command power PW31 (the value calculated in step S42) from the load required power PW1 (see step S1 in FIG. 6) as the FC output command power PW43. Then, the controller 90 causes the process flow to proceed to step S71.

[0094] In step S51, the controller 90 compares the capacitor command power PW31 (see step S31) with the capacitor maximum discharge power PW51 (see FIG. 4). Specifically, the controller 90 determines whether the capacitor command power PW31 exceeds the capacitor maximum discharge power PW51 (a positive value). If the capacitor command power PW31 exceeds the capacitor maximum discharge power PW51 (YES in step S51), the controller 90 advances the process flow to step S52. If the capacitor command power PW31 is equal to or less than the capacitor maximum discharge power PW51 (NO in step S51), the controller 90 advances the process flow to step S63.

[0095] Step S52 is a process that is performed when the capacitor command power PW31 (see step S31) exceeds the capacitor maximum discharge power PW51 (positive value) (see FIG. 4) (YES in step S51). If the capacitor 61 is discharged at this capacitor command power PW31, there is a risk that the capacitor 61 will deteriorate. Therefore, the controller 90 limits the capacitor command power PW31 to the capacitor maximum discharge power PW51. Specifically, the controller 90 sets the capacitor maximum discharge power PW51 as the new capacitor command power PW31. Then, the controller 90 causes the process flow to proceed to step S53.

[0096] In step S53, the controller 90 calculates the FC output command power PW43 in the same manner as in step S43. Then, the controller 90 advances the processing flow to step S71.

[0097] Step S63 is a process that is performed when the capacitor command power PW31 is equal to or greater than the capacitor maximum charge power PW41 (negative value) (NO in step S41) and equal to or less than the capacitor maximum discharge power PW51 (positive value) (NO in step S51). In this case, the capacitor command power PW31 does not need to be limited by the capacitor maximum charge power PW41 and the capacitor maximum discharge power PW51. Therefore, the controller 90 sets the FC output target power PW12 (see FIG. 6) as the final FC output command power PW43 (see step S43). Note that, similar to steps S43 and S53, the controller 90 may set the value (difference) obtained by subtracting the capacitor command power PW31 from the load required power PW1 as the FC output command power PW43. Even in this case, since the capacitor command power PW31 has not been changed since step S31, the FC output command power PW43 has the same value as the FC output target power PW12. Then, the controller 90 advances the process flow to step S71.

[0098] In step S71, the controller 90 calculates hydraulic maximum power PW71. The hydraulic maximum power PW71 is the maximum power (work) of the hydraulic pump 21 driven by the electric motor 77. The controller 90 calculates the sum (PW43+PW51) of the FC output command power PW43 determined in step S43, S53, or S63 and the capacitor maximum discharge power PW51 (see FIG. 4) (the total of the electric power that can be output by the fuel cell 51 and the capacitor 61). The controller 90 determines the hydraulic maximum power PW71 by subtracting the auxiliary equipment required power PW1b (see step S1 in FIG. 6) from this sum (PW43+PW51). Then, the controller 90 ends the current series of processes and starts the next series of processes (returning the process flow to the start of FIG. 6).

[0099] The controller 90 limits the load required power PW1 (see step S1 in FIG. 6) when the load required power PW1 exceeds the sum (PW43+PW51) of the power supplied to the load by the fuel cell 51 and the capacitor 61. Specifically, the controller 90 limits the load required power PW1 (see step S1 in FIG. 6) by limiting the power (work, absorption power) of the hydraulic pump 21. The controller 90 limits the power of the hydraulic pump 21 so that the power (work) of the hydraulic pump 21 does not exceed the maximum hydraulic power PW71. Specifically, the controller 90 limits the power of the hydraulic pump 21 by controlling (limiting) the capacity of the hydraulic pump 21 (for example, by performing PQ control) in accordance with the discharge pressure of the hydraulic pump 21.

[0100] (Program, Method) The power control device 40 shown in FIG. 2 is configured to perform each of the above operations. A power control program may be set to cause a controller 90 (computer) to execute processing to perform each of the above operations. A power control method may be implemented to perform each of the above operations. Each of the above operations may be considered a "step" in the program and method. For example, the calculation of the power share amount by the controller 90 may be considered a "power share calculation step."

[0101] (Effects of the first invention) The effects of the power control device 40 (work machine power control device) shown in Figure 2 are as follows. The power control device 40 includes a fuel cell 51, a fuel cell converter 53, a capacitor 61, a capacitor converter 63, an electric motor 77, and a controller 90. The fuel cell converter 53 controls the power output by the fuel cell 51. The capacitor converter 63 controls the power charged and discharged by the capacitor 61. The electric motor 77 is configured to be able to supply power from the fuel cell 51 and the capacitor 61. The electric motor 77 is used to drive the work machine 10.

[0102] [Configuration 1] The controller 90 calculates the power sharing amount between the fuel cell 51 and the capacitor 61 based on the power supplied to the electric motor 77, the actual voltage of the capacitor 61, and the limit value of the fluctuation amount of the power output by the fuel cell 51 (see steps S12 and S22 in FIG. 6). Based on the calculated power sharing amount, the controller 90 instructs the fuel cell converter 53 on the power to be output by the fuel cell 51, and instructs the capacitor converter 63 on the power to charge and discharge the capacitor 61.

[0103] In the above [Configuration 1], the controller 90 calculates the power share based on the actual voltage of the capacitor 61. Therefore, the power share of the capacitor 61 can be calculated so that the charge / discharge amount of the capacitor 61 is appropriate. As a result, deterioration of the capacitor 61 can be suppressed.

[0104] In the above [Configuration 1], the controller 90 calculates the power share based on the limit value of the fluctuation amount of the power output by the fuel cell 51 (see steps S12 and S22 in FIG. 6). This makes it possible to make the output of the fuel cell 51 an appropriate output. Specifically, it is possible to suppress deterioration of the fuel cell 51 due to excessive fluctuation in the output of the fuel cell 51.

[0105] In the above [Configuration 1], the controller 90 calculates the power share based on the power (load) supplied to the electric motor 77. Therefore, the controller 90 can calculate the power share of the capacitor 61 and the fuel cell 51 so that power is appropriately supplied from the capacitor 61 and the fuel cell 51 to the electric motor 77. As a result, it is possible to prevent a shortage of power supply to the electric motor 77 and to prevent a decrease in the output of the electric motor 77.

[0106] Therefore, the controller 90 can calculate the power sharing amount between the fuel cell 51 and the capacitor 61, which can suppress deterioration of the fuel cell 51 and the capacitor 61, and can appropriately supply power to the electric motor 77. Then, in the above [Configuration 1], the controller 90 instructs the fuel cell converter 53 on the power to be output by the fuel cell 51, and instructs the capacitor converter 63 on the power to charge and discharge the capacitor 61, based on the calculated power sharing amount. Therefore, the power control device 40 can supply power from the fuel cell 51 and the capacitor 61 to the electric motor 77 in an appropriate distribution that can suppress deterioration of the fuel cell 51 and the capacitor 61.

[0107] (Effects of the second invention) [Configuration 2] The controller 90 controls the capacitor converter 63 so that the voltage input to the motor inverter 71 that drives the motor 77 (the voltage of the high voltage DC unit 73) is kept constant.

[0108] The above [Configuration 2] suppresses fluctuations in the voltage input to the motor inverter 71. As a result, it is possible to stabilize the control of the power supplied from the fuel cell 51 and the capacitor 61 to the motor inverter 71. As a result, it is possible to stabilize the control of the motor 77.

[0109] (Effect of the third invention) [Configuration 3] The controller 90 calculates a capacitor maximum charging power PW41 (see FIG. 3), which is a limit value of the charging power of the capacitor 61, based on the actual voltage of the capacitor 61 and a capacitor upper limit voltage (see FIG. 3) preset in the controller 90. The controller 90 calculates a capacitor maximum discharging power PW51 (see FIG. 4), which is a limit value of the discharging power of the capacitor 61, based on the actual voltage of the capacitor 61 and a capacitor lower limit voltage (see FIG. 4) preset in the controller 90. The controller 90 controls the capacitor converter 63 to limit the charging and discharging power of the capacitor 61 (see steps S41 to S53 in FIG. 7), based on the calculated capacitor maximum charging power PW41 and capacitor maximum discharging power PW51.

[0110] According to the above [Configuration 3], the charging / discharging power of capacitor 61 can be limited to capacitor maximum charging power PW41 and capacitor maximum discharging power PW51 (see steps S41 to S53 in FIG. 7). This makes it possible to prevent overcharging and overdischarging of capacitor 61. This makes it possible to prevent deterioration of capacitor 61.

[0111] (Effect of the fourth invention) [Configuration 4] Controller 90 sets a voltage lower than the upper limit voltage of capacitor 61, which is preset in controller 90, as the target voltage of capacitor 61. Controller 90 controls capacitor converter 63 so that the actual voltage of capacitor 61 becomes the target voltage (see step S2 in FIGS. 5 and 6).

[0112] The above [Configuration 4] makes it possible to suppress deterioration of the capacitor 61 caused by the actual voltage of the capacitor 61 being too high (exceeding the upper limit voltage). More specifically, if the power required by the load (such as the electric motor 77) suddenly decreases while the fuel cell 51 is outputting power, the fuel cell 51 cannot suddenly reduce the output power. Therefore, the capacitor 61 needs to absorb the power output by the fuel cell 51. In such a situation, the above [Configuration 4] makes it possible to increase the likelihood that the actual voltage of the capacitor 61 will be a voltage lower than the upper limit voltage of the capacitor 61 (at or near the target voltage). Therefore, the capacitor 61 can appropriately absorb the power output by the fuel cell 51.

[0113] (Effect of the fifth invention) [Configuration 5] The controller 90 limits the charging and discharging current of the capacitor 61 based on the temperature of the capacitor 61 (see FIGS. 3, 4, and 5).

[0114] The above [Configuration 5] provides the following effects. The current that can be passed through capacitor 61 when charging or discharging capacitor 61 varies depending on the temperature of capacitor 61. Therefore, controller 90 limits the current for charging or discharging capacitor 61 based on the temperature of capacitor 61. This makes it possible to set the current that flows through capacitor 61 when charging or discharging capacitor 61 to an appropriate value. This makes it possible to suppress deterioration of capacitor 61.

[0115] (Variation) The above-described embodiments (including modified examples within the embodiments (the same applies hereinafter)) may be modified in various ways. For example, the number of components in the above-described embodiments may be changed, or some of the components may not be provided. For example, the connections between the components shown in FIG. 2 and other figures may be changed. For example, the inclusion relationships between the components may be changed in various ways. For example, a component described as a lower-level component included in a higher-level component may not be included in this higher-level component, but may be included in another component. For example, what is described as multiple different elements may be combined into a single element. For example, what is described as a single element may be provided as multiple different elements. For example, the order of the steps in the flowcharts shown in FIGS. 6 and 7 may be changed, or some of the steps may not be performed. For example, various pieces of information (values, ranges, etc.) may be set in the controller 90 in advance, or may be set by being read into the controller 90 from an external storage device of the controller 90. The various pieces of information may be set directly by manual operation by an operator, or may be set in the controller 90 based on information set by manual operation by the operator. The various pieces of information may be set in the controller 90 based on information detected by the sensor 80. For example, the various pieces of information may not be changeable, may be changeable by manual operation, or may be automatically changed by the controller 90 in response to certain conditions. For example, the controller 90 may perform substantially the same processing (calculation, determination, etc.) as the processing of the above-described embodiment. For example, the mathematical formulas, processing procedures, information used in the processing, etc. may be changed in various ways. The controller 90 may perform processing using information that can be converted into the various pieces of information used in the above-described embodiment. The processing performed by the controller 90 may be combined in various ways. For example, each component may have only a portion of its respective characteristics (function, arrangement, shape, operation, etc.). [Explanation of symbols]

[0116] 10. Work Machinery 40 Power control device (work machine power control device) 51 Fuel Cell 53 Fuel Cell Converter 61 Capacitor 63 Capacitor Converter 71 Motor inverter 77 Electric motor 90 Controller PW41 Capacitor Maximum Charging Power PW51 Capacitor Maximum Discharge Power

Claims

1. A fuel cell; a fuel cell converter that controls the power output by the fuel cell; A capacitor; a capacitor converter that controls the charging and discharging power of the capacitor; an electric motor configured to be able to receive power from the fuel cell and the capacitor and for driving a work machine; A controller; Equipped with the controller calculates the amount of power shared between the fuel cell and the capacitor based on the power supplied to the electric motor, the actual voltage of the capacitor, and a limit value of the amount of fluctuation in the power output by the fuel cell; the controller instructs the fuel cell converter on the power to be output by the fuel cell and instructs the capacitor converter on the power to be charged and discharged to the capacitor based on the calculated power allocation amount; Work machine power control device.

2. 2. The work machine power control device according to claim 1, the controller controls the capacitor converter so that a voltage input to an electric motor inverter that drives the electric motor is kept constant. Work machine power control device.

3. 2. The work machine power control device according to claim 1, the controller calculates a capacitor maximum charging power, which is a limit value of charging power of the capacitor, based on an actual voltage of the capacitor and a capacitor upper limit voltage preset in the controller; the controller calculates a capacitor maximum discharge power, which is a limit value of the discharge power of the capacitor, based on the actual voltage of the capacitor and a capacitor lower limit voltage preset in the controller; the controller controls the capacitor converter so as to limit the power of charging and discharging the capacitor based on the calculated maximum capacitor charging power and maximum capacitor discharging power. Work machine power control device.

4. 2. The work machine power control device according to claim 1, the controller sets a voltage lower than an upper limit voltage of the capacitor preset in the controller as a target voltage of the capacitor, and controls the capacitor converter so that the actual voltage of the capacitor becomes the target voltage; Work machine power control device.

5. 2. The work machine power control device according to claim 1, The controller limits the charging and discharging current of the capacitor based on the temperature of the capacitor. Work machine power control device.

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