JP2005302446A - Fuel cell power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell power supply device capable of reducing an inrush current from a fuel cell to a capacitor after starting a fuel cell system. <P>SOLUTION: This fuel cell power supply device 1 is composed by connecting the fuel cell 11 and the capacitor 12 in parallel with each other. A fuel cell connection switch 16 and a reverse connection prevention diode 17 are serially connected at a positive-side output end of the fuel cell; and a load such as a capacitor electric accessory and an inverter 2 are connected in parallel with each other on the downstream side relative to the reverse connection prevention diode 17. The positive-side terminal of the capacitor is connected to the downstream side of the reverse connection prevention diode at the positive-side output end of the fuel cell through a capacitor connection switch 18. When it is detected that the voltage of the capacitor is set lower than the open voltage of the fuel cell, the capacitor is separated, power is supplied to the load by the fuel cell, and, when the output voltage of the fuel cell is lowered and coincides with the capacitor voltage, the capacitor is connected to the fuel cell and the load. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell power supply device configured by connecting a fuel cell and a capacitor in parallel.

Conventionally, a fuel cell power supply device in which a fuel cell and a capacitor are connected in parallel is known (see Patent Document 1).
The fuel cell generates electric power by causing an electrochemical reaction between air sent to the air electrode side and hydrogen sent to the hydrogen electrode side. Therefore, when starting up the fuel cell system, a procedure such as rotating the air compressor to supply air, supplying hydrogen, and starting the circulation of water is required, and a predetermined time is required. Therefore, in order to start the fuel cell system, a so-called “startup power” is required, which is generally covered by a secondary battery such as a capacitor or a lead storage battery attached to the fuel cell power supply device. is there.

In a fuel cell vehicle equipped with a fuel cell power supply device in which a fuel cell and a capacitor are combined, when the capacitor power is consumed to start the fuel cell system, the capacitor voltage becomes the fuel cell open voltage when the fuel cell starts operating. It may be in a lower state.
When the fuel cell is connected to the capacitor in this state, an excessive inrush current is generated from the fuel cell toward the capacitor due to the potential difference between the two. The fuel cell is slow in response to sudden load fluctuations, and in such a case, the reaction gas runs short, that is, a so-called gas shortage.
If the fuel cell is out of gas, the electrolyte membrane of the fuel cell is deteriorated, resulting in deterioration of the performance of the fuel cell and shortening the life. In addition, the contact of the circuit switch may be welded due to the inrush current when the fuel cell and the capacitor are connected.

  In order to solve this problem at the time of starting the fuel cell system, a switching element is incorporated between the fuel cell and the capacitor, and the switching element is controlled from a low duty ratio to a high duty ratio by connecting the circuit by duty control, Finally, a method has been proposed in which the voltage at the connection point between the capacitor and the fuel cell is adjusted by always turning on the switching element to limit the current flowing from the fuel cell to the capacitor (see Non-Patent Document 1). .

In this method, the switching element is interposed in a current circuit in which a large current from the fuel cell to the load steadily flows, and it is necessary to increase the power capacity of the switching element. Loss occurs.
As a result, since a switching element having a large power capacity is used, there has been a problem that the cost is increased, the weight of the fuel cell power supply device is increased, and fuel consumption is reduced due to the occurrence of steady power loss.
JP 2002-305011 A Automobile Engineering Association of Japan Lecture Meeting 2003 Autumn Meeting Preprints No. 80-03, lecture number 92

  In order to solve the above-described problems, the present invention provides a fuel cell power supply device that can alleviate the inrush current from the fuel cell to the capacitor after starting the fuel cell system without using a switching element having a large power capacity. The purpose is to provide.

  For this reason, in the present invention, when it is detected that the capacitor voltage has fallen below the open voltage of the fuel cell after starting the fuel cell, the capacitor is disconnected and power is supplied to the load by the fuel cell, and the output voltage of the fuel cell decreases. When the capacitor voltage approaches, the capacitor is connected to the fuel cell and the load.

  According to the present invention, when the capacitor voltage becomes lower than the open voltage at the output end of the fuel cell as a result of power supply from the capacitor to the fuel cell auxiliary machine for starting the fuel cell, the capacitor is disconnected from the load, Since the capacitor is connected to the load when the fuel cell voltage drops and approaches the capacitor voltage due to power supply from the battery to the load, an excessive inrush current from the fuel cell to the capacitor can be prevented.

Embodiments of the present invention will be described below.
FIG. 1 is a block diagram of a power unit of an electric vehicle to which the fuel cell power supply device of the embodiment is applied.
The fuel cell power supply device 1 of the present embodiment is mounted on a vehicle and functions as a power source for driving the motor of the vehicle. The fuel cell power supply device 1 includes a fuel cell 11 that generates electric power by generating an electrochemical reaction using hydrogen and air as reaction gases, and an electric double layer capacitor 12 (hereinafter simply referred to as a capacitor 12) connected in parallel. It is a hybrid type constructed. In FIG. 1, a thick solid line indicates a current circuit for supplying a drive current.

The fuel cell 11, the reaction gas supply unit 13 for supplying hydrogen and air to the fuel cell 11, and the reaction gas supply unit 13 so that the output current of the fuel cell 11 becomes a target value (hereinafter referred to as a supply target current value). The fuel cell control unit 14 that controls the above constitutes a fuel cell system. The fuel cell 11 has a structure in which a large number of fuel cells are stacked in a stack.
As for the output power of the entire fuel cell power supply device 1, the fuel cell control unit 14 and the power control unit that inputs the supply target current value to the fuel cell control unit 14 and controls the output current from the fuel cell 11 and the capacitor 12 to open and close. 15.

In addition to the motor 3 through the inverter 2, the electric power from the fuel cell power supply device 1 is supplied to the air of the reaction gas supply unit 13, which is an electric auxiliary device, for example, an auxiliary device of the fuel cell power supply device 11 (hereinafter referred to as a power supply auxiliary device) Supplied for charging a 12V load (12V) 43 or a secondary battery (not shown) such as a lead storage battery or a lithium ion battery via a compressor unit 41, an air conditioner 42, and a DC / DC converter (not shown). .
The 12V load 43 includes a fuel cell control unit 14, a power control unit 15, a motor control unit 21 and an energy control unit 22 which will be described later. The fuel cell control unit 14, the power control unit 15, the motor control unit 21, and the energy control unit 22 are also supplied with power from the above-described secondary battery.

At the output end of the fuel cell 11, a fuel cell current sensor (IFC) 35 that detects an output current (hereinafter referred to as fuel cell current) If, a fuel cell that detects an output voltage (hereinafter referred to as fuel cell voltage) Vf. A voltage sensor (VFC) 36 is provided, and each detection signal is input to the power control unit 15.
Further, a fuel cell connection switch 16 and a reverse connection prevention diode 17 are connected in series to the positive output terminal of the fuel cell 11, and a capacitor 12, a load such as an electrical accessory, and the inverter 2 are arranged downstream of the reverse connection prevention diode 17. Are connected in parallel. The fuel cell connection switch 16 is controlled to be turned on and off by the power control unit 15.

The positive terminal of the capacitor 12 is connected via the capacitor connection switch 18 to the downstream side of the reverse connection prevention diode 17 at the positive output terminal of the fuel cell 11, that is, the load side. The capacitor connection switch 18 is controlled to be turned on and off by the power control unit 15.
The capacitor 12 includes a capacitor current sensor (Icap) 33 that detects a charging / discharging current (hereinafter referred to as a capacitor current) Ic and a capacitor voltage sensor (Vcap) 34 that detects a terminal voltage (hereinafter referred to as a capacitor voltage) Vc. The detection signals of these sensors are also input to the power control unit 15.

  A load current sensor (Iload) 38 and a load voltage sensor (Vload) 39 are provided to grasp the power consumed by the electrical auxiliary equipment other than the motor 3 to which power is supplied from the fuel cell 11 or the capacitor 12. The detection signals of these sensors are input to the power control unit 15.

Next, the structure of the energy control part 22 and the motor control part 21 which perform drive control of an electric vehicle is demonstrated.
The energy control unit 22 includes an ON signal of a key switch (not shown), an accelerator signal corresponding to the depression amount of the accelerator pedal from the accelerator sensor 23, a wheel speed signal from the vehicle speed sensor 24, and a brake signal from the brake sensor 26. Is entered. When the key switch is turned on from off, a fuel cell activation signal is output from the energy control unit 22 to the power control unit 15.
Further, the energy control unit 22 can supply power from the power control unit 15 to the inverter 2 by both the fuel cell 11 and the capacitor 12 in accordance with the connection state of the fuel cell connection switch 16 and the capacitor connection switch 18. A level signal is input.

The energy control unit 22 outputs a torque command to the motor control unit 21 according to the accelerator signal so that the power level that can be supplied to the inverter 2 is not exceeded. The motor control unit 21 controls the inverter 2 so that the motor 3 generates torque according to the input torque command.
Further, the motor control unit 21 calculates the required power required by the inverter 2 based on the rotation speed of the motor 3 and the voltage applied to the armature of the motor 3 and the current flowing through the armature via the inverter 2. Then, a signal indicating the required power level of the inverter 2 is sent to the energy control unit 22.
The inverter 2 detects an electrical angle of a rotor (not shown) of the motor 3 by the angle sensor 25, outputs a three-phase AC voltage corresponding to the electrical angle to an armature (not shown) of the motor 3, and flows to the armature of the motor 3. Control the current. At this time, the inverter 2 controls the current flowing through the armature of the motor 3 by vector control that controls the q-axis current and the d-axis current independently and at high speed.
The driving force of the motor 3 is transmitted to driving wheels via a transmission (not shown).

  FIG. 2 is a diagram showing the structure of the capacitor 12. The capacitor 12 includes capacitor modules 31a and 31b and series-parallel changeover switches 32A and 32B. The series-parallel change-over switches 32A and 32B are controlled by the power control unit 15 and can be switched between the parallel state (a) and the series state (b). The capacitor modules 31a and 31b are configured by collecting a large number of capacitor cells (not shown) and connecting the electrode terminals of the capacitor cells in parallel or in series so as to meet the required specifications.

Next, a configuration of the reaction gas supply unit 13 and an outline of control of the reaction gas supply unit 13 and the fuel cell 11 by the fuel cell control unit 14 will be described (see Patent Document 1).
The reactive gas supply unit 13 includes an air compressor unit 41 for supplying a desired amount of air to the air electrode, and a hydrogen tank (not shown) that supplies a required amount of hydrogen in proportion to the amount of air supplied to the air electrode. Consists of equipment.

A target supply current value is input from the power control unit 15 to the fuel cell control unit 14, and an air compressor unit 41 that supplies air to the air electrode of the fuel cell 11 so that the target supply current value is obtained. Outputs the rotation speed command value.
The air compressor unit 41 supplies air at a flow rate corresponding to the target supply current value to the air electrode of the fuel cell 11. At this time, the reaction gas supply unit 13 supplies hydrogen from the hydrogen tank to the hydrogen electrode of the fuel cell 11 in accordance with the supply amount of air.

A signal such as pressure and amount of air supplied to the air electrode of the fuel cell 11 and a signal such as pressure and amount of hydrogen supplied to the hydrogen electrode of the fuel cell 11 are sent from the reaction gas supply unit 13 to the fuel cell control unit. 14 is input. Further, the state signal of each fuel cell of the fuel cell 11 is input to the fuel cell control unit 14.
The fuel cell control unit 14 determines the upper limit value of the current that can be supplied from the fuel cell 11 in consideration of the state of the fuel cell 11 grasped from these signals.
The obtained upper limit value of the current that can be supplied from the fuel cell 11 is output to the power control unit 15, and further output to the energy control unit 22 via the power control unit 15.

Next, the function of the power control unit 15 will be described.
The power control unit 15 grasps the power consumed by the electrical auxiliary equipment other than the motor 3 based on detection signals from the load current sensor (Iload) 38 and the load voltage sensor (Vload) 39.
The power control unit 15 detects the upper limit value of the current that can be supplied from the fuel cell 11 output from the fuel cell control unit 14 and the capacitor voltage Vc. The target supply current value of the fuel cell 11 is determined according to the total power with the power consumed by the electrical accessory, and a signal indicating the target supply current value is output to the fuel cell control unit 14.

In addition, the power control unit 15 generates fuel based on the fuel cell voltage Vf of the fuel cell 11 and the upper limit value of the current that can be supplied from the fuel cell 11, the signal of the power level consumed by the electrical accessory, and the capacitor voltage Vc. A signal of a power level that can be supplied to the inverter 2 by the battery 11 and the capacitor 12 is output to the energy control unit 22.
The power control unit 15 controls ON / OFF of the fuel cell connection switch 16 and the capacitor connection switch 18, supplies power to the load from the fuel cell power supply device 1 or the capacitor 12, and charges the capacitor 12 with regenerative current from the motor 3. Control.
Furthermore, the power control unit 15 switches and controls the series connection and the parallel connection of the capacitor modules 31a and 31b when the capacitor 12 is connected to the load in accordance with the charge / discharge state of the capacitor 12 after the fuel cell 11 is started.

The series / parallel switching control of the fuel cell connection switch 16, the capacitor connection switch 18, and the serial parallel switching switches 32A and 32B will be described based on the flowcharts of FIGS.
This control is processed as a program in the energy control unit 22 and the power control unit 15.

In step 101, by turning on the key switch, the fuel cell control unit 14, the power control unit 15, the motor control unit 21, and the energy control unit 22 are turned on, and the energy control unit 22 sends the fuel cell activation signal to the power control unit 15. Output to.
In step 102, the power control unit 15 puts the capacitor modules 31a and 31b in a parallel connection state as shown in FIG.
Thereafter, in step 103, the power control unit 15 turns on the capacitor connection switch 18. Thereby, the electric power charged in the capacitor 12 can be supplied to a power supply auxiliary machine such as the air compressor unit 41 of the reaction gas supply unit 13.

In step 104, the fuel cell control unit 14 activates the power auxiliary device in response to the fuel cell activation signal from the power control unit 15. Thereby, in step 105, the fuel cell 11 is started.
In step 106, the power control unit 15 checks whether or not the fuel cell 11 has been started.
When the detection signal of the fuel cell voltage sensor 36 is equal to or greater than a predetermined value and the upper limit value of the current that can be supplied from the fuel cell 11 from the fuel cell control unit 14 is equal to or greater than a predetermined level, the power control unit 15 If it is determined that the activation has been completed, step 106 is repeated.

In step 107, the power control unit 15 checks whether the capacitor voltage Vc is equal to or higher than the open circuit voltage Vf 0 of the fuel cell 11. If the capacitor voltage Vc is equal to or higher than the open circuit voltage Vf0 of the fuel cell 11, the process proceeds to step 108, and if not, the process proceeds to step 111.
In step 108, the power control unit 15 turns on the fuel cell connection switch 16, proceeds to step 109, and outputs a vehicle travel permission signal to the energy control unit 22.

After step 109, the process proceeds to step 110 to enter the normal control state.
In the normal control state, the capacitor 12 and the fuel cell 11 are in parallel, and are connected to the inverter 2 and the power supply auxiliary machine, the air conditioner 42, and the 12V load 43. When the capacitor voltage Vc is higher than the fuel cell voltage Vf, the capacitor 12 Is prevented from flowing back into the fuel cell 11 by the reverse connection prevention diode 17, and power is supplied from the capacitor 12 to the load. If the fuel cell voltage Vf is higher, the capacitor 12 is automatically charged to the fuel cell voltage Vf.

  Further, the energy control unit 22 determines the acceleration state, coast state, and deceleration state of the vehicle based on the accelerator signal, the wheel speed signal, and the brake signal, and determines each vehicle state, accelerator signal, wheel speed signal, and power control. A torque command is issued to the motor control unit 21 based on the signal of the power level that can be supplied from the unit 15 to the inverter 2 and the upper limit value of the current that can be supplied from the fuel cell 11.

The motor control unit 21 sends a signal of the required power level of the inverter 2 according to the torque command back to the energy control unit 22, and the energy control unit 22 transfers the signal of the required power level of the inverter 2 to the power control unit 15. The output current from the fuel cell 11 is controlled via the control unit 15 and the fuel cell control unit 14.
In particular, during deceleration, the energy control unit 22 performs regenerative power generation control of the inverter 2 via the motor control unit 21 in order to charge the capacitor 12 by regenerative power generation of the motor 3.

When the process proceeds from step 107 to step 111, the power control unit 15 turns off the capacitor connection switch 18.
In step 112, the power control unit 15 checks whether or not the capacitor voltage Vc is higher than the half-value voltage Vf1 of the open circuit voltage Vf0 of the fuel cell 11. If it is higher, the process proceeds to Step 113, and if it is the following, the process proceeds to Step 201.
In step 113, the power control unit 15 turns on the fuel cell connection switch 16, and outputs a vehicle travel permission signal to the energy control unit 22 in step 114.

In response to this, the energy control unit 22 issues a torque command to the motor control unit 21 in accordance with the accelerator signal and the signal of the power level that can be supplied to the inverter 2 from the power control unit 15. A signal of the required power level of the inverter 2 is output to the power control unit 15. The power control unit 15 instructs the fuel cell control unit 14 to supply a target current value so as to supply all the required power of the inverter 2 and the power consumption of the electrical auxiliary equipment from the fuel cell 11, and the fuel control unit 14 supplies the reaction gas. The unit 13 is controlled.
In step 115, the power control unit 15 checks whether or not the fuel cell 11 has started supplying power and the fuel cell voltage Vf has decreased to be equal to the capacitor voltage Vc.

FIG. 6 is an output current-voltage characteristic diagram of the fuel cell in which the vertical axis indicates the fuel cell voltage Vf and the horizontal axis indicates the fuel cell current If.
Thus, when the fuel cell 11 having the open circuit voltage Vf0 is connected to the load and the fuel cell current If increases, the fuel cell voltage Vf decreases. Note that, when the supply current increases, for example, when the fuel cell vehicle is accelerated, the fuel cell voltage Vf drops to near the half value Vf1 of the open circuit voltage Vf0, which frequently occurs.
When the fuel cell voltage Vf becomes the same as the capacitor voltage Vc, the routine proceeds to step 116, otherwise proceeds to step 117.
In step 116, the power control unit 15 turns on the capacitor connection switch 18, proceeds to step 110, and enters the normal control state of the fuel cell power supply device 1.

In step 117, the energy control unit 22 checks whether the acceleration state continues. When the acceleration continues, the process returns to step 115 and waits for the fuel cell voltage Vf to decrease.
If the acceleration is completed before the fuel cell voltage Vf reaches the capacitor voltage Vc following the acceleration, the process proceeds to step 118, where the energy control unit 22 instructs the motor control unit 21 to increase the d-axis current, and the step Return to 115.

By the inverter control for increasing the d-axis current, the motor control unit 21 increases the Id current calculated from the Id-Iq map corresponding to the motor rotation speed-torque characteristic, and the inverter 2 does not increase the motor torque so much. Therefore, the fuel cell voltage Vf further decreases.
Since the increase in Id current slightly affects the motor torque, the Iq current is corrected together.
As a result, while repeating steps 115, 117, and 118, the fuel cell voltage Vf becomes the same as the capacitor voltage Vc, the process proceeds to step 116, the capacitor connection switch 18 is turned on, and the normal control state of step 110 is entered.

When the process proceeds from step 112 to step 201, the power control unit 15 switches the capacitor modules 31a and 31b in series.
As a result, even when the capacitor voltage Vc is equal to or less than the half value Vf1 of the open voltage of the fuel cell in the case of parallel connection, it becomes higher than the half value Vf1 due to the series connection.

In step 202, the power control unit 15 turns on the fuel cell connection switch 16, and then outputs a vehicle travel permission signal to the energy control unit 22 in step 203.
In response to this, the energy control unit 22 issues a torque command to the motor control unit 21 in accordance with the accelerator signal and the signal of the power level that can be supplied to the inverter 2 from the power control unit 15. The required power signal is output to the power control unit 15. The power control unit 15 instructs the fuel cell control unit 14 to supply a target current value so that all required power is supplied from the fuel cell 11, and the fuel control unit 14 controls the reaction gas supply unit 13.
The fuel cell voltage Vf decreases from the open circuit voltage Vf0 as shown in FIG.

In step 204, the power control unit 15 starts supplying power to the fuel cell 11, the fuel cell voltage Vf decreases, and the capacitor modules 31a and 31b become the same as the capacitor voltage Vc of the capacitor 12 in the serial connection state. Check whether or not When it becomes the same voltage as the capacitor voltage Vc, the routine proceeds to step 205, and otherwise, step 204 is repeated.
In step 205, the power control unit 15 turns on the capacitor connection switch 18.
Thereafter, when the driver loosens the accelerator, the vehicle enters a coasting state, and the capacitor 12 is charged by the current from the fuel cell 11.

In the coast state, the energy control unit 22 instructs the power control unit 15 and the motor control unit 21 to perform coast state power control, the required power of the inverter 2 becomes almost zero, and the fuel cell current If charges the capacitor 12. When the capacitor 12 is charged, the capacitor voltage Vc increases and the fuel cell current If, that is, the capacitor current Ic decreases.
When the capacitor current Ic, which is the charging current to the capacitor 12, becomes zero, the fuel cell voltage Vf becomes a value close to the open circuit voltage Vf0, and the capacitor 12 is charged to close to the open circuit voltage Vf0 when the capacitor modules 31a and 31b are in series. Is done.

In step 206, the energy control unit 22 checks whether the vehicle is in a coasting state based on the accelerator signal, the brake signal, and the wheel speed signal, and the power control unit 15 checks whether the capacitor current Ic is zero.
If the capacitor current Ic is zero in the coast state, the process proceeds to step 207, and if not, step 206 is repeated.

In step 207, the power control unit 15 turns off the capacitor connection switch 18, and in step 208, the capacitor modules 31a and 31b are changed from the series state shown in FIG. 2B to the parallel state shown in FIG. Switch.
The capacitor voltage Vc immediately after switching to the parallel state becomes a value near the half value Vf1 of the open circuit voltage of the fuel cell 11.
In step 209, the energy control unit 22 determines whether acceleration or deceleration of the vehicle is detected or not from the accelerator signal, the brake signal, and the wheel speed signal.
If acceleration is detected, the process proceeds to step 210. If deceleration is detected, the process proceeds to step 231. If none of them is detected, step 209 is repeated.

In step 210, the power control unit 15 receives the acceleration determination from the energy control unit 22, monitors the fuel cell voltage Vf as the fuel cell current If increases, and the fuel cell voltage Vf becomes the capacitor voltage Vc. Check if they are the same. When both voltages become the same, the process proceeds to step 116, and when not, the process proceeds to step 211.
In step 211, the energy control unit 22 checks whether the acceleration state continues. When the acceleration continues, the process returns to step 210 and waits for the fuel cell voltage Vf to decrease.
If the acceleration is completed before the fuel cell voltage Vf reaches the capacitor voltage Vc following the acceleration, the process proceeds to step 212, and the energy control unit 22 instructs the motor control unit 21 to control the d-axis current increase. Return to step 210.

  While step 210 to step 212 are repeated, the fuel cell voltage Vf becomes the same as the capacitor voltage Vc, the process proceeds to step 116, the capacitor connection switch 18 is turned on, and the normal control state of step 110 is entered.

If it is determined in step 209 that the vehicle is decelerating and the process proceeds to step 231, the energy control unit 22 issues a regenerative power generation control command to the power control unit 15 and the motor control unit 21.
In step 231, the power control unit 15 receives the regenerative power generation control command, turns off the fuel cell connection switch 16, and then turns on the capacitor connection switch 18 in step 232.
In step 233, the motor control unit 21 performs regenerative power generation control of the inverter 2, and the regenerative current from the inverter 2 is charged in the capacitor 12.

In step 234, the power control unit 15 monitors whether the capacitor 12 is charged and the capacitor voltage Vc rises, and checks whether or not the open voltage Vf0 of the fuel cell 11 has been reached. When the capacitor voltage Vc becomes the same as the open circuit voltage Vf0, the process proceeds to step 235, and when not, the process proceeds to step 236.
In step 235, the power control unit 15 turns on the fuel cell connection switch 16, proceeds to step 110, and enters the normal control state.
In step 236, the energy control unit 22 checks whether deceleration continues. If the deceleration continues, the process returns to step 234, and if the deceleration ends before the capacitor voltage Vc reaches the open circuit voltage Vf0 of the fuel cell 11 after the deceleration continues, the regenerative power generation control is terminated and the process returns to step 237. move on.

In step 237, the power control unit 15 turns off the capacitor connection switch 18, and then turns on the fuel cell connection switch 16 in step 238.
After step 238, the process returns to step 209, where the fuel cell voltage Vf is decreased by the acceleration, until the fuel cell voltage Vf and the capacitor voltage Vc become the same, or the capacitor voltage Vc accompanying the charging of the capacitor 12 by regenerative power generation during deceleration. Is repeated until the open circuit voltage Vf0 of the fuel cell 11 becomes equal to the capacitor voltage Vc.

Hereinafter, the flow in the case where the fuel cell 11 is activated by the power supply from the capacitor 12 and the capacitor voltage Vc is equal to or less than the half value Vf1 of the open voltage Vf0 of the fuel cell at that time (steps 101 to 107, then steps 111 and 112). 201-212 and finally step 116), the behavior of the voltage and current of the fuel cell 11 and capacitor 12 will be described with reference to FIG.
In FIG. 7A, the horizontal axis shows the control time lapse, the vertical axis shows the change in the capacitor current and the fuel cell current, and FIG. Changes in capacitor voltage and fuel cell voltage are shown.

  In order to start the fuel cell 11 at time t0, the power supply auxiliary device is started with the power supplied from the capacitor 12, and the fuel cell 11 is brought into an operating state (steps 101 to 106). The capacitor current Ic flows as shown in FIG. 7A, and the capacitor voltage Vc decreases as shown in FIG. 7B.

Between times t1 and t2, the process proceeds to steps 111, 112, 201, and 202 based on the determination in step 107. That is, in step 111, the capacitor connection switch 18 is turned off, and in step 201, the capacitor modules 31a and 31b are switched from the parallel connection state to the series connection state.
When the capacitor modules 31a and 31b are connected in parallel, the capacitor voltage Vc that is lower than the half value Vf1 of the fuel cell open circuit voltage Vf0 exceeds the half value Vf1 by switching to the series connection state.

In step 202, the fuel cell connection switch 16 is turned on and connected to the load.
At time t2, the vehicle travel is permitted, the energy control unit 22 detects the driver's accelerator depression, calculates a predetermined torque command value, the motor control unit 21 operates the inverter 2 in accordance with the torque command value, and the motor 3 is supplied with current.
As shown in FIG. 7A, the fuel cell current If increases in accordance with the current supply to the motor 3, and as shown in FIG. 7B, the fuel cell voltage Vf decreases from the open circuit voltage Vf0. As shown in the output current-voltage characteristic of the fuel cell in FIG. 6, the fuel cell voltage Vf decreases to near the half value Vf1 of the open circuit voltage.
The power control unit 15 monitors the fuel cell voltage Vf, turns on the capacitor connection switch 18 and connects the capacitor 12 to the load at time t3 coincident with the capacitor voltage Vc (steps 204 and 205).

The capacitor 12 connected to the load begins to supply current to the load. When the driver relaxes the accelerator at time t4, the energy control unit 22 detects this, sets the torque command value to zero, and outputs it to the motor control unit 21. Transition to a so-called coast state.
The fuel cell current If is charged in the capacitor 12. As shown in FIG. 7A, the capacitor current Ic is a negative value indicating charging.
The fuel cell voltage Vf rises to the open circuit voltage Vf0, and the capacitor voltage Vc rises to approximately Vf0 accordingly.
At time t5 when the energy control unit 22 determines that the coasting state is established and the power control unit 15 determines that the capacitor current Ic is zero, the capacitor connection switch 18 is turned off and disconnected from the load (steps 206 and 207).

Thereafter, the capacitor modules 31a and 31b are switched to the parallel connection state (step 208). As a result, the capacitor voltage becomes approximately the half value Vf1 of the fuel cell open circuit voltage as shown in FIG.
When the driver depresses the accelerator pedal again at time t6, current is supplied from the fuel cell 11 to the motor 3, and the fuel cell voltage Vf decreases. Here, when the acceleration ends at time t7 before the fuel cell voltage Vf decreases to coincide with the capacitor voltage Vc (when the process proceeds from step 211 to step 212), the energy control unit 22 sends the motor control unit 21 A control command for increasing the d-axis current is issued, the consumption current of the inverter 2 is increased, and the fuel cell voltage Vf is controlled to further decrease as shown in FIG.

The power control unit 15 monitors the fuel cell voltage Vf, and when it coincides with the capacitor voltage Vc (in this case, the half value Vf1 of the open circuit voltage), it turns on the capacitor connection switch 18 (step 116) and returns to the normal control state.
In this flowchart, steps 206 and 207 are simplified for the sake of simplicity. The capacitor 12 in which the capacitor modules 31a and 31b are in series in the initial coast state is opened by the current from the fuel cell 11. Although it is assumed that the battery is charged up to near the voltage Vf0, if the battery is not charged up to near the open circuit voltage Vf0, acceleration and deceleration are repeated again with the capacitor 12 in the series state, and the torque command from the energy control unit 22 is zero and the capacitor current is zero. When zero, capacitor 12 is disconnected from the load, switching capacitor modules 31a, 31b to a parallel state.

  In the flowchart of the present embodiment, steps 107, 112, 206, and 234 are charging / discharging state detection means of the present invention, steps 115, 204, and 210 are fuel cell voltage detection means, and steps 118 and 212 are d-axis current control means. Configure.

As described above, according to the present embodiment, in a fuel cell power supply apparatus in which a capacitor is connected to a load in parallel with a fuel cell, when the starting power of the fuel cell is covered by the power charged in the capacitor, the fuel cell of the current circuit 11 is connected to the positive side terminal of the capacitor 12 via the capacitor connection switch 18 on the load side of the reverse connection prevention diode 17 provided at the positive side output terminal of the fuel cell 11 and connected to the fuel cell between the fuel cell output terminal and the reverse connection prevention diode 17. Since the switch 16 is arranged, the capacitor connection switch is turned on before the fuel cell connection switch 16 is turned on even when the capacitor voltage Vc is lower than the open circuit voltage Vf0 of the fuel cell 11 when the fuel cell 11 is completely started. 18 can be turned off and current can be supplied from the fuel cell 11 to the load.
Therefore, immediately after the fuel cell 11 is connected to the load, an excessive inrush current from the fuel cell 11 to the capacitor 12 occurs, the switch contact of the current circuit melts, or the performance of the electrolyte membrane of the fuel cell 11 deteriorates. There is no.

  Further, the power control unit 15 monitors the output voltage Vf and the capacitor voltage Vc of the fuel cell 11 by the fuel cell voltage sensor 36 and the capacitor voltage sensor 34, and the current from the fuel cell 11 to the load is disconnected with the capacitor 12 disconnected from the load. When the fuel cell voltage Vf decreases in accordance with the supply and coincides with the capacitor voltage Vc, the capacitor connection switch 18 is turned on, and the fuel cell 11 and the capacitor 12 are both connected to the load. Generation of inrush current from the battery 11 to the capacitor 12 is prevented.

  In particular, at the time after the completion of the start-up of the fuel cell 11 as described above, the capacitor voltage Vc is lower than the open-circuit voltage Vf0 of the fuel cell 11, and the travel start power of the fuel cell vehicle is supplied only from the fuel cell 11, so If the fuel cell voltage Vf does not drop to the capacitor voltage Vc at the first acceleration, the motor control unit 21 controls the inverter 2 to increase the d-axis current, thereby increasing the power consumption of the inverter 2 and the fuel cell voltage Vf. Therefore, the capacitor 12 can be connected to the load in the acceleration operation process for a short time after the vehicle starts to travel.

  If the capacitor voltage Vc is equal to or less than the half value Vf1 of the fuel cell open voltage when the fuel cell 11 is started, the capacitor 12 is disconnected and the capacitor modules 31a and 31b are switched from the parallel connection state to the series connection state, and the capacitor voltage Vf is changed. Since the value is increased by a factor of 2 to the half value Vf1 or more, the capacitor 12 can be easily connected in parallel to the load and the fuel cell when the fuel cell voltage Vf decreases due to the output characteristics of the fuel cell 11.

  Further, when the vehicle is in a coast driving state and the capacitor current Ic is zero, the capacitor 12 is disconnected, the capacitor modules 31a and 31b are switched from the series connection state to the parallel connection state, and the fuel cell voltage Vf during acceleration thereafter is Since the capacitor 12 is connected to the load and the fuel cell 11 when the capacitor voltage Vc rises to the open-circuit voltage Vf0 of the fuel cell 11 due to the reduction to the capacitor voltage Vc or the charging due to regenerative power generation to the capacitor 12 during deceleration, Finally, the capacitor modules 31a and 31b can return to the normal parallel connection control state of the fuel cell 11 and the capacitor 12 in the state of the capacitor 12 in the normal parallel connection state.

As described above, when the power of the capacitor 12 is used for starting the fuel cell 11 and the capacitor voltage Vc becomes lower than the open-circuit voltage Vf0 at the completion of starting the fuel cell 11, the fuel cell 11 is used as a load. Instead of providing a large-capacity switching element on the output end side of the conventional fuel cell 11 in order to suppress an excessive inrush current to the capacitor 12 when connected, the fuel control switch 15 and the capacitor connection switch 18 are provided by the power control unit 15. Therefore, general-purpose relay switches can be used for these switches.
As a result, there is no increase in cost and weight of the fuel cell power supply device due to the large capacity switching element, and no steady power loss due to the switching element.

In steps 115, 204, 210, and 234 in the flowchart of the present embodiment, it is assumed that the capacitor voltage Vc and the fuel cell voltage Vf or the open voltage Vf0 of the fuel cell 11 coincide with each other. It is also possible to enter the range.
Furthermore, in the present embodiment, the power control unit 15 and the energy control unit 22 are separate, but a single microcomputer may be used.

In this embodiment, when the capacitor voltage Vc after activation of the fuel cell 11 is less than the open-circuit voltage Vf0 of the fuel cell 11 and is equal to or greater than the half-value Vf1 of the open-circuit voltage, the capacitor modules 31a and 31b remain in a parallel connection state. Waiting for the battery voltage Vf to drop to the capacitor voltage Vc, the capacitor 12 is connected to the load and the fuel cell 11, but the capacitor modules 31a and 31b are switched to the series connection state, and the capacitor voltage Vc is set to the open voltage. The capacitor 12 may be connected to the load and the fuel cell 11 by making it larger than Vf0.
In this case, the output current from the capacitor 12 can be used for acceleration at the start of vehicle travel.

  Thereafter, when the capacitor current Ic is zero in the vehicle coast state, the capacitor 12 is disconnected, the capacitor modules 31a and 31b are switched to the parallel state, and the fuel cell voltage Vf during the subsequent vehicle acceleration is reduced to the capacitor voltage Vc. Alternatively, when the capacitor voltage Vc increases to the open circuit voltage Vf0 due to charging of the capacitor 12 by regenerative power generation during deceleration, the capacitor 12 and the fuel cell 12 are simultaneously connected to the load in parallel.

  Further, when the capacitor voltage Vc after starting of the fuel cell 11 is less than the open circuit voltage Vf0 of the fuel cell 11 and is equal to or greater than the half value Vf1 of the open circuit voltage, the fuel cell voltage Vf is reduced to the capacitor voltage Vc at the first acceleration in step 115. If not, instead of causing the motor control unit 21 to control the d-axis current increase to decrease the fuel cell voltage Vf by one more step, the capacitor voltage is increased by charging the capacitor 12 by regenerative power generation during subsequent deceleration. The fuel cell voltage Vf during acceleration is monitored to decrease, and when the capacitor voltage Vc increases to the open circuit voltage Vf0 or when the fuel cell voltage Vf decreases to the capacitor voltage Vc, the capacitor 12 and the fuel cell 12 are simultaneously parallel to the load. It may be in a connected state.

It is a figure which shows the structure of embodiment of this invention. It is a figure which shows the connection state of a capacitor module. It is a flowchart which shows the flow of the connection control to the load of a capacitor and a fuel cell. It is a flowchart which shows the flow of the connection control to the load of a capacitor and a fuel cell. It is a flowchart which shows the flow of the connection control to the load of a capacitor and a fuel cell. It is a figure which shows the output current-voltage characteristic of a fuel cell. It is a figure explaining the reconnection after a capacitor overdischarge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell power supply device 2 Inverter 3 Motor 11 Fuel cell 12 Electric double layer capacitor 13 Reaction gas supply part 14 Fuel cell control part 15 Power control part 16 Fuel cell connection switch 17 Reverse connection prevention diode 18 Capacitor connection switch 21 Motor control part 22 Energy Control unit 23 Accelerator sensor 24 Vehicle speed sensor 25 Angle sensor 26 Brake sensor 31a, 31b Capacitor module 32A, 32B Series parallel switch 33 Capacitor current sensor 34 Capacitor voltage sensor 35 Fuel cell current sensor 36 Fuel cell voltage sensor 38 Load current sensor 39 Load voltage sensor 41 Air compressor section 42 Air conditioner 43 12V load

Claims (7)

A fuel cell, a capacitor connected in parallel to the fuel cell to a load by a current circuit, a reaction gas supply unit for supplying a reaction gas to the fuel cell, and the reaction gas supply unit from the reaction gas supply unit based on a target supply power signal A fuel cell control unit that controls a supply amount of a reaction gas supplied to the fuel cell; a power control unit that outputs the target supply power signal to the fuel cell control unit in accordance with a required power of the load; and a current circuit A reverse connection prevention diode inserted and disposed to prevent a reverse flow of current from the capacitor to the fuel cell, wherein the capacitor is a fuel cell power supply that supplies start-up power of the fuel cell;
One terminal side of the capacitor is connected to the load side of the reverse connection prevention diode via a capacitor connection switch,
The power control unit includes charge / discharge state detection means for detecting a charge / discharge state of the capacitor, and fuel cell voltage detection means for detecting an output voltage of the fuel cell,
When the charging / discharging state detecting means detects that the voltage of the capacitor is lower than the open voltage of the fuel cell after the fuel cell is started, the capacitor connection switch is turned off, and the fuel cell is used for driving a load vehicle An electric power is supplied to the motor, and when the output voltage of the fuel cell decreases and approaches the voltage of the capacitor, the capacitor connection switch is turned on. The motor for driving the vehicle is driven by an inverter controlled by receiving a torque command from a motor control unit,
In addition to the normal motor torque control, the motor control unit includes d-axis current control means for performing control to consume more field current while matching the output torque of the motor with a torque command.
The power control unit
When the charging / discharging state detecting means detects that the voltage of the capacitor is lower than the open voltage of the fuel cell after the fuel cell is started, the capacitor connection switch is turned off, and the fuel cell is used for driving a load vehicle Power to the motor
2. The d-axis current control means of the motor control unit lowers the output voltage of the fuel cell to a desired value as necessary, and the capacitor connection switch is turned on when approaching the voltage of the capacitor. The fuel cell power supply device described in 1. The current circuit includes a fuel cell connection switch between the reverse connection prevention diode and the fuel cell,
The power control unit
When the charge / discharge state detection means detects that the voltage of the capacitor is lower than the open voltage of the fuel cell after the fuel cell is started, the motor for driving the vehicle of the load is driven by the fuel cell,
During regenerative power generation, the fuel cell connection switch is turned off and the capacitor connection switch is turned on, the capacitor is charged by regenerative power generation, and the capacitor connection switch is turned on when the capacitor voltage approaches the open voltage of the fuel cell. The fuel cell power supply device according to claim 1 or 2, wherein The capacitor comprises a plurality of capacitors configured to be switchable between series connection and parallel connection,
When the charge / discharge state detection means detects that the voltage of the capacitor in the parallel connection state of the plurality of capacitors has fallen below the open voltage of the fuel cell after the fuel cell is started, the power control unit 4. The fuel cell power supply device according to claim 1, wherein the plurality of capacitors are switched to a serial connection state when the capacitor connection switch is in an off state, and then the capacitor connection switch is turned on. 5. In the series connection state of the plurality of capacitors, when the capacitor and the fuel cell are electrically connected in parallel to the load,
When the charging / discharging state detection means detects a zero state of the capacitor current, the power control unit turns off the capacitor connection switch, switches the plurality of capacitors to a parallel connection state,
When the voltage of the capacitor is higher than the open voltage of the fuel cell, turn on the capacitor connection switch,
When the voltage of the capacitor is lower than the open voltage of the fuel cell, power is supplied to the load by the fuel cell, and when the output voltage of the fuel cell decreases and approaches the voltage of the capacitor, the capacitor connection switch The fuel cell power supply device according to claim 4, wherein the fuel cell power supply device is turned on. In the series connection state of the plurality of capacitors, when the capacitor and the fuel cell are electrically connected in parallel to the load,
When the charging / discharging state detection means detects a zero state of the capacitor current, the power control unit turns off the capacitor connection switch, switches the plurality of capacitors to a parallel connection state,
When the voltage of the capacitor is higher than the open voltage of the fuel cell, turn on the capacitor connection switch,
When the voltage of the capacitor is lower than the open voltage of the fuel cell, the motor for driving the vehicle of the load is driven by the fuel cell,
During regenerative power generation, the fuel cell connection switch is turned off and the capacitor connection switch is turned on, the capacitor is charged by regenerative power generation, and the capacitor connection switch is turned on when the capacitor voltage approaches the open voltage of the fuel cell. The fuel cell power supply device according to claim 4, wherein A fuel cell, a capacitor connected in parallel to the fuel cell to a load by a current circuit, a reaction gas supply unit for supplying a reaction gas to the fuel cell, and the reaction gas supply unit from the reaction gas supply unit based on a target supply power signal A fuel cell control unit that controls a supply amount of a reaction gas supplied to the fuel cell; a power control unit that outputs the target supply power signal to the fuel cell control unit in accordance with a required power of the load; and a current circuit A reverse connection prevention diode inserted and arranged to prevent a reverse flow of current from the capacitor to the fuel cell, and the capacitor is a capacitor of a fuel cell power supply device that supplies startup power required for startup of the fuel cell A connection control method,
When it is detected that the capacitor voltage of the capacitor is lower than the open voltage of the fuel cell after the fuel cell is started, the capacitor is disconnected, and the fuel cell supplies power to the load, and the output voltage of the fuel cell A capacitor connection control method for a fuel cell power supply apparatus, comprising: connecting the capacitor to a fuel cell and a load when the voltage drops and approaches a capacitor voltage.

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