JP2009163947A - Fuel cell system, and power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system or the like capable of boosting a voltage to a step-up ratio higher than an existing fuel cell system. <P>SOLUTION: The fuel cell system is provided with a fuel cell and a soft switching converter of pulse width modulation type for boosting the output voltage of the fuel cell. When the step-up ratio required is higher than a prescribed value ("second threshold"), a system or the like is provided that can change the control period of the soft switching converter to one longer than a normal one ("special control period"). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system for supplying power to a power consuming device and a power supply device for boosting a voltage input from the fuel cell or the like.

  As is well known, as a DC-DC converter capable of controlling the transformation ratio (buck-boost ratio), a type that controls the transformation ratio by changing the switching frequency (the reciprocal of the control time for one cycle) (for example, Patent Documents 1 to 4) and a type that controls the transformation ratio by changing the ON time of the switch element (for example, refer to Patent Document 5) exist.

JP 2005-304289 A Japanese Patent Laid-Open No. 2001-190062 JP-A-7-123718 JP-A-11-289759 JP 2004-96827 A

  The type of DC-DC converter that controls the transformation ratio by changing the ON time of the switch element (hereinafter referred to as a pulse width modulation type converter) can change the switching frequency in terms of the circuit configuration. It is. However, with respect to the pulse width modulation system converter, “to reduce the ripple of the input current, the switching frequency is corrected based on the temperature of the pulse width modulation system converter (switching power supply)” (see Patent Document 5). It is the current situation that is not done.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel cell system and a power supply apparatus including a pulse width modulation type soft switching converter (pulse width modulation type converter capable of soft switching), and a soft switching converter (pulse width modulation type converter). ) To provide a fuel cell system and a power supply device that can control (change) the switching frequency to improve performance more directly.

  In order to solve the above-described problems, a fuel cell system for supplying power to a power consuming apparatus that operates by consuming electric power according to the present invention includes a fuel cell and a pulse for boosting the output voltage of the fuel cell. A width-modulation type soft switching converter and a control unit for controlling the transformation ratio of the soft switching converter, the control unit changing the control cycle of the soft switching converter according to the target transformation ratio.

In other words, the pulse width modulation type soft switching converter has a circuit configuration that realizes a process for realizing soft switching (a process for setting the applied voltage or conduction current of the switch element to 0 V or 0 A; a process for soft switching). Is a converter that takes a certain amount of time (a converter in which the upper limit of the step-up ratio is determined by the time required for the soft switching process). In addition, the pulse width modulation type soft switching converter is a converter that cannot realize soft switching if the step-up ratio is low due to its circuit configuration. However, the fuel cell system of the present invention has such a pulse width modulation type. Soft switching converter control cycle (carrier cycle, reciprocal of switching frequency)
Is changed according to a target (necessary) transformation ratio.

  And, as a control unit, for example, if the control unit of the soft switching converter is made longer when the target transformation ratio is higher than a predetermined prescribed transformation ratio, the soft switching process As a result of being able to reduce the time ratio, it is possible to realize a fuel cell system capable of boosting to a higher boost ratio than a fuel cell system that does not have such a control cycle changing function. In addition, as a control unit, for example, when the target transformation ratio is a low transformation ratio where soft switching control is not possible, if the control unit of the soft switching converter is extended, the target transformation ratio is adopted. Since a fuel cell system with low switching loss (switching loss at system startup, etc.) when the ratio is low can be realized, the fuel cell system of the present invention controls (changes) the switching frequency of the soft switching converter. Therefore, it has a configuration for performing the direct improvement of performance.

  Further, the power supply device of the present invention is a pulse width modulation type soft switching converter for boosting an input voltage, and a control unit for controlling the transformation ratio of the soft switching converter. Therefore, the apparatus includes a control unit that changes the control period of the soft switching converter. Therefore, it can be said that the power supply device of the present invention is also a device for controlling (changing) the switching frequency of the soft switching converter for more direct performance improvement.

  ADVANTAGE OF THE INVENTION According to this invention, a fuel cell system and a power supply device with a better performance than the existing fuel cell system and power supply device which do not have a control cycle change function are realizable.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  First, an outline of a fuel cell system 10 according to an embodiment of the present invention will be described with reference to FIG.

  As shown, a fuel cell system 10 according to an embodiment of the present invention includes a fuel cell 11, an FC boost converter 12, a battery 13, a battery boost converter 14, an inverter 15, an electronic control unit 16, a hydrogen tank 17, and The system includes a compressor 18. The fuel cell system 10 is a system for supplying power to the motor 20 of the vehicle 1 (a so-called three-phase AC motor in this embodiment).

  An electronic control unit 16 (hereinafter also referred to as ECU 16) provided in the fuel cell system 10 includes an FC boost converter 12, a battery boost converter 14, an inverter 15 based on a signal from an accelerator pedal sensor 21, a signal from a motor 20, and the like. , A unit for controlling the hydrogen tank 17 and the compressor 18 in an integrated manner. The accelerator pedal sensor 21 is a sensor for detecting the accelerator opening (information indicating the degree of depression of the access pedal provided in the vehicle 1). The signal from the motor 20 is a signal indicating the rotation speed of the motor 20.

  The inverter 15 is a circuit that converts DC power into AC power for driving the motor 20. The fuel cell 11 (hereinafter also referred to as FC 11) is a battery that generates power by an electrochemical reaction between hydrogen gas from the hydrogen tank 17 and oxygen in the air that is pumped by the compressor 18.

  The FC boost converter 12 is a DC-DC converter for boosting the output voltage of the FC 11.

  The battery 13 is a secondary battery (storage battery) that functions as a supply source of insufficient power when desired power cannot be supplied from the fuel cell 11 to the inverter 15. The battery 13 is charged by the electric power generated by the motor 20 when the vehicle 1 is decelerated or the electric power from the FC 11.

  The battery boost converter 14 is a DC-DC converter for boosting the output voltage of the battery 13. The battery boost converter 14 is formed by connecting a plurality of boost switching converters having the same configuration in parallel as in the existing multiphase converter.

  Based on the above, the configuration and operation of the fuel cell system 10 according to the present embodiment will be described more specifically below.

  First, the circuit configuration of the FC boost converter 12 will be described with reference to FIG. The load 40 in FIG. 2 refers to a portion (see FIG. 1) that includes the battery 13, the battery boost converter 14, the inverter 15, and the motor 20.

  As is apparent from the figure, the FC boost converter 12 includes a pulse width modulation boost converter (a circuit comprising a coil L1, a diode D5, a switch element S1, a capacitor C3 (and a feedback diode D4)), an auxiliary circuit 30, A smoothing capacitor C1 and a smoothing capacitor C4 are added. The pulse width modulation type boosting switching converter is a converter that can adjust the boosting ratio by changing the ON time (so-called duty ratio) of the switching element S1 per control cycle.

  The auxiliary circuit 30 added to the FC boost converter 12 is a circuit for enabling soft switching (zero voltage switching) of the switching element S1 (in this embodiment, IGBT).

  More specifically, the auxiliary circuit 30 includes a capacitor C2, a coil L2, and a circuit in which the FC11, the coil L2, the capacitor C2, and the diode D2 are connected in series by turning it on (a kind of LC circuit; hereinafter This is a circuit having a switch element S2 as a main component. Further, the auxiliary circuit 30 is a circuit in which the same voltage as that applied to the switch element S1 is applied to the capacitor C2.

  Accordingly, when the switch element S2 of the auxiliary circuit 30 is turned on while the voltage is applied to the switch element S1, the energy stored in the capacitor C2 is transferred to the coil L2, thereby causing the voltage of the capacitor C2 (= switch element). S1 voltage) is lowered. In order to perform this energy transfer in a form that can be completed in a short time and that does not significantly affect the output voltage, the auxiliary circuit 30 has a low capacitance as a capacitor C2 and a coil L2, respectively. The circuit uses capacitance and low inductance.

  Next, functions of the ECU 16 used in the fuel cell system 10 according to the present embodiment will be described.

The ECU 16 obtains a required boost ratio (output voltage of the FC boost converter 12 / output voltage of the FC 11) from the accelerator opening, the rotation speed of the motor 20, the output voltage of the FC 11, and the like, and performs a boost operation at the boost ratio. This is a unit that controls the FC boost converter 12 to perform the control.

  More specifically, as schematically shown in FIG. 3, the ECU 16 repeats the control to turn on the switch element S1 for a time corresponding to the required step-up ratio (and one control time). It is a unit. Further, the ECU 16 is a unit that turns on the switch element S2 and turns off the switch element S2 when the switch element S1 is turned off before the S2 preceding time of the ON time of the switch element S1. The S2 preceding time is a time required for setting the voltage of the switch element S1 to “zero” (or lowering to a certain level), which is determined by the inductance of C2, the capacitance of L2, and the like.

  Furthermore, the ECU 16 according to the present embodiment is a unit that changes the control cycle of the FC boost converter 12 depending on the required boost ratio.

  Specifically, the ECU 16 is configured as a unit that performs processing of the procedure shown in FIG.

  That is, when the fuel cell system 10 is activated, the ECU 16 first starts a special control process that is a process for controlling the FC boost converter 12 at a control cycle longer than a normal control cycle (details will be described later) (step). S101). Thereafter, the ECU 16 performs a process of specifying a required step-up ratio from the accelerator opening, the rotation speed of the motor 20, the output voltage of the FC 11 and the like (step S102).

  When the specified step-up ratio is a value within a range between a predetermined first threshold value (“2” in the present embodiment) to the second threshold value (step S103; YES), the ECU 16 It is determined whether or not the control process is a special control process (step S104).

  When the control process being executed is a special control process (step S104; YES), the ECU 16 starts a normal control process that is a process for controlling the FC boost converter 12 at a normal control cycle (step S105). After that, the processing after step S102 is started again. In addition, when the control process being executed is not the special control process (step S104; NO), the ECU 16 does not perform the process of step S105 (without changing the control process to be executed) and thereafter. Start processing.

  On the other hand, when the specified step-up ratio is not a value within the range of the first threshold value to the second threshold value (step S103; NO), the ECU 16 determines whether or not the control process being executed is a normal control process. (Step S106).

  Then, when the control process being executed is a normal control process (step S106; YES), the ECU 16 starts the special control process (step S107), and then starts the processes after step S102 again. Further, when the control process being executed is not the normal control process (step S106; NO), the ECU 16 starts the processes after step S102 without changing the control process to be executed.

  As is clear from the above description, the ECU 16 in the fuel cell system 10 according to the present embodiment starts from the state where the required step-up ratio is between the first threshold value and the second threshold value. When the state becomes higher than that (corresponding to the specified transformation ratio of the present invention), the control cycle of the FC boost converter 12 is changed to a unit longer than the normal control cycle (lowering the switching frequency). ing.

Then, as schematically shown in FIG. 5, when the control ratio of the FC boost converter 12 is changed to a longer one when the boost ratio is equal to or greater than the second threshold, the ratio that can be set to one control period of the S2 preceding time Therefore, the duty ratio (time during which the switch element S1 is actually turned on / control cycle) can be increased. Therefore, it can be said that the fuel cell system 10 is a system capable of boosting to a higher boost ratio than a fuel cell system having no control cycle changing function.

  Further, the FC boost converter 12 (FIG. 2) has a circuit configuration in which the voltage of the capacitor C2 does not drop to zero unless the voltage of the capacitor C2 when the switch element S2 is turned on is more than twice the output voltage of the FC11. Although it is a circuit, the ECU 16 changes the control cycle of the FC boost converter 12 to a longer one than the normal control cycle when the required boost ratio is lower than the first threshold value (“2”). It has become.

  For this reason, the fuel cell system 10 according to the present embodiment is also a system with little switching loss when operated at a low step-up ratio.

<Deformation>
The fuel cell system 10 described above can be variously modified. For example, the FC boost converter 12 can be modified into a boost converter or a step-up / down converter having a specific circuit configuration different from that described above. Further, the fuel cell system 10 may be modified to be used for a device / system other than a fuel cell vehicle, and the FC boost converter 12 is used for boosting an output voltage from a power source other than the fuel cell 11. Of course, what you can do is.

It is explanatory drawing of a structure and usage pattern of the fuel cell system which concerns on one Embodiment of this invention. It is explanatory drawing of the circuit structure of FC boost converter used for the fuel cell system which concerns on embodiment. It is a figure for demonstrating the control content with respect to FC boost converter of the electronic control unit used for the fuel cell system which concerns on embodiment. It is the flowchart which showed the change procedure of the control period with respect to FC boost converter of an electronic control unit. It is a figure for demonstrating the reason which is changing the control period.

Explanation of symbols

1 .... Vehicle 10 .... Fuel cell system 11 .... Fuel cell (FC)
12 .... FC boost converter 13 .... Battery 14 .... Battery boost converter 15 .... Inverter 16 .... Electronic control unit (ECU)
20 ... Motor 21 ... Accelerator pedal sensor 30 ... Auxiliary circuit S1, S2, S3 ... Switch elements C1, C2, C3, C4 ... Capacitors L1, L2, L3 ... Coils D1, D2, D3, D4, D5, D6 ... Diodes

Claims (4)

In a fuel cell system for supplying power to a power consuming device that consumes power and operates,
A fuel cell;
A pulse width modulation type soft switching converter for boosting the output voltage of the fuel cell;
A fuel cell system comprising: a control unit for controlling a transformation ratio of the soft switching converter, wherein the control unit changes a control cycle of the soft switching converter according to a target transformation ratio. The control unit is
2. The fuel cell system according to claim 1, wherein the unit is a unit that lengthens a control cycle of the soft switching converter when a target transformation ratio is higher than a predetermined regulation transformation ratio. The control unit is
The fuel according to claim 1 or 2, wherein when the target transformation ratio is a low transformation ratio where soft switching control is impossible, the control cycle of the soft switching converter is lengthened. Battery system. A pulse width modulation type soft switching converter for boosting the input voltage;
A control unit for controlling a transformation ratio of the soft switching converter, the control unit changing a control cycle of the soft switching converter according to a target transformation ratio.

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