JP2011205735A - Fuel cell vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a situation where, for example, a surplus generating capacity of a fuel cell is excessively supplied to a rechargeable battery in a sudden motor stop in a fuel cell vehicle.SOLUTION: A control device 22 determines that the motor 10 has stopped suddenly according to a signal of a rotational speed sensor 24 when a dropping ratio of the rotational speed of the motor 10 exceeds a threshold, and stops the operation of a converter 16 for fuel cells. Thus, the fuel cell 14 is electrically and directly connected to an inverter 12. In this case, a voltage in an output terminal of the fuel cell 14 rises to a voltage of the inverter 12 and exceeds an open-circuit voltage in a general situation, thus stopping the power generation of the fuel cell 14. Thus, the surplus power generation of the fuel cell 14 is reduced at a sudden motor stop.

Description

  The present invention relates to a fuel cell vehicle, and more particularly to control of a fuel cell when a motor suddenly stops.

  In the drive system of a fuel cell vehicle, a fuel cell and a storage battery are connected in parallel to a motor for driving the vehicle via an inverter, and a converter is provided between the fuel cell and the inverter and between the storage battery and the inverter, respectively. A configuration for controlling the output voltage from each battery is widely used.

  In such a configuration, when the motor suddenly stops, due to circumstances such as using a rotational speed dulled by a filter or the like instead of the raw motor rotational speed for communication delay, control stability, etc. There is a certain time lag from the stop until the control command corresponding to the sudden stop is transmitted to the converter between the fuel cell and the inverter. During this time lag, although the motor does not consume power, the converter between the fuel cell and the inverter is in a state of continuing the power generation of the fuel cell. Since the electric power generated by the fuel cell during this time is not consumed by the motor, it is charged to the storage battery via the converter between the storage battery and the inverter.

  Such surplus power can be absorbed by the storage battery to some extent, but depending on the surplus power generation, there is a possibility that it cannot be absorbed by the storage battery. If excessive power generation that cannot be absorbed by the storage battery is performed in this manner, there is a possibility that the power control of the system is adversely affected.

  In Patent Document 1, in a vehicle that charges the storage battery with the surplus power generation amount of the fuel cell, when the inter-vehicle distance from the preceding vehicle is shorter than the reference distance, a branch point between the fuel cell, the storage battery converter, and the motor is disclosed. It is disclosed that the surplus power generation amount is suppressed by boosting the voltage of the current.

  Patent Document 2 discloses a hybrid system that includes a fuel cell and a storage battery and supplies electric power from a fuel cell system to a motor via a fuel cell side boost converter, and controls the fuel cell side boost converter according to a motor load. It is disclosed that when the step-up ratio is 1 or less, the fuel cell side boost converter is stopped to electrically connect the fuel cell and the motor directly. In the system of this document, when the required voltage of the motor is lower than the required voltage of the fuel cell, the switching loss due to the converter is reduced by stopping the fuel cell side boost converter.

JP 2009-165304 A JP 2009-165244 A

  The method disclosed in Patent Document 1 relates to the control of surplus power generation, but is based on the inter-vehicle distance from the preceding vehicle, and does not focus on the surplus power when the motor suddenly stops. Further, the method disclosed in Patent Document 2 is for reducing the switching loss of the converter in a low load region, and there is no suggestion about the problem at the time of sudden stop of the motor. It does not solve the problem.

  An object of the present invention is to suppress a situation in which excessive electric power generated by a fuel cell is excessively supplied to a storage battery during a sudden motor stop in a fuel cell vehicle.

  A fuel cell vehicle according to the present invention includes a fuel cell, a vehicle motor, an inverter for driving the vehicle motor, and a terminal voltage of the fuel cell provided between the fuel cell and the inverter. A fuel cell converter for converting the input voltage to the vehicle motor; a storage battery connected to the vehicle motor in parallel with the fuel cell via the inverter; and the battery provided between the storage battery and the inverter. A storage battery converter that converts the terminal voltage of the storage battery into an input voltage to the motor, a sudden stop detection means that detects a sudden stop of the vehicle motor, and a sudden stop of the vehicle motor is detected by the sudden stop detection means And a converter control means for performing control to stop the fuel cell converter.

  In one aspect, the fuel cell vehicle includes the inverter while the converter control unit stops the fuel cell converter after the sudden stop of the vehicle motor is detected by the sudden stop detection unit. Inverter control means for setting the voltage command value for to a value equal to or greater than the open circuit voltage of the fuel cell.

  In a further aspect, the inverter control means has a voltage command value when the sudden stop of the vehicle motor is detected by the sudden stop detection means when the voltage command value for the inverter is equal to or higher than the open circuit voltage. While the command value is held and the fuel cell converter is stopped, the held voltage command value is given to the inverter.

  In a further aspect, the fuel cell vehicle further includes power consumption measuring means for measuring power consumption of the vehicle motor, and output power measuring means for measuring output power of the fuel cell, wherein the converter control means is The fuel cell output power measured by the output power measuring means after the fuel cell converter is stopped in response to the sudden stop detection of the vehicle motor being detected by the sudden stop detection means, When the power consumption of the vehicle motor measured by the power consumption measuring means falls below, the fuel cell converter is driven.

  In a further aspect, the sudden stop detection means causes the vehicle motor to stop suddenly when a reduction amount per unit time of the power consumption measured by the power consumption measurement means is equal to or greater than a predetermined threshold. Detect the effect.

  In another aspect, the sudden stop detection unit is configured to reduce the power consumption per unit time obtained from the power consumption measuring unit that measures the power consumption of the vehicle motor when a predetermined threshold value or more is reached. Detecting that the vehicle motor has stopped suddenly.

  According to the present invention, it is possible to suppress a situation in which excessive electric power generated by the fuel cell is excessively supplied to the storage battery when the motor suddenly stops in the fuel cell vehicle.

It is a figure which shows the example of the drive mechanism of the fuel cell vehicle to which control of embodiment is applied. It is a flowchart which shows a part of example of the control procedure of embodiment. It is a flowchart which shows the remaining part of an example of the control procedure of embodiment. It is a figure for demonstrating the effect by control of embodiment. It is a flowchart which shows a part of example of the control procedure of the modification of embodiment. It is a flowchart which shows the remaining part of an example of the control procedure of the modification of embodiment. It is a flowchart which shows an example of the control procedure of the 2nd modification of embodiment.

FIG. 1 shows an example of a drive system of a fuel cell vehicle to which the control of this embodiment is applied.
In this example, the motor 10 is a three-phase AC motor, for example, and generates a driving force for driving the driving wheels of the fuel cell vehicle. The inverter 12 converts DC power supplied from the fuel cell 14 and the battery 18 into three-phase AC power supplied to the motor 10.

  The fuel cell 14 generates power by an electrochemical reaction between, for example, hydrogen gas stored in a hydrogen tank (not shown) and oxygen in the air pumped by a compressor (not shown). A fuel cell converter 16, which is a DC-DC converter, is electrically connected between the fuel cell 14 and the inverter 12. In general, the motor 10 is more efficient when driven at a voltage much higher than the voltage that can be output by the fuel cell 14 as described in the above-mentioned patent document. The voltage is boosted by the converter 16 and applied to the inverter 12. It is also possible to control the terminal voltage of the fuel cell 14 by the boosting operation of the fuel cell converter 16.

  The battery 18 is a storage battery that can be charged and discharged. A battery converter 20, which is a DC-DC converter, is electrically connected between the battery 18 and the inverter 12 so as to be parallel to the fuel cell converter 16 with respect to the inverter 12. Thereby, the output voltage from the battery 18 is boosted to a relatively high voltage suitable for driving the motor 10 by the battery converter 20 and applied to the inverter 12.

  The control device 22 is a computer for electronically controlling each element of the drive system including those exemplified above, and is also called an ECU or the like. The control device 22 receives, for example, a signal indicating the opening degree of the accelerator pedal, and controls the amount of power generated by the fuel cell 14 and the amount of charge / discharge of the battery 18 based on this signal and a detection signal of the number of revolutions of the motor 10. I do. The control device 22 also controls the inverter 12, the fuel cell converter 16, and the battery converter 20.

  The rotation speed sensor 24 is a sensor such as a resolver that measures the rotation speed of the motor 10. A signal representing the motor rotational speed measured by the rotational speed sensor 24 is supplied to the control device 22. The control device 22 performs various controls using the signal of the rotational speed.

  Next, the control procedure of the present embodiment executed by the control device 22 will be described with reference to FIGS. 2 and 3. The control device 22 executes the processes of FIGS. 2 and 3 after the drive system illustrated in FIG. 1 is activated and the drive of the motor 10 is started.

  FIG. 2 shows a control procedure for switching the value of a control flag (referred to as “sudden stop flag”) for converter control according to this embodiment in accordance with a sudden stop of the motor 10 and a departure from the sudden stop. In the process of FIG. 2, the control device 22 determines whether or not the motor 10 has suddenly stopped, for example, at regular time intervals (S10). In one example, the sudden stop of the motor 10 is determined that the motor 10 has stopped suddenly when the time reduction rate of the rotation speed notified from the rotation speed sensor 24 exceeds a predetermined threshold value. To do. The reduction rate of the motor rotation speed may be obtained, for example, by dividing the reduction amount of the motor rotation speed at the current determination from the motor rotation speed at the previous determination by the difference between the previous determination time and the current determination time. (If the determination interval is constant, the reduction amount itself has the same meaning as the reduction rate, so division is not necessary). When the vehicle suddenly stops for some reason such as sudden braking or failure, the motor 10 also generally stops suddenly, and the sudden stop of the motor 10 is detected as a sudden decrease in the motor rotational speed as described above.

  In addition, for the control of the power generation amount of the fuel cell 14, the rotational speed signal blunted by a filter or the like is used for the stability of the control. However, in the determination of S10, the raw output signal of the rotational speed sensor is used. Or at least the output signal of the rotation speed sensor that has passed through an integration filter having a smaller time constant (and therefore less time delay) than the rotation speed signal filter for controlling the power generation amount.

  If it is determined in S10 that the motor 10 has suddenly stopped, the control device 22 immediately sets the value of the sudden stop flag to “ON” (S12). Note that the value of the sudden stop flag is initialized to “OFF” when the drive system is started.

  After setting the sudden stop flag to ON, the control device 22 determines whether or not the motor 10 has left the sudden stop state (S14). For example, when the magnitude of the temporal decrease rate of the rotational speed notified from the rotational speed sensor 24 is equal to or less than the above-described threshold value for sudden stop determination (including the case where the motor rotational speed increases), What is necessary is just to determine with the motor 10 having escaped from the sudden stop state. Until the departure of the motor 10 from the sudden stop state is detected, for example, the determination of S14 is periodically repeated. If it is determined in S14 that the motor 10 has departed from the sudden stop state, the control device 22 changes the value of the sudden stop flag to “OFF” (S16). After this change, the process of the control device 22 returns to S10.

  Note that the determination in S10 is performed at sufficiently short time intervals so that a sudden stop of the motor can be detected. The determination interval of S14 may be the same as the determination interval of S10, but is not limited thereto.

  FIG. 3 shows an example of a drive control procedure for the fuel cell converter 16 based on the sudden stop flag. For example, the control device 22 periodically executes the procedure of FIG. The execution interval of the procedure of FIG. 3 may be approximately the same as the execution interval of S10 (rapid stop determination) of the procedure of FIG.

  In the procedure of FIG. 3, the control device 22 checks the value of the sudden stop flag (S20). If the value of the sudden stop flag is ON, the fuel cell converter 16 is stopped (S22) (if already driven, the stopped state is maintained). On the other hand, if the sudden stop flag is OFF, the fuel cell converter 16 is driven (S24) (if already driven, the driving state is maintained).

  According to this control, as shown in FIG. 4, when a sudden decrease in the rotation speed of the motor 10 is detected, it is determined that the motor is suddenly stopped, and at the timing when this determination is made, Converter 16 is immediately stopped. When the fuel cell converter 16 stops, the fuel cell 14 and the inverter 12 are electrically connected directly. As a result, as shown in FIG. 4, the output terminal voltage V <b> 1 (see FIG. 1) of the fuel cell 14 becomes equal to the input terminal voltage V <b> 2 of the inverter 12. In a general operation situation, the input terminal voltage V2 of the inverter 12 is much higher than the output terminal voltage V1 of the fuel cell 14, and the open circuit voltage (abbreviated as OCV: Open Circuit Voltage; about 1V. Open circuit voltage). Much higher than that). Therefore, in a general situation, when the fuel cell converter 16 is stopped, V1 exceeds the OCV of the fuel cell 14, so that the fuel cell 14 does not generate power and excess generated power is not output. . Thereby, large surplus generated power does not go to the battery 18 via the battery converter 20, and adverse effects on the converter 20 and the inverter 12 due to such surplus generated power can be reduced.

  If V2 is lower than V1 when the motor suddenly stops (although it does not occur so much), surplus power generation of the fuel cell 14 is facilitated by stopping the fuel cell converter 16. However, in this case as well, V2 rises when surplus power generated cannot flow to the battery 18 side, and V1 also rises and reaches OCV accordingly, and surplus power generation of the fuel cell 14 stops. It will be. Here, when such a sudden stop occurs, if V2 is lower than OCV, control may be performed to change the command value indicating the value of V2 to a value equal to or higher than OCV. This control is a countermeasure against the possibility that an overcurrent may occur in the converter 20 depending on the surplus power generation amount when V2 is kept lower than the OCV and the voltage value is maintained.

  Then, after the fuel cell converter 16 is stopped in this manner, when the motor 10 leaves the sudden stop state, the drive of the fuel cell converter 16 is resumed under the control of the control device 22. By resuming the driving, preparations for responding to a new power demand due to depression of the accelerator or the like can be made.

  As described above, according to the present embodiment, when the sudden stop of the motor is detected, the surplus power generation of the fuel cell 14 can be stopped by stopping the fuel cell converter 16, which has an adverse effect on the power control of the system. Can be reduced.

  Next, a modification of the above embodiment will be described with reference to FIGS. 5 and 6 show examples of the control procedure of the control device 22 and correspond to FIGS. 2 and 3, respectively. Steps similar to those shown in FIGS. 2 and 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this modification, as shown in FIG. 5, the control device 22 detects the sudden stop of the motor 10 and then sets the sudden stop flag to ON, and the input voltage supplied to the inverter 12 at the time of detection. Latch command value. Hereinafter, the latched input voltage command value is referred to as a latch value. In the procedure of FIG. 6, after the fuel cell converter 16 is stopped in FIG. 22, the latch value latched at that time is compared with the normal input command value obtained by the normal inverter control routine. (S32). The normal input command value corresponds to the actual value of V2. If it is determined in S32 that the normal input command value is equal to or greater than the latch value, the control device 22 sets the normal voltage command value to the input voltage command value for the inverter 12 (S34) (however, At this time, the set value is not instructed to the inverter 12). If it is determined in S32 that the latch value is lower than the normal input command value, the control device 22 sets the latch value to the input voltage command value for the inverter 12 (S36) (also in this case) Then, the set value is not instructed to the inverter 12).

  And the control apparatus 22 performs a lower limit guard process with respect to the set input voltage command value (S38). The lower limit guard process is a process of changing the setting of the input voltage command value to a predetermined value equal to or higher than the OCV if the set input voltage command value is smaller than the OCV of the fuel cell 14.

  According to the control of the modification shown in FIGS. 5 and 6, the input voltage command to the inverter 12 is set to be equal to or higher than V2 (the input terminal voltage of the inverter 12) at the time of detection after the sudden motor stop is detected. The value is controlled. Therefore, even when V2, that is, the input terminal voltage of the inverter 12 is variably controlled, it is possible to reduce an adverse effect on the power control at the time of sudden motor stop. In addition, since the lower limit guard process of the input voltage command to the inverter 12 is controlled so that V2 does not fall below the OCV of the fuel cell 14, even if V2 is lower than the OCV at the time of detection of a sudden motor stop. Thus, it is possible to prevent the fuel cell 14 from performing excessive power generation.

  The lower limit guard process (S38) of the input voltage command to the inverter 12 can also be applied to the procedure of FIG.

  Next, a second modification of the above embodiment will be described with reference to FIG. FIG. 7 is obtained by adding S40 to the procedure of FIG.

  That is, in this second modification, after the sudden stop flag is set to ON, the power consumption of the motor 10 exceeds the output power of the fuel cell 14 even when the motor 10 has not left the sudden stop state. When it is detected that the former may be greater than the latter, the sudden stop flag is changed to OFF (S16). That is, even when the motor 10 is in the middle of a sudden stop (that is, the absolute value of the rate of decrease in the motor rotation speed is equal to or greater than the threshold), the generated power of the fuel cell 14 becomes smaller than the power consumption of the motor 10. Then, the driving of the fuel cell converter 16 is resumed. As a result of this drive resumption, V1 that had risen in accordance with V2 so far falls, and power generation of the fuel cell 14 is resumed. Even when the power generation is resumed in this way, at this point of time, the power consumption of the motor 10 is larger, so that it is difficult to generate surplus power generation and there is little adverse effect on the power control.

  The power consumption of the motor 10 is obtained from, for example, an output value of an ammeter that measures the current flowing through the motor 10 and an output value of a voltmeter that measures the output voltage of the inverter 12 (or an output voltage command value for the inverter 12). That's fine. Of course, this is only an example, and other methods may be used.

  According to the second modification, there is a case where the resumption of driving of the fuel cell converter 16 can be accelerated as compared with the case of waiting for separation from the sudden stop state. If the fuel cell converter 16 is stopped when the accelerator is stepped on after the sudden stop, it takes some time to resume the drive of the converter 16, but the motor is accordingly operated after the accelerator is stepped on. There will be some time delay before the 10 output increases. On the other hand, in this modification, the driving of the fuel cell converter 16 can be resumed by using the earlier one of the departure from the sudden stop state or the fuel cell output being lower than the motor power consumption as a trigger. Thus, the resumption of driving of the fuel cell converter 16 can be accelerated, and as a result, an improvement in response when the accelerator is stepped on after a sudden stop can be expected.

  In the above, embodiment and its modification were demonstrated. In the above, the determination of the sudden stop of the motor 10 in S10 is performed based on the rotation speed signal from the rotation speed sensor 24. However, this is only an example.

  For example, as an extreme example, consider a case where the motor 10 suddenly stops for some reason on a downhill (that is, suddenly no driving force is generated). In this case, the motor 10 stops suddenly in the sense that it does not generate driving force, but since the vehicle goes downhill due to gravity, the driving wheel rotates, and the motor 10 also rotates accordingly. . For this reason, even when the motor 10 is suddenly stopped, the magnitude of the rate of decrease in the rotational speed indicated by the rotational speed sensor 24 may not exceed the threshold value. In this case, if it is determined by the motor rotation speed, it is not determined to be a sudden stop, so that the problem of surplus power generation described above occurs.

  Therefore, when the control device 22 monitors the power consumption of the motor 10 instead of the rotation speed of the motor 10 as the operation of S10, and the magnitude of the power consumption reduction rate exceeds a predetermined threshold value, It may be determined that the motor 10 has stopped suddenly. If the determination is made based on the motor power consumption in this way, even if the rotation speed of the motor 10 does not rapidly decrease, if the power consumption of the motor 10 is rapidly decreased, the countermeasure processing for the surplus power generation described above (of the converter 16). Stop).

  In this case, the drive of the converter 16 is resumed when the reduction in the power consumption of the motor is mitigated (that is, when the reduction rate is equal to or smaller than the threshold value or when the power consumption increases). Also good.

  Further, both the determination of the sudden decrease in the motor rotation speed and the determination of the rapid decrease in the motor power consumption are executed, and when the earlier determination is established, the countermeasure process for the surplus power generation described above is executed. Also good.

  In the above example, the process of the control device 22 is divided into the process of FIG. 2 and the process of FIG. 3 (or the process of FIG. 5 and the process of FIG. 6), but this is merely an example. Instead, the same control may be realized by a single flow in which both are integrated, or the same control may be realized by three or more flows.

  DESCRIPTION OF SYMBOLS 10 Motor, 12 Inverter, 14 Fuel cell, 16 Fuel cell converter, 18 Battery, 20 Battery converter, 22 Control apparatus, 24 Speed sensor.

Claims (6)

A fuel cell;
A vehicle motor;
An inverter for driving the vehicle motor;
A fuel cell converter provided between the fuel cell and the inverter and converting a terminal voltage of the fuel cell into an input voltage to the vehicle motor;
A storage battery connected to the vehicle motor in parallel with the fuel cell via the inverter;
A storage battery converter that is provided between the storage battery and the inverter and converts a terminal voltage of the storage battery into an input voltage to the motor;
A sudden stop detecting means for detecting a sudden stop of the vehicle motor;
Converter control means for performing control to stop the fuel cell converter when the sudden stop of the vehicle motor is detected by the sudden stop detection means;
A fuel cell vehicle comprising: While the converter control means stops the fuel cell converter after the sudden stop detection means detects the sudden stop of the vehicle motor, the voltage control value for the inverter is set to open the fuel cell. Inverter control means with a value greater than the circuit voltage,
The fuel cell vehicle according to claim 1, further comprising: The inverter control means holds the voltage command value when the voltage command value for the inverter at the time when the sudden stop of the vehicle motor is detected by the sudden stop detection means is equal to or higher than the open circuit voltage. The voltage command value held while stopping the fuel cell converter is given to the inverter.
The fuel cell vehicle according to claim 2. Power consumption measuring means for measuring power consumption of the vehicle motor;
Output power measuring means for measuring the output power of the fuel cell;
Further comprising
The converter control means stops the fuel cell converter in response to the sudden stop detection of the vehicle motor by the sudden stop detection means, and then the output power measuring means measures the fuel cell. When the output power falls below the power consumption of the vehicle motor measured by the power consumption measuring means, the fuel cell converter is driven;
The fuel cell vehicle according to any one of claims 1 to 3, wherein: The sudden stop detection means includes
Detecting that the vehicular motor has stopped suddenly when a reduction amount per unit time of the power consumption measured by the power consumption measuring means is equal to or greater than a predetermined threshold;
The fuel cell vehicle according to claim 4. The sudden stop detection means includes
Detects that the vehicular motor has stopped suddenly when the reduction amount per unit time of the power consumption obtained from the power consumption measuring means for measuring the power consumption of the vehicular motor exceeds a predetermined threshold. To
The fuel cell vehicle according to any one of claims 1 to 3, wherein:

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