JP2012175765A - Electric vehicle controller - Google Patents

Abstract

A control device for an electric vehicle capable of making a pedestrian notice the approach of a vehicle is proposed.
A plurality of power converters (30, 40, 50) perform a desired power conversion operation by controlling driving of switching elements based on respective carrier frequencies. When the vehicle speed is less than a predetermined value, the control device (60) for an electric vehicle synchronizes the carrier frequencies of the plurality of power converters (30, 40, 50) and increases the sound pressure of the operating sound.
[Selection] Figure 1

Description

  The present invention relates to a control device for an electric vehicle for controlling a plurality of power converters.

  A fuel cell is a power generation device that directly converts chemical energy released by an oxidation reaction into electrical energy by oxidizing fuel by an electrochemical process. For example, Japanese Patent Application Laid-Open No. 2008-98134 is known as a patent document relating to an electric vehicle in which a fuel cell is mounted as an on-vehicle power source. In this type of electric vehicle, a traction motor is driven by electric power supplied from a fuel cell or a battery to obtain driving propulsion.

JP 2008-98134 A

  However, since an electric vehicle has a low operating noise (noise), it has been pointed out from a safety point of view that it is difficult for a pedestrian to notice, particularly when traveling at a low speed.

  Then, this invention makes it a subject to propose the control apparatus for electric vehicles which can make a pedestrian notice the approach of a vehicle.

  In order to solve the above problems, a control device for an electric vehicle according to the present invention is an electric vehicle for controlling a plurality of power converters that perform a power conversion operation by switching control of a switching element based on a carrier frequency. And a synchronization means for synchronizing the carrier frequencies of the plurality of power converters when the vehicle speed is less than a predetermined value. By synchronizing the carrier frequencies of the plurality of power converters, the sound pressure of the operating sound of the electric vehicle is increased, so that the pedestrian can be aware of the approach of the vehicle during low-speed traveling.

  In order to make the pedestrian notice the approach of the vehicle, it is preferable to synchronize the carrier frequencies of the plurality of power converters in the audible band.

  The plurality of power converters are, for example, a DC / DC converter for a fuel cell for boosting the output voltage of the fuel cell to a predetermined DC voltage, and for stepping up / stepping a DC voltage input / output to / from the battery to a predetermined DC voltage Any two or more of traction inverters for converting DC power supplied from a battery DC / DC converter, a fuel cell, or a battery into AC power may be included.

  According to the present invention, since the sound pressure of the operating sound of the electric vehicle can be increased during low-speed traveling, the pedestrian can be made aware of the approach of the vehicle.

It is a functional block diagram of the electric power system of the electric vehicle concerning this embodiment. It is a circuit diagram of the FC converter concerning this embodiment. It is explanatory drawing of the switching control signal of the FC converter concerning this embodiment. It is a flowchart which shows the process for raising the sound pressure level of the operation sound which the electric vehicle concerning this embodiment generate | occur | produces. It is explanatory drawing which shows the example of the synchronization of the carrier frequency concerning this embodiment. It is explanatory drawing which shows the example of the synchronization of the carrier frequency concerning this embodiment.

Embodiments according to the present invention will be described below with reference to the drawings.
FIG. 1 shows functional blocks of an electric power system of an electric vehicle 10 according to this embodiment. The electric vehicle 10 supplies power to the traction inverter 50 using the fuel cell 20 that generates electricity by an electrochemical reaction between the oxidizing gas and the fuel gas as a main power source and the chargeable / dischargeable battery 70 as an auxiliary power source. To drive. The fuel cell 20 is, for example, a polymer electrolyte fuel cell, and has a stack structure in which a large number of single cells are stacked. The single cell includes an air electrode formed on one surface of an electrolyte membrane made of an ion exchange membrane, a fuel electrode formed on the other surface of the electrolyte membrane, and a pair of separators that sandwich the air electrode and the fuel electrode from both sides. Have The battery 70 is a power storage device that functions as a surplus power storage source, a regenerative energy storage source during regenerative braking, and an energy buffer during load fluctuations associated with acceleration or deceleration of the electric vehicle 10. Cadmium storage batteries, nickel / hydrogen storage batteries, lithium secondary batteries, etc.) are preferred.

  The output voltage of the fuel cell 20 is boosted to a predetermined DC voltage by a DC / DC converter 30 (hereinafter referred to as an FC converter 30), which is a DC voltage converter for the fuel cell, and supplied to the traction inverter 50. On the other hand, the output voltage of the battery 70 is boosted to a predetermined DC voltage by a DC / DC converter 40 (hereinafter referred to as a battery converter 40) which is a DC voltage converter for the battery, and is supplied to the traction inverter 50. The traction inverter 50 converts DC power supplied from either or both of the fuel cell 20 and the battery 70 into AC power (for example, three-phase AC), and controls the rotational torque of the traction motor 80. The traction motor 80 is, for example, a three-phase AC motor, and generates a driving propulsion force when the vehicle is traveling, and functions as a motor generator when the vehicle is braked, and converts kinetic energy into electric energy to recover regenerative power. The battery converter 40 steps down the surplus power of the fuel cell 20 or the regenerative power collected by the traction motor 80 and charges the battery 70.

  The control unit 60 is a control device including a CPU, a ROM, a RAM, and an input / output interface, and controls the operation of the fuel cell 20 and the switching control of the on-vehicle power converters (FC converter 30, battery converter 40, and traction inverter 50). I do. For example, when the control unit 60 receives the activation signal from the ignition switch, the control unit 60 starts the operation of the electric vehicle 10 and is based on the accelerator opening signal output from the accelerator sensor, the vehicle speed signal output from the vehicle speed sensor 90, or the like. Request the required power. This required power is the total value of the vehicle travel power and the auxiliary power. Auxiliary power includes power consumed by in-vehicle accessories (humidifiers, air compressors, hydrogen pumps, cooling water circulation pumps, etc.), and equipment required for vehicle travel (transmissions, wheel control devices, steering devices, and Power consumed by a suspension device or the like, and power consumed by a device (such as an air conditioner, a lighting fixture, or audio) disposed in the passenger space. The control unit 60 determines the distribution of the output power of each of the fuel cell 20 and the battery 70 and supplies the fuel gas and the oxidizing gas to the fuel cell 20 so that the generated power of the fuel cell 20 matches the target power. And the FC converter 30 to adjust the output voltage of the fuel cell 20, thereby controlling the operating point (output voltage, output current) of the fuel cell 20. Further, the control unit 60 outputs the U-phase, V-phase, and W-phase AC voltage command values to the traction inverter 50 as switching commands, for example, so as to obtain a target torque according to the accelerator opening. The output torque and rotation speed of the traction motor 80 are controlled.

  FIG. 2 shows a circuit configuration of the FC converter 30. Here, a known DC chopper is shown as an example of the FC converter 30. The FC converter 30 includes a transistor Tr as a switching element that periodically turns on and off according to the carrier frequency, a smoothing reactor L, a smoothing capacitor C, and a diode D as a rectifying element. When the transistor Tr is turned on, the energy supplied from the fuel cell 20 is accumulated in the smoothing reactor L, and the accumulated energy is transferred to the smoothing capacitor C via the diode D when the transistor Tr is turned off. The By repeating this process, the energy stored in the smoothing capacitor C increases, and the output voltage E2 can be increased compared to the input voltage E1. Here, the input voltage E1 corresponds to the output voltage of the fuel cell 20, and the output voltage E2 is supplied to the traction inverter 50. In such a DC chopper, the degree of boosting is determined according to the ratio (duty ratio) between the ON period and the OFF period that occupies within one cycle of the switching operation of the transistor Tr. In order to adjust the duty ratio, for example, as shown in FIG. 3, the carrier wave 100 is compared with the duty command value 110, and when the duty command value 110 exceeds the carrier wave 100, the transistor Tr is commanded to turn on. When the duty command value 110 is equal to or lower than the carrier wave 100, the switching control signal 120 for commanding the transistor Tr to be turned off is generated, and the transistor Tr is controlled to be switched based on the switching control signal 120. If the switching period is T, the carrier frequency f of the carrier wave 100 satisfies the relationship f = 1 / T.

  The battery converter 40 is configured by a known DC chopper or the like, and the traction inverter 50 is configured by a known PWM inverter or the like. In any case, desired power conversion is performed by driving and controlling the switching element in synchronization with the carrier frequency.

  FIG. 4 is a flowchart showing a processing routine for increasing the sound pressure level of the operating sound generated by the electric vehicle 10. This processing routine is repeatedly executed at regular intervals. The control unit 60 determines whether or not the vehicle speed is less than a predetermined value (for example, 20 km / h) based on the vehicle speed signal output from the vehicle speed sensor 90 (step 401). When the vehicle speed is equal to or higher than the predetermined value (step 401; NO), this processing routine ends. When the vehicle speed is less than the predetermined value (step 401; YES), the control unit 60 sets each of the plurality of power converters (FC converter 30, battery converter 40, and traction inverter 50) mounted on the electric vehicle 10. The carrier frequency is acquired (step 402), and it is determined whether or not to synchronize these carrier frequencies in consideration of heat loss and the like accompanying the carrier frequency change (step 403). If the carrier frequencies are not synchronized (step 403; NO), this processing routine ends. When synchronizing the carrier frequencies (step 403; YES), the control unit 60 synchronizes the carrier frequencies of at least two or more power converters among all the power converters (step 404). For example, as shown in FIG. 5, when the carrier frequency of the FC converter 30 is f1, the carrier frequency of the battery converter 40 is f2, and the carrier frequency of the traction inverter 50 is f3, as shown in FIG. Both are changed to the carrier frequency f4 within the audible band range. Here, f4 may be the same carrier frequency as either f1 or f2, or may be a carrier frequency different from either f1 or f2. The control unit 60 functions as a synchronization unit that synchronizes the carrier frequencies of the plurality of power converters when the vehicle speed is less than a predetermined value. By synchronizing the carrier frequencies of the FC converter 30 and the battery converter 40, it is possible to increase the sound pressure of these operating sounds, and to make the pedestrian notice the approach of the vehicle during low-speed traveling.

  Note that the combination of power converters that synchronize the carrier frequency is not limited to the above-described example, and may be any two or more of the FC converter 30, the battery converter 40, and the traction inverter 50. Moreover, the example of a power converter is not restricted to the above-mentioned example, What is necessary is just to perform a power conversion operation | movement by driving-controlling a switching element based on a carrier frequency. Further, although the fuel cell 20 is illustrated as the main power source of the electric vehicle 10, a known in-vehicle generator other than the fuel cell may be used as the main power source.

  The present invention is useful for an electric vehicle including a plurality of power converters that perform a power conversion operation by driving and controlling a switching element based on a carrier frequency.

DESCRIPTION OF SYMBOLS 10 ... Electric vehicle 30 ... FC converter 40 ... Battery converter 50 ... Traction inverter 60 ... Control unit 70 ... Battery 80 ... Traction motor 90 ... Vehicle speed sensor 100 ... Carrier wave 110 ... Duty command value 120 ... Switching control signal

Claims (3)

A control device for an electric vehicle for controlling a plurality of power converters that perform a power conversion operation by switching control of a switching element based on a carrier frequency,
A control device for an electric vehicle comprising synchronization means for synchronizing carrier frequencies of the plurality of power converters when a vehicle speed is less than a predetermined value. The control device for an electric vehicle according to claim 1,
The synchronization means is a control device for an electric vehicle that synchronizes carrier frequencies of the plurality of power converters in an audible band. A control device for an electric vehicle according to claim 1 or 2,
The plurality of power converters include a fuel cell DC / DC converter for boosting the output voltage of the fuel cell to a predetermined DC voltage, and a battery for stepping up and down the DC voltage input to and output from the battery to the predetermined DC voltage. The control apparatus for electric vehicles containing any two or more among DC / DC converters for vehicles, the traction inverter for converting the direct-current power supplied from the said fuel cell or the said battery into alternating current power.

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