JP2004080907A - Motor drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the power consumption of an on-board power supply for electric vehicles, provided with a system for storing electricity regenerated from a motor, with respect to a motor drive unit which is driven by a direct-current power supply, such as batteries. <P>SOLUTION: The motor drive unit comprises a chopper which switches between the positive side and the negative side of the direct-current power supply at a predetermined duty ratio; a series circuit, which is connected between the output terminal of the chopper and the negative side of the direct-current power supply, comprises a capacitor and a reactor; and a chopper controller which controls the duty ratio so as to make the output current of the direct-current power supply zero. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a system for storing electric power regenerated from a motor in a motor driving device driven by a DC power supply such as a battery.
[0002]
[Prior art]
For example, in a system in which a DC power supply is mounted on a vehicle and a motor is driven, such as an electric vehicle, when the vehicle is stopped by a brake operation or runs downhill at a constant speed, electric power is regenerated from the motor. This regenerative electric power is consumed as heat by connecting a resistor in parallel with the fuel cell when the fuel cell is used as a DC power supply. Further, when a battery is used instead of the fuel cell, it is consumed as heat or stored by charging the battery as in the case of the fuel cell.
[0003]
[Problems to be solved by the invention]
As described above, the regenerative electric power is consumed as heat in the conventional technology. If acceleration and deceleration are performed frequently, the power consumption increases, and when a battery is used, the travel distance per charge becomes short. In addition, when a fuel cell is used, fuel efficiency deteriorates. Even if the regenerative power is used for charging the battery, the battery cannot charge a large amount of power in a short period of time. Therefore, even when the vehicle is normally stopped, more than half of the regenerative power is not charged and is consumed as heat.
[0004]
[Means for Solving the Problems]
The present invention has been developed to solve the above problems.
A chopper for switching between a positive side and a negative side of the DC power supply at a predetermined duty ratio, a series circuit of a capacitor and a reactor connected between an output terminal of the chopper and the negative side of the DC power supply, And a chopper controller for adjusting the duty ratio so that the output current of the chopper becomes zero.
[0005]
The chopper controller includes a DC power supply current detector for detecting an output current of the DC power supply, an amplifier for amplifying an output of the DC power supply current detector, and a limiter for limiting the output of the amplifier to a predetermined range. A capacitor voltage detector for detecting or estimating the voltage of the capacitor, and a limiter for outputting a limit value of the limiter so that the voltage of the capacitor falls within a predetermined value range in accordance with an output of the capacitor voltage detector. A value generator; and a reactor current controller that adjusts the duty ratio so that the current of the reactor follows the output of the limiter.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention is shown in FIG. 1 and will be described below with reference to FIG.
Electric power is supplied from the DC power supply 3 to the motor 1 via the inverter 2. The chopper 4 switches between the positive side and the negative side of the DC power supply 3 at a predetermined duty ratio. The series circuit of the capacitor 6 and the reactor 5 is connected between the output terminal of the chopper 4 and the negative side of the DC power supply 3. In the above configuration, it is possible to control the magnitude of the current Is flowing through the reactor 5 by adjusting the switching duty ratio D of the chopper 4. Assuming that the output current of the DC power supply is IB and the current required by the inverter 2 is IA, the relationship of IA = IB + D · Is holds on average, so that Is can be adjusted so that IB = 0. That is, the duty ratio D can be adjusted by the chopper controller 13 so that IB = 0. The following describes the specific means.
[0007]
The amplifier 8 amplifies the output of the DC power supply current detector 7 that detects the output current IB of the DC power supply 3. The limiter 9 limits the output of the amplifier 8 within a predetermined range. The limit value generator 12 outputs the limit value of the limiter 9 according to the output of the capacitor voltage detector 11 for detecting or estimating the voltage Vs of the capacitor 6. In other words, the limit value generator 12 outputs the solid line that varies according to Vs as the upper limit value and outputs the dashed line as the lower limit value, and the limiter 9 limits the output of the amplifier 8 to be equal to or higher than the lower limit value and equal to or lower than the upper limit value. It is. The reactor current controller 10 uses the output of the limiter 9 as a command value Isr of the reactor current Is and controls the duty ratio D of the chopper 4 so that Is follows the command value. As described above, when the output of the amplifier 8 is not limited by the limiter 9, the operation is performed such that the DC power supply output current IB = 0. It is to be noted that Isr is limited by the limiter 9 so that Is does not exceed the maximum allowable current of the chopper 4 and that the capacitor voltage Vs falls within a predetermined range (Vs1 to Vs2). Can be
[0008]
【The invention's effect】
By setting the DC power supply output current to 0 in the present invention, the regenerative power generated when the vehicle is stopped by a brake operation or when traveling downhill at a constant speed is efficiently charged into a capacitor having high charging efficiency. The battery can be stored, so that it is not necessary to flow it through a resistor and consume it as heat, or to charge a battery with low charging efficiency. At the time of acceleration, the energy of the capacitor having high discharge efficiency is preferentially used, so that the energy consumption of the DC power supply can be suppressed.
[0009]
As described above, when the present invention is applied to a system in which a DC power supply is mounted on a vehicle and a motor is driven, such as an electric vehicle, the output current of the DC power supply can be obtained by charging / discharging the capacitor even when the vehicle frequently runs with acceleration and deceleration. By setting the value to 0 as much as possible, the energy consumed from the DC power supply can be reduced, the running distance per charge can be extended when a battery is used, and the fuel efficiency can be improved in the case of a fuel cell.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Motor 2 ... Inverter 3 ... DC power supply 4 ... Chopper 5 ... Reactor 6 ... Capacitor 7 ... DC power supply current detector 8 ... Amplifier 9 ... Limitation Unit 10 Reactor current controller 11 Capacitor voltage detector 12 Limit value generator 13 Chopper controller

Claims (2)

In a motor drive device that supplies power to a motor from a DC power supply via an inverter,
A chopper for switching between a positive side and a negative side of the DC power supply at a predetermined duty ratio, a series circuit of a capacitor and a reactor connected between an output terminal of the chopper and the negative side of the DC power supply, And a chopper controller for adjusting the duty ratio so that the output current of the motor becomes zero. A DC power supply current detector for detecting an output current of the DC power supply; an amplifier for amplifying an output of the DC power supply current detector; and a limiter for limiting an output of the amplifier to a predetermined range. A capacitor voltage detector for detecting or estimating a voltage of the capacitor, and a limit value for outputting a limit value of the limiter such that the voltage of the capacitor falls within a predetermined value range in accordance with an output of the capacitor voltage detector. 2. The motor drive device according to claim 1, further comprising a generator and a reactor current controller that adjusts the duty ratio so that the current of the reactor follows the output of the limiter.

Images