JP5413565B2 - Motor drive device and electric vehicle - Google Patents

Description

  The present invention relates to a motor drive device using a secondary battery and a voltage variable energy storage element in combination as a power source, and an electric vehicle equipped with the motor drive device.

In Patent Document 1, in order to efficiently recover energy during regeneration, a capacitor as a voltage variable type energy storage element having excellent charge / discharge characteristics as a power supply, and a stable power supply with inferior charge / discharge efficiency are provided. An assist circuit in combination with a secondary battery such as a possible lead storage battery is described.
In this prior art, a capacitor is connected in parallel with a secondary battery with a transient charging / discharging operation of a predetermined pattern, and in order to keep the voltage fluctuation due to the transient charging / discharging operation of the secondary battery within a predetermined allowable range, The capacitance of the capacitor is set so that the charge or discharge capacity of the capacitor that occurs when a voltage fluctuation corresponding to the allowable voltage fluctuation of the secondary battery is greater than or equal to the transient charge or discharge power energy of the predetermined pattern. Is.

In Patent Document 2, in order to adjust the stored energy amount of a capacitor as a voltage variable energy storage element, the terminal voltage of the capacitor is controlled, and energy can be freely exchanged between the capacitor and the secondary battery. A power storage device that can be controlled is described.
This prior art is a power storage device for a vehicle having a power generation device and a running motor, and a capacitor connected to a main circuit, a secondary battery, and stored power between the capacitor and the secondary battery. And a bidirectional buck-boost converter that can move relative to each other.

JP 2001-359244 A (paragraphs [0009] to [0019], FIG. 1 etc.) Japanese Patent Laying-Open No. 2005-160154 (paragraphs [0017], [0018], FIG. 1 and the like)

  Generally, a voltage variable energy storage element such as an electric double layer capacitor has a smaller internal resistance than a secondary battery such as a lead storage battery. Here, the energy loss of the power source such as the secondary battery or the energy storage element is determined by the product of the square of the current during the charge / discharge time and the internal resistance of the power source, as shown in Equation 1.

In Equation 1, the energy loss of the power source is E _loss , the internal resistance of the power source is R, the charge / discharge time is T, and the charge / discharge current is i.

For this reason, as described in Patent Documents 1 and 2, when a secondary battery and a variable voltage energy storage element are used in combination as a power source for a motor drive device, an internal resistance is required during acceleration or deceleration that requires a large current. The power supply efficiency can be improved by preferentially using the voltage variable type energy storage element having a small voltage to transfer power.
However, for example, when an electric vehicle travels uphill, it is expected that energy consumption during acceleration will be large, and if the energy is always stored to the maximum so that the energy of the voltage variable energy storage element is not insufficient, When the energy consumption during acceleration is low, such as when driving downhill, the energy of the voltage variable energy storage element cannot be discharged sufficiently, and the energy regenerated when the vehicle is decelerated is The storage capacity of the energy storage element may be exceeded and the storage element may be damaged.

However, Patent Documents 1 and 2 described above do not disclose any countermeasures in these cases.
On the other hand, it is conceivable to use a voltage variable energy storage element having a large storage capacity in view of a margin of energy regenerated when the vehicle is decelerated. However, this causes a problem of increasing the cost.

  Accordingly, the problem to be solved by the present invention is that the voltage variable energy storage element can be controlled so that the energy storage amount of the voltage variable energy storage element becomes appropriate according to the traveling state of the electric vehicle, and the voltage variable energy storage element is prevented from being damaged, and the cost is reduced. It is in providing the motor drive device which can suppress the increase in this, and the electric vehicle provided with this motor drive device.

In order to solve the above-described problem, a motor drive device according to a first aspect includes a secondary battery as a first power source, a voltage variable energy storage element as a second power source, and first and second power sources. In a motor drive device having a drive power converter that is powered by one or both to drive a motor,
A step-up / down converter for transferring power between the first power source and the second power source and between the second power source and the driving power converter ;
Control means for controlling the buck-boost converter so that the energy storage amount of the second power source matches the target value using the voltage of the second power source and the value corresponding to the speed of the motor ,
The control means includes
When the speed of the motor is near zero, the second power source is charged from the first power source by controlling the buck-boost converter so that the energy storage amount of the second power source becomes a maximum value,
As the speed of the motor increases, the buck-boost converter is controlled so as to decrease the energy storage amount, and the first power source is charged from the second power source .

According to a second aspect of the present invention, there is provided the motor driving device according to the first aspect, further comprising a boost converter that boosts the voltage of the first power source .

Motor driving apparatus according to claim 3, characterized by Oite the motor driving apparatus as claimed in claim 1 or 2, wherein the voltage deformable energy storage device is an electric double layer capacitor or an electrochemical capacitor.

An electric vehicle according to a fourth aspect includes a motor drive device according to any one of the first to third aspects, a motor driven by the motor drive device, a vehicle body on which the motor drive device and the motor are mounted, , With .

An electric vehicle according to a fifth aspect of the present invention is the electric vehicle according to the fourth aspect, further comprising an inclination detection unit that detects the inclination of the vehicle body, and the control unit sets a plurality of target values of the energy storage amount of the second power source. And the buck-boost converter is controlled according to the target value selected according to the amount of inclination detected by the inclination detecting means .

Electric vehicle according to claim 6 is the electric vehicle according to claim 5, wherein the control means, the amount of tilt detected by the tilt detection means, determining that the vehicle is traveling on a travel path of the up-ramp In this case, when the target value of the energy storage amount in the vicinity of the motor speed of zero is set to the maximum value and it is determined that the vehicle is traveling on a downhill traveling path, The target value of the energy storage amount in is made smaller than the maximum value .

  According to the present invention, it is possible to give and receive a large current during acceleration / deceleration of a vehicle by giving priority to a voltage variable energy storage element having high charge / discharge efficiency. As a result, the capacity of the voltage variable energy storage element can be reduced, the power efficiency can be improved, and the cost can be reduced.

It is a block diagram which shows 1st Embodiment of this invention. It is a figure which shows the relationship between the motor speed in 1st Embodiment, and the energy storage amount of an electric double layer capacitor. It is a block diagram which shows 2nd Embodiment of this invention. It is a block diagram which shows 3rd Embodiment of this invention. It is a figure which shows the relationship between the motor speed in 3rd Embodiment, and the energy storage amount of an electric double layer capacitor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 assumes an electric vehicle equipped with a motor drive device 100A of the present invention.
In the main circuit of the motor drive device 100A, both ends of the lead storage battery 1 as a secondary battery are connected to a DC bus of a current reversible buck-boost converter 10 having a variable buck-boost ratio and a three-phase inverter 20 as a driving power converter. The positive electrode P and the negative electrode N are connected. The electric reversible buck-boost converter 10 is connected to an electric double layer capacitor 2 as a voltage variable energy storage element. Further, a three-phase AC motor M is connected to the AC output terminals U, V, W of the three-phase inverter 20.
In the above configuration, for convenience, the lead storage battery 1 is referred to as a first power source, and the electric double layer capacitor 2 is referred to as a second power source.

  In addition, the current reversible buck-boost converter 10 exchanges (charges and discharges) power between the lead storage battery 1 and the electric double layer capacitor 2, and further, between the electric double layer capacitor 2 and the three-phase inverter 20. A pair of terminals connected to the lead storage battery 1 and a pair of terminals connected to the electric double layer capacitor 2 are reversibly an input terminal and an output terminal.

A speed detection means 3 is attached to the output shaft of the motor M, and the output shaft is connected to a gear box 4 incorporating a reduction gear and a differential gear. Reference numeral 5 denotes a wheel.
Further, 6 is current detection means for detecting the charge / discharge current flowing through the lead storage battery 1, and 7 is voltage detection means for detecting the voltage of the capacitor 2.

Reference numeral 50 denotes a control circuit for the main circuit, which includes a microprocessor having a storage function and an interface circuit for inputting / outputting signals to / from the outside.
An acceleration command and a braking command for the motor M are input to the control circuit 50 from the outside, and a speed detection value by the speed detection unit 3, a current detection value by the current detection unit 6, and a voltage detection value by the voltage detection unit 7 are input. It is configured to output a control signal (gate signal) to the semiconductor switching elements of the current reversible buck-boost converter 10 and the three-phase inverter 20 by a control operation described later.

The control circuit 50 roughly performs the following two control operations.
In the first control operation, a control signal is given to the switching element of the three-phase inverter 20 based on the input acceleration command and braking command, the current of the motor M is controlled, and the torque of the motor M is controlled. Since the specific method is well-known, description is omitted here.
The second control operation generates a buck-boost command value for current reversible buck converter 10 based on the voltage value detected by the speed detection value, the voltage-detection means 7 by the speed detecting means 3, the converter 10 according to the command value By controlling the switching element, the terminal voltage of the capacitor 2 charged / discharged with the lead storage battery 1, that is, the energy storage amount is controlled.

Next, a method for controlling the amount of energy stored in the capacitor 2 will be described.
FIG. 2 shows the relationship between the motor speed and the energy storage amount (target value) of the capacitor 2. The maximum energy allowed by the capacitor 2 is charged from the lead-acid battery 1 so that the capacitor 2 can be used to the maximum as an acceleration energy source when the motor speed is near zero. In the case of other speeds, the energy storage amount of the capacitor 2 is adjusted according to the motor speed so that the capacitor 2 can be preferentially charged by regenerative energy by braking.

  When the motor speed is low, the amount of electric power regenerated by braking is small. On the other hand, when the motor speed is high, for example, close to the upper limit of the speed, less energy is consumed for further acceleration, and the amount of power regeneration by braking increases. Therefore, it is desirable to reduce the energy storage amount of the capacitor 2 in proportion to the speed.

Specifically, when the acceleration command or braking command to the control circuit 50 is inputted, by adjusting the output voltage of the current reversible buck converter 10, preferentially between capacitor 2 is the three-phase inverter 20 Control to give and receive energy. However, the energy storage amount of the capacitor 2 is adjusted by performing the following operation according to the energy storage amount of the capacitor 2.

That is, when the energy storage amount of the capacitor 2 at a certain motor speed is in the region of FIG. 2A, the current reversible buck-boost converter so that the energy storage amount of the capacitor 2 with respect to the motor speed becomes the target value. The output voltage of the capacitor 10 is increased, and the charge of the capacitor 2 is gradually discharged to the lead storage battery 1 to decrease the voltage of the capacitor 2.
On the other hand, when the energy storage amount of the capacitor 2 is in the region of FIG. 2B, the output voltage of the current reversible buck-boost converter 10 is lowered, and the capacitor 2 is gradually charged from the lead storage battery 1. Increase the voltage.
By such an operation, the energy storage amount of the capacitor 2 coincides with the target value over the entire range of the motor speed.

  In the above embodiment, the speed detection value of the motor M is used to determine the energy storage amount of the capacitor 2. However, the detection amount proportional to the motor speed such as the vehicle speed and the axle rotation speed, or the estimated motor speed (these and the speed) are used. Even if the detected values are collectively referred to as a value corresponding to the speed of the motor M), the energy storage amount can be similarly controlled.

Next, FIG. 3 shows a motor drive device 100B according to a second embodiment of the present invention.
In this embodiment, a lead-acid battery is connected via a current reversible boost converter (fixed boost ratio) 30 for boosting the output voltage of the lead-acid battery 1 as a first power supply for the purpose of increasing the output voltage of the three-phase inverter 20. This is an example in which 1 is connected to a DC bus.
The operation of this embodiment is the same as that of the first embodiment except that the output voltage of the lead storage battery 1 is boosted. The control circuit 50 uses a motor speed detection value as shown in FIG. As described above, the energy storage amount of the capacitor 2 can be adjusted by using the detected amount proportional to the motor speed, the estimated motor speed value, and the like.

Next, FIG. 4 shows a motor drive device 100C according to a third embodiment of the present invention.
This embodiment is different from the first embodiment in that when the motor driving device 100C is mounted on an electric vehicle, a tilt detecting means 60 for detecting the tilt of the vehicle body is provided, and the tilt amount as the detection signal is set. This is a point inputted to the control circuit 50.

When the traveling path of the electric vehicle is inclined downward, the regenerative energy is larger than the consumed energy. Therefore, in order to supply the regenerative energy to the capacitor 2 without leakage, the energy storage amount of the capacitor 2 is reduced in advance. It is necessary to keep.
On the other hand, when the travel path is uphill, the energy consumption is larger than the regenerative energy, so that the amount of energy stored in the capacitor 2 needs to be increased as much as possible.

From the above viewpoint, it is desirable to change the target value of the stored energy of the capacitor 2 with respect to the motor speed in accordance with the inclination of the travel path, as indicated by a in FIG.
For example, if it is determined that the vehicle is traveling on an uphill traveling road, the target value of the energy storage amount near the zero speed of the motor M is set to the maximum value, and the vehicle travels on a downhill traveling road. If it is determined that the energy is stored, the target value of the energy storage amount near the zero speed of the motor M is made smaller than the maximum value.
Here, for example, when the vehicle is traveling on an uphill traveling road and the energy is insufficient with only the energy stored in the capacitor 2, the lead storage battery 1 is discharged and the energy is also supplied to the three-phase inverter 20. .

Specifically, data corresponding to FIG. 5 is stored in the control circuit 50 in advance, and the corresponding one of the various characteristic lines in FIG. 5 is selected according to the amount of inclination input from the inclination detecting means 60, What is necessary is just to determine the energy storage amount target value of the capacitor 2 with respect to the motor speed, and the control circuit 50 may control the current reversible buck-boost converter 10 so that the actual energy storage amount matches this target value.
Also in this embodiment, in addition to the detected motor speed value, a detection amount proportional to the motor speed such as a vehicle speed, a motor speed estimated value, and the like can be used.

  In each of the above embodiments, an electrochemical capacitor may be used as the variable voltage energy storage element that is the second power source.

The motor drive device according to the present invention is not limited to an electric vehicle, and can be used for various devices and devices using a motor as a power source.
The electric vehicle according to the present invention can be used for various industrial vehicles including cargo handling machines.

1 Lead acid battery (secondary battery as the first power source)
2 Electric double layer capacitor (variable voltage energy storage element as the second power source)
3 Speed detection means 4 Gear box 5 Wheel 6 Current detection means 7 Voltage detection means 10 Current reversible buck-boost converter (variable buck-boost ratio)
20 Three-phase inverter 30 Current reversible boost converter (fixed boost ratio)
50 Control circuit 60 Inclination detection means 100A, 100B, 100C Motor drive device M Motor P Positive polarity of DC bus N Negative polarity of DC bus U, V, W AC output terminal

Claims (6)

A secondary battery as a first power source, a voltage variable energy storage element as a second power source, and a drive power converter for driving a motor by being fed by one or both of the first and second power sources In a motor drive device having
A step-up / down converter for transferring power between the first power source and the second power source and between the second power source and the driving power converter ;
Control means for controlling the buck-boost converter so that the energy storage amount of the second power source matches the target value using the voltage of the second power source and the value corresponding to the speed of the motor;
Equipped with a,
The control means includes
When the speed of the motor is near zero, the second power source is charged from the first power source by controlling the buck-boost converter so that the energy storage amount of the second power source becomes a maximum value,
A motor drive device that controls the step-up / step-down converter to charge the first power source from the second power source so as to decrease the energy storage amount as the speed of the motor increases . In the motor drive device according to claim 1,
A motor drive device further comprising a boost converter that boosts the voltage of the first power supply . In the motor drive device according to claim 1 or 2,
The motor drive device characterized in that the voltage variable energy storage element is an electric double layer capacitor or an electrochemical capacitor . A motor drive device according to any one of claims 1 to 3, a motor driven by the motor drive device, and a vehicle body on which the motor drive device and the motor are mounted. Electric vehicle. In the electric vehicle according to claim 4 ,
Inclination detecting means for detecting the inclination of the vehicle body,
The control means includes
An electric vehicle having a plurality of target values of the energy storage amount of the second power source, and controlling the step-up / down converter according to the target value selected according to the amount of inclination detected by the inclination detecting means . The electric vehicle according to claim 5,
The control means includes
When it is determined that the vehicle is traveling on an uphill traveling path based on the amount of inclination detected by the inclination detecting means, the target value of the energy storage amount in the vicinity of zero speed of the motor is set to the maximum value, An electric vehicle characterized in that, when it is determined that the vehicle is traveling on a downhill traveling path, a target value of the energy storage amount near zero speed of the motor is made smaller than the maximum value .

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