JPH0638550A - Inverter apparatus of electric vehicle - Google Patents

Abstract

PURPOSE:To provide the inverter apparatus of an electric vehicle, in which the breakdown of a switching element by an excessive regenerated voltage can be avoided without the interruption of a regenerative operation. CONSTITUTION:The apparatus is equipped with a means 43 for detecting a regenerated voltage and with an ON/OFF control means 12 for controlling the ON/OFF ratio of respective switching elements Q2, Q4, Q6 constituting an inverter apparatus lest the regenerated voltage should exceed a predetermined value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for an electric vehicle used for driving a motor of an electric vehicle.

[0002]

2. Description of the Related Art An inverter device used for driving a motor of an electric vehicle is arranged between a battery and an AC motor, and converts DC power supplied from the battery into AC power and supplies the AC power to the motor when the motor is driven. It is supposed to do. In this type of electric vehicle inverter device,
It also has the function of regenerative operation that converts the AC electromotive force generated by the motor while the electric vehicle is traveling downhill into DC power by the boost chopper method and returns it to the battery as regenerative power.

When an electric vehicle is running on a long and steep downhill, a large amount of regenerative electric power is generated for a long period of time, so that the regenerative voltage may be excessively large enough to exceed the withstand voltage of each switching element constituting the inverter device. There is.

Jikken Sho 6 entitled "Inverter Security Device"
In JP-A-35594, in order to protect the switching element from the excessive regenerative voltage as described above, a regenerative voltage detecting means and a switch are provided between the battery and the inverter circuit, and the detected regenerative voltage is predetermined. A structure is disclosed in which when the threshold value is exceeded, the switch is opened to stop the regenerative operation, thereby avoiding destruction of the switching element.

[0005]

In the conventional inverter device with a protection function during regeneration, the regenerative operation to the battery is stopped when the regenerative voltage exceeds a predetermined threshold value. For this reason, there is a problem that the regenerative efficiency to the battery is reduced and the inverter device, which consumes the regenerated power as Joule heat loss, overheats.

[0006]

SUMMARY OF THE INVENTION An inverter device of the present invention uses a regenerative voltage detecting means for detecting a regenerative voltage during a regenerative operation, and a step-up chopper system so that the detected regenerative voltage does not exceed a predetermined value. An ON / OFF control unit that controls the ON / OFF time rate of each operating switching element is provided.

[0007]

The regenerative voltage of the inverter device is inversely proportional to the off time of the switching element operating in the step-up chopper method. Therefore, the regenerative voltage that is actually generated is detected by the regenerative voltage detecting means, and when it is about to exceed a predetermined threshold value that is lower than the withstand voltage of the switching element by a margin for safety, the off time rate of the switching element is increased. On / off control of the switching element is performed to reduce the regenerative voltage. As a result, destruction of the switching element is effectively avoided without stopping the regenerative operation.

[0008]

1 is a circuit diagram showing the configuration of a three-phase inverter device 10 according to an embodiment of the present invention together with related batteries 20 and a motor 30. This three-phase inverter device 10
Is a switching circuit 11 in which bipolar type switching transistors Q _{1 to} Q ₆ are connected in a bridge shape as an example of a switching element, and each switching transistor Q _{1 to} Q constituting the switching circuit 11.
_The ON / OFF control unit 12 controls the opening and closing of ₆ by raising and lowering the voltage supplied to each base voltage.

Reference numeral 41 is a three-phase rotation sensor for detecting the rotation position of the rotor of the motor 30 (represented by three-phase stator windings U, V, W), and the rotation position detected by this is electric. Three-phase control signals Cu and C whose angles are shifted by 120 °
It is supplied to the on / off control unit 12 of the inverter circuit 20 as v and Cw. The on / off control unit 12 receives the three-phase control signals Cu, Cv, Cw received from the rotation sensor 41.
And, a DC current or DC voltage received from the ammeter 42 and the voltmeter 43, based on a motor designated from the external output, six constituting the switching circuit 11 of the switching transistors Q ₁ to Q ₆ on / Off control.

The on / off control unit 12 controls the six switching transistors Q ₁ during the driving operation of the motor 30.
A rotating magnetic field is generated by passing the three-phase stator windings U while Yuki by migrating a pair at a time sequentially turned on at different electrical angles by 120 ° of the to Q _6, V, successively current W , Rotate the rotor of the motor 30. At this time, the on / off control unit 12 determines the on / off time of the switching transistors Q _{1 to} Q ₆ based on the motor output designated from the outside, the supply power obtained by the ammeter 42 and the voltmeter 43, and the like. Control the rate.

During the regenerative operation, the motor 30 operates as a three-phase AC generator, and AC voltage is sequentially induced in the three-phase winding. During this regenerative operation, the switching transistor to Q ₁ high-pressure side, Q _3, Q ₅ is is held always turned off, the diode D ₁ of the parallel-connected high-voltage side to these switching transistors, D _3, D _5, and the low-voltage side switching transistors Q ₂ , Q ₄ , and Q ₆ perform a boost chopper-type regenerative operation.

Assuming that the highest AC voltage is induced in the U-phase winding, the equivalent circuit under this condition is shown in FIG.
As shown in. High-voltage side switching transistors Q ₁ and Q that are held in the off state during regenerative operation
_{Since 3} and Q ₅ are in a high impedance state, only the diodes D ₁ , D ₃ and D ₅ connected in parallel with each other need to be considered. In addition, the induced voltage in the U-phase winding is higher than the induced voltage in the V-phase and W-phase windings, and the diodes D ₃ , D
_{Since 5} is reverse biased, it is excluded from this equivalent circuit.

Further, under the condition that the highest AC voltage is induced in the U-phase winding, as shown in the waveform diagram of FIG. 3, the switching transistors Q ₄ and Q ₆ are both in the high impedance OFF state. Therefore, it is necessary to consider only the diodes D ₄ and D ₆ connected in parallel with each other. Therefore, in this state, as shown in FIG. 2, the diode D ₁ , the switching transistor Q ₂ , and 3
A step-up chopper circuit mainly composed of the inductances of the phase windings U, V, W and the induced voltage Em is formed.

The switching transistor Q ₂ is turned on / off at a frequency sufficiently higher than the rotation frequency of the rotor of the motor 30. The on time of the switching transistor Q ₂ is t _on , the off time is t _off , and the regenerative voltage is V
If o, then Vo = [(t _on + t _off ) / t _off ] Em.

The on / off control section 12 controls the off time t _off of the switching transistor Q _{2 in} an increasing direction when the regenerative voltage Vo detected by the voltmeter 43 is approaching a predetermined threshold value. The regenerative voltage Vo is controlled so as not to exceed the threshold value. This predetermined threshold value is set to a value obtained by subtracting an appropriate safety margin from the breakdown voltage between the emitter and collector of the switching transistor Q ₂ . As shown in FIG. 3, the switching transistor Q
_The same applies to the step-up chopper operation by ₄ and Q ₄ .

The case where the bipolar transistor is used as the switching element forming the inverter has been described above. However, the present invention can be applied to the case where other appropriate switching elements such as MOSFET are used.

Although the inverter circuit of the present invention has been illustrated for the case of driving a three-phase AC motor, the present invention can be applied to the case of using another appropriate motor such as a six-phase AC motor.

[0018]

As described in detail above, the inverter circuit of the present invention is configured to detect the regenerative voltage and control the on / off time rate of each switching element so that it does not exceed a predetermined value. Therefore, it is possible to effectively avoid the destruction of the switching element without stopping the regenerative operation.

As a result, the regeneration efficiency to the battery is improved and the temperature rise due to the heat generation of the switching element is effectively avoided.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an inverter device for an electric vehicle according to an embodiment of the present invention together with related batteries and a motor.

FIG. 2 is an equivalent circuit diagram for explaining the operation during regeneration by the inverter device of the electric vehicle of FIG.

FIG. 3 is a waveform diagram for explaining the operation during regeneration by the inverter device of the electric vehicle of FIG.

[Explanation of symbols]

 10 inverter device 11 switching circuit 12 on / off control circuit 20 battery 30 three-phase motor 41 rotation sensor 43 voltmeter for detecting regenerative voltage

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoyuki Ito 1-4-1 Chuo, Wako City, Saitama Stock Company Honda R & D Co., Ltd.

Claims (1)

[Claims] 1. A step-up chopper system which is arranged between a battery and a motor, converts DC power supplied from the battery into AC power when the motor is driven, and supplies the AC power to the motor, and AC power generated by the motor during regenerative operation. An inverter device for an electric vehicle which supplies DC power as regenerative power to a battery by converting the DC power into a regenerative power, wherein the regenerative voltage detecting means detects a regenerative voltage during the regenerative operation, and the detected regenerative voltage has a predetermined value. An inverter device for an electric vehicle, comprising: an on / off control means for controlling an on / off time rate of each switching element constituting the inverter so as not to exceed the limit.