JP2001211511A - Electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high efficiency, energy saved, and low cost electric vehicle by reducing loss of a converter and a driving motor, and achieve miniaturization and weight reduction of the vehicle. SOLUTION: Setting up a booster circuit between a battery and an inverter circuit in an electric vehicle having a battery as a driving power source. The booster supplies the inverter with a higher voltage than a battery voltage when a higher torque is required such as for starting, accelerating, or having a vehicle climbing a gradient; the booster circuit activates the inverter circuit, boosts an input d.c. current to the inverter circuit above the battery voltage, and decreases an element current of a main controller of the inverter. When a low torque is allowed such as for constant driving on the ground, an d.c. input voltage to the inverter is kept the same level as a battery voltage and the booster circuit is stopped, so that an iron loss of the driving motor is decreased. In this way, an appropriate d.c. current is supplied to the inverter corresponding to a driving condition of the electric moving vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an electric traveling vehicle.

[0002]

2. Description of the Related Art At present, an electric traveling vehicle runs a driving motor from a battery as a driving energy source by operating a driving motor through a chopper circuit or an inverter circuit shown in FIG. 2 as shown in FIG. Therefore, the operating voltage of the motor cannot be higher than the battery voltage. Therefore, when a large torque is required, a large current needs to be supplied. Therefore,
The switching element and the electrolytic capacitor constituting the chopper and the inverter also need to have a large current capacity, and the size of the cooler for dissipating the heat generated by the loss increases. As a result, the size of the driving device is increased and the weight is increased.

[0003] For an electric traveling vehicle, an increase in the loaded weight leads to an increase in the capacity of a battery as an energy source, which is not preferable from the viewpoint of energy saving and environmental destruction. Further, the semiconductor element which is the main control element of the chopper circuit and the inverter has a low voltage and a large current, and the market demand is small and the semiconductor element is not commercially available. Therefore, to control a large current, it is necessary to use a large number of elements in parallel or to develop a new large current element. These are problematic in terms of cost because they are costly.

[0004]

SUMMARY OF THE INVENTION An inexpensive electric traveling vehicle which is highly efficient and energy saving by reducing the loss of the conversion device and the drive motor constituting the electric traveling vehicle and reducing the size and weight. The task is to provide.

[0005]

SUMMARY OF THE INVENTION An electric traveling vehicle according to the present invention for solving the above-mentioned problems is in the scope of the claims. A booster circuit is provided between the battery and the inverter circuit so that the voltage supplied to the inverter can be supplied to a voltage higher than the battery voltage. When the torque is required, the booster circuit is operated to boost the input DC voltage of the inverter circuit to the battery voltage or more, thereby reducing the current of the main control element that constitutes the inverter and increasing the supply voltage to the drive motor to reduce the current. Plan. In addition, when low torque is required as in the case of steady driving on level ground, the DC input voltage of the inverter is used as the battery voltage, so the operation of the booster circuit is stopped, and the inverter output voltage is lowered to reduce iron loss of the traveling motor. According to the present invention, an optimum DC voltage can be supplied to an inverter according to the driving condition of an electric traveling vehicle.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 3 shows the required torque of the motor in the driving state of the electric traveling vehicle according to the embodiment of the present invention. FIG. 4 is a configuration diagram of an electric control circuit and a control unit of a booster of the traveling system of the present invention, and FIG. 5 is a control configuration diagram of an inverter unit.

In FIG. 3, τ0 is a torque required when the electric traveling vehicle is traveling on a flat ground, and Tmax is a torque required when traveling uphill. In the case of a traveling vehicle, τ0 / τmax = 1
The difference due to the allowable uphill gradient of the vehicle is large, such as / 5 to 1/20. Therefore, the torque τmax can be guaranteed in the low-speed running region of the starting and the uphill running, and the torque τ0 is guaranteed in the running speed region higher than the uphill running speed. The sum of the torque and the acceleration torque is the required torque of the electric traveling vehicle. FIG. 3 shows the envelope of τ obtained by adding the acceleration torque in the hatched portion to τmax and τ0. In FIG. 3, the acceleration torque immediately after the uphill traveling speed is large, but the greater the acceleration torque, the more reserve power is obtained, and the traveling vehicle has excellent acceleration performance. However, if the motor supply voltage is kept constant,
When the speed is increased, the generated torque is represented by the squared reduction torque. In the case of a general electric traveling vehicle having the maximum supply voltage at the maximum climbing speed, the characteristic shown in FIG. 3 is obtained.

Here, since the torque generated by the induction motor is proportional to the square of the voltage, the relationship between the traveling speed and the motor voltage when the required torque is small as in the case of steady traveling is shown in FIG.
By controlling the relationship between the traveling speed and the motor voltage when a large torque is required, such as when starting, accelerating, and traveling uphill, by controlling with a high voltage as indicated by Vh. The motor current can be reduced and the required torque can be obtained efficiently. In order to control the motor voltage in this manner, it is effective to increase the inverter DC input voltage to a value equal to or higher than the battery voltage when the battery voltage (96 V or less) is low as in an electric traveling vehicle.

FIG. 4 shows a booster circuit for boosting the DC voltage of the inverter to a voltage higher than the battery voltage. When the semiconductor switch 43 is turned on, the battery 41 and the reactor 4
2. The closed loop current i of the semiconductor switch 43 and the current detector 50 is i = Vb /
It increases by L × t. When the current i reaches the target value and the semiconductor switch 43 is turned off, 1 /
The energy of 2Li × i is released to the electrolytic capacitor 45 via the diode 44. As a result, the voltage of the electrolytic capacitor 45 increases.

In FIG. 4, Vref is a target value of the inverter DC input voltage, and is a voltage detection value Vd of the electrolytic capacitor 45.
An error amplifier 53 with a limiter error-amplifies the difference voltage from the signal et, and the output of the error amplifier 53 is used as a current target value to amplify the error with a current detection value 1 det and an error amplifier 55 with a limiter. The output of the error amplifier 55 is a sawtooth wave generator 5
6 is compared with a comparator 58. The comparator 58 operates to turn on the semiconductor switch 43 when the output of the error amplifier 55 is large, and to turn off the semiconductor switch 43 when the sawtooth wave is large. The drive circuit 60 power-amplifies the output of the comparator 58 by the drive circuit of the semiconductor switch 43. By repeating the above operation, the inverter DC input voltage is controlled so as to be boosted to the target voltage, and the relationship between the traveling speed of the electric traveling vehicle and the motor voltage is operated at the voltage indicated by the voltage Vh line in FIG. .

Next, the operation of the semiconductor switch 48 will be described. When the traveling vehicle finishes accelerating and enters a steady driving state,
Since the motor-generated torque may be small, it is required to operate the inverter DC input voltage at the battery voltage from the viewpoint of efficiency. However, since the voltage of the electrolytic capacitor C is boosted, the voltage is higher than the battery voltage. In this state, the outputs of the error amplifiers 53 and 55 have polarities opposite to those at the time of the boosting operation, and are compared with the output of the sawtooth wave generator 57 by the comparator 59. When the output of the error amplifier 55 is at a high potential, the output of the comparator 59 operates to turn on the semiconductor switch 48. On the other hand, when it is at a low potential, it turns off. When the inverter is in the regenerative operation state, the voltage of the electrolytic capacitor 45 rises. In this case also, the regenerative energy is regenerated to the battery 41 by the control of the semiconductor switch 48, and the inverter DC input voltage is maintained at the target voltage value. .

Next, how the booster circuit operates and deactivates according to the required torque of the electric traveling vehicle will be described with reference to FIG. FIG. 5 is a control block diagram of the inverter unit according to the present invention, showing vector control. FIG.
The difference between the accelerator speed command 71 and the output of the speed estimating unit 75 is error-amplified by the PI amplifier 72. If the output of the error amplifier 72 is at the limit value and the difference between the speed command value ω ^* and the output ω of the speed estimating unit 75 or the speed calculating unit 74 is equal to or greater than the allowable slip speed difference of the motor, the vehicle is in an acceleration state. Is determined, and the value of the inverter input DC voltage target value Vref in FIG. 4 is set to a value to increase the battery voltage to the battery voltage or higher in order to operate the booster circuit. However, if the difference between the speed command value ω ^* and the detected speed value ω is within the allowable slip speed, it is determined that the vehicle is traveling normally, and the inverter input DC voltage target value V
The value of ref is such that the voltage characteristic of the line VL in FIG. 3 can be obtained. That is, in order to stop the boost operation of the boost circuit,
Set to the battery voltage value.

Next, according to the traveling state of the electric traveling vehicle,
The speed-torque pattern setting unit 76, the magnetic flux setting pattern unit 77, and the torque limit setting pattern unit 83 in the vector control block diagram also need to be switched according to the inverter input DC voltage target value. In FIG. 5, h of each pattern is selected when the inverter DC input voltage is at a value higher than the battery voltage, and L is selected when the inverter DC input voltage is at the battery voltage value. By doing so, the motor can be operated stably and energy-saving by the inverter.

[0015]

As described above in detail with the embodiments of the present invention, when the driving device for an electric traveling vehicle according to the present invention requires a high torque, it is operated at a high voltage higher than the mounted battery voltage. In addition, at the time of low torque operation, by operating the battery voltage, the currents of the inverter and the motor can be reduced, and the loss can be reduced.

By reducing the current, the inverter components and the electrolytic capacitor can be miniaturized, and at the same time, the traveling drive unit can be miniaturized and the load weight can be reduced. Therefore, it is possible to reduce the capacity of the battery or extend the traveling distance.

Commercially available mass-produced products can be applied by reducing the current of the inverter element. As a result, an inexpensive electric traveling vehicle can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a traveling drive system of a conventional chopper type electric traveling vehicle.

FIG. 2 is a configuration diagram of a traveling drive system of a conventional inverter-type electric traveling vehicle.

FIG. 3 is a characteristic diagram showing a relationship between a motor generated torque, a motor terminal voltage, and a traveling speed required for an electric traveling vehicle.

FIG. 4 is a circuit configuration diagram of the present invention.

FIG. 5 is a control block diagram of an inverter unit according to the present invention.

[Explanation of symbols]

 1,21,41 Battery 2 Chopper circuit 3 DC motor armature 4 Field winding 5,44,49 Diode 6 Closing contactor 22,45 Electrolytic capacitor 23,46 Inverter 24,47 Induction motor 42 Reactor 43,48 Semiconductor switch 50 , 54 Current detector 51 Inverter DC input voltage target value 52 DC voltage detector 53, 55, 72 PI error amplifier (with limiter) 56 Sawtooth wave generator (positive side) 57 Sawtooth wave generator (negative side) 58 Comparator (positive side) 59 Comparator (negative side) 60, 61 Drive circuit 71 Accelerator 73 Slip operation unit 74 Speed operation unit 75 Speed estimation unit 76 Speed-torque pattern setting unit 77 Magnetic flux setting pattern unit 78 Speed pulse detector 79 Current control Units 80, 81 2-axis to 3-axis conversion unit 82 Phase angle calculating section 83 torque limit pattern unit

Claims (1)

[Claims] In an electric traveling vehicle provided with a booster circuit between a battery and an inverter, the booster circuit is operated in a running state requiring a large torque, such as at the time of starting acceleration or uphill running. By increasing the inverter DC input voltage to a level higher than the battery voltage, the inverter output voltage is increased.In low-torque driving conditions such as when driving on flat ground, the inverter operates at the battery voltage without boosting the inverter DC input voltage. An electric traveling vehicle characterized by suppressing an increase in motor current, reducing iron loss and copper loss, and achieving energy saving operation.