JPS62236302A - Controlling method for induction motor of electric vehicle - Google Patents

Abstract

PURPOSE:To shorten the regulating time of a motor magnetic flux until a target torque is obtained by applying a correcting motor magnetic flux larger than the optimum motor magnetic flux when the motor magnetic flux is transiently regulated at an output torque increasing time. CONSTITUTION:A torque calculator 12 outputs a target torque T* in response to a travel command and traveling conditions. The torque T* is converted by an efficiency optimizing circuit 14 together with a motor frequency fm into an optimum motor magnetic flux phi* and optimum torque current I*T for minimizing a general motor loss. It instructs larger motor magnetic flux phi*n than the magnetic flux phi* at transient regulating time until the motor magnetic flux rises to the optimum motor magnetic flux. A correcting motor magnetic flux phi*n and the current I*T are supplied to a vector calculator 16, the output of which is supplied through a PWM controller 18 to an inverter main circuit 20.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling an induction motor for electric motor vehicle 1'JJ (7) relates to a method of controlling a dielectric motor for an electric vehicle.

[Prior Art] Electric vehicles are being researched as pollution-free vehicles that do not produce harmful exhaust gases, and some are already at the stage of practical application.

In the early days, easy-to-control DC motors were used as the drive source for electric vehicles, but maintenance of brushes and other parts of these DC motors was troublesome, so in recent years, easy-to-maintain inverter control has been used as the drive source for electric vehicles. Induction motors have come into use.

As is well known, motors used in electric vehicles are torque-controlled, unlike ordinary industrial motors, and in order to perform the necessary torque control and stabilize the vehicle's maneuverability, vector control or slip frequency control is used. The induction motor is controlled 1IIIJ.

[Problem to be Solved by the Invention 1] As is well known, the output torque of an induction motor is proportional to the product of the motor magnetic flux and the torque Ti current, and in order to reduce the required torque by 1!7, the motor magnetic flux and torque current must be All you have to do is change one of these to give the necessary primary current to the induction motor.

However, in the conventional device J3, control was performed in the magnetic flux-window region, and the output torque was changed only by changing the torque current.

According to such a conventional control method, the control process can be simplified, but on the other hand, there is a problem in that the motor loss cannot always be reduced in response to widely varying torque.

In other words, the motor loss of an induction motor includes both magnetic flux loss due to motor magnetic flux and torque current loss due to torque current, and both of these losses depend on the set motor magnetic flux and torque current, respectively. When the magnetic flux is held constant, there is a problem in that the loss increases significantly depending on the output torque of the induction motor.

In particular, in the case of control in which the motor magnetic flux is kept constant, the constant magnetic flux is usually set as a region where the motor magnetic flux is fixed at the maximum value, and the optimum efficiency is always maintained at 1! over a wide range of output torque regions. ? It is impossible.

Such an increase in motor loss increases the power consumption of electric vehicles and reduces the distance that they can travel on the limited number of used batteries, which has been a major impediment to the development of electric vehicles.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to adjust the motor magnetic flux and torque current by controlling the primary current in the entire range of output torque that fluctuates greatly, and to reduce magnetic flux loss and torque current. It is an object of the present invention to provide a control method for an induction motor for an electric vehicle, in which the total motor loss of both losses is minimized, and the time required to adjust the motor magnetic flux until a target torque is obtained is shortened.

[Means for Solving the Problems 1] In order to achieve the above object, the present invention, unlike conventional motor magnetic flux constant control, provides an optimal motor that minimizes the total motor loss depending on the required target torque and motor rotation speed. First calculate the magnetic flux, then calculate the optimal torque current for outputting the target torque at this determined optimal motor magnetic flux, and calculate the target torque required for all induction based on the travel command and travel conditions, In the control method for an electric vehicle induction motor that supplies a desired primary current to the Xi motor so that the target torque is output, Calculate the optimal motor magnetic flux that minimizes motor loss, then calculate the optimal torque current for outputting the target torque with the determined optimal motor magnetic flux from the motor magnetic flux/torque current characteristic data, and further calculate the optimal motor magnetic flux. Based on the difference between the current motor magnetic flux and the current motor magnetic flux, a correction motor magnetic flux greater than the optimum motor magnetic flux is calculated to compensate for the delay in motor magnetic flux change that occurs during transient increases in motor magnetic flux adjustment. During the magnetic flux adjustment transition, the primary Ti flow command is supplied to the induction motor determined by the magnetizing current to obtain the corrected motor magnetic flux and the optimum torque current, and when the adjusted motor magnetic flux reaches the optimum motor magnetic flux, The present invention is characterized in that a primary current command that minimizes motor loss is supplied to the induction motor from the magnetizing current for obtaining the optimum motor magnetic flux and the optimum torque current.

[Operation] Therefore, according to the present invention, both the motor magnetic flux and the torque current can be adjusted to optimal values and with good responsiveness in order to obtain the necessary target torque, and the required target torque can be adjusted in the entire torque range and frequency range. As a result of controlling the current consumption to a minimum, it becomes possible to dramatically expand the travel distance of an electric vehicle.

In the present invention, the target torque is determined by a predetermined calculation formula from the given travel command and travel data. The optimum motor magnetic flux that minimizes the motor loss in terms of the number is determined. Then, the torque current that can obtain the required target torque according to this 1q R total - evening magnetic flux is determined, and the optimum is further calculated based on the monthly evening magnetic flux and the current motor magnetic flux. , a corrected motor magnetic flux that compensates for the delay in the change in motor magnetic flux during an adjustment transient is determined, and a magnetizing current is set to obtain a corrected motor magnetic flux that is larger than the optimum motor magnetic flux during an adjustment transient of the motor magnetic flux when the output torque increases. , and after the adjusted motor magnetic flux reaches the optimum motor magnetic flux, the primary current given to the induction motor is finally calculated from both the magnetizing current that increases the optimum motor magnetic flux by 1":J and the optimum torque current. .

[Example] Preferred embodiments of the present invention will be described below based on the drawings.

Figure 3 shows an ideal vector diagram of the induction motor.A magnetizing current of 1° on the vertical axis produces a magnetic flux Φ of the induction motor, and a torque current I□ on the horizontal axis causes Along with the motor magnetic flux, torque can be generated in the motor. Therefore, the magnetizing current I in the induction motor. and torque current 1. A primary current 11, which is the vector sum of , is supplied.

Therefore, by controlling the f2 magnetizing current 1° and the torque current I□ so that the -order current 11 moves on the constant torque line, it is possible to always maintain a constant constant torque. That is, in the present invention, unlike the conventional method, even when the motor magnetic flux Φ is changed, the torque current 1. By setting , it is possible to obtain the required target torque.

The motor magnetic flux Φ and the torque current IT are also determined by the separate losses determined by the primary current 1 such that the total loss of each is minimized and a constant torque is output.
It is understood that 1 can be arbitrarily selected.

In addition, in Fig. 3, the constant 1 to lq line shows the ideal characteristic of constant torque, ignoring the phase shift due to the resistance component and inductance component of the motor coil, but in reality, when adjusting the -order current, Due to these components, the magnetic flux lags behind the torque current.

Therefore, during the transition period until the magnetic flux reaches the optimum motor magnetic flux, the required target torque by the 11th-order current supply has not yet been obtained.

In the present invention, based on such a principle, first, the optimum motor magnetic flux Φ1 that results in the minimum motor loss is determined in order to reduce the required target torque by 1!7, and then the target torque T" is determined by this motor magnetic flux Φ". Optimal torque current to obtain1.
Further, calculate the corrected motor magnetic flux Φ*n for responsively adjusting the motor magnetic flux during the motor magnetic flux adjustment transient when the target torque T1 increases, and calculate the optimum motor magnetic flux Φ1 during the motor magnetic flux adjustment transient. Magnetizing current necessary to obtain larger correction motor magnetic flux Φ*n@ and optimal torque current ■
After the motor magnetic flux reaches the optimum motor magnetic flux after adjusting the induction motor with the primary current determined from It is characterized by

Figure 4 shows the magnetic flux/U loss characteristics for determining the overall minimum motor loss of 10 times for an induction motor, and the horizontal axis shows the motor magnetic flux Φ
The vertical axis shows the total temperature loss η caused by both the motor magnetic flux and the torque current.

In Figure 4, the rotational speed of the induction motor is held constant, and the three characteristics are each made up of Tanabata's output torque, and the characteristics of large, medium, and small motor output torque are illustrated as shown in the figure. ing.

Therefore, from FIG. 4, by connecting the regions where the bottom values of each characteristic occur, it is possible to find the minimum motor loss region indicated by diagonal lines in the diagram. It is understood that as the motor output 1-lux decreases, the motor loss tends to be minimized where the motor magnetic flux is small. Of course, FIG. 4 shows the characteristics at an arbitrarily determined constant rotation speed, and it is possible to obtain such characteristics for all motor rotation speeds required for an electric vehicle.

Figure 5 is a diagram showing the magnetic flux/loss characteristics explained in Figure 4 above on a map showing the motor that minimizes the overall motor loss according to each change in the motor rotation speed N, and the required motor output. In order to obtain the torque T, it becomes clear whether the value of the motor magnetic flux with the minimum loss should be determined according to the current motor U rotation speed N.

Such magnetic flux/IC1 loss characteristic data differs depending on each induction motor or electric vehicle to be installed, and these data are determined in advance by experiment and 31r1 for a specific model of electric vehicle. This map data can be readably incorporated into a motor control circuit as ROM or other stored information.

If the optimal motor magnetic flux Φ" is determined as described above, it becomes possible to obtain the necessary optimal torque current Φ" based on the constant torque characteristics shown in FIG. can be easily derived from predetermined data, and such data can also be recorded on the ROM of the circuit.

FIG. 6 shows an example of a map for determining the optimum torque current I*. The motor torque current ■, which is determined according to the motor rotation speed N and the motor output torque T, is displayed on the map as shown in the figure. Such motor torque current data can also be recorded on the ROM of the circuit in a readable manner as described above.

FIG. 1 shows a case where the control method according to the present invention described above is used for actual control of an induction motor for an electric vehicle.
A control circuit for overriding the flow rate of FIG. 1 is shown in FIG.

In FIG. 2, an induction motor 10, which is a drive source of an electric vehicle, is controlled by an inverter, and a vector calculation circuit is used to control the inverter 1111.

1 to the torque calculation device ￥ff12 outputs the necessary target torque TI according to the vehicle running command and running conditions, and this target torque is sent to the efficiency optimization circuit 14 to calculate the optimum motor magnetic flux Φ8 characteristic of the present invention. The corrected motor magnetic flux Φ*n is calculated based on the calculation of both the optimum torque current Ibi and the optimum motor magnetic flux Φ9 and the current motor magnetic flux. and,
The corrected motor magnetic flux Φ*n and the optimum torque current IT' obtained in this way are supplied to the vector calculation circuit 16 for vector control, and the output of the correction motor magnetic flux Φ*n is supplied to the PWM control circuit 18.
is supplied to the inverter main circuit 20, and the primary current of the induction motor 10 is controlled.

The current of the induction motor 10 is supplied from a battery 22 via the inverter main circuit 20.Furthermore, the voltage of the battery 22 is detected by a voltage detection circuit 24 and is supplied to the induction motor 10 from the inverter main circuit 2 Ohs. The current detected by the induction motor 10 is detected by the current detection circuit 26, and the rotation speed of the induction motor 10 is detected by the pulse generator 28, and each of these detection signals is supplied to a desired arithmetic unit and control circuit.

When the control circuit is initialized in FIG. 1, motor control according to the present invention is executed, and various data are read in step 101.

The read data is a forward/reverse switch, an accelerator sensor,
Accelerator switch, brake sensor, and play: Contains both the running command given from the V switch and the running line '1' including motor temperature, inverter temperature, motor rotation speed, battery temperature, and battery voltage, and the torque estimating device 12 These runs) F? Calculate the required target 1~lux T* based on the command and driving conditions (step 102.10
3>.

In the embodiment, step 103 shows a correction effect based on battery temperature or inverter temperature, and if the temperature is above 7? n
), normally, the required torque TI is reduced by a predetermined amount to determine the required target torque T.

Setting of the target 1 Herc in the motor running command and running conditions (, 1) is calculated from characteristic data determined for each electric vehicle as in the conventional case, and FIG. 7 shows an example of such characteristic data.

In FIG. 7, the horizontal axis represents the motor rotation speed N, with a positive region representing forward rotation and a negative region representing reverse rotation.

Further, the vertical qsl+ indicates the output torque T.

When the electric vehicle is currently stopped, it is in the position indicated by the symbol a, and when moving forward 3W in this state, the accelerator is opened, and the accelerator is 100%. , ; The motor output torque increases rapidly toward b.

The electric car starts when this motor output 1-lux is generated, and as shown by the thick solid line, the motor rotation speed N increases sequentially, and when the motor rotation speed is constant, the motor output torque also gradually reaches d at position C. It decreases towards the end. When the accelerator is released from d, the motor output torque decreases to T+Je while maintaining a constant motor rotation speed N, and further, at this accelerator opening, the motor rotation speed N increases toward f.

When stopping the car from f, the accelerator is released and the brake is depressed, and the motor output torque T shifts to the negative region, and the motor output torque T is maintained at q, which is determined by the brake depression state, and this state is a regeneration state. It shows. As the brake is depressed, the motor rotation speed N gradually decreases,
At h, the car stops and returns to its original position, Fia.

The characteristics shown in FIG. 7 are determined in advance by each electric vehicle.
This characteristic data is written in the ROMW of the torque calculating device 12 shown in FIG. 2, and this target torque is read out as appropriate according to the traveling command and traveling conditions.

The target torque TI is the motor rotation speed output from the pulse generator 28, and in the embodiment, together with the motor frequency fm, the efficiency F1 optimization circuit 17I calculates the optimum motor magnetic flux Φ8 and the optimum motor to minimize the overall motor loss. It is converted into torque current TT'. This calculation is performed by fortune-telling in step 104 of FIG. In step 104, an optimum motor is selected based on the required target torque T* and motor rotational speed N (fm) and the magnetic flux/loss characteristic data shown in FIG. Magnetic flux Φ9 is determined.

Furthermore, the necessary optimum torque current 11* is obtained from the optimum motor magnetic flux Φ9 obtained above based on the data shown in FIG. 3 or 6 described above.

Next, in step 105, the delay in change of the motor magnetic flux with respect to the torque current is taken into account, and the corrected motor magnetic flux is
Calculate. This corrected motor magnetic flux Φ1o is determined to be larger than the optimal motor magnetic flux Φ1, considering that it is not possible to achieve the desired target torque T* (9) during the adjustment transition until the motor magnetic flux rises to the optimum motor flux. By commanding the magnetic flux Φ1, the motor magnetic flux is changed with good response.This is set in order to shorten the adjustment transient time.By supplying a magnetizing current larger than the magnetizing current corresponding to the optimum motor magnetic flux. This speeds up the rise of motor magnetic flux.

The calculation for changing this corrected motor magnetic flux Φ8 is performed by the following equation.

Φ n=medium +1/2 (Φ1-01)...(1
) In Equation (1), Φ9 represents the current motor magnetic flux, and the corrected motor magnetic flux 9 is determined according to the difference between the optimum magnetic flux Φ1 and the current motor magnetic flux Φゝn-1.

Therefore, after the motor magnetic flux Φ8 rises to the optimum motor magnetic flux Φ9, the optimum motor magnetic flux Φ1 is commanded.

The rAq processing 11p in steps 104 and 105 described above is constantly performed by the efficiency optimization circuit 14 in FIG.

When the corrected motor magnetic flux Φ*n and the optimum torque current r- are determined as described above, (1) Next, in this embodiment, the calculation of the motor voltage V1 and the motor next frequency f1 is performed by vector control. l
1 by the numbing circuit 16 (step 106).

There is a pulse generator 28 in the vector control path 16.
The motor frequency fm given from
Battery voltage V detected from . are input 8, and these detection ports and the given correction motor magnetic flux Φ*n
The desired vector calculation is performed using the optimum torque current 1''.The result of the vector calculation is PW
It is supplied to the M control circuit 18, and the round slip frequency FS'/
fi is added to the motor frequency fm and the motor frequency f1 is set as PW M ii! Itin circuit 18
is supplied to

, j The PWM control circuit 18 supplies a pulse signal P, which is an inverter control signal, to the inverter main circuit 20 from the supplied motor voltage ■1 and motor frequency f1 (step 107), and the inverter main circuit 20 receives this input. Based on the generated pulse signal P, the direct current power of the battery 22 is converted into necessary alternating current power, and the desired primary current is supplied to the induction motor 16.

Therefore, according to this embodiment, the induction motor 10 adjusts the motor magnetic flux Φ and the torque current 11 by controlling the supplied primary current in the target torque range and the motor rotation speed range that fluctuate over a wide range, The mutual motor loss of both magnetic flux loss and torque current loss is minimized, and the adjustment time is shortened by changing the motor magnetic flux with good responsiveness during the motor magnetic flux adjustment transient until the target l·ruq is obtained. As a result, consumption of the battery 22 can be significantly reduced.

[Effects of the Invention] As described above, according to the present invention, the motor magnetic flux adjustment time until the target torque is obtained is shortened, and in normal times after the target torque is obtained, the induction motor is always kept at the minimum value. It is driven at total loss, and as a result, it is possible to significantly extend the battery charging mileage and expand the range of action of the electric UJ vehicle.

Extending the mileage reduces the number of times the battery needs to be charged,
It is extremely useful for the practical application of electric vehicles because it reduces the complexity of maintenance.

Of course, extending the mileage can lead to the miniaturization of the battery itself and the reduction of vehicle Φ suspension by setting the necessary mileage short, and miniaturization of the battery also increases the degree of freedom in the design of the vehicle. produce an effect.

[Brief explanation of drawings]

Fig. 1 is a flow rate diagram showing a preferred embodiment of the control method according to the present invention, Fig. 2 is a control circuit diagram for executing flowchart 17 of Fig. 1, and Fig. 3 is a motor magnetic flux in an induction motor. A characteristic diagram showing the relationship between Φ and torque current [1, Figure 4 is a motor magnetic flux/loss characteristic diagram with the motor output torque as a parameter when the rotation speed is constant, and Figures 5 and 6 are the main characteristics, respectively. FIG. 7 is a data map diagram of motor magnetic flux and motor torque current used in the present invention, and is a characteristic diagram that does not show the driving state of a vehicle using the present invention. 10... Induction motor 12... Torque calculation device 14... Efficiency optimization circuit 16... Vector calculation circuit 18... PWM i! III control circuit 20 ・
... Inverter main circuit 22 ... Battery.

Claims (1)

[Claims] (1) A method for controlling an induction motor for an electric vehicle, in which a target torque required for the induction motor is determined based on a travel command and travel conditions, and a desired primary current is supplied to the induction motor so that the target torque is output. The optimal motor magnetic flux that minimizes motor loss is calculated according to the target torque and motor rotation speed from predetermined magnetic flux/loss characteristic data, and then the determined optimal motor magnetic flux is calculated from the motor magnetic flux/torque current characteristic data. Calculates the optimum torque current for outputting the target torque using the magnetic flux, and further compensates for a delay in change in the motor magnetic flux that occurs during the transition of increasing adjustment of the motor magnetic flux, based on the difference between the optimum motor magnetic flux and the current motor magnetic flux. Calculate a corrected motor magnetic flux that is larger than the optimum motor magnetic flux for the purpose, and adjust the motor magnetic flux according to the increase in output torque.During a transition, the primary current command for the induction motor is determined from the magnetizing current and the optimum torque current to obtain the corrected motor magnetic flux. After the adjusted motor magnetic flux reaches the optimum motor magnetic flux, a primary current command that minimizes motor loss is supplied to the induction motor from the magnetizing current that obtains the optimum motor magnetic flux and the optimum torque current. A method for controlling an induction motor for an electric vehicle, characterized in that: