JPS62250802A - Controlling method for induction motor for electromobile - Google Patents

Abstract

PURPOSE:To obtain necessary set torque and enable motor loss to be minimized, by regulating both motor flux and torque current, and by controlling primary current. CONSTITUTION:By a torque arithmetic-unit 12, necessary set torque T* is performed arithmetic according to the running command and running conditions off car bodies. By an efficiency optimizing circuit 14, optimum motor flux phi*for minimum motor loss to obtain the necessary set torque T* based on the set torque T* and motor frequency fm is found, and after that, with magnet izing current to obtain the optimum motor flux phit*, transient motor flux phi*to a degree that the variation delay of motor flux does not exceed a specified value is performed arithmetic step by step, and according to the transient motor fluxphit*, transient torque current Iq' is performed arithmetic. By a vector arithmetic-circuit 16, motor voltage V1 and slip frequency fs are performed arithmetic according to the transient motor flux phit* and the transient torque current Iq' and the like.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ilJ a method for an induction motor for an electric vehicle, and in particular to an optimal control method for controlling the primary current applied to the induction motor while minimizing motor loss. be.

[Conventional technology] Electric cars are used as pollution-free vehicles that do not produce harmful exhaust gases.
II is being researched, 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 handling performance, the motors used in electric vehicles are controlled by vector control or slip frequency control, etc. data is under control.

[Problems to be Solved by the Invention] As is well known, the output torque of an induction motor is proportional to the product of the motor magnetic flux and the torque current, and in order to obtain the necessary torque, either the motor magnetic flux or the torque current must be increased. All you have to do is change it to give the necessary primary current to the induction motor.

However, in conventional devices, utg is performed in the magnetic flux-window region, and the output torque can be obtained only by changing the torque current.

According to such conventional control methods, the control process can be simplified, but on the other hand, there is a problem in that the E-71 loss cannot always be reduced in response to torque that fluctuates over a wide range. .

Of course, the motor loss of a V4 induction motor includes both magnetic flux loss due to motor magnetic flux and torque ff1l loss due to torque current, and both of these losses depend on the set motor magnetic flux and torque current, respectively, and are When the motor 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 it is impossible to always obtain optimal efficiency in a wide output torque region. It is possible.

Such an increase in motor loss increases the current consumption of electric vehicles and reduces the distance that they can travel with limited dispersion, 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 perform optimal control that always minimizes the total motor loss of both magnetic flux loss and torque current loss over the entire range of output torque that fluctuates widely. The purpose is to provide a method.

[Means for Solving the Problems] In order to achieve the above object, the present invention, unlike the conventional constant motor magnetic flux control, controls the primary ffi current by adjusting both the motor magnetic flux and the torque current. First, the optimum motor magnetic flux that minimizes the total motor loss is calculated based on the required target torque and motor rotation speed, and then the delay in change of the motor magnetic flux with respect to the motor magnetic flux command due to the secondary current exceeds a predetermined value. Calculate the transient motor magnetic flux command value step by step, and from the transient motor magnetic flux and motor rotation speed at each stage, calculate the transient torque that is the motor output 1 to lk that minimizes the motor loss at the time of the transient motor magnetic flux. Then, in accordance with the transient torque and the transient motor magnetic flux calculated in stages, a transient torque current is deduced from the motor magnetic flux/torque current characteristic data, and adjustment is performed until the optimum motor magnetic flux is obtained. A primary current command is supplied to the induction motor that minimizes the motor loss obtained from the magnetizing current that obtains the transient motor magnetic flux that is controlled by the torque, and the transient torque of 74 vol, so that the transient motor magnetic flux reaches the optimum motor magnetic flux. After that, the magnetizing current that increases the optimum motor magnetic flux by 1q, and the motor magnetic flux / according to the target torque and the optimum motor magnetic flux.
The primary current 11 that minimizes the calculation loss based on the torque current characteristics is supplied to the induction motor, and the primary current 11 is supplied to the induction motor to minimize calculation loss. The feature is that the primary current that provides the highest efficiency is always supplied to the induction motor in any case.

[Operation] Therefore, according to the present invention, the transient torque output is generated during the adjustment transient of the motor magnetic flux and I-lux current until the target torque obtained from the given running command and running conditions is obtained by a predetermined calculation formula. It is possible to supply the induction motor with the primary Ti flow that always has the highest efficiency, that is, the lowest motor loss, at both the time and the target torque output after adjustment, and always provides the necessary primary Ti flow in the entire torque range and frequency range. As a result of controlling current consumption to a minimum, it becomes possible to significantly expand the traveling distance of an electric vehicle.

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

FIG. 3 shows an ideal vector diagram in an induction motor, where the vertical axis represents the magnetizing current I. A motor magnetic flux Φ of induction Celsius is generated, and a torque T can be generated in the motor along with the motor magnetic flux Φ by one torque current on the horizontal axis.

Therefore, the induction motor is supplied with a primary current 11 which is the vector sum of the magnetizing current 1° and the torque current 11.

Therefore, in the present invention, unlike the conventional case, the motor magnetic flux Φ
Even when changing the torque current 1 corresponding to this change,
By setting 1, it is possible to obtain the necessary target torque TI.

From this, it is understood that it is possible to arbitrarily select the primary current ■1 that minimizes the total loss of the separate losses determined by the motor magnetic flux Φ and the torque current I□.

In addition, in Figure 3, the constant torque 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, due to these components, the motor magnetic flux Φ causes a change delay with respect to the torque current.

Therefore, during the transition period until the motor magnetic flux reaches the optimum motor magnetic flux, the motor output torque does not reach 1TIJIA torque T8, and the total motor loss cannot be minimized.

In the present invention, based on such a principle, first, in order to obtain the necessary target torque T8, the minimum motor loss and lz
Find the optimum motor magnetic flux Φ1 to obtain the optimum motor magnetic flux Φ1, and then consider the change delay in the motor magnetic flux that occurs when adjusting the motor magnetic flux with the magnetizing current to obtain the optimum motor magnetic flux Φ1, and calculate the transient value so that the change delay does not exceed a predetermined value. The motor magnetic flux command value is calculated step by step, and the transient torque T at which the motor loss is minimized when the transient motor magnetic flux Φ8t is calculated at each step is determined, and the transient torque Tt and the motor magnetic flux calculated step by step are The transient torque current I′ is expressed according to Φ“, and i
T During the adjustment transient until the optimum motor magnetic flux is obtained, the transient motor magnetic flux Φ
*, the magnetizing current and the transient torque to obtain? ! ! F
The primary current ■1 determined from both t I and 7- is supplied to the induction motor, and when the adjusted backward wave motor magnetic flux Φ* reaches the optimal motor magnetic flux Φ1, the magnetizing current to obtain the optimal motor magnetic flux Φ1 is and target torque TI and optimal motor magnetic flux Φ
The present invention is characterized in that the primary current 11 determined from the rain sound with the optimum torque current 11* corresponding to the current is supplied to the induction motor.

Figure 4 shows the magnetic flux/loss characteristics for determining the overall minimum motor loss of an induction motor. The motor loss η is shown.

In Fig. 4, the rotational speed of the induction motor is held constant, and the three characteristics are set using the output torque of the motor as a parameter, and the characteristics of the motor output torque of large, medium, and small are illustrated as shown in the figure. There is.

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. From this figure, it is understood that as the motor output torque decreases, the motor loss tends to be minimized where the motor magnetic flux is low. 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 electric automation.

FIG. 5 is a map showing the magnetic flux/loss characteristics explained in FIG. According to the current motor rotational speed N, it becomes clear to which value the motor magnetic flux Φ with minimum loss should be determined in order to obtain the following.

Such magnetic flux/loss characteristic data are of course responsible for each induction motor or electric vehicle to be implemented, and these data can be determined in advance either by experiment or calculation for a particular model of electric vehicle, and this The map data can be readably incorporated into the motor control circuit as ROM or other stored information.

Then, if the optimum motor magnetic flux Φ9 is determined in the above J: manner, it becomes possible to obtain the optimum 1~Rukuden IIT'' based on the above-mentioned constant torque characteristic shown in Fig. 3, and this torque current IT * can be easily derived from predetermined data, and such data can also be stored in the circuit's ROM.
can be recorded on.

FIG. 6 shows an example of a map for determining a constant torque current ■1, and the motor torque IFi flow ■1 determined according to the motor rotation speed N and motor output torque T is displayed on the map as shown, Such motor torque Ti flow data can also be recorded on the ROM of the circuit in a readable manner as described above.

FIG. 1 shows 70-days when the control method according to the present invention described above is used for actual control of an induction motor for an electric vehicle, and further shows 1. The If control circuit 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 tiIItID is used to perform the inverter control.

The torque generator T3 device V112 outputs the necessary target torque T1 according to the vehicle running command and running conditions, and this target torque is sent to the efficiency optimization circuit 14, which calculates the characteristic motor magnetic flux and torque current of the present invention. Both calculations are performed. Then, the optimal motor magnetic flux Φ obtained in this way and −
[- Adjustment of evening magnetic flux Torque electric itq which changes from the transient torque current Ibi to the adjusted optimal torque current Ibi according to the change characteristics in J3 during transient is supplied to the vector calculation circuit 16 for vector control, The output is supplied to the inverter main circuit 20 by the PWM control circuit 18, and the primary current of the induction motor 10 is υ controlled.

Current for 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 also connected to the induction motor 1 from the inverter main circuit 20.
0 is detected by the current detection circuit 26, and the rotation speed of the induction motor 10 is detected by the pulse generator 2.
8, and each of these detection signals is supplied to a desired arithmetic unit and a, II m @ path, respectively.

In FIG. 1, when the &IJtl11 circuit is initialized, motor υ control according to the present invention is executed, and step 1
At step 01, various data are read.

The read data is a forward/reverse switch, an accelerator sensor,
Torque calculation unit 12 includes both driving commands given from the accelerator switch, brake sensor, and brake switch, and driving conditions including motor temperature, inverter temperature, motor rotation speed, and battery voltage.
arbitrates the necessary target torque T* based on these travel commands and travel conditions (steps 102 and 103>).

In the embodiment, step 103 shows a correction effect based on the fluctuation temperature or inverter temperature, and when the temperature reaches the upper limit, the required torque normally obtained in step 102 is subtracted by a predetermined amount to determine the target torque T8.

As in the past, the settings of the motor running command and the target values 1 to 1 to 1 to 1, which are applied to the running conditions, are calculated from the characteristic data set for each electric VJ vehicle, and FIG. 7 shows an example of such characteristic data. show.

In FIG. 7, the horizontal axis indicates the motor rotation speed N, a positive region indicates normal rotation, and a negative region indicates reverse rotation.

Further, the vertical axis indicates the motor output torque T.

When the electric vehicle is currently stopped, it is in the position indicated by the symbol a, and when moving forward in this state, the axle is opened and the motor output torque is increased to the characteristic of 100% accelerator.
It increases rapidly towards .

The electric vehicle starts with the generation of this motor output torque, and as shown by the thick solid line, the rotation speed N increases sequentially, and at a constant motor rotation speed, that is, the 0 position, the motor output torque also gradually increases toward d. Decrease. When the accelerator is released from d, the motor output torque T also decreases to e while maintaining a constant motor rotation speed N, and furthermore, at this accelerator opening degree, the motor rotation speed N increases toward 1''.

When stopping the car from f, the accelerator is released and the brake is depressed, the motor output torque T shifts to the negative region, and the motor output reaches 9, which is determined by the brake depression state! −
The torque T is maintained, and this state indicates a regenerative state. As the brake is depressed, the motor rotational speed N gradually decreases, and at h, the vehicle stops and returns to the original position a.

The characteristics shown in FIG. 7 are determined in advance according to the rock type of each electric vehicle, and this characteristic data is stored in the ROM etc. of the torque calculation device 12 shown in FIG. This target torque T* is adjusted as appropriate according to the command and driving conditions.
is escaped.

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 optimization circuit 14 adjusts the motor magnetic flux to the optimum motor magnetic flux Φ8 while always minimizing the overall motor loss. Transient motor magnetic flux command Φ1 to increase stepwise. and is converted into a torque current (2) that corresponds to this transient motor magnetic flux and has the highest efficiency. This operation is the first
This is performed in steps 104 to 107 in the figure. first,
In step 104, target torque TI and motor rotation speed N
(fm), the optimum motor magnetic flux Φ8 that minimizes the overall motor loss is determined based on the magnetic flux/loss characteristic data shown in FIG. 4 or 5 described above.

Then, in step 105, an actual motor magnetic flux change delay with respect to the motor magnetic flux command is taken into account, which occurs when a magnetizing current is supplied to obtain the obtained optimum motor magnetic flux Φ. The transient magnetic flux command value Φ is calculated step by step to such an extent that Φ does not exceed a predetermined value.

The transient motor magnetic flux Φ9. is the predetermined calculation formula according to the difference between the optimal motor magnetic flux Φ1 and the current motor magnetic flux Φ“,
For example, (1)', -〇" +K (O"-cD*)-
(1) Derived at t-1t-1.

The transient term constant for determining the transient motor magnetic flux Φ□ is determined from the circuit time constant of the induction motor, and is mainly determined from the resistance component and the inductance component of the coil.

Therefore, if the time constant of the induction motor is small, that is, there is little transient delay when the motor magnetic flux increases, then the constant K
For motors where the induction motor has a large time constant and a large magnetic flux rise delay, the constant diameter is set small to slowly control the transient rise in motor magnetic flux. Also, in step 105,
When the difference between the optimum motor magnetic flux Φ1 and the current motor magnetic flux Φ1 becomes less than a predetermined value, the calculation according to equation (1) is stopped and the optimum motor magnetic flux Φ' is controlled.

Next, in step 106, the transient upper magnetic flux Φ8. Based on the map shown in Fig. 5 from the motor rotation speed N,
The most efficient motor output torque (transient torque T,) at each stage of the transient motor magnetic flux Φ1t is determined.

Then, in step 107, the obtained excess I
Considering the motor rotation speed N from the torque Tt and the transient motor magnetic flux Φ*, and further based on the data shown in FIG. 3 or 6 described above, the transient motor magnetic flux Φ8. A torque 5FIlt corresponding to is determined.

The above calculations from steps 104 to 107 are constantly repeated in the efficiency optimization circuit 14, for example, every few m5ec. Therefore, even during the transient period until the motor magnetic flux reaches the optimum motor magnetic flux Φ The actual motor magnetic flux that follows the change without any delay is obtained.

Therefore, the efficiency optimization circuit 14 always outputs a torque current I that minimizes the motor loss determined in response to the transient motor magnetic flux Φ□ that increases stepwise up to the optimum motor magnetic flux Φ1. Therefore, torque fH! if also changes in a stepwise manner.

As described above, transient motor magnetic flux Φ8t and torque current! , is determined, in this embodiment, the motor voltage V1 and the motor next frequency f1 are calculated by the vector calculation control in the vector vJtiX circuit 16 (J:).
Step 108).

The vector calculation circuit 16 includes a pulse generator 28.
motor frequency fm given by, motor current 11 detected from current detection circuit 26, and voltage detection circuit 24.
The battery voltage V0 detected from J3 is input,
8 of these detection signals and the given transient motor flux.
A desired vector calculation is performed by the and the torque generator 11.

The result of vector calculation is PwM a as motor voltage V1
Ill i11 circuit 18 and also has a slip frequency F
s is added to the above frequency fm and supplied to the PWM DI 11 circuit 18 as the motor next frequency f1.

The PWMMI11 circuit 18 receives the supplied motor voltage v
1 and motor frequency f1 to supply the inverter main circuit 20 with a pulse signal P, which is an inverter control signal (step 109), and the inverter main circuit 20 requires DC power from the battery 22 based on this supplied pulse signal P. The AC power is converted into AC power and the desired primary current is supplied to the induction motor 16.

That is, a magnetizing current that obtains a transient motor magnetic flux Φ*1 that is increased step by step to the optimum value, and a torque current ■ that minimizes the total loss of the motor corresponding to each step of the motor magnetic flux. The primary current determined by is commanded.

Therefore, through the above primary current control to obtain the target torque T1, the motor magnetic flux can be increased to the optimum motor magnetic flux Φ8 without any delay in following the motor magnetic flux command, and the target torque range that fluctuates over a wide range and In the motor rotation speed range, the motor is always driven with the minimum total motor loss, and as a result, it is possible to significantly reduce the consumption of the battery 22.

[Effects of the Invention] As described above, according to the present invention, the induction motor is always driven with the most efficient < i, II controlled primary current not only in steady state but also during transient adjustment of the motor magnetic flux. As a result, it becomes possible to dramatically extend the range of electric vehicles on a separate charge and expand the range of action of electric vehicles.

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, the mileage can be extended by making the battery itself smaller and by setting the required mileage shorter.
This can lead to a reduction in distortion, and the miniaturization of the battery also has the effect of increasing the degree of freedom in the design of automobiles.

[Brief explanation of drawings]

Fig. 1 is a flowchart of a preferred embodiment of the control method according to the present invention, Fig. 2 is a u control circuit diagram for executing the flowchart of Fig. 1, and Fig. 3 is a diagram showing motor magnetic flux Φ in an induction motor. Torque If
Fig. 4 is a characteristic diagram showing the relationship between the current and current, Fig. 4 is a motor magnetic flux/loss characteristic diagram with the motor output torque as a parameter when the rotation speed is constant, and Figs. used for -shi-
A data map diagram of the evening magnetic flux and motor torque current, and FIG. 7 are characteristic diagrams showing the driving state of a vehicle using the present invention. Efficiency optimization circuit 16... Vector calculation circuit 18... PWM control circuit 20... Inverter main circuit 22... Dispersion.

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 optimum motor magnetic flux that minimizes the motor loss is calculated according to the target torque and motor rotation speed from predetermined magnetic flux/loss characteristic data, and then the delay in motor magnetic flux change relative to the motor magnetic flux command due to the primary current is calculated. A transient motor magnetic flux command value that does not exceed a predetermined value is calculated in stages, and from the transient motor magnetic flux and motor rotation speed at each stage, the transient torque is the motor output torque that causes the least motor loss at the time of the transient motor magnetic flux. and calculate the transient torque current from the motor magnetic flux/torque current characteristic data according to the transient torque and the stepwise calculated transient motor magnetic flux, and during the adjustment period until the optimum motor magnetic flux is obtained, the above-mentioned Supplying the induction motor with a primary current command that minimizes the motor loss obtained from the magnetizing current that obtains the transient motor magnetic flux that is calculated in stages and the transient torque current, so that the transient motor magnetic flux reaches the optimum motor magnetic flux. After that,
A primary current command that minimizes motor loss obtained from a magnetizing current that obtains an optimal motor magnetic flux, and an optimal torque current that is calculated based on the motor magnetic flux/torque current characteristics according to the target torque and the optimal motor magnetic flux. The primary current must be supplied to the induction motor so that the primary current always has the highest efficiency, both during transient torque output during adjustment of motor magnetic flux and torque current, and during target torque output after adjustment. A method for controlling an induction motor for an electric vehicle, characterized by: