JP6766487B2 - Electric vehicle control device - Google Patents

Description

The present invention relates to a technique for improving torque imbalance of a plurality of induction motors in an electric vehicle control device for driving an electric vehicle by driving a plurality of induction motors by one inverter.

The exciting current (d-axis current) and torque current (q-axis current) that generate magnetic flux by separating the current of the induction motor in the magnetic flux direction (d-axis direction) and the torque direction (q-axis direction) orthogonal to this are independent. As an electric vehicle control device to which the vector control for controlling the electric current is applied, the first conventional technique described in Patent Document 1 is known.

FIG. 5 is a block diagram of this prior art. In the main circuit of FIG. 5, 1 is a DC overhead wire, 2 is a pantograph, 3 is a VVVF (variable voltage variable frequency) type inverter, 5 is an induction motor for driving a vehicle, 41 is a filter capacitor, and 42 is a voltage detector. 43 is a wheel and 44 is a rail.

Further, in the control device of the inverter 3, 20 is a magnetic flux command value calculation unit, and 30 is a vector control means.
The magnetic flux command value calculation unit 20 has an output angle frequency (inverter angle frequency) ω _i , a d-axis voltage command value V _dr , a q-axis voltage command value V _qr , a rotor rotation angle frequency W _r1 , a DC voltage detection value E _dc , and a torque. The magnetic flux command value F _2R is calculated from the command value T _mr, and the magnetic flux command value F _2R and the torque command value T _mr are input to the vector control means 30.

The vector control means 30 includes a current command value calculation unit 31 for calculating the d-axis current command value I _dr and the q-axis current command value I _qr from the magnetic flux command value F _2R and the torque command value T _mr, and the d-axis current command value I. _The slip angle frequency calculation unit 32 that calculates the slip angle frequency ω _s from the _dr and q-axis current command value I _qr , the d-axis current command value I _dr , the q-axis current command value I _qr , and the d-axis current detection value I _d , The voltage vector control calculation unit 33 that calculates the d-axis voltage command value V _dr and the q-axis voltage command value V _qr from the q-axis current detection value I _q and the output angle frequency ω _i , and each phase current I _u of the induction motor 5 I _v, a current detector 35 for detecting the _{I w,} the phase currents _{I u, I v,} a coordinate converter 36 which converts the _{I w} d-axis current detection value _I d, the q-axis current detection value _{I q,} Rotor rotation angle for calculating rotor rotation angle frequency W _r1 from d-axis current detection value I _d , q-axis current detection value I _q , d-axis voltage command value V _dr , q-axis voltage command value V _qr , output angle frequency ω _i The frequency calculation unit 38, the adder 34 that adds the slip angle frequency ω _s and the rotor rotation angle frequency W _r1 to obtain the output angle frequency ω _i, and the adder 34 that integrates the output angle frequency ω _i to obtain the phase angle θ. The device 37 and the gate control unit 39 that generates a gate signal for a semiconductor switching element such as an IGBT in the inverter 3 based on the d-axis voltage command value V _dr , the q-axis voltage command value V _qr, and the phase angle θ. It is configured.

Further, FIG. 6 shows the configuration of the magnetic flux command value calculation unit 20 in FIG.
The magnetic flux command value calculation unit 20 calculates the magnetic flux command value back calculation based on the output of the magnetic flux command value back calculation calculation unit 21, the rotor rotation angle frequency W _r1 and the set value W _rm , and the comparison device 22. a switch 23 for outputting one of the output _{F 2 RB} and the magnetic flux command reference value _{F 2RM} parts 21 as the magnetic flux command value _{F 2R,} and a.

In the above-mentioned conventional technique, the induction motor 5 is driven by controlling the inverter 3 by using the gate signal calculated by giving the magnetic flux command value F _2R and the torque command value T _mr to the vector control means 30 of FIG. ing.
The magnetic flux command value F _2R, during low-speed operation of the induction motor 5, except when switching on the magnetic flux command value F _{2 RB} from the magnetic flux command value back calculation arithmetic section 21 by switch 23 in FIG. 6, the magnetic flux command reference value F _2RM It is used, and even if the torque command value _Tmr changes according to the operating state of the electric vehicle other than the speed, the magnetic flux command value F _2R does not switch.

Here, FIG. 7 shows the relationship between the estimated speed of the induction motor 5 and the input voltage (output voltage of the inverter 3).
As shown in FIG. 7, until the induction motor 5 reaches a predetermined speed, the input voltage is increased according to the increase in the estimated speed value under constant V / f control regardless of the torque command value _Tmr. The magnetic flux command value F _{2R (} not shown) is constant. Then, when the speed of the induction motor 5 reaches the one-pulse operation region of the inverter 3 normally used for controlling an electric vehicle, the magnetic flux command value F _2R is gradually reduced so that the voltage becomes constant.

As shown in FIG. 6, the input voltage of the induction motor 5 is constant even when the magnetic flux command value F _2R is switched to the magnetic flux command value F _2RB from the magnetic flux command value back calculation calculation unit 21 during low-speed operation of the induction motor 5. The magnetic flux command value is output so as to be, and the magnetic flux command value is increased rather than decreased.

Further, as another control method of an electric vehicle by an induction motor, a second conventional technique described in Patent Document 2 is known.
In this conventional technology, in a system in which a plurality of induction motors are driven by one inverter, if there is a difference in the diameters of the wheels driven by each induction motor, the difference becomes the difference in the sliding frequency of each electric motor. It has been pointed out that an induction motor with a large absolute value of slip frequency is overheated by generating excessive torque and current. As a solution for this, Patent Document 2 discloses that the magnitude of the current command value of the induction motor is limited, but the torque imbalance (each induction motor) generated between a plurality of induction motors is disclosed. The imbalance of the ratio of the minimum value to the maximum value of the generated torque) and its solution are not specifically mentioned.

Japanese Unexamined Patent Publication No. 2006-94646 (paragraphs [0011] to [0051], FIGS. 1, 2, 2, 5, etc.) Japanese Unexamined Patent Publication No. 2015-50779 (paragraphs [0015] to [0041], FIGS. 3 to 6, etc.)

As mentioned above, when driving or controlling an electric vehicle by driving multiple induction motors with one inverter, the torque generated by the induction motors with a large absolute value of the slip frequency due to the difference in wheel diameter is different. It will be larger than the electric motor.
Here, when the induction motor is driven using vector control, the torque command value is T ^* , the magnetic flux command value is φ ^* , the torque current command value (q-axis current command value) is i _q ^* , and the slip frequency is set. If f _s , the relationship of formula 1 and formula 2 is established between them.

[Formula 1]
i _q ^* = k ₁・ (T ^* / φ ^* )
[Formula 2]
f _s = k ₂・ (i _q ^* / φ ^* )
However, k ₁ and k ₂ are constants determined by the constant (motor constant) of the induction motor.

FIG. 8 shows the magnetic flux command value φ ^* , torque current command value i _q ^* , slip frequency f _s, etc. when the electric vehicle is full with many passengers and operates under the maximum torque command value. It is a graph.
Of the multiple induction motors driven by one inverter, the rotor frequency of the induction motor that drives the wheels with the largest diameter is the smallest, so this rotor frequency is set to _{fr (min)} and the diameter is the smallest. Since the rotor frequency of the induction motor that drives the wheels is the maximum, when this rotor frequency is _{fr (max)} , the difference between the two frequencies _{(fr (max)} −fr _(min) ) is the rotor frequency difference Δf. _It is shown in the figure as _r . The rotor frequency difference Delta] f _r is a waveform which rises in proportion to the increase in speed.
The example of FIG. 8 shows a case where the inverter output frequency _finv is operated so as to be the equation 3.
[Formula 3]
f _inv = _{fr (min)} + f _s

Then, for example, an electric vehicle passenger decreases the torque command value T ^* when decreased to 60% of the maximum _{^{φ *, i q *, f}} s, when graphed as in FIG 8 a Delta] f _r, etc. , As shown in FIG. It is assumed that each wheel diameter has exactly the same conditions as in FIG.
At this time, in the prior art, the magnetic flux command value φ ^* is generated according to a certain pattern regardless of the magnitude of the torque command value T ^* , so that the magnetic flux command value φ ^* has exactly the same waveform as in FIG. Further, from Equation 1, the torque current command value i _q ^* decreases in proportion to the torque command value T ^*, and from Equation 2, the slip frequency f _s is also 60% of f _s in FIG. 8 in proportion to i _q ^* . Has decreased to. The conditions of the wheel diameter are the same as FIG. 8, the waveform of the rotor frequency difference Delta] f _r is the same as FIG.

As it can be seen by comparing FIG. 9 and FIG. 8, the torque command value T ^{* _(*} torque current command value i ^_q) is reduced, also reduced the frequency f _s slip in proportion thereto. Therefore, the ratio of the minimum value f _{s (min) to} the maximum value f _{s (max)} of the slip frequency f _s of a plurality of induction motors driven by one inverter is higher in FIG. Is also getting smaller. If the magnetic flux does not change, the torque generated by the induction motor is proportional to the slip frequency f _s. Therefore, in FIG. 9, the ratio of the minimum value to the maximum value of the torque generated by the induction motor is also the slip frequency f _s as compared with FIG. It becomes smaller as well.

Therefore, when considered as a ratio, the torque imbalance is larger in FIG. 9 in which the torque command value T ^* is reduced. Incidentally, FIG. 8, both 9, the induction motor other than the induction motor for driving a wheel of greatest diameter, the current flowing through them motor decreases by the actual slip frequency f _s is lower. Actually, the current of the electric motor is corrected by the current regulator in the vector control means, but the magnetic flux command value φ ^* is given according to a certain pattern regardless of the magnitude of the torque command value T ^*. The tendency for the torque imbalance as a ratio to increase when the torque command value is reduced does not change.

In this way, when the torque command value decreases due to a decrease in the number of passengers in the electric vehicle, the torque imbalance between the plurality of induction motors driven by one inverter increases, so that there are a plurality of torque imbalances. In the wheels driven by the induction motor that generates the maximum torque in the table, slipping is likely to occur during power running and sliding is likely to occur during braking.
Therefore, there is a problem that the frequency of executing the control for re-adhesion of the wheels is significantly increased, the acceleration performance and the deceleration performance of the electric vehicle are deteriorated, and the riding comfort is also deteriorated.

In particular, in recent years, there has been a strong need for energy saving in electric vehicles, and in order to improve the efficiency of induction motors for driving electric vehicles, which had been inefficient until now, the secondary resistance is reduced as a characteristic of the induction motor itself, that is, There is a tendency to reduce the slip frequency. In this case, the slip frequency based on the wheel diameter difference and the ratio of the maximum value to the minimum value of the motor generated torque tend to increase more than ever, and as described above, the torque when the torque command value decreases.・ The problem of increasing imbalance is becoming more prominent.

Therefore, the problem to be solved by the present invention is to improve the torque imbalance between a plurality of induction motors driven by one inverter, prevent the wheels from slipping and slipping, and improve the acceleration / deceleration performance and the riding comfort. The purpose is to provide an electric vehicle control device.

In order to solve the above problems, the invention according to claim 1 is an electric vehicle control device for driving the wheels of an electric vehicle by a plurality of induction motors connected in parallel to the output side of one inverter. Te, the torque command value for driving the induction motor in accordance with the single rotational speed equivalent value and operation command and the minimum or maximum value or an average value of the rotational speed of the plurality of induction motors and the magnetic flux command A means for generating a value, a control calculation means for generating an output voltage command value of the inverter using the torque command value, the magnetic flux command value, the rotation speed equivalent value, and the current of the induction motor are provided. In the electric vehicle control device
The maximum torque command value is set as the torque command value when the electric vehicle is started and accelerated when the passengers are full.
When the torque command value operated with reduced than the maximum torque command value when starting accelerating the electric vehicle, wherein the magnetic flux command value, and lower than the magnetic flux command value in the maximum torque command value the It is given to the control calculation means.

In the present invention, in an operating state in which the torque command value is reduced below the maximum torque command value, the magnetic flux is reduced by operating with the magnetic flux command value reduced from the magnetic flux command value at the maximum torque command value. increasing the slip frequency f _s of equation 2 as compared to the prior art do not alter. As a result, the torque imbalance between the induction motors is alleviated, the frequency of idling and sliding is reduced, and acceleration / deceleration performance and riding comfort can be improved.
The driving state in which the torque command value is maximized is a relatively short time, for example, during a rush hour when the passengers of the electric vehicle are full, and the other driving time is much longer. According to the present invention, the torque imbalance between a plurality of induction motors can be improved during the long operation time.

In the invention according to claim 2, in the electric vehicle control device according to claim 1, the reduction rate or the magnetic flux command value according to the reduction amount of the torque command value with respect to the maximum torque command value is predetermined as a function. The magnetic flux command value obtained from the function is given to the control calculation means.
As in the present invention, if the reduction rate of the torque command value with respect to the maximum torque command value or the magnetic flux command value corresponding to the reduction amount is predetermined as a function, it is appropriate to make the function into software or a table. The magnetic flux command value can be easily obtained.

The invention according to claim 3 is the electric vehicle control device according to claim 2, wherein the function is a function in which the magnetic flux command value is proportional to the square root of the reduction rate of the torque command value with respect to the maximum torque command value. It is characterized by that.

Here, by substituting the i _q ^* shown in the above-mentioned formula 1 into the formula 2, the formula 4 is obtained.
[Formula 4]
f _s = k ・ (T ^* / φ ^{* 2} )
However, k = k ₁ · k ₂ (constant)
Then, T _{0 *} the maximum torque command ^value, the maximum magnetic flux command value and phi ₀ ^*, when the slip frequency corresponding to these and f _s0, Equation 5 is satisfied by substituting these into Equation 4.
[Formula 5]
f _s0 = k ・ (T ₀ ^* / φ ₀ ^{* 2} )

Further, the magnetic flux command value φ ^* is changed according to the torque command value T ^* as shown in Equation 6, and the magnetic flux command value φ is a reduction rate proportional to the square root of the torque command value T ^{* with} respect to the maximum torque command value T ₀ ^* . ^* Reduce.
[Formula 6]
φ ^* = φ ₀ ^*・ √ (T ^* / T ₀ ^* )
Substituting Equation 6 into Equation 4 yields Equation 7.
[Formula 7]
^{_{f s = k · [T *}} / {φ 0 * 2 · (T * / T o *)}] = k · (T 0 * / φ 0 * 2)
The above formula 7, for equal right side of Equation 5, after _all, a _f s ₌ f _s0.

Therefore, when calculating a magnetic flux command value phi ^* according to Equation 6, also the slip frequency f _s by reducing the torque command value T ^* will not change, the maximum torque command value T ₀ ^* equivalent torque in the case of It can be improved to imbalance.
Therefore, as compared with claims 1 and 2, the frequency of wheel slipping and sliding is further reduced, and acceleration / deceleration performance and riding comfort can be further improved.

The invention according to claim 4 is the electric vehicle control device according to any one of claims 1 to 3.
The rotational speed equivalent value is the minimum value, maximum value, or average value of the speed detection value or speed estimation value of all induction motors or wheels driven by these induction motors.
As in the present invention, if the rotation speeds of all induction motors or wheels are known, the rotor frequency _{fr (min)} corresponding to the lowest speed among them can be easily selected, and according to Equation 3, in vector control. The inverter output frequency _wheel can be easily calculated. Further, since the inverter output frequency _finv as shown in Equation 3 can be calculated if a rotor frequency corresponding to at least one rotation speed is obtained, according to the present invention, the rotation speeds of all induction motors are detected. The number of a plurality of speed detectors for estimating the rotation speed and a plurality of current detectors and a speed estimator for estimating the rotation speed can be made single, which can contribute to the simplification of the configuration and the reduction of the cost. ..

According to the present invention, it is possible to operate the plurality of induction motors under variation of the maximum torque command at the same slip frequency f _s in the case of reduced torque command value, improving the torque imbalance can do. In addition, the variation in the current flowing through each induction motor, in other words, the variation in the temperature rise of each motor is reduced to prevent overheating and shortening of the life of a specific induction motor, as well as to prevent wheel slipping and sliding, acceleration / deceleration performance, etc. It is possible to improve the ride quality.

It is a block diagram of the electric motor control device which concerns on 1st Embodiment of this invention. It is a block diagram of the electric motor control device which concerns on 2nd Embodiment of this invention. It is a graph which shows the magnetic flux command value φ ^* , the torque current command value i _q ^* , the slip frequency f _s, etc. in the 2nd Embodiment of this invention. It is a block diagram of the electric motor control device which concerns on 3rd Embodiment of this invention. It is a block diagram of the prior art described in Patent Document 1. It is a block diagram of the magnetic flux command value calculation part in FIG. It is a figure which shows the relationship between the speed estimate value of an induction motor, and an input voltage. It is a graph which shows the magnetic flux command value φ ^* , torque current command value _iq ^* , slip frequency f _s, etc. when operating an induction motor under the maximum torque command value. It is a graph which shows the magnetic flux command value φ ^* , the torque current command value i _q ^* , the slip frequency f _s, etc. when operating an induction motor by reducing the torque command value to 60% of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an electric vehicle control device according to a first embodiment of the present invention, and corresponds to the inventions according to claims 1, 2, and 4.

In FIG. 1, two induction motors 5A and 5B are connected in parallel to each other on the output side of the inverter 3 supplied from the overhead wire 1 via the pantograph 2, and the wheels of the electric vehicle are connected by these induction motors 5A and 5B. It is configured to drive. Induction motor 5A, the speed detector 6A provided in 5B, 6B sends the electric motor 5A, the rotor frequency _{f r1, f r2} corresponding to the rotational speed of the 5B to the reference speed calculator 10 detects respectively.
The number of induction motors driven by the inverter 3 is not limited to two, and may be three or more.

Reference speed calculator 10 selects the minimum value of the rotor frequency _{f r1, f r2,} to output as the reference rotor frequency f _{r (ref).} As the reference rotor frequency _{fr (ref)} , the maximum value or the average value of the rotor frequencies _fr1 and _fr2 may be used, and these may be switched according to the operating conditions such as power running / braking operation of the electric vehicle. Is also good.

The reference rotor frequency _{fr (ref)} is input to the maximum magnetic flux command calculator 7, the torque command calculator 8 and the maximum torque command calculator 9 together with the operation command.
Each of the arithmetic units 7, 8 and 9 calculates the maximum magnetic flux command value φ ₀ ^* , the torque command value T ^* , and the maximum torque command value T ₀ ^* , and outputs them to the magnetic flux command arithmetic unit 11.

For example, when the torque command value T ^* and the maximum torque command value T ₀ ^* are both positive, the magnetic flux command calculator 11 calculates the magnetic flux command value φ ^* by the mathematical formula 8 using each command value.
[Formula 8]
φ ^* = φ ₀ ^* −A ・ (T ₀ ^* −T ^* ) (A: Positive constant)

Using the magnetic flux command value φ ^* calculated in this way, the torque command value T ^* , the reference rotor frequency _{fr (ref)} , and the output current detection value of the inverter 3 by the current detector 4, the vector control calculator 12 d. The shaft voltage command value V _d ^* and the q-axis voltage command value V _q ^* are calculated and output to the gate control unit 13. The gate control unit 13 generates a gate signal for the semiconductor switching element of the inverter 3 so that the inverter 3 outputs a voltage corresponding to the voltage command values V _d ^* and V _q ^* .

As described above, the magnetic flux command calculator 11 by performing the calculation of Equation 8, when operating with reduced torque command value T ^* from the maximum torque command value T ₀ ^*, according to the torque command value T ^* The magnetic flux command value φ ^* can also be reduced.
As described above, as long as the magnetic flux command value phi ^* unchanged, but also decreases the slip frequency f _s the smaller the torque command value T ^*, the magnetic flux command in response to the reduction of the torque command value T ^* as in this embodiment If the value φ ^* is reduced, the slip frequency f _s can be made larger than before, as is clear from Equation 2, and the ratio of the minimum value to the maximum value of the generated torque of multiple induction motors is increased for each. Torque imbalance between electric motors can be improved.

Next, FIG. 2 is a block diagram of the electric vehicle control device according to the second embodiment of the present invention, and corresponds to the inventions according to claims 3 and 4.
This second embodiment differs from the first embodiment only in the calculation content by the magnetic flux command calculator 11. In this embodiment, the magnetic flux command value φ ^* is calculated by the above-mentioned mathematical formula 6.

3, in the second embodiment, with respect to the torque command maximum value, the flux command phi ^* in the case of reducing the torque command value to about ^80%, shows the waveform of such slip frequency f _s. Each wheel diameter is drawn under the same conditions as in FIG. In this case, by reducing the magnetic flux command value phi ^* according to Equation 6, the slip frequency f _s is the same waveform as FIG. 8, the torque imbalance as ratio improved to equivalent FIG.

As described in the prior art, in an inverter for driving an electric vehicle, one-pulse operation is usually performed in a region where the speed is relatively high in order to reduce the loss of the switching element of the inverter 3. However, in recent years, it has become possible to apply a switching element using SiC (silicon carbide) to an inverter instead of a switching element using Si (silicon). For this reason, the loss due to the switching element tends to decrease, and the operation by PWM control has become possible even in the speed region in which the one-pulse operation has been conventionally performed.
In this case, the magnitude of the output voltage of the inverter can be controlled at the same time as the frequency and phase in the full speed range, and the magnetic flux of the induction motor can also be controlled in the full speed range. Therefore, for example, as shown in FIG. , It is possible to operate with the magnetic flux command value φ ^* reduced in the entire speed range.

Next, FIG. 4 is a block diagram of the electric vehicle control device according to the third embodiment of the present invention, and corresponds to the invention according to claim 5.
In the third embodiment, the speed estimator 14 is provided in place of the speed detectors 6A and 6B and the reference speed calculator 10 in the first and second embodiments. The calculation method of the magnetic flux command value φ ^* by the magnetic flux command calculator 11 is the same as that of the second embodiment, and the difference from the second embodiment is the d-axis input from the vector control calculator 12 by the speed estimator 14. , Q-axis voltage command value V _d ^* , V _q ^* , d-axis, q-axis current detection values _id , i _q , and slip frequency f _s , equivalent to the average speed of two induction motors 5A, 5B The point to estimate the rotor frequency _fr to be used and use this rotor frequency _fr as the reference rotor frequency _{fr (ref)} for the calculation of the maximum magnetic flux command value φ ₀ ^* , torque command value T ^* , and maximum torque command value T ₀ ^*. Is.
According to this embodiment, since a plurality of speed detectors and the like are not required, it is possible to contribute to simplification of the configuration and cost reduction.

1: Overhead wire 2: Pantograph 3: Inverter 4: Current detectors 5A, 5B: Induction motors 6A, 6B: Speed detector 7: Maximum magnetic flux command calculator 8: Torque command calculator 9: Maximum torque command calculator 10: Reference Speed calculator 11: Magnetic flux command calculator 12: Vector control calculator 13: Gate control unit 14: Speed estimator

Claims (4)

An electric vehicle control device for driving the wheels of an electric vehicle by a plurality of induction motors connected in parallel to the output side of one inverter, and the minimum value of the rotation speed of the plurality of induction motors or Means for generating a torque command value and a magnetic flux command value for driving the induction motor according to a single rotation speed equivalent value which is a maximum value or an average value and an operation command, the torque command value, and the magnetic flux command. In an electric vehicle control device including a value, a value equivalent to the rotation speed, and a control calculation means for generating an output voltage command value of the inverter using the current of the induction motor.
The maximum torque command value is set as the torque command value when the electric vehicle is started and accelerated when the passengers are full.
When the torque command value operated with reduced than the maximum torque command value when starting accelerating the electric vehicle, wherein the magnetic flux command value, and lower than the magnetic flux command value in the maximum torque command value the An electric vehicle control device characterized by being given to a control calculation means. In the electric vehicle control device according to claim 1,
A feature is that the reduction rate of the torque command value with respect to the maximum torque command value or the magnetic flux command value corresponding to the reduction amount is predetermined as a function, and the magnetic flux command value obtained from the function is given to the control calculation means. Electric vehicle control device. In the electric vehicle control device according to claim 2.
The electric vehicle control device is characterized in that the magnetic flux command value is a function proportional to the square root of the reduction rate of the torque command value with respect to the maximum torque command value. In the electric vehicle control device according to any one of claims 1 to 3.
An electric vehicle control device, wherein the rotation speed equivalent value is a minimum value, a maximum value, or an average value of speed detection values or speed estimation values of all induction motors or wheels driven by these induction motors.

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