JP2910517B2 - Induction motor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an induction motor used in an electric vehicle or the like, and more particularly to a control technique for performing regenerative braking.

[0002]

2. Description of the Related Art There is known a regenerative braking system in which an induction motor is driven from a load to generate electric power when a vehicle is braked, so that electric power is recovered to a power supply. A conventional induction motor control device for performing regenerative braking is disclosed in, for example,
There is one described in US Pat. The control device includes a means for generating a slip frequency command signal and a calculating means for calculating a current command value for driving the induction motor based on the slip frequency command signal. A slip frequency command signal with a different target value is generated at the time of regeneration when the induction motor is driven from the load, and the transition from power running to regeneration is performed gently. It is configured to prevent this. For example, the magnetic flux is φ _r , the torque current command value is i _T , the output torque is _Te , the slip frequency is ω _se , the power supply frequency is ω, and the motor speed (electric angle) is ω.
_{If re} , k ₁ and k ₂ are constants, it can be expressed as ω _se = ω−ω _re = k ₁ · i _T / φ _{r Te} = k ₂ · φ _r · i _T. In the above conventional example, in the above equation, when the command value of the slip frequency ω _se is given, the desired regenerative torque is generated by keeping the magnetic flux φ _r constant and increasing or decreasing the torque current command value i _T. It has become. As described above, the conventional torque control is performed by designating the slip frequency ω _se , and is set independently of the efficiency (loss) in the steady state and the transient state.

[0003]

As described above, in the conventional induction motor control method, the induction motor is driven in accordance with a torque current command value determined in accordance with a slip frequency command signal set independently of a loss. Therefore, there is a problem that the regenerative operation is performed without considering the loss at the time of transition and at the time of steady state, and the efficiency is low. The present invention has been made in order to solve the problems of the prior art as described above, and an induction motor control capable of avoiding a sudden torque fluctuation at the time of transition from power running to regeneration and reducing transient loss. It is intended to provide a device.

[0004]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as described in the claims. That is, according to the first aspect of the present invention, in addition to the vector control operation unit and the motor driving unit similar to the conventional one, a torque command value corresponding to the driver's operation is generated when the load is driven by the induction motor. A torque command value generating unit that outputs a torque command value having the opposite sign to that during power running during regenerative power generation by driving an induction motor from a load; an absolute value circuit unit that outputs an absolute value of the torque command value; A steady-state loss minimum magnetic flux calculation unit that calculates a rotor magnetic flux that minimizes the steady-state loss of the induction motor at the absolute value of the torque command value given via the value circuit unit; A target magnetic flux calculating section for calculating a target magnetic flux and a first-order differential value of the target magnetic flux based on a transfer function having a torque function, and a torque command value from the torque command value generating section, which are input during power running and regeneration. Different low-pass in
A target torque calculator for calculating a target torque of the induction motor from the torque command value based on a predetermined transfer function having characteristics . Further, the torque command value generating unit generates a positive torque command value corresponding to the driver's operation at the time of power running to drive the load from the induction motor, for example, as described in claim 2, and controls the induction motor from the load. At the time of regenerative driving and power generation, a negative torque command value having a magnitude corresponding to a state at the time of switching from power running to regenerating is generated. The target torque calculation unit calculates a target torque based on a predetermined transfer function having a low-pass characteristic during power running, and converts the target torque to the torque command value during regeneration, for example, as described in claim 3. When powering is set in advance according to
Different is for calculating a target torque transfer function with low pass characteristics. In addition, the target magnetic flux calculation unit may be configured to control the low-power
A predetermined transfer function having a transfer characteristic is selected, and during regeneration, a time constant for minimizing a loss according to the torque command value is selected .
Select a transfer function having Pasu properties, based on their
To calculate the target magnetic flux and the first derivative of the target magnetic flux . The above-described torque command value generating section, absolute value circuit section, steady-state minimum loss magnetic flux calculating section, target magnetic flux calculating section and target torque calculating section are, for example, a command value generating section 9 in the embodiment of FIG. It corresponds to the circuit section 10, the steady-state minimum magnetic flux calculation section 11, the target magnetic flux calculation section 12, and the target torque calculation section 15, respectively. The current command value corresponds to, for example, the excitation current command value i _φ ′, the torque current command value i _T ′, and the current phase angle θ in the embodiment of FIG. 1 or FIG.

[0005]

As described above, in the present invention, the steady-state loss minimum magnetic flux calculating section, the target magnetic flux calculating section, and the target torque calculating section are added to a general vector control calculating section, and the torque response and the magnetic flux responsiveness are improved. By adopting a control system configuration that can be changed independently, the slip frequency is steadily set to the minimum loss slip frequency ω _se-opt, and the magnetic flux response is transiently controlled to an optimum value according to the torque response. Thus, the configuration is designed to reduce the transient loss. Further, a torque command value generating section for outputting a torque command value having the opposite sign to that during power running during regeneration is provided, whereby a negative torque is obtained during regeneration. The torque Te is expressed as: Te = k · φ _r · i
_T (where k is a constant). Therefore, in order to set the torque to a negative value, one of the polarities of the magnetic flux φ _r and the torque current i _T may be reversed. However, the magnetic flux φ _r is not preferable because it does not immediately follow even _{if the} exciting current i _φ is changed. Therefore, in the present invention, thereby generating a negative torque by reversing the sign of the torque current i _T. In order to realize the above function, in the present invention, an absolute value circuit section is provided, and even if the torque command value becomes negative during regeneration, a positive value is always given to the steady-state loss minimum magnetic flux calculating section, and the target magnetic flux Is always positive. Since the torque command value is directly supplied to the target torque calculation unit, if the torque command value becomes negative during regeneration, the torque current command value also becomes negative, and a negative torque can be obtained. Note that the above-described control for reducing the transient loss is the same throughout power running and regeneration. Further, by setting the transfer function in the target torque calculation unit to be different between powering and regeneration, it is possible to prevent a sudden torque fluctuation from occurring during transition from powering to regeneration. The transfer function may be switched according to the value of the torque command value. However, as shown in the embodiments of FIGS. 1 and 3 below, a regenerative command signal for switching is separately generated and used. Alternatively, the time constant of the transfer function may be switched. This regenerative command signal is also a signal having a magnitude corresponding to the operating state at the time of transition at the time of regenerating, like the torque command value.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
1 to 3 show one embodiment of the present invention, and FIG.
FIG. 2 is a block diagram showing details of the high-efficiency drive control operation unit 1 in FIG. 2, FIG.
FIG. 3 is a block diagram showing details of a torque command value generator 9. First, in FIG. 2, reference numeral 1 denotes a high-efficiency drive control calculation unit (details will be described later), and a torque command value _Te ′ given from a torque command value generation unit 9 (details described later) and a motor rotation detected by the rotation speed sensor 5. The speed N (rpm) is input, the excitation current command value i _φ ′, the torque current command value i _T ′, and the phase angle θ of the current are calculated and output. Reference numeral 2 denotes a coordinate conversion unit which converts the excitation current command value i _φ ′, torque current command value i _T ′, and current phase angle θ calculated in a coordinate system rotating at the power frequency of the motor into a three-phase AC. The current command value i _u ′,
Convert to _iv ', _iw '. Reference numeral 3 denotes a current control PWM (pulse width modulation) inverter which causes the three-phase AC currents i _u , i _v , i _w flowing through the induction motor 4 to follow respective command values. Reference numeral 5 denotes a rotation speed sensor that detects the rotation speed of the induction motor 4, and 6 denotes a DC power supply (power supply for driving the induction motor) that supplies power to the current control PWM inverter 3. Next, in FIG. 2, 9 is a torque command value generating section, 10 is an absolute value circuit section, 11 is a steady loss minimum magnetic flux calculating section, 12 is a target magnetic flux calculating section, 13 is an exciting current calculating section, and 14 is a time constant setting. Department,
15 is a target torque calculation unit, 16 is a torque current calculation unit, 1
7 is a slip frequency calculation unit, 18 is a motor rotation speed calculation unit,
19 is an integral operation unit. In addition, the excitation current calculation unit 13,
The torque current calculation unit 16, the slip frequency calculation unit 17, the motor rotation speed calculation unit 18, and the integration calculation unit 19 are units that perform general vector control calculation.

Next, the operation will be described. First, the general operation of each arithmetic section will be described, and then the characteristic features of the present embodiment will be described in detail. In FIG. 1, a torque command value generator 9 includes a torque command value T _e ′ corresponding to an operation amount of an accelerator pedal operated by a driver and a regeneration command signal C.
Output _s . Incidentally, in FIG. 2, the above T _e '
And C _s are collectively indicated as _Te ′. Power running above the torque command value T _e 'is a positive value, the signal comprising the regenerative and negative value, regeneration command signal C _s is different according to the operating state when switched during regeneration from power running Value. Also,
The absolute value circuit section 10 outputs the absolute value of the torque command value _Te ′. Therefore, the value output from the absolute value circuit section 10 is always a positive value regardless of whether the torque command value _Te 'is positive or negative, that is, regardless of whether the power is running or during regeneration. The steady loss minimum magnetic flux calculation unit 11 always receives the positive torque command value _Te ′ given from the absolute value circuit unit 10 and minimizes the loss (copper loss) in the steady state at the torque command value _Te ′. operation and outputs the magnetic flux φ _r 'to. Further, the time constant setting unit 14 discriminates the regenerative mode depending on the regeneration command signal C _s provided from the torque command value generating unit 9, the target magnetic flux response time constant tau _phi and the target torque response time constant tau _T accordingly Is calculated. Further, the target magnetic flux computing unit 12, 'enter the, during steady steady loss minimum flux phi _r of the' aforementioned constant loss minimum flux phi _r corresponds to, depending on the torque response flux response in transient Target flux φ _r to be the optimal value,
The first derivative d / dt φ _r is calculated and output. In the calculation of the target magnetic flux φ _r , a calculation is performed based on a predetermined transfer function during power running, and a target magnetic flux response time constant given from the time constant setting unit 14 as a time constant of the transfer function during regeneration during regeneration. It is calculated by using the τ _φ.
Further, the target torque calculation unit 15 receives the torque command value _Te ′, and sets the target torque Te based on a predetermined transfer function (set in accordance with a required responsiveness, an allowable current capacity, and the like).
Calculate _m . At the time of regeneration, calculation is performed using the target torque response time constant τ _T given from the time constant setting unit 14 as the time constant of the transfer function. In addition, the excitation current calculation unit 13,
The portions of the torque current calculation section 16 and the slip frequency calculation section 17 are sections for performing general vector control calculation. First, the excitation current calculation unit 13 calculates and outputs an excitation current command value i _φ ′ based on the target magnetic flux φ _r provided from the target magnetic flux calculation unit 12 and the first derivative d / dt φ _r. . The torque current calculation unit 16 inputs the target magnetic flux phi _r of the target torque T _m and the target magnetic flux calculating unit 12 of the target torque calculating section 15 calculates and outputs a torque current command value i _T '. Further, the slip frequency calculation unit 17 receives the target magnetic flux φ _r of the target magnetic flux calculation unit 12 and the torque current command value i _T ′ of the torque current calculation unit 16 and calculates and outputs the slip frequency ω _se . The motor rotation speed calculation unit 18 multiplies the motor rotation speed N given from the rotation speed sensor 5 in FIG. 2 by the number of pole pairs P unique to the induction motor to obtain a motor rotation speed (electrical angle).
Calculate ω _re . That is, ω _re = (π / 30) N × P. This motor rotation speed ω _re and the above slip frequency ω _se
Is the power supply frequency ω. That is, ω
= Ω _se + ω _re . Then, the integration calculator 19 outputs a value obtained by integrating the power supply frequency ω as a phase angle θ of the current. The above exciting current command value i _φ ′, torque current command value i _T ′, and current phase angle θ are sent to the coordinate conversion unit 2 in FIG. 2 as current command values.

Next, the details of each operation unit will be described.
First, the excitation current calculation unit 13, the torque current calculation unit 16, and the slip frequency calculation unit 17 perform a general vector control calculation, and a detailed description thereof will be omitted. by providing omega _se below (equation 1), and guides the output torque T _e of the induction motor in the form of the following equation 2.

[0009]

(Equation 1)

Where ω: power supply frequency, ω _re : motor speed (electrical angle), M: mutual inductance, L _r : rotor self-inductance, R _r : rotor resistance, i _T : torque current, φ _r : Rotor flux

[0011]

(Equation 2)

Here, P is the number of pole pairs. At this time, the relationship between the rotor magnetic flux φ _r and the exciting current i _φ is expressed by the following equation (3).

[0013]

(Equation 3)

However, S: Laplace operator Therefore, the equation for calculating the excitation current command value i _φ ′ performed in the excitation current calculation unit 13 is as shown in the following equation (4) from the above equation (3). .

[0015]

(Equation 4)

The equation for calculating the torque current command value i _T ′ performed by the torque current calculation section 16 is as shown in the following equation (5) from the above equation (2).

[0017]

(Equation 5)

Here, T _e ': torque command value Note that the slip frequency ω in the slip frequency calculation unit 17
The arithmetic expression of _se is as shown in the above (Equation 1).
The calculations in the motor rotation speed calculation unit 18 and the integration calculation unit 19 are as described above.

Next, the parts of the torque command value generator 9, the time constant setting unit 14, the steady-state minimum loss magnetic flux calculator 11, the target magnetic flux calculator 12, and the target torque calculator 15 which are features of the present embodiment will be described. . FIG. 3 is a block diagram of one embodiment of the torque command value generator 9. In FIG. 3, reference numeral 21 denotes an accelerator sensor, which comprises a potentiometer and a power supply interlocked with an accelerator pedal operated by a driver. Also 22
Is a variable reference power supply that outputs a negative voltage, and outputs different values of negative voltage according to the regeneration command signal Cs. Also 23
Is an idle switch interlocked with the accelerator sensor 21, and switches to the variable reference power supply 22 when the accelerator pedal is released (in a state where the accelerator pedal is not depressed at all),
At other times, it switches to the accelerator sensor 21 side.
The differentiating circuit 24 outputs a differential value of the output S1 of the accelerator sensor 21. The negative voltage comparator 25 outputs “1” when the input value is equal to or more than a predetermined negative value. The switch circuit 26 is turned on while the output of the negative voltage comparator 25 is "1". The comparator 27 outputs “1” when the input value is equal to or more than a predetermined positive value. Also, the sample hold circuit 28
While the switch circuit 26 is on, the output S3 of the differentiating circuit 24 is held and output, and is reset by the output S6 of the comparator 27. And this sample and hold circuit 2
The output of 8 becomes the regeneration command signal Cs. Further, the output of the idle switch 23 becomes the torque command value _Te '.

FIG. 4 is an example of a signal waveform in the circuit of FIG. As shown in FIG. 4, when the output S1 of the accelerator sensor 21 changes as shown, the output S3 of the differentiating circuit 24 becomes a positive signal when the output S1 increases,
When it is decreasing, it becomes a negative signal. The switch circuit 26 is turned on only when the output S4 of the negative voltage comparator 25 is present, that is, when the output S3 of the differentiating circuit 24 is negative. The sample hold circuit 28 holds the output S5 of the switch circuit 26, and is reset when the output S6 of the comparator 27 is given, that is, when the output S3 of the differentiating circuit 24 becomes positive. Therefore, the regeneration command signal Cs output from the sample hold circuit 28 is equal to the output S
It is output only when 3 is negative, and has a value corresponding to the negative value. The variable reference power supply 22 is switched by the regeneration command signal Cs, and a negative voltage S2 corresponding to the regeneration command signal Cs is output. On the other hand, the output of the idle switch 23 becomes the torque command value T _e ′, but when the accelerator pedal is depressed, the accelerator sensor 21
Is output as the torque command value T _e ′. This is a positive value corresponding to the amount of depression of the accelerator pedal. At this time, the regeneration command signal Cs is 0. When the accelerator pedal is released, the idle switch 23
Is switched, and the output S2 of the variable reference power supply 22 is output as the torque command value T _e ′. This output S2 is a negative value corresponding to the regeneration command signal Cs. That is, the torque command value T _e ′ is a positive value during power running, a negative value during regeneration, and the negative value is a value according to the operating state when switching from power running to regeneration. For example, when the accelerator pedal is suddenly released from a state in which the accelerator pedal is fully depressed, the torque command value T _e 'becomes a large negative value. On the other hand, when the accelerator pedal is released from being depressed slightly, the torque command value _Te 'becomes a small negative value. The value of the torque command value T _e ′ is set more precisely according to the time during which the accelerator pedal is depressed, the acceleration of the vehicle, the vehicle speed, the motor rotation speed, the torque current, the excitation current, the use state of the foot brake, and the like. It may be configured as follows.

Next, returning to FIG. 1, the time constant calculator 14 will be described. The time constant computing unit 14 discriminates the regenerative mode depending on the regeneration command signal C _s provided from the torque command value generating unit 9, and a target magnetic flux response time constant tau _phi and the target torque response time constant tau _T accordingly calculate. That is, regeneration command to the signal C _s is power running of 0, and outputs a pre-specified target flux response time constant that is determined tau _phi and the target torque response time constant tau _T. At this time, the time constant is set to a small value so as to obtain a quick response. On the other hand, during regenerative, changing the target magnetic flux response time constant tau _phi and the target torque response time constant tau _T in response to the regeneration instruction signal C _s. For example, if suddenly released from the large-depth state the accelerator pedal, since regeneration instruction signal C _s is increased, relatively to the target magnetic flux response time constant tau _phi and the target torque response time constant tau _T in this case Set a small value (larger value than during power running). In contrast, if released from the small-depth state the accelerator pedal, since regeneration instruction signal C _s is small, relatively the target magnetic flux response time constant tau _phi and the target torque response time constant tau _T in this case Use a large value. Based on the calculated value, the target magnetic flux response time constant τ _{φ of the} steady loss minimum magnetic flux calculator 11 and the target torque response time constant τ _{T of the} target torque calculator 15 are set. Incidentally, as described above, 'from a value a value also corresponding to the state at the time of transition, the torque command value T _e instead of the regeneration command signal C _s' torque command value T _e when the target magnetic flux respond with itself It may be configured to switch the constant tau _phi and the target torque response time constant tau _T. That is, when the torque command value T _e ′ is positive power running, a predetermined target magnetic flux response time constant τ _φ and a target torque response time constant τ _T are output, and at the time of regeneration, the torque command value T _e ′ is negative. What is necessary is just to change the value of the target magnetic flux response time constant τ _φ and the target torque response time constant τ _T according to the magnitude of the value in the same manner as described above.

Next, the parts of the steady-state minimum loss magnetic flux calculator 11, the target magnetic flux calculator 12, and the target torque calculator 15 will be described. In the ordinary vector control, the rotor magnetic flux φ _r is fixed (the exciting current i _φ is constant), and only the torque current i _T is changed, so that the torque current i _{T of the} output torque is changed.
To obtain linearity and responsiveness to However, such a constant vector control of the rotor magnetic flux φ _r supplies a constant exciting current i _φ regardless of the load, so that the efficiency generally deteriorates at a light load. Therefore, copper loss is considered as the loss of the induction motor, and a condition for minimizing the loss is determined.
First, a .gamma .-. Delta. Coordinate model as shown in FIG. 5, that is, a .gamma .-. Delta. Coordinate model rotating at a power supply frequency well known as an induction motor model is used. 5, if the vector control is established, the current components of the respective axes, is between the rotor flux phi _r, it is known that the following equation (6) is established. Here, each current component i _γs ,
In i _δs , i _γr , and i _δr , subscripts γ and δ represent each axis component, r represents a rotor, and s represents a stator.

[0023]

(Equation 6)

On the other hand, the copper loss L _c of the induction motor is as shown in the following equation (7) from FIG. 5 and the equation (6).

[0025]

(Equation 7)

[0026] However, R _s: stator resistance, K _1, K _2: In constant above (7) determined by the motor type, because the differential term d / dt φ _r of phi _r given the steady state becomes 0 , And the slip frequency ω _se-opt that minimizes the copper loss L _c can be obtained by the following equation (8) from the condition of dL _c / dω _se = 0.

[0027]

(Equation 8)

Therefore, the slip frequency ω _se is given by ( _Equation 8)
By keeping the value of the equation, it is possible to perform driving that minimizes copper loss.
Specifically, from the above equation (1), in order to keep the slip frequency at the minimum loss slip frequency ω _se-opt , the torque current i
The relationship between _T and the magnetic flux phi _r It can be seen that it is sufficient as shown in the following equation (9) below.

[0029]

(Equation 9)

Next, when the equation (9) is substituted into the equation (2) to eliminate i _T , the torque command value _Te ′ and the magnetic flux φ _r
Is expressed by the following equation (10).

[0031]

(Equation 10)

Therefore, when the torque command value _Te ′ is input, the minimum steady-state loss magnetic flux φ _r ′ is derived by the equation (10), and the torque current command value i _T ′ is obtained by the equation (9). The command value i _φ ′ is calculated by equation (4), and the slip frequency ω _se is calculated by equation (1), so that it is possible to constantly drive to minimize the copper loss. At this time, the slip frequency ω _se matches the minimum loss slip frequency ω _se-opt , and the output torque _Te follows the torque command value _Te ′. However, the torque command value T _e 'when changes stepwise from equation (10), the steady loss minimum flux phi _r' becomes likewise stepwise. Then, as shown in equation (4), since the calculation of the excitation current command value i _φ ′ includes dφ _r / dt, when a step-like change in the torque command value occurs, the excitation current command value i _φ 'Becomes a transiently large value, thereby increasing the transient loss. The above phenomenon is expressed by equation (7).
It can also be seen from the fact that L _c is a function of dφ _r / dt.
In this embodiment, only the copper loss is considered as the loss. However, as described in the above-described conventional example (Japanese Patent Laid-Open No. 23085/1990), the same problem occurs when the copper loss and the iron loss are considered. Occurs. Therefore, when the transient loss is also considered, the slip frequency is changed to the loss minimum slip frequency ω.
_{Keeping se-opt} is not a good idea in terms of efficiency.
Further, when the upper limit of the current is determined from the current capacity of the semiconductor switching element used in the current control PWM inverter 3 of FIG. 2, the response of the torque must be slowed down during a transient when the current becomes large. Therefore, in the present embodiment, the target torque calculation unit 15 for determining the response of the torque, the steady-state loss minimum magnetic flux calculation unit 11 and the target magnetic flux calculation unit 12 are replaced with a general vector control calculation unit 13,
By adding a control system configuration that can independently change the torque response and the magnetic flux response in addition to 15 and 16, the slip frequency is steadily set to the loss minimum slip frequency ω _se-opt, and the magnetic flux response is changed transiently. Is controlled so as to have an optimum value according to the torque response, thereby reducing the transient loss.

First, the calculation content of the steady-state minimum loss magnetic flux calculation unit 11 is expressed by the following equation (10), and calculates the rotor magnetic flux that constantly minimizes the loss, that is, the steady-state minimum loss magnetic flux φ _r ′.

The target magnetic flux calculating section 12 for calculating the target magnetic flux φ _r is a filter having a steady gain of 1. In this embodiment, it is a first-order low-pass filter as shown in the following equation (11).

[0035]

[Equation 11]

Where τ _{φ is} the time constant of the target magnetic flux, and S is the Laplace operator. The time constant τ _φ of the target magnetic flux is, as described above,
At the time of regeneration, it is a variable value according to the regeneration command signal Cs (or the torque command value T _e ′) (details will be described later). Further, in the present embodiment, the target torque calculation unit 15 that calculates the target torque _Tm has a transfer function as shown in the following equation (12). This transfer function is set according to the required responsiveness, and at the time of regeneration, according to the regeneration command signal Cs.

[0037]

(Equation 12)

Here, τ _{T is} the time constant of the target torque. The time constant τ _T of the target torque is variable during regeneration according to the regeneration command signal Cs (or the torque command value _Te ′) as described above. Value (details described later).

FIG. 6 shows the peak value of the loss of the induction motor and the peak value of the induction motor loss with respect to the time constant τ _φ of the target magnetic flux when a stepwise input is applied as the torque command value _Te ′ in the control system shown in FIG. FIG. 4 is a characteristic diagram showing a calculated value of loss energy within a predetermined time. FIG. 6 shows that each loss has a characteristic having a minimum value, and that each loss has a minimum value when the time constant τ _φ is a certain value. Therefore, in the control system shown in FIG. 1, when the torque response is given by the equation (12), the magnetic flux response is determined using the time constant τ _φ of the target magnetic flux that minimizes the transient loss obtained from FIG. If this is done, it is possible to drive the motor with little loss both during the transition and during the steady state. That is, the value of τ _φ that minimizes the loss in FIG. 6 may be used in equation (11).

FIGS. 7 and 8 are characteristic diagrams showing speed control simulation results. FIG. 7 shows the case where the method of maintaining the slip frequency at the minimum loss slip frequency ω _se-opt in both the transient and steady states is used. 8 shows the characteristics when the method according to the present embodiment is used. Note that the torque response was the same for both. 7 and 8, the characteristics (response) of the torque T and the rotation speed N are the same, but the copper loss L
The characteristic of _c is clearly reduced in the present embodiment in the transient state, and at the steady state, the slip frequency drive is performed to minimize the copper loss as in the conventional case. Therefore, in the present embodiment, it is possible to reduce the loss at the time of transition while maintaining the same response characteristics. Further, in the present embodiment, as described above, in the calculation in the target torque calculation unit 15, the value of the time constant τ _T of the target torque is:
During regeneration, it changes according to the regeneration command signal Cs (or the torque command value _Te ′). The characteristic shown in FIG. 6 is a characteristic corresponding to the predetermined time constant τ _T. If the time constant τ _T changes, the value of the time constant τ _φ of the target magnetic flux that minimizes the loss also changes. Therefore, the time constant τ _φ of the target magnetic flux in the calculation of the target magnetic flux calculator 12 is also changed as described above.
The time constant τ _φ of the target magnetic flux in this case is a value that minimizes the loss in the characteristic of FIG. 6 corresponding to the time constant τ _T of the target torque at that time.

Next, FIG. 9 is a characteristic diagram showing operation characteristics when shifting from power running to regeneration. In FIG. 9, φ _r
Is a magnetic flux, i _T is a torque current, i _φ is an exciting current, i _T is a torque current, and Te is a torque. As described above, in the present embodiment, the time constant between the exciting current i _φ and the torque current i _T is made variable, and the distribution ratio between i _φ and i _T is controlled so that the efficiency is maximized. This control is the same during power running and regeneration. Further, negative torque required during regeneration is done by reversing the polarity of the torque current i _T. Therefore, as shown in FIG. 9, the torque current i _T has a negative value during regeneration, and accordingly, the torque Te has a negative value. Torque Te _{is, Te = k · φ r ·} i T ( where k is a constant) given by. Therefore, in order to set the torque to a negative value, one of the polarities of the magnetic flux φ _r and the torque current i _T may be reversed. However, the magnetic flux φ _r is not preferable because it does not immediately follow even _{if the} exciting current i _φ is changed. Therefore, in the present embodiment, by generating a negative torque by reversing the sign of the torque current i _T. In order to realize the above function, in the present embodiment, as shown in FIG. 1, an absolute value circuit unit 10 is provided, and even when the torque command value Te 'becomes negative during regeneration, 11 is always given a positive value so that the target magnetic flux φ _r always has a positive value. And the target torque calculation unit 1
5, the torque command value Te 'is given as it is,
If the torque command value Te ′ becomes a negative value during regeneration, the torque current command value i _T ′ becomes negative. Further, as described above, the time constant calculating section 14 determines the regenerative state according to the regenerative command signal C _s (or the torque command value _Te ′) given from the torque command value generating section 9 and determines the target magnetic flux according to the regenerative state. Response time constant τ _φ
And a target torque response time constant τ _T are calculated. For example, if suddenly released from the large-depth state the accelerator pedal, since regeneration instruction signal C _s is increased, the target magnetic flux response time constant tau _phi and the target torque response time constant in this case tau _T
Are relatively small values (larger values than during power running).
Therefore the target torque the T _m varies relatively quickly. On the other hand, the target magnetic flux φ _r is always a positive value, and the magnetic flux φ changes toward it so that the transient loss is minimized and a sudden change in torque does not occur. Also, if you release from a state in which depressed small accelerator pedal, since regeneration instruction signal C _s is small, and a relatively large value and a target magnetic flux response time constant tau _phi and the target torque response time constant tau _T in this case I do. Therefore changes in the target torque T _m and the target magnetic flux phi _r becomes more gradual.

In this embodiment, the magnetic flux response is expressed by (Equation 1).
Equation (1) and the torque response are given by Equation (12), but are not necessarily limited to this transfer function. For example, a secondary vibration system [G (S) = ω _n ² /
S ² + 2ζω _n S + ω _n ² ], and similarly, the magnetic flux responsiveness may be provided by a secondary vibration system. However, in order to obtain the first derivative of the target magnetic flux without performing the differential operation,
It is necessary that the relative degree between the numerator and the denominator be 1 or more. When the magnetic flux response is given by a secondary vibration system, the relationship shown in FIG. 6 is obtained for the damping rate ζ and the natural frequency ω _n , and the magnetic flux is calculated using ζ and ω _{n at} which the transient loss is minimized. I just need.

[0043]

As described above, according to the present invention, the means for calculating the minimum steady-state loss magnetic flux for minimizing the steady-state loss from the torque command value and the target torque of the induction motor from the torque command value are calculated. Means and means for causing the torque of the induction motor to follow the target torque from the steady-state loss minimum magnetic flux, and for calculating the magnetic flux responsiveness in which the transient loss is minimized. When the torque response is the same as the method of maintaining the loss minimum slip frequency ω _se-opt , the transient loss can be reduced. Conversely, if the current capacity is the same, the torque responsiveness can be increased. In a steady state, motor drive control that minimizes loss becomes possible as in the conventional method. Furthermore, even during the transition from power running to regeneration, abrupt torque fluctuations can be prevented while minimizing transient loss, smooth regenerative braking can be performed, and the torque response and magnetic flux response during regeneration can be shifted. Is set in accordance with the traveling state of the vehicle, so that the regenerative brake responsiveness corresponding to the traveling state can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing details of a high-efficiency drive control calculation unit 1 according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of the entire system according to an embodiment of the present invention.

FIG. 3 is a block diagram showing details of a torque command value generator 9;

FIG. 4 is a signal waveform diagram in a torque command value generator 9;

FIG. 5 is a diagram showing a γ-δ coordinate model of an induction motor.

FIG. 6 shows the peak value of the loss of the induction motor with respect to the time constant τ _φ of the target magnetic flux and the calculated value of the energy loss within a certain time when a stepwise input is applied as the torque command value _Te ′. FIG.

FIG. 7 is a characteristic diagram showing speed control simulation results in a conventional example.

8 is a characteristic diagram showing speed control simulation results in the embodiment of FIG.

FIG. 9 is a characteristic diagram showing operation characteristics when shifting from power running to regeneration.

[Explanation of symbols]

1: High-efficiency drive control operation unit 4: Induction motor 2: Coordinate conversion unit 5: Rotation speed sensor 3: Current control PWM inverter 6: DC power supply (battery) 9: Torque command value generation unit 10: Absolute value circuit unit 15: Target torque calculation unit 11: Minimum steady-state loss magnetic flux calculation unit 16: Torque current calculation unit 12: Target magnetic flux calculation unit 17: Slip frequency calculation unit 13: Excitation current calculation unit 18: Motor speed calculation unit 14: Time constant setting unit 19 : Integral operation unit 21: Accelerator sensor 25: Negative voltage comparator 22: Variable reference power supply 26: Switch circuit 23: Idle switch 27: Comparator 24: Differential circuit 28: Sample and hold circuit _Te ': Torque command value _Tm : Target torque τ _φ : Time constant of target magnetic flux response τ _T : Time constant of target torque response φ _r ': Minimum steady-state loss magnetic flux φ _r : Target magnetic flux N: Motor rotation speed (Rpm) ω: power supply frequency ω _se : slip frequency ω _re : motor rotation speed (electrical angle) i _φ ': excitation current command value i _T ': torque current command value θ: current phase angle i _u ', _iv ', I _w ': three-phase alternating current command value _iu , _iv , i _w : three-phase alternating current

Continuation of front page (56) References JP-A-2-23086 (JP, A) JP-A-58-186387 (JP, A) JP-A-59-169382 (JP, A) JP-A-57-142185 (JP) , A) JP-A-59-14386 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02P 5/408-5/412 H02P 7/628-7/632 H02P 21/00

Claims (4)

(57) [Claims] An induction motor control device for calculating a current command value according to a torque command value and a rotation speed of an induction motor, and driving the induction motor with a polyphase alternating current corresponding to the current command value. A torque command value generator that generates a torque command value corresponding to the driver's operation during power running to drive the load, and outputs a torque command value with the opposite sign to that during power running during regeneration when driving the induction motor from the load to generate power. And an absolute value circuit section for outputting an absolute value of the torque command value; and calculating a rotor magnetic flux that minimizes a steady loss of the induction motor at the absolute value of the torque command value given via the absolute value circuit section. A steady-state loss minimum magnetic flux calculation unit, and a target magnetic flux calculation for calculating the target magnetic flux and a first-order differential value of the target magnetic flux based on a transfer function having a low-pass characteristic by inputting the steady-state loss minimum magnetic flux. And a torque command value from the torque command value generating section,
Transmission with low-pass characteristics that differ between power running and regeneration
A target torque calculation unit that calculates a target torque of the induction motor from the torque command value based on a function; and a first-order differential value of the target magnetic flux and the target magnetic flux, the target torque and the target torque, based on a circuit constant of the induction motor. A vector control calculation unit that calculates the current command value according to the rotation speed of the induction motor; and a motor drive unit that causes the current flowing through the induction motor to follow the current command value. The output torque of the induction motor Motor control device for controlling a value corresponding to the target torque. The torque command value generating section generates a positive torque command value corresponding to a driver's operation when the load is driven from the induction motor, and generates the torque command value during regeneration when the load drives the induction motor to generate power. 2. The induction motor control device according to claim 1, wherein a negative torque command value having a magnitude corresponding to a state when switching from power running to regeneration is generated. 3. The target torque calculating section according to claim 1, wherein said target torque calculating section is low during power running.
A target torque is calculated based on a predetermined transfer function having a path characteristic, and during regeneration, a target torque is set using a transfer function having a low-pass characteristic different from that during power running, which is set in advance according to the torque command value. The induction motor control device according to claim 1 or 2, wherein the device calculates a torque. 4. A target magnetic flux calculating unit according to claim 1, wherein said target magnetic flux calculating unit is a low-power
A predetermined transfer function having a transfer characteristic is selected, and during regeneration, a time constant for minimizing a loss according to the torque command value is selected .
Select a transfer function having Pasu properties, based on their
4. The induction motor control device according to claim 1, wherein the target magnetic flux and a first-order differential value of the target magnetic flux are calculated .