JP7180149B2 - AC motor controller - Google Patents

Description

The present invention relates to a control device for an AC motor.

In order to improve the efficiency of the motor, it is preferable to control the terminal voltage of the motor to be high. On the other hand, in order to control the torque of the electric motor with high responsiveness and high accuracy, it is preferable to perform feedback control so that the current matches the current command value for outputting the desired torque. However, when the terminal voltage of the electric motor is increased, the stability of the current control system may deteriorate due to restrictions on the maximum output voltage of a power converter such as an inverter that supplies power to the electric motor.

As a conventional technology for improving the stability of the current control system, for example, a control device that maximizes the efficiency of the motor under the condition that the terminal voltage of the motor is equal to or lower than the voltage limit value and calculates a current command value that outputs a desired torque. is known (see, for example, Patent Document 1).

JP-A-2009-124811

However, since the conventional method of calculating the current command value does not consider the transient state of the current control system, there is a possibility that the control accuracy of the current of the AC motor may be lowered.

Accordingly, the present disclosure provides a control device for an AC motor that can improve the current control accuracy of the AC motor.

数１８に従って導出された前記端子電圧の最適値を使って、前記端子電圧の大きさを前記電圧制限値に制御し、かつ、前記端子電圧の角度を前記角度の最適値に制御したときの前記電流の推定値を、前記第２の電流指令値と設定する、交流電動機の制御装置が提供される。
As one aspect of the technology of the present disclosure,
A control device for controlling current and voltage supplied to an AC motor by a power converter,
a first current command unit that calculates a first current command value based on a torque command value and a speed detection value of the AC motor;
The magnitude of the terminal voltage of the AC motor becomes equal to or less than the voltage limit value equal to or less than the maximum output voltage of the power converter, and the deviation between the first current command value and the second current command value is minimized. a second current command unit that calculates the second current command value,
a terminal voltage control unit that controls the terminal voltage of the AC motor so that the current of the AC motor matches the second current command value;
The second current command unit,
estimating an estimated value of the current of the AC motor based on the estimated value of the terminal voltage of the AC motor;
Optimizing the angle of the estimated value of the terminal voltage that minimizes the deviation between the first current command value and the estimated value of the current when the magnitude of the estimated value of the terminal voltage is controlled to the voltage limit value. Calculate the value of
The voltage limit value is V _alim , the optimum value of the angle at time k+1 after current time k is δ _vaopt (k+1|k), and the optimum value of the terminal voltage at time k+1 after current time k is v _dqopt ( k+1|k), then
The optimum value of the terminal voltage is calculated according to the following equation 18 using the optimum value of the angle,

Using the optimum value of the terminal voltage derived according to Equation 18, the magnitude of the terminal voltage is controlled to the voltage limit value, and the angle of the terminal voltage is controlled to the optimum value of the angle. A control device for an AC motor is provided , which sets an estimated current value as the second current command value .

According to the technology of the present disclosure, it is possible to improve the current control accuracy of an AC motor.

1 is a control block diagram illustrating the overall configuration of a control device for an AC motor according to the present disclosure; FIG. FIG. 3 is a block diagram showing a configuration example of a current command calculator; It is a figure which illustrates the concept of model predictive control. It is a figure which illustrates the hardware constitutions of the arithmetic unit with which a control apparatus is provided.

Hereinafter, embodiments of an AC motor control device according to the present disclosure will be described with reference to the drawings. The same reference numerals are given to the same components, and redundant explanations are omitted. It should be noted that the present invention is not limited to the following embodiments, and can be modified as appropriate without changing the gist of the invention.

The control device according to the present disclosure controls an AC motor such as a permanent magnet synchronous motor (hereinafter also referred to as PMSM) or an induction motor, and increases the terminal voltage of the AC motor to achieve high efficiency operation, and at the same time, current response to achieve highly responsive torque control.

<First control example>
FIG. 1 is a control block diagram illustrating the overall configuration of an AC motor control device according to the present disclosure. The control device 100 shown in FIG. 1 realizes high-performance torque control and speed control by controlling the PMSM 80 on the d and q axes, which are orthogonal rotating coordinate axes that rotate in synchronization with the rotor. The north pole direction of the magnetic poles of the rotor of the motor is defined as the d-axis, and the direction 90 degrees ahead of the d-axis is defined as the q-axis.

First, speed control, current control, and voltage control of PMSM 80 will be described.

A position/speed detector 90 that detects the magnetic pole position of the PMSM 80 and the rotational speed of the PMSM 80 is attached to the PMSM 80 . A position/speed detection circuit 91 provided in the control device 100 detects a speed detection value (electrical angular frequency) ω _re and A position detection value (electrical angle) θ _re is detected. The velocity detection value ω _re represents the electrical angular velocity detection value of the PMSM 80 , and the position detection value θ _re represents the electrical angle detection value of the PMSM 80 . A mechanical angular velocity calculator 92 calculates a detected velocity value (mechanical angular frequency) ω _rm based on the detected velocity value (electrical angular frequency) ω _re and the number of poles of the PMSM 80 . The velocity detection value ω _rm represents the mechanical angular velocity detection value of the PMSM 80 .

The detected speed value ω _re and the detected position value θ _re may be calculated based on the terminal current and terminal voltage of the PMSM 80 without using the position/speed detector 90 and the position/speed detection circuit 91 .

A subtractor 16 calculates the deviation between the speed command value (mechanical angular frequency) ω _rm ^* and the speed detection value (mechanical angular frequency) ω _rm . The speed command value ω _rm ^* represents the command value of the mechanical angular speed of the PMSM 80 supplied from the outside. The torque command value τ ^* is calculated by amplifying the deviation calculated by the subtractor 16 by the speed controller 17 . A torque command value τ ^* represents a torque command value of the PMSM 80 .

Based on the torque command value τ ^* and the speed detection value ω _re , the current command calculation unit 18 maximizes the efficiency of the PMSM 80 under the condition that the terminal voltage of the PMSM 80 is equal to or lower than the voltage limit value V _alim and reduces the torque to the torque command value τ ^d -axis current command value i _d ^* and q-axis current command value i _q ^* to be controlled are calculated. The current command calculation unit 18 is an example of a first current command unit, and the d-axis current command value i _d ^* and the q-axis current command value i _q ^* are examples of first current command values. The voltage limit value V _alim is a value equal to or less than the maximum output voltage of power converter 70 .

FIG. 2 is a block diagram showing a configuration example of a current command calculator. Note that the specific configuration of the current command calculation unit is not limited to the configuration shown in FIG.

The current command calculator 18 shown in FIG. 2 includes a magnetic flux command calculator 111, a magnetic flux limit value calculator 141, an output limiter 142, a load angle command calculator 112, a load angle adjuster 132, a current command calculator 133, a torque A calculator 134 , a subtractor 131 and an adder 135 are provided.

A magnetic flux command calculator 111 calculates a first magnetic flux command value Ψ ₀ ^* from the torque command value τ ^* . The first flux command value Ψ ₀ ^* is calculated under conditions that maximize the efficiency of the PMSM 80, but it may be difficult to perform this calculation online. In this case, for example, a table of magnetic flux command values that maximizes the efficiency of the PMSM 80 is prepared ⁱⁿ advance. A magnetic flux command value Ψ ₀ ^* of 1 may be calculated.

Magnetic flux limit value calculator 141 calculates magnetic flux limit value Ψ _lim using voltage limit value V _alim and speed detection value ω _re in order to limit the terminal voltage of PMSM 80 to the maximum output voltage of power converter 70 or less. For example, the magnetic flux limit value calculator 141 calculates the magnetic flux limit value Ψ _lim according to the formula "Ψ _lim =V _alim /|ω _re |".

The second magnetic flux command value Ψ ^* is output after the first magnetic flux command value Ψ ₀ ^* is limited by the output limiter 142 to the magnetic flux limit value Ψ _lim or less.

A load angle command calculator 112 calculates a feedforward compensation value δ ₀ ^* of the load angle command value based on the torque command value τ ^* . Further, the load angle adjuster 132 amplifies the deviation between the torque command value τ ^* calculated by the subtractor 131 and the torque calculation value _τcalc to calculate a correction value δ _PI ^* of the load angle command value. The load angle adjuster 132 is composed of, for example, a proportional-integral amplifier.

The adder 135 adds the feedforward compensation value δ ₀ ^* and the correction value δ _PI ^* to calculate the load angle command value δ ^* .

Note that the torque calculation value τ _calc is calculated by the torque calculator 134 based on the d- and q-axis current command values _id ^* and _iq ^* . For example, the torque calculator 134 uses the d- and q-axis current command values i _d ^* , i _q ^* and various constants L _d , L _q , and Ψ _m to calculate the formula “τ _calc = Ψ _m i _q ^* + (L _d −L _q )i _d ^* i _q ^* ”, the torque calculation value τ _calc is calculated. L _d , L _q , and Ψ _m represent d-axis inductance, q-axis inductance, and permanent magnet magnetic flux, respectively.

A current command calculator 133 calculates d- and q-axis magnetic flux command values Ψ d ^{* and} _{Ψ q *} ^based on the second magnetic flux command value Ψ * and the load angle command value δ ^* . For example, the current command computing unit 133 computes the d- and q-axis ^magnetic flux command values Ψ d * and Ψ _q ^* in accordance with the formulas "Ψ _d ^* = Ψ ^* cos δ ^* , Ψ _q ^* = Ψ ^* sin _δ ^* ". Furthermore, the current command calculator 133 calculates d- and q-axis current command values i _d ^* and i _q ^* based on the magnetic flux command values Ψ _d ^* and Ψ _q ^* . For _{example ,} ^{the current} command ^calculator _{133 calculates} the d- and _{q -} axis ^current _command values i Calculate _d ^* and _iq ^* .

Thus, in the case of FIG. 2, the first magnetic flux command value Ψ ₀ ^* that maximizes the efficiency of the PMSM 80 is calculated, and the first magnetic flux command value Ψ ₀ ^* exceeds the magnetic flux limit value Ψ _lim . A second magnetic flux command value Ψ ^* , which is a value corrected so that The d- and q-axis current command values _id ^* and _iq ^* are calculated based on the second magnetic flux command value Ψ ^* . As a result, the terminal voltage of PMSM 80 can be controlled to be equal to or lower than the maximum output voltage of power converter 70, and the torque can be controlled with high precision.

In FIG. 1 , the current command correction unit 30 makes the magnitudes of the voltage command values v _d ^* and v _q ^* equal to or less than the voltage limit value V _alim even in the transient state, and the current command values _id ^* and i _q The current command values _idACR ^{* and} _iqACR ^* are calculated so that the deviation between * and the current command values _idACR ^* and _iqACR ^* is minimized. The current command correction unit 30 is an example of a second current command unit, and the d-axis current command value _idACR ^* and the q-axis current command value _iqACR ^* are examples of the second current command values. Details of the current command correction unit 30 will be described later.

The DC voltage detection circuit 12 is provided in the control device 100 and detects a DC voltage that is rectified by the rectification circuit 60 and input to the power converter 70 . Based on the DC voltage detection value _Edc detected by the DC voltage detection circuit 12, the voltage limit value calculator 22 calculates a voltage limit value _Valim corresponding to the magnitude of the DC voltage detection value _Edc . The DC voltage detection value _Edc represents the detection value of the DC voltage rectified by the rectifier circuit 60 and input to the power converter 70 . The voltage limit value calculator 22 calculates, for example, a voltage limit value V _alim that is approximately proportional to the DC voltage detection value _Edc and is less than or equal to the maximum output voltage of the power converter 70 determined according to the DC voltage detection value _Edc . do.

The u-phase current detector 11u detects a u-phase current flowing between the power converter 70 and the PMSM 80, and outputs a u-phase current detection value _iu representing the magnitude of the u-phase current. The w-phase current detector 11w detects a w-phase current flowing between the power converter 70 and the PMSM 80, and outputs a w-phase current detection value _iw representing the detected value of the magnitude of the w-phase current. The current coordinate converter 14 coordinate-transforms the phase current detection values i _u and i _w into d- and q-axis current detection values _id and i _q using the position detection value θ _re .

The d-axis current controller 20a amplifies the deviation between the d-axis current command value _idACR ^* calculated by the subtractor 19a and the d-axis current detection value _id to calculate the d-axis voltage command value _vd ^* . The q-axis ^current controller 20b amplifies the deviation between the q-axis current command value _iqACR ^* calculated by the subtractor 19b and the q-axis current detection value iq to calculate the q-axis voltage command value _{vq *} .

The voltage coordinate converter 15 converts the d- and q-axis voltage command values _vd ^* and _vq ^* to the u-, v- and w-phase voltage command values _vu ^* and _vv ^* using the position detection value _θre . , v _w ^* .

The rectifier circuit 60 rectifies the AC power from the three-phase AC power supply 50, converts it into DC power, and supplies this DC power to a power converter 70 such as an inverter.

PWM (Pulse Width Modulation) circuit 13 converts the output voltage of power converter 70 to phase voltage command value vu based on phase ^{voltage command values vu*} _{, vv} ^* , _vw ^* and DC voltage detection value _{Edc .} Generate a plurality of gate signals for controlling ^* , _vv ^* , _vw ^* . Based on a plurality of gate signals from the PWM circuit 13, the power converter 70 controls a plurality of semiconductor switching elements inside the power converter 70 to change the terminal voltage of the PMSM 80 to the phase voltage command values v _u ^* , v Control to _v ^* and _vw ^* .

The control device 100 includes a terminal voltage control section that controls the terminal voltage of the PMSM 80 so that the current of the PMSM 80 matches the current command values _idACR ^* and _iqACR ^* . For example, the current coordinate converter 14, the d-axis current controller 20a, the q-axis current controller 20b, the voltage coordinate converter 15 and the PWM circuit 13 function as the terminal voltage controller.

Through the control described above, the speed of the PMSM 80 can be controlled to the command value (more specifically, the speed command value ω _rm ^* ).

Next, the details of the current command correction unit 30 will be described.

The current command correction unit 30 makes the magnitudes of the d- and q-axis voltage command values v _d ^* and v _q ^* equal to or less than the voltage limit value V _alim and the current command value i _d ^* even in the transient state of the current control system. , _iq ^* and the current command values _idACR ^* and _iqACR ^* are calculated so as to minimize the deviation between the current command values _idACR ^* and _iqACR ^* . More specifically, the current command correction unit 30 uses model predictive control (hereinafter referred to as MPC) technology to calculate the current command values i _dACR ^* and i _qACR ^* .

First, an outline of MPC will be described.

FIG. 3 shows the principle of MPC in a state equation model of a discrete value system in which the input vector is u and the output vector is y. In FIG. 2, each symbol is
s(t): set value trajectory vector r(t|k): reference trajectory vector of sample point t after current time k u _est (t|k): input vector estimation of sample point t after current time k Value y _est (t|k): Output vector estimate value of sample point t after current time k H _P : Prediction horizon. The reference trajectory vector r represents an ideal trajectory that the output y(t) should return to the set value trajectory vector s(t) starting from the output y(k) at the current time.

First, the current command correction unit 30 uses the set value trajectory vector s(t) corresponding to the target value at the sample point k to calculate the reference trajectory vector r(t|k) from the sample point k to (k+H _P ). to calculate The reference trajectory vector r(t|k) is calculated so as to approach the set value trajectory vector s(t) over time. The current command correction unit 30 defines an evaluation function that is a function of the reference trajectory vector r(t|k), the input vector estimated value u _est (t|k), and the output vector estimated value y _est (t|k). , the optimal solution for the input vector estimate u _est (t|k) that minimizes the evaluation function. Since the state vector estimate x _est (t|k) can be calculated using the state equation model using the output y(k) of the sample point k and the input vector estimate u _est (t|k), the evaluation function can be transformed into a function of only the input vector estimate u _est (t|k).

Next, a method of calculating a current command value using MPC will be described.

When the control delay of the output voltage of the power converter 70 such as an inverter is one sample period, the discrete value system model of the current control system of the PMSM 80 can be expressed by the following equation.

System matrices A and B are defined by the following equations using PMSM electrical constants. T _s in system matrices A and B represents the sampling period.

The set value trajectory vector s of the MPC is assumed to be the current command value i _dq ^* . The current command value i _dqr ^* corresponding to the reference trajectory vector r has its initial value set to the previous value of the current command value i _dqACR ^* output from the current command correction unit 30, and the control delay of the output voltage of the power converter 70 to Considering this, the following equation is set so that the current response becomes the fastest.

The current command value i _dr ^* corresponds to the d-axis current command value i _d ^* calculated by the current command calculation section 18, and the current command value i _qr ^* corresponds to the q-axis current command calculated by the current command calculation section 18. corresponds to the value i _q ^* .

In order to minimize the deviation between the current command value i _dqr ^* (corresponding to the reference trajectory vector r) and the current estimated value vector i _dquest (corresponding to the output vector estimated value y _est ), the evaluation function is, for example, as follows: is set to

The current command correction unit 30 can calculate (estimate) the current estimated value vector i _dquest according to Equation 1 according to the following equation based on the voltage estimated value vector v _dquest (corresponding to the input vector estimated value u _est ).

The voltage estimate vector v _dquest corresponds to estimates of the terminal voltages of PMSM 80 . According to Equation 5, the current estimated value vector i _dquest can be expressed as a function of the voltage estimated value vector v _dquest , so the evaluation function V shown in Equation 4 can be expressed as a function of the voltage estimated value vector v _dquest . .

Also, the constraint on the voltage command value due to the maximum output voltage of the power converter 70 can be expressed as the constraint on the square norm of the voltage estimation value vector v _dquest as in the following equation.

From the above, the current command correction unit 30 makes the magnitude of the estimated voltage vector v _dquest equal to or less than the voltage limit value V _alim and sets the voltage optimum value vector v _dqopt that minimizes the evaluation function V of Equation 4 to It can be derived by solving the following constrained optimization problem.

Current command correction unit 30 calculates current command value i _dqACR ^* according to the following equation using voltage optimum value vector v _dqopt derived according to Equation (7).

Therefore, the current command correction unit 30 sets the estimated value of the current of the PMSM 80 when the terminal voltage of the PMSM 80 is controlled to the voltage optimum value vector v _dqopt as the current command value i _dqACR ^* .

As described above, according to the first control example, the current command correction unit 30 causes the terminal voltage of the PMSM 80 to become equal to or less than the voltage limit value V _alim and the current command values _id ^* , _iq ^* and The current command values _idACR ^* and _iqACR ^* are calculated so that the deviation from the current command values _idACR ^* and _iqACR ^* is minimized. As a result, the current command values idACR ^* and _iqACR ^* obtained by correcting the current _command values _id ^* and _iq ^* once calculated by the current command calculation unit 18 are used for current control. It is possible to improve the current control accuracy in the transient state of the system. In particular, since the estimated value of the current of the PMSM 80 when the terminal voltage of the PMSM 80 is controlled to the voltage optimum value vector v _dqopt is used as the current command value i _dqACR ^* , the current command value i _dqACR ^* can be calculated with high accuracy. can improve current control accuracy and current response.

<Second control example>
The second control example simplifies the computation of the current command correction unit 30 in the first control example. In the calculation of the current command value using the MPC of the first control example, the prediction horizon _HP and the window parameter _Hw are set to the minimum values as shown in the following equations.

In this case, the current command value i _dqr ^* corresponding to the reference trajectory vector r shown in Equation 3 is transformed into the following equation.

Also, the evaluation function V shown in Equation 4 is transformed into the following equation.

The current estimated value vector _idquest in Equation 5 is transformed into the following equation.

Furthermore, the constraint on the voltage command value due to the maximum output voltage of power converter 70 in Equation 6 is transformed into the following equation.

Next, a method of calculating the voltage optimum value vector v _dqopt that makes the magnitude of the voltage estimated value vector v _dquest equal to or less than the voltage limit value V _alim and that minimizes the evaluation function V of Equation 11 will be described.

First, the current command correction unit 30 calculates the initial value v _dquest0 of the voltage estimation value vector v _dquest according to the following equation.

When the magnitude of the initial value v _dquest0 of the voltage estimation value vector is equal to or less than the voltage limit value V _alim , the current can be controlled to the current command value i _dqr ^* (corresponding to the reference trajectory vector r). Therefore, the current command value i _dqACR ^* is controlled to the current command value i _dqr ^* (corresponding to the reference trajectory vector r). Furthermore, according to Equation 10, the current command value i _dqACR ^* is controlled as in the following equation.

On the other hand, when the magnitude of the initial value v _dquest0 of the voltage estimation value vector is greater than the voltage limit value V _alim , the current cannot be controlled to the current command value i _dqr ^* (corresponding to the reference trajectory vector r). In this case, the magnitude of the voltage optimum value vector v _dqopt that minimizes the evaluation function V of Equation 11 is equal to the voltage limit value V _alim . Therefore, the voltage estimation value vector v _dquest is represented by a vector whose magnitude is the voltage limit value V _alim and whose angle is a function of the angle estimation value δ _vaest , as in the following equation.

Thereby, the current command correction unit 30 makes the magnitude of the voltage estimation value vector v _dquest equal to or less than the voltage limit value V _alim and optimizes the angle of the voltage estimation value vector v _dquest that minimizes the evaluation function V of Equation 11. The value δ _vaopt can be derived by solving the optimization problem of

Since the optimization problem of Equation 17 has only one decision variable, it can be solved by a relatively simple algorithm such as the golden section method.

The current command correction unit 30 can calculate the voltage optimum value vector v _dqopt according to the following equation using the optimum value δ _vaopt .

Then, as in the first control example, the current command correction unit 30 calculates the current command value i _dqACR ^* according to Equation 8 using the voltage optimum value vector v _dqopt derived according to Equation 18.

Therefore, the current command correction unit 30 controls the magnitude of the terminal voltage vector of the PMSM 80 to the voltage limit value V _alim and controls the angle of the terminal voltage vector to the optimum value δ _vaopt . Set the vector i _dquest as the current command value i _dqACR ^* . Thus, according to the second control example, it is possible to improve the current control accuracy and the current response with a simpler control calculation.

<Third control example>
The third control example is obtained by improving the accuracy of the calculation of the current command correction unit 30 in the second control example. In order to use MPC, an accurate state equation model is required as shown in Equations 5 and 12. If there is an error between the electrical constants of the motor and the electrical constants inside the control device, control operation cannot be realized. Therefore, the current command correction unit 30 performs control calculations using a state equation model that treats errors in electrical constants as voltage disturbances. The current command correction unit 30 estimates the voltage disturbance using a disturbance observer that receives the current of the PMSM 80 and the terminal voltage.

A discrete value system model of the current control system of the PMSM 80 in consideration of voltage disturbance can be expressed by the following equation.

From Equation 19, the calculation of the current estimated value vector _{i_dquest} of Equation 12 can be expressed as the following equation when voltage disturbance is taken into consideration.

The current command value i _dqACR ^* is calculated by the current command correction unit 30 in the same manner as in the second embodiment, by replacing the calculation of the current estimated value vector i _dquest in Equation 12 with Equation 20. As a result, the current command correction unit 30 can accurately calculate the optimum current command value i _dqACR ^* even when there is an error in the electrical constants.

Next, a method for estimating voltage disturbance will be described.

For example, the current command correction unit 30 calculates the voltage disturbance estimated value v _dqdisest according to the following equation using a minimum order observer designed based on the state equation model of Equation 19.

The voltage command values v _d ^* and v _q ^* are used for the voltage v _dq (v _d and v _q ) in Equation 21. Alternatively, the three-phase voltages v _u , v _v , _{and v w} are detected using a voltage detection circuit, and the detected values of the three-phase voltages v _u , v _v , and v _w are coordinate-transformed using the position detection value θ _re . The obtained d- and q-axis voltage detection values may be used for the voltage v _dq in Equation (21).

Thus, according to the third control example, the current command correction unit 30 estimates the voltage disturbance based on the terminal voltage and the current of the PMSM 80, and the estimated value of the terminal voltage and the estimated value of the voltage disturbance Estimate the current of the PMSM 80 based on and. As a result, even if there is an error between the electrical constants of the PMSM 80 and the electrical constants inside the control device 100, the current control accuracy and the current response can be improved.

FIG. 4 is a diagram illustrating a hardware configuration of an arithmetic unit included in the control device; FIG. 4 shows a microcomputer 110, which is an example of an arithmetic device included in the control device 100. As shown in FIG. The microcomputer 110 includes a memory 121 , a CPU (Central Processing Unit) 122 , an AD (Analog to Digital) conversion section 123 , a PWM module 124 , a communication section 125 and a timer 126 . The CPU 122 is a processor that controls the control device 100 . The communication unit 125 communicates with a host controller outside the microcomputer 110 . The timer 126 counts timer values. The memory 121 stores programs and the like. A program in the memory 121 causes the CPU 122 to operate. The function of each control block in FIG. 1 is implemented by the CPU 122 operating according to a program stored in the memory 121 in a readable manner.

Each control block in FIG. 1 includes, for example, subtractors 16, 19a, 19b, mechanical angular velocity calculator 92, speed controller 17, current command calculator 18, current command corrector 30, current controllers 20a, 20b, voltage They are the coordinate converter 15 , the voltage limit calculator 22 , and the current coordinate converter 14 .

The function of each control block in FIG. 1 can be provided by a program that causes a computer to implement each function. Also, the function of each control block can be provided by a computer-readable recording medium recording the above program, or a computer program product such as the above program. Examples of recording media that can be used include flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, magnetic tapes, nonvolatile memory cards, and ROMs.

Although the control device for the AC motor has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications and improvements such as combination or replacement with part or all of other embodiments are possible within the scope of the present invention.

For example, in the above-described embodiment, the AC motor controlled by the control device is a PMSM, but the AC motor controlled by the control device may be an induction motor, a synchronous reluctance motor, or other AC motor.

11u u-phase current detector 11w w-phase current detector 12 DC voltage detection circuit 13 PWM circuit 14 current coordinate converter 15 voltage coordinate converter 16 subtractor 17 speed controller 18 current command calculator 19a, 19b subtractor 20a d axis Current controller 20b q-axis current controller 22 Voltage limit calculator 30 Current command corrector 50 Three-phase AC power supply 60 Rectifier circuit 70 Power converter 80 PMSM
90 position/velocity detector 91 position/velocity detection circuit 92 mechanical angular velocity calculator 100 controller 110 microcomputer

Claims (2)

A control device for controlling current and voltage supplied to an AC motor by a power converter,
a first current command unit that calculates a first current command value based on a torque command value and a speed detection value of the AC motor;
The magnitude of the terminal voltage of the AC motor becomes equal to or less than the voltage limit value equal to or less than the maximum output voltage of the power converter, and the deviation between the first current command value and the second current command value is minimized. a second current command unit that calculates the second current command value,
a terminal voltage control unit that controls the terminal voltage of the AC motor so that the current of the AC motor matches the second current command value;
The second current command unit,
estimating an estimated value of the current of the AC motor based on the estimated value of the terminal voltage of the AC motor;
Optimizing the angle of the estimated value of the terminal voltage that minimizes the deviation between the first current command value and the estimated value of the current when the magnitude of the estimated value of the terminal voltage is controlled to the voltage limit value. Calculate the value of
The voltage limit value is V _alim , the optimum value of the angle at time k+1 after current time k is δ _vaopt (k+1|k), and the optimum value of the terminal voltage at time k+1 after current time k is v _dqopt ( k+1|k), then
The optimum value of the terminal voltage is calculated according to the following equation 18 using the optimum value of the angle,

Using the optimum value of the terminal voltage derived according to Equation 18, the magnitude of the terminal voltage is controlled to the voltage limit value, and the angle of the terminal voltage is controlled to the optimum value of the angle. A control device for an AC motor , wherein an estimated current value is set as the second current command value . The second current command unit,
estimating a voltage disturbance based on the terminal voltage and current of the AC motor;
2. The control device according to claim 1 , wherein the current of said AC motor is estimated based on said terminal voltage estimated value and said voltage disturbance estimated value.

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