KR101726687B1

KR101726687B1 - Method of predicting driving-current value for alternative-current motor, and system for controlling alternative-current motor

Info

Publication number: KR101726687B1
Application number: KR1020120041151A
Authority: KR
Inventors: 김상민
Original assignee: 한화테크윈 주식회사
Priority date: 2012-04-19
Filing date: 2012-04-19
Publication date: 2017-04-13
Also published as: KR20130118170A

Abstract

A method for predicting a drive-current value of a next sampling period in a system for controlling an alternating-current motor in accordance with a sampling period is disclosed. The method includes a derivation step and a correction step. In the deriving step, the current prediction equation of the AC motor is used to derive the predicted drive-current value in the current sampling period. In the correction step, the predicted drive-current value derived in the current sampling period is corrected in accordance with the prediction error of the predicted drive-current value derived in the previous sampling period.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of predicting a driving current value of an AC motor and a control system of the AC motor,

The present invention relates to a method of predicting a drive-current value of an alternating-current motor and a control system of the alternating-current motor, and more particularly, to a method of predicting a drive-current value of a next sampling period in a system for controlling an alternating- And a control system of an alternating-current motor employing this method.

Permanent magnet synchronous motor (PMSM) is mainly used as a motor used for driving a wheel in a hybrid vehicle or an electric vehicle.

The control system of the AC motor controls the AC motor according to the sampling period. Here, for example, a PWM (Pulse Width Modulation) inverter included in the control system drives an AC motor according to a sampling period while predicting a drive-current value of a next sampling period.

The reason why the inverter for driving the motor must predict the driving-current value in the next sampling period will be described in detail as follows.

The inverter for driving the motor includes a switching unit for switching transistors such as IGBTs (Insulated Gate Bipolar Transistors), and a switching control unit for driving the switching unit.

As well known in the art, the switching control unit controls the switching transistors so that the dead-time as the simultaneous off time for preventing the upper and lower totempole transistors from being turned on at the same time, Dead-time is required.

Here, when the dead-time is fixedly used, the inverter for driving the motor eventually outputs a voltage lower than the command voltage, so that the drive voltage is distorted.

Therefore, to set an adaptive dead-time for each sampling period, the drive-current value of the next sampling period must be predicted. In particular, in order to accurately determine the current polarity of each phase, the drive-current value of the next sampling period should be accurately estimated.

In predicting the drive-current value at the next sampling period in the control system of the AC motor as described above, conventionally, the predicted drive-current value at the present sampling period is derived simply by using the current prediction equation of the AC motor.

However, due to the theoretical limitations of the current prediction equation itself, the error between the predicted drive-current value and the actual drive-current value is significant, resulting in poor adaptive dead-time setting accuracy.

U.S. Published Patent Application No. 2010-0148707 (Applicant: Hitachi Industrial Equipment System Co., Ltd., entitled Speed controller of magnetic motor)

Embodiments of the present invention provide a method for predicting a drive-current value of an AC motor that can overcome the theoretical limit of the current prediction equation itself, and a control system for an AC motor employing the method.

The method of the first aspect of the present invention includes a derivation step and a correction step in a method for predicting a drive-current value of a next sampling period in a system for controlling an AC motor according to a sampling period.

In the derivation step, the current predictive equation of the AC motor is used to derive the predicted drive-current value at the present sampling period.

In the correction step, the predicted drive-current value derived in the current sampling period is corrected according to the prediction error of the predicted drive-current value derived in the previous sampling period.

Also, in the correction step, the prediction error may be added to or subtracted from the predicted drive-current value derived in the current sampling period.

Also, in the correction step, the current prediction error to be applied in the current sampling period can be obtained by adjusting the previous prediction error applied in the previous sampling period.

In the correction step, if the actual drive-current value measured in the current sampling period is larger than the predicted drive-current value derived in the previous sampling period, a value proportional to the difference is added to the previous prediction error, Current value measured in the current sampling period is smaller than the predicted drive-current value derived in the previous sampling period, a value proportional to the difference is subtracted from the previous prediction error, .

Also, in the correction step, if the actual drive-current value measured in the current sampling period is equal to the predicted drive-current value derived in the previous sampling period, the previous prediction error can be used as the current prediction error.

The method of the first aspect of the present invention includes a step (a) to (d) in a method for predicting a drive-current value of a next sampling period in a system for controlling an alternating current motor in accordance with a sampling period.

In the step (a), the current predictive equation of the AC motor is used to derive a first predicted drive-current value.

In the step (b), a prediction error due to the difference between the predicted drive-current value derived in the previous sampling period and the actual drive-current value measured in the current sampling period is obtained.

In the step (c), the first predictive drive-current value is corrected according to the predictive error to obtain a second predictive drive current value.

In the step (d), the second predicted drive-current value is set as a final predicted drive-current value.

Also, in the step (c), the second predictive driving current value may be obtained by adding or subtracting the predictive error to the first predictive driving current value.

Also, in step (b), the current prediction error to be applied in the current sampling period can be obtained by adjusting the previous prediction error applied in the previous sampling period.

If the actual drive-current value measured in the current sampling period is larger than the predicted drive-current value derived in the previous sampling period in the step (b), a value proportional to the difference is added to the previous prediction error, If the actual drive-current value measured in the current sampling period is smaller than the predicted drive-current value derived in the previous sampling period, a value proportional to the difference is subtracted from the previous prediction error, Can be obtained.

In the step (b), if the actual drive-current value measured in the current sampling period is equal to the predicted drive-current value derived in the previous sampling period, the previous prediction error can be used as the current prediction error.

An apparatus according to another aspect of the present invention is a system for controlling an AC motor according to a sampling period while predicting a drive-current value of a next sampling period, the system comprising: Value. Then, the predicted drive-current value derived in the current sampling period is corrected according to the prediction error of the predicted drive-current value derived in the previous sampling period.

According to the method of predicting the drive-current value of the AC motor of the present invention and the control system of the AC motor employing this method, according to the prediction error of the predicted drive-current value derived in the previous sampling period, The predicted drive-current value derived from the drive-current value is corrected.

Therefore, the theoretical limit of the current prediction equation itself can be overcome by a closed loop method. That is, the error between the predicted drive-current value and the actual drive-current value is minimized, so that the accuracy of the adaptive dead-time setting can be improved.

1 is a block diagram showing a system in which a method of predicting a drive-current value of an AC motor according to embodiments of the present invention is employed.
2 is a diagram for explaining the configuration and operation of a PWM (Pulse Width Modulation) inverter of FIG.
3 is a waveform diagram showing three-phase currents flowing between the switching unit in the PWM inverter of FIG. 2 and the permanent magnet synchronous motor (PMSM).
4 is a flow chart illustrating a method of predicting a drive-current value of an alternating-current motor of an embodiment of the present invention to be applied to the system of FIG.
5 is a flowchart showing the detailed steps of step S43 of FIG.
6 is a timing chart for explaining the operation of the PWM inverter of FIG.
7 is a flowchart showing a method of predicting a drive-current value of an alternating-current motor in another embodiment of the present invention to be applied to the system of FIG.
8 is a measurement graph showing the waveforms of the drive-currents and the waveforms of the actual drive-currents predicted by the embodiment of FIG.

The following description and accompanying drawings are for understanding the operation according to the present invention, and parts that can be easily implemented by those skilled in the art can be omitted.

Furthermore, the specification and drawings are not intended to limit the present invention, and the scope of the present invention should be determined by the claims. The terms used in the present specification should be construed to mean the meanings and concepts consistent with the technical idea of the present invention in order to best express the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows a system in which a method of predicting a drive-current value of an alternating-current electric motor 18 of an embodiment of the present invention is employed. The permanent magnet synchronous motor (PMSM) 18 as the alternating-current motor of FIG. 1 is driven by an inverter, for example, a PWM (Pulse Width Modulation)

Referring to FIG. 1, an AC motor control system of an embodiment of the present invention controls a permanent magnet synchronous motor (PMSM) 18 according to a sampling period. Here, the PWM inverter 17 derives the predicted drive-current value in the current sampling period using the current prediction equation of the alternating-current motor. Further, the PWM inverter 17 corrects and uses the predicted drive-current value derived in the current sampling period according to the prediction error of the predicted drive-current value derived in the previous sampling period.

In general, the control system of the AC motor of the embodiment of FIG. 1 is configured to control the current command value (i _ds ^{r *} ) of the magnetic flux-axis (D-axis) ), the command current value (i _qs ^{r *)} in accordance with, the final flux in the motor driving inverter (17) - the axis (D- axis) reference voltage value (V ^* _dse) and the last rotating force-axis (Q- axis) reference voltages Value (V ^* _qse ). Here, the superscript * means to be related to the target values.

More specifically, the control system of the permanent magnet synchronous motor (PMSM) 18 of the embodiment of the present invention includes an inverter 17 for driving the motor, an actual current measurement unit 191, a coordinate conversion unit 192, A generating unit 13, a current adjusting unit 15, and an over-modulating unit 16.

The actual current measuring unit 191 measures the actual driving current values Ia, Ib and Ic flowing in each phase of the AC electric motor 18. [

The coordinate converter 192 converts the magnetic flux-axis (D-axis) drive current value (i ^m _dse ) of the AC motor from the actual three-phase drive current values Ia, Ib, Ic from the actual current measurement unit 191, And the rotational force-axis (Q-axis) driving current value (i ^m _qse ). Here, the superscript m means to relate to actual measured values.

Current command generating section 13 commands the rotational force (Te ^*) according to the magnetic flux-axis (D- axis) current command values (i _ds ^r ^*) and the rotating force-axis (Q- axis) current command values (i ^r _qs ^* ).

Between the axis (D- axis) driving current value (i ^m _dse) - current adjustment section 15, the current adjustment section (15), flux-axis (D- axis) current command values (i _ds ^{r *)} and the flux Axis (D-axis) according to the deviation between the command current value (i _qs ^{r *} ) and the rotational force-axis (Q-axis) driving current value (i ^m _qse ) Generates a command voltage value (V _ds ^{r **} ) and a primary rotational force-axis (Q-axis) command voltage value (V _qs ^{r **} ).

And a modulation unit 16, a primary magnetic flux from the current adjusting unit (15) axis (D- axis) reference voltage (V _ds ^r ^**) and the primary rotating force-axis (Q- axis) reference voltage value (V _qs ^{r **)} and the modulation (over-modulation) by limiting by the method, the final flux-axis (D- axis) reference voltage value (V ^* _dse) and the final rotational force-axis (Q- axis) reference voltage (V ^* _qse ).

As described above, the PWM inverter 17 derives the predicted drive-current value in the current sampling period using the current prediction equation of the AC motor. Further, the PWM inverter 17 corrects and uses the predicted drive-current value derived in the current sampling period according to the prediction error of the predicted drive-current value derived in the previous sampling period.

Hereinafter, driving-current predicting methods employed in the PWM inverter 17 will be described in detail with reference to FIGS. 2 to 8. FIG.

Fig. 2 is a diagram for explaining the configuration and operation of the PWM inverter 17 of Fig. 3 is a waveform diagram showing three-phase currents (ia, ib, ic) flowing between the switching units SW1 to SW6 and the permanent magnet synchronous motor (PMSM) 18 in the PWM inverter 17 of FIG. In Fig. 2, the same reference numerals as those in Fig. 1 denote objects having the same function. In Fig. 2, reference numeral Vdc denotes a DC voltage to be used in the switching units SW1 to SW6. In FIG. 3, reference symbol t denotes a time, + I denotes a positive maximum current value, and -I denotes a positive maximum current value.

2 and 3, the motor drive inverter 17 includes switching units SW1 to SW6 of switching transistors such as insulated gate bipolar transistors (IGBTs) and a switching control unit 201 for driving the switching units SW1 to SW6.

When the switching control unit 201 controls the switching units SW1 to SW6 to simultaneously turn off the upper transistors SW1 to SW3 and the lower transistors SW4 to SW6 ) Dead-time as time is needed.

Therefore, in order to accurately set an adaptive dead-time for each sampling period, the switching controller 201 sets the value of the flux-axis (D-axis) drive-current value i ^p _dse (k) The current value of each phase of the next sampling period should be accurately predicted by accurately predicting the driving current value and the rotational force-axis (Q-axis) driving-current value (i ^p _qse (k)).

For example, in the case of the C phase current ic in FIG. 3, in order to accurately determine the current polarity around the time t2 and t6, in the case of the B phase current ic in FIG. 3, t3 And the current polarity around the time point t8, and in the case of the A phase current (ia) in FIG. 3, the switching control unit 201 determines the current polarity around the time point t5 and the time point t9, (I ^p _dse (k)) and the torque-axis (Q-axis) drive-current value (i ^p _qse (k)) of the next sampling period do. Here, superscript p means to relate to predicted values. Also, (k) means the current sampling period which is the prediction-performing sampling period.

4 shows a method of predicting the drive-current value of an alternating-current electric motor 18 of an embodiment of the invention to be applied to the system of FIG. 5 is a flowchart showing the detailed steps of step S43 of FIG. In Fig. 5, the same reference numerals as those in Figs. 1 and 2 denote objects having the same function. 6 is a timing chart for explaining the operation of the PWM inverter 17 of FIG. In Fig. 6, reference character T _SW denotes a time between a current sampling point and a next switching point, and T _samp denotes a sampling period.

Referring to FIGS. 4 to 6, a method of predicting the drive-current value of the AC electric motor 18 according to an embodiment of the present invention will be described.

6) (step S41), the switching control section 201 uses the current estimation equation of the permanent-magnet synchronous motor (PMSM) 18 as an alternating-current electric motor A predicted drive-current value is derived in the current sampling period (step S42).

Step S42 will be described in detail as an example of an interior permanent magnet synchronous motor (PMSM) 18 as follows.

First, the magnetic flux-axis (D-axis) voltage equation of the permanent magnet synchronous motor (PMSM) 18 is expressed by Equation 1 below.

In Equation 1, v _dse are permanent - the voltage value, R _s is the stator resistance, magnetic flux is _dse i-axis (D- axis) driving-magnetic flux of magnet synchronous motor (PMSM, 18) axis (D -axis) driving - a current value, L _ds is the magnetic flux - the axis (D- axis) inductance, λ _qse the rotational force - the shaft (Q- axis) flux value, and ω _r indicates a driving rotation force, respectively.

Similarly, the torque-axis (Q-axis) voltage equation of the permanent magnet synchronous motor (PMSM) 18 is shown in Equation 2 below.

In Equation 2, v _qse a permanent-magnet synchronous rotating force of the electric motor (PMSM, 18) - the axis (Q- axis) driving-voltage value, R _s is the stator resistance, i is the rotational force _qse-axis (Q -axis) driving - a current value, L is _qs rotational force - the shaft (Q- axis) inductance, λ _dse is flux-axis (D- axis) flux value, and ω _r indicates a driving rotation force, respectively.

On the other hand, the rotational force-axis (Q-axis) magnetic flux value? _Qse in Equation (1) can be obtained by the following Equation (3).

In Equation (3), L _qs denotes a rotational force-axis (Q-axis) inductance and i _qse denotes a rotational force-axis (Q-axis) driving-current value.

Further, if the magnetic flux value due to the permanent-magnet is? _F , the magnetic flux-axis (D-axis) magnetic flux value? _Dse in Equation (2) can be obtained by the following expression (4).

On the other hand, at the middle point of the time T _SW between the present sampling time (t0 in Fig. 6) and the next switching time (for example, t7 in Fig. 6) The value (i ^m ) and the drive-current value (i ^p ) at the next sampling period (to to t4) act simultaneously.

Therefore, after Equation (3) is substituted into Equation (1), Equation (1) can be replaced with Equation (5) below in which the drive-current is discretized. Similarly, after Equation (4) is substituted into Equation (2), Equation (2) can be replaced with Equation (6) below in which the drive-current is discretized.

In the value of current, i ^p is the sampling period and then _dse (t4 ~ t8) - in the above Equation 5 and 6, i ^m _dse current sampling period (t0 ~ t4), the magnetic flux in-axis (D- axis) driving flux-axis (D- axis) driving - a current value, i ^m _qse current sampling period (t0 ~ t4), the rotational force of the up-axis (Q- axis) driving - a current value, and ^p i is the next sampling period _qse (Q-axis) drive-current value at the time t4 to t8.

In the equation (5), the flux-axis (D-axis) drive-voltage value _Vdse is expressed as a final flux-axis (D-axis) command voltage value V ^* _dse from the overmodulation section Can be replaced. (Q-axis) drive-voltage value V _qse is _substituted for the final rotational force-axis (Q-axis) command voltage value V ^* _qse from the overmodulation section 16 in _Equation (6) .

Therefore, the switching control section (201 in Fig. 2) in the PWM inverter (17 in Fig. 1) in the PWM inverter (17 in Fig. i ^p _dse , and the rotational force-axis (Q-axis) driving-current value i ^p _qse in the next sampling period (t4 to t8). That is, the equations (5) and (6) can be expressed by the equations (5) and (6), which are obtained by subtracting the flux-axis (D-axis) drive current value i ^p _{dse in the} next sampling period (t4 to t8) Q-axis) drive-current value i ^p _qse as variables. Therefore, by solving this simultaneous equations, predicted flux-axis (D-axis) drive-current value i ^p _dse and predicted torque-axis (Q-axis) drive-current value i ^p _qse can be obtained. That is, the predicted flux-axis (D-axis) driving current value i ^p _dse and the predicted rotational force-axis (Q-axis) driving current value i ^p _qse can be _obtained by the matrix equation of Equation .

In Equation 7, a to f are coefficients, V ^* _dse final flux-axis (D- axis) reference voltage, V ^* _qse final rotational force - the command voltage value axis (Q- axis), λ _f is the magnetic flux value by the permanent magnet, and _r is the drive torque.

In Equation (7), the coefficient a is obtained by the following Equation (8).

In Equation 8, R _s is the stator resistance, L is the magnetic flux _ds-axis (D- axis) inductance, and T _SW are, for the time (for example, between the present sampling point and a next switching point in time, t0 ~ t7 ).

Here, since the time T _SW between the present sampling time and the next switching time (for example, t0 to t7) has a very small value of 50 microseconds (μs) to 2000 microseconds (μs), L _ds / T _SW is much larger than the value of R _s / 2. Therefore, the term of R _s / 2 in Equation (8) can be removed. That is, Equation (8) can be replaced with Equation (9) below.

The coefficient b in Equation (7) is obtained by the following Equation (10).

In Equation (10), L _qs denotes a rotational force-axis (Q-axis) inductance, and _r denotes a driving rotational force.

The coefficient c in Equation (7) is obtained by the following Equation (11).

In Equation (11), L _ds denotes the flux-axis (D-axis) inductance, and _r denotes the drive torque.

The coefficient d in Equation (7) is obtained by the following Equation (12).

In the equation 12, R _s is the stator resistance, L is _qs rotational force - the shaft (Q- axis) inductance, and T _SW are, for the time (for example, between the present sampling point and a next switching point in time, t0 ~ t7 ).

Here, since the time T _SW between the present sampling time and the next switching time (for example, t0 to t7) has a very small value of 50 microseconds (μs) to 2000 microseconds (μs), _Lqs / T _SW is much larger than the value of R _s / 2. Therefore, the term of R _s / 2 in Equation (12) can be removed. That is, Equation (12) can be replaced with Equation (13) below.

The coefficient e in Equation (7) is obtained by the following Equation (14).

In Equation 14, L is the magnetic flux _ds-axis (D- axis) for the inductance, the T _SW (for example, t0 ~ t7) between the time of current sampling time and the next switching time, and R _s is the stator resistance Respectively.

Here, since the time T _SW between the present sampling time and the next switching time (for example, t0 to t7) has a very small value of 50 microseconds (μs) to 2000 microseconds (μs), L _ds / T _SW is much larger than the value of R _s / 2. Therefore, the term of R _s / 2 in Equation (14) can be removed. That is, Equation (14) can be replaced with Equation (15) below.

The coefficient f in Equation (7) is obtained by the following Equation (16).

In Equation 16, L is the rotational force _qs-axis (Q- axis) of the inductance, T is _SW (for example, t0 ~ t7) between the time of current sampling time and the next switching time, and R _s is the stator resistance Respectively.

Here, since the time T _SW between the present sampling time and the next switching time (for example, t0 to t7) has a very small value of 50 microseconds (μs) to 2000 microseconds (μs), _Lqs / T _SW is much larger than the value of R _s / 2. Therefore, the term of R _s / 2 in Equation (16) can be removed. That is, Equation (16) can be replaced with Equation (17) below.

Therefore, by substituting the above Equations 9, 10, 11, 13, 15, and 17 into Equation 7, the following Equation 18 can be obtained.

6) (step S41), the switching control section 201 switches the current estimation equation of the permanent magnet synchronous motor (PMSM) 18 as an alternating-current electric motor (18) is used to derive the predicted drive-current value at the current sampling period (step S42).

As described above, when the predictive drive-current value is derived using only the current predictive equation such as Equation (18), due to the theoretical limit of the current predictive equation itself, the predicted drive-current value and the actual drive- Can be considerably large. Thus, the accuracy of the adaptive dead-time setting may be reduced.

Accordingly, in step S43 of FIG. 4, the switching controller 201 corrects the predicted drive-current value derived in the current sampling period according to the prediction error of the predicted drive-current value derived in the previous sampling period.

The above steps S41 to S43 are repeatedly performed until the end signal is generated (step S44).

The correction step S43 will be described in detail with reference to FIG. 5 as follows.

In the correction step S43, the current prediction error D, K is _basically added or subtracted to the predicted drive-current value i ^p _dse , i ^p _qse derived in the current sampling period (step S55).

For example, if the number of the current sampling period is k, the flux-axis (D-axis) prediction error in the current sampling period is D (k), the rotational- the Q (k), the magnetic flux of the current sampling cycle (k) - the axis (D- axis) prediction drive-rotation force from the value of current i _dse ^p (k), and the current sampling cycle (k) - the axis (Q- _Assuming that the predicted driving-current value is i ^p _qse (k), the steps S42 and S43 of FIG. 4 can be performed simultaneously by the following equation (19).

That is, according to Equation (19), the prediction errors D (k) and Q (k) are added or subtracted from the predicted drive-current values derived in the current sampling period (k)

Here, the current prediction errors D (k) and Q (k) to be applied in the current sampling period k are the previous prediction errors D (k-1) and Q (k-1) ) Is adjusted. The steps S51 to S54 required before the step S55 of FIG. 5 will be described below.

In step S51, the actual drive-current values i ^m _dse (k) and i ^m _qse (k) measured in the current sampling period k are multiplied by the predicted drive-current values i ^p _dse (k-1) and i ^p _qse (k-1).

More specifically, the magnetic flux-axis (D-axis) actual drive-current value i ^m _dse (k) measured at the current sampling period (k) - axis) predicted drive-current value i ^p _dse (k-1). Also, the rotational force-axis (Q-axis) actual driving-current value i ^m _qse (k) _{measured at the} current sampling period (k) Is compared with the predicted drive-current value i ^p _qse (k-1).

As a result of the comparison in the step S51, it is determined that the actual drive-current values i ^m _dse (k) and i ^m _qse (k) measured in the current sampling period (k) respectively added to the current value ^{_{i p d se (k-1}} ), i p qse (k-1) is greater than, the value proportional to the difference between the previous prediction error d (k-1), Q (k-1) As the The current prediction errors D (k) and Q (k) are obtained (step S52).

The above-mentioned step S52 will be described in more detail. The magnetic flux-axis (D-axis) actual drive-current value i ^m _dse (k) measured in the current sampling period (k) (D-axis) predictive drive-current value i ^p _dse (k-1), a value proportional to the difference is added to the magnetic flux-axis (D- The flux-axis (D-axis) current prediction error D (k) is obtained. Similarly, the rotational force-axis (Q-axis) actual driving-current value i ^m _qse (k) measured at the current sampling period (k) Axis Q (k-1) by adding a value proportional to the difference to the predicted drive-current value i ^p _qse (k-1) - axis) The current prediction error Q (k) is found.

As a result of the comparison in the step S51, it is determined that the actual drive-current values i ^m _dse (k) and i ^m _qse (k) measured in the current sampling period (k) current value ^{_{i p d se (k-1}} ), i p qse (k-1) than Yabe, a value of each of the subtraction before the prediction error d (k-1), Q (k-1) is proportional to the difference The current prediction errors D (k) and Q (k) are obtained (step S53).

The step S53 will be described in more detail. The magnetic flux-axis (D-axis) actual drive-current value i ^m _dse (k) measured in the current sampling period k is calculated from the magnetic flux (D-axis) predictive drive-current value i ^p _dse (k-1), a value proportional to the difference is subtracted from the magnetic flux-axis (D- (D-axis) current prediction error D (k) is obtained. Similarly, the rotational force-axis (Q-axis) actual driving-current value i ^m _qse (k) measured at the current sampling period (k) ) prediction driving-current value i ^p is less than _qse (k-1), is a value proportional to the difference between the rotational force-axis (Q- axis) by subtracting As previously prediction error Q (k-1) rotating force-axis ( Q-axis) The current prediction error Q (k) is obtained.

As a result of the comparison in the step S51, it is determined that the actual drive-current values i ^m _dse (k) and i ^m _qse (k) measured in the current sampling period (k) current value ^{_{i p d se (k-1}} ), i p qse (k-1) and equal to, the previous prediction error D (k-1), Q (k-1) , the current prediction error D (k), Q ( k) (step S54).

(D-axis) actual drive-current value i ^m _dse (k) measured in the current sampling period (k) is the magnetic flux _density (D-axis) predictive drive-current value i ^p _dse (k-1), the magnetic flux-axis (D- Is set as a prediction error D (k). Similarly, the rotational force-axis (Q-axis) actual driving-current value i ^m _qse (k) measured at the current sampling period (k) ) prediction driving-current value i ^p _qse (k-1) and equal, the rotational force-axis (Q- axis) before prediction error Q (k-1) a rotating force-axis (Q- axis) current prediction error Q (k) .

In the case of this embodiment, the steps S51 to S54 may be performed simultaneously by the following Equation (20). That is, the current predicted error D (k) and the rotational force-axis (Q-axis) current predictive error Q (k) in the equation (19) can be obtained by the following equation have.

In Equation 20, T _samp indicates a sampling period (see FIG. 6). In addition, g11 and g22 indicate correction coefficients corresponding to feedback of the current error.

Fig. 7 shows a method of predicting the drive-current value of an alternating-current motor of another embodiment of the present invention to be applied to the system of Fig. Referring to FIGS. 2 and 7, a method of predicting the drive-current value of the alternating-current motor 18 according to another embodiment of the present invention will be described.

6) (step S71), the switching control section 201 uses the current estimation equation of the permanent magnet synchronous motor (PMSM) 18 as an alternating-current electric motor The first predicted drive-current value is derived at the current sampling period (k) (step S72).

The details of the step S72 are as described in detail with reference to Equations 1 to 18 above. That is, the first predicted drive-current value is derived according to Equation (18).

Next, the switching control unit 201 compares the predicted drive current values i ^p _dse (k-1) and i ^p _qse (k-1) and the current sampling period k that were derived in the previous sampling period (k- (K), Q (k) based on the difference between the actual drive-current values i ^m _dse (k) and i ^m _qse (k) _{measured in} step S73. The details of this step S73 are as described in detail with reference to FIG. 5 and the above-described equation (20).

To summarize, the present prediction errors D (k) and Q (k) to be applied in the current sampling period (k) are calculated by using the previous prediction errors D (k-1) and Q (k- 2) is adjusted.

More specifically, the actual drive-current values i ^m _dse (k) and i ^m _qse (k) measured in the current sampling period (k) are _{compared with} the predicted drive current values i ^{_{p dse (k-1),}} i p qse (k-1) is greater than, the previous prediction error is a value proportional to the difference D (k-1), the current prediction error by As each added to the Q (k-1) D (k) and Q (k) are obtained (see step S52 in FIG. 5).

Current drive current values i ^m _dse (k) and i ^m _qse (k) measured in the current sampling period (k) are _{compared with} predicted drive current values i ^p _dse (k) k-1), the current prediction error by As is less than ^{_{i p qse (k-1)}} , is a value proportional to the difference between each of the subtraction before the prediction error D (k-1), Q (k-1) D ( k) and Q (k) are obtained (see step S53 in Fig. 5).

Current drive current values i ^m _dse (k) and i ^m _qse (k) measured in the current sampling period (k) are _{compared with} predicted drive current values i ^p _dse (k) equal to ^{_{k-1), i p qse}} (k-1) and, before the prediction error D (k-1), Q (k-1) is set as the current prediction error D (k), Q (k ) ( Fig. 5, step S54).

Next, the switching controller 201 corrects the first predictive drive-current value according to the obtained predictive errors D (k) and Q (k) to obtain a second predictive drive current value i ^p _dse (k), i ^p _qse (k) is obtained (step S74). That is, the second predicted drive-current values i ^p _dse (k) and i ^p _qse (k) are calculated by adding or subtracting the predictive errors D (k) and Q It becomes. The details of this step S74 are as described in detail with reference to the above-mentioned equation (19).

Then, the switching control unit 201 sets and uses the obtained second predicted drive-current values i ^p _dse (k) and i ^p _qse (k) as the final predicted drive-current values (step S75).

The steps S71 to S75 are repeatedly performed until a termination signal is generated (step S76).

8 is a measurement graph showing the waveforms of the drive-currents and the waveforms of the actual drive-currents predicted by the embodiment of FIG. 8, waveforms with stepped shapes are waveforms of predicted three-phase drive-currents, and waveforms with no stepped shape are waveforms of actual three-phase drive-currents measured (ia, ib, ic Reference). Here, the predicted waveforms of the three-phase drive-currents are the result of the coordinate-transformed results of the predicted drive-current values i ^p _dse (k) and i ^p _qse (k) to be.

As shown in FIG. 8, the waveforms of the actual three-phase drive-currents have been confirmed to pass through the center of the waveforms of the predicted three-phase drive-currents. That is, it can be confirmed that the predicted drive-current values according to the present embodiments are almost the same as the actual drive-current values.

As described above, according to the method of predicting the drive-current value of the AC motor according to the embodiments of the present invention and the control system of the AC motor employing this method, the predicted drive- Based on the prediction error, the predicted drive-current value derived in the current sampling period is corrected.

The present invention has been described above with reference to preferred embodiments. It will be understood by those skilled in the art that the present invention may be embodied in various other forms without departing from the spirit or essential characteristics thereof.

Therefore, the above-described embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and the inventions claimed by the claims and the inventions equivalent to the claimed invention are to be construed as being included in the present invention.

It can be used not only for AC motors but also for DC motors in which it is necessary to accurately predict drive-current values.

13: current command generator, 15: current controller,
16: Over modulation section,
17: PWM (Pulse Width Modulation) Inverter,
18: permanent-magnet synchronous motor (PMSM), 191: actual current measuring part,
192: Coordinate transformation unit, 201: Switching control unit,
SW1 to SW6: switching parts.

Claims

A method for predicting a drive-current value of a next sampling period in a system for controlling an AC motor according to a sampling period,
Deriving a predicted drive-current value at a current sampling period using the current prediction equation of the AC motor; And
A correction step of correcting the predicted drive-current value derived in the current sampling period according to the prediction error of the predicted drive-current value derived in the previous sampling period,
In the correction step,
The prediction drive-current value in the next sampling period is obtained by adding or subtracting the prediction error to the predicted drive-current value derived in the current sampling period,
The current prediction error to be applied in the current sampling period is obtained by adjusting the previous prediction error applied in the previous sampling period,
If the actual drive-current value measured in the current sampling period is larger than the predicted drive-current value derived in the previous sampling period, a value proportional to the difference is added to the previous prediction error,
Current value measured in the current sampling period is smaller than a predicted drive-current value derived in the previous sampling period, a value proportional to the difference is subtracted from the previous prediction error to obtain a current prediction error. Of the drive-current value.

delete

A method for predicting a drive-current value of a next sampling period in a system for controlling an AC motor according to a sampling period,
(a) deriving a first predicted drive-current value using a current prediction equation of the AC motor;
(b) obtaining a prediction error due to a difference between a predicted drive-current value derived in a previous sampling period and an actual drive-current value measured in a current sampling period;
(c) obtaining a second predicted driving current value by correcting the first predicted driving current value according to the prediction error; And
(d) setting the second predicted drive-current value as a final predicted drive-current value,
In the step (c)
The second predictive drive-current value is obtained by adding or subtracting the predictive error to the first predictive drive-current value,
In the step (b)
The current prediction error to be applied in the current sampling period is obtained by adjusting the previous prediction error applied in the previous sampling period,
If the actual drive-current value measured in the current sampling period is larger than the predicted drive-current value derived in the previous sampling period, a value proportional to the difference is added to the previous prediction error,
Current value measured in the current sampling period is smaller than a predicted drive-current value derived in the previous sampling period, a value proportional to the difference is subtracted from the previous prediction error to obtain a current prediction error. Of the drive-current value.

delete

A system for controlling an AC motor according to a sampling period while predicting a drive-current value of a next sampling period,
Deriving a predicted drive-current value at a current sampling period using the current prediction equation of the AC motor,
Correcting the predicted drive-current value derived in the current sampling period according to the prediction error of the predicted drive-current value derived in the previous sampling period,
The prediction drive-current value in the next sampling period is obtained by adding or subtracting the prediction error to the predicted drive-current value derived in the current sampling period,
The current prediction error to be applied in the current sampling period is obtained by adjusting the previous prediction error applied in the previous sampling period,
If the actual drive-current value measured in the current sampling period is larger than the predicted drive-current value derived in the previous sampling period, a value proportional to the difference is added to the previous prediction error,
Current value measured in the current sampling period is smaller than a predicted drive-current value derived in the previous sampling period, a value proportional to the difference is subtracted from the previous prediction error to obtain a current prediction error. Of the control system.