WO2012029715A1

WO2012029715A1 - Electric motor drive device

Info

Publication number: WO2012029715A1
Application number: PCT/JP2011/069457
Authority: WO
Inventors: 健太塚越; 孝英小澤; 正和駒井; 希美畑林
Original assignee: 株式会社荏原製作所
Priority date: 2010-08-30
Filing date: 2011-08-29
Publication date: 2012-03-08
Also published as: JP2012050285A; JP5595835B2

Abstract

A vector control unit (11) is provided with a torque voltage control unit (21) for determining a torque voltage command value on the basis of the deviation between the torque current command value and the torque current, a magnetizing voltage control unit (22) for determining the magnetizing voltage command value on the basis of the deviation of the magnetizing current command value and the magnetizing current, a target magnetizing current determination unit (26) for determining a magnetizing current command value on the basis of the deviation between the output voltage of an inverter (10) and the target output voltage, and a target output voltage determination unit (27) for determining the target output voltage. The target output voltage determination unit (27) stores a V/ω pattern showing the relation between target output voltage and angular velocity, and determines the target output voltage from the angular velocity in accordance with said V/ω pattern.

Description

Electric motor drive

The present invention relates to a drive device that drives an electric motor such as a synchronous motor or an induction motor, and more particularly to a drive device that performs vector control based on an output current of an inverter.

Conventionally used motor control methods include V / F control that keeps the motor flux constant by outputting a voltage corresponding to the command frequency, and the inverter output current is decomposed into an excitation current and a torque current. In addition, vector control for controlling the excitation voltage and the torque voltage so that a motor current corresponding to the load can flow can be used.

V / F control does not require high-speed computation, and the motor can be controlled with a simple configuration. However, in this V / F control, since feedback information is scarce, high-efficiency control that matches the characteristics of individual motors cannot be expected. Moreover, since the position of the motor rotor is not detected, the motor rotor may step out in the case of a synchronous machine.

On the other hand, there is a sensorless vector control as a control method capable of preventing the synchronous machine from stepping out and controlling the synchronous machine without using an expensive position sensor. A control block of this sensorless vector control is shown in FIG. The output current of the inverter 110 is detected by the current detector 112, and the detected three-phase current is converted into a two-phase current Id on the rotating coordinate system by the 3 / 2-phase converting unit 117 and the stationary / rotating coordinate converting unit 118. , Iq, and then input to the magnetization voltage control unit 122 and the torque voltage control unit 121. The magnetization voltage control unit 122 obtains the magnetization voltage command value Vd * such that the deviation between the magnetization current Id and the magnetization current command value Id * is 0 by PI calculation. Torque voltage control unit 121 obtains a torque voltage command value Vq * by PI calculation such that the deviation between torque current Iq and torque current command value Iq * is zero.

The target torque current determination unit 124 performs the PI calculation so that the deviation between the angular velocity command value ω * input from the outside and the current angular velocity ω becomes zero, and determines the torque current command value Iq *. The current angular velocity ω is obtained by the axis error estimator 129 and the differentiator 132 based on the voltage command values Vd *, Vq * and the feedback currents Id, Iq. The magnetizing current command value Id * is an ideal magnetizing current calculated using a motor model. The voltage command values Vd * and Vq * are converted to a three-phase voltage command value on the fixed coordinate system via the rotation / stationary coordinate conversion unit 135 and the 2/3 phase conversion unit 136 and then sent to the inverter 110.

The sensorless vector control shown in FIG. 1 is a control method for estimating the position of the rotor from the fed back motor current without using a position sensor. Since this control method performs optimal control corresponding to the load state based on the motor model, the efficiency of the motor can be maximized.

However, in the sensorless vector control, it is necessary to calculate the voltage command value from the fed back motor current at a high speed cycle. Further, since a motor model is required, it is necessary to use many motor constants such as winding resistance and reactance of the motor M for control. In order to grasp an accurate motor constant, it takes time and it is necessary to consider the temperature dependence of the winding resistance and reactance.

JP 2000-341999 A

The present invention has been made in view of the above-described conventional problems, and is required for conventional sensorless vector control while realizing high efficiency and optimum torque control that cannot be achieved by conventional V / F control alone. Another object of the present invention is to provide an electric motor drive device that can drive a motor without using motor constants such as winding resistance and reactance of the motor.

In order to achieve the above-described object, one embodiment of the present invention includes an inverter, a current detector that detects an output current of the inverter, and an output current detected by the current detector is converted into a torque current and a magnetizing current. And a vector controller that controls the torque current and the magnetizing current, wherein the vector controller converts the three-phase current detected by the current detector into a two-phase current. A 3/2 phase converter, and a static / rotary coordinate converter for converting the two-phase current on the stationary coordinate system converted by the 3/2 phase converter into a torque current and a magnetizing current on the rotating coordinate system; A torque voltage control unit that determines a torque voltage command value based on a deviation between the torque current command value and the torque current; and a magnetization voltage command value that is determined based on a deviation between the magnetization current command value and the magnetization current A magnetization voltage control unit; a rotation / stationary coordinate conversion unit that converts the torque voltage command value and the magnetization voltage command value on a rotating coordinate system into a torque voltage command value and a magnetization voltage command value on a stationary coordinate system; A 2 / 3-phase converter that converts the torque voltage command value and the magnetization voltage command value converted by the rotation / stationary coordinate converter to a three-phase voltage command value; the torque voltage controller; and the magnetization voltage controller A torque calculating unit that calculates an angular velocity of the rotor of the electric motor from the torque voltage command value and the magnetized voltage command value obtained by the step, and determining the torque current command value based on a deviation between the angular velocity and the angular velocity command value. A target torque current determining unit; a target magnetizing current determining unit that determines the magnetization current command value based on a deviation between an output voltage of the inverter and a target output voltage; and the target A target output voltage determination unit that determines a force voltage, and the target output voltage determination unit stores a V / ω pattern indicating a relationship between the target output voltage and the angular velocity, and according to the V / ω pattern The target output voltage is determined from the angular velocity.

In a preferred aspect of the present invention, the relationship between the target output voltage and the angular velocity indicated by the V / ω pattern is a relationship in which a ratio between the target output voltage and the angular velocity is constant.
In a preferred aspect of the present invention, the relationship between the target output voltage and the angular velocity indicated by the V / ω pattern is a relationship in which a ratio between the target output voltage and the angular velocity is represented by a secondary reduction curve. It is characterized by.
In a preferred aspect of the present invention, the target output voltage determination unit stores a plurality of V / ω patterns indicating a relationship between the target output voltage and the angular velocity, and is selected from the plurality of V / ω patterns. The target output voltage is determined from the angular velocity according to one V / ω pattern.

In a preferred aspect of the present invention, the relationship between the target output voltage indicated by the V / ω pattern and the angular velocity is such that after the target output voltage reaches the rated voltage of the motor, the target output voltage is It is characterized in that the relationship is kept constant with voltage.
In a preferred aspect of the present invention, the relationship between the target output voltage indicated by the V / ω pattern and the angular velocity is such that after the target output voltage reaches the rated output voltage of the inverter, the target output voltage is It is characterized in that the relationship is maintained constant at the rated output voltage.
In a preferred aspect of the present invention, when the angular velocity is equal to or less than a predetermined value, the target magnetization current determination unit outputs a lower limit value stored in the target magnetization current determination unit as the magnetization current command value. Features.
In a preferred aspect of the present invention, the magnetization voltage control unit outputs a lower limit value stored in the magnetization voltage control unit as the magnetization voltage command value when the angular velocity is equal to or less than a predetermined value. To do.

According to the present invention, determining the target output voltage requires only the rated voltage and rated frequency of the motor, and does not require motor constants such as the winding resistance and reactance of the motor. Furthermore, since the target output voltage is determined according to the V / ω pattern stored in the target output voltage determination unit, complicated calculation is not necessary. Therefore, stable driving of the electric motor can be realized.

It is a figure which shows the control block of the conventional sensorless vector control. It is a block diagram which shows the drive device which concerns on one Embodiment of this invention. It is a schematic diagram which shows the inverter shown in FIG. 2 in detail. It is a figure which shows the equivalent circuit of a synchronous motor. It is a figure which shows the equivalent circuit of a synchronous motor. It is the figure which represented the output current Iout and the output voltage Vout of the inverter with a vector. It is a figure which shows the control block which determines the target value of torque current. It is a figure which shows the relationship between the current vector on a dq axis | shaft and the current vector on an MT axis | shaft in a state with the best operating efficiency. It is the figure which represented Vout corresponding to Iout shown in FIG. 7A by a vector. It is a figure which shows the relationship of the electric current vector Iout in the case of Id <0, Iq, It, Im. It is a figure which shows the voltage vector Vout corresponding to the current vector Iout shown to FIG. 8A. It is a figure which shows the relationship between the current vectors Iout, Iq, It, Im when Id> 0. It is a figure which shows the voltage vector Vout corresponding to the current vector Iout shown to FIG. 9A. It is a figure which shows the block of control which determines the magnetizing current command value Im * which is the target value of the magnetizing current Im. It is a figure which shows the example by which Vout-d / (omega) is represented by a linear function. It is a figure which shows the example by which Vout-d / (omega) is represented by a secondary reduction curve. It is a figure which shows the example which boosts the magnetization current command value in a low frequency area | region. It is a figure which shows the example of compensation of a motor efficiency fall when the torque meter is provided in the load connected to the motor. It is a graph which shows the relationship between a torque signal and a bias voltage. It is a figure which shows the example of compensation of a motor efficiency fall in case the load connected to a motor is a pump, and the piping connected with a pump is equipped with the flowmeter. It is a graph which shows the relationship between a flow volume and a bias voltage. It is a figure which shows the example which compensates for the efficiency of the whole system including an inverter. It is a graph which shows the relationship between the output current of an inverter, and a bias voltage. It is a figure which shows the modification of the drive device which concerns on embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 is a block diagram showing a driving apparatus according to an embodiment of the present invention. This drive device is an inverter device (power conversion device) for driving the motor M, and includes a plurality of elements including the inverter 10 and the vector control unit 11 as shown in FIG. That is, the drive device includes an inverter 10 that generates a voltage supplied to the motor M, a vector control unit 11 that determines a voltage command value to the inverter 10, and a current that detects a current supplied from the inverter 10 to the motor M. And a detector (ammeter) 12.

FIG. 3 is a schematic diagram showing in detail the inverter 10 shown in FIG. The inverter 10 is basically composed of an inverter circuit 10A as a power conversion unit and a gate driver 10B that drives the inverter circuit 10A. In the inverter circuit 10A, three sets of upper and lower arms are arranged in parallel between a positive electrode line P and a negative electrode line N to which DC power (for example, DC power from a DC power source obtained by full-wave rectification of a commercial power source) is supplied. An antiparallel circuit composed of switching elements (IGBT) S1 to S6 and diodes D1 to D6 is incorporated in the upper and lower arms of each phase. Symbol C1 is a capacitor. These switching elements S1 to S6, diodes D1 to D6, and capacitor C1 constitute an inverter circuit 10A. The gate driver 10B drives the switching elements S1 to S6 of the inverter circuit 10A so that a voltage according to the voltage command value sent from the vector control unit 11 is generated.

The current detector 12 measures the three-phase currents Iu, Iv, Iw supplied from the inverter 10 to the motor M. The measured value is amplified by the gain adjuster 15 and then input to the vector control unit 11. The gain adjuster 15 can be omitted. The three-phase currents Iu, Iv, and Iw may be measured by measuring an arbitrary two-phase current and obtaining the remaining current from the equation Iu + Iv + Iw = 0. The vector control unit 11 generates three-phase voltage command values Vu *, Vv *, Vw * based on the three-phase currents Iu, Iv, Iw and the angular velocity command values input from the outside. Further, the vector control unit 11 generates a PWM signal corresponding to these three-phase voltage command values Vu *, Vv *, Vw *, and sends this PWM signal to the gate driver 10B. The gate driver 10B generates a gate drive PWM signal based on the PWM signal corresponding to the three-phase voltage command values Vu *, Vv *, Vw *, and the six switching elements S1 to S6 are based on the gate drive PWM signal. Are operated (on, off). Thus, the inverter 10 generates a voltage based on the three-phase voltage command value from the vector control unit 11 and applies it to the motor M.

The basic operation of the vector control unit 11 is as follows. The three-phase output current of the inverter 10 detected by the current detector 12 is converted into a two-phase current (vector) on the rotating coordinate system. Here, when one axis of the rotating coordinate system is made coincident with the direction of the primary linkage magnetic flux, the other axis is orthogonal to the primary linkage flux. Therefore, the torque of the motor M can be controlled by controlling the current vector on the axis orthogonal to the primary linkage flux. That is, PI control is performed so that there is no deviation between the converted two-phase current and each target value, and a two-phase voltage command value is obtained. The obtained two-phase voltage command values on the rotating coordinate system are converted into three-phase voltage command values on the stationary coordinate system. Then, a PWM signal corresponding to the voltage command value of each phase is generated, and this PWM signal is sent to the gate driver 10B of the inverter 10. The vector control unit 11 can be configured by a CPU (Central Processing Unit) or a dedicated processing device.

Next, the vector control unit 11 will be described in detail with reference to FIG. The three-phase currents Iu, Iv, Iw detected by the current detector 12 are sent to the 3 / 2-phase conversion unit 17, where the three-phase currents Iu, Iv, Iw on the stationary coordinate system are Converted to phase current. The two-phase current on the stationary coordinate system is sent to the stationary / rotational coordinate converter 18 where it is converted into a two-phase current on the rotational coordinate system, that is, a magnetizing current Im and a torque current It based on the phase θ.

The torque current It and the magnetizing current Im are sent to the torque voltage control unit 21 and the magnetizing voltage control unit 22, respectively. A torque current command value It * is input from the target torque current determination unit 24 to the torque voltage control unit 21. Then, the torque voltage control unit 21 performs the PI calculation so that the deviation between the torque current command value It * and the torque current It becomes zero, and obtains the torque voltage command value Vt *. The target torque current determination unit 24 is a speed control unit, and a torque current command value such that the deviation between the angular velocity command value ω * input from the outside of the vector control unit 11 and the current angular velocity ω of the motor M becomes zero. It * is obtained by PI calculation.

The magnetizing voltage control unit 22 receives the magnetizing current command value Im * from the target magnetizing current determining unit 26. The magnetization voltage control unit 22 performs a PI calculation so that the deviation between the magnetization current command value Im * and the magnetization current Im becomes 0, and obtains the magnetization voltage command value Vm *. The target magnetizing current determining unit 26 sets the magnetizing current command value Im so that the deviation between the target output voltage Vout-d sent from the target output voltage determining unit 27 (detailed later) and the current output voltage V becomes zero. * Is obtained by PI calculation.

The output voltage V of the inverter 10 is obtained by the output voltage calculation unit 30 from the torque voltage command value Vt * and the magnetizing voltage command value Vm *. Further, the torque voltage command value Vt * and the magnetizing voltage command value Vm * are also sent to the speed calculation unit 31, where the current angular speed ω of the rotor is obtained. The angular velocity ω is input to the target torque current determination unit 24, the target output voltage determination unit 27, and the integrator 33. The integrator 33 integrates the angular velocity ω to obtain the rotor phase θ. This phase θ is input to the stationary / rotational coordinate converter 18 and the rotational / static coordinate converter 35.

The magnetization voltage command value Vm * and the torque voltage command value Vt * are input to the rotation / stationary coordinate converter 35, where the magnetization voltage command value Vm * and the torque voltage command value Vt * on the rotation coordinate system have the phase θ Is converted into a torque voltage command value and a magnetization voltage command value on the stationary coordinate system. Further, the 2/3 phase converter 36 converts the torque voltage command value and the magnetization voltage command value on the stationary coordinate system into voltage command values Vu *, Vv *, Vw * for three phases (u phase, v phase, w phase). Is converted to As described above, the inverter 10 generates a voltage according to the voltage command values Vu *, Vv *, and Vw *.

Here, the case where the vector control unit 11 controls the permanent magnet type synchronous motor will be described.
In the dq rotating coordinate system, assuming that the direction of the magnetic flux by the permanent magnet of the rotor is the d axis and the axis orthogonal to the d axis is the q axis, the equivalent circuit of the synchronous motor is as shown in FIGS. 4A and 4B. 4A and 4B, R represents winding resistance, Ld represents inductance in the d-axis direction, Lq represents inductance in the q-axis direction, ω represents angular velocity, and E represents induced voltage.

4A shows an equivalent circuit when the current Id flows in the direction of the d-axis, and FIG. 4B shows an equivalent circuit when the current Iq flows in the direction of the q-axis. 4A and 4B, the voltage equation is expressed as follows.
Vd = Id · R + pLdId−ωLqIq (1)
Vq = Iq · R + pLqIq + ωLdId + E (2)
Here, p represents time differentiation (d / dt). The symbol j shown in FIGS. 4A and 4B represents an imaginary unit. When the interference components jωLqIq and jωLdId are represented on the dq axis (motor shaft), the direction of the vector is converted and the symbol j can be obtained. In the equations (1) and (2), the induced voltage E is the product of the angular velocity ω and the interlinkage magnetic flux ψ by the permanent magnet.

Here, since there is an inductance component (L), a phase lag occurs in the output voltage Vout with respect to the output current Iout of the inverter 10. FIG. 5 is a diagram showing the output current Iout and the output voltage Vout of the inverter 10 as vectors. In FIG. 5, an axis that matches the phase of the output voltage Vout-i when the motor is in an ideal control state is defined as a T axis, and an axis perpendicular to the T axis is defined as an M axis. A phase difference β exists between the MT axis and the dq axis. In this embodiment, motor vector control is performed using the voltage Vt and current It on the T-axis and the voltage Vm and current Im on the M-axis.

Since the MT axis is an axis that controls the inverter 10, it is referred to as an inverter axis in this specification. In order to grasp the phase difference β, Ψ, Ld, Lq, etc. are required, and therefore detailed motor constants are required. In this embodiment, it is assumed that It and Im are not required even if there are no such detailed motor constants. A method that can be controlled is adopted.

In this embodiment, the T-axis is used as a reference axis, the voltage Vt is applied to the T-axis, the voltage Vm is applied to the M-axis, and the output current Iout is controlled to coincide with the q-axis. By performing such control, even if the phase difference β is unknown, the output current Iout can be made to coincide with the q axis, so that the constant of the motor M is not required.

FIG. 6 shows a control block for determining the target value of the torque current It. The target value of the torque current, that is, the torque current command value It * is generated by the target torque current determination unit 24. The target torque current determination unit 24 receives the angular velocity command value ω * and the current angular velocity ω, and the target torque current determination unit 24 sets the torque current command for setting the deviation between the two values ω * and ω to zero. The value It * is determined. The angular velocity command value ω * is a desired angular velocity required for the motor M, and is input to the target torque current determination unit 24 from the outside of the vector control unit 11. On the other hand, the angular velocity ω is given by the velocity calculation unit 31. The speed calculation unit 31 obtains an estimated angular velocity by processing signals of the voltage command values Vm * and Vt * on the MT axis obtained as a result of vector control, and uses the obtained estimated angular velocity as the current angular velocity ω. Is done. The speed calculation unit 31 is not particularly limited as long as it can calculate the angular speed ω based on the torque voltage command value Vt * and the magnetization voltage command value Vm *. For example, the speed calculation unit 31 may perform a PLL (Phase Locked Loop) circuit or an equivalent regression calculation thereof, or represents the relationship between the voltage command value and the angular velocity in a relational expression in advance. Also good.

If the angular velocity command value ω * is greater than the current angular velocity ω (that is, if ω *> ω), the target torque current determination unit 24 increases the torque to increase the torque to increase the torque current command value It *. Is output. On the other hand, if the angular velocity command value ω * is smaller than the current angular velocity ω (that is, if ω * <ω), a smaller torque current command value It * is output in order to reduce the torque for deceleration.

Next, a process for determining the magnetizing current command value Im * that is the target value of the magnetizing current Im will be described. In order to simplify the description, consider a case where the synchronous motor is an SPM motor (surface magnet type motor, Surface Permanent Magnet motor). In the case of the SPM motor, the operation efficiency is best when the output current Iout from the inverter 10 flows perpendicularly to the d-axis. That is, it is desirable to control the output current of the inverter 10 so that the current Id on the d axis becomes zero. FIG. 7A shows the relationship between the current vector on the dq axis and the current vector on the MT axis in a state where the operating efficiency is the best.

On the other hand, the output voltage Vout of the inverter 10 is obtained as follows from the equations (1) and (2).
Vout (→) = Vd (→) + Vq (→) (3)
Vout = Id · R + pLdId−ωLqIq
+ Iq · R + pLqIq + ωLdId + ωΨ (4)
The symbol (→) represents a vector.

When the motor M is operating stably, the feedback current is a clean sine wave. At this time, the currents It and Im that have undergone coordinate conversion hardly change, and thus can be said to be in a steady state. Therefore, since the differential term of the above equation (4) can be ignored, the above equation (4) is
Vout = Id · R−ωLqIq + Iq · R + ωLdId + ωΨ
= Id · R + Iq · R + ω (LdId−LqIq + Ψ) (5)
It is expressed.
Furthermore, since the vector Iout is a combination of the vector Id and the vector Iq, the above equation (5) is
Vout = Iout · R + ω (LdId−LqIq + Ψ) (6)
It is expressed.

In the state shown in FIG. 7A, since Id = 0, Iq = Iout. Therefore, Formula (6) is expressed as follows.
Vout = Iq · R−ωLqIq + ωΨ (7)
FIG. 7B is a diagram showing Vout corresponding to Iout shown in FIG. 7A as a vector. FIG. 7A shows an ideal state where Id is 0, and the output voltage at this time is assumed to be an ideal output voltage Vout-i. The T axis coincides with the vector direction of the ideal output voltage Vout-i.

FIG. 8A shows the relationship among Iout, Iq, Id, It, and Im when the output current Iout is in phase advance with respect to the current Iq, that is, when Id <0. Under the condition that the torque current It is controlled to the same magnitude as in FIG. 7A based on the torque current command value It *, the tip of the vector Iout passes through the tip of the vector It and is a straight line perpendicular to the T axis. It's above. Therefore, the vector Iq is smaller than that in the ideal state shown in FIG. 7A. The vector of the voltage Vout at this time is as shown in FIG. 8B. Since Id <0, IdR is a leftward vector, and ωLdId is a downward vector. Because of the presence of these vectors and Iq, the output voltage Vout becomes smaller than the ideal output voltage Vout-i (see FIG. 7B) indicated by the dotted line. At this time, the current Im on the M axis is smaller than the current Im in the ideal state shown in FIG. 7A.

On the other hand, FIG. 9A shows the relationship between Iout, Iq, Id, It, and Im when the output current Iout is delayed in phase with respect to the current Iq, that is, when Id> 0. Under the condition that the torque current It is controlled to the same magnitude as in FIG. 7A based on the torque current command value It *, Iq becomes larger than that in the ideal state shown in FIG. 7A. The vector of the voltage Vout at this time is as shown in FIG. 9B. Since Id> 0, IdR is a rightward vector, and ωLdId is an upward vector. Since these vectors are present and Iq is increased, the output voltage Vout is larger than the ideal output voltage Vout-i (see FIG. 7B) indicated by a dotted line. At this time, the current Im on the M-axis is larger than the current Im in the ideal state shown in FIG. 7A.

7A to 9B show the following regarding the magnetizing current Im. When the actual output voltage Vout is smaller than a certain ideal output voltage Vout-i, the magnetizing current Im is increased and the phase of the output current Iout is delayed to change the output voltage Vout to the ideal output voltage Vout-i. Can be approached. On the other hand, when the actual output voltage Vout is larger than the ideal output voltage Vout-i, the magnetizing current Im is decreased and the phase of the output current Iout is advanced to change the output voltage Vout to the ideal output voltage Vout-i. You can get closer. That is, the magnetizing current command value Im * can be determined by determining a target output voltage for a certain operating state and obtaining a deviation between the target output voltage and the actual output voltage.

In the SPM motor described above, the magnetic flux generated by the motor stator winding is uniformly subjected to the magnetic resistance by the permanent magnet. Therefore, the d-axis inductance Ld and the q-axis inductance Lq are equal to each other. On the other hand, in the case of an IPM motor (embedded magnet type motor, Interior Permanent Magnet motor), the magnetic flux in the d-axis direction is subjected to magnetic resistance by the permanent magnet, but the magnetic flux in the q-axis direction passes only through the iron core. Therefore, there is a difference between the d-axis inductance Ld and the q-axis inductance Lq. For this reason, the drive efficiency is best when the output current Iout has a phase advance from the q axis. However, this phase advance angle cannot be calculated without detailed motor constants.

However, even in the case of an IPM motor, the relationship shown in FIGS. 8A to 9B is established. That is, with respect to the ideal output voltage Vout-i, when Im is increased, Vout increases, and when Im is decreased, Vout decreases. Therefore, also in the IPM motor, the magnetizing current command value Im * can be determined by determining a target output voltage for a certain operating state and obtaining a deviation between the target output voltage and the actual output voltage.

In the case of an induction motor, unlike a synchronous motor, it is necessary to flow a large amount of magnetizing current Id to generate a magnetic flux, and an induced electric power E is generated on a d-axis orthogonal to the magnetic flux generated thereby. However, even in the case of the induction motor, the relationships shown in FIGS. 8A to 9B are similarly established. That is, with respect to the ideal output voltage Vout-i, when Im is increased, Vout increases, and when Im is decreased, Vout decreases. Therefore, the magnetizing current command value Im * can be determined by determining a target output voltage for a certain operating state and obtaining a deviation between the target output voltage and the actual output voltage.

In this embodiment, a target output voltage Vout-d corresponding to the ideal output voltage Vout-i is determined in advance, and based on the deviation between the target output voltage Vout-d and the current output voltage, the target of the magnetizing current is determined. The value Im * is determined. As will be described in detail later, the vector control unit 11 stores a V / ω pattern indicating the relationship between the target output voltage Vout-d and the angular velocity ω, and the vector control unit 11 corresponds to the current angular velocity ω. The target output voltage Vout-d to be determined is determined according to the V / ω pattern, and the target value of the magnetizing current is determined based on the deviation between the target output voltage Vout-d and the current output voltage V.

FIG. 10 shows a control block for determining the magnetizing current command value Im *, which is the target value of the magnetizing current Im. As shown in FIG. 10, the magnetizing current command value Im * is obtained by inputting the target output voltage Vout-d and the output voltage V to the target magnetizing current determining unit 26. The output voltage V can be obtained by synthesizing signals of voltage command values Vm * and Vt * on the MT axis obtained as a result of vector control (V = √ (Vm * ² + Vt * ² )). The target magnetizing current determination unit 26 obtains a magnetizing current command value Im * such that the deviation between the target output voltage Vout-d and the output voltage V becomes zero. That is, the target magnetization current determination unit 26 outputs a larger Im * so as to delay the phase of the output current Iout if Vout-d> V, and advances the phase of the output current Iout if Vout-d <V. Output a smaller Im *.

The torque current command value It * and the magnetizing current command value Im * are input to the torque voltage control unit 21 and the magnetizing voltage control unit 22, respectively, as shown in FIG. Then, as described above, the torque voltage controller 21 calculates the torque voltage command value Vt * based on the deviation between the torque current It and the torque current command value It *. The magnetization voltage control unit 22 calculates the magnetization voltage command value Vm * based on the deviation between the magnetization current Im and the magnetization current command value Im *. In this way, vector control using a vector on the MT axis that is the inverter axis becomes possible.

The target output voltage Vout-d is output from the target output voltage determination unit 27 and input to the target magnetization current determination unit 26. The target output voltage determination unit 27 determines the target output voltage Vout-d based on the current angular velocity ω. More specifically, the target output voltage determination unit 27 stores a V / ω pattern indicating the relationship between the target output voltage Vout-d and the angular velocity ω. This V / ω pattern defines the correspondence between the angular velocity ω and the target output voltage Vout-d for determining the target output voltage Vout-d corresponding to the current angular velocity ω of the rotor. The V / ω pattern is stored in the target output voltage determination unit 27 as a function or table data indicating the relationship between the target output voltage Vout-d and the angular velocity ω. The target output voltage determination unit 27 determines a target output voltage Vout-d corresponding to the current angular velocity ω based on the V / ω pattern. Since the frequency F can be obtained from the angular velocity ω using the well-known formula ω = 2πF, a V / F pattern indicating the relationship between the target output voltage Vout-d and the frequency F is displayed in the target output voltage determination unit 27. It may be memorized.

The relationship between the target output voltage Vout-d and the angular velocity ω may be a relationship in which the ratio between Vout-d and ω is constant, or a pump or fan whose load torque is proportional to the square of the rotational speed of the motor is driven. In this case, the ratio between Vout-d and ω may be represented by a square reduction curve along the square reduction torque characteristic. The V / ω pattern can be set from the rated voltage and the rated frequency of the motor M according to the same method as the conventional V / F control.

In order to maximize the motor efficiency, it is desirable that the target output voltage Vout-d matches the ideal output voltage Vout-i. However, if the target output voltage Vout-d does not deviate significantly from the ideal output voltage Vout-i, the motor M can be controlled. Unlike the conventional V / F control, the drive device according to the present embodiment can avoid the step-out of the rotor by feeding back the output current of the inverter 10 to the vector control unit 11. Further, since the output voltage V is fed back to the target magnetization current determination unit 26, control with higher accuracy and efficiency than simple V / F control is possible.

Furthermore, in order to set a linear function in which Vout-d / ω is constant, as shown in FIG. 11A, it is sufficient if the rated voltage and rated frequency (or rated rotational speed) of the motor M are known. A motor constant is not required. Further, even when the ratio between the target output voltage Vout-d and the angular velocity ω is represented by a square reduction curve, if the rated voltage and rated frequency of the motor M are known as shown in FIG. Can do.

It should be noted that field weakening control can also be performed in the drive device of this embodiment. That is, when the frequency (rotational speed) of the motor M exceeds the rated frequency of the motor M, the magnetizing current Im is lowered so that the output power of the inverter 10 is maintained at the rated voltage of the motor M. Thereby, the rotational speed of the motor M can be increased while suppressing the output voltage of the inverter 10. In the V / ω pattern shown in FIG. 11A and FIG. 11B, after the target output voltage Vout-d reaches the rated voltage of the motor M, the target output voltage Vout-d is kept constant at the rated voltage of the motor M. In other words, the target output voltage Vout-d is maintained at the rated voltage of the motor M in the region equal to or higher than the angular velocity corresponding to the rated frequency of the motor M. When the output upper limit voltage (calculated from the DC link voltage) of the inverter 10 is smaller than the rated voltage of the motor M, the target output voltage Vout-d is equal to or higher than the angular velocity corresponding to the rated frequency of the motor M. The output upper limit voltage of the inverter 10 is maintained.

Here, the target output voltage determination unit 27 may store a plurality of V / ω patterns indicating the relationship between the target output voltage Vout-d and the angular velocity ω. In this case, one V / ω pattern is selected from a plurality of V / ω patterns by a setting operation from an input unit (not shown), and the target output voltage determination unit 27 performs angular velocity ω according to the selected V / ω pattern. To determine the target output voltage Vout-d. For example, the target output voltage determination unit 27 uses, as a plurality of V / ω patterns, a V / ω pattern in which Vout-d / ω is constant, and a V / ω pattern in which Vout-d / ω is represented by a square reduction curve. And an appropriate V / ω pattern can be selected depending on the type of load connected to the motor M.

In this embodiment, it is possible to perform torque boost in the low frequency region. In general, in a region where the frequency (rotational speed) of the motor is low, the output current of the inverter 10 becomes small, so that the motor is difficult to control. Therefore, as shown in FIG. 12, in the region where the angular velocity of the motor M is not more than a predetermined value, a lower limit value of the magnetizing current command value Im * is provided to boost the magnetizing current command value Im * in the low frequency region. Is preferred. In the example shown in FIG. 12, when the angular velocity of the rotor of the motor M is equal to or less than ω1, the target magnetizing current determination unit 26 outputs the lower limit value stored in advance as the magnetizing current command value Im *. On the other hand, when the angular velocity is larger than ω1, the target magnetization current determination unit 26 outputs the magnetization current command value Im * obtained as a result of the PI control. Thus, by compensating the magnetizing current command value Im * in the low frequency region, torque boost in the low speed region of the motor can be realized. In FIG. 12, the reason why the line graph indicating the lower limit value of the magnetizing current command value Im * is inclined is that if the command value Im * is large, overexcitation occurs and efficiency is deteriorated. In order to avoid such an overexcitation state and perform rapid control with an appropriate command value, the lower limit value of the magnetizing current command value Im * is decreased as the angular velocity increases to reduce the command value Im *.

In addition, instead of the magnetizing current command value Im *, a lower limit value may be provided for the magnetizing voltage command value Vm *. Also in this case, similarly to the example of FIG. 12, when the angular velocity is equal to or lower than the predetermined value, the magnetization voltage control unit 22 outputs the previously stored lower limit value as the magnetization voltage command value Vm *. Is larger than a predetermined value, the magnetizing voltage command value Vm * obtained as a result of the PI control is output. Also in this case, as in the example shown in FIG. 12, the lower limit value of the magnetization voltage command value Vm * is decreased as the angular velocity increases, so that the control can be quickly performed with an appropriate command value.

The torque boost in the low frequency region described above may be performed by selecting either the magnetizing current command value Im * or the magnetizing voltage command value Vm *. More specifically, the lower limit value is provided for both the magnetizing current command value Im * and the magnetizing voltage command value Vm *, and either of the magnetizing current command value Im * and the magnetizing voltage command value Vm * is selected. Alternatively, the output may be output from the target magnetization current determination unit 26 or the magnetization voltage control unit 22. When the lower limit value of the magnetizing voltage command value Vm * is selected, an upper limit value is provided for the magnetizing current command value Im * to prevent overcurrent, and overexcitation due to an excessive magnetizing voltage command value Vm * It is preferable to perform overcurrent protection.

In the present embodiment, the target output voltage determination unit 27 determines the target output voltage Vout-d from the angular velocity ω, but the target output voltage Vout-d output from the target output voltage determination unit 27 is not necessarily the ideal output voltage. It does not always match. In the present invention, a reduction in motor efficiency due to the difference between the target output voltage Vout-d and the ideal output voltage can be compensated as follows.

FIG. 13 is a diagram illustrating an example of compensation for a decrease in motor efficiency when a torque meter 42 is provided in the load 41 connected to the motor M. The vector control unit 11 is shown with its details omitted, and only the target output voltage determination unit 27 and its output are described. The bias voltage determining unit 43 receives the angular velocity command value ω * and the torque signal output from the torque meter 42, and the bias voltage determining unit 43 outputs the bias voltage. The bias voltage is added to the target output voltage Vout-d which is the output of the target output voltage determination unit 27, and the value obtained as a result is input to the target magnetization current determination unit 26 (see FIG. 2). Here, the bias voltage can take not only a positive value but also a negative value.

The bias voltage determination unit 43 increases or decreases the bias voltage so that the torque detected by the torque meter 42 is maximized when there is no change in the angular velocity command value ω *. FIG. 14 is a graph showing the relationship between the torque signal and the bias voltage. In the example shown in FIG. 14, the torque signal becomes maximum when the bias voltage is −10V. The bias voltage determination unit 43 compares torque signals before and after increasing / decreasing the bias voltage and determines increase / decrease of the bias voltage. When the angular velocity command value ω * changes, the bias voltage is returned to zero. In this way, the bias voltage determination unit 43 increases or decreases the bias voltage so that the torque becomes maximum until the angular velocity command value ω * changes.

Generally, the calculation cycle of the angular velocity command value ω * is longer than the vector control cycle. For example, the angular velocity command value ω * is calculated at an interval of 100 ms, whereas the angular velocity command value ω * is constant if the vector control cycle (target output voltage Vout-d determination cycle) is 1 ms. In the meantime, there is an opportunity to increase or decrease the bias voltage at least 100 times. The increase / decrease of the bias voltage may be the same as the cycle of vector control or may be performed at a cycle longer than the cycle of vector control. For example, in the above example, the bias voltage may be increased or decreased every 5 ms.

FIG. 15 is a diagram showing an example of compensation for a decrease in motor efficiency when the load connected to the motor M is the pump P and the pipe connected to the pump P is provided with the flow meter 52. FIG. 16 is a graph showing the relationship between the flow rate and the bias voltage. The example shown in FIG. 15 is different from the example shown in FIG. 13 in that the signal input to the bias voltage determination unit 43 is not a torque signal but a flow signal output from the flow meter 52, and the increase or decrease of the bias voltage. However, it is performed so that the flow rate becomes maximum. Other configurations and operations are the same as the example shown in FIG.

Thus, using the sensors (torque meter 42, flow meter 52) that detect the state of the load connected to the motor M, the bias that is added to the target output voltage Vout-d so that the load state is maximized. By increasing or decreasing the voltage, it is possible to perform control to further increase the motor efficiency.

Also, it is possible not to compensate for the motor efficiency itself, but to control the efficiency of the inverter so that the efficiency of the entire system can be compensated. The example shown in FIGS. 13 and 15 is control aiming at the highest efficiency point of the motor, but the operation at the highest efficiency point of the motor is not always the most efficient operation in the entire system including the inverter and the like. . Therefore, although different from the maximum torque point of the motor, the bias voltage added to the target output voltage Vout-d is increased / decreased so that the inverter output current is minimized to maximize the inverter efficiency.

FIG. 17 is a diagram showing such an example. FIG. 18 is a graph showing the relationship between the output current of the inverter and the bias voltage. The example shown in FIG. 17 is different from the examples shown in FIGS. 13 and 15 in that the signal input to the bias voltage determination unit 43 is not a signal indicating the state of the load connected to the motor M, but the inverter 10 It is a signal indicating the output current and a point where the increase / decrease of the bias voltage is performed such that the output current of the inverter 10 is minimized. As the output current of the inverter 10, a signal from the sensor 12 that detects the output current of the inverter 10 may be input to the bias voltage determination unit 43.

Also, the bias voltage may be controlled so that the output power is minimized rather than the output current of the inverter. Since the output power of the inverter 10 is calculated from the output current and output voltage of the inverter 10, a sensor 40 for detecting the output voltage of the inverter 10 is provided as shown by a two-dot broken line in FIG. A signal from the

sensors

12 and 40 that detect the output voltage may be input to the bias voltage determination unit 43. Further, as the output voltage of the inverter 10, the voltage command value used in the vector control unit 11 or the output of the output voltage calculation unit 30 may be used instead of using the signal from the sensor 40.

FIG. 19 is a view showing a modification of the drive device according to the embodiment of the present invention. In this modification, the output voltage is not obtained from the voltage command values Vm * and Vt *, but the three-phase output voltage of the inverter 10 is directly detected by the voltage detector 40. The detected three-phase output voltage is sent to the output voltage calculation unit 30, where the output voltage V of the inverter 10 is obtained. The obtained output voltage V is input to the target magnetization current determination unit 26 as in the above example.

The above-described embodiments are described for the purpose of enabling the person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in the widest scope according to the technical idea defined by the claims.

The present invention can be applied to a drive device that drives an electric motor such as a synchronous motor or an induction motor, and is particularly applicable to a drive device that performs vector control based on an output current of an inverter.

DESCRIPTION OF SYMBOLS 10 Inverter 11 Vector control part 12 Current detector 17 3/2 phase conversion part 18 Static / rotation coordinate conversion part 21 Torque voltage control part 22 Magnetization voltage control part 24 Target torque current determination part 26 Target magnetization current determination part 27 Target output voltage Determination unit 30 Output voltage calculation unit 31 Speed calculation unit 33 Integrator 35 Rotation / static coordinate conversion unit 36 2/3 phase conversion unit 40 Voltage detector

Claims

An inverter, a current detector that detects an output current of the inverter, and a vector control unit that converts the output current detected by the current detector into a torque current and a magnetizing current, and controls the torque current and the magnetizing current. An electric motor drive device comprising:
The vector control unit
A 3/2 phase converter for converting a three phase current detected by the current detector into a two phase current;
A stationary / rotating coordinate conversion unit that converts the two-phase current on the stationary coordinate system converted by the 3/2 phase conversion unit into a torque current and a magnetization current on a rotating coordinate system;
A torque voltage control unit that determines a torque voltage command value based on a deviation between the torque current command value and the torque current;
A magnetization voltage control unit that determines a magnetization voltage command value based on a deviation between the magnetization current command value and the magnetization current;
A rotation / stationary coordinate converter that converts the torque voltage command value and the magnetization voltage command value on the rotation coordinate system into a torque voltage command value and a magnetization voltage command value on the stationary coordinate system;
A 2 / 3-phase converter that converts the torque voltage command value and the magnetization voltage command value converted by the rotating / stationary coordinate converter to a three-phase voltage command value;
A speed calculation unit that calculates an angular velocity of the rotor of the motor from the torque voltage command value and the magnetization voltage command value obtained by the torque voltage control unit and the magnetization voltage control unit;
A target torque current determination unit that determines the torque current command value based on a deviation between the angular velocity and the angular velocity command value;
A target magnetizing current determining unit that determines the magnetizing current command value based on a deviation between the output voltage of the inverter and the target output voltage;
A target output voltage determination unit for determining the target output voltage,
The target output voltage determination unit stores a V / ω pattern indicating a relationship between the target output voltage and the angular velocity, and determines the target output voltage from the angular velocity according to the V / ω pattern. A drive device.
2. The driving apparatus according to claim 1, wherein the relationship between the target output voltage and the angular velocity indicated by the V / ω pattern is a relationship in which a ratio between the target output voltage and the angular velocity is constant. .
2. The relationship between the target output voltage and the angular velocity indicated by the V / ω pattern is a relationship in which a ratio between the target output voltage and the angular velocity is represented by a secondary reduction curve. The drive device described in 1.
The target output voltage determination unit stores a plurality of V / ω patterns indicating a relationship between the target output voltage and the angular velocity, and one V / ω selected from the plurality of V / ω patterns. The drive device according to claim 1, wherein the target output voltage is determined from the angular velocity according to a pattern.
The relationship between the target output voltage and the angular velocity indicated by the V / ω pattern is that the target output voltage is kept constant at the rated voltage after the target output voltage reaches the rated voltage of the motor. The drive device according to claim 1, wherein the drive device is a relationship.
The relationship between the target output voltage and the angular velocity indicated by the V / ω pattern is that the target output voltage is kept constant at the rated output voltage after the target output voltage reaches the rated output voltage of the inverter. 5. The driving device according to claim 1, wherein the relationship is a
The target magnetizing current determining unit outputs a lower limit value stored in the target magnetizing current determining unit as the magnetizing current command value when the angular velocity is a predetermined value or less. The drive device as described in any one of 6.
The magnetizing voltage controller outputs a lower limit value stored in the magnetizing voltage controller as the magnetizing voltage command value when the angular velocity is equal to or less than a predetermined value. The drive device as described in any one.