JP2010148330A - Control system for ac motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve responsiveness in control by compensating the variation of torque corresponding to a change in the operating state of an AC motor, without waiting for feedback control. <P>SOLUTION: Torque variation ΔTtl generated by the change in the operating state of a motor is computed, according to a torque operational expression which shows the operating state of a motor and the property of output torque to the voltage phase of a rectangular wave voltage. Furthermore, according to an expression being obtained by differentiating the torque operational expression with a voltage phase, the present motor operating state of the motor is obtained and the ratio of the torque variation to the variation of a voltage phase, at a voltage phase (θ0), is computed as the inclination Ktl of a tangent TL at an operating point Pc. Then, in accordance with the amount θsf of shift of voltage phase obtained by ΔTtl/Ktl, an integration term by feedback control for changing the voltage phase is shifted, according to torque deviation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an AC motor control system, and more particularly to motor control in which a DC voltage is converted into a rectangular wave AC voltage by an inverter and applied to the AC motor.

  A motor control system that drives and controls an AC motor by converting a DC voltage into an AC voltage by an inverter is generally used. In such a motor control system, generally, in order to drive an AC motor with high efficiency, the motor current is controlled according to sinusoidal pulse width modulation (PWM) control based on vector control.

  However, the sinusoidal PWM control has a problem that it is difficult to obtain a high output in a high speed region because the fundamental wave component of the output voltage of the inverter cannot be sufficiently increased and the voltage utilization rate is limited. In view of this point, it has been proposed to adopt a control method capable of outputting a voltage having a larger fundamental wave component than the sine wave PWM control.

  Japanese Patent Laying-Open No. 2006-320039 (Patent Document 1) describes a control system in which a rectangular wave voltage having an amplitude of a voltage variably controlled by a converter is applied to an AC motor. In particular, in Patent Document 1, basically, the voltage phase of the rectangular wave voltage is changed according to the torque deviation, and when the motor rotation speed changes abruptly, the converter is changed according to the change ratio of the motor rotation speed. Control for changing the output voltage is described.

  Japanese Patent No. 3755424 (Patent Document 2) controls a rectangular wave voltage applied to an AC motor based on a torque deviation in a drive control device that rotates by applying a rectangular wave voltage to the AC motor. A configuration for realizing rectangular wave voltage control without detecting the position of the rotor is described.

Furthermore, in Japanese Patent Application Laid-Open No. 2006-54995 (Patent Document 3), in a drive control device that controls an AC motor that rotates by applying a rectangular wave voltage, an actual torque value based on a detected voltage / current value, a command torque value, A control method has been proposed in which a first voltage phase according to, an estimated torque value based on an electric motor model and a second voltage phase according to a command torque value are calculated, and a weighted value thereof is used as the phase of the rectangular wave voltage. Furthermore, Japanese Patent Laid-Open No. 2001-145381 (Patent Document 4) describes that in a brushless DC motor, the torque can be changed even at the same rotational speed by advancing or retarding the phase of the rectangular wave signal. Has been.
JP 2006-320039 A Japanese Patent No. 3755424 JP 2006-54995 A JP 2001-145381 A

  The above Patent Documents 1 to 4 are common in a control configuration that feedback-controls the torque performance of the AC motor. However, the output torque of the AC motor varies depending not only on the voltage phase, which is the operation amount of the rectangular wave voltage control, but also on the motor operating state represented by the rotation speed. That is, even if the phases of the rectangular wave voltages are the same, the output torque changes when the motor operating state changes.

  Therefore, in the torque feedback control as described above, when the operating state of the AC motor changes, the torque change amount associated with the change in the operating state is detected as the torque deviation, and then the torque deviation is eliminated. The voltage phase changes according to the control calculation. As a result, when the operating state changes, torque fluctuations and overcurrent may occur temporarily, which may cause problems in control response and stability.

  The present invention has been made to solve such a problem, and an object of the present invention is in AC motor control in which the voltage phase of a rectangular wave voltage applied to an AC motor is changed according to a torque deviation. The control responsiveness is improved by compensating the torque change amount corresponding to the change in the operating state of the AC motor without waiting for feedback control.

  An AC motor control system according to the present invention includes an inverter and a rectangular wave control unit. The inverter is configured to convert the DC voltage into an AC voltage for driving the AC motor. The rectangular wave control unit is configured to change the voltage phase of the rectangular wave voltage applied from the inverter to the AC motor in accordance with feedback control of the torque deviation of the AC motor. The rectangular wave control unit includes a proportional control calculation unit, an integration control calculation unit, a control signal generation unit, and an integral term correction unit. The proportional control calculation unit sets the first control amount of the voltage phase based on the current value of the torque deviation. The integration control calculation unit sets the second control amount of the voltage phase based on the torque deviation integration process. The control signal generator generates an inverter control command in correspondence with the voltage phase according to the sum of the first and second control amounts. The integral term correction unit cancels the torque change amount corresponding to the change amount of the motor variable and the torque change amount according to the torque calculation formula using the voltage phase as at least one motor variable related to the operating state of the AC motor. It is comprised so that the voltage phase shift amount for doing may be calculated. Further, the integral control calculation unit is configured to change the second control amount in accordance with the voltage phase shift amount.

  Preferably, the integral term correcting unit corrects the torque with respect to the change in the voltage phase at the first operating point corresponding to the current operating state and the voltage phase according to the differential expression obtained by differentiating the torque calculation expression with the voltage phase. A first slope, which is a change ratio, is calculated. Then, the integral term correction unit calculates the voltage shift amount according to the first phase change amount obtained by dividing the torque change amount by the first slope.

  More preferably, the integral term correction unit further performs a second operation corresponding to the first voltage phase and the current operation state in which the voltage phase is changed from the current value by the first phase change amount according to the torque calculation formula. A torque value at the point is calculated, and a second gradient that is a ratio of the torque difference to the voltage phase difference between the first and second operating points is calculated. Then, the integral term correction unit calculates the voltage shift amount according to the second phase change amount obtained by dividing the torque change amount by the second slope.

  More preferably, the integral term correction unit further performs a third operation corresponding to the second voltage phase and the current operation state in which the voltage phase is changed from the current value by the second phase change amount according to the torque calculation formula. A point is set and a torque value at the third operating point is calculated. The integral term correcting unit determines whether or not the deviation between the calculated torque value and the torque target value is smaller than a predetermined value. If the deviation is equal to or larger than the predetermined value, the third and first operations are performed. A third gradient (k ′) that is a ratio of the torque difference to the voltage phase difference between the points is calculated. Further, the integral term correction unit calculates the voltage shift amount according to the third phase change amount obtained by dividing the torque change amount by the third inclination.

  Particularly in such a configuration, the integral term correction unit further moves the third operating point to the operating point corresponding to the voltage phase obtained by changing the voltage phase from the current value by the third phase change amount and the current operating state. And the torque value at the third operating point is updated according to the torque calculation formula. Then, every time the third operating point is updated, the integral term correction unit compares the deviation between the updated torque value and the torque target value with a predetermined value, and while the deviation is equal to or greater than the predetermined value. The third operation point update process is repeatedly executed.

  Also preferably, the motor variable includes a rotational speed and / or a DC voltage of the AC motor.

  More preferably, the control system for the AC motor further includes a converter. The converter is provided between the power storage device and the inverter, and is configured to control the DC voltage on the DC side of the inverter according to the voltage command value.

  Preferably, the AC motor is configured to be mounted on an electric vehicle and generate a vehicle driving force of the electric vehicle.

  According to the present invention, in the AC motor control in which the voltage phase of the rectangular wave voltage applied to the AC motor is changed according to the torque deviation, the control response is suppressed by suppressing the torque fluctuation caused by the change in the operating state of the AC motor. Can be improved.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

[Embodiment 1]
(Overall configuration of control system)
FIG. 1 is an overall configuration diagram of an AC motor control system according to an embodiment of the present invention.

  Referring to FIG. 1, motor control system 100 includes a DC voltage generation unit 10 #, a smoothing capacitor C0, an inverter 14, a control device 30, and an AC motor M1.

  AC motor M1 is a driving motor that generates torque for driving the driving wheels of an electric vehicle such as a hybrid vehicle or an electric vehicle. In other words, in the present embodiment, the electric vehicle includes all vehicles equipped with a motor for generating wheel driving force, including an electric vehicle not equipped with an engine. Note that AC motor M1 is generally configured to have both functions of an electric motor and a generator. Further, this AC motor M1 may be configured to have a function of a generator driven by an engine in a hybrid vehicle. Further, AC electric motor M1 may operate as an electric motor for the engine, and may be incorporated in a hybrid vehicle as one that can start the engine, for example.

  DC voltage generation unit 10 # includes a DC power supply B, system relays SR1 and SR2, a smoothing capacitor C1, and a converter 12.

  The DC power source B is composed of a secondary battery such as nickel metal hydride or lithium ion, a fuel cell, an electric double layer capacitor, or a combination thereof. The DC voltage Vb output from the DC power source B is detected by the voltage sensor 10. Voltage sensor 10 outputs detected DC voltage Vb to control device 30.

  System relay SR 1 is connected between the positive terminal of DC power supply B and power line 6, and system relay SR 2 is connected between the negative terminal of DC power supply B and ground line 5. System relays SR1 and SR2 are turned on / off by signal SE from control device 30. Smoothing capacitor C <b> 1 is connected between power line 6 and ground line 5.

  Converter 12 includes a reactor L1, power semiconductor switching elements Q1, Q2, and diodes D1, D2.

  Power semiconductor switching elements Q 1 and Q 2 are connected in series between power line 7 and ground line 5. On / off of power semiconductor switching elements Q 1 and Q 2 is controlled by switching control signals S 1 and S 2 from control device 30.

In the embodiment of the present invention, as a power semiconductor switching element (hereinafter, simply referred to as “switching element”), an IGBT (Insulated Gate Bipolar Transistor),
A power MOS (Metal Oxide Semiconductor) transistor, a power bipolar transistor, or the like can be used. Anti-parallel diodes D1, D2 are arranged for switching elements Q1, Q2.

  Reactor L1 is connected between a connection node of switching elements Q1 and Q2 and power line 6. Further, the smoothing capacitor C 0 is connected between the power line 7 and the ground line 5.

  Inverter 14 includes a U-phase arm 15, a V-phase arm 16, and a W-phase arm 17 provided in parallel between power line 7 and ground line 5. Each phase arm is composed of a switching element connected in series between the power line 7 and the ground line 5. For example, U-phase arm 15 includes switching elements Q3 and Q4, V-phase arm 16 includes switching elements Q5 and Q6, and W-phase arm 17 includes switching elements Q7 and Q8. Further, antiparallel diodes D3 to D8 are connected to switching elements Q3 to Q8, respectively. Switching elements Q3 to Q8 are turned on / off by switching control signals S3 to S8 from control device 30.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of AC electric motor M1. Typically, AC electric motor M1 is a three-phase permanent magnet motor, and is configured such that one end of three coils of U, V, and W phases are commonly connected to a midpoint. Furthermore, the other end of each phase coil is connected to the midpoint of the switching elements of each phase arm 15-17.

  During the boosting operation, the converter 12 boosts the DC voltage Vb supplied from the DC power supply B (this DC voltage corresponding to the input voltage to the inverter 14 is hereinafter also referred to as “system voltage”) VH to the inverter 14. To supply. In the step-down operation, converter 12 steps down the DC voltage (system voltage) supplied from inverter 14 via smoothing capacitor C0 and charges DC power supply B. During the step-up operation and the step-down operation, on / off of switching elements Q1, Q2 is controlled in response to switching control signals S1, S2 from control device 30, respectively. If switching elements Q1 and Q2 are fixed to ON and OFF, respectively, VH = Vb (voltage ratio = 1.0) can be obtained.

  Smoothing capacitor C 0 smoothes the DC voltage from converter 12 and supplies the smoothed DC voltage to inverter 14. The voltage sensor 13 detects the voltage across the smoothing capacitor C 0, that is, the system voltage VH, and outputs the detected voltage to the control device 30.

  When the torque command value of AC motor M1 is positive (Tqcom> 0), inverter 14 responds to switching control signals S3 to S8 from control device 30 when a DC voltage is supplied from smoothing capacitor C0. The AC motor M1 is driven so as to output a positive torque by converting the DC voltage into an appropriate motor applied voltage (AC voltage) by the switching operation of the elements Q3 to Q8. Further, when the torque command value of the AC motor M1 is zero (Tqcom = 0), the inverter 14 converts the DC voltage to an appropriate motor applied voltage (AC voltage) by a switching operation in response to the switching control signals S3 to S8. The AC electric motor M1 is driven so that the torque becomes zero by converting to. Thus, AC electric motor M1 is driven to generate zero or positive torque designated by torque command value Tqcom.

  Further, during regenerative braking of an electric vehicle equipped with motor control system 100, torque command value Tqcom of AC electric motor M1 is set to be negative (Tqcom <0). In this case, the inverter 14 converts the AC voltage generated by the AC motor M1 into a DC voltage by a switching operation in response to the switching control signals S3 to S8, and converts the converted DC voltage (system voltage) to the smoothing capacitor C0. To the converter 12 via The regenerative braking here refers to braking with regenerative power generation when the driver operating the electric vehicle performs a footbrake operation, or regenerative braking by turning off the accelerator pedal while driving, although the footbrake is not operated. This includes decelerating (or stopping acceleration) the vehicle while generating electricity.

  Current sensor 24 detects a motor current flowing through AC electric motor M <b> 1 and outputs the detected motor current to control device 30. Since the sum of instantaneous values of the three-phase currents iu, iv, and iw is zero, the current sensor 24 has a motor current for two phases (for example, a V-phase current iv and a W-phase current iw) as shown in FIG. It is sufficient to arrange it so as to detect.

  The rotation angle sensor (resolver) 25 detects the rotor rotation angle ANG of the AC electric motor M1 and sends the detected rotation angle ANG to the control device 30. The control device 30 can calculate the rotational speed (represented by the rotational speed per unit time (typically rpm)) and the angular speed ω (rad / s) based on the rotational angle ANG. Note that the rotation angle sensor 25 may be omitted by directly calculating the rotation angle ANG from the motor voltage or current in the control device 30.

  The control device 30 is configured by a CPU (Central Processing Unit) (not shown) and an electronic control unit (ECU) with a built-in memory, and based on a map and a program stored in the memory, an operation using a detection value by each sensor. Perform processing. The control device 30 controls the operation of the motor control system 100 by such arithmetic processing so that the AC motor M1 is operated according to the operation command from the host ECU. Note that a part of the control device 30 may be configured to execute predetermined numerical / logical operation processing by hardware such as an electronic circuit.

  Specifically, the control device 30 determines the torque command value Tqcom, the battery voltage Vb detected by the voltage sensor 10, the system voltage VH detected by the voltage sensor 13, the motor currents iv and iw from the current sensor 24, and the rotation angle. Based on the rotation angle ANG from the sensor 25, the operations of the converter 12 and the inverter 14 are controlled so that the AC motor M1 outputs a torque according to the torque command value Tqcom by a method described later. That is, switching control signals S1 to S8 for controlling converter 12 and inverter 14 as described above are generated and output to converter 12 and inverter 14.

  During the boosting operation of converter 12, control device 30 feedback-controls output voltage VH of smoothing capacitor C0, and generates switching control signals S1 and S2 so that output voltage VH becomes a voltage command value.

  In addition, when control device 30 receives signal RGE indicating that the electric vehicle has entered the regenerative braking mode from the host ECU, switching control signal S <b> 3 to convert the AC voltage generated by AC motor M <b> 1 into a DC voltage. S8 is generated and output to the inverter 14. Thereby, the inverter 14 converts the AC voltage generated by the AC motor M <b> 1 into a DC voltage and supplies it to the converter 12.

  Further, when receiving a signal RGE indicating that the electric vehicle has entered the regenerative braking mode from the external ECU, control device 30 generates switching control signals S1 and S2 so as to step down the DC voltage supplied from inverter 14. And output to the converter 12. As a result, the AC voltage generated by AC motor M1 is converted to a DC voltage, stepped down, and supplied to DC power supply B. Furthermore, control device 30 generates signal SE for turning on / off system relays SR1, SR2 and outputs the signal SE to system relays SR1, SR2.

(Control configuration)
Next, power conversion in the inverter 14 controlled by the control device 30 will be described in detail.

  As shown in FIG. 2, in motor control system 100 according to the embodiment of the present invention, three control modes are switched and used for power conversion in inverter 14.

  The sine wave PWM control is used as a general PWM control, and the switching elements in each phase arm are turned on / off according to a voltage comparison between a sine wave voltage command value and a carrier wave (typically a triangular wave). Control. As a result, for a set of a high level period corresponding to the on period of the upper arm element and a low level period corresponding to the on period of the lower arm element, the duty is set so that the fundamental wave component becomes a sine wave within a certain period. The ratio is controlled. As is well known, in the sine wave PWM control, the fundamental wave component (effective value) of the line voltage applied to the AC motor M1 can be increased only to about 0.61 times the inverter input voltage. Hereinafter, in this specification, the ratio of the fundamental wave component (effective value) of the line voltage of the AC motor M1 to the DC link voltage (that is, the system voltage VH) of the inverter 14 is referred to as “modulation rate”.

  On the other hand, in the rectangular wave voltage control, one pulse of the rectangular wave having a ratio of the high level period to the low level period of 1: 1 is applied to the AC motor M1 within the predetermined period. As a result, the modulation rate is increased to 0.78.

  The overmodulation PWM control performs PWM control similar to the sine wave PWM control in a range where the amplitude of the voltage command is larger than the carrier wave amplitude. In particular, the fundamental wave component can be increased by distorting the voltage command from the original sine wave waveform, and the modulation rate can be increased from the maximum modulation rate in the sine wave PWM control mode to a range of 0.78.

  In the AC motor M1, the induced voltage increases as the rotational speed and the output torque increase, so the required drive voltage (motor required voltage) increases. The boosted voltage by the converter 12, that is, the system voltage VH needs to be set higher than the required voltage of the motor. On the other hand, there is a limit value (VH maximum voltage) in the boosted voltage by converter 12, that is, system voltage VH.

  Therefore, a PWM control mode by sine wave PWM control or overmodulation PWM control that controls the amplitude and phase of the motor applied voltage (AC) by feedback of the motor current according to the operating state of AC motor M1, and rectangular wave voltage One of the control modes is selectively applied. In the rectangular wave voltage control, since the amplitude of the motor applied voltage is fixed, the torque control is executed by the phase control of the rectangular wave voltage pulse based on the deviation between the actual torque value and the torque command value.

FIG. 3 shows the correspondence between the operating state of AC electric motor M1 and the control mode described above.
Referring to FIG. 3, sine wave PWM control is generally used to reduce torque fluctuation in the low speed region A1, overmodulation PWM control in the medium speed region A2, and rectangular wave in the high speed region A3. Voltage control is applied. In particular, application of overmodulation PWM control and rectangular wave voltage control can improve the output of AC electric motor M1. As described above, which of the control modes shown in FIG. 2 is used is basically determined within the range of the modulation rate that can be realized.

  Of the above control modes, any known control configuration can be applied to the sine wave PWM control and overmodulation PWM control. For example, the d-axis and q-axis current command values are obtained from the torque command value Tqcom so that the output torque of the AC motor M1 matches the torque command value Tqcom, and the motor current (Id, Iq) for these current command values is obtained. PWM control can be realized by performing feedback control.

(Rectangular wave voltage control)
The control system for an AC motor according to the present invention is characterized by rectangular wave voltage control in which the torque of the AC motor M1 is feedback-controlled every predetermined control cycle. Therefore, hereinafter, the control configuration of the rectangular wave voltage control will be described in detail.

  The rectangular wave voltage control of the AC motor according to the present embodiment is performed according to the change characteristic of the output torque with respect to the voltage phase θv as shown in FIG.

  Referring to FIG. 4, generally, when a positive torque is generated (Tqcom> 0), the voltage phase θv is advanced when torque is insufficient, while the voltage phase θv is delayed when torque is excessive, according to the torque deviation. Thus, the voltage phase θv is controlled. On the other hand, when negative torque occurs (Tqcom <0), the voltage phase θv is controlled according to the torque deviation so that the voltage phase θv is delayed when the torque is insufficient and the voltage phase θv is advanced when the torque is excessive. The

  FIG. 5 is a functional block diagram for explaining a specific control configuration of the rectangular wave voltage control. Referring to FIG. 5, rectangular wave voltage control unit 400 includes power calculation unit 410, torque calculation unit 420, deviation calculation unit 425, proportional control calculation unit 430, integral control calculation unit 440, and integral term correction. Unit 450, addition unit 455, rectangular wave generator 460, and signal generation unit 470. Note that each functional block in FIG. 5 is realized by a control program executed by a predetermined program executed by the control device 30 and / or an electronic circuit (hardware) in the control device 30.

  The power calculation unit 410 uses the phase currents obtained from the V-phase current iv and the W-phase current iw by the current sensor 24 and the voltages (u-phase, v-phase, w-phase) voltages Vu, Vv, Vw as follows ( 1) Calculate the power supplied to the motor (motor power) Pmt according to the equation (1).

Pmt = iu · Vu + iv · Vv + iw · Vw (1)
The torque calculation unit 420 uses the motor power Pmt obtained by the power calculation unit 410 and the angular velocity ω calculated from the rotation angle ANG of the AC electric motor M1 detected by the rotation angle sensor 25, according to the following equation (2). Estimated value Tq is calculated.

Tq = Pmt / ω (2)
Note that the estimated torque value Tq is not limited to the estimation method by the power calculation unit 410 and the torque calculation unit 420, but a point that can be obtained by an arbitrary method will be described. Alternatively, the estimated torque value Tq may be obtained by arranging a torque sensor instead of the electric power calculation unit 410 and the torque calculation unit 420.

  Deviation calculation unit 425 calculates torque deviation ΔTq (ΔTq = Tqcom−Tq) according to estimated torque value Tq and torque command value Tqcom.

  The proportional control calculation unit 430 calculates the phase control amount θp related to P (proportional) control based on the product of the torque deviation ΔTq in the current control cycle, that is, the current value of the torque deviation ΔTq and a predetermined proportional gain Kp. To do. That is, it is calculated by θp = Kp · θp.

  On the other hand, the integral control calculation unit 440 calculates a phase control amount θi related to I (integration) control based on the integral value of the torque deviation ΔTq and a predetermined integral gain Ki. Adder 455 sets voltage phase θv according to the sum of phase control amount θp by proportional control operation unit 430 and phase control amount θi by integration control operation unit 440.

  The rectangular wave generator 460 generates each phase voltage command value (rectangular wave pulse) Vu, Vv, Vw according to the voltage phase θv set by the adding unit 455. The signal generator 470 generates switching control signals S3 to S8 according to the phase voltage command values Vu, Vv, and Vw. When inverter 14 performs a switching operation according to switching control signals S3 to S8, a rectangular wave voltage according to voltage phase θv is applied as each phase voltage of the motor.

  Thus, according to the functional part excluding the integral term correction unit 450 from the configuration of the rectangular wave voltage control unit 400 shown in FIG. 5, general torque feedback control is realized. However, in such general feedback control, there is a possibility that sufficient control responsiveness cannot be ensured when the operating state of AC motor M1 (hereinafter simply referred to as “motor operating state”) changes. A general problem of feedback control will be described with reference to FIG.

  FIG. 6 shows an output torque behavior when the rotational speed of AC electric motor M1 is changed from N1 (high rotation) to N2 (low rotation) as an example of the motor operation state change.

  Referring to FIG. 6, the rotation speed is changed from the state where the output torque matches the torque command value Tqcom (operating point Pa) by setting the voltage phase to θ0 by feedback control under the state where the rotation speed is N1. Changes to N2, the output torque increases even when the voltage phase remains at θ0 (operating point Pc). The voltage phase θv gradually changes so as to eliminate the torque deviation ΔTq between the output torque at the operating point Pc and the torque command value Tqcom by feedback control under the state where the rotation speed is N2. When the output torque matches the torque command value Tqcom (operating point Pb), the voltage command is θ0 #.

  As described above, in general feedback control by PI control, when the motor operating state (typically, rotational speed) changes, the torque deviation generated as a result is detected, and then the torque deviation is feedback-controlled. Torque deviation inevitably occurs during the period until it is resolved by. That is, since the control operation gradually reaches the final operating point Pb from the operating point Pa through the operating point Pc, the control responsiveness when the motor operating state changes is not sufficient. In addition, torque fluctuation and motor current at the moment when the motor operating state changes may be excessive.

  Therefore, in the rectangular wave voltage control according to the embodiment of the present invention, feedback control in which the integral term correction unit 450 (FIG. 5) is introduced is executed in order to quickly cope with a change in the operating state of the AC motor. The integral term correction unit 450 obtains an integral term shift amount θsf corresponding to the “voltage phase shift amount” for canceling out the torque change amount corresponding to the change in the motor operation state. The integral control calculation unit 440 is configured to change the phase control amount θi according to the integral term shift amount θsf from the integral term correction unit 450. Further, the phase control amount (proportional term) θp corresponds to the “first control amount”, and the phase control amount (integral term) θi corresponds to the “second control amount”.

  In describing the function of the integral term correction unit 450, first, the characteristics of the output torque with respect to the motor operating state and the voltage phase represented by the rotation speed (hereinafter simply referred to as “torque characteristics”) will be described.

  The torque characteristic reflecting the motor operating state is grasped by a torque calculation formula described below. As is generally known, voltage equations and torque equations on d-axis and q-axis in a permanent magnet type synchronous motor are expressed by the following equations (3) to (5).

  In the expressions (3) and (4), Ra represents the armature winding resistance, Ψ represents the number of armature linkage fluxes of the permanent magnet, and P represents the number of pole pairs of the AC motor M1. Further, ω represents the electrical angular velocity of the AC motor M1. The electrical angular velocity ω can be obtained by ω = 2π · (Nm / 60) · P) using the motor rotation speed Nm (rpm).

  The voltage component depending on the winding resistance contributes in a very low speed region, and other components become dominant as the rotational speed increases. For this reason, when the rectangular wave voltage control is applied in the high speed region (FIG. 2), the winding resistance component in the equations (3) and (4) can be ignored. Therefore, the above equations (4) and (5) are expressed by the following equations (6) and (7) when the rectangular wave voltage control is applied.

  Furthermore, when the rectangular wave voltage control is performed, considering that the fundamental wave component of the motor applied voltage (line voltage) indicated by the d-axis voltage and the q-axis voltage is 0.78 times the system voltage VH, (6) By applying the expressions (7) and (7) to the above expression (3), the torque calculation expression (8) indicating the relationship between the voltage phase θ of the rectangular wave voltage and the output torque T of the AC motor M1 is obtained. Can do.

  As understood from the equation (8), the relationship between the voltage phase θ and the torque T in the current operation state is obtained by substituting the motor variables VH and ω (Nm) indicating the motor operation state into the torque calculation equation. Therefore, it is obtained by calculation without referring to the map. In the equation (8), ψ represents a counter electromotive voltage coefficient of the AC motor M1. Since the constant terms Ka and Kb are fixed in advance as motor constants, the above equation (8) can be transformed into the following equation (9). That is, the equations (8) and (9) are torque calculation equations using the motor variables VH and ω and the voltage phase θ as variables.

  The torque characteristic lines 500 and 510 are expressed in accordance with the equation (9) when the rotation speed Nm is a motor variable while the other motor operation states are constant. Specifically, the rotation speed is expressed as N1 in the equation (9). And N2 is derived by substituting the angular velocity ω for N2, respectively.

  As can be understood from the comparison of the torque characteristic lines 500 and 510, generally, for the same voltage phase, the characteristic that the output torque decreases as the rotational speed increases is shown. In addition, although embodiment is described below according to the torque characteristic of a power running area | region including FIG. 6, similarly with respect to the same voltage phase also in the regeneration area | region which is not shown in figure as understood from Formula (9), There is a characteristic that the absolute value of the output torque decreases as the rotational speed increases.

  Next, the calculation of the integral term shift amount θsf by the integral term correction unit 450 (FIG. 5) for coping with changes in the motor operating state will be described in detail with reference to FIG. In the first embodiment, the integral term correction unit 450 (FIG. 5) calculates the integral term shift amount θsf according to the change in the motor rotation speed Nm among the motor variables indicating the motor operation state.

  Referring to FIG. 7, from the operating point Pa corresponding to the current voltage phase θ0 on the torque characteristic line 500 corresponding to the current motor operating state (Nm = N1), the change in the motor operating state, specifically the motor When the rotational speed Nm changes from N1 to N2, the operating point Pc corresponding to the voltage phase θ0 on the torque characteristic line 510 corresponding to the changed motor operating state is determined. Therefore, from the torque value T0 at the operating point Pa and the torque value T1 at the operating point Pc calculated from the equation (9), the motor rotation speed Nm changes from N1 to N2, that is, the motor operating state. A torque change amount ΔTtl (ΔTtl = T1−T0) corresponding to the change is obtained.

  Furthermore, the following equation (10) for calculating the tangent slope Ktl on each torque characteristic line is derived by differentiating the above equation (9) with the voltage phase θ.

  By substituting θ = θ0 and ω = 2π · (N2 / 60) · P into equation (10), the slope Ktl of the tangent TL at the operating point Pc of the torque characteristic line 510 is calculated. Then, on the tangent line TL, the operating point Pb # obtained by changing the output torque by the torque change amount ΔTtl can be obtained from the operating point Pc according to the tangent slope Ktl. That is, the voltage phase shift amount necessary to cancel the torque change amount ΔTtl can be obtained by the following equation (11). That is, the operating point Pc corresponds to the “first operating point”, the inclination Ktl corresponds to the “first inclination”, and θsf according to the equation (11) corresponds to the “first phase change amount”.

θsf = ΔTtl / Ktl (11)
As understood from the equation (9), according to the equation (9), an operation for calculating back the voltage phase θ corresponding to the target torque value from the current motor operation state and the target torque value, that is, on the torque characteristic line 510. It is difficult to directly calculate the operating point Pb corresponding to the target torque. On the other hand, according to the integral term correction unit 450 (FIG. 5), according to the torque characteristic line 510, the relatively simple calculation process based on the torque change amount ΔTtl and the tangential slope Ktl at the operating point Pc, The integral term shift amount θsf can be obtained.

  Referring to FIG. 5 again, the integral term correcting unit 450 outputs the integral term shift amount θsf obtained as described above to the integral control calculating unit 440. Specifically, in addition to the integration process of the torque deviation ΔTq, the integration control calculation unit 440 calculates the phase control amount θi according to the following equation (12) by executing a correction calculation using the integral term shift amount θsf.

θi (i) = θi (i−1) + ki · ΔTq−θsf (12)
In equation (12), θi (i−1) represents the phase control amount θi in the previous control cycle, and θi (i) represents the phase control amount θi calculated in the current control cycle. To do.

  Referring to FIG. 7 again, the voltage phase θv is obtained by introducing an integral term shift amount θsf for canceling the torque change amount ΔTtl (here, ΔTtl> 0) due to the change in the motor rotation speed (motor operating state). , Θ0 to θ1 (θ1 = θ0−θsf). As a result, AC electric motor M1 operates at operating point Pd corresponding to voltage phase θ1 on torque characteristic line 510, and its output torque is T2. The torque deviation (T0-T2) with respect to the target torque T0 corresponding to the torque command value Tqcon is compensated by the feedback control loop of FIG. As a result, feedback control is performed so that the voltage phase θv changes from the operating point Pd to the original operating point Pb, that is, the voltage phase changes from θ1 to θ0 #.

  As understood from the comparison between FIG. 6 and FIG. 7, comparison is made with general feedback control in which the voltage phase is controlled toward the operating point Pb according to the torque deviation after the operating point is moved from Pa to Pc. Thus, according to the rectangular wave voltage control of the first embodiment, the operating point can be directly shifted from Pa to Pd in response to a change in the motor rotation speed (motor operating state). Therefore, it is possible to reduce the torque deviation caused by the change of the motor operating state, which becomes a disturbance to the torque feedback control according to the normal PI (proportional integral) control, and the control responsiveness can be improved.

  Further, details of a control processing procedure for realizing the rectangular wave voltage control according to the first embodiment will be described using the flowcharts of FIGS. 8 and 9. The control process according to FIGS. 8 and 9 is executed at predetermined control cycles.

  In addition, each step of each flowchart demonstrated below including FIG. 8 and FIG. 9 is implement | achieved by the software processing by the predetermined | prescribed program execution previously stored by the control apparatus 30, or the hardware processing by the action | operation of an electronic circuit. be able to.

  Referring to FIG. 8, in step S100, control device 30 calculates deviation ΔTq of torque that is a target of feedback control of AC electric motor M1 with respect to torque command value Tqcom. The processing in step S100 corresponds to the functions of the power calculation unit 410, torque calculation unit 420, and deviation calculation unit 425 in FIG.

  In step S110, control device 30 calculates proportional term θp based on deviation ΔTq obtained in step S100. Specifically, the proportional term θp = Kp · ΔTq is calculated according to the product of a predetermined proportional gain Kp and deviation ΔTq. The processing in step S110 corresponds to the function of the proportional control calculation unit 430 in FIG.

  The control device 30 executes the integration process in step S120. That is, the integration process is executed so that the product of the deviation ΔTq in the current control cycle and the predetermined integration gain Ki is integrated with the previous value of the integration term θi.

  Further, in step S130, control device 30 calculates integral term shift amount θsf in accordance with the change in the motor operating state. That is, the process of step S130 corresponds to the function of the integral term correction unit 450 in FIG. Details of the control processing procedure in step S130 will be described later.

  Then, in step S140, the control device 30 obtains the integral term θi by correcting the integral processing result in step S120 using the integral term shift amount θsf obtained in step S130. Further, in step S150, control device 30 calculates voltage phase θv in the current control cycle in accordance with the sum of proportional term θp and integral term θi. That is, the processing in steps S120 and S140 corresponds to the function of integration control calculation unit 440 in FIG. 5, and the processing in step S150 corresponds to the function of addition unit 455 in FIG.

  Then, the switching command of the inverter 14, that is, the switching control of the switching elements Q3 to Q8, for realizing the voltage phase θv calculated in step S150 by the rectangular wave generator 460 and the signal generator 470 shown in FIG. Signals S3-S8 are generated.

  Next, the details of the integral term shift amount calculation processing in step S130 in FIG. 8 will be described with reference to FIG.

  Referring to FIG. 9, control device 30 uses step S200 to use the current voltage phase command (θ0) set in the previous control cycle and the rotation speed (N1) in the previous control cycle, Torque calculation is performed using equation (9). The calculation in step S200 corresponds to a calculation for obtaining the torque value T0 at the operating point Pa corresponding to the voltage phase θ0 on the torque characteristic line 500 according to the motor operating state (rotational speed) in the previous control cycle.

  Further, in step S210, control device 30 performs torque calculation according to equation (9) using the current voltage command (θ0) and the rotation speed (N2) in the current control cycle. The calculation in step S210 corresponds to a calculation for obtaining the torque value T1 at the operating point Pc corresponding to the voltage phase θ0 on the torque characteristic line 510 according to the motor operating state (rotational speed) in the current control cycle.

  Further, the control device 30 calculates a tangential slope Ktl at the operating point Pc in step S220. As described above, the slope Ktl of the tangent TL at the operating point Pc is calculated according to the equation (10).

  Further, in step S230, the control device 30 calculates a torque change amount ΔTtl corresponding to a change in the motor operating state, that is, a change in the rotational speed from N1 to N2, from the torque calculation results in steps S200 and S210. .

  In step S240, the control device 30 calculates an integral term shift amount θsf = Δtl / Ktl based on the torque change amount ΔTtl obtained in step S230 and the tangential slope Ktl obtained in step S220.

  In step S240, as shown in FIG. 7, according to the slope of the tangent TL at the operating point Pc corresponding to the current motor operating state (rotational speed N2) and the voltage phase (θ0), under the current motor operating state, Θsf can be obtained as the amount of torque change necessary to cancel the torque change amount ΔTtl accompanying the change in the motor operating state.

  According to the rectangular wave voltage control according to the first embodiment, when the rotational speed, which is one of the motor operating states, changes, the integral term shift amount θsf for canceling the torque change amount due to the change is expressed as a torque calculation formula and Calculations can be performed according to the differential equations (Equations (9) and (10)), and can be reflected in feedback control as the shift amount of the integral term θi.

  As a result, in the rectangular wave voltage control in which the torque of the AC motor M1 is feedback-controlled every predetermined control cycle, the voltage phase can be immediately changed so as to cancel out the torque change amount due to the change in the motor operation state. It is possible to prevent the torque deviation from increasing even when the motor operating state changes, and to ensure control response.

[Variation 1 of Embodiment 1]
In the first embodiment, the control when the rotational speed of AC electric motor M1 is changed as the motor operating state has been described. In the first modification of the first embodiment, a rectangular wave voltage control corresponding to a change in the system voltage VH that is the DC side voltage of the inverter 14 will be described as another example of the motor operating state.

  FIG. 10 shows the behavior of the rectangular wave voltage control when the system voltage VH is changed from V1 (low voltage) to V2 (high voltage) while the other motor operation states are not changed as compared with FIG. The conceptual diagram explaining is shown.

  FIG. 10 shows an output torque behavior when the system voltage corresponding to the applied voltage amplitude of the AC motor M1 is changed from V1 (low voltage) to V2 (high voltage) as an example of the motor operating state change.

  Referring to FIG. 10, torque characteristic lines 500 and 510 are obtained by substituting V1 and V2 into system voltage VH in equation (9) when other motor operation states are fixed, respectively. As can be understood from the comparison of the torque characteristic lines 500 and 510, generally, for the same voltage phase, the characteristic that the output torque increases as the system voltage increases is shown. Similarly, in the regenerative region (not shown), the absolute value of the output torque increases as the system voltage increases for the same voltage phase.

  When the system voltage VH rises to V2 from the state where the output torque is controlled to the torque command value Tqcom and the voltage phase θv = θ0 (operating point Pa) when the system voltage VH = V1, the voltage phase becomes θ0. Even if it remains, the output torque rises to T1 (operating point Pc). In general feedback control, the voltage phase θv is equal to the voltage phase θ0 # (the operating point Pb) at which the output torque becomes the torque command value Tqcom on the torque characteristic line 510 so as to eliminate the resulting torque deviation ΔTq. ) To gradually change. Therefore, in the same way as described with reference to FIG. 6, in general feedback control, after a torque deviation due to a change in the motor operation state (for example, system voltage) occurs, a control operation is performed to compensate for the torque deviation. It is.

  Therefore, in the rectangular wave voltage control according to the first modification of the first embodiment, as shown in FIG. 11, the integral term shift amount θsf is calculated by the integral term correction unit 450 (FIG. 5).

  Referring to FIG. 11, when system voltage VH changes from V1 to V2, tangent line TL at operating point Pc at voltage phase θv = θ0 on torque characteristic line 510 when system voltage VH = V2. The integral term shift amount θsf is calculated as a voltage phase for canceling the torque change amount ΔTtl caused by the change in the system voltage VH (V1 → V2). That is, the process described with reference to FIG. 11 corresponds to the process in FIG. 7 in which the rotation speed is replaced with the system voltage, and thus the description thereof will not be repeated.

  FIG. 12 is a flowchart illustrating a calculation processing procedure of the integral term shift amount θsf in the first modification of the first embodiment. In the rectangular wave voltage control according to the first modification of the first embodiment, the calculation of the integral term shift amount (step S130 in FIG. 8) is compared with the rectangular wave voltage control according to the first embodiment in the flowchart shown in FIG. Instead, it is executed in accordance with the flowchart shown in FIG. Since other points are the same as in the first embodiment, detailed description will not be repeated.

  Comparing the flowcharts of FIG. 12 and FIG. 9, in Modification 1 of Embodiment 1, control device 30 executes steps S212 to S232 instead of steps S200 to S230.

  In step S202, the control device 30 uses the current voltage phase command (θ0) set in the previous control cycle and the system voltage (V1) in the previous control cycle to calculate the torque according to equation (9). To do. The calculation in step S202 corresponds to the operation in which the rotation speed N1 is replaced with the system voltage V1 in step S200 of FIG.

  Further, in step S212, control device 30 performs torque calculation according to equation (9) using current voltage command (θ0) and system voltage (V2) in the current control cycle. The calculation in step S212 corresponds to the operation in which the rotation speed N2 is replaced with the system voltage V2 in step S210 of FIG.

  Further, the control device 30 calculates a tangent slope Ktl at the operating point Pc in step S222. Specifically, the gradient Ktl of the tangent TL at the operating point Pc is calculated by substituting the system voltage VH = V2 and the voltage phase θ0 into the equation (10) into the equation (10).

  In step S232, control device 30 calculates a torque change amount ΔTtl (ΔTtl = T1-T0) that is generated when the system voltage changes from V1 to V2. That is, the processing in step S232 also corresponds to the processing in which the rotation speed change is replaced with the system voltage change in step S230 in FIG.

  In step S240, control device 30 calculates integral term shift amount θsf (θsf = ΔTtl / Ktl) in accordance with tangential slope Ktl obtained in step S222 and torque change amount ΔTtl obtained in step S232.

  As described above, according to the rectangular wave voltage control of the first modification of the first embodiment, the DC link voltage of the inverter 14 corresponding to the amplitude of the motor drive voltage, which is one of the motor operation states, that is, the system voltage VH. When the voltage changes, the voltage phase change amount for canceling the torque change amount due to the change is calculated as an integral term shift amount θsf according to the torque calculation formula and its differential formula (formulas (9) and (10)). The amount of shift of the integral term θi can be reflected in the feedback control.

  As a result, as in the first embodiment, in the rectangular wave voltage control in which the torque of the AC motor M1 is feedback-controlled every predetermined control period, the amount of torque change due to the change in the motor operating state (system voltage) is canceled out. Since the voltage phase can be changed immediately, it is possible to prevent the torque deviation from increasing even when the motor operating state changes and to ensure control responsiveness.

  In particular, as in the control system configuration shown in FIG. 1, in the configuration in which the system voltage VH is actively variably controlled by the converter 12 in accordance with the output (rotation speed, torque, etc.) of the AC motor M1, the motor drive The frequency of the voltage amplitude, that is, the frequency with which the system voltage VH changes increases. Therefore, the effect of reflecting the change in the system voltage VH as the change in the motor operating state and reflecting it in the integral term shift amount is enhanced.

  As for system voltage VH, the above-described arithmetic processing may be performed using the detection value of voltage sensor 13, or command value VHref of system voltage VH may be used.

[Modification 2 of Embodiment 1]
In the second modification of the first embodiment, the integral term shift amount corresponding to the change in the motor operating state is calculated based on both the motor rotation speed and the system voltage by combining the first embodiment and the first modification. The control configuration will be described.

  FIG. 13 is a conceptual diagram for explaining the behavior of the rectangular wave voltage control when both the system voltage VH and the rotation speed Nm are changed, compared with FIG. In FIG. 13, as yet another example of the change in the motor operating state, the system voltage corresponding to the applied voltage amplitude of the AC motor M1 changes from V1 (low voltage) to V2 (high voltage), and the rotational speed Nm is The torque behavior when changing from N1 (high rotation) to N2 (low rotation) is shown.

  Referring to FIG. 13, torque characteristic lines 500 and 510 are obtained by substituting V1, ω (N1) and V2, ω (N2) for system voltage VH and angular velocity ω in equation (9), respectively. . That is, even if both the rotational speed (angular speed) and the system voltage are used as motor variables, the torque characteristic lines 500 and 510 can be set when the motor operating state changes according to the equation (9).

  For example, when the system voltage V1 and the rotation speed N1 are set, the output torque is controlled to the torque command value Tqcom and the voltage phase θv = θ0 (the operating point Pa on the torque characteristic line 500), so that the system voltage V2 When the rotational speed changes to N2, the output torque rises to T1 even when the voltage phase remains at θ0 (operating point Pc). In general feedback control, after a torque deviation ΔTq due to a change in the motor operation state occurs once, the voltage phase θv is a voltage phase θ0 # at which the output torque becomes the torque command value Tqcom along the torque characteristic line 510. It gradually changes toward (operating point Pb).

  In the rectangular wave voltage control according to the second modification of the first embodiment, as shown in FIG. 14, both the motor rotational speed and the system voltage are reflected in the calculation of the integral term shift amount θsf as the motor operating state.

  Referring to FIG. 14, in each control cycle, system voltage and rotation are calculated from slope Ktl of tangent TL at operating point Pc on torque characteristic line 510 corresponding to the current motor operating state and voltage phase (θv = θ0). The integral term shift amount θsf is calculated as a voltage phase for canceling the torque change amount ΔTtl caused by the change in speed (change in the motor operation state).

  FIG. 15 is a flowchart illustrating a calculation processing procedure of the integral term shift amount θsf in the second modification of the first embodiment. In the rectangular wave voltage control according to the second modification of the first embodiment, the calculation of the integral term shift amount (step S130 in FIG. 8) is compared with the rectangular wave voltage control according to the first embodiment in the flowchart shown in FIG. Instead, it is executed in accordance with the flowchart shown in FIG. Since other points are the same as in the first embodiment, detailed description will not be repeated.

  15 and FIG. 9, in the second modification of the first embodiment, control device 30 executes steps S214 to S234 instead of steps S200 to S230.

  In step S204, the control device 30 uses the current voltage phase command (θ0) set in the previous control cycle, the system voltage (V1) and the rotation speed (N1) in the previous control cycle, Torque calculation according to (9) is performed. The calculation in step S204 corresponds to the calculation in which the rotation speed N1 is replaced with both the rotation speed N1 and the system voltage V1 in step S200 of FIG.

  Further, in step S214, control device 30 performs torque calculation according to equation (9) using current voltage command (θ0), system voltage (V2) and rotation speed (N2) in the current control cycle. The calculation in step S212 corresponds to the operation in which the rotation speed N2 is replaced with both the rotation speed N2 and the system voltage V2 in step S210 of FIG.

  Further, the control device 30 calculates a tangential slope Ktl at the operating point Pc in step S224. Specifically, the tangent TL at the operating point Pc is obtained by substituting the system voltage VH = V2, the angular velocity ω (N2) corresponding to the rotational speed N2, and the voltage phase θ0 into the equation (10). Is calculated.

  In step S234, control device 30 calculates a torque change amount ΔTtl (ΔTtl = T1-T0) that is generated when the system voltage and the rotation speed change (V1, N1 → V2, N2).

  In step S240, control device 30 calculates integral term shift amount θsf (θsf = ΔTtl / Ktl) according to tangential slope Ktl obtained in step S224 and torque change amount ΔTtl obtained in step S234.

  As described above, according to the rectangular wave voltage control of the second modification of the first embodiment, both the motor rotation speed and the amplitude of the motor drive voltage, that is, the DC link voltage (system voltage VH) of the inverter 14 are changed. , The integral term shift amount θsf, which is the voltage phase change amount for canceling out the torque change amount due to the change, can be calculated according to the torque calculation expression and its differential expressions (expressions (9) and (10)).

  That is, according to the AC motor control system shown in the first embodiment and its modifications 1 and 2, in the rectangular wave voltage control in which the torque of AC motor M1 is feedback-controlled every predetermined control cycle, the motor rotation speed and Because the voltage phase can be changed immediately so that the amount of torque change due to changes in motor operating conditions represented by system voltage can be offset, torque deviations can be prevented from increasing even when motor operating conditions change. Thus, control responsiveness can be ensured.

[Embodiment 2]
In the first embodiment and the first and second modifications thereof, the integral term shift amount is calculated by using the slope of the tangent at the current operating point Pc on the torque characteristic line 510 according to the current motor operating state in FIGS. Based on the above, the operation point Pb # is executed instead of the operation point Pb that should originally be obtained. Therefore, depending on the voltage phase region, the difference between the operating points Pb # and Pb due to the difference in the tangential slope between the operating points Pa and Pb may increase the setting error of the integral term shift correction amount θsf. There is sex.

  Therefore, in the second embodiment, the current operating point Pc and the original operating point Pb in the method for more accurately obtaining the integral term shift amount θsf for compensating for the change in the motor operating state, that is, in FIGS. A calculation process for making the voltage phase difference (θ0−θ0 #) of the current and the integral term shift correction amount θsf closer to each other will be described.

  Referring to FIG. 16, torque characteristic line 500 is obtained by substituting motor operating state (system voltage and / or motor rotational speed) in the previous control cycle into equation (9). Is obtained by substituting the current motor state (system voltage and / or motor rotational speed) into equation (9).

  Voltage phase difference (θ0−θ1) between the operating point Pb # obtained from the torque change amount ΔTtl caused by the change in the motor operating state and the slope Ktl of the tangent TL at the operating point Pc, and the current operating point Pc Corresponds to the integral term shift amount in the rectangular wave voltage control according to the first embodiment.

  In the rectangular wave voltage control according to the second embodiment, the operating point Pd (torque value T2) on the torque characteristic line 510 at the voltage phase θ1 at the operating point Pb # on the tangent line TL is further obtained. Then, an operating point Pe that is the torque value T0 of the straight line 520 connecting the operating points Pd and Pc is obtained. From FIG. 16, it is geometrically understood that the voltage phase θ2 at the operating point Pe is closer to the voltage phase θ0 # at the original operating point Pb than the voltage phase θ1 at the operating point Pb #.

  In the rectangular wave voltage control according to the second embodiment, the calculation of the integral term shift amount (step S130 in FIG. 8) is shown in FIG. The difference is that it is executed according to the flowchart shown. Since the other points are the same as in the first embodiment or its modifications 1 and 2, detailed description will not be repeated. The voltage phase between the operating points Pa and Pe is obtained according to the arithmetic processing shown in FIG.

  Referring to FIG. 17, in step S300, control device 30 executes torque calculation according to equation (9) using current voltage phase θ0 and the motor operating state in the previous control cycle. That is, according to the torque characteristic line 500, the torque value T0 at the operating point Pa is calculated. Further, in step S310, control device 30 executes torque calculation according to equation (9) using the current voltage phase θ0 and the motor operating state in the current control cycle. That is, the torque value T1 at the operating point Pc on the torque characteristic line 510 is calculated.

  Further, in step S320, the control device 30 calculates the slope Ttl of the tangent TL of the operating point Pc according to the equation (10) using the motor operating state in the current control cycle, and in step S330, the motor operating state is calculated. A torque change amount ΔTtl (ΔTtl = T1−T0) due to the change is calculated. In step S340, control device 30 obtains voltage phase θ1 of operating point Pb # based on slope Ktl of tangent TL and torque change amount ΔTtl (θ1 = θ0−ΔTtl / Ktl). The processes in steps S300 to S340 are the same as the rectangular wave voltage control according to the first embodiment.

  In step S350, control device 30 performs torque calculation on torque characteristic line 510 using voltage phase θ1. Thereby, the torque value T2 of the operating point Pd is obtained. In step S360, control device 30 calculates slope k = (T1-T2) / (θ0−θ1) of straight line 520 passing through operating points Pc and Pd.

  Further, in step S400, control device 30 sets voltage phase difference ΔTtl / k between operating points Pa and Pe obtained from slope k and torque change amount ΔTtl obtained in step S360 as integral term shift amount θsf. The operating point Pd corresponds to the “second operating point”, the inclination k corresponds to the “second inclination”, and θsf by ΔTtl / k corresponds to the “second phase change amount”.

  As described above, according to the rectangular wave voltage control according to the second embodiment, the voltage phase change amount for canceling the torque change amount ΔTtl due to the change in the motor operation state, that is, the integral term shift amount, according to the torque calculation formula and its differential formula. θsf can be set more precisely.

  As a result, in the rectangular wave voltage control in which the torque of the AC motor M1 is feedback-controlled every predetermined control cycle, it is possible to further suppress the deviation generated according to the change of the motor operation state and to ensure the control responsiveness. It becomes.

[Modification of Embodiment 2]
In the modification of the second embodiment, a method for more accurately obtaining the integral term shift amount θsf for compensating for the change in the motor operation state will be described.

  FIG. 18 is a conceptual diagram for explaining the calculation of the integral term shift amount in the rectangular wave voltage control according to the modification of the second embodiment.

  Referring to FIG. 18, in the modification of the second embodiment, after obtaining the operating point Pe as in the second embodiment, the operating point Pf (on the torque characteristic line 510 at the voltage phase θ2 of the operating point Pe) is obtained. Torque value T3) is further obtained. When the torque difference | T3−T0 | is equal to or larger than a predetermined value, the slope k ′ of the straight line 530 is obtained, and the voltage phase is ΔTtl / k ′ from the operating point Pc (voltage phase θ0) on the straight line 530. The operating point Pe is updated to the moved operating point. Thereby, the voltage phase of the updated operating point Pe can be brought closer to the voltage phase θ0 # of the original operating point Pb than the voltage phase of the operating point Pe before the update.

  Since the operating point Pf is also updated in accordance with the update of the operating point Pe, the torque difference | T3-T0 | can be evaluated again. Therefore, each time the operating point Pe is updated, the torque difference | T3-T0 | is compared with a predetermined value, and the updating process of the operating points Pe and Pf is repeated while the torque difference | T3-T0 | With this configuration, the torque deviation after application of the integral term shift amount θsf can be suppressed within a certain range.

  Also in the rectangular wave voltage control according to the modification of the second embodiment, the integral term shift amount is calculated (step S130 in FIG. 8) as compared with the rectangular wave voltage control according to the first embodiment and its modifications 1 and 2. The difference is that it is executed according to the flowchart shown in FIG. Since other points are the same as in the first embodiment or the first and second modifications, detailed description will not be repeated. According to the arithmetic processing shown in FIG. 19, the voltage phase between the operating points Pa and Pe is obtained.

  Referring to FIG. 19, after the processing in steps S300 to S360 similar to FIG. 17, control device 30 changes voltage phase θv from operating point Pc (voltage phase θ0) on line 520 to ΔTtl / k in step S400. The voltage phase θ2 of the operating point Pe moved by only this is calculated.

  Further, in step S410, control device 30 obtains torque value T3 of operating point Pf, which is voltage phase θ2 on torque characteristic line 510, according to equation (9) using the motor operating state in the current control cycle. . In step S420, the control device 30 calculates a torque difference (absolute value) between the torque value T0 corresponding to the torque target value (torque command value Tqcom) and the torque value T3 of the operating point Pf obtained in step S410. It is determined whether it is smaller than a predetermined threshold value ε.

  When the torque difference | T3−T0 | <ε (when YES is determined in S420), the torque deviation caused by adopting the operating point Pf is predicted to be smaller than the threshold value ε. Therefore, control device 30 sets the voltage phase difference between operating points Pa and Pe to the integral term shift amount in step S370 #. That is, the integral term shift amount θsf = θ0−θ2 is set.

  On the other hand, if deviation | T3−T0 | ≧ ε in step S420 (when NO is determined in S420), control device 30 is shown in FIG. 20 in order to bring operating point Pf closer to original operating point Pb. The operating points Pe and Pf are updated by the processing.

  Referring to FIG. 20, when NO is determined in step S420, control device 30 obtains slope k ′ of straight line 530 passing through operating points Pc and Pf in step S430. In step S440, control device 30 updates operating point Pe to a point where voltage phase is moved by ΔTtl / k ′ from operating point Pc on straight line 530. Further, in step S450, control device 30 updates operating point Pf to a point on torque characteristic line 510 in the voltage phase of operating point Pe updated in step S440. Along with this, the torque value T3 of the operating point Pf is also updated. Then, based on the updated torque value T3, the determination in step S420 is performed again.

  Until the deviation | T3−T0 | <ε and step S420 is YES, the updating process of the operating points Pe and Pf in steps S430 to S450 in FIG. 20 is repeatedly executed. As a result, the integral term shift amount θsf can be set so that the torque deviation when the integral term shift amount θsf is applied is equal to or less than ε when the motor operating state changes. In consideration of the calculation load of the control device 30 and the calculation required time, the number of executions of the update processing of the operating points Pe and Pf (steps S430 to S450) at the time of NO determination in step S420 is a predetermined number (one time). (Multiple times) can be limited in advance.

  As described above, according to the rectangular wave voltage control according to the modification of the second embodiment, the voltage phase change amount for canceling the torque change amount ΔTtl due to the change in the motor operating state, that is, the integral, according to the torque calculation equation and the differential equation thereof. The term shift amount θsf can be set more precisely so that the torque deviation is smaller than a predetermined value (threshold value ε).

  In the present embodiment, as a preferable configuration example, DC voltage generation unit 10 # of the motor control system includes buck-boost converter 12 so that the input voltage (system voltage VH) to inverter 14 can be variably controlled. However, as long as the input voltage to inverter 14 can be variably controlled, DC voltage generation unit 10 # is not limited to the configuration exemplified in this embodiment. Further, it is not always indispensable that the inverter input voltage is variable, and the present invention is also applied to a configuration in which the output voltage of the DC power supply B is directly input to the inverter 14 (for example, a configuration in which the step-up / down converter 12 is omitted). The invention can be applied. Further, the motor variable reflected in the torque calculation formula is not limited to the above description (Nm and VH).

  Further, with regard to the AC motor serving as a load of the motor control system, in the present embodiment, a permanent magnet motor mounted for driving a vehicle on an electric vehicle (hybrid vehicle, electric vehicle, etc.) is assumed. The present invention can also be applied to a configuration in which an arbitrary AC motor used in the above is used as a load.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is an overall configuration diagram of an AC motor control system according to an embodiment of the present invention. FIG. It is a conceptual diagram explaining the control system used for the power conversion in the inverter in the motor control system shown in FIG. It is a conceptual diagram which shows the rough relationship between the driving | running state of an alternating current motor, and control mode. It is a conceptual diagram which shows the correspondence of the voltage phase and torque in rectangular wave voltage control. It is a functional block diagram for demonstrating the specific control structure of rectangular wave voltage control. It is a conceptual diagram explaining the torque behavior at the time of the motor rotational speed change at the time of application of general feedback control. FIG. 6 is a conceptual diagram for explaining in detail the calculation of an integral term shift amount by an integral term correction unit shown in FIG. 5. 3 is a flowchart showing a control processing procedure for realizing rectangular wave voltage control according to the first embodiment. It is a flowchart explaining the detail of the integral term shift amount calculation process in FIG. It is a conceptual diagram explaining the torque behavior at the time of the system voltage change at the time of application of general feedback control. 6 is a conceptual diagram for explaining calculation of an integral term shift amount by an integral term correction unit in rectangular wave voltage control according to Modification 1 of Embodiment 1. FIG. 10 is a flowchart illustrating details of integral term shift amount calculation processing in rectangular wave voltage control according to Modification 1 of Embodiment 1. It is a conceptual diagram explaining the torque behavior at the time of the system voltage and rotation speed change at the time of application of general feedback control. FIG. 10 is a conceptual diagram for explaining calculation of an integral term shift amount by an integral term correction unit in rectangular wave voltage control according to Modification 2 of Embodiment 1. 10 is a flowchart illustrating details of integral term shift amount calculation processing in rectangular wave voltage control according to Modification 2 of Embodiment 1; 6 is a conceptual diagram for explaining calculation of an integral term shift amount in rectangular wave voltage control according to Embodiment 2. FIG. 10 is a flowchart illustrating details of integral term shift amount calculation processing in rectangular wave voltage control according to the second embodiment. FIG. 11 is a conceptual diagram for explaining calculation of an integral term shift amount in rectangular wave voltage control according to a modification of the second embodiment. 10 is a flowchart (part 1) illustrating details of integral term shift amount calculation processing in rectangular wave voltage control according to a modification of the second embodiment. 10 is a flowchart (part 2) illustrating details of integral term shift amount calculation processing in rectangular wave voltage control according to a modification of the second embodiment.

Explanation of symbols

  5 Ground wire, 6, 7 Power line, 10, 13 Voltage sensor, 10 # DC voltage generator, 12 Converter, 14 Inverter, 15-17 Each arm, 24 Current sensor, 25 Rotation angle sensor, 30 Control device (ECU) , 100 motor control system, 400 rectangular wave voltage control unit, 410 power calculation unit, 420 torque calculation unit, 425 deviation calculation unit, 430 proportional control calculation unit, 440 integral control calculation unit, 450 integral term correction unit, 455 addition unit, 460 square wave generator, 470 signal generator, 500 torque characteristic line (previous motor operation state), 510 torque characteristic line (current motor operation state), 520, 530 straight line, A1 low speed range, A2 medium speed range, A3 High speed range, ANG rotor rotation angle, B DC power supply, C0, C1 smoothing capacitor, D1-D8 Ode, iu, iv, iw Three-phase current (motor current), Ki integral gain, Kp proportional gain, L1 reactor, M1 AC motor, Nm, N1, N2 Motor rotational speed, Pa, Pb, Pc, Pd, Pe, Pf Operating point, Pmt motor power, Q1-Q8 power semiconductor switching element, S1-S8 switching control signal, SR1, SR2 system relay, T0-T3 torque value, TL tangent, Tq torque estimated value, Tqcom torque command value, V1, V2, VH DC voltage (system voltage), Vb DC voltage (battery voltage), VHref voltage command value (system voltage), Vu, Vv, Vw phase voltage command values, ΔTq torque deviation, ΔTtl torque change, θ0 #, θ0 to θ2, θv Voltage phase, θi phase control amount (integral term), θp phase control amount (ratio) Section), θsf integral term shift amount, ω electrical angular velocity.

Claims (9)

An inverter that converts a DC voltage into an AC voltage for driving an AC motor;
A rectangular wave control unit configured to change a voltage phase of a rectangular wave voltage applied from the inverter to the AC motor according to feedback control of torque deviation of the AC motor; and
The rectangular wave control unit
A proportional control calculation unit that sets a first control amount of the voltage phase based on a current value of the torque deviation;
An integration control calculation unit that sets a second control amount of the voltage phase based on the integration process of the torque deviation;
A control signal generator for generating a control command for the inverter in correspondence with the voltage phase according to the sum of the first and second control amounts;
The amount of change in torque corresponding to the amount of change in the motor variable and the amount of change in torque are offset according to a torque calculation equation using at least one motor variable related to the operating state of the AC motor and the voltage phase as a variable. An integral term correction unit configured to calculate a voltage phase shift amount,
The control system for an AC motor, wherein the integral control calculation unit is configured to change the second control amount in accordance with the voltage phase shift amount.   The integral term correction unit changes the voltage phase at the first operating point corresponding to the current operating state and the voltage phase according to a differential expression obtained by differentiating the torque calculation expression with the voltage phase. And calculating the voltage shift amount according to a first phase change amount obtained by dividing the torque change amount by the first inclination. The control system for an AC motor according to claim 1.   The integral term correction unit further includes a first voltage phase obtained by changing the voltage phase from the current value by the first phase change amount according to the torque calculation formula, and a second voltage corresponding to the current operating state. A torque value at an operating point is calculated, a second slope that is a ratio of a torque difference to a voltage phase difference between the first and second operating points is calculated, and the torque change amount is calculated as the torque change amount. The control system for an AC motor according to claim 2, wherein the voltage shift amount is calculated according to a second phase change amount obtained by dividing by a second slope. The integral term correction unit further includes a third voltage phase corresponding to a second voltage phase obtained by changing the voltage phase from the current value by the second phase change amount according to the torque calculation formula and a current operation state. A torque value at the third operating point is calculated, and it is determined whether or not a deviation between the calculated torque value and the torque target value is smaller than a predetermined value.
The integral term correction unit further includes a third slope that is a ratio of a torque difference to a voltage phase difference between the third and first operating points when the deviation is equal to or greater than the predetermined value. 4. The control system for an AC motor according to claim 3, wherein the voltage shift amount is calculated according to a third phase change amount obtained by dividing the torque change amount by the third slope. The integral term correcting unit further moves the third operating point to a voltage phase obtained by changing the voltage phase from the current value by the third phase change amount and an operating point corresponding to the current operating state. And updating the torque value at the third operating point according to the torque calculation formula,
The integral term correction unit compares the deviation between the updated torque value and the torque target value with the predetermined value each time the third operating point is updated, and the deviation is the predetermined value. The control system for an AC motor according to claim 4, configured to repeatedly execute the update process of the third operating point while the value is equal to or greater than a value.   The control system for an AC motor according to claim 1, wherein the motor variable includes a rotation speed of the AC motor.   The AC motor control system according to claim 1, wherein the motor variable includes the DC voltage.   The control system for an AC motor according to claim 7, further comprising a converter provided between the power storage device and the inverter and configured to control the DC voltage on the DC side of the inverter according to a voltage command value.   The control system for an AC motor according to any one of claims 1 to 8, wherein the AC motor is configured to be mounted on an electric vehicle and generate a vehicle driving force of the electric vehicle.

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