JP5618948B2 - Motor control system - Google Patents

Description

  The present invention relates to a motor control system, and more particularly to a motor control system that drives and controls an AC motor by converting a DC voltage boosted by a converter into an AC voltage by an inverter and applying the converted AC voltage.

  2. Description of the Related Art Conventionally, there has been known an electric vehicle including an electric motor that is driven by electric power from a battery and outputs power as a driving power source. A three-phase synchronous AC motor may be used for the electric motor. This three-phase synchronous AC motor is driven by converting a DC voltage supplied from a power source into a three-phase AC voltage by an inverter and applying it.

  In the electric vehicle, the DC voltage supplied from the battery may not be supplied to the inverter as it is, but may be boosted to a predetermined command value by a step-up / down converter and then input to the inverter. Thus, by boosting with the step-up / step-down converter and increasing the system voltage VH, there is an advantage that it is possible to drive the AC motor at higher torque and higher rotation.

  As a control method for the three-phase AC motor, sinusoidal pulse width modulation (PWM) control, overmodulation control, and rectangular wave control are well known. It is widely used that these control methods are selectively switched according to the driving conditions of the vehicle, a modulation factor described later, and the like.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 2006-31768) discloses maintaining a modulation rate at a specific control method at a target value in a motor control system capable of variably controlling an input voltage to an inverter. Yes. In this motor control system, the inverter (14) converts the system voltage VH into an AC voltage and applies it to the AC motor (M1) in accordance with torque control by the PWM control block (200). The modulation factor target value setting unit (310) sets a modulation factor that reduces the loss of the entire system in a specific control method in the inverter (14) in which the modulation factor is not fixed. The modulation factor target value (Kmd #) Set as. The modulation factor calculation unit (330) calculates the ratio of the amplitude (Vamp) of the necessary motor voltage to the input voltage to the inverter (14), that is, the system voltage (VH), and obtains the actual modulation factor (Kmd). The voltage command value generation unit (340) generates a voltage command value (VH #) for the system voltage (VH) based on a comparison between the actual modulation factor (Kmd) and the modulation factor target value (Kmd #). The converter (12) variably controls the system voltage (VH) based on the voltage command value (VH #).

JP 2006-31768 A

  In a motor control system including a converter, an inverter, and an AC motor as in the motor control system of Patent Document 1, the converter can operate by operating the AC motor by so-called one-pulse rectangular wave control by lowering the boosted voltage by the converter. Although it is advantageous to reduce the switching loss in the inverter, the rectangular wave control is voltage phase control under the field weakening control, and therefore the motor loss increases when the field weakening current increases. Conversely, operating the AC motor with sine-wave PWM control with a boosted voltage from the converter can reduce the motor loss, but the loss in the converter and inverter will increase due to the switching loss that accompanies an increase in the number of switchings. Become. Therefore, the loss of the entire system including the AC motor is minimized when the current vector of the motor current is on or near the optimum current advance line that outputs the maximum torque in the rectangular wave control.

  Thus, when attempting to control the operation of the AC motor in the rectangular wave control mode in which the current phase of the motor current is on or near the optimum current advance line, the modulation factor in the rectangular wave control is constant (for example, 0.78). Therefore, as described in Patent Document 1, the system voltage cannot be variably controlled with the modulation rate as a target.

  An object of the present invention is to provide a motor control system that can effectively reduce the loss of the entire system by positively using rectangular wave control on or near the optimum current advance line in an AC motor. .

A motor control system according to the present invention includes a converter capable of stepping up and down a DC voltage supplied from a power supply according to a system voltage command value, an inverter that converts a DC voltage as a system voltage output from the converter into an AC voltage, An AC motor driven by applying an AC voltage from an inverter, and the AC motor is controlled by sine wave PWM control, overmodulation control and rectangular wave control by controlling the converter and the inverter in accordance with an input torque command value. A control unit that can be driven and controlled by any one of the control methods, wherein the control unit is configured such that when the AC motor is under rectangular wave control, d of the motor current flowing through the AC motor The system is arranged such that the current phase of the current vector on the axis q-axis plane approaches the optimum current advance line. All SANYO for correcting the voltage command value, the system voltage correction value for correcting the system voltage command value changes the current phase of the motor current to the optimal current phase of the optimum current advance line on or near Ru is generated based on the system voltage deviation required to.

  In the motor control system according to the present invention, the control unit may include a system voltage correction unit that corrects the system voltage command value by current phase feedback control of a current vector of the motor current.

  In this case, the system voltage correction unit includes a system voltage deviation generation unit that generates a system voltage deviation based on the motor current, and a proportional integration control unit that generates a system voltage correction value to eliminate the system voltage deviation. It may be.

  In the motor control system according to the present invention, the control unit may define a step-up threshold line on the advance side of the optimum current advance line on the d-axis and q-axis planes, and a step-down threshold value on the retard side. A map in which a line is defined is stored, and when the current phase falls below the boost threshold line, the converter is boosted at a predetermined rate so as to return to the optimum current advance line, and the current phase However, the converter may be stepped down at a predetermined rate when it exceeds the step-down threshold line on the retard side.

  Furthermore, in the motor control system according to the present invention, the control unit corrects the system voltage command value by performing voltage phase feedback control so that the voltage phase of the AC voltage applied to the AC motor becomes a target voltage phase. A system voltage correction unit may be included.

  In this case, the system voltage correction unit generates a target voltage phase according to the corrected system voltage command value, and cancels the deviation between the target voltage phase and the actual command voltage phase. It may consist of a proportional integral control part which generates a system voltage correction value.

  According to the motor control system of the present invention, the AC motor can be operated by the rectangular wave control with the current phase on or near the optimum current advance line while suppressing the boosted voltage by the converter as low as possible. Thereby, the loss of the whole system can be reduced effectively.

1 is a diagram schematically showing an overall configuration of a motor control system. It is a figure which shows the voltage waveform and modulation factor of sine wave PWM control, overmodulation PWM control, and rectangular wave control. It is a figure which shows the map which prescribes | regulates the driving | running condition of a motor with a torque and rotation speed. It is a figure which shows the electric current phase of the motor electric current of sine wave PWM control, overmodulation control, and rectangular wave control on the d-axis q-axis plane. (A) is a graph showing the relationship between the system voltage VH and the system loss in the 3 control mode, (b) is a graph showing the relationship between the system voltage and the modulation factor in the 3 control mode, and (c) is the system in the 3 control mode. It is a graph which shows the relationship between a voltage and a motor electric current value. It is a block diagram which shows a control part. It is a block diagram which shows an example of the current phase feedback part in FIG. It is a figure similar to FIG. 3 which shows a mode that a control system switching line displaces by correct | amending a system voltage. It is a block diagram which shows the modification of the current phase feedback part in FIG. FIG. 7 is a block diagram similar to FIG. 6 showing a control unit including a voltage phase feedback unit instead of the current phase feedback unit. It is a block diagram which shows an example of the voltage phase feedback part in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments according to the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the accompanying drawings. In this description, specific shapes, materials, numerical values, directions, and the like are examples for facilitating the understanding of the present invention, and can be appropriately changed according to the application, purpose, specification, and the like. In addition, when a plurality of embodiments and modifications are included in the following, it is assumed from the beginning that these characteristic portions are used in appropriate combinations.

  FIG. 1 is a diagram illustrating an overall configuration of a motor control system 10 according to an embodiment. The motor control system 10 can be suitably used for a hybrid vehicle, an electric vehicle, or the like equipped with a motor as a driving power source.

  The motor control system 10 includes a battery 11 as a DC power source, voltage sensors 12 and 14, system main relays SMR 1 and SMR 2, smoothing capacitors 16 and 18, and a step-up / down converter (hereinafter simply referred to as “converter”) 20. The inverter 22, the current sensor 24, the control unit 26, and the AC motor M1 are provided.

  AC motor M1 is, for example, a drive motor for generating torque for driving drive wheels of a hybrid vehicle or an electric vehicle. Alternatively, AC motor M1 may be configured to have a function of a generator driven by an engine, or may be configured to have both functions of an electric motor and a generator. Furthermore, AC motor M1 may operate as an electric motor for the engine, and may be incorporated into a hybrid vehicle so that the engine can be started, for example.

  The battery 11 is a secondary battery such as nickel metal hydride or lithium ion. Alternatively, in addition to the secondary battery, a capacitor without a chemical reaction or a fuel cell may be used as the power supply device. Voltage sensor 12 detects a DC voltage or battery voltage Vb output from battery 11 and outputs the detected DC voltage Vb to control unit 26. The battery 11 is provided with a temperature sensor 28. The battery temperature Tb detected by the temperature sensor 28 is output to the control unit 26.

  System main relay SMR1 is connected between the positive terminal of battery 11 and power line 30, and system main relay SMR2 is connected between the negative terminal of battery 11 and ground line 32. System main relays SMR1 and SMR2 are turned on / off by a signal SE from control unit 26. More specifically, system main relays SMR1 and SMR2 are turned on by an H (logic high) level signal SE from control unit 26, and are turned off by an L (logic low) level signal SE from control unit 26. . Smoothing capacitor 16 is connected between power line 30 and ground line 32.

  Converter 20 includes a reactor L, power semiconductor switching elements E1 and E2, and diodes D1 and D2. Power semiconductor switching elements E 1 and E 2 are connected in series between power line 30 and ground line 32. On / off of power switching elements E1 and E2 is controlled by switching control signals S1 and S2 from control unit 26.

  As a power semiconductor switching element (hereinafter simply referred to as “switching element”), an IGBT (Insulated Gate Bipolar Transistor) or the like can be suitably used. Anti-parallel diodes D1 and D2 are arranged for switching elements E1 and E2.

  Reactor L is connected between a connection node of switching elements E1 and E2 and power line 30. The smoothing capacitor 16 is connected between the power line 30 and the ground line 32. The smoothing capacitor 16 has a function of smoothing the battery voltage Vb and supplying it to the inverter 22.

  Inverter 22 includes a U-phase arm 34, a V-phase arm 36, and a W-phase arm 38 that are provided in parallel between power line 30 and ground line 32. Each of the phase arms 34 to 38 includes a switching element connected in series between the positive power line 31 and the ground line 32. For example, the U-phase arm 34 includes switching elements E3 and E4, the V-phase arm 36 includes switching elements E5 and E6, and the W-phase arm 38 includes switching elements E7 and E8. Further, antiparallel diodes D3 to D8 are connected to the switching elements E3 to E8, respectively. On / off of the switching elements E3 to E8 is controlled by switching control signals S3 to S8 from the control unit 26.

  The midpoint of each phase arm 34-38 is connected to each phase end of each phase coil of AC motor M1. That is, the AC motor M1 is a three-phase synchronous permanent magnet motor, and is configured such that one end of three coils of U, V, and W phases are connected in common to the neutral point 39. Furthermore, the other end of each phase coil is connected to the midpoint of the switching elements of each phase arm 34-38.

  During the boosting operation, converter 20 supplies to inverter 22 a DC voltage obtained by boosting the DC voltage supplied from battery 11 (this DC voltage corresponding to the input voltage to inverter 22 is hereinafter referred to as “system voltage VH”). . More specifically, in response to the switching control signals S1 and S2 from the control unit 26, the ON period of the switching element E1 and the ON period of E2 are alternately provided, and the step-up ratio is equal to the ratio of these ON periods. It will be a response.

The step-up / step-down converter 20 is capable of boosting a DC voltage of, for example, 300 V supplied from the battery 11 up to a boosting upper limit voltage of, for example, 600 V. However, the boost upper limit voltage is not a fixed value, and may be variable according to, for example, the demand of the vehicle. For example, when the eco mode is selected by the driver's switch operation, an ECO signal is sent to the control unit 26. By inputting, the boost upper limit value of the converter 20 may be limited to, for example, 400V.

  Further, during the step-down operation, the step-up / step-down converter 20 steps down the DC voltage supplied from the inverter 22 via the smoothing capacitor 18 and charges the battery 11. More specifically, in response to the switching control signals S1, S2 from the control unit 26, a period in which only the switching element E1 is turned on and a period in which both the switching elements E1, E2 are turned off are alternately provided, The step-down ratio is in accordance with the duty ratio during the ON period.

  The smoothing capacitor 18 has a function of smoothing the DC voltage from the converter 20 and supplying it to the inverter 22. The voltage sensor 14 detects the voltage across the smoothing capacitor 18, that is, the system voltage VH, and outputs the detected value VH to the control unit 26.

  When the torque command value Tq * of AC motor M1 is positive (Tq *> 0), inverter 22 responds to switching control signals S3 to S8 from control unit 26 when DC voltage is supplied from smoothing capacitor 18. The AC motor M1 is driven so that the DC voltage is converted into an AC voltage by the switching operation of the switching elements E3 to E8 and a positive torque is output. Further, when the torque command value Tq * of AC motor M1 is zero (Tq * = 0), inverter 22 converts the DC voltage into an AC voltage by a switching operation in response to switching control signals S3 to S8. The AC motor M1 is driven so that the torque becomes zero. As a result, AC motor M1 is driven to generate a positive or zero torque designated by torque command value Tq *.

  Further, during regenerative braking of a vehicle equipped with motor control system 10, torque command value Tq * of AC motor M1 is set to a negative value (Tq * <0). In this case, the inverter 22 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 through the smoothing capacitor 18 into a converter. 20 is supplied. Note that regenerative braking here refers to braking with regenerative power generation when the driver driving a hybrid vehicle or electric vehicle performs foot braking, or turning off the accelerator pedal while driving, although the foot brake is not operated. This includes decelerating the vehicle (or stopping acceleration) while generating regenerative power.

  Current sensor 24 detects a motor current flowing through AC motor M <b> 1 and outputs the detected motor current to control unit 26. 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 AC motor M1 is provided with a rotation angle sensor 40 such as a resolver. The rotation angle sensor 40 detects the rotor rotation angle θ of the AC motor M <b> 1 and sends the detected rotation angle θ to the control unit 26. The control unit 26 calculates the rotation speed and rotation speed of the AC motor M1 based on the rotation angle θ.

  The control unit 26 includes a torque command value Tq * input from an external electronic control unit (ECU), a battery voltage Vb detected by the voltage sensor 12, a system voltage VH detected by the voltage sensor 14, and a current sensor. Based on the motor currents iu and iv from 24 and the rotation angle θ from the rotation angle sensor 40, the switching control signals S1 to S1 are output so that the AC motor M1 outputs torque according to the torque command value Tq * by a method described later. S8 is generated to control the operations of the converter 20 and the inverter 22.

  During the boosting operation of converter 20, control unit 26 performs feedback control on output voltage VH of smoothing capacitor 18, and generates switching control signals S1 and S2 such that output voltage VH of converter 20 becomes system voltage command value VH *. .

  Further, when the control unit 26 receives a signal indicating that the vehicle has entered the regenerative braking mode from the external ECU, the control unit 26 outputs the switching control signals S3 to S8 so as to convert the AC voltage generated by the AC motor M1 into a DC voltage. It is generated and output to the inverter 22. Thereby, inverter 22 converts the AC voltage generated by AC motor M <b> 1 into a DC voltage and supplies it to converter 20.

  Further, when receiving a signal indicating that the vehicle has entered the regenerative braking mode from the external ECU, the control unit 26 generates the switching control signals S1 and S2 so as to step down the DC voltage supplied from the inverter 22, and the converter 26 20 output. As a result, the AC voltage generated by AC motor M1 is converted into a stepped-down DC voltage and charged to battery 11.

  Next, power conversion in the inverter 22 controlled by the control unit 26 will be described in detail. In the motor control system 10 of the present embodiment, three control methods (or control modes) as shown in FIG.

  The sine wave PWM control method is used as a general PWM control. The switching element in each phase arm is turned on / off by changing the voltage between a sine wave voltage command value and a carrier wave (typically, a triangular wave). Control according to the comparison. 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 fundamental wave component is a sinusoidal AC voltage (motor) within one control cycle. The duty ratio is controlled so as to be the required voltage. As is well known, in a general sine wave PWM control system, the modulation factor Kmd, which is defined as the ratio of the amplitude of the required motor voltage to the system voltage VH, can be increased to 0.61. However, it is known that the modulation factor Kmd can be increased to 0.70 in the case of sinusoidal PWM control by the two-phase modulation method or the third harmonic superposition control.

  On the other hand, in the rectangular wave control method, one pulse of a rectangular wave whose ratio between the high level period and the low level period is 1: 1 is applied to the AC motor M1 within the one control period. In the rectangular wave control method, since the amplitude of the fundamental wave component is fixed, torque control is executed by voltage phase control of the rectangular wave pulse based on the deviation between the actual torque value obtained by power calculation and the torque command value. Thereby, the modulation factor Kmd is increased to 0.78.

  The overmodulation control method performs PWM control according to a voltage comparison between a sinusoidal voltage command value and a carrier wave as in the sine wave PWM control method. In this case, the voltage command value is larger than the carrier wave. As a result of generating a rectangular pulse having a relatively large duty ratio, the amplitude of the fundamental wave component having a substantially sinusoidal shape can be expanded, thereby increasing the modulation factor Kmd in the range of 0.61 to 0.78. Can do.

  In the motor control system 10 of the present embodiment, the AC motor M1 is driven by one of the above three control methods by supplying the battery voltage Vb as the system voltage VH to the inverter 22 without boosting the converter 20. Can do. FIG. 3 shows an example of a map showing application of the control method in that case. In this map, the horizontal axis represents the motor rotation speed and the vertical axis represents the motor output torque. As shown in FIG. 3, sine wave PWM control is applied from the low rotation speed region to the medium rotation speed region, overmodulation control is applied from the medium rotation region to the high rotation region, and rectangular wave control is performed in the higher rotation region. Is to be applied.

  The control unit 26 selects a control method from the three control methods as follows. In response to the torque command value Tq * of the AC motor M1 being calculated and inputted from the required vehicle output based on the accelerator opening etc. in an external ECU (not shown), the control unit 26 is set as shown in FIG. The required motor voltage is calculated from the torque command value Tq * of the AC motor M1 and the motor speed N based on a simple map.

  Then, the control unit 26 applies either the field weakening control (rectangular wave control method) or the maximum torque control (sine wave PWM control method / overmodulation control method) according to the relationship between the required motor voltage and the battery voltage Vb. Select whether to perform motor control. Whether to use the sine wave PWM control method or the overmodulation control method when applying the maximum torque control is selected according to the modulation rate range of the voltage command value according to the vector control. In other words, sine wave PWM control is selected when 0 <modulation rate ≦ 0.61, and overmodulation control is selected when 0.61 <modulation rate <0.78. Further, when the modulation factor ≦ 0.78, the rectangular wave control is selected.

  As described above, since the modulation factor Kmd is constant at 0.78 in the rectangular wave control, there is a limit to the output torque and the rotational speed obtained by the rectangular wave control executed using the battery voltage Vb as it is as the system voltage VH. is there. Therefore, when the output voltage corresponding to the torque command value cannot be output with the battery voltage Vb, the boost operation by the converter 20 is started and the system voltage VH is controlled to be increased. However, the converter 20 has a boost upper limit value (or a boost maximum value) due to the pressure resistance performance of the switching elements and the like constituting the converter 20 and the inverter 22. Therefore, when the system voltage VH reaches the boost upper limit value, the rectangular wave control method according to the field weakening control is applied while maintaining the state.

  FIG. 4 is a graph showing the current phases of the motor currents of sine wave PWM control, overmodulation control and rectangular wave control on the d-axis and q-axis planes. In this graph, the horizontal axis represents the d-axis current id and the vertical axis represents the q-axis current iq. The optimum current advance line is indicated by a broken line. This optimum current advance line is a line drawn by connecting the points of the optimum current phase (id, iq) opt at which the loss in the AC motor M1 is minimized, and memorizes those obtained beforehand by experiments, simulations, etc. I can leave it to you.

  As shown in FIG. 4, when the AC motor M1 is driven by sinusoidal PWM control and overmodulation control, the motor current generated by the inverter 22 is adjusted so that the current phase of the motor current matches the optimal current advance line. Control is performed. On the other hand, in the rectangular wave control, the absolute value of the d-axis current id, which is a field current, increases in order to perform field weakening control, so that the tip position of the current vector with the zero point position as the base point, that is, the current phase is the optimum current. The motor loss increases because it moves away from the advance line to the left side (or advance side) in the figure. This will be described next with reference to FIG.

  FIG. 5A is a graph showing the relationship between the system voltage VH and the system loss in the three control mode, and FIG. 5B is a graph showing the relationship between the system voltage VH and the modulation factor Kmd in the three control mode. These are graphs showing the relationship between the system voltage VH and the motor current phase in the three control modes.

  Referring to FIG. 5 (a), operating the AC motor M1 by so-called one-pulse rectangular wave control by lowering the boosted voltage of the converter 20 reduces the switching loss in the converter 20 and the inverter 22 and the entire system. It is advantageous to minimize the loss. However, since the rectangular wave control is voltage phase control under the field weakening control as described above, the motor loss increases as the field weakening current increases, and the loss of the entire system increases accordingly.

  Conversely, when the boosted voltage by the converter 20 is increased and the AC motor M1 is operated by sine wave PWM control, the motor loss can be reduced, but the loss in the converter and the inverter increases due to the switching loss accompanying the increase in the number of times of switching. It will be. Therefore, the loss of the entire system including the AC motor M1 is minimized when the current vector of the motor current is on or near the optimum current advance line that outputs the maximum torque in the rectangular wave control. Hereinafter, such a current phase on or near the optimum current advance line is referred to as optimum current phase (id, iq) opt. Further, in FIG. 4 and FIG. 5A, the operating point of the AC motor M1 by the rectangular wave control at the optimum current phase (id, iq) opt is indicated by reference numeral 42.

  Thus, when the motor current is the optimum current phase (id, iq) opt and the operation of the AC motor M1 is to be controlled by the rectangular wave control, the rectangular wave is shown in FIGS. 5B and 5C. Since the modulation rate Kmd in the control is constant (0.78), the system voltage VH cannot be optimally variably controlled by feedback control of the modulation rate Kmd.

  Therefore, in the motor control system 10 of the present embodiment, the control unit 26 corrects the system voltage command value VH * by feedback control of the current phase (id, iq) of the motor current flowing through the AC motor M1, thereby achieving the above optimum. The rectangular wave control with the current phase (id, iq) opt was actively utilized. Next, correction control of the system voltage command value by feedback control of the current phase in the control unit 26 will be described with reference to FIG.

  FIG. 6 is a block diagram illustrating a control configuration related to rectangular wave control and current phase feedback control in the control unit 26. The control configuration shown in FIG. 6 is realized by control arithmetic processing according to a predetermined program executed by the control unit, but part or all of the control configuration may be realized by hardware elements.

  The control unit 26 includes a three-phase / two-phase conversion unit 50, a torque estimation unit 52, a subtraction unit 53, a torque feedback unit 54, a system voltage command generation unit 56, a current phase feedback unit (system voltage correction unit) 58, and a system voltage. A feedback unit 60 is included.

  The three-phase / two-phase conversion unit 50 converts the three-phase motor currents iu, iv, iw flowing through the AC motor M1 into the two-phase currents id, iq of the d-axis and q-axis by coordinate conversion using the rotor rotation angle θ. Output function. Specifically, a U-phase current iu (= − (iv + iw)) is calculated from the V-phase current iv and the W-phase current iw detected by the current sensor 24, and based on these iu, iv and iw, the rotation angle sensor 40 is calculated. The d-axis current id and the q-axis current iq are generated and output according to the rotation angle θ detected by.

  The torque estimation unit 52 has a relationship between torque and current measured in advance as a map. By referring to the map based on the d-axis current id and the q-axis current iq input from the three-phase / two-phase conversion unit 50, The actual torque Tq is derived.

  The subtraction unit 53 generates a torque deviation ΔTq by comparing the torque command Tq * input from the external ECU with the actual torque Tq derived as described above, and inputs the torque deviation ΔTq to the torque feedback unit 54.

  The torque feedback unit 54 performs a PI operation with a predetermined proportional gain Gp and integral gain Gi on the torque deviation ΔTq to obtain a control deviation, and sets the phase Φv of the rectangular wave voltage according to the obtained control deviation. Specifically, when positive torque is generated (Tq> 0), the voltage phase is advanced when torque is insufficient, while when the torque is excessive, the voltage phase is delayed, and when negative torque is generated (Tq <0), the voltage phase is increased when torque is insufficient. While delaying, the voltage phase is advanced when the torque is excessive. In the present embodiment, description will be made on the assumption that proportional-integral control is executed in order to eliminate the torque deviation ΔTq. However, the present invention is not limited to this, and proportional-integral-derivative control (PID control) may be performed.

Further, the torque feedback unit 54 obtains the two-phase voltage command values Vd * and Vq * according to the voltage phase Φv, and converts these two-phase voltage command values Vd * and Vq * using the rotation angle θ. 2 phase → 3 phase) to convert to 3 phase voltage command value (rectangular wave pulse) Vu *, Vv *, Vw * and switch control signal according to these 3 phase voltage command values Vu *, Vv *, Vw * to generate a S 3 ~S8. As a result, when the inverter 22 performs a switching operation according to the switching control signals S3 to S8, a rectangular wave pulse according to the voltage phase Φv is applied as each phase voltage Vu, Vv, Vw of the AC motor M1.

  Based on the torque command value Tq * input from the external ECU and the motor rotation speed N calculated from the rotation angle θ, the system voltage command generation unit 56 refers to a preset table or map, etc. System voltage command value VH * is generated and output.

  System voltage feedback unit 60 generates switching control signals S <b> 1 and S <b> 2 to boost battery voltage Vb to input system voltage command value VH * and outputs it to converter 20. The switching elements E1 and E2 are turned on / off in response to this control signal, whereby the system voltage VH corresponding to the voltage command value VH * is supplied from the converter 20 to the inverter 22 via the smoothing capacitor 18.

  System voltage VH, which is the output voltage of converter 20, is detected by voltage sensor 14 and input to system voltage feedback unit 60. Thereby, a closed control loop is formed, and feedback control of the system voltage VH is performed. Specifically, the operation amount (specifically, the duty ratios of the switching elements E1 and E2 of the converter) so that the deviation between the system voltage command value VH * and the system voltage VH detected by the voltage sensor 14 is eliminated. ) Is subjected to, for example, PI calculation and feedback control.

  The current phase feedback unit 58 has a function of receiving the current phase (id, iq), which is the motor actual current generated by the three-phase / two-phase conversion unit 50, and outputting the system voltage correction value Cvh accordingly. Specifically, as shown in FIG. 7, the current phase feedback unit 58 includes a VH deviation generation unit 62 and a PI control unit 64.

  The VH deviation generator 62 is a system voltage deviation required to change the current phase (id, iq) of the motor current flowing through the AC motor M1 to the optimum current phase (id, iq) opt without changing the torque. ΔVH is generated, and a map referred to for this purpose is stored in the control unit 26 in advance. FIG. 7 shows an example in which the system voltage deviation ΔVH required to change the actual current phase to the optimum current phase indicated by reference numeral 42 is +60 volts.

  The system voltage deviation ΔVH is negative when the actual current phase (id, iq) is on the retarded side of the optimum current advance line and is changed to the optimum current phase (id, iq) opt. (That is, the step of decreasing the system voltage VH).

  The PI control unit 64 executes proportional-integral control for eliminating the system voltage deviation ΔVH generated by the VH deviation generation unit 62. Specifically, the PI control unit 64 performs a PI calculation with a predetermined proportional gain and integral gain to obtain a control deviation, specifically, a system voltage correction value Cvh, and then uses the system voltage correction value Cvh as a system The system voltage command value VH * generated by the voltage command generation unit 56 is added by the adding unit 59 to generate a corrected system voltage command value (VH * + Cvh). Such correction of the system voltage command value VH * is repeatedly executed in a closed control loop including the current phase feedback unit 58, whereby the current phase (id, iq) of the AC motor M1 is changed to the optimum current phase (id, iq) It is possible to accurately and quickly shift to a state in which the rectangular wave is controlled by opt.

  Note that the correction value Cvh of the system voltage VH may not be changed for a predetermined time after the control method of the AC motor M1 is switched. Further, the correction of the system voltage VH may not be performed for a predetermined time after the boosting operation by the converter 20 is started. These are effective in preventing hunting when the control mode is switched.

  FIG. 8 shows how the system voltage VH is corrected as described above on the rotational speed torque map. For example, as shown in the upper diagram of FIG. 8, the current overmodulation control region A2 of the AC motor M1 in a state where the battery voltage Vb is supplied as it is to the inverter 22 as the system voltage VH when the converter 20 is not boosting. Consider a case where the middle operating point X1 greatly exceeds the overmodulation rectangular wave switching line 70 and is about to move to the operating point X2 in the rectangular wave control region A3. The operating point X2 after this change is an operating point that can be driven by rectangular wave control without boosting by the converter 20. Here, the operating point X1 before the change is exemplified as the operating point in the overmodulation control region A2, but the same applies when the operating point X1 is in the sine wave PWM region A1.

  In such a case, in the motor control system 10 of the present embodiment, the boosting operation by the converter 20 is started and the system voltage VH is set high by correcting as described above, and as shown in the lower diagram in FIG. The overmodulation rectangular wave switching line 70 is shifted to the high rotation side (that is, the right side in the figure). Thereby, the operating point X2 becomes an operating point in the vicinity of the overmodulation rectangular wave switching line 70 and in the rectangular wave control region A3.

  On the contrary, the converter 20 is in a step-up operation, and the operating point of the AC motor M1 exceeds the rectangular wave control switching line 70 from the rectangular wave control region A3 to the overmodulation region A2 or the sine wave PWM region A1. When shifting to (1), the system voltage VH is set low by correcting the system voltage VH as described above. That is, the boosted voltage by converter 20 is lowered. As a result, the overmodulation rectangular wave switching line 70 shifts to the low rotation side (that is, the left side in the figure), and again becomes an operating point in the vicinity of the overmodulation rectangular wave switching line 70 and in the rectangular wave control region A3. In this case, when the corrected system voltage command value (VH * + Cvh) becomes lower than the battery voltage Vb, the converter 20 stops the boosting operation and performs overmodulation control or a sine wave with the battery voltage Vb as the system voltage VH. PWM control is executed.

  As described above, according to the motor control system 10 of the present embodiment, the AC motor M1 can be operated by the rectangular wave control at the optimum current phase (id, iq) opt while suppressing the boosted voltage by the converter 20 as low as possible. Thereby, the loss of the whole system including converter 20, inverter 22, and AC motor M1 can be effectively reduced.

  Next, a modification of the current phase feedback unit 58 will be described with reference to FIG. The buck-boost control of the converter 20 in this modification can be applied in combination with the correction of the system voltage VH described above, but may be used alone to correct the system voltage VH. Even when used alone, AC motor M1 can be operated by rectangular wave control while maintaining the motor current at or near the optimum current phase (id, iq) opt while keeping the boosted voltage by converter 20 as low as possible. It is.

  Current phase feedback unit 58 includes a step-up / step-down command unit 72, a step-up / step-down rate setting unit 74, and an integration control unit 76.

  The step-up / step-down command unit 72 stores a map 73 in which a step-up threshold line is defined on the advance side of the optimum current advance line on the d-axis q-axis plane and a step-down threshold line is defined on the retard side in the ROM or the like. I remember it. Then, when the current phase (id, iq) of the input motor current falls below the boost threshold line to the advance side, the converter 20 is commanded to return to the optimum current advance line, while the current is When the phase (id, iq) exceeds the step-down threshold line to the retard side, the step-down operation is commanded to the converter 20.

  Here, in the map 73, the margin m2 between the optimum current advance line and the step-down threshold line is preferably set smaller than the margin m1 between the optimum current advance line and the step-up threshold line. If the step-down control is delayed when the system voltage VH is a considerably high boost voltage, an overcurrent may occur in the inverter 22 and the like, so the overcurrent is effective by setting the margin m2 as described above. Can be suppressed.

  The step-up / step-down rate setting unit 74 sets a predetermined step-up rate + a when receiving a step-up command from the step-up / step-down command unit 72, and sets the step-down / step-up rate setting unit 74 to a predetermined step-down rate -b when receiving a step-down command from the step-up / step-down command unit 72. . Then, the integration control unit 76 performs integration control at the step-up rate + a or the step-down rate −b set by the step-up / step-down rate setting unit 74 to generate a correction value Cvh for the system voltage command value VH *.

  In this case, the step-up rate value a and the step-down rate value b may be the same or different. If they are different, it is preferable to set the step-up rate a smaller than the step-down rate b for the same reason as when the margins m1 and m2 are set.

  By controlling the step-up / step-down operation of the converter 20 by such hysteresis control, it is possible to suppress hunting for switching the control mode in the AC motor M1.

  Next, a motor control system 80 as another embodiment will be described with reference to FIGS. 10 and 11. Here, as the difference from the motor control system 10 will be mainly described, the same components are denoted by the same reference numerals, and redundant description will be omitted with the aid of the description.

  FIG. 10 is a block diagram similar to FIG. 6, showing a control unit including a voltage phase feedback unit instead of the current phase feedback unit. FIG. 11 is a block diagram illustrating an example of the voltage phase feedback unit in FIG. In the motor control system 80 of the present embodiment, the control unit 26 includes a voltage phase feedback unit (system voltage correction unit) 82 instead of the current phase feedback unit 58 that performs feedback control of the current phase of the current vector. Other configurations are the same as those of the motor control system 10.

  As shown in FIG. 10, the voltage phase feedback unit 82 receives an input of the command voltage phase Φv from the torque feedback unit 54 of the rectangular wave control block, generates a system voltage correction value Cvh based on this, and supplies the system voltage correction value Cvh to the adding unit 59. Has a function to output. The voltage phase feedback unit 82 is inputted with a system voltage command value VH * (exactly “VH * + Cvh”) corrected by adding a system voltage correction value Cvh described later.

  More specifically, the voltage phase feedback unit 82 includes a target voltage phase generation unit 84, a subtraction unit 86, and a PI control unit 88, as shown in FIG.

  In the target voltage phase generation unit 84, a map 85 that defines the relationship between the corrected system voltage command value VH * and the target voltage phase Φv_target is stored in advance in a ROM or the like, and the input system voltage command value VH *. Based on the above, the target voltage phase Φv_target is derived from the map 85. Here, the “target voltage phase Φv_target” is necessary to change the current phase (id, iq) of the motor current flowing through the AC motor M1 to the optimum current phase (id, iq) opt without changing the torque. This is the voltage phase of a square wave pulse.

  The target voltage phase Φv_target output from the target voltage phase generation unit 84 is compared or subtracted with the command voltage phase Φv by the subtraction unit 86 to generate a voltage phase deviation ΔΦv. The voltage phase deviation ΔΦv is input to the PI controller 88.

  The PI control unit 88 executes proportional integration control for eliminating the voltage phase deviation ΔΦv. Specifically, the PI control unit 88 obtains a control deviation, specifically a system voltage correction value Cvh, by performing a PI calculation with a predetermined proportional gain and integral gain, and the system voltage correction value Cvh The system voltage command value VH * generated by the voltage command generation unit 56 is added by the adding unit 59 to generate a corrected system voltage command value (VH * + Cvh).

  Such correction of the system voltage command value VH * is repeatedly executed in a closed control loop including the voltage phase feedback unit 82, whereby the current phase (id, iq) of the AC motor M1 becomes the optimum current phase (id, iq) It is possible to accurately and quickly shift to a state in which the rectangular wave is controlled by opt.

  Similarly, the motor control system 80 according to the present embodiment performs the voltage phase feedback control of the rectangular wave pulse, thereby controlling the AC motor M1 with the optimum current phase (id, iq) opt while keeping the boosted voltage by the converter 20 as low as possible. It can be operated by rectangular wave control. Thereby, the loss of the whole system including converter 20, inverter 22, and AC motor M1 can be effectively reduced.

  The motor control system according to the present invention is not limited to the configurations of the above-described embodiments and modifications, and various modifications and improvements can be made within the scope of the matters described in the claims. is there.

  10, 80 Motor control system, 11 Battery, 12, 14 Voltage sensor, 16, 18 Smoothing capacitor, 20 Buck-boost converter, 22 Inverter, 24 Current sensor, 26 Control unit, 28 Temperature sensor, 30, 31 Power line, 32 Ground line , 34 U-phase arm, 36 V-phase arm, 38 W-phase arm, 39 neutral point, 40 rotation angle sensor, 50 3-phase 2-phase conversion unit, 52 torque estimation unit, 53,86 subtraction unit, 54 torque feedback unit, 56 system voltage command generation unit, 58 current phase feedback unit, 59 addition unit, 60 system voltage feedback unit, 62 VH deviation generation unit, 64, 88 PI control unit, 70 overmodulation rectangular wave switching line, 72 step-up / down pressure command unit, 73, 85 Map, 74 Buck-boost rate setting unit, 76 Integration control unit, 82 Pressure phase feedback unit, 84 target voltage phase generation unit, a step-up rate, A1 sine wave PWM control region, A2 overmodulation control region, A3 rectangular wave control region, b step-down rate, Cvh system voltage correction value, D1-D8 diode, E1-E8 Power semiconductor switching element, id d-axis current, iq q-axis current, iv V-phase current, iw W-phase current, Kmd modulation factor, L reactor, m1, m2 margin, M1 AC motor, N motor speed, S1-S8 switching control signal, SE signal, SMR1, SMR2 system main relay, Tb battery temperature, Tq * torque command, Tq actual torque, Vb battery voltage, Vdd d-axis voltage command value, VH system voltage, VH * system voltage command Value, X1, X2 operating point, ΔTq torque deviation, ΔVH Temu voltage deviation, Derutafaiv voltage phase deviation, theta rotor rotation angle,? V voltage phase, Faibui_targ target voltage phase, omega motor speed.

Claims (6)

A converter capable of stepping up and down a DC voltage supplied from a power supply according to a system voltage command value, an inverter for converting a DC voltage as a system voltage output from the converter into an AC voltage, and an AC voltage applied from the inverter Drive control of the AC motor by any one of sine wave PWM control, overmodulation control and rectangular wave control by controlling the operation of the converter and the inverter according to the input torque command value. A motor control system comprising a possible control unit,
The control unit is configured so that when the AC motor is in the rectangular wave control, the current phase of the current vector on the d-axis and q-axis planes of the motor current flowing through the AC motor approaches the optimum current advance line. The voltage command value is corrected , and the system voltage correction value for correcting the system voltage command value changes the current phase of the motor current to an optimum current phase on or near the optimum current advance line. Generated based on the system voltage deviation required for
Motor control system. The motor control system according to claim 1,
The control unit includes a system voltage correction unit that corrects the system voltage command value by current phase feedback control of a current vector of the motor current. The motor control system according to claim 2,
The system voltage correction unit includes a system voltage deviation generation unit that generates a system voltage deviation based on the motor current, and a proportional integration control unit that generates a system voltage correction value to eliminate the system voltage deviation. Control system. In the motor control system according to any one of claims 1 to 3,
The control unit stores a map in which a step-up threshold line is defined on the advance side of the optimum current advance line and a step-down threshold line is defined on the retard side on the d-axis / q-axis plane. When the current phase falls below the step-up threshold line to the advance side, the converter is boosted at a predetermined rate so as to return to the optimum current advance line, and the current phase exceeds the step-down threshold line to the retard side. A motor control system that causes the converter to perform a step-down operation at a predetermined rate. The motor control system according to claim 1,
The control unit includes a system voltage correction unit that corrects the system voltage command value by performing voltage phase feedback control so that a voltage phase of an AC voltage applied to the AC motor becomes a target voltage phase. . The motor control system according to claim 5, wherein
The system voltage correction unit includes a target voltage phase generation unit that generates a target voltage phase according to a corrected system voltage command value, and a system voltage correction to eliminate a deviation between the target voltage phase and an actual command voltage phase. A motor control system comprising a proportional-integral control unit that generates a value.

Images