JP2020048381A - Motor control device, motor system and inverter control method - Google Patents

Abstract

To reduce pulsation of a current flowing to a motor.SOLUTION: A motor control device comprises: an inverter that drives a motor on the basis of a plurality of energization patterns; a current detector that outputs a detection signal corresponding to a current value of a current flowing to a DC side of the inverter; a current detection part that detects a phase current of each phase flowing to the motor by acquiring the detection signal on the basis of the energization patterns; an energization pattern generation part that generates the energization patterns on the basis of a detection value of the phase current of each phase; and a storage part that stores therein an electric angle at which switching between the energization patterns occurs. The energization pattern generation part sets an energization pattern, which is used by the current detection part to acquire the detection signal at the electric angle stored in the storage part, the same as an energization pattern immediately preceding the acquisition of the detection signal by the current detection part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a motor control device, a motor system, and an inverter control method.

  When detecting the current of each phase of U, V, and W to control the motor, there is a technique for detecting the current using one shunt resistor inserted in the DC section of the inverter circuit. In order to detect all three-phase currents by this method, it is necessary to generate an energization pattern so that two or more phases of current can be detected within one period of a PWM (Pulse Width Modulation) carrier. (For example, see Patent Document 1).

JP 2013-66340 A

  However, if the energization pattern at the time of current detection is different from the immediately preceding energization pattern, the current flowing through the motor may pulsate (also referred to as hunting).

  Thus, the present disclosure provides a motor control device, a motor system, and an inverter control method that can reduce pulsation of a current flowing through a motor.

The present disclosure
An inverter that drives the motor based on a plurality of energization patterns;
A current detector that outputs a detection signal corresponding to a current value of a current flowing to the DC side of the inverter;
A current detection unit that detects a phase current of each phase flowing through the motor by acquiring the detection signal based on the energization pattern;
An energization pattern generation unit that generates the energization pattern based on a detected value of the phase current of each phase,
A storage unit that stores an electrical angle at which switching of the energization pattern occurs,
The energization pattern generation unit sets the energization pattern when the current detection unit acquires the detection signal at the electrical angle stored in the storage unit, and the energization pattern immediately before the current detection unit acquires the detection signal. And a motor control device.

In addition, the present disclosure,
Motor and
An inverter that drives the motor based on a plurality of energization patterns;
A current detector that outputs a detection signal corresponding to a current value of a current flowing to the DC side of the inverter;
A current detection unit that detects a phase current of each phase flowing through the motor by acquiring the detection signal based on the energization pattern;
An energization pattern generation unit that generates the energization pattern based on a detected value of the phase current of each phase,
A storage unit that stores an electrical angle at which switching of the energization pattern occurs,
The energization pattern generation unit sets the energization pattern when the current detection unit acquires the detection signal at the electrical angle stored in the storage unit, and the energization pattern immediately before the current detection unit acquires the detection signal. Provide a motor system that is the same as

In addition, the present disclosure,
A detection signal corresponding to the current value of the current flowing to the DC side of the inverter that drives the motor is obtained based on a plurality of conduction patterns,
By acquiring the detection signal based on the energization pattern, a phase current of each phase flowing through the motor is detected,
Based on the detected value of the phase current of each phase, the energization pattern is generated,
An inverter control method for energizing the inverter based on the energization pattern,
The electrical angle at which the switching of the energization pattern occurs is stored in a storage unit, and the energization pattern when acquiring the detection signal with the electrical angle stored in the storage unit is an energization pattern immediately before acquiring the detection signal. And an inverter control method.

  According to the technology of the present disclosure, pulsation of the current flowing through the motor can be reduced.

1 is a diagram illustrating a configuration of a motor control system according to an embodiment of the present disclosure. 5 is a timing chart illustrating an example of an upper arm-side three-phase PWM signal generated by a PWM signal generation unit. 9 is a flowchart illustrating an example of a process of adjusting a conduction time by adjusting a phase of a PWM signal in a case of two-phase modulation. 6 is a timing chart illustrating an example of switching of an energization pattern. It is a figure showing an example of a pulsation reduction method in the case of three-phase modulation. It is a figure showing an example of a pulsation reduction method in the case of two-phase modulation. It is a figure which shows an example of the current waveform in the case where the energization pattern at the time of current detection differs from the immediately preceding energization pattern, and is the same. FIG. 7 is a diagram illustrating an example of a relationship between the number of occurrences of switching of an energization pattern and an electrical angle. It is a flowchart which shows an example of a pulsation reduction method.

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

  FIG. 1 is a diagram illustrating a configuration of a motor system according to an embodiment of the present disclosure. The motor system 1 shown in FIG. 1 controls the rotation operation of the motor 4. Specific examples of the equipment on which the motor system 1 is mounted include OA equipment such as a copy machine and home electric appliances such as a personal computer and a refrigerator, but the equipment is not limited thereto. The motor system 1 includes at least a motor 4 and a motor control device 100.

  The motor 4 has a plurality of coils. The motor 4 has, for example, a three-phase coil including a U-phase coil, a V-phase coil, and a W-phase coil. Specific examples of the motor 4 include a three-phase brushless motor.

  The motor control device 100 controls on / off of a plurality of switching elements connected in a three-phase bridge according to an energization pattern including a two-phase or three-phase PWM signal, thereby controlling the motor via an inverter that converts DC to three-phase AC. Drive. The motor control device 100 includes an inverter 23, a current detector 24, a current detection unit 27, an energization pattern generation unit 35, a drive circuit 33, a current detection timing adjustment unit 34, and a storage unit 36.

  The inverter 23 is a circuit that converts a DC supplied from the DC power supply 21 into a three-phase AC by switching a plurality of switching elements, and causes a driving current of the three-phase AC to flow through the motor 4 to rotate the rotor of the motor 4. is there. The inverter 23 converts a plurality of energization patterns generated by the energization pattern generation unit 35 (more specifically, a two-phase or three-phase PWM signal generated by the PWM signal generation unit 32 in the energization pattern generation unit 35). Based on this, the motor 4 is driven.

  The inverter 23 has a plurality of switching elements 25U +, 25V +, 25W +, 25U-, 25V-, 25W- connected in a three-phase bridge. The switching elements 25U +, 25V +, and 25W + are high-side switching elements (upper arms) connected to the positive electrode side of the DC power supply 21 via the positive-side bus 22a. Each of the switching elements 25U-, 25V-, and 25W- is a low-side switching element (lower arm) connected to the negative electrode side (specifically, the ground side) of the DC power supply 21. The plurality of switching elements 25U +, 25V +, 25W +, 25U−, 25V−, and 25W− correspond to a plurality of drive signals supplied from the drive circuit 33 based on the PWM signal included in the above-described energization pattern, respectively. It is turned on or off according to the drive signal.

  A connection point between the switching element 25U + and the switching element 25U- is connected to one end of a U-phase coil of the motor 4. A connection point between the switching element 25V + and the switching element 25V- is connected to one end of a V-phase coil of the motor 4. The connection point between the switching element 25W + and the switching element 25W- is connected to one end of the W-phase coil of the motor 4. The other ends of the U-phase coil, the V-phase coil, and the W-phase coil are connected to each other.

  Specific examples of the switching element include an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and an IGBT (Insulated Gate Bipolar Transistor). However, the switching elements are not limited to these.

  The current detector 24 outputs a detection signal Sd corresponding to the current value of the current flowing on the DC side of the inverter 23. The current detector 24 shown in FIG. 1 generates a detection signal Sd corresponding to the value of the current flowing through the negative bus 22b. The current detector 24 is, for example, a current detection element arranged on the negative bus 22b, and more specifically, a shunt resistor inserted into the negative bus 22b. A current detection element such as a shunt resistor generates a voltage signal corresponding to a current value of a current flowing therein as a detection signal Sd.

  The current detection unit 27 obtains the detection signal Sd based on a plurality of conduction patterns (more specifically, two-phase or three-phase PWM signals) generated by the conduction pattern generation unit 35, and , The phase currents Iu, Iv, Iw of the respective phases U, V, W are detected. More specifically, the current detection unit 27 obtains the detection signal Sd at an acquisition timing synchronized with a plurality of energization patterns (more specifically, two-phase or three-phase PWM signals), and thus flows to the motor 4. The phase currents Iu, Iv, Iw of the U, V, W phases are detected. The acquisition timing of the detection signal Sd is set by the current detection timing adjustment unit 34.

  For example, the current detection unit 27 takes in the analog voltage detection signal Sd generated by the current detector 24 into an AD (Analog to Digital) converter at the acquisition timing set by the current detection timing adjustment unit 34. Then, the current detection unit 27 AD-converts the received analog detection signal Sd into a digital detection signal Sd, and digitally processes the digital detection signal Sd after the AD conversion, whereby the U, V, W of the motor 4 is converted. The phase currents Iu, Iv, Iw of each phase are detected. The detected values of the phase currents Iu, Iv, Iw of each phase detected by the current detection unit 27 are supplied to the energization pattern generation unit 35.

  The energization pattern generation unit 35 generates a pattern for energizing the inverter 23 (an energization pattern of the inverter 23) based on the detected values of the phase currents Iu, Iv, Iw of the motor 4 detected by the current detection unit 27. The energization pattern of the inverter 23 may be rephrased as a pattern for energizing the motor 4 (energization pattern of the motor 4). The energization pattern of the inverter 23 includes, for example, a two-phase or three-phase PWM signal for energizing the inverter 23 so that the motor 4 rotates.

  The energization pattern generation unit 35 determines the rotor position of the motor 4 based on, for example, the detected values of the phase currents Iu, Iv, Iw of the motor 4 detected by the current detection unit 27, and sets the motor 4 to the determined rotor position. A plurality of energization patterns are generated such that the rotor follows.

  The energization pattern generation unit 35 has at least a duty ratio setting unit 31 and a PWM signal generation unit 32, for example. The duty ratio setting unit 31 sets the duty ratio of each phase of the two-phase or three-phase PWM signal based on the detected values of the phase currents Iu, Iv, Iw of the motor 4 detected by the current detection unit 27. The PWM signal generation unit 32 compares the duty ratio of each phase (set value of the duty ratio of each phase) set by the duty ratio setting unit 31 with the level of the carrier C, and the level changes with the set value. A two-phase or three-phase PWM signal is generated. The carrier C is a carrier signal whose level periodically increases and decreases.

  When the energization pattern of the inverter 23 is generated by vector control, the energization pattern generation unit 35 includes at least a vector control unit 30, a duty ratio setting unit 31, and a PWM signal generation unit 32.

  When the rotational speed command ωref of the motor 4 is given from outside, the vector control unit 30 determines the torque current command Iqref and the exciting current based on the difference between the measured or estimated value of the rotational speed of the motor 4 and the rotational speed command ωref. Generate a command Idref. The vector control unit 30 determines the rotor position θ of the motor 4 based on the phase currents Iu, Iv, Iw of the U, V, and W phases of the motor 4, and performs a vector control operation using the determined rotor position θ. , The torque current Iq and the excitation current Id. The vector control unit 30 performs, for example, a PI control operation on the difference between the torque current command Iqref and the torque current Iq to generate a voltage command Vq. The vector control unit 30 performs, for example, a PI control operation on a difference between the exciting current command Idref and the exciting current Id, and generates a voltage command Vd. The vector control unit 30 converts the voltage commands Vq, Vd into phase voltage commands Vu, Vv, Vw of U, V, W phases using the above rotor position θ. The phase voltage commands Vu, Vv, Vw of each phase are supplied to the duty ratio setting unit 31.

  The duty ratio setting unit 31 generates duty ratios Udu, Vdu, Wdu for generating two-phase or three-phase PWM signals based on the phase voltage commands Vu, Vv, Vw of each phase supplied from the vector control unit 30. Set.

  The PWM signal generation unit 32 compares the duty ratios Udu, Vdu, and Wdu of each phase set by the duty ratio setting unit 31 with the level of the carrier C, thereby generating an energization pattern including a two-phase or three-phase PWM signal. Generate. The PWM signal generation unit 32 also generates a lower-arm driving PWM signal obtained by inverting the upper-arm driving two-phase or three-phase PWM signal, adds a dead time if necessary, and then generates the generated PWM signal. Is output to the drive circuit 33.

  The drive circuit 33 outputs a drive signal for switching the six switching elements 25U +, 25V +, 25W +, 25U-, 25V-, and 25W- included in the inverter 23 according to the energization pattern including the applied PWM signal. As a result, a three-phase AC driving current is supplied to the motor 4, and the rotor of the motor 4 rotates.

  The current detection timing adjustment unit 34 allows the current detection unit 27 to control each of the currents within one cycle of the carrier C based on the carrier C supplied from the PWM signal generation unit 32 and the PWM signal generated by the PWM signal generation unit 32. An acquisition timing for detecting two phase currents among the phase currents of the phases is determined.

  The current detection unit 27 detects the phase currents Iu, Iv, Iw by acquiring the detection signals Sd at a plurality of acquisition timings determined by the current detection timing adjustment unit 34.

  The functions of the current detection unit 27, the energization pattern generation unit 35, and the current detection timing adjustment unit 34 are realized by the operation of a CPU (Central Processing Unit) by a program readablely stored in a storage device (not shown). Is done. For example, each of these functions is realized by cooperation of hardware and software in a microcomputer including a CPU.

  FIG. 2 is a timing chart showing an example of the upper-arm three-phase PWM signals (U +, V +, W +) generated by the PWM signal generator 32. The triangular wave in the PWM counter shown in FIG. 2 indicates the count value of the carrier counter (that is, the level of the carrier C). The two-phase PWM signal has an energization pattern in which a specific one-phase (for example, W-phase) PWM signal among the three-phase PWM signals is always fixed at a low level.

  In the present embodiment, the active level of the PWM signal is defined as a high level. In this case, when the PWM signal is at a high level, the switching element is turned on, and when the PWM signal is at a low level, the switching element is turned off. The active level of the PWM signal may be defined as a low level according to a circuit configuration or the like.

  In the present embodiment, the PWM signal generation unit 32 generates a PWM signal of each phase using one carrier C common to each phase. Since the carrier C is a symmetrical triangular wave centered on the phase tb, the circuit configuration for generating the PWM signal waveform of each phase can be simplified. The carrier counter is counting down to phase ta, counting up from phase ta to phase tb, and counting down from phase tb. Thus, the count-up period and the count-down period are repeated.

  The PWM signal generator 32 compares each set value of the duty ratio of each phase with the level of the carrier C. The PWM signal generation unit 32 sets the level of the PWM signal to a high level during a period in which the set value of the duty ratio of the PWM signal is larger than the level of the carrier C based on the comparison result. On the other hand, based on the comparison result, the PWM signal generation unit 32 sets the level of the PWM signal to the low level during a period in which the set value of the duty ratio of the PWM signal is smaller than the level of the carrier C.

  In a state where the inverter 23 outputs the PWM-modulated three-phase alternating current, the current detection unit 27 can detect a current of a specific phase according to the energization pattern for the switching elements 25U +, 25V +, and 25W + on the upper arm side. . Alternatively, in a state where the inverter 23 is outputting the PWM-modulated three-phase alternating current, the current detection unit 27 outputs a specific phase according to the energization pattern to the lower-arm switching elements 25U-, 25V-, and 25W. The current may be detected.

  For example, as shown in FIG. 2, during the energizing time T21 in which only the U-phase PWM signal is at the high level and both the V-phase and W-phase PWM signals are at the low level, both ends of the current detector 24 such as a shunt resistor are connected. The voltage value of the generated voltage corresponds to the current value of the positive U-phase current Iu +. Therefore, the current detection unit 27 can detect the current value of the positive U-phase current Iu + by acquiring the detection signal Sd at the acquisition timing A within the conduction time T21. The energization time T21 is a time from t4 to t5. The current detection timing adjustment unit 34 determines when the PWM signal transitions to a logic level different from the other two phases (in this case, the timing t4 when the U-phase PWM signal transitions from the same low level as the V-phase and W-phase to the high level). ), The acquisition timing A is set when a predetermined delay time tda has elapsed. At this time, the current detection timing adjustment unit 34 sets the acquisition timing A within the energization time T21.

  In addition, as shown in FIG. 2, for example, during the energization time T11 in which both the U-phase and V-phase PWM signals are at the high level and only the W-phase PWM signal is at the low level, the current detector 24 such as a shunt resistor is used. The voltage value of the voltage generated at both ends corresponds to the current value of the negative W-phase current Iw-. Therefore, the current detection unit 27 can detect the current value of the negative W-phase current Iw− by acquiring the detection signal Sd at the acquisition timing B within the conduction time T11. The energization time T11 is a time from t1 to t2. The current detection timing adjustment unit 34 determines when the PWM signal transitions to a logic level different from the other two phases (in this case, the timing t1 when the W-phase PWM signal transitions from the same high level as the U-phase and V-phase to the low level). ), The acquisition timing B is set when a predetermined delay time tdb has elapsed. At this time, the current detection timing adjustment unit 34 sets the acquisition timing B within the energization time T11.

  Similarly, the current detection unit 27 can detect the current values of other phase currents.

  As described above, if the two phase currents of the phase currents Iu, Iv, and Iw are sequentially detected and stored according to the energization pattern including the two-phase or three-phase PWM signals, the three-phase currents are time-divided. Can be detected. Since the sum of the three phase currents is zero, in the case of three-phase modulation, if the current detection unit 27 can detect two phase currents among the three phase currents, it can also detect the remaining one phase current. .

  Immediately after the timing when each switching element changes from on to off or from off to on (for example, from t1 to t6), the waveform of the current detected by the current detector 24 tends to be unstable. Therefore, in order to acquire the detection signal Sd generated in the current detector 24 in a stable state, the energization times T11 and T21 each need to have an energization width longer than the minimum stabilization time (hereinafter, also referred to as the minimum time τ). . The minimum time τ is, for example, 4 microseconds.

  In order for the current detection unit 27 to stably acquire the detection signal Sd corresponding to the current value of the specific one-phase current, the specific one-phase PWM signal among the three phases is low and the remaining two It is necessary to keep the energized state in which the PWM signal is high level for a minimum time τ or more. Alternatively, it is necessary to keep the energized state in which the PWM signal of the specific one of the three phases is at a high level and the PWM signals of the remaining two phases are at a low level for a minimum time τ or longer. If the energization time is shorter than the minimum time τ, the detection error of the phase current tends to increase.

  Therefore, in the present embodiment, the PWM signal generation unit 32 calculates the energization times T11 and T21 based on the duty ratio of each phase set by the duty ratio setting unit 31 based on the detected value of the phase current of each phase. I do. Then, the PWM signal generation unit 32 determines, based on the calculated values of the energization times T11 and T21, an energization width (minimum time τ or more) at which the current detection unit 27 can detect two phase currents among the phase currents of each phase. ), The energization times T11 and T21 are adjusted. The energization time T11 is an example of a first energization time in the first half cycle period of the carrier C, and represents a period during which one of the two phase currents can be detected. The energization time T21 is an example of a second energization time in the latter half cycle period of the carrier C, and represents a period during which the phase current of the other phase of the two phase currents can be detected.

  As described above, the PWM signal generation unit 32 adjusts the energizing times T11 and T21 to the energizing width equal to or longer than the minimum time τ based on the calculated values of the energizing times T11 and T21, thereby reducing the increase in the phase current detection error. Can be suppressed. For example, the PWM signal generation unit 32 acquires the set value of the duty ratio of each phase derived from the phase current of each phase through control processing such as vector control based on the detected value from the duty ratio setting unit 31 and acquires the acquired value. The energization time T11 is calculated from the set value of the duty ratio of each phase. If the calculated energization time T11 is less than the minimum time τ, the PWM signal generation unit 32 performs a correction process of extending the energization time T11 to an energization width equal to or longer than the minimum time τ. With this correction process, the current detection unit 27 can accurately detect a phase current that can be detected within the energization time T11. Similar correction processing can be performed on the calculated value of the energization time T21. Therefore, at least two phase currents can be accurately detected within one cycle of the carrier C.

  The energization time T11 for detecting one phase current of the two phases and the energization time T21 for detecting the other phase current are determined by the first half period and the second half period of one cycle of the carrier C. The period is divided into: Therefore, compared with the case where there are two acquisition timings in the half cycle period of the carrier C, the time interval between the acquisition timings A and B (interruption processing time interval) can be more relaxed. With this allowance, it is possible to suppress a delay in the acquisition timing even when a CPU having a relatively low processing capacity is used. In FIG. 3, as an example of a case where there are two acquisition timings in the half cycle period of the carrier C, the acquisition timing B shown by a solid line and the acquisition timing A shown by a broken line are shown in the first half cycle period of one cycle of the carrier C. And the case where there is.

  For example, as shown in FIG. 3, the PWM signal generation unit 32 shifts the phase of at least one of the two-phase or three-phase PWM signals so that the energization times T11 and T21 are longer than the minimum time τ. It is preferable to adjust the width of the current. In particular, the PWM signal generation unit 32 preferably shifts the phase of at least one of the two-phase or three-phase PWM signals without changing the duty ratio of the at least one PWM signal. The voltage between the phases applied to the motor 4 via the inverter 23 does not change even if the rising position and the falling position of the PWM signal pulse are shifted by the same time as long as the difference in the duty ratio between the phases is constant. It is. Since the voltage between the phases does not change, hunting of the current flowing through the motor 4 can be suppressed.

  However, even if the phase of the PWM signal of at least one phase is shifted without changing the duty ratio of the PWM signal of at least one phase, each of the calculated values of the energization times T11 and T21 becomes a value that cannot secure the minimum time τ. There are cases. If the minimum time τ cannot be ensured even if the phase is shifted in this way, the PWM signal generation unit 32 adjusts the duty ratio of each phase of the PWM signal so that the energization times T11 and T21 are longer than the minimum time τ. The width may be adjusted. As described above, in the adjustment of only the phase shift, even when the energization widths of the energization times T11 and T21 cannot be set to the minimum time τ or more, the duty ratios are also adjusted to minimize the energization widths of the energization times T11 and T21. It can be adjusted to the time τ or more.

  In addition, even if the duty ratio of each phase is adjusted, there are cases where the calculated values of the energization times T11 and T21 are values that cannot secure the minimum time τ. If the minimum time τ cannot be secured even if the duty ratio is adjusted in this way, the PWM signal generation unit 32 sets the duty of each phase to a fixed value that allows the current detection unit 27 to detect two phase currents of each phase. The ratio may be changed. As described above, in the adjustment of both the phase and the duty ratio, even when each of the energization widths of the energization times T11 and T21 cannot be equal to or longer than the minimum time τ, the current detection unit 27 applies the phase current of two phases of each phase to the energization time. It can be detected at each of T11 and T21.

  Further, in the present embodiment, the PWM signal generation unit 32 determines, based on the duty ratio of each phase set by the duty ratio setting unit 31, which of the plurality of energization patterns should control energization of the inverter 23. Is determined.

  In the present embodiment, six energization patterns P1 to P6 are prepared. The plurality of energization patterns are divided according to the magnitude relationship between the OFF widths of the PWM signals of the respective phases extending to both the phase delay side and the phase advance side around the reference phase tb (see FIG. 2) of the carrier C. For example, in the energization pattern P1 shown in FIG. 2, the OFF width is small, medium, and large in the order of U phase, V phase, and W phase (OFF width of W phase> OFF width of V phase> U phase Off width). The off widths of the other energization patterns P2 to P6 are small, medium, large, medium, large, small, large, medium, small, large, medium, and small, respectively, in the order of U phase, V phase, and W phase.

  By the way, if the energization pattern when the current detection unit 27 acquires the detection signal Sd is different from the energization pattern immediately before the current detection unit 27 acquires the detection signal Sd, the current flowing through the motor 4 pulsates (also referred to as hunting). May be. This is presumed to be caused by a change in the current waveform due to a change in the phase to be energized, or an increase in the duty ratio for compensating the shortage of the current detection width such as the energization times T11 and T21.

  FIG. 4 is a timing chart showing an example of switching of the energization pattern. The PWM signal generation unit 32 repeatedly switches between the energization pattern P5 having a large, medium, and small off-width and the energization pattern P4 having a small off-size, medium, large, and small. To indicate the situation. The PWM signal generation unit 32 sets the energization pattern for each carrier C cycle (carrier cycle). As shown in FIG. 4, the energization pattern P4 (middle, large, and small) when the current detection unit 27 acquires the detection signal Sd is the energization pattern P5 (large, medium, and small) immediately before the current detection unit 27 acquires the detection signal Sd. Otherwise, an unintended increase or decrease in current may occur. FIG. 4 shows that an unintended increase or decrease has occurred in the current (U-phase current) flowing through the U-phase coil of the motor 4. Such an unintended increase or decrease of the current appears as a pulsation of the current flowing through the motor 4. In particular, when the PWM signal generation unit 32 intentionally widens the energization width obtained by the vector operation or the like by adjusting the duty ratio to secure the energization width equal to or longer than the minimum time τ, such pulsation (unintended) occurs. (Increase / decrease in current) appears remarkably.

  Therefore, the motor control device 100 of the present embodiment includes the storage unit 36 that stores the electrical angle at which the switching of the energization pattern occurs. The energization pattern generation unit 35 determines the energization pattern when the current detection unit 27 acquires the detection signal Sd based on the “electrical angle at which the energization pattern switching occurs” stored in the storage unit 36. The same as the energization pattern immediately before acquiring Sd. In this way, when the energization pattern at the time of current detection is the same as the immediately preceding energization pattern, pulsation of the current flowing through the motor 4 can be reduced as compared with the case where the energization pattern at the time of current detection is different from the immediately preceding energization pattern. It is considered that this is because the change in the phase to be energized is suppressed, and the increase in the duty ratio for compensating for the shortage of the current detection width such as the energization times T11 and T21 is suppressed. Hereinafter, the “electric angle at which the switching of the energization pattern occurs” may be referred to as a “pattern switching angle”.

  FIG. 5 is a diagram illustrating an example of a pulsation reduction method in the case of three-phase modulation. The energization pattern generation unit 35 determines the energization pattern to be used when the current detection unit 27 acquires the detection signal Sd at the pattern switching angle stored in the storage unit 36, just before the current detection unit 27 acquires the detection signal Sd. The same as the energization pattern P5 (see the lower part of FIG. 5). Then, the energization pattern generation unit 35 changes the energization pattern P4 scheduled to be used before being made the same as the immediately preceding energization pattern at the pattern switching angle stored in the storage unit 36 to the same as the immediately preceding energization pattern. It is used as the next energization pattern after the energization pattern. Thus, the energization pattern generation unit 35 switches the energization pattern not at the time of current detection but at the next carrier cycle at the time of current detection. By switching the energization pattern as shown in FIG. 5, pulsation flowing through the motor 4 can be reduced.

  FIG. 6 is a diagram illustrating an example of a pulsation reduction method in the case of two-phase modulation. The energization pattern generation unit 35 determines the energization pattern to be used when the current detection unit 27 acquires the detection signal Sd at the pattern switching angle stored in the storage unit 36, just before the current detection unit 27 acquires the detection signal Sd. The same as the energization pattern P5 (see the lower part of FIG. 6). Then, the energization pattern generation unit 35 determines that the current detection unit 27 detects the energization pattern P4 that was to be used before the current energization pattern was made the same as the current energization pattern at the pattern switching angle stored in the storage unit 36 by the detection signal Sd. Is used as an energization pattern to be used next time. In this way, the energization pattern generation unit 35 uses the energization pattern that was to be used at the time of current detection at the time of current detection. By switching the energization pattern as shown in FIG. 6, pulsation flowing through the motor 4 can be reduced.

  The shapes of the energization patterns shown in FIGS. 5 and 6 are examples. For example, in FIGS. 5 and 6, the OFF width at the time of “large” may be a length over one entire period of the PWM signal (the length of one period). FIG. 6 shows an energization pattern in which the W-phase is fixed to the low-level OFF state and the U-phase and the V-phase are switched. However, an energization pattern in which the V phase is fixed to the low level off state and the U phase and the W phase are switched may be adopted, or the U phase is fixed to the low level off state and the V phase and the W phase are switched. An energization pattern may be employed.

  FIG. 7 is a diagram illustrating an example of a current waveform in the case where the energization pattern at the time of current detection is different from the immediately preceding energization pattern. In FIG. 7, “before improvement” indicates that the energization pattern P4 at the time of current detection is different from the immediately preceding energization pattern P5, and “after improvement” indicates that the energization pattern P5 at the time of current detection is the same as the immediately preceding energization pattern P5. Show the case. When the energization pattern P5 at the time of current detection is the same as the immediately preceding energization pattern P5, pulsation of the current flowing through the motor 4 can be reduced as compared with the case where the energization pattern P4 at the time of current detection is different from the immediately preceding energization pattern P5. When the energization pattern is switched from P5 to P4, the energization direction to the motor 4 changes before and after the energization pattern is switched. However, if the same energization pattern P5 as used immediately before the current detection is used, the direction of energization to the motor 4 does not change between immediately before the current detection and when the current is detected.

  Next, a method of specifying an electrical angle for executing the pulsation reduction process will be described.

  It is preferable that the energization pattern generation unit 35 executes the pulsation reduction process of the current flowing through the motor 4 when the energization pattern is switched at a specific electrical angle of the motor 4. This is to prevent a stable current waveform from being broken by performing the pulsation reduction process at an electrical angle at which switching of the energization pattern does not occur. The pulsation factor occurs at almost the same electrical angle. Therefore, the storage unit 36 stores map data of the electrical angle at which the energization pattern switching occurs, and the energization pattern generation unit 35 performs the energization pattern switching based on the map data stored in the storage unit 36. Identify the electrical angle. The energization pattern generation unit 35 does not execute the pulsation reduction process at an electrical angle at which switching of the energization pattern does not occur.

  For example, the energization pattern generation unit 35 accumulates the history of the electrical angle at which the energization pattern switching occurs in the storage unit 36. Then, the energization pattern generation unit 35 obtains the energization pattern when the current detection unit 27 obtains the detection signal Sd with the electrical angle remaining in the history stored in the storage unit 36, and the current detection unit 27 obtains the detection signal Sd. Make it the same as the previous energization pattern.

  Specifically, the energization pattern generation unit 35 detects an electrical angle at which energization pattern switching occurs in a stable state where the number of revolutions of the motor 4 exceeds a specified number of revolutions (for example, 600 rpm). For example, the map data is represented by 128 pieces of array data defined in a random access memory (RAM). On the software, since the electrical angles 0 ° to 360 ° are represented by values of 0 to 65535, a 9-bit bit shift is used to access the array data. Since the electrical angle of 360 ° is divided into 128, the electrical angle is divided about every 2.8 °. Each time the energization pattern switching is detected, the energization pattern generation unit 35 counts up the array corresponding to the electrical angle to measure the electrical angle at which energization pattern switching occurs. An electrical angle having a large number of counts indicates an electrical angle at which current pulsation is likely to occur.

  FIG. 8 is a diagram illustrating an example of the relationship between the number of occurrences (counts) of switching of the energization pattern and the electrical angle. The energization pattern generation unit 35 accumulates the number of occurrences of switching of the energization pattern in the storage unit 36 for each electrical angle, and identifies an electrical angle in which the number of occurrences exceeds a specified number as an electrical angle at which current pulsation easily occurs. Thereby, the energization pattern generation unit 35 determines the energization pattern when the current detection unit 27 acquires the detection signal Sd at the electrical angle in which the number of occurrences exceeds the specified number, and immediately before the current detection unit 27 acquires the detection signal Sd. Can be made the same as the energization pattern. On the other hand, the energization pattern generation unit 35 determines the energization pattern when the current detection unit 27 acquires the detection signal Sd when the number of occurrences is an electrical angle equal to or less than the specified number, immediately before the current detection unit 27 acquires the detection signal Sd. No pulsation reduction processing is performed to make the same as the energization pattern of FIG. Thus, it is possible to prevent the current waveform from being disturbed by the execution of the pulsation reduction process.

  FIG. 9 is a flowchart illustrating an example of the pulsation reduction method.

  After the activation of the motor 4 (step S10), the energization pattern generation unit 35 waits to count the number of occurrences of energization pattern switching until the number of rotations of the motor 4 exceeds the specified number of revolutions (step S20).

  The energization pattern generation unit 35 starts counting the number of times of switching of the energization pattern for each electrical angle in a state where the rotation speed of the motor 4 exceeds the specified rotation speed and the fluctuation amount of the rotation speed is within a certain range. (Step S30). The energization pattern generation unit 35 accumulates the number of occurrences of switching of the energization pattern in the storage unit 36 for each electrical angle, and identifies an electrical angle in which the number of occurrences exceeds a specified number as an electrical angle at which current pulsation easily occurs. The energization pattern generation unit 35 converts the electrical angle (pattern switching angle) specified as the electrical angle at which current pulsation easily occurs into map data (step S40).

  The energization pattern generation unit 35 monitors the pulsation (hunting) of the phase current detected by the current detection unit 27 (Step S50). If the energization pattern generation unit 35 detects that the energization pattern at the time of current detection is different from the immediately preceding energization pattern at the pattern switching angle present in the map data, the energization pattern at the time of current detection changes the energization pattern immediately before the current detection. (Step S60). The energization pattern generation unit 35 does not execute the pulsation reduction process until the next pattern switching angle is reached. If the current detection that intentionally widens the conduction width is performed, an error may be included in the acquired value of the current. Therefore, the current detection unit 27 determines the current detected in the conduction pattern subjected to the pulsation reduction process in step S60. The value information is corrected (step S70). For example, the current detection unit 27 performs a correction for subtracting the current increase due to the energization width from the current detection value.

  As described above, the motor control device, the motor system, and the inverter control method have been described with the embodiments, but the present invention is not limited to the above embodiments. Various modifications and improvements, such as combinations and substitutions with some or all of the other embodiments, are possible within the scope of the present invention.

  For example, the current detector that outputs the detection signal corresponding to the current value of the current flowing to the DC side of the inverter may output the detection signal corresponding to the current value of the current flowing to the positive bus. Further, the current detector may be a sensor such as a CT (Current Transformer).

4 Motor 21 DC power supply 22a Positive bus 22b Negative bus 23 Inverter 24 Current detector 27 Current detector 30 Vector controller 31 Duty ratio setting unit 32 PWM signal generation unit 33 Drive circuit 34 Current detection timing adjustment unit 35 Current generation pattern generation Unit 36 storage unit

Claims (7)

An inverter that drives the motor based on a plurality of energization patterns;
A current detector that outputs a detection signal corresponding to a current value of a current flowing to the DC side of the inverter;
A current detection unit that detects a phase current of each phase flowing through the motor by acquiring the detection signal based on the energization pattern;
An energization pattern generation unit that generates the energization pattern based on a detected value of the phase current of each phase,
A storage unit that stores an electrical angle at which switching of the energization pattern occurs,
The energization pattern generation unit sets the energization pattern when the current detection unit acquires the detection signal at the electrical angle stored in the storage unit, and the energization pattern immediately before the current detection unit acquires the detection signal. The same as the motor control device.   The energization pattern generation unit accumulates the history of the electrical angle in the storage unit, the energization pattern when the current detection unit acquires the detection signal at the electrical angle remaining in the history, the energization pattern immediately before The motor control device according to claim 1, which is the same.   The energization pattern generation unit accumulates the number of occurrences of the energization pattern switching in the storage unit for each electrical angle, and the current detection unit acquires the detection signal at an electrical angle where the number of occurrences exceeds a specified number. 3. The motor control device according to claim 1, wherein the energization pattern is set to be the same as the immediately preceding energization pattern.   The energization pattern generation unit changes the energization pattern that was scheduled to be used before being made the same as the immediately preceding energization pattern with the electric angle stored in the storage unit, the energization pattern being made the same as the immediately preceding energization pattern. The motor control device according to claim 1, wherein the motor control device is used as an energization pattern next to the pattern.   The energization pattern generation unit, the energization pattern that was scheduled to be used before being made the same as the immediately before energization pattern in the electrical angle stored in the storage unit, the current detection unit next to the detection signal The motor control device according to any one of claims 1 to 4, which is used when acquiring. Motor and
An inverter that drives the motor based on a plurality of energization patterns;
A current detector that outputs a detection signal corresponding to a current value of a current flowing to the DC side of the inverter;
A current detection unit that detects a phase current of each phase flowing through the motor by acquiring the detection signal based on the energization pattern;
An energization pattern generation unit that generates the energization pattern based on a detected value of the phase current of each phase,
A storage unit that stores an electrical angle at which switching of the energization pattern occurs,
The energization pattern generation unit sets the energization pattern when the current detection unit acquires the detection signal at the electrical angle stored in the storage unit, and the energization pattern immediately before the current detection unit acquires the detection signal. The same as the motor system. A detection signal corresponding to the current value of the current flowing to the DC side of the inverter that drives the motor is obtained based on a plurality of conduction patterns,
By acquiring the detection signal based on the energization pattern, a phase current of each phase flowing through the motor is detected,
Based on the detected value of the phase current of each phase, the energization pattern is generated,
An inverter control method for energizing the inverter based on the energization pattern,
The electrical angle at which the switching of the energization pattern occurs is stored in a storage unit, and the energization pattern when acquiring the detection signal with the electrical angle stored in the storage unit is an energization pattern immediately before acquiring the detection signal. Inverter control method to be the same as.