JP7382884B2 - Motor control device, motor system and motor control method - Google Patents

Description

The present disclosure relates to a motor control device, a motor system, and a motor control method.

Conventionally, a one-shunt current detection method is known in which one shunt resistor connected to a DC bus of an inverter circuit is used to detect the phase current of each phase for controlling a motor (for example, see Patent Document 1). ).

Japanese Patent Application Publication No. 2015-208071

When controlling a motor using the one-shunt current detection method, the current flowing through the one-shunt current detector may be detected before the inverter rotates the rotor (before starting the motor). The current detected before the motor starts can be used, for example, to detect failures before the motor starts, or to improve the accuracy of current detection and failure detection when the motor is started by an inverter and the inverter is rotating the rotor. be used.

However, if a current flowing through a single-shunt current detector is detected while the rotor is idling before the inverter rotates the rotor, the rotation of the rotor will be inhibited by the regenerative brake generated in the idling rotor. There is. If the rotation of the idling rotor is inhibited, unintended behavior such as deceleration of the motor or abnormal noise may occur, for example.

The present disclosure provides a motor control device, a motor system, and a motor control method that can reduce inhibition of rotor idling by detecting a current flowing through a current detector.

A motor control device according to an embodiment of the present disclosure includes:
an inverter that energizes a motor having a rotor by turning on some of the arms that are different for each energization pattern among all the arms;
a current detector connected to the DC side of the inverter;
A first period in which all the arms are turned off while the rotor is idling; a second period in which some of the arms are turned on in a first energization pattern while the rotor is idling; and a second energization in some of the arms while the rotor is idling. a PWM signal generation unit that generates a PWM signal for each phase including a third period of turning on in a pattern in one cycle;
A current detection unit that detects a first reference current flowing to the current detector during the second period and a second reference current flowing to the current detector during the third period.

According to the present disclosure, by detecting the current flowing through the current detector, it is possible to reduce the inhibition of rotor idling.

1 is a diagram showing a configuration example of a motor system according to Embodiment 1 of the present disclosure. FIG. 3 is a diagram illustrating waveforms of a plurality of PWM signals, carrier waveforms per cycle of these PWM signals, and waveforms of phase voltage commands for each phase. It is a figure which shows an example of the switching state of each arm at the time of energization. It is a figure which shows an example of the switching state of each arm at the time of non-energization. Both are timing charts illustrating the offset current of each phase flowing to a current detector by turning on some of the arms of the inverter according to the PWM signal of each phase with a duty ratio of 50%. When the inverter is rotating the rotor according to the PWM signal of each phase whose duty ratio is different from 50%, by turning on some of the arms as shown in Fig. 5, the phase current of each phase flowing to the current detector can be detected. It is an illustrative timing chart. FIG. 7 is a diagram showing a comparative example of the waveform of a PWM signal when detecting the current value of the current flowing through the current detector before the inverter rotates the rotor. It is a figure which shows the case where all the lower arms are in an ON state in a non-energized area. FIG. 7 is a diagram showing a case where all upper arms are in an on state in a non-energized section. FIG. 6 is a diagram showing a case where all the upper and lower arms are in an off state in a non-energized section. FIG. 6 is a diagram showing a first example of the waveform of a PWM signal when detecting the current value of the current flowing through the current detector before the inverter rotates the rotor. FIG. 6 is an enlarged view showing an example of the current waveform of the U-phase current flowing through the current detector by turning on some of the arms of the inverter according to the PWM signal of each phase with a duty ratio of 50%. FIG. 7 is a diagram showing a second example of the waveform of a PWM signal when the inverter detects the current value of the current flowing through the current detector before rotating the rotor. FIG. 6 is a diagram showing a switching state in which a negative U-phase current "-Iu" flows through the current detector. FIG. 6 is a diagram showing a switching state in which a positive U-phase current "+Iu" flows through a current detector. FIG. 7 is a waveform diagram showing an example of processing for calculating a U-phase offset current value in 10 cycles of a PWM signal when the rotor is idling. 17 is an enlarged view of a portion surrounded by a dotted line frame shown in FIG. 16. FIG. FIG. 3 is a waveform diagram showing an example of processing for calculating a U-phase offset current value. FIG. 7 is a waveform diagram showing an example of processing for calculating a W-phase offset current value.

Hereinafter, a motor control device, a motor system, and a motor control method according to embodiments of the present disclosure will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration example of a motor system 1-1 according to Embodiment 1 of the present disclosure. Motor system 1-1 shown in FIG. 1 controls the rotational operation of motor 4. Motor system 1-1 shown in FIG. Examples of devices equipped with the motor system 1-1 include a copy machine, a personal computer, a refrigerator, and a pump, but the devices are not limited to these. Motor system 1-1 includes at least a motor 4 and a motor control device 100-1.

Motor 4 is a permanent magnet synchronous motor with multiple 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. A specific example of the motor 4 is a three-phase brushless DC motor. The motor 4 has a rotor in which at least one permanent magnet is arranged, and a stator arranged around the axis of the rotor. The motor 4 is a sensorless motor that does not use a position sensor that detects the angular position (magnetic pole position) of the magnet of the rotor. The motor 4 is, for example, a fan motor that rotates a fan for blowing air.

The motor control device 100-1 controls an inverter that converts direct current into three-phase alternating current by controlling on/off (ON, OFF) a plurality of switching elements connected in a three-phase bridge according to an energization pattern including three-phase PWM signals. Drive the motor through. The motor control device 100-1 includes an inverter 23, a current detection section 27, a current detection timing adjustment section 34, a drive circuit 33, an energization pattern generation section 35, a carrier generation section 37, and a clock generation section 36.

The inverter 23 is a circuit that converts the DC supplied from the DC power supply 21 into three-phase AC by switching a plurality of switching elements, and rotates the rotor of the motor 4 by passing the three-phase AC drive current to the motor 4. be. The inverter 23 operates based on a plurality of energization patterns generated by the energization pattern generation section 35 (more specifically, three-phase PWM signals generated by the PWM signal generation section 32 in the energization pattern generation section 35). Drive the motor 4. PWM means Pulse Width Modulation.

The inverter 23 has a plurality of arms Up, Vp, Wp, Un, Vn, and Wn connected in a three-phase bridge. Upper arms Up, Vp, and Wp are high-side switching elements that are each connected to the positive electrode side of the DC power supply 21 via the positive bus bar 22a. Lower arms Un, Vn, and Wn are low-side switching elements connected to the negative electrode side (specifically, the ground side) of the DC power supply 21, respectively. The plurality of arms Up, Vp, Wp, Un, Vn, and Wn each follow a corresponding drive signal among the plurality of drive signals supplied from the drive circuit 33 based on the PWM signal included in the above-mentioned energization pattern. Turns on or off. Below, the plurality of arms Up, Vp, Wp, Un, Vn, and Wn may be simply referred to as arms unless they are particularly distinguished.

A connection point between the U-phase upper arm Up and the U-phase lower arm Un is connected to one end of the U-phase coil of the motor 4. A connection point between the V-phase upper arm Vp and the V-phase lower arm Vn is connected to one end of the V-phase coil of the motor 4. A connection point between the W-phase upper arm Wp and the W-phase lower arm Wn is connected to one end of the W-phase coil of the motor 4 . The other ends of the U-phase coil, V-phase coil, and W-phase coil are connected to each other.

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

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

The current detection unit 27 detects the U flowing through the motor 4 by acquiring the detection signal Sd based on the plurality of energization patterns (more specifically, three-phase PWM signals) generated by the energization pattern generation unit 35. , V, W phase currents Iu, Iv, and Iw of each phase are detected. More specifically, the current detection unit 27 detects the U and V flowing through the motor 4 by acquiring the detection signal Sd at an acquisition timing synchronized with a plurality of energization patterns (more specifically, three-phase PWM signals). , W detect the phase currents Iu, Iv, and Iw of each phase. The acquisition timing of the detection signal Sd is set by the current detection timing adjustment section 34.

For example, the current detection unit 27 captures 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. The AD converter is provided in the current detection section 27. Then, the current detection unit 27 AD converts the captured analog detection signal Sd into a digital detection signal Sd, and digitally processes the digital detection signal Sd after the AD conversion. Detect phase currents Iu, Iv, and Iw of each phase. The detected values of the phase currents Iu, Iv, and Iw of each phase detected by the current detection section 27 are supplied to the energization pattern generation section 35.

The clock generator 36 is a circuit that generates a clock of a predetermined frequency using a built-in oscillation circuit and outputs the generated clock to the carrier generator 37. Note that the clock generator 36 starts operating, for example, at the same time as the motor control device 100-1 is powered on.

The carrier generating section 37 generates the carrier C based on the clock generated by the clock generating section 36. Carrier C is a carrier signal whose level increases and decreases periodically.

The energization pattern generation unit 35 generates a pattern for energizing the inverter 23 (an energization pattern for the inverter 23). The energization pattern of the inverter 23 may be rephrased as the pattern for energizing the motor 4 (the energization pattern of the motor 4). The energization pattern of the inverter 23 includes three-phase PWM signals that energize the inverter 23 . The energization pattern generation unit 35 generates a three-phase PWM signal to energize the inverter 23 so that the motor 4 rotates, based on the detected values of the phase currents Iu, Iv, and Iw of the motor 4 detected by the current detection unit 27. It has a PWM signal generation section 32 that generates a PWM signal.

The energization pattern generation section 35 further includes a vector control section 30 when generating the energization pattern of the inverter 23 by vector control. Note that in this embodiment, the energization pattern of the inverter is generated by vector control, but the present invention is not limited to this, and the phase voltage of each phase may be determined using vf control or the like.

When the rotational speed command ωref of the motor 4 is given from the outside, the vector control unit 30 controls the torque current command Iqref and the excitation based on the difference between the measured value or estimated value of the rotational speed of the motor 4 and the rotational speed command ωref. Generate current command Idref. The vector control unit 30 calculates the torque current Iq and the excitation current Id based on the phase currents Iu, Iv, and Iw of the U, V, and W phases of the motor 4 through vector control calculation using the rotor position θ. The vector control unit 30 performs, for example, a PI control calculation on the difference between the torque current command Iqref and the torque current Iq, and generates a voltage command Vq. The vector control unit 30 performs, for example, PI control calculation on the difference between the excitation current command Idref and the excitation current Id, and generates a voltage command Vd. The vector control unit 30 converts the voltage commands Vq and Vd into phase voltage commands Vu*, Vv*, and Vw* for each phase of U, V, and W using the rotor position θ. The rotor position θ represents the magnetic pole position of the rotor of the motor 4.

The PWM signal generation section 32 generates a three-phase PWM signal by comparing the phase voltage commands Vu*, Vv*, Vw* generated by the vector control section 30 with the level of the carrier C generated by the carrier generation section 37. Generate an energization pattern that includes a signal. The PWM signal generation unit 32 also generates a PWM signal for lower arm drive which is an inversion of the three-phase PWM signal for upper arm drive, and after adding dead time as necessary, energization including the generated PWM signal is performed. The pattern is output to the drive circuit 33.

The drive circuit 33 outputs a drive signal that switches the six arms Up, Vp, Wp, Un, Vn, and Wn included in the inverter 23 in accordance with the energization pattern including the applied PWM signal. As a result, a three-phase AC drive 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 one cycle of the carrier C based on the carrier C supplied from the carrier generation unit 37 and the energization pattern including the PWM signal generated by the PWM signal generation unit 32. The acquisition timing for detecting the phase current of any one of the three phases is determined.

The current detection unit 27 detects the phase currents Iu, Iv, and Iw by acquiring the detection signal Sd at a plurality of acquisition timings determined by the current detection timing adjustment unit 34. The current detection unit 27 detects the phase currents Iu, Iv, and Iw using a method of detecting a plurality of phase currents from one current detector 24 (so-called one-shunt current detection method).

By the way, there is a method called inductive sensing as a method for estimating the magnetic pole position (initial position) of a rotor when a sensorless permanent magnet synchronous motor is stopped. Inductive sensing is a method of detecting the magnetic pole position of a rotor magnet of a permanent magnet synchronous motor by using the dependence of inductance on the rotor position. Since this position detection method does not use the induced voltage of the motor, the magnetic pole position of the rotor magnet can be detected even when the rotor of the motor is stopped or at an extremely low speed. The state in which the rotor is at extremely low speed refers to a state in which the rotor is rotating at such a low speed that the motor control device cannot detect the induced voltage. In this specification, for convenience of explanation, "a state in which the rotor is stopped or at an extremely low speed" is simply referred to as a "state in which the rotor is stopped".

The motor control device 100-1 according to the first embodiment includes an initial position estimation unit 38 that estimates an initial position θs, which is the magnetic pole position of the motor rotor in a stopped state, by inductive sensing. The energization pattern generation unit 35 uses the initial position θs estimated by the initial position estimation unit 38 to output an energization pattern including a PWM signal for rotating the rotor of the motor 4 to the drive circuit 33. The vector control unit 30 converts the voltage commands Vq and Vd into phase voltage commands Vu*, Vv*, and Vw* using the initial position θs estimated by the initial position estimation unit 38 as the initial value of the rotor position θ. In the present disclosure, the initial position θs has a width of 30 degrees, for example. In such a case, the motor 4 is controlled using a predetermined value determined based on the initial position θs.

FIG. 2 shows the waveforms of multiple PWM signals U, V, and W, the waveform of carrier C per cycle of these PWM signals, and the waveforms of phase voltage commands Vu*, Vv*, and Vw* for each phase. It is a figure which illustrates.

The PWM signal generation unit 32 generates a plurality of PWM signals U, V, W based on the magnitude relationship between the phase voltage commands Vu*, Vv*, Vw* of each phase and the level of the carrier C.

The PWM signal U is a PWM signal for driving two switching elements forming the upper and lower arms of the U phase. In this example, when the PWM signal U is at a low level, the switching element in the lower arm of the U phase is turned on (the switching element in the upper arm of the U phase is turned off), and when the PWM signal U is at a high level, the switching element in the lower arm of the U phase is turned on (the switching element in the upper arm of the U phase is turned off). The switching element of the arm is turned off (the switching element of the upper arm of the U phase is turned on). In response to changes in the level of the PWM signal U, the two switching elements forming the upper and lower arms of the U phase turn on and off in a complementary manner.

The PWM signal V is a PWM signal for driving two switching elements forming the upper and lower arms of the V phase. In this example, when the PWM signal V is low level, the switching element in the lower arm of the V phase is turned on (the switching element in the upper arm of the V phase is turned off), and when the PWM signal V is high level, the switching element in the lower arm of the V phase is turned on (the switching element in the upper arm of the V phase is turned off). The switching element of the arm is turned off (the switching element of the upper arm of the V phase is turned on). In response to changes in the level of the PWM signal V, the two switching elements forming the upper and lower arms of the V phase turn on and off in a complementary manner.

The PWM signal W is a PWM signal for driving two switching elements forming the upper and lower arms of the W phase. In this example, when the PWM signal W is at a low level, the switching element in the lower arm of the W phase is turned on (the switching element in the upper arm of the W phase is turned off), and when the PWM signal W is at a high level, the switching element in the lower arm of the W phase is turned on. The switching element of the arm is turned off (the switching element of the upper arm of the W phase is turned on). In response to changes in the level of the PWM signal W, the two switching elements forming the upper and lower arms of the W phase turn on and off in a complementary manner.

Note that in FIG. 2, illustration of dead time for preventing short circuit between the upper and lower arms is omitted. In addition, in FIG. 2, when a PWM signal is at a high level, the upper arm of the phase corresponding to that PWM signal is on, and when the PWM signal is at a low level, the lower arm of the phase corresponding to that PWM signal is on. ing. However, the relationship between the logic level of the PWM signal and the on/off status of each arm may be defined in the opposite manner, taking into account the circuit configuration and the like.

One period Tpwm of each of the plurality of PWM signals U, V, and W corresponds to the period of the carrier C (reciprocal of the carrier frequency). The change point (t1 to t6) represents the timing at which the logic level of the PWM signal changes.

As shown in FIG. 2, the PWM signal generation unit 32 may generate PWM signals for 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 waveform of the PWM signal of each phase can be simplified. The counter of carrier C is counting down to phase ta, counting up from phase ta to phase tb, and counting down from phase tb. In this way, the count-up period and the count-down period are repeated. Note that the PWM signal generation unit 32 may generate a PWM signal for each phase using a plurality of carriers C corresponding to each phase, or may generate a PWM signal for each phase using another known method. You may.

FIG. 2 illustrates a case where the first current detection timing Tm1 is set to the energization period T21 and the second current detection timing Tm2 is set to the energization period T22. Note that the energization period in which the first current detection timing Tm1 and the second current detection timing Tm2 are set is not limited to these periods.

When the inverter 23 is outputting PWM-modulated three-phase alternating current, the current detection unit 27 can detect the current of a specific phase according to the energization pattern for the upper arms Up, Vp, and Wp. Alternatively, in a state where the inverter 23 is outputting PWM-modulated three-phase AC, the current detection unit 27 may detect a specific phase current according to the energization pattern for the lower arms Un, Vn, and Wn. good.

For example, as shown in FIG. 2, during the energization time T21, the voltage value of the voltage generated across the current detector 24 corresponds to the current value of the positive U-phase current "+Iu" flowing out from the U-phase terminal of the motor 4. . The energization time T21 is the time from t4 to t5. The energization time T21 corresponds to a period in which the lower arm Un and the upper arms Vp, Wp are on and the remaining three arms are off. Therefore, the current detection unit 27 detects the current value of the positive U-phase current "+Iu" flowing out from the U-phase terminal of the motor 4 by acquiring the detection signal Sd at the first current detection timing Tm1 within the energization time T21. Can be detected.

The current detection timing adjustment unit 34 controls the current detection timing adjustment unit 34 when one phase of the PWM signal transitions to a logic level different from the other two phases (for example, when the U-phase PWM signal changes from the same high level as the V-phase and W-phase to the V-phase The first current detection timing Tm1 is set when a predetermined delay time td has elapsed from the timing of transition to a low level different from the W phase (t4). At this time, the current detection timing adjustment section 34 sets the first current detection timing Tm1 within the energization time T21.

In addition, as shown in FIG. 2, for example, the voltage value of the voltage generated across the current detector 24 during the energization time T22 is the current value of the negative W-phase current "-Iw" flowing from the W-phase terminal of the motor 4. corresponds to The energization time T22 is the time from t5 to t6. The energization time T22 corresponds to a period in which the lower arms Un, Vn and the upper arm Wp are on and the remaining three arms are off. Therefore, by acquiring the detection signal Sd at the second current detection timing Tm2 within the energization time T22, the current detection unit 27 determines the current value of the negative W-phase current "-Iw" flowing from the W-phase terminal of the motor 4. can be detected.

The current detection timing adjustment unit 34 controls the current detection timing adjustment unit 34 when one phase of the PWM signal transitions to a logic level different from the other two phases (for example, when the V-phase PWM signal changes from the same high level as the W phase to the same low level as the U phase). The second current detection timing Tm2 is set when a predetermined delay time td has elapsed from the timing (t5) at which the W phase becomes a different logic level from the U and V phases due to the transition to the current level. At this time, the current detection timing adjustment section 34 sets the second current detection timing Tm2 within the energization time T22.

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

In this way, by sequentially detecting and storing the two-phase currents among the phase currents Iu, Iv, and Iw according to the energization pattern including three-phase PWM signals, the three-phase currents can be detected in a time-sharing manner. It becomes possible to do so. Since the sum of the phase currents of the three phases is zero (iu+iv+iw=0), if the current detection unit 27 can detect the phase currents of two phases among the phase currents of the three phases, it can also detect the phase current of the remaining one phase.

FIG. 3 is a diagram showing an example of the switching state of each arm during energization. FIG. 4 is a diagram illustrating an example of the switching state of each arm when the arm is not energized. As shown in FIG. 3, during the energization period when the upper arm Up and the lower arms Vn, Wn are on and the remaining three arms are off, the current detection unit 27 detects a negative current flowing from the U-phase terminal of the motor 4. The current value of the U-phase current "-Iu" can be detected. On the other hand, as shown in FIG. 4, when all the upper arms Up, Vp, and Wp are on and all the lower arms Un, Vn, and Wn are off, no current flows to the current detector 24, so the current detecting section No. 27 cannot detect the phase current of each phase. Even if all the upper arms Up, Vp, Wp are off and all the lower arms Un, Vn, Wn are on, no current flows to the current detector 24, so the current detection unit 27 detects the phase current of each phase. Undetectable.

In this manner, in the one-shunt current detection method, the phase current of each phase cannot be detected unless a current-carrying period (current-carrying time) is provided. In the 1-shunt current detection method, the phase current that can be detected in one energization time is only for one phase, so at least two energization times are provided during one cycle of the PWM signal (see Figure 2), and the formula (iu + iv + iw = 0), the phase currents of the three phases are detected separately. However, if a current is provided to detect the phase currents of each phase separately, the current flowing through the current detector 24 will be amplified. Sometimes it is not possible to measure the detection error included in the detected value of the phase current of each phase.

Therefore, when the motor is stopped, by turning on some of the arms of the inverter 23 in accordance with the PWM signals of each phase, which have the same duty ratio, the current of each phase flowing to the current detector 24 is controlled. Sometimes defined as offset current. In this case, the current detection unit 27 turns on some of the arms of the inverter 23 according to the PWM signals of the respective phases, which have the same duty ratio, so that the offset current of each phase flows to the current detector 24. The current value is detected as an offset current value (detection error).

As an example, FIG. 5 shows the offset current of each phase flowing to the current detector 24 by turning on some of the arms of the inverter 23 according to the PWM signal of each phase when the duty ratio is 50%. It is an illustrative timing chart. In FIG. 6, when the inverter 23 is rotating the rotor according to the PWM signal of each phase whose duty ratio is different from 50%, the current flows to the detector 24 by turning on some of the arms as in FIG. 5. 5 is a timing chart illustrating phase currents of each phase.

In FIG. 5, the current detection unit 27 detects the offset current of the three phases by detecting the current at least twice every cycle of the PWM signal before the inverter 23 rotates the rotor (before starting the motor 4). Detect each current value. The current detection unit 27 stores each detected current value in a memory as a three-phase offset current value. In FIG. 5, the current detection unit 27 detects the offset current values of the positive U-phase current "Iu" and the negative W-phase current "-Iw", and based on the detection results, the offset current of the remaining V-phase current A case will be exemplified in which a value is detected (calculated) and the detected three-phase offset current values are stored in a memory. After the three-phase offset current values are stored in the memory, the motor 4 is started by the inverter 23, and the inverter 23 rotates the rotor.

In FIG. 6, when the inverter 23 is rotating the rotor according to the PWM signal of each phase whose duty ratio is different from 50%, the current detection unit 27 detects the same energization as in FIG. 5 for each cycle of the PWM signal. By performing current detection at least twice in the pattern, the current value of each of the three phase currents is detected. The current detection unit 27 subtracts the three-phase offset current value stored in advance in the memory from the current value of each of the three phase currents detected for each period of the PWM signal, for each period of the PWM signal. In this way, the detected current values of the three phase currents Iu, Iv, and Iw are calculated. As a result, detection errors are removed from the current detection values of each of the three phase currents Iu, Iv, and Iw. The PWM signal generation unit 32 generates three-phase PWM signals when the inverter 23 is rotating the rotor, based on the detected current values of the three-phase phase currents Iu, Iv, and Iw from which detection errors have been removed. By generating this, the rotation of the motor 4 can be controlled with high precision by the inverter 23.

However, even when the inverter 23 is not rotating the rotor with three-phase alternating current, the rotor may be idling due to disturbances such as wind. In particular, a rotor that rotates a rotating body such as a fan that has relatively low frictional resistance tends to spin idly. When the rotor is idling before the inverter 23 rotates the rotor with three-phase alternating current, if a current flowing to the current detector 24 is detected, the rotation of the rotor is inhibited by the regenerative brake generated in the idling rotor. may be done. If the rotation of the idling rotor is inhibited, unintended behavior such as deceleration of the motor 4 or abnormal noise may occur, for example.

FIG. 7 shows a comparative example of the waveform of the PWM signal when the inverter detects the current value of the current flowing through the current detector before rotating the rotor, and the duty ratio of the PWM signal of each phase is 50%. Here is an example of the case. Depending on the waveform of the PWM signal of each phase, a period in which regenerative current flows (regenerative section) and a period in which regenerative current does not flow (non-regenerative section) occur. The non-energized section shown in FIG. 7 corresponds to the regeneration section. In the regeneration section (non-energized section), either the upper or lower arms are all in the on state.

FIG. 8 is a diagram showing a case where all the lower arms are in the on state in the non-energized section, and shows the switching state in the non-energized sections on both sides of FIG. 7. FIG. 9 is a diagram showing a case where all the upper arms are in the on state in the non-energized section, and shows a switching state in the middle non-energized section sandwiched between the non-energized sections on both sides of FIG. When the rotor of the motor 4 idles due to an external force such as wind, an induced voltage is generated in the coils of each phase of the motor 4 due to the rotor's idle rotation. Due to these induced voltages, as shown in FIGS. 8 and 9, a regenerative current is generated from the motor 4 to the inverter 23 in the non-energized section shown in FIG. 7, and a regenerative brake is applied to the idling rotor. If the rotation of the idling rotor is inhibited by the regenerative brake, unintended behavior such as deceleration of the motor or abnormal noise may occur, for example.

<Current detection method 1 when rotor is idling>
In the "current detection method 1 during rotor idling" in the present disclosure, the PWM signal generation unit 32 turns off all arms of the inverter 23, as shown in FIG. 10, so that regenerative current does not flow in the non-energized section. Generate PWM signals for each phase to be set to . As a result, even if the rotor is idling, all arms of the inverter 23 are in the off state in the non-energized section, so theoretically no regenerative current flows from the motor 4 to the inverter 23. Therefore, the rotation of the rotor is less inhibited by the regenerative brake generated in the idling rotor, and for example, the possibility of unintended behavior such as deceleration of the motor 4 or abnormal noise can be reduced.

FIG. 11 is a diagram showing a first example of the waveform of the PWM signal when the inverter detects the current value of the current flowing through the current detector before rotating the rotor. The inverter 23 energizes the motor 4 having a rotor by turning on some of the arms, which are different for each energization pattern, among all the arms. The PWM signal generation unit 32 has a first period in which all the arms are turned off while the rotor is idling, a second period in which some of the arms are turned on in the first energization pattern while the rotor is idling, and a part of the arms in the idling period of the rotor. A PWM signal for each phase is generated, including in one cycle a third period in which the current is turned on in the second energization pattern. As a result, the switching state of each arm as shown in FIG. 11 is obtained.

In the example shown in FIG. 11, the non-energized period T1 in which all arms are in the OFF state is an example of the first period, and the current detection period T1 in which some arms are in the ON state in the first energized pattern. The first half section T2 is an example of the second period, and the second half section T3 of the current detection section in which some arms are in the on state in the second energization pattern is an example of the third period.

In the first half period T2 of the current detection period (an example of the second period), the lower arm Un and the upper arms Vp, Wp are in the on state in the first energization pattern, so the positive current flowing out from the U-phase terminal of the motor 4 is A U-phase current “+Iu” flows to the current detector 24. In the second half section T3 (an example of the third period) of the current detection section, the lower arms Un, Vn and the upper arm Wp are in the on state in the second energization pattern, so the negative current flowing from the W-phase terminal of the motor 4 is A W-phase current "-Iw" flows to the current detector 24. The current detection unit 27 detects a first reference current (positive U-phase current "+Iu" in this example) flowing to the current detector 24 in the first half period T2 and a second reference current (in this example, positive U-phase current "+Iu") flowing to the current detector 24 in the second half period T3. In this example, a negative W-phase current "-Iw") is detected.

In this way, according to the current detection method 1, all arms are in the off state in the non-energized section T1, so generation of unnecessary torque that causes regenerative braking is suppressed. Therefore, even if the current detection unit 27 detects the current flowing to the current detector 24 in the current detection period when the rotor is idling before the inverter 23 rotates the rotor with three-phase alternating current, all the arms Since there is a non-energized section T1 in which the rotor is in an off state, the rotor is less likely to be inhibited from idling.

In the example shown in FIG. 11, the current detection period, which is an example of the total period of the second period and the third period, is set shorter than the non-energized period, which is an example of the first period. In the non-energized section, the regenerative braking state is cut off, so generation of unnecessary torque that would cause regenerative braking is suppressed. On the other hand, since the current detection section is shorter than the non-energized section, only a small current flows during the energization time within the current detection section. Therefore, even if the current detection section 27 detects the current flowing to the current detector 24 in the current detection period when the rotor is idling before the inverter 23 rotates the rotor with three-phase alternating current, it will not be detected that the rotor is idling. The rotation of the rotor is prevented from being obstructed. As a result, for example, the occurrence of unintended behavior such as deceleration of the motor 4 or abnormal noise can be suppressed.

For example, the current detection unit 27 detects the phase current of the first phase flowing through the current detector 24 when the inverter 23 rotates the rotor according to the first reference current of the first phase detected in the second period. It may be corrected. Similarly, the current detection unit 27 detects the phase current of the second phase flowing through the current detector 24 when the inverter 23 rotates the rotor according to the second reference current of the second phase detected in the second period. It may be corrected by For example, the first phase is the U phase and the second phase is the W phase, but other combinations may be used. Since no current flows through the current detector 24 during the first period of one cycle, the first reference current flows through the current detector 24 during the second period, and the second reference current flows through the current detector 24 during the third period. can be treated as a two-phase reference current like the offset current described above.

For example, the current detection unit 27 determines whether the sum of the phase currents of the three phases is zero based on the first reference current of the first phase detected in the second period and the second reference current of the second phase detected in the third period. By utilizing this fact, the third reference current of the third phase flowing through the current detector 24 while the rotor is idling may be detected (calculated). The third electric reference current of the third phase can also be treated as a one-phase reference current like the above-mentioned offset current. The third phase is, for example, a V phase. The current detection unit 27 corrects the third phase current flowing through the current detector 24 when the inverter 23 rotates the rotor according to the detected (calculated) third reference current of the third phase. Good too.

For example, the value of the first reference current of the first phase is set as the first reference current value, the value of the second reference current of the second phase is set as the second reference current value, and the value of the third reference current of the third phase is set as the first reference current value. 3 standard current value. The current detection unit 27 detects the first reference current value in the second period, the second reference current value in the third period, and detects (calculates) the remaining third reference current value from the detection results. , the detected three-phase reference current values are stored in the memory. After the three-phase reference current values are stored in the memory, the motor 4 is started by the inverter 23, and the inverter 23 rotates the rotor.

The current detection unit 27 detects the current of each of the three phases by performing current detection at least twice in the same energization pattern as in FIG. 11 for each period of the PWM signal when the inverter 23 rotates the rotor. Detect the current value. The current detection unit 27 subtracts the reference current value of the three phases stored in advance in the memory from the current value of each of the three phase currents detected every cycle of the PWM signal, for each cycle of the PWM signal. In this way, the detected current values of the three phase currents Iu, Iv, and Iw are calculated. As a result, the current detection unit 27 corrects the phase current of each phase flowing to the current detector 24 when the inverter 23 rotates the rotor according to the reference current of each phase, so that Detection errors are removed from the current detection values of each of the phase currents Iu, Iv, and Iw. The PWM signal generation unit 32 uses the current detection values of the corrected three-phase phase currents Iu, Iv, and Iw from which detection errors have been removed to calculate the three-phase currents when the inverter 23 is rotating the rotor. By generating the PWM signal, the rotation of the motor 4 can be controlled with high precision by the inverter 23.

Note that as a method other than the above, for example, the state shown in FIG. 10 may be created by simply outputting an on/off signal from the port using a general-purpose port function without using the PWM function.

<Current detection method 2 when rotor is idling>
Next, "current detection method 2 during rotor idling" in the present disclosure will be described.

FIG. 12 shows an example of the current waveform of the U-phase current flowing through the current detector 24 by turning on some of the arms of the inverter according to the PWM signals of each phase, each of which has a duty ratio of 50%. FIG. In FIG. 12, the upper waveform shows when the rotor is stopped, and the lower waveform shows when the rotor is idling. FIG. 12 illustrates a waveform of approximately 16 cycles of the PWM signal. Both waveforms are vertically shifted with almost no change, and this vertical shift is caused by the induced voltage generated in the coils of each phase of the motor 4 due to idle rotation of the rotor.

FIG. 13 is a diagram showing a second example of the waveform of the PWM signal when the inverter detects the current value of the current flowing through the current detector 24 before rotating the rotor. The inverter 23 energizes the motor 4 having a rotor by turning on some of the arms, which are different for each energization pattern, among all the arms. The PWM signal generation unit 32 generates a first section in which some arms are turned on in a first energization pattern while the rotor is idling, and a second section in which some arms are turned on in a second energization pattern while the rotor is idling. A PWM signal for each phase having a first cycle section including a third section in which the upper arm or all the lower arms is turned on in a third energization pattern while the rotor is idling is generated with the same duty ratio. do. As a result, the switching state of each arm as shown in FIG. 13 is obtained.

In the example shown in FIG. 13, the first current detection period P1 (period including the timing of the first detection) in which some of the arms are in the on state in the first energization pattern is an example of the first current period, and The second current detection period P2 (period including the timing of the second detection) in which the arm of the current controller is in the on state in the second energization pattern is an example of the second period. The non-energized section P3 in which all the upper arms are in the on state and all the lower arms are in the off state is an example of the third section. In this example, the third section exists between the first section and the second section.

In the first current detection section P1 (an example of the first section), the upper arm Up and the lower arms Vn, Wn are in the ON state in the first energization pattern, so the negative U flowing from the U-phase terminal of the motor 4 A phase current "-Iu" flows into the current detector 24 (see FIG. 14). In the second current detection section P2 (an example of the second section), the lower arm Un and the upper arms Vp, Wp are in the on state in the second energization pattern, so the positive U flowing out from the U-phase terminal of the motor 4 A phase current "+Iu" flows into the current detector 24 (see FIG. 15). The current detection unit 27 detects a first current value of the first phase flowing to the current detector 24 in the first period and a second current value of the first phase flowing to the current detector 24 in the second period. In this example, the first current value is the current value of the negative U-phase current "-Iu (=Iv+Iw)", and the second current value is the current value of the positive U-phase current "+Iu".

In current detection method 2, the current detection unit 27 uses the fact that the phase currents of the first phase detected within one cycle of the PWM signal form a pair, and calculates the first current value of the first phase and the first current value of the first phase. The difference between half of the sum with the second current value and zero is detected as the influence due to the induced voltage. Then, the current detection unit 27 subtracts the influence of the detected induced voltage from the first current value or second current value detected at the first or second detection timing, thereby obtaining the offset current value of the first phase. Calculate. The current detection unit 27 can also calculate the offset current value for the second phase or the third phase other than the first phase using the same method even when the rotor is idling.

FIG. 16 is a waveform diagram showing an example of a process for calculating a U-phase offset current value in 10 cycles (for example, 400 μs) of a PWM signal when the rotor is idling. FIG. 17 is an enlarged view of the part surrounded by the dotted line frame shown in FIG. 16, and waveforms showing an example of processing for calculating the U-phase offset current value in one cycle (for example, 40 μs) of the PWM signal when the rotor is idling. It is a diagram. The U phase is an example of the first phase.

The current detection unit 27 detects a first current value (-Iu+e) of the U phase flowing to the current detector 24 at the first detection in the first section and a first current value (-Iu+e) of the U phase flowing to the current detector 24 at the second detection in the second section. By calculating half of the sum of the two current values (Iu+e), the influence component e due to the induced voltage can be derived. In the examples shown in FIGS. 16 and 17, the current detection unit 27 can calculate the U-phase offset current value Iu by subtracting the influence component e from the second U-phase current value (Iu+e) detected for the second time.

In this manner, according to the second current detection method, the U-phase offset current value can be calculated in one cycle of the PWM signal. That is, since the U-phase offset current value can be calculated in a short time even when the rotor is idling, the idling of the rotor is less likely to be inhibited. As a result, for example, the occurrence of unintended behavior such as deceleration of the motor 4 or abnormal noise can be suppressed.

FIG. 18 is a waveform diagram illustrating an example of a process for calculating a U-phase offset current value. FIG. 19 is a waveform diagram illustrating an example of processing for calculating the W-phase offset current value. As shown in FIG. 19, the W-phase offset current value (or V-phase offset current value) can also be calculated in the same way as the U-phase offset current value.

FIG. 18 exemplifies a case where the PWM signal generation unit 32 generates PWM signals of each phase having the first period section, all with a duty ratio of 50%. The PWM signal generation unit 32 generates a first section Q1 in which some arms are turned on in a first energization pattern while the rotor is idling, and a second section Q2 in which some arms are turned on in a second energization pattern while the rotor is idling. and a third period Q3 in which all the upper arms or all the lower arms are turned on in the third energization pattern while the rotor is idling. In the example shown in FIG. 18, the first cycle section includes a first section Q1 including the timing of the first detection, a second section Q2 including the timing of the second detection, and a third section Q3 in which all upper arms are turned on. include. The current detection unit 27 detects half of the sum of the first current value of the first phase flowing to the current detector 24 in the first section Q1 and the second current value of the first phase flowing to the current detector 24 in the second section Q2. is subtracted from the first current value or the second current value. In this example, the current detection unit 27 calculates the first phase offset current value by subtracting it from the second current value. FIG. 18 illustrates a case where the first phase is the U phase.

FIG. 19 exemplifies a case in which the PWM signal generation unit 32 generates PWM signals for each phase having a second period section, all with a duty ratio of 50%. The PWM signal generation unit 32 generates a fourth section Q4 in which some arms are turned on in a fourth energization pattern while the rotor is idling, and a fifth section Q5 in which some arms are turned on in a fifth energization pattern while the rotor is idling. and a sixth period Q6 in which all the upper arms or all the lower arms are turned on in the sixth energization pattern while the rotor is idling. In the example shown in FIG. 19, the second cycle section includes a fourth section Q4 that includes the timing of the first detection, a fifth section Q5 that includes the timing of the second detection, and a sixth section Q6 that turns on all the upper arms. include. The current detection unit 27 detects half of the sum of the third current value of the second phase flowing to the current detector 24 in the fourth section Q4 and the fourth current value of the second phase flowing to the current detector 24 in the fifth section Q5. is subtracted from the third current value or the fourth current value. In this example, the current detection unit 27 calculates the second phase offset current value by subtracting it from the fourth current value. FIG. 19 illustrates a case where the second phase is the W phase. Note that the second periodic section may be a section adjacent to the first periodic section, a section with one or more periodic sections sandwiched between it and the first periodic section, or even the same section as the first periodic section. good.

For example, the current detection unit 27 may correct the current value of the first phase current flowing through the current detector 24 when the inverter 23 rotates the rotor, according to the first phase offset current value. . Similarly, the current detection unit 27 may correct the current value of the second phase current flowing through the current detector 24 when the inverter 23 rotates the rotor according to the second phase offset current value. good. For example, the first phase is the U phase and the second phase is the W phase, but other combinations may be used.

For example, the current detection unit 27 calculates the third phase offset current value from the first phase offset current value and the second phase offset current value, using the fact that the sum of the three phase currents is zero. It may be detected (calculated). The third phase is, for example, a V phase. The current detection unit 27 may correct the third phase current flowing through the current detector 24 when the inverter 23 rotates the rotor according to the detected (calculated) third phase offset current value. good.

For example, the current detection unit 27 calculates the offset current value of the first phase, calculates the offset current value of the second phase, calculates the remaining offset current value of the third phase from the results of these calculations, and calculates the offset current value of the remaining third phase. Store the three-phase offset current values in memory. After the three-phase offset current values are stored in the memory, the motor 4 is started by the inverter 23, and the inverter 23 rotates the rotor.

The current detection unit 27 detects the current value of each of the three phase currents by detecting the current at least twice while the inverter 23 rotates the rotor. The current detection unit 27 subtracts the three-phase offset current value stored in advance in the memory from the current value of each of the three phase currents detected for each period of the PWM signal, for each period of the PWM signal. In this way, the detected current values of the three phase currents Iu, Iv, and Iw are calculated. As a result, the current detection unit 27 corrects the phase current of each phase flowing to the current detector 24 when the inverter 23 rotates the rotor according to the offset current value of each phase, so the three-phase Detection errors are removed from the current detection values of each of the phase currents Iu, Iv, and Iw. The PWM signal generation unit 32 uses the current detection values of the corrected three-phase phase currents Iu, Iv, and Iw from which detection errors have been removed to calculate the three-phase currents when the inverter 23 is rotating the rotor. By generating the PWM signal, the rotation of the motor 4 can be controlled with high precision by the inverter 23.

Note that each function of the current detection section 27, energization pattern generation section 35, current detection timing adjustment section 34, and initial position estimation section 38 is executed by a CPU (Central Processing Unit) by a program readably stored in a storage device (not shown). This is realized by the operation of For example, each of these functions is realized by cooperation between hardware and software in a microcomputer including a CPU.

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

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

1-1 Motor system 4 Motor 21 DC power supply 22a Positive bus 22b Negative bus 23 Inverter 24 Current detector 27 Current detection section 30 Vector control section 32 PWM signal generation section 33 Drive circuit 34 Current detection timing adjustment section 35 Energization pattern generation Section 36 Clock generation section 37 Carrier generation section 38 Initial position estimation section 100-1 Motor control device Up, Vp, Wp, Un, Vn, Wn Arm

Claims (8)

an inverter that energizes a motor having a rotor by turning on some of the arms that are different for each energization pattern among all the arms;
a current detector connected to the DC side of the inverter;
A first period in which all the arms are turned off while the rotor is idling; a second period in which some of the arms are turned on in a first energization pattern while the rotor is idling; and a second energization in some of the arms while the rotor is idling. a PWM signal generation unit that generates a PWM signal for each phase including a third period of turning on in a pattern in one cycle;
A motor control device comprising: a current detection unit that detects a first reference current flowing to the current detector during the second period and a second reference current flowing to the current detector during the third period. The motor control device according to claim 1, wherein a total period of the second period and the third period is shorter than the first period. The current detection section includes:
correcting a first phase current flowing in the current detector when the inverter rotates the rotor according to the first reference current of the first phase;
The motor according to claim 1 or 2, wherein a second phase current flowing through the current detector when the inverter rotates the rotor is corrected according to the second reference current of the second phase. Control device. The PWM signal generation section includes:
Using the corrected phase current of the first phase, generating a PWM signal of the first phase when the inverter is rotating the rotor;
The motor control device according to claim 3, wherein the corrected phase current of the second phase is used to generate the PWM signal of the second phase when the inverter is rotating the rotor. The current detection section includes:
calculating a third reference current of a third phase from the first reference current of the first phase and the second reference current of the second phase;
The motor control according to claim 3, wherein the phase current of the third phase flowing to the current detector when the inverter rotates the rotor is corrected according to the third reference current of the third phase. Device. The PWM signal generation section includes:
6. The motor control device according to claim 5, wherein the corrected phase current of the third phase is used to generate the PWM signal of the third phase when the inverter is rotating the rotor. A motor system comprising the motor control device according to claim 1 and the motor. A motor control method performed by a motor control device that energizes a motor having a rotor by turning on some arms that are different for each energization pattern among all arms of an inverter, the method comprising:
A first period in which all the arms are turned off while the rotor is idling; a second period in which some of the arms are turned on in a first energization pattern while the rotor is idling; and a second energization in some of the arms while the rotor is idling. Generate a PWM signal for each phase including a third period of turning on in a pattern in one cycle,
A motor control method, comprising detecting a first reference current flowing in the second period to a current detector connected to the DC side of the inverter and a second reference current flowing in the third period to the current detector.

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