JP2021164280A - Motor controller, motor system, and motor control method - Google Patents

Abstract

To mitigate inhibition of idling of a rotor caused by detecting current flowing through a current detector.SOLUTION: A motor control method to be performed by a motor controller for energizing a motor having a rotor by turning on arms of all arms of an inverter, the arms varying among energization patterns, includes: generating a PWM signal of each phase having one cycle including a first period in which all the arms are turned off during idling of the rotor, a second period in which the arms are turned on during the idling in a first energization pattern, and a third period in which the arms are turned on during the idling in a second energization pattern; and detecting first reference current flowing through a current detector in the second period and second reference current flowing through the current detector in the third period.SELECTED DRAWING: Figure 11

Description

The present disclosure relates to motor control devices, motor systems and motor control methods.

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

Japanese Unexamined Patent Publication No. 2015-208071

When the motor is controlled by 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 the motor is started). The current detected before the motor starts is used, for example, for failure detection before the motor starts, or for improving the accuracy of current detection and failure detection when the motor is started by the inverter and the inverter is rotating the rotor. It is used.

However, if the current flowing through the current detector of one shunt is detected when the rotor is idling before the inverter rotates the rotor, the regenerative brake generated in the idling rotor hinders the rotation of the rotor. There is. If the rotation of the rotor during idling is hindered, unintended behavior such as deceleration of the motor or abnormal noise may occur.

The present disclosure provides a motor control device, a motor system, and a motor control method capable of reducing the hindrance of idling of a rotor by detecting a current flowing through a current detector.

The motor control device according to the embodiment of the present disclosure is
An inverter that energizes a motor with a rotor by turning on some of the arms that are different for each energization pattern,
A current detector connected to the DC side of the inverter and
The first period in which all the arms are turned off during the idling of the rotor, the second period in which some of the arms are turned on in the first energization pattern during the idling, and the second energization of the part of the arms during the idling. A PWM signal generator that generates a PWM signal for each phase that includes a third period that is turned on in a pattern in one cycle.
A current detection unit for detecting a first reference current flowing through the current detector in the second period and a second reference current flowing through the current detector in the third period is provided.

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

It is a figure which shows the structural example of the motor system which concerns on Embodiment 1 of this disclosure. It is a figure which illustrates the waveform of a plurality of PWM signals, the waveform of a carrier per one cycle of these PWM signals, and the waveform of the phase voltage command of 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 de-energization. Each is a timing chart illustrating the offset current of each phase flowing through the current detector by turning on a part of all the arms of the inverter according to the PWM signal of each phase having 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 same arms as in FIG. 5, the phase current of each phase flowing through the current detector is changed. It is an example timing chart. It is a figure which shows a comparative example of the waveform of the PWM signal at the time of detecting the current value of the current flowing through the current detector before the inverter rotates a rotor. It is a figure which shows the case where all the lower arms are turned on in a non-energized section. It is a figure which shows the case where all the upper arms are turned on in a non-energized section. It is a figure which shows the case where all the upper and lower arms are off state in a non-energized section. It is a figure which shows the 1st example of the waveform of the PWM signal at the time of detecting the current value of the current flowing through the current detector before the inverter rotates a rotor. Each is an enlarged view showing an example of the current waveform of the U-phase current flowing through the current detector by turning on a part of all the arms of the inverter according to the PWM signal of each phase having a duty ratio of 50%. It is a figure which shows the 2nd example of the waveform of the PWM signal at the time of detecting the current value of the current flowing through the current detector before the inverter rotates a rotor. It is a figure which shows the switching state in which a negative U-phase current "-Iu" flows through a current detector. It is a figure which shows the switching state in which a positive U-phase current "+ Iu" flows through a current detector. It is a waveform diagram which shows an example of the process of calculating the U-phase offset current value in 10 cycles of the PWM signal at the time of idling of a rotor. It is an enlarged view of the part surrounded by the dotted line frame shown in FIG. It is a waveform diagram which shows an example of the process of calculating the U-phase offset current value. It is a waveform diagram which shows an example of the process of calculating the W phase offset current value.

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

FIG. 1 is a diagram showing a configuration example of the motor system 1-1 according to the first embodiment of the present disclosure. The motor system 1-1 shown in FIG. 1 controls the rotational operation of the motor 4. The equipment on which the motor system 1-1 is mounted is, for example, a copier, a personal computer, a refrigerator, a pump, and the like, but the equipment is not limited thereto. The motor system 1-1 includes at least a motor 4 and a motor control device 100-1.

The motor 4 is a permanent magnet synchronous motor having 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 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 type motor that does not use a position sensor that detects the angular position (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) of a plurality of switching elements connected by a three-phase bridge according to an energization pattern including a three-phase PWM signal. Drive the motor through. The motor control device 100-1 includes an inverter 23, a current detection unit 27, a current detection timing adjustment unit 34, a drive circuit 33, an energization pattern generation unit 35, a carrier generation unit 37, and a clock generation unit 36.

The inverter 23 is a circuit that rotates the rotor of the motor 4 by converting the direct current supplied from the DC power supply 21 into a three-phase alternating current by switching a plurality of switching elements and passing a driving current of the three-phase alternating current through the motor 4. be. The inverter 23 is based on a plurality of energization patterns generated by the energization pattern generation unit 35 (more specifically, a three-phase PWM signal generated by the PWM signal generation unit 32 in the energization pattern generation unit 35). Drives the motor 4. PWM means Pulse Width Modulation.

The inverter 23 has a plurality of arms Up, Vp, Wp, Un, Vn, and Wn connected by a three-phase bridge. The upper arms Up, Vp, and Wp are high-side switching elements connected to the positive electrode side of the DC power supply 21 via the positive bus 22a, respectively. The 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 the 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. In the following, a plurality of arms Up, Vp, Wp, Un, Vn, and Wn may be simply referred to as arms unless otherwise specified.

The 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. The 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. The 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, the V-phase coil, and the 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 arm is 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 on 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 arranged 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 it as a detection signal Sd.

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

For example, the current detection unit 27 takes in the detection signal Sd of the analog voltage generated by the current detector 24 into the 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 unit 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, thereby U, V, W of the motor 4. The phase currents Iu, Iv, and Iw of each phase are detected. The detected values of the phase currents Iu, Iv, and Iw of each phase detected by the current detection unit 27 are supplied to the energization pattern generation unit 35.

The clock generation unit 36 is a circuit that generates a clock having a predetermined frequency by a built-in oscillation circuit and outputs the generated clock to the carrier generation unit 37. The clock generation unit 36 starts operation at the same time when the power of the motor control device 100-1 is turned on, for example.

The carrier generation unit 37 generates the carrier C based on the clock generated by the clock generation unit 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 (the energization pattern of the inverter 23). 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 a three-phase PWM signal for energizing the inverter 23. The energization pattern generation unit 35 generates a three-phase PWM signal for energizing 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 unit 32 to generate.

The energization pattern generation unit 35 further includes a vector control unit 30 when the energization pattern of the inverter 23 is generated by vector control. In the present 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 obtained by using vf control or the like.

When the rotation speed command ωref of the motor 4 is given from the outside, the vector control unit 30 excites the torque current command Iqref based on the difference between the measured value or the estimated value of the rotation speed of the motor 4 and the rotation speed command ωref. Generates the current command Idref. The vector control unit 30 calculates the torque current Iq and the exciting current Id by the vector control calculation using the rotor position θ based on the phase currents Iu, Iv, and Iw of the U, V, and W phases of the motor 4. 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, and generates the voltage command Vq. The vector control unit 30 performs, for example, a PI control calculation on the difference between the exciting current command Idref and the exciting current Id, and generates the 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 of the U, V and W phases 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 unit 32 compares the phase voltage commands Vu *, Vv *, Vw * generated by the vector control unit 30 with the level of the carrier C generated by the carrier generation unit 37, thereby performing a three-phase PWM. Generate an energization pattern that includes a signal. The PWM signal generation unit 32 also generates a PWM signal for driving the lower arm by inverting the three-phase PWM signal for driving the upper arm, adds a dead time as necessary, and then energizes the generated PWM signal. The pattern is output to the drive circuit 33.

The drive circuit 33 outputs a drive signal for switching the six arms Up, Vp, Wp, Un, Vn, and Wn included in the inverter 23 according to the energization pattern including the given PWM signal. As a result, a three-phase alternating current drive current is supplied to the motor 4, and the rotor of the motor 4 rotates.

In the current detection timing adjustment unit 34, the current detection unit 27 performs 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 signals 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 by 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 of estimating the magnetic pole position (initial position) of the rotor when the sensorless permanent magnet synchronous motor is stopped. Inductive sensing is a method of detecting the magnetic pole position of the rotor magnet of a permanent magnet synchronous motor by utilizing the rotor position dependence of inductance. 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 extremely low speed means a state in which the rotor is rotating at such a low speed that the motor control device cannot detect the induced voltage. In the present specification, for convenience of explanation, the "rotor stopped or extremely low speed state" is simply referred to as the "rotor stopped state".

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

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

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 constituting 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 of the lower arm of the U phase is on (the switching element of the upper arm of the U phase is off), and when the PWM signal U is at a high level, it is below the U phase. The switching element of the arm is turned off (the switching element of the upper arm of the U phase is turned on). The two switching elements constituting the upper and lower arms of the U phase complementarily operate on and off in response to a change in the level of the PWM signal U.

The PWM signal V is a PWM signal for driving two switching elements constituting the upper and lower arms of the V phase. In this example, when the PWM signal V is at a low level, the switching element of the lower arm of the V phase is on (the switching element of the upper arm of the V phase is off), and when the PWM signal V is at a high level, it is below the V phase. The switching element of the arm is turned off (the switching element of the upper arm of the V phase is turned on). The two switching elements constituting the upper and lower arms of the V phase complementarily operate on and off in response to a change in the level of the PWM signal V.

The PWM signal W is a PWM signal for driving two switching elements constituting 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 of the lower arm of the W phase is on (the switching element of the upper arm of the W phase is off), and when the PWM signal W is at a high level, it is below the W phase. The switching element of the arm is turned off (the switching element of the upper arm of the W phase is turned on). The two switching elements constituting the upper and lower arms of the W phase complementarily operate on and off in response to a change in the level of the PWM signal W.

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

Each one cycle Tpwm of the plurality of PWM signals U, V, W corresponds to the cycle of the carrier C (the reciprocal of the carrier frequency). The change points (t1 to t6) represent 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 a PWM signal for each phase by 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 the carrier C is down-counting from phase ta, up-counting from phase ta to phase tb, and down-counting from phase tb. In this way, the count-up period and the count-down period are repeated. The PWM signal generation unit 32 may generate the PWM signal of each phase by using a plurality of carriers C corresponding to each of the phases, or generate the PWM signal of each phase by 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. 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.

In a state where the inverter 23 outputs 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 outputs PWM-modulated three-phase alternating current, the current detection unit 27 may detect the current of a specific phase according to the energization pattern for the lower arms Un, Vn, and Wn. good.

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

When one phase of the PWM signal transitions to a logic level different from that of the other two phases (for example, the PWM signal of the U phase changes from the same high level as the V phase and the W phase to the V phase, the current detection timing adjusting unit 34 is used. The first current detection timing Tm1 is set when a predetermined delay time td elapses from the timing of transitioning to a low level different from that of the W phase: t4). At this time, the current detection timing adjusting unit 34 sets the first current detection timing Tm1 within the energization time T21.

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

When one phase of the PWM signal transitions to a logic level different from that of the other two phases (for example, the PWM signal of the V phase 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 the predetermined delay time td elapses from the timing when the W phase becomes a logical level different from the U phase and the V phase due to the transition to the level: t5). At this time, the current detection timing adjusting unit 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, if the two-phase phase currents of the two-phase currents Iu, Iv, and Iw are sequentially detected and stored according to the energization pattern including the three-phase PWM signals, the currents for the three phases are detected in time division. It becomes possible to do. Since the total of the three-phase phase currents is zero (iu + iv + iwa = 0), the current detection unit 27 can detect the phase currents of the remaining one phase if it can detect the phase currents of two of the three phase currents.

FIG. 3 is a diagram showing an example of a switching state of each arm when energized. FIG. 4 is a diagram showing an example of a switching state of each arm when the power is off. As shown in FIG. 3, during the energization period in which the upper arm Up and the lower arms Vn and Wn are on and the remaining three arms are off, the current detection unit 27 receives a negative current 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, Wp are on and all the lower arms Un, Vn, Wn are off, no current flows through the current detector 24, so that the current detection unit 27 cannot detect the phase current of each phase. Even when all the upper arms Up, Vp, and Wp are off and all the lower arms Un, Vn, and Wn are on, no current flows through the current detector 24, so the current detector 27 determines the phase current of each phase. Cannot be detected.

As described above, in the one-shunt current detection method, the phase current of each phase cannot be detected unless the energization section (energization time) is provided. In the one-shunt current detection method, only one phase current can be detected in one energization time. Therefore, at least two energization times are provided during one cycle of the PWM signal (see FIG. 2), and the equation (iu + iv + iv) is provided. The three-phase phase currents are detected separately based on = 0). However, if an energizing time is provided to distinguish and detect the phase currents of each phase, the current flowing through the current detector 24 is amplified, so that the current detecting unit 27 has zero current flowing through the current detector 24. Sometimes it is not possible to measure the detection error included in the detection value of the phase current of each phase.

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

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

In FIG. 5, the current detection unit 27 detects the current at least twice for each cycle of the PWM signal before the inverter 23 rotates the rotor (before the motor 4 is started), so that the three-phase offset current is generated. Each current value of is detected. The current detection unit 27 stores each detected current value in the 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 the offset current of the remaining V-phase current is obtained from the detection results. An example shows a case where a value is detected (calculated) and the detected three-phase offset current value is 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, the current detection unit 27 energizes the same as in FIG. 5 for each cycle of the PWM signal when the inverter 23 rotates the rotor according to the PWM signal of each phase whose duty ratio is different from 50%. By performing current detection at least twice in the pattern, the current value of each of the three-phase phase currents is detected. The current detection unit 27 subtracts the three-phase offset current value stored in advance in the memory from each of the three-phase phase currents detected in each cycle of the PWM signal for each cycle of the PWM signal. Therefore, the current detection values of the three-phase phase currents Iu, Iv, and Iw are calculated. As a result, the detection error is removed from the current detection values of the three-phase phase currents Iu, Iv, and Iw. The PWM signal generation unit 32 generates a three-phase PWM signal when the inverter 23 is rotating the rotor based on the current detection values of the three-phase phase currents Iu, Iv, and Iw from which the detection error has been removed. By generating it, the rotation of the motor 4 can be controlled with high accuracy by the inverter 23.

However, even in a state where the inverter 23 does not rotate the rotor with a three-phase alternating current, the rotor may idle due to disturbance such as wind. In particular, a rotor that rotates a rotating body such as a fan having a relatively small frictional resistance tends to slip. When the rotor is idling before the inverter 23 rotates the rotor with three-phase alternating current, if the current flowing through the current detector 24 is detected, the regenerative brake generated in the idling rotor hinders the rotation of the rotor. May be done. If the rotation of the rotor during idling is hindered, unintended behavior such as deceleration of the motor 4 or abnormal noise may occur.

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

FIG. 8 is a diagram showing a case where all the lower arms are in the non-energized section in the non-energized section, and shows a switching state in the non-energized section on both sides of FIG. 7. FIG. 9 is a diagram showing a case where all the upper arms are in the non-energized section in the non-energized section, and shows a switching state in the intermediate 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 idling of the rotor. As shown in FIGS. 8 and 9, these induced voltages generate a regenerative current from the motor 4 to the inverter 23 in the non-energized section shown in FIG. 7, and regenerative braking is applied to the idling rotor. If the rotation of the rotor during idling is hindered by the regenerative brake, unintended behavior such as deceleration of the motor or abnormal noise may occur.

<Current detection method 1 when the rotor is idling>
In the "current detection method 1 when the rotor is idling" in the present disclosure, the PWM signal generation unit 32 turns off all the arms of the inverter 23 as shown in FIG. 10 so that the regenerative current does not flow in the non-energized section. Generates a PWM signal for each phase set to. As a result, even if the rotor is idling, all the arms of the inverter 23 are off in the non-energized section, so that the regenerative current flowing from the motor 4 to the inverter 23 is theoretically not generated. Therefore, it is possible to reduce the possibility that the rotation of the rotor is hindered by the regenerative brake generated in the rotor during idling, and to reduce the possibility of unintended behavior such as deceleration of the motor 4 and abnormal noise.

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

In the example shown in FIG. 11, the non-energized section T1 in which all the arms are in the off state is an example of the first period, and is a current detection section in which some arms are in the on state in the first energization 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 turned on in the second energization pattern is an example of the third period.

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

As described above, according to the current detection method 1, since all the arms are in the off state in the non-energized section T1, the generation of unnecessary torque for generating the regenerative brake is suppressed. Therefore, even if the current detector 27 detects the current flowing through the current detector 24 in the current detection section when the rotor is idling before the inverter 23 rotates the rotor with the three-phase alternating current, all arms Since there is a non-energized section T1 in the off state, the idling of the rotor is less likely to be hindered.

In the example shown in FIG. 11, the current detection section, which is an example of the total period of the second period and the third period, is set shorter than the non-energized section, which is an example of the first period. In the non-energized section, since the regenerative braking state is cut off, the generation of unnecessary torque that generates the regenerative braking is suppressed. On the other hand, since the current detection section is shorter than the non-energized section, only a minute current flows during the energization time in the current detection section. Therefore, when the rotor is idling before the inverter 23 rotates the rotor with the three-phase alternating current, even if the current detector 27 detects the current flowing through the current detector 24 in the current detection section, it is idling. The impediment to the rotation of the rotor is reduced. As a result, for example, it is possible to suppress the occurrence of unintended behavior such as deceleration of the motor 4 and abnormal noise.

For example, the current detection unit 27 sets the phase current of the first phase flowing through the current detector 24 when the inverter 23 is rotating 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 makes the phase current of the second phase flowing through the current detector 24 when the inverter 23 is rotating the rotor correspond to the second reference current of the second phase detected in the second period. May be corrected. 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 in the first period of one cycle, the first reference current flowing through the current detector 24 in the second period and the second reference current flowing through the current detector 24 in the third period Can be treated as a two-phase reference current such as the offset current described above.

In the current detection unit 27, for example, the sum of the phase currents of the three phases is zero from 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. Therefore, the third reference current of the third phase flowing through the current detector 24 during idling of the rotor may be detected (calculated). The third electric reference current of the third phase can also be treated as a one-phase reference current such as the offset current described above. The third phase is, for example, the V phase. The current detection unit 27 corrects the phase current of the third phase flowing through the current detector 24 when the inverter 23 is rotating the rotor according to the detected (calculated) third reference current of the third phase. May be good.

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 the third. 3 Use the reference current value. The current detection unit 27 detects the first reference current value in the second period, detects the second reference current value in the third period, and detects (calculates) the remaining third reference current value from those detection results. , The detected reference current value of the three phases is 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.

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

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

<Current detection method 2 when the rotor is idling>
Next, the "current detection method 2 when the rotor is 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 a part of all the arms of the inverter according to the PWM signal of each phase having a duty ratio of 50%. It is an enlarged view which shows. In FIG. 12, the upper waveform shows the rotor when the rotor is stopped, and the lower waveform shows the rotor when the rotor is idling. FIG. 12 illustrates a waveform in which the PWM signal has about 16 cycles. Both waveforms are shifted up and down 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 the idling of the rotor.

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

In the example shown in FIG. 13, the first current detection section P1 (the period including the timing of the first detection) in which some of the arms are turned on in the first energization pattern is an example of the first section. The second current detection section P2 (the period including the timing of the second detection) in which the arm of the unit is turned on in the second energization pattern is an example of the second section. 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 and Wn are turned on in the first energization pattern, so that the negative U flowing in from the U phase terminal of the motor 4 A phase current "-Iu" flows through 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 and Wp are turned on in the second energization pattern, so that the positive U flowing out from the U-phase terminal of the motor 4 A phase current "+ Iu" flows through the current detector 24 (see FIG. 15). The current detection unit 27 detects the first current value of the first phase flowing through the current detector 24 in the first section and the second current value of the first phase flowing through the current detector 24 in the second section. 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 the current detection method 2, the current detection unit 27 utilizes the fact that the phase currents of the first phase detected in one cycle of the PWM signal are paired, and the first current value of the first phase and the first phase are The difference between half of the sum of the second current value and zero is detected as the effect of the induced voltage. Then, the current detection unit 27 subtracts the influence of the detected induced voltage from the first current value or the second current value detected at the first or second detection timing, so that the offset current value of the first phase is obtained. Is calculated. The current detection unit 27 can calculate the offset current value even during idling of the rotor by the same method for the second phase or the third phase other than the first phase.

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

The current detection unit 27 has a first current value (−Iu + e) of the U phase flowing through the current detector 24 at the first detection of the first section and a U-phase first current value (−Iu + e) flowing through the current detector 24 at the second detection of 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 influential component e from the second current value (Iu + e) of the U-phase for the second detection.

As described above, according to the current detection method 2, the U-phase offset current value can be calculated in the time of one cycle of the PWM signal. That is, since the U-phase offset current value can be calculated in a short time even during the idling of the rotor, the idling of the rotor is less likely to be hindered. As a result, for example, it is possible to suppress the occurrence of unintended behavior such as deceleration of the motor 4 and abnormal noise.

FIG. 18 is a waveform diagram showing an example of processing for calculating the U-phase offset current value. FIG. 19 is a waveform diagram showing 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 be calculated in the same manner as the U-phase offset current value.

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

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

For example, the current detection unit 27 may correct the current value of the phase current of the first phase flowing through the current detector 24 when the inverter 23 is rotating the rotor according to the offset current value of the first phase. .. Similarly, the current detection unit 27 may correct the current value of the phase current of the second phase flowing through the current detector 24 when the inverter 23 is rotating the rotor according to the offset current value of the second phase. 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 obtains the offset current value of the third phase from the offset current value of the first phase and the offset current value of the second phase by utilizing the fact that the sum of the phase currents of the three phases is zero. It may be detected (calculated). The third phase is, for example, the V phase. Even if the current detection unit 27 corrects the phase current of the third phase flowing through the current detector 24 when the inverter 23 is rotating the rotor according to the detected (calculated) offset current value of the third phase. 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 offset current value of the remaining third phase from those calculation results, and calculates the calculation. The three-phase offset current value is stored in the 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 phase currents by detecting the current at least twice while the inverter 23 is rotating the rotor. The current detection unit 27 subtracts the three-phase offset current value stored in advance in the memory from each of the three-phase phase currents detected in each cycle of the PWM signal for each cycle of the PWM signal. Therefore, the current detection values of the three-phase phase currents Iu, Iv, and Iw are calculated. As a result, the current detection unit 27 corrects the phase current of each phase flowing through the current detector 24 when the inverter 23 is rotating the rotor, according to the offset current value of each phase. Therefore, the three-phase current detection unit 27 corrects the phase current of each phase. The detection error is removed from each of the current detection values of the phase currents Iu, Iv, and Iw. The PWM signal generation unit 32 uses the current detection values of the corrected three-phase currents Iu, Iv, and Iw from which the detection error has been removed, and uses the current detection values of the three-phase when the inverter 23 is rotating the rotor. By generating the PWM signal, the rotation of the motor 4 can be controlled with high accuracy by the inverter 23.

The functions of the current detection unit 27, the energization pattern generation unit 35, the current detection timing adjustment unit 34, and the initial position estimation unit 38 are CPUs (Central Processing Units) by a program readable and stored in a storage device (not shown). Is realized by the operation of. For example, each of these functions is realized by the collaboration of hardware and software in a microcomputer including a CPU.

Although the motor control device, the motor system, and the motor control method have been described above by the embodiment, the present invention is not limited to the above embodiment. 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 on the DC side of the inverter may output the detection signal corresponding to the current value of the current flowing on the positive 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 side bus 22b Negative side bus 23 Inverter 24 Current detector 27 Current detection unit 30 Vector control unit 32 PWM signal generation unit 33 Drive circuit 34 Current detection timing adjustment unit 35 Energization pattern generation Part 36 Clock generation part 37 Carrier generation part 38 Initial position estimation part 100-1 Motor control device Up, Vp, Wp, Un, Vn, Wn arm

Claims (8)

An inverter that energizes a motor with a rotor by turning on some of the arms that are different for each energization pattern,
A current detector connected to the DC side of the inverter and
The first period in which all the arms are turned off during the idling of the rotor, the second period in which some of the arms are turned on in the first energization pattern during the idling, and the second energization of the part of the arms during the idling. A PWM signal generator that generates a PWM signal for each phase that includes a third period that is turned on in a pattern in one cycle.
A motor control device including a current detection unit that detects a first reference current flowing through the current detector in the second period and a second reference current flowing through the current detector in the third period. The motor control device according to claim 1, wherein the total period of the second period and the third period is shorter than that of the first period. The current detector
The phase current of the first phase flowing through the current detector when the inverter is rotating the rotor is corrected according to the first reference current of the first phase.
The motor according to claim 1 or 2, wherein the phase current of the second phase flowing through the current detector when the inverter is rotating the rotor is corrected according to the second reference current of the second phase. Control device. The PWM signal generation unit
Using the corrected phase current of the first phase, the PWM signal of the first phase when the inverter is rotating the rotor is generated.
The motor control device according to claim 3, wherein the corrected phase current of the second phase is used to generate a PWM signal of the second phase when the inverter is rotating the rotor. The current detector
From the first reference current of the first phase and the second reference current of the second phase, the third reference current of the third phase is calculated.
The motor control according to claim 3, wherein the phase current of the third phase flowing through the current detector when the inverter is rotating the rotor is corrected according to the third reference current of the third phase. Device. The PWM signal generation unit
The motor control device according to claim 5, wherein the corrected phase current of the third phase is used to generate a PWM signal of the third phase when the inverter is rotating the rotor. A motor system comprising the motor control device according to any one of claims 1 to 6 and the motor. This is a motor control method performed by a motor control device that energizes a motor having a rotor by turning on some of all the arms of the inverter, which are different for each energization pattern.
The first period in which all the arms are turned off during the idling of the rotor, the second period in which some of the arms are turned on in the first energization pattern during the idling, and the second energization of the part of the arms during the idling. Generate a PWM signal for each phase that includes the third period to be turned on in the pattern in one cycle.
A motor control method for detecting a first reference current flowing in the second period and a second reference current flowing in the current detector in the third period in a current detector connected to the DC side of the inverter.

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