JP2021164278A - Motor controller, motor system, and motor control method - Google Patents

Abstract

To secure detection accuracy of an off-set current value at the time of idling of a rotor.SOLUTION: A motor controller comprises: an inverter for turning on arms of all arms according to PWM signals of respective phases to energize a motor having a rotor; a current detector connected to a DC side of the inverter; and a current detection unit for detecting phase current of each phase flowing through the motor on the basis of current flowing through the current detector. The current detection unit calculates a detection value of the phase current of each phase by subtracting an average current value of off-set current of each phase made to flow through the current detector by turning on the arms at the time of idling of the rotor according to PWM signals of the respective phases having the same duty ratio value from a current value of phase current of each phase made to flow through the current detector by turning on the arms when the inverter rotates the rotor according to PWM signals of the respective phases, any of which has a duty ratio value differing from the same duty ratio value.SELECTED DRAWING: Figure 1

Description

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

1 In the technology to detect the magnetic pole position of the rotor by the shunt current detection method, the magnetic pole position and rotation speed of the rotor are detected by detecting the induced voltage generated by the rotor idling due to the wind before the motor starts. Is known (see, for example, Patent Document 1).

JP-A-2007-166695

When the motor is controlled by the one-shunt current detection method, the current value of the current flowing through the one-shunt current detector may be detected as an offset current value before the inverter rotates the rotor (before the motor is started). The offset current value is used, for example, to improve the accuracy of current detection and failure detection when the motor is started by the inverter and the inverter is rotating the rotor.

However, if the rotor is idling before the inverter rotates the rotor, the offset current value may not be detected correctly due to the induced voltage generated by the idling of the rotor.

The present disclosure provides a motor control device, a motor system, and a motor control method capable of ensuring the detection accuracy of the offset current value when the rotor is idling.

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 according to the PWM signal of each phase.
A current detector connected to the DC side of the inverter and
A current detection unit that detects the phase current of each phase flowing through the motor based on the current flowing through the current detector is provided.
The current detector
In each case, the offset current value of the phase current of each phase flowing through the current detector is obtained by turning on a part of the arms when the rotor idles according to the PWM signal of each phase having the same duty ratio.

According to the present disclosure, it is possible to secure the detection accuracy of the offset current value when the rotor is idling.

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 illustrates the waveform of the induced voltage generated in each phase by idling of a rotor at the time of idling of a rotor. It is a figure which illustrates the waveform of the offset current of each phase when the rotor is stopped. It is a figure which illustrates the waveform of the phase current of each phase at the time of idling of a rotor. It is a figure which illustrates the phase current of each phase which flows at the time of idling of a rotor, and the average current value thereof. It is a figure which illustrates the relationship between the phase current of each phase which flows at the time of idling of a rotor, the magnetic pole position and idling speed of a rotor during idling.

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. If the rotor is idling before the inverter 23 rotates the rotor with the three-phase alternating current, the induced voltage generated by the idling of the rotor interferes with the applied voltage when the offset current is detected. It may not be detected correctly.

FIG. 7 is a diagram illustrating a waveform of an induced voltage generated in each phase due to the idling of the rotor when the rotor idling. In the motor 4 which is a permanent magnet synchronous motor, the induced voltage _eMU generated in the U-phase coil when the rotor idles is represented by the equation (1) and is generated in a waveform as shown in FIG. 7. _{The induced voltage e MV} generated in the V-phase coil and _{the induced voltage e MW} generated in the W-phase coil are represented by equations that are out of phase with the equation (1).

FIG. 8 is a diagram illustrating the waveform of the offset current of each phase. FIG. 9 is a diagram illustrating a waveform of the phase current of each phase when the rotor is idling. As shown in FIG. 8, when the rotor is stopped, the current of each phase hardly fluctuates, so that the current detection unit 27 can detect the offset current of each phase with relatively high accuracy. On the other hand, as shown in FIG. 9, when the rotor idles, the induced voltage generated by the rotor idling fluctuates the phase current of each phase in a sinusoidal manner, so that the current detection unit 27 performs the offset current of each phase. Is difficult to detect with high accuracy.

Since the sine wave that moves in parallel up and down each phase as shown in FIG. 9 is generated by the interference of the induced voltage represented by the equation (1), the average value (median value) of the sine wave is the interference due to the induced voltage. It can be said that the current value generated when is eliminated (that is, the offset current value). Utilizing this point, as shown in FIG. 10, the current detection unit 27 in the first embodiment of the present disclosure calculates the average current value of the phase currents of each phase in a certain range, so that even when the rotor is idling. The detection accuracy of the offset current value can be ensured.

FIG. 10 is a diagram illustrating a phase current of each phase flowing when the rotor idles and an average current value thereof. The current detection unit 27 averages each of the three-phase phase currents, and detects the average value as the current value of each of the three-phase offset currents. The current detection unit 27 can further secure the detection accuracy of each current value of the three-phase offset currents by averaging the current values of the phase currents of each phase in a period of one cycle or more of the PWM signals of each phase. ..

Further, since the sine wave that moves in parallel to the top and bottom of each phase as shown in FIG. 9 is generated by the interference of the induced voltage represented by the equation (1), the phase of the sine wave is almost equivalent to the phase of the induced voltage. Is. The phase of the induced voltage represents the position of the magnetic poles of the rotor. Taking advantage of this point, the energization pattern generation unit 35 of the motor control device 100-1 according to the first embodiment of the present disclosure shown in FIG. 1 idles based on the phase current of each phase detected by the current detection unit 27. A position / speed estimation unit 45 for estimating the magnetic pole position and idling speed of the rotor inside is provided. The magnetic pole position and idling speed of the rotor during idling estimated by the position / speed estimation unit 45 are used by the vector control unit 30 as initial values at the start of the motor 4, for example.

When starting a permanent magnet synchronous motor, either detect the magnetic pole position of the rotor magnet using inductive sensing to accelerate the motor, or accelerate the motor in any direction with speed open loop control without detecting the magnetic pole position. Often. However, since it is difficult to estimate the magnetic pole position by inductive sensing when the rotor is idling, if the motor is started without detecting the magnetic pole position or idling speed during idling, abnormal noise or other abnormalities will occur in the motor. There is a risk. In order to start the rotor smoothly when idling, it is required to detect the position of the magnetic pole during idling by a method other than inductive sensing and detect the idling speed of the motor.

FIG. 11 is a diagram illustrating the relationship between the phase current of each phase flowing during idling of the rotor and the magnetic pole position and idling speed of the rotor during idling. The position / velocity estimation unit 45 is based on the relationship between the induced voltage and the magnetic pole position during idling of the rotor and the sinusoidal phase current detected during idling of the rotor, and the magnetic pole position and idling of the rotor during idling. Estimate the speed. The position / speed estimation unit 45 includes a position estimation unit and a speed estimation unit.

The phase when one of the phase currents of each phase crosses zero represents the rotor position θ (rotor magnetic pole position). Therefore, the position estimation unit estimates the magnetic pole position of the rotor during idling based on the phase in which one of the phase currents of each phase (the phase current of the U phase in FIG. 11) crosses zero. As a result, the detection of the offset current during idling and the estimation of the magnetic pole position of the rotor during idling can be executed in parallel, so that the vector control unit 30 and the PWM signal generation unit 32 can quickly drive the motor 4 in which the rotor is idling. And it can be started smoothly. The position estimation unit selects, for example, one phase current having the above-mentioned offset current value (average current value) closest to zero among the phase currents of each phase, and based on the phase in which the selected one phase current crosses zero. , Estimate the magnetic pole position of the rotor during idling.

Further, one cycle of one phase current corresponds to the time for one rotation of the rotor. Therefore, the speed estimation unit estimates the idling speed of the rotor based on the period in which one phase current crosses zero. As a result, the detection of the offset current during idling and the estimation of the idling speed of the rotor during idling can be executed in parallel, so that the vector control unit 30 and the PWM signal generation unit 32 can quickly and quickly drive the motor in which the rotor is idling. It can be started smoothly.

The speed estimation unit may estimate the idling speed of the rotor based on the period of at least one phase current of each phase current. For example, the speed estimation unit may measure the period of the phase current of the V phase or the W phase and estimate the idling speed of the rotor from the measured value of the period. As a result, the detection of the offset current during idling and the estimation of the idling speed of the rotor during idling can be executed in parallel, so that the vector control unit 30 and the PWM signal generation unit 32 can quickly drive the motor 4 in which the rotor is idling. And it can be started smoothly. Further, the speed estimation unit may estimate the idling speed of the rotor from the average value of the cycles of at least two phase currents of the phase currents of each phase.

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 45 Position / speed estimation part 100-1 Motor control device Up, Vp, Wp, Un, Vn, Wn arm

Claims (10)

An inverter that energizes a motor with a rotor by turning on some of the arms according to the PWM signal of each phase.
A current detector connected to the DC side of the inverter and
A current detection unit that detects the phase current of each phase flowing through the motor based on the current flowing through the current detector is provided.
The current detector
Motor control that obtains the offset current value of the phase current of each phase flowing through the current detector by turning on a part of the arms when the rotor idles according to the PWM signal of each phase having the same duty ratio. Device. Each of the current flows to the current detector by turning on the same arm as the part of the arm when the inverter is rotating the rotor according to the PWM signal of each phase whose duty ratio is different from the same value. The motor control device according to claim 1, wherein the offset current value is subtracted from the current value of the phase current of each phase, and the detected value of the phase current of each phase is calculated. The motor control device according to claim 2, wherein the offset current value is the average of the current values of the phase currents of the respective phases in a period of one cycle or more of the PWM signals of the respective phases. The motor control device according to claim 2 or 3, further comprising a position estimation unit that estimates the magnetic pole position of the rotor during idling based on the phase in which one of the phase currents of each phase crosses zero. The motor control device according to claim 4, further comprising a speed estimation unit that estimates the idling speed of the rotor based on a period in which the one phase current crosses zero. The motor control according to any one of claims 2 to 5, further comprising a PWM signal generation unit that generates a PWM signal for each phase when the inverter is rotating the rotor based on the detected value. Device. The motor control device according to any one of claims 1 to 6, further comprising a speed estimation unit that estimates the idling speed of the rotor based on the period of at least one phase current of each phase current. The motor control device according to any one of claims 1 to 7, wherein the same value is 50%. A motor system comprising the motor control device according to any one of claims 1 to 8 and the motor. It is a motor control method performed by a motor control device that energizes a motor having a rotor by turning on a part of all arms of the inverter according to the PWM signal of each phase.
In each case, the offset current of each phase flows through the current detector connected to the DC side of the inverter by turning on a part of the arms when the rotor idles according to the PWM signal of each phase having the same duty ratio. Calculate the average current value of
Each of the current flows to the current detector by turning on the same arm as the part of the arm when the inverter is rotating the rotor according to the PWM signal of each phase whose duty ratio is different from the same value. A motor control method for calculating the detected value of the phase current of each phase by subtracting the average current value of the offset current of each phase from the current value of the phase current of each phase.

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