Motor control device, motor system, and motor control method

Abstract

A motor control device includes an observer that estimates a gamma-axis induced voltage and a delta-axis induced voltage during free rotation of a rotor of a motor, a derivation unit that derives a phase difference between a dq-axis and a gamma-delta-axis from the gamma-axis induced voltage and the delta-axis induced voltage, and an estimation unit that estimates a free rotation state of the rotor from the phase difference. For example, the estimation unit estimates a free rotation speed of the rotor from a period of the phase difference. For example, the estimation unit estimates a magnetic pole position during free rotation of the rotor from the phase difference, a sign of the gamma-axis induced voltage, and a sign of the delta-axis induced voltage.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a motor control device, a motor system, and a motor control method. BACKGROUND

[0002] In a technique of detecting a magnetic pole position of a rotor by a one shunt current detection method, it is known to detect the magnetic pole position and the rotational speed of the rotor by detecting an induced voltage generated by the rotation of the rotor by wind before the start of the motor (see, for example, Patent Document 1).

[0003] [Citation List]

[0004] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2007-166695 SUMMARY

[0006] [Problems to be Solved by the Invention]

[0007] In a case where a permanent magnet synchronous motor in a stopped state is started, the magnetic pole position of a rotor magnet is often detected by so-called inductive sensing to start the motor. However, in a state where the rotor is rotating by itself, it is difficult to estimate the magnetic pole position based on inductive sensing.

[0008] The present disclosure provides a motor control device, a motor system, and a motor control method capable of estimating the state of rotation by itself of the magnetic pole position and the like when the rotor is rotating by itself.

[0009] [Technical Solution]

[0010] The motor control device of one embodiment of the present disclosure includes:

[0011] an observer that estimates a γ-axis induced voltage and a δ-axis induced voltage of a rotor of a motor when the rotor is rotating by itself;

[0012] a derivation unit that derives a phase difference between a dq-axis and a γδ-axis from the γ-axis induced voltage and the δ-axis induced voltage; and

[0013] an estimation unit that estimates the state of rotation by itself of the rotor based on the phase difference.

[0014] [Advantageous Effects]

[0015] According to the present disclosure, the state of rotation by itself of the magnetic pole position and the like when the rotor is rotating by itself can be estimated. BRIEF DESCRIPTION OF DRAWINGS

[0016] [ Figure 1 ]Schematic diagram of a configuration example of the motor system of Embodiment 1 of the present disclosure.

[0017] [ Figure 2 ]Exemplary diagrams of waveforms of plural PWM signals, waveforms of carriers of each cycle of the PWM signals, and waveforms of phase voltage commands of each phase.

[0018] [ Figure 3 ]Schematic diagram of an example of switching states of each arm at the time of energization.

[0019] [ Figure 4 ]Schematic diagram of an example of switching states of each arm at the time of non-energization.

[0020] [ Figure 5 ]Exemplary timing chart of offset currents of each phase flowing into a current detector by turning on a part of arms of an inverter by PWM signals of each phase whose duty ratio is 50%.

[0021] [ Figure 6 ]Exemplary timing chart of phase currents of each phase flowing into a current detector by turning on the same part of arms as Figure 5 when the inverter rotates a rotor based on PWM signals of each phase whose duty ratio is not 50%.

[0022] [ Figure 7 ]Exemplary diagram of a coordinate system used in sensorless vector control performed by a vector control section.

[0023] [ Figure 8 ]Schematic diagram of an example of a configuration of an observer in a position and velocity estimation section.

[0024] [ Figure 9 ]Schematic diagram of behavior of a phase difference when idling in a direction in which a magnetic pole position increases.

[0025] [ Figure 10 ]Schematic diagram of behavior of a phase difference when idling in a direction in which a magnetic pole position decreases.

[0026] [ Figure 11 ]Timing chart showing relationships among an induced voltage, a phase difference, and a magnetic pole position when idling in a direction in which a magnetic pole position increases.

[0027] [ Figure 12This is a timing diagram showing the relationship between the induced voltage, phase difference, and magnetic pole position during idling in the direction of decreasing magnetic pole position.

[0028] [ Figure 13 A schematic diagram illustrating an example of the processing flow of the windmill start function.

[0029] [ Figure 14 [A block diagram representing an example of a magnetic pole position prediction system.]

[0030] [ Figure 15 An example timing diagram illustrating the estimated time until the estimated velocity value stabilizes. Detailed Implementation

[0031] The motor control device, motor system, and motor control method of the present disclosure will now be described in detail with reference to the accompanying drawings.

[0032] Figure 1 This is a schematic diagram of a configuration example of the motor system 1-1 according to Embodiment 1 of this disclosure. Figure 1 The motor system 1-1 shown controls the rotation of the motor 4. Devices that can install the motor system 1-1 include, for example, a photocopier, a personal computer, a refrigerator, a pump, etc., but are not limited to these. The motor system 1-1 includes at least the motor 4 and a motor control device 100-1.

[0033] Motor 4 is a permanent magnet synchronous motor with multiple coils. Motor 4 may have, for example, a three-phase coil including a U-phase coil, a V-phase coil, and a W-phase coil. Specific examples of motor 4 include a three-phase brushless DC motor (electric motor). Motor 4 has a rotor equipped with at least one permanent magnet and a stator arranged around a shaft surrounding the rotor. Motor 4 is a sensorless motor that does not use a position sensor to detect the angular position (pole position) of the rotor's magnets. Motor 4 may be, for example, a fan motor that rotates a fan used for ventilation.

[0034] The motor control device 100-1 drives the motor via an inverter that converts DC to AC by controlling the on / off states of multiple switching elements in a 3-phase bridge based on a power-on pattern including 3-phase PWM signals. 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, a power-on pattern generation unit 35, a carrier wave generation unit 37, and a clock signal generation unit 36.

[0035] The inverter 23 is a circuit that rotates the rotor of the motor 4 by converting the direct current supplied from the direct current power supply 21 into 3-phase alternating current by switching using a plurality of switching elements and causing the 3-phase alternating current to flow as a drive current into the motor 4. The inverter 23 drives the motor 4 in accordance with a plurality of energization patterns (specifically, 3-phase PWM signals generated by the PWM signal generation section 32 within the energization pattern generation section 35) generated by the energization pattern generation section 35. PWM stands for Pulse Width Modulation.

[0036] The inverter 23 has a plurality of arms Up, Vp, Wp, Un, Vn, Wn of 3-phase bridges. The upper arms Up, Vp, Wp are high side switching elements that are connected to the positive side of the direct current power supply 21 via a positive side bus (positive bus) 22a, respectively. The lower arms Un, Vn, Wn are low side switching elements that are connected to the negative side (specifically, the ground side) of the direct current power supply 21, respectively. The plurality of arms Up, Vp, Wp, Un, Vn, Wn are turned on or off in accordance with corresponding drive signals among a plurality of drive signals supplied from the drive circuit 33 based on the PWM signals included in the above-described energization patterns, respectively. Hereinafter, in cases where it is not necessary to distinguish the plurality of arms Up, Vp, Wp, Un, Vn, Wn, they will be simply referred to as arms.

[0037] The connection points of the U-phase upper arm Up and the U-phase lower arm Un are connected to one end of the U-phase coil of the motor 4. The connection points of the V-phase upper arm Vp and the V-phase lower arm Vn are connected to one end of the V-phase coil of the motor 4. The connection points of the W-phase upper arm Wp and the W-phase lower arm Wn are 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.

[0038] As a specific example of the arms, an N-channel type MOSFET (Metal Oxide Semiconductor Field Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor), or the like can be cited. However, the arms are not limited thereto.

[0039] The current detector 24 is connected to the direct current side of the inverter 23 and outputs a detection signal Sd corresponding to the current value of the current flowing into the direct current side of the inverter 23. Figure 1The current detector 24 shown generates a detection signal Sd corresponding to the current value of the current flowing through the negative side bus (negative bus) 22b. The current detector 24 is, for example, a current detection element provided on the negative bus 22b, specifically, a shunt resistor inserted in the negative bus 22b. The current detection element such as the shunt resistor generates a voltage signal corresponding to the current value of the current flowing therethrough, and outputs the same as the detection signal Sd.

[0040] The current detection section 27 acquires the detection signal Sd based on the plurality of energizing patterns (specifically, the 3-phase PWM signals) generated by the energizing pattern generation section 35, thereby detecting the phase currents Iu, Iv, Iw flowing into the U, V, W phases of the motor 4. In detail, the current detection section 27 acquires the detection signal Sd at an acquisition timing synchronized with the plurality of energizing patterns (specifically, the 3-phase PWM signals), thereby detecting the phase currents Iu, Iv, Iw flowing into the U, V, W phases of the motor 4. The acquisition timing of the detection signal Sd is set by the current detection timing adjustment section 34.

[0041] For example, the current detection section 27 inputs the detection signal Sd of the analog voltage generated by the current detector 24 to an AD (Analog to Digital) converter at the acquisition timing set by the current detection timing adjustment section 34. The AD converter is provided in the current detection section 27. Thereafter, the current detection section 27 converts the input analog detection signal Sd into a digital detection signal Sd, and performs digital processing on the AD-converted digital detection signal Sd, thereby detecting the phase currents Iu, Iv, Iw of the U, V, W phases of the motor 4. The detection values of the phase currents Iu, Iv, Iw of the respective phases detected by the current detection section 27 are supplied to the energizing pattern generation section 35.

[0042] The clock signal generation section 36 is a circuit that generates a clock signal of a predetermined frequency by means of a built-in oscillation circuit, and outputs the generated clock signal to the carrier generation section 37. Note that the clock signal generation section 36 starts operating (operating / working) at the same time as the power supply of the motor control device 100-1 is turned on, for example.

[0043] The carrier generation section 37 generates a carrier C in accordance with the clock signal generated by the clock signal generation section 36. The carrier C is a carrier signal whose level periodically increases and decreases.

[0044] The energization pattern generating section 35 generates a pattern for energizing the inverter 23 (energization pattern of the inverter 23). The energization pattern of the inverter 23 can also be referred to as a pattern for energizing the motor 4 (energization pattern of the motor 4). The energization pattern of the inverter 23 contains 3-phase PWM signals for energizing the inverter 23. The energization pattern generating section 35 has the PWM signal generating section 32 that generates 3-phase PWM signals for energizing the inverter 23 from the detected values of the phase currents Iu, Iv, Iw of the motor 4 detected by the current detecting section 27, so as to rotate the motor 4.

[0045] The energization pattern generating section 35 also has the vector control section 30 in the case of generating the energization pattern of the inverter 23 by vector control. Note that the energization pattern of the inverter is generated by vector control in this embodiment.

[0046] When the rotational speed command ωref of the motor 4 is given from the outside, the vector control section 30 generates the torque current command Iqref and the field current command Idref from the difference between the measured value or the estimated value of the rotational speed of the motor 4 and the rotational speed command ωref. The vector control section 30 calculates the torque current Iq and the field current Id by a vector control operation using the rotor position θ, from the phase currents Iu, Iv, Iw of the U, V, W phases of the motor 4. The vector control section 30, for example, performs a PI control operation on the difference between the torque current command Iqref and the torque current Iq, thereby generating the voltage command Vq. The vector control section 30, for example, performs a PI control operation on the difference between the field current command Idref and the field current Id, thereby generating the voltage command Vd. The vector control section 30 converts the voltage commands Vq, Vd into the phase voltage commands Vu*, Vv*, Vw* of the U, V, W phases using the above-described rotor position θ. The rotor position θ indicates the magnetic pole position of the rotor of the motor 4.

[0047] The PWM signal generating section 32 generates the energization pattern containing 3-phase PWM signals by comparing the phase voltage commands Vu*, Vv*, Vw* generated by the vector control section 30 with the levels of the carrier C generated by the carrier generating section 37. The PWM signal generating section 32 also generates PWM signals for the lower arm drive for which the 3-phase PWM signals for the upper arm drive are inverted, and outputs the energization pattern containing the generated PWM signals to the drive circuit 33 after adding a dead time as necessary.

[0048] The drive circuit 33 outputs a drive signal that switches the 6 arms Up, Vp, Wp, Un, Vn, Wn included in the inverter 23 in accordance with the energization pattern output including the PWM signal imparted. Accordingly, a drive current of 3-phase AC is supplied to the motor 4, and the rotor of the motor 4 can be rotated.

[0049] The current detection timing adjustment section 34 determines acquisition timings for causing the current detection section 27 to detect the phase current of any one of the 3 phases within one cycle of the carrier C, in accordance with the carrier C supplied from the carrier generation section 37 and the energization pattern including the PWM signal generated by the PWM signal generation section 32.

[0050] The current detection section 27 acquires the detection signal Sd at the plurality of acquisition timings determined by the current detection timing adjustment section 34, thereby detecting the phase currents Iu, Iv, Iw. The current detection section 27 detects the phase currents Iu, Iv, Iw in a manner that a plurality of phase currents are detected from one current detector 24 (so-called 1-shunt current detection manner).

[0051] In addition, as a method of estimating the magnetic pole position (initial position) of the rotor when the sensorless permanent magnet synchronous motor is in a stopped state, there is a method called induction detection. The induction detection is a method of detecting the magnetic pole position of the rotor magnet of the permanent magnet synchronous motor using the rotor position dependency of inductance. This position detection method does not use the induced voltage of the motor, and thus the magnetic pole position of the rotor magnet can be detected even when the rotor of the motor is in a stopped or extremely low speed state. The rotor in an extremely low speed state means a state in which the rotor rotates at a low speed at which the motor control device cannot substantially detect the induced voltage. In this specification, for convenience of description, the "rotor in a stopped or extremely low speed state" is simply referred to as "stopped state of the rotor".

[0052] The motor control device 100-1 of the present embodiment 1 is provided with an initial position estimation section 38 that estimates the magnetic pole position in the stopped state of the rotor of the motor, that is, the initial position θs, by the induction detection. The energization pattern generation section 35 outputs the energization pattern including the 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 section 38. The vector control section 30 uses the initial position θs estimated by the initial position estimation section 38 as an initial value of the rotor position θ, thereby converting the voltage command Vδ, Vγ into the phase voltage command Vu*, Vv*, Vw*. Note that, in the present disclosure, the initial position θs is a value having a width of 30 degrees, for example. In this case, the control of the motor 4 is performed using a predetermined value determined in accordance with the initial position θs.

[0053] Figure 2are diagrams illustrating waveforms of the plurality of PWM signals U, V, W, waveforms of the carrier C for each cycle of the PWM signals, and waveforms of the phase voltage commands Vu*, Vv*, Vw* of the phases.

[0054] The PWM signal generation section 32 generates the plurality of PWM signals U, V, W in accordance with the magnitude relationship between the phase voltage commands Vu*, Vv*, Vw* of the phases and the level of the carrier C.

[0055] The PWM signal U is a PWM signal for driving the 2 switching elements of the upper and lower arms that constitute the U phase. In this example, when the PWM signal U is at the low level, the switching element of the lower arm of the U phase becomes on (the switching element of the upper arm of the U phase becomes off), and when the PWM signal U is at the high level, the switching element of the lower arm of the U phase becomes off (the switching element of the upper arm of the U phase becomes on). The 2 switching elements of the upper and lower arms that constitute the U phase complementarily perform the on / off operation in response to the change in the level of the PWM signal U.

[0056] The PWM signal V is a PWM signal for driving the 2 switching elements of the upper and lower arms that constitute the V phase. In this example, when the PWM signal V is at the low level, the switching element of the lower arm of the V phase becomes on (the switching element of the upper arm of the V phase becomes off), and when the PWM signal V is at the high level, the switching element of the lower arm of the V phase becomes off (the switching element of the upper arm of the V phase becomes on). The 2 switching elements of the upper and lower arms that constitute the V phase complementarily perform the on / off operation in response to the change in the level of the PWM signal V.

[0057] The PWM signal W is a PWM signal for driving the 2 switching elements of the upper and lower arms that constitute the W phase. In this example, when the PWM signal W is at the low level, the switching element of the lower arm of the W phase becomes on (the switching element of the upper arm of the W phase becomes off), and when the PWM signal W is at the high level, the switching element of the lower arm of the W phase becomes off (the switching element of the upper arm of the W phase becomes on). The 2 switching elements of the upper and lower arms that constitute the W phase complementarily perform the on / off operation in response to the change in the level of the PWM signal W.

[0058] Note that, Figure 2 In the above, the illustration of the dead time for preventing short-circuiting of the upper and lower arms is omitted. Furthermore, Figure 2 In the above, the following definition is made, that is, when the PWM signal is at the high level, the upper arm of the phase corresponding to the PWM signal is on, and when the PWM signal is at the low level, the lower arm of the phase corresponding to the PWM signal is on. However, the relationship between the logic level of the PWM signal and the on / off of the arms can also be defined in the opposite manner, taking into account the configuration of the circuit, etc.

[0059] The one-cycle Tpwm of multiple PWM signals U, V, and W is equivalent to the period of the carrier C (the reciprocal of the carrier frequency). The transition points (t1 to t6) represent the timing when the logic level of the PWM signal transitions (changes).

[0060] like Figure 2 As shown, the PWM signal generation unit 32 can use a single carrier C shared by all phases to generate the PWM signal for each phase. Since the carrier C is a left-right symmetrical triangular wave centered on phase tb, the circuit structure for generating the waveform of the PWM signal for each phase can be simplified. The carrier C counter counts down to phase ta, counts up from phase ta to phase tb, and counts down from phase tb. The countdown and countdown periods are repeated in this manner. It should be noted that the PWM signal generation unit 32 can also use multiple carrier Cs corresponding to each phase to generate the PWM signal for each phase, or other known methods can be used to generate the PWM signal for each phase.

[0061] Figure 2 An example is shown where the first current detection timing Tm1 is set during the energizing period T21 and the second current detection timing Tm2 is set during the energizing period T22. It should be noted that the energizing periods for setting the first current detection timing Tm1 and the second current detection timing Tm2 are not limited to these periods.

[0062] When the inverter 23 is outputting PWM-modulated three-phase AC, the current detection unit 27 can detect the current of a specific phase according to the energizing mode corresponding to the upper arms Up, Vp, and Wp. Alternatively, when the inverter 23 is outputting PWM-modulated three-phase AC, the current detection unit 27 can detect the current of a specific phase according to the energizing mode corresponding to the lower arms Un, Vn, and Wn.

[0063] For example, such as Figure 2 As shown, during the energizing period T21, the voltage value generated across the current detector 24 corresponds to the positive U-phase current "+Iu" flowing from the U-phase terminal of the motor 4. The energizing period T21 is the time (period) from t4 to t5. The energizing period T21 corresponds to the period when the lower arm Un and the upper arms Vp and Wp are conducting and the remaining three arms are cut off. For this purpose, the current detection unit 27 can detect the positive U-phase current "+Iu" flowing from the U-phase terminal of the motor 4 by acquiring the detection signal Sd during the first current detection timing Tm1 during the energizing period T21.

[0064] The current detection timing adjustment section 34 sets the first current detection timing Tml when a predetermined delay time td has elapsed from the time when the 1 phase in the PWM signal transitions to a logic level different from the other 2 phases (for example, the time when the PWM signal of the U phase transitions from the same high level as the V and W phases to a low level different from the V and W phases: t4). At this time, the current detection timing adjustment section 34 sets the first current detection timing Tml within the energization period T21.

[0065] Further, for example, as shown in FIG. 6, within the energization period T22, the voltage value of the voltage generated across the current detector 24 corresponds to the current value of the negative W phase current "-Iw" flowing from the W phase terminal of the motor 4. The energization period T22 is the time (period) from t5 to t6. The energization period T22 corresponds to the period in which the lower arm Un, Vn and the upper arm Wp are on and the remaining 3 arms are off. For this reason, the current detection section 27 can detect the current value of the negative W phase current "-Iw" flowing from the W phase terminal of the motor 4 by acquiring the detection signal Sd at the second current detection timing Tm2 within the energization period T22. Figure 2 The current detection timing adjustment section 34 sets the second current detection timing Tm2 when a predetermined delay time td has elapsed from the time when the 1 phase in the PWM signal transitions to a logic level different from the other 2 phases (for example, the time when the PWM signal of the V phase transitions from the same high level as the W phase to a low level different from the U phase: t5). At this time, the current detection timing adjustment section 34 sets the second current detection timing Tm2 within the energization period T22.

[0066] Similarly, the current detection section 27 can also detect the current value of the other phase currents.

[0067] As described above, if the phase currents of 2 phases among the phase currents Iu, Iv, Iw are detected and stored in order according to the energization pattern of the PWM signal including the 3 phases, the currents of the 3 phases can be detected in a time division manner. Since the sum of the phase currents of the 3 phases is zero (iu+iv+iw=0), if the current detection section 27 can detect the phase currents of 2 phases among the phase currents of the 3 phases, it can also detect the phase current of the remaining 1 phase.

[0068]

[0069] is a diagram showing an example of the on / off state of each arm during energization. Figure 3 is a diagram showing an example of the on / off state of each arm during non-energization. As shown in FIG. 5, the lower arm Un, Vn and the upper arm Wp are off and the remaining 3 arms are on during non-energization. Figure 4 is a diagram showing an example of the on / off state of each arm during non-energization. As shown in FIG. 5, the lower arm Un, Vn and the upper arm Wp are off and the remaining 3 arms are on during non-energization. Figure 3As shown, the current detection section 27 can detect the current value of the negative U-phase current "-Iu" flowing from the U-phase terminal of the motor 4 during the conduction period in which the upper arms Up and the lower arms Vn, Wn are turned on and the remaining three arms are turned off. On the other hand, as shown, the current does not flow into the current detector 24 in the state in which all the upper arms Up, Vp, Wp are turned on and all the lower arms Un, Vn, Wn are turned off, so the current detection section 27 cannot detect the phase currents of the respective phases. In the state in which all the upper arms Up, Vp, Wp are turned off and all the lower arms Un, Vn, Wn are turned on, the current also does not flow into the current detector 24, so the current detection section 27 also cannot detect the phase currents of the respective phases. Figure 4 As shown, the current detection section 27 can detect the current value of the negative U-phase current "-Iu" flowing from the U-phase terminal of the motor 4 during the conduction period in which the upper arms Up and the lower arms Vn, Wn are turned on and the remaining three arms are turned off. On the other hand, as shown, the current does not flow into the current detector 24 in the state in which all the upper arms Up, Vp, Wp are turned on and all the lower arms Un, Vn, Wn are turned off, so the current detection section 27 cannot detect the phase currents of the respective phases. In the state in which all the upper arms Up, Vp, Wp are turned off and all the lower arms Un, Vn, Wn are turned on, the current also does not flow into the current detector 24, so the current detection section 27 also cannot detect the phase currents of the respective phases.

[0070] As described above, in the 1 -shunt current detection method, if the conduction interval (conduction period) is not set, the phase currents of the respective phases cannot be detected. In addition, in the 1 -shunt current detection method, the phase current that can be detected in one conduction period is only one phase, so it is necessary to set at least two conduction periods in one cycle of the PWM signal (see FIG. 6) and to distinguish and detect the phase currents of the three phases in accordance with the formula (iu+iv+iw=0). However, if the conduction period is set in order to distinguish and detect the phase currents of the respective phases, the current flowing into the current detector 24 is amplified, so when the current flowing into the current detector 24 is zero, the current detection section 27 cannot determine the detection error contained in the detected values of the phase currents of the respective phases. Figure 2

[0071] For this reason, there is a case in which, when the motor is in a stopped state, the current flowing into the current detector 24 by turning on a part of the arms of the inverter 23 in accordance with the PWM signals of the respective phases in which the duty ratios are all the same value is defined as an offset current. In this case, the current detection section 27 detects the current value of the offset current flowing into the current detector 24 by turning on a part of the arms of the inverter 23 in accordance with the PWM signals of the respective phases in which the duty ratios are all the same value as an offset current value (detection error).

[0072] Figure 5 is a timing chart illustrating the offset current flowing into the current detector 24 by turning on a part of the arms of the inverter 23 in accordance with the PWM signals of the respective phases in which the duty ratios are all 50% as an example. Figure 6 is a timing chart illustrating the phase currents flowing into the current detector 24 by turning on the same part of the arms as in Figure 5 .

[0073] ​Figure 5 In this case, the current detection section 27 detects the current value of each of the offset currents of the three phases at least twice in each cycle of the PWM signal before the inverter 23 rotates the rotor (before the motor 4 is started). The current detection section 27 stores each of the detected current values as the offset current value of the three phases in the memory. Figure 5 The case is exemplified in which the current detection section 27 detects the offset current value of each of the positive U-phase current "Iu" and the negative W-phase current "-Iw", and detects (calculates) the offset current value of the remaining V-phase current based on these detection results, and then stores the detected offset current values of the three phases in the memory. After the offset current values of the three phases are stored in the memory, the motor 4 is started by the inverter 23, and the inverter 23 rotates the rotor.

[0074] Figure 6 In this case, when the inverter 23 rotates the rotor based on the PWM signal of each phase whose duty ratio is not 50%, the current detection section 27 detects the current value of each of the phase currents of the three phases at least twice in each cycle of the PWM signal using the same energization pattern as Figure 5 In each cycle of the PWM signal, the current detection section 27 subtracts the offset current value of the three phases stored in advance in the memory from the current value of each of the phase currents of the three phases detected in each cycle of the PWM signal, thereby calculating the current detection value of each of the phase currents Iu, Iv, Iw of the three phases. According to this, it is possible to remove the detection error from the current detection value of each of the phase currents Iu, Iv, Iw of the three phases. Based on the current detection value of each of the phase currents Iu, Iv, Iw of the three phases from which the detection error is removed, the PWM signal generation section 32 generates the three-phase PWM signal at the time when the inverter 23 rotates the rotor, thereby making it possible to control the rotation of the motor 4 with high precision by the inverter 23.

[0075] In addition, even in a state in which the inverter 23 does not rotate the rotor by the three-phase alternating current, the rotor can be idling due to the disturbance of wind or the like. In particular, in the case of a rotor that rotates a rotating body such as a fan having a small frictional resistance, idling is more likely to occur.

[0076] In the case of starting a permanent magnet synchronous motor, generally, either the position of the magnetic pole of the rotor is detected by induction detection to start the motor, or the position of the magnetic pole is not detected and the motor is started by speed open loop control in an arbitrary direction. However, it is difficult to estimate the position of the magnetic pole by induction detection in a state where the rotor is idling, and for this reason, if the motor is started without detecting the position of the magnetic pole and the idling speed while idling, the motor can possibly generate an abnormality such as abnormal sound. In order to smoothly start the rotor while idling, it is necessary to detect the position of the magnetic pole while idling by a method other than induction detection, and to detect the idling speed of the motor.

[0077] Figure 1 The energization pattern generation section 35 of the motor control device 100-1 of Embodiment 1 of the present disclosure illustrated in the drawing has a position and speed estimation section 45 for estimating the position of the magnetic pole and the rotational speed of the rotor while idling. Note that the position of the magnetic pole while idling is sometimes referred to as "idling position", and the rotational speed while idling is sometimes referred to as "idling speed". The idling position and the idling speed are each one of the indexes indicating the idling state of the rotor. The idling position and the idling speed of the rotor estimated by the position and speed estimation section 45 are used by the vector control section 30, for example, as initial values at the time of starting the motor 4.

[0078] Figure 7 is an example of the coordinate system used in sensorless vector control performed by the vector control section.

[0079] The d-axis is a real axis extending in a real angle direction indicating the actual position of the magnetic pole of the rotor (direction of the magnetic flux generated by the magnet of the rotor), and the q-axis is a real axis extending in a direction advancing (increasing) by 90° of the electrical angle from the d-axis. The d-axis and the q-axis can be collectively referred to as the dq-axis. The dq-axis is an axis on a model in sensorless vector control. The position of the magnetic pole of the rotor θ is indicated by an angle advancing from the d-axis with the position of the reference coil (for example, the U-phase coil) of the motor as a reference. The d-q coordinate system advances from the reference coil by θ.

[0080] The γ-axis is a control axis extending in an estimated angle direction indicating the estimated position of the magnetic pole of the rotor, and the δ-axis is a control axis extending in a direction advancing (increasing) by 90° of the electrical angle from the γ-axis. The γ-axis and the δ-axis can be collectively referred to as the γδ-axis. The γδ-axis is an axis on a model in sensorless vector control. The estimated position of the magnetic pole of the rotor θ m is indicated by an angle advancing from the γ-axis with the position of the reference coil (for example, the U-phase coil) of the motor as a reference. The γ-δ coordinate system advances from the reference coil by θ m .

[0081] The phase difference Δθ is a phase difference between the real axis (dq axis) and the control axis (γδ axis). The phase difference Δθ can be expressed by a phase difference between the q axis and the δ axis or a phase difference between the d axis and the γ axis. When the phase difference Δθ is zero, the γ-δ coordinate system coincides with (is identical to) the d-q coordinate system.

[0082] The vector control section 30 has a well-known structure of a speed control section, a current control section, an output conversion section, an input conversion section, and the like. In brief, the speed control section is a speed control system that generates a γ-axis current command value I m * and a δ-axis current command value I γ * in the γ-δ coordinate system in such a manner that a difference between the rotational speed command ωref from the outside and a speed estimation value ω δ * estimated by the position·speed estimation section 45 converges to zero. The current control section generates a γ-axis voltage command value V γ * and a δ-axis voltage command value V γ in such a manner that a difference between the γ-axis current command value I γ * generated by the speed control section and a γ-axis detected current value I δ * generated by the input conversion section converges to zero. The current control section generates the δ-axis voltage command value V δ in such a manner that a difference between the δ-axis current command value I δ * generated by the speed control section and a δ-axis detected current value I m * generated by the input conversion section converges to zero. The output conversion section converts the γ-axis voltage command value V γ * and the δ-axis voltage command value V δ * into phase voltage commands Vu*, Vv*, Vw* of the U, V, W phases. The input conversion section converts the phase currents Iu, Iv, Iw of the three phases detected by the current detection section 27 into the γ-axis detected current value I m * and the δ-axis detected current value I γ * in such a manner that the phase currents Iu, Iv, Iw of the three phases detected by the current detection section 27 are converted into the γ-axis detected current value I δ .

[0083] The position·speed estimation section 45 estimates the estimated magnetic pole position θ γ * and the speed estimation value ω δ from the γ-axis detected current value I γ * and the δ-axis detected current value I δ * generated by the input conversion section and the γ-axis voltage command value V m * and the δ-axis voltage command value V m * generated by the current control section. The position·speed estimation section 45 includes a position estimation section for estimating the estimated magnetic pole position θ m * and a speed estimation section for estimating the speed estimation value ω mA speed estimation unit that estimates the speed. The position / speed estimation unit 45 estimates the magnetic pole position θ m and the speed estimation value ω m in a state where the motor 4 is started by the inverter 23 and the rotor is rotated by the inverter 23 using a known estimation method.

[0084] The position / speed estimation unit 45 of Embodiment 1 of the present disclosure also has a so-called windmilling start function for estimating the windmilling position and the windmilling speed of the rotor. The windmilling start function can estimate the windmilling state of the rotor (for example, the phase at the time of windmilling (windmilling position), the windmilling speed, the direction of rotation at the time of windmilling (windmilling direction), and the like) based on the phase difference Δθ, thereby achieving smooth rotation control at the time of windmilling of the rotor. For example, the position / speed estimation unit 45 estimates the windmilling state of the rotor before the induction detection, thereby making a determination (discrimination) as to whether the rotor is in a stopped state or is windmilling. In the case of determining that it is in a stopped state, the initial position estimation unit 38 estimates the magnetic pole position and the like of the rotor in the stopped state by the induction detection, and in the case of determining that it is windmilling, the position / speed estimation unit 45 estimates the windmilling position and the windmilling speed and the like of the rotor by the windmilling start function.

[0085] The windmilling start function of the present disclosure has various modes. The first mode is a mode in which the estimation magnetic pole position θ m and the speed estimation value ω m are input to the vector control unit 30 as initial values at the time of start, thereby entering sensorless vector control (hereinafter referred to as windmilling start function 1). The second mode is a mode in which the estimation magnetic pole position θ m and the speed estimation value ω m are derived by inputting the phase difference Δθ to the magnetic pole position estimation system of the position / speed estimation unit 45, and these values to be derived are input to the vector control unit 30 after they are stabilized, thereby entering sensorless vector control (hereinafter referred to as windmilling start function 2). These two functions are the same in that the phase difference Δθ is detected (estimated) by the observer, but differ in the method of entering sensorless vector control.

[0086] <Windmilling start function 1>

[0087] The processing content of the windmilling start function 1 will be described with reference to FIG. 8. Figures 8-13 The processing content of the windmilling start function 1 will be described with reference to FIG. 8.

[0088] In the windmilling start function 1, the vector control unit 30 fixes the γ axis and the δ axis to the position where the estimation magnetic pole position θ m is zero, and inputs the γ axis current command value I γ * and the δ axis current command value I δ* is fixed to zero, and the current control section starts current control. Then, the vector control section 30 inputs the voltage command value (γ-axis voltage command value V γ and δ-axis voltage command value V δ ) output from the current control section and the detected current value (γ-axis detected current value I γ and δ-axis detected current value I δ ) output from the input conversion section into the observer in the position and speed estimation section 45.

[0089] Figure 8 is an example of the configuration of the observer in the position and speed estimation section. Figure 8 The observer 48 shown in FIG. 8 is provided in the position and speed estimation section 45. The observer 48 estimates the induced voltage e (γ-axis induced voltage e γ and δ-axis induced voltage e δ ) generated in the coil of the motor 4 due to the free rotation of the rotor. The γ-axis induced voltage e γ is the induced voltage component on the γ-axis of the induced voltage e, and the δ-axis induced voltage e δ is the induced voltage component on the δ-axis of the induced voltage e. The observer 48 has a first observer 46 and a second observer 47. The first observer 46 estimates the γ-axis induced voltage e γ during the free rotation of the rotor based on the γ-axis voltage command value V γ and the γ-axis detected current value I γ input from the wind-up starting function 1. The second observer 47 estimates the δ-axis induced voltage e δ during the free rotation of the rotor based on the δ-axis voltage command value V δ and the δ-axis detected current value I δ input from the wind-up starting function 1. As a specific example of the first observer 46 and the second observer 47, there is a known extended induced voltage observer, but the observer 48 can estimate the γ-axis induced voltage e γ and the δ-axis induced voltage e δ during the free rotation of the rotor in a manner different from the extended induced voltage observer.

[0090] Note that the position and speed estimation section 45 can not use the observer, but can obtain the induced voltage by calculation based on a general voltage equation.

[0091] The observer 48 has a derivation section for deriving the phase difference ΔΘ between the dq-axis and the γδ-axis from the γ-axis induced voltage e γ and the δ-axis induced voltage e δ . For example, the observer 48 can derive the phase difference ΔΘ by dividing the γ-axis induced voltage e γ by the δ-axis induced voltage eδ of the arctangent function shown in FIG. 9 to calculate the phase difference Δθ. Figure 8

[0092] Figure 9 is a graph showing behavior of the phase difference Δθ when the freewheeling is performed in the direction in which the magnetic pole position θ is increased (increases). Figure 10 is a graph showing behavior of the phase difference Δθ when the freewheeling is performed in the direction in which the magnetic pole position θ is decreased (decreases). The phase difference Δθ indicates a phase difference of the γ axis, which is a position at which the actual magnetic pole position (d axis) is fixed with respect to the estimated magnetic pole position θ m is zero. The phase difference Δθ is detected in a periodic sawtooth waveform shape of -90° to 90°. Two periods of the sawtooth waveform correspond to one rotation (one revolution) of the rotor. The position and speed estimation section 45 uses the periodicity of the phase difference Δθ and estimates the freewheeling speed based on the time required for one rotation of the rotor (the time of two periods of the sawtooth waveform), and then inputs the estimated value of the freewheeling speed as an initial value at the time when the phase difference Δθ is zero to the speed control section of the vector control section 30. Accordingly, the vector control section 30 can smoothly rotate the rotor that is freewheeling, and at the same time, can control the same by sensorless vector control. Next, more detailed description will be made with reference to Figure 11 and Figure 12 .

[0093] Figure 11 is a timing chart showing the relationship among the induced voltage e, the phase difference Δθ, and the magnetic pole position θ when the freewheeling is performed in the direction in which the magnetic pole position θ is increased. Figure 12 is a timing chart showing the relationship among the induced voltage e, the phase difference Δθ, and the magnetic pole position θ when the freewheeling is performed in the direction in which the magnetic pole position θ is decreased.

[0094] The position and speed estimation section 45 estimates the freewheeling speed of the rotor based on the period of the phase difference Δθ derived by the observer 48. Two periods of the sawtooth waveform of the phase difference Δθ correspond to one revolution of the electrical angle, and therefore the position and speed estimation section 45 can derive (estimate) the freewheeling speed by measuring the time of two periods of the sawtooth waveform of the phase difference Δθ.

[0095] The position and speed estimation section 45 estimates the direction in which the rotor is freewheeling based on the increase or decrease of the phase difference Δθ derived by the observer 48. For example, the position and speed estimation section 45 determines that the rotor is freewheeling in the direction in which the magnetic pole position θ is increased when the phase difference Δθ is decreased as shown in FIG. 9, and determines that the rotor is freewheeling in the direction in which the magnetic pole position θ is decreased when the phase difference Δθ is increased as shown in FIG. 10. Figure 11 Figure 12

[0096] ​​​The position and velocity estimation unit 45 estimates the phase difference Δθ derived from the observer 48 and the γ-axis induced voltage e estimated by the first observer 46. γ The sign of the δ-axis induced voltage e inferred from the second observer 47 δ The relationship between these factors allows for the estimation of the magnetic pole position (idle position) during rotor idling.

[0097] For example, such as Figure 11 As shown, when idling with the magnetic pole position θ increasing, the sign of the predicted value of the induced voltage e changes from (e γ = positive and e δ =positive) becomes (e γ = Negative and e δ At the point when the magnetic pole position θ is zero (positive), the position and speed estimation unit 45 inputs the estimated value of the idle speed as an initial value into the speed control unit of the vector control unit 30 at that point, so that the speed control unit of the vector control unit 30 can start the speed control of the rotor at that point.

[0098] On the other hand, for example, such as Figure 12 As shown, when the device idles along the direction of decreasing magnetic pole position θ, the sign of the predicted value of the induced voltage e changes from (e... γ = positive and e δ =negative) becomes (e γ = Negative and e δ At the point when the position is negative, the magnetic pole position θ is zero. The position and speed estimation unit 45 inputs the estimated value of the idle speed as the initial value into the speed control unit of the vector control unit 30 at that point, so that the speed control unit of the vector control unit 30 can start the speed control of the rotor at that point.

[0099] Furthermore, the position and velocity estimation unit 45 uses the estimated value of the idling speed as the initial value for the rotational speed command ωref and the estimated speed value ωm of the speed control unit of the vector control unit 30, and uses it as the magnetic pole position estimation system 50 of the position and velocity estimation unit 45 (see...). Figure 14 The initial value of the integral control 52 is input. Accordingly, the vector control unit 30 can smoothly rotate the idling rotor and simultaneously begin sensorless vector control.

[0100] Figure 13 This is a schematic diagram illustrating an example of the processing flow for the wind turbine start-up function. Figure 13 It can be applied not only to wind turbine start-up function 1, but also to wind turbine start-up function 2.

[0101] The position / speed estimation section 45 determines whether the rotor is idling based on whether the phase difference Δθ has changed (step S10). In the case where the change in the phase difference Δθ is not a sawtooth waveform, the position / speed estimation section 45 determines that the rotor is in a stopped state (step S10, NO). In this case, after the induction detection, the vector control section 30 performs speed open-loop control (step S20), and performs speed control to rotate the rotor in the forward direction (step S30). On the other hand, in the case where the change in the phase difference Δθ is a sawtooth waveform, the position / speed estimation section 45 determines that the rotor is idling (step S10, YES). In this case, the position / speed estimation section 45 estimates the idling direction of the rotor based on the phase difference Δθ (steps S40, S60).

[0102] Note that the forward direction refers to a state of rotating in the desired rotation direction (command rotation direction), and the reverse direction refers to a state of rotating in the direction opposite to the desired rotation direction (command rotation direction). Idling in the forward direction refers to a state of idling in the desired rotation direction (command rotation direction), and idling in the reverse direction refers to a state of idling in the direction opposite to the desired rotation direction (command rotation direction).

[0103] In the case where it is determined that the idling direction of the rotor is the forward direction (step S40, YES), the position / speed estimation section 45 estimates the idling position and the idling speed using the wind-up start function. The vector control section 30 uses the estimated values as initial values, and performs speed control to rotate the rotor in the forward direction (step S50).

[0104] In the case where it is determined that the idling direction of the rotor is neither the forward direction nor the reverse direction (step S60, NO), the position / speed estimation section 45 outputs error information for notifying an abnormality to the outside (step S70).

[0105] In the case where it is determined that the idling direction of the rotor is the reverse direction (step S60, YES), the position / speed estimation section 45 estimates the idling position and the idling speed using the wind-up start function. The vector control section 30 uses the estimated values as initial values, and performs speed control to rotate the rotor in the reverse direction so as to decelerate (step S80). Thereafter, the vector control section 30 performs speed open-loop control (step S90), and performs speed control to rotate the rotor in the forward direction (step S100).

[0106] By performing such control, even if the rotor has idled in the forward direction or the reverse direction, it is possible to smoothly start the rotor in the desired direction.

[0107] <Wind-up start function 2>

[0108] Referring to Figure 8 , Figure 14 and Figure 15 the processing contents of the wind-up starting function 2 will be described.

[0109] In the wind-up starting function 2, the method of estimating the phase difference Δθ up to this point can be the same as that of the wind-up starting function 1 as described with reference to Figure 8 . In the wind-up starting function 2, the phase difference Δθ estimated by the observer 48 is input to the magnetic pole position estimation system 50 of the position and speed estimation section 45 (see Figure 14 ). After the estimated phase difference Δθ is input to the magnetic pole position estimation system 50 of the position and speed estimation section 45, the magnetic pole position estimation system 50 controls and outputs the estimated magnetic pole position θ m and the speed estimation value ω m in such a manner that the phase difference Δθ becomes zero.

[0110] Figure 14 is a block diagram of an example of the magnetic pole position estimation system. The magnetic pole position estimation system 50 of the position and speed estimation section 45 estimates the idle speed of the rotor (the speed estimation value ω m ) from the phase difference Δθ and by means of proportional-integral control 51, and then estimates the magnetic pole position at the time of the rotor idling (the estimated magnetic pole position θ m ) from the estimated speed estimation value ω m and by means of integral control 52. Figure 14 In the above, K P represents the proportional gain, K I represents the integral gain, and s represents the Laplace operator.

[0111] The position and speed estimation section 45 estimates the estimated magnetic pole position θ m at the time of the rotor idling from the relationship between the phase difference Δθ derived by the observer 48, the sign of the γ-axis induced voltage e γ estimated by the first observer 46, and the δ-axis induced voltage e δ estimated by the second observer 47 before the magnetic pole position estimation system 50 is caused to operate. In addition, when the estimated estimated magnetic pole position θ m is zero, the position and speed estimation section 45 inputs the phase difference Δθ to the proportional-integral control 51, whereby the operation of the magnetic pole position estimation system 50 is started, and the proportional-integral control 51 and the integral control 52 are started. By this means, hunting of the current flowing into the motor 4 can be suppressed.

[0112] After the operation of the magnetic pole position estimation system 50 is started, the output of the magnetic pole position estimation system 50, that is, the speed estimation value ω mand estimated pole position θ m At the time when the stabilization is achieved, the position and velocity estimation unit 45 causes the vector control unit 30 to start the velocity control. Thereby, smooth start of the motor at the time of the rotor idling can be performed. The velocity estimation value ωm m and estimated pole position θ m The time when the stabilization is achieved depends on (is dependent on) the gains of the proportional integral control 51 and the integral control 52.

[0113] Figure 15 is an example timing chart of the estimation time until the velocity estimation value ωm is stabilized. The start point of the velocity control of the velocity control unit (velocity control system) of the vector control unit 30 at which the velocity control is started is after the velocity estimation time determined depending on the gains of the proportional integral control 51 and the integral control 52. The position and velocity estimation unit 45 inputs the estimation value of the idling speed as the rotational speed command ωref of the velocity control unit of the vector control unit 30 and the velocity estimation value ωm m Thereby, the vector control unit 30 can smoothly rotate the rotor that is idling, and at the same time, can start the sensorless vector control and start the velocity control of the rotor.

[0114] Note that, as for each function 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, the CPU (Central Processing Unit) is caused to operate by a program that is readably stored in a storage device not shown. For example, these functions are realized by cooperation of hardware and software in a microcomputer including the CPU.

[0115] The motor control device, the motor system, and the motor control method have been described above through the embodiments, but the present application is not limited to the above-described embodiments, and various modifications and improvements can be made to the above-described embodiments as long as they do not depart from the technical scope recited in the claims.

[0116] For example, as for the current detector that outputs the detection signal corresponding to the current value of the current flowing into the DC side of the inverter, it can also be the current detector that outputs the detection signal corresponding to the current value of the current flowing into the positive bus. In addition, the current detector can also be a sensor such as a CT (Current Transformer).

[0117] This international application claims priority from Japanese Patent Application No. 2020-064146 filed on March 31, 2020, and the content of Japanese Patent Application No. 2020-064146 is incorporated herein in its entirety.

[0118] Explanation of Reference Signs:

[0119] 1-1 Motor system

[0120] 4 Motor

[0121] 21 DC power supply

[0122] 22a Positive bus

[0123] 22b Negative bus

[0124] 23 Inverter

[0125] 24 Current detector

[0126] 27 Current detection section

[0127] 30 Vector control section

[0128] 32 PWM signal generation section

[0129] 33 Drive circuit

[0130] 34 Current detection timing adjustment section

[0131] 35 Conduction mode generation section

[0132] 36 Clock signal generation section

[0133] 37 Carrier generation section

[0134] 38 Initial position estimation section

[0135] 45 Position / speed estimation section

[0136] 46 First observer

[0137] 47 Second observer

[0138] 48 Observer

[0139] 50 Magnetic pole position estimation system

[0140] 51 Proportional integral control

[0141] 52 Integral control

[0142] 100-1 Motor control device

[0143] Up, Vp, Wp, Un, Vn, Wn Arm

Claims

1. A motor control device comprising: an deriving section that estimates a γ-axis induced voltage and a δ-axis induced voltage at the time of freewheeling of a rotor of a motor, and derives a phase difference between a dq axis and a γδ axis from the γ-axis induced voltage and the δ-axis induced voltage; and an estimating section that estimates a freewheeling state of the rotor from the phase difference, wherein the phase difference has a period defined by a linear increase or a linear decrease, and the estimating section estimates a freewheeling speed of the rotor from the phase difference having the period.

2. The motor control device according to claim 1, wherein the phase difference is detected in a periodic sawtooth waveform of -90° to 90°.

3. The motor control device according to claim 1 or 2, wherein the estimating section estimates a magnetic pole position at the time of freewheeling of the rotor from the phase difference, a sign of the γ-axis induced voltage, and a sign of the δ-axis induced voltage. wherein 4. The motor control device according to claim 3, further comprising: a vector control section that starts speed control of the rotor using the freewheeling speed estimated by the estimating section as an initial value when the magnetic pole position is zero.

5. The motor control device according to claim 1, wherein the estimating section estimates a direction of freewheeling of the rotor from an increase or a decrease of the phase difference.

6. The motor control device according to claim 1, wherein the estimating section estimates the freewheeling speed of the rotor by proportional-integral control from the phase difference, and estimates the magnetic pole position at the time of freewheeling of the rotor by integral control from the estimated freewheeling speed.

7. The motor control device according to claim 6, further comprising: a vector control section that starts speed control of the rotor using the freewheeling speed estimated by the estimating section as an initial value.

8. The motor control device according to claim 1, wherein the γ-axis induced voltage and the δ-axis induced voltage are estimated by an observer.

9. The motor control device according to claim 6, wherein the estimating section starts the proportional-integral control from when the magnetic pole position is zero.

10. A motor system comprising: the motor control device according to any one of claims 1 to 9; and the motor.

11. A motor control method executed by a motor control device for energizing a motor having a rotor, the motor control method comprising: estimating a γ-axis induced voltage and a δ-axis induced voltage at the time of freewheeling of the rotor; deriving a phase difference between a dq axis and a γδ axis from the γ-axis induced voltage and the δ-axis induced voltage; and estimating a freewheeling state of the rotor from the phase difference, wherein the phase difference has a period defined by a linear increase or a linear decrease, and the freewheeling speed of the rotor is estimated from the phase difference having the period. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ wherein ​ ​

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