Motor control device and motor control method

Abstract

To estimate an idling state of a motor with a small amount of calculation.SOLUTION: A motor control device according to an embodiment is a motor control device that drives a three-phase motor that rotates a fan, and includes: a PWM signal generation part that generates a PWM signal; and an inverter part that includes a switching element of an upper arm and a lower arm corresponding to a three phase, and converts a DC power supplied from a DC power supply into a three-phase AC power by switching control based on the generated PWM signal, and supplies the AC power to the three-phase motor; a current detection part configured to detect a current of the inverter part during a switching control based on a complementary PWM signal generated by the PWM signal generation part such that a plurality of switching patterns for turning on the switching element of an upper arm of at least one phase of the three phases and the switching element of a lower arm of the at least one phase of the three phases are set as one cycle before starting the three-phase motor; and an idling estimation part configured to estimate at least one of an idling direction or an idling rotation speed of the three-phase motor based on the detected current.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a motor control device and a motor control method. [Background technology]

[0002] The outdoor unit of an air conditioner has a heat exchanger, a fan (hereinafter sometimes referred to as the "outdoor unit fan"), and a motor (hereinafter sometimes referred to as the "fan motor") that rotates the outdoor unit fan.

[0003] When the air conditioner starts operating, the outdoor unit fan is rotated by the fan motor, and outdoor air that has been drawn in from the outdoors and exchanged heat in the heat exchanger is blown out to the outside. However, for example, even when the rotation of the fan motor is stopped, the outdoor unit fan may rotate (idle) due to an external force such as wind.

[0004] When the fan motor is started, if the rotor is spinning freely together with the outdoor unit fan due to an external force, the fan motor can be started quickly if the spinning direction of the fan motor and the rotor rotation speed (hereinafter referred to as the "spinning state") can be detected in advance.

[0005] One method for detecting the idling state of a fan motor is to use a detection sensor such as a magnetic encoder (e.g., a Hall element) to obtain information on the rotor's rotation speed, position, etc. On the other hand, for fan motors that do not have a detection sensor, a method has also been proposed that estimates the idling state without using a detection sensor (sensorless).

[0006] A conventional technology for sensorless estimating the idling state of a fan motor uses a single shunt method to detect the phase current of a fan motor during idling, generating a three-phase PWM signal pattern corresponding to a zero vector, and then shifting the on-timing of at least two PWM pulses (called pulse shift) to estimate the idling direction and rotation speed (Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6718356 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the above-mentioned conventional technology has a problem in that the amount of calculation required by the microcomputer to estimate the spin state is large. For example, the method of outputting a pattern corresponding to a zero vector requires pulse shifting, but pulse shifting is a heavy process, takes time, and places a heavy load on the computer.

[0009] The present disclosure proposes a technique that can estimate the free-spinning state of a motor with a small amount of calculation. [Means for solving the problem]

[0010] The motor control device disclosed herein is a motor control device that drives a three-phase motor that rotates a fan, and includes: a PWM signal generation unit that generates a PWM signal; an inverter unit that has upper arm and lower arm switching elements corresponding to the three phases and converts DC power supplied from a DC power source into three-phase AC power through switching control based on the generated PWM signal and supplies it to the three-phase motor; a current detection unit that detects the current in the inverter unit during switching control based on complementary PWM signals generated by the PWM signal generation unit before starting the three-phase motor so that one cycle consists of multiple switching patterns that turn on the upper arm switching elements of at least one phase of the three phases and the lower arm switching elements of at least one phase; and an idling estimation unit that estimates at least one of the idling direction or idling rotation speed of the three-phase motor based on the current detected before starting the three-phase motor. [Effects of the Invention]

[0011] According to the present disclosure, the idling state of the motor can be easily obtained. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram illustrating an example of a motor control system. [Figure 2] FIG. 2 is a block diagram illustrating an example of the configuration of the motor control device according to the embodiment. [Figure 3] FIG. 3 is an explanatory diagram showing an example of a PM. [Figure 4] FIG. 4 is an explanatory diagram illustrating the switching pattern of the PM. [Figure 5] FIG. 5 is an explanatory diagram illustrating an example of a PWM pulse pattern. [Figure 6] FIG. 6 is an explanatory diagram illustrating an example of a PWM pulse pattern. [Figure 7] FIG. 7 is an explanatory diagram illustrating an example of a path of a circulating current. [Figure 8] FIG. 8 is an explanatory diagram illustrating an example of a path of a circulating current. [Figure 9] FIG. 9 is an explanatory diagram for explaining an outline of the thinning number setting. [Figure 10] FIG. 10 is an explanatory diagram illustrating an example of pulse dispersion. [Figure 11] FIG. 11 is an explanatory diagram illustrating an example of the operation of the motor control device according to the embodiment. [Figure 12] FIG. 12 is an explanatory diagram illustrating an example of a PWM pulse pattern. [Figure 13] FIG. 13 is an explanatory diagram illustrating an example of a PWM pulse pattern. [Figure 14] FIG. 14 is an explanatory diagram illustrating an example of a current detection point. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, motor control devices and motor control methods according to embodiments will be described with reference to the drawings. Components having the same functions in the embodiments will be assigned the same reference numerals, and duplicated descriptions will be omitted. Note that the motor control devices and motor control methods described in the following embodiments are merely examples and are not intended to limit the embodiments. Furthermore, the following embodiments may be combined as appropriate within a consistent range.

[0014] Fig. 1 is a block diagram showing an example of a motor control system. The motor control system 200 shown in Fig. 1 includes a motor 1, a fan 1a attached to the motor 1, and a motor control device 100, and controls the motor 1, which rotates the fan 1a of an air conditioner, for example. The motor control system 200 also includes an AC power supply 31, a rectifier circuit 32, a control power supply 33, and a voltage divider circuit 34.

[0015] The motor 1 is a three-phase motor that is rotationally driven by three-phase AC power generated by the motor control system 200. The fan 1a blows air in the direction of the arrow in FIG.

[0016] The rectifier circuit 32 converts the AC power output from the AC power supply 31 into DC power and outputs it. The control power supply 33 supplies power to, for example, signal circuits. The voltage divider circuit 34 resistively divides the DC voltage Vdc supplied from the outside and applies the divided voltage to the microcomputer 10. The output of the voltage divider circuit 34 is used to calculate the peak value of the PWM.

[0017] The motor control device 100 includes a microcomputer 10, a PM 23, and a current detection unit 24, as shown in FIG.

[0018] The power module 23 (hereinafter referred to as "PM23"), which serves as an inverter unit having switching elements, is a semiconductor device with a built-in transistor bridge that controls the motor 1 using PWM (Pulse Width Modulation). Specifically, the PM23 has upper and lower arm switching elements corresponding to three phases (U, V, W). The PM23 chops an externally supplied DC voltage Vdc to generate three-phase AC voltages to be applied to the U, V, and W phases of the motor 1, based on six-phase (U, V, W, X, Y, Z) PWM (Pulse Width Modulation) drive signals (hereinafter referred to as PWM signals) generated by the microcomputer 10 and corresponding to the upper and lower arm switching elements of the U, V, and W phases, respectively, and supplies the three-phase AC voltages to the motor 1.

[0019] The current detection unit 24 includes a current detection circuit 24a and a shunt resistor 24b. The current detection circuit 24a is an interface amplifier circuit for amplifying the current flowing through the shunt resistor 24b. The current detection unit 24 detects the current of the PM 23, i.e., a U-phase current Iu, a V-phase current Iv, and a W-phase current Iw flowing from the PM 23 to the motor 1 (details will be described later).

[0020] The microcomputer 10 has a rotation speed extraction processing unit 10a. The rotation speed extraction processing unit 10a extracts at least one of the rotation speed and rotation direction of the motor 1 connected to the fan 1a based on the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current detection unit 24. For example, the rotation speed extraction processing unit 10a extracts at least one of the rotation speed and rotation direction of the motor 1 when the fan 1a is forced to idle due to an external force such as wind, based on the current detected by the current detection unit 24 before the motor 1 is started. In other words, the rotation speed extraction processing unit 10a is an example of an idle rotation estimation unit.

[0021] Fig. 2 is a block diagram showing an example of the configuration of a motor control device 100 according to an embodiment. Specifically, Fig. 2 is a block diagram showing an example of the configuration of a motor control device 100 that uses a vector control method for controlling the speed of a motor 1.

[0022] 2, a motor 1 that drives a load such as a fan 1a is connected to a motor control device 100. The motor control device 100 includes a microcomputer 10, a PM 23, and a current detection unit 24.

[0023] The microcomputer 10 is an example of a processing device, and includes a subtractor 11, a speed controller 12, an excitation current controller 13, a subtractor 14, a subtractor 15, a d-axis current controller 16, a q-axis current controller 17, a decoupling controller 18, a subtractor 19, an adder 20, a dq / u,v,w converter 21, a PWM modulator 22, a u,v,w / dq converter 25, and a rotor position detection unit 30.

[0024] The rotor position detection unit 30 is an example of a sensorless drive unit that uses the current (or output voltage) detected by the current detection unit 24 to calculate the axis error Δθ from a voltage equation of a so-called motor model and estimates the rotor position.

[0025] If the rotor position detection unit 30 cannot detect the induced voltage of the motor 1 and the sensorless drive unit does not function, the entire motor control device 100 will not operate. Therefore, when the motor 1 is stopped, it is necessary to set the d-axis voltage command value Vd*, the q-axis voltage command value Vq*, and the rotation speed command value ω* to predetermined values ​​and forcibly start operation using synchronous operation. However, if the load at start-up is unstable due to external forces such as wind, it becomes extremely difficult to set the d-axis voltage command value Vd*, the q-axis voltage command value Vq*, and the rotation speed command value ω*. Therefore, in the case of a sensorless drive method, it is important to know the load state at start-up for control purposes.

[0026] The rotor position detection unit 30 includes an axis error estimation processor 26 , a PLL (Phase Locked Loop) controller 27 , an integrator 28 , and a divider 29 .

[0027] The subtractor 11 outputs to the speed controller 12 a speed deviation (mechanical angular velocity deviation) Δω obtained by subtracting the actual velocity (actual mechanical angular velocity) ωm, which is the estimated current angular velocity output from the divider 29, from the speed command value (command rotation speed) ωm* input to the microcomputer 10.

[0028] The speed controller 12 generates a q-axis current command value Iq* that reduces the speed deviation Δω output from the subtractor 11, and outputs it to the subtractor 14. The excitation current controller 13 generates a d-axis current command value Id* from the q-axis current command value Iq* output from the speed controller 12, and outputs it to the subtractor 15.

[0029] The subtractor 14 subtracts the q-axis current Iq output from the u,v,w / dq converter 25 from the q-axis current command value Iq* output from the speed controller 12 to generate a q-axis current deviation ΔIq, and outputs the q-axis current deviation ΔIq to the q-axis current controller 17. The subtractor 15 subtracts the d-axis current Id output from the u,v,w / dq converter 25 from the d-axis current command value Id* to generate a d-axis current deviation ΔId, and outputs the d-axis current deviation ΔId to the d-axis current controller 16.

[0030] The d-axis current controller 16 generates a d-axis voltage command value Vda** from the d-axis current deviation ΔId output from the subtractor 15. The q-axis current controller 17 generates a q-axis voltage command value Vqa** from the q-axis current deviation ΔIq output from the subtractor 14.

[0031] The decoupling controller 18 generates a d-axis decoupling correction value Vda and a q-axis decoupling correction value Vqa to cancel inter-axis interference between the d-axis voltage command value Vda** and the q-axis voltage command value Vqa** and to control them independently. The subtractor 19 subtracts the d-axis decoupling correction value Vda from the d-axis voltage command value Vda** output from the d-axis current controller 16 to generate a d-axis voltage command value Vd* and outputs it to the dq / u,v,w converter 21. The adder 20 adds the q-axis decoupling correction value Vqa to the q-axis voltage command value Vqa** output from the q-axis current controller 17 to generate a q-axis voltage command value Vq* and outputs it to the dq / u,v,w converter 21.

[0032] The dq / u,v,w converter 21 converts the decoupled two-phase d-axis voltage command value Vd* and q-axis voltage command value Vq* into a three-phase U-phase output voltage command value Vu*, a V-phase output voltage command value Vv*, and a W-phase output voltage command value Vw*, using the rotation angle θe output from the integrator 28. The dq / u,v,w converter 21 then outputs the U-phase output voltage command value Vu*, the V-phase output voltage command value Vv*, and the W-phase output voltage command value Vw* to the PWM modulator 22.

[0033] It should be noted that Vu*, Vv*, Vw* and Iu, Iv, and Iw, which will be described later, are voltages and currents in a three-phase fixed coordinate system.

[0034] The PWM modulator 22 generates PWM signals (U, V, W, X, Y, Z) from the U-phase output voltage command value Vu*, the V-phase output voltage command value Vv*, the W-phase output voltage command value Vw*, and the PWM carrier signal, and outputs the PWM signals to the PM 23. That is, the PWM modulator 22 is an example of a PWM signal generating unit.

[0035] The PM 23 chops the DC voltage Vdc supplied from the outside based on the six-phase PWM signal output from the PWM modulator 22 to generate a three-phase AC voltage, which is then supplied to the motor 1 .

[0036] The current detection unit 24 has a current detection circuit 24a (see FIG. 1) that detects the current flowing through the motor 1. The current detected by the current detection unit 24 is the current that flows from the DC voltage Vdc through the PM 23 to the motor 1 and then flows through the PM 23 to the current detection unit 24. The current detection unit 24 calculates the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw of the motor 1 from the six-phase PWM switching information output from the PWM modulator 22 and the bus current detected by a shunt resistor 24b (see FIG. 1) using a single-shunt current detection method. The currents detected by the current detection unit 24 are converted into digital data by an AD (Analog to Digital) converter (not shown) included in the microcomputer 10. The converted detected currents are input into the microcomputer 10 and processed by software. For example, the components other than the PM 23 including the control driver and the current detection unit 24 are implemented as software on the microcomputer 10.

[0037] The current detection method may be a 2CT method in which two CTs (Current Transformers) detect the U-phase current Iu and the V-phase current Iv and calculate the remaining W-phase current Iw from the relational expression Iu+Iv+Iw=0, or another current detection method such as a 3-shunt current detection method. Current detection unit 24 outputs the calculated U-phase current Iu, V-phase current Iv, and W-phase current Iw of motor 1 to u, v, w / dq converter 25.

[0038] The u,v,w / dq converter 25 converts the three-phase U-phase current Iu, V-phase current Iv, and W-phase current Iw output from the current detection unit 24 into two-phase d-axis current Id and q-axis current Iq using the rotation angle θe output from the integrator 28. The u,v,w / dq converter 25 then outputs the d-axis current Id to the subtractor 15, the decoupling controller 18, and the axis error estimation processor 26, and outputs the q-axis current Iq to the subtractor 14, the decoupling controller 18, and the axis error estimation processor 26.

[0039] The axis error estimation processor 26 calculates the axis error Δθ from the d-axis current Id and q-axis current Iq output from the u,v,w / dq converter 25, the d-axis voltage command value Vd* output from the subtractor 19, and the q-axis voltage command value Vq* output from the adder 20, and outputs the calculated axis error Δθ to the PLL controller 27.

[0040] The PLL controller 27 calculates an estimated electrical angle angular velocity ωe, which is an estimated current angular velocity, from the axis error Δθ output from the axis error estimation processor 26, and outputs it to the decoupling controller 18, the integrator 28, and the divider 29. The integrator 28 integrates the angular velocity ωe to generate a rotation angle θe. The divider 29 divides the estimated current angular velocity ωe output from the PLL controller 27 by the number Pn of pole pairs of the motor 1, converts it into an actual velocity (actual mechanical angle velocity) ωm, and outputs it.

[0041] Fig. 3 is an explanatory diagram showing an example of PM23. As shown in Fig. 3, PM23 converts an externally supplied DC voltage Vdc into three-phase AC power of U, V, and W and supplies it to motor 1. PM23 has a switching element S41, a diode D41, a switching element S42, and a diode D42 as U-phase elements. PM23 also has a switching element S51, a diode D51, a switching element S52, and a diode D52 as V-phase elements. PM23 also has a switching element S61, a diode D61, a switching element S62, and a diode D62 as W-phase elements. Diodes D41 to D62 are freewheeling diodes (freewheeling diodes).

[0042] The switching elements S41 to S62 are switching elements such as IGBTs (Insulated Gate Bipolar Transistors), FETs (Field Effect Transistors), etc. Diodes D41 to D62 are connected in parallel to the switching elements S41 to S62, respectively, to conduct a return current generated by a back electromotive force generated when the conduction phase of the inverter unit (PM23) is switched.

[0043] Further, a shunt resistor 24b is connected to the emitters of the switching elements S42, S52, and S62.

[0044] In other words, PM23 is configured with six switching elements connected in a bridge. Each of the U, V, and W phases is switched by a semiconductor in the upper and lower arms, and the magnitude and direction of the current for each phase supplied to motor 1 is controlled by the combination of on and off of the six switching elements.

[0045] The gates U, X, V, Y, W, and Z of the switching elements S41 to S62 in FIG. 3 are connected to a drive circuit (not shown) that turns on and off the switching elements S41 to S62 based on the PWM signals (U, V, W, X, Y, and Z) generated by the PWM modulator 22.

[0046] For example, when gate U of switching element S41 in the upper arm of U-phase is turned on, the U-phase terminal of motor 1 is connected to DC voltage Vdc, and when gate X of switching element S42 in the lower arm of U-phase is turned on, the U-phase terminal of motor 1 is connected to ground. Similarly, gates V and Y, and gates W and Z supply power to the V-phase terminal and W-phase terminal, respectively.

[0047] When energizing the lower arm (gates X, Y, Z), switching elements S41 to S62 and diodes D41 to D62 of PM23 can control each gate with respect to ground, but when energizing the upper arm (gates U, V, W), they must be controlled with respect to the power supply voltage. A common way to deal with this is to float the drive power supply for the upper arm.

[0048] When starting the motor 1, it is necessary to estimate (detect) the direction and speed of rotation of the motor 1 caused by the fan 1a rotating due to external forces such as wind, and select a start-up pattern (described later). The direction of rotation of the motor 1 can be detected from the phase relationship of the current in at least two of the three phases. The speed of rotation can be detected by filtering the current detected by switching and taking the period. In this way, by detecting the voltage induced in the stator winding, detection can be performed simply without using an encoder or hall element.

[0049] There are two main methods for detecting induced voltage. The first method is to directly detect the induced voltage. This method directly detects the voltage generated in the winding via a voltage dividing resistor, making it possible to detect it accurately. However, this method requires an additional circuit to detect the induced voltage.

[0050] The second method is a method in which PM23 is switched to form a closed circuit including the inverter unit (PM23) and the stator winding of the motor 1, and a current proportional to the induced voltage is detected from the circuit current. In the embodiment, the second method is adopted, that is, a method in which PM23 is switched to form a closed circuit and a current proportional to the induced voltage is detected to extract the rotation speed and rotation direction of the rotor (hereinafter referred to as the "induced voltage current detection method").

[0051] When using the one-shunt method, pulse shifting is essential during vector control, but pulse shifting is a heavy process (the amount of calculation required by the microcomputer 10 is large), and the load on the microcomputer 10 for performing this processing also increases.

[0052] Therefore, in this embodiment, before starting the motor 1, the PWM modulator 22 of the microcomputer 10 generates complementary PWM signals (hereinafter referred to as specific complementary PWM signals) having one cycle consisting of multiple switching patterns that turn on the upper-arm switching element of at least one of the three phases and the lower-arm switching element of at least one phase. The specific complementary PWM signals are generated appropriately at predetermined time intervals (details will be described later). During switching control based on the generated specific complementary PWM signals, a closed circuit is formed that includes the inverter unit (PM23) and the stator windings of the motor 1. Therefore, the rotation speed extraction processing unit 10a can estimate at least one of the idling direction and the number of idling occurrences of the motor 1 using an induced voltage current detection method based on the inverter current detected by the current detection unit 24.

[0053] Fig. 4 is an explanatory diagram illustrating switching patterns in complementary PWM of PM 23. As shown in Fig. 4, there are eight switching patterns for the U, V, and W phases in PM 23, from i (000) to viii (111), and when either the upper arm or the lower arm is turned on, the other is turned off. The numbers in parentheses indicate the on / off status of (U, V, W phase) as 0 / 1.

[0054] Of the eight switching patterns corresponding to complementary PWM signals, i(000) to viii(111), six of them correspond to specific complementary PWM signals: ii(100), iii(110), iv(010), v(011), vi(001), and vii(101).

[0055] 5 is an explanatory diagram illustrating an example of a PWM pulse pattern. In the PWM pulse pattern shown in FIG. 5, the PWMs for the U, V, V, Y, W, and Z phases correspond to the on / off of gates U, X, V, Y, W, and Z of switching elements S41 to S62 of PM23. For example, the U-phase PWM corresponds to the on / off of gate U of switching element S41 of the upper arm of U-phase. Furthermore, the X-phase PWM corresponds to the on / off of gate X of switching element S42 of the lower arm of U-phase.

[0056] When the PWM modulator 22 generates a PWM pulse pattern such as that shown in Figure 5, at timings ii(100) and iii(110), the U-phase and W-phase currents modulated by the circulating current generated by the induced voltage due to the idling of the motor 1 can be detected in the closed circuit including the inverter unit (PM23) and the stator windings of the motor 1. However, with this PWM pulse pattern, the U-phase terminal of the motor 1 continues to be connected to the DC voltage Vdc in the closed circuit. In other words, because the upper arm of the U-phase continues to be on, the modulated current flows in only one direction and rises as a DC current, which may cause the motor to trip.

[0057] Therefore, in this embodiment, in order to prevent the modulated current from flowing in only one direction, the PWM modulator 22 generates a PWM pulse pattern that turns on and off the upper and lower arms of the U, V, and W phases in sequence.

[0058] Fig. 6 is an explanatory diagram illustrating an example of a PWM pulse pattern. As shown in Fig. 6, the PWM modulator 22 generates a PWM pulse pattern in which the upper and lower arms of the U, V, and W phases are turned on in order, such as ii (100), v (011), etc., sandwiched between i (000), which turns off the upper arms of the U, V, and W phases and turns on the lower arms.

[0059] Specifically, after ii(100), which turns on the U-phase upper arm (and turns on the V- and W-phase lower arms), i(000) turns off the U-, V-, and W-phase upper arms, and then v(011) turns off the U-phase upper arm (and turns on the V- and W-phase upper arms). The PWM modulator 22 generates a PWM pulse pattern that turns on the most recently turned-off phase in the next pattern. In the closed circuit described above, ii(100) and v(011) have opposite current vectors. This prevents the U-phase upper arm from being continuously turned on, preventing the modulated current from flowing in only one direction and rising as a direct current. This allows the current due to the induced voltage generated by the idling of the motor 1 to circulate. Furthermore, when generating the PWM pulse patterns ii(100) and v(011), the PWM modulator 22 sandwiches i(000) between them. This causes current to circulate inside the motor due to the induced voltage, making it possible to detect the current in subsequent PWM pulse patterns.

[0060] 7 and 8 are explanatory diagrams illustrating an example of a circulating current path. In Fig. 7, when the switching pattern is ii(100), the arrows indicate the path along which the current modulated by the circulating current generated by the induced voltage circulates. In Fig. 8, when the switching pattern is v(011), the arrows indicate the path along which the modulated current by the induced voltage circulates.

[0061] 7 and 8, the current modulated by the freewheeling current generated by the induced voltage circulates, allowing the current detection unit 24 to detect the current through the shunt resistor 24b. For example, as shown in Fig. 7, at the timing when the switching pattern is ii(100), the current from the U phase modulated by the freewheeling current generated by the induced voltage is detected.

[0062] Furthermore, as is clear from the direction of the arrows shown in Figures 7 and 8, the directions of the current flowing through motor 1 are opposite for ii(100) and v(011), so unidirectional current increases can be suppressed.

[0063] Similarly, for the V and W phases, for example, after iv (010) in which the V-phase upper arm is turned on (the U- and W-phase lower arms are turned on), i (000) is sandwiched between vii (101) in which the V-phase lower arm is turned on (the U- and W-phase upper arms are turned on). Furthermore, after vi (001) in which the W-phase upper arm is turned on (the U- and V-phase lower arms are turned on), i (000) is sandwiched between vii (110) in which the W-phase lower arm is turned on (the U- and V-phase upper arms are turned on). In this way, by generating the PWM pulse pattern shown in FIG. 6 (in other words, a current detection pattern in which one cycle of a PWM pulse pattern that sequentially turns on and off only the upper arm of each phase for the U-, V-, and W-phase upper arms) it is possible to suppress a unidirectional current rise. Furthermore, by sandwiching a pattern that turns off all upper arms (turns on all lower arms) between PWM pulse patterns that sequentially turn on and off the upper arms of each phase, braking action by the zero vector is applied, and the motor is decelerated. This braking action makes it easier to brake the motor, making it easier to start even under high load conditions. In addition, using the PWM pulse pattern described above reduces the amount of calculation required for pulse output, which also has the effect of reducing the processing load on the microcomputer.

[0064] 6 is set as one cycle, and the PWM modulator 22 generates this one cycle of PWM pulse pattern intermittently at predetermined intervals (for example, for several tens of carriers). More specifically, the PWM modulator 22 periodically generates a PWM pulse pattern during an ON period, during which it generates one cycle of PWM pulse pattern, followed by a predetermined OFF period during which it does not generate any PWM pulse pattern for a predetermined period (for example, for several tens of carriers), and then generates a PWM pulse pattern again during the ON period.

[0065] By generating such PWM pulse patterns and periodically setting off periods in which no PWM pulse patterns are generated, for example, in switching pattern i (000) (or viii (111)) state, all phases of the upper arm are on and all phases of the lower arm are off (or all phases of the upper arm are off and all phases of the lower arm are on), and current circulates within the motor. The circulating current generates heat and braking torque, which brakes the rotation of motor 1 and reduces the idling rotation speed. If the idling rotation speed is reduced when motor 1 starts, the energy generated by rotation is reduced, making it easier to brake the motor and improving the success rate of motor 1 starts.

[0066] Furthermore, since noise in the current waveform detected by the current detection circuit 24a is suppressed, the current detection unit 24 can detect the idling state (rotation direction, rotation speed) of the motor 1 with higher accuracy.

[0067] For example, limiting the range of current detection reduces the variation in the detected current value. Limiting the range of current detection reduces the frequency with which the detected current is updated, widening the range in which the current remains constant (reducing variation). This makes it easier for the current detection unit 24 to calculate the idling state (rotation direction, rotation speed) of the motor 1.

[0068] It is also possible to suppress abnormal audible noise generated in the motor control device 100. One characteristic of the human ear is that it has poor sensitivity to low frequencies and good sensitivity to sounds around 3000 to 4000 Hz. That is, to make low-frequency sounds audible at the same volume as high-frequency sounds, a higher sound pressure level is required for the low-frequency sounds (= sounds around 3000 to 4000 Hz are easy to hear, but low-frequency sounds (such as 20 Hz or lower) are difficult to hear).

[0069] For example, if the carrier frequency is 16 kHz and the current is detected over six carrier cycles, the frequency for current detection is 16 kHz / 6 = 2.666... ​​kHz. Therefore, the above current detection generates a sound of 2.666... ​​kHz, which is easily perceived by humans as an abnormal sound.

[0070] In contrast, if the section in which no PWM pulse pattern is generated is set to, for example, 144 PWM carriers, then the frequency becomes 16 [kHz] / 150 = 106.66... ​​[Hz] (150: 144 (thinning number) + 6 (number of carriers in the current detection section)), which is less likely to be perceived as an abnormal sound by humans.

[0071] Furthermore, the setting of the above thinning number (the period during which no PWM output is performed and the switching pattern is set to i (000) or viii (000)) is based on the maximum detectable idling speed (the maximum value of the rotation speed to be detected). The maximum value of the rotation speed to be detected is basically determined as the maximum idling speed that can be achieved by the outside wind, measured through testing or statistical data. This may be changed as appropriate depending on the environment in which the outdoor unit is installed. For example, the maximum value of the rotation speed to be detected may be set to a higher value in areas with frequent typhoons or coastal areas.

[0072] Fig. 9 is an explanatory diagram outlining the setting of the thinning number. For example, let us assume that the maximum rotation speed to be detected is 400 [rpm], and four points at which current is detected (hereinafter referred to as sampling points) are set within one current cycle, as shown in Fig. 9. The thinning number is determined using the following equations (1) to (4).

[0073] Equation (1): Express the time required for one cycle of current in terms of frequency when the maximum rotation speed to be detected is 400 [rpm] and the number of pole pairs is 4. Specifically, it is (400 [rpm] x 4 (number of pole pairs)) / 60 [s] = 26.666… [Hz].

[0074] Equation (2): Calculate the total number of carriers for one cycle of current when the carrier frequency is 16 kHz. Specifically, 16 kHz (carrier frequency) / 26.666… Hz = 600 carriers.

[0075] Equation (3): Calculate the total number of carriers for one current cycle by dividing the number of sampling points by 4. Specifically, 600 / 4 (sampling points) = 150 [carriers].

[0076] Equation (4): Calculate the number (=thinning-out number) by subtracting the number of carriers at the sampling point from equation (3). Specifically, 150-6 (number of carriers in the current detection section) = 144 [carriers].

[0077] FIG. 10 is an explanatory diagram illustrating an example of pulse distribution. As shown in FIG. 10, when setting the current detection decimation, pulses may be generated in a distributed manner within 106.666... ​​[Hz] of 16 [kHz] / 150 [carrier]. Pulses may be generated randomly within 150 [carrier]. In this case, since off periods are provided as needed between on periods, current does not flow continuously in one direction, and there is no need to use a switching pattern that causes current to flow in the opposite direction.

[0078] 11 is an explanatory diagram showing an example of the operation of the motor control device 100 according to the embodiment. For example, when a user starts up an air conditioner, as shown in FIG. 11, power is supplied to the microcomputer 10 (ST1), and an initialization process is performed (ST2).

[0079] Once initialization is complete, the microcomputer 10 waits for an operation command from the control unit of the air conditioner (ST3). Upon receiving the operation command, the microcomputer 10 immediately detects the idling state (rotation direction and rotation speed) of the motor 1 as described above (hereinafter also referred to as idling detection) (ST4).

[0080] Next, the start-up processing unit in the microcomputer 10 selects a start-up pattern that corresponds to the idling state of the motor 1 from a plurality of start-up patterns previously stored in a memory or the like, and starts the motor 1 with the selected start-up pattern (ST5 to ST7). If the motor is idling at 300 rpm or more, the motor 1 is not started and the process returns to ST3. Thereafter, idling detection is performed at predetermined time intervals (for example, 10 seconds) until a rotation speed within the range in which the motor 1 can be started is detected.

[0081] For example, if the rotation direction of motor 1 is forward and the rotation speed is 200 to 300 rpm, microcomputer 10 starts motor 1 using a forward rotation start pattern (ST5). If motor 1 is rotating at -200 to 200 rpm (forward / reverse rotation at 200 rpm or less), microcomputer 10 starts motor 1 using a low rotation start pattern (ST6). If motor 1 is rotating in the reverse direction and the rotation speed is -200 to -300 rpm, microcomputer 10 starts motor 1 using a reverse rotation start pattern (ST7).

[0082] If the motor 1 is successfully started using the selected start pattern, the microcomputer 10 performs vector control of the motor 1 using the vector control method described above until an instruction to stop operation is received (ST8).

[0083] If the start of the motor 1 according to the selected start pattern fails (ST9), the microcomputer 10 requests the control unit to retry, returns to ST3, and waits for the process to retry starting the motor 1 after a certain time.

[0084] 12 and 13 are explanatory diagrams illustrating an example of a PWM pulse pattern. As shown in Fig. 12, all phases of the upper arm and the lower arm are in an off state [0] until slip detection starts.

[0085] Next, when slip detection begins, the PWM modulator 22 generates a PWM pulse pattern that turns on each phase in turn, as described above, to detect the current caused by the induced voltage [1]. Next, the PWM modulator 22 turns off all phases of the upper arms (U, V, W) and turns on all phases of the lower arms (X, Y, Z) [2]. Setting the PWM pulse pattern in this way can suppress abnormal noise.

[0086] Specifically, as shown in case C1 in Figure 13, if there are no periodic intervals [2] in which no PWM pulse patterns are generated, a sound of 16 [kHz] / 6 = 2.666... ​​[kHz] will be generated, which will be perceived by humans as an abnormal noise.

[0087] In contrast, as shown in case C2 in Figure 13, if there are periodic intervals [2] where no PWM pulse pattern is generated, a sound of 16 [kHz] / 150 = 106.66... ​​[Hz] will be generated, which will be difficult to hear at the auditory level.

[0088] FIG. 14 is an explanatory diagram illustrating an example of current detection points. In the induced voltage current detection method, current must be detected at intervals (= setting of the thinning number) that allow the maximum rotation speed to be detected. For example, assume that the current to be detected is as shown by the dotted line in FIG. 14. Here, if current detection points are set at intervals such as in case C3, the current may be detected as shown by the solid line in case C4. Therefore, when setting the thinning number, an interval is set that results in sampling points that satisfy the so-called sampling theorem.

[0089] As described above, the motor control device 100 includes the PWM modulator 22, the PM 23, the current detector 24, and the rotation speed extraction processor 10a. The PWM modulator 22 generates a PWM signal. The PM 23 has upper and lower arm switching elements (S41-S62) corresponding to three phases, and converts DC power supplied from a DC power source into three-phase AC power through switching control based on the generated PWM signal. The current detector 24 detects the current of the PM 23 during switching control based on the complementary PWM signal generated by the PWM modulator 22 before starting the motor 1, so that one cycle is made up of multiple switching patterns that turn on the upper arm switching element of at least one phase and the lower arm switching element of at least one phase of the three phases. The rotation speed extraction processor 10a estimates at least one of the idling direction and rotation speed of the motor 1 based on the current detected before starting the motor 1.

[0090] As a result, motor control device 100 does not need to perform pulse shift processing as in the one-shunt system, and can therefore estimate the free-spinning state of motor 1 with a small amount of calculation.

[0091] Also, just before the idle rotation detection is turned ON in FIG. 12, the switching pattern becomes state i (000) or viii (111), the so-called zero vector state. At this time, the motor 1 is braked, and the idle rotation speed obtained by this detection means is detected as a value lower than the idle rotation speed before the motor 1 started. If it is desired to obtain the idle rotation speed before the motor starts, a rotation speed table can be created in advance by calculating the correlation (difference) with the idle rotation speed at the time of the zero vector and correcting the detected idle rotation speed so that it is higher. This makes it possible to accurately detect the idle rotation speed before the motor starts with a small amount of calculation. Furthermore, by doing so, it is possible to determine when the motor is idle at a high rotation speed before starting, and thereby reduce power consumption by rotating the fan without starting the motor.

[0092] Furthermore, the PWM modulator 22 generates a complementary PWM signal in which, during one cycle, the PM 23 has an ON period during which at least one of the three phases is ON and a predetermined OFF period during which all three phases are OFF.

[0093] As a result, the motor control device 100 can reduce the number of idling rotations by braking the rotation of the motor 1. In this way, the motor control device 100 can improve the success rate of starting the motor 1 by reducing the number of idling rotations when starting the motor 1.

[0094] Furthermore, the PWM modulator 22 generates a complementary PWM signal that turns on the phase that was most recently turned off in the next pattern during the on-period of one cycle.

[0095] As a result, in the motor control device 100, when detecting at least one of the idling direction and the idling rotation speed of the motor 1 before starting the motor 1, it is possible to suppress a unidirectional current increase in the current flowing through the PM 23.

[0096] Furthermore, the off period of the complementary PWM signals is set based on the maximum detectable idling rotation speed.

[0097] This allows the motor control device 100 to appropriately set the period during which the complementary PWM signals are turned off.

[0098] Furthermore, the microcomputer 10 selects one of a plurality of start patterns based on at least one of the estimated idling direction and the idling rotation speed, and starts the motor 1.

[0099] As a result, the motor control device 100 can start the motor 1 appropriately depending on the direction of idling of the motor 1 or the rotation speed of the idling. [Explanation of symbols]

[0100] 1...Motor 1a...Fan 10...Microcomputer 10a...rotation speed extraction processing section 11, 14, 15, 19...Subtractor 12...Speed ​​controller 13...Excitation current controller 16...d-axis current controller 17...q-axis current controller 18...Decoupling controller 20...Adder 21...dq / u,v,w converter 22...PWM modulator 23…PM 24...Current detection section 24a...Current detection circuit 24b...Shunt resistor 25...u,v,w / dq converter 26...Axis error estimation processor 26 27...PLL controller 28...Integrator 29...Divider 30...Rotor position detection unit 31…AC power supply 32... Rectifier circuit 33...Control power supply 34...Voltage divider circuit 100...Motor control device 200...Motor control system A1…Current C1~C4...Cases D41 to D62: Diodes Iu…U phase current Iv…V phase current Iw…W phase current S41 to S62: Switching elements Vdc: DC voltage

Claims

1. A motor control device that drives a three-phase motor that rotates a fan, a PWM signal generating unit that generates a PWM signal; an inverter unit having upper arm and lower arm switching elements corresponding to three phases, which converts DC power supplied from a DC power supply into three-phase AC power by switching control based on the generated PWM signal and supplies the AC power to the three-phase motor; a current detection unit that detects a current in the inverter unit during switching control based on complementary PWM signals generated by the PWM signal generation unit so that a plurality of switching patterns in which the upper arm switching element of at least one phase and the lower arm switching element of at least one phase are turned on, among the three phases, before start-up of the three-phase motor, constitute one cycle; an idling estimation unit that estimates at least one of an idling direction and an idling rotation speed of the three-phase motor based on the current detected before the start of the three-phase motor; A motor control device comprising:

2. the PWM signal generating unit generates the complementary PWM signals in which, during one cycle, an ON period in which the inverter unit turns on at least one of the three phases and a predetermined OFF period in which the inverter unit turns off all of the three phases are provided.

2. The motor control device according to claim 1.

3. the PWM signal generating unit generates the complementary PWM signals that turn on the phase that was most recently turned off in the next pattern during the on-period of the one cycle.

3. The motor control device according to claim 2.

4. The off period is set based on the maximum detectable idling rotation speed.

3. The motor control device according to claim 2.

5. a start-up processing unit that selects one start-up pattern from a plurality of start-up patterns based on at least one of the estimated idling direction and the estimated idling rotation speed, and starts the three-phase motor; 2. The motor control device according to claim 1.

6. the idling estimation unit has a table for estimating the rotation speed by further correcting the idling rotation speed estimated based on the current detected before start-up of the three-phase motor.

2. The motor control device according to claim 1.

7. A motor control method for controlling driving of a three-phase motor that rotates a fan, comprising: Before starting the three-phase motor, a current of an inverter unit is detected during switching control based on complementary PWM signals generated so that one cycle is a plurality of switching patterns that turn on an upper arm switching element of at least one phase and a lower arm switching element of at least one phase among the three phases; and estimating at least one of the direction of idling and the rotational speed of the three-phase motor based on the current detected before starting the three-phase motor. Motor control methods.

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