Motor driving device and motor driving method

Abstract

To provide a permanent magnet synchronous motor drive device and a motor drive method which suppress a motor current with a current controller and can highly accurately calculate a position and a speed of a motor rotor without use of a special PWM control mode and current detection processing.SOLUTION: A control part 5 comprises a first control part and a second control part which provide a control output of an inverter 2. The second control part uses a feedback controller so as to make a motor current at a predetermined value when a permanent magnet synchronous motor 3 is in an idling state and controls an output voltage of the inverter 2 with a current detection value from current detection means and calculates a rotational position, rotational speed, and rotational direction under idling of the permanent magnet synchronous motor 3 under idling based on the output voltage and the current detection value. The first control part controls the inverter 2 based on the calculated rotational position, rotational speed, and rotational direction under idling so that the permanent magnet synchronous motor 3 starts to rotate from an idle state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a motor drive device and a motor drive method that are provided with a means for restarting a motor from an idling state. [Background technology]

[0002] Motor drive systems consisting of an inverter that converts direct current to alternating current and a permanent magnet synchronous motor are widely used in home appliances and industrial equipment.

[0003] Generally, to drive a permanent magnet synchronous motor with high efficiency, information on the rotor position of the motor is required. The rotor position of the motor can be directly detected using a position detector such as an encoder, but this has problems in terms of cost and reliability. Therefore, in recent years, position sensorless control, which detects the rotor position of a permanent magnet synchronous motor without using a position detector, has been proposed and is being applied to various products.

[0004] One of the challenges in position sensorless control of permanent magnet synchronous motors is how to restart them when the rotor is free-spinning (called "free-run start"). For example, motors such as fans may already be rotating before they are started due to the inertia of the load or external forces (external wind). Without information on the rotor position, rotation speed, and rotation direction in the free-spinning state, it is necessary to wait until the motor stops, or to forcibly apply brake control to stop the rotation and then restart the motor from the stopped state, which increases the time until restart.

[0005] In response to this, Patent Documents 1 and 2 describe a technology that utilizes the induced voltage generated when a permanent magnet synchronous motor spins to short-circuit the motor windings using an inverter, and estimates the rotor position, etc. based on the current that flows at this time.

[0006] In the technology described in Patent Document 1, three upper (lower) arm elements among the switching elements that make up the motor drive inverter are turned on simultaneously to pass a short-circuit current through the motor windings, and the rotor position and rotation speed are calculated based on the detection information of the three-phase motor current.

[0007] In the technology described in Patent Document 2, elements of different arms for two phases of a motor drive inverter are turned on and off simultaneously to detect the bus (shunt) current on the DC side of the inverter and calculate the motor rotor position and rotational speed. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6317904 [Patent Document 2] JP 2018-170928 A Summary of the Invention [Problem to be solved by the invention]

[0009] In the technology described in Patent Document 1, the short-circuit current of the motor winding when the inverter is in short-circuit operation is determined by the motor induced voltage, winding resistance, and inductance, so there is a risk of overcurrent occurring during short-circuit operation depending on the idling speed.

[0010] The technology described in Patent Document 2 uses a special PWM control mode and current detection processing by detecting the current flowing through a bus (shunt) resistor, which makes the calculations to calculate the motor rotor position and rotational speed complex, making it prone to errors in the estimation results.

[0011] Therefore, the present invention provides a motor drive device and a motor drive method that can calculate the position and speed of the motor rotor with high accuracy by suppressing the motor current with a current controller without using a special PWM control mode or current detection processing. [Means for solving the problem]

[0012] In view of the above, the present invention provides a motor drive device including an inverter that outputs AC power converted from DC power to a permanent magnet synchronous motor, a current detection means that detects the output current of the inverter, and a control unit that controls the operation of the inverter, wherein the control unit , by vector control The inverter control unit includes a first control unit that provides a control output of the inverter, and a second control unit that provides a control output of the inverter when the permanent magnet synchronous motor is in an idling state, and the second control unit, when the permanent magnet synchronous motor is in an idling state, three phase Motor current zero A feedback controller is used to control the current from the current detection means. three phase The inverter is controlled by the current detection value. three phase Adjust the output voltage three phase Output voltage and three phase Current detection value The three-phase induced voltage is calculated based on the three-phase induced voltage and a first control unit controls an inverter so that the permanent magnet synchronous motor starts rotating from the idling state based on the calculated rotation position, rotation speed and rotation direction of the idling state of the permanent magnet synchronous motor.

[0013] The present invention also provides a motor drive method for converting DC power into AC power and outputting the AC power to a permanent magnet synchronous motor via an inverter, comprising: During normal operation of the permanent magnet synchronous motor, the inverter is controlled by vector control. When the permanent magnet synchronous motor is in an idling state, three phase Motor current zero The inverter three phase Adjust the output voltage and inverter three phase Output voltage and three phase Current detection value The three-phase induced voltage is calculated based on the three-phase induced voltage and calculating a rotation position, a rotation speed and a rotation direction of the permanent magnet synchronous motor in an idling state based on the calculated rotation position, the rotation speed and the rotation direction of the idling state, and controlling an inverter so that the permanent magnet synchronous motor starts rotating from the idling state based on the calculated rotation position, the rotation speed and the rotation direction of the idling state. Effect of the Invention

[0014] According to the present invention, it is possible to provide a motor control method and a motor drive device using the same that can calculate the position and speed of the motor rotor with high accuracy by suppressing the motor current with a current controller without using a special PWM control mode or current detection processing.

[0015] More specifically, by eliminating the need for sensors to detect the rotation phase of the motor while it is idling and induced voltage detection circuits, circuit costs, board area, and the number of A / D ports used by the microcontroller can be reduced. In addition, the rotor state can be calculated with high accuracy without passing excessive motor current during the period when the rotor position and rotation speed are calculated. This improves the reliability of the motor drive unit and the startup control of various devices that use it, such as fans.

[0016] Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0017] [Figure 1] 1 is a diagram showing an example of the overall configuration of a motor drive device according to an embodiment of the present invention. [Diagram 2] FIG. 4 is a block diagram showing an example of a control configuration of a control unit. [Diagram 3] 2 is a diagram showing an example of the configuration of an idling state detector 17 that calculates the rotor position and rotation speed of a permanent magnet synchronous motor in an idling state. FIG. [Figure 4] FIG. 2 is a diagram showing a configuration example of a current controller. [Diagram 5] FIG. 4 is a diagram showing an example of time waveforms of a motor current and an output voltage when a phase and a speed are calculated. [Figure 6] FIG. 11 is a diagram showing an example of state transition showing transition of the operating state of the motor drive device during idling. [Figure 7] FIG. 4 is a diagram showing an example of schematic waveforms indicating a current command value and a rotational speed command value when a motor is started. [Figure 8] FIG. 4 is a diagram showing an example of schematic waveforms indicating a current command value and a rotational speed command value when a motor is started. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the first embodiment, the transition from an idling state to a normal operation state will be described, and in the second embodiment, the transition of the operation state of the motor drive device when restarting the permanent magnet synchronous motor during idling will be described. EXAMPLES

[0019] In the first embodiment, the transition from an idling state to a normal operation state will be described. First, the overall configuration of the device that enables this will be described. FIG. 1 is a diagram showing an example of the overall configuration of a motor drive device according to an embodiment of the present invention. The motor drive device shown in FIG. 1 includes a DC power supply 1, an inverter 2 that converts DC power from the DC power supply 1 into AC power, a permanent magnet synchronous motor 3 to be driven, a mechanical motor load 4 driven by the permanent magnet synchronous motor 3, a control unit 5 that controls the inverter 2, a shunt resistor 6 between the DC power supply 1 and the inverter 2, and an amplifier 7 that amplifies a signal from the shunt resistor 6. In this embodiment, the motor load 4 is a blower fan.

[0020] The DC power supply 1 may be a power converter (eg, a diode rectifier or a stabilized power supply) that converts AC power received from an AC power supply such as a commercial AC power supply (not shown) into DC power, or a battery.

[0021] In the inverter 2, two arm circuits in which semiconductor switching elements (IGBTs, MOSFETs, etc.) and diodes are connected in anti-parallel, i.e., a series-connected circuit in which an upper arm and a lower arm are connected in series, are connected between a pair of positive and negative terminals of the DC power supply 1. As the inverter 2 is a three-phase inverter, it has three such series-connected circuits, the number of which is the number of AC phases. Here, the upper arm and the lower arm are connected to the high potential side and the low potential side of the DC power supply 1, respectively. The series connection point of the upper and lower arms is connected to AC terminals, and the AC terminals are connected to a permanent magnet synchronous motor 3.

[0022] The low potential side busbar of the inverter 2 is connected to the negative terminal of the DC power supply 1 via a shunt resistor 6 for current detection. A current detection signal detected by the shunt resistor 6 is input to the control unit 5 via an amplifier 7. Here, other current detection means such as a current sensor may be used instead of the shunt resistor 6. Note that for digital calculation in the control unit 5, the output signal of the amplifier 7 is converted into a digital signal by a sampling and holding circuit, an A / D converter, etc.

[0023] The control unit 5 is implemented by a semiconductor arithmetic device such as a microcomputer or a DSP (digital signal processor).

[0024] In this embodiment, as will be described later, the control unit 5 executes position sensorless control in which the control unit 5 detects the rotor position of the permanent magnet synchronous motor and performs synchronization without using a position detector. Therefore, the permanent magnet synchronous motor 3 is not provided with a magnetic pole position detection means such as a Hall element for detecting the position of the rotor or the rotating shaft.

[0025] Next, the overall control will be described. Fig. 2 is a block diagram showing an example of the control configuration of the control unit 5 according to the embodiment. The control unit 5 has each function shown by each block by the arithmetic unit of the computer executing a predetermined program.

[0026] The control unit 5 calculates a voltage command signal to be applied to the motor by dq-axis vector control, and generates a PWM (Pulse Width Modulation) control signal for the inverter. The control unit 5 includes a speed controller 10, a d-axis current command generator 11, a voltage controller 12, a two-axis / three-phase converter 13, a speed and phase estimator 14, a three-phase / two-axis converter 15, a current reproduction calculator 16, a slip state calculator 17, a voltage command switch 18, and a PWM controller 19. The slip state calculator 17 and the voltage command switch 18, which are functions related to start-up control during slip, will be described later with reference to FIG. 3.

[0027] In the control unit 5 of FIG. 2, the current reproduction calculator 16 first reproduces the current detection signal i sh and the three-phase voltage command v u * , v v * , v w * Using the above, the three-phase motor current i from inverter 2 is u , i v , i w Since the method of reproducing the three-phase motor current from the current signal of the shunt resistor 6 is well known, a detailed description will be omitted here. In FIG. 1, the current detection signal i detected by the shunt resistor 6 is sh In this embodiment, a method of reproducing the three-phase current from the shunt resistor 6 is adopted, but this is not a limitation of the embodiment. Therefore, a current detection means such as a current sensor may be used instead of the shunt resistor 6 to detect the AC current that is the output of the inverter circuit 2. In this case, the three-phase current detected by the current detection means may be input to the three-phase / two-axis converter 15.

[0028] The three-phase / two-axis converter 15 outputs the reproduced three-phase output current i u , i v , i w and the phase information θ estimated by the velocity and phase estimator 14. dc Based on the DC axial current i dc and qc-axis current i qc and are calculated based on equations (1) and (2). Equation (1) represents the so-called three-phase / two-axis transformation, and equation (2) represents the transformation into a rotating coordinate system.

[0029]

number

[0030]

number

[0031] The dc-qc axes are estimated axes of a vector control system based on estimated position information, and the dq axis is the motor rotor axis. Here, the axis error between the dq axes and the dc-qc axes is defined as Δθc.

[0032] In FIG. 2, a speed controller 10 receives a speed command value ω * Based on the above, the deviation between the speed command value and the estimated speed ω estimated by the speed and phase estimator 14 is adjusted to approach 0, that is, the estimated speed ω is adjusted to the speed command value ω * The qc-axis current command value i qc * In order to minimize the motor current, the current command generator 11 generates a dc-axis current command value i dc * occurs.

[0033] The voltage controller 12 in FIG. 2 is a dc-axis current command value i dc * and the qc-axis current command value i given by the speed controller 10. qc * and the dc-axis current detection value i given by the three-phase / two-axis converter 15. dc and qc-axis current detection value i qc and the speed command value ω * and the motor constants are used to calculate the dc-axis voltage command value v dc * and the qc-axis voltage command value v qc * Calculate and output.

[0034] The two-axis / three-phase converter 13 converts the dc-qc axis voltage command v calculated by the voltage controller 12 into dc * , v qc * and the phase information θ from the velocity and phase estimator 14 dc Using the above, the three-phase voltage command v is calculated based on equations (3) and (4). u * , v v * , v w *The formula (3) represents the transformation from the rotating coordinate system to the fixed coordinate system, and the formula (4) represents the so-called two-axis / three-phase transformation.

[0035]

number

[0036]

number

[0037] The speed and phase estimator 14 uses the dc-axis current detection value i dc and qc-axis current detection value i qc and the voltage command v of the dc-qc axis dc * , v qc * Using these, the rotor position and rotation speed are estimated, and the phase information θ dc and output as the estimated speed ω.

[0038] As a result, in this embodiment, position sensorless control becomes possible, and the cost of the entire drive system can be reduced. Note that since the specific estimation means in the speed and phase estimator 14 are well known, detailed description thereof will be omitted here.

[0039] 2 has been explained above to show the concept of motor control in a normal operating state, in which the voltage command switch 18 is switched to the 2-axis / 3-phase converter 13 side to control the motor by the output of the voltage controller 12. In contrast, the operation according to the present invention, which will be described below, deals with the operation during idling, in which the voltage command switch 18 is switched to the idling state calculator 17 side to control the motor by the output of the idling state detector 17.

[0040] Next, phase detection during idling will be described. When the permanent magnet synchronous motor 3 is restarted from an idling state, depending on the rotation speed of the permanent magnet synchronous motor 3, it may be difficult to start the motor using the control shown in Fig. 2 unless rotor position and rotation speed information is obtained.

[0041] In contrast to this, the present embodiment includes a means for calculating the rotor position and rotation speed when the permanent magnet synchronous motor 3 is in an idling state. The means will be described below.

[0042] When the permanent magnet synchronous motor 3 rotates idly, an induced voltage is generated in the windings. The induced voltage is applied to the U-phase, V-phase, and W-phase AC terminals that are the connection points between the permanent magnet synchronous motor 3 and the inverter. The electrical phase θ of the permanent magnet synchronous motor 3 d If the reference is the U-phase winding position and the neutral point of the three-phase winding of the permanent magnet synchronous motor 3 is the reference potential, the phase induced voltage e of the U-phase, V-phase, and W-phase is u , e v , e w is expressed by equation (5). In equation (5), ω is the motor speed, and Ke is the motor induced voltage constant.

[0043]

number

[0044] 3 is a diagram showing an example of the configuration of the slip state detector 17 that calculates the rotor position and rotation speed of the permanent magnet synchronous motor in the slip state. The slip state detector 17 is composed of a current command 20, a current controller 21, an induced voltage phase calculator 22, a speed calculator 23, and an initial phase calculator 24. The three-phase voltage command v u * , v v * , v w * is given to the PWM controller 19 via the voltage command switch 18, and executes motor control in the idling state. The initial speed and initial phase calculated here are given to the speed & phase estimator 14.

[0045] In FIG. 3, the current command 20 outputs a constant current command, for example, a current command value of 0, and the detected three-phase current i u , i v , i w The difference between the current and the three-phase voltage command v is input to the current controller 21. u * , v v * , v w * This three-phase voltage command v u * , v v * , v w * is given to the PWM controller 19 via the voltage command switch 18, and a voltage is output from the inverter 2 in accordance with this and applied to the motor 3. At this time, the three-phase current i u , i v , i w and the three-phase voltage command v u * , v v * , v w * and induced voltage e u , e v , e w The relationship between these two is expressed by equation (6). In equation (6), R is the motor winding resistance value, and L is the motor winding inductance value.

[0046]

number

[0047] Therefore, according to equation (7), the voltage command v u * , v v * , v w * and the detected current i u , i v , i w From the motor constants, the induced voltage e during idling is u , e v , e w can be calculated.

[0048]

number

[0049] Also, as can be seen from equation (6), the voltage command v u * , v v * , v w * and induced voltage e u , e v , e w The difference between the motor current i u , i v , i w In this case, the voltage command v u * , v v * , v w * Let e ​​be the induced voltage. u , e v , e w Therefore, control that approaches this is necessary.

[0050] Therefore, in this embodiment, the current controller 21 uses a PI controller to calculate the voltage command v u * , v v * , v w * The three-phase voltage command v u * , v v * , v w * There are several known methods for generating the current difference Δi u , Δi v , Δi w 4, which has three PI controllers 25a, 25b, and 25c for each phase, may be used. For example, the current difference Δi u、 Δi wIt is also possible to use the method shown in the middle part of FIG. 4, which uses three PI controllers 25a, 25c for these phases with these inputs and obtains the value for the v-phase by synthetic addition, or the method shown in the lower part of FIG. 4, which includes three-phase / two-axis conversion processing using equations (1) and (3).

[0051] The gains of these PI controllers 25 in Fig. 4 may be set so that the maximum motor current does not become an overcurrent. However, when a rechargeable battery is used as the DC power supply, the gains of the PI controllers may be adjusted so that the regenerative current (charging current) to the rechargeable battery is equal to or lower than an upper limit.

[0052] Next, the calculation of the phase will be described. In the induced voltage phase calculator 22 in FIG. 3, the induced voltage e u , e v , e w Therefore, the induced voltage phase θ e Calculate the following.

[0053]

number

[0054] Next, we will explain how to calculate the speed from the phase difference. e From the second calculation onwards, the phase of the induced voltage before and after θ e1 and θ e0 From the difference and the time difference Δt, the speed calculator 23 calculates the initial rotation speed ω e0 Calculate the following.

[0055]

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[0056] Furthermore, the rotation direction of the motor is determined from the sign of the rotation speed, and the initial phase θ of the motor rotor is calculated by the initial phase calculator 24 using the equation (10). d0 Calculate the following.

[0057]

number

[0058] In addition, in order to improve the accuracy of the calculation of the rotation speed, various statistical processes may be performed, such as averaging the results of multiple calculations.

[0059] The initial rotation speed ω from the speed calculator 23 and the initial phase calculator 24 e0 and the initial phase of the motor rotor θ d0 is set to the initial value of the speed & phase estimator 14 in FIG. 2, and the control in FIG. 2 is started.

[0060] FIG. 5 shows an example of the operation waveforms of the control described above. Here, from the top of FIG. 5, the motor induced voltage 30 (e u , e v , e w ), Voltage Command 31(v u * , v v * , v w * ), detection current 32(i u , i v , i w ), estimated phase information 33(θ dc ), the initial phase of the motor rotor 34(θ d0 ), initial rotation speed 35(ω e0 ) along the horizontal time axis.

[0061] In this example, the idling state detector 17 operates from 0.05 seconds to 0.1 seconds on the time axis. In other words, from 0.05 seconds to 0.1 seconds, the voltage command switch 18 is switched to the idling state detector 17 side to perform operation during idling, and after 0.1 seconds has elapsed, the voltage command switch 18 is switched to the two-axis / three-phase converter 13 side to switch to motor control during so-called normal operation.

[0062] Here, the voltage command 31 (v u * , v v * , v w *Since the initial value (before 0.05 seconds) of the detection current 32 (i u , i v , i w ) is rapidly increasing, but the voltage command 31 (v u * , v v * , v w * ) rises, and the motor current (detection current 32(i u , i v , i w After the operation of the current controller 21 becomes stable (for example, from 0.06 seconds in the illustrated example), the induced voltage phase 34 (θ d0 ) and initial rotation speed 35(ω e0 ) is calculated.

[0063] This induced voltage phase 34(θ d0 ) and initial rotation speed 35(ω e0 ), the speed and phase estimator 14 in Fig. 2 calculates the induced voltage phase θ dcand estimated speed ω, and start the control of FIG. 2. The motor drive device described in the above embodiment 1 is, in short, a motor drive device including "an inverter 2 that outputs AC power converted from DC power to a permanent magnet synchronous motor 3, a current detection means 7 that detects the output current of the inverter 2, and a control unit 5 that controls the operation of the inverter 2, the control unit 5 including a first control unit (a control system including a voltage control unit 12) that provides a control output for the inverter during normal operation of the permanent magnet synchronous motor 3, and a second control unit (idling state estimator 17) that provides a control output for the inverter 2 when the permanent magnet synchronous motor 3 is idling, "The motor drive device is configured as follows: when the permanent magnet synchronous motor 3 is in an idling state, a feedback controller (current controller 21) is used to adjust the output voltage of the inverter based on the current detection value from the current detection means 7 so that the motor current becomes a predetermined value; the rotational position, rotational speed and rotational direction of the idling state of the permanent magnet synchronous motor 3 in the idling state are calculated based on the output voltage and current detection values; and a first control unit (a control system including a voltage control unit 12) controls the inverter 2 so that the permanent magnet synchronous motor starts rotating from the idling state based on the calculated rotational position, rotational speed and rotational direction in the idling state." EXAMPLES

[0064] In the second embodiment, the transition of the operating state when restarting the permanent magnet synchronous motor during idling will be described. Fig. 6 is a diagram showing an example of state transition showing the transition of the operating state of the motor drive device 2 when restarting the permanent magnet synchronous motor 3 during idling.

[0065] In the idling state, the rotor information (rotor phase, rotation speed and rotation direction) is calculated as described above, and the operating state transitions according to the calculated rotation speed ω. If the rotor is rotating in the reverse direction in the idling state calculation mode md1, for example, the magnitude of the rotation speed ω is less than or equal to the preset position sensorless minimum speed value ω th1If it exceeds the first threshold value ω, the calculated rotor phase and speed are set as the initial values ​​of the speed and phase estimator 14, and the control of FIG. 2 is started to control the operation state to transition successively as shown by the arrows in the figure in the order of reverse rotation position sensorless operation mode md2, reverse rotation synchronous operation mode md3, forward rotation synchronous operation mode md4, and forward rotation position sensorless operation mode md5. For example, when the motor in the idling state exceeds the first threshold value ω th1 If it is calculated that the motor is rotating in reverse at the rotation speed ω or more, the operation mode is changed to the reverse position sensorless operation mode, and then the operation mode is sequentially changed to another operation mode.

[0066] In the determination of the idling state calculation mode md1, the motor in the idling state is determined to be equal to or lower than the second threshold value ω th2 is greater than the first threshold ω th1 If it is calculated that the motor is rotating in the reverse direction at a rotation speed ω smaller than the rotation speed ω, the motor transitions to the reverse synchronous operation mode md3, and then to other operation modes in sequence.

[0067] In the determination of the idling state calculation mode md1, the motor in the idling state is determined to be equal to or lower than the second threshold value ω th2 When it is calculated that the motor is rotating in the forward direction at a rotation speed ω that is greater than the first threshold value ωth1 and smaller than the first threshold value ωth2, the motor is transitioned to a forward rotation synchronous operation mode md4, and then to other operation modes in sequence.

[0068] In the determination of the idling state calculation mode md1, the motor in the idling state is determined to be equal to or smaller than the first threshold value ω th1 If it is calculated that the motor is rotating forward at the rotation speed ω or more, a transition to a forward rotation position sensorless operation mode md5 is made.

[0069] Fig. 7 shows the current command value I at motor startup corresponding to the case where the rotation speed calculated while the motor is rotating in the forward direction exceeds the position sensorless minimum speed value. dc * , I qc * and the rotation speed command value ω * 1 is a schematic waveform diagram showing a rotation speed ω in an idling state when the rotation speed ω is a position sensorless minimum speed value ω th1If the dc-axis current command value I dc * remains at 0, and when the mode transitions to the forward rotation position sensorless operation mode md5, the qc-axis current command value I qc * is given and the motor rotates at a predetermined rotational speed.

[0070] In addition, when the calculated rotation speed is lower than the set minimum level (the second threshold ω th2 ) (for example, when the rotation speed in an idling state is nearly zero regardless of whether the motor is rotating in the forward or reverse direction), the operation state first transitions to the positioning mode md6, and then to the forward rotation synchronous operation mode md4 and the forward rotation position sensorless operation mode md5, in that order.

[0071] FIG. 8 is a schematic waveform diagram showing the current command value and the rotation speed command value at the time of starting the motor in this case. As shown in FIG. 8, the operation mode is a dc-axis current command value I dc * The positioning mode md6, which fixes the rotor at a predetermined rotational position by gradually increasing dc * and the rotation speed command value ω1 * and a synchronous operation mode md4 that controls the voltage applied to the permanent magnet synchronous motor 3 according to the dc-axis current command value I dc * is attenuated to 0, and the qc-axis current command value I qc * and a position sensorless mode md5 that adjusts the inverter frequency. Three types of operation modes are set and executed in this order.

[0072] As described above, according to this embodiment, when phase detection is performed during idling, the current controller 21 is used to adjust the inverter output voltage to suppress the motor current. Therefore, the rotor rotation state can be calculated highly accurately without a sensor, without causing an excessive current to flow. Furthermore, by controlling the inverter based on the calculated rotor state, the permanent magnet synchronous motor can efficiently start rotating from an idling state.

[0073] In addition, in this embodiment, only small-scale functions (program additions) are added to generate a PWM control signal and estimate rotor information for the idle start control, and no significant circuit additions are required. Therefore, the start-up performance can be improved without increasing the size or cost of the device.

[0074] According to the embodiments of the present invention described above, it is possible to provide a motor drive device that can calculate the state of the rotor with high accuracy without causing an excessive short-circuit current to flow, and a device such as a fan that uses the motor drive device.

[0075] Although the present invention has been described above with reference to an embodiment, the present invention is not limited to the above-described embodiment, and as long as the functions and effects of the present invention are achieved within the scope of embodiments that a person skilled in the art can imagine, they are included in the scope of the present invention.

[0076] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the configurations described. In addition, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0077] For example, the current detection means may be a current transformer (CT) instead of a shunt resistor. In this case, the current detection point may be the inverter output section. Also, the permanent magnet synchronous motor may be an embedded magnet type or a surface magnet type. [Explanation of symbols]

[0078] 1...DC power supply, 2...inverter, 3...permanent magnet synchronous motor, 4...motor load, 5...control unit, 6...shunt resistor, 7...amplifier, 10...speed controller, 11...d-axis current command generator, 12...voltage controller, 13...two-axis three-phase converter, 14...speed and phase estimator, 15...three-phase two-axis converter, 16...current reproduction calculator, 17...idling detector, 18...voltage command switch, 19...PWM controller, 20...current command generator, 21...current controller, 22...induced voltage phase calculator, 23...speed calculator, 24...initial phase calculator, 30...motor current waveform, 31...voltage command waveform, 32...induced voltage phase waveform, 33...rotational speed waveform, 40...dc-axis current command waveform, 41...qc-axis current command waveform, 42...rotational speed command waveform

Claims

1. A motor drive device comprising: an inverter that outputs AC power converted from DC power to a permanent magnet synchronous motor; a current detection means that detects an output current of the inverter; and a control unit that controls an operation of the inverter, the control unit includes a first control unit that provides a control output of the inverter by vector control during normal operation of the permanent magnet synchronous motor, and a second control unit that provides a control output of the inverter during idling of the permanent magnet synchronous motor, the second control unit adjusts the three-phase output voltage of the inverter using a feedback controller based on the three-phase current detection values ​​from the current detection means so as to make the three-phase motor current zero when the permanent magnet synchronous motor is in an idling state; calculating a three-phase induced voltage based on the three-phase output voltage and the three-phase current detection values, and calculating a rotational position, a rotational speed, and a rotational direction of the permanent magnet synchronous motor in the idling state based on the three-phase induced voltage; a first control unit that controls the inverter so that the permanent magnet synchronous motor starts rotating from the idling state based on the calculated rotational position, rotational speed, and rotational direction of the idling state,

2. 2. The motor drive device according to claim 1, The second control unit calculates a difference between a motor current command value and the three-phase current detection value from the current detection means, and adjusts the three-phase output voltage of the inverter using a PI controller.

3. 3. The motor drive device according to claim 2, A motor drive device, wherein the PI controller sets a gain of the PI controller so that the three-phase motor current is equal to or less than a predetermined value.

4. A motor driving method for outputting AC power converted from DC power to a permanent magnet synchronous motor via an inverter, comprising: During normal operation of the permanent magnet synchronous motor, the inverter is controlled by vector control; adjusting a three-phase output voltage of the inverter so as to make a three-phase motor current zero when the permanent magnet synchronous motor is in an idling state, calculating a three-phase induced voltage based on the three-phase output voltage and three-phase current detection values ​​of the inverter, and calculating a rotational position, a rotational speed and a rotational direction of the permanent magnet synchronous motor in the idling state based on the three-phase induced voltage; a motor driving method comprising: controlling the inverter so that the permanent magnet synchronous motor starts rotating from the idling state based on the calculated rotational position, rotational speed, and rotational direction in the idling state.

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