Motor control device and motor control method

Abstract

The present invention controls the operation of a permanent magnet synchronous motor by controlling the operation of an inverter by means of a control signal based on a voltage command, and is provided with: a first control unit that generates the control signal of the inverter during normal operation of the permanent magnet synchronous motor; and a second control unit that generates a control signal for the inverter when the permanent magnet synchronous motor is idling, the second control unit outputting a voltage command for causing a direct current having a predetermined initial value to flow through the permanent magnet synchronous motor when the permanent magnet synchronous motor is in an idling state. The controller calculates a rotor position and a rotational speed of the permanent magnet synchronous motor on the basis of the voltage command and a current value of the permanent magnet synchronous motor corresponding to the voltage command, estimates an induced voltage of the permanent magnet synchronous motor on the basis of the calculated rotational speed, and adjusts the voltage command so as to be greater than the estimated induced voltage. As a result, the position and speed of the motor rotor can be calculated with higher accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to a motor control device and a motor control method. BACKGROUND

[0002] In the field of home electric appliances and industrial equipment, a motor drive system composed of an inverter that converts direct current power into alternating current power and a permanent magnet synchronous motor is widely popular. In order to efficiently drive such a permanent magnet synchronous motor, generally, rotor position information of the motor is required. The rotor position of the motor can be directly detected by using a position detector such as an encoder, but there are problems in terms of cost and reliability. Therefore, in recent years, a sensorless control that detects the rotor position of the permanent magnet synchronous motor without using a position detector has been proposed and applied to various products.

[0003] On the other hand, as one of the problems in the sensorless control of the permanent magnet synchronous motor, a technique related to a method of restarting from a state in which the rotor is idling (referred to as "free-run start") is known. For example, a motor of a washing machine or the like sometimes rotates before start-up due to inertia of a load. In this case, if there is no information of the rotor position, the rotational speed, and the rotational direction of the idling state, it is necessary to wait until the motor stops, or forcibly apply brake control to stop rotation, and after becoming a stopped state, restart again, so the time until the restart becomes long.

[0004] Therefore, for example, as the related art described in Patent Documents 1 and 2, a technique has been developed in which, focusing on an induced voltage generated when the permanent magnet synchronous motor is idling, the winding of the motor is short-circuited by the inverter, and the position of the rotor and the like are estimated based on the current flowing at that time.

[0005] In Patent Document 1, three upper (lower) arm elements among the switching elements that constitute the inverter for driving the motor are simultaneously turned on to make a short-circuit current flow through the motor winding, and the position and the rotational speed of the rotor are calculated based on detection information of the motor current of the three phases.

[0006] In addition, in Patent Document 2, elements of different arms of 2 phases of the inverter for driving the motor are simultaneously subjected to on-off operation, a bus (shunt) current of the direct current side of the inverter is detected, and the rotor position and the rotational speed of the motor are calculated.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT DOCUMENTS

[0009] Patent Document 1: Japanese Patent Application Publication No. 2015-73361

[0010] Patent Document 2: Japanese Patent Application Publication No. 2018-170928 SUMMARY

[0011] Problem to be Solved by the Invention

[0012] However, in the above-described prior art, the following problems exist.

[0013] In the prior art described in Patent Literature 1, the short-circuit current of the motor winding at the time of short-circuit operation of the inverter is determined by the motor induced voltage and the winding resistance and inductance, and thus depending on the idling speed, overcurrent at the time of short-circuit operation can occur.

[0014] In the prior art described in Patent Literature 2, by detecting the current flowing through the bus (shunt) resistor, a special PWM control mode and current detection processing are used, and thus the operation for calculating the rotor position and speed of the motor becomes complicated, and the estimation result is likely to have an error.

[0015] The present application has been achieved in view of the above-described circumstances, and aims to provide a motor control device and a motor control method capable of calculating the position and speed of the rotor of a motor with higher accuracy.

[0016] Means for Solving the Problem

[0017] The present application contains a plurality of means for solving the above-described problem, and if one example thereof is cited, it is a motor control device that controls the operation of an inverter that converts direct-current power into alternating-current power and supplies it to a permanent-magnet synchronous motor, thereby controlling the operation of the permanent-magnet synchronous motor, by a control signal based on a voltage command, comprising: a first control section that generates a control signal of the inverter when the permanent-magnet synchronous motor is normally operated; and a second control section that generates a control signal of the inverter when the permanent-magnet synchronous motor is idling, the second control section outputting a voltage command that causes a direct-current current of a predetermined initial value to flow through the permanent-magnet synchronous motor when the permanent-magnet synchronous motor is in an idling state, the second control section calculating a rotor position and a speed of the permanent-magnet synchronous motor from the voltage command and a current value of the permanent-magnet synchronous motor corresponding to the voltage command, estimating an induced voltage of the permanent-magnet synchronous motor from the calculated speed, and adjusting the voltage command in a manner greater than the estimated induced voltage.

[0018] Effects of the Invention

[0019] According to the present application, the position and speed of the rotor of a motor can be calculated with higher accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a diagram that schematically represents the overall structure of a motor control system and a motor control device and its associated structure.

[0021] Figure 2is a functional block diagram showing the processing content of the motor control device.

[0022] Figure 3 is an explanatory diagram showing a current vector when a direct current flows in a permanent magnet synchronous motor.

[0023] Figure 4 is a functional block diagram showing the processing content of the idling state estimation section.

[0024] Figure 5 is a functional block diagram showing the processing content of the voltage command generation section. DETAILED DESCRIPTION

[0025] Hereinafter, an embodiment of the present application will be described with reference to the drawings. In the following description, as a control object of the motor control device, a permanent magnet synchronous motor (PMSM) is exemplarily described.

[0026] Figure 1 is a diagram schematically showing the overall structure of the motor control system of the present embodiment and the motor control device and its associated structure.

[0027] As shown in Figure 1 , the motor control device 4 controls the operation of the permanent magnet synchronous motor 3 by controlling the inverter 2 that converts the direct current power from the direct current power source 1 into alternating current power and supplies it to the permanent magnet synchronous motor 3 as a drive object. As the motor control device 4, for example, a semiconductor arithmetic device such as a microcomputer, a DSP (Digital Signal Processor), or the like is used.

[0028] As the direct current power source 1, for example, a power conversion device (for example, a diode rectifier, a stabilized power source, or the like) that converts alternating current power received from an alternating current power source such as a commercial alternating current power source not shown into direct current power, a battery, or the like is used.

[0029] The inverter 2 is configured by connecting two arm circuits in which semiconductor switching elements (IGBT, MOSFET, or the like) and diodes are connected in reverse parallel, in other words, series connection circuits of upper arms and lower arms, in series between a pair of positive and negative terminals of the direct current power source 1. The inverter 2 has an amount of phases of alternating current output from the series connection circuits, for example, in the present embodiment, a three-phase inverter having three-phase series connection circuits. The upper arms and the lower arms of the inverter 2 are connected to the high potential side and the low potential side of the direct current power source 1, respectively. The series connection points of the upper arms and the lower arms are connected to alternating current terminals, and the alternating current terminals are connected to the permanent magnet synchronous motor 3.

[0030] The bus bar on the low potential side of the inverter 2 is connected to the negative terminal of the direct current power supply 1 via a shunt resistor 5 for current detection. A current detection signal detected by the shunt resistor 5 is input to the motor control device 4 via an amplifier 6. The output signal from the amplifier 6 to the motor control device 4 is converted to a digital signal by a sampling and holding circuit and an A / D converter, etc. not shown, for digital operation in the motor control device 4. That is, the shunt resistor 5 and the amplifier 6 constitute a direct current detector that detects a direct current flowing through the bus bar on the low potential side of the inverter 2 and outputs a current detection signal to the motor control device 4. Alternatively, another current detection unit such as a current sensor can be used instead of the shunt resistor 5.

[0031] Further, in the inverter 2, between the bus bar on the high potential side connected to the positive terminal of the direct current power supply 1 and the bus bar connected to the negative terminal of the direct current power supply 1, a direct current voltage detector 50 that detects a direct current voltage between the bus bars on the high potential side and the low potential side and outputs a direct current voltage detection signal to the motor control device 4 is provided. The output signal from the direct current voltage detector 50 to the motor control device 4 is converted to a digital signal as with the direct current detector.

[0032] Further, in the present embodiment, as described later, the motor control device 4 performs so-called sensorless control that detects the position of the rotor of the permanent magnet synchronous motor to perform synchronization without using a position detector, and no magnetic pole position detection unit such as a Hall element that detects the position of the rotor, the rotary shaft is provided in the permanent magnet synchronous motor 3.

[0033] Figure 2 is a functional block diagram showing the processing contents of the motor control device. Further, as described above, the motor control device 4 is a semiconductor operation device such as a microcomputer, a DSP, and each function is realized by executing a prescribed program.

[0034] As shown in Figure 2 , the motor control device 4 is provided with a speed control section 7, a d-axis current command generation section 8, a current control section 9, a voltage command switching section 10, a 2-phase / 3-phase conversion section 11, a speed / phase estimation section 13, a voltage command generation section 12, an idling state estimation section 14, a 3-phase / 2-phase conversion section 15, a current reproduction operation section 16, and a control signal generation section 17 (PWM controller).

[0035] The motor control device 4 calculates a voltage command to be applied to the permanent magnet synchronous motor 3 by d-q axis vector control, generates a PWM (Pulse Width Modulation) control signal of the inverter 2 based on the voltage command, and thereby controls the operation of the permanent magnet synchronous motor 3. The motor control device 4 performs operation control in a normal operation state (normal operation control) and transition control from an idle state to the normal operation state (start-up control) of the permanent magnet synchronous motor 3.

[0036] <Normal operation control>

[0037] First, the operation of each functional block in the operation control in the normal operation state will be described.

[0038] The current reproduction operation section 16 reproduces the three-phase motor currents iu, iv, iw from the inverter 2 using the current detection signal ish output from the amplifier 6 constituting the direct current detector and the three-phase voltage commands Vu*, Vv*, Vw* output from the 2-phase / 3-phase conversion section 11 to the control signal generation section 17. The method of reproducing the three-phase motor currents from the current signal of the shunt resistor 5 can use a publicly known method, and detailed description thereof will be omitted here.

[0039] Further, in the present embodiment, in order to reduce the cost, a method of reproducing the three-phase motor currents iu, iv, iw from the current detection signal ish detected by the shunt resistor 5 in the current reproduction operation section 16 and inputting to the 3-phase / 2-phase conversion section 15 is adopted, but is not limited thereto. For example, it can be configured to detect the output of the inverter 2, that is, the alternating current, using a current detection unit such as a current sensor instead of the shunt resistor 5, and it can be configured to input the three-phase motor currents iu, iv, iw detected by the current detection unit to the 3-phase / 2-phase conversion section 15.

[0040] The 3-phase / 2-phase conversion section 15 operates the α-axis current iα, the β-axis current iβ, the dc-axis current idc, and the qc-axis current iqcin accordance with the following (Equation 1) and (Equation 2) based on the three-phase output currents iu, iv, iw reproduced by the current reproduction operation section 16 and the phase information θd_est estimated by the speed / phase estimation section 13. In addition, the following (Equation 1) represents so-called 3-phase / 2-phase conversion, and (Equation 2) represents conversion to a rotating coordinate system.

[0041] [Equation 1]

[0042]

[0043] [Equation 2]

[0044]

[0045] The dc-qc axis is an estimated axis of a vector control system based on estimated position information, and the d-q axis is a motor rotor axis, where an axis error of the d-q axis and the dc-qc axis is defined as Δθc.

[0046] The speed and phase estimation section 13 estimates the position and the speed of the rotor using the dc-axis current detection value idc and the qc-axis current detection value iqc, and the voltage commands Vdc* and Vqc* of the dc-qc axis, and outputs the estimated speed ωest and the phase information θd_est. The specific estimation unit in the speed and phase estimation section 13 can use a known unit, and detailed description thereof is omitted here.

[0047] The speed control section 7 generates the qc-axis current command value Iqc* so that the deviation calculated by the operation section 25 from the speed command value ω* generated by a function section (not shown) in the motor control device 4 based on an instruction from the outside and the estimated speed ωest estimated by the speed and phase estimation section 13 is close to 0 (zero), i.e., the estimated speed ωest is close to the speed command value ω*.

[0048] The d-axis current command generation section 8 generates the dc-axis current command value Idc* for minimizing the three-phase motor currents iu, iv, and iw.

[0049] The current control section 9 calculates and outputs the dc-axis voltage command value Vdc* and the qc-axis voltage command value Vqc* using the dc-axis current command value Idc* supplied from the d-axis current command generation section 8, the qc-axis current command value Iqc* supplied from the speed control section 7, the dc-axis current detection value idc and the qc-axis current detection value iqc supplied from the 3-phase / 2-phase conversion section 15, the speed command value ω*, and motor constants.

[0050] The voltage command switching section 10 outputs either the voltage commands Vdc* and Vqc* of the dc-qc axis calculated by the current control section 9 or the voltage commands Vα* and Vβ* of the α-β axis calculated by the voltage command generation section 12 to the 2-phase / 3-phase conversion section 11 according to a switching signal from the outside. Specifically, the voltage command switching section 10 outputs the voltage commands Vdc* and Vqc* of the dc-qc axis calculated by the current control section 9 according to the switching signal in the normal operation state to the 2-phase / 3-phase conversion section 11. Further, the voltage command switching section 10 outputs the voltage commands Vα* and Vβ* of the α-β axis calculated by the voltage command generation section 12 based on the switching signal in the idling state (start-up control) to the 2-phase / 3-phase conversion section 11.

[0051] 2-phase / 3-phase conversion section 11 calculates three-phase voltage commands Vu*, Vv*, Vw* by the following (Equation 3) and (Equation 4) using the voltage commands Vdc*, Vqc* of the dc-qc axis calculated by the current control section 9 and input via the voltage command switching section 10 and the phase information θd_est from the speed·phase estimation section 13 in the normal operation state, and outputs them. In addition, the following (Equation 3) indicates conversion from the rotating coordinate system to the fixed coordinate system, and (Equation 4) indicates so-called 2-phase / 3-phase conversion.

[0052] [Equation 3]

[0053]

[0054] [Equation 4]

[0055]

[0056] The control signal generation section 17 generates a control signal based on the three-phase voltage commands Vu*, Vv*, Vw* from the 2-phase / 3-phase conversion section 11 and the detection value (direct current voltage detection signal) from the direct current voltage detector 50, and outputs it to the inverter 2.

[0057] <Start-up control>

[0058] Next, the operation of each functional block in the transition control from the idling state to the normal operation state (start-up control) will be described. In addition, in the start-up control, only the points different from the normal operation state will be described.

[0059] First, the basic principle of the phase detection (estimation of the rotor position and the rotational speed) at the time of idling will be described.

[0060] In the case where the permanent magnet synchronous motor 3 is restarted from the idling state without using the rotor position and the rotational speed information, it is sometimes difficult to start up by the normal operation control depending on the rotational speed of the permanent magnet synchronous motor 3. Therefore, in the present embodiment, the rotor position and the rotational speed are calculated in the idling state of the permanent magnet synchronous motor 3, and used for the start-up control.

[0061] Figure 3 is an explanatory diagram showing the current vector at the time when a direct current flows in the permanent magnet synchronous motor.

[0062] In Figure 3 , in the case where the permanent magnet synchronous motor 3 does not idle, a current Ia_DC corresponding to the direct current with the a-axis as the reference flows in the permanent magnet synchronous motor 3. In this case, the β-axis current Iβ is 0 (zero).

[0063] On the other hand, in the case where the permanent magnet synchronous motor 3 is idling (in the case of an idling state), the current Ie, which is the amount of influence of the induced voltage, is added to the current Ia DC, and the current Iaβ (= Ia DC+ Ie) that is the vector sum flows through the permanent magnet synchronous motor 3. That is, as shown in FIG. 8, the phase angle of the current Iaβ varies depending on the rotational speed and the rotation direction of the permanent magnet synchronous motor 3 in the idling state. Figure 3

[0064] Therefore, in the present embodiment, the rotational speed and the rotation direction of the permanent magnet synchronous motor 3 in the idling state are estimated using the fact that the currents Ia, Iβ flowing through the permanent magnet synchronous motor 3 vary depending on the idling state.

[0065] Further, in the present embodiment, the case where a direct current flows in one phase in the permanent magnet synchronous motor 3 that is a three-phase motor is exemplified and described, but a direct current can flow in a plurality of phases and the rotational speed and the rotation direction can be estimated respectively.

[0066] Figure 4 is a functional block diagram showing the processing contents of the idling state estimation section.

[0067] In Figure 4 , the idling state estimation section 14 is a functional section that calculates the initial phase θd0 that is the rotor position of the permanent magnet synchronous motor 3 in the idling state and the initial speed ωe0 that is the rotational speed, and outputs them to the voltage command generation section 12 and the speed / phase estimation section 13, and is composed of a flux estimation section 18, an idling phase estimation section 19, and an idling speed estimation section 20.

[0068] The flux estimation section 18 calculates the estimated fluxes Ψa_est, Φβ_est using the voltage commands Vα*, Vβ* of the α-β axes calculated by the voltage command generation section 12 and the motor currents iα, iβ of the α-β axes calculated by the 3-phase / 2-phase conversion section 15 by the following (Equation 5) and (Equation 6), and outputs them to the idling phase estimation section 19. In (Equation 5) and (Equation 6), R is the motor winding resistance value, and Ψa(0), Φβ(0) are initial values of the estimated fluxes Ψa_est, Φβ_est, respectively.

[0069] [Equation 5]

[0070]

[0071] [Equation 6]

[0072]

[0073] ​The freewheeling phase estimation section 19 calculates an initial phase θd0 using the estimated magnetic fluxes Ψα_est, Φβ_est calculated by the magnetic flux estimation section 18, by the following (Equation 7), and outputs it to the freewheeling speed estimation section 20 and to the speed / phase estimation section 13.

[0074] [Equation 7]

[0075]

[0076] The freewheeling speed estimation section 20 calculates and outputs an initial speed ωe0 using the initial phase θd0 calculated by the freewheeling phase estimation section 19. Specifically, for example, the estimated speed ωest (= Δθd0 / Δt) is calculated and output by dividing the difference Δθd0 (= θd0_2- θd0_1) between the previous value θd0_1 and the current value θd0_2 of the initial phase θd0 repeatedly calculated at a prescribed control period by the time Δt (= t2-t1) from the time t1 at which the previous value θd0_1 was calculated to the time t2 at which the current value θd0_2 was calculated.

[0077] Figure 5 is a functional block diagram showing the processing contents of the voltage command generation section.

[0078] In Figure 5 , the voltage command generation section 12 is a functional section that calculates the α-β axis voltage commands Vα*, Vβ* required for controlling the permanent magnet synchronous motor 3 in the freewheeling state, and outputs them to the freewheeling state estimation section 14 and the voltage command switching section 10 (in other words, the 2-phase / 3-phase conversion section 11), and is composed of an α-axis voltage command generation section 21, a β-axis voltage command generation section 22, and a voltage command correction value calculation section 23.

[0079] The α-axis voltage command generation section 21, for example, calculates or experimentally obtains an α-axis voltage command value that can estimate the maximum speed of the permanent magnet synchronous motor 3 assumed to be in the freewheeling state (for example, the speed assumed to be in low-speed operation), and outputs it as an initial α-axis voltage command value Vα0*.

[0080] The β-axis voltage command generation section 22, for example, sets 0 (zero) as the voltage command Vβ* as a β-axis voltage command value and outputs it.

[0081] The voltage command correction value operation section 23 calculates the voltage command correction value ΔVα* using the initial speed ωe0 calculated by the idling speed estimation section 20 of the idling state estimation section 14 and the voltage command Vα0* that is the output of the α-axis voltage command generation section 21, for example, based on the following (Equation 8), (Equation 9), and (Equation 10). In (Equation 8), Ke is the induced voltage constant of the permanent magnet synchronous motor 3, and Eest is the estimated induced voltage. In (Equation 9), ΔVVα0_E is the deviation of the estimated induced voltage Eest from the initial α-axis voltage command value Vα0*. In (Equation 10), VCO is the correction amount for making the α-axis voltage command Vα* larger than the estimated induced voltage Eest, which is calculated or experimentally determined and set in advance.

[0082] [Equation 8]

[0083]

[0084] [Equation 9]

[0085]

[0086] [Equation 10]

[0087]

[0088] In the operation section 24, the voltage command Vα0* that is the output of the α-axis voltage command generation section 21 and the voltage command correction value ΔVα* are used to calculate the α-axis voltage command Vα* that is the output of the voltage command generation section 12 based on the following (Equation 11).

[0089] [Equation 11]

[0090]

[0091] The speed and phase estimation section 13 sets the initial speed ωe0 from the idling speed estimation section 20 of the idling state estimation section 14 and the initial phase θd0 from the idling phase estimation section 19 as initial values and performs transition control (start-up control) of the permanent magnet synchronous motor 3 from the idling state to the normal operation state.

[0092] The voltage command switching section 10 outputs the α-β-axis voltage commands Vα*, Vβ* calculated by the voltage command generation section 12 to the 2-phase / 3-phase conversion section 11 based on the switching signal from the outside in the case of the idling state (start-up control).

[0093] The speed control section 7 generates a qc-axis current command value Iqc* in the idling state (start-up control) so that the deviation of a speed command value ω* generated by a function section (not shown) in the motor control device 4 from an instruction from the outside from an estimated speed ωest (= ωeo (initial value)) from the speed / phase estimation section 13 is close to 0 (zero), i.e., the estimated speed ωest is close to the speed command value ω*.

[0094] The 2-phase / 3-phase conversion section 11 generates and outputs three-phase voltage commands Vu*, Vv*, Vw* by (Equation 3) and (Equation 4) using the α-β-axis voltage commands Vα*, Vβ* calculated by the voltage command generation section 12 and input via the voltage command switching section 10 and the phase information θd_est (= θdo (initial value)) from the speed / phase estimation section 13 in the idling state (start-up control).

[0095] The effects of the present embodiment configured as described above will be described.

[0096] In the related art, the short-circuit current of the motor winding at the time of short-circuit operation of the inverter is determined by the motor induced voltage and the winding resistance and inductance, and thus depending on the idling speed, overcurrent at the time of short-circuit operation can occur. In addition, by detecting the current flowing through the bus (shunt) resistor, a special PWM control pattern and current detection processing are used, and thus the operation of calculating the rotor position and the rotational speed of the motor becomes complicated, and the estimation result is likely to have an error.

[0097] In contrast, in the present embodiment, in a motor control device that controls the operation of an inverter that converts direct-current power into alternating-current power and supplies the alternating-current power to a permanent magnet synchronous motor, thereby controlling the operation of the permanent magnet synchronous motor, a first control section that generates a control signal of the inverter in normal operation of the permanent magnet synchronous motor and a second control section that generates a control signal of the inverter in idling of the permanent magnet synchronous motor are provided, and the second control section outputs a voltage command that causes a direct-current current of a predetermined initial value to flow through the permanent magnet synchronous motor in the case where the permanent magnet synchronous motor is in an idling state, and calculates a rotor position and a rotational speed of the permanent magnet synchronous motor on the basis of the voltage command and a current value of the permanent magnet synchronous motor corresponding to the voltage command, estimates an induced voltage of the permanent magnet synchronous motor on the basis of the calculated rotational speed, and adjusts the voltage command to be greater than the estimated induced voltage, and thus the position and the speed of the rotor of the motor can be calculated with higher accuracy.

[0098] <Notes>

[0099] Further, the present application is not limited to the above-described embodiments, and includes various modifications, combinations thereof, within a scope not departing from the gist thereof. In addition, the present application is not limited to having all the structures described in the above-described embodiments, and includes a structure in which a part of the structures is deleted.

[0100] For example, in the motor control device 4, moving average processing or low pass filter processing can be applied to values used for various calculations, in order to avoid the influence of disturbance and noise.

[0101] Further, each structure, function, and the like of the motor control device 4 described in the present embodiment can realize a part or all thereof by, for example, designing with an integrated circuit, or the like. Further, each structure, function, and the like described above can be realized by software by a processor interpreting and executing a program realizing each function.

[0102] Symbol explanation

[0103] 1: DC power supply, 2: inverter, 3: permanent magnet synchronous motor, 4: motor control device, 5: shunt resistor, 6: amplifier, 7: speed control section, 8: d-axis current command generation section, 9: current control section, 10: voltage command switching section, 11: 2-phase / 3-phase conversion section, 12: voltage command generation section, 13: speed / phase estimation section, 14: idling state estimation section, 15: 3-phase / 2-phase conversion section, 16: current reproduction operation section, 17: control signal generation section, 18: flux estimation section, 19: idling phase estimation section, 20: idling speed estimation section, 21: a-axis voltage command generation section, 22: β-axis voltage command generation section, 23: voltage command correction value operation section, 24, 25: operation sections, 50: DC voltage detector.

Claims

1. A motor control device that controls the operation of an inverter that converts direct current (DC) power into alternating current (AC) power and supplies it to a permanent magnet synchronous motor via a control signal based on a voltage command, thereby controlling the operation of the permanent magnet synchronous motor, characterized in that, have: A first control unit generates control signals for the inverter during normal operation of the permanent magnet synchronous motor; and The second control unit generates control signals for the inverter when the permanent magnet synchronous motor is idling. When the permanent magnet synchronous motor is in an idling state, the second control unit outputs a voltage command to make a predetermined initial value of DC current flow through the permanent magnet synchronous motor. The second control unit calculates the rotor position and speed of the permanent magnet synchronous motor based on the voltage command and the corresponding current value of the permanent magnet synchronous motor. The induced voltage of the permanent magnet synchronous motor is estimated based on the calculated rotational speed. The voltage command is adjusted to be greater than the estimated induced voltage.

2. The motor control device according to claim 1, characterized in that, The second control unit outputs a voltage command that causes the DC current of the initial value to flow through one of the multiple phases of the armature of the permanent magnet synchronous motor.

3. The motor control device according to claim 1, characterized in that, The initial DC current is a current value that can be used to estimate the speed at which the permanent magnet synchronous motor is expected to operate at low speed.

4. The motor control device according to claim 1, characterized in that, The second control unit estimates the induced voltage based on the rotational speed of the permanent magnet synchronous motor and the induced voltage constant. Calculate the deviation between the voltage command and the induced voltage of the DC current flowing through the initial value. The difference between the predetermined correction value and the deviation is calculated as the voltage command correction value. The voltage command is adjusted by adding the voltage command correction value to the voltage command of the DC current flowing through the initial value.

5. A motor control method, which controls the operation of an inverter that converts DC power into AC power and supplies it to a permanent magnet synchronous motor via a control signal based on a voltage command, thereby controlling the operation of the permanent magnet synchronous motor, characterized in that... The following steps are required: When the permanent magnet synchronous motor is in an idling state, a voltage command is output to make a predetermined initial value of DC current flow through the permanent magnet synchronous motor. Based on the voltage command and the current value of the permanent magnet synchronous motor corresponding to the voltage command, calculate the rotor position and speed of the permanent magnet synchronous motor; The induced voltage of the permanent magnet synchronous motor is estimated based on the calculated rotational speed. as well as The voltage command is adjusted to be greater than the estimated induced voltage.

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