Motor control device

Abstract

This motor control device comprises: an inverter circuit that outputs a three-phase AC voltage to a motor by switching a power supply voltage of a DC power supply; a current calculation unit that calculates, on the basis of a current flowing between the DC power supply and the inverter circuit, a d-axis current flowing in a d-axis of the motor and a q-axis current flowing in a q-axis of the motor; a rotation speed estimation unit that calculates an estimated rotation speed of the motor on the basis of the d-axis current and the q-axis current; a target rotation speed calculation unit that calculates a target rotation speed of the motor on the basis of an operation command for the motor; and a voltage command calculation unit that calculates, on the basis of the difference between the target rotation speed and the estimated rotation speed, a duty command for controlling switching performed by the inverter circuit. The rotation speed estimation unit includes: an induced voltage calculation unit that calculates, on the basis of the d-axis current and the q-axis current, an induced voltage residual angle that indicates the angle of a vector with respect to the q axis, the vector having a d-axis estimated induced voltage residual, which represents the residual of an induced voltage induced in the d-axis of the motor, as a d-axis component, and a q-axis estimated induced voltage residual, which represents the residual of an induced voltage induced in the q-axis of the motor, as a q-axis component; a first switching unit that switches between zero and the induced voltage residual angle in a first period in which the three-phase AC voltage is within a predetermined phase range and a second period other than the first period, respectively, and outputs a resulting signal; and a first proportional integral operation unit that performs a proportional integral operation using the signal output from the first switching unit as an input signal, to calculate an estimated rotation speed.

Description

Motor control device

[0001] The present disclosure relates to a motor control device that controls a motor.

[0002] 2. Description of the Related Art Conventionally, motor control devices are known that control a motor by controlling a three-phase AC voltage supplied to the motor.

[0003] For example, Patent Documents 1, 2, and 3 disclose motor control devices that employ a method (hereinafter also referred to as a "single-shunt current detection method") in which the current flowing in each phase of three-phase AC is calculated based on the current flowing between an inverter circuit that outputs a three-phase AC voltage to a motor by switching the power supply voltage of a DC power supply and the DC power supply (hereinafter also referred to as a "DC bus current"), and the calculated current for each phase is used to control the timing of the switching in the inverter circuit.

[0004] However, in a motor control device that employs a single-shunt current detection method, it may not be possible to uniquely identify the current flowing through each phase of the three-phase AC during the period when the three-phase AC voltage is within a specified phase range (hereinafter, this period will also be referred to as the "specific phase period").

[0005] A specific phase period corresponds to, for example, a period in which, in the above switching performed by the inverter circuit, the difference between the switching timing of one phase of the three-phase AC and the switching timing of another phase is shorter than the detection period required for a current sensor that detects the DC bus current to detect the current.

[0006] JP 2017-312611 A JP 2018-86139 A JP 2019-55748 A

[0007] Therefore, an object of the present disclosure is to provide a motor control device that employs a one-shunt current detection method and is capable of controlling a motor even when a specific phase period exists.

[0008] A motor control device according to one aspect of the present disclosure includes an inverter circuit that outputs a three-phase AC voltage to a motor by switching a power supply voltage of a DC power supply; a current calculation unit that calculates a d-axis current flowing in a d-axis of the motor and a q-axis current flowing in a q-axis of the motor based on a current flowing between the DC power supply and the inverter circuit; a rotational speed estimation unit that calculates an estimated rotational speed of the motor based on the d-axis current and the q-axis current; a target rotational speed calculation unit that calculates a target rotational speed of the motor based on an operation command of the motor; and a voltage command calculation unit that calculates a duty command to control the switching performed by the inverter circuit based on a difference between the target rotational speed and the estimated rotational speed. The rotation speed estimation unit includes an induced voltage calculation unit that calculates, based on the d-axis current and the q-axis current, an induced voltage residual angle that indicates an angle with respect to the q-axis of a vector having a d-axis estimated induced voltage residual that indicates a residual of an induced voltage induced on the d-axis of the motor as its d-axis component and a q-axis estimated induced voltage residual that indicates a residual of an induced voltage induced on the q-axis of the motor; a first switching unit that switches between outputting zero and the induced voltage residual angle during a first period in which the three-phase AC voltage is within a predetermined phase range and during a second period other than the first period; and a first proportional integral calculation unit that performs proportional integral calculation using the signal output from the first switching unit as an input signal to calculate the estimated rotation speed.

[0009] According to one aspect of the present disclosure, a motor control device is provided that employs a single-shunt current detection method and is capable of controlling a motor even when a specific phase period exists.

[0010] Fig. 1 is a block diagram showing the configuration of a motor control system according to an embodiment. Fig. 2 is a schematic diagram showing a typical voltage waveform of a three-phase AC voltage output by an inverter circuit according to an embodiment. Fig. 3 is a schematic diagram showing the relationship between the conduction pattern of each switching element and the DC bus current according to an embodiment. Fig. 4 is a schematic diagram showing an example of a state in which the current sensor cannot correctly detect the DC bus current when the conduction pattern switching period is shorter than the detection time of the current sensor. Fig. 5 is a block diagram showing the configuration of a rotation speed estimator according to an embodiment.

[0011] (How one aspect of the present disclosure was achieved) Conventionally, in a motor control device that employs a single-shunt current detection method, the following two control methods are known as control methods for controlling a motor when a specific phase period may exist.

[0012] As a first control method, for example, Patent Document 1 discloses a control method in which the current value of each phase in a specific phase period is calculated based on the DC bus current detected immediately before the specific phase period.

[0013] However, in this first control method, the amount of calculation required to calculate the current value of each phase during a specific phase period is large based on the DC bus current detected immediately before the specific phase period. Therefore, even if an attempt is made to implement this first control method using an inexpensive microcomputer with low processing power, it cannot be implemented due to the insufficient processing power of the microcomputer. Thus, in order to implement this first control method, an expensive microcomputer with high processing power must be used. Even if this first control method is implemented using an expensive microcomputer with high processing power, there is a problem that the large amount of calculation required results in high power consumption.

[0014] As a second control method, for example, Patent Document 2 discloses a control method in which the voltage waveform of each phase of a three-phase AC voltage supplied to a motor is intentionally distorted from an ideal sine wave so that a specific phase period does not occur.

[0015] However, in this second control method, the voltage waveform of each phase of the three-phase AC voltage supplied to the motor is distorted from an ideal sine wave, which causes the problem of louder rotation noise from the rotating motor.

[0016] Therefore, the inventors conducted repeated experiments and studies in order to realize a motor control method for controlling a motor in cases where a specific phase period may exist in a motor control device that employs a single-shunt current detection method, which can be realized using an inexpensive microcomputer with low processing power, and which does not intentionally distort the voltage waveform of each phase of the three-phase AC voltage supplied to the motor from an ideal sine wave.

[0017] In this regard, the inventors conducted repeated experiments and studies, focusing particularly on the fact that in a motor that rotates at a constant speed for a long period of time and only accelerates and decelerates slowly (hereinafter, this motor will also be referred to as a "specific type motor." For example, this includes a blower fan motor that drives a blower fan that cools an on-board battery), the induced voltage residual angle, which indicates the angle with respect to the q-axis of a vector whose d-axis component is a d-axis estimated induced voltage residual indicating the residual of the induced voltage induced on the d-axis of the motor and whose q-axis component is a q-axis estimated induced voltage residual indicating the residual of the induced voltage induced on the q-axis of the motor, always fluctuates around a value close to zero.

[0018] As a result, the inventors have found that in a motor control device that employs a single-shunt current detection method, if the motor to be controlled is a specific type motor, even if the induced voltage residual angle is replaced with a fixed value of zero during a specific phase period and the current value of each phase during the specific phase period is calculated, (1) no practical problems will arise in controlling the specific type motor, and (2) the amount of calculation required to calculate the current value of each phase during the specific phase period will not increase compared to the amount of calculation during other periods.

[0019] Based on these findings, the inventors conducted further experiments and studies and came up with the motor control device according to the present disclosure described below.

[0020] A motor control device according to one aspect of the present disclosure includes an inverter circuit that outputs a three-phase AC voltage to a motor by switching a power supply voltage of a DC power supply; a current calculation unit that calculates a d-axis current flowing in a d-axis of the motor and a q-axis current flowing in a q-axis of the motor based on a current flowing between the DC power supply and the inverter circuit; a rotational speed estimation unit that calculates an estimated rotational speed of the motor based on the d-axis current and the q-axis current; a target rotational speed calculation unit that calculates a target rotational speed of the motor based on an operation command of the motor; and a voltage command calculation unit that calculates a duty command to control the switching performed by the inverter circuit based on a difference between the target rotational speed and the estimated rotational speed. The rotation speed estimation unit includes an induced voltage calculation unit that calculates, based on the d-axis current and the q-axis current, an induced voltage residual angle that indicates an angle with respect to the q-axis of a vector having a d-axis estimated induced voltage residual that indicates a residual of an induced voltage induced on the d-axis of the motor as its d-axis component and a q-axis estimated induced voltage residual that indicates a residual of an induced voltage induced on the q-axis of the motor; a first switching unit that switches between outputting zero and the induced voltage residual angle during a first period in which the three-phase AC voltage is within a predetermined phase range and during a second period other than the first period; and a first proportional integral calculation unit that performs proportional integral calculation using the signal output from the first switching unit as an input signal to calculate the estimated rotation speed.

[0021] During the first period, the motor control device calculates a duty command (sometimes referred to as a PWM (Pulse Width Modulation) command) that controls inverter switching without using a DC bus current, which is a current that flows between a DC power supply and an inverter circuit.

[0022] Therefore, according to the motor control device, by setting the first period as the specific phase period, it is possible to calculate a duty command for controlling the switching of the inverter even during the specific phase period.

[0023] The motor control device is a motor control device that employs a single shunt current detection method.

[0024] Therefore, the motor control device described above is a motor control device that employs a one-shunt current detection method and is capable of controlling a motor even when a specific phase period exists.

[0025] The above motor control device can be realized using an inexpensive microcomputer with low processing power, and does not intentionally distort the voltage waveform of each phase of the three-phase AC voltage supplied to the motor from an ideal sine wave.

[0026] The induced voltage calculation unit includes a d-axis induced voltage residual calculation unit that calculates the d-axis estimated induced voltage residual based on the d-axis current and the q-axis current, a q-axis induced voltage residual calculation unit that calculates the q-axis estimated induced voltage residual based on the d-axis current and the q-axis current, and an induced voltage residual angle calculation unit that calculates the induced voltage residual angle based on the d-axis estimated induced voltage residual and the q-axis estimated induced voltage residual, and the d-axis induced voltage residual calculation unit switches between zero and a d-axis estimated current residual indicating the residual of the d-axis current during the first period and the second period, respectively. and a second proportional integral calculation unit that performs a proportional integral calculation using the signal output from the second switching unit as an input signal to calculate the d-axis estimated induced voltage residual, and the q-axis induced voltage residual calculation unit may have a third switching unit that switches between zero and a q-axis estimated current residual indicating a residual of the q-axis current, and outputs the resultant signal, during the first period and the second period, respectively, and a third proportional integral calculation unit that performs a proportional integral calculation using the signal output from the third switching unit as an input signal to calculate the q-axis estimated induced voltage residual.

[0027] The predetermined phase may be a phase in which a voltage difference between any two phases of the three-phase AC voltage is equal to or less than a predetermined value.

[0028] A specific example of a motor control device according to one aspect of the present disclosure will be described below with reference to the drawings. The embodiment shown here illustrates one specific example of the present disclosure. Therefore, the numerical values, shapes, components, the arrangement and connection of the components, steps (processes), and the order of steps shown in the following embodiment are merely examples and are not intended to limit the present disclosure. Each figure is a schematic diagram and is not necessarily an exact illustration. In each figure, the same reference numerals are used for components that are substantially the same as those in other figures, and duplicate explanations are omitted or simplified.

[0029] (Embodiment) <Configuration> FIG. 1 is a block diagram showing the configuration of a motor control system 1 according to an embodiment.

[0030] As shown in FIG. 1 , the motor control system 1 includes a motor control device 100 , a motor 200 , a DC power supply 300 , a shunt resistor 400 , and a current sensor 500 .

[0031] The motor 200 is a three-phase AC motor. The three-phase AC voltage that is the power source of the motor 200 is supplied from the motor control device 100.

[0032] Motor 200 is a brushless blower fan motor that drives blower fan 210 that cools the vehicle battery. That is, motor 200 is a brushless motor that rotates at a constant speed for a long period of time and accelerates and decelerates only slowly.

[0033] Motor control device 100 receives an operation command transmitted from a higher-level device (not shown) that instructs the operation of motor 200, and controls motor 200 so that motor 200 operates in accordance with the received operation command. More specifically, motor control device 100 generates a three-phase AC voltage to be supplied to motor 200 so that motor 200 operates in accordance with the operation command, and outputs the generated three-phase AC voltage to motor 200.

[0034] The motor control device 100 compares the rotational speed of the motor 200 indicated in the operation command (hereinafter also referred to as the "target rotational speed") with the estimated actual rotational speed of the motor 200 (hereinafter also referred to as the "estimated rotational speed"), and performs feedback control so that the actual rotational speed matches the target rotational speed. In this case, the motor control device 100 calculates the actual rotational speed based on the current flowing in each phase of the three-phase AC.

[0035] As an example that does not necessarily need to be limited, the motor control device 100 operates the feedback loop in the above feedback control at 16 KHz.

[0036] As an example, but not necessarily limited to, motor control device 100 outputs a three-phase AC voltage of 500 Hz, which is a frequency sufficiently lower than 16 KHz.

[0037] DC power supply 300 is a power supply source for the three-phase AC voltage output by motor control device 100. As will be described later, motor control device 100 generates the three-phase AC voltage to be output to motor 200 by an inverter circuit 10 (described later), which is a component of motor control device 100, switching the power supply voltage of DC power supply 300.

[0038] The shunt resistor 400 is a resistor disposed in the current path of the DC bus current that flows between the negative terminal of the DC power supply 300 and the inverter circuit 10 (described later).

[0039] The current sensor 500 is a sensor that detects a DC bus current flowing between the DC power supply 300 and an inverter circuit 10 (described later). More specifically, the current sensor 500 detects the DC bus current by detecting the voltage across a shunt resistor.

[0040] As shown in FIG. 1 , the motor control device 100 includes an inverter circuit 10 , a current calculation unit 20 , a rotational speed estimation unit 30 , a target rotational speed calculation unit 40 , and a voltage command calculation unit 50 .

[0041] As an example of the motor control device 100, which is not necessarily limited to this example, among the components of the motor control device 100, the inverter circuit 10 is realized by dedicated hardware, and the current calculation unit 20, the rotational speed estimation unit 30, the target rotational speed calculation unit 40, and the voltage command calculation unit 50 are realized by a microcomputer executing a program stored in memory.

[0042] The inverter circuit 10 generates a three-phase AC voltage consisting of a U phase, a V phase, and a W phase by switching the power supply voltage of the DC power supply 300. The inverter circuit 10 outputs the generated three-phase AC voltage to the motor 200.

[0043] The inverter circuit 10 performs the above switching based on a duty command output from a voltage command calculation unit 50 (described later).

[0044] The duty command is composed of three PWM signals (Pulse Width Modulation signals): an Upwm signal, a Vpwm signal, and a Wpwm signal. The Upwm signal is a PWM signal that controls the conduction state of a switching element (hereinafter also referred to as a "U-phase switching element"; here, this corresponds to a pair of high-side and low-side transistors) connected to a wiring that supplies a U-phase voltage to the motor 200. The Vpwm signal is a PWM signal that controls the conduction state of a switching element (hereinafter also referred to as a "V-phase switching element"; here, this corresponds to a pair of high-side and low-side transistors) connected to a wiring that supplies a V-phase voltage to the motor. The Wpwm signal is a PWM signal that controls the conduction state of a switching element (hereinafter also referred to as a "W-phase switching element"; here, this corresponds to a pair of high-side and low-side transistors) connected to a wiring that supplies a W-phase voltage to the motor.

[0045] FIG. 2 is a schematic diagram showing a typical voltage waveform of a three-phase AC voltage output by the inverter circuit 10 according to the embodiment.

[0046] As shown in FIG. 2, the inverter circuit 10 outputs a U-phase AC voltage Uo, a V-phase AC voltage Vo, and a W-phase AC voltage Wo, which are three sinusoidal AC voltages that are 120 degrees out of phase with each other and have the same amplitude.

[0047] 2, the relationship between the voltage levels of the U-phase voltage, V-phase voltage, and W-phase voltage of the three-phase AC voltage changes over time. This relationship is determined by the conduction patterns of the U-phase switching element, the V-phase switching element, and the W-phase switching element, which are determined by the duty command.

[0048] FIG. 3 is a schematic diagram showing the relationship between the conduction pattern of each switching element and the DC bus current according to the embodiment.

[0049] As shown in FIG. 3 , the current conduction patterns include: (1) a conduction pattern “LLL” in which the low-side element of the U-phase switching element is conductive, the low-side element of the V-phase switching element is conductive, and the low-side element of the W-phase switching element is conductive; (2) a conduction pattern “LLH” in which the low-side element of the U-phase switching element is conductive, the low-side element of the V-phase switching element is conductive, and the high-side element of the W-phase switching element is conductive; (3) a conduction pattern “LHL” in which the low-side element of the U-phase switching element is conductive, the high-side element of the V-phase switching element is conductive, and the low-side element of the W-phase switching element is conductive; and (4) a conduction pattern “LHH” in which the low-side element of the U-phase switching element is conductive, the high-side element of the V-phase switching element is conductive, and the high-side element of the W-phase switching element is conductive. (5) a conduction pattern "HLL" in which the high-side element of the U-phase switching element is conductive, the low-side element of the V-phase switching element is conductive, and the low-side element of the W-phase switching element is conductive; (6) a conduction pattern "HLH" in which the high-side element of the U-phase switching element is conductive, the low-side element of the V-phase switching element is conductive, and the high-side element of the W-phase switching element is conductive; (7) a conduction pattern "HHL" in which the high-side element of the U-phase switching element is conductive, the high-side element of the V-phase switching element is conductive, and the low-side element of the W-phase switching element is conductive; and (8) a conduction pattern "HHH" in which the high-side element of the U-phase switching element is conductive, the high-side element of the V-phase switching element is conductive, and the high-side element of the W-phase switching element is conductive.

[0050] As shown in FIG. 3 , (1) in the conduction pattern “LLL,” no DC bus current flows; (2) in the conduction pattern “LLH,” the DC bus current becomes a W-phase current flowing through the W-phase; (3) in the conduction pattern “LHL,” the DC bus current becomes a V-phase current flowing through the V-phase; (4) in the conduction pattern “LHH,” the DC bus current becomes a current flowing in the opposite direction to the U-phase current flowing through the U-phase; (5) in the conduction pattern “HLL,” the DC bus current becomes a U-phase current; (6) in the conduction pattern “HLH,” the DC bus current becomes a current flowing in the opposite direction to the V-phase current; (7) in the conduction pattern “HHL,” ​​the DC bus current becomes a current flowing in the opposite direction to the W-phase current; and (8) in the conduction pattern “HHH,” no DC bus current flows.

[0051] Therefore, in theory, it is possible to uniquely identify the current flowing through each phase of the three-phase AC current from the DC bus current and the conduction pattern.

[0052] However, in reality, current sensor 500 requires a certain detection time to detect the DC bus current. Therefore, if the period from one conduction pattern to the next (hereinafter also referred to as the "conduction pattern switching period") is shorter than the detection time of current sensor 500, the DC bus current during that period cannot be correctly detected. Therefore, if the conduction pattern switching period is shorter than the detection period of current sensor 500, the current flowing through each phase of the three-phase AC cannot be correctly calculated.

[0053] FIG. 4 is a schematic diagram showing an example of a state in which the current sensor 500 cannot correctly detect the DC bus current when the conduction pattern switching period is shorter than the detection time of the current sensor 500.

[0054] 4, the horizontal axis represents time, and the vertical axis represents the voltage of each PWM signal and the current of the DC bus current.

[0055] As shown in Figure 4, if the period from when the voltage of one of the three PWM signals that make up the duty command changes to when the voltage of the other PWM signal changes is shorter than the detection time Ta of the current sensor 500, that is, the period from time T2 to time T3 and the period from time T4 to time T5, the DC bus current cannot be detected correctly during that period.

[0056] The period (T3-T2 or T5-T4) from when the voltage of one of the two PWM signals out of the three PWM signals constituting the duty command changes until the other PWM signal changes is shorter than the detection time Ta of the current sensor 500, and corresponds to a period near the timing when the voltages of any two phases of the three-phase AC voltage intersect. That is, the period from when the voltage of one of the two PWM signals out of the three PWM signals constituting the duty command changes until the other PWM signal changes corresponds to the period surrounded by circles in the waveform of the three-phase AC voltage output by the inverter circuit 10 shown in FIG. 2 near the timing when the voltages of any two phases of the three-phase AC voltage intersect, that is, the period of the phase (hereinafter also referred to as the "predetermined phase") when the voltage difference between any two phases of the three-phase AC voltage is equal to or less than a predetermined value.

[0057] Returning to FIG. 1, the description of motor control device 100 will continue.

[0058] The current calculation unit 20 calculates a d-axis current di flowing through the d-axis of the motor 200 and a q-axis current qi flowing through the q-axis of the motor 200 based on the DC bus current detected by the current sensor 500 .

[0059] As shown in FIG. 1 , the current calculation unit 20 includes a three-phase current calculation unit 21 and a d / q axis conversion unit 22 .

[0060] The three-phase current calculation unit 21 calculates a U-phase current Ui, a V-phase current Vi, and a W-phase current Wi based on the DC bus current detected by the current sensor 500 .

[0061] However, as described above, only during the period in which the three-phase AC voltage is within a predetermined phase range (hereinafter also referred to as the "first period"), the DC bus current detected by the current sensor 500 does not necessarily have a correct value. Therefore, only during this first period, the U-phase current Ui, V-phase current Vi, and W-phase current Wi calculated by the three-phase current calculation unit 21 do not necessarily have correct values.

[0062] The d / q axis converter 22 converts the U-phase current Ui, V-phase current Vi, and W-phase current Wi calculated by the three-phase current calculator 21 into a d-axis current di and a q-axis current qi.

[0063] However, during the first period only, the d-axis current di and the q-axis current qi converted by the d / q-axis converter 22 do not necessarily have correct values, similar to the U-phase current Ui, the V-phase current Vi, and the W-phase current Wi.

[0064] The rotational speed estimation unit 30 calculates an estimated rotational speed ω of the motor 200 based on the d-axis current di and the q-axis current qi calculated by the current calculation unit 20, and a d-axis applied voltage command dv_req (described later) to be applied to the d-axis of the motor 200 and a q-axis applied voltage command qv_req (described later) to be applied to the q-axis of the motor 200, which are calculated by a voltage command calculation unit 50 (described later).

[0065] As shown in FIG. 1 , the rotation speed estimation unit 30 includes an induced voltage calculation unit 31 , a first switching unit 32 , and a first proportional-plus-integral calculation unit 33 .

[0066] The induced voltage calculation unit 31 calculates an induced voltage residual angle θerror indicating the angle with respect to the q-axis of a vector having a d-axis estimated induced voltage residual ed indicating the residual of the induced voltage induced on the d-axis of the motor 200 as its d-axis component and a q-axis estimated induced voltage residual eq indicating the residual of the induced voltage induced on the q-axis of the motor 200 as its q-axis component, based on the d-axis current di and the q-axis current qi calculated by the current calculation unit 20, the d-axis applied voltage command dv_req (described later) and the q-axis applied voltage command qv_req (described later) calculated by the voltage command calculation unit 50 (described later), and the estimated rotational speed ω calculated by the rotational speed estimation unit 30.

[0067] Here, the value of the induced voltage residual angle θerror is specifically expressed by the following equation.

[0068]

[0069] However, only during the first period, the induced voltage residual angle θerror calculated by the induced voltage calculation unit 31 is not necessarily a correct value, similar to the d-axis current di and the q-axis current qi.

[0070] The first switching unit 32 switches between outputting zero and the induced voltage residual angle θerror calculated by the induced voltage calculation unit 31 during a first period and a second period other than the first period.

[0071] Here, "zero" refers to a dummy value that does not substantially affect the control of the motor 200.

[0072] As described above, motor 200 is a brushless motor that rotates at a constant speed for a long period of time and accelerates and decelerates only slowly. For this reason, the value of induced voltage residual angle θerror in motor 200 always fluctuates near zero.

[0073] Therefore, even if the value of the induced voltage residual angle θerror, which is not necessarily a correct value in the first period, is switched to zero only in the first period, there is substantially no effect on the control of the motor 200.

[0074] The first proportional integral calculation unit 33 performs proportional integral calculation using the signal output from the first switching unit 32 as an input signal, and calculates an estimated rotational speed ω of the motor 200 and an estimated rotational position θ of the motor 200.

[0075] FIG. 5 is a block diagram showing the configuration of the rotation speed estimating unit 30 according to the embodiment.

[0076] As shown in FIG. 5 , the induced voltage calculation unit 31 includes a d-axis induced voltage residual calculation unit 301 , a q-axis induced voltage residual calculation unit 302 , and an induced voltage residual angle calculation unit 303 .

[0077] The d-axis induced voltage residual calculation unit 301 calculates a d-axis estimated induced voltage residual ed based on the d-axis current di and the q-axis current qi calculated by the current calculation unit 20, a d-axis applied voltage command dv_req (described later) calculated by the voltage command calculation unit 50 (described later), and the estimated rotational speed ω calculated by the rotational speed estimation unit 30.

[0078] The q-axis induced voltage residual calculation unit 302 calculates a q-axis estimated induced voltage residual eq based on the d-axis current di and the q-axis current qi calculated by the current calculation unit 20, a q-axis applied voltage command qv_req (described later) calculated by a voltage command calculation unit 50 (described later), and the estimated rotational speed ω calculated by the rotational speed estimation unit 30.

[0079] The induced voltage residual angle calculation unit 303 calculates an induced voltage residual angle θerror based on the d-axis estimated induced voltage residual ed calculated by the d-axis induced voltage residual calculation unit 301 and the q-axis estimated induced voltage residual eq calculated by the q-axis induced voltage residual calculation unit 302.

[0080] As shown in FIG. 5 , the d-axis induced voltage residual calculation unit 301 includes a second switching unit 312 and a second proportional-plus-integral calculation unit 322 .

[0081] The second switching unit 312 switches between outputting zero and a d-axis estimated current residual indicating the residual of the d-axis current di during a first period and outputting a second period other than the first period.

[0082] Here, "zero" refers to a dummy value that does not substantially affect the control of the motor 200.

[0083] As described above, motor 200 is a brushless motor that rotates at a constant speed for a long period of time and accelerates and decelerates only slowly. For this reason, the d-axis estimated current residual of motor 200 always fluctuates near zero.

[0084] Therefore, even if the value of the d-axis estimated current residual, which is not necessarily a correct value during the first period, is switched to zero only during the first period, there is substantially no effect on the control of the motor 200.

[0085] The second proportional integral calculation unit 322 performs proportional integral calculation using the signal output from the second switching unit 312 as an input signal, and calculates the d-axis estimated induced voltage residual ed.

[0086] As shown in FIG. 5 , the q-axis induced voltage residual calculation unit 302 includes a third switching unit 313 and a third proportional-plus-integral calculation unit 323 .

[0087] The third switching unit 313 switches between outputting zero and a q-axis estimated current residual indicating the residual of the q-axis current qi during a first period and a second period other than the first period.

[0088] Here, "zero" refers to a dummy value that does not substantially affect the control of the motor 200.

[0089] As described above, motor 200 is a brushless motor that rotates at a constant speed for a long period of time and accelerates and decelerates only slowly. For this reason, the q-axis estimated current residual of motor 200 always fluctuates near zero.

[0090] Therefore, even if the value of the q-axis estimated current residual, which is not necessarily a correct value in the first period, is switched to zero only in the first period, there is substantially no effect on the control of the motor 200.

[0091] The third proportional integral calculation unit 323 performs proportional integral calculation using the signal output from the third switching unit 313 as an input signal, and calculates the q-axis estimated induced voltage residual eq.

[0092] Returning to FIG. 1, the description of motor control device 100 will continue.

[0093] The target rotation speed calculation unit 40 acquires an operation command for the motor 200 output from an external device, and calculates the target rotation speed ω of the motor 200 based on the acquired operation command. ＊ Calculate.

[0094] As an example, but not necessarily limited to, the operation command is a PWM signal with a fixed cycle of 500 Hz, the duty ratio of which indicates the target rotation speed.

[0095] As shown in FIG. 1, the target rotation speed calculation unit 40 includes a PWM signal detection unit 41 , a duty ratio detection unit 42 , and a target rotation speed conversion unit 43 .

[0096] The PWM signal detection unit 41 detects a PWM signal that is an operation command for the motor 200 and is output from an external device, and acquires the detected PWM signal.

[0097] The duty ratio detector 42 detects the duty ratio of the PWM signal obtained by the PWM signal detector 41 .

[0098] The target rotation speed conversion unit 43 converts the target rotation speed ω indicated by the operation command based on the duty ratio detected by the duty ratio detection unit 42. ＊ Calculate.

[0099] The target rotation speed conversion unit 43 stores, for example, a table showing the correspondence relationship between the duty ratio and the target rotation speed, and converts the target rotation speed ω ＊ may be calculated.

[0100] The voltage command calculation unit 50 calculates the target rotation speed ω calculated by the target rotation speed calculation unit 40. ＊ and the estimated rotation speed ω calculated by the rotation speed estimator 30, a duty command is calculated.

[0101] As shown in FIG. 1, the voltage command calculation unit 50 includes a speed PI control unit 51, a current PI control unit 52, an inverse d / q axis conversion unit 53, and a duty ratio calculation unit .

[0102] The speed PI control unit 51 calculates the target rotation speed ω calculated by the target rotation speed calculation unit 40. ＊ and the estimated rotational speed ω calculated by the rotational speed estimator 30, the speed PI controller 51 calculates a d-axis command current di_req and a q-axis command current qi_req for proportional-plus-integral control of the rotational speed of the motor 200 so as to bring this difference closer to zero. The speed PI controller 51 normally calculates the q-axis command current qi_req as a fixed value.

[0103] Based on the d-axis command current di_req and q-axis command current qi_req calculated by the speed PI control unit 51 and the d-axis current di and q-axis current qi converted by the d / q-axis conversion unit 22, the current PI control unit 52 calculates a d-axis applied voltage command dv_req and a q-axis applied voltage command qv_req for proportional-plus-integral control of the current flowing through the motor 200 so that the difference between the d-axis command current di_req and the d-axis current di approaches zero and the difference between the q-axis command current qi_req and the q-axis current qi approaches zero.

[0104] Based on the d-axis application voltage command dv_req and the q-axis application voltage command qv_req calculated by the current PI control unit 52 and the estimated rotational position θ calculated by the rotational speed estimator 30, the inverse d / q-axis conversion unit 53 converts the d-axis application voltage command dv_req and the q-axis application voltage command qv_req into a U-phase application voltage command Uv_req, a V-phase application voltage command Vv_req, and a W-phase application voltage command Wv_req.

[0105] The duty ratio calculation unit 54 converts the U-phase applied voltage command Uv_req, V-phase applied voltage command Vv_req, and W-phase applied voltage command Wv_req, which have been converted by the inverse d / q axis conversion unit 53, into duty ratios, calculates a duty command in PWM format, and outputs the calculated duty command in PWM signal format to the inverter circuit 10.

[0106] <Considerations> When calculating the estimated rotation speed ω of the motor 200, the motor control device 100 configured as described above calculates the estimated rotation speed ω of the motor 200 by switching between zero and the induced voltage residual angle θerror during a first period in which the DC bus current detected by the current sensor 500 is not necessarily a correct value, i.e., during a first period in which the calculated value of the induced voltage residual angle θerror is not necessarily a correct value, and during a second period other than the first period.

[0107] On the other hand, as described above, motor 200 is a brushless motor that rotates at a constant speed for a long period of time and only accelerates and decelerates slowly. For this reason, the value of induced voltage residual angle θerror in motor 200 always fluctuates near zero.

[0108] Therefore, even if the value of the induced voltage residual angle θerror, which is not necessarily a correct value in the first period, is switched to zero only in the first period, there is substantially no effect on the control of the motor 200.

[0109] In this way, the motor control device 100 having the above configuration is a motor control device that employs a one-shunt current detection method and is capable of controlling the motor even when the first period exists.

[0110] Unlike the motor control device described in Patent Document 1, the motor control device 100 configured as described above does not calculate the current values ​​of each phase of the three-phase AC during the first period based on the DC bus current detected immediately before the first period.

[0111] Therefore, in the motor control device 100 configured as described above, the amount of calculation required to calculate the current values ​​of each phase of the three-phase AC in the first period does not increase compared to the amount of calculation required in other periods.

[0112] Therefore, the motor control device 100 having the above configuration can be realized by using an inexpensive microcomputer with low processing power, without using the expensive microcomputer with high processing power that is required for the motor control device described in Patent Document 1.

[0113] With the motor control device 100 configured as described above, the amount of calculation required to calculate the current values ​​of each phase of the three-phase AC during the first period does not increase compared to the amount of calculation required during other periods, thereby reducing power consumption during control of the motor 200 compared to the motor control device described in Patent Document 1.

[0114] Unlike the motor control device described in Patent Document 2, the motor control device 100 configured as described above does not intentionally distort the voltage waveform of each phase of the three-phase AC voltage supplied to the motor 200 from an ideal sine wave.

[0115] Therefore, with the motor control device 100 configured as described above, no rotation noise of the motor 200 occurs, which would be caused by intentionally distorting the voltage waveform of each phase of the three-phase AC voltage supplied to the motor 200 from an ideal sine wave.

[0116] As described above, the motor control device 100 of this embodiment includes the inverter circuit 10 that outputs a three-phase AC voltage to the motor 200 by switching the power supply voltage of the DC power supply 300, a current calculation unit 20 that calculates a d-axis current flowing in the d-axis of the motor 200 and a q-axis current flowing in the q-axis of the motor based on the current flowing between the DC power supply 300 and the inverter circuit 10, a rotational speed estimation unit 30 that calculates an estimated rotational speed of the motor 200 based on the d-axis current and the q-axis current, a target rotational speed calculation unit 40 that calculates a target rotational speed of the motor 200 based on an operation command for the motor 200, and a voltage command calculation unit 50 that calculates a duty command to control the switching performed by the inverter circuit 10 based on the difference between the target rotational speed and the estimated rotational speed. The rotation speed estimation unit 30 includes an induced voltage calculation unit 31 that calculates, based on the d-axis current and the q-axis current, an induced voltage residual angle that indicates the angle with respect to the q-axis of a vector having a d-axis estimated induced voltage residual that indicates the residual of the induced voltage induced on the d-axis of the motor 200 as its d-axis component and a q-axis estimated induced voltage residual that indicates the residual of the induced voltage induced on the q-axis of the motor 200 as its q-axis component; a first switching unit 32 that switches between outputting zero and the induced voltage residual angle during a first period in which the three-phase AC voltage is within a predetermined phase range and during a second period other than the first period; and a first proportional integral calculation unit 33 that performs proportional integral calculation using the signal output from the first switching unit 32 as an input signal to calculate an estimated rotation speed.

[0117] As a result, motor control device 100 is a motor control device that employs a one-shunt current detection method and can control a motor even when a specific phase period exists.

[0118] The induced voltage calculation unit 31 includes a d-axis induced voltage residual calculation unit 301 that calculates a d-axis estimated induced voltage residual based on the d-axis current and the q-axis current, a q-axis induced voltage residual calculation unit 302 that calculates a q-axis estimated induced voltage residual based on the d-axis current and the q-axis current, and a induced voltage residual angle calculation unit 303 that calculates a induced voltage residual angle based on the d-axis estimated induced voltage residual and the q-axis estimated induced voltage residual. The d-axis induced voltage residual calculation unit 301 has a second switching function that switches between outputting zero and a d-axis estimated current residual indicating the residual of the d-axis current during the first period and the second period. It is preferable that the q-axis back electromotive force residual calculation unit 302 has a third switching unit 313 which switches between and outputs zero and a q-axis estimated current residual indicating the residual of the q-axis current, between the first period and the second period, and a third proportional integral calculation unit 323 which performs a proportional integral calculation using the signal output from the third switching unit 313 as an input signal, and calculates the q-axis estimated back electromotive force residual.

[0119] Furthermore, the predetermined phase is preferably a phase in which the voltage difference between any two phases of the three-phase AC voltage is equal to or less than a predetermined value.

[0120] (Supplementary Note) As described above, the present disclosure has been described based on the embodiments as examples of the technology disclosed in the present application. However, the present disclosure is not limited to these embodiments. As long as they do not deviate from the spirit of the present disclosure, various modifications conceivable by those skilled in the art to the present embodiments, and forms constructed by combining components in different embodiments or modifications, are also included within the scope of one or more aspects of the present disclosure.

[0121] The present disclosure is widely applicable to motor control devices that control motors.

[0122] REFERENCE SIGNS LIST 1 Motor control system 10 Inverter circuit 20 Current calculation unit 21 Three-phase current calculation unit 22 d / q axis conversion unit 30 Rotational speed estimation unit 31 Induced voltage calculation unit 32 First switching unit 33 First proportional integral calculation unit 40 Target rotational speed calculation unit 41 PWM signal detection unit 42 Duty ratio detection unit 43 Target rotational speed conversion unit 50 Voltage command calculation unit 51 Speed ​​PI control unit 52 Current PI control unit 53 Inverse d / q axis conversion unit 54 Duty ratio calculation unit 100 Motor control device 200 Motor 210 Blower fan 300 DC power supply 301 d-axis induced voltage residual calculation unit 302 q-axis induced voltage residual calculation unit 303 Induced voltage residual angle calculation unit 312 Second switching unit 313 Third switching unit 322 Second proportional integral calculation unit 323 Third proportional integral calculation unit 400 Shunt resistor 500 Current sensor

Claims

1. A motor drive system comprising: an inverter circuit which outputs a three-phase AC voltage to a motor by switching a power supply voltage of a DC power supply; a current calculation unit which calculates a d-axis current flowing in a d-axis of the motor and a q-axis current flowing in a q-axis of the motor based on a current flowing between the DC power supply and the inverter circuit; a rotational speed estimation unit which calculates an estimated rotational speed of the motor based on the d-axis current and the q-axis current; a target rotational speed calculation unit which calculates a target rotational speed of the motor based on an operation command of the motor; and a voltage command calculation unit which calculates a duty command for controlling the switching performed by the inverter circuit based on a difference between the target rotational speed and the estimated rotational speed, wherein the rotational speed estimation unit comprises: an induced voltage calculation unit which calculates an induced voltage residual angle indicating the angle with respect to the q-axis of a vector having a d-axis estimated induced voltage residual indicating the residual of an induced voltage induced on the d-axis of the motor as a d-axis component and a q-axis estimated induced voltage residual indicating the residual of an induced voltage induced on the q-axis of the motor as a q-axis component based on the d-axis current and the q-axis current; a first switching unit that switches between zero and the induced voltage residual angle and outputs the angle during a first period in which the three-phase AC voltage is within a predetermined phase range and during a second period other than the first period; and a first proportional integral calculation unit that performs a proportional integral calculation using a signal output from the first switching unit as an input signal to calculate the estimated rotation speed.

2. The induced voltage calculation unit includes: a d-axis induced voltage residual calculation unit that calculates the d-axis estimated induced voltage residual based on the d-axis current and the q-axis current; a q-axis induced voltage residual calculation unit that calculates the q-axis estimated induced voltage residual based on the d-axis current and the q-axis current; and an induced voltage residual angle calculation unit that calculates the induced voltage residual angle based on the d-axis estimated induced voltage residual and the q-axis estimated induced voltage residual. The d-axis induced voltage residual calculation unit includes: a second switching unit that switches between zero and a d-axis estimated current residual indicating the residual of the d-axis current and outputs the switched signal during the first period and the second period; and a second proportional integral calculation unit that performs proportional integral calculation using the signal output from the second switching unit as an input signal to calculate the d-axis estimated induced voltage residual. The q-axis induced voltage residual calculation unit includes:

2. The motor control device according to claim 1, further comprising: a third switching unit that switches between zero and a q-axis estimated current residual indicating a residual of the q-axis current during the first period and the second period, and outputs the switched value; and a third proportional and integral calculation unit that performs a proportional and integral calculation using the signal output from the third switching unit as an input signal to calculate the q-axis estimated induced voltage residual.

3. A motor control device according to claim 1 or 2, wherein the predetermined phase is a phase in which a voltage difference between any two phases of the three-phase AC voltage is equal to or smaller than a predetermined value.