Control device

Abstract

A control device according to the present invention generates, if a position cannot be estimated when starting a motor (M) or during sensor-less control or the like, an upper arm short-circuit drive signal that simultaneously turns ON upper arm switching elements (SW1, SW3, SW5) of three phases and simultaneously turns OFF lower arm switching elements (SW2, SW4, SW6) of three phases of an inverter (2), or a lower arm short-circuit drive signal that simultaneously turns OFF the upper arm switching elements (SW1, SW3, SW5) and simultaneously turns ON the lower arm switching elements (SW2, SW4, SW6).

Description

Control device

[0001] The present invention relates to a motor control device.

[0002] There is a motor control device that estimates the position (electrical angle) of the rotor of the motor using an extended induced voltage estimated based on a voltage command value, and controls the operation of each switching element of the inverter using a voltage command value generated based on that position.

[0003] However, variations in the on / off timing of each switching element due to differences in individual switching elements and temperature characteristics result in an error between the voltage command value and the true value. Furthermore, the magnitude of this error is constant regardless of the magnitude of the rotor angular velocity. Therefore, when the rotor angular velocity is relatively low (low-speed range), the extended electromotive force becomes smaller, resulting in a relatively large error. This deteriorates the signal-to-noise ratio of the extended electromotive force, and reduces the accuracy of rotor position estimation.

[0004] Therefore, when starting a motor, if the angular velocity of the motor's rotor is relatively low, the accuracy of estimating the rotor's position may decrease, causing the motor to lose synchronization and making it impossible to restart the motor.

[0005] Japanese Patent Application Laid-Open No. 2022-85227

[0006] An object according to one aspect of the present invention is to prevent a motor from going out of step when it is started.

[0007] A control device according to one aspect of the present invention is a control device that generates a drive signal for controlling an inverter that drives a motor, and includes a current value converter that converts a current flowing through the motor into a γ-axis current value and a δ-axis current value; a γ-δ current command value output unit that outputs a γ-axis current command value and a δ-axis current command value; a γ-δ voltage command value calculator that calculates a γ-axis voltage command value based on the γ-axis current value and the γ-axis current command value and calculates a δ-axis voltage command value based on the δ-axis current value and the δ-axis current command value; a drive signal converter that converts the γ-axis voltage command value and the δ-axis voltage command value into the drive signal; an estimator that calculates an estimated position that is an estimated value of the position of the motor; and a third estimator that determines whether or not the position of the motor can be estimated by the estimator. and a first determination unit, wherein when starting the motor or when the first determination unit determines that position estimation is not possible, an upper arm short-circuit drive signal is generated as the drive signal for simultaneously turning on upper arm switching elements of the three phases of the inverter and simultaneously turning off lower arm switching elements of the three phases of the inverter, or a lower arm short-circuit drive signal is generated as the drive signal for simultaneously turning off upper arm switching elements of the three phases of the inverter and simultaneously turning on lower arm switching elements of the three phases of the inverter, and when the upper arm short-circuit drive signal or the lower arm short-circuit drive signal is generated, the estimation unit calculates an estimated position that is an estimate of the position of the motor based on the current flowing through the motor.

[0008] The control device may have a second determination unit, and the second determination unit may be configured to determine whether or not the position of the motor can be estimated based on the current flowing through the motor due to the upper arm short-circuit drive signal or the lower arm short-circuit drive signal.

[0009] In this way, when starting the motor or when it is determined that position estimation is not possible, the upper arm short-circuit drive signal or the lower arm short-circuit drive signal is generated, which prevents errors from occurring between the voltage command value and the true value due to variations in the on / off states of each switching element. This makes it possible to prevent a decrease in the accuracy of rotor position estimation and suppress a loss of synchronism, even when the angular velocity of the motor is relatively low.

[0010] Furthermore, the control device may be configured to generate the drive signal for supplying a three-phase AC current to the motor when the second determination unit determines that the position of the motor can be estimated.

[0011] Furthermore, the control device may be configured to start a timer and generate the drive signal such that the current flowing through the motor becomes a constant value when the second judgment unit determines that the current value flowing through the motor is smaller than a threshold current and that the position of the motor can be estimated, and to generate the upper arm short-circuit drive signal or the lower arm short-circuit drive signal after a first predetermined time has elapsed.

[0012] The estimation unit may be configured to calculate an estimated extension electromotive force, which is an estimate of an extension electromotive force generated in the motor, based on the γ-axis current value, the δ-axis current value, and the γ-axis voltage command value and the δ-axis voltage command value, and to calculate an estimated position, which is an estimate of a position of the motor, based on the estimated extension electromotive force, and the first determination unit may be configured to determine that position estimation is not possible when the estimated extension electromotive force is smaller than a threshold value, and to generate the upper arm short-circuit drive signal or the lower arm short-circuit drive signal.

[0013] According to the present invention, it is possible to prevent a motor from going out of step when starting the motor.

[0014] It is a diagram showing an example of a control system in an embodiment. It is a flowchart showing the operation of a calculation unit when restarting a motor. It is a diagram showing an example of an actual angular velocity and an angular velocity command value when restarting a motor.

[0015] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0016] FIG. 1 is a diagram illustrating an example of a control system according to an embodiment.

[0017] The control system 1 shown in FIG. 1 includes a motor M mounted on a vehicle such as an electric forklift or a plug-in hybrid vehicle, an inverter 2 that drives the motor M, and a control device 3 that outputs a drive signal to the inverter 2.

[0018] The motor M is, for example, a surface permanent magnet synchronous motor or an interior permanent magnet synchronous motor.

[0019] The inverter 2 drives the motor M using power supplied from a power source P and includes a capacitor C, switching elements SW1 to SW6 (e.g., IGBTs (Insulated Gate Bipolar Transistors)), and current sensors Se1 to Se3. Specifically, one terminal of the capacitor C is connected to the positive terminal of the power source P and the collector terminals of the switching elements SW1, SW3, and SW5 (upper-arm switching elements), and the other terminal of the capacitor C is connected to the negative terminal of the power source P and the emitter terminals of the switching elements SW2, SW4, and SW6 (lower-arm switching elements). The junction between the emitter terminal of the switching element SW1 and the collector terminal of the switching element SW2 is connected to a U-phase input terminal of the motor M via a current sensor Se1. The junction between the emitter terminal of the switching element SW3 and the collector terminal of the switching element SW4 is connected to a V-phase input terminal of the motor M via a current sensor Se2. The connection point between the emitter terminal of the switching element SW5 and the collector terminal of the switching element SW6 is connected to the W-phase input terminal of the motor M via a current sensor Se3.

[0020] The capacitor C smoothes the voltage output from the power supply P and input to the inverter 2 .

[0021] Switching element SW1 is turned on or off based on a drive signal s1 output from the control device 3. Switching element SW2 is turned on or off based on a drive signal s2 output from the control device 3. Switching element SW3 is turned on or off based on a drive signal s3 output from the control device 3. Switching element SW4 is turned on or off based on a drive signal s4 output from the control device 3. Switching element SW5 is turned on or off based on a drive signal s5 output from the control device 3. Switching element SW6 is turned on or off based on a drive signal s6 output from the control device 3. By switching elements SW1 to SW6 on or off, respectively, the DC voltage output from power supply P is converted into three AC voltages that are 120 degrees out of phase with each other, and these AC voltages are applied to the U-phase, V-phase, and W-phase input terminals of motor M, causing the rotor of motor M to rotate.

[0022] The current sensor Se1 is configured with a Hall element, a shunt resistor, etc., and detects a U-phase current value Iu flowing through the U-phase of the motor M and outputs the detected current to the control device 3. The current sensor Se2 is configured with a Hall element, a shunt resistor, etc., and detects a V-phase current value Iv flowing through the V-phase of the motor M and outputs the detected current to the control device 3. The current sensor Se3 is configured with a Hall element, a shunt resistor, etc., and detects a W-phase current value Iw flowing through the W-phase of the motor M and outputs the detected current to the control device 3. In this embodiment, three current sensors Se1 to Se3 are provided, but a configuration in which any two of the three current sensors are provided is also possible.

[0023] The control device 3 includes a storage unit 4, a drive circuit 5, and a calculation unit 6. The control device 3 controls the inverter 2 to drive the motor M.

[0024] The storage unit 4 is configured by a RAM (Random Access Memory) or a ROM (Read Only Memory).

[0025] The drive circuit 5 is configured with an IC (Integrated Circuit) or the like, and compares the voltage value of a carrier wave (such as a triangular wave, a sawtooth wave, or an inverse sawtooth wave) with the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* output from the calculation unit 6, and outputs drive signals s1 to s6 according to the comparison results to the gate terminals of the switching elements SW1 to SW6, respectively.

[0026] For example, when the U-phase voltage command value Vu* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal s1 and a low-level drive signal s2; when the U-phase voltage command value Vu* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal s1 and a high-level drive signal s2; when the V-phase voltage command value Vv* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal s3 and a low-level drive signal s4; when the V-phase voltage command value Vv* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal s3 and a high-level drive signal s4; when the W-phase voltage command value Vw* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal s5 and a low-level drive signal s6; and when the W-phase voltage command value Vw* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal s5 and a high-level drive signal s6.

[0027] The calculation unit 6 is configured by a microcomputer or the like, and includes a current value conversion unit 7, an estimation unit 8, a subtraction unit 9, a torque command value calculation unit 10, a γ-δ current command value output unit 11, subtraction units 12 and 13, a voltage command value calculation unit 14, switches 15 and 16, a voltage command value conversion unit 17, and a determination unit 18. For example, the current value conversion unit 7, the estimation unit 8, the subtraction unit 9, the torque command value calculation unit 10, the γ-δ current command value output unit 11, the subtraction units 12 and 13, the voltage command value calculation unit 14, the switches 15 and 16, the voltage command value conversion unit 17, and the determination unit 18 are configured by the microcomputer executing a program stored in the storage unit 4.

[0028] The current value converter 7 converts the U-phase current value Iu, the V-phase current value Iv, and the W-phase current value Iw into a γ-axis current value Iγ and a δ-axis current value Iδ using the estimated rotor position θ^ output from the estimator 8. That is, the current value converter 7 converts the current flowing through the motor M into a γ-axis current value Iγ and a δ-axis current value Iδ. The current value converter 7 may have a function of receiving current values ​​of two phases out of the U-phase current value Iu, the V-phase current value Iv, and the W-phase current value Iw, and calculating a current value of the remaining phase from the input current values ​​of the two phases.

[0029] The γ-δ coordinate system is an estimated rotating coordinate system in which the axis equivalent to the d-axis of the d-q coordinate system is the γ-axis, and the axis equivalent to the q-axis is the δ-axis. The d-q coordinate system is a rotating coordinate system in which the direction of the north pole of the magnet of motor M is the d-axis, and the direction perpendicular to the d-axis is the q-axis. The estimated position θ^ is an estimated value of the position θ of the rotor of motor M.

[0030] For example, the current value converter 7 converts the U-phase current value Iu, the V-phase current value Iv, and the W-phase current value Iw into the γ-axis current value Iγ and the δ-axis current value Iδ using a conversion matrix C1 shown in the following equation 1.

[0031]

[0032] The subtractor 9 calculates the angular velocity difference Δω between the estimated angular velocity ω^ output by the estimator 8 and the angular velocity command value ω* input from the outside.

[0033] The torque command value calculation unit 10 calculates the torque command value T* using the angular velocity difference Δω output from the subtraction unit 9. For example, the torque command value calculation unit 10 refers to information (not shown) stored in the storage unit 4 that associates the angular velocity of the motor M with the torque of the motor M, and determines, as the torque command value T*, the torque corresponding to the angular velocity equivalent to the angular velocity difference Δω.

[0034] The γ-δ current command value output unit 11 outputs a γ-axis current command value Iγ* and a δ-axis current command value Iδ* using the torque command value T*. For example, the γ-δ current command value output unit 11 determines the γ-axis current command value Iγ* and the δ-axis current command value Iδ* corresponding to the torque equivalent to the torque command value T* by referring to information (not shown) stored in the storage unit 4, in which the torque of the motor M is associated with the γ-axis current command value Iγ* and the δ-axis current command value Iδ*. The γ-δ current command value output unit 11 may be configured to output the γ-axis current command value Iγ* and the δ-axis current command value Iδ* using the torque command value T* input from an external device. In such a configuration, the subtraction unit 9 and the torque command value calculation unit 10 are omitted.

[0035] The subtractor 12 calculates the specified γ-axis current difference ΔIγ between the specified γ-axis current value Iγ* output from the specified γ-δ current value output unit 11 and the specified γ-axis current value Iγ output from the current value converter 7 .

[0036] The subtractor 13 calculates the specified δ-axis current value ΔIδ, which is the difference between the specified δ-axis current value Iδ* output from the specified γ-δ current value output unit 11 and the specified δ-axis current value Iδ output from the current value converter 7 .

[0037] The voltage command value calculation unit 14 converts the differential γ-axis current command value ΔIγ output from the subtraction unit 12 and the differential δ-axis current command value ΔIδ output from the subtraction unit 13 into a γ-axis voltage command value Vγ* and a δ-axis voltage command value Vδ*. For example, the voltage command value calculation unit 14 calculates the γ-axis voltage command value Vγ* by calculating the following equation 2, and calculates the δ-axis voltage command value Vδ* by calculating the following equation 3. Here, Kp is a constant of the proportional term of the PI control, Ki is a constant of the integral term of the PI control, ω^ is the estimated angular velocity calculated by the estimator 8 in the previous control cycle, Ld is a d-axis inductance component of the motor M, Lq is a q-axis inductance component of the motor M, and KE is an induced voltage constant.

[0038] Vγ*=KpΔIγ+∫(KiΔIγ)-ω^LqIγ...Formula 2 Vδ*=KpΔIδ+∫(KiΔIδ)+ω^LdIδ+ω^KE...Formula 3

[0039] That is, the subtraction units 12, 13 and the voltage command value calculation unit 14 function as a γ-δ voltage command value calculation unit that calculates the γ-axis voltage command value Vγ* based on the γ-axis current value Iγ and the γ-axis current command value Iγ*, and calculates the δ-axis voltage command value Vδ* based on the δ-axis current value Iδ and the δ-axis current command value Iδ*.

[0040] The switch 15 is configured to be able to select whether to output a γ-axis voltage command value Vγ*″ (an upper-arm short-circuit drive signal or a lower-arm short-circuit drive signal to be described later) for performing three-phase short-circuit control to be described later as the γ-axis voltage command value Vγ*′ to the voltage command value converter 17, or to output the γ-axis voltage command value Vγ* calculated by the voltage command value calculator 14 as the γ-axis voltage command value Vγ*′ to the voltage command value converter 17. Furthermore, the switch 16 is configured to be able to select whether to output a δ-axis voltage command value Vδ*″ (an upper-arm short-circuit drive signal or a lower-arm short-circuit drive signal to be described later) for performing three-phase short-circuit control to be described later as the δ-axis voltage command value Vδ*′ to the voltage command value converter 17, or to output the δ-axis voltage command value Vδ* calculated by the voltage command value calculator 14 as the δ-axis voltage command value Vδ*′ to the voltage command value converter 17.

[0041] The voltage command value converter 17 converts the γ-axis voltage command value Vγ*' and the δ-axis voltage command value Vδ*' into a U-phase voltage command value Vu*, a V-phase voltage command value Vv*, and a W-phase voltage command value Vw*, using the estimated position θ^ output by the estimator 8. For example, the voltage command value converter 17 converts the γ-axis voltage command value Vγ*' and the δ-axis voltage command value Vδ*' into a U-phase voltage command value Vu*, a V-phase voltage command value Vv*, and a W-phase voltage command value Vw*, using a conversion matrix C2 shown in the following equation 4.

[0042]

[0043] The voltage command value converter 17 outputs the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* to the drive circuit 5. In other words, the voltage command value converter 17 and the drive circuit 5 function as a drive signal converter that converts the γ-axis voltage command value Vγ* and the δ-axis voltage command value Vδ* into drive signals and outputs them to the inverter 2.

[0044] The determination unit 18 as a first determination unit determines whether or not the position of the motor M can be estimated by the estimation unit 8. This determination is made in step S10 during normal sensorless control, similar to step S9 in the flowchart of FIG. 2 showing the operation of the calculation unit 6 when the motor M is restarted, which will be described later.

[0045] The estimation unit 8 has a function of calculating an estimated angular velocity ω^ and an estimated position θ^. As a method for calculating the estimated angular velocity ω^ and the estimated position θ^, for example, a method using an extended induced voltage can be considered.

[0046] Example of <Method Using Extended Electromotive Force> The estimator 8 calculates an estimated extended electromotive force (EEMF) e, which is an estimate of the extended electromotive force (EEMF) e generated in the motor M, based on the γ-axis current value Iγ, the δ-axis current value Iδ, the γ-axis voltage command value Vγ*', the δ-axis voltage command value Vδ*', the estimated angular velocity ω^ stored in the storage unit 4, and motor parameters that can be estimated in advance. That is, the estimator 8 calculates an estimated extended electromotive force e, which is an estimate of the extended electromotive force e generated in the motor M, based on the γ-axis current value Iγ, the δ-axis current value Iδ, the γ-axis voltage command value Vγ*', and the δ-axis voltage command value Vδ*'. Specifically, the estimator 8 calculates the estimated extended electromotive force e^ using an observer (motor model) shown in the following equation 5. The estimated extended electromotive force e^ includes the γ-axis estimated extended electromotive force eγ^ and the δ-axis estimated extended electromotive force eδ^ as vector components.

[0047]

[0048] Note that p represents the time differential operator d / dt. The winding resistance R^, d-axis inductance Ld^, and q-axis inductance Lq^ are estimated values ​​of the motor parameters of the motor M to be controlled, and are estimated in advance by measurements using the motor M. The reason that the motor parameters of the motor M are estimated values ​​rather than actual values ​​is that the motor parameters vary depending on the current flowing through the motor M and the temperature.

[0049] Next, the estimation unit 8 calculates the position error Δθ^ based on the estimated extension electromotive force e^. Specifically, the estimation unit 8 calculates the position error Δθ^ from the estimated extension electromotive force e^ using the following equation 6.

[0050]

[0051] Next, the estimator 8 calculates an estimated angular velocity ω^ based on the position error Δθ^. Specifically, the estimator 8 calculates the estimated angular velocity ω^, for example, by multiplying the position error Δθ^ by a predetermined transfer function. Then, the estimator 8 calculates the estimated position θ^ based on the estimated angular velocity ω^ and the position error Δθ^. Specifically, the estimator 8 calculates the estimated position θ^ by adding a tentative estimated position obtained by integrating the estimated angular velocity ω^ to a corrected position error obtained by multiplying the position error Δθ^ by a predetermined transfer function. Note that although the position error Δθ^ is multiplied by the predetermined transfer function, multiplication by a predetermined transfer function is not necessarily required. Thereafter, the estimator 8 stores the calculated estimated angular velocity ω^ and estimated position θ^ in the memory 4, outputs the estimated angular velocity ω^ to the subtractor 9 and the voltage command value calculator 14, and outputs the estimated position θ^ to the current value converter 7 and the voltage command value converter 17.

[0052] Here, when the control device 3 receives a request to stop the motor M from the higher-level device, it stops outputting the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* without forcibly stopping the motor M. Therefore, the motor M enters a free-running state in which it rotates by inertia. Thereafter, when the control device 3 receives a request to restart the motor M from the higher-level device, it restarts the motor M.

[0053] 2 is a flowchart showing the operation of the calculation unit 6 when restarting the motor M. Note that, in normal times other than when restarting, if the determination unit 18 determines that position estimation cannot be performed based on the extended induced voltage (Equation 8 described later), this is the same as determining Yes in step S10 described later, and will be described below.

[0054] First, the calculation unit 6 resets the time T of the timer to zero and then starts the timer (step S1). Next, the calculation unit 6 performs three-phase short-circuit control to simultaneously turn off the switching elements SW1, SW3, and SW5 of the three-phase upper arms included in the inverter 2 and simultaneously turn on the switching elements SW2, SW4, and SW6 of the three-phase lower arms included in the inverter 2 (step S2).

[0055] Specifically, the switch 15 is switched so as to output the γ-axis voltage command value Vγ*″ for performing the three-phase short circuit control to the voltage command value converter 17, and the switch 16 is switched so as to output the δ-axis voltage command value Vδ*″ for performing the three-phase short circuit control to the voltage command value converter 17.

[0056] As a result, the voltage command value conversion unit 17 outputs a U-phase voltage command value Vu*, a V-phase voltage command value Vv*, and a W-phase voltage command value Vw* for performing three-phase short circuit control, and the drive circuit 5 outputs a lower arm short circuit drive signal, which is a drive signal for performing three-phase short circuit control, to the inverter 2.

[0057] The lower arm short circuit drive signal in step S2 is output for a short period (e.g., several μs). Alternatively, instead of the lower arm short circuit drive signal, an upper arm short circuit drive signal may be output from drive circuit 5 to inverter 2, which is a drive signal that simultaneously turns on switching elements SW1, SW3, and SW5 and simultaneously turns off switching elements SW2, SW4, and SW6.

[0058] Next, the calculation unit 6 calculates the γ-δ-axis current value Iγδ from the γ-axis current value Iγ and the δ-axis current value Iδ calculated from the current value flowing through the motor M in response to the lower-arm short-circuit drive signal using the following equation (7). The determination unit 18, which serves as a second determination unit, determines whether the calculated γ-δ-axis current value Iγδ is equal to or greater than a first threshold current I0 (step S3). The first threshold current I0 is, for example, the minimum value of the γ-δ-axis current value Iγδ at which an estimated position θ^ can be calculated with the required estimation accuracy, and is determined in advance through experiments, simulations, or the like. Note that the higher the rotor rotation speed, the higher the current value flowing through the motor M. This increases the accuracy of the calculated estimated position θ^, thereby reducing the probability of loss of synchronization. Therefore, the required estimation accuracy refers to, for example, an estimation accuracy that reduces the likelihood of loss of synchronization even when sensorless control is performed.

[0059]

[0060] In step S3, if the γ-δ-axis current value Iγδ is smaller than the first threshold current I0 (step S3: No), the process proceeds to step S4.

[0061] In step S4, it is determined whether the γ-δ-axis current value Iγδ is equal to or greater than a second threshold current I1. The second threshold current I1 is, for example, a value smaller than the first threshold current I0, and is the minimum value of the γ-δ-axis current value Iγδ at which the estimated position θ^ can be calculated, and is determined in advance by experiment, simulation, or the like.

[0062] In step S4, if the γ-δ-axis current value Iγδ is equal to or greater than the second threshold current I1 (step S4: Yes), the timer is reset to zero after the time T of the timer is started, and an estimated position θ^ is calculated from the estimated extended electromotive force e^ calculated by setting the terms including Vγ*', Vδ*' and ω^ in Equation 5 to zero from the γ-axis current value Iγ and the δ-axis current value Iδ calculated from the current value flowing to the motor M in response to the lower-arm short-circuit drive signal (step S5). That is, if the γ-δ-axis current value Iγδ is equal to or greater than the second threshold current I1, the determination unit 18 serving as a second determination unit determines that position estimation is possible, and transitions from three-phase short-circuit control to current control.

[0063] Then, the control device 3 performs current control using the estimated position θ^ calculated in step S5 (step S6). In current control, the control device 3 controls the on / off of the switching elements SW1 to SW6 so that the current flowing through the motor M is constant for a predetermined time, thereby increasing the angular velocity of the rotor. For example, the control device 3 sets a δ-axis current command value Iδ* (described later) to a constant value (e.g., the maximum value) and repeatedly turns on and off the switching elements SW1 to SW6. In this embodiment, the control device 3 controls the on / off of the switching elements SW1 to SW6 so that the current flowing through the motor M is constant.

[0064] During current control, the control device 3 may control the current flowing through the motor M to a constant value for a predetermined period of time, and thereafter may control the current flowing through the motor M to fluctuate.

[0065] Next, the calculation unit 6 determines whether the time T is equal to or greater than the first predetermined time T1 (step S7).

[0066] In step S7, if the time T is less than the first predetermined time T1 (step S7: No), current control continues, and if the time T is equal to or greater than the first predetermined time T1 (step S7: Yes), the process returns to step S1. The first predetermined time T1 is the time required to increase the γ-δ-axis current value Iγδ by a predetermined current value by increasing the rotation speed of the rotor, and is determined in advance by experiment, simulation, or the like.

[0067] Furthermore, when the γ-δ-axis current value Iγδ is equal to or greater than the first threshold current I0 (step S3: Yes), the calculation unit 6 calculates an estimated angular velocity ω^ and an estimated position θ^ from an estimated extension induced voltage e^ calculated using all of the parameters in Equation 5 from the γ-axis current value Iγ and the δ-axis current value Iδ calculated from the value of the current flowing through the motor M by the lower-arm short-circuit drive signal (step S8). That is, when the γ-δ-axis current value Iγδ is equal to or greater than the first threshold current I0, the determination unit 18 as a second determination unit determines that position estimation is possible and transitions from three-phase short-circuit control to sensorless control.

[0068] Then, the control device 3 performs sensorless control using the estimated angular velocity ω^ and estimated position θ^ calculated in step S8 (step S9). During sensorless control, the control device 3 generates a drive signal for supplying a three-phase AC current to the motor M. In other words, the control device 3 controls the on / off of the switching elements SW1 to SW6 so that the motor M rotates at a desired rotation speed.

[0069] The calculation unit 6 also determines whether the γ-δ-axis extension induced voltage eγδ calculated from the estimated extension induced voltage e^, which is an estimate of the extension induced voltage e generated by the drive signal for supplying three-phase AC current to the motor M, is equal to or greater than a threshold value th (step S10).

[0070]

[0071] If it is determined in step S10 that the γ-δ-axis extension induced voltage eγδ is equal to or greater than the threshold value th (step S10: No), the sensorless control continues. If the γ-δ-axis extension induced voltage eγδ becomes smaller than the threshold value th (step S10: Yes), the process returns to step S1. For example, the threshold value th is the minimum value of the γ-δ-axis extension induced voltage eγδ when sensorless control is possible, and is determined in advance through experiments, simulations, or the like. That is, if the γ-δ-axis extension induced voltage eγδ is equal to or greater than the threshold value th, the determination unit 18 serving as the first determination unit determines that the estimator 8 can perform speed estimation and position estimation, and continues the sensorless control. If the γ-δ-axis extension induced voltage eγδ becomes smaller than the threshold value th, the determination unit 18 determines that the estimator 8 cannot perform position estimation, and transitions from sensorless control to three-phase short-circuit control.

[0072] Furthermore, if the γ-δ-axis current value Iγδ is smaller than the second threshold current I1 (step S4: No), the calculation unit 6 terminates the drive control of the motor M (step S11). That is, if the γ-δ-axis current value Iγδ is smaller than the second threshold current I1, the determination unit 18 as the second determination unit determines that, despite the execution of three-phase short-circuit control, a state in which at least position estimation can be performed has not been achieved, and terminates the drive control of the motor M.

[0073] 3 is a diagram showing an example of the actual angular velocity and the angular velocity command value ω* when the motor M is restarted. The horizontal axis of the two-dimensional coordinate system shown in FIG. 3 represents time, and the vertical axis represents angular velocity. The solid line in FIG. 3 represents the actual angular velocity, and the dashed line represents the angular velocity command value ω*.

[0074] First, at time t1, the angular velocity command value ω* changes from ω1 to zero, and drive control of the motor M stops. After that, the actual angular velocity gradually decreases.

[0075] Next, when the motor M is restarted at time t2, the angular velocity command value ω* switches from zero to ω1, and three-phase short circuit control is performed. If the γ-δ-axis current value Iγδ calculated based on the γ-axis current value Iγ and the δ-axis current value Iδ calculated from the current values ​​flowing through the motor M by the three-phase short circuit control is smaller than the first threshold current I0 and the γ-δ-axis current value Iγδ is equal to or greater than the second threshold current I1, current control and three-phase short circuit control are alternately performed repeatedly until the γ-δ-axis current value Iγδ becomes equal to or greater than the first threshold current I0, thereby increasing the angular velocity of the rotor. In the example shown in FIG. 3 , current control is performed three times until the γ-δ-axis current value Iγδ becomes equal to or greater than the first threshold current I0. Note that there are cases where current control is performed only once, depending on the γ-δ-axis current value Iγδ at the time of restarting the motor M.

[0076] Then, at time t3, when the γ-δ-axis current value Iγδ becomes equal to or greater than the first threshold current I0, the control is switched from three-phase short circuit control to sensorless control.

[0077] As described above, the control device 3 of the embodiment is configured to perform three-phase short-circuit control when the determination unit 18 serving as the first determination unit determines that position estimation is impossible because the extended induced voltage is relatively low at the start of the motor M or during sensorless control, or after current control has been performed for a certain period of time, thereby improving the estimation accuracy of the estimated position θ^. Generally, in normal sensorless control (PWM control), when the extended induced voltage is relatively low at the start of the motor M or when the extended induced voltage is relatively low (when the angular velocity of the rotor is relatively low), the extended induced voltage becomes low, and therefore the errors (dead time errors) between the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* and their true values ​​become relatively large. This deteriorates the signal-to-noise ratio of the extended induced voltage, and reduces the estimation accuracy of the rotor position. Therefore, as in this embodiment, when the motor M is started or when the determination unit 18 determines that position estimation is not possible because the extended induced voltage is relatively low, three-phase short-circuit control is performed, which can eliminate the influence of dead time errors compared to normal sensorless control (PWM control), thereby improving the signal-to-noise ratio of the extended induced voltage and the estimation accuracy of the estimated position θ^. As a result, even when the angular velocity of the motor M is relatively low, it is possible to prevent a decrease in the estimation accuracy of the rotor position and to prevent a loss of synchronism.

[0078] Furthermore, in the control device 3 of the embodiment, when the γ-δ-axis current value Iγδ is smaller than the first threshold current I0 and the γ-δ-axis current value Iγδ is equal to or larger than the second threshold current I1, the actual angular velocity can be increased by performing current control, and therefore the transition from start-up of the motor M to sensorless control can be performed in a relatively short time.

[0079] Furthermore, in the control device 3 of the embodiment, when the γ-δ-axis current value Iγδ is smaller than the first threshold current I0 and the γ-δ-axis current value Iγδ is smaller than the second threshold current I1, the drive control of the motor M is terminated. This makes it possible to prevent a loss of synchronization in sensorless control.

[0080] The present invention is not limited to the above-described embodiments, and various improvements and modifications are possible without departing from the spirit and scope of the present invention.

[0081] For example, the first threshold current I0 and the second threshold current I1 do not need to be two, and only one may be used. In this case, the current control may be eliminated, and either sensorless control or drive control of the motor M may be selected.

[0082] Furthermore, the determination unit 18 as the second determination unit determines whether or not position estimation is possible based on the current flowing through the motor M due to the three-phase short circuit control, but the second determination unit may be omitted, i.e., position estimation may be performed in step S5 or S8 without making a determination. In this case, position estimation may fail, but the control may be terminated, for example, when failure occurs a predetermined number of times.

[0083] In addition, the determination unit 18 has both the function as a first determination unit and the function as a second determination unit, but these may be provided separately. Also, the configuration may include two observers: one is the observer shown in Equation 5, and the other is an observer obtained by removing the terms including Vγ*′, Vδ*′, and ω^ from Equation 5.

[0084] Furthermore, in steps S3 and S4, the determination may be made based on the magnitude of the γ-axis current value Iγ or the magnitude of the δ-axis current value Iδ, rather than the magnitude of the γ-δ-axis current value Iγδ.

[0085] Furthermore, methods for calculating the estimated angular velocity ω^ and the estimated position θ^ include, in addition to the above-mentioned <method using extended induced voltage>, for example, <method using zero-cross timing of induced voltage>, <method using speed electromotive force>, and <method using magnetic flux>, and are not particularly limited.

[0086] Example of <Method Using Zero-Cross Timing of Induced Voltage> First, the estimator 8 calculates the estimated position θ^ based on the phase of the induced voltage generated in the phase through which no current flows at the zero-cross timing when the voltage of the phase through which no current flows, among the U-phase, V-phase, and W-phase of the motor M, reaches the midpoint potential of the voltage of the power supply P (half the voltage of the power supply P). Note that the method of calculating the estimated angular velocity ω^ from the estimated position θ^ is the same as the above-mentioned <Method Using Extended Induced Voltage>, and therefore its description will be omitted. Furthermore, when the <Method Using Zero-Cross Timing of Induced Voltage> is adopted as the method of calculating the estimated angular velocity ω^ and the estimated position θ^, the calculator 6 calculates the induced voltage at the zero-cross timing based on the input U-phase current value Iu, V-phase current value Iv, and W-phase current value Iw.

[0087] Furthermore, when the method of using the zero-cross timing of the induced voltage is employed as the method of calculating the estimated angular velocity ω^ and the estimated position θ^, the calculation unit 6 returns to step S1 and performs three-phase short-circuit control when the motor M is started or when the induced voltage of any phase becomes smaller than the threshold value th' in step S10 of FIG. 2 (step S10: Yes). Note that if the calculation unit 6 determines that the induced voltage of any phase is equal to or greater than the threshold value th' (step S10: No), it continues to perform sensorless control. For example, the threshold value th' is the minimum value of the induced voltage of any phase when sensorless control is possible, and is determined in advance by experiment, simulation, or the like. That is, when the induced voltage of any phase is equal to or greater than the threshold value th', the judgment unit 18 as the first judgment unit judges that the estimation unit 8 is in a state where it can perform speed estimation and position estimation, and continues sensorless control, and when the induced voltage of any phase becomes smaller than the threshold value th', the judgment unit 18 judges that the estimation unit 8 is in a state where it cannot perform speed estimation and position estimation, and transitions from sensorless control to three-phase short-circuit control.

[0088] Even when the method of using the zero-cross timing of the induced voltage is employed as a method for calculating the estimated angular velocity ω^ and the estimated position θ^, the three-phase short-circuit control is performed when the motor M is started or when the induced voltage is relatively low and the determination unit 18 serving as the first determination unit determines that position estimation is not possible. This configuration improves the estimation accuracy of the estimated position θ^. Generally, in normal sensorless control (PWM control), when the motor M is started or when the induced voltage is relatively low (when the rotor angular velocity is relatively low), the current flowing through the motor M is relatively small, making the zero-cross timing of the induced voltage unclear, deteriorating the signal-to-noise ratio of the induced voltage, and reducing the estimation accuracy of the rotor position. Therefore, in this embodiment, when the motor M is started or when the induced voltage is relatively low and the determination unit 18 determines that position estimation is not possible, the three-phase short-circuit control is performed to increase the current flowing through the motor M compared to normal sensorless control (PWM control). This makes the zero-cross timing of the induced voltage clearer, thereby improving the estimation accuracy of the estimated position θ^.

[0089] Example of <Method Using Speed ​​Electromotive Force> First, the estimator 8 calculates the speed electromotive force eM generated in the motor M based on the γ-axis current value Iγ, the δ-axis current value Iδ, the γ-axis voltage command value Vγ*', the δ-axis voltage command value Vδ*', the estimated angular velocity ω^ stored in the memory unit 4, and motor parameters that can be estimated in advance. Specifically, the estimator 8 calculates the speed electromotive force eM using the following equation 9. Note that p represents the time differential operator d / dt. KE represents the induced voltage constant. The winding resistance R^, the d-axis inductance Ld^, and the q-axis inductance Lq^ are estimated values ​​of the motor parameters of the motor M to be controlled, and are estimated in advance by measurements using the motor M, for example. The reason that the motor parameters of the motor M are estimated values ​​rather than actual values ​​is that the motor parameters vary depending on the current flowing through the motor M and the temperature.

[0090]

[0091] Next, the estimation unit 8 determines the estimated value of the current flowing through the motor M and the actual current based on the calculated speed electromotive force eM, and calculates the estimated angular velocity ω^ and estimated position θ^ based on the current error between the estimated value and the actual current.

[0092] Furthermore, when the method using speed electromotive force is employed as a method for calculating the estimated angular velocity ω^ and the estimated position θ^, as in the case where the method using zero-cross timing of induced voltage is employed as a method for calculating the estimated angular velocity ω^ and the estimated position θ^, the calculation unit 6 returns to step S1 and performs three-phase short-circuit control when the motor M is started or when the induced voltage of any phase becomes smaller than the threshold value th′ in step S10 of FIG. 2 (step S10: Yes). Note that, when the calculation unit 6 determines that the induced voltage of any phase is equal to or greater than the threshold value th′ (step S10: No), the calculation unit 6 continues to perform sensorless control. That is, when the induced voltage of any phase is equal to or greater than the threshold value th′, the determination unit 18 serving as a first determination unit determines that the estimator 8 is in a state where it can perform speed estimation and position estimation and continues the sensorless control. However, when the induced voltage of any phase becomes smaller than the threshold value th′, the determination unit 18 determines that the estimator 8 is in a state where it cannot perform speed estimation and position estimation and transitions from sensorless control to three-phase short-circuit control.

[0093] In this way, even when the method of using an estimated speed electromotive force is adopted as the method of calculating the estimated angular velocity ω^ and the estimated position θ^, the configuration is such that three-phase short-circuit control is performed when the motor M is started or when the induced voltage is relatively low and the determination unit 18 serving as the first determination unit determines that position estimation is not possible, thereby improving the estimation accuracy of the estimated position θ^. Generally, in normal sensorless control (PWM control), when the motor M is started or when the induced voltage is relatively low (when the angular velocity of the rotor is relatively low), the induced voltage is low, and therefore the errors (dead time errors) between the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* and their true values ​​become relatively large. This deteriorates the signal-to-noise ratio of the induced voltage and reduces the estimation accuracy of the rotor position. Therefore, as in this embodiment, when the motor M is started or when the induced voltage is relatively low and the judgment unit 18 judges that position estimation is not possible, by performing three-phase short-circuit control, the influence of dead time error can be eliminated compared to normal sensorless control (PWM control), thereby improving the signal-to-noise ratio of the induced voltage and improving the estimation accuracy of the estimated position θ^.

[0094] Example of <Method Using Magnetic Flux> First, the estimation unit 8 calculates the α-axis magnetic flux λα and the β-axis magnetic flux λβ based on the γ-axis current value Iγ, the δ-axis current value Iδ, the γ-axis voltage command value Vγ*', the δ-axis voltage command value Vδ*', and motor parameters that can be estimated in advance. Specifically, the estimation unit 8 calculates the α-axis magnetic flux λα and the β-axis magnetic flux λβ using the following equation 10. Note that the following equation 10 can be obtained from the following equations 11 to 13. That is, when the observer (motor model) shown in the following equation 11 is defined as shown in the following equation 12, the following equation 11 becomes the following equation 13. Next, when the following equation 13 is converted into the α-β axis system (fixed coordinate system), the following equation 10 is obtained. The α-axis voltage Vα in the fixed coordinate system corresponds to the γ-axis voltage command value Vγ*', the β-axis voltage Vβ in the fixed coordinate system corresponds to the δ-axis voltage command value Vδ*', the α-axis current iα in the fixed coordinate system corresponds to the γ-axis current value Iγ, and the β-axis current iβ in the fixed coordinate system corresponds to the δ-axis current value Iδ. Also, λd is the d-axis magnetic flux, and λq is the q-axis magnetic flux.

[0095]

[0096]

[0097]

[0098]

[0099] Next, the estimation unit 8 calculates the estimated position θ^ by substituting the calculated α-axis magnetic flux λα and β-axis magnetic flux λβ into the following equation 14. Note that the method for calculating the estimated angular velocity ω^ from the estimated position θ^ is the same as the above <method using extended induced voltage>, and therefore a description thereof will be omitted.

[0100]

[0101] Furthermore, when the method of using magnetic flux is employed as the method of calculating the estimated angular velocity ω^ and the estimated position θ^, the calculation unit 6 returns to step S1 and performs three-phase short-circuit control when the motor M is started or when the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' becomes smaller than the threshold value th" in step S10 of FIG. 2 (step S10: Yes). Note that, when the calculation unit 6 determines that the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is equal to or greater than the threshold value th" (step S10: No), it continues to perform sensorless control. For example, the threshold value th" is set to the minimum value of the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' when sensorless control is possible, and is determined in advance by experiment, simulation, or the like. That is, when the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is equal to or greater than the threshold value th'' the determination unit 18 as a first determination unit determines that the estimator 8 is in a state where it can perform speed estimation and position estimation, and continues the sensorless control, but when the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' becomes smaller than the threshold value th'' the determination unit 18 determines that the estimator 8 is in a state where it cannot perform speed estimation and position estimation, and transitions from sensorless control to three-phase short-circuit control.

[0102] In this way, even when the method of using magnetic flux is adopted as the method of calculating the estimated angular velocity ω^ and the estimated position θ^, the three-phase short-circuit control is performed when the motor M is started or when the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is relatively small and the determination unit 18 serving as the first determination unit determines that position estimation is not possible, and therefore the estimation accuracy of the estimated position θ^ can be improved. Generally, in normal sensorless control (PWM control), when the motor M is started or when the γ-δ-axis current value Iγδ or the specified γ-δ-axis voltage value Vγδ*' is relatively small (when the angular velocity of the rotor is relatively low), the γ-δ-axis current value Iγδ or the specified γ-δ-axis voltage value Vγδ*' becomes small, and accordingly, the error (dead time error) between the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, the W-phase voltage command value Vw* and the true value becomes large. As a result, the signal-to-noise ratio of the γ-δ-axis current value Iγδ or the specified γ-δ-axis voltage value Vγδ*' deteriorates, and the estimation accuracy of the rotor position decreases. Therefore, as in this embodiment, when the motor M is started or when the determining unit 18 determines that position estimation is not possible because the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*' is relatively low, by performing three-phase short-circuit control, the influence of dead time error can be eliminated compared to normal sensorless control (PWM control), thereby improving the signal-to-noise ratio of the phase voltages of the motor M and improving the estimation accuracy of the estimated position θ^. Note that instead of the γ-δ-axis current value Iγδ or the γ-δ-axis voltage command value Vγδ*', the γ-axis current value Iγ, the γ-axis voltage command value Vγ*', the δ-axis current value Iδ, and the δ-axis voltage command value Vδ*' may be used for determination.

[0103] REFERENCE SIGNS LIST 1 control system 2 inverter 3 control device 4 storage unit 5 drive circuit 6 calculation unit 7 current value conversion unit 8 estimation unit 9 subtraction unit 10 torque command value calculation unit 11 γ-δ current command value output unit 12 subtraction unit 13 subtraction unit 14 voltage command value calculation unit 15, 16 switch 17 voltage command value conversion unit 18 determination unit (first determination unit, second determination unit) P power supply C capacitor Se1 current sensor Se2 current sensor Se3 current sensor

Claims

1. A control device that generates a drive signal to control an inverter that drives a motor, a current value converter that converts the current flowing through the motor into a γ-axis current value and a δ-axis current value; a γ-δ current command value output unit that outputs a γ-axis current command value and a δ-axis current command value; a γ-δ voltage command value calculation unit that calculates a γ-axis voltage command value based on the γ-axis current value and the γ-axis current command value, and calculates a δ-axis voltage command value based on the δ-axis current value and the δ-axis current command value; a drive signal converter that converts the γ-axis voltage command value and the δ-axis voltage command value into the drive signals; an estimation unit that calculates an estimated position that is an estimated value of the position of the motor; a first determination unit that determines whether the estimation unit can estimate the position of the motor; and When starting the motor or when the first determination unit determines that position estimation is not possible, an upper arm short-circuit drive signal is generated, which is the drive signal that simultaneously turns on upper arm switching elements of three phases of the inverter and simultaneously turns off lower arm switching elements of three phases of the inverter, or a lower arm short-circuit drive signal is generated, which is the drive signal that simultaneously turns off upper arm switching elements of three phases of the inverter and simultaneously turns on lower arm switching elements of three phases of the inverter, When the upper arm short circuit drive signal or the lower arm short circuit drive signal is generated, the estimation unit calculates an estimated extension induced voltage, which is an estimate of an extension induced voltage generated in the motor, from the γ-axis current value and the δ-axis current value, and calculates an estimated position, which is an estimate of a position of the motor, based on the estimated extension induced voltage. Control device.

2. The control device according to claim 1, A second determination unit is provided, The second determination unit determines whether or not the position of the motor can be estimated based on a current flowing through the motor due to the upper arm short-circuit drive signal or the lower arm short-circuit drive signal. Control device.

3. The control device according to claim 2, When the second determination unit determines that the position of the motor can be estimated, the drive signal for supplying a three-phase AC current to the motor is generated. Control device.

4. The control device according to claim 3, when the second determination unit determines that the value of the current flowing through the motor is smaller than a threshold current and that position estimation of the motor is possible, start a timer, generate the upper arm short circuit drive signal or the lower arm short circuit drive signal, calculate the estimated extension induced voltage which is an estimate of an extension induced voltage generated in the motor from the γ-axis current value and the δ-axis current value, calculate the estimated position which is an estimate of the position of the motor based on the estimated extension induced voltage, and generate the drive signal using the calculated estimated position so that the current flowing through the motor becomes a constant value; After a first predetermined time has elapsed, the upper arm short circuit drive signal or the lower arm short circuit drive signal is generated. Control device.

5. The control device according to claim 3, the estimator calculates an estimated extended electromotive force, which is an estimate of an extended electromotive force generated in the motor, based on the γ-axis current value, the δ-axis current value, the specified γ-axis voltage value, and the specified δ-axis voltage value, and calculates an estimated position, which is an estimate of a position of the motor, based on the estimated extended electromotive force; The first determination unit determines that position estimation is not possible when the estimated extension induced voltage is smaller than a threshold, and generates the upper arm short circuit drive signal or the lower arm short circuit drive signal. Control device.