Control device and control method for electric motor

Abstract

Provided are a control device and a control method for an electric motor, which do not adversely affect the detection accuracy of a direct current estimation value even when a control mode of a power conversion unit is changed.　A control device for an electric motor comprises a power conversion unit 10 and a control unit 11 for controlling the power conversion unit, and further comprises: a control mode setting unit 30 that selectively sets a plurality of control modes for the power conversion unit 10; and a direct current estimation unit 32 that estimates the value of a direct current flowing through the power conversion unit, on the basis of the value of an alternative current flowing through the electric motor and an on-duty value of a PWM signal for controlling the power conversion unit. The direct current estimation unit 32 comprises an energization-time correction unit 40 that, when the polarity of the alternative current is on the negative side, adds a dead time ⊿t existing between on-timing and off-timing of an upper arm 12u and a lower arm 13u to an energization time of the upper arm. The energization-time correction unit obtains the dead time ⊿t corresponding to a currently-executed control mode among the plurality of control modes, and adds said dead time ⊿t to the energization time of the upper arm 12u.

Description

Motor control device and control method

[0001] The present invention relates to a control device for an electric motor used in an automobile or the like, and more particularly to a control device and control method for an electric motor that performs inverter control.

[0002] A motor control device that controls the motor that drives a hybrid vehicle or electric vehicle is equipped with a power conversion device to drive the motor. The power conversion device converts direct current (DC) supplied from a battery into alternating current (AC) by switching the switching elements of the power converter, thereby driving the three-phase motor. In the following description, alternating current will sometimes be referred to as "AC" and direct current as "DC."

[0003] This power conversion device is equipped with a three-phase AC current sensor that measures the current flowing through the motor, as well as a DC current sensor that measures the direct current supplied from the battery to the power converter. Recently, however, there has been a demand to eliminate the DC current sensor in this type of motor control device in order to reduce the number of parts and manufacturing costs.

[0004] In this case, the DC current value can be estimated using the control parameters of the motor. For example, Japanese Patent Application Laid-Open No. 2020-127361 (Patent Document 1) discloses estimating the DC current value by multiplying the on-duty value of the switching element of the upper arm of the power converter by the AC current value flowing through the motor detected by an AC current sensor.

[0005] Japanese Patent Application Laid-Open No. 2020-127361

[0006] As will be described in detail later, in a power converter, the duration of current flow through the AC current sensor differs depending on the polarity of the AC current. This is because when the polarity is negative, current flows through the diode in the upper arm during the dead time caused by the difference between the on-timing and off-timing of the switching elements in the upper and lower arms.

[0007] Therefore, when the method of Patent Document 1 is adopted, if the polarity of the AC current is negative, it is necessary to estimate the DC current value by multiplying the on-duty value to which the dead time has been added by the AC current value. Note that if the polarity is positive, no correction is necessary because no current flows through the diode, and the DC current value is estimated by multiplying the on-duty value to which the dead time has not been added by the AC current value.

[0008] Recently, in the control of electric motors, it has been proposed to change the control mode (sometimes referred to as switching mode) of a power converter depending on the range of load and rotation speed of the electric motor. For example, it has been proposed to drive a power converter by selecting between an SVPWM (space vector pulse width modulation) control mode and another control mode (for example, a one-pulse control mode).

[0009] However, when the control mode differs, the number of times the switching elements are switched within a PWM period (here, the period of the carrier signal) differs, and the number of times the above-mentioned dead time occurs also differs. Therefore, for example, sharing the dead time set in the SVPWM control mode with another control mode creates a problem of adversely affecting the detection accuracy when estimating the DC current value. In the following description, the estimated DC current value is defined as the DC current estimate value.

[0010] An object of the present invention is to provide a motor control device and control method that do not adversely affect the detection accuracy of a DC current estimate value even when the control mode of a power converter is changed.

[0011] The present invention provides a motor control device comprising a power conversion unit that converts DC current to AC current to drive the motor, and a control unit that controls the power conversion unit, wherein the control unit comprises a control mode setting unit that selectively sets a plurality of control modes for the power conversion unit, and a DC current estimation unit that estimates a DC current value flowing in the power conversion unit from the AC current value flowing in the motor and the on-duty value of a PWM signal that controls the arms of the power conversion unit, and wherein the DC current estimation unit comprises a current flow time correction unit that, when the polarity of the AC current is negative, adds a dead time existing between the on-timing and off-timing of the upper arm and the lower arm of the power conversion unit to a current flow time that determines the on-duty value, and the current flow time correction unit determines the dead time corresponding to a control mode currently being executed from a plurality of control modes and adds it to the current flow time.

[0012] According to the present invention, the dead time corresponding to the control mode of the motor is determined, and this dead time is reflected in the current conduction time of the upper arm, thereby making it possible to obtain an accurate DC current estimate value.

[0013] FIG. 2A is a configuration diagram showing the configuration of a motor control device; FIG. 2B is an explanatory diagram explaining the direction of current flow in the upper arm and the lower arm when AC current is on the positive side; FIG. 2C is an explanatory diagram explaining the dead time in the upper arm and the lower arm in FIG. 2A; FIG. 2D is an explanatory diagram explaining the direction of current flow in the upper arm and the lower arm when AC current is on the negative side; FIG. 3E is an explanatory diagram explaining the dead time in the upper arm and the lower arm in FIG. 3A; FIG. 3F is an explanatory diagram explaining the concept of a current conduction time correction unit that corrects dead time in the related art; FIG. 3G is an explanatory diagram explaining dead time in SVPWM control mode; FIG. 3H is an explanatory diagram explaining dead time in peak / valley synchronous control mode; FIG. 3I is an explanatory diagram explaining dead time in 1 pulse (or 3 pulse) control mode; FIG. 3I is an explanatory diagram explaining the concept of a current conduction time correction unit that corrects dead time according to an embodiment of the present invention; and FIG. 3J is a flowchart showing the control flow of a current conduction time correction unit according to an embodiment of the present invention.

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment, and various modifications and application examples within the technical concept of the present invention are also included within its scope.

[0015] First, the configuration of the motor control device will be briefly explained with reference to Figure 1. The motor control device INV is composed of a power conversion unit 10 and a control unit 11. The control unit 11 shows the configuration of the main part of the present invention, which will be described later. The control device INV operates to drive and control a three-phase motor MTR. The three-phase motor MTR is a three-phase brushless motor that has a stator with U-phase, V-phase, and W-phase coils, and a rotor with a magnet that is rotatably supported relative to the stator.

[0016] As described above, the control device INV includes the power conversion unit 10 and the control unit 11. The power conversion unit 10 includes a U-phase arm in which the upper arm switching element 12u and the lower arm switching element 13u are connected in series, a V-phase arm in which the upper arm switching element 12v and the lower arm switching element 13v are connected in series, and a W-phase arm in which the upper arm switching element 12w and the lower arm switching element 13w are connected in series.

[0017] The arms of the power conversion unit 10 are connected in parallel between a positive electrode line Lp of an on-board DC power supply 14 and a negative electrode line Ln of the DC power supply 14, forming a three-phase bridge circuit. A connection switch 15 is interposed between the DC power supply 14 and the positive electrode line Lp.

[0018] A smoothing capacitor 16 is connected in parallel with each arm between the positive electrode line Lp and the negative electrode line Ln. Each of the switching elements 12u to 13w includes an anti-parallel diode and is configured with a power semiconductor element such as a field effect transistor (FET) or an insulated gate bipolar transistor (IGBT). In this embodiment, an IGBT is used.

[0019] The upper arm switching elements 12u to 12w are provided with an upper arm conduction time detector 17A. Similarly, the lower arm switching elements 13u to 13w are provided with a lower arm conduction time detector 17B.

[0020] The upper arm current conduction time detector 17A and the lower arm current conduction time detector 17B can detect the on timing and off timing of the switching elements 12u to 12w and 13u to 13w, and can also detect the current conduction time.

[0021] The power conversion unit 10 also includes an AC current sensor 18 for detecting the AC current value of each phase. The detected AC current value Iac from the AC current sensor 18 for each phase is input to the control unit 11. The detected AC current value Iac from the AC current sensor 18 is multiplied by the on-duty value of the pulse of the PWM signal of the power conversion unit 10 to obtain a DC current estimate value.

[0022] The electric motor MTR is provided with an angle sensor 19, which detects the rotation angle for calculating the rotation speed of the rotor. A resolver or the like can be used for this.

[0023] The control unit 11 is configured to communicate with an external control device via a CAN (Controller Area Network) or the like, and its main components are a microcomputer having an A / D converter, a processor such as a CPU (Central Processing Unit), a writable memory element such as a RAM (Random Access Memory), a read-only memory element such as a ROM (Read Only Memory), etc. The current control unit 30, the control mode determination unit 31, and the DC current estimation unit 32 will be described later.

[0024] Next, we will explain why the duration of current flow through the AC current sensor in a power converter varies depending on the polarity of the AC current. Note that while the following will describe the upper and lower arms of the U phase, the same applies to the V and W phases.

[0025] 2A and 2B show a state in which the polarity of the AC current is positive in the SVPWM control mode.

[0026] 2A and 2B, the command voltage signal for the upper arm switching element 12u is turned on at time t2 and turned off at time t3. In contrast, the lower arm switching element 13u is turned off at time t1 and turned on at time t4. Dead times Δta and Δtr are set between the turn-on and turn-off. The dead times Δta and Δtr are set in this way to prevent the upper arm and lower arm from being turned on simultaneously and causing a short circuit.

[0027] Therefore, when the polarity of the AC current is positive, the current flows as shown by the dashed arrow only during the period from time t2 to time t3 when the upper arm switching element 12u is on, and the AC current sensor 18 detects the positive current only during this period.

[0028] On the other hand, FIGS. 3A and 3B show a state in which the polarity of the AC current is negative in the SVPWM control mode.

[0029] 3A and 3B, the command voltage signal for the upper arm switching element 12u is turned on at time t2 and turned off at time t3. In contrast, the lower arm switching element 13u is turned off at time t1 and turned on at time t4. Dead times Δta and Δtr are set between the turn-on and turn-off. The dead times Δta and Δtr are set in this way to prevent the upper arm and lower arm from being turned on simultaneously and causing a short circuit. This is the same as for the positive side.

[0030] However, when the polarity of the AC current is negative, even if the upper arm switching element 12u is off, current flows through the diode only between times t1 and t4, as indicated by the dashed arrow. Therefore, the AC current sensor 18 detects negative current during this time as well. Therefore, when calculating the DC current estimate, the on-duty value can be used as is for the positive side, but for the negative side, it is necessary to add dead times Δta and Δtr to the on-duty value.

[0031] In the following description, the dead time may be referred to as "Δt," "Δta," or "Δtr" depending on the content of the explanation.

[0032] Next, a specific method for adding this dead time will be explained with reference to Fig. 4. Fig. 4 shows a functional block for correcting the above-mentioned dead times Δta and Δtr. In practice, this is executed by software on a microcomputer.

[0033] 4, in order to calculate the DC current estimate, it is first necessary to calculate the on-duty value of the pulse of the PWM signal that drives the power conversion unit 10. For this purpose, a PWM period calculation unit 20 calculates the PWM period of the pulse that drives the power conversion unit 10 (here, the period of the carrier signal), and also calculates the current conduction time of the upper arm.

[0034] The obtained PWM period and current application time are divided by a divider 21 to obtain an on-duty value. The on-duty value is obtained for each of the U, V, and W phases. The obtained on-duty value is sent to a multiplier 22, where it is multiplied by the AC current detection value Iac from the AC current sensor 18 to calculate the designated DC current value for each phase.

[0035] The DC current estimate value of each phase thus obtained is sent to an adder 23, where the DC current estimate values ​​of the U-phase, V-phase, and W-phase are added together to obtain a final DC current estimate value.

[0036] As described above, the current conduction time due to the dead times Δta and Δtr of the upper and lower arms differs between the positive and negative sides depending on the polarity of the AC current. For this reason, the current conduction time correction unit 24 is provided. The current conduction time correction unit 24 includes a negative side detection unit 25 that detects the negative side of the AC current, a dead time switching unit 26, a negative side dead time setting unit 27, and a positive side dead time setting unit 28.

[0037] For example, in the SVPWM control mode, when the upper arm and the lower arm are in an on-off state within a PWM period, the negative side detection unit 25 does not detect the negative side when the AC current is in a positive state, so the dead time switching unit 26 selects the positive side dead time setting unit 28. In this case, since there is no need to take the dead times Δta and Δtr into consideration, the dead times Δta and Δtr are set to "0," and the dead times Δta and Δtr are not reflected in the upper arm current conduction time adding unit 29. Note that the dead times Δta and Δtr may be collectively referred to as dead time Δt. For example, in FIG. 4, the dead times Δta and Δtr are indicated as "Δt."

[0038] On the other hand, when the AC current is negative, the negative side detection unit 25 detects the negative side, so the dead time switching unit 26 selects the negative side dead time setting unit 27. In this case, since the dead times Δta and Δtr must be taken into consideration on the negative side, the dead time Δt is set to "Δta + Δtr." If the dead times Δta and Δtr are equal, it may be set to "Δta × 2." In the following description, it is assumed that Δta = Δtr.

[0039] In the SVPWM control mode, turn-on and turn-off occur within one PWM cycle, so the dead time Δt occurs twice. Therefore, the dead time is set to "Δta + Δtr," and the dead time "Δta + Δtr" is added to the upper arm current conduction time adder 29 and reflected.

[0040] As mentioned above, in recent motor control, it has been proposed to change the control mode (switching mode) of the power converter depending on the load and rotation speed range of the motor. For example, it has been proposed to drive the power converter by selecting between the SVPWM control mode and another control mode (for example, one-pulse control mode).

[0041] However, when the control mode is different, the number of times the switching element switches within a PWM cycle differs, and the number of times the above-mentioned dead time occurs also differs. Therefore, for example, if the dead time Δt set in the SVPWM control mode is shared with other control modes, there is a problem that the detection accuracy of the DC current estimation value is adversely affected.

[0042] Next, an embodiment of the present invention for solving such problems will be described. As shown in Fig. 1, this embodiment includes a current control unit 30, a control mode determination unit 31, and a DC current estimation unit 32.

[0043] After receiving a torque command value from the upper controller, the current control unit 30 sets a control mode based on the motor speed, AC current detection values ​​of the U-phase, V-phase, and W-phase AC current sensors 18, the input voltage of the power conversion unit 10, etc. In this way, the current control unit 30 has the function of a control mode setting unit. Of course, it is possible to set the control mode by other methods.

[0044] The control modes are, for example, SVPWM control mode (referred to as the first control mode in the claims), peak / valley synchronous control mode (referred to as the second control mode in the claims), and one-pulse (or three-pulse) control mode (referred to as the third control mode in the claims).

[0045] Here, two or three of these three control modes are set, although it goes without saying that other control modes may also be used.

[0046] Furthermore, the current control unit 30 can select the peak or valley side of the carrier signal depending on the control mode and use it for control, and can generate a command voltage signal for the peak or valley side of the carrier signal. The control mode is not limited to the above-mentioned control modes, and an appropriate control mode can be used depending on the operating state.

[0047] The control mode determination unit 31 can determine the control mode from the command voltage signal from the current control unit 30. For example, it can determine the SVPWM control mode, peak / valley synchronous control mode, or one-pulse (or three-pulse) control mode set by the current control unit 30. There are various methods for determining the control mode, and the method is not limited to these.

[0048] DC current estimation unit 32 switches between negative and positive dead time Δt depending on the polarity of the AC current, using the control mode from control mode determination unit 31 and the detection value of AC current sensor 18. DC current estimation unit 32 also calculates a DC current estimate using the AC current detection value from AC current sensor 18, the conduction time from upper arm conduction time detector 17A, the PWM period of current control unit 30, and the dead time Δt.

[0049] Here, since the conduction time is corrected by the dead time Δt, the on-duty value divided by the PWM period is also changed, and therefore, a DC current estimate value that reflects the dead time Δt is obtained.

[0050] Next, the dead time Δt in the above-described multiple control modes will be described. In this embodiment, the multiple control modes are selected based on the rotation speed range of the electric motor. For example, the rotation speed range is set to (1) an extremely low rotation speed range (0 rpm to 1000 rpm), (2) a low / medium rotation speed range (1000 rpm to 5000 rpm), and (3) a high rotation speed range (5000 rpm or higher).

[0051] Since the low / medium speed range is the most commonly used speed range, the well-known SVPWM control mode is assigned to the low / medium speed range, the peak / valley synchronous control mode is assigned to the extremely low speed range, and the one-pulse (or three-pulse) control mode is assigned to the high speed range.

[0052] The SVPWM control mode is a mode in which the command voltage signal is updated only on the peak or valley side of the carrier signal. Also, as shown in Figure 5, this is a switching mode in which both turn-on and turn-off are performed only once during one PWM period (corresponding to the period of the carrier signal), resulting in two dead times, Δta and Δtr, occurring during turn-on and turn-off. Therefore, it is necessary to add the dead time "Δta + Δtr" to the conduction time of the upper arm.

[0053] The peak / valley synchronous control mode is a mode in which the command voltage signal is updated on both the peak and valley sides of the carrier signal. Furthermore, as shown in FIG. 6 , the peak / valley synchronous control mode treats two PWM cycles as one control cycle. Therefore, this is a switching mode in which turn-on or turn-off occurs only once during one PWM cycle, and one dead time Δta or dead time Δtr occurs during one PWM cycle. Therefore, it is necessary to add the dead time Δta or dead time Δtr to the conduction time of the upper arm during one PWM cycle.

[0054] The 1-pulse (or 3-pulse) control mode is a mode in which carrier signal comparison is not performed. Also, as shown in Figure 7, no switching of the upper and lower arms occurs within the PWM period, so no dead time Δt occurs. Therefore, the dead time Δt is "0".

[0055] In this way, a different dead time Δt occurs in each control mode. For example, dead times Δt of "Δta×2," "Δta or Δtr," and "0" occur within one PWM period. Therefore, when executing a control mode corresponding to the rotation speed range of the electric motor MTR, it is necessary to select and use the above-mentioned dead time Δt.

[0056] Next, an embodiment that satisfies this requirement will be described with reference to Fig. 8. Fig. 8 shows a functional block for selecting and correcting the above-mentioned dead time Δt. In practice, this is executed by software on a microcomputer.

[0057] 8, a new current conduction time correction unit 40 is provided. The current conduction time correction unit 40 includes a negative side detection unit 41 that detects the negative side of the AC current, a dead time switching unit 42, a negative side dead time setting unit 43, and a positive side dead time setting unit 44. The negative side dead time setting unit 43 has a function of adjusting (selecting) the length of the dead time Δt in accordance with the control mode. Here, the control mode is switched in accordance with the range of the rotational speed of the electric motor MTR, as described above.

[0058] The negative side dead time setting unit 43 includes a dead time selection unit 45, which includes a mode selection unit 46, an SVPWM dead time setting unit 47, a peak / valley synchronization dead time setting unit 48, and a one-pulse (or three-pulse) dead time setting unit 49. The negative side dead time setting unit 43 also includes a control mode determination unit 50, which executes the function of determining the current control mode.

[0059] The negative side dead time setting unit 43 is provided with a first dead time generating unit 51 that generates dead time used by the SVPWM dead time setting unit 47 and the peak / valley synchronization dead time setting unit 48. The first dead time generating unit 51 has a function of doubling one dead time (Δta×2) in order to generate two dead times in one PWM period, and a function of generating one dead time (Δta) in order to generate one dead time in one PWM period.

[0060] That is, when the SVPWM control mode is selected, the SVPWM dead time setting unit 47 sets the dead time by "Δta x 2", and when the peak / valley synchronization control mode is selected, the peak / valley synchronization dead time setting unit 48 sets the dead time by "Δta or Δtr".

[0061] The dead time selection unit 45 is also provided with a second dead time generation unit 52 that generates dead time to be used in the one-pulse (or three-pulse) dead time setting unit 49. The second dead time generation unit 52 has a function of setting the dead time to "0" because no dead time occurs in the one-pulse control (or three-pulse) mode.

[0062] As described above, in this embodiment, the dead time has the relationship "Δta × 2" > "Δta" > "0" depending on the control mode. These dead times are stored in a memory element such as a flash ROM. Furthermore, since the dead time Δta is commonly used, the memory area can be reduced. When the motor is driven in the SVPWM control mode, the upper arm and the lower arm are turned on and off within one PWM cycle. When the AC current is positive, the negative side detection unit 41 does not detect the negative side, so the dead time switching unit 42 selects the positive side dead time setting unit 44. In this case, the dead time Δt does not need to be considered, so the dead time Δt is set to "0," and the dead time is not reflected in the upper arm current conduction time adding unit 29.

[0063] On the other hand, when the AC current is negative, the negative side detection unit 41 detects the negative side, so the dead time switching unit 42 selects the negative side dead time setting unit 43. In this case, the mode selection unit 46 selects the SVPWM dead time setting unit 47. In this SVPWM control mode, the dead time setting unit 47 turns on and off within one PWM period, so the dead time Δt occurs twice. Therefore, the dead time is set to twice "Δta," and the upper arm current conduction time adding unit 29 adds the dead time "Δta × 2" to the current conduction time of the upper arm and reflects this.

[0064] Furthermore, when the motor is driven in the peak / valley synchronization control mode, if the AC current is negative, the negative side detection unit 41 detects the negative side, and therefore the dead time switching unit 42 selects the negative side dead time setting unit 43. In this case, the mode selection unit 46 selects the peak / valley synchronization dead time setting unit 48. In the peak / valley synchronization control mode, turn-on and turn-off are performed within two PWM periods, so the dead time Δt occurs once per PWM period. Therefore, the dead time is set to "Δta," and the upper arm conduction time adding unit 29 adds the dead time "Δta" to the conduction time of the upper arm and reflects the result.

[0065] Furthermore, when the motor is driven in the 1-pulse (or 3-pulse) control mode, if the AC current is negative, the negative-side detection unit 41 detects the negative side, and so the dead time switching unit 42 selects the negative-side dead time setting unit 43. In this case, the mode selection unit 46 selects the 1-pulse (or 3-pulse) dead time setting unit 49. In the 1-pulse (or 3-pulse) control mode, this 1-pulse (or 3-pulse) dead time setting unit 49 does not compare the carrier signal, so no dead time Δt is generated. Therefore, the dead time is set to "0," and the upper arm energization time adding unit 29 does not add the dead time to the energization time of the upper arm, so the dead time is not reflected.

[0066] Next, a specific control flow of software for executing the functions of the current application time correction unit 40 shown in Fig. 8 will be described with reference to Fig. 9. This control flow is started by a regular interrupt at predetermined intervals.

[0067] <Step S10> In step S10, it is determined whether the polarity of the AC current is positive. If it is determined to be positive (YES determination), the process proceeds to step S11, and if it is determined not to be positive (NO determination), the process proceeds to step S12.

[0068] <Step S11> In step S11, since the polarity is determined to be positive, an estimated positive DC current value is calculated. The calculation formula is "estimated positive DC current value = AC current value x upper arm conduction time / PWM period", where "upper arm conduction time / PWM period" is the on-duty value. This also applies to the following steps. Once the estimated positive DC current value is calculated in step S11, the process proceeds to step S18.

[0069] <Step S12> Since it is determined in step S10 that the polarity of the AC current is not positive, that is, negative, it is determined in step S12 whether or not the one-pulse (or three-pulse) control mode is in effect.

[0070] If it is determined in step S12 that the control mode is one pulse (or three pulses) (YES), the process proceeds to step S13, and if it is determined that the control mode is not one pulse (or three pulses) (NO), the process proceeds to step S14.

[0071] <Step S13> In step S13, since it is determined that the control mode is one-pulse (or three-pulse) control, an estimated negative DC current value is calculated. The calculation formula is "estimated negative DC current value = AC current value x upper arm conduction time / PWM period." In this case, as shown in FIG. 8, the dead time is "0," so only the conduction time of the upper arm is used. Once the estimated negative DC current value is calculated in step S13, the process proceeds to step S18.

[0072] <Step S14> Since it is determined in step S12 that the one-pulse (or three-pulse) control mode is not in effect, it is determined in step S14 whether or not the peak / valley synchronization control mode is in effect.

[0073] If it is determined in step S14 that the mode is the peak / valley synchronous control mode (YES), the process proceeds to step S15, and if it is determined that the mode is not the peak / valley synchronous control mode (NO), the process proceeds to step S16.

[0074] <Step S15> In step S15, since it is determined that the peak / valley synchronous control mode is in effect, an estimated negative DC current value is calculated. The calculation formula is "estimated negative DC current value = AC current value x (upper arm conduction time + dead time) / PWM period." In this case, as shown in FIG. 8, the dead time is "Δta." Once the estimated negative DC current value is calculated in step S15, the process proceeds to step S18.

[0075] <Step S16> Since it is determined in step S14 that the peak / valley synchronous control mode is not in effect, it is determined in step S16 whether or not the control mode is the SVPWM control mode.

[0076] If it is determined in step S16 that the control mode is SVPWM (YES), the process proceeds to step S17, but if it is determined that the control mode is not SVPWM (NO), the process goes to END and waits for the next activation timing.

[0077] <Step S17> In step S17, since it is determined that the SVPWM control mode is in effect, an estimated negative DC current value is calculated. The calculation formula is "estimated negative DC current value = AC current value x (upper arm conduction time + dead time x 2) / PWM period." In this case, as shown in FIG. 8, the dead time is "Δta x 2." Once the estimated negative DC current value is calculated in step S15, the process proceeds to step S18.

[0078] <Step S18> In step S18, the estimated positive DC current value calculated in step S11 is added to the estimated negative DC current value calculated in step S13, step S15, or step S17 to calculate the estimated total DC current value for each control mode. Once the estimated total DC current value is calculated, the process exits to END. The process then waits for the next startup timing.

[0079] In this way, in this embodiment, the dead time corresponding to the control mode of the motor is calculated, and this dead time is reflected (added) to the current conduction time of the upper arm, thereby making it possible to obtain an accurate DC current estimation value.

[0080] As described above, the present invention is a motor control device comprising a power conversion unit that converts DC current to AC current to drive an electric motor, and a control unit that controls the power conversion unit, wherein the control unit comprises a control mode setting unit that selectively sets a plurality of control modes for the power conversion unit, and a DC current estimation unit that estimates a DC current value flowing in the power conversion unit from the AC current value flowing in the electric motor and the on-duty value of a PWM signal that controls the arms of the power conversion unit, and the DC current estimation unit comprises a current flow time correction unit that, when the polarity of the AC current is negative, adds dead time existing between the on-timings and off-timings of the upper arm and the lower arm of the power conversion unit to the current flow time that determines the on-duty value, and the current flow time correction unit determines the dead time corresponding to the control mode currently being executed from the plurality of control modes and adds it to the current flow time.

[0081] According to this, by determining the dead time corresponding to the control mode of the motor and reflecting this dead time in the current conduction time of the upper arm, it becomes possible to obtain an accurate DC current estimate value.

[0082] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0083] 10...power conversion unit, 11...control unit, 12u, 12v, 12w...switching elements (upper arm), 13u, 13v, 13w...switching elements (lower arm), 14...battery, 16...capacitor, 18...AC current sensor, 29...adder, 30...current control unit, 31...control mode determination unit, 32...DC current estimation unit, 40...current flow time correction unit, 41...negative side detection unit, 42...dead time switching unit, 43...negative side dead time setting unit, 44...positive side dead time setting unit, 45...dead time selection unit, 46...mode selection unit, 47...SVPWM dead time setting unit, 48...peak / valley synchronization dead time setting unit, 49...1 pulse (or 3 pulse) dead time setting unit, 50...control mode determination unit, 51...first dead time generation unit, 52...second dead time generation unit.

Claims

1. A motor control device comprising a power conversion unit that converts DC current to AC current to drive a motor, and a control unit that controls the power conversion unit, wherein the control unit comprises: a control mode setting unit that selectively sets a plurality of control modes for the power conversion unit; and a DC current estimation unit that estimates a DC current value flowing through the power conversion unit from the AC current value flowing through the motor and the on-duty value of a PWM signal that controls the arms of the power conversion unit, wherein the DC current estimation unit comprises a current flow time correction unit that, when the polarity of the AC current is negative, adds dead time existing between the on-timing and off-timing of the upper arm and lower arm of the power conversion unit to the current flow time that determines the on-duty value, and the current flow time correction unit determines the dead time corresponding to the control mode currently being executed from a plurality of control modes and adds it to the current flow time.

2. A control device for an electric motor according to claim 1, wherein the current conduction time correction unit selects the corresponding dead time from a plurality of dead times corresponding to each of a plurality of control modes in accordance with the control mode currently being executed, and adds the selected dead time to the current conduction time.

3. An electric motor control device according to claim 2, wherein the plurality of dead times are stored in a memory element provided in the control unit.

4. An electric motor control device according to claim 2, wherein the control modes are at least two of a first control mode in which the dead time occurs twice in one cycle of the PWM signal, a second control mode in which the dead time occurs once in one cycle of the PWM signal, and a third control mode in which the dead time does not occur in one cycle of the PWM signal.

5. An electric motor control device according to claim 2, characterized in that the control modes are at least three, namely a first control mode in which the dead time occurs twice in one cycle of the PWM signal, a second control mode in which the dead time occurs once in one cycle of the PWM signal, and a third control mode in which the dead time does not occur in one cycle of the PWM signal.

6. An electric motor control device according to claim 1, wherein the on-duty value is determined by dividing the energization time of the upper arm of the power conversion unit by the period of the PWM signal, and the dead time is added to the energization time of the upper arm.

7. A control method for an electric motor comprising a power conversion unit that converts DC current to AC current to drive the electric motor, and a control unit that controls the power conversion unit, wherein the control unit executes a mode setting step that selectively sets a plurality of control modes for the power conversion unit, and executes a DC current estimation step that estimates a DC current value flowing in the power conversion unit from the AC current value flowing in the electric motor and the on-duty value of a PWM signal that controls the arms of the power conversion unit, and wherein in the DC current estimation step, when the polarity of the AC current is on the negative side, executes a current flow time correction step that calculates dead time existing between the on-timing and off-timing of the upper arm and the lower arm in the control mode that is currently being executed among the plurality of control modes, and adds the calculated dead time to the current flow time that determines the on-duty value.

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