Control device and electric vehicle

Abstract

A control device that generates a voltage command for a power conversion device that drives a motor and controls the motor includes: a current threshold value calculation unit that calculates a current threshold value of the power conversion device; a current threshold calculation unit that calculates a current threshold on the basis of a dead time of the power conversion device, a parasitic capacitance of a switching element included in the power conversion device, and a DC voltage input to the power conversion device; a phase current command calculation unit that calculates a phase current command for the motor; and a compensation amount calculation unit that calculates a dead time compensation amount on the basis of the phase current command and the current threshold value, and the control device corrects the voltage command on the basis of the dead time compensation amount.

Description

Technical Field

[0001] The invention relates to a control device and an electric vehicle. Background Art

[0002] The recent proliferation of electric vehicles powered by motors such as permanent magnet synchronous motors and induction motors has fueled a desire not only to reduce greenhouse gases but also to enhance ride comfort and drivability by leveraging motor characteristics that meet driver demands. Furthermore, there is a growing demand for highly accurate and responsive torque control technology that can achieve vehicle vibration suppression.

[0003] Typically, inverters use a dead time interval to prevent the semiconductor elements in the upper and lower arms from turning on simultaneously. This dead time interval is the time during which both elements are turned off. However, during this dead time interval, an applied voltage that differs from the voltage command is generated, resulting in an error in the inverter's output voltage. As a method for suppressing this output voltage error, for example, Patent Document 1 discloses a technology that includes the voltage error caused by the dead time in the voltage command and compensates for it, thereby achieving higher precision and responsiveness in motor torque control. Prior art literature Patent Literature

[0004] Patent Document 1: International Publication No. 2018 / 220968. Summary of the Invention Problems to be solved by the invention

[0005] The technology described in Patent Document 1 will cause problems when driving at low speeds. When the vehicle is driving at low speeds, the required motor torque is small and the applied voltage required to drive the motor is also small, so the impact of the output voltage error becomes relatively large. In addition, since the motor is running at a low speed, the time for the current to flow through the current zero point (small current area) where the polarity of the phase current changes becomes longer, and the characteristics of the output voltage error caused by the dead time will undergo complex changes due to the influence of current pulsation. Furthermore, in the vibration suppression control of the vehicle, it is necessary to generate positive and negative alternating motor torque, and the magnitude and polarity of the phase current also change complexly. In addition, when the current flowing through the motor is small, the charging and discharging action in the parasitic capacitance proceeds relatively slowly, resulting in discontinuous changes in the output voltage.

[0006] In this case, low current regions frequently occur during low-speed vehicle operation and vibration suppression control. Therefore, failure to accurately compensate for dead time even in these low current regions can lead to a decrease in vehicle ride comfort. Therefore, it is necessary to consider the output voltage during the dead time in low current regions to accommodate the high-precision torque control required when the influence of torque errors is significant. This, in turn, improves the motor's torque control and responsiveness, thereby enhancing vehicle ride comfort. Technical means to solve the problem

[0007] A control device for generating a voltage command for a power conversion device that drives an electric motor and controlling the electric motor, comprising: a current threshold calculation unit that calculates a current threshold based on a dead time of the power conversion device, a parasitic capacitance of a switching element of the power conversion device, and a DC voltage input to the power conversion device; a phase current command calculation unit that calculates a phase current command to the electric motor; and a compensation amount calculation unit that calculates a dead time compensation amount based on the phase current command and the current threshold, and corrects the voltage command based on the dead time compensation amount. Effects of the Invention

[0008] According to the present invention, it is possible to provide a control device and an electric vehicle capable of improving the torque accuracy and responsiveness of motor control. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a block diagram of a motor drive system according to a first embodiment of the present invention. Figure 2 This is a block diagram of a dead time compensation unit according to the first embodiment of the present invention. Figure 3 This is an example of a problem that occurs during the dead time of a power conversion device. Figure 4 This is an example of a problem that occurs during the dead time of a power conversion device. Figure 5 This is a block diagram of a compensation amount calculation unit according to the first embodiment of the present invention. Figure 6 This is a block diagram of a phase current command calculation unit according to a second embodiment of the present invention. Figure 7 This is a block diagram of a dead time compensation unit according to a third embodiment of the present invention. Figure 8 This is a diagram showing the structure of an electric vehicle having the structure of the present invention. DETAILED DESCRIPTION

[0010] The following describes embodiments of the present invention with reference to the accompanying drawings. The following description and drawings are examples for illustrating the present invention and have been appropriately omitted or simplified for clarity. The present invention may also be implemented in various other ways. Unless otherwise specified, each component may be single or multiple.

[0011] The positions, sizes, shapes, and ranges of the components shown in the drawings may not represent their actual positions, sizes, shapes, and ranges in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the positions, sizes, shapes, and ranges disclosed in the drawings.

[0012] (First embodiment and overall structure of the present invention) ( Figure 1 ) The motor drive system includes a control device 100, a power conversion device 500, and a motor 700. The control device 100 is connected to the power conversion device 500. The power conversion device 500 is connected to the motor 700, which is a three-phase AC motor, and a DC power supply 900. The control device 100 detects a voltage Vdc input from the DC power supply 900 to the power conversion device 500.

[0013] A current detection unit 600 is provided between the power conversion device 500 and the motor 700 . The current detection unit 600 detects a phase current flowing from the power conversion device 500 to each phase of the motor 700 and transmits the detected value to the control device 100 .

[0014] Motor 700 is, for example, a permanent magnet synchronous motor and is driven by the voltage output from power converter 500 . Position detector 800 detects and acquires rotation angle (electrical angle) information for driving motor 700 and transmits the information to controller 100 .

[0015] The control device 100 generates voltage commands Vu*, Vv*, and Vw* and transmits these commands to the power converter 500, thereby performing PWM drive on the power converter 500 to control the motor 700. The PWM drive in the power converter 500 is performed by a switching element (not shown). The on / off signal of the switching element is determined by comparing the magnitude of the triangular wave (carrier) with the voltage command in a known manner.

[0016] The control device 100 receives as input signals a torque command τ* from a higher-level controller (not shown), current values ​​Iu, Iv, and Iw input from the current detection unit 600, a voltage value Vdc received from the DC power supply 900, and a rotation angle θ received from the position detection unit 800. Based on these input signals, the control device 100 calculates voltage commands Vu*, Vv*, and Vw* to be output to the power conversion device 500. The control device 100 transmits the calculated voltage commands Vu*, Vv*, and Vw to the power conversion device 500. The power conversion device 500 applies voltages Vu, Vv, and Vw to the motor 700 based on the input voltage commands Vu, Vv*, and Vw*.

[0017] The configuration of the control device 100 will be described. The control device 100 includes a dq-axis current command generating unit 200 , a current control unit 300 , a calculation unit 400 , and a dead time compensating unit 1000 .

[0018] Based on the torque command τ*, the dq-axis current command generator 200 calculates the dq-axis currents Id* and Iq* flowing through the motor 700 and transmits the calculated dq-axis currents Id* and Iq* to the current control unit 300 and the dead-time compensation unit 1000. While the dq-axis current command generator 200 shown in the figure performs calculations based solely on the torque command τ, it may also be configured to perform calculations based on the DC voltage Vdc and the rotational speed of the motor 700.

[0019] Current control unit 300 receives phase currents Iu, Iv, and Iw as input signals and performs coordinate transformation on phase currents Iu, Iv, and Iw based on the rotation angle θ received from position detection unit 800 to calculate actual d / q axis currents Id and Iq. Current control unit 300 applies vector control to ensure that d / q axis current commands Id* and Iq* match the calculated actual d / q axis currents Id and Iq, thereby calculating d / q axis voltage commands Vd* and Vq* for motor 700.

[0020] Furthermore, the current control unit 300 performs coordinate transformation on the dq-axis voltage commands Vd* and Vq* based on the rotation angle θ, outputs first voltage commands Vu1*, Vv1*, and Vw1*, and sends them to the arithmetic unit 400. The current control unit 300 may be configured as a known vector control method.

[0021] The dead time compensation unit 1000 takes the dq axis current instructions Id*, Iq*, the DC voltage Vdc and the rotation angle θ as input signals, generates dead time compensation amounts dVu, dVv, dVw for suppressing (compensating) the voltage error caused by the dead time of the power conversion device 500, and sends the generated dead time compensation amounts dVu, dVv, dVw to the operation unit 400.

[0022] The calculation unit 400 calculates the voltage commands Vu*, Vv*, Vw* output to the power converter 500 by reflecting the compensation amounts dVu, dVv, dVw input from the dead time compensator 1000 on the first voltage commands Vu1*, Vv1*, Vw1 input from the current controller 300 .

[0023] ( Figure 2 ) The dead time compensating unit 1000 includes a phase current command calculating unit 1100 , a current threshold calculating unit 1200 , and a compensation amount calculating unit 1300 .

[0024] Phase current command calculation unit 1100 calculates phase current commands Iu, Iv*, and Iw* for motor 700 based on dq-axis current commands Id* and Iq and rotation angle θ. Phase current command calculation unit 1100 performs calculation processing (coordinate transformation processing) of phase current commands Iu*, Iv*, and Iw* using equations (1) to (3) below.

[0025] Iu*=Id*×cos(θ)-Iq*×sin(θ)...Equation (1)

[0026] Iv*=Id*×cos(θ-2π / 3)-Iq*×sin(θ-2π / 3)...Equation (2)

[0027] Iw*=Id*×cos(θ-4π / 3)-Iq*×sin(θ-4π / 3)...Equation (3)

[0028] The phase current command calculation unit 1100 sends the calculated phase current commands Iu*, Iv*, and Iw* to the compensation amount calculation unit 1300 .

[0029] The current threshold value calculation unit 1200 calculates the current threshold value Ith based on the DC voltage Vdc and the parasitic capacitance C of the switching element and the dead time Td as parameters. The calculated current threshold value Ith is sent to the compensation amount calculation unit 1300.

[0030] The compensation amount calculation unit 1300 calculates the dead time compensation amounts dVu, dVv, and dVw based on the phase current commands Iu*, Iv*, and Iw*, the parasitic capacitance C, the dead time Td, the DC voltage Vdc, and the current threshold Ith. The compensation amounts dVu, dVv, and dVw are input to the calculation unit 400 ( Figure 1 By doing so, the voltage command output from the control device 100 to the power conversion device 500 can be corrected based on the dead time compensation amount, and the dead time compensation of the power conversion device 500 can be achieved through the corrected voltage command.

[0031] In addition, in the dead time compensating unit 1000 , the parasitic capacitance C and the dead time Td may be calculated values ​​or values ​​preset as constants.

[0032] ( Figure 3 ) The following describes problems that occur during the dead time of switching elements. Figure 3 (a) is a circuit diagram of a series circuit of upper and lower arms of one phase in a three-phase AC inverter included in the power conversion device 500 . Figure 3 (b) means that when Figure 3 (a) The flow direction of the upper and lower bridge arms series circuit Figure 1 Graph showing the relationship between switching action and voltage when the current 10 (current polarity is positive) of the motor 700 is greater than a predetermined current threshold value Ith. Figure 3 (c) is a diagram showing the relationship between the switching operation and the voltage when the current 10 is smaller than the predetermined current threshold value Ith.

[0033] like Figure 3 As shown in (b) and (c), in the power conversion device 500, when the switch element S2 of the lower bridge arm changes from the on state to the off state, and the switch element S1 of the upper bridge arm is in the off state (within the dead time), the current 10 flows through the switch element S2 to the motor 700 ( Figure 1 ). As a result, point P is grounded, and the output voltage is zero. Therefore, the voltage Vact during the dead time is zero relative to the ideal voltage Videal. Therefore, an output voltage error occurs during the dead time Td1.

[0034] Next, when the switch element S1 of the upper bridge arm is in the on state and the switch element S2 of the lower bridge arm is in the off state, the potential at point P is Vdc until the switch element S1 of the upper bridge arm and the switch element S2 of the lower bridge arm are turned off. Therefore, the capacitance component (parasitic capacitance) connected in parallel with the switch element S2 is in the charged state. Figure 3 As shown in (b), even if the upper arm switching element S1 transitions from on to off (within the dead time), the actual voltage does not instantaneously reach zero during the dead time Td2 due to the discharge of the parasitic capacitance of the capacitor. Instead, the voltage gradually transitions toward zero. In this case, the flowing current I0 remains greater than the specified current threshold Ith. A dead time compensation method for this situation is disclosed in Patent Document 1.

[0035] However, when the flowing current I0 is less than the specified current threshold Ith, as shown in FIG. Figure 3As shown in (c), during the dead time Td2, the voltage slope becomes flat. Even if switch element S1 switches from on to off, the parasitic capacitance discharge is not complete during the dead time, resulting in the voltage not reaching zero. In this state, the output voltage reaches zero only when switch element S2 switches from on to ground after the dead time expires.

[0036] As described above, during the dead time period, the output voltage varies depending on whether the magnitude of the current 10 is greater than or less than the prescribed current threshold value Ith.

[0037] ( Figure 4 ) The following describes a problem that occurs during the dead time of the switching element when the electric motor 700 flows a current 20 (current polarity is negative) into the power conversion device 500. Figure 4 (a) is a series circuit of upper and lower arms of one phase in a three-phase AC inverter included in the power conversion device 500 .

[0038] Figure 4 (b) means from Figure 4 (a) Figure 1 A diagram showing the relationship between the switching action and the voltage when the current 20 (current polarity is positive) flowing through the upper and lower arm series circuits of the motor 700 is greater than the specified current threshold Ith. Figure 4 (c) is a diagram showing the relationship between the switching operation and the voltage when the current 20 is smaller than the predetermined current threshold value Ith.

[0039] When the switch element S2 of the lower bridge arm changes from the on state to the off state, and the switch element S1 of the upper bridge arm is in the off state (within the dead time), since the potential of point P is zero, the capacitance component (parasitic capacitance) in parallel with the switch element S1 is in a state of no charge accumulation. Figure 4 As shown in (b), during the dead time Td1, the actual output voltage does not rise instantaneously due to the charging action of the parasitic capacitance, but rather transitions with a slope. In this case, the flowing current 20 is greater than the predetermined current threshold Ith.

[0040] However, if Figure 4 As shown in (c), when current 20 is less than the specified current threshold Ith, the voltage slope becomes flat, and the charging of the parasitic capacitance during the dead time Td1 is not completed, resulting in a phenomenon in which the voltage does not rise completely. In this case, the output voltage reaches Vdc only after switching element S1 turns on and the dead time expires, and the output voltage is connected to DC power supply 900.

[0041] As described above, even when electric motor 700 flows current 20 (negative current polarity) into power converter 500, the output voltage during the dead time period varies depending on whether current 20 is greater than or less than a predetermined current threshold value Ith (depending on the magnitude and polarity of the phase current). Therefore, when calculating the dead time compensation amount for power converter 500, it is desirable to use the phase current value at the time of output voltage.

[0042] The present invention considers the output voltage when the current is less than the predetermined current threshold Ith to perform dead time compensation. This can suppress the output voltage error of the power converter 500 and improve the torque control accuracy and responsiveness of the motor 700.

[0043] As mentioned above, whether the charge and discharge of the parasitic capacitance are completed within the dead time is determined by the specified current threshold Ith. The voltage slope affected by the parasitic capacitance C can be expressed by the following formula (4).

[0044] (Voltage slope) = i / C...Equation (4)

[0045] Therefore, within the dead time Td, the current value at which the voltage having the slope of equation (4) transitions from zero to voltage Vdc or from voltage Vdc to zero can be expressed as the specified current threshold value Ith by the following equation (5).

[0046] Ith=C×Vdc / Td...Formula (5)

[0047] The current threshold calculation unit 1200 of the dead time compensation unit 1000 ( Figure 2 ) calculates the specified current threshold value Ith represented by formula (5), and outputs the calculated specified current threshold value Ith to the compensation amount calculation unit 1300 and reflects it in the calculation, so that the voltage error caused by the dead time in the power conversion device 500 can be compensated with high precision.

[0048] ( Figure 5 ) Compensation amount calculation unit 1300 of dead time compensator 1000 includes a U-phase compensation amount calculation switching process 1310U, a U-phase voltage error averaging process 1320U, a V-phase compensation amount calculation switching process 1310V, a V-phase voltage error averaging process 1320V, a W-phase compensation amount calculation switching process 1310W, and a W-phase voltage error averaging process 1320W. Compensation amount calculation unit 1300 executes these processes to output dead time compensation amounts dVu, dVv, and dVw to calculation unit 400. Since the calculation method of compensation amount calculation unit 1300 is the same for the U, V, and W phases, the following description uses the U-phase calculation as an example.

[0049] The U-phase compensation quantity operation switching process 1310U calculates the first U-phase compensation quantity dVu1 based on the input of the U-phase current command value Iu*, dead time Td, parasitic capacitance C, DC voltage Vdc, and current threshold Ith. The U-phase compensation quantity operation switching process 1310U outputs the calculated first U-phase compensation quantity dVu1 to the U-phase voltage error averaging process 1320U.

[0050] As described above, since the voltage characteristics change according to the magnitude relationship between the current threshold Ith and the U-phase current command value Iu*, the U-phase compensation quantity operation switching process 1310U switches the operation method of the dead time compensation quantity according to the mutual magnitude relationship between the current threshold Ith and the U-phase current command value Iu*.

[0051] The U-phase compensation quantity operation switching process 1310U, for example, uses the following equations (6) to (8) to determine the first U-phase compensation quantity dVu1 based on the current threshold Ith and the U-phase current command value Iu*. Equations (6) to (8) describe the difference in area between the ideal voltage and the output voltage according to the magnitude relationship between the U-phase current command Iu* and the current threshold Ith. The first equation (6) is used when Ith < Iu*, the second equation (7) is used when -Ith < Iu* < Ith, and the third equation (8) is used when Iu* < Ith. Additionally, in the second equation (7), the first current threshold -Ith and the second current threshold Ith are included as the current thresholds.

[0052] dVu1 = Td × Vdc - C / 2 / Iu* × Vdc × Vdc... Equation (6)

[0053] dVu1 = Iu* / 2 / C × Td × Td... Equation (7)

[0054] dVu1 = -Td × Vdc - C / 2 / Iu* × Vdc × Vdc... Equation (8)

[0055] In this way, since the operation method is switched according to the mutual magnitude relationship between the U-phase current command Iu* and the current threshold Ith, it is possible to reflect whether the charge and discharge action of the parasitic capacitance is completed within the dead time, thereby performing dead time compensation on the power conversion device 500.

[0056] The U-phase voltage error averaging process 1320U calculates the value to be reflected in the voltage command Vu* based on the input first U-phase compensation quantity dVu1. Figure 1) compensation amount dVu. Since the first U-phase compensation amount dVu1 is the area difference between the ideal voltage and the actual voltage, when it is reflected in the voltage command for compensation, by averaging it over one PWM execution cycle, the compensation amount for each PWM cycle can be calculated. For example, in a PWM based on comparing a triangular wave with the voltage command, the U-phase voltage error averaging process 1320U is a process that multiplies the voltage by the triangular wave frequency fc.

[0057] The compensation amount calculation switching process shown in this embodiment does not necessarily need to be in the form of equations (6) to (8). For example, a lookup table with phase current commands as parameters may also be used. Furthermore, in the case of a system in which the triangular wave frequency fc is variable, the value of frequency fc may be reflected at each time to adapt to the operating state of the power conversion device 500.

[0058] As described above, the present invention calculates a current threshold Ith, which indicates the charge and discharge state of the parasitic capacitance C, based on the parasitic capacitance C of the switching element, the dead time Td, and the DC voltage Vdc serving as the input voltage of the power conversion device. This calculated current threshold Ith is reflected in the compensation amount calculation unit 1300, thereby switching the calculation of the dead time compensation amount based on the phase current command and the current threshold Ith. This allows for highly accurate compensation of output voltage errors when small currents flow, thereby improving motor torque accuracy and responsiveness.

[0059] (Second embodiment) ( Figure 6 ) The phase current command calculation unit 1100 of the dead time compensation unit 1000 includes a d-axis current estimation unit 1110 , a q-axis current estimation unit 1120 , a speed calculation unit 1130 , a phase compensation unit 1140 , a calculation means 1150 , and a coordinate conversion unit 1160 .

[0060] Based on the d-axis current command Id*, the d-axis current estimation unit 1110 sends an operator as the estimated d-axis current value Id^ to the coordinate transformation unit 1160, which then performs calculations using equations (1) to (3) described above. Similarly, based on the q-axis current command Iq*, the q-axis current estimation unit 1120 sends an operator as the estimated q-axis current value Iq^ to the coordinate transformation unit 1160, which then performs calculations using equations (1) to (3) described above. Each of the d-axis current estimation units 1110 and q-axis current estimation units 1120 is comprised of, for example, a first-order lag filter.

[0061] Current control unit 300 ( Figure 1) performs vector control on the input d / q axis current commands Id* and Iq* so that the actual d / q axis currents Id and Iq have a predetermined response. Utilizing this, the d-axis current estimating unit 1110 and the q-axis current estimating unit 1120 are equipped with characteristics that simulate the responses of the actual d / q axis currents Id and Iq to the d / q axis current commands Id* and Iq*. Consequently, the actual d / q axis currents Id and Iq can be estimated.

[0062] The speed calculation unit 1130 uses the rotation angle (electrical angle) θ of the motor 700 as an input signal, calculates the electrical angular velocity ω of the motor 700, and transmits the calculated value to the phase compensation unit 1140. The speed calculation unit 1130 may be configured to perform differential processing to calculate the electrical angular velocity ω of the motor 700. Furthermore, if there is a concern about noise amplification due to the differential operation, a filter may be applied to remove the noise component.

[0063] Phase compensator 1140 calculates phase compensation amount dθ using electrical angular velocity ω calculated by velocity calculator 1130, and transmits the calculated phase compensation amount dθ to arithmetic operator 1150. Phase compensation amount dθ is a compensation amount for compensating for the rotation angle when a voltage reflecting voltage commands Vu*, Vv*, and Vw* is output from power converter 500 to motor 700 based on detected rotation angle θ.

[0064] For example, if there is a time delay of K × Tc (K is a constant, and Tc is the control period of control device 100) between the detection of rotation angle θ and the output of voltage by power converter 500, the rotation angle at the time of voltage output will be ahead of the detected rotation angle θ by an amount dθ = ω × K × Tc. The phase compensation amount dθ is used to compensate for this difference.

[0065] The calculation unit 1150 reflects the phase compensation amount dθ input from the phase compensator 1140 in the input rotation angle θ, calculates the compensated rotation angle θcmp when the power converter 500 outputs voltage to the motor 700, and outputs the calculated compensated rotation angle θcmp to the coordinate converter 1160.

[0066] The coordinate conversion unit 1160 performs the same processing as the aforementioned equations (1) to (3) based on the d-axis current estimated value Id^, the q-axis current estimated value Iq^, and the compensated rotation angle θcmp as input signals, thereby calculating the phase current commands Iu*, Iv*, and Iw*, and outputs the calculated phase current commands Iu*, Iv*, and Iw* to the compensation amount calculation unit 1300 ( Figure 2 ).

[0067] This configuration allows calculation of the average phase current value at the time the power converter 500 outputs voltage to the motor 700. This ensures temporal alignment between the voltage output and the current value, allowing for higher accuracy in dead time compensation calculations. Furthermore, the phase current values ​​at the time of voltage output used for dead time compensation calculations typically have a time lag between current detection and voltage output. Therefore, using current detection values ​​or dq-axis current command values ​​directly as phase current command values ​​can lead to inadequate dead time compensation. However, this configuration prevents such problems.

[0068] In addition, although the phase current command calculation unit 1100 of the dead time compensation unit 1000 calculates the estimated values ​​Id^ and Iq^ from the dq axis current commands Id* and Iq* so as not to be affected by the noise or current ripple of the detection current, it may be configured to be based on the detection currents Iu, Iv, and Iw directly input from the current detection unit 600 ( Figure 1 ) to calculate the actual d and q axis currents Id and Iq. In this case, the d axis current estimating unit 1110 and the q axis current estimating unit 1120 can be omitted.

[0069] (Third embodiment) ( Figure 7 ) In addition to the phase current command calculation unit 1100 , the current threshold calculation unit 1200 , and the compensation amount calculation unit 1300 , the dead time compensation unit 1000 further includes an electrical characteristics calculation unit 1400 and an electrical characteristics reflection unit 1500 .

[0070] The compensation amount calculation unit 1300 calculates second compensation amounts dVu2, dVv2, dVw2 based on the phase current commands Iu*, Iv*, Iw* output from the phase current command calculation unit 1100 and outputs the calculated second compensation amounts dVu2, dVv2, dVw2 to the electrical characteristics reflection unit 1500.

[0071] The electrical characteristics calculation unit 1400 calculates the third compensation amounts dVu3, dVv3, dVw3 taking into account the electrical characteristics of the switching elements based on the phase current instructions Iu*, Iv*, Iw* output from the phase current instruction calculation unit 1100, and outputs the calculated third compensation amounts dVu3, dVv3, dVw3 to the electrical characteristics reflection unit 1500.

[0072] The electrical characteristics of the switching elements considered by the electrical characteristics calculation unit 1400 will be described. For example, the voltage drop component of the switching element, one of the electrical characteristics of the switching element, is a factor in output error in the power conversion device 500, similar to the dead time, and affects the torque control accuracy and responsiveness of the motor 700. The electrical characteristics calculation unit 1400 calculates the compensation amount by considering the electrical characteristics of the switching element.

[0073] For example, when electrical characteristics calculation unit 1400 calculates the electrical characteristics of a switching element based on phase current command Iu*, if the switching element's on-resistance Ron is used, the voltage drop across the switching element can be expressed as Ron × Iu*. Furthermore, when the on-resistance Rdiode of a freewheeling diode connected in antiparallel with the switching element is used for calculation, the voltage drop can be expressed as Rdiode × Iu*. Furthermore, since either the switching element or the freewheeling diode is turned on depending on the polarity of the current, the polarity of phase current command Iu* is also taken into account when calculating the electrical characteristics.

[0074] The electrical characteristic reflection unit 1500 reflects (corrects) the third compensation amounts dVu3 , dVv3 , dVw3 input from the electrical characteristic calculation unit 1400 on the second compensation amounts dVu2 , dVv2 , dVw2 input from the compensation amount calculation unit 1300 , and calculates the dead time compensation amounts dVu, dVv, dVw.

[0075] In this way, by performing dead time compensation in consideration of the electrical characteristics of the switching elements, the output voltage error of the power conversion device 500 can be further reduced, and the accuracy and responsiveness of the torque control of the motor 700 can be improved.

[0076] ( Figure 8 ) The control device 100 having the structure of the present invention can be applied to an electric vehicle 1600. The electric vehicle 1600 includes a motor drive system 1B1 including a motor 700, an inverter 500, and the control device 100, and a motor drive system 1B2 for power generation having the same structure.

[0077] A differential 611, serving as a power distribution mechanism, is located in the center of the front axle. The engine 610 or motor 700 distributes the rotational drive force transmitted via the transmission 612 to the left and right front axles. The engine 610 and motor 700 have a mechanism for mechanically connecting and disconnecting them using a mechanism mounted on the transmission 612. This allows for selective switching between two modes: a series hybrid mode, in which the engine 610 and motor 700 are mechanically coupled, with only the motor 700's mechanical output transmitted to the differential 611 for vehicle propulsion; and a parallel hybrid mode, in which the combined mechanical outputs of the engine 610 and motor 700 are transmitted to the differential 611 for vehicle propulsion. This allows the electric vehicle 1600 to switch between series and parallel hybrid modes, depending on driving scenarios, such as urban and highway driving, to balance vehicle performance and range.

[0078] The inverter 500 converts the DC power supplied from the battery 900 into three-phase AC power under the control of the control device 100. The three-phase AC power output from the inverter 500 is supplied to the stator coil of the stator of the motor 700. As a result, the rotor of the motor 700 rotates, generating a rotational driving force corresponding to the three-phase AC power (current). In addition, the rotor of the motor 700 is driven to rotate by the mechanical output from the engine 610. As a result, three-phase AC power is generated in the stator coil of the motor 700 and input to the inverter 500. Under the control of the control device 100, the inverter 500 converts the three-phase AC power input from the motor 700 into DC power and charges the high-voltage battery 900.

[0079] In addition, the electric vehicle 1600 using the structure of the present invention is not limited to hybrid electric vehicles, but can also be applied to plug-in hybrid electric vehicles, pure electric vehicles, etc., and the same effects can be achieved in these cases.

[0080] According to the embodiment of the present invention described above, the following effects can be obtained.

[0081] (1) A control device 100 that generates a voltage command for a power converter 500 that drives a motor 700 and controls the motor 700 includes: a current threshold calculation unit 1200 that calculates a current threshold based on the dead time of the power converter 500, the parasitic capacitance of a switching element of the power converter 500, and the DC voltage input to the power converter 500; a phase current command calculation unit 1100 that calculates a phase current command for the motor 700; and a compensation amount calculation unit 1300 that calculates a dead time compensation amount based on the phase current command and the current threshold. Dead time compensation is performed on the voltage command based on the dead time compensation amount. This improves the torque accuracy and responsiveness of the motor control.

[0082] (2) The compensation amount calculation unit 1300 switches the calculation method of the dead time compensation amount according to the relationship between the phase current command and the current threshold. This allows for high-precision compensation of the output voltage error when a small current flows.

[0083] (3) When the phase current command value is greater than the current threshold, the compensation amount is calculated using the first equation. This allows for high-precision compensation of output voltage errors when a small current flows.

[0084] (4) The current thresholds include a first current threshold and a second current threshold. When the phase current command value is greater than the first current threshold and less than the second current threshold, the compensation amount is calculated using the second equation. This allows for high-precision compensation of output voltage errors when small currents flow.

[0085] (5) When the phase current command value is less than the current threshold, the compensation amount is calculated using the third equation. This allows for high-precision compensation of output voltage errors when a small current flows.

[0086] (6) Phase current command calculation unit 1100 calculates the average value of the phase current at the time when power converter 500 outputs voltage based on the electrical angle of motor 700, the electrical angular velocity of motor 700, and the dq-axis current command of motor 700. This allows for temporal matching of the voltage output and current values, resulting in higher accuracy in dead time compensation calculations.

[0087] (7) The compensation amount calculation unit 1300 corrects the dead time compensation amount based on the electrical characteristics of the switching element and calculates the corrected dead time compensation amount. This can further reduce the output voltage error of the power conversion device 500.

[0088] (8) An electric vehicle 1600 including the control device 100 is used. This can provide an electric vehicle 1600 in which the torque accuracy and responsiveness of the motor control are improved.

[0089] In addition, the present invention is not limited to the above-mentioned embodiment, and various modifications or combinations of other structures are possible without departing from the scope of the present invention. In addition, the present invention is not limited to having all the structures described in the above-mentioned embodiment, and also includes a scheme in which some of the structures are deleted. Explanation of symbols

[0090] 100 Control Device 200 dq axis current command generation unit 300 Current Control Unit 400 arithmetic units 500 Power conversion device 600 Current Detection Unit 700 electric motor 800 Position Detection Unit 900 DC power supply 1000 Dead time compensation unit 1100 Phase current command calculation unit 1200 Current threshold calculation unit 1300 Compensation calculation unit 1400 Electrical Characteristics Calculation Unit 1500 Electrical characteristics reflection unit 1600 Electric vehicles.

Claims

1. A control device that generates a voltage command for a power conversion device that drives an electric motor and controls the electric motor, characterized in that: The control device comprises: a current threshold calculation unit configured to calculate a current threshold based on a dead time of the power conversion device, a parasitic capacitance of a switching element included in the power conversion device, and a DC voltage input to the power conversion device; a phase current command calculation unit that calculates a phase current command for the electric motor; and a compensation amount calculation unit that calculates a dead time compensation amount based on the phase current command and the current threshold, The control device corrects the voltage command based on the dead time compensation amount.

2. The control device according to claim 1, characterized in that The compensation amount calculation unit switches a calculation method of the dead time compensation amount according to a relationship between the phase current command and the current threshold.

3. The control device according to claim 2, characterized in that When the value of the phase current command is greater than the current threshold, the dead time compensation amount is calculated using the first equation.

4. The control device according to claim 2, characterized in that The current threshold includes a first current threshold and a second current threshold, When the value of the phase current command is greater than the first current threshold and less than the second current threshold, the dead time compensation amount is calculated using a second formula.

5. The control device according to claim 2, characterized in that: When the value of the phase current command is less than the current threshold, the dead time compensation amount is calculated using the third equation.

6. The control device according to claim 1, characterized in that The phase current command calculation unit calculates an average value of phase currents at a time when the power conversion device outputs a voltage based on an electrical angle of the motor, an electrical angular velocity of the motor, and dq-axis current commands of the motor.

7. The control device according to claim 1, characterized in that The compensation amount calculation unit corrects the dead time compensation amount based on the electrical characteristics of the switching element, and calculates the corrected dead time compensation amount.

8. An electric vehicle, characterized in that: A control device according to any one of claims 1 to 4 is provided.

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