JP2024149236A - Control device, electric vehicle - Google Patents

Abstract

A control device and an electric vehicle are provided that improve the torque accuracy and responsiveness of electric motor control.
SOLUTION
A control device generates a voltage command for a power conversion device that drives an electric motor and controls the electric motor. The control device includes 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.
[Selected figure] Figure 2

Description

The present invention relates to a control device and an electric vehicle.

In recent years, the widespread use of electric vehicles powered by electric motors such as permanent magnet synchronous motors and induction motors is expected to not only reduce greenhouse gas emissions, but also improve the ride comfort and driving performance of vehicles by taking advantage of the characteristics of electric motors that satisfy the driving requirements of the driver. There is also a demand for highly accurate and responsive torque control technology to achieve vibration suppression control of vehicles.

In general, inverters have a dead time during which both semiconductor elements of the upper and lower arms are off so that they are not on at the same time. During this dead time, however, an applied voltage different from the voltage command is generated, resulting in an output voltage error in the inverter. As a method for suppressing such output voltage errors, for example, Patent Document 1 discloses a technology that realizes high accuracy and high responsiveness of motor torque control by including the voltage error due to the dead time in the voltage command in advance and compensating for it.

International Publication No. 2018/220968

The technology described in Patent Document 1 has 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 is relatively large. In addition, because the motor rotates at a low speed, the time that the current flows near the current zero crossing (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 change in a complex manner due to the influence of the current ripple. Furthermore, the vibration suppression control of the vehicle requires the generation of a motor torque that alternates between positive and negative, and the magnitude and polarity of the phase current change in a complex manner. And when the current flowing through the motor is small, the charging and discharging operation in the parasitic capacitance is performed slowly, so the output voltage changes discontinuously.

Under these circumstances, regions of minute current frequently occur when implementing low-speed vehicle operation and vibration suppression control. Therefore, unless dead-time compensation is performed with high precision even in regions of minute current, issues arise that could lead to a deterioration in the ride comfort of the vehicle. For this reason, it was necessary to improve the ride comfort of the vehicle by improving the torque control and responsiveness of the electric motor, taking into account the output voltage during dead time in regions of minute current, and responding to the high-precision torque control required when the effects of torque error are significant.

A control device that generates a voltage command for a power conversion device that drives an electric motor and controls the electric motor includes a current threshold calculation unit that calculates a current threshold based on the dead time of the power conversion device, the 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.

The present invention provides a control device and an electric vehicle that improve the torque accuracy and responsiveness of electric motor control.

Block diagram of a motor drive system according to a first embodiment of the present invention. FIG. 1 is a block diagram of a dead time compensation unit according to a first embodiment of the present invention; An example showing the challenges during dead time in a power converter An example showing the challenges during dead time in a power converter Block diagram of a compensation amount calculation unit according to a first embodiment of the present invention. A block diagram of a phase current command calculation unit according to a second embodiment of the present invention. A block diagram of a dead time compensation unit according to a third embodiment of the present invention. FIG. 1 is a diagram showing the configuration of an electric vehicle equipped with the configuration of the present invention;

The following describes an embodiment of the present invention with reference to the drawings. The following description and drawings are examples for explaining the present invention, and some parts have been omitted or simplified as appropriate for clarity of explanation. The present invention can also be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc., in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

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

A current detection means 600 is provided between the power conversion device 500 and the electric motor 700. The current detection means 600 detects the phase current flowing from the power conversion device 500 to each phase of the electric motor 700 and transmits the value to the control device 100.

The electric motor 700 is, for example, a permanent magnet type synchronous motor, and is driven by the voltage output by the power conversion device 500. The position detection means 800 detects and acquires information on the rotation angle (electrical angle) used to drive the electric motor 700, and transmits it to the control device 100.

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

The control device 100 receives as input signals the torque command τ* transmitted from a higher-level control (not shown), the current values Iu, Iv, and Iw input from the current detection means 600, the voltage value Vdc received from the DC power supply 900, and the rotation angle θ received from the position detection means 800. Based on these input signals, the control device 100 calculates the 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 electric motor 700 based on the input voltage commands Vu*, Vv*, and Vw*.

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 means 400, and a dead time compensation unit 1000.

The dq-axis current command generating unit 200 calculates the dq-axis currents Id* and Iq* to be passed through the electric motor 700 based on the torque command τ*, and transmits the calculated dq-axis currents Id* and Iq* to the current control unit 300 and the dead time compensation unit 1000. Note that although the dq-axis current command generating unit 200 is illustrated as performing calculations based only on the torque command τ*, it may also be configured to perform calculations in response to the DC voltage Vdc and the rotation speed of the electric motor 700 in addition to this.

The current control unit 300 receives the phase currents Iu, Iv, and Iw as input signals, and calculates the actual dq-axis currents Id and Iq by performing coordinate transformation of the phase currents Iu, Iv, and Iw based on the rotation angle θ received from the position detection means 800. The current control unit 300 calculates the dq-axis voltage commands Vd* and Vq* to the motor 700 by performing vector control so that the dq-axis current commands Id* and Iq* match the calculated actual dq-axis currents Id and Iq.

The current control unit 300 also performs coordinate conversion on the d-axis and q-axis voltage commands Vd* and Vq* based on the rotation angle θ to output the first voltage commands Vu1*, Vv1*, and Vw1*, which are then transmitted to the calculation means 400. The configuration of the current control unit 300 may be any commonly known form of vector control.

The dead time compensation unit 1000 uses the dq axis current commands Id*, Iq*, the DC voltage Vdc, and the rotation angle θ as input signals to generate dead time compensation amounts dVu, dVv, and dVw that suppress (compensate) the voltage error caused by the dead time of the power conversion device 500, and transmits the generated dead time compensation amounts dVu, dVv, and dVw to the calculation means 400.

The calculation means 400 calculates the voltage commands Vu*, Vv*, Vw* to be output to the power conversion device 500 by reflecting the compensation amounts dVu, dVv, dVw input from the dead time compensation unit 1000 to the first voltage commands Vu1*, Vv1*, Vw1 input from the current control unit 300.

(Figure 2)
The dead time compensation unit 1000 includes a phase current command calculation unit 1100 , a current threshold calculation unit 1200 , and a compensation amount calculation unit 1300 .

The phase current command calculation unit 1100 calculates the phase current commands Iu*, Iv*, and Iw* for the motor 700 based on the dq-axis current commands Id* and Iq* and the rotation angle θ. The phase current command calculation unit 1100 performs calculation processing (coordinate conversion processing) of the phase current commands Iu*, Iv*, and Iw* using the following equations (1) to (3).

Iu*=Id*×cos(θ)−Iq*×sin(θ)...Formula (1)

Iv*=Id*×cos(θ-2π/3)-Iq*×sin(θ-2π/3)...Formula (2)

Iw*=Id*×cos(θ-4π/3)-Iq*×sin(θ-4π/3)...Formula (3)

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

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

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 means 400 (Figure 1). In this way, the voltage command output from the control device 100 to the power conversion device 500 is corrected based on the dead-time compensation amount, and the dead-time compensation of the power conversion device 500 can be realized by the corrected voltage command.

In addition, in the dead time compensation unit 1000, the parasitic capacitance C and the dead time Td may be calculated or may be preset as constants.

(Figure 3)
Problems that occur during the dead time of the switching elements will be described. Fig. 3(a) is a circuit diagram of upper and lower arm series circuits for one phase of a three-phase AC inverter included in the power conversion device 500. Fig. 3(b) is a diagram showing the relationship between switching operation and voltage when a current 10 (current polarity is positive) flowing from the upper and lower arm series circuits of Fig. 3(a) to the electric motor 700 of Fig. 1 is greater than a predetermined current threshold Ith. Fig. 3(c) is a diagram showing the relationship between switching operation and voltage when the current 10 is smaller than a predetermined current threshold Ith.

As shown in Figures 3(b) and (c), in the power conversion device 500, when the lower arm switching element S2 changes from the on state to the off state and the upper arm switching element S1 is in the off state (during dead time), the current 10 flows into the electric motor 700 (Figure 1) via the switching element S2. As a result, point P is grounded and the output voltage becomes zero, so that the voltage Vact during the dead time becomes zero with respect to the ideal voltage Videal. Therefore, an output voltage error occurs during the dead time Td1.

Next, when the upper arm switching element S1 is on and the lower arm switching element S2 is off, the potential at point P is voltage Vdc until just before the upper arm switching element S1 and the lower arm switching element S2 are turned off, so the capacitance component (parasitic capacitance) connected in parallel to the switching element S2 is charged. Therefore, as shown in FIG. 3(b), even if the upper arm switching element S1 changes from the on state to the off state (during dead time), the actual voltage does not instantly become zero during the dead time Td2 due to the discharge operation of the parasitic capacitance via the capacitor, but rather the voltage transitions to zero with a slope. In this case, the flowing current 10 is greater than the predetermined current threshold Ith. Note that a dead time compensation method for such a case is disclosed in the above-mentioned Patent Document 1.

However, when the flowing current 10 is smaller than a predetermined current threshold Ith, as shown in FIG. 3(c), during the dead time Td2, the voltage slope becomes gentler, and even if the switching element S1 changes from the on state to the off state, the discharge operation of the parasitic capacitance is not completed during the dead time, and the voltage does not transition to zero. In this state, when the switching element S2 turns on and the dead time ends, it becomes grounded and the output voltage becomes zero.

As explained above, during the dead time period, the output voltage changes depending on whether the magnitude of the current 10 is greater than or less than a predetermined current threshold Ith.

(Figure 4)
A problem that occurs during the dead time of the switching elements when a current 20 (current polarity is negative) flows from the electric motor 700 to the power conversion device 500 will be described. Note that Fig. 4(a) shows an upper and lower arm series circuit for one phase of a three-phase AC inverter included in the power conversion device 500.

Figure 4(b) is a diagram showing the relationship between the switching operation and the voltage when the current 20 (positive polarity of the current) flowing from the motor 700 in Figure 1 to the upper and lower arm series circuits in Figure 4(a) is greater than a predetermined current threshold Ith. Figure 4(c) is a diagram showing the relationship between the switching operation and the voltage when the current 20 is less than the predetermined current threshold Ith.

When the lower arm switching element S2 changes from the on state to the off state and the upper arm switching element S1 is in the off state (during dead time), the potential at point P is zero, so the capacitance component (parasitic capacitance) connected in parallel to the switching element S1 is in a state where no charge has accumulated. Therefore, as shown in Figure 4 (b), during the dead time Td1, the actual output voltage does not rise instantly due to the charging operation of the parasitic capacitance, but transitions with a slope. In this case, the flowing current 20 is greater than a predetermined current threshold Ith.

However, as shown in FIG. 4(c), when the current 20 is smaller than a predetermined current threshold Ith, the voltage slope becomes gentler, so that the charging operation of the parasitic capacitance does not complete during the dead time Td1, and the voltage does not fully rise. In this case, when the switching element S1 is turned on and the dead time ends, the DC power supply 900 is connected, and the output voltage becomes Vdc.

As explained above, even when the current 20 flows from the motor 700 to the power conversion device 500 (current polarity is negative), the output voltage changes during the dead time period depending on whether the magnitude of the current 10 is greater than or smaller than a predetermined current threshold Ith (depending on the magnitude and polarity of the phase current). Therefore, it is desirable to use the phase current value when a voltage is being output to calculate the dead time compensation amount for the power conversion device 500.

The present invention performs dead time compensation by taking into account the output voltage when the current is smaller than a predetermined current threshold Ith. This makes it possible to suppress the output voltage error of the power conversion device 500 and improve the accuracy and responsiveness of the torque control of the electric motor 700.

As mentioned above, whether the charging and discharging of the parasitic capacitance is completed during the dead time is determined by a certain current threshold Ith. The slope of the voltage affected by the parasitic capacitance C can be expressed by the following equation (4).

(Voltage slope) = i/C...Equation (4)

Therefore, the current value at which the voltage with the slope of equation (4) transitions from zero to voltage Vdc or from voltage Vdc to zero during the dead time Td can be expressed as a predetermined current threshold Ith by the following equation (5).

Ith=C×Vdc/Td...Formula (5)

The current threshold calculation unit 1200 (Figure 2) of the dead time compensation unit 1000 calculates the predetermined current threshold Ith expressed by equation (5), and outputs the calculated predetermined current threshold Ith to the compensation amount calculation unit 1300 to reflect it in the calculation, thereby making it possible to compensate for the voltage error caused by the dead time in the power conversion device 500 with high accuracy.

(Figure 5)
The compensation amount calculation unit 1300 of the dead time compensation unit 1000 includes U phase compensation amount calculation switching processing 1310U, U phase voltage error averaging processing 1320U, V phase compensation amount calculation switching processing 1310V, V phase voltage error averaging processing 1320V, W phase compensation amount calculation switching processing 1310W, and W phase voltage error averaging processing 1320W. The compensation amount calculation unit 1300 executes these processes to output dead time compensation amounts dVu, dVv, and dVw to the calculation means 400. Note that the calculation method of the compensation amount calculation unit 1300 is the same for the U, V, and W phases, so the following description will be given taking the calculation of the U phase as an example.

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

As mentioned above, the voltage characteristics change depending on the magnitude relationship between the current threshold Ith and the phase current command value Iu*, so the U-phase compensation amount calculation switching process 1310U switches the calculation method for the dead time compensation amount depending on the magnitude relationship between the current threshold Ith and the phase current command value Iu*.

The U-phase compensation amount switching process 1310U determines the first U-phase compensation amount dVu1 based on the current threshold Ith and the phase current command value Iu*, for example, using the following formulas (6) to (8). Formulas (6) to (8) describe the difference in area of the output voltage relative to the ideal voltage, divided according to the magnitude relationship between the U-phase current command Iu* and the current threshold Ith. The first formula (6) is used when Ith<Iu*, the second formula (7) is used when -Ith<Iu*<Ith, and the third formula (8) is used when Iu*<Ith. Note that the second formula (7) includes the first current threshold -Ith and the second current threshold Ith as current thresholds.

dVu1=Td×Vdc-C/2/Iu*×Vdc×Vdc...Formula (6)

dVu1=Iu*/2/C×Td×Td...Formula (7)

dVu1=-Td×Vdc-C/2/Iu*×Vdc×Vdc...Formula (8)

In this way, the calculation method is switched depending on the relative magnitude of the U-phase current command Iu* and the current threshold Ith, so dead-time compensation can be performed for the power conversion device 500, reflecting whether or not the charging and discharging operation of the parasitic capacitance is completed during the dead time.

The U-phase voltage error averaging process 1320U calculates the compensation amount dVu to be reflected in the voltage command Vu* (Figure 1) from the input first U-phase compensation amount dVu1. Since the first U-phase compensation amount dVu1 is the difference in area between the ideal voltage and the actual voltage, when reflecting it in the voltage command and performing compensation, the compensation amount per PWM cycle can be obtained by averaging over one cycle in which the PWM is executed. For example, in a PWM based on a comparison between a triangular wave and a voltage command, the U-phase voltage error averaging process 1320U is a process that multiplies by the frequency fc of the triangular wave.

The compensation amount calculation switching process shown in this embodiment does not necessarily have to be in the form of equations (6) to (8) and may be, for example, a lookup table with a phase current command as an argument. In addition, in the case of a system in which the frequency fc of the triangular wave is variable, the configuration may be such that the value of frequency fc is reflected each time and adjusted to the operating state of the power conversion device 500.

As described above, the present invention calculates the current threshold Ith representing the charge/discharge operation 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, which is the input voltage of the power conversion device, and reflects the calculated current threshold Ith 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 makes it possible to highly accurately compensate for the output voltage error when a small current is flowing, and to improve the motor torque accuracy and responsiveness.

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

The d-axis current estimation unit 1110 transmits the operator, based on the d-axis current command Id*, as the d-axis current estimate Id^ to the coordinate conversion unit 1160, which performs calculations using the above-mentioned equations (1) to (3). Similarly, the q-axis current estimation unit 1120 transmits the operator, based on the q-axis current command Iq*, as the q-axis current estimate Iq^ to the coordinate conversion unit 1160, which performs calculations using the above-mentioned equations (1) to (3). The d-axis current estimation unit 1110 and the q-axis current estimation unit 1120 are configured, for example, by first-order lag filters.

The current control unit 300 (Fig. 1) performs vector control so that the actual dq-axis currents Id, Iq have a predetermined response to the input dq-axis current commands Id*, Iq*, and by using this, the d-axis current estimation unit 1110 and the q-axis current estimation unit 1120 are provided with characteristics that simulate the response of the actual dq-axis currents Id, Iq to the dq-axis current commands Id*, Iq*. This makes it possible to estimate the actual dq-axis currents Id, Iq.

The speed calculation unit 1130 uses the rotation angle (electrical angle) θ of the electric motor 700 as an input signal to calculate the electric angular velocity ω of the electric motor 700 and transmits it to the phase compensation unit 1140. The speed calculation unit 1130 may be configured to perform, for example, differential calculation processing to calculate the electric angular velocity ω of the electric motor 700. Note that if there is concern that the differential calculation will amplify noise, a configuration may be used in which a filter is applied to remove noise components.

The phase compensation unit 1140 calculates the phase compensation amount dθ using the electrical angular velocity ω calculated by the velocity calculation unit 1130, and transmits the calculated phase compensation amount dθ to the calculation means 1150. The phase compensation amount dθ is a compensation amount that compensates for the rotation angle when the voltage reflecting the voltage commands Vu*, Vv*, and Vw* is output from the power conversion device 500 to the electric motor 700 based on the detected rotation angle θ.

For example, in the control device 100, if there is a time lag of K x Tc (K is a constant, and Tc is the control period of the control device 100) between the detection of the rotation angle θ and the voltage output of the power conversion device 500, the rotation angle at the time of the voltage output will be ahead of the detected rotation angle θ by dθ = ω x K x Tc. The phase compensation amount dθ compensates for this difference.

The calculation means 1150 reflects the phase compensation amount dθ input from the phase compensation unit 1140 in the input rotation angle θ, calculates the compensated rotation angle θcmp when the power conversion device 500 outputs a voltage to the electric motor 700, and outputs the calculated compensated rotation angle θcmp to the coordinate conversion unit 1160.

The coordinate conversion unit 1160 calculates the phase current commands Iu*, Iv*, and Iw* by performing processing similar to that of the above-mentioned equations (1) to (3) based on the input signals, d-axis current estimate Id^, q-axis current estimate Iq^, and compensated rotation angle θcmp, and outputs the calculated phase current commands Iu*, Iv*, and Iw* to the compensation amount calculation unit 1300 (Figure 2).

This configuration makes it possible to calculate the average value of the phase current when the power conversion device 500 is outputting voltage to the electric motor 700, thereby achieving temporal consistency between the voltage output and the current value, and enabling more accurate dead-time compensation calculations. In addition, for the phase current value when voltage is being output, which is used to calculate the dead-time compensation amount, there is generally a time difference between the timing of current detection and voltage output, so if the current detection value or the dq-axis current command value is used as is to set the phase current command value, dead-time compensation becomes inappropriate; however, this problem can be prevented by the above-mentioned configuration.

The phase current command calculation unit 1100 of the dead time compensation unit 1000 is designed to be free from the effects of noise and current ripple in the detected current by calculating the estimated values Id^ and Iq^ from the d-axis and q-axis current commands Id* and Iq*, but it may also be configured to calculate the actual d-axis and q-axis currents Id and Iq based on the detected currents Iu, Iv, and Iw (Figure 1) directly input from the current detection means 600. In this case, the d-axis current estimation unit 1110 and the q-axis current estimation unit 1120 can be omitted.

Third Embodiment
(Figure 7)
The dead time compensation unit 1000 includes a phase current command calculation unit 1100 , a current threshold calculation unit 1200 , and a compensation amount calculation unit 1300 , as well as an electrical characteristic calculation unit 1400 and an electrical characteristic reflection unit 1500 .

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

The electrical characteristic calculation unit 1400 calculates third compensation amounts dVu3, dVv3, and dVw3 that take into account the electrical characteristics of the switching elements based on the phase current commands Iu*, Iv*, and Iw* output from the phase current command calculation unit 1100, and outputs the calculated third compensation amounts dVu3, dVv3, and dVw3 to the electrical characteristic reflection unit 1500.

The electrical characteristics of the switching element taken into account by the electrical characteristics calculation unit 1400 are described below. For example, the voltage drop component of the switching element, which is one of the electrical characteristics of the switching element, can cause an output error in the power conversion device 500, similar to dead time, and affects the accuracy and responsiveness of the torque control of the electric motor 700. The electrical characteristics calculation unit 1400 calculates the compensation amount taking into account the electrical characteristics of the switching element.

For example, when the electrical characteristic calculation unit 1400 calculates the electrical characteristics of a switching element based on the phase current command Iu*, if the on-resistance Ron of the switching element is used, the voltage drop in the switching element can be expressed as Ron x Iu*. In addition, if the on-resistance Rdiode of the freewheeling diode connected in inverse parallel to the switching element is used for calculation, the voltage drop can be expressed as Rdiode x Iu*. Note that, since the switching element or the freewheeling diode is either turned on or off depending on the polarity of the current, the electrical characteristics are calculated taking into account the polarity of the phase current command Iu*.

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

In this way, by performing dead time compensation taking into account the electrical characteristics of the switching elements, the output voltage error of the power conversion device 500 can be further reduced, improving the accuracy and responsiveness of the torque control of the electric motor 700.

(Figure 8)
Control device 100 having the configuration of the present invention can be applied to an electric vehicle 1600. Electric vehicle 1600 has a motor drive system 1B1 including a motor 700, an inverter 500, and control device 100, and a power generation motor drive system 1B2 having a similar configuration.

A differential gear 611, which is a power distribution mechanism, is provided in the center of the front axle, and the engine 610 or the motor 700 distributes the rotational driving force transmitted through the transmission 612 to the left and right front axles. The engine 610 and the motor 700 have a mechanism that allows them to be mechanically connected/separated using a mechanism implemented in the transmission 612. Therefore, it is possible to selectively switch between a series hybrid mode in which the engine 610 and the motor 700 are mechanically connected and only the mechanical output of the motor 700 is transmitted to the differential gear 611 to run the vehicle, and a parallel hybrid mode in which the mechanical outputs of the engine 610 and the motor 700 are combined and transmitted to the differential gear 611 to run the vehicle. As a result, the electric vehicle 1600 can arbitrarily switch between the series hybrid mode and the parallel hybrid mode according to the driving scene, such as driving in urban areas or on a highway, thereby achieving both vehicle dynamics and vehicle range.

The inverter 500 converts the DC power supplied from the battery 900 into three-phase AC power according to 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. This causes the rotor of the motor 700 to rotate, generating a rotational driving force according to the three-phase AC power (current). The rotor of the motor 700 is also driven to rotate by the mechanical output from the engine 610. This generates three-phase AC power in the stator coil of the motor 700, which is input to the inverter 500. The inverter 500 converts the three-phase AC power input from the motor 700 into DC power according to the control of the control device 100, and charges the high-voltage battery 900.

The electric vehicle 1600 to which the configuration of the present invention is applied is not limited to hybrid vehicles, but can also be applied to plug-in hybrid vehicles, electric vehicles, etc., and the same effects can be obtained in these cases as well.

The above-described embodiment of the present invention provides the following advantages:

(1) A control device 100 that generates a voltage command for a power conversion device 500 that drives an electric motor 700 and controls the electric motor 700 includes a current threshold calculation unit 1200 that calculates a current threshold based on the dead time of the power conversion device 5000, the parasitic capacitance of the switching elements of the power conversion device 500, and the DC voltage input to the power conversion device 500, a phase current command calculation unit 1100 that calculates a phase current command to the electric 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 for the voltage command is performed based on the dead time compensation amount. In this way, the torque accuracy and responsiveness of the electric motor control are improved.

(2) The compensation amount calculation unit 1300 switches the calculation method of the dead time compensation amount based on the relationship between the phase current command and the current threshold. In this way, it is possible to highly accurately compensate for the output voltage error when a small current is flowing.

(3) When the phase current command value is greater than the current threshold, the compensation amount is calculated using the first formula. In this way, the output voltage error when a small current is flowing can be compensated for with high accuracy.

(4) The current threshold includes a first current threshold and a second current threshold, and 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 formula. In this way, the output voltage error when a small current is flowing can be compensated for with high accuracy.

(5) When the phase current command value is smaller than the current threshold, the compensation amount is calculated using the third formula. In this way, the output voltage error when a small current is flowing can be compensated with high accuracy.

(6) The phase current command calculation unit 1100 calculates the average value of the phase current at the time when the power conversion device 500 outputs a voltage based on the electrical angle of the electric motor 700, the electrical angular velocity of the electric motor 700, and the dq-axis current commands of the electric motor 700. By doing so, the voltage output and the current value are time-consistent, and the dead-time compensation calculation can be performed with higher accuracy.

(7) The compensation amount calculation unit 1300 corrects the electrical characteristics of the switching element to the dead-time compensation amount and calculates the corrected dead-time compensation amount. In this way, the output voltage error of the power conversion device 500 can be further reduced.

(8) An electric vehicle 1600 equipped with the above-described control device 100 is adopted. In this way, an electric vehicle 1600 with improved torque accuracy and responsiveness of the electric motor control can be provided.

The present invention is not limited to the above-described embodiment, and various modifications and other configurations can be combined without departing from the spirit of the invention. Furthermore, the present invention is not limited to those having all of the configurations described in the above-described embodiment, and also includes those in which some of the configurations have been omitted.

REFERENCE SIGNS LIST 100 Control device 200 Dq-axis current command generating unit 300 Current control unit 400 Calculation means 500 Power conversion device 600 Current detection means 700 Electric motor 800 Position detection means 900 DC power supply 1000 Dead time compensation unit 1100 Phase current command calculation unit 1200 Current threshold calculation unit 1300 Compensation amount calculation unit 1400 Electrical characteristic calculation unit 1500 Electrical characteristic reflection unit 1600 Electric vehicle

Claims (8)

2. A control device that generates a voltage command for a power conversion device that drives an electric motor and controls the electric motor,
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 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;
a compensation amount calculation unit that calculates a dead time compensation amount based on the phase current command and the current threshold value,
The control device corrects the voltage command based on the dead time compensation amount. 2. The control device according to claim 1,
The compensation amount calculation unit switches a method of calculating the dead time compensation amount based on a relationship between the phase current command and the current threshold. 3. The control device according to claim 2,
When the value of the phase current command is greater than the current threshold value, the control device calculates the dead time compensation amount by a first equation. 3. The control device according to claim 2,
the current thresholds include a first current threshold and a second current threshold;
the control device calculating the dead time compensation amount by a second equation when the value of the phase current command is greater than the first current threshold and smaller than the second current threshold. 3. The control device according to claim 2,
When the value of the phase current command is smaller than the current threshold value, the control device calculates the dead time compensation amount by a third equation. 2. The control device according to claim 1,
The phase current command calculation unit calculates an average value of a phase current 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. 2. The control device according to claim 1,
The compensation amount calculation unit corrects the dead-time compensation amount for an electrical characteristic of the switching element, and calculates the corrected dead-time compensation amount. An electric vehicle equipped with a control device according to any one of claims 1 to 4.

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