Inverter control device, electric vehicle system

Abstract

The inverter control device of the present application reduces the DC component, current ripple of the inverter output current generated in the vicinity of the zero-crossing region. The inverter control device (200) includes a PWM control section (220) that generates a PWM pulse for controlling an inverter (100), and a pulse edge control section (250) that performs pulse edge control that corrects (shifts) the phase of the pulse edge of the PWM pulse generated by the PWM control section (220). The PWM control section (220) generates the PWM pulse based on the modulation rate of the voltage command (Vd*, Vq*). The pulse edge control section (250) corrects the PWM pulse so that the phase difference between the zero-crossing point at which the modulation wave changes across 0 and the pulse edge of the PWM pulse is within a prescribed range.

Description

Technical Field

[0001] The present invention relates to an inverter control device and an electric vehicle system utilizing the inverter control device. Background Technology

[0002] Inverter control devices that drive a motor to rotate by controlling the inverter using PWM (Pulse Width Modulation) are widely used. In such inverter control devices, a technique is known where, to achieve high motor rotation speed, the inverter operates in an overmodulation mode (overmodulation region) where the output voltage command exceeds the inverter's maximum output level (sine wave), and simultaneously, to further increase the output voltage, it operates in a single-pulse mode (single-pulse region) where the PWM pulse train is connected into a single pulse.

[0003] When the inverter control device switches from the overmodulation region to the single-pulse region, a voltage error is generated in the inverter output. This increases the DC component and pulsation component in the inverter output current, resulting in fluctuations in the motor's output torque and noise vibration. Therefore, a technology is needed to suppress the voltage error during the transition from the overmodulation region to the single-pulse region and to reduce the DC component and pulsation component of the current.

[0004] Regarding the reduction of current ripple in the overmodulation region, the technology of Patent Document 1 is known. Patent Document 1 describes an inverter device that generates PWM pulses when performing trapezoidal wave modulation using a trapezoidal wave in the overmodulation region, such that the values ​​obtained by integrating the areas of the on-state and off-state pulses of multiple PWM pulses in the inverted region of the modulation wave that varies from the bottom edge to the top edge of the trapezoidal wave are equal. Existing technical documents Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2015-19458 Summary of the Invention The technical problem that the invention aims to solve

[0006] In the technology of Patent Document 1, the timing of the zero-crossing point and the timing of the PWM pulse edge cannot be properly controlled in the region near the zero-crossing point, including the zero-crossing point where the modulated wave changes across 0. Therefore, the inverter's output voltage will have errors, and the DC component and current ripple in the inverter's output current may increase. Technical solutions adopted to solve technical problems

[0007] The inverter control device of the present invention includes: a PWM control unit that generates a PWM pulse for controlling the inverter using a modulation rate based on a voltage command; and a pulse edge control unit that corrects the PWM pulse such that the phase difference between the zero-crossing point of the modulation wave and the pulse edge of the PWM pulse is within a specified range. The electric vehicle system of the present invention includes an inverter control device, an inverter controlled by the inverter control device, and a three-phase synchronous motor driven by the inverter, wherein the electric vehicle system uses the rotational driving force of the three-phase synchronous motor to travel. Invention Effects

[0008] According to the present invention, it is possible to reduce the DC component and current ripple of the inverter output current generated in the region near zero crossing. Attached Figure Description

[0009] Figure 1 This is a block diagram illustrating the structure of a motor device having an inverter control device according to one embodiment of the present invention. Figure 2 It is a waveform diagram representing the modulated wave in one implementation. Figure 3 This is an illustrative diagram illustrating an example of pulse edge control in one implementation method. Figure 4 This is a flowchart illustrating the PWM pulse generation and pulse edge control process in one implementation. Figure 5 This is an illustrative diagram of another example of pulse edge control in one implementation. Figure 6 This is a structural diagram of an electric power steering system that utilizes an inverter control device. Figure 7 This is a structural diagram of an electric vehicle that utilizes an inverter control device. Detailed Implementation

[0010] This invention provides an inverter control device that controls the inverter using PWM control. In the overmodulation region where the modulation rate is above a specified value, for example, when using trapezoidal wave modulation (which transforms a sine wave into a trapezoidal wave as the modulating wave), the pulse edge of the output PWM pulse ensures that the phase difference between the output PWM pulse and the zero-crossing point of the modulating wave is within a specified range. This reduces the DC component and pulsation component of the inverter's output current, while simultaneously maximizing the inverter's output. An embodiment of this invention will now be described using the accompanying drawings.

[0011] Figure 1This is a block diagram showing the structure of a motor unit 1 having an inverter control device 200 according to one embodiment of the present invention. The motor unit 1 is connected to a battery 2 and includes an inverter 100, an inverter control device 200, and a motor 300.

[0012] Battery 2 is the DC voltage source for inverter 100. The DC voltage DCV of battery 2 is converted into a three-phase AC voltage with variable voltage and variable frequency by inverter 100 and applied to motor 300.

[0013] The motor 300 is a synchronous motor driven by a three-phase AC voltage. A rotary position sensor 320 is mounted to the motor 300 to control the phase of the three-phase AC voltage applied to the motor 300 from the inverter 100 based on the phase of the induced voltage in the motor 300. Here, the rotary position sensor 320 can be, for example, a rotary transformer consisting of an iron core and windings. Alternatively, a GMR sensor or a Hall element can be used to construct the rotary position sensor 320.

[0014] The inverter control device 200 includes a current control unit 210, a PWM control unit 220, a pulse edge control unit 250, a drive signal generation unit 260, a rotational position detection unit 270, and a current detection unit 280.

[0015] The rotational position detection unit 270 detects the rotational position θ of the rotor in the motor 300 based on the output signal of the rotational position sensor 320.

[0016] The current detection unit 280 acquires the three-phase current detection values ​​(Iu, Iv, Iw) flowing through the motor 300 from the current sensor Ict, and performs a three-phase / two-phase conversion on these current detection values ​​based on the rotational position θ detected by the rotational position detection unit 270, thereby obtaining the current detection values ​​(Id, Iq) of the dq axis.

[0017] The inverter control unit 200 has a current control function for controlling the output of the motor 300. The current control unit 210 outputs voltage commands (Vd*, Vq*) so that the current detection values ​​(Id, Iq) detected by the current detection unit 280 are consistent with the current command values ​​(Id*, Iq*) input by the upper controller (not shown).

[0018] The PWM control unit 220 uses the voltage commands (Vd*, Vq*) obtained by the current control unit 210, the DC voltage DCV of the battery 2, and the rotational position θ to implement three-phase pulse width modulation (PWM) and generate PWM pulses for controlling the inverter 100. Specifically, the PWM control unit 220 performs two-phase / three-phase conversion on the voltage commands (Vd*, Vq*) based on the rotational position θ to generate three-phase voltage commands (Vu*, Vv*, Vw*). Then, it calculates the modulation rate based on the voltage commands (Vd*, Vq*) or the three-phase voltage commands (Vu*, Vv*, Vw*) and the DC voltage DCV of the battery 2, and uses the modulation rate and a carrier signal of a predetermined frequency to generate a modulated wave corresponding to the modulation rate. At this time, in the region where the modulation rate is less than a predetermined value, for example, less than 1.15, the PWM control unit 220 performs normal PWM modulation by comparing the carrier signal and the modulating wave to generate PWM pulses, and in the region where the modulation rate is above the predetermined value, for example, above 1.15, trapezoidal wave modulation is performed, using a trapezoidal wave as the modulating wave. Details of trapezoidal wave modulation will be explained later.

[0019] The pulse edge control unit 250 performs pulse edge control, which corrects (shifts) the phase of the pulse edge of the PWM pulse generated by the PWM control unit 220. Through this pulse edge control, the PWM pulse is adjusted so that the phase difference between the zero-crossing point of the modulating wave and the pulse edge of the PWM pulse is within a specified range. Furthermore, the zero-crossing point of the modulating wave is the point where the modulating wave changes across zero. The method for adjusting the PWM pulse performed by the pulse edge control unit 250 will be described in detail later.

[0020] The drive signal generation unit 260 converts the PWM pulse obtained by correcting the phase of the pulse edge through pulse edge control performed by the pulse edge control unit 250 into a drive signal DR, and outputs the drive signal DR to the inverter 100. The inverter 100 has multiple semiconductor switching elements corresponding to each phase of the three-phase AC voltage, and each semiconductor switching element is turned on / off controlled by the drive signal DR. Therefore, the output voltage of the inverter 100 is adjusted according to the control of the inverter control device 200.

[0021] In addition, in the above, through Figure 1 This paper describes a structural example of a motor device 1 that controls the current of motor 300 according to a current command from a host controller. However, it is also possible to apply this method even when other control methods are used. Figure 1The structure is as follows. For example, when controlling the rotational speed of motor 300, the motor speed ωr is calculated based on the time change of the rotational position θ, and a voltage command or current command is generated to match the speed command from the upper controller. Additionally, when controlling the output torque of motor 300, a current command (Id*, Iq*) is generated using the relationship or mapping between the motor current (Id, Iq) and the motor torque.

[0022] Next, use Figure 2 The diagram illustrates a waveform of the modulated wave in one embodiment of the present invention. Furthermore, the following describes a PWM modulation operation that generates a PWM pulse by comparing the modulated signal waveform with a triangular carrier signal; however, in trapezoidal wave modulation, where a trapezoidal wave that at least transforms a sine wave into a trapezoid is used as the modulated wave, it is preferable to generate the PWM pulse (described later) through direct computation.

[0023] Figure 2 (a) Examples of modulation signal waveforms and carrier signal waveforms are shown. In the modulation signal waveforms, waveforms are shown for a modulation signal with a relatively low modulation rate (modulation wave 1), the largest modulation wave capable of sinusoidal modulation (modulation wave 2), a trapezoidal modulation wave approximating a straight line of sinusoidal modulation (modulation wave 3), and a modulation wave that becomes the largest rectangular wave at the inverter output (modulation wave 4). In the carrier signal waveforms, a triangular wave carrier signal is shown that is compared in magnitude with the modulation wave signal to generate PWM pulses.

[0024] Figure 2 (b) represents the PWM pulse signal when modulating wave 2. Figure 2 (c) represents the PWM pulse signal when modulating wave 3. Figure 2 In (c), almost 100% of the PWM pulses are continuously turned on in the range of electrical angles of 30 to 150 degrees. Figure 2 (d) represents the PWM pulse signal of modulation wave 4. This PWM pulse signal is turned on throughout the entire electrical angle range of 0 to 180 degrees.

[0025] Each modulation wave is equivalent to a one-phase modulation wave H(θ) of the three-phase voltage command (Vuc, Vvc, Vwc). If the dead time is ignored, it is almost equal to the U-phase modulation wave Hu(θ) = Vuc / (DCV / 2). If the effective value of the sine wave with a modulation rate of 1 when the inverter output is unsaturated is set to 1, then the fundamental component contained in the modulation wave H(θ) with the superimposed third harmonic is 1.15 times (115%) (modulation wave 2). That is, the inverter output is unsaturated until the voltage command with a modulation rate of 1.15 is reached.

[0026] like Figure 2As shown, the modulation wave H(θ) that overlaps with the third higher harmonic can be approximated as a straight line near its zero crossing. Furthermore, the higher the modulation rate, the closer the modulation wave H(θ) becomes to a trapezoidal wave like modulation wave 3, instead of the shape of modulation wave 2. Therefore, in the region where the modulation rate is above a specified value, for example, 1.15 or higher, a PWM pulse can be generated through computation by using a trapezoidal wave like modulation wave 3. This simplifies PWM modulation processing using a microcomputer, and simultaneously allows control of voltage errors in the PWM pulse caused by the asynchrony between the modulation wave H(θ) and the carrier signal. In this case, the computation period of the PWM pulse corresponds to the period of the carrier signal.

[0027] In addition, considering that when the modulation wave is 2, a linear approximation can be made for the angle range of ±30 degrees with the zero crossing of the modulation wave as the center, but considering the voltage error near saturation, it is preferable to set the angle range of ±35 degrees.

[0028] In PWM pulse operation using trapezoidal wave modulation, the slope A of the modulated wave in the interval near zero that can be approximated by a straight line is proportional to the modulation rate corresponding to the voltage command value, and the modulated wave is proportional to the angular position θ. For example, if the angle near the zero crossing is set as θ', and θ' is set as -30≤θ'≤30, then the modulated wave H(θ') near the zero crossing can be represented by equation (1). H(θ')=A·θ' (1)

[0029] That is, since the modulation wave H(θ) near the zero crossing can be represented by the slope A of the modulation wave instead of the modulation rate, the inverter output pulse near the zero crossing, i.e. the PWM pulse, can be determined by the slope A of the modulation wave.

[0030] In addition, under the condition that |H(θ)|<|A·θ|, when 0<θ<180, the inverter output pulse is determined to be 100%, and when 180<θ<360, the inverter output pulse is determined to be 0%.

[0031] Next, use Figure 3 This section describes an example of pulse edge control in one embodiment of the present invention.

[0032] Figure 3 (a) shows a normalized modulated waveform of a portion of a modulated wave containing zero crossings. Figure 3 (a) shows a normalized modulated wave that is a modified trapezoidal wave ( Figure 2 (a) The modulated wave 3) The normalized modulated wave, whose magnitude varies from 0% to 100%. The point where the normalized modulated wave magnitude is 50% represents the zero-crossing point of the modulated wave.

[0033] Figure 3(b) shows the results of Figure 1 The PWM control unit 220 generates PWM pulses. The PWM control unit 220 is based on... Figure 3 (a) The duty cycle of the PWM pulse is determined by the area of ​​the normalized modulation wave in each period of the carrier signal shown. The PWM pulse corresponding to this duty cycle is calculated, thereby generating the PWM pulse. Figure 3 The PWM pulse shown in (b). Additionally, in Figure 3 In (a), the carrier signal of the triangular wave is shown by dashed lines. However, as mentioned above, when the PWM pulse is directly calculated without using the carrier signal, its calculation period is equivalent to the period of the carrier signal. Hereinafter, the calculation period of the PWM pulse and the period of the carrier signal will be referred to as the "PWM period".

[0034] For example, time TH1 is the timing of the zero-crossing point where the modulated wave reverses from negative to positive. In the PWM period that includes this zero-crossing point, i.e., the interval from time T1 to time T2, the area of ​​the normalized modulated wave is 25%, and a PWM pulse with a duty cycle of 25% is generated accordingly.

[0035] The interval from time T2 to time T3 corresponds to the upper base of the trapezoidal wave, during which the magnitude of the normalized modulated wave remains unchanged from 100%. This indicates that the modulated wave is in saturation. During this interval, the duty cycle of the PWM pulse is 100%.

[0036] Time TL1 is the timing of the zero-crossing point where the modulated wave reverses from positive to negative. In the PWM period that includes this zero-crossing point, i.e., the interval from time T3 to time T4, the area of ​​the normalized modulated wave is 70%, and a PWM pulse with a duty cycle of 70% is generated accordingly.

[0037] Figure 3 (c) shows that in Figure 1 In the pulse edge control performed by the pulse edge control unit 250, pulse shifting is performed by shifting the phase of the pulse edge in accordance with the zero-crossing point. The pulse edge control unit 250 shifts the pulse edge of each PWM pulse generated corresponding to each PWM cycle, specifically those corresponding to the PWM cycle including the zero-crossing point, so that the phase of the pulse edge is aligned with the zero-crossing point. Figure 3 The shift is performed as shown in (c). At the zero-crossing point where the modulating wave reverses from negative to positive, the PWM pulse is shifted so that the rising edge of the PWM pulse is in phase with the zero-crossing point. Similarly, at the zero-crossing point where the modulating wave reverses from positive to negative, the PWM pulse is shifted so that the falling edge of the PWM pulse is in phase with the zero-crossing point. This corrects the PWM pulse so that the phase difference between the zero-crossing point of the modulating wave and the pulse edge of the PWM pulse is within a specified range.

[0038] Furthermore, the aforementioned range is set, for example, based on the phase range corresponding to the dead time of the inverter 100. During the dead time, the actual output voltage of the inverter 100 varies depending on the conduction state of the freewheeling diode of the inverter 100. Therefore, in order to reduce the computational load on the inverter control device 200 implemented by a microcomputer or the like, the control logic of the pulse edge control unit 250 is preferably simplified by setting the phase error range of the pulse edge shifted relative to the zero-crossing point to a phase range equivalent to the dead time.

[0039] Generally, PWM pulse generation is performed using a microcomputer's comparator-matched timer. In PWM pulse operation using trapezoidal wave modulation, a timer value corresponding to the duty cycle of the PWM pulse to be generated is set in the comparator-matched timer, and a reset signal is output from the comparator-matched timer at the specified timer value. At this time, by inverting the level of the reset signal during the rise and fall of the PWM pulse, PWM pulses can be generated with arbitrary phase and duty cycle. In such PWM pulse operation, pulse shifting performed by the pulse edge control unit 250 can be achieved by changing the set timer value in accordance with the zero-crossing point.

[0040] Here, in the interval from time T1 to time T2, such as Figure 3 As shown in (c), the pulse edge of the PWM pulse can be shifted in sync with the zero-crossing timing TH1. In this case, by integrating the shifted PWM pulse with the PWM pulse of the next PWM cycle, the number of PWM pulses contained in one cycle of the modulated wave is reduced.

[0041] On the other hand, in the interval from time T3 to time T4, even if the pulse edge of the PWM pulse with a duty cycle of 70% is made to coincide with the timing TL1 of the zero-crossing point, the phase difference between the zero-crossing point and the pulse edge does not converge to the range specified above, but instead produces a portion exceeding that range. Figure 3 (c) The pulse error Te). Therefore, the positive voltage error equivalent to the pulse error Te overlaps with the PWM signal. That is, with Figure 3 (a) The ideal positive-direction PWM pulse corresponding to one cycle of such a trapezoidal modulated wave is the pulse (Hi signal) from the timing TH1 of the zero-crossing point where the modulated wave reverses from negative to positive to the timing TL1 of the next zero-crossing point where the modulated wave reverses from positive to negative. However, Figure 3 (c) The pulse width of the positive pulse is wider than the ideal PWM pulse by an amount equivalent to the pulse error Te. Therefore, as the output voltage of the inverter 100, an excessive voltage is applied to the motor 300. On the other hand, with Figure 3(a) The ideal PWM pulse in the negative direction corresponding to one cycle of such a trapezoidal modulated wave is the pulse (Lo signal) from the timing TL1 of the zero-crossing point of the modulated wave from positive to negative to the timing (not shown) of the next zero-crossing point of the modulated wave from negative to positive. However, Figure 3 (c) The pulse width of the negative pulse is narrower than that of an ideal PWM pulse by an amount equivalent to the pulse error Te. Therefore, the negative voltage in the output voltage of inverter 100 is insufficient compared to the original voltage. For these reasons, Figure 3 (c) shows that the PWM pulse after pulse shifting is the reason why the overall output voltage of inverter 100 is shifted in the positive direction.

[0042] As explained above, the pulse error Te in the shifted PWM pulse is the cause of the voltage offset that causes the overall output voltage of inverter 100 to shift in the positive direction. This voltage offset causes an error in which the DC current component overlaps with the output current of inverter 100. In particular, in the overmodulated state, the effect of the voltage offset tends to be greater due to the reduced number of pulses, and the DC component contained in the output current of inverter 100 becomes the cause of large torque ripple in motor 300. Therefore, eliminating the pulse error Te caused by PWM pulse shifting is an important issue for reducing the DC component and current ripple of the inverter output current generated in the region near zero crossing.

[0043] Figure 3 (d) shows that Figure 1 This is an example of a cyclic pulse shift in pulse edge control performed by the pulse edge control unit 250, which separates and configures the pulse error Te. While maintaining a 70% duty cycle for the PWM pulse during the interval from time T3 to time T4, the pulse edge control unit 250 separates the pulse error Te from the shifted PWM pulse to ensure the pulse edge of the PWM pulse is in phase with the zero-crossing point, and configures it in other phases during the interval from time T3 to time T4. Specifically, as... Figure 3 As shown in (d), a PWM pulse (Hi signal) with a pulse width equivalent to the pulse error Te exceeding the zero crossing point is generated, and the shift amount is set so that the phase of its falling edge is configured to be consistent with time T4. Therefore, these PWM pulses can be cyclically configured within one PWM cycle, so that the total duty cycle of the PWM pulses from time T3 to the zero-crossing timing TL1 and up to time T4 is 70%.

[0044] By performing the cyclic pulse shifting as described above, the pulse error Te is eliminated, thus preventing voltage offset in the output voltage of the inverter 100. As a result, the DC component and current ripple of the inverter output current generated in the region near zero crossing can be reduced.

[0045] In the pulse edge control unit 250, by performing pulse edge control, including the pulse shift described above, on the PWM pulse generated by the PWM control unit 220, the output voltage of the inverter 100 can be controlled according to the timing of the zero-crossing point in asynchronous PWM control, from the overmodulation region using a trapezoidal modulation wave to the single-pulse region that becomes a rectangular wave output. This enables the suppression of torque ripple.

[0046] Furthermore, in the pulse edge control unit 250, cyclic pulse shifting as described above is performed as needed in pulse edge control. Therefore, within one PWM cycle, a PWM pulse that is timed synchronously with the zero-crossing point and whose duty cycle switches from 0% to 100% or from 100% to 0% at one edge can be mixed with a PWM pulse that is between two edges and whose duty cycle switches from 0% to 100% or from 100% to 0%. This allows for fine control of the inverter 100's output voltage from the overmodulation region to the single-pulse region.

[0047] Next, use Figure 4 This invention describes pulse edge control in one embodiment. Figure 4 This is a flowchart illustrating the process of PWM pulse generation and pulse edge control. Figure 4 The process shown in the flowchart is implemented in the inverter control device 200, for example, by executing a prescribed program via a CPU, and is performed in each prescribed operation cycle. Hereinafter, Figure 1 The PWM control unit 220 and the pulse edge control unit 250 are the main processing units, as explained below. Figure 4 The flowchart.

[0048] In step S1, the PWM control unit 220 acquires the rotational position θ of the rotor detected by the rotational position detection unit 270.

[0049] In step S2, the PWM control unit 220 calculates the modulation rate based on the voltage commands (Vd*, Vq*) input from the current control unit 210 and the DC voltage DCV of the battery 2. Additionally, the arctangent function is used to determine the voltage phase angle corresponding to the voltage commands (Vd*, Vq*).

[0050] In step S3, the PWM control unit 220 calculates the change in rotational position Δθ based on the difference between the rotational position θ obtained in step S1 during the previous calculation and the rotational position θ obtained in step S1 during the current calculation. For example, when the rotational position θ during the previous calculation is represented as θ(n-1) and the rotational position θ during the current calculation is represented as θ(n), the change in rotational position Δθ(n) can be calculated using the following formula (2). Δθ(n)=θ(n)-θ(n-1) (2)

[0051] Furthermore, the next change in rotational position Δθ(n+1) can be calculated using the following equation (3). In equation (3), α represents the acceleration of the rotational position θ. When the motor 300 rotates at a certain speed, α = 0. Δθ(n+1)=Δθ(n)+α (3)

[0052] In step S4, the PWM control unit 220 calculates the duty cycle of the PWM pulse to be output in the next PWM cycle based on the rotational position θ(n) obtained in step S1, the modulation rate calculated in step S2, and the next rotational position change Δθ(n+1) calculated in step S3. Here, for example, the rotational position θ(n+1) in the next PWM cycle is predicted based on the rotational position θ(n) and the next rotational position change Δθ(n+1), and then... Figure 2 Based on the relationship between the modulation rate and the modulation wave, the duty cycle of the PWM pulse for each phase corresponding to the rotation position θ(n+1) is calculated.

[0053] In step S5, the PWM control unit 220 sets the timer values ​​corresponding to the duty cycles obtained in step S4 into the comparison matching timers set for each phase. Thus, for each phase, the phases of the rising and falling edges of the PWM pulse before pulse edge control in the next PWM cycle are determined.

[0054] In step S6, the pulse edge control unit 250 determines whether the modulation rate calculated in step S2 is above or below a predetermined value. If the modulation rate is above or below the predetermined value, the process proceeds to step S7. On the other hand, if the modulation rate is below the predetermined value, it is determined that pulse edge control is not required, and the process ends. Figure 4 The process is shown in the flowchart. In this case, the pulse edge control unit 250 does not perform pulse edge control, but instead generates a PWM pulse corresponding to the timer value set in step S5 by comparing the matched timer.

[0055] Furthermore, the specified modulation rate used as the determination condition in step S6 is, for example, a value of 1.15 to 1.25 as an overmodulation state. Preferably, the determination condition in step S6 is set to a modulation rate of 1.24 to 1.25, in which the modulated wave reverses from 0% to 100% within one PWM cycle.

[0056] In step S7, the pulse edge control unit 250 determines whether a zero-crossing point exists in the next PWM cycle. A zero-crossing point, as described above, is the point where the modulated wave crosses 0. As described above, when the modulation rate is set to 1.24 to 1.25 as the determination condition in step S6, the modulated wave will be sandwiched between the zero-crossing point and either reverse from 0% to 100% or from 100% to 0%. If a zero-crossing point exists in the next PWM cycle, it is determined that pulse edge control is needed, and the process proceeds to step S8. On the other hand, if no zero-crossing point exists in the next PWM cycle, it is determined that pulse edge control is not needed, and the process ends. Figure 4 The process is shown in the flowchart. In this case, the pulse edge control unit 250 does not perform pulse edge control, but instead generates a PWM pulse corresponding to the timer value set in step S5 by comparing the matched timer.

[0057] In step S8, the pulse edge control unit 250 determines whether the zero-crossing direction in the next PWM cycle, i.e., the reversal direction of the modulation wave sandwiched between the zero-crossing points, is from positive (100%) to negative (0%). If the zero-crossing direction is from positive to negative, i.e., the slope of the modulation wave approximated by a straight line in the region near the zero-crossing point, including the zero-crossing point, is negative, and the modulation wave reverses from positive to negative while sandwiching the zero-crossing point in the middle, it is determined that pulse edge control to shift the PWM pulse to the left, i.e., left pulse shift, is implemented, and the process proceeds to step S9. Conversely, if the zero-crossing direction is not from positive to negative, i.e., from negative to positive, it is determined that pulse edge control to shift the PWM pulse to the right, i.e., right pulse shift, is implemented, and the process proceeds to step S10. Furthermore, the case where the zero-crossing direction is from negative to positive refers to the case where the slope of the modulation wave approximated by a straight line in the region near the zero-crossing point, including the zero-crossing point, is positive, and the modulation wave reverses from negative to positive while sandwiching the zero-crossing point in the middle.

[0058] In step S8, as explained above, the left pulse shift and right pulse shift are switched according to the zero-crossing direction. That is, the shift direction of the PWM pulse is determined based on the slope of the modulation wave obtained by approximation with a straight line in the region near the zero crossing. Thus, even when the phase of the modulation wave reverses according to the driving state of the motor 300, such as when the driving state of the motor 300 switches between power operation and regeneration, and the zero-crossing direction reverses accordingly, pulse edge control can be performed according to the same algorithm.

[0059] In step S9, the pulse edge control unit 250 performs a left pulse shift to shift the PWM pulse to the left, so that the falling edge of the PWM pulse in the next PWM cycle is timed to coincide with the zero-crossing point of the modulated wave. Here, by changing the timer value set in the comparison matching timer in step S5 in the decreasing direction, the phase of the PWM pulse is shifted to the left, so that the phase difference between the zero-crossing point of the modulated wave and the falling edge of the PWM pulse is within a specified range.

[0060] In step S10, the pulse edge control unit 250 performs a right pulse shift to shift the PWM pulse to the right, so that the rising edge of the PWM pulse in the next PWM cycle is timed to coincide with the zero-crossing point of the modulation wave. Here, the pulse shift is performed in the opposite direction to step S9. That is, by changing the timer value set in the comparison matching timer in step S5 in the increasing direction, the phase of the PWM pulse is shifted to the right, so that the phase difference between the zero-crossing point of the modulation wave and the rising edge of the PWM pulse is within a specified range.

[0061] After performing step S9 or S10, proceed to step S11.

[0062] In step S11, the pulse edge control unit 250 determines whether there is a pulse error in the shifted PWM pulse processed in step S9 or S10. If the timer value changed based on the left pulse shift in step S9 does not converge and underflows in the next PWM cycle, or if the timer value changed based on the right pulse shift in step S10 does not converge and overflows in the next PWM cycle, a pulse error is determined to exist, and the process proceeds to step S12. On the other hand, if the timer value changed based on the left pulse shift in step S9 or the timer value changed based on the right pulse shift in step S10 converges in the next PWM cycle, a pulse error is determined to exist, and the process proceeds to step S13. In this case, the cyclic pulse shifting in step S12 is not performed.

[0063] In step S12, the pulse edge control unit 250 performs the following steps to correct the pulse error in the shifted PWM pulse processed in step S9 or S10: Figure 3 (d) describes such a cyclic pulse shift. Here, the pulse error is divided from the shifted PWM pulse and configured at the end or beginning of the next PWM cycle, thereby performing the cyclic pulse shift.

[0064] Specifically, when the pulse error is configured on the end side, compared with Figure 3Similarly, in the interval from time T3 to time T4 (d), a timer value corresponding to the pulse error caused by the underflow in step S9 is set at the end of the next PWM cycle. In this case, preferably, the level of the reset signal output from the comparison matching timer is switched to high (rising), thereby causing a PWM pulse of an amount corresponding to the pulse error to rise with a predetermined phase difference based on the timing of the zero-crossing point of the modulation wave. On the other hand, when the pulse error is configured on the start side, and... Figure 3 (d) In contrast to the time interval T3 to T4, a timer value corresponding to the pulse error overflowed in step S10 is set at the beginning of the next PWM cycle. In this case, preferably, the level of the reset signal output from the comparison matching timer is switched low (falling), thereby causing the PWM pulse to fall by an amount corresponding to the pulse error with a predetermined phase difference based on the timing of the zero crossing of the modulation wave.

[0065] In step S13, the pulse edge control unit 250 reflects the processing results of step S9 or S10 and step S12, and changes the timer value set in the comparison matching timer in step S5. Alternatively, if the cyclic pulse shift in step S12 is not performed, the timer value can be changed based on the processing result of either step S9 or S10. Therefore, for the PWM pulse in the next PWM cycle calculated by the PWM control unit 220, the result of the pulse edge control performed by the pulse edge control unit 250 can be reflected, and the PWM pulse can be corrected.

[0066] In this embodiment, by performing the processing described above in the pulse edge control unit 250, the PWM pulse is corrected so that the phase difference between the zero-crossing point of the modulation wave and the pulse edge of the PWM pulse is within a specified range. Therefore, the inverter control device 200 of this embodiment can output a PWM pulse with reduced output voltage error of the inverter 100 in a control mode that transitions from the overmodulation region to the single-pulse region. As a result, it is possible to reduce the DC component or pulsation component in the output current of the inverter 100.

[0067] In addition, Figure 4 In step S12, the cyclic pulse shift can also be implemented using a different method than described above. See below for reference. Figure 5 Examples of other cyclic pulse shifts are provided.

[0068] Figure 5 This is an illustrative diagram of another example of pulse edge control in one embodiment of the present invention. Figure 5 In, with Figure 3 The same symbol represents the same action. Figure 5 In the example, Figure 5(d) shows the cyclic pulse shifting action (correction method) and Figure 3 (d) Different.

[0069] Figure 5 (d) shows that Figure 1 An example of pulse error Te in pulse edge control performed by the pulse edge control unit 250 is configured to separate the amount of pulse error Te in a cyclic pulse shift at multiple zero crossing points. This is to compensate for... Figure 5 In (c), the pulse error Te is distributed by the pulse edge control unit 250 with a pulse width of 1 / 2·Te at the timing TL1 of the zero-crossing point corresponding to the pulse error Te and the timing TH2 of the next zero-crossing point. Thus, in Figure 5 In the example, with Figure 3 The difference is that the error in the inverter output voltage caused by the pulse error Te is compensated by distributing the pulse error Te across multiple zero-crossing points within one cycle of the modulated wave.

[0070] By performing the cyclic pulse shift as described above, and Figure 3 Similarly, the pulse error Te is eliminated, thus preventing voltage offset in the output voltage of inverter 100. As a result, the DC component and current ripple of the inverter output current generated near the zero-crossing region can be reduced. Furthermore, in Figure 3 In the example, at the zero-crossing timing, it is necessary to switch the level of the reset signal output from the microcomputer's compare-match timer as described above, but... Figure 5 In the example, this switching may not be necessary. Therefore, it has the advantage of simplifying the logic installation of the pulse edge control unit 250.

[0071] In the pulse edge control unit 250 of this embodiment, the following is performed: Figure 3 or Figure 5 The pulse edge control is shown. Therefore, in the control mode from the overmodulation region to the single-pulse region, the inverter control device 200 of this embodiment can simplify the control logic installed in the microcomputer, while outputting PWM pulses that can reduce the error of the inverter 100's output voltage. Thus, it is possible to reduce the DC component or pulsation component of the inverter output current generated near the zero-crossing region.

[0072] Furthermore, while the above explanation uses asynchronous PWM as an example, synchronous PWM can also be controlled using a trapezoidal modulation wave in the same way. In synchronous PWM, unlike asynchronous PWM, the phase of the modulation wave remains constant relative to the phase of the carrier signal, and the period of the modulation wave is, for example, set to an integer multiple of the period of the carrier signal. Apart from this, synchronous PWM and asynchronous PWM are identical.

[0073] As explained above, in one embodiment of the present invention, the PWM pulse is adjusted (corrected) by the pulse edge control unit 250, so that regardless of whether the PWM control method is asynchronous PWM or synchronous PWM, the phase difference between the zero-crossing point of the modulation wave and the pulse edge of the PWM pulse is within a specified range in the region near the zero-crossing point, including the zero-crossing point of the modulation wave. As a result, the DC component or pulsation component of the current generated from the overmodulation region to the single-pulse region can be reduced without changing the output voltage of the inverter 100.

[0074] Next, use Figure 6 The structure of an electric power steering device using an inverter control device 200 according to one embodiment of the present invention will be described.

[0075] Figure 6 This is a structural diagram of an electric power steering device using an inverter control device 200 according to one embodiment of the present invention.

[0076] like Figure 6 As shown, the electric actuator of the electric power steering system consists of a torque transmission mechanism 902, a motor 300, an inverter 100, and an inverter control device 200. The electric power steering system includes an electric actuator, a steering wheel (steering) 900, a steering detector 901, and an operation command device 903. The operating force of the steering wheel 900, which is turned by the driver, has a structure that uses the electric actuator for torque assistance.

[0077] The torque command τ* of the electric actuator is generated by the operation quantity command unit 903 as a steering assist torque command for the steering wheel 900. The output of the electric actuator driven by the torque command τ* is used to reduce the steering force required by the driver. The inverter control unit 200 receives the torque command τ* as an input command and controls the operation of the inverter 100 to control the current flowing through the motor 300 in a manner that follows the torque command value from the torque constant of the motor 300 and the torque command τ*.

[0078] The motor output τm, which is directly connected to the rotor of the motor 300, transmits torque to the rack 910 of the steering device via a torque transmission mechanism 902. This torque transmission mechanism 902 utilizes a reduction mechanism such as a worm gear, wheel, or planetary gear, or a hydraulic mechanism. Through the torque transmitted to the rack 910, the steering force (operating force) of the driver's steering wheel 900 is reduced (assisted) by electric power, and the steering angles of the wheels 920 and 921 are operated.

[0079] The auxiliary quantity is determined as follows: the steering angle and steering torque are detected by the steering detector 901 mounted on the steering shaft, and considering state quantities such as vehicle speed and road conditions, the torque command τ* is calculated by the operation quantity command unit 903.

[0080] An inverter control device 200 according to one embodiment of the present invention has the advantage of achieving low vibration and low noise even when the motor 300 is rotating at high speed, by averaging the output voltage of the inverter 100.

[0081] Figure 7 This figure shows an electric vehicle 600 that utilizes the inverter control device 200 according to the present invention. The electric vehicle 600 has a powertrain that uses an electric motor 300 as a motor / generator.

[0082] The front axle 601 is rotatably supported at the front of the electric vehicle 600, and the front wheels 601 and 602 are located at both ends of the front axle 601. The rear axle 604 is rotatably supported at the rear of the electric vehicle 600, and the rear wheels 605 and 606 are located at both ends of the rear axle 604.

[0083] The differential gear 611, serving as a power distribution mechanism, is located at the center of the front axle 601 and distributes the rotational driving force transmitted from the engine 610 via the transmission 612 to the left and right front axles 601. The engine 610 and the electric motor 300 are mechanically connected via a belt, which is mounted between a pulley mounted on the crankshaft of the engine 610 and a pulley mounted on the rotating shaft of the electric motor 300.

[0084] Thus, the rotational driving force of the motor 300 can be transmitted to the engine 610, and the rotational driving force of the engine 610 can be transmitted to the motor 300. In the motor 300, the three-phase AC power output from the inverter 100 is provided to the stator coil of the rotor according to the control of the inverter control device 200, thereby causing the rotor to rotate and generating a rotational driving force corresponding to the three-phase AC power.

[0085] In other words, the motor 300 is controlled by the inverter 200 and operates as a motor, while the rotor is driven by the rotational force of the engine 610 and rotates, thus operating as a generator to produce three-phase alternating current.

[0086] Inverter 100 is a power conversion device that converts DC power supplied by a high-voltage (42V or 300V) system power source, namely high-voltage battery 622, into three-phase AC power. It controls the three-phase AC current flowing through the stator coil of motor 300 according to the operating command value and the magnetic pole position of the rotor.

[0087] The three-phase alternating current obtained from the discharge of the electric motor 300 is converted into direct current by the inverter 100 and used to charge the high-voltage battery 622. The high-voltage battery 622 is electrically connected to the low-voltage battery 623 via a DC-DC converter 624. The low-voltage battery 623 constitutes the low-voltage (14V) system power supply for the electric vehicle 600 and is used as a power source for the starter motor 625 for initial starting (cold start) of the engine 610, the radio, lights, etc.

[0088] When the electric vehicle 600 is stopped (idle stop mode) while waiting at a traffic light, the engine 610 is stopped. When the vehicle starts again, the engine 610 is restarted (hot start), and the inverter 100 drives the electric motor 300 to restart the engine 610.

[0089] Furthermore, in idle stop mode, even if the high-voltage battery 622 is undercharged or the engine 610 is not sufficiently heated, the engine 610 continues to operate without stopping. Additionally, in idle stop mode, it is necessary to ensure that auxiliary equipment such as the air conditioner compressor, which uses the engine 610 as its drive source, is powered. In this case, the drive motor 300 drives the auxiliary equipment.

[0090] Even in acceleration mode and high-load operation mode, the electric motor 300 is driven to assist the engine 610. Conversely, when the high-voltage battery 622 is in a charging mode that requires charging, the engine 610 drives the electric motor 300 to generate electricity, thereby charging the high-voltage battery 622. In other words, the electric motor 300 operates regeneratively during braking or deceleration of the electric vehicle 600.

[0091] The electric vehicle 600 includes: an inverter control unit 200 that generates PWM pulses for converting DC voltage to AC voltage based on a motor output request; an inverter 100 that drives a motor 300 by converting DC voltage to AC voltage using the generated PWM pulses; and a DC / DC converter 624 that boosts the DC voltage. The inverter control unit 200 adjusts the PWM pulses through processing by the pulse edge control unit 250 as described above, thereby reducing the voltage error of the inverter output voltage in the zero-crossing region, including the zero-crossing point of the modulating wave, when trapezoidal wave modulation is used from the over-modulation region to the single-pulse region. This reduces the DC component and pulsation of the current generated in the zero-crossing region, and enables adjustment of the output voltage of the DC / DC converter 624 of the electric vehicle 600 and stable control to expand the output range of the inverter 100.

[0092] The inverter control device of the present invention described above has the following effects.

[0093] (1) The inverter control device 200 of the present invention includes: a PWM control unit 220 that generates a PWM pulse for controlling the inverter 100 using a modulation rate based on a voltage command; and a pulse edge control unit 250 that corrects the PWM pulse so that the phase difference between the zero-crossing point of the modulation wave and the pulse edge of the PWM pulse is within a specified range. As a result, the DC component and current ripple of the inverter output current generated in the region near the zero-crossing point can be reduced. As a result, the motor can be stably controlled up to high speed.

[0094] (2) Preferably, in the inverter control device 200 of the present invention, the PWM control unit 220 approximates the modulation wave with a straight line in a region near a predetermined zero-crossing point that includes the zero-crossing point, and calculates the duty cycle of the PWM pulse based on the modulation wave obtained by the straight-line approximation, thereby generating the PWM pulse. In this way, the PWM modulation processing performed by a microcomputer or the like for generating the PWM pulse can be simplified.

[0095] (3) In the inverter control device 200 of the present invention, the pulse edge control unit 250 determines the shift direction of the PWM pulse based on the slope of the modulation wave obtained by approximation by a straight line (step S8), and shifts the PWM pulse in the determined shift direction to correct the PWM pulse (steps S9, S10). Therefore, even if the phase of the modulation wave is reversed according to the driving state of the motor 300 and the zero-crossing direction is also reversed, the same algorithm can be used to correct the PWM pulse. As a result, the processing of the pulse edge control unit 250 can be simplified. Furthermore, when the inverter control device 200 is mounted on an electric vehicle, even if the power operation and regenerative operation of the motor are repeatedly performed with the rapid acceleration and deceleration of the electric vehicle, the motor can be stably controlled.

[0096] (4) In the inverter control device 200 of the present invention, when the phase difference between the zero-crossing point and the pulse edge of the shifted PWM pulse is not within a specified range (step S11: Yes), the pulse edge control unit 250 performs cyclic pulse shifting (step S12). In this cyclic pulse shifting, as... Figure 3 As shown in (d), the portion of the shifted PWM pulse that exceeds a specified range is defined as the pulse error Te, and the pulse error Te is configured separately from the shifted PWM pulse. Alternatively, as... Figure 5 As shown in (d), the portion of the shifted PWM pulse that exceeds the specified range is set as the pulse error Te, which is distributed across multiple zero-crossing points. This smooths and suppresses the inverter output voltage error, enabling stable control of the motor up to high-speed rotation.

[0097] (5) In the inverter control device 200 according to the present invention, the pulse edge control unit 250 does not perform PWM pulse correction when the modulation rate based on the voltage command is less than a predetermined value (step S6: No). Therefore, the error of the inverter output voltage from the overmodulation region to the single pulse region can be effectively suppressed and reduced.

[0098] (6) Preferably, in the inverter control device 200 of the present invention, the pulse edge control unit 250 corrects the PWM pulse, thereby reducing the number of PWM pulses contained in one cycle of the modulation wave. In this way, even under control conditions where the over-modulation region and single-pulse region repeatedly change, errors in the inverter output voltage can be effectively suppressed, and the motor can be stably controlled until high-speed rotation. Furthermore, since the number of inverter switching operations can be reduced, inverter control with reduced switching losses can be achieved.

[0099] In the inverter control device 200 of the present invention described above, the PWM control unit 220 can correct the modulation rate and the phase of the modulation wave based on voltage commands, so that when the motor 300 is subjected to field weakening control, the amount of current output from the inverter 100 to the motor 300 is reduced in order to perform field weakening control on the motor 300. This further expands the operating range of the motor under overmodulation and effectively utilizes the single-pulse region. Therefore, inverter control can be achieved, which effectively suppresses the error of the inverter output voltage and reduces the inverter's conduction and switching losses.

[0100] Furthermore, although the electric vehicle 600 described in one embodiment is a hybrid vehicle, the same effect can be obtained in the case of hybrid vehicles, electric vehicles, etc.

[0101] Furthermore, in the above embodiments, the inverter control device was described as a single unit. If it has the above-described functions, the present invention can also be applied to an inverter device that integrates the inverter control device and the inverter, and to a motor drive system that integrates the inverter device and the motor.

[0102] Furthermore, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Label Explanation

[0103] 1. Electric motor assembly 2 batteries 100 inverter 200 Inverter Control Unit 210 Current Control Unit 220 PWM Control Unit 250 Pulse Edge Control Unit 260 Drive Signal Generation Unit 270 Rotational Position Detection Unit 280 Current Detection Unit 300 electric motor 320 Rotary Position Sensor 600 Electric vehicles.

Claims

1. An inverter control device, comprising: The PWM control unit uses a voltage command-based modulation wave to generate PWM pulses for controlling the inverter. as well as The pulse edge control unit shifts the phase of the pulse edge of the PWM pulse, ensuring that the phase difference between the zero-crossing point of the modulated wave (which changes when crossing 0) and the pulse edge of the PWM pulse is within a specified range. The specified range is set based on the phase range corresponding to the dead time of the inverter.

2. The inverter control device as described in claim 1, characterized in that, The PWM control unit approximates the modulation wave with a straight line in a region near a predetermined zero-crossing point, including the zero-crossing point, and calculates the duty cycle of the PWM pulse based on the modulation wave obtained by the straight-line approximation, thereby generating the PWM pulse.

3. The inverter control device as described in claim 2, characterized in that, The pulse edge control unit determines the shift direction of the PWM pulse based on the slope of the modulation wave obtained by approximation with a straight line, and shifts the PWM pulse in the determined shift direction to correct the PWM pulse.

4. The inverter control device as described in claim 3, characterized in that, When the phase difference between the zero-crossing point and the pulse edge of the shifted PWM pulse is not within the specified range, the pulse edge control unit sets the portion of the shifted PWM pulse that exceeds the specified range as a pulse error, and configures the pulse error separately from the shifted PWM pulse.

5. The inverter control device as described in claim 3, characterized in that, When the phase difference between the zero-crossing point and the pulse edge of the shifted PWM pulse is not within the specified range, the pulse edge control unit defines the portion of the shifted PWM pulse that exceeds the specified range as a pulse error, and distributes the pulse error in a distributed manner across multiple zero-crossing points.

6. The inverter control device as described in claim 1, characterized in that, The pulse edge control unit does not perform correction of the PWM pulse when the modulation rate based on the voltage command is less than a specified value.

7. The inverter control device as described in claim 1, characterized in that, The pulse edge control unit corrects the PWM pulse, thereby reducing the number of PWM pulses contained in one cycle of the modulation wave.

8. The inverter control device as described in claim 1, characterized in that, The inverter is connected to the motor. The PWM control section corrects the modulation rate based on the voltage command and the phase of the modulation wave, thereby reducing the current output from the inverter to the motor in order to perform field weakening control on the motor.

9. An electric vehicle system, characterized in that, include: Inverter control device as claimed in any one of claims 1 to 8; The inverter controlled by the inverter control device; as well as A three-phase synchronous motor driven by the inverter, The electric vehicle system uses the rotational driving force of the three-phase synchronous motor to move.

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