JP2021069138A - Power converter control method and power converter control device - Google Patents

Abstract

To suppress the generation of narrow pulses when a pulse pattern is switched.SOLUTION: A power converter control method includes a switching determination step (S104) of determining whether to switch a pulse pattern, a pulse width estimation step (S107) of estimating a pulse width (Tpwm) of a pulse straddling switching timing when it is determined to switch the pulse pattern in the switching determination step, and a determination step (S108) of determining whether the pulse width (Tpwm) exceeds a threshold value (Tth), and a switching step (S109) of changing the pulse pattern at the switching timing when it is determined that the pulse width exceeds the threshold value in the determination step.SELECTED DRAWING: Figure 5

Description

The present invention relates to a control method for a power converter and a control device for the power converter.

The power converter has a plurality of switching elements, and the DC power is converted into AC power by operating these switching elements. In the operation of the switching element, the pulse width of the on or off section is changed. Such pulse width control is generally referred to as PWM (Pulse Width Modulation) control. In PWM control, the output from the power converter is controlled by changing the pulse pattern at a predetermined cycle.

For example, Patent Document 1 shows an example in which the load is a motor, and when PWM control is performed to drive the motor, sine wave control, overmodulation control, and , A technique for switching the control mode between the square wave control and the rectangular wave control is disclosed. Among these control modes, in the sine wave control and the overmodulation control, PWM control is performed, respectively, and the switching element is operated using a pulse pattern according to the operating state of the motor.

Japanese Unexamined Patent Publication No. 2010-21348

Here, if the switching interval in the switching element of the power converter is shortened, a surge voltage may be generated and the durability of the power converter may be lowered. On the other hand, in the technique disclosed in Patent Document 1, the pulse pattern stored in advance can be designed so as not to include a narrow pulse having an extremely short pulse width. However, even when the pulse pattern is designed in this way, when the pulse pattern is switched, the switching interval becomes short before and after the switching, and a narrow pulse may occur.

The present invention provides a power converter control method and a power converter control device, which have been made to solve the above problems and can suppress the generation of narrow pulses when the pulse pattern is switched. To do.

The control method of the power converter of the present invention is a power conversion that converts DC power into AC power by changing the conduction state of the switching element by using PWM control according to a pulse pattern repeated in a predetermined control cycle. It is a control method of the vessel. The control method of the power converter is determined to switch the pulse pattern in the switching determination step of determining whether or not to switch the pulse pattern and the switching determination step according to the control command value for the load connected to the power converter. When this is done, the time between the change timing of the conduction state in the first pulse pattern immediately before the switching timing and the change timing of the conduction state in the second pulse pattern immediately after the switching timing is set as the time of the pulse straddling the switching timing. It is determined in the determination step and the determination step that the pulse width estimated as the pulse width, the pulse width estimation step, and the pulse width estimation step, which is estimated in the pulse width estimation step, exceeds the threshold value. If so, it has a switching step of switching the pulse pattern at the switching timing.

According to the motor control method of the present invention, the generation of narrow pulses can be suppressed.

FIG. 1 is a schematic configuration diagram of a motor system including a control device for a power converter according to the first embodiment. FIG. 2 is a schematic configuration diagram of the control device. FIG. 3 is a schematic configuration diagram of the PWM output unit. FIG. 4 is a schematic configuration diagram of the PWM pattern switching output unit. FIG. 5 is a flowchart of determination control of the final command pulse pattern. FIG. 6 is a diagram showing an example of switching the command pulse pattern. FIG. 7 is a diagram showing an example of switching other command pulse patterns. FIG. 8 is a graph showing the relationship between the pulse width and the surge voltage. FIG. 9 is a schematic configuration diagram of the PWM pattern switching output unit according to the second embodiment. FIG. 10 is a flowchart of determination control of the final command pulse pattern. FIG. 11 is a diagram showing an example of switching the command pulse pattern.

Hereinafter, the power converter control method and the power converter control device according to the embodiment of the present invention will be described with reference to the drawings.

(First Embodiment)
FIG. 1 is a schematic configuration diagram of a power converter according to the first embodiment and a motor system including the control device thereof.

The power converter 1 is an inverter composed of a plurality of switching elements, and is connected between the positive electrode (P) line and the negative electrode (N) line of the battery 2. The power converter 1 converts the DC power supplied from the battery 2 into AC power and supplies it to the motor 3.

In the power converter 1, the switching element is operated according to the command pulse pattern output from the control device 10. Then, according to the on / off operation of the switching element, the DC power output from the battery 2 is converted into AC power, and the converted AC power is supplied to the motor 3.

In the present embodiment, the motor 3 is driven by three phases, and the power converter 1 is provided with six switching elements so that it can be driven by three phases and six arms. The configuration of the power converter 1 and the motor 3 is an example, and is not limited to the example of the present embodiment. Further, the load connected to the power converter 1 is not limited to the motor 3, and may be another device driven by AC power, such as an audio amplifier or a radio.

The capacitor 4 is provided between the positive electrode line and the negative electrode line, and smoothes ripples caused by the operation of the switching element in the power converter 1. Further, voltage sensors 5 are provided at both ends of the capacitor 4, and when the voltage sensor 5 _{detects the DC voltage V dc} which is the voltage difference between the positive electrode line and the negative voltage line, the voltage sensor 5 controls the DC voltage V _dc. Output to 10. The DC voltage V _dc is the input power to the power converter 1, and is used for controlling the power converter 1 by the control device 10.

Further, a current sensor 6 is provided between the power converter 1 and the motor 3. Current sensor 6, current measurement values i _u of uvw phases supplied to the motor 3, i _v, measured to i _w, and outputs the current measurement values i _u, i _v, and i _w to the control device 10.

A resolver 7 is provided in the motor 3, and the motor rotation angle detection unit included in the control device 10 uses the magnetic flux signal output from the excited resolver 7 to perform the rotor position θe of the motor 3 and the rotor position θe of the motor 3. Calculate the number of revolutions N.

The control device 10 controls the entire motor system 100 including the power converter 1. The control device 10 is configured to be able to execute a predetermined program by a microcomputer provided with a central arithmetic unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). Will be done. The control device 10 may be composed of a plurality of microcomputers.

The control device 10 generates a command pulse pattern having a desired pulse width based on ^{the torque command value T *} and the rotation speed N of the motor 3 in order to perform PWM control for changing the pulse width, and the generated command. The pulse pattern is output to the power converter 1. In this way, the switching element included in the power converter 1 is controlled.

FIG. 2 is a block diagram showing a detailed configuration of the control device 10.

The control device 10 includes a current command value calculation unit 11, a current control unit 12, a modulation rate conversion unit 13, a PWM output unit 14, and a three-phase / two-phase conversion unit 15. The configuration from the current command value calculation unit 11 to the three-phase / two-phase conversion unit 15 may be logically arranged inside the control device 10 or may be configured by different microcomputers.

The current command value calculation unit 11 receives the torque command value T ^* from the host device and the rotation speed N of the motor 3 from the motor rotation angle detection unit of the control device 10. Based on these inputs, the current command value calculation unit 11 calculates the current command values i _d ^* and i _q ^* for the motor 3 using the map stored in advance, and the current command values i _d ^* and i _q ^*. Is output to the current control unit 12.

The current control unit 12 has current command values _id ^* and i _q ^* _{output from the current command value calculation unit 11 and current measurement values id} and i output from the three-phase / two-phase conversion unit 15 described later. Accept _q. The current control unit 12 _{determines the voltage command values V d} ^* and V _q ^* so that the deviation between the _{current command values i d} ^* and i _q ^* and the current measurement values i _d and i _q becomes zero. The determined voltage command values V _d ^* and V _q ^* are output to the modulation factor conversion unit 13.

The modulation factor conversion unit 13 includes a DC voltage V _{dc output from the voltage sensor 5, a rotor position θ e} and a rotation speed N output from the motor rotation angle detection unit, and a voltage command output from the current control unit 12. Accepts the values V _d ^* and V _q ^* as inputs. ^{The modulation rate conversion unit 13 calculates the modulation rate M *} of the AC power output from the power converter 1 based on these inputs.

The PWM output unit 14 receives the rotor position θ _e ^{and the rotation speed N output from the motor rotation angle detection unit and the modulation factor M *} output from the modulation rate conversion unit 13 as inputs. Based on these inputs, the PWM output unit 14 selects and outputs an appropriate pulse pattern from the pulse patterns stored in advance for PWM control. Further, the pulse pattern is selected every predetermined control cycle T. In the present embodiment, as shown in FIG. 3 described later, the PWM pattern switching output unit 142 included in the PWM output unit 14 controls the pulse pattern switching timing. By controlling the command pulse pattern in this way, it is possible to suppress the generation of narrow pulses.

3-phase / 2-phase conversion unit 15 uses the rotor position theta _e output from the motor rotation angle detecting section, current measurements uvw phases obtained by the current sensor 6 i _u, i _v, to i _w On the other hand, phase conversion processing is performed to generate _{current measurement values i d} and i _q. Then, the three-phase / two-phase conversion unit 15 outputs the current measurement values i _d and i _q obtained by the conversion process to the current control unit 12.

FIG. 3 is a block diagram of a detailed configuration of the PWM output unit 14. The PWM output unit 14 includes a PWM generation unit 141 and a PWM pattern switching output unit 142.

When the PWM generation unit 141 receives the modulation rate M ^* output from the modulation rate conversion unit 13 and the rotation speed N output from the motor rotation angle detection unit, the PWM generation unit 141 refers to a table stored in advance and modulates the modulation. The optimum control mode according to the rate M ^* and the rotation speed N, and the command pulse pattern corresponding to the control mode are determined. The control mode and the command pulse pattern are determined every predetermined control cycle T, and the command pulse pattern determined at a certain timing is used in the next control cycle T starting after the control cycle T. ..

The PWM generation unit 141 selects either a rectangular wave control mode or a PWM control mode as the control mode. When the square wave control mode is selected, the PWM generation unit 141 outputs a square wave pulse, which is one pulse in the entire period of the control cycle T in a certain control cycle T, as a command pulse pattern. When the PWM control mode is selected, the PWM generation unit 141 selects and outputs a pulse pattern used for PWM control according to ^{the modulation factor M * and the rotation speed N.}

When the square wave control mode is selected, the PWM pattern switching output unit 142 receives the square wave pulse from the PWM generation unit 141, and outputs the square wave pulse as the final command pulse pattern in the next control cycle T. ..

On the other hand, when the PWM control mode is selected, when the PWM pattern switching output unit 142 receives a predetermined command pulse pattern from the PWM generation unit 141, it receives the command pulse pattern currently being output and the PWM generation unit 141. It is determined whether or not the command pulse pattern in the next control cycle T is the same.

When both command pulse patterns are the same, the PWM pattern switching output unit 142 continues to output the same command pulse pattern. On the other hand, when the command pulse patterns are different, as will be described later, the PWM pattern switching output unit 142 switches _{the command pulse pattern by using the rotation speed N and the rotor position θ e} so as not to generate a narrow pulse. Determine the timing. Then, the PWM pattern switching output unit 142 outputs the final command pulse pattern so that the new command pulse pattern can be switched at the determined switching timing.

FIG. 4 is a block diagram of a detailed configuration of the PWM pattern switching output unit 142. The PWM pattern switching output unit 142 includes an angle estimation unit 1421 and a final command output unit 1422.

Here, when the pulse width (pulse width) when PWM control is performed is _{a narrow pulse that is lower than the pulse threshold value T th} , the interval between the switching operations performed at the start timing and the end timing of the narrow pulse is set. It becomes shorter and a surge voltage is generated. In the pulse pattern prepared in advance, the pulse width is set to exceed the _{pulse threshold value T th.}

However, before and after the switching timing, the pulse width may be shorter than the _{pulse threshold value T th.} That is, the pulse width of the pulse starting from the change timing of the last conduction state of the pulse pattern before the switching timing and ending at the change timing of the first conduction state of the pulse pattern after the switching timing has a pulse width from the pulse threshold value T _th . Is not compensated for longer. Therefore, by performing the following control, the pulse width of the pulse straddling the switching timing _{can be made longer than the pulse threshold value T th} , so that the generation of a narrow pulse can be suppressed.

Further, the PWM control used for controlling the motor 3 in the present embodiment is called angle-synchronous PWM control. In the command pulse pattern in the angle synchronous PWM control, the rotor position θ _e and the conduction state (on / off) are associated with each other. Therefore, even when the switching timing of the command pulse pattern is changed, the final command output unit 1422 outputs a level indicating the continuity state shown in the command pulse pattern according to the _{rotor position θ e.} ..

First, when the angle estimation unit 1421 receives _{the input of the rotor position θ e} of the motor 3 and the rotation speed N, these inputs, the control cycle T corresponding to the command pulse pattern stored in advance, and the control cycle T corresponding to the command pulse pattern stored in advance, and Using the pole logarithm P of the motor 3, the estimated electric angle θ _est is calculated by the following equation.

The estimated electric angle θ _est indicates the switching timing from the current command pulse pattern n to the next command pulse pattern n + 1 by the electric angle of the motor 3. The angle estimation unit 1421 _{calculates the estimated electric angle θ est} at a predetermined cycle, and at a certain switching timing, calculates the _{estimated electric angle θ est indicating the next switching timing.}

Therefore, as shown in Eq. (1), the _{estimated electric angle θ est, which} is the next switching timing, is calculated by adding the electric angle corresponding to the control cycle T _{to the current rotor position θ e.} .. In the equation (1), "(N / 60) · P · 360" is multiplied in order to convert the unit system from time to electric angle with respect to the control cycle T.

Then, the final command output unit 1422 uses the estimated electric angle θ _est output from the angle estimation unit 1421 according to the following equation, and the command pulse output from the PWM generation unit 141 from the command pulse pattern n currently being output. When switching to the pattern n + 1, the pulse width T _pwm of the pulse straddling the switching timing is calculated.

However, the parameters in Eq. (2) are as follows.
θ ₁ : Electric angle at which the conduction state changes last in the _{command pulse pattern n θ 2} : Electric angle at which the conduction state changes first in the command pulse pattern n + 1.

The electric angle θ ₁ is an electric angle indicating the timing at which the conduction state of the final switching element in the command pulse pattern n changes before the _{estimated electric angle θ est} , which is the switching timing. The electric angle θ ₂ is an electric angle indicating the timing at which the conduction state of the first switching element in the command pulse pattern n + 1 changes after the estimated electric angle θ _est.

That is, (θ _est − θ ₁ ) indicates the pulse width before the estimated electric angle θ _est by the electric angle, and (θ ₂ − θ _est ) indicates the pulse width after the estimated electric angle θ _est. It is shown by a corner. Therefore, in order to convert the unit system from the electrical angle to time for the sum of the two, "(θ _est − θ ₁ ) + (θ ₂ − θ _{est)", "360 · (N / 60)" ) ・ P ”is removed to obtain the pulse width T pwm} of the pulse that straddles the switching timing, as shown in Eq. (2).

In this example, it is assumed that the conduction state of the command pulse pattern n and the command pulse pattern n + 1 is the same at _{the estimated electric angle θ est.} Therefore, the conduction state is _{switched on at the electric angle θ 1} and turned off at the electric angle θ ₂ , and as a result, the electric angle θ ₁ and the electric angle θ _{2 before and after the estimated electric angle θ est} are switched. It becomes a pulse that straddles the timing and becomes an on section. An example in which the command pulse pattern n and the command pulse pattern n + 1 are different in the estimated electric angle θ _{est will be described in the second embodiment.}

Then, when the pulse width T _pwm is equal to or greater than the pulse threshold value T _th , the final command output unit 1422 switches the command pulse pattern at the _{estimated electric angle θ est.} On the other hand, the angle estimation unit 1421, when the pulse width T _pwm is shorter than the pulse threshold T _th, in order to suppress the generation of narrow pulses, so that the pulse width T _pwm is not shorter than the pulse threshold T _th, Reset the switching timing. The resetting of the switching timing and the output control of the final command pulse pattern will be described with reference to FIG.

FIG. 5 is a flowchart of determination control of the final command pulse pattern. In the control device 10, this determination control is repeatedly performed at a predetermined timing. In the following, for the sake of clarification of the description, the blocks that realize the predetermined functions in the control device 10 shown in FIGS. 2 to 4 will be described as performing the respective processes. A predetermined function may be realized by the control device 10 performing a predetermined process.

First, in step S101, the PWM generation unit 141 determines whether or not PWM control is being performed. When the PWM generation unit 141 is performing PWM control (S101: Yes), the PWM generation unit 141 then performs the process of step S103. The PWM generation unit 141 performs rectangular wave control, and if PWM control is not performed (S101: No), then the process of step S102 is performed.

In step S102, the PWM generation unit 141 outputs the pulse pattern in the rectangular wave control, which is the selected control mode, as the final command pulse pattern. When the square wave control is performed, the PWM generation unit 141 outputs an on or off conduction state so that one pulse is generated over the entire control cycle T.

In step S103, the modulation factor conversion unit 13 includes a DC voltage V _{dc , a rotor position θ e} and a rotation speed N output from the motor rotation angle detection unit, _{and a voltage command value V d} output from the current control unit 12. ^It accepts inputs such as * and V _q ^*, and calculates the ^{modulation factor M * based on these inputs.} The rotation speed N may be calculated by the modulation factor conversion unit 13 _{time-differentiating the rotor position θ e.} Then, the process of step S104 is performed.

In step S104, the PWM generation unit 141 determines the command pulse pattern based on ^{the modulation factor M * generated in step S102 and the rotation speed N.} Then, the final command output unit 1422 determines whether or not the current command pulse pattern being output and the determined next command pulse pattern are the same. If both are the same and no change is required (S104: No), then the process of step S105 is performed. If the two are different and it is necessary to change the output command pulse pattern (S104: Yes), then the process of step S106 is performed.

In step S105, the final command output unit 1422 outputs the same command pulse pattern as the command pulse pattern currently being output without changing the command pulse pattern in the next control cycle T. In this way, the final command pulse pattern is determined.

In step S106, when the angle estimation unit 1421 receives _{the input of the rotor position θ e} and the rotation speed N, these input values, the control cycle T corresponding to the pulse pattern stored in advance, and the control cycle T corresponding to the pulse pattern stored in advance, and Using the pole logarithm P of the motor 3, the pulse pattern switching timing is calculated as the _{estimated electric angle θ est indicated by the electric angle according to the equation (1).} This estimated electric angle θ _est indicates the timing when switching is performed every predetermined control cycle T. After the estimated electric angle θ _est is calculated, the process of step S107 is performed next.

In step S107, the angle estimation unit 1421 _{switches the electrical angle θ 1} in which the conduction state is switched in the command pulse pattern n before the _{estimated electric angle θ est} , and the electrical angle in which the conduction state is switched in the command pulse pattern n + 1 after the estimated electric angle θ _est. Using θ ₂ , the number of rotations N of the motor 3 and the number of pole pairs P, _{the pulse width T pw} m when the command pulse pattern is switched at the _{estimated electric angle θ est} is calculated. After the pulse width T _pwm is calculated, the process of step S108 is performed next.

In step S108, the final command output unit 1422 determines whether or not _{the pulse width T pwm} calculated in step S106 is equal to or greater than a predetermined pulse threshold value T _th. When the pulse width T _pwm is equal to or greater than the pulse threshold value T _th (S108: Yes), the final command output unit 1422 determines that the pulse width T _pwm is sufficiently long and no narrow pulse is generated, and then the step. The process of S109 is executed. If the pulse width T _pwm is not equal to or greater than the pulse threshold value T _th (S108: No), the final command output unit 1422 determines that a narrow pulse may occur, and then performs the process of step S110. Execute.

In step S109, the final command output section 1422, defines the estimated electrical angle theta _est timing of switching a command pulse pattern, in estimated electrical angle theta _est previously outputs a command pulse pattern n, after the estimated electrical angle theta _est Outputs the command pulse pattern n + 1. In this way, the final command pulse pattern is determined so that the pulse pattern is switched at the estimated electric angle θ _est.

In step S110, the angle estimation unit 1421 sets the electrical angle _{after the estimated electrical angle θ est} , and then sets the electrical angle at which the conduction state in the command pulse pattern n and the conduction state in the command pulse pattern n + 1 are the same. _Reset as the estimated electrical angle θ est, which is the pattern switching timing. Since the command pulse pattern can be switched at the timing when the conduction state of the command pulse pattern n and the command pulse pattern n + 1 coincides, the timing is reset as the _{estimated electric angle θ est.} The resetting process may be referred to as a first resetting process in order to distinguish it from the resetting process in the second embodiment.

Then, the process of step S107 is executed again using the estimated electric angle θ _{est reset in step S110.} Such resetting of the estimated electric angle θ _{est is repeated until the pulse width T pwm} becomes equal to or higher than the pulse threshold value T _th (S108: Yes).

Next, the output control of the command pulse pattern in the present embodiment will be described with reference to FIGS. 6 and 7. In these figures, in order from the top, the command pulse pattern n currently being output, the command pulse pattern n + 1 in the next control cycle T generated by the PWM generation unit 141, and the final command output unit 1422 are output. The final command pulse pattern is shown. The current command pulse pattern n is shown by a solid line before the switching timing and by a dotted line after the switching timing. Further, in the next command pulse pattern n + 1, before the switching timing is shown by a dotted line, and after the switching timing is shown by a solid line.

In FIG. 6, the estimated electric angle θ _est calculated in step S106 is the command pulse pattern switching timing, and in FIG. 7, the estimated electric angle θ _est reset in step S110 is the command pulse pattern switching timing. It shall be.

First, the example of FIG. 6 will be described.

In FIG. 6, the estimated electrical angle θ _est calculated in step S106 is shown. Then, the upper electrical angle theta ₁ which the last conducting state by the command pulse pattern n in prior estimated electrical angle theta _est switched is shown in the middle, at the command pulse pattern n + 1 after than the estimated electrical angle theta _est The electrical angle θ _{2 at} which the initial conduction state switches is shown.

By the process of step S107, the pulse width T _{pwm corresponding to these electric angles θ 1} and θ ₂ is calculated. Here, since the pulse width T _pwm is equal to or greater than the pulse threshold value T _th (S108: Yes), the command pulse pattern is changed _{at the estimated electric angle θ est} as shown in the lower part of the figure.

Next, the example of FIG. 7 will be described.

In Figure 7, the upper, the estimated electrical angle theta _est which is calculated in step S106, and re-set the estimated electrical angle theta _est is shown in step S110.

In the upper part, the _{electric angle θ 1} at which the conduction state is finally switched by the command pulse pattern n before _{the estimated electric angle θ est} is shown. In the middle, the command pulse pattern in the first the first conducting state and the electrical angle theta ₂ to switch on the command pulse pattern n + 1 after than the estimated electrical angle theta _est calculated, after the estimated electrical angle theta _est to be reconfigured _{The electric angle θ 2} at which the conduction state is first switched at n + 1 is shown. The final command pulse pattern that is finally output is shown in the lower row.

First, by the process of step S107, the pulse width T _{pwm is calculated using the estimated electric angle θ est} calculated first and the corresponding electric angles θ ₁ and θ _2, and this pulse width T _pwm is the pulse threshold value T _th. Shorter (S108: No). Therefore, it is determined that a narrow pulse may be generated, and then the process of step S110 is executed. In step S110, the angle estimation unit 1421 is the conduction state (on state in this figure) in the command pulse pattern n during output after the _{estimated electric angle θ est calculated first.} The electric angle at which the conduction state (on state) is the same in the command pulse pattern n + 1 is reset as the _{estimated electric angle θ est.}

Then, again, by the process of step S107, the pulse widths T _{pw m corresponding to the estimated electric angles θ est} to be reset and the electric angles θ ₁ and θ ₂ are calculated. Here, since the pulse width T _pwm is equal to or greater than the pulse threshold value T _th (S108: Yes), the command pulse pattern is switched _{at the recalculated estimated electric angle θ est} as shown in the lower part of the figure. _{Therefore, since the pulse width T pwm} of the pulse straddling the switching timing of the command pulse pattern becomes the pulse threshold value T _th or more, the generation of the narrow pulse can be suppressed.

Note that FIG. 8 is a graph showing the relationship between _{the pulse width T pwm and the generated surge voltage.} In this graph, the pulse width T _pwm is shown in the x-axis direction, and the generated surge voltage is shown in the y-axis direction. Further, according to this figure, the characteristics change according to the temperature of the power converter 1, and the respective characteristics when the power converter 1 is at 40 ° C., 20 ° C., 0 ° C., and −40 ° C. are shown by solid lines. , One-dot chain line, two-dot chain line, and dashed line.

For example, by setting the pulse threshold value T _th to 1.65 μs, the pulse width T _pwm becomes 1.65 μs or more, and as a result, the surge voltage can be prevented from being generated at any of these temperatures. In this way, the determination criteria in step S108 can be set in advance using the characteristics of the surge voltage according to the temperature of the power converter 1.

According to the first embodiment, the following effects can be obtained.

According to the control method of the power converter 1 of the first embodiment, it is determined whether or not to switch the command pulse pattern according to the ^{torque command value T * for the motor 3 which is the load connected to the power converter 1.} The switching determination step (S104) and the pulse width estimation step (S107) for estimating the pulse width T _{pwm across the estimated electric angle θ est} , which is the switching timing, when it is determined to switch the command pulse pattern in the switching determination step. A determination step (S108) for determining whether or not _{the pulse width T pwm} estimated in the pulse width estimation step exceeds the pulse threshold T _{th , and a determination that the pulse width T pw} m exceeds the pulse threshold T _th. In the case (S108: Yes), it has a switching step (S109) for switching the command pulse pattern at the _{estimated electric angle θ est.}

With such a configuration _{, the command pulse pattern is switched only when the pulse width T pwm} is longer than the pulse threshold value T _th. Therefore, even in a transient condition in which the command pulse pattern is switched. , It is possible to prevent the generation of narrow pulses.

Further, in the pulse width estimation step (S107), _{the operation timing (θ 1} ) of the command pulse pattern n immediately before the _{estimated electric angle θ est} , which is the switching timing, and the operation of the command pulse pattern n + 1 immediately after the estimated electric angle θ _est. The time corresponding to the timing (θ ₂ ) is estimated as the pulse width T _{pwm. As a result, the pulse width T pwm} is estimated using the estimated electric angle θ _est , the command pulse pattern n, and the command pulse pattern n + 1. _{As described above, since it is not necessary to add a new sensor for resetting the estimated electric angle θ est} , which is the switching timing, it is possible to prevent the generation of narrow pulses without increasing the processing load.

According to the control method of the power converter 1 of the first embodiment, the first resetting step (S110) for resetting the _{estimated electric angle θ est} , which is the switching timing, so _{that the pulse width T pwm} exceeds the pulse threshold value T _th. ).

With such a configuration, when the pulse width T _pwm is shorter than the pulse threshold value T _{th , the estimated electric angle θ est} , which is the switching timing, is reset, and the pulse width T _pw m is the pulse threshold value T _th. Exceeds. Therefore, it is possible to prevent the generation of a narrow pulse even in a transient condition in which the command pulse pattern is switched.

According to the control method of the power converter 1 of the first embodiment, in the resetting step (S110), _{after the estimated electric angle θ est} calculated in step S106, then the first pulse pattern and The timing at which the conduction state becomes the same as that of the second pulse pattern is reset as the _{estimated electric angle θ est.}

If the timing at which the conduction state in the command pulse pattern is different is set as the estimated electric angle θ _{est after the estimated electric angle θ est} , which is the switching timing, the conduction state changes at the estimated electric angle θ _{est, and the pulse width T. The pwm} may fall below the pulse threshold T _th. However, by resetting the timing at which the conduction state becomes the same as the estimated electric angle θ _est , the pulse width T _pwm can be made to exceed the pulse threshold value T _th , so that the occurrence of a narrow pulse can be prevented.

According to the control method of the power converter 1 of the first embodiment, the load connected to the power converter 1 is the motor 3, and the PWM generator 141 has a torque command value T ^* for the motor 3 and the motor 3. A pulse pattern is generated based on the number of rotations N of. With such a configuration, it is possible to suppress the generation of narrow pulses even when the load is the motor 3.

According to the control method of the power converter 1 of the first embodiment, the power converter 1 outputs AC power to the motor 3. Then, as shown in FIG. 3, in the determination step (S104) performed by the PWM generation unit 141 ^{, the command pulse pattern is based on the modulation factor M *} of the AC power with respect to the DC power and the rotation speed N of the motor 3. It is determined whether or not to switch.

Further, in the pulse width guessing step (S106), the electrical angle theta ₁ of the motor 3 that shows the timing of conduction state is switched to the first pulse pattern at the immediately preceding estimated electrical angle theta _est, first immediately after the estimated electrical angle theta _est 2 _{The pulse width T pwm} is estimated _{according to the electric angle θ 2 of} the motor 3 indicating the timing at which the conduction state is switched at the beginning of the pulse pattern and the rotation speed N of the motor 3.

_{By being controlled in this way, the power converter 1 controls the pulse width T pwm} to exceed the pulse threshold T _th based on the parameters related to the motor 3 which is the output destination of the AC power, thereby achieving the design accuracy. It is possible to prevent the generation of narrow pulses while increasing the value.

According to the control method of the power converter 1 of the first embodiment, the pulse threshold value T _th is determined by the surge voltage characteristic according to the temperature of the switching element of the power converter 1. As a result, the pulse threshold value T _th can be obtained in advance, so that the generation of a narrow pulse can be prevented depending on the operating environment.

(Second Embodiment)
In the first embodiment, an example in which the rotation speed N calculated by the motor rotation angle detection unit is used when calculating the _{estimated electric angle θ est has been described.} In the second embodiment, an example of estimating the rotation speed N of the motor 3 at the timing when the command pulse pattern is switched when the rotation speed N of the motor 3 changes will be described.

FIG. 9 is a schematic configuration diagram of the PWM pattern switching output unit 142 of the second embodiment. Compared with the PWM pattern switching output unit 142 of the first embodiment shown in FIG. 3, the rotation speed estimation unit 901 is provided in front of the angle estimation unit 1421.

The rotation speed estimation unit 901 stores the rotation speed N for each control cycle T that is the switching timing. In the following, the rotation speed N _n indicates the rotation speed of the motor 3 in the nth control cycle T.

The rotation speed estimation unit 901 estimates the estimated rotation speed N _est , _{which is an estimated value of the rotation speed N n + 1 at} the next switching timing, using the following equation.

However, the parameters in the equation (3) are as follows.
N _n-1 : Rotation speed N at the previous (n-1st) switching timing
N _n : Rotation speed N at the current (nth) switching timing
N _est : Estimated value of rotation speed N at the next (n + 1) switching timing

According to equation (3), it is assumed that the amount of change in the number of revolutions N from the previous switching timing to the current switching timing is equal to the amount of change in the number of revolutions N from the current switching timing to the next switching timing. _{Therefore, the estimated value N n + 1} of the rotation speed N at the next switching timing is estimated.

FIG. 10 is a flowchart of determination control of the final command pulse pattern. Compared with the flowchart of the first embodiment shown in FIG. 5, the process of step S106 is changed to step S202, and the processes of steps S201, S203, and S204 are added.

Step S201 is a process performed when it is necessary to change the output command pulse pattern (S104: Yes). In this process, the rotation speed estimation unit 901 calculates the _{estimated rotation speed est at the next change timing based on the equation (3).} Then, the process of step S202 is performed.

In step S202, the angle estimation unit 1421 compares the current rotation speed N with the estimated rotation speed N _est, and calculates the _{estimated electric angle θ est} by the equation (1) using the larger rotation speed. By this control, even when the rotation speed N changes significantly from the sudden decrease state to the steady state, the larger rotation speed N is used, so that the pulse width T _pwm becomes shorter. Therefore, the pulse width T _pwm is less likely to be determined that the pulse threshold T _th or more, can be suppressed that the pulse width T _pwm to reduce the possibility of a narrow pulse.

In step S202, the angle estimation unit 1421 may calculate the _{estimated electric angle θ est} by the equation (1) using _{the estimated rotation speed N est.} By doing so, the processing load can be reduced.

In step S203, the angle estimation unit 1421 determines whether or not the conduction state in the previous command pulse pattern and the conduction state in the next command pulse pattern are the same in _{the estimated electric angle θ est.} If they are the same (S203: Yes), then step S107 is performed. On the other hand, if the two are different (S203: No), then step S204 is performed.

In step S204, the angle estimation unit 1421 newly estimates the electrical angle at which the conduction state of the current command pulse pattern n and the conduction state of the next command pulse pattern n + 1 match after the _{estimated electrical angle θ est. Reset} as the electrical angle θ est. The resetting process may be referred to as a second resetting process in order to distinguish it from the resetting process (first resetting process) in step S110.

The process corresponding to step S204 may be included in the control that does not include the estimation process of the rotation speed N as in the first embodiment. By doing so, at the estimated electric angle θ _est , the conduction state between the current command pulse pattern n and the next command pulse pattern n can be made the same, so that the generation of narrow pulses can be suppressed.

Next, the output control of the command pulse pattern in the present embodiment will be described with reference to FIG. In these figures, in order from the top, the command pulse pattern n currently being output, the command pulse pattern n + 1 in the next control cycle T generated by the PWM generation unit 141, and the final command output unit 1422 are output. The final command pulse pattern is shown.

In FIG. 11, the estimated electric angle θ _est calculated in step S204 is the command pulse pattern switching timing.

As shown in this figure, in the estimated electric angle θ _est first calculated in step S106, the conduction state of the command pulse pattern n and the conduction state of the command pulse pattern n + 1 are different (S203: No), therefore. After the estimated electrical angle θ _est, the timing at which the conduction state of the command pulse pattern n and the conduction state of the command pulse pattern n + 1 are the same is newly _{reset as the estimated electrical angle θ est} (S204). ..

In this case, as shown in the upper part, the electrical angle theta ₁ which the conducting state of the command pulse pattern n in the previous estimated electrical angle theta _est after resetting are switched, the estimated electrical angle after resetting theta _est Matches with. Further, in the middle stage, the _{electric angle θ 2 at} which the conduction state of the command pulse pattern n + 1 is switched immediately _{after the estimated electric angle θ est} after resetting is shown.

By the process of step S107, the pulse width T _{pwm corresponding to these electric angles θ 1} and θ ₂ is calculated. Here, since the pulse width T _pwm is equal to or greater than the pulse threshold value T _th (S108: Yes), the command pulse pattern is changed _{at the estimated electric angle θ est} as shown in the lower part of the figure. Therefore, it is possible to prevent the _{pulse width T pwm} that straddles the switching timing of the command pulse pattern from becoming a narrow pulse.

According to the second embodiment, the following effects can be obtained.

According to the control method of the power converter 1 of the second embodiment, the rotation speed estimation step (S201) for estimating the rotation speed N at the switching timing based on the change of the rotation speed N for each control cycle T is further provided. .. In the pulse width estimation step (S106), the pulse width T _pwm is estimated _{using the estimated rotation speed est estimated in the rotation speed estimation step.} With such a configuration, it is possible to prevent the generation of a narrow pulse even when the rotation speed N of the motor 3 is rapidly increasing.

According to the control method of the power converter 1 of the second embodiment, in the pulse width estimation step (S202), the estimated rotation speed _est estimated in the rotation speed estimation step (S201) and the current rotation speed N The larger of these is used to estimate the _{pulse width T pwm.} By a such a configuration, since the pulse width T _pwm is calculated shorter becomes the pulse width T _pwm is hardly determined to pulse the threshold T _th or more, the pulse width T _pwm to reduce the possibility of a narrow pulse Can be suppressed.

According to the control method of the power converter 1 of the second embodiment, the current command pulse is obtained at the estimated electric angle θ _{est calculated by using the estimated rotation speed N est estimated in the rotation speed estimation step (S201).} When the pattern and the next command pulse pattern are different (S203: No), the electric angle at which the current command pulse pattern and the next command pulse pattern have the same conduction state is defined as the estimated electric angle θ _est . It has 2 reset steps (S204). With this configuration, by resetting the timing when the conduction state becomes the same as the estimated electrical angle θ _est , the pulse width T _pwm exceeds the pulse threshold value T _th, and the occurrence of narrow pulses is prevented. be able to.

Although the embodiments of the present invention have been described above, the above embodiments are only a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configurations of the above embodiments. Absent. In addition, the above embodiments can be combined as appropriate.

1 Power converter 3 Motor 6 Current sensor 10 Control device 11 Current command value calculation unit 12 Current control unit 13 Modulation rate conversion unit 14 PWM output unit 141 PWM generation unit 142 PWM pattern switching output unit 1421 Angle estimation unit 1422 Final command output unit 100 motor system 901 rotation speed estimation unit

Claims (10)

It is a control method of a power converter that converts DC power into AC power by changing the conduction state of a switching element by using PWM control according to a pulse pattern repeated in a predetermined control cycle.
A switching determination step for determining whether or not to switch the pulse pattern according to a control command value for a load connected to the power converter, and
When it is determined in the switching determination step that the pulse pattern is to be switched, the change timing of the conduction state in the first pulse pattern immediately before the switching timing and the change in the conduction state in the second pulse pattern immediately after the switching timing. A pulse width estimation step that estimates the time between the timings as the pulse width of the pulse that straddles the switching timing, and
A determination step for determining whether or not the pulse width estimated in the pulse width estimation step exceeds a threshold value.
A power converter control method comprising a switching step of switching the pulse pattern at the switching timing when the pulse width is determined to exceed the threshold value in the determination step. The power converter control method according to claim 1.
If it is determined in the determination step that the pulse width does not exceed the threshold, the power further includes a first reset step that resets the switching timing so that the pulse width exceeds the threshold. How to control the converter. The power converter control method according to claim 2.
Control of the power converter in the first resetting step, after the switching timing, the timing at which the conduction state of the first pulse pattern and the second pulse pattern becomes the same is reset as the switching timing. Method. The power converter control method according to any one of claims 1 to 3.
If the conduction state between the first pulse pattern and the second pulse pattern is different at the switching timing determined in the switching determination step, it is after the switching timing and with the first pulse pattern. A power converter control method further comprising a second resetting step of resetting the timing at which the conduction state becomes the same as that of the second pulse pattern as the switching timing. The power converter control method according to any one of claims 1 to 4.
The load is a motor
A power converter control method further comprising a pulse pattern determination step of determining the pulse pattern based on a torque command value for the motor and a rotation speed of the motor. The power converter control method according to claim 5.
A power converter control method for determining whether or not to switch a pulse pattern based on the modulation factor of the AC power with respect to the DC power in the power converter and the rotation speed in the switching determination step. The power converter control method according to claim 5 or 6.
A rotation speed estimation step for estimating the rotation speed at the switching timing based on the change in the rotation speed for each control cycle is further provided.
A power converter control method for estimating a pulse width by using the estimated rotation speed estimated in the rotation speed estimation step as the rotation speed in the pulse width estimation step. The power converter control method according to claim 5 or 6.
A rotation speed estimation step for estimating the rotation speed at the switching timing based on the change in the rotation speed for each control cycle is further provided.
In the pulse width estimation step, a power converter that estimates the pulse width by using the larger of the estimated rotation speed estimated in the rotation speed estimation step and the current rotation speed as the rotation speed. Control method. The power converter control method according to any one of claims 1 to 8.
The threshold value is a control method for a power converter, which is determined by the characteristics of a surge voltage according to the temperature of the switching element. A power converter control device that converts DC power into AC power by changing the conduction state of the switching element using PWM control according to a pulse pattern that is repeated in a predetermined control cycle.
The control device is
It is determined whether or not to switch the pulse pattern according to the control command value for the load connected to the power converter.
When it is determined to switch the pulse pattern, the time between the change timing of the conduction state in the first pulse pattern immediately before the switching timing and the change timing of the conduction state in the second pulse pattern immediately after the switching timing. Is estimated as the pulse width of the pulse that straddles the switching timing.
It is determined whether or not the estimated pulse width exceeds the threshold value.
A control device for a power converter that switches the pulse pattern at the switching timing when it is determined that the pulse width exceeds the threshold value.

Images