JP2019161900A - Electric power conversion device - Google Patents

Abstract

To reduce a high-frequency spectrum to suppress inductive interference from being caused.SOLUTION: An electric power conversion device 10 according to the present invention comprises a carrier frequency generation part 15 which generates a carrier frequency, a carrier generation part 16 which generates a carrier of the generated carrier frequency, and a PWM signal generation part 18 which compares the generated carrier with a control command to generate a PWM control signal for controlling switching of a switching element of an electric power converter 14, and the carrier frequency generation part 15 comprises a random number generator 153 which generates a frequency signal for increasing and decreasing the carrier frequency at random within a predetermined range based upon a random number, and a cycle generator 154 which generates a frequency varying in predetermined cycles around a reference carrier frequency, and then outputs the frequency, obtained by adding the frequency signal to the frequency generated by the cycle generator 154, as a carrier frequency to the carrier generation part 16.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion device that converts DC power into AC power by switching of a switching element.

  Conventionally, as a control method of a power conversion device that drives an induction motor for an electric vehicle, asynchronous control is performed when the vehicle is traveling at a low speed, and synchronous control is performed when the vehicle is traveling at a high speed. The method of performing is often used.

  FIG. 9 is a diagram illustrating a configuration example of a general power conversion device 30.

  9 includes a reactor 12, a capacitor 13, a power converter 14, a carrier frequency generation unit 31, a carrier generation unit 16, a control command unit 17, and a PWM signal generation unit 18. Prepare.

  The reactor 12 and the capacitor 13 are connected in series between the positive electrode and the negative electrode of the DC power supply 11. The power converter 14 is connected to the capacitor 13 in parallel. The power converter 14 includes a switching element, converts the DC power from the DC power supply 11 into AC power by switching of the switching element, and supplies the AC power to the motor 1 that is an induction motor. As a method for switching on / off the switching element of the power converter 14, the switching element is controlled by a PWM (Pulse Width Modulation) control signal (control signal) having a different pulse width according to the comparison between the carrier and the control command. There is a method of controlling by the PWM method.

  The carrier frequency generation unit 31 generates a carrier frequency (carrier frequency) and outputs the carrier frequency to the carrier generation unit 16. The carrier generation unit 16 generates a triangular wave or the like having the carrier frequency output from the carrier frequency generation unit 31 as a carrier, and outputs the carrier to the PWM signal generation unit 18. The control command unit 17 generates a control command and outputs it to the PWM signal generation unit 18. The PWM signal generation unit 18 generates a PWM control signal for controlling the switching of the switching element of the power converter 14 by comparing the carrier output from the carrier generation unit 16 with the control command output from the control command unit 17. To do. By using this PWM control signal to control the switching of the switching element of the power converter 14, the DC power can be converted into AC power.

  When the PWM method is used during asynchronous control, if the carrier frequency generated by the carrier frequency generation unit 31 is constant, electromagnetic noise due to the carrier frequency is generated, which may cause noise.

  Therefore, Patent Document 1 discloses a technique for suppressing noise using two random number generators. FIG. 10 is a diagram illustrating a configuration example of the carrier frequency generation unit 31 when the technique disclosed in Patent Document 1 is applied.

  The carrier frequency generation unit 31 shown in FIG. 10 includes random number generators 311 and 313, a timer 312, and an adder 314.

  The random number generator 311 randomly determines the duration of the carrier frequency within a predetermined range based on the random number, and sets the determined duration in the timer 312.

  The timer 312 notifies the random number generator 313 when the duration set by the random number generator 311 expires.

  When notified from the timer 312, the random number generator 313 generates a frequency signal that randomly changes (increases or decreases) the carrier frequency within a predetermined range based on the random number, and outputs the frequency signal to the adder 314.

  The adder 314 outputs a frequency obtained by adding the frequency signal output from the random number generator 313 to the reference carrier frequency, which is a reference carrier frequency, to the carrier generation unit 16 as a carrier frequency.

JP-A-6-14557

  In the power conversion device 30 shown in FIG. 9, during asynchronous control, among frequency components included in the current flowing through the reactor 12, a specific frequency spectrum due to the carrier frequency becomes high, and the induction that causes trouble in communication of signals and the like Failure may occur.

  FIG. 11 is a spectrum diagram obtained by fast Fourier transform of the simulation result of the direct current flowing through the reactor 12 when the carrier frequency generated by the carrier frequency generation unit 31 is constant (750 Hz). As shown in FIG. 11, a spectrum of about 0.1 A stands at 1.5 kHz, and a spectrum stands also in a high frequency range. From this, it can be seen that a direct current includes a high-frequency current.

  The technique disclosed in Patent Document 1 is intended to reduce electromagnetic noise, and does not consider the suppression of the high-frequency spectrum as described above.

  An object of the present invention made in view of the above problems is to provide a power conversion device that can reduce the high-frequency spectrum and suppress the occurrence of an induction failure.

  In order to solve the above problems, a power conversion device according to the present invention is a power conversion device that converts DC power into AC power by switching of a switching element, and generates a carrier frequency that is a carrier frequency. A carrier generation unit that generates a carrier having a carrier frequency generated by the carrier frequency generation unit, and a control signal that controls switching of the switching element by comparing the carrier generated by the carrier generation unit and a control command The carrier frequency generation unit generates a frequency signal that randomly increases / decreases the carrier frequency within a predetermined range based on a random number, and a carrier frequency generator Centering on the reference carrier frequency that is the reference, the frequency changes at a predetermined cycle. A frequency generator that generates a number, and outputs a frequency obtained by adding the frequency signal generated by the first random number generator to the frequency generated by the cycle generator to the carrier generator as the carrier frequency .

  Further, in the power conversion device according to the present invention, the carrier frequency generation unit further includes a second random number generator that randomly determines a duration of the carrier frequency within a predetermined range based on a random number, The random number generator preferably generates the frequency signal each time the duration determined by the second random number generator elapses.

  Moreover, in order to solve the said subject, the power converter device which concerns on this invention is a power converter device which converts direct-current power into alternating current power by switching of a switching element, Comprising: The carrier frequency which produces | generates the carrier frequency which is a carrier frequency The switching of the switching element is controlled by comparing the generation unit, the carrier generation unit that generates the carrier of the carrier frequency generated by the carrier frequency generation unit, and the carrier generated by the carrier generation unit and a control command A signal generation unit that generates a control signal, and the carrier frequency generation unit randomly sets the carrier frequency within a predetermined range based on a difference between a reference carrier frequency that is a reference of the carrier frequency and a current carrier frequency. A random number range changer that determines the range of frequency signals to be increased or decreased; A third random number generator for generating the frequency signal based on a random number within a range determined by the random number range changer, and generated by the third random number generator at the current carrier frequency. The frequency obtained by adding the frequency signals is output to the carrier generation unit as the carrier frequency.

  Further, in the power conversion device according to the present invention, the carrier frequency generation unit further includes a fourth random number generator that randomly determines a duration of the carrier frequency within a predetermined range based on a random number, The random number generator generates the frequency signal every time the duration determined by the fourth random number generator elapses.

  According to the power conversion device of the present invention, it is possible to reduce the high frequency spectrum and suppress the occurrence of inductive failure.

It is a figure which shows the structural example of the power converter device which concerns on the 1st Embodiment of this invention. It is a figure which shows the structural example of the carrier frequency production | generation part shown in FIG. It is a figure which shows an example of the carrier frequency which the carrier frequency generation part shown in FIG. 1 produces | generates. It is the spectrum figure which carried out the fast Fourier transform of the simulation result of the direct current which flows into the reactor shown in FIG. It is a figure which shows the structural example of the power converter device which concerns on the 2nd Embodiment of this invention. It is a figure which shows the structural example of the carrier frequency production | generation part shown in FIG. It is a figure which shows an example of the carrier frequency which the carrier frequency generation part shown in FIG. 5 produces | generates. FIG. 6 is a spectrum diagram obtained by performing a fast Fourier transform on the simulation result of the direct current flowing through the reactor shown in FIG. 5. It is a figure which shows the structural example of the conventional power converter device. It is a figure which shows the structural example of the carrier frequency production | generation part shown in FIG. FIG. 10 is a spectrum diagram obtained by performing a fast Fourier transform on the simulation result of the direct current flowing through the reactor shown in FIG. 9.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected about a common structure and description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration example of a power conversion device 10 according to the first embodiment of the present invention. The power converter 10 shown in FIG. 1 converts DC power into AC power, and the carrier frequency generator 31 is changed to the carrier frequency generator 15 as compared with the power converter 30 shown in FIG. Is different. That is, the power conversion device 10 according to the present embodiment includes a reactor 12, a capacitor 13, a power converter 14, a carrier frequency generation unit 15, a carrier generation unit 16, a control command unit 17, and a PWM signal generation unit. 18 (signal generation unit).

  The carrier frequency generation unit 15 generates a carrier frequency and outputs it to the carrier generation unit 16. Here, the carrier frequency generation unit 15 randomly determines the duration of the carrier frequency, and changes the carrier frequency randomly each time the determined duration elapses.

  FIG. 2 is a diagram illustrating a configuration example of the carrier frequency generation unit 15.

  The carrier frequency generator 15 shown in FIG. 2 includes random number generators 151 and 153, a timer 152, a period generator 154, and an adder 155.

  The random number generator 151 (second random number generator) randomly determines the duration of the carrier frequency within a predetermined range based on the random number, and sets the determined duration in the timer 152.

  The timer 152 notifies the random number generator 153 when the duration set by the random number generator 151 expires.

  When notified from the timer 152, the random number generator 153 (first random number generator) generates a frequency signal that randomly changes (increases / decreases) the carrier frequency within a predetermined range based on the random number, and an adder 155 Output to.

  The period generator 154 generates a frequency that changes at a predetermined period around the reference carrier frequency that is a reference of the carrier frequency, and outputs the generated frequency to the adder 155.

  The adder 155 outputs a frequency obtained by adding the frequency signal output from the random number generator 153 to the frequency output from the period generator 154 to the carrier generation unit 16 as a carrier frequency.

  FIG. 3 is a diagram illustrating an example of the carrier frequency output from the carrier frequency generation unit 15. In FIG. 3, the period generator 154 shows an example in which the frequency is changed in a triangular wave shape having a predetermined period around the reference carrier frequency.

  As shown in FIG. 3, when viewed macroscopically, the carrier frequency is a triangular wave with a predetermined period centered on the reference carrier frequency generated by the period generator 154. When viewed microscopically, the random number generator Increase or decrease in accordance with the frequency signal generated by 153. That is, the duration of the carrier frequency set by the random number generator 151 is sufficiently smaller than the period in which the period generator 154 changes the frequency. Further, the change amount (increase / decrease) of the carrier frequency due to the frequency signal generated by the random number generator 153 is smaller than the change amount of the frequency by the period generator 154.

  FIG. 4 is a spectrum diagram obtained by fast Fourier transform of the simulation result of the direct current flowing through the reactor 12 when the carrier frequency shown in FIG. 3 is used.

  As shown in FIG. 4, in this embodiment, it can be seen that the spectrum standing at 1.5 kHz is suppressed to about 1/10 compared to the case where a constant carrier frequency is used (FIG. 11). Therefore, it is possible to reduce the high frequency spectrum and suppress the occurrence of inductive disturbance.

  In the above-described example, the period generator 154 has been described using an example in which the frequency is changed in a triangular wave shape around the reference carrier frequency. However, the present invention is not limited to this. The period generator 154 may change the frequency in a sine wave shape or a sawtooth wave shape, for example. Further, the cycle generator 154 may change the cycle for changing the frequency. In this case, one random number generator is added, and the period generator 154 can change the period according to the output from the random number generator.

  In the above-described example, the example in which the duration of the carrier frequency is randomly changed has been described. However, the present invention is not limited to this, and the duration of the carrier frequency may be constant. Therefore, the random number generator 151 and the timer 152 are not essential components. When the duration of the carrier frequency is constant, the random number generator 153 generates a frequency signal every predetermined period.

  As described above, in the present embodiment, the power conversion device 10 includes the carrier frequency generation unit 15 that generates the carrier frequency, the carrier generation unit 16 that generates the carrier of the carrier frequency generated by the carrier frequency generation unit 15, and the carrier A PWM signal generation unit 18 that generates a PWM control signal (control signal) for controlling switching of the switching element of the power converter 14 by comparing the carrier generated by the generation unit 16 and the control command. The carrier frequency generation unit 15 generates a frequency that changes at a predetermined cycle centered on the reference carrier frequency and a random number generator 151 that generates a frequency signal that randomly increases or decreases the carrier frequency within a predetermined range based on the random number. The frequency generator 154 is provided, and a frequency obtained by adding the frequency signal generated by the random number generator 151 to the frequency generated by the cycle generator 154 is output to the carrier generator 16 as a carrier frequency.

  A frequency obtained by adding a frequency signal that is randomly increased or decreased to a frequency that changes at a predetermined period around the reference carrier frequency is used as the carrier frequency, so that the carrier frequency is changed randomly, and the spectrum of the direct current flowing through the reactor 12 is obtained. Can be dispersed. Therefore, it is possible to reduce the high frequency spectrum and suppress the occurrence of induction disturbance.

(Second Embodiment)
FIG. 5 is a diagram illustrating a configuration example of the power conversion device 20 according to the second embodiment of the present invention. The power conversion device 20 according to the present embodiment is different from the power conversion device 10 according to the first embodiment in that the carrier frequency generation unit 15 is changed to the carrier frequency generation unit 21. Therefore, the carrier frequency generation unit 21 will be described below.

  FIG. 6 is a diagram illustrating a configuration example of the carrier frequency generation unit 21.

  The carrier frequency generator 21 shown in FIG. 6 includes random number generators 211 and 214, a timer 212, a random number range changer 213, and an adder 215.

  The random number generator 211 (fourth random number generator) randomly determines the duration of the carrier frequency within a predetermined range based on the random number, and sets the determined duration in the timer 212.

  The timer 212 notifies the random number generator 214 when the duration set by the random number generator 211 has expired.

  The random number range changer 213 changes the range of the frequency signal for changing (increasing / decreasing) the carrier frequency based on the difference between the carrier frequency (current carrier frequency) output from the adder 215 described later and the reference carrier frequency. To the random number generator 214.

  When notified from the timer 212, the random number generator 214 (third random number generator) changes the carrier frequency randomly within a predetermined range based on the random number within the range set by the random number range changer 213. A frequency signal to be increased / decreased is generated and output to the adder 155.

  The adder 215 outputs the frequency obtained by adding the frequency signal output from the random number generator 214 to the current carrier frequency to the carrier generation unit 16 and the random number range changer 213 as the carrier frequency.

  FIG. 7 is a diagram illustrating an example of the carrier frequency output from the carrier frequency generation unit 21. In FIG. 7, the random number range changer 213 has a frequency signal range (random number range) so that the current carrier frequency approaches the reference carrier frequency as the difference between the current carrier frequency and the reference carrier frequency increases. The example which narrows is shown.

  FIG. 8 is a spectrum diagram obtained by fast Fourier transform of the simulation result of the direct current flowing through the reactor 12 when the carrier frequency shown in FIG. 7 is used.

  As shown in FIG. 8, in this embodiment, it can be seen that the spectrum standing at 1.5 kHz is suppressed to about a quarter compared to the case where a constant carrier frequency is used (FIG. 11). Therefore, it is possible to reduce the high frequency spectrum and suppress the occurrence of inductive disturbance.

  In the example described above, the example in which the duration of the carrier frequency changes at random is described. However, the present invention is not limited to this, and the duration of the carrier frequency may be constant. Therefore, the random number generator 211 and the timer 212 are not essential components. When the duration of the carrier frequency is constant, the random number generator 214 generates a frequency signal every predetermined period.

  As described above, in this embodiment, the power conversion device 20 includes the carrier frequency generation unit 21 that generates the carrier frequency, the carrier generation unit 16 that generates the carrier of the carrier frequency generated by the carrier frequency generation unit 21, and the carrier A PWM signal generation unit 18 that generates a PWM control signal (control signal) for controlling switching of the switching element of the power converter 14 by comparing the carrier generated by the generation unit 16 and the control command. The carrier frequency generator 21 includes a random number range changer 213 that determines a range of a frequency signal that randomly increases or decreases the carrier frequency within a predetermined range based on the difference between the reference carrier frequency and the current carrier frequency, and a random number range changer 213, a random number generator 214 that generates a frequency signal based on a random number within a range determined by 213. The carrier frequency is a frequency obtained by adding the frequency signal generated by the random number generator 214 to the current carrier frequency. Output to the generator 16.

  By determining the range of the frequency signal based on the difference between the reference carrier frequency and the current carrier frequency, and adding a frequency signal that randomly increases or decreases within the range to the current carrier frequency as a new carrier frequency, The spectrum of the direct current flowing through the reactor 12 can be dispersed by changing the carrier frequency at random. Therefore, it is possible to reduce the high frequency spectrum and suppress the occurrence of induction disturbance.

  Although the above embodiments have been described as representative examples, it will be apparent to those skilled in the art that many changes and substitutions can be made within the spirit and scope of the invention. Accordingly, the present invention should not be construed as being limited by the above-described embodiments, and various modifications and changes can be made without departing from the scope of the claims. For example, it is possible to combine a plurality of constituent blocks described in the configuration diagram of the embodiment into one, or to divide one constituent block.

DESCRIPTION OF SYMBOLS 1 Motor 10 Power converter 11 DC power supply 12 Reactor 13 Capacitor 14 Power converter 15 Carrier frequency generation part 16 Carrier generation part 17 Control command part 18 PWM signal generation part 21 Carrier frequency generation part 151 Random number generator (2nd random number generation) vessel)
152 timer 153 random number generator (first random number generator)
154 Period generator 155 Adder 211 Random number generator (fourth random number generator)
212 timer 213 random number range changer 214 random number generator (third random number generator)
215 Adder

Claims (4)

A power conversion device that converts DC power into AC power by switching of a switching element,
A carrier frequency generation unit that generates a carrier frequency that is a carrier frequency;
A carrier generation unit that generates a carrier having a carrier frequency generated by the carrier frequency generation unit;
A signal generation unit that generates a control signal for controlling switching of the switching element by comparing the carrier generated by the carrier generation unit with a control command;
The carrier frequency generator is
A first random number generator for generating a frequency signal based on a random number to randomly increase or decrease the carrier frequency within a predetermined range;
A period generator that generates a frequency that changes at a predetermined period around a reference carrier frequency that is a reference of the carrier frequency;
The power conversion device, wherein a frequency obtained by adding a frequency signal generated by the first random number generator to a frequency generated by the period generator is output to the carrier generation unit as the carrier frequency. The power conversion device according to claim 1,
The carrier frequency generator is
A second random number generator for randomly determining a duration of the carrier frequency based on a random number within a predetermined range;
The first random number generator generates the frequency signal every time the duration determined by the second random number generator elapses. A power conversion device that converts DC power into AC power by switching of a switching element,
A carrier frequency generation unit that generates a carrier frequency that is a carrier frequency;
A carrier generation unit that generates a carrier having a carrier frequency generated by the carrier frequency generation unit;
A signal generation unit that generates a control signal for controlling switching of the switching element by comparing the carrier generated by the carrier generation unit with a control command;
The carrier frequency generator is
A random number range changer that determines a range of a frequency signal that randomly increases or decreases the carrier frequency within a predetermined range based on a difference between a reference carrier frequency that is a reference of the carrier frequency and a current carrier frequency;
A third random number generator for generating the frequency signal based on a random number within a range determined by the random number range changer;
The power conversion device, wherein a frequency obtained by adding the frequency signal generated by the third random number generator to the current carrier frequency is output to the carrier generation unit as the carrier frequency. The power conversion device according to claim 3,
The carrier frequency generator is
A fourth random number generator for randomly determining a duration of the carrier frequency in a predetermined range based on a random number;
The power converter according to claim 3, wherein the third random number generator generates the frequency signal each time the duration determined by the fourth random number generator elapses.

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