JP2015106979A - Switching control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit not only noise generated by an inverter but noise of a component electrically connected to the inverter.SOLUTION: An inverter control device 9 of the present embodiment comprises a carrier frequency selection part 13 which selects a carrier frequency in a manner such that a selection ratio of selecting a carrier frequency on a lower frequency side among a plurality of carrier frequencies set within a predetermined frequency range becomes lower than a selection ratio of selecting a carrier frequency on a higher frequency side when a carrier frequency diffusion mode is executed.

Description

  The present invention relates to a switching control device that controls a switching device for converting electric power from a DC power source and supplying the power to a load.

  Conventionally, Patent Document 1 is disclosed as a technique for preventing noise generated by an inverter from being concentrated on a specific frequency by irregularly using a plurality of carrier frequencies in an inverter control device.

JP 2006-174645 A

  However, although the conventional inverter control device described above is effective against noise generated from the inverter, there is a problem in that the noise is worsened depending on the components electrically connected to the inverter. .

  Therefore, the present invention has been proposed in view of the above-described circumstances, and an object of the present invention is to provide a switching control device that can also suppress noise of components electrically connected to an inverter.

  In order to solve the above-described problem, the present invention executes a carrier frequency spreading mode for selecting a carrier frequency to be used from among a plurality of carrier frequencies set within a predetermined frequency range. In this carrier frequency spreading mode, the carrier frequency is selected such that the selection ratio for selecting the carrier frequency on the low frequency side among the plurality of carrier frequencies is lower than the selection ratio for selecting the carrier frequency on the high frequency side.

  According to the present invention, since the carrier frequency is selected in consideration of the characteristics of the components electrically connected to the switching device, the noise of the components electrically connected to the switching device can also be suppressed.

FIG. 1 is a block diagram showing a configuration of a power conversion system including an inverter control device according to the first embodiment of the present invention. FIG. 2 is a diagram showing a map used in the inverter control apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram for explaining the effect of the inverter control apparatus according to the first embodiment of the present invention. FIG. 4 is a diagram showing a map used in the inverter control device according to the second embodiment of the present invention. FIG. 5 is a diagram showing a map used in the inverter control apparatus according to the third embodiment of the present invention. FIG. 6 is a diagram showing a map used in the inverter control device according to the fourth embodiment of the present invention. FIG. 7 is a block diagram showing a configuration of a power conversion system including an inverter control device according to the fifth embodiment of the present invention. FIG. 8 is a diagram for explaining a carrier frequency spreading mode switching method by the inverter control apparatus according to the fifth embodiment of the present invention.

  Hereinafter, first to fifth embodiments to which the present invention is applied will be described with reference to the drawings.

[First Embodiment]
[Configuration of power conversion system]
FIG. 1 is a block diagram illustrating a configuration of a power conversion system including an inverter control device according to the present embodiment. As shown in FIG. 1, the power conversion system 1 includes a battery 3, an inverter 5, a motor 7, and an inverter control device 9.

  The power conversion system 1 is a system for converting power from a DC power supply and supplying it to a load. In the present embodiment, the DC power supplied from the battery 3 is converted into AC power by the inverter 5 by switching control of the inverter control device 9 and supplied to the motor 7.

  The battery 3 is a DC power source such as an in-vehicle battery, and supplies DC power to the inverter 5.

  The inverter 5 is a switching device that converts DC power supplied from the battery 3 and supplies it to a load. In the present embodiment, the inverter 5 that converts DC to AC will be described as an example. However, it may be a switching device that converts direct current to direct current, such as a DC-DC converter. The inverter 5 of the present embodiment converts DC power into three-phase AC power and supplies it to the motor 7. The inverter 7 outputs a three-phase AC by an internal switching element such as an IGBT to drive the motor 7 with PWM drive. To do.

  The motor 7 is a load such as a three-phase AC motor, and is driven by AC power output from the inverter 5. However, the load need not be driven by AC power, and may be a load driven by DC power.

  The inverter control device 9 is a switching control device that controls a switching device such as the inverter 5 or a DC-DC converter. In the present embodiment, the inverter control device 9 will be described as an example of the switching control device. The inverter control device 9 outputs a drive pulse for PWM control of the inverter 5, and selects a carrier frequency spreading mode for selecting a carrier frequency to be used from a plurality of carrier frequencies set within a predetermined frequency range. Run. The inverter control device 9 includes a PWM control unit 11 and a carrier frequency selection unit 13.

  The PWM control unit 11 executes the carrier frequency spreading mode using the carrier frequency selected by the carrier frequency selection unit 13 and performs PWM control on the inverter 5.

  When the carrier frequency selection unit 13 executes the carrier frequency spreading mode, the selection ratio for selecting the carrier frequency on the low frequency side among the plurality of carrier frequencies is lower than the selection ratio for selecting the carrier frequency on the high frequency side. Select the carrier frequency. Therefore, the carrier frequency selection unit 13 stores in advance a map 15 used when selecting a carrier frequency.

  The inverter control device 9 includes a general-purpose electronic circuit including a microcomputer, a microprocessor, and a CPU, and peripheral devices. By executing a specific program, the inverter control device 9 serves as a PWM control unit 11 and a carrier frequency selection unit 13. Operate.

[Carrier frequency selection method]
Next, a carrier frequency selection method by the carrier frequency selector 13 will be described with reference to the map of FIG. FIG. 2 is a diagram showing a map 15 stored in the carrier frequency selection unit 13.

  As shown in FIG. 2, a plurality of carrier frequencies f1 to fn are set within a predetermined frequency range set in advance, and f1 is the lowest frequency and fn is the highest frequency. In this embodiment, the selection frequencies of the carrier frequencies f1 to fn are all constant, but the frequency interval between adjacent carrier frequencies is set to be wider on the low frequency side than on the high frequency side. The selection ratio is low.

  A dotted line 21 in FIG. 2 indicates the number of carrier frequencies set within a certain frequency width. In FIG. 2, since the dotted line 21 indicates a low value on the low frequency side and indicates a high value on the high frequency side, the number of carrier frequencies set within a certain frequency range is smaller on the low frequency side than on the high frequency side. It has become. That is, since the density of the carrier frequency on the low frequency side is low, it indicates that the frequency interval of the carrier frequency is wider on the low frequency side than on the high frequency side.

  Further, as indicated by the dotted line 21, in the present embodiment, the number of carrier frequencies set within a certain frequency width continuously decreases from the high frequency side to the low frequency side. As a result, the carrier frequency selection ratio also continuously decreases from the high frequency side to the low frequency side.

[Effect of the first embodiment]
Next, with reference to FIG. 3, the effect by the inverter control apparatus 9 which concerns on this embodiment is demonstrated.

  FIG. 3 is a diagram showing the ripple current value of ripple current generated in the battery 3 and the power affecting sound vibration noise when the inverter 5 is driven using the carrier frequency selection method described above. FIG. 3 shows the peak value of the ripple current generated in the battery 3 while using a certain carrier frequency, unlike the so-called FFT (Fast Fourier Transform) waveform, and excludes the direct current component.

  As shown in FIG. 3, the peak value of the ripple current generated in the battery 3 is highest at the carrier frequency f1 on the low frequency side, decreases as the frequency increases, and becomes lowest at the carrier frequency fn on the high frequency side. ing.

  Here, in this embodiment, as shown in FIG. 2, the frequency interval of the carrier frequency is wider on the low frequency side than on the high frequency side. Thereby, as shown in FIG. 3, the power 31 that affects sound vibration noise can be made constant with respect to the change in frequency.

  Conventionally, sound noise also increased on the low frequency side as the ripple current increased. However, in this embodiment, the frequency interval on the low frequency side is widened, so the sound noise on the low frequency side is reduced. Thus, the frequency characteristics of sound vibration noise can be made constant. Therefore, additional parts such as a sound absorbing material are not required, and the cost can be reduced.

  In particular, in the conventional patent document 1, noise at a specific frequency is converted into white noise by diffusing the carrier frequency. However, even with the same level of noise, the way the noise is felt is different for each frequency depending on the human sensitivity, and humans feel that the noise is greater at lower frequencies. Therefore, simply reducing noise from concentrating on a specific frequency is not sufficient in reducing noise. However, in this embodiment, sound vibration noise on the low frequency side can be reduced, so that human sensitivity characteristics are considered. Thus, the noise reduction effect can be increased.

  As described above in detail, in the inverter control device 9 according to the present embodiment, the selection ratio for selecting the carrier frequency on the low frequency side selects the carrier frequency on the high frequency side when executing the carrier frequency spreading mode. Lower than selection ratio. Accordingly, since the carrier frequency can be selected in consideration of the characteristics of the battery 3 electrically connected to the inverter 5, not only the noise of the inverter 5 but also the sound vibration noise of the battery 3 electrically connected to the inverter 5 Can also be suppressed.

  In particular, by reducing the selection ratio of the carrier frequency on the low frequency side, the low frequency component of the current of the battery 3 excited by the inverter 5 can be reduced, so that sound vibration noise generated from the battery 3 is effectively reduced. Can be reduced. For this reason, additional parts, such as a sound-absorbing material, become unnecessary and the cost of the whole system can be reduced.

  Further, in the inverter control device 9 according to the present embodiment, the selection rate on the low frequency side is lowered by making the frequency interval of the carrier frequency wider on the low frequency side than on the high frequency side. Thereby, the selection ratio on the low frequency side can be reliably reduced, and sound vibration noise of the battery 3 electrically connected to the inverter 5 can be reliably suppressed.

  Furthermore, in the inverter control device 9 according to the present embodiment, the carrier frequency selection ratio is continuously reduced from the high frequency side to the low frequency side, so that the frequency characteristics of sound vibration noise generated in the battery 3 are constant over the entire frequency range. can do. Thereby, sound vibration noise of the battery 3 electrically connected to the inverter 5 can be reliably suppressed.

[Second Embodiment]
Next, an inverter control apparatus according to a second embodiment of the present invention will be described with reference to the drawings. In addition, since the structure of the inverter control apparatus which concerns on this embodiment is the same as 1st Embodiment, detailed description is abbreviate | omitted.

[Carrier frequency selection method]
Next, a carrier frequency selection method by the carrier frequency selector 13 will be described with reference to the map of FIG. FIG. 4 is a diagram showing a map 15 stored in the carrier frequency selection unit 13.

  As shown in FIG. 4, a plurality of carrier frequencies f1 to fn are set within a predetermined frequency range set in advance, and f1 is the lowest frequency and fn is the highest frequency. In this embodiment, the selection frequencies of the carrier frequencies f1 to fn are all constant, but the frequency interval is set to be wider on the low frequency side than on the high frequency side, thereby reducing the selection ratio on the low frequency side. doing.

  However, in the present embodiment, as indicated by the dotted line 41, the number of carrier frequencies set within a certain frequency width is gradually reduced from the high frequency side to the low frequency side as in the first embodiment. It is different. As a result, the carrier frequency selection ratio also gradually decreases from the high frequency side to the low frequency side.

  As shown in FIG. 4, the dotted line 41 indicates that the number of carrier frequencies set within a certain frequency width gradually decreases from the section S1 to the section S5. That is, in each section S1 to S5, the frequency interval of the carrier frequency is constant, but the frequency interval of the carrier frequency becomes wider on the low frequency side than on the high frequency side as it goes from the section S1 to the section S5. .

  In addition, when mounting a map, you may make it create and implement a map for every area. Thereby, the memory capacity for storing the map can be further reduced, and the cost can be reduced.

[Effects of Second Embodiment]
As described above in detail, according to the inverter control device 9 according to the present embodiment, the carrier frequency selection ratio is gradually reduced from the high frequency side to the low frequency side, so the memory capacity when storing the map is reduced. The cost can be reduced.

[Third Embodiment]
Next, an inverter control apparatus according to a third embodiment of the present invention will be described with reference to the drawings. In addition, since the structure of the inverter control apparatus which concerns on this embodiment is the same as 1st Embodiment, detailed description is abbreviate | omitted.

[Carrier frequency selection method]
Next, a carrier frequency selection method by the carrier frequency selector 13 will be described with reference to the map of FIG. FIG. 5 is a diagram showing a map 15 stored in the carrier frequency selection unit 13.

  As shown in FIG. 5, a plurality of carrier frequencies f1 to fn are set within a predetermined frequency range set in advance, and f1 is the lowest frequency and fn is the highest frequency. In this embodiment, the frequency intervals of the carrier frequencies f1 to fn are all constant, but the selection frequency is set to be lower on the low frequency side than on the high frequency side, thereby reducing the selection ratio on the low frequency side. doing. Therefore, in the present embodiment, as indicated by the dotted line 51, the number of carrier frequencies set within a certain frequency width is constant.

  As described in the second embodiment, the intervals S1 to S5 are set as the carrier frequency, and the carrier frequency selection frequency is gradually reduced on the low frequency side from the high frequency side in a stepwise manner from the interval S1 to the interval S5. May be.

[Effect of the third embodiment]
As described above in detail, in the inverter control device 9 according to the present embodiment, the selection frequency on the low frequency side is lowered by reducing the selection frequency of the carrier frequency on the low frequency side than on the high frequency side. Thereby, the selection ratio on the low frequency side can be reliably reduced, and sound vibration noise of the battery 3 electrically connected to the inverter 5 can be reliably suppressed.

[Fourth Embodiment]
Next, an inverter control apparatus according to a fourth embodiment of the present invention will be described with reference to the drawings. In addition, since the structure of the inverter control apparatus which concerns on this embodiment is the same as 1st Embodiment, detailed description is abbreviate | omitted.

  In the inverter control device 9 according to the present embodiment, the PWM control unit 11 calculates a frequency average value of a plurality of carrier frequencies based on a selection frequency of the plurality of carrier frequencies set within a predetermined frequency range. Then, PWM control is performed so that this frequency average value is equal to or lower than the carrier frequency that is a reference in the thermal design of the inverter 5.

  Specifically, taking the first embodiment as an example, as shown in FIG. 6, in the first embodiment, the carrier frequency selection frequency is constant and the frequency interval is widened on the low frequency side.

In this case, the PWM control unit 11 performs PWM control so that the frequency average value fa of the carrier frequency is equal to or lower than the carrier frequency f ₀ that is a reference in the thermal design of the inverter 5 as shown in FIG.

Here, the carrier frequency f ₀ is the fundamental frequency at the time of thermal design of the inverter 5, beyond this frequency, the inverter 5 may exceed the allowable range of the thermal design.

  On the other hand, the frequency average value fa of the carrier frequency is calculated based on the selection frequency of the carrier frequency. For example, when the selection frequency of the carrier frequency f1 is x1, the selection frequency of the carrier frequency f2 is x2,..., The selection frequency of the carrier frequency fn is xn, the frequency average value of the carrier frequency is expressed by the following equation (1). fa can be obtained.

fa = (f1 * x1 + f2 * x2 ++ ... + fn * xn) / (x1 + x2 + ... + xn) (1)
Accordingly, the PWM control unit 11 calculates the frequency average value fa of the carrier frequency based on the equation (1), performs the PWM control so that the frequency average value fa of the carrier frequency is the carrier frequency f ₀ below.

  Although the case of the first embodiment has been described with reference to FIG. 6 as an example, the present invention can also be applied to the maps described in the second and third embodiments.

[Effect of Fourth Embodiment]
As described in detail above, in the inverter control device 9 according to the present embodiment, the frequency average value fa is calculated based on the selection frequency of the carrier frequency, and this frequency average value fa is determined based on the thermal design reference of the inverter 5. PWM control such that the carrier frequency _{f 0} below which will become. Thereby, PWM control in consideration of the thermal performance of the inverter 5 can be performed, so that stable PWM control can be executed.

[Fifth Embodiment]
Next, an inverter control apparatus according to a fifth embodiment of the present invention will be described with reference to the drawings. In addition, the same number is attached | subjected to the component same as 1st Embodiment, and detailed description is abbreviate | omitted.

[Configuration of power conversion system]
FIG. 7 is a block diagram illustrating a configuration of a power conversion system including the inverter control device according to the present embodiment. As shown in FIG. 7, the inverter control device 71 according to the present embodiment acquires the torque and the rotational speed from the motor 7 and determines the timing for shifting to the carrier frequency spreading mode according to the first embodiment. Is different.

  This embodiment is applied when the load is the motor 7 and the inverter 5 is mounted as a switching device. The PWM control unit 11 uses the carrier frequency spreading mode when the motor 7 is in a specific operation region. Execute. As this specific operation region, as shown in FIG. 8, an operation region A in which the motor 7 has a predetermined torque or more, an operation region B in which the motor 7 has a predetermined rotation speed or more, or both operation regions A and B. It becomes.

  The ripple current of the inverter 5 has a positive correlation with the motor phase current and the modulation rate. Further, when the motor 7 has high torque or high rotation, the motor phase current and the modulation rate are increased. For this reason, since the ripple current of the inverter 5 increases when the motor 7 is in an operation region where the torque is high or the rotation is high, the ripple current generated in the battery 3 increases as a result, and the noise vibration of the battery 3 increases.

  On the other hand, since the inverter 5 generates a large amount of heat in these operating regions, it can be considered to simply lower the carrier frequency in order to reduce the heat generation. However, when the carrier frequency is lowered, the ripple current of the inverter 5 is further increased, and as a result, the sound vibration noise of the battery 3 is increased.

  Therefore, if the carrier frequency diffusion mode is executed when the motor 7 has high torque or high rotation, the average value of the carrier frequency can be lowered, so that the heat generation of the inverter 5 can be reduced and sound noise is reduced. It is also possible to suppress the adverse effects of.

[Effect of Fifth Embodiment]
As described above in detail, in the inverter control device 71 according to the present embodiment, when the motor 7 is in a specific operation region, the carrier frequency spreading mode is executed. As a result, the motor 7 executes the carrier frequency spreading mode in a specific operation region and makes the carrier frequency constant in other operation regions, so that the calculation load of the inverter control device 71 can be reduced and the cost can be reduced. be able to.

  In the inverter control device 71 according to the present embodiment, as a specific operation region, an operation region in which the motor 7 has a predetermined torque or more, an operation region in which the motor 7 has a predetermined rotation speed or more, or the motor 7 has a predetermined operation region. Set the operating range where the torque or rotation speed is exceeded. Thereby, since the average value of the carrier frequency can be lowered in a high torque and high rotation region where the thermal load of the inverter 5 becomes high, the thermal load of the inverter 5 can be reduced and the inverter 5 can be downsized.

  The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and even if it is a form other than this embodiment, as long as it does not depart from the technical idea of the present invention, it depends on the design and the like. Of course, various modifications are possible.

DESCRIPTION OF SYMBOLS 1 Power conversion system 3 Battery 5 Inverter 7 Motor 9, 71 Inverter control apparatus 11 PWM control part 13 Carrier frequency selection part 15 Map

Claims (8)

A switching control device for controlling a switching device for converting electric power from a DC power source and supplying the converted power to a load,
When executing a carrier frequency spread mode for selecting a carrier frequency to be used from among a plurality of carrier frequencies set within a predetermined frequency range, a low one of the plurality of carrier frequencies set within the predetermined frequency range is selected. A carrier frequency selection unit that selects a carrier frequency so that a selection ratio for selecting a carrier frequency on the frequency side is lower than a selection ratio for selecting a carrier frequency on the high frequency side;
A switching control device comprising: a PWM control unit that executes the carrier frequency spreading mode using the carrier frequency selected by the carrier frequency selection unit and performs PWM control of the switching device.   The carrier frequency selection unit lowers the selection ratio on the low frequency side by widening the frequency interval of the plurality of carrier frequencies set in the predetermined frequency range on the low frequency side than on the high frequency side. The switching control device according to claim 1.   The carrier frequency selection unit lowers the selection ratio on the low frequency side by reducing the selection frequency of the plurality of carrier frequencies set in the predetermined frequency range on the low frequency side than on the high frequency side. The switching control device according to claim 1.   The carrier frequency selection unit continuously reduces the selection ratio of a plurality of carrier frequencies set within the predetermined frequency range from a high frequency side to a low frequency side. The switching control apparatus according to claim 1.   The carrier frequency selection unit reduces the selection ratio of a plurality of carrier frequencies set within the predetermined frequency range stepwise from a high frequency side to a low frequency side. The switching control apparatus according to claim 1.   The PWM control unit calculates a frequency average value of the plurality of carrier frequencies based on a selection frequency of the plurality of carrier frequencies set within the predetermined frequency range, and the frequency average value is a thermal design of the switching device. The switching control device according to claim 1, wherein PWM control is performed so that the carrier frequency is equal to or lower than the above reference carrier frequency. When the load is a motor and the switching device is an inverter,
The switching control device according to claim 1, wherein the PWM control unit executes the carrier frequency spreading mode when the motor is in a specific operation region.   The specific operation region of the motor is an operation region where the motor becomes a predetermined torque or more, an operation region where the motor becomes a predetermined rotation number or more, or an operation region where the motor becomes a predetermined torque or rotation number or more. The switching control device according to claim 7, wherein the switching control device is provided.

Images