JP2011172306A - Pwm inverter device, and pwm inverter control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PWM inverter device having low noise while suppressing an increase in a motor system loss, and to provide a method of controlling a PWM inverter. <P>SOLUTION: The PWM inverter device includes a carrier frequency calculator of randomly varying a carrier frequency used for drive control of an inverter for supplying power to a rotary electric machine. The carrier frequency calculator reduces the occurrence frequency of the carrier frequency, where a motor system loss becomes larger than a reference motor system loss in comparison with the occurrence frequency of a prescribed carrier frequency, and increases the occurrence frequency of a carrier frequency where the motor system loss becomes smaller than the reference motor system loss in comparison with the occurrence frequency of the prescribed carrier frequency within a frequency range to be varied on the basis of the motor system loss expressed as a sum of a loss of the rotary electric machine and a loss of the inverter at the prescribed carrier frequency within the frequency range to be varied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a PWM inverter device and a PWM inverter control method.

  The conventional PWM inverter device outputs an arbitrary voltage and frequency to the motor by using a constant carrier frequency. In general, the output voltage accuracy is maintained by changing the carrier frequency according to the output frequency instead of the constant carrier frequency.

  And in a PWM inverter apparatus, the electromagnetic noise based on a carrier frequency generate | occur | produces from the motor to drive. Specifically, a high frequency component (ripple current) having a carrier frequency or an integral multiple of the carrier frequency is generated in the stator winding of the motor, which becomes a vibration component of the motor and generates noise.

  For example, Patent Document 1 proposes a low-noise PWM inverter device. Specifically, the carrier frequency is varied within a certain fluctuation range around the basic carrier frequency. At that time, the carrier frequency is changed so that the average value of the changed carrier frequency becomes the basic carrier frequency. Thereby, the specific frequency component resulting from a carrier frequency can be disperse | distributed and generation | occurrence | production of noise can be suppressed.

JP 2007-20320 A JP 2009-11028 A

Takao, “Low Loss Inverter with SiC Hybrid Pair”, Toshiba Review, 2009, Vol. 64, No. 7, p. 44-47

  However, as in Patent Document 1, when the carrier frequency is changed so that the average value of the changed carrier frequency becomes the basic carrier frequency, the inverter loss and the rotating electrical machine loss (motor loss) are compared with the case where the carrier frequency is not changed. There is a problem that the motor system loss as a sum increases. Specifically, when the carrier frequency is increased, the inverter loss is increased (see, for example, Non-Patent Document 1), and when the carrier frequency is decreased, the rotating electrical machine loss is increased (for example, see Patent Document 2).

  Therefore, an object of the present invention is to provide a low-noise PWM inverter device and a PWM inverter control method while suppressing an increase in motor system loss.

  The present invention is a PWM inverter device including carrier frequency calculation means for randomly changing a carrier frequency used for drive control of an inverter that supplies electric power to a rotating electrical machine, wherein the carrier frequency calculation means is within a frequency range to be changed. Based on the motor system loss expressed as the sum of the loss of the rotating electrical machine and the loss of the inverter at a predetermined carrier frequency, the motor system loss becomes larger than the reference motor system loss within the fluctuating frequency range. The occurrence frequency of the carrier frequency is less than the occurrence frequency of the predetermined carrier frequency, and the occurrence frequency of the carrier frequency in which the motor system loss is smaller than the reference motor system loss is increased more than the occurrence frequency of the predetermined carrier frequency. .

  Further, the present invention is a PWM inverter control method including a carrier frequency calculation step for randomly changing a carrier frequency used for drive control of an inverter that supplies electric power to a rotating electrical machine, wherein the carrier frequency calculation step includes a frequency to be changed. Based on the motor system loss expressed as the sum of the loss of the rotating electrical machine and the loss of the inverter at a predetermined carrier frequency within the range, the motor system loss is the reference motor system loss within the variable frequency range. The occurrence frequency of the carrier frequency that is larger than the occurrence frequency of the predetermined carrier frequency is reduced, and the occurrence frequency of the carrier frequency that is smaller than the reference motor system loss is reduced to the occurrence frequency of the predetermined carrier frequency. Do more.

  According to the present invention, it is possible to provide a low-noise PWM inverter device and a PWM inverter control method while suppressing an increase in motor system loss.

It is a schematic diagram which shows an example of a structure of a motor system provided with the PWM inverter apparatus which concerns on this embodiment. (A) It is a figure which shows the relationship between the fluctuation | variation carrier frequency and motor system loss in case an inverter loss is dominant, (B) The relationship between the fluctuation | variation carrier frequency and motor system loss in the case where a rotary electric machine loss is dominant FIG. It is a figure which shows the relationship between the conventional fluctuation | variation carrier frequency and generation frequency. It is a map showing the generation frequency of the fluctuation | variation carrier frequency in case an inverter loss is dominant. It is a map showing an example of the occurrence frequency of the variable carrier frequency when the rotating electrical machine loss is dominant. It is a figure which shows the relationship between the fluctuation | variation carrier frequency and motor system loss in case an inverter loss is dominant.

  Embodiments of the present invention will be described below.

  FIG. 1 is a schematic diagram illustrating an example of a configuration of a motor system including a PWM inverter device according to the present embodiment. A motor system 10 shown in FIG. 1 includes a power storage device 12 as a power supply circuit, smoothing capacitors 14 and 18, a voltage converter 16, inverters 20 and 22, two rotating electrical machines 24 and 26, a PWM inverter device 40, an external device And a power supply 60.

  The rotating electrical machines (24, 26) in the present embodiment are, for example, a motor / generator mounted on a vehicle or a stationary motor / generator other than those mounted on the vehicle. In addition, the rotating electrical machine may simply have a function as a motor, or may simply have a function as a generator. In addition, the configuration of the power supply circuit according to the present embodiment will be described using an example having the power storage device 12, the voltage converter 16, the smoothing capacitors 14 and 18, and the inverters 20 and 22. For example, other elements may be omitted as appropriate, and other elements may be added as appropriate.

  The external power source 60 is a commercial AC power source, and is used to charge the power storage device 12 by controlling the operation of the inverters 20 and 22 using the rotating electrical machines 24 and 26 as reactors. Specifically, an appropriate connection terminal is provided on two cables drawn from the neutral point of each of the two rotating electric machines 24 and 26, and the connection terminal is, for example, a charging terminal of a charging stand or a general household. By connecting to the power outlet, the external power source 60 is connected to the motor system 10 including the rotating electrical machines 24 and 26 and the inverters 20 and 22. As a result, when the state of charge of the power storage device 12 mounted on the vehicle becomes low, charging can be performed from an appropriate external power source 60.

  Here, the external power supply 60 is connected to the motor system 10 to charge the power storage device 12 of the power supply circuit. However, instead of the external power supply 60, two electric appliances that operate with alternating current are used as loads. It can be connected to the neutral point of the rotating electrical machines 24 and 26. In this case, the two rotating electrical machines 24 and 26 are used as reactors, and the electric power of the power storage device 12 can be supplied to the load by the operation control of the inverters 20 and 22. Thus, the load can be driven using the power storage device 12 mounted on the vehicle in a situation where there is no appropriate power supply device.

  Of the two rotating electrical machines 24 and 26, the first rotating electrical machine (MG1) 24 is, for example, a motor / generator (MG) mounted on a vehicle, and in this case, connected to an engine (not shown). And a three-phase synchronous rotating electric machine having a function of generating electric power by the driving force of the engine.

  The second rotating electrical machine (MG2) 26 is a motor / generator (MG) mounted on the vehicle, which functions as an electric motor when electric power is supplied and functions as a generator during braking. Electric. The second rotating electrical machine 26 mounted on the vehicle has a function of assisting engine power transmitted to a vehicle axle (not shown) to increase driving force.

  As described above, the power supply circuit includes the power storage device 12, the smoothing capacitor 14 on the power storage device side, the voltage converter 16, the smoothing capacitor 18 on the inverter side, and the two inverters 20 and 22.

  The power storage device 12 is a chargeable / dischargeable secondary battery. As the power storage device 12, for example, a lithium ion assembled battery, a nickel hydride assembled battery, a capacitor, or the like can be used.

  The smoothing capacitor 14 on the power storage device side provided between the power storage device 12 and the voltage converter 16 is a capacitor having a function of suppressing voltage fluctuation on the low voltage side of the voltage converter 16.

  The voltage converter 16 is a step-up / step-down circuit that includes a reactor and a switching element. The voltage converter 16 is a circuit having a function of boosting a low voltage (for example, about 200 V to about 300 V) on the power storage device 12 side to a high voltage (for example, about 600 V) by using the energy storage action of the reactor. Therefore, it is also called a boost converter. In addition, the voltage converter 16 has a bidirectional function, and when the electric power from the two inverters 20 and 22 side is supplied as the charging power to the power storage device 12 side, the high voltage on the two inverters 20 and 22 side is supplied. It has the effect of stepping down to a low voltage suitable for the power storage device 12.

  The inverter-side smoothing capacitor 18 provided between the voltage converter 16 and the inverters 20 and 22 is a capacitor having a function of suppressing voltage fluctuation on the high voltage side of the voltage converter 16.

  The two inverters 20 and 22 both convert high-voltage direct current power into alternating current three-phase drive power and supply it to the rotating electrical machines 24 and 26 connected thereto, and conversely from the respective rotating electrical machines 24 and 26. This is a circuit having a function of converting the AC three-phase regenerative power into high-voltage DC charging power. As described above, of the two inverters 20 and 22, the one connected to the first rotating electrical machine (MG1) 24 is connected to the first rotating electrical machine (MG1 inverter) 20 and the second rotating electrical machine (MG2) 26. This can be referred to as a second inverter (MG2 inverter) 22.

  As shown in FIG. 1, the inverters 20 and 22 have the same basic configuration, and include a plurality of switching elements and a plurality of diodes. The inverters 20 and 22 correspond to the three-phase coils of the rotating electrical machines 24 and 26 that are three-phase synchronous types, and two switching elements connected in series are for U-phase, V-phase, and W-phase. 3 are arranged in parallel. A diode is connected to each switching element in parallel. Each connection point is connected to a U-phase coil, a V-phase coil, and a W-phase coil of the rotating electrical machines 24 and 26, respectively.

  The PWM inverter device 40 has a function of controlling the operation of each element constituting the motor system 10 as a whole. In particular, the PWM inverter device 40 functions as drive control of the inverters (20, 22). The PWM inverter device 40 includes a carrier frequency calculation unit 42 and a PWM control calculation unit 44.

  The carrier frequency calculation unit 42 has a function of randomly changing the carrier frequency used for driving control of the inverters (20, 22) within a certain fluctuation range as will be described later. The PWM control calculation unit 44 has the above-described changed carrier. A PWM signal for generating AC power having a predetermined voltage and frequency is generated based on the frequency. As a result, the rotating electrical machines (24, 26) are driven via the inverters (20, 22). The function and operation of the carrier frequency calculation unit 42 used in the present embodiment will be specifically described below.

Ｌ（Ｆ）：モータシステム損失
Ｆ_ｃ：キャリア周波数
Ｆ_ｃ０：中心キャリア周波数（（ΔＦ_ｃ＋ΔＦ_ｃ）／２）
ΔＦ_ｃ：キャリア周波数変動幅 Generally, when the carrier frequency used for drive control of the inverters (20, 22) is varied, the inverter loss increases when the carrier frequency is increased, and the rotating electrical machine loss increases when the carrier frequency is decreased. Therefore, the increase / decrease in motor system loss (sum of inverter loss and rotating electrical machine loss) due to carrier frequency fluctuation depends on whether the loss of inverter loss or rotating electrical machine loss is dominant, but FIG. , (B), the characteristic is downwardly convex with respect to the carrier frequency. Therefore, the average loss of the motor system when the carrier frequency represented by the following formula is changed is always larger than the motor system loss at the center carrier frequency.

L (F): Motor system loss F _c : Carrier frequency F _c 0: Center carrier frequency ((ΔF _c + ΔF _c ) / 2)
ΔF _c : Carrier frequency fluctuation range

  Therefore, as shown in FIG. 3, for example, the average loss of the motor system when the carrier frequency is fluctuated (± 400 centered on 2500 Hz) with a constant occurrence frequency regardless of the fluctuating frequency is a constant carrier frequency of 2500 Hz. In this case, the motor system loss increases (however, the noise of the PWM inverter device 40 is suppressed).

  Therefore, in this embodiment, in order to suppress an increase in motor system loss and suppress noise of the PWM inverter device 40, the carrier frequency calculation unit 42 performs motor system loss at a predetermined carrier frequency within a frequency range to be changed ( The frequency of occurrence of the carrier frequency in which the motor system loss is greater than the reference motor system loss within the frequency range to be fluctuated, based on the sum of the rotating electrical machine loss and inverter loss), is less than the frequency of the predetermined carrier frequency, The generation frequency of the carrier frequency at which the motor system loss is smaller than the reference motor system loss is set to be higher than the generation frequency of the predetermined carrier frequency. Here, the predetermined carrier frequency is the center carrier frequency of the frequency range to be varied (for example, as shown in FIG. 6, when the carrier frequency is varied in the range of 2100 Hz to 2900 Hz, the center carrier frequency is 2500 Hz). However, there is no particular limitation as long as a carrier frequency serving as a reference for efficiently suppressing motor system loss is set.

  As shown in FIGS. 2A and 6, when the inverter loss is dominant among the motor system losses, the motor system loss increases as the carrier frequency increases. Therefore, when the inverter loss is dominant, for example, the frequency of occurrence of a frequency higher than the center carrier frequency (2500 Hz in FIG. 6) is reduced, and the frequency of occurrence of a frequency lower than the center carrier frequency is increased. On the other hand, as shown in FIG. 2B, when the rotating electrical loss is dominant among the motor system losses, the motor system loss increases as the carrier frequency decreases. Therefore, when the rotating electrical loss is dominant, for example, the frequency of occurrence of a frequency greater than the center carrier frequency (the center carrier frequency when the carrier frequency is varied in the range of 2100 Hz to 2900 Hz is 2500 Hz) is increased. Reduce the frequency of occurrence of frequencies lower than the center carrier frequency.

  Specifically, as shown in FIG. 4, a map showing the frequency of occurrence of a variable carrier frequency when the inverter loss is dominant, and a fluctuation when the rotating electrical machine loss is dominant as shown in FIG. A map representing the occurrence frequency of the carrier frequency is stored in advance in the carrier frequency calculation unit 42. In the map shown in FIG. 4 (in the case where the inverter loss is dominant in the motor system loss), the frequency of occurrence is gradually reduced in the frequency region higher than the center carrier frequency with reference to the center carrier frequency, and the frequency region lower than the center carrier frequency. Then, the frequency of occurrence is increasing step by step. Further, in the map shown in FIG. 5 (when the rotating electrical machine loss is dominant in the motor system loss), the frequency of occurrence is increased stepwise in the frequency region higher than the center carrier frequency with reference to the center carrier frequency. In the frequency region smaller than the frequency, the frequency of occurrence is gradually reduced.

  If the inverter loss is dominant, the carrier frequency is generated based on the map shown in FIG. 4, and if the rotating electrical machine loss is dominant, the carrier frequency is calculated based on the map shown in FIG. generate.

  Here, the determination of whether the inverter loss is dominant or the rotating electrical machine loss is dominant can be performed as follows, for example. Usually, when the rotational speed of the rotating electrical machine (24, 26) is large, the rotating electrical machine loss is dominant, and when the rotational speed of the rotating electrical machine (24, 26) is small, the inverter loss is dominant. The map shown in FIG. 5 is used when the rotational speed of the rotating electrical machine (24, 26) is greater than or equal to a predetermined value, and FIG. 4 is used when the rotational speed of the rotating electrical machine (24, 26) is less than the predetermined value. Use the map shown. Alternatively, the rotational speed of the rotating electrical machine (24, 26) may be divided into a plurality of regions, and a map representing the frequency of occurrence of the variable carrier frequency for each region may be set. Further, the case where the rotational speed of the rotating electrical machine (24, 26) is used has been described as an example. However, the present invention is not limited to this. For example, the current value of the rotating electrical machine (24, 26) or the depression of the accelerator pedal is used. It is also possible to determine whether the inverter loss is dominant or the rotating electrical machine loss is dominant from the quantity or the like.

  In the present embodiment, as described above, the frequency of occurrence of each carrier frequency is set such that the frequency of occurrence of the carrier frequency at which the motor system loss is greater than the reference motor system loss is less than the frequency of occurrence of the predetermined carrier frequency. There is no particular limitation as long as the generation frequency of the carrier frequency at which the motor system loss is smaller than the reference motor system loss is greater than the generation frequency of the predetermined carrier frequency. However, the average loss of the motor system when the carrier frequency is varied matches the motor system loss at the center carrier frequency in terms of suppressing the noise of the PWM inverter device while efficiently suppressing the increase of the motor system loss. Thus, it is preferable to set the frequency of occurrence of each carrier frequency.

  In the present embodiment, when the inverter loss is dominant in the motor system loss, as shown in FIG. 4, the frequency of occurrence is gradually reduced in the frequency region larger than the center carrier frequency with reference to the center carrier frequency. In the frequency region smaller than the center carrier frequency, the frequency of occurrence increases stepwise, and when the rotating electrical machine loss is dominant in the motor system loss, as shown in FIG. The frequency of occurrence is increased stepwise in a frequency region higher than the frequency, and the frequency of occurrence is decreased stepwise in a frequency region lower than the center carrier frequency, but is not necessarily limited to this. For example, when the inverter loss is dominant in the motor system loss, the frequency of occurrence is higher than the center carrier frequency in the frequency region larger than the center carrier frequency with reference to the center carrier frequency. In the frequency region smaller than the center carrier frequency with reference to the frequency, the frequency of occurrence is lower than that of the center carrier frequency, but the frequency of occurrence may be a constant value or the like. If the rotating electrical machine loss is dominant in the motor system loss, the above setting is reversed.

  4 and 5 exemplify a case where the center carrier frequency is 2500 Hz and the frequency fluctuates by ± 400 Hz. However, the variation range of the carrier frequency is not limited to the above, and can be set as appropriate. Good.

  DESCRIPTION OF SYMBOLS 10 Motor system, 12 Power storage device, 14, 18 Smoothing capacitor, 16 Voltage converter, 20, 22 Inverter, 24, 26 Rotating electric machine, 40 PWM inverter device, 42 Carrier frequency calculation unit, 44 PWM control calculation unit, 60 External power supply .

Claims (2)

A PWM inverter device comprising carrier frequency calculation means for randomly changing a carrier frequency used for drive control of an inverter that supplies electric power to a rotating electrical machine,
The carrier frequency calculation means is based on the motor system loss expressed as the sum of the loss of the rotating electrical machine and the loss of the inverter at a predetermined carrier frequency within the frequency range to be varied, and within the frequency range to be varied, The occurrence frequency of the carrier frequency at which the motor system loss is greater than the reference motor system loss is less than the occurrence frequency of the predetermined carrier frequency, and the occurrence frequency of the carrier frequency at which the motor system loss is less than the reference motor system loss. More than the occurrence frequency of the predetermined carrier frequency. A PWM inverter control method comprising a carrier frequency calculation step for randomly changing a carrier frequency used for drive control of an inverter that supplies electric power to a rotating electrical machine,
In the carrier frequency calculation step, based on the motor system loss represented as the sum of the loss of the rotating electrical machine and the loss of the inverter at a predetermined carrier frequency within the frequency range to be varied, within the frequency range to be varied, The occurrence frequency of the carrier frequency at which the motor system loss is greater than the reference motor system loss is less than the occurrence frequency of the predetermined carrier frequency, and the occurrence frequency of the carrier frequency at which the motor system loss is less than the reference motor system loss. More than the frequency of occurrence of the predetermined carrier frequency.

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