JP2017192198A - Inverter controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter controller that improves control stability and also reduces noise emitted due to electromagnetic sound.SOLUTION: In a modulator 60 for an inverter controller, a PWM signal generating section 66 generates a PWM signal by comparing a phase voltage and a carrier wave, as a system for specifying a voltage waveform output by an inverter 30. A carrier wave frequency setting section 67 that sets a frequency Fc for a carrier wave used by the PWM signal generating section 66 has a basic-frequency adjusting section 68 and a spread-frequency adjusting section 69. The basic-frequency adjusting section 68 periodically and continuously changes, in a predetermined variable range, a basic frequency used as a basis for a carrier wave frequency. The spread-frequency adjusting section 69 adds a spread frequency distributing in a range within the maximum variation relative to the basic frequency, to the basic frequency at an interval shorter than a variable period of the basic frequency. Since the basic frequency initiatively spreads frequency, and the spread frequency has an auxiliary spread function, the need to especially greatly set the maximum variation for the spread frequency is eliminated.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an inverter control device that controls an inverter by PWM control.

2. Description of the Related Art Conventionally, in an inverter control apparatus that controls an inverter by PWM control, a technique for spreading noise of a carrier wave and reducing noise due to electromagnetic sound is known. For example, the PWM inverter control device disclosed in Patent Documents 1 and 2 adds the spread frequency (ΔFc × k1) obtained by multiplying the basic carrier frequency Fc0 by the maximum variation ΔFc and the coefficient k1 by the following equation. To calculate the carrier frequency Fc.
Fc = Fc0 + ΔFc × k1
Here, the basic carrier frequency Fc0 is calculated according to the voltage command. The maximum variation ΔFc is a preset constant. The coefficient k1 is defined as table data that randomly changes in a range from “−1” to “+1”, and an average value of all data is approximately zero.

Japanese Patent No. 4974457 Japanese Patent No. 5121895

In the prior arts of Patent Documents 1 and 2, assuming that the basic carrier frequency Fc0 is constant, the variation in the spread frequency becomes the variation in the carrier frequency Fc as it is. Further, the change of the coefficient k1 is set at random. If the coefficient k1 changes at a stretch from the lower limit “−1” to the upper limit “+1”, the carrier frequency Fc is about a difference that is twice the maximum variation ΔFc. It changes rapidly.
Therefore, if the maximum variation ΔFc is set to be relatively large in order to sufficiently spread the carrier frequency Fc, the output voltage of the inverter may change suddenly depending on the amount of change of the coefficient k1, and the control may become unstable. On the other hand, if the maximum variation ΔFc is set to be relatively small, the carrier frequency Fc is not sufficiently diffused, and noise due to electromagnetic sound cannot be reduced.

  The present invention was created in view of the above points, and an object thereof is to provide an inverter control device that improves control stability and reduces noise caused by electromagnetic noise.

The inverter control apparatus of this invention is an apparatus which controls the inverter (30) which converts the direct-current power input from a power supply (11) into alternating current power by operation | movement of a some switching element (31-36). The inverter control device includes a voltage command calculation unit (580), a PWM signal generation unit (66), and a carrier frequency setting unit (67).
The voltage command calculation unit calculates a voltage vector commanded to the inverter.
The PWM signal generation unit compares the phase voltage with a carrier wave to generate a PWM signal as a method for specifying the voltage waveform output from the inverter. The carrier frequency setting unit sets the frequency (Fc) of the carrier used by the PWM signal generation unit.

The carrier frequency setting unit includes a basic frequency adjustment unit (68) and a spread frequency adjustment unit (69).
The fundamental frequency adjustment unit periodically and continuously changes the fundamental frequency that is the basis of the carrier frequency within a predetermined fluctuation range (Tb).
The spread frequency adjusting unit adds a spread frequency distributed in a range within a maximum variation (± ΔF) with respect to the fundamental frequency to the fundamental frequency at an interval shorter than the variation period (Tb) of the fundamental frequency.

  Here, the term “continuous” that specifies the change in the fundamental frequency is interpreted with reference to the fluctuation range of the fundamental frequency. For example, a step change that changes the frequency difference from the lower limit frequency to the upper limit frequency in one step is excluded as a “discontinuous” change. On the other hand, a relatively small step change with respect to the variation range is regarded as a “continuous change”, and is interpreted as satisfying the constituent requirements of the present invention.

In the present invention, the carrier frequency is set by a fundamental frequency that changes periodically and a spread frequency that is added to the fundamental frequency at intervals shorter than the fluctuation period of the fundamental frequency. The fundamental frequency that changes periodically and continuously leads to the frequency spreading, and the spreading frequency has an auxiliary spreading function.
Therefore, in the present invention, it is not necessary to set a particularly large maximum fluctuation of the spread frequency in order to reduce noise due to electromagnetic sound, and thus it is possible to prevent a sudden change in the carrier frequency due to the spread frequency fluctuation. Therefore, the inverter control device of the present invention can appropriately achieve both improvement of control stability and reduction of noise due to electromagnetic sound.

Preferably, the spreading range in which the spreading frequency is distributed is set smaller than the fluctuation range of the basic frequency. As a result, a sudden change in the carrier frequency due to the spread component can be prevented, and the control stability can be improved.
Preferably, the fundamental frequency adjustment unit monotonously increases the fundamental frequency from the lower limit frequency (Fm) to the upper limit frequency (FM) of the fluctuation range, and monotonically decreases from the upper limit frequency to the lower limit frequency. As a result, a sudden change in the carrier frequency can be prevented, and the control stability can be further improved.

The schematic block diagram of the MG drive system with which the inverter control apparatus of each embodiment is applied. The control block diagram of the inverter control apparatus of each embodiment. The control block diagram of the modulator of each embodiment. The figure explaining the switching of the voltage waveform specific system according to a modulation rate. (A) The figure which shows the period fluctuation | variation of a fundamental frequency by 1st Embodiment, (b) Frequency distribution figure of a spreading | diffusion frequency, (c) Carrier frequency-frequency characteristic figure. The figure which shows the setting of the fluctuation period of the fundamental frequency by 2nd Embodiment. (A) Time-frequency characteristic diagram and (b) Carrier frequency-frequency characteristic diagram when the variation range of the three-phase fundamental frequency is dispersed according to the third embodiment. The figure which shows the period fluctuation | variation of the fundamental frequency by other embodiment. The frequency distribution table of the spreading | diffusion frequency by other embodiment. The carrier frequency distribution map according to the prior art.

Hereinafter, a plurality of embodiments of an inverter control device will be described based on the drawings. The following first to third embodiments are collectively referred to as “this embodiment”.
The inverter control device of this embodiment is a device that controls an inverter that supplies three-phase AC power to the MG in a system that drives a motor generator (hereinafter referred to as “MG”) that is a power source of a hybrid vehicle or an electric vehicle.

[System configuration]
First, an overall configuration of an MG drive system to which the inverter control device of each embodiment is applied will be described with reference to FIG. FIG. 1 illustrates a system including one MG.
The MG drive system 90 is a system that converts DC power of the battery 11 as a “power source”, which is a chargeable / dischargeable secondary battery, into three-phase AC power by the inverter 30 and supplies it to the MG 80. In the MG drive system 90, the MG control device 10 mainly includes an inverter 30 and an inverter control device 50.
The MG control device 10 may be applied to an MG drive system that includes a converter that boosts the voltage of the battery 11 and outputs the boosted voltage to the inverter 30. Further, the MG control apparatus 10 can be similarly applied to an MG drive system including two or more MGs.

  The MG 80 is, for example, a permanent magnet type synchronous three-phase AC motor. In the present embodiment, the MG 80 has a function as an electric motor that generates torque for driving driving wheels of a hybrid vehicle and a function as a generator that recovers energy by generating electric power transmitted from the engine and driving wheels.

A current sensor for detecting a phase current is provided in a current path connected to the two-phase winding among the three-phase windings 81, 82, and 83 of the MG 80. In the example of FIG. 1, current sensors 87 and 88 for detecting phase currents Iv and Iw are provided in current paths connected to the V-phase winding 82 and the W-phase winding 83, respectively, and the remaining U-phase current Iu is estimated based on Kirchhoff's law. In other embodiments, any two-phase current may be detected, and a three-phase current may be detected. Or you may employ | adopt the technique which estimates the other two-phase electric current based on the electric current detection value of one phase.
The electrical angle θe of the MG 80 is detected by a rotation angle sensor 85 such as a resolver.

  In the inverter 30, six switching elements 31-36 of upper and lower arms are bridge-connected. Specifically, the switching elements 31, 32, and 33 are upper-arm switching elements of the U phase, the V phase, and the W phase, respectively, and the switching elements 34, 35, and 36 are below the U phase, the V phase, and the W phase, respectively. This is an arm switching element. The switching elements 31-36 are made of, for example, IGBTs, and are connected in parallel with freewheeling diodes that allow current flowing from the low potential side to the high potential side.

The inverter 30 converts the DC power into three-phase AC power by the switching elements 31-36 operating according to the gate signals UU, UL, VU, VL, WU, WL from the inverter control device 50. Then, phase voltages Vu, Vv, Vw corresponding to the voltage command calculated by the inverter control device 50 are applied to the phase windings 81, 82, 83 of the MG 80. The smoothing capacitor 25 smoothes the system voltage Vsys input to the inverter 30.
The voltage sensor 37 detects the system voltage Vsys.

  The inverter control device 50 is configured by a microcomputer or the like, and includes a CPU, a ROM, an I / O (not shown), a bus line that connects these configurations, and the like. The microcomputer executes control by software processing by executing a program stored in advance by the CPU or hardware processing by a dedicated electronic circuit.

  The inverter control device 50 acquires the system voltage Vsys detected by each sensor, the two-phase currents Iv and Iw, and the electrical angle θe. Further, the inverter control device 50 acquires the electrical angular velocity ω [deg / s] obtained by time-differentiating the electrical angle θe by the differentiator 86. Since the electrical angular velocity ω is converted to the rotational speed N [rpm] by multiplying by a proportionality constant, “the rotational speed converted from the electrical angular velocity ω” is omitted in this specification and referred to as “the rotational speed ω”. Note that a differentiator 86 may be provided inside the inverter control device 50.

Further, the inverter control device 50 receives the torque command Trq ^* from the host control circuit, and calculates the gate signals UU, UL, VU, VL, WU, WL for operating the inverter 30 based on the information. The inverter 30 operates the switching elements 31-36 according to the gate signals UU, UL, VU, VL, WU, WL, thereby converting the DC power input from the battery 11 into AC power and supplying the AC power to the MG 80.

[Configuration and operation of inverter control device]
The configuration of the inverter control device 50 will be described with reference to FIGS.
FIG. 2 shows a configuration of an inverter control device 50 including a torque feedback control unit 540 and a current feedback control unit 580 as a “voltage command calculation unit” that calculates a voltage vector commanded to the inverter 30. In the figure, “feedback control unit” is referred to as “FB control unit”.

The characteristic effect of this embodiment is expressed on the assumption that the voltage waveform output to the inverter 30 is specified by the PWM signal generated by comparing the phase voltage and the carrier wave.
Note that, as a configuration that is actually applied to the MG drive system 90 of a hybrid vehicle, a configuration that includes both the torque feedback control unit 540 and the current feedback control unit 580 is common, and therefore, the configuration is representative here. Will be described as a specific embodiment.

  In this configuration, the feedback method for calculating the voltage vector is switched according to the modulation factor calculated from the calculated amplitude of the voltage vector and the system voltage Vsys. That is, there are a case where the torque feedback control unit 540 and the current feedback control unit 580 cooperate to calculate a voltage vector, and a case where the current feedback control unit 580 calculates a voltage vector independently.

  As shown in FIG. 2, the inverter control device 50 includes a dq converter 51, a torque estimator 52, a torque subtractor 53, a controller 54, a current command calculator 55, a current subtractor 56, a controller 57, and a controller 58. A voltage amplitude / phase calculation unit 59, a modulator 60, a gate signal generation unit 79, and the like. Among these, the controller 57, the controller 58, and the voltage amplitude / phase calculation part 59 are selectively provided according to the structure of the above-mentioned feedback control part.

First, a configuration common to both feedback systems will be described.
The dq conversion unit 51 converts the phase current acquired from the current sensors 87 and 88 into dq axis currents Id and Iq based on the electrical angle θe, and feeds it back to the current subtractor 56.
Based on the torque command Trq ^* , the current command calculation unit 55 calculates the dq-axis current commands Id ^* and Iq ^* using a map or a mathematical formula so that the maximum torque per current can be obtained, for example.
The current subtracter 56 of the current feedback control unit 580 calculates current deviations ΔId and ΔIq between the dq axis current commands Id ^* and Iq ^* and the dq axis currents Id and Iq fed back from the dq conversion unit 51.

Next, a configuration when the torque feedback control unit 540 and the current feedback control unit 580 cooperate to calculate a voltage vector will be described.
Torque estimation unit 52 calculates estimated torque value Trq_est using equation (1) based on dq-axis currents Id and Iq and the motor constant of MG80. Note that in a system in which the MG 80 includes a torque sensor, the torque estimation unit 52 may not be provided, and the detected torque value may be acquired.
Trq_est = p × {Iq × ψ + (Ld−Lq) × Id × Iq} (1)
However,
p: number of pole pairs of MG ψ: counter electromotive voltage constant Ld, Lq: d-axis inductance, q-axis inductance

Torque subtractor 53 of torque feedback control unit 540 calculates torque deviation ΔTrq between torque command Trq ^* and estimated torque value Trq_est. The controller 54 calculates the voltage phase φ by PI calculation so as to converge the torque deviation ΔTrq to 0, and outputs it to the modulator 60.
The controller 57 of the current feedback control unit 580 calculates the voltage amplitude Vr by PI calculation so as to converge the current deviations ΔId and ΔIq to 0, and outputs the voltage amplitude Vr to the modulator 60.

Next, a configuration in the case where the current feedback control unit 580 independently calculates a voltage vector will be described.
The controller 58 of the current feedback control unit 580 calculates the dq axis voltage commands Vd ^* and Vq ^* by PI calculation so that the current deviations ΔId and ΔIq converge to 0. The voltage amplitude / phase calculation unit 59 converts the dq axis voltage commands Vd ^* and Vq ^* into a voltage amplitude Vr and a voltage phase φ, and outputs them to the modulator 601. In FIG. 2, the voltage phase φ is shown with reference to the d axis, but the voltage phase may be defined with reference to the q axis.

Thus, the modulator 60 receives the voltage amplitude Vr and the voltage phase φ calculated by any feedback method. Further, the modulator 60 receives information such as the system voltage Vsys, the electrical angle θe, and the rotational speed ω.
Based on this information, the modulator 60 outputs at least a PWM signal as an output waveform of a pulse voltage for operating the inverter 30. Here, description will be made assuming that the modulator 60 can output a pulse pattern or a PWM signal.

As shown in FIG. 3, the modulator 60 includes a modulation factor calculation unit 61, a method switching unit 62, and a voltage waveform specifying unit 63. The voltage waveform specifying unit 63 includes a pulse pattern setting unit 64, a storage unit 65, a PWM signal generation unit 66, and a carrier wave frequency setting unit 67.
The modulation factor calculation unit 61 calculates the modulation factor m according to Expression (2) based on the voltage amplitude Vr output from the current feedback control unit 580 and the system voltage Vsys.
m = 2√ (2/3) × (Vr / Vsys) (2)

The method switching unit 62 switches the voltage waveform specifying method by the voltage waveform specifying unit 63 based on the modulation factor m or the like. For example, as shown in FIG. 4, the method switching unit 62 employs a PWM method based on carrier wave comparison when the modulation factor m is less than the predetermined value α, and employs a pulse pattern method when the modulation factor m is greater than the predetermined value α. To do.
The voltage waveform specifying unit 63 specifies the voltage waveform output from the inverter 30. Specifically, a pulse pattern or a PWM signal is generated as a signal for driving the inverter 30, and is output to the gate signal generation unit 79. The gate signal generation unit 79 generates gate signals UU, UL, VU, VL, WU, WL based on the pulse pattern or PWM signal output from the modulator 60 and outputs the generated signals to the switching elements 31-36 of the inverter 30. .

Next, a detailed configuration of the voltage waveform specifying unit 63 will be described.
The pulse pattern setting unit 64 selects one of the pulse patterns from a plurality of voltage waveforms stored in advance in the storage unit 65 as a method for specifying the voltage waveform output from the inverter 30. The pulse pattern is selected according to the modulation rate m, the rotational speed ω, and the like.
In this specification, the pulse pattern includes a pattern that outputs a rectangular wave of one pulse in one electrical cycle. Typically, when the modulation factor is 1.27, a rectangular wave pulse pattern is selected. The pulse pattern other than the rectangular wave selected when the modulation rate is less than 1.27 is defined by the number of pulses in one electrical cycle, the position and width of each pulse, according to the modulation rate m, the rotational speed ω, and the like. .

The PWM signal generation unit 66 compares the phase voltage calculated based on the output of the current feedback control unit 580 with the carrier wave as a method for specifying the voltage waveform output from the inverter 30, and generates a PWM signal. The voltage waveform output from the inverter 30 is specified.
Specifically, the PWM signal is generated by comparing the duty in which the phase voltage is converted with a carrier wave such as a triangular wave. For example, the sine wave PWM is used in the range of the modulation rate of 0 to 1.15, and the overmodulation PWM is used in the range of the modulation rate of 1.15 to 1.27.

The carrier frequency setting unit 67 sets the frequency of the carrier used by the PWM signal generation unit 66 (hereinafter “carrier frequency Fc”).
By the way, the carrier frequency Fc is reflected in the frequency component included in the voltage waveform of the PWM signal. Then, when the switching elements 31-36 of the inverter 30 operate at the frequency, electromagnetic noise is generated. When this frequency is included in the human audible frequency band, if the sound of the same frequency continues for a certain period of time, it may be heard as noise by a user near the apparatus. In particular, in the inverter control device 50 applied to the MG drive system 90 of a hybrid vehicle, there is a risk of affecting the merchantability of the vehicle.

  Therefore, the carrier frequency setting unit 67 of this embodiment “spreads” the carrier frequency Fc in order to prevent the electromagnetic sound having the same frequency from being continuously generated by the switching operation of the inverter 30. As a configuration for that purpose, the carrier frequency setting unit 67 includes a fundamental frequency adjustment unit 68 and a spread frequency adjustment unit 69.

The fundamental frequency adjustment unit 68 changes the fundamental frequency that is the basis of the carrier frequency Fc periodically and continuously within a predetermined fluctuation range. Note that the interpretation of “continuous” is supplemented in the section “Other Embodiments”.
The spread frequency adjusting unit 69 adds a spread frequency distributed within a range within the maximum fluctuation amount with respect to the fundamental frequency to the fundamental frequency at an interval shorter than the fluctuation period of the fundamental frequency.
Specific settings of the fundamental frequency and the spread frequency will be described later.

  As described above, the characteristic effects of the present embodiment are expressed on the premise that the voltage waveform output to the inverter 30 is specified by the PWM signal. The characteristic is that the carrier frequency Fc used for generating the PWM signal is not fixed, but the carrier frequency Fc is variably adjusted by the carrier frequency setting unit 67 and the fundamental frequency adjustment unit 68.

In short, in the modulator 60 shown in FIG. 3, when the method switching unit 62 selects the PWM method in accordance with the modulation factor m, a characteristic effect is exhibited. In other words, the inverter control device 50 according to the present embodiment does not always need to perform control by carrier wave comparison, and only needs to variably adjust the carrier frequency Fc only when control using a carrier wave is performed under a specific condition.
The significance of describing the configuration of the inverter control device 50 including the pulse pattern setting unit 64 and the storage unit 65 that are not directly related to the characteristic operational effects as a representative embodiment is to clearly show this point. .

Hereinafter, detailed operational effects of the carrier frequency setting unit 67 will be described for each embodiment.
(First embodiment)
The effect of 1st Embodiment is demonstrated with reference to FIG. In the first embodiment, attention is paid to the frequency Fc of the carrier wave used for generating a certain one-phase PWM signal.

  Here, for example, it is assumed that the lower limit frequency Fm and the upper limit frequency FM of the fundamental frequency are fixed with respect to a change in the rotational speed ω of the MG 80. In other embodiments, the lower limit frequency Fm and the upper limit frequency FM of the fundamental frequency may be variable according to the rotational speed ω of the MG 80 or the like. However, the change in the rotational speed ω occurs on a relatively long time axis of several hundred ms to s order or more, whereas the fundamental frequency fluctuation period Tb is set in the order of several tens μs to several ms, for example. It is assumed that Therefore, when considering the periodic fluctuations of the fundamental frequency, the rotational speed ω may be considered to be substantially constant.

  As shown in FIG. 5A, the fundamental frequency monotonously increases with a constant positive gradient from the lower limit frequency Fm to the upper limit frequency FM. Then, when reaching the upper limit frequency FM, it turns back and monotonously decreases to the lower limit frequency Fm with a constant negative gradient obtained by inverting the gradient at the time of increase. Thus, the basic frequency repeats increase and decrease periodically and continuously in the fluctuation range Rb from the lower limit frequency Fm to the upper limit frequency FM.

FIG. 5 (a) shows a state where a spread frequency is added to the base frequency and spread. In the illustrated example, the spreading frequency is randomly added, but the spreading frequency may be added so that a predetermined pattern is repeated in a short cycle or a long cycle.
Thus, the spread frequency is added to the fundamental frequency at intervals shorter than the fluctuation period Tb of the fundamental frequency. The PWM signal generation unit 66 generates a PWM signal by comparing the carrier wave of the frequency Fc thus obtained and the phase voltage, and specifies the output voltage waveform of the inverter 30.

As shown in FIG. 5 (b), for example, the spreading frequency is distributed in a positive and negative symmetrical mountain shape within a spreading range Rsp within the maximum variation ± ΔF with respect to the fundamental frequency Fb. That is, the frequency of the fundamental frequency Fb is the highest, and the frequency decreases as the variation from the fundamental frequency Fb increases. The frequency at the frequency having the upper limit variation + ΔF and the lower limit variation −ΔF converges to zero.
The variation Δf from the fundamental frequency Fb at an arbitrary frequency within the spreading range Rsp is expressed by Expression (3) using a coefficient k (−1 ≦ k ≦ 1).
Δf = k × ΔF (3)
Further, as shown in Expression (4), the width of the diffusion range Rsp is twice the one-side maximum variation ΔF.
Rsp = 2ΔF (4)

Here, as shown in FIG. 5A, the spreading range Rsp is set to be smaller than the fluctuation range Rb of the fundamental frequency. That is, regarding the fluctuation of the carrier frequency Fc, the period fluctuation of the basic frequency contributes predominantly, and the diffusion by the spreading frequency contributes supplementarily.
By adding the spreading frequency around the periodically changing basic frequency, the carrier frequency Fc changes within a range obtained by adding the maximum variation ± ΔF of the spreading frequency to the lower limit Fm and the upper limit FM of the basic frequency. Therefore, the carrier frequency Fc varies in the range of (Fm−ΔF) to (FM + ΔF).

Therefore, as shown in FIG. 5 (c), the frequency distribution of the carrier frequency Fc is constant in the range from the lower limit Fm to the upper limit FM of the fundamental frequency, and further in the range of the lower limit Fm and the upper limit FM. Distribution due to the maximum variation ± ΔF of the spread frequency is added.
The frequency distribution of the carrier frequency Fc is a distribution of frequency components included in the voltage waveform of the PWM signal. As a result, for example, it is reflected in the frequency characteristics of the spectrum amplitude obtained by fast Fourier transform of the inverter bus current. In addition, the frequency distribution of the carrier frequency Fc affects the generation of electromagnetic sound due to the operation of the inverter 30.

(effect)
(1) The effect of this embodiment will be described in comparison with the prior art.
The prior art disclosed in Patent Documents 1 and 2 (Japanese Patent No. 4974457, Japanese Patent No. 5121895) is shown in FIG. In the prior art, the carrier frequency Fc is calculated by adding the spread frequency (ΔFc × k1) obtained by multiplying the basic carrier frequency Fc0 by the maximum variation ΔFc and the coefficient k1 according to the equation (5).
Fc = Fc0 + ΔFc × k1 (5)

  In the prior arts of Patent Documents 1 and 2, assuming that the basic carrier frequency Fc0 is constant, the variation in the spread frequency becomes the variation in the carrier frequency Fc as it is. Further, the change of the coefficient k1 is set at random. If the coefficient k1 changes at a stretch from the lower limit “−1” to the upper limit “+1”, the carrier frequency Fc is about a difference that is twice the maximum variation ΔFc. It changes rapidly.

Therefore, as shown in FIG. 10A, when the maximum variation ΔFc is set relatively large in order to sufficiently spread the carrier frequency Fc, the output voltage of the inverter changes suddenly depending on the amount of change of the coefficient k1, and the control is performed. May become unstable.
On the other hand, as shown in FIG. 10B, when the maximum variation ΔFc is set to be relatively small, the carrier frequency Fc is not sufficiently diffused, and noise due to electromagnetic sound cannot be reduced.

On the other hand, in the present embodiment, the carrier frequency Fc is set by a fundamental frequency that changes periodically and a spread frequency that is added to the fundamental frequency at intervals shorter than the fluctuation period Tb of the fundamental frequency. The fundamental frequency that changes periodically and continuously leads to the frequency spreading, and the spreading frequency has an auxiliary spreading function.
Therefore, in this embodiment, since it is not necessary to set the maximum variation of the spread frequency to be particularly large in order to reduce noise due to electromagnetic sound, it is possible to prevent a sudden change in the carrier frequency Fc accompanying the variation of the spread frequency. . Therefore, the inverter control device 50 can appropriately achieve both improvement in control stability and reduction in noise due to electromagnetic noise.

(2) In the present embodiment, the spreading range Rsp in which the spreading frequency is distributed is set smaller than the fluctuation range Rb of the basic frequency. Thereby, it is possible to prevent a sudden change in the carrier frequency Fc due to the spread component and to improve the control stability.
(3) In the present embodiment, the fundamental frequency adjusting unit 68 monotonously increases or monotonously decreases the fundamental frequency in the fluctuation range Rb of the fundamental frequency. This further prevents sudden changes in the carrier frequency Fc and further improves the control stability.
Further, the fundamental frequency adjustment unit 68 may limit the time change rate of the monotone increase or the monotone decrease of the fundamental frequency.

(Second Embodiment)
A second embodiment will be described with reference to FIG. The second embodiment is based on the premise that the inverter 30 is a three-phase inverter, and the basic frequency adjusting unit 68 sets the fluctuation frequency Tb of the basic frequency to 1 / 3n of one electric cycle of the inverter output voltage (n is a natural number). ).

  FIG. 6 shows an example in which n = 3, that is, the variation period Tb of the fundamental frequency is set to 1/9 of one electrical period. The horizontal axis of FIG. 6 represents an electrical angle based on the phase at which the amplitude of the U-phase voltage Vu crosses from negative to positive zero. That is, the amplitudes of the U-phase voltage Vu, the V-phase pressure Vv, and the W-phase pressure Vw zero-cross from negative to positive at electrical angles 0, 120, and 240 [degE], respectively. The voltage amplitude of each phase zero-crosses from positive to negative at electrical angles 180, 300, and 420 [degE], respectively.

Here, by setting the fluctuation period Tb at an interval of 40 [degE] corresponding to 1/9 of one electrical period, the fundamental frequency has a lower limit in any phase where each phase voltage amplitude is zero-crossed from negative to positive. In the phase where the frequency Fm is zero and each phase voltage amplitude is zero-crossing from positive to negative, the fundamental frequency is the upper limit frequency FM. Therefore, the symmetry between the three phases can be ensured for the periodic fluctuation of the fundamental frequency. As a result, current offset can be suppressed and control stability can be improved.
In general, for an M-phase inverter having three or more phases, the fundamental frequency adjustment unit 68 sets the fluctuation period Tb of the fundamental frequency to “(M × n) / (n is a natural number)” of the electrical period of the inverter output voltage. It is preferable.

(Third embodiment)
A third embodiment will be described with reference to FIG. The third embodiment is based on the premise that the inverter 30 is a multi-phase inverter having three or more phases, and the fundamental frequency adjusting unit 68 is set so as to avoid the fluctuation ranges Rb of the fundamental frequencies of the respective phases from overlapping each other. . In other words, the fundamental frequency adjusting unit 68 independently adjusts so that the fluctuation range Rb of the fundamental frequency of each phase is dispersed.

As shown in FIG. 7A, for example, the basic frequency fluctuation ranges Rbu and Rbw for specifying the U-phase and W-phase voltage waveforms are lower than the basic frequency fluctuation range Rbv for specifying the V-phase voltage waveform. The frequency side and the high frequency side are set so as not to overlap each other.
FIG. 7B is based on the frequency distribution of the carrier frequency Fc when the three-phase voltage waveform specifying basic frequency variation ranges Rb are the same, or the voltage waveform generated using the carrier frequency Fc. The amplitude of the inverter current spectrum is indicated by a broken line. In this case, since the amplitude of the inverter current spectrum is concentrated in a specific frequency range, the sound pressure of the electromagnetic sound is increased.

On the other hand, in the third embodiment, by dispersing the fluctuation range Rb of the fundamental frequency of each phase, the amplitude of the inverter current spectrum based on the voltage waveform generated by using the carrier wave frequency obtained by spreading the fundamental frequency using Fc is obtained. Can be reduced.
Thereby, the sound pressure of the electromagnetic sound of the inverter 30 can be reduced.

(Other embodiments)
(A) The periodic function that defines the periodic fluctuation of the fundamental frequency is not limited to a triangular wave shape that linearly increases or decreases with respect to the time axis, as shown in FIGS. 5 (a) and 7 (a). In addition, as shown in FIGS. 8A and 8B, for example, a sine wave, a semi-ellipse, or a cycloid may be used. In these examples, the fundamental frequency is changing periodically and continuously. Further, it monotonically increases from the lower limit frequency Fm to the upper limit frequency FM, and monotonically decreases from the upper limit frequency FM to the lower limit frequency Fm. In other embodiments, the increase / decrease may be repeated a plurality of times within the fluctuation range Rb in one fluctuation cycle Tb, not limited to monotonous increase or monotonic decrease. By finely adjusting the shape of the periodic function in this way, it may be possible to make the electromagnetic sound more difficult to hear.

Further, FIG. 8C shows a periodic function that increases or decreases in steps. Here, strictly, the triangular wave-shaped periodic function shown by a straight line in FIGS. 5A and 7A also increases or decreases in a stepped manner in a minimum control unit corresponding to the resolution of the apparatus.
However, the example shown in FIG. 8 (c) does not mean a step at the minimum control unit level, but is an order larger than the minimum control unit and a step having a size smaller than the fluctuation range Rb of the fundamental frequency. is there.

Then, the step-like change in size is interpreted as being included in the “continuously changing” specified for the fundamental frequency in the claims. That is, the configuration using the fundamental frequency defined by the periodic function in FIG. 8C corresponds to the “embodiment for carrying out the invention described in the claims”.
In short, in the claims, the term “continuous” specifying the change in the fundamental frequency is interpreted with reference to the fluctuation range Rb of the fundamental frequency in view of the problem of the present invention “improving control stability”. It is appropriate.

For example, a sawtooth wave that changes in a range from the lower limit frequency Fm to the upper limit frequency FM of the fluctuation range Rb is assumed. When the sawtooth wave rises, the frequency increases linearly, reaches the upper limit frequency FM, and at the same time decreases to the lower limit frequency Fm. As described above, the step change that changes the frequency difference from the lower limit frequency Fm to the upper limit frequency FM of the fluctuation range Rb in one step is a “discontinuous” change. A configuration in which the fundamental frequency fluctuates in a sawtooth shape, that is, periodically and discontinuously cannot eliminate the problem of “improving control stability”, and thus is excluded from the present invention.
In contrast, in a configuration in which the fundamental frequency changes stepwise at a small level with respect to the fluctuation range Rb, the effect of improving the control stability is not affected. Therefore, in the present invention, such a relatively small step change including a change in the minimum control unit level is regarded as a “continuous” change.

  (B) Instead of the distribution curve shown in FIG. 5B, the spreading frequency may be discretely defined for the spreading frequency coefficient k using a distribution table as shown in FIG. In this table, the frequency corresponding to the coefficient k is defined so that the total is 100% symmetrically in the positive area and the negative area, with the frequency when the coefficient k is 0 being the maximum value. For example, the frequency when k = 1.0 is 2%, and the frequency when k = (− 0.4) is 10%.

  By the way, it can be considered that the distribution curve shown in FIG. 5B is exactly equal to a discrete table being defined with a minimum interval corresponding to the resolution of the apparatus. However, the example shown in FIG. 9 is intended to discretely define the frequency corresponding to the coefficient k at an interval sufficiently larger than the minimum interval according to the resolution. Thereby, the calculation load concerning the production | generation of a spreading | diffusion frequency can be reduced.

(C) In the above embodiment, the spread range Rsp of the spread frequency is set to be smaller than the fluctuation range Rb of the basic frequency to prevent a sudden change in the carrier frequency Fc due to the spread component. However, it is also possible to set the diffusion range Rsp to be larger than the fluctuation range Rb, for example, by limiting the amount of change of the diffusion frequency once.
(D) The frequency distribution of the spread frequency is not limited to an example in which the frequency is distributed symmetrically with respect to the fundamental frequency Fb as shown in FIG. 5B, but may be asymmetric with respect to the fundamental frequency Fb. The same applies to FIG.

(E) The inverter control device of the present invention may be any device that generates an inverter output voltage by PWM control that compares a phase voltage with a carrier wave, and does not matter the type of inverter load. Therefore, the inverter control device of the present invention is not limited to the MG drive system of a hybrid vehicle or an electric vehicle, but may be applied to a system for driving a load other than a motor for a general machine or a motor.
As mentioned above, this invention is not limited to the said embodiment at all, In the range which does not deviate from the meaning of invention, it can implement with a various form.

11 ... battery (power supply),
30 ... Inverter, 31-36 ... Switching element,
50: Inverter control device,
580 ... Current feedback control unit (voltage command calculation unit),
66... PWM signal generator,
67 ... Carrier frequency setting unit,
68: Fundamental frequency adjustment unit,
69... Spreading frequency adjustment unit,
80: MG (AC motor).

Claims (6)

An inverter control device that controls an inverter (30) that converts DC power input from a power source (11) into AC power by operation of a plurality of switching elements (31-36),
A voltage command calculation unit (580) for calculating a voltage vector commanded to the inverter;
As a method for specifying the voltage waveform output from the inverter, a PWM signal generation unit (66) that compares the phase voltage with a carrier wave to generate a PWM signal;
A carrier frequency setting unit (67) for setting a frequency (Fc) of a carrier used by the PWM signal generation unit;
With
The carrier frequency setting unit is
A fundamental frequency adjusting unit (68) that periodically and continuously changes a fundamental frequency that is a basis of the carrier wave frequency within a predetermined fluctuation range (Tb);
A spreading frequency adjusting unit (69) for adding a spreading frequency distributed in a range within a maximum fluctuation (± ΔF) to the fundamental frequency to the fundamental frequency at an interval shorter than a fluctuation period (Tb) of the fundamental frequency; ,
An inverter control device comprising:   The inverter control device according to claim 1, wherein a spread range (Rsp) in which the spread frequency is distributed is set to be smaller than a fluctuation range of the basic frequency. The fundamental frequency adjustment unit is
3. The inverter control device according to claim 1, wherein the basic frequency is monotonously increased from a lower limit frequency (Fm) to an upper limit frequency (FM) and is monotonously decreased from the upper limit frequency to the lower limit frequency. The fundamental frequency adjustment unit is
The fluctuation period (Tb) of the fundamental frequency is set to 1 / (M × n) of an electrical cycle of the output voltage of the inverter (n is a natural number) for an M-phase inverter having three or more phases. The inverter control device according to any one of 3. The fundamental frequency adjustment unit is
The multi-phase inverter having three or more phases is set so as to avoid the overlapping ranges (Rbu, Rbv, Rbw) of the fundamental frequency used for specifying each phase voltage waveform from overlapping each other. The inverter control device according to one item. As a method for specifying the voltage waveform output by the inverter, a pulse pattern setting unit (64) for selecting any one of a plurality of pulse patterns stored in advance,
A method switching unit (62) for switching a method of specifying a voltage waveform by the PWM signal generation unit or the pulse pattern setting unit;
The inverter control device according to any one of claims 1 to 5, further comprising:

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