JP5169118B2 - Power conversion device and power conversion method - Google Patents

Description

  The present invention relates to a power conversion device and a power conversion method used for motor control and the like.

Conventionally, there is a power converter using a PWM (Pulse-Width Modulation) modulation method (see Patent Document 1). In the power converter, the carrier frequency is changed with time in order to reduce harmonic noise generated by opening and closing the switch. Thereby, the energy of the harmonic noise can be diffused in a wide frequency band, and the peak level of the harmonic noise is reduced.
JP 2000-184731 A

  However, in the conventional power converter, since the carrier frequency is changed with time by digital control, the value of the carrier frequency becomes discrete. In addition, an interrupt cycle, which is a cycle in which the carrier frequency holds one value and then discretely changes to another value, is equal to a carrier cycle that is the inverse of the carrier frequency. Further, the energy of the harmonic noise in a certain frequency band is proportional to the time that the value of the carrier frequency exists in the band. Furthermore, since the carrier frequency values are equally spaced, the bandwidth is also equally spaced. From this, the larger the carrier frequency value, the smaller the energy per bandwidth. Therefore, the peak level of the harmonic noise diffused within the band by changing the carrier frequency with time is not uniform, and there is a problem that the peak level cannot be sufficiently reduced.

  This invention is made | formed in view of the said problem, and it aims at providing the power converter device and the power conversion method which can make the harmonic noise of a carrier frequency more uniform.

To achieve the above object, in the power conversion device according to the present invention, the carrier frequency changing means for changing the frequency of the carrier wave output to the control signal generating means for generating the control signal for outputting the output value from the output means, higher the first value of the plurality of values of the carrier frequency is increased, to reduce the difference between the value adjacent to the value of the first value and the one in the case of arranging the plurality of values in ascending or descending order The frequency of the carrier wave having the one value and then discretely changing to a value adjacent to the one value is defined as the carrier wave period .

  According to the present invention, the harmonic noise of the carrier frequency can be made more uniform.

  As an example of a power converter according to the present invention, an inverter system including an inverter that supplies sinusoidal AC power to a motor by PWM-modulating the output of a DC power supply will be described. Hereinafter, an inverter system according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 11.

(First embodiment)
(Inverter system configuration)
Hereinafter, the configuration and operation of the inverter system 1 will be described with reference to FIG. FIG. 1 is a diagram showing a configuration of an inverter system 1 according to a first embodiment of the present invention, and FIG. 2 is a diagram showing a relationship between a carrier frequency changed by a carrier frequency changing unit 9 shown in FIG. 1 and a carrier cycle Tc. . As shown in FIG. 1, the inverter system 1 that is a power conversion device includes a PWM inverter 2 that is an output unit and a three-phase brushless DC motor (hereinafter referred to as a motor) 3. Furthermore, a current detection unit 4 including current sensors 4a, 4b, and 4c, a control device 10 incorporating an arithmetic device (hereinafter referred to as a CPU), a battery B, and a capacitor C are provided as main components. Further, the control device 10 includes a current command generation unit 5 that is a command value output unit, PID control units 6a, 6b, and 6c, and a carrier signal generation unit 7 that is a carrier wave output unit. Furthermore, it includes comparators 8a, 8b, 8c that are control signal generating means and a carrier frequency changing unit 9 that is a carrier frequency changing means.

  The PWM inverter 2 includes six switching elements Tu +, Tu−, Tv +, Tv−, Tw +, and Tw−. These switching elements select a positive electrode or a negative electrode of a DC power source composed of a battery B and a capacitor C according to the control of the comparators 8a, 8b, and 8c, and select the selected electrodes for the U phase, V phase, and W phase of the motor 3, Connect to the electrode. The switching elements Tu +, Tu−, Tv +, Tv−, Tw +, and Tw− are configured by a semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor).

  The current sensors 4a, 4b, and 4c detect U-phase, V-phase, and W-phase current values supplied from the PWM inverter 2 to the motor 3, respectively. The current command generation unit 5 generates a sinusoidal current command value so that the detected current values of the current sensors 4a, 4b, and 4c are converted into a sinusoidal alternating current. The PID controllers 6a, 6b, and 6c detect the current detection values of the current sensors 4a, 4b, and 4c so that the current detection values of the current sensors 4a, 4b, and 4c follow the current command values generated by the current command generator 5. Is PID controlled.

  The carrier frequency changing unit 9 changes the frequency of the carrier signal that is the carrier wave generated by the carrier signal generating unit 7 (hereinafter referred to as carrier frequency; see FIGS. 5 and 6 to be described later). At this time, the carrier frequency changing unit 9 sets a plurality of carrier signal periods (hereinafter referred to as carrier periods) Tc. As shown in FIG. 2, since the carrier frequency and the carrier period Tc are in an inversely proportional (reciprocal) relationship, the carrier frequency can be changed by setting a plurality of carrier periods Tc. Furthermore, after the carrier frequency is held at one value, the interrupt cycle, which is a cycle that discretely changes to another value, is made equal to the carrier cycle Tc. Then, the carrier signal generation unit 7 outputs a triangular wave carrier signal having a carrier frequency that is a carrier frequency to the comparators 8a, 8b, and 8c.

  The comparators 8a, 8b, and 8c compare the magnitude relationship between the output values of the PID controllers 6a, 6b, and 6c and the triangular wave carrier signal. A signal for controlling on / off of the switching elements Tu +, Tu−, Tv +, Tv−, Tw +, and Tw− of the PWM inverter 2 is input to the PWM inverter 2 in accordance with the magnitude relationship. The operation of the comparator 8a will be specifically described taking control of the U-phase switching elements Tu + and Tu− as an example. The comparator 8a applies a positive voltage to the U phase of the motor 3 by controlling Tu + and Tu− to be in an on state and an off state, respectively, when the output value of the PID controller 6a is larger than the triangular wave carrier signal. To do. Conversely, when the output value of the PID control unit 6a is smaller than the triangular wave carrier signal, a negative voltage is applied to the U phase of the motor 3 by controlling Tu + and Tu− to be in an off state and an on state, respectively. To do.

(When changing the carrier frequency value at regular intervals)
Next, the time change of the carrier frequency when the value of the carrier frequency used in the conventional power conversion apparatus is changed at equal intervals will be described. FIG. 3 is a diagram of the time change of the carrier frequency when changing at equal intervals. As shown in FIG. 3, the plurality of carrier frequency values are discrete values. FIG. 3 shows a time change when a plurality of carrier periods Tc are set so as to increase in ascending order from the minimum value to the maximum value among the plurality of values of the carrier frequency. Moreover, in FIG. 3, the time change for a half cycle is shown. The other half cycle is a time change when a plurality of carrier cycles Tc are set so as to be descending from the maximum value to the minimum value of the plurality of values of the carrier frequency. A time change for one cycle is obtained by combining a time change of a half cycle (not shown) with FIG. From this, the time change of one cycle of the carrier frequency becomes a triangular wave.

  Specifically, in FIG. 3, 11 values of 5 kHz, 6 kHz,..., 15 kHz are used as a plurality of values of the carrier frequency. The intervals of the plurality of values 5 kHz,..., 15 kHz are all 1 kHz and are equal. Further, a plurality of carrier periods Tc are set so that a plurality of values 5 kHz,..., 15 kHz are in ascending order from a minimum value 5 kHz to a maximum value 15 kHz at a plurality of values 5 kHz,. . Similarly, a plurality of carrier periods Tc are set so that a plurality of values 5 kHz,..., 15 kHz are in descending order from a maximum value 15 kHz to a minimum value 5 kHz at a plurality of values 5 kHz,. Yes. Also, the set value of the carrier cycle Tc is made equal to the interrupt cycle. As a result, the carrier frequency value does not change and remains constant for less than the interrupt period. Then, the value of the carrier frequency changes discretely for each interrupt cycle. From this, the set value of the carrier period Tc decreases as the value of the carrier frequency increases. Therefore, the greater the carrier frequency value, the smaller the interrupt period.

  Furthermore, the noise spectrum and frequency density in the case of the above time change will be described. FIG. 4 is a diagram showing the noise spectrum and frequency density in the case of the time change shown in FIG. 4A shows the frequency density of the fundamental frequency (first harmonic) in the case of the time change shown in FIG. 3, and FIG. 4B shows the noise spectrum of the fundamental frequency in the case of the time change shown in FIG. is there. Here, a value obtained by dividing the energy of the harmonic noise in a certain frequency band by the bandwidth of the frequency band is defined as a frequency density. Then, the peak level of the harmonic noise in a certain frequency band is proportional to the frequency density. Further, the energy of harmonic noise in a certain frequency band is the time during which n (n = 1, 2,. Is proportional to

  More specifically, as shown in FIG. 4A, when the carrier frequency changes with time, each spectrum (solid line) has a plurality of carrier frequency values of 5 kHz,. ) Appears. That is, a spectrum appears at 5 kHz,. As described above, the greater the carrier frequency value, the shorter the interrupt period. For example, the interrupt period of the minimum value 5 kHz in the plurality of carrier frequency values is 0.2 msec, while the interrupt period of the maximum value 15 kHz in the plurality of carrier frequency values is 0.066 ·· msec. For this reason, the time during which the fundamental frequency of one value among the plurality of values of the carrier frequency exists in the frequency band becomes shorter as the value of the carrier frequency increases. As shown in FIG. 4A, the higher the carrier frequency value, the smaller the harmonic noise energy in the frequency band, and the smaller the spectrum.

  Further, each frequency band for a plurality of fundamental frequencies of the carrier frequency is defined. In FIG. 3, as described above, 11 values of 5 kHz, 6 kHz,..., 15 kHz are used as a plurality of values of the carrier frequency. For this reason, FIG. 4A shows 11 frequency bands for a plurality of values of 5 kHz,..., 15 kHz with respect to a basic frequency of 5 kHz,. The 11 frequency bands are not overlapped with each other in order to make the harmonic noise more uniform. Further, all the 11 frequency bands have the same bandwidth. As described above, since the intervals between the plurality of carrier frequency values 5 kHz,..., 15 kHz are all 1 kHz, the bandwidth of the 11 frequency bands is also 1 kHz. That is, the frequency band with respect to the fundamental frequency 5 kHz of the minimum value 5 kHz in the plurality of values of the carrier frequency is 4.5 kHz to 5.5 kHz. On the other hand, the frequency band with respect to the fundamental frequency 15 kHz of the maximum value 15 kHz among the plurality of values of the carrier frequency is 14.5 kHz to 15.5 kHz.

  In FIG. 4A, the frequency density (dotted line) for each frequency band is also shown. As described above, the higher the carrier frequency value, the lower the harmonic noise energy in the frequency band. And all the 11 frequency bands have the same bandwidth. From this, the frequency density for each frequency band becomes smaller as the value of the carrier frequency becomes larger. That is, the frequency density of the frequency band 14.5 kHz to 15.5 kHz with respect to the basic frequency 15 kHz having the maximum value of 15 kHz is smaller than the frequency density of the frequency band 4.5 kHz to 5.5 kHz with respect to the basic frequency 5 kHz having the minimum value of 5 kHz. Therefore, as a result, the noise spectrum in the case of the time change shown in FIG. 3 becomes smaller as the value of the carrier frequency becomes larger as shown in FIG. 4B. This is apparent from the fact that the peak level of the harmonic noise for each frequency band is proportional to the frequency density for each frequency band. That is, even when the carrier frequency is spread over time, the peak level of the harmonic noise for each frequency band is not uniform, and the peak level cannot be sufficiently reduced. Therefore, in the first embodiment, the carrier frequency values are changed at unequal intervals in order to make the bandwidths of the 11 frequency bands unequal.

(When the carrier frequency value is changed at unequal intervals)
Next, the time change of the carrier frequency when the value of the carrier frequency is changed at unequal intervals according to the first embodiment of the present invention will be described. FIG. 5 is a diagram showing a half cycle of the time change of the carrier frequency according to the first embodiment, and FIG. 6 is a diagram showing a half cycle following the time change shown in FIG. Similar to FIG. 3, the plurality of values of the carrier frequency are discrete values. FIG. 5 shows a time change when a plurality of carrier periods Tc are set so as to be in ascending order from the minimum value to the maximum value among the plurality of values of the carrier frequency. FIG. 6 shows the change over time when a plurality of carrier periods Tc are set so that the carrier frequency is in descending order from the maximum value to the minimum value among the plurality of values of the carrier frequency. The time change shown in FIGS. 5 and 6 is combined to be a time change for one cycle. From this, the time change of one cycle of the carrier frequency becomes a triangular wave.

  Specifically, in FIGS. 5 and 6, as in FIG. 3, 11 values of 5 kHz,..., 15 kHz are used as a plurality of values of the carrier frequency. As in FIG. 3, the carrier period Tc is such that the plurality of values 5 kHz,..., 15 kHz are in ascending order from the minimum value 5 kHz to the maximum value 15 kHz in the plurality of values 5 kHz,. Multiple settings are made. Further, a plurality of carrier periods Tc are set so that a plurality of values 5 kHz,..., 15 kHz are in descending order from a maximum value 15 kHz to a minimum value 5 kHz at a plurality of values 5 kHz,. . Similarly to FIG. 3, each set value of the carrier cycle Tc is made equal to the interrupt cycle. From now on, the carrier frequency value does not change and remains constant for less than the interrupt period. Then, the value of the carrier frequency changes discretely for each interrupt cycle. As in FIG. 3, the set value of the carrier period Tc decreases as the value of the carrier frequency increases. Therefore, the greater the carrier frequency value, the smaller the interrupt period. However, in the first embodiment, unlike FIG. 3, a plurality of carrier frequency values 5 kHz,..., 15 kHz are changed at unequal intervals.

  Further, the noise spectrum and frequency density in the case of the above time change will be described. FIG. 7 is a diagram showing a noise spectrum and a frequency density in the case of the time change shown in FIGS. FIG. 7A shows the frequency density of the fundamental frequency (first harmonic) in the case of the time change shown in FIGS. 5 and 6, and FIG. 7B shows the case of the time change shown in FIGS. It is a noise spectrum of the fundamental frequency. As shown in FIG. 7A, as in FIG. 4A, when the carrier frequency changes with time, each spectrum (solid line) appears at a plurality of fundamental frequencies of the carrier frequency. That is, a spectrum appears at 5 kHz,. As described above, the greater the carrier frequency value, the shorter the interrupt period. Therefore, as in FIG. 4A, the time in which a fundamental frequency of one of a plurality of values of the carrier frequency exists in a certain frequency band becomes shorter as the value of the carrier frequency increases. As in FIG. 4A, as the carrier frequency value increases, the harmonic noise energy in the frequency band decreases and the spectrum decreases.

  As shown in FIGS. 5 and 6, 11 values of 5 kHz,..., 15 kHz are used as a plurality of values of the carrier frequency. Therefore, in FIG. 7A, 11 frequency bands are shown for a plurality of values of 5 kHz,..., 15 kHz with respect to a basic frequency of 5 kHz,. The 11 frequency bands are not overlapped with each other in order to make the harmonic noise more uniform. Here, in the first embodiment, unlike FIG. 4A, a plurality of carrier frequency values 5 kHz,..., 15 kHz are changed at unequal intervals. Specifically, as one value fc1 (see FIG. 8) of a plurality of values 5 kHz,..., 15 kHz is increased, one value when the plurality of values 5 kHz,. The difference between fc1 and the adjacent value fc2 (see FIG. 8) is reduced. Therefore, the bandwidth for each frequency band decreases as the carrier frequency value increases. The eleven frequency bands (dotted lines) according to the first embodiment are shown in FIG.

  As described above, the higher the carrier frequency value, the lower the harmonic noise energy in the frequency band. However, in the first embodiment, as described above, as the value of the carrier frequency increases, the bandwidth is reduced. Therefore, as shown in FIG. The density can be made flatter. That is, each spectrum appearing in a plurality of fundamental frequencies of the carrier frequency has a different peak, but each spectrum is spread within a frequency band with respect to the fundamental frequencies of the plurality of values of the carrier frequency due to changes in the carrier frequency over time. For example, a spectrum that appears in one of the plurality of carrier frequency values has a higher level than a spectrum that appears in another fundamental frequency that is larger than the one value, but is spaced from adjacent spectra. Becomes wider. On the other hand, the spectrum that appears in the fundamental frequency of one value among the plurality of values of the carrier frequency has a lower level than the spectrum that appears in the fundamental frequency of another value that is smaller than the one value, but the interval between adjacent spectrums. Becomes narrower. Therefore, when viewed over the entire frequency band with respect to a plurality of carrier frequency values of 5 kHz,..., 15 kHz and a basic frequency of 5 kHz,..., 15 kHz, the frequency density for each frequency band can be made more uniform. Therefore, the noise spectrum in the case of the time change shown in FIGS. 5 and 6 becomes uniform as shown in FIG. 7B. From this, the peak level of the harmonic noise for each frequency band becomes uniform, and the peak level can be further reduced.

(Calculation method of value fc2 adjacent to one value fc1)
Next, a method for calculating the value fc2 adjacent to one value fc1 among the plurality of values of the carrier frequency of the inverter system 1 according to the first embodiment will be described. FIG. 8 is a diagram illustrating a method of calculating a value fc2 adjacent to one value fc1 among a plurality of values of the carrier frequency. In FIG. 8, a value fc2 (fc1 <fc2) adjacent to one value fc1 among a plurality of values of the carrier frequency is calculated. Here, the carrier cycle Tc of one value fc1 is Tc1, and the carrier cycle Tc of the adjacent value fc2 is Tc2. Further, the frequency band for the fundamental frequency of one value fc1 is Δfc1, and the frequency band for the fundamental frequency of the adjacent value fc2 is Δfc2 (Δfc1> Δfc2). A value obtained by dividing the sum of the minimum value of the frequency band Δfc1 and the maximum value of the frequency band Δfc1 by 2 is one value fc1. Similarly, the value obtained by dividing the sum of the minimum value of the frequency band Δfc2 and the maximum value of the frequency band Δfc2 by 2 is the adjacent value fc2.

  Here, the relational expression is derived from FIG.

更に、詳細な関係式を求めると、次に関係式が導かれる。

Further, when a detailed relational expression is obtained, the relational expression is derived next.

これから、次に関係式が導かれる。

From this, the relational expression is derived next.

このように、キャリア周波数の複数の値のうちの一の値ｆｃ１と、一の値ｆｃ１の基本周波数に対する周波数帯域Δｆｃ１を設定することで、一の値ｆｃ１に隣接する値ｆｃ２を計算することが可能となる。これから、キャリア周波数の複数の値のうちの一の値ｆｃ１が大きくなる程、複数の値を昇順に並べた場合における一の値ｆｃ１と一の値ｆｃ１に隣接する値ｆｃ２との差が小さくなるように、隣接する値ｆｃ２を計算できる。

Thus, by setting one value fc1 of a plurality of carrier frequency values and the frequency band Δfc1 for the fundamental frequency of the one value fc1, the value fc2 adjacent to the one value fc1 can be calculated. It becomes possible. From this, the difference between one value fc1 and the value fc2 adjacent to the one value fc1 when the plurality of values are arranged in ascending order becomes smaller as the value fc1 of the plurality of carrier frequency values increases. Thus, the adjacent value fc2 can be calculated.

(Internal configuration of carrier frequency changing unit 9 and control processing executed by it)
Next, an internal configuration of the carrier frequency changing unit 9 and a control process executed by the carrier frequency changing unit 9 will be described. FIG. 9 is a block diagram showing an internal configuration of the carrier frequency changing unit 9 shown in FIG. As illustrated in FIG. 9, the carrier frequency changing unit 9 sets an initial value that is a minimum value among a plurality of values of the carrier frequency, a maximum value among the plurality of values of the carrier frequency, and a frequency band for the basic frequency of the initial value. A setting unit 91 is provided. Furthermore, a calculation unit 92 that executes the calculation method shown in FIG. 8, a storage unit 94 that stores a carrier cycle Tc that is the reciprocal of the calculation value calculated by the calculation unit 92, and whether the calculation value is larger than the maximum value. And a calculated value determination unit 95 for determining whether or not. In addition, an interrupt signal generator 96 that generates an interrupt signal for discretely changing the carrier frequency to one value after being held at one value, and a timer 97 that counts the interrupt cycle are provided. In addition, a count value determination unit 98 that determines whether the counter value is equal to or greater than the carrier cycle Tc stored in the storage unit 94 is provided. Further, the control unit 93 mainly controls the timing of the setting unit 91, the calculation unit 92, the storage unit 94, the calculated value determination unit 95, the interrupt signal generation unit 96, the timer unit 97, and the count value determination unit 98.

  FIG. 10 is a flowchart for executing the calculation method shown in FIG. As illustrated in FIG. 10, the setting unit 91 causes the user to set an initial value that is a minimum value among a plurality of values of the carrier frequency, a maximum value among the plurality of values of the carrier frequency, and a frequency band for the basic frequency of the initial value. (Step S101). Here, a usable range may be given as the carrier frequency value. For example, it depends on system requirements (for example, suppression of heat generation of the switching elements Tu +, Tu−, Tv +, Tv−, Tw +, Tw− of the PWM inverter 2, suppression of generation of acoustic noise, etc.). The minimum value among the plurality of values of the carrier frequency is the minimum frequency of the usable range, and the maximum value of the plurality of values of the carrier frequency is the maximum frequency of the usable range. In the first embodiment, the minimum value is 5 kHz and the maximum value is 15 kHz. Next, the calculation unit 92 calculates a calculated value from the initial value set by the setting unit 91 and the frequency band for the fundamental frequency of the initial value by the calculation method shown in FIG. 8 (step S102).

  Next, the calculated value determination unit 95 compares the calculated value calculated by the calculation unit 92 with the maximum value set by the setting unit 91 to determine whether the calculated value is larger than the maximum value (step) S103). When the calculated value determination unit 95 determines that the calculated value is not larger than the maximum value (step S103: No), the calculation unit 92 substitutes the calculated value for the initial value (step S104). Next, the computing unit 92 calculates a carrier cycle Tc that is the reciprocal of the calculated value (step S105). The control unit 93 stores the carrier cycle Tc calculated by the calculation unit 92 in the storage unit 94. In the first embodiment, a plurality of carrier periods Tc are stored in an array having the storage unit 94. Thereafter, the process proceeds to step S102, and the next calculated value is calculated from the frequency band set by the setting unit 91 and the current initial value substituted by the calculation unit 92. Thereafter, until the calculated value determination unit 95 determines that the calculated value is larger than the maximum value, the control processing of Step S102 to Step S105 is repeatedly executed. Thereby, a plurality of calculated values and a plurality of carrier periods Tc can be automatically calculated. Further, since the calculation unit 92 executes the calculation method shown in FIG. 8, as the one value fc1 among the calculated values increases, the one value fc1 and the value fc2 adjacent to the one value fc1 Can be reduced.

  On the other hand, when the calculated value determination unit 95 determines that the calculated value is larger than the maximum value (step S103: Yes), the control unit 93 rearranges the plurality of carrier periods Tc stored in the storage unit 94 (step S103). S106), this control process is terminated. Specifically, in the first embodiment, the plurality of carrier periods Tc stored in an array of the storage unit 94 are arranged in descending order. Therefore, a plurality of carrier periods Tc arranged in descending order are stored in another array of the storage unit 94. Further, the plurality of carrier periods Tc stored in an array of the storage unit 94 are rearranged in ascending order and stored in the other array. At this time, after the carrier cycles Tc arranged in descending order, the carrier cycles Tc rearranged in ascending order are stored. In this way, a plurality of set values for the carrier period Tc are set.

FIG. 11 is a flowchart for executing the time change shown in FIGS. 5 and 6. As shown in FIG. 11, first, the count value determination unit 98 acquires the first set value of the carrier cycle Tc stored in another array of the storage unit 94 as an interrupt cycle.
Next, after holding the carrier frequency at one value, the count value determining unit 98 generates an interrupt signal for discretely changing to another value from the interrupt signal generating unit 96 (step S201). Next, the time measuring unit 97 starts a counting operation by a built-in counter based on the interrupt signal from the interrupt signal generating unit 96 (step S202). Next, the count value determination unit 98 determines whether the value of the counter (hereinafter referred to as a count value) is equal to or greater than the first set value of the interrupt cycle, that is, the carrier cycle Tc, based on the interrupt signal. (Step S203). When the count value determination unit 98 determines that the count value is not greater than or equal to the interrupt cycle (step S203: No), the carrier frequency changing unit 9 waits until the count value determination unit 98 determines that the count value is greater than or equal to the interrupt cycle. To do.

  On the other hand, when the count value determination unit 98 determines that the count value is equal to or greater than the interrupt cycle (step S203: Yes), the count value determination unit 98 acquires the next set value of the carrier cycle Tc as the interrupt cycle ( Step S204). Thereafter, the process returns to step S <b> 201, and the count value determination unit 98 generates an interrupt signal again from the interrupt signal generation unit 96. Thereafter, the control processing from step S201 to step S204 is repeatedly executed. As a result, interrupt signals can be generated in the order of the set values of the carrier period Tc stored in another array of the storage unit 94. From this, it is possible to change the carrier frequency so that a plurality of values are in ascending order from the minimum value to the maximum value in a plurality of values of the carrier frequency, and a plurality of values are in descending order from the maximum value to the minimum value. it can. Therefore, the time change of the carrier frequency shown in FIGS. 5 and 6 can be realized.

  As described above, in the inverter system 1 according to the first embodiment, the current command generation unit 5 that outputs the command value, the carrier signal generation unit 7 that outputs the carrier signal, and the carrier frequency change unit 9 that changes the carrier frequency. Is provided. In addition, comparators 8a, 8b, and 8c that compare the command value with the carrier signal and generate a control signal according to the comparison result, and a PWM inverter 2 that outputs an output value based on the control signal are provided. . Then, the carrier frequency changing unit 9 is adjacent to the one value fc1 and the one value fc1 when the plurality of values are arranged in ascending order as the one value fc1 of the plurality of carrier frequency values increases. The difference from fc2 is reduced. From this, the harmonic noise of the carrier frequency can be made more uniform.

  The embodiment described above is an example of the implementation of the present invention, and the scope of the present invention is not limited thereto, and other various embodiments are within the scope described in the claims. It is applicable to. For example, in the first embodiment, the present invention is applied to the inverter system 1, but is not particularly limited thereto. For example, in a system that converts power by switching, such as a DC motor drive system or a DC-DC converter having an H-bridge configuration, the system can be applied as long as the switching frequency is changed with time by a discrete value.

  In the first embodiment, the time change of the carrier frequency is changed to a triangular wave shape, but is not particularly limited to this, and other shapes may be used. A value fc2 adjacent to one value fc1 when the plurality of values 5kHz,..., 15kHz are arranged in ascending order as the value fc1 of the plurality of values 5kHz,. Any shape can be used as long as the difference is reduced. For example, the time change when the time change shown in FIG. 5 is one period, that is, a sawtooth wave shape may be used. Similarly, a time change when the time change shown in FIG. 6 is one cycle, that is, a sawtooth wave shape may be used. Furthermore, the time change of the carrier frequency may be changed randomly as shown in FIG. Note that the shape of the carrier frequency over time can be easily changed by the control process in step S106 of FIG. 10, that is, the rearrangement process of the carrier period Tc by the control unit 93.

  In the first embodiment, 5 kHz,..., 15 kHz are used as a plurality of values of the carrier frequency. However, the present invention is not particularly limited to this, and other values may be used. Further, although 11 values are used as the plurality of values of the carrier frequency, the number is not particularly limited to this, and any number may be used.

  Further, in the first embodiment, the value of the carrier frequency at the time of increase (see FIG. 5) and the value of the carrier frequency at the time of decrease (see FIG. 6) are set to the same value. It is not a thing and may be different.

  In the first embodiment, the difference between one value fc1 and the value fc2 adjacent to the one value fc1 when a plurality of carrier frequency values 5 kHz,..., 15 kHz are arranged in ascending order is reduced. However, it is not particularly limited to this. When a plurality of carrier frequency values 5 kHz,..., 15 kHz are arranged in descending order, the difference between one value fc1 and a value fc2 adjacent to one value fc1 may be reduced.

  In the first embodiment, the value fc2 adjacent to one value fc1 is calculated using the calculation method shown in FIG. 8, but the present invention is not particularly limited to this. As long as the difference between the one value fc1 and the value fc2 adjacent to the one value fc1 can be reduced, other methods may be used.

  In the first embodiment, the calculation unit 92 of the carrier frequency changing unit 9 calculates the calculated value by the calculation method shown in FIG. 8 and calculates the carrier period Tc. However, the present invention is particularly limited to this. It may be calculated by the user in advance.

  In the first embodiment, the user sets the minimum value among a plurality of values of the carrier frequency as an initial value. However, the present invention is not particularly limited to this, and a value different from the minimum value is set as the initial value. It is also good.

  Further, in the first embodiment, the bandwidth for each frequency band with respect to a plurality of carrier frequency values of 5 kHz,..., 15 kHz and a basic frequency of 5 kHz,. ing. Then, the frequency density is made more uniform by dividing each spectrum appearing at a plurality of carrier frequency values of 5 kHz,..., 15 kHz into fundamental frequencies of 5 kHz,. However, it is not particularly limited to this. Multiple values of carrier frequency 5 kHz,..., 15 kHz m (m is an integer of any integer) order harmonics m × 5 kHz,. However, the same effect can be acquired.

  In the first embodiment, a plurality of carrier frequency values 5 kHz,..., 15 kHz are used twice, when increasing (see FIG. 5) and when decreasing (see FIG. 6). In addition, the time during which the fundamental frequency of one value among the plurality of values of the carrier frequency exists in the frequency band becomes shorter as the value of the carrier frequency becomes larger. Energy is also reduced. Therefore, in the first embodiment, the bandwidth for each frequency band with respect to a plurality of carrier frequency values of 5 kHz,..., 15 kHz and a basic frequency of 5 kHz,. . Then, the frequency density is made more uniform by dividing each spectrum appearing at a plurality of carrier frequency values of 5 kHz,..., 15 kHz into fundamental frequencies of 5 kHz,. However, it is not particularly limited to this.

  Even if the bandwidth for each frequency band with respect to the fundamental frequency of the plurality of values of the carrier frequency is kept the same, the time during which the fundamental frequency of one value among the plurality of values of the carrier frequency exists in the frequency band is made the same. , You can get the same effect. That is, the existing times may be made the same by changing the number of times of use of a plurality of values of the carrier frequency. Specifically, for example, consider a case where there are three carrier frequency values of 5 kHz, 10 kHz, and 15 kHz. The time change of one cycle of the carrier frequency is 10 kHz, 15 kHz, 10 kHz, 5 kHz, 15 kHz, and 10 kHz. That is, 5 kHz is used once, 10 kHz is used twice, and 15 kHz is used three times during one period. From this, the time during which the plurality of carrier frequency values 5 kHz, 10 kHz, and 15 kHz and the fundamental frequencies 5 kHz, 10 kHz, and 15 kHz exist in each frequency band is as follows.

よって、上記存在する時間が等しくなる。このようにしても、周波数密度をより均一にすることが可能となる。

Thus, the existing times are equal. Even in this case, the frequency density can be made more uniform.

The figure which shows the structure of the inverter system which concerns on the 1st Embodiment of this invention. The figure which shows the relationship of the carrier frequency and carrier period which change in the carrier frequency change part shown in FIG. Diagram of time variation of carrier frequency when changing at equal intervals The figure which shows the noise spectrum and frequency density in the case of the time change shown in FIG. The figure which shows the half cycle of the time change of the carrier frequency which concerns on 1st Embodiment. The figure which shows the half cycle following the time change shown in FIG. The figure which shows the noise spectrum and frequency density in the case of the time change shown to FIG. 5 and FIG. The figure which shows the calculation method of the value adjacent to one value of several values of a carrier frequency The block diagram which shows the internal structure of the carrier frequency change part shown in FIG. Flowchart for executing the calculation method shown in FIG. Flowchart for executing the time change shown in FIG. 5 and FIG. Diagram of time variation of carrier frequency when calculation value is set at random

Explanation of symbols

1 Inverter system that is a power converter,
2 Output means PWM inverter, 3 three-phase brushless DC motor,
4 Current detector, 4a, 4b, 4c Current sensor,
5 current value generating means as command value output means, 6a, 6b, 6c PID control part,
7 Carrier signal generation unit which is carrier wave output means,
8a, 8b, 8c Comparator as control signal generating means,
9 Carrier frequency changing unit as carrier frequency changing means,
10 control device,
91 setting unit, 92 calculation unit, 93 control unit, 94 storage unit,
95 Calculated value judgment part, 96 Interrupt signal generation part, 97 Timekeeping part,
98 count value determination unit,
B battery, C capacitor, fc1 one value, fc2 adjacent value,
Δfc1, Δfc2 frequency band, Tc, Tc1, Tc2 carrier period,
Tu +, Tu−, Tv +, Tv−, Tw +, Tw− switching elements,
θ angle

Claims (6)

Command value output means for outputting the command value;
Carrier wave output means for outputting a carrier wave;
Carrier frequency changing means for changing the frequency of the carrier;
Control signal generating means for comparing the command value with the carrier wave and generating a control signal based on the comparison result;
Output means for outputting an output value based on the control signal,
The carrier frequency changing means has a value adjacent to the one value and the one value when the plurality of values are arranged in ascending order or descending order as one value of the plurality of values of the frequency increases. the difference between the smaller,
The power conversion device according to claim 1, wherein a period in which the frequency of the carrier wave is discretely changed to a value adjacent to the one value after holding the one value is a period of the carrier wave . The carrier frequency changing means is configured so that the plurality of values are in ascending order from the minimum value to the maximum value of the frequency, and the plurality of values are in descending order from the maximum value to the minimum value. The power conversion device according to claim 1, wherein: The power conversion apparatus according to claim 1, wherein the carrier frequency changing unit changes the frequency randomly. When the one value is fc1 and the adjacent value is fc2,
The difference | fc2−fc1 |
| Fc2−fc1 | = α × (1 / fc1 + 1 / fc2) (where α is a positive number)
It is represented by these. The power converter device in any one of the Claims 1 thru | or 3 characterized by the above-mentioned. The energy density of the harmonic noise for each frequency band centered on the frequency of the plurality of values is uniform throughout the frequency band.
The power converter according to any one of claims 1 to 4. The control signal generating means compares the command value from the command value output means with the carrier wave from the carrier wave output means, and generates a control signal according to the comparison result,
An output means outputs an output value based on the control signal,
The one value and the value adjacent to the one value when the plurality of values are arranged in ascending order or descending order as the value of one of the plurality of values of the frequency increases by the carrier frequency changing means. The carrier frequency is changed so that the difference between
The power conversion method , wherein a period in which the frequency of the carrier wave discretely changes to a value adjacent to the one value after holding the one value is set as a period of the carrier wave .

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