JP5968010B2 - Power converter control device - Google Patents

Description

  The present invention controls a power converter that drives a motor at a variable speed, and suppresses unnecessary harmonic current from flowing through the motor and the power converter and reduces noise and loss of the motor. The present invention relates to a power converter control device capable of stable drive control.

  The power converter is a device that is connected between an AC power system and a DC power system and converts power into DC-AC. Generally, when an electric motor is driven by a power converter that is controlled by pulse width modulation (PWM), current harmonics are generated, which adversely affects the system such as increased loss. As a method of reducing this current harmonic, there are a method of setting a high switching frequency for PWM control, a method of appropriately designing a switching pulse phase so as to reduce harmonics, and the like.

In the method of setting the switching frequency high, the switching element is turned on / off at an asynchronous switching timing in which the phase of the switching frequency is not synchronized with the rotation phase of the electric motor, and switching is performed at a high frequency. However, when the switching frequency is set high, the switching loss in the switching element of the power converter increases, the loss generated in the power converter increases, and the heat generation amount increases.
Also, as a method of designing the switching pulse phase appropriately, the switching phase is controlled by synchronous PWM control that synchronizes the switching timing with the rotation phase of the motor, and the switching on / off phase is designed appropriately. An apparatus for reducing harmonic components of the order has been disclosed (for example, see Patent Document 1).
Further, in order to reduce the harmonic component of the target higher harmonic order, a method is disclosed in which the switching phase of the triangular wave comparison PWM is shifted to reduce the harmonics while improving the voltage utilization factor. (For example, refer to Patent Document 2).

JP-A-6-276747 (paragraphs [0016] to [0022], FIG. 1) JP-A-11-146654

Any conventional power converter control device exhibits the function of suppressing harmonic components of a specific harmonic order. However, when the power converter controls the motor at a variable speed, the frequency generated by the power converter changes every moment, while the noise and loss generated by the motor depend on the rotation speed of the motor.
For this reason, the conventional method for suppressing harmonic components of a specific harmonic order has a problem in that noise and loss generated in an electric motor driven and controlled at a variable speed cannot be effectively reduced. It was.

  The present invention has been made to solve the above-described conventional problems, and obtains a power converter control device that can always effectively suppress noise and loss generated in an electric motor that is driven and controlled at a variable speed. For the purpose.

Comprising a switching element and controlling a power converter that supplies a variable frequency output to the motor by a switching operation of the switching element in order to drive the motor at a variable speed based on an output from the command unit;
A position detector that detects the magnetic pole position of the rotor of the motor, a speed calculation unit that calculates the rotation speed of the motor from the magnetic pole position signal from the position detector, an output from the command unit, and a rotation speed of the motor from the speed calculation unit A pulse pattern calculation unit for calculating a pulse pattern of a switching pulse for determining a switching timing of a switching element for suppressing a harmonic component of a predetermined order with respect to a fundamental frequency of an output to an electric motor, and a pulse pattern calculation A gate pulse output unit that outputs a gate pulse for driving the switching element on and off based on the pulse pattern from the unit and the magnetic pole position signal from the position detector,
The pulse pattern calculation unit suppresses harmonic components of the order when there is a harmonic component of the order whose frequency is in a frequency range corresponding to the human audible range, and the rotation speed of the motor is relatively low. The pulse pattern is calculated so that there is no harmonic component of the order whose frequency is in the frequency range corresponding to the human audible range, and the loss generated by the motor is reduced when the rotational speed of the motor is relatively high. Therefore, the pulse pattern is calculated so as to suppress the harmonic components of different orders according to the rotation speed of the motor so as to suppress the harmonic components of the order in which the frequency falls within the frequency range causing the loss increase. .

  As described above, the pulse pattern calculation unit according to the present invention calculates the pulse pattern so as to suppress the harmonic components of different orders according to the rotation speed of the motor. Therefore, the pulse pattern calculation unit is generated depending on the rotation speed of the motor. Therefore, it is possible to obtain a power converter control device that effectively reduces the noise and loss regardless of the rotational speed of the electric motor.

It is a system configuration figure concerning the power converter control device of Embodiment 1 of this invention. It is a timing chart which shows the relationship between the pulse pattern and voltage command which concern on the power converter control device of Embodiment 1 of this invention. It is a 1st spectrum figure which shows the relationship between the frequency of a harmonic component, and the frequency of the noise area of an electric motor. It is a 2nd spectrum figure which shows the relationship between the frequency of a harmonic component, and the frequency of the noise area of an electric motor. It is a 3rd spectrum figure which shows the relationship between the frequency of a harmonic component, and the frequency of the noise area of an electric motor. It is a block diagram which shows the internal structure of the gate pulse output part 7 which concerns on the power converter control device of Embodiment 1 of this invention. It is a pulse phase table which concerns on the power converter control device of Embodiment 1 of this invention. It is a system configuration figure concerning the power converter control device of Embodiment 2 of this invention. It is a pulse phase table concerning the power converter control device of Embodiment 2 of this invention. It is a system configuration figure concerning the power converter control device of Embodiment 3 of this invention. It is a system block diagram which concerns on the power converter control apparatus of Embodiment 4 of this invention.

Embodiment 1 FIG.
FIG. 1 is a system configuration diagram showing an overall configuration of a power converter control device according to Embodiment 1 of the present invention. First, an overview of the overall configuration will be described with reference to FIG. A power converter 8 having a switching element converts a DC voltage from a DC power source into an AC voltage having a variable voltage and a variable frequency and supplies the AC voltage to the motor 9. Although this DC power supply is not particularly shown in the present invention and is not shown in the drawings, for example, an AC voltage from an AC power system may be converted into a DC voltage by a separate power converter to form a DC power supply.

The voltage command unit 1 receives a torque command or a speed command from a host (not shown) in the control system, and generates voltage commands Vd * and Vq * expressed in a quadrature two-phase coordinate system based on the command. Are output to the modulation factor calculation unit 2 and the gate pulse output unit 7. The modulation factor calculation unit 2 calculates the modulation factor m based on the voltage commands Vd * and Vq * from the voltage command unit 1, and the first harmonic suppression of the pulse pattern switching control unit 3 as the pulse pattern calculation unit. It outputs to the pulse pattern part 31, the 2nd harmonic suppression pulse pattern part 32, ... nth harmonic suppression pulse pattern part 3n.
The voltage command unit 1 and the modulation factor calculation unit 2 constitute a command unit in the claims of the present application.

  The magnetic pole position signal θe of the rotor of the electric motor 9 detected by the position sensor 11 provided in the electric motor 9 is output to the gate pulse output unit 7 and also to the speed calculation unit 10. The speed calculation unit 10 calculates the rotation speed signal ωe from the magnetic pole position signal θe detected by the position sensor 11 and outputs it to the selection circuit 30 of the pulse pattern switching control unit 3.

The first, second,... Nth harmonic suppression pulse pattern units 31, 32,... 3n will be described in detail later, but are preset based on the modulation rate m from the modulation rate calculation unit 2. A pulse pattern of a switching pulse (hereinafter, abbreviated as a pulse pattern as appropriate) for determining the switching timing of the switching element for suppressing harmonic components having different orders according to the rotational speed range of the electric motor 9 is calculated.
The selection circuit 30 selects any one of the pulse patterns output from the plurality of harmonic suppression pulse pattern units 31, 32,... 3n according to the rotation speed signal ωe calculated by the speed calculation unit 10, and outputs a gate pulse output unit. 7 is output.
As described above, the pulse pattern switching control unit 3 selects an appropriate pulse pattern based on the modulation rate m from the modulation rate calculation unit 2 and the rotation speed signal ωe from the speed calculation unit 10 and selects a gate pulse output unit. 7 is output.

The gate pulse output unit 7 converts power based on the voltage commands Vd * and Vq * from the voltage command unit 1, the pulse pattern from the selection circuit 30, and the magnetic pole position signal θe of the rotor of the motor 9 from the position sensor 11. The device 8 is PWM-controlled.
In the first embodiment, for example, an incremental encoder or a resolver is used as the position sensor 11 that detects the magnetic pole position of the rotor of the electric motor 9.

Next, the operation of the power converter control apparatus according to Embodiment 1 of the present invention will be described.
First, the operation from the voltage command unit 1 to the pulse pattern switching control unit 3 in FIG. 1 will be described.
In FIG. 1, the voltage command unit 1 generates voltage commands Vd * and Vq * expressed in a quadrature two-phase coordinate system based on a torque command or a speed command from the upper control system. In general, the orthogonal two-phase coordinate system uses a dq axis of a rotational coordinate system, Vd * is represented on the d axis, and Vq * is represented on the q axis, for controlling the motor 9. It is a directive.

  The modulation factor calculation unit 2 calculates the modulation factor m based on the voltage commands Vd * and Vq * from the voltage command unit 1. When the voltage command is Vd * and Vq *, the modulation factor m is calculated by the equation (1).

  In equation (1), Vdc is the voltage of a DC power supply (not shown) supplied to the power converter 8, and Vdc / 2 is the maximum value of the phase voltage command that can be output. √2 / 3 is a coefficient for converting the effective value of the dq-axis voltage command into the instantaneous value of the phase voltage command.

  As mentioned earlier, in general, noise and loss generated in an electric motor depend on the rotational speed of the electric motor. Therefore, in Embodiment 1 of the present invention, switching pulses corresponding to the rotational speed of the electric motor 9 are used. Select the pulse pattern. In the first embodiment, a synchronous PWM method is applied in which the switching timing of each switching element of the power converter 8 is synchronized with the rotational phase of the rotor of the electric motor 9.

The first, second,..., Nth harmonic suppression pulse pattern units 31, 32,... 3n have different harmonic suppression characteristics from the modulation factor m, and therefore have different harmonic orders at which harmonics should be suppressed. The pattern is calculated and output to the selection circuit 30.
In the first embodiment of the present invention, since the control is based on the synchronous PWM method, the pulse pattern output by each harmonic suppression pulse pattern unit is calculated based on the rotational phase of the rotor of the electric motor 9. This pulse pattern is calculated so as to be a pattern that reduces the harmonic component of the specific order of the current in the power converter 8.
And in Embodiment 1 of this invention, the pulse pattern according to the rotational speed of the rotor of the electric motor 9 is selected, and the harmonics of different orders are reduced in the low speed range and the high speed range of the rotational speed. Can respond.

The details of the pulse pattern will be described below with reference to FIG. FIG. 2 shows the relationship between the voltage command and the pulse pattern, where the voltage command is represented by a dotted line and the pulse pattern is represented by a solid line.
Generally, in the synchronous PWM control, when a harmonic component of a specific order in the current is deleted, switching is performed with a symmetric pulse phase at π / 2, which is the center of a half cycle of the fundamental wave. If the number of times of switching in a 1/2 cycle is k times (k is an odd number of 3 or more), (k-1) / 2 times of switching are performed in the 1/4 cycle, and the electrical angle phase 0 [rad] is set. The pulse phases θ _{1 to} θ _n that determine the pulse pattern are defined as a reference, and the harmonics are reduced by appropriately calculating the pulse phases θ _{1 to} θ _n .

The example of FIG. 2 is a case where switching is performed three times in a quarter cycle. Assuming that the gate signal for switching the switching element is GP, the pulse pattern in FIG. 2 is as shown in Expression (2) depending on the relative relationship between the pulse phases θ _{1 to} θ ₃ and the electrical phase θ described later. .

  At this time, the gate signal GP has an odd-symmetric waveform at π. In this example, switching is performed three times in a quarter cycle, but the idea is the same even if the number of times of switching increases.

Next, an example of a pulse pattern design method in the synchronous PWM method that reduces the harmonic component of a specific order will be described.
The nth-order harmonic component E in the output waveform of the power converter 8 subjected to PWM control is expressed by Expression (3) using the switching frequency k of 1/2 cycle.

Here, switching is always performed in phase 0 [rad] and phase π [rad], and switching in phase 0 [rad] is not counted. As shown in FIG. 2, in the case of 3 switching patterns in 1/4 cycle (7 switching patterns in 1/2 cycle), a pulse pattern for reducing the 5th and 7th harmonics of the low order component , The pulse phases θ ₁ , θ ₂ , and θ ₃ of the pulse pattern that satisfy the following formula (4) are obtained.

Equation (4) shows a condition in which the gate pulse waveform to be PWM-controlled is expanded in the Fourier series, the fundamental wave component is the same value as the modulation factor m, and the fifth and seventh order terms are zero. By solving the equation (4) as simultaneous equations and obtaining the solution, the pulse phases θ ₁ , θ ₂ , and θ ₃ of the pulse pattern can be obtained.

  In the example of Expression (4), the fifth and seventh harmonic components are uniformly zero, but the frequency of each harmonic component also changes according to the rotation speed of the motor 9, so that all rotation speeds It is effective not to always reduce the fifth-order and seventh-order components to zero but to change them according to the rotational speed. In particular, the harmonic component of the output current of the power converter 8 that most adversely affects the noise and loss of the electric motor 9 is set to be reduced.

  3 to 5 are spectrum diagrams showing the relationship between motor noise and the frequency of generated harmonics. Generally, the frequency band that is most audible to human hearing is about 1 to 4 KHz. Therefore, when current harmonics in this frequency band occur, the noise of the audible motor increases. That is, when the fundamental frequency for controlling the power converter 8 is 200 Hz to 800 Hz, the fifth-order harmonic component corresponds to the above frequency band and greatly affects noise.

  3 to 5, a frequency band of about 1 to 4 KHz is displayed as a noise range, and FIG. 3 illustrates a case where fifth and seventh harmonic components are generated in the noise range. FIG. 4 shows a case where the fifth and seventh harmonic components are lower than the noise range, but the eleventh and thirteenth harmonic components are generated in the noise range. FIG. 5 shows the fifth and seventh harmonic components. The case where the wave component is higher than the noise range is shown. Therefore, for the control of the pulse phase, the fifth-order and seventh-order harmonic components are suppressed as much as possible in the case as shown in FIG. 3, and in the case as shown in FIG. Although it is necessary to suppress the wave component, in the case as shown in FIG. 5, it is not necessary to give priority to the suppression of the fifth-order and seventh-order harmonic components, but rather the pulse phase giving priority to the loss reduction of the electric motor 9. It may be effective to perform the design.

In addition, when the rotational speed is relatively large and the 5th and 7th harmonic components do not occur in the noise range, the efficiency priority is designed, and the motor 9 has a characteristic that loss increases at a specific frequency. When the pulse phase of the pulse pattern is designed, it may be designed to reduce the harmonics of the order in which the harmonic component is in the vicinity of the frequency.
In this case, the power converter 8 is controlled with the pulse phase in which the 5th and 7th lower harmonics are reduced most in the relatively low speed region where the 5th and 7th harmonic components are generated in the noise range. In the middle and high speed regions beyond that, the harmonic component of the specific order is suppressed, and the power converter 8 is controlled by the pulse phase giving priority to the loss reduction of the electric motor 9.

Next, the configuration and operation of the gate pulse output unit 7 will be described. The gate pulse output unit 7 includes voltage commands Vd * and Vq * output from the voltage command unit 1, pulse phases θ _{1 to} θ _{n of} the pulse pattern output from the selection circuit 30, and a magnetic pole position signal θe detected by the position sensor 11. Based on the above, a gate signal for PWM control of the power converter 8 is obtained.
FIG. 6 shows the internal configuration of the gate pulse output unit 7.

In FIG. 6, pulse phases θ _{1 to} θ _n of the pulse pattern from the selection circuit 30 are input to the input terminal 13. The voltage commands Vd * and Vq * expressed by the orthogonal two-phase coordinate system from the voltage command unit 1 are input to the input terminal 14. A magnetic pole position signal θe of the rotor of the electric motor 9 from the position sensor 11 is input to the input terminal 15.

  The phase angle calculation unit 16 calculates the control phase angle THV according to Equation (5) based on the voltage commands Vd * and Vq * from the input terminal 14.

  Since the magnetic pole position signal θe from the input terminal 15 is a cosine output, 90 is added by the phase advance circuit 18 to convert it into a sine output. The adder 17 calculates the voltage phase θ by adding the control phase angle THV from the phase angle calculation unit 16 and the signal (θe + π / 2) from the phase advance circuit 18 based on Expression (6).

This voltage phase θ is added by 120 ° by the 120 ° phase advance circuit 19 and subtracted by 120 ° by the 120 ° phase delay circuit 20.
With respect to the U phase, switching on / off is determined by the U phase determination circuit 21 based on a relative comparison between the pulse phases θ _{1 to} θ _n and the U phase of the voltage phase θ output from the adder 17. With respect to the V phase, the switching circuit ON / OFF is determined to be a V phase based on a relative comparison between the pulse phases θ _{1 to} θ _n and the 120 ° advanced voltage phase θ output from the 120 ° phase advance circuit 19 and the V phase. It is determined by. With respect to the W phase, the switching circuit ON / OFF switching state is determined based on the relative relationship between the pulse phase θ _{1 to} θ _n and the 120 ° delayed voltage phase θ output from the 120 ° phase delay circuit 20. It is determined by.

  Based on the output of the U-phase determination circuit 21, the U-phase gate output unit 24 amplifies the U-phase voltage signal for driving the power converter 8 and outputs the amplified signal to the output terminal 27. Based on the output of the V-phase determination circuit 22, the V-phase gate output unit 25 amplifies the V-phase voltage signal for driving the power converter 8 and outputs the amplified signal to the output terminal 28. Based on the output of the W-phase determination circuit 23, the W-phase gate output unit 26 amplifies the W-phase voltage signal for driving the power converter 8 and outputs the amplified signal to the output terminal 29.

  Next, the switching operation of the pulse phase of the pulse pattern will be described. The pulse pattern switching control is performed by the pulse pattern switching control unit 3 shown in FIG. 1 calculates and outputs the pulse phase of a pulse pattern for controlling the power converter 8 from the modulation factor m. As shown in the table of FIG. 7, the selection circuit 30 includes parameters m1, m2,... M12 related to the modulation factor m obtained by the modulation factor calculator 2, and parameters related to the rotational speed signal ωe detected by the speed calculator 10. The pulse phase of the pulse pattern is selected and controlled according to v1, v2, and v3. That is, even when the modulation factor is the same, the pulse pattern differs when the rotation speed changes.

In this example, the rotation speed is switched from 1000 [rpm] to 8000 [rpm] in 1000 [rpm] steps, and the modulation rate is switched in 0.1 steps.
And the correspondence with each case demonstrated previously in FIGS. 3-5 is illustrated as follows.
That is, in FIG. 7, the speed range of 5000 and 6000 [rpm] corresponds to the case shown in FIG. 3, and the pulse pattern for suppressing the fifth and seventh harmonic components that increase the noise of the motor 9. Is calculated by the second harmonic suppression pulse pattern unit 32, and the selection circuit 30 selects it. In addition, the low speed range of 3000 and 4000 [rpm] corresponds to the case shown in FIG. 4, and a pulse pattern for suppressing the 11th and 13th harmonic components in which the noise of the electric motor 9 becomes relatively large. Is calculated by the first harmonic suppression pulse pattern unit 31, and the selection circuit 30 selects it. Furthermore, the high frequency range of 7000 and 8000 [rpm] corresponds to the case shown in FIG. 5, and a pulse pattern for suppressing a harmonic component of a specific order that increases the loss of the electric motor 9 is nth. The harmonic suppression pulse pattern unit 3n calculates and the selection circuit 30 selects it.

  In FIG. 7, the pulse pattern column corresponding to the speed range of 1000 and 2000 [rpm] is blank, but in this example, synchronous PWM control is difficult in such a low speed region. This is because the application of asynchronous PWM control is more appropriate, and is excluded from the selection of the pulse pattern according to the present invention.

  Further, the rotation speed and the modulation rate change continuously. For this reason, when referring to the pulse phase table shown in FIG. 7, the values of the rotation speed and the modulation rate may be rounded off and then the data of the pulse phase table may be referred to. As another method, the pulse phase value corresponding to the rotational speed and the modulation rate value may be obtained by linear extrapolation using the data of the pulse phase table.

In the above, the case where the pulse phase of the pulse pattern is obtained by referring to the pulse phase table of FIG. 7 instead of the calculation has been described, but it can also be calculated using an approximate expression.
For example, θ ₁ to θ ₃ can be approximately calculated using the cubic function (7).

Here, a _{1 to} a ₃ , b _{1 to} b ₃ , c _{1 to} c ₃ , or d _{1 to} d ₃ are preset coefficients.
Therefore, the first harmonic suppression pulse pattern unit 31 uses the coefficients a _{1 to} a ₃ , b _{1 to} b ₃ , c _{1 to} c ₃ , and d _{1 to} d ₃ that are set in advance. 7), the pulse phases θ _{1 to} θ ₃ of this pulse pattern are calculated and output to the selection circuit 30.
In addition, the second harmonic suppression pulse pattern unit 32 can perform similar approximation, calculate the pulse phases θ _{1 to} θ ₃ of the pulse pattern, and output them to the selection circuit 30.

  In Embodiment 1 of the present invention, a three-phase AC motor is described as an example of the motor. However, the present invention is intended for a multi-phase motor, and the number of phases is not particularly limited. The target motor may be either a permanent magnet type synchronous motor, an induction motor, or any other motor. Moreover, although this invention demonstrated the method of using the polynomial which expanded the Fourier series as a design method of the pulse phase of the pulse pattern which a power converter control device uses, there are various design methods in the method of reducing a harmonic. It is conceivable and is not limited to the method described above.

In addition to controlling so as to avoid a general noise frequency band, it is also possible to control so as to avoid a resonance frequency unique to a device generated in an electric motor system.
Further, in the expression (4), switching (pulse phases θ ₁ , θ ₂ , θ ₃ ) is performed three times in a quarter cycle in order to suppress harmonic components of two kinds of orders of the fifth order and the seventh order. Although the pulse pattern is set, a pulse pattern that suppresses harmonic components of three or more orders may be set on condition that switching is performed five times or more in a quarter cycle.

  As described above, the power converter control device according to Embodiment 1 has the modulation calculated by the modulation factor calculation unit 2 based on the voltage commands Vd * and Vq * from the voltage command unit 1 as the pulse pattern calculation unit. A first calculating a pulse pattern for suppressing harmonic components of different orders set in advance according to the rotational speed signal ωe based on the rate m and the rotational speed signal ωe calculated by the speed calculator 10; Based on the second, nth harmonic suppression pulse pattern portions 31, 32, 3n and the rotation speed signal ωe, the first, second, nth harmonic suppression pulse pattern portions 31, 32, 3n Is selected and the pulse pattern is output to the gate pulse output unit 7. Therefore, the noise and loss generated depending on the rotation speed of the electric motor 9 are converted into the rotation speed of the electric motor 9. Detained Not there is an effect that it is possible to always effectively reduced.

  In addition, the calculation of the pulse pattern in the pulse pattern calculation unit is performed by referring to the pulse phase table in which the pulse phase data is calculated and stored in advance, or by using an approximate expression. Can be

Embodiment 2. FIG.
Unlike the first embodiment, the power converter control device according to the second embodiment has a configuration in which a torque command is input from the host and the power converter 8 is PWM-controlled.
Hereinafter, Embodiment 2 of the present invention will be described based on FIG. 8 which is a system configuration diagram related to a power converter control device and FIG. 9 which is a pulse pattern switching table.
First, an overall system configuration including a power converter control device according to Embodiment 2 of the present invention will be described. In FIG. 8, the same or corresponding parts as in FIG.

FIG. 8 shows a system configuration of a power converter control device including a plurality of harmonic suppression pulse pattern units, as in the first embodiment, and the difference from the first embodiment will be mainly described below.
In FIG. 8, the torque command unit 4 as a command unit generates a torque command t based on a speed command from a higher level. The voltage command calculation unit 5 calculates voltage commands Vd * and Vq * expressed in the orthogonal two-phase coordinate system based on the torque command t from the torque command unit 4.

The first harmonic suppression pulse pattern unit 61 of the pulse pattern switching control unit 6 as the pulse pattern calculation unit determines the switching timing of each switching element of the power converter 8 based on the torque command t from the torque command unit 4. The pulse pattern of the switching pulse to be determined is calculated and output to the selection circuit 60.
Similarly, the second harmonic suppression pulse pattern unit 62 calculates a pulse pattern of a switching pulse different from the first harmonic suppression pulse pattern unit 61 based on the torque command t from the torque command unit 4, Output to the selection circuit 60.
Similarly, the nth harmonic suppression pulse pattern unit 6n calculates a switching pulse pattern different from other harmonic suppression pulse pattern units based on the torque command t from the torque command unit 30, and selects the selection circuit. 60.

  The selection circuit 60 of the pulse pattern switching control unit 6 selects one of the pulse patterns output from the plurality of harmonic suppression pulse pattern units 61, 62... 6n according to the rotational speed signal ωe calculated by the speed calculation unit 10. Select and output to the gate pulse output unit 7.

  Next, the switching operation of the pulse phase of the pulse pattern will be described. The plurality of harmonic suppression pulse pattern units 61, 62,... 6n in FIG. 8 calculate and output the pulse phase of the pulse pattern that controls the power converter 8 from the torque command t. As shown in the table of FIG. 9, the selection circuit 60 includes parameters t1, t2,... T10 related to the torque command t generated by the torque command unit 4, and a parameter v1 related to the rotational speed signal ωe calculated by the speed calculation unit 10. , V2, and v3, the pulse phase of the pulse pattern is selected and controlled. That is, even if the torque command value is the same, the pulse pattern will be different if the rotational speed changes.

The rotation speed is switched from 1000 [rpm] to 8000 [rpm] in 1000 [rpm] steps, and the torque command is switched in 10% steps.
In FIG. 9, the columns of the rotational speeds 1000 and 2000 [rpm] are blank as in FIG. 7, but synchronous PWM control is difficult in the low speed region, and it is more appropriate to apply asynchronous PWM control. This is because the pulse pattern is not selected according to the present invention.

When the noise and loss characteristics of the motor 9 are torque-dependent, by selecting the pulse pattern while referring to the torque command t, the specific order of the output current of the power converter 8 can be selected according to the motor characteristics. By designing the pulse phase of the pulse pattern that reduces the harmonic components, the noise reduction effect and loss reduction effect can be increased.
Since the torque command t is directly related to the current flowing through the electric motor 9, a pulse pattern having a strong harmonic suppression effect is selected even in a region where the rotational speed is low. Accordingly, even when the rotation speed range is the same, when controlling with a voltage command, for example, a pulse pattern for suppressing the 11th and 13th harmonic components is selected, but when controlling with a torque command, for example, It is also conceivable to select a pulse pattern for suppressing fifth-order and seventh-order harmonic components.

  As described above, the power converter control device according to the second embodiment is based on the torque command t from the torque command unit 4 and the rotation speed signal ωe calculated by the speed calculation unit 10 as the pulse pattern calculation unit. , First, second,..., Nth harmonic suppression pulse pattern units 61, 62,... For calculating pulse patterns for suppressing harmonic components of different orders set in advance according to the rotational speed signal ωe. 6n and the rotation speed signal ωe, and select one of the first, second, nth harmonic suppression pulse pattern sections 61, 62, 6n and output the pulse pattern to the gate pulse output section 7 Since the selection circuit 60 is provided, the noise and loss generated depending on the rotation speed of the electric motor 9 can be effectively reduced regardless of the rotation speed of the electric motor 9.

Embodiment 3 FIG.
The power converter control device of the third embodiment is different from the power converter control device of the first embodiment in that the operation of the pulse pattern switching control unit 3 in FIG. This is configured to be performed by the wave suppression pulse pattern unit 71. The harmonic suppression pulse pattern unit 71 of the third embodiment outputs a pulse phase to the gate pulse output unit 7 based on the pulse pattern table shown in FIG.

In the harmonic suppression pulse pattern unit 71, n θ 1 to _n are arranged in each of the two-dimensional tables having the rotation speed signal ωe and the modulation factor m as inputs, and the rotation speed is 1000 [rpm] to 8000. [Rpm] is switched at 1000 [rpm] steps, the modulation rate is switched at 0.1 steps, and the pulse phase related to the pulse pattern is output. In the third embodiment, it is possible to obtain the same effect as in the first embodiment with a simpler configuration.

Embodiment 4 FIG.
The power converter control device according to the fourth embodiment is different from the power converter control device according to the second embodiment in that the operation of the pulse pattern switching control unit 6 in FIG. This is configured to be performed by the wave suppression pulse pattern unit 72. The harmonic suppression pulse pattern unit 72 of the fourth embodiment outputs a pulse phase to the gate pulse output unit 7 based on the pulse pattern table shown in FIG.

In the harmonic suppression pulse pattern unit 72, n θ 1 to _n are arranged in each of the two-dimensional tables having the rotation speed signal ωe and the torque command t as inputs, and the rotation speed is 1000 [rpm] to 8000. [Rpm] is switched in steps of 1000 [rpm], the torque command is switched in steps of 10%, and the pulse phase related to the pulse pattern is output. In the fourth embodiment, it is possible to obtain the same effect as in the second embodiment with a simpler configuration.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

1 voltage command unit, 2 modulation factor calculation unit, 3 pulse pattern switching control unit,
30 selection circuit,
31, 32... 3n first, second, n th harmonic suppression pulse pattern part,
4 Torque command section, 5 Voltage command calculation section, 6 Pulse pattern switching control section,
60 selection circuit,
61, 62,... 6n, first, second, n th harmonic suppression pulse pattern portion,
7 Gate pulse output section, 8 Power converter, 9 Electric motor, 10 Speed calculation section,
11 Position sensor, 71, 72 Harmonic suppression pulse pattern part.

Claims (5)

Comprising a switching element, and for controlling a power converter that supplies a variable frequency output to the electric motor by a switching operation of the switching element in order to drive the electric motor at a variable speed based on an output from the command unit;
A position detector that detects the magnetic pole position of the rotor of the motor, a speed calculator that calculates the rotational speed of the motor from the magnetic pole position signal from the position detector, an output from the command unit, and a speed calculator A pulse for calculating a pulse pattern of a switching pulse for determining a switching timing of the switching element for suppressing a harmonic component of a predetermined order with respect to the fundamental frequency of the output to the electric motor based on the rotation speed of the electric motor A gate pulse output unit for outputting a gate pulse for driving the switching element on and off based on the pulse pattern from the pattern calculation unit and the pulse pattern calculation unit and the magnetic pole position signal from the position detector;
The pulse pattern calculation unit has a harmonic component of the order whose frequency is in a frequency range corresponding to a human audible range, and the harmonic component of the order when the rotational speed of the motor is relatively low. The pulse pattern is calculated so as to be suppressed, and there is no harmonic component of the order whose frequency is in a frequency range corresponding to a human audible range, and the motor is generated in a relatively high speed range of the motor. In order to reduce the loss to be generated, the pulse has a frequency that suppresses harmonic components of different orders depending on the rotation speed of the motor so as to suppress harmonic components of the order whose frequency falls within a frequency range that causes an increase in loss. A power converter control device that calculates a pattern . The pulse pattern calculation unit calculates the pulse pattern with reference to a pulse phase table storing a pre-calculated result using the output from the command unit and the rotation speed of the motor from the speed calculation unit as variables. The power converter control device according to claim 1 . The pulse pattern calculation unit calculates the pulse pattern using an approximate expression set in advance with an output from the command unit and a rotation speed of the motor from the speed calculation unit as variables. Item 4. The power converter control device according to Item 1 . The command unit calculates a modulation factor based on a voltage command unit that generates a voltage command, and a voltage command from the voltage command unit, and outputs the modulation factor to the pulse pattern calculation unit as an output from the command unit The power converter control device according to claim 1, further comprising a rate calculation unit . 4. The torque command unit according to claim 1, further comprising a torque command unit that generates a torque command and outputs the torque command to the pulse pattern calculation unit as an output from the command unit. 2. The power converter control device according to item 1 .

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