JPH07177753A - Control method and equipment for power converter unit - Google Patents

Abstract

PURPOSE:To prevent the occurrence of heating due to switching loss, shortage of operating time, increase in ripple and others by reducing magnetic sound caused by higher harmonics. CONSTITUTION:ON-time signal generating means 12 is provided, which is capable of generating a signal proportional to ON time within a period of carrier signal of a switching element 3 obtaining an output signal by inputting a voltage command signal and a carrier signal. Further provided are timing signal generating means 13 generating a timing signal for changing with time either ON timing or OFF timing of the switching element 3 for each of a plurality of periods of the carrier signal, and switching signal generating means 11 outputting the switching signal driving the switching element 3 in response to the ON time signal and timing signal.

Description

Detailed Description of the Invention

[0001]

This invention relates to pulse width modulation control (P
The present invention relates to a control method and device for a power converter such as a chopper or an inverter whose output voltage is controlled by WM control).

[0002]

2. Description of the Related Art FIG. 15 is a block diagram showing a PWM inverter as a conventional power conversion device disclosed in, for example, Japanese Patent Publication No. 3-79959. In FIG. 15, 51 is an output side of a three-phase AC power supply 59. Is a power converter such as a PWM inverter which converts the direct current from the rectifier circuit 51 into an alternating current and supplies the alternating current electric motor 57 as a load. For example, a self-extinguishing type such as a transistor or a GTO thyristor. It is configured using a switching element.

Reference numeral 61 is an adder for adding the output of the carrier control circuit 53 and the output of the carrier center frequency setting circuit 60, 54 is a carrier signal generation circuit connected to the output side of the adder 61, and 55 is a carrier signal generation. The output of the circuit 54 and the output of the output voltage pattern generation circuit 56 are compared and P
A comparator 58 which outputs a WM signal, and 58 is a gate circuit which amplifies the PWM signal and supplies it to the PWM inverter 52.

Next, the operation will be described. The rectification bridge 51 converts alternating current from the three-phase alternating current power supply 59 into direct current and supplies the direct current to the power conversion device 52. The carrier control circuit 53 outputs a pattern signal such as a sine wave or a triangular wave that periodically changes the frequency of the carrier signal, and the carrier center frequency setting circuit 60 outputs a constant signal (DC signal) for setting the center frequency of the carrier signal. ) Is output. Subsequently, the pattern signal and the center frequency setting signal are added by the adder 61 and input to the carrier signal generation circuit 54 as a carrier frequency command signal.

The carrier signal generating circuit 54 generates a carrier signal whose frequency is proportional to the amplitude of the carrier frequency command signal. Then, the comparator 55 compares the amplitude of the carrier signal with the amplitude of the control signal output from the output voltage pattern generation circuit 56, and outputs the comparison result as the PWM signal having the pulse width determined by the pulse width modulation control. Output to the gate circuit 58. Next, the gate circuit 58
Controls the power converter 52 by amplifying the PWM signal.

By the above PWM control operation, the power conversion device 52 outputs an AC voltage proportional to the output signal of the output voltage pattern generation circuit 56 and drives the AC motor 57. Here, the carrier control circuit 53 temporally changes the frequency of the carrier signal output from the carrier signal generation circuit 54. Therefore, the frequency of the harmonic component included in the output voltage of the PWM inverter 52 changes with time, and the harmonic of the same frequency is not continuously applied to the AC motor 57. As a result, the AC motor 57
The magnetic sound generated by is distributed in frequency distribution by changing the carrier frequency, that is, the frequency of the PWM signal with time. Therefore, the peak level of the magnetic sound is reduced and the magnetic sound can be reduced.

[0007]

Since the conventional power converter is constructed as described above, if the carrier frequency is changed significantly in order to increase the effect of reducing the magnetic noise, the carrier frequency will be changed to this carrier frequency. The switching loss of the switching element which comprises a power converter increases proportionally. Therefore, there is a problem of heat generation due to switching loss in a region where the carrier frequency is high.

At present, a microcomputer is often used for performing PWM control, but in this case, PWM control is usually performed in synchronization with the carrier frequency. When the carrier frequency is changed with time, the carrier period, that is, the calculation period of the PWM control becomes short in a region where the carrier frequency becomes high, so that the calculation time becomes short.

On the other hand, in the region where the carrier frequency is low, the problem of the calculation time does not occur, but the calculation cycle of the PWM control becomes long, so that the update cycle of the voltage command becomes long. As a result, there has been a problem that the ripple of the primary current supplied to the AC motor increases, which in turn causes an increase in torque ripple and harmonic loss of the AC motor.

The present invention has been made in order to solve the above-mentioned conventional problems. Claims 1 and 2
Another object of the present invention is to provide a method of controlling a power conversion device, which can temporally change the generation timing of an output voltage during one cycle of a carrier signal to reduce magnetic noise caused by harmonic components. And

It is an object of the present invention to provide a control device for a power conversion device, which is suitable for hardware control and can reduce magnetic noise caused by harmonic components.

It is an object of the present invention to provide a control device for a power conversion device, which is suitable for software control and can reduce magnetic noise as in the above-mentioned invention.

An object of the present invention is to provide a control device for a power conversion device, which is suitable for software control of a three-phase inverter and can reduce magnetic noise as in the above-mentioned inventions.

It is an object of the invention of claim 6 to provide a control device for a power conversion device, which can reduce magnetic noise more efficiently than the above inventions.

[0015]

According to a first aspect of the present invention, there is provided a power converter control method, wherein the average value of the output voltage during one cycle of a carrier signal is made to coincide with a voltage command and the control is determined by pulse width modulation control. The generation timing of the output voltage is temporally changed without changing the pulse width.

According to a second aspect of the present invention, there is provided a method for controlling a power converter in which the average value of the output voltage during one cycle of the carrier signal is made to coincide with the voltage command and the pulse width determined by the pulse width modulation control is changed. Instead, either the on timing or the off timing of the switching element that obtains the output voltage is temporally changed.

According to a third aspect of the present invention, there is provided a control device for a power conversion device, which outputs a signal proportional to an on-time within a cycle of a carrier signal of a switching element which receives a voltage command signal and a carrier signal and obtains an output voltage. An on-time signal generating means for generating, a timing signal generating means for generating a timing signal that temporally changes either one of the on-timing and off-timing of the switching element for each plurality of cycles of the carrier signal, and the on-time And a switching signal generating means for outputting a switching signal for driving the switching element according to a signal and the timing signal.

According to a fourth aspect of the present invention, there is provided a control device for a power converter, in which the first and second control signals whose amplitude difference is proportional to the voltage command signal are calculated and the amplitudes of the first and second control signals are calculated. According to the magnitude relation between the amplitudes of the carrier signal and the first and second control signals, and a control signal calculating means for temporally changing the carrier signal for each plurality of cycles within a range not exceeding the amplitude of the carrier signal. And a switching signal generating means for outputting a switching signal of a switching element for obtaining an output voltage.

According to a fifth aspect of the present invention, there is provided a control device for a power conversion device, in which each region formed by connecting three apexes of a voltage vector determined corresponding to a switching state of each phase is connected to each other. Two zero voltage vectors forming one vertex and two voltage vectors forming the remaining vertices are selected in advance and the order of outputting these voltage vectors in one cycle of the carrier signal is determined in advance. And a voltage vector selection unit that stores the output order thereof, a voltage command signal generation unit that outputs the voltage command signal in the form of a vector, and the voltage command signal that receives the voltage command signal and outputs the position of the voltage command signal at each cycle of the carrier signal. Area determining means for determining the area to be operated and the area determining means so that the output voltage of the inverter matches the voltage command signal. The operating time of the sum of the two zero voltage vectors selected in the selected region and the operating time of the other two voltage vectors, and operating time determining means for determining the distribution within one cycle of the carrier signal; An operating time changing means for temporally changing the distribution of the operating time of the zero voltage vector for each plurality of cycles of the carrier signal, and a switching signal for driving the switching element of each phase from the operating time of each voltage vector is output. And a switching signal generating means.

A control device for a power conversion device according to a sixth aspect of the present invention includes a carrier signal generating means for outputting a carrier signal of a variable frequency whose frequency changes with time.

[0021]

According to the control method of the power converter of the present invention, the average value of the output voltage during one cycle of the carrier signal is made to coincide with the voltage command, and the pulse width determined by the pulse width modulation control is not changed. By changing the generation timing of the output voltage with time, harmonics of the same frequency are not continuously applied to the load, and the generation of magnetic noise due to the harmonic component can be reduced.

According to a second aspect of the present invention, there is provided a method for controlling a power converter in which the average value of the output voltage during one cycle of a carrier signal is made to coincide with a voltage command and the pulse width determined by the pulse width modulation control is not changed. The same effect as that of the first aspect of the invention can be obtained by temporally changing either the on timing or the off timing of the switching element that obtains the output voltage.

According to another aspect of the present invention, in the control device for a power converter, a signal proportional to an on-time within a cycle of a carrier signal of a switching element which obtains an output signal, and an on-timing or off-timing of the switching element. Suitable for hardware control by outputting a switching signal for driving the switching element from the switching signal generating means in response to a timing signal which changes one of the carrier signals with respect to time in every plural cycles of the carrier signal, and has the same frequency. It is possible to reduce the generation of magnetic noise due to the harmonic components by preventing the harmonics of No. 1 from being continuously applied to the load.

According to a fourth aspect of the present invention, there is provided a control device for a power conversion device, wherein the first and second control signals are temporally changed every plural cycles of the carrier signal within a range not exceeding the amplitude of the carrier signal, and the above-mentioned control signal. Suitable for software control by outputting the switching signal from the switching signal generation means according to the magnitude relationship of the amplitude with the carrier signal,
It is possible to reduce the generation of magnetic sound due to the harmonic components.

According to a fifth aspect of the present invention, in the control device for the power converter, the switching signal generating means outputs a switching signal for driving the switching element of each phase from the operating time of each voltage vector, so that the three-phase inverter is operated. It is suitable for software control and can reduce the generation of magnetic noise due to harmonic components.

According to the sixth aspect of the present invention, the control device for the power conversion device uses the carrier signal having a variable frequency whose frequency changes with time, thereby temporally determining the generation timing of the output voltage during one cycle of the carrier signal. Together with the changing point, it is possible to more effectively reduce the generation of magnetic sound due to the harmonic component.

[0027]

EXAMPLES Example 1. Embodiments of the present invention will be described below with reference to the drawings. 1 is a circuit diagram showing an embodiment of the invention of claims 1 to 3, and in FIG. 1, reference numeral 1 is a step-down chopper circuit. In this step-down chopper circuit 1, a switching element 3 such as a transistor and a reactor 5 are connected in series between one terminal 8 of the output terminals 7 and 8 and one terminal 9 of the input terminals 9 and 10, and the output terminal 7 is connected. , 8, a capacitor 6 is connected, the cathode of the diode 4 is connected to the connection point of the switching element 3 and the reactor 5, and the anode of the diode is connected to the input terminal 10, and between the input terminals 9 and 10. Is connected to a DC power supply 2, and a load (not shown) such as a motor is connected between the output terminals 7 and 8. Therefore, when the switching element 3 is turned on and off,
The output voltage is supplied to the load.

Reference numeral 11 is a switching signal generating means connected to the switching element 3 and is composed of, for example, a delay circuit. 12 and 13 are switching signal generating means 11
Is a comparator and timing signal generating means, and 14 is a voltage command signal generating means connected to the comparator 12, and has, for example, a ROM 14a storing a V / F pattern, and corresponds to a speed command signal F given from the outside. The voltage command signal V ^* is output. Reference numeral 15 is a carrier signal generating means connected to the comparator 12 and the timing signal generating means 13, and has, for example, a crystal oscillator 15a and a counter 15b for counting the output signal of the crystal oscillator, and the output signal of the counter 15b is directly clocked. And the carrier signal a through the digital / analog (D / A) converter 15c.

The timing signal generating means 13 receives a clock synchronized with the trailing edge of the carrier signal (sawtooth wave) and counts the number of clocks.
6 and the count number thereof as addresses, the ROM 17 which outputs the timing signal t for changing the on-timing of the switching element 3 within the carrier cycle T by the delay time Td as a pattern signal such as a sine wave, a triangular wave or a random wave. It is configured.

Next, the operation of the first embodiment will be described.
The DC power supply 2 applies a DC voltage between the input terminals 9 and 10 of the step-down chopper circuit 1. The carrier signal generating means 15 outputs a carrier signal a (sawtooth wave) having a carrier period T and a clock signal synchronized with the trailing edge of the carrier signal. The voltage command signal generating means 14 outputs the voltage command signal V ^* .

The comparator 12 corresponds to the on-time signal generating means, and inputs the carrier signal a (sawtooth wave) of the carrier period T from the carrier signal generating means 15 and the voltage command signal V ^* from the voltage command signal generating means 14. As shown in FIG. 2, the amplitudes of the two signals are compared, and when the voltage command signal V ^* is larger than the carrier signal a, a high level signal is output. Output to the generating means 11. The on-time signal O is the switching element 3 that constitutes the step-down chopper circuit 1.
A signal proportional to the on time T _on in the carrier period T.

The switching signal generating means 11 inputs the on-time signal O and the timing signal t output from the timing signal generating means 13, and the on-time signal O is delayed by the delay time Td by the timing signal t as shown in FIG. The switching signal s for driving the switching element 3 is generated and sent to the switching element 3 without delaying the pulse width determined by the pulse width modulation control. As a result, between the output terminals 7 and 8 of the step-down chopper circuit 1, V _out = T _on / T × V _in (= V ^* ) as an average value for one period T of the carrier signal a. ... An output voltage that matches the voltage command signal V ^* of (1) is obtained.

Here, since the switching signal generating means 11 temporally changes the on-timing of the on-time signal O output from the comparator 12 with the timing signal t from the timing signal generating circuit 13, the step-down chopper circuit 1
The harmonic component contained in the output voltage of the above changes temporally even if the carrier frequency is constant, and the harmonics of the same frequency do not continue.

Example 2. FIG. 4 is a diagram showing an embodiment of the invention of claim 4, the same parts as those of the embodiment 1 shown in FIG. In FIG. 4, the switching signal generating means 11 comprises an exclusive OR means 21 connected to the switching element 3 and comparators 19 and 20 connected to the exclusive OR means 21. Reference numeral 18 is a microcomputer as a control signal calculating means connected to the comparators 19 and 20, and a voltage command signal generating means 14 and a carrier signal generating means 15 are connected to the microcomputer 18, and the carrier signal generating means 15 is compared. It is also connected to the devices 19 and 20.

The voltage command signal generating means 14 is a ROM 14a storing a V / F pattern and an A / D converter 1 for converting an analog signal from the ROM into a digital signal.
4b and. Further, the carrier signal generating means 15 has a crystal oscillator 15a and a counter 15b for counting the output signal of the crystal oscillator, and outputs the output signal of the counter 15b directly as the carrier signal a and the clock signal.

Next, the operation of the second embodiment will be described.
In FIG. 4, the DC power supply 2 applies a DC voltage between the input terminals 9 and 10 of the step-down chopper circuit 1. The voltage command generating means 14 outputs a voltage command signal V ^* . The carrier signal generating means 15 outputs a carrier signal a (sawtooth wave) having a carrier period T and a clock signal synchronized with the trailing edge of the carrier signal.

FIG. 5 is a flow chart showing the flow of processing for calculation inside the microcomputer 18. The calculation of the flow chart shown in FIG. 5 is performed in synchronization with the clock signal output from the carrier signal generating means 15. A control signal required for pulse width modulation control is output.

First, in step ST5-1, the input voltage signal V _in of the step-down chopper circuit 1 and the voltage command signal V ^* are set to A /
It is taken in through a D converter (not shown). Continuing,
In step ST5-2, the on-time T _on and the off-time T _off of the switching element 3 when the carrier period is T based on the voltage command signal V ^* and the input voltage signal V _in are (2).
Calculate by formula. T _on = V _in / V ^* T _off = T−T _on ... (2)

Next, in step ST5-3, the clock signals synchronized with the trailing edge of the carrier signal a (sawtooth wave) output from the carrier signal generating means 15 are counted. Then, in step ST5-4, the coefficient b corresponding to the timing signal is read from the table prepared in advance using the count number of the clock signal as an address. At this time, the coefficient b stored in the table is a pattern signal such as a sine wave, a triangular wave, or a random wave. From step ST5-5 the on time T _on and the off time T _off and coefficient b, and calculates the first and second control signals S1 and S2 as shown in equation (3). The control signals S1 and S2
Is a voltage value corresponding to time (the slope of the sawtooth wave is a constant of proportionality). S1 = b × T _off S2 = S1 + T _on ... (3)

However, the coefficient b in the above equation is limited to (0≤b≤1) so that the amplitudes of the first and second control signals do not exceed the amplitude of the carrier signal. In step ST5-6, the first and second control signals S
1 and S2 are output from the microcomputer 18 to the switching signal generating means 11.

Next, the operation of the switching signal generating means 11 will be described with reference to FIG. First, the first and second control signals S1 and S2 and the carrier signal a are input to the switching signal generating means 11, and the comparator 19,
At 20, the amplitudes of the first and second control signals S1 and S2 and the carrier signal a are compared, and when the control signal is larger than the carrier signal, the high level is set;
The binary signals P1 and P2 of the level are output, and the binary signal P
The exclusive OR of the P1 and P2 is taken by the exclusive OR means 21, and the switching signal Psw for driving the switching element 3 is created and sent to the switching element 3. As a result, between the output terminals 7 and 8 of the step-down chopper circuit 1 as an average value for one period T of the carrier signal a,
From the equation (1), an output voltage that matches the voltage command signal V ^* can be obtained.

Here, since the switching signal generating means 11 temporally changes the on-timing of the switching element 3 by temporally changing the value of the coefficient b, the harmonics contained in the output voltage of the step-down chopper circuit 1 are changed. The component changes with time even if the carrier frequency is constant, and harmonics of the same frequency do not continue.

Example 3. FIG. 7 is a diagram showing an embodiment of the invention of claim 5, and in FIG. 7, 46 is a three-phase inverter circuit, and this inverter circuit 46 is a DC power source 22.
A pair of switching elements 24, 25, 2 connected in series with a capacitor 23 connected between the positive electrode and the negative electrode of
7. 28, 30 and 31 are connected in parallel with the capacitor 23, and each pair of switching elements 24, 25 and 27 is connected.
・ Connecting points of 28, 30 and 31 are output terminals 26, 29, 3
The configuration is 1.

33 is the switching element 24, 25,
A switching signal generating means connected to 27, 28, 30 and 31 is used as a switching signal generating means and a polarity reversal output section Pu for reversing the polarity and outputting the direct output sections Pu, Pv, Pw for directly outputting the phase inputs Pu, Pv, Pw. This is a configuration having ', Pv', and Pw '.

34 to 36 are switching signal generating means 3
3, exclusive OR means for supplying phase inputs Pu, Pv, Pw to 3, 3/38, 39/40, 41/42 are comparators connected to exclusive OR means 34, 35, 36, and 43 is a comparison Microcomputer connected to the devices 37 to 42, 44
Is a voltage command signal generating means connected to the microcomputer 43, and has an A / D converter 44a for converting the speed command signal F given from the outside into a digital signal, and the speed command signal F having a frequency proportional to its amplitude. A V / F converter 44b for converting to a pulse train, a ROM 44c storing a V / F pattern for outputting a modulation factor k corresponding to the signal from the A / D converter 44a, and the V
And a counter 44d that counts the output of the / F converter 44b and outputs the phase Q.

Reference numeral 45 is a carrier signal generating means connected to the comparators 37 to 42 and the microcomputer 43. The carrier signal generating means 45 is a crystal oscillator 45a.
And a counter 45b for counting the output signal of the crystal oscillator. The output signal of the counter 45b is directly output as the carrier signal a and the clock signal.

Before explaining the operation of the third embodiment, first, the voltage vector that can be output from the inverter circuit 46 will be described. As shown in FIG. 7, the inverter circuit 4
6 is 8 (= 2) because the voltages Vu, Vv and Vw of the respective phases (U, V and W) output from the output terminals 26, 29 and 32 can take two values of positive and 0, respectively. ×
2 × 2) voltage vector can be output. Here, for example, a voltage vector at which Vu = E, Vv = 0, and Vw = 0 is expressed as (100). From the above, FIG. 8 is obtained when the voltage vector that can be output by the inverter circuit 46 is illustrated. In FIG. 8, each vertex of the regular hexagon is a voltage vector (001) to (101) that can be output. Here, since the line voltage of the two vectors (000) and (111) is zero, it is called a zero voltage vector.

Next, pulse width modulation by the spatial voltage vector will be described. First, as shown in FIG. 9, the voltage command vector v ^* is converted into two voltage vectors V4 [= (10
0)] and V6 [= (110)] and two zero voltage vectors {V0 [= (100)] and V7 [= (11
1)]} inside an equilateral triangle with its vertices as described below, these two voltage vectors and 2
The output voltage is controlled by selecting one zero voltage vector.

First, the voltage command vector v ^* has an amplitude of k.
Assuming that it rotates clockwise at a frequency of ω, output is performed using the length of the arc locus drawn by the tip of the voltage command vector v ^* in a certain predetermined period T and the above two voltage vectors and two zero voltage vectors. Since the length of the trajectory drawn by the generated combined vector becomes equal, the equation (4) is obtained. 1 / √3 · t4 + 1 / √3 · e (jπ / 3) · t6 = k · e (jθ) · T (4) However, in the equation θ = ωt (4), t4 and t6 are The duration of the voltage vectors V4 and V6, respectively. Further, for convenience, in FIG. 9, the length from the origin to V4 (or V6) is set to 1 / √3.

Next, these two voltage vectors V4, V
Since the sum of the durations of the six and two zero voltage vectors V0 and V7 is equal to the predetermined period T, the equation (5) is obtained. t4 + t6 + t0 + t7 = T (5)

In equation (5), t0 and t7 are the durations of the zero voltage vectors (V0 and V7).
From equations (4) and (5), the duration of these two voltage vectors V4 and V6 and the two zero voltage vectors V0 and V7 is calculated to obtain equation (6). t4 = T · k · sin (π / 3−θ) t6 = T · k · sin θ t0 + t7 = T {1-k · sin (π / 3 + θ)} (6)

Here, the phase θ of the voltage command vector v ^*
The pulse width modulation method in the case where is in the range of 0 to π / 3 has been described. However, if the two voltage vectors selected are changed each time the phase θ changes by π / 3, the phase θ becomes π /.
The same control can be performed even in the range of 3 to 2π. By the above method, it is possible to obtain a three-phase AC output voltage whose pulse width is modulated according to the voltage command vector. here,
It is obvious that the amplitude and frequency of the output voltage can be controlled according to the amplitude k and the frequency ω of the voltage command vector v ^* , respectively.

Next, the selection order of the two voltage vectors and the two zero voltage vectors will be described with reference to FIG. First, two voltage vectors and two zero voltage vectors are selected along the arrows shown in FIG. For example, the phase θ of the voltage command vector v ^* is 0 to π /
In the range of 3, V0 → V4 during the predetermined period T.
→ V6 → V7 → V6 → V4 → V0 in order of two voltage vectors (V4 and V6) and two zero voltage vectors (V0
And V7).

When the phase θ of the voltage command vector v ^* increases and shifts to the range of π / 3 to 2π / 3, the predetermined period T
During this period, two voltage vectors (V2 and V6) and two zero voltage vectors (V0 and V7) are selected in the order of V0 → V2 → V6 → V7 → V6 → V2 → V0. When two voltage vectors and two zero voltage vectors are selected in such a selection order, the phase θ of the voltage command vector v ^* is π.
Even if it changes at / 3 as a boundary, only the voltage vectors V4 and V2 are exchanged, and the remaining voltage vector and the two zero voltage vectors do not change. Moreover, as can be seen from FIG. 10, the duration of the voltage vectors V4 and V2 is almost zero in the vicinity of the phase θ = π / 3 of the voltage command vector v ^* .

Next, the operation of the third embodiment will be described with reference to FIG. The voltage command signal generating means 44 outputs the voltage command signal V ^* in the form of a vector of the modulation factor k and the phase θ. FIG. 11 is a flow chart showing the flow of processing performed inside the microcomputer 43. The calculation of the flow chart shown in FIG. 11 is performed in synchronization with the clock signal output from the carrier signal generating means 45, and pulse width modulation is performed. A control signal necessary for control is output.

First, in step ST11-1, the microcomputer 43 inputs the voltage command vector of the modulation factor k and the phase θ from the voltage command signal generating means 44, and inputs the clock from the carrier signal generating means 45. Subsequently, in step ST11-2, the voltage command vector v ^*
Is divided by 60 degrees, and the quotient is used to determine in which π / 3 section the output voltage command vector v ^* exists. If the quotient is a section signal, the section signal takes six values (for example, values from 0 to 5) according to the phase θ, and corresponds to sections (a) to (f) in FIG. 10, respectively.

Next, in step ST11-3, 2
Equation (7) is calculated as the duration of one voltage vector and two zero voltage vectors. The phase used at this time is
It is reset each time the section signal changes, so 0-π /
Takes the value of 3. ta = T {1-k · sin (π / 3 + θ)} tb = T · k · sin (π / 3−θ) tc = T · k · sin θ (7)

Next, in step ST11-4, a clock signal having a frequency doubled in synchronization with the fall of the carrier signal output from the carrier signal generating means 45 is counted. In step ST11-5, the coefficient b is read from a table prepared in advance using the count number of the clock signal as an address. At this time, the coefficient b stored in the table is a sine wave, a triangular wave, a random value, or the like.

Next, in step ST11-6, U,
Control signals Sa and Sa ', Sb and Sb', S of V and W phases
Sections (a) to (c) of FIG.
It is created in accordance with the calculation order of the control signals shown in FIG. 12 according to (f). And the last step ST11-7
Outputs 6 control signals.

Further, FIG. 13 shows the case where the coefficient b = 0.5, and as shown in the figure, the microcomputer 43
The six control signals Sa, Sa ′, Sb output from
And Sb ', Sc and Sc', and the carrier signal 2a of the period 2T output from the carrier signal generating means 45 are compared by the comparators 37 to 42, and when the control signal is larger than the carrier signal, the high level is set. , When it is small, Lo
w level binary signals Pa and Pa ', Pb and Pb', Pc
And Pc 'are output.

Further, the binary signals Pa and Pa ', Pb
And Pb ', and Pc and Pc' are obtained by exclusive OR means 34 to 36 to obtain binary signals Pu, Pv and Pw of U, V and W phases, respectively, and switching signal generating means 33.
Output to.

Here, as can be seen from FIG.
The selection order and duration of the voltage vector to be selected are determined by the two binary signals Pu, Pv, Pw. In other words, the level of the binary signal changes once from 0 to 1 during a predetermined period T corresponding to a half cycle of the carrier signal 2a, so that each time one of these signals changes,
The selected voltage vector is changed. The duration of the selected voltage vector is the time from when one of the two adjacent binary signals changes from 0 to 1 until the other signal changes from 0 to 1.

Conventionally, the coefficient b is constant at 0.5, but in the third embodiment, the coefficient b is randomly changed with time. When the coefficient b is changed as can be seen from the timing diagram of the phase voltage and the line voltage shown in FIG. 14, the on-time of the three binary signals Pu, Pv, Pw (corresponding to the phase voltage) changes. The ON time of the two differences (corresponding to the line voltage) between the binary signals does not change, but the position changes.

Next, the above three binary signals Pu, Pv, P
When w is input to the switching signal generating means 33, the switching signal generating means 33 drives the inverter circuit 46.
Inside switching elements 24, 25, 27, 28, 30,
31 is an on / off signal Pu / Pu ', Pv / Pv', P
w · Pw ′ is output. Here, since it is clear which switching element is turned on / off according to the voltage vector, the switching signal generating means 33 can be easily configured by using a logic circuit. Therefore, the detailed circuit configuration and operation of the switching signal generating means 33 will be omitted.

Next, the switching elements 24, 25, 27, 28, 30, 31 are switched in response to these on / off signals, and three-phase pulse width modulated in accordance with the voltage command vector v ^* . AC voltage output terminals 26, 2
It is output from 9,32.

Example 4. In each of the above embodiments, the frequency of the carrier signal is not changed, but by using a variable frequency carrier signal whose frequency changes with time within a range that does not cause problems such as heat generation and calculation time. Therefore, it is possible to more effectively reduce the generation of magnetic noise.

Further, in each of the above-described embodiments, either the on timing or the off timing of the switching element during one cycle of the carrier signal is temporally changed, but the on / off timing of the switching element is For example, a delay circuit is provided in the system that supplies the output of the switching element to the load without changing it, and the delay time of this delay circuit is changed to change the power supply timing to the load during one cycle of the carrier signal. Also, the same effect as that of each of the above embodiments can be obtained.

[0068]

As described above, claim 1 and claim 2 are as follows.
According to the invention, the generation timing of the output voltage during one cycle of the carrier signal is temporally changed without changing the pulse width determined by the pulse width modulation control. In order to change it, either the on-timing or off-timing of the switching element is configured to change with time, so that harmonics of the same frequency are not continuously applied to the load, and There is an effect that it is possible to reduce the generation of the magnetic sound caused by it. Moreover, since the frequency of the carrier signal is not changed, it is possible to prevent heat generation due to switching loss in a high frequency region, shortage of calculation time, or increase of ripples in a low frequency region.

According to the third aspect of the present invention, the signal proportional to the on-time within the period of the carrier signal of the switching element and either one of the on-timing and the off-timing of the switching element are provided in a plurality of periods of the carrier signal. It is configured to output a switching signal for driving the switching element from the switching signal generating means in accordance with a timing signal which is changed with time, so that it is suitable for hardware control, and a magnetic sound caused by a harmonic component is generated. There is an effect that the reduction of the occurrence can be easily realized.

According to the fourth aspect of the present invention, the amplitudes of the carrier signal and the first and second control signals which are temporally changed for each plurality of cycles of the carrier signal within a range not exceeding the amplitude of the carrier signal. Since a switching signal is output from the switching signal generating means in accordance with the magnitude relationship of the above, there is an effect that it is suitable for software control and that the generation of magnetic noise due to the harmonic component can be reduced.

According to the invention of claim 5, the switching signal generating means outputs the switching signal for driving the switching element of each phase from the operation time of each voltage vector. It is suitable for control and has the effect of reducing the generation of magnetic noise due to harmonic components.

According to the sixth aspect of the invention, since the carrier signal of a variable frequency whose frequency changes with time is used, the generation timing of the output voltage during one cycle of the carrier signal is changed with time. In combination with the dots,
There is an effect that it is possible to more effectively reduce the generation of magnetic noise due to the harmonic component.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a control device of a power conversion device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing operation waveforms of the comparator in Embodiment 1 of the present invention.

FIG. 3 is an explanatory diagram showing operation waveforms of the switching signal generating means according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram showing a control device of a power conversion device according to a second embodiment of the present invention.

FIG. 5 is a flow chart showing the contents of arithmetic processing of the microcomputer in the second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing operation waveforms of the switching signal generating means according to the second embodiment of the present invention.

FIG. 7 is a configuration diagram showing a control device of a power conversion device according to a third embodiment of the present invention.

FIG. 8 is an explanatory diagram of voltage vectors that can be output by the inverter according to the third embodiment of the present invention.

FIG. 9 is an explanatory diagram of pulse width modulation using a spatial voltage vector according to the third embodiment of the present invention.

FIG. 10 is an explanatory diagram of a voltage vector selection order according to the third embodiment of the present invention.

FIG. 11 is a flowchart showing the contents of arithmetic processing of the microcomputer in the third embodiment of the present invention.

FIG. 12 is a diagram illustrating a calculation sequence of control signals according to the third embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a method of creating a signal to be input to the switching signal generation circuit according to the third embodiment of the present invention.

FIG. 14 is an explanatory diagram showing a switching signal when the ON timing of the ON signal is changed according to the third embodiment of the present invention.

FIG. 15 is a configuration diagram showing a control device of a conventional power conversion device.

[Explanation of symbols]

Reference Signs List 3 switching element 11 switching signal generating means 12 comparator (on-time signal generating means) 13 timing signal generating means 14 voltage command signal generating means 15 carrier signal generating means 18 microcomputer (control signal calculating means) 33 switching signal generating means 43 micro Computer (voltage vector selection means,
Area judging means, operating time determining means, operating time changing means) 44 voltage command signal generating means 45 carrier signal generating means 46 inverter circuit

Claims (6)

[Claims] 1. A control method for a power converter that controls an output voltage by pulse width modulation control, wherein an average value of the output voltage during one cycle of a carrier signal is made to coincide with a voltage command and is determined by the pulse width modulation control. A method of controlling a power converter, wherein the generation timing of the output voltage is temporally changed without changing the generated pulse width. 2. A control method for a power converter that controls an output voltage by pulse width modulation control, wherein an average value of the output voltage during one cycle of a carrier signal is made to coincide with a voltage command and is determined by the pulse width modulation control. A method of controlling a power conversion device, characterized in that one of the on timing and the off timing of the switching element that obtains the output voltage is temporally changed without changing the generated pulse width. 3. A power converter for controlling an output voltage by pulse width modulation control, a voltage command signal generating means for outputting a voltage command signal, a carrier signal generating means for outputting a carrier signal, the voltage command signal and the voltage command signal. An on-time signal generating means for inputting a carrier signal and generating a signal proportional to an on-time within the cycle of the carrier signal of the switching element for obtaining the output voltage, and either on-timing or off-timing of the switching element Timing signal generating means for generating a timing signal for temporally changing one of them for each plurality of cycles of the carrier signal, and outputting a switching signal for driving the switching element according to the on-time signal and the timing signal. A power conversion device comprising switching signal generating means. Control device. 4. A power converter for controlling an output voltage by pulse width modulation control, wherein a voltage command signal generating means for outputting a voltage command signal, a carrier signal generating means for outputting a carrier signal, and the voltage command signal are inputted. However, the first and second control signals whose amplitude difference is proportional to the voltage command signal are calculated, and the amplitudes of the first and second control signals are adjusted so that the amplitude of the carrier signal does not exceed the amplitude of the carrier signal. A control signal calculating unit that temporally changes every plural cycles, and a switching signal that drives a switching element that obtains the output voltage in accordance with the magnitude relation between the amplitudes of the carrier signal and the first and second control signals. And a switching signal generating means for outputting the control signal of the power converter. 5. The first and second switching elements are connected in series between the positive electrode and the negative electrode of the DC power supply, and
In a power conversion device provided with three phases of inverters having an output terminal of the inverter at a connection point of the first and second switching elements, a carrier signal generating means for outputting a carrier signal and a state of the switching element of each phase are set. For each region formed by connecting adjacent three vertices of the corresponding voltage vector, two zero voltage vectors forming one vertex of the region and two voltage vectors forming the remaining vertices are defined. A voltage vector selecting means for preselecting and predetermining the order of outputting these voltage vectors within one cycle of the carrier signal, and storing the voltage vectors and the output order thereof, and outputting the voltage command signal in the form of a vector The voltage command signal generating means and the voltage command signal are input, and the voltage command signal is input at every cycle of the carrier signal. A region determining means for determining the area that,
Of the operating time of the sum of the two zero voltage vectors selected in the region determined by the region determining means so that the output voltage of the inverter matches the voltage command signal, and the operating time of the other two voltage vectors. Operating time determining means for determining distribution of the carrier signal within one cycle;
Outputting a switching signal for driving the switching element of each phase from the operating time of each voltage vector and operating time changing means for temporally changing the distribution of the operating time of one zero voltage vector for each plurality of cycles of the carrier signal. And a switching signal generating means for controlling the power converter. 6. The control device for a power conversion device according to claim 3, further comprising carrier signal generation means for outputting a carrier signal having a variable frequency whose frequency changes with time.