WO2017034028A1 - Control method and control device for inverter, and inverter device - Google Patents

Abstract

Provided are a control method, a control device and an inverter device that can suppress the heat generated by a capacitor of a direct-current part of an inverter, reduce the overall size of a device and reduce costs. The control method causes an n phase (for example, three phase) alternating-current voltage of a desired size and frequency to be output from an inverter by changing a direct-current voltage time ratio of a direct-current voltage source B that appears at alternating-current output terminals U, V, W by switching semiconductor switching elements U_P-W_N on and off. The switching elements U_P-W_N are switched on/off so that a state in which an alternating-current output terminal of one phase is connected to the positive terminal or negative terminal of the direct-current voltage source B is maintained for a fixed period of time, so that an alternating-current output terminal of another phase is connected to the negative terminal or positive terminal of the direct-current voltage source B for a period of time shorter than the fixed period of time, and so that a period of time in which all of the alternating-current output terminals U, V, W are simultaneously connected to the positive terminal or negative terminal of the direct-current voltage source B is minimized in the fixed period of time.

Description

INVERTER CONTROL METHOD AND CONTROL DEVICE, AND INVERTER DEVICE

The present invention relates to an inverter control method and control device for suppressing heat generation of a capacitor provided in a DC portion of the inverter, and an inverter device to which these control method or control device is applied.

FIG. 1 is a configuration diagram of a three-phase inverter. The term “inverter” in the following description mainly indicates a main circuit having a DC voltage source and a plurality of semiconductor switching elements, and the entire apparatus including the “inverter” (main circuit) and a control device is referred to as “ Inverter device ".
In FIG. 1, a capacitor C is connected in parallel to the DC voltage source B, and semiconductor switching elements U _P , V _P , W _P , U _N , such as IGBTs constituting a three-phase bridge circuit are connected to both ends of the capacitor C. V _N and W _N are connected. A connection point between the switching elements of each phase is connected to a three-phase AC load M such as an electric motor via AC output terminals U, V, and W.

In FIG. 1, L is a reactor (a reactor that is intentionally connected or a floating reactor that is unintentionally present on the wiring), and P and N are a positive electrode and a negative electrode of the DC voltage source B. E _d is the voltage of the DC voltage source B, V _c is the voltage of the capacitor C, I _bat is the output current of the DC voltage source B, I _c is the current flowing through the capacitor C, and I _dc is the current flowing through the DC portion of the inverter. , I _u , I _v , I _w are the output currents of each phase.

In this three-phase inverter, the switching elements U _P , V _P , W _P , U _N , V _N , and W _N are turned on / off at a predetermined time ratio, so that the DC voltage has a desired frequency and magnitude. It is converted into phase AC voltage and supplied to the load M.
Here, the switching elements _{U P, V P, W P} , U N, V N, a method for turning on / off _{W N,} the inverter control method in other words, a triangular wave and three-phase phase output voltage as a carrier switching elements _U P is compared with the modulation signal corresponding to the _{command, V P, W P, U} N, V N, a method of obtaining a drive signal (gate signal) _{W N} are generally known. This type of control method is disclosed as a PWM control method in Patent Literature 1 and Non-Patent Literature 1, for example.

FIG. 7 shows an example of an operation waveform when the switching elements U _P to W _N in FIG. 1 are turned on / off by a drive signal obtained by comparing a triangular wave as a carrier and a modulated signal of each phase. ing. This operation waveform is obtained when the output currents I _u , I _v , and I _{w of} each phase are sine waves and the power factor is 1.

The modulation signals V _u , V _v , and V _{w in} FIG. 7 are based on so-called two-arm modulation or two-phase modulation, and this two-arm modulation is performed by turning on the switching element of one phase of the three phases over a certain period. This is well known as a modulation method for fixing the / off state and controlling the on / off of the remaining two-phase switching elements. The detailed contents of the two-arm modulation are described in Non-Patent Document 1, for example, and thus the description thereof is omitted here.
When the inverter is controlled by two-arm modulation, the switching loss caused by switching on / off of the switching element can be suppressed while the three-phase output line voltage is maintained as a sine wave, and the voltage utilization rate of the inverter is reduced. Advantages such as improvement are obtained.

FIG. 8 shows an operation waveform when two-arm modulation is performed using a sawtooth wave for the carrier. The operation in this case is basically the same as when a triangular wave is used for the carrier.

According to FIG. 7 and FIG. 8, the current I _dc flowing in the DC part of the inverter becomes a pulse train waveform with the switching elements U _P to W _N being turned on / off, and includes a DC component and an AC component. I know that.
As shown in FIG. 1, a reactor L exists between the DC voltage source B and the capacitor C, and the current I _dc flowing through the DC unit is supplied from the DC voltage source B and flows through the reactor L. This is the sum of the current component I _bat and the alternating current component I _c supplied from the capacitor C. That is, the current I _dc = I _bat + I _c .

At this time, the capacitor C, the temperature rises due to self-heating due to the above-mentioned alternating current component I _c flows. Capacitors generally have a shorter life as the temperature rises. Therefore, to suppress the rise in temperature, use a capacitor that is larger (larger capacity) than necessary, or actively cool the capacitor. It is necessary to take measures such as providing cooling means.
Note that Non-Patent Document 2 discloses a technique for cooling the capacitor by thermally conducting the heat of the capacitor to a water-cooling jacket disposed around it as a cooling means for the capacitor in the inverter.

JP2013-183636A (FIG. 3 etc.)

As described above, conventionally, it is necessary to take measures for suppressing or cooling the heat generation of the capacitor provided in the DC portion of the inverter, which hinders downsizing and cost reduction of the device. .
Therefore, the problem to be solved by the present invention is to reduce the current flowing in the capacitor of the DC part of the inverter and suppress the heat generation of the capacitor, and the inverter that enables downsizing and cost reduction of the entire apparatus including the main circuit and the cooling means. It is providing the control method and control apparatus of this, and an inverter apparatus.

In order to solve the above-mentioned problem, a control method according to claim 1 is provided with n (n is a plurality) series circuits of two semiconductor switching elements, and the n series circuits are all parallel to a DC voltage source. An inverter control method comprising: connecting and connecting each of two semiconductor switching elements constituting the series circuit as a one-phase AC output terminal to each phase of an n-phase AC load; In a control method for outputting an n-phase AC voltage of a desired magnitude and frequency from the inverter by changing a time ratio of a DC voltage of the DC voltage source appearing at the AC output terminal by turning on / off a switching element. ,
An AC output terminal of at least one specific phase among n phases is maintained in a state where it is connected to a positive electrode or a negative electrode of the DC voltage source for a certain period, and an alternating current of another phase other than the specific phase among the n phases The output terminal is connected to the negative electrode or the positive electrode of the DC voltage source for a period shorter than the predetermined period, and all the n-phase AC output terminals are simultaneously connected to the positive electrode or the negative electrode of the DC voltage source within the predetermined period. The semiconductor switching element of each phase is turned on / off so that the period of time to be shortened.

The control method according to claim 2 includes n (n is a plurality) series circuits of two semiconductor switching elements, the n series circuits are all connected in parallel to a DC voltage source, and the series circuit Is a control method for an inverter in which a connection point between two semiconductor switching elements constituting the circuit is connected to each phase of an n-phase AC load as a one-phase AC output terminal, and the semiconductor switching element is turned on / off. In the control method of outputting an n-phase AC voltage having a desired magnitude and frequency from the inverter by changing a time ratio of the DC voltage of the DC voltage source appearing at the AC output terminal.
An AC output terminal of at least one specific phase among the n phases is maintained in a state of being connected to the positive electrode or the negative electrode of the DC voltage source for a certain period within the operation period, and other than the specific phase among the n phases The AC output terminal of the other phase is connected to the negative electrode or the positive electrode of the DC voltage source for a period shorter than the predetermined period, respectively,
At least one cycle of the on / off cycle of the semiconductor switching element within the operation period is a cycle in which there is no state in which all n-phase AC output terminals are simultaneously connected to the positive electrode or the negative electrode of the DC voltage source. The semiconductor switching element of each phase is turned on / off.

The control method according to claim 3 is the inverter control method according to claim 1 or 2,
Which phase of the AC output terminal is maintained in a state of being connected to the positive electrode or the negative electrode of the DC voltage source over a certain period, and whether the AC output terminal is connected to the positive electrode or the negative electrode of the DC voltage source, It is switched according to the phase or magnitude of the output voltage.

A control method according to claim 4 is the inverter control method according to any one of claims 1 to 3,
A plurality of triangular waves are provided as a plurality of carriers having different phases, and each of n modulation signals corresponding to the n-phase output voltage command is converted into one carrier with a modulation signal corresponding to another phase other than the specific phase. A drive signal that corresponds to any of the plurality of carriers so as not to overlap, compares each of the n modulated signals with the corresponding carrier, and turns on / off the semiconductor switching element of the corresponding phase. Is to be generated.

A control method according to claim 5 is the inverter control method according to any one of claims 1 to 3,
A plurality of sawtooth waves are provided as a plurality of carriers having different waveforms, and each of n modulation signals corresponding to the n-phase output voltage command has one modulation signal corresponding to a phase other than the specific phase. Corresponding to one of the plurality of carriers so as not to overlap the carrier, each of the n modulated signals is compared with the corresponding carrier, and the semiconductor switching element of the phase corresponding to each modulated signal is turned on / off The drive signal to be generated is generated.

The control method according to claim 6 is the inverter control method according to claim 4 or 5,
Of the n modulated signals, the magnitude of at least one modulated signal selected according to the phase or magnitude of the output voltage is made equal to the maximum value or the minimum value of the carrier, and the magnitude of the modulated signal Whether the same value as the maximum value or the minimum value of the carrier is determined according to the phase or magnitude of the output voltage.

The control method according to claim 7 is the control method according to any one of claims 1 to 6 as a first control method,
A control method for generating a drive signal for turning on / off an n-phase semiconductor switching element by comparing n modulation signals corresponding to the n-phase output voltage command with a single carrier is referred to as a second control method. ,
The first control method and the second control method are switched according to the phase or magnitude of the output voltage and the polarity or phase of the output current.

The control device according to claim 8 includes n (n is a plurality) series circuits of two semiconductor switching elements, and the n series circuits are all connected in parallel to a DC voltage source, and the series circuit The AC switching terminal is turned on / off by switching the semiconductor switching element of each inverter connected to each phase of the n-phase AC load using the connection point between the two semiconductor switching elements constituting the circuit as a one-phase AC output terminal. In the control device for outputting an n-phase AC voltage having a desired magnitude and frequency from the inverter by changing a time ratio of the DC voltage of the DC voltage source appearing in
An AC output terminal of at least one specific phase among n phases is maintained in a state where it is connected to a positive electrode or a negative electrode of the DC voltage source for a certain period, and an alternating current of another phase other than the specific phase among the n phases The output terminal is connected to the negative electrode or the positive electrode of the DC voltage source for a period shorter than the predetermined period, and all the n-phase AC output terminals are simultaneously connected to the positive electrode or the negative electrode of the DC voltage source within the predetermined period. The semiconductor switching element of each phase is turned on / off so that the period of time to be shortened.

The control device according to claim 9 includes n (n is a plurality) series circuits of two semiconductor switching elements, and the n series circuits are all connected in parallel to a DC voltage source, and the series circuit The AC switching terminal is turned on / off by switching the semiconductor switching element of each inverter connected to each phase of the n-phase AC load using the connection point between the two semiconductor switching elements constituting the circuit as a one-phase AC output terminal. In the control device for outputting an n-phase AC voltage having a desired magnitude and frequency from the inverter by changing a time ratio of the DC voltage of the DC voltage source appearing in
An AC output terminal of at least one specific phase among the n phases is maintained in a state of being connected to the positive electrode or the negative electrode of the DC voltage source for a certain period within the operation period, and other than the specific phase among the n phases The AC output terminal of the other phase is connected to the negative electrode or the positive electrode of the DC voltage source for a period shorter than the predetermined period, respectively,
At least one cycle of the on / off cycle of the semiconductor switching element within the operation period is a cycle in which there is no state in which all n-phase AC output terminals are simultaneously connected to the positive electrode or the negative electrode of the DC voltage source. The semiconductor switching element of each phase is turned on / off.

A control device according to claim 10 is the control device for an inverter according to claim 8 or 9,
A carrier generating means for generating a plurality of triangular waves having different phases or a plurality of sawtooth waves having different waveforms as a plurality of carriers;
According to the phase or magnitude of the output voltage, each of the n modulation signals corresponding to the n-phase output voltage command is not duplicated in one carrier with the modulation signal corresponding to the other phase other than the specific phase. Modulation signal selection means corresponding to any of the plurality of carriers,
Comparing means for comparing each of the n modulation signals selected by the modulation signal selection means with the corresponding carrier;
The output signal of the comparison means is used to turn on / off the n-phase semiconductor switching element.

A control device according to an eleventh aspect is the control device for an inverter according to the tenth aspect,
Of the plurality of carriers generated by the carrier generation means, further comprises a carrier selection means for giving the carrier selected according to the phase or magnitude of the output voltage and the polarity or phase of the output current to the comparison means,
The comparison means turns on / off the n-phase semiconductor switching element using an output signal obtained by comparing the carrier selected by the carrier selection means and the n modulation signals.

According to a twelfth aspect of the invention, the semiconductor switching element of each phase is turned on / off by the control method according to any one of the first to seventh aspects.
An inverter device according to claim 13 is one in which the semiconductor switching element of each phase is turned on / off by the control device according to any one of claims 8 to 11.

According to the present invention, the current flowing through the capacitor in the DC part of the inverter is reduced to suppress the heat generation of the capacitor, thereby reducing the size and cost of the entire apparatus including the main circuit and the cooling means.

It is a block diagram of a three-phase inverter (main circuit). FIG. 5 is an operation waveform diagram at the time of two-arm modulation when a triangular wave is used for the first and second carriers in the first embodiment of the present invention. It is a wave form diagram which shows the computer simulation result of a prior art and 1st Embodiment. As a modification of the first embodiment, it is an operation waveform diagram during two-arm modulation when sawtooth waves are used for the first and second carriers. FIG. It is a wave form diagram which shows the computer simulation result of prior art, 1st Embodiment, and 2nd Embodiment. It is a functional block diagram which shows the principal part of the control apparatus which concerns on embodiment of this invention. In the prior art, it is an operation waveform diagram at the time of two-arm modulation when using a triangular wave as a carrier. In the prior art, it is an operation waveform diagram at the time of two-arm modulation when a sawtooth wave is used for a carrier.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
An inverter to which each of the following embodiments is applied is, for example, a three-phase inverter as shown in FIG. 1, but as will be described later, the number of phases of the inverter to which the present invention is applied is particularly limited. is not.

First, a first embodiment of the control method according to the present invention will be described with reference to FIG.
2 includes a triangular wave 1 and a triangular wave 2 as first and second carriers. The triangular wave 1 and the triangular wave 2 are compared with a modulation signal corresponding to an output voltage command for each phase, and the inverter of FIG. It is an example of the operation waveform in the case of controlling. As in FIG. 7, it is assumed that the output currents I _u , I _v , I _w of each phase flowing through the load M are sine waves and the power factor is 1.

The first embodiment is different from the prior art of FIG. 7 in that the present embodiment includes a triangular wave 1 and a triangular wave 2 having the same amplitude and different phases by 180 °, for example, period 1 (triangular wave 1, 2), the triangular wave 1 is compared with the two modulation signals V _u and V _v, and the triangular wave 2 and the modulation signal V _w are compared, whereby the switching elements U _P and V _P shown in FIG. , W _P , U _N , V _N , W _N are determined on / off.

For example, in period 1 of FIG.
When the modulation signal V _u ≧ triangular wave 1, the switching element _UP is turned on, and when the modulation signal V _u <triangular wave 1, the switching element U _N is turned on,
When the modulation signal V _v ≧ triangular wave 1, the switching element _VP is turned on. When the modulation signal V _v <triangular wave 1, the switching element V _N is turned on,
For the modulation signal _{V w} ≧ triangular wave 2, turn on the switching elements _{W P,} in the case of the modulation signal _{V w} <triangular wave 2, the switching element _{W N} ON, and.

Further, the modulation signal whose magnitude is maintained at the maximum value or the minimum value of the triangular waves 1 and 2 is changed in accordance with the output voltage phase (or magnitude, the same applies hereinafter), and the modulation signal to be compared with the triangular wave 2 is also output. Change according to voltage phase.
Specifically, as shown in FIG. 2, the modulation signal V _u maintained at the maximum value of the triangular waves 1 and 2 → the modulation signal V _w maintained at the minimum value of the triangular waves 1 and 2 → the maximum value of the triangular waves 1 and 2 is the modulated signal V _v → ...... varied as maintenance, modulation signal is also _{V w → V v → V u} → ...... as the changing of comparing the triangular wave 2.

In the period 1 of FIG. 2, the magnitude of the modulation signal V _u is maintained at the maximum value of the triangular wave 1, by turning on the switching elements U _P, the output terminal U of the U-phase, the DC voltage source B Continue to be connected to the positive electrode P.
On the other hand, V-phase, W-phase output terminals V, W, respectively, a triangular wave, 2 and the modulation signal _V v, based on the magnitude relation between _{V w,} on the switching elements _{V P} or _{V N,} the switching element _{W P} or by turning on the W _N, are alternately connected to the positive electrode P and a negative electrode N of the DC voltage source B.

At this time, the time ratios at which the V-phase and W-phase output terminals V and W are connected to the positive electrode P and the negative electrode N of the DC voltage source B within the period 1 respectively are as shown in FIG. This is the same as in the embodiment. That is, the U-phase, V-phase, and W-phase time average output voltages are the same in the conventional technique and the present embodiment.

On the other hand, the timing at which the output terminals V and W are connected to the positive electrode P or the negative electrode N of the DC voltage source B is different between the prior art of FIG. 7 and the present embodiment of FIG.
What is more characteristic is that in the prior art of FIG. 7, there is a period in which all of the output terminals U, V, W are connected to the positive electrode P in the period 1, whereas in the present embodiment of FIG. There is no period in which all of U, V, and W are connected to the positive electrode P. In this regard, when attention is paid to the direct current I _dc , in the prior art of FIG. 7, the direct current I _dc does not flow during the period in which all of the output terminals U, V, W are connected to the positive electrode P, and 0 Become. On the other hand, in the present embodiment of FIG. 2, there is no period in which all of the output terminals U, V, W are connected to the positive electrode P, so there is no period in which the DC current I _dc is zero.
That is, according to the present embodiment, the amount of change in the direct current I _dc is smaller than that in the prior art of FIG. 7, and as a result, the alternating current component included in the direct current I _dc , in other words, I _c flowing through the capacitor C is Therefore, the heat generation of the capacitor C is suppressed.

In addition, what was shown in FIG. 2 is an operation | movement waveform at the time of assuming the magnitude | size of a certain output voltage as an example. In this example, there is no period in which the output terminals U, V, and W of all phases are simultaneously connected to the positive electrode P or the negative electrode N. For example, when the output voltage decreases, the output terminals U, V, and W During which the positive electrode P or the negative electrode N are simultaneously connected. However, since the period is shorter than that of the prior art of FIG. 7, the same effect as in the case of FIG. 2 can be obtained.
That is, at least one cycle of the on / off cycle of the semiconductor switching element within the operation period is a state in which all the n-phase AC output terminals U, V, W are simultaneously connected to the positive electrode P or the negative electrode N of the DC voltage source B. If the switching element of each phase is turned on / off so as to have a non-existing cycle, the direct current I _dc does not become zero in the above-described at least one cycle, so that the amount of change in I _dc becomes small and the current of the capacitor C I _c is reduced, heat generation can be suppressed.

Table 1 summarizes an example of the control operation of the present embodiment. The modulation signal to be compared with the triangular waves 1 and 2 and the maximum value of the triangular waves 1 and 2 according to the output voltage phase. Or it shows whether the modulation signal is maintained at the minimum value, and whether the magnitude of the modulation signal is maintained at the maximum value or the minimum value of the triangular waves 1 and 2. The electrical angles described in the table are based on the U-phase modulation signal V _u , and are based on the premise that the U-phase modulation signal V _u is maximized when the electrical angle is 0 °.

FIG. 3 is a waveform diagram showing computer simulation results of the prior art and the present embodiment, where (a) is the prior art and (b) is the present embodiment. In this simulation result, the current delay angle = 0 ° (load power factor: 1.0), and the symbols attached to the waveforms in the figure are the same as the current and voltage symbols described so far. FIG. 3 also shows the result of calculating the effective value I _dcacrms of the alternating current component I _c of the direct current I _dc with the period of the triangular wave as the basic period.

As apparent from the comparison between FIGS. 3A and 3B, according to the present embodiment, the effective value I _dcacrms of the AC component I _c of the DC current I _dc is reduced, that is, flows to the capacitor C. it can be seen that the effective value of the current I _c is decreased.
In Table 1, for example, in the period of the electrical angle 0 ° ~ 30 °, the modulation signal has been compared to the modulation signal V _w and the triangular wave 2, to be compared of the triangular wave 2, the maximum value of the triangular wave 1 Alternatively, it may be other than the modulation signal maintained at the minimum value. Therefore, in the period of the electrical angle 0 ° ~ 30 °, the modulation signal V _v compared with the triangular wave 2, the modulation signal V _w may be compared with the triangular wave 1. The same applies to other electrical angle ranges.

Next, FIG. 4 is an operation waveform diagram showing a modification of the first embodiment.
In this modified example, sawtooth waves 1 and 2 having the same amplitude and different waveforms are used as the first and second carriers instead of the triangular waves 1 and 2. Here, the sawtooth wave 1 is a sawtooth wave that increases with time, and the sawtooth wave 2 is a sawtooth wave that decreases with time.
Also in this modified example, the amount of change in the direct current I _dc in FIG. 4 is smaller than that in the prior art in FIG. 8, and the AC component included in the direct current I _dc , that is, I _c flowing through the capacitor C is reduced. Heat generation of the capacitor C can be suppressed.

Next, FIG. 5 is an operation waveform diagram showing the computer simulation result of the second embodiment of the control method according to the present invention in comparison with the prior art and the first embodiment, (a) is the prior art, ( b) is the first embodiment, and (c) is the second embodiment. Here, the current delay angle is set to 45 ° (load power factor: 0.71), and the symbols attached to the waveforms in the figure are the same as the symbols of current and voltage described so far. FIG. 5 also shows the result of calculating the effective value I _dcacrms of the alternating current component I _c of the direct current I _dc with the period of the triangular wave as the basic period.

When comparing the prior art of FIG. 5A with the first embodiment of FIG. 5B, the effective value I _dcacrms of the AC component I _c of the DC current I _dc is increased in FIG. _5B . I understand that. This is because the load power factor is lower in the simulation condition of FIG. 5 (load power factor: 0.71) than the load power factor condition ((load power factor: 1.0) in the first embodiment described above. In other words, the control method of the first embodiment has no meaning to be applied when the load power factor is bad.

In order to solve this problem, in the second embodiment, a comparison is made with the first and second carriers (for example, triangular waves 1 and 2) according to the output voltage phase and output current polarity (or phase, the same applies hereinafter) of the inverter. The phase of the modulated signal of each phase is changed, and the phase of the modulated signal of each phase that maintains the maximum or minimum value of the first and second carriers is changed I decided to change it.
Further, in the second embodiment, depending on the output voltage phase and the current polarity, the two carriers and the modulation signal of each phase are not compared, but a single carrier and all of them are compared as in the prior art of FIG. The phase modulation signals V _u , V _v , and V _w are respectively compared.

Table 2 below shows the modulation signal to be compared with the triangular waves 1 and 2 according to the output voltage phase and output current polarity, the modulation signal whose magnitude is maintained at the maximum value or the minimum value of the triangular wave, and the modulation It shows whether the magnitude of the signal is maintained at the maximum value or the minimum value of the triangular wave. The electrical angle described in the table is based on the U-phase modulation signal V _u , and is a premise that the U-phase modulation signal V _u becomes maximum when the electrical angle is 0 °. In addition, the output current polarity described in Table 2 is “+” when current flows from the inverter toward the load M.
The mode described as “conventional” in the remarks column of Table 2 is a mode for comparing a single triangular wave with all-phase modulation signals V _u , V _v , and V _w .

For example, in Table 2, when the output voltage phase is in the range of 0 ° to 60 °, and the output current polarity is “+” for the U phase, “−” for the V phase, and “−” for the W phase. Compares the modulation signals V _u and V _w with the triangular wave 1 and the modulation signal V _v with the triangular wave 2.
At this time, the modulation signal V _u is maintained at the maximum value of the triangular wave 1, and the other modulation signals V _v and V _w are set to a desired output in consideration that V _u is maintained at the maximum value of the triangular wave 1. Correction is made so that a line voltage is obtained.
On the other hand, even if the output voltage phase is in the range of 0 to 60 °, as long as the output current polarity does not satisfy the conditions described in Table 2, a single triangular wave and the modulation signals V _u , V _v and V _w are respectively compared.

FIG. 5C shows a simulation result when the on / off state of the switching element is determined by selecting the modulation signals V _u , V _v , V _w and the triangular waves 1, 2 according to Table 2.
When FIG. 5C is compared with the prior art of FIG. 5A, it can be seen that the effective value I _dcacrms of the AC component I _c of the DC current I _dc is reduced. 5A and 5C are different in the waveforms of the modulation signals V _u , V _v , and V _w , this is because the modulation signal of a predetermined phase is corrected as described above. The same value is obtained for the output line voltage between the UV phase, the VW phase, and the WU phase.

That is, according to the second embodiment, even when the load power factor is low, the current flowing through the capacitor can be reduced while obtaining the same output line voltage, and the heat generation can be suppressed.
The second embodiment is also applicable to the case where sawtooth waves 1 and 2 are used instead of triangular waves 1 and 2.

Here, FIG. 6 is a functional block diagram showing a main part of the control device for realizing the first and second embodiments of the control method described above. This control device is for a three-phase inverter and uses two triangular waves for the carrier.
In FIG. 6, the modulation signal selection means 10 includes modulation signals V _u , V _v , V _w for each phase, an output voltage phase (or magnitude) based on a certain phase (for example, U phase), and each phase. Output current polarity (or phase). Further, for example, triangular wave 1 and triangular wave 2 having the same amplitude and different 180 ° phase are output from the carrier generating means 20, and these triangular wave 1 and triangular wave 2 are carrier-selected together with the output voltage phase and output current polarity. Input to means 30.

From the carrier selection means 30, the triangular wave 1 and the triangular wave 2 (or triangular wave 1) are output to the comparison means 41 and the comparison means 42, respectively. In the comparison means 41, the two phases selected by the modulation signal selection means 10 are output. The modulation signal is compared with the triangular wave 1, and the comparison means 42 compares the remaining one phase modulation signal selected by the modulation signal selection means 10 with the triangular wave 2 (or triangular wave 1).
Then, the drive signal based on the output of the comparison means 41, comparison means 42, the switching elements _U P of the inverter Figure _1, V _{P, W} P, so as to be respectively distributed to the U _N, V _{N, W N} Yes.

Here, in the first embodiment described above, the carrier selection unit 30 outputs the triangular wave 1 to the comparison unit 41 and the triangular wave 2 to the comparison unit 42. Also, the modulation signal selection means 10 outputs a predetermined two-phase modulation signal and a predetermined one-phase modulation signal to the comparison means 41 and 42, respectively, according to the output voltage phase based on Table 1.
The comparison means 41 and 42 compare the inputted modulation signal of each phase with the triangular wave 1 or the triangular wave 2 to generate driving signals for the switching elements U _P to W _N. In this case, the triangular wave maximum value / minimum value maintaining modulation signal in Table 1 is one of the two modulation signals input to the comparison means 41.

Further, in the second embodiment described above, the carrier selecting means 30 is based on Table 2 and the triangular wave 1 is compared to the comparing means 41 and the triangular wave 2 (or triangular wave 1) is compared according to the output voltage phase and output current polarity. 42 respectively.
Here, the mode in which the triangular wave 1 is output to the comparison means 42 is the case where the output current polarity is “other than the above” in Table 2 and “conventional” is described in the remarks column. In this mode, a single triangular wave, that is, a triangular wave 1 is supplied to the comparison means 41 and 42, whereby the modulation signals V _u , V _v and V _w of all phases are compared with the single triangular wave 1.

In the second embodiment, the modulation signal selection unit 10 outputs a predetermined two-phase modulation signal and a predetermined one-phase modulation signal to the comparison units 41 and 42 according to the output voltage phase and the output current polarity, respectively. The comparison means 41 and 42 compare the input modulation signal of a predetermined phase with the triangular wave 1 and the triangular wave 2 or when only the single triangular wave 1 is compared when performing the same control method as the conventional one, Drive signals for the switching elements U _P to W _N are generated.
Here, each function of the control device shown in FIG. 6 can be realized by an arithmetic processing device such as a microcomputer and a program mounted thereon.

The semiconductor elements (switching elements and diodes) of the inverter to which the above embodiments are applied include not only conventional semiconductor elements made of silicon but also SiC (silicon carbide) that can be used in a high temperature environment. A wide band gap semiconductor element using may be used.
In this case, the response to the high temperature environment remains as a problem for the peripheral parts of the wide band gap semiconductor element. However, according to the present invention, since the heat generation of the capacitor in the DC part of the inverter is suppressed, Sometimes it can be used.

The present invention can be used for a control method and a control device for a single-phase inverter, a multi-phase inverter other than a three-phase inverter, and an inverter device controlled using these control methods or control devices.

B: direct-current voltage source C: Capacitor L: Reactor _{U P, V P, W P} , U N, V N, W N: semiconductor switching element M: the three-phase AC load P: positive N: negative U, V, W: AC output terminal 10: modulation signal selection means 20: carrier generation means 30: carrier selection means 41, 42: comparison means

Claims (13)

1. N series circuits of two semiconductor switching elements are provided (n is a plurality), the n series circuits are all connected in parallel to a DC voltage source, and two semiconductor switching elements constituting the series circuit are connected to each other. Is an inverter control method in which each connection point is connected to each phase of an n-phase AC load as a one-phase AC output terminal, and the DC that appears at the AC output terminal by turning on and off the semiconductor switching element. In a control method for outputting an n-phase AC voltage having a desired magnitude and frequency from the inverter by changing the time ratio of the DC voltage of the voltage source,
   An AC output terminal of at least one specific phase among n phases is maintained in a state where it is connected to a positive electrode or a negative electrode of the DC voltage source for a certain period, and an alternating current of another phase other than the specific phase among the n phases The output terminal is connected to the negative electrode or the positive electrode of the DC voltage source for a period shorter than the predetermined period, and all the n-phase AC output terminals are simultaneously connected to the positive electrode or the negative electrode of the DC voltage source within the predetermined period. A method for controlling an inverter, comprising: turning on / off the semiconductor switching element of each phase so that a period of time to be shortened is shortened.
2. N series circuits of two semiconductor switching elements are provided (n is a plurality), the n series circuits are all connected in parallel to a DC voltage source, and two semiconductor switching elements constituting the series circuit are connected to each other. Is an inverter control method in which each connection point is connected to each phase of an n-phase AC load as a one-phase AC output terminal, and the DC that appears at the AC output terminal by turning on and off the semiconductor switching element. In a control method for outputting an n-phase AC voltage having a desired magnitude and frequency from the inverter by changing the time ratio of the DC voltage of the voltage source,
   An AC output terminal of at least one specific phase among the n phases is maintained in a state of being connected to the positive electrode or the negative electrode of the DC voltage source for a certain period within the operation period, and other than the specific phase among the n phases The AC output terminal of the other phase is connected to the negative electrode or the positive electrode of the DC voltage source for a period shorter than the predetermined period, respectively,
   At least one cycle of the on / off cycle of the semiconductor switching element within the operation period is a cycle in which there is no state in which all n-phase AC output terminals are simultaneously connected to the positive electrode or the negative electrode of the DC voltage source. A method for controlling an inverter, wherein the semiconductor switching element of each phase is turned on / off.
3. In the inverter control method according to claim 1 or 2,
   Which phase of the AC output terminal is maintained in a state of being connected to the positive electrode or the negative electrode of the DC voltage source over a certain period, and whether the AC output terminal is connected to the positive electrode or the negative electrode of the DC voltage source, A method for controlling an inverter, wherein switching is performed according to the phase or magnitude of the output voltage.
4. The inverter control method according to any one of claims 1 to 3,
   A plurality of triangular waves are provided as a plurality of carriers having different phases, and each of n modulation signals corresponding to the n-phase output voltage command is converted into one carrier with a modulation signal corresponding to another phase other than the specific phase. A drive signal that corresponds to any of the plurality of carriers so as not to overlap, compares each of the n modulated signals with the corresponding carrier, and turns on / off the semiconductor switching element of the corresponding phase. An inverter control method comprising: generating an inverter;
5. The inverter control method according to any one of claims 1 to 3,
   A plurality of sawtooth waves are provided as a plurality of carriers having different waveforms, and each of n modulation signals corresponding to the n-phase output voltage command has one modulation signal corresponding to a phase other than the specific phase. Corresponding to one of the plurality of carriers so as not to overlap the carrier, each of the n modulated signals is compared with the corresponding carrier, and the semiconductor switching element of the phase corresponding to each modulated signal is turned on / off A control method for an inverter, characterized in that a drive signal to be generated is generated.
6. In the inverter control method according to claim 4 or 5,
   Of the n modulated signals, the magnitude of at least one modulated signal selected according to the phase or magnitude of the output voltage is made equal to the maximum value or the minimum value of the carrier, and the magnitude of the modulated signal A method for controlling an inverter, wherein whether the same value as the maximum value or the minimum value of the carrier is determined according to the phase or magnitude of the output voltage.
7. The control method according to any one of claims 1 to 6 is a first control method,
   A control method for generating a drive signal for turning on / off an n-phase semiconductor switching element by comparing n modulation signals corresponding to the n-phase output voltage command with a single carrier is referred to as a second control method. ,
   An inverter control method, wherein the first control method and the second control method are switched according to the phase or magnitude of the output voltage and the polarity or phase of the output current.
8. N series circuits of two semiconductor switching elements are provided (n is a plurality), the n series circuits are all connected in parallel to a DC voltage source, and two semiconductor switching elements constituting the series circuit are connected to each other. A DC voltage of the DC voltage source that appears at the AC output terminal when the semiconductor switching element of the inverter is connected to each phase of the n-phase AC load using the connection point as a one-phase AC output terminal. In the control device for outputting the n-phase AC voltage having a desired magnitude and frequency from the inverter by changing the time ratio of
   An AC output terminal of at least one specific phase among n phases is maintained in a state where it is connected to a positive electrode or a negative electrode of the DC voltage source for a certain period, and an alternating current of another phase other than the specific phase among the n phases The output terminal is connected to the negative electrode or the positive electrode of the DC voltage source for a period shorter than the predetermined period, and all the n-phase AC output terminals are simultaneously connected to the positive electrode or the negative electrode of the DC voltage source within the predetermined period. A control device for an inverter, wherein the semiconductor switching element of each phase is turned on / off so that a period of time to be shortened.
9. N series circuits of two semiconductor switching elements are provided (n is a plurality), the n series circuits are all connected in parallel to a DC voltage source, and two semiconductor switching elements constituting the series circuit are connected to each other. A DC voltage of the DC voltage source that appears at the AC output terminal when the semiconductor switching element of the inverter is connected to each phase of the n-phase AC load using the connection point as a one-phase AC output terminal. In the control device for outputting the n-phase AC voltage having a desired magnitude and frequency from the inverter by changing the time ratio of
   An AC output terminal of at least one specific phase among the n phases is maintained in a state of being connected to the positive electrode or the negative electrode of the DC voltage source for a certain period within the operation period, and other than the specific phase among the n phases The AC output terminal of the other phase is connected to the negative electrode or the positive electrode of the DC voltage source for a period shorter than the predetermined period, respectively,
   At least one cycle of the on / off cycle of the semiconductor switching element within the operation period is a cycle in which there is no state in which all n-phase AC output terminals are simultaneously connected to the positive electrode or the negative electrode of the DC voltage source. An inverter control device that turns on / off the semiconductor switching element of each phase.
10. In the inverter control device according to claim 8 or 9,
    A carrier generating means for generating a plurality of triangular waves having different phases or a plurality of sawtooth waves having different waveforms as a plurality of carriers;
    According to the phase or magnitude of the output voltage, each of the n modulation signals corresponding to the n-phase output voltage command is not duplicated in one carrier with the modulation signal corresponding to the other phase other than the specific phase. Modulation signal selection means corresponding to any of the plurality of carriers,
    Comparing means for comparing each of the n modulated signals selected by the modulated signal selecting means with the corresponding carrier;
    With
    An inverter control device that turns on / off the n-phase semiconductor switching element using an output signal of the comparison means.
11. In the control apparatus of the inverter according to claim 10,
    Of the plurality of carriers generated by the carrier generation means, further comprises a carrier selection means for giving the carrier selected according to the phase or magnitude of the output voltage and the polarity or phase of the output current to the comparison means,
    The comparison means turns on / off the n-phase semiconductor switching element using an output signal obtained by comparing the carrier selected by the carrier selection means and the n modulation signals. Inverter control device.
12. An inverter device, wherein the semiconductor switching element of each phase is turned on / off by the control method according to any one of claims 1 to 7.
13. 12. An inverter device, wherein the semiconductor switching element of each phase is turned on / off by the control device according to any one of claims 8 to 11.

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