JP2007288958A - Control method for direct power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method for a direct power converter, capable of preventing commutation failures, without having to adopt a method of increasing the current rating of a semiconductor switch. <P>SOLUTION: This control method of a direct power converter determines the magnitude relation of a three-phase AC voltage in the inside of the control device. When switching on/off a bidirectional switch S<SB>1</SB>is on/off switched, between the maximum voltage phase and one output phase and a bidirectional switch S<SB>2</SB>between the middle voltage phase and the output phase for commutation, a unidirectional switch S<SB>12</SB>for flowing a current from the output phase to the maximum voltage phase inside the bidirectional switch S<SB>1</SB>; and a unidirectional switch S<SB>22</SB>for making a current flow from the output phase to the intermediate voltage phase inside the bidirectional switch S<SB>2</SB>, are turned on, as well as, via a unidirectional switch S<SB>32</SB>, that makes a current flow from the minimum voltage phase to the output phase in the inside of the bidirectional switch S<SB>3</SB>between the minimum voltage phase and the output phase is turned on, and the bidirectional switches S<SB>1</SB>, S<SB>2</SB>are switched on/off. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention uses at least three bidirectional switches composed of a combination of a plurality of semiconductor unidirectional switches capable of controlling a current flowing in one direction, and directly converts a three-phase AC voltage into a multiphase AC voltage having a different magnitude and frequency. The present invention relates to a method for controlling a direct power converter to be converted.

FIG. 7 shows a typical example of this type of direct power converter using nine bidirectional switches formed by combining two semiconductor unidirectional switches (in the figure, two reverse blocking IGBTs having reverse blocking capability). 2 is a diagram showing a matrix converter together with peripheral circuits. FIG.
In FIG. 7, 20 is a three-phase AC power source, 30 is a filter, 40 is a three-phase load, R, S, and T are input terminals (input phases), U, V, and W are output terminals (output phases). The converter 10 includes bidirectional switches S _{1 to} S ₉ connected between the three phases on the output side of the filter 30 and the output terminals U, V, and W, respectively.

The matrix converter 10 can convert the three-phase AC voltage on the power source 20 side into a three-phase AC voltage having an arbitrary magnitude and frequency by repeatedly turning on and off the bidirectional switches S _{1 to} S ₉ . Since the operation is well known, the description is omitted here.

By the way, as shown in FIG. 8, the maximum voltage phase on the input side (hereinafter also referred to as the maximum phase), the intermediate voltage phase (hereinafter also referred to as the intermediate phase), the minimum voltage phase (hereinafter also referred to as the minimum phase), and the output When the three bidirectional switches S _{1 to} S ₃ connected to the U phase on the side are set as one unit, when the bidirectional switch being passed is switched from the bidirectional switch S ₁ to S ₂ , for example. (Hereinafter, such an operation is referred to as commutation), the ON / OFF timing of the unidirectional switches S _{11 to} S ₂₂ constituting each of the bidirectional switches S ₁ and S ₂ is appropriately adjusted, and the power supply short circuit and the load end opening are controlled. This prevents the bidirectional switches S ₁ and S ₂ from being destroyed.

Such a technique is described in Non-Patent Document 1 below, where the R phase voltage is larger than the S phase voltage when commutating from the bidirectional switch S ₁ to the bidirectional switch S _2. When the R phase is the maximum phase and the S phase is the intermediate phase as shown in FIG. 8, the on / off timings of the unidirectional switches S _{11 to} S ₂₂ are adjusted according to the commutation sequence as shown in FIG. . During this time, the unidirectional switches S ₃₁ and S ₃₂ constituting the bidirectional switch S ₃ connected to the minimum phase are kept off.

FIG. 10 is an operation explanatory diagram in each of the periods a to e in FIG. 9, and the unidirectional switch in the on state is shown in bold.
That is, in the period a, the unidirectional switches S ₁₁ and S ₁₂ are turned on, in the period b, S ₁₁ , S ₁₂ and S ₂₁ are turned on, in the period c, S ₁₂ and S ₂₁ are turned on, and in the period d, S ₁₂ , S ₂₁ , on the S _22, the sequence of turning on the period in e _{S 21, S 22,} to prevent the power short-circuit and the load end open during commutation from the bidirectional switch _{S 1} to the bidirectional switch _{S 2.}
Note that the same operation is basically performed even when commutation between the other bidirectional switches or when the voltage magnitude relationship is different.

Jun Koyama, Tsuyoshi Higuchi, Masafumi Kawasaki, Eiji Yamada, Takashi Koga, T.A. Lipo, “Sequence of PWM Cycloconverter Using SITh”, 1990 Annual Conference of the Institute of Electrical Engineers of Japan No.516, pp. 5-76-5-77

Now, in the commutation sequence described above, even though the actual R-phase voltage is smaller than the S-phase voltage, the control device erroneously detects R-phase voltage> S-phase voltage and determines the magnitude relationship thereof. When the commutation operation is performed in the sequence shown in FIGS. 9 and 10, the power supply is short-circuited via the unidirectional switches S ₂₁ and S ₁₂ in the periods b to d of FIGS. A short-circuit current flows from the phase to the R-phase (hereinafter, such a state is referred to as commutation failure).
As can be seen from the above, it is important to accurately detect the magnitude relationship between the phase voltages of the power supply. However, especially when the voltage values of the two phases of the power supply are approximately equal, the magnitude relationship between the voltages due to detection errors and the like. As a result, commutation failure may occur and a short-circuit current may flow.
For this reason, conventionally, in order to reduce the influence of the short circuit current on the semiconductor switch, it is necessary to increase the current rating of the semiconductor switch more than necessary, which leads to an increase in size and cost of the entire device.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a control method for a direct power converter that enables reliable commutation without increasing the current rating of a semiconductor switch.

In order to solve the above problems, the invention described in claim 1 is a semiconductor unidirectional switch capable of controlling a current flowing from the first terminal to the second terminal and a current flowing from the second terminal to the first terminal. Control method for direct power converter using at least three bidirectional switches combined with controllable semiconductor unidirectional switch, and directly converting three-phase AC voltage into multi-phase AC voltage of different magnitude and frequency In
A first bidirectional switch connected between the maximum voltage phase and one output phase of the three-phase AC voltage whose magnitude relationship is determined inside the control device, and between the intermediate voltage phase and the output phase When commutating by switching on and off with the connected second bidirectional switch,
A unidirectional switch for flowing current from the output phase to the maximum voltage phase in the first bidirectional switch, and a unidirectional switch for flowing current from the output phase to the intermediate voltage phase in the second bidirectional switch And, and
Via a state in which a unidirectional switch for passing a current from the minimum voltage phase to the output phase in a third bidirectional switch connected between the minimum voltage phase and the output phase of the three-phase AC voltage is turned on. And
The first and second bidirectional switches are switched on and off.

The invention described in claim 2 is a semiconductor unidirectional switch capable of controlling a current flowing from the first terminal to the second terminal, and a semiconductor unidirectional switch capable of controlling a current flowing from the second terminal to the first terminal. In a direct power converter control method for directly converting a three-phase AC voltage into a multi-phase AC voltage having a different magnitude and frequency using at least three bidirectional switches in combination with
The second bidirectional switch connected between the intermediate voltage phase and the one output phase among the three-phase AC voltages whose magnitude relationship is determined inside the control device, and between the minimum voltage phase and the output phase. When commutating by switching on and off with the connected third bidirectional switch,
A unidirectional switch for flowing current from the intermediate voltage phase to the output phase in the second bidirectional switch, and a unidirectional switch for flowing current from the minimum voltage phase to the output phase in the third bidirectional switch And, and
In a first bidirectional switch connected between the maximum voltage phase and the output phase of the three-phase AC voltage, through a state of turning on a unidirectional switch for passing a current from the output phase to the maximum voltage phase And
The second and third bidirectional switches are switched on and off.

  According to a third aspect of the present invention, in the control method according to the first aspect, when the difference between the maximum voltage phase voltage and the intermediate voltage phase voltage is not more than a predetermined value, the first and second bidirectional switches Is switched on and off.

  According to a fourth aspect of the present invention, in the control method according to the second aspect, when the difference between the voltage of the intermediate voltage phase and the voltage of the minimum voltage phase is a predetermined value or less, the second and third bidirectional switches Is switched on and off.

  According to the present invention, by turning on a predetermined unidirectional switch constituting a bidirectional switch other than the two bidirectional switches involved in commutation during the commutation period, a misjudgment of the magnitude relationship of each phase voltage of the power supply. A commutation failure due to another can be prevented. As a result, the current rating of the semiconductor switch need not be increased more than necessary, and the apparatus can be reduced in size and cost.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 shows a commutation sequence according to the first embodiment of the present invention, which corresponds to the invention according to claim 1. That is, the control device of the matrix converter 10 as shown in FIG. 7 has the same magnitude of the two-phase voltages as the magnitude relationship between the two-phase power supply voltages (for example, the R-phase voltage V _R and the S-phase voltage V _S ). maximum R-phase voltage V _R, including a case, it is determined that the S-phase voltage V _S is an intermediate (which corresponds to a period a in FIG. 5 showing a phase voltage waveform), and U-phase of the R-phase and the output side The commutation sequence in the case of commutation from the bidirectional switch (S ₁ in FIGS. 7 and 8) connected between the two to the bidirectional switch (also S ₂ ) connected between the S phase and the U phase. It is.

2 is an operation explanatory diagram in each of the periods a to g in FIG. 1, and the unidirectional switch in the on state is shown in bold as in FIG.
That is, in the period a, the unidirectional switches S ₁₁ and S ₁₂ are turned on, in the period b, S ₁₁ , S ₁₂ and S ₃₂ are turned on, in the period c, S ₁₂ and S ₃₂ are turned on, and in the period d, S ₁₂ , S ₂₂ , on the S _{32, S} 22 in the period _{e, S 32} oN, on the time at _{f S 21, S 22, S} 32, the sequence of turning on the _{S 21, S 22} in the period g, the bidirectional switch _{S 1} thereby preventing the power short-circuit and the load end opening of the case of when the commutation to the bidirectional switch S _2.

Figure 1, as is clear from FIG. 2, FIG. 9 is a prior art, significantly different from that of FIG. 10, despite the commutation from the bidirectional switch S ₁ to the bidirectional switch S _2, involved in the commutation temporarily unidirectional switches S ₃₂ of the bidirectional switch S ₃ not to a point to be turned on.

Hereinafter, the commutation sequence will be described in detail.
In the period A of FIG. 5, the internal control unit, the detection value of each phase voltage, R-phase voltage V _R to perform commutation over the designated decision to magnitude relationship greater than the S-phase voltage V _S .
In this case, in the present embodiment, as in the period d in the commutation period of FIGS. 1 and 2, a unidirectional switch S ₁₂ that flows current from the U phase on the output side to the R phase on the power supply side (from the U phase to the control device) The unidirectional switch S ₂₂ (current flow from the U phase to the S phase on the power supply side) is turned on, and the unidirectional switch S ₂₂ (current phase from the U phase to the intermediate phase determined inside the controller) is turned on. The unidirectional switch S ₃₂ (unidirectional switch for supplying current from the minimum phase determined in the control device to the U phase) for turning on current and turning the current from the T phase to the U phase on the power supply side. An on state is provided.

By providing such a state during the commutation period, approximately equal in magnitude to the R-phase voltage V _R and S-phase voltage V _S as around the time II in Fig. 5, the magnitude relation of the control apparatus inside was determined Even if the actual magnitude relationship (V _R <V _S ) is different from (V _R > V _S ), commutation failure can be prevented.
For example, even if the S-phase voltage V _S is larger than the R-phase voltage V _R during the period d in FIG. 2, there is no short-circuit path from the S-phase to the R-phase or T-phase, and the load current flow path is the load Since it is secured by the unidirectional switches S ₁₂ , S ₂₂ , S _{32 in the} on state regardless of the polarity of the current, it is possible to prevent the generation of a short circuit path and the opening of the load end regardless of the magnitude relationship of the power supply voltage. .

Incidentally, FIG. 1, 2, before and after the period b around the period d, c, e, and turns on the unidirectional switch S ₃₂ also f, the power supply short-circuit and load the same action also these periods It is possible to prevent the end opening.

Next, FIG. 3 shows a commutation sequence according to the second embodiment of the present invention, which corresponds to the invention according to claim 2.
In this embodiment, the control device has an intermediate S-phase voltage V _S including a case where the magnitudes of the two-phase voltages are equal, for example, as a magnitude relationship between the S-phase voltage V _S and the T-phase voltage V _T. It is determined that V _T is the minimum (corresponding to the period A in FIG. 5), and the bidirectional switch S ₂ connected between the S phase and the U phase is connected between the T phase and the U phase. and a commutation sequence for commutating the bidirectional switch S _3.

FIG. 4 is an operation explanatory diagram for each period a to g in FIG. 3, and the unidirectional switch in the on state is represented in bold as in the above case.
In this embodiment, the period a in unidirectional switches _{S 21,} on the _{S 22,} the period in _{b S 12, S 21, S} 22 on-period on the _{S 12, S 21} in c, the period in d _{S 12,} on the S _{21, S 32,} on the time the e _{S 12, S 32,} the period in _{f S 12, S 31, S} 32 oN, the sequence to turn on the _{S 31, S 32} in the period g, the bidirectional switch thereby preventing the power short-circuit and the load end open during commutation from S ₂ to the bidirectional switch S _3.
The sequence differs greatly from that in FIGS. 9 and 10 in that the unidirectional switch constituting the bidirectional switch S ₁ that does not participate in commutation despite the commutation from the bidirectional switch S ₂ to the bidirectional switch S ₃ . is the point to temporarily turn on the S _12.

Hereinafter, the commutation sequence will be described in detail.
In the period A in FIG. 5, commutation is executed in the control device by determining that the S-phase voltage V _S is larger than the T-phase voltage V _T.
In this embodiment, as in the period d in the commutation period of FIGS. 3 and 4, the unidirectional switch S ₁₂ that flows current from the U phase to the R phase (current from the U phase to the maximum phase determined inside the controller). the flow turns the unidirectional switch), and turns on the unidirectional switch) supplying a current to the U phase from the intermediate phase, which is determined by the internal unidirectional switch S _{21 (controller} supplying a current to the U phase from the S-phase, T A state is provided in which a unidirectional switch S ₃₂ (unidirectional switch for flowing current from the minimum phase determined in the control device to the U phase) that flows current from phase to U phase is turned on.

By providing the above state during the commutation period, the magnitudes of the S-phase voltage V _S and the T-phase voltage V _T are substantially equal as in the vicinity of time I in FIG. Even if the actual magnitude relationship (V _S <V _T ) differs from (V _S > V _T ), commutation failure can be prevented.
In other words, even if the S phase voltage V _S is smaller than the T phase voltage V _T during the period d in FIG. 4, there is no short circuit path from the T phase to the S phase, or from the R phase to the S phase. Since the current path is secured by the unidirectional switches S ₁₂ , S ₂₁ , S _{32 in the} on state regardless of the polarity of the load current, the generation of a short circuit path and the opening of the load end are prevented regardless of the magnitude of the power supply voltage. be able to.

As in the first embodiment, FIG. 3, the period before and after about a period d as shown in FIG. 4 b, c, e, but also to turn on the unidirectional switch S ₁₂ for f, these periods For the above, it is possible to prevent the power supply short circuit and the load end opening by the same action.

Next, third and fourth embodiments of the present invention corresponding to claims 3 and 4 will be described.
In the commutation sequence of the first embodiment, in the period A in FIG. 5, the unidirectional switch S ₁₂ that flows current from the U phase to the R phase as in the period d in FIG. 2, and the current from the U phase to the S phase. flow unidirectional switch S _22, are provided a condition for turning on the unidirectional switches S ₃₂ to flow a current to the U phase from the T phase.

However, actually there is a possibility that commutation failure occurs, for example, as time II in Fig. 5, the magnitude of the size and the S-phase voltage V _S of the R-phase voltage V _R and is approximately equal, determined by the control device in a case where the actual size relationship between magnitude of supply voltage is different, R-phase, connected bidirectional switches S ₁ and S phase between U-phase, the bidirectional switch S ₂ connected between the U-phase It is a case where it is made to commutate between.

Here, FIG. 1 described above, in the commutation sequence shown in FIG. 2, although turns on the unidirectional switches S ₃₂ to flow a current to the U phase from the T phase over a period b to f, the polarity of the load current is positive In the case of (the current polarity in the direction of the arrow in FIG. 2 is positive), in the commutation sequence of FIG. 1, the R phase or S phase must be connected to the U phase in spite of the period. The T phase is connected to the U phase over b to f, thereby generating a large error voltage and causing output voltage distortion.

Therefore, in the third embodiment of the present invention, the bidirectional switch S connected between the maximum phase and the output phase, in which the difference between the maximum phase voltage and the intermediate phase voltage of the three-phase AC power supply is not more than a predetermined value. ₁ and the control sequence of FIG. 1 and FIG. 2 according to the first embodiment is executed when commutation is performed between the intermediate switch ₁ and the bidirectional switch S ₂ connected between the intermediate phase and the output phase.

Similarly, in the fourth embodiment of the present invention, the bidirectional switch S ₂ that connects the intermediate phase and the output phase when the difference between the intermediate phase voltage and the minimum phase voltage of the three-phase AC power supply is not more than a predetermined value. If, when the commutated between the bidirectional switch S ₃ which connects the minimum phase and the output phase, FIG. 3 according to the second embodiment, so as to perform the commutation sequence of Figure 4.

  That is, as in the period B shown in FIG. 6, at the time of commutation from the maximum phase to the intermediate phase or from the intermediate phase to the minimum phase, the power source voltage of the commutation source phase and the phase of the commutation destination By executing the commutation sequence of the first embodiment or the second embodiment only when the difference from the power supply voltage is equal to or less than a predetermined value, the frequency of occurrence of error voltage is reduced and the output voltage distortion is reduced. It becomes possible to plan.

It is a commutation sequence which shows 1st Embodiment of this invention. It is operation | movement explanatory drawing in each period of FIG. It is a commutation sequence which shows 2nd Embodiment of this invention. It is operation | movement explanatory drawing in each period of FIG. It is a wave form diagram of each phase power supply voltage. It is a wave form diagram of each phase power supply voltage. It is a block diagram of a matrix converter and a peripheral circuit. It is a block diagram of the principal part in FIG. It is a figure which shows an example of the commutation sequence in FIG. It is operation | movement explanatory drawing in each period of FIG.

Explanation of symbols

10: Matrix converter 20: Three-phase AC power supply 30: Filter 40: Three-phase load R, S, T: Input terminal (input phase)
U, V, W: Output terminal (output phase)
S ₁ to S _9: bidirectional switch S ₁₁ to S _32: unidirectional switch

Claims (4)

A bidirectional switch comprising a combination of a semiconductor unidirectional switch capable of controlling a current flowing from the first terminal to the second terminal and a semiconductor unidirectional switch capable of controlling a current flowing from the second terminal to the first terminal. In a control method for a direct power converter that uses at least three and directly converts a three-phase AC voltage into a multi-phase AC voltage of different magnitude and frequency,
A first bidirectional switch connected between the maximum voltage phase and one output phase of the three-phase AC voltage whose magnitude relationship is determined inside the control device, and between the intermediate voltage phase and the output phase When commutating by switching on and off with the connected second bidirectional switch,
A unidirectional switch for flowing current from the output phase to the maximum voltage phase in the first bidirectional switch, and a unidirectional switch for flowing current from the output phase to the intermediate voltage phase in the second bidirectional switch And, and
Via a state in which a unidirectional switch for passing a current from the minimum voltage phase to the output phase in a third bidirectional switch connected between the minimum voltage phase and the output phase of the three-phase AC voltage is turned on. And
A control method for a direct power converter, wherein the first and second bidirectional switches are switched on and off. A bidirectional switch comprising a combination of a semiconductor unidirectional switch capable of controlling a current flowing from the first terminal to the second terminal and a semiconductor unidirectional switch capable of controlling a current flowing from the second terminal to the first terminal. In a control method for a direct power converter that uses at least three and directly converts a three-phase AC voltage into a multi-phase AC voltage of different magnitude and frequency,
The second bidirectional switch connected between the intermediate voltage phase and the one output phase among the three-phase AC voltages whose magnitude relationship is determined inside the control device, and between the minimum voltage phase and the output phase. When commutating by switching on and off with the connected third bidirectional switch,
A unidirectional switch for flowing current from the intermediate voltage phase to the output phase in the second bidirectional switch, and a unidirectional switch for flowing current from the minimum voltage phase to the output phase in the third bidirectional switch And, and
In a first bidirectional switch connected between the maximum voltage phase and the output phase of the three-phase AC voltage, through a state of turning on a unidirectional switch for passing a current from the output phase to the maximum voltage phase And
A control method for a direct power converter, wherein the second and third bidirectional switches are switched on and off. The control method according to claim 1,
Direct power conversion characterized in that when the difference between the voltage of the maximum voltage phase and the voltage of the intermediate voltage phase is equal to or less than a predetermined value, the first and second bidirectional switches are switched on and off for commutation. Control method. In the control method according to claim 2,
Direct power conversion characterized in that when the difference between the voltage of the intermediate voltage phase and the voltage of the minimum voltage phase is equal to or less than a predetermined value, the second and third bidirectional switches are switched on and off for commutation. Control method.

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