JPH1140429A - Transformer, detecting device for direct current magnetic deviation of transformer and evaluating device for direct current magnetic deviation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate influence of leak magnetic flux produced by a main magnetic flux leaking from an iron core or by winding current upon a direct current magnetic deviation detecting device which detects amount of direct current magnetic deviation of the iron core of a transformer. SOLUTION: A detecting coil 8 is wound around a magnetic core 7 (7a-7c) of magnetic material. Ends 7a and 7b of the magnetic core 7 are extended in parallel and in the opposed direction between laminated steel plates 12 comprising an iron core of a transformer. A part 7c around which the detecting coil 8 is wound is formed in such a way that it is kept separated from the laminated surface of the laminated steel plates 12 by a specific distance. In this case, the detecting coil 8 is separated from the iron core by a specific distance in order to prevent or minimize a main magnetic flux leaking from the iron core from crossing the detecting coil 8. The influence of the main magnetic flux leaking from the iron core is accordingly avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting a DC bias amount of a transformer, and more specifically, to a DC bias detecting element,
The present invention relates to a transformer and a DC bias evaluation apparatus provided with the transformer.

[0002]

2. Description of the Related Art Along with advances in power electronics technology, a self-excited power converter using a self-extinguishing semiconductor device such as a GTO has been applied to the electric power field. Generally, when a self-excited power converter is connected to a power system, it is connected via a conversion transformer. In such a conversion transformer, the DC component is superimposed on the applied voltage due to a variation in the firing angle of the semiconductor switch element of the power converter, so that the magnetic flux passing through the inside of the iron core has a positive or negative polarity. A biased DC bias phenomenon occurs. If the core of the transformer is DC-polarized, it causes loss and noise of the transformer. Further, depending on the degree of DC bias, the iron core is magnetically saturated and an excessive exciting current flows through the winding, which may cause damage to the semiconductor switch element of the power converter connected to the winding.

Conventionally, in order to prevent the magnetic saturation of the iron core due to the DC magnetic polarization of such a conversion transformer, the output voltage of the power converter, ie, the output voltage of the power converter, that is, the amount of the DC magnetic polarization of the iron core is detected so as to cancel this. DC bias suppression control for adjusting the voltage applied to the conversion transformer is performed. As a method for detecting the amount of direct current magnetization of the iron core, for example, in Japanese Patent Publication No. 50-33213, a direct current magnetization detection element is installed on the laminated core of the transformer, and the main magnetic flux (excitation magnetic flux) in the iron core is directly And a method of detecting the amount of DC bias by monitoring the temperature. In this method, a detection coil is wound around a magnetic core having an extremely high initial magnetic permeability to form a DC bias detecting element, and legs (both ends) of the magnetic core of the DC bias detecting element are attached to a laminated steel sheet of a transformer core. In this method, a part of a main magnetic flux passing through an iron core is diverted to a magnetic core having a high magnetic permeability, and a voltage induced in a detection coil is monitored to detect a DC bias amount. The magnetic core has a lower saturation magnetic flux density than the laminated steel sheet forming the iron core of the transformer, and is magnetically saturated before the laminated steel sheet. Therefore, even if the main magnetic flux passing through the laminated steel sheet changes sinusoidally, the magnetic flux shunted to the magnetic core (magnetic flux linked to the detection coil) has a trapezoidal positive / negative shape in which the wave front of the sinusoidal wave is suppressed by magnetic saturation. It becomes a waveform. Therefore, a steep pulse-like voltage is induced in the detection coil near the zero point where the positive / negative polarity of the magnetic flux changes. The time interval at which this pulse-like voltage appears depends on the positive or negative DC bias amount, so that by measuring the time interval of the pulse-like voltage, the DC bias amount and its polarity are detected. You can do it.

[0004]

When the magnetic flux density of the main magnetic flux (exciting magnetic flux) passing through the laminated steel sheet constituting the iron core of the transformer becomes high to some extent, the main magnetic flux leaking from the steel sheet and passing through the outside of the steel sheet. (Hereinafter referred to as leakage main magnetic flux) increases. The leakage main magnetic flux is
No. 213), the output voltage of the detection coil is affected if the amount is increased. In other words, the leakage main magnetic flux increases near the maximum value of the main magnetic flux passing through the iron core, and the magnetic core is magnetically saturated and interlinks with the detection coil of the DC bias detection element in an air-core state. At this time, the linkage magnetic flux waveform of the detection coil, which should have a trapezoidal waveform, is a waveform in which the leakage main magnetic flux is superimposed near the middle part of the trapezoidal wave front. Therefore, in addition to the pulse voltage generated near the zero point of the main magnetic flux passing through the iron core, a voltage may be induced in the detection coil also near the maximum value of the main magnetic flux passing through the iron core. The pulse-like voltage generated by the main leakage magnetic flux is a so-called disturbance that may or may not be generated depending on the magnitude of the main leakage magnetic flux. It becomes an error factor and poses a problem in terms of accuracy and reliability.
As a result, when such a DC bias detection element is applied to a DC bias evaluation device of a power conversion system, DC bias suppression control of a transformer may fail and the core may be magnetically saturated.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to eliminate the influence of a main magnetic flux leaking from an iron core, which is linked to a detection coil of a DC bias detecting element for detecting a DC bias amount of a transformer. I do.

[0006]

The object of the present invention can be achieved by the following means.

The principle of the present invention is to prevent the main magnetic flux leaking from the iron core, which is a disturbance, from interlinking the detection coil of the DC bias detecting element.

As a specific means, a detection coil is wound around a magnetic core of a magnetic material, and is disposed on a transformer core to detect a DC bias of the transformer. The laminated core is formed so as to be in contact with the laminated surface of the laminated steel sheet forming the transformer core, and a portion where the detection coil of the magnetic core is wound is formed at a certain distance from the surface of the transformer core. As a result, it is possible to prevent or minimize the leakage main magnetic flux existing near the lamination surface of the laminated steel sheet forming the transformer core, or to minimize the leakage main magnetic flux. Can be eliminated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a description will be given based on an embodiment of the present invention.

FIG. 1 shows an overall configuration diagram of a power conversion system according to an embodiment of the present invention, and FIG. 2 shows a detailed view of main parts. As shown in FIG. 1, an AC side winding 2 of a conversion transformer 1 is connected to an AC system (not shown), and a converter side winding 3 is a power converter 4 formed by using a semiconductor switch element. It is connected to the. The iron core 5 of the conversion transformer 1 is formed by laminating electromagnetic steel sheets in a direction perpendicular to the plane of the paper, and a DC magnetic field detecting element 6 is attached to the iron core 5. The DC bias detection element 6 is formed by winding a detection coil 8 around a plate-shaped magnetic core 7 formed in, for example, a π shape. The output terminal of the detection coil 8 is connected to the arithmetic unit 9. The DC bias detection element 6 and the arithmetic unit 9 constitute a bias evaluation device 10. The arithmetic unit 9 takes in the induced voltage of the detection coil 8, calculates the amount of DC bias of the conversion transformer 1 based on this, and outputs it to the control unit 11. Control device 11
Controls the ignition timing of the semiconductor switch element of the power converter 4 on the basis of the input DC bias amount and its polarity to eliminate the DC bias of the conversion transformer 1. Note that the function of the arithmetic unit 9 for calculating the amount of DC bias may be provided to the control device 11, and the arithmetic unit 9 may be omitted.

FIG. 2 is an enlarged perspective view of a portion of the iron core 5 to which the DC bias detecting element 6 is attached. As shown in the figure, the magnetic core 7 of the DC bias detecting element 6 is, for example, π
It is formed in a mold plate shape, and both ends 7a and 7b are
It is attached in close contact with the surface of the laminated steel sheet 12 forming the iron core 5. The portion 7c (the π-shaped central portion) of the magnetic core 7 around which the detection coil 8 is wound is the iron core 5
The detection coils 8 are arranged so as to be out of the lamination plane with a certain dimension, and are arranged so that the detection coil 8 extends out of the iron core 5. Magnetic core 7
Is preferably formed of a magnetic material having an extremely high initial magnetic permeability, such as an iron-nickel alloy or an amorphous magnetic material (amorphous). Although FIG. 2 shows that both end portions 7a and 7b of the magnetic core 7 of the DC bias detecting element 6 are inserted into the lamination gap of the laminated steel plate, it may be attached to the outermost steel plate surface. Further, although an example in which the shape of the magnetic core is a π type has been described here, the present invention does not particularly limit the shape of the magnetic core as long as the portion around which the detection coil is wound can be arranged outside the iron core.

The operation of the embodiment thus formed will be described below.

[0013] As shown in FIG. 2, a portion of the main magnetic flux [Phi ₁ through the laminated steel 12 medium to form the core 5 of the converting transformer 1, permeability to flow to the end 7a of the very high magnetic core 7 min The shunt magnetic flux Φ ₂ is transmitted from the end 7 b to the laminated steel sheet 12 via the portion 7 c of the magnetic core 7 around which the detection coil 8 is wound.
Merges with the main magnetic flux Φ ₁ passing through it. At this time, the shunt magnetic flux Φ ₂
Are linked to the detection coil 8, and a voltage is induced in the detection coil 8. Figure 3 (a), (b) , (c), the main magnetic flux [Phi ₁ of the waveform of time changes in the laminated steel sheet, the time variation of the flow flux [Phi ₂ interlinked in the detection coil 8 to shunt magnetic core 7 And the waveform of the change over time of the output voltage V of the detection coil 8 are shown. As shown in the figure, the main magnetic flux Φ ₁ changes sinusoidally, but the magnetic core 7 has a lower saturation magnetic flux density than the laminated steel sheet 12 and is magnetically saturated before the laminated steel sheet 12, so the shunt magnetic flux Φ ₂ is as shown in the figure. It becomes a trapezoidal waveform. Therefore, the terminal 8a of the detection coil 8, the waveform of the output voltage V appearing on 8b, when the shunt magnetic flux [Phi ₂ is suddenly changed, i.e. steep pulse appears near the zero point of the main magnetic flux [Phi _1. This pulse-like voltage appears alternately by changing the positive and negative polarities. By utilizing the fact that the time intervals Δt ₁ and Δt ₂ between the maximum value and the minimum value of the pulsed voltage change in accordance with the DC bias amount of the laminated steel sheet 12, the DC bias amount and its polarity can be detected. Can be.

Next, a description will be given of how the embodiment of FIG. 1 can eliminate the influence of the main magnetic flux leaking from the steel plate. This leakage main magnetic flux is a magnetic flux through the steel external leaks from the steel plate 12 in the vicinity of the maximum value of the main magnetic flux [Phi ₁ through in the steel plate, indicated by [Phi _a in FIG. As is apparent from the figure, since the spaced apart a predetermined dimension detection coil 8 of a steel plate laminated surface, there is no leakage main magnetic flux [Phi _a in the vicinity of the detection coil 8 is wound, a detection coil 8 is not interlinked leakage main magnetic flux Φ _a in. Further, the leakage main magnetic flux [Phi _a larger is the vicinity of the maximum value of the main magnetic flux [Phi ₁ in the steel sheet, this time the magnetic core 7 permeability and magnetic saturation is in the state close to an air core decreases. Therefore, the leakage main magnetic flux [Phi _a existing between laminated surfaces of the laminated steel sheet,
Since the magnetic core 7 penetrates the magnetic core 7 without forming a magnetic path, the detection coil 8
Is not interlinked leakage magnetic flux Φ _a in. Therefore, according to the present embodiment, only the shunt magnetic flux Φ ₂ is linked to the detection coil 8.
Therefore, no voltage is induced by the leakage main magnetic flux [Phi _a is the output voltage of the detection coil 8, as shown in Figure 3 (c).

[0015] In contrast, as in the prior art, when mounted across DC polarization磁検detecting element 6 is brought into close contact on the surface of the laminated steel plates 12 forming the core 5, the leakage main magnetic flux [Phi _a is a chain in the detection coil 8 Intersect. As a result, the effects as shown in FIGS. In other words, the increase of the leakage main magnetic flux [Phi _a becomes a problem is the vicinity of the maximum value of the main magnetic flux [Phi _1, when it reaches a level which can not be ignored, the diagram _{(a) (Φ 2 + Φ} a)
As shown in the figure, the magnetic flux linked to the detection coil 8 is added with the magnetic flux in the hatched portion at the center of the trapezoidal waveform,
In response to this, the output voltage V of the detection coil 8 is shown in FIG.
The disturbance pulse indicated by the hatched portion appears in the lower stage. As a result, the time intervals Δt ₁ and Δt ₂ of the pulses used in calculating the DC bias amount may not be specified or may be incorrectly specified, and the DC bias amount is accurately and reliably evaluated. Can not do it. Therefore, there is a possibility that the DC bias suppression control of the transformer may fail. In addition, FIG.
There is a waveform diagram of each part shows the influence of the leakage main magnetic flux [Phi _a in a state in which only the DC magnetic deviation DC magnetic flux [Phi _dc.

FIG. 5 is a sectional view of a conversion transformer to which another embodiment of the DC bias detecting element according to the present invention is applied, and FIG.
FIG. 2 shows an enlarged view of the vicinity of the DC bias detecting element. Here, the case where the DC bias detecting element 6 according to the present invention is attached to the main leg of the iron core 5 having a single-phase center core structure, that is, the iron leg around which the AC side winding 2 and the converter side winding 3 are wound. Will be described as an example. The iron core 5 is formed by stacking steel plates in a direction perpendicular to the plane of the drawing. In the figure, the magnetic flux distribution of the operating transformer is indicated by arrows. In the iron core 5, a main magnetic flux Φ corresponding to the integrated value of the applied voltage of the winding as shown by a solid arrow in the drawing.
₁ (Excitation flux) exists. On the other hand, around the winding, there is a so-called leakage magnetic flux Φ _L generated by a load current flowing through the winding as shown by a broken arrow in the figure. The distribution of the leakage flux Φ _L depends on the winding configuration and arrangement of the transformer. In such a case, the DC bias detection element 6
The leakage magnetic flux Φ _L of the winding interlinks with the detection coil 8 and appears as an induced voltage component in the output voltage of the detection coil 8, which may cause disturbance.

Therefore, as shown in FIG. 6, the magnetic core 7 of the DC bias detecting element 6 is formed in, for example, a π-shaped plate shape, and both end portions 7a and 7b are brought into close contact with the surface of the laminated steel plate 12 constituting the iron core 5. And attach it. A portion 7c of the magnetic core 7 around which the detection coil 8 is wound is formed so as to be out of the lamination plane of the iron core 5, and the detection coil 8 is arranged so as to protrude outside the iron core 5. Further, in this embodiment, the detection coil 8 is perpendicular to the direction of the leakage magnetic flux Φ _L of the windings 2 and 3 of the transformer, that is, the axis of the detection coil 8 is perpendicular to the leakage magnetic flux Φ _{L of the} winding. It is arranged so that it becomes.

By doing so, the leakage magnetic flux Φ _L generated by the load current flowing through the windings 2 and 3 is
Therefore, no induced voltage is generated in the detection coil 8 due to magnetic fluxes other than the magnetic flux Φ ₂ shunted from the main magnetic flux Φ ₁ passing through the steel plate 12. As a result, the output voltage V shown in FIG. 3C is obtained as described in the first embodiment.
Applied to DC bias evaluation device of conversion transformer or power conversion system using the same, DC bias of transformer can be evaluated accurately and reliably, and DC bias suppression control of transformer Can be performed stably.

FIG. 7 is a cross-sectional view of a main part of a conversion transformer to which another embodiment of the DC bias detecting element according to the present invention is applied. This embodiment is an example in which, when the DC magnetic field detecting element is arranged on the iron main leg as shown in FIG. 5, the DC magnetic field detecting element is magnetically shielded so as not to interlink the leakage magnetic flux around the winding. . That is, as shown in FIG.
Is formed in, for example, a π-shaped plate shape, and both end portions 7a and 7b are attached to the surface of the laminated steel plate 12 forming the iron core 5 in close contact with each other. A portion 7c of the magnetic core 7 around which the detection coil 8 is wound (a π-shaped central portion)
Are formed apart from each other by a predetermined distance so as to be outside the lamination plane of the iron core 5, and are arranged so that the detection coil 8 extends outside the iron core 5. The DC bias detection element 6 is covered with the shield member 14 except for the surface in contact with the laminated steel plate 12. For the shield member 14, it is desirable to use a magnetic body whose surface is insulated. Further, a non-magnetic conductor such as copper or aluminum whose surface is insulated may be used.

By providing such a shield member 14, since the leakage magnetic flux Φ _L generated by the load current flowing through the winding of the transformer does not interlink with the detection coil 8, the detection coil 8 passes through the steel plate 12. voltage due to the magnetic flux Φ ₂ other than the magnetic flux that is diverted from the main magnetic flux Φ ₁ is not induced. As a result, as described in the first embodiment, the output voltage V shown in FIG. 3C is obtained. Therefore, the output voltage V is applied to a DC bias evaluation device for a conversion transformer or a power conversion system using the same. The DC bias of the transformer can be accurately and reliably evaluated, and the DC bias suppression control of the transformer can be stably performed.

FIG. 8 is a sectional view of a main part of a conversion transformer to which another embodiment of the DC bias detecting element according to the present invention is applied. In the present embodiment, when the DC bias detecting element is arranged on the iron core main leg, the induced voltage component generated in the DC bias detecting element by the leakage magnetic flux of the winding is detected by the compensating element to compensate for the disturbance. To eliminate the effects of The DC bias detecting element 6 is formed in the same manner as in FIG. The compensating element 20 is attached to the laminated steel plate 12 in the vicinity of the magnetic field detecting element 6.
The compensating element 20 is formed by winding a compensating coil 22 around a bobbin 21 formed in the same shape as the magnetic core 7. The winding frame 21 is formed of a non-magnetic insulator. The winding directions of the detection coil 8 and the compensation coil 22 are opposite to each other, and the number of turns, the coil cross-sectional area, and the like are adjusted to predetermined values so that the output voltages of the two become equal. And the detection coil 8
And the compensation coil 22 connect the terminal 8a and the terminal 22b so that the induced voltages cancel each other, and
b and 22a are connected in series with the output terminals.

[0022] From such a configuration, the DC polarization磁検detecting element 6, a portion of the main magnetic flux [Phi ₁ is laminated steel plates 1
The magnetic flux is shunted to the magnetic core 7 provided in close contact with the surface of the magnetic field ₂ , and a voltage is induced in the detection coil 8 according to the magnitude and polarity of the shunt magnetic flux Φ ₂ . Further, since the leakage magnetic flux Φ _L of the winding is also linked to the detection coil 8, a voltage due to the Φ _L is also induced. On the other hand, since the winding frame 21 of the compensating element 20 is formed of a non-magnetic material, a part of the main magnetic flux Φ ₁ does not flow to the compensating element 20. Therefore, only the leakage magnetic flux Φ _L of the winding is linked to the compensation coil 22, and only the voltage due to the leakage magnetic flux Φ _L is induced. The number of turns, the effective cross-sectional area, and the like of both coils are previously adjusted so that the induced voltage components due to the leakage magnetic flux Φ _L generated in the detection coil 8 and the compensation coil 22 have the same magnitude and opposite polarities. Hence, both are canceled each other, the output voltage V appearing at the terminal 8b and 22a does not include the voltage component due to leakage flux [Phi _L.

As a result, similar to the above-described embodiment, FIG.
Since the output voltage V shown in (c) is obtained, the present invention is applied to a DC bias evaluation device for a conversion transformer or a power conversion system using the same, and the DC bias amount of the transformer is accurately and reliably measured. Therefore, the DC bias suppression control of the transformer can be stably performed.

FIG. 9 is a sectional view of a main part of a conversion transformer to which another embodiment of the DC bias detecting element according to the present invention is applied. In the present embodiment, when the DC bias detecting element is arranged on the iron core main leg, the induced voltage component generated in the DC bias detecting element by the leakage magnetic flux of the winding is detected by the compensating element to compensate for the disturbance. This is another example of eliminating the influence. The DC bias detecting element 6 is formed in the same manner as in FIG. The compensating element 23 is attached to the laminated steel plate 12 in the vicinity of the magnetic field detecting element 6.
The compensating element 23 is formed, for example, by winding a compensating coil 25 around a winding frame 24 formed in the same shape as the magnetic core 7. The winding frame 24 is formed of a non-magnetic insulator. Then, the output voltages V ₁ and V of the detection coil 8 and the compensation coil 25 are output.
₂ is input to the arithmetic unit 26 from the terminals 8a and 8b and the terminals 25a and 25b, respectively.

With this configuration, the shunt magnetic flux Φ ₂ is applied to the DC bias detecting element 6 as in the embodiment of FIG.
And the leakage flux Φ _{L of the} winding according to the magnitude and polarity of
A voltage V ₁ on which a voltage corresponding to the above is superimposed is induced. on the other hand,
A voltage V ₂ according to the leakage magnetic flux Φ _L is induced in the compensation element 23. The arithmetic unit 26 takes in these voltages V ₁ and V ₂ , and obtains a voltage V according to the magnitude and polarity of the shunt magnetic flux Φ ₂ by the following equation (1).

V = V ₁ −k · V ₂ (1) Here, k is an adjustment coefficient for completely canceling the induced voltage component due to the leakage magnetic flux Φ ₁ of the winding, and the detection coil 8 and the compensation coil It is for adjusting the difference between the number of turns of 25, the effective area, and the like.

As a result, the output voltage V shown in FIG. 3C is obtained as the voltage V output from the arithmetic unit 26 in the same manner as in the above-described embodiment. By applying the present invention to a device or a power conversion system using the same, the amount of DC bias of the transformer can be accurately and reliably evaluated, and the DC bias suppression control of the transformer can be stably performed.

The above is an example of the case where the DC bias detecting element of the present invention is installed at a position where the leakage magnetic flux Φ _L generated by the load current flowing through the winding is affected. A case where the device is installed in a portion where the influence of the leakage magnetic flux Φ _L does not affect will be described.

FIG. 10 shows an embodiment of the installation position of the DC bias detecting element according to the present invention. The iron core 5 of the conversion transformer 1 is formed by laminating steel plates 12, and a DC bias detecting element 6 is attached to the iron core 5. The DC bias detection element 6 is formed by winding a detection coil 8 around a plate-shaped magnetic core 7 formed in, for example, a π shape. Both ends 7 of magnetic core 7
a and 7b are attached in close contact with the surface of the laminated steel plate 12 constituting the iron core 5. The portion 7c (the central part of the π shape) of the magnetic core 7 around which the detection coil 8 is wound is formed so as to be outside the lamination plane of the iron core 5, and is arranged so that the detection coil 8 protrudes outside the iron core 5. doing. Here, the magnetic core 7 of the DC bias detecting element 6 is disposed on the upper or lower yoke or the side leg of the iron core 5 where the winding is not wound, and the detecting coil 8 is opposed to the windings 2 and 3. It is formed so as to be arranged on the surface opposite to the surface.

In this way, since the iron core 5 plays a role of a kind of magnetic shield for the leakage magnetic flux Φ _L of the winding, the detecting coil 8 has the leakage magnetic flux Φ _L generated by the load current flowing through the winding. Therefore, no induced voltage is generated in the detection coil 8 by a magnetic flux other than the magnetic flux Φ ₂ shunted from the main magnetic flux Φ ₁ passing through the steel plate 12. Thereby, the first
Since the output voltage V shown in FIG. 3C is obtained as described in the embodiment, the present invention is applied to a DC bias evaluation device for a conversion transformer or a power conversion system using the same, and the DC voltage of the transformer is reduced. The amount of magnetization can be evaluated accurately and reliably, and the DC bias suppression control of the transformer can be stably performed.

FIG. 11 shows a configuration diagram of an embodiment of the DC bias amount evaluation apparatus according to the present invention. In this example, the amount of DC bias is evaluated based on the output of the DC bias detecting element. As shown in the figure, the DC bias amount evaluating device includes a DC bias detecting element 6 and an arithmetic unit 9, and the arithmetic unit 9 amplifies an output voltage V of the DC bias detecting element 6 to a predetermined level. An A / D converter 31 for converting the output of the amplifier 30 from analog to digital, and an A / D converter 31
And an operation unit 32 for calculating the amount of DC bias of the transformer core 5 based on the output signal of the transformer core 5.

The calculating section 32 calculates the Δt shown in FIG. 12 from the output voltage V of the DC bias detecting element 6 converted into a digital value.
₁ and Δt ₂ are obtained, and for example, a DC bias amount Φ _dc is obtained by the following equation (2).

Φ _dc = Φ _max · sin {(Δt ₁ −Δt ₂ ) / (Δt ₁ −Δt ₂ )} (2) Alternatively, as shown in the waveform at the bottom of FIG. Then, the output voltage V of the DC bias detecting element 6 converted into a digital value is integrated, and a ΔV _dt waveform corresponding to a magnetic flux linking to the DC bias detecting element 6 is obtained, and the waveform is zero. Δt as the interval between points crossing the level
By obtaining ₁ and Δt ₂ , it is possible to obtain the DC bias amount Φ _dc in the same manner as in equation (2). Here, the zero level of the waveform of ΔV _dt is, for example, an intermediate value between the maximum value and the minimum value because the magnetic core 7 is positively or negatively magnetically saturated. This method is effective when the exciting voltage of the conversion transformer is a non-sine wave such as a PWM waveform. In other words, in the case of a PWM waveform or the like, the linkage magnetic flux of the DC bias detecting element has a sudden change even near the zero point of the main magnetic flux, so that a pulse-like voltage may be generated other than near the zero point of the main magnetic flux. From the waveform of the output voltage V, Δt ₁ ,
Δt ₂ cannot be unambiguously determined. However, even in such a case, Δt ₁ ′ and Δt ₂ ′ are uniquely determined.
Even when the excitation voltage is distorted, the amount of magnetization can be obtained.

In FIG. 12, when the output voltage V of the DC bias detecting element 6 is sufficiently large, the amplifier 30 may be omitted. Further, the method of calculating the amount of DC bias in the calculation unit 32 is not limited to the above-described method.

FIGS. 13 to 15 show application examples of the power conversion system to which the DC bias evaluation apparatus according to the present invention is applied, respectively.

FIG. 14 is a conceptual configuration diagram when applied to a DC power transmission system. In the figure, the AC / DC converter 41,
Reference numeral 42 denotes a power converter for converting alternating current to direct current or direct current to alternating current, which are connected to each other via a DC transmission line 43 and connected to an AC system via conversion transformers 44 and 45, respectively. ing. Transformers 44, 45
Are connected to DC bias evaluation devices 46 and 47, respectively. Any of the above-described embodiments is applied to the DC bias evaluation devices 46 and 47, and the conversion transformers 44 and 4 are respectively used.
And outputs to the controller 48, 49 5 of seeking DC polarization磁量[Phi _dc. The control device 48, 49, AC-DC to cancel DC polarization磁量[Phi _dc input converter 4
The ignition timing of the semiconductor switching elements constituting the first and second switching devices is corrected, and a command is sent to the AC / DC converters 41 and. As a result, the DC bias of the conversion transformers 44 and 45 is eliminated, and the inconvenience associated with the DC bias can be prevented.

FIG. 14 is a conceptual configuration diagram when applied to a reactive power compensation system. The power converter 51 is connected to a power system 53 via a conversion transformer 52. Also,
The power converter 51 is connected to a starting power supply 54 such as a capacitor. A DC bias evaluation device 55 is connected to the conversion transformer 52. DC bias evaluation device 55
Applies any of the above-described embodiments, calculates the DC bias amount Φ _dc of the conversion transformer 52, and outputs it to the control device 56. The control device 56 corrects and controls the firing timing of the semiconductor switch elements constituting the power converter 51 so as to cancel the input DC bias amount Φ _dc . As a result, the DC bias of the conversion transformer 52 is eliminated, the inconvenience associated with the DC bias is prevented, and the desired reactive power compensation can be stably performed.

In the configuration shown in FIG. 14, if a power storage device such as a battery or SMES is used in place of the starting power supply 54, it can be used as a power storage system.
Can be used for load leveling.

FIG. 15 is a conceptual configuration diagram when applied to a phase adjustment system. In the figure, a power converter 61 has a function of forward conversion and reverse conversion, and is connected to an AC system 63 via an adjustment transformer 62 and to a series transformer 64 connected in series to the AC system 63. Have been. Further, a DC bias evaluation device 65 is connected to the series transformer 64. Any of the above-described embodiments is applied to the DC bias evaluation device 65, and the DC bias amount Φ _dc of the series transformer 64 is applied.
And outputs it to the controller 66. In the control device 66,
Power converter 61 so as to cancel the polarization磁量[Phi _dc input
And corrects and controls the ignition timing of the semiconductor switch element that constitutes.

According to the phase adjustment system configured as described above, the power converter 61 applies an arbitrary phase difference to the ground voltages V ₁₁ and V ₁₂ at both ends of the power system 63 via the series transformer 64. the voltage V _s having applied to the power system 63, it is possible to arbitrarily adjust the phase difference between V ₁₁ and V _12. Then, by the action of the DC bias evaluation device 65 and the control device 66, the DC bias of the series transformer 64 is eliminated, the inconvenience associated with the DC bias is prevented, and the intended phase adjustment can be stably performed. it can.

[0041]

According to the present invention, when the main magnetic flux leaking from the laminated steel sheet and the leakage magnetic flux generated by the winding current interlink with the DC bias detecting element for detecting the DC bias amount or the like of the transformer. Can be eliminated.

[Brief description of the drawings]

FIG. 1 shows an overall configuration diagram of a power conversion system according to an embodiment to which a DC bias evaluation apparatus of the present invention is applied.

FIG. 2 is an enlarged perspective view of a DC bias detecting element according to FIG. 1;

FIG. 3 is an operation waveform diagram of each unit in the embodiment of FIG. 1;

FIG. 4 is an operation waveform diagram of each section of the related art shown for comparison with FIG.

FIG. 5 is an installation diagram of an embodiment of an orthogonal DC bias detecting element according to the present invention.

FIG. 6 is an enlarged view of the vicinity of the DC bias detection element in FIG. 5;

FIG. 7 is a schematic view of an embodiment of a shield type DC bias detecting element according to the present invention.

FIG. 8 is a schematic view of an embodiment of a compensation type DC bias detection element according to the present invention.

FIG. 9 is a schematic diagram of another embodiment of the compensation type DC bias detection element according to the present invention.

FIG. 10 is a schematic view showing a mounting position of a DC bias detecting element according to the present invention.

FIG. 11 is an overall configuration diagram of an embodiment of a DC bias evaluation apparatus of the present invention.

FIG. 12 is a waveform chart for explaining the operation of the DC bias evaluation apparatus.

FIG. 13 is a conceptual configuration diagram of an embodiment of a DC power transmission system to which the DC bias evaluation device of the present invention is applied.

FIG. 14 is a conceptual configuration diagram of an embodiment of a reactive power compensation system to which the DC bias evaluation apparatus of the present invention is applied.

FIG. 15 is a conceptual configuration diagram of an embodiment of a phase adjustment system to which the DC bias evaluation device of the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transformer for conversion, 4 ... Power converter, 5 ... Iron core, 6 ... DC bias detection element, 7, 13, 15 ... Magnetic core, 8 ... Detection coil, 9, 26 ... Calculation device, 10 ... DC bias Evaluation device, 1
DESCRIPTION OF SYMBOLS 1 ... Control device, 12 ... Laminated steel plate, 14 ... Shield member,
20, 23 ... compensating element, 21, 24 ... winding frame, 22, 25
... Compensation coil, 30 ... Amplifier, 31 ... A / D converter, 3
2. Arithmetic unit.

Claims (15)

[Claims] 1. A DC bias detecting element for detecting a DC bias of a transformer by arranging a detection coil around a magnetic core of a magnetic material and detecting the DC bias of the transformer by arranging the detection coil on both ends of the transformer. DC bias detection of a transformer characterized by being arranged in contact with a lamination surface of a laminated steel sheet to be formed, and a portion where the detection coil is wound is arranged at a fixed distance from a surface of the transformer core. element. 2. A transformer in which a DC bias detection element formed by winding a detection coil around a magnetic core of a magnetic material is disposed on a transformer core, wherein both ends of the core of the DC bias detection element are connected to the transformer. A transformer characterized by being arranged in contact with a laminated surface of a laminated steel sheet forming a core of a transformer, and wherein a portion where the detection coil is wound is arranged at a fixed distance from a surface of the transformer core. 3. A transformer in which a DC bias detection element formed by winding a detection coil around a magnetic core of a magnetic material is disposed on a transformer core, wherein both ends of the core of the DC bias detection element are connected to the transformer. The detection coil is disposed in contact with the lamination surface of the laminated steel sheet forming the device core, and the portion where the detection coil is wound is separated from the surface of the transformer core by a certain distance, and the axis direction of the detection coil is the axis of the transformer winding. A transformer characterized by being formed so as to be orthogonal to a direction. 4. A transformer in which a DC bias detection element formed by winding a detection coil around a magnetic core of a magnetic material is disposed on a transformer core, wherein both ends of the core of the DC bias detection element are connected to the transformer. The transformer core is disposed in contact with the laminated surface of the laminated steel sheet forming the iron core, and a portion where the detection coil is wound is separated from the surface of the transformer core by a predetermined distance. A transformer characterized by being covered with a shield member made of a magnetic material or a non-magnetic material except for a surface in contact with the transformer. 5. A transformer in which a DC bias detection element formed by winding a detection coil around a magnetic core made of a magnetic material is disposed on a transformer core, wherein a compensation coil is wound around an air core or a winding frame made of a non-magnetic material. A transformer, wherein a compensating element is disposed near the DC bias detecting element and is connected so as to subtract the induced voltage of the compensation coil from the induced voltage of the detection coil. 6. A transformer in which a DC bias detecting element according to claim 1 is disposed on a transformer core, wherein a detecting coil of the DC bias detecting element faces a winding of the transformer core. A transformer characterized by being arranged at a certain distance from a surface opposite to an iron core surface. 7. A DC bias detecting element, which is formed by winding a detecting coil around a magnetic core made of a magnetic material, is disposed in a transformer core, and a magnetic flux passing through the transformer core based on a voltage induced in the detecting coil. In the DC bias evaluation device for calculating the amount of DC bias and its polarity, the detection coil, the detection coil so that the magnetic flux passing between and outside of the laminated steel sheet forming the transformer core does not interlink. DC bias evaluation apparatus characterized by being arranged. 8. The DC bias evaluation apparatus according to claim 7, wherein both ends of the magnetic core of the DC bias detection element are arranged in contact with a laminated surface of a laminated steel sheet forming the transformer core, and the detection is performed. A DC bias evaluation apparatus characterized in that a portion where a coil is wound is formed at a certain distance from a surface of the transformer core. 9. The DC bias evaluation apparatus according to claim 7, wherein both ends of the magnetic core of the DC bias detecting element are arranged in contact with a laminated surface of a laminated steel sheet forming the transformer core, and the detection is performed. A part where the coil is wound is separated from the surface of the transformer core by a certain dimension, and an axial direction of the detection coil is formed to be orthogonal to an axial direction of the transformer winding. Evaluation device. 10. The DC bias evaluation apparatus according to claim 7, wherein both ends of a magnetic core of the DC bias detection element are arranged in contact with a laminated surface of a laminated steel sheet forming the transformer core, and the detection is performed. The wound portion of the coil is separated from the surface of the transformer core by a certain distance, and is covered with a shield member made of a magnetic material or a non-magnetic material except for a portion of the periphery of the DC bias detecting element which is in contact with the transformer core. DC bias evaluation apparatus characterized by the fact that 11. The DC bias evaluation apparatus according to claim 7, wherein the detection coil of the DC bias detection element is separated from the transformer core by a predetermined distance from a surface of the transformer core opposite to a core surface facing a winding. DC bias evaluation apparatus characterized by being arranged in a position. 12. A transformer comprising a DC magnetic field detecting element formed by winding a detecting coil around a magnetic core made of a magnetic material, and a magnetic flux passing through the transformer core based on a voltage induced in the detecting coil. In a DC bias evaluation device that calculates the amount of DC bias and its polarity, a compensating element formed by winding a compensation coil around an air core or a non-magnetic material winding frame is disposed near the DC bias detecting element, A DC bias evaluation apparatus characterized by being connected so that the induced voltage of the compensation coil is subtracted from the induced voltage of the detection coil. 13. A transformer having a DC magnetic field detecting element formed by winding a detection coil around a magnetic core of a magnetic material, and a magnetic flux passing through the transformer core based on a voltage induced in the detection coil. In a DC bias evaluation device that calculates the amount of DC bias and its polarity, a compensating element formed by winding a compensation coil around an air core or a non-magnetic material winding frame is disposed near the DC bias detecting element, A DC bias evaluation device for evaluating a DC bias amount of the transformer core based on outputs of a detection coil and the compensation coil. 14. The DC bias evaluation device according to claim 7, wherein the magnetic core of the DC bias detection element is formed of an iron-nickel alloy or an amorphous magnetic material. DC bias evaluation device. 15. A power converter using a semiconductor switch element, a conversion transformer connected to the AC side of the power converter, and a DC bias evaluation device for evaluating the bias of the conversion transformer. And a DC bias suppression control unit that controls the power converter so as to cancel the DC bias of the conversion transformer based on the evaluation of the DC bias evaluation device. A power conversion system, wherein the DC bias evaluation device is the DC bias evaluation device according to any one of claims 7 to 13.