Control device for power conversion device

Abstract

The present invention provides a control device for an electric power conversion device, which can suppress direct current magnetic flux by electrical control during three-phase operation when using a three-phase magnetic coupling inductor with a planar core. A DC-DC converter (10) has a three-phase magnetic coupling inductor, which has: a first outer coil (11), a second outer coil (13), an inner coil (12) and an iron core (20), wherein, in any combination, the directions of the magnetic fluxes generated in the first outer coil (11), the second outer coil (13) and the inner coil (12) are opposite to each other. The control device CTR of the DC-DC converter (10) performs control during three-phase operation so that the current value flowing through the inner coil (12) is close to the current value flowing through the first outer coil (11) and the second outer coil (13).

Description

Technical Field

[0001] The invention relates to a control device for a power conversion device. Background Art

[0002] In DC-DC converters of electric vehicles, HEVs (Hybrid Electrical Vehicles), etc., a reactor is used, which is formed by installing a coil around an iron core. In recent years, in order to adjust the ripple of the output current of the DC-DC converter, it has been proposed to use a three-phase magnetic coupling reactor as a reactor. In addition, it is preferred that the three-phase magnetic coupling reactor has a reduced size and improved cooling efficiency.

[0003] Therefore, non-patent document 1 describes a core having a three-dimensional structure, which is centered on a central core portion (center leg), and has outer core portions (outer legs) arranged every 120° on its circumference, and the central core portion and the outer core portions are connected at one end and the other end in the longitudinal direction, and the volume of the core is smaller than that of a case where three separate inductors are used. In addition, non-patent document 1 also describes a core having a planar structure in which an inner core portion and a pair of outer core portions arranged on both sides of the inner core portion are connected at one end and the other end in the longitudinal direction.

[0004] The core with a planar structure can be miniaturized in the same manner as the core with a three-dimensional structure, and has better cooling performance than the core with a three-dimensional structure. However, since the magnetic flux generated by the inner coil and the magnetic flux generated by the outer coil of the core with a planar structure are not uniform during three-phase drive, the DC magnetic flux cannot be fully offset, so there is a tendency to increase the volume in order to prevent the magnetic flux from being saturated.

[0005] On the other hand, in the three-phase magnetic coupling reactor described in Patent Document 1, it is described that a groove is provided on the contact surface of the middle leg to increase the magnetic resistance of the middle leg.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2002-208519

[0009] Non-patent literature

[0010] Non-patent document 1: A Current Sharing Method Utilizing Single BalancingTransformer for a Multiphase LLC Resonant Converter With Integrated Magnetics {IEEE Journal of Emerging and Selected Topics in Power Electronics (Volume: 6, Issue: 2, June 2018)}

[0011] A method of suppressing the DC magnetic flux on the core having a planar structure by adopting the structure described in Patent Document 1 is known, but there is room for considering other methods. Summary of the invention

[0012] The present invention provides a control device for a power conversion device capable of suppressing a DC magnetic flux by electrical control during a three-phase operation in a three-phase magnetic coupling reactor using an iron core having a planar structure.

[0013] The present invention provides a control device for a power conversion device using a three-phase magnetic coupling reactor, comprising:

[0014] a first outer coil;

[0015] a second outer coil;

[0016] an inner coil disposed between the first outer coil and the second outer coil; and

[0017] The core comprises: a first outer core portion on which the first outer coil is wound; a second outer core portion on which the second outer coil is wound; and an inner core portion on which the inner coil is wound, wherein:

[0018] The first outer core portion, the second outer core portion, and the inner core portion are respectively extended along a first direction and arranged in a second direction orthogonal to the first direction.

[0019] The first outer core portion, the second outer core portion, and one end side of the inner core portion in the first direction are connected by a first connecting portion extending in the second direction.

[0020] The first outer core portion, the second outer core portion, and the other end side of the inner core portion in the first direction are connected by a second connecting portion extending in the second direction.

[0021] In any combination, directions of the magnetic fluxes generated in the first outer coil, the second outer coil, and the inner coil are opposite to each other, wherein,

[0022] The control device controls, in a three-phase operation in which current flows through all coils of the first outer coil, the second outer coil, and the inner coil, so that the current value flowing through the inner coil approaches the current value flowing through the first outer coil and the second outer coil.

[0023] According to the present invention, in a power conversion device using a three-phase magnetic coupling reactor having a planar structure, during three-phase operation, a DC magnetic flux can be suppressed by electrical control. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 1 is a circuit diagram of a three-phase interleaved DC-DC converter 10 .

[0025] Figure 2 1 is a perspective view of a three-phase magnetic coupling reactor 1 used in a DC-DC converter 10 .

[0026] Figure 3 It is a plan view of the three-phase magnetic coupling reactor 1 and is used to explain the magnetic flux generated inside the core 20 .

[0027] Figure 4 1 is a graph showing currents flowing through the respective coils when the current values ​​of the first outer coil 11 , the second outer coil 13 , and the inner coil 12 are controlled to be equal in the three-phase operation.

[0028] Figure 5 It is shown in Figure 4 A graph of the magnetic flux density of the first outer core portion 21, the second outer core portion 23 and the inner core portion 22 under the control of .

[0029] Figure 6 1 is a graph showing currents flowing through the coils in a case where the current value of the inner coil 12 is controlled to be larger than the current values ​​of the first outer coil 11 and the second outer coil 13 in the three-phase operation.

[0030] Figure 7 It is shown in Figure 6 A graph of the magnetic flux density of the first outer core portion 21, the second outer core portion 23 and the inner core portion 22 under the control of .

[0031] Description of Reference Numerals

[0032] 1 Three-phase magnetic coupling reactor

[0033] 10. DC-DC Converter

[0034] 11 First outer coil

[0035] 12 Inner coil

[0036] 13 Second outer coil

[0037] 20 Iron Heart

[0038] 21 First outer core portion

[0039] 22 Inner core

[0040] 23 Second outer core part

[0041] CTR Control Unit DETAILED DESCRIPTION

[0042] Hereinafter, a control device for a power conversion device according to an embodiment of the present invention will be described with reference to the drawings.

[0043] First, a three-phase interleaved DC-DC converter as an example of a power conversion device to be controlled by the control device of the present invention will be described. Figure 1 is a circuit diagram showing a three-phase interleaved DC-DC converter.

[0044] Figure 1 The three-phase interleaved DC-DC converter 10 shown (hereinafter referred to as the DC-DC converter 10) includes: a smoothing capacitor C1, a three-phase magnetic coupling inductor 1 having three coils 11 to 13 (hereinafter referred to as the three-phase inductor), switching units SW1, SW2, SW3, SW4, SW5, SW6, a smoothing capacitor C2 and a control device CTR.

[0045] This DC-DC converter steps up the input voltage V1 when operating with the voltage V1 on the smoothing capacitor C1 side as an input voltage and the voltage V2 on the smoothing capacitor C2 side as an output voltage.

[0046] In the three-phase reactor 1, the input terminals of the coils 11 to 13 are connected in parallel to the power supply line on the high potential side. The output terminal of the coil 11 of the three-phase reactor 1 is connected to the middle node of the switch section SW1 and the switch section SW2 connected in series, forming a first voltage conversion section 14. The output terminal of the coil 12 of the three-phase reactor 1 is connected to the middle node of the switch section SW3 and the switch section SW4 connected in series, forming a second voltage conversion section 15. The output terminal of the coil 13 of the three-phase reactor 1 is connected to the middle node of the switch section SW5 and the switch section SW6 connected in series, forming a third voltage conversion section 16. The switch sections SW1, SW2, SW3, SW4, SW5, and SW6 each have a switching element such as an IGBT (Insulated Gate Bipolar Transistor) and a return diode connected in parallel with the switching element. It should be noted that the "three phases" of the three-phase inductor 1 means that the number of conversion units is three, the single-phase operation described later means that the number of conversion units performing operations in the first voltage conversion unit 14 to the third voltage conversion unit 16 is one, the two-phase operation means that the number of conversion units performing operations in the first voltage conversion unit 14 to the third voltage conversion unit 16 is two, and the three-phase operation means that the number of conversion units performing operations in the first voltage conversion unit 14 to the third voltage conversion unit 16 is three.

[0047] Each switching element of the switch section SW1 to SW6 is controlled to be turned on and off according to a signal from the control device CTR. The three voltage conversion sections 14, 15, and 16 of the DC-DC converter 10 are electrically connected in parallel, and by turning on and off the switching element of at least one voltage conversion section 14, 15, and 16 at a desired time, the voltage V1 is directly boosted in a direct current manner and the voltage V2 is output. The on and off switching operation of the switch sections SW1, SW2, SW3, SW4, SW5, and SW6 of the voltage conversion sections 14, 15, and 16 is controlled by a switching signal having a pulse-shaped prescribed duty ratio from the switch control section to the DC-DC converter 10.

[0048] When the switching elements of the voltage conversion units 14, 15, and 16 are controlled to be switched on and off, in the on operation, the input current to the DC-DC converter 10 flows to the switching element side, and the three-phase reactor 1 stores energy, and in the off operation, the input current to the DC-DC converter 10 flows to the diode side, and the three-phase reactor 1 releases the stored energy. In the single-phase operation of driving only one of the three voltage conversion units 14, 15, and 16 of the DC-DC converter 10, the current flowing through one of the voltage conversion units of the DC-DC converter 10 in the off operation is output. In addition, in the two-phase operation of driving two of the three voltage conversion units 14, 15, and 16 of the DC-DC converter 10, the on-off switching phases of the driven voltage conversion units 14, 15, and 16 are staggered by 180 degrees. In the three-phase operation for driving all the three voltage conversion units 14, 15, 16 of the DC-DC converter 10, staggered control is performed to shift the on / off switching phases of the voltage conversion units 14, 15, 16 by 120 degrees.

[0049] The ripple of the output current can be reduced by increasing the number of driven voltage conversion units 14, 15, 16. In addition, as the number of driven voltage conversion units 14, 15, 16 increases, the switching loss increases, but the conduction loss decreases. The control device CTR selects the number of driven voltage conversion units 14, 15, 16 using a map or the like representing the energy efficiency of the DC-DC converter 10 in consideration of the loss of each of the driven voltage conversion units 14, 15, 16.

[0050] The structure of the three-phase reactor 1 is described below. In the following description, the coils 11 and 13 arranged on the outside of the three coils 11 to 13 are respectively referred to as the first outer coil 11 and the second outer coil 13, and the coil 12 sandwiched between the first outer coil 11 and the second outer coil 13 is referred to as the inner coil 12. Figure 2 and Figure 3 As shown in FIG. 1 , the positional relationship of each part of the three-phase reactor 1 will be described using an orthogonal coordinate system of an X-axis, a Y-axis, and a Z-axis.

[0051] like Figure 2 As shown, the three-phase reactor 1 includes a first outer coil 11 , a second outer coil 13 , an inner coil 12 , an iron core 20 , and a case 40 that accommodates them.

[0052] The core 20 may be formed, for example, by press-forming soft magnetic powder, or by laminating thin electromagnetic steel sheets. Figure 3As shown, the core 20 includes: a first outer core portion 21, an inner core portion 22, and a second outer core portion 23, which are extended along the X-axis direction and arranged parallel to each other along the Y-axis direction; a first connecting portion 24, which is extended along the Y-axis direction at one end side in the X-axis direction, and connects the first outer core portion 21, the inner core portion 22, and the second outer core portion 23; and a second connecting portion 25, which is extended along the Y-axis direction at the other end side in the X-axis direction, and connects the first outer core portion 21, the inner core portion 22, and the second outer core portion 23. In other words, the core 20 is a core having a planar structure arranged on an XY plane formed along the X-axis direction and the Y-axis direction. The X-axis direction is the first direction of the present invention, and the Y-axis direction is the second direction of the present invention.

[0053] The first outer core portion 21 is wound with the first outer coil 11, the second outer coil 13 is wound with the second outer core portion 23, and the inner coil 12 is wound with the inner core portion 22. Therefore, the first outer core portion 21, the inner coil 12, and the second outer coil 13 are respectively extended in the X-axis direction and arranged in the Y-axis direction.

[0054] In the three-phase reactor 1, when current flows through any two or more coils among the coils 11, 12, and 13, the directions of the magnetic fluxes generated in the coils (hereinafter referred to as the magnetic flux directions) are controlled to be opposite to each other in any combination, so that the DC magnetic flux generated in the core can be reduced. As a result, the magnetic saturation of the core 20 can be suppressed.

[0055] In the two-phase operation, by selecting the first outer coil 11 and the second outer coil 13, the DC magnetic flux generated in the core becomes uniform due to the current flowing in the coils 11 and 13, thereby canceling the DC magnetic flux generated in the core. It should be noted that in the single-phase operation, since the operation of canceling the magnetic flux does not occur, any one of the coils 11, 12, and 13 can be selected as the coil to be operated.

[0056] In three-phase operation, the current flowing through each coil 11, 12, 13 cancels out at least a portion of the magnetic flux generated in the iron core, thereby reducing the magnetic flux generated in the iron core of each coil 11, 12, 13. However, in order to cancel out more magnetic flux, the magnetic flux generated in the iron core needs to be made uniform.

[0057] Figure 4 1 is a graph showing currents flowing through the respective coils when the current values ​​of the first outer coil 11 , the second outer coil 13 , and the inner coil 12 are controlled to be equal in the three-phase operation. Figure 5 It is shown in Figure 4A graph of the magnetic flux density of the first outer core portion 21, the second outer core portion 23 and the inner core portion 22 under the control of .

[0058] from Figure 4 and Figure 5 It can be seen that in the three-phase operation of the three-phase reactor 1, the magnetic flux density of the first outer core portion 21, the second outer core portion 23, and the inner core portion 22 is not uniform even when the current values ​​of the first outer coil 11, the second outer coil 13, and the inner coil 12 are controlled to be equal. In this example, it can be seen that the magnetic flux density of the inner core portion 22 is greater than the magnetic flux density of the first outer core portion 21 and the second outer core portion 23.

[0059] Therefore, the control device CTR controls the current value I2 flowing through the inner coil 12 to be close to the current value I0 flowing through the first outer coil 11 and the second outer coil 13. Specifically, the control device CTR controls the current value I2 flowing through the inner coil 12 by adjusting the duty ratio in the on-off switching operation of the switch parts SW3 and SW4 of the second voltage conversion part 15.

[0060] Figure 6 1 is a graph showing currents flowing through the coils in a case where the current value of the inner coil 12 is controlled to be larger than the current values ​​of the first outer coil 11 and the second outer coil 13 in the three-phase operation. Figure 7 It is shown in Figure 6 A graph of the magnetic flux density of the first outer core portion 21, the second outer core portion 23 and the inner core portion 22 under the control of .

[0061] from Figure 6 and Figure 7 It can be seen that in the three-phase operation of the three-phase reactor 1, by controlling the current value of the inner coil 12 to be smaller than the current value of the first outer coil 11 and the second outer coil 13, the magnetic flux density of the first outer core portion 21, the second outer core portion 23 and the inner core portion 22 is substantially uniform. It should be noted that in this example, the magnetic resistance of the inner core portion 22 is lower than the magnetic resistance of the first outer coil 11 and the second outer coil 13, but in the case where the magnetic resistance of the inner core portion 22 is higher than the magnetic resistance of the first outer coil 11 and the second outer coil 13, by controlling the current value of the inner coil 12 to be larger than the current value of the first outer coil 11 and the second outer coil 13, the magnetic flux density of the first outer core portion 21, the second outer core portion 23 and the inner core portion 22 can be substantially uniform.

[0062] In the above, various embodiments are described with reference to the accompanying drawings, but the present invention is certainly not limited to these examples. Obviously, those skilled in the art can think of various variations or modifications within the scope described in the claims, and it should be understood that these variations and modifications also belong to the technical scope of the present invention. In addition, the various constituent elements in the above embodiments may also be arbitrarily combined within the scope of the gist of the invention.

[0063] At least the following matters are described in this specification. It should be noted that, although corresponding components and the like in the above-mentioned embodiments are shown in brackets, the present invention is not limited thereto.

[0064] (1) A control device for a power conversion device, the control device being a control device (control device CTR) for a power conversion device (DC-DC converter 10) using a three-phase magnetic coupling reactor (three-phase magnetic coupling reactor 1),

[0065] The three-phase magnetic coupling reactor comprises:

[0066] A first outer coil (a first outer coil 11);

[0067] A second outer coil (a second outer coil 13);

[0068] an inner coil (inner coil 12) disposed between the first outer coil and the second outer coil; and

[0069] The core (core 20) includes: a first outer core portion (first outer core portion 21) on which the first outer coil is wound; a second outer core portion (second outer core portion 23) on which the second outer coil is wound; and an inner core portion (inner core portion 22) on which the inner coil is wound, wherein:

[0070] The first outer core portion, the second outer core portion, and the inner core portion are respectively extended along a first direction (X-axis direction), and arranged in a second direction (Y-axis direction) orthogonal to the first direction.

[0071] The first outer core portion, the second outer core portion, and one end side of the inner core portion in the first direction are connected by a first connecting portion (first connecting portion 24) extending in the second direction.

[0072] The other ends of the first outer core portion, the second outer core portion, and the inner core portion in the first direction are connected by a second connecting portion (second connecting portion 25) extending in the second direction.

[0073] In any combination, directions of the magnetic fluxes generated in the first outer coil, the second outer coil, and the inner coil are opposite to each other,

[0074] The control device controls, in a three-phase operation in which current flows through all coils of the first outer coil, the second outer coil, and the inner coil, so that the current value flowing through the inner coil approaches the current value flowing through the first outer coil and the second outer coil.

[0075] In a three-phase magnetic coupling reactor having a planar structure, since the magnetic resistance of the magnetic circuit when the current flows through the first outer coil and the second outer coil is different from the magnetic resistance of the magnetic circuit when the current flows through the inner coil in terms of structure, the current values ​​of the current flowing through the first outer coil and the second outer coil and the current flowing through the inner coil are different during three-phase operation. If the current values ​​are different, the DC magnetic flux generated in the core cannot be fully offset, so in order to prevent the magnetic flux from being saturated, the size of the core has to be increased. According to (1), in the three-phase operation of the power conversion device, by controlling the current value flowing through the inner coil to be close to the current value flowing through the first outer coil and the second outer coil, the magnetic flux generated in the core can be offset against each other, and the core can be miniaturized.

[0076] (2) The control device for the power conversion device according to (1), wherein:

[0077] The control device is in the three-phase operation,

[0078] When the magnetic resistance of the inner core portion is greater than the magnetic resistance of the first outer core portion and the second outer core portion, control is performed so that the current value flowing through the inner coil is greater than the current value flowing through the first outer coil and the second outer coil,

[0079] When the magnetic resistance of the inner core portion is smaller than the magnetic resistance of the first outer core portion and the second outer core portion, control is performed so that the current value flowing through the inner coil is smaller than the current value flowing through the first outer coil and the second outer coil.

[0080] According to (2), when the magnetic resistance of the inner core portion is large, the value of the current flowing through the inner coil is increased, and when the magnetic resistance of the inner core portion is small, the value of the current flowing through the inner coil is reduced, thereby making the magnetic flux generated in the core uniform.

Claims

1. A control device for a power conversion device, the control device being a control device for a power conversion device using a three-phase magnetic coupling reactor, the three-phase magnetic coupling reactor comprising: a first outer coil; a second outer coil; an inner coil disposed between the first outer coil and the second outer coil; and The core comprises: a first outer core portion on which the first outer coil is wound; a second outer core portion on which the second outer coil is wound; and an inner core portion on which the inner coil is wound, wherein: The first outer core portion, the second outer core portion, and the inner core portion are respectively extended along a first direction and arranged in a second direction orthogonal to the first direction. The first outer core portion, the second outer core portion, and one end side of the inner core portion in the first direction are connected by a first connecting portion extending in the second direction. The first outer core portion, the second outer core portion, and the other end side of the inner core portion in the first direction are connected by a second connecting portion extending in the second direction. The first outer coil, the second outer coil, and the inner coil are configured such that, in a three-phase operation in which currents in the same direction flow through all of the first outer coil, the second outer coil, and the inner coil, magnetic fluxes generated in the first outer core portion, the second outer core portion, and the inner core portion cancel each other out, wherein: The control device, in the three-phase operation in which current is flown through all of the first outer coil, the second outer coil, and the inner coil, performs the operation, When the magnetic resistance of the inner core portion is greater than the magnetic resistance of the first outer core portion and the second outer core portion, control is performed so that the current value flowing through the inner coil is greater than the current value flowing through the first outer coil and the second outer coil, When the magnetic resistance of the inner core portion is smaller than the magnetic resistance of the first outer core portion and the second outer core portion, control is performed so that the current value flowing through the inner coil is smaller than the current value flowing through the first outer coil and the second outer coil.

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