Power conversion system

Abstract

To provide a power conversion system having a multiple-core multi-coil transformer structure for increasing a power capacity, whole suppressing cost and complexity of magnetic design.SOLUTION: A power conversion system has a power conversion unit 100 having at least two power electronics converters 102a, 102b and a high frequency transformer 101. The high frequency transformer has a transformer core 103. A first to a third coils 104a, 104b, 105 are wound around the transformer core. The first coil is connected to the power electronics converter 102a, the second coil 104b is connected to the second power electronics converter 102b, and the third coil 105 is connected to a coil of another power conversion unit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the configuration of a power conversion system. More specifically, the present invention relates to the configuration of a solid-state transformer (SST) equipped with a high-frequency transformer.

Background Art

[0002] As is known in this technical field, in power electronics, there is a classification of circuits called power converter circuits (or more simply "power converters"). A power converter converts electrical energy from one form to another. For example, a power converter converts between AC power and DC power and changes the voltage or frequency of a signal, or a combination thereof.

[0003] Also, as is known, conventionally, power converters having an insulating structure based on a high-frequency transformer have been widely used. Hereinafter, "high-frequency transformer" and "transformer" will be used synonymously.

[0004] Also, as is known, a single-core multi-winding transformer configuration is applied to power exchange between various power electronics converters connected to a transformer core. The power exchange is performed by transmission of magnetic energy through the transformer core. This configuration is suitable for applications having three or more input / output ports, that is, multi-port applications.

[0005] As background art in this technical field, for example, there is a technology such as Patent Document 1. Patent Document 1 relates to the structure of a single-core multi-winding high-frequency transformer.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] Figure 10 shows a simplified configuration of the prior art, corresponding to Patent Document 1, illustrating the magnetic coupling of multiple power converters

[0102] via a single transformer core

[0103] multi-winding transformer

[0900] .

[0008] The single-core, multi-winding transformer configuration presents the following technical problems:

[0009] To increase the power capacity that a power conversion system can handle, it is necessary to increase the number of power electronics converters connected to the transformer core.

[0010] However, increasing power capacity by increasing the number of power electronics converters connected to the transformer core requires redesigning the original multi-winding transformer to accommodate the additional transformer windings. Furthermore, after redesign, the original transformer must be replaced with the newly designed one. This significantly increases the cost of power expansion.

[0011] Furthermore, the complexity of the magnetic design increases because multiple windings are wound around the same transformer core. For example, if four power electronics converters are connected to one transformer core, the magnetic design consists of six (i.e., 4C2) mutual inductances, while if six power electronics converters are connected to one transformer core, the magnetic design consists of fifteen (i.e., 6C2) mutual inductances, and so on. Therefore, the complexity of the magnetic design increases with the number of power electronics converters connected to the transformer core.

[0012] Therefore, the object of the present invention is to provide a power conversion system having a multi-core, multi-winding transformer configuration that can increase power capacity while suppressing costs and the complexity of magnetic design. [Means for solving the problem]

[0013] To solve the above problems, the present invention provides a power conversion unit having a high-frequency transformer together with at least two power electronics converters, wherein the high-frequency transformer has a transformer core, and first, second, and third windings are wound around the transformer core, the first winding being connected to a first power electronics converter, the second winding being connected to a second power electronics converter, and the third winding being connected to a winding of another power conversion unit. A power conversion system used in an EV charging device, the EV charging device having a plurality of power conversion units that input AC power and output DC power, and the number of power conversion units connected to a single EV charging port is changeable, each of the plurality of power conversion units has a converter cell including an AC / DC conversion circuit that inputs AC power and a DC / DC conversion circuit connected to the AC / DC conversion circuit via a capacitor and outputting DC power, the DC / DC conversion circuit has a three-winding high-frequency transformer between the DC / AC conversion stage and the AC / DC conversion stage, the third winding of the three-winding high-frequency transformer of all converter cells is connected in parallel to establish magnetic coupling between all power conversion units, the plurality of AC input terminals of the plurality of AC / DC conversion circuits are connected in series with each other, and the plurality of DC outputs of the three three-phase converter cells provided in each power conversion unit are connected in parallel with each other. The present invention provides a power conversion system characterized by the following features. [Effects of the Invention]

[0014] According to the present invention, a power conversion system having a multi-core, multi-winding transformer configuration can be realized that can increase power capacity while suppressing costs and the complexity of magnetic design.

[0015] This expands the applications of power conversion systems and can contribute, for example, to the widespread adoption of multi-port chargers for electric vehicles (EVs).

[0016] Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0017] [Figure 1] This figure shows the schematic configuration of the power conversion system according to Example 1. [Figure 2] Figure 1 shows an example of power electronics converters 102a and 102b. [Figure 3] Figure 1 shows an example of power electronics converters 102a and 102b. [Figure 4] This figure shows the schematic configuration of the power conversion system according to Example 2. [Figure 5] This figure shows the schematic configuration of the power conversion system according to Example 3. [Figure 6] Figure 5 is a conceptual diagram illustrating the flow of power (current) in the power conversion system. [Figure 7] It is a diagram showing a schematic configuration of a power conversion system according to Example 4. [Figure 8] It is a diagram showing a schematic configuration and the flow of power (current) of a power conversion system according to Example 5. [Figure 9] It is a diagram showing a schematic configuration of a power conversion system according to Example 6. [Figure 10] It is a diagram showing a schematic configuration of a single-core multi-winding high-frequency transformer shown in Patent Document 1 which is a prior art document.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and detailed descriptions of overlapping parts are omitted.

Examples

[0019] Referring to FIGS. 1 to 3, a power conversion system according to Example 1 of the present invention will be described.

[0020] FIG. 1 is a block diagram showing magnetic coupling of a plurality of power electronics converters [102a, 102b] via a plurality of three-winding high-frequency transformers

[0101] as an embodiment of the present invention.

[0021] Each unit

[0100] includes a three-winding high-frequency transformer

[0101] having two power electronics converters [102a, 102b]. Of the windings wound around the transformer core

[0103] , two windings [104a, 104b] are connected to the power electronics converter blocks [102a, 102b] respectively. The third winding

[0105] is connected in parallel with the third windings of all the other units. Thereby, the power electronics converters of 'n' units are magnetically coupled.

[0022] All power electronics converters [102a,102b] have AC ports [108a,109a,108b,109b] at one end and DC ports [106a,107a,106b,107b] at the other end. The power conversion circuits [102a,102b] can operate as bidirectional power conversion circuits with power flow from the DC ports [106,107] to the AC ports [108,109] or vice versa.

[0023] According to the power conversion system of this embodiment, the cost of expanding power capacity is reduced because an additional power electronics converter can be integrated into the system via a three-winding transformer configuration without replacing the original transformer.

[0024] Furthermore, since each transformer has only three windings, the magnetic design of the transformer is simplified. Even when using multiple power electronics converters, the number of windings per transformer core remains at three.

[0025] Figure 2 is a circuit diagram showing an exemplary power electronics converter [102a, 102b].

[0026] As shown in Figure 2, the power electronics converter [102a, 102b] comprises a single-phase full-bridge circuit using semiconductor devices

[0200] such as MOSFETs and IGBTs (in Figure 2, the IGBT and diode are connected in antiparallel to each other), and a DC link capacitor

[0201] connected in parallel to the single-phase full-bridge circuit. The connection points at the midpoints of each half-bridge constitute AC ports [108b, 109b].

[0027] The AC ports [108b,109b] are always connected to the transformer core

[0103] via the winding [104b]. Meanwhile, the parallel connection point between the two half-bridge circuits and the DC link capacitor

[0201] constitutes the DC ports [106b,107b]. The power conversion circuits [102a,102b] can operate as bidirectional power conversion circuits with power flow from the DC ports [106b,107b] to the AC ports [108b,109b] or vice versa.

[0028] Figure 3 is a circuit diagram showing another exemplary power electronics converter [102a, 102b].

[0029] As shown in Figure 3, the power electronics converter [102a, 102b] is a parallel connection of a half-bridge circuit using semiconductor devices

[0200] such as MOSFETs and IGBTs (in Figure 3, the IGBT and diode are connected in antiparallel to each other) and a series connection circuit of DC link capacitors

[0201] .

[0030] The connection points at the midpoint of the half-bridge and the midpoint of the DC link capacitor

[0201] constitute AC ports [108b, 109b]. The AC ports [108b, 109b] are always connected to the transformer core

[0103] via the winding [104b]. On the other hand, the parallel connection points between the half-bridge circuit and the DC link capacitor

[0201] constitute DC ports [106b, 107b]. The power conversion circuits [102a, 102b] can operate as bidirectional power conversion circuits with power flow from the DC ports [106b, 107b] to the AC ports [108b, 109b] or vice versa. [Examples]

[0031] Referring to Figure 4, a power conversion system according to Embodiment 2 of the present invention will be described.

[0032] Figure 4 is a block diagram showing the expansion from four to six power electronics converters [102a, 102b]. For simplicity, only the transformer windings for the AC ports [108a, 108b, 109a, 109b] are shown in Figure 4, and the power electronics converters [102a, 102b] are omitted.

[0033] The left side of Figure 4 shows the arrangement of two 3-winding high-frequency transformers

[0101] for connecting four power electronics converters [102a, 102b] with four AC ports [108a, 109a, 108b, 109b]. The right side of Figure 4 shows the arrangement of three 3-winding high-frequency transformers

[0101] for connecting six power electronics converters [102a, 102b] with six AC ports [108a, 109a, 108b, 109b].

[0034] As shown in Figure 4, expanding the power electronics converters [102a,102b] from four to six does not require redesigning and replacing the original two three-winding high-frequency transformers

[0101] in the four-power electronics converter [102a,102b] system. Rather, expanding the power electronics converters [102a,102b] from four to six only requires adding three three-winding high-frequency transformers

[0101] .

[0035] For four power electronics converters [102a,102b] or six power electronics converters [102a,102b], the number of windings per transformer core remains the same, i.e., three. Therefore, the number of mutual inductances per transformer core also remains the same, i.e., three. This simplifies the design of the additional three-winding high-frequency transformer

[0101] for expanding the power electronics converters [102a,102b] from four to six. [Examples]

[0036] A power conversion system according to Embodiment 3 of the present invention will be described with reference to Figures 5 and 6.

[0037] Figure 5 is a block diagram showing an EV charging device

[0500] for an electric vehicle

[0508] that uses magnetic coupling between a three-winding high-frequency transformer

[0101] and power electronics converters [102a, 102b, 102c].

[0038] The EV charging device

[0500] comprises a three-phase four-wire AC power supply

[0501] and a plurality of (m) converter units

[0502] that receive three-phase AC power via a three-phase reactor

[0503] . A three-phase three-wire AC power supply can be used instead of the three-phase four-wire AC power supply

[0501] , in which case the fourth (neutral) wire [505a] does not exist.

[0039] Each converter unit

[0502] is equipped with three three-phase converter cells

[0504] for inputting single-phase AC power from one phase of a three-phase four-wire AC power supply

[0501] .

[0040] Each converter cell

[0504] includes an AC / DC conversion circuit [102c] that converts single-phase AC power to DC power, a DC / AC conversion circuit [102a] that subsequently converts the DC power to single-phase AC power for magnetic coupling, and an AC / DC conversion circuit [102b] that converts the AC power output by the DC / AC conversion circuit [102a] to DC power.

[0041] The DC output terminal of the AC / DC converter circuit [102c] is connected to the DC input terminal of the DC / AC converter circuit [102a] by the DC link [106a, 107a]. The third winding

[0105] of the three-winding high-frequency transformer

[0101] of all converter cells

[0504] is connected in parallel to establish magnetic coupling between all converter units

[0502] .

[0042] In each phase, multiple (m) AC / DC conversion circuits [102c] are connected in series with each other. One end of the AC input terminal [108c] is connected to one phase (e.g., U phase) of a three-phase four-wire AC power supply

[0501] , and the other end

[0505] is connected to the neutral point N of the three-phase four-wire AC power supply

[0501] via a neutral wire [505a]. In a three-phase three-wire AC power supply, there is no neutral wire [505a], so the other end

[0505] is not connected to the AC power supply.

[0043] The DC output terminals [106b, 107b] of the three AC / DC conversion circuits [102b] for each three phases of each converter unit

[0502] are connected in parallel. This shows how the DC output of each converter unit

[0502] is configured.

[0044] Each DC output of the multiple (m) converter units

[0502] is connected to an EV charging port (charging station)

[0506] via a connecting cable

[0507] . Each of the multiple (m) EV charging ports (charging stations)

[0506] is connected to an EV

[0508] via a charging cable

[0509] . "m" indicates the number of converter units

[0502] and EV charging ports

[0506] , and is an integer of 2 or more.

[0045] Figure 6 is a block diagram showing the flow of power (current)

[0600] from a three-phase four-wire AC power supply

[0501] to multiple EVs

[0508] through a magnetically coupled three-winding high-frequency transformer

[0101] .

[0046] In the EV charging device

[0500] , multiple EVs

[0508] are connected to the EV charging port

[0506] . The flow of power (current) from the three-phase four-wire AC power supply

[0501] to the EVs

[0508] is indicated by the shaded arrow

[0600] . The connected EVs

[0508] are in charging mode because power (current) flows from the three-phase four-wire AC power supply

[0501] to the EVs

[0508] . Similarly, reverse power flow from the EVs

[0508] to the three-phase four-wire AC power supply

[0501] is also possible, but is not shown in this diagram.

[0047] The power consumed by the EV

[0508] is shared by all converter units

[0502] through the power (current) flowing through the third winding

[0105] of the three-winding high-frequency transformer

[0101] of all converter units

[0502] . [Examples]

[0048] Referring to Figure 7, a power conversion system according to Embodiment 4 of the present invention will be described.

[0049] Figure 7 shows another possibility for connecting the converter units

[0502] to the EV charging ports

[0506] . Two converter units

[0502] are connected to one EV charging port

[0506] . Similarly, three or more converter units

[0502] can be connected to one EV charging port

[0506] . In this case, the number of converter units

[0502] and EV charging ports

[0506] are not the same. Therefore, "m" is an integer of 2 or more indicating the number of converter units, and "n" is an integer of 1 or more indicating the number of EV charging ports. [Examples]

[0050] Referring to Figure 8, a power conversion system according to Embodiment 5 of the present invention will be described.

[0051] Figure 8 is a block diagram showing the flow of power (current)

[0600] from a three-phase four-wire AC power supply

[0501] to a single EV

[0508] through a magnetically coupled three-winding high-frequency transformer

[0101] .

[0052] In the EV charging device

[0500] , only one EV

[0508] is connected to the EV charging port

[0506] of one converter unit

[0502] . The remaining EV charging ports

[0506] are not connected to any of the EVs

[0508] . The connected EV

[0508] is in charging mode, and power (current) flows from the three-phase four-wire AC power supply

[0501] to the EV

[0508] . Similarly, reverse power flow from the EV

[0508] to the three-phase four-wire AC power supply

[0501] is also possible, but is not shown in this diagram. The flow of power (current) from the three-phase four-wire AC power supply

[0501] to the EV

[0508] is indicated by a shaded arrow

[0600] .

[0053] The power consumed by the EV

[0508] is shared by all converter units

[0502] through the power (current) flowing through the third winding

[0105] of the three-winding high-frequency transformer

[0101] of all converter units

[0502] . [Examples]

[0054] Referring to Figure 9, a power conversion system according to Embodiment 6 of the present invention will be described.

[0055] Figure 9 is a block diagram showing the magnetic coupling of multiple power electronics converters [102a, 102b] via multiple multi-winding high-frequency transformers

[0801] as an extension of the present invention.

[0056] Each power conversion unit

[0800] comprises a multi-winding high-frequency transformer

[0801] having multiple power electronics converters [102a, 102b] ranging from 1 to "j". All windings [104a, 104b] wound around the transformer core

[0103] except for one winding

[0802] are connected to the power electronics converters [102a, 102b]. The winding

[0802] not connected to the power electronics converters [102a, 102b] is connected in parallel to the similar windings of all other power conversion units

[0800] . This configuration magnetically couples the power electronics converters [102a, 102b] of n power conversion units

[0800] .

[0057] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0058] 100: Power conversion unit (one unit consisting of two power electronics converters and one three-winding high-frequency transformer) 101:3 winding high-frequency transformer 102, 102a, 102b, 102c: Power Electronics Converters 103: Transformer core 104: Transformer windings 104a, 104b: First and second windings of the transformer 105: Third winding of the transformer 106, 106a, 106b, 107, 107a, 107b: DC ports 108, 108a, 108b, 108c, 109, 109a, 109b, 109c: AC port 200: Semiconductor Equipment 201: DC Link Capacitor 500:EV charging equipment 501: Three-phase four-wire AC power supply 502: Converter Unit 503: Three-phase reactor 504: Converter Cell 505: One end of the AC input terminal 505a: The fourth wire (neutral wire) of an AC power supply. 506: EV charging port (charging station) 507: Connection Cable 508: Electric vehicle (EV) 509: Charging cable 600: Power (current) flow path 800: Power conversion unit (a single unit consisting of multiple power electronics converters and one multi-winding high-frequency transformer) 801: Multi-winding high-frequency transformer 802: Windings not connected to the power electronics converter 900: Single-core multi-winding high-frequency transformer

Claims

1. A power conversion unit comprising a high-frequency transformer along with at least two power electronics converters, The high-frequency transformer has a transformer core, and first, second, and third windings are wound around the transformer core. A power conversion system in which the first winding is connected to a first power electronics converter, the second winding is connected to a second power electronics converter, and the third winding is connected to a winding of another power conversion unit, Used in EV charging devices, The EV charging device has a plurality of power conversion units that input AC power and output DC power, and the number of power conversion units connected to a single EV charging port can be changed. Each of the aforementioned power conversion units has a converter cell that includes an AC / DC conversion circuit that receives AC power and a DC / DC conversion circuit that is connected to the AC / DC conversion circuit via a capacitor and outputs DC power. The DC / DC conversion circuit has a three-winding high-frequency transformer between the DC / AC conversion stage and the AC / DC conversion stage. The third winding of the three-winding high-frequency transformer in all converter cells is connected in parallel to establish magnetic coupling between all power conversion units. The multiple AC input terminals of the multiple AC / DC conversion circuits are connected in series with each other, and the multiple DC outputs of the three converter cells for each three phase provided in each power conversion unit are connected in parallel with each other. A power conversion system characterized by the following features.

2. A power conversion system according to claim 1, All of the aforementioned third windings are connected in parallel to each other. A power conversion system characterized by the following features.

3. A power conversion system according to claim 2, All of the aforementioned power electronics converters are magnetically coupled. A power conversion system characterized by the following features.

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