Inductive fast charger

Abstract

The invention relates to a power electronic converter (700) comprising a plurality of converter cells (300); wherein each converter cell (300) comprises: an inductive power transfer stage (106) comprising a coupling inductor (301) coupling a first side of the converter cell (300) to a second side of the converter cell (300), wherein the coupling inductor (301) comprises a first winding (314) around a first magnetic core (312) connected to the first side of the converter cell (300) and a second winding (324) around a second magnetic core (322) connected to the second side of the converter cell (300); wherein the first winding (314) and the first magnetic core (312) are separated from the second winding (324) and the second magnetic core (322) by a planar electrically insulating layer (302) providing electrical insulation between the first side and the second side of the converter cell (300); wherein at least two of the coupling inductors (301) are arranged such that their insulating layers (302) form a single continuous insulating layer (302).

Description

Technical Field

[0001] This invention relates to a power electronic converter, a converter unit, the use of a power electronic converter, a charger including a power electronic converter, and a wireless vehicle charging station. Background Technology

[0002] For electric vehicle charging infrastructure connected to medium-voltage (MV) grids, particularly fast car chargers, the use of solid-state transformers (SST) with medium-frequency transformers (MFTs) to replace 50 or 60 Hz transformers is attractive. However, especially in the case of low-power MFTs, the insulation requirements of the MV grid pose a challenge to MFTs. The size, weight, and cost of converters based on medium-frequency or high-frequency transformers have been very successful in low-voltage (LV) applications, particularly in the power supplies of electronic devices such as computers and laptops. In MV applications, electrical insulation challenges the attractiveness of MFTs. While the transformer core shrinks with increasing frequency, the insulation distance does not. For high-frequency, low-power transformers, the transformer size is determined by the insulation distance between the LV and high-voltage (HV) windings and between the HV windings and the core. Summary of the Invention

[0003] Conventional solutions are expensive, bulky, and heavy, and therefore may require solid-state transformers to save on size, weight, and cost.

[0004] The problem is solved by the subject matter of this invention application. Embodiments are provided in the following description and accompanying drawings.

[0005] The embodiments also relate to power electronic converters, converter units, the use of power electronic converters, chargers, and wireless vehicle charging stations. Synergistic effects may arise from different combinations of embodiments, but these may not be described in detail.

[0006] Furthermore, it should be noted that all embodiments of the method of the present invention can be performed in the order of the described steps; however, this is not the only or fundamental order of the method steps. Unless the opposite is explicitly mentioned below, the method presented herein can be performed using an alternative order of the disclosed steps without departing from the corresponding method embodiments.

[0007] Technical terms are used based on common sense. If a term is to express a specific meaning, its definition will be given in the context in which it is used.

[0008] According to a first aspect, a power electronic converter comprising multiple converter units is provided. Each converter unit includes an inductive power transfer stage, which includes an inductor that couples a first side of the converter unit to a second side of the converter unit. The inductor includes a first winding around a first magnetic core and a second winding around a second magnetic core, the first winding being connected to the first side of the converter unit and the second winding being connected to the second side of the converter unit. The first winding and the first magnetic core are separated from the second winding and the second magnetic core by a flat electrical insulating layer that provides electrical insulation between the first and second sides of the converter unit. At least two of the coupled inductors are arranged such that their insulating layers form a single continuous insulating layer.

[0009] That is, a power electronic converter is provided, which may include multiple inductors. Each inductor consists of two halves. These two halves are separated by an insulator and face each other. However, the size of the insulator is not limited to the area covered by the surfaces of the two facing halves. Instead, the size of the insulator is extended so that one or more other inductors can use the same insulator section. The two inductor halves are part of a converter unit that may include other devices. That is, one inductor half is associated with and connected to one side of the converter unit, and the other half is associated with and connected to a second side of the converter unit.

[0010] The term "coupled inductor" refers to the two halves of an inductor, which are also designated as an "inductor pair" in this disclosure. Furthermore, "core" is designated as "core portion".

[0011] According to one embodiment, converter units are connected to each other on a first side and a second side, wherein the connection on the first side is a series connection and the connection on the second side is a parallel connection. That is, the voltage on the first side (e.g., medium voltage) is stepped down, while on the second side, for example, a DC voltage is obtained, which is equal to the DC voltage of a single unit after rectification. The first side can be the input voltage, and the second side can be the output voltage. The output energy with the DC voltage is therefore provided by the current from all the units of the converter. In this context, MV refers to the line-to-line root mean square voltage, typically in the range of 10 to 20 kV or, for example, 50 kV or higher.

[0012] According to one embodiment, the coupled inductors are arranged side-by-side in the plane of the insulating layer to form a rectangular pattern or a coupled inductor matrix. If they are arranged in a matrix, a single row or column of coupled inductors can use the same insulating segment, or all inductors can use the same insulating segment when they are arranged in a matrix. That is, for all inductors of the converter, a single insulator can exist between the first and second halves of the inductor. Therefore, on the one hand, a low volume can be achieved due to the use of inductor pairs, and on the other hand, the effort to manufacture the converter is reduced because only the inductor halves need to be produced. The first and second halves can be assembled on the substrate in the same manner, and finally the insulator is sandwiched between the two substrates and assembled together.

[0013] According to one embodiment, the coupled inductor is immersed in a dielectric liquid such as oil or ester. The dielectric liquid can, for example, insulate the windings.

[0014] According to one embodiment, a power electronic converter includes a tank containing a dielectric liquid, wherein the tank includes a first liner made of a dielectric material. The liner is in a plane parallel to an insulating layer and includes bushings for connecting conductors to a first winding. This arrangement allows inductors or windings to be easily and economically connected to other components of the unit, respectively. The inductor half, or more specifically, the winding, mounted on the frame, can be connected to a connector inside the liner in a first step. Other components can be connected to the connector outside the liner in subsequent steps as the tank is assembled. Furthermore, the tank is filled with a dielectric liquid for insulation of the winding and cooling by natural convection. The liner is made of a dielectric material. In this way, conductors can be directly attached to the liner to connect windings to a first or second side of each unit.

[0015] According to one embodiment, the tank comprising a matrix of coupled inductors immersed in a dielectric liquid is vertically oriented. That is, the liner and parallel insulating layer are also vertically oriented. This vertical arrangement allows natural convection current to flow upwards along the insulating layer and core, and downwards along the tank walls, without any horizontal obstructions hindering the vertical flow of the dielectric liquid. Cooling fins inside the tank and (optionally) at the top receive heat, which is then transferred to cooling fins outside the tank.

[0016] In other words, the plane of the insulating layer includes the vertical direction, and a dielectric fluid such as oil flows upward by natural convection to cool the core and windings of the coupled inductor. The oil flows downward along the tank walls to transfer heat to the environment, thus providing passive cooling to the inside of the tank.

[0017] According to one embodiment, the core of the coil is a pot-shaped core, thereby receiving a circular winding in an annular groove in the core, wherein the pot-shaped cores of the first and second windings are opposite each other with an insulating layer between them. In other words, the coils surround a cylindrical inner portion, geometrically including the axis of rotation of the core, and are themselves surrounded by an outer portion of the core. Furthermore, they are covered by a portion located on the top side, i.e., perpendicular to the axis of rotation, and open on the bottom side to the corresponding portion of the insulating layer and the core half (i.e., the second half). The directions "top" and "bottom" are used here for illustrative purposes only and can vary depending on the angle. The outer shape of the core can be circular or rectangular, such as with rounded edges, or any other suitable shape.

[0018] According to one embodiment, the insulating layer includes an arrangement of oil or oil and oil blocking elements, wherein the oil blocking elements are derived from an oil-impregnated material, such as cardboard, Nomex, or a polymer.

[0019] According to a further embodiment, the power electronic converter is configured to connect to an MV power grid having a line-to-line RMS voltage of 1 to 50 kV.

[0020] According to a further embodiment, the insulator has a substantially flat shape. The substantially flat shape follows the maximum distance between the two core halves and the arrangement of the coupled inductors in the slot (e.g., a matrix), wherein the distance between the coupled inductors is small and the insulating layer is a common insulating layer.

[0021] According to a second aspect, a converter unit is provided. The converter unit includes an inductive power transmission stage, wherein the inductive power transmission stage includes an inductor coupling a first side of the converter unit to a second side of the converter unit. The inductor includes a first winding around a first magnetic core and a second winding around a second magnetic core, the first winding being connected to the first side of the converter unit and the second winding being connected to the second side of the converter unit. The first winding and the first magnetic core are separated from the second winding and the second magnetic core by an insulating layer that provides electrical insulation between the first and second sides of the converter unit. The insulating layer is geometrically extended such that the converter unit can share the insulating layer with adjacent converter units. That is, a converter unit is a unit whose inductors and connected unit sides are configured such that they are suitable for assembling a power electronic converter as described above. For example, a coupled inductor is integrated in a slot of the power electronic converter, the slot including an extended insulating layer shared by one or more adjacent coupled inductors of other units. The unit may include any of the features described above relating to the unit of the power electronic converter.

[0022] According to the third aspect, the use of the power electronic converter for a vehicle charging station as described above is provided. That is, the power electronic converter is used to charge a vehicle coupled to a vehicle charging station including the power electronic converter.

[0023] According to the fourth aspect, a charger including the aforementioned power electronic converter is provided.

[0024] According to the fifth aspect, a wireless vehicle charging station including a power electronic converter is provided. The vehicle charging station can therefore be a wireless charging station. However, it can also alternatively be a wired charging station.

[0025] Therefore, according to the present invention, by employing, for example, a matrix arrangement of inductive power transfer (IPT) units instead of a closed core MFT, the volume, weight, and cost of the electrically insulated power conversion stage are reduced. The units share a common planar insulation layer, thereby minimizing the space required for electrical insulation.

[0026] These and other features, aspects and advantages of the invention will be better understood with reference to the accompanying drawings and the following description. Attached Figure Description

[0027] Figure 1 This is a block diagram of a solid-state transformer (SST) unit.

[0028] Figure 2 This is a flowchart of the SST branch.

[0029] Figure 3 This is a block diagram of a coupled inductor.

[0030] Figure 4 A block diagram of a coupled inductor sharing the same flat insulating layer is shown.

[0031] Figure 5 A schematic diagram of the unit connection scheme is shown.

[0032] Figure 6a A three-dimensional schematic diagram of the coupled inductor is shown.

[0033] Figure 6b It shows Figure 6a A three-dimensional schematic diagram of a coupled inductor.

[0034] Figure 7 A schematic diagram showing the front and side views of the slot for an IPT inductor is provided.

[0035] Figure 8 A three-dimensional schematic diagram of the IPT inductor in the slot is shown.

[0036] Figure 9 A three-dimensional schematic diagram of the IPT inductor in the slot is shown. Detailed Implementation

[0037] Figure 1 A block diagram of a solid-state transformer (SST) unit is shown. The electric vehicle charging infrastructure market is also experiencing strong growth due to the current and anticipated robust increase in the number of electric vehicles. This market includes fast car chargers that can be directly connected to the medium-voltage (MV) AC grid. For safety reasons, standards require electrical separation between the MV grid and the low-voltage (LV) output of the charger that can be connected to the electric vehicle via a transformer. To reduce the cost, size, and weight of chargers, it is attractive to replace conventionally used low-frequency transformers operating at 50 or 60 Hz with solid-state transformers (SSTs) (including medium-frequency transformers (MFTs) 106 operating at frequencies of 10 to 20 kHz). The reduction in transformer size, and the corresponding weight and cost, is significant, disregarding electrical insulation, as it is inversely proportional to frequency. While the transformer core shrinks with increasing frequency, the insulation distance does not. For high-frequency, low-power transformers, the size is primarily determined by the insulation distance between the LV and HV windings, and between the HV winding and the core. The solution is to ensure that the power of each MFT 106 is high enough, or in other words, that the number of MFTs per charging system (fixed total power) is small enough. For high power per MFT, the increase in size due to insulation requirements is not significant.

[0038] like Figure 2 As shown, the SST 150 consists of individual converter units 100 connected to branches. These are connected in series on the MV side 152 and in parallel on the LV side 154. This creates a step voltage drop from the MV grid to the LV DC bus. The three branches are connected to the three-phase MV AC grid in either a star or delta configuration. If the total power of the SST 150 (charging system) is P, then the power per MFT is P / (3n), where n is the number of units 100 per branch. For the MF inverter 104 of the SST unit 100, using a two-stage topology and semiconductors with relatively low rated blocking voltages (due to cost) is the simplest and most economical approach. This results in relatively low DC voltages and input voltages per unit. Therefore, many units are needed per branch to block the line-to-line voltage of the MV AC grid, and the power per MFT is low.

[0039] Numerical examples:

[0040] Power of each charging system: P = 630 kW

[0041] Root mean square of line-to-line voltage in an AC power grid: V LL = 17.5 kV

[0042] Rated semiconductor blocking voltage: V b,r = 1.7 kV

[0043] The voltage utilization factor of semiconductors (to achieve the necessary reliability and lifespan):

[0044] .

[0045] DC voltage of the SST unit:

[0046] In the case of a star connection, the number of units in each branch (without redundancy):

[0047]

[0048] Number of MFTs:

[0049] Power per MFT:

[0050] For a combination of low power (15kW) and high insulation voltage (17.5kV), designing a compact and cost-effective MFT is nearly impossible. Some improvements can be made by first connecting the three-phase rectifier to the grid and then connecting a single SST branch to the DC link of the three-phase rectifier. In this case, the total number of units and MFTs is: This results in slightly higher power per MFT. However, designing a compact and cost-effective MFT remains a challenge. The problem arises from the insulation distance between the HV winding and the grounded core, as the core (in this case, a closed core) is built around the HV winding. This leads to poor use of the core window.

[0051] Figure 3 A cross-sectional schematic diagram of a coupling inductor 301 inside a converter unit 300 according to one embodiment is shown. The inductor 301 includes a first core half 312, a first winding 314, a second core half 322, a second winding 324, and an insulator 302. The unit 300 may include, for example... Figure 1 The additional components are as described. The first winding 314 is wound around the center portion 316 of the core half 312 using a rotating shaft 110, that is, the winding 314 is arranged according to... Figure 3The upper portion 316 of the horizontally wound inductor 301 is shown. Similarly, the second winding 324 surrounds the second core 322 around the center portion 316 of the core half 322, such that the core halves 312, 322 and the windings 314, 324 are opposite to each other. This arrangement is designated as a pot-shaped core in this disclosure. The core material may be ferrite. The upper portions 312, 314 may be the medium voltage side (MV), and the lower portions 322, 324 may be the low voltage side (LV). Between the MV and LV sides, an insulator 302 is arranged such that, during operation, a voltage V is generated between the medium voltage side (MV) and the low voltage side (LV). LL The insulator 302 may be a flat electrical insulating layer 302, which provides electrical insulation between the first and second sides of the converter unit 300. The insulating layer 302 is geometrically extended such that, as follows: Figure 4 Further described, the converter unit 300 is able to share the insulating layer 302 with adjacent converter units.

[0052] The key is that the core halves 312 and 322 have different potentials, and the electrical insulation 302 is located between the core halves 312 and 322. Therefore, the electrical insulation 302 penetrates the magnetic circuit, or in other words, the magnetic flux penetrates the electrical insulation 302. The electrical insulation 302 is a single flat layer, and is therefore simpler and more space-saving than a closed core MFT. According to the above example, a total of N coupled inductors 301 are required, as are N closed core MFTs, for example, N=24. According to the invention, multiple coupled inductors 301 are arranged such that the inductors share a common... Figure 4 The schematic diagram shows the same flat insulating layer 302. Therefore, the insulation 302 retains the simplest shape, i.e., a single flat layer, and can save a lot of space. Strong insulation is not required between adjacent coupled inductors 300 because the inter-cell voltage V between adjacent inductors 301 is... CC The system voltage V that requires insulation between the core halves 312 and 322 of the coupled inductor 301 and the windings 314 and 324 is higher than the required insulation between the core halves 312 and 322 and the windings 314 and 324. LL Much smaller. The maximum voltage between adjacent cells 300 depends on the connection scheme of cells 300. Minimum value use Figure 5 The zigzag pattern 510 on the left side of the middle section is obtained. Figure 5 The meandering design 520 shown on the right produces a higher V. CC However, shorter connections.

[0053] The arrangement described above corresponds to an IPT system with multiple IPT units connected in series and parallel. The IPT unit corresponds to unit 100 introduced in Section 2, where each closed core MFT is replaced by a pair of coupled inductors 301. Because the insulation 302 penetrates the magnetic circuit, and the air gap of the core is much wider than that of the closed core MFT, the magnetic coupling coefficient between the two windings is much lower than that of the closed core MFT. Therefore, the IPT system needs to operate in resonant mode and compensate for stray inductance.

[0054] Figure 6a A possible design for a coupled inductor 301 is shown in a three-dimensional schematic diagram. The coupled inductor 301 has a first winding 314, a second winding 324, a first half-core 312, a second half-core 322, a conductor 602, and a rotating shaft 110. The insulator is not shown in the figure.

[0055] Figure 6b The diagram shows... Figure 6a The cross-section of the coupled inductor 301 is shown.

[0056] Figure 7 A three-dimensional schematic diagram shows an example of an arrangement of a total of N = 24 inductor pairs in a 4×6 matrix.

[0057] The design has the following characteristics:

[0058] Inductor 300 is immersed in oil. 4×6 coupled inductors 301 or inductor pairs 301 are respectively arranged in vertical slots 700.

[0059] refer to Figure 7 and Figure 8 The combination of slots, such as Figure 8 The diagram shows a liner 802 and a metal frame 702. A connector or conductor 602 is fed via the liner 802. The metal frame 702 provides walls for a top 704 and a bottom 706, as well as sidewalls with integrated cooling fins 708 and 710 facing inwards and outwards. The inner fins 710 facilitate heat transfer from oil to the wall, while the outer fins 708 facilitate heat transfer from the wall to ambient air. Figure 8 The top view 810, side view 820 and front view 830 of the slot 700 are shown.

[0060] Cardboard stop 702 is used to keep the opposing core halves at a fixed, well-defined insulation distance. Cardboard pin 712 is used to hold the core halves in place. As an alternative to cardboard 702, an oil stop of Nomex or any other suitable polymer can be used.

[0061] like Figure 9As indicated by arrow 902, the oil circulates upwards along the coupled inductor via natural convection (i.e., without a pump) and downwards through the inner fins of the oil. The dielectric fluid can be mineral oil, ester, or any other suitable fluid. In the example, an insulation thickness of 17.7 mm is provided, which is for the use of mineral oil and cardboard barriers. It is designed for line-to-line AC voltage. The windings can be made of Litz wire.

[0062] Other variations of the disclosed embodiments can be understood and implemented by those skilled in the art in practicing the claimed invention, based on the disclosure and study of the invention. In this invention, the word "comprising" does not exclude other elements or steps, and the indefinite articles "(a) a" or "(an) an" do not exclude the plural. The fact that certain measures are described in mutually different disclosures of the invention does not indicate that combinations of these measures cannot be used advantageously. Any reference numerals in the disclosures should not be construed as limiting the scope of the invention.

Claims

1. A power electronic converter (700) comprising a plurality of converter units (300); wherein each converter unit (300) comprises: An inductive power transfer stage (106) includes a coupling inductor (301) that couples a first side of the converter unit (300) to a second side of the converter unit (300), wherein the coupling inductor (301) includes a first winding (314) around a first magnetic core (312) and a second winding (324) around a second magnetic core (322), the first winding (314) being connected to the first side of the converter unit (300) and the second winding (324) being connected to the second side of the converter unit (300); The first winding (314) and the first magnetic core (312) are separated from the second winding (324) and the second magnetic core (322) by a flat electrical insulating layer (302), which provides electrical insulation between the first side and the second side of the converter unit (300); At least two of the coupled inductors (301) are arranged such that the insulating layers (302) of the at least two coupled inductors form a single continuous insulating layer; as well as The coupled inductors (301) are arranged side by side in the plane of the insulating layer (302) to form a matrix (510, 520) of converter units (300), and the converter units (300) are connected in a zigzag or meandering pattern.

2. The power electronic converter (700) according to claim 1, wherein the converter units (300) are connected to each other on the first side and the second side of the converter unit (300), and wherein the connection on the first side is a series connection and the connection on the second side is a parallel connection.

3. The power electronic converter (700) according to claim 1, wherein the coupling inductors (301) are arranged side by side in the plane of the insulating layer (302) to form a rectangular pattern.

4. The power electronic converter (700) according to claim 1, wherein the coupling inductor (301) is immersed in a dielectric liquid, the dielectric liquid comprising oil or ester.

5. The power electronic converter (700) of claim 4, comprising a tank containing a dielectric liquid, wherein the tank includes a first liner (802) from a dielectric material; wherein the liner (802) is located in a plane parallel to the insulating layer (302); and wherein the liner (802) includes a bushing for connecting a conductor (602) to the first winding (314).

6. The power electronic converter (700) of claim 5, wherein the slots of the coupled inductor (301) matrix immersed in a dielectric liquid are vertically oriented.

7. The power electronic converter (700) according to any one of claims 1-5, wherein the core of the winding is a pot-shaped core, thereby receiving a circular winding in an annular groove in the core, and wherein the pot-shaped cores of the first winding and the second winding (324) are opposite to each other, and the insulating layer (302) is located between the pot-shaped cores of the first winding and the second winding.

8. The power electronic converter (700) according to any one of claims 1-5, wherein the insulating layer (302) comprises oil, or an arrangement of oil and oil blocking elements, wherein the oil blocking elements are derived from an oil-impregnated material, the oil-impregnated material comprising cardboard or a polymer.

9. The power electronic converter (700) according to claim 8, wherein the polymer comprises Nomex.

10. The power electronic converter (700) according to any one of claims 1-5, wherein the power electronic converter (700) is configured to be connected to an MV power grid with a line-to-line root mean square voltage of 1 kV to 50 kV.

11. A converter unit (300) including an inductive power transfer stage (106) including a coupling inductor (301) coupling a first side of the converter unit (300) to a second side of the converter unit (300), wherein the coupling inductor (301) includes a first winding (314) around a first magnetic core (312) and a second winding (324) around a second magnetic core (322), the first winding (314) being connected to the first side of the converter unit (300) and the second winding (324) being connected to the second side of the converter unit (300); The first winding (314) and the first magnetic core (312) are separated from the second winding (324) and the second magnetic core (322) by an insulating layer (302), which provides electrical insulation between the first side and the second side of the converter unit (300); The insulating layer (302) is geometrically extended such that the converter unit (300) is enabled to share the insulating layer (302) with adjacent converter units (300); and The coupling inductor (301) is arranged side by side with another coupling inductor in the plane of the insulating layer (302), such that the coupling inductor (301) becomes the inductor of the converter unit (300) matrix (510, 520), and the converter units (300) are connected in a Z-shaped or meandering connection scheme.

12. Use of a power electronic converter (700) according to any one of claims 1 to 10 for a vehicle charging station.

13. A charger comprising a power electronic converter (700) according to any one of claims 1 to 10.

14. A wireless vehicle charging station comprising a power electronic converter (700) according to any one of claims 1 to 10.

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