Bidirectional charging system for vehicle

Abstract

A bidirectional charging system for a vehicle is disclosed, comprising: a first bridge circuit having a plurality of legs each including two first switching elements connected in series between the two ends of a battery; a second bridge circuit having a plurality of legs each including two second switching elements connected in series between the two ends of the battery; a transformer having a plurality of primary windings connected to a grid or load side and a plurality of secondary windings insulated from the plurality of primary windings; a plurality of relays each selectively connecting the plurality of secondary windings to one of the connection nodes of two first switching elements included in one leg of the first bridge circuit and one of the connection nodes of two second switching elements included in one leg of the second bridge circuit; a motor connected to the connection nodes of two first switching elements included in each leg of the first bridge circuit to receive the voltage of each phase; and a controller that controls the connection state of the plurality of relays according to a preset operating mode.

Description

Technology Field

[0001] The present invention relates to a bidirectional charging system for a vehicle, and more specifically, to a bidirectional charging system for a vehicle capable of power conversion for charging a battery within a vehicle, and power conversion for providing power stored in the battery within the vehicle to a grid, a load, or a motor equipped in the vehicle. Background Technology

[0003] Recently, driven by the global trend of reducing carbon dioxide emissions, there has been a significant increase in demand for electric vehicles, which generate driving power by driving a motor with electrical energy stored in energy storage devices such as batteries, instead of typical internal combustion engine vehicles that generate driving power through the combustion of fossil fuels.

[0004] In the case of an electric vehicle, it is equipped with a battery that stores electrical energy supplied to a motor to generate driving power for the vehicle, and is equipped with an onboard charger that converts external power into power used for charging the battery to charge the battery.

[0005] Meanwhile, as the capacity of batteries equipped in electric vehicles has recently increased, there is a growing demand for the development of V2G (Vehicle to Grid) or V2L (Vehicle to Load) technologies to supply energy stored in the vehicle's battery to the grid or electrical load. Additionally, torque vectoring technology is being researched and developed to ensure driving stability by equipping auxiliary motors on the wheels connected to both sides of the drive shaft to individually control the speed of each drive wheel.

[0006] As such, electric vehicles require not only chargers for simply charging batteries, but also various power conversion circuits, such as circuits for implementing V2G or V2L and circuits for driving auxiliary motors for torque vectoring.

[0007] If these various power conversion circuits are individually equipped in a vehicle, a large number of electrical components are required to implement each circuit. Consequently, this can lead to problems such as increased circuit structure complexity and higher costs for implementation.

[0009] The matters described as background technology above are intended only to enhance understanding of the background of the present invention and should not be construed as an acknowledgment that they constitute prior art already known to those skilled in the art. Prior art literature

[0011] (Patent Document 0001) KR 10-2017-0126053 A(Patent Document 0002) KR 10-2013-0138954 A The problem to be solved

[0012] Accordingly, the present invention aims to solve the technical problem of providing a bidirectional charging system for a vehicle that can implement power conversion for charging a battery in a vehicle and power conversion for providing power stored in the battery in the vehicle to a grid, a load, or a motor equipped in the vehicle using a minimum number of electrical components. means of solving the problem

[0014] As a means to solve the above technical problem, the present invention is,

[0015] A first bridge circuit having a plurality of legs, each including two first switching elements connected in series between the two ends of a battery;

[0016] A second bridge circuit having a plurality of legs, each including two second switching elements connected in series between the two ends of the battery;

[0017] A transformer having a plurality of primary windings connected to a system or load side and a plurality of secondary windings insulated from the plurality of primary windings;

[0018] A plurality of relays, each selectively connecting the plurality of secondary windings to one of the connection nodes of two first switching elements included in one leg of the first bridge circuit and one of the connection nodes of two second switching elements included in one leg of the second bridge circuit;

[0019] A motor connected to a connection node of two first switching elements included in each of the plurality of legs of the first bridge circuit, receiving the voltage of each phase; and

[0020] A controller that controls the connection status of the plurality of relays according to a preset operation mode;

[0021] A bidirectional charging system for vehicles including

[0022] In one embodiment of the present invention, the controller may connect the plurality of secondary windings to the connection nodes of two first switching elements included in one leg of the first bridge circuit, respectively, in a first operation mode for charging the battery while the vehicle is stopped and a second operation mode for supplying power from the battery to an external grid or load while the vehicle is stopped.

[0023] In one embodiment of the present invention, the controller can control the first switching element to rectify the voltage of the secondary winding and provide it to the battery in the first operation mode.

[0024] In one embodiment of the present invention, the controller can control the first switching element to convert the voltage of the battery into an alternating current voltage and provide it to the secondary winding in the second operating mode.

[0025] In one embodiment of the present invention, the controller may, in a third operating mode in which it drives the motor or supplies power to a load while driving a vehicle, connect the plurality of secondary windings to the connection nodes of two second switching elements included in one leg of the second bridge circuit.

[0026] In one embodiment of the present invention, the controller controls the first switching element so that the first bridge circuit operates as an inverter that generates driving power for driving the motor, and controls the second switching element so that the second bridge circuit converts the voltage of the battery into an alternating voltage and provides it to the secondary winding.

[0027] In one embodiment of the present invention, the first bridge circuit includes three legs, and the second bridge circuit may be composed of two legs.

[0028] In one embodiment of the present invention, the plurality of relays may include two three-point relays that selectively connect two of the plurality of secondary windings to one of the connection nodes of two first switching elements included in two legs of the first bridge circuit and one of the connection nodes of two second switching elements included in two legs of the second bridge circuit, respectively, and one two-point relay that connects / opens one of the plurality of secondary windings to the connection node of two first switching elements included in one leg of the first bridge circuit. Effects of the invention

[0030] According to the above-described bidirectional charging system for vehicles, vehicle performance and marketability can be improved by simultaneously performing torque vectoring to secure vehicle driving performance in motor drive / V2L mode while driving and supplying power to small loads inside the vehicle.

[0031] In addition, according to the above-described bidirectional charging system for vehicles, an auxiliary drive motor for torque vectoring is driven by utilizing the bridge circuit of a DC-DC converter provided within the charger, thereby eliminating the need for a separate inverter for the auxiliary drive motor. Accordingly, according to the above-described bidirectional charging system for vehicles, it is possible to suppress the increase in circuit size and cost resulting from the addition of a motor drive circuit.

[0033] The effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below. Brief explanation of the drawing

[0035] FIGS. 1 and FIGS. 2 are circuit diagrams illustrating the state of a bidirectional charging system for a vehicle according to an embodiment of the present invention, according to an operation mode. FIG. 3 is a waveform diagram showing the voltage / current at key locations within the circuit during the battery charging mode while the vehicle is stationary, according to one embodiment of the present invention. FIG. 4 is a waveform diagram showing the voltage / current at key locations within the circuit during V2G / V2L mode while the vehicle is stationary in a bidirectional charging system for a vehicle according to one embodiment of the present invention. Specific details for implementing the invention

[0036] Hereinafter, a bidirectional charging system for a vehicle according to various embodiments will be described in more detail with reference to the attached drawings.

[0037] FIGS. 1 and FIGS. 2 are circuit diagrams illustrating the state of a bidirectional charging system for a vehicle according to an embodiment of the present invention, according to an operation mode.

[0038] Referring to FIGS. 1 and 2, a bidirectional charging system for a vehicle according to one embodiment of the present invention comprises: a first bridge circuit (40) having a plurality of legs (41, 42, 43) each including two first switching elements connected in series between the two ends of a battery (100); a second bridge circuit (50) having a plurality of legs (51, 52) each including two second switching elements connected in series between the two ends of a battery (100); a transformer (30) having a plurality of primary windings connected to a grid or load side and a plurality of secondary windings insulated from the plurality of primary windings; and a plurality of secondary windings, one of which is selectively connected to a connection node of two first switching elements included in one leg (41, 42, 43) within the first bridge circuit (40) and a connection node of two second switching elements included in one leg (51, 52) within the second bridge circuit (50). It may be configured to include relays (R1, R2, R3), a motor (200) connected to a connection node of two first switching elements included in each of the multiple legs (41, 42, 43) of the first bridge circuit (40) to receive the voltage of each phase, and a controller (300) that controls the connection state of the multiple relays (R1, R2, R3) according to a preset operation mode.

[0039] Generally, a bidirectional charger is a charger equipped with a DC-DC converter capable of bidirectional powering, and may include a Power Factor Correction (PFC) circuit that receives AC power from the grid for battery charging, compensates the power factor, and forms a DC voltage, and a bidirectional DC-DC converter that converts the magnitude of the DC voltage output from the PFC circuit to a magnitude suitable for battery charging. For V2G or V2L operation supplying power from the battery, the bidirectional DC-DC converter appropriately converts the voltage magnitude of the battery, and the PFC circuit operates as an inverter to provide AC power to an external grid or load.

[0040] A bidirectional charging system according to various embodiments of the present invention may also include a power factor compensation circuit (10), a bridge circuit (20, 40) constituting a bidirectional DC-DC converter, and a transformer (30).

[0041] The power factor compensation circuit (10) can be implemented with inductors and switching elements. The power factor compensation circuit (10) illustrated in FIGS. 1 and FIGS. 2 is shown as a circuit configuration for responding to single-phase and three-phase AC inputs.

[0042] More specifically, the power factor compensation circuit (10) may have a form comprising a plurality of inductors, each having one end connected to a system or load of each phase, and a plurality of switching elements forming a bridge circuit. The other end of one inductor may be connected to a connection node of two switching elements forming one leg (11, 12, 13) of the bridge circuit. Both ends of each leg (11, 12, 13) of the power factor compensation circuit (10) may be connected to both ends of a capacitor (Cdc) for forming a DC voltage.

[0043] Due to these connection relationships, the connection relationships of the inductors and switching circuits corresponding to each phase form a boost converter topology applied to a conventional power factor compensation circuit (10).

[0044] Among the bridge circuits constituting the bidirectional DC-DC converter, the bridge circuit (20) directly connected to the grid or load side, i.e., the power factor compensation circuit (10), may include a plurality of legs (21, 22, 23) connected in parallel to each other at both ends of the capacitor (Cdc), and each leg (21, 22, 23) may include two switching elements connected in series to each other.

[0045] The primary winding of the transformer (30) can be connected to the connection node of the switching element included in each leg (21, 22, 23).

[0046] In one embodiment of the present invention, a bridge circuit (20) connected to the primary winding of the transformer (30) of a bidirectional DC-DC converter may be configured to have three legs and implemented to generate alternating current voltages of three different phases.

[0047] Accordingly, the bridge circuit (first bridge circuit) (40) connected to the secondary winding of the bidirectional DC-DC converter can also be composed of three legs (41, 42, 43) for rectifying three different phase AC voltages, which are scaled by the transformer (30), into DC voltages.

[0048] In particular, various embodiments of the present invention may add an additional bridge circuit (50) for generating power for a small load provided in the interior of a vehicle, directly connect the phase voltage input terminal of an auxiliary motor (200) for torque vectoring to the battery-side bridge circuit (40) of a DC-DC converter, and add separate relays (R1-R3) to selectively connect the secondary side, i.e., the battery-side winding of a transformer (30) that constitutes a bidirectional DC-DC converter, to the bridge circuits (40, 50) according to the operating mode.

[0049] An additional bridge circuit (second bridge circuit) (50) is intended to provide power for small loads used in the vehicle, and may have two legs (51, 52) considering that most small loads are single-phase. That is, the bridge circuit (50) may be an inverter circuit that generates single-phase alternating current.

[0050] As described above, for power transfer between bridge circuits (20, 40) having at least three legs, the transformer (30) can be implemented as a multiphase transformer in which each of the primary and secondary windings is composed of at least three and electromagnetic induction is formed between them.

[0051] The battery (100) is a component that stores electrical energy to provide high-voltage direct current power to a vehicle drive motor in an eco-friendly vehicle driven by electric energy, such as an electric vehicle. The battery (100) can be charged by receiving charging power provided through a power factor compensation circuit (10) and a DC-DC converter as described above.

[0052] In one embodiment of the present invention, the battery (100) may be a power source that supplies power to a grid or load through a charger capable of bidirectional powering, and may also be a power source that supplies driving energy to an auxiliary driving motor (200) provided for torque vectoring.

[0053] In one embodiment of the present invention, the motor (200) may be an auxiliary drive motor installed on each drive wheel for torque vectoring. Of course, the motor (200) may be another motor that is provided in a vehicle and can operate by high voltage. The motor (200) may have each phase input terminal, into which the drive voltage and drive current are input, directly connected to the connection node of two switching elements included in each leg of the bridge circuit (40).

[0054] The relay (R1-R3) can be operated by the control of the controller (300) according to the driving mode and may be a three-point relay that selectively connects the secondary winding of the transformer (30) to the connection node of two switching elements included in each leg of the bridge circuit (40) and the connection node of two switching elements included in each leg of the bridge circuit (50).

[0055] As described above, the bridge circuit (40) has three legs corresponding to three phases, and the bridge circuit (50) can have two legs for a single-phase output, so one of the relays (R3) can be implemented as a two-point relay that determines only the connection state between the secondary winding and the connection node of two switching elements within one leg of the bridge circuit (40).

[0056] The controller (300) receives an operation mode determined by the upper controller based on the vehicle's operating status and driver input, and can control the state of the relays (R1-R3) according to the received operation mode. Additionally, the controller (300) can appropriately control the switching elements included in each component to correspond to each operation mode so that power ring corresponding to each operation mode is achieved.

[0057] Below, the control of relays (R1, R2, R3) and the operation control of each circuit, which are performed by the controller (300) for each operation mode, will be explained in detail.

[0058] A bidirectional charging system for a vehicle according to one embodiment of the present invention can operate in a battery charging mode while stationary, a V2G / V2L mode while stationary, and a motor driving / V2L mode while driving.

[0059] Battery charging mode while stopped

[0060] In a battery charging mode while stationary, the controller (300) receives instructions for the mode from the upper controller and can control the state of the relays as shown in FIG. 1. More specifically, the controller (300) can control the state of the relays (R1, R2, R3) so that the connection nodes of two switching elements within each of the secondary windings of the transformer (30) and the legs (41, 42, 43) of the bridge circuit (40) form an electrical connection with each other.

[0061] By this control, the secondary winding of the transformer (30) can form an electrical connection with the bridge circuit (40), and as the bridge circuit (40) operates as a rectifier, the energy transferred from the grid side to the secondary winding is supplied to the battery (100) so that the battery (100) can be charged.

[0062] In this charging mode, each component circuit can operate as a component of a typical charger. That is, the controller (10) can appropriately control the switching elements within the power factor compensation circuit (10) so that a DC voltage of a preset size is applied to the capacitor (Cdc), and can appropriately control the switching elements within the bridge circuit (20, 40) so that the output voltage and output current of the DC-DC converter, which consists of the bridge circuit (20), the transformer (30), and the bridge circuit (40), correspond to preset command values.

[0063] The control of the switching element of the power factor compensation circuit (10) and the control of the switching element of the bridge circuit (20, 40) provided in the DC-DC converter can be performed by various methods already known in the art.

[0064] FIG. 3 is a waveform diagram showing the voltage / current at key locations within the circuit during the battery charging mode while the vehicle is stationary, according to one embodiment of the present invention.

[0065] As shown in (a) of FIG. 3, the voltage (Vout) provided to the battery (100) is a constant DC voltage value, and as shown in (b), the current (I(L1), I(L2), I(L3)) of each secondary winding of the transformer (30) appears in the form of a three-phase AC current, and (c) indicates that the charging system is operating at a constant rate so that the output power becomes the maximum output.

[0066] In one embodiment of the present invention, since the connection node of two switching elements in each leg (41, 42, 43) of the bridge circuit (40) is always connected to the motor input terminal, it is important whether the voltage / current provided from the secondary winding of the transformer (40) affects the motor. This is because if torque is generated in the motor (200) by the supply of charging power while charging in a stationary state, the vehicle may move, and problems such as accidents may occur.

[0067] As shown in FIG. 3 (d) and (e), although a small amount of current (Iu, Iv, Iw) is generated at the input terminal of the motor (200), it can be confirmed that the actual motor cannot be rotated because the switching frequency of the bridge circuit (20, 40) in the DC-DC converter uses a high frequency range that is much higher than the frequency for driving the motor (speed=0).

[0068] V2G / V2L mode while stationary

[0069] In the V2G / V2L mode while stationary, the controller (300) can control the state of the relays (R1, R2, R3) in the same way as the battery charging mode while stationary as described above.

[0070] That is, in V2G / V2L mode while stationary, the controller (300) receives instructions for the mode from the upper controller, controls the state of the relay as shown in FIG. 1, controls the DC-DC converter so that power ring is made from the battery (100) side toward the grid side, and can operate the power factor compensation circuit (10) to convert the DC voltage formed in the DC capacitor (Cdc) into AC power corresponding to the grid or load power.

[0071] The control of the switching element of the power factor compensation circuit (10) applied in such a reverse power ring and the control of the switching element of the bridge circuit (20, 40) provided in the DC-DC converter can be performed by various methods already known in the art.

[0072] FIG. 4 is a waveform diagram showing the voltage / current at key locations within the circuit during V2G / V2L mode while the vehicle is stationary in a bidirectional charging system for a vehicle according to one embodiment of the present invention.

[0073] As shown in FIG. 4 (a) to (c), when the DC-DC converter operates in reverse, an AC current (I(L4), I(L5), I(L6)) is supplied to the secondary winding of the transformer (30) through the switching of the bridge circuit (40), and a constant DC voltage (Vlink) can be formed in the DC capacitor (Cdc) by the bridge circuit (20) rectifying the voltage induced on the primary side. In addition, the DC voltage (Vlink) can be converted into an AC voltage / current (Vgrid / Igrid) through the switching operation of the switching element in the power factor compensation circuit (10) and supplied to the grid or load.

[0074] Similar to the battery charging mode, it is important to determine whether the voltage / current provided to the secondary winding of the transformer (40) affects the motor in the V2G / V2L mode while stationary.

[0075] As shown in FIG. 4 (d) and (e), although a small amount of current (Iu0, Iv0, Iw0) is generated at the input terminal of the motor (200), it can be confirmed that the actual motor cannot be rotated (speed=0) because the switching frequency of the bridge circuit (20, 40) in the DC-DC converter, similar to the battery charging mode, uses a high frequency range that is much higher than the frequency for motor driving.

[0076] Motor drive / V2L mode while driving

[0077] In the driving motor drive / V2L mode, the controller (300) receives instructions for the mode from the upper controller and can control the state of the relays as shown in FIG. 2. More specifically, the controller (300) can control the state of the relays (R1, R2, R3) so that the connection nodes of the two switching elements within each of the secondary windings of the transformer (30) and the legs (51, 52) of the bridge circuit (50) form an electrical connection with each other. If the bridge circuit (50) has two legs, the relay (R3) may be in a state where the connection with the bridge circuit (40) is only open.

[0078] By this control, the secondary winding of the transformer (30) can form an electrical connection with the bridge circuit (50), and the bridge circuit (50) can convert the DC voltage of the battery (100) into AC voltage and supply it to the secondary side of the transformer (30). Similar to the V2G / V2L mode, the controller (300) controls the DC-DC converter so that power is generated from the battery (100) side toward the grid side, and by operating the power factor compensation circuit (10) to convert the DC voltage formed in the DC capacitor (Cdc) into AC power corresponding to the load power source, power can be supplied to the load inside the vehicle through the load connection port provided inside the vehicle when the vehicle is driven.

[0079] Additionally, the controller (300) can drive the motor (200) for torque vectoring during vehicle driving by controlling the bridge circuit (40) to operate as an inverter for driving the motor (200).

[0080] In this way, one embodiment of the present invention can simultaneously perform torque vectoring to secure vehicle driving performance in motor drive / V2L mode while driving and supply power to a small load inside the vehicle.

[0081] In particular, one embodiment of the present invention drives an auxiliary drive motor for torque vectoring by utilizing the bridge circuit of a DC-DC converter provided in the charger, thereby eliminating the need for a separate inverter for the auxiliary drive motor. Accordingly, the increase in circuit size and cost resulting from the addition of a motor drive circuit can be suppressed.

[0083] Although specific embodiments of the present invention have been illustrated and described above, it will be obvious to those skilled in the art that the present invention can be modified and varied in various ways within the scope of the claims. Explanation of the symbols

[0085] 10: Power factor correction circuit 20, 40, 50: Bridge circuit 30: Transformers 100: Battery 200: Auxiliary drive motor 300: Controller R1-R3: Relay

Claims

Claim 1 A bidirectional charging system for a vehicle comprising: a first bridge circuit having a plurality of legs, each including two first switching elements connected in series between the two ends of a battery; a second bridge circuit having a plurality of legs, each including two second switching elements connected in series between the two ends of the battery; a transformer having a plurality of primary windings connected to a grid or load side and a plurality of secondary windings insulated from the plurality of primary windings; a plurality of relays each selectively connecting the plurality of secondary windings to one of the connection nodes of two first switching elements included in one leg of the first bridge circuit and one of the connection nodes of two second switching elements included in one leg of the second bridge circuit; a motor connected to the connection nodes of two first switching elements included in each leg of the first bridge circuit to receive the voltage of each phase; and a controller that controls the connection state of the plurality of relays according to a preset operating mode. Claim 2 A bidirectional charging system for a vehicle according to claim 1, wherein the controller is characterized by connecting the plurality of secondary windings to the connection nodes of two first switching elements included in one leg of the first bridge circuit, respectively, in a first operating mode for charging the battery while the vehicle is stopped and a second operating mode for supplying power from the battery to an external grid or load while the vehicle is stopped. Claim 3 A bidirectional charging system for a vehicle according to claim 2, wherein the controller controls the first switching element to rectify the voltage of the secondary winding and provide it to the battery in the first operating mode. Claim 4 A bidirectional charging system for a vehicle according to claim 2, wherein the controller controls the first switching element to convert the voltage of the battery into an alternating current voltage and provide it to the secondary winding in the second operating mode. Claim 5 A bidirectional charging system for a vehicle according to claim 1, wherein the controller, in a third operating mode for driving the motor or supplying power to a load while the vehicle is in motion, connects the plurality of secondary windings to the connection nodes of two second switching elements included in one leg of the second bridge circuit, respectively. Claim 6 A bidirectional charging system for a vehicle according to claim 5, wherein the controller controls the first switching element so that the first bridge circuit operates as an inverter that generates driving power for driving the motor, and controls the second switching element so that the second bridge circuit converts the voltage of the battery into an AC voltage and provides it to the secondary winding. Claim 7 A bidirectional charging system for a vehicle according to claim 1, characterized in that the first bridge circuit includes three legs and the second bridge circuit is composed of two legs. Claim 8 A bidirectional charging system for a vehicle according to claim 7, wherein the plurality of relays comprises: two three-point relays that selectively connect two of the plurality of secondary windings to one of the connection nodes of two first switching elements included in two legs of the first bridge circuit and one of the connection nodes of two second switching elements included in two legs of the second bridge circuit, respectively; and one two-point relay that connects / opens one of the plurality of secondary windings to the connection nodes of two first switching elements included in one leg of the first bridge circuit.

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