Bi-directional charge / discharge system for ev battery

Abstract

The present invention relates to a bi-directional charge / discharge system for an EV battery and, more particularly, to a bi-directional charge / discharge system for an EV battery capable of performing charge and discharge tests on a battery of an electrically driven hybrid vehicle or electric vehicle, while also enabling vehicle-to-grid (V2G) applications using the electric vehicle. The present invention provides a bi-directional charge / discharge system for an EV battery, comprising: a first cabinet having a power inlet into which three-phase AC power is introduced; a second cabinet connected to a side of the first cabinet and including an initial charging unit for filtering the applied three-phase AC power and preparing for charging, and an AC / DC converter unit for converting the AC power transmitted from the initial charging unit into DC power; a third cabinet connected to a side of the second cabinet and including a DC / DC converter unit for adjusting a voltage level of the converted DC power to a DC voltage suitable for charging and discharging a battery; and a control cabinet including a control unit for controlling the AC / DC converter unit and the DC / DC converter unit.

Description

Bidirectional charging and discharging system for EV batteries

[0001] The present invention relates to a bidirectional charging and discharging system for EV batteries, and more specifically, to a bidirectional charging and discharging system for EV batteries capable of performing charging and discharging tests on batteries of electric-powered hybrid or electric vehicles, as well as enabling V2G application using electric vehicles.

[0002] Until now, most vehicles have used fossil fuels, but with the recent emergence of environmental issues caused by fine dust, efforts are continuing to reduce emissions such as soot resulting from the use of fossil fuels in automobiles. As part of these efforts, examples include requiring large vehicles that generate a lot of soot, such as trucks, to be equipped with a Diesel Particulate Filter (DPF) in their exhaust systems, or reducing the purchase costs of hybrid or electric vehicles.

[0003] Electric vehicles include pure electric vehicles (EVs), hybrid vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). With the proliferation of hybrid or electric vehicles, the number of hybrid or electric vehicles in circulation is gradually increasing.

[0004] Furthermore, driven by global trends of tightening environmental regulations and reduced energy costs, there is a growing demand for eco-friendly electric vehicles to replace existing products. It is anticipated that the growth of the eco-friendly electric vehicle market will continue as it responds to CO2 reduction, improved fuel efficiency, and stricter environmental regulations. Therefore, the establishment of charging infrastructure is essential to expand the adoption and promote the active use of electric vehicles.

[0005] Under these circumstances, there is a demand for the development of systems capable of testing, charging, and discharging batteries, alongside the establishment of charging infrastructure. In other words, performance evaluation systems for electronic components that simulate adverse natural conditions are continuously in demand due to the increasing demand for electronic components and batteries as the development of eco-friendly electric vehicles accelerates. While electronic components are becoming increasingly smaller, lighter, and modularized, EV batteries used in electric vehicles require high capacity. With the recent frequent occurrence of fires caused by EV batteries, the process of testing these electronic components and EV batteries to identify previously undetected defects and issues and to implement improvements has become an essential requirement. Furthermore, there is a demand for systems capable of applying V2G (Vehicle to Grid) or G2V (Grid to Vehicle) technologies using the same equipment.

[0006] To solve the above-mentioned problems, the present invention aims to provide a bidirectional charging and discharging test system for EV batteries that enables testing of EV batteries and application of V2G through electric vehicles via bidirectional charging and discharging.

[0007] To achieve the above objective, the present invention provides a bidirectional charging and discharging system for an EV battery, characterized by comprising: a first cabinet having a power input unit into which a three-phase AC power is input; a second cabinet connected to the side of the first cabinet and having an initial charging unit for filtering the applied three-phase AC power and preparing for charging, and an AC / DC converter unit for converting the AC power transmitted from the initial charging unit into DC power; a third cabinet connected to the side of the second cabinet and having a DC / DC converter unit for adjusting the voltage level of the converted DC power to a DC voltage suitable for charging and discharging the battery; and a control cabinet having a control unit for controlling the AC / DC converter unit and the DC / DC converter unit.

[0008] In the present invention, the power input unit comprises: a circuit breaker to which a three-phase AC power is connected; a first instrument current transformer for detecting an abnormal state of the applied AC power and transmitting the detected signal to a control unit; a first transformer connected to the circuit breaker to step up the applied AC power; a second transformer connected to the circuit breaker to step down the applied AC power; a noise filter connected to the second transformer to remove noise from the applied AC power that has been stepped down through the second transformer; a power cutoff unit comprising a first electronic contactor to which the AC power filtered through the noise filter is connected, and a circuit breaker connected to the first electronic contactor to turn the AC power ON / OFF; and a PLC control unit comprising a control SMPS that receives the AC power filtered through the noise filter and supplies control power to a PLC control unit, and a PLC module to which control power is applied through the control SMPS to control the operation of an electronic contactor used in the system. It is characterized by comprising a relay socket consisting of a plurality of relay switches for transmitting an ON / OFF switching signal of an electronic contactor used in the system according to a control signal of the PLC control unit.

[0009] In the present invention, the initial charging unit comprises: a main power wiring circuit breaker to which AC power stepped up from a first transformer is applied; a second instrument current transformer for detecting an abnormal state of AC power applied to the main power wiring circuit breaker and transmitting the detected signal to a PLC control unit; and a precharge unit comprising an AC filter for removing noise from AC power applied through the main power wiring circuit breaker, and an AC filter capacitor and a resistor for gradually increasing the current applied through the AC power.

[0010] In the present invention, the AC / DC converter unit is characterized by comprising: an electronic contactor for a main power supply to which an AC power supplied from a precharge unit is connected; an AC reactor connected to the electronic contactor for the main power supply for filtering and stabilizing the supplied AC power; and an AC / DC converter connected to the AC reactor for converting the stabilized AC power into DC power.

[0011] In the present invention, the DC / DC converter unit comprises: a DC / DC converter to which a converted DC power is applied and which regulates the voltage level of the applied DC power; a power supply unit for supplying power to a control board of the DC / DC converter; a second electronic contactor connected to the control board of the DC / DC converter; a resistor connected to the second electronic contactor to remove residual voltage generated when the second electronic contactor is turned ON / OFF; and a first capacitor for stably supplying the voltage supplied by the DC / DC converter.

[0012] In the present invention, the third cabinet is further provided with a switching unit formed on one side of the lower portion of the DC / DC converter unit for connecting DC power sources, whose voltage levels have been adjusted in the DC / DC converter unit, in series or in parallel.

[0013] In the present invention, the switching unit comprises: a DC reactor connected to a DC / DC converter for filtering and stabilizing the DC power supply; a switching device to which the DC power supply, whose voltage level is regulated in the DC reactor, is connected; a two-pole circuit breaker connected to the switching device to output the DC power supply; a voltage converter that measures the voltage supplied to the switching device and transmits the measured voltage signal to the control unit; a current converter that measures the current supplied to the switching device and transmits the measured current signal to the control unit; and a second capacitor for stably supplying the voltage supplied to the switching device.

[0014] In the present invention, the control unit comprises: a DAQ system that receives temperature and voltage signal data of a battery to monitor the state of the battery and transmit the temperature and voltage signal data to a control PC, or receives current and voltage data from the power input unit, the initial charging unit, the AC / DC converter unit, the DC / DC converter unit, and the switching unit to control the charging and discharging of the battery; an uninterruptible power supply for protecting the control PC and the bidirectional charging and discharging system in the event of a power outage; and a communication unit for transmitting and receiving the data.

[0015] The bidirectional charging and discharging system of the present invention is characterized by further including a control PC connected to a DAQ system to receive current and voltage data from the power input unit, the initial charging unit, the AC / DC converter unit, the DC / DC converter unit, and the switching unit, or to receive temperature and voltage data of the battery from the DAQ system to control the charging and discharging of the battery.

[0016] The bidirectional charging and discharging system according to the present invention has the advantage of enabling charging and discharging tests of batteries for electric vehicles.

[0017] In addition, the bidirectional charging and discharging system according to the present invention has the advantage of being able to charge a battery for an electric vehicle.

[0018] In addition, the bidirectional charging and discharging system according to the present invention has the advantage of enabling V2G implementation through electric vehicles.

[0019] In addition, the bidirectional charging and discharging system according to the present invention has the advantage of enabling energy saving and energy circulation because it can utilize energy during discharge.

[0020] In addition, the bidirectional charging and discharging system according to the present invention has the advantage of enabling multitasking testing by utilizing energy savings.

[0021] FIG. 1 is a structural diagram of a bidirectional charging and discharging system according to the present invention.

[0022] FIG. 2 is a front perspective view of a bidirectional charging and discharging system according to the present invention.

[0023] FIG. 3 is a rear perspective view of a bidirectional charging and discharging system according to the present invention.

[0024] FIG. 4 is a front view of a bidirectional charging and discharging system according to the present invention with the door removed.

[0025] FIG. 5 is a rear view of a bidirectional charging and discharging system according to the present invention with the door removed.

[0026] FIGS. 6 and 7 are a perspective view and a front view of a switching unit of a bidirectional charging and discharging system according to the present invention.

[0027] FIG. 8 is a series and parallel connection structure diagram of a switching unit according to the present invention.

[0028] FIG. 9 is a V2G structure diagram using a bidirectional charging and discharging system according to the present invention.

[0029] FIG. 10 is a structural diagram of a battery charge / discharge test using a bidirectional charge / discharge system according to the present invention.

[0030] Embodiments of the present invention, in which the above objectives can be specifically realized, will be described in detail below with reference to the attached drawings. In describing these embodiments, the same names and reference numerals are used for identical components, and additional explanations thereof will be omitted.

[0031]

[0032] FIG. 1 is a structural diagram of a bidirectional charging and discharging system according to the present invention. As shown in the drawing, the structure of the bidirectional charging and discharging system (1) for an EV battery comprises a power input unit (200) to which a three-phase AC power is applied, an initial charging unit (300) provided after the three-phase AC power is connected in parallel, an AC / DC converter unit (400) that converts the AC power passing through the initial charging unit (300) into DC power, a DC / DC converter unit (500) that converts the DC power converted by the AC / DC converter unit (400) into DC power suitable for an electric vehicle, and a switching unit (600) connected to the DC / DC converter unit (500) to connect DC power suitable for an electric vehicle in series or parallel. A DC circuit breaker is connected to the switching unit (600), and a battery (100) can be connected to the DC circuit breaker. A control unit (700) connected to the system (1) and the battery (100) is further provided, and the control unit (700) is connected to a control PC (800). As shown in the drawing, the control unit (700) can communicate with the system (1) and the control PC (800) using Ethernet or CAN (Controller Area Network) communication.

[0033] FIG. 2 is a perspective view of a bidirectional charging and discharging system (1) according to the present invention. As shown in the drawing, the bidirectional charging and discharging system (1) is installed in a cabinet and comprises a first cabinet (2) equipped with a power input unit (200) into which a three-phase AC power is input, a second cabinet (3) equipped with an initial charging unit (300) and an AC / DC converter unit (400) on the side of the first cabinet (2), a third cabinet (4) equipped with a DC / DC converter unit (500) connected to the side of the second cabinet (3) and adjusting the voltage level of the DC voltage, and a control cabinet (5) equipped with a control unit (700).

[0034] With reference to FIGS. 2 to 5, each component will be described in detail. As shown in the drawings, the first cabinet (2) consists of a first cabinet body (21), a first cabinet front door (22) and a first cabinet rear door (23) installed on the front and rear sides of the first cabinet body (21), and a fan (24) installed on the top of the first cabinet body (21), and a voltage input unit (200) is installed inside. A caster (25) is provided on the bottom surface of the first cabinet body (21) and configured to be fixed in position. In addition, the caster (25) is made of a vibration-damping rubber pad to provide electrical insulation from the floor and protection from vibration.As illustrated in FIGS. 4 and 5, the voltage input section (200) comprises a wiring circuit breaker (201) to which a three-phase AC power source is connected, a first instrument current transformer (202) for detecting an abnormal state of the applied AC power source and transmitting the detected signal to a control unit (700), a first transformer (203) connected to the wiring circuit breaker (201) for stepping up the applied AC power source, a second transformer (204) connected to the wiring circuit breaker (201) for stepping down the applied AC power source, a noise filter (206) connected to the second transformer (204) for removing noise from the applied AC power source that has been stepped down through the second transformer (204), a first electronic contactor (2051) to which the AC power source filtered through the noise filter (206) is connected, and a circuit breaker (2052) connected to the first electronic contactor (2051) for turning the AC power source ON / OFF. It comprises a PLC control unit (207) consisting of a blocking unit (205), a control SMPS (2071) that receives AC power filtered through a noise filter (206) and supplies control power to the PLC control unit (207), and a PLC module (2072) that controls the operation of an electronic contactor used in the system (1) by receiving control power through the control SMPS (2071); a relay socket (208) consisting of a plurality of relay switches for transmitting an ON / OFF switching signal of an electronic contactor used in the system (1) according to a control signal of the PLC control unit (207); a fuse switch (209) connected to a first transformer (203); and a first busbar (210) connected to the fuse switch (209) to transmit AC power.

[0035] When the system (1) is operated, AC three-phase power is applied to the first transformer (203) through the wiring circuit breaker (201). In the first transformer (203), the applied AC voltage of 380V is stepped up to 400V. The stepped-up AC voltage is transmitted to the initial charging unit (300) through the first busbar (210). Additionally, the second transformer (204) steps down the applied AC voltage of 380V to 220V. The AC power reduced to 220V is connected to a noise filter (206), and the noise filter (206) filters out harmonics, etc. from the AC power. The filtered AC power is connected to the first electronic contactor (2051), and the first electronic contactor (2051) is connected to the circuit breaker (2052). Additionally, the AC power with filtered harmonics, etc. supplies power to the control SMPS (2071). The control SMPS (2071) supplies the necessary power to the PLC module (2072). The PLC module (2072) is involved in the control of the first transformer (203), the ON / OFF control of the electronic contactor used in the system (1), and the sequential operation of the AC / DC converter unit (400) and the DC / DC converter unit (500). The PLC control unit (207) is connected to the relay socket (208) to transmit control signals, thereby transmitting control signals to electronic components such as each electronic contactor.

[0036] The configuration of the second cabinet (3) is described in detail with reference to FIGS. 2 to 5. The second cabinet (3) consists of a second cabinet body (31), a second cabinet front door (32) and a second cabinet rear door (33) installed on the front and rear sides of the second cabinet body (31), and a fan (34) installed on the upper side of the second cabinet body (31). Inside, an initial charging unit (300) and an AC / DC converter unit (400) are provided. Casters (35) are provided on the bottom surface of the second cabinet body (31) and configured to be fixed in position. In addition, the casters (35) are made of anti-vibration rubber pads to provide electrical insulation from the floor and protection from vibration. The initial charging unit (300) is composed of a main power wiring circuit breaker (301) to which AC power boosted from the first transformer (203) is applied, a second instrument current transformer (302) for detecting an abnormal state of AC power applied to the main power wiring circuit breaker (301) and transmitting the detected signal to the PLC control unit (207), an AC filter (3031) for removing noise from AC power applied through the main power wiring circuit breaker (301), and a pre-charge unit (303) composed of an AC filter capacitor (3032) and a resistor (3033, 3034) for gradually increasing the current applied through the AC power. The main power wiring circuit breaker (301) is connected to a busbar (210) and receives power boosted to 400V. The main power wiring circuit breaker (301) is configured to cut off power when an overvoltage is applied. Additionally, a second instrument current transformer (302) is installed in front of the main power wiring circuit breaker (301) to measure the current of the AC power supplied to the main power wiring circuit breaker (301), determine whether there is an overcurrent, and transmit a current signal to the PLC control unit (207). The precharge unit (303) is configured to prevent excessive initial inrush current from being applied to the AC / DC converter unit (400), thereby preventing damage to components caused by excessive power supply.The precharge unit (303) is composed of an AC filter (3031) for filtering noise such as harmonics of the applied AC power, an AC filter capacitor (3032) for assisting the AC filter to suppress harmonics and noise of current and voltage and to improve the quality of the power signal, and a first resistor (3033) and a second resistor (3034) for preventing excessive initial voltage and current from being applied. The first resistor (3033) can be made larger than the second resistor (3034) so ​​that the incoming voltage and current can be gradually increased. Additionally, the precharge unit (300) further includes a charging electronic contactor (304) for controlling the ON / OFF of a control power to check whether the AC filter capacitor (3032) is operating during charging, and a discharging electronic contactor (305) for controlling the ON / OFF of a control power to check whether the AC filter capacitor (3032) is operating during discharging.

[0037] The AC power that has passed through the initial charging unit (300) is supplied to the AC / DC converter unit (400). The AC / DC converter unit (400) includes an electronic contactor (401) for main power to which the AC power supplied from the precharge unit (303) is connected, an AC reactor (402) connected to the electronic contactor (401) for main power for filtering and stabilizing the supplied AC power, an AC / DC converter (403) connected to the AC reactor (402) for converting the stabilized AC power into DC power, a blower (404) for heat dissipation of the AC / DC converter (403), and the DC power converted from the AC / DC converter (403) is supplied to the DC / DC converter unit (500) through the second busbar (405).

[0038] The configuration of the third cabinet (4) is described in detail with reference to FIGS. 2 to 5. The third cabinet (4) consists of a third cabinet body (41), a third cabinet front door (42) and a third cabinet rear door (43) installed on the front and rear sides of the third cabinet body (41), and a fan (44) installed on the top of the third cabinet body (41), and a DC / DC converter unit (500) and a switching unit (600) are provided inside. Casters (35) are provided on the bottom surface of the third cabinet body (31) and are configured to be fixed in position. In addition, the casters (35) are made of anti-vibration rubber pads to provide electrical insulation from the floor and protection from vibration.

[0039] The DC / DC converter section (500) comprises a DC / DC converter (501) for adjusting the voltage level of the applied DC power, a power supply unit (503) for supplying power to the control board of the DC / DC converter (501), a second electronic contactor (504) connected to the control board of the DC / DC converter (501), a resistor (505) connected to the second electronic contactor (504) for removing residual voltage generated when the second electronic contactor (504) is turned ON / OFF, and a first capacitor (506) for stably supplying the voltage supplied from the DC / DC converter (501). The DC / DC converter (501) functions to adjust the voltage level of the applied DC power. The DC / DC converter (501) converts the DC power to a voltage level suitable for the EV battery and supplies it to the battery. When connected in series, the voltage level is converted to have a range of 0 to 1500V, and when connected in parallel, it is converted to have a range of 0 to 750V. Additionally, a second electronic contactor is provided to turn ON / OFF the power supply to the control circuit, which is connected to a control board equipped with a control circuit that is a component of the DC / DC converter (501). Additionally, a resistor (505) is provided to remove residual voltage generated when the second electronic contactor (504) is turned ON / OFF, and a first capacitor (506) is provided to store energy and smooth the voltage and current to supply a stable voltage.

[0040] The switching unit (600) will be described in detail with reference to FIGS. 6 and 7. The DC voltage converted in the DC / DC converter unit (500) is applied to the switching unit (600). The switching unit (600) is composed of a DC reactor (601) connected to a DC / DC converter (501) for filtering and stabilizing the DC power, a switching device (602) to which the DC power with a voltage level adjusted in the DC reactor (601) is connected, a two-pole circuit breaker (603) connected to the switching device (602) to output the DC power, a voltage converter (604) that measures the voltage input to the switching device (602) and transmits the measured voltage signal to the control unit (700), a current converter (605) that measures the current input to the switching device (602) and transmits the measured current signal to the control unit (700), and a second capacitor (606) for stably supplying the voltage input to the switching device (602). FIG. 8 illustrates a method of connecting in series or in parallel using three relay switches (602a, 602b, 602c). In FIG. 8(a), current flows only through the central relay switch (602b), and accordingly, a pair of DC / DC converter units (500) are connected in series, allowing high voltage to be applied to the two-pole circuit breaker (603). FIG. 8(b) illustrates a state where only the central relay switch (602b) is open. When only the central relay switch (602b) is open, the DC / DC converter units (500) are connected in parallel, allowing low voltage to be applied to the two-pole circuit breaker (603). The bidirectional charger / discharger according to the present invention is 0 to 1500 V dc Voltage can be applied.

[0041] A control cabinet (5) is described with reference to FIGS. 2 and FIGS. 5. The control cabinet (5) comprises a control cabinet body (51), a control cabinet front door (42) installed on the front of the control cabinet body (51), and a control unit (700) inside. A fixing member (53) for fixing may be provided on the bottom surface of the control cabinet body (51). The fixing member (53) is made of a vibration-damping rubber pad to provide electrical insulation from the floor and protection from vibration.

[0042] The control unit (700) is composed of a DAQ system (701) that receives current and voltage data from a power input unit (200), an initial charging unit (300), an AC / DC converter unit (400), a DC / DC converter unit (500), and a switching unit (600) to receive temperature and voltage signal data of the battery (100) to monitor the state of the battery and transmit the temperature and voltage signal data to a control PC (800) or to control the charging and discharging of the battery (100), an uninterruptible power supply (702) for protecting the control PC (800) and the bidirectional charging and discharging system (1) in the event of a power outage, a communication unit (703) for transmitting and receiving data, and a wiring circuit breaker (704) and an electronic contactor (705) capable of cutting off the power supply. The DAQ system (701) receives data directly from the battery (100), monitors the status of the battery (100), receives the battery data, and transmits it to the control PC (800). The battery monitoring data includes cell voltage and cell temperature, etc.

[0043] Additionally, the bidirectional charging and discharging system (1) according to the present invention may further include a control PC (800) connected to a DAQ system (701) to receive current and voltage data from a power input unit (200), an initial charging unit (300), an AC / DC converter unit (400), a DC / DC converter unit (500), and a switching unit (600), or to receive temperature and voltage data of the battery from the DAQ system (701) to control the charging and discharging of the battery (100).

[0044] FIG. 9 is a schematic diagram of implementing V2G using a bidirectional charging and discharging system (1) according to the present invention. As shown in the drawing, the electric vehicle (EV) can be charged by connecting to the EV through an EV-dedicated interface (100'), or DC power can be received from the battery of the electric vehicle and transmitted to the power grid (Grid) in the opposite direction.

[0045] FIG. 10 shows that the reverse current applied through the charging of a battery and the discharging and regeneration of an electric vehicle (EV) using the bidirectional charging and discharging system (1) according to the present invention can be sent to the power grid, but the energy can also be circulated internally using the reverse current to operate charging and discharging with minimal electrical energy. By utilizing this energy circulation and regeneration effect, the charging and discharging of multiple batteries can be performed simultaneously (e.g., one side can be charged and the other side can be discharged). In addition, the combination of the battery and the electric vehicle has the advantage of enabling simultaneous battery charging and discharging tests and EV V2G tests.

[0046]

[0047] It is obvious to those skilled in the art that the present invention is not limited to the above embodiments and can be implemented with various modifications and variations within the scope of the technical essence of the present invention.

[0048] The present invention relates to a bidirectional charging and discharging system for EV batteries capable of performing charging and discharging tests on batteries of electric-driven hybrid or electric vehicles, as well as enabling V2G application using electric vehicles, and is an invention with high industrial applicability.

Claims

1. In a bidirectional charging and discharging system for EV batteries, A first cabinet equipped with a power input section into which three-phase AC power is input; A second cabinet connected to the side of the first cabinet and equipped with an initial charging unit for filtering applied three-phase AC power and preparing for charging, and an AC / DC converter unit for converting AC power transmitted from the initial charging unit into DC power; A third cabinet connected to the side of the second cabinet and equipped with a DC / DC converter unit that adjusts the voltage level from the converted DC power source to a DC voltage suitable for charging and discharging the battery; and A control cabinet equipped with a control unit for controlling the above AC / DC converter unit and the above DC / DC converter unit; A bidirectional charging and discharging system for an EV battery characterized by being composed of 2. In Paragraph 1, The above power input unit is, A circuit breaker connected to a three-phase AC power supply; A first instrument current transformer for detecting an abnormal state of the above-mentioned authorized AC power and transmitting the detected signal to a control unit; A first transformer connected to the above-mentioned circuit breaker to step up the applied AC power; A second transformer connected to the above-mentioned circuit breaker to reduce the applied AC power; A noise filter connected to the second transformer to remove noise from the AC power applied after voltage reduction through the second transformer; A power cutoff unit comprising a first electronic contactor to which AC power filtered through the noise filter is connected, and a circuit breaker connected to the first electronic contactor to turn the AC power ON / OFF; A PLC control unit comprising a control SMPS that receives AC power filtered through the noise filter and supplies control power to the PLC control unit, and a PLC module that controls the operation of an electronic contactor used in the system by receiving control power through the control SMPS; and A relay socket comprising a plurality of relay switches for transmitting ON / OFF switching signals of electronic contactors used in the system according to the control signal of the above PLC control unit; A bidirectional charging and discharging system for an EV battery characterized by being composed of 3. In Paragraph 2, The above initial charging unit is, A circuit breaker for main power wiring to which AC power stepped up from the first transformer is applied; A second instrument current transformer for detecting an abnormal state of the AC power applied to the circuit breaker for the main power supply and transmitting the detected signal to the PLC control unit; and A precharge section comprising an AC filter for removing noise from the AC power applied through the circuit breaker for the main power supply, and an AC filter capacitor and a resistor section for gradually increasing the current applied through the AC power supply; A bidirectional charging and discharging system for an EV battery characterized by being composed of 4. In Paragraph 3, The above AC / DC converter unit is, An electronic contactor for a main power supply to which the AC power applied from the above-mentioned precharge unit is connected; An AC reactor connected to the above-mentioned main power contactor for filtering and stabilizing the applied AC power; and An AC / DC converter connected to the above AC reactor to convert stabilized AC power into DC power; A bidirectional charging and discharging system for an EV battery characterized by being composed of 5. In Paragraph 4, The above DC / DC converter unit is, A DC / DC converter to which the converted DC power is applied and which regulates the voltage level of the applied DC power; A power supply for supplying power to the control board of the above DC / DC converter; A second electronic contactor connected to the control board of the above DC / DC converter; A resistor connected to the second electronic contactor to remove residual voltage generated when the second electronic contactor is turned ON / OFF; and A first capacitor for stably supplying the voltage supplied by the above DC / DC converter; A bidirectional charging and discharging system for an EV battery characterized by being composed of 6. In Paragraph 5, A bidirectional charging and discharging system for an EV battery, characterized in that the third cabinet further comprises a switching unit formed on one side of the lower portion of the DC / DC converter unit to connect DC power sources with voltage levels adjusted in the DC / DC converter unit in series or in parallel.

7. In Paragraph 6, The above switching unit is, A DC reactor connected to the above DC / DC converter for filtering and stabilizing the DC power supply; A switching device to which a DC power source with a voltage level adjusted in the above DC reactor is connected; A two-pole circuit breaker connected to the above-mentioned switching device and outputting DC power; A voltage converter that measures the voltage input to the switching device and transmits the measured voltage signal to the control unit; A current converter that measures the current flowing into the switching device and transmits the measured current signal to the control unit; and A second capacitor for stably supplying the voltage supplied to the above switching device; A bidirectional charging and discharging system for an EV battery characterized by being composed of 8. In Paragraph 7, The above control unit is, A DAQ system that receives temperature and voltage signal data of the battery to monitor the state of the battery and transmits the temperature and voltage signal data to a control PC, or receives current and voltage data from the power input unit, the initial charging unit, the AC / DC converter unit, the DC / DC converter unit, and the switching unit to control the charging and discharging of the battery; An uninterruptible power supply for protecting the control PC and the bidirectional charging and discharging system in the event of a power outage; and A communication unit for transmitting and receiving the above data; A bidirectional charging and discharging system for an EV battery characterized by being composed of 9. In Paragraph 8, The above-described bidirectional charging and discharging system for an EV battery further comprises a control PC connected to the DAQ system to receive current and voltage data from the power input unit, the initial charging unit, the AC / DC converter unit, the DC / DC converter unit, and the switching unit, or to receive temperature and voltage data of the battery from the DAQ system to control the charging and discharging of the battery.

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