System and method for protecting an inverter in a vehicle from overvoltage

Abstract

The present invention relates to a system and method for protecting an inverter in a vehicle from an overvoltage. A system for protecting an inverter in a vehicle from an overvoltage can include an inverter including a plurality of switching elements and converting energy supplied from an energy storage into alternating current, a motor driven by the alternating current converted by the inverter, a capacitor connected in parallel between the inverter and the energy storage, storing regenerative energy of the motor during regenerative braking, and a controller, when a voltage (DC bus voltage) of the capacitor measured by a voltage sensor is equal to or greater than a preset first voltage, causing a relay connecting the energy storage and the motor to be turned off, and operating the switching elements in the inverter in response to a current command (Id*, Iq*) for applying a zero vector to the motor, which is stored in advance.

Description

Technical Field

[0001] The present invention relates to a system and method for protecting an inverter in a vehicle from overvoltage. Background Technology

[0002] Recently, in response to the crises of air pollution and oil depletion, technologies related to environmentally friendly vehicles powered by electricity are being actively developed. Environmentally friendly vehicles include hybrid electric vehicles, fuel cell electric vehicles, and electric vehicles.

[0003] Meanwhile, electric vehicles include inverter systems to drive, for example... Figure 1 The motor is shown. However, when the DC bus voltage of inverter 30 (the voltage across capacitor 20) exceeds a predetermined voltage level, electric vehicles, including those with conventional inverter systems, disconnect the relay 50 connecting the high-voltage battery 10 and the motor 40. In this situation, electrical energy flows excessively from the motor to capacitor 20, causing a sharp rise in the DC bus voltage across capacitor 20, which is designed into the inverter system. Therefore, overvoltage can cause the inverter to burn out.

[0004] Accordingly, a technology is needed to prevent inverters from burning out due to overvoltage.

[0005] The above description is merely to help understand the background of the present invention and does not imply that the present invention falls within the scope of related technologies already known to those skilled in the art. Summary of the Invention

[0006] The present invention is intended to solve the above-mentioned problems in the prior art. The purpose of the present invention is to provide a system and method for protecting inverters in vehicles from overvoltage, which can prevent the inverter from burning out due to overvoltage.

[0007] To achieve the objectives of this invention, the present invention provides a system for protecting an inverter in a vehicle from overvoltage, the system comprising: an inverter including a plurality of switching elements and converting energy supplied from an energy storage device into alternating current; a motor driven by the alternating current converted by the inverter; a capacitor connected in parallel between the inverter and the energy storage device to store regenerative energy of the motor during regenerative braking; and a controller that disconnects a relay connecting the energy storage device and the motor when the voltage (DC bus voltage) of the capacitor measured by a voltage sensor is equal to or greater than a preset first voltage, and operates the switching elements in the inverter in response to a pre-stored current command (Id*, Iq*) to apply a zero vector current to the motor.

[0008] The inverter can include a first bridge arm including a first switching element and a second switching element at a lower end of the first switching element, a second bridge arm including a third switching element and a fourth switching element at a lower end of the third switching element, and a third bridge arm including a fifth switching element and a sixth switching element at a lower end of the fifth switching element, wherein output terminals of the first, second, and third bridge arms can be connected to respective phases of the motor.

[0009] When the plurality of switching elements are driven, the current command (Id*, Iq*) can turn on the first, third, and fifth switching elements, or turn on the second, fourth, and sixth switching elements to apply a zero vector to the motor during driving of the motor and cause the motor to generate a negative torque. If the first, third, and fifth switching elements are turned on, the second, fourth, and sixth switching elements are turned off.

[0010] The controller can include a memory storing a map of current commands (Id*, Iq*) to apply a zero vector to the motor during driving of the motor, an overvoltage detector determining whether a voltage across the capacitor measured by the voltage sensor is equal to or greater than a first voltage, a current control part generating voltage commands (Vd*, Vq*) to cause d-axis and q-axis currents (Id, Iq) fed back from the motor to follow d-axis and q-axis current commands (Id*, Iq*) stored in the memory, and a switching element control part operating the plurality of switching elements in the inverter in response to the generated voltage commands (Vd*, Vq*).

[0011] When the measured voltage across the capacitor is equal to or greater than the first voltage, the controller can turn off the relay and can cause the current supplied to the motor from the inverter to follow the current command.

[0012] When the voltage across the capacitor is equal to or greater than the first voltage, the controller can turn off the relay, can discharge the voltage of the capacitor to a preset second voltage, and then can maintain the voltage of the capacitor within an error range based on the second voltage.

[0013] When the voltage across the capacitor decreases below the error range based on the second voltage, the controller can increase the voltage of the capacitor through regenerative braking, and when the voltage across the capacitor exceeds the error range based on the second voltage, the controller can discharge the voltage of the capacitor by driving the motor.

[0014] According to another aspect of the present application, a method for protecting an inverter in a vehicle from an overvoltage can include determining whether a voltage across a capacitor measured by a voltage sensor is equal to or greater than a first voltage, causing a relay connected to an energy storage and a motor to be turned off when the voltage across the capacitor is equal to or greater than the first voltage, and operating switching elements in the inverter in response to current commands (Id*, Iq*) for applying a zero vector to the motor.

[0015] The method can further include storing a map of the current commands (Id*, Iq*) for applying the zero vector to the motor in a memory before determining whether the voltage across the capacitor measured by the voltage sensor is equal to or greater than the first voltage.

[0016] Operating the switching elements in the inverter in response to the current commands (Id*, Iq*) for applying the zero vector to the motor can include generating voltage commands (Vd*, Vq*) by a current control part to cause a d-axis current (Id) and a q-axis current (Iq) fed back from the motor to follow d-axis current commands (Id*) and q-axis current commands (Iq*) stored in a memory, and operating the switching elements in the inverter by a switching element control part in response to the generated voltage commands (Vd*, Vq*).

[0017] The method can further include, when the voltage across the capacitor is equal to or greater than the first voltage, discharging the voltage of the capacitor to a preset second voltage after causing the relay connected to the energy storage and the motor to be turned off, and maintaining the voltage of the capacitor within an error range based on the second voltage.

[0018] Maintaining the voltage of the capacitor within the error range based on the second voltage can include increasing the voltage of the capacitor by regenerative braking by a controller when the voltage across the capacitor decreases below the error range based on the second voltage, and discharging the voltage of the capacitor by driving the motor by the controller when the voltage across the capacitor exceeds the error range based on the second voltage.

[0019] According to the present application, an inverter in a vehicle can be protected from an overvoltage.

[0020] Further, by maintaining a DC bus voltage (voltage across a capacitor) in an inverter system at a predetermined voltage and providing a corresponding voltage to other electronic elements in the vehicle, a driving time of the other electronic elements can be increased.

[0021] Further, since a pre-charge time of a capacitor is reduced by maintaining the voltage across the capacitor in the inverter system at a predetermined voltage when the vehicle is restarted during driving, the vehicle can have a fast response time at the time of restart. BRIEF DESCRIPTION OF DRAWINGS

[0022] The above and other objects, features and other advantages of the present application will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0023] Figure 1 is a schematic diagram illustrating an inverter system included in a general electric vehicle;

[0024] Figure 2 is a schematic diagram illustrating a system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application;

[0025] Figure 3 is a diagram illustrating the system before a failure occurs in the system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application;

[0026] Figure 4 is a diagram illustrating a case where a relay is turned off when a failure occurs in the system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application;

[0027] Figure 5 is a diagram illustrating a state where a voltage of a capacitor is discharged after a failure occurs in the system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application;

[0028] Figure 6 is a diagram illustrating a state where a voltage across the capacitor is maintained at a predetermined voltage in the system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application;

[0029] Figure 7 is a diagram illustrating an operation of the system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application; and

[0030] Figure 8 is a flowchart illustrating a method for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application. DETAILED DESCRIPTION

[0031] Hereinafter, a system and a method for protecting an inverter in a vehicle from an overvoltage according to a preferred embodiment of the present application will be described in detail with reference to the accompanying drawings.

[0032] Figure 2 is a schematic diagram illustrating a system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application; Figure 3 is a diagram illustrating the system before a failure occurs in the system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application; Figure 4 is a diagram illustrating a case where a relay is turned off when a failure occurs in the system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application;Figure 5 is a diagram illustrating a state in which the voltage of a capacitor is discharged after a malfunction occurs in a system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application; Figure 6 is a diagram illustrating a state in which the voltage across a capacitor is maintained at a predetermined voltage in a system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application; Figure 7 is a diagram illustrating the operation of a system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application.

[0033] As shown in Figure 2 , a system for protecting an inverter in a vehicle from an overvoltage according to the present application can include an energy storage 100, an inverter 200, a capacitor 300 connected in parallel between the inverter 200 and the energy storage 100, a motor 400, and a controller 500. The system can also include a voltage sensor 600 that measures the voltage across the capacitor 300, a rotational angle sensor 700 that detects the rotational angle of the rotor of the motor 400, and a current sensor 900 that measures the current input to the motor 400.

[0034] The energy storage 100 is an element that stores electrical energy that drives the motor 400 in the form of direct current (e.g., a battery) and outputs DC power.

[0035] The capacitor 300 is connected in parallel between the inverter 200 (the inverter 200 is connected to both ends of the energy storage 100, and is described in detail below) and the energy storage 100, and stores the regenerative energy of the motor 400 during regenerative braking to form a DC bus voltage Vdc. The DC bus voltage Vdc becomes the input voltage of the inverter 200.

[0036] The inverter 200 includes a plurality of switching elements (whose on / off states are controlled by a pulse width modulation signal provided from the controller 500), and converts the DC power provided from the energy storage 100 into AC power for driving the motor 400. Specifically, the inverter 200 can include a first bridge arm 210 including a first switching element S1 and a second switching element S2 located at the lower end of the first switching element S1, a second bridge arm 220 including a third switching element S3 and a fourth switching element S4 located at the lower end of the third switching element S3, and a third bridge arm 230 including a fifth switching element S5 and a sixth switching element S6 located at the lower end of the fifth switching element S5. In this regard, it should be understood that the switching of the inverter 200 means the switching of the three-phase voltage output from the inverter 200. Furthermore, the output terminals of the first bridge arm 210, the second bridge arm 220, and the third bridge arm 230 are connected to the corresponding phases of the motor 400.

[0037] The motor 400 is driven by AC power converted through the inverter 200. Various types of motors known to those skilled in the art can be used. The motor of an eco-friendly vehicle can be a driving motor that provides rotational force to the driving wheels of the vehicle.

[0038] The voltage sensor 600 is used to measure the voltage across the capacitor 300 (DC bus voltage: Vdc). Information about the measured voltage across the capacitor 300 can be transmitted to the controller 500 and used by the controller 500 to determine whether an overvoltage has occurred.

[0039] The rotational angle sensor 700 is an element that detects the position of the rotor of the motor 400 (i.e., the rotational angle of the rotor of the motor 400). The rotational angle sensor 700 is used to detect the angle of the rotor of the motor 400 and continuously outputs a rotational angle detection signal including information about the detected rotational angle of the rotor of the motor 400. According to embodiments, the rotational angle sensor 700 can be implemented with a resolver or the like.

[0040] The current sensor 900 is used to measure the current output from the inverter 200 and input to the phases of the motor 400. According to embodiments, when the motor 400 is a three-phase motor having phases a, b, and c, two or more current sensors 900 can be provided to measure the current input to at least two of the phases a, b, and c.

[0041] The controller 500 can perform a control operation by a pulse width modulation method in which the duty ratio (duty cycle) of the switching elements S1 to S6 of the inverter 200 is appropriately adjusted to control the torque of the motor 400 to a desired value (torque command).

[0042] To perform the control operation, when the voltage across the capacitor 300 measured by the voltage sensor 600 is equal to or greater than a preset first voltage, the controller 500 controls the switching elements S1 to S6 in the inverter 200 such that the motor 400 outputs a value corresponding to the torque command value for the motor 400 (torque target value desired to be obtained by the motor) output from an external device.

[0043] Specifically, the controller 500 can include a memory 510, an overvoltage detector 520, a current control portion 530, and a switching element control portion 540. The memory 510 stores a map of current commands (Id*, Iq*) to apply a zero vector to the motor 400 during driving of the motor 400. The overvoltage detector 520 determines whether a voltage across the capacitor 300 measured from the voltage sensor 600 is equal to or greater than a first voltage. The current control portion 530 generates voltage commands (Vd*, Vq*) to cause a d-axis current (Id) and a q-axis current (Iq) fed back from the motor 400 to follow the d-axis current command (Id*) and the q-axis current command (Iq*) stored in the memory 510. The switching element control portion 540 operates the switching elements S1 to S6 in the inverter 200 in response to the generated voltage commands (Vd*, Vq*).

[0044] Here, the current commands (Id*, Iq*) stored in the memory 510 are current command values that cause a zero vector to be applied to the motor 400 during driving of the motor 400, so that a negative torque is generated in the motor 400 by turning on the first switching element S1, the third switching element S3, and the fifth switching element S5 or the second switching element S2, the fourth switching element S4, and the sixth switching element S6 when the plurality of switching elements are driven by the controller 500. The current command values can have different values for each motor.

[0045] In other words, the current commands (Id*, Iq*) stored in the memory 510 are command values for applying a zero vector to the motor 400, so that a negative torque is generated in the motor 400. When the switching elements S1 to S6 of the current-controlled inverter 200 input to the motor 400 follow the corresponding current commands, a negative torque can be generated in the motor 400. Here, the current commands can be current commands for characteristic current values for applying a zero vector to the motor 400 during driving of the motor 400. The current command values can have different values for each motor.

[0046] In addition, the controller 500 can further include a coordinate conversion device that converts two-phase coordinates into three-phase coordinates or converts three-phase coordinates into two-phase coordinates. According to embodiments, when the motor 400 is a three-phase motor having phases a, b, and c, the coordinate conversion device can convert the d-axis current (Id) and the q-axis current (Iq) into three-phase currents (Ia, Ib, Ic) of a, b, and c, and can convert the three-phase currents (Ia, Ib, Ic) of a, b, and c into the d-axis current (Id) and the q-axis current (Iq). Since converting two-phase coordinates into three-phase coordinates or converting three-phase coordinates into two-phase coordinates is a well-known technology, a detailed description thereof will be omitted.

[0047] Hereinafter, a description will be given with reference to Figures 3 to 7The working principle of a system for protecting an inverter in a vehicle from an overvoltage according to the present application is described.

[0048] As Figure 3 shown, in a normal state in which no malfunction occurs, during regenerative braking, the capacitor 300 can be charged with regenerative energy of the motor 400, so that the voltage of the capacitor 300 can be raised. The voltage sensor 600 measures the voltage across the capacitor 300 and transmits the measured voltage across the capacitor 300 to the controller 500. The controller 500 determines whether the voltage of the capacitor is equal to or greater than a preset first voltage. In this regard, the first voltage can be a value extracted from an experimental value, and can be a voltage level at which a switching element included in the inverter can be burnt out.

[0049] When it is determined that the voltage of the capacitor 300 measured by the voltage sensor 600 is equal to or greater than the preset first voltage, the controller 500 causes the relay 800 connecting the energy storage 100 and the motor 400 to be disconnected, as Figure 4 shown.

[0050] Meanwhile, as Figure 4 shown, after the controller 500 causes the relay 800 connecting the energy storage 100 and the motor 400 to be disconnected, the voltage of the capacitor 300 should be discharged to prevent the switching element in the inverter from being burnt out. The controller 500 according to the present application can operate the switching element in the inverter in response to current commands (Id*, Iq*) pre-stored in the memory to apply a zero vector to the motor, thereby allowing the voltage of the capacitor 300 to be discharged.

[0051] As Figure 4 shown, when the relay 800 is disconnected, a closed loop circuit is formed between the capacitor 300, the inverter 200, and the motor 400. The motor 400 is driven via control of the switching element in the inverter using the voltage charged in the capacitor 300 in such a closed loop circuit, and the voltage of the capacitor 300 can be discharged.

[0052] Meanwhile, as Figure 4As shown, during the process of relay 800 being disconnected and capacitor 300 being discharged, a problem may occur: during coasting and downhill driving, the electrical energy of capacitor 300 rises rapidly due to the back electromotive force of motor 400, potentially causing inverter 400 to burn out. To solve this problem, it is necessary to suppress the back electromotive force generated by motor 400 during the discharge of capacitor 300 during coasting and downhill driving. In this case, to suppress the back electromotive force generated by motor 400, it is necessary to reduce the speed of motor 400. According to the present invention, during the driving of motor 400, a zero vector is applied to motor 400 to generate negative torque in motor 400, thereby controlling the switching elements S1 to S6 in inverter 200 in response to current commands (Id*, Iq*) that can prevent the motor from generating back electromotive force. Therefore, the problem of back electromotive force generated by motor 400 can be solved.

[0053] In other words, when the voltage across the capacitor 300, as measured by the voltage sensor 600, is equal to or greater than the first voltage, the controller 500 disconnects the relay 800 and causes the current supplied from the inverter 200 to the motor 400 to follow the current command pre-stored in the memory 510, thereby discharging the voltage of the capacitor 300 and suppressing the motor 400 from generating back electromotive force.

[0054] Simultaneously, when the voltage across capacitor 300, measured by voltage sensor 600, is equal to or greater than the first voltage, controller 500... Figure 4 The relay 800 is disconnected, and the current supplied from the inverter 200 to the motor 400 follows the current command pre-stored in the memory 510, thereby discharging the voltage of the capacitor 300 to a preset second voltage. After the voltage of the capacitor is discharged to the second voltage, the voltage of the capacitor 300 is adjusted as follows: Figure 6 The error is maintained within the range based on the second voltage.

[0055] Specifically, when the voltage across capacitor 300 drops below the error range based on the second voltage, controller 500 can increase the voltage of capacitor 300 through regenerative braking. When the voltage across capacitor 300 exceeds the error range based on the second voltage, controller 500 can discharge the voltage of capacitor by driving a motor, thereby maintaining the voltage of capacitor within the error range based on the second voltage.

[0056] Meanwhile, although not shown in detail in the accompanying drawings, multiple electronic components included in the vehicle are connected to the energy storage unit 100 via circuitry, and the corresponding electronic components are driven by power supplied from the energy storage unit 100. However, in situations such as Figure 4In the case where the illustrated relay 800 is turned off, there is a problem that the circuit connection between the electronic components and the energy storage 100 is cut off, and thus power supply can not be possible, and thus a safety accident can occur.

[0057] To solve the above problem, according to the present application, in the case where the relay 800 is turned off, the controller 500 discharges the voltage of the capacitor 300 to a second voltage, but maintains the voltage of the capacitor 300 within an error range based on the second voltage in the above method, so that the energy stored in the capacitor 300 is supplied to the electronic components within the vehicle, thereby increasing the driving time of the corresponding electronic components and preventing the occurrence of a safety accident. Figure 4

[0058] In addition, the controller 500 maintains the voltage of the capacitor 300 at a predetermined voltage level. Thus, since the pre-charge time of the capacitor 300 can be shortened at the time of restart of the vehicle during driving, the vehicle can have a fast response time at the time of restart.

[0059] A system for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application will be described with reference to Figure 7 When the voltage of the capacitor 300 rises to be equal to or greater than the first voltage as in the A section, the controller 500 turns off the relay 800 connected to the energy storage 100 and the motor 400, and operates the switching elements S1 to S6 in the inverter 200 to drive the motor 400 in response to a current command for applying a zero vector to the motor 400 during driving of the motor 400, thereby discharging the voltage of the capacitor 300 as shown in the B section.

[0060] In addition, when the voltage reaches the second voltage, the controller 500 discharges the voltage of the capacitor 300, but maintains the voltage of the capacitor within an error range based on the second voltage as shown in the C section.

[0061] Figure 8 is a flowchart illustrating a method for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application. As shown in Figure 8 The method for protecting an inverter in a vehicle from an overvoltage according to an embodiment of the present application can include a step of determining whether a voltage across a capacitor measured by a voltage sensor is equal to or greater than a first voltage, a step of turning off a relay connected to an energy storage and a motor when the voltage across the capacitor is equal to or greater than the first voltage, and a step of operating switching elements in an inverter in response to a current command (Id*, Iq*) for applying a zero vector to the motor.

[0062] ​The method can further include, before the step of determining whether the voltage across the capacitor measured by the voltage sensor is equal to or greater than the first voltage, the step of storing a map of current commands (Id*, Iq*) that apply a zero vector to the motor in the memory.

[0063] Further, the step of operating the switching elements in the inverter in response to the current commands (Id*, Iq*) that apply a zero vector to the motor can include the step of generating voltage commands (Vd*, Vq*) in the current control section that cause the d-axis current (Id) and the q-axis current (Iq) fed back from the motor to follow the d-axis current command (Id*) and the q-axis current command (Iq*) stored in the memory, and the step of operating the switching elements in the inverter in response to the generated voltage commands (Vd*, Vq*) in the switching element control section. The method can further include, when the voltage across the capacitor is equal to or greater than the first voltage, the step of discharging the voltage of the capacitor to a preset second voltage after the step of turning off the relay connecting the energy storage device and the motor, and the step of maintaining the voltage of the capacitor within an error range based on the second voltage.

[0064] Specifically, in the step of maintaining the voltage of the capacitor within an error range based on the second voltage, when the voltage across the capacitor decreases below the error range based on the second voltage, the controller can increase the voltage of the capacitor by regenerative braking, and when the voltage across the capacitor exceeds the error range based on the second voltage, the voltage of the capacitor can be discharged by driving the motor.

[0065] Meanwhile, since the specific technical features of the respective steps of the method for protecting the inverter in the vehicle from an overvoltage are the same as the technical features of the detailed configuration of the above-described system for protecting the inverter in the vehicle from an overvoltage, a detailed description thereof will be omitted.

[0066] The above-described operations / functions performed by the controller can be embodied as computer-readable codes / algorithms / software stored on a computer-readable recording medium. The computer-readable recording medium is any data storage device that can store data that can be read later by a computer or a processor / microprocessor. Examples of the computer-readable recording medium include a hard disk drive (HDD), a solid state drive (SSD), a silicon disk drive (SDD), a read-only memory (ROM), a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, etc.

[0067] The above-described controller can include one or more processors / microprocessors. The controller can perform the above-described operations / functions by executing the computer-readable codes / algorithms / software stored on the computer-readable recording medium.

[0068] While the application has been described with reference to the specific embodiments illustrated in the attached drawings, it will be apparent that those skilled in the art can devise variations and modifications to the application without departing from the scope of the application described in the appended claims.

Claims

1. A system for protecting an inverter in a vehicle from an overvoltage, the system comprising: an inverter including a plurality of switching elements and converting energy supplied from an energy storage into alternating current; a motor driven by the alternating current converted by the inverter; a capacitor connected in parallel between the inverter and the energy storage, storing regenerative energy of the motor during regenerative braking; and a controller, when a voltage of the capacitor measured by a voltage sensor is equal to or greater than a preset first voltage, causing a relay connecting the energy storage and the motor to be disconnected, and operating the switching elements in the inverter in response to a current command (Id*, Iq*) for applying a zero vector to the motor that is stored in advance, wherein the system includes only one inverter and only one motor; when the voltage across the capacitor is equal to or greater than the first voltage, the controller causes the relay to be disconnected, discharges the voltage of the capacitor to a preset second voltage, and then maintains the voltage of the capacitor within an error range based on the second voltage, the first voltage being a voltage level at which the plurality of switching elements included in the inverter are burned out. the inverter includes:

2. The system for protecting an inverter in a vehicle from overvoltages according to claim 1, wherein, a first bridge arm including a first switching element and a second switching element located at a lower end of the first switching element; a second bridge arm including a third switching element and a fourth switching element located at a lower end of the third switching element; and a third bridge arm including a fifth switching element and a sixth switching element located at a lower end of the fifth switching element; wherein output terminals of the first bridge arm, the second bridge arm, and the third bridge arm are connected to respective phases of the motor. when the plurality of switching elements are driven, the current command (Id*, Iq*) causes the first switching element, the third switching element, and the fifth switching element to be turned on, or causes the second switching element, the fourth switching element, and the sixth switching element to be turned on, to apply a zero vector to the motor during driving of the motor, and to cause the motor to generate a negative torque.

3. The system for protecting an inverter in a vehicle from overvoltages according to claim 2, wherein, the controller includes:

4. The system for protecting an inverter in a vehicle from overvoltages according to claim 2, wherein, a memory storing a map of the current command (Id*, Iq*) for applying a zero vector to the motor during driving of the motor; an overvoltage detector determining whether the voltage across the capacitor measured by the voltage sensor is equal to or greater than the first voltage; a current control part generating a voltage command (Vd*, Vq*) causing a d-axis current (Id) and a q-axis current (Iq) fed back from the motor to follow a d-axis current command (Id*) and a q-axis current command (Iq*) stored in the memory; and a switching element control part operating the plurality of switching elements in the inverter in response to the generated voltage command (Vd*, Vq*). when the measured voltage across the capacitor is equal to or greater than the first voltage, the controller causes the relay to be disconnected, and causes the current supplied from the inverter to the motor to follow the current command.

5. The system for protecting an inverter in a vehicle from overvoltage of claim 1, wherein, when the voltage across the capacitor decreases below the error range based on the second voltage, the controller increases the voltage of the capacitor by regenerative braking, and when the voltage across the capacitor exceeds the error range based on the second voltage, the controller discharges the voltage of the capacitor by driving the motor.

6. The system for protecting an inverter in a vehicle from overvoltages of claim 1, wherein, 7.A method for protecting an inverter in a vehicle from an overvoltage, the method comprising: ​ determining whether a voltage across the capacitor measured by the voltage sensor is equal to or greater than a first voltage; disconnecting a relay connecting the energy storage device and the motor when the voltage across the capacitor is equal to or greater than the first voltage; operating the switching elements in the inverter in response to current commands (Id*, Iq*) to apply a zero vector to the motor; wherein the vehicle includes only one inverter and only one motor; discharging the voltage of the capacitor to a preset second voltage after disconnecting the relay connecting the energy storage device and the motor when the voltage across the capacitor is equal to or greater than the first voltage; and maintaining the voltage of the capacitor within an error range based on the second voltage, the first voltage being a voltage level at which the plurality of switching elements included in the inverter are burned out.

8. The method of claim 7, further comprising: before determining whether the voltage across the capacitor measured by the voltage sensor is equal to or greater than the first voltage, storing a map of current commands (Id*, Iq*) to apply a zero vector to the motor in the memory.

9. The method of claim 8, wherein, operating the switching elements in the inverter in response to the current commands (Id*, Iq*) to apply a zero vector to the motor includes: generating voltage commands (Vd*, Vq*) by the current control portion, the voltage commands (Vd*, Vq*) causing d-axis current (Id) and q-axis current (Iq) fed back from the motor to follow d-axis current commands (Id*) and q-axis current commands (Iq*) stored in the memory; operating the switching elements in the inverter by the switching element control portion in response to the generated voltage commands (Vd*, Vq*).

10. The method of claim 7, wherein, maintaining the voltage of the capacitor within an error range based on the second voltage includes: increasing the voltage of the capacitor by the controller through regenerative braking when the voltage across the capacitor decreases below the error range based on the second voltage; discharging the voltage of the capacitor by the controller through driving the motor when the voltage across the capacitor exceeds the error range based on the second voltage.

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