System and method for protecting inverters in a vehicle from overvoltage

Abstract

The present invention relates to a system and method for protecting an inverter in a vehicle from overvoltage. The system includes a first inverter having switching elements and converting energy of an energy storage device into alternating current, a first motor driven by receiving the converted alternating current, a second inverter connected in parallel with the first inverter, including switching elements and converting energy of the energy storage device into alternating current, a second motor driven by receiving the converted alternating current, a first capacitor connected in parallel between the first inverter and the energy storage device and storing electric energy of the first motor during regenerative braking, and a controller disconnecting a relay connecting the energy storage device and the motor when a voltage of the first capacitor is equal to or greater than a predetermined voltage and operating the switching elements in the inverters in response to a first current command and a second current command.

Description

TECHNICAL FIELD

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

[0002] In order to cope with recent air pollution and oil depletion crises, technologies regarding eco-friendly vehicles using electric energy as a power source of vehicles are being actively developed. The eco-friendly vehicles include a hybrid electric vehicle, a fuel cell electric vehicle, and an electric vehicle.

[0003] As shown in the related art Figure 1 An electric vehicle having a disconnector on a front wheel and two drive motors includes two inverter systems for driving the two motors. In such an electric vehicle, when the disconnector is released, the connection between the motors and the drive system is released, and the front wheel motor is in an unloaded state. Specifically, the electric energy of the front wheel motor diverging as the front wheel motor diverges excessively flows to a capacitor (not shown) connected in parallel to the front wheel inverter, and thus, a direct current (DC) link voltage across a capacitor designed in the front wheel inverter system rapidly increases. As a result, damage to the inverter due to overvoltage occurs. Therefore, there is a need to develop a technology capable of preventing damage to the inverter due to overvoltage.

[0004] The above description of background art is merely provided for the purposes of enhancing the understanding of the background of the present invention and should not be accepted as an acknowledgement that the described art corresponds to the prior art of the present invention. SUMMARY

[0005] The present invention provides a system and method for protecting an inverter in a vehicle from overvoltage, which prevents damage to the inverter in the vehicle due to overvoltage.

[0006] According to an aspect of the present application, a system for protecting inverters in a vehicle from overvoltage can include a first inverter having a plurality of switching elements and configured to convert energy provided from an energy storage device into alternating current (AC) electricity, a first motor configured to be driven by receiving the AC electricity converted by the first inverter, a second inverter connected in parallel with the first inverter, including a plurality of switching elements, and configured to convert energy provided from the energy storage device into AC electricity, a second motor configured to be driven by receiving the AC electricity converted by the second inverter, a first capacitor connected in parallel between the first inverter and the energy storage device, and configured to store electric energy of the first motor during regenerative braking, and a controller configured to, when a voltage of the first capacitor measured by a voltage sensor is equal to or greater than a predetermined first voltage, disconnect a relay connecting the energy storage device and the motors, and operate the switching elements in the first inverter and the second inverter in response to first current commands 1_Id* and 1_Iq* that cause zero vectors to be applied to each of the motors and second current commands 2_Id* and 2_Iq* that cause zero torque to be generated in each of the motors, the current commands being pre-stored.

[0007] The controller can be configured to, when a voltage of the first capacitor measured by the voltage sensor is equal to or greater than a predetermined first voltage, disconnect a relay connecting the energy storage device and the first motor, can operate the switching elements in the first inverter in response to first current commands 1_Id* and 1_Iq*, and can operate the switching elements in the second inverter in response to second current commands 2_Id* and 2_Iq*.

[0008] The system can further include a second capacitor connected in parallel between the second inverter and the energy storage device, and configured to store electric energy of the second motor during regenerative braking. The controller can be configured to, when a voltage of the second capacitor measured by the voltage sensor is equal to or greater than a predetermined first voltage, disconnect a relay connecting the energy storage device and the second motor, operate the switching elements in the first inverter in response to the second current commands 2_Id* and 2_Iq*, and operate the switching elements in the second inverter in response to the first current commands 1_Id* and 1_Iq*.

[0009] The first inverter can include a first branch having a first switching element and a second switching element at a lower end of the first switching element, a second branch having a third switching element and a fourth switching element at a lower end of the third switching element, and a third branch having a fifth switching element and a sixth switching element at a lower end of the fifth switching element, and output ends of the first, second, and third branches can be connected to each phase of the first motor. The second inverter can include a fourth branch having a seventh switching element and an eighth switching element at a lower end of the seventh switching element, a fifth branch having a ninth switching element and a tenth switching element at a lower end of the ninth switching element, and a sixth branch having an eleventh switching element and a twelfth switching element at a lower end of the eleventh switching element, and output ends of the fourth, fifth, and sixth branches can be connected to each phase of the second motor.

[0010] When driving the plurality of switching elements, the first current commands 1_Id* and 1_Iq* can cause the first, third, and fifth switching elements or the seventh, ninth, and eleventh switching elements to be turned on, and thus, during driving of the first or second motor, a zero vector can be applied to the first or second motor, thereby enabling generation of a negative torque in the first or second motor. When driving the plurality of switching elements in the first or second inverter, the second current commands 2_Id* and 2_Iq* can cause generation of a zero torque in the first or second motor.

[0011] The controller can include a memory, an overvoltage detector, a current controller, and a switching element controller, the memory configured to store a first current command (1_Id* or 1_Iq*) map and a second current command (2_Id* or 2_Iq*) map, the first current command map causing a zero vector to be applied to each motor during driving of each motor, thereby enabling generation of a negative torque in each motor, the second current command map causing a zero torque to be generated in each motor, the overvoltage detector configured to determine whether a voltage across each capacitor measured by a voltage sensor is equal to or greater than a first voltage, the current controller configured to generate first voltage commands 1_Vd* and 1_Vq* and second voltage commands 2_Vd* and 2_Vq* to enable d-axis current Id and q-axis current Iq fed back from each motor to follow first d-axis current commands 1_Id* and first q-axis current commands 1_Iq* stored in the memory, second d-axis current commands 2_Id*, and second q-axis current commands 2_Iq*, and the switching element controller configured to operate switching elements in the first and second inverters in response to the generated first and second voltage commands.

[0012] When the measured voltage across the first capacitor is equal to or greater than the first voltage, the controller can be configured to: turn off the relay, discharge the voltage of the first capacitor to a predetermined second voltage, and then maintain the voltage of the first capacitor within an error range based on the second voltage. The controller can be configured to: when the measured voltage across the first capacitor decreases below the error range based on the second voltage, increase the voltage of the first capacitor by regenerative braking, and when the voltage across the first capacitor exceeds the error range based on the second voltage, discharge the voltage of the first capacitor by driving of the first motor and the second motor.

[0013] When the measured voltage across the first capacitor is equal to or greater than the first voltage, the controller can be configured to turn off the relay, discharge the voltage of the first capacitor to a predetermined second voltage, and then maintain the voltage of the first capacitor within an error range based on the second voltage. The controller can be configured to: when the measured voltage across the first capacitor decreases below the error range based on the second voltage, increase the voltage of the first capacitor by regenerative braking, and when the voltage across the first capacitor exceeds the error range based on the second voltage, discharge the voltage of the first capacitor by driving of the first motor and the second motor.

[0014] In response to determining that the voltage of the first capacitor measured by the voltage sensor is equal to or greater than a predetermined first voltage, the controller can be configured to turn on the first switching element, the third switching element, and the fifth switching element, or to turn on the second switching element, the fourth switching element, and the sixth switching element while the relay connecting the energy storage device and the first motor is turned off, and can be configured to operate the switching elements in the second inverter in response to the second current commands 2_Id* and 2_Iq*.

[0015] In response to determining that the voltage of the second capacitor measured by the voltage sensor is equal to or greater than a predetermined first voltage, the controller can be configured to turn on the seventh switching element, the ninth switching element, and the eleventh switching element, or to turn on the eighth switching element, the tenth switching element, and the twelfth switching element while the relay connecting the energy storage device and the second motor is turned off, and can be configured to operate the switching elements in the first inverter in response to the first current commands 1_Id* and 1_Iq*.

[0016] According to an aspect of the present application, a method of protecting inverters in a vehicle from overvoltage can include: determining whether a voltage across a first capacitor measured by a voltage sensor is equal to or greater than a first voltage; when the voltage across the first capacitor is equal to or greater than the first voltage, turning off a relay connecting an energy storage device and a motor; and operating switching elements in first and second inverters in response to first current commands 1_Id* and 1_Iq* such that zero vectors are applied to each motor and second current commands 2_Id* and 2_Iq* such that zero torque is generated in each motor.

[0017] Before determining whether the voltage across the first capacitor measured by the voltage sensor is equal to or greater than the first voltage, the method can include storing a first current command (1_Id* or 1_Iq*) map and a second current command (2_Id* or 2_Iq*) map in the memory, the first current command map causing a zero vector to be applied to each motor, the second current command map causing zero torque to be generated in each motor.

[0018] Operating the switching elements in the first inverter and the second inverter in response to the first current commands 1_Id* and 1_Iq* causing a zero vector to be applied to each motor and the second current commands 2_Id* and 2_Iq* causing zero torque to be generated in each motor can include generating first voltage commands 1_Vd* and 1_Vq* and second voltage commands 2_Vd* and 2_Vq* to enable d-axis currents Id and q-axis currents Iq fed back in the current controller from each motor to follow the first d-axis current command 1_Id*, the first q-axis current command 1_Iq*, the second d-axis current command 2_Id*, and the second q-axis current command 2_Iq* stored in the memory; operating the switching elements in the first inverter and the second inverter in response to the generated first voltage commands and second voltage commands.

[0019] When the voltage across the first capacitor is equal to or greater than the first voltage, after the relay connecting the energy storage device and the motors is disconnected, the method can include discharging the voltage of the first capacitor to a predetermined second voltage; maintaining, by the switching element controller, the voltage of the first capacitor within an error range based on the second voltage.

[0020] While maintaining the voltage of the first capacitor within the error range based on the second voltage, the controller can be configured to increase the voltage of the first capacitor by regenerative braking when the voltage across the first capacitor decreases below the error range based on the second voltage, and discharge the voltage of the first capacitor by driving the first motor and the second motor when the voltage across the first capacitor exceeds the error range based on the second voltage.

[0021] When the voltage across the first capacitor is equal to or greater than the first voltage, after the relay connecting the energy storage device and the motors is disconnected, the method can include turning on, by the controller, the first switching element, the third switching element, and the fifth switching element, or turning on the second switching element, the fourth switching element, and the sixth switching element; operating the switching elements in the second inverter in response to the second current commands 2_Id* and 2_Iq*.

[0022] According to the present application, it is possible to prevent the inverter in the vehicle from being affected by overvoltage. Further, by maintaining the DC link terminal voltage (e.g., voltage across the capacitor) in the inverter system at a constant voltage and providing the corresponding voltage to other electrical components in the vehicle, it is possible to increase the driving time of the other electrical components. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and other aspects, features, and advantages of the present application will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0024] Figure 1 A schematic diagram of an electric vehicle including two drive motors according to the related art is shown schematically;

[0025] Figure 2 A schematic diagram of a system for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application is shown schematically;

[0026] Figure 3 A schematic diagram of a system for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application is shown schematically before a fault occurs;

[0027] Figure 4 A schematic diagram of a system for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application is shown schematically when a fault occurs in the system for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application;

[0028] Figure 5 A schematic diagram of a system for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application is shown schematically when a fault occurs in the system for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application;

[0029] Figure 6 A schematic diagram of a system for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application is shown schematically when a fault occurs in the system for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application;

[0030] Figure 7 A schematic diagram of a system for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application is shown schematically when a fault occurs in the system for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application;

[0031] Figure 8 A flowchart of a method for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application is shown schematically; and

[0032] Figure 9 A detailed flowchart of a method for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present application is shown schematically. DETAILED DESCRIPTION

[0033] It should be understood that the terms "vehicle" or "vehicular" or other similar terms used herein generally include motor vehicles, such as passenger cars, including sport utility vehicles (SUVs), buses, large trucks, various commercial vehicles, including passenger cars, boats, ships, including various watercraft, aircraft, and the like, and include hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen powered vehicles, and other alternative fuel vehicles (e.g., fuel derived from non-fossil sources). As referred to herein, a hybrid vehicle is a vehicle having two or more power sources, such as a vehicle having both gasoline power and electric power.

[0034] While the example embodiments are described as utilizing a plurality of units to perform the example processes, it should be understood that the example processes can also be performed by one or more modules. In addition, it should be understood that the term controller / control unit denotes a hardware device that includes a memory and a processor, and is specifically programmed to perform the processes described herein. The memory is configured to store modules, and the processor is specifically configured to run the modules to perform one or more processes described further below.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] The term "about" as used herein is understood as within the normal tolerances of the art, for example within the standard deviation of the mean. "About" can be understood to be within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the indicated value. Unless otherwise clear from context, all numerical values provided herein are modified by the term "about."

[0037] Hereinafter, a system and method for protecting an inverter in a vehicle from overvoltage, according to an example embodiment of the present application, will be described with reference to the accompanying drawings.

[0038] The system for protecting inverters in a vehicle from overvoltage according to the present application can include a breaker on the front wheels and two drive motors, and can protect inverters in an electric vehicle including two inverter systems for driving two motors from overvoltage. As shown in Figure 2 The system for protecting inverters in a vehicle from overvoltage according to the present application can include an energy storage device 100, a first inverter 200, a second inverter 300, a controller 400, a first capacitor 500, a second capacitor 600, a first motor 700, a second motor 800, a relay 900, a voltage sensor 910, a rotation angle sensor 920, and a current sensor 930.

[0039] The energy storage device 100 can be configured to output direct current as an element that stores electric energy for driving the first motor 700 and the second motor 800 in a direct current form, for example, a battery. The first capacitor 500 can be connected to both ends of the energy storage device 100, and can be connected in parallel between the first inverter 200 and the energy storage device 100 described later. Specifically, electric energy of the first motor 700 can be stored in the first capacitor 500 during regenerative braking to form a DC link voltage Vdc. The DC link voltage can be an input voltage of the first inverter 200.

[0040] The second capacitor 600 can be connected to both ends of the energy storage device 100, and can be connected in parallel between the second inverter 300 and the energy storage device 100 described later. Specifically, electric energy of the second motor 800 can be stored in the second capacitor 600 during regenerative braking to form a DC link voltage Vdc. The DC link voltage can be an input voltage of the second inverter 300.

[0041] The first inverter 200 can include a plurality of switching elements, can adjust on / off states of the plurality of switching elements through a pulse width modulation signal provided from the controller 400, and can convert direct current provided from the energy storage device 100 into alternating current for driving the first motor 700. Specifically, the first inverter 200 can include a first branch 210 having a first switching element S1 and a second switching element S2 arranged at a lower end of the first switching element S1, a second branch 220 having a third switching element S3 and a fourth switching element S4 arranged at a lower end of the third switching element S3, and a third branch 230 having a fifth switching element S5 and a sixth switching element S6 arranged at a lower end of the fifth switching element S5. The switching of the inverter 200 can be understood to refer to switching of a three-phase voltage output from the inverter. In addition, output ends of the first branch 210, the second branch 220, and the third branch 230 can be connected to each phase of the first motor 700.

[0042] The second inverter 300 can include a plurality of switching elements, can adjust the on / off state of the plurality of switching elements by a pulse width modulation signal provided from the controller 400, and can be configured to convert the direct current provided from the energy storage device 100 into alternating current for driving the second motor 800. The second inverter 300 can include a fourth leg 310 having a seventh switching element S7 and an eighth switching element S8 arranged at a lower end of the seventh switching element S7, a fifth leg 320 having a ninth switching element S9 and a tenth switching element S10 arranged at a lower end of the ninth switching element S9, and a sixth leg 330 having an eleventh switching element S11 and a twelfth switching element S12 arranged at a lower end of the eleventh switching element S11. Specifically, the output ends of the fourth leg 310, the fifth leg 320, and the sixth leg 330 can be connected to each phase of the second motor 800.

[0043] The first motor 700 can be driven by receiving the alternating current converted by the first inverter 200, and can employ various types of motors known in the art as the first motor 700. In an eco-friendly vehicle, the motor can refer to a drive motor that provides a rotational force to a drive wheel of the vehicle. In addition, the second motor 800 can be driven by receiving the alternating current converted by the second inverter 300, and can employ various types of motors known in the art as the second motor 800.

[0044] The voltage sensor 910 can be configured to measure a voltage (e.g., a DC link voltage: Vdc) across the first capacitor 500 or the second capacitor 600, information about the measured voltage across the capacitor can be transmitted to the controller 400, and can be used to determine whether overvoltage has occurred.

[0045] The rotation angle sensor 920 can be configured to detect the position of the rotor of each of the first motor 700 and the second motor 800, i.e., to detect the rotation angle of the rotor of each motor, and to continuously output a rotation angle detection signal including information about the detected rotation angle of the rotor. According to an exemplary embodiment, the rotation angle sensor 920 can be implemented as a resolver or the like.

[0046] The current sensor 930 can be configured to measure the current input from the first inverter 200 to the phase of the first motor 700 and the current input from the second inverter 300 to the phase of the second motor 800. According to an exemplary embodiment, when each of the first motor 700 and the second motor 800 is a three-phase motor having a phase a, a phase b, and a phase c, two or more current sensors 930 can be provided to measure the current input to at least two of the phase a, the phase b, and the phase c.

[0047] The controller 400 can be configured to perform control of a pulse width modulation method to appropriately adjust a duty cycle (e.g., duty ratio) of the switching elements S1 to S12 of the first inverter 200 and the second inverter 300 to adjust a torque of each of the first motor 700 and the second motor 800 to a desired value (e.g., torque command). For this control, when the voltage across the first capacitor 500 measured by the voltage sensor 910 is equal to or greater than a predetermined first voltage, the controller 400 can be configured to operate the switching elements S1 to S12 in the first inverter 200 and the second inverter 300 such that each of the first motor 700 and the second motor 800 can output a value corresponding to a torque command value (e.g., a torque target value obtained by each motor) of each motor input from the outside.

[0048] Specifically, the controller 400 can include a memory 410 configured to store a first current command (1_Id* or 1_Iq*) map that enables a zero vector to be applied to each motor during driving of each motor, thereby enabling a negative torque to be generated in each motor, and a second current command (2_Id* or 2_Iq*) map that enables a zero torque to be generated in each motor, an overvoltage detector 420 configured to determine whether a voltage across each capacitor measured by a voltage sensor is equal to or greater than a first voltage, a current controller 430 configured to generate first voltage commands 1_Vd* and 1_Vq* and second voltage commands 2_Vd* and 2_Vq* to enable d-axis currents Id and q-axis currents Iq fed back from each motor to follow first d-axis current commands 1_Id* and first q-axis current commands 1_Iq* stored in the memory 410, and second d-axis current commands 2_Id* and second q-axis current commands 2_Iq*, and a switching element controller 440 configured to operate switching elements in the first inverter and the second inverter in response to the generated first voltage commands and second voltage commands.

[0049] Specifically, the first current commands 1_Id* and 1_Iq* stored in the memory 410 are current command values that, when the plurality of switching elements are driven by the controller 400, by turning on the first switching element S1, the third switching element S3, and the fifth switching element S5 or turning on the seventh switching element S7, the ninth switching element S9, and the eleventh switching element S11, apply a zero vector to the first motor 700 or the second motor 800 during driving of the first motor 700 or the second motor 800, thereby enabling generation of a negative torque in the first motor 700 or the second motor 800. The first current command values can be characteristic current values such that, during driving of each motor, a zero vector can be applied to each motor, and the current command values can have different values for each motor.

[0050] In addition, the first current commands 1_Id* and 1_Iq* can be current commands that, when the plurality of switching elements are driven by the controller 400, by turning on the second switching element S2, the fourth switching element S4, and the sixth switching element S6 or turning on the eighth switching element S8, the tenth switching element S10, and the twelfth switching element S12, apply a zero vector to the first motor 700 or the second motor 800 during driving of the first motor 700 or the second motor 800, thereby enabling generation of a negative torque in the first motor 700 or the second motor 800.

[0051] In other words, the first current commands 1_Id* and 1_Iq* stored in the memory 410 are command values that, during driving of a motor, apply a zero vector to the motor, thereby enabling generation of a negative torque in the motor. When the switching elements of the inverter are operated so that the current input to the motor can follow the corresponding current command, a negative torque can be generated in the motor during driving of the motor.

[0052] In addition, the second current commands 2_Id* and 2_Iq* stored in the memory 410 are current command values that, when the switching elements in the first inverter 200 or the second inverter 300 are driven by the controller 400, enable generation of a zero torque in the first motor 700 or the second motor 800. According to an exemplary embodiment, the second d-axis current command 2_Id* can be -10 A, and the second q-axis current command 2_Iq* can be 0 A. In this way, in response to the command that the second d-axis current command 2_Id* is -10 A and the second q-axis current command 2_Iq* is 0 A, when the switching elements in the first inverter 200 or the second inverter 300 can be driven, a zero torque can be generated in the first motor 700 or the second motor 800.

[0053] In other words, the second current commands 2_Id* and 2_Iq* stored in memory 410 are command values ​​that cause zero torque to be generated in the motor. Zero torque can be generated in the motor when the switching elements of the inverter are operated so that the current input to the motor follows the second current commands. Additionally, the controller 400 may further include a coordinate transformation unit configured to convert two-phase coordinates to three-phase coordinates or to convert three-phase coordinates to two-phase coordinates. According to an exemplary embodiment, when the first motor 700 and the second motor 800 are three-phase motors having phases a, b, and c, the coordinate transformation unit may be configured to convert the d-axis current Id and the q-axis current Iq to three-phase currents Ia, Ib, and Ic of phases a, b, and c, or it may be configured to convert the three-phase currents Ia, Ib, and Ic of phases a, b, and c to d-axis current Id and q-axis current Iq. Converting two-phase coordinates to three-phase coordinates or three-phase coordinates to two-phase coordinates is a known technique, and its detailed description will be omitted.

[0054] The following text will refer to Figures 3 to 7 The operating principle of a system according to the present invention for protecting an inverter in a vehicle from overvoltage is described. For example... Figure 3 As shown, under normal conditions where no fault occurs, during regenerative braking, the electrical energy of the first motor 700 can charge the first capacitor 500, increasing its voltage. At this time, the voltage sensor 910 can be configured to measure the voltage across the first capacitor 500 and send the measured voltage to the controller 400. The controller 400 can be configured to determine whether the voltage of the first capacitor 500 is equal to or greater than a predetermined first voltage. Specifically, the first voltage is a value extracted from experimental data and can be greater than or equal to the voltage of the switching elements included in the inverter.

[0055] At the same time, Figure 3 As previously described, the first motor 700, the first inverter 200, and the first capacitor 500 were primarily described. However, the present invention can also be driven by a second motor 800, a second inverter 300, and a second capacitor 600. In other words, under normal conditions where no fault occurs, during regenerative braking, the electrical energy of the second motor 800 can charge the second capacitor 600, increasing its voltage. At this time, the voltage sensor 910 can be configured to measure the voltage across the second capacitor 600 and send the measured voltage to the controller 400, which can be configured to determine whether the voltage of the second capacitor 600 is equal to or greater than a predetermined first voltage.

[0056] In response to determining that the voltage of the first capacitor 500 measured by the voltage sensor 910 is equal to or greater than a first voltage, such as Figure 4As shown, the controller 400 can be configured to turn off the relay 900 connecting the energy storage device 100 and the first motor 700. At the same time, as shown Figure 4 As shown, after turning off the relay 900 connecting the energy storage device 100 and the first motor 700, the voltage of the first capacitor 500 should be discharged by the controller 400 to prevent damage to the switching elements in the first inverter 200. However, the voltage of the first capacitor 500 can be discharged by the controller 400 according to the present application by operating the switching elements in the first inverter 200 and the second inverter 300 in response to the first current commands 1_Id* and 1_Iq* that enable the application of a zero vector to each motor and the second current commands 2_Id* and 2_Iq* that enable the generation of a zero torque in each motor, which are pre-stored in the memory.

[0057] Specifically, when the voltage of the first capacitor 500 measured by the voltage sensor 910 is equal to or greater than a predetermined first voltage, the controller 400 can be configured to discharge the voltage of the first capacitor 500 by turning off the relay 900 connecting the energy storage device 100 and the first motor 700, operating the switching elements in the first inverter in response to the first current commands 1_Id* and 1_Iq*, and operating the switching elements in the second inverter in response to the second current commands 2_Id* and 2_Iq*.

[0058] At the same time, as shown Figure 4 As shown, during the process of turning off the relay 900 and discharging the voltage of the first capacitor 500, the voltage of the first capacitor 500 can rapidly increase due to the back electromotive force of the first motor 700 during coasting or downhill driving, whereby the inverter can be damaged due to the generated overvoltage. Therefore, during the discharge of the voltage of the first capacitor 500, the generation of the back electromotive force of the motor needs to be suppressed during coasting or downhill driving.

[0059] In the present application, during the driving of the first motor 700, a zero vector can be applied to the first motor 700 to generate a negative torque in the first motor 700. Therefore, by driving the switching elements in the first inverter in response to the first current commands 1_Id* and 1_Iq* that can prevent the generation of a back electromotive force in the first motor 700, the generation of the back electromotive force of the first motor 700 can be prevented. In addition, by driving the switching elements in the second inverter in response to the second current commands 2_Id* and 2_Iq* that can enable the generation of a zero torque in the second motor 800, the voltage of the first capacitor 500 can be discharged.

[0060] In other words, when the voltage across the first capacitor 500 measured by the voltage sensor 910 is equal to or greater than the first voltage, the controller 400 can be configured to turn off the relay 900 so that the current supplied from the first inverter 200 to the first motor 700 follows the first current command and the current supplied from the second inverter 200 to the second motor 800 follows the second current command, thereby suppressing the generation of the back electromotive force of the motor while discharging the voltage of the first capacitor.

[0061] According to another exemplary embodiment, when the voltage of the second capacitor 600 measured by the voltage sensor 910 is equal to or greater than a predetermined first voltage, the controller 400 can be configured to turn off the relay connecting the energy storage device 100 to the second motor 800, operate the switching elements in the first inverter 200 in response to the second current commands 2_Id* and 2_Iq*, and operate the switching elements in the second inverter in response to the first current commands 1_Id* and 1_Iq*.

[0062] In summary, as Figure 4 shown, when the measured voltage across the first capacitor 500 is equal to or greater than the first voltage, the controller 400 can be configured to turn off the relay 900 so that the current supplied from the first inverter 200 to the first motor 700 follows the first current command and the current supplied from the second inverter 300 to the second motor 800 follows the second current command, or so that the current supplied from the first inverter 200 to the first motor 700 follows the second current command and the current supplied from the second inverter 300 to the second motor 800 follows the first current command, thereby discharging the voltage of the capacitor in the overvoltage state while suppressing the generation of the back electromotive force of the motor.

[0063] Meanwhile, when the voltage across the first capacitor 500 measured by the voltage sensor 910 is equal to or greater than the first voltage, as Figure 4 shown, the controller 400 can be configured to turn off the relay 900 so that the current supplied from the first inverter 200 to the first motor 700 follows the first current command and the current supplied from the second inverter 300 to the second motor 800 follows the second current command, thereby discharging the voltage of the first capacitor 500 to a predetermined second voltage and allowing the voltage of the first capacitor 500 to be discharged to the second voltage. Next, the voltage of the first capacitor 500 can be discharged to the second voltage, and then, as Figure 6 shown, the controller 400 can be configured to maintain the voltage of the first capacitor 500 within an error range based on the second reference voltage.

[0064] Specifically, in response to determining that the measured voltage drop across the first capacitor 500 is reduced below the error range based on the second voltage, the controller 400 can be configured to increase the voltage of the first capacitor 500 by regenerative braking, and in response to determining that the voltage across the first capacitor 500 exceeds the error range based on the second voltage, the controller 400 can be configured to discharge the voltage of the first capacitor 500 by driving of the first motor 700 and the second motor 800, thereby maintaining the voltage of the first capacitor within the error range based on the second voltage.

[0065] Meanwhile, according to another exemplary embodiment, when the voltage of the first capacitor 500 measured by the voltage sensor 910 is equal to or greater than the first voltage, the controller 400 can be configured to turn on the first switching element S1, the third switching element S3, and the fifth switching element S5 while the relay 900 connecting the energy storage device 100 and the first motor 700 is turned off, or can be configured to operate the switching elements in the second inverter in response to the second current command while the second switching element S2, the fourth switching element S4, and the sixth switching element S6 are turned on.

[0066] As described above, in the present application, the controller 400 can be configured to turn on the first switching element S1, the third switching element S3, and the fifth switching element S5, or can be configured to turn on the second switching element S2, the fourth switching element S4, and the sixth switching element S6, so that a zero vector can be applied to the first motor 700 during driving of the first motor 700, enabling generation of a negative torque in the first motor 700, thereby preventing generation of a counter electromotive force in the first motor 700, and the switching elements in the second inverter are driven in response to a second current command enabling generation of a zero torque in the second motor 800, thereby discharging the voltage of the first capacitor 500.

[0067] On the contrary, when the voltage of the second capacitor 600 measured by the voltage sensor 910 is equal to or greater than a predetermined first voltage, the controller 400 can be configured to turn on the seventh switching element S7, the ninth switching element S9, and the eleventh switching element S11 while the relay 900 is turned off, or can be configured to turn on the eighth switching element S8, the tenth switching element S10, and the twelfth switching element S12, and can be configured to operate the switching elements in the first inverter 200 in response to a first current command.

[0068] Meanwhile, although not shown in detail in the drawings, a plurality of electrical components included in a vehicle can be connected in a circuit to the energy storage device 100, and the electrical components can be driven by receiving power from the energy storage device 100. As Figure 4As shown, when relay 900 is disconnected, multiple electrical components have the problem of being disconnected from the circuit connection of energy storage device 100, thus failing to supply power and increasing the risk of safety accidents.

[0069] In this invention, in order to solve the above-mentioned problems, in the relay such as Figure 4 When disconnected as shown, the controller 400 can be configured to, according to the method described above, discharge the voltage of the first capacitor 500 to the second voltage while maintaining the voltage of the first capacitor 500 within an error range based on the second voltage, thereby increasing the driving time of the corresponding electrical components by providing the energy stored in the first capacitor 500 to multiple electrical components in the vehicle, and preventing the occurrence of safety accidents.

[0070] Reference Figure 7 In the description of a system for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present invention, when the voltage of the first capacitor rises and becomes equal to or greater than a first voltage (e.g., interval A), the controller can be configured to disconnect the relay connecting the energy storage device and the motor, can be configured to drive the first motor by operating a switching element in the first inverter in response to a first current command, and can be configured to drive the second motor by operating a switching element in the second inverter in response to a second current command, thereby discharging the voltage of the first capacitor (e.g., interval B). Additionally, the controller 400 can be configured to discharge the voltage of the first capacitor, but when the voltage of the first capacitor reaches a second voltage, the controller 400 can be configured to maintain the voltage of the first capacitor within an error range based on the second voltage (e.g., interval C).

[0071] Figure 8 A flowchart illustrating a method for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present invention is provided. Figure 9 A detailed flowchart illustrating a method for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present invention is provided.

[0072] like Figure 8 As shown, a method for protecting an inverter in a vehicle from overvoltage according to an exemplary embodiment of the present invention may include: determining whether the voltage across a first capacitor, measured by a voltage sensor, is equal to or greater than a first voltage; disconnecting a relay connecting an energy storage device to a motor when the voltage across the first capacitor is equal to or greater than the first voltage; and operating switching elements in a first inverter and a second inverter in response to applying first current commands 1_Id* and 1_Iq* to each motor with zero vector and second current commands 2_Id* and 2_Iq* to generate zero torque in each motor.

[0073] In addition, before determining whether the voltage across the first capacitor measured by the voltage sensor is equal to or greater than the first voltage, the method may further include storing in memory a mapping of a first current command (1_Id* or 1_Iq*) that causes a zero vector to be applied to each motor and a mapping of a second current command (2_Id* or 2_Iq*) that causes zero torque to be generated in each motor.

[0074] At the same time, such as Figure 9 As shown, operating the switching elements in the first inverter and the second inverter in response to applying a first current command 1_Id* and 1_Iq* to each motor with zero vector and a second current command 2_Id* and 2_Iq* to generate zero torque in each motor may include: generating a first voltage command 1_Vd* and 1_Vq* and a second voltage command 2_Vd* and 2_Vq* such that the d-axis current Id and q-axis current Iq fed back from each motor in the current controller can follow the first d-axis current command 1_Id* and the first q-axis current command 1_Iq* and the second d-axis current command 2_Id* and the second q-axis current command stored in the memory; and operating the switching elements in the first inverter and the second inverter in response to the first voltage command and the second voltage command generated in the switching element controller.

[0075] Meanwhile, when the voltage across the first capacitor is equal to or greater than the first voltage, after disconnecting the relay connecting the energy storage device and the motor, the method may further include: discharging the voltage of the first capacitor to a predetermined second voltage; and maintaining the voltage of the first capacitor within an error range based on the second voltage.

[0076] Specifically, when maintaining the voltage of the first capacitor within an error range based on the second voltage, the controller can be configured to: increase the voltage of the first capacitor by regenerative braking when the voltage across the first capacitor drops below the error range based on the second voltage; and discharge the voltage of the first capacitor by driving the first motor and the second motor when the voltage across the first capacitor exceeds the error range based on the second voltage.

[0077] Meanwhile, according to another exemplary embodiment, when the voltage across the first capacitor is equal to or greater than the first voltage, after disconnecting the relay connecting the energy storage device and the motor, the method may further include: turning on the first, third, and fifth switching elements, or turning on the second, fourth, and sixth switching elements by the controller, and operating the switching elements in the second inverter in response to the second current commands 2_Id* and 2_Iq*.

[0078] Meanwhile, detailed technical features of each operation of the method of protecting the inverter in the vehicle from overvoltage are the same as the detailed configuration of the technical features of the system of protecting the inverter in the vehicle from overvoltage described above, and thus a detailed description thereof will be omitted.

Claims

1. A system for protecting inverters in a vehicle from overvoltage, comprising: a first inverter including a plurality of switching elements and configured to convert energy supplied from an energy storage device into alternating current; a first motor configured to be driven by receiving the alternating current converted by the first inverter; a second inverter connected in parallel with the first inverter, including a plurality of switching elements, and configured to convert energy supplied from the energy storage device into alternating current; a second motor configured to be driven by receiving the alternating current converted by the second inverter; a first capacitor connected in parallel between the first inverter and the energy storage device, and configured to store electric energy of the first motor during regenerative braking; and a controller configured to disconnect a relay connecting the energy storage device and the motors in response to determining that a voltage of the first capacitor measured by a voltage sensor is equal to or greater than a predetermined first voltage, and configured to operate the switching elements in the first inverter and the second inverter in response to first current commands 1_Id* and 1_Iq* causing zero torque to be applied to each motor and second current commands 2_Id* and 2_Iq* causing zero torque to be generated in each motor, the first current commands 1_Id* and 1_Iq* and the second current commands 2_Id* and 2_Iq* being pre-stored.

2. The system of claim 1, wherein, The controller is configured to disconnect a relay connecting the energy storage device and the first motor when the voltage of the first capacitor measured by the voltage sensor is equal to or greater than the predetermined first voltage, operate the switching elements in the first inverter in response to the first current commands 1_Id* and 1_Iq*, and operate the switching elements in the second inverter in response to the second current commands 2_Id* and 2_Iq*. 3.The system for protecting inverters in a vehicle from overvoltage according to claim 1, further comprising: a second capacitor connected in parallel between the second inverter and the energy storage device, and configured to store electric energy of the second motor during regenerative braking; wherein the controller is configured to disconnect a relay connecting the energy storage device and the second motor in response to determining that a voltage of the second capacitor measured by a voltage sensor is equal to or greater than a predetermined first voltage, operate the switching elements in the first inverter in response to the second current commands 2_Id* and 2_Iq*, and operate the switching elements in the second inverter in response to the first current commands 1_Id* and 1_Iq*.

4. The system of protecting an inverter in a vehicle from overvoltage, according to claim 3, wherein, The first inverter includes: a first branch including a first switching element and a second switching element located at a lower end of the first switching element, a second branch including a third switching element and a fourth switching element located at a lower end of the third switching element, and a third branch including a fifth switching element and a sixth switching element located at a lower end of the fifth switching element, and outputs of the first branch, the second branch, and the third branch being connected to each phase of the first motor; wherein the second inverter includes: a first branch including a first switching element and a second switching element located at a lower end of the first switching element, a second branch including a third switching element and a fourth switching element located at a lower end of the third switching element, and a third branch including a fifth switching element and a sixth switching element located at a lower end of the fifth switching element, and outputs of the first branch, the second branch, and the third branch being connected to each phase of the second motor. a fourth branch including a seventh switching element and an eighth switching element located at a lower end of the seventh switching element, a fifth branch including a ninth switching element and a tenth switching element located at a lower end of the ninth switching element, and a sixth branch including an eleventh switching element and a twelfth switching element located at a lower end of the eleventh switching element, and output ends of the fourth branch, the fifth branch, and the sixth branch are connected to each phase of the second motor.

5. The system of protecting an inverter in a vehicle from overvoltage, according to claim 4, wherein, When driving the plurality of switching elements, the first current commands 1_Id* and 1_Iq* cause the first switching element, the third switching element, and the fifth switching element or the seventh switching element, the ninth switching element, and the eleventh switching element to be turned on to apply a zero vector to the first motor or the second motor during driving of the first motor or the second motor, thereby generating a negative torque in the first motor or the second motor.

6. The system of claim 4, wherein, When driving the plurality of switching elements in the first inverter or the second inverter, the second current commands 2_Id* and 2_Iq* cause a zero torque to be generated in the first motor or the second motor.

7. The system of claim 1, wherein, The controller includes: a memory configured to store a first current command 1_Id* or 1_Iq* map causing a zero vector to be applied to each motor during driving of each motor, thereby enabling a negative torque to be generated in each motor, and a second current command 2_Id* or 2_Iq* map causing a zero torque to be generated in each motor; an overvoltage detector configured to determine whether a voltage across each capacitor measured by the voltage sensor is equal to or greater than a first voltage; a current controller configured to generate first voltage commands 1_Vd* and 1_Vq* and second voltage commands 2_Vd* and 2_Vq* to enable d-axis currents Id and q-axis currents Iq fed back from each motor to follow first d-axis current commands 1_Id* and first q-axis current commands 1_Iq* stored in the memory, second d-axis current commands 2_Id*, and second q-axis current commands 2_Iq*; and a switching element controller configured to operate switching elements in the first inverter and the second inverter in response to the generated first voltage commands and second voltage commands.

8. The system of claim 1, wherein, When the measured voltage across the first capacitor is equal to or greater than the first voltage, the controller is configured to open the relay, cause a current supplied from the first inverter to the first motor to follow the first current commands, and cause a current supplied from the second inverter to the second motor to follow the second current commands, or cause a current supplied from the first inverter to the first motor to follow the second current commands, and cause a current supplied from the second inverter to the second motor to follow the first current commands.

9. The system of claim 1, wherein, When the measured voltage across the first capacitor is equal to or greater than the first voltage, the controller is configured to open the relay, discharge the voltage of the first capacitor to a predetermined second voltage, and maintain the voltage of the first capacitor within an error range based on the second voltage.

10. The system of protecting an inverter in a vehicle from overvoltage, according to claim 9, wherein, The controller is configured to increase the voltage of the first capacitor by regenerative braking when the measured voltage across the first capacitor decreases below an error range based on the second voltage, and to discharge the voltage of the first capacitor by driving of the first motor and the second motor when the voltage across the first capacitor exceeds the error range based on the second voltage.

11. The system of claim 4, wherein, The controller is configured to: turn on the first, third, and fifth switching elements, or turn on the second, fourth, and sixth switching elements, while the relay connecting the energy storage device and the first motor is turned off; operate the switching elements in the second inverter in response to second current commands 2_Id* and 2_Iq*.

12. The system of claim 4, wherein, The controller is configured to: turn on the seventh, ninth, and eleventh switching elements, or turn on the eighth, tenth, and twelfth switching elements, while the relay connecting the energy storage device and the second motor is turned off; operate the switching elements in the first inverter in response to first current commands 1_Id* and 1_Iq*.

13. A method of protecting inverters in a vehicle from overvoltage, comprising: determining, by a controller, whether a voltage across a first capacitor measured by a voltage sensor is equal to or greater than a first voltage; turning off, by the controller, a relay connecting an energy storage device and a motor in response to determining that the voltage across the first capacitor is equal to or greater than the first voltage; operating, by the controller, switching elements in first and second inverters in response to first current commands 1_Id* and 1_Iq* that cause zero vectors to be applied to each motor and second current commands 2_Id* and 2_Iq* that cause zero torque to be generated in each motor.

14. The method of claim 13, wherein, The method includes, prior to determining whether the voltage across the first capacitor measured by the voltage sensor is equal to or greater than the first voltage: storing, in a memory, first current command 1_Id* or 1_Iq* maps that cause zero vectors to be applied to each motor and second current command 2_Id* or 2_Iq* maps that cause zero torque to be generated in each motor.

15. The method of claim 14, wherein, operating the switching elements in the first and second inverters in response to the first current commands 1_Id* and 1_Iq* that cause zero vectors to be applied to each motor and the second current commands 2_Id* and 2_Iq* that cause zero torque to be generated in each motor includes: generating, by a current controller, first voltage commands 1_Vd* and 1_Vq* and second voltage commands 2_Vd* and 2_Vq* to enable d-axis currents Id and q-axis currents Iq fed back from each motor to follow first d-axis current commands 1_Id* and first q-axis current commands 1_Iq* stored in a memory, second d-axis current commands 2_Id*, and second q-axis current commands 2_Iq*; The switching elements in the first inverter and the second inverter are operated by the switching element controller in response to the generated first voltage command and second voltage command.

16. The method according to claim 13, when the voltage across the first capacitor is equal to or greater than the first voltage after the relay connecting the energy storage device and the motor is disconnected, the method comprising: discharging, by the controller, the voltage of the first capacitor to a predetermined second voltage; maintaining, by the controller, the voltage of the first capacitor within an error range based on the second voltage.

17. The method of claim 16, wherein, The method comprises: increasing, by the controller, the voltage of the first capacitor through regenerative braking when the voltage across the first capacitor decreases below the error range based on the second voltage; discharging, by the controller, the voltage of the first capacitor through driving of the first motor and the second motor when the voltage across the first capacitor exceeds the error range based on the second voltage.

18. The method according to claim 13, when the voltage across the first capacitor is equal to or greater than the first voltage after the relay connecting the energy storage device and the motor is disconnected, the method comprising: turning on, by the controller, the first switching element, the third switching element and the fifth switching element, or turning on the second switching element, the fourth switching element and the sixth switching element; operating, by the controller, the switching elements in the second inverter in response to the second current commands 2_Id* and 2_Iq*.

19. The method according to claim 13, when the voltage across the first capacitor is equal to or greater than the first voltage after the relay connecting the energy storage device and the motor is disconnected, the method comprising: turning on, by the controller, the first switching element, the third switching element and the fifth switching element, or turning on the second switching element, the fourth switching element and the sixth switching element; operating, by the controller, the switching elements in the second inverter in response to the second current commands 2_Id* and 2_Iq*.

20. The method according to claim 13, when the voltage across the first capacitor is equal to or greater than the first voltage after the relay connecting the energy storage device and the motor is disconnected, the method comprising: turning on, by the controller, the first switching element, the third switching element and the fifth switching element, or turning on the second switching element, the fourth switching element and the sixth switching element; operating, by the controller, the switching elements in the second inverter in response to the second current commands 2_Id* and 2_Iq*.

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