Electric vehicle and control method thereof

Abstract

The present invention relates to an electric vehicle and a control method thereof, in which the electric vehicle includes: a main battery and an auxiliary battery; a motor system connected to the main battery and including a dual inverter for driving a motor according to a motor driving mode and a selector switch for switching between a first driving mode and a second driving mode included in the motor driving mode; and a charging switch that is connected between the motor system and the auxiliary battery, and forms a boost charging path connected from the auxiliary battery to the main battery through the motor system when the first driving mode is converted to a charging mode during travel.

Description

Technical Field

[0001] The invention relates to an electric vehicle and a control method thereof for controlling charging and discharging of a battery during driving. Background Art

[0002] Recently, with the global trend of reducing carbon dioxide emissions, the demand for electric vehicles that generate driving power by driving a motor using electric energy stored in a battery is increasing significantly, replacing conventional internal combustion engine vehicles that generate driving power by burning fossil fuels.

[0003] Typically, one end of each phase winding included in a motor of an electric vehicle is connected to an inverter, and the other ends are connected to each other, thereby forming a Y-type connection.

[0004] When the motor is driven, the switching elements in the inverter are turned on or off by pulse width modulation control, and alternating current is generated by applying a line voltage to the windings of the Y-connected motor, thereby generating torque.

[0005] The fuel efficiency (or electrical efficiency) of environmentally friendly vehicles such as electric vehicles that use the torque generated by the motor as power is determined by the power conversion efficiency of the inverter-motor. Therefore, in order to improve fuel efficiency, it is particularly important to maximize the power conversion efficiency of the inverter and the efficiency of the motor.

[0006] The efficiency of the inverter-motor system is mainly determined by the voltage utilization of the inverter. When the operating point of the vehicle is determined by the relationship between the motor speed and torque in the range of high voltage utilization, the fuel efficiency of the vehicle can be improved.

[0007] However, when the number of windings of the motor is increased in order to increase the maximum torque of the motor, the high voltage utilization interval will be away from the low torque area which is the main operating point of the vehicle, resulting in a problem of reduced fuel efficiency. In addition, from the perspective of fuel efficiency, when the main operating point is designed to be included in the high voltage utilization interval, the maximum torque of the motor may be limited, resulting in a problem of reduced acceleration performance of the vehicle.

[0008] In this technical field, since a motor driving technology that can take into account both low output and high output ranges using one motor and improve system efficiency is required, a technology that uses two inverters and a mode switching switch to drive one motor in two different modes has been recently introduced.

[0009] The contents described in the background technology of the present invention are only used to help understand the background of the present invention and cannot be regarded as falling within the scope of the prior art known to those skilled in the art. Summary of the invention

[0010] The technical problem to be solved by the present invention is to effectively increase the driving distance of an electric vehicle by boosting the voltage of an auxiliary battery through a motor system to charge a main battery during driving.

[0011] The technical issues of the present invention are not limited to the above-mentioned technical issues. For other technical issues not mentioned, those skilled in the art can clearly understand them from the following description.

[0012] As a means for solving the above-mentioned technical problems, the electric vehicle based on the present invention can include: a main battery and an auxiliary battery; a motor system, which is connected to the above-mentioned main battery and includes a dual inverter that drives the motor according to the motor drive mode and a switching switch for switching between a first drive mode and a second drive mode included in the above-mentioned motor drive mode; and a charging switch, which is connected between the above-mentioned motor system and the above-mentioned auxiliary battery, and when the above-mentioned first drive mode is converted into a driving charging mode, forms a boost charging path from the above-mentioned auxiliary battery to the above-mentioned main battery through the above-mentioned motor system.

[0013] In addition, as a means to solve the above-mentioned technical problems, the electric vehicle based on the present invention can include: a main battery and an auxiliary battery; a motor system, which drives the motor through an inverter connected to the above-mentioned main battery; and a controller, which is configured to perform a predetermined pulse width modulation control on the above-mentioned inverter when executing a driving charging mode to control the DC offset of the phase current of the above-mentioned motor, so that the above-mentioned motor system boosts the voltage of the above-mentioned auxiliary battery to charge the above-mentioned main battery.

[0014] In addition, as a means to solve the above-mentioned technical problems, the control method of the electric vehicle based on the present invention may include: a step of driving the motor through an inverter according to the voltage of the main battery in the motor system; and a step of forming a boost charging path from the auxiliary battery to the main battery through the motor system when the driving charging mode is executed in the state where the motor is driven.

[0015] According to the present invention, the voltage of the auxiliary battery is boosted by the motor system during driving to charge the main battery, thereby effectively increasing the driving distance of the electric vehicle.

[0016] The effects that can be obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a circuit diagram of an example of a motor driving device according to an embodiment of the present invention.

[0018] Figure 2This is a diagram for explaining the switching of the motor drive mode according to one embodiment of the present invention.

[0019] Figure 3 The present invention is a circuit diagram of a motor drive device included in an electric vehicle according to an embodiment of the present invention.

[0020] Figure 4 1 is a waveform diagram of the phase current of the motor and the current of the auxiliary battery when the running charging mode according to one embodiment of the present invention is executed.

[0021] Figure 5 and Figure 6 1 is a waveform diagram for explaining an operation of a controller according to an embodiment of the present invention controlling a switching state of an inverter in a running charging mode.

[0022] Figure 7 The present invention is a circuit diagram of a motor driving device included in an electric vehicle according to another embodiment of the present invention.

[0023] Figure 8 This is a flowchart for explaining a control method of an electric vehicle according to an embodiment of the present invention.

[0024] Fig. 9 and Fig.10 This is a block diagram of an example of a motor drive system to which the present invention is applied.

[0025] Description of Reference Numerals

[0026] 10: First inverter

[0027] 20: Second inverter

[0028] 30: Motor

[0029] 40: Mode switching unit

[0030] 50: Main battery

[0031] 51: Auxiliary battery

[0032] 60: DC capacitor

[0033] 70: Controller

[0034] 100, 100': Motor system

[0035] 200: driving wheel

[0036] 300: Main driving wheel

[0037] 400: Auxiliary drive wheel. DETAILED DESCRIPTION

[0038] Hereinafter, the embodiments disclosed in this specification will be described in detail with reference to the accompanying drawings. In this specification, for the same or similar elements, no matter in which figure, the same figure mark is attached and repeated description thereof is omitted. . The suffixes "module" and "unit" for the elements used in the following specification are only added or mixed for the convenience of writing the specification, and do not mean that they themselves have meanings or functions that distinguish each other. In addition, when describing the embodiments disclosed in this specification, when it is judged that the specific description of the known technology related to the embodiments of the present invention may obscure the main purpose of the embodiments of the present invention, the detailed description thereof is omitted. In addition, it should be understood that the drawings are only used to easily understand the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the drawings, including various modified embodiments, equivalent embodiments and even alternative embodiments within the ideas and technical scope of the present invention.

[0039] The terms including the first, second, etc., which include serial numbers, are used to describe various elements, and the elements are not limited by the terms. The terms are used only for the purpose of distinguishing one element from another.

[0040] When a certain element is described as being "connected" or "in contact with" another element, it should be understood that it may be directly connected or indirectly connected to the other element, or other elements may be present in between. On the contrary, when a certain element is described as being "directly connected" or "directly in contact with" another element, it should be understood that no other element is present in between.

[0041] Unless the context clearly indicates a different meaning, an expression in the singular includes an expression in the plural.

[0042] In this specification, it should be understood that terms such as "including" or "configured" are used to specify the features, values, steps, actions, elements, parts or their combinations recorded in the specification, and do not exclude the existence or addition of one or more other features, values, steps, actions, elements, parts or their combinations.

[0043] In addition, the unit (Unit) or control unit (ControlUnit) included in the name of the motor control unit (MCU) is only a widely used term in the naming of the control device (Controller) that controls a specific function of the vehicle, and does not represent a generic function unit (Generic function unit). For example, each controller may include a communication device for communicating with other controllers or sensors, a memory for storing an operating system or logic commands and input and output information, and one or more processors for performing judgments, calculations, determinations, etc. required for controlling the function.

[0044] Figure 11 is a circuit diagram showing an example of a motor driving device according to an embodiment of the present invention.

[0045] Reference Figure 1 The motor driving device according to an embodiment of the present invention can include a main battery 50 , a DC capacitor (or a DC support capacitor) 60 , a controller 70 , and a motor system 100 .

[0046] The motor system 100 can include: dual inverters 10, 20; a motor 30 having a plurality of windings C1, C2, C3 corresponding to the plurality of windings C1, C2, C3; and a mode switching unit 40. The first inverter 10 can include a plurality of first switching elements S11-S16 connected to one end of the plurality of windings C1, C2, C3, and the second inverter 20 can include a plurality of second switching elements S21-S26 connected to the other end of the plurality of windings C1, C2, C3. The mode switching unit 40 can include a plurality of switching switches S31, S32, S33. The controller 70 can control the on / off states of the first switching elements S11-S16, the second switching elements S21-S26, and the switching switches S31-S33 according to the required output of the motor (i.e., the torque command to the motor), the DC terminal voltage of the inverters 10, 20 (i.e., the voltage of the main battery), the phase current of the motor, and the motor angle.

[0047] The first inverter 10 can include a plurality of branches 11, 12, 13, to which a DC voltage formed in a DC capacitor 60 connected between the two ends of the main battery is applied. Each branch 11, 12, 13 can correspond to a plurality of phases of the motor 30, respectively, to form an electrical connection. More specifically, the first branch 11 includes two switching elements S11, S12 connected in series between the two ends of the DC capacitor 60, and a connection node of the two switching elements S11, S12 can be connected to one end of a winding C1 of one phase in the motor 30, thereby inputting and outputting an alternating current corresponding to one phase in the plurality of phases. Similarly, the second branch 12 includes two switching elements S13, S14 connected in series between the two ends of the DC capacitor 60, and a connection node of the two switching elements S13, S14 can be connected to one end of a winding C2 of one phase in the motor 30, thereby inputting and outputting an alternating current corresponding to one phase in the plurality of phases. In addition, the third branch 13 includes two switching elements S15 and S16 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S15 and S16 can be connected to one end of the winding C3 of one phase in the motor 30, thereby inputting and outputting alternating current corresponding to one phase among multiple phases.

[0048] The second inverter 20 can include a plurality of branches 21, 22, 23, to which a DC voltage formed in a DC capacitor 60 connected between the two ends of the main battery is applied. Each branch 21, 22, 23 can correspond to a plurality of phases of the motor 30, respectively, to form an electrical connection. More specifically, the first branch 21 includes two switching elements S21, S22 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S21, S22 can be connected to the other end of a winding C1 of one phase in the motor 30, thereby inputting and outputting an alternating current corresponding to one phase in the plurality of phases. Similarly, the second branch 22 includes two switching elements S23, S24 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S23, S24 can be connected to the other end of a winding C2 of one phase in the motor 30, thereby inputting and outputting an alternating current corresponding to one phase in the plurality of phases. In addition, the third branch 23 includes two switching elements S25 and S26 connected in series between the two ends of the DC capacitor 60, and the connection node of the two switching elements S25 and S26 can be connected to the other end of the winding C3 of one phase in the motor 30, thereby inputting and outputting alternating current corresponding to one phase among multiple phases.

[0049] One end of the plurality of switching switches S31, S32, S33 is respectively connected to a different one of the other ends of the plurality of windings C1, C2, C3, and the other ends of the plurality of switching switches S31, S32, S33 can be connected to each other at an internal node N. The plurality of switching switches S31, S32, S33 can adopt various switching devices known in the art, such as MOSFET, IGBT, transistor, relay, etc.

[0050] Although in Figure 1 Although not shown in the figure, the motor driving device can also include a Y capacitor (Y-Cap), that is, two capacitors are connected in series between the positive (+) DC terminal and the negative (-) DC terminal, and the connection node between the capacitors is grounded.

[0051] The controller 70 can switch the first switch elements S11-S16 and the second switch elements S21-S26 through pulse width modulation control according to the required output of the motor 30, thereby driving the motor 30. The controller 70 switches the dual inverters 10 and 20 according to the motor drive mode to control the drive of the motor 30, and can control the on / off state of the switching switches S31, S32, and S33 for switching between the CEW mode and the OEW mode included in the motor drive mode. At this time, the first drive mode can be called "closed end winding (CEW) mode" and the second drive mode can be called "open end winding (OEW) mode". More specifically, when the controller 70 executes the CEW mode, it turns on the switching switches S31, S32, and S33 to form the neutral point of the motor 30 at the internal node N, and can control the drive of the motor 30 through the first inverter 10 of the first inverter 10 and the second inverter 20. In contrast, when executing the OEW mode, the controller 70 turns off the switches S31 , S32 , and S33 so as not to form a neutral point of the motor 30 at the internal node N, and can control the driving of the motor 30 through the first inverter 10 and the second inverter 20 .

[0052] Figure 2 This is a diagram for explaining the switching of the motor drive mode according to one embodiment of the present invention.

[0053] Reference Figure 2 , shows an operating point diagram of the motor, which displays an output limit curve L1 of the CEW mode, an output limit curve L2 of the OEW mode, and a mode switching reference line L3 based on the efficiency diagram.

[0054] The output limit curves L1 and L2 can represent the output torque limit value of the motor according to the rotation speed (e.g., RPM) of the motor in each motor drive mode. The output limit curve L2 has an output limit greater than the output limit curve L1 in at least a part of the RPM region. The output limit curves L1 and L2 can be set in consideration of the durability, heat generation, and current controllability of the motor and the inverter.

[0055] The mode switching reference line L3 based on the efficiency diagram (not shown) is equivalent to the boundary line between the high efficiency area of ​​the CEW mode and the high efficiency area of ​​the OEW mode. The efficiency diagram includes information on the more efficient mode in the CEW mode and the OEW mode in each combination of the torque and the reverse flux of the motor, and the efficiency diagram can have a tabular form depending on the implementation. For example, the efficiency diagram can be obtained by experimentally measuring the results of the motor loss according to the speed and torque of the motor under each motor drive mode according to the DC terminal voltage of the inverter. At this time, the reverse flux of the motor is inversely proportional to the DC terminal voltage of the inverter (i.e., the voltage of the battery) and is proportional to the speed of the motor.

[0056] According to the embodiment, the mode switching reference line L3 can also have a form such as L3' according to the specifications of the motor drive device. Figure 2 The mode switching reference lines L3 and L3 ′ shown are only exemplary and are not limited thereto.

[0057] In order to switch the motor drive mode according to the mode switching reference line L3, the controller 70 can refer to the efficiency map and bidirectionally switch the CEW mode and the OEW mode according to the torque command value and the reverse flux value of the motor. At this time, the reverse flux value can be calculated according to the torque command of the motor, the DC terminal voltage of the inverter, and the required speed of the motor. According to an embodiment, the controller 70 can correct the mode switching reference line in consideration of the output limit or hysteresis for the motor drive mode, and in this case, the motor drive mode can be switched according to the torque command value and the reverse flux value of the motor based on the corrected mode switching reference line.

[0058] The following describes an electric vehicle that forms a boost charging path from an auxiliary battery to a main battery via a motor system when executing a running charging mode, thereby boosting the voltage of the auxiliary battery during running to control charging of the main battery. Figure 3 The structure for this is shown.

[0059] Figure 3 The present invention is a circuit diagram of a motor drive device included in an electric vehicle according to an embodiment of the present invention.

[0060] Reference Figure 3 The motor drive device according to an embodiment of the present invention may include a main battery 50, an auxiliary battery 51, a DC capacitor 60, a controller 70, a motor system 100, charging switches T1, T2, a DC capacitor Cn, main relays MRLY1, MRLY2, sub-relays SRLY1, SRLY2 and a pre-charging circuit PRE-C.

[0061] The motor system 100 is electrically connected to the main battery 50 and can include dual inverters 10, 20, a motor 30, a mode switching unit 40 and a diode d1. At this time, the anode of the diode d1 is connected to the internal node N, and the cathode is connected to the positive (+) DC terminal of the second inverter 20.

[0062] The main relay MRLY1 is connected between the positive (+) electrode of the main battery 50 and the positive (+) DC terminal of the first inverter 10, and the main relay MRLY2 is connected between the negative (-) electrode of the main battery 50 and the negative (-) DC terminal of the first inverter 10. The DC capacitor 60 can be connected between the positive (+) DC terminal and the negative (-) DC terminal of the first inverter 10 to reduce the current ripple to the main battery 50.

[0063] The sub-relay SRLY1 is connected between the positive (+) electrode of the auxiliary battery 51 and the internal node N, and the sub-relay SRLY2 is connected between the negative (-) electrode of the auxiliary battery 51 and the negative (-) DC terminal of the second inverter 20. The DC capacitor Cn can be connected between the positive (+) electrode and the negative (-) electrode of the auxiliary battery 51 to reduce the current ripple to the auxiliary battery 51. The pre-charging circuit PRE-C is connected to the positive (+) electrode of the auxiliary battery 51 and can be connected in parallel with the sub-relay SRLY1. The pre-charging circuit PRE-C can be implemented by a circuit in which a resistor and a relay are connected in parallel, but is not limited thereto.

[0064] The charging switches T1 and T2 can be connected in series between the internal node N of the motor system 100 and the positive (+) electrode of the auxiliary battery 51. More specifically, the collector of the charging switch T1 is connected to the internal node N, the collector of the charging switch T2 is connected to the positive (+) electrode of the auxiliary battery 51 through the sub-relay SRLY1, and the emitters of the charging switches T1 and T2 are connected to each other to form a common node. In this embodiment, the charging switches T1 and T2 are implemented by IGBTs (Insulated Gate Bipolar Transistors), but according to embodiments, they can also be implemented by MOSFETs.

[0065] The following describes an operation method of the controller 70 controlling the motor driving modes including the CEW mode and the OEW mode and executing the running charging mode.

[0066] When the CEW mode is executed, the controller 70 can turn on the switching switches S31, S32, and S33 to form a neutral point of the motor 30 at the internal node N, turn off the charging switches T1 and T2 to cut off the boost charging path connected to the main battery 50 from the auxiliary battery 51 through the motor system 100, and drive the motor 30 through the first inverter 10 of the first inverter 10 and the second inverter 20. When the OEW mode is executed, the controller 70 can turn off the switching switches S31, S32, and S33 to not form a neutral point of the motor 30 at the internal node N, turn off the charging switches T1 and T2 to cut off the boost charging path, and drive the motor 30 through the first inverter 10 and the second inverter 20. When the CEW mode or the OEW mode is executed, the controller 70 can perform space vector pulse width modulation (SVPWM) control without direct current (DC) offset for each of the phase currents Iu, Iv, and Iw of the motor 30. The controller 70 can set the zero-phase current command value for the direct current (DC) offset to “0.” Here, the SVPWM control refers to a method of synthesizing a reference voltage vector using a zero voltage vector and two effective voltage vectors adjacent to the reference voltage vector in a complex space.

[0067] The controller 70 can switch the CEW mode to the running charging mode according to a predetermined command for executing the charging mode. In the case of executing the running charging mode, the controller 70 can turn on the switching switches S31, S32, and S33 to form a neutral point of the motor 30 at the internal node N, turn on the charging switches T1 and T2 to form a boost charging path connected to the main battery 50 from the auxiliary battery 51 through the motor system 100, and drive the motor 30 through the first inverter 10 of the first inverter 10 and the second inverter 20. In addition, when executing the running charging mode, the controller 70 can apply a direct current (DC) offset to the phase currents Iu, Iv, and Iw of the motor 30 having multiple phases according to the charging current command for the auxiliary battery 51. More specifically, when executing the running charging mode, the controller 70 divides the value of the charging current command by the number of multiple phases (for example, 3), generates a zero-phase current command for the direct current (DC) offset, and outputs a plurality of switch signals for pulse width modulation control according to the zero-phase current command.

[0068] Reference Figure 4, shows an example of the waveform of the phase currents Iu, Iv, Iw of the motor 30 and the charging current Ia_bat of the auxiliary battery 51 when executing the driving charging mode. The phase currents Iu, Iv, Iw of the motor have a DC offset respectively and can have a phase difference of 120° with each other. The charging current Ia_bat is the same as the sum of the phase currents Iu, Iv, Iw of the motor, so it can have a DC waveform that is the DC offset multiplied by the number of phases (for example, 3). Therefore, when the controller 70 applies a negative (-) DC offset to the phase currents Iu, Iv, Iw of the motor respectively, the charging current Ia_bat is output from the auxiliary battery 51 to the main battery 50, so the motor system 100 can transmit the power of the auxiliary battery 51 to the main battery 50. In contrast, when the controller 70 applies a positive (+) direct current (DC) offset to the motor's phase currents Iu, Iv, and Iw, respectively, the charging current Ia_bat is output from the main battery 50 to the auxiliary battery 51, so that the motor system 100 can transfer power from the main battery 50 to the auxiliary battery 51.

[0069] When executing the charging mode during driving, the controller 70 outputs a plurality of switch signals Su, Sv, Sw for executing a preset pulse width modulation control on the first inverter 10, so that the motor system 100 boosts the voltage of the auxiliary battery 51 to charge the main battery 50, and can control the DC offset of each of the phase currents Iu, Iv, Iw of the motor 30. At this time, the plurality of switch signals Su, Sv, Sw correspond to the first branch 11, the second branch 12, and the third branch 13, respectively. In the present embodiment, the preset pulse width modulation control can be set to any one of space vector pulse width modulation (SVPWM) control or remote state pulse width modulation (RSPWM: Remote State Pulse Width Modulation) control. Among them, RSPWM control refers to a method of synthesizing a reference voltage vector using three effective voltage vectors having a phase difference of 120° in complex space.

[0070] Reference Figure 5 , shows that when the controller 70 performs SVPWM control, multiple switching signals Su, Sv, Sw and common mode voltage V CM Here, the plurality of switching signals Su, Sv, and Sw each have a waveform that is centrally aligned within one duty cycle. When SVPWM control is performed, the common mode voltage V CM The maximum amplitude is equivalent to the voltage of the main battery 50. Among them, the common mode voltage V CM Equivalent to the potential difference between the ground terminal and the neutral point of the motor.

[0071] Reference Figure 6, shows that when the controller 70 performs RSPWM control, multiple switching signals Su, Sv, Sw and common mode voltage V CM When RSPWM control is performed, the common mode voltage V CM The maximum amplitude of is equivalent to the value obtained by dividing the voltage of the main battery 50 by 3. That is, Figure 6 Compared with the RSPWM control method Figure 5 SVPWM control method, the common mode voltage V CM The pulsation generated is less, so the controller 70 can reduce the current ripple generated at the neutral point of the motor 30 through RSPWM control in the driving charging mode.

[0072] Next, refer to Figure 3 , describing an operation method of controlling the motor system 100 when the controller 70 switches between the CEW mode and the driving charging mode.

[0073] When the CEW mode is switched to the driving charging mode, the controller 70 can pre-charge the DC capacitor Cn connected between the positive (+) electrode and the negative (-) electrode of the auxiliary battery 51 through the pre-charging circuit PRE-C connected to the auxiliary battery 51. After pre-charging the DC capacitor Cn, the controller 70 switches the plurality of branches 11, 12, and 13 respectively to set the neutral point voltage (i.e., the common mode voltage) of the motor 30 to the voltage of the auxiliary battery 51. At this time, the controller 70 can switch the pulse width modulation control mode from the SVPWM control mode to a preset pulse width modulation control mode (e.g., RSPWM). Thereafter, the controller 70 turns on the charging switches T1 and T2 that are in the off state, and can apply a direct current (DC) offset to the phase currents Iu, Iv, and Iw of the motor 30 respectively according to the charging current command value for the auxiliary battery 51.

[0074] When the charging mode is switched to the CEW mode during driving, the controller 70 sets the zero-phase current command value for the DC offset to "0" and then switches the multiple branches 11, 12, and 13 to maintain the neutral point voltage of the motor 30. At this time, the controller 70 can turn off the charging switches T1 and T2 that are in the on state. When the charging switches T1 and T2 are turned off, the controller 70 can switch the multiple branches 11, 12, and 13 respectively through SVPWM control.

[0075] Figure 7 1 is a circuit diagram showing a structure of a motor system included in an electric vehicle according to another embodiment of the present invention.

[0076] Reference Figure 7, the charging switch T1 and the charging switch T2 can be connected in parallel between the internal node N and the positive (+) electrode of the auxiliary battery 51. More specifically, the collector of the charging switch T1 and the emitter of the charging switch T2 are connected to the internal node N, and the emitter of the charging switch T1 and the collector of the charging switch T2 are connected to the positive (+) electrode of the auxiliary battery 51 through the sub-relay SRLY1. Figure 7 In the connection mode shown, when the charging switches T1 and T2 are turned on, only one of the charging switches T1 and T2 is in the on state according to the current direction of the internal node N, so the conduction loss of the charging switches T1 and T2 can be minimized. At this time, the charging switches T1 and T2 can be implemented by transistors without reverse conduction characteristics (for example, IGBTs).

[0077] Figure 8 This is a flowchart for explaining a control method of an electric vehicle according to an embodiment of the present invention.

[0078] Reference Figure 8 , the controller 70 can determine whether to execute the CEW mode (S101).

[0079] When the OEW mode is executed (No in S101), the controller 70 can make the motor system 100 drive the motor 30 through the first inverter 10 and the second inverter 20 according to the voltage of the main battery 50 (S102). At this time, the controller 70 turns off the switching switches S31, S32, and S33 so as not to form a neutral point of the motor 30 at the internal node N, and in order to cut off the boost charging path from the auxiliary battery 51 to the main battery 50 through the motor system 100, the charging switches T1 and T2 can be turned off.

[0080] When the CEW mode is executed (Yes in S101), the controller 70 can make the motor system 100 drive the motor 30 through the first inverter 10 of the first inverter 10 and the second inverter 20 according to the voltage of the main battery 50 (S103). At this time, the controller 70 turns on the switching switches S31, S32, and S33 to form a neutral point of the motor 30 at the internal node N, and turns off the charging switches T1 and T2 to cut off the boost charging path. Among them, the zero-phase current command for the DC offset can be set to "0".

[0081] Thereafter, the controller 70 can determine whether the running charging mode is executed ( S104 ). If the running charging mode is not executed ( “No” in S104 ), S101 can be executed again.

[0082] When the running charging mode is executed in a state where the motor 30 is driven by the first inverter 10 (Yes in S104), the controller 70 sequentially executes S105, S106, and S107, thereby switching the CEW mode to the running charging mode. More specifically, the controller 70 can precharge the DC capacitor Cn connected between the positive (+) electrode and the negative (-) electrode of the auxiliary battery 51 through the precharging circuit PRE-C connected to the auxiliary battery 51 (S105). After precharging the DC capacitor Cn, the controller 70 switches the plurality of branches 11, 12, and 13, respectively, thereby setting the neutral point voltage of the motor 30 to the voltage of the auxiliary battery 51 (S106). Thereafter, the controller 70 can turn on the charging switches T1 and T2 to form a boost charging path connected from the auxiliary battery 51 to the main battery 50 through the motor system 100 (S107).

[0083] The controller 70 can perform a preset pulse width modulation control for the first inverter 10 to control the DC offset of each phase current of the motor 30 having multiple phases when executing the driving charging mode (S108). More specifically, the controller 70 divides the charging current command value for the auxiliary battery 51 by the number of multiple phases, generates a zero-phase current command for the DC offset, and performs a preset pulse width modulation control (for example, SVPWM control or RSPWM control) according to the zero-phase current command, thereby switching the multiple branches 11, 12, and 13 respectively. Therefore, the motor system 100 discharges the auxiliary battery 51 to charge the main battery 50 when the DC offset is negative (-), and discharges the main battery 50 to charge the auxiliary battery 51 when the DC offset is positive (+).

[0084] Thereafter, the controller 70 can determine whether the running charging mode has been terminated (S109). If the running charging mode has not been terminated (No in S109), S108 is executed again.

[0085] When the driving charging mode ends ("Yes" in S109), the controller 70 sequentially executes S110, S111, and S112, thereby switching the driving charging mode to the CEW mode. More specifically, the controller 70 can set the zero-phase current command value for the DC offset to "0" (S110). Thereafter, the controller 70 switches the plurality of branches 11, 12, and 13 respectively to maintain the neutral point voltage of the motor 30 (S111), and in order to cut off the boost charging path from the auxiliary battery 51 to the main battery 50 through the motor system 100, the charging switches T1 and T2 can be turned off (S112). Thereafter, S103 can be executed again.

[0086] Fig. 9 and Fig.10 This is a block diagram of an example of a motor drive system to which the present invention is applied.

[0087] Reference Fig. 9 , the motor system 100 according to the present embodiment transmits power to the drive wheels 200 (e.g., rear wheels) in the two-wheel drive electric vehicle in the motor drive mode according to the voltage of the main battery 50. In this case, the motor system 100 transmits power to the drive wheels 200 in the driving charging mode, and can also control the power transmission between the main battery 50 and the auxiliary battery 51.

[0088] Reference Fig.10 The motor system 100 according to the present embodiment can be applied to a four-wheel drive electric vehicle having a main drive wheel 300 (e.g., a rear wheel) and an auxiliary drive wheel 400 (e.g., a front wheel). The four-wheel drive electric vehicle always transmits power to the main drive wheel 300 through the motor system 100 according to the voltage of the main battery 50 during driving, and selectively transmits power to the auxiliary drive wheel 400 through the motor system 100' according to whether the four-wheel drive is performed during driving. In this case, the motor system 100 transmits power to the main drive wheel 300 in the charging mode during driving, and can also control the power transmission between the main battery 50 and the auxiliary battery 51.

Claims

1. An electric vehicle, in, include: Main and auxiliary batteries; a motor system connected to the main battery and comprising a dual inverter for driving the motor according to a motor driving mode and a switch for switching between a first driving mode and a second driving mode included in the motor driving mode; as well as A charging switch is connected between the motor system and the auxiliary battery and forms a boost charging path from the auxiliary battery through the motor system to the main battery when the first driving mode is switched to a running charging mode.

2. The electric vehicle according to claim 1, in, The dual inverter comprises: a first inverter connected to the main battery and to one end of a plurality of windings included in the motor; and a second inverter connected to the main battery and to the other ends of the plurality of windings, One end of the switch is connected to any one of the other ends of the plurality of windings, and the other end of the switch is connected to an internal node. The charging switch is connected between the internal node and one electrode of the auxiliary battery.

3. The electric vehicle according to claim 2, in, The first driving mode is as follows: The switching switch is turned on, the charging switch is turned off to cut off the boost charging path, and the motor is driven by the first inverter of the first inverter and the second inverter. The second driving mode is as follows: The changeover switch is turned off, the charging switch is turned off to cut off the boost charging path, and the motor is driven by the first inverter and the second inverter.

4. The electric vehicle according to claim 2, in, The driving charging mode is as follows: The switching switch is turned on, the charging switch is turned on to form the boost charging path, and the motor is driven by the first inverter of the first inverter and the second inverter.

5. The electric vehicle according to claim 4, in, The system further includes a controller, wherein when the driving charging mode is executed, the controller performs a preset pulse width modulation control on the first inverter. The preset pulse width modulation control setting is any one of space vector pulse width modulation control and remote state pulse width modulation control.

6. The electric vehicle according to claim 1, in, When the running charging mode is executed, a DC offset is applied to the phase current of the motor.

7. The electric vehicle according to claim 1, in, A controller is further included, which pre-charges a DC capacitor connected between one electrode and the other electrode of the auxiliary battery through a pre-charging circuit connected to the auxiliary battery when the first driving mode is switched to the running charging mode.

8. The electric vehicle according to claim 7, in, When the first driving mode is switched to the running charging mode, the controller sets the neutral point voltage of the motor to the voltage of the auxiliary battery after precharging the DC capacitor, and turns on the charging switch that is in an off state.

9. The electric vehicle according to claim 1, in, The system further includes a controller, which maintains the neutral point voltage of the motor and turns off the charging switch that is in the on state when the charging mode is converted to the first driving mode during driving.

10. An electric vehicle, in, include: Main and auxiliary batteries; a motor system that drives a motor via an inverter connected to the main battery; as well as The controller is configured to perform a preset pulse width modulation control on the inverter to control a DC offset of a phase current of the motor when executing a driving charging mode, so that the motor system boosts the voltage of the auxiliary battery to charge the main battery.

11. The electric vehicle according to claim 10, in, The preset pulse width modulation control setting is any one of space vector pulse width modulation control and remote state pulse width modulation control.

12. The electric vehicle according to claim 10, in, The inverter comprises: a first inverter connected to the main battery and to one end of a plurality of windings included in the motor; and a second inverter connected to the main battery and to the other ends of the plurality of windings, The motor system further includes a plurality of switching switches, one end of each of the plurality of switching switches is connected to different ones of the other ends of the plurality of windings, and the other ends of the plurality of switching switches are connected to each other at an internal node.

13. The electric vehicle according to claim 12, in, The system further includes a charging switch connected between the internal node and one electrode of the auxiliary battery, and forming a boost charging path from the auxiliary battery to the main battery through the motor system when the driving charging mode is executed.

14. The electric vehicle according to claim 13, in, The controller controls the on-state of the plurality of switches according to the motor driving mode, The motor driving modes include: a first driving mode, wherein the plurality of switching switches are turned on, the charging switch is turned off to cut off the boost charging path, and the motor is driven by the first inverter of the first inverter and the second inverter; and In the second driving mode, the plurality of switching switches are turned off, the charging switch is turned off to cut off the boost charging path, and the motor is driven by the first inverter and the second inverter.

15. The electric vehicle according to claim 13, in, The driving charging mode is as follows: The plurality of switching switches are turned on, the charging switch is turned on to form the boost charging path, and the motor is driven by the first inverter of the first inverter and the second inverter.

16. The electric vehicle according to claim 14, in, The controller is configured to precharge a DC capacitor connected between one electrode and the other electrode of the auxiliary battery through a precharging circuit connected to the auxiliary battery when the first driving mode is switched to the running charging mode.

17. The electric vehicle according to claim 16, in, The controller is configured to, when the first driving mode is switched to the running charging mode, set the neutral point voltage of the motor to the voltage of the auxiliary battery after precharging the DC capacitor and turn on the charging switch that is in an off state.

18. The electric vehicle according to claim 14, in, The controller is configured to maintain a neutral point voltage of the motor and turn off the charging switch that is in an on state when the charging mode during driving is switched to the first driving mode.

19. A control method for an electric vehicle, in, include: In a motor system, a step of driving a motor through an inverter according to a voltage of a main battery; as well as When the running charging mode is executed in a state where the motor is driven, a step of forming a boost charging path connected from the auxiliary battery to the main battery through the motor system is formed.

20. The control method of the electric vehicle according to claim 19, in, Also includes: When the driving charging mode is executed, a preset pulse width modulation control is performed on the inverter to control a DC offset of a phase current of the motor.

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