JP2012186905A - Electrical system of electric vehicle and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly set an output voltage of a converter to increase vehicle driving force while evading an instrument fault in an electrical system of an electric vehicle including a converter to carry out variable control of DC side voltage of an inverter that performs drive control of an electric motor for vehicle drive.SOLUTION: An ECU 30 includes: a current detecting means for detecting amplitudes of current applied to the electric motor; a margin calculation means for calculating a system voltage margin to a default value of the upper limit value of a system voltage that is set beforehand corresponding to the maximum value of the amplitude based on the margin of the detection value of the current detection means to the maximum value of the amplitude of the current applied to the electric motor; an upper limit value default value correction means for correcting the upper limit value by adding the calculated margin of the system voltage to a default value; and a voltage command value generation means for generating a voltage command value according to the driving force requested for the electric motor so that the system voltage VH does not exceed the corrected upper limit value.

Description

  The present invention relates to an electric system for an electric vehicle and a control method therefor, and more particularly to an electric system for an electric vehicle including a converter for variably controlling a DC side voltage of an inverter that drives and controls an AC electric motor.

  As an electric system including a converter for variably controlling the DC side voltage of an inverter that drives and controls an AC motor, for example, Japanese Patent Laying-Open No. 2006-101636 (Patent Document 1) describes a DC voltage variably controlled by a converter. A power supply device that converts an AC motor to drive an AC voltage using an inverter is disclosed.

  In the power supply device described in Patent Document 1, the load current of the boost converter is detected, and when the load current is equal to or lower than a limit start current value that is lower than a predetermined limit current value, the output voltage of the inverter By setting the voltage amplitude value to 100% and reducing the voltage amplitude value according to the load current so that the voltage amplitude value becomes 0% at the limit current value, the protection function is activated due to temporary overload. The output of the boost converter is prevented from being stopped.

JP 2006-101636 A JP 2009-017716 A JP 2008-017682 A

  On the other hand, for example, a semiconductor switching element such as an IGBT (Insulated Gate Bipolar Transistor) element or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is used as the inverter. appear. This surge voltage indicates the voltage increase from the inverter input voltage (system voltage) to the back electromotive voltage generated by the parasitic inductance. In order to prevent the back electromotive voltage from exceeding the breakdown voltage of the semiconductor switching element, it is necessary to determine the inverter input voltage in consideration of the voltage increase due to the surge voltage.

  Here, the voltage increase due to the surge voltage is calculated by multiplying the cutoff current passing rate (di / dt) during switching and the parasitic impedance L. Therefore, the inverter input voltage can be determined based on the voltage increase due to the surge voltage when the surge voltage is maximized, that is, when the breaking current change rate is maximized.

  However, in the configuration in which the inverter input voltage is set to a predetermined value in anticipation of the maximum voltage increase due to the surge voltage as described above, when the surge voltage is lower than the maximum value, that is, when the breaking current change rate is small Even so, the inverter input voltage cannot be increased. As a result, there arises a problem that the driving force that can be generated by the AC motor is limited by the inverter input voltage.

  SUMMARY OF THE INVENTION Therefore, the present invention has been made in order to solve such a problem, and an object of the present invention is to provide an electric vehicle including a converter for variably controlling the DC side voltage of an inverter that drives and controls the electric motor for driving the vehicle. In the electric system, the output voltage of the converter is appropriately set so as to increase the vehicle driving force while avoiding equipment failure.

  In one aspect of the present invention, there is provided an electric system for an electric vehicle equipped with an electric motor for driving a vehicle, the DC power source, a converter for converting a DC voltage output from the DC power source, and a plurality of switching elements. The inverter is configured to convert the DC voltage output from the converter by the switching operation of a plurality of switching elements into the drive voltage of the motor, and the converter is controlled so that the input voltage to the inverter matches the voltage command value And a control device. The control device is based on current detection means for detecting the amplitude of the current applied to the electric motor, and a margin of the detection value of the current detection means with respect to a maximum value of the amplitude of the current applied to the electric motor assumed in advance. A margin calculating means for calculating a margin of the inverter input voltage with respect to a default value of the upper limit value of the inverter input voltage determined in advance corresponding to the maximum value of the amplitude, and an inverter input calculated by the margin calculating means Depending on the driving force required for the motor so that the inverter input voltage does not exceed the corrected upper limit value, the upper limit correction means for correcting the upper limit value by adding the voltage margin to the default value Voltage command value generation means for generating a voltage command value.

  Preferably, the default value is a predetermined upper limit value of the inverter input voltage by considering a surge voltage generated by a switching operation of a plurality of switching elements at least when the amplitude of the current applied to the electric motor becomes maximum. It is. The margin calculating means calculates the margin of the inverter input voltage based on the margin of the surge voltage at least when the amplitude of the current applied to the electric motor becomes maximum.

  In another aspect of the present invention, an electric system for an electric vehicle equipped with a first electric motor and a second electric motor for driving a vehicle, wherein the direct-current power source is switched by a switching operation of a switching element of a plurality of switching elements. A converter that converts the DC voltage output from the converter into a voltage, and a first inverter that converts the DC voltage output from the converter into a drive voltage of the first electric motor by the switching operation of the switching elements of the plurality of switching elements; The second inverter that converts the DC voltage output from the converter to the drive voltage of the second motor by the switching operation of the plurality of switching elements, and the input voltage to the first and second inverters match the voltage command value And a control device for controlling the converter. The control device includes a first current detection unit for detecting the amplitude of the current applied to the first motor, and a second current detection unit for detecting the amplitude of the current applied to the second motor. And a third current detection means for detecting a current flowing through the converter, and a margin of a detection value of the first current detection means with respect to a maximum value of an amplitude of a current applied to the first electric motor assumed in advance. And a first margin calculating means for calculating a margin of the inverter input voltage with respect to a default value of the upper limit value of the inverter input voltage determined in advance corresponding to the maximum value of the amplitude. Based on the margin of the detected value of the second current detecting means with respect to the maximum value of the amplitude of the current applied to the second electric motor, an upper limit of the inverter input voltage that is determined in advance corresponding to the maximum value of the amplitude Value diff Based on the second margin calculating means for calculating the margin of the inverter input voltage with respect to the default value and the margin of the detected value of the third current detecting means with respect to the maximum value of the current flowing through the converter assumed in advance. A third margin calculating means for calculating a margin of the inverter input voltage with respect to a default value of a predetermined upper limit value of the inverter input voltage corresponding to the maximum value of the current, and first to third An upper limit correction means for correcting the upper limit value by adding the minimum value of the margins of the inverter input voltage calculated by the margin calculation means to the default value, and an upper limit for correcting the inverter input voltage Voltage command value generation means for generating a voltage command value according to the driving force required for the first and second electric motors so as not to exceed the value.

  Preferably, the default value is determined in advance by considering a surge voltage generated by a switching operation of the plurality of switching elements when the amplitude of the current applied to at least the first and second motors is maximized. This is the upper limit value of the inverter input voltage. The first margin calculating means calculates the margin of the inverter input voltage based on at least the margin of the surge voltage when the amplitude of the current applied to the first motor is maximized. The second margin calculation means calculates the margin of the inverter input voltage based on at least the margin of the surge voltage with respect to the maximum amplitude of the current applied to the second motor. The third margin calculating means calculates the margin of the inverter input voltage based on at least the margin of the surge voltage with respect to the maximum current flowing through the converter.

  Preferably, the electric vehicle includes an engine that operates by combustion of fuel, an output member that is connected to the second electric motor and outputs power to the drive wheels, an output member, an output shaft of the engine, and the first electric motor. A plurality of rotating elements respectively coupled to the output shaft are connected to each other so as to be rotatable relative to each other, and at least a part of the output from the engine is output to the output member with input and output of electric power and power by the first electric motor And a power split mechanism.

  In another aspect of the present invention, there is provided a method for controlling an electric system of an electric vehicle equipped with an electric motor for driving a vehicle, the electric system performing a voltage conversion on a DC power source and a DC voltage output from the DC power source and outputting the voltage. And a converter configured to include a plurality of switching elements, and an inverter that converts a DC voltage output from the converter by a switching operation of the plurality of switching elements into a drive voltage of the electric motor. The control method includes a step of detecting the amplitude of the current applied to the motor and a maximum amplitude based on a margin of a detected value of the current amplitude with respect to a maximum value of the current amplitude applied to the motor that is assumed in advance. A step of calculating a margin of the inverter input voltage with respect to a default value of a predetermined upper limit value of the inverter input voltage corresponding to the value, and an upper limit by adding the calculated margin of the inverter input voltage to the default value A step of correcting the value, a step of generating a voltage command value according to the driving force required for the motor so that the inverter input voltage does not exceed the corrected upper limit value, and the inverter input voltage matches the voltage command value The step of controlling the converter.

  Preferably, the default value is a predetermined upper limit value of the inverter input voltage by considering a surge voltage generated by a switching operation of a plurality of switching elements at least when the amplitude of the current applied to the electric motor becomes maximum. It is. In the step of calculating the margin, the margin of the inverter input voltage is calculated based on at least the margin of the surge voltage with respect to the maximum amplitude of the current applied to the electric motor.

  According to the present invention, in an electric system of an electric vehicle including a converter for variably controlling a DC side voltage of an inverter that drives and controls an electric motor for driving a vehicle, the vehicle driving force is increased while avoiding equipment failure. The output voltage of the converter can be set appropriately.

1 is a schematic configuration diagram of a hybrid vehicle shown as an example of a vehicle equipped with an electric system for an electric vehicle according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining details of a power train in the hybrid vehicle of FIG. 1. It is a schematic block diagram which shows the control structure of motor generator MG1, MG2. It is a block diagram explaining the motor control structure in ECU. It is a block diagram explaining the voltage conversion control structure by the converter control part in FIG. It is a figure which illustrates notionally the upper limit of system voltage VH. It is a figure which illustrates notionally the surge voltage by an IGBT element. It is a figure explaining the process of the system voltage upper limit setting by a system voltage command generation part. It is a conceptual diagram which shows the operation possible area | region of motor generator MG2 by the motor control by embodiment of this invention. It is a figure explaining the transition of the amplitude of motor current MCRT1, MCRT2 and reactor current IL at the time of full open acceleration. It is a figure explaining the process which produces | generates the system voltage command by the system voltage command generation part shown in FIG. It is a figure explaining an example of the pressure | voltage resistant margin calculation map memorize | stored in a memory | storage part. It is a flowchart explaining the production | generation method of the system voltage command value according to embodiment of this invention. It is a flowchart explaining the production | generation method of the system voltage command value according to embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic configuration diagram of a hybrid vehicle 5 shown as an example of a vehicle equipped with an electric system for an electric vehicle according to an embodiment of the present invention.

  Referring to FIG. 1, hybrid vehicle 5 includes an engine ENG, motor generators MG1 and MG2, a battery 10, a power conversion unit (PCU: Power Control Unit) 20, a power split mechanism PSD, a reduction gear RD, Front wheels 70L and 70R, rear wheels 80L and 80R, and an electronic control unit (ECU) 30 are provided. The control device according to the present embodiment is realized, for example, by a program executed by ECU 30. 1 illustrates the hybrid vehicle 5 using the front wheels 70L and 70R as drive wheels, the rear wheels 80L and 80R may be used as drive wheels instead of the front wheels 70L and 70R. Alternatively, in addition to the configuration shown in FIG. 1, a motor generator for driving the rear wheels 80L and 80R may be further provided to provide a 4WD configuration.

  The driving force generated by the engine ENG is divided into two paths by the power split mechanism PSD. One is a path for driving the front wheels 70L and 70R via the reduction gear RD. The other is a path for generating electric power by driving the motor generator MG1.

  Motor generator MG1 is typically constituted by a three-phase AC synchronous motor generator. Motor generator MG1 generates electricity as a generator by the driving force of engine ENG divided by power split mechanism PSD. Motor generator MG1 has not only a function as a generator but also a function as an actuator for controlling the rotational speed of engine ENG.

  The electric power generated by motor generator MG1 is selectively used according to the driving state of the vehicle and the state of charge (SOC) of battery 10. For example, during normal running or sudden acceleration, the electric power generated by motor generator MG1 is used as power for driving motor generator MG2 as a motor. On the other hand, when the SOC of battery 10 is lower than a predetermined value, the power generated by motor generator MG1 is converted from AC power to DC power by power conversion unit 20 and stored in battery 10.

  The motor generator MG1 is also used as a starter when starting the engine ENG. When starting engine ENG, motor generator MG1 is supplied with electric power from battery 10 and is driven as an electric motor. Then, motor generator MG1 cranks engine ENG and starts it.

  Motor generator MG2 is typically constituted by a three-phase AC synchronous motor generator. When motor generator MG2 is driven as an electric motor, it is driven by at least one of electric power stored in battery 10 and electric power generated by motor generator MG1. The driving force of motor generator MG2 is transmitted to front wheels 70L and 70R via reduction gear RD. Thus, motor generator MG2 assists engine ENG to travel the vehicle or causes the vehicle to travel only by the driving force of motor generator MG2.

  During regenerative braking of the vehicle, the motor generator MG2 is driven by the front wheels 70L and 70R via the reduction gear RD, and the motor generator MG2 is operated as a generator. Thus, motor generator MG2 acts as a regenerative brake that converts braking energy into electric energy. The electric power generated by motor generator MG2 is stored in battery 10 via power conversion unit 20.

  The battery 10 is constituted by a secondary battery such as nickel hydride or lithium ion, for example. In the embodiment of the present invention, the battery 10 is shown as a representative example of “DC power supply”. That is, another DC power source such as an electric double layer capacitor can be used in place of the battery 10. The battery 10 supplies a DC voltage to the power conversion unit 20 and is charged by the DC voltage from the power conversion unit 20.

  The power conversion unit 20 performs bidirectional power conversion between DC power supplied by the battery 10, AC power for driving and controlling the motor, and AC power generated by the generator.

  The hybrid vehicle 5 further includes a handle 40, an accelerator position sensor 44 that detects the accelerator pedal position AP, a brake pedal position sensor 46 that detects the brake pedal position BP, and a shift position sensor 48 that detects the shift position SP. Prepare.

  Motor generators MG1 and MG2 are further provided with rotation angle sensors 51 and 52 for detecting the rotor rotation angle. Rotor rotation angle θ1 of motor generator MG1 detected by rotation angle sensor 51 and rotor rotation angle θ2 of motor generator MG2 detected by rotation angle sensor 52 are transmitted to ECU 30. The rotation angle sensors 51 and 52 estimate the rotor rotation angle θ1 from the current, voltage and the like of the motor generator MG1 in the ECU 30, and estimate the rotor rotation angle θ2 from the current, voltage and the like of the motor generator MG2. The arrangement may be omitted.

  ECU 30 is electrically connected to engine ENG, power conversion unit 20 and battery 10. Based on detection signals from various sensors, ECU 30 determines the engine ENG operation state, motor generator MG1 and MG2 drive states, and battery 10 charge state so that hybrid vehicle 5 is in a desired travel state. Integrated control.

  FIG. 2 is a schematic diagram for explaining details of the power train in the hybrid vehicle 5 of FIG. 1.

  Referring to FIG. 2, the power train (hybrid system) of hybrid vehicle 5 includes motor generator MG2, reduction gear RD connected to output shaft 160 of motor generator MG2, engine ENG, motor generator MG1, A splitting mechanism PSD.

  In the example shown in FIG. 2, the power split mechanism PSD is constituted by a planetary gear mechanism, and a sun gear 151 coupled to a hollow sun gear shaft penetrating the crankshaft 150 through the center of the shaft is rotatable coaxially with the crankshaft 150. Are supported between the ring gear 152, the sun gear 151 and the ring gear 152. The pinion gear 153 revolves while rotating on the outer periphery of the sun gear 151. The rotation shaft of each pinion gear 153 is coupled to the end of the crankshaft 150. And a planetary carrier 154 for supporting the

  In power split mechanism PSD, three axes of a sun gear shaft coupled to sun gear 151, a ring gear case 155 coupled to ring gear 152, and crankshaft 150 coupled to planetary carrier 154 serve as power input / output shafts. When the power input / output to / from any two of the three axes is determined, the power input / output to the remaining one axis is determined based on the power input / output to the other two axes.

  A counter drive gear 170 for extracting power is provided outside the ring gear case 155 and rotates integrally with the ring gear 152. Counter drive gear 170 is connected to power transmission reduction gear RG. The ring gear case 155 corresponds to the “output member” in the present invention. In this way, power split device PSD operates to output at least a part of the output from engine ENG to the output member with the input and output of electric power and power by motor generator MG1.

  Further, power is transmitted between the counter drive gear 170 and the power transmission reduction gear RG. The power transmission reduction gear RG drives a differential gear DEF coupled to the front wheels 70L and 70R that are drive wheels. On the downhill or the like, the rotation of the driving wheel is transmitted to the differential gear DEF, and the power transmission reduction gear RG is driven by the differential gear DEF.

  Motor generator MG1 includes a stator 131 that forms a rotating magnetic field, and a rotor 132 that is disposed inside stator 131 and has a plurality of permanent magnets embedded therein. Stator 131 includes a stator core 133 and a three-phase coil 134 wound around stator core 133. Rotor 132 is coupled to a sun gear shaft that rotates integrally with sun gear 151 of power split device PSD. The stator core 133 is formed by laminating thin electromagnetic steel plates, and is fixed to a case (not shown).

  Motor generator MG1 operates as an electric motor that rotationally drives rotor 132 by the interaction between the magnetic field generated by the permanent magnet embedded in rotor 132 and the magnetic field formed by three-phase coil 134. Motor generator MG1 also operates as a generator that generates electromotive force at both ends of three-phase coil 134 due to the interaction between the magnetic field generated by the permanent magnet and the rotation of rotor 132.

  Motor generator MG2 includes a stator 136 that forms a rotating magnetic field, and a rotor 137 that is disposed inside stator 136 and has a plurality of permanent magnets embedded therein. Stator 136 includes a stator core 138 and a three-phase coil 139 wound around stator core 138.

  The rotor 137 is coupled to a ring gear case 155 that rotates integrally with the ring gear 152 of the power split mechanism PSD via a reduction gear RD. Stator core 138 is formed, for example, by laminating thin magnetic steel sheets, and is fixed to a case (not shown).

  Motor generator MG2 also operates as a generator that generates an electromotive force at both ends of three-phase coil 139 by the interaction between the magnetic field generated by the permanent magnet and the rotation of rotor 137. Motor generator MG2 operates as an electric motor that rotates rotor 137 by the interaction between the magnetic field generated by the permanent magnet and the magnetic field formed by three-phase coil 139.

  The speed reducer RD performs speed reduction by a structure in which a planetary carrier 166 that is one of rotating elements of a planetary gear is fixed to a case. That is, reduction device RD meshes with sun gear 162 coupled to output shaft 160 of rotor 137, ring gear 168 that rotates integrally with ring gear 152, ring gear 168 and sun gear 162, and transmits the rotation of sun gear 162 to ring gear 168. Pinion gear 164. For example, by reducing the number of teeth of the ring gear 168 to more than twice the number of teeth of the sun gear 162, the reduction ratio can be increased more than twice.

  Thus, the rotational force of motor generator MG2 is transmitted to output member (ring gear case) 155 that rotates integrally with ring gears 152 and 168 via reduction gear RD. That is, motor generator MG2 is configured to apply power between output member 155 and the drive wheel. Note that the arrangement of the reduction gear RD may be omitted, that is, the output shaft 160 of the motor generator MG2 and the output member 155 may be connected without providing a reduction ratio.

  Power conversion unit 20 includes a converter 12 and inverters 14 and 22. Converter 12 converts DC voltage Vb from battery 10 and outputs DC voltage VH between power supply line PL and ground line GL. Converter 12 is configured to be capable of voltage conversion in both directions, and converts DC voltage VH between power supply line PL and ground line GL into charging voltage Vb of battery 10.

  Inverters 14 and 22 are constituted by general three-phase inverters, convert DC voltage VH between power supply line PL and ground line GL into an AC voltage, and output the AC voltage to motor generators MG2 and MG1, respectively. Inverters 14 and 22 convert the AC voltage generated by motor generators MG2 and MG1 into DC voltage VH and output the voltage between power supply line PL and ground line GL.

  In the configuration shown in FIGS. 1 and 2, the DC voltage sides of inverters 14 and 22 are connected to converter 12 through common power supply line PL and ground line GL. Motor generator MG1 corresponds to the “first electric motor” in the present invention, and motor generator MG2 corresponds to the “second electric motor” in the present invention. The inverter 22 corresponds to the “first inverter” in the present invention, and the inverter 14 corresponds to the “second inverter” in the present invention. Hereinafter, the DC voltage VH of the power supply line PL corresponding to the input voltage of the inverters 14 and 22 is also referred to as “system voltage VH”.

FIG. 3 is a schematic block diagram showing a control configuration of motor generators MG1 and MG2.
Referring to FIG. 3, power conversion unit 20 includes capacitors C <b> 1 and C <b> 2, converter 12, inverters 14 and 22, and current sensors 24 and 28.

  ECU 30 shown in FIGS. 1 and 2 performs switching control of converter 12 and inverters 14 and 22 so that motor generators MG1 and MG2 operate according to the operation commands of motor generators MG1 and MG2 input from the host electronic control unit. Switching control signals PWMC, PMWI1, and PMWI2 are generated.

  Converter 12 includes a reactor L1, IGBTs (Insulated Gate Bipolar Transistor) elements Q1, Q2, and diodes D1, D2. Reactor L1 has one end connected to the power supply line of battery 10, and the other end connected to an intermediate point between IGBT element Q1 and IGBT element Q2, that is, between the emitter of IGBT element Q1 and the collector of IGBT element Q2. The IGBT elements Q1, Q2 are connected in series between power supply line PL and ground line GL. IGBT element Q1 has a collector connected to power supply line PL, and IGBT element Q2 has an emitter connected to ground line GL. Further, diodes D1 and D2 for flowing current from the emitter to the collector side are connected between the collector and emitter of each of the IGBT elements Q1 and Q2.

  Inverter 14 includes U-phase arm 15, V-phase arm 16, and W-phase arm 17. U-phase arm 15, V-phase arm 16, and W-phase arm 17 are provided in parallel between power supply line PL and ground line GL. U-phase arm 15 includes IGBT elements Q3 and Q4 connected in series, V-phase arm 16 includes IGBT elements Q5 and Q6 connected in series, and W-phase arm 17 includes IGBT elements Q7 and Q7 connected in series. Consists of Q8. Further, diodes D3 to D8 that flow current from the emitter side to the collector side are connected between the collectors and emitters of the IGBT elements Q3 to Q8, respectively.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of motor generator MG2. That is, one end of the three coils of U, V, and W phases is commonly connected to the neutral point, the other end of the U phase coil is at the middle point of the IGBT elements Q3 and Q4, and the other end of the V phase coil is the IGBT. The other end of the W-phase coil is connected to an intermediate point between the elements Q5 and Q6 and an intermediate point between the IGBT elements Q7 and Q8, respectively.

The inverter 22 has the same configuration as the inverter 14.
Voltage sensor 11 detects DC voltage Vb output from battery 10 and outputs the detected DC voltage Vb to ECU 30. Capacitor C <b> 1 smoothes DC voltage Vb supplied from battery 10, and supplies the smoothed DC voltage Vb to converter 12.

  Converter 12 boosts DC voltage Vb supplied from capacitor C1 and supplies the boosted voltage to capacitor C2. Specifically, when converter 12 receives signal PWMC from ECU 30, converter 12 boosts DC voltage Vb according to the period during which IGBT element Q2 is turned on by signal PWMC and supplies it to capacitor C2.

  When converter 12 receives signal PWMC from ECU 30, converter 12 steps down DC voltage (system voltage VH) supplied from inverter 14 and / or inverter 22 via capacitor C2, and charges battery 10. Current sensor 26 detects a reactor current IL flowing through reactor L1, and outputs the detected reactor current IL to ECU 30.

  Capacitor C2 smoothes the DC voltage from converter 12, and supplies the smoothed DC voltage to inverters 14 and 22 via power supply line PL and ground line GL. The voltage sensor 13 detects the voltage across the capacitor C2, that is, the output voltage VH of the converter 12 (corresponding to the input voltage of the inverters 14 and 22. The same applies hereinafter), and the detected output voltage (system voltage) VH. Is output to the ECU 30.

  When the system voltage VH is supplied from the capacitor C2, the inverter 14 converts the DC voltage into an AC voltage based on the signal PWMI2 from the MG-ECU 35 and drives the motor generator MG2. Thereby, motor generator MG2 is driven so as to generate torque specified by torque command value TR2.

  Inverter 14 also converts the AC voltage generated by motor generator MG2 during regenerative braking of hybrid vehicle 5 into a DC voltage (system voltage VH) based on signal PWMI2 from ECU 30, and converts the converted DC voltage to capacitor C2. To the converter 12 via The regenerative braking here refers to braking accompanied by regenerative braking when the driver driving the hybrid vehicle 5 performs a regenerative braking, or turning off the accelerator pedal during traveling, although the foot brake is not operated. This includes decelerating the vehicle (or stopping acceleration) while generating regenerative power.

  When system voltage VH is supplied from capacitor C2, inverter 22 converts DC voltage to AC voltage based on signal PWMI1 from ECU 30 to drive motor generator MG1. Thereby, motor generator MG1 is driven to generate torque specified by torque command value TR1.

  Current sensor 24 detects motor current MCRT1 flowing through motor generator MG1, and outputs the detected motor current MCRT1 to ECU 30. Current sensor 28 detects motor current MCRT2 flowing through motor generator MG2, and outputs the detected motor current MCRT2 to ECU 30.

  Further, the rotor rotation angle θ1 of motor generator MG1 detected by rotation angle sensor 51 and the rotor rotation angle θ2 of motor generator MG2 detected by rotation angle sensor 52 are transmitted to ECU 30.

  ECU 30 receives DC voltage Vb from voltage sensor 11, receives motor currents MCRT1 and MCRT2 from current sensors 24 and 28, receives output voltage (system voltage) VH of converter 12 from voltage sensor 13, and receives rotation angle sensor 51, 52 receives rotor rotation angles θ1 and θ2, respectively. ECU 30 can calculate rotation speeds MRN1 and MRN2 of motor generators MG1 and MG2 based on rotor rotation angles θ1 and θ2, respectively.

  Further, ECU 30 receives operation commands for motor generators MG1 and MG2 from the host ECU. The operation command sent from the host ECU includes torque command values TR1 and TR2 of motor generators MG1 and MG2.

FIG. 4 is a block diagram illustrating a motor control configuration in the ECU 30.
Referring to FIG. 4, ECU 30 includes an inverter control unit 42 that performs power conversion control in inverters 14 and 22, and a converter control unit 40 that performs voltage conversion control in converter 12.

  Based on system voltage VH, motor current MCRT2, rotor rotation angle θ2 (motor rotation speed MRN2), and torque command value TR2, inverter control unit 42 drives IGBT generator of inverter 14 when inverter 14 drives motor generator MG2. A signal PWMI2 for switching control of Q3 to Q8 is generated, and the generated signal PWMI2 is output to inverter 14. Inverter control unit 42 also controls inverter 22 when inverter 22 drives motor generator MG1 based on system voltage VH, motor current MCRT1, rotor rotational angle θ1 (motor rotational speed MRN1), and torque command value TR1. A signal PWMI1 for switching control of IGBT elements Q3 to Q8 is generated, and the generated signal PWMI1 is output to inverter 22. At these times, the signals PWMI1 and PWMI2 are generated by feedback control using sensor detection values according to, for example, a well-known PWM control method.

  Converter control unit 40 generates a voltage command value (system voltage command value) VHcom of converter 12 and controls converter 12 so that output voltage (system voltage) VH of converter 12 follows system voltage command value VHcom. . Specifically, converter control unit 40 generates a signal PWMC for switching control of IGBT elements Q1, Q2 of converter 12 based on system voltage command value VHcom, DC voltage Vb, and system voltage VH. Output to the converter 12.

  Next, voltage conversion control in converter 12 by converter control unit 40 will be described in detail.

  FIG. 5 is a block diagram illustrating a voltage conversion control configuration by converter control unit 40 in FIG.

  Referring to FIG. 5, converter control unit 40 includes a system voltage command generation unit 50, a converter duty ratio conversion unit 53, and a converter PWM signal conversion unit 54.

  System voltage command generation unit 50 generates system voltage VH based on torque command values TR1, TR2 from the host ECU, rotor rotation angles θ1, θ2 (motor rotation speeds MRN1, MRN2), motor currents MCRT1, MCRT2, and reactor current IL. , That is, the system voltage command value VHcom is calculated, and the calculated system voltage command value VHcom is output to the converter duty-ratio converter 53.

  When converter duty-ratio conversion unit 53 receives system voltage command value VHcom from system voltage command generation unit 50 and DC voltage Vb from voltage sensor 11, converter duty ratio conversion unit 53 converts system voltage VH from voltage sensor 13 to system voltage command value VHcom. The duty ratio for setting is calculated, and the calculated duty ratio is output to the converter PWM signal converter 54.

  Converter PWM signal converter 54 generates signal PWMC for switching control of IGBT elements Q1 and Q2 of converter 12 based on the duty ratio given from converter duty ratio converter 53, and generates the generated signal PWMC. Output to the converter 12.

(Generation of system voltage command value VHcom)
In the configuration shown in FIG. 5, in order to smoothly drive motor generator MG (generally representing MG1 and MG2, hereinafter the same), a converter is used according to the operating point, rotational speed and torque of motor generator MG. The output voltage (system voltage) VH of 12 needs to be set appropriately.

  On the other hand, in the inverters 14 and 22, a surge voltage is generated as the IGBT element is turned on / off. This surge voltage is superimposed on the input voltage (system voltage) VH of the inverters 14 and 22, and is applied between the collector and emitter of the IGBT element. Therefore, when the surge voltage exceeds the withstand voltage of the IGBT element, there is a risk that equipment failure may occur due to breakdown of the IGBT element, dielectric breakdown that occurs in the coating of the motor winding, or the like. In order to avoid such a device failure, the upper limit voltage that can be output from the converter 12, that is, the upper limit value of the system voltage VH is limited by the breakdown voltage of the IGBT element.

FIG. 6 is a diagram conceptually illustrating the upper limit value of system voltage VH.
As shown in FIG. 6, the surge voltage ΔVH is added to the inverter input voltage (system voltage) VH. Therefore, upper limit value (hereinafter also referred to as “system voltage upper limit value”) VHmax of system voltage VH needs to be determined so as not to exceed the withstand voltage of the IGBT element of the inverter in consideration of at least a surge voltage.

  Here, the surge voltage shown in FIG. 6 includes the surge voltage due to the IGBT elements Q3 to Q8 and the surge voltage due to the antiparallel diodes D3 to D8, as the IGBT elements Q3 to Q8 are turned on and off. The surge voltage due to IGBT elements Q3 to Q8 is generated according to di / dt when the motor current is turned off. FIG. 7 is a diagram conceptually illustrating a surge voltage due to the IGBT element. This surge voltage (hereinafter referred to as “turn-off surge”) ΔVH increases as the switching speed of the IGBT element increases. When the switching speed is constant, the turn-off surge increases as the passing current of the IGBT element increases. The maximum is obtained when the IGBT element is turned on / off at the timing when the passing current of the IGBT element becomes maximum, that is, when the amplitude of the motor current becomes maximum.

  On the other hand, the surge voltage (hereinafter also referred to as “recovery surge”) generated by the antiparallel diodes D3 to D8 is an IGBT element at the timing when the diode current becomes zero and the reverse recovery current is generated, that is, near the zero cross timing of the motor current. Maximum when turning on and off. Note that which of the turn-off surge generated in the IGBT elements Q3 to Q8 and the recovery surge generated in the antiparallel diodes D3 to D8 increases depends on the hardware configuration of the electric system and the current region used.

  In the motor control according to the embodiment of the present invention, paying attention to the relationship between the turn-off surge and the magnitude of the motor current, the system voltage upper limit value VHmax is made variable according to the magnitude of the motor current according to FIG. 8 described below. Set.

  FIG. 8 is a diagram for explaining the process of setting the system voltage upper limit value by the system voltage command generation unit 50.

  FIG. 8A is a conceptual diagram showing the relationship between system voltage VH and the operable region of motor generator MG2. Referring to FIG. 8A, the operable region of motor generator MG2 is indicated by a combination of the rotational speed and torque. In motor generator MG2, the induced voltage increases as the rotational speed and torque increase, and the required voltage increases. The maximum value of the necessary motor voltage (induced voltage) is determined by the system voltage VH.

  The solid line L1 in the figure indicates the limit (maximum output line) of the operable region when the system voltage VH = VHmax (system voltage upper limit value). When system voltage VH increases above VHmax, the operable region is expanded as shown by broken line L2. That is, the torque upper limit value (maximum torque that can be output) of motor generator MG2 increases.

  The torque upper limit value is constant at the maximum value when the rotational speed is less than N2. This maximum value is due to current limitation in the maximum torque control. Then, after the voltage limit is reached by the maximum torque control due to the increase in the required motor voltage with the increase in the rotational speed, the required motor voltage is increased to the system voltage upper limit value VHmax by increasing the field weakening current. Control not to exceed. In the range where the rotational speed is N2 or more, the torque upper limit value decreases as the rotational speed increases.

  FIG. 8B shows the current (motor current) applied to the motor generator MG2 shown in FIG. 8A when the accelerator pedal position AP is operated to the fully open position WOT (Wide Open Throttle) by the driver. FIG. In the figure, in the state where the operating point of the motor generator MG2 transitions on the maximum output line L1, that is, in the state where the motor generator MG2 outputs the torque upper limit value, the state where the amplitude of the motor current MCRT2 transitions. It is shown. In the range where the rotational speed is less than N2, the amplitude of the motor current MCRT2 is increased by the maximum torque control, whereas in the range where the rotational speed is N2 or more, the amplitude of the motor current MCRT2 is decreased by the field weakening control. . The amplitude of the motor current MCRT2 becomes a maximum value (maximum motor current MCRT2_max) when the rotation speed is N2.

  As described above, the turn-off surge generated in IGBT elements Q3 to Q8 increases as the amplitude of motor current MCRT2 increases. Therefore, when the amplitude of the motor current MCRT2 changes in the manner shown in FIG. 8B, the turn-off surge generated in the IGBT elements Q3 to Q8 is less than N2, as shown in FIG. 8C. The region where the rotational speed is N2 or more is smaller than the region. Further, when the rotational speed is N2, the turn-off surge becomes the maximum value (maximum turn-off surge ΔVHmax). Therefore, in order to reliably avoid a device failure, it is necessary to set system voltage upper limit value VHmax in consideration of maximum turn-off surge ΔVHmax that can occur during operation of motor generator MG2.

  On the other hand, in the region where the rotational speed is N2 or more, the amplitude of the motor current MCRT2 decreases as the rotational speed increases. Therefore, it can be seen that, in this region, the degree of margin with respect to the maximum turn-off surge ΔVHmax increases as the rotational speed increases even in the turn-off surge.

  In the embodiment of the present invention, the margin of occurrence of turn-off surge with respect to the maximum turn-off surge ΔVHmax is reflected in the setting of the system voltage upper limit value VHmax. Specifically, as shown in FIG. 8D, a system voltage upper limit value VHmax0 preset in correspondence with the maximum motor current MCRT2 is set as a default value. Then, based on the amplitude of the current MCRT2 actually applied to the motor generator MG2, a turn-off surge margin ΔVH2 with respect to the maximum turn-off surge ΔVHmax is calculated, and the calculated margin ΔVH2 is added to the default value VHmax0. The system voltage upper limit value VHmax is corrected (raised).

  Here, the turn-off surge margin ΔVH2 is such that the amplitude of the motor current MCRT2 decreases when the rotational speed is N2 or more, that is, when the operating point of the motor generator MG2 is located in the middle rotational speed range and the high rotational speed range. Has increased in response to. Therefore, by reflecting the turn-off surge margin ΔVH2 in the system voltage upper limit value VHmax, the system voltage upper limit value VHmax is higher than the default value VHmax0 when the operating point is located in the middle speed range and the high speed range. The voltage is corrected.

  FIG. 9 is a conceptual diagram showing an operable region of motor generator MG2 by motor control according to the embodiment of the present invention.

  Referring to FIG. 9, maximum output line L1 indicates the limit of the operable region when system voltage VH = VHmax0 (default value). On the other hand, in the maximum output line L3 according to the present invention, the torque upper limit value in the medium speed range and the high speed range is increased. As described with reference to FIG. 8D, this is because the system voltage upper limit value VHmax is corrected to a voltage higher than the default value VHmax0 in the medium speed range and the high speed range. As a result, the operable region of motor generator MG2 according to the present invention is enlarged by the region indicated by the hatching in the drawing. Therefore, the vehicle driving force in the medium rotation speed range and the high rotation speed range increases during full-open acceleration.

  In the hybrid vehicle 5 shown in FIG. 1, when the accelerator pedal position AP is operated to the fully open position WOT by the driver, the amplitude of the current (motor current MCRT2) applied to the motor generator MG2 changes. In parallel, the amplitudes of the current applied to motor generator MG2 (motor current MCRT1) and the current flowing through converter 12 (reactor current IL) transition. FIG. 10 shows that the amplitudes of motor currents MCRT1, MCRT2 and reactor current IL change in a state where the operating point of motor generator MG2 is transitioning on maximum output line L1, that is, in a state where a torque upper limit value is being output. It shows how to do.

  Referring to FIG. 10, the amplitude of motor current MCRT1 takes a maximum value when engine ENG is cranked (when the rotational speed is N1). In the range where the rotational speed is N1 or more, the amplitude of the motor current MCRT1 decreases as the rotational speed increases. Similarly, the amplitude of reactor current IL becomes the maximum value when cranking engine ENG, and decreases as the rotational speed increases in the range where the rotational speed is N1 or more.

  That is, in FIG. 10, when motor motors MG2 and MCRT2 and reactor current IL are all in the middle rotation speed range and the high rotation speed range, the amplitude is smaller than the maximum value. ing. Therefore, it can be understood that, in both the medium rotation speed region and the high rotation speed region, there is a margin for maximum turn-off surge ΔVHmax in any of motor generators MG1, MG2 and converter 12. Therefore, the margin with respect to this maximum turn-off surge ΔVHmax can be reflected in the setting of system voltage upper limit value VHmax, and as a result, the operation region of motor generator MG2 shown in FIG. 9 can be expanded.

  FIG. 11 is a diagram illustrating a process of generating a system voltage command by the system voltage command generating unit 50 shown in FIG.

  Referring to FIG. 11, system voltage command generation unit 50 includes a system voltage upper limit value setting unit 500, a storage unit 502, and a system voltage command value calculation unit 510.

  System voltage upper limit setting unit 500 receives reactor current IL from current sensor 26, and receives motor currents MCRT 1 and MCRT 2 from current sensors 24 and 28. System voltage upper limit setting unit 500 sets system voltage upper limit value VHmax based on reactor current IL and motor currents MCRT1 and MCRT2, and outputs the set system voltage upper limit value VHmax to system voltage command value calculation unit 510. .

  Specifically, when system voltage upper limit setting unit 500 obtains motor current MCRT1 from current sensor 24, obtains motor current MCRT2 from current sensor 28, and obtains reactor current IL from current sensor 26, storage unit 502 By referring to the withstand voltage map read out from, the withstand voltage allowance ΔVH is calculated based on the motor currents MCRT1 and MCRT2 and the reactor current IL. The withstand voltage margin ΔVH corresponds to the margin of turn-off surge with respect to the maximum turn-off surge ΔVHmax.

  In the storage unit 502, an MG2 withstand voltage margin calculation map 504, an MG1 withstand voltage margin calculation map 506, and a converter withstand voltage margin calculation map 508 are stored in advance. The MG2 withstand voltage margin calculation map 504 is a map for calculating the margin of the turn-off surge with respect to the maximum turn-off surge in the inverter 14. The MG1 withstand voltage margin calculation map 506 is a map for calculating the margin of the turn-off surge with respect to the maximum turn-off surge in the inverter 22. The converter withstand voltage margin calculation map 508 is a map for calculating the margin of the turn-off surge with respect to the maximum turn-off surge in the converter 12. FIG. 12 is a diagram illustrating an example of a pressure tolerance margin calculation map stored in the storage unit 502. 12A shows an example of the MG2 withstand voltage margin calculation map 504, FIG. 12B shows an example of the MG1 withstand voltage margin calculation map 506, and FIG. 12C shows the converter. 6 shows an example of a map 508 for calculating a withstand voltage margin. In addition, the numerical value of the electric current and withstand pressure | voltage tolerance shown by each map is an example, Comprising: It is not limited to this. The numerical value of the withstand voltage margin is determined in consideration of the withstand voltage of the smoothing capacitor C2 provided on the DC side of the inverters 14 and 22.

  Referring to FIG. 12 (a), in inverter 14, withstand voltage margin ΔVH2 is such that the withstand voltage margin when motor current MCRT2 has the maximum amplitude (for example, 300 A) is 0 V, the amplitude is small. Accordingly, the withstand pressure margin is set to be large. This withstand voltage margin ΔVH2 corresponds to the margin of turn-off surge with respect to the maximum turn-off surge ΔVHmax described with reference to FIGS.

  Similarly, in FIG. 12B, the withstand voltage margin ΔVH1 in the inverter 22 is small when the withstand voltage margin when the amplitude of the motor current MCRT1 becomes the maximum value (for example, 100 A) is 0V. Accordingly, the withstand pressure margin is set to be large. In FIG. 12C, the withstand voltage margin ΔVHc in the converter 12 is set to 0 V when the amplitude of the reactor current IL reaches the maximum value (for example, 200 A), and the withstand voltage decreases as the amplitude decreases. The margin is set to be large. The maps shown in FIGS. 12A to 12C are obtained by preliminarily obtaining the relationship between the current amplitude and the withstand voltage margin by experiments or the like and storing them in the storage unit 502 in advance.

  Referring to FIG. 11 again, system voltage upper limit setting unit 500 calculates a withstand voltage margin ΔVH2 from the amplitude of motor current MCRT2 from current sensor 28 by referring to MG2 withstand voltage margin calculation map 504. Further, system voltage upper limit setting unit 500 calculates withstand voltage margin ΔVH1 from the amplitude of motor current MCRT1 from current sensor 24 by referring to MG1 withstand voltage margin calculation map 506. Further, system voltage upper limit setting unit 500 calculates withstand voltage margin ΔVHc from the amplitude of reactor current IL from current sensor 26 by referring to converter withstand voltage margin calculation map 508.

  Then, system voltage upper limit setting unit 500 selects the minimum value among the calculated withstand voltage margins ΔVH2, ΔVH1, and ΔVHc, and sets the selected minimum value as the withstand voltage margin ΔVH for the entire power conversion unit 20. When system voltage upper limit setting unit 500 adds withstand voltage margin ΔVH to default value VHmax0, system voltage upper limit value setting unit 500 outputs the addition result to system voltage command value calculation unit 510 as system voltage upper limit value VHmax.

  System voltage command value calculation unit 510 calculates system voltage VH necessary for realizing the operating point of motor generator MG2 from torque command value TR2 of motor generator MG2 and rotation speed MRN2 (hereinafter also referred to as a command operating point). To do. At this time, system voltage command value calculation unit 510 sets system voltage VH to a voltage value equal to or lower than system voltage upper limit value VHmax.

  Similarly, system voltage command value calculation unit 510 calculates system voltage VH necessary for realizing the operating point of motor generator MG1 from torque command value TR1 of motor generator MG1 and rotation speed MRN1 (command operating point). . System voltage command value calculation unit 510 sets system voltage VH to a voltage value equal to or lower than system voltage upper limit value VHmax.

  System voltage command value calculation unit 510 sets system voltage VH corresponding to motor generator MG2 and the maximum value of system voltage VH corresponding to motor generator MG1 to the target value of system voltage VH. This target value corresponds to voltage command value VHcom to converter 12. Voltage command value VHcom is sent to converter duty ratio converter 53.

  Next, a method for generating the system voltage command value VHcom controlled by the ECU 30 will be described with reference to the drawings. FIGS. 13 and 14 are flowcharts illustrating a method for generating system voltage command value VHcom according to the embodiment of the present invention. The processing shown in FIGS. 13 and 14 is executed by the ECU 30 at a predetermined cycle. 13 and 14 is realized by the ECU 30 shown in FIG. 1 functioning as the control blocks shown in FIGS. 2, 3, and 11.

  Referring to FIG. 13, system voltage upper limit setting unit 500 sets a default value VHmax0 of the system voltage upper limit (step S01). The default value VHmax0 is determined in consideration of a turn-off surge (maximum turn-off surge ΔVHmax), a control variation, a sensor error, and the like when the amplitude of the motor current MCRT2 reaches a maximum value (maximum motor current MCRT2).

  Next, system voltage upper limit setting unit 500 determines whether or not hybrid vehicle 5 is traveling in a high altitude (step S02). The determination in step S02 is performed based on the detected atmospheric pressure value transmitted from the atmospheric pressure sensor that detects the atmospheric pressure around the vehicle. When hybrid vehicle 5 is traveling on a high altitude (when YES is determined in step S02), system voltage upper limit value setting unit 500 is a system voltage upper limit value for high altitude travel (hereinafter also referred to as an upper limit value for high altitude travel). ) VHmax_h is calculated (step S03).

  The processes shown in steps S02 and S03 are intended to suppress deterioration of the insulation performance of the insulator in motor generators MG1 and MG2. That is, in a highland such as a mountainous area, the atmospheric pressure is low and the dielectric constant of the air increases, which causes a problem that the amount of partial discharge into the insulator increases in motor generators MG1 and MG2. When the partial discharge amount increases, the insulating performance of the insulator deteriorates, which may lead to deterioration of the durable life. Therefore, in order to prevent the deterioration of the insulation performance due to such a change in atmospheric pressure, the upper limit value VHmax_h for highland travel is within an allowable range in which the partial discharge amount can suppress the promotion of the insulation performance of the insulator by step S03. Is set to be

  Next, system voltage upper limit setting unit 500 determines whether or not the temperature of the IGBT elements constituting inverters 14 and 22 is equal to or lower than a predetermined threshold (step S04). The determination in step S04 is performed based on the detected temperature value transmitted from the temperature sensor that detects the temperature of the IGBT element. The predetermined threshold is set to about −20 ° C., for example, assuming that the IGBT element is in a very low temperature state. When the temperature of the IGBT element is higher than a predetermined threshold (when NO is determined in step S04), system voltage upper limit setting unit 500 sets highland travel upper limit VHmax_h calculated in step S03 to system voltage upper limit VHmax. Set (step S08).

  On the other hand, when the temperature of the IGBT element is equal to or lower than a predetermined threshold (when YES is determined in step S04), system voltage upper limit setting unit 500 sets a system voltage upper limit for low temperature (hereinafter referred to as low temperature). VHmax_l (also referred to as a time upper limit value) is calculated (step S05).

  The processes shown in steps S04 and S05 are based on the fact that the breakdown voltage of the IGBT element decreases as the element temperature decreases. The turn-off surge generated in the IGBT element increases as the switching speed increases, and increases as the passing current of the IGBT element increases. If the system voltage upper limit value VHmax is constant regardless of the element temperature, the allowable amount of turn-off surge is limited at low temperatures, so the switching speed must be limited, increasing the loss in the inverter and decreasing the efficiency. Will be invited.

  On the other hand, the allowable amount of turn-off surge can be increased by reducing the system voltage upper limit value at a low temperature when the breakdown voltage of the IGBT element is lowered. As a result, the switching speed can be maintained at a level equivalent to that at room temperature even at a low temperature, so that the loss of the inverter can be reduced and the efficiency can be improved.

  Next, system voltage upper limit value setting unit 500 sets Min (VHmax_h, VHmax_l), which is the minimum value of high altitude traveling upper limit value VHmax_h and low temperature upper limit value VHmax_l, as system voltage upper limit value VHmax (step S06). . Thus, system voltage command value calculation unit 510 performs a system operation based on command operation points (torque command value and rotation speed) of motor generators MG1 and MG2 within a range not exceeding system voltage upper limit value VHmax set in step S06. A voltage command value VHcom is calculated (step S07).

  By performing the processing of steps S02 to S08 described above, the system voltage upper limit value VHmax is reduced during high altitude traveling or at extremely low temperatures in consideration of the deterioration in the insulation performance of the motor generator and the decrease in the breakdown voltage of the IGBT element. Is set.

  Furthermore, in the embodiment of the present invention, the protection of the equipment is hindered during low-altitude travel and normal temperature, where restrictions on the system voltage are relaxed compared to during high-altitude travel and extremely low temperatures. The system voltage upper limit value VHmax is raised from the default value within a range that does not exist. As described with reference to FIG. 12, the raising amount is variably set based on the withstand voltage margin according to the amplitudes of the motor current and the reactor current. As a result, the system voltage can be increased while avoiding equipment failure, so that the operating area of the motor generator is expanded as shown in FIG. As a result, the driving force of the hybrid vehicle 5 can be increased.

  Referring to FIG. 14, when system voltage upper limit setting unit 500 acquires the detected value of motor current MCRT2 from current sensor 28 (step S10), MG2 withstand voltage calculation map 504 for MG2 is calculated from the amplitude of motor current MCRT2. With reference to (FIG. 12A), the withstand pressure margin ΔVH2 is calculated (step S11).

  Further, when the system voltage upper limit setting unit 500 obtains the detected value of the motor current MCRT1 from the current sensor 24 (step S12), the MG1 withstand voltage margin calculation map 506 (FIG. 12B) is obtained from the amplitude of the motor current MCRT1. )) Is calculated to calculate the withstand pressure margin ΔVH1 (step S13).

  Further, when system voltage upper limit setting unit 500 obtains the detected value of reactor current IL from current sensor 26 (step S14), converter withstand voltage margin calculation map 508 (FIG. 12 (c)) is obtained from the amplitude of reactor current IL. )) Is calculated to calculate the withstand pressure margin ΔVHc (step S15).

  Next, the system voltage upper limit setting unit 500 uses Min (ΔVH2, ΔVH1, ΔVHc), which is the minimum value of the withstand pressure margin ΔVH2, ΔVH1, ΔVHc calculated in steps S13, S15, S17, respectively, for the entire power conversion unit 20. Is set to the withstand pressure margin ΔVH at (step S16). Then, the system voltage upper limit value VHmax is calculated by adding the withstand voltage margin ΔVH to the default value VHmax0 set in step S01 (step S17). System voltage upper limit setting unit 500 sends calculated system voltage upper limit value VHmax to system voltage command value calculation unit 510 (FIG. 11).

  System voltage command value calculation unit 510 is a system voltage command value based on command operating points (torque command value and rotation speed) of motor generators MG1 and MG2 within a range not exceeding system voltage upper limit value VHmax set in step S17. VHcom is calculated (step S18).

  As described above, according to the embodiment of the present invention, the upper limit value of the system voltage is calculated based on the margin of the amplitude of the current actually applied to the motor generator with respect to the maximum amplitude of the motor current. It is variably set according to the withstand pressure margin. As a result, the upper limit value of the system voltage is increased in the medium rotation speed range and the high rotation speed range where the withstand pressure margin increases, and thus the torque upper limit value of the motor generator increases. As a result, the operable region of the motor generator is expanded, and the driving force of the hybrid vehicle 5 can be increased.

  Furthermore, in the medium speed range and the high speed range, the field voltage is increased to control the required motor voltage so that it does not exceed the system voltage upper limit value. For example, the field weakening current can be reduced by increasing the upper limit value of the system voltage in the rotation speed range. As a result, power loss such as loss (copper loss) generated in the motor generator and loss (on loss) generated in the inverter can be reduced, so that the thermal performance can be improved.

  In addition, since the upper limit value of the system voltage is increased, the operating range of motor generator MG1 is also expanded, so that motor generator MG1 can be driven to a high rotational speed range. In hybrid vehicle 5 according to the present embodiment, when engine ENG is started, motor generator MG1 is driven as an electric motor, and torque of motor generator MG1 is converted to planetary carrier 154 and crankshaft of power split device PSD (FIG. 2). The engine ENG is cranked (rotated) by being transmitted to the engine ENG via 150. Since motor generator MG1 can be used up to a high rotational speed range, the operating range of engine ENG that is restricted by the rotational speed of motor generator MG1 can be expanded.

  In the embodiment of the present invention, the electric system of the hybrid vehicle is representatively exemplified, but the application of the present invention is not limited to such a case. That is, the electric system of the electric vehicle according to the present invention can be commonly applied to electric vehicles equipped with an electric motor for generating vehicle driving force, such as an electric vehicle, a hybrid vehicle, and a fuel cell vehicle.

  Further, the drive system of the electric vehicle is not limited to the configuration shown in FIG. 3 as long as an electric system including a converter for variably controlling the DC voltage of the inverter that drives and controls the AC motor is adopted. It can be set as this structure.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  5 Hybrid vehicle, 10 Battery, 11, 13 Voltage sensor, 12 Converter, 14, 22 Inverter, 15 U-phase arm, 16 V-phase arm, 17 W-phase arm, 20 Power conversion unit, 24, 26, 28 Current sensor, 30 ECU, 40 Converter control unit, 41 Handle, 42 Inverter control unit, 44 Accelerator position sensor, 46 Brake pedal position sensor, 48 Shift position sensor, 50 System voltage command generation unit, 51, 52 Rotation angle sensor, 53 Duty ratio for converter Converter, 54 PWM signal converter for converter, 70L, 70R Front wheel, 80L, 80R Rear wheel, 131, 136 Stator, 132, 137 Rotor, 133, 138 Stator core, 134, 139 Three-phase coil, 150 k Link shaft, 151, 162 Sun gear, 152 Ring gear, 152, 168 Ring gear, 153, 164 Pinion gear, 154, 166 Planetary carrier, 155 Ring gear case, 155 Output member, 160 Output shaft, 170 Counter drive gear, 500 System voltage upper limit setting Unit, 501 system voltage command value calculation unit, 502 storage unit, 504 MG2 withstand voltage margin calculation map, 506 MG1 withstand voltage margin calculation map, 508 converter withstand voltage margin calculation map, 510 system voltage command value calculation Part, C1, C2 capacitor, D1-D8 reverse parallel diode, DEF differential gear, ENG engine, L1 reactor, MG1, MG2 motor generator, PSD power split mechanism, Q1-Q8 IG BT element, RD reduction gear, RG power transmission reduction gear.

Claims (7)

An electric system for an electric vehicle equipped with an electric motor for driving the vehicle,
DC power supply,
A converter that converts a DC voltage output from the DC power source and outputs the voltage;
An inverter that includes a plurality of switching elements, and that converts a DC voltage output from the converter into a drive voltage of the motor by a switching operation of the plurality of switching elements;
A controller for controlling the converter so that an input voltage to the inverter matches a voltage command value;
The controller is
Current detection means for detecting the amplitude of the current applied to the motor;
An upper limit of the inverter input voltage determined in advance corresponding to the maximum value of the amplitude based on the margin of the detection value of the current detection unit with respect to the maximum value of the amplitude of the current applied to the electric motor assumed in advance A margin calculating means for calculating a margin of the inverter input voltage with respect to a default value;
An upper limit correction means for correcting the upper limit value by adding the margin of the inverter input voltage calculated by the margin calculation means to the default value;
And a voltage command value generating means for generating the voltage command value according to the driving force required for the electric motor so that the inverter input voltage does not exceed the corrected upper limit value. system. The default value is a predetermined upper limit of the inverter input voltage by considering a surge voltage generated by a switching operation of the plurality of switching elements when an amplitude of a current applied to the electric motor is maximized. Value,
The said margin calculation means calculates the margin of the said inverter input voltage based on the margin of the said surge voltage with respect to when the amplitude of the electric current applied to the said motor becomes the maximum at least. Electric system for electric vehicles. An electric system for an electric vehicle equipped with a first electric motor and a second electric motor for driving the vehicle,
DC power supply,
A converter that converts the DC voltage output from the DC power supply by the switching operation of the switching elements of the plurality of switching elements and outputs the voltage;
A first inverter that converts a DC voltage output from the converter into a drive voltage of the first electric motor by a switching operation of a plurality of switching elements;
A second inverter that converts a DC voltage output from the converter by a switching operation of a plurality of switching elements into a drive voltage of the second motor;
A control device that controls the converter so that input voltages to the first and second inverters match a voltage command value;
The controller is
First current detection means for detecting the amplitude of the current applied to the first motor;
Second current detection means for detecting the amplitude of the current applied to the second electric motor;
Third current detection means for detecting current flowing through the converter;
Based on the degree of margin of the detected value of the first current detection means with respect to the maximum value of the amplitude of the current applied to the first electric motor, which is assumed in advance, a predetermined value corresponding to the maximum value of the amplitude is predetermined. First margin calculating means for calculating a margin of the inverter input voltage with respect to a default value of the upper limit value of the inverter input voltage;
Based on the margin of the detection value of the second current detection means with respect to the maximum value of the amplitude of the current applied to the second electric motor, which is assumed in advance, the predetermined value is determined in advance corresponding to the maximum value of the amplitude. Second margin calculating means for calculating a margin of the inverter input voltage with respect to a default value of an upper limit value of the inverter input voltage;
An upper limit value of the inverter input voltage determined in advance corresponding to the maximum value of the current based on the margin of the detection value of the third current detection unit with respect to the maximum value of the current flowing through the converter A third margin calculating means for calculating a margin of the inverter input voltage with respect to a default value of
Upper limit correction means for correcting the upper limit value by adding the minimum value of the margins of the inverter input voltage respectively calculated by the first to third margin calculation means to the default value. When,
Voltage command value generating means for generating the voltage command value according to the driving force required for the first and second electric motors so that the inverter input voltage does not exceed the corrected upper limit value. Including an electric system of an electric vehicle. The default value is determined in advance by considering a surge voltage generated by a switching operation of the plurality of switching elements at least when the amplitude of the current applied to the first and second motors is maximized. The upper limit of the inverter input voltage,
The first margin calculating means calculates the margin of the inverter input voltage based on at least the margin of the surge voltage with respect to when the amplitude of the current applied to the first electric motor becomes maximum,
The second margin calculating means calculates the margin of the inverter input voltage based on the margin of the surge voltage with respect to at least when the amplitude of the current applied to the second electric motor becomes maximum,
4. The electric motor according to claim 3, wherein the third margin calculating means calculates the margin of the inverter input voltage based on at least the margin of the surge voltage with respect to when the current flowing through the converter becomes maximum. Vehicle electrical system. The electric vehicle is
An engine that operates by burning fuel,
An output member connected to the second electric motor for outputting power to the drive wheels;
A plurality of rotating elements respectively coupled to the output member, the output shaft of the engine, and the output shaft of the first electric motor are coupled so as to be relatively rotatable with each other, and input / output of electric power and power by the first electric motor 5. The electric vehicle electric system according to claim 3, further comprising: a power split mechanism that outputs at least a part of the output from the engine to the output member. A method for controlling an electric system of an electric vehicle equipped with an electric motor for driving a vehicle,
The electrical system
DC power supply,
A converter that converts a DC voltage output from the DC power source and outputs the voltage;
An inverter that includes a plurality of switching elements, and that converts a DC voltage output from the converter by a switching operation of the plurality of switching elements into a drive voltage of the electric motor;
The control method is:
Detecting the amplitude of the current applied to the motor;
An upper limit of the inverter input voltage determined in advance corresponding to the maximum value of the amplitude based on the margin of the detected value of the amplitude of the current with respect to the maximum value of the amplitude of the current applied to the electric motor assumed in advance Calculating a margin of the inverter input voltage with respect to a default value;
Correcting the upper limit value by adding the calculated margin of the inverter input voltage to the default value;
Generating a voltage command value according to a driving force required for the electric motor so that the inverter input voltage does not exceed the corrected upper limit value;
Controlling the converter so that the inverter input voltage matches the voltage command value. The default value is a predetermined upper limit of the inverter input voltage by considering a surge voltage generated by a switching operation of the plurality of switching elements when an amplitude of a current applied to the electric motor is maximized. Value,
The step of calculating the margin includes calculating the margin of the inverter input voltage based on at least the margin of the surge voltage with respect to when the amplitude of the current applied to the electric motor is maximized. The control method of the electric system of the described electric vehicle.

Images