JP6079437B2 - Electric vehicle control method - Google Patents

Description

  The present invention relates to a control method for controlling an electric vehicle.

  In recent years, electric vehicles such as electric vehicles and hybrid vehicles equipped with AC motors have attracted attention as a power source for vehicles due to social demands for low fuel consumption and low exhaust emissions. In general, in an electric vehicle, a power storage device composed of a secondary battery or the like is connected to an electric motor via a power conversion unit composed of a boost converter, an inverter, or the like, and the direct current power of the power storage device is converted into alternating current power to generate alternating current. Drive the electric motor. Some power supply relays are provided between the power storage device and the power conversion unit to cut off power supply from the power storage device.

  For example, in the hybrid vehicle disclosed in Patent Document 1, when a battery as a power storage device fails, the power relay (system main relay) is cut off, and the power generation amount of the generator (first motor) and the electric motor (second Battery-less travel is performed by balancing the power consumption of the motor. When the power relay is cut off, the gate drive of the inverter that drives the electric motor is prohibited, and the discharge of the power from the battery is made zero to prevent welding of the contact of the power relay.

JP 2001-329884 A

  When the battery breaks down while the electric vehicle is running, the measures that can be taken after the power relay is cut off are not limited to running without using the battery as in Patent Document 1. For example, in an electric vehicle having only an electric motor as a power source, it is conceivable that when the battery fails, the power supply relay is cut off and the vehicle is stopped after inertial traveling or by forced braking.

By the way, the higher the number of revolutions of the motor, the higher the back electromotive voltage generated by the motor. Therefore, when the power relay is shut off in a high speed range where the back electromotive voltage exceeds the system voltage of the inverter, the voltage generated by the motor is not regenerated by the battery but is applied to the smoothing capacitor provided at the input part of the inverter. It will be charged.
As a result, the system voltage input to the inverter may exceed the normal range, leading to an overvoltage abnormality. Furthermore, there is a risk that the switching elements constituting the inverter may be damaged.

  The present invention has been created in view of the above points, and the purpose of the present invention is to reduce the inverter voltage by the back electromotive force generated by the motor when the power relay between the power storage device and the inverter that drives the motor is cut off. An object of the present invention is to provide a method for controlling an electric vehicle that prevents a system voltage from rising and an overvoltage abnormality.

According to the control method of the present invention, an electric motor that constitutes a power source that drives wheels of an electric vehicle, a power storage device that can store DC power, and power generated by the engine power can be supplied to the power storage device or the motor. and Do generator, an inverter for driving the converted electric motor into AC power to DC power of the power storage device, a motor control device, a power storage device abnormality detecting means is applied and a smoothing capacitor, an electric vehicle that includes a power relay This is a control method for cutting off the power supply relay when an abnormality of the power storage device is detected by the power storage device abnormality detection means.
The electric vehicle is a hybrid vehicle having both an electric motor and the engine as a dynamic force source.

The motor control device calculates a dq-axis current command to be output to the inverter, and controls energization of the motor by switching on / off a plurality of switching elements constituting the inverter.
The smoothing capacitor is connected in parallel to the power storage device at the input portion of the inverter. The voltage between the electrodes of the smoothing capacitor is the system voltage input to the inverter.
The power relay is provided between the power storage device and the smoothing capacitor and can cut off power supply from the power storage device to the inverter.

This control method includes the following steps (1) to (4) .
(1) A step of acquiring a counter electromotive voltage generated with the rotation of the electric motor. This “acquire” includes, for example, a case where the counter electromotive voltage is obtained with reference to a map in addition to the case where the counter electromotive voltage is calculated by a calculation formula.
(2) When the acquired back electromotive voltage is higher than the system voltage, the inverter is allowed to drive, and the d-axis current command for exciting the motor among the dq-axis current commands output by the motor control device to the inverter is rotated. Performing a field weakening control to increase the absolute value of the d-axis current command, which is a negative value, so as to cancel the positive field current generated along with the control.
(3) The step of shutting off the power relay.
(4) A step of stopping the power generation by the generator by instructing the engine to stop after cutting off the power relay.

  In the present invention, in a high speed region where the back electromotive voltage exceeds the system voltage of the inverter, the power relay is not interrupted as it is, but the field relay is controlled so as to cancel the field current of the motor, and the power relay is Cut off. Thereby, when the power supply relay is cut off, it is possible to prevent the system voltage of the inverter from rising due to the counter electromotive voltage generated by the electric motor and leading to an overvoltage abnormality. Therefore, breakage of the switching element that constitutes the inverter can be prevented.

  In the stage of executing field weakening control, it is preferable to set the value of the q-axis current command that contributes to the torque of the motor to zero. Thereby, when the power supply relay is cut off, it is possible to prevent the driver from feeling uncomfortable.

In the stage of acquiring the counter electromotive voltage, it is preferable to calculate the counter electromotive voltage based on the rotation speed of the electric motor and a counter electromotive voltage constant that is a proportional constant of the counter electromotive voltage with respect to the rotation speed.
According to common technical knowledge, the motor control device is highly likely to acquire the electrical angle of the motor from the rotation angle sensor, convert it into information on the electrical angular velocity and the number of rotations, and use it for control during normal travel. Therefore, the counter electromotive voltage can be easily obtained using the rotation speed, which is known information.

1 is a system diagram of an electric vehicle that is an electric vehicle according to a first embodiment to which a control method of the present invention is applied. It is a schematic diagram of the electric motor drive circuit of the electric vehicle of 1st Embodiment. It is a figure which shows the electric current which flows into an electric motor drive circuit by the counter electromotive force which generate | occur | produces in an electric motor when a power supply relay is interrupted | blocked. It is a flowchart which shows the power supply relay interruption | blocking process by the control method of the electric vehicle of this invention. (A): It is a figure explaining the field-weakening control of an inverter by a dq axis current coordinate. (B): It is a figure explaining the voltage control of an inverter by a dq axis voltage coordinate. It is a system diagram of a series hybrid vehicle which is an electric vehicle of a second embodiment to which the control method of the present invention is applied. It is a system diagram of a series parallel hybrid vehicle which is an electric vehicle of a third embodiment to which the control method of the present invention is applied. It is a schematic block diagram of the motive power division mechanism in the series parallel hybrid vehicle of 3rd Embodiment.

Hereinafter, a plurality of embodiments of an electric vehicle to which a control method of the present invention is applied will be described with reference to the drawings. About the substantially same structure by embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted. The second or third embodiment corresponds to a mode for carrying out the invention described in the claims.
(First embodiment)
An electric vehicle according to a first embodiment to which a control method of the present invention is applied will be described with reference to FIGS. The electric vehicle according to the first embodiment shown in FIG. 1 is an electric vehicle including only the electric motor 33 as a power source for driving the wheels 14.

The rotation shaft of the electric motor 33 is connected to the reduction gear mechanism 18, and the rotation of the electric motor 33 is transmitted to the propeller shaft 17 with an increase in torque and a decrease in torque. The power of the propeller shaft 17 is transmitted to the wheels 14 via the differential gear mechanism 19 and the axle 13.
The electric motor 33 is a permanent magnet type synchronous three-phase AC electric motor. In a broad concept, the electric motor 33 is a “motor generator” having a function as an electric motor that generates torque and a function as a generator that generates electric power by receiving torque. is there. In the present embodiment, the electric motor 33 functions as a device that performs a power running operation while mainly consuming electric power.

The electric motor 33 is driven by an electric motor drive circuit 311 including a battery 44, a power supply relay 45, and a power conversion unit 201. The electric motor drive circuit 311 will be described with reference to FIGS.
In FIG. 2, the electric motor 33 is exemplified by Y connection, but may be Δ connection.

The battery 44 is a chargeable / dischargeable “power storage device” composed of, for example, a secondary battery such as nickel hydride or lithium ion, or an electric double layer capacitor. The battery 44 is charged in a range where SOC (State Of Charge) is equal to or less than the limit charge amount, and can store DC power supplied to the power conversion unit 201.
Information such as the temperature, current, and voltage of the battery 44 is monitored by the monitoring unit 43. The monitoring unit 43 communicates this information to the battery control unit 42.

The power supply relay 45 is provided between the battery 44 and the power conversion unit 201 and can cut off power supply from the battery 44 to the power conversion unit 201. As shown in FIG. 2, during normal running, the power supply relay 45 is in a closed state, that is, a conductive state.
The power supply relay 45 of this embodiment is composed of a total of three relays, one on the high potential side of the battery 44 and two on the low potential side. One of the relays on the low potential side is provided in a bypass circuit via a current limiting resistor. By defining the switching order of these relays, contact welding due to inrush current can be prevented (see Patent Document 1).

The power conversion unit 201 includes a boost converter 21, a smoothing capacitor 24, and one inverter 23, converts DC power of the battery 44 into AC power, and supplies the AC power to the motor 33.
Boost converter 21 is a DCDC converter, and boosts the voltage of battery 44 to system voltage VH for output. The system voltage VH corresponds to a voltage between the high potential line Lp and the low potential line Lg of the inverter 23 and is also referred to as “inverter input voltage”. The system voltage VH is a reference for the degree of modulation or the voltage utilization rate that is an index of the output voltage of the inverter 23.
The smoothing capacitor 24 is connected to the input part of the inverter 23 in parallel with the battery 44, and suppresses and smoothes the pulsation of the system voltage VH.

Inverter 23 includes switching elements 61-66 that are bridge-connected. Switching elements 61, 62, and 63 are U-phase, V-phase, and W-phase upper arm switching elements, and switching elements 64, 65, and 66 are U-phase, V-phase, and W-phase lower arm switching elements. is there. As the switching elements 61-66, MOSFET (metal oxide semiconductor field effect transistor), IGBT, other bipolar transistors, etc. are used.
The inverter 23 generates the three-phase AC voltages Vu, Vv, and Vw by controlling on / off of the switching elements 61-66 based on the PWM signal output from the electric motor control device 30. The drive of the electric motor 33 is controlled by applying the three-phase AC voltages Vu, Vv, and Vw generated by the inverter 23.

  As described above, the electric motor 33 basically generates torque by the power running operation while consuming the DC power of the battery 44. On the other hand, the induced electromotive force generated in the coil along with the rotation of the electric motor 33 acts on the electric motor drive circuit 311 as “back electromotive force”. The counter electromotive force increases in proportion to the rotation speed of the electric motor 33, and the counter electromotive voltage Vbe may exceed the system voltage VH in a high rotation region. At this time, the current based on the counter electromotive force flows through the inverter 23, the boost converter 21, and the power supply relay 45, and excess power is regenerated in the battery 44.

  Returning to FIG. 1, the description will be continued. The overall control device 40 is constituted by a microcomputer or the like, and includes a CPU, a ROM, an I / O, and a bus line for connecting them. The overall control device 40 comprehensively controls the entire electric vehicle by software processing by executing a program stored in advance by the CPU and hardware processing by a dedicated electronic circuit.

The overall control device 40 receives an accelerator signal from the accelerator sensor, a brake signal from the brake switch, a shift signal from the shift switch, a vehicle speed signal related to the vehicle speed, and the like. In particular, the overall control device 40 of the present embodiment includes a vehicle drive control unit 41 and a battery control unit 42 inside.
The vehicle drive control unit 41 is a central part responsible for vehicle drive control.

The battery control unit 42 estimates the remaining battery level of the battery 44 or detects an abnormality based on the information acquired from the monitoring unit 43. As an indicator of the remaining battery level, the above-described SOC, or dischargeable power Wout / chargeable power Win (see, for example, JP 2010-98882 A) is used. The battery control unit 42 determines that the battery 44 is abnormal when the SOC does not change despite charge / discharge, or when the temperature becomes abnormal, and the vehicle drive control unit 41. To communicate. The battery control unit 42 corresponds to “power storage device abnormality detection unit” described in the claims.
The overall control device 40 comprehensively detects the driving state of the vehicle, and outputs a request to the motor control device 30, the power supply relay 45, etc. according to the driving state of the vehicle.

The electric motor control device 30 controls energization of the electric motor 33 by controlling the switching operation of the boost converter 21 and the inverter 23 of the power conversion unit 201 based on a request from the overall control device 40. During normal travel, the motor control device 30 calculates a dq-axis current command to be output to the inverter 23 according to the torque command from the overall control device 40, and switches the switching elements 61-66 on / off to change the motor. 33 energization is controlled.
The rotation angle sensor 34 is provided near the rotor of the electric motor 33 and detects the electrical angle θ. The electric motor control device 30 performs calculations such as coordinate conversion based on the electrical angle θ detected by the rotation angle sensor 34. Further, the electrical angular velocity ω and the rotational speed Nm of the electric motor 33 are calculated based on the change amount of the electrical angle θ.

  In the electric vehicle having the above configuration, it is assumed that the battery control unit 42 detects an abnormality of the battery 44 based on information from the monitoring unit 43 during traveling. In this case, from the viewpoint of fail-safe, it is desirable that the overall control device 40 requests the power supply relay 45 to be cut off and stops the power supply from the battery 44 to the power conversion unit 201. The problem assumed in this case will be described with reference to FIG.

  In FIG. 3, the power supply relay 45 is in an open state, that is, a cut-off state as compared with FIG. In this case, in the high rotation region of the electric motor 33, when the back electromotive voltage Vbe exceeds the system voltage VH, a current Ibe due to the back electromotive force flows through the free wheel diode of the switching elements 61-66 of the inverter 23. If the current entering the neutral point of the coil of the motor 33 is positive and the current exiting from the neutral point is negative, for example, at the timing when the U-phase current is negative and the V-phase and W-phase are positive, the current Ibe is It flows through a route as shown by a broken line. However, since the power supply relay 45 is cut off, excess electric power is not regenerated in the battery 44 but charged in the smoothing capacitor 24.

If this state continues, the system voltage VH rises and an overvoltage abnormality may occur. Furthermore, the switching elements 61 to 66 constituting the inverter 23 may be damaged.
Therefore, in order to solve such a problem, the control method of the present invention does not cut off the current relay 45 as it is when the abnormality of the battery 44 is detected, but instead cuts off the power relay through the “power relay cut-off process” described below. 45 is cut off.

Next, the flow of power supply relay cutoff processing by the overall control device 40 will be described with reference to the flowchart of FIG. In the description of the flowchart, the symbol “S” means a step.
In S <b> 01, it is determined whether there is a “request to shut off the power supply relay 45” based on the abnormality detection signal communicated from the monitoring unit 43 to the battery control unit 42. When there is a blocking request (S01: YES), the following S02 to S06 are executed.

In S02, the counter electromotive voltage Vbe is calculated by the following equation (1) based on the rotational speed Nm of the motor 33 communicated from the motor control device 30 and the counter electromotive voltage constant Kbe which is a proportional constant stored in advance. .
Vbe [V] = Kbe [V / rpm] × Nm [rpm] (1)
In addition to the above calculation, the counter electromotive voltage Vbe may be obtained by referring to a characteristic map between the rotational speed Nm and the counter electromotive voltage Vbe. Obtaining the counter electromotive voltage Vbe with reference to the map is also included in “acquiring the counter electromotive voltage” recited in the claims.

Since the motor control device 30 acquires the electrical angle θ of the motor 33 from the rotation angle sensor 34 and converts it into information such as the electrical angular velocity ω and the rotation speed Nm, it is used for control during normal travel, and thus is known information. The counter electromotive voltage Vbe can be easily obtained using the rotational speed Nm.
However, since the rotational speed Nm of the electric motor 33 is correlated with the rotational speed of the propeller shaft 17 and the axle 13 through the gear ratio of the reduction gear mechanism 18, in another embodiment, instead of the rotational speed Nm of the electric motor 33, the propeller The counter electromotive voltage Vbe may be acquired based on the rotational speed of the shaft 17 or the axle 13 or the vehicle speed.

In subsequent S03, the obtained back electromotive voltage Vbe is compared with the system voltage VH. When the back electromotive voltage Vbe is equal to or lower than the system voltage VH (S03: NO), it is determined that the system voltage VH is not likely to increase due to the back electromotive voltage Vbe even if the power supply relay 45 is shut off. Therefore, the process proceeds to S06 and commands to shut off the power supply relay 45.
On the other hand, when the back electromotive voltage Vbe exceeds the system voltage VH (S03: YES), when the power supply relay 45 is cut off as it is, the system voltage VH rises due to the back electromotive voltage Vbe, and the switching elements 61-66 of the inverter 23 There is a risk of damage. In order to avoid this, the process proceeds to S04, and the motor control device 30 is allowed to drive the inverter 23.

  In S05, the motor controller 30 is requested to control the inverter 23 to “weak field and zero torque” in order to cancel the influence of the counter electromotive voltage Vbe and not to give the driver a sense of incongruity. To do. Details of the “weak field and zero torque” control will be described later.

Thus, the inverter 23 is subjected to field-weakening control to cancel the influence of the back electromotive voltage Vbe and prepare a situation in which the system voltage VH does not increase when the power supply relay 45 is cut off. Command off. This completes the power supply relay cutoff process.
Thereafter, depending on the situation, the driver can drive the vehicle within a range where the inertia torque can be used, or can operate the brake to forcibly brake the vehicle.

Next, the “field weakening and zero torque” control in S05 will be described with reference to FIG.
The inverter 23 is controlled by a current feedback control system that controls the dq-axis voltage command so that the deviation between the command value and the detected value for the dq-axis current supplied to the electric motor 33 is zero.
In general, the dq axis voltage equation of an electric motor is expressed by equations (2) and (3).
Vd = (R + PLd) × Id−ω × Lq × Iq (2)
Vq = ω × Ld × Id + (R + PLq) × Iq + ω × ψ (3)
Further, the torque T of the electric motor is expressed by Expression (4).
T = pm × {Iq × ψ + (Ld−Lq) × Id × Iq} (4)

The symbols are as follows.
Vd, Vq: d-axis voltage, q-axis voltage Id, Iq: d-axis current, q-axis current R: armature resistance P: time derivative (= d / dt)
Ld, Lq: d-axis self-inductance, q-axis self-inductance ω: electrical angular velocity ψ: armature linkage flux of permanent magnet pm: number of pole pairs of motor

  By the way, if the electric motor 33 outputs a torque unintended by the driver in a situation where the power supply relay 45 is to be cut off because the battery 44 has failed during traveling, the driver may feel uncomfortable. Therefore, the overall control device 40 requests the motor control device 30 to perform “zero torque control” in which the torque of the motor 33 is zero. Here, the torque being zero is not limited to strict 0 [Nm], but is, for example, a minute value that is substantially equal to a little that is less than the total mechanical resistance of the reduction gear mechanism 18, the wheel 14, or the like. Including a wide range of torque.

From equation (4), if the q-axis current command Iq is zero (Iq≈0), the torque T of the electric motor 33 becomes zero. Here, the current “zero” is not limited to strict 0 [A] but includes a value in a range substantially equivalent to 0 [A], as in the above torque.
Further, the d-axis current command Id when the electric power is consumed by excitation in the power running operation of the electric motor 33 becomes a negative value. Therefore, as indicated by the dq current coordinates in FIG. 5A, the current command vector I for zero torque control is “Id <0, Iq≈0”.

Next, assuming that “Iq≈0” in Expressions (2) and (3), Expressions (2 ′) and (3 ′) are obtained for the dq-axis voltage commands Vd and Vq.
Vd = (R + PLd) × Id (2 ′)
Vq = ω × Ld × Id + ω × ψ (3 ′)
The second term “ω × ψ” of the q-axis voltage command Vq is a voltage caused by the counter electromotive force and increases in proportion to the rotational speed Nm of the electric motor 33.
Moreover, the magnitude | size of the voltage command vector V is represented by Formula (5).
V = √ (Vd ² + Vq ² ) (5)

As shown in the dq voltage coordinate of FIG. 5B, the second term “ω × ψ” of the q-axis voltage command Vq is shown in the positive direction on the Vq axis. On the other hand, the first term “ω × Ld × Id” is indicated in the negative direction on the Vq axis because the d-axis current command Id is a negative value. Therefore, a value obtained by subtracting the absolute value of the first term from the value of the second term becomes the q-axis voltage command Vq indicated by the block arrow.
Here, so-called “weakening field control” is control for increasing the absolute value of the d-axis current command Id, which is a negative value, so as to cancel the positive field current (d-axis current) generated by the rotation of the electric motor 33. Say. By increasing the absolute value of the negative d-axis current command Id, the first term “ω × Ld × Id” increases in the negative direction, and the q-axis voltage command Vq indicated by the block arrow decreases. That is, the armature magnetic flux ψ is canceled by the magnetic flux (Ld × Id) generated by the d-axis inductance Ld. By doing so, the voltage command vector V by Formula (5) is made small, and the voltage which the inverter 23 produces | generates is made into the system voltage VH or less, ie, the inner side of a broken line circle.

In the present embodiment, the field weakening control is executed as described above in the power supply relay cut-off process, thereby preventing the system voltage VH from increasing when the power supply relay 45 is cut off and leading to an overvoltage abnormality. Therefore, breakage of the switching elements 61-66 constituting the inverter 23 can be prevented.
Further, by executing zero torque control in which the q-axis current command that contributes to the torque of the electric motor 33 is performed together with the field weakening control, it is possible to prevent the driver from feeling uncomfortable when the power supply relay 45 is cut off. .

(Second Embodiment)
An electric vehicle according to a second embodiment to which the control method of the present invention is applied will be described with reference to FIG. The electric vehicle according to the second embodiment is a so-called series hybrid vehicle.
The series hybrid vehicle includes an engine 11, a generator 32, and an electric motor 33 as power sources, and the electric motor 33 drives the wheels 14 using electric power generated by the generator 32 with the power of the engine 11.

The engine 11 is, for example, a 4-cylinder gasoline engine, and the output torque of the engine 11 is transmitted to the rotating shaft of the generator 32 via the crankshaft 15. The engine control device 10 acquires information such as the crank angle of the crankshaft 15 and the engine rotation speed based on a crank angle signal input from a crank angle sensor (not shown), and controls the operation of the engine 11.
Further, the overall control device 40 transmits and receives signals between the engine control device 10 and the electric motor control device 30 to adjust driving of the engine 11, the generator 32 and the electric motor 33.

The generator 32 and the electric motor 33 are both “motor generators”. In the second embodiment and the next third embodiment, a motor generator mainly used as a generator in a hybrid vehicle is referred to as a “generator 32”, and a motor generator mainly used as an electric motor is referred to as an “motor 33”.
In the main operation of the present embodiment, the generator 32 generates power by the power of the engine 11, and the electric motor 33 drives the wheels 14 via the axle 13 while consuming electric power by a power running operation.

In the electric motor drive circuit 312 of the second embodiment, the power conversion unit 202 includes the boost converter 21, the smoothing capacitor 24 (not shown in FIG. 6), the first inverter 22 that drives the generator 32, and the electric motor 33. A second inverter 23 to be driven is provided. The second inverter 23 is substantially the same as the inverter 23 in the first embodiment.
The generator 32 is connected to the battery 44 via the first inverter 22, the boost converter 21, and the power supply relay 45. The electric motor 33 is connected to the battery 44 via the second inverter 23, the boost converter 21, and the power supply relay 45.

That is, in the motor drive circuit 312, the first inverter 22 and the generator 32, the second inverter 23, and the motor 33 are connected in parallel to the motor drive circuit 311 of FIG. It is the structure which was made.
Driving of the generator 32 and the motor 33 is controlled by the motor control device 30 controlling the first inverter 22 and the second inverter 23. That is, the term “motor” in the term “motor controller” is used to mean “motor generator”.

  In the second embodiment, the engine 11 rotates under relatively stable operating conditions only for generating power from the generator 32. The generator 32 basically charges the battery 44 with the generated power, and the electric motor 33 is driven by the power of the battery 44. However, it is theoretically possible to drive the electric motor 33 using a part of the electric power generated by the generator 32 as it is.

When the abnormality of the battery 44 is detected by the battery control unit 42, the overall control device 40 executes a power supply relay cutoff process as in the first embodiment. That is, when the back electromotive voltage Vbe of the electric motor 33 is larger than the system voltage VH of the second inverter 23, the electric motor control device 30 is requested to perform field weakening control, preferably zero torque control, on the second inverter 23. The relay 45 is cut off.
Therefore, also in the electric vehicle of the second embodiment, the same effect as that of the first embodiment can be obtained by the control method of the present invention.

Note that after the power supply relay 45 is shut off, the overall control device 40 may execute two types of processing.
When stopping the vehicle, the engine control device 10 is instructed to stop the engine 11 and the power generation by the generator 32 is stopped. Thereby, the electric power supply to the electric motor 33 is interrupted, and the vehicle can be stopped after inertial traveling or by forced braking as in the first embodiment.
On the other hand, there is a possibility of running without using the power of the battery 44 by balancing the power generation amount of the generator 32 and the power consumption amount of the electric motor 33 under predetermined operating conditions.

(Third embodiment)
An electric vehicle according to a third embodiment to which the control method of the present invention is applied will be described with reference to FIGS. The electric vehicle of the third embodiment shown in FIG. 7 is a so-called series parallel hybrid vehicle.
In the series-parallel hybrid vehicle, the power of the engine 11 is divided by the power split mechanism 16, the wheels 14 are directly driven by one power, and the generator 32 is caused to generate power by the other power. The electric motor 33 drives the wheel 14 using electric power generated by the generator 32 and charged in the battery 44 or directly using electric power generated by the generator 32. It is characterized in that it is possible to switch between traveling by only the engine 11, traveling by only the electric motor 33, and traveling by both the engine 11 and the electric motor 33 depending on the traveling condition of the vehicle.

  In the system of the series parallel hybrid vehicle, the power split mechanism 16 is added as a main component to the series hybrid vehicle of the second embodiment, and other configurations are basically the same as those of the second embodiment. The power split mechanism 16 splits the power of the crankshaft 15 of the engine 11 into two systems.

  As shown in FIG. 8, the power split mechanism 16 includes a planetary gear mechanism including a sun gear 16a, a pinion gear (planetary carrier) 16b, a ring gear 16c, and the like. A crankshaft 15 of the engine 11 is connected to the pinion gear 16b via a carrier, and a rotating shaft of a generator 32 is connected to the sun gear 16a. The power of the ring gear 16c is transmitted to the propeller shaft 17, and the power of the propeller shaft 17 is transmitted to the wheels 14 via the differential gear mechanism 19 and the axle 13 or the like.

  The rotating shaft of the electric motor 33 is connected to the propeller shaft 17 via the reduction gear mechanism 18. The reduction gear mechanism 18 includes a planetary gear mechanism that includes a sun gear 18a, a pinion gear 18b, a ring gear 18c, and the like. The sun gear 18 a is connected to the rotating shaft of the electric motor 33, and the power of the ring gear 18 c is transmitted to the propeller shaft 17. The ring gear 16 c of the power split mechanism 16 is connected to the ring gear 18 c of the reduction gear mechanism 18.

  In the power split mechanism 16, when the rotational speed of two of the three axes of the sun gear 16a, the pinion gear 16b, and the ring gear 16c is determined, the rotational speed of the remaining one axis is determined. That is, the rotational speed of the generator 32, the engine 11 and the electric motor 33, and the torque determined by the rotational speed and the gear ratio of the reduction gear mechanism 18 are correlated with each other. Therefore, the overall control device 40 that controls the entire system comprehensively determines how it is optimal to drive the generator 32, the engine 11, and the electric motor 33 according to the running conditions of the vehicle.

When the abnormality of the battery 44 is detected by the battery control unit 42, the overall control device 40 executes a power relay cutoff process as in the above embodiment. That is, when the back electromotive voltage Vbe of the electric motor 33 is larger than the system voltage VH of the second inverter 23, the electric motor control device 30 is requested to perform field weakening control, preferably zero torque control, on the second inverter 23. The relay 45 is cut off.
Therefore, also in the electric vehicle of the third embodiment, the same effects as those of the first and second embodiments can be obtained by the control method of the present invention.

  In addition, the processing executed by the overall control device 40 after the power supply relay 45 is cut off may have two possibilities as in the second embodiment. Among them, “travel without using the power of the battery 44 performed by balancing the power generation amount of the generator 32 and the power consumption amount of the electric motor 33” corresponds to the conventional technique described in Patent Document 1.

(Other embodiments)
(A) In the power relay disconnection process of the above embodiment, the driver feels uncomfortable by executing zero torque control in addition to field weakening control. However, zero torque control is not an essential requirement in the power supply relay cut-off processing of the present invention, and at least field weakening control may be performed.

  (A) In the flowchart of FIG. 4, steps S02 and S03 are executed regardless of the rotational speed Nm of the electric motor 33. However, for example, the rotational speed Nm is determined before S02, and in a low rotational speed region where the possibility that the back electromotive voltage Vbe does not exceed the system voltage VH is apparent, the process proceeds directly to S06, and only in the region above the predetermined rotational speed. , S02 to S05 may be executed.

(C) The DCDC converter of the power conversion unit is not limited to the step-up converter but may be a step-down converter. Further, the battery voltage may be used as it is as the system voltage VH without providing a DCDC converter.
(D) Although the electric motor of the above embodiment is a permanent magnet type synchronous three-phase AC electric motor, other than this, an induction motor or other synchronous electric motor may be used.

(E) In FIG. 1 of the first embodiment, the overall control device 40 and the motor control device 30 are shown as separate blocks from the point of commonality with the second and third embodiments. However, if the first embodiment is considered independently, the motor control device 30 may be included in the overall control device 40.
On the other hand, in the second and third embodiments, the overall control device 40 that comprehensively controls the engine control device 10 and the motor control device 30 may be referred to as a “hybrid vehicle control device”.

(F) The engines of the second and third embodiments are not limited to gasoline engines, but may be diesel engines, vaporized fuel engines, or the like.
(G) The power split mechanism of the third embodiment is constituted by a planetary gear mechanism, and the driving force is mechanically transmitted. In addition, an electromagnetic clutch or a fluid coupling may be used as the power split mechanism.
As mentioned above, this invention is not limited to the said embodiment at all, In the range which does not deviate from the meaning of invention, it can implement with a various form.

23... Inverter, second inverter,
24: Smoothing capacitor,
30 ... Electric motor control device,
33 ... Electric motor,
42 ... Battery control unit (electric storage device abnormality detection means),
44 ... battery (power storage device),
45: Power relay 61-66: Switching element.

Claims (3)

An electric motor (33) constituting a power source for driving the wheels (14) of the electric vehicle;
A power storage device (44) capable of storing DC power;
A generator (32) capable of generating electric power by the power of the engine (11) and supplying the generated electric power to the power storage device or the electric motor;
An inverter (23) for converting the DC power of the power storage device into AC power and driving the motor;
A motor control device (30) for calculating a dq-axis current command to be output to the inverter, and switching on / off of a plurality of switching elements (61-66) constituting the inverter to control energization of the motor;
A smoothing capacitor (24) connected in parallel to the power storage device at the input of the inverter and having a voltage between the electrodes as a system voltage (VH) input to the inverter;
Power storage device abnormality detection means (42) for detecting abnormality of the power storage device;
A power supply relay (45) provided between the power storage device and the smoothing capacitor and capable of interrupting power supply from the power storage device to the inverter;
A control method for cutting off the power supply relay when an abnormality of the power storage device is detected by the power storage device abnormality detection means,
Obtaining a back electromotive voltage (Vbe) generated with rotation of the electric motor (S02);
When the acquired back electromotive voltage is greater than the system voltage, the d-axis current command for permitting driving of the inverter and for exciting the motor among the dq-axis current commands output to the inverter by the motor control device is described above. Performing field weakening control to increase the absolute value of the d-axis current command, which is a negative value, so as to cancel the positive field current generated with the rotation of the motor (S03-S05);
Cutting off the power relay (S06);
Commanding the engine to stop after shutting off the power relay, and stopping power generation by the generator;
The control method of the electric vehicle characterized by including. In performing the field weakening control,
The method for controlling an electric vehicle according to claim 1, wherein a value of a q-axis current command that contributes to the torque of the electric motor is set to zero. In obtaining the counter electromotive voltage,
3. The counter electromotive voltage is calculated based on a rotation speed (Nm) of the electric motor and a counter electromotive voltage constant (Kbe) that is a proportional constant of the counter electromotive voltage with respect to the rotation speed. The control method of the electric vehicle as described.

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