JP2008183961A - Four-wheel drive control unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a four-wheel drive control unit which has a function to suppress voltage rise quickly since when an inverter for motor drive stops the operation, voltage of a direct current link section of a rectifier output rises excessively, and there is a problem to damage a peripheral circuit part in a hybrid four-wheel drive car which has a main driving wheel driven by an engine and a sub driving wheel driven by a motor. <P>SOLUTION: This control unit is composed to monitor the voltage of the direct current link section which starts to rise at the same time when the inverter stops the operation, reverse the direction of the current to be applied to the field winding wire of an alternator when reached the predefined voltage, and intercept this current after flowing a predetermined period. Therefore, voltage rise after stopping of inverter operation is suppressed quickly, and use parts of small power can be used. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a safety measure technique when an overvoltage occurs in a control system of a field winding type motor in a four-wheel drive hybrid vehicle.

  An electric vehicle, particularly a four-wheel drive hybrid vehicle having both a gasoline engine (hereinafter referred to as an engine) drive and an electric motor (hereinafter referred to as a motor) drive, has a drive system for driving the vehicle, and motor drive power. The power system for generating and supplying power and the control system for controlling power supply and motor drive. That is, the drive system is, for example, an engine that drives the front wheels that are the main drive wheels, an AC generator that is simultaneously coupled to the engine, and a rear wheel that is driven by the AC power obtained by the AC generator. And a motor for driving the motor.

  The power system includes an AC generator that generates electric power by rotating the engine, a rectifier that temporarily converts the AC power that is output from the AC generator into DC power, and the DC power that is the rectified output is again converted into AC power. And a DC link unit that couples the rectifier and the inverter. The inverter converts the rectifier to drive the motor and the capacitor for removing the ripple component contained in the rectifier output.

  Further, the control system detects the slippage of the motor controller unit that controls the generator field current, the motor field current, and the inverter switching by PWM, etc. And a 4WD controller unit that calculates a driving torque required for the driving wheel and outputs an auxiliary driving wheel torque command to the motor controller while generating an electric power required for the motor by the AC generator. Also, if the inverter stops operating due to a failure during operation, the voltage of the DC link section temporarily rises due to the electric power from the AC generator and the magnetic energy stored in the armature winding of the AC generator. However, when the AC generator is rotating at a high speed, the breakdown voltage of the power element and the capacitor of the inverter may be exceeded. For this reason, in the conventional apparatus, the field stop circuit for monitoring the voltage of the DC link unit and stopping the voltage generation of the AC generator when the voltage exceeds a predetermined value, and the predetermined value The voltage suppression element which absorbs the above excessive voltage was provided in the DC link part.

  In the conventional configuration as described above, in order to avoid damage to peripheral circuit components due to the voltage rise of the DC link portion that occurs when the operation of the inverter stops during operation, The stop circuit is operated to cut off the field current. This rise in voltage is due to the magnetic energy remaining in the magnetic circuit of the AC generator, so that the power generation does not stop immediately after the field current is cut off, and the operation of the inverter that is the load stops. This is due to the accumulation of electrical energy that is generated transiently.

Further, when the operation of the inverter is stopped during operation as described above, the voltage of the DC link unit rises. As a result, the voltage suppression element inserted in the DC link unit is turned ON, and a current corresponding to the voltage increase flows. There is a problem that current flows through the armature of the AC generator, the field is strengthened by the armature reaction caused by the armature current, a larger current flows out from the armature, and the voltage suppression element is overheated.
JP-A-2005-318753

  As described above, when a conventionally known four-wheel drive control device is in operation, for example, when the inverter stops its operation due to a failure or the like, peripheral electrons due to a temporary voltage increase in the DC link immediately after the operation stops. There were problems such as damage to parts or overheating of the voltage suppression element due to a transient large current. An object of the present invention is to provide a highly reliable four-wheel drive control device by forming a fail-safe circuit for solving these problems.

  In order to achieve the above object, in the present invention, the voltage of the DC link unit is monitored, and the voltage detection circuit detects that the inverter has stopped operating due to a failure or the like and the voltage of the DC link unit has exceeded a predetermined value. When detected, the polarity of the current supplied to the field winding of the AC generator is reversed by the field current reversing means, so that the reverse current is supplied only for a predetermined time.

  According to the present invention, when the inverter in operation is stopped, the increase in the DC voltage of the DC link part that occurs transiently due to the influence of the residual magnetic field in the AC generator, etc. is suppressed, and the accuracy of preventing damage to electronic components due to overvoltage is improved. This makes it possible to realize a highly reliable four-wheel drive control device.

  FIG. 1 shows the configuration of a four-wheel drive control device according to the present invention. FIG. 2 shows a configuration example of the field current reversing circuit 14 for reversing the direction of the current supplied to the AC generator field winding 6 according to the present invention. FIG. 3 shows a four-wheel drive control device according to the present invention in which the DC link unit 11 is brought into a no-load state due to the stop of the operation of the inverter 4 due to the failure of the inverter 4 or the failure of the motor controller 9 controlling the operation of the inverter 4. As a result, the DC voltage in the DC link unit 11 rises, and the fail-safe operation for the damage to the circuit components due to this increases. FIG. 4 is an operation diagram for explaining a movement state of the operating point in the DC link unit 11 which is a connecting part between the rectifier 3 and the inverter 4 when performing the above fail-safe operation according to the present invention.

  In FIG. 1, the AC generator 2 is driven with a torque provided by an engine 1 that drives main drive wheels 16. The three-phase AC power thus obtained is rectified to DC power by the rectifier 3 and supplied to the inverter 4 via the DC link unit 11. The inverter 4 converts this DC power into a three-phase AC by a switching element and supplies it to the motor 5. In FIG. 1, only one phase of three-phase alternating current is described, and the remaining two phases are the same circuit configuration and are not described. The AC generator 2 and the motor 5 have field windings 6 and 7, respectively. In the AC generator 2, the generated voltage of the AC generator 2 is controlled by controlling the field current supplied to the field winding 6. The motor 5 generates torque by the field current supplied to the field winding 7 and the armature current supplied from the inverter 4. The supply and control of these field currents are performed via choppers built in respective field winding drive circuits (not shown).

  The torque of the motor 5 is controlled by the 4WD controller 8 and the motor controller 9. In the 4WD controller 8, the torque value generated by the motor 5 is determined from the rotation speed (wheel speed) of each wheel in the main drive wheel 16 and the sub drive wheel 17 and the accelerator opening, and is transmitted to the motor controller 9 as a torque command value. . The motor controller 9 outputs the output voltage of the AC generator 2 necessary for generating the required torque from the rotational speed of the motor 5 and the torque command value, the field current flowing through the field winding 7 of the motor 5 and The armature voltage and phase of the motor 5 are obtained, the phase from the magnetic pole position is determined from the detected value of the rotational position sensor of the motor 5 (not shown), and the power MOSFETs built in the inverter 4 are determined using the values obtained by these values. The inverter 4 is commanded to turn on / off switching to generate a three-phase alternating current. The field current of the AC generator 2 and the motor 5 is controlled by a chopper built in a field winding drive circuit (not shown), and is attached to the driven wheel 17 via the speed reducer and the clutch 10 with the torque generated by the motor 5. Drive the rear wheels.

  In FIG. 1, for example, when the operation of the inverter 4 is stopped due to a failure of the switching element of the inverter 4 or the motor controller 9, the voltage in the DC link unit 11 increases as will be described later, and the voltage of the capacitor 18 or the switching element of the inverter 4 is increased. May exceed the breakdown voltage. In order to prevent damage to circuit components due to this, the voltage of the DC link unit 11 is monitored by the voltage sensor 12, and a DC voltage detection circuit determines whether or not this voltage value exceeds a predetermined voltage (for example, the breakdown voltage of these components). 13 to detect.

  Here, when it is detected that the DC voltage exceeds the predetermined voltage and an overvoltage state is detected, the field current of the AC generator 2 is controlled via the motor controller 9 at that time, and the current direction is also controlled. Reverse the direction. The operation of reversing the current direction is performed by the field current reversing circuit 14. These processes are performed by the motor controller 9 using an overvoltage generation signal from the DC voltage detection circuit 13 as a trigger.

  As described above, in the present invention, the AC generator 2 driven by the engine 1 that drives the main drive wheel 16, the rectifier 3 that converts AC power from the AC generator 2 into DC power, and the DC Inverter 4 that converts electric power again into AC power, motor 5 that drives driven wheels 17 by this converted second AC power, and a field for controlling the operation of AC generator 2 and motor 5 The present invention aims to improve safety measures of a hybrid four-wheel drive vehicle having a hybrid type composed of a winding and a control device having a motor controller 9 and a 4WD controller. For this reason, the DC voltage detecting means 13 for measuring the voltage of the DC link unit 11 and the DC voltage rise to the DC link unit 11 connecting the rectifier 3 and the inverter 4 to the hybrid vehicle. Field current reversing means for reversing the direction of the current supplied to the field winding 6 of the AC generator 2 when the DC voltage detecting means 13 detects that a predetermined voltage value has been reached. It is configured.

  FIG. 2 shows a specific configuration example of the field current reversing circuit 14 for switching the direction of the current flowing in the field winding 6 of the AC generator 2 according to the present invention. A circuit that reverses the direction of the field current flowing through the wire 6 has a so-called H-bridge circuit configuration.

FIG. 3 is a diagram showing changes in voltage and current on the horizontal axis for explaining the fail-safe operation according to the present invention when the operation of the inverter 4 is stopped due to a failure, for example. When the inverter 4 stops operating as shown in FIG. 3 (a), the DC link unit 11 enters a no-load state, and the current flowing from the AC generator 2 via the DC link unit 11 decreases rapidly [Fig. 3 (b) t ₁ ], the voltage drop due to the internal impedance of the AC generator 2 is reduced, and the voltage at the DC link section 11 starts to increase by this amount [t ₁ → t _{2 in} FIG. ].

  Further, one of the field magnetic fluxes generated in the AC generator 2 by the field winding 6 of the AC generator 2 is used as a chopper with a built-in motor controller for controlling the field current. Electric power generation continues due to the continuous freewheeling of the diode and the magnetic flux in the magnetic circuit remaining transiently even when the field current is interrupted [FIG. 3 (e)]. For this reason, the generated voltage in the AC generator 2 continues to rise. Further, the induced voltage in the motor 5 increases when the operation of the inverter 4 is stopped when the motor 5 is operated by performing field weakening on the stator.

Hereinafter, the case where the DC voltage of the DC link unit 11 by the AC generator 2 increases will be described. During the operation of the four-wheel drive control device according to the present invention, the operation of the inverter 4 is stopped due to a failure or the like, whereby the voltage sensor 12 detects the DC voltage rise of the DC link unit 11, and the detected DC voltage is the voltage. When a voltage value (overvoltage detection voltage) preset in the detection circuit 13 is exceeded (FIG. 3 (a) t ₂ ), the field current reversal that is part of the drive circuit for the field winding 6 of the AC generator 2 is reversed. The circuit 14 reverses the direction of the field current flowing in the field coil 6 of the AC generator 2 [FIG. 3 (c) t ₂ ]. For example, by turning MOSFETs Q1 and Q4 in the conducting state and MOSFETs Q2 and Q3 in the cut-off state in the circuit of FIG. It can be reversed to the field current I2.

Here, when the field current is reversed [FIG. 3 (d) t ₂ ], the inductance of the field winding 6 increases the voltage of the field winding 6 and the flywheel current flows and instantaneously. The current is never reversed. However, as described above, when a voltage is applied in the reverse direction, the field current and the resulting field magnetic flux rapidly decrease [FIG. 3 (d)]. However, during this time, the DC voltage continues to rise [FIG. 3 (a) t ₁ → t ₃ ], and when this rise reaches the starting voltage of the suppression operation of the voltage suppression element 15 [FIG. 3 (a) t ₃ ]. The voltage suppression element 15 is in a conductive state and further voltage increase is suppressed. In this case, the operation start voltage of the voltage suppression element 15 may be set to a value lower than the lowest withstand voltage of the circuit elements in the peripheral circuit including the inverter 4 serving as the load of the DC link unit 11.

  As a result, a loop is formed in which a current flows when the voltage of the DC link portion 11 becomes an overvoltage, so that the current from the AC generator 2 flows again through this loop, and this current causes the armature reaction of the AC generator 2. Thus, the field current increases, and the generation of electric power is continued thereafter. On the other hand, the residual field magnetic flux is suppressed by the reverse field voltage applied to the field winding 6 (FIG. 3C), and the power generation accompanying the operation of the voltage suppression element 15 is rapidly suppressed. Thus, conventionally, when the field magnetic flux remains, a large amount of power generated from the AC generator 2 has to be absorbed by the voltage suppression element 15, but the voltage suppression is achieved by rapidly reducing the generated power. The capacitance of the element 15 can be greatly reduced. As a result, the drive system of the field winding 6 can be controlled with relatively small electric power, so that the circuit for preventing the switching power element used in the inverter 4 from being destroyed can be miniaturized.

FIG. 4 shows the movement of the operating point in the DC link unit 11 of the output voltage and current of the AC generator 2. Even if the operation of the inverter 4 is stopped due to a failure or the like, the field magnetic flux does not change suddenly. Therefore, the DC current temporarily decreases at the operating point P before the inverter stops, and the operating point moves to the point Q. Then the voltage rises. When the voltage further rises and the voltage of the DC link unit 11 becomes overvoltage as described above, the voltage suppression element 15 operates and a loop through which the output current of the AC generator 2 flows is formed. The current from the generator 2 flows again, and due to this current, the field current increases due to the armature reaction of the AC generator 2 and moves to the point R. Thus, since the field current, that is, the field magnetic flux is enhanced by the armature reaction of the AC generator 2, the voltage of the DC link unit 11 is clamped to the level of the overvoltage detection voltage.
By rapidly reducing the field magnetic flux in the circuit according to the present invention, the voltage and current of the generator can be rapidly reduced. However, after the current flowing through the field winding 6 is further reversed, If it continues to flow, power generation will continue with the magnetic flux in the opposite direction increasing. In order to avoid this, it is necessary to stop the current flowing through the field winding 6 after a time sufficient to suppress the initial DC current has elapsed [FIG. 3 (c) t ₄ ]. A circuit for performing this operation is built in the motor controller 9, for example, or the decrease in the voltage value of the DC link unit 11 is monitored, and when this voltage value reaches a preset voltage value, the field winding A configuration in which the current flowing to 6 is stopped may be used. In the above description, the field circuit using the MOSFET has been described. However, in order to reverse the voltage applied to the field winding 6, for example, the same operation can be realized by using a relay or a combination circuit of a relay and a transistor. be able to.

The block diagram of the four-wheel drive control apparatus which concerns on this invention. The reverse circuit diagram of a generator field winding current. The time change figure of the electric current and voltage of each part of the device by the present invention. The operation | movement figure explaining the operating point movement in a DC link part.

Explanation of symbols

1: Engine 2: AC generator 3: Rectifier 4: Inverter 5: Motor 6: AC generator field winding 7: Motor field winding 8: 4WD controller 9: Motor controller 10: Reducer and clutch 11: DC Ring unit 12: Voltage sensor 13: DC voltage detection circuit 14: Field current reverse circuit 15: Voltage suppression element 16: Main drive wheel 17: Sub drive wheel

Claims (6)

An AC generator having two main drive wheels and two slave drive wheels, driven by an engine that drives the main drive wheels, and a rectifier that converts first AC power from the AC generator into DC power An inverter that converts the DC power into second AC power, a motor that drives the driven wheels with the converted second AC power, and a control device that controls the operation of the AC generator and the motor In a four-wheel drive control device having
DC voltage detecting means for measuring the voltage of the DC link unit provided in the DC link unit connecting the rectifier and the inverter;
When the detected DC voltage rises and reaches the predetermined voltage value by the DC voltage detecting means, the direction of supplying the supply current to the field winding of the AC generator is reversed, and the reverse direction A four-wheel drive control device comprising field current reversing means for energizing as a field current. In the four-wheel drive control device according to claim 1,
The field current reversing means detects the direction of the field current of the AC generator when the detected DC voltage rises and reaches the first predetermined voltage value by the DC voltage detecting means. The field current in the reverse direction is supplied to the field winding of the AC generator for a predetermined time from the time when the direction of the field current is reversed, and then the field current in the reverse direction is supplied. A four-wheel drive control device comprising control means for stopping. In the four-wheel drive control device according to claim 1,
The field current reversing means detects the direction of the field current of the AC generator when the detected DC voltage rises and reaches the first predetermined voltage value by the DC voltage detecting means. Reverse
4. The four-wheel drive control device according to claim 1, wherein when the DC voltage detecting means detects that the voltage of the DC link section has reached a second predetermined voltage value, the reverse field current is cut off. In the four-wheel drive control device according to claim 1 or 2,
A voltage suppression element is provided in a DC link unit provided between the rectifier and the inverter, and a third voltage value at which the voltage suppression element starts operating is a load circuit of the DC link unit. A four-wheel drive control device characterized by having a lower voltage value than a minimum voltage value of a circuit element in a peripheral circuit including the circuit element. In the four-wheel drive control device according to any one of claims 1 to 3,
The field current reversing means has four switching elements, and among these four switching elements, the first and second switching elements and the third and fourth switching elements are connected in series, respectively.
The open side terminal of the first switching element and the open side terminal of the third switching element are connected to each other, and the open side terminals of the second and fourth switching elements are also connected to each other,
Applying a DC voltage of the DC link portion between the connection point of the first and third switching elements connected to each other and the second and fourth connection points;
A configuration in which the field winding of the AC generator is connected between two connection points connected in series of the two sets of power switching elements connected in series,
The first and fourth switching elements are simultaneously conducting, and the second and third switching elements are simultaneously shut off, or the first and fourth switching elements are simultaneously shut off, and A four-wheel drive control device characterized by reversing the field current by switching so that the second and third switching elements are in a conductive state simultaneously. The engine that drives the main drive wheel also drives the AC generator, and the first AC power from the AC generator is rectified by the rectifier to become DC power, and the DC power is changed to the second AC power by the inverter. A four-wheel drive control device for driving a motor coupled to the driven wheels by the second AC power, wherein the AC generator and the motor are controlled by a 4WD controller and a motor controller;
Measure the voltage of the DC link part connecting the rectifier and the inverter by DC voltage detection means,
When the detected voltage of the DC link rises and reaches a predetermined voltage value, the polarity of the current supplied to the field winding of the AC generator is reversed by the field current reversing means and energized for a predetermined time. A four-wheel drive control device.

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