JP2007306679A - Controller of motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of a motor which can stably supply power, without causing deterioration in the output of a generator, even when sudden rise in torque command is inputted to a motor of rear wheels. <P>SOLUTION: The AC motor 6 is driven directly with the output power of the generator 4. A controller 15 controls the field voltage of the generator 4 for controlling the output power of the generator 4. A motor control section 20 of the controller 15 calculates a voltage command Vdc1* of a capacitor 9. Furthermore, if the rate of change of the torque command is not less than a predetermined value, the control section 20 obtains a voltage command increment ΔVdc* for increasing a target value of the output power of the generator, adds the obtained value to the voltage command Vdc1*, and calculates a voltage command Vdc*. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric motor control device, and more particularly to an electric motor control device used in an electric motor system in which a generator is driven by a rotational force of an engine and an AC motor is directly driven by electric power generated by the generator.

  In recent years, an increasing number of automobiles run using a motor as a power source. It is an environmentally-friendly vehicle represented by electric vehicles and hybrid vehicles. The main characteristics of these environmentally-friendly automobiles are that they are equipped with a battery, and the electric power is used to generate torque from a motor to drive a tire and run. Recently, an AC motor typified by a permanent magnet synchronous motor is used for this motor, and miniaturization (high power density) is being promoted. Further, an inverter is used to supply the DC power of the battery to the AC motor, and converts the DC power from the battery into AC power. By controlling this inverter, variable speed control of the AC motor becomes possible.

  In the above-mentioned environment-friendly vehicle, since a battery is mounted as a power supply source to the motor, stable power supply is always performed to the inverter, and the power reception voltage is almost constant. Therefore, efficient torque control is always possible for the power supply source.

  More recently, electric four-wheel drive vehicles in which the front wheels are driven by an engine and the rear wheels are driven by a motor have begun to spread. In this electric four-wheel drive vehicle, a dedicated generator is connected to the engine, DC power is generated from the generator by the rotational force of the engine, and the DC ( Torque is generated from a (direct current) motor to drive the vehicle (see, for example, Patent Document 1). In such an electric four-wheel drive vehicle, the rear wheels are driven by a motor having excellent responsiveness, so that it is possible to travel stably even on slippery road conditions. Furthermore, since a generator (alternator type that rectifies generated AC power with a diode bridge) is used without using a battery as a power source, it is excellent in mountability at low cost.

  This electric four-wheel drive vehicle equipped with a DC motor is a very stable system in which the power generation amount (DC power) of the generator is directly supplied to the DC motor (without power conversion). The electric four-wheel drive system equipped with this DC motor is mainly applied to a 1-liter class small automobile from the viewpoint of mountability. In an electric four-wheel drive vehicle using this DC motor, there is a limit in increasing the motor output from the viewpoint of vehicle mounting, and it is difficult to apply it to an automobile of about 2 liter class. Therefore, in order to apply to such a car of about 2 liter class, an electric four-wheel drive vehicle using an AC (alternating current) motor that is superior in power density and can be downsized as compared with a DC motor is conceivable.

Japanese Patent Laid-Open No. 2001-9239852

  Such an electric four-wheel drive vehicle that drives the rear wheels with a motor adopts a batteryless type in order to realize cost reduction, and obtains power by electric power from a generator connected to the engine. This generator is usually an “alternator” in which a diode bridge is arranged at the output part in order to convert the generated AC power into DC power. Since this alternator cannot control the current on the stator side, the generated power is adjusted only by controlling the field current flowing in the field winding. Therefore, control of electric power has a slower response than normal inverter control. On the other hand, in the case of an electric four-wheel drive vehicle, when the front wheel driven by the engine slips on a slippery low μ road, the motor torque of the rear wheel having a steep rising slope may be required. At this time, if the rise of the generator field current is not sufficient, the increase in the generator output cannot follow the increase in the output torque of the motor (that is, the increase in the power consumption of the motor). This causes a problem that the required torque is not output from the rear wheel motor and the required running performance cannot be obtained.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a motor control device that can stably supply power without causing a drop in the output of a generator even when a sudden torque command rise is input to a rear wheel motor. It is in.

(1) In order to achieve the above object, the present invention converts the DC power output from the generator driven by the internal combustion engine into AC power using an inverter, and then supplies the AC power to the AC motor. In the motor control device, wherein the motor is directly driven and has control means for controlling the output voltage of the generator by controlling the field voltage of the generator, the control means has a predetermined rate of change in the torque command. In the case described above, a torque command change rate calculation unit for increasing the target value of the output power of the generator is provided.
With this configuration, even when a sudden torque command rise is input to the rear wheel motor, power can be stably supplied without causing a drop in the output of the generator.

  (2) In the above (1), preferably, the torque command change rate calculation unit calculates a difference ΔP between the maximum target power Pmax corresponding to the engine speed of the generator and the current output power Pout from the generator. By dividing by the output current Idc, an increase in the target value of the output voltage of the generator is calculated.

  According to the present invention, even when a sudden torque command rise is input to the rear wheel motor, power can be stably supplied without causing a drop in the output of the generator.

Hereinafter, the configuration and operation of a motor control device according to an embodiment of the present invention will be described with reference to FIGS.
First, the system configuration of an electric four-wheel drive vehicle to which the motor control device according to the present embodiment is applied will be described with reference to FIG.
FIG. 1 is a system configuration diagram of an electric four-wheel drive vehicle to which an electric motor control device according to a first embodiment of the present invention is applied.

  In the electric four-wheel drive vehicle 1, a dedicated generator 4 is connected to an engine 3 that drives a front wheel 2, and power is generated from an AC motor 6 based on generated power generated by the generator 4. . Here, as a motor applied to the electric four-wheel drive vehicle, a field winding type synchronous motor capable of realizing a wide operating range for realizing a large torque in a low speed region and a high speed drive may be used. The rear wheel 5 is driven by the power generated by the AC motor 6, but this power is distributed to the left and right by the differential 7 and transmitted to the rear wheel 5.

  A 4WD clutch 10 that opens and closes the power transmission path is provided between the motor 6 and the differential 7. An inverter 8 is provided so that the torque of the AC motor 6 can be controlled to a required value. The inverter 8 converts the DC power output from the generator 4 into AC power, and supplies the AC power to the AC motor 6. . Here, the input portion of the inverter 8 becomes electric power having considerable pulsation due to the switching operation of the power element. The capacitor 9 smoothes this.

  The inverter 8, the AC motor 6 and the generator 4 are controlled by the controller 15.

  The above is the configuration of the electric four-wheel drive vehicle using an AC motor. This electric four-wheel drive vehicle is a system that is conscious of low cost, is battery-free without a battery, and drives the motor only by the electric power generated by the generator 4.

Next, the electric power flow in the electric four-wheel drive vehicle to which the motor control device according to the present embodiment is applied will be described with reference to FIG.
FIG. 2 is a power flow diagram of the electric four-wheel drive vehicle to which the motor control device according to the first embodiment of the present invention is applied. In FIG. 2, the same reference numerals as those in FIG. 1 denote the same parts.

  FIG. 2 shows a power flow between the generator 4 and the AC motor 6 in the electric four-wheel drive vehicle. In an ordinary hybrid vehicle or the like, a battery is connected in parallel with the capacitor 9 as a power generation source and a power recovery source. However, the electric four-wheel drive vehicle has a problem that the cost is kept lower than that of the conventional mechanical four-wheel drive vehicle, and a battery is often not mounted from the viewpoint of cost reduction.

  Thus, since the electric four-wheel drive system using an AC motor does not have a battery that absorbs electric power, the generated energy Pg output from the generator 4 driven by the engine 3 and the inverter 8 / AC motor 6 It is necessary to perform coordinated control of electric power so that the drive energy Pm input to is equal.

  However, when the balance between the generated energy Pg and the drive energy Pm is lost, for example, when the generated energy Pg is larger than the drive energy Pm, surplus power flows into the smoothing capacitor 9 and the voltage of the DC bus unit rises. Will do. If the voltage of the DC bus part exceeds the allowable value, the power element of the capacitor 9 or the inverter 8 may be destroyed. Further, when the generated energy Pg is smaller than the drive energy Pm, the electric power stored in the capacitor 9 is consumed by the inverter 8 and the AC motor 6, so that the voltage decreases and the required torque cannot be output. The output voltage of the generator 4 will fall.

Next, a power cooperative control method between the generator 4 and the motor 6 / inverter 8 by the motor control apparatus according to the present embodiment will be described with reference to FIGS.
FIG. 3 is a hardware configuration diagram of a power cooperative control system between the generator and the motor / inverter by the motor control device according to the first embodiment of the present invention. FIG. 4 is a control block diagram of a power cooperative control system between the generator and the motor / inverter by the motor control apparatus according to the first embodiment of the present invention. 3 and 4, the same reference numerals as those in FIGS. 1 and 2 denote the same parts.

  Here, the “DC voltage feedback control method” for feeding back the DC bus section voltage (smoothing capacitor voltage) will be described. The capacitor voltage command Vdc * shown in FIG. 4 corresponds to the command value of the DC bus voltage. In the cooperative control, the capacitor voltage Vdc is feedback-controlled with respect to the voltage command Vdc *. If the capacitor voltage Vdc can be stably controlled with respect to the voltage command Vdc * as described above, cooperative control of electric power can be performed between the generator and the motor / inverter.

  Here, the capacitor voltage command Vdc * is determined according to the operating state of the generator and the operating point of the motor (motor rotation speed, motor torque). As described above, the motor control unit 20 of the controller 15 performs motor control based on the voltage Vdc of the DC bus unit, and outputs a PWM command to the inverter 8 and a field voltage command to the motor 6. On the other hand, the power generation control unit 21 of the controller 15 performs power generation control of the generator (dedicated alternator) 4 so that the capacitor voltage Vdc becomes the command value Vdc *. The power generated by the generator 4 is determined by the rotational speed and the field. Among these, since the rotation speed is determined by the engine rotation speed, the amount operated by the power generation control unit 21 is the field voltage. When the capacitor voltage Vdc matches (or is considered to match) the command value Vdc *, it is a cooperative state in which motor control and power generation control are performed in a well-balanced manner.

Here, the configuration and operation of the power generation control unit 21 used in the motor control apparatus according to the present embodiment will be described with reference to FIG.
FIG. 5 is a block diagram showing a configuration of a power generation control unit used in the motor control apparatus according to the first embodiment of the present invention. In FIG. 5, the same reference numerals as those in FIG. 4 denote the same parts.

  In the power generation control unit 21, the capacitor voltage command Vdc * shown in FIG. 4 corresponds to a command value of the DC bus voltage (capacitor voltage), and the capacitor voltage Vdc is feedback-controlled with respect to the voltage command Vdc *.

  As shown in FIG. 5, with respect to the voltage command Vdc * from the motor control unit 20, the subtractor 21A of the power generation control unit 21 calculates the difference between the voltage command Vdc * and the capacitor voltage Vdc, and calculates this difference as PI. By inputting to the controller 21B and outputting the field voltage command value Vgf, the capacitor voltage Vdc is feedback controlled with respect to the command value Vdc *. Here, the PI controller 21B is illustrated as a controller, but the present invention is not limited to this. Further, in order to improve the responsiveness, the control amount may be compensated with a feedforward term in the output part of the PI controller 21C. The operation amount of the power generation control is the field voltage Vgf of the generator 4, and the field current is adjusted by this field voltage Vgf to control the generated power of the generator 4.

  As described above, if the capacitor voltage Vdc can be stably controlled with respect to the voltage command Vdc *, the power is balanced between the generator 4 and the motor 6 / inverter 8, so that cooperative control of the resulting power can be performed. .

  Here, the AC motor 6 serving as a driving force source has an electrical time constant of about several ms to 10 ms on the stator side, and since it is controlled by the inverter 8, it can be controlled with high response and high accuracy. On the other hand, when the generator is an alternator composed of a diode bridge, the generator 4 cannot control the current on the stator side. Only control will be performed.

  In order to operate a generator and a motor with greatly different control responsiveness in cooperation as described above, it is basically necessary to output power from the motor in accordance with the power generation state of the generator having a slow response. However, when the control is performed in this way, there is a possibility of impairing the performance of the four-wheel drive in a driving scene where a sudden torque rise is required, such as a slope start on a low μ road where the characteristics of the electric four-wheel drive vehicle can be obtained. is there. In such a case, the motor control unit 20 predicts the sudden change degree of the required torque command in advance and increases the generated power. This can be achieved by increasing the excitation of the generator compared to normal driving. In order to realize this in this embodiment, a large capacitor voltage command Vdc * is output in advance in consideration of the response delay of the field.

Next, the configuration and operation of the motor control unit 20 used in the motor control apparatus according to the present embodiment will be described with reference to FIG.
FIG. 6 is a block diagram showing a configuration of a motor control unit used in the motor control apparatus according to the first embodiment of the present invention. In FIG. 6, the same reference numerals as those in FIG. 4 denote the same parts.

  The motor control unit 20 in the controller 15 receives the torque command Tr * to be generated by the rear wheel AC motor 6 and the current motor rotational speed ωm, and performs torque control of the motor 6 with respect to this required operating point. .

  The motor control unit 20 includes a current command map 20A, a capacitor voltage command calculation unit 20B, a torque command change rate calculation unit 20C, and an addition unit 20D. The current command map 20A outputs current commands Id * and Iq * at the operating point based on the input motor torque command TR * and the motor rotational speed ωm. The current commands Id * and Iq * are current command values on the rotation coordinate dq axes used for the control of the AC motor, and are generally current components generally used in vector control. The motor control unit 20 generates a PWM command for the inverter 8 from the current commands Id * and Iq *.

  Further, the capacitor voltage command calculation unit 20B, based on the current commands Id * and Iq * output from the current command map 20A and the input motor rotation speed ωm, the minimum voltage required for the motor operating point, that is, the capacitor voltage. The command value Vdc * is calculated. An example of the calculation method of the capacitor voltage command value Vdc * is as follows.

First, as shown in the following formulas (1) and (2), voltage commands Vd * and Vq * on the rotation coordinate dq axis are calculated from the current commands Id * and Iq *.

Here, R represents winding resistance, ωm represents motor speed, Ld and Lq represent inductance on the dq axis, and φ represents field main magnetic flux.

Further, the capacitor voltage Vdc1 * is calculated by the following equation (3) as an example.

  In an electric four-wheel drive vehicle during normal running, power generation control of the alternator is performed using the voltage Vdc1 * shown in Expression (3) as an output voltage command. If the output voltage of the alternator is equal to the voltage command Vdc1 *, as a result, the motor 6 can generate torque according to the command value by controlling the inverter 8. In this case, the motor torque command is input in accordance with the field response speed of the generator.

  However, the behavior of an electric four-wheel drive vehicle cannot always function by generating torque in accordance with the response of the generator, and there are cases where a rapid rise is required for the rear wheel torque. For example, if the front wheel driven by the engine slips on a hill climbing on a hill with extremely low frictional resistance, such as a snowy road, it will naturally slip down, so the rear wheel torque is generated as soon as possible to grip the front wheel. It is necessary to let However, as described above, since the generator can only control a field with a slow response, when the torque command of the motor is rapidly increased as it is, it may cause an unstable operation such as a voltage drop on the generator side. .

  Therefore, in this embodiment, as shown in FIG. 6, a torque command change rate calculation unit 20C is provided. The torque command change rate calculation unit 20C always monitors the change rate of the motor torque command, and considers the field rise delay, and adds the capacitor voltage command Vdc1 * according to the change rate of the motor torque command ( The voltage command increase ΔVdc *) is calculated.

For example, the torque command change rate calculation unit 20C operates as follows. First, since the power that can be generated and output is determined by the current engine speed, the alternator sets the maximum target power Pmax according to the engine speed at that time. Next, a torque command change rate ΔTr * for each predetermined sampling period is calculated. At this time, since the motor speed is measured at any time, the motor output power change rate ΔPout for each predetermined sampling can be obtained. Further, when it is determined that the change rate ΔPout of the current motor output power exceeds the power generation response speed of the alternator with respect to the maximum target power Pmax, this corresponds to the difference ΔP between the current output power Pout and the maximum target power Pmax. A capacitor voltage command increase ΔVdc * to be calculated is calculated. For example, the arithmetic expression of ΔVdc * can be expressed by the following expression (4).

Here, Idc is an output current from the alternator.

  Then, the adder 30D adds ΔVdc * obtained as described above to the current capacitor voltage Vdc1 * to obtain a final voltage command Vdc *. Since the power generation control unit 21 controls the field current of the alternator with the added voltage command Vdc * as a target, the speed at which the field current increases can be made faster than the normal response speed by this operation. It becomes.

In this way, when the voltage command is increased, the power generation control unit shown in FIG. 5 acts in the direction in which the field increases, so that the generated power increases and it becomes possible to follow the torque command with faster response. .

1 is a system configuration diagram of an electric four-wheel drive vehicle to which an electric motor control device according to a first embodiment of the present invention is applied. 1 is a power flow diagram of an electric four-wheel drive vehicle to which an electric motor control device according to a first embodiment of the present invention is applied. It is a hardware block diagram of the electric power cooperation control system between the generator and motor / inverter by the control apparatus of the electric motor by the 1st Embodiment of this invention. It is a control block diagram of the electric power cooperative control system between the generator and motor / inverter by the control apparatus of the electric motor by the 1st Embodiment of this invention. It is a block diagram which shows the structure of the electric power generation control part used for the control apparatus of the electric motor by the 1st Embodiment of this invention. It is a block diagram which shows the structure of the motor control part used for the control apparatus of the electric motor by the 1st Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electric four-wheel drive vehicle 2 ... Front wheel 3 ... Engine 4 ... Generator 5 ... Rear wheel 6 ... AC motor 7 ... Differential gear 8 ... Inverter 9 ... Smoothing capacitor 10 ... 4WD clutch 15 ... Controller 20 ... Motor control part 20A ... Current command map 20B ... Capacitor voltage command calculator 20C ... Torque command change rate calculator 21 ... Power generation controller 21B ... PI calculator

Claims (2)

After the DC power output from the generator driven by the internal combustion engine is converted into AC power by an inverter, the AC motor is directly driven by supplying the AC power to the AC motor,
In the motor control device having a control means for controlling the output voltage of the generator by controlling the field voltage of the generator,
The control unit includes a torque command change rate calculation unit that increases a target value of output power of the generator when the change rate of the torque command is equal to or greater than a predetermined value. . The motor control device according to claim 1,
The torque command change rate calculation unit divides the difference ΔP between the maximum target power Pmax corresponding to the engine speed of the generator and the current output power Pout by the output current Idc from the generator, and An electric motor control device that calculates an increase in a target value of an output voltage.

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