JP2006050863A - Controller of motor for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress temperature rise of a step-up converter during idling of a motor in a controller of a motor for vehicle comprising the step-up converter 4 for supplying the voltage of a DC power supply 1, while stepping up, to inverters 7a and 7b for driving motors 9a and 9b. <P>SOLUTION: After discriminating that a motor is in a state prone to idling by detecting idling of the motor and raising the output voltage of a step-up converter up to the level of a voltage induced in the motor, downward change is limited. More specifically, the motor is controlled to sustain a constant level or downward change becomes more gentle than upward change. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for an electric motor for a vehicle, and more particularly to a technique for preventing overheating of a boost converter during idling of the electric motor.

As a conventional control device, there is one described in Patent Document 1 below.
In a control device for an electric motor including a boost converter capable of boosting and outputting a battery voltage as described in Patent Document 1, usually, the output voltage command value V _D ^* of the boost converter is set in accordance with the rotational speed of the electric motor. calculated, the calculated reactor current command value I _L ^* of the boost converter based on a difference between the output voltage command value V _D ^* and actual voltage values V _D, reactor current command value I _L ^* and the actual reactor current by controlling the reactor current based on the difference between I _L, the output voltage of the boost converter is controlled to be equal to or greater than the induced voltage of the motor.

JP 2003-134606 A

In controlling a motor for a vehicle, torque control by feedback is generally performed. Therefore, for example, when the load of the motor suddenly drops due to idling of the wheel, the load torque is suddenly reduced and a large difference is generated between the output torque and the load torque. This torque difference is sequentially reduced by feedback control. During the reduction, the rotational speed of the motor increases due to the torque difference. At that time, if the boost converter as described above is provided, the output voltage is boosted and stepped down according to the rotation speed of the motor, so that, for example, when the motor is idling intermittently due to idling of the wheel, When the step-down is repeated frequently, the reactor of the step-up converter generates heat, and there is a problem that the allowable temperature may be exceeded.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for a vehicle motor that can suppress an increase in temperature of a boost converter during idling of the motor.

  In order to achieve the above object, in the present invention, it is determined that the motor is idling by detecting idling of the motor, and after raising the output voltage of the boost converter to be higher than the induced voltage of the motor, It is configured to limit the change in the descending direction.

  When the motor is in an idling state, the output voltage of the boost converter is raised above the induced voltage of the motor, and then the change in the direction of descending is limited. It is possible to suppress the output voltage from repeatedly increasing and decreasing. Therefore, heat generation in the reactor of the boost converter can be reduced, and the temperature rise of the boost converter can be suppressed.

Example 1
FIG. 1 is a block diagram of a control apparatus for a vehicle motor according to the present invention.
The apparatus of FIG. 1 is a system that boosts the voltage of the DC power supply 1 using a boost converter 4 and supplies the boosted voltage to inverters 7a and 7b, and drives the two generator motors 9a and 9b with the two inverters. In such a system, normally, one of the generator motors is operated as a motor, and the other is operated as a generator, so that the power output and the generated output are balanced as much as possible. If the power running output and the power generation output are not balanced, the difference is that the DC power supply 1 is discharged or charged. If this difference is large, the DC power supply 1 is increased in size and life, the boost converter 4 is increased in size, etc. The effect of.
In addition, one of the two generator motors is connected to the drive engine as a generator, and the other is connected to the drive shaft of the vehicle as a drive motor, or both are connected to the drive shaft via a planetary gear. There is also a configuration connected to.
Moreover, although the example using two generator motors is shown in FIG. 1, the case where one motor is used is applicable similarly.

  In FIG. 1, reference numeral 1 denotes a DC power source, and 2 a reactor, which smoothes a ripple current generated by the boost converter 4. Reference numeral 3 denotes a current sensor which detects a current flowing through the reactor 2. 4 is a step-up converter, 4a and 4b are switching elements of the step-up converter, and the step-up converter 4 controls the step-up rate by controlling the current flowing through the reactor 2 when the switching elements 4a and 4b are switched. Is boosted and output. A capacitor 5 smoothes the switching ripple voltage generated by the boost converter 4 and the inverters 7a and 7b. A voltage sensor 6 detects the inverter input voltage (the output voltage of the boost converter). Reference numerals 7a and 7b denote inverters that drive the generator motor. Reference numerals 8a and 8b denote current sensors, which detect currents flowing through the phases of the generator motor. Reference numerals 9a and 9b denote generator motors. The operation modes include a power running operation mode in which the motor operates as a motor and generates a driving force, and a power generation operation mode in which the motor is driven from others and operates as a generator (drive by a driving engine or the like). Regenerative operation by driving from wheels). Reference numerals 10a and 10b denote speed sensors, which detect the rotational speeds of the generator motors 9a and 9b. 11a and 11b are idling detection means that detect idling of the generator motors 9a and 9b (details will be described later). A control device 20 controls the boost converter 4 and the inverters 7a and 7b based on the detection signals.

  In such a system, by boosting the voltage of the DC power supply 1 with the boost converter 4, the output of the generator motor in the high rotation range can be increased. That is, when there is no step-up converter 4, the voltage of the DC power supply 1 becomes the inverter input voltage. However, when the rotational speed of the generator motor becomes high and the induced voltage exceeds the inverter input voltage, control becomes impossible. Therefore, it is necessary to perform field-weakening control so that the induced voltage does not exceed the inverter input voltage in the operating range where the rotational speed is high.

  On the other hand, when the boost converter 4 is provided, even if the rotational speed of the generator motor increases and the induced voltage becomes equal to or higher than the voltage of the DC power source 1, the boost converter 4 boosts the voltage of the DC power source 1 and the inverter. Therefore, it is not necessary to perform field-weakening control even in the high rotation range of the generator motor, and the output can be increased.

FIG. 2 is a diagram showing the output voltage characteristics (inverter input voltage characteristics) of boost converter 4. In FIG. 2, the vertical axis represents voltage, and the horizontal axis represents the rotational speed of the generator motor. Also, V _D is the inverter input voltage, the V _M is the induced voltage of the generator motor. V _M starts boosting operation of the boost converter 4 becomes the rotation speed N _M1 that exceeds the voltage V _D1 of the DC power source 1, can be boosted to a voltage V _D2 breakdown voltage of the device is permitted.

Thus, the rotational speed for starting the field weakening control can be increased from N _M1 to N _M2, it is possible to increase the output at the N _M1 or more high rpm. Stops the boosting converter 4 is N _M1 following areas (turns on the switching element 4a, the switching element 4b secured to off) it is sufficient to be allowed, the voltage V _D1 of the DC power supply 1 is an inverter input voltage V _D in this state .

When there are two or more generator motors as in this system, the design of each generator motor is generally different, and furthermore, since the rotational speed is usually operated differently, the induced voltage of each generator motor is It is necessary to determine the inverter input voltage V _D from the characteristics.

FIG. 3 is a block diagram showing the configuration of the control device 20. Generally, in order to perform torque control in the control device for the vehicle motor, a torque command is given to the generator motors 9a and 9b. Reference numerals 21a and 21b denote current command calculation units which calculate current commands based on the torque command and the rotational speed of the generator motor. The torque command is a value determined according to, for example, the accelerator opening of the vehicle, the state of charge of the DC power source 1, the gear ratio of the transmission interposed between the generator motor and the wheels, and the like, from the outside of the control device 20. Given.
Reference numerals 22a and 22b denote vector control units, which perform vector control by separating the voltage / current of the generator motor into d-axis and q-axis, and calculate an inverter output voltage command. Reference numerals 23a and 23b denote PWM circuit units, which compare an inverter output voltage command with a carrier signal (for example, a triangular wave or a sawtooth wave) to generate a PWM switching pattern and transmit a gate signal to the inverter. The switching signals of the inverters 7a and 7b are controlled to open and close by this gate signal.
The configurations of the above 21a, 21b, 22a, 22b, 23a, and 23b are the same as the configuration of torque control of a normal AC motor.

31 is an inverter input voltage command calculation part, and calculates an inverter input voltage command from the rotational speed and induced voltage characteristic of each generator motor. This inverter input voltage command uses the higher value of the inverter input voltage in the two generator motors.
An inverter input voltage control unit 32 calculates a control signal that matches the inverter input voltage command value and the inverter input voltage detection value (output of the voltage sensor 6).
A PWM circuit unit 33 compares a control signal from the inverter input voltage control unit 32 with a carrier signal (not shown) to generate a PWM switching pattern, and transmits a gate signal to the boost converter 4. The boost converter is controlled by controlling the switching elements 4a and 4b of the boost converter 4 with this gate signal.

The idling detector 34 is a means for detecting idling of the generator motors 9a, 9b, calculates the rotational acceleration by differentiating the rotational speed of the generator motors 9a, 9b with respect to time, and when the rotational acceleration is equal to or greater than a predetermined value, Judge. In addition, in FIG. 1, although the example (it mentions later in detail) which provided the idling detection means 11a and 11b which detect idling of each generator motor 9a, 9b is shown, as shown in FIG. The idling may be detected from the differential value of the rotational speed of 9b.
When the idling detection unit 34 detects idling of the generator motor, the inverter input voltage command in the inverter input voltage command calculation unit 31 is limited as will be described in detail later.

The operation will be described below.
In the control system shown in FIG. 3, a case is considered where the load on the generator motor suddenly drops and the generator motor is in an idling state (no load state). Such a load drop may be caused by slipping of the tire due to rain or snow in the automobile, idling of the tire due to running on an uneven road surface, and the like. Since the control device 20 performs torque control, control is performed so as to produce a constant torque even when the load is dropped, so that the rotational speed of the generator motor increases rapidly. As a result, the induced voltage also increases rapidly, and when the rotational speed is equal to or higher than _{NM1 in} FIG. 2, the inverter input voltage must also be increased rapidly in response to the sudden increase in induced voltage. In order to increase the inverter input voltage rapidly, energy (electric power) is supplied from the DC power source 1 to increase the voltage across the capacitor 5, and the energy passes through the boost converter 4, so that the reactor 2 of the boost converter 4 Current flows, energy loss occurs, and the temperature of the reactor 2 rises. The temperature rise of the reactor 2 of the boost converter 4 does not become a problem in a steady state, but the energy loss becomes large and the temperature rise becomes large in a transient state where boosting and stepping down are repeated. Therefore, if such idling frequently occurs in a short time, the temperature of the boost converter may exceed the allowable value.

FIG. 4 is a diagram showing a rotational speed N _M , an inverter input voltage command V _D ^* , a reactor current I _L , and a boost converter temperature T when idling frequently occurs in a short time. The horizontal axis indicates time.
When idling occurs, soared rotational speed N _M is (triangular chevron in the figure), also rapidly increases inverter input voltage command V _D ^* accordingly. To rapidly the inverter input voltage V _D is, since it is necessary to charge the capacitor 5, the DC power supply 1 supplies the energy, the reactor current I _L flows as in FIG. Direction of flow of I _L (in the Figure -) direction to charge the DC power supply when to sharply next orientation (in the figure +) of the DC power source discharges, the inverter input voltage when to surge the inverter input voltage to the flows. As the slope of the rise and fall of the inverter input voltage V _D is large, the reactor current I _L is large. When flows reactor current I _L, the reactor 2 is heated by the copper loss due to the internal resistance of the reactor 2, the temperature is increased. Since the reactor 2 has a relatively large heat capacity, if idling frequently occurs in a short time, heat is stored, and the allowable temperature may be exceeded. If the allowable temperature is exceeded, the insulator deteriorates and the life is shortened. In addition, if the design is made with a large margin so as not to exceed the allowable temperature, the apparatus becomes larger and the cost increases. Therefore, it is necessary to prevent the temperature of the boost converter from being raised in a driving bear in which idling frequently occurs in a short time.

For the above purpose, an idling detector 34 is provided. When the idling detection unit 34 detects idling of the generator motors 9a and 9b, control as described below is performed.
FIG. 5 is a flowchart illustrating control of the boost converter according to the first embodiment.
In FIG. 5, in step 101, the rotational speeds of the generator motors 9a and 9b are input.
In step 102, an inverter input voltage command is calculated from the rotational speeds and induced voltage characteristics of the generator motors 9a and 9b. In this case, the inverter input voltage command for each of the generator motors 9a and 9b is calculated, but the larger one is selected as the inverter input voltage command.

  In step 103a, the rotational speed of the generator motor selected in step 102 is time-differentiated to calculate the rotational acceleration. In step 103b, it is determined whether or not the rotational acceleration is equal to or greater than a predetermined value. If the rotational acceleration is greater than or equal to a predetermined value, it is determined that the vehicle is idling. Since this predetermined value varies depending on each generator motor, it is determined by determining the rotational acceleration during idling in an experiment.

If No in Step 103b, the process goes to Step 108, and the inverter input voltage command V _D ^* calculated in Step 102 is output as it is.
In step 104, it is determined whether or not idling has occurred a predetermined number of times or more within a predetermined time. If Yes, the process proceeds to Step 105, and if No, the process proceeds to Step 108. Since the predetermined time and the predetermined number of times vary depending on the system, the values are obtained through experiments.
In step 105, it is determined whether or not V _D ^* > V _D1 is satisfied. That is, in the low rotation range where V _D = V _D1 , the voltage of the DC power supply 1 becomes the inverter input voltage as it is, and therefore it is not necessary to boost the inverter input voltage even when idling occurs.

When all of Steps 103b, 104, and 105 are Yes, that is, when the rotational acceleration is idling at a predetermined value or more, idling occurs for a prescribed number of times within a prescribed time, and V _D ^* > V _D1 The case shows a state in which idling is likely to occur frequently and the inverter input voltage needs to be boosted. In this case, go to Step 106.

In step 106, the maximum value of the inverter input voltage V _D ^* generated within the predetermined time in step 104 is stored.
In step 107, the maximum value of V _D ^* is held and output.
On the other hand, in step 108, V _D ^* calculated in step 102 is output. Step 108 corresponds to the case where the idling is not performed or the number of idling is small and it is not necessary to perform the control method proposed here.

FIG. 6 is a diagram illustrating a state of idling control in the first embodiment.
The “idle determination” at the bottom indicates the determination in step 105. Since it is determined that the driving state is easy to idle at time t ₀ , the inverter input voltage command V _D ^* is set to the maximum value of V _D ^* generated within a predetermined time. After that, even if idling occurs, as long as V _D ^* calculated in step 102 does not exceed the past maximum value, no further boosting is necessary, and as long as the power running output and the power generation output are balanced, the reactor current I _L does not flow. Therefore, the temperature T of the boost converter is lowered and is not overheated. Incidentally, at time t ₀ after 6, the reactor current I _L is up to narrow pulsed show that V _D ^* calculated in step 102 at this point exceeds the maximum value of the past.

  The return from the above state to the normal control is performed when, for example, idling does not occur for a predetermined time or more in the determination in step 103b or when the occurrence frequency of idling is lower than the predetermined number in the determination in step 104. It is determined that the operation state that is likely to occur frequently has been lost, and the output holding of the maximum value in steps 106 and 107 is canceled. In addition, it may be possible to return to normal control when a predetermined time has elapsed since the occurrence of idling.

(Example 2)
FIG. 7 is a flowchart showing the control of the boost converter in the second embodiment.
The difference from FIG. 5 is that steps 109 and 110 are provided instead of steps 106 and 107.
In step 109, the inverter input voltage command V _D ^* calculated in step 102 is output. The function is the same as step 108. Step 110 rise of _V ^{D *} is to follow the _V ^{D *} in step _109, but not to follow the step 109 when lowers the _V ^{D *,} delaying the return of the (reduced). That is, the change in the direction of decreasing V _D ^* is made slower than the change in the direction of increasing.

The method of decreasing may be a constant slope or a linear delay function. There are many ways to delay.
If it is determined by the above control that the idling is likely to occur, the rise of the inverter input voltage command V _D ^* is normal, but the fall is gentle.

FIG. 8 is a diagram showing a state of idling control in the second embodiment.
After it is determined that it is in a state where it is easy to idle at time t ₀ , the inverter input voltage command V _D ^* rises suddenly but falls with a small slope. Thus, the frequency flows reactor current I _L decreases from substantially the case of FIG. 4, can suppress the temperature rise of the boost converter.

In the above control, by setting the predetermined number of times in step 104 to one, it is possible to delay the return of V _D ^* and suppress the temperature rise every time idling.

(Example 3)
Next, in the example described so far, as a means for detecting idling of the generator motor, the rotational speed of the generator motor is differentiated with respect to time to calculate the rotational acceleration, and when the rotational acceleration is equal to or greater than a predetermined value, the idling state is determined. Exemplified what to do. According to this method, there is no need to use a special idling sensor, and there is an advantage that idling can be detected only by calculation in the control device 20.
However, the idling may be detected by other means. For example, in an automobile equipped with a means for detecting tire slip (idling) for brake control, since the tire and the motor are mechanically connected, the tire slip is detected as idling of the motor. May be. As a means of detecting tire slip, the tire rotation speed corresponding to the ground speed is calculated from the output of a sensor (such as Doppler radar) that detects the ground speed of the car, and compared with the actual tire rotation speed. There is a device for detecting the presence or absence of idling.

  In addition, when there are a large number of wheels connected to a connected vehicle, such as a train, the presence / absence of idling is detected by comparing the rotation speed of each wheel with the average rotation speed of many wheels as a reference. I can do it. As described above, when there is another means for detecting the slip, it is not necessary to provide a new sensor by using it for the main control.

  As described above, when the idling detection means provided outside is used, in the flowcharts of FIG. 5 and FIG. 7, instead of “Rotational acceleration greater than a predetermined value?” A determination may be made as to “Is there an input of the idling detection signal?”.

  As described above, by adopting the present control device, it is possible to suppress the temperature rise of the boost converter during frequent idling.

The block diagram of the control apparatus of the motor for vehicles concerning the present invention. The figure which shows the output voltage characteristic (inverter input voltage characteristic) of the boost converter 4. FIG. FIG. 2 is a block diagram showing a configuration of a control device 20. Rotational speed N _M at the time when the idling is frequently in a short period of _time, the inverter input voltage command V _{D ^*,} the reactor current I _L, illustrates a boost converter temperature T. 3 is a flowchart showing control of the boost converter in the first embodiment. The figure which shows the state of the idling control in Example 1. FIG. 7 is a flowchart illustrating control of a boost converter according to a second embodiment. The figure which shows the state of the idling control in Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... DC power supply 2 ... Reactor 3 ... Current sensor 4 ... Boost converter 4a, 4b switching element 5 ... Capacitor 6 ... Voltage sensor 7a, 7b ... Inverter 8a, 8b ... Current sensor 9a, 9b ... Generator motor 10a, 10b ... Speed sensor 11a, 11b ... idling detection means 20 ... control device 21a, 21b ... current command calculation unit 22a, 22b ... vector control unit 23a, 23b ... PWM circuit unit 31 ... inverter input voltage command calculation unit 32 ... inverter input voltage control unit 33 ... PWM circuit part 34 ... idling detection part

Claims (6)

A boost converter that boosts the voltage of the DC power supply;
An inverter that inputs the output of the boost converter and converts it into AC power to drive the motor;
Rotation speed detection means for detecting the rotation speed of the electric motor;
Input voltage detection means for detecting a voltage input to the inverter;
Voltage command value calculation means for calculating a voltage command value based on the rotation speed of the electric motor detected by the rotation speed detection means and the input voltage of the inverter detected by the input voltage detection means, In a control device for a vehicle motor that controls an output voltage of the boost converter based on a voltage command value,
Comprising idling detection means for detecting idling of the electric motor,
The voltage command value calculation means determines from the detection result of the idling detection means that the electric motor is likely to idling when the idling of the electric motor more than a predetermined number of times within a predetermined time, and outputs the output voltage of the boost converter A control apparatus for a motor for a vehicle, wherein the voltage command value is set so as to limit a change in a direction in which the electric motor is lowered after being increased to an induced voltage or more of the electric motor.   2. The vehicle motor control according to claim 1, wherein the voltage command value calculating means sets the voltage command value so as to keep the voltage command value constant after increasing the output voltage of the boost converter. apparatus.   The voltage command value calculation means sets the voltage command value to be the maximum value of the induced voltage generated within the predetermined time after increasing the output voltage of the boost converter. The control apparatus for a vehicle electric motor according to claim 1.   2. The vehicle motor according to claim 1, wherein the voltage command value calculation means increases the output voltage of the boost converter and then makes the change in the decrease direction slower than the change in the increase direction. Control device.   2. The voltage command value calculation means cancels the restriction on the voltage command value after increasing the output voltage of the boost converter when the state in which the motor is likely to idle is resolved. The control apparatus of the motor for vehicles in any one of thru | or 4.   The idling detection means obtains a rotational acceleration by time-differentiating the rotational speed of the electric motor detected by the rotational speed detection means, and determines that the idling is in a case where the rotational acceleration is a predetermined value or more. The control device for a motor for a vehicle according to any one of claims 1 to 5.

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