JP4123706B2 - Inverter control device for vehicle AC motor generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inverter control device for a vehicle AC motor generator.
[0002]
[Prior art and problems to be solved by the invention]
When inverter control is performed on a conventional AC rotating electric machine, the PWM carrier frequency is set sufficiently high (usually 10 to 15 kHz) for noise reduction.
[0003]
However, increasing the PWM carrier frequency increases the power loss (switching loss) of the switching elements of the inverter and increases the possibility of destruction of the switching elements. This is because the turn-on power loss is relatively small because the turn-on resistance is small although the turn-on current is large, and the switching loss in the transient period is relatively large because the turn-on resistance is large although the turn-on current is relatively small.
[0004]
JP-A-6-141402 and JP-A-4-295278 measure the temperature and current of a switching element, and reduce the PWM carrier frequency of the inverter at a predetermined temperature or a predetermined current value or more, thereby destroying the switching element. It proposes to achieve both avoidance and switching loss reduction.
[0005]
However, the above-described conventional PWM carrier frequency switching technology requires additional detection circuit systems such as temperature detection and current detection, and increases the possibility of destruction of switching elements when these detection circuit systems fail. Contains the problem.
[0006]
In addition, when operating at a low PWM carrier frequency, there is also a problem that noise increases due to the PWM carrier frequency approaching the mechanical resonance frequency value of the AC rotating electrical machine.
[0007]
The present invention has been made in view of the above problems, and provides an inverter control device for an AC motor generator for a vehicle capable of avoiding destruction of a switching element, reducing switching loss, and suppressing noise increase with a simple circuit configuration. This is a problem to be solved.
[0008]
[Means for Solving the Problems]
An inverter control apparatus for an AC motor generator for a vehicle according to claim 1 is disposed between an AC motor generator that transmits and receives power to and from an engine and drives an on-vehicle device, and the AC motor generator and a battery. And an inverter that performs orthogonal bidirectional power conversion, and a control unit that controls the inverter. The control unit operates the AC motor generator as the engine starting motor when the engine is started. A vehicle, a power generation mode in which the AC motor generator is operated as a generator after completion of starting the engine, and an on-vehicle device that separates the engine and the power transmission means and drives the vehicle-mounted device when the engine is stopped In the vehicular generator motor control device that switches between the device drive modes,
The control means drives the inverter at a first PWM carrier frequency in the in-vehicle device drive mode, and drives the inverter at a frequency lower than the first PWM carrier frequency in the start mode. It is characterized by being driven at the second PWM carrier frequency.
[0009]
According to the present invention, in a vehicle AC motor generator that performs engine start and on-vehicle equipment drive (for example, at an idle stop such as an intersection) in addition to power generation, the largest current flows through the switching element of the inverter, and the switching element has the highest temperature. The focus is on the point at which the engine starts.
[0010]
Therefore, if the PWM carrier frequency is lowered in the engine start mode in which a much larger current is passed through the switching element than in the in-vehicle device drive mode, heat generation of the inverter switching element can be suppressed. . When the engine is started, the noise of the vehicle alternator increases due to the decrease in the PWM carrier frequency. However, since the period for starting the engine is short and the noise of the engine itself is large, the overall noise is not so great in auditory theory. Furthermore, since the engine start period can be determined by the output signals of existing detection means such as an ignition switch and a rotation speed sensor, it is not necessary to add a detection circuit system such as a current sensor or a temperature sensor. No measures to ensure reliability are required. In the in-vehicle device drive mode, the inverter is operated at a high PWM carrier frequency, but the current is small, so that noise can be reduced while preventing overheating of the switching element. Further, since the engine is stopped in the in-vehicle device drive mode, the noise of the vehicle alternator is conspicuous in the auditory theory, and the reduction is particularly effective. It is publicly known that the PWM carrier frequency in the in-vehicle device drive mode is set to, for example, 15 KHz or more in order to make the noise of the vehicle alternator resulting therefrom higher than the audible frequency range.
[0011]
In a preferred embodiment, in the power generation mode, it is preferable to set the PWM carrier frequency high as in the in-vehicle device drive mode. For example, the PWM carrier frequency in the power generation mode is the same as that in the in-vehicle device drive mode, but may be higher than the PWM carrier frequency in the engine start mode and lower than that in the in-vehicle device drive mode. .
[0012]
According to a second aspect of the present invention, in the inverter control device for a vehicle AC motor generator according to the first aspect, the first PWM carrier frequency is higher than a predetermined mechanical resonance frequency value of the AC motor generator. And the second PWM carrier frequency is set lower than the predetermined mechanical resonance frequency value.
[0013]
In this way, the PWM carrier frequency can be greatly changed without interfering with the mechanical resonance frequency value of the vehicle alternator in either the in-vehicle device drive mode or engine start mode, and the engine start mode. Switching loss at the time can be greatly reduced, and noise in the in-vehicle device drive mode can be reduced satisfactorily.
[0014]
According to the configuration of claim 3, in the inverter control device for a vehicle AC motor generator according to claim 2, the mechanical resonance frequency value is a claw-shaped magnetic pole portion of a rotor of the Landel type AC motor generator. The mechanical resonance frequency value of
[0015]
In the Landel type vehicle AC generator, the resonance frequency of the claw-shaped magnetic pole portion of the rotor core is 5 to 8 KHz. Therefore, the PWM carrier frequency in the in-vehicle device drive mode is set to a higher value (for example, 13 KHz) If the PWM carrier frequency in the mode is set to a lower value (for example, 3 KHz), it is possible to suitably achieve both noise suppression and thermal destruction prevention of the switching element.
[0016]
According to a fourth aspect of the present invention, in the inverter control apparatus for an AC motor generator for a vehicle according to the second or third aspect, the control means further comprises a predetermined value in which the engine speed is lower than an idle speed value of the engine. And the PWM carrier frequency is set to the second carrier at the time of engine start mode.
[0017]
According to this configuration, when the engine start mode (the engine speed is less than the engine idle speed value) and less than the predetermined value less than the idle speed value, the low engine speed in the engine start mode is set. The PWM carrier frequency is lowered only in the band.
[0018]
In the engine start mode, a large current flows through the switching element of the inverter at the initial stage of the engine start mode, and the switching loss at this time is reduced. As a result, the PWM carrier frequency can be increased late in the engine start mode in which the current decreases from the initial level of the engine start mode, and noise can be reduced without worrying about the destruction of the switching element.
[0019]
According to a fifth aspect of the present invention, in the inverter control device for an AC motor generator for a vehicle according to the second or third aspect, the control means further includes a case where the current of the AC motor generator is equal to or greater than a predetermined value and the engine. In the start mode, the PWM carrier frequency is set to the second carrier.
[0020]
In this way, when a large current flows through the switching element, the PWM carrier frequency is lowered to a predetermined part of the vehicle alternator, particularly preferably less than the mechanical resonance frequency value of the claw-shaped magnetic pole portion. It is possible to suppress overheating of the switching element while suppressing increase in noise.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings.
[0022]
DESCRIPTION OF SYMBOLS 1 is an inverter, 2 is a controller for inverter control, 3 is a Landel type vehicle AC motor generator, 4 is a clutch, 5 is an engine, 6 is a rotation sensor for detecting the rotation speed of the vehicle AC motor generator 3, 7 is a current sensor, 8 is a vehicle electronic control unit (ECU) that controls an engine (not shown), 9 is an in-vehicle battery, and 10 is a smoothing capacitor.
[0023]
The inverter 1 is constituted by a known three-phase inverter circuit composed of six switching elements (in this case, IGBT elements), and further includes a flywheel diode (not shown) individually connected in reverse parallel to each IGBT element. And an input smoothing capacitor C. A pair of DC input terminals of the inverter 1 exchange DC power with the battery 9, and a three-phase AC terminal of the inverter 1 exchanges AC power with the three-phase armature coil of the AC motor generator 3.
[0024]
The controller 2 includes a microcomputer 21, a field current switching transistor 22, and a flywheel diode 23. In this embodiment, the controller 2 is configured as a microcomputer in order to facilitate understanding of the operation, but it is needless to say that the controller 2 may be configured as a hardware circuit. The microcomputer 21 reads the rotation signal of the vehicle alternator 3 detected by the rotation sensor 6, the predetermined one-phase AC current of the inverter 1 detected by the current sensor 7, and the battery voltage + B, and reads from the vehicle ECU 8. Based on the command, each IGBT of the inverter 1 is PWM-controlled, and the transistor 22 is P-controlled to adjust the field current supplied to the field coil 31 of the vehicular AC generator 3.
[0025]
The vehicle alternator 3 is connected to the engine 5 via the clutch 4 so as to be able to exchange power. The rotor core of the Landel-type vehicle alternator 3 has a core portion fitted and fixed to a rotating shaft, and an even number of claw shapes arranged at a constant pitch in the circumferential direction inside the stator core. The odd-numbered claw-shaped magnetic pole portion extends in the axial direction from one axial end of the core portion, and the even-numbered claw-shaped magnetic pole portion extends in the axial direction from the other axial end of the core portion. ing. A field coil 31 is wound around the core.
[0026]
The current sensor 7 can be omitted, and may be replaced with another electric quantity having a correlation with the current of the vehicle alternator 2.
[0027]
Since the circuit configuration itself is already well known, detailed description is omitted, and the control operation by the microcomputer 21 will be described below with reference to the flowchart of FIG.
[0028]
First, the detection signal of each sensor, the battery voltage, and the command of the vehicle ECU 8 are read (S100), and the optimum operation mode is selected based on them (S102). If the operation mode is the engine start mode, the process proceeds to S104. Proceed to execute the engine start mode. If in-vehicle device drive mode, proceed to S106 to implement the in-vehicle device drive mode. If in power generation mode, proceed to S108 to set the power generation mode. carry out.
[0029]
The engine start mode means a control operation of the vehicle alternator 2 that is detected directly or through the vehicle ECU 8 during an on-state period of an ignition switch (not shown), but instead of the on-period period of the ignition switch, The period from when the engine is turned on until the engine speed reaches a predetermined value may be set as the engine start mode period. In the engine start mode of this embodiment, the microcomputer 21 receives a predetermined phase angle (electric mode) based on the rotational position of the rotor of the vehicle alternator 2 input from the rotation sensor 6 and its rotational speed. The inverter 1 is subjected to PWM (pulse width modulation) control so that a three-phase AC voltage having a matching frequency is output to the vehicle AC generator 2. The duty ratio of the PWM control can be controlled so that the current target value matches the current value detected by the current sensor 7.
[0030]
The in-vehicle device drive mode is an operation mode in which the vehicle ECU 8 is in a state where the clutch 4 is disengaged and drives a predetermined in-vehicle device (for example, a vehicle air conditioning compressor),
This is carried out when a clutch-on is detected from the vehicle ECU 8 and a switch-on for operating a predetermined vehicle-mounted device (for example, a vehicle air-conditioning compressor) is electrically read. In the in-vehicle device drive mode of this embodiment, the microcomputer 21 performs PWM control on the inverter 1 so that the rotational speed of the vehicle alternator 2 read from the rotation sensor 6 is set within a predetermined range. It is also possible to control the duty ratio of PWM control so that the current target value and the current value detected by the current sensor 7 are matched.
[0031]
The microcomputer 21 is implemented by PWM control in each switching element of the inverter 1 in the engine start mode and the in-vehicle device drive mode. The carrier frequency used for PWM control in the engine start mode is as follows. f1 (here, 3 to 4 kHz) is set, and the carrier frequency used for PWM control in the in-vehicle device drive mode is set to f2 (here, 13 to 16 kHz).
[0032]
The power generation mode is an operation mode in which the vehicle alternator 2 charges the battery 9. The battery voltage is compared with a predetermined reference voltage value, and the transistor 22 is intermittently controlled based on the comparison result. The magnetic current is adjusted to converge the battery voltage to the reference voltage value. In the power generation mode, the power generation output generated by the vehicle alternator 2 is three-phase full-wave rectified by a diode (not shown) individually connected in reverse parallel with each switching element of the inverter 1 and sent to the battery 9. The microcomputer 21 turns on the transistor 22 100%, but PWM-controls the transistor 22 as the rotational speed increases, and gradually reduces its duty ratio to lower the generated voltage of the vehicle alternator 2. Is preferred.
[0033]
This power generation mode can be implemented by using a known alternator regulator circuit instead of controlling the transistor 22 by the microcomputer 21. However, when this regulator circuit is adopted, this regulator circuit either turns on the transistor 22 100% in the engine start mode and turns on the transistor 22 100% in the in-vehicle device drive mode, or has a predetermined duty ratio. PWM control is performed.
[0034]
(Effect of Example)
The mechanical resonance frequency of the normally used Landell type vehicle alternator 2 is in the range of 5 KHz to 9 KHz. Therefore, in this embodiment, the PWM carrier frequency in the engine start mode is set to be less than the mechanical resonance frequency range and set to a range exceeding it in the in-vehicle device drive mode.
[0035]
As a result, mechanical resonance of the vehicle alternator 2 can be avoided, audible noise can be reduced in the in-vehicle device drive mode, and heat generation of the switching element of the inverter 1 can be reduced in the engine start mode. It was.
[0036]
FIG. 3 shows a relationship between the mechanical vibration characteristics of the claw-shaped magnetic pole portions of several commercially available AC generators for the claw-shaped magnetic pole portions and the output frequency of the inverter 1.
[0037]
(Modification)
In this modification, steps S110, S112, and S114 shown in FIG. 4 are added between steps S102 and S104 shown in FIG.
[0038]
In step S110, when the current i read from the current sensor 7 exceeds the predetermined threshold value ith, the process proceeds to step S112, where it is determined whether the rotational speed exceeds the predetermined threshold value Nth. Under the condition, the process proceeds to S114, the PWM carrier frequency is fixed to 15 kHz, and the process proceeds to S114. Note that either step S110 or S112 may be omitted. If it does in this way, the noise in the latter electric current decrease period or engine speed increase period of engine starting mode can be reduced, suppressing the overheating of a switching element.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram of a vehicular generator motor control apparatus according to a first embodiment;
FIG. 2 is a flowchart showing a control operation of the microcomputer of FIG. 1;
FIG. 3 is a characteristic diagram showing vibration characteristics of an AC generator for a Landell type vehicle.
FIG. 4 is a flowchart showing a modified embodiment.
[Explanation of symbols]
1 Inverter 2 Inverter control controller (control means)
3 AC motor generator 4 for Landel type vehicle 4 Clutch 5 Engine 6 Rotation sensor 7 Current sensor 8 Electronic control unit (ECU) for vehicle
9 Car battery

Claims (5)

An AC motor / generator that exchanges power with an engine and that drives an on-vehicle device, an inverter that is arranged between the AC motor / generator and a battery and performs orthogonal bidirectional power conversion, and a control that controls the inverter Means and
The control means includes
An engine start mode for operating the AC motor generator as the engine start motor when the engine is started;
A power generation mode in which the AC motor generator is operated as a power generator after the start of the engine is completed;
An in-vehicle device drive mode for separating the engine and the power transmission means and driving the in-vehicle device when the engine is stopped;
In the vehicular generator motor controller,
The control means drives the inverter at a first PWM carrier frequency in the in-vehicle device drive mode, and drives the inverter at a frequency lower than the first PWM carrier frequency in the start mode. An inverter control device for an AC motor generator for a vehicle, wherein the inverter control device is driven at a second PWM carrier frequency. The inverter control device for an AC motor generator for a vehicle according to claim 1,
The first PWM carrier frequency is set higher than a predetermined mechanical resonance frequency value of the AC motor generator, and the second PWM carrier frequency is set lower than the predetermined mechanical resonance frequency value. An inverter control device for a vehicle AC motor generator. The inverter control device for an AC motor generator for a vehicle according to claim 2,
The inverter control device for a vehicle AC motor generator, wherein the mechanical resonance frequency value is a mechanical resonance frequency value of a claw-shaped magnetic pole portion of a rotor of the Landel type AC motor generator. In the inverter control apparatus of the AC motor generator for vehicles according to claim 2 or 3,
The control means sets the PWM carrier frequency to the second carrier when the engine speed is lower than a predetermined value lower than the engine idle speed value and in engine start mode. Inverter control device for vehicle AC motor generator. In the inverter control apparatus of the AC motor generator for vehicles according to claim 2 or 3,
The control means sets the PWM carrier frequency to the second carrier when the current of the AC motor generator is greater than or equal to a predetermined value and in an engine start mode. Machine inverter control device.

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