JP2004048923A - Inverter system for driving polyphase motor, and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To raise the switching efficiency in a high output region. <P>SOLUTION: The positive electrode of an auxiliary battery 18 is connected to the neutral point of a motor 14, and also auxiliary load 20 is connected to it. Then, the voltage in the power line to this auxiliary load 20 is detected with a voltmeter 22, and it is supplied to a control circuit 24 to control the neutral point voltage. Here, a motor 14 is provided with a resolver 26, and it detects a rotor's angle with high accuracy. Then, the control circuit 24 generates a voltage control signal of each phase current having the amplitude equal to the carrier amplitude at start, according to the output of the resolver 26, and compares it with carriers. There, a signal in the same frequency as the carrier frequency can be obtained as a gate signal to control an inverter 12, and in the switching of the inverter 12, it becomes possible to prevent a large neutral point current from being generated by reducing the period when all are on or off. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an inverter system for driving a multi-phase motor including an AC motor driven by an inverter and generating power, and a power supply connected to a neutral point of the AC motor.
[0002]
[Prior art]
Conventionally, AC motors have been widely used as a power source for various devices. Even in electric vehicles and hybrid vehicles, normally, DC power from a battery is converted into desired AC power by an inverter and supplied to the motor. System is adopted. This system has the advantage that the output torque can be controlled over a wide range and the electric power by regenerative braking can be used for charging the battery.
[0003]
Here, a high-voltage motor is highly efficient as a power source for a high-output motor. For an electric vehicle or a hybrid vehicle, a high-voltage battery of several hundred volts is used as a main battery connected to the input side of the inverter. I have. On the other hand, at the neutral point of the star-connected motor coil, a voltage half of the inverter input voltage is normally obtained. Therefore, by connecting a battery to this neutral point, it is possible to output two types of DC voltage from the system, and to control the transfer of power between the two batteries by, for example, chopper controlling the motor coil. You can also.
[0004]
Therefore, in a hybrid vehicle or the like, by using the motor as a generator, a system for obtaining two power supply voltages by using the generated power to charge two batteries can be adopted. In particular, a capacitor can be used instead of a battery. Such a system is disclosed in Japanese Patent Application Laid-Open No. H11-178114.
[0005]
Here, various electric devices are mounted on the vehicle, and about 12 V (about 14 V at the time of charging) of these auxiliary batteries is usually mounted. The voltage at the motor neutral point described above is about one half of the voltage at the inverter input side, and in a normal electric vehicle or hybrid vehicle, even a neutral point voltage becomes a considerably high voltage. It is difficult to connect to. Therefore, a DCDC converter provided separately is used to charge the auxiliary battery.
[0006]
On the other hand, as a practical application example of such a system, a so-called dual power supply system having a 36V power supply and a 12V power supply has been studied. In this two-power supply system, the inverter input voltage is set to about 42 V when charging the 36 V power supply, and the neutral point voltage may be set to about 14 V when charging the 12 V power supply. Power can be transferred between power sources.
[0007]
Therefore, according to the multi-phase motor driving inverter system, the electric charge can be transferred between the high-voltage side battery and the low-voltage side battery by using the motor coil, and an advantage that a DCDC converter is unnecessary is obtained.
[0008]
[Problems to be solved by the invention]
Here, in the above-mentioned conventional system, a hall sensor is usually used as the position sensor, and the position of the rotor is detected only every 60 degrees. Then, when starting the motor, it is desired to obtain a sufficient starting torque. For this reason, 180-degree energization is normally performed at the time of startup. That is, as shown in FIG. 6, a switching control signal (gate signal Su, Sv, gate signal Su, Sv, Sw). Therefore, the motor drive current is rectangular wave conduction. In the case of a three-phase motor, gate signals Su, Sv, Sw of 180-degree conduction deviated by 120 degrees are generated, and the motor is driven by this. Therefore, in both phases, a period of ON or OFF occurs during a period of 1/6 of the current cycle. Furthermore, if the maximum current regulation that turns off the phase when the current value reaches a predetermined value is applied to each phase current, an ON or OFF period occurs for all three phases.
[0009]
As described above, when the same switching state continues for a relatively long period in the inverter and the amount of deviation between the neutral point potential and the low-voltage target voltage increases, the neutral point current greatly fluctuates, and the low-voltage system There is a problem that the power supply line fluctuates greatly.
[0010]
Japanese Patent Application Laid-Open No. 200-324857 discloses that a relay is arranged between a low-voltage power supply and a neutral point, and the low-voltage power supply line is separated from the neutral point by the relay at the time of starting. According to this configuration, it is possible to suppress the voltage fluctuation of the low-voltage power supply line at the time of starting, but a separate relay must be provided and turned on and off.
[0011]
The present invention has been made in view of the above problems, and has as its object to provide a multi-phase motor driving inverter system that can effectively suppress a large change in neutral point current at the time of starting.
[0012]
[Means for Solving the Problems]
The present invention includes a high-voltage power supply, an inverter in which the high-voltage power supply is connected to an input side, and an AC motor connected to an output side, and a low-voltage power supply connected to a neutral point of the AC motor, In a multi-phase motor driving inverter system that controls the driving of an AC motor and the movement of electric power between the high-voltage power supply and the low-voltage power supply by controlling the driving of the inverter, the switching of the inverter has a sine wave. A voltage signal and a gate signal are obtained from a comparison of the carrier, and the on / off of the switching element of the inverter is controlled based on the gate signal, thereby limiting the voltage command of the sine wave to a value within a predetermined range from the carrier amplitude. It is characterized by the following.
[0013]
As described above, by limiting the sine wave voltage command to one within a predetermined range from the carrier amplitude, a gate signal having the same frequency as the carrier frequency can be obtained. Therefore, the switching pattern becomes the same for a long time, and it is possible to prevent a large current from flowing as a neutral point current.
[0014]
Further, a high-voltage power supply, an inverter in which the high-voltage power supply is connected to the input side and an AC motor is connected to the output side, and a low-voltage power supply connected to a neutral point of the AC motor, In a multi-phase motor drive inverter system for controlling the driving of the AC motor and controlling the movement of electric power between the high-voltage power supply and the low-voltage power supply by controlling the driving, the drive control of the AC motor includes at least a stop. There is a power generation mode and a power generation mode. In a transient state of these modes, a feedforward element is included in the neutral point voltage command.
[0015]
Thereby, it is possible to prevent the neutral point voltage control from being delayed in the control transition period, and to perform stable control.
[0016]
The present invention also relates to a control method for the system as described above.
[0017]
Preferably, the AC motor is a vehicle AC motor.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a diagram illustrating an overall configuration of an inverter system for driving a multiphase motor according to an embodiment. An inverter 12 is connected to a 36 V (42 V at charging) battery 10 that is a main power supply. That is, 36 V which is the output of the battery 10 is applied between the positive bus and the negative bus of the inverter 12.
[0020]
The inverter 12 has, for example, three arms in which two switching elements (transistors) are arranged in parallel between a positive bus and a negative bus, and a three-phase motor output terminal is provided between the transistors of each arm.
[0021]
The three-phase motor output terminal of this inverter is connected to the three-phase motor coil terminal of the three-phase AC motor 14. Therefore, one upper transistor of the inverter 12 is sequentially turned on, and while the one upper transistor is turned on, the transistors of the other arm are sequentially turned on. Supply motor current.
[0022]
A positive electrode of an auxiliary battery 18 and various auxiliary loads 20 are connected to a neutral point of the AC motor 14 via a reactor 16. A voltmeter 22 for detecting the voltage of the power supply line of the auxiliary battery 18 on the auxiliary battery 18 side from the reactor 16 is provided, and the output of the voltmeter 22 (battery voltage: Vbs) is supplied to the control circuit 24. Have been.
[0023]
The control circuit 24 normally controls the switching of the inverter 12 based on the output Vbs of the voltmeter 22 to control the current supplied to the motor 14, so that the voltage Vbs becomes a desired value (for example, 14 V). The power generation of the motor 14 is controlled so that
[0024]
That is, the neutral point voltage can be controlled by changing the ratio of the on-duty of the upper transistor to the on-duty of the lower transistor in the inverter 12. That is, if both ON periods are the same, the neutral point voltage becomes equal to the inverter input voltage (battery 10 voltage). On the other hand, if the ON period of the upper transistor is “2” with respect to the ON period of the lower transistor “1”, the neutral point voltage is １ ／ of the voltage of the battery 10.
[0025]
For example, when the voltage of the battery 10 is 36 V (42 V at the time of charging), the voltage of the auxiliary battery 18 is 12 V (14 V at the time of charging). Then, the AC motor 14 is driven by the electric power from the battery 10 to perform torque assist such as when starting the vehicle, and the various auxiliary loads 20 are operated by the electric power from the auxiliary battery 18.
[0026]
In the present embodiment, the resolver 26 is provided to detect the rotation angle of the motor 14. This resolver is a high-precision angle sensor that has a configuration similar to that of an AC motor and generates sine waves having phases different from each other by 90 degrees in a secondary coil according to the rotation angle of a primary coil. The output of the resolver 26 is supplied to the control circuit 24 and is used for controlling each phase current of the motor 14. In particular, at the time of starting, the sine wave phase voltage command value is changed according to the output of the resolver 26. create. Then, the phase voltage command values are set to a range not exceeding the amplitude of the carrier or a predetermined range not exceeding the amplitude.
[0027]
For example, as shown in FIG. 2, each phase voltage command value is set to a value slightly smaller than the carrier amplitude. As a result, a gate signal having the same frequency as the carrier frequency is obtained. Therefore, the switching pattern becomes the same for a long time, and it is possible to prevent a large current from flowing as a neutral point current.
[0028]
The neutral point potential is an average value of the phase voltage command values, and the neutral point voltage can be controlled to the target value by setting the average value to the target neutral point voltage. FIG. 2 shows an example in which the neutral point voltage is half of the inverter input voltage for the sake of convenience. However, even when the neutral point voltage is 1/3, there is basically no difference. The amplitude of each phase voltage command may be adjusted so that it can be generated.
[0029]
FIG. 3 shows a circuit for creating a gate signal in the control circuit 24. The torque command Tmg *, the phase currents Iu, Iv, Iw, and the resolver position signal θ are supplied to the voltage command calculation unit 30. The voltage command calculation unit 30 calculates and calculates each phase voltage command Vu, Vv, Vw having a phase shift of 120 degrees from each other in FIG. 2 and an amplitude equal to the amplitude of the carrier of the triangular wave, and supplies this to the correction circuit 32. .
[0030]
This correction circuit 32 is supplied with a neutral point voltage command Vn * and a battery 10 voltage Vbm. The neutral point voltage command Vn * is calculated by the feedback (F / B) unit 34 from the difference between the power supply line voltage Vbs of the auxiliary battery 18 and its target voltage value Vbs *. Then, the correction circuit 32 adjusts the average value of the phase voltage commands Vu, Vv, Vw to Vn * from the supplied Vn * and Vbm, and outputs torque Tmg * such that Vbm matches its target value Vbm *. Is corrected. Thus, the corrected phase voltage commands Vu ', Vv', Vw 'are output from the correction circuit 32 and supplied to the carrier comparison circuit 36.
[0031]
The carrier comparison circuit 36 is supplied with a triangular wave as a carrier. Here, each phase voltage command Vu ′, Vv ′, Vw ′ is compared with the carrier, and the gate signals Su, Sv, Sw shown in FIG. 2 are output. Is done.
[0032]
Here, in the present embodiment, the amplitude of each phase voltage command is suppressed within a predetermined value by the calculation in the voltage command calculation unit 30. Therefore, the gate signals Su, Sv, Sw become signals that repeatedly turn on and off at the carrier frequency, thereby preventing a large change in the neutral point voltage.
[0033]
FIG. 4 shows the configuration of another embodiment. In this embodiment, an ammeter 28 for measuring the neutral point current In is provided. Then, the control circuit 24 uses the neutral current In to control the neutral point voltage command in a feedforward manner when switching the control mode.
[0034]
In the present system, the control mode of the motor 14 includes a stop mode, a start mode, a power generation mode, and the like. A control transition caused by switching of the control mode such as a transition from the stop mode to the start mode, a transition from the power generation mode to the stop mode, and the like. In this state, the feedback control for controlling the neutral point voltage to the target voltage cannot catch up, transiently deviating from the auxiliary power supply line target voltage, and at the same time the neutral point current fluctuates.
[0035]
FIG. 5 shows the configuration of the control circuit 24 in this embodiment. As described above, in the present embodiment, in this configuration, the Vn calculation unit 38 is provided, and the target voltage Vbs * of the auxiliary power supply line and the neutral point current In are considered in consideration of the voltage drop due to the reactor. Thus, the neutral point voltage command Vn * is calculated from Vn * = Vbs * + RI × In.
[0036]
Then, both the output Vn * of the Vn operation unit 38 and the output Vn * of the feedback (F / B) unit 34 are input to the switching unit 40. Here, the output of the Vn operation unit 38 at the time of starting is output. After the start, the output of the feedback (F / B) unit 36 is selected, and the selected Vn * is supplied to the correction circuit 32.
[0037]
As a result, only In is fed back, Vbs * can always use a correct target value, and feedforward neutral point voltage control including a feedforward element can be performed. As a result, it is possible to effectively prevent the neutral point voltage from greatly fluctuating from Vbs *, and to perform stable control during the control transition period.
[0038]
Such control is effective not only at the time of start-up when shifting from the stop mode to the power generation mode, but also at the time of shifting from the power generation mode to the stop mode.
[0039]
This control is preferably performed in combination with the above-described control for adjusting each phase voltage command in accordance with the amplitude of the carrier.
[0040]
Here, it is preferable that the AC motor 14 of the present embodiment is for a vehicle mounted on a vehicle. The accessory load 20 includes various accessories mounted on the vehicle. Further, as the AC motor 14 mounted on a vehicle, a motor generator for an eco-run system described in JP-A-2002-155773 is suitable.
[0041]
That is, the motor generator runs (i) the vehicle running while automatically starting the engine at the time of starting after performing idle stop control for stopping the engine while the vehicle is stopped, and (ii) via the drive system at the time of vehicle deceleration. Regenerative power generation performed by transmitting the rotation of wheels, (iii) driving of an air conditioner compressor or a power steering pump when the engine is stopped due to vehicle stop, (iv) power generation when the engine is driven, and (v) operation. Control to suppress the generation of vibration when the engine is stopped by controlling the rotation of the stopped engine. (Vi) Prevent engine stall that cuts fuel supply to the engine during deceleration and then recovers the engine speed when fuel supply is started. Used for, for example.
[0042]
【The invention's effect】
As described above, according to the present invention, the gate signal having the same frequency as the carrier frequency can be obtained by limiting the voltage command of the sine wave to within a predetermined range from the carrier amplitude. Therefore, the switching pattern becomes the same for a long time, and it is possible to prevent a large current from flowing as a neutral point current.
[0043]
Further, according to the present invention, in the transient state of the mode, by including the feedforward element in the neutral point voltage command, it is possible to prevent the neutral point voltage control from being delayed and to perform stable control. it can.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a system according to an embodiment.
FIG. 2 is a diagram showing an operation of carrier comparison of the embodiment.
FIG. 3 is a diagram showing a configuration of a control circuit of the embodiment.
FIG. 4 is a diagram showing a configuration of a system according to another embodiment.
FIG. 5 is a diagram showing a configuration of a control circuit of the embodiment.
FIG. 6 is a diagram showing an operation of a conventional carrier comparison.
[Explanation of symbols]
Reference Signs List 10 main battery, 12 inverter, 14 AC motor, 16 reactor, 18 auxiliary battery, 20 auxiliary load, 22 voltmeter, 24 control circuit, 26 resolver, 28 ammeter, 30 voltage command calculator, 32 correction circuit, 34 Switching unit, 36 carrier comparison circuit.

Claims (5)

A high-voltage power supply, including an inverter in which the high-voltage power supply is connected to the input side and an AC motor connected to the output side, and a low-voltage power supply connected to the neutral point of the AC motor, and By controlling, in a multi-phase motor drive inverter system that controls the drive of the AC motor and the movement of power between the high-voltage power supply and the low-voltage power supply,
The switching of the inverter is performed by obtaining a gate signal from a comparison between a sine wave voltage command and a carrier, and controlling ON / OFF of a switching element of the inverter based on the gate signal. An inverter system for driving a multiphase motor, wherein the inverter is limited to a predetermined amplitude or less. A high-voltage power supply, including an inverter in which the high-voltage power supply is connected to the input side and an AC motor connected to the output side, and a low-voltage power supply connected to the neutral point of the AC motor, and By controlling, in a multi-phase motor drive inverter system that controls the drive of the AC motor and the movement of power between the high-voltage power supply and the low-voltage power supply,
The drive control of the AC motor includes at least a stop mode and a power generation mode, and in a transient state of these modes, a neutral point voltage command includes a feedforward element in a multi-phase motor drive inverter system. A high-voltage power supply, including an inverter in which the high-voltage power supply is connected to the input side and an AC motor connected to the output side, and a low-voltage power supply connected to the neutral point of the AC motor, and Controlling the movement of the AC motor and the movement of power between the high-voltage power supply and the low-voltage power supply.
The switching of the inverter is performed by obtaining a gate signal from a comparison between a sine wave voltage command and a carrier, and controlling ON / OFF of a switching element of the inverter based on the gate signal. A method of controlling an inverter system for driving a polyphase motor, wherein the control is limited to a predetermined amplitude or less. A high-voltage power supply, including an inverter in which the high-voltage power supply is connected to the input side and an AC motor connected to the output side, and a low-voltage power supply connected to the neutral point of the AC motor, and Controlling the movement of the AC motor and the movement of power between the high-voltage power supply and the low-voltage power supply.
The drive control of the AC motor includes at least a stop mode and a power generation mode. In a transition state of these modes, a neutral point voltage command includes a feedforward element in the control of the inverter system for driving a multiphase motor. Method. The system or method according to any one of claims 1 to 4,
A method for controlling a polyphase motor driving inverter system or a polyphase motor driving inverter, wherein the AC motor is a vehicle AC motor.

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