JP4135425B2 - Inverter system for driving multiphase motor and control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inverter system for driving a multiphase motor having an AC motor driven by an inverter and generating electric power, and a power source 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, and even in electric and hybrid vehicles, DC power from batteries is usually converted to desired AC power by an inverter and supplied to the motor. System is adopted. This system makes it possible to control the output torque over a wide range, and has the advantage that the electric power generated by regenerative braking can be used for charging the battery.
[0003]
Here, a high-voltage power source for a high-output motor is efficient, and an electric vehicle or a hybrid vehicle uses a high-voltage battery of several hundred volts as the main battery connected to the input side of the inverter. Yes. On the other hand, at the neutral point of the star connection motor coil, a voltage half of the inverter input voltage is usually obtained. Therefore, by connecting a battery to this neutral point, it is possible to output two types of DC voltage from the system, and also to control power transfer between the two batteries by chopper-controlling the motor coil. You can also.
[0004]
Therefore, in a hybrid vehicle or the like, a system that obtains two power supply voltages by using the generated power for charging two batteries by using the motor as a generator can be employed. In particular, a capacitor can be used instead of the battery. Such a system is disclosed in Japanese Patent Application Laid-Open No. 11-178114.
[0005]
Here, various electric devices are mounted on the vehicle, and a battery of about 12V (14V at the time of charging) is usually mounted as the auxiliary battery. The voltage at the neutral point of the motor is about ½ of the voltage on the inverter input side. In ordinary electric vehicles and hybrid vehicles, the neutral point voltage is considerably high, and the auxiliary battery is used here. It is difficult to connect to. Therefore, a DCDC converter provided separately is used for charging the auxiliary battery.
[0006]
On the other hand, as a practical application example of such a system, a so-called dual power supply system including a 36V power supply and a 12V power supply has been studied. In this dual power supply system, the inverter input voltage is set to about 42V when charging the 36V power supply, and the neutral point voltage is set to about 14V when charging the 12V power supply. Power can be exchanged between power supplies.
[0007]
Therefore, according to this 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 there is an advantage that no DCDC converter is required.
[0008]
Here, in the inverter system for driving a multiphase motor as described above, a large number of auxiliary loads are connected to the low-voltage side battery, and the low-voltage side battery stably supplies power to these auxiliary loads. Playing a role. In order to maintain the state of charge of the low voltage side battery at a predetermined level, the low voltage side battery is connected to the generated power corresponding to the power used in the auxiliary load connected to the low voltage side battery. It is necessary to supply the power line. For this purpose, conventionally, the voltage of the low-voltage power line is sensed, and the power generated by the motor is feedback controlled so that this voltage is constant.
[0009]
[Problems to be solved by the invention]
However, when the voltage sensing of the low-voltage side power supply line becomes abnormal due to disconnection or the like, there is a problem that the generated power cannot be controlled and the generated voltage becomes overvoltage or low voltage.
[0010]
The present invention has been made in view of the above problems, and an object thereof is to provide an inverter system for driving a multiphase motor that can perform appropriate power generation control even when an abnormality occurs in sensing of a low-voltage power supply line. .
[0011]
[Means for Solving the Problems]
The present invention includes an AC motor that is driven by an inverter and outputs a driving force and generates power, and a power source connected to a neutral point of the AC motor, and the power source is charged by the generated power of the AC motor. In addition, in a multiphase motor drive inverter system that supplies power from the power source to a plurality of electrical devices, a power line voltage detecting unit that detects a voltage of the power source, a power source current detecting unit that detects a current of the power source, And normally controlling the inverter according to the output of the power supply line voltage detection means, and controlling the inverter according to the output of the power supply current detection means when the power supply line voltage detection means is abnormal. And
[0012]
If the voltage of the power source connected to the motor neutral point cannot be measured, the neutral point voltage of the inverter cannot be controlled. However, according to the present invention, the feedback control can be continued by the power source current.
[0013]
Further, it is preferable that the power supply current is controlled to be zero according to the output of the power supply current detection means when the power supply line voltage detection means is abnormal. The power supply current is the difference between the neutral point current of the motor and the consumption current of the auxiliary load connected to the power supply. If this is 0, the charge capacity of the power supply does not change and proper neutral point voltage control is possible. Yes.
[0014]
The present invention also includes an AC motor that is driven by an inverter and outputs a driving force and generates power, and a power source connected to a neutral point of the AC motor, and the power source is generated by the generated power of the AC motor. In a multi-phase motor drive inverter system that charges and supplies power to a plurality of electric devices from the power source, a power line voltage detecting means for detecting the voltage of the power source, and a middle point entering and exiting the neutral point of the AC motor Neutral point current detection means for detecting a neutral point current, and normally controls the inverter according to the output of the power line voltage detection means, and when the power line voltage detection means is abnormal, the neutral point The inverter is controlled according to the output of the current detection means.
[0015]
The neutral point current may be equal to the total consumption current in the auxiliary load or the like. Therefore, by controlling the neutral point current so as to match the consumption current of the auxiliary load, appropriate inverter control can be performed. Also, the consumption current of the auxiliary load is usually unknown. Therefore, it is preferable to detect the minimum current consumption of the entire auxiliary load in advance and set this as the target value of the neutral point current. As a result, overcharging of the power supply can be reliably prevented, and rapid discharge of the power supply can be prevented.
[0016]
Further, it is preferable that the neutral point current detecting means detects a three-phase current of the AC motor, and detects a neutral point current based on the detected value. The three-phase current of the AC motor is information necessary for motor drive control, and is originally provided in the system. Therefore, this control can be performed without adding a special sensor.
[0017]
The present invention includes an AC motor that is driven by an inverter and outputs a driving force and generates power, and a power source connected to a neutral point of the AC motor, and the power source is charged by the generated power of the AC motor. And a power line voltage detecting means for detecting the voltage of the power supply in a multi-phase motor drive inverter system for supplying electric power from the power source to a plurality of electric devices, and the power line voltage detecting means in a normal state. And controlling the inverter according to a neutral point voltage command corresponding to the target voltage of the power source when the power line voltage detecting means is abnormal.
[0018]
The neutral point voltage is an appropriate voltage as the power supply voltage of the auxiliary machine load. Therefore, for example, by setting the voltage to 14 V or the like, the control can be continued for a while with a simple method.
[0019]
Further, it is preferable that the neutral point voltage command is corrected based on at least one of the rotational speed of the AC motor, the output torque command, and the inverter input side voltage. As a result, the control can be corrected in accordance with the operating state of the motor.
[0020]
The present invention also relates to a method for controlling the system as described above and a program for executing the control.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
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 the battery 10 which is a main power source. That is, the output of the battery 10 is applied between the positive electrode bus and the negative electrode bus of the inverter 12. The output voltage Vbm of the battery 10 is 36V (42V when charging).
[0023]
The inverter 12 is provided with, for example, three arms in which two switching elements (transistors) are arranged in parallel between a positive bus and a negative bus inside, and a three-phase motor output end is provided between the transistors of each arm.
[0024]
The three-phase motor coil end of the three-phase AC motor 14 is connected to the three-phase motor output end of the inverter. Accordingly, one upper transistor of the inverter 12 is sequentially turned on, and the transistors of the other arms are sequentially turned on while the one upper transistor is turned on, so that each phase coil of the AC motor 14 has a 120 ° phase difference. Supply motor current.
[0025]
Further, a positive point 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 (battery voltage: Vbs) of the voltmeter 22 is supplied to the control circuit 24. Has been. The output voltage Vbs of the auxiliary battery 18 is 12V (14V during charging).
[0026]
Further, an ammeter 26 for detecting the current (battery current: Ibs) of the auxiliary battery 18 is provided between the auxiliary battery 18 and the power supply line, and this output is also input to the control circuit 24.
[0027]
Then, the control circuit 24 controls the supply current to the motor 14 by controlling the switching of the inverter 12 based on the output Vbs of the voltmeter 22 so that the voltage Vbs is a desired value (for example, 14V). The power generation of the motor 14 is controlled so that
[0028]
Here, in the control circuit 24, countermeasures for abnormal conditions as shown in FIG. 2 are taken. It is determined whether or not there is an abnormality in voltage sensing of the power line (14V system power line) to which the auxiliary battery 18 is connected (S11). This is determined by whether or not the output Vbs from the voltmeter 22 is a normal value. For example, if this voltage is a voltage of 8 V or less, normal driving of various auxiliary loads cannot be performed, and in such a case, it is determined that there is an abnormality. In particular, if Vbs is 0V, it is a failure.
[0029]
If the determination in S11 is NO, there is no problem, so switching of the inverter 12 is controlled based on the detected Vbs (14V system voltage) (S12).
[0030]
On the other hand, if it is determined in S11 that there is an abnormality, an abnormality warning is issued (S13). For example, a display indicating 14V battery sensing abnormality is displayed on the display panel, or an auxiliary battery abnormality lamp is turned on.
[0031]
Then, the detection value Ibs of the ammeter 26 is detected. This Ibs is the difference between the current flowing through the auxiliary load and the neutral point current. For this reason, by controlling the inverter 12 so that this Ibs becomes 0, the power used by the auxiliary machine load and the power generated by the motor 14 can be matched. Therefore, in this embodiment, the inverter 12 is controlled so that the current Ibs becomes zero.
[0032]
When the 14V system voltage sensing becomes abnormal, feedback control cannot be performed, and the generated voltage is greatly shifted from the correct target voltage, which is likely to cause overvoltage or voltage drop. In this case, the auxiliary battery 18 is not allowed to travel due to overcharge or rapid discharge, the auxiliary load is malfunctioned due to overvoltage or malfunction due to voltage drop, and further, the CPU is reset. appear. In the present embodiment, feedback control based on sensing of the current Ibs is performed, so that the generated power of the motor 14 can be maintained almost correct. Therefore, the occurrence of the above problem can be prevented. In addition, by issuing an abnormality warning, voltage sensing can be restored at an appropriate timing, and can be returned to a normal state before a major problem occurs.
[0033]
FIG. 3 shows the configuration of the control circuit 24. The voltage Vbm of the battery 10 on the high voltage side is measured, and the difference from the target voltage Vbm * is supplied to the Vbm feedback (F / B) unit 30. The Vbm feedback (F / B) unit 30 determines the torque command Tmg * of the motor 14 so that the battery 10 voltage Vbm becomes the target voltage Vbm *, and supplies this to the switching calculation unit 32. The torque command Tmg * corresponds to the generated power command of the motor 14.
[0034]
The switching operation unit 32 is also supplied with the phase coil currents Iu, Iv, Iw of the motor 14 and the detection signal θ for the rotor position, and a signal Su for controlling the switching of the switching element of each phase of the inverter according to these. , Sv, Sw are generated, and each phase current of the motor 14 is controlled by this. As a result, the output torque (power generation) of the motor 14 is controlled to coincide with the torque command Tmg *.
[0035]
Here, the command value Vn of the neutral point voltage of the motor 14 is supplied to the switching operation unit 32, and thereby the ratio of the ON period of the upper switching element and the lower switching element of the inverter is controlled, and the neutral point is controlled. The voltage is controlled.
[0036]
The neutral point voltage Vn supplies the difference between the normal auxiliary battery 18 voltage Vbs and its command value Vbs * to the feedback (F / B) unit 36 via the switching unit 34, whereby Vbs becomes Vbs. Vn is determined so as to match *. However, if it is determined in S11 in FIG. 2 that there is an abnormality, a switching signal is output in S14, whereby the switching unit 34 feeds back the difference between the auxiliary battery current Ibs and the command value Ibs * ( F / B) part 36 is supplied. Accordingly, in the feedback (F / B) unit 36, Vn is generated based on the current Ibs of the auxiliary battery, and the switching calculation unit 32 controls the switching of the inverter 12 based on this Vn. Is controlled to a voltage according to the power consumption of the auxiliary load.
[0037]
Here, the control of the neutral point voltage Vn and the battery 10 voltage Vbm will be briefly described.
[0038]
In this system, the neutral point voltage is controlled by changing the ratio of the on-duty of the upper transistor and 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 voltage is “2” with respect to the ON period “1” of the lower transistor, the neutral point voltage is 1/3 of the battery 10 voltage.
[0039]
For example, when the battery 10 voltage is 36 V (42 V during charging), the auxiliary battery 18 voltage is 12 V (14 V during charging). The AC motor 14 is driven by the electric power from the battery 10 to perform torque assist such as when the vehicle starts, and various auxiliary loads 20 are operated by the electric power from the auxiliary battery 18.
[0040]
Here, in order to control the neutral point voltage to be 1/3 of the battery 10 voltage, the ON period of the upper transistor and the lower transistor in the inverter 12 is unbalanced, and the neutral point voltage is the motor. It will vibrate according to the current supply phase to each phase. The reactor 16 plays a role of smoothing the oscillating neutral point voltage to some extent, and the output voltage of the auxiliary battery 18 is maintained at a substantially constant value by the auxiliary battery 18.
[0041]
In Figure 4, there is shown a construction of another embodiment, ammeter 28u measuring the current of each phase coil of the motor instead of the ammeter 26 In this example, 28v, 2 8 w is adopted . Here, as shown in FIG. 3 described above, each phase coil current Iu, Iv, Iw of the motor 14 is necessary for calculating the torque command Tmg *, and these ammeters 28u, 28v, 28w are originally provided. ing. In this embodiment, each phase coil current is used.
[0042]
Here, when there is no neutral point current, the sum total of each phase coil current should be zero. Accordingly, the sum of the phase coil currents Iu, Iv, and Iw becomes the neutral point current In. Then, if the neutral point current is controlled so that this neutral point current In matches the current consumption of the entire auxiliary load connected to the 14V power supply line, the correct generated power is supplied to the 14V power supply. Therefore, the current consumption of the auxiliary load is measured, and based on this, the target value In * of the neutral point current is determined, and control is performed so that the neutral point current In matches In *.
[0043]
However, it is generally not possible to measure current consumption at all auxiliary loads. Therefore, in this embodiment, the minimum current consumption of the entire auxiliary load is checked in advance, and this minimum current consumption is set to the target neutral point current In *.
[0044]
As a result, overcharging of the auxiliary battery 18 can be prevented. When the consumption current in the auxiliary load increases, this cannot be coped with, and the auxiliary battery 18 is discharged. However, the sudden discharge of the auxiliary battery 18 can be prevented.
[0045]
FIG. 5 shows the configuration of the control circuit 24 in this embodiment. As described above, at the time of abnormality, the switching unit 34 selects the difference (In * −In) from the target value of the neutral point current, which is supplied to the feedback (F / B) unit 36, based on this. The feedback (F / B) unit 36 creates the neutral point voltage target value Vn and supplies it to the switching calculation unit 32.
[0046]
Further, as a simple method, the neutral point voltage command Vn is calculated by open loop feedforward control without performing feedback of the battery current and the neutral point current. For example, the neutral point voltage command Vn is set to 14V. As a result, although the accuracy of control of the generated voltage is lowered, improved control can be performed as compared with the case where no control is performed.
[0047]
FIG. 6 shows an example in which the accuracy is increased in the open loop control. In this example, normally, the difference between the auxiliary machine load power line voltage command Vbs * and the voltage Vbs is input to the control circuit 24, and the control of the inverter 12 is corrected based on these.
[0048]
FIG. 7 shows a configuration of the control circuit 24 of the present embodiment.
[0049]
The difference between the auxiliary load power supply line voltage command Vbs * and the voltage Vbs is input to the feedback (F / B) unit, where a neutral point voltage command Vn is created, and this is converted via the switching unit 34 to the switching calculation unit 32. To supply. On the other hand, at the time of abnormality, the motor rotation speed Nmg, the motor output torque command Tmg *, and the battery 10 voltage Vbm are input to the map 38, and the corrected neutral point voltage command Vn is output. This output is supplied to the switching operation unit 32 via the switching unit 34.
[0050]
As a result, when an abnormality occurs, Vn can be corrected based on the operation state at that time, and inverter drive control in accordance with the current situation can be performed.
[0051]
Here, the AC motor 14 of the present embodiment is preferably for a vehicle mounted on a vehicle. Examples of the auxiliary machine load 20 include various auxiliary machines mounted on the vehicle. Moreover, as the AC motor 14 mounted on the vehicle, a motor generator for an eco-run system described in JP-A-2002-155773 is suitable.
[0052]
That is, this motor generator is (i) vehicle running while automatically starting the engine after the start of the engine after idling stop control for stopping the engine, and (ii) via the drive system during vehicle deceleration. Regenerative power generation performed by transmitting wheel rotation, (iii) driving of an air conditioner compressor or a power steering pump when the engine is stopped by stopping the vehicle, (iv) power generation when driving the engine, and (v) driving Control that controls the rotation of the stopped engine to suppress vibrations when the engine stops. (Vi) Prevents engine stall by cutting off the fuel supply to the engine during deceleration and then recovering the engine speed when fuel supply is started. , Etc.
[0053]
【The invention's effect】
As described above, according to the present invention, when the voltage of the power source connected to the motor neutral point cannot be measured, the feedback control can be continued by the power source current.
[0054]
Moreover, appropriate inverter control can be performed by controlling the neutral point current so as to match the consumption current of the auxiliary load.
[0055]
Moreover, control can be continued by a simple method by setting the neutral point voltage to an appropriate voltage as the power supply voltage of the auxiliary machine load.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a system according to an embodiment.
FIG. 2 is a flowchart for explaining the operation of the embodiment of the embodiment.
FIG. 3 is a diagram showing a configuration of a control circuit of the same embodiment.
FIG. 4 is a diagram illustrating a configuration of a system according to another embodiment.
FIG. 5 is a diagram showing a configuration of a control circuit of the same embodiment.
FIG. 6 is a diagram showing a system configuration according to still another embodiment.
FIG. 7 is a diagram showing a configuration of a control circuit of the same embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Main battery, 12 Inverter, 14 AC motor, 16 Reactor, 18 Auxiliary battery, 20 Auxiliary machine load, 22 Voltmeter, 24 Control circuit, 32 switching calculating part, 34 Switching part, 36 Feedback (F / B) part

Claims (10)

An AC motor that is driven by an inverter and outputs a driving force and generates power; and a power source connected to a neutral point of the AC motor, and the power source is charged by the generated power of the AC motor. In an inverter system for driving a multiphase motor that supplies power to a plurality of electrical devices
Power supply line voltage detection means for detecting the voltage of the power supply line to which the power supply is connected;
Power supply current detection means for detecting the current of the power supply;
Have
An inverter system for driving a multi-phase motor that normally controls the inverter according to the output of the power supply line voltage detection means and controls the inverter according to the output of the power supply current detection means when the power supply line voltage detection means is abnormal . The system of claim 1, wherein
An inverter system for driving a multi-phase motor that performs control so that a power supply current becomes zero according to an output of the power supply current detection means when the power supply line voltage detection means is abnormal. An AC motor that is driven by an inverter and outputs a driving force and generates power; and a power source connected to a neutral point of the AC motor, and the power source is charged by the generated power of the AC motor. In an inverter system for driving a multiphase motor that supplies power to a plurality of electrical devices from
Power supply line voltage detection means for detecting the voltage of the power supply line to which the power supply is connected;
Neutral point current detection means for detecting a neutral point current entering and exiting the neutral point of the AC motor;
Have
For driving a multi-phase motor that normally controls the inverter according to the output of the power line voltage detection means, and controls the inverter according to the output of the neutral point current detection means when the power line voltage detection means is abnormal Inverter system. The system of claim 3, wherein
The neutral point current detecting means detects a three-phase current of the AC motor, and detects a neutral point current based on the detected value. An AC motor that is driven by an inverter and outputs a driving force and generates power; and a power source connected to a neutral point of the AC motor, and the power source is charged by the generated power of the AC motor. In an inverter system for driving a multiphase motor that supplies power to a plurality of electrical devices from
Power supply line voltage detection means for detecting the voltage of the power supply line to which the power supply is connected;
Have
The inverter is controlled according to the output of the power supply line voltage detection means during normal times, and the inverter is controlled according to a neutral point voltage command corresponding to the target voltage of the power supply when the power supply line voltage detection means is abnormal. Phase motor drive inverter system. The system of claim 5, wherein
The neutral point voltage command is corrected based on at least one of the rotational speed, output torque command, and inverter input side voltage of the AC motor, and is a multiphase motor drive inverter system. An AC motor that is driven by an inverter and outputs a driving force and generates power; and a power source connected to a neutral point of the AC motor, and the power source is charged by the generated power of the AC motor. In a control method of an inverter system for driving a multiphase motor that supplies power to a plurality of electric devices from
An inverter system for driving a multi-phase motor that controls an inverter according to a voltage of a power supply line to which the power supply is connected in a normal state and controls the inverter according to a current of the power supply when an abnormality is detected in the power supply line voltage. Control method. An AC motor that is driven by an inverter and outputs a driving force and generates power; and a power source connected to a neutral point of the AC motor, and the power source is charged by the generated power of the AC motor. In a control method of an inverter system for driving a multiphase motor that supplies power to a plurality of electric devices
An inverter system for driving a multi-phase motor that normally controls the inverter according to the voltage of the power line to which the power source is connected, and controls the inverter according to the current at the neutral point when the power line voltage detection is abnormal Control method. An AC motor that is driven by an inverter and outputs a driving force and generates power; and a power source connected to a neutral point of the AC motor, and the power source is charged by the generated power of the AC motor. In a control method of an inverter system for driving a multiphase motor that supplies power to a plurality of electric devices from
An inverter system for driving a multi-phase motor that normally controls the inverter according to the voltage of the power source and controls the inverter according to a neutral point voltage command corresponding to the target voltage of the power source when the power line voltage is abnormal Control method.   A control program for an inverter system for driving a multiphase motor, which causes the system to execute the control method for an inverter system for driving a multiphase motor according to any one of claims 7 to 9.

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