JPH0956167A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor controller, wherein complicated circuitry is avoided and further reverse connection current, which is caused when a switching inverter is connected in reverse to a d.c. power supply, can be out off. SOLUTION: A sub-contactor 5 is turned on before a main contactor 3 is turned on, and a smoothing capacitor 6 is charged from a battery 1 through a current-limiter element 4 and the sub-contactor 5. If a switching inverter 7 is connected in reverse to the battery 1, the smoothing capacitor 6 is clamped by a diode D for the reflux of the switching inverter 7, and its terminal voltage Vc is reduced to a small value. Therefore, reverse connection is simply judged by detecting that.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter control device for an AC electric motor.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 6-219139 discloses a main contactor for opening and closing a current supplied from a DC power source, a power source opening / closing means having a current limiting resistor connected in parallel with the main contactor, and a power source opening / closing means. A switching inverter that is supplied with power and controls the AC motor, and a reverse current prevention diode is provided in series with this current limiting resistor to limit the current-carrying direction of the current limiting resistor to one direction, and the switching inverter when the battery is connected in the positive / negative reverse direction. Energization is prohibited.

Japanese Laid-Open Patent Publication No. 6-219141 discloses that the reverse connection state is prevented by positively applying a reverse flow overcurrent to blow the main fuse at the time of the reverse connection.

[0004]

However, in addition to the drawback of requiring the addition of a diode in the prior art of the former publication, a diode connected in parallel to a semiconductor switch in a switching inverter at the time of battery reverse connection of a battery terminal has been proposed. Although the current flowing can be blocked, the high-order input terminal of the switching inverter is connected to the low-order terminal of the battery, and the low-order input terminal of the switching inverter is connected to the output side terminal of the power supply switching means. There is a problem that the current flowing through the diode connected in parallel with the switch cannot be blocked.

On the other hand, in the prior art of the latter publication, in order to cut off the current (reverse connection current) at the time of reverse connection quickly (for example, within 2 seconds), the resistance value of the current limiting resistor must be set low. Absent. For example, in order to blow the main fuse within 1 second, a current more than twice the rated blow current of the main fuse must be supplied. However, there is a problem that such reduction of the current limiting resistance causes deterioration of the main fuse and the smoothing capacitor and a reduction in life due to an increase in current flowing at the time of normal motor startup. There is also a problem that the main fuse needs to be replaced every time a reverse connection occurs.

The present invention has been made to solve the above problems, and can prevent reverse connection current when a switching inverter is reversely connected to a DC power supply while avoiding complication of the circuit configuration. It is an object of the invention to provide an electric motor control device.

[0007]

A first structure of the present invention is a main contactor for opening and closing a current supplied from a DC power supply, and a switching inverter for supplying power from the main contactor to control an AC electric motor. A smoothing capacitor that is connected in parallel with the switching inverter and absorbs an alternating current component of the switching inverter; and a current limiter that is connected in parallel with the main contactor and that reduces the inrush current of the smoothing capacitor when the motor is started. An element and control means for controlling the opening and closing of the main contactor, wherein the switching inverter has a plurality of semiconductor switches that individually connect the phase input terminals of the electric motor to the high-order input terminal and the low-order input terminal, and It is connected in parallel with each semiconductor switch and current is supplied from the motor to the power supply side. In a motor control device having a diode for causing the current to flow, the control means is configured such that the voltage after a predetermined time from start-up is a predetermined value based on a physical quantity related to the detected voltage between the input terminals of the switching inverter. When it is determined to be small, the switching inverter is reversely connected to the DC power supply, and the conduction of the main contactor is prohibited. According to this configuration, it is possible to provide a motor control device that can prevent a reverse connection current when the switching inverter is reversely connected to the DC power supply while avoiding a complicated circuit configuration.

More specifically, when a voltage is applied to the switching inverter and the smoothing capacitor through the current limiting element in the normal connection state, the voltage across the switching inverter is the resistance value r of the current limiting element and the electrostatic capacitance of the smoothing capacitor. It increases exponentially over time based on the cr time constant determined by c and. On the other hand, in the reverse connection state, since the smoothing capacitor is bypassed by the diode of the switching inverter, the voltage drop across the switching inverter (= smoothing capacitor) depends on the impedance ratio between the diode and the current limiting element over time. It converges to a predetermined value. Especially, since the lower end of the smoothing capacitor or the switching inverter is normally grounded to the vehicle body, etc., the other end of the smoothing capacitor becomes a negative potential due to the bypass of the switching inverter by the diode, and the constant potential lower than the ground potential. It will converge to the potential.

More specifically, the combined resistance of the diode bridge of the switching inverter is rd, the resistance of the current limiting element is rr, the voltage of the DC power supply is V, and the transmission loss is neglected. The voltage drop ΔV of −rr · V / (rd
+ Rr). Therefore, by setting the predetermined value larger than this ΔV and setting the normal connection state ΔV at the time of determination larger than the predetermined value, the reverse connection state can be reliably determined and at least conduction of the main contactor is prohibited. Therefore, the diode can be prevented from burning.

Further, according to this structure, the circuit structure is simplified by adding an additional program for a control operation to the controller forming the control means, and the reverse connection of the battery is the reverse of the switching inverter (and the smoothing capacitor). Both connections can be detected, and the adverse effects of the detection such as deterioration and shortening of service life do not occur.

A second structure of the present invention is the same as the first structure, wherein the current limiting element is connected to one end of the main contactor through a sub-contactor, and the control means controls the both contactors at the time of determining the reverse connection. The feature is that conduction is prohibited. According to this configuration, since the sub-contactor is used, the reverse connection current (rush current) generated at each time when the sub-contactor is conducted at the time of reverse connection can be cut off, which is more effective.

A third structure of the present invention is the above-mentioned first or second structure.
In the above configuration, the control means further issues an alarm when the reverse connection is determined. According to this configuration, a diode leakage current due to reverse connection can be warned. A fourth configuration of the present invention is characterized in that, in the first or second configuration, the DC power source is an on-vehicle battery of an electric vehicle.

A fifth aspect of the present invention is the first or second aspect described above.
In the above configuration, the DC power source is further composed of an engine-driven power generator.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the motor control device of the present invention will be described with reference to the following embodiments.

[0015]

【Example】

(Embodiment 1) FIG. 1 shows an electric circuit of an air-conditioning compressor for an electric vehicle having a motor control device of the present invention. (Structure) 1 is a battery for running the vehicle having a rated voltage of 288V, and its high end is connected to the high input end 70 of the switching inverter 7 through the main fuse 2 and the main contactor 3. Reference numeral 5 is a sub-contactor connected in series with a resistor (current limiting element) 4, and the sub-contactor 5 and the resistor 4 are connected in parallel with the main contactor 3.

The lower end of the battery 1 is connected to the lower input end of the switching inverter 7, and the smoothing capacitor 6 is connected in parallel with the switching inverter 7. Reference numeral 9 denotes a voltage detection circuit including, for example, a voltage dividing circuit, which detects the voltage of the smoothing capacitor 6 and outputs the detected voltage to the motor-side controller 12. The motor-side controller 12 receives a power supply voltage from the vehicle electric load driving battery 10 having a rated voltage of 12 V through the sub fuse 11, and controls the main contactor 3, the sub contactor 5, and the switching inverter 7. Further, the motor-side controller 12 transmits / receives a signal to / from the vehicle-side controller 13, receives a drive command from the vehicle-side controller 13, and outputs an abnormality alarm to the controller 13.

The switching inverter 7 comprises a U-phase inverter 71, a V-phase inverter 72 and a W-phase inverter 73.
The output terminals of the inverters 71 to 73 are individually connected to the phase input terminals U, V, W of the motor 8 for driving the compressor. Each inverter 71-73,
A high-side switch composed of an IGBT that individually connects the input terminals U, V, W of each phase and the high-level input terminal 70 of the switching inverter 7, and the input terminals U, V, W of each phase and the low-level input terminal of the switching inverter 7. IGB that connects each
It consists of a low side switch consisting of T. Each IGBT
A diode D for circulating a current from the motor 8 to the smoothing capacitor 6 is individually connected in parallel with.

The smoothing capacitor 6 exchanges an alternating current component with the motor 8 to reduce a current change in the battery 1, and the resistor 4 keeps the rush current into the smoothing capacitor 6 below a predetermined value when the auxiliary contactor 5 is turned on. This is to limit the deterioration of the characteristics of the battery 1 and to prevent the deterioration of the characteristics of the capacitor 6 that normally uses an electrolytic capacitor. Also,
As a matter of course, the resistance value of the resistor 4 is set so that the current flowing through the main fuse 2 when the sub-contactor 5 is turned on is smaller than the fusing current value of the main fuse 2. (Operation) Next, the operation of the above circuit will be described.

Switching inverter 7 when driving the motor
The respective IGBTs are alternately turned on and off based on the control voltage from the controller 12, and the three-phase AC voltage formed thereby is applied to the motor 8. The magnetic energy accumulated in the coil of the motor 8 when the IGBT is off is returned to the smoothing capacitor 6 through the diode D, that is, to the power supply side. The operation of generating a three-phase AC voltage of a desired frequency by the switching inverter 7 and the rotation speed control itself of the motor 8 which is an AC electric motor by this three-phase AC voltage are well known, and a further description will be omitted.

Next, the control operation of the motor side controller 12 will be described with reference to the flow chart of FIG. First, the controller 13 on the vehicle side waits until an on command for turning on the compressor is input (100), and if input, the sub-contactor 5 is turned on (102). When the sub contactor 5 is turned on, the battery 1 charges the smoothing capacitor 6 through the resistor 4 and the sub contactor 5.

Next, it is checked whether or not a predetermined time (for example, 0.01 to 1 second) is delayed from the turning on of the sub-contactor 5 (1
04) When the delay is completed, it is checked whether the terminal voltage (accumulation voltage) Vc of the smoothing capacitor 6 exceeds a predetermined threshold voltage Vth (106). Note that the delay of the predetermined time is because the voltage drop of the smoothing capacitor 6 is small immediately after the sub-contactor 5 is turned on.
Since the terminal voltage Vc is difficult to discriminate between the forward connection state (positive potential state) and the reverse connection state (negative potential state), the determination time is delayed. In this embodiment, the switching inverter 7 and the smoothing capacitor 6 are integrally mounted on a circuit board (not shown), and their lower ends are grounded to the vehicle body.

Since the switching inverter 7 is in the OFF state in the forward connection state shown in FIG. 1, the terminal voltage Vc is substantially determined by the resistance value r of the resistor 4 and the electrostatic capacitance c of the smoothing capacitor 6. Therefore, the threshold voltage Vth (for example, 0.2 to 0.5 V) is equal to the terminal voltage Vc at the time of the forward connection.
It should be set smaller. Therefore, if the terminal voltage Vc is larger than the threshold voltage Vth, it is determined that the forward connection shown in FIG. 1 is established, and the main contactor 3 is turned on (110),
After a predetermined time delay (112), the sub-contactor 5 is turned off (114), and it is checked whether an off command is input from the controller 13 (116). If the off command is not input, the command rotation speed from the controller 13 is set. Step 11 by operating the switching inverter 7 at the corresponding frequency
Returning to 6 (118), if the OFF command is input, the main contactor 3 is turned off and the process returns to step 100.

On the other hand, if the terminal voltage Vc is less than the threshold voltage Vth in step 106, an alarm indicating that the connection is reverse is output (108), and the process returns to step 114. More specifically, when the high end of the battery 1 is connected to the low input end of the switching inverter 7 and the low end of the battery 1 is connected to the high input end 70 of the switching inverter 7, the high end of the battery 1 and the low side switch side are connected. The diode D, the coil of the motor 8, the diode D on the high side switch side, the auxiliary contactor 5, the resistor 4, and the circuit surrounding the low end of the battery 1 are formed, and the smoothing capacitor 6 includes two series diodes and the coil resistance of the motor 8. Will be bypassed in. Therefore, the terminal voltage Vc of the smoothing capacitor 6 is clamped at about -1.5 to -3V. Therefore, if the threshold voltage Vth is set to a value higher than this, step 10
It can be seen that reverse connection can be discriminated in 6.

FIG. 3 shows voltage waveforms at various portions during forward connection and reverse connection. The battery 1 may be, for example, a DC power source obtained by rectifying an AC power source, or may be an engine-driven DC power generation device in a hybrid electric vehicle.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a motor control device of the present invention.

FIG. 2 is a flowchart showing a control operation of a controller 12 of FIG.

FIG. 3 is a timing chart showing voltage waveforms of respective parts of the circuit of FIG.

[Explanation of symbols]

 1 is a battery (DC power supply) 3 is a main contactor 4 is a resistance (current limiting element) 5 is a sub-contactor 6 is a smoothing capacitor 7 is a switching inverter 8 is a motor 12 is a controller (control means)

Claims (5)

[Claims] 1. A main contactor that opens and closes a current supplied from a DC power source, a switching inverter that is supplied from the main contactor to control an AC motor, and an AC current component of the switching inverter that is connected in parallel with the switching inverter. A smoothing capacitor that absorbs
The switching inverter includes a current limiting element that is connected in parallel with the main contactor to reduce an inrush current of the smoothing capacitor at the time of starting the electric motor, and a control unit that controls opening and closing of the main contactor. It has a plurality of semiconductor switches that individually connect each phase input terminal to the high-level input terminal and the low-level input terminal, and a diode that is connected in parallel with each of the semiconductor switches and that returns a current from the electric motor to the power supply side. In the electric motor control device, the control means, when it is determined that the voltage after a predetermined time from the start time is less than a predetermined value based on the detected physical quantity related to the voltage between the input terminals of the switching inverter. Assuming that the switching inverter is reversely connected to the DC power source, An electric motor control device which prohibits conduction of a tactor. 2. The electric motor control device according to claim 1, wherein the current limiting element is connected to one end of the main contactor through a sub-contactor, and the control means prohibits conduction of the both contactors when the reverse connection is determined. 3. The electric motor control device according to claim 1, wherein the control means issues an alarm when the reverse connection is determined. 4. The electric motor control device according to claim 1, wherein the DC power source is an on-vehicle battery of an electric vehicle. 5. The electric motor control device according to claim 1, wherein the DC power source is an engine-driven power generator.