JPH0634590B2 - Inverter protection device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a power factor adjustable pulse width modulation (P
The present invention relates to an inverter protection device in which a WM) type inverter is arranged and boost control is performed to control a DC output voltage constant.

[Technical background of the invention and its problems]

Generally, in a motor control device such as a thyristor Leonard device or a cycloconverter device, in which voltage adjustment is performed by phase control, there are the following problems.
Since the control current with respect to the power supply voltage is delayed by the phase control angle to control the power factor, the power supply must supply reactive power to the control device. Therefore, in such a control device, since the power supply capacity must be set to a value obtained by adding the reactive power capacity, the power supply capacity becomes large and the power supply equipment requires a great deal of expense.

Therefore, in recent years, in order to improve the above problems, various electric motor control devices having a good power factor have been proposed. FIG. 2 is a circuit diagram showing a configuration example of this type of control device. In FIG. 2, 1 is an AC power supply busbar, 2 is an inverter device in which an AC input terminal is connected to this AC power supply busbar 1 via an electromagnetic contactor 3 and a reactor 4, and 5 is a DC output terminal of this inverter device 2. DC power bus 6
A variable voltage variable frequency control device connected via the variable voltage frequency control device 5 is provided as a power conversion device for controlling the three-phase induction motor 7. A smoothing capacitor 8 is connected to the DC power source bus 6 and constitutes a main circuit of the voltage source inverter. Further, 9 is a DC voltage detector connected to the DC power source bus 6. On the other hand, 10 is a voltage controller to which the detection signal 9a of the DC voltage detector 9 and the voltage reference signal 11a of the voltage reference setting device 11 are input, and 12 is connected to the output signal 10a of this voltage controller 10 and the AC bus 1. The current reference command device to which the voltage signal 13a of the AC voltage detector 13 is input, and 14 is the current control reference signal 12a of the current reference command device 12 and the current detector provided on the AC power supply bus 1.
This is a current controller to which 15 current signals 15a are input. 16 is the voltage command value 14a output from the current controller 14.
This PWM control device 16
Is for controlling the switching of the inverter device 2.

Now, in FIG. 2, the variable voltage variable frequency control device 5
Is a sinusoidal current control method for controlling the current in a sinusoidal manner by pulse width modulation (PWM) control using a switching element capable of self-extinguishing such as GTR and GTO, and an exciting current component and a torque component of the induction motor 7. Excellent control can be performed by a vector control method for controlling. Further, the inverter device 2 is also an inverter device using a switching element capable of self-extinguishing, such as GTR or GTO, as in the above, and the inverter device 2 has a voltage and an AC The current of the power bus 1 is controlled as follows.

For example, the voltage reference signal 11a of the voltage setter 11 and the detection signal 9a of the voltage detector 9 provided on the DC power supply bus 6 in FIG.
Is input to the voltage controller 10, the voltage controller 10 outputs its deviation output 10a to the voltage detector provided on the AC power bus 1.
It is input to the current reference command device 12 together with the voltage signal 13a of 13. In the current reference command device 12, the deviation output 10a is used to convert the current control reference signal 12a of the inverter device 2 synchronized with the phase of the phase voltage of the AC power supply bus 1 into the current control reference signal 12a and the AC power supply bus 1. Current detector provided
The current signal 15a from 15 is input to the current controller 14. The current controller 14 outputs a voltage command value 14a to the PWM control device 16 when the current signal 15a is input, and the PWM control device 16 receives the signal to control the switching of the inverter device 2.

In this way, by controlling the current of each phase using the current control reference signal 12a as a sine wave reference synchronized with the phase of the phase voltage of the AC power source bus 1, it is possible to operate with a high power factor. In this case, the voltage signal 13a is used as a sinusoidal reference and the output 10a of the voltage controller 10 determines the amplitude of the current control reference signal 12a. Further, the detector, the controller and the like have different configurations according to the number of phases of the AC bus 1. The inverter device 2 turns on the electromagnetic contactor 3 provided on the AC power bus 1 to
After charging the smoothing capacitor 8 of the DC power source bus 6, the control is started, and by the boosting action of the reactor 4 and the inverter device 2, it is controlled to the value of the voltage reference signal 11a of the voltage setter 11, and then the operating state of the load. DC power bus 6 according to
The current of the AC power supply bus bar 1 is controlled so that the voltage of 1 follows the voltage reference signal 11a.

By the way, in the electric motor control device as shown in FIG.
If the voltage of the DC bus 6 does not reach the specified value, the inverter device 2 is in an abnormal state, and it is not preferable to continue the control in that state in terms of control of the entire system.

[Object of the Invention]

The present invention has been made to solve the above problems, and temporally confirms the state of the DC output voltage by the AC power supply side inverter device, and disconnects the power supply side inverter device from the AC power supply in the event of an abnormality, and controls the entire control device. It is an object of the present invention to provide a protection device for an inverter, which can appropriately protect the inverter.

[Outline of Invention]

The present invention provides a detector for detecting the establishment of voltage after the start of voltage control on the DC output side of the AC power supply side inverter device, and when the DC voltage is not established even after a certain time has elapsed after the start of voltage control, the AC power supply is provided. Turn off the electromagnetic contactor on the side to disconnect the inverter from the AC power supply.

Example of Invention

The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 shows an example of the circuit configuration of a control device for driving an induction machine as an electric motor. Further, in FIG. 1, the same parts as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, 17 is a voltage setting device for determining the specified value of the DC output voltage of the inverter device 2, and 18 is a time calculation comparator for comparing the signals 9a and 17a from the voltage detector 9 and the voltage setting device 17. is there. Signal even after a certain period of time has passed since the start of voltage control
If 9a is smaller than the signal 17a, the comparator 18 gives the contactor OFF command signal 18a to the exciting circuit 19 of the electromagnetic contactor 3 on the AC power supply side.

Next, the operation of the inverter protection device configured as described above will be described.

In FIG. 1, the inverter device 2 starts the control after charging the smoothing capacitor 8 of the DC power supply bus 6 by turning on the electromagnetic contactor 3 provided on the AC power supply bus 1 as described above in a normal state. By the boosting action of the inverter 4 and the inverter device 2, the value of the voltage reference signal 11a of the voltage setting device 11 is controlled. That is, in FIG. 1, the voltage setting device 17
The set value 17a of is set to the intermediate value between the normal charging voltage value of the DC bus 6 when the electromagnetic contactor 3 is turned on and the voltage value of the DC bus 6 set by the voltage reference signal 11a.
Is larger than the signal 17a, the comparator 18 does not give the OFF command signal 18a to the electromagnetic contactor 3.

By the way, in controlling the inverter device 2, the inverter device 2 is in an abnormal state due to a control problem or the like.
If the voltage of the DC bus 6 does not rise and the signal 9a is smaller than the signal 17a even after a lapse of a certain time after the control is started, the comparator 18
Indicates to the exciting circuit 19 of the electromagnetic contactor 3 that the contactor OFF command signal 18
a is applied, the electromagnetic contactor 3 is turned off, and the inverter device 2
Disconnect from AC power supply.

〔The invention's effect〕

As described above, according to the present invention, a power-factor-adjustable pulse-width-modulation (PWM) type inverter device is arranged in an inverter device in which boost control is performed to control a DC voltage at a constant level. If the DC output voltage of the inverter device is not established within a certain period of time after the start of control, the inverter device on the power supply side can be disconnected by turning off the electromagnetic contactor on the AC power supply side. The entire control device can be appropriately protected even in the event of an abnormality.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a configuration example of a conventional inverter control device. 2 ... Power supply side inverter device 3 ... Electromagnetic contactor, 8 ... Smoothing capacitor 9 ... Voltage detector, 11 ... Voltage reference setting device 17 ... Voltage setting device, 18 ... Time calculation comparator 19 ... Excitation circuit

Claims (1)

[Claims] 1. A power factor adjustable pulse width modulation type inverter device connected to an AC power source through a contactor to control a DC output voltage, and a smoothing capacitor connected to a DC output side of the inverter device. An inverter protection device having a time operation comparator which compares the voltage across the smoothing capacitor with a set value for a predetermined time and outputs an OFF command to the contactor.