JPH0236796A - Power converter - Google Patents

Abstract

PURPOSE:To perform a recovery drive by a later normal driving operation even if a protecting operation except an overvoltage protection is conducted by validating the overvoltage detection of a DC bus voltage only during the operation of a converter of a power source side. CONSTITUTION:If a voltage at both terminals of a DC capacitor 4 exceeds a predetermined value when a motor is driven, a drive stop signal 1a is output, and the operations of a converter 3 and an inverter 5 are stopped. When the power source side converter 3 is not operated, i.e., when a drive command signal 13b is negative, a DC bus voltage exceeds a predetermined value, and even if an overvoltage detection signal 9a becomes active, an overvoltage detection signal 15a of the logic sum of the signal and a power source side converter drive command signal 13b does not become active.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a power conversion device that protects an inverter.

(Prior Art) Fig. 2 shows a conventional voltage source inverter motor control device. In Fig. 2, 1 is a three-phase AC power supply, 1a is a reactor, 2 is a contactor, and 3 is a power supply that converts three-phase AC into DC. The side converter is configured by connecting transistors 38 to 3f in a bridge manner, and each transistor 38 to 3f is connected in a bridge manner.
Diodes 3g to 3a are connected between the emitter and collector of f.
is connected. 4 is a capacitor for smoothing the DC voltage converted by the converter on the power source side; 5 is an inverter on the motor side that converts the DC power converted by the converter on the power source side into AC power with variable voltage and variable frequency; Similar to the converter on the power supply side, transistors 58 to 5
f and diodes 5g to 5e.

6 is an AC motor, 7 is a voltage detector that detects the voltage of the DC bus across the smoothing capacitor, 7a is a voltage detection signal, 8 is a set value generation circuit that generates a set value, 8a is a set value signal;
9 is a comparison circuit that compares the voltage detection signal 7a and the set value signal 8a; 9a is an overvoltage detection signal output from the comparison circuit; 10 is a hold circuit that holds the overvoltage detection signal;
10a is an inverter stop signal output from the hold circuit, 11.13 is a control circuit on the motor side and power supply side, respectively, lla, and 13a is a signal from the control circuit to transistors 3a to 13.
3f, gate signal given to the bases of 5a to 5f, 1
3b and 14b are each on the power supply side.

Operation command signal to the converter on the motor side, 12 is a DC bus voltage confirmation circuit, 12a is a DC bus voltage confirmation signal, 1
4 is an AND element, and 14a is its output signal.

The operating operation and DC bus overvoltage protection operation of the motor control device configured in this way will be explained.

When the contactor 2 is turned on, the DC bus smoothing capacitor 4 is charged through the diodes h to 3Q of the power supply side inverter, and the DC bus voltage ■Dc is the effective value of the power line voltage Ea.
In order to keep the power supply power factor at 1 and enable power regeneration to the power supply, the power supply side converter operation command 13b is activated from the host microcontroller, and the power supply side converter control circuit 13 activates the gate The DC bus voltage VDC is boosted to a higher value V by outputting the signal and starting switching of the transistors. The DC bus voltage VOC is always controlled to this value by the power supply side inverter 3.6 Next, the motor side inverter operation command 14b is activated from the host microcomputer, and the DC bus voltage confirmation circuit 1
When step-up of the DC bus voltage is confirmed by 2 and the output of this circuit is activated, the AND output 14a becomes active, a gate signal is output by the motor side inverter control circuit 11, and switching of the transistor is started. Electric motor 6 is driven. In cases where there is no significant load fluctuation, such as in elevators, the DC bus voltage is always kept at a constant value by the power supply side converter.

Furthermore, if the DC bus voltage increases while the transistors of the inverter are in the trench, losses within the transistors will increase and secondary breakdown will occur, leading to destruction of the transistors.

For these reasons, the comparison circuit 9 compares the DC bus voltage detection signal detected by the voltage detector 7 with a predetermined value set at a value slightly higher than the DC bus voltage in the set value generation circuit 8. When the voltage exceeds a predetermined value, the overvoltage detection signal 9a, which is the output of the comparator circuit, is activated and held by the hold circuit 10, and is output as a stop signal 10a to the control circuit 11 on the motor side and the power supply side.
．． 13, the gate signals 11a, 13a
After that, the inverter stopped operating continuously.

(Problem to be Solved by the Invention) In a conventional device, when protection other than DC bus overvoltage protection is activated to suddenly stop the motor, the power supply side inverter operation command signal 13b from the host microcomputer is made negative, and the power supply side and motor The side gate signal is cut off, inverter operation is stopped, and the electric motor is stopped using the mechanical brake. In this case, immediately after the gate signal is cut off and the transistor becomes non-conductive, the current flowing through the motor and the energy accumulated by the motor's inductance are instantaneously returned to the DC bus through diodes 5g-5Q. The DC bus voltage increases instantaneously.

When the motor output capacity is large or there is an overload, the motor current is large relative to the DC bus voltage, so the bus voltage increases significantly after the gate signal is cut off, and the overvoltage detection signal 10a becomes active. If the cause of the protection has been removed and recovery operation is required, there is a problem in which the inverter does not start operating even if the operation command signal 13b on the power supply side is activated again by the host microcomputer, making recovery operation impossible. Ta.

The purpose of the present invention is to solve this problem, and to provide a power supply system that enables recovery operation after a protection operation other than overvoltage protection is performed and even if the DC bus voltage rises and exceeds the set range after the inverter stops. The purpose of the present invention is to provide a conversion device.

[Structure of the invention]

(Means for solving the problem) This converter has an inverter that is connected via a capacitor to a converter that converts AC power into DC power and outputs it, converts DC power into wake power and supplies it to a motor. A voltage detector is installed to detect the voltage across the capacitor connected to the output side.

A power conversion device comprising comparison means for detecting an abnormality when the output signal of the voltage detector exceeds a predetermined value and outputting a converter and inverter stop signal when an operation start command signal is output to the converter.

(Function) When an overvoltage of the capacitor is detected when the converter operation start command signal is output, this overvoltage detection signal is used as a stop signal for the converter and inverter.

(Embodiment) An embodiment according to the present invention is shown in FIG. 1. In FIG. 1, a logic element 15 is installed between the comparison circuit 9 and the hold circuit 10 in FIG. The logical product of the commands 13b is used as an overvoltage detection signal 15a, and the signal held by the hold circuit 10 is given to the control circuit 11.13 as a stop signal.The other configuration is the same as that in FIG. 2.

Power supply side converter operation command signal 13b from the host microcomputer
is activated and the motor is in operation, when the voltage across the DC capacitor 4 exceeds a predetermined value, an operation stop signal 10a is output and the operation of the converter 3 and inverter 5 is stopped.

Furthermore, when the power supply side converter 3 is not operating, that is, when the operation command signal 13b is negative, even if the DC bus voltage exceeds a predetermined value and the overvoltage detection signal 9a becomes active, this signal and the power supply side The overvoltage detection signal 15a, which is the logical sum of the coiper drive command signal 13b, does not become active. Therefore, the stop signal 10a also does not become active.

Operation can be restarted by activating the inverter operation command signal from the host microcomputer.

As mentioned above, while the electric motor 6 is in operation, some kind of protection activates and suddenly stops the electric motor. Therefore, if the host microcomputer sends a negative power supply side converter operation command signal to stop the electric motor using a mechanical brake, the electric motor Even if the DC bus voltage rises instantaneously due to the energy stored in the inductance and exceeds the set value, the stop signal will not become active. Therefore, when recovery operation is required from now on, inverter operation is started and recovery operation is possible by activating the operation command signal from the host microcomputer as in normal operation.

[Effects of the Invention] According to the present invention, only while the converter on the power supply side is operating,
By enabling the overvoltage detection operation for the DC bus voltage, the overvoltage detection operation will not be performed even if the DC bus voltage rises due to the energy stored in the motor's inductance immediately after the motor suddenly stops, and exceeds a preset value. After that, recovery operation is possible through normal operation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment based on the present invention, and FIG. 2 is a block diagram of a conventional device. 3...Converter 5...Inverter 6...
・Electric motor 7... Voltage detector 10... Hold circuit 14.15... AND element Figure 1

Claims (1)

[Claims] A converter that converts AC power into DC power and outputs it; A capacitor connected to the output side of this converter; a voltage detector that detects the output voltage of the converter; a voltage detector that detects an abnormality when the output signal of the voltage detector exceeds a predetermined value, and outputs an operation start command signal to the converter; A power conversion device comprising a converter and comparison means for outputting an inverter stop signal.