JPS61266081A - Regenerative operation controller of inverter - Google Patents

Abstract

PURPOSE:To remove the unnecessary factor of an inverter by generating a transient variation in an input power source, interrupting a regenerative operation for the prescribed time until a synchronizing signal is established, and interrupting the regenerative operation for the prescribed time when an excess regenerative current is detected. CONSTITUTION:When the excess regenerative current of an inverter is detected by an overcurrent discriminator 21, a regenerative operation is temporarily stopped during a period set by a oneshot timer 22. When the voltage of an AC power source 11 is reduced or interrupted, the outputs of a synchronizing signal generator 25 and a voltage drop discriminator 26 become 'L', an AND element 33 an inverter 18 is stopped. Thereafter, even if this voltage drop is recovered, the inverter 18 is stopped by an ON-ready timer 27 for the regenerative operation for the prescribed time. The generator 25 can establish a synchronizing signal by utilizing the stopping period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a regenerative operation control circuit for an inverter that regenerates power from a load to a power source.

[Prior art and its problems]

When attempting to operate an induction motor at variable speed, the purpose of variable speed operation can be achieved by using an inverter as a power source and controlling the voltage and frequency of the AC power output from the inverter. When trying to slow down or stop a running induction motor in this way, if you perform so-called regenerative operation in which the rotational energy of the induction motor is converted into electric power and regenerated to the power source, you can quickly decelerate the motor and at the same time waste energy. It saves resources because energy that would otherwise have been wasted can be recovered.

By the way, as mentioned above, inverters that regenerate power on the power supply side generally generate a synchronization signal from the input power supply.Based on this synchronization signal, a logic circuit is constructed and the signal is sent to a specified arm of the inverter. It decides which arm should be made conductive at the appropriate timing. To this end, the stability of this synchronization signal as well as the signal power supply must be maintained within a predetermined range.

Incidentally, the input power source is subject to voltage fluctuations and momentary power outages, and both the synchronous power source and the synchronous signal are affected by this, and there is no guarantee that the logic circuit will be able to secure a regular name. Therefore, if the input voltage drops below a predetermined value, the regenerative operation of the inverter is stopped, and if the regenerative current becomes larger than the normal operating state and exceeds the overcurrent setting value, it is detected. Countermeasures such as stopping regenerative operation are being taken.

However, there is a possibility that the synchronization signal will not be established when the regeneration operation is restarted after the power outage or voltage drop is restored, and even if the regeneration operation is stopped due to excessive regeneration current, the regeneration When the current value decreases, the regenerative operation starts again, and this repetition of restarting and stopping the regenerative operation causes problems such as a kind of oscillation or running over.

[Purpose of the invention]

An object of the present invention is to provide a regenerative operation control circuit for an inverter that can prevent the regenerative operation of the inverter from becoming unstable due to transient fluctuations in the power supply of the inverter during regenerative operation or excessive regenerative current. do.

[Key points of the invention]

This invention provides a timer that prevents regeneration from occurring for a certain period of time until a synchronization signal is established even if the fluctuation recovers when a transient fluctuation occurs in the inverter input power source during regenerative operation, and also provides a timer that prevents regeneration from occurring due to excessive regenerative current. By providing a timer that suspends the regenerative operation for a predetermined period of time even when the inverter detects this, it is possible to eliminate the instability factor when the inverter restarts the regenerative operation.

[Embodiments of the invention]

Figure tg1 is a block diagram showing an embodiment of the present invention. In FIG. 1, AC power from an AC power source 11 is input to a power source inverter 13, which is a power source converter, and is converted into DC power, which is composed of diodes and transistors. This DC power is transferred to the load-side inverter 1, which is a load-side converter consisting of diodes and transistors.
8, the AC power is converted back to AC power and given to the induction motor 19 as a load, but since the voltage and frequency of the AC power output by the load-side inverter 18 can be changed freely, the AC power is can be driven at the desired speed. A smoothing capacitor 17 is provided in a so-called DC intermediate circuit that couples the DC side of the power supply side inverter 13 and the DC side of the load side inverter 18 to remove and smooth ripples in the DC power. Further, this DC intermediate circuit includes a parallel circuit of a diode 14 and a limiting resistor 15 to limit the magnitude of the regenerative current, and the regenerative current is detected by a regenerative current detector 16. Further, an instrument transformer 12 is connected to the AC power source 11, and serves both of detecting current and voltage and generating a synchronous power source.

With the inverter configured as described above, for example, if a command is issued to stop the induction motor 19 in operation, the kinetic energy held by the induction motor 19 is converted into electrical energy and the induction motor 19→ Load side inverter 18 → limiting resistor 15 → power supply side inverter 1
Since regenerative operation is commanded to return this energy via the path 3→AC power supply 11, the induction motor 19 rapidly reduces its speed.

The regenerative current during this regenerative operation is detected by the regenerative current detector 16, but when this detected current is less than the overcurrent setting value, the overcurrent discriminator 21 outputs a logic H signal, and the one-shot Since the logic H signal is output as is from the timer 22, if there is no drop in power supply voltage or loss of synchronization signal, this logic H signal is transmitted to the base drive circuit 28 via the AND elements 32 and 33, so that the load side inverter 18 continues the operation of regenerating energy to the DC intermediate circuit. However, when the overcurrent discriminator 21 detects an overcurrent of the regenerative current and outputs a logic signal, the one-shot timer 2
2 also becomes a logic high signal, and the above-mentioned regeneration operation is temporarily interrupted. Along with this, the overcurrent of the regenerative current is also eliminated, and the overcurrent discriminator 21 outputs a logic H signal again, but the one-shot timer 22 continues to output a logic 1 signal during the set time. In other words, when this inverter detects an overcurrent in the regenerative current, the regenerative operation is temporarily interrupted for the period set in the one-shot (Ima 22) even if the overcurrent has been resolved. After the time elapses, the output of the one-shot timer 22 returns to the logic H signal, so the load-side inverter 18 automatically resumes regenerative operation.

The output of the instrument transformer 12 is given to the regeneration mode discriminator 24 via the rectifier 23, but the smoothing capacitor 17
Since the voltage across the , that is, the DC intermediate circuit voltage is also input to the regeneration mode discriminator 24, it is determined whether or not it is in the regeneration mode by comparing it with the voltage of the AC power supply 11.
In the regeneration mode, a logic H signal is input to the AND element 31, so when a synchronization signal is output from the synchronization signal generator 25, a logic H signal is output from the AND elements 31 and 32. Furthermore, if the voltage of the AC power supply 11 has not decreased, the logic H signal output from the voltage drop discriminator 26 is given to the AND element 33 via the on-delay timer 27, so that the logic H signal output from the ND element 33 is The signal is given to the pace drive circuit 28 to cause the load side inverter 28 to perform regenerative operation.

Here, if the voltage of the AC power supply 11 drops or there is a power outage, the output of the synchronizing signal generator 25 and the output of the voltage drop discriminator 26 become logical signals, so the AND cume 33 also outputs a logical signal and the inverter 18 regenerates. Operation will be stopped. Even after this voltage drop is restored, the on-delay timer 27 continues to output a logic signal for a certain period of time after the voltage is restored, so the load-side inverter 18 remains in the stopped regenerative operation and synchronizes using that time. A signal generator 25 can establish a synchronization signal. When the time set by the on-delay timer 27 elapses after the power supply voltage is restored, the output of the on-delay timer 27 changes again to a logic H signal, and at this time the synchronization signal generator 25 also outputs a logic H signal. (the synchronization signal is established), the regeneration mode discriminator 24 also has a logic H signal (regeneration mode), and the one-shot timer 22 also has a logic H signal (regeneration overcurrent has not occurred). Then, the load-side inverter 18 can enter regenerative operation again.

Although the setting time of the above-mentioned one-shot timer 22 and the setting time of the on-delay timer 27 must be determined through verification, the procedure is easy and the cost and time required for this can be ignored.

〔Effect of the invention〕

According to this invention, if an inverter that is capable of regenerating power from the load side to the power source side has a drop in power supply voltage or a power outage during regenerative operation and restarts regenerative operation immediately when the voltage is restored, a synchronization signal is not established. However, a timer is provided to prevent this, and if an overcurrent is detected in the regenerative current, the regenerative operation is interrupted for a predetermined period of time using a shot timer. This prevents repeated starting and stopping of the regenerative motor, so the addition of only a few parts is effective in avoiding disturbances during regenerative operation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention. 11... AC power supply, 12... Instrument transformer, 13.
...[Power supply side impark as a source side converter, 14...
・Diode, 15...Limiting resistor, 16...Regeneration current detector, 17...Smoothing capacitor, 18...Load side inverter as load side converter, 19...Induction motor as load , 21... Overcurrent discriminator, 22...
・One-shot timer, 23... Rectifier, 24...
Regeneration mode discriminator, 25... synchronous signal generator, 26.
... Voltage drop discriminator, 27... On-delay timer, 2
8...Pace drive circuit, 31, 32, 33...AN
D element.

Claims (1)

[Claims] 1) A power running operation in which a power source side converter and a load side converter convert an AC power source into an AC source of a desired voltage and frequency to drive a load, and a regenerative operation in which power is regenerated from the load to the AC power source. In an inverter capable of detecting an excessive regenerative current, the inverter has a means for stopping the regenerative operation if the inverter detects a drop in the synchronous power supply voltage during regenerative operation, a means for prohibiting the regenerative operation for a certain period of time after the synchronous power supply voltage is recovered, and A regenerative operation control circuit for an inverter, comprising means for interrupting regenerative operation for a predetermined period of time when detecting.