JPH01295681A - Power converter - Google Patents

Abstract

PURPOSE:To improve the reliability of an apparatus by detecting the short- circuit mode of said apparatus in a thyristor-ON state and by restoring the ON-state of an inverter circuit to its normal state, before an overcurrent is generated. CONSTITUTION:A current type inverter is composed of a rectifier circuit 2, a DC reactor 3, an inverter circuit 4, an induction motor 5, a voltage controller 13, a current controller 14, a phase controller 15, a ring counter 17, a frequency controller 18 and others. Also, said inverter is provided with an element voltage detector 32 monitoring the ON-state of a thyristor element constituting said inverter circuit 4, a short-circuit detector 34 detecting a short-circuit mode, and a phase selector 35 so that the selected thyristor of the inverter circuit 4 is forcibly fired in said frequency controller 18 by short-circuit detection signal and by selection signal of said phase selector 35. Thus, when said short- circuit mode is detected, another phase capable of firing of said inverter circuit 4 is selected and said thyristor is fired forcibly to suppress the rise of DC current.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention relates to a power conversion device, which detects the energization state of an element and forcibly switches other phases when a short circuit mode occurs. The present invention relates to a power conversion device in which the protection function of the device is improved by commutation.

(Prior Art) Examples of AC motors related to the present invention include induction motors, and examples of power converters include current source inverters. The configuration of a conventional power conversion device is shown in FIG. 4. In FIG. 4, 1 is an AC power supply, 2 is a rectifier circuit, 3 is a DC reactor, 4 is an inverter circuit, 5 is an induction motor, 11 is a current transformer, 12 is a current detector, 13 is a voltage controller, 14 is a current controller, 15 is a phase controller, 16 is an oscillator, and 17 is a ring counter.

18 is a frequency controller, 19 is a transformer, 20 is a voltage detector, 21 is a speed setter, 31 is an overcurrent detector, 32 is an element voltage detector, and 33 is an OR circuit. The basic operation of the current source inverter shown in this figure is described in detail in ``New Drive Electronics'' (Published by Denkishoin, edited by Naohiko Ueyama), for example, in Chapter 4, pages 103 to 144. Only the overcurrent protection operation that occurs due to erroneous firing of the thyristor element constituting 4 will be described.

In order to explain this operation, FIG. 5 shows the energization state of the thyristor and the waveforms of each part.

5O-5Z is the energization state of each of the six thyristor elements, 3
2U to 32Z indicate the presence or absence of a voltage across each of the thyristor elements, 51 (Idc) indicates the direct current of the power conversion device, 52
(GS) indicates the phase aperture signal of the rectifier circuit, 53 (GB) indicates the gate block signal of the inverter circuit, and tl
indicates the abnormality occurrence point, and tl indicates the overcurrent detection point. As shown in this figure, in the inverter circuit 4, if the thyristor Sv is erroneously fired at time t1 due to an erroneous pulse caused by external factors such as noise, the thyristor SY is in a energized state,
DC short circuit mode occurs. As a result, the DC voltage of the inverter circuit 4 suddenly changes.

The voltage across the DC reactor rises rapidly. At this time.

The rectifier circuit 2 detects a sudden rise in direct current (Idc) 51 using a current transformer 11 and a current detector 12, and detects the rise in current by a current controller 14 and a one-phase controller! 5 tries to reduce the DC power, but the current increases and the operation starts for the first time. Also, due to the DC short circuit, current no longer flows to the induction motor 5, so the inverter output voltage decreases, and this is transferred to the transformer. 19, and the current controller 14 and phase controller 15 to increase the current reference, which is an input signal of the current controller 14, in order to increase the voltage detected by the voltage detector 20 and the voltage controller 13.
The overcurrent suppression operation is further delayed, and the current increase cannot be suppressed.

The overcurrent detection point is reached at time t2. At this time, the thyristor element conducts and cuts off this fault current.

During this operation, the overvoltage caused by the circuit inductance and the sudden increase in current often result in destruction, or the device stops. Element voltage detector 3 described here
It is generally well known that the circuit 2 has a function of detecting element abnormality, narrowing the phase of the rectifier circuit 2, and blocking the gate pulse of the inverter circuit 4.

(Problems to be Solved by the Invention) As described above, the prior art has the following problems.

(2) Since an increase in current caused by a DC short circuit in the inverter circuit 4 is detected and an attempt is made to suppress the overcurrent by a current control operation, the overcurrent suppression operation is delayed.

■ Due to the above operation delay, a large fault current flows through the power converter.

■ Thyristor elements are destroyed due to excessive fault current and overvoltage generated by circuit inductance.

) If the commutation circuit has a capacitor such as a current source inverter, the capacitor may be overcharged due to fault current,
The thyristor element is destroyed by overvoltage.

■ The device stops due to overcurrent.

The present invention has been made in view of the above-mentioned conventional drawbacks, and provides a power conversion device that can reliably protect thyristor elements, etc., without causing overcurrent to flow even if a DC short circuit occurs in an inverter circuit. It is intended to.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides element voltage detectors 320 to 32Z that monitor the energization state of thyristor elements constituting the inverter circuit 4;
A short circuit detector 34 receives this detection signal and detects the short circuit mode of the inverter circuit 4. This short circuit detection signal causes
A power conversion device is provided that includes a phase selector 35 that selects another phase of the inverter circuit 4 that can be fired.

(Function) In the above configuration, when the thyristor element constituting the inverter circuit 4 is erroneously fired, a DC short circuit occurs due to the relationship with other thyristors that are energized at that time. As a result, the DC voltage of the inverter circuit 4 suddenly changes, and the voltage across the DC reactor rises rapidly. At this time, the short circuit mode is detected by the short circuit detector 34 based on the output signal of the element voltage detector 32, another phase of the inverter circuit 4 that can be started is selected by the phase selector 35, and the signal is sent to the frequency controller 18.
input, forcibly fires the thyristor, eliminates the DC short circuit in the inverter circuit, suppresses the rise in DC current, and then returns to normal operation mode.

(Embodiment) An embodiment of the present invention is shown in FIG. 1. The basic circuit of the power conversion device in this figure is the same as that in FIG. 4 described above, so the explanation thereof will be omitted here. Inverter circuit 4
An element voltage detector (32U to 32z) 32 that monitors the energization state of the thyristor elements constituting the inverter circuit 4, and a circuit detector 34 that receives this detection signal and detects the short circuit mode of the inverter circuit 4. A phase selector 35 selects a thyristor capable of firing in the inverter circuit 4, and a frequency at which the selected thyristor of the inverter circuit 4 is forcibly fired based on the short circuit detection signal and the selection signal of the phase selector 35. It is composed of a controller 18.

To explain the operation of the above configuration, FIG. 2 shows the waveforms of each part. This diagram shows the waveforms of almost the same parts as in FIG. 5 described above, and the explanation of each waveform will be omitted. In this configuration, if the thyristor Sv of the thyristor element constituting the inverter circuit 4 is erroneously fired at time t4 due to an external factor such as noise, the commutation is completed and a DC short circuit mode occurs. The short circuit detector 34 detects the short circuit mode of the inverter circuit based on the element energization state signal from the element voltage detector 32. An example of the configuration of this circuit is shown in FIG.
It is comprised of six thyristor elements 20 to 32X and a failure detection logic 32a that detects an abnormality in the thyristor element based on this signal. Further, the short circuit detector 34 includes three AND circuits 34a to 34c that receive signals from the six element voltage detectors 320 to 32X, and an OR circuit 34d that receives output signals from the AND circuits 34a to 34c. In the above configuration, when the thyristor short-circuit mode occurs, the V-phase iris iris energization signal from the element voltage detector 32V and the Y-phase iris iris energization signal from the element voltage detector 32Y cause The output of the AND circuit 34b of the short circuit detector 34 becomes 1'' indicating a short circuit state, and the output of the OR circuit 34d at the subsequent stage also becomes #J 1 ps to detect a short circuit.

This signal is input to the frequency controller 18, and at time t5, the selected thyristor of the inverter circuit is forcibly fired by the output signal of the phase selector 35.

The phase selector 35 has six element voltage detectors 32U to 3.
The 2Z output signal selects the thyristor with a phase that is 60 degrees behind the thyristor that caused the short-circuit mode if it is in power mode operation, and selects the thyristor that is delayed by 60 degrees in electrical angle from the thyristor that caused the short-circuit mode if it is in regeneration mode. On the other hand, select a thyristor whose phase is advanced by 60 degrees in electrical angle. For example, if thyristor Sv is erroneously fired and a short circuit occurs between it and thyristor SY, thyristor SZ is selected if it is in operation, and thyristor Sx is selected if it is in regeneration. As a result, the DC short circuit in the inverter circuit 4 is eliminated and no overcurrent occurs.

In addition, the thyristor of the inverter circuit 4 can be safely and reliably protected without being damaged, and after that, the thyristor can be commutated twice from Sv to SU, and from SZ to SY, to return to the normal operation mode.

Continuous operation is possible. Also, during regeneration, Sallista is
It is possible to return to the normal operation mode by three commutation operations: from V to sw, from sx to sy, and from sw to SU.

〔Effect of the invention〕

The present invention detects the short-circuit mode of the device based on the thyristor energization state and restores the energization state of the inverter circuit to the normal state before overcurrent occurs, so that the device can be protected safely and reliably. , it is possible to provide a highly reliable power conversion device that can continue to operate. This has the following effects.

- Since the DC short circuit mode of the thyristor in the inverter circuit can be detected based on the energization state of the thyristor, the device can be safely and reliably protected without overcurrent.

■ In order to complete the protection operation without passing overcurrent to the device,
Thyristor elements can be reliably protected without generating overvoltage due to circuit inductance.

■ In order to complete the protection operation without passing overcurrent to the device,
Even in a device having an internal commutating capacitor, the commutating capacitor will not be overcharged and the thyristor element will not be damaged due to overvoltage.

) It is possible to forcibly fire the thyristor in the inverter circuit and then return to normal operation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing waveforms of various parts of the embodiment of FIG. 1, and FIG. FIG. 4 is a block diagram showing a conventional configuration example, and FIG. 5 is a diagram showing waveforms of various parts of the conventional example shown in FIG. 1... AC power supply, 2... Rectifier circuit. 3...DC reactor, 4...Inverter circuit. 5...Induction motor, 11...Current transformer. 12... Current detector, 13... Voltage controller. 14... Current controller, 15... Phase controller. 16... Oscillator, 17... Ring counter. 18... Frequency controller, 19... Transformer. 20... Voltage detector, 21... Speed setting device. 31... Overcurrent detector, 32... Element voltage detector. 33...OR circuit, 34...Short circuit detector. 51...DC current, 52...GS. 53...GB, 35...Phase selector. 1st figure 4 is 2nd figure 3rd figure 71+ f2

Claims (1)

[Claims] A rectifier circuit that converts AC power to DC power, an inverter circuit that converts DC power to arbitrary AC power, and a phase control circuit that controls the firing phase of the elements of the rectifier circuit to adjust the DC power. In this configuration, a first means detects the voltage across the elements of the inverter circuit, and a second means detects a short circuit mode when the positive side element and the negative side element of the inverter circuit are energized in the same phase in response to this signal. 2 means,
a third means for selecting an element in an OFF state that is in a state where it can be energized, outputting an ignition pulse to an element in another phase of the inverter circuit based on this signal and a signal from the second means; , a power conversion device characterized by comprising a third means for eliminating a short-circuit condition.