JPS5819160A - Defect detector for stationary power converter - Google Patents

Abstract

PURPOSE:To enable to open a main power switch while a shortcircuiting current flowing in the switch is small by detecting the fact that the deviation between the detected current value of DC side and the detected current value of AC side becomes larger than the set value and judging a defect. CONSTITUTION:When a switching element S2 is shortcircuited and damaged, a shortcircuiting current flows from the R phase of a power source through switching elements S1, S2 to the S phase of the power source. At the normal time, the detected AC side value IAC is equal to the detected DC side value IL, and the output of an analog switch AS becomes ''0''. On the other hand, when the shortcircuiting current flows so that epsilon3(=IAC-IL)>0 and exceeds the set deviation value epsilon3*, the switch AS generates an output signal ''1'', and applies an open command through a main power open controller MCC to the main power switch MC. In this manner, the power source can be opened before the current flowing the switch MC becomes large.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a failure detection device for a static bath power converter that performs og and og conversion between alternating current and direct current, or between direct current and alternating current.

In general, as a means for converting power between alternating current and direct current, or between direct currents, or between alternating currents, a nine-stop power converter using a semiconductor switching element of SIRIS JIII is widely used. Since the components of the Iristor system are selected and used with voltage and current capacity suitable for the capacity of the device, it is highly unlikely that malfunctions such as element destruction will occur during normal operation. Who?

However, normal operation may not be maintained if the element is destroyed, for example due to overload operation, erroneous operation, external causes such as lightning strikes, or natural deterioration* of the element. In such a case, it can no longer be expected to function as a power converter, and it is desirable to open the power switch as soon as possible to prevent further failure.

FIG. 1 is a schematic diagram showing the configuration of a conventional failure detection device for a static power converter that converts alternating current to direct current. In FIG. 1, R, B, and T are J-phase AC power supply terminals.

MO is the main power switch, TE is the power transformer, 88 is the power converter, LOAD load, 0TE, , o'r is the AC current transformer, D is the diode rectifier circuit, and r is the resistor.

81 to 8 are thyristor type switching elements.

D1 to D. each indicate a diode.

During normal operation, the current 1L flowing through Klfi, load If 1L of current is flowing through the 8 power supply phases through the
, detects a current of magnitude 1L in the direction indicated by the arrow 1Ac in the figure, and AC current transformer OT detects a current of magnitude 1x in the direction 11Y - opposite to the direction of the arrow IAo in the figure. I will do it. Therefore, the diodes DI and Ds in the diode rectifier circuit are electrically connected.

A voltage corresponding to a current proportional to the load current fILILK is generated across the resistor r. General KJ phase AC power supply R18,
Current flowing in each phase 'Ae-! l#tAe-s
e'AC-T #C is a three-phase equilibrium condition, i.e. '10-1
＋ 'A(1-1+ 'AC-? ” ' ・・・・・・
- Since (1) holds true, the current flowing in the Te phase is the R phase.

From the a-phase current (1), it is arbitrarily determined.

Therefore, as an AC current transformer, it is sufficient to prepare OT, 0TE, and other tips.

The current XL (-Xl(2) a comparator 01KLD negative 1N compared with the current command value B, the deviation asC-X knee XL) proportional to the load current 1LK detected in this manner is sent to the current control circuit IOK. . The output signal of the current control circuit 0 is sent to the gate control circuit G (1), and the firing phase of the O switch elements 81 to 8 in the power converter SS is controlled.

The load current 1L is controlled to increase the load wire command value X\)K.

Next, consider a case where the switching element 82 is short-circuited and destroyed, causing a short-circuit to the power supply.

The current flows from the power supply R phase through the switching element 81° and the switching element Bm (all broken) through the 8-phase power supply circuit. In this case, although the power supply is short-circuited, the transformer TH
Due to leakage inductance, wire inductance, etc., the above short-circuit current does not become large all at once.The short-circuit current XAc detected through the diode rectifier circuit
The setting value of the overload current setting device 00H is “20” by the company comparator 01.
When the deviation 'l (="Aa-I:c) becomes positive 0fIIIK, the main power switch MOK open command signal is issued from the main power open controller MOO. Note that 8 is an analog switch. Then, when the deviation a becomes a positive value, %11 is given to the output.

When the main power switch C is opened in this way, if the load LOAII is an inductive load, the load LOADK
There is no path to discharge the stored energy with a load current of 1°, and an excessive voltage is generated across the main power switch MO.As a result, the open command signal from the main power open controller MOO is In addition, power converter Bs
It is necessary to send an ignition signal to all switching elements 8-fold to B-, and to cause a load current of 1 Ltll to flow.

For this purpose, a gate control command device Goo is provided.

In the conventional failure detection device as described above, the setting value "AC" of the overcurrent setting device OCR must be set to a value that is t+m larger than the detected value of the maximum value of the load current 11.iL, and moreover, the current ripple current Considering the carvings and overload capacity, it was necessary to set it to a fairly large value.

Ninth, short-circuit current "AC takes time to reach the set value" and has the drawback of delay in giving the main power switch MOK opening command.Also.

The main power switch MO had to be opened while a fairly large It current was flowing, causing an arc.

This caused an increase in the open time and an increase in the capacity of the main power switch MO.

An object of the present invention is to detect a failure of a JIII element as soon as possible, and to issue a command to open the main power switch while the short circuit current flowing through the main power switch is still small. Our goal is to provide the following.

In this invention, if the deviation between the current detection value of the direct RII and the current detection value of the AC side exceeds a set value, it is detected that a failure has occurred, and a command to open the main power switch is given. and K., are trying to achieve the above objective.

Embodiments of the ζO invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram showing one embodiment of the present invention. The same parts as shown in FIG. 1 are denoted by the same reference numerals. 81 is a current shunt for detecting load current.

80 is an isolation amplifier, -01*'4 is a comparator, and VR is a deviation setter.

The load current 1L during normal operation is detected by the shunt BHK and inputted to one input terminal of the comparator 01 via the isolation amplifier xgo. On the other hand, the load current command value xH is input to the other terminal of the comparator C1, and its deviation 11
Accordingly, the firing phase of the switching element in the power converter 88 is controlled via the current control circuit ZC and the gate control circuit GO.

As shown in the circuit of FIG. 1, the deviation #i from the load current command value B can be calculated using the load current fIL1LK detected on the AC side and the proportionally large current xL.

The detected current value on the AC side is the difference between the detected values IL and O on the AC and DC sides using the comparator OsK, and the deviation (s+4
A,-! L) and the deviation setter VRK are also set at 9, and the comparator 04 outputs the difference between the good setting deviation at and O (=Lee 81). During normal operation, the detected value on the AC side, including current ripple. and the detection value xL on the DC side are the same (therefore, the deviation is 0 and tb, and the setting deviation ai) is negative for the small rounding difference. Because of ζO, the analog switch 8
does not operate and generates 1% OI output.

Next, consider the case where switching element a is short-circuited and destroyed. The fIi circuit current flows from the IFI phase to the power supply 1 phase OIM path via Chinda element 8- and switching element @1 (short-circuited). Figure 3 shows the change in the short-circuit current AC detected on the AC side around the time when the short-circuit current RO starts flowing. It is completely equal to the direct iue detection value xL, that is.

Even if the load voltage is @LLK, there is a pull, and the detected value of the 4° AC value is also the same, so a pull is generated.

xAc and xL#i completely match. Therefore, 1 at time t
3 (-work..-work L) -〇 ・・・・・・(
) is established, and the output of analog switch and chim day is %, 7
It becomes 1. The short-circuit current begins to flow - ``AC becomes I, so large υ, and am (-!AC-IL,)〉O...-(J), and at time t1 it exceeds the deviation set value at, the analog switch is activated. A8 generates an output signal of %11, and main power release controller M
Give the main power switch MOK open command via OO.

Here, the deviation setting value 1 can be a value of several percent of the maximum value of the load current 1L, because it is not affected by the ripple component of the load current 1L and the load current IL stiffness K is not related, so the overload This is because a small deviation setting value is sufficient even in a design that takes into account tolerance.

As shown in FIG. 3 at the same time, the conventional fault detection device detects an overcurrent setting value of 4kc and an AC side detection value.

Engineering. . >Engineering;.・The time when the relationship between song and (see) is established, that is, time t! Main power switch with MOK
He had given the command to open. On the other hand, in the device according to the present invention, the opening command can be given to the main power switch MC at time t3, so the power supply can be opened before the current flowing through the main power switch MOK becomes large. In Figure 3, MOa
, Mob indicate the state of the open command of the main power switch MO according to the conventional type and the present invention, respectively. This is K
This prevents the spread of failures, and also achieves excellent effects such as reducing the main power switch capacity, shortening the opening time, and preventing arc-free opening.

In the above embodiment, a current shunt 811 and an isolation amplifier ISO were used to detect the DC side load current IL, but the present invention is not limited to this. For example, a DC current transformer may be used. can also be detected in the same way. Furthermore, the present invention can be applied not only to the thyristor power conversion device for converting alternating current to direct current shown in the above embodiment, but also to a wide range of power conversion devices such as static Leonard devices and cycloconverters.

[Brief explanation of drawings]

FIG. 7 is a block diagram of a conventional failure detection device for a static power converter, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a time chart for explaining the present invention in detail. . R,II,? ...3-phase AC power supply terminal 1MO...main power switch, 8B...power converter, LOAD...load. OTRr 0T11...AC current transformer, 8T...current shunt. 180...Isolation amplifier, 01-04...Comparator, v
R... Deviation setter, As... Analog switch, I
O...Current control circuit, MOO...Main power supply open controller. Goo...Gate control command device.

Claims (1)

[Claims] A first detector for detecting the input side Ot current of the static bath power converter, a main detector for detecting the output side current, and output signals of the first detector and the second detector. A first comparator that outputs a deviation signal when the static bath power converter does not output a KFi deviation signal during normal operation but outputs a deviation signal when a failure occurs; and a deviation setting device that sets a predetermined standard deviation. , a second comparator that compares the deviation signal from the first comparator and a reference deviation signal from the deviation setter and generates an output signal when the deviation signal exceeds the reference deviation signal; A failure detection device for a static bath power converter, comprising: