JP2563806B2 - Arm short circuit detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to an arm short circuit detection device for detecting a short circuit between an upper arm and a lower arm of an inverter.

[Conventional technology]

FIG. 2 is a diagram showing a simplified circuit of an upper and lower arm short circuit detection device for a GTO thyristor inverter, which is published in, for example, Mitsubishi Electric Technical Report Vol.58.No.12.1984. In the figure, 1 is a chemicon connected to both ends of a DC power supply (not shown), 2 and 3 are GTO (gate turn off) thyristors,
4,5 are freewheeling diodes, GTO thyristors 2 and 3 are connected in series, and freewheeling diodes 4,5 are connected in antiparallel to the GTO thyristors 2 and 3, respectively. These are provided for each of the U phase, V phase and W phase, and FIG. 2 shows only the U phase. The GTO thyristors 2 and 3 are the main components of the DC-AC converter.

20 is a DCPT (transformer for direct current instrument), which is connected in parallel to the series circuit of the GTO thyristors 2 and 3. Reference numerals 21 and 22 are anode reactors for suppressing an excessive current when the upper and lower arms are short-circuited, and are connected between the GTO thyristor 2 and 3 anand and the above DC power source between the positive side bus L1 and the negative side bus L2. ing.

Next, the operation will be described. Upper GTO during steady operation
Since either the thyristor 2 or the lower GTO thyristor 3 is off, the voltage detection value of the DCPT 20 is equal to the voltage of the chemicon 1.

When an arm short circuit occurs, both the upper GTO thyristor 2 and the lower GTO thyristor 3 are turned on, and the voltage across the DCPT 20 becomes zero. Thus, the occurrence of arm short circuit is detected.

[Problems to be solved by the invention]

Since the conventional arm short-circuit detecting device is configured as described above, it has a drawback that it cannot be applied when the DC voltage changes significantly.

The present invention has been made in order to solve the above problems, and an object thereof is to obtain an arm short circuit detection device capable of detecting an arm short circuit even when the DC voltage changes.

[Means for solving problems]

The arm short-circuit detecting device according to the present invention detects the arm short-circuit by penetrating the positive and negative DC buses of the DC current transformer in opposite directions for each arm pair.

[Work]

Since the DC current transformer of the present invention penetrates the positive and negative DC buses in the primary winding in opposite directions, the arm short-circuit state is detected even when the upper power semiconductor and the lower power semiconductor are short-circuited.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 10 is a DC current transformer (hereinafter referred to as DCCT) as a converter, and this DCCT 10 is between the positive side of a DC power source (not shown) and the anode of a GTO thyristor 2 as a power semiconductor. Bus L1, DC power supply, and GTO thyristor 3
The negative side bus L2 between the cathodes is inserted, and the DC buses L1 and L2 are penetrated by the DCCT 10 so as to be in opposite directions. Other configurations are the same as those in FIG. 2, and the same parts as those in FIG. 2 are denoted by the same reference numerals.

The AC output for one of the three phases is supplied to the load (not shown) from the connection point between the GTO thyristors 2 and 3. Further, in FIG. 1, the illustration of the anode reactors 21 and 22 shown in FIG. 2 is omitted.

Next, the operation will be described. Positive side bus L1, negative side bus L2
The by penetrating in the opposite directions DCCT10, arm short-circuit current I _s flowing out Chemicon 1, the primary winding of the two DCCT10 penetrating in the same direction. On the other hand, if the load current is I _L , the detected current I _{ct of the} DCCT 10 is as follows.

I _ct = 2 × I _s ± I _L (1) From this, even if the current is reversed, I _ct ≧ I _s (2) when I _s ≧ I _L , and the short-circuit current can be detected. Is.

Although the pair of upper and lower arms has been described in the above embodiment, three identical circuits are required in the case of a three-phase bridge. Further, the power semiconductor that converts direct current to alternating current by on / off operation may be of any type as long as it has a switch function, such as a thyristor transistor. further,
The converter mainly composed of the power semiconductor may be a current type.

〔The invention's effect〕

As described above, according to the present invention, the detection of the arm short circuit is performed by the DC in which the positive side bus bar and the negative side bus bar are passed in opposite directions for each phase.
Since it is configured to use CT, the device is inexpensive, short-circuits on both the upper side and the lower side of the arm can be detected, and high performance can be obtained. Further, the DCCT has an effect that it can be used as an output current device in a normal state and as a short circuit detector in an abnormal state.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an arm short circuit detecting device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional arm short circuit detecting device. 2, 3 are GTO thyristors (power semiconductors), 10 are DCCT (converters), L1 is the positive side bus, and L2 is the negative side bus. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. An arm short-circuit detecting device provided in a converter for converting direct current into alternating current by using power semiconductors in the upper arm and the lower arm, respectively, for each arm pair of the upper arm and the lower arm. A DC current transformer, which is provided for each phase, has a positive side bus bar and a negative side bus line that supply DC power to the conversion device and are penetrated in opposite directions to detect a short circuit between the upper arm and the lower arm. Arm short circuit detection device.