JPH05111143A - Protector for ac/dc converter - Google Patents

Abstract

PURPOSE:To prevent the burning of a snubber circuit part accompanying the increase of the snubber circuit heat loss in the case that the operation at and around alpha=90 deg. continues, in an AC/DC converter. CONSTITUTION:This protector has a means, which seeks the control angle alphaof an AC/DC converter based on the AC-side voltage, the DC-side voltage, and the DC-side current of the AC/DC converter, and a means, which seeks the loss of a snubber circuit by this control angle alpha. Moreover, this is a protector for the AC/DC converter, which is equipped with a means which seeks the allowable operation time by the loss property curve being determined by the ambient temperature and the cooling condition, and 1 a digital operation means 30 which outputs an alarm signal 31 or a trip signal 32 to outside in the case that the continuity time of the operation at and around alpha=90 deg. exceeds the allowable value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC / DC conversion device which prevents burnout of snubber circuit parts due to an increase in snubber circuit heat loss when the operation in the vicinity of α = 90 ° is continued in an AC / DC converter. The present invention relates to a device protection device.

[0002]

2. Description of the Related Art Conventionally, in the operation of an inverse converter of an AC / DC converter, even if an operation near α = 90 ° occurs due to a commutation failure or the like, this state is usually recovered in a few cycles, and the snubber circuit loss is a problem. It wasn't seen.

However, the power situation has deteriorated due to the recent increase in switching power equipment such as inverter air conditioners. Therefore, the chance of inducing commutation failure of the inverter based on the waveform distortion increases, and the responsibility for the snubber circuit becomes more severe than before.

On the other hand, the snubber circuit loss varies depending on the ambient temperature and the cooling conditions, and the allowable operating time varies depending on the above parameters, but the time has not been sufficiently calculated.

[0005]

In view of the above situation, the present invention calculates the heat loss of the snubber circuit every moment, and especially when the operation for a long time near α = 90 ° continues, the snubber circuit burns out. It is an object of the present invention to provide a control device for an AC / DC converter that can externally display an alarm or output a trip signal as necessary to prevent the above.

[0006]

In order to achieve the above-mentioned object, the present invention provides a snubber provided in a semiconductor device constituting a converter in an AC / DC converter based on an operation control angle, an AC voltage and an overlapping angle of the converter. A means for obtaining the heat loss of the circuit, a means for obtaining the allowable operating time according to the ambient temperature and cooling conditions from the predetermined heat loss-operating allowable time characteristic curve, and the operation in the vicinity of the controller α = 90 ° continues. However, when the operation allowable time is exceeded, a means for displaying an operation alarm or outputting a device trip signal is provided.

[0007]

According to the present invention thus constructed, α =
When the operation duration near 90 ° exceeds the allowable time calculated from the loss of the snubber circuit, an alarm display or trip is output to the outside to prevent the snubber circuit parts from burning and prevent the AC / DC converter from operating. It is possible to prevent obstacles that stop driving.

[0008]

1 is a block diagram showing an embodiment of the present invention.
0 is a reverse conversion bridge, 11 is a snubber circuit resistance, 12 is a snubber circuit capacitor, 13 is a transformer for interconnection, 20 is a DC voltage detector, 21 is a DC current detector, 22 is an AC voltage detector, and 30 is a digital. Arithmetic circuit, 31 is a display panel, 32
Indicates a trip signal, 100 indicates a DC bus, and 200 indicates an AC bus.

FIG. 1 shows a normal AC-DC converter, which operates an inverse conversion bridge 10 to supply electric power on the DC bus 100 side.
This is a system that transmits power to the AC bus 200 side. In this case, generally, the AC-DC converter performs power conversion by switching, and as an example, a voltage of several hundred KV is applied to the arm forming the inverse conversion bridge 10. Such a sudden voltage is applied, and due to the transient high voltage,
To prevent the elements that make up the arm from being damaged,
A snubber circuit is provided. The snubber circuit, together with an anodic reactor (not shown), shares the applied voltage and prevents an excessive voltage from being applied to the element. However, in the snubber circuit, since charging and discharging are repeated depending on whether the thyristor is on or off, heat is generated in the resistance portion. Loss of snubber circuits generally, P = K1 · Cd · Vs 2 [Sin ² α + sin ² (Α + u)] ... It is a function of the AC voltage Vs and the control angle α obtained by (1). On the other hand, the control angle α is obtained in the AC / DC converter by the following relationship: Ed = 1.35Vscosα- (1/2) XiId (2) Further, the overlapping angle u can be obtained by u = K2. (Id / Ed) (3). K1 in the equation (1) and K2 in the equation (3) are constants. From the equation (2), if EdVs and Id are known, the control angle α can be obtained. (Xi is known.) Also, u can be obtained from the equation (3). Therefore, the loss P of the snubber circuit can be obtained from the control angle α and the overlapping angle u using the equation (1).

On the other hand, the loss P of the snubber circuit and the allowable operation time generally have a relationship of anti-time characteristic, and as the characteristic temperature of FIG. 2 increases, the ambient temperature becomes higher or the cooling condition becomes worse. The curve moves downward as shown by the arrow.

As an example, when a failure such as a commutation failure occurs in the inverse conversion device, the control angle α is changed from the normal operating angle of 150 ° to 140 ° to 90 ° in order to widen the margin angle.
Move to °. In such an operation near α = 90 °, the loss P reaches the maximum according to the equation (1). However, usually
The commutation failure stops in 1 to 2 cycles and the loss rarely increases.

However, when the commutation failure continues for a long time due to the voltage waveform distortion due to the recent deterioration of the electric power situation or for some other reason, the operation continues at about 90 °, the loss increases, and the heat loss increases. The stress may burn the resistance component. Therefore, it is necessary to always calculate the allowable operation time.

The digital arithmetic unit 30 performs this monitoring function and calculates the loss from the DC voltage Ed, the DC current Id, and the AC voltage Vs according to the equations (1), (2), and (3). Next, from the loss P, the allowable operating time in the case where the operation near α = 90 ° occurs using the loss-allowable time characteristic curve of FIG.

By the way, the characteristic curve generally differs depending on the ambient conditions. That is, the permissible time varies depending on the ambient temperature, the cooling condition, or the day and night season. Therefore,
The digital arithmetic unit 30 stores in advance a characteristic curve when these conditions change, and calculates the allowable time from moment to moment depending on the ambient temperature and cooling conditions (not shown). However, if the operation in the vicinity of α = 90 ° continues and the predetermined allowable time is exceeded, the alarm signal is directly displayed on the display panel 31 or the trip signal 32 is output as necessary. Therefore, even if the operating conditions change, the snubber circuit can be prevented from being burnt out by the operation of the digital operation device 30.

In the above description, the inverse converter side of the AC / DC converter is taken as an example, but the operation near α = 90 ° is also performed on the forward converter side. That is, during the inverter side bypass pair operation at the time of an accident or stop, the forward converter side is set to an operating state near α = 90 °. The condition of the snubber circuit on the forward converter side in such an operation is exactly the same as the above-described operation, and the present invention can also be applied to the forward converter side.

In the above description, the operation control angle α is
Although the example calculated using the equation (2) is shown, however, since the recent digital control device controls the control angle α itself, the control angle α can be directly calculated without using the equation (2). You can use it as you know it.
Further, the value on the AC side of the direct converter is used as the AC voltage Vs used in the above equations (1) and (2), but if it cannot be detected from this place, tap position information of the interconnection transformer 13 23, the value obtained from the transformer primary side AC voltage detector 24 may be used.

[0017]

As described above, according to the present invention, in the AC / DC converter, due to the failure of commutation or some other cause,
When the operation near α = 90 ° continues and the loss of the snubber circuit increases, the loss is
Since the operating permissible time is monitored using the operating time characteristic curve, when the operating time exceeds the permissible time, an alarm or a trip signal can be output as necessary. Therefore, it is possible to avoid the operation stop of the converter due to the burnout of the semiconductor element due to the burnout of the snubber circuit.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic curve diagram showing the relationship between the loss and the operation allowable time in the snubber circuit.

[Explanation of symbols]

10 ... Inverse conversion bridge 11 ...
Snubber circuit resistance 12 ... Snubber circuit capacitor 13 ...
Transformer for interconnection 20 ... DC voltage detector 21 ...
DC current detector 22 ... AC voltage detector 23 ...
Tap position information 24 ... AC voltage detector 30 ...
Digital arithmetic unit 31 ... Display panel 32 ...
Trip signal 100 ... DC bus 200 ...
AC bus

Claims (1)

[Claims] 1. In an AC / DC converter, a means for obtaining a heat loss of a snubber circuit provided in a semiconductor element forming the converter based on an operation control angle, an AC voltage, and an overlapping angle of the converter, and a predetermined unit. Heat loss-means for determining the allowable operating time according to the ambient temperature and cooling conditions from the operating allowable time characteristic curve, and the operation error when the operation near the controller α = 90 ° continues and exceeds the allowable operating time. A protection device for an AC / DC converter, comprising means for displaying a system indication or outputting a device trip signal to prevent burning of the snubber circuit.