JPS61293176A - Overvoltage suppressor circuit of power converter - Google Patents

Abstract

PURPOSE:To improve the protecting function of an inverter by using an input DC smoothing condenser for absorbing an excess energy. CONSTITUTION:The output of a power converter 1 is supplied through a power converter 2' such as an inverter to a load 3. Capacitors 226, 228 are connected through fuses 221, 225, 223, 227 between the output buses P and N of the converter 1. The series circuit of the fuse 225 and the capacitor 226 is connected in parallel with power elements 21, 22 connected in series, and the series circuit of the fuse 227 and the capacitor 228 is connected in parallel with power elements 25, 26 connected in series. For example, even if the element 25, 26 connected in series. For example, even if the element 21 is shortcircuited so that the fuse 221 is melted, the excess voltage and the abnormal energy are bypassed through the diode 23, the fuse 225 and the capacitor 226, thereby suppressing the overvoltage to the element 22.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to power conversion devices such as inverters, and in particular, suppresses overvoltage to power elements not only by using snubber circuits but also by using snubber circuits.
By having the DC input smoothing capacitor also share the load,
This invention relates to an overvoltage suppression circuit for a power conversion device that improves the reliability of the device.

[Conventional technology and problems]

In recent years, large-capacity transistors or gate turn-off thyristors (GTO thyristors) have been frequently used as power elements in uninterruptible power supplies for computers and energy-saving power converters, and the switching of these power elements has increased the In order to suppress overvoltage, a snubber circuit is installed near the power element to suppress overvoltage.

In the overvoltage suppression circuit of this type of power conversion device, in order to simplify the circuit, a method has often been used in which the overvoltage suppression circuit is inserted between the input power sources of the power conversion device.

However, the above-mentioned power supply device is normally driven by connecting two or more power elements in series between the input power sources and switching them alternately. This can be suppressed with a snubber circuit, but if one of the power elements connected in series generates excessive energy due to damage, the snubber circuit alone cannot absorb the energy, and this prevents normal output from occurring. This will lead to problems such as deterioration and even damage to the power elements.

Figure 2 shows a basic power conversion device, where 1 is a forward converter that receives AC power and converts it into DC power, 2 is a power converter such as an inverter, 3 is a load, and 4 is a forward converter 1 Fuse 5 is a smoothing capacitor for smoothing the output of the forward converter 1, which is used to protect the output buses P and N from short-circuiting. Here, P
A+, PA2 is the power conversion part and 8N1.8N
2 indicates a snubber circuit, for example, the power conversion part PA1
consists of power elements 21°22, and snubber circuit 8N+
is diode 211°, capacitor 212 and resistor 2
This is an example consisting of 13 pieces.

In other words, the overvoltage suppression function is applied to the power conversion part PA+.

To explain the power element 21 in the inverter circuit of PA2 and the snubber circuits 8Ns and 8N2, when an overvoltage is generated between the collector and emitter of the power element 21, that voltage is applied to the diode of the snubber circuit SN+. 211. The capacitor 212 is bypassed through the diode 24, and the overvoltage applied to the gravity element 21 is absorbed and suppressed by the capacitor 212, so that the voltage across the smoothing capacitor 5 (output bus P, N
(fit pressure between).

Such an inverter circuit has an aspect that is difficult to coordinate in practice, that is, protection against short-circuit failures, including the power elements 21, 22, 25, 26 and diodes 23, 24, 27, 28, depends on the heaters 4. Since the fuse 4 is located in the common part of the DC current, W-M also becomes large and the power elements 21, 22, 25, 26
This makes it impossible to coordinate protection.

For this reason, a circuit as shown in FIG. 3 has been proposed and adopted.

FIG. 3 shows a conventional power converter, in which 2' is a power converter, 4' is a fuse, and 5' is a smoothing capacitor. In the figure, the same reference numerals as in FIG. 2 indicate the same components. Here, the power converter 2' has fuses 221 on the output bus P' side and the output bus N side of each DC link as shown in the figure.
222, 223, and 224 are attached.In this way, coordination with the power elements was attempted by arranging the four fuses, but in the example shown in FIG. If the fuses 221, 222, 223, and 224 blow out due to damage to power elements, the overvoltage generated by the fuse blowout cannot be handled by the snubber circuit SN1.8N2, and even normal power elements may be damaged. arise.

[Means for solving problems]

With the recent increase in demand for uninterruptible power supplies and variable voltage variable frequency power supplies, the present invention has been developed by connecting input DC smoothing capacitors in series in order to suppress overvoltage of power elements incorporated in these devices. This device improves the protection function of the inverter circuit by connecting it to both ends of the power element and using the input DC smoothing capacitor not only for smoothing, which is its original duty, but also for absorbing excessive energy. It is a manifestation.

[Effect]

The present invention uses an input DC smoothing capacitor to suppress unnecessary overvoltage from being applied to other power elements not only during normal operation but also due to malfunction of the power element. By doing so, it is possible to minimize the spread of defects in the inverter circuit. The present invention is described below:
A! will be described in detail with reference to the drawings.

〔Example〕

FIG. 1 shows the main part configuration of an embodiment of the present invention similar to FIGS. 2 and 3, and 2'' is a power conversion section. The same reference numerals as in the figure indicate parts having the same function.Here, the power converter 2'' is the third
The fuse 221 is connected in the same way as the power converter 2' shown in the figure.
, 222 , 223 , 224 , and further includes a fuse 225 and a capacitor 226 . A fuse 227 and a capacitor 228 are attached.

That is, in FIG. 1, the smoothing capacitor 5 connected between the output bus lines P and N as shown in FIGS. 2 and 3 and the smoothing capacitor 5' connected between the output bus lines P' and N as shown in FIGS. are divided into capacitors 226 and 228, and fuses 225 and 227 for short circuit protection are added to the capacitors P7 226 and 228, respectively. Katsu Hee's 225
The series circuit of fuse 227 and capacitor 226 is connected in parallel to power elements 21 and 22 connected in series, and the series circuit of fuse 227 and capacitor 228 is connected in parallel to similar power elements 25 and 26.

Therefore, with this connection configuration, even if a problem such as a short circuit occurs in the power element 21 and the heater 221 blows out, the diode 23. Fuse 22
5. Overvoltage and abnormal energy are bypassed through capacitor 226, and overvoltage to power element 22 can be suppressed.

〔Effect of the invention〕

As described above, the present invention is not only effective in suppressing overvoltage during normal operation, but also absorbs excessive surges when the arm fuse of the DC link is blown. Furthermore, by dividing the input DC smoothing capacitor, it is possible to balance the power distribution of the DC stage due to the increase in the capacity of the device, and it goes without saying that this is a useful feature that contributes to the reliability and stable operation of the device.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a main part configuration of an embodiment of the present invention, and FIGS. 2 and 3 are circuit diagrams showing a basic power converter and a conventional power converter, respectively. 2, 2', 2''...Power conversion section, 21, 2
2, 25, 26... Power element, 4, 4'
, 221, 222, 223, 224° 225 , 22
7...Fuse, 226, 228...
Capacitor, PAI, PA2...Power conversion part, SN+, SN2...Snubber circuit.

Claims (1)

[Claims] A pair of power conversion parts in which two series-connected power elements that perform alternate switching operations are connected via a fuse between the DC power sources, and power generated by connecting two or more of the pair of power conversion parts in parallel. An overvoltage suppression circuit for a power conversion device, characterized in that the conversion device includes a DC smoothing capacitor connected in parallel for each of the pair of power conversion parts, and the DC smoothing capacitor is configured to have an overvoltage suppression function.