JPH08242589A - Power converting equipment - Google Patents

Abstract

PURPOSE: To provide a power converting equipment capable of stably continuing the operation of a fuel cell without stopping the power supply to other unit after one of the units fails, in the case where the power is being supplied with multiple outputs from the output of the fuel cell. CONSTITUTION: A DC load 5 is connected to the output of a fuel cell 1 through a DC converting equipment 3, and also an AC load 4 linked with a commercial power supply 6 is connected through an AC power converting equipment 2 having an AC converting section 20, a linked reactor 22, a circuit breaker 21, an anomaly detecting section 23, a protecting & controlling circuit 24 and a drive circuit 25. An input overvoltage preventing circuit 26 comprising a high- speed opening type short-circuit switch 264 connected in parallel to a reverse- current preventing diode 263 is connected to the input side of the AC power converting equipment 2. Accordingly, any rise in the output voltage of the fuel cell 1 can be prevented thereby permitting power supply from the fuel cell 1 to a DC converting equipment 3 even when the AC power converting equipment 2 stops.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply system for supplying a DC output of a fuel cell to a DC load and an AC load, and supplies the AC load to the AC load due to an abnormality generated in the output of the AC power converter or a commercial power supply system. The present invention relates to a highly reliable and stable power conversion device that continues to supply the output of a fuel cell to a DC load even when power supply is stopped.

[0002]

2. Description of the Related Art In a fuel cell, hydrogen obtained by reforming city gas or the like is chemically reacted with oxygen in the air to directly take out electric energy and also effectively generate thermal energy accompanying the reaction. By using it, a clean and highly efficient cogeneration system can be constructed. When both electric energy and thermal energy are used, the maximum thermal energy was obtained when the electric output was maximum. Therefore, in order to operate the fuel cell at maximum efficiency, the electric output of the fuel cell is operated at a constant rating. The method is taken. In addition, the method of configuring the power supply system in the case of using the electric output of the fuel cell is to convert the DC output of the fuel cell into AC power by the AC power converter and supply the power to the AC load in cooperation with the commercial power supply. Although the method is generally used, since the output of the fuel cell is a DC voltage, it is higher by converting the DC output of the fuel cell into the DC voltage required by the load and supplying the power to the DC load. Conversion efficiency is obtained. When constructing a power supply system, which power supply method should be used should be selected depending on the capacity of the AC and DC loads, but a method of combining AC power supply and DC power supply from the fuel cell output is also used. .
FIG. 6 shows a configuration example of a power conversion device used in such a power feeding system that uses both AC power feeding and DC power feeding. In FIG. 6, 1 is a fuel cell, 2 is an AC power converter for converting DC into AC and supplying power to an AC load, 3 is a DC converter for supplying power to a DC load, 4 is an AC load, and 5 is DC load, 6 commercial power supply, 20 AC conversion unit composed of conversion element for converting DC to AC, 21 circuit breaker, 22
Is an interconnection reactor, 23 is an abnormality detection unit, 24 is a protection / control circuit, 25 is a drive circuit, and 26 is an input overvoltage prevention circuit. The input overvoltage prevention circuit 26 includes a discharge switch 261 and a resistor 262. Further, FIG. 7 shows a configuration example of the AC converter 20 of the AC power converter 2 of FIG.
In FIG. 7, 11 to 16 are conversion elements, and 31 to 36.
Is a diode, 21 is a circuit breaker, and 22 is an interconnection reactor.

In such a conventional power supply system configuration, when an output of the AC power converter 2 shown in FIG. 6 causes an overcurrent or abrupt phase change, frequency fluctuation, overvoltage, undervoltage, etc. in six commercial power supply systems. Detects an anomaly by the anomaly detector 23 and sends an anomaly signal, and the protection / control circuit 24 turns off the drive signal of the drive circuit 25 to stop the operation of the AC power converter 2 and open the circuit breaker. The breaker 21 is opened by the signal.

However, when the operation of the AC power converter 2 is stopped during the above-mentioned abnormal operation, the operation shown in FIG.
Since the conversion elements 11 to 16 shown in (1) are gated off, the opening time of the circuit breaker 21 for mechanically cutting off and the gate off time are deviated from several tens ms to one hundred and several tens ms. Therefore, during the period from when the conversion elements 11 to 16 are gated off to when the circuit breaker 21 is opened, the energy stored in the interconnection reactor 22 and the commercial power supply 6
The inflow energy from the
There may be a reverse flow to the input side via the diodes 31 to 36 connected in parallel with 6. In this case, an overvoltage is generated at the input point A of the AC power converter 2 of FIG. 6, so that the fuel cell 1 and the conversion elements 11 to 16 and the elements of the DC converter 3 are prevented from being destroyed, and the conventional circuit is discharged. With the input overvoltage prevention circuit 26 composed of the switch 261 and the resistor 262, when the DC voltage at the point A exceeds the set voltage, the discharge switch 261 is turned on to consume the energy flowing into the input side and suppress the overvoltage. are doing.

[0005]

FIG. 8 shows a protection operation at the time of detecting an abnormality of the power supply system according to the conventional technique. In FIG. 8, (1) is the voltage at point A in FIG.
(2) is the input current I ₁ of the AC power converter 2, and (3) is the input current I ₂ of the DC converter 3. The output of the fuel cell 1 is supplied from the AC power converter 2 in parallel with the commercial power supply 6 to the AC load 4, and the DC converter 3 supplies DC power to the DC load 5. When abnormalities such as overcurrent or sudden phase change, frequency fluctuation, overvoltage, undervoltage, etc. occur in the system of the commercial power supply 6 at the output of 2, drive through the protection / control circuit 24 by the signal detected by the abnormality detection unit 23. The drive signal of the circuit 25 is stopped and the AC converter 20 is gated off. The AC power converter 2 is stopped by the gate off of the AC converter 20, and the input current I ₁ of the AC power converter 2 becomes zero. At the same time, the protection / control circuit 24 is activated by the abnormality detection signal to open the circuit breaker 21.

However, since there is a time lag from the gate-off of the AC conversion unit 20 to the opening of the circuit breaker 21, the energy stored in the interconnection reactor 22 and the inflow energy from the commercial power source 6 are superposed during this period. Side, and the input current I ₁ flows in the opposite direction to return to the fuel cell 1 side, the voltage at point A rises, and the circuit breaker 21 opens, so that the input current I ₁ becomes zero and point A Voltage drops. Here, from the gate-off of the AC converter 20 to the breaker 2
In the period until 1 opens, the voltage at point A is higher than the output voltage of the fuel cell 1 and is in the cut-off state,
Input current I ₂ of the DC converter 3 supplied from the fuel cell 1
No longer flows, and the voltage at the point A drops at the same time when the circuit breaker 21 is opened, causing a sudden flow. If the input overvoltage prevention circuit 26 shown in FIG. 6 is not provided in FIG.
Although the overvoltage at the point is suppressed to some extent, it is difficult to make it equal to or less than the output voltage of the fuel cell 1.
Therefore, such a change in the input current I ₂ causes the supply to the DC load to be temporarily interrupted and causes a rapid power fluctuation in the fuel cell 1. In particular, the amount of the input current I _{2 to} the DC converter 3 is shared. If it is large, it has been an obstacle to the reliability of the power supply system and the prevention of overvoltage of the fuel cell.

The present invention was devised to solve the above problems, and an object thereof is to provide an overcurrent or a commercial output at the output of an AC power converter while supplying power from a fuel cell output to an AC load and a DC load. Raise the output voltage of the fuel cell even when an abnormality such as a sudden phase change, frequency fluctuation, overvoltage, or undervoltage occurs in the power supply system and the AC power converter stops and the power supply to the AC load is stopped. It is another object of the present invention to provide a safe and highly reliable power conversion device that can stably operate a fuel cell and supply power to a DC load without interruption.

[0008]

In order to achieve the above object, the present invention has an AC power converter and a DC converter connected in parallel to the output of a fuel cell, and a DC load is connected to the DC converter. The AC power conversion device is a power conversion device that is connected to supply DC power, converts the AC power into AC power, and links the AC power obtained from a commercial power supply to supply power to an AC load. The power conversion device connects the output of the fuel cell to the AC load via an AC conversion unit, an interconnection reactor, and a circuit breaker, and provides an abnormality detection point between the interconnection reactor and the circuit breaker and between the circuit breaker and the AC load. The abnormality detection point is connected to the abnormality detection unit, the output signal of the abnormality detection unit is input to the protection / control circuit, one of the outputs of the protection / control circuit is connected to the circuit breaker, and the other is output to the drive circuit. Connected to the AC power converter output overcurrent Properly phase sudden change in the commercial power system, frequency variation, overvoltage, when detecting an abnormality of the undervoltage, etc.,
In the power conversion device that operates the protection / control circuit in the AC power conversion device by the abnormality detection signal generated by the abnormality detection unit to stop the operation of the AC conversion unit and opens the output circuit breaker, A backflow prevention diode is connected in series in the forward direction to the input of the AC power converter, and a short-circuit switch which is closed in parallel with the backflow prevention diode when a start signal is sent and when the abnormality detection signal disappears is connected to detect the abnormality. Sometimes, it is characterized by having a means for opening the short-circuit switch at high speed after the AC power converter is stopped and before the breaker is opened.

In the power converter of the present invention, the abnormality detecting section for detecting an abnormality is provided as means for opening the short-circuit switch at high speed when the abnormality is detected.
Separately from the abnormality detection signal based on the abnormality detection such as the overcurrent of the AC power converter output or the sudden phase change in the commercial power supply system, the frequency fluctuation, the overvoltage, the undervoltage, etc., another detection value of a level lower than the abnormality detection signal Is provided, and the protection / control circuit is operated by a signal transmitted based on the other detected value, and the short-circuit switch is opened.

[0010]

With the above-mentioned means, the present invention provides an input overvoltage protection which is constructed by connecting a short-circuit switch which is closed when a start signal is sent to the input of the AC power converter and when the abnormality detection signal disappears, and a backflow prevention diode connected in parallel therewith. A circuit is provided so that when the output of the AC power converter outputs an abnormal current such as an overcurrent or a sudden phase change in the commercial power system, frequency fluctuation, overvoltage, undervoltage, etc. In order to suppress the rise in the input voltage of the AC power conversion device that occurs during the opening, the short-circuit switch is opened at high speed so that the reverse current prevention diode acts to cut the feedback current to the input. It is a thing.

As means for opening the short-circuit switch at high speed, the means for opening the conversion element of the AC converting unit by the abnormality detection signal for gate-off and a case of detecting the value lower than the abnormality detection signal are used. The signal to be sent is released.

Therefore, due to the operation of the above-mentioned input overvoltage prevention circuit, the above-mentioned operation is performed at the output of the AC power converter or the commercial power supply system in a state where the fuel cell output is supplying power to the AC load and the DC load. Even if an abnormality occurs and the AC power supply is stopped, the fuel cell output voltage can be suppressed from rising and the fuel cell operation can be stably continued to supply power to the DC load without interruption. , Has increased reliability.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. In the figure, the same parts as those described in the prior art of FIGS. 6 to 8 are designated by the same reference numerals. FIG. 1 is a block diagram showing an embodiment of the present invention. 1 is a fuel cell,
2 is an AC power converter for converting DC to AC to supply AC power, 3 is a DC converter for supplying DC power to a DC load, 4 is an AC load, 5 is a DC load, 6 is a commercial power supply, 2
0 is an AC conversion unit, 21 is a circuit breaker, 22 is an interconnection reactor, 23 is an abnormality detection unit, 24 is a protection / control circuit, 25 is a drive circuit, 26 is a backflow prevention diode 263, and an input short-circuit switch 264 is opened at high speed. The input overvoltage prevention circuit and 27 are activation signal generation circuits.

An AC power converter 2 and a DC converter 3 are connected in parallel to the output of the fuel cell 1, and a DC load 5 is connected to the DC converter 3 to supply DC power.
The AC power converter 2 converts the AC power into a commercial power supply 6
A power conversion device that supplies power to the AC load 4 by connecting with the AC power obtained from the AC power conversion device 2. The AC power exchange device 2 connects the output of the fuel cell 1 with the AC conversion unit 20, the connection reactor 22, and the circuit breaker 21. Connected to the AC load 4 via the interconnection reactor 2
2 and the circuit breaker 21 and between the circuit breaker 21 and the AC load 4 are provided with abnormality detection points, the abnormality detection points are connected to the abnormality detection section 23, and the output signal of the abnormality detection section 23 is input to the protection / control circuit 24. Then, one of the outputs of the protection / control circuit 24 is connected to the circuit breaker 21.
In addition, the other side is connected to the drive circuit 25, and an abnormality such as an overcurrent at the output of the AC power converter 2 or a sudden phase change in the commercial power supply system 6, a frequency variation, an overvoltage, an undervoltage or the like occurs, and the abnormality is detected. In this case, the protection / control circuit 24 of the AC power converter 2 is detected by the abnormality detection signal from the abnormality detection unit 23.
Is operated to gate off the AC converter 20 by the drive circuit 25 to stop the AC converter 20 and to open the output circuit breaker 21, and the AC power converter 2
Backflow prevention diode 263 between the input of AC and the AC conversion unit 20
Are connected in series in the forward direction, and a backflow prevention diode 263
The short-circuit switch 264 is connected in parallel with. Further, the short-circuit switch 264 is connected to the protection / control circuit 24 to receive a closing signal when the abnormality detection signal disappears, and also connected to the starting signal generating circuit 27 to receive a closing signal when the starting signal is generated.

The abnormality detecting section 23 detects the output of the AC power converter 2 and the AC voltage and AC current of the six commercial power source systems at the abnormality detecting point and converts them into a DC voltage level. In comparison with the DC voltage, the output is sent to the protection / control circuit 24 as an abnormality detection signal when the output exceeds a certain level.

The abnormality detecting section 23 of the AC power converter 2 shown in FIG. 1 will now be described with reference to FIG.
A brief explanation is added. In the figure, 231 is a comparator, 2
33 is a commercial power supply frequency detection point, and 234 is a reference frequency part, which is normally set to 47 Hz to 53 Hz (50 ± 3 Hz). When the commercial power supply frequency is within this range, it is the normal operating range, and the comparator 231 No signal is sent from the output of. Similarly, voltage detection and phase detection are also detected from the commercial power supply side. However, in the case of overcurrent detection, it is detected from the AC conversion unit side of the circuit breaker 21, but since the basic detection circuit is the same, it is omitted here. When the commercial power frequency deviates from the normal frequency range, the comparator 231 causes the reference frequency unit 2
In comparison with 34, the abnormality detection signal is sent from the output of the comparator 231 to the protection / control circuit 24. The abnormality detection signal corresponds to the signal X described later in the embodiments of the present invention.

Specific frequency detection and comparison methods include a method of directly comparing the detected frequency with a reference frequency and a method of once rectifying and converting to a DC voltage level for comparison. However, since it is the same, the description thereof is omitted here.

Input overvoltage prevention circuit 26 in this embodiment
The short-circuit switch 264 is closed when the activation signal of the AC power converter 2 is transmitted and after the signal based on the abnormality detection signal from the protection / control circuit 24 disappears, that is, normally, the output of the AC power converter 2 is output. When there is an overcurrent or abnormalities such as sudden phase changes, frequency fluctuations, overvoltages, and undervoltages in the six systems of the commercial power supply, it has a function to open at high speed by the abnormality detection signal. Therefore, when the AC power conversion device 2 detects an abnormality and stops, the backflow prevention diode 263 conducts, and when operating normally, the short-circuit switch 264 is closed. A method may be considered in which the backflow prevention diode 263 is always turned on and the short-circuit switch 264 is not provided. In this case, the backflow prevention diode 263 is always turned on, which causes a loss, and the backflow prevention diode 263 is always radiated. Fins are also required, which is not suitable for downsizing the device and improving efficiency.

The operation and action of the embodiment configured as described above will be described. 4 and 5 show an example of the operation at the time of abnormality detection as time on the horizontal axis. FIG. 4 shows an example of detection in the case of frequency fluctuations in a commercial power supply system, in which the vertical axis is the DC voltage level obtained by detecting an AC voltage and converting it in proportion to the frequency, and (a) is the frequency abnormality detection level, b) is the level before the frequency abnormality is detected, and (c) is the normal frequency level.
FIG. 5 shows the operation at the time of detection in FIG. 4, and (1) is the operation shown in FIG.
At point A, (2) at point B, (3) at input current I ₁ of the AC power converter, and (4) at input current I ₂ of the DC converter. The DC output of the fuel cell 1 is converted into AC power via the AC power converter 2 to convert the AC load 4
To the DC load 5 through the DC converter 3, the output of the AC power converter 2 causes an overcurrent or a sudden phase change in the system of the commercial power supply 6, a frequency fluctuation,
When a frequency fluctuation occurs in the system of the commercial power supply 6 among abnormalities such as overvoltage and undervoltage, first, in FIG. 4, the abnormality detection unit 23 detects the AC voltage of the system of the commercial power supply 6 from the abnormality detection point. Then, when the DC voltage level converted in proportion to the frequency reaches the frequency abnormality detection level of (a),
The protection / control circuit 24 outputs the signal X that outputs a signal compared with the reference DC voltage of the abnormality detection unit 23 as an abnormality detection signal.
Send to. With the signal X, the operation of FIG. 5 stops the drive signal of the drive circuit 25 via the protection / control circuit 24 and gates off the AC conversion unit 20. This AC converter 20
When the gate is turned off, the AC power converter 2 stops, and the input current I ₁ of the AC power converter 2 becomes zero. At the same time, the protection / control circuit 24 is activated by the signal X to open the circuit breaker 21. However, since there is a time lag from the gate-off of the AC conversion unit 20 to the opening of the circuit breaker 21, the stored energy of the interconnection reactor 22 and the inflow energy from the commercial power source 6 are superposed and flow to the input side during this period. Therefore, the voltage at point B rises. Here, the short-circuit switch 264 of the input overvoltage prevention circuit 26 is closed when the AC power converter 2 is operating normally, but is a signal X sent from the abnormality detection unit 23 that detects an abnormality when an abnormality occurs.
Thus, the protection / control circuit 24 is operated to open the short-circuit switch 264 at high speed. As a result, the rise in the input voltage of the AC power converter 2 is cut by the backflow prevention diode 263, so the voltage at point A, which is the DC output of the fuel cell 1, does not rise. Therefore, when an abnormality occurs in the output of the AC power converter 2 or the system of the commercial power supply 6, the AC converter 20 is gated off and stopped, and the breaker 21 is opened to input the input current of the AC power converter 2. While I ₁ becomes zero, the input current I ₂ of the DC converter 3 is kept constant, and interruption of power supply to the DC load 5 can be avoided.

Next, as another embodiment, a case where the input short-circuit switch 264 is opened at high speed will be described.
In the configuration of FIG. 1 and the AC power converter 2, when an output of the AC power converter 2 causes an overcurrent or a sudden phase change in the system of the commercial power supply 6, a frequency change, an overvoltage, an undervoltage, or the like, In addition to the signal X for detecting and transmitting an abnormality by the abnormality detecting unit 23, a function of transmitting a signal Y based on the detected value is provided with a detection value having a level lower than that of the abnormality detection signal.

Regarding the operation in this embodiment, an example of detection in the case where the commercial battery 6 system has frequency fluctuation will be described with reference to FIGS. 4 and 5. The DC output of the fuel cell 1 is converted into AC power via the AC power converter 2 to convert the AC load 4
To the DC load 5 through the DC converter 3, the output of the AC power converter 2 causes an overcurrent or a sudden phase change in the system of the commercial power supply 6, a frequency fluctuation,
Of the abnormalities such as overvoltage and undervoltage, when the frequency fluctuations occur in the system of the commercial power supply 6, the abnormality detection unit 23 in FIG. 4 detects the AC voltage of the commercial power supply 6 system from the abnormality detection point. When the DC voltage level converted in proportion to the frequency reaches the frequency abnormality detection level of (a), the signal X that outputs the signal compared with the reference DC voltage of the abnormality detection unit 23 as the abnormality detection signal is protected. It is sent to the control circuit 24. The operation of FIG.
The drive signal of the drive circuit 25 is stopped via the gate, and the AC converter 20 is gated off. The AC power converter 2 is stopped by the gate off of the AC converter 20, and the input current I ₁ of the AC power converter 2 becomes zero. Signal X again at the same time
Thus, the protection / control circuit 24 operates to open the circuit breaker 21. Since there is a time lag from the gate-off of the AC conversion unit 20 to the opening of the circuit breaker 21, during this period, the stored energy of the interconnection reactor 22 and the inflow energy from the commercial power supply 6 are superimposed and flow to the input side. The voltage at point B rises. Here, the short-circuit switch 264 of the input voltage prevention circuit 26 is closed when the AC power converter 2 is operating normally, but there is an abnormality in the output of the AC power converter 2 or the system of the commercial power supply 6. As an example, when a frequency fluctuation occurs in the system of the commercial power source 6, the abnormality detection unit 23 detects the AC voltage of the system of the commercial power source 6 in FIG. 4 and converts the DC voltage level in proportion to the frequency. Reaches a frequency abnormality detection level of (a), the signal X that outputs a signal compared with the reference DC voltage of the abnormality detection unit 23 as an abnormality detection signal is separately lower than the frequency abnormality detection level of (a) ( At the level before the frequency abnormality detection of b), the protection / control circuit 24 is operated by sending a signal Y that outputs a signal that is compared with the reference DC voltage of the abnormality detection unit 23, and the short-circuit switch operates at high speed. Action is to so as to open the pitch 264. By this operation, the rise in the input voltage of the AC power converter 2 is cut by the backflow prevention diode 263, so that the voltage at the point A, which is the DC output of the fuel cell 1, does not rise. Therefore, the AC converter 20 of the AC power converter 2 is gated off and stopped, the circuit breaker 21 is opened, and the input current I ₁ of the AC power converter 2 becomes zero. The input current I ₂ is kept constant.

Here, the abnormality detector 23 in another embodiment of the present invention will be briefly described with reference to FIG. 3 by taking the case of frequency abnormality as an example. 231, 23 in the figure
2 is a comparator, 233 is a commercial power source frequency detection point, 234,
235 is a reference frequency part 1 and a reference frequency part 2,
Reference numeral 6 is an AND circuit. The reference frequency part 1 of 234 is usually 47 Hz to 53 Hz (50 ± 3 Hz), and the reference frequency part 2 of 235 is 49 Hz to 51 Hz (5
It is set to 0 ± 1 Hz), and when the commercial power frequency is within this range, it is the normal operating range, 49 Hz to 51 H.
When it is less than z, it is in the normal operation range, and the comparators 231 and 231
No signal is emitted from the output of 32. Similarly, voltage detection,
Phase detection is also detected from the commercial power supply side. However, in the case of overcurrent detection, it is detected from the AC conversion unit side of the circuit breaker 21,
Since the basic detection circuit is the same, the description is omitted here. Commercial power frequency becomes abnormal and 49Hz-51Hz
If the range is exceeded, an abnormal signal (so-called Y signal) is sent from the comparator 232 to the protection / control circuit 24. This signal Y opens the input short-circuit switch 264. After that, when the commercial power supply frequency deviates from 47 Hz to 53 Hz, the comparator 231 operates, and the abnormality detection signal X from the comparator 231 is added to the abnormality signal Y from the comparator 232 via the AND circuit 236. It is sent to the protection / control circuit 24. The drive circuit 2 of the AC converter 20 is generated by this signal X.
The stop of the drive signal to 5 and the cutoff signal of the circuit breaker 21 are sent out. As a result, there is a time difference between the opening of the circuit breaker 21 and the opening of the input short-circuit switch 264, so that it is possible to solve the problem as in the above embodiment.

In this description, the abnormal signals X and Y are explained by using two signal lines, but it is naturally possible to send the abnormal signal by one signal line by changing the signal level of both signals.

As a concrete frequency detecting and comparing method, there are a method of directly comparing the detected frequency and a reference frequency, and a method of once rectifying and converting to a DC voltage level for comparison. However, since it is the same, the description thereof is omitted here.

As in the present embodiment, the short circuit switch 264 is operated so as to be opened at a high speed by the signal Y transmitted based on the detected value of the level lower than the signal X transmitted upon detecting the abnormal value. In the operation of the above-described embodiment, even if the opening time of the short-circuit switch 264 is delayed compared with the gate-off of the AC converter 20, the present embodiment is faster than the gate-off of the AC converter 20. Since the short circuit switch 264 can be opened, a more stable operation is possible.

Next, in the protection operation of the above embodiment,
9 and 10 show experimental operations comparing the case where the short-circuit switch 264 of the input overvoltage protection circuit 26 is not opened and the case where the short-circuit switch 264 is opened before the AC conversion unit 20 is gated off. FIG. 9 shows the operation when the short-circuit switch 264 is not opened. During the period in which the AC converter 20 is gated off and the circuit breaker 21 is opened, the AC power converter input current I ₁ becomes zero and the DC converter input. The current I ₂ also becomes zero once, and the DC converter input current I ₂ rapidly flows at the same time that the circuit breaker 21 opens. FIG. 10 shows the operation when the short circuit switch 264 is opened.
Although the AC power converter input current I ₁ becomes zero due to the gate-off of 0, the DC converter input current I ₂ is constant,
The interruption of the power supply to the DC load 5 is avoided.

As described above, in this embodiment, the overvoltage prevention circuit 26 provided at the input of the AC power converter 2 does not cause power loss during normal operation, and is parallel to the backflow prevention diode 263 when an abnormality is detected. The short-circuit switch 264 connected to is opened at high speed before the gate of the AC converter 20 is turned off, thereby preventing the output voltage of the fuel cell 1 which is the input of the DC converter 3 from rising.

Therefore, even if the AC power converter 2 stops and the supply of AC power stops when an abnormality occurs, the DC power can be continuously supplied from the fuel cell 1 without interruption, and the power to the fuel cell can be continuously supplied. Since the fluctuation can be suppressed to be small, it is possible to maintain the stable operation state of the fuel cell with high system reliability.

[0029]

As is apparent from the above description, the power converter of the present invention is connected to the output of a fuel cell to convert direct current to alternating current, and is connected to a commercial power source to supply alternating current power. , In a power supply configuration that uses both AC and DC power supply to supply DC power to the output of the fuel cell with a DC converter, an abnormality occurred in the output of the commercial power system or the AC power converter and the power supply to the AC load was stopped. In this case, the output voltage of the fuel cell can be prevented from rising by adding an input overvoltage protection circuit and control circuit consisting of a simple short-circuit switch and backflow prevention diode, and power can be supplied from the fuel cell to the DC load without interruption. It is possible to on the other hand,
Since it is possible to suppress the power fluctuations to the fuel cell to be small, there is an advantage that the reliability of the system and the fuel cell can be improved.

[Brief description of drawings]

FIG. 1 is a configuration explanatory view showing one embodiment of the present invention.

FIG. 2 is a configuration explanatory view showing an example of an abnormality detection unit of the present invention.

FIG. 3 is a configuration explanatory view showing another example of the abnormality detection unit of the present invention.

FIG. 4 is a characteristic diagram for explaining the operation of the embodiment of the present invention.

FIG. 5 is a characteristic diagram for explaining the operation of the embodiment of the present invention.

FIG. 6 is a configuration explanatory diagram showing an example of a conventional power conversion device.

FIG. 7 is a configuration explanatory view showing an example of an AC conversion unit of a conventional AC power converter.

FIG. 8 is a characteristic diagram for explaining the operation of the conventional power conversion device.

FIG. 9 is a characteristic diagram showing an example of an experimental operation when the input short-circuit switch of the present invention is not closed.

FIG. 10 is a characteristic diagram showing an example of an experimental operation when the input short-circuit switch of the present invention is closed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... AC power converter, 3 ... DC converter, 4 ... AC load, 5 ... DC load, 6 ... Commercial power source, 20 ... AC converter, 21 ... Circuit breaker, 22 ... Interconnection reactor, 23 ... Abnormality detection part, 24 ... Protection / control circuit, 25 ... Drive circuit, 26 ... Input overvoltage prevention circuit, 27 ... Start signal generation circuit, 11, 12, 13, 14, 15, 16 ... Conversion element, 31, 32 , 33, 34, 35, 36 ... Diode, 261 ... Discharge switch, 262 ... Resistor, 263 ... Backflow prevention diode, 264 ... Short circuit switch, 231, 232 ... Comparator, 236 ... AND circuit.

Claims (2)

[Claims] 1. An AC power converter and a DC converter are connected in parallel to the output of the fuel cell, and a DC load is connected to the DC converter to supply DC power, and the AC power converter is A power converter for converting to AC power and connecting to AC power obtained from a commercial power source to supply power to an AC load, wherein the AC power converter outputs the output of the fuel cell to an AC converter and an interconnector. Connect to the AC load via a reactor and a circuit breaker, provide an abnormality detection point between the interconnection reactor and the circuit breaker and between the circuit breaker and the AC load, and connect the abnormality detection point to the abnormality detection unit to detect the abnormality. The output signal of the detection unit is input to the protection / control circuit, one of the outputs of the protection / control circuit is connected to the circuit breaker, and the other is connected to the drive circuit, and an overcurrent or commercial power source is output at the output of the AC power converter. Abrupt phase change, frequency fluctuation, overvoltage, When an abnormality such as undervoltage is detected,
In the power conversion device that operates the protection / control circuit in the AC power conversion device by the abnormality detection signal generated by the abnormality detection unit to stop the operation of the AC conversion unit and opens the output circuit breaker, A backflow prevention diode is connected in series in the forward direction to the input of the AC power converter, and a short-circuit switch which is closed in parallel with the backflow prevention diode when a start signal is sent and when the abnormality detection signal disappears is connected to detect the abnormality. At times, the power conversion apparatus further comprises means for opening the short-circuit switch at high speed after the AC power conversion apparatus is stopped and before the breaker is opened. 2. The power conversion device according to claim 1,
As means for opening the short-circuit switch at high speed at the time of detecting the abnormality, the abnormality detecting unit for detecting abnormality includes an overcurrent of the output of the AC power converter or a sudden phase change in the commercial power system, frequency fluctuation, overvoltage, and shortage. In addition to the abnormality detection signal based on the abnormality detection of voltage or the like, another detection value having a lower level than the abnormality detection signal is provided, and the protection / control circuit is operated by the signal transmitted based on the another detection value, A power conversion device, wherein the short-circuit switch is opened.