JPH08289475A - Failure detection method and system switching method for inverter parallel operation system - Google Patents

Abstract

PURPOSE: To stop a load in safety or make a switching to an auxiliary power supply system before all inverters are stopped by making a decision that a system has failed on condition that at least one of a plurality of inverters operating in parallel has failed or the output current from one inverter has exceeded a predetermined level. CONSTITUTION: Output signals 111-115 from individual current detectors are fed to AND circuits 911-915 and logical product of the inverted values of output signals 101-105 from individual failed current detectors is produced. When an individual current detector detects an output current from any one inverter exceeding a predetermined level, an OR gate 903 produces an output thus detecting the overcurrent at the time of inspection and failure. On the other hand, outputs 101-105 from individual failed current detectors are fed to an OR gate circuit 905 in order to detect failure of these inverters. With such constitution, the failure of system is detected surely and the load can be stopped in safety or a switching can be made to an auxiliary power supply system before all inverters are stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fault detection method and a system switching method for an inverter parallel operation system in which a plurality of inverters are connected in parallel.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional example of an inverter parallel operation system consisting of five inverters that are operated in parallel, 11 to 15 are inverters, 21 to 25 are switches,
Reference numeral 3 is a parallel bus bar, and 4 is a load. Where each inverter
11 to 15 include individual fault detectors not shown. That is, in the operation of a plurality of inverters 11 to 15 that are operated in parallel, if a failure occurs in any of the inverters and the individual failure detector detects this, the inverters are stopped and the switches are connected in parallel. It disconnects from the bus bar 3 and continues to supply power to the load 4 with the remaining healthy inverter.

FIG. 4 shows another conventional example.
Is a backup power source, and 61 to 62 are switches. Here, FIG. 4 has the configuration of FIG.
Is provided. That is, this is an example of an inverter parallel operation system capable of switching between the inverter system and the standby power supply system. As the standby power source 5, a commercial power source, a generator, or a separately configured inverter system,
Applied.

In FIG. 4, the electric power of the inverters 11 to 15 is normally supplied to the load 4 via the switches 21 to 25 and the switch 61. When a failure occurs in any of the inverters, the inverter is disconnected and the remaining healthy inverters continue to supply power to the load, as in the case of FIG. In the case of failure of all the inverters, the switch 61 is turned off and the switch 62 is turned on to switch from the inverter system to the standby power system, and the power supply to the load 4 is continued. Although the switches 61 and 62 are shown by symbols of mechanical switches, a high-speed semiconductor switch (not shown) is also used in order to perform the above-mentioned switching without interruption.

In such an inverter parallel operation system, it is necessary to detect that all the inverters have failed or have a possible failure state, that is, a system failure has occurred. This is shown in FIG.

FIG. 5 shows a conventional example for detecting this type of system failure, and 101 to 105 are output signals of individual failure detectors incorporated in the inverters 11 to 15 shown in FIGS. 3 and 4, respectively. Reference numeral 901 is an AND gate circuit, and 902 is a system failure detection signal. That is, the fact that all of the inverters 11 to 15 in FIGS. 3 and 4 have failed is detected by the AND gate circuit 901 which receives the individual failure detector output signals 101 to 105, and the system failure detection signal 902 is obtained. Here, the system failure detection signal 902 is sent to the load 4 in the example of FIG. 3 and is used as an automatic processing signal for allowing the load 4 to stop as safely as possible when the power is lost, or an emergency processing operation after the power is lost. Used as an alarm for. Further, in FIG. 4, it is used as a signal for switching from the above-mentioned inverter system to the standby power system.

[0007]

However, the conventional fault detection method and system switching method for the inverter parallel operation system have the following problems. That is, in the inverter parallel operation system of FIG. 3 using the failure detection method of FIG.
The loss of the power source of will occur at almost the same timing. When the load 4 is an electronic calculator or the like, it is extremely difficult to safely stop at such a timing, which causes data destruction or equipment damage. The restoration requires a long time, and in some cases it may develop into a social problem.

Further, in the inverter parallel operation system of FIG. 4 using the failure detection method of FIG. 5, since the system is switched to the backup power supply 5 system due to a system failure, loss of the power supply of the load 4 can be avoided. However, all inverters
The output signals 101 to 105 of the individual fault detectors 11 to 15 do not occur at the same time, and the system fault occurs from the individual fault of one of the inverters. That is, due to the stoppage of any of the inverters due to the individual failure, the remaining inverter becomes an overcurrent. Here, the inverter 11 ~
15 has an overcurrent time-delay characteristic as shown in FIG.
There are variations in the detected values of overcurrent and overcurrent time-delay characteristics of each inverter, and the inverter that reached the time-delay characteristic sooner then has an individual failure, and the remaining inverter becomes a higher level overcurrent. Follow to reach system failure.

In this process, when the inverter is stopped due to an individual failure in a state where the number of parallel-operated units is small, the remaining inverters undergo extremely large fluctuations in the output current, and the load 4 accordingly undergoes large voltage fluctuations. Therefore, in a load such as an electronic computer that is sensitive to fluctuations in the power supply voltage, the voltage fluctuations at this time cause the power to stop or the data to be destroyed. Further, in FIG. 3 and FIG. 4, not all the inverters 11 to 15 are always operated, and there is a period in which one of the inverters is stopped for periodic inspection or repair due to a failure, for example. To do.

In such a situation, even if all the inverters are stopped after the above-mentioned progress due to the failure of one of the inverters which is continuing the parallel operation, even if the inverter is inspecting or repairing, Since the individual failure detection signal is not input to the
No 902 occurs and no fault output is obtained. Therefore, switching to the standby power supply system in FIG. 4 is not performed, and the load 4 suddenly loses power without any information being obtained, and damage is increased.

[0011]

In order to solve the problems caused by the conventional fault detection method and system switching method, the fault detection method according to the present invention includes at least one of a plurality of inverters operated in parallel. System failure is determined on the condition that the inverter has failed and the output current of at least one of the inverters that continue to operate in parallel exceeds a specified value. In this system, the inverter system is switched to the standby power system by the fault detection output detected by this method.

Another fault detection method and system switching method according to the present invention are that at least one of a plurality of inverters that are operated in parallel has failed and at least one of the inverters that is continuously operating. Condition that the output current of the inverter exceeds the first specified value, the system is judged to have a minor failure and the operation of the inverter is continued. At the same time, at least one inverter has failed and parallel operation is continued. If the output current of at least one of the existing inverters exceeds the second specified value, which is larger than the first specified value, the system is judged to be a major failure and a failure is detected, and the system is protected from the inverter system. It is designed to switch to the power system.

[0013]

With such a solution, the system failure is detected in a state before all the inverters are stopped, and the load is safely stopped or the standby power system is switched to in a state where the load voltage is less disturbed. At the initial stage of system failure, the overcurrent state is eliminated by disconnecting the less important load so that the highly reliable inverter can continue to supply power to the more important load. Furthermore, the system failure can be surely detected during maintenance or repair of any of the inverters.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the essential structure of an embodiment of a fault detecting method according to the present invention, in which the same reference numerals as those in FIG. 5 indicate parts having the same functions. In FIG. 1, 111 to 11
Reference numeral 5 denotes an output signal of an individual current detector incorporated in each of the inverters 11 to 15 in FIGS. 3 and 4 and detecting that the output current thereof exceeds a specified value. 911 to 915 are AND gate circuits, and 903 and 905 are OR gate circuits.
That is, the output signals 111-115 of the individual current detectors of the inverters 11-15 are output by the AND gate circuits 911-915 of the individual failure detectors of the respective inverters.
AND conditions with the inverted values of 101 to 105 are taken, and signals are generated as the output signals 921 to 925 of the AND gate circuits 911 to 915.

Here, the inverter which is stopped by inspection or the like does not generate an output current, and the output signal of the individual current detector is blocked in the inverter in which a failure is detected, and the output signal is output to the corresponding AND gate circuit. Does not occur. In this state, when the individual current detector detects that the output current of any other inverter exceeds the specified value, the AND gate circuit corresponding to that inverter outputs. As a result, the OR gate circuit 903 outputs.

On the other hand, the individual failure detector outputs 101 to 105 of the respective inverters 11 to 15 are input to the OR gate circuit 905, and therefore, the output 906 of the OR gate circuit 905 detects the failure of one of the inverters. Therefore, as a result of taking these AND conditions in the AND gate circuit 901, the system failure signal 902 of the output indicates that one of the inverters has failed and the output current of any one of the inverters that continue to operate. Is detected as a condition that the value exceeds the specified value, that is, a system failure is detected. The inverters 11 to 15 have a time-delaying characteristic against an output overcurrent as shown in FIG. 6, and therefore, at the time when a system failure is detected, all the inverters are stopped by T as shown in the figure until they stop. It has the indicated time margin.
In the system of FIG. 3, the load 4 can be safely stopped during this period.

Further, according to this detection method, the first state in which an output current more than the specified value is generated in the inverter which continues to operate due to the failure of the inverter is detected. Therefore, the fluctuation of the load voltage at this stage is small, and in the system having the standby power supply 5 as shown in FIG. 4 and capable of switching between the inverter system and the standby power system, at this stage It is possible to switch to the standby power system.

FIG. 2 shows the construction of the main part of another embodiment according to the present invention, in which 909, 931 to 935 are AND gate circuits, and 907.
Is an OR gate circuit. That is, the difference from FIG.
The individual current detector in FIG. 1 is arranged as the second current detector, and the inverter 11 is provided at a lower level than this.
The output signals 121 to 125 of the individual current detector as the first current detector for detecting the output currents of .about.15 are obtained.
Further, the AND gate circuits 931 to 935 perform AND conditions between the output signals 121 to 125 of the individual current detectors and the inverted signals of the outputs 101 to 105 of the individual fault detectors of the corresponding inverter, and the AND gate circuits 931 by the OR gate circuit 907.
The OR conditions of the output signals 941 to 945 of ~ 935 are taken respectively. Furthermore, the AND gate circuit 909 takes an AND condition between the output signal 908 of the OR gate circuit 907 and the output signal 906 of the OR gate circuit 905 to obtain the system minor failure signal.
910 is to get the output.

In FIG. 2, when a system failure is detected by the system failure signal 902, the procedure is the same as in FIG. When a system minor fault is detected by the system minor fault signal 910, the overcurrent state of the inverter that continues to operate is resolved by taking measures such as stopping the less important one of the loads 4. It is possible to prevent the system from being stopped and to continuously supply power to highly important loads with a highly reliable inverter. In addition, it goes without saying that such a detection method according to the present invention can perform detection irrelevant to the stopped inverter by inspection or repair. Further, the present invention is not limited to the specific configuration shown in FIGS. 1 and 2, and further, FIGS.
It is obvious that the configuration and the number of inverters are not limited.

[0020]

As described above, according to the present invention, a system failure can be detected before the power supply to the load is lost, and the load can be dealt with before the power supply is lost. It is possible to prevent the data from being damaged including data destruction. Further, since it is possible to detect a system failure and switch from the inverter system to the standby power system at an early stage when the load voltage disturbance is small, it is possible to prevent the load from being damaged including data destruction.

Furthermore, by taking measures such as detecting a system minor failure at the first specified value and stopping a less important load, it becomes possible to continue supplying power to the important load with a highly reliable inverter. The reliability of the entire system including can be improved. In addition, a system failure can be detected regardless of the presence or absence of a stopped inverter for maintenance or repair, and the reliability of detection can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment to which the present invention is applied.

FIG. 2 is a circuit diagram showing another embodiment to which the present invention is applied.

FIG. 3 is a system diagram showing an example of an inverter parallel operation system.

FIG. 4 is a system diagram showing another example of the inverter parallel operation system.

FIG. 5 is a circuit diagram shown for explaining the prior art.

FIG. 6 is a circuit diagram showing an example of an overcurrent time delay characteristic of an inverter.

[Explanation of symbols]

 4 Load 5 Standby power supply 11 Inverter 12 Inverter 13 Inverter 14 Inverter 15 Inverter 21 Switch 61 Switch 101 Output signal of individual failure detector 111 Output signal of individual current detector 121 Output signal of individual current detector 901 AND gate circuit 902 System failure Detection signal 903 OR gate circuit 905 OR gate circuit 907 OR gate circuit 909 AND gate circuit 910 System minor failure detection signal 911 AND gate circuit 931 AND gate circuit

Claims (4)

[Claims] 1. In an inverter parallel operation system composed of a plurality of inverters that are operated in parallel, at least one inverter has failed, and an output current of at least one of the inverters that continue to operate. A method for detecting a failure in an inverter parallel operation system, characterized in that a system failure is determined on the condition that the value exceeds a specified value. 2. In an inverter parallel operation system composed of a plurality of inverters that are operated in parallel, at least one of the inverters has failed and the output current of at least one of the inverters that continue to operate is The system is considered to have a minor failure on the condition that the first specified value is exceeded, and at least one inverter has a failure and the output current of at least one of the inverters that is continuing to operate is the first A method for detecting a failure in an inverter parallel operation system, wherein a system failure is determined on the condition that a second specified value larger than the specified value is exceeded. 3. In an inverter parallel operation system capable of switching between an output of an inverter system composed of a plurality of inverters that are operated in parallel and an output of a standby power supply system, at least one inverter has failed and operation has been continued. The method of switching the inverter parallel operation system is characterized in that the inverter system is switched to the standby power supply system on condition that the output current of at least one of the inverters exceeds the specified value. 4. In an inverter parallel operation system capable of switching between an output of an inverter system composed of a plurality of inverters that are operated in parallel and an output of a standby power supply system, at least one inverter has failed and operation has been continued. Among the existing inverters, if the output current of at least one of the inverters exceeds the first specified value, it is judged that the system has a minor failure and the operation of the inverter is continued.
An inverter provided that at least one of the inverters has failed and the output current of at least one of the inverters that are still operating exceeds a second specified value that is larger than the first specified value. A system switching method for an inverter parallel operation system, characterized in that the system is switched to a standby power system.