JPH09140149A - Fault detection circuit of parallel operation inverter system apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a fault condition of an inverter system under the parallel operation by detecting a voltage of an output bus and an output voltage and cross current of an inverter system. SOLUTION: If an inverter system 1a fails, frequency Fa of an output voltage Va becomes smaller than frequency setting value. Current detectors 3a, 3b detect an output current of the inverter systems 1a, 1b and gives it to a difference current detector 30. The difference current detector 30 outputs difference currents Iba, Ibb of cross current of the inverter systems 1a, 1b. A reactive power calculator 8a inputs a difference current Iba and an output Va of a voltage detector 4a and outputs a reactive power Qa. The voltage detector 6 detects an output bus voltage Vv and a frequency detector detects frequency Fv of the output bus voltage. A discriminator 9a inputs the reactive power Qa and output bus frequency Fv and judges the operating condition of the inverter system 1a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure detection circuit of a parallel operation inverter system device for supplying power to a common load device by an inverter system connected in parallel such as an uninterruptible power supply device.

[0002]

2. Description of the Related Art FIG. 5 is shown for explaining the prior art.
a, 1b and 1c are inverter systems, 2 is a common load device connected to the output bus of the example of parallel installation of three inverter systems, 3a, 3b and 3c are current detectors, 30 is a differential current detector, 31a, 31b and 31c are rectifiers, 32a, 32b and 32c are dummy resistors, and 33a, 33b and 33c are detecting resistors. That is, the output currents of the inverter systems 1a, 1b, 1c are obtained by the current detectors 3a, 3b, 3c, respectively, and input to the differential current detector 30, and the respective output currents should originally flow in the differential current detector 30. Difference currents (hereinafter referred to as cross currents) Iba, Ibb, Ibc from the output current are detected. Also, the difference current detector
The cross currents of 30 outputs are input to the rectifiers 31a, 31b, 31c, respectively, and the dummy resistors 32a, 32b, 32c are connected to the outputs,
Further, they are commonly connected through detection resistors 33a, 33b, 33c.

Assuming that the inverter system 1a out of the three inverter systems operating in parallel fails and the remaining inverter systems 1b and 1c are operating normally, the cross currents Ibb and Ibc are Being the same, the cross current Iba
Is a current whose phase is double that of the cross current Ibb, and
The voltage Vra across the resistance of the detection resistor 33a has a positive voltage value, and the voltage Vrb and Vrc across the resistance have a negative voltage value. Therefore, the inverter system in which the voltage across the resistance of the detection resistor has a positive voltage value may be detected as the defective inverter system.

An individual inverter system used in such a parallel operation inverter system device is shown in FIG.
This will be described below. FIG. 6 is shown for explaining the control method of the inverter system, and 4a is a voltage detector. In the inverter system 1a, 11a is an inverter, 12a is a filter reactor, 13a is a filter capacitor, 14a is a current detector, 111a, 113a and 116a are arithmetic units, 112a and 114a are control amplifiers, and 115a is a triangular wave generator. , 117a is a comparator. In FIG. 6, the deviation between the instantaneous voltage set value V * and the output voltage Va is calculated by the calculator 111a, the output is input to the control amplifier 112a, and the deviation between the output of the control amplifier 112a and the output current Iia is calculated. Is calculated by the controller 113a and the output is calculated by the control amplifier 114a.
Give to a. Further, the deviation between the output of the control amplifier 114a and the output of the triangular wave generator 115a is calculated by the calculator 116a, and the output is input to the comparator 117a to obtain the gate signal Sg.
It controls the inverter 11a.

[0005]

However, in the prior art of this type, for example, the cross current of the inverter system which has failed due to the parallel operation of two inverter systems and the cross current of the normal inverter system are large in magnitude. However, the voltage between both ends of the detection resistor becomes 0, and the defective inverter system cannot be detected.

However, the object of the present invention is to determine the inverter from the reactive power or the instantaneous active power and the output bus voltage.
It is an object of the present invention to provide a failure detection circuit for a special parallel operation inverter system device for discriminating the failure state of the inverter system.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has the following structure. That is, first, a current detector and a first voltage detector that detect the output current and the output voltage of the inverter system, a second voltage detector that detects the voltage of the output busbar, and a second voltage detector. A frequency detector that detects a frequency from the detector output, a difference current detection unit that obtains a difference between the current detector output and the output current that should originally flow, and a reactive power from the difference current detection circuit output and the first voltage detector output. And when the reactive power calculation means outputs a positive value and the frequency detector output is less than the frequency set value, or when the reactive power calculation means output is a negative value and the frequency detector output is the frequency set value. When it is larger than the above, the first judgment means for judging a failure state is provided. Second, a current detector and a first voltage detector that detect the output current and the output voltage of the inverter system, a second voltage detector that detects the voltage of the output busbar, a current detector output and the original The difference current detection means for obtaining the difference from the output current to be passed, the instantaneous active power calculation means for calculating the instantaneous active power from the output of the difference current detection circuit and the output of the first voltage detector, and the output of the instantaneous active power calculation means are positive. And the second voltage detector output is larger than the instantaneous voltage set value, or when the instantaneous active power computing means output has a negative value and the second voltage detector output is smaller than the instantaneous voltage set value, it is determined to be a failure state. And a second determining means for performing the operation.

By the means for solving the problems, the following operational effects can be obtained. Now, in the control of the inverter system in FIG. 6, assuming that there is no load and the frequency Fa of the output voltage Va becomes larger than the frequency set value F * due to some influence, the delay of the control amplifier 112a at this time will occur. If it is not too large, the output of the control amplifier 112a is a phase delayed by approximately 90 degrees from the phase of the instantaneous voltage setting value V *. Moreover, since the output of the control amplifier 112a becomes the output current command,
If the gain of the control amplifier 114a is sufficiently large, the output current Iia becomes substantially the same value, and the output current Iia has a phase delayed by approximately 90 degrees from the instantaneous voltage set value V *. Here, the output current Iia can be decomposed into a capacitor current Ica component flowing in the filter capacitor 13a and a difference current Iba component which becomes a cross current, but if the gain of the control amplifier 112a is large, Iia becomes Ica.
The phase of the difference current Iba is substantially the same as the phase of the output current Iia. That is, when there is a deviation between the frequency setting value and the frequency of the output voltage, the phase of Iba becomes a phase shifted by approximately 90 degrees from the phase of V *.

Further, the frequency of the output voltage Va of the inverter system 1a is F due to the failure of the inverter system 1a.
Assuming that a becomes smaller than the frequency set value F *, at this time, the frequency Fv of the output bus voltage Vv becomes smaller than the frequency set value Fa *, and I of the inverter system 1a becomes smaller.
Since ba is a current having a phase delayed by 90 degrees from Va, the reactive power based on these Va and Iba has a positive value. Then, the reactive power between Vb and Ibb of the inverter system 1b has a negative value. Similarly, when the inverter system 1a fails and Fa becomes larger than F *, Fv becomes F
If it becomes larger than a *, Iba becomes a current having a phase advanced by 90 degrees from Va, the reactive power by Va and Iba becomes a negative value, and the reactive power by Vb and Ibb becomes a positive value. it is obvious.

Next, assuming that there is no load and Va suddenly changes for some reason and becomes smaller than V *,
At this time, if the delay of the control amplifier 112a is not too large, the output of the control amplifier 112a becomes almost the same phase as V *. Further, since the output of the control amplifier 112a serves as an output current command, if the gain of the control amplifier 114a is sufficiently large, it will be substantially the same value as the output current Iia, and Iia will have substantially the same phase as V *. Then, if the gain of the control amplifier 112a is large, Iia becomes considerably larger than Ica, and as a result, the phase of Iba becomes substantially the same as the phase of Iia. That is, when the set value of the instantaneous voltage and the magnitude of the output voltage are different, the phase of Iba becomes substantially the same as the phase of V *.

If the inverter system 1a fails and the output voltage Va of the inverter system 1a becomes larger than the instantaneous voltage set value V *, the output bus voltage Vv is naturally the instantaneous voltage set value V. It becomes larger than *, and Iba becomes a current in the same phase as Va.
The instantaneous active power based on a and Iba has a positive value. The instantaneous active power of Vb and Ibb has a negative value. Similarly, when the inverter system 1a fails and Va becomes smaller than V *, Vv becomes smaller than V * and I
Since ba has a current opposite in phase to Va, the instantaneous active power of Va and Iba has a negative value, and the instantaneous active power of Vb and Ibb has a positive value.

As described above, the cases can be divided, and the operating states of the inverter systems operating in parallel can be determined by detecting the output bus voltage, the output voltage of the inverter system and the cross current. It can be judged exceptionally.

[0013]

More specifically, first, reactive power is obtained from each output of the differential current detection circuit and the output voltage of each inverter system, and the reactive power value and output bus voltage The configuration is such that the failure state of each inverter system is determined from the frequency. Second,
In particular, the configuration is such that instantaneous active power is obtained from each output of the differential current detection circuit and output voltage of each inverter system, and the fault status of each inverter system is determined from the instantaneous active power and output bus voltage. Is. Further, the present invention will be described in detail with reference to the accompanying drawings.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of the essential part of an embodiment of the present invention in a manner similar to FIG. 5, in which 4a and 4b are voltage detectors, 5a and 5b are wiring impedances, 6 is a voltage detector and 7 Is a frequency detector, 8a and 8b are reactive power calculators, and 9a and 9b are decision devices. The operation of this configuration is as follows.

Now, it is assumed that the inverter system 1a fails and the frequency Fa of the output voltage Va of the inverter system 1a becomes smaller than the frequency set value F *. The output currents of the inverter systems 1a and 1b are detected by the current detectors 3a and 3b and are supplied to the differential current detector 30. Differential current detector
The reference numeral 30 outputs the cross current difference currents Iba, Ibb of the inverter systems 1a, 1b. At this time, the differential currents Iba, Ibb
Is a current having the same magnitude and a reversed phase, and the difference current Iba has a phase delayed by 90 degrees from the output voltage Va.
The reactive power calculator 8a inputs the differential current Iba and the output voltage Va of the output of the voltage detector 4a, and outputs the reactive power Qa. At this time, the reactive power Qa has a positive value. Similarly, the reactive power calculator 8b outputs a negative reactive power Qb from the difference current Ibb and the output voltage Vb output from the voltage detector 4b.

The voltage detector 6 detects the output bus voltage Vv, and the frequency detector 7 detects the output bus voltage Vv.
The output bus frequency Fv of is detected. At this time, the output bus frequency Fv becomes a value smaller than the frequency setting value F *. The determiner 9a inputs the reactive power Qa and the output bus frequency Fv, and can determine the operating state of the inverter system 1a according to the determination conditions shown in FIG. That is, FIG. 2 shows the operation of the discriminator of FIG.
Is smaller than F * and Qa has a positive value, the inverter system 1a is determined to be in a failure state. Similarly, the determiner 9
b inputs the reactive power Qb and the output bus frequency Fv to determine the operating state of the inverter system 1b, and therefore,
Since Fv is smaller than F * and Qa is a negative value,
The system 1b is determined to be in a normal state.

FIGS. 3 and 4 show the construction of the essential parts of another embodiment of the present invention similar to FIGS. 1 and 2, wherein 8a 'and 8b' are instantaneous active power calculators. 9a ', 9
b'is a determiner. Now, it is assumed that the inverter system 1a fails and the output voltage Va of the inverter system 1a becomes larger than the instantaneous voltage set value V *. At this time, a difference current detector that obtains a difference current from the outputs of the current detectors 3a and 3b
The difference currents Iba and Ibb of the output of 30 are currents having the same magnitude and inverted phases, and the difference current Iba has the same phase as the output voltage Va. The instantaneous active power calculator 8a 'has a difference current Iba
And the output voltage Va are input, and the instantaneous active power Pa having a positive value is input.
Is output. Similarly, the instantaneous active power calculator 8b 'outputs the instantaneous active power Pb having a negative value from the difference current Ibb and the output voltage Vb.

The output bus voltage Vv detected by the voltage detector 6 becomes a value larger than the instantaneous voltage set value V *.
The determiner 9a 'determines the instantaneous active power Pa and the output bus voltage Vv.
In accordance with the determination condition as shown in FIG. 4, Vv is larger than V * and Pa is a positive value, so that the inverter system 1a is determined to be in a failure state. Similarly,
The determiner 9b 'inputs the instantaneous active power Pb and the output bus voltage Vv. Since Vv is a value larger than V * and Pb is a negative value, the inverter system 1b is determined to be in a normal state.

[0019]

As described above in detail, according to the present invention, by detecting the voltage of the output bus, the output voltage of the inverter system, and the cross current, the failure state of the inverter systems operating in parallel can be detected. A device with a simple configuration to obtain
Can be provided.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing the operation of the determiner of FIG.

FIG. 3 is a circuit configuration diagram showing another embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the operation of the determiner of FIG.

FIG. 5 is a circuit configuration diagram shown for explaining a conventional technique.

FIG. 6 is a system diagram shown for explaining an inverter system control method.

[Explanation of symbols]

 1 Inverter system 11a Inverter 12a Filter reactor 13a Filter capacitor 14a Current detector 112a Control amplifier 114a Control amplifier 115a Triangular wave generator 117a Comparator 2 Load device 3 Current detector 30 Differential current detector 31 Rectifier 32 Damper resistance 33 Detection resistance 4 Voltage detector 5 Wiring impedance 6 Voltage detector 7 Frequency detector 8 Reactive power calculator 8'Instantaneous active power calculator 9 Judger 9'Judger Iba Differential current Vv Output bus voltage V * Instant Voltage setting value Va Output voltage Sg Gate signal Qa Reactive power Pa Instant active power

Claims (2)

[Claims] 1. A parallel operation inverter system device for supplying power to a common load device by an inverter system connected in parallel, wherein a current detector for detecting an output current and an output voltage of the inverter system, and a first detector. Second voltage detector and second for detecting output bus voltage
Voltage detector, a frequency detector for detecting a frequency from the output of the second voltage detector, a difference current detecting means for obtaining a difference between the output of the current detector and an output current that should originally flow, and the difference current detection. Reactive power calculating means for calculating the reactive power from the circuit output and the first voltage detector output, and when the reactive power calculating means output is a positive value and the frequency detector output is smaller than the frequency set value, or the reactive power calculating means A failure detection circuit for a parallel operation inverter system device, comprising: first determination means for determining a failure state when the output has a negative value and the frequency detector output is greater than a frequency set value. 2. A parallel operation inverter system device for supplying electric power to a common load device by an inverter system connected in parallel, wherein a current detector for detecting an output current and an output voltage of the inverter system, and a first detector. Second voltage detector and second for detecting output bus voltage
Voltage detector, differential current detection means for obtaining the difference between the output of the current detector and the output current that should originally flow, and the moment of calculating the instantaneous active power from the output of the differential current detection circuit and the output of the first voltage detector. Active power calculation means, and when the instantaneous active power calculation means output is a positive value and the second voltage detector output is greater than the instantaneous voltage set value, or the instantaneous active power calculation means output is a negative value and a second voltage A failure detection circuit for a parallel operation inverter system device, comprising a second judging means for judging a failure state when the detector output is smaller than the instantaneous voltage set value.