JP2009239985A - Power conversion system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a power conversion system which can elongate the life of an optical signal transmission path for transmission of a control signal and can speedily detect abnormality, even when a signal system becomes abnormal. <P>SOLUTION: The power conversion system is provided with: a control circuit 403, which compares the frequency of a bypass power source 3 with the output frequency of uninterruptible power units 2a and 2b and outputs a positive polarity of control signal 6c, when the frequency of the power source 3 is higher than the output frequency of 2a and 2b and outputs a negative polarity of control signal 6d, when the frequency of 3 is lower than the output frequency of 2a and 2b; optical signal transmission paths 8c and 8d, which are arranged between a control circuit that switches on or switches off the main circuit elements of the inverters of 2a and 2b and the control circuit 403 and can transmit 6c and 6d each independently; and a phase conforming circuit 20, which has a reference oscillator 21 for conforming the phase of the power source 3 to the phase of the output voltages of the inverters of 2a and 2b, based on the control signals of 6c and 6d from 8c and 8d, control amount detecting circuits 23 and 23a, and adders 25 and 25a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention connects a plurality of power converters for obtaining an AC output and a commercial AC power supply for backup to a common output bus, and when each power converter is normal, the power converters are operated in parallel to perform a common operation. The present invention relates to a power conversion system that supplies power to an output bus and operates when switched to a commercial AC power source when each of the power converters fails, and supplies power to the output bus.

  An uninterruptible power supply using an inverter is equipped with a switching circuit for operating multiple inverters in parallel and switching to a commercial AC power source as a backup without interruption as demand for higher capacity and higher reliability increases. Power conversion systems are increasing.

  FIG. 5 is a block diagram for explaining the contents described in Patent Document 1 as an example. This connects the uninterruptible power supply (USP) 2a, 2b and the outputs of the uninterruptible power supply 2a, 2b to the common bus 7, and connects to the common bus 7 via the switching circuit 4 to the load 5. A commercial AC power source (hereinafter referred to as a bypass power source) 3 as a backup is connected to the switching circuit 4.

  The switching circuit 4 is a frequency difference detection circuit that detects the difference between the output frequencies of the bypass power supply 3 and the uninterruptible power supply devices 2a and 2b, and the changeover switches 401 and 402 that switch the outputs of the bypass power supply 3 and the uninterruptible power supply devices 2a and 2b. 404.

  The uninterruptible power supply devices 2a and 2b are both converters 2ac and 2bc for converting AC inputs 1a and 1b to DC, respectively, and inverters 2ai and 2bi for converting DC converted by the converters 2ac and 2bc to AC. And a storage battery (not shown).

  In such a power conversion system, the phases of the output voltages of the inverters 2ai and 2bi are matched to suppress the cross current between the inverters 2ai and 2bi, and the phases of the output voltages of the inverters 2ai and 2bi and the bypass power source 3 Must be in phase.

  To satisfy this condition, the main circuit element control circuit of each inverter 2ai, 2bi includes a reference oscillator 21, a polarity discrimination circuit 22, a control amount detection circuit 23, a multiplier 24, and an adder shown in FIG. It is conceivable to provide a phase matching circuit 20B composed of 25. The oscillator 21 outputs an AC waveform having a predetermined frequency. The polarity discrimination circuit 22 takes in the frequency difference detection signal 6 from the frequency difference detection circuit 404 in FIG. 5 (a signal in which the difference between the frequency of the bypass power supply 3 and the output frequency of the inverter is detected), and is shown as 6b in FIG. Such + (plus) and-(minus) polarities are discriminated. The control amount detection circuit 23 takes in the frequency difference detection signal 6 from the frequency difference detection circuit 404 in FIG. 5, and detects a pulse control amount as indicated by 6a in FIG. The multiplier 24 multiplies the output of the polarity discrimination circuit 22 (shown by 6b in FIG. 7) and the output of the control amount detection circuit 23 by the output of the polarity discrimination circuit 22 (shown by 6a in FIG. 7). And convert it to a controlled variable with polarity. The adder 25 adds the control amount with polarity, which is the output of the multiplier 24, and the AC waveform from the oscillator 21.

As described above, the phase matching circuit 20B shown in FIG. 6 can match the phases of the output voltages of the inverters 2ai and 2bi, suppress the cross current between the inverters 2ai and 2bi, and suppress the inverters 2ai and 2bi. The phase of the output voltage and the phase of the bypass power supply 3 can be matched.
JP 2002-27684 A

  In FIG. 5, the frequency difference detection signal 6 from the frequency difference detection circuit 404 is transmitted to the control circuits in the uninterruptible power supply devices 2a and 2b that are operated in parallel, specifically, to the phase matching circuit 20B. When the signal transmission line 8 is an electric signal transmission line, for example, an electric wire, there is a problem that electric signal noise is generated and noise tolerance is reduced. In order to improve the noise immunity, the signal transmission path 8 may be constituted by an optical signal transmission path, for example, an optical fiber. However, when the polarity signal 6b shown in FIG. In some cases, the life of the optical signal transmission path and the optical component including the optical signal transmission path is shortened. In addition, there is a problem that an abnormality of the signal system that transmits the polarity signal 6b cannot be detected, and it takes time to detect the abnormality of the control signal system.

  The present invention has been made to solve the above-described problems, and can extend the life of the optical signal transmission path for control signal transmission. Also, even when the signal system becomes abnormal, the abnormality is promptly detected. It is voluntary to obtain a power conversion system that can detect.

  In order to achieve the above object, the invention corresponding to claim 1 is configured such that a plurality of power converters for obtaining AC output and a commercial AC power source for backup are connected to a common output bus, and each power converter is normal. The power converters are operated in parallel to supply power to the common output bus, and when the power converters fail, they are switched to the commercial AC power source and operated to supply power to the output bus. In the power conversion system, the frequency of the commercial AC power supply and the output frequency of the power converter are compared, and when the frequency of the commercial AC power supply is higher than the output frequency of the power converter, a positive polarity control signal is output, When the frequency of the commercial AC power supply is lower than the output frequency of the power converter, a control circuit that outputs a negative polarity control signal and a control circuit that controls on / off of the main circuit element of each power converter. An optical signal transmission path disposed between the circuit and the control circuit, capable of independently transmitting the positive polarity control signal and the negative polarity control signal, and the positive polarity from the optical signal transmission path. A power conversion system comprising: a phase matching circuit for matching the phase of the commercial AC power supply and the phase of the output voltage of each power converter based on a control signal and the negative polarity control signal is there.

  In order to achieve the above object, the invention corresponding to claim 2 connects a plurality of power converters for obtaining AC output and a backup commercial AC power source to a common output bus, and each power converter is normal. The power converters are operated in parallel to supply power to the common output bus, and when the power converters fail, they are switched to the commercial AC power source and operated to supply power to the output bus. In the power conversion system, the frequency of the commercial AC power supply and the output frequency of the power converter are compared, and when the frequency of the commercial AC power supply is higher than the output frequency of the power converter, a positive polarity control signal is output, When the frequency of the commercial AC power supply is lower than the output frequency of the power converter, a control circuit that outputs a negative polarity control signal and a control circuit that controls on / off of the main circuit element of each power converter. An optical signal transmission path disposed between the circuit and the control circuit, capable of independently transmitting the positive polarity control signal and the negative polarity control signal, and the positive polarity from the optical signal transmission path. Based on the control signal and the negative polarity control signal, the phase of the commercial AC power supply and the phase matching circuit for matching the phase of the output voltage of each power converter, the absolute value of the positive polarity control signal, and the A power conversion system comprising: an abnormality detection circuit that determines that the control signal is abnormal when the absolute value of the negative polarity control signal is received simultaneously.

  ADVANTAGE OF THE INVENTION According to this invention, the lifetime of the optical signal transmission path for control signal transmission can be extended, and even if a signal system becomes abnormal, the power conversion system which can detect abnormality rapidly can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram for explaining an embodiment of the present invention, and FIG. 2 is for explaining a first embodiment of the present invention, and describes the phase matching circuit 20 of FIG. FIG.

  The premise of the embodiment of the present invention is common to a plurality of power converters such as the uninterruptible power supply devices 2a and 2b that obtain AC output as shown in FIG. When the uninterruptible power supply units 2a and 2b are normal, the uninterruptible power supply units 2a and 2b are operated in parallel to supply power to the load 5 connected to the common output bus line 7. In this power conversion system, when the uninterruptible power supply devices 2a and 2b are out of order, they are switched to the bypass power source 3 by the changeover switches 401 and 402 included in the changeover circuit 4 and operate to supply power to the load 5.

  The uninterruptible power supply 2a includes a converter 2ac, an inverter 2ai, a storage battery (not shown), a main circuit element control circuit (not shown) that controls on / off of the main circuit elements of the converter 2ac and the inverter 2ai, and the like. The uninterruptible power supply 2b includes a converter 2bc, an inverter 2bi, a storage battery (not shown), a main circuit element control circuit (not shown) that controls on / off of the main circuit elements of the converter 2bc and the inverter 2bi, and the like. .

  Then, the frequency of the bypass power supply 3 is compared with the output frequency of the uninterruptible power supply 2a, 2b. When the frequency of the bypass power supply 3 is higher than the output frequency of the uninterruptible power supply 2a, 2b, the positive polarity control signal of FIG. 6c and when the frequency of the bypass power supply 3 is lower than the output frequency of the uninterruptible power supply devices 2a and 2b, the control circuit 403 outputs the negative polarity control signal 6d of FIG. 3 (this is included in the switching circuit 4). And a control circuit (not shown) for controlling on / off of the main circuit elements of the inverters of the uninterruptible power supply devices 2a and 2b, and the control circuit 403, and a positive polarity control signal 6c and a negative polarity control signal. 6d based on optical signal transmission paths 8c and 8d capable of transmitting independently, plus a positive polarity control signal 6c and a negative polarity control signal 6d from the optical signal transmission paths 8c and 8d. 2 for making the phase of the bypass power supply 3 coincide with the phase of the output voltage of the inverter of the uninterruptible power supply 2a, 2b, and adding the reference oscillator 21 and the control amount detection circuits 23, 23a of FIG. The phase matching circuit 20 including the units 25 and 25a is provided.

  According to the first embodiment of the present invention described above, the following operational effects can be obtained. When the frequency of the bypass power supply 3 is high and the frequency of the uninterruptible power supply devices 2a and 2b needs to be high, only the control signal 6c shown in FIG. Sent to. When the frequency of the bypass power supply 3 is low and the frequency of the uninterruptible power supply devices 2a and 2b needs to be lowered, only the control signal 6d shown in FIG. It is transmitted to the circuit 23.

  The control amount received by the control amount detection circuits 23a and 23 is converted into a control amount that takes into account + and one control amount by the adder 25a. The control amount converted by the adder 25 a is added to or subtracted from the output of the reference oscillator 21 by the adder 25. The output of the addition / subtraction 25 becomes the output frequency 26 of the uninterruptible power supply 2a, 2b. As a result, the uninterruptible power supply 2a, 2b outputs a voltage synchronized with the bypass power supply 3. Since the present embodiment has the above-described configuration, there is an advantage that even when an optical signal is used from the control circuit 403, continuous light emission does not occur and the lifetime of the optical signal transmission path is not impaired.

  FIG. 4 is for explaining the second embodiment of the present invention, and is different only in that an abnormality detection circuit 27 is newly added to the first embodiment described above. The abnormality detection circuit 27 can determine that the control signals 6c and 6d are abnormal when the absolute value of the positive polarity control signal 6c and the absolute value of the negative polarity control signal 6d are received simultaneously.

  This embodiment can obtain not only the same effects as the first embodiment but also the following effects. That is, since the control signals (control amounts) 6c and 6d transmit the control signal only when the polarity is + polarity, the control amount is not output at the same time. Therefore, when a control signal (control amount) is received at the same time, it can be detected as an abnormality in the optical signal transmission paths 8c and 8d. Since such a configuration is provided, there is an advantage that abnormality in the signal transmission system can be detected immediately.

(Modification)
In the above-described embodiment, the uninterruptible power supply device has been described as an example of the power converter. However, any power converter that can obtain an AC output may be used.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram for demonstrating 1st Embodiment of the power conversion system by this invention. The figure for demonstrating the phase matching circuit of FIG. The time chart for demonstrating the control circuit of FIG. The schematic block diagram for describing 2nd Embodiment of the power conversion system by this invention, Comprising: The schematic block diagram for demonstrating an example of the conventional power conversion system. The figure for demonstrating the phase matching circuit of FIG. The time chart for demonstrating the frequency difference detection circuit of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1a, 1b ... AC input, 2a, 2b ... Uninterruptible power supply, 2ac, 2bc ... Converter, 2ai, 2bi ... Inverter, 3 ... Commercial AC power supply (bypass power supply), 4 ... Switching circuit, 5 ... Load, 6c, 6d Control signal, 7 Output bus, 8 Signal transmission path, 8c, 8d Optical signal transmission path, 20B Phase matching circuit, 20 Phase matching circuit, 21 Reference oscillator, 22 Polarity discrimination circuit, 23 Control Quantity detection circuit, 23, 23a ... Control quantity detection circuit, 24 ... Multiplier, 25 ... Adder, 25, 25a ... Adder, 27 ... Abnormality detection circuit, 401, 402 ... Changeover switch, 403 ... Control circuit, 404 ... Frequency difference detection circuit.

Claims (2)

A plurality of power converters for obtaining AC output and a commercial AC power supply for backup are connected to a common output bus, and when the power converters are normal, the power converters are operated in parallel to perform the common output. In the power conversion system for supplying power to the bus and supplying power to the output bus by switching to the commercial AC power source when each of the power converters fails,
The frequency of the commercial AC power supply is compared with the output frequency of the power converter, and when the frequency of the commercial AC power supply is higher than the output frequency of the power converter, a positive polarity control signal is output, and the commercial AC power supply A control circuit for outputting a negative polarity control signal when the frequency is lower than the output frequency of the power converter;
Arranged between the control circuit and the main circuit element control circuit for controlling on / off of the main circuit element of each power converter, the positive polarity control signal and the negative polarity control signal can be transmitted independently. An optical signal transmission line;
A phase matching circuit for matching the phase of the commercial AC power supply based on the positive polarity control signal and the negative polarity control signal from the optical signal transmission line, and the phase of the output voltage of each power converter;
A power conversion system comprising: A plurality of power converters for obtaining AC output and a commercial AC power supply for backup are connected to a common output bus, and when the power converters are normal, the power converters are operated in parallel to perform the common output. In the power conversion system for supplying power to the bus and supplying power to the output bus by switching to the commercial AC power source when each of the power converters fails,
The frequency of the commercial AC power supply is compared with the output frequency of the power converter, and when the frequency of the commercial AC power supply is higher than the output frequency of the power converter, a positive polarity control signal is output, and the commercial AC power supply A control circuit for outputting a negative polarity control signal when the frequency is lower than the output frequency of the power converter;
Arranged between the control circuit and the main circuit element control circuit for controlling on / off of the main circuit element of each power converter, the positive polarity control signal and the negative polarity control signal can be transmitted independently. An optical signal transmission line;
A phase matching circuit for matching the phase of the commercial AC power source based on the positive polarity control signal and the negative polarity control signal from the optical signal transmission line, and the phase of the output voltage of each power converter;
An abnormality detection circuit that determines that the control signal is abnormal when the absolute value of the positive polarity control signal and the absolute value of the negative polarity control signal are received simultaneously;
A power conversion system comprising:

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