JP5903593B2 - Input circuit and power converter - Google Patents

Description

  The present invention relates to an input circuit that inputs DC power supplied from a DC power source such as a solar cell, a fuel cell, and a storage battery, and a power converter that converts DC power obtained through the input circuit into AC power. is there.

  In recent years, an AC power supply system has been developed that converts DC power generated by a solar cell, a fuel cell, a storage battery, and the like into AC power, and supplies the converted AC power to a load. For example, since a photovoltaic cell has a small individual electromotive force and output current, a plurality of photovoltaic modules in which a plurality of photovoltaic cells are connected in series are connected in parallel to obtain a desired DC power. Yes. Also, an appropriate number of fuel cells and storage batteries are connected in parallel / series so that a desired output can be obtained.

  For example, in the case of a solar power generation system, in addition to a plurality of solar battery modules, a power collecting unit that collects outputs of these solar modules and a power conversion unit that converts DC power into AC power are provided. This current collector forms one output line by connecting wirings connected to a plurality of solar cell modules in a box. Thereby, a current collection part can connect several solar cell modules in parallel, and can combine the output electric power of several solar cell modules into one. The DC output power of the plurality of solar cell modules collected by the current collector is output to the power converter, and after being converted into AC power synchronized with the frequency of the commercial power system by the power converter, the commercial power system ( Superimposed on the load). In some cases, AC power is supplied directly to the load without using the wiring of the commercial power system.

  In such a current collector, a DC switch is interposed in each of the positive line and the negative line of the DC power, and the DC power source such as a solar cell can be disconnected when performing system maintenance. (See Patent Document 1 below). By the way, if the contact piece of the DC switch is opened while current is flowing through the DC switch, arc discharge occurs. That is, in a power circuit in which a large current flows, even if the contact of the DC switch is opened from the contact in order to cut off the current, the air around the contact and the contact is ionized by arc discharge, In addition, the distance between the contacts is close and arc discharge may be sustained depending on various conditions. This arc discharge heats the contacts and the piece, and the DC switch breaks down due to the heat of the arc discharge. For this reason, the DC switch provided with the arc extinguishing mechanism which extinguishes arc discharge is provided (refer the following patent document 2).

  As this arc extinguishing mechanism, for example, there is one using a magnet as disclosed in Patent Document 2. Specifically, the arc extinguishing mechanism utilizes the fact that the direction of arc discharge is changed by the force generated according to the direction of current and the direction of magnetic flux when a magnet is arranged near the contact piece. The arc extinguishing mechanism has a magnetic plate at the tip of arc discharge, draws arc discharge into the magnetic plate, divides and cools, and extinguishes arc discharge. For this reason, the DC switch having the arc extinguishing mechanism fixes the direction of the current and directs the arc discharge to the magnetic plate side. For this reason, the polarity (positive electrode, negative electrode) of the DC switch is determined in advance when connecting to the DC power source.

JP 2010-41758 A JP2011-129385A

  However, if the DC power is mistakenly connected to the DC switch with a predetermined polarity, a current circulation path is formed depending on the circuit configuration, and if the DC switch contact is closed, the current flows as it is. May end up. Opening the DC switch contacts in this state causes arc discharge, but the direction of the flowing current is opposite to the arc discharge, so the direction of the magnetic plate is reversed due to the action of the magnet of the arc extinguishing mechanism. It will turn. Therefore, the arc discharge does not disappear and the DC switch may fail.

  The arc discharge that occurs when the contact piece of the DC switch is released from the contact includes a concern that it will continue. Arc discharge also occurs when the contact piece is closed to the contact, but the arc discharge lasts for a period of time while the contact piece is closed, and is shorter than the duration when the contact piece is released from the contact. However, even in this case, if the number of occurrences of arc discharge increases, the same problem as described above may occur.

  This invention is made in view of such a point, and suppresses the failure of the DC switch due to arc discharge even when the DC power is mistaken for the predetermined polarity and connected to the DC switch. It is an object of the present invention to provide an input circuit and a power conversion device that can perform the above.

In order to achieve the above object, the input circuit of the present invention is an input circuit that connects DC power having a positive electrode and a negative electrode corresponding to each input terminal of a double-pole single-throw switch having a positive electrode input terminal and a negative electrode input terminal. And
The double pole single throw switch is an arc extinguishing system that attenuates arc discharge during operation of the switch when the positive pole of the DC power is connected to the positive input terminal and the negative pole of the DC power is connected to the negative input terminal. And a diode is electrically connected in a direction in which a current flows from the negative input terminal to the positive input terminal.

  In the input circuit of the present invention, even if the positive electrode and the negative electrode of DC power are mistakenly connected to the negative input terminal or the positive input terminal of the double-pole single-throw switch as a DC switch, the DC power is connected in front of the double-pole single-throw switch. Since the power is short-circuited by the diode, no current flows through the double-pole single-throw switch. Therefore, according to the input circuit of the present invention, since arc discharge does not occur in the double pole single throw switch, the possibility of failure of the double pole single throw switch due to arc discharge is reduced. The DC switch of the present invention can be applied to a solar cell module, a fuel cell, and a storage battery as a DC power source.

  In the input circuit of the present invention, a booster circuit having a reactance, a switching element, a rectifier diode, and a capacitor is connected to an output-side terminal of the double-pole single-throw switch, and the switching element is operated during operation of the switching element. A free-wheeling diode that enables energization in the direction opposite to the current direction may be provided.

  According to the input circuit of the present invention, it is possible to protect the double-pole single-throw switch even when the free-wheeling diode of such a booster circuit acts as a current circulation path when DC power is reversely connected. become.

  In the input circuit of the present invention, the DC power is preferably generated by a solar cell.

  Since a photovoltaic cell has a small electromotive force and output current of each cell, a desired DC power can be obtained by using a plurality of photovoltaic modules in which a plurality of photovoltaic cells are connected in series and in parallel. The For this reason, when applied to a power generated by a solar cell as DC power, there is a high possibility that the positive electrode and the negative electrode are erroneously connected, so that the operational effect of the input circuit of the present invention can be confirmed well.

  Furthermore, the power conversion device of the present invention is the power conversion device in which the DC power is input through the input circuit, and then the voltage is boosted by the boost circuit, converted into AC power by the inverter circuit, and supplied to the load. The input circuit is connected to a positive pole and a negative pole of the DC power corresponding to respective input terminals of a double pole single throw switch having a positive pole input terminal and a negative pole input terminal, and the double pole single throw switch is connected to the DC power When the positive electrode is connected to the positive electrode input terminal and the negative electrode of the DC power is connected to the negative electrode input terminal, the arc-extinguishing mechanism for attenuating arc discharge during operation of the double-pole single-throw switch, A diode is electrically connected in a direction in which a current flows from the negative input terminal to the positive input terminal, and the boost circuit includes a reactance, a switching element, a rectifier It has a diode and a capacitor, wherein the switching element, characterized in that the freewheeling diode which allows energization current direction opposite to the direction of operation of the switching elements are juxtaposed.

  According to the power conversion device of the present invention, even if the positive electrode and the negative electrode of DC power are mistakenly connected to the negative input terminal or the positive input terminal of the double-pole single throw switch, a current circulation path through the return diode can be obtained. Since DC power is short-circuited by a diode in front of the switch, no current flows through the switch and no arc discharge occurs. As a result, the possibility of failure of this switch due to arc discharge is reduced.

  In the power conversion device of the present invention, it is preferable that the DC power is generated by a solar cell.

  When applied to a power generated by a solar battery as DC power, as described above, even when the positive electrode and the negative electrode are erroneously connected to the power converter, the effects of the power converter of the present invention can be confirmed well. Become.

It is a block diagram of the alternating current power supply system of Embodiment 1. 3 is a circuit diagram of a current collector in Embodiment 1. FIG. FIG. 2 is a circuit diagram of an inverter in the first embodiment. 6 is a circuit diagram of a current collector in Modification 1. FIG. 10 is a circuit diagram of a current collector in Modification 2. FIG. It is a circuit diagram of the power converter device in Embodiment 2.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the embodiments and the drawings. However, each embodiment described below is an example of an input circuit and a power conversion device for embodying the technical idea of the present invention, and the input circuit described in these embodiments is described in the present invention. And is not intended to be specific to a power converter, and the invention is equally applicable to other embodiments within the scope of the claims. In addition, the present invention can be equally applied to any case where a solar cell, a fuel cell, or a storage battery is used as DC power, but in the following, a plurality of solar cells connected in series and in parallel as DC power. A case where a battery module is used will be described as a representative.

[Embodiment 1]
Initially, the schematic structure of the alternating current power supply system 1 of Embodiment 1 is demonstrated using FIG. The AC power supply system 1 includes a current collector (also referred to as a current collector box or a relay terminal box) 3 that bundles the generated power of a plurality of (for example, four) solar cell modules 2A to 2D into one DC power. The inverter unit 4 converts the DC power into AC power. The AC power output from the inverter unit 4 is appropriately supplied to the load 6 or superimposed on the commercial power supply system 7 via the interconnection relay 5. It has become so.

  Each of the solar cell modules 2A to 2D has a configuration in which a plurality (14 in the drawing) of solar cells are connected in series, and a plurality (two in the drawing) are connected in parallel. FIG. 2 shows a solar cell module 2A according to the first embodiment, which is an open / close switch 13A (a contact and a contact piece are one circuit, at least two of these circuits are built in, and the contact pieces of the two circuits are linked to each other) The solar cell module 2A is connected to the corresponding positive input terminal 11a and negative input terminal 12 provided in the current collector 3, respectively. .

  In the current collector 3, the positive and negative electrodes of the solar cell module 2A are connected to the positive electrode input terminal 11a and the negative electrode negative input terminal 12a, respectively, and the first diode 10a and the open / close switch 13A are provided. The output side of the open / close switch 13A is connected to the positive output terminal 14 and the negative output terminal 15, respectively. That is, the current collector 3 controls the DC power output from the positive electrode output terminal 14 and the negative electrode output terminal 15 by controlling the generated power of the solar cell module 2 </ b> A with the open / close switch 13 </ b> A.

  The open / close switch 13A used here has a double-pole single-throw switch for large currents in which the combination of the contact and the intercept is one circuit, and is interposed in the positive and negative lines, respectively. An arc extinguishing mechanism that extinguishes arc discharge generated during the opening / closing operation is provided. The arc extinguishing mechanism is configured to operate the switch when the positive electrode of the DC power is connected to the positive input terminal of the open / close switch 13A and the negative electrode of the DC power is connected to the negative input terminal of the open / close switch 13A. It is provided to attenuate the arc discharge. This arc extinguishing mechanism guides arc discharge in a specific direction from the magnetic material that is specifically arranged in the direction of current flow when the connection is made and the positional relationship between the current and the magnetic material. It is comprised from the arc-extinguishing member arrange | positioned in this direction. As an open / close switch having such a function, for example, there is a DC switch as disclosed in Patent Document 2. And in the current collection part 3 of this Embodiment 1, the 1st diode 10a is connected so that an electric current may flow toward the positive input terminal 11a side from the negative input terminal 12a.

  Further, the outputs of the positive output terminal 14 and the negative output terminal 15 of the current collector 3 are input to the positive input terminal 16 and the negative input terminal 17 of the inverter 4, respectively, as shown in FIG. The inverter 4 is mainly a DC / AC conversion circuit, and may be called a power conversion circuit, a PV inverter, a power conditioner, or the like. The inverter 4 converts the DC power into a specific AC power of 50 Hz to 60 Hz, that is, an AC power having the same phase as the AC power of the commercial power supply system, and outputs the AC power.

  The DC power input to the positive input terminal 16 and the negative input terminal 17 of the inverter 4 is input to the switch element module 18 via the DC reactor DCL. The switch element module 18 is configured as an IC as a step-up switching circuit 19 and a single-phase full bridge circuit 20 each having a parallel circuit of a transistor and a free wheel diode. The output side of the direct current reactor DCL is connected to the input side A point of the step-up switching circuit 19, and the smoothing capacitor CON is connected between the connection points B and C of the step-up switching circuit 19 and the full bridge circuit 20. Is connected. Further, the output points D and E of the full bridge circuit 20 are connected to an AC reactor ACL, respectively. As the direct current reactor DCL and the alternating current reactor ACL, those having a large reactance with respect to a frequency of 50 Hz to 60 Hz are used, and the smoothing capacitor CON having a large capacity is also used.

  Here, the DC reactor DCL, the boosting switching circuit 19 and the smoothing capacitor CON constitute a boost DC / DC converter circuit, and the full bridge circuit 20 and the pair of AC reactor ACLs constitute a DC / AC converter circuit. ing. The capacitor Xc connected to the output side of the AC reactor ACL is for noise removal. These step-up switching circuit 19 and full-bridge circuit 20 are controlled by signals from a separate control circuit, but these specific control methods are not related to the operation of the present invention, and ordinary ones are used. The detailed description thereof is omitted.

  Further, the AC output from the pair of AC reactors ACL is connected to the load 6 and the commercial power supply system 7 (see FIG. 1) through the pair of AC output terminals 21 and 22 and the interconnection relay 5.

  Here, the function of the first diode 10a will be described with reference to FIG. An electrician who connects the solar cell module 2A and the current collector 3 and an installer who installs the solar cell module 2A are usually performed by different operators. Therefore, an operator may mistakenly connect the positive electrode and the negative electrode of the solar cell module 2 </ b> A to the positive electrode input terminal 11 and the negative electrode input terminal 12 a of the current collector 3 in reverse.

  When such an erroneous connection is made, if a circuit for connecting a direct current is formed in the circuit connected to the positive output terminal 14 and the negative output terminal 15, the open / close switch 13A is opened and closed by closing the contact piece. A large current flows through the switch 13A. When the contact piece of the open / close switch 13A is opened from the contact in this state, arc discharge occurs between the contact and the contact piece inside the open / close switch 13A. In this arc discharge, since the direction of the current flowing through the open / close switch 13A is opposite to the design direction, the arc discharge direction due to the action of the magnetic material of the arc extinguishing mechanism correctly connected the positive electrode and the negative electrode of the solar cell module 2A. In some cases, the arc extinguishing member did not function in the opposite direction, and as a result, arc discharge continued without being reduced. If arc discharge is continued in the opening / closing switch 13A, the temperature in the opening / closing switch 13A becomes high, and the possibility of failure of the opening / closing switch 13A increases.

  However, in the AC power supply system 1 of the first embodiment, the first diode 10a is connected so that a current flows from the negative input terminal 12 of the current collector 3 toward the positive input terminal 11a. With such a configuration, when the positive electrode and the negative electrode of the solar cell module 2A are correctly connected to the positive electrode input terminal 11a and the negative electrode input terminal 12a of the current collector 3, current flows through the first diode 10a. It does not flow, and there is no influence such as change in the input impedance of the open / close switch 13A. However, when the positive electrode and the negative electrode of the solar cell module 2A are connected in reverse to the positive electrode input terminal 11a and the negative electrode input terminal 12a of the current collector 3, the reversely connected solar cell module 2A is placed in front of the open / close switch 13A. A short circuit occurs via the first diode, and no current flows to the open / close switch 13A. Therefore, the open / close switch 13A does not flow a current that may cause arc discharge when the contact piece of the open / close switch 13A is operated.

[Modifications 1 and 2]

  4A is a case where the solar cell modules are arranged in four rows of solar cell modules 2A to 2D. The current collector 3A in the first modification is similar to the current collector 3 of the first embodiment in that the open / close switches 13A to 13D, the positive input terminals 11a to 11d, the negative input terminals 12a to 12d, and the negative input terminals 12a to 12d are positive. In addition to the first diodes 10a to 10d connected so that current flows to the input terminals 11a to 11d side, the positive output terminals 14 and the positive output terminals 14 of the open / close switches 13A to 13D are provided. The second diodes 23a to 23d are inserted in the forward direction, respectively. Further, unlike the first modification, the current collector 3B according to the second modification is configured such that the second diodes 23e to 23h are disposed in the opposite directions between the negative output contact side of the on / off switches 13A to 13D and the negative output terminal 15, respectively. Inserted.

With such a configuration, when any of the positive and negative electrodes of the solar cell modules 2A to 2D is erroneously connected, a current flows through the first diodes 10a to 10d, and the open / close switches 13A to 13D. Since no current flows through the open / close switches 13A to 13D, no arc discharge occurs. However, if the output of another solar cell module wraps around the first diodes 10a to 10d, the diode may fail, for example, an open failure, and in this case, protection can be performed by incorrect connection of the solar cell modules. Disappear. In order to prevent this output wraparound, second diodes 23a to 23h are provided.
[Embodiment 2]
FIG. 6 shows the power conversion device 24 according to the second embodiment in which the input circuit having the configuration shown in the first modification is used as the input circuit of the inverter unit 4. That is, in the power conversion device 24 of the second embodiment, the positive output terminal 14 and the negative output terminal 15 of the first modification shown in FIG. 4 (the diodes 10a to 10d may be omitted) are the same as those of the inverter 4 shown in FIG. When connecting to the positive input terminal 16 and the negative input terminal 17, an input circuit composed of another open / close throw switch 13E and the first diode 10e is interposed.

  The open / close switch 13E includes an arc extinguishing mechanism that attenuates arc discharge, as in the case of the open / close switches 13A to 13D described above. The first diode 10e is electrically connected so that a current flows from the negative input terminal 12e of the open / close switch 13E to the positive input terminal 11e. Also in the power conversion device 24 of the second embodiment, the positive output terminal 14 of the current collector 3 is mistakenly connected to the negative input terminal 17 as in the case of the input circuit having the configuration shown in Modification 1 described above. When the negative output terminal 15 is connected to the positive input terminal 16, current is prevented from flowing through the open / close switch 13E.

  The DC power applied to the negative input terminal 17 constitutes a circulation circuit that returns to the positive input terminal 16 via a free wheel diode and a direct current reactor DCL that are provided in addition to the switch element of the switching circuit 19 of the booster, and the open / close switch 13E. However, no current flows through this circuit by the first diode 10e.

DESCRIPTION OF SYMBOLS 1 ... AC power supply system 2A-2D ... Solar cell module 3, 3A, 3B ... Current collection part (relay terminal box)
DESCRIPTION OF SYMBOLS 4 ... Inverter 5 ... Interconnection relay 6 ... Load 7 ... Commercial power supply system 10a-10e ... 1st diode 11a-11e ... Positive electrode input terminal 12a-12e ... Negative electrode input terminal 13A-13E ... Open / close switch 14 ... Positive electrode output terminal 15 ... Negative output terminal 16 ... Positive input terminal 17 ... Negative input terminal 18 ... Switch element 19 ... Switching circuit 20 ... Full bridge circuits 21, 22 ... AC output terminals 23a to 23h ... Second diode 24 ... Power converter DCL ... DC Reactor ACL ... AC reactor CON ... Smoothing capacitor Xc ... Capacitor RLY ... System relay

Claims (5)

Keep the input circuit connected to the DC power having positive and negative electrodes so as to correspond to respective input terminals of a bipolar single-throw switch having a positive input terminal and negative input terminals,
The double-pole single-throw switch is configured such that when a positive electrode of the DC power is connected to a positive input terminal and a negative electrode of the DC power is connected to a negative input terminal, a current flows when the switch is operated.
Together with the arc extinguishing mechanism for attenuating the arc discharge magnetic body disposed identify and countercurrent, the
An input circuit, wherein a diode is electrically connected in a direction in which a current flows from the negative input terminal to the positive input terminal so that the DC power is short-circuited in front of the switch . A booster circuit having a reactance, a switching element, a rectifier diode and a capacitor is connected to an output side terminal of the double-pole single-throw switch,
2. The input circuit according to claim 1, wherein the switching element is provided with a free-wheeling diode that enables energization in a direction opposite to a current direction during operation of the switching element. The input circuit according to claim 1, wherein the DC power is generated by a solar cell. In a power converter that inputs DC power through an input circuit, boosts the voltage with a booster circuit, converts the voltage into AC power with an inverter circuit, and supplies the AC power to a load.
Wherein the input circuit, the DC power is connected to the corresponding positive and negative electrodes to respective input terminals of a bipolar single-throw switch having a positive input terminal and negative input terminals, said bipolar single-throw switch, the DC When the positive electrode of power is connected to the positive electrode input terminal and the negative electrode of the DC power is connected to the negative electrode input terminal, the direction of current flow when operating this switch is specified.
Together with the arc extinguishing mechanism for attenuating the arc discharge magnetic body arranged Te, the switch
A diode is electrically connected in a direction in which a current flows from the negative input terminal to the positive input terminal so that the DC power is short-circuited before, and the booster circuit includes a reactance and a switching element. A power conversion device comprising a rectifier diode and a capacitor, wherein the switching element is provided with a free-wheeling diode capable of energizing in a direction opposite to a current direction during operation of the switching element. The power converter according to claim 4, wherein the DC power is generated by a solar battery.

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