JP2004208408A - Initial charging method of grid connected inverter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow initial charging with no overcharge, in an inverter which is operated in connection with a power system. <P>SOLUTION: If an inverter INV is connected to a grid power supply through thyristors THRF-THTR, a filter capacitor C13 is included in the initial charge path of a DC capacitor C1 when, for example, the thyristors of various phases such as THRF, THSR, and THTF are ignited. And the DC capacitor C1 is charged at such a voltage as the voltage of the capacitor C13 is added to an inter-system voltage VRS, resulting in over charging. Here, with one single phase of thyristor (for example S-phase) among three phases extinguished, the thyristors of remaining two phases are phase-controlled, to exclude the DC capacitor C1 from charging/discharging paths of filter capacitors C11-C13 (see arrowed path). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a grid-connected inverter operated in connection with a power grid (hereinafter, also simply referred to as a grid), and particularly to an initial charging method thereof.
[0002]
[Prior art]
FIG. 5 shows a conventional example of this type (for example, see Patent Document 1).
This is to prevent an excessive current from flowing through the DC capacitor C1 during the initial charging by performing phase control to gradually open the firing angle of the thyristor TSY11 from 180 ° and the firing angle of the thyristor TSY12 from 360 °. Is what you do.
[0003]
[Patent Document 1]
JP-A-07-241084 (page 4-5, FIG. 1)
[0004]
[Problems to be solved by the invention]
However, the apparatus shown in FIG. 5 has the following problems.
FIG. 6 is a circuit diagram for explaining the problem. This means that FIG. 5 has a three-phase configuration and that the filter capacitors C11 to C13 are connected between the thyristors THRF to THTR and the AC reactor ACL1.
[0005]
In the circuit diagram of FIG. 6, if the thyristors THRF, THSR, and THTF are ignited at a certain timing, for example, the DC capacitor C1 is included in the charging and discharging paths of the filter capacitors C11 to C13 (see FIG. 6). (See the path indicated by the arrow.), The DC capacitor C1 is charged with a voltage obtained by adding the voltage of the filter capacitor C13 (VC13) to the system line voltage VRS, and there is a problem that a charge pump operation is performed and overcharging occurs. .
Therefore, an object of the present invention is to prevent overcharging from occurring during initial charging of a grid-connected inverter.
[0006]
[Means for Solving the Problems]
In order to solve such a problem, according to the first aspect of the invention, when initially charging a grid-connected inverter having a thyristor inserted between the inverter and the power system,
The phase control is performed on the remaining two thyristors while any one of the three phases is extinguished.
According to the first aspect of the present invention, the thyristors of the remaining two phases for performing the phase control are fired only in one direction of the alternating current, and the thyristors in the opposite direction can be kept extinguished (the invention of the second aspect). .
Further, in the first or second aspect of the invention, a capacitor can be connected between each phase of the power system (the third aspect of the invention).
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a circuit diagram for explaining a first embodiment of the present invention, and FIG. 2 is an explanatory diagram of a charge / discharge path in FIG.
In the circuits of FIGS. 1 and 2, when the thyristor is fired, the DC capacitor C1 is charged, and the charging and discharging of the filter capacitors C11 to C13 occur. At this time, if the thyristors THSF and THSR of, for example, the S-phase among the three phases are kept extinguished and the phase control is performed between the two phases, the charging and discharging of the filter capacitors C11 to C13 are performed as indicated by the arrows in FIG. In a path that does not pass through the DC capacitor C1.
[0008]
Therefore, the charge pump operation of charging the DC capacitor C1 with the voltage obtained by adding the voltages of the filter capacitors C11 to C13 to the system line voltage does not occur, and as a result, the DC capacitor C1 exceeds the system voltage. It will not be charged. This initial charging operation by thyristor phase control of only two phases corresponds to single-phase full-wave rectification. After the completion of the initial charging, the inverter INV is operated, and when the inverter INV generates the same voltage as the system voltage, the thyristor may be fired in a firing pattern required for the inverter INV, such as all firings.
[0009]
FIG. 3 is a circuit diagram for explaining a second embodiment of the present invention, and FIG. 4 is an explanatory diagram of a charge / discharge path in FIG.
In the circuits of FIGS. 3 and 4, when the thyristor is fired, the DC capacitor C1 is charged, and the charging and discharging of the filter capacitors C11 to C13 occur. At this time, if, for example, the thyristors THSF and THSR of the S-phase among the three phases are kept extinguished, and the thyristors THRR and THTF are kept extinguished to perform phase control in only one direction between the remaining two phases, for example, The charging and discharging of the capacitors C11 to C13 are performed through a path that does not pass through the DC capacitor C1, as indicated by a path indicated by an arrow in FIG.
[0010]
Therefore, the charge pump operation of charging the DC capacitor C1 with the voltage obtained by adding the voltages of the filter capacitors C11 to C13 to the system line voltage does not occur, and as a result, the DC capacitor C1 exceeds the system voltage. It will not be charged. This initial charging operation by the thyristor phase control of only two phases corresponds to single-phase half-wave rectification. After the completion of the initial charging, the inverter INV is operated, and when the inverter INV generates the same voltage as the system voltage, the thyristor may be fired in a firing pattern necessary for the inverter INV, such as all firings.
[0011]
【The invention's effect】
According to the present invention, in a system interconnection inverter in which a thyristor is inserted between an inverter and a system, overcharging does not occur even when the DC capacitor is initially charged by controlling the phase of the thyristor. As a result, in grid-connected inverters such as uninterruptible power supplies, a thyristor may be inserted between the grid and the inverter to separate the grid from the inverter when the grid fails. By charging, the device can be reduced in size without the need for a dedicated charger.
[Brief description of the drawings]
FIG. 1 is a circuit diagram illustrating a first embodiment of the present invention. FIG. 2 is an explanatory diagram of a charge / discharge path in FIG. 1. FIG. 3 is a circuit diagram illustrating a second embodiment of the present invention. FIG. 4 is an explanatory diagram of a charge / discharge path in FIG. 3; FIG. 5 is a configuration diagram showing a conventional example; FIG. 6 is a circuit diagram for explaining a problem in FIG.
1 ... 2 ... 3 ... 4 ... 5 ... 6 ... 7 ... VR, VS, VT ... System voltage, THRF, THRR, THSF, THSR, THTF, THTR ... Thyristor, C11, C12, C13 ... Filter capacitor, ACL1: AC reactor, INV: Inverter, C1: DC capacitor.

Claims (3)

When initially charging a grid-connected inverter with a thyristor inserted between the inverter and the power grid,
An initial charging method for a grid-connected inverter, characterized in that phase control is performed on the remaining two-phase thyristors while any one of the three phases is extinguished. 2. The initial charging of the grid-connected inverter according to claim 1, wherein the remaining two-phase thyristors for performing the phase control are fired only in one direction of alternating current, and the thyristors in the opposite direction are kept extinguished. Method. The method according to claim 1 or 2, wherein a capacitor is connected between each phase of the power system.

Images