JPH02184268A - Starting of system interconnecting inverter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for starting an inverter for grid connection using a secondary battery as a DC power source.

(Prior technology) Recent high-capacity, high-performance rechargeable and dischargeable secondary batteries (hereinafter referred to as new batteries or secondary batteries) convert DC power into AC power using an inverter and connect a grid reactor or transformer. If you connect it to the power grid via the
Since it can be discharged during the daytime when electricity is in short supply and used to level the electricity load, it is attracting attention as an effective use of energy.

A third generation grid-connected inverter using conventional new batteries
In Fig. 3 shown in the figure, 1 is a new type of battery, 2 is a DC switch that connects and disconnects the new type of battery 1 and the inverter, and 3 is a smoothing reactor.

4 is a smoothing capacitor, 5A to 5F is a self-extinguishing element such as GTO (hereinafter referred to as GTO) that makes up the inverter circuit, 6A to 6F is a feedback diode that makes up the inverter circuit, and 7 is a system for controlling the inverter output voltage. A transformer for matching the voltage, 8 a grid interconnection reactor, 9 an AC switch for interconnecting the grid interconnection inverter and the power grid, 10 the power grid, 11 for charging the smoothing capacitor 4 Charging current suppression resistor, 12 is smoothing capacitor 4
13 is a transformer.

14 is a switch that turns on and off the smoothing capacitor 4 and the charging circuit, and 15 is a charging power source.

The circuit shown in FIG. 3 operates as follows. First, the switch 14 of the charging circuit is turned on, and the smoothing capacitor 4 is charged through the charging current suppressing resistor 11. When charging is completed, open the switch 14 and close the DC switch 9.
Then, the AC switch 2 is turned on, the grid connection inverter is started, and normal operation begins.

(Problem to be solved by the invention [) The starting method in the circuit shown in Figure 3 is suitable if the voltage of the new type of battery has been established, but with the new type of battery, the initial voltage
There is also operation from V, and in that case, when the switch 9 is turned on, there is a problem in that the battery charging current flows indefinitely until it reaches the voltage generated by the rectifier circuit by the feedback diodes 6A to 6F. For this reason, smoothing capacitor 4
A method of charging the battery through a charging circuit is also considered, but since the capacity of the charging circuit is usually smaller than that of the inverter circuit, there is a problem in that it takes time to charge the battery. Furthermore, it is uneconomical to provide a charging circuit with a large capacity.

Therefore, an object of the present invention is to convert DC power supplied from a secondary battery via a DC switch into AC power using a self-excited inverter, and supply the AC power to the power grid via a grid interconnection reactor and an AC switch. To provide a method for starting a grid-connected inverter which can omit a conventionally used charging circuit and can be operated even when the voltage of a secondary battery is Ov. It is in.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention converts DC power supplied from a secondary battery via a DC switch into AC power using a self-excited inverter, and connects the AC power. In a grid-connected inverter configured to supply power to the power grid via a system reactor and an AC switch, a first switch is provided between the secondary battery and the DC side of the self-excited inverter via a first switch. and a second current suppressing element provided via a second switch between the power system and the alternating current side of the self-commutated inverter; 1. The second switch is closed, and after detecting that charging of the smoothing capacitor of the self-excited inverter and the secondary battery is completed, the first and second switches are opened, and the DC switch and The invention is characterized in that the self-excited inverter is activated by turning on an AC switch.

(Function) As described above, by closing the first and second switches prior to starting the self-excited inverter, through the series circuit of the first switch and the first current suppressing element, Since the AC voltage of the power system is applied to the AC side of the self-excited inverter, the smoothing capacitor of the self-excited inverter has
It is charged by the DC voltage applied through the feedback diode of the self-commutated inverter, and its charging current is limited by the first current suppressing element. If the voltage of the secondary battery is Ov at this time, the secondary battery is also charged by the DC voltage applied via the feedback diode of the self-excited inverter,
The charging current is limited by the first current suppressing element and the second current suppressing element.

After detecting completion of charging of the smoothing capacitor and the secondary battery, the first and second switches are opened, and the DC switch and AC switch are turned on to start the self-excited inverter.

(Example) An example of the present invention will be described below with reference to FIG. In FIG. 1, the same elements as those in FIG. 5, which have already been explained, are given the same reference numerals, and their explanation will be omitted.

In FIG. 1, 16 is a first switch that is closed before starting the grid-connected inverter, 17 is a first current suppressing element that suppresses the charging current of the secondary battery, and 18 is a grid-connected inverter. The second switch 19, which is closed prior to activation of the smoothing capacitor 4, is a second current suppressing element that suppresses the charging current of the smoothing capacitor 4. 20 is a current detector for detecting the charging current of the secondary battery l, 21 is a voltage detector for detecting the voltage of the smoothing capacitor 4, and 22 is a control device for controlling the sequence of the entire system.

Next, the operation of FIG. 1 will be explained. 6 When a start command 51 is input to the control device 22 from a control device not shown in FIG. , enters the second switch 18 and issues a command 52. As a result, the first switch 16 and the second switch 18 are closed. Then, the smoothing capacitor 4 is charged from the power system 10 through the second current suppressing element 19, the second switch 18, and the feedback diodes 6A to 6F of the self-commutated inverter.

On the other hand, at this time, the voltage of the secondary battery 1 is
, the secondary battery 1 is also charged by the DC voltage obtained through the feedback diodes 68 to 6F of the self-excited inverter, and the charging current is limited by the first current suppressing element 17.

If the voltage of the secondary battery 1 is higher than the voltage of the smoothing capacitor 4 when the first switch 16 and the second switch 18 are closed, the smoothing capacitor 4 is charged from the secondary battery 1. There is also.

After the first switch 16 and the second switch 18 are closed, the current flowing through the first switch 16 is detected by a current detector 2.
0, and when it is detected that the value is below a predetermined value, the first switch I6 and the second switch 18 are opened, and immediately after, the switch 2 and the AC switch 9 are turned on, and the operation command 56 is sent to the inverter. output and resume normal operation.

In the above description, the first switch 16 and the second switch 18 are closed at the same time, but the second switch 18 is closed first, and after the smoothing capacitor 4 is charged, the first switch 16 is closed. may be closed.

2. The same parts as in Figs. 1 and 3 are given the same reference numerals.
The figure shows another embodiment of the present invention, in which a first switch I6 is connected in series with a parallel circuit of a first current suppressing element 17 and a DC switch 2, and a second current suppressing element 17 and a DC switch 2 are connected in series. An example is shown in which the second switch 18 is connected in series in a parallel circuit with an AC switch. In this embodiment, prior to starting the self-excited inverter, the first switch 16
and the second switch 18 is closed, and the smoothing capacitor 4 is closed.
After charging of the secondary battery 1 is completed, the first switch 16 and the second switch 18 are closed.

Turn on the DC switch 2 and AC switch 9.

Note that in the above explanation, the first term refers to the completion of charging.
It is detected by the current flowing through the switch 16 of
For example, it may be detected by a common means of detecting the difference between the secondary battery voltage and the smoothing capacitor voltage.

〔Effect of the invention〕

As explained above, according to the present invention, whether the voltage of the secondary battery is established or not, it can be started without flowing an excessive charging current, and the charging circuit used conventionally can be omitted. It is possible to provide a method for starting a grid-connected inverter that can also be used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing another embodiment of the present invention, and FIG. 3 is a block diagram of a conventional device. 1... Secondary battery 2... DC switch 3... Smoothing reactor 4... Smoothing capacitor 5... A~5F... GTO6A~6F... Feedback diode 7... Transformer Vessel 8...
Grid connection reactor 9... AC switch 10.
...Power system 16...First switch 17.
...First current suppressing element 18...Second switch
19...Second current suppressing element 20...Current detector 21...Voltage detector 22...Control device agent Patent attorney Noriyuki Chika Ken Yudo Daishimaru Ken

Claims (1)

[Claims] For grid connection, DC power supplied from a secondary battery via a DC switch is converted to AC power by a self-excited inverter, and the AC power is supplied to the power grid via a grid interconnection reactor and an AC switch. In the inverter, a first
a first current suppressing element provided via a switch;
A second current suppressing element is provided between the power system and the alternating current side of the self-commutated inverter via a second switch, and the first and second The switch is closed, and after detecting that charging of the smoothing capacitor of the self-excited inverter and the secondary battery is completed, the first and second switches are opened, and the DC switch and the AC switch are closed. A method for starting an inverter for grid connection, characterized in that the self-excited inverter is started by turning on the self-excited inverter.