Method for stabilizing an AC voltage grid

Abstract

A configuration for stabilizing an AC voltage grid has a rotating phase-shifter that is configured to exchange reactive power with the AC voltage grid. The configuration is distinguished by a converter which has a grid side for connection to the AC voltage grid and a machine side for connection to the phase-shifter. A method is furthermore taught for stabilizing the AC voltage grid by way of the configuration.

Claims

1. A method for stabilizing an AC voltage grid, which comprises the steps of: providing a rotating phase-shifter that exchanges reactive power with the AC voltage grid during normal operation; connecting the rotating phase-shifter to the AC voltage grid by way of a converter upon identification of a predetermined frequency drop in the AC voltage grid; disconnecting the rotating phase-shifter from the AC voltage grid, upon identification of a frequency drop, by opening a switch and instead connecting the rotating phase-shifter to the AC voltage grid via the converter by further closing an input switch between the rotating phase-shifter and the converter; and feeding stored energy of the rotating phase-shifter into the AC voltage grid in a form of active power.

2. The method according to claim 1, which further comprises performing frequency regulation at the converter so as to control an infeed of the active power.

3. The method according to claim 1, which further comprises stepping up a converter voltage generated on a grid side by way of a main transformer that is disposed between the converter and the AC voltage grid.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a schematic illustration of an exemplary embodiment of an arrangement according to the invention; and

(2) FIG. 2 is a schematic flowchart of an exemplary embodiment of a method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown an arrangement 1 for stabilizing an AC voltage grid 2. The AC voltage grid 2 is a three-phase distribution grid with a nominal voltage of 400 kV and a nominal frequency of 50 Hz. The arrangement 1 contains a rotating phase-shifter 14 having a synchronous machine 10 (synchronous generator) and an exciter system 11. The phase-shifter 14 is connected to a secondary side 6 of a main transformer 4 (“step-up transformer”) by way of a generator-side switching device 7. A primary side 5 of the main transformer 4 is able to be connected to the AC voltage grid 2 by way of a further switching device 3.

(4) The arrangement 1 furthermore comprises a thyristor-based converter 12 having a machine side 15 for connection to the phase-shifter 14 and having a grid side 16 for connection to the main transformer 4. The connection to the main transformer 4 may be implemented by way of a further transformer 8 having a primary winding 81 and secondary winding 82 and a power switch 9. The converter 12 is able to be connected to the phase-shifter 14 by way of an input switch 17.

(5) A control and regulation device 13 is configured to regulate (in particular regulate the frequency of) the converter 12.

(6) The process during operation of the arrangement according to FIG. 1 is illustrated in FIG. 2.

(7) In a first step 101, the phase-shifter 14 is connected to the AC voltage grid 2 for normal operation and reactive power is exchanged between the phase-shifter 14 and the AC voltage grid 2. The frequency in the AC voltage grid 2 is monitored.

(8) Upon identification of a frequency drop, that is to say a frequency in the AC voltage grid 2 below a frequency threshold (for example below 47 Hz), in a second step 102, the phase-shifter is disconnected from the AC voltage grid by opening the switching device 7.

(9) In a third step 103, the phase-shifter 14 is instead connected to the AC voltage grid 2 via the converter 12 by closing the input switch 17 disposed in the AC voltage grid.

(10) In a fourth step 104, frequency regulation of the converter 12 is started, and residual energy of the phase-shifter 14 begins to be fed into the AC voltage grid 2 in the form of active power.