Abb Schweiz Ag

Abb Technology Ag

John Daniel

Madhav Manjrekar

Philippe Maibach

David L Dickmander

Ulf Andersson

Bilal Gerhard

Philippe Fischer

A distribution and power transformer has its primary connected to the high voltage bus of the network and its secondary connected to a switching device. Upon the occurrence of a condition known to cause a dynamic overvoltage (DOV) and the occurrence of the DOV, a control system causes the switching device to change from a nonconductive mode to a conductive mode in less than the time for one cycle of the operating frequency of the AC network. This change in switching device conduction places a short circuit across the transformer secondary and thus mitigates the DOV.

Method and apparatus for mitigation of dynamic overvoltage

A method is specified for operating a charger ( ) for a voltage-maintaining device ( ), in which a rectifier ( ), connected to phase inputs (P , P ; P ) via a transformer ( ) with an electric AC voltage supply system ( ), of the charger ( ) is driven by means of a drive signal (S) formed from reference charging voltages (U ; U ; U ). Furthermore, a charging voltage (U ; U ; U ) for the corresponding phase (A; B; C) is generated at each phase input (P ; P ; P ) a substantially constant DC voltage (U ) being generated-on the DC voltage side of the rectifier ( ). Each charging voltage (U ; U ; U ) is generated in such a way that in the corresponding phase (A; B; C) a charging current (I ; I ; I ) is injected in a fashion substantially proportional to a phase system voltage (U ; U ; U ) of the corresponding phase (A; B; C) of the electric AC voltage supply system ( ). An apparatus for carrying out the method is also disclosed.

Method for operating a charger for a voltage-maintaining device, and an apparatus for carrying out the method

A converter circuit is specified for voltage maintenance in an electrical AC supply network ( ), with the electrical AC supply network ( ) having an associated voltage source (UR; US; UT) for each phase (R; S; T) for supplying an electrical load ( ), with the converter circuit having a respective inverter ( ) for each phase (R; S; T), which inverter ( ) is connected on the DC side via an energy-storage capacitor ( ) to a supply device ( ). On the AC side, each inverter ( ) is connected in series between the associated voltage source (UR; US; UT) and the electrical load ( ) in the respective phase (R; S; T), and in that, on the AC side, the supply device ( ) is connected to at least two phases (R; S; T) between the associated voltage sources (UR; US; UT) and the respective inverters ( ).

Converter circuit having an inverter for each phase

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John Daniel