Asea Brown Boveri Ag

Abb Schweiz Ag

Abb Management Ag

Osvin Gaupp

Peter Dahler

Gerhard O Linhofer

Beat Ronner

Jean-Francedillaois Ravot

Horst Gruning

Peter D&auml;hler

Peter D{umlaut Over (a)}hler

Christoph Tschudi

Jean-Fran&ccedil;ois Ravot

The disclosure specifies a method for operating a converter circuit, the converter circuit having a converter unit with a large number of drivable power semiconductor switches and with a three-phase electrical AC voltage system, in which the drivable power semiconductor switches are driven by means of a drive signal (S) formed from a control signal ((S), and the control signal (S) is formed by adjusting an H-th harmonic component of system currents (i) to a system current setpoint value (i), where H=1, 2, 3, . . . . In order to reduce a harmonic component in the system voltages, the system current setpoint value (i) is formed by adjusting an H-th harmonic component of system voltages (u) to a predeterminable system voltage setpoint value (u), the control difference (u) from the H-th harmonic component of the system voltages (u) and the system voltage setpoint value (u) being weighted by a system impedance (y) determined with respect to the H-th harmonic component. In addition, an apparatus is disclosed for implementing the method.

Method for operating a converter circuit and apparatus for implementing the method

A method for operating a converter circuit is disclosed. Such a converter circuit has a converter unit with a multiplicity of actuatable power semiconductor switches and is connected to a three-phase electrical AC mains system and in which the actuatable power semiconductor switches are actuated by means of an actuation signal (S) formed from a control signal (S), and the control signal (S) is formed by adjusting an H-th harmonic component of system currents (i) to a system current setpoint value (i), wherein H=1, 2, 3 . . . . For the purpose of reducing a harmonic component in the system voltages, the system current setpoint value (i) is formed by adjusting the absolute value of an H-th harmonic component of the system voltages (u) to the absolute value of a prescribable system voltage setpoint value (u). An exemplary apparatus carries out the method.

Method for operating a converter circuit, and apparatus for carrying out the method

A converter circuit arrangement is disclosed for matching a variable DC voltage to a drive circuit for producing drive signals and having a three-point DC voltage intermediate circuit ( ), which three-point DC voltage intermediate circuit ( ) is formed by a first capacitor ( ) and a second capacitor ( ) connected in series with it, with one connection of the first capacitor ( ) forming an upper connection ( ) of the three-point DC voltage intermediate circuit ( ), and the first capacitor ( ) forming a center point connection ( ) at the junction point with the second capacitor ( ) and one connection of the second capacitor ( ) forming a lower connection ( ) of the three-point DC voltage intermediate circuit ( ). A first partial converter system ( ) and a second partial converter system ( ) are provided, with the input side of the first partial converter system ( ) being connected to a first pole ( ) of a DC voltage source ( ) which produces the DC voltage, and the input side of the second partial converter system ( ) being connected to a second pole ( ) of the DC voltage source ( ), a first output ( ) of the first partial converter system ( ) being connected to the upper connection ( ), and a first output ( ) of the second partial converter system ( ) being connected to the lower connection ( ). Furthermore, a second output ( ) of the first partial converter system ( ) is connected in series with a second output ( ) of the second partial converter system ( ) via the center point connection ( ). A method for matching a variable DC voltage is also specified.

Converter circuit arrangement, as well as a method for matching a variable DC voltage

An invertor having a plurality of invertor bridges which operate in parallel and whose output voltages are summed. The invertor bridges are driven with pulse duration modulation according to an auxiliary control voltage. The auxiliary control voltages of the individual invertor bridges have a constant phase difference between one another. The output voltages of the bridges are summed by a center tap which is grounded by a ground connection. Effective suppression of the common-mode current distortion is achieved by having the switch arranged in the ground connection.

Invertor

A power converter circuit arrangement which comprises a first power converter and at least one further power converter is specified. The power converters are connected to the DC voltage intermediate circuit and feed a load circuit, in particular a single-phase railway grid. The or each further power converter has an output transformer on the load side. The secondary windings of the output transformers are connected in series with the primary winding of a load transformer, which feeds the load circuit, and the load-side terminals of a first power converter. This permits the turns ratios of the output transformers to be selected to be greater than or equal to one and said turns ratios between said output transformers to be selected to be gradated in a binary or ternary manner, for example. As a result, power converter stages having a gradated output voltage are available, and a finely stepped approximation to a sinusoidal output voltage can be achieved without the necessity of providing an uneconomically large number of stages.

Power breaker

An inverter having a plurality of inverter bridges which operate in parallel and whose output voltage is summed by way of a transformer. The transformer has a number of primary windings and associated secondary windings which correspond to the number of inverter bridges. Each inverter bridge is connected on the output side to a primary winding. The secondary windings are connected in series to sum the output voltages. The transformer has a center tap which is grounded by a ground connection. The suppression of in-phase or common-mode interference currents flowing by the ground connection and the interference voltages associated therewith is achieved by dividing the secondary windings into a first and second identical partial secondary winding. The partial secondary windings are connected to one another in the center tap in such a way that the common-mode currents and voltages induced in the partial secondary windings mutually cancel.

Invertor with reduced common mode voltage

An invertor (15) includes a plurality of invertor bridges (B1, . . . ,B8), which are connected in parallel and whose output voltages are summed via a transformer (19). The transformer (19) has a number of primary windings (P1, . . . ,P8) and associated secondary windings (S1, . . . ,S8) which corresponds to the number of invertor bridges (B1, . . . ,B8). Each invertor bridge (B1, . . . ,B8) is connected on the output side to one of the primary windings (P1, . . . ,P8), and the secondary windings (S1, . . . ,S8) are connected in series to sum the output voltages. The transformer (19) has a center tap (23) which is grounded via a ground connection (24). Tertiary windings (T1, . . . ,T8) are assigned to the primary windings (P1, . . . ,P8) and to the secondary windings (S1, . . . ,S8). The tertiary windings (T1, . . . ,T8) are also connected to a common-mode filter (51). The common-mode filter (51) is tuned to common mode interference voltages associated with in-phase or common-mode interference currents flowing via the ground connection (24). Thus, a circuit is formed that attenuates or suppresses the in-phase or common-mode interference currents and the associated interference voltages.

Invertor with suppression of interference currents

A method and a device for correcting the DC offset of a converter are specified. The invention is defined in that the output voltage of the converter on the AC voltage side is fed to an essentially passive low-pass filter which reduces the output voltage to a level which can be processed electronically. Connected downstream of the low-pass filter is a controller which controls the DC offset essentially to zero by delaying the switching commands. The low-pass filter and the controller are arranged at a high-voltage potential.

Device for compensating the DC offset of a converter using a controller

A common turn-off circuit for a thyristor power converter is specified. The common turn-off circuit is particularly suitable for AC converters such as, for example, railway grid couplings. The turn-off thyristors are directly connected to the secondary transformer windings. Additionally provided is a special freewheeling path via which the energy stored, in particular, in the transformer inductors or other relevant inductors can be drawn away. What is advantageous is the fact that all of the thyristors of the power converter can be turned off reliably and without any special precautions, since the common turn-off circuit is automatically ready for turning off. Overvoltages are avoided, moreover, by the special freewheeling path.

Common turn-off circuit for a thyristor power converter

In operation, DC arc furnaces produce reactive load fluctuations which lead to undesirable flickering phenomena especially in a frequency range from 2 Hz-20 Hz. In order to reduce these flickering phenomena, comparatively fast reactive power regulation is superimposed on slow current regulation of the DC arc furnace which is controlled by rectifiers. In consequence, the use of a reactive-power compensator to compensate for reactive power fluctuations in superfluous.

Regulation method for a DC arc furnace

A converter bridge includes at least two half bridges, which are connected together by bus bars. The bus bars include at least two directly opposite bus bar segments and are arranged mirror symmetrically relative to a median plane in the converter bridge. The directly opposite bus bar segments exhibit a relatively small line cross section. Due to the mirror symmetrical arrangement, a high frequency secondary current component, which flows in the opposite direction and belongs to the current flowing through the bus bars, is concentrated in the directly opposite segments of the bus bar and is damped effectively via the relatively small line cross section. In contrast, the low frequency main current component flows in essence uniformly distributed over the profile of the bus bar.

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Baden, Switzerland

Osvin Gaupp