Abstract: A thyristor bridge of an electrical converter is connected to at least one DC link and including at least one phase leg for each output phase and each phase leg being composed of two series-connected thyristor arms. The thyristor arms of a thyristor bridge are cyclically switched by: determining an upper bound for a firing angle of a thyristor arm, wherein the upper bound is determined from voltage and current measurements; and determining a firing angle for the thyristor bridge, which firing angle determines a switching time of the thyristor arm, wherein the firing angle is determined, such that it is less or equal to the upper bound.

Abstract: An electrical converter with at least two output phases includes a rectifier and a thyristor-based inverter interconnected by a DC link with an inductor, wherein the thyristor-based inverter includes a half-bridge with at least two half-bridge arms for each output phase of the electrical converter and each arm being provided by a thyristor. A method for switching the electrical converter includes: cyclically switching the thyristors of the inverter, such that at least one time instant, two thyristors of different half-bridge arms are switched on simultaneously, such that a pulse number, which determines at how many time instants thyristors of the inverter are switched during one stator voltage period, is lower than the number of half-bridge arms of the inverter.

Abstract: A thyristor bridge of an electrical converter is connected to at least one DC link and including at least one phase leg for each output phase and each phase leg being composed of two series-connected thyristor arms. The thyristor arms of a thyristor bridge are cyclically switched by: determining an upper bound for a firing angle of a thyristor arm, wherein the upper bound is determined from voltage and current measurements; and determining a firing angle for the thyristor bridge, which firing angle determines a switching time of the thyristor arm, wherein the firing angle is determined, such that it is less or equal to the upper bound.

Abstract: An electrical converter with at least two output phases includes a rectifier and a thyristor-based inverter interconnected by a DC link with an inductor, wherein the thyristor-based inverter includes a half-bridge with at least two half-bridge arms for each output phase of the electrical converter and each arm being provided by a thyristor. A method for switching the electrical converter includes: cyclically switching the thyristors of the inverter, such that at least one time instant, two thyristors of different half-bridge arms are switched on simultaneously, such that a pulse number, which determines at how many time instants thyristors of the inverter are switched during one stator voltage period, is lower than the number of half-bridge arms of the inverter.

Abstract: A system for controlling an electrical drive including the steps of: receiving an input reference value for a first mechanical variable; estimating a second mechanical variable for a predefined time based on a model based on: a first equation for predicting a future state of the drive system a second equation for predicting at least an actual value of the second mechanical variable; and selecting a first future value from development of the second mechanical variable.

Abstract: A load commutated converter interconnects an AC power grid with an AC load and comprises a grid-side converter, a DC link and a load-side converter. A method for controlling the load commutated converter comprises: determining a gridside firing angle for the grid-side converter; determining a load-side firing angle for the load-side converter; determining a grid voltage of the AC power grid; modifying the grid-side firing angle and/or the load-side firing angle based on the grid voltage, such that when an undervoltage condition in the AC power grid occurs, the operation of the load commutated converter is adapted to a change in the grid voltage; and applying the grid-side firing angle to the grid-side converter and the load-side firing angle to the load-side converter.

Abstract: A load commutated converter interconnects an AC power grid with an AC load and comprises a grid-side converter, a DC link and a load-side converter. A method for controlling the load commutated converter comprises: determining a gridside firing angle for the grid-side converter; determining a load-side firing angle for the load-side converter; determining a grid voltage of the AC power grid; modifying the grid-side firing angle and/or the load-side firing angle based on the grid voltage, such that when an undervoltage condition in the AC power grid occurs, the operation of the load commutated converter is adapted to a change in the grid voltage; and applying the grid-side firing angle to the grid-side converter and the load-side firing angle to the load-side converter.

Abstract: A system for controlling an electrical drive including the steps of: receiving an input reference value for a first mechanical variable; estimating a second mechanical variable for a predefined time based on a model based on: a first equation for predicting a future state of the drive system a second equation for predicting at least an actual value of the second mechanical variable; and selecting a first future value from development of the second mechanical variable.

Abstract: An exemplary method for controlling an electrical converter includes receiving an actual electrical quantity relating to the electrical converter and a reference quantity; determining a future state of the electrical converter by minimizing an objective function based on the actual electrical quantity and the reference quantity as initial optimization variables; and determining the next switching state for the electrical converter from the future state of the electrical converter. The objective function is iteratively optimized by: calculating optimized unconstrained optimization variables based on computing a gradient of the objective function with respect to optimization variables; and calculating optimization variables for a next iteration step by projecting the unconstrained optimization variables on constraints. The computation of the gradient and/or the projection is performed in parallel in more than one computing unit.

Abstract: A modular converter is disclosed which includes plural converter cells connected in series on a first side, and connected on a second side, wherein each converter cell includes an AC-to-DC converter connected to the first side and a DC-to-DC converter connected to the second side. Exemplary embodiments estimate power transferred by the modular converter; compare the transferred power with a threshold value; when the transferred power exceeds the threshold value, operate in a normal load operation mode; when the transferred power is below the threshold value, operate in a low load operation mode with reduced switching losses.