An operating circuit and a method for operating a synchronous machine on a voltage supply network is disclosed. The operating circuit has a converter circuit with controllable converter switches and a controllable switching arrangement to switch the converter circuit between a start converter configuration and a direct converter configuration. The power supply network is connected to a converter output and the synchronous machine is connected to a converter input of the converter circuit. In the direct converter configuration, an AC voltage is provided at the converter output with a preset AC voltage frequency. In the direct converter configuration, the switching of the AC voltage between the converter input and the converter output takes place without intermediate rectification.

The present invention corresponds to a method and an apparatus for detecting faults in transmission and distribution systems. The method is characterized by the steps of: a) Rectifying the ac current signal of the “auxiliary services” triphasic system; b) Rectifying and inverting the ac current signal of the transmission and distribution system; c) Connecting the step b signal to step a signal; d) Measuring the ac current signal obtained in step b; e) Measuring the dc current signal rectified in step a; f) Scaling the value of the current measured in step e by a scale k factor; g) Calculating the rms value of the signal measured in step d; h) Finding the difference between the values obtained in steps f and g; i) Comparing the absolute value of the step h difference with a reference value m; j) If the comparison made in step i is greater than the reference value m, a trigger signal is generated and the tension is maintained between the dc points of step b in about from 0 to 90%, of the operating tension with no fault. The apparatus comprises, a rectifier; an inverter connected to the rectifier; current measuring means at the rectifier and inverter outlets; and a control unit connected with the rectifier, the inverter and the current measuring means that makes the tripping command of the rectifier and the inverter, and compares the dc current measure at the rectifier outlet with the inverter outlet current, sending a tripping signal according to said comparison.

A power conversion system includes an inverter circuit, a harmonic reducer, and a synchronizer. The inverter circuit is operable with electric power supplied from an alternating-current power source. The harmonic reducer is connected to the alternating-current power source. The inverter circuit includes a circuit main portion and a conversion control unit configured to control the circuit main portion. The harmonic reducer includes a current control unit configured to perform control to reduce a harmonic current flowing to the alternating-current power source. The synchronizer is configured to synchronize a state of the harmonic reducer with a state of the inverter circuit.

The invention provides an inverter system and a method of using said inverter system. A rectifier stage of the inverter system is used to charge a DC link stage to a first voltage level and a control module determines whether voltages over series connected capacitors of the DC link stage are balanced. If those voltages are balanced, the rectifier stage charges the DC link stage to a second voltage level higher than the first voltage level.

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.

An energy conversion system includes a low-impedance generator having at least one armature winding set. The armature winding set includes a plurality of single-phase coils. The system also includes a current source converter assembly electrically coupled to an armature of the generator. The current source converter assembly includes at least one current source converter that includes a current source rectifier coupled to a current source inverter via a DC link and at least one capacitor across the plurality of single-phase armature coils. The capacitor(s) of the current source converter(s) is configured to absorb high frequency components of current pulses generated by the current source converter so as to minimize current ripple in a current applied to the plurality of single-phase coils.

A thyristor starter accelerates a synchronous machine from a stop state to a predetermined rotation speed by sequentially performing a first mode of performing commutation of an inverter by intermittently setting DC output current of a converter to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine. In the thyristor starter, during a first time period from start of performance of the second mode to arrival of the induced voltage of the synchronous machine at a first voltage value, a phase control angle of the inverter is changed such that a value thereof becomes larger as a rotation speed of the synchronous machine becomes higher.

For a power supply with a reduced number of semiconductor devices, a transformer receives a three-phase primary voltage and steps the three-phase primary voltage up or down to a secondary voltage with a plurality of secondary winding sets to a plurality of first phase voltages, a plurality of second phase voltages, and a plurality of third phase voltages. A plurality of power cell sets each include a plurality of power cells cascaded connected. Each power cell comprises a rectifier and an inverter. The rectifier includes two first active switches that are serially connected and receive a phase voltage at a first switch midpoint, two second active switches that are serially connected and receive another phase voltage at a second switch midpoint, and two capacitors that are serially connected and receive another phase voltage at a capacitor midpoint between the capacitors.

For a power supply with a reduced number of semiconductor devices, a transformer receives a three-phase primary voltage and steps the three-phase primary voltage up or down to a secondary voltage with a plurality of secondary winding sets to a plurality of first phase voltages, a plurality of second phase voltages, and a plurality of third phase voltages. A plurality of power cell sets each include a plurality of power cells cascaded connected. Each power cell comprises a rectifier and an inverter. The rectifier includes two first active switches that are serially connected and receive a phase voltage at a first switch midpoint, two second active switches that are serially connected and receive another phase voltage at a second switch midpoint, and two capacitors that are serially connected and receive another phase voltage at a capacitor midpoint between the capacitors.

A wind power converter device is provided. The wind power converter device includes grid side converters, generator side converters and a DC bus module. Each of the grid side converters includes grid side outputs electrically coupled to a grid and a first and a second DC inputs. Each two of the neighboring grid side converters are connected in series at the second and the first DC inputs. Each of the generator side converters includes generator side inputs electrically coupled to a generator device and a first and a second DC outputs. Each two of the neighboring generator side converters are coupled in series at the second and the first DC outputs. The DC bus module is electrically coupled between the grid side converters and the generator side converters.