A converter controller configured to control a firing phase of a converter includes an integral element integrating a deviation of DC current from a current command value and generates a voltage command value of output voltage of the converter by performing control calculation of the deviation. In a first mode of performing commutation of an inverter by intermittently setting DC current to zero, the converter controller sets DC current to zero for a predetermined pause time by narrowing a phase control angle simultaneously with a commutation command for the inverter. When the control calculation is resumed immediately after the pause time, the converter controller uses a control amount calculated in control calculation immediately before the pause time as a preset value of the integral element immediately after the pause time.

A thyristor starter is configured to accelerate 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 a first case in which a first synchronous machine having a first inductance is started, a switching rotation speed for switching from the first mode to the second mode is set to a higher rotation speed, compared with a second case in which a second synchronous machine having a second inductance larger than the first inductance is started.

A converter station has two line-commutated converters for energy transmission via a bipolar high voltage direct current transmission line. In a first operating mode of the converter station the two converters are electrically connected in an anti-parallel circuit to the same pole of the high voltage direct current transmission link and one of the converters is operated as a rectifier and the other converter is operated as an inverter in an network. In a second operating mode the two converters are connected to different poles of the high voltage direct current transmission link and both converters are operated as either rectifiers or inverters in the AC network. In both operating modes a station active power exchanged between the converter station and the AC network is controlled by active power specifications for converter active powers which are exchanged between the converters and the AC network.

A motor driving apparatus and a control method thereof, including a dc-link capacitor configured to store DC power, an inverter including a plurality of switching elements and converting the DC power stored in the dc-link capacitor into AC power to output the power to a motor, a dc-link resistor element disposed between the dc-link capacitor and the inverter; and a controller configured to control an operation of the inverter. The controller calculates a phase difference between a first reference voltage vector among a plurality of reference voltage vectors that are preset on the space vector and a voltage command, generates a switching frequency, determines a first operating point located in a dead band that is a one-phase current undetectable area in one switching cycle and a second operating point located at an outer position including a boundary of the dead band, and controls operation of the plurality of switching elements.

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 to zero and a second mode of performing commutation of the inverter by induced voltage of the synchronous machine. A second controller controls the firing phase of a thyristor in a converter such that DC output current of the converter matches a current command value, based on a detection signal of a position detector. In the first mode, the current command value is set such that the current value is higher as the rotation speed of the synchronous machine is higher.

A DFIG power system defines a generator power path and a converter power path. The generator power path has a DFIG with a rotor and a stator. The converter power path has a power converter with a rotor-side converter coupled to a line-side converter via a DC link. The power converter has at least two power bridge circuits connected in parallel. A method of operating the DFIG power system includes monitoring, via one or more sensors, at least one electrical condition thereof. The method also includes comparing, via a control system, the at least one electrical condition to a predetermined threshold, the predetermined threshold being indicative of an occurrence of a transient overloading event. Further, the method includes alternating between non-interleaving and interleaving intervals if the at least one electrical condition exceeds the predetermined threshold so as to reduce harmonics of the DFIG power system.

A thyristor starter is configured to accelerate 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 a first case in which a first synchronous machine having a first inductance is started, a switching rotation speed for switching from the first mode to the second mode is set to a higher rotation speed, compared with a second case in which a second synchronous machine having a second inductance larger than the first inductance is started.

A method for operating an inverter for coupling an electric machine designed for operation on AC voltage, to an AC voltage network, includes the steps of determining a torque-related machine current component composed of electrical machine currents of the electrical machine, detecting an actual value for a magnetic flux, determining an actual value of a machine torque of the electric machine by linking the detected magnetic flux to the torque-related machine current component, determining a torque difference between the actual value of the machine torque and a setpoint value of the machine torque of the electric machine, filtering the torque difference by a bandpass filter which is tuned to a machine-side natural frequency, determining a compensation signal by processing a filter output signal of the bandpass filter, and superimposing the compensation signal on the network control signal and/or the machine control signal.

A power converter system comprising a power source; a plurality of voltage source converters for driving respective loads; the plurality of voltage converters connected to the power source via a common DC-link, control means (10a, 10b) for driving the voltage source converters by means of respective control signals modulated onto respective modulation carriers; and means for synchronizing the control means such that the respective modulation carriers are interleaved with a selected phase shift therebetween.

A system for reducing a resonant oscillation on a direct current bus of a power inverter/converter for an electric machine having a variable frequency drive is disclosed. The system includes a battery, a first capacitor connected in parallel with the battery; an inductor connected in series with the first capacitor; a first diode connected in series with the inductor; a second diode connected in parallel with the inductor and the first diode; a second capacitor connected in series with the first diode; and a starter-generator connected to the second capacitor. During a re-generation mode for charging the battery, a re-generation current flows from the starter-generator to the battery, passing through the first diode and the inductor and bypassing the second diode. During a motor mode, a motor current flows from the battery to the starter-generator, passing through the second diode and bypassing the first diode and the inductor.