An example power system for supplying AC output power to an AC load includes: a variable-speed generator configured to be driven by a prime mover, the generator comprising a first winding and a reference tap in the first winding; a rectifier configured to rectify an input voltage from the first winding to output a positive DC signal with respect to the reference tap and a negative DC signal with respect to the reference tap; a first boost converter configured to convert the positive DC signal to generate a positive DC bus voltage with respect to the reference tap; a second boost converter configured to convert the negative DC signal to generate a negative DC bus voltage with respect to the reference tap; and an inverter circuit configured to convert the positive DC bus voltage and the negative DC bus voltage to an AC output signal with respect to the reference tap.

A method of controlling an induction generator is provided connected to a utility grid, the method including: receiving an actual grid frequency; and controlling rotor windings of the generator by a rotor control signal having a rotor winding reference frequency being set in dependence of the actual grid frequency.

An example power system for supplying AC output power to an AC load includes: a variable-speed generator configured to be driven by a prime mover, the generator comprising a first winding and a reference tap in the first winding; a rectifier configured to rectify an input voltage from the first winding to output a positive DC signal with respect to the reference tap and a negative DC signal with respect to the reference tap; a first boost converter configured to convert the positive DC signal to generate a positive DC bus voltage with respect to the reference tap; a second boost converter configured to convert the negative DC signal to generate a negative DC bus voltage with respect to the reference tap; and an inverter circuit configured to convert the positive DC bus voltage and the negative DC bus voltage to an AC output signal with respect to the reference tap.

A method of operating a wind turbine wherein the wind turbine includes a doubly-fed induction generator that converts rotational mechanical power to electrical power. The method includes operating the wind turbine in a first operational mode in which a speed of a rotor of the wind turbine is controlled to maximize the power generation by the wind turbine. Upon a monitored parameter reaching or dropping below a respective threshold, the wind turbine is operated in a second operational mode. The monitored parameter may include at least one of the rotational speed of the rotor, the rotational speed of the doubly-fed induction generator, a wind speed, an active electrical power, or generator torque. Operating the wind turbine in the second operational mode may include increasing the rotational speed of the doubly-fed induction generator at the expense of the generation of active electrical power by the power generating system.

A method for controlling a three-level back-to-back voltage source power conversion assembly includes receiving an indication of a DC or AC unbalance occurring in voltage of a DC link. The power conversion assembly has a first power converter coupled to a second power converter via the DC link. In response to receiving the indication, the method includes activating a balancing algorithm that includes determining a deviation of a midpoint voltage of the DC link as a function of a total voltage of the DC link, calculating a voltage compensation needed for pulse-width modulation signals of the power conversion assembly based on the deviation, and coordinating common mode voltage injection from each of the power converters independently at a neutral point of the power conversion assembly based on the voltage compensation, thereby minimizing the at least one of the DC unbalance or the AC unbalance at any given operating condition.

The present invention provides an acceleration method for V/f controlled induction motor in flux-weakening region, which comprises: acquiring no-load magnetizing current I.sub.m of the induction motor at current stator frequency; selecting a smaller one of 0.5.Math.I.sub.m(1/σ+1) and (I.sub.m.sup.2+σ)/(I.sub.m+σI.sub.m) as magnetizing current set point, in which σ is an estimated total leakage inductance coefficient; getting an error signal by subtracting the magnetizing current of the induction motor from the magnetizing current set point; determining the stator frequency for the next control period according to the error signal which is provided as a controlling variable of negative feedback. The acceleration method of the present invention can provide the maximum output torque in flux-weakening region and has a larger tolerance for the error of the estimated leakage inductance.

An electromagnetic induction power generator includes: a current transformer attached to a power transmission line; a rectifier circuit for rectifying an AC voltage output from the current transformer; and a regulator circuit for regulating a DC voltage output from the rectifier circuit. The current transformer has a magnetic core attached to the power transmission line serving as a primary winding and a secondary winding magnetically coupled to the power transmission line through the magnetic core. The magnetic core is configured to start to be magnetically saturated around the minimum value within the fluctuation range of a current flowing through the power transmission line.

A propulsion channel for aircraft at least one first dual-fed polyphase asynchronous rotating electric machine configured to be mechanically coupled to a turbine engine. The propulsion channel further includes at least one second polyphase rotating electric machine electrically coupled to the first asynchronous rotating electric machine, and a control and storage module configured to control the first polyphase asynchronous rotating electric machine. The module is connected to the first dual-feed polyphase asynchronous rotating electric machine as well as to the at least second polyphase rotating electric machine. The at least second polyphase rotating electric machine includes a polyphase synchronous rotating electric machine with permanent magnet.

An auxiliary power unit (APU) generator system for an APU can include a doubly-fed induction generator (DFIG) configured to be operatively connected to an APU to be turned by an APU and to have an output frequency that is a function of an excitation frequency and an APU speed. The system can include a generator control module configured to control the excitation frequency to the DFIG to output a substantially constant frequency with changing APU speed to supply the substantially constant frequency to a load.

An intelligent electronic device (IED) according to the present disclosure can estimate a full load rotor resistance value as a function of motor positive-sequence resistance. The IED may estimate the full load rotor resistance value by measuring zero-crossings of voltage after a motor disconnect. The IED may also acquire motor current and voltage measurements and calculate motor slip using the acquired motor current and voltage measurements and the estimated full load rotor resistance value.