A propulsion system (100) comprises: a generator (30) driven by a shaft (22) of a thermal engine (20) and configured to generate electrical power; an induction motor (60) that is electrically coupled to the output of the generator (30) and is configured to generate a rotational output in response to electrical power provided by the generator (30); a generator control unit (40) that is configured to control an output voltage of the generator (30) to limit a current supplied to the induction motor (60) during start-up of the propulsion system (100); and a switch (50) that is electrically coupled between the generator (30) and the induction motor (60), wherein the switch (50) is controllable by the generator control unit (40).

A propulsion system (100) comprises: a generator (30) driven by a shaft (22) of a thermal engine (20) and configured to generate electrical power; an induction motor (60) that is electrically coupled to the output of the generator (30) and is configured to generate a rotational output in response to electrical power provided by the generator (30); a generator control unit (40) that is configured to control an output voltage of the generator (30) to limit a current supplied to the induction motor (60) during start-up of the propulsion system (100); and a switch (50) that is electrically coupled between the generator (30) and the induction motor (60), wherein the switch (50) is controllable by the generator control unit (40).

The invention relates to controlling a power generating unit. Aspects of the invention include determining a virtual impedance value (Zvir), determining a virtual grid power (Pvsm) based on the virtual resistance value (Rvir) and the grid current (Igrid), determining a virtual synchronous machine rotational speed (ωVSM) and/or a synchronous machine angle (θVSM) of a virtual synchronous generator, and determining a voltage reference (Vabc) for controlling a line side converter to generate the desired reactive power (Qgrid) based on the virtual synchronous machine rotational speed or angle (ωVSM, θVSM), a virtual voltage (ΔVαβ, ΔVdq) and the voltage magnitude reference (Vqref).

Systems and methods are provided for braking a translator of a linear multiphase electromagnetic machine. The system detects a fault event, and in response to detecting the fault event, causes the translator to brake using an electromagnetic technique. Braking includes causing the translator to stop reciprocating, by applying a force opposing an axial motion, which may occur within one cycle, or over many cycles. The fault event may include, for example, a fault associated with an encoder, a controller, an electrical component, a communications link, a phase, or a subsystem. The system includes a power electronics system configured to apply current to the phases. The system may use position information, current information, operating parameters, or a combination thereof to brake. Alternatively, the system need not use position information, current information, and operating parameters, and may brake the translator independent of such information.

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 switched reluctance generator and devices and methods for its control are concerned with generators and controls which can operate in an aerospace environment. The generator may have: a rotor having rotor poles; a stator having stator poles; and a controller. Either the rotor or stator poles each have windings to which current can be supplied to energise the poles and from which current can be drawn to a load; and the controller is arranged to: periodically excite each of the windings in turn to a pre-determined level of current; measure the current generated in each winding; cease the excitation when the current generated in each winding exceeds the excitation current; and direct the generated current in each winding to the load. The generator may thereby avoid the need to determine the position of the rotor poles relative to the stator poles to provide the commutation of the generator.

A switched reluctance generator and devices and methods for its control are concerned with generators and controls which can operate in an aerospace environment. The generator may have: a rotor having rotor poles; a stator having stator poles; and a controller. Either the rotor or stator poles each have windings to which current can be supplied to energise the poles and from which current can be drawn to a load; and the controller is arranged to: periodically excite each of the windings in turn to a pre-determined level of current; measure the current generated in each winding; cease the excitation when the current generated in each winding exceeds the excitation current; and direct the generated current in each winding to the load. The generator may thereby avoid the need to determine the position of the rotor poles relative to the stator poles to provide the commutation of the generator.

A method of monitoring a split wind-turbine-converter system with at least one generator-side converter and at least one grid-side converter arranged at distant locations, and a DC-link in the form of an elongated conductor arrangement with at least one positive and at least one negative conductor. The impedance of the DC-link conductor arrangement is determined by means of DC-voltage sensors. The voltages between the positive and the negative conductors are determined at the generator-side converter and at the grid-side converter, and the difference between the voltages is determined. The impedance of the DC-link conductor arrangement is determined by putting the determined voltage difference in relation to the DC current flowing through the DC-link conductor arrangement. If the impedance exceeds a given impedance threshold a fault state is recognized.

Systems and methods for controlling operation of a power converter based on grid conditions are provided. In particular, a first gating voltage can be applied to a switching element of a power converter associated with a wind-driven power generation system. The first gating voltage can be greater than a threshold voltage for the switching element. A grid event associated with an electrical grid coupled to the power generation system can be detected. A second gating voltage can be applied to the gate of the switching element during the detected grid event. The second gating voltage can be greater than the first gating voltage.

An example system includes drive circuitry having outputs configured to provide drive current based on control parameters and having inputs configured to receive an output voltage of an electrical device. Simulation circuitry is configured to provide simulation signals based on the drive current and the output voltage. A controller sets the control parameters based on the simulation signals to control the drive circuitry to provide the drive current with an amplitude and phase to simulate a predetermined load condition for the electrical device.