The invention provides a device for operative connection between a subsea step out cable far end and subsea loads such as pumps, compressors and control systems, distinctive in that the device is a rotating frequency stepper device, more specifically a rotating step up or step down device, and it comprises: a motor and a generator operatively connected so that the motor drives the generator, at least one gas and/or liquid filled vessel into which at least one of the motor and generator are arranged, and the step out length is long, which means long enough to cause problems due to the Ferranti effect at frequency and power levels feasible for subsea pump and compressor motors, and where the device via the step out cable receives input electrical power at a low enough frequency to have stable transmission and the device, operatively connected to the subsea motor, delivers an output electrical frequency, amperage and voltage feasible for operation of the connected motors. System for pressure boosting of hydrocarbon fluid or other fluid subsea, comprising the device.

The invention provides a device for operative connection between a subsea step out cable far end and subsea loads such as pumps, compressors and control systems, distinctive in that the device is a rotating frequency stepper device, more specifically a rotating step up or step down device, and it comprises: a motor and a generator operatively connected so that the motor drives the generator, at least one gas and/or liquid filled vessel into which at least one of the motor and generator are arranged, and the step out length is long, which means long enough to cause problems due to the Ferranti effect at frequency and power levels feasible for subsea pump and compressor motors, and where the device via the step out cable receives input electrical power at a low enough frequency to have stable transmission and the device, operatively connected to the subsea motor, delivers an output electrical frequency, amperage and voltage feasible for operation of the connected motors. System for pressure boosting of hydrocarbon fluid or other fluid subsea, comprising the device.

A wind power plant for providing electrical power to a utility grid is provided, the wind power plant including: at least one wind turbine having a wind turbine generator coupled to a wind turbine rotation shaft to which plural rotor blades are mounted, the wind turbine providing electric power at an output terminal; at least one power conversion system, each including: a plant motor electrically coupled and configured to receive the electric power from the output terminal of the at least one wind turbine and convert it into rotational power of a plant motor shaft; a plant generator mechanically coupled to the plant motor shaft and electrically coupleable to the electric utility grid.

Circuits comprising: an inductor having a first side connected to V.sub.IN; a first switch having a first side connected to a second side of the inductor; a second switch having a first side connected to V.sub.IN; a first capacitor having a first side connected to a second side of the second switch; a third switch having a first side connected to a second side of the first switch; a fourth switch having a first side connected to a second side of the third switch; a fifth switch having a first side connected to a second side of the first capacitor and to a second side of the fourth switch, and having a second side coupled to a voltage source; and a second capacitor having a first side connected to the first side of the fourth switch, and having a second side connected to the second side of the fifth switch.

Circuits comprising: an inductor having a first side connected to V.sub.IN; a first switch having a first side connected to a second side of the inductor; a second switch having a first side connected to V.sub.IN; a first capacitor having a first side connected to a second side of the second switch; a third switch having a first side connected to a second side of the first switch; a fourth switch having a first side connected to a second side of the third switch; a fifth switch having a first side connected to a second side of the first capacitor and to a second side of the fourth switch, and having a second side coupled to a voltage source; and a second capacitor having a first side connected to the first side of the fourth switch, and having a second side connected to the second side of the fifth switch.

A drive system for an electric motor includes a first inverter that includes first switching elements, a second inverter that includes second switching elements, and a control unit that includes a first inverter control calculation section controlling on-off operation of each of the first switching elements based on a first carrier wave and a first modulation wave, a second inverter control calculation section controlling on-off operation of each of the second switching elements based on a second carrier wave and a second modulation wave, and a control synchronization section synchronizing the first carrier wave with the second carrier wave. When a sum of voltages of the first voltage source and the second voltage source is more than a voltage determination threshold, and torque of a rotating electric machine is smaller than a torque determination threshold, the control synchronization section synchronizes the first carrier wave with the second carrier wave.

A drive system for an electric motor includes a first inverter that includes first switching elements, a second inverter that includes second switching elements, and a control unit that includes a first inverter control calculation section controlling on-off operation of each of the first switching elements based on a first carrier wave and a first modulation wave, a second inverter control calculation section controlling on-off operation of each of the second switching elements based on a second carrier wave and a second modulation wave, and a control synchronization section synchronizing the first carrier wave with the second carrier wave. When a sum of voltages of the first voltage source and the second voltage source is more than a voltage determination threshold, and torque of a rotating electric machine is smaller than a torque determination threshold, the control synchronization section synchronizes the first carrier wave with the second carrier wave.

Circuits comprising: an inductor having a first side connected to V.sub.IN; a first switch having a first side connected to a second side of the inductor; a second switch having a first side connected to V.sub.IN; a first capacitor having a first side connected to a second side of the second switch; a third switch having a first side connected to a second side of the first switch; a fourth switch having a first side connected to a second side of the third switch; a fifth switch having a first side connected to a second side of the first capacitor and to a second side of the fourth switch, and having a second side coupled to a voltage source; and a second capacitor having a first side connected to the first side of the fourth switch, and having a second side connected to the second side of the fifth switch.

Circuits comprising: an inductor having a first side connected to V.sub.IN; a first switch having a first side connected to a second side of the inductor; a second switch having a first side connected to V.sub.IN; a first capacitor having a first side connected to a second side of the second switch; a third switch having a first side connected to a second side of the first switch; a fourth switch having a first side connected to a second side of the third switch; a fifth switch having a first side connected to a second side of the first capacitor and to a second side of the fourth switch, and having a second side coupled to a voltage source; and a second capacitor having a first side connected to the first side of the fourth switch, and having a second side connected to the second side of the fifth switch.

Circuits comprising: an inductor having a first side connected to V.sub.IN; a first switch having a first side connected to a second side of the inductor; a second switch having a first side connected to V.sub.IN; a first capacitor having a first side connected to a second side of the second switch; a third switch having a first side connected to a second side of the first switch; a fourth switch having a first side connected to a second side of the third switch; a fifth switch having a first side connected to a second side of the first capacitor and to a second side of the fourth switch, and having a second side coupled to a voltage source; and a second capacitor having a first side connected to the first side of the fourth switch, and having a second side connected to the second side of the fifth switch.