A system for controlling reactive power generated in a power, the power system having a power source system, a plurality of load units, each of the load systems, including a cyclic current type cycloconverter system, connected to the power source and a plurality of condenser systems. The system includes a voltage detection unit for detecting a voltage of power supplied from the power source, a current detection unit for detecting a current of the power supplied from the power source, a main control unit for detecting reactive power of the power supplied from the power source and for generating a control signal to control the reactive power generated in the power system, and a plurality of circulating current control units installed in each of the load units, responsive to the control signal generated from the main control unit, for controlling each of the circulating current type cycloconverter systems corresponding to the each of the load units to adjust the reactive power generated in the power system.

A ship propulsion system includes a ship electrical system and an electric propulsion system that is supplied with power from the electrical system, and which is equipped with a cascade control for the propeller motor. The rotational speed of the propeller motor is preset by a higher-order controller whose command variable is issued by the throttle lever. Filters means are provided for suppressing impairments to the ship's operation that result due to the high dynamics of the propulsion system.

A variable speed wind turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator windings of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator windings. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility.

A variable velocity apparatus includes a wound-rotor induction machine having a primary winding connected to a power system having a power system frequency, a secondary winding excited by an alternating current (AC), a generator-motor shaft, and a load united with the generator-motor shaft. The apparatus includes a frequency detection element for detecting a change in the power system frequency, and a controller for changing a rotational speed of the induction machine based on the detected change in the power system frequency. The change in the rotational speed is made substantially equivalent to the detected change in the power system frequency, so as to maintain a slip frequency of the induction machine essentially constant when the power system frequency changes.

A variable speed system for use in systems, such as, for example, wind turbines, is described. The system comprises a wound rotor induction generator, a torque controller and a proportional, integral derivative (PID) pitch controller. The torque controller controls generator torque using field oriented control, and the PID controller performs pitch regulation based on generator rotor speed.