The invention relates to the real-time determination of the forces applied by waves incident upon the moving part (2) of a wave-energy system (1). The method according to the invention is based on the construction of a model of the radiation force applied to the moving part (2) and a model of the dynamics of the wave-energy system (1). The invention uses only measurements of the kinematics of the moving part (2) and the force applied by the conversion machine (3) to the moving part (2).

A stepwise operating parallel-type hydro power generation system having a fixed flow path includes a parallel pipe, a first power generation facility, a second power facility generation facility, first and second flow regulators, and a controller. The parallel pipe includes an inlet pipe, an outlet pipe, and a first straight pipe and a second straight pipe. The first and second straight pipes connected between the inlet pipe and the outlet pipe. Each of the first and second power generation facilities includes a water turbine rotating with the water introduced thereinto and a power generator operating according to the rotation of the water turbine. The controller is configured to open and close either or both of the first and second flow rate regulators at the same time.

An electric rotating machine having a stator and a rotor, wherein the rotor is provided with rotor windings connected to electric contacts to carry a field current. A control device is provided to adjust the field current carried by the rotor windings. At least one sensor is provided to give information about the temperature at the location of the at least one sensor. The at least one sensor is located on or embedded in the rotor windings, and the at least one sensor is connected to the control device such that the control device is able to read the information given by the at least one sensor. The control device is further arranged to adjust the field current carried by the rotor windings and/or power output or power input of the electric rotating machine based on the information given by the at least one sensor.

A system and method of operating a pumped storage power plant using a double fed induction machine with a frequency converter in a rotor circuit is disclosed. A current target value for the rotor current frequency is determined based on a target power to be transmitted between an electrical grid and the double fed induction machine depending on measured actual operating variables. A current inadmissible synchronous deadband is determined depending on variables characterizing a current state of the pumped storage power plant. The synchronous deadband is determined by a permissible minimum required rotor current frequency or speed difference of the rotor speed from the synchronous speed for the stationary operation. The converter is controlled to generate voltages and currents with the current target value of the rotor current frequency if the current target value of the rotor current frequency or speed does not fall in the current inadmissible synchronous deadband.

A variable-speed pumped storage power generation apparatus sets a maximum change rate of a power output command constant when a slip frequency is within a normal operating range, limits the maximum change rate of the power output command by multiplying the maximum change rate by a value in a range of one to zero when the slip frequency is within a range falling below a lower limit of the normal operating range by a predetermined value or less or within a range exceeding an upper limit of the normal operating range by a predetermined value or less, and limits the maximum change rate of the power output command by multiplying the maximum change rate by zero when the slip frequency is in a range falling below the lower limit by the predetermined value or more or in a range exceeding the upper limit by the predetermined value or more.

A buoyancy powered electrical generator. A source of compressed gas is provided. The gas, which may be air, is compressed using a conventional compressor. In one embodiment, the compressor is powered by a windmill, turbine, or other conventional means. The compressed gas may be stored in a tank for an indefinite period. If necessary, the tank may be transported to the generator via truck, train or other conventional transportation means. During generation, compressed gas is released into a series of hollow, flooded drums mounted on a wheel in a liquid filled chamber. Introducing gas into the drums closes a valve in the drums and evacuates liquid from the drums, causing the drums to become buoyant. The buoyant drums exert a buoyant force on the wheel, causing it to rotate. The wheel is connected to a rotor in a magnetic generator. Rotating the wheel turns the rotor, thereby generating electricity.

An electrical generator (114) and a power electronics interface (115) for a direct-drive turbine (110). The turbine (110) may include a rotor (112) for transforming kinetic (from, e.g., wind, water, steam) into mechanical energy, the generator (114) for transforming the mechanical into electrical energy, and the power electronics interface (115) for conditioning the electrical energy for delivery to a power distribution grid (124). The interface (115) includes a three-phase single-stage boost inverter (120) for converting a lower DC voltage into a higher AC voltage, and which uses a synchronous reactance of the generator (114) as a DC link inductance. The turbine (110) has neither the gearbox of indirect-drive designs nor the electrolytic capacitor bank of conventional direct-drive designs, while still allowing for a substantially smaller number of generator poles, resulting in reduced size, weight, complexity, and cost.

A method for operating a power generation system is presented. The method includes estimating, by a controller, at least one of a required load and input power of the doubly-fed induction generator for a pre-determined future time duration. The method includes comparing, by the controller, the estimated at least one of the required load and the input power with a corresponding threshold value. Moreover, the method includes transitioning, by the controller, operation of the power generation system from a partial power conversion mode to a full power conversion mode by controlling switching of one or more of a plurality of switches if the estimated at least one of the required load and the input power is less than the corresponding threshold value, wherein the plurality of switches includes a first set of switches coupled to stator winding of the doubly-fed induction generator.

A stepwise operating parallel-type hydro power generation system having a fixed flow path includes a parallel pipe, a first power generation facility, a second power facility generation facility, first and second flow regulators, and a controller. The parallel pipe includes an inlet pipe, an outlet pipe, and a first straight pipe and a second straight pipe. The first and second straight pipes connected between the inlet pipe and the outlet pipe. Each of the first and second power generation facilities includes a water turbine rotating with the water introduced thereinto and a power generator operating according to the rotation of the water turbine. The controller is configured to open and close either or both of the first and second flow rate regulators at the same time.

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.