A system for converting wave energy into electricity is provided. The system includes a wave energy mechanical interface, a power take off coupled with the wave energy mechanical interface, and a generator coupled with the power take off. A controller is coupled with the power take off. The controller is configured to regulate impedance of energy transferred from the power take off to the generator.

A system for converting wave energy into electricity is provided. The system includes a wave energy mechanical interface, a power take off coupled with the wave energy mechanical interface, and a generator coupled with the power take off. A controller is coupled with the power take off. The controller is configured to regulate impedance of energy transferred from the power take off to the generator.

The invention concerns a method for starting a hydroelectric turbine (10) in a pumping mode, said turbine being provided with a runner (6) mechanically coupled to a shaft line (8) and a variable speed electric motor connected to a grid, a distributor (4) comprising guide vanes to control a flow of water to said runner, the method comprising: a) a step of operating the variable speed motor at least partly at fixed speed, said guide vanes being only partially opened, and of defining or calculating: data of a plurality of hydraulic characteristics (C.sub.1, C.sub.2, C.sub.i) of the turbine for an operation without cavitation; data of an operation range of the electric motor, giving the speed of the motor as a function of its power; b) then a step of operating the turbine in a power control mode.

A variable speed pumping system includes a generator motor including a frequency converter, in which the variable speed pumping system, in the pumping mode, supply a power command to the generator motor to perform power control, and the power control correction signal generator adds a value obtained by multiplying a signal based on a difference between the power input command and an actual power input measured by a power detector in the pumping mode by a constant gain to a signal based on the deviation and inputs the added value to an integration control element to generate the power control correction signal based on an output signal of the integration control element.

A fluid apparatus includes a hydraulic machine, a rotary electric machine connected to the hydraulic machine, and a power conversion controller that converts power from the rotary electric machine. A non-normal operation is performed in a warning state that differs from a normal state in which a normal operation is continued and an anomalous state in which operation is stopped to continue a stopped condition.

Disclosed are a wave power generation system for generating electrical energy by means of a hydraulic circuit, and a method for controlling same. The wave power generation system comprises a hydraulic motor for storing motion energy in a form of fluid pressure and volume if a plurality of tension transmission members, for transmitting motion energy by means of six-degrees-of-freedom motion of a movable object floating on the waves, move in one direction, and for maintaining the tension of the tension transmission members by means of the stored energy if the tension transmission members move in the other direction. Electric energy is alternately generated by means of the bidirectional motion of the plurality of tension transmission members.

An aquifer storage and recovery system can include a pump, an electric motor coupled to the pump, a drive unit configured to control operation of the electric motor, and a controller. The controller can be configured to flow water into a well bore from a source reservoir through the pump such that the pump rotates in a reverse direction and drives the electric motor coupled to the pump in the reverse direction to operate as a generator, determine a power output of the electric motor, determine a difference between the power output of the electric motor and a power output set point, and operate the drive unit to control a rotational speed of the electric motor based at least in part on the difference between the power output of the electric motor and the power output set point.

A wave energy converter (WEC) system includes a float, a drivetrain, a reaction structure coupled to the drivetrain by at least one tendon, and a power dissipation system coupled to the drivetrain. The power dissipation system is configured to manage peak loads in the WEC system by dissipating peak energy spikes caused by relative movement of the reaction structure and the float.

A startup method of a Francis turbine according to an embodiment includes: a bypass-valve opening step of opening the bypass valve with the inlet valve closed; an inlet-valve opening step of opening the inlet valve after the bypass-valve opening step; and a first rotation-speed increasing step of increasing a rotation speed of the runner by opening the guide vane at an opening that is 50% or more of a maximum opening before a flow velocity of a swirling flow flowing around the runner reaches 90 m/sec.

A method of controlling energy conversion and/or applied wave loads for a membrane power conversion wave energy converter (WEC) having a longitudinal axis and at least one cell having a membrane. The method includes acquiring data and determining a value relating to a local sea state at the WEC or to a WEC state of the WEC. Depending on the value determined from the acquired data, one or both of the vertical position of the at least one WEC cell relative to a free surface at still water and/or the angle of incidence of the WEC is adjusted.