A method and apparatus for operating a variable speed power generation system in which the generated output of an induction generator is adjusted by controlling current in the secondary side of the induction generator. Rotation speeds of the induction generator coupled to a prime mover are detected, a secondary current command for controlling a difference between a detected rotation speed and a speed command to be zero is generated, and current in the secondary side of the induction generator is controlled on the basis of the secondary current command. In addition, the generated output of the induction generator is sequentially detected in order that a command value of the speed command is sequentially changed when a detected generated output shows a tendency to increase and, when a detected generated output shifts from an increasing tendency to a decreasing tendency, the command value of the speed command is once changed to a lower speed value and thereafter returned to a higher speed value, thereby maximizing efficiency of the variable speed power generation system and reducing costs.
An electric power generating device including an induction type electric rotating machine rotating in interlock with an engine comprises an inverter connected at the AC side to and end of an armature winding and at the DC side to an electric power storing device, a detecting means for detecting the quantity of state related to the electric power generating voltage of the induction type electric rotating machine excluding the measured RPM of the induction type electric rotating machine but including the electric power storing voltage of the electric power storing device, and an electric power generation controlling means for maintaining the electric power storing voltage within the preset range by controlling the frequency of the controlling voltage of the inverter based on the quantity of state related to the electric power generating voltage. This electric power generating device can control the electric power generation without using any RPM detecting device for the induction electric machine, and as a result, the composition of the device can be simplified. The frequency can be controlled so that the frequency can be changed in the direction in which the difference between the electric power storing voltage and the preset reference voltage is reduced.
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 power unit comprises an input mechanism for inputting kinetic energy as a rotary motion, a storing mechanism connected to the input mechanism for storing the kinetic energy as rotary motion, a first speed-regulating mechanism connected to the storing mechanism for increasing the speed of the rotary motion released from the storing mechanism, and a second speed-regulating mechanism connected to the first speed-regulating mechanism for braking the rotary motion to regulate the speed of the rotary motion. A converting mechanism is connected to the first speed-regulating mechanism for converting the rotary motion whose speed has been increased into electricity. A control circuit is connected to the converting mechanism for controlling the generated electricity, and a positive electrode output terminal and a ground electrode terminal are connected to the control circuit.
The generator includes an asynchronous machine with a wound rotor driven mechanically and a stator connected to the network. The rotor is excited by a constant DC voltage source via an inverter controlled by a pulse width modulation control circuit. In accordance with the invention, the following are generated: a stator frequency set point, a rotor frequency set point which is a function of the stator frequency set point and the rotation speed of the machine, an rms stator voltage set point, an error signal which is a function of the difference between the rms stator voltage set point and the actual rms stator voltage. A rotor voltage set point is imposed on the control circuit which is a function of the error signal and the rotor frequency set point.
An object of the present invention is to minimize the torsional vibration caused on the shafting of the wind turbine genarator system so as to operate the windmill stably.A wind turbine genarator system according to the present invention, equipped with a synchronous generator connected to the shaft of a windmill, converter connected to the stator of the synchronous generator, and inverter connected to the converter and also to an electric power system, extracts the torsional vibration component of the shafting between the windmill and synchronous generator from the detected rotation speed of the synchronous generator, regulates the active component of the current command to the converter according to the vibration component, and controls so as to minimize the rotation speed variation of the synchronous generator.
