1. A push-pull amplifier comprising a pair of transistors, wherein each of the transistors includes a control terminal, a first terminal, and a second terminal, and wherein a current that flows between the first terminal and the second terminal is controlled in accordance with signals applied to the control terminal, such that when an amount of current flowing between the first terminal and the second terminal of one of the transistors is within a predetermined range, a high-frequency component of the signals input to the control terminal of one of the transistors is amplified, and when this current is outside the predetermined range, the high frequency component is not amplified.
2. The push-pull amplifier according to claim 1, further comprising:
a detector that detects the current that flows between the first and second terminals of one of the transistors; and
a filter that extracts the high-frequency component from an input signal and outputs the high-frequency component only when the current detected by the detector is within the predetermined range.
3. The push-pull amplifier according to claim 2, wherein said filter has a signal amplifier.
4. A push-pull amplifier comprising:
an input terminal;
an output terminal;
a pair of transistors, wherein the pair of transistors amplifies signals received at said input terminal, and output to said output terminal, wherein each of the transistors includes a control terminal, a first terminal, and a second terminal that controls a current flowing between the first terminal and the second terminal in accordance with signals applied to the control terminal; and
an amplifier for amplifying only a high-frequency component extracted from said signals received at said input terminal, and outputting said amplified signal to said output terminal when an amount of current flowing between the first and second terminals of one of the transistors is within a predetermined range, wherein the amplifier is turned off when the amount of current flowing is outside the predetermined range.
5. The push-pull amplifier according to claim 4, wherein said amplifier comprises:
a detector which detects the current flowing between the first and second terminals of one of the transistors;
a filter which extracts and outputs the high-frequency component from signals received at the input terminal only when the current detected by the detector is within the predetermined range; and
a transistor that is disposed parallel to one of the transistors and operates in response to the output signals of the filter.
6. The push-pull amplifier according to claim 5, wherein said filter has a signal amplifier.
7. A power amplifying apparatus comprising: a push-pull amplifier having a pair of transistors, wherein each of the transistors has a control terminal, a first terminal, and a second terminal, and wherein a current that flows between the first terminal and the second terminal is controlled in accordance with signals applied to the control terminal, such that when an amount of current flowing between the first terminal and the second terminal of one of the transistors is within a predetermined range, a high-frequency component of signals input to the control terminal of one of the transistors is amplified, and when this current is outside the predetermined range, the high-frequency component is not amplified.
8. A power amplifying apparatus comprising:
a push-pull amplifier having:
an input terminal;
an output terminal; and
a pair of transistors, wherein the pair of transistors amplifies signals received at said input terminal and output to said output terminal, wherein each of the transistors includes a first terminal, and a second terminal, and a control terminal that controls a current flowing between the first terminal and the second terminal in accordance with signals applied to the control terminal; and
an amplifier for amplifying only a high-frequency component extracted from said signals received at said input terminal and outputting an amplified signal to said output terminal when an amount of current flowing between the first and second terminals of one of the transistors is within a predetermined range, wherein the amplifier is turned off when the amount of current flowing is outside the predetermined range.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An adaptive pitch control system for a wind generator, the wind generator being a doubly fed induction generator (DFIG) having blade pitch servos for adjusting blade pitch of the DFIG wind generator, the system comprising:
means for determining a theoretically maximum reference power of the wind generator based on rotor speed and a plurality of given pitch angles;
a proportional-integral (PI) pitch controller having an input, a proportional gain constant KP, an integral gain constant KI, and an output adapted for connection to the blade pitch servos, the PI pitch controller output including means for sending pitch angle commands \u03b2 to the blade pitch servos to control pitch angle of the blades;
means for feeding back system states of the wind generator to said PI pitch controller;
means for determining actual power output of the wind generator;
means for determining the difference between the actual power output of the wind generator and the theoretically maximum reference power, the difference resulting in an error power signal;
means for applying said error power signal to the PI pitch controller input;
means for additively combining the KP multiplied by the error power signal with the KI multiplied by a time integral of the error power signal, the additive combination means forming the PI pitch controller output of the pitch angle commands \u03b2; and
means for adaptively adjusting the KP and the KI based on the error power signal.
2. The adaptive pitch control system according to claim 1, wherein said PI controller is a back propagation neural network (BPNN) having a plurality of signal paths and a corresponding plurality of weights applied to said plurality of signal paths.
3. The adaptive pitch control system according to claim 2, further comprising means for tuning said plurality of weights based on said feedback of said system states,
4. The adaptive pitch control system according to claim 3, wherein said means for tuning said plurality of weights further comprises means for generating a training dataset applied to said BPNN.
5. The adaptive pitch control system according to claim 4, further comprising:
means for generating a random number having values of said wind speeds between a first predetermined wind speed and a second predetermined wind speed to define a randomly generated wind speed;
means for saving the randomly generated wind speed in an input vector;
means for picking a wind speed from the input vector;
means for generating said KP and said KI for the input vector wind speed
means for saving said KP and said KI in an output vector; and
means for collecting a predetermined number of values in the input vector and the output vector, the input vector and the output vector forming said neural network training dataset used to train said back propagation neural network.
6. The adaptive pitch control system for a DFIG wind generator according to claim 5, wherein said means for generating said training dataset further comprises evolutionary computation means for optimizing said KP and said KI.
7. The adaptive pitch control system for a DFIG wind generator according to claim 6, wherein said evolutionary computation means for optimizing said KP and said KI comprises:
means for inputting said wind speed;
means for generating an initial population having a predetermined size by taking said random values of said KP and said KI defined between said first and second predetermined wind speeds;
means for applying crossover and mutation to said KP and said KI values;
means for evaluating an objective function of said KP and said KI values, said objective function expressing a difference in damping ratio obtained from dominant eigenvalues in a closed loop \u03b1-matrix defining states and instantaneous state changes of said DFIG wind generator;
means for selecting said KP and said KI values based on said objective function evaluation means;
means for pushing said Eigen values until a required damping is reached;
means for generating a trial vector and a mutated vector therefrom;
means for extracting values of said KP and said KI based on a minimum of said objective function;
means for iterating through said objective function evaluation, Eigen evaluation, Eigenvalues pushing, trial vector generation, KP and said KI value extraction until said objective function has reached its minimum value; and
means for updating said output vectors with optimized values of said KP and said KI.
8. The adaptive pitch control system for a DFIG wind generator according to claim 7, wherein said DFIG system states include direct and quadrature stator and rotor currents, direct and quadrature converter currents, turbine and generator speeds, torsion angle, initial and current pitch angle, and DC link capacitor voltage, said instantaneous state changes being represented by said closed loop a-matrix multiplied by said DFIG states.
9. The adaptive pitch control system for a DFIG wind generator according to claim 8, wherein said BPNN further comprises means for performing an approximate steepest descent on said weights when an error difference exists between said KI and KP gain constants of said output vector and said KI and KP gain constants output by said BPNN.