Doubly fed generator variable speed generation control system

An energy conversion generation system for receiving resource energy from a resource and converting the resource energy into an electrical power output for supply to a polyphase electric power grid operating at a system frequency, the energy conversion system comprising:

• a variable speed generation system including turbine means for converting a resource energy input from the resource into mechanical energy at a rotor speed;
• energy converter means for producing excitation power;
• a doubly fed generator coupled to the turbine means and having a rotor with excitation rotor windings and with means for applying the excitation power from the energy converter means to the rotor windings, the rotor being driven by the mechanical energy from the turbine means, and a stator with stator windings to supply the electrical power output to the power grid;
• input sensor means for sensing at least one parameter of the resource energy received by the turbine means, and for producing a turbine input sensor signal;
• generator output sensor means for sensing the output power from the doubly fed generator which is supplied to the power grid, and for producing a generator output sensor signal;
• converter signal processing means for receiving and processing the generator output sensor signal and the turbine input sensor signal, the converter signal processing means comprising means for producing a converter control signal in response to the generator output sensor signal and the turbine input sensor signal;
• and
• the energy converter means comprising means for controlling the excitation power in response to the converter control signal to vary the rotor speed to reduce power losses in the generator.

An energy conversion generation system for receiving resource energy from a resource and converting the resource energy into an electrical power output for supply to a polyphase electric power grid operating at a system frequency, the energy conversion system comprising:

• a variable speed generation system including turbine means for converting a resource energy input from the resource into mechanical energy at a rotor speed, the variable speed generation system further including energy converter means for producing excitation power, and a doubly fed generator coupled to the turbine means and having a rotor with excitation rotor windings and with means for applying the excitation power from the energy converter means to the rotor windings, the rotor being driven by the mechanical energy from the turbine means, and a stator with stator windings to supply the electrical power output to the power grid;
• turbine input sensor means for sensing at least one parameter of the resource energy input received by the turbine means, and for producing a turbine input sensor signal;
• generator output sensor means for sensing the output from the doubly fed generator supplied to the power grid, and for producing a generator output sensor signal;
• a variable speed generation controller including turbine signal processing means for receiving and processing the generator output sensor signal to produce a turbine control signal, and converter signal processing means for receiving and processing the generator output sensor signal, the turbine input sensor signal, and the turbine control signal to produce the converter control signal;
• resource energy adjustment means coupled to the variable speed generation controller for receiving the turbine control signal and for controlling the energy delivered to the turbine means, and thereby the resource energy converted into rotational mechanical energy, in response to the turbine control signal;
• the energy converter means comprising means for controlling the excitation power in response to the converter control signal;
• and
• the variable speed generation controller comprising means for controlling the excitation power and the resource input energy delivered to the turbine means to control the efficiency of the variable speed generation system, irrespective of variations in the resource energy.

A method for converting resource energy from a resource into electrical power for supply to a polyphase electric power grid operating at a system frequency, using a doubly fed generator coupled to a turbine having an adjustable turbine setting, the method comprising the steps of:

• monitoring the resource energy received by the turbine and producing a turbine input sensor signal;
• sensing the doubly fed generator output power supplied to the power grid and producing a generator output power sensor signal;
• sensing the generator output terminal voltage and producing a generator output terminal voltage signal;
• setting a power demand signal;
• setting a generator voltage reference demand signal;
• processing the generator output power sensor signal and the power demand signal to produce a turbine control signal;
• processing the generator output power sensor signal, the turbine input sensor signal, the turbine control signal, a generator voltage reference demand signal, and the generator output terminal voltage signal to produce a converter control signal;
• receiving and converting the resource energy into mechanical energy with the turbine;
• driving the coupled doubly fed generator at a rotor speed with the mechanical energy supplied by the turbine;
• adjusting the resource energy received by the turbine to control the rotor speed;
• converting power received from an excitation power source into excitation power for the doubly fed generator in response to the converter control signal, and
• exciting rotor windings of the doubly fed generator with the excitation power to produce generator output power at the system frequency for supply to the electric power grid.

A variable speed generation controller for controlling a variable speed generation system having a turbine responsive to a turbine control signal which receives resource energy from a resource, a doubly fed generator driven by the turbine at a rotor speed, and a converter responsive to a converter control signal for exciting the doubly fed generator with excitation power converted from an excitation power source, the generation system producing electrical power having real and reactive components for supply to a polyphase electrical power grid operating at a system frequency, the system providing signals including a turbine input sensor signal, a generator terminal voltage sensor signal, an output power sensor signal, a power demand signal and a generator voltage reference demand signal, the variable speed generation controller comprising:

• first voltage subcontroller means for receiving and processing the generator terminal voltage sensor signal and the generator voltage reference demand signal, the first voltage subcontroller means comprising means for controlling the reactive component of the electrical power by producing a maximum excitation amplitude signal from the received and processed signals;
• second turbine power subcontroller means for receiving and processing the output power sensor signal and the power demand signal, the second turbine power subcontroller means comprising means for controlling the real component of the electrical power by producing a turbine control signal from the received and processed signals, the resource energy received by the turbine being controlled in response to the turbine control signal;
• third rotor speed subcontroller means for receiving and processing the turbine input sensor signal, the output power sensor signal and the turbine control signal, the third rotor speed subcontroller means comprises means for producing an excitation frequency signal from the received and processed signals;
• and
• signal generator means for receiving the maximum excitation amplitude signal and the excitation frequency signal, the signal generator means comprising means for controlling the converter and the generator excitation by producing the converter control signal from the received and combined signals.

An energy conversion generation system for receiving resource energy from a resource and converting the resource energy into an electrical power output for supply to a polyphase electrical power grid operating at a system frequency, the energy conversion generation system comprising:

• a variable speed generation system including a turbine of a type which converts a resource energy input from the resource into mechanical energy at a rotor speed;
• an energy converter of a type which produces excitation power;
• a doubly-fed generator coupled to the turbine and having a rotor with excitation rotor windings which receive the excitation power from the energy converter, the rotor being driven by the mechanical energy from the turbine, with the doubly-fed generator also having a stator with stator windings to supply the electrical power output to the power grid;
• and
• a controller for varying the rotor speed in response to the power output and resource energy input to increase the ratio of the electrical output power to the resource energy input received from the resource.