Method and circuit for controlling an electric power plant

An electric power plant comprising:

• an asynchronous generator of an AC voltage;
• a motor to rotate a rotor of the asynchronous generator as a function of a first control signal of a developed motor torque;
• a bank of capacitors coupled to said asynchronous generator and having a capacitance and varying as function of a second control signal;
• and
• a control circuit to generate the first and second control signals by soft-computing techniques both as a function of the frequency and of a representative value of an amplitude of the AC voltage to make the AC voltage have a desired amplitude and frequency.

A method of generating electric power comprising:

• installing an asynchronous generator of an AC voltage;
• installing a motor for rotating a rotor of the asynchronous generator to be input with a first control signal of a generated motor torque;
• installing a bank of capacitors coupled to the asynchronous generator and having a total capacitance varying as function of a second control signal;
• and
• generating the first and second control signals by soft-computing techniques both as a function of the frequency and of a representative value of an amplitude of the AC voltage to make the AC voltage have a desired amplitude and frequency.

A mono-phase switched L-C device for matching an AC mono-phase load comprising:

• first and second output terminals to be coupled to the AC mono-phase load;
• an internal node;
• a controlled switch coupled between the first output terminal and the internal node, turned on and off at instants determined as a function of a phase difference between an AC voltage and AC current absorbed by the AC mono-phase load;
• an inductor coupled between said internal node and the second output terminal;
• and
• a capacitor coupled between said first and second output terminals.

A three-phase switched L-C device for matching an AC three-phase load comprising:

• three mono-phase L-C devices coupled together in triangle fashion, each comprising
• first and second output terminals to be coupled to a respective AC phase load,
• an internal node,
• a controlled switch coupled between the first output terminal and the internal node, turned on and off at instants determined as a function of a phase difference between an AC voltage and AC current absorbed by the respective AC phase load,
• an inductor coupled between said internal node and the second output terminal, and
• a capacitor coupled between said first and second output terminals;
• and
• a driver that senses an AC voltage and AC current absorbed by the AC three-phase load and operates said controlled switches at instants determined as a function of a phase difference between the AC voltage and AC current.

An electric power plant comprising:

• an asynchronous generator of a AC voltage having three-phases;
• a prime mover to rotate a rotor of the asynchronous generator as a function of a first control signal of a developed prime mover torque;
• a bank of capacitors coupled to said asynchronous generator and having a capacitance and varying as function of a second control signal;
• and
• three mono-phase L-C devices coupled together in triangle fashion to said asynchronous generator, each comprising
• first and second output terminals to be coupled to a respective AC phase,
• an internal node,
• a controlled switch coupled between the first output terminal and the internal node, turned on and off at instants determined as a function of a phase difference between an AC voltage and AC current absorbed by the respective AC phase,
• an inductor coupled between said internal node and the second output terminal, and
• a capacitor coupled between said first and second output terminals;
• and
• a driver that senses AC voltage and AC current and operates said controlled switches at instants determined as a function of a phase difference between the AC voltage and AC current.

A driver for a thyristor connected to an AC line, generating pulses for turning on in correspondence with a desired electrical angle of a voltage of the AC line, comprising:

• a zero-cross block being input with the AC voltage and that generates a zero-cross pulse at each detected zero-crossing during a leading or a trailing edge of the AC voltage;
• a clock that generates clock pulses;
• a counter reset with a delayed replica of pulses generated by the zero-cross block and that counts clock pulses supplied by said clock;
• a latch that stores a counting value of said counter at each zero-crossing pulse;
• a logic circuit input with the counting value stored in said latch and the reference value of the electrical angle and that converts the counting value stored in said latch into a corresponding number of clock pulses;
• and
• a comparator that compares the counting value of the counter with the corresponding number of clock pulses and generates a pulse for turning on the thyristor when they are equal to each other.

A load estimator connectable to an AC supply line of a load, for generating an estimated value of reactive power absorbed by the load, comprising:

• a voltage peak detector that senses the AC voltage supplied to the load and generates a first signal that represents a detected peak value thereof;
• a current peak detector that senses the AC current supplied to the load and generates a second signal that represents a detected peak value thereof;
• a phase difference estimator that generates a third signal that represents a phase difference between the AC current and AC voltage supplied to the load;
• and
• a calculation block being input with the first, second and third signals and that generates a signal representative of the reactive power absorbed by the load.