An electrical system for connecting a rotary electric machine to dc networks operating at different voltages, the electric machine having polyphase winding sets each having a respective index. The electrical system has a first set of ac-dc converter circuits connected in a modular multilevel configuration, each ac-dc converter circuit having a respective index and an ac interface for connection with a corresponding winding set, and in which the modular multilevel configuration has dc outputs each having a respective index. The electrical system also has a set of dc-dc converter circuits each having a respective index and being configured to convert dc power between a voltage at a first dc interface and a voltage at a second dc interface, where a first dc interface of the nth dc-dc converter circuit is connected with the dc outputs of the modular multilevel configuration.

Electrical systems for connecting rotary electric machines to dc networks operating at different voltages V and W where V>W along with gas turbine engine arrangements incorporating such systems.

A generalized frequency conversion system for a steam turbine generator unit. The system comprises at least a variable speed steam turbine with an adjustable rotating speed, a water feeding pump, a variable frequency generator operating at a variable speed, a speed increasing gearbox with a fixed rotating speed ratio, a variable frequency bus and an auxiliary machine. With a change in load of the unit, parameters of steam entering the variable speed steam turbine and an extracted steam amount are adjusted (changed) accordingly, so that the rotating speed of the steam turbine changes accordingly. In this way, on one hand, the rotating speed of the water feeding pump is changed through the speed increasing gearbox; and on the other hand, the frequency of alternating current outputted by the variable frequency generator is changed. In the present invention, there is no need to additionally provide other types of frequency converters, and the system is simple, reliable, low in cost and high in efficiency.

A method for starting a steam turbine can comprise electrically decoupling a generator configured to be driven by the steam turbine from a power supply, controlling power from the power supply to a frequency converter, and operating the generator as a starter motor with power from the frequency converter to turn the steam turbine. A power plant system can comprise a steam turbine, a generator configured to be driven by the steam turbine to supply power to a grid system, a first switch to electrically couple and decouple the generator from the grid system, a frequency converter electrically coupled to the generator, and a second switch to electrically couple and decouple the frequency converter form the grid system.

A control system for a power generation system includes a generator coupled to a turbine via a shaft. The control system includes a memory storing instructions. The control system also includes a processor coupled to the memory and configured to execute the instructions. When the instructions are executed it causes the processor to receive a direct current (DC)-link voltage from an automatic voltage regulator (AVR), wherein the AVR is configured to control voltage characteristics of the generator, and to determine a speed of the generator based on the DC-link voltage.

In a thyristor starter, an inverter converts DC power provided from a converter through a DC reactor into AC power having a variable frequency, and supplies the AC power to a synchronous machine. A controller controls the inverter based on a phase control angle. A voltage regulator regulates an induced voltage of the synchronous machine by supplying a field current to the synchronous machine. When a rotation speed of the synchronous machine exceeds a reference rotation speed during acceleration of the synchronous machine, the voltage regulator controls the field current such that the induced voltage increases with an increase in the rotation speed of the synchronous machine. The controller decreases a rate of increase in the phase control angle relative to the rotation speed of the synchronous machine, as compared with when the rotation speed of the synchronous machine is less than the reference rotation speed.

A method for operating a steam turbine, wherein the pressure of the cooling medium in the generator is changed not only for cooling but also for increasing or decreasing the torque of the generator on the steam turbine, this being utilized for the purpose of the start-up or shut-down process.

Electrical systems for connecting rotary electric machines to dc networks operating at different voltages V and W where V>W along with gas turbine engine arrangements incorporating such systems.

A generalized frequency conversion system for a steam turbine generator unit. The system comprises at least a variable speed steam turbine with an adjustable rotating speed, a water feeding pump, a variable frequency generator operating at a variable speed, a speed increasing gearbox with a fixed rotating speed ratio, a variable frequency bus and an auxiliary machine. With a change in load of the unit, parameters of steam entering the variable speed steam turbine and an extracted steam amount are adjusted (changed) accordingly, so that the rotating speed of the steam turbine changes accordingly. In this way, on one hand, the rotating speed of the water feeding pump is changed through the speed increasing gearbox; and on the other hand, the frequency of alternating current outputted by the variable frequency generator is changed. In the present invention, there is no need to additionally provide other types of frequency converters, and the system is simple, reliable, low in cost and high in efficiency.

A method for starting a steam turbine can comprise electrically decoupling a generator configured to be driven by the steam turbine from a power supply, controlling power from the power supply to a frequency converter, and operating the generator as a starter motor with power from the frequency converter to turn the steam turbine. A power plant system can comprise a steam turbine, a generator configured to be driven by the steam turbine to supply power to a grid system, a first switch to electrically couple and decouple the generator from the grid system, a frequency converter electrically coupled to the generator, and a second switch to electrically couple and decouple the frequency converter form the grid system.