Variable-speed and constant-frequency power generation system and method based on screw expander

Abstract

The invention discloses a variable-speed and constant-frequency power generation system based on a screw expander. The variable-speed and constant-frequency power generation system comprises the screw expander, a drive mechanism, an asynchronous generator, a four-quadrant frequency converter, a controller, a pressure feedback device and / or an output power feedback device, wherein an output shaft of the screw expander is connected with a rotor of the asynchronous generator through the drive mechanism; a power supply side of the four-quadrant frequency converter is connected with a power grid, and a motor side is connected with the asynchronous generator; an output end of the pressure feedback device and / or an output end of the output power feedback device are / is connected with an input end of the controller; an output end of the controller is connected with a signal input end of the four-quadrant frequency converter. The invention further discloses a variable-speed and constant-frequency power generation method based on the screw expander. The power generation system based on the screw expander can adapt to gas flow change under the condition that internal and external pressure ratios of the screw expander are not changed, the working efficiency is high, and high-efficiency power generation can be also realized when the gas flow is small.

Description

technical field [0001] The invention relates to a screw expander power generation system and a power generation method. Background technique [0002] The screw expander is a prime mover with internal expansion, which is widely used in energy recovery of pressurized gas, and can be used as a prime mover for mechanical drives or generator sets. The screw expander is a rotary volumetric expander, and the volume flow at the inlet mainly depends on the diameter of the rotor, the internal volume ratio, the rotational speed and the internal clearance. Regardless of whether the conventional screw expander is equipped with a synchronous generator or an asynchronous generator, due to the restriction of the grid frequency, the speed remains basically constant, so the volume flow at the inlet is also relatively constant. At the same time, when designing the orifice, the internal volume ratio of the expander is mainly designed according to the external pressure ratio, so that the situat...

AI Technical Summary

Problems solved by technology

Therefore, the inlet of the screw expander needs to be equipped with an automatic control valve with high precision, which is expensive and inconvenient to operate

When the screw expander is equipped with an asynchronous generator, although there is no need for high-precision speed control, the asynchronous generator set will consume the reactive power of the grid, which will reduce the power factor of the grid, and there will be a large inrush current at the moment of grid connection

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