A pressure energy recovery system and grid connection method

Abstract

The invention discloses a pressure energy recovery system and a grid connection method. The grid connection method comprises the steps of: a controller firstly controls a second regulating valve to increase the opening degree at a first pulse speed; when the actual opening degree of the second regulating valve is ≥When the opening degree is opened, the controller controls the first regulating valve to increase the opening degree at the first pulse speed; the controller then adjusts the pulse speed of the first regulating valve and the second pulse speed respectively according to the inlet pressure and rotational speed of the dual-rotor expander. The pulse speed of the regulating valve; when both the first regulating valve and the second regulating valve increase the opening at the fourth pulse speed, and when the state of the grid and the asynchronous generator satisfies the grid connection condition, the controller controls the grid connection The switch is closed; when the inlet pressure and rotational speed of the dual-rotor expander meet the stable conditions, the controller controls the first regulating valve and the second regulating valve to keep the opening degree unchanged; the grid connection method disclosed in the present application adjusts the opening degree through multi-speed adjustment. It can ensure the smooth start of the system and improve the stability of the grid connection process.

Description

technical field [0001] The invention relates to the technical field of natural gas pressure energy recovery, in particular to a pressure energy recovery system and a grid connection method. Background technique [0002] Trunk natural gas is generally transported under high pressure, and its delivery pressure has reached 10MPa, while the natural gas delivery pressure of the urban pipeline network is 0.4Mpa. Therefore, in order to meet the user's requirements, before the natural gas is delivered to the downstream gas pipeline network, it is generally necessary to set up a natural gas receiver. Gate station or regulator station to regulate the pressure of natural gas. [0003] In order to utilize the pressure energy lost during the pressure regulation process of natural gas, a dual-rotor expansion generator set can be installed between the high-pressure pipeline network and the low-pressure urban gas pipeline network to replace the traditional receiving gate station or pressure...

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Problems solved by technology

[0004] At present, asynchronous generators are gradually being used in pressure energy generation. Compared with synchronous generators, asynchronous generators have the advantages of low power consumption, small size, and easy maintenance. However, in the direct grid-connected mode, the grid-connected temporary However, the state is much more serious than that of synchronous generators; when the asynchronous generator is directly connected to the grid, since the asynchronous generator itself has no voltage before it is connected to the grid, an inrush current several times larger than the rated current will be generated at the moment of grid connection. As a result, serious voltage drops and deterioration of power quality

[0005] In order to reduce the negative impact of the asynchronous generator in the grid connection process, before the grid connection, the speed and power of the valve on the high-pressure side of the inlet are generally adjusted first. When the rated speed is reached, the SCR soft start or three-phase series connection Grid-connected in the form of resistance to reduce the inrush current generated at the instant of grid-connected; the single-valve adjustment method cannot stably control the pressure and flow of the inlet high-pressure side and the outlet low-pressure pipe network and cannot achieve smooth start-up and shutdown; and the use of silicon controlled rectifiers The grid connection method of soft start will cause current distortion, and the grid connection method using three-phase series resistance will increase the cost of grid connection

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