A method for seamless switching between isolated grid and grid-connected modes in a combined cooling, heating, and power supply system

Abstract

The invention discloses a method for realizing seamless switching between an isolated-network mode and a grid-connected mode in a CCHP (combined cooling, heating and power) system. The method for switching the isolated-network mode into the grid-connected mode comprises the following steps: a synchronizing device is added with a mode switching function; when a CCHP mode controller receives a request instruction for switching the isolated-network mode into the grid-connected mode and a power grid runs in a normal state, the synchronizing device is started to adjust the frequency and voltage of a generator; when the frequency and voltage of the generator meet synchronous connection requirement, and the absolute value of phase difference of the generator and network voltage is smaller than a fixed value 1, an action instruction for switching the isolated-network mode into the grid-connected mode is output; the CCHP mode controller changes from frequency regulation and voltage regulation control to power control; when the frequency and voltage of the generator meet synchronous connection requirement, and the absolute value of phase difference of the generator and network is smaller than a fixed value 2, a generator grid connection instruction is output; and the isolated-network mode is switched into the grid-connected mode. Therefore, the problems of power failure in the switching process and overlarge disturbance and the like of the mode switching process in the CCHP system due to stop of output power of the generator are solved.

Description

technical field [0001] The invention belongs to the field of comprehensive utilization of energy, and in particular relates to a method for seamlessly switching between an isolated grid and a grid-connected mode in a combined cooling, heating, and power supply system. Background technique [0002] CCHP (Combined Cooling, Heating and Power), refers to the use of natural gas as the main fuel to drive gas-fired power generation equipment such as gas engines, micro-combustion engines or internal combustion engines to operate, and the electricity generated is supplied to users' electricity needs, and the electricity generated by the system is discharged The waste heat is supplied to users for heating and cooling through waste heat recovery and utilization equipment (waste heat boiler, refrigerator, etc.). In this way, the primary energy utilization rate of the entire system is greatly improved, and the cascade utilization of energy is realized. It can also provide grid-connected...

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Problems solved by technology

[0004] The technical problem to be solved by the present invention is to provide a method for seamless switching between the isolated grid and the grid-connected mode in the combined cooling, heating and power supply system, so as to solve the problem of switching from the grid-connected mode to the isolated grid in the combined cooling, heating and power supply system in the prior art. Grid mode or transition from isolated grid mode to grid-connected mode, the generator needs to stop output power, resulting in power outage during the switching process, and technical problems such as excessive disturbance during the mode switching process of the combined cooling, heating and power system.

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