Urgent frequency modulation (FM) control method of energy storage system in micro-grid

Abstract

Disclosed is an urgent FM control method of an energy storage system in a micro-grid. The technical scheme includes that distributed power supplies and the energy storage system in the micro-grid are in a communication connection; a diesel-driven generator, a microturbine or other synchronous generators serves as a main power supply, the energy storage system serves as a micro-grid auxiliary adjusting unit, a PQ control method is adopted for the merging into the micro-grid through a monopolar type DC/AC or a bipolar type DC-DC/AC, and one of the functions is configured to be urgent FM. The control method includes providing an active power output reference value of the energy storage system according to the governing equation P<ref> =P0+PI*delta f; controlling the energy storage system output P to follow the active power reference value Pref by adoption of the PQ control method; and enabling the system frequency to be within an allowed range under the joint adjustment of the main power source and the energy storage system of the micro-grid. The governing equation P<ref> =P0+PI*delta f is adopted for the urgent FM function of the energy storage system in the micro-grid, wherein PI is a PI controller capable of setting a dead band, therefore urgent FM can be performed well, the problem of pulse power output or poor coordinating control of two main power sources of the energy storage system is avoided, and the system stability and service life are effectively improved.

Description

technical field [0001] The invention belongs to the technical field of electric power system micro-grid, and relates to an emergency frequency regulation control method for a micro-grid energy storage system. Background technique [0002] As smart grid technology continues to gain popularity, distributed power supply technology and micro-grid technology have developed rapidly, and micro-grid has therefore become an important supplement and part of the distribution network and plays an important role in user terminals. The so-called micro-grid refers to a small power generation and distribution system composed of distributed power sources, energy storage devices, energy conversion devices, related loads, monitoring and protection devices. Managed autonomous systems. Microgrids are usually composed of distributed power generation (wind, light, diesel generators, gas turbines, etc.) and energy storage systems. Energy storage can be used as the main power supply or as an auxili...

AI Technical Summary

Problems solved by technology

[0005] (2) System frequency modulation is mainly achieved by simulating the droop control characteristic curve of synchronous generators, which is similar to primary frequency modulation in large power grids, that is, when the frequency drops, active power is generated, and when the frequency rises, reactive power is generated. The control equation is: P ref =K*Δf, this function will lead to frequent charging and discharging of energy storage, which will affect the service life of the battery. At the same time, if the non-difference frequency adjustment method P ref =PI*Δf, then the system will have two main power sources at the same time, and effective coordinated control cannot be carried out according to the current technology

The main disadvantage of this control method is that when the sudden load increase is greater than the main power supply of the microgrid (diesel generator or gas turbine), it will cause system frequency oscillation, resulting in pulsed active power output from the energy storage. The process is as follows: load sudden increase -> Frequency drop—>energy storage active output—>temporary balance—>frequency return to normal—>energy storage exits operation—>active power deficit—>frequency drop

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