Method for stably controlling switchover from micro-grid connection into island state

A stability control method and microgrid technology, which is applied to AC networks with different sources of the same frequency, etc., can solve the problems that the response speed cannot guarantee the stability of the microgrid system, is not a solution, lag, etc., and achieves fast response speed, Achieve smooth switching and achieve the effect of output power balance

Inactive Publication Date: 2014-02-19
STATE GRID CORP OF CHINA +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When the inverter collects the electrical quantity of the system and judges the change of the electrical quantity of the microgrid, the microgrid is already running in a state of unbalanced power, and the parameters such as P, V, Q, and f have been developing in an unstable direction. is lagging
[0008] 2. The response speed cannot guarantee the stability of the microgrid system
[0009] Therefore, it is not a perfect solution to maintain the stability of the microgrid only by the regulation of the inverter

Method used

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Examples

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Embodiment 1

[0025] This embodiment is a stable control method when the grid-connected microgrid is planned to switch to the island state. It is assumed that the transmission power of the grid-connected point is Pc, and the output power of the energy storage inverter is Ppcs, including the following steps:

[0026] a) When the micro-grid is in grid-connected operation state, the power system will track and balance load fluctuations, and give priority to the use of energy from the micro-grid;

[0027] b) After the microgrid receives the grid-connected to island switching command, before the microgrid and the power system are decoupled, the microgrid stability control system collects the power of the grid-connected point, configures the power supply and load to make it basically balanced, and at the same time sends power to the energy storage inverter Transmission power at the grid-connected point before sending out decoupling;

[0028] In this embodiment, the method of configuring the power...

Embodiment 2

[0031] This embodiment is a stability control method when the microgrid is switched from grid-connected to unplanned island, including the following steps:

[0032] 1) When the microgrid is in grid-connected operation, the power system will track and balance load fluctuations, and give priority to the use of energy from the microgrid.

[0033] 2) The microgrid is suddenly decoupled from the power system to form an isolated island. According to the difference between the power flow before the decoupling of the grid connection point and the maximum output power of the energy storage inverter, load shedding or cutting off part of the power branch within 10ms ensures that the system Stability at the moment of switching.

[0034] In this embodiment, the islanding detection and judgment technology is adopted to actively detect the occurrence of unplanned islanding.

[0035] 3) The energy storage inverter with the maximum capacity is set to immediately switch to V / F control to estab...

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Abstract

The invention relates to a method for stably controlling switchover from micro-grid connection into an island state. When switchover is planned, a micro-grid stability control system collects grid connection point power before the micro-grid is sectionalized from an electric system, a power source and a load are configured to be basically balanced, and meanwhile the grid connection point transmission power before sectionalization is sent to an inverter; a grid connection point breaker is stably cut off, the output power of the inverter is maintained as the grid connection point transmission power before the sectionalization, and power can reach the balance immediately after the micro-grid becomes off-grid. When the switchover is not planned, the micro-grid is sectionalized with the electric system suddenly to form an island, the load or the partial power branch circuit is cut within 10ms according to the difference between currents before the sectionalization of a grid connection point and the maximum output power of an energy storing inverter, and the stability of the system switchover moment is ensured; the energy storing inverter with the maximum capacity is immediately transferred into V/F control, and other power sources are set to be P/Q control. According to the method, the micro-grid connection can be smoothly switched over to the island state.

Description

technical field [0001] The invention relates to a stable control method when a micro grid is connected to an island state and belongs to the technical field of electric power system control. Background technique [0002] The microgrid has two operating modes. Under normal circumstances, the microgrid is connected to the distribution network through the PCC point and operates in parallel with the distribution network, and exchanges power with the distribution network; The microgrid actively disconnects from the distribution network and enters the island operation mode, and the micropower supplies power to the loads in the microgrid independently. [0003] Correspondingly, the microgrid has four operating states: two stable operating states: grid-connected operating state and island operating state; two transient operating states: grid-connected switching transient state and island switching transient state. [0004] The transient characteristics of the microgrid are relative...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/06
Inventor 吴鸣盛万兴季宇刘海涛李洋
Owner STATE GRID CORP OF CHINA
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