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Mode self-adaptive improved droop control method based on composite virtual impedance

A control method and virtual impedance technology, which are applied in the parallel feeding arrangement of a single network, wind power generation, AC network circuits, etc., which can solve the problem of fast frequency response speed, weak inverter overcurrent capability, and inability to flexibly realize connection and off-grid. Problems such as state switching and tie line power control to increase response time, avoid measurement, and avoid failure downtime

Inactive Publication Date: 2019-09-06
STATE GRID CORP OF CHINA +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0002] Aiming at the weak overcurrent capability and fast frequency response of traditional droop control inverters, which cannot be operated in parallel with synchronous motor type micro-sources, and cannot flexibly realize on-off-grid state switching and tie-line power control, a method based on composite virtual The mode adaptive improvement of impedance droop control can realize the stable operation of the microgrid in the island operation state, the power control of the tie line according to the dispatching instruction in the grid connection state and the smooth switching of the connection and off-grid operation state

Method used

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  • Mode self-adaptive improved droop control method based on composite virtual impedance
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  • Mode self-adaptive improved droop control method based on composite virtual impedance

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Experimental program
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Effect test

Embodiment 1

[0072] The first is the anti-truth analysis of the grid-connected operation of the micro-grid. In the present invention, the battery energy storage device is used as the main control micro-source, and the PQ control is adopted when the grid is connected. The improved droop control is adopted when the island is running, which can effectively reduce the voltage and voltage of the system during operation. The impact of frequency changes. When the microgrid is connected to the grid, the battery can absorb the electric energy from the large grid for charging, which is equivalent to a load. When the island is running, the power generated by the wind and photovoltaic units cannot meet the load demand. External discharge makes up for the power shortage and ensures the normal power supply of local loads. At the same time, it can make the voltage and frequency of the microgrid transition smoothly during the process of grid-connected to island.

[0073] At the beginning of the simulation...

Embodiment 2

[0078] When the island is running, the system needs to provide 65KW power at the beginning of operation to maintain the normal operation of the load. These powers will be provided by the distributed power supply, so the active power output by the distributed power supply is 65KW in total, which are: photovoltaic power generation unit 28KW, wind power generation Unit 17KW, battery 20KW.

[0079] Case 1: The load changes.

[0080] The microgrid operates under the condition that the wind speed, light intensity and temperature remain stable. When t=0.3s, the load with active power demand of 4KW is put into the microgrid. When t=0.5s, 8KW is removed from the microgrid. load, the specific simulation results are as follows Figure 15-17 shown.

[0081] pass Figure 15 It can be seen that at the moment of t=0.3s, the active load of the microgrid increases by 4KW. In order to meet the power demand of the load, the output power of the battery also increases by 4KW. When t=0.5s, the l...

Embodiment 3

[0088] Simulation analysis of microgrid operation mode switching process

[0089] When the system first started running, the active power demand of the microgrid load was 65KW, and the active power output by the distributed power generation was 65KW in total, which were: 28KW for the photovoltaic power generation unit, 17KW for the wind power generation unit, and 20KW for the storage battery; when t=0.2s, the microgrid The power grid is connected to the grid; at t=0.4s, the microgrid is switched to the island state; on the premise that all natural environmental conditions remain unchanged, we conduct a simulation experiment of the switching process; the simulation results are as follows Figure 21-23 shown.

[0090] Depend on Figure 21 It can be seen that at the beginning of the simulation, the microgrid operates in the island mode, and when t=0.2s, it is switched to the grid-connected operation mode. It can be clearly seen in the figure that the battery is discharged to the...

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Abstract

The invention relates to a mode self-adaptive improved droop control method based on composite virtual impedance. The control method comprises an improved droop control method in an isolated-island state, a dual-mode smooth switching control method and an improved droop control method in a networked state. The output power is quickly adjusted by changing a droop control strategy during isolated-island operation of a micro-grid, so that the frequency of the micro-grid is within an allowable range, the voltage almost does not fluctuate, and the stability of the isolated-island mode of the micro-grid is maintained; the PQ control is adopted during grid-connected operation, and the droop control is adopted during the isolated-island operation, so that the influence of voltage and frequency changes in an operation process of a system can be effectively reduced, and meanwhile, the smooth transition of the voltage and frequency of the micro-grid in a grid-connected to isolated-land process can be realized; and the method has the advantages of being stable in operation and smooth in isolated-land and grid-connected state switching.

Description

technical field [0001] The invention relates to the technical field of power grid control, in particular to a mode adaptive improved droop control method based on composite virtual impedance. Background technique [0002] Aiming at the weak overcurrent capability and fast frequency response of traditional droop control inverters, which cannot be operated in parallel with synchronous motor type micro-sources, and cannot flexibly realize on-off grid state switching and tie-line power control, a composite virtual based inverter is proposed. The mode adaptive improvement of impedance droop control can realize the stable operation of the microgrid in the island operation state, the power control of the tie line according to the dispatching instruction in the grid-connected state, and the smooth switching of the grid-connected and off-grid operating states. Contents of the invention [0003] The purpose of the present invention is to overcome the deficiencies of the prior art, a...

Claims

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Application Information

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IPC IPC(8): H02J3/38
CPCH02J3/383H02J3/386H02J3/388H02J2203/20Y02E10/56Y02E10/76
Inventor 付冬孟凡斌陈上吉党彬王振华刘伟苗桂喜王静
Owner STATE GRID CORP OF CHINA
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