Island detection method and system

An island detection and coordinate system technology, which is applied in the direction of measuring electricity, measuring devices, and measuring electrical variables, can solve the problems of affecting the quality of inverter output power and large blind areas of island detection, and achieves the elimination of island detection blind areas and steady-state power Good quality, easy to control effects

Active Publication Date: 2020-02-21
HEFEI WIN POWER
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Problems solved by technology

[0005] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide an islanding detection method and an islanding detection system, which are used to solve the problems in the prior art that the blind area of ​​the islanding detection is large and the quality of the inverter output power is affected by the amount of disturbance injected. question

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Embodiment 1

[0042] The invention provides an island detection method, which is suitable for grid-connected inverters that adopt grid voltage orientation, and the grid-connected inverters have local loads, and the local loads can be pure resistive loads, inductive loads, and capacitive loads. random combination.

[0043] see figure 1 , is a grid-connected inverter topology with local load (RLC), point A is the grid-connected point, and its power equation can be described as:

[0044] P load +jQ load =(P inv +ΔP)+j(Q inv +ΔQ)

[0045] Among them, P load Active power consumed by the local load, Q load Reactive power consumed by local loads, P inv is the active power output by the grid-connected inverter, Q inv is the reactive power output by the grid-connected inverter, ΔP is the active power exchanged between the grid-connected point and the grid, and ΔQ is the reactive power exchanged between the grid-connected point and the grid. When it is zero, that is, the grid-connected invert...

Embodiment 2

[0072] see Figure 7 , the present application also discloses an islanding detection system, the system includes: a sampling module (not shown), used to sample the three-phase voltage and three-phase current signals of the grid-connected point; The three-phase voltage signal U of the outlet a , U b , U c Perform phase locking, and output the angle orientation error value err_q of the grid-connected point voltage; the proportional differential regulator 2 is used to perform proportional differential adjustment on the angle orientation error value err_q to obtain the disturbance amount of the reactive power command of the grid-connected inverter ΔVq; the adder 3 is used to superimpose the disturbance ΔVq of the reactive power command on the reactive current command Iq_ref of the grid-connected inverter; the reactive power control module 4 is used to superimpose the reactive power according to the superimposed disturbance The current command Iq'_ref controls the reactive power...

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Abstract

The invention provides an island detection method. An orientation error of the power-grid voltage phase angle is used as disturbance quantity which is superposed to a reactive current instruction by positive feedback, reactive power output of a grid-connected inverter is adjusted, when a power grid contactor is disconnected and an island effect occurs, voltage frequency deviation of a grid-connected point causes generation of a directional angle error, further, the reactive current instruction is subjected to positive feedback adjustment, the frequency deviation degree of the grid-connected point voltage is increased, a threshold is exceeded, passive protection of a detection system is triggered, and shutdown succeeds. Via the detection method and system, blind areas of island detection are eliminated, control is simple, island detection of the inverter can be carried out quickly and accurately, and electric energy quality during grid-connected operation is not influenced.

Description

technical field [0001] The invention relates to the technical field of grid-connected power generation, in particular to an island detection method and an island detection system. Background technique [0002] As an energy exchange device between renewable energy and the grid, grid-connected inverters have been widely used in new energy power generation systems including wind power generation, photovoltaic power generation, and wave power generation. Distributed power generation systems are usually composed of new energy power generation devices, local loads and distribution networks, and the grid-connected inverters and the grid jointly supply power to the loads. [0003] When the grid is disconnected from the inverter due to a fault or line cut off, the grid-connected inverter is connected to the load, and the grid-connected point loses the support of voltage and frequency. The voltage amplitude and frequency of the grid-connected point are determined by the characteristic...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/00G01R19/00
CPCG01R19/00G01R31/00
Inventor 张为民周一晨庞博
Owner HEFEI WIN POWER
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