MPPT-based island detection method

Abstract

The invention, which belongs to the technical field of photovoltaic generating and distributed generating inverter control, relates to an MPPT-based island detection method. A voltage amplitude value of a grid-connected point is affected by disturbance on MPPT; whether an island occurs is determined based on the voltage amplitude value of the grid-connected point; and disturbance on the MPPT is carried out by increasing a duty ratio D of a boost circuit, so that an objective of reduction of the photovoltaic output voltage and power can be achieved. In an off-grid state, with reduction of the photovoltaic output power, the voltage of the grid-connected point is reduced; and when the voltage of the grid-connected point deviates from a normal range, an island state is determined. According to the invention, with fully consideration of an active matching situation of a local load and a distributed photovoltaic generating system, the parameter setting becomes reasonable, the blind detection area is eliminated, the disturbance period setting becomes reasonable, the power loss is reduced, and the influence on the electric energy quality is affected.

Description

technical field [0001] The invention belongs to the technical field of distributed generation inverter control, and relates to an island detection method based on MPPT. Background technique [0002] With the depletion of fossil fuels, more and more attention is paid to renewable and clean energy. As a clean and renewable energy, solar energy has developed rapidly. With the advancement of photovoltaic power generation technology, more and more distributed photovoltaic power generation systems have been put into use. A large number of distributed photovoltaic power generation systems are connected to the grid, which also brings some new problems. One of the key problems is how to detect the islanding effect. The islanding effect refers to the fact that after the power grid is powered off, some lines and loads continue to be charged due to the existence of Distributed Power Generation (DG), forming a local power supply network that the power company cannot control. [0003] ...

AI Technical Summary

Problems solved by technology

The active detection method can reduce or eliminate the detection blind zone, but it needs to disturb the inverter output parameters, resulting in the degradation of power quality and power loss

[0004] The sliding mode frequency shift method and the active frequency shift method are widely used, but both methods will introduce additional harmonics, and the detection blind zone is greatly affected by the quality factor of the load

The active power disturbance method will not introduce additional harmonics, and the detection blind zone will not be affected by the quality factor, but most of the existing literature is based on the disturbance of the inverter output current, which will cause a gap between the inverter output power and the photovoltaic output power. unbalanced, resulting in fluctuations in the DC bus voltage

June 2011. Chongqing University. The document "Research on Islanding Detection Method in Photovoltaic Grid-connected Power Generation System" proposed an active power disturbance algorithm based on MPPT, which effectively made up for this deficiency. However, due to the unreasonable design of its disturbance parameters, there are detection blind spots. high power loss

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