Island detection method for photovoltaic grid-connected inverter based on comprehensive frequency and phase information

Abstract

The invention discloses an island detection method for a photovoltaic grid-connected inverter based on comprehensive frequency and phase information. Active frequency shifting detection can be realized based on frequency and phase information of the last period; the main principle is as follows: in the k zero-crossing point of an end voltage, the power grid voltage frequency of the last period is measured firstly; then an active frequency disturbance value f[k] is set to be equal to f[k-1] plus or minus <delta> f according to the frequency; meanwhile, a phase angle, which is as shown in the specification, is also changed according to the frequency f[k-1] of the inverter in the last period; island detection hardware performs active drifting on the frequency and phase of the power grid voltage and then the processed power grid voltage is used as the set frequency of the grid-connected inverter; in addition, the grid-connected current is reset in voltage zero-crossing; in grid-connection, the system frequency detected by the island detection hardware in each time is unchanged; in an off-network state, the system frequency detected in each time can rapidly achieve upper limit and lower limit of protection to perform protection actions so as to realize an anti-island function; and by virtue of the island detection method disclosed by the invention, non-detection regions in the conditions that the load is close to photovoltaic power generation power and the load is less than the photovoltaic power generation power can be obviously reduced.

Description

technical field [0001] The invention relates to the technical field of power system fault detection, in particular to a photovoltaic grid-connected inverter island detection method that integrates frequency and phase information. Background technique [0002] The island effect of the photovoltaic grid-connected power generation system means that when the grid line connected to the photovoltaic power generation system is disconnected due to failure, accident or power outage maintenance, the photovoltaic grid-connected power generation system continues to supply power to the load, thus forming a situation that the power supply company cannot control. The self-sufficient power supply island, the island effect will cause serious harm to the distribution network system and users. Therefore, it is of great significance to study the detection methods and protection measures of the island effect to minimize the harm of the island effect. [0003] The detection methods of the island...

AI Technical Summary

Problems solved by technology

The passive detection method has the advantages of simple principle, easy implementation, and no harmonic influence on the power system. However, due to the basic balance between the power of the photovoltaic power source and the power of the local grid load, the output voltage and The frequency change is very small, so when the passive island detection method is used, there will be a large detection blind area

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