Study On Islanding Detection Of Multi-Inverter Connected To Grid Based On Phase Angle Disturbance

With the global energy and environmental problems,renewable energy research has been accelerated in many countries.With the diversity of the development of distributed systems,there are various challenges in the power system with distributed generation,among which islanding detection is one of the serious problems.Traditional islanding detection methods are mostly based on the research of grid-connected inverters with constant power control and current control.With the continuous development of grid-connected inverters with other control strategies such as droop control and the wide application of multi-machine grid-connected inverters,the effectiveness of traditional islanding detection methods is challenged,and a more versatile detection method must be found to adapt to the development of distributed generation systems.In order to study the islanding detection of grid-connected inverters with different control strategies,this paper firstly introduces and compares the common constant power control strategy and droop control strategy,including the selection of inverters' topology,the modeling of inverters,the analysis of control principle,etc.In addition,the principle and design of phase-locked loop and active synchronization control are introduced in detail.Finally,a simulation is built to simulate and analyze it,which lays a foundation for further research on islanding detection methods.An improved islanding detection method based on phase-locked loop(PLL)phase-angle cluster perturbation is proposed for constant power control strategy.Compared with the traditional method,this method enhances the anti-interference ability of islanding detection by adding harmonic clusters.For drop control strategy,an islanding detection method based on P-f active power loop phase-angle cluster perturbation is proposed.phase-angle cluster disturbance is realized by extracting the harmonic amplitudes and summing them up by Goertzel algorithm to detect island.Finally,preliminary verification is carried out by simulation,which verifies that the proposed method is suitable for distributed generation systems under two control strategies.Finally,based on the above theoretical analysis,an experimental platform for grid-connected inverters is built.Firstly,the strategy of constant power control and drop control is tested and analyzed by using DSP and FPGA software control.Finally,the improved islanding detection schemes of constant power control and drop control are verified by experiments,which verifies the reliability and rapidity of the proposed improved islanding detection method.