Overview of anti-islanding algorithms for PV systems. Part I: passive methods

This paper offers an overview of the passive methods used for islanding detection. A monitoring PLL has been adopted for the estimation of the voltage amplitude and frequency. Passive inverter resident methods discussed are the over/under voltage (OUV), over/under frequency (OUF), the voltage harmonic monitoring (with a study on the effects of the grid impedance value and of the inverter DC voltage ripple) and the phase monitoring (different from the classical phase jump method). A harmonic synchronization PLL is used to monitor the 3 rd , 5 th and 7 th harmonics. All the proposed algorithms are validated by simulations and experimental results obtained in accordance with the IEEE Std. 929-2000 procedure