Abstract
Summary
To carry out the study and simulations of anti‐islanding systems, it is necessary to take into account the generic system proposed by the IEEE 929‐2000 and IEEE 1547 standards, where the network, the RLC load, and PV inverter are connected in parallel to the PCC. The IEEE 929‐2000 standard defines the quality factor to have a standard test condition. The paper presents a modified Active Frequency Drift (AFD) algorithm to detect the islanding of grid‐connected photovoltaic (PV) systems with low harmonics levels without degrading their power factor. Severe issues such as deterioration in power quality and electric shock can occur when a PV inverter operates in islanding mode. Various islanding detection techniques have been investigated in the literature in the last two decades among which, AFD is a typical method. However, a prominent drawback of AFD is its relatively large Non‐Detection Zone (NDZ). The improved AFD method that this paper suggests allows the frequency of the inverter current to be controlled slightly lower (or higher) than the frequency of the terminal voltage. The islanding condition is detected by calculating the changing parameter that relates to the change of the chopping fraction and the line frequency periodically. The frequency deviation is then detected to determine the chopping and a changing parameter, which accumulates to the threshold value when the inverter is shut down. The proposed algorithm overcomes the conventional AFD issues by improving the accuracy of detection, eliminating the NDZ, and reducing the current harmonic distortion. The proposed method is validated with the help of simulated and experimental results of a 350 W PV inverter using IEEE Standards.
The “islanding” effect is an electrical phenomenon that occurs when a distributed generation source continues to energize a part of the electrical grid after a portion of the grid has been interrupted or disconnected. In this way, the electrical grid stops to control that isolated part of the distribution system, which contains both load and generation, so that the safety, restoration of service, and equipment reliability can be compromised. This paper proposes an effective method using improved AFD technique for detecting islanding as well as to maintain the power quality of grid connected PV systems.