Simulation and result of AFD

According to the previous description of AFD theoretical a 1 kW single-phase PV power generation system is established in Matlab/Simulink. This control was designed to monitor the\(\text{\ \ F}_{\text{PCC}}\text{\ and\ }V_{\text{PCC}}\). The AFD controller will produce a signal to the inverter to stop supplying to the local load if voltage and frequency are out of the limits determined by IEEE 1547 [18]. The simulation module includes the inverter circuit connected to a utility grid control and AFD islanding Detection section at the . The function of AFD controller module was achieved by using the s-function in Matlab/Simulink. The \(V_{\text{PCC}}\ \)and\(I_{Pv-inv}\) are in phase at the initial setting. The grid supply was set to be disconnected at t=0.1 s.
So the sequence of the AFD detection algorithm Firstly, the frequency data was taken and tested against the UFP/OFP threshold, if it is not in the threshold, the islanding occurred, else it is not islanding. If there is no islanding, a source with frequency modified by the\(C_{f}\ \)is then injected into the inverter output current every half cycle and every full cycle to produce a \(t_{z}\ \)on the output current waveform. The value of the \(C_{\text{f\ }}\)will slightly increase every half cycle to drift the current frequency from voltage frequency until islanding is detected and a signal will be sent to stop the inverter from operating.
Figures 11-13 are the cases result for AFD controller which these cases were difficult to be detected by the passive IDM.
The results show that the AFD is capable of detecting islanding effectively with very small NDZ and a detection time within 0.06 s. The disturbance injection plays a significant role in performing islanding detection to meet the PV grid interconnection standard. The simulation results show the more disturbances injected the faster the islanding detection time but the higher the harmonic distortion.