Power system load flow and optimal power flow (OPF) techniques have been considered as an important part of modern power system analytical techniques. This special issue is focused on the recent developments of load flow and optimal power flow techniques such as new methods, new applications and modelling of new power system components. Power system load flow and optimal power flow (OPF) techniques have been considered as an important part of modern power system analytical techniques. This special issue is focused on the recent developments of load flow and optimal power flow techniques such as new methods, new applications and modeling of new power system components.