Application of the extension pq theory to a mains-coupled photovoltaic system

A mains-coupled photovoltaic system is economical because of having no storage battery. In the coupled photovoltaic system, the currents flowing from or into the power system must have no distortion. This system,must have the function supplying the appropriate reactive power at the coupling point. In other words, a coupled photovoltaic system must have the function of an active power filter. Even if the three phase voltage is unsymmetrical, these two functions must be given to the coupled photovoltaic system. In that case, the extension pq theory which the authors had previously published for the active power filter control may be used. In this paper, the authors develop the effectiveness of applying the extension pq theory to the coupled photovoltaic system.