To prevent the occurrence of interference with a single operation detection through the means of an active system in performing parallel operation by connecting a plurality of power conditioners.

With a preset power conditioner 41 of a plurality of power conditioners 41 to 43 as a parent device, a synchronizing signal is outputted to power conditioners 42, 43 through a synchronizing signal line 14. The respective power conditioners 41 to 43 micro-changes an output, in synchronization with the synchronizing signal to detect single operation by means of an active system.