A method to synchronize single-phase floating with grid without high voltage measurement or high bandwidth communication

Most of FACTS devices and grid connected converters need the information about the frequency and phase of the grid for synchronization and control. In some cases, the value to be measured that is used as synchronization signal is at remote bus or at a different voltage potential, which would require expensive high voltage measurements or high bandwidth communication. A new synchronization method for single-phase floating convertert is presented, which neither requires high voltage measurements nor high bandwidth communication. The method is applied to a new FACTS device - Distributed Power Flow Controller (DPFC) which is derived from the UPFC. Within the DPFC, multiple single-phase converters are distributed along the transmission line instead of one big 3-phase converter. The principle of this method is to use the line current as the rotation reference frame which enables the series converter to read the phase and frequency information locally. In this case, only the signals in dc quantity are communicated, and the system stability during communication failure is greatly improved.