Novel PLL systems which suffer little influence from voltage unbalance and distortion

In this paper, novel methods of making standard sin/cos signals for PWM converters, and novel PLL systems for STATCOM will be proposed. The single-phase utility voltage is transformed to pseudo-three-phase signals, and these three-phase signals are used for the phase detection. Standard sin/cos signals composed by these methods suffer little influence from the voltage unbalance and the distortion of utility voltages. Therefore these methods can be used for the STATCOM to reduce the influence of unbalanced system voltage disturbances such as 2LS.