A Comparative Study of Phase Locked Loops for Microgrid and Storage Converter Applications

The Phase Locked Loop (PLL) is a key subsystem for any inverter used in microgrid or energy storage applications. The PLL is used to recover the relative power system angle and frequency at the point of connection. The electrical angle defines the sine and cosine reference waveform sets used to control real and reactive power injection. The PLL must operate in non-ideal power system conditions and be immune to fluctuation in frequency, voltage unbalance, temporary loss of voltage, harmonic distortion and measurement noise. This paper presents a comparative study for PLLs based on instantaneous power (IP-PLL), Double Synchronous Reference Frame (DSRF-PLL) and Second Order Generalised Integrator (SOGI-PLL) under above non-ideal situations. These high performance PLLs are quantitatively compared for immunity to power systems disturbances.