An Inner-Loop Control Method for the Filter-less, Voltage Sensor-less, and PLL-less Grid-Following Inverter-Based Resource

This paper presents an inner-loop control method for the filter-less, voltage sensor-less, and PLL-less inverter-based resource (IBR) under grid-following operation mode. The innovative concepts of the proposed control structure incorporate the removal of the voltage sensors at the point of common coupling (PCC), the removal of the inverter output filter or interface inductance, and the removal of the traditional phase-locked loop (PLL) circuits. Furthermore, the virtual impedance control is applied to compensate for the inverter voltage reference change due to the removal of the interface inductance. With the proposed control method, the physical interface inductor and the bulky high-voltage sensors can be offloaded, but the inverter can still synchronize with the grid and respond to the control command with fast speed and small steady state error.