Voltage sensorless predictive direct power control for renewable energy integration under grid fault conditions

With the increasing penetration of distributed generation (DG) systems based on renewable energies into the power grid, the fault ride-through capability of them is stressed by recent grid codes. Aiming to adapting this requirement, this paper proposes a voltage sensorless predictive direct power control (PDPC) for the grid-interactive DC/AC converter utilized in DG systems. In order to realize a voltage sensorless operation independent of the grid frequency deviation, a second order generalized integrator (SOGI)-based virtual flux (VF) observer is adopted. Moreover, through specific fluctuating power compensations calculated base on the estimated VF, the proposed control strategy offers positive sequence current, constant active and reactive power behaviors, respectively. Simulation studies were conducted in MATLAB/Simulink under gird fault conditions, including the grid frequency deviation, distorted grid voltage by negative sequence voltage and higher harmonics. The simulation results verify that the proposed voltage sensorless PDPC presents superior steady-state and transient performance against the foregoing grid faults.