Analysis and hardware implementation of virtual resistance based PV inverters for harmonics suppression

Traditional PV inverter is designed for power generation and reducing harmonic distortion without capability of actively participating in harmonic elimination of power grid. This study proposes a virtual resistance based PV inverter to suppress the voltage harmonics at point of common coupling (PCC), in which PV inverters could simultaneously deliver power for fundamental and behave as a series of virtual resistances to absorb power harmonics and then convert them into fundamental power; as a result, voltage distortion of each node of power grid is significantly reduced. No additional sensors are required to measure the non-linear load current, such that a more flexible installation location of PV inverter can be achieved. Furthermore, current harmonics are controlled by PI controller to track the voltage harmonics multiplied by harmonic conductance, i.e. K h, such that the PV inverter can be equivalent to a virtual resistance. In particular, the absorbed power harmonics are used to evaluate the harmonic suppression, while harmonic conductance K h is regulated automatically to maximise the absorbed power harmonics. Both the simulation and experiment results demonstrate that the effectiveness of the propose method.