A single-phase DG generation unit with shunt active power filter capability by adaptive neural filtering

This paper deals with a single-phase distributed generation (DG) system With active power filtering (APF) capability, devised for utility current harmonic compensation. The idea is to integrate the DG unit functions with shunt APF capabilities, because the DG is connected in parallel to the grid. With the proposed approach, control of the DG unit is performed by injecting into the grid a current with the same phase and frequency of the grid voltage and with an amplitude depending on the power available from renewable sources. On the other hand, load harmonic current compensation is performed by injecting into the alternating current system harmonic currents like those (if the load but with an opposite phase, thus keeping the line current almost sinusoidal. Both detection of the grid voltage fundamental and computation of the load harmonic compensation current have been performed by two neural adaptive filters with the same structure, one in a configuration "notch" and the other in the complementary configuration "band." The "notch" filter has been used to compute the compensationg current by eliminating only the contribution of the fundamental of the load current, whereas the "band" configuration is able to extract the fundamental of the coupling point voltage. Furthermore, because the active power generation and the APF features require current control of components at different frequencies, respectively, a multiresonant current controller has been adopted. The methodology has been tested successfully both in numerical simulation and experimentally on a suitably devised test setup. The stability analysis of the proposed control approach has been performed in the discrete domain.