Inductance-Independent Nonlinearity Compensation for Single-Phase Grid-Tied Inverter Operating in Both Continuous and Discontinuous Current Mode

This paper proposes a control for a single-phase grid-tied inverter operating in both continuous current mode (CCM) and discontinuous current mode (DCM) to minimize inductors without worsening a current total harmonic distortion (THD). In a conventional CCM/DCM control, an inductance is required in a DCM nonlinearity compensation; consequently, the control becomes inductance-dependent. In the proposed control, a duty ratio at a previous calculation period is utilized to compensate for the DCM nonlinearity and detect current modes independently from the inductance. A 4-kW 100-kHz prototype of the inverter with two designs of the inductor is realized to confirm the effectiveness of the proposed control. When the inductor impedance, which is normalized by an inverter impedance, is reduced from 1.8% to 0.5%, volume and material cost of the inductor are reduced by 51% and 62%, respectively, whereas the loss at a light load of 0.1 p.u. is reduced by 35%. However, due to this inductor minimization, the current THD at a rated load increases from 2.3% to 8.7% with the conventional control, violating the grid current harmonic constraint regulated by standard IEEE-1547. The proposed CCM/DCM control reduces the current THD from 8.7% to 2.1%, enabling the inductor minimization and satisfies the grid standard.