Nonlinearity Compensation for Single-Phase Grid-Tied Inverters in Continuous and Discontinuous Current Mode without Inductance

PROJECT TITLE :

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

ABSTRACT:

One-phase grid-tied inverters are addressed in this study, which presents a control strategy for reducing inductors without aggravating total harmonic distortion in the continuous current mode (CCM) and discontinuous current mode (DCM) (THD). Control becomes inductance-dependent in a standard CCM/DCM control because of the requirement for an inductor for DCM nonlinearity compensation. To compensate for the DCM nonlinearity and detect current modes independently of inductance, the suggested control uses a duty ratio from a previous calculation period. To verify the efficacy of the suggested control, a 4-kW, 100-kHz inverter prototype with two inductor designs is built. The volume and material cost of the inductor are decreased by 51% and 62%, respectively, while the loss at a light load of 0.1 p.u. is lowered by 35% when the inductor impedance is reduced from 1.8 percent to 0.5 percent. Even if a smaller inductor is used, the current THD at rated load increases from 2.3% to 8.7% with conventional regulation, contravening the IEEE-1547 standard for grid current harmonics. For inductor minimization, the suggested CCM/DCM control decreases the current THD from 8.7 percent to 2.1 percent.

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