The Design of a New Double Loop Controller For Simultaneous Adjustment of Input and Output Voltages of Single-Phase Grid-Connected Inverter

Abstract

Although LCL filters are used widely in the grid connected inverters to reduce high-order<br />harmonics, such a system increases system order and therefore sustainable design of closed-loop<br />controller system will be complicated. Recently, the single-loop control strategy has been<br />suggested for L or LC filter based grid-connected inverters. However, the use of single-loop<br />control directly in LCL filter-based inverters may cause instability. In this paper, a new doubleloop<br />control strategy is presented which includes a voltage external loop and an internal loop of<br />filter capacitor current. The external loop controls the input voltage of the grid-connected<br />inverter. The internal loop improves system stability margin and removes the resonance of LCL<br />filter. To obtain the transfer function of system, single-phase instantaneous power theory is used.<br />The computer simulation has proved the feasibility of the proposed control