the design of a new double loop controller for simultaneous adjustment of input and output voltages of single-phase grid-connected inverter

although lcl filters are used widely in the grid connected inverters to reduce high-orderharmonics, such a system increases system order and therefore sustainable design of closed-loopcontroller system will be complicated. recently, the single-loop control strategy has beensuggested for l or lc filter based grid-connected inverters. however, the use of single-loopcontrol directly in lcl filter-based inverters may cause instability. in this paper, a new doubleloopcontrol strategy is presented which includes a voltage external loop and an internal loop offilter capacitor current. the external loop controls the input voltage of the grid-connectedinverter. the internal loop improves system stability margin and removes the resonance of lclfilter. to obtain the transfer function of system, single-phase instantaneous power theory is used.the computer simulation has proved the feasibility of the proposed control