Coupled-mode theory (CMT) is widely used in the analysis of optical systems, such as arrays of parallel waveguides, coupled resonator optical waveguides (CROWs) and phaselocked arrays of VCSELs. In this work we combined vectorial CMT equations for finite arrays with the concept of Bloch waves. Thus, we extended CMT analysis to the case of infinite perfect photonic structures: arrays of identical waveguides and photonic crystal superlattices. Next, we combined extended CMT with so-called Supercell method for the analysis of infinite photonic crystals with point and linear defects. It has been found that this approach can provide very fast and accurate evaluation of finite, but large, 2D photonic crystals, both perfect and with introduced irregularities.