A comparison of different methods used to detect the fundamental positive sequence component of grid voltage, is analyzed in this work. These detection methods are necessary to achieve proper synchronization between generation systems, based on renewable energy, and the grid where this systems are connected. Two different structures commonly used as positive sequence detectors based on PLL are analyzed: SOGI and q-PLL. The performance of the detectors is tested in simulation, in continuous and discrete time. A experimental implementation of the detectors in a floating point DSP is realized. Different discretization methods of integrators is analyzed. Experimental results validate detection methods presented.