The generated power's frequency, rotating sequence, and phase angle must be conditioned corresponding to both of power grid specifications, and energy system needs. This paper proposes a novel DSP-based simple and efficient synchronizer for three-phase grid-connected renewable energy systems. "Efficient" refers to its low-cost, fast response, and immunity to distorted voltage of the power grid. The proposed synchronizer contains two parts: 1. Peripheral hardware part, which employs a conventional simple photocoupler-based zero-crossing detector. 2. Embedded software part, which processes the only single signal-generated by the zero-crossing detector-to safely extract power grid information, and to efficiently synchronize the turning on/off of the power switches. A simulation model is developed in MATLAB Simulink and is implemented using a fixed-point digital signal processor (DSP) TMS320F2812. Moreover, a breadboard circuit is built-up for experimental investigations in a three-phase grid-connected PV system. Both of simulation and experimental results show that proposed synchronizer attains a good performance.