Optimal system control of a back-to-back power converter for wind grid-connected converter

The most common topology for micro wind turbine systems is composed of the wind turbine directly connected to a Permanent Magnet Synchronous Generator (PMSG) followed by a AC/DC/AC converter. The converter is realized with a AC/DC passive rectifier, a DC/DC boost converter and a DC/AC full-bridge inverter which injects the electric power into the grid. Considering the cost reduction of power switches and Digital Signal Processors (DSP), back-to-back inverter topologies have to be considered for new projects, since they allow to obtain better energy productivity of the wind systems. In this paper a complete solution based on back-to-back topology is presented. This solution includes the sensorless vector control for the PMSG, the Maximum Power Point Tracker (MPPT) algorithm, the d-q vector control of the single-phase grid connected inverter and the power flow control strategies from the PMSG to the grid. It is worth noticing that the two full-bridge power converters are controlled by two different DSP which can exchange information only through the value of the DC Link voltage. Experimental results confirm the effectiveness of the adopted solutions.