Simplified Synchronous Reference Frame Control of the three phase grid connected inverter

This paper presents the optimized control of a three-phase grid connected inverter, considering as basis of analysis the observation of the dynamics of the system with two inputs and two outputs (TITO SYSTEM). This model allows the design of the inverter control in a direct way, by means of two PI controllers to control the instantaneous active and reactive power. By means of the control of the instantaneous active power p, the inverter duty cycle, dd, is controlled in a direct way. By means of the control of the instantaneous reactive power q, the inverter duty cycle, dq, is controlled in a direct way. Thus, the implementation of the power control becomes easier, with DC signals, obtained with PI controllers and with a very simple algorithm regarding calculations. Also, a phase locked PLL is used for achieve the synchronization of the system with the grid frequency. The proposed control is compared with the conventional Synchronous Reference Frame Control (SRFC), showing the advantages of this new simplified control.