Three-phase inverter synchronization control utilizing internal model principle

In order to ensure synchronized operation of inverters used in renewable energy systems, the output voltage magnitude, frequency and phase angle must be consistent with that of the power grid when it is in islanding operation. Based on author's previous work on single-phase inverter synchronization control with internal model principle, this paper extends the application of that principle to achieving synchronized operation of three-phase inverters with balanced load, in islanding operation; without the need for conventional Phase-Locked Loop. Linear Quadratic Regulator was utilized to enhance stability; offset voltage canceller was included in the switching system to compensate for switching components' nonlinearities; and digital redesign was performed to reduce computational burden in real-time by prolonging the calculation period. The simulation results obtained validated the effectiveness of the proposed method.