Controller Design in <i>αβ</i> domain for Grid-Forming Inverters by Complex Vector Theory

Grid-forming inverter control plays an important role in ensuring frequency and voltage stability in a microgrid (MG). This paper proposes a novel power and voltage control in the αβ domain. The proposed method includes two control loops; an outer loop for power droop control and an inner loop for output voltage control. With the proposed controller, active and reactive powers can be controlled according to simple complex power control principles described only in the αβ-domain. Controller gain tuning for both the outer droop and the inner voltage regulator is also proposed; the droop control gains are tuned based on transfer functions around an operating point and the voltage regulator is tuned by a linear quadratic regulator (LQR). The proposed control method is investigated and validated by simulations with a C control program and by experiments with a DSP-based digital control system.