Robust controller design and analysis for distributed three-phase inverter voltage tracking

For distributed inverter voltage tracking, phase-locked loop are conventionally utilized to achieve synchronization. Its implementation requires a separate Phase-Locked Loop (PLL) with the necessary hardware, and there is still a constant offset in the reference tracking. In previous work, authors proposed a controller “matrix” based on Internal Model Principle to achieve synchronization control for three-phase inverters with balanced loads; and the proposed system does not need PLL, including its corresponding hardware. This paper presents the design and performance analysis of the proposed controller for voltage tracking, considering different plant models with unbalanced loads. Furthermore, robust stability analysis is performed to define robustness boundary, and robust performance analysis is conducted to specify performance limit of the controller with respect to unstructured uncertainty in the plant. The simulation results confirm the effectiveness of the proposed methodology in assuring robust, offset-free, voltage vector tracking for distributed three-phase inverters.