Parallel VSIs wireless control by emulation of output current state using optimal linear controller

The paper presents an optimal approach to design a linear controller for parallel connection of Voltage Source Inverters (VSI) without data exchange between VSI units for applications in renewable energy systems. An Enhanced Phase Lock Loop (EPLL) provides accurate output voltage derivative in order to emulate each output current state for wireless control of parallel VSIs. Additionally, the EPLL locks the reference voltage phase in each VSI unit with grid or common load voltage for interfacing renewable energy or distributed energy storage systems. The LQR method is used to address the sinusoidal output voltage tracking; this optimal control method is extended from its original application of regulation problems. The controller is designed for two VSI units and consequently simulation and experimental results are provided to validate performance of the proposed control strategy.