Autonomous adaptive sensorless controller of inverter-based islanded-distributed generation system

A control method for inverter operation in an islanded-distributed generation system is presented. The controller provides sufficient active and reactive power to match the connected load, therein providing high power quality. Control in this mode is based on voltage and frequency droops. Detailed analysis, based on the concept of harmonic impedance, establishes the appropriateness of inductor current feedback against capacitor current feedback, with respect to inverter output power quality. Steepest descent adaptive control is embedded to estimate the output voltage for sensorless operation, which enhances system robustness and performance. To compensate the DSP calculation delay, a modified Kalman filter design is discussed. Simulation and experimental results demonstrate the validity of the proposed control method.