A Novel Speed Adaptive Stator Current Compensator for Voltage and Frequency Control of Standalone SEIG Feeding Three-Phase Four-Wire System

This paper presents the operating principle and performance of a generalized impedance controller (GIC)-based novel speed adaptive stator current compensator for voltage and frequency regulation of self-excited induction generator (SEIG) in standalone system feeding three-phase four-wire (3P4W) loads. The GIC has three one-phase full-bridge voltage source converters in 3P4W configuration with a battery bank at common dc bus. Before installing the SEIG on site, its rotor speed versus stator current characteristics is established by driving SEIG over a range of supersynchronous speeds, while the stator is connected to the ac source of rated voltage and frequency. The key aspect of this method is restoration of SEIG stator current in each phase to the pre-established speed-dependent stator current reference under unbalanced load and source perturbations. This is attained by identifying the modulation index and angle of individual GIC phase voltages using time integrals of active-reactive current amplitude errors of the respective stator phase. When these integrals attain steady value, the SEIG phase currents and voltages get restored, while the GIC operating in grid-forming mode locks the system frequency at a desired value. Integrated system model is simulated in MATLAB/Simulink to study the effects of perturbations on regulating the SEIG stator phase currents, voltages, and frequency. Efficacy of the scheme is validated experimentally by DSP-based implementation of the control algorithm.