A new control strategy with saturation effect compensation for an autonomous induction generator driven by wide speed range turbines

This paper presents a variable speed autonomous squirrel cage generator excited by a current-controlled voltage source inverter to be used in stand-alone micro-hydro power plants. The paper proposes a system control strategy aiming to properly excite the machine as well as to achieve the load voltage control. A feed-forward control sets the appropriate generator flux by taking into account the actual speed and the desired load voltage. A load voltage control loop is used to adjust the generated active power in order to sustain the load voltage at a reference value. The control system is based on a rotor flux oriented vector control technique which takes into account the machine saturation effect. The proposed control strategy and the adopted system models were validated both by numerical simulation and by experimental results obtained from a laboratory prototype. Results covering the prototype start-up, as well as its steady-state and dynamical behavior are presented.

Research highlights
► A novel control strategy for autonomous induction generators with variable rotor speed.
► Generator excitation achieved using a current controlled voltage source inverter.
► Machine optimized use with stability and saturation effect compensation.
► Both saturation and cross-saturation effects discussed upon generator modeling.
► Efficient excitation and continuous load voltage control in a wide rotor speed range.