Vector based hysteresis control for self-excited induction generators

The paper presents a novel control approach for induction generators (IG), that can equally be applied in systems with speeds ranging from normal to ultrahigh levels. As an example of application, an energy system is shown developed for utilising waste and renewable energy sources, using ultrahigh speed turbine-generator set for electromechanical energy conversion. The proposed solution combines space vector control (SVC) with hysteresis control (HC) for self-excited induction generators (SEIG). Application of IGs instead of synchronous generators (SG) have significant advantages, such as lower cost, brushless construction (in squirrel cage construction), ruggedness, and that they are practically maintenance free. In high speed and ultrahigh speed applications SEIG systems due to their advantageous properties nowadays get greater attention. The solution presented makes it possible to operate the IG in a wide speed and load range cost effectively, compared to the alternative solution, where a PWM AC/DC converter is used to ensure the magnetizing current for the induction machine. The design and modelling of the system are based on theoretical analyses and computer simulation techniques. The proposed control scheme has shown symmetrical three phase currents and voltages and excellent voltage and current regulation with significantly reduced current ripples and voltage distortions.