New control technique for performance improvement of static Kramer induction generator

Abstract

Purpose This paper presents the mathematical models of Static Kramer Induction Generator (SKIG) that greatly improves its performance to be competitor for wind energy and hydraulic power generation. Design/methodology/approach Two models of control strategies are proposed, the first is to control the imposed rotor voltage, thus an angular relationship between stator voltage and rotor voltage vectors over the operating speed range is established. which may be achieved by regulating the slip of the machine through the Grid Side Converter (GSC) to fix the operating technique. The second one is to control the rotor current via GSC. GSC is a PWM Voltage Source Converter Findings A comparison between the two techniques is given and very good matching is obtained. Both control strategies can be achieved in terms of the GSC firing angle as shown. In addition to the greatly improved power factor. The paper illustrates the availability of extending the operating speed range up to twice of the synchronous speed, however, the speed range must be limited by the GSC ratings to achieve the slip recovery advantage of lowering the interfacing grid converter rating in analogy the system may be applied for electric drives as well. Originality/value The operational advantages of the proposed system can be summarized as follows: 1- The system is capable of increasing the operating speed range up to twice of synchronous speed. For slip energy recovery system the required super synchronous speed range is given by 1/3 synchronous speed. 2- The system provides significant improved power factor controllability over the operating speed range. 3- The system provides controllability for either excitation rotor voltage or rotor current through the firing angle control of the grid side converter. 4- Near constant stator and rotor currents overall the speed range. 5- Near constant magnetization current. 6- Higher efficiency and reliability.