Air‐gap flux‐oriented vector control of dual stator induction generator used in wind energy conversion system with novel 13‐zone time optimized space vector‐based hybrid bus clamping PWM

Abstract

This work presents a novel speed sensor less air-gap flux-oriented vector control of dual stator induction generator (DSIG) used for grid connected, variable speed wind energy generation system. The DSIG consists of two stator windings electrically separated by an angle of 30 with dissimilar pole numbers, which are in the ratio of 1:3. This arrangement offers reduced magnetic core saturation and less harmonics in stator currents, which results into reduced stator winding losses. Moreover, presence of two stator windings makes DSIG suitable to be used in high power application. In conventional rotor-fluxoriented control, the rotor flux is oriented along the d-axis of the rotor winding. But the rotor flux is not easily accessible. Air-gap flux-oriented vector control (AGFOVC) is advantageous as compared to conventional vector control because the air-gap flux is easily accessible and does not require any special arrangement for the measurement of variables. Moreover incorporation of this novel speed sensor less air-gap flux-oriented vector control also eliminates the use of speed encoder as the rotor speed is estimated from the machine terminal variables.Elimination of speed encoder not only reduces the cost of the overall system but also nullifies the error due to mismeasurement of speed and enhances control flexibility and robustness. As a result of which robustness of the system increases. Here, two separate converters are used for the two stator windings of the machine. And the converter switching's are being performed by space vector-based novel dwell time optimized 13-zone hybrid PWM. This special List of Symbols and Abbreviations: L m , mutual inductance between any stator winding to rotor; L 1 , per phase value of leakage inductances for stator I; L 2 , per phase value of leakage inductances for stator II; ψ, flux; ψ stator , stator flux ripple vector; ψ dr , dψaxis rotor flux; ψ qr , q-axis rotor flux; ψ dm , d-axis air gap flux linkage; ψ qm , q-axis air gap flux linkage; i dr , d-axis rotor current; i qr , q-axis rotor current; V dr , rotor voltage along d-axis; V qr , rotor voltage along q-axis; ω sl , slip speed; ω r , rotor speed; ω e , synchronous speed; T e , electromagnetic torque; V REF , reference voltage vector; V ERR , error voltage vector; α, angle between reference voltage vector and stator I voltage vector; X d , stator flux ripple component along the d-axis