Simplified Analysis Technique for Double Layer Non-overlap Multiphase Slip Permanent Magnet Couplings in Wind Energy Applications

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1 Simplified Analysis Technique for Double Layer Non-overlap Multiphase Slip Permanent Magnet Couplings in Wind Energy Applications Petrus JJ van Wyk - Prof. Maarten J. Kamper Renewable Energy Postgraduate Symposium July 13, 2015 Petrus JJ van Wyk EMLAB - Stellenbosch University 1/22

2 Presentation Outline 1 Introduction 2 Slip Coupler Concept 3 Proposed Analysis Technique 4 Modelling 5 Results 6 Conclusion Petrus JJ van Wyk EMLAB - Stellenbosch University 2/22

3 Introduction Electromagnetic couplings are well known in industry Permanent magnet couplings Eddy current couplings Recently a new concept wind generator was introduced 1 Slip PM coupling Sharing common PM rotor with a Synchronous Generator Called Slip Synchronous PMG Slip-PMC filters transient torque Double layer, non-overlap winding slip-pmc introduced in Potgieter (2014) 2 Calculations made for these machines - accurate, but not necessarily applicable to all machines 1 J.H.J. Potgieter and M.J. Kamper (2012), Design of New Concept Direct Grid-Connected Slip-Synchronous Permanent-Magnet Wind Generator, IEEE Transactions on Industry Applications 48(3), J.H.J. Potgieter and M.J. Kamper (2014), Optimum Design and Comparison of Slip Permanent-Magnet Couplings With Wind Energy as Case Study Application, IEEE Transactions on Industry Applications 50(5), Petrus JJ van Wyk EMLAB - Stellenbosch University 3/22

4 Introduction SS-PMG PMSG Grid Gearbox Slip PMC PMSG Grid Petrus JJ van Wyk EMLAB - Stellenbosch University 4/22

5 Slip Coupler Concept The machine analysed in this paper is a Double layer, Short Circuited, Non-overlap winding, Permanent magnet motor Operating under slip conditions as a coupling. This machine is thus referred to as a slip coupler. Petrus JJ van Wyk EMLAB - Stellenbosch University 5/22

6 Slip Coupler Concept Slip coupler specifications: 28 poles 30 slots Solid aluminium windings Output speed of 600 r/min Rated slip of 3% Torque at rated slip - 35 Nm Petrus JJ van Wyk EMLAB - Stellenbosch University 6/22

7 Proposed Analysis Technique The slip coupler concept presents several unique analysis problems: It is a 30 phase machine Different cross sectional areas between upper and lower layer coils Different resistance values Thus different current values Cannot be analysed using standard three-phase analysis methods How can such a machine be analysed? Petrus JJ van Wyk EMLAB - Stellenbosch University 7/22

8 Proposed Analysis Technique Flux Linkage (mwb turn) Rotor Angle (degrees, electrical) Petrus JJ van Wyk EMLAB - Stellenbosch University 8/22

9 Proposed Analysis Technique Phases are divided into sets of three: Each phase is chosen 120 electrical degrees apart 28 pole machine, also 120 mechanical degrees apart 30 phase machine means 10 sets Phases in set must be from same winding layer A1 B1 C1 a 1 a1 b 1 b1 c 1 c a2 a 2 b2 b 2 c2 c 2 A2 Slot 1 Slot 2 Slot 3 B2 Slot 10 Slot 11 Slot 12 Slot 13 C2 Slot 20 Slot 21 Slot 22 Slot 23 Petrus JJ van Wyk EMLAB - Stellenbosch University 9/22

10 Proposed Analysis Technique Flux Linkage (mwb turn) Rotor Angle (degrees, electrical) Petrus JJ van Wyk EMLAB - Stellenbosch University 10/22

11 Proposed Analysis Technique Flux Linkage (mwb turn) Rotor Angle (degrees, electrical) Petrus JJ van Wyk EMLAB - Stellenbosch University 11/22

12 Proposed Analysis Technique Each set contains balanced three-phase quantities Sets can be analysed separately ( 10 separate machines ) Calculated torques are added to get total torque Allows use of all existing three-phase theory Flux Linkage (mwb) Rotor Angle (degrees, electrical) Petrus JJ van Wyk EMLAB - Stellenbosch University 12/22

13 Modelling I di R i Iqi R i I qi q ω sle λ qi + ω sle λ di + I di φ 2IRMSi d dq Voltage equations are written as: 0 = R i I di ω sle λ qi (1) 0 = R i I qi + ω sle λ di (2) with i as the set number. Petrus JJ van Wyk EMLAB - Stellenbosch University 13/22

14 Results After machine optimisation is done, method is assessed: Method uses four time-stepped static FE solutions Machine is also simulated using a transient FE solution Transient is considered as most accurate method available Results between static and transient are compared Unfortunately, prototype still under construction, thus no experimental results Petrus JJ van Wyk EMLAB - Stellenbosch University 14/22

15 Results - Flux Linkage Per Phase Flux Linkage (mwb) Rotor Angle (degrees, electrical) λ upper coil static λ upper coil transient λ lower coil static λ lower coil transient Petrus JJ van Wyk EMLAB - Stellenbosch University 15/22

16 Results - Current 400 Per Phase Current (A) Rotor Angle (degrees, electrical) I upper coil static I upper coil transient I lower coil static I lower coil transient Petrus JJ van Wyk EMLAB - Stellenbosch University 16/22

17 Results - Torque 36.5 Torque (Nm) Rotor Angle (degrees, electrical) T static T transient Petrus JJ van Wyk EMLAB - Stellenbosch University 17/22

18 Results - Slip vs Torque 150 Torque (Nm) Slip (%) T static T transient Petrus JJ van Wyk EMLAB - Stellenbosch University 18/22

19 Conclusion It is concluded that Static and transient Currents and flux linkages- Torque, over a large slip rangeare in excellent agreement Proposed method of grouping phases into sets gives accurate results Fast results - only four static FE simulations Can be used for optimisation of similiar machines Much faster than transient solutions Method can be used on any double layer, non-overlap, multiphase PM machine Petrus JJ van Wyk EMLAB - Stellenbosch University 19/22

20 Recent Progress on Prototype Petrus JJ van Wyk EMLAB - Stellenbosch University 20/22

21 Recent Progress on Prototype Petrus JJ van Wyk EMLAB - Stellenbosch University 21/22

22 Thank You Petrus JJ van Wyk EMLAB - Stellenbosch University 22/22