Permanent Magnet Wind Generator Technology for Battery Charging Wind Energy Systems Casper J. J. Labuschagne, Maarten J. Kamper Electrical Machines Laboratory Dept of Electrical and Electronic Engineering Stellenbosch University September 2018 (Stellenbosch University) 1 / 39
Outline Outline 1 Introduction 2 Wind Turbine Battery Charging System 3 Steady-State FE Simulation Method 4 Optimisation 5 Simulation Results 6 Optimisation Results 7 Conclusions 8 Extras (Stellenbosch University) 2 / 39
Introduction Introduction (Stellenbosch University) 3 / 39
Introduction Active Battery Charging System Active synchronous rectifier E Z LC I V Load Figure 1: Single line diagram of PM wind generator connected to active battery charging system with actively synchronous rectifier. (Stellenbosch University) 4 / 39
Introduction Passive Battery Charging System Diode rectifier E Z V I Load Figure 2: Single line diagram of PM wind generator connected to passive battery charging system with uncontrolled diode rectifier. (Stellenbosch University) 5 / 39
Introduction PMSG Permanent magnet synchronous generator Direct-drive Low cogging torque Relatively large internal synchronous inductance Figure 3: Cross section of the radial flux outer rotor PMSG configuration with surface mounted PMs (Stellenbosch University) 6 / 39
Introduction Passive Battery Charging System Diode rectifier E Z Z ext V I Load Figure 4: Single line diagram of PM wind generator connected to passive battery charging system with uncontrolled diode rectifier. (Stellenbosch University) 7 / 39
Introduction Passive Battery Charging System E α Diode rectifier I V E Z Z ext V I Load Figure 5: Single line diagram of PM wind generator connected to passive battery charging system with uncontrolled diode rectifier. Static FEA method is proposed to achieve maximum power point matching for a turbine-specific design using an external inductance. (Stellenbosch University) 8 / 39
Introduction Active Battery Charging System Active synchronous rectifier E Z LC I V Load Figure 6: Single line diagram of PM wind generator connected to active battery charging system with actively synchronous rectifier. (Stellenbosch University) 9 / 39
Wind Turbine Battery Charging System Wind Turbine Battery Charging System (Stellenbosch University) 10 / 39
Wind Turbine Battery Charging System Power Matching Power (kw) 7 6 5 4 3 2 1 13 m/ 12 m/s 11 m/s 10 m/s 9 m/s 8 m/s P assive 0 0 100 200 300 400 500 600 Turbine speed (r/min) Figure 7: Wind turbine power versus turbine speed curves with wind speed a parameter, and operating power curves for passive and active systems. (Stellenbosch University) 11 / 39
Wind Turbine Battery Charging System Power Matching Power (kw) 7 6 5 4 3 2 1 P assive Optimum 13 m/ 12 m/s 11 m/s 10 m/s 9 m/s 8 m/s 0 0 100 200 300 400 500 600 Turbine speed (r/min) Figure 7: Wind turbine power versus turbine speed curves with wind speed a parameter, and operating power curves for passive and active systems. (Stellenbosch University) 11 / 39
Wind Turbine Battery Charging System Power Matching 7 6 P assive Optimum 5 13 m/ Power (kw) 4 3 2 1 n c 12 m/s 11 m/s 10 m/s 9 m/s 8 m/s 0 0 100 200 300 400 500 600 Turbine speed (r/min) Figure 7: Wind turbine power versus turbine speed curves with wind speed a parameter, and operating power curves for passive and active systems. (Stellenbosch University) 11 / 39
Wind Turbine Battery Charging System Power Matching 7 6 P assive Optimum Power (kw) 5 4 3 2 1 n c n r 13 m/ 12 m/s 11 m/s 10 m/s 9 m/s 8 m/s 0 0 100 200 300 400 500 600 Turbine speed (r/min) Figure 7: Wind turbine power versus turbine speed curves with wind speed a parameter, and operating power curves for passive and active systems. (Stellenbosch University) 11 / 39
Wind Turbine Battery Charging System System Requirements Table 1: Wind generator operating points for passive battery charging system Wind speed 3 m/s 12 m/s Turbine speed 100 r/min 320 r/min Power 0 kw 4.2 kw n c n r (Stellenbosch University) 12 / 39
Steady-State FE Simulation Method Steady-State FE Simulation Method (Stellenbosch University) 13 / 39
Steady-State FE Simulation Method Steady-State FE Simulation Method State of the PMSG? (α = ) External Inductance L ext? (Stellenbosch University) 14 / 39
Steady-State FE Simulation Method Static FEA Iterations 1 st Iteration d I s V s q (α ) (Stellenbosch University) 15 / 39
Steady-State FE Simulation Method Static FEA Iterations 1 st Iteration 2 nd Iteration d I s d V s V s I s q q (α ) (α ) (Stellenbosch University) 15 / 39
Steady-State FE Simulation Method Static FEA Iterations 1 st Iteration 2 nd Iteration 3 rd Iteration d I s d d V s V s I s V s I s q q q (α ) (α ) (α ) (Stellenbosch University) 15 / 39
Steady-State FE Simulation Method External Inductance Calculation External Inductance L ext L ext = L 1 L ext = L 2 L ext = L 3 (Stellenbosch University) 16 / 39
Steady-State FE Simulation Method External Inductance Calculation f 2 (y) P g(l 1) L 1 y Figure 8: Second degree polynomial obtained from curve fitting of the static FEA solutions, and calculating L ext from the rated power P g. (Stellenbosch University) 17 / 39
Steady-State FE Simulation Method External Inductance Calculation f 2 (y) P g(l 1) P g(l 2) L 1 L 2 y Figure 8: Second degree polynomial obtained from curve fitting of the static FEA solutions, and calculating L ext from the rated power P g. (Stellenbosch University) 17 / 39
Steady-State FE Simulation Method External Inductance Calculation f 2 (y) P g(l 1) P g(l 2) P g(l 3) L 1 L 2 L 3 y Figure 8: Second degree polynomial obtained from curve fitting of the static FEA solutions, and calculating L ext from the rated power P g. (Stellenbosch University) 17 / 39
Steady-State FE Simulation Method External Inductance Calculation f 2 (y) P g(l 1) P g(l 2) P g(l 3) L 1 L 2 L 3 y Figure 8: Second degree polynomial obtained from curve fitting of the static FEA solutions, and calculating L ext from the rated power P g. (Stellenbosch University) 17 / 39
Steady-State FE Simulation Method External Inductance Calculation f 2 (y) P g(l 1) P g(l 2) 4.2 kw P g(l 3) L 1 L 2 L ext L 3 y Figure 8: Second degree polynomial obtained from curve fitting of the static FEA solutions, and calculating L ext from the rated power P g. (Stellenbosch University) 17 / 39
Steady-State FE Simulation Method Static FEA method Design for cut-in point. (1) Solve for L ext = L 1. (3) Solve for L ext = L 2. (3) Solve for L ext = L 3. (3) Determine actual L ext. Solve PMSG. (3) Evaluate final performance. (Stellenbosch University) 18 / 39
Optimisation Optimisation (Stellenbosch University) 19 / 39
Optimisation Figure 9: Cross section of the double layer non-overlap winding PMSG indicating the relevant dimensions for design and optimisation. X = d o h rotor h mag θ mag h slot w tooth h stator l (1) (Stellenbosch University) 20 / 39
Optimisation Non-dominated Sorting Genetic Algorithm II Performance constraints U = P gen η = J 4.2kW 90% 6A/mm 2 Objective function minimise F(X) = M active(x) M P M (X) (Stellenbosch University) 21 / 39
Simulation Results Simulation Results (Stellenbosch University) 22 / 39
Simulation Results Simulation Results Effect of L ext on power point matching Effect of number of poles Effect of generator size Static FEA performance (Stellenbosch University) 23 / 39
Simulation Results Effect of L ext on Power Point Matching Power (kw) 7 6 5 4 3 2 1 L ext = 0 mh (G 1) 13 m/s 12 m/s 11 m/s 10 m/s 9 m/s 8 m/s 0 0 100 200 300 400 500 600 Turbine speed (r/min) Figure 10: Power matching of the 28/30 wind generator (G 1 and G 1) with L ext a parameter. (Stellenbosch University) 24 / 39
Simulation Results Effect of L ext on Power Point Matching Power (kw) 7 6 5 4 3 2 1 L ext = 0 mh (G 1) L ext = 2.84 mh (G 1) 13 m/s 12 m/s 11 m/s 10 m/s 9 m/s 8 m/s 0 0 100 200 300 400 500 600 Turbine speed (r/min) Figure 10: Power matching of the 28/30 wind generator (G 1 and G 1) with L ext a parameter. (Stellenbosch University) 24 / 39
Simulation Results Effect of L ext on Power Point Matching Power (kw) 7 6 5 4 3 2 1 L ext = 3.86 mh (G 1) L ext = 2.84 mh (G 1) L ext = 0 mh (G 1) 13 m/s 12 m/s 11 m/s 10 m/s 9 m/s 8 m/s 0 0 100 200 300 400 500 600 Turbine speed (r/min) Figure 10: Power matching of the 28/30 wind generator (G 1 and G 1) with L ext a parameter. (Stellenbosch University) 24 / 39
Simulation Results Table 2: Static FEA results for 28/30 pole PMSG. G 1 G 2 G 1 P g, kw 4.22 4.25 3.86 f s, Hz 74.67 74.67 116.67 T urns per winding, N s 14 10 14 V rms 23.5 23.6 23.65 J, A/mm 2 4.67 3.29 4.37 α 54.4 54.4 68.8 η, % 90.4 92.4 88.6 X s, p.u. 0.58 0.46 0.83 X ext, p.u. 1.88 1.99 3.59 L ext, mh 2.84 3.06 3.74 X ext/x s 3.26 4.33 4.32 Outer Diameter, mm 384 384 384 Axial Length, mm 70.55 100 70.55 M active 22.08 32.1 22.7 M P M 2.77 3.72 2.63 (Stellenbosch University) 25 / 39
Optimisation Results Optimisation Results (Stellenbosch University) 26 / 39
Optimisation Results 35 30 Active Mass (kg) 25 20 15 10 Passive 5 Active Optimum 0 0 0.5 1 1.5 2 2.5 3 PM Mass (kg) Figure 11: Pareto fronts of PM mass versus active mass of the PMSGs for the passive and acive systems, with the chosen optimal design points indicated. (Stellenbosch University) 27 / 39
Optimisation Results Table 3: Design optimisation results and component ratios Parameters Passive Active Pas:Act Outer diameter, d o (mm) 384 350 1:0.91 Stator height, h rotor (mm) 6.8 4.74 1:0.70 Magnet height, h mag (mm) 6.2 3 1:0.48 Magnet pitch, θ mag (%) 0.7 0.7 1:1 Slot height, h slot (mm) 35.1 31.6 1:0.90 Tooth width, w tooth (mm) 12 8 1:0.67 Rotor height, h stator (mm) 5.8 4.125 1:0.71 Axial length, l (mm) 70.55 50 1:0.71 Active iron mass (kg) 14.24 6.41 1:0.45 Copper mass (kg) 5.07 3.76 1:0.74 PM mass (kg) 2.77 0.88 1:0.32 Total active mass (kg) 22.08 11.05 1:0.50 External reactance, X ext (p.u.) 1.88 - Current density, (A/mm 2 ) 4.67 6.0 Current angle, α (degrees) 54.4 0 Rated power, P g (kw) 4.22 4.26 Efficiency, η (%) 90.4 90 (Stellenbosch University) 28 / 39
Optimisation Results Figure 12: To scale representation of the optimised PMSGs in Table 3 for (a) passive and (b) active systems. (Stellenbosch University) 29 / 39
Conclusions Conclusions (Stellenbosch University) 30 / 39
Conclusions Conclusions Static FE Simulation Method Passive charging systems have poor power matching with no external inductance. The proposed method is accurate and not computationally expensive. For maximum power point matching using non-overlap winding machines, X ext /X s is about a factor 4. Higher frequency generators require a much reduced external inductance, although slightly less efficiency. The proposed calculation method can be used excellently to do a wind site specific design optimization of the system, maximizing annual wind energy harvesting and minimizing generator and external inductance sizes. (Stellenbosch University) 31 / 39
Conclusions Conclusions Optimal Design The passive system s generator active mass is almost twice that of the active system s generator active mass. The active system generator also outperforms the passive system generator in terms of PM mass, where it is found that the active system generator s PM mass is three times less. The passive system PMSG is more expensive to manufacture and the wind tower structure will most likely also be more expensive. Also requires large L ext. The active system requires an LC filter and an expensive rectifier with complex position-sensorless control. (Stellenbosch University) 32 / 39
Thank you Thank you. Contact: Casper Labuschagne E-mail: 17539455@sun.ac.za (Stellenbosch University) 33 / 39
Extras Effect of Number of Poles (a) Figure 13: Different pole-slot configurations for PMSG where (a) 28/30 pole-slot combination and (b) 56/60 pole-slot combination. (b) (Stellenbosch University) 34 / 39
Extras Table 4: Static FEA results for 28/30 pole PMSG and 56/60 pole PMSGs. G 1 G 2 G 1 G 3 G 4 P g, kw 4.22 4.25 3.86 4.20 4.25 f s, Hz 74.67 74.67 116.67 149.33 149.33 T urns per winding, N s 14 10 14 7 5 V rms 23.5 23.6 23.65 24.0 24.0 J, A/mm 2 4.67 3.29 4.37 4.58 3.15 α 54.4 54.4 68.8 54.6 54.7 η, % 90.4 92.4 88.6 89.62 90.46 X s, p.u. 0.58 0.46 0.83 0.571 0.449 X ext, p.u. 1.88 1.99 3.59 1.87 1.96 L ext, mh 2.84 3.06 3.74 1.47 1.61 X ext/x s 3.26 4.33 4.32 3.27 4.37 Outer Diameter, mm 384 384 384 384 384 Axial Length, mm 70.55 100 70.55 70.55 100 M active 22.08 32.1 22.7 22.08 32.1 M P M 2.77 3.72 2.63 2.77 3.72 (Stellenbosch University) 35 / 39
Extras Table 4: Static FEA results for 28/30 pole PMSG and 56/60 pole PMSGs. G 1 G 2 G 1 G 3 G 4 P g, kw 4.22 4.25 3.86 4.20 4.25 f s, Hz 74.67 74.67 116.67 149.33 149.33 T urns per winding, N s 14 10 14 7 5 V rms 23.5 23.6 23.65 24.0 24.0 J, A/mm 2 4.67 3.29 4.37 4.58 3.15 α 54.4 54.4 68.8 54.6 54.7 η, % 90.4 92.4 88.6 89.62 90.46 X s, p.u. 0.58 0.46 0.83 0.571 0.449 X ext, p.u. 1.88 1.99 3.59 1.87 1.96 L ext, mh 2.84 3.06 3.74 1.47 1.61 X ext/x s 3.26 4.33 4.32 3.27 4.37 Outer Diameter, mm 384 384 384 384 384 Axial Length, mm 70.55 100 70.55 70.55 100 M active 22.08 32.1 22.7 22.08 32.1 M P M 2.77 3.72 2.63 2.77 3.72 (Stellenbosch University) 35 / 39
Extras Effect of Generator Size Geometric dimensions held constant. Axial Length (Stellenbosch University) 36 / 39
Extras Table 5: Static FEA results for 28/30 pole PMSG and 56/60 pole PMSGs. G 1 G 2 G 1 G 3 G 4 P g, kw 4.22 4.25 3.86 4.20 4.25 f s, Hz 74.67 74.67 116.67 149.33 149.33 T urns per winding, N s 14 10 14 7 5 V rms 23.5 23.6 23.65 24.0 24.0 J, A/mm 2 4.67 3.29 4.37 4.58 3.15 α 54.4 54.4 68.8 54.6 54.7 η, % 90.4 92.4 88.6 89.62 90.46 X s, p.u. 0.58 0.46 0.83 0.571 0.449 X ext, p.u. 1.88 1.99 3.59 1.87 1.96 L ext, mh 2.84 3.06 3.74 1.47 1.61 X ext/x s 3.26 4.33 4.32 3.27 4.37 Outer Diameter, mm 384 384 384 384 384 Axial Length, mm 70.55 100 70.55 70.55 100 M active 22.08 32.1 22.7 22.08 32.1 M P M 2.77 3.72 2.63 2.77 3.72 (Stellenbosch University) 37 / 39
Extras Table 5: Static FEA results for 28/30 pole PMSG and 56/60 pole PMSGs. G 1 G 2 G 1 G 3 G 4 P g, kw 4.22 4.25 3.86 4.20 4.25 f s, Hz 74.67 74.67 116.67 149.33 149.33 T urns per winding, N s 14 10 14 7 5 V rms 23.5 23.6 23.65 24.0 24.0 J, A/mm 2 4.67 3.29 4.37 4.58 3.15 α 54.4 54.4 68.8 54.6 54.7 η, % 90.4 92.4 88.6 89.62 90.46 X s, p.u. 0.58 0.46 0.83 0.571 0.449 X ext, p.u. 1.88 1.99 3.59 1.87 1.96 L ext, mh 2.84 3.06 3.74 1.47 1.61 X ext/x s 3.26 4.33 4.32 3.27 4.37 Outer Diameter, mm 384 384 384 384 384 Axial Length, mm 70.55 100 70.55 70.55 100 M active 22.08 32.1 22.7 22.08 32.1 M P M 2.77 3.72 2.63 2.77 3.72 (Stellenbosch University) 37 / 39
Extras Table 5: Static FEA results for 28/30 pole PMSG and 56/60 pole PMSGs. G 1 G 2 G 1 G 3 G 4 P g, kw 4.22 4.25 3.86 4.20 4.25 f s, Hz 74.67 74.67 116.67 149.33 149.33 T urns per winding, N s 14 10 14 7 5 V rms 23.5 23.6 23.65 24.0 24.0 J, A/mm 2 4.67 3.29 4.37 4.58 3.15 α 54.4 54.4 68.8 54.6 54.7 η, % 90.4 92.4 88.6 89.62 90.46 X s, p.u. 0.58 0.46 0.83 0.571 0.449 X ext, p.u. 1.88 1.99 3.59 1.87 1.96 L ext, mh 2.84 3.06 3.74 1.47 1.61 X ext/x s 3.26 4.33 4.32 3.27 4.37 Outer Diameter, mm 384 384 384 384 384 Axial Length, mm 70.55 100 70.55 70.55 100 M active 22.08 32.1 22.7 22.08 32.1 M P M 2.77 3.72 2.63 2.77 3.72 (Stellenbosch University) 37 / 39
Extras Table 5: Static FEA results for 28/30 pole PMSG and 56/60 pole PMSGs. G 1 G 2 G 1 G 3 G 4 P g, kw 4.22 4.25 3.86 4.20 4.25 f s, Hz 74.67 74.67 116.67 149.33 149.33 T urns per winding, N s 14 10 14 7 5 V rms 23.5 23.6 23.65 24.0 24.0 J, A/mm 2 4.67 3.29 4.37 4.58 3.15 α 54.4 54.4 68.8 54.6 54.7 η, % 90.4 92.4 88.6 89.62 90.46 X s, p.u. 0.58 0.46 0.83 0.571 0.449 X ext, p.u. 1.88 1.99 3.59 1.87 1.96 L ext, mh 2.84 3.06 3.74 1.47 1.61 X ext/x s 3.26 4.33 4.32 3.27 4.37 Outer Diameter, mm 384 384 384 384 384 Axial Length, mm 70.55 100 70.55 70.55 100 M active 22.08 32.1 22.7 22.08 32.1 M P M 2.77 3.72 2.63 2.77 3.72 (Stellenbosch University) 37 / 39
Extras Static FEA Performance Table 6: General performance of the static FEA simulations G 1 G 3 Mesh Elements 17731 18241 FEA iterations 13 13 Total simulation time, s 28.8 33.7 (Stellenbosch University) 38 / 39
Extras Static FEA Performance Table 6: General performance of the static FEA simulations G 1 G 3 Mesh Elements 17731 18241 FEA iterations 13 13 Total simulation time, s 28.8 33.7 (Stellenbosch University) 38 / 39
Extras Verification 150 Torque (Nm) 125 Transient Static 100 0 5 10 15 20 Mechanical rotation (deg) Figure 14: Developed torque versus mechanical rotation obtained from transient (ANSYS Maxwell) and static (SEMFEM) solutions. (Stellenbosch University) 39 / 39