16 3 2012 3 ELECTRI C MACHINES AND CONTROL Vol. 16 No. 3 Mar. 2012 1 1 1 2 2 3 1. 250061 2. 250014 3. 251010 3. 3% U 469. 72 A 1007-449X 2012 03-0053- 07 The optimization of EV powertrain s efficiency control strategy under dynamic operation condition HUANG Wan-you 1 CHENG Yong 1 JI Shao-bo 1 LI Chuang 2 ZHANG Xiao-wen 2 ZHANG Hai-bo 3 1. College of Energy & Power Engineering Shandong University Jinan 250061 China 2. Jinan Electric Vehicle Operation Co. Ltd Jinan 250014 China 3. Shandong Baoya New Energy Vehicle Co. Ltd Jinan 251010 China Abstract A control strategy of Electric Vehicle EV powertrain under dynamic operation conditions was optimized in order to lower power consumption and prolong EV's endurance mileage. Based on measured data from an AC asynchronous motor and a LiFePO4 /C Li-ion battery pack a powertrain's working efficiency describing model was developed. An optimal control method to improve EV powertrain's efficiency was deduced following the model. To verify the method a powertrain's simulating model was established and its validation was conformed in contrast to the results of experiments. An EV s start acceleration process control strategy was optimized according to the simulating results and the strategy was implemented in the test bench. The testing results show a 3. 3% efficiency improvement of the new strategy over the original one which suggests that this powertrain efficiency model can be used to optimize the control strategy at dynamic operation conditions. Key words electric vehicles optimal control strategy dynamic operation condition efficiency model powertrain simulating model 2011-09 - 10 863 2009AA11A118 2011GGX10506 yzc10123 1983 1963 1979 1967 1968 1972
54 16 0 75% state of charge SOC 1-2 2 2. 1 3-5 4 2 6 Matlab /SIMULINK 2 1 1 192 V /100 Ah CAN 20 kw 8 η m 1 GB /T Fig. 1 Real curves of power-train's working parameters 18488. 2-2006 SOC 7 50 3 50 ± 5 Fig. 2 Schematic of test bench CAN SOC 2. 2
3 55 SOC 9 20 ~ 40 5 6 34 ± 3 Fig. 3 3 Efficiency curve of driving motor 3 η m = - 5. 958 10-12 n 4 + 3. 813 10-8 n 3-7. 723 10-5 n 2 + 4. 341 10-2 n - 1. 099 10-4 P 4 + 1. 423 10-2 P 3-6. 477 10-1 P 2 + 3. 24 P - 8. 345 10-7 np 3 + 8. 899 10-5 np 2-9. 074 10-3 np - 8. 459 10-9 n 2 P 2-4. 759 10-6 n 2 P + 7. 456 10-10 n 3 P + 55. 126 1 η m % n r /min P kw Fig. 5 1 4 4 5 Real battery pack s temperature vs time 4 Fig. 4 p SOC 2-9. 226 10-2 p SOC - 3. 913 10-5 Comparison of measured driving motor system s efficiency and simulation s 2. 3 Fig. 6 6 Discharge efficiency of battery pack Simulink 6 SOC 6 η b = - 8. 988 10-6 p SOC 3 + 2. 031 10-3 P 3-7. 126 10-4 P 2-3. 929 10-1 P - 1. 842 10-5 p SOC 2 P + 3. 021 10-5 p SOC P 2 + 1. 192 10-3 p SOC P + 98. 9 2
56 16 η b % p SOC 10-4 P 4 + 1. 488 10-2 P 3-5. 728 10-1 % P kw P 2 + 3. 202 P + 7. 546 10-6 np 2 + 7. 322 7 10-2 np - 2. 995 10-4 n 2 P + 4. 022 10-7 n 3 P + 55. 268-9. 832 10-6 p SOC 3 + 1. 03% 1. 723 10-3 p SOC 2-4. 612 10-2 p SOC - 8. 664 10-6 P 3-1. 031 10-3 P 2-0. 361 P + 97. 613 /100 5 Table 1 1 Simplifying of motor system s efficiency model 7 n 2 p 3 380 2 438 1. 386 Fig. 7 Comparison of measured battery pack s discharge efficiency and simulation s n 2 p 2 n 3 p 2 438 3 314 2 438 2 438 1 1. 359 2. 4 8 1 200 r /min η = η m η b /100 3 η % 1 2 S S S = n i = 1 x f i - x i 2 4 x f i x i i = 1 2 n n 484 n 180 S b S K - 2 438 - np 2 19 959 2 438 8. 186 np 3 2 438 2 438 1 np 3 635 2 438 1. 491 np 3 + n 2 p 2 2 443 2 438 1. 002 K = S b S S b S Fig. 8 Efficiency MAP of powertrain at 1 200 r / min SOC 1 5 np 3 n 2 P 2 2 1. 08% SOC 2. 5 η = - 4. 05 10-8 n 4 + 2. 869 10-5 n 3-10 6. 538 10-3 n 2 + 4. 109 10-1 n - 1. 375 8 1 200 r /min
3 57 10 T f T w T limit1 4 T j T limit2 T limit1 = T f + T w T limit2 = T limit1 + ct j T dem T limit1 a > 0 T dem T limit2 a > 0 T dem T limit1 a < 0 T dem T limit2 a < 0 6 T dem a c 5 SOC 11 5 P p k + 1 = p k - η' p k k = 0 η p k 1 2 3 7 7 P k + 1 - p k ε p dem = p k + 1 T dem 3. 2 9 10 Fig. 10 EV powertrain's simulation model 1 SOC 2 11 Fig. 9 9 Optimal control diagram at dynamic operation conditions 9 Fig. 11 Real curves of motor speed and torque S - 11 SOC 10 2 3 2 3. 1 4% Matlab /Simulink 11
58 16 2 Infineon XC164CM Table 2 Data table of powertrain s efficiency / r /min /N m /A SOC /% /% /% /% 333 143. 7 22. 0 98. 24 71. 7 74. 6 4. 0 710 172. 8 52. 9 97. 6 77. 4 79. 1 2. 2 845 129. 9 44. 6 97. 12 82. 0 84. 2 2. 7 820 79. 5 25. 8 96. 45 84. 0 86. 5 3. 0 883 35. 0 13. 4 96. 17 76. 7 79. 7 3. 9 892 21. 4 9. 6 96. 07 66. 3 68. 9 3. 9 845 43. 5 15. 2 95. 86 80. 3 82. 6 2. 9 908 79. 0 28. 2 95. 6 84. 4 86. 8 2. 8 1 124 133. 4 61. 2 94. 77 82. 1 84. 5 2. 9 1 345 132. 1 73. 1 94. 17 82. 9 83. 8 1. 1 1 493 128. 8 79. 5 93. 14 81. 7 83. 1 1. 7 1 601 109. 6 71. 7 92. 16 82. 5 83. 3 1. 0 1 710 92. 6 64. 3 91. 2 82. 9 84 1. 3 1 854 77. 9 58. 4 90. 65 83. 1 84. 5 1. 7 1 947 74. 4 58. 8 89. 91 82. 7 84. 5 2. 2 2 024 71. 5 58. 9 89. 14 82. 5 84. 4 2. 3 2 090 96. 7 85. 4 88. 04 80 81. 9 2. 4 2 206 70. 3 63. 9 87. 3 81. 6 84 2. 9 2 263 66. 1 61. 6 86. 48 81. 5 84. 1 3. 2 12 Fig. 12 Relationship between powertrain s efficiency and motor torque 10 13 2 335 65. 2 62. 8 85. 87 81. 5 84 3. 1 2 392 60. 8 60. 1 84. 72 81. 3 83. 9 3. 2 2 472 52. 2 53. 6 84. 19 80. 9 83. 4 3. 1 2 513 49. 1 51. 1 83. 06 80. 9 82. 9 2. 5 2 554 44. 3 46. 5 81. 81 81. 4 82 0. 7 2 687 44. 0 49 79. 51 80. 9 81. 5 0. 7 4 13 Fig. 13 Comparison of EV s start acceleration process = 1. 4 i 0 = 4. 4 m = 3 900 kg r = 0. 294 m 32 kw 100 Ah SOC 80% 1 200 r /min i g between new strategy and the original's 12 13 88. 46% 5 3. 3% SOC
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