Switched capacitor voltage boosting converter for electric and hybrid electric vehicle drives

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1. Switched-Capacitor Voltage Boost Converter for Electric and Hybrid Electric Vehicle Drives

2. Abstract To a switched-capacitor (SC) voltage boost converter and its control methods for implementing dc-ac and ac-dc power conversion. A bidirectional SC converter for dc-ac and ac-dc power conversion in electric and hybrid electric vehicles. To presents the switched-capacitor voltage boost (SC) converter and its control methods.

3. The switched capacitor circuit is used to create a multi-leveled dc-link voltage. Therefore, the proposed switched-capacitor circuit differs from the conventional one by not having the reverse blocking diode at the load side or the large filtering capacitor. The regulation of the output current and voltage is realized by unified control of both the inverter and the switched-capacitor stages

4. Existing system/Drawbacks The power rating of the dc-dc converter must match the battery pack power, leading to a proportionally large inductor. The inductor is a heavy and costly component. Furthermore, the inductor copper and core losses increase proportionally with the size of the inductor. When boosted by a high-voltage ratio, the boost converter must operate with a high duty cycle where the efficiency is relatively low

5. Existing circuit diagram

6. Proposed Circuit diagram Switched capacitor Voltage Boost Converter

7. Proposed Topology To overcome the above limitations of the traditional drive trains, this project presents the switched-capacitor voltage boost (SC) converter and its control methods. It employs a switched capacitor circuit with the inverter to form a unified circuit. The switched capacitor circuit is used to create a multi-leveled dc-link voltage. The proposed switched-capacitor circuit differs from the conventional one by not having the reverse blocking diode at the load side or the large filtering capacitor. The regulation of the output current and voltage is realized by unified control of both the inverter and the switched-capacitor stages

8. Block diagram Battery Boost converter inverter motor Hall sensor

9. Boost converter We’ve all come across pesky situations where we need a slightly higher voltage than our power supplies can provide. We need 12 volts, but have only a 9 volt battery. Or maybe we have a 3.3V supply when our chip needs 5V. That too, in most cases, the current draw is quite decent. Eventually, we ask ourselves the question, is it possible to convert one DC voltage to another?

10. Lucky for us, the answer is yes. It is possible to convert one DC voltage to another, however the methods are a slightly on the clever side. And no, it does not involve the conversion of DC to AC and back again. As it involves too many steps. Anything that has too many steps is inefficient; this is a good life lesson too. Enter the world of switch mode DC-DC converters! They’re called switch mode because there’s usually a semiconductor switch that turns on and off very rapidly.

11. Switched capacitor boost voltage When the switch is then closed and the right hand side is shorted out from the left hand side, the  capacitor  is therefore able to provide the  voltage  and energy to the load. During this time, the blocking diode prevents the  capacitor  from discharging through the switch.

12. Switched capacitor advantages SC  converter  are the continuous input current achieving high  voltage  gain with low  voltage  and current stress on the  power  components , no use of a high-frequency transformer easy to increase the  voltage  by adding the SC cell.

13. INT R O D U C TION Brushless DC motor are synchronous motors which are powered by a DC electric source, through an integrated Inverter, which produces an AC signal to drive the motor.

14. Con s truction Similarities with AC Induction Motor and brushed DC motor Y pattern gives high torque at low RPM and the ∆ pattern gives low torque at low RPM. This is because in the ∆ configuration, half of the voltage is applied across the winding that is not driven, thus increasing losses and, in turn, efficiency and torque.

15. STATOR Steel laminations in the stator can be slotted or slot less. A slot less core has lower inductance, thus it can run at very high speeds. Because of the absence of teeth in the lamination stack, requirements for the cogging torque also go down, thus making them an ideal fit for low speeds too.

16. ROTOR The rotor of a typical BLDC motor is made out of permanent magnets. Depending upon the application requirements, the number of poles in the rotor may vary. Increasing the number of poles does give better torque but at the cost of reducing the maximum possible speed. Another rotor parameter that impacts the maximum torque is the material used for the construction of permanent magnet; the higher the flux density of the material the higher the torque.

17. Detected by HALL SENSOR

18. Two Coils Excited at the same instant to Maximize Performance

19. TORQUE – SPEED CHARACTERSTICS

20. Control Signals from HALL SENSORS

21. BLDC MOTOR WITH CONTROLLER

22. C ONT R OL

23. SPEED CONTROL Motor speed depends upon the amplitude of the applied voltage. The amplitude of the applied signal is adjusted by using PWM. The higher side transistors are driven using PWM. By controlling the duty cycle of the PWM signal, the amplitude of the applied voltage can be controlled, which in turn will control the speed of the motor.

24. TORQUE CONTROL Torque can be controlled by adjusting the magnetic flux. However, magnetic flux is dependent upon the current flowing through the windings. Thus, by controlling current, torque of a motor can be controlled.

25. MOTOR PROTECTION Peak current : － This is the maximum instantaneous current allowed to flow through the windings for safe operation. This condition occurs in case of a short circuit. Under Voltage : – When the system is running on batteries, it becomes important to cut off the supply if the battery voltage drops below a particular limit. Hall Sensor Failure : – The commutation sequence will break, which may cause the BLDC motor to become stuck and the current to rise above a particular limit. Signal changes its logic level or not. If it gets stuck to a particular level, then it can be detected as a failure and the motor drive can be disconnected, letting it run on inertia or be stopped by applying the brake.

26. A D V AN T A G E S Accelerate and decelerate easily because of low rotor inertia. High performance motor that provides large torque per unit volume over a vast speed range. Such motors cooled by conduction and no air flow are required for inside cooling. As brushes are absent, the mechanical energy loss due to friction is less which enhanced efficiency , more reliable, high life expectancies, and maintenance free operation. BLDC motor can operate at high-speed under any condition. There is no sparking and much less noise during operation.

27. Simulation result

28. Switched capacitor controller

29. Hall sensor

30. Switched capacitor output voltage

31. Motor speed

32. Stator current and back emf

33. Conclusion switched-capacitor power converter (SC) for implementing dc-ac and ac-dc power conversion . The SC converter employs a switched- Capacitor circuit augmented with the main converter circuit to the power source , thus providing unique features that cannot be Attained by the traditional VSI or boost VSI. One of these unique features is doubling the area of the linear modulation region. The SC converter eliminates the need for the cumbersome and costly inductor to boost the voltage. Instead, it relies on only the capacitors to achieve voltage boost, which allows higher power density. The formulation of the maximum voltage drop across the capacitor and the minimum charging current are analytically derived . The analytical results provide a clear insight into the design elements that affect the behavior of the charging current , thus allowing the operation at higher power.

34. Reference [1] Reda Cherif , Fuad Hasanov , and Aditya Pande , “Riding the Energy Transition : Oil Beyond 2040,” IMF Working Papers, May 2017. [2] Y. Song and B. Wang, “Evaluation Methodology and Control Strategies for Improving Reliability of HEV Power Electronic System,” in IEEE Transactions on Vehicular Technology, vol. 63, no. 8, pp. 3661-3676, Oct. 2014. [3] Y. Song and B. Wang, “Survey on Reliability of Power Electronic Systems ,” in IEEE Transactions on Power Electronics, vol. 28, no. 1, pp . 591-604, Jan. 2013. [4] Fang Zheng Peng, “Z-source inverter,” in IEEE Transactions on Industry Applications , vol. 39, no. 2, pp. 504-510, March-April 2003. [5] W. Qian, H. Cha, F. Z. Peng and L. M. Tolbert, “55-kW Variable 3X DCDC Converter for Plug-in Hybrid Electric Vehicles,” in IEEE Transactions on Power Electronics, vol. 27, no. 4, pp. 1668-1678, April 2012.