A New Approach to Sensorless Control Method for Brushless DC Motors

ABSTRACT:

This paper proposes a new position sensorless drive for brushless DC (BLDC) motors. Typical sensorless control methods such as the scheme with the back-EMF detection method show high performance only at a high speed range because the magnitude of the back-EMF is dependent upon the rotor speed. This paper presents a new solution that estimates the rotor position by using an unknown input observer over a full speed range. In the proposed method, a trapezoidal back-EMF is modelled as an unknown input and the proposed unknown input observer estimating a line-to-line back-EMF in real time makes it possible to detect the rotor position. In particular, this observer has high performance at a low speed range in that the information of a rotor position is calculated independently of the rotor speed without an additional circuit or complicated operation process. Simulations and experiments have been carried out for the verification of the proposed control scheme.

KEYWORDS:

1.      BLDC motor

2.      Full speed range

3.      Sensorless control

4.      Unknown input observer

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Overall structure of the proposed sensorless drive system.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Response waveforms at under step change of load torque. (Speed reference: 50 rpm, Load: 0.2 → 0.5 Nm).

Fig. 3. Response waveforms under step change of load torque. (Speed reference: 1650 rpm, Load: 0.75 → 1.5 Nm).

Fig. 4. Response waveforms under step change of speed reference. (Load: 0.75 Nm, Speed reference: 50 → 1650 → 50 rpm).

CONCLUSION:

This paper presented a new approach to the sensorless control of the BLDC motor drives using the unknown input observer. This observer can be obtained effectively by using the equation of augmented system and an estimated line-to-line back- EMF that is modelled as an unknown input. As a result, the actual rotor position as well as the machine speed can be estimated strictly even in the transient state from the estimated line-to-line back-EMF.

The novel sensorless method using an unknown input observer can

·          be achieved without additional circuits.

·         estimate a rotor speed in real time for precise control.

·         make a precise commutation pulse even in transient state as well as in steady state.

·         detect the rotor position effectively over a full speed range, especially at a low speed range.

·         calculate commutation function with a noise insensitive.

·         be easily realized for industry application by simple control algorithm.

The simulation and experimental results successfully confirmed the validity of the developed sensorless drive technique using the commutation function.

REFERENCES:

[1] N. Matsui, “Sensorless PM brushless DC motor drives,” IEEE Trans. on Industrial Electronics, vol. 43, no. 2, pp. 300-308, 1996.

[2] K. Xin, Q. Zhan, and J. Luo, “A new simple sensorless control method for switched reluctance motor drives,” KIEE J. Electr. Eng. Technol., vol. 1, no. 1, pp. 52-57, 2006.

[3] S. Ogasawara and H. Akagi, “An approach to position sensorless drive for brushless DC motors,” IEEE Trans. on Industry Applications, vol. 27, no. 5, pp. 928-933, 1991.

[4] J. C. Moreira, “Indirect sensing for rotor flux position of permanent magnet AC motors operating over a wide speed range,” IEEE Trans. on Industry Applications, vol. 32, no. 6, pp. 1394-1401, 1996.

[5] J. X. Shen, Z. Q. Zhu, and D. Howe, “Sensorless flux-weakening control of permanent-magnet brushless machines using third harmonic back EMF,” IEEE Trans. on Industry Applications, vol. 40, no. 6, pp. 1629-1636, 2004.

A Low Cost Speed Estimation Technique for Closed Loop Control of BLDC Motor Drive

ABSTRACT:

This paper proposes a sensorless speed control technique for Brushless DC Motor (BLDC) drives by estimating speed from the hall sensor signals. Conventionally, the speed is measured using precision speed encoders. Since these encoders cost almost half of the entire drive system, there arises the need for a low cost speed estimation technique. This is proposed by measuring the frequency of the in-built-hall sensor signals. Here, a closed loop speed control of BLDC motor is proposed using a current controlled pulse width modulation (PWM) technique. Since BLDC motor is an electronically commutated machine, the commutation period is determined by a switching table that shows the hall signals’ status. The entire system was simulated in MATLAB/Simulink and the performance of the system was analyzed for different speed and torque references.

KEYWORDS:

1.      Brushless DC Motor (BLDC)

2.      Speed estimation

3.      Hall sensors

4.      Current controlled PWM

5.       Inverter

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Proposed Block Diagram

EXPECTED SIMULATION RESULTS:

Fig. 2. Speed and Torque response of the BLDC drive for reference speed of 3000rpm; (a) Speed; (b) Electromagnetic torque developed

 Fig. 3. Speed and Torque response of the BLDC drive for reference speed of

2000rpm; (a) Speed; (b) Electromagnetic torque developed

Fig. 4. Stator current measured for speed (reference) of 3000rpm and applied

torque 0.5Nm

Fig. 5. Back EMF measured for speed (reference) of 3000rpm and applied

torque 0.5Nm

 Fig. 6. Speed and Torque response in sensored and sensorless mode for a reference speed of 2500rpm; (a) Speed response in sensored mode; (b) Speed response in sensorless mode; (c) Change in applied torques

 CONCLUSION:

This paper proposes a low cost speed estimation technique for BLDC motor drive. This method was found to be working for the entire range of speeds below the rated speed. The performance of the system was comparable with that of the conventional speed encoder based control technique. Actual speed was found to maintain the reference speed for different values of load torques. This was verified successfully by using MATLAB/Simulink. Since the proposed speed estimation technique does not require the motor parameters like resistance, inductance etc., the system is suitable for robust applications, especially in industries.

The future scope of the work can be extended as explained below:

• Although the work emphasizes on speed encoder-less control technique, the cost of the system can be further reduced by replacing the hall sensors with a suitable low cost counterpart.

• Since the torque-ripples are found to be appreciably high, novel techniques for its reduction can be studied.

 REFERENCES:

[1] Hsiu-Ping Wang and Yen-Tsan Liu, “Integrated Design of Speed- Sensorless and Adaptive Speed Controller for a Brushless DC Motor,” IEEE Transactions on Power Electronics, Vol. 21, No. 2, March 2006.

[2] K.S.Rama Rao, Nagadeven and Soib Taib, “Sensorless Control of a BLDC Motor with Back EMF Detection Method using DSPIC,” 2^nd IEEE International Conference on Power and Energy, pp. 243-248, December 1-3, 2008.

[3] W. Hong, W. Lee and B. K. Lee, “Dynamic Simulation of Brushless DC Motor Drives Considering Phase Commutation for Automotive Applications,” Electric Machines & Drives Conference,2007 lEMDC’07 IEEE International, , pp. 1377-1383, May 2007.

[4] B. Tibor, V. Fedak and F. Durovsky, “Modeling and Simulation of the BLDC motor in MATLAB GUI,” Industrial Electronics (lSIE), 2011 IEEE International Symposium on Industrial Electronics, Gdansk, pp. 1403-1407, June 2011.

[5] V. P. Sidharthan, P. Suyampulingam and K. Vijith, “Brushless DC motor driven plug in electric vehicle,” International Journal of Applied Engineering Research, vol. 10, pp. 3420-3424, 2015.

A New Approach of Minimizing Commutation Torque Ripple for Brushless DC Motor Based on DC–DC Converter

ABSTRACT:

Brushless dc motor still suffers from commutation torque ripple, which mainly depends on speed and transient line current in the commutation interval. This paper presents a novel circuit topology and a dc link voltage control strategy to keep incoming and outgoing phase currents changing at the same rate during commutation. A dc–dc single-ended primary inductor converter (SEPIC) and a switch selection circuit are employed in front of the inverter. The desired commutation voltage is accomplished by the SEPIC converter. The dc link voltage control strategy is carried out by the switch selection circuit to separate two procedures, adjusting the SEPIC converter and regulating speed. The cause of commutation ripple is analyzed, and the way to obtain the desired dc link voltage is introduced in detail. Finally, simulation and experimental results show that, compared with the dc–dc converter, the proposed method can obtain the desired voltage much faster and minimize commutation torque ripple more efficiently at both high and low speeds.

KEYWORDS:

1.      Brushless dc motor (BLDCM)

2.      Commutation,

3.      Dc link voltage control

4.      Single-ended primary inductor converter (SEPIC)

5.      Torque ripple

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Configuration of BLDCM driving system with a SEPIC converter

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulated phase currents at n = 1000 r/min. (a) Without dc link voltage control. (b) With dc link voltage control by a SEPIC converter.

Fig. 3. Simulated phase currents at n = 2500 r/min. (a) Without dc link voltage control. (b) With dc link voltage control by a SEPIC converter.

Fig. 4. Simulated electromagnetic torque at n = 1000 r/min. (a) Without DC link voltage control. (b)With DC link voltage control by a SEPIC converter.

Fig. 5. Simulated electromagnetic torque at n = 2500 r/min. (a) Without dc link voltage control. (b) With dc link voltage control by a SEPIC converter.

CONCLUSION:

A new circuit topology and control strategy has been proposed to suppress commutation torque ripple of BLDCM in this paper. A SEPIC converter is placed at the input of the inverter, and the desired dc link voltage can be achieved by appropriate voltage switch control. The switch control separates the two procedures, adjustment of SEPIC converter, and regulation of speed so that torque can respond immediately during transient commutation and robustness can be improved. Furthermore, no exact value of the commutation interval T is required, and the proposed method can reduce commutation torque ripple effectively within a wide speed range. Finally, the simulated and measured results show an improved performance of the proposed method.

REFERENCES:

[1] Y.-C. Son, K.-Y. Jang, and B.-S. Suh, “Integrated MOSFET inverter module of low-power drive system,” IEEE Trans. Ind. Appl., vol. 44, no. 3, pp. 878–886, May/Jun. 2008.

[2] A. Sathyan, N. Milivojevic, Y.-J. Lee, M. Krishnamurthy, and A. Emadi, “An FPGA-based novel digital PWM control scheme for BLDC motor drives,” IEEE Trans. Ind. Electron., vol. 56, no. 8, pp. 3040–3049, Aug. 2009.

[3] G. J. Su and J. W. Mckeever, “Low-cost sensorless control of brushless DC motors with improved speed range,” IEEE Trans. Power Electron., vol. 19, no. 2, pp. 296–302, Mar. 2004.

[4] C.-T. Pan and E. Fang, “A phase-locked-loop-assisted internal model adjustable-speed controller for BLDC motors,” IEEE Trans. Ind. Electron., vol. 55, no. 9, pp. 3415–3425, Sep. 2008.

[5] C. Xia, Z. Li, and T. Shi, “A control strategy for four-switch threephase brushless dc motor using single current sensor,” IEEE Trans. Ind. Electron., vol. 56, no. 6, pp. 2058–2066, Jun. 2009.

A Modified SEPIC Converter with High Static Gain For Renewable Applications

ABSTRACT:

Two high static gain step-up DC-DC converters based on the modified SEPIC converter are presented in this paper. The proposed topologies present low switch voltage and high efficiency for low input voltage and high output voltage applications. The configurations with magnetic coupling and without magnetic coupling are presented and analyzed. The magnetic coupling allows the increase of the static gain maintaining a reduced switch voltage. The theoretical analysis and experimental results show that both structures are suitable for high static gain applications as a renewable power sources with low DC output voltage. Two experimental prototypes were developed with an input voltage equal to 15 V and an output power equal to 100 W. The efficiency at nominal power obtained with the prototype without magnetic coupling was equal to 91.9% with an output voltage of 150 V. The prototype with magnetic coupling operating with an output voltage equal to 300 V, presents an efficiency at nominal power equal to 92.2%.   

KEYWORDS: 

1.      DC-DC power conversion

2.      Voltage multiplier and Solar power generation.

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Two-stage AC module structure.

EXPECTED SIMULATION RESULTS:

Fig.2. Input current (CH4), output voltage (CH3), switch current (CH2) and voltage (CH1) of the modified SEPIC converter without magnetic coupling (10 A/div, 50 V/div,10 μs/div).

Fig. 3. Switch current (CH2) and voltage (CH1) of the modified SEPIC converter without magnetic coupling (10 A/div, 50 V/div, 2.5 μs/div).

Fig.4. L1 (CH4) and L2 (CH2) inductor current of the Modified SEPIC converter without magnetic coupling (10 A/div, 10 μs/div).

Fig.5. Output diode Do voltage (CH1) and current (CH4) of the modified SEPIC converter without magnetic coupling (5 A/div, 50 V/div, 5 μs/div).

Fig.6. Reverse recovery current of the output diode Do (CH4) and output diode Voltage (CH1) of the modified SEPIC converter without magnetic coupling (2 A/div, 50 V/div, 100 ns/div).

Fig.7. Input current (CH4), output voltage (CH3), switch current (CH2) and switch voltage (CH1) of the Modified SEPIC converter with magnetic coupling and voltage multiplier (10 A/div, 50 V/div,10 μs/div).

Fig. 8. Switch current (CH2) and switch voltage (CH1) of the Modified SEPIC converter with magnetic coupling and voltage multiplier (2 A/div, 50 V/div, 1 μs/div).

Fig. 9. L1 (CH3) and L2 (CH4) inductor current of the Modified SEPIC converter with magnetic coupling (5 A/div, 10 μs/div).

Fig.10. Output diode Do voltage (CH1) and current (CH2) of the Modified SEPIC converter with magnetic coupling (2 A/div, 50 V/div, 2.5 μs/div).

Fig.11. Input current (CH3), output voltage (CH2), switch current (CH4) and switch voltage (CH1) of the Modified SEPIC converter with magnetic coupling and voltage multiplier operating with Vi=15 V and Po=50 W (5 A/div, 50 V/div, 5 μs/div).

Fig.12. Input current (CH3), output voltage (CH2), switch current (CH4) and switch voltage (CH1) of the Modified SEPIC converter with magnetic coupling and voltage multiplier operating with Vi=24 V and Po=50 W

(5 A/div, 50 V/div, 5 μs/div).

CONCLUSION:

Two new topologies of non isolated high static gain converters are presented in this paper. The first topology without magnetic coupling can operate with a static gain higher than 10 with a reduced switch voltage. The structure with magnetic coupling can operate with static gain higher than 20 maintaining low the switch voltage. The efficiency of proposed converter without magnetic coupling is equal to 91.9% operating with input voltage equal to 15 V, output voltage equal 150 V and output power equal 100 W.

The efficiency of proposed converter with magnetic coupling is equal to 92.2% operating with input voltage equal to 15 V, output voltage equal 300 V and output power equal 100 W. The commutation losses of the proposed converter with magnetic coupling are reduced due to the presence of the transformer leakage inductance and the secondary voltage multiplier that operates as a non dissipative clamping circuit to the output diode voltage.

REFERENCES:

[1] C. W. Li, X. He, “Review of Non-Isolated High Step-Up DC/DC Converters in Photovoltaic Grid-Connected Applications”, IEEE Transactions on Industrial Electronics, vol. 58, no. 4, pp.1239-1250, April 2011.

[2] C. S. B. Kjaer, J. K. Pedersen and F. Blaabjerg, “A Review of Single-Phase Grid-Connected Inverters for Photovoltaic Modules”, IEEE Transactions on Industry Applications, vol. 41, no. 5, pp. 1292-1306, September 2005.

[3] D. Meneses, F. Blaabjerg, O. Garcia and J. A. Cobos, “Review and Comparison of Step-Up Transformerless Topologies for Photovoltaic AC-Module Application”, IEEE Transactions on Power Electronics, vol. 28, no. 6, pp. 2649- 2663, June 2013.

[4] D. Zhou, A. Pietkiewicz and S. Cuk, “A Three-Switch High-Voltage Converter”, IEEE Transactions on Power Electronics, vol. 14, no. 1, pp. 177-183, January 1999.

[5] M. Prudente, L. L. Pfitscher, G. Emmendoerfer, E. F. Romaneli and R. Gules, “Voltage Multiplier Cells Applied to Non-Isolated DC–DC Converters”, IEEE Transactions on Power Electronics, vol. 23, no 2, pp. 871-887, March 2008.

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