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Friday, 17 January 2020

A Torque Ripple Compensation Technique for a Low Cost Brushless DC Motor Drive



ABSTRACT:
This paper presents a torque ripple compensation technique for a Brushless DC (BLDC) motor drive that is operated without a DC link capacitor. The motor drive, which uses a single switch control strategy, resembles that of a buck converter during operation at any switching state. A simple buck converter based model is therefore proposed to predict the behaviour of the BLDC motor drive at constant speed. Using the model, the impact of operation without the DC link capacitor on the torque produced by the BLDC motor drive is investigated in detail. Theoretical behaviour of the BLDC motor drive is compared with Matlab/Simulink based simulations to demonstrate the validity of the compensation technique and the analysis. Experimental results of a 250 W prototype motor drive are also presented to further validate the theoretical analysis as well as the effectiveness of the proposed technique. Results convincingly indicate that the BLDC motor drive with torque ripple compensation offers comparable performance.

KEYWORDS:
1.      Brushless machines
2.      Torque ripple compensation

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:


Fig. 1. (a) A typical BLDC motor drive; and (b) a BLDC motor drive without
a DC link capacitor.
 EXPERIMENTAL RESULTS:



Fig. 2. Case 1 with M1 for E = 95V: (a) vin(t) and E; (b) im(t) by theoretical
analysis; (c) im(t) by simulation; and (d) im(t) by experiment.



Fig. 3. Case 2 with M2 for E = 80V: (a) vin(t) and E; (b) im(t) by theoretical
analysis; (c) im(t) by simulation; and (d) im(t) by experiment.



Fig. 4. Case 3 with M1 for E = 65 V: (a) vin(t) and E; (b) im(t) by
theoretical analysis; (c) im(t) by simulation; and (d) im(t) by experiment.


Fig. 5. A comparison between the comprehensive model and the simple
model: (a) case 1 with M1; (b) case 2 with M2; and (c) case 3 with
M1.



Fig. 6. Proposed compensation for case 1: (a) simulated im(t) without a capacitor and with a 150 μF capacitor; (b) simulated im(t) with proposed compensation; (c) experimental im(t); and (d) DC link voltage with proposed compensation.





Fig. 7. Proposed compensation for case 3: (a) simulated im(t) without a capacitor and with a 150 μF capacitor; (b) simulated im(t) with proposed compensation; (c) experimental im(t); and (d) DC link voltage with proposed compensation.


CONCLUSION:
A simple mathematical model and a compensation technique for inherent torque ripples of a BLDC motor drive, operated without a DC link capacitor, have been proposed. The simplicity of the model permits the controller to be implemented on inexpensive microcontroller platforms with very low resources. With the proposed technique for compensating torque ripples, comparable performance to a conventional BLDC motor drive with a large DC link capacitor can be achieved. However, with the torque ripple compensation technique, the overall complexity of the motor drive has been increased, which is a major disadvantage. Based on the application, major augmentations in both hardware and firmware may be required. The good agreement between the theoretical results, simulated results and experimental results demonstrate the accuracy of the simple buck model and the effectiveness of the proposed compensation technique. The proposed compensation technique is expected to be useful for manufacturing low cost BLDC motor drives with comparable performance.
REFERENCES:
[1] R. Krishnan, Electric Motor Drives, Modeling, Analysis, and Control. Prentice Hall, 2001.
[2] R. Krishnan, Permanent Magnet Synchronous and Brushless DC Motor Drives. CRC Press, 2010.
[3] J. F. Gieras, Permanent Magnet Motor Technology - Design and Applications: CRC Press, 2010.
[4] V. Sankaran, F. Rees, and C. Avant, “Electrolytic capacitor life testing and prediction,” in Industry Applications Conference, 1997. Thirty- Second IAS Annual Meeting, IAS ’97., Conference Record of the 1997 IEEE, vol. 2, Oct. 1997, pp. 1058–1065.
[5] H. K. Samitha Ransara and U. K. Madawala, "A Low Cost Brushless DC Motor Drive," in 6th IEEE Conference on Industrial Electronics and Applications, (IEEE ICIEA), Jun. 2011, pp. 2723-2728.

Thursday, 16 January 2020

Design of Speed Control and Reduction of Torque Ripple Factor in BLdc Motor Using Spider Based Controller



ABSTRACT:
It is a very difficult process to achieve smooth drivers for the motor operating under variable speed mode. In brushless direct current motor (BLdc) when back electromotive force waveform is of trapezoidal type, the developed torque is constant in ideal conditions. However, practically, torque ripple is present in  the output torque because of the physical design of the motor and its parameters. Also, the produced ripples are associated with the control and driver side of the motor. In the previous literature, the drive without a dc-link capacitor is presented but the torque ripple reduction is not effective. Hence in another work, the usage of the small capacitor is recommended and the results are improved. In this work, the quick stabilization with torque ripple reduction is presented using a bio-inspired algorithm-based technique in a BLdc motor drive. A Spider based controller is built to generate the pulse width modulation signals applied to the inverter and the control signal applied to the capacitor. The effect of utilizing small dc-link capacitor, on the torque ripple reduction and speed control is investigated. The performance is also compared with the case of large capacitor utilization and without a capacitor case. The proposed control strategy is verified experimentally by implementing with dsPIC30F4011 and the hardware circuit.
KEYWORDS:
1.      Brushless direct current (BLdc) motor
2.      Dc-link capacitor
3.      PWM sequence
4.      Spider based controller
5.      Spider web construction
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:





Fig. 1. Proposed technique for torque ripple compensation.

 EXPERIMENTAL RESULTS:



 Fig. 2. im compensation. (a) Im (A) - without capacitor. (b) Im (A) - with
capacitor. (c) Im (A) - with small capacitor. (d) Im (A) - with spider.





Fig. 3. Torque comparison. (a) Torque (Nm) - without capacitor. (b) Torque  (Nm) - with capacitor. (c) Torque (Nm) - with small capacitor. (d) Torque (Nm) - with spider.



 Fig. 4. Speed comparison. (a) RPM (speed) - without capacitor. (b) RPM (speed) - with capacitor. (c) RPM (speed) - with small capacitor. (d) RPM  (speed) - with spider.

CONCLUSION:
The method of designing a three-phase BLdc motor drive by using a single-phase voltage source is presented with the intention of employing small dc-link capacitor. In addition, the strategy for reducing torque ripple concern which is generally presenting in BLdc motor is considered in the work. The mathematical equations are developed to determine the capacitor rating and the parameters are set in the simulation to validate the theoretical results. The utilization of a small dc-link capacitor is evaluated by assessing the torque compensation waveform and current compensation  waveform with the capacitor-less case and large capacitor case. Besides, the application of spider web building algorithm in generating the necessary switching control pulses are observed by comparing waveforms with the utilization of fuzzy based control algorithm also with the capacitor and without capacitor case. The utilization of spider web-based control algorithm to develop the control pulses make the system to  be more stabilized with respect to its speed. Though the scheme has a switch and a small capacitor as additional components, the total price of the drive is reduced. Similarly, the control process used for the switches is simple, extra components are not used.  When the large capacitors are used, the motor reliability is reduced since the large capacitors are rated for the small period only. In addition, the simulation results are validated by designing the corresponding hardware using dsPIC30F4011 and the simulation results are validated.
REFERENCES:
[1] H. Le-Huy, R. Perret, and R. Feuillet, “Minimization of torque ripple in brushless DC motor drives,” IEEE Trans. Ind. Appl., vol. IA-22, no. 4,  pp. 748–755, Jul. 1986.
[2] J. Y. Hung, and Z. Ding, “Design of currents to reduce torque ripple in brushless permanent magnet motors,” IEE Proc. B (Electric Power Appl.), vol. 140, no. 4, pp. 260–266, 1993.
[3] E. Favre, L. Cardoletti, and M. Jufer, “Permanent-magnet synchronous motors: A comprehensive approach to cogging torque suppression,” IEEE Trans. Ind. Appl., vol. 29, no. 6, pp. 1141–1149, Nov./Dec. 1993.
[4] D. C. Hanselman, “Minimum torque ripple, maximum efficiency excitation of brushless permanent magnet motors,” IEEE Trans. Ind. Electron., vol. 41, no. 3, pp. 292–300, Jun. 1994.
[5] Z. Q. Zhu, L. J.Wu, and M. L. Mohd Jamil, “Distortion of back-EMF and torque of PM brushless machines due to eccentricity,” IEEE Trans. Magn. vol. 49, no. 8, pp. 4927–4936, Aug. 2013.

Sunday, 5 January 2020

Design of a PEV Battery Charger with High Power Factor using Half-bridge LLC-SRC Operating at Resonance Frequen



ABSTRACT:
This paper presents a two stage battery charger for plug-in electric vehicles (PEV) based on half-bridge LLC series resonant converter (SRC) operating at resonance frequency. The first stage is power factor correction (PFC) stage comprising of boost converter topology using hysteresis band control of inductor current. The PFC stage reduces the total harmonic distortion (THD) of the line current for achieving high power factor and regulates the voltage to follow the battery voltage at DC link capacitor. The input of the boost converter is a single phase 50 Hz, 220V AC from grid. At the second stage, a half bridge LLC-SRC is used for constant-current, constant-voltage (CC-CV) based battery charging and for providing galvanic isolation. The resonant converter is designed to operate around resonance frequency to have maximum efficiency and low turnoff current of power switches to reduce switching losses. The circuit is simulated using MATLAB Simulink with 1.5 Kw maximum output power. Simulation results show that the PFC  stage achieves THD less than 0.07% and high power factor value  as 0.9976. The DC/DC stage meets all the CC-CV charging requirements of the battery over wide voltage range 320V—420V for depleted to fully charged battery.
KEYWORDS:
1.      LLC Resonant converter
2.      PEV battery charger
3.      PFC
4.      Hysteresis band control
5.      FHA
SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Typical power architecture of a battery charger.

CIRCUIT DIAGRAM:


Fig. 2. Schematic of the proposed battery charger.
EXPERIMENTAL RESULTS:


Fig. 3. Boost inductor current for a half cycle of input voltage.



Fig. 4. AC voltage and current after power factor correction.


Fig. 5. LLC-SRC operating at key point A (V0 = 320V, and I0 = 3.57A).



Fig. 6. LLC-SRC operating at key point B (V0 = 360V, and I0 = 3.57A).


Fig. 7. LLC-SRC operating at key point C (V0 = 420V, and I0 = 3.57A).



Fig. 8. LLC-SRC operating at key point D (V0 = 420V, and I0 = 0.25A).


CONCLUSION:
In this paper, a 1.5 kW PEV battery charger with emphasis on the design of LLC-SRC for DC-DC stage of the battery charger is presented. A method for improvement in the power  factor with boost converter is presented using hysteresis current control to keep line input voltage and current in phase using  phase shift in inductor current. Simulation results show that the PFC stage achieves minimum THD as 0.07% and a power factor of 0.9976 having line current and voltage in phase. The LLC-SRC is designed to operate around resonance frequency to achieve maximum benefits of LLC converter,  having minimum circulating energy, avoiding hard  commutation of secondary rectifier diodes. Simulation results for the converter performance are presented which show that the turning off current of power switches have very low value throughout the charging process and is below 2.4A. Hence, the converter have minimum switching and conduction losses.
REFERENCES:
[1] H. Wang, S. Dusmez, and A. Khaligh, "A novel approach to design EV battery chargers using SEPIC PFC stage and optimal operating point tracking technique for LLC converter," Applied Power Electronics Conference and Exposition (APEC), 2014 Twenty-Ninth Annual IEEE, pp.1683-1689, 16-20 March 2014.
[2] H. Wang, S. Dusmez, and A. Khaligh, "Design and Analysis of a Full-Bridge LLCBased  PEV Charger Optimized for Wide Battery Voltage Range," Vehicular Technology, IEEE Transactions on, Vol. 63, No. 4, pp.1603-1613, May 2014.
[3] J. Deng, S. Li, S. Hu, C.C. Mi, and R. Ma, "Design Methodology of LLC Resonant Converters for Electric Vehicle Battery Chargers," Vehicular Technology, IEEE Transactions on, Vol. 63, No. 4, pp.1581-1592, May 2014.
[4] Marian K. Kazimierczuk, "Pulse-width Modulated DC-DC Power Converters," Ohio, USA: John Wiley & Sons Ltd, pp. 129-134, 2008.
[5] H. Wang, and A. Khaligh, "Comprehensive Topological Analyses of Isolated Resonant Converters in PEV Battery Charging Applications," Transportation Electrification Conference and Expo (ITEC), 2013 IEEE, pp.1-7, 16-19 June 2013.

Saturday, 28 December 2019

Improved pulse-width modulation scheme for T-type multilevel inverter


ABSTRACT: 

In recent times, reduced switch count multilevel inverter (RSC-MLI) has become an emerging area of research in power electronic converters. To control these RSC-MLI topologies, various novel modulation schemes are reported. Multi reference is one of such modulation scheme reported for various RSC topologies, such as T-type. However, the performance of this conventional scheme results in high total harmonic distortion (THD) in line voltages, when compared with the conventional level shifted pulse-width modulation scheme. This observation is clearly presented in this study and the reason for its degraded THD performance has been deeply discussed. To alleviate this problem, a modified multi-reference dual-carrier modulation technique with multiple references and two carriers is proposed. To implement this proposed modulation technique, an alternate carrier and modulation signals arrangement with multiple carriers and single reference is also presented. Finally, a comparative THD performance of the proposed and conventional modulation schemes is carried out on a five-level T-type MLI and obtained simulation results are validated experimentally.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:




Fig. 1 Five-level T-type topology

EXPERIMENTAL RESULTS: 


Fig. 2 Performance analysis of multi-reference modulation scheme on five-level T-type configuration with ma = 0.95 and fc = 1500 Hz (a) Phase voltage, line voltage and load current, (b) Respective harmonic spectra, (c) Comparative harmonic performance of conventional multi-reference modulation scheme for five-level T-type MLI and LSPWM for five-level CHB





Fig. 3 Comparison of LSPWM-OPD and multi-reference modulation scheme with ma = 0.95 and fc = 1500 Hz
(a) Conventional multi-reference modulation scheme for a five-level T-type, (b) Comparison of position of carriers in multi-reference modulation in terms of LSPWM-OPD scheme,
(c) Position of carriers in LSPWM-OPD modulation scheme, (d) Phase and line harmonic spectra of LSPWM-OPD for a five-level CHB


Fig. 4 Modified multi-reference dual-carrier modulation scheme for a five-level T-type topology with ma = 0.95 and fc = 1500 Hz (a) Proposed scheme, (b) Carriers of proposed scheme in terms of LSPWM-IPD, (c) Phase voltage, line voltage and load current, (d) Respective harmonic spectra

CONCLUSION:

In this paper, the poor harmonic performance of the conventional multi-reference modulation method for T-type MLI topology is analysed. To address this problem, a modified multi-reference dual-carrier modulation is proposed. The performance of the proposed modulation scheme is identical to LSPWM-IPD technique which is the best PWM technique with lowest THD value available. Further, to implement the proposed PWM scheme, an alternate carrier and modulation signals arrangement is also proposed which can be easily realisable on digital platforms. The performance of the proposed modulation schemes is evaluated with simulation and experimental studies on a five-level T-type MLI topology. The experimental studies are in good agreement with simulation studies and also verify the superior performance of the proposed schemes over conventional modulation schemes. A generalisation of the modified reduced carrier modulation to implement any number of levels for a T-type is presented with the help of a flowchart.

REFERENCES:

[1] Singh, B., Singh, B.N., Chandra, A., et al.: ‘A review of three-phase improved power quality AC–DC converters’, IEEE Trans. Ind. Electron., 2004, 51, (3), pp. 641–660
[2] Franquelo, L.G., Rodriguez, J., Leon, J.I., et al.: ‘The age of multilevel converters arrives’, IEEE Ind. Electron. Mag., 2008, 2, (2), pp. 28–39
[3] Kouro, S., Malinowski, M., Gopakumar, K., Pou, J., Franquelo, L.G., Wu, B., Rodriguez, J., Pérez, M.A., Leon, J.I.: ‘Recent advances and industrial applications of multilevel converters’, IEEE Trans. Ind. Electron., 2010, 57, (8), pp. 2553–2580
[4] Rodriguez, J., Lai, J.-S., Peng, F.Z.: ‘Multilevel inverters: a survey of topologies, controls, and applications’, IEEE Trans. Ind. Electron., 2002, 49, (4), pp. 724–738, doi: 10.1109/TIE.2002.801052
[5] McGrath, B.P., Holmes, D.G.: ‘Multicarrier PWM strategies for multilevel inverters’, IEEE Trans. Ind. Electron., 2002, 49, (4), pp. 858–867

Tuesday, 17 December 2019

Vector Current Control Derived from Direct Power Control for Grid-Connected Inverters



ABSTRACT:
We propose a vector current control derived from direct power control (VCC-DPC) for a three-phase voltage source inverter (VSI) in the synchronous rotating frame through instantaneous real and reactive powers. The proposed VCC-DPC method has the same control structure as the conventional VCC except for the coordinate transformation, since we obtain the d–q axes currents model of VSI without using Park transformation  and the PLL system. Consequently, the proposed method has the same property as the conventional VCC if the PLL extracts the phase angle of the grid voltage correctly. However, with the consideration of the slow dynamics of the PLL, the proposed method has an enhanced dynamical performance feature compared with the conventional VCC. Moreover, it has another benefit that the reduction of the computational burden could be expected since  there is no Park transformation and the PLL in the controller implementation. We can guarantee that the closed-loop system with the proposed method is exponentially stable in the operating  range. Finally, both simulation and experimental results using a 15-kW-inverter system match the theoretical expectations closely.
KEYWORDS:
1.      Voltage source inverter
2.      Vector current controller
3.      Instantaneous real and reactive powers
4.      Exponentially stable

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:


Fig. 1. Block diagram of (a) the standard VCC with PLL; (b) the proposed method without PLL.

EXPERIMENTAL RESULTS:




Fig. 2. Performance of the inverter when the reference of id is changed from 5 A to 10 A at 1:51 s. (a) grid voltage, (b) id, (c) iq. (red-solid line: conventional method; blue-dashed line: proposed method).





Fig. 3. Performance of the inverter when the inverter is connected at 0:51 s and the reference of id is changed to 5 A. (a) grid voltage, (b) real power, (c) reactive power, (d) id, (e) iq, (red-solid line: conventional VCC method; green-solid line: conventional VCC method with faster PLL; blue-dashed line: proposed method)

CONCLUSION:
In this paper, we have introduced a VCC-DPC for three phase VSI with instantaneous real and reactive powers. We obtained the d–q axes currents model of VSI without using Park transformation and the PLL. For fair comparison, we designed a PI controller with feed forward. Thus, the proposed method has the same control structure as the conventional VCC except for the coordinate transformation and PLL. Moreover, the proposed VCC-DPC will reduce the computational burden since there is no Park transformation and as well as the PLL. Simulation results show that the proposed method has the same properties as the conventional VCC when the PLL extracts the correct phase angle of the grid voltage. However, in the case where the slow dynamics of the PLL is activated,   the proposed method has improved dynamical performance in  comparison with the conventional VCC. We have also tested the performance of the proposed method with a 15-kW inverter system. Experimental results show that the proposed method has a robust property for the parameter uncertainness as well. This work is an initial start for the VCC-DPC through the DPC model. In the future, we will design a compensator for the harmonics or unbalanced issues based on this concept.
REFERENCES:
[1] F. Blaabjerg, R. Teodorescu, M. Liserre, and A. V. Timbus, “Overview of control and grid synchronization for distributed power generation systems,” IEEE Trans. Ind. Electron., vol. 53, no. 5, pp. 1398–1409, 2006.
[2] F. Blaabjerg, M. Liserre, and K. Ma, “Power electronics converters for wind turbine systems,” IEEE Trans. Ind. Appl., vol. 48, no. 2, pp. 708–  719, 2012.
[3] F. Blaabjerg, Y. Yang, D. Yang, and X. Wang, “Distributed power generation  systems and protection,” Proc. IEEE, vol. 105, no. 7, pp. 1311–1331, 2017.
[4] Q.-C. Zhong, “Power-electronics-enabled autonomous power systems: Architecture and technical routes,” IEEE Trans. Ind. Electron., vol. 64, no. 7, pp. 5907–5918, 2017.
[5] X. Wang, F. Blaabjerg, M. Liserre, Z. Chen, J. He, and Y. Li, “An active damper for stabilizing power-electronics-based AC systems,”  IEEE Trans. Power Electron., vol. 29, no. 7, pp. 3318–3329, 2014.