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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Design of External Inductor for Improving Performance of Voltage Controlled DSTATCOM

ABSTRACT:

A distribution static compensator (DSTATCOM) is used for load voltage regulation and its performance mainly depends upon the feeder impedance and its nature (resistive, inductive, stiff, non-stiff). However, a study for analyzing voltage regulation performance of DSTATCOM depending upon network parameters is not well defined. This paper aims to provide a comprehensive study of design, operation, and flexible control of a DSTATCOM operating in voltage control mode. A detailed analysis of the voltage regulation capability of DSTATCOM under various feeder impedances is presented. Then, a benchmark design procedure to compute the value of external inductor is presented. A dynamic reference load voltage generation scheme is also developed which allows DSTATCOM to compensate load reactive power during normal operation, in addition to providing voltage support during disturbances. Simulation and experimental results validate the effectiveness of the proposed scheme.

KEYWORDS :

      1.      Distribution static compensator (DSTATCOM)

2.      Current control

3.      Voltage control

4.      Power factor

5.      Power quality

SOFTWARE: MATLAB/SIMULINK

EQUIVALENT CIRCUIT DIAGRAM:

Fig. 1. Three phase equivalent circuit of DSTATCOM topology in distribution system.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Voltage regulation performance of conventional DSTATCOM with resistive feeder. (a) PCC voltages. (b) Load Voltages. (c) Source currents. (d) Filter currents. (e) Load currents.

Fig. 3. Simulation results. (a) During normal operation (i)-(v). (b) During voltage sag (vi)-(x). (c) During voltage swell (xi)-(xv).

CONCLUSION:

This paper has presented design, operation, and control of a DSTATCOM operating in voltage control mode (VCM). After providing a detailed exploration of voltage regulation capability of DSTATCOM under various feeder scenarios, a benchmark design procedure for selecting suitable value of external inductor is proposed. An algorithm is formulated for dynamic reference load voltage magnitude generation. The DSTATCOM has improved voltage regulation capability with a reduced current rating VSI, reduced losses in the VSI and feeder. Also, dynamic reference load voltage generation scheme allows DSTATCOM to set different constant reference voltage during voltage disturbances. Simulation and experimental results validate the effectiveness of the proposed solution. The external inductor is a very simple and cheap solution for improving the voltage regulation, however it remains connected throughout the operation and continuous voltage drop across it occurs. The future work includes operation of this fixed inductor as a controlled reactor so that its effect can be minimized by varying its inductance.

REFERENCES:

[1] M. H. Bollen, Understanding power quality problems. vol. 3, IEEE press New York, 2000.

[2] S. Ostroznik, P. Bajec, and P. Zajec, “A study of a hybrid filter,” IEEE Trans. Ind. Electron., vol. 57, no. 3, pp. 935–942, Mar. 2010.

[3] C. Kumar and M. Mishra, “A voltage-controlled DSTATCOM for power quality improvement,” IEEE Trans. Power Del., vol. 29, no. 3, pp. 1499– 1507, June 2014.

[4] Q. Liu, L. Peng, Y. Kang, S. Tang, D. Wu, and Y. Qi, “A novel design and optimization method of an LCL filter for a shunt active power filter,” IEEE Trans. Ind. Electron., vol. 61, no. 8, pp. 4000–4010, Aug. 2014.

[5] T. Aziz, M. Hossain, T. Saha, and N. Mithulananthan, “VAR planning with tuning of STATCOM in a DG integrated industrial system,” IEEE Trans. Power Del., vol. 28, no. 2, pp. 875–885, Apr. 2013.

Dynamic voltage restorer employing multilevel cascaded H-bridge inverter

ABSTRACT

This study presents design and analysis of a dynamic voltage restorer (DVR) which employs a cascaded multilevel inverter with capacitors as energy sources. The multilevel inverter enables the DVR to connect directly to the medium voltage networks, hence, eliminating the series injection transformer. Using zero energy compensation method, the DVR does not need active energy storage systems, such as batteries. Since the energy storage system only includes capacitors, the control system will face some additional challenges compared with other DVR systems. Controlling the voltage of capacitors around a reference voltage and keeping the balance between them, in standby and compensation period, is one of them. A control scheme is presented in this study that overcomes the challenges. Additionally, a fast three-phase estimation method is employed to minimise the delay of DVR and to mitigate the voltage sags as fast as possible. Performance of the control scheme and estimation method is assessed using several simulations in PSCAD/EMTDC and MATLAB/SIMULINK environments, and experiments on a 7-level cascaded H-bridge converter.

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1 DVR strcuctures

a Conventional DVR

b CHB-based DVR

EXPECTED SIMULATION RESULTS

   

Fig. 2 Three-phase voltage sag

a Network voltage

b Injected voltage by the DVR

c Load-side voltage

Fig. 3 Voltages of the DC link capacitors

Fig. 4 Unbalanced voltage sag (a 20% voltage sag on phase A)

a Source voltage

b Injected voltage by the DVR

c Load-side voltage

Fig. 5 Three-phase 20% voltage sag with voltage harmonics

a Network voltage

b Injected voltage by the DVR

c Load-side voltage

CONCLUSION

This paper presented design and performance assessment of a DVR based on the voltage sag data collected from MWPI. Using a multilevel converter, the proposed DVR was capable of direct connection to the medium voltage-level network without a series injection transformer. In addition, development of zero active power compensation technique helps to achieve voltage restoration goal just by the capacitors as energy storages. Due to internal losses of H-bridge cells and probable inaccuracies in measurements, voltage of DC link capacitors may become unequal, which prevents proper operation of the converter. A voltage control scheme, comprised of three separate controllers, was proposed in this paper for keeping voltage balance among the DC link capacitors within nominal range. A fast estimation method was also employed for calculation of phase and magnitude terms in an unbalanced three-phase system. This estimation method is able to recognise voltage sags in approximately half a cycle. Several simulations were performed in PSCAD/EMTDC environment to verify the performance of CHB-based DVR. Additionally, a laboratory-scale prototype of the proposed DVR was built and tested. Results of the experimental test also confirmed validity of the proposed control system.

REFERENCES

1 Chapman, D.: ‘The cost of poor power quality’ (European Copper Institute, Copper Development Association, 2001), March

2 Radmehr, M., Farhangi, S., Nasiri, A.: ‘Effects of power quality distortions on electrical drives and transformer life in paper industries’, IEEE Ind. Appl. Mag., 2007, 13, (5), pp. 38–48

3 Lamoree, J., Mueller, D., Vinett, P.: ‘Voltage sag analysis case studies’, IEEE Trans. Ind. Appl., 1994, 30, (4), pp. 1083–1089

4 Bollen, M.H.J.: ‘Understanding power quality problems: voltage sags and interruptions’ (New York, Saranarce University of Technology, 2000)

5 Ghosh, A., Ledwich, G.: ‘Power quality enhancement using custom power devices’ (Berlin, Kluwer Academic Publications, 2002)

DSTATCOM supported induction generator for improving power quality

ABSTRACT

This paper presents an implementation of sliding mode controller (SMC) along with a proportional and integral (PI) controller for a DSTATCOM (Distribution STATic COMpensator) for improving current induced power quality issues and voltage regulation of three-phase self-excited induction generator (SEIG). The use of SMC for regulating the DC link voltage of DSTATCOM offers various advantages such as reduction in number of sensors for estimating reference currents and the stable DC link voltage during transient conditions. The use of PI controller for terminal voltage control gives the error free voltage regulation in steady state conditions. The voltage regulation feature of DSTATCOM offers the advantages of single point voltage operation at the generator terminals with the reactive power compensation which avoids the saturation in the generator. Other offered advantages are balanced generator currents under any loading condition, harmonic currents mitigation, stable DC link voltage and the reduced number of sensors. The SMC algorithm is successfully implemented on a DSTATCOM employed with a three-phase SEIG feeding single phase or three phase loads. The performance of the proposed control algorithm is found satisfactory for voltage regulation and mitigation of power quality problems like reactive power compensation, harmonics elimination, and load balancing under nonlinear/linear loads.

SOFTWARE: MATLAB/SIMULINK

SCHEMATIC DIAGRAM:

Fig. 1 Configuration of DSTATCOM supported induction generator

a Schematic diagram of induction generator supported by VSC-based DSTATCOM

CONTROL DIAGRAM:

b Control algorithm of DSTATCOM for estimation of reference currents using SMC

with PI controller

EXPECTED SIMULATION RESULTS

Fig. 2 Simulation results of DSTATCOM

a Performance of DSTATCOM under three-phase and single-phase non-linear load

b, c Harmonic content of load current ila and generator current

 CONCLUSION

A DSTATCOM supported induction generator has been implemented with the SMC with PI control algorithm for mitigating the power quality problems and it has enhanced the active power capability of the generator. The SMC has been verified for the dynamics in the DC-link voltage and found robust and acceptably fast to avoid large variations in DC-link voltage. Moreover, from the experimental results it has been inferred that the sliding mode control with PI controller algorithm has been found capable of meeting various functionalities of DSTATCOM such as voltage regulation, source currents balancing, harmonics mitigation, and reactive power compensation.

REFERENCES

1 Bansal, R.C.: ‘Three phase self-excited induction generators: an overview’, IEEE Trans. Energy Convers., 2005, 20, (2), pp. 292–299

2 Murthy, S.S., Singh, B., Gupta, S., et al.: ‘General steady-state analysis of three-phase self-excited induction generator feeding three-phase unbalanced load/ single-phase load for stand-alone applications’, IEE Proc. Gener. Transm. Distrib., 2003, 150, (1), pp. 49–55

3 Rai, H., Tandan, A., Murthy, S.S., et al.: ‘Voltage regulation of self-excited induction generator using passive elements’. Proc. IEEE Int. Conf. Electric Machines and Drives, September 1993, pp. 240–245

4 Singh, B., Shilpakar, L.: ‘Analysis of a novel solid state voltage regulator for a self-excited induction generator’, IEE Proc. Gener. Transm. Distrib., 1998, 145, (6), pp. 647–655

5 Singh, B., Murthy, S.S., Gupta, S.: ‘A solid state controller for self-excited induction generator for voltage regulation, harmonic compensation and load balancing’, J. Power Electron., 2005, 5, (2), pp. 109–119