Novel Approach Employing Buck-Boost Converter as DC-Link Modulator and Inverter as AC-Chopper for Induction Motor Drive Applications: An Alternative to Conventional AC-DC-AC Scheme

 

ABSTRACT:

Induction motor (IM) is the workhorse of the industries. Amongst various speed control schemes for IM, variable-voltage variable-frequency (VVVF) is popularly used. Inverters are broadly used to produce variable/controlled frequency and variable/controlled output voltage for various applications like ac machine drives, switched mode power supply (SMPS), uninterruptible power supplies (UPS), etc. This paper presents the two-fold solution of control for such loads. In this novel solution, rms values of output voltage is varied by controlling the inverter duty ratio which operates as an ac chopper, while the fundamental frequency of output voltage is varied by controlling the buck-boost converter according to the reference frequency given to it. The buck-boost converter shuffles between buck-mode and boost-mode to produce required frequency by generating the modulated dc-link for the inverter, unlike conventional fixed dc-link in case of ac-dc-ac converters. The proposed technique eliminates over modulation (as in conventional pulse width modulated inverters) and hence the non-linearity, and lower order harmonics are absent. Further, it reduces dv/dt in the output voltage resulting less stress on the insulation of machine winding, and electromagnetic interference. However, the proposed scheme demands more number of power semiconductor devices as compared to their conventional ac-dc ac counterparts. Simulation studies of proposed single-phase as well as three-phase topologies are carried out in MATLAB/Simulink. Hardware implementation of proposed single-phase topology is done using dSPACE DS1104 R&D controller board and results are presented.

KEYWORDS:

  1. Ac-chopper
  2. Buck-boost converter
  3. Dc-link modulation
  4. Inverter
  5. Variable-voltage variable-frequency
  6. V/f  induction motor drive

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Block diagram for the proposed topology.

EXPECTED SIMULATION RESULTS:

 

 (a) Plot of output voltage (rms) of inverter v/s duty ratio.

 

(b) Output voltage waveform of the proposed inverter: [X-axis: 1 div. = 0.01 s, Y-axis: 1 div. = 100 V].

(c) Output voltage of conventional inverter for unipolar SPWM: [X-axis: 1 div. = 0.01 s, Y-axis: 1 div. = 100 V].

(d) FFT plot of the output voltage with the proposed topology.

(e) FFT plot of output voltage with unipolar SPWM inverter.

Fig. 2. Analysis of the proposed topology.

 

(a) Output voltage of the proposed topology: [X-axis: 1 div. = 0.01 s, Y-axis:

1 div. = 50 V].

(b) Comparison of reference voltage and input voltage (upper trace), comparison of reference voltage and output voltage (lower trace) of buck-boost converter Upper trace: [X-axis: 1 div. = 0.01 s, Y-axis: 1 div. = 100 V] Lower trace: [X-axis: 1 div. = 0.01 s, Y-axis: 1 div. = 50 V].

(c) Output voltage and reference voltage of buck-boost converter at f=10 Hz,

f=20 Hz, f=25 Hz: [X-axis: 1 div. = 0.01 s, Y-axis: 1 div. = 100 V].

(d) Output voltage and reference voltage of buck-boost converter at f=30 Hz,

f=40 Hz, f=50 Hz: [X-axis: 1 div. = 0.01 s, Y-axis: 1 div. = 100 V].

Fig. 3 Simulation results of the proposed buck-boost converter.

(b) Gate pulses of MOSFETs M2 and M3, Comparison of input voltage and reference voltage, Gate pulses M1, M2, M3: [X-axis: 1 div. = 0.002 s, Y-axis: 1 div. = 1 V], Voltage: [X-axis: 1 div. = 0.002 s, Y-axis: 1 div. = 100 V].

(c) Output voltage waveforms of buck-boost converter without La Output voltage of buck-boost converter and reference voltage with La: [X-axis: 1 div. = 0.02 s, Y-axis: 1 div. = 50 V], Output voltage of inverter with La: [Xaxis: 1 div. = 0.02 s, Y-axis: 1 div. = 100 V].

(d) Output voltage of buck-boost converter and inverter and inverter with La Blue color: Reference voltage, Green color: Actual output voltage of buckboost converter, Output voltage of buck-boost converter and reference voltage without La: [X-axis: 1 div. = 0.02 s, Y-axis: 1 div. = 50 V], Output voltage of inverter without La: [X-axis: 1 div. = 0.02 s, Y-axis: 1 div. = 100 V].

Fig. 4 Results for improving output voltage of inverter.

(b) Pole voltage of phase A and output of buck-boost converter compared with reference voltage of three-phase system Blue color: Reference voltage Green color: Actual output voltage of buck-boost converter for three-phase Pole voltage of phase A: [X-axis: 1 div. = 0.05 s, Y-axis: 1 div. = 50 V] Output voltage of buck-boost converter of phase A: [X-axis: 1 div. = 0.05 s,

Y-axis: 1 div. = 50 V].

Fig. 5 Simulation result of proposed three-phase topology.

CONCLUSION:

Relation between fundamental output voltage (rms) and duty ratio of switches of ac chopper operating as inverter is linear. So, on increasing the duty ratio of pulses given to switches, output voltage of inverter increases linearly. To get 100 % inverter output voltage, no need to go in over modulation region, which eliminates the non-linearity. The profile of output voltage of inverter (with chopping depending on the duty ratio of its switches) is sinusoidal because of modulated dc-link provided by the buck-boost converter, which reduces lower order harmonics, and %THD. It also reduces dv/dt as envelope of output voltage is sinusoidal as full dc-link voltage is not switched. This reduction in dv/dt reduces the stresses on the enameled copper wire of the stator winding of the motor. It will reduce the inter-turn short circuit failure of stator winding. Also this reduction of dv/dt will reduce the electromagnetic interference generated by the inverter in the drive system. In the proposed scheme, output voltage of buck-boost converter follows the reference voltage very closely for different frequencies, so when reference voltage is greater than input voltage, converter has to operate in boost mode else operates in buck mode. Hardware implementation of proposed single phase scheme is carried out. The hardware results have very close resemblance with the simulation results. The proposed concept is novel, and with appropriate refinements, can offer new era of control of inverter for V/f three-phase induction motor drive applications. However, it demands more number of power semiconductor devices compared to that needed for the conventional ac-dc-ac approach.

REFERENCES:

[1] Jose Thankachan, and Saly George, “A novel switching scheme for three phase PWM ac chopper fed induction motor,” in Proc. IEEE 5th India International Conference on Power Electronics (IICPE), pp. 1-4, 2012.

[2] Amudhavalli D., and Narendran L., “Speed control of an induction motor by V/f method using an improved Z-source inverter,” in Proc. International Conference on Emerging Trends in Electrical Engineering and Energy Management (ICETEEEM), pp. 436-440, 2012.

[3] G. W. Heumann, “Adjustable frequency control of high-speed induction motors,” Electrical Engineering, vol. 66, no. 6, pp. 576-579, June 1947. [4] Mineo Tsuji, Xiaodan Zhao, He Zhang, and Shinichi Hamasaki, “New simplified V/f control of induction motor for precise speed operation,” in Proc. International Conference on Electrical Machines and Systems (ICEMS), pp. 1-6 , 2011.

[5] V. K. Jayakrishnan, M. V. Sarin, K. Archana, and A. Chitra, “Performance analysis of MLI fed induction motor drive with IFOC speed control,” in Proc. Annual IEEE India Conference (INDICON), pp. 1-6, 2013.

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,” 2nd 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.

Diode Clamped Three Level Inverter Using Sinusoidal PWM

 

ABSTRACT:

An inverter is a circuit which converts dc power into ac power at desired output voltage and frequency. The ac output voltage can be fixed at a fixed or variable frequency. This conversion can be achieved by controlled turn ON & turn OFF or by forced commutated thyristors depending on applications. The output voltage waveform of a practical inverter is non sinusoidal but for high power applications low distorted sinusoidal waveforms are required. The filtering of harmonics is not feasible when the output voltage frequency varies over a wide range. There is need for alternatives. Three level Neutral Point Clamped inverter is a step towards it.

KEYWORDS:

  1. Harmonics
  2. Inverter
  3. THD
  4. PWM

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Figure1.Diode clamped three level inverter

EXPECTED SIMULATION RESULTS:

 

 Figure2. Upper triangular pulse width modulation

Figure3. lower triangular pulse width modulation

Figure4. three level voltage waveform

Figure5.Matlab model of three level inverter feeding induction motor

 Figure 6. stator waveform of three level inverter

 CONCLUSION:

In normal inverters odd harmonics are present which causes distortion of the output waveform. By using the “THREE LEVEL DIODECLAMPED INVERTER” we can eliminate some number of harmonics hence increasing the efficiency of the inverter.

 REFERENCES:

[1] A.Mwinyiwiwa, Zbigneiw Wolanski, ‘Microprocessor Implemented SPWM for Multiconverters with Phase-Shifted Triangle Carriers’ IEEE Trans. On Ind. Appl., Vol. 34, no. 3, pp 1542-1549, 1998.

[2] J. Rodriguez, J.S. Lai, F. Z. Peng, ’ Multilevel Inverters: A Survey of Topologies, Controls and Applications’, IEEE Trans. On Ind. Electronics, VOL. 49, NO. 4, pp. 724-738, AUGUST 2002

[3] D. Soto, T. C. Green, ‘A Comparison of High Power Converter Topologies for the Implementation of FACTS Controller’, IEEE Trans. On Ind. Electronics, VOL. 49, NO. 5, pp. 1072-1080, OCTOBER 2002.

[4] Muhammad H. Rashid, Power Electronics: Circuits, Devices and Applications, Third edition, Prentice Hall of India, New Delhi, 2004.

[5] Dr. P. S. Bimbhra, Power Electronics, Khanna Publishers, Third Edition, Hindustan Offset Press, New Delhi-28, 2004.

Simulation Analysis of SVPWM Inverter Fed Induction Motor Drives

ABSTRACT:

In this paper represent the simulation analysis ofspace vector pulse width modulated(SVPWM) inverter fedInduction motor drives. The main objective of this paper isanalysis of Induction motor with SVPWM fed inverter and harmonic analysis of voltages & current. for control of IMnumber of Pulse width modulation (PWM) schemes are used tofor variable voltage and frequency supply. The most commonlyused PWM schemes for three-phase voltage source inverters(VSI) are sinusoidal PWM (SPWM) and space vector PWM(SVPWM). There is an increasing trend of using space vectorPWM (SVPWM) because of it reduces harmonic content involtage, Increase fundamental output voltage by 15% & smoothcontrol of IM. So, here present Modeling & Simulation ofSVPWM inverter fed Induction motor drive inMATLAB/SIMULINK software. The results of Total HarmonicDistortion (THD), Fast Fourier Transform (FFT) of current areobtained in MATLAB/Simulink software.

KEYWORDS:

  1. Inverter
  2. VSI
  3. SPWM
  4. SVPWM
  5. IM drive

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

  Figure 1.Simulation Block Diag. of SVPWM Three level inverter with IM load

EXPECTED SIMULATION RESULTS:

 

Figure 2 Inverter Line voltage

Figure 3 Inverter Line currents

Figure 4 Stator Current

Figure 5 Rotor Current

Figure 6 Mechanical Speed

Figure 7 Torque

Figure 8 Harmonic (FFT) Analysis of Line current

 CONCLUSION:

The SVPWM Inverter fed induction motor driveModeling & then simulation is done in MATLAB/SIMULINK 12. From simulation results of THD & FFT analysis concluded that SVPWM technique is better overall PWM techniques which gives less THD in Inverter current 4.89%., which under the permissible limit.

 REFERENCES:

[1] A. R. Bakhshai H. R. Saligheh Rad G. Joos, space vectormodulation based on classification method in three-phasemulti-level voltage source inverters, IEEE 2001

[2] Bimal K Bose, modern power electronics and ac drives © 2002Prentice hall ptr.

[3] Dorin O. Neacsu, space vector modulation –An introductiontutorial at IECON2001 IEEE 2001

[4] Fei Wang, Senior Member, “Sine-Triangle versus Space-VectorModulation for Three-Level PWM Voltage-Source Inverters”,IEEE transactions on industry applications, vol. 38, no. 2,March/April 2002. The 27th Annual Conference of the IEEEIndustrial Electronics Society

[5] F. Wang, Senior, Sine-Triangle vs. space vector modulation forthree-level voltage source inverters ,IEEE 2000