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International Journal of Electrical Engineering & Technology (IJEET) Volume 7, Issue 5, Sep–Oct, 2016, pp.79–88, Article ID: IJEET_07_05_008

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REDUCTION OF HARMONIC DISTORTION IN BLDC

DRIVE USING BL-BUCK BOOST CONVERTER BLDC

DRIVE

Rajesh A V, Bindu S J. and Rekha T.

Electrical and Electronics Engineering, College of Engineering Perumon/CUSAT, India.

ABSTRACT

Conventional dc motors have many attractive properties such as high efficiency and linear

torque speed characteristics. The main drawback of the dc motor is the need of periodic

maintenance. The brushes of the mechanical commutator eventually wear out and cause

undesirable effects such as sparks and acoustic noise. Brushless dc motors (BLDC) in many cases

replace conventional dc motors . This paper presents the simulation of a PFC bridgeless (BL)

buck-boost convertor fed brushless direct current motor drive and compares its performance with a

conventional boost converter drive. The speed control the BLDC motor is done by controlling the

dc link voltage of the voltage source inverter (VSI). A BLDC motor when fed by a diode bridge

rectifier (DBR)with a high value of DC link capacitor draws peaky current which causes total

harmonic distortion (THD) of the supply current in the order of 65% and power factor as low as

0.8 . A BL configuration of the buck-boost converter offers the elimination of DBR reducing the

conduction losses. The performance of the proposed model is simulated in MATLAB/Simulink

environment.

Key words: Bridgeless (BL,) diode bride rectifier (DBR), power factor corrected (PFC), total

harmonic distortion (THD), discontinuous inductor current mode (DICM).

Cite this Article: Rajesh A V, Bindu S J.and Rekha T., Reduction of Harmonic Distortion in

BLDC Drive using Bl-Buck Boost Converter BLDC Drive. International Journal of Electrical

Engineering & Technology, 7(5), 2016, pp. 79–88.

http://www.iaeme.com/IJEET/issues.asp?JType=IJEET&VType=7&IType=5

1. INTRODUCTION

BLDC Motors are actually a type of permanent magnet synchronous motors. It has a rotor with permanent

magnets and stators with windings .They are driven by dc voltage but current commutation is done by solid

state switches. The commutation instants are determined by the rotor position and the position of the rotor

is detected either by position sensors or by sensor less techniques. BLDC motors have many advantages

over conventional DC motors. Few of the advantages are long operating life, high dynamic response, high

efficiency better speed v/s torque characteristics noiseless operation higher speed range and higher torque-

weight ratio. These BLDC motors are not limited to household applications but are also used in

automotive, aerospace, consumer, medical, industrial automation equipments and instrumentation. Power

quality problems have become important issues to be considered due to recommended limit of harmonics

Rajesh A V, Bindu S J.and Rekha T.


in the supply current by various international power quality standards such as the International Electro-

technical Commission (IEC). A BLDC motor when fed by a DBR with high value of dc link capacitor

draws peaky current which leads to a THD of supply current of the order of 65% and power factor as low

as 0.8.So as to avoid the disadvantages a DBR followed by a power factor corrected converter is utilized

for improving the power quality at ac mains.

This paper attempts to study and compare the improved BL-buck boost converter fed BLDC motor

drive with the conventional boost converter drive. The comparative analysis is done using a MATLAB /

SIMULINK environment.

2. BL-BUCK BOOST CONVERTER FED BLDC MOTOR DRIVE

The parameters of the BL buck-boost converter are designed such that it operates in discontinuous inductor

mode (DCIM) to achieve an inherent power factor correction at ac mains. The speed control of BLDC

motor is achieved by the dc link voltage control of VSI using a BL buck-boost converter .This reduces the

switching losses in VSI due to the low frequency operation of VSI for the electronic commutation of the

BLDC motor. The proposed converter is shown in figure 1

Figure 1 Proposed BL Buck Boost Converter

2.1. Operating Principle of PFC Buck-Boost Converter

In the proposed drive of BL BUCK BOOST converter, switches Sw1 and Sw2 operate for the positive and

negative half cycles of the supply voltage respectively. During positive half cycle of the supply voltage,

switch Sw1, inductor Li1, diodes D1 and Dp are operated to transfer energy to dc link capacitor Cd .

Similarly, for the negative half cycle of the supply voltage, switch Sw2, inductor Li2, and diodes D2 and

Dn conducts to transfer energy to the dc link voltage . Working of the proposed converter is shown in

figure 2.

Reduction of Harmonic Distortion in BLDC Drive using Bl-Buck Boost Converter BLDC Drive


Figure 2 (a)

Figure 2 (b)

Figure 2 Shows the working of BL buck- boost converter during positive and negative half cycles

2.2. Design of Proposed BL Buck Boost Converter

�� = 2√2 × � = 2√2 × 220 ≈ 198

The voltage conversion ratio for a buck boost converter is given as

� = �� + ��

Here the proposed converter is designed for dc link voltage from 50V (Vdc min) to 200V (Vdc

max).Hence the minimum and maximum duty ratio as dmin= 0.2016 ,dmax=0.5025.

2.2.1. Design of Input Inductors (Li1 and Li2)

For the buck-boost converter, the value of Lic1 required to operate in critical conduction mode is given as,

�� = �(��)�� .

When R is the equivalent load resistance , d is the duty ratio and fs is the switching frequency. Since the converter operates even at low duty ratio in DICM , the value of Lic1 is calculated at

the worst duty ratio of dmin

�� = ��

(1 − �)�2!" = 50�

90(1 − 0.2016)�

2 × 2000 = 442.67() . The value of inductances Li1 and Li2 are taken less than 1/10th of the minimum critical value of

inductances to ensure deep DICM condition; hence the value of inductance is approximately taken as

35μH. 2.2.2. Design of DC link Capacitance (Cd)

The value of the dc link capacitor is calculated for the designed value of Vdc des,

,� = -.2/∆�� =�1 �� 2" 3

2/∆�� = 350 100⁄2 × 314 × 0.03 × 100 = 1857.7(6

Nearest possible value of dc link capacitance is selected as 2200μF



2.2.3. Design of Input Filter (Lf and Cf)

,�89 = -:28;/<�:28; tan(@) = 350220 ( 1

314 × 220√2 )tan(1°) = 401.98(6

Approximately the value of Cf is taken as 330Nf

�� = �B2C + � → 14,��!��

�B2C = 14� × 2000� × 330 × 10�E − 0.04 F 1

314G H200�350 I = 1.57J).

Finally, a low pass filter with inductor and capacitor of 1.6 mH and 330 nF is selected for this

particular application

3. SIMULATED PERFORMANCE OF THE PROPOSED BLDC MOTOR DRIVE

The proposed model is shown in figure 4. The parameters associated with the BLDC motor such as speed

(N), electro-magnetic torque (Te), and stator current (ia) are analyzed for the proper functioning of the

BLDC motor. Parameters such as supply voltage (Vs), supply current (is), dc link voltage (Vdc), inductor’s

currents (iLi1, iLi2), switch voltages (Vsw1, Vsw2), and switch currents (isw1, isw2) of the PFC BL

buck–boost converter are evaluated to demonstrate its proper functioning.

Figure 3 Block diagram of PFC BL buck boost converter fed BLDC motor drive

4. RESULT ANALYSIS

The simulation of the proposed BL buck boost converter is performed in MATLAB 2014/simulink.



4.1. Steady State Performance of Proposed Drive

The performance of the proposed converter BLDC motor drive at speed control by varying dc link voltage

from 50 to 200 V is tabulated in Table I. The harmonic spectra of the supply current at rated and light load

conditions, i.e., dc link voltages of 200Vand 50 V, are also shown in figure 4.

Table 1 Variation of PF & THD with varying dc link voltage

Vdc

(v)

N

(rpm)

THD of

Is(%)

PF

50 372 4.65 0.9776

100 850 4.32 0.9794

150 1425 3.85 0.9803

200 1528 3.99 0.9813

Figure 4 (a)

Figure 4 (b)

Figure 4 Harmonic spectra of supply current at rated supply voltage and rated loading on proposed BLDC motor

drive for a dc link voltage of (a) 200v and (b) 50v



4.2. Performance of Proposed Drive under Supply Voltage Variation

The performance of the proposed drive is evaluated under different supply voltage (90 & 270). Figure 5 (

a) and (b) shows the harmonic spectra of supply current at ac mains at rated conditions of dc link voltage

and load on the BLDC motor with supply voltage as 90 and 270 V, respectively. It is obtained that for 90v

supply THD is 3.98 and for 270V it is 4.00.

Figure 5 (a)

Figure 5 (b)

Figure 5 Harmonic spectra of supply current at rated loading on proposed BLDC motor drive with dc link voltages

as 200V and supply voltages as (a) 90v and (b) 270v

Figure 6 waveform showing current in switches (Q1&Q), diodes (d1&d2), inductor (L1&L2)



Figure 7 Waveform showing THD analysis of BLDC drive under rated condition using BL Buck Boost Converter

Table 2 Comparison between conventional and proposed system

4.3. Obtained Simulated Result

From the simulation of the proposed BL-Buck boost converter, it is obtained that the power factor and

THD shows a great improvement than conventional BLDC drives. The corresponding waveforms of the

proposed drive are shown in figure 6. The THD analysis of the proposed drive is shown in figure 7.

5. HARDWARE VALIDATION OF PROPOSED BLDC MOTOR DRIVE

The control section for the proposed drive is developed by using an ATMEGA 16 microcontroller. The

necessary circuitry for isolation between controller and gate drivers of solid-state switches is developed

using the TLP 250 IC’s. A pre-filtering and isolation circuit for the Hall-Effect sensor is also developed for

sensing the Hall-effect position signals. Test results are discussed in the following sections.

5.1. Steady State Performance

The performance of the proposed drive is evaluated with the experimental setup developed as shown in

figure 8.The output waveforms from different sections such as drivers, controllers, synchronizers and

inverters where taken. These are shown under figure

S L NO:

TOPOLOGIES POWER FACTOR THD

(%)

1.

2.

3.

4.

Bridged Boost Converter Drive

Bridged Buck Boost Converter Drive

Bridgeless Boost Converter Drive

BL-Buck Boost Converter Drive

0.74

0.83

0.92

0.98

90.85

64.81

43.59

3.86



Figure 8 Experimental setup

Figure 9 Pulses to inverter complimentary switches 180 phase shift (A-A’)

Figure 10 Pulses to adjacent inverter switches 60 Phase shift (A, B)



Figure 11 Output of inverter

Figure 12 (a)

Figure 12 (b)

Figure 12 Waveforms showing pulses to converter switches (Sw1 & Sw2)



6. CONCLUSION

The performance of the PFC BL buck boost converter has been evaluated both simulation and hardware

wise. The proposed drive is evaluated under variation of different motor load, dc link voltages and supply

voltage variations. The proposed drive is compared with the conventional BLDC drive using boost

converter. The results show that the PFC BL buck boost converter BLDC drive has a greater efficiency

than the conventional drive. There is a greater improvement in supply current and hence PF compared to

conventional drive. It is a recommended solution applicable to low power BLDC motor drives.

REFERENCE

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IEEE Transactions On Industrial Electronics, Vol. 61, No. 6, June 2014

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[7] B. Singh, B. N. Singh, A. Chandra, K. Al-Haddad, A. Pandey, and D. P. Kothari, “A review of single-

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[8] Ansia Assis and Saritha Sathyan, High Step up Boost Converter Based Micro Inverter with MPPT and

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