CARRIER BASED HYBRID PWM ALGORITHM WITH REDUCED COMMON MODE VOLTAGE FOR THREE PHASE VOLTAGE SOURCE INVERTER FED INDUCTION MOTOR DRIVES

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1 INERNAIONAL JOURNAL OF ELECRICAL ENGINEERING & ISSN Online olume 6, Iue, January 05, pp. 0- IAEME ECHNOLOGY IJEE ISSN Print ISSN Online olume 6, Iue, January 05, pp. -8 IAEME: Journal Impact Factor 04: 6.80 Calculated by GISI IJEE I A E M E CARRIER BASED HYBRID PWM ALGORIHM WIH REDUCED COMMON MODE OLAGE FOR HREE PHASE OLAGE SOURCE INERER FED INDUCION MOOR DRIES Pradeep B Jyoti, Dr. J Amarnath, Dr. Subba Rayadu, Dept. of Electrical & Electronic Engineering, R.Y.M Engineering College, Bellary, Karnataka, India, Dept. of Electrical & Electronic Engineering, JNUH College of Engineering, Hyderabad, Andhrapradeh, India Dept. of Electrical & Electronic Engineering, G. Pulla Reddy Engineering College, Kurnool, Andhrapradeh, India ABSRAC hi paper propoe a imple carrier baed hybrid PWM algorithm HPWM to mitigate the common mode voltage CM variation. hough the pace vector PWM SPWM give, it reult in large CM value. Hence, to reduce the CM and complexity, which i involved in the SPWM technique, thi paper preent imple calar baed PWM technique. By adding the zero equence voltage to the phae voltage, the modulating ignal are derived for the active zero tate PWM AZSPWM technique. Alo, to reduce the harmonic ditortion further, a HPWM technique i preented baed on the concept of the tator flux ripple. A the propoed AZSPWM and HPWM technique do not ue zero tate, the CM variation can be minimized from ± dc to ± dc 6 when compared with the SPWM algorithm. o evaluate the propoed algorithm imulation tudie have been carried on v/f controlled induction motor drive and the reult are preented. Index erm: AZSPWM, common mode voltage, SPWM, vector control

2 ISSN Online olume 6, Iue, January 05, pp. -8 IAEME I. INRODUCION he Pule width Modulated oltage Source Inverter PWMSI fed ariable Speed Drive are increaingly ued in many application. A detailed urvey of newly developed PWM algorithm which are different in concept and performance are decribed in []. Compared with the inuoidal modulation, the PWM method baed on the voltage pace vector reult in reduced harmonic ditortion and excellent dc bu utilization []. In SPWM, baed on the magnitude of the reference voltage the witching time are calculated. hough thi algorithm give out uperior waveform quality, it give more witching loe and harmonic ditortion at higher modulation indice. In order to obtain uperior waveform quality at higher modulation indice, the Dicontinuou PWM DPWM technique are propoed [-4]. But, at all modulation indice SPWM and DPWM algorithm give large amount of Common Mode oltage CM variation between ± dc due to the preence of zero tate. Moreover, with the increae in CM, the Common Mode Current CM flow through the winding which caue bearing problem and early mechanical failure of the machine [5]. In the traditional day, the effect of CM and CMC i reduced uing paive and active filter which are explained in detail in [6]. But, an active and paive filter require power electronic converter, inductor and capacitor which increae the cot and require additional hardware. In the recent year, many reearcher are focuing their interet on the development of variou reduced CM PWM algorithm without the requirement of additional equipment [7-8]. hi paper firt preent a imple pace vector approach for the generation of different PWM technique uch a SPWM, AZSPWM, NSPWM and DPWM algorithm. hen, by utilizing the concept of tator flux ripple, the rm tator flux ripple characteritic are plotted, from which finally Hybrid PWM algorithm HPWM technique uing flux ripple are preented with reduced common mode voltage and leer harmonic ditortion. II. PROPOSED AZSPWM ALGORIHMS A. Principal of Carrier Comparion Approach olt-second balance i the mot commonly ued principle for all the PWM algorithm. According to thi principle, the generation of the required reference voltage ha to be done within a ampling time period. he principle of the carrier comparion approach involve the comparion of the triangular carrier ignal with the modulating ignal of a, b, c phae. he interection point of both the waveform give the witching intant of the witche. Out of the two witche of each leg of the inverter, at any intant either the top or bottom witch will conduct. he derivation of the fundamental output voltage depend on hape of modulating ignal. In a inuoidal PWM SPWM technique, three inuoidal ignal, which are hifted by 0o are compared with a common triangular ignal for the generation of gating pule. hi technique i mot commonly ued for variable peed drive application. But, the line current in SPWM algorithm give more harmonic ditortion. In a -phae SI with iolated neutral point of the load, the voltage between the neutral point and midpoint of the dc bu no, which i alo known a CM a hown in Fig. can be varied freely. 4

3 ISSN Online olume 6, Iue, January 05, pp. 0- IAEME Fig. wo-level inverter fed induction motor drive In order to maintain the contant poition of the pule, a zero equence voltage can be added to the inuoidal ignal which do not affect the average value of the line voltage. But, due to the change in the pule poition, witching frequency characteritic and the harmonic propertie will be affected. B. Propoed Scalar Approach he claical pace vector approach which i explained in [] require the ector and angle information which increae the calculation burden. For implicity, a imple calar carrier approach i preented in thi paper. So, in the propoed approach, the calculation of zero equence ignal i carried out uing voltage magnitude tet. hen, the modulating ignal are generated by adding the zero equence ignal to the reference phae voltage. he et of intantaneou reference phae voltage can be aumed a θ - r - in ref co for i a, b, c and r,, he calculated unique zero equence ignal z baed on the voltage magnitude tet i given in. dc z ko k omax ko min he maximum and minimum value of in are repreented a max and min. By adding thi zero equence ignal to the in the modulating wave *in are derived a given in. * in in z k he variation of the contant o between 0 and, the modulating ignal for variou PWM technique can be generated. In thi paper, the main demontration i regarding AZSPWM algorithm due to the abence of zero tate in the witching equence. But the modulating k waveform of SPWM and AZSPWM are imilar due to which the contant o value i fixed a 0.5. In general carrier approach, the generated modulating waveform are compared with a common triangular waveform to generate the pule pattern. But, AZSPWM algorithm require, two triangular ignal tri and tri which are in phae oppoition with each other. hen, by changing the polarity of the triangular ignal different AZSPWM algorithm uch a AZSPWM, AZSPWM 5

4 ISSN Online olume 6, Iue, January 05, pp. -8 IAEME and AZSPWM can be generated. he following procedure can be ued to change the polarity of the carrier ignal. he generation of for AZSPWM, AZSPWM and AZSPWM technique involve the three et of -phae voltage are aumed a given in 4-6 repectively. hee ignal are ued a tet ignal for the comparion with triangular wave. θ - r - ix ref co for i a, b, c and r,, iy θ - r - / ref co for i a, b, c and r,, 4 5 iz θ - r - ref co for i a, b, c and r,, 6 he change in polarity of carrier ignal depend on the region. For all AZSPWM algorithm, the correponding modulating ignal of that phae will be compared with the tri if the lope of the correponding tet ignal i poitive. Similarly, if the lope of the tet ignal i negative then the modulating ignal of that phae will be compared with the -tri. After oberving the obtained pule pattern, the equence of AZSPWM are hown in table.. Alo, the propoed calar approach i a hown in Fig. Fig. Propoed calar approach ABLE I. REGION DEPENDEN SWICHING SEUENCES FOR ARIOUS AZSPWM ALGORIHMS Sector AZSPWM AZSPWM AZSPWM

5 ISSN Online olume 6, Iue, January 05, pp. 0- IAEME III. PROPOSED HYBRID PWM ALGORIHM A. Analyi of Stator Flux Ripple he meaurement of the waveform quality generated by a PWM inverter i defined a the total harmonic ditortion HD of a line current. It i given by I IHD I n I n 8 where, I I and n are the rm value of the fundamental and the nth harmonic component of the noload current repectively. All the AZPWM method maintain volt-econd balance to generate a voltage pace vector, which equal to reference pace vector in an average ene. he difference between the applied voltage vector and reference voltage i the ripple voltage vector. he error volt-econd correponding to ripple voltage vector can be developed a given in []. For the AZPWM equence the d-axi tator flux ripple component are given in term of D,P,S and R and q-axi tator flux ripple component are given in term of,,, 5, 7, which are defined a -5 and 6- are common for all the equence. he ripple voltage vector and trajectory of the tator flux ripple for AZSPWM equence are hown in Fig.. he correponding d-axi and q-axi component of the tator flux ripple vector are a hown in Fig. 4. Here,, z are the witching time of the voltage vector,, and zero voltage vector. Fig. oltage ripple vector and trajectory of the flux ripple 7

6 ISSN Online olume 6, Iue, January 05, pp. -8 IAEME Fig. 4 q-axi and d-axi component of the flux ripple vector for AZSPWM he error volt-econd correponding to the ripple voltage vector for AZSPWM-I are a follow: in α j α rip dc dc co ref 0 0 rip dc in 60 α j dc co 60 α ref 0 0 rip Z dc in 60 α Z j dc co 60 α ref Z 0 0 rip6 Z dc in 60 α Z j dc co 60 α ref Z D j D j P j P j Fig. 5 voltage ripple vector and trajectory of the flux ripple for AZSPWM-II 8

7 ISSN Online olume 6, Iue, January 05, pp. 0- IAEME Fig. 6 q-axi and d-axi component of the flux ripple vector for AZSPWM-II Similarly, the error volt-econd correponding to ripple voltage vector of AZPWM equence are given in -4. rip Z dc in α Z j dc co α ref Z rip 4 Z dc in α Z j co α ref Z S j 7 S j 7 4 Fig. 7 voltage ripple vector and trajectory of the flux ripple for AZSPWM-III 9

8 ISSN Online olume 6, Iue, January 05, pp. -8 IAEME Fig. 8 q- and d-axi component of the flux ripple vector for ABCPWM-II he error volt-econd correponding to ripple voltage vector of AZPWM equence are given in rip Z dc in60 α Z j dc co60 α ref Z R j 5 0 co60 0 rip5 Z in60 α j dc Z α dc ref Z R j 5 6 From the active tate witching time of claical SPWM algorithm, the following expreion can be derived 0 in60 α * M 0.5 co α * M co60 0 α * 0.5 * M 0 in60 α * M * co60 α * M 0 dc D M dc R M

9 ISSN Online olume 6, Iue, January 05, pp. 0- IAEME dc P M 4 M dc S M ref dc M ref dc 7 M ref dc 8 6 M ref dc M ref dc M ref dc he total rm ripple over a ubcycle can be calculated a given in dt dt q d rm 0 0 he rm tator flux ripple for different equence are derived a hown in -5 D P D P z P z z F z D S D S z S z F. * 7 * 7 * 7 0.5*. 7 7 * 7 0.5* 4 4 z D R D R z R z F. * * * 0.5 *. * 0.5 * 5 5

10 ISSN Online olume 6, Iue, January 05, pp. -8 IAEME hu, the rm tator flux ripple characteritic can be obtained for all the witching equence. he tator flux ripple characteritic at a frequency of 45 Hz modulation index of are hown in Fig. 7. From the ripple characteritic it i found that the AZSPWM-II and AZSPWM-III will give the ame ripple characteritic. Hence, in the propoed hybrid AZSPWM HAZSPMW algorithm AZSPWM-I and AZSPWM-III are conidered. Baed on the ripple characteritic, the zone of uperior performance which reult in reduced ripple can be found for each equence. hen, the identified equence will be applied to the SI, o that the harmonic ditortion can be reduced at all modulation indice. Fig. 9 RMS tator flux ripple variation of AZSPWM algorithm at a upply frequency of 45 Hz III. SIMULAION RESULS AND DISCUSSION o prove the performance of propoed HPWM algorithm, the imulation tudie have been carried out on v/f controlled induction motor drive by uing the MALAB. he witching frequency i taken a 5 khz. he teady tate reult during the no-load condition at a modulation index of 0.85 operating upply frequency of 45 Hz are hown in From Fig. 8 to Fig. along with the harmonic pectra of line current and CM variation. a

11 ISSN Online olume 6, Iue, January 05, pp. 0- IAEME b c Fig. 0 a teady tate plot for SPWM algorithm baed v/f controlled induction motor drive b Harmonic pectra of line current c CM variation a

12 ISSN Online olume 6, Iue, January 05, pp. -8 IAEME b c Fig. a teady tate plot for AZSPWM algorithm baed v/f controlled induction motor drive b Harmonic pectra of line current c CM variation a 4

13 ISSN Online olume 6, Iue, January 05, pp. 0- IAEME b c Fig. a teady tate plot for AZSPWM algorithm baed v/f controlled induction motor drive b Harmonic pectra of line current c CM variation a 5

14 ISSN Online olume 6, Iue, January 05, pp. -8 IAEME b c Fig. a teady tate plot for AZSPWM algorithm baed v/f controlled induction motor drive b Harmonic pectra of line current c CM variation a 6

15 ISSN Online olume 6, Iue, January 05, pp. 0- IAEME b c Fig. 4 a teady tate plot for propoe HPWM algorithm baed v/f controlled induction motor drive b Harmonic pectra of line current c CM variation I. SIMULAION RESULS AND DISCUSSION o reduce the complexity of the PWM algorithm, a implified calar baed approach ha been preented in thi paper. Moreover, to reduce the harmonic ditortion further, a HPWM algorithm i developed by uing the tator flux ripple concept. he propoed HPWM technique elect a uitable equence that reult in reduced harmonic ditortion. o evaluate the performance of the propoed HPWM algorithm, imulation tudie have been carried out and reult were preented. From the reult it can be oberved that the propoed HPWM algorithm give reduced CM variation ± 6 between dc with lightly increaed ripple when compared to the SPWM technique due to the oppoite pule in the line to line voltage.. REFERENCES. Joachim Holtz, Pule width modulation A urvey IEEE ran. Ind. Electron., vol. 9, no. 5, Dec 99, pp Heinz Willi ander Broeck, Hna-Chritoph Skudelny and Georg iktor Stanke, Analyi and realization of a pulewidth modulator baed on voltage pace vector IEEE ran. Ind. Applicat., vol. 4, no., Jan/Feb 988, pp Ahmet M. Hava, Ruel J. Kerkman and homa A. Lipo, Simple analytical and graphical method for carrier-baed PWM-SI drive IEEE ran. Power Electron., vol. 4, no., Jan 999, pp

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