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INTERNATIONAL JOURNAL OF PROFESSIONAL ENGINEERING STUDIES Volume IV /Issue 5 / FEB 2015

IJPRES

ANALYSIS OF A DUAL BUCK CONVERTER FED FOUR-QUADRANT DC DRIVE FOR

IMPROVING POWER QUALITY

M. Lakshmi Narayana

K.O.R.M.C.E, kadapa, email: [email protected]

C. Subbarami Reddy

K.S.R.M.C.E, kadapa, email: [email protected]

Abstract: The four-quadrant DC drive operation is well established, however, the increased use of the existing at same time to improved power quality AC-DC converters (IPQC’s). In this paper the performance of the separately excited dc machine fed by a single-phase, symmetrical multipulse modulated, improved power quality, dual AC-DC buck converter is investigated from the power quality in each quadrant of operation. The Symmetrical Multi pulse Modulation (SMM) technique is adopted; where in several equidistant pulses per half cycle (M) are used to obtain an output voltage that can be continuously varied by varying the duty cycle (δ) of the pulses. The technique continues to evoke interest as it is relatively less complex and, therefore, easy to implement. The armature control method of the dc machine that provides constant torque operation is undertaken in both clockwise and anticlockwise directions in the motoring and generating modes. The simulation based performance evaluation of the drive indicate that the proposed drive has potential for better values of Total Harmonic Distortion (THD), use of economical and compact filters apart from energy saving. Keywords: Dual converter, Improved Power Quality AC-DC Converter (IPQC), Symmetric Multi-pulse Modulation (SMM), total harmonic distortion (THD) I. INTRODUCTION

Solid state ac/dc conversion of electric power is widely used in a variety of industry and other applications, such as Adjustable-Speed Drives (ASDs), Switch-Mode Power Supplies (SMPSs), Uninterrupted Power Supplies (UPSs) etc. Moreover, these converters are also used in utility Interface with nonconventional energy sources such as solar PV, etc., Battery Energy Storage Systems (BESSs), in process technology such as electroplating, separately excited DC machine based drive is chosen to

welding units, etc. [1],[2]. Traditionally solid state ac/dc converters are designed using diodes and thyristors to provide controlled and uncontrolled unidirectional and bi-directional AC/DC power conversion. They have problems of injected current harmonics, resultant voltage distortion and poor power factor at input ac mains and a rippled dc output at load end, low efficiency, and large size of ac and dc filters. In view of stringent requirements of power quality at the ac mains [3],[4] and their increased applications, a new breed of converters have been emerged using new solid-state self-commutating devices such as MOSFETs, IGBTs, GTOs, etc. Such converters are classified as boost, buck, buck-boost, multilevel and multi-pulse ac-dc converters and are referred to as improved power quality converters (IPQCs) [5], [6].

IPQC technology has matured at a reasonable level for

AC-DC conversion with reduced harmonic currents, high power factor, low electromagnetic interference (EMI) and Radio Frequency Interference (RFI) at input ac mains and well-regulated and good quality dc output to feed loads ranging from fraction of kW to MW power ratings.

The symmetrical multipulse modulation (SMM) [2] technique is adopted, wherein; several equidistant pulses per half cycle (M) are used to obtain an output voltage that can be continuously varied by varying the duty cycle (δ) of the pulses. The technique continues to evoke interest [9]-[10] as it is relatively less complex and, therefore, easy to implement. The exploit the advantages.

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Fig.1.Improved power quality, single-phase, dual ac-dc buck converter fed four-quadrant, armature controlled, separately

excited dc machine drive

armature and excitation electromagnetic systems including better dynamic response, better stability, etc. The circuit diagram of the proposed four-quadrant drive is shown in Fig.1. It comprises the dual buck converter that is essentially inverse-parallel connection of two bi-directional buck converters that has the single-phase source connected to the ac side via a step up transformer, TR, and the armature winding, A1A2, of the DC machine connected to the dc side. II. TOPOLOGICAL CONSIDERATIONS: DUAL BUCK

CONVERTER

The power semiconductor switches, employed in the dual AC-DC buck converters, are GTOs at higher power ratings and transistors at low power ratings with high switching frequency. The use of transistors viz. BJTs, MOSFETs andIGBTs necessitate a series diode with every transistor to provide the reverse voltage blocking capability. This two device combination comprising series connection of atransistor and a diode constitutes a two-quadrant switch (2QSW) with controllable turn-on and turn-off of unidirectional current and bi-directional voltage blocking capability. The diodes have to be of the fast recovery type to ensure that the low turn-on and turn-off times characteristic of the IGBTs are not compromised. The series diodes apart from providing the bipolar blocking ability to the transistors also ensure that the relevant IGBTs alone are effective in a particular half cycle.

In the circuit shown in Fig. 1, there are two sets of devices (I and II), each set comprising four 2QSWs (IGBT and diode in series) constitutes a bi-directional buck converter. The four 2QSWs of set I are – M1D1, M2D2, M3D3, that are inherent to decoupling between the M4D4, and those of set II are – M1’D1’, M2’D2’, M3’D3’, M4’D4’. It is clear from the Fig. that converter topology comprising the two sets of 2QSWs is simply the inverse-connection of two bidirectional buck converters and is, hence, referred to as dual buck converter. From Fig. 1 it is apparent that there are four combinations of two 2QSWs in inverse-parallel in the dual buck converter. Each inverse-parallel connection of 2QSWs constitutes a four-quadrant switch (4QSW) that can provide controllable turn-on and turn-off of bi-directional current and bi-directional voltage blocking. The topology can, therefore, also be construed to be one with four 4QSWs and two limbs, with each limb having two 4QSWs. In Fig. 1, E = Induced e.m.f. in the armature and DFW = Freewheeling diode. III. PWM TECHNIQUE IN THE SINGLE-PHASE DUAL

AC-DC BUCK CONVERTER

The operation of the dual buck converter in the rectification or inversion mode, corresponding to the dc machine functioning in the motoring or generating mode respectively, and in a particular quadrant in the speed-torque plane, shown in Fig. 2, is determined by the conditioning of the switching states of the IGBTs of the two sets (I and II) of devices.

Fig 2.speed-torque plane with the fourquadrants demarcated

TABLE I

CONDITIONING OF SWITCHING STATES OF THE TWO SETS OF IGBTS IN THE DUAL BUCK CONVERTER CONDITIONING OF SWITCHING STATES OF THE TWO SETS OF IGBTS IN THE DUAL BUCK CONVERTER

Mode

Converter operation

Set I

IGBTs(M1,M2,M3,M4)

Set I

IGBTs(M1,M2,M3,M4)

Armature winding

(A1,A2)connection & other criterion

Motoring

rectificatio

n

SMM switching pattern A

OFF

A1to P, A2 to N

SMM switching

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rectification

OFF pattern A display 1800

A1to P, A2 to N, reverse DFW.

Generating

inversion


A display 1800

OFF

A2to P, A1 to N, |E|> amplitude of H.V. winding voltage, reverse

DFW.

inversion

OFF


A2to P, A1 to N, |E|> amplitude of H.V. winding voltage.

Fig.3. Gate signals (switching pattern A) of the set I IGBTs, as per SMM technique with M = 6 and δ = 0.8, for I quadrant operation of dc drive. Fig2The various parameters indicated are as follows:

TL = Load (external mechanical) torque. TM = Electromagetic (internal) torque. ω = Rotor (mechanical) speed. The armature winding, A1A2, with reverse

polarity across thedc link keeping the magnitude of its induced emf, E, greater than the amplitude of the transformer HV side voltage andimparting a phase shift of 180º to the gate switching controlpattern of the set I or set II IGBTs corresponding to therectification operation in quadrant I or III to obtain inversionin quadrant II or IV respectively.

The field winding F1F2 is connected to a time-invariant dcvoltage source. The armature winding A1A2 is connected to thedc side of the dual converter. The symmetrical multipulse- modulation (SMM) involves chopping of the sinusoidal sourcevoltage by several equidistant pulses per half cycle (M). Theoutput voltage is practically free of even harmonics because ofthe symmetrical placement of the pulses in the two half cycles.The magnitude of the fundamental component and, hence, that of the r.m.s. value of the output voltage and its harmonicprofile can be continually varied by changing the duty cycle(δ) of the pulses and M. Thus, in the case of the SMMtechnique there are options of changing either the number ofpulses per half cycle (M) keeping δ

constant or the duty cycle(δ) keeping M fixed to obtain a specific output voltage. Boththe strategies have been used in this paper; and the change inthe power quality parameters viz. power factor and THD onthe ac side have been recorded and interpreted. The switchingpattern A referred to in Table I is shown in Fig. 3 for theSMM technique with M = 6 and δ = 0.8.

IV. FOUR-QUADRANT DC DRIVE MODELLING

The torque and rotation (ω) in the anti-clockwise and clockwise directions are considered to be positive and negative respectively. The motion of the drive is said to be forward and reverse when it rotates in the anticlockwise and clockwise directions respectively. The load torque always opposes the electromagnetic torque. In the motoring mode the electromagnetic torque is greater than the load torque i.e. TM > TL. This implies that in this mode TM is the driving torque and, therefore, the angular speed, ω, has a direction of rotation same as that of TM. In the generating mode, TL > TM i.e. TL is the driving torque and, hence, ω has the direction of TL. The magnitude of ω is proportional to the difference in the magnitudes of TM and TL. The electrical power of the machine is given by the product of the electromagnetic torque TM and the angular speed, ω. If the electrical power, thus computed (taking the direction sign convention as stated above) is positive or negative then the drive is deemed to be absorbing or delivering power respectively, corresponding to the motoring or generating mode respectively. The drive direction (forward

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or reverse) is determined by the direction of ω. From the above, the four quadrants of operation are

defined as follows:

QI = Forward motoring QII = Forward generating QIII = Reverse motoring QIV = Reverse generating the armature control of the dc machine is obtained by keeping the field excitation flux almost constant by connecting the field winding, F1F2, to a stiff time-invariant dc source and applying varying voltages to the armature winding, A1A2, by judiciously changing the duty cycle (δ) and the number of pulses per half cycle (M) so as to ensure non-adverse impact viz. lack of adequate voltage at start, polarity, etc. Reversal of the electromagnetic torque is obtained by reversing the armature current, Ia, direction. No filters for mitigating ripple on the dc link and harmonics on the ac side have been considered in the simulation model. The machine magnetics are assumed to be in the linear region free from saturation. A .dynamic mode of dc motor drive: To be modelling a dc motor, simple circuit of its electrical diagram as shown in fig.4considered. To modelling and simulate the dc motor.To perform the simulation of the system, an appropriate model needs to be established. Therefore, a model based on the motor specifications needs to be obtained.

Fig 4 Schematic diagram of DC motor

Dc Systems:

All the power semiconductor devices are assumed to be ideal. An ideal sinusoidal ac voltage source is used in the simulation of the drive. Operation in each quadrant is done maintaining a load torque of constant magnitude to ensure the electrical loading of the machine remains the same for both phase-control and the symmetrical multi-pulse modulation technique to facilitate a fair comparison of the characteristics.

V. RESULTS AND DISCUSSION

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Here the simulation is carried out by two cases IGBT Based Dual Buck Converter Fed Four-Quadrant

Operation of DC Drive Phase-Controlled Dual Buck Converter Fed Four-Quadrant

Operation Of DC Drive Using Thyristors.

Fig 5.MATLAB/SIMULINK model of IGBT based dual buck converter fed four quadrant operation of DC drive

Phase-Controlled Dual Converter Fed Four-Quadrant Operation of DC Drive

The freewheeling diode is used in both the phase-

control and SMM models of the dc drive. Figs 5(a) and 5(b) depict quadrant I operation i.e. forward (anticlockwise, positive) motoring of the dc drive in which the ac side functions as the source delivering power to the machine via the dc link for the delay angle, α = 0.

Fig 5.(a) Quadrant I operation: H.V. ac side voltage and

current for α = 0º.

Fig 5.(b) Quadrant I: Speed and Electromagnetic torque for α=00

The electromagnetic torque and the speed are

positive and, therefore, the power developed by the machine is positive indicating absorption of power by it. Fig 5(a) indicates the high initial transient in the source current because of starting.

Figs 6(a) and 6(b) show the characteristics

pertaining to the ac and machine sides respectively for II quadrant operation wherein the drive performs forward generation.It is clear that the ac side voltage and current in Fig. 6(a) are displaced by 180º while the torque and speed of the machine are negative and positive respectively, indicative of negative power developed by the machine corresponding to deliverance of power by it to the ac side.

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Fig.6(a) Quadrant II operation: H.V. ac side voltage and current for

α = 140.8º.

Fig .6.(b) Quadrant II: Speed and Electromagnetic torque for α=140.80

Figs 7(a) and 7(b), and Figs 8(a) and 8(b) show the dc drive motoring and generating modes respectively in the reverse (clockwise, negative) direction. The external mechanical torque on the machine shaft is not shown as it is maintained time-invariant (constant).

Fig .7.(a) Quadrant III operation: H.V. ac side voltage

and current for α_ =65.80

Fig.7. (b) Quadrant III: Speed and Electromagnetic

torque for α=65.8

The voltage and current constitute the ac side characteristics and these are shown in the various figures for the transformer high voltage (H.V.) side that actually is electrically connected to the dual converter. The Figs. 4(a) and 4(b) show the actual characteristics pertaining to the machine as the delay angleα = 0º and, hence, the rated voltage is applied to the machine armature and there is no intentional distortion of the current. Figs. 5(a) and 5(b) show the II quadrant operation with α = 140.8º for the load torque magnitude considered in I quadrant operation. In fact, the operation in all the four quadrants for both phase-control and symmetrical multi pulse modulation techniques have been considered with the load torque magnitude being maintained constant to facilitate comparison.

푇 ∝ 훷퐼 (2)

E = Induced E.M.F. in the armature.

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퐸 훼 ∅휔 (3) 푉푑푐 + 퐼푎푅푎 = 퐸(4) 휔 = ∓

∅(5)

Fig.8. (a) Quadrant III operation: H.V. ac side voltage and current for α_ =155.8º.

Fig .8.(b) Quadrant III: Speed and Electromagnetic torque for α=155.80

The above equations define the dc machine characteristics in all the modes of operation. The parameters in these are:

TM = Electromagnetic (internal) torque. ω = Rotor (mechanical) speed. pulse modulation techniques as the pulses are of

Ia = Armature current. Ra = Armature resistance. Vdc = Terminal voltage across the armature.

ϕ = Field flux.

Since armature control is investigated in this paper the field flux is kept constant and, therefore, it is clear that the torque is proportional to the armature current and the induced EMF is proportional to the speed from (2) and (3) respectively. The freewheeling diode helps in the armature current being continuous and, therefore, aids development of a smooth torque by the armature. In the various quadrants constant torque operation typical of armature control at various speeds is ensured by maintaining the value of the armature current.The positive sign is used in equations (4) and (5) for analysing the generating mode operation of the dc machine. Thus, it is evident from equation (4) that the induced EMF of the machine in the generating mode will be higher than that of the motoring mode. Apart from this, from equation (5) it is evident that the speed too will have to be greater than that of the motoring mode. A higher speed at constant torque implies that the magnitude of the induced EMF will increase. When the EMF magnitude attains values greater than the terminal voltage at the ac side and is of reverse polarity to that of the dc link then generation operation takes place. In Fig. 6(a) the dc link magnitude is lowered by having a delay angle α = 140.8º<180º.Thus, |E| >Vdc is maintained. The higher values of the electromagnetic torque, TM, and the speed, characteristic of the generating mode is clear from Figs. 6(b) and 8(b) corresponding to forward generation and reverse generation respectively. In Figs. 6(b) and 7(b) the steady state magnitudes of TM and ω are greater than those corresponding to Figs. 5(b) and 5(b) respectively. It is noteworthy that Figs. 5(a) and 6(b) are for rated voltage (α = 0º) while Figs. 5(a) and 5(b) are for0.8 p.u. (per unit) rated voltage (α = 140.8º<180°). Similarly, Figs. 6(a) and 6(b) pertain to 0.7 p.u. rated voltage (α = 65.8º >0°) while Figs. 8(a) and 8(b) are obtained with 0.8 p.u. rated voltage (α = 155.8º<180°).

The forward and reverse motoring characteristics are shown in Figs. 6(a), 6(b), and 8(a), 8(b), respectively. The plots in Fig. 4 are for rated voltage while those in Fig. 6 are for 0.7 p.u., however, the steady state torque of 20Nm is the same in both cases with a higher speed of 1800 r.p.m. in the former and a lower 1300 r.p.m. in the latter. These figures, thus, reveal clearly the constant torque at variable speed (hence, variable power) operation associated with armature control.

B. Symmetrical Multi pulse Modulated (SMM) Dual Buck

Converter Fed Four-Quadrant Operation Of DC Drive

The SMM is perhaps the most simple of multi

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equal width and placed equidistant from each other and, therefore, do not require the usual reference and carrier wave control combination for generation. They can be predetermined by digital logic synchronized with a zero crossing detector output latched to the ac side fundamental frequency. The output voltage in the SMM technique is controlled by the number of digital logic synchronized with a zero crossing detector output latched to the ac side fundamental frequency. The output voltage in the SMM technique is controlled by the number of pulses per half cycle (M) and their duty cycle (δ).

Fig.9. MATLAB/SIMULINK model of phase controlled dual buck converter fed four quadrant operation of DC drive using thyristors.The characteristics of the dc drive obtained by use of the technique with M = 6 is illustrated in Figs. 8, 9, 10, and 11 pertaining to forward motoring (quadrant I), forward generating (quadrant2), reverse motoring (quadrant3) and reverse generating (quadrant4) respectively.

Fig.9. (a).Quadrant: H.V.ac side voltage& current for M=6 & δ=0.8.

Fig.9.(b) Quadrant I: speed & electromagnetic torque for M=6 & δ=0.8

Fig.10.(a). Quadrant II: H.V.ac side voltage& current for M=6 & δ=0.8.

Fig.10.(b) Quadrant II: speed & electromagnetic torque for M=6 & δ=0.8

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Fig.11.(a). Quadrant III: H.V.ac side voltage& current for M=6 & δ=0.7.

Fig.11. (b) Quadrant III: speed & electromagnetic torque for M=6 & δ=0.7

The duty cycle (δ) of the pulses has been kept at 0.8 and 0.7 corresponding to 0.8 p.u. and 0.7 p.u. of the rated armature voltage for quadrants I, II, and quadrants III, IV, respectively. The transient involving the starting of the drive has been shown for the forward and reverse motoring operations in Figs. 9(a) and 11(a) respectively.It is clear that the starting in 11(a) is relatively softer (less starting current) and the magnitude of the maximum torque is lower because of the application of reduced voltage, however the steady state torque in both cases is the same i.e. 20Nm. Figs. 10(a), 10(b) and 12(a),12(b) show the plots for forward and reverse generating modes respectively that correspond to 0.8 p.u. and 0.7 p.u. of the rated armature voltage.

As explained in the previous section the generating

mode in both directions is characterized by high speed. The initial transient wherein the induced emf builds up in the armature winding is not shown in Figs. 10(a) and 12(a).The

SMM involves multiple switching of the conducting devices within the relevant half cycle and, therefore, the role of the freewheeling diode across the armature is very important. It ensures that the armature current is continuous and of low ripples content. These are essential for the torque developed in the armature to be smooth and non-jerky. The freewheeling also ensures that the voltage is free from spikes of large magnitudes and is unipolar. This is very important for the protection of the insulation of the armature winding and if not provided for leads to failure of the winding and, hence, the machine itself.

The SMM technique involves multiple pulses

within a half cycle (M) hence the duration of each pulse for is small. The duty cycle of the pulses (δ) is usually high (above 0.6), except, perhaps, during starting, therefore, the off-time is low. The technique provides better power quality in terms of total harmonic distortion (THD) when M and δ are high. The SMM is, therefore, usually used with a high M. The self-commutating devices such as IGBTs employed in the converter are, thus, better utilized in terms of their switching speed and this also implies that the off-time is lowered. The moment of inertia of the rotor is a factor as well. These aspects ensure that the armature current, hence, torque of the machine is smooth and machine characteristics are not comprised. The machine characteristics compare well with those of phase-control.

The four-quadrant operation has been shown for a single value of M = 6, however, simulations have been conducted with higher values of M and the parameters obtained including the total harmonic distortion (THD) of the ac side current.

Fig.12.(a). Quadrant IV: H.V.ac side voltage& current for M=6 & δ=0.7.

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The data pertaining to the SMM technique for higher M with 80% and 70% of the rated armature voltage ratingcorresponding to δ = 0.8 and 0.7 respectively for the four quadrants of operation of the drive are shown in Table II.

Fig.12.(b) Quadrant IV: speed & electromagnetic torque for M=6 & δ=0.7

TABLE II

Data for harmonic distortion with symmetrical multi pulse modulation technique

Quadrant,Operation &Total Harmonic Distortion (THD)

of the H.V. ac side current

No. of pulses per half cycle (M)

Duty Cycle δ %

Per unit output voltage

(Vab/VAB) 6 9 12 15 18 21 24 27 Quadrant I(Forward

Motoring)Total Harmonic Distortion(THD)%

85.07 84.12 81.92 80.87 82.83 83.86 81.16 84.12 0.7 0.7

69.93 69.22 69.64 66.60 68.26 69.91 64.4 68.35 0.8 0.8 Quadrant II (Forward

Motoring)Total Harmonic Distortion(THD)%

134.77 134.69 131.04 123.54 117.44 119.67 109.25 113.73 0.7 0.7 129.71 128.02 117.64 105.64 101.29 115.45 96.62 98.34 0.8 0.8

Quadrant III(Reverse Motoring)Total Harmonic

Distortion(THD)%

85.07 84.12 81.92 80.87 82.23 83.86 81.16 84.12 0.7 0.7 69.93 69.22 69.64 6.60 68.26 69.91 64.4 68.35 0.8 0.8

Quadrant IV (Forward Motoring)Total Harmonic

Distortion(THD)%

135.27 136.06 132.42 124.95 118.76 121.14 110.59 115.17 0.7 0.7

130.88 129.39 118.95 106.97 101.31 115.47 96.64 98.35 0.8 0.8

Table III

Data for harmonic distortion with phase control technique

Quadrant & operation Delay angle (α) Pwe unit output voltage(Vab/VAB) Total harmonic distortion(THD)% Quadrant I forward Motoring 65.8 0.7 41.48

50.8 0.8 33.85 Quadrant II forward Generator 155.8 0.7 67.43

140.8 0.8 60.93 Quadrant III reverse Motoring 65.8 0.7 41.48

50.8 0.8 33.83 Quadrant IV reverse Motoring 155.8 0.7 67.43

140.8 0.8 60.93 It is clear that the THD ofthe ac side current generally decreases with increase in M for aspecific duty cycle for a particular p.u. value of the voltageFor instance in Table II the THD of the acside current for δ is a better

The data for the phase-control method are tabulated in Table III. It is apparent that the values of THD obtained by this method are lower and, therefore,

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technique than SMM. However, the in this method neither can the harmonic profile be altered nor is

= 0.7 in the I quadrant operation is 85.07% for M= 6 and 81.16 for M = 24. It is alsoevident that for a

given p.u. value of the voltage and a specific value of M the THD of the ac side current decreases for a higher

value of δ. For instance, in the I quadrant operation for M = 27 for 0.7 p.u. voltage the THD of the ac side

current for δ = 0.7 is 84.12% but reduces drastically to 68.35% for δ = 0.8.

The harmonic profile by FFT (fast

Fouriertransform) analysis of the ac side current for forward motoring for 0.8 p.u. of the voltage with M=6

and δ = 0.8 is shown in Fig. 13. The THD is obtained to be 69.93%. It has also been observed that the harmonic profile for a specific voltage can be altered by changing

M keeping δ constant andvice-versa. This feature of SMM is used to manipulate the harmonic profile to

ensure that the lower order harmonics are suppressed or even eliminated by judiciously selecting M andδ,

thereby ensuring only those of the higher order are present. The higher order harmonics are filtered

relatively easily and results in the use of filters that are economical, compact, andof lower weight.

Fig 13. FFT of ac side current for quadrant I operation for M=6 & δ=0.8

harmonic mitigation and selective harmonic elimination inherent. It has been verified [9] by the author that the SMM method gives much lower values of THD as well for higher value of M for static loads. Contemporary power quality standards [10] are stringent that necessitate the exploration of various pulse width modulation techniques to ensure drive performance power quality parameters conforming to limits prescribed by them.

VI.CONCLUSIONS The Improved Power Quality AC-DC Converters

(IPQCs) provide enhanced power quality at the utility interface. DC motors are in general much more adaptable to adjustable speed drives than ac motors which are associated with a constant speed rotating fields. The simulation based performance evaluations of the drive indicate that the proposed drive has potential for better values.

The separately excited dc machine drive has been

analyzed for harmonic content in the four quadrants of operation with phase-controlled and symmetrical multiples modulated dual buck Converter and speed control of dc drive using IGBT’s in motoring mode is simulate and controlled. Finally the proposed drive checks out themachine performance.A MATLAB/SIMULINK based model is developed and simulation results are presented.

VII.REFERENCES

[1] IEEE Recommended Practices and Requirements for Harmonics Control In Electric Power Systems, IEEE Std. 519, 1992. [2] H. Wei and I. Batarseh, “Comparison of basic converter topologies for power correction,” in Proc. IEEE SOUTHEASTCON’98, 1998, pp. 348–353. [3] IEEE Recommended Practices and Requirements for Harmonics Control in Electric Power Systems, IEEE Std. 519,1992. [4] Draft-Revision of Publication IEC 555-2: Harmonics, Equipment for Connection to the Public Low Voltage Supply System, IEC SC 77A, 1990. [5] Bhim Singh, B. N. Singh, A. Chandra, Kamal Al-Haddad, AshishPandey, and D. P. Kothari, "A Review of Single-Phase Improved Power Quality AC-DC Converters," IEEE Trans. Ind. Electron., vol. 50, No. 5, pp. 962-981, October 2003. [6] Bhim Singh, B. N. Singh, A. Chandra, Kamal Al-Haddad, AshishPandey, And D. P. Kothari, "A Review of Three-Phase Improved Power Quality AC-DC Converters," IEEE Trans. Ind. Electron., vol. 51, No. 3, pp. 641-660, June 2004. [7] K. E. Addoweesh and A. L. Mohamadein, “Microprocessor based harmonic elimination in chopper type AC voltage regulators,” IEEE Trans. Power Electron.,

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vol. 5, pp. 191-200, Apr.1990. [8] A. N. Arvindan and V. K. Sharma, “Microprocessor based SymmetricalMultipulse Modulation in a Three-Phase Improved Power QualityAC-AC Converter using Four Quadrant Switch Realizations” in theInstitution of Electronics and Telecommunication Engineers (IETE), New Delhi, India, Journal of Research (ISSN 0377-2063), Vol 53, No. 6,pp. 563-571, Nov.- Dec.2007. [9] A. N. Arvindan, “Power Quality Assessment in a Bi-directional AC/ACConverter with Four-Quadrant Switch Realizations” in Proc. IEEETENCON’08, 2008,session P12. [10] IEEE Recommended Practices and Requirements for Harmonics Control in Electric Power Systems, IEEE Std. 519, 1992.

VIII. APPENDIX

A. DC Machine Parameters

The parameters of the separately excited DC machine considered in the simulation model are as follows: Machine Rating: 5 H.P, 240V, 1750 RPM, Field: Vf = 300V Armature Winding: Ra = 2.581Ω, La = 0.028H Field Winding: Rf = 281.3Ω, Lf = 156H Field-armature mutual inductance: Laf = 0.9483H Total inertia: J = 0.02215Kg-m2 Viscous friction coefficient: Bm = 0.002953NmS Coulomb friction torque: Tf = 0.5161Nm Initial speed: 1rad.sec-1

B. Transformer Parameters The Value of the DC voltage commensurate with the

armature voltage and ratingof the DC Machine. Its parameters are: Rating: 10KVA, 50Hz L.V. Winding: V1 = 230V, R1 = 0.002p.u. L1 = 0.078p.u. H.V. Winding: Vs= 265V, R2 = 0.002p.u. L2 = 0.08p.u. Core: Rm = 500p.u. Lm = 500p.u. The transformer voltage ratio is determined on the basis of the average value of the dc voltage of the converter for δ = 1.0 given by (1).

√ 푉 푉 (1) Where, Vs = transformer H.V. side terminal voltage (rms value) Vdc = average value of dc voltage of the converter For Vdc = 240V (rated armature voltage corresponding to δ=1.0) from (1) the value of Vs =

266.57V 265V. Thus the transformer voltage ratio has been fixed at 230/265.

AUTHOR BIBLIOGRAPHY

M. Lakshmi Narayana was born in 1984. He received B.Tech in 2007 from Narsaraopeta Engineering College which is affiliated by JNTU. And also awarded with M.Tech (DSCE) degree from the same college. Presently doing M.Tech with specialization PE&ED in KORM college of engineering, kadapa, Andhra Pradesh, India.

C. Subbarami Reddy completed M.Tech,Ph.D and working as Associate Professor in Electrical and Electronics Department in Kandula Srinivasa Reddy Memorial College of Engineering, Kadapa, and Andhra Pradesh, India.

Gurmeet

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