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An Improved Electronic Load Controller for Self-

Excited Induction Generator in Micro-Hydel

Applications

Bhim Singh, S. S. Murthy and Sushma Gupta

Abstract--This paper describes the mathematical modelling of self-excited induction generators (SEIGs) with are improved electronicload controller (IELC) for microhydel applications supplying variety

of loads. In small hydro plants, governor unit of turbine can beeliminated using IELC, which is simple and cost effective. Theimproved electronic load controller is a combination of a three-phaseinsulated gate bipolar transistor (IGBT) based current controlled

voltage source inverter (CC-VSI) and a high frequency DC chopperwhich keeps the generated voltage and frequency constant in spite ofchange of balanced/unbalanced loads. A dynamic model of the SEIG-IELC suppling different types of loads using stationary d-q axesreference frame is developed for predicting the behavior of the

system under transient conditions. The simulation is carried out forcompensation of balanced/unbalanced loading conditions. Thesimulated results show that generated frequency and voltage remainconstant with change in load. The proposed IELC acts as reactive

power compensator, harmonic eliminator, load balancer and loadcontroller.

Key Words: Self-excited induction generator, improved electronic

load controller, Microhydel, Voltage and FrequencyRegulation.

I. INTRODUCTION

In hilly and isolated areas plenty of hydro potential is

available. These hydro potentials can be used to drive hydro

turbine to generate the electricity. However, induction

machine can be used as a generator provided its reactivepower requirement is fulfilled by capacitor banks, is called

self-excited induction generator (SEIG). The SEIG has

advantages like simplicity, low cost, rugged, maintenance free,

absence of DC, brushless etc. as compared to the conventional

synchronous generator.

The analysis of the SEIG is complicated because its

operation depends on the prime-mover speed, capacitor and

load. Capacitance requirement with load and speed for the

SEIG is reported in the literature [1-3]. Considerable literature

is also reported on the transient analysis of the SEIG under

balanced/unbalanced resistive, reactive and motor loads. In the

literature [4-6], d-q axes modeling are reported for the

transient analysis of SEIG under balanced and unbalancedexcitation system. Jain et al. [7] have given a generalized

model for the transient analysis of SEIG under symmetrical

and unsymmetrical conditions.

In hydro plants, a turbine is used with governor to control

power generation. In micro hydel application, water is

available free of cost then a turbine without governor can be

used as prime mover and capacitors are connected across theBhim Singh (e-mail: bsingh@ee.iitd.ac.in), S.S. Murthy (e-mail:

ssmurthy@ee.iitd.ac.in) and Sushma Gupta (e-mail: sush_gupta@yahoo.com)are with the Department of Electrical Engineering, Indian Institute of

Technology, Delhi, Huaz Khas New Delhi-16, INDIA

SEIG according to the rated power and the constant voltage

can be maintained by electronic load controller (ELC) [8-14].

Thus electronic load controller (ELC) keeps the load constant

on the SEIG under balanced and unity pf load. But in case of

unbalanced loads, SEIG currents and voltage are unbalanced

and at lagging PF loads SEIG voltage drops down because

SEIG and load demands the reactive power, which is not

fulfilled by the ELC. Most of the reported electronic load

controllers are based on controlled and uncontrolled rectifier

with DC chopper, which injects the harmonics in the SEIG.

Due to harmonics injection, SEIG is derated and voltage and

current of SEIG are non-sinusoidal. In case of unbalancedload, SEIG is further derated due to presence of positive and

negative sequence component. The current controlled voltage

source inverter with self-supporting DC bus employed as

static compensator (STATCOM) can be used for filtering the

harmonics and balancing the load. In the reported literature

[15-19] STATCOM acts as a voltage regulator to maintain

constant voltage for the SEIG. Larsen et al [15] have

mentioned the advantage of the STATCOM. Marra and

Pomilio [19] have given the VS-PWM bi-directional converter

for SEIG, which can regulate the frequency and voltage in

case of balanced and linear load. However, there is hardly any

attempts on the voltage and frequency regulation under

unbalanced and non-linear loads.

In this paper, an improved electronic controller (IELC) is

presented which is the combination of CC-VSI and DC

chopper. The IELC consists of current controlled voltage

source inverter, which acts as a voltage regulator, and a DC

chopper at DC bus of VSI keeps the rated power on the SEIG.

A control technique is developed such that SEIG generates the

constant power. In microhydel applications, turbine speed is

kept constant and for a constant value excitation capacitor

SEIG generates constant voltage, frequency and power, which

is known as single point operation. Connecting the capacitor

across the SEIG according to the balanced and unity PF power

can reduce the rating of the CC-VSI. In this case, load

balancing, reactive power compensation and harmonic

elimination should be provided for the load by the CC-VSI. Amathematical model is developed for the transient analysis of

IELC under the resistive, reactive and nonlinear loads with

balanced/unbalanced conditions. The improved electronic load

controller acts as a voltage and frequency regulator, harmonic

eliminator, and load balancer.

II. SYSTEM CONFIGURATION AND CONTROL

SCHEME

The schematic diagram of SEIG with excitation capacitor,

improved electronic load controller ((CC-VSI)+DC chopper),

mailto:bsingh@ee.iitd.ac.inmailto:bsingh@ee.iitd.ac.inmailto:ssmurthy@ee.iitd.ac.inmailto:ssmurthy@ee.iitd.ac.inmailto:sush_gupta@yahoo.commailto:sush_gupta@yahoo.commailto:sush_gupta@yahoo.commailto:ssmurthy@ee.iitd.ac.inmailto:bsingh@ee.iitd.ac.in

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consumer load and control scheme is shown in Fig.1.

Excitation capacitors are selected to generate the rated voltage

of SEIG at no load. The reactive power requirement of SEIG

and load is fulfilled by the CC-VSI with self-supporting DC

bus. The SEIG generates constant power and when consumer

power changes then DC chopper of IELC dumps the

difference power (generated consumed) by consumers in the

IELC. Thus, generated voltage and frequency are not affected

by the application and removal of the consumer load.The IELC consists of a three-phase IGBT based current

controlled voltage source inverter, DC bus capacitor, DC

chopper and AC inductors. The output of the inverter is

connected through the AC filtering inductor to the SEIGterminals. The DC bus capacitor is used as an energy storage

device and provides self-supporting DC bus. DC Chopper is

used to control dump power in IELC due to change in the

consumer load.

The control technique to regulate the terminal voltage, load

balancing, and harmonic elimination of the SEIG is based on

the controlling of source currents (have two components in-

phase and quadrature with AC voltage). The in-phase unit

vectors (ua, ub and uc) are three-phase sinusoidal functions,computed by dividing the AC voltages va, vb and vc by their

amplitude Vt. Another set of quadrature unit vectors (wa, wb

and wc) is sinusoidal function obtained from in-phase vectors

(ua, ub and uc). To regulate AC terminal voltage (Vt) it is

sensed and compared with the reference voltage. The voltage

error is processed in the PI controller. The output of the PI

controller (I*smq) for AC voltage control loop decides the

amplitude of reactive current to be generated by the CC-VSI.

Multiplication of quadrature unit vectors (wa, wb and wc) with

the output of PI based AC voltage controller (I *smq) yields the

quadrature component of the source reference currents (i*saq,

i*sbq and i*scq). For self-supporting DC bus of CC-VSI, its DC

bus voltage is sensed and compared with DC referencevoltage. The error voltage is processed in another PI

controller. The output of the PI controller (I*smd) decides the

amplitude of active current. Multiplication of in-phase unit

vectors (ua, ub and uc) withoutput of PI controller (I*smd) yields

the in-phase component of the source reference currents (i*sad,

i*sbd and i*scd). The sum of quadrature and in-phase

components is the total source reference currents (i*sa, i*sb and

i*sc), which are compared with the source line current (isa, isb

and isc). These current error signals are amplified and

compared with the triangular carrier wave. If the amplified

current error signal is equal to or greater than the triangular

carrier wave, lower device of the inverter phase lag is turned

on and upper device turned off. If the amplified current error

signal is equal to or less than the triangular carrier wave lower

device of the inverter phase is turned off and upper device is

turned on.

The generated power by the SEIG is maintained constant

by the third PI controller. The generated power is compared

with the reference rated power. The PI controller processes

output error of the comparator. The output of the PI controller

is compared with triangular wave. If output of PI controller is

more than the triangular wave, gate pulse of chopper switch

(IGBT) is made high and its current increases through chopper

switch so that SEIG experience same load. If controller output

is less than PWM carrier triangle wave, gate pulse of IGBT is

low and chopper switch is made open.

III. MODELLING OF SEIG-IELC SYSTEM

The schematic diagram is shown in Fig. 1, which consists

of SEIG, IELC, its control scheme and loads. The

mathematical modelling of each component is as follows.

A. Modelling of control scheme of IELC

Three-phase voltages at the SEIG terminals (va, vb and vc)

are considered sinusoidal and hence their amplitude iscomputed as:

Prime Mover

Capacitor Bank

Consumer

Load

Induction Generator

ia

ib

ic

icca

iccb

iccc

ila

ilb

ilc

va

vb

vc

Ca

Cb

Cc

isa

isb

isc

Unit voltage

template

generator

In-phase

component

reference

current

Quadratureuniit current

template

Quadratuure

component

reference

current

PI controller

PI

controller

PWM current

controller

+-

++

+-

a

b

c

a

b

Vdcref

Vtref

Fig. 1 Schematic and power diagram of the improved SEIG-IELC system

IELC

-+

c

ica

icb

icc

Lf,R

f

Vdc

ua

ub

uc

wa

wb

wc

i*saq

i*sbq

i*scq

i*sad

i*sbd

i*scd

i*sa

i*sb

i*sc

isa

isbi

sc

i*smq

i*smd

1

1

35

24 6

Vt

Vdc

PI

controller

Vtri

Ver

Pref

Power

calculator

Pgen

PWM

controller

Cdc

Vsa

Vsb Vsc

Vt = {(2/3) (va2 +vb2 +vc2)}1/2

(1)

The unit vector in phase with va, vb and vcare derived as:

ua = va/Vt; ub = vb/Vt ; uc = vc/Vt (2)

The unit vectors in quadrature with va, vb and vc may be

derived using a quadrature transformation of the in-phase unit

vectors ua, ub and uc [17] as:

wa = -ub /3 + uc /3 (3)

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wb = 3 ua / 2 + (ub uc) / 23 (4)wc = -3 ua / 2 + (ub uc) / 23 (5)1) Quadrature Component of Source Reference Currents:

The AC voltage error Verat the nth sampling instant is:

Ver(n)= Vtref (n) Vt(n) (6)

Where Vtref (n) is the amplitude of reference AC terminal

voltage and Vt(n)is the amplitude of the sensed three-phase AC

voltage at the SEIG terminals at nthinstant. The output of the

PI controller (I*smq(n)) for maintaining AC terminal voltage

constant at the nth sampling instant is expressed as:

I*smq(n) = I*smq(n-1)+ Kpa { Ver(n) Ver(n-1)} + Kia Ver(n) (7)

Where Kpa and Kia are the proportional and integral gain

constants of the proportional integral (PI) controller, Ver(n) and

Ver(n-1) are the voltage errors in nth and (n-1)th instant and I*smq(n-1)

is the amplitude of quadrature component of the source

reference current at (n-1)th instant. The quadrature components

of the source reference currents are estimated as:

i*saq = I*smq wa; i*sbq = I*smq wb; i*scq = I*smq wc (8)

2) In-Phase Component of Source Reference Currents:

The DC bus voltage error Vdcer at nth sampling instant is:

Vdcer(n) = Vdcref Vdc(n) (9)

Where Vdcrefis the reference DC voltage and Vdc(n) is the sensedDC link voltage of the CC-VSI. The output of the PI controller

for maintaining DC bus voltage of the CC-VSI at the n th

sampling instant, is expressed as:

I*smd(n) = I*smd(n-1) + Kpd { Vdcer(n) Vdcer(n-1)} + Kid Vdcer(n) (10)

I*smd(n) is considered as the amplitude of active source current.

Kpd and Kid are the proportional and integral gain constants of

the DC bus PI voltage controller. In-phase components of

source reference currents are estimated as:

i*sad = I*smd ua; i*sbd = I*smd ub; i*scd = I*smd uc (11)

3) Total Source Reference Currents:

Total source reference currents are sum of in-phase and

quadrature components of the source reference currents as:

i*sa = i*saq +i*sad (12)i*sb = i*sbq +i*sbd (13)

i*sc = i*scq +i*scd (14)

4) PWM current controller:

The total reference currents (i*sa, i*sb and i*sc) are compared

with the sensed source currents (isa, isb and isc). The ON/OFF

switching patterns of the gate drive signals to the IGBTs are

generated from the PWM current controller. The current errors

are computed as:

isaerr = i*sa isa (15)

isberr = i*sb isb (16)

iscerr = i*sc isc (17)

These current error signals are amplified and then

compared with the triangular carrier wave. If the amplified

current error signal corresponding to phase a (isaerr) is greater

than the triangular wave signal switch S4 (lower device) is ON

and switch S1 (upper device) is OFF, and the value of

switching function SA is set to 0. If the amplified current error

signal corresponding to isaerr is less than the triangular wave

signal switch S1 is ON and switch S4 is OFF, and the value of

SA is set to 1. Similar logic applies to other phases.

B. Modelling of DC bus chopper

The generated power of the SEIG is calculated by

transforming three-phase quantity (a-b-c) into two-phase

quantity (- axes) as follows [20]:v = 2/3 (va vb/2 vc /2) v =2/3 (3/2 vb -3/2 vc) (19)i = 2/3 (ia ib/2 ic /2)

i =2/3 (3/2 ib -3/2 ic) (21)The generated instantaneous power of SEIG can be defined as:Pgen = v i + v i (22)

Power (Pgen) is compared with reference power according to

rated power of generator (Pref) as:

Per(n) = Pref Pgen(n) (23)

Power error is processed in the PI controller to maintain the

constant generated power at the SEIG at the nth sampling

instant, is expressed as:

V*con(n) = V*con(n-1) + Kpp { Per(n) Per(n-1)} + Kpi Per(n) (24)

Kpp and Kpi are the proportional and integral gain constants of

the power controller. The PI controller output (V*con(n)) is

compared with the triangular carrier (Vtri) waveform and

output is fed to the gate of the chopper switch (IGBT).

when V*con(n)> Vtri, SD = 1 andwhen V*con(n)< Vtri, SD = 0 (25)The SD is the switching function used for generating the

gating pulse of IGBT of the chopper of ELC.

C. Modelling of CC-VSI

The CC-VSI is a current controlled VSI and modeled as

follows:

The derivative of its DC bus voltage is defined as:

pvdc = (SA ica + SB icb + SC icc - SD Vdc/Rd)/ Cdc (26)

Where SA, SB and SC are the switching functions for the

ON/OFF positions of the VSI bridge switches S1-S6 and SD is

the switching function of chopper.

The DC bus voltage reflects at the output of the inverter inthe form of the three-phase PWM AC voltage ea, eb and ec.

These voltages may be expressed as:

ea = vdc (2 SA- SB- SC) / 3 (27)

eb = vdc (- SA+ 2 SB- SC) / 3 (28)

ec = vdc (- SA- SB + 2 SC) / 3 (29)

The (CC-VSI) line voltages are given as:

eab = ea - eb; ebc = eb - ec; eca = ec - ea (30)

The volt-amp equations of the output of voltage source

inverter (CC-VSI) are as:

va = Rf ica + Lf pica + eab - Rf icb - Lf picb (31)

vb = Rf icb + Lf picb + ebc - Rf icc- Lf picc (32)

ica + icb + icc = 0 (33)

Value of iccfrom eqn (33) is substituted in to eqn. (32) whichresults in:

vb = Rficb + Lf picb + ebc + rf ica + Lf pica + Rf icb + Lf p icb (34)

Rearranging the eqn. (31) and eqn. (34) it results in:

Lfpica- Lf picb = va - eab - Rf ica + Rf icb (35)

Lf pica + 2 Lf picb = vb - ebc - Rf ica- 2 Rf icb (36)

Hence, the CC-VSI current derivatives are obtained by solving

the eqn (35) and (36) as:

pica = {( vb - ebc) + 2 (va - eab) - 3 Rf ica}/(3Lf) (37)

picb = {(vb - ebc) - (va - eab) - 3 Rf ica}/(3Lf) (38)

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D. Modelling of SEIG

The dynamic model of the three-phase SEIG is developed

using stationary d-q axes references frame, whose voltage-

ampere equations are [17]:

[v] = [R] [i] + [L] p [i] + r [G] [i] (39)From which, current derivatives can be expressed as:

p[i] = [L]1

{ [v] [R] [i] - r [G] [i] } (40)Where [v] = [vds vqsvdr vqr] T; [i] = [ids iqsidr iqr]

T

[R] = diag [ Rs Rs Rr Rr]

[ ]

++

++

=

mLrL0mL00mLrL0mL

mL0mLsL00mL0mLsL

L [ ]

++=

0mLrL0mLmLrL0mL0

00000000

G

(41)

The electromagnetic torque balance equation of SEIG is

defined as:

T shaft= Te+ J (2/P) p r (42)The derivative of rotor speed of the SEIG from eqn. (42) is:

pr = {P/(2J)} (T shaft - Te) (43)where the developed electromagnetic torque of the SEIG is

expressed as [17]:

Te = (3P/4) Lm(iqs idr ids iqr) (44)In microhdel system, prime mover have drooping

characteristic and may be expressed as:

Tshaft = (3370- 10 wr) (45)

The SEIG operates in the saturation region and its

magenetizing characteristics is non-linear in nature. Therefore

the magnetizing current should be calculated in each step of

integration in terms of stator and rotor currents as:

Im= (ids +idr)2+ (iqs+ iqr)2 (46)Magnetizing inductance is calculated from the magnetizing

characteristics between Lmand Im. Relation between Lm and Im

is obtained by synchronous speed test [17] and can be written

as:

Lm= 0.1407 + 0.0014 Im 0.0012 Im2 + 0.000048Im3 (47)

E. AC line voltage at the point of common coupling

From direct and quadrature axis currents of the SEIG (ids

and iqs) are converted in to three-phase (a, b and c). The

derivative of AC terminal voltage of the SEIG is defined as:

p va = {(ia ila ica) (ib ilb icb)} / (3 C) (48)

p vb = {(ia ilc ica) +2 (ib ilb icb)} / (3 C) (49)

va+vb + vc= 0. (50)

where ia, ib and icare SEIG stator line currents, ila, i lb and ilc are

3-phase load currents and ica, icb and icc are CC-VSI currents. C

is per phase no load excitation capacitor value connected

parallel to SEIG.

IV. RESULTS AND DISCUSSION

The SEIG system with IELC feeding resistive and reactive

balanced/unbalanced loads is simulated and results are shown

in Figs. 2-4. For the simulation, a 7.5 kW, 230V, 15.6 A, 4-

pole machine has been used as a generator and parameters of

the generator are given in Appendix.

A. SEIG-IELC System behaviour Feeding Three-phase

resistive load

Fig.2 shows the transient waveforms of 3-phase generator

voltages (vsabc), generator currents (isabc), three-phase resistive

load currents (ila, ilb and ilc), three-phase IELC currents (ica, icb

and icc), generated power and its reference (Pgen) amplitude of

SEIG terminal voltage and its reference (Vt/Vtref), DC bus

voltage and its reference (Vdc/ Vdcref) and generator speed (wg)

demonstrating the response of IELC for regulating the SEIG

terminal voltage supplying with pure resistive load (7.5 kW).

At 5.1-sec. one and 5.2-sec. two-phase of the load aredisconnected from the SEIG. Consequently IELC currents

increase to balance the SEIG system and chopper current

increases to maintain the constant power on the SEIG. At 5.3-

sec. one phase and at 5.4-sec. two-phase of load is reconnected

Fig. 2 Performance waveforms of three-phase SEIG-IELC system supplying

resistive load (7.5 kW)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 -500

0

500

vsabc(V)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55

-20

0

20

isabc(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 -10

0

10

ila(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 -10

0

10

ilb(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 -10

0

10

ilc(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 -10

0

10

ica(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 -10

0

10

icb(A)

5.1. 5.15. 5.2. 5.25. 5.3. 5.35. 5.4. 5.45. 5.5. 5.55. -10

0

10

icc(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 7000

7500

8000

Pgen(W)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 300

350

Vt/Vtref(V)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55

600

650

700

Vdc/Vdcref(V)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 334

336

338

Wg(r/s)

Time (Sec)

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on SEIG. At application of load and under steady state,

generator speed remains constant, which shows that generated

voltage and frequency are constant. Under three-phase load on

the SEIG, IELC current decreases which shows power on the

SEIG remains constant. Load currents, generator currents and

voltages are sinusoidal and harmonic free.

B. SEIG-IELC system behavior Feeding Three-phase

Reactive load

Fig. 3 Performance of three-phase SEIG-IELC supplying reactive load (7.5kW at 0.8 PF)

Fig.3 shows the transient waveforms of the three-phase SEIG-

IELC supplying reactive load (0.8 PF). At 5.2-sec one phase

load is disconnected from the SEIG consequently IELC

current of one-phase increases to balance the SEIG system. At

5.3-sec. two-phases of load is disconnected from the load and

hence IELC currents of two phases increase for balancing the

SEIG system. At 5.4-sec. one-phase and 5.5-sec. two-phases

of load are reconnected on the SEIG. In this case, IELC

currents decrease because SEIG system is balanced. Choppercurrent also increases and decreases when consumer load

decreases and increases respectively which shows that the

generated power of the SEIG remains constant in spite of

variation in consumer load. In reactive load, generator voltage

is constant and perfectly sinusoidal which shows that IELC is

acting as a voltage regulator and load balancer. The speed of

SEIG remains constant, which shows that the generator is

generating constant voltage, frequency and power.

C. SEIG-IELC system behavior Feeding Three-phase Non-

Linear load

Fig. 4 Transient waveforms of three-phase SEIG-IELC system supplying non-

linear load

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6-500

0

500

vsabc(V)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6

-20

0

20

isabc(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6

-20

0

20

ila(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6-10

0

10

ilb(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6-10

0

10

ilc(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6-10

0

10

ica(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6

-20

0

20

icb(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6-20

0

20

icc(A)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.67000

7500

Pgen(W)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6300

350

Vt/Vtref(V)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6600

650

700

Vdc/Vdcref(V)

5.1 5.15 5.2 5.25 5.3 5.35 5.4 5.45 5.5 5.55 5.6334

336

338

Wg(r/s)

Time (Sec)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85-500

0

500

vsabc(V)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85-50

0

50

isabc(A)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85-20

0

20

ila(A)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85-20

0

20

ilb(A)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85

-20

0

20

ilc(A)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85-20

0

20

ica(A)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85-20

0

20

icb(A)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85-20

0

20

icc(A)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.856000

8000

Pgen(W)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85300

350

Vt/Vtref(V)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85600

650

700

Vdc/Vdcref(V

)

6.4 6.45 6.5 6.55 6.6 6.65 6.7 6.75 6.8 6.85330

335

340

Wg(r/s)

Time (Sec)

8/3/2019 P1470

6/6

Fig. 4 shows the SEIG-IELC system behavior supplying the

non-linear load. A three-phase rectifier with R load and

capacitive filter is taken as a non-linear load. At 6.5-sec

loading on the rectifier load increases because of that load

current increases. It is observed from the figure that generator

voltages and currents remain constant and sinusoidal. At 6.75-

sec. loading on rectifier load is decreased consequently

rectifier load currents decrease however the SEIG voltages

and currents remain constant and sinusoidal which shows thatIELC is acting as a harmonic eliminator. The SEIG speed

remains constant in complete duration, which proofs that it is

generating constant frequency, voltage and power.

V. CONCLUSION

The developed mathematical model of three-phase SEIG

IELC system has been found an appropriate tool to study the

behavior of SEIG with IELC at different types of loads under

transient conditions. Simulations have been carried out and

simulated results show that SEIG terminal voltage and

frequency remain constant while supplying the resistive,

reactive and non-linear loads with balanced/unbalanced

conditions. When unbalancing of load takes place then IELCgenerates compensating currents and balances the generator

currents and voltage thus IELC acts as load balancer. In case

of variation in consumer load, chopper of IELC operates

accordingly and generated power of the generator remains

constant. The SEIG generates constant voltage and frequency

as it is operating at constant power. Therefore, improved

electronic load controller acts as voltage regulator, frequency

regulator, load balancer and harmonic eliminator.

VI. APPENDICES

A. STATCOM control parameters

Lf= 1.5 mH, Rf = 0.05 and Cdc = 4000F.

AC voltage PI controller: Kpa =0.05, Kia= 0.04.DC bus voltage PI controller Kpd = 0.04, Kid =0.005

Carrier frequency = 20 kHz

Power PI controller Kpp = 0.4 Kpi = 0.05

B. Machines parametersThe parameters of the induction machines are given below.

Rs= 1.0, Rr = 0.77, Xls = Xlr = 1.0 , J = 0.1384 kg/m2

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