Engineering, 2011, 3, 508-516
doi:10.4236/eng.2011.35059 Published Online May 2011 (http://www.SciRP.org/journal/eng)
Detailed Analysis of Micro-Grid Stability during Islanding
Mode under Different Load Conditions
Rashad M. Kamel, Aymen Chaouachi, Ken Nagasaka
Environmental Energy Engineering, Department of Electronics & Information Engineering,
Tokyo University of Agriculture and Technology, Koganei-shi, Tokyo, Japan
Received January 21, 2011; revised March 4, 2011; accepted April 6, 2011
Abstract
Today, several types of DGs are connected together and formed a small power system called micro-grid
(MG). MG is connected to the primary distribution network and usually operates in normal connecting mode.
When a severe fault occurs in the primary distribution network, then the MG will transfer to islanding mode.
In this paper a complete model is developed to simulate the dynamic performance of the MG during and
subsequent to islanding process. The model contains of a solid oxide fuel cell (SOFC), a single shaft micro
turbine, a flywheel, two photovoltaic panels and a wind generator system. All these micro sources are con-
nected to the MG through inverters except the wind generation system. The inverters are modeled with two
control strategies. The first strategy is PQ control which the inverter will inject a certain active and reactive
powers. This type of inverter is used to interface micro turbine, fuel cell and photovoltaic panels to the MG.
The second strategy is Vf control. This model is used to interface flywheel will act as the reference bus
(slack bus) for the MG when islanding occurs. Two cases are studied: the first case discusses the effect of
islanding process on frequency, voltage and active power of all micro sources when the MG imports active
and reactive power from the primary distribution network. The second studied case, also, shows the effect of
islanding on the previous quantities particularly when the MG exports active and reactive power to the pri-
mary distribution network. Results showed that the existence of storage device (flywheel) with appropriate
control of its inverter can keep the frequency of the MG and the voltages of all buses within their limited
levels. The developed model is built in Matlab® Simulink® environment.
Keywords: MG, Dynamic Performance, Islanding, Inverter and Distributed Generators
1. Introduction
Micro-scale Distributed Generators (DGs), or micro
sources, are being applied increasingly to provide elec-
tricity for the expanding energy demands in the network.
The development of micro DGs also help to reduce green
house gas emissions and increase energy efficiency [1].
The MG usually consists of a cluster of micro DGs, en-
ergy storage system (e.g. flywheel, battery, ….) and
loads, operating as a single controllable system. The
voltage level of the MG at the load is about 400V or less.
The architecture of the MG is formed to be radial with a
few feeders. It often provides both electricity and heat to
the local area. It can be operated in both grid-connected
mode and islanded mode. From the customer point of
view, the MG can provide both heat and electricity and
also can enhance the local reliability, reduce emissions,
improve power quality (by supporting voltage and re-
ducing voltage dip), and can potentially lower the costs
of energy supply. Fro m the utility point of view, applica-
tion of distributed energy sources can potentially reduce
the demand for distribution and transmission facilities [2].
Clearly, distributed generations located close to loads
can reduce the flows in transmission and distribution
circuits with two important effects: loss reduction and
substitute for network assets. Further, the presence of
generations close to demand could increase the service
quality for the end customers. The MG can provide net-
work support in times of stress by relieving congestions
and aiding restoration after fault occurrence [2].
Development of the MG can contribute to reduction of
emissions and mitigation of climate changes. This is be

R. M. KAMEL ET AL. 509
cause available and currently developing technologies
for distributed generation units are based on renewable
sources and micro sources that are characterized by very
low emissions [2]. The new micro sources technologies
(e.g. micro gas turbine, fuel cells, photovoltaic system
and several kinds of wind turbines) used in the MG are
not suitable for supplying energy to the grid directly
[3-4]. They have to be interfaced to the grid through in-
verters. Thus, the use of power electronic interfaces in
the MG leads to a series of challenges in the design and
operation of the MG [5].
Technical challenges associated with the operation and
control of the MG are immense. Ensuring stable opera-
tion during network disturbances, maintaining stability
and power quality in the islanding mode of operation
requires sophisticated control strategies development for
the MG’s inverters in order to provide stable frequency
and voltage in the presence of arbitrarily varying loads.
The aim of this paper is to demonstrate the transients of a
MG due to intentional islanding process and to illustrate
the maintenance of stability of the MG in the isolated
mode of operation.
Reference [6] is discussed about the MG autonomous
operation during and subsequent to islanding process
however no renewable micro sources is included. In ref-
erences [7] and [8], a control scheme based on droop
concepts (to operate inverters feeding a standalone ac
system) is presented. References [9] and [10] are dis-
cussed about the behavior of distributed generator (DGs)
connected to distribution networks, however, the dy-
namics of the primary energy sources is not considered.
The full picture of the MG long-term dynamic behavior,
which is largely influenced by the micro sources dynam-
ics, is also missing in this reference.
In the present paper, we developed a complete model
to simulate the dynamic performance of the MG. All MG
components are simulated in details. In our previous re-
search [11] and [12], we developed a model for all MG
components (each component operates in standalone
mode). In reference [11], a detailed model is developed
for inverter with three different control schemes. In ref-
erence [12], some models are developed for the micro
sources exist in the MG (micro turbine, fuel cell, wind
turbine and photovoltaic). This paper collects all indi-
vidual models developed in references [11] and [12] in
one complete model and apply a suitable control scheme
which can arrange the operation of all models simulta-
neously. The developed model is general and can be used
to study any disturbance which may occur in the MG.
The model is built in Matla b® Simulink® environment.
The rest of the paper is organized as follows: Section 2
illustrates a single line diagram of the studied MG. Sec-
tion 3 gives a brief description of all MG components
models. Section 4 presents a description of the complete
model with the applied controls. Two studied cases with
results and discussions are explained in Section 5. Con-
clusions are presented in Section 6.
2. Single Line Diagram of the Studied
Micro-Grid
Figure 1 shows the single line diagram of the studied
MG [13]. It consists of 7 buses. Flywheel is connected to
bus 1. Wind generation system is connected to bus 2.
Two photovoltaic panels with rating 10 kW and 3 kW
are connected to buses 4 and 5, respectively. A single
shaft micro turbine with rating 30 kW is connected to
bus 6. Bus 7 is provided with a solid oxide fuel cell
(SOFC) with rating 30 kW. The loads and line parame-
ters of the MG are given in the appendix.
3. Description of Micro-Grid Individual
Components Models
3.1. Inverter Models
In reference [11], three different control models of the
inverter are developed to interface micro sources to the
MG. The first model is PQ model, which control the ac-
tive and reactive power injected by the inverter into the
MG. This model is suitable for interfacing micro turbine,
fuel cell and photovoltaic panels. Figure 2(a) shows the
terminal block diagram of PQ inverter model. The input
terminals are active power (P) and reactive power (Q)
produced by the micro sources, the output is the three
phase terminals (Va, Vb and Vc) which connected the in-
verter to the MG.
The second model is the PV model, which controls the
active power (P1) injected by the inverter and keep the
voltage of the inverter bus (V) at constant value as shown
in Figure 2b. The third model is the Vf model, which
keeps the voltage (V) at constant value and return the
frequency (fo) to its nominal after disturbance by control-
ling the amount of the active power injected in the MG.
The Vf inverter is used to interface the flywheel to the
MG and represents the reference bus (slack bus) of the
MG during and subsequent to islanding occurrence
(Figure 2(c)).
3.2. Micro Sources Models
In reference [12], detailed standalone models are devel-
oped for single shaft micro turbine, solid oxide fuel cell,
photovoltaic panels and wind generation system. These

R. M. KAMEL ET AL. 510
standalone models are described as follows.
3.2.1. Single Shaft Micro Turbine (SSMT) Model
Figure 3(a) shows the developed model of the single
shaft micro turbine. In this figure, the input input termi-
nal Pref represents the desired power. The output terminal
is Pe (electrical power output from permanent magnet
synchronous generator which coupled with micro turbine).
Pe is connected to P input term inal of the PQ inverter.
3.2.2. Solid Oxide Fuel Cell (SOFC) Model
Figure 3(b) shows the developed model of the SOFC. In
this figure, the input terminals are Pref (desired power)
and rated voltage (Vrated). The output terminal is Pe which
represents the electrical power output from fuel cell. This
terminal is applied to P input terminal of the PQ inverter.
3.2.3. Photovoltaic Model
Photovoltaic model is shown in Figure 3(c). Input termi-
nals are Irradiance (Ga W/m2) and ambient temperature
(Ta Kelvin). Maximum power point tracking (MPPT) is
included inside the model. The output terminal is Pmax,
which represents the maximum output power developed
by photovoltaic panel; this terminal is applied also to the
input terminal of the PQ inverter.
3.2.4. Wind Generation System Model
Wind generator system model is shown in Figure 3(d).
The wind turbine is coupled to a squirrel cage induction
generator. The input terminals of the wind turbine are
wind speed (m/sec.) and pitch angle of the turbine blades
(degree). The output terminal of the wind turbine is me
Figure 1. Single line diagram of the studied MG.
50
f0
f
Vout
fo
Er ef
f
Vout
Va
Vb
Vc
Vf Inverter (VSI)
( c )
V V
Qout
Q
Pout
Pref
Vref
Pout
Vout
Va
Vb
Vc
PV In verter
( b )
Pr ef
Qref
Pout
Qout
Va
Vb
Vc
PQ Inverter
( a )
P1
P
A
B
C
a
b
c
Output
of Vf
A
B
C
a
b
c
Output
of PV
A
B
C
a
b
c
Output
of PQ
Vout
Pout
Figure 2. Inverter control models.
2
Pm ax
1
Pe
Go to
Invert er
wind
speed m/s
0
pitch
angle
Generator speed (pu)
Pitch angle (de g)
Wind speed (m/s)
Tm (pu )
Wi nd Turbine
( d )
-C-
Vrated
A B C
Virtual
Load
Temperature
(Ta)
Pm
wm
Pe
Va
Vb
Vc
Synchrounous
Generato r
( a )
A
B
C
RLc
load
Pre f
pm
Pm
Pe
Ga
Ta
Pmax
PV Mod el
( C )
P ref
wm
Pref
Pm
Microt urbine
Irradiance
(Ga)
Tm
wm
Pm
Pe
Va
Vb
Vc
Induction
Generator
Vrated
Pref
Pout
Fuell cell model
( b )
Pe
Active
power
Figure 3. Micro sources standalone models.

R. M. KAMEL ET AL. 511
chanical torque (Tm), which applied to the shaft of the
induction generator. The terminals of the induction gen-
erator are connected directly to the MG.
4. Complete Model of the MG
The operation of the MG with several PQ inverters and a
single voltage source inverter (Vf) is similar to the opera-
tion of the MG with synchronous machine as a reference
bus (slack bus). The VSI provides the voltage reference
for the operation of the PQ inverters when the MG is
isolated from the main power grid. Acting as a voltage
source, the Vf inverter requires a significant mount of
storage capability in the DC link or a prime power source
with a very fast response in order to maintain the DC link
voltage constant. In other words, the power requested by
a VSI needs to be available almost instantaneously in the
DC link. In fact, this kind of behavior models the action
of the flywheel system. Flywheel is connected at the DC
bus of the Vf inverter to provide instantaneous power
required. The Vf inverter is responsible for fast load-
tracking during transients and for voltage control. During
normal operation conditions (stable frequency at nominal
value), the output active power of the Vf inverter is zero
and only reactive po wer is injected into the MG for volt-
age control.
4.1. Active Power Control in Each Micro Sources
During islanded (autonomous) operation, when an im-
balance between load and local generation occurs, the
grid frequency drifts from its nominal value. Storage
devices (flywheel) keep injecting power into the network
as long as the frequency differed from the nominal value.
Micro turbine and fuel cell are controllable sources
which the power output can be controlled. A PI control-
ler (being the input of this controller the frequency devia-
tion) which acts directly in the primary machine (Pref of
fuel cell and micro turbine) allows frequency restoration.
After frequency restoration, storage devices will operate
again at the normal operation point (zero active power
output). This controller can not apply to wind turbine and
photovoltaic panels because they are uncontrollable
sources and their output power depend on wind speed,
irradiance and ambient temperature. Figure 4 shows the
PI controller block diagram used to control the output
power of fuel cell and micro turbine.
4.2. Voltage and Reactive Power Control
In Figure 5, the adopted voltage control strategy is de-
scribed. Knowing the network characteristics, it is possi-
ble to define the maximum voltage droop. To maintain
the voltage between acceptable limits, the voltage
sources inverter (VSI) or Vf inverter connected to the
flywheel will adjust the reactive power in the MG. It will
inject reactive power when voltage falls from the nomi-
nal value and will absorb reactive power if the voltage
rises above its nominal value.
4.3. Frequency and Active Power Control
The transition to islanded operation mode and the opera-
tion of the network in islanded mode require micro gen-
eration sources to particulate in active power-frequency
control, so that the generation can match the load. During
this transient period, the participation of the storage de-
vices (flywheel) in system operation is very important,
since the system has very low inertia, and some micro
sources (micro turbine and fuel cell) have very slow re-
sponse to the power generation increase. As already
mentioned, the power necessary to provide appropriate
load-following is obtained from storage devices (fly-
wheel). Knowing the network characteristics, it is possi-
ble to define the maximum frequency droop as shown in
Figure 6. To maintain the frequency between acceptable
limits, the Vf inverter connected to flywheel will adjust
the active power in the network. It will inject active
power when frequency falls from the nominal value and
will absorb active power if the frequency rises above its
nominal value.
2
P
Active Power
R eference for
microsource
( F uel Cell an d
Microturbine )
50
f0 0.6
Pset
Kp
Proportiona l
gain
1
s
Integrator
KI
Integral
gain
1
Grid
frequency
Figure 4. Control of active power in controllable micro
source.
Figure 5. Droop control of the inverter terminal voltage.

R. M. KAMEL ET AL. 512
Figure 6. Frequency droop control of Vf inverter.
4.4. Complete Model of the MG
A complete model which collects all micro sources mod-
els, all inverter models and all control strategies is de-
scribed in the previous sections and also shown in Fig-
ure 7. This model is general and can be used to describe
any disturbances which may occur in the MG during
connected and islanding modes.
5. Results and Discussions
In the simulation platform, the PV panels, a SOFC and a
single shaft micro turbine are associated with a PQ in-
verter type. As the inverter control is quite fast and pre-
cise, it is possible to neglect the DC link voltage fluctua-
tions; if losses are also neglected, the output active
power of a PQ inverter becomes equal to the output
power of the associated micro source. Flywheel is con-
nected to the Vf inverter.
Case1: MG Imports Active and Reactive Powers
from the Main Grid
In this case, the amounts of active power and reactive
power generated from micro sources are adjusted to
make the MG imports 13 kW and 16 kVAr from the
main grid. After finding suitable control parameters for
the Vf inverter, disconnection of the upstream main grid
is simulated at t = 60 sec. and the simulation results are
presented for the main electrical quantities (frequency,
voltages, and active powers).
From the previous figures (Figures 8-12), the se-
quence of the events can be interpreted as follows:
 Before t = 60 sec., the MG is at steady state and its
frequency is at nominal value (50 Hz). The MG im-
ports 13 kW and 16 kVAr from the main grid as
shown in Figure 12.
 At t = 60 sec., islanding occurred, the MG’s loads are
larger than the power generated by micro sources so
that the frequency dropped to about 49.8 Hz and the
voltages dropped to about 96% of their nominal val-
ues as shown in Figures 8 and 9, respectively.
 The difference between load powers (active and reac-
tive) and generated power (active and reactive) is in-
jected by flywheel as shown in Figure 10.
wind
speed
0
pitch
angle
A
B
C
A
B
C
line betw we n
bus 4 and 5
A
B
C
A
B
C
line betwwen
bus 2 and 3
A
B
C
A
B
C
line betw w en
bus 1 and 2
A
B
C
A
B
C
line betw w en
bus 5 and 6
A B C
A B C
line betwwen
bus 3 and 7
A
B
C
A
B
C
li ne betwwen
bus 3 an d 4
50
fo2
50
fo
50
f0 [ HZ]
[f]
f
Generator speed (pu)
Pitch angle (deg)
Wind speed (m/s)
Tm ( pu)
Wind Turbine
Vref [ Volt ]
333.8
Vrated1
A B C
Virtual
Loa d
A B C
A B C
Transformer
Te mp erature
(Ta)1
Tempe r ature
(Ta)
-K-
T
Base
Pm
wm
Pe
Va
Vb
Vc
Synchrounous
Ge n erator
Q7
Q5
Q4
Q
0.7
Pr ef 1
0.4
Pr ef
Ga
Ta
Pmax
PV panel1
Ga
Ta
Pmax
PV Pane l 2
wt
Q
P
Vabc
Ia bc
Va
Vb
Vc
PQ inverter 7
wt
Q
P
Vabc
Iabc
Va
Vb
Vc
PQ inverter 5
wt
Q
P
Vabc
Iabc
Va
Vb
Vc
PQ inverter 4
wt
Q
P
Vabc
Ia bc
Va
Vb
Vc
PQ
Inverter
for
microturbine
wm
Pref
Pm
Microturbine
A B C
Main
Grid
A B C
Load at
bus 5
A B C
Load at
bus 4
A B C
Load
at bus 7
A
B
C
Load
at bus 6
Irradiance
(Ga)1
Irradiance
(Ga)
1
s
Inte grator
Tm
m
A
B
C
Induction
Generator
1
s
INt1
-K-
Gai n
Vrate d
Pref
Pout
Fuell cell
model
[wt]
From9
[wt]
From4
[wt]
From3
[f1]
From11
[wt]
From10
fo
Eref
f outp ut
Vout
Va
Vb
Vc
Flywheel wi th
VSI Inverter
mwm
De m ux7
A
B
C
A
B
C
Coupling
Inductance
A B C
Ca p acitor
bank
-K-
8
-K-
7
A B C
3phase
load2
A B C
a b c
3phase
breaker2
-K-
14 -K-
13
Figure 7. Complete system model.
P
/
P
N

R. M. KAMEL ET AL. 513
50 60 70 80 90100110 120
49. 75
49.8
49. 85
49.9
49. 95
50
Time(sec.)
Frequenc y (HZ )
Frequency of the m icrogrid durin g and subsequent islanding
Figure 8. System fre que ncy.
6080100 120
0. 9 6
0. 9 8
1
time (sec)
V oltage ( pu )
Bu s # 1( fly wheel)
6080100 120
0. 9 6
0. 9 8
1
time (sec)
V oltage ( pu )
B us # 2 ( Wi nd turbi n e )
6080100 120
0. 9 6
0. 9 8
1
time (sec)
Voltage ( pu )
Bus # 4 (PV2)
6080100 120
0. 9 6
0. 9 8
1
time (sec)
V oltage ( pu )
Bus # 5 (PV1)
6080100 120
0. 9 6
0. 9 8
1
time (sec)
V oltage ( pu )
Bu s # 6 ( M i cro tu rbi ne )
6080100 120
0. 9 6
0. 9 8
1
time (sec)
V oltage ( pu )
Bu s # 7 ( F uel Cel l)
Figure 9. Voltages at all micro sources buses.
60 70 80 90100 110 120
-5
0
5
10
15
20
25
30
Time
(
sec.
)
Power
Acti ve and reacti ve power injected by t he flywheel (VS I)
Active power( KW )
Reacti ve power( KV A r )
Reacti ve Power
Acti ve power
Figure 10. Flywheel (Vf) active and reactive powers.
 Due to frequency deviation, PI controllers connected
to SOFC and SSMT increase the reference powers of
those micro sources. The output powers of SOFC and
SSMT begin to increase and help frequency restora-
tion as shown in Figure 11.
 The powers produced by photovoltaic panels are con -
stant because the ambient temperature and irradiance
are assumed to be constant. This assumption is ac-
ceptable because the interval of simulations after
islanding (50 sec) is small.
 Wind generator output power suffers from some
fluctuations.
50 60 70 8090100110120
0
2
4
6
8
10
12
14
16
Ti me ( sec. )
A ctiv e po wer ( KW )
Fuel cell po wer
Mi croturbi ne power
Power of PV at bus # 4
Wi nd Turbine Power
Power of PV at bus # 5
Figure 11. SOFC, SSMT, wind generator and photovoltaic
panels active powers.
Figure 12. Active and reactive powers of the main grid.
 As the power generated by micro sources increases,
the amount of power injected by flywheel decreases.
 When the power generated by the micro sources be-
comes equal to the demand by the load, active power
injected by flywheel returns to zero and frequency
returns to its nominal value.
 The dynamic performance of the studied MG needs
about 50 seconds to return back to its steady state.
 Results proved that by using a storage device (fly-
wheel) with a suitable rating, the MG can restore its
stability after high disturbance (islanding) occurrence.
 In conclusions, MG is a very good solution for feed-
ing sensitive loads and represents uninterruptable
power supply for those loads.
Case2: MG Exports Active and Reactive Powers to
the Main Grid
In this case, the reference powers of SOFC and SSMT
are adjusted so that the amounts of active and reactive
powers generated by all micro sources become greater
than the demand. The MG exports about 21 kW and 20

R. M. KAMEL ET AL. 514
kVar to the main grid. The disconnection of the upstream
main grid simulated at t = 70 sec., the simulation results
are shown in the following figures.
From the previous figures (Figures 13-17), the se-
quence of the events can be interpreted as follows:
 Before islanding occurrence, the MG operates at its
steady state and exports active and reactive powers to
the main grid (Figure 17). The frequency of the MG
60 70 80 90100 110 120
49.95
50
50.05
50.1
50.15
50.2
50.25
50.3
50.35
50.4
Time
(
sec.
)
Frequenc y (HZ )
Frequenc y of t he mi crogrid duri ng and s ubs equent i sl andin g oc cur
Figure 13. System frequency.
6080100 120
0.98
1
1.02
time (sec)
V ol tage ( p u )
Bus # 1
60 80 100 120
0.98
1
1.02
time (sec)
V ol tage ( p u )
Bus # 2
6080100 120
0.98
1
1.02
time (sec)
V ol tage ( pu )
Bus # 4
60 80 100 120
0.98
1
1.02
time (sec)
V ol tage ( pu )
Bus # 5
6080100 120
0.98
1
1.02
time (sec)
V oltage ( pu )
Bus # 6
60 80 100 120
0.98
1
1.02
time (sec)
V oltage ( pu )
Bus # 7
Figure 14. Voltages of all micro sources buses.
Figure 15. Flywheel (Vf) active and reactive powers.
60 70 8090 100 110120
0
5
10
15
20
25
Time
(
sec.
)
A c ti v e power (K W )
Fuel Cell active power
Microturbine active power
Power of PV at b us #4
Windturbine active power
Power of PV at b us #5
Figure 16. SOFC, SSMT, wind generator and photovoltaic
panels active powers.
Figure 17. Active and reactive powers of the main grid.
is at its nominal value (50 Hz).
 Islanding occurs at t = 70 sec., the MG loads are less
than the power generated by micro sources which led
the frequency increases to 50.35Hz. At this time, the
voltages increases to about 102% of their nominal
values as shown in Figures 13 and 14, respectively.
 The difference between load powers (active and reac-
tive) and generated power (active and reactive) is ab-
sorbed by flywheel as shown in Fi gure 15.
 Due to frequency deviation, the PI controllers con-
nected to SOFC and SSMT decrease the reference
powers of those micro sources. The output powers of
SOFC and SSMT begin to decrease and help fre-
quency restoration as shown in Figure 16.
 By injecting a suitable amount of active and reactive
power by the staorgae devices (flywheel), the fre-
quency and voltages of the MG can be kept with the
limited values.
 And when the power generated by the micro sources
becomes equal to the power demand, the active
power absorbed by flywheel returns to zero and the
frequency returns to its nominal value. The MG needs
about 40 seconds to restore to its steady state.
 In conclusions, by using a suitable control strategy

R. M. KAMEL ET AL. 515
inside the MG, MG can keep its stability after island-
ing occurrence from the main grid under different
load condition s.
6. Conclusions
This paper developed a complete model which can de-
scribe the dynamic behavior of the MG. All MG’s com-
ponents are modeled in detail. Two cases are studied: the
first case investigates the dynamic performance of the
MG during and subsequent to islanding when the MG
imports active and reactive powers from the main grid.
The second case shows the dynamic performance when
the micro grid exports a large amount of active and reac-
tive powers to the main grid . It was proved that the stor-
age devices are absolutely essential to implement ade-
quate control strategies for MG operation in islanded
mode. The importance of storage devices due to the fact
that the micro sources present in the MG have a very low
inertia and slow ram-up rates. A combination of droop
control mode (applied to Vf inverter) together with an
integral control loop (applied to controllable micro
sources) are effective in controlling the frequency during
islanded operation. It is found that appropriate control of
Vf inverter coupled flywheel to the MG can keep the
voltages and frequency within their acceptable limit val-
ues in the two studied cases. MG must contain at least
one controllable micro source (fuel cell or micro turbine)
to help frequency restoration when islanding occurs. If
there are no controllable micro sources in the MG, the
storage devices will still inject power in the MG until
their energy are consumed and black out is occurred.
Author’s next step research aims to study the dynamic
performance of the MG under different disturbances
conditions such as failures of one micro source, load
following, unbalanced loads, faults occur in MG feeders
and so on.
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R. M. KAMEL ET AL. 516
Appendix
Line Impedance Loads
Send Bus Receive Bus R (p.u) X (p.u) Bus P (kW) Q kVar
0 1 0.0025 0.01 2 10 2.5
1 2 0.0001 0.0001 4 19 11.7
2 3 0.0125 0.00375 5 10 2.7
3 4 0.0125 0.00375 6 19 11.7
4 5 0.0125 0.00375 7 6 2.7
5 6 0.0125 0.00375
3 7 0.0218 0.00437
Total 70 33.8
The units of the lines impedances have been calculated in power base of 100 kVA and voltage base 400V. Bus 0 represents the main grid.