1. INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING &
International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 10, October (2014), pp. 33-42 © IAEME
TECHNOLOGY (IJEET)
ISSN 0976 – 6545(Print)
ISSN 0976 – 6553(Online)
Volume 5, Issue 10, October (2014), pp. 33-42
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IJEET
© I A E M E
FREQUENCY CONTROL IN A MICROGRID INCLUDING
33
CONTROLLABLE LOAD
1Mahyar Saviss, 2Mohammad Ahi Andy
1Department of Azad University Science and Research Saveh Branch Faculty of Complementary
Educations
2Department of Tarbiat Modares University
ABSTRACT
In recent years, with the development of DG with loads lead to increase the number of
microgrid in the main network. When the microgrid is connected to the main network, voltage and
frequency are regulated by the main network. In case of errors upstream line or network, microgrid is
isolated from the main network (the island state). In this case, adjustment of the voltage and
frequency should be done by the microgrid. As a result, much research has been done to adjust the
frequency and voltage of the microgrid. In this paper, a method is presented for frequency control
using storages and Controllable load. Tools used in the proposed microgrid include Solar Power,
Wind Power Generation, Super Capacitor, Battery and Electric Water Heaters (EWH). In this paper,
the storages used and their relations are expressed. Then, the proportional integral (PI) controllers
used to coordinate the storages and producers of network-connected and island state and are
optimized by Particle Swarm Optimization (PSO). Finally, a control method is presented for applying
the EWH in order to adjust of frequency that helps frequency control. The methods is used to control
EWH, prevents damaging and sublation of EWH and reducing of joint comfort level.
Keywords: Frequency Control, Microgrid, Controllable Load, Solar Water Heater.
1. INTRODUCTION
Power systems are used on long distances for many years due to high transmission power
output at different voltage levels. In recent years due to environmental problems caused by standard
fossil-fuel powerhouse, several renewable energy conversion systems in distribution systems of ac
week-voltage were installed as DG units and ac microgrids. In general, a microgrid includes a set of
loads and small production units that as a controllable system and connected to distribution low or
Medium voltage network or apart from the upstream network (island), is utilized and (if necessary)

2. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 10, October (2014), pp. 33-42 © IAEME
are provide the power and heat for the desired area. Due to the expressed features of microgrids can
provide more reliable capability than distribution systems.
34
Figure 1: The overall structure of a microgrid [1].
When the microgrid is in parallel with the main network, frequency and voltage control is
performed by upstream network. But when microgrid is separated from the upstream network due to
the occurred error (to be island), microgrid supplies required power of loads by existing producer
units. Figure 2 shows a microgrid in island state. Microgrid in island state does not have network
support for controlling frequency and voltage. As a result, other strategies must be used to control
stability.
Figure 2: An island microgrid[1]
With detachable microgrid from power systems, the performance tasks and resources of the
existing resources are changed. The new tasks of resources include adjustment voltage / frequency,
proper division of required power of load between all the resources and quick and appropriate
respond to changes of load. The microgrid have non-dispatch producer power sources, such as a
generating powerhouse of solar, wind and etc. that is not able to harmonize with changes of
microgrid in island state. Sources named are highly dependent on environmental conditions and are
not configurable by the injection energy. This can cause instability frequency and thus the whole of
system.
To avoid instability, we need to find ways to control the frequency. These solutions are
various according to the type of energy producers and used instruments. Thus, there is the need for
researches to control the frequency of the microgrid including non-dispatch resources.

3. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 10, October (2014), pp. 33-42 © IAEME
35
2. INSTRUMENTS USED IN THE PROPOSED MICROGRID
In this thesis, a system includes photovoltaic and a wind turbine is introduced to generate
electricity. Also, the system includes a battery storage and super capacitor that are used to maintain
stability. Also, in addition to the normal loads, a Controllable electric water heater is intended to help
system stability. In proposed microgrid, desired unit , through a boost converter dc / dc is
connected to shane to eliminate high-frequency ripples and a capacitor is used with the output voltage
PV.
A three-phase inverter as main converter of the dc / ac bidirectional with an RLC filter and an
isolation transformer (for voltage reduction in inverter to decrease nominal values of instruments of
switching inverter and the capacitor section) is connected Shane dc to Shane ac. When the total
output powers of production units in dc section (PV, battery and super capacitor) be greater than the
sum of dc loads in this section (with the proviso that the battery is fully charged), the main converter
acts as an inverter and transfer additional generated power from the dc to ac section: but when the
total of generating capacity of the above dc units is less than total of consumable loads is, the main
converter acts as a rectifier and transfer power from ac to dc section. Also, when the total generating
powers in microgrid, is more than the total consumable loads (with the proviso that the battery is
fully charged), the surplus generating power of microgrid is injected into the main upstream network.
Otherwise, the lacks of power from the main network microgrid receive. At Fashion Island, dc bus
voltage only by storage units, kept steady and the exchanger in order to create a sustainable and high
quality ac voltage controlled buses. The Fashion Island, PV and wind units can trace the maximum
power point tracking (MPPT) off mode based on system requirements can be exploited. In this study,
the assumption is that the battery is not fully charged, so the units are operating at the maximum
power point [2].
3. SIMULATION RESULTS
This chapter discusses the simulation results of the voltage and frequency control and
frequency control by controlling the time allowed (EWH) is discussed. Scenarios are considered in
this chapter in the event of a major disturbance like an island being checked. Simulation results are
usually the voltage, ac frequency component, ac grade point work, EWH (Td) the temperature of the
water tank EWH (TH) are shown.
3.1 The values and assumptions of the proposed system
In this section, the values used for the system under consideration, including nominal values
and inputs of solar cells, wind turbines input, battery and super capacitor values and the values used
in the EWH expressed. These values are used for system simulation., A battery of 200 V, 65 Ah for
long-term energy storage instrument for energy exchange at steady state[3], and a 200 V super
capacitors Saver and 5F as an energy Saver is a super-fast response to changes in the dc bus voltage
of the storage battery, which are considered via a Convert dc / dc Bidirectional Qin to dc have a
connection.
The dc and ac loads, respectively, the dc and ac shins attached. Once a variable dc
(20-10 kW) only once Ohm which is connected directly to the dc bus., But once ac importance of
variable loads (15- 45 kW) inductive proof (10 kvar and capacitive constant (1 kvar) respectively.
Shins dc and ac voltages respectively ratings for 400 V and 400 V rms have been considered. an
inverter Tuesday the main phase converters dc / ac with a bi-directional filter and a transformer
isolation RCL) to reduce the voltage of the inverter and the inverter switching instruments in order to
reduce the nominal value of the capacitor (dc bus dc) to Shane ac is connected.

4. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 10, October (2014), pp. 33-42 © IAEME
In this study, the cutoff frequency of the LPF used in Figure 4-1 y, respectively, for the
control of hybrid energy storage in batteries and super capacitors connected to the network utilization
of the 79/0 and 25 Hz were considered. Nominal values and the values of the elements used in DFIG
are presented in table 1.
36
Table 1: parameters of the DFIG [4]
Unit Valu Symbol Parameters
kW 50 Nominal power
V 400 Vnom Nominal voltage
Pu 0/00706 Rs Stator resistance
Pu 0/171 Ls Stator inductance
Pu 0/005 Rc Rotor resistance
Pu 0/156 Lc Rotor inductance
Pu 2/9 Lm Parallel inductance
S 3/1 J Rotor inertia constant
6 Npa Pole numbers
V 800 Vdc_nom Nominal dc voltage in ac/dc/ac
kW 45 Nominal mechanical power
Nominal values and the values of the components used in solar cells are presented in Table 2.
Table 2: Parameters used in PV with the introduction of symbols and units [5]
Unit Value Symbol Parameter
V 403 Voc Nominal burden voltage
C 1/602×10-19 q Electron burden
J/k 1/50 A Ideal coefficient
1/38×10-23 K Boltsman constant
A 3/27 IRRo Short link current
1/7×10-3 K1 Temporal short link current
coefficient
K 301/18 Tr Source temperature
A 2/0793×10-6 Irr Inverted saturated current in
Tr
eV 1/1 Egcp Band gap energy for silicon
40 np Number of parallel cell
900 ng Number of sequential cells
w/m2 0800 S Sun shine surface
k 350 T PV temperature
Of PV, one of DG in recent years in many parts of the world used to be, is. The PV unit is a
fundamental physical process is carried out by the solar energy directly into electrical energy is.
Physics A cell PV, similar to a classical diode is a P-N Junction [6]. Figures 3 show the performance
of the PV.

5. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 10, October (2014), pp. 33-42 © IAEME
37
Figure 3: Production of the photon and electron holes [1]
Solar power generation units to achieve maximum throughput is to use a template. This model
uses the power electronics for maximum power point tracking is implemented. Figure 5 indicates
how the MPPT. Control of boost converter for PV module maximum power point tracking (MPPT) is
considered. By regulating the terminal voltage of the boost converter is able to track the maximum
power point [7].
Figure 5: show the MPPT voltage-current curve of a solar cell -power [1]
Figure 6: MPPT control algorithm for a unit PV [8]

6. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 10, October (2014), pp. 33-42 © IAEME
Figure 7: Block diagram of the boost converter controller in parallel operation mode microgrid [9]
In this study, we tried to use the integrated control system frequency in the 0/8 Hz of nominal
38
frequency, control [10]
Working at the base point, (Tdb at work when integrated control point is disabled, Td is the
frequency of the system). Tdb amount equal to 120°F defined. The value of a constant nominal
frequency), the frequency is 60 Hz, which corresponds to the main network) is. Amount m is very
important because of its impact on Td. If m is too large, Td with large amounts of increase or
decrease, which may lead to lower levels of customer comfort, and be EWH on and off repeatedly. If
m is too small, integrated control will have a significant impact on reducing the frequency deviation.
Values of m have to keep Td in an acceptable range; (Tdmax-Tdmin) that °F001-041 is designed. The
temperature range for consumer welfare and to prevent excessive depreciation EWH is considered. In
addition, m must be between fmin and fmax is designed to maintain the frequency. As a result, the
value of m can be used with the performance of low-frequency (fmin and Tdmin) and high frequency
performance (fmax and Tdmax) is selected. M must be the same in both cases. Td + , Td and Td_
linear system with frequency change. . The thesis is intended to 2/5 °F. , Td 60/8 Hz when the
frequency is equal to the maximum value (140°F) and Td when the system frequency is equal to 59 /
2Hz is the lowest (100°F) appears. Notably, when 60/8 Hz frequencies above or below the Hz2 / 95
to go, Td should be equal to 140°F or 100°F. Therefore, a limit must be used to keep the Td in this
area. With respect numbered 4-4, m is obtained. Table 5-3 shows the values used EWH.

7. Table 3: Parameters of EWH [11]
unit Value Symbol Parameters
kW 4 Prated Nominal power
Btu/h 13652 Q Input energy
gal 50 V Chamber volume
Btu/ 417 C Temporal capacity of chamber
water
60 Tin Cold water temperature
67/5 TQ Environment temperature
1b/gal 8/35 Water density
Btu/1b. 1 Special temperature of water
Btu/.h 3/6 G Temporal loss coefficient per
chamber surface
v 240 VL-L Line to Line voltage

8. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 10, October (2014), pp. 33-42 © IAEME
EWH used in this system by a resistor and a switch capable of handling the simulation to
simulate thermostat. The strength of the relationship can be calculated easily. Substituting nominal
values in the throughput, resistance value is obtained as follows.
39
!
#$
# % $'
## (
Microgrid for frequency control, a main transformer inverter, as the division of power in the
dq coordinate system runs handled by using the PI controllers used PSO algorithm, a number of
parameters, is optimized. EWH presented in this thesis is a method for controlling the encoding of
the original control system. Here are two algorithms to reduce the number shimmer EWH shown in
Figures 8 and 9, Figure 8 shows algorithm that used to increase the frequency and Figure 9 shows
algorithm that used to reduce the frequency.
Figure 8: Frequency control algorithm Figure 9: frequency control algorithm
for adding frequencies [12] for a drop in frequency [12]
At the end of a PSO optimization method to optimize the use of the PI controller is used. By
implementing PSO using the following values are obtained:
)*'
+,---).'
+/, )*0
1#-, ).0
#2#, )*
-3, ).
+,
)*
)*4
+, ).
).4
33/1, )*506
##, )*56=)*546=25/3, ).56
).546
/3,
)*56
/, ).56
3$1

9. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 10, October (2014), pp. 33-42 © IAEME
40
Figure 10: The optimization algorithm PSO
3.2 Display and analysis of simulation results
In this section, simulations performed in MatLab / Simulink to verify the frequency is
controlled by the controller, are shown. Under the terms of disruption microgrid Island, the Optimum
frequency oscillation is on damping parameters. Occurrence islanding occurred in 7.0 seconds.
Figure 11: Changes in frequency Figure 12: Changes in the effective
during islanding supply voltage during islanding

10. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976
ISSN 0976 – 6553(Online) Volume 5, Issue 10, October (2014), pp.
In the islands of the super capacitor element
– 6545(Print),
the super-capacitor controls system which is inten
battery. Figures 13 and 14 show the performance of batteries and super capacitors. Deviations high
frequency capacitors initially by the cloud and by the low
compensated by the battery. In Figures 15 and 18 show the performance of the EWH.
Figure 13: capacitors on the island
of cloud condensation
Figure 15: Frequency change with temperature
change EWH working point in the island state
Figure 17: displays shimmer on the
island of EWH
nternational 33-42 © IAEME
41
microgrid is the fastest reaction is shown. After
intended to EWH, it acts and finally start
starts charging the
high-frequency
low-frequency response and distortions are
ated Figure 14: Flow batteries on the island
of disruption
Figure 16: EWH tank temperature changes
during islanding
Figure 18: Changes in the terms
of Btu / h in the island of

11. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 – 6545(Print),
ISSN 0976 – 6553(Online) Volume 5, Issue 10, October (2014), pp. 33-42 © IAEME
42
4. CONCLUSIONS
In this study, a Microgrid includes a power generation system, PV power generation system,
wind, batteries, super capacitors and a Controllable load capability (EWH) is introduced.
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