Microgrid Design

Student
Instructor
Electrical Power System
Date

Microgrid design
1
Abstract
In order to curb atmospheric pollution which has been posing a menace to the existence of
ecological system, mainly caused by unbridled emission of hazardous gases and fumes, all
sectors of economy has a role to play. The possible solution in the energy sector has been
made possible by embracing green energy technology. This technology has numerous
advantages just to mention a few; they can be operated in a stand-alone mode, they can be set
anywhere on the planet with existence of driving forces (considerable wind and solar
insolation), and construction time is very minimal compared to other forms of energy
generation utility. This report has dealt with method of estimating capacity of prerequisite
components of microgrid for the given peal load and average load demand. It has also
explained load scheduling ford the different generation unities in analysis and flowchart
representation.
Introduction
A micro grid standalone system consists of the PV modules, wind turbine, diesel generators
and inverters and controllers, battery storage banks and panel controllers [1]. Wind power
energy is a form of green energy produced by conversion of kinetic energy of the wind into
electrical energy. Naturally, wind flows is caused by pressure difference caused by
heterogeneous solar radiation reaching earth’s atmospheric structures. To meet load
requirement of the grid based on the consumers’ need, the grid need to be supplied with
dispatchable electricity. Wind power is not dispatchable by the fact that it solely depends on
the natural characteristic of the wind. Therefore, the output power is not guaranteed to meet
consumers’ demand since the system is vulnerable to fluctuation patterns of wind speed.
Solar energy if very friendly to the environment since it is clean, soundless and does not emit
fumes into the atmosphere [2]. Electrical energy is generated by conversion solar energy from
sunlight into electrical energy using photovoltaic cells. Photons energy greater than
semiconductor’s band gap energy is absorbed when light strikes on the surface of the solar
cell ejecting electrons and creating numerous pair of electron-hole pair [8].
Modelling of wind power turbines.
The actual mechanical power of the rotor blades is extracted from the difference between
[3] upstream wind power and downstream wind power as shown in the equation below.
Pw= 1
2 (ρA V + V O
2 ) (V 2−V 2
O ) (1)
Where Pw power of the rotor, V ∧V oare upstream entrance and downstream exit wind
velocity.
Volumetric mass flow rate= ρA V +V O
2 (2)
Rearranging equation (1) algebraically;

Microgrid design
2
Pw= 1
2 ρA V 3
( 1+ V O
V ) [ 1− ( V O
V )
2
]
2
(3)
The above equation comprises of two fundamental concepts namely; the general wind power
formulae and the fraction of upstream wind.
Pw= 1
2 ρA V 3 CP (4)
Where CP the rotor’s power coefficient that is basically the fraction of the upstream wind
energy converted to mechanical energy and fed to electrical transducer.
Theoretically, for maximum power output of the wind power, CP is 0.59, which is greatly
defined by¿). This fraction is the function of Tip-speed Ratio (TSR) of the rotor.
For this design, horizontal-type rotor is highly recommended since it possesses higher TSR
compared to vertical-type rotor such as savonious and darrieus [3]. Location for the
installation of wind turbine should be characterized by continuous flow wind at a
considerable speed.. When the wind speed exceeds considered safe speed, known as cut-out
speed, that could pose damage risk to the rotor blades, braking system is triggered to bring
rotor to a standstill [4].
Bar graph showing wind factor characteristic for the period of twelve days was plotted in
Matlab. Average normalized wind power was calculated using data in table (7) located in the
appendix section
Fig 2: Distributed normalized wind factor for a period of 12 days
C p=
∑
i=1
i=12
C pi
12days = 0.48+0.44+ 0.41+ 0.38+0.40+0.42+0.35+ 0.38+0.42+0.38+0.44 +0.46
12 day
(5)

Microgrid design
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C p=0.413
Using data from table (3) in the appendix, and equation (5)
Pw= 1
2 ×1.225 kg /m3 ×31.9 m2 × ( 14 m
s )
3
×0.413 (6)
Pw=22142.72W
Mathematical modeling of the PV module.
The amount of electricity generated depends on factors such as the amount of solar
irradiance, type of the panels, and types of the inverters and converters used. Available power
(kWh) on the PV panel was calculated by the expression below.
PPV −out=PPV × Ƞpr × p . f × t (7)
Where Ƞpr is the performance ratio, p.f is the combined power factor, andt is the peak sun
hours. Number of panels required for the system can be estimated as;
N p= Average daily load demand
PPV −out
(8)
Using data in table 7, appendix section, a bar graph of peak hour of solar was programmed in
Matlab.
Fig 3: Distributed solar insolation for a period of 12 days