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OFF-GRID POWER SUPPLY SYSTEMS AS INNOVATIVE SOLUTIONS FOR IMPROVING AGROTECHNICAL IRRIGATION MEASURES: TECHNICAL ASPECTS AND PRACTICAL IMPLEMENTATIONS

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Abstract

The growth of the population on Earth, the impact of climate change, increasing industrial and communal pollution on the one hand and the development of scientific and technological achievements in agriculture on the other hand, determine the dynamic development of this sector. The growth of the world's population and, consequently, the increase in demand for food and food products are in contradiction with the fact that due to climate change and its immediate consequences (drought and floods, pollution of land, water and air), arable agricultural land is constantly decreasing. In addition to this, demographic trends are of such a character that the number of inhabitants in urban areas is growing significantly, while in rural areas the population is very small. These facts lead to a disproportion between the requirements and the possibilities of agricultural production. Agriculture is one of the key components of the economic development of the Republic of Serbia because, in addition to economic, it also has a pronounced social and environmental significance. However, agriculture in Serbia is still significantly carried out in the traditional way, without the introduction of modern knowledge and agro-technical measures appropriate to developed and environmentally-conscious countries. Where agro-technical measures are applied, it is done in an irrational and economically unsustainable way. An example is the measure of crop irrigation, which is a key link in the production chain in the conditions of climate change. Although only about 2% of usable agricultural land is irrigated in Serbia, this agro-technical measure is carried out mostly with the use of fossil fuel aggregates (petrol and diesel), which release harmful gases that go into the atmosphere and intensify the greenhouse effects, polluting the ecosystem and thus causing significant economic losses. This lecture will present practical realizations OFF-GRID and hybrid power supply systems mainly based on renewable energy sources (RES), primarily solar and wind energy, which were used for irrigation of vegetable crops and for smart management of agricultural land in several locations in Republic Serbia. Based on the design experience of lecturer in the field of OFF-GRID systems design, in the lecture will present the specifics and methods of designing these power supply systems, as well as control structures, with emphasis on application in irrigation systems. All types of power conversion DC/DC, DC/AC, AC/DC, AC/DC/AC take a special place in these systems and as such largely determine the behavior of the entire OFF-GRID system. The lecture will present the latest topologies of converters used in these systems, as well as some exploitation problems and technical aspects of practical implementation. Finally, directions for further development of OFF-GRID systems for the improvement of agrotechnical irrigation measures will be given, as well as directions for further development of power converter topologies applied in these systems.
OFF-GRID POWER SUPPLY SYSTEMS AS INNOVATIVE SOLUTIONS
FOR IMPROVING AGROTECHNICAL IRRIGATION MEASURES:
TECHNICAL ASPECTS AND PRACTICAL IMPLEMENTATIONS
Institute Nikola Tesla, Univeristy of Belgrade, Serbia
Željko V. Despotović PhD.E.E,
IEEE Senior Member
Institute “Mihajlo Pupin“,
University of Belgrade,
Volgina 15, Belgrade, Serbia ,
zeljko.despotovic@pupin.rs
Belgrade, 28.04.2022.
Invited Lecture
INTRODUCTION
The growth of the population on Earth, the impact of climate change, increasing industrial and communal
pollution on the one hand and the development of scientific and technological achievements in agriculture on
the other hand, determine the dynamic development of this sector.
The growth of the world's population and, consequently, the increase in demand for food and food products are
in contradiction with the fact that due to climate change and its immediate consequences (drought and floods,
pollution of land, water and air), arable agricultural land is constantly decreasing.
In addition to this, demographic trends are of such a character that the number of inhabitants in urban areas is
growing significantly, while in rural areas the population is very small.
These facts lead to a disproportion between the requirements and the possibilities of agricultural production.
Agriculture is one of the key components of the economic development of the Republic of Serbia because, in
addition to economic, it also has a pronounced social and environmental significance. However, agriculture in
Serbia is still significantly carried out in the traditional way, without the introduction of modern knowledge and
agro-technical measures appropriate to developed and environmentally-conscious countries.
Where agro-technical measures are applied, it is done in an irrational and economically unsustainable way. An
example is the measure of crop irrigation, which is a key link in the production chain in the conditions of climate
change. Although only about 2% of usable agricultural land is irrigated in Serbia, this agro-technical measure is
carried out mostly with the use of fossil fuel aggregates (petrol and diesel), which release harmful gases that go
into the atmosphere and intensify the greenhouse effects, polluting the ecosystem and thus causing significant
economic losses.
MOTIVATION
Considering that crop irrigation is realized mainly, in periods when the strongest solar insolation's in
the mentioned hybrid systems play a significant role in solar irrigation systems.
Solar irrigation is used for smaller agricultural plots during the summer months in places where
there is no connection to the electricity distribution network.
The problem of irrigation is the latter years is extremely relevant because climate change is evident
so that summers are getting warmer and with less rainfall.
Solar irrigation is mainly used for irrigating larger gardens and smaller plots, bearing in mind that
the source of electricity still has less energy to power large plots and farms.
In relation to irrigation with diesel generators, this irrigation has an advantage environmentally
and does not have exhaust gases or combustion ingredients, so it can be used for irrigation of
environmentally prepared food.
The problem is very actual in the world, especially in countries where there is a lot of sun and
underground water sources for irrigation and additionally, on the place where the electricity
distribution network is unavailable.
LECTURE CONTENT
This lecture will present practical realizations OFF-GRID and hybrid power supply systems
mainly based on renewable energy sources (RES), primarily solar and wind energy, which
were used for irrigation of vegetable crops and for smart management of agricultural land in
several locations in Republic Serbia.
Based on the design experience of lecturer in the field of OFF-GRID systems design, in the
lecture will present the specifics and methods of designing these power supply systems, as
well as control structures, with emphasis on application in irrigation systems.
All types of power conversion DC/DC, DC/AC, AC/DC, AC/DC/AC take a special place in these
systems and as such largely determine the behavior of the entire OFF-GRID system.
The lecture will present the latest topologies of converters used in these systems, as well as
some exploitation problems and technical aspects of practical implementation.
Finally, directions for further development of OFF-GRID systems for the improvement of
agrotechnical irrigation measures will be given, as well as directions for further development
of power converter topologies applied in these systems.
OFF GRID-solar and (or) wind power→OFF GRID HYBRID POWER SYSTEMS (surface irrigation)
Solar energy in combination
with wind energy are one of the
most commonly used hybrid
energy sources for various
purposes, which relate to the
application and improvement of
agro-technical measures in
irrigation systems.
The advantage is the fact that in
periods when there are lower
intensities of solar radiation
(late autumn, winter or early
spring), wind energy dominates.
Also, in the summer period
(which otherwise implies the
dominant energy of the sun),
especially in mountainous areas,
but often in plains, at night
when there is no solar energy,
wind energy becomes dominant.
groundwater source
surface
Complementary Regimes of Solar and Wind Energy in Serbia
Annual of average (by month) course of
solar and wind energy in Belgrade from
1961. to 1990. (Wind at the height of
100m, solar at the surface)
Source: Petar Gburčik, Verica Gburčik, Milivoj Gavrilov,
Vladimir Srdanović, Sreten Mastilović:Complementary
Regimes of Solar and Wind Energy in Serbia
in periods when there are lower intensities of solar radiation (late
autumn, winter or early spring), wind energy dominates.
TYPICALLY DAILY PROFILES of Wind Farm + Solar Farm and Hybrid System
Generation profile of hybrid versus solar versus wind output
(Source: TLT Analysis)
Tipically in the summer period (6h a.m.-6h p.m.)
which otherwise implies the dominant energy of
the sun, especially in mountainous areas, but
often in plains, and at night (10h p.m- 6h a.m.)
when there is no solar energy, wind energy
becomes dominant
Surface irrigation system drip irigation ("drop by drop„)
1. Pump 9. Air valve
2. Check valve 10. Control valve
3. Normal valve 11. Distribution pipeline
4. Manometer 12. Irrigation pipeline (lateral)
5. Filters 13. Dropper
6. Fertilizer tank 14. Shutter
7. Fertilizer injector 15. Draain
8. Main pipeline
Drip irrigation belongs to the group of the most
modern watering methods. Water is supplied to
each plant or group of plants through a network of
densely branched pipelines, under low pressure,
while moistening a small part of the surface.
The "Agro Kapilaris" irrigation system is a method of sub-surface capillary irrigation in which the basic principle is to
distribute water to the plant roots by specifically constructed water transmitters, which are installed below the depth
of tillage.
The water transmitters are located at a depth of thirty centimeters, so that the water is delivered directly to the root.
It is a system of underground channels that always keep the water at a certain level and the water moves capillary
through the soil, radially upwards and sideways, and this is what gives the plant the ability to feed from the soil
More on this in the key reference:
Zloh, Z., AGRO KAPILARIS" A Revolutionary Method of Irrigation,
PROCEEDINGS of The 1st International Congress on Soil Science, XIII National
Congress in Soil Science SOIL WATER PLANT, September 23 26th, Belgrade,
SERBIA, 2013
Sub-surface irrigation system "Agro Kapilaris
OFF GRID HYBRID power supply systems-GENERAL
Hybrid power supply systems (HPSS) are power systems
that contain more than one power source.
In general, HPSS supply consumers with electrical energy,
which is obtained mainly from renewable energy sources
(RES)
These systems usually consist of wind turbines with
generators, PV panels, hydro-generators, and in some
cases when greater power autonomy is required, diesel
electric generators (DEG) or gasoline electric generators
(GEG) are added as auxiliary power sources; DEG,
GEG=emision CO2, noise, vibrations!!
HPSS are mainly found in the form of the two most common topologies:
(1) centralized DC bus“, (2) centralized AC bus".
Centralized "DC-bus" topology (application with DC submerisble pump)
Power supply systems for
DRIP IRRIGATION and with
one or two storages:
-electrical (battery bank)
and (or)
-water storage
Idc
Idc
Idc
For pump power of 2.2kW and
battery voltage 24Vdc
Idc≈100A!!!!
Centralized "DC-bus" topology (but application with AC submerisble pump)
Power supply systems for
DRIP IRRIGATION and with
two storages:
-electrical (battery bank)
-water storage
Centralized "DC-bus" topology (application with AC 3ph or 1ph submerisble pump)
Power supply systems for DRIP IRRIGATION and with one storage:
-water storage
-water storage is is cheaper than battery storage
Centralized "DC-bus" topology (application with DC, AC 1ph or 3ph submerisble pump)
Power supply systems for SPINKLERS
IRRIGATION with one storage or without
storage:
-battery bank storage
DEG (or GEG), which pollutes the environment, makes noise
and does not fit into agricultural systems for the production
of "organic food“!!!!.
spinklers
spinklers
spinklers
Centralized "DC-bus" topology (application with AC 3ph or 1ph submerisble pump)
Power supply systems for SPINKLERS IRRIGATION with one storage:
-battery bank storage
DEG (or GEG), which pollutes the environment,
makes noise and does not fit into agricultural systems
for the production of "organic food“!!!!.
spinklers
spinklers
Centralized "DC-bus" topology without DEG/GEG and with reinforced battery bank
(application with AC 3ph or 1ph submerisble pump)
Solution for pump electrical power
up to Pin=2.2kW
Solution for pump electrical power
up to Pin > 2.2kW (Typical 5.5kW or 7.5kW)
Pin Pin
spinklers spinklers
Centralized „AC-bus" topology (application with AC 3Ph submerisble pump)
Power supply systems for
DRIP IRRIGATION and with
two storages:
-electrical storage (battery bank)
-water storage
Power supply systems for
DRIP IRRIGATION and with
one storages:
-water storage
Centralized „AC-bus" topology (application with AC 3Ph submerisble pump)
Power supply systems for
SPinklers IRRIGATION with
one storage:
-battery bank storage
DEG, GEG:
emision CO2, noise, vibrations!!
DEG (or GEG), which pollutes the environment, makes noise and does
not fit into agricultural systems for the production of "organic
food“!!!!.
Centralized „AC-bus" topology (application with AC 3Ph submerisble pump)
Power supply systems for
DRIP IRRIGATION and with
one storages:
-battery bank storage
spinklers
Typical OFF-GRID system
Typical performance curves and design relations for a centrifugal pump
Head, power consumption, efficiency and NPSH are
shown as a function of the flow
1.Efficiency, the η-curve :
1
ρ- the density of the liquid in kg/m³ (1000kg/m³
for water),
g -the acceleration of gravity in m/s²,
Q-the flow in m³/h and H is the head in m
Ph-the power which pump deliver to water
For water at 20ºC and with Q measured in m³/h and H in m, the hydraulic
power can be calculated as :
2. Power consumption, the P2-curve :
2
load
characteristic
H-Q curve
operating
point
3. NPSH-curve (Net Positive Suction Head)
3The NPSH-value of a pump is the minimum absolute pressure that has to be
present at the suction side of the pump to avoid cavitation. The NPSH-value is
measured in [m] and depends on the flow; when the flow increases, the NPSH-
value increases as well.
8
Pp=5.5kW, 3~
ηp≈0.6
H=60m
Q=17·10³ l/h
A=8 hectars
Projected capacity of the
single-phase (power 2.2
KW) and three-phase
(power 5.5 kW) solar
generator at surface
spinklers irrigation,
depending on the depth of
pumping water from a
source (flow rate in liters
per hour and surface of
irrigated land )
Typical capacities of 1Ph and 3Ph centrifugal pump (surface spinklers irrigation)
x10²
The type of watering for typical vegatable plot
If watering is possible during the sunny part of the
day (high insolation), the simplest system with PV
panels and distribution cabinet with control
modules a pump and watering pipes is used.
In the other cases, it is necessary that the system
has rechargeable batteries for storing a certain
amount of energy and (or) a tank for storing the
daily amount of water for irrigation.
Continuous watering during 24 hours means filling
the tank during insolation and emptying the unit
24 hours a day.
Evening watering, which is mostly and most
present, involves filling the tank with water during
insolation and watering the terrain during the
evening without the presence of the sun
The sizing of the hybrid power supply system for crop irrigation,
in addition to the design of the pumping plant, includes the
following items:
-Design of solar power (PV) subsystem
-Design od wind power subsystem
-Design of battery bank
-Control and system optimization
In the continuation of the presentation, an example of sizing a
hybrid power supply system for a crop irrigation pump will be
given (the plot area is about 10 acres). The pump has an input
power of 4 kW, it is used in combination with a frequency
regulator (pressure regulation in the irrigation system); The input
power of the frequency regulator is about 5.5 kW.
The location of agricultural plot: village BELEGIS (close to
Belgrade)
LATITUDE/LONGITUDE 45.020N/20.343E
DESIGNING of HYBRID POWER SYSTEM (off-grid)
BELEGIŠ
For the observed longer period 2005-2022,
the most unfavorable case regarding
irradiation was adopted (2014); conservative
approach
Village BELEGIŠ
The months of May-September 2014
(season of watering crops on a given plot)
are of interest for the process of watering
agricultural crops.
Optimal angle of inclination: 38°
ΣH38=162.79+179.11+191.27+194.51+120.18=848kWh/m²
Average value of daily solar irradiation for the months of May-
September 2014: 848kWh/m²/153 days=5542Wh/ /day
Monthly solar irradiations in summer period-location Belegiš
„PEAK SUN HOURS-PSH
Based on the previously adopted value of irradiation under
the most unfavorable conditions and at an inclination angle
of 38 °, the average number of hours of so-called "Peak
sun" is calculated according to the relation:
]/[1000
]/[
2
2
_38 mWh
mWhH
PSH sr
h
mWh mWh
PSH 542.5
]/[1000 ]/[5542 2
2
Total energy consumption in the irrigation system: E= 5.5kWx6h≈33kWh (6h time duration o irrigation)
Assuming that the efficiency of the MPPT charger controller is 90% and the efficiency of the batteries is 90% (obtained
from the manufacturer's catalog), the required power of the solar panel under these conditions is:
batreg
PV PSH E
P
kWPPV 35.7
9.09.054.5 33
Mobile solar generator (MSG
with two-axes tracking) has 4
panels each 350W: 4x350W =
1400W; Therefore P*pv =7400W-
1400W = 6000W;
Since the remaining panels are
250W, then the number of fixed
panels on the ground is
6000W/250W = 24 (two groups
of 12 PV panels each)
DISPOSITION OF HYBRID POWER PLANT
Wind generator
MSG PUMP
STATION
Fixed PV
Fixed PV
Battery bank
SIZING THE BATTERY BANK
The required battery capacity in this case is calculated from the relation:
tbatbatbat
bat KVU tt
WhE
AhC
)(
][
][ 0
][WhE
-required energy consumption
t/to scaled amount of the total part of the irrigation time (in this case it is 3 hours, so the ratio is equal to 3/6)
][VUbat
-rated battery voltage (in this case 48Vdc)
100/[%]
bat
-allowed discharge depth of the battery (in this case 0.5)
- AGM VRLA battery efficiency (in this case 0.9)
t
K
-correction factor for battery capacity drop due to temperature drop (in this case 1; favorable
conditions since irrigation is carried out in summer)
Ah
V
Wh
AhCbat 720~
153.09.0)(48 6
3
][33000
][
WIND GENERATOR
The characteristics of the wind generators differ from one type to another and from a manufacturer to other
of the same power.
The most important parameter is the output power, which strictly depends on the speed of the wind “V” and
the area of the wind turbine. The wind speed varies using the height to the ground “H” according to the
following function (Zghal 2011):
n
H
H
V
V
00
Vo: wind speed at the height Ho;
• n: coefficient that varies between 0,1 and 0,4.
The lowest values correspond generally to the strongest and vice versa.
The transmitted power by wind generator “Pt” is generally deduced from the wind power using the power
coefficient “Cp” (Zghal 2011):
3
2
1VSCP pt
For a wind turbine, the available energy “Ew” on day (24h), by unit of surface,
is calculated by the expression:
tw PE 24
Output power generator characteristic wind turbine AEOLOS H500
MSG
Wind turbine AEOLOS H500
In the last 10 years, the Institute Mihajlo Pupin has implemented several
projects related to OFF-GRID power for crop irrigation at several locations
around Belgrade:
Mobile solar electric generator MobiSun Pro Energy™, developed in the Mihailo Pupin
Institute (locations: Veliko Selo and Glogonj (Pancevo municipality) ( 2014.-2017.)
HYBRID POWER SUPPLY OF THE AGROKAPILARIS® SYSTEM FOR IRRIGATION OF VEGETABLE
CROPS IN "GRABOVAC" OBRENOVAC MUNICIPALITY (2019.-2020.)
Realization of a hybrid power supply system based on renewable energy sources (sun and
wind) which is used for irrigation of vegetable crops and for smart management of
agricultural land on a plot of about 8ha at the location of the village "Belegiš„ (2020.-2021.)
OFF GRID SYSTEMS -PRACTICAL REALISATION
1.Mobile solar electrical generator MobiSun Pro Energy™
Mobile solar electric generator
(SEG) MobiSun Pro Energy™,
developed in the Mihailo Pupin Institute, is a
modern automated device for electrical power
production based on the use of renewable energy
of sun.
It is intended for individual users, small and
medium customers of electrical power, like
alternative resource for off-grid supplying.
It has universal purpose and can be used in
household, agriculture, industry, tourism, etc.
MobiSun Pro Energy™ is designed to be
autonomous device without connecting to the
electrical network (off-grid) and any kind of
construction and energy infrastructure is not
required.
Suitable for use on variety of terrains (rural or
urban) where natural conditions for the exploitation
of solar energy exist and there are no conditions
for use of electric power infrastructure.
It is designed to be steadfast for various
weather conditions rain, sun and wind (up to
80km/h).
Mobile solar electric generator MobiSun Pro Energy™ -disposition
MobiSun Pro Energy™ consists of five basic modules (technical
subsystems):
Transport module with lateral stabilizers (1)
Mechanical structure and two-axis robotic mechanism for solar tracking (2)
Three photovoltaic panels of 3 x 300 W power (3)
Power conversion subsystem: MPPT solar charger DC/DC (4), battery bank
storage (5), inverter DC/AC (6)
Control and communication block: microcontroller of two-axis robotic solar
tracking system (7) and GSM module (8) for remote control and data
transmission from the device to the user
(1)
(2)
(3)
(3)
(5)
(6)
(4)
(5)
(5)
(5)
(5) (5)
(7)
(8)
(2)
TECHNICAL PERFORMANCE
PV input
PV panels (1600x1000mm) 3 pcs
Peak power 3x300W=900W,
Peak power voltage: 32VDC
Peak power current: 3x9.5A=28.5A
AUTOMATIC SUN TRACKING (dual axis solar tracking algorithm)
BATTERY CHARGER
Input voltage 10-36VDC
Nominal current In=40A
Implemented algorithm MPPT
Monitoring of state of the charge (SOC) and displaying of all
operative statuses (nominal regime and alarm state)
CAN bus communications port
BATTERY
Gel, special designed for solar application
3000-5000 cycles of charging/discharging
5x(2x12V/100Ah)
Total capacity 500Ah
INVERTER
Input voltage: 24VDC (nominal), range:18-40VDC
Output voltage: 230V,(50Hz±0.1%), range: 180-240VAC
Output current: In=13A
Peak power: 6kW (short time)
Efficiency: 95%
Total harmonic distortion (THD)<3%
Protections (output short circuit, overload, battery voltage too high,
battery voltage too low, temperature too high, 230 V AC on inverter
output, input voltage ripple too high)
CAN bus communications port
Mobile solar electric generator MobiSun Pro Energy™ -principal block scheme
FIRST OPTIMIZATION in MobiSun Pro Energy™ generator :
MAXIMUM POWER POINT TRACKING
D
D
VV inout
1
Digital Controlled Four Switch Synchronous Buck-Boost
Power Converter based on PIC18F4520 Microcontroller
SOLAR MPPT CONTROLLER
The basic topology of
"buck-boost four switch converter"
time interval 0 < t < DTs
time interval DTs < t < Ts The characteristic waveforms of power converter
for continuous conduction mode (CCM).
Basic control structure of four switch “buck-boost”
power converter
Electrical scheme of realized four switch
“buck-boost” power converter realized prototype of power converter
Digital Implementation of MPPT Algorithm in Ćuk DC/DC
Power Converter Based on PIC18F4520 Microcontroller
0
)( dU
dI
UI
dU
UId
dU
dP
)0(; dU
dP
U
I
dU
dI
)0(; dU
dP
U
I
dU
dI
)0(; dU
dP
U
I
dU
dI
Wiring diagram of MPPT converter based on Cuk's converter
Basic control structure
MPPT algorithm based on the method of incremental
conductance (INC)
Battery bank storage
typical
MPPT- Benefits?
output power of PV
panels /without
battery
MobiSun Pro Energy™
MobiSun Pro Energy™
output power of PV
panels/with battery
SECOND OPTIMIZATION in MobiSun Pro Energy™ generator :
DUAL AXIS DRIVE and TRACKING OF SUN TRAJECTORY
Chronological tracking based on natural observation
of the position of the sun in a given area and a given
time period during the year.
This means that for certain geographic coordinates
and a certain period of time the program (software)
can determine the position of the sun during daylight
In accordance with the program can be controlled by
the position of the solar panels throughout the day,
during the period of use of the solar
This method of positioning is independent of cloud
cover because the is known position of the sun at any
time.
The only thing that need to take into account the
orientation of the local coordinate system of solar
panels in relation to the global coordinate system
(Earth).
MECHANICAL STRUCTURE of MobiSun Pro Energy™
Construction with
two linear actuators
SMART actuator
include:
-servo driver of linear
motor
-position sensor
LINEAR DRIVE
Assuming that the axis drives
turning-on incorporate every
15 minutes to be at the
beginning and at the end of
the day (sunset / sunrise) had
angular displacement α
around 2º-3º, amid-day
5º- 8ºazimuth, while the
elevation of βchange milder
than 1º- 2º.
To accomplish this, we chose
a system with two
independent degrees of
freedom i.e. two actuators.
Range of azimuth and elevation angles-dual axis tracking
Construction with rotational drives
Construction with
two rotational actuators :
Slewing drive with two
smart actuators
SMART actuator include:
-servo driver /motor
-position sensor (inclinometer)
SOURCE:
5. MKOIEE, Beograd, 12. i 13. oktobar 2017
5th ICREPS, Belgrade, 12th and 13th October 2017
Block diagram of two-axes control system of solar tracking implemented on mobile solar generator
MobiSun Pro Energy
According to the current date
and time, current global position
in the field provided by the
satellite using global GPS sensor,
measuring the magnetic North
by the compass and using the
correction of the angle of the
current position by measuring
the inclination by two axis
inclinometer it is possible to
correctly determine where is the
current Sun position on the
horizon. According to this
mathematical measurement and
correction two axis position
system (azimuth and elevation) is
capable to find current position
of the Sun on the horizon.
TWO AXES CONTROL SYSTEM
TRACKING of SUN TRAJECTORY-Benefits?
MobiSun Pro Energy™
output power of PV panels
DC/AC power converter(s)
Push-pull
Neutral Point
Clamp Inverter
Single inverter start from the open circuit to
nominal load 1600 W; CH1load voltage (200
V/div), CH2load current (5 A/div)
Coupling and
synchronization of
inverters group
Waveforms
Parameters
Experimental setup-testing
The solution with single-phase output
(three 1ph inverters in parallel coupling)
Single phase
synchronization
Parallel connection of the three inverters, load 2000 W,
CH1– system’s output voltage (300 V/div), CH2
MASTER inverter output current (1 A/V), CH3SLAVE 1
inverter output current (1 A/V), CH4SLAVE 2 inverter
output current (1 A/V)
The solution with three-phase output
(three 1ph inverters in „STAR“ connection
Three-phase
synchronization
Three-phase connection, load of 3000 W, CH1MASTER inverter output current (1
A/V), CH2SLAVE 1 inverter output current (1 A/V), CH3SLAVE 2 inverter output
current (1 A/V)
Irrigation system with centrifugal pump and variable frequency drive (VFD)
5. MKOIEE, Beograd, 12. i 13. oktobar 2017
5th ICREPS, Belgrade, 12th and 13th October 2017
At the inlet of suction pipe, which was inserted into the water tank, a check valve is place.
Check valve allows water flow in one direction i.e. from water tank to the centrifugal pump.
Before pump starts, impellers blades have to be under water.
PROBLEM AT THE DIRECT START OF THE PUMP WHICH POWERED FROM
INVERTER !!!
-The start of the pump (that starts directly) is accompanied by a very pronounced
electric shock and a very pronounced drop in voltage on the battery bank
-Typically for a 4kW pump, rated current 8A, the peak current is about 80A
-This results in a voltage drop of up to 40-50% (deep discharge)
-CONCLUSION: The AC voltage source (inverter) must have a built-in SOFT-START
-Since the regulation of the PRESSURE or FLOW of the pump (ie speed control)
is also required, the use of a FREQUENCY REGULATOR is imposed.
Principal block scheme of pressure control in PV irrigation system
5. MKOIEE, Beograd, 12. i 13. oktobar 2017
5th ICREPS, Belgrade, 12th and 13th October 2017
The frequency converter (DC/AC) is with implemented scalar voltage/frequency (V/f) control.
The three phase full bridge IGBT inverter is based on Space Vector Pulse Width Modulation (SVPWM).
The frequency reference at the input of V/f control block is actually the output of PI controller.
Voltage reference is at the output of V/f block.
Both frequency and voltage reference are input signals to SVPWM control algorithm of the IGBT inverter.
In the PI pressure controller is additionally implemented soft-start function in order to provide controlled and gradually start
of pump motor, without wonted current peak.
Also, this greatly saves battery storage i.e. battery bank which is located between input DC photovoltaic system
(solar panels, DC/DC charger with MPPT control) and DC inverter input.
FREQUENCY REGULATION adapted to the solar system
In solar OFF-GRID systems, the frequency regulator is actually a three-phase DC / AC converter that converts the DC voltage
of the battery into a three-phase voltage of 3x230 / 380V in the frequency range 0 ...... 100Hz.
In this way it is possible to change the speed of the electric motor of the pump !!!!
No need for a three-phase
input rectifier !!!
Battery bank:
12VDC
24VDC
48VDC
72VDC......
The minimum
required DC
voltage for FR is
200VDC !!!
Battery bank
TOPOLOGY of preregulator converter without galvanic isolation from the battery bank
AC motor pumpe
Three phase inverter
(classical FR)
VOLTAGE STEP-UP (boost“)
Vbat 200VDC - 300VDC
24VDC
48VDC
72VDC
96VDC
DC/DC DC/AC
H- bridge
DC/AC
AC/AC
NN/VN
HF transformer
voltage step-up
AC/DC
HF rectifier
DC/AC
24VDC
48VDC
72VDC
96VDC
300VDC
-The HF transformer converts low AC voltage to relatively high AC voltagewhich is then rectified
via a classic diode rectifier in 300VDC.
-The HF transformer is with a ferrite core and for frequencies 20kHz-50KHz(small in size and weight)
The key component is the HF transformer !!!
AC motor
pumpe
Three phase inverter
(classical FR)
TOPOLOGY of preregulator converter with galvanic isolation from the battery bank
PRESSURE CONTROL IN IRRIGATION SYSTEM-Experimental results
In addition to the mobile solar generator Mobi Sun Pro Energy™ ,in the irrigation system, it was applied the three phase, two stage centrifugal pump PEDROLLO-
2CP40/180C, with following parameters: output power 4kW, input line voltage 400V, 50Hz and rated output speed of 2900rpm; Measurements are conducted on the
specific irrigation system with sprinkles; Pressure measurements are performed with an analogue pressure transmitter WIKA-A10 (range 0 to 16bar); The analogue output
from the pressure transmitter (4-20mA) is connected to analogue input of VFD, creating feedback connection in the system of pressure control; In the experiments is
measure the line electrical current of electrical motor of pump; The measurement of current is performed by current probe C35N CHAUVIN ARNOUX with three
measurement range (10A-100A-1000A/ 1V) and bandwidth 1Hz-100 kHz.
The pump motor start with two stage pressure rise in pipeline; (a) first and second stage during time interval
of 40s, (b) zoomed time interval of 150ms in the second stage; CH1 - current measured at the pump motor
terminals (10A/div); CH2 - pressure within the pipeline system (2.8bar/div)
Start of pump motor and tuning of parameters of PI pressure controller; (a) the parameters of PI controller Kp=0.7
(without integral term), (b) the parameters of PI controller Kp=0.7, Ti=0.4. CH1 - current measured at the pump motor
terminals (10A/div); CH2 - pressure within the pipeline system (1.65bar/div)
Start of pump motor and setting the frequency reference f*; (a) transient state, (b) steady state
Location 1-Village Glogonj (Pančevo municipality): Mobile SEG in transport
mode (top left); Device in operation (top right); Vacuum agro-pump 2200W,
connected to reniwell (bottom left); Villager WP35 petrol-powered motor pump
(bottom right).
APP-1
Location2-Veliko selo: Mobile SEG in the yard of the agricultural household (top left);
Greenhouses with tomato plantations (top right); Garden Villager pump 1500W connected to
the drip irrigation system (bottom left); Tubes of drip irrigation system (bottom right)
APP-2
Location 3-Glogonj: Reni well and vacuum pump in the garden with cabbage
(top left); Mobile SEG in operation (right); Moderate sunshine also allows the
device to operate (bottom left).
APP-3
Location 4: Mobile SEG in operation in Veliko selo (top left); Greenhouses with
lettuce and leek plantations in the open (top right); Awell (pool) used as a source of water
for irrigation (bottom left); A greenhouse with a salad plantation that was irrigated in order
to test the device (bottom right).
APP-4
The Financial Support
This development is financially
supported form Serbian Ministry of
Education and Science Innovation
Project: ”Development of remote
controlled robotic solar electro
generator for improvement of
agriculture production”, year
2014/2015
Also, this project is logistic
supported from Chamber of
Commerce and Industry of Serbia
2. HYBRID POWER SUPPLY OF THE AGROKAPILARIS® SYSTEM FOR IRRIGATION
OF VEGETABLE CROPS IN "GRABOVAC" OBRENOVAC MUNICIPALITY
Basic block diagram of the irrigation system and the
associated HPSS on the experimental estate “Grabovac”
The main power consumers in this system are: (1) water pump with mechanical power 750W (for the given pump efficiency of
57%, input electrical power is about 1300W), which serves to pump water into the water storage tank, (2) drive of the compressor
with power of 100Win the greenhouse (serves for inflating a double foil in order to create thermal insulation and tightening of the
foils), (3) drive for raising and lowering the greenhouse blinds, i.e. for controlled ventilation of the greenhouse, with power 2x100W
(two drives were realized on each side of the greenhouse).
Only when it
is really needed!!!!
HPSS on the experimental agricultural plot "Grabovac"
Only when it
is really needed!!!!
Practical realization of HPSS
The practical realization of a HPSS within the pumping and irrigation system on the estate
"Grabovac" included ten main activities:
(1) installation of wind turbine poles,
(2) digging of earth channels for accommodation of power and
signal cables,
(3) laying of power and signal cables at depth of 0.8m,
(4) installation of cable PVC shields and warning strips,
(5) installation of protective earthing systems: earthing probes
1.5m, earth conductors (or 25x4 Fe-Zn strips),
(6) backfilling of cables and earthing systems,
(7) installation of MDC,
(8) installation of solar panels,
(9) connection of consumers with MDC,
(10) functional testing and commissioning of the entire system.
(a) HPSS after installation, (b) solar panels, (c) foundation of the main distribution cabinet (MDC)
Installation of Hybrid power supply systems (HPSS)
The main distribution cabinet (MDC)
(a) side of the MDC, (b) interior of the MDC, (c) detail of the static circuit-breaker and
other protective and switching equipment
(1) MPPT wind controller, (2) MPPT solar controller , (3) DC/AC converters ( 2x1300W)
(4) electronic circuit for monitoring battery bank, (5) battery bank, (6) air conditioning fans
(7) heaters, (8) ATS assembly and other protective and switching equipment, (9) MDC ventilation drain with blinds
Disposition of equipment in the greenhouse
(a) blinds lifting system, (b) position of water storage tanks, (c) Agro Kapilaris®
irrigation system, (d) detailed appearance of water storage tanks
The presented realizations of the hybrid power supply system are one of the key
results of the realization of the project: "Natural resources of wind, sun and
water in order to improve agro-technical irrigation measures: application of
green technologies in the function of sustainable rural development of Serbia"
(topic 9).
The project was implemented within the Incentive Program for the improvement
of the system of creation and transfer of knowledge through the development
of technical-technological, applied, development and innovative projects in
agriculture and rural development in 2019/2020.
Project number 680-00-00029 / 2019-02 is funded by the Ministry of Agriculture,
Forestry and Water Management of the Republic of Serbia - Directorate for
Agrarian Payments, Belgrade (Implementation period 02.10.2019 -02.10.2020).
The Project within which all this was realized
3. Hybrid power supply system - Irrigation of vegetable crops and for smart management of
agricultural SMART LAND of 10 ha at the location of the village "Belegiš"
GENERAL INFORMATIONS ABOUT PROJECT
The presented results are part of the project of the Mihajlo Pupin Institute, "Smart management of
agricultural land and natural resources using modern technologies".
The project is supported by the United Nations Development Agency and the Ministry of Environment of
Republic Serbia.
The implemented technical solution was awarded as one of the 11 best innovative and climate-smart
solutions within the program "Local Development Resistant to Climate Change" implemented by the
United Nations Development Program (UNDP) in partnership with the Ministry of Environment, with
financial support from the Global Environment Fund (GEF).
Within the power supply system are realized the solar power plant with an output power of 8 kW, the
wind generator system with a power of 0.5 kW and battery bank of 48 Vdc / 720Ah, as primary power
sources and a diesel electric generator (DEG) with a power of 7.5 kW as an auxiliary power source.
In addition to this power supply system, a system for remote management of irrigation and smart
management of land and natural resources has been implemented.
The project also included a system of protection against atmospheric discharges and a complete video
surveillance system on a given plot.
SMART LANDplant
Wind generator
MSG
PUMP
STATION
Fixed PV
Fixed PVBattery bank
View from the dron on the "Smart Land" plant for remote
production management on the family farm in Belegiš - view
of the plot (above) and view of the power plant itself based
on RES (below).
(1) Entrance to the protected space "Smart Land" farm, (2) an artesian well including a
pumping station with a distribution cabinet and abase station, (3) Mobile solar electrical
generator MobiSun Pro Energy, (4) Stationary PV systems (two string, 2x12 PV panels, max
power 6kW (5) Mini wind turbine with power 500W at 48VDC, (6) Digital meteorological
station, (7) DC combiner box, (8) Submersible water pump; P2=3kW; P1=4kW, (9) Water
filter, (10) Reservoir for liquid fertilizer and phyto-protective preparations, (11) pump check
valve, (12) Electromagnetic valve of irrigation system, (13) Video surveillancesystem, (14)
Auxiliary economic facility, (15) GSM/GPRS antenna, (16) Human-operator with personal
device, (17) Fence of core Smart Land, (18) Irrigation system sprinklers, (19) Temperature
and humidity sensors (in the air and the terrain) (20)pH sensors of the terrain, (21) Irrigation
system pipeline, (22) Electrical cable installations, (23) Control lines, (24) land that is
cultivated in the traditional way/ land that is cultivated using the SMART LAND system
Functional presentation of the "Smart Land" plant for remote monitoring and management of agricultural production on
an open agricultural plot in Belegiš
Principal diagram of the OFF GRID power supply and control system of the "Smart Land" plant with remote monitoring and management
CONSUMER Power(W)
AC Pump drive (pump+
frequency converter +regulator)
5300
Irrigation controller 110
Video-surveillance system 100
Wireless routers (2 pcs.) 30
GSM/GPRS modem (2 pcs.) 60
Electronic circuit in stand by 100
ΣP 5700
Block diagram of the control part of the hybrid power supply system "Smart Land" plant
The construction is conceived as a folding
pillar. Supporting pole (1), of wind generator
(13)is supported by a vertical rod (3), main
support (4) and lateral support (10), to the
pedestal (5), which is by foots (2) funded for
the surface of the earth. The base of the pillar
is fixed to the base with four small pillars (7)
with concrete weights (6). The pillar support
(8), together with the counterweights (9) is
used in the event that the pole descent into a
horizontal position (installation or servicing of
wind turbines and associated equipment).
WIND POLE (PILLAR) CONSTRUCTION
horizontal position
The characteristics Q-H curves for CFG pumps PEDROLLO 4SR10-15 and 4SR12
Diagrams of production and consumption of electricity on the
agricultural plot Smart Land "Belegiš" for the period July 2021-
March 2022.Detailed diagram of electricity consumption (from PV panels and battery
bank) on the agricultural plot Smart Land "Belegiš" for the period July
2021-March 2022.
Diagram of average monthly electricity production for the month of August
2021 on the agricultural plot Smart Land "Belegiš"
Diagram of average monthly electricity consumption (from PV panels and
battery bank) on the agricultural plot Smart Land "Belegiš" for the month of
August 2021.
Characteristic diagrams of electricity production and consumption oh the agricultural plot Smart Land-Belegiš
Integral diagrams of the average monthly production and consumption of electricity on the
agricultural plot Smart Land "Belegiš" for the month of August Diagrams of daily electricity production on the agricultural plot Smart
Land "Belegiš"on August 4, 2021.
Diagrams of daily electricity consumption on the agricultural plot Smart Land
"Belegiš" on August 4, 2021.
Integral diagrams of daily production and consumption of electricity, as well as the accumulated
energy of the battery bank on the agricultural plot Smart Land "Belegiš"on August 4, 2021.
Characteristic diagrams of electricity production and
consumption for the the most favorable day in month
August 2021
Battery bank and accessories; (a) layout of the MSG device with 4 solar panels with a total PV power
of 4x350W, (b) layout of the battery bank with accompanying power electronics devices (DC / DC, DC
/ AC), (c) layout of the control panel with integrated CCGX controller and battery monitor BMW702,
(d) display of parameters in operating mode
Disposition of the solar panel system (total power 2x12x250W = 6kW) and wind turbine
mounting pole.
Wind turbine disposition; (a) layout of the
folding mounting pole and mounting position of
the MPPT wind controller within the battery
bank, (b) meteorological station on its own pole
Display of equipment in the room for storing the pump set and DEG; (a) door of the RO pump
unit with control and signaling equipment, (b) internal appearance of the RO pump unit and
position of the frequency converter FR output power 5.5kW, (c) disposition of the DEA and the
accompanying switch cabinet
Control unit of DEG
New version of mobile solar electrical generator (MSEG) device with 4 solar panels with a total PV power of
4x350W=1400W
Battery bank
48Vdc/720Ah
Wind turbine and wind pole construction
Support and Funding
The results the realizatioin of Smart Land
plot are to achieve in scope of the project:
"Smart management of agricultural land and
natural resources using modern
technologies".
The project is supported by the United
Nations Development Agency and the Ministry
of Environment of Republic Serbia.
The implemented technical solution was
awarded as one of the 11 best innovative and
climate-smart solutions within the program
"Local Development Resistant to Climate
Change" , implemented by the United Nations
Development Program (UNDP) in partnership
with the Ministry of Environment, with financial
support from the Global Environment Fund
(GEF).
https://www.youtube.com/embed/f1_gVfaVCNY?start=00&
end=138
https://www.rs.undp.org/content/serbia/en/home/stories/k
lima-i-mi.html
CONCLUSIONS
In this lecture, the role and importance of hybrid OFF-GRID power supply systems in
crop irrigation systems are presented.
The emphasis in the lecture is given to power electronics devices used in these
systems.
Practically all types of electrical conversion (AC/DC, DC/DC, DC/AC, AC/AC) are
represented in these systems.
The lecture presents the practical realizations of the M. Pupin Institute in this field,
within several development projects.
The advantages and disadvantages of these power supply systems were also pointed
out, as well as some exploitation problems that were noticed during the
implementation.
This presentation represents a small contribution in the field of quality of sustainable
development and use of "green energy", but the author hopes that it will be
stimulating and instructive for those who are just entering this complex and
interdiciplinary field.
DISCUSSION, QUESTIONS ??
Belgrade, April 2022.
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