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European Journal of Applied Sciences – Vol. 12, No. 2
Publication Date: April 25, 2024
DOI:10.14738/aivp.122.16386
Big-Alabo, A. (2024). Analysis of A 5 Kw Solar - PV System with Model Predictive Controlled: Boost Converter for An Office Suite.
European Journal of Applied Sciences, Vol - 12(2). 197-204.
Services for Science and Education – United Kingdom
Analysis of A 5 Kw Solar - PV System with Model Predictive
Controlled: Boost Converter for An Office Suite
Ameze Big-Alabo
ORCID: 0000-0001-5384-888X
Department of Electrical/Electronic Engineering,
Faculty of Engineering University of Port-Harcourt
East-West Road, Choba, Port Harcourt, Rivers State, P.M.B. 5323
ABSTRACT
This study considers the design analysis and simulation of a 5 kW Solar –
Photovoltaic (PV) system with Model Predictive Controlled (MPC) – boost converter
for a typical office suite. A departmental office at the faculty of Engineering,
University of Port Harcourt is used as a case study. Measurement readings of the
power consumed by the office is conducted to ascertain the average load power of
the building. The maximum power recorded is 3.52 kW. Therefore, a 5 by 5 series- parallel solar PV array is designed to yield a total output power of 5 kW to cover for
possible additional loads in the system. The MPC – boost converter with parameters
L = 1 mH and C = 600 mF and R= 0.01 Ω was designed to help maintain stable voltage
whenever there is a drop in solar irradiance or variation in the consumer load. The
focus of this study is on the variation in consumer load while the solar irradiation
is maintained at maximum value. Thus, the designed PI controller is more of an
integral action with values of Kp = 0.012, and Ki = 10. The MPC – boost converter
and PI controller was able to maintain stable total voltage of 132 V ± 15% despite
the load variation due to switching on and off of consumer load.
Keywords: PV array, Maximum power, Load variation, Model Predictive Control, PI
controller.
INTRODUCTION
The use of PV systems for commercial applications such as offices has gained popularity due to
its ability to overcome some of the challenges encountered with inconsistent power supply
from the utility grid. These challenges include hindered facilitation and smooth running of the
key activities such as Printing, Photocopying, Typing, Scanning of Documents, Data, Information
and Forms conducted at the departmental levels. Another challenge encountered due to
inconsistent power supply is the high cost of maintenance and operation of diesel generators
which are used as a backup power supply for the facilities used at the departmental offices.
These generators are noisy and emit carbon-monoxide which has a negative environmental
impact to the surroundings of the building. Another challenge is the high cost of electricity bills.
These factors and many more have affected the facilitation and smooth running of the
aforementioned activities.
This research work is conducted using a departmental office located at the University of Port
Harcourt, Nigeria. The research objectives include: monitoring and recording the energy
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consumption of loads in the department, calculations and sizing of the solar PV system, design
of the boost converter to improve and stabilize the voltage from the PV array. The PV boost
converter system is designed to produce and maintain an output power of 5 kW. Similar works
has been designed but for an output power of 6 kW [1].
A boost converter is a DC-DC power electronic converter that steps-up the voltage from its input
to output [2 – 6]. This implies that the output of the boost converter is greater than the input
voltage. In the literatures [7 – 10], the boost converter is controlled using Pulse Width
Modulation (PWM) control strategy. The generation of PWM control signals is achieved by
implementing MPPT algorithm such as the Hill Climbing or Perturb and Observe (P&O) method.
This method has a good performance, and it is easy to implement when considering variation
in input voltage due to the intermittency of the solar irradiance. However, in this study,
variation in the output load assuming constant input voltage source at an irradiance of 1000
W/m2, is considered.
The performance of a boost converter is normally affected by the dynamic nature of the load it
drives. Model Predictive Control (MPC) offers a dynamic and predictive approach that can
significantly improve the response of boost converters under varying load conditions.
ESTIMATION OF THE AVERAGE DAILY ENERGY CONSUMPTION
The first step in the design of a PV system is to estimate the energy requirements of the office
suite. This will require knowledge of the average daily energy consumption of the office. The
departmental office suite comprises of the Head of Department office, two (2) administrative
offices, exams and records office, a conference hall and the departmental toilet. Some of the
basic loads and appliances used and its quantity are stated in Tables 1:
Table 1: Basic loads and appliances used in the departmental office.
Appliances Quantity
Offices HOD Admin 1 Admin 2 Conference hall Exams and record Store and Toilet
Fan 2 1 1 2 1 1
Led light 8 4 4 12 2 4
Ac 2 1 1 2
Fridge 1
Ceiling fan 1 1 1 1 1 1
Television 1 1
Charging 2 2 2
Printing machine 1 1
Projector 1
Energy meters were used to monitor and record the energy consumption of these appliances
by taking direct measurement from the departmental distribution board for a period two
weeks. The energy consumption is represented using bar chart in figure 1. There are no
readings taken during the weekend since there are usually no activities on those days.
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199
Big-Alabo, A. (2024). Analysis of A 5 Kw Solar - PV System with Model Predictive Controlled: Boost Converter for An Office Suite. European Journal
of Applied Sciences, Vol - 12(2). 197-204.
URL: http://dx.doi.org/10.14738/aivp.122.16386
Figure 1: Energy consumption bar chart for a period of two weeks
From the readings obtained, it can be seen that the maximum energy consumed is 3518 1.1watt (approx. 3.52
kWh)
DETERMINATION OF THE NUMBER OF SOLAR PV ARRAY
PV modules are rated based on Standard Test Condition (STC) which is made available from the
manufacturer’s datasheet. Thus, the mathematical model uses that information to predict the
performance of the system at any given condition accurately. Models of the PV have been
proposed, varying in complexity and accuracy; ranging from ideal models to practical models
[11, [12]. The practical PV model takes into account the leakage current, the internal resistance
and wiring resistance.
A rated 200 W solar PV panel is used for this design. The specifications at STC are as follows:
Table 2: Solar PV specification at STC
Parameter Rated value
Rated Power (Pmp) 200 W
Voltage at max power (Vmp) 26.4 V
Current at max power (Imp) 7.58 A
Open circuit voltage (Voc) 32.9 V
Short circuit current (Isc) 8.21 A
Total no of cells in series (Ns) 54
Total number of cells in parallel (Np) 1
This 200 W solar PV array is designed in series and parallel combination to obtain an output
power of 5 kW. Voltages are added in series and currents are added in parallel. Therefore, in
order to obtain an output of 5 kW to cater for the office loads, it will be necessary to have a
configuration set-up of five (5) panels in series and another 5 panels in parallel. The analysis of
this configuration is given below.
5 panels are connected in series to give a total voltage output of
VT = 5 × 26.4 = 132 V
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Another set of 5 panels are connected in parallel to give a total current output of
IT = 5 × 7.58 = 37.9 A
Therefore, the total power output obtain from 5 x 5 configuration set-up is obtained by
multiplying Equations (1) and (2) to give
P = VT × IT = 132 × 37.9 = 50002.8 W
≈ 5 kW
Thus, maximum power is transferred when the load resistance is 3.48 ohms. Slight Variation of
load resistance will result in a drop in power. Therefore, there is the need for a boost converter.
Figure 2: IV and PV characteristics of the 5 x 5 PV array for 5 kW @ irradiance of 1000, W/m2
Based on these plots, it can be seen that the desirable maximum voltage and current that will
yield a power output of 5 kW is: 132 V and 37.9 A as designed in equations (1) and (2) above.
These values will now be used as reference values in the design of the boost converter.
DESIGN OF THE BOOST CONVERTER WITH MODEL PREDICTIVE CONTROL
The parameters of the boost converter can be estimated as follows
D = 1 −
Vin
Vo
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... . . ... . . (1)
Lmin ≥
D(1 − D)
2V0
Io2 fs
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... . . (2)
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Big-Alabo, A. (2024). Analysis of A 5 Kw Solar - PV System with Model Predictive Controlled: Boost Converter for An Office Suite. European Journal
of Applied Sciences, Vol - 12(2). 197-204.
URL: http://dx.doi.org/10.14738/aivp.122.16386
Cmin ≥
Io × D
fs × ∆Vo
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... (3)
∆Vo is taken as 2%
Design Considerations for MPC in Boost Converter
Inorder to implement MPC, an accurate model of the boost converter and its load is essential.
The model used captures the dynamic behavior of the system under various operating
conditions. This includes the dynamics of the power switches, inductors, L and capacitors, C as
well as the load characteristics [13]. The finite control set of the Model predictive control is
shown below:
i. iL
: control variable
ii. g = iLref (k) − iL (k + 1) : cost function, where iLref(k) is the inductor current
reference, and iL (k + 1) is the predictive current of the inductor current.
iii. iL
: iL (k + 1): Prediction of control variable:
Based on Euler’s forward method:
di
dt ≈
iL (k + 1) − iL(k)
Ts
Making the prediction function subject of the formular,
iL (k + 1) =
di
dt Ts + iL(k)
Where iL(k)
is the measured value of the inductor current. Ts
is the sampling time of the control
algorithm.
SIMULATION AND RESULTS
The input voltage from the 5-kW solar PV is fed to an inductor L, which stores energy in a
magnetic field. When the input voltage is switched off, the inductor releases the stored energy,
which boosts the output voltage. The output voltage is regulated by controlling the duty cycle
(D) of a switch using either a MOSFET or a transistor that connects the inductor to the output
load.
The MPC is an advanced control strategy that utilizes the predictive model of the boost
converter to optimize control actions over a finite time horizon. Unlike traditional controllers,
MPC considers future system behavior and selects control inputs that minimize a predefined
cost function. In the context of boost converters, MPC can anticipate changes in load conditions
and adjust the control parameter, in this case iL
accordingly, leading to improved transient
response and overall system efficiency as shown in the matlab/Simulink diagram in figure 3
and the corresponding plots in figures 4 below.
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Figure 3: Simulink diagram of PV with MPC – Boost converter
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Big-Alabo, A. (2024). Analysis of A 5 Kw Solar - PV System with Model Predictive Controlled: Boost Converter for An Office Suite. European Journal
of Applied Sciences, Vol - 12(2). 197-204.
URL: http://dx.doi.org/10.14738/aivp.122.16386
Figure 4: Simulated plots of stable Voltage output, induction current iL and switching signals
It can be seen from the plots in Figure 4 that the voltage output of the system is raised from 132
V to 150 V and it is able to follow the desired reference voltage set at Vref = 150 V because of
the action of the MPC – Boost converter. It can be seen that the boost converter augments the
short fall in power supply when additional load is added to the system, by discharging the
stored energy into the system.
CONCLUSION
The design analysis of a 5-kW boost converter solar PV system is presented in this study. The
energy requirements of a typical departmental office suite were estimate via energy
consumption meter readings. The average energy consumption was measured to be 3.48 kW.
The size of the PV system required to meet the energy requirements of the office was
determined to give a 5 by 5 configuration set-up with an output power of 5 kW. The PV is so
designed to give a higher output power so that it can cater for additional loads in the system.
The last step is to design a boost converter in order to maintain a stable voltage output during
load variation. This load variation comes about through the switch off and switch on of
appliances in the office suite. Further work can be done by incorporating a battery storage
energy monitoring system to monitor the loads connected to the solar – PV system thereby
enhancing the performance of the system.
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