Study of a LowCost PV Emulator for Testing MPPT Algorithm Under Fast Irradiation and Temperature Change
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Abstract
This paper presents a study of a lowcost photovoltaic (PV) emulator to test the real implementation of maximum power point tracking (MPPT) algorithm. This PV emulator is composed of a variable DC supply in series with a variable resistor; it is based on the maximum power transfer theorem in order to provide a curve that exhibits a peak which can be tracked by an MPPT algorithm. Moreover, this emulator can be used to test the performance of the MPPT algorithm under fast variation of the solar irradiance and temperature. For this reason, the P&O MPPT algorithm with a boost DCDC converter is used in order to validate the functionality of the PV emulator. Finally, the experimental results show that our PV emulator can provide a simple, efficient and lowcost way for users (researchers, engineers, students, etc.) to test and validate their MPPT algorithms.
Keywords
DC supply Low cost PV emulator MPPT PhotovoltaicNomenclatures
 E,
DC supply output voltage [V]
 I,
PV emulator output current [A]
 I_{0},
the output current of the Boost converter [A]
 I_{mpp},
Panel output maximum power point current [A]
 G,
Solar irradiance level [W/m2]
 P_{load},
Load power [W]
 R_{load},
Load resistance [Ω]
 R_{Series},
Series resistance [Ω]
 R_{mpp},
Resistor value at MPP [Ω]
 T,
Temperature [°C]
 V,
PV emulator output voltage [V]
 V_{mpp},
Voltage at MPP [V]
 V_{0},
Boost output voltage [V]
 \(V^{\prime }_{oc} \),
PV emulator opencircuit voltage [V]
 V_{oc},
Panel opencircuit voltage [V]
Greek Letters
 α,
Duty cycle
Abbreviations
 CV
Constant Voltage
 DC
Direct Current
 INC
Incremental Conductance
 MPP
Maximum Power Point
 MPPT
Maximum Power Point Tracking
 PV
Photovoltaic
 P & O
Perturb and Observe
Introduction
Today, solar energy has taken a large part of the market due to the continued development of PV system technology and its lower prices [1]. Therefore, several reseachers are working on the optimization of this source of energy in order to extract power with high reliability, low cost, and improve energy efficiency [2].
The energy production of PV panels is dramatically affected by climatic conditions in terms of solar irradiance and temperature [3, 4]. Besides, the power provided by the PV panels is maximum only when the latter operates at its maximum power point (MPP). Therefore, the MPPT controller is used to track the MPP. In this context, a large number of MPPT methods have been developed in the literature, such as: Perturb & Observe (P&O) [5, 6], incremental conductance (INC) [7, 8, 9], fractional open circuit voltage [10], fractional shortcircuit current [5], fuzzy logic control [11], and neural network [12], etc.
On the other hand, to validate the performance of such MPPT algorithm, it is required to test it under different values of temperature and irradiance. However, it is difficult to realize the desired test case because we cannot control the climatic conditions [13].
For that, this work aims to study a lowcost PV emulator to provide a simple and lowcost way to test the real implementation of MPPT algorithms. This PV emulator is composed of a variable DC supply in series with a variable resistor.
This paper is organized as follows. The next section presents operating configuration which describes: maximum power transfer theorem, sizing of PV emulator, and PV emulator for testing the fast variation of Solar irradiance and temperature. Next, the Experimental and validation are presented in “Experimental and Validation”. And the conclusion is given in “Conclusion”.
Operating Configuration
Maximum Power Transfer Theorem
The ‘maximum power transfer theorem’ can be explained as follows [22]:
Sizing of the PV Emulator
Characteristics of the PV panel TDCM2036 at STC
Characteristics TDCM2036  

Maximum power, Pmax  20 W 
Voltage at Pmax, Vmp  18.76 V 
Current at Pmax, Imp  1.07 A 
Shortcircuit current, Isc  1.17 A 
Opencircuit voltage, Voc  22.70 V 
Temperature coefficient of Voc, Kv  − 0.35%/°C 
Temperature coefficient of Isc, Ki  − 0.043%/°C 
Number of cells  36 
PV Emulator for Testing the Fast Variation of Solar Irradiance and Temperature

Fast variation of the solar irradiance
Obtained solar irradiance values according to the switches states by using four floors
K1  K2  K3  K4  

G = 1000 W/m^{2}  1  1  1  1 
G = 800 W/m^{2}  1  1  1  0 
G = 600 W/m^{2}  1  1  0  0 
G = 400 W/m^{2}  1  0  0  0 
G = 200 W/m^{2}  0  0  0  0 

Fast variation of temperature
Different temperature values according to the switches states
K1  K2  K3  K4  

T3 (\(\mathrm {V}^{\prime }_{\text {oc}}= 16.5~ V)\)  0  1  0  1 
T2 (\(\mathrm {V}^{\prime }_{\text {oc}}= 18.3~ V)\)  1  0  0  1 
T1 (\(\mathrm {V}^{\prime }_{\text {oc}}= 21.1~ V)\)  1  0  1  0 
Experimental and Validation
PV Emulator Validation
Effect of the Solar Irradiance Variation
Effect of Temperature Variation
Consequently, we can simulate the effects of the solar irradiance and temperature variations by varying, respectively, the value of the series resistor and the voltage of the DC supply.
Implementation of MPPT Algorithm Using the PV Emulator
MPPT Algorithm
The Boost Converter Construction and Parameters
Parameters of the boost DC/DC converter
Parameters of the boost DC/DC converter  

Inductor (L)  20 mH 
Input capacitor (C_{in})  220 μF 
Output capacitor (C_{out})  470 μF 
Switching frequency  1 kHz 
Test Results
Consequently, the experimental results validated that the used PV emulator to be a suitable lowcost solution by the performance average compared to the commercial emulator for PV systems.
The Used Emulator Comparison with Other Emulators
Comparison between the used emulator and other emulators
Work, year  Material used  Cost  Complexity 

[17], 2012   Programmable DC  2800.00$  High 
Power Supply  
(TDK Lambda GEN30011)  
 dSPACE DS1104  
[16], 2014   PV Solar Array  3500.00$  High 
Simulator  
(Agilent E4360A)  
Our work   DC regulated  64.99$  Less 
power supply  www.ebayshopkorea.com/itm/10A30VDCPowerSupply—AdjustableDualDigital/251705177148  
 variable resistor  
320 W 100 Ω  15.00$  
Conclusion
The high cost of commercial PV emulators requires finding new solutions for building lowcost system having similar behavior of PV panel. Therefore, this paper describes a lowcost PV emulator by which we replace a PV panel to test the real implementation of MPPT algorithms for PV applications. In this work, the results of experiments test are shown that our PV emulator can provide a PV curve that it presents a power peak, which can be followed by the MPPT algorithm. In addition, an explication of the PV emulator to simulate a fast variation of the solar irradiance and the temperature in case of PV systems is presented in this work. Moreover, the P&O MPPT algorithm with a boost DCDC converter is used in order to validate the functionality of used PV emulator. Finally, the results of the rapid change of irradiance and temperature on the PV emulator confirmed the effectiveness of the PV emulator system and show that our solution has several advantages over existing such as low cost, less complexity, and can provide a simple way for users (researchers, engineers, students, etc.) to test and verify their MPPT algorithms.
As perspective, two prospects for improvement can be done: (i) find a general method to calculate the emulated values of temperature as we did for irradiance. (ii) Improve the present PV emulator design to be suitable for testing shading conditions.
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