Modern scientific advances have enabled remarkable efficacy for photovoltaic systems with regard to the exploitation of solar energy, boosting them into having a rapidly growing position among the systems developed for the production of renewable energy. However, in many cases the design, analysis, and control of photovoltaic systems are tasks which are quite complex and thus difficult to be carried out. In order to cope with this kind of problems, appropriate software tools have been developed either as standalone products or parts of general purpose software platforms used to model and simulate the generation, transmission, and distribution of solar energy. The utilization of this kind of software tools may be extremely helpful to the successful performance evaluation of energy systems with maximum accuracy and minimum cost in time and effort. The work presented in this paper aims on a first level at the performance analysis of various configurations of photovoltaic systems through computeraided modelling. On a second level, it provides a comparative evaluation of the credibility of two of the most advanced graphical programming environments, namely, Simulink and LabVIEW, with regard to their application in photovoltaic systems.
Serious economic concerns along with the growing worries about the disastrous effects that technological progress accumulatively causes to world environment, impose a shift towards renewable energy resources, which constitute an environmental friendly approach for power generation with satisfactory efficiency [
The renewable energy resources which have the most enhanced exploitation, thanks to relevant advances in modern scientific research, are solar, hydropower, geothermal, biomass, and wind energy [
Solar energy refers to the solar radiation that reaches the Earth and can be converted into other forms of energy, such as heat and electricity. The transformation of solar radiation into electric current is performed by using photovoltaic (PV) cells. A PV cell is practically a pn junction placed in the interior of a thin wafer of semiconductor. The solar radiation falling on a PV cell can be diconverted to electricity through the socalled photovoltaic effect. This is a physical phenomenon in which photons of light excite electrons into higher energy states letting them act as charge carriers for electric current. Specifically, the exposure of a PV to sunlight triggers the creation of electronhole pairs proportional to the incident irradiation by photons having energy greater than the bandgap energy of the semiconductor material of the PV cell.
Over the last decades, the international interest in the PV conversion of solar radiation is continuously growing. In this way, the use of PV systems is nowadays widespread to an extent that is considered to constitute the third greater renewable energy source in terms of globally installed capacity, after hydro and wind power.
On the other hand, the brilliant prospects of PV systems for further evolution get obstructed due to various technical and economic issues that have yet to be resolved. For this reason modern scientific and technological research focuses on the development of methodologies and equipment for the increase of energy efficiency of PV systems, the reduction of their production cost, the improvement of their market penetration, and the enhancement of their environmental performance [
These research activities can be greatly assisted by the utilization of software tools for the development of models of the PV systems under consideration and the analysis of their performance by carrying out simulation tests.
The aim of this paper is to perform the computeraided design and performance analysis of both gridconnected and standalone PV systems by using in parallel the two most widely used graphical programming environments, namely, Simulink by Mathworks and LabVIEW by National Instruments. This task is accomplished by taking advantage of the potential provided through the adaptation of these two software platforms to systems of PV nature. The parallel utilization of MATLAB and LabVIEW enables the comparative evaluation of their accuracy, validity, and their overall performance under various simulation scenarios. According to the knowledge of the authors of this paper, this is the first comparative study of this kind which is performed in the field of photovoltaics, although similar studies have been carried out in other scientific areas such as [
The rest of the paper is organized as follows: Section
The performance of PV plant is subject to many parameters, the influence of which should be accurately estimated before any investment is made for the establishment of this plant. Actually, the temperature and solar radiation are the two main factors affecting the performance of PV systems. Specifically, ambient temperature should definitely be taken into consideration because the relationship between the temperature and the efficiency of solar cells is inversely proportional [
In order to calculate the energy efficiency of PV systems in an accurate and systematic modern research works focus on the computeraided design and analysis of this type of systems [
For instance, a PV array simulation model incorporated in Simulink GUI environment was developed using basic circuit equations of the PV solar cells including the effects of solar irradiation and temperature changes. The developed model was tested by means of both a directly coupled DC load and an AC load via an inverter [
In another work a model for a solar PV array (PV), with an AC/DC converter and load, a maximum power point tracker, a battery, and a charger, was built. The whole model was simulated under four testing scenarios some of which included cloudy and sunny conditions along with constant and varying load [
Similarly, an approach to determine the characteristic of a particular PV cell panel and to study the influence of different values of solar radiation at different temperatures concerning performance of PV cells in Simulink was proposed [
In [
Concentrating on educational applications, [
The procedure of building accurate PV models is extremely important in order to achieve high efficiency in the decision making related to establishment and operation of PV systems. This justifies why, as already discussed in Section
Generally, modelling of PV systems is based on the assumption that the operation of PV cells may be simulated by examining the operation of analogous electronic circuits. The simplest PV model found in bibliography comprises a single diode connected in parallel with a light generated current source (
Electronic circuit equivalent to the model of an ideal PV cell.
Going one step further, a series resistance
Electronic circuit representing a onediode with serial resistance model of PV cell.
Other scientific researches make use of a model which is derived by the addition of shunt resistance
A few research works adopt an ever more complex model, known as the twodiode model aiming to take into consideration recombination losses, that is, the elimination of mobile electrons and electron holes due to the existence of impurities or defects at the front or/and the rear surfaces of a cell. This model includes a second diode placed in parallel to the current source and the initial diode, thus calling for the simultaneous calculation of seven parameters based on either iteration approaches or more analytical methodologies [
When simulating a PV module, no matter which model is adopted, the goal is to calculate the
Another technical feature that is taken into consideration during the simulation tests performed is the socalled total harmonic distortion (THD). Generally, THD of a signal is a measurement of the harmonic distortion present and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency. In energy systems THD is used to characterize their power quality of electric power.
Finally, in order to carry out the comparative performance analysis of the modelling accuracy of Simulink and Labview the so called coefficient of determination was calculated. This is a statistic term denoted as
In accordance with the aforementioned, in Section
The first modelling procedure performed refers to the modelling and performance analysis of a single PV panel for the production of
The specific PV panel examined is Solarex SX50. The characteristic features of this PV panel along with their typical values, for solar irradiance
Technical features of SX50 PV panel.
Feature  Value 

Maximum power ( 
50 W 
Voltage at 
16.8 V 
Current at 
2.97 A 
Guaranteed minimum 
45 W 
Shortcircuit current ( 
3.23 A 
Temperature coefficient of 
( 
Temperature coefficient of 
−( 
Temperature coefficient of power  −( 
Characteristic
Overview of an SX50 PV panel in Simulink.
Simulation model of an SX50 panel in Simulink.
Simulation model of an SX50 panel in LabVIEW.
The second modelling procedure performed refers to the modelling and performance analysis of a typical integrated PV system, consisting of a PV energy source, a DC/DC converter, a DC/AC inverter, a filter, and a load as shown in Figure
Overview of the integrated PV system modeled.
The modelling was performed both in Simulink and LabVIEW based on the assumptions that the power of the photovoltaic generator is equal to 4.6 KW and the operation temperature is set to 25°C. Additionally, solar irradiance is supposed to have a stable value equal to 1000 W/m^{2} while the load magnitude is equal to 2 KW. The system was connected to a lowvoltage grid by using alternatively a low load (1.5 KW) or a high load (6.5 KW).
The filter is an LC circuit aiming to cut off the range of the output current which produces the DCAC inverter harmonic frequencies. Similarly, an RL circuit was incorporated in the line that connects the filter with the load. Figure
Integrated PV system model in Simulink.
Integrated PV system model in LabVIEW.
The third modelling task performed refers to the model development and performance analysis of a typical integrated PV system, having the structure shown in Figure
The filter incorporated in the overall system structure is an LC circuit aiming to cut off the range of the output current which produces the DCAC inverter harmonic frequencies. Similarly, an RL circuit was used in the line which connects the filter with the load. Figure
Gridconnected integrated PV system model in Simulink.
Gridconnected integrated PV system model in LabVIEW.
In the following subsections of Section
The basic assumption in all simulations tests carried out for the performance analysis of the solar panel modeled in Section
The values of
Simulation results for





Simulink  2.995  18.226  54.607 
LabVIEW  2.987  18.811  56.198 
Simulation results for





Simulink  3.002  14.916  44.782 
LabVIEW  3.041  15.152  46.108 
Simulation results for





Simulink  2.998  13.024  38.925 
LabVIEW  3.029  13.834  41.91 
In a similar way, in Table
Simulation results for





Simulink  2.998  16.86  50.55 
LabVIEW  2.977  16.909  50.344 
Solarex  2.97  16.8  50 
The percentage deviation of the simulation data of
Percentage deviation between default values and simulation results for





Simulink  +0.951  +0.357  +1.1 
LabVIEW  +0.247  +0.648  +0.688 
The evaluation of the correlation existing between the simulation results attained alternatively via Simulink and LabVIEW for
Schematic comparison of the values of
Schematic comparison of the values of
Schematic comparison of the values of
The performance analysis of the integrated PV described in Section
The results of the simulation of these two features in Simulink are depicted in Figures
Voltage at load with no grid connection in Simulink.
Current at load with no grid connection in Simulink.
By applying fast Fourier transformation, it was found that the total harmonic distortion at load is 2.08%, while the amplitude of the voltage at the fundamental frequency is 313.2 V and the amplitude of the current at the fundamental frequency is 11.84 A.
The corresponding simulation results in LabVIEW proved that the total harmonic distortion at load is 3.78%, while the amplitude of the voltage at the fundamental frequency is 219.53 V RMS, that is, 310.46 V, and the amplitude of the current at the fundamental frequency is 8.3 A RMS, that is, 11.74 A, as shown correspondingly in Figures
Voltage at load with no grid connection in LabVIEW.
Current at load with no grid connection in LabVIEW.
The comparison of these data shows that the simulation through Simulink and LabVIEW leads to results which have a percentage deviation less than 0.9% for both voltage at load and current at load.
By using the same software tools as in the last subsection, the performance analysis of the, described in Section
First, the low load (1.5 KW) case was examined, starting with the output voltage at load and current at load. The subsequent simulation results via Simulink are shown in Figures
Voltage at load 1.5 KW with grid connection in Simulink.
Current at load 1.5 KW with grid connection in Simulink.
Based on these plots it was found that the total harmonic distortion at load is 1.67%, while the amplitude of the voltage at load at the fundamental frequency is 331.9 V and the amplitude of the current at the fundamental frequency is 9.428 A.
The corresponding simulation results in LabVIEW proved that the amplitude of the voltage at the fundamental frequency is 236.71 V RMS, that is, 334.76 V, and the amplitude of the current at the fundamental frequency is 6.74 A RMS, that is, 9.53 A, while the total harmonic distortion at load is 11.25% as shown correspondingly in Figures
Voltage at load 1.5 KW with grid connection in LabVIEW.
Current at load 1.5 KW with grid connection in LabVIEW.
Similarly, the total current at the connection of the system to the load and network was investigated. The resultant simulation plots drawn through the alternative utilization of Simulink and LabVIEW are depicted in Figures
Current to load 1.5 KW and network with grid connection in Simulink.
Current to load 1.5 KW and network with grid connection in LabVIEW.
Based on these plots it was found that according to Simulink the amplitude of the total current at the connection of the system to the load and network is equal to 26.56 A while the total harmonic distortion is equal to 8.16%. The corresponding simulation results in LabVIEW proved that the current amplitude is equivalent to 18.34 A RMS, that is, 25.94 A, while THD is 6.65%.
Similarly, the current at the connection of the system to the network was examined. The resultant simulation plots via Simulink and LabVIEW are depicted in Figures
Current to network with grid connection and load 1.5 KW in Simulink.
Current to network with grid connection and load 1.5 KW in LabVIEW.
The comparative examination of the aforementioned simulation results regarding the 1.5 KW load case shows that the percentage deviation between Simulink and LabVIEW is equal to 0.85% for the voltage at load, 1.07% for the current at load, 2.33% for the total current to load and network, and 3.44% for the current to network.
Finally, the high load (6.5 KW) case was examined, starting with the output voltage at load and current at load. The subsequent simulation results via Simulink are shown in Figures
Voltage at load 6.5 KW with grid connection in Simulink.
Current at load 6.5 KW with grid connection in Simulink.
Based on these plots it was found that the amplitude of the voltage at load at the fundamental frequency is 319.1 V, and the amplitude of the current at the fundamental frequency is 39.89 A, while the total harmonic distortion at load is 0.82%. The equivalent results in LabVIEW proved that the amplitude of the voltage at the fundamental frequency is 227.95 V RMS, that is, 322.37 V, and the amplitude of the current at the fundamental frequency is 28.49 A RMS, that is, 40.29 A while the total harmonic distortion at load is 7.83%, as shown correspondingly in Figures
Voltage at load 6.5 KW with grid connection in LabVIEW.
Current at load 6.5 KW with grid connection in LabVIEW.
Similarly, the total current at the connection of the system to the load and network was investigated. The resultant simulation plots via Simulink and LabVIEW are depicted in Figures
Current to load 6.5 KW and network with grid connection in Simulink.
Current to load 6.5 KW and network with grid connection in LabVIEW.
Based on these plots it was found that according to Simulink the amplitude of the total current at the connection of the system to the load and network is equal to 19.76 A while the total harmonic distortion is equal to 9.88%. The corresponding simulation results in LabVIEW proved that the current amplitude is equivalent to 13.99 A RMS, that is, 19.78 A, while THD is 11.54%.
Similarly, the current at the connection of the system to the network was examined. The resultant simulation plots via Simulink and LabVIEW are depicted in Figures
Current to network with grid connection and load 6.5 KW in Simulink.
Current to network with grid connection and load 6.5 KW in LabVIEW.
Based on these plots it was found that according to Simulink the amplitude of the total current at the connection to the network is equal to 23.53 A while the total harmonic distortion is equal to 7.89%. The corresponding simulation results in LabVIEW proved that the current amplitude is equivalent to 16.38 A, RMS that is, 23.16 A, while THD is 10.4%.
The comparative examination of the aforementioned simulation results regarding the 6.5 KW load case shows that the percentage deviation between Simulink and LabVIEW is equal to 1.0% for the voltage at load, 1.0% for the current at load, 0.1% for the total current to load and network, and 1.57% for the current to network.
The correlation between the results attained via Simulink and LabVIEW for the performance simulation of the gridconnected integrated PV system can be synoptically evaluated in terms of the coefficient of determination (
Specifically, in the 1.5 KW case
Coefficient of determination
Coefficient of determination
The work presented in this paper focused on computeraided model development and performance analysis of photovoltaic systems. For this reason, suitable models were built for various formations of photovoltaic schemes. All tasks performed were based on the use of two advanced graphical programming environments, namely, Simulink and LabVIEW. In this way, a comparative evaluation of the credibility of these software platforms was carried out.
Specifically, the case of a commercially available PV panel was studied. A model representing this panel was built and its operation was simulated. The simulation results regarding its characteristic features were compared to those provided by the PV panel manufacturer. The results of this comparison were positive in terms of both the modelling performed and the convergence between the outcomes of the two programming environments.
Next, the model of an integrated PV system having no grid connection was built and the performance analysis of this system was carried out by applying fast Fourier transformation. The simulation tests performed showed that both software platforms provide results which are almost the same regarding the electric entities simulated and slightly different regarding the signal total harmonic distortion.
Finally, the case of an integrated photovoltaic system connected to lowvoltage grid was examined. Once again the model development was followed by the overall system performance analysis by examining the cases having a relatively low load and alternatively a higher load connected to the network. The application of fast Fourier transformation provided again results which have a small deviation regarding the electric entities simulated and a bigger one regarding the total harmonic distortion of the signals, thus indicating the existence of different noise influence.
The authors declare that there is no conflict of interests.