Nowadays a hot topic among the research community is the harnessing energy from the free sunlight which is abundant and pollutionfree. The availability of cheap solar photovoltaic (PV) modules has to harvest solar energy with better efficiency. The nature of solar modules is nonlinear and therefore the proper impedance matching is essential. The proper impedance matching ensures the extraction of the maximum power from solar PV module. Maximum power point tracking (MPPT) algorithm is acting as a significant part in solar power generating system because it varies in the output power from a PV generating set for various climatic conditions. This paper suggested a new improved work for MPPT of PV energy system by using the optimized novel improved fractional order variable step size (FOVSS) incremental conductance (IncCond) algorithm. The new proposed controller combines the merits of both improved fractional order (FO) and variable step size (VSS) IncCond which is well suitable for design control and execution. The suggested controller results in attaining the desired transient reaction under changing operating points. MATLAB simulation effort shows MPPT controller and a DC to DC Luo converter feeding a battery load is achieved. The laboratory experimental results demonstrate that the new proposed MPPT controller in the photovoltaic generating system is valid.
Renewable energy sources are considered as an important source of energy in the 21st century that is in use to fulfill our needs and growing demands of electricity. Among all renewable energy sources, solar energy is readily available free of cost. The production cost of solar photovoltaic based system is decreased considerably. The advancement in PV technology also causes less cost per unit and thus PV technology do not contribute to global warming [
Different methods have been reported in literature for tracking the maximum power point (MPP). Among the 20 distinct methods reported by [
In this paper we suggested a novel technique that will tune the online MPPT techniques based on changing weather conditions. The proposed algorithm modifies the existing conventional IncCond controller based on improved fractional order variable step size which differs from the existing. The difference is based on the datasheet of the panel on the novel controller and is constant for any particular PV array. The proposed algorithm is implemented into MATLAB/Simulink environment and it is tested and validated.
The structure of the system is organized as follows. Section
The schematic circuit diagram for the suggested system is shown in Figure
The proposed optimized novel FOVSS IncCond MPPT system.
PV systems convert sunlight into electrical energy without causing any environmental issues. Various equivalent models are available in the literature for better understanding of concept of PV array. Among the models, Figure
Equivalent circuit model of solar cell.
A FO system comprised by a fractional differential or an integral equation, and systems covering few equations, has been deliberate in engineering and physical appliances, for example, active control, signal processing, and linear and nonlinear response controller. The generally utilized approaches have been anticipated for numerical assessment of fraction derivatives by RiemannLioville and GrunwaldLetnikov definition [
For generalization, it is suitable to adopt
If we expand
If
So, an integral power of
Equation (
A general fractional order differentiator can be expressed as follows:
For all
Generally step size is fixed for the IncCond MPPT technique. The produced power from the PV panel with a higher step size plays to quicker dynamics but results in extreme steady state fluctuations and subsequent poor efficiency [
In this report, a VSS procedure is suggested for the improved IncCond tracking technique and is dedicated to search an easier and active way to increase tracking dynamic as well as correctness. In every tracking application, the possible power follower is attained by joining a DC to DC converter among the PV panel and load system [
Novel improved FOVSS IncCond MPPT algorithm.
In the above equation
In the above written equation
The
In the above equation
In the equation above, the VSS improved IncCond tracking will be operating with FSS of the early set superior controller
The
The efficiency of the weighing
Figure
Situation one: if
Situation two: if (
Situation three: if (
Situation four: calculated power output is equal to multiplication of voltage and current output,
When recommending a MPP tracker, the most important process is to choose and analyze a highly suitable converter, which is invented to function as the foremost fragment of the tracker (MPPT). Therefore switching mode power supplies are suitable to operate with high efficiency. Among all the complete topologies existing, the series of buckboost converters provide the opportunity to have either higher or lower output voltage compared with the input voltage. The conventional buckboost formation is cheaper than the Luo one, even though some drawbacks occur, such as less efficient, weak transient reaction, high peak current in power apparatuses, and discontinuous current input. On the other side, the Luo converter has the highest efficiency with low switching losses amongst nonisolated DC to DC converters and no negative polarity regulated output voltage compared to the input voltage. It can deliver an improved current output characteristic due to the output stage inductor. Thus, the Luo configuration is an appropriate converter to be active in deceiving the MPPT [
The DC to DC Luo converter provides a positive polarity regulated output voltage with respect to the input voltage which is shown in Figure
DC to DC Luo converter.
In mode one operation, when the power switch
Equivalent modes of converter: (a) main switch on; (b) main switch off.
In the mode 2 process, when the switch is in turned off state, the input current drawn from the source becomes zero, as shown in Figure
The PV array is modeled and coupled with the DC to DC Luo converter and is controlled by suggested tracking algorithm. To examine the performance and effectiveness of suggested FOVSS IncCond controller, it is tested on the experimental prototype of the photovoltaic MPPT controller and the complete simulation structure of a proposed system is illustrated in Figure
Electrical parameters of PV module.
Designation  Peak maximum power  Peak maximum voltage  Peak maximum current  Open circuit voltage  Short circuit current 

Value [units]  10 Wp  16.4 V  0.610 A  21 V  0.700 A 
Simulation layout of the proposed FOVSS IncCond system.
To confirm the enactment of the suggested system the
Simulated
To distinguish the enactment of the designed improved FOVSS IncCond MPPT control algorithm which can automatically regulate the step size with the traditional incremental conductance algorithm, the MATLAB simulations are constructed under similar circumstances. The sampling period carried out for the conventional IncCond algorithm was selected as 0.02 second. Consequently, the PWM duty cycle (
Simulated photovoltaic power output response under sudden change in G&T: (a) conventional IncCond algorithm; (b) designed improved FOVSS IncCond tracking technique.
The performance is compared between conventional IncCond and proposed FOVSS IncCond tracking algorithm and is obtained in Table
Comparison of conventional and proposed tracking algorithm performance.
Technique  Parameter  Irradiance200 W/m^{2} and temperature is −25°C  Irradiance800 W/m^{2} and temperature is −27°C  Under steady state conditions  

Output power  Sampling period in seconds  Output power  Sampling period in seconds  
Conventional 


0.02 seconds 

0.5 seconds  More fluctuation takes place 
Proposed FOVSS IncCond algorithm 


0.02 seconds 

0.5 seconds  Eliminate the fluctuation 
The process of improved FOVSS IncCond maximum tracking algorithm has been assessed by experiment. The experimental test was carried out on the laboratory test bench of the standalone PV system installed on the floor of the Electrical and Electronics Engineering at Government College of Engineering, Salem, India, sponsored by IIT, Bombay. A model of the suggested scheme depicted in Figure
Photos of prototype setup: (a) PV array; (b) DC to DC Luo converter with improved FOVSS IncCond MPPT algorithm.
The initial graph with improved FOVSS IncCond peak tracking control algorithm is illustrated in Figure
Initial waveforms of MPPT with PV array (channel1: PV voltage, channel2: PV current, channel3: gate pulse).
Change in power when the number of PV modules is increased from three to four.
Change in power when the number of PV modules is decreased from four to three.
In this paper, a novel improved fractional order variable step size (FOVSS) incremental conductance (IncCond) tracking algorithm is designed and verified with MATLAB simulation and experimental environment. The major difference between the suggested technique and existing tracking technique includes elimination of the additional PI control loop and investigates the effect of novel Improved FOVSS IncCond control technique. This paper includes huge contributions such as how improved VSS IncCond is derived based on fractional order derivative method, how DC to DC soft switching Luo converter is designed, and how comparison between the proposed scheme and existing system is done with the help of simulation and experimental arrangement. The experimental and simulation results demonstrate that the suggested controller tracks the peak power of the photovoltaic scheme in variable insulation with quick transient response. Since current and voltage of the solar photovoltaic are utilized as input elements, it has controller characteristics with variable step size. Thus, fluctuations around peak power are significantly eliminated. Thus the suggested FOVSS IncCond based peak tracking algorithm increase the power output 4.75 times the conventional power output for low load conditions. Accordingly, it is seen that the suggested technique is favorable for quick varying climatic situation.
Temperature
Irradiance
Maximum power point tracking
Maximum power point
Photovoltaic
Incremental conductance
Analog to digital converter
Fixed step size
Fractional order variable step size
Duty cycle
Appendix
Switch
Variable step size
Current
Voltage
Maximum power
Fractional order
Fractional order derivative
Zero voltage switching
Zero current switching.
The authors declare that there is no conflict of interests regarding the publication of this paper.