Experimental Analysis of hill-climbing MPPT algorithms under low irradiance levels. (October 2021)

• Record Type: Journal Article
• Authors: Jately, Vibhu; Azzopardi, Brian; Joshi, Jyoti; Venkateswaran V, Balaji; Sharma, Abhinav; Arora, Sudha
• Is Part Of: Renewable & sustainable energy reviews. Volume 150(2021)
• Publication Date: 2021-10
• Subjects: Hill-climbing -- MPPT -- Perturb and Observe -- Perturbation step-size -- ADC -- Incremental conductance; ADC Analog to Digital Converter -- AHC Adaptive Hill-Climbing -- AI Artificial Intelligence -- ANN Artificial Neural Network -- ASF Adaptive Scaling Factor -- BST Bisection Search Theorem -- C/A-P&O Conventional/Adaptive Perturb and Observe -- C/A-INC Conventional/Adaptive Incremental Conductance -- C/A-DF Conventional/Adaptive Drift-Free -- C-INR Conventional Incremental Resistance -- CCL Current Control Loop -- CHC Conventional Hill-Climbing -- CSAM Current sensor-less method with auto-modulation -- CV Constant voltage -- DCPA Duty-cycle perturbations adaptation -- ESC Extremum seeking control -- FLC Fuzzy logic control -- GAF-VPF Gaussian–Arctangent Function Variable Perturbation Frequency -- I&T Irradiance & Temperature -- MPP Maximum power point -- MPPT Maximum power point tracking -- OSS Optimum step-size -- OC Open circuit -- PI Proportional Integral -- PSO Particle swarm optimization -- PV Photovoltaic -- SA Simulated Annealing -- SC Short circuit -- SM-ESC Sliding-mode extremum seeking control -- SS Steady-state -- SSS Suboptimal step-sizes -- STC Standard Test Condition -- TG Temperature gradient -- VCL Voltage Control Loop; Renewable energy sources -- Periodicals; Power resources -- Periodicals; Énergies renouvelables -- Périodiques; Ressources énergétiques -- Périodiques; 333.794
• DOI: 10.1016/j.rser.2021.111467
• Languages: English
• ISSNs: 1364-0321

Abstract

Abstract: Adaptive hill-climbing MPPT algorithms have superior performance as opposed to their conventional counterparts under medium-high irradiance. However, the performance of these hill-climbing algorithms remains mostly unknown under low irradiance condition. The low irradiance conditions are prominent in tropical countries during rainy seasons and niche PV applications. Additionally, several thin-film photovoltaic (PV) technologies have better efficiency under low irradiance conditions. Hence, the optimum operation of MPPT algorithms under low irradiance conditions is vital. In the real-time implementation, MPPT algorithms can fail to detect the incremental changes in voltage and current under low irradiance conditions. Hence, analog to digital converter (ADC) resolution becomes a critical constraint that governs the performance of hill-climbing (HC) MPPT algorithms. This work entails a detailed calculation to determine the perturbation step-sizes of the MPPT algorithms under a wide range of irradiance. Two distinct perturbation step-sizes are determined corresponding to the minimum and optimum change in voltage and current due to perturbation, that is sensed by the ADC. The authors also defined a general expression to determine the optimum digitized step-size for duty-based perturb and observe algorithm under low irradiance condition. This expression is formulated by considering the resolution of the ADC and the desirability of keeping the power oscillations at an acceptable level. Finally, the performance of eight hill-climbing algorithms for two distinct step-sizes is analyzed on a small-scale experimental prototype under both uniform and sudden changes in low values of irradiance. The statistical analysis validates that the adaptive HC drift-free MPPT algorithm outperforms other HC algorithms when implemented with the optimum perturbation step-size under low irradiance conditions. Highlights: The perturbation step-size should be evaluated based on the resolution of the analog to digital converter (ADC) of the controller. The performance of the HC algorithms are similar when implemented with the large perturbation step-size which is determined corresponding to the resolution of the ADC. Among P&O, INC and INR algorithms, the P&O algorithm has the highest tracking speed due to the use of duty as a perturbation parameter which helps in reducing the tracking time. The perturbation step-size should be optimized for the worst condition, i.e. analysis should be carried out for the lower end of irradiance. The proposed methodology to determine the optimum step-size helped in lowering the steady-state oscillations and maintaining a good tracking speed.