Maximum power point tracking (MPPT) techniques are employed in photovoltaic (PV) systems to make full utilization of PV array output power which depends on solar irradiation and ambient temperature. Among all the MPPT strategies, the incremental conductance (INC) algorithm is widely used due to the high tracking accuracy at steady state and good adaptability to the rapidly changing atmospheric conditions. In this paper, a modified variable step size INC MPPT algorithm is proposed, which automatically adjusts the step size to track the PV array maximum power point. Compared with the conventional fixed step size method, the proposed approach can effectively improve the MPPT speed and accuracy simultaneously. Furthermore, it is simple and can be easily implemented in digital signal processors. A theoretical analysis and the design principle of the proposed method are provided and its feasibility is also verified by simulation and experimental results.

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A Variable Step Size INC MPPT Method for PV Systems

This paper presents evaluations among the most usual maximum power point tracking (MPPT) techniques, doing meaningful comparisons with respect to the amount of energy extracted from the photovoltaic (PV) panel [tracking factor (TF)] in relation to the available power, PV voltage ripple, dynamic response, and use of sensors. Using MatLab/Simulink and dSPACE platforms, a digitally controlled boost dc-dc converter was implemented and connected to an Agilent Solar Array E4350B simulator in order to verify the analytical procedures. The main experimental results are presented for conventional MPPT algorithms and improved MPPT algorithms named IC based on proportional-integral (PI) and perturb and observe based on PI. Moreover, the dynamic response and the TF are also evaluated using a user-friendly interface, which is capable of online program power profiles and computes the TF. Finally, a typical daily insulation is used in order to verify the experimental results for the main PV MPPT methods.

Evaluation of the Main MPPT Techniques for Photovoltaic Applications

This paper presents simulation and hardware implementation of incremental conductance (IncCond) maximum power point tracking (MPPT) used in solar array power systems with direct control method. The main difference of the proposed system to existing MPPT systems includes elimination of the proportional-integral control loop and investigation of the effect of simplifying the control circuit. Contributions are made in several aspects of the whole system, including converter design, system simulation, controller programming, and experimental setup. The resultant system is capable of tracking MPPs accurately and rapidly without steady-state oscillation, and also, its dynamic performance is satisfactory. The IncCond algorithm is used to track MPPs because it performs precise control under rapidly changing atmospheric conditions. MATLAB and Simulink were employed for simulation studies, and Code Composer Studio v3.1 was used to program a TMS320F2812 digital signal processor. The proposed system was developed and tested successfully on a photovoltaic solar panel in the laboratory. Experimental results indicate the feasibility and improved functionality of the system.

Simulation and Hardware Implementation of Incremental Conductance MPPT With Direct Control Method Using Cuk Converter

Solar photovoltaic (PV) energy has witnessed double-digit growth in the past decade. The penetration of PV systems as distributed generators in low-voltage grids has also seen significant attention. In addition, the need for higher overall grid efficiency and reliability has boosted the interest in the microgrid concept. High-efficiency PV-based microgrids require maximum power point tracking (MPPT) controllers to maximize the harvested energy due to the nonlinearity in PV module characteristics. Perturb and observe (PO second, no steady-state oscillations around the MPP; and lastly, no need for predefined system-dependent constants, hence provides a generic design core. A design example is presented by experimental implementation of the proposed technique. Practical results for the implemented setup at different irradiance levels are illustrated to validate the proposed technique.

High-Performance Adaptive Perturb and Observe MPPT Technique for Photovoltaic-Based Microgrids

The energy utilization efficiency of commercial photovoltaic (PV) pumping systems can be significantly improved by employing simple perturb and observe (P&O) maximum power point tracking algorithms. Two such P&O implementation techniques, reference voltage perturbation and direct duty ratio perturbation, are commonly utilized in the literature but no clear criteria for the suitable choice of method or algorithm parameters have been presented. This paper presents a detailed theoretical and experimental comparison of the two P&O implementation techniques on the basis of system stability, performance characteristics, and energy utilization for standalone PV pumping systems. The influence of algorithm parameters on system behavior is investigated and the various advantages and drawbacks of each technique are identified for different weather conditions. Practical results obtained using a 1080-Wp PV array connected to a 1-kW permanent magnet dc motor-centrifugal pump set show very good agreement with the theoretical analysis and numerical simulations.

Assessment of Perturb and Observe MPPT Algorithm Implementation Techniques for PV Pumping Applications

The power available at the output of solar arrays keeps changing with solar insolation and ambient temperature. Expensive and inefficient, the solar arrays must be operated at maximum power point (MPP) continuously for economic reasons. Of the numerous algorithms for this purpose, perturb and observe (P&O) is a standard. A derivative of gradient ascent method used in the optimization theory, this algorithm introduces a tradeoff between tracking and dynamic performance. This algorithm also has a tendency to drift the system away from the MPP as atmospheric conditions change. With continually changing atmospheric conditions, these inadequacies lead to poor utilization of solar arrays. This paper addresses both the issues. A variable-step-length algorithm is proposed to eliminate the tradeoff. The drift is minimized by evaluating the entire trend in a power versus voltage curve. Analytical results, validated on a prototype system show excellent performance.

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High-Performance Algorithms for Drift Avoidance and Fast Tracking in Solar MPPT System

Maximum power point trackers (MPPTs) are used to ensure optimal utilization of solar cells. The implementation essentially involves sensing input current and voltage. An MPPT algorithm uses this information to maximize power drawn from the solar cells. Understandably, such realization is costly. Current state of the art allows replacing one of the sensors by complicated computations. In the present work, an empirical observation is used to develop a strategy, which employs a single voltage sensor and carries out simple computations for a buck converter-based MPPT

A Simple Single-Sensor MPPT Solution

In solar cells, the output power is maximized only at a specific output voltage This output power and the corresponding operating voltage is also affected by solar irradiation and ambient temperature leading to continual variation in total power available at the output of the solar cells Considering high installation costs, it is required to track this Maximum Power Point (MPP) at all times This is done using a system called MPP Trackers (MPPT) MPPTs utilize a power converter in series with the solar panel to extract energy from solar cells The operating point at which the power is maximized is located using a variety of algorithms essentially based on well-known gradient following method Algorithmic deficiencies, in this method lead to a tradeoff between dynamic performance and steady state oscillations With continually changing atmospheric conditions, this tradeoff leads to poor utilization of solar cells - an avoidable situation for obvious reasons The present work discusses design issues in implementing algorithms to eliminate this tradeoff

Design Issues in Implementing MPPT for Improved Tracking and Dynamic Performance

The power available from photovoltaic sources peaks at a particular operating point only. This point continuously varies with varying atmospheric conditions. Due to load characteristic mismatch, electronic maximum power point trackers are often employed to continuously follow this changing peak power for optimum utilization. This paper proposes a maximum power point tracking algorithm that uses only a current sensor at the array side. Auto tuning of ad-hoc factors such as variable search step size and scaling parameter are also introduced. This results in efficient startup, drift avoidance and dynamic & steady state performances of the tracker. Experimental results based on solar array simulator as a source feeding a laboratory boost converter based tracker are presented to validate the proposed technique.

Current-sensor-based photovoltaic MPP tracking algorithm with efficient dynamic response

A current-fed half-bridge oscillator has been used to light a 400 watts high intensity discharge (HID) lamp for lighting factories, car parks or streets. The efficiency of the oscillator is approximately 89 %. This oscillator is self driven and not dependent on any patented driver circuits, withstands short circuit conditions indefinitely and is not damaged even if the lamp fails or is accidentally removed. It also starts at low dc voltages as compared to conventional half bridge circuits. When used with suitable voltage multiplier circuits it can also be used with high voltage gas discharge and fluorescent lamps

A.K. Mukerjee

Papers

High-Performance Algorithms for Drift Avoidance and Fast Tracking in Solar MPPT System

A Simple Single-Sensor MPPT Solution

Design Issues in Implementing MPPT for Improved Tracking and Dynamic Performance

Current-sensor-based photovoltaic MPP tracking algorithm with efficient dynamic response

A Current-Fed Half-Bridge Oscillator for 400 Watt HID Lamp