This paper presents a practical implementation of a photovoltaic I-V curves and maximum power point estimation algorithm (IVMPPE). The IVMPPE estimates the I-V curve and sets the operation of the solar panels at a voltage that extracts the maximum available power without tracking. The operation is based on solving the parameters of the solar array equivalent electrical model, in real time, only with the measurements of six voltage and current coordinates near the operating point. Moreover, the strategy for selecting the measured points and the discard procedures for incorrect estimated curves are also detailed. To validate the IVMPPE, it has been tested under different operating conditions, and its accuracy has been compared with the classical perturb and observe (P&O) technique. The distinguishing feature of the IVMPPE is that complete I-V model is obtained, not only the MPP, enlarging the capabilities to other fields, e.g., real-time monitoring and prediction.

In-Site Real-Time Photovoltaic I–V Curves and Maximum Power Point Estimator

This paper examines the application of various classical root-finding methods to digital maximum power point tracking (DMPPT). An overview of root-finding methods such as the Newton Raphson method, Secant method, bisection method, regula falsi method, and a proposed modified regula falsi method (MRFM) applied to photovoltaic (PV) applications is presented. These methods are compared among themselves. Some of their features are also compared with other commonly used maximum power point (MPP) tracking methods. Issues found when implementing these root-finding methods based on continuous variables in a digital domain are explored. Some of these discussed issues include numerical stability, digital implementation of differential operators, and quantization error. Convergence speed is also explored. The analysis is used to provide practical insights into the design of a DMPPT based on classical root-finding algorithms. A new DMPPT based on an MRFM is proposed and used as the basis for the discussion. It is shown that this proposed method is faster than the other discussed methods that ensure convergence to the MPP. The discussion is approached from a practical perspective and also includes theoretical analysis to support the observations. Extensive simulation and experimental results with hardware prototypes verify the analysis.

Analysis of Classical Root-Finding Methods Applied to Digital Maximum Power Point Tracking for Sustainable Photovoltaic Energy Generation

The solar photovoltaic power has received great attention and experienced impressive progress in the countries all over the world in recent years because of more and more serious energy crisis and environmental pollution. This paper proposes a novel power management control strategy for stand-alone photovoltaic power system, which consists of a solar cell array, a battery, a uni-directional DC-DC converter, and a bi-directional DC-DC converter. The solar cell array powers the steady state energy and the battery compensates the dynamic energy. The goal of the power management control strategy is to control the un-directional DC-DC converter and bi-direction DC-DC converter to operate in suitable modes according to the condition of solar cell and battery, so as to coordinate the two sources of solar cell and battery supplying power and ensure the system operates with high efficiency and behaviors with good dynamic performance. A 500W experimental prototype of stand-alone photovoltaic power system was built in the lab. Experimental results are shown to verify the effectiveness of the proposed power management strategy.

A novel power management control strategy for stand-alone photovoltaic power system

This paper reviews different types of maximum power point tracking (MPPT) techniques for solar photovoltaic (PV) application. Since the PV output power is known affected by sun radiation and temperature, it is necessary to search for an effective method for extracting maximum amount of power from PV cell/modules. In this study, a total of seven control algorithms were selected, comprising the most popular methods among the established techniques. A comparison in terms of convergence speed, complexity, as well as the basic concept of each method had been carried out for future reference. Based on the accessible simulation results, modified Perturb and Observe (P&O) method had shown its effectiveness for obtaining actual maximum power point while solving major drawbacks of the conventional P&O. This paper also discusses typical solar MPPT system, including the pros and cons of each part of the system.

A Review on Favourable Maximum Power Point Tracking Systems in Solar Energy Application

This paper considers selection of the suitable simulation model for solar panels [1]. Two models for silicon polycrystalline photovoltaic solar cells [2], [3] were analysed. The selection is made by comparing the Power vs. Voltage and Current vs. Voltage curves obtained from the simulation to those obtained experimentally. The goal is to identify if a simulation model gives correct information about the behaviour of one single solar panel for varying temperature and irradiance. Final validation is done by comparing experimental and simulation results. The single panel model was integrated into array of 16 elements. This can be integrated in the simulation of an isolated micro grid or in a hybrid energy system [4], [5] By comparing simulation results from both models with experimental results we can conclude that model 2 is the most reliable one.

http://lib.tkk.fi/Conf/2008/urn011694.pdf

Selecting the accurate solar panel simulation model

Solar power is considered as a kind of "clean power". The problems of using solar power include varying weather condition brings different power output of the photovoltaic cells, which may cause a serious waste of solar power. For solving this problem, a maximum power point tracking (MPPT) strategy is required to make Solar cells keep giving maximum power under different environment condition. In this paper, a variable step MPPT method is proposed for faster and more precise tracking process, based on an applicable solar cell model. The new MPPT method gives a second order convergence speed, compared with the traditional MPPT methods, which always behave as one order convergence. According to the applicable solar cell model, a series of differential equations are established to describe the MPPT process, and the maximum power point is present as the solution of those equations. Using a Newton iterative method can not only get the solution of the equations, but also set up ever search step of the tracking process. A matlab-simulink model was established as a two stage PV system including a DC/DC regulator and a load converter to analysis the performance of the proposed MPPT strategy. Simulation result in the last part proved that this MPPT method is practical with a better performance than the traditional strategies.

Shangxu Duan

Papers

A Variable Step Maximum Power Point Tracking Method Using Differential Equation Solution