A novel photovoltaic maximum power point tracking technique based on grasshopper optimized fuzzy logic approach

The maximum power point tracking (MPPT) in the PV system has become complex due to the stochastic nature of the load, intermittency in solar irradiance and ambient temperature. To address this problem, a novel Grasshopper optimized fuzzy logic control (FLC) approach based MPPT technique is proposed in this paper. In this proposed MPPT, grasshopper optimization is used to tune the membership functions (MFs) of FLC to handle all uncertainties caused by variable irradiances and temperatures. The performance of the proposed grasshopper optimized FLC based MPPT is studied under rapidly changing irradiance and temperature. The proposed MPPT overcomes the limitations such as slow convergence speed, steady-state oscillations, lower tracking efficiency as encountered in conventional methods viz. perturb & observed (P&O) and FLC techniques. The feasibility of the proposed MPPT is validated through experimentation. The effectiveness of the proposed scheme is compared with P&O and also with FLC MPPT.     

Maximum power point tracking using adaptive fuzzy logic control for grid-connected photovoltaic system

This paper proposes a method of maximum power point tracking using adaptive fuzzy logic control for grid-connected photovoltaic systems. The system is composed of a boost converter and a single-phase inverter connected to a utility grid. The maximum power point tracking control is based on adaptive fuzzy logic to control a switch of a boost converter. Adaptive fuzzy logic controllers provide attractive features such as fast response, good performance. In addition, adaptive fuzzy logic controllers can also change the fuzzy parameter for improving the control system. The single phase inverter uses predictive current control which provides current with sinusoidal waveform. Therefore, the system is able to deliver energy with low harmonics and high power factor. Both conventional fuzzy logic controller and adaptive fuzzy logic controller are simulated and implemented to evaluate performance. Simulation and experimental results are provided for both controllers under the same atmospheric condition. From the simulation and experimental results, the adaptive fuzzy logic controller can deliver more power than the conventional fuzzy logic controller.     

A novel maximum power point tracking technique based on fuzzy logic for photovoltaic systems

Maximum power point tracking (MPPT) techniques are considered a crucial part in photovoltaic system design to maximise the output power of a photovoltaic array. Whilst several techniques have been designed, Perturb and Observe (P&O) is widely used for MPPT due to its low cost and simple implementation. Fuzzy logic (FL) is another common technique that achieves vastly improved performance for MPPT technique in terms of response speed and low fluctuation about the maximum power point. However, major issues of the conventional FL-MPPT are a drift problem associated with changing irradiance and complex implementation when compared with the P&O-MPPT. In this paper, a novel MPPT technique based on FL control and P&O algorithm is presented. The proposed method incorporates the advantages of the P&O-MPPT to account for slow and fast changes in solar irradiance and the reduced processing time for the FL-MPPT to address complex engineering problems when the membership functions are few. To evaluate the performance, the P&O-MPPT, FL-MPPT and the proposed method are simulated by a MATLAB-SIMULINK model for a grid-connected PV system. The EN 50530 standard test is used to calculate the efficiency of the proposed method under varying weather conditions. The simulation results demonstrate that the proposed technique accurately tracks the maximum power point and avoids the drift problem, whilst achieving efficiencies of greater than 99.6%.     

基于新型扰动观察算法MPPT控制

文章结合光伏阵列的数学模型及其输出特性,提出一种固定电流法结合扰动法的控制方法。对该方法进行了理论分析,并在Matlab/Simulink环境下建立了光伏发电系统的仿真模型。仿真结果表明,光伏系统在正常情况下以及光照强度发生突变的时,都能够快速得追踪到最大功率点,该方法具有良好的控制性能。     

Review of the maximum power point tracking algorithms for stand-alone photovoltaic systems

A survey of the algorithms for seeking the maximum power point (MPP) is proposed. As has been shown, there are many ways of distinguishing and grouping methods that seek the MPP from a photovoltaic (PV) generator. However, in this article they are grouped as either direct or nondirect methods. The indirect methods (“quasi seeks”) have the particular feature that the MPP is estimated from the measures of the PV generator's voltage and current PV, the irradiance, or using empiric data, by mathematical expressions of numerical approximations. Therefore, the estimation is carried out for a specific PV generator installed in the system. Thus, they do not obtain the maximum power for any irradiance or temperature and none of them are able to obtain the MPP exactly. Subsequently, they are known as “quasi seeks”.Nevertheless, the direct methods (“true seeking methods”) can also be distinguished. They offer the advantage that they obtain the actual maximum power from the measures of the PV generator's voltage and current PV. In that case, they are suitable for any irradiance and temperature. All algorithms, direct and indirect, can be included in some of the DC/DC converters, Maximum power point trackings (MPPTs), for the stand-alone systems.     

Comprehensive review and performance evaluation of maximum power point tracking algorithms for photovoltaic system

A photovoltaic array is environmentally friendly and a source of unlimited energy generation. However, it is presently a costlier energy generation system than other non-renewable energy sources. The main reasons are seasonal variations and continuously changing weather conditions, which affect the amount of solar energy received by the solar panels. In addition, the non-linear characteristics of the voltage and current outputs along with the operating environment temperature and variation in the solar radiation decrease the energy conversion capability of the photovoltaic arrays. To address this problem, the global maxima of the PV arrays can be tracked using a maximum power point tracking algorithm (MPPT) and the operating point of the photovoltaic system can be forced to its optimum value. This technique increases the efficiency of the photovoltaic array and minimizes the cost of the system by reducing the number of solar modules required to obtain the desired power. However, the tracking algorithms are not equally effective in all areas of application. Therefore, selecting the correct MPPT is very critical. This paper presents a detailed review and comparison of the MPPT techniques for photovoltaic systems, with consideration of the following key parameters: photovoltaic array dependence, type of system (analog or digital), need for periodic tuning, convergence speed, complexity of the system, global maxima, implemented capacity, and sensed parameter(s). In addition, based on real meteorological data (irradiance and temperature at a site located in Addis Ababa, Ethiopia), a simulation is performed to evaluate the performance of tracking algorithms suitable for the application being studied. Finally, the study clearly validates the considerable energy saving achieved by using these algorithms.     

Adaptive fuzzy gain scheduling PID controller for maximum power point tracking of photovoltaic system

This paper proposes a methodology of designing a Maximum Power Point Tracking (MPPT) controller for photovoltaic systems (PV) using a Fuzzy Gain Scheduling of Proportional-Integral-Derivative (PID) type controller (FGS-PID) with adaptation of scaling factors (SF) for the input signals of FGS. The proposed adaptive FGS-PID method is based on a two-level control system architecture, which combines the advantages of fuzzy logic and conventional PID control. The initial values of the PID's gains are determined by the Ziegler–Nichols tuning method. During transient and steady states, the PID's gains are adapted by the FGS-PID to damp out the transient oscillations, to reduce settling time and to guarantee system stability and accuracy. Also, the conditioned input signals of the FGS-PID are tuned dynamically by gain factors which are based on fuzzy logic system (FLS). The FLS is characterized by a set of fuzzy rules which are fuzzy conditional statements expressing the relationship between inputs (error and change of error) and outputs. This approach creates an adaptive MPPT controller and achieves better overall system performance. The simulation results demonstrate the effectiveness of the proposed adaptive FGS-PID and show that this approach can achieve a good maximum power operation under any conditions such as different levels of solar radiation and PV cell temperature for varying PV sources. Compared to conventional methods (PID, perturb and observe method P&O), this method shows a considerable high tracking performance.     

A photovoltaic powered electrolysis converter system with maximum power point tracking control

One of the main problems for renewable and other innovative energy sources is the storage of energy for sustainability. This study focuses on two different scenarios to benefit from solar energy more efficiently. Photovoltaic (PV) energy is converted to the desired voltage level using a buck converter for generating hydrogen with electrolysis process. A maximum power point tracking (MPPT) algorithm is used to benefit from the photovoltaic sources more efficiently. The basic electrolysis load for hydrogen production needs low voltage and high current and controlled sensitively to supply these conditions. The photovoltaic powered buck converter for electrolysis load was simulated in MATLAB/Simulink software using a perturb and observe (P and O) MPPT algorithm and PI controller. The simulation results show that in normal, short circuit and open circuit working conditions the PV and load voltages are stabilized. The efficiency of the proposed system is reached more than 90% for high irradiance levels.     

Fuzzy-PSO controller design for maximum power point tracking in photovoltaic system

Photovoltaic power generation system becomes increasingly important, highly attractive as a clean and renewable energy sources, widely used today in many applications. Recently, researchers have strongly promoted the use of solar energy as a viable source of energy due to its advantages and which it can be integrated into local and regional power supplies. The P–V curve of photovoltaic system exhibits multiple peaks under various conditions of functioning and changes in meteorological conditions which reduces the effectiveness of conventional maximum power point tracking (MPPT) methods and the Particle swarm optimization (PSO) algorithm is considered to be highly efficient for the solution of complicated problems.In this paper, the application of this approach based MPPT algorithm for Photovoltaic power generation system operating under variable conditions is proposed to optimize and to design an intelligent controller comparing to conventional one. PSO Approaches is considered to select and generate an optimal duty cycle which varies with photovoltaic parameters in order to extract the maximum Power. Simulation results show that the proposed approach can track the maximum power point faster and can improve the performance of the system compared to the conventional method.     

分布式光伏发电系统最大功率点跟踪技术比较研究

基于当前光伏阵列最大功率点跟踪技术的研究现状,介绍了适用于分布式光伏发电系统最大功率点跟踪的各种常用控制方法,阐述了每一种控制方法的技术原理,分析和比较了这些常用控制方法的特点,总结了各自的优点和缺点,最后对分布式光伏发电系统最大功率点跟踪方法的选择问题进行了探讨,并指出了具体选择方法时应综合考虑的各种因素。     

Terminal sliding mode control for maximum power point tracking of photovoltaic power generation systems

This paper presents a novel terminal sliding mode control (TSMC) method for maximum power tracking of photovoltaic (PV) power systems. First, an incremental conductance method is used for maximum power point (MPP) searching. It provides good efficiency under rapidly changing atmospheric conditions, but the accuracy for finding the MPP is highly related to the MPP tracking control. Therefore, a TSMC-based controller is developed to regulate the system to the searched reference MPP. Different from traditional sliding mode control, the developed TSMC assures finite convergence time for the MPP tracking. Furthermore, a common singularity problem that exists in traditional TSMC is removed in this paper. Even if considering uncertainty in the PV power system, the TSMC guarantees high robustness. Finally, several simulations and experiments show the expected control performance.     

光伏系统在局部阴影条件下避免困于局部最大功率点跟踪算法研究

光伏阵列受到局部阴影遮蔽时其P-V特性会呈现多峰特性,出现多个局部峰值。为了避免传统最大功率点跟踪算法在此情况下难以找到全局的最大功率点,文章提出了一种优化最大功率点跟踪算法,该算法适用于局部和全局阴影发生的情况。在局部阴影情况下,通过MATLAB仿真和样机试验与传统最大功率点跟踪算法相比,该优化算法能够判断阴影遮蔽情况是否发生,在局部和全局均一阴影的情况下都能够跟踪到全局最大功率点,避免光伏阵列的功率损失,提高光伏系统效率。     

An improved maximum power point tracking method for photovoltaic systems

In most of the maximum power point tracking (MPPT) methods described currently in the literature, the optimal operation point of the photovoltaic (PV) systems is estimated by linear approximations. However these approximations can lead to less than optimal operating conditions and hence reduce considerably the performances of the PV system. This paper proposes a new approach to determine the maximum power point (MPP) based on measurements of the open-circuit voltage of the PV modules, and a nonlinear expression for the optimal operating voltage is developed based on this open-circuit voltage. The approach is thus a combination of the nonlinear and perturbation and observation (P&O) methods. The experimental results show that the approach improves clearly the tracking efficiency of the maximum power available at the output of the PV modules. The new method reduces the oscillations around the MPP, and increases the average efficiency of the MPPT obtained. The new MPPT method will deliver more power to any generic load or energy storage media.     

Power quality improvement of solar photovoltaic transformer-less grid-connected system with maximum power point tracking control

This paper presents a transformer-less single-stage grid-connected solar photovoltaic (PV) system with active reactive power control. In the absence of active input power, grid-tied voltage source converter (VSC) is operated in the reactive power generation mode, which powers control circuitry and maintains regulated DC voltage. Control scheme has been implemented so that the grid-connected converter continuously serves local load. A data-based maximum power point tracking (MPPT) has been implemented at maximum power which performs power quality control by reducing total harmonic distortion (THD) in grid-injected current under varying environmental conditions. Standards (IEEE-519/1547) stipulates that current with THD greater than 5% cannot be injected into the grid by any distributed generation (DG) source. MPPT tracks actual variable DC link voltage while deriving maximum power from PV array and maintains DC link voltage constant by changing the converter modulation index. Simulation results with the PV model and MPPT technique validations demonstrate effectiveness of the proposed system.     

A hybrid maximum power point tracking method for photovoltaic systems

Solar panels exhibit non-linear current–voltage characteristics producing maximum power at only one particular operating point. The maximum power point changes with temperature and light intensity variations. Different methods have been introduced for tracking the maximum power point based on offline and online methods. In this paper a new method is presented to improve the performance of maximum power point tracking in solar panels. The proposed algorithm is a combination of two loops, set point calculation and fine tuning loops. First the set point loop approximates the maximum power using offline calculation of the open circuit voltage. The exact amount of the maximum power will, then, be tracked by the fine tuning loop which is based on perturbation and observation (P&O) method. The proposed method is simulated in Matlab/Simulink environment and experimentally verified using a laboratory prototype. In maximum power point tracking, the effects of frequency variation and disturbance amplitude on dynamic response and steady state performance are examined. Simulation and experimental results are compared with other methods and the effectiveness of the proposed method is evaluated.     

基于模糊控制的光伏发电系统MPPT

光伏电池的输出功率随外部环境和负载的变化而变化,为充分发挥光伏器件的效能,需采用最大功率点跟踪电路。根据最大功率点跟踪的基本原理及常用光伏发电系统控制的优缺点．提出了一种基于模糊控制,具有在线参数调整的自适应占空比扰动法。该方法在不干扰系统正常工作的情况下,能迅速地感知外界的环境变化。实验结果证明,该方法能够快速、准确地跟踪太阳能电池的最大功率点。     

改进型Sepic变换器在光伏MPPT系统中的应用

设计了一种基于三开关的改进型Sepic变换器,将其应用于光伏发电系统最大功率跟踪(MPPT)控制中。基于改进型Sepic变换器的光伏发电实验系统进行了实验研究,实验结果表明了采用该改进型的Sepic变换器在传输效率和故障隔离方面的优越性。     

A ripple-based maximum power point tracking algorithm for a single-phase, grid-connected photovoltaic system

This paper describes a maximum power point tracking algorithm for a single-phase, grid-connected photovoltaic system with a transformerless, diode-clamped inverter. The algorithm is based on the fact that in single-phase systems the instantaneous power oscillates at twice the line frequency. The oscillation of the AC power also causes a ripple of twice the line frequency on the DC voltage and DC power of the photovoltaic array. The described algorithm requires the analysis of the phase relationship between the DC voltage and DC power ripple to determine the maximum power point. To establish a steady state balanced system a secondary DC-voltage controller is applied. Simulation results are presented and compared with the perturb and observe method and show the superiority of the proposed algorithm.     

Critical factors affecting the photovoltaic characteristic and comparative study between two maximum power point tracking algorithms

This paper presents the characterization and the modeling of the electric characteristics of currentvoltage and power–voltage of the photovoltaic (PV) panels. The philosophy behind digital simulation of solar energy systems is that experiments which normally should be done on real systems under high assembling costs can be done numerically in a short time on a computer, thus saving time and investments. The electric parameters of PV cells and the optimal electric quantities of PV panels have been analyzed (voltage and power) according to the meteorological variations (Temperature, solar irradiation …). The obtained results show that the diode parameters of the PV cells depend on solar irradiation: the current saturation increases with solar irradiation. This induces a decrease of the optimal voltage with solar irradiation; when the solar irradiation varies from 600 W/m² to 1000 W/m². By taking into consideration all the modeling results, the electric behavior of the cells association in parallels or in series, as well as the aging of a PV panel have been analyzed. Moreover, a comparative study between two types of MPPT techniques that are used in photovoltaic systems to extract the maximum power have been introduced which are Perturb and Observe (P &O) and Incremental Conductance (INC).