New algorithm using only one variable measurement applied to a maximum power point tracker

A novel algorithm for seeking the maximum power point of a photovoltaic (PV) array for any temperature and solar irradiation level, needing only the PV current value, is proposed. Satisfactory theoretical and experimental results are presented and were obtained when the algorithm was included on a 100 W 24 V PV buck converter prototype, using an inexpensive microcontroller. The load of the system used was a battery and a resistance. The main advantage of this new maximum power point tracking (MPPT), when is compared with others, is that it only uses the measurement of the photovoltaic current, I_PV.     

Maximum photovoltaic power tracking for the PV array using the fractional-order incremental conductance method

This paper proposes maximum photovoltaic power tracking (MPPT) for the photovoltaic (PV) array using the fractional-order incremental conductance method (FOICM). Since the PV array has low conversion efficiency, and the output power of PV array depends on the operation environments, such as various solar radiation, environment temperature, and weather conditions. Maximum charging power can be increased to a battery using a MPPT algorithm. The energy conversion of the absorbed solar light and cell temperature is directly transferred to the semiconductor, but electricity conduction has anomalous diffusion phenomena in inhomogeneous material. FOICM can provide a dynamic mathematical model to describe non-linear characteristics. The fractional-order incremental change as dynamic variable is used to adjust the PV array voltage toward the maximum power point. For a small-scale PV conversion system, the proposed method is validated by simulation with different operation environments. Compared with traditional methods, experimental results demonstrate the short tracking time and the practicality in MPPT of PV array.     

A Novel Auto-Scaling MPPT Algorithm based on Perturb and Observe Method for Photovoltaic Modules under Partial Shading Conditions

Maximum Power Point Tracking (MPPT) controller is required in a solar photovoltaic (PV) system to deliver the maximum power to load from PV module. This paper proposes a novel stepped MPPT method to realize a simple MPPT controller, which can track the real maximum power point (RMPP) even under partial shading conditions. The proposed algorithm is started by scanning the characteristic curve of the PV modules to detect the global maximum power point and then the algorithm will be switched to the conventional P&O algorithm to track the true maximum power point. The obtained simulation results, using Power electronic simulation software (PSIM), are compared with those found using the P&O method to confirm the performance of our proposed MPPT method even under non-uniform solar irradiation.     

New maximum power point tracker for PV arrays using fuzzy controller in close cooperation with fuzzy cognitive networks

The studies on the photovoltaic (PV) generation are extensively increasing, since it is considered as an essentially inexhaustible and broadly available energy resource. However, the output power induced in the photovoltaic modules depends on solar radiation and temperature of the solar cells. Therefore, to maximize the efficiency of the renewable energy system, it is necessary to track the maximum power point of the PV array. In this paper, a maximum power point tracker using fuzzy set theory is presented to improve energy conversion efficiency. A new method is proposed, by using a fuzzy cognitive network, which is in close cooperation with the presented fuzzy controller. The new method gives a very good maximum power operation of any PV array under different conditions such as changing insolation and temperature. The simulation studies show the effectiveness of the proposed algorithm.     

Photovoltaic field emulation including dynamic and partial shadow conditions

In this paper the development of a new laboratory prototype for the emulation of a photovoltaic (PV) field is presented. The proposed system is based on a DC/DC step-down converter topology and allows to obtain the solar array I–V curves, taking into account the environmental changes in solar irradiance and cell temperature. The DC/DC converter control strategy is deduced by using a comprehensive mathematical model of the PV field whose parameters are obtained from the knowledge of: (a) maximum power point data, measured when the PV plant power converter is running, (b) open circuit voltage and short-circuit current, measured off-line. This approach allows the most accurate representation of the PV source. Computer simulations and experimental results demonstrate that the proposed circuit acts as a highly accurate and efficient laboratory simulator of the photovoltaic array electrical characteristics both in steady state and transient conditions. Partial shading and fluctuating conditions can be reproduced too. Moreover the dynamic behaviour of the proposed laboratory emulator is suitable to its effective connection to power electronic interface to the utility or to load through a DC/DC boost converter.     

Vectorial command of an asynchronous motor fed by a photovoltaic generator

In order to promote renewable energy, Tunisia has developed a large program to exploitate photovoltaïc systems (PV) to provide electric power in rural electrification. These needs increase continually following standard of living improvements, from lighting and media communication (radio, TV) to motors, refrigeration and pumping. The fluctuation of solar energy on one hand, and the necessity to optimise available solar energy on the other, it is useful to develop new efficient and flexible modes to control motors. A vectorial control of an asynchronous motor fed by a photovoltaïc system is proposed. In this case, the control of the circulating current becomes an important objective in the algorithm design. This paper presents an efficient current controller scheme that can achieve high accuracy and a fast dynamic response of induction machine. This scheme uses voltage decoupling and proportional integral controller loops (PI). Furthermore, to operate the PV array at its maximum power point for every instant, the PV system must contain a maximum power point tracking controller (MPPT). Good static and dynamic performances were obtained in simulation of the proposed structure.     

A cell-to-module-to-array detailed model for photovoltaic panels

This paper presents a modified current–voltage relationship for the single-diode model. The single-diode model has been derived from the well-known equivalent circuit for a single photovoltaic (PV) cell. A cell is defined as the semiconductor device that converts sunlight into electricity. A PV module refers to a number of cells connected in series and in a PV array, modules are connected in series and in parallel. The modification presented in this paper accounts for both parallel and series connections in an array. Derivation of the modified current–voltage relationships begins with a single solar cell and is expanded to a PV module and finally an array. Development of the modified current–voltage relationship was based on a five-parameter model, which requires data typically available from the manufacturer. The model accurately predicts voltage–current (V–I) curves, power–voltage (P–V) curves, maximum power point values, short-circuit current and open-circuit voltage across a range of irradiation levels and cell temperatures. The versatility of the model lies in its accurate prediction of the aforementioned criteria for panels of different types, including monocrystalline and polycrystalline silicon. The model is flexible in the sense that it can be applied to PV arrays of any size, as well as in simulation programs such as EMTDC/PSCAD and MatLab/Simulink. Accuracy of the model was validated through a series of experiments performed outdoors for different configurations of a PV array.     

光伏发电的最大功率跟踪算法研究

太阳能光伏阵列的输出特性受外界环境因素的影响,为了跟踪太阳能光伏阵列输出功率最大点,实现光伏阵列和负载的匹配,常在系统中加入最大功率跟踪器。准确跟踪太阳能光伏阵列的最大输出功率点依赖于有效的搜索算法。分析了传统的扰动观察法和增量电导法的特点,并提出了一种新的变步长寻优算法。通过验证表明,这种算法能够快速准确地跟踪最大功率点。     

A control scheme with performance prediction for a PV fed water pumping system

This paper focuses on modeling and performance predetermination of a photovoltaic (PV) system with a boost converter fed permanent magnet direct current (PMDC) motor-centrifugal pump load, taking the converter losses into account. Sizing is done based on the maximum power generated by the PV array at the average irradiation. Hence optimum sizing of the PV array for the given irradiation at the geographical location of interest is obtained using the predetermined values. The analysis presented here involves systems employing maximum power point tracking (MPPT) as they are more efficient than directly coupled systems. However, the voltage and power of the motor might rise above rated values for irradiations greater than the average when employing MPPT, hence a control scheme has been proposed to protect the PMDC motor from being damaged during these conditions. This control scheme appropriately chooses the optimum operating point of the system, ensuring long-term sustained operation. The numerical simulation of the system is performed in Matlab/Simulink and is validated with experimental results obtained from a 180 V, 0.5 hp PMDC motor coupled to a centrifugal pump. The operation of the system with the proposed control scheme is verified by varying the irradiation levels and the relevant results are presented.     

The coupling factor: A new metric for determining and controlling the efficiency of solar photovoltaic power utilization

The production of electricity and hydrogen in a renewable fashion, such as using solar energy, can provide a clean and sustainable energy source for electric-powered vehicles, including fuel-cell and battery-electric vehicles. Our research on generating hydrogen and charging batteries using renewable solar photovoltaic (PV) electricity has led to the development of a simple and convenient new metric called the coupling factor that describes the fraction of the maximum PV power transferred to electrical loads. The keystone of the coupling factor concept is a regression model to calculate the maximum PV voltage, current, and power as a function of the instantaneous incident solar irradiance and the photovoltaic module temperature. The coupling factor can range from zero to one, i.e., no transfer of power from the PV system to the load, to complete transfer of the PV power. We describe the derivation of regression models to compute important PV electrical output variables, such as the open circuit voltage, the short circuit current, the maximum power point voltage, the maximum power point current, and the coupling factor as a function of the fundamental measured variables affecting those quantities. The models are derived for PV modules used in our previous research to power an electrolyzer and charge high-voltage batteries. In addition, we develop models for other modules using PV cell technologies different from those used in our PV system. Some of the calculated quantities are compared to measurements for our PV system. The usefulness of these quantities, and especially the coupling factor, in rating the transfer of PV power to electrolyzer and battery loads, is illustrated. Finally, we discuss how the predicted maximum power point voltage can be used for real-time control and efficiency optimization of a dynamic PV-load system.     

Highly efficient maximum power point tracking using DC–DC coupled inductor single-ended primary inductance converter for photovoltaic power systems

Solar photovoltaics (PVs) have nonlinear voltage–current characteristics, with a distinct maximum power point (MPP) depending on factors such as solar irradiance and operating temperature. To extract maximum power from the PV array at any environmental condition, DC–DC converters are usually used as MPP trackers. This paper presents the performance analysis of a coupled inductor single-ended primary inductance converter for maximum power point tracking (MPPT) in a PV system. A detailed model of the system has been designed and developed in MATLAB/Simulink. The performance evaluation has been conducted on the basis of stability, current ripple reduction and efficiency at different operating conditions. Simulation results show considerable ripple reduction in the input and output currents of the converter. Both the MPPT and converter efficiencies are significantly improved. The obtained simulation results validate the effectiveness and suitability of the converter model in MPPT and show reasonable agreement with the theoretical analysis.     

硅太阳电池工程用数学模型

为实现光伏电站、光伏户用系统、光伏水泵系统、"风 -光-柴-蓄"等各种涉及太阳能光伏利用复合能源系统的设计、数字仿真和动态模拟实验 ,以电子学理论为基础,讨论了满足工程应用精度且便于运算的太阳电池数学模型.该模型的特点是仅采用生产厂家为用户提供的太阳电池组件在标准测试条件(STC)下测出的I sc、Voc、Im、Vm作为参数,通过引入相应系数来考虑环境影响,并给出系数的典型值.实验结果表明模型的误差一般都在6%以下,可以满足对绝大多数工程项目进行物理模拟的精度要求.     

基于空间矢量PWM法的光伏水泵变频控制系统

介绍一种基于空间矢量PWM控制的光伏水泵变频控制系统。该空间矢量PWM算法具有对光伏阵列母线电压的动态补偿功能，保证在光伏阵列工作电压大范围变化条件下，变频驱动电机满足恒磁通调速控制。同时结合光伏水泵系统的工作特点，提出了一种简单实用的光伏阵列最大功率点跟踪控制方式，稳定可靠地实现了系统的最大功率点跟踪控制。     

Calculating the shading reduction coefficient of photovoltaic system efficiency using the anisotropic sky scattering model

The front-row shading reduction coefficient is a key parameter used to calculate the system efficiency of a photovoltaic (PV) power station. Based on the Hay anisotropic sky scattering model, the variation rule of solar radiation intensity on the surface of the PV array during the shaded period is simulated, combined with the voltage–current characteristics of the PV modules, and the shadow occlusion operating mode of the PV array is modeled. A method for calculating the loss coefficient of front shadow occlusion based on the division of the PV cell string unit and Hay anisotropic sky scattering model is proposed. This algorithm can accurately evaluate the degree of influence of the PV array layout, wiring mode, array spacing, PV module specifications, and solar radiation on PV power station system efficiency. It provides a basis for optimizing the PV array layout, reducing system loss, and improving PV system efficiency.     

An improved thermal and electrical model for a solar photovoltaic thermal (PV/T) air collector

In this paper, an attempt is made to investigate the thermal and electrical performance of a solar photovoltaic thermal (PV/T) air collector. A detailed thermal and electrical model is developed to calculate the thermal and electrical parameters of a typical PV/T air collector. The thermal and electrical parameters of a PV/T air collector include solar cell temperature, back surface temperature, outlet air temperature, open-circuit voltage, short-circuit current, maximum power point voltage, maximum power point current, etc. Some corrections are done on heat loss coefficients in order to improve the thermal model of a PV/T air collector. A better electrical model is used to increase the calculations precision of PV/T air collector electrical parameters. Unlike the conventional electrical models used in the previous literature, the electrical model presented in this paper can estimate the electrical parameters of a PV/T air collector such as open-circuit voltage, short-circuit current, maximum power point voltage, and maximum power point current. Further, an analytical expression for the overall energy efficiency of a PV/T air collector is derived in terms of thermal, electrical, design and climatic parameters. A computer simulation program is developed in order to calculate the thermal and electrical parameters of a PV/T air collector. The results of numerical simulation are in good agreement with the experimental measurements noted in the previous literature. Finally, parametric studies have been carried out. Since some corrections have been down on thermal and electrical models, it is observed that the thermal and electrical simulation results obtained in this paper is more precise than the one given by the previous literature. It is also found that the thermal efficiency, electrical efficiency and overall energy efficiency of PV/T air collector is about 17.18%, 10.01% and 45%, respectively, for a sample climatic, operating and design parameters.     

Enhancement of grid-connected photovoltaic system using ANFIS-GA under different circumstances

In recent years, many different techniques are applied in order to draw maximum power from photovoltaic (PV) modules for changing solar irradiance and temperature conditions. Generally, the output power generation of the PV system depends on the intermittent solar insolation, cell temperature, efficiency of the PV panel and its output voltage level. Consequently, it is essential to track the generated power of the PV system and utilize the collected solar energy optimally. The aim of this paper is to simulate and control a grid-connected PV source by using an adaptive neuro-fuzzy inference system (ANFIS) and genetic algorithm (GA) controller. The data are optimized by GA and then, these optimum values are used in network training. The simulation results indicate that the ANFIS-GA controller can meet the need of load easily with less fluctuation around the maximum power point (MPP) and can increase the convergence speed to achieve the MPP rather than the conventional method. Moreover, to control both line voltage and current, a grid side P/Q controller has been applied. A dynamic modeling, control and simulation study of the PV system is performed with the Matlab/Simulink program.     

A robust hybrid method for maximum power point tracking in photovoltaic systems

In this paper a new hybrid method for maximum power point tracking in PV systems has been proposed. This method combines offline and online methods in order to estimate duty cycle of converter in maximum power point. In the offline phase, temperature and radiation intensity are the inputs of the system to estimate the approximate maximum power based on analytical equations of solar cell. These equations which give the relation of maximum power with temperature and irradiation can be derived from characteristics of cell provided by manufacturer or experiments. Afterwards the duty cycle of converter would be estimated using circuit equations of measured Thevenin model of the load and battery. Measuring Thevenin equation results in robustness of method respecting variations of load and battery. In the online phase, the classic perturbation and observation (P&O) method will be utilized for fine tuning and tracking of maximum power point. The proposed method has been simulated in MATLAB/SIMULINK workspace and compared with some other MPPT methods. The results reveal that this hybrid method outperforms other methods in term of performance and speed of tracking.     

卫星太阳翼在轨输出功率预测模型

该文介绍一种卫星太阳翼在轨功率输出预测方法,由单体太阳电池根据固体物理理论推导出来直流理论分析模型获得其等效电路,通过对单体太阳电池串、并联后组成的太阳翼电气电路,获得太阳翼等效电路,并根据该等效电路推导出太阳翼的直流分析模型。将太阳翼的直流分析模型转化为由单片太阳电池片开路电压Voc、短路电流Isc、最大功率点电压Vmp、最大功率点电流Imp这4个参数决定的太阳翼工程应用方程。同时,通过地面试验获得单体太阳电池的电压和电流衰降系数,获取太阳翼实际在轨不同时刻的开路电压VAoc、短路电流IAsc、最大功率点电压VAmp、最大功率点电流IAmp,并通过计算获取太阳翼工作点电压、电流,得到太阳翼的在轨预测工作输出功率。通过将该文模型预测值与太阳翼实际在轨输出电流、电压遥测值进行比较,验证该预测模型的有效性。该预测模型可通过单体太阳电池的4个工程参数,获得整个太阳翼的直流分析模型,便于太阳翼设计阶段建模分析的工程化应用。     

Power quality investigation of a solar PV transformer-less grid-connected system fed DVR

This paper presents a single stage transformer-less grid-connected solar photovoltaic (PV) system with an active and reactive power control. In the absence of active input power, the grid-tied voltage source converter (VSC) is operated in a reactive power generation mode, which powers the control circuitry, and maintains a regulated DC voltage to the VSC. A data-based maximum power point tracking (MPPT) control scheme which performs power quality control at a maximum power by reducing the total harmonic distortion (THD) in grid injected current as per IEEE-519/1547 standards is implemented. A proportional-integral (PI) controller based dynamic voltage restorer (DVR) control scheme is implemented which controls the grid side converter during single-phase to ground fault. The analysis includes the grid current THD along with the corresponding variation of the active and reactive power during the fault condition. The MPPT tracks the actual variable DC link voltage while deriving the maximum power from the solar PV array, and maintains the DC link voltage constant by changing the modulation index of the VSC. Simulation results using Matlab/Simulink are presented to demonstrate the feasibility and validations of the proposed novel MPPT and DVR control systems under different environmental conditions.     

Hybrid control approach for PV/FC fed voltage source converter tied to grid

A hybrid and adaptive control approach for solar photovoltaic system and fuel cell fed voltage source converter (VSC) is presented in this work. Further maximum power from solar photovoltaic array is extracted by using incremental conductance (INC) based maximum power point tracking approach. This hybrid approach combines I cos ? technique and gradient descent back propagation learning (GDBP) neural network (NN) to extract fundamental components from load current for efficient harmonics compensation and provides power quality improvement and support the three-phase AC grid by supplying power to the grid and as well as connected loads. The proposed system includes photovoltaic (PV) array, a voltage source converter (VSC), ripple filter and combination of linear and non-linear loads. The proposed control approach provides a fast response during dynamic conditions as well. Results of the proposed control technique also compared with the other available control techniques for its superiority analysis. The developed control technique is demonstrated by using MATLAB/SIMULINK platform.