Theoretical assessment of the maximum power point tracking efficiency of photovoltaic facilities with different converter topologies

The operating point of a photovoltaic generator that is connected to a load is determined by the intersection point of its characteristic curves. In general, this point is not the same as the generator’s maximum power point. This difference means losses in the system performance. DC/DC converters together with maximum power point tracking systems (MPPT) are used to avoid these losses. Different algorithms have been proposed for maximum power point tracking. Nevertheless, the choice of the configuration of the right converter has not been studied so widely, although this choice, as demonstrated in this work, has an important influence in the optimum performance of the photovoltaic system. In this article, we conduct a study of the three basic topologies of DC/DC converters with resistive load connected to photovoltaic modules. This article demonstrates that there is a limitation in the system’s performance according to the type of converter used. Two fundamental conclusions are derived from this study: (1) the buck–boost DC/DC converter topology is the only one which allows the follow-up of the PV module maximum power point regardless of temperature, irradiance and connected load and (2) the connection of a buck–boost DC/DC converter in a photovoltaic facility to the panel output could be a good practice to improve performance.     

A simple photo-voltaic tracking system

This paper describes a simple photo-voltaic (PV) tracking system which has been designed and manufactured using a pyramidal stand as a base. A rotating unit consisting of two pairs of modules fixed at an angle of 170° between them was installed at the upper edge of the stand. The four modules and a DC motor were connected to a bridge circuit making the system sensitive to solar tracking. The PV tracker has a DC–DC (24/2 V) converter, DC–AC (24/220 V) inverter and a battery. The modules are able to provide a maximum power of 100 W, which feeds the converter, inverter and DC motor. Wind resistance of the tracker is quite low. The total area of the four modules is 1.26 m². The inclination angle between the modules and the horizontal plane is adjustable (34°±11°) and the tracking angle is 120°. The system can track solar motion with an error of ±10°. The designed PV tracking system, with modules fixed at an angle of 170° to feed the load as well as the DC motor, exhibited it to be an efficient energy-conversion system. The fabricated system offers low wind resistance. The cost analysis data revealed that the proposed design was very economical and cost effective.     

A maximum power point tracking for photovoltaic-SPE system using a maximum current controller

Processes to produce hydrogen from solar photovoltaic (PV)-powered water electrolysis using solid polymer electrolysis (SPE) are reported. An alternative control of maximum power point tracking (MPPT) in the PV-SPE system based on the maximum current searching methods has been designed and implemented.Based on the characteristics of voltage–current and theoretical analysis of SPE, it can be shown that the tracking of the maximum current output of DC–DC converter in SPE side will track the MPPT of photovoltaic panel simultaneously.This method uses a proportional integrator controller to control the duty factor of DC–DC converter with pulse-width modulator (PWM).The MPPT performance and hydrogen production performance of this method have been evaluated and discussed based on the results of the experiment.     

Grid connected fuel cell and PV hybrid power generating system design with Matlab Simulink

Renewable energy sources have been taken the place of the traditional energy sources and especially rapidly developments of photovoltaic (PV) technology and fuel cell (FC) technology have been put forward these renewable energy sources (RES) in all other RES. PV systems have been started to be used widely in domestic applications connected to electrical grid and grid connected PV power generating systems have become widespread all around the world. On the other hand, fuel cell power generating systems have been used to support the PV generating so hybrid generation systems consist of PV and fuel cell technology are investigated for power generating. In this study, a grid connected fuel cell and PV hybrid power generating system was developed with Matlab Simulink. 160 Wp solar module was developed based on solar module temperature and solar irradiation by using real data sheet of a commercial PV module and then by using these modules 800 Wp PV generator was obtained. Output current and voltage of PV system was used for input of DC/DC boost converter and its output was used for the input of the inverter. PV system was connected to the grid and designed 5 kW solid oxide fuel cell (SOFC) system was used for supporting the DC bus of the hybrid power generating system. All results obtained from the simulated hybrid power system were explained in the paper. Proposed model was designed as modular so designing and simulating grid connected SOFC and PV systems can be developed easily thanks to flexible design.     

Combined operation of DC isolated distribution and PV systems for supplying unbalanced AC loads

This paper describes a DC isolated network which is fed by distributed generation (DG) from photovoltaic (PV) renewable sources to supply unbalanced AC loads. The battery energy storage bank has been connected to the DC network via DC/DC converter called storage converter to control the network voltage and optimize the operation of the PV generation units. The PV units are connected to the DC network via its own DC/DC converter called PV converter to ensure the required power flow. The unbalanced AC loads are connected to the DC network via its own DC/AC converter called load converter without transformer. This paper proposes a novel control strategy for storage converter which has a DC voltage droop regulator. Also a novel control system based on Clarke and Park rotating frame has been proposed for load converters. In this paper, the proposed operation method is demonstrated by simulation of power transfer between PV units, unbalanced AC loads and battery units. The simulation results based on PSCAD/EMTDC software show that DC isolated distribution system including PV units can provide the balanced voltages to supply unbalanced AC loads.     

Experimental evaluation of V-trough (2 suns) PV concentrator system using commercial PV modules

V-trough photovoltaic (PV) concentrator systems along with conventional 1-sun PV module is designed and fabricated to assess PV electricity cost ($/W) reduction. V-trough concentrator (2-sun) system is developed for different types of tracking modes: seasonal, one axis north–south and two axes tracking. Three design models based on these tracking modes are used to develop the V-trough for a 2-sun concentration. Commercially available PV modules of different make and types were evaluated for their usability under 2-sun concentration. The V-trough concentrator system with geometric concentration ratio of 2 (2-sun) increases the output power by 44% as compared to PV flat-plate system for passively cooled modules. Design models with lower trough angles gave higher output power because of higher glass transmittivity. PV modules with lower series resistance gave higher gain in output power. The unit cost ($/W) for a V-trough concentrator, based on different design models, is compared with that of a PV flat plate system inclined at latitude angle (Mumbai, φ=19.12°).     

Optimized photovoltaic generator–water electrolyser coupling through a controlled DC–DC converter

The coupling of a photovoltaic generator and an electrolyser is one of the most promising options for obtaining hydrogen from a renewable energy source. Both are well known technologies, however, since the high variability of the solar radiation, an efficient coupling still presents some challenges. Direct or through a DC–DC converter couplings are the options in isolated applications. In this work, three models, respectively, for a photovoltaic (PV) generator, a controlled DC–DC converter and a complete proton exchange membrane (PEM) electrolyser have been designed by using Matlab/Simulink. A PV-electrolyser specific algorithm to search for the optimum and safe working point for both elements is presented. Simulation results demonstrate that the use of a controlled DC–DC converter with the proposed algorithm shows better adaptability to the variable radiation conditions than the other coupling options. Therefore, it leads to a better compliance between the electrolyser and the sizing of the PV generator.     

Power conversion in renewable energy systems: A review advances in wind and PV system

Grid‐connected photo voltaic (PV) systems are being developed very fast and systems from a few kW to tenths of a MW are now in operation. As an important source of distributed generation (DS) the PV systems need to comply with a series of standard requirements in order to ensure the safety and the seamless transfer of the electrical energy to the grid. Multilevel voltage source converters (VSC) is a heart of the PV system and are emerging as an important power converter options for low, medium, and high‐power applications. These VSCs have bought numerous advantages, especially in renewable energy systems such as PV and wind energy systems. In this article, several topologies of VSCs, which brings together some concepts from traditional converters and multi‐level converters, are presented. Also, several control strategies for controlling current, voltage, active power and reactive power have also been reviewed. Various topologies with their technical aspects have been reviewed and the best suitable topology and control scheme for grid connected PV and wind energy systems has been suggested. Copyright © 2016 John Wiley & Sons, Ltd.     

局部阴影条件下基于改进电导增量法的光伏系统最大功率跟踪方法

在局部阴影的情况下,由于串联式光伏组件的输出特性不同而产生多个极值点,使得传统的最大功率追踪（maximum power point tracking, MPPT）方法陷入局部极值点而失效。文中提出一种针对两级并网光伏系统的改进电导增量法以适应光伏阵列在局部阴影下的多峰值最大功率跟踪,通过分析最大功率点电压的变化范围,设定最大功率电压搜索范围以提高搜索效率,并通过DC/DC Boost变换器占空比实现输入电压控制,保证算法不陷入局部极值点。最后利用仿真实验验证了该算法在有、无阴影情况下均能准确地跟踪光伏方阵最大功率,有效提高了光伏阵列输出效率。     

100 MW production PV plant

This article announces the availability of patented technology and production equipment for the manufacture of thin-film CdTe photovoltaic (PV) modules capable of providing utility scale power. It further discusses ongoing R&D, for the period 2000–2010, which will produce PV power at costs competitive with conventional fossil fuel systems.     

Design and analysis of a high frequency DC–DC converters for fuel cell and super-capacitor used in electrical vehicle

This work focuses on the application of the high frequency DC–DC converters used in electric vehicles. Two converters are necessary. The first converter is interposed between the fuel cell and the DC–AC inverter. It is unidirectional. The second one is used as interface between the ultra-capacitor and the DC–AC inverter. It allows the bidirectional of the power transfer. Each converter is composed of two full bridges, LC resonant filter and two planar transformers. The use of high frequency transformer allows to minimize the size and weight of the converter, produce a higher voltage in secondary side from input voltage (fuel cell or super-capacitor) and isolate the full bridges. The control strategy of the converters is the phase shift. The converters have been designed, realised and controlled by an FPGA board. To demonstrate the converters feasibility, two converters are implemented and tested. The switching frequency of two converters is 20 kHz. The first converter has a 24-V input and 200 V/1.2 kW output. But, the second converter has a 12.5-V input and 100 V/400 W output.     

光伏并网发电功率波动与对策

分析了光伏并网发电功率波动对电网可能造成的危害及储能型光伏并网系统的运行工况,提出了并网功率的给定方法,即以光伏阵列输出功率进行低通滤波后的值作为参考并网功率,还详细分析了低通滤波器的设计、双向DC/DC变换器的功率控制,最后进行了仿真研究。仿真结果表明,采用此控制策略可以有效控制功率的波动,减小其变化率,即使光照波动较大,光伏系统输出的电流波形也很好,储能系统随着光伏阵列发出功率的波动而改变功率流动的方向和大小。     

Photovoltaic modules in buildings: Performance and safety

Many PV systems exhibit a poorer performance as is to be expected using installed peak power. Performance ratios of ‘reasonable’ systems have experimentally been determined in the range of 60%–85% of STC (=standard test conditions) performance. A significant part of the losses is due to the performance deviation of PV modules from their rating at STC due to the outdoor conditions (realistic reporting conditions, RRC). This is due to low light level dependence, temperature coefficients, nominal operating cell temperatures and reflectivity at the module surface. Due to the special operating conditions, this is of special importance if PV modules are integrated into buildings. To overcome the problems in module performance evaluation and to assist system sizing, a realistic PV efficiency map and performance data for commercial PV modules are presented. In a similar way as the European radiation atlas for solar irradiation, this RRC market survey of PV modules gives detailed information on module performance at many sites for various installation conditions.As the International Electrotechnical Commission is currently preparing a new international standard, dealing with the safety of PV modules in a variety of application classes, performance data on PV modules is supplemented by information on possible module safety tests and module integration into buildings.     

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.     

Simulation model for sizing of stand-alone solar PV system with interconnected array

Solar PV arrays made of interconnected modules are comparatively less susceptible to shadow problem and power degradation resulting from the aging of solar cells. This paper presents a simulation model for the sizing of stand-alone solar PV systems with interconnected arrays. It considers the electricity generation in the array and its storage in the battery bank serving the fluctuating load demand. The loss of power supply probability (LPSP) is used to connote the risk of not satisfying the load demand. The non-tracking (e.g., fixed and tilted) and single-axis tracking aperture arrays having cross-connected modules of single crystalline silicon solar cells in a (6×6) modular configuration are considered. The simulation results are illustrated with the help of a numerical example wherein the load demand is assumed to follow uniform probabilistic distribution. For a given load, the numbers of solar PV modules and batteries corresponding to zero values of LPSP on diurnal basis during the year round cycle of operation are presented. The results corresponding to the surplus and deficit of energy as a function of LPSP are also presented and discussed to assess the engineering design trade offs in the system components.Furthermore, a simple cost analysis has also been carried out, which indicates that for Delhi the stand-alone solar PV systems with fixed and tilted aperture arrays are better option than those with single-axis tracking aperture (with north–south oriented tracking axis) arrays.     

SMC-DPC based active and reactive power control of grid-tied three phase inverter for PV systems

In this paper, sliding mode control (SMC) – direct power controller (DPC) based active and reactive power controller for three-phase grid-tied photovoltaic (PV) system is proposed. The proposed system consists of two main controllers: the DC/DC boost converter to track the possible maximum power from the PV panels and the grid-tied three-phase inverter. The Perturb and Observe (P&O) algorithm is used to transfer the maximum power from the PV panels. Control of the active and reactive powers is performed using the SMC-DPC strategy without any rotating coordinate transformations or phase angle tracking of the grid voltage. In addition, extra current control cycles are not used to simplify the system design and to increase transient performance. The fixed switching frequency is obtained by using space vector modulation (SVM). The proposed system provides very good results both in transient and steady states with the simple algorithms of P&O and SMC-DPC methods. Moreover, the results are evaluated by comparing the SMC-DPC method developed for MPPT and the traditional PI control method. The proposed controller method is achieved with TMS320F28335 DSP processor and the system is experimentally tested for 12 kW PV generation systems.     

Modeling and simulation of three phase multilevel inverter for grid connected photovoltaic systems

This paper presents a control for a three phase five-level neutral clamped inverter (NPC) for grid connected PV system. The maximum power point tracking (MPPT) is capable of extracting maximum power from the PV array connected to each DC link voltage level. The MPPT algorithm is solved by fuzzy logic controller. The fuzzy MPPT is integrated with the inverter so that a DC–DC converter is not needed and the output shows accurate and fast response. A digital PI current control algorithm is used to remain the current injected into the grid sinusoidal and to achieve high dynamic performance with low total harmonic distortion (THD). The validity of the system is verified through MATLAB/Simulink and the results are compared with three phase three-level grid connected NPC inverter in terms of THD.     

不同技术类型光伏组件的户外发电性能及衰减分析

对在广东省顺德地区(属于亚热带季风气候)运行的异质结(HIT)光伏组件、铜铟镓硒(CIGS)薄膜光伏组件、碲化镉(CdTe)薄膜光伏组件这3种不同技术类型的光伏组件的户外发电性能进行了比较,并对这3种光伏组件的功率衰减情况进行了定量分析.截至2019年12月,上述3种光伏组件的户外累计运行时间长达12年,其室内I-V特...     

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.     

A highly efficient PV system using a series connection of DC–DC converter output with a photovoltaic panel

A photovoltaic (PV) power conditioning system (PCS) must have high conversion efficiency and low cost. Generally, a PV PCS uses either a single string converter or a multilevel module integrated converter (MIC). Each of these approaches has both advantages and disadvantages. For a high conversion efficiency and low cost PV module, a series connection of a module integrated DC–DC converter output with a photovoltaic panel was proposed. The output voltage of the PV panel is connected to the output capacitor of the fly-back converter. Thus, the converter output voltage is added to the output voltage of the PV panel. The isolated DC–DC converter generates only the difference voltage between the PV panel voltage and the required total output voltage. This method reduces the power level of the DC–DC converter and enhances energy conversion efficiency compared with a conventional DC–DC converter.