A Distributed Photovoltaics Ordering Grid-Connected Method for Analyzing Voltage Impact in Radial Distribution Networks

In recent years,distributed photovoltaics(DPV)has ushered in a good development situation due to the advantages of pollution-free power generation,full utilization of the ground or roof of the installation site,and balancing a large number of loads nearby.However,under the background of a large-scale DPV grid-connected to the county distribution network,an effective analysis method is needed to analyze its impact on the voltage of the distribution network in the early development stage of DPV.Therefore,a DPV orderly grid-connected method based on photovoltaics grid-connected order degree(PGOD)is proposed.This method aims to orderly analyze the change of voltage in the distribution network when large-scale DPV will be connected.Firstly,based on the voltagemagnitude sensitivity(VMS)index of the photovoltaics permitted grid-connected node and the acceptance of grid-connected node(AoGCN)index of other nodes in the network,thePGODindex is constructed to determine the photovoltaics permitted grid-connected node of the current photovoltaics grid-connected state network.Secondly,a photovoltaics orderly grid-connected model with a continuous updating state is constructed to obtain an orderly DPV grid-connected order.The simulation results illustrate that the photovoltaics grid-connected order determined by this method based on PGOD can effectively analyze the voltage impact of large-scale photovoltaics grid-connected,and explore the internal factors and characteristics of the impact.

Evaluation of the Performances of the First Grid-Connected Photovoltaic System in Sénégal

This document presents the evaluation and the monitoring of the performances of the first grid-connected photovoltaic system installed in the Center of Studies and Researches on the Renewable Energies (CERER) inaugurated on December 4th, 2012 by the governmental authorities of Senegal and Tenerife. This mini power plant of 3.15 kWc is a perfect example of the political will of the government which is to reduce the production cost of the electricity, with the diversification of the sources of production, and the greater use of the other sources such as the natural gas, the coal, the renewable energies. The evaluation of the performances of the installation is realized by using the indicators of efficiency and performance as the photovoltaic surface yield, the ratio of photovoltaic performance, the photovoltaic specific yield, and the losses of captures. The obtained results show that a big part of the energy shone during the period of observation was not able to be used further to circumstances such as the losses of conductivity, the heat losses or for example the defects on components. The analysis also shows that a large part of the produced energy is not injected because of the dilapidation of the network, the defects of landing but especially one disjunction sees frequently at the level of the point of injection.

Large-Scale Distributed Photovoltaic Power Dispatching and Operation Management Review

Distributed photovoltaic power (PV) is the main development model of distributed generation. It is necessary to research on dispatching and operation management with large-scale distributed PV connected. This paper analyzes development status, technical requirement and dispatching and operation management situation of distributed PV in Germany and China. Then introduce the preparation of distributed PV dispatching and operation management criterion. Through summarizing the experiences and lessons of large-scale distributed PV development in Germany, it gives advice to the development of distributed PV dispatching and operation management in China.

Research on Control Method of Inverters for Large-scale Grid Connected Photovoltaic Power System

A grid-connected inverter controlling method to analyze dynamic process of large-scale and grid-connected photovoltaic power station is proposed. The reference values of control variables are composed of maximum power which is the output of the photovoltaic array of the photovoltaic power plant, and power factor specified by dispatching, the control strategy of dynamic feedback linearization is adopted. Nonlinear decoupling controller is designed for realizing decoupling control of active and reactive power. The cascade PI regulation is proposed to avoid inaccurate parameter estimation which generates the system static error. Simulation is carried out based on the simplified power system with large-scale photovoltaic plant modelling, and the power factor, solar radiation strength, and bus fault are considered for the further research. It’s demonstrated that the parameter adjustment of PI controller is simple and convenient, dynamic response of system is transient, and the stability of the inverter control is verified.

Forecast of Power Generation for Grid-Connected Photo-voltaic System Based on Grey Theory and Verification Model

Being photovoltaic power generation affected by radiation strength, wind speed, clouds cover and environment temperature, the generating in each moment is fluctuating. The operational characteristics of grid-connected PV systems are coincided with gray theory application conditions. A gray theory model has been applied in short-term forecast of grid-connected photovoltaic system. The verification model of the probability of small error will help to check the accuracy of the gray forecast results. The calculated result shows that the ?model accuracy has been greatly enhanced.

A composite controller for grid connected photovoltaic systems

This paper addresses a new composite controller for a boost-buck inverter to interface the photovoltaic array with the power grid. Based on dynamically tracking the maximum power point, two novel control methodologies are proposed to control the DC-bus and the output current for the inverter. First, a new linear cycle discrete control algorithm is introduced to realize linear control of the DC-bus voltage and synchronously get the reference current for the inner current loop with a little calculation. Then, to assure a good adaptability to noise and model uncertainty, an auto-disturbance rejection controller is chosen as the output current controller, which does not depend on precise mathematics model. Thus, output current of PV system to the grid is with low harmonic distortion and unity power factor. Simulations and experiments are performed, and the results show that the system is of excellent robustness and effective.

A Robust Single-Sensor MPPT Strategy for Shaded Photovoltaic-Battery System

A robust single-sensor global maximum power point tracking(MPPT)strategy based on modern optimization for photovoltaic systems considering shading conditions is proposed in this work.The proposed strategy is designed for battery charging applications and direct current(DC)microgrids.Under normal operation,the curve of photovoltaic(PV)output power versus PV voltage contains only a single peak point.This point can be simply captured using any traditional tracking method like perturb and observe.However,this situation is completely different during the shadowing effect where several peaks appear on the power voltage curve.Most of these peaks are local with only a single global.This condition leads to the incapability of traditional tracking approaches to extract the global peak power due to their inability to distinguish between the local and global peak points.They are trapped in the first peak point even when the point is local.Therefore,global tracking approaches based on modern optimization are highly required.A recent marine predators algorithm(MPA)has been used to solve the problem of tracking the global MPP under shadowing influence.Different shadowing scenarios are used to test and evaluate the performance of MPA based tracker.The obtained results are compared with particle swarm optimization(PSO)and ant lion optimizer(ALO).The results of the comparison con-firmed the effectiveness and robustness of the proposed global MPPT-MPA based tracker over PSO and ALO.

Quasi-Z Source Inverter Control of PV Grid-Connected Based on Fuzzy PCI

The photovoltaic grid-connected inverter is an important interface between the photovoltaic power generation system and power grid.Its high-quality operation is directly related to the output power quality of the power grid.In order to further optimize the control effect of the quasi-Z source grid-connected photovoltaic inverter,a fuzzy proportional complex integral control(PCI)method is proposed for the current internal loop control.This method can eliminate the steady-state error,and has the characteristic of zero steady-state error adjustment for the AC disturbance signal of a specific frequency.The inductance-capacitance-inductance(LCL)filter is adopted in the grid-connected circuit,and the feedback capacitive current is taken as the control variable of the inner loop to form the active damping control method,which can not only effectively suppress the resonance of the LCL circuit,but also significantly inhibit the high-order harmonics in the grid-connected current.Finally,a system simulation model is built in MATLAB/Simulink to verify the superiority and effectiveness of the proposed method.

FCS-MPC Strategy for PV Grid-Connected Inverter Based on MLD Model

In the process of grid-connected photovoltaic power generation,there are high requirements for the quality of the power that the inverter breaks into the grid.In this work,to improve the power quality of the grid-connected inverter into the grid,and the output of the system can meet the grid-connected requirements more quickly and accurately,we exhibit an approach toward establishing a mixed logical dynamical(MLD)model where logic variables were introduced to switch dynamics of the single-phase photovoltaic inverters.Besides,based on the model,our recent efforts in studying the finite control set model predictive control(FCS-MPC)and devising the output current full state observer are exciting for several advantages,including effectively avoiding the problem of the mixed-integer quadratic programming(MIQP),lowering the THD value of the output current of the inverter circuit,improving the quality of the power that the inverter breaks into the grid,and realizing the current output and the grid voltage same frequency and phase to meet grid connection requirements.Finally,the effectiveness of the mentioned methods is verified by MATLAB/Simulink simulation.

Outdoor Performance Evaluation of Grid-Connected PV Technologies in Cyprus

This paper presents the outdoor performance evaluation of different grid-connected PV technologies installed in Cyprus over a two year period. The PV research and testing facility at the University of Cyprus was commissioned in 2006 to perform continuous measurements of meteorological and PV operational parameters. The test site is appropriately equipped to undertake such evaluations at a very high resolution （1 measurement per second）. The perfromance results obtained for the two year evaluation period clearly show how each PV technology has performed under the climatological conditions in Cyprus. Finally the high average energy yield of the fixed plate systems under test, 1580 kWh/kWp and 1609 kWh/kWp during the first and second year of evaluation respectively, also verifies that solar energy is a very promising renewable source of energy for countries with a high solar resource.

A Simulation Research on the Grid-Connected Control Technology of Single-Phase Inverters Based on MATLAB

This paper primarily discusses the main circuit of single-phase inverter circuits.It begins by introducing the research context and the significance of the subject,then discusses the topology of grid-connected single-phase inverter circuits,continues by discussing the control strategy for grid-connected single-phase inverter circuits,realizes a sinusoidal pulse width modulation(SPWM)signal generation circuit and an inverse control algorithm program,and finally ensures good output waveform and fast dynamic response.In view of the hysteresis feature of the grid voltage’s synchronous signal sampling circuit,the acquisition function in digital signal processing(DSP)control chips is applied,and the reasons for the hysteresis phenomenon are thoroughly investigated.The reliability of the SPWM control algorithm is revealed through the results.

海上光伏外围防护-固定式透空堤结构型式研究进展

固定式透空堤能改善海上漂浮式光伏发电系统的深海运维环境。依据不同的消浪原理和构造将固定式透空堤分为排桩透空堤、桩基透空堤、沉箱透空堤、桩基沉箱透空堤、横板透空堤和组合透空堤6种型式,针对固定式透空堤的研究和发展进行文献综述,回顾和讨论不同结构型式研究方法、结构特点、消浪性能和实际工程应用等方面的内容,总结了当前研究存在的不足并展望了未来发展方向。

Performance Assessment of a Real PV System Connected to a Low-Voltage Grid

The generation of photovoltaic(PV)solar energy is increasing continuously because it is renewable,unlimited,and clean energy.In the past,generation systems depended on non-renewable sources such as oil,coal,and gas.Therefore,this paper assesses the performance of a 51 kW PV solar power plant connected to a low-voltage grid to feed an administrative building in the 6th of October City,Egypt.The performance analysis of the considered grid-connected PV system is carried out using power system simulator for Engineering(PSS/E)software.Where the PSS/E program,monitors and uses the power analyzer that displays the parameters and measures some parameters such as current,voltage,total power,power factor,frequency,and current and voltage harmonics,the used inverter from the type of grid inverter for the considered system.The results conclude that when the maximum solar radiation is reached,the maximum current can be obtained from the solar panels,thus obtaining the maximum power and power factor.Decreasing total voltage harmonic distortion,a current harmonic distortion within permissible limits using active harmonic distortion because this type is fast in processing up to 300 microseconds.The connection between solar stations and the national grid makes the system more efficient.

船用太阳能光伏柔性支架风荷载数值模拟

为了进一步实现航运业节能减排,可以在面积开阔、光照充足的大型油轮甲板表面铺设船用太阳能光伏(PV)柔性支架。通过计算流体力学(CFD)数值计算方法研究船用柔性支架风荷载影响因素及分布规律。结果表明:光伏阵列风荷载与纵向间距成反比,当纵向间距比超过1.8时,各排光伏板风荷载基本不随纵向间距比变化,此时各排光伏板力矩值相差小于3倍。增加纵向光伏板数量可使中间位置光伏板荷载分布更加均匀。基于计算结果,在设计船用柔性支架时,首排可选用强度较大的钢索,并布置15排以上的光伏阵列,控制纵向间距比为1.8,以针对性地提升结构可靠性,避免前排光伏板弯矩超限;同时使各排光伏板风荷载分布更加均匀,相关研究结论将为船用柔性支架的工程设计和布置提供依据。

海上漂浮光伏发电技术及其融合发展展望

[目的]在“双碳”背景下,我国沿海省市逐步加大向海洋开发清洁能源的力度。海上风电场建设已经初具规模并已逐步实现平价上网,海上漂浮式光伏(Floating Photovoltaic,FPV)试点项目正在不断涌现。探索多种海洋资源的综合开发,在能源领域集约用海,打造海上综合能源系统,对于沿海省份高质量地实现碳中和具有重要意义。[方法]总结了目前国内外海上FPV技术发展及工程试点情况,分析了各种海上FPV技术的优势及挑战,预测了在中国近海发展FPV的市场规模,提出并探讨了海上FPV与海上其他基础设施的融合发展方式,并结合案例给出了融合建设场景及经济性分析。[结果]海上FPV技术目前总体处于试验和试点阶段,未来在国内外市场应用空间广阔,其主要技术难点是浮体在严苛海洋环境条件下的生存能力,现有试点工程单位造价相对较高,但与其他海洋设施结合发展潜力巨大。[结论]海上漂浮式光伏与海上风电等其他海上设施融合建设可以有效提高能源设施的利用效率,降低建设和运行的成本。海上风光互补还较好地解决了单一能源供应的稳定性和安全性问题。

Energy and exergy analysis of a 20-MW grid-connected PV plant operating under harsh climatic conditions

Large grid-connected photovoltaic(PV)plants are increasingly being installed around the world,including in harsh desert climates.Evaluating their performance can help improve the design and operation of PV systems.This study performed an energy and exergy analysis of a 20-MW grid-connected PV plant under desert climatic conditions in southern Algeria over a period of 1 year.The PV plant was divided into two 10-MW subsystems.Energy analysis was performed using actual irradiation,power output,wind speed and ambient temperature data.The annual average energy efficiency of the plant and subsystems was 10.82%,10.95%and 10.69%,respectively.Solar radiation had the most significant impact(80%determination coefficient)on thermal exergy loss.The exergy efficiency of the plant was lower than the literature values,likely due to the harsh desert conditions.The comprehensive energy and exergy analysis provides insights into the performance of large-scale PV plants in desert climates.The results can help guide the system design and operation improvements for such conditions.Regular cleaning and cooling could improve performance.

海洋环境下漂浮光伏电站浮体HDPE材料的抗疲劳性能与优化策略

研究旨在深入探讨高密度聚乙烯(HDPE)材料在海洋环境下应用于漂浮光伏电站浮体的抗疲劳性能。通过试验研究、理论分析和案例研究,探讨了海洋环境因素对漂浮光伏电站浮体HDPE材料疲劳性能的影响,并提出了改进策略。研究发现,在海洋环境中,改良的HDPE材料在漂浮光伏浮体中表现出优越的抗疲劳特性。使用高效的光屏蔽剂、光吸收助剂和合金混合物作为物理保护,同时使用持久的高低温抗氧化剂、聚合物抗紫外线稳定剂、抗疲劳剂和紫外线活化增韧系统,可以增强HDPE材料的抗老化和加工性能。改良的HDPE材料在海洋环境中的漂浮光伏电站浮体的耐久性和稳定性得到了提升。

The Resonance Suppression for Parallel Photovoltaic Grid-connected Inverters in Weak Grid

Obvious resonance peak will be generated when parallel photovoltaic grid-connected inverters are connected to the weak grid with high grid impedance, which seriously affects the stability of grid-connected operation of the photovoltaic system. To overcome the problems mentioned above, the mathematical model of the parallel photovoltaic inverters is established. Several factors including the impact of the reference current of the grid-connected inverter, the grid voltage interference and the current disturbance between the photovoltaic inverters in parallel with the grid-connected inverters are analyzed. The grid impedance and the LCL filter of the photovoltaic inverter system are found to be the key elements which lead to existence of resonance peak. This paper presents the branch voltage and current double feedback suppression method under the premise of not changing the topological structure of the photovoltaic inverter, which effectively handles the resonance peak, weakens the harmonic content of the grid current of the photovoltaic grid-connected inverter and the voltage at the point of common coupling, and improves the stability of the parallel operation of the photovoltaic grid-connected inverters in weak grid. At last, the simulation model is established to verify the reliability of this suppression method.

Generating capacity adequacy evaluation of large-scale, grid-connected photovoltaic systems

Large-scale, grid-connected photovoltaic sys- tems have become an essential part of modem electric power distribution systems. In this paper, a novel approach based on the Markov method has been proposed to investigate the effects of large-scale, grid-connected photovoltaic systems on the reliability of bulk power systems. The proposed method serves as an applicable tool to estimate performance （e.g., energy yield and capacity） as well as reliability indices. The Markov method frame- work has been incorporated with the＇ multi-state models to develop energy states of the photovoltaic systems in order to quantify the effects of the photovoltaic systems on the power system adequacy. Such analysis assists planners to make adequate decisions based on the economical expectations as well as to ensure the recovery of the investment costs over time. The failure states of the components of photovoltaic systems have been considered to evaluate the sensitivity analysis and the adequacy indices including loss of load expectation, and expected energy not supplied. Moreover, the impacts of transitions between failures on the reliability calculations as well as on the long- term operation of the photovoltaic systems have been illustrated. Simulation results on the Roy Billinton test system has been shown to illustrate the procedure of the proposed frame work and evaluate the reliability benefits of using large-scale, grid-connected photovoltaic system on the bulk electric power systems. The proposed method can be easily extended to estimate the operating and maintenance costs for the financial planning of the photovoltaic system projects.

Interharmonic Analysis Model of Photovoltaic Grid-connected System with Extended Dynamic Phasors

The interactions between randomly fluctuating power outputs from photovoltaic(PV) at the DC side and background voltage distortions at the AC side could generate interharmonics in the PV grid-connected system(PVGS). There is no universal method that can reveal the transmission mechanism of interharmonics and realize accurate calculation in different scenarios where interharmonics exist in the PVGS. Therefore, extended dynamic phasors(EDPs) and EDP sequence components(EDPSCs) are employed in the interharmonic analysis of the PVGS. First, the dynamic phasors(DPs) and dynamic phasor sequence components(DPSCs) are extended into EDPs and EDPSCs by selecting a suitable fundamental frequency other than the power frequency. Second, an interharmonic analysis model of the PVGS is formulated as a set of state space equations. Third, with the decoupling characteristics of EDPSCs,generation principles and interactions among the interharmonics in the PVGS are presented by the sequence components,and its correctness is verified by simulation and experiment.The presented model can be used to accurately calculate the interharmonics generated in the PVGS both at the AC and DC sides. Because of the decoupling among the EDPSCs, the set of state space equations can effectively describe the principle.