Technico-economic analysis of off grid solar PV/Fuel cell energy system for residential community in desert region

A technico-economic analysis based on integrated modeling, simulation, and optimization approach is used in this study to design an off grid hybrid solar PV/Fuel Cell power system. The main objective is to optimize the design and develop dispatch control strategies of the standalone hybrid renewable power system to meet the desired electric load of a residential community located in a desert region. The effects of temperature and dust accumulation on the solar PV panels on the design and performance of the hybrid power system in a desert region is investigated. The goal of the proposed off-grid hybrid renewable energy system is to increase the penetration of renewable energy in the energy mix, reduce the greenhouse gas emissions from fossil fuel combustion, and lower the cost of energy from the power systems. Simulation, modeling, optimization and dispatch control strategies were used in this study to determine the performance and the cost of the proposed hybrid renewable power system. The simulation results show that the distributed power generation using solar PV and Fuel Cell energy systems integrated with an electrolyzer for hydrogen production and using cycle charging dispatch control strategy (the fuel cell will operate to meet the AC primary load and the surplus of electrical power is used to run the electrolyzer) offers the best performance. The hybrid power system was designed to meet the energy demand of 4500 kWh/day of the residential community (150 houses). The total power production from the distributed hybrid energy system was 52% from the solar PV, and 48% from the fuel cell. From the total electricity generated from the photovoltaic hydrogen fuel cell hybrid system, 80.70% is used to meet all the AC load of the residential community with negligible unmet AC primary load (0.08%), 14.08% is the input DC power for the electrolyzer for hydrogen production, 3.30% are the losses in the DC/AC inverter, and 1.84% is the excess power (dumped energy). The proposed off-grid hybrid renewable power system has 40.2% renewable fraction, is economically viable with a levelized cost of energy of 145 $/MWh and is environmentally friendly (zero carbon dioxide emissions during the electricity generation from the solar PV and Fuel Cell hybrid power system).     

Optimal operation of DC smart house system by controllable loads based on smart grid topology

From the perspective of global warming mitigation and depletion of energy resources, renewable energy such as wind generation (WG) and photovoltaic generation (PV) are getting attention in distribution systems. Additionally, all-electric apartment houses or residence such as DC smart houses are increasing. However, due to the fluctuating power from renewable energy sources and loads, supply-demand balancing of power system becomes problematic. Smart grid is a solution to this problem. This paper presents a methodology for optimal operation of a smart grid to minimize the interconnection point power flow fluctuation. To achieve the proposed optimal operation, we use distributed controllable loads such as battery and heat pump. By minimizing the interconnection point power flow fluctuation, it is possible to reduce the electric power consumption and the cost of electricity. This system consists of photovoltaic generator, heat pump, battery, solar collector, and load. To verify the effectiveness of the proposed system, results are used in simulation presented.     

Grid integrated renewable DG systems: A review of power quality challenges and state-of-the-art mitigation techniques

Increased energy demands due to rapid industrialization, environmental concerns with fossil fuel–based generation, diminishing fossil energy resources, transmission network congestion, and technical performance deterioration are the motivations behind the integration of small renewable distributed generation (DG) units and turning the existing power systems into a restructured one. Optimizing the technical benefits offered by DG placement is a well-known challenge for distribution network operators (DNOs) for both fossil and renewable energy resource–based DGs, but renewable DG systems have several power quality (PQ) challenges associated additionally. Power quality is a very significant characteristic of renewable DG systems because today's loads are more sensitive to PQ disturbances and penetration of renewable energy as well as nonlinear loads is proliferating in distribution power networks. So the need for innovative power quality improvement (PQI) techniques becomes inevitable due to ongoing reformation in traditional distribution networks by the integration of renewable energy. This article presents a comprehensive analysis of power quality challenges with grid integration of renewable DG systems and current research status of associated mitigation techniques. Firstly, this paper puts emphasis on theoretically illustrating all the crucial power quality challenges associated with grid integration of renewable energy, and secondly, a thorough survey, of all PQI techniques introduced till date, is elaborated along with highlighting the opportunities for future research. Furthermore, all the crucial power quality issues, the impact of high penetration of renewable energy and mitigation techniques on power quality, are demonstrated also by simulating a grid integrated PV-based DG system in MATLAB/Simulink. This article is believed to be very beneficial for academics as well as industry professionals to understand existing PQ challenges, PQI techniques, and future research directions for renewable energy technologies.     

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.     

Adaptive fuzzy control with an optimization by using genetic algorithms for grid connected a hybrid photovoltaic–hydrogen generation system

The integration of significant amounts of renewable-storage hybrid power generation systems to the electric grid poses a unique set of challenges to utilities and system operators. This article deals with the designing methodology of an intelligent control based grid-connected a hybrid system composed of renewable energy source (RES) and storage system (SS). RES is a photovoltaic (PV) source and SS is a process of hydrogen transformation system (H₂TS) which composed of alkaline water electrolysis (AWE) for decomposition water by using the PV power, a tank used for gas storage and a proton exchange membrane (PEM) fuel cell (FC) to transform the H₂ to the electrical energy. The interconnection of the grid with the power generation system (PGS) is ensured through using a DC/AC hysteresis converter and it can synchronize current with the grid voltage among an independent control of active (P) and reactive (Q) power through a possibility of the Q compensation. In the proposed system, three algorithms are applied; two used inside generation and the third is used inside the grid. Perturb and observe (P&O) maximum power point tracking (MPPT) control algorithm always finds optimal power in the PV generator. A simple cascade controls loop of DC-DC boost converter and operate the FC generator to ensure maximum power and to regulate the DC Bus voltage. In addition, adaptive fuzzy logic control (FLC) unit is developed to control the DC/AC inverter, with adopting an off-line optimization based on genetic algorithms (GAs) applauded for tune different issues as scaling factors of the FLC and PIDs gains of the PV and the H₂TS control loops. Simulated results prove a big success of the proposed controls of the grid connected the hybrid PV-H₂TS with good performance.     

A novel method to investigate voltage stability of IEEE-14 bus wind integrated system using PSAT

The maximum demand of power utilization is increasing exponentially from base load to peak load in day to day life. This power demand may be either industrial usage or household applications. To meet this high maximum power demand by the consumer, one of the options is the integration of renewable energy resources with conventional power generation methods. In the present scenario, wind energy system is one of the methods to generate power in connection with the conventional power systems. When the load on the conventional grid system increases, various bus voltages of the system tend to decrease, causing serious voltage drop or voltage instability within the system. In view of this, identification of weak buses within the system has become necessary. This paper presents the line indices method to identify these weak buses, so that some corrective action may be taken to compensate for this drop in voltage. An attempt has been made to compensate these drops in voltages by integration of renewable energy systems. The wind energy system at one of the bus in the test system is integrated and the performance of the system is verified by calculating the power flow (PF) using the power system analysis tool box (PSAT) and line indices of the integrated test system. The PF and load flow results are used to calculate line indices for the IEEE-14 bus test system which is simulated on PSAT.     

Energy storage for enhancing transmission capacities and trans-regional reserves of a UHV AC/DC power grid

探索应用储能为弱受端电网提供故障后大功率支撑以提升特高压交直流输电线稳态输送能力,同时兼作送端电网调峰的跨区备用源以增加新能源发电空间,以有效促进新能源跨区外送降低弃风弃光率。基于特高压交直流馈入受端电网的功率缺额与频率变化间的对应关系,提出在电网频率最低点满足要求的前提下,电网受电能力提升程度与储能容量配置间的数学模型;依据送端电网典型日各时段负荷特性建立可释放的新能源发电空间与所需储能备用调峰容量间的数学模型。结合考虑事故功率支撑与跨区调峰备用的容量需求特性及优先级别,探索两种功能联合应用下的容量需求方案和技术经济可行性。以交直流馈入的弱受端河南电网及新能源富集的送端新疆电网为例,验证了该新能源消外送纳能力提升方案的有效性。     

Fuzzy neural control of a hybrid fuel cell/battery distributed power generation system

An innovative control strategy is proposed of hybrid distributed generation (HDG) systems, including solid oxide fuel cell (SOFC) as the main energy source and battery energy storage as the auxiliary power source. The overall configuration of the HDG system is given, and dynamic models for the SOFC power plant, battery bank and its power electronic interfacing are briefly described, and controller design methodologies for the power conditioning units and fuel cell to control the power flow from the hybrid power plant to the utility grid are presented. To distribute the power between power sources, the fuzzy switching controller has been developed. Then, a Lyapunov based-neuro fuzzy algorithm is presented for designing the controllers of fuel cell power plant, DC/DC and DC/AC converters; to regulate the input fuel flow and meet a desirable output power demand. Simulation results are given to show the overall system performance including load-following and power management of the system.     

基于水电站大坝的太阳能融合型并网发电系统研究与应用

针对双可再生能源融合发电模式的诸多技术难题,提出了一种在水电站大坝上建设太阳能电站并进行融合发电的创新模式,重点突破了水电与太阳能发电共享型控制技术、光伏逆变谐波抑制技术、无功补偿和共享型直流技术等技术难题。水电和太阳能发电共享型控制技术实现了水电现地控制单元、太阳能现地控制单元、共享型公用现地控制单元的分布式构架;实现了光伏对水电的逆变谐波抑制和无功补偿装置的研发;实现了太阳直流技术补偿水电站直流系统。应用实践表明,太阳能与水能融合发电模式可节约投资、增加无功补偿效益、减少国土资源的占用,是双可再生能源融合发电的创新性应用,具有很好的推广价值。     

An utility interactive power electronics interface foralternate/renewable energy systems

The foreseeable shortages in conventional sources of electric power has increased the emphasis on the research and development of alternate sources of energy. In order to make a noteworthy impact, the alternate sources of energy need to be utility interactive by means of a power electronic interface (a DC to AC converter). The inherent assumption in the control of DC to AC converters is, that the DC voltage available at the input of the converter is constant. However, when the input is an unregulated DC source such as a battery, fuel cell, photovoltaic cells or any other form of alternate source, maintenance of the constant DC voltage at the input of the converter is often impossible. A modified inverter switching technique is proposed for the interface with the utility grid such that the AC output of the inverter becomes immune to fluctuations in the unregulated input DC obtained from alternate energy sources     

A topological reconfiguration procedure for maximising local consumption of renewable energy in (Italian) active distribution networks

Distribution networks (DNs) are facing great changes, due to the strong increase in distributed generation (DG), often driven by renewable energy sources. Designed to deliver electrical power from the transmission system to the final consumers, they are now becoming active and may inject power into the transmission network. In case of large DN, a portion of the system can be absorbing power from the transmission grid, while another portion injects power into it. In order to satisfy the power balance as much as possible at the local level, the distribution system operators are interested in the minimisation of the power exchange with the transmission network, maximising the local consumption of DG energy. This paper presents a topological reconfiguration procedure, based on the branch exchange technique, for the maximisation of the local consumption of renewable energy. A case study is presented, based on a real DN located in northern Italy.     

The ‘low power’ revolution: Rural off-grid consumer technologies and portable micropower systems in non-industrialised regions

This review analyses the growth in small ‘low power’ renewable energy and consumer product technologies and their potential utility in rural and remote economic development. The historical legacy of increasingly industrial-scale and expensive centralised high voltage alternating current (AC) systems contrasts starkly against the dynamic plethora of energy efficient portable low power direct current (DC) devices and consumer goods that underpin a modern economy. Advantages of portable DC devices are their inherent utility as a deferrable load and imbedded storage, enabling the appliance to become the balance of system (BOS) component and the power management system when coupled to portable renewable energy system or a microgrid. These developments present the opportunity to revise broad assumptions of appropriate energy system investment models for non-industrialised nations without an expensive historical centralised high voltage AC industrialisation legacy. It also presents the opportunity to revisit appropriate rural clean energy stand-alone or microgrid system designs and configurations, and engage the information and communication technology (ICT) sector as a major new investor in energy services and infrastructure.     

交直流线路并行架设时的电磁环境横向分布监测

随着电网的不断建设,交直流输电线路同走廊并行架设已在多处出现。目前,交直流混合电磁环境监测多以单点离散测量为主,无法实现横向分布的连续实时测量。通过建立工频电场、无线电干扰、合成电场等测量设备沿同一路径的分布式实时数据采集系统,实现交直流并行线路电磁环境移动式横向分布测量及数据的动态管理,并以典型合成电场数据为例,研究了垂直于线路走廊155m的横向断面合成电场分布趋势。结果表明,实测数据与仿真计算结果趋势较吻合,为交直流并行线路合成电场研究提供了参考。     

Passivity control via Power Shaping of a wind turbine in a dispersed network

The connection of renewable energy conversion systems in distribution networks must comply with codes for assuring power quality as well as the grid assistance demands. The new operating requirements cannot always be achieved from the control strategies that have been employed for years in conventional distribution systems. In this context, this paper addresses the problem of controlling a wind turbine from passivity control concepts. In particular a control strategy based on a new approach to the passivity theory, known as Power Shaping, is proposed. This approach allows to consider pervasive dissipation. The proposed strategy is evaluated in the context of extreme operating conditions showing capability to ride through grid failures. In this way, the simulation results encourage the application of concepts of Power Shaping in more complex systems of distributed generation.     

Survey on microgrids: Unplanned islanding and related inverter control techniques

Nowadays, the importance of electrical generation based on renewable energies is increasing, due to its low emissions of greenhouse gases. At the same time, Distributed Generation and Microgrids (MG) are becoming an important research line because of their peculiar characteristics. MGs are composed of small power sources which can be renewable, placed near customer sites. Moreover, they have the inherent property of islanding: the disconnection of either the MG from the main grid or a portion of a MG from the rest of the MG. There are two kinds of islanding: intentional or planned (for maintenance purposes), and unintentional or unplanned. The latter is mainly due to disturbances and it is used to avoid damages in sources and loads. It is the most critical case because it must be detected as soon as possible to activate all the control systems which allow continuing the energy production and distribution despite the disconnection. In islanding, it is crucial to ensure the power and the electrical signal quality. In grid-connected mode, the inverters use the electrical signal of the main grid as reference. Once in islanding, the main grid reference is lost and new control techniques for the inverters are needed in order to obtain the correct values of voltage magnitude and frequency in the MG.The main objective of this paper is to make a survey on MGs focussed on two important features: unplanned islanding and control of inverters in that scenario. The idea is to present the basic architectures and regulation techniques of MGs and to study the islanding behaviour, mainly the different detection techniques and the inverters’ control once islanded.     

基于超级电容储能的风电并网功率调节控制系统

风能是一种随机变化的能源,风速变化会导致风电机组输出功率的波动,对电网的电能质量产生影响,使用储能装置可以改善风电质量。通过在风电场并网的交流侧母线上并联超级电容储能单元,能实现对风电场功率的调节,减小功率的波动。文章设计了风电场并网及储能系统各部分的控制策略,在Matlab/Simulink仿真环境下创建了系统的仿真模型,验证了控制策略的正确性。仿真系统最终实现了电机侧变流器最大风能跟踪、电网侧变流器单位功率因数并网和超级电容储能单元对风电场并网功率的调节。     

一种基于三端口能量路由的单级式光储并网系统及其高压穿越技术

该文提出一种具有高压穿越能力的基于三端口能量路由的单级式光储并网系统（PV-ESS）。光伏最大功率跟踪始终由三相变换器控制完成。多端口能量路由器可根据不同运行工况使储能灵活接入,平抑光伏输出,使得系统具有更高的效率。在电网高压故障下,通过储能装置抬升直流母线电压,从而使系统具有高压穿越的能力,可在电网高压状态下不脱网连续运行,直至故障恢复。     

Design and evaluation of PV-wind hybrid system with hydroelectric pumped storage on the National Power System of Egypt

National and international policies encourage increased penetration of solar and wind energy into electrical networks in order to reduce greenhouse gas emission. Solar radiation and wind speed variations complicate the integration of wind and solar generation into power systems and delay the transition of these sources from centralized to distributed energy sources. The increased penetration of nontraditional energy sources into the electric grid stimulates the demand for large capacities in the field of energy storage. A mathematical model, which describes the operation of a proposed hybrid system, including solar PV, wind energy, and a pumped storage hydroelectric power plant is developed in this paper. This hydropower plant utilizes seawater as a lower reservoir, and only a tank has to be built in order to reduce the installation cost of the storing system. The pumped storage power plant used for compensation of the variation of the output energy from the PV and wind power plants by discharging water from the upper reservoir, which is previously pumped in the case of surplus energy from PV and wind turbine power plants. The impact of the proposed system on the grid utility is investigated in accordance with the values of energy exchange (deficits and surpluses of energy) between the considered hybrid system and the grid. The optimum design is determined by the pump and turbine capacities, upper reservoir volume, and the volume of water left in the tank for emergencies. Different scenarios of the optimum operations are presented for analysis. The results obtained from the examined scenarios indicate the ability of such a hybrid energy system to reduce the exchange of energy with the grid. This paper indicates the technical feasibility of seawater pumped-storage hydropower plant for increasing the Egyptian national grid’s ability to accept high integration of renewable energy sources.     

可再生能源交流孤网转并网运行中的电压控制策略

柔性直流远距离输送有仅通过直流送出模式和交直流混联送出模式。两种送出模式下,系统的运行点存在较大差异,直接切换会对电网产生较大冲击。文章首先分析了两种送出模式下系统的调压控制特点,指出并网点电压幅值偏差是切换过程的关键点,设计了以可再生能源集群并网点电压偏差最小为主目标,换流站综合无功裕度最大为次目标的柔性切换策略。最后,基于某柔直电网可再生能源送端规划系统进行仿真,验证了所提策略的有效性。     

基于水库大坝的水能与太阳能融合型并网发电系统研究与应用

针对中国大中型面南的水库电站大坝,向光性比较好,具备安装太阳能光伏发电系统的条件,并使得2种可再生能源融合并网发电模式具有一定的创新性.水库电站的发电系统是已建成的,增加太阳能光伏发电系统并建设融合型并网发电系统,不仅体现了投资成本低发电效益高等特点,同时具有节约国土资源、保护大坝和节能减排等社会效益.在设计和实践过程...