Dynamic and Power Generation Features of A Wind-Wave Hybrid System Consisting of A Spar-Type Wind Turbine and An Annular Wave Energy Converter in Irregular Waves

Combining wave energy converters(WECs)with floating offshore wind turbines proves a potential strategy to achieve better use of marine renewable energy.The full coupling investigation on the dynamic and power generation features of the hybrid systems under operational sea states is necessary but limited by numerical simulation tools.Here an aero-hydro-servo-elastic coupling numerical tool is developed and applied to investigate the motion,mooring tension,and energy conversion performance of a hybrid system consisting of a spar-type floating wind turbine and an annular wave energy converter.Results show that the addition of the WEC has no significant negative effect on the dynamic performance of the platform and even enhances the rotational stability of the platform.For surge and pitch motion,the peak of the spectra is originated from the dominating wave component,whereas for the heave motion,the peak of the spectrum is the superposed effect of the dominating wave component and the resonance of the system.The addition of the annular WEC can slightly improve the wind power by making the rotor to be in a better position to face the incoming wind and provide considerable wave energy production,which can compensate for the downtime of the offshore wind.

Short-term power generation scheduling rules for cascade hydropower stations based on hybrid algorithm

Power generation dispatching is a large complex system problem with multi-dimensional and nonlinear characteristics. A mathematical model was established based on the principle of reservoir operation. A large quantity of optimal scheduling processes were obtained by calculating the daily runoff process within three typical years, and a large number of simulated daily runoff processes were obtained using the progressive optimality algorithm （POA） in combination with the genetic algorithm （GA）. After analyzing the optimal scheduling processes, the corresponding scheduling rules were determined, and the practical formulas were obtained. These rules can make full use of the rolling runoff forecast and carry out the rolling scheduling. Compared with the optimized results, the maximum relative difference of the annual power generation obtained by the scheduling rules is no more than 1%. The effectiveness and practical applicability of the scheduling rules are demonstrated by a case study. This study provides a new perspective for formulating the rules of power generation dispatching.

Allocation of Hybrid Distributed Generations and Energy Management in Radial Electrical Systems

This paper presents a method for optimal sizing of a Micro grid connected to a hybrid source to ensure the continuity and quality of energy in a locality with a stochastically changing population. The hybrid system is composed of a solar photovoltaic system, a wind turbine, and an energy storage system. The reliability of the system is evaluated based on the voltage level regulation on IEEE 33-bus and IEEE 69-bus standards. Power factor correction is performed, despite some reliability and robustness constraints. This work focuses on energy management in a hybrid system considering climatic disturbances on the one hand, and on the other hand, this work evaluates the energy quality and the cost of energy. A combination of genetic algorithms of particle swarm optimization (CGAPSO) shows high convergence speed, which illustrates the robustness of the proposed system. The study of this system shows its feasibility and compliance with standards. The results obtained show a significant reduction in the total cost of production of this proposed system.

Figure of Merit Analysis of a Hybrid Solar-geothermal Power Plant

Figure of merit analysis is a general methodology used to evaluate whether a hybrid power plant could produce more power than two stand-alone power plants. In this paper, the assessment methodology using figure of merit analysis was re-examined for a hybrid solar-geothermal power plant. A new definition of the figure of merit was introduced specifically for a solar boosted geothermal plant to include both the technical and economic factors. The new definition was then applied in a case study of a hypothetical demonstration hybrid solar-geothermal power plant in Australia. The power plant was considered to have a typical net power output of 2.2 MW with a solar energy fraction of 27%. The analysis was performed to compare the power output and capital cost of the hybrid plant with the state-of-the-art (SoA) and existing stand-alone solar and geothermal plants. Based on the new definition, the hybrid plant was found to generally outperform the two existing stand-alone plants. Moreover, at an ambient temperature of 5 °C, the hybrid plant was found to outperform the SoA stand-alone plants when the geothermal temperature was greater than 150 °C. For geothermal temperature of 180 °C on the other hand, the hybrid plant outperformed the SoA stand-alone plants at ambient temperatures lower than 33 °C.

Integrated generation-transmission expansion planning for offshore oilfield power systems based on genetic Tabu hybrid algorithm

To address the planning issue of offshore oil-field power systems, an integrated generation-transmission expansion planning model is proposed. The outage cost is considered and the genetic Tabu hybrid algorithm(GTHA)is developed to find the optimal solution. With the proposed integrated model, the planning of generators and transmission lines can be worked out simultaneously,which outweighs the disadvantages of separate planning,for instance, unable to consider the influence of power grid during the planning of generation, or insufficient to plan the transmission system without enough information of generation. The integrated planning model takes into account both the outage cost and the shipping cost, which makes the model more practical for offshore oilfield power systems. The planning problem formulated based on the proposed model is a mixed integer nonlinear programming problem of very high computational complexity, which is difficult to solve by regular mathematical methods. A comprehensive optimization method based on GTHA is also developed to search the best solution efficiently.Finally, a case study on the planning of a 50-bus offshore oilfield power system is conducted, and the obtained results fully demonstrate the effectiveness of the presented model and method.

Call for Papers Special Issue on"Hybrid-augmented Intelligence in Power Systems Operation and Control"

Power systems operation and control is concerned essentilly with the cognition,management,and control(CMC)process for complex power systems.A power system with high a penetration rate of renewable energies,i.e.,the"Next-Generation Power Systems",has featured characteristics of open operational environments,complex system components,diverse operational modes,tightly coupled component behaviours,stringent demand on real-time response performance,high criticality.

Solar aided power generation:A review

Solar Aided Power Generation(SAPG)is the most efficient and economic ways to hybridise solar thermal energy and a fossil fuel fired regenerative Rankine cycle(RRC)power plant for power generation purpose.In such an SAPG plant,the solar thermal energy is used to displace the extraction steam by preheating the feedwater to the boiler.The displaced/saved extraction steam can,therefore,expand further in the steam turbine to generate power.The research and development of the SAPG technology started in the 1990s.This paper is trying to reviews and summarises the progress of research and development of the SAPG plant technology in last almost 30 or so years,including the technical and economic advantages of SAPG over other solar thermal power generation tech-nologies(e.g.solar alone power generation),various modelling techniques used to simulate SAPG perforamnce,impacts of SAPG plant’s configuration,size of solar field and strategies to adjust mass flow rate of extraction steam on the plant perforamnce,exergy analysis of SAPG plant and operation strategies to maximise plant’s economic returns etc.In addition,the directions for future R&D about SAPG technology have been pointed/proposed in this paper.

Towards Implementation of Smart Grid: An Updated Review on Electrical Energy Storage Systems

A smart grid will require, to greater or lesser degrees, advanced tools for planning and operation, broadly accepted communications platforms, smart sensors and controls, and real-time pricing. The smart grid has been described as something of an ecosystem with constantly communication, proactive, and virtually self-aware. The use of smart grid has a lot of economical and environmental advantages;however it has a downside of instability and unpredictability introduced by distributed generation (DG) from renewable energy into the public electric systems. Variable energies such as solar and wind power have a lack of stability and to avoid short-term fluctuations in power supplied to the grid, a local storage subsystem could be used to provide higher quality and stability in the fed energy. Energy storage systems (ESSs) would be a facilitator of smart grid deployment and a “small amount” of storage would have a “great impact” on the future power grid. The smart grid, with its various superior communications and control features, would make it possible to integrate the potential application of widely dispersed battery storage systems as well other ESSs. This work deals with a detailed updated review on available ESSs applications in future smart power grids. It also highlights latest projects carried out on different ESSs throughout all around the world.

Electricity Price of Hybrid Power System and Decision Making of Renewable Energy Investment Capacity

In the existing electricity market,the traditional power suppliers and renewable energy generators coexist in the power supply side. In the power supply side,renewable energy generators generate power by wind and other natural conditions,leading renewable energy output a certain randomness. However,the low marginal generating cost and the reduction of carbon emissions,and thus brings a certain advantage for renewable energy compared to alternative energy. Electricity,as a special commodity,stable and adequate power supply is a necessary guarantee for economic and social development. Power shortage situation is not allowed in the power system,and the extra power needs to be handled for the purpose of safety. In this paper,the hybrid power generated by renewable energy generators and traditional energy generators is used as power supply,and then the electricity market sells hybrid power to electricity consumers,the hybrid power system determines the optimal daytimeprice,nighttime price,and the optimal installed capacity of the renewable energy suppliers. We find that the installed capacity of renewable energy increases first and then decreases with the increase of the price sensitivity coefficient of traditional energy supply. Electricity demand is negatively related to electricity price in the current period,and is positively related to price in the other period. The average price of day and night is only related to the total potential demand of day and night and the total generation probability of renewable energy. The price difference between daytime and nighttime is positively related to potential electricity demand,and negatively related to the sensitivity coefficient of electricity price.

Performance Analysis of Grid Connected and Islanded Modes of AC/DC Microgrid for Residential Home Cluster

This paper presents performance analysis on hybrid AC/DC microgrid networks for residential home cluster. The design of the proposed microgrid includes comprehensive types of Distributed Generators (DGs) as hybrid power sources (wind, Photovoltaic (PV) solar cell, battery, fuel cell). Details about each DG dynamic modeling are presented and discussed. The customers in home cluster can be connected in both of the operating modes: islanded to the microgrid or connected to utility grid. Each DG has appended control system with its modeling that will be discussed to control DG performance. The wind turbine will be controlled by AC control system within three sub-control systems: 1) speed regulator and pitch control, 2) rotor side converter control, and 3) grid side converter control. The AC control structure is based on PLL, current regulator and voltage booster converter with using of photovoltaic Voltage Source Converter (VSC) and inverters to connect to the grid. The DC control system is mainly based on Maximum Power Point Tracking (MPPT) controller and boost converter connected to the PV array block and in order to control the system. The case study is used to analyze the performance of the proposed microgrid. The buses voltages, active power and reactive power responses are presented in both of grid-connected and islanded modes. In addition, the power factor, Total Harmonic Distortion (THD) and modulation index are calculated.

Control of hybrid AC/DC microgrid under islanding operational conditions

This paper presents control methods for hybrid AC/DC microgrid under islanding operation condition.The control schemes for AC sub-microgrid and DC sub-microgrid are investigated according to the power sharing requirement and operational reliability.In addition,the key control schemes of interlinking converter with DC-link capacitor or energy storage,which will devote to the proper power sharing between AC and DC sub-microgrids to maintain AC and DC side voltage stable,is reviewed.Combining the specific control methods developed for AC and DC sub-microgrids with interlinking converter,the whole hybrid AC/DC microgrid can manage the power flow transferred between sub-microgrids for improving on the operational quality and efficiency.

Combining solar power with coal-fired power plants,or cofiring natural gas

Coal-fired power operators continue to look for ways to increase the efficiency and extend the working lives of their plants by improving operational flexibility and reducing environmental impact.Two possible options are explored here:combining solar energy with coal-fired power generation,and cofiring natural gas in coal-fired plants.Both techniques show potential.Depending on the individual circumstances,both can increase the flexibility of a power plant whilst reducing its emissions.In some cases,plant costs could also be reduced.Clearly,any solar-based system is limited geographically to locations that receive consistently high levels of solar radiation.Similarly,although many coal-fired plants already burn limited amounts of gas alongside their coal feed,for cofiring at a significant level,a reliable,affordable supply of natural gas is needed.This is not the case everywhere.But for each technology,there are niche and mainstream locations where the criteria can be met.The need for good solar radiation means that the uptake of coal-solar hybrids will be limited.Cofiring natural gas has wider potential:currently,the largest near-term market appears to be for application to existing coal-fired plants in the USA.However,where gas is available and affordable,potential markets also exist in some other countries.