Feasibility of Wind Power Generation for the Reduction of Power Costs in Residential Buildings

The installation of wind power generators on buildings located in areas with regular winds may be a suitable investment in a renewable power source. Brazil has a high eolic potential, where the annual mean wind speed may reach over eight meters per second. This case study is aimed to assess the economic feasibility of the installation of small wind power plants in urban areas. This work evaluates a project for the installation of a vertical axis wind turbine in three buildings （15-, 22-, and 26-story） including the following stages： （1） installation of a real-time power meter in the 15-store unit; （2） demand analysis of the 26-store building＇s power consumption; （3） winds survey along the coast of the State of Ceara; （4） analysis of the wind turbines available in the market; （5） simulation aimed to choose the system. Vertical wind power generators offer better conditions of use in urban areas. The turnover time was established to be between four and six years in the three studied units. The installation of a wind power generator on buildings in regions with an adequate eolic regimen reaches a financial return of the investment before the end of the equipment＇s lifespan.     

Design and Evaluation Tool for Operations and Maintenance Logistics Concepts for Offshore Wind Power Plants

In this article, the authors give an overview of different logistics concepts for operation and maintenance of OWPP （offshore wind power plants）. These can be generally classified into onshore based and offshore based concepts. The operation of OWPPs can still be improved as research has shown that the availability of OWPPs is low compared to onshore wind power plants. There are a few tools to calculate operating costs and to evaluate the different concepts. However, most tools have a weak focus on logistics although logistics account for a big share of the costs. The tool the authors are introducing in this article focuses on the logistics processes. It is first explained and then tested with an OWPP scenarin     

Simulation Analysis for Massive Deployment of Variable Renewables Employing an Optimal Power Generation Mix Model

This paper develops a high time-resolution optimal power generation mix model in its time resolution of 10 minutes on 365 days by linear programming technique. The model allows us to analyse the massive deployment of photovoltaic system and wind power generation in power system explicitly considering those short-term output variation. PV （photovoltaic） and wind output are estimated, employing meteorological database. Simulation results reveal that variable fluctuation derived from a high penetration level of those renewables is controlled by quick load following operation of natural gas combined cycle power plant, pumped-storage hydro power, stationary NAS （sodium and sulfur） battery and the output suppression control of PV and wind. It additionally turns out that the operational configuration of those technologies for the renewable variability differs significantly depending on those renewable output variations in each season and solving the seasonal electricity imbalance as well as the daily imbalance is important if variable renewables are massively deployed.     

Germany＇s Energy Transition and the European Electricity Market： Mutually Beneficial？

Germany＇s energy system is in transition towards less nuclear, lower carbon emissions and more renewables. Notwithstanding widespread neglect of its European dimension, this Energiewende will further exacerbate current network fluctuations due to the significant increase in wind and solar power. Key data from Denmark show that this transition will soon bring the German national power system to its limits for absorbing the resulting intermittency, and increase the need for more cross-border power transfers. Yet network analysis of import/export data shows that Germany＇s position in the European power system is contrary to the Danish case. The need for a European solution for Germany＇s energy transition will therefore soon become evident. In order to establish the necessary infrastructure, the Energiewende needs hence to be guided by an economic approach designed to prevent further fractures in the Internal Electricity Market. Constructive negotiations with neighbouring countries on market designs and price signals will be important preconditions. The article emphasizes the still neglected European paradox of Germany＇s energy transition and presents working examples and possible solutions to uphold electricity supply in Europe＇s power house.     

Stability Study of a Mixed Islanded Power Network

This paper presents the modelling, simulation and analysis of the dynamic behaviour of a mixed power network of 2.78 GW including hydro, thermal and wind power plants. The modelling of each power plant is described. The set of parameters of the turbine speed governor of the hydroelectric power plant is determined with a specific identification procedure to achieve stable operation for different cases such as interconnected, isolated or islanded operation. The analysis of the stability of the entire mixed islanded power plant is investigated through time domain simulations for different sets of controllers parameters and for different disturbances （load rejection and turbulent wind speed profile）.     

Merit Figures for the Optical Design of CSP Plants

This work proposes some optical merit figures useful for solar concentration in the phase of optical design. The examined systems are CSP （concentrated solar power） plants with heliostats fields. In order to characterize them, it is suggested to use some optical merit figures, applicable to every CSP plant and synthetize its optical performance. The proposed merit figures have the aim of assessing mirrors field efficiency and receiver optical efficiency. In particular, they are identified using a new definition of the input flux on the mirrors field. The practical advantage of using the optical merit figures is illustrated by means of a simulation.     

Design of Capacitor Bank in Parallel to Photovoltaic Power Plant

The purpose of the paper is to develop a solution for application of PV （photovoltaic） generators in MV （medium voltage） distribution system without unacceptable voltage changes due to drops of PV power output. The proposed solution includes operation of PV with predetermined leading power factor and addition of a capacitor bank in parallel to PV plant in order to compensate the reactive power absorbed by the PV inverters. The analytical expression of required power factor angle is derived. Adding a capacitor bank in parallel to PV power plant may pose a problem because of space limitations. The dimensions and cost of small MV capacitor banks depend significantly on the capacitor bank protection against internal faults. Application of the developed negative-sequence current difference method for the unbalance protection of the capacitor banks enables to achieve a compact and cost-reduced design of the banks connected in parallel to PV power plants. A real-world example of operation of the PV plant in parallel to the capacitor bank with the novel protection scheme is described.     

Advanced Reactive Power Control at Individual Residences to Smooth Energy Loss Fluctuation for a Clustered Grid-Interconnected PV System

Reactive power control can control voltage within the proper range from the power network side or from the distribution generation （PV （photovoltaic）） side. Reactive power control from the power network side is simpler because little controlled object apparatus, such as STATCOM, is required. However, it is difficult to optimize the individual voltages of residential consumers because few data have been obtained by the power network side as compared with the power generation side. Energy loss at each residence with PV is different due to the difference in the grid-interconnection condition, such as distribution line impedance when the same operating voltage is set at all residences. Therefore, in this paper, the authors propose an advanced reactive power control method for residential PV systems in order to optimally control the voltage at individual residences so as to minimize energy loss fluctuation. The effectiveness of the proposed reactive power control is demonstrated by numerical simulation.     

Dynamic Voltage Restorer with Active Disturbance Rejection Control

Power quality is one of the major concerns among consumers and electric utility companies. CUPS （custom power systems） devices are used to improve the quality of power and enhance the reliability of the power supply in the distribution networks. The DVR （dynamic voltage restorer） is an important CUPS device used to mitigate voltage sag/swell and imbalances. Various control techniques have been implemented to control the DVR, among which the PID （proportional-integral-derivative） controller is dominant because of its model independent property and its error driven technique. In this paper, a new controller based on the ADRC （active disturbance rejection control） concept is developed, and its performance is compared to that of the PID controller. The model of the DVR and its ADRC and PID controllers were developed under the MATLAB （matrix laboratory）/Simulink environment. The simulation results demonstrated the effectiveness of the ADRC over the PID controller.     

Examination for Experimental Verification of Improvement of Power Quality in Distribution System by PCS

In the future, the power quality will decrease by the introduction of a lot of renewable energy sources. The topic of this research is a new method of operation of PCS （power conditioning systems） in the future distribution system. The purpose of this research is development of PCS with a function of improvement of the distribution system. Therefore, the authors propose a method of the power quality improvement of the distribution system by PCS. In addition, the authors construct the control logic to use in PCS The control logic suggests adding harmonic restraint function to conventional control. These were verified by simulation and an experiment. As the results, we confirmed that basic operation of PCS being carried out, harmonics were restrained, and power quality had improved.     

Experimental Study of Condensation Heat Transfer on Tube Bundles in Large Power Plant Condensers

In order to clarify the effect of condensate inundation on steam condensation in a large tube bundle, condensation heat transfer and the condensate flow pattern in the tube bundle have been experimentally investigated. Test tube bundle consists of 36 cooling tubes, 12 condensate supply tubes and 24 un-cooled dummy tubes. Cooling test tubes are made of copper and have an outer diameter of 19.1 mm and condensing length of 150 mm, Steam flows horizontally through the test tube bundle at gap velocities 15-27 m/s at pressures of 8.8 kPa. In this study, experimental data about condensate flow pattern and condensation heat transfer in a tube bundle were collected for the optimization of tube arrangement in large power plant condensers.     

Numerical Flow Simulation in Turbine Mode of Counter-Rotating Type Pumping Unit to Cooperate with Wind Turbine

This serial research has proposed the hybrid power system combined the wind power unit with the counter-rotating type pump-turbine unit, to provide the constant output for the grid system, even at the suddenly fluctuating/turbulent wind circumstance. In this paper, the tandem impellers prepared for the counter-rotating type pumping unit were operated at the turbine mode, and the performances and the flow conditions were investigated numerically with accompanying the experimental results. Even though providing the pumping unit for the turbine mode, the maximum hydraulic efficiency is close to one of the counter-rotating type hydroelectric unit designed exclusively for the turbine mode. Besides, the runners/impellers of the unit work evidently so as to coincide the angular momentum change through the front runners/impellers with that through the rear runners/impellers, namely to take the axial flow at not only the inlet but also the outlet, without the guide vanes. From these results, it can be concluded that this type unit is effective to work at not only the pumping but also the turbine modes.     

Counter-Rotating Type Pump-Turbine Unit Stabilizing Momentarily Fluctuating Power from Renewable Energy Resources

It is difficult for renewable energy resources to provide constant power with excellent quality for the grid system. This serial research proposes a power stabilization system with a pumped storage to guarantee power quality and capacity, while the outputs from the energy resources are at unstable and/or fluctuating conditions. The power stabilization system with a counter-rotating type pump-turbine unit was prepared and operated at the pumping and the turbine modes. The unit composed of the tandem impellers/runners connected to the inner and the outer armatures of the unique motor/generator. The experiments have verified that this type pump-turbine unit is reasonably effective to stabilize momentarily/instantaneously the fluctuating power from the renewable energy resources.     

Assessing Micro-generation＇s and Non-linear Loads＇ Impact in the Power Quality of Low Voltage Distribution Networks

Distribution networks face an increasing penetration of solar PV （photovoltaic） and small WTG （wind turbine generator） as well as other forms of micro-generation. To this scenario, one must add the dissemination of non-linear loads such as EV （electric vehicles）. There is something in common between those loads and sources： the extensive use of power electronic converters with commutated switches. These devices may be a source of medium-to-high frequency harmonic distortion and their impact on the local distribution grid must be carefully assessed in order to evaluate their negative impacts on the network, on the existing conventional loads and also on other active devices. In this paper, methodologies to characterize effects such as： harmonics, network unbalances, damaging power line resonance conditions, and over/under voltages are described and applied to a real local grid configuration.     

Electromagnetic Zero-Sequence Harmonics Blocker： Modeling and Experimental Analysis

This paper reveals new contributions to the analysis and development of devices for harmonic distortion mitigation. Considering the sequential distribution of harmonic currents, zero-sequence components could be diminished using electromagnetic devices, particularly the eZSB （electromagnetic zero-sequence blocking）. One important characteristic of this device, which has received particular attention on this research, is its robustness and low cost of construction. Theoretical and experimental results related to the behavior of the electromagnetic blocking devices are presented. The results illustrate the consistence of the theoretical aspects related with the model in the frequency domain, as well as the performance of the blocking devices, reducing zero-sequence harmonic currents, mainly by the conjunct action of the eZSF （electromagnetic zero-sequence harmonic filter）, working as a impedance coupler. In this context, aiming the evaluation of the reliability of the results obtained through mathematical modeling, experimental tests have been carried out using a low-power prototype, highlighting particular aspects related to its function as a zero-sequence harmonic blocker.     

Development and Static Mode Characterization of a New Low-Loss AC Switch Based on Super-gain BJT

This paper deals with an innovative low-loss AC switch, named as TBBS （transistor based bidirectional switch）, based on the association of super-gain BJTs developed by the GREMAN laboratory. The main characterization results of the super-gain BJT are reminded to identify the key parameters that are essential to build the TBBS. A complete characterization database in static mode of this new AC switch is discussed. In particular, its forward and reverse-biased features have been measured to see the evolution of the DC current gain as a function of the current density. The TBBS makes sense when using the super-gain BJT （bipolar junction transistor） in reverse mode. It means that the reverse DC current gain has to be sufficient （at least higher than l compared with the conventional BJT one）. This new AC switch is bidirectional in current and voltage, totally controllable （turn-on and turn-off） and the most attractive solution in terms of on-state power losses. Further, its manufacturing process is as easier as existing device such as triac.     

Analysis of Short Circuit Faults in a System Fed by Wind Turbine

Short circuit and ground failures that are quite common in power transmission lines are investigated. These failures are designed considering a system that is supplied by this wind system, and analyses are interpreted. In the study, a system is set up and it is fed by the wind turbine. Furthermore, the mathematical model of wind turbine and generator is prepared and the results obtained from the simulation are evaluated. The short circuit and ground fault analyzes were performed separately for each of the three phases. ATP （alternative transient program）-EMTP （electromagnetic transients program） program is used in the analysis and the results obtained were found to be quite compatible.     

A Review of Direct Driven PMSG for Wind Energy Systems

This paper presents a comprehensive overview study of the DDPMSG （direct driven permanent magnet synchronous generator） for wind energy generation system. Wind turbine controls are provided. The PMSG （permanent magnet synchronous generator） is introduced as construction and model. Configurations of different power converters are presented for use with DDPMSG in wind systems at variable speed operation and maximum power capture. Control techniques for the system are discussed for both machine-side and grid-side in details. Grid integration is provided with focus on how to insure power quality of the system and the performance at disturbances.     

Development of a Full Parameterized FE-modeling Tool for Efficient Vibration Investigations on End Windings of Turbo- and Hydro-Generators

End windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage and noise. To avoid this, it is important to predict the natural frequencies and modes of the end windings with finite elements. Due to the complex structure and unknown boundary conditions, the conventionally calculation of stator end windings has been very difficult and time consuming up to now. This paper describes the development of a full parameterized modeling tool, which allows a quick calculation of natural frequencies during the design phase of the generator. To keep the computing time low, it is important to find a way to get exact calculation results without detailed modeling of all pans. Additionally, special attention was paid to the active part, which has been replaced by spring-damper elements, and the determination of their stiffness via experimental modal analysis combined with finite element calculations.     

Prototype Line Crawler for Power Line Inspection

In South Africa, electricity is supplied through thousands-of-kilometers of overhead power cables, which is owned by Eskom the national energy supplier. Currently monitoring of these overhead power cables are done by means of helicopter inspection flights and foot patrols, which are infrequent and expensive. In this paper, the authors present the design of a prototype power line crawler （inspection robot） for the monitoring of these overhead power lines in South Africa. The designed prototype power line crawler is capable of driving on the wire, balancing on the wire and is capable of maneuvering past certain obstacles found on the overhead power cables. The prototype power line crawler is designed to host a monitoring system that monitors the power line as the inspection robot drives on it. Various experimental tests were performed and are presented in this paper, showing the capability of performing these tasks. This prototype inspection robot ensures a platform for future development in this area.