Energy Losses In System Research Articles

Optimum allocation of distributed generation in multi-feeder systems using long term evaluation and assuming voltage-dependent loads

Abstract The analysis of actual distribution systems with penetration of distributed generation requires powerful tools with capabilities that until very recently were not available in distribution software tools; for instance, probabilistic and time mode simulations. This paper presents the work made by the authors to expand some procedures previously implemented for using OpenDSS, a freely available software tool for distribution system studies, when it is driven as a COM DLL from MATLAB using a parallel computing environment. The paper details the application of parallel computing to the allocation of distributed generation for optimum reduction of energy losses in a multi-feeder distribution system when the system is evaluated during a long period (e.g., the target is to minimize energy losses for periods longer than one year) and voltage-dependent load models are used. The long term evaluation is carried out by assuming that the connection of the generation units is sequential, and using a divide and conquer approach to speed up calculations. The main goals are to check the viability of a Monte Carlo method in some studies for which parallel computing can be advantageously applied and propose a procedure for quasi-optimum allocation of photovoltaic generation in a multi-feeder distribution system.

Load Sharing by Decentralized Control in an Islanded Inverter-based Microgrid using Frequency Tracking

Microgrids have been defined as an efficient and practical concept to cover flaws in traditional power system related to system expansion and renewable energy utilization. By increasing demand energy, the need to generate more electric power is raised. However, the distance between generation centers and consumption centers causes more energy loss in power system and power system expansion is considered costly and to some extent infeasible. In addition, nowadays using renewable energies such as wind energy is inevitable, as a result using power electronic mediums is necessary. Microgrids are mostly preferable because of the ability to perform in islanded mode. In order to have stable-islanded Microgrid, electric loads inside the network should be shared on Voltage Source Converters respect to their nominal capacity. Droop control has been known as a method to share loads in decentralized way, although it has shortcomings. In this paper by introducing novel method named Frequency Tracking and applying that on droop control system, electric loads inside an islanded Microgrid are shared on generation units properly with fast and acceptable dynamics and droop control system is modified. Simulation results in PSCAD are confirmation of proposed system to have stable islanded Microgrid.

An Analysis of the Effect of Molten Salt Thermal Storage on Parabolic Trough Concentrated Solar Power Plant Efficiency

In the development of renewable energy sources, there has been a trend toward increasing and stabilising the power output of Concentrated Solar Power Plants (CSPPs) during times of reduced solar resource through the use of Thermal Energy Storage Devices (TESDs). This study investigates whether the use of a molten salt TESD decreases the efficiency of a parabolic trough CSPP due to additional system energy losses despite prolonging the operational time of the CSPP. A theoretical analysis of a simplified CSPP was made to determine if a TESD would impact the efficiency of the CSPP. This was followed up by a survey of currently active parabolic trough CSPPs both with and without molten salt TESDs. The theoretical analysis illustrated that a TESD would have no effect on the efficiency of a CSPP. However, the survey revealed that the use of a TESD improved the efficiency of a CSPP. The results of the study don't support the theoretical analysis or the hypothesis suggesting that a property has been overlooked. This property is most likely to be that generators tend to operate best within a certain temperature range, and in a CSPP the optimum temperature range cannot be maintained. This results in a generator being selected capable of operating for the longest period with the lowest amount of excess solar energy. When a TESD is implemented, the excess solar energy is stored for later use, prolonging the generator's running time and increasing the useable energy. The realisation of the ability of a TESD to increase the efficiency of a CSPP as well as extending its operating time shows a promising area of development in CSPP technology and increasing its application in electricity generation.

Determination of Optimal Location, Sizing and Power Factor of Grid-Connected Solar PV Plant

The increasing number of grid-connected solar PV plants today has brought great benefits to the power system. However, it has also created several technical issues that need to be addressed by planning engineers. Due to this reason, the optimization for interconnection of solar PV plants has attracted their attentions, in order to operate these plants safely and economically. In this paper, three key parameters which are the location, size and operating power factor of the solar PV plant are optimized. The proposed method considers the technical constraints of the network such as voltage limits, together with the intermittency of PV generation and system loads. Two case studies are simulated on a typical 11kV distribution system with 54 buses. Results show a reduction in system energy losses for the optimized values, without violating any power system requirements.

Wheel Torque Distribution of Four-Wheel-Drive Electric Vehicles Based on Multi-Objective Optimization

The wheel driving torque on four-wheel-drive electric vehicles (4WDEVs) can be modulated precisely and continuously, therefore maneuverability and energy-saving control can be carried out at the same time. In this paper, a wheel torque distribution strategy is developed based on multi-objective optimization to improve vehicle maneuverability and reduce energy consumption. In the high-layer of the presented method, sliding mode control is used to calculate the desired yaw moment due to the model inaccuracy and parameter error. In the low-layer, mathematical programming with the penalty function consisting of the yaw moment control offset, the drive system energy loss and the slip ratio constraint is used for wheel torque control allocation. The programming is solved with the combination of off-line and on-line optimization to reduce the calculation cost, and the optimization results are sent to motor controllers as torque commands. Co-simulation based on MATLAB® and Carsim® proves that the developed strategy can both improve the vehicle maneuverability and reduce energy consumption.

Hierarchical Decentralized Network Reconfiguration for Smart Distribution Systems—Part II: Applications to Test Systems

A hierarchical decentralized network reconfiguration approach to minimize power losses for smart distribution systems was presented in Part I. In this paper, the proposed approach is applied to four test distribution systems to examine its performance. A demonstration system consisting of the test system and distributed intelligent agents is built using MATLAB/Simulink to illustrate how the decentralized approach is implemented. Simulation results of the proposed approach are then compared with results of a centralized implementation and the harmony search method. It is shown that the decentralized approach can achieve similar results as other methods with significantly reduced computation time. The impacts of time-varying loads and faults are also studied through dynamic network reconfiguration on the 118-bus test system. Simulation results illustrate that dynamic network reconfiguration with time-ahead planning can determine the optimal configuration for each operating period to significantly reduce system energy losses. The enhanced performance of the hierarchical decentralized approach is clearly established.

Subharmonic Response of Linear Vibroimpact System with Fractional Derivative Damping to a Randomly Disrobed Periodic Excitation

The subharmonic response of single-degree-of-freedom vibroimpact oscillator with fractional derivative damping and one-sided barrier under narrow-band random excitation is investigated. With the help of a special Zhuravlev transformation, the system is reduced to one without impacts, thereby permitting the applications of asymptotic averaging over the period for slowly varying random process. The analytical expression of the response amplitude is obtained in the case without random disorder, while only the approximate analytical expressions for the steady-state moments of the response amplitude are obtained in the case with random disorder. The effects of the fractional order derivative term, damping term, random disorder, and the coefficient of restitution and other system parameters on the system response are discussed. Theoretical analyses and numerical simulations show that fractional derivative makes both the system damping and stiffness coefficients increase, such that it changes the system parameters region at which the response amplitude reaches the maximum. The system energy loss in collision is equivalent to increasing the damping coefficient of the system. System response amplitude will increase when the excitation frequency is close to the resonant frequency and will decay rapidly when the excitation frequency gradually deviates from the resonance frequency.

Control of soil moisture with radio frequency in a photovoltaic-powered drip irrigation system

Solar-powered irrigation systems are becoming increasingly widespread. However, the initial setup costs of these systems are very high. To reduce these costs, both the energy usage and the prevention of losses from irrigation systems are very important. In this study, a drip irrigation control system of 1000 dwarf cherry trees was controlled using soil moisture sensors in order to prevent excessive water consumption and energy losses in a solar-powered irrigation system. The control system comprises units that are energized with solar panels, and the flow of information is implemented via radio frequency. Thus, by removing the cables that create difficulties in the cultivation of gardens, both the easy cultivation of the soil is enabled and cable costs are eliminated. The portability of the units is enabled by using solar energy; thus, units might be mounted wherever the user wishes. It has been indicated that the moisture of the application area varies depending on the data obtained regarding volumetric water content and the defined area in need of irrigation. In this way, there are reductions in the dependence on instantaneous water demand, the amount of water to be pumped, and the energy requirements needed for irrigation. In addition, pump power and the power of the motor that drives the pump are also reduced. According to the obtained measurement values, it was calculated that hourly water demand decreased by 36%. Thus, the numbers of solar panels, electrical machines, batteries, and units of power control that supply all the energy of the system and constitute a large part of the initial setup costs are reduced at the same rate by means of the applied technique. Thanks to the developed site-specific irrigation system, unnecessary energy consumption was avoided. Along with the elimination of excessive and unnecessary irrigation, problems with trees were also eliminated.

Optimal ESS Allocation for Load Management Application

The recent deployment of distributed generation has led to a revolution in the use of distribution systems and the emergence of “smart grid” concepts. Smart grids are intended primarily as a means of facilitating the integration of renewable energy sources and of achieving greater system reliability and efficiency. Energy storage systems (ESSs) offer a number of benefits that can help utilities move toward those goals. One of those benefits is the capacity to improve the utilization of network infrastructure by means of proper load management. This paper proposes a methodology for allocating ESSs in distribution systems in order to defer system upgrades, minimize system losses, and take advantage of the arbitrage benefit. The cost and arbitrage benefit of energy storage installation are optimized with respect to system upgrade and energy losses costs. The primary goal of this research is to determine the optimal size and location of storage units to be installed, in addition to their optimal operation, so that total system costs are minimized, while system benefits are maximized. In this paper, a probabilistic load model is adopted instead of utilizing time-series based models, which provide an optimal solution that is valid only for the time-series pattern that is applied.

Numerical Modeling and Experimental Verification for High-Speed and Heavy-Load Planar Mechanism with Multiple Clearances

Transmission mechanism is one of the most important parts of the Ultra-High Voltage (UHV) circuit breaker. It has specific characteristics such as fast response, high speed, and heavy load in the processes of open and close actions. This paper studies the effects of multiple clearances on the working characteristics of transmission mechanism system, especially the motion of its journal center path during operation. It builds a nonlinear kinetic model of transmission mechanism considering the system energy losses due to the impact and friction between the journal and bearing inside clearance joints. Also, an experimental platform is built to measure the displacement and velocity of the moving contact. The results show that the existence of 15 clearance joints in our mechanism system can cause hysteresis effects on the velocity and acceleration of the moving contact, as well as its acceleration fluctuation. Meanwhile, the increase of friction coefficient will stabilize the dynamic characteristic. In addition, both the experimental and simulation results indicate that the motion of the journal center, which is unevenly distributed along the circle, is characterized by three phases: free flight motion, contact motion, and impact motion.

The Analysis of Exhaust Gas Thermal Energy Recovery Through a TEG Generator in City Traffic Conditions Reproduced on a Dynamic Engine Test Bed

We present an analysis of thermal energy recovery through a proprietary thermoelectric generator (TEG) in an actual vehicle driving cycle reproduced on a dynamic engine test bed. The tests were performed on a 1.3-L 66-kW diesel engine. The TEG was fitted in the vehicle exhaust system. In order to assess the thermal energy losses in the exhaust system, advanced portable emission measurement system research tools were used, such as Semtech DS by Sensors. Aside from the exhaust emissions, the said analyzer measures the exhaust mass flow and exhaust temperature, vehicle driving parameters and reads and records the engine parameters. The difficulty related to the energy recovery measurements under actual traffic conditions, particularly when passenger vehicles and TEGs are used, spurred the authors to develop a proprietary method of transposing the actual driving cycle as a function V = f(t) onto the engine test bed, opn which the driving profile, previously recorded in the city traffic, was reproduced. The length of the cycle was 12.6 km. Along with the motion parameters, the authors reproduced the parameters of the vehicle and its transmission. The adopted methodology enabled high repeatability of the research trials while still ensuring engine dynamic states occurring in the city traffic.

Optimal allocation of stochastically dependent renewable energy based distributed generators in unbalanced distribution networks

This paper proposes an algorithm for modeling stochastically dependent renewable energy based distributed generators for the purpose of proper planning of unbalanced distribution networks. The proposed algorithm integrate the diagonal band Copula and sequential Monte Carlo method in order to accurately consider the multivariate stochastic dependence between wind power, photovoltaic power and the system demand. Secondly, an efficient algorithm based on modification of the traditional Big Bang-Big crunch method is proposed for optimal placement of renewable energy based distributed generators in the presence of dispatchable distributed generation. The proposed optimization algorithm aims to minimize the energy loss in unbalanced distribution systems by determining the optimal locations of non-dispatchable distributed generators and the optimal hourly power schedule of dispatchable distributed generators. The proposed algorithms are implemented in MATLAB environment and tested on the IEEE 37-node feeder. Several case studies are done and the subsequent discussions show the effectiveness of the proposed algorithms.

Capacitor placement of distribution systems using particle swarm optimization approaches

Capacitor placement plays an important role in distribution system planning and operation. In distribution systems of electrical energy, banks of capacitors are widely installed to compensate the reactive power, reduce the energy loss in system, voltage profile improvement, and feeder capacity release. The capacitor placement problem is a combinatorial optimization problem having an objective function composed of power losses and capacitor installation costs subject to bus voltage constraints. Recently, many approaches have been proposed to solve the capacitor placement problem as a mixed integer programming problem. This paper presents a new capacitor placement method which employs particle swarm optimization (PSO) approaches with operators based on Gaussian and Cauchy probability distribution functions and also in chaotic sequences for a given load pattern of distribution systems. The proposed approaches are demonstrated by two examples of application. Simulation results show that the proposed method can achieve an optimal solution as the exhaustive search can but with much less computational time.

Studying the development of asynchronous rolling of the rotor over the stator with the turbine unit protection systems having different response times

The possibility to stabilize the developing asynchronous rolling of the rotor over the stator under the conditions of power unit protections coming in action with different response times is considered. Asynchronous rolling of the rotor over the stator may develop when the rotating rotor comes in contact with the stator at high amplitudes of vibration caused by an abrupt loss of rotor balancing, by forced or self-excited vibration of the rotor, and by other factors. The danger of asynchronous rolling is connected with almost instantaneous development of self-excited vibration of the rotor when it comes in contact with the stator and with the rotor vibration amplitudes and forces of interaction between the rotor and stator dangerous for the turbine unit integrity. It is assumed that the turbine unit protection systems come in action after the arrival of signal of exceeding the permissible vibration level and produce commands to disconnect the generator from the grid, and to stop the supply of working fluid into the flow path, due to which an accelerating torque ceases to act on the turbine unit shaft. The protection system response speed is determined by a certain time t = ABtime that is taken for its components to come in action from the commencement of the event (application of the signal) to closure of the stop valves. The time curves of the main rolling parameters as functions of the ABtime value are presented. It is shown that the response time of existing protection systems is not sufficient for efficiently damping the rolling phenomenon, although the use of an electrical protection system (with the response time equal to 0.40–0.45 s) may have a positive effect on stabilizing the vibration amplitudes to a certain extent during the rolling and on smoothing its dangerous consequences. The consequences of rotor rolling over the stator can be efficiently mitigated by increasing the energy losses in the rotor-stator system (especially in the stator) and by fulfilling the recommendations of the machinery unit catastrophe prevention system.

Design and Control of a Multi-Functional Energy Recovery Power Accumulator Battery Pack Testing System for Electric Vehicles

In this paper, aiming at the energy loss and harmonic problems in the conventional power accumulator battery pack testing system (PABPTS), an improved multi-functional energy recovery PABPTS (ERPABPTS) for electric vehicles (EVs) was proposed. The improved system has the functions of harmonic detection, suppression, reactive compensation and energy recovery. The ERPABPTS, which contains a bi-directional buck-boost direct current (DC)-DC converter and a bi-directional alternating current (AC)-DC converter with an inductor-capacitor-inductor (LCL) type filter interfacing to the AC-grid, is proposed. System configuration and operation principle of the combined system are discussed first, then, the reactive compensation and harmonic suppression controller under balanced grid-voltage condition are presented. Design of a fourth order band-pass Butterworth filter for current harmonic detection is put forward, and the reactive compensator design procedure considering the non-linear load is also illustrated. The proposed scheme is implemented in a 175-kW prototype in the laboratory. Simulation and experimental results show that the combined configuration can effectively realize energy recovery for high accuracy current test requirement, meanwhile, can effectively achieve reactive compensation and current harmonic suppression.

Energy Loss in Pulse Detonation Engine due to Fuel Viscosity

Fluid viscosity is a significant factor resulting in the energy loss in most fluid dynamical systems. To analyze the energy loss in the pulse detonation engine (PDE) due to the viscosity of the fuel, the energy loss in the Burgers model excited by periodic impulses is investigated based on the generalized multisymplectic method in this paper. Firstly, the single detonation energy is simplified as an impulse; thus the complex detonation process is simplified. And then, the symmetry of the Burgers model excited by periodic impulses is studied in the generalized multisymplectic framework and the energy loss expression is obtained. Finally, the energy loss in the Burgers model is investigated numerically. The results in this paper can be used to explain the difference between the theoretical performance and the experimental performance of the PDE partly. In addition, the analytical approach of this paper can be extended to the analysis of the energy loss in other fluid dynamic systems due to the fluid viscosity.

Impact of physical properties of mixture of diesel and biodiesel fuels on hydrodynamic characteristics of fuel injection system

One of the alternative fuels, originating from renewable sources, is biodiesel fuel, which is introduced in diesel engines without major construction modifications on the engine. Biodiesel fuel, by its physical and chemical properties, is different from diesel fuel. Therefore, it is expected that by the application of a biodiesel fuel, the characteristic parameters of the injection system will change. These parameters have a direct impact on the process of fuel dispersion into the engine cylinder, and mixing with the air, which results in an impact on the quality of the combustion process. Method of preparation of the air-fuel mixture and the quality of the combustion process directly affect the efficiency of the engine and the level of pollutant emissions in the exhaust gas, which today is the most important criterion for assessing the quality of the engine. The paper presents a detailed analysis of the influence of physical properties of a mixture of diesel and biodiesel fuels on the output characteristics of the fuel injection system. The following parameters are shown: injection pressure, injection rate, the beginning and duration of injection, transformation of potential into kinetic energy of fuel and increase of energy losses in fuel injection system of various mixtures of diesel and biodiesel fuels. For the analysis of the results a self-developed computer program was used to simulate the injection process in the system. Computational results are verified using the experiment, for a few mixtures of diesel and biodiesel fuels. This paper presents the verification results for diesel fuel and biodiesel fuel in particular.

Automotive Reclaiming Energy Vibration Reduction System Based on Electric Control Rectifying Valve

With the automotive popularization, energy dilemma and environmental problems are further severe. Now the mechanic vibration energy recovery devices which have been invented could not break the bottleneck of low energy recovery efficiency and bad high frequency response. This system is based on hydro-electric reclaiming energy vibration damper electric control rectifying valve with independent intellectual property rights, and is composed with electrical and hydraulic multi-system, converting the automobile suspension vibration energy to electric energy to recycle. Compared with the same kind products, this system avoids their shortcomings and has great advantages. Through automatic and accurate rectification control on liquid flow, the system is able to improve system high-frequency response characteristics, reduce system energy loss, and enhance the system working reliability. This paper will present Automotive Reclaiming Energy Vibration Reduction System Based on Electric Control Rectifying Valve in 7 parts.

Comprehensive Operational Planning Framework for Self-Healing Control Actions in Smart Distribution Grids

Self-healing is a major driving force in the smart grid vision. This paper proposes a comprehensive design and operational planning framework to generate optimum self-healing control actions in a distribution system. For this purpose, a distribution system with optimally allocated distributed generators (DGs) is divided into a set of microgrids with high self-adequacy through allocation of distributed energy storage resources (DESRs) and distributed reactive sources (DRSs). Afterwards, by using the predicted load and generation of renewable-based distributed generators for the next hour of the day and other important factors (self-adequacy in the unfaulted microgrids, total distribution system's energy losses and the total supplied loads according to their requested reliability), the optimum self-healing strategy is planned for the system for all possible future faults. The IEEE 123-bus distribution system is selected as the test system; optimum microgrids are designed and several case studies are presented to demonstrate the effects of optimization coefficients on the optimum self-healing control actions.

Measured and modeled photovoltaic system energy losses from snow for Colorado and Wisconsin locations

A study was conducted to measure the photovoltaic (PV) system energy production losses caused by the presence of snow for Colorado and Wisconsin locations, and to develop a model for predicting PV system performance losses from snowfall. The PV system performance and associated meteorological data for six PV systems in Colorado and Wisconsin were measured during the winters of 2010–2011 and 2011–2012. The PV systems included two residential systems with stand-off roof mounts; two small commercial systems — one with stand-off mounts on a tilted roof and the other rack-mounted on a flat roof; a 100-kW rack-mounted PV system on a flat roof; and a 200-kW PV system with ground-mounted racks. The measured monthly PV system energy losses caused by snow were as high as 90%. Losses expressed as a percentage of annual energy production ranged from 1% to 12%. A model was developed that uses daily snow depth to identify the presence of new snow; an hourly plane-of-array irradiance and air temperature relationship to identify when snow slides down the PV array; the PV array tilt angle to determine how far the snow slides; and the extent of snow coverage on the PV array to determine the fractional energy output of the PV array. On average, the model worked well. For the two-year period, the modeled annual energy losses were within 0.5% (absolute) of those measured for the non-residential systems. For the residential systems, the modeled annual energy losses were about 1.5% (absolute) less than measured losses. Larger differences between modeled and measured energy losses should be expected for monthly or shorter time periods. The standard deviation of the differences between modeled and measured monthly losses was 10.5% (absolute).