Decrease Power Loss Research Articles

Optimization of Power Distribution Networks in Megacities

The study deals with the problem of city electrical networks optimization in big towns and megacities to increase electrical energy quality and decrease real and active power losses in the networks as well as in domestic consumers. The optimization is carried out according to the location selection and separate reactive power source in 10 kW networks of Swarm Intelligence algorithms, in particular, of Particle Swarm one. The problem solution based on Particle Swarm algorithm is determined by variables being discrete quantities and, in addition, there are several local minimums (troughs) to be available for a global minimum to be found. It is proved that the city power supply system optimization is carried out by the additional reactive power source to be installed at consumers location reducing reactive power flow, thereby, ensuring increase of power supply system quality and decrease of power losses in city networks.

Interleaved full ZVZCS DC–DC boost converter: analysis, design, reliability evaluations and experimental results

In this study, a new interleaved full soft switching DC-DC boost converter with a high power reliability is proposed. To achieve soft switching, a simple auxiliary circuit consisting of one switch, one diode, one inductor and two capacitors is employed in each single-phase DC-DC boost converter connected in parallel. All switches and diodes, including main and auxiliary ones, operate under soft switching conditions. These soft switching conditions consist of zero voltage and zero current switching (ZVZCS) for all switches and diodes at switching transitions except the output diodes, which turn off only with zero current switching. The soft switching technique used in this study decreases power losses which leads the converter to have higher efficiency and reliability. Also, the auxiliary circuit is located out of the main power path preventing high voltage and current stresses on the switches. In this study, operational modes analysis, design procedure, power reliability evaluations and laboratory prototype results with switching frequency of 20 kHz, input voltage of 48 V and output power of 40 W are presented.

Dynamic Load Balancing and Reactive Power Compensation Switch Embedded in Power Meters

This brief proposes a dynamic intelligent load balancing and reactive power compensation switch plugin for power meters and a smart scalable system architecture applicable as an add-on to the existing power distribution networks. The load-balancing module will improve the load balance in a network and thus decrease power losses, whereas the distributed reactive power compensator will decrease the total reactive power. The novel approach is presented from its IT/networks perspective as well as from the physical layer with oscilloscope measurements and time analysis of the phase-swapping event.

Mitigation of voltage unbalance by using static load transfer switch in bipolar low voltage DC distribution system

In this paper, a method is proposed to mitigate voltage unbalance and to reduce power loss due to neutral current in a bipolar Low-Voltage DC (LVDC) distribution system by using a static load transfer switch (SLTS). Furthermore, an algorithm to determine the proper position of loads by using the SLTS is presented; this algorithm is developed by considering the neutral current at each load point. The underlying strategy of the SLTS method is that a local substation generates switching signals by using the proposed algorithm on the basis of data measured by a DC/DC converter; thereafter, SLTSs, which are placed in the DC/DC converter, are operated to reconfigure the structure of loads. To evaluate the performance of the proposed method, the conventional method for calculating the percent voltage unbalance for an AC system is modified and made applicable for a DC system. The modeling of a 1500V bipolar LVDC distribution system carried out using the ElectroMagnetic Transients Program (EMTP) is also presented herein. Finally, a simulation carried out by employing the SLTS method under various load conditions is presented; the results show a decrease in power loss and mitigation of voltage unbalance.

A conventional dynamic voltage restorer with fault current limiting capability

In this paper, a new topology of conventional dynamic voltage restorer (DVR) with fault current limiting capability is proposed. The structure uses a grid-tied transformer which is utilized for both supplying energy to the DVR, and revers voltage supply as a FCL function. In order to limit the fault current, a fast bidirectional switch is employed during fault condition to supply revers voltage to avoid high current levels. However, the ratio of transformer is consequential for the proper operation. Also, for decreasing power losses across isolation transformer and semiconductors, a switch is added to flow the current during normal state. The design methodology of the proposed structure is discussed and the results are carried out based on power systems computer aided design (PSCAD)/electromagnetic transients including dc (EMTDC) simulation.

Power Quality Improvement by an Active Power Filter in Grid-connected Photovoltaic Systems with Optimized Direct Power Control Strategy

In this article, a grid-connected photovoltaic system with functionality of power quality enhancement is studied. The integration of the photovoltaic generator into the grid takes place in one stage, using a three-phase voltage source inverter. A direct power control algorithm strategy with a new switching table has been proposed to decrease power losses into the voltage source inverter, to enhance power quality, to optimize the control of instantaneous active and reactive powers, and to perform as a multi-function device by incorporating shunt active power filter functionality. In addition to this control strategy, a maximum power point tracking perturb and observe algorithm is applied to the inverter to extract optimal available power from the photovoltaic array. The proposed system can provide the power factor correction, harmonic elimination, reactive power compensation, and simultaneously inject the maximum power available from the photovoltaic array to the load and/or grid. The multifunctional features of the proposed control algorithm are demonstrated using extensive simulation studies and are validated through experimental results.

Generation, performance evaluation and control design of single‐phase differential‐mode buck–boost current‐source inverters

Differential-mode inverter topologies are promising for renewable energy generation since they offer advantages such as passive elements sizes reduction, having decreased power losses and reduced total cost. Single phase buck-boost differential-mode current-source inverters (DMCSIs) can deliver wider range of output voltage above or below the input dc voltage, which is necessary for high-efficiency modern renewable energy applications. Since these inverters have continuous input currents, they are suitable for maximum power point tracking (MPPT) operation of photovoltaic systems. Yet, the investigation, operation and implementation of these types of inverters have not been extensively discussed. As a drawback, the total dc side input current of a single-phase inverter consists of a dc component and an undesirable ac component. This ac component frequency is double the output voltage frequency and thus it affects MPPT resulting in reduced total efficiency. In this study, five promising DMCSIs are proposed and compared in terms of their total efficiencies, high-frequency ripple current in the dc side, total harmonic distortion, devices sizes and ratings. Moreover, the sliding mode controller's design and possible methods of eliminating the input second harmonic current are discussed. 2.5 kW bidirectional inverters are implemented to confirm the design flexibility of the proposed DMCSIs.

Energy efficient data centre infrastructure—Development of a power loss model

The design of a complex power supply infrastructure and the satisfaction of the concentrated high energy demand is a constant challenge for data centre owners. Furthermore, economics of the operation and ideas of sustainability are getting more and more attention lately as well. Green data centres are designed to minimize the effect on the natural environment. One of the primary goals of such units is to decrease the energy needs both for the computing infrastructure and the supporting systems (e.g. thermal management), which can be achieved either by increasing the efficiency of processes or by integrating renewable energy sources.Present paper introduces results of an ongoing research and development cooperation between the Centre for Energy Research of the Hungarian Academy of Sciences and Persecutor Ltd., supported by the Hungarian Government’s “PIAC_13” programme. The project aims to develop a new, highly energy efficient data centre infrastructure, which is able to supply IT needs at a high-level, while minimizing power losses. Present paper focuses on decreasing power losses in the distribution and power conversion infrastructure. A power loss model, capable of supporting the optimal selection of different subsystems of the technological chain, is introduced and two case studies are shown to demonstrate the effect of different loss reduction options.

Amorphous Soft Magnetic Core for the Stator of the High-Speed PMBLDC Motor With Half-Open Slots

Several papers have appeared in recent years on the application of the amorphous soft magnetic materials in the stators of the electric motors. In our previous work, we demonstrated that the replacement of a slotless stator from the FeSi electrical steel with the stator from an amorphous alloy Metglas 2605 SA1 in a high-speed permanent magnet brushless direct current (PMBLDC) motor resulted in a substantial decrease of power losses in this stator, even by three times at the rotary frequency of 70 000 r/min. This paper was concentrated on the development of the cores for stators with half-open slots, which are technologically more difficult to produce than the slotless cores. The cores were made by cutting out suitable amount of $25~\mu \text{m}$ -thick rings from the FeSiB amorphous ribbon by a laser technique, followed by stacking up the rings and their consolidation, and suitable heat treatment of the compressed stacks. Next, the measurements of the magnetic properties of the sample cores with half-open slots were made using the Remacomp C-1200 hysteresisgraph and the Lakeshore 450 Gaussmeter. Based on the results of measurements, the sample cores of different heights (17.5 and 10 mm) were selected for application in a stator of the prototype high-speed PMBLDC motor, 800 W in rated power and with a maximum rotary speed of 60 000 r/min. The preliminary performance tests with this prototype motor showed that after 1 h of uninterrupted operation, the temperature of a motor housing did not exceed 60 °C. It was also found that the operating efficiency of the PMBLDC motor incorporating a stator with half-open slots, made from an amorphous material, was almost 90% over a wide range of torques (from 40 to 140 mN $\cdot \text{m}$ ).

Research on a novel high stiffness axial passive magnetic bearing for DGMSCMG

To increase the displacement stiffness and decrease power loss of double gimbals magnetically suspended control momentum gyro (DGMSCMG), this paper researches a new structure of axial passive magnetic bearing (APMB). Different from the existing APMB, the proposed APMB is composed of segmented permanent magnets and magnetic rings. The displacement stiffness and angular stiffness expressions are derived by equivalent magnetic circuit method and infinitesimal method based on the end magnetic flux. The relationships are analyzed between stiffness and structure parameters such as length of air gap, length of permanent magnet, height of permanent magnet and end length of magnetic ring. Besides, the axial displacement stiffness measurement method of the APMB is proposed, and it verified the correctness of proposed theoretical method. The DGMSCMG prototype is manufactured and the slow-down characteristic experiment is carried out, and the experimental result reflects the low power loss feature of the APMB.

Multi-objective optimization for GPU3 Stirling engine by combining multi-objective algorithms

Stirling engine has become preferable for high attention towards the use of alternate renewable energy resources like biomass and solar energy. Stirling engine is the main component of dish Stirling system in thermal power generation sector. Stirling engine is an externally heating engine, which theoretical efficiency is as high as Carnot cycle's, but actual ones are always far below compared with the Carnot efficiency. A number of studies have been done on multi-objective optimization to improve the design of Stirling engine. In the current study, a multi-objective optimization method, which is a combination of multiple optimization algorithms including differential evolution, genetic algorithm and adaptive simulated annealing, was proposed. This method is an attempt to generalize and improve the robustness and diversity with above three kinds of population based meta-heuristic optimization techniques. The analogous interpreter was linked and interchanged to find the best global optimal solution for Stirling engine performance optimization. It decreases the chance of convergence at a local minimum by powering from the fact that these three algorithms run parallel and members from each population and technique are swapped. The optimization considers five decision variables, including engine frequency, mean effective pressure, temperature of heating source, number of wires in regenerator matrix, and the wire diameter of regenerator, as multiple objectives. The Pareto optimal frontier was obtained and a final optimal solution was also selected by using various multi-criteria decision making methods including techniques for Order of Preference by Similarity to Ideal Solution and Simple Additive Weighting. The multi-objective optimization indicated a way for GPU-3 Stirling engine to obtain an output power of more than 3 kW and an increase by 5% in thermal efficiency with significant decrease in power loss due to flow resistance.

A Multi-Objective Approach for Improving Technical Factors of Distribution Networks Considering Uncertainties in Loads and Wind Turbines

Objectives: Objectives of this paper are to achieve decreasing power losses, maintaining permissible voltage profiles in distribution networks and also considering the uncertainties of network Components like loads and wind turbines. Methods/ Statistical Analysis: A new method is proposed for Distribution Feeder Reconfiguration (DFR) and capacitor placement considering Wind Turbine (WT) based on an improved reconfiguration technique. The employed DFR method is based on a single loop reconfiguration method which selects the optimal branch in each loop to achieve maximum loss reduction. Moreover, sequence of loops selection is optimized by using an optimization algorithm. Findings: A joint optimization algorithm has been proposed for combination of the capacitor placement and the improved network reconfiguration. This is due to the inherent coupling relationship between these methods, and therefore, simultaneous implementation of them is more effective than considering them separately. For more practical application of the proposed method, stochastic nature of loads and wind turbine generators of the network have been considered. Teaching-Learning Based Optimization (TLBO) algorithm has been employed for the proposed joint optimization problem and its results have been compared to the PSO and GA. The objective function has been proposed for minimizing the total cost due to capacitor placement and energy losses during 2 years with considering the constraints of bus voltages and the current carrying capacity of conductors. The obtained results confirmed the effectiveness of the proposed method. Application/Improvements: Simultaneous implementation of capacitor placement and reconfiguration method, considering stochastic nature of network and also employing TLBO algorithm for the proposed optimization problem. Keywords: Load and Technical Improvement, Distribution Network, Uncertainty, Wind Turbine

Optimum islanded microgrid reconfiguration based on maximization of system loadability and minimization of power losses

Abstract Distribution grids are being transformed from passive to active networks. The active distribution systems are constructed through the implementation of microgrids (MGs) which are characterized as the “building blocks of smart grids”. This type of network eases the integration of distributed generation into power networks and makes it possible to define a new index for voltage stability, power flow development and a development reconfiguration method. In this paper, an improved indicator is proposed to estimate the voltage stability margin of a two-bus system based on both saddle node and limited induced bifurcations. A new concept named reduced islanded MG network (RIN), is used for generalization of the proposed index to n-bus islanded MGs and a development power flow algorithm by splitting these networks. The increasing loadability index of microgrids in the islanding mode is more important than the index of the grid-connected mode due to its operational limitations such as reactive power generation. In this process, islanded microgrid reconfiguration (IMGR) is proposed as an operational tool for improving loadability as well as decreasing power losses using an Adaptive Multi Objective Harmony Search Algorithm. The performance and effectiveness of the proposed method are demonstrated on 33- and 69-bus test systems.

Coordinated Reconfiguration and Voltage Control for Increasing the Allowable Distributed Generation Penetration using Modified Binary Particle Swarm Optimization

Background/Objectives: Several advantages of Distributed Generation (DG) have created incentives to increase DG penetration in distribution networks. In order to meet this requirement, Coordinated Reconfiguration and Voltage Control (CRVC) is used in this paper. Methods: To do so, simulations are done in two parts. In the first part, the power loss of a distribution system is decreased through CRVC, and in the second part, DG allowable capacity is increased through CRVC. In order to decrease the computational time for finding the best network configuration and voltage control devices values, modified Binary Particle Swarm Optimization (BPSO) is used. The method has been tested on a 33-bus radial distribution system. Findings and Improvements: Simulation results in both two parts show the efficiency of the method. In the first part, CRVC method could decrease power loss 33%. In the second part, the DG allowable penetration is increased 140% thorough CRVC. This shows that this method is more robust than various techniques that have been proposed to increase DG allowable capacity in the past. Moreover, without using complex voltage control methods, CRVC improved the voltage of all busses considerably. Furthermore, simulations verified the decrease in computational time for reconfiguration which is an important challenge in using reconfiguration.

Optimisation of reactive power compensation of HVAC cable in off‐shore wind power plant

High voltage AC (HVAC) transmission system is preferred to be used in off-shore wind power plant which is located within 40km from the seashore. Capacitance of HVAC cables is naturally higher than that of overhead lines, and it should be properly compensated. P model of three-core XLPE cable which is widely used in off-shore wind power plant was applied in the paper. Based on this model, impacts of reactive power compensation on HVAC transmission system, including capacity and location of compensation equipment, were analyzed and simulated then. Research showed that inductive compensation at off-shore side of the cable is more effective to decrease power loss along the cable and increase its transmission capacity than that at onshore side, while the latter is more appropriate to improve the power factor at onshore access point of the wind power plant to grid. Compensation capacity was optimized to realize the best economy with designated certain parameters of HVAC system by Sequential Quadratic Programming (SQP) method. Finally by SQP costs of 35kV and 220kV HVAC transmission system were compared, critical distance and transmission capacity of these two systems adoption were found. These results can be a reference of HVAC transmission system design of off-shore wind power plant.

On the running-in behavior of rough surface of piston rings in mixed lubrication regime

Purpose – The purpose of this paper is to study the real-time change of surface roughness at different small regions of piston rings during running-in process. Meanwhile, the effects of real-time change of the rough surface topography on the lubrication and friction of piston rings are investigated. Design/methodology/approach – An uneven wear model has been developed to research the running-in behavior at the different small regions of piston rings. The model is verified by comparing the simulation results with the experimental results on a reciprocating friction and wear test rig. Findings – This research shows that the wear process of piston ring surface is uneven during running-in. At most time of the operating cycle except the vicinity of top dead center and bottom dead center, the minimum oil film thickness ratio increases while the friction force and power loss decrease after the running-in period. Originality/value – Through this research, the running-in behavior of piston rings is investigated in detail. The interaction between the running-in and the lubrication and friction of piston rings is understood more deeply.

Analysis of Power Loss for Crystalline Silicon Solar Module during the Course of Encapsulation

During the course of solar module encapsulation, the output power of crystalline silicon solar module is less than the sum of the maximum output power of the constituents because of power loss. So it is very important to investigate the power loss caused by encapsulation materials and module production process. In this paper, the power loss of crystalline silicon solar module is investigated by experiments systematically for the first time. It is found that the power loss is mainly caused by the resistance of ribbon and mismatch of solar cells; the total power loss is as high as 3.93% for solar module composed of 72 cells (125 mm × 125 mm) connected in series. Analyzing and reducing the power losses are beneficial to optimizing encapsulation process for the solar module. The results presented in this study give out a direction to decreasing power loss and optimizing encapsulation process of crystalline silicon solar module.

Development of High Efficiency Boost DC/DC Converter For EV

In this paper, reactorless high efficiency boost DC/DC converter for EV is proposed. In proposed converter, improves efficiency because decrease power loss when the switches are turned on/off using zero current switching (ZCS) at all switch of primary full bridge. By replacing reactance ingredients of L-C resonance circuit for ZCS with leakage inductance ingredients of high frequency transformer, it reduces system size and expense because of not add special reactor. For validity verification of proposed converter, in the paper implements simulation using PSIM and perform experiment by making 5KW DC/DC converter. In experimental results, efficiency of proposed converter conformed superiority. Today the use of electricity is increasing with the development of industries and vehicles with internal combustion engine are rapidly increasing for convenience of travel. To produce electricity and drive internal combustion engines, fossil fuels must be used, causing serious environmental problems. These days many people are making efforts to reduce CO2 which is the main culprit for the destruction of global environment. In particular, as vehicles account for over 50% of the CO2 emissions, active efforts to reduce them are being made all over the world. Typical examples of such efforts are the improvement of fuel economy and the introduction of electric vehicles. Recently, hybrid vehicles that use both internal combustion engine and electric motor have been developed with effective improvement of fuel economy. It is expected that in the future, the percentage of vehicles using internal combustion engine will gradually decrease and ultimately be replaced with pure electric vehicles and fuel-cell vehicles(1)(2). As the use of electric motors is increasing, traction motors mainly use 300 V or higher voltages considering losses and advantages in motor design. However, since such high- voltage power supply systems have such problems as electric shock, systems like NEV (Neighborhood Electric Vehicle) use low voltage batteries of maximum 70 V. Due to safety and efficiency issues, batteries are using low voltage while motors use high voltages. Thus, it is essential to develop a boost DC/DC converter with at least 4-fold boosting efficiency(3)(4). Furthermore, an insulation-type converter needs to be developed to address the electric safety issue. Accordingly, this paper proposes an insulated DC/DC converter that uses a voltage multiplier circuit composed of diodes and condensers at the output for high voltage multiplication, in particular, a new insulation-type DC/DC converter with a serial connection of two voltage multiplier circuits for 4-fold boosting. The proposed method maintained the ratio of the transformer as 1:1 for identical input and output characteristics of the converter considering the regenerative braking of vehicles in the future. Furthermore, the proposed converter reduced the switching loss of the power switch using a serial L-C resonance, and the size and cost of the total system can be reduced by replacing the reactance component required for the L-C resonance circuit with a transformer leakage reactance(5) . To verify the feasibility of the proposed insulated DC/DC converter using a voltage multiplier circuit, a simulation was conducted using PSIM, and the real converter was fabricated and tested. It was found that up to 4-fold boosting was possible with the voltage multiplier circuit and a serial circuit only with no separate control, and the maximum efficiency of the converter was very high at around 97%.

Optimal control of mutual impact of electric grids for the reduction of their electric energy losses

The subject of the research comprise the methods, aimed at determination of additional losses of active power, caused by forced displacement of transit transfers from high voltage (HV) into low voltage (LV) grids, which contain besides the transformers with tap-changing under load, also cross-transformers (CT). The research for the first time performs the analysis of the impact of CT location and its angle on the losses of active power in the branches of LV grid and on general system losses, that takes into consideration the change of additional losses of active power at the expense of forced displacement of transit transfers from LV grids into HV grids and vice versa. The paper contains the algorithms and explanation of their operation, that enables to determine optimal branch and CT angle, as well as, in case of their implementation, allow to decrease power losses. Results of research, considered in the paper are used in power industry, namely for calculation of normal modes and optimal parameters of control impacts vectors in order to degrease active power losses in electric grids. The results obtained in the process of the research prove that application of CT with optimal phase angle in the branch, defined by the suggested method of CT determination of CT optimal place location allows to decrease, both losses of active power in LV grids and general system losses, the degree of mutual and transit power transfers impact on the level of active electric energy losses changes depending on autotransformers transformation ratios, value of CT phase-shifting angle, circuit parameters and electric grid loading mode; studies of additional losses of active power change, caused by the displacement of transit transfers of power from HV grids into LV grids shows that sometimes: uncoordinated usage of regulating devices of the transformers in HV and LV grids leads to growth of these additional power losses; usage of transformers tap-changing under load does not allow to decrease maximally losses of active power, greater decrease of these losses can be achieved by optimal usage of СT.

600-V 27-mΩ normally off SiC junction field effect transistors for high-efficiency power supply

Normally-off SiC junction field effect transistors (JFETs) with high blocking voltage and low gate leakage current were developed by localized current-path doping (LCD). Numerical simulation of electric field revealed that LCD effectively decreases the on-resistance of SiC JFETs without degrading blocking voltage. On the basis of the obtained simulation results, 600-V 27-mΩ normally off SiC JFETs were fabricated by LDC. The gate leakage current of the fabricated JFETs was suppressed by surface oxynitridation. By applying in a server power supply, we found that these improved JFETs decreased power loss due to FETs by 66%.