Search

Copyright of Gazi Üniversitesi Fen Bilimleri Dergisi Part C: Tasarım ve Teknoloji is the property of Gazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Variable renewable generation and load fluctuations induce significant balancing cost in power system operation. To overcome this issue, this paper proposes a control architecture that leverages inherent regulation capabilities of wind turbines to minimize the system‐wide balancing costs. Instead of handling wind power fluctuations via power filtering algorithms that are agnostic to system‐wide power imbalance, this paper aims to optimize the wind power generation profile from system perspective. In the proposed method, wind turbines are modelled as semi‐dispatchable units, where the dispatch command is dynamically generated at every automatic generation control cycle by considering mileage payments as an indicator of system‐wide imbalance. As a result, local resources of wind turbines are optimally leveraged in real‐time to mitigate system‐wide power imbalances. The proposed strategy and state‐of‐the‐art techniques are compared in comprehensive high‐fidelity case studies. Our simulation results demonstrate that the proposed system‐aware regulation scheme can alleviate system balancing costs without investments into energy storage systems. [ABSTRACT FROM AUTHOR]

Independent microgrids are widely used in islands and remote townships. However, power imbalance often leads to fluctuations in voltage and frequency, which inhibit the development of AC microgrids. To overcome such problems, this paper proposes an optimized full-bridge converter energy storage structure to realize power balance and optimization of the microgrid. The proposed structure has the characteristics of simple design, easy modularization, and flexible power regulation. First, the working structure and mathematical model are analyzed, and the power model is then established. From the viewpoint of capacitor charging and discharging and inverter, the active and reactive power control technology of the full-bridge structure is analyzed, and a multimode power coordinated control strategy is adopted to adjust and optimize the target power. Finally, the feasibility of the structure and control strategy is verified through a simulation and an experiment. In summary, this study is of great significance to the future promotion and application of AC microgrids. [ABSTRACT FROM AUTHOR]

Abstract Due to the unpredictable nature of wind energy and non-coincidence between wind units output power and demand peak load, wind units is deemed as an unreliable source of energy. In order to compensate for the short-term fluctuation of wind energy, deployment of energy storage (ES) units in various types have been introduced as a viable solution. This paper develops a stochastic mathematical model for the optimal allocation of ES units in active distribution networks (ADNs) in order to reduce wind power spillage and load curtailment while managing congestion and voltages deviation. Nonlinearities of the original formulation are converted to linear equivalents and the final model lies within the computationally tractable mixed-integer linear programming (MILP) fashion. The IEEE 33-bus 12.66 kV radial distribution test system is utilized to illustrate the effectiveness of the proposed methodology. It was found that the rated power and capacity of ES units are depends on wind units' location and penetration level, in such a way that ES units are allocated near wind units to absorb excessive wind energy as much as possible. Furthermore, the results indicate ES units are useful for other purposes such as voltage management issue even if the wind units are not allocated. Highlights • A new stochastic optimization model is developed to optimal allocation of ES units in active distribution networks. • The linear OPF equations are derived here, which can be used to calculate the power flows directly. • Line Congestion and voltage deviation are managed through optimal scheduling of ES units. • Harvesting higher wind energy through optimal scheduling of ES units. [ABSTRACT FROM AUTHOR]

This paper presents the theory and methodology for the adjustment of the negative sequence current protection function (PF) ANSI 46 of a synchronous generator with poles and poles, for a multifunctional relay SIEMENS 7UM62 that uses for its logic of decision the curve of time of heating allowed of the machine before the increase of the magnitude of negative sequence Also the consequences and the damages that can be caused by the excess of current of negative sequence circulating by the stator of the generator are explained. In addition, its functional diagram is illustrated by identifying its input signals: data (settings), analog and binary signals; It also describes in detail its decision process and exit signals. This logical diagram was divided into 3 sub-diagrams to identify the causes that originate their outputs: alarms, startup, firing or blocking, this way of illustrating the process by stages allows greater clarity, since the explanation process is more didactic than the one presented by the manufacturer in the manual. As an example of an illustration, the calculations of the adjustment criteria of the ANSI 46 PF applied to a salient pole generator from Unit 1 of the Salvajina Hydroelectric Plant are presented in detail. This protection function protects the machine by heating load imbalance and asymmetric faults. [ABSTRACT FROM AUTHOR]

Abstract Owing to the increasing demand for deep sea exploration, remotely operated vehicles (ROVs) that can conduct scientific tasks up to a depth of 6000 m are essential for exploring unknown areas. For electrically propelled ROVs, a voltage regulation system is used to maintain the load-side voltage within a limited range during power load variation. The load-side voltage fluctuated frequently during load variation, thus challenging the design of the voltage regulation system. Hence, we propose a novel voltage regulation strategy in the ship-side of a 6000-m-deep ROV system. In this strategy, the nonlinear relationship of the compensated voltage in the ship-side and the active current in the umbilical cable are solved by piecewise linear fitting using the least-squares method. Subsequently, a feedback PID controller is designed to achieve a faster dynamic response and maintain a stable load-side voltage. The real applications of the ROV system for oceanographic surveys demonstrated that the fast response and high accuracy of the voltage regulation system for intense fluctuations of the load-side voltage could be achieved. [ABSTRACT FROM AUTHOR]

Copyright of Przeglad Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

SUMMARY: From growing interests in the environment issues, promotion of photovoltaic power generation (PV) is accelerated in the world. Meanwhile, rapid chargers (RCs) for popularized electric vehicles are being installed in urban areas. These two trends in distribution system might cause severer voltage fluctuation problems. On the other hand, a RC can provide the reactive power support, which is capable of voltage regulation. Based on this viewpoint, this paper proposes a new framework of voltage regulation, in which the reactive power compensation by RCs is actively utilized. The proposed voltage regulation method combines two different control functions with consideration for over‐compensation avoidance. This paper ascertains the validity of proposed voltage regulation method through numerical simulations. [ABSTRACT FROM AUTHOR]

One the problem of electric power stability is due to load fluctuations in distribution system especialy during peak load conditions. One solution which is applied in Smart Grid scheme is through load shifting or power shifting. In load shifting the load with high power consumption which operates at peak load shifted its operations outside of the peak load or s some loads with high power consumption do not operate at the same time, there is a load whose operating time is shifted to reduce peak power. Power shifting is used when energy from renewable source not directly suplied to load but storage first and supplied to reduce high power consumption to reduce peak power. Low load factor, ratio between average power to peak power, may affect to power system operation. If load factor of residential load can keep in low, it will be certainly help improve the stability of the power system. In this study we will examine the comparison of load shifting method with power shifting in improving load factor. Load shifting is done to water pumps and washing machines, because washing machine is shiftable load. Power shifting is made to the output power of the solar power plant, which is used to reduce peak power from the water pump. Test results show that power shifting can increase load factor value up to 54,9% while load shifting give load factor value equal to 43,9%. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a maiden alternative approach to the cost based allocation over the transmission network for individual generators associated with the system. A modified method is proposed by which the proportion of power going from an individual generator to the loads, and to the rest of the transmission network can be traced in a grid system. Also, the revenue collected from the customer side for all associated producers separately can be determined. The developed technique has been experimented successfully on a 39-bus New England Power System and to validate the method, the outcomes of the projected algorithm of the test system are compared with the power flow solution obtained by using the sequential quadratic programming method. The comparative analysis reveals that the results obtained from both the methods are nearly the same under different loading conditions, proving the accuracy and robustness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents the design procedure for a new multicycle resonance-based voltage boosting rectifier (MCRR) capable of delivering a desired amount of power to the load (PDL) at a designated high voltage through a loosely coupled inductive link. This is achieved by shorting the receiver (Rx) LC\--\tank for several cycles to harvest and accumulate the wireless energy in the RX inductor before boosting the voltage by breaking the loop and transferring the energy to the load in a quarter cycle. By optimizing the geometries of the transmitter (Tx) and Rx coils and the number of cycles, $N$, for energy harvesting, through an iterative design procedure, the MCRR can achieve the highest PDL under a given set of design constraints. Governing equations in the MCRR operation are derived to identify key specifications and the design guidelines. Using an exemplary set of specs, the optimized MCRR was able to generate 20.9 $V_{{\rm{dc}}} across a 100 kΩ load from \text1.8\,Vp, 6.78-MHz sinusoid input in the industrial-scientific-medical-band at a Tx/Rx coil separation of 1.3 cm, power transfer efficiency of 2.2%, and N=9 cycles. At the same coil distance and loading, coils optimized for a conventional half-wave rectifier were able to reach only 13.6 $V_{{\rm{dc}}}$ from the same source. [ABSTRACT FROM PUBLISHER]

This paper proposes a new design for a fast-locked digitally controlled low-dropout regulator (FDLDO) for an ultra-low voltage input. The proposed design involves a fast-locked control mechanism that reduces the settling time of the load transient response in the tracking mode and decreases the quiescent current in the regulating mode. For an ultra-low input voltage of 0.35 V, the proposed FDLDO is capable of providing a regulated output voltage of 0.3 V with a dropout voltage of 50 mV and delivering a maximal load current of 2.4 mA with current and power efficiencies of 99.74 and 85.49%, respectively. Measurement results showed that in the regulating mode, the quiescent current is only 5.15 $$\upmu \hbox {A}$$ for the maximal load current; furthermore, for the maximal load current, the load regulation and the line regulation are 1.5 mV/mA and 4.916 mV/V, respectively. Under the load regulation, the transient response time is less than 15 $$\upmu \hbox {s}$$ . No external output capacitor is required to stabilize the control loop, and there is no external input clock. The proposed FDLDO is suitable for low-power system-on-a-chip applications of wearable electronic devices with an ultra-low supply voltage. [ABSTRACT FROM AUTHOR]

With increasing penetration of wind power, the impact of its intermittence and volatility on power systems becomes more severe. A predictive control strategy for wind turbines (WTs) is proposed to deal with wind power ramping events and reduce WT load on the blades. The blade load model is based on the Blade Element Momentum (BEM) theory. The generator speed and pitch angle are simultaneously regulated to realize the control objectives. A two-stage optimization is designed in order to reduce the computational complexity. The objectives of the first stage are minimizing the ramping rate and maximizing the power generation. A trade-off is made between the two contradictory objectives by setting weight coefficients. The second stage reduces the WT load and meanwhile guarantees the power reference from the first stage is tracked. Feedback is designed based on neural network prediction to compensate the error of the prediction model. Case studies with a 1.5 MW WT were conducted to demonstrate the efficacy of the proposed predictive control strategy. Simulation results show that the proposed control can reduce the WT load during ramping events and the risk of ramping events. [ABSTRACT FROM AUTHOR]

Load patterns have a significant effect on the configuration of an energy system. With a smoother load profile, the initial investment cost and operation and maintenance costs can be reduced. Adjustments in the area ratio of different types of buildings during early planning stage can be useful in leveling the loads. However, there are few studies till date on the guidelines for making such adjustments. This paper proposes a method to evaluate the performance of load leveling. Before evaluation, the load profile is obtained using a method that combines simulation and scenario analysis. Optimization of energy configuration for a typical case is conducted before and after load leveling adjustment to demonstrate the benefits of load leveling. [ABSTRACT FROM AUTHOR]

Recent approaches in load profiling involve the utilization of clustering algorithms to classify a load data set with little or no external information on its structure and relationships between the data is available. In the load profiling literature many algorithms have been presented. K-means is the most commonly used algorithms. While its robustness is already displayed, the main limitation lies on its dependence on the initialization phase. The present paper proposes two novel modified versions of the algorithm in order to deal with the aforementioned problem. Clustering is part of a multi-stage load profiling framework. Apart from the clustering itself, other stages include the selection of pattern representation technique and the extraction of “ representative ” consumers. Apart from the expressing the patterns as time sequences of load values, two other are utilized that refer to a dimensionality reduction method and statistical indexes. The comparison of the algorithms is held through four clustering validity indicators. Simulation results indicate that the proposed modified versions of the K-means lead to higher clustering accuracy in all cases examined. Moreover, the multi-stage clustering approach followed in this study leads to lower clustering time requirements, a fact that is significant in cases with vast amount of data. [ABSTRACT FROM AUTHOR]

Since the inception of non-intrusive appliance load monitoring (NILM), extensive research has focused on identifying an effective set of features that allows to form a unique appliance signature to discriminate various loads. Although an abundance of features are reported in literature, most works use only a limited subset of them. A systematic comparison and combination of the available features in terms of their effectiveness is still missing. This paper, as its first contribution, offers a concise and updated review of the features reported in literature for the purpose of load identification. As a second contribution, a systematic feature elimination process is proposed to identify the most effective feature set. The analysis is validated on a large benchmark dataset and shows that the proposed feature elimination process improves the appliance classification accuracy for all the appliances in the dataset compared to using all the features or randomly chosen subsets of features. [ABSTRACT FROM AUTHOR]

In order to save more energy and quicken the load change speed of air-cooled steam condenser units, the closed-loop optimized control on the fan speed is proposed and its realization is worth making intensive study. In this regard, the study presents the static and dynamic models of air-cooled steam condenser, and the characteristics of turbine power output affected by fan speed. Then, the structure of closed-loop control on fan speed is designed. Furthermore, two optimized methods on condenser pressure based on fan speed control are separately discussed: the optimum condenser pressure is solved by the genetic algorithm to save more energy, and the condenser pressure regulation is combined with traditional boiler-turbine coordinated control to accelerate the load response. Case study in our paper proves that the fan speed optimization can significantly improve the unit load-following capability, and furthermore unit coal consumption has been significantly reduced when the unit operating in a stable load condition. [ABSTRACT FROM AUTHOR]

The 3GPP has proposed enhanced intercell interference coordination (eICIC) by making the macrocell silent in the almost blank subframes (ABSs) to mitigate interference for low-power base stations (BSs) in the downlink direction. However, two important challenges are introduced: 1) the underutilization for macrocell in ABS and 2) the optimal downlink association may not be optimal for uplink transmission, i.e., downlink/uplink decoupling (DUDe). In this paper, we first propose a novel method based on configuring uplink transmission in the macrocell in ABSs (UM-ABS) for eICIC to improve the efficiency of the ABS. Then, the UM-ABS and DUDe are formulated as an optimization problem of investigating the joint load balancing of downlink and uplink for eICIC in heterogeneous networks (HetNets) while considering different service classes. The problem is actually a mixed binary integer programming problem, which is difficult to solve. We provide a relaxed-rounding solution to the model. Numerical results illustrate that the proposed algorithm achieves superior performance in comparison to state-of-the-art methods in terms of system throughput and the rate gain for users. [ABSTRACT FROM PUBLISHER]

A new internally compensated low drop-out voltage regulator based on the cascoded flipped voltage follower is presented in this paper. Adaptive biasing current and fast charging/discharging paths have been added to rapidly charge and discharge the parasitic capacitance of the pass transistor gate, thus improving the transient response. The proposed regulator was designed with standard 65-nm CMOS technology. Measurements show load and line regulations of 433.80 μV/mA and 5.61 mV/V, respectively. Furthermore, the output voltage spikes are kept under 76 mV for 0.1 mA to 100 mA load variations and 0.9 V to 1.2 V line variations with rise and fall times of 1 μs. The total current consumption is 17.88 μA (for a 0.9 V supply voltage). [ABSTRACT FROM AUTHOR]

To develop electric vehicle (EV) is an efficient method to deal with energy shortage and environment pollution. Based on the comparison among three battery charging modes, this paper first clarifies the advantage of battery swapping mode. Compared with normal charging mode and fast charging mode, battery swapping mode is much easier to control the charging and discharging behaviour of EVs. Reflect on the load curve, the load curve of EV battery swapping stations (EVBSS) have more potential to be optimized. Then, the profit pattern, load characteristics and effects to grid of the mode is analysed in detail. After that, an optimal charge/discharge strategy for an EVBSS is established and studied. And the optimized load curve of an EVBSS can be obtained. Furthermore, sensitivity analysis is made to improve the profit of the EVBSS. Finally, some conclusions are made, and some suggestions for electric vehicle development are prospected. [ABSTRACT FROM AUTHOR]

Information on residential power consumption patterns disaggregated at the single-appliance level is an essential requirement for energy utilities and managers to design customized energy demand management strategies. Non-Intrusive Load Monitoring (NILM) techniques provide this information by decomposing the aggregated electric load measured at the household level by a single-point smart meter into the individual contribution of each end-use. Despite being defined non-intrusive , NILM methods often require an intrusive data sampling process for training purpose. This calibration intrusiveness hampers NILM methods large-scale applications. Other NILM challenges are the limited accuracy in reproducing the end-use consumption patterns and their trajectories in time, which are key to characterize consumers’ behaviors and appliances efficiency, and the poor performance when multiple appliances are simultaneously operated. In this paper we contribute a hybrid, computationally efficient, algorithm for NILM, called Hybrid Signature-based Iterative Disaggregation (HSID), based on the combination of Factorial Hidden Markov Models, which provide an initial approximation of the end-use trajectories, and Iterative Subsequence Dynamic Time Warping, which processes the end-use trajectories in order to match the typical power consumption pattern of each appliance. In order to deal with the challenges posed by intrusive training, a supervised version of the algorithm, requiring appliance-level measurements for calibration, and a semi-supervised version, retrieving appliance-level information from the aggregate smart-metered signal, are proposed. Both versions are demonstrated onto a real-world power consumption dataset comprising five different appliances potentially operated simultaneously. Results show that HSID is able to accurately disaggregate the power consumption measured from a single-point smart meter, thus providing a detailed characterization of the consumers’ behavior in terms of power consumption. Numerical results also demonstrate that HSID is robust with respect to noisy signals and scalable to dataset including a large set of appliances. Finally, the algorithm can be successfully used in non-intrusive experiments without requiring appliance-level measurements, ultimately opening up new opportunities to foster the deployment of large-scale smart metering networks, as well as the design and practical implementation of personalized demand management strategies. [ABSTRACT FROM AUTHOR]

This article describes designing, implementation and tuning processes of multiple-tapped-delay-line (MTDL). Obtained MTDL can be implemented in various field-programmable-logic-devices (FPGA) devices and applied for time-to-digital-converters (TDC) construction. The task of tuning process is the tapped-delay-line (TDL) linearisation, and consists of two stages. The first stage depends on selecting an appropriate configurable-logic-block (CLB) for particular delay-segment realization and selecting proper connection between these blocks. The second tuning stage, that is essential from this article viewpoint, depends on inter CLBs connecting wires delay regulation realized directly by load regulation. The Load regulation depends on connecting an appropriate number of unused three-state-buffers or CLB inputs to the wire which delay is adjusted. Depending on the number of inputs connected to the wire its capacitance changes that influences its time-constant and finally changes its time-delay. The MTDL mathematical model, obtained characteristics and results of time-interval (TI) measurements are also presented. The derived TDL model provides information about how the particular wire delay should be changed and in which order the changes should be executed. This makes the designing process predictable and easy to carry out. Presented characteristics confirm the proper operation of presented linearisation technique. The proper operation of the whole measuring module is confirmed by obtained TIs histograms presentation. [ABSTRACT FROM AUTHOR]

A novel digital constant output current controller with demagnetization-time compensation for flyback converter is proposed in this paper. The secondary winding demagnetization time is sampled from the comparison module output signal by output voltage sampling state machine. The ratio between and switching period is kept constant by bidirectional counter module to achieve constant output current based on invariable primary-side peak-current. Meanwhile, demagnetization-time compensation is proposed in order to enhance load regulation ratio. The compensation acquired from a look-up table, is utilized to compensate the impacts caused by the delay from the process of sampling the signal of . The digital controller (DC) is implemented by hardware description language Verilog HDL. Experimental results of the proposed 2A constant current output flyback converter based on FPGA(EP2C8Q208C8N) indicate that the constant current precision is within 1% in a wide range of universal-input AC voltage from 110V to 240V and the voltage load range between 2V and 8V. [ABSTRACT FROM AUTHOR]

This paper considers the operation of hydro plants, tackles the problem of daily hydro-generation scheduling (DHGS), and obtains the optimal hourly operation of cascade hydropower reservoirs. To meet the practical operational demands of power grid, an improved benefit-maximization model in which the peak shaving demands are taken as constraints is proposed for DHGS, and the joint peak load regulation (JPLR) method is applied to the proposed model. The model can enhance the power-generation efficiency and reduce the water spillage significantly under the condition of peak load regulation. Meanwhile, a hybrid method that combines discrete differential dynamic programming with progressive optimality algorithm is proposed to solve the JPLR problem. The complicated constraints can be handled by the proposed algorithm effectively. Moreover, the hydro-unit-commitment problem is solved by a rapid searching algorithm based on equal incremental principle and empirical methods. With this unit-commitment strategy, the computation speed can be accelerated and approximate optimal solutions can be obtained in a reasonable time frame. The proposed model and methods are applied to the DHGS of cascade hydro plants in Zagunao River in China and achieve good performance. [ABSTRACT FROM AUTHOR]

Load management has been an enigma despite the adequate level of production of electricity. This research focuses on the short-term evaluation of the maximum output of various electricity generation facilities to meet the required system load at minimum possible cost without disrupting the regular power supply to the end users and aimed to give overview of the economic load dispatch problem regarding abrupt variations in monthly load demand and generation throughout the year. The research analysis was conducted by using daily data regarding the generation, load demand across the country and power system constraints of generation and transmission. The aspect of reduction in share of Hydel generation during canals closure at water scarcity season every year has also been taken into account. By analyzing both the actual and predicted values at load dispatch center, it provides monthly trend of generation, consumer demand and load shed at the same time. Daily and monthly data figures of the last 06 years in MW/GWh is analyzed and executed. Values have been plotted in graphs to understand the monthly/annual variations in total generation and total demand. Research is aimed to improving the quality of power dispatch and deriving workable solutions. [ABSTRACT FROM AUTHOR]

Maintaining voltage stability, within acceptable levels, for islanded Microgrids (MGs) is a challenge due to limited exchange power between generation and loads. This paper proposes an algorithm to enhance the dynamic performance of islanded MGs in presence of load disturbance using Static VAR Compensator (SVC) with Fuzzy Model Reference Learning Controller (FMRLC). The proposed algorithm compensates MG nonlinearity via fuzzy membership functions and inference mechanism imbedded in both controller and inverse model. Hence, MG keeps the desired performance as required at any operating condition. Furthermore, the self-learning capability of the proposed control algorithm compensates for grid parameter's variation even with inadequate information about load dynamics. A reference model was designed to reject bus voltage disturbance with achievable performance by the proposed fuzzy controller. Three simulations scenarios have been presented to investigate effectiveness of proposed control algorithm in improving steady-state and transient performance of islanded MGs. The first scenario conducted without SVC, second conducted with SVC using PID controller and third conducted using FMRLC algorithm. A comparison for results shows ability of proposed control algorithm to enhance disturbance rejection due to learning process. [ABSTRACT FROM AUTHOR]

Reconfiguration is a valuable technique that can support the distribution grid from different aspects such as operation cost and loss reduction, reliability improvement, and voltage stability enhancement. An intelligent and efficient optimization framework, however, is required to reach the desired efficiency through the reconfiguration strategy. This paper proposes a new multi-objective optimization model to make use of the reconfiguration strategy for minimizing the power losses, improving the voltage profile, and enhancing the load balance in distribution grids. The proposed model employs the min-max fuzzy approach to find the most satisfying solution from a set of nondominated solutions in the problem space. Due to the high complexity and the discrete nature of the proposed model, a new optimization method based on harmony search (HS) algorithm is further proposed. Moreover, a new modification method is suggested to increase the harmony memory diversity in the improvisation stage and increase the convergence ability of the algorithm. The feasibility and satisfying performance of the proposed model are examined on the IEEE 32-bus distribution system. [ABSTRACT FROM AUTHOR]

This article presents a low quiescent current output-capacitorless quasi-digital complementary metal-oxide-semiconductor (CMOS) low-dropout (LDO) voltage regulator with controlled pass transistors according to load demands. The pass transistor of the LDO is segmented into two smaller sizes based on a proposed segmentation criterion, which considers the maximum output voltage transient variations due to the load transient to different load current steps to find the suitable current boundary for segmentation. This criterion shows that low load conditions will cause more output variations and settling time if the pass transistor is used in its maximum size. Furthermore, this situation is the worst case for stability requirements of the LDO. Therefore, using one smaller transistor for low load currents and another one larger for higher currents, a proper trade-off between output variations, complexity, and power dissipation is achieved. The proposed LDO regulator has been designed and post-simulated in HSPICE in a 0.18 µm CMOS process to supply a stable load current between 0 and 100 mA with a 40 pF on-chip output capacitor, while consuming 4.8 μA quiescent current. The dropout voltage of the LDO is set to 200 mV for 1.8 V input voltage. The results reveal an improvement of approximately 53% and 25% on the output voltage variations and settling time, respectively. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper addresses a new distributed cost optimization (DCO) method for load shedding (LS) of an islanded microgrid considering cost. A two-layer improved average consensus algorithm (IACA) of multi-agent system (MAS) is proposed, and the consensus characteristic of which is analyzed in detail. With the global information discovered in the first layer of the IACA, the DCO of LS can be solved by using the synchronization processing of the IACA in the second layer. PSCAD/EMTDC-based simulation models are built to study the value settings of consensus constants and the performances of the proposed DCO method. Simulation results verified the convergence improvement of the IACA and the effectiveness of the proposed DCO. [ABSTRACT FROM AUTHOR]

In this paper, we propose mathematical optimization models of household energy units to optimally control the major residential energy loads while preserving the user preferences. User comfort is modelled in a simple way, which considers appliance class, user preferences and weather conditions. The wind-driven optimization (WDO) algorithm with the objective function of comfort maximization along with minimum electricity cost is defined and implemented. On the other hand, for maximum electricity bill and peak reduction, min-max regret-based knapsack problem (K-WDO) algorithm is used. To validate the effectiveness of the proposed algorithms, extensive simulations are conducted for several scenarios. The simulations show that the proposed algorithms provide with the best optimal results with a fast convergence rate, as compared to the existing techniques. [ABSTRACT FROM AUTHOR]

This paper proposes a novel simple reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy may be applicable for adjustment of the source-side power factor under the balanced load condition. Only dc capacitor voltage control is used in the proposed control strategy. Therefore, the calculation blocks of the active and reactive components of the load currents are not necessary. The authors, thus, offer the simplest control strategy to control reactive power under the balanced load condition on three-phase four-wire distribution feeders. The basic principle of dc-capacitor-voltage-control-based reactive power control strategy is discussed in detail and then confirmed by digital computer simulation. A prototype experimental system was constructed and tested. Experimental results demonstrate that balanced source currents with reactive power control are achieved on three-phase four-wire distribution feeders. These experimental results also demonstrate that controlling the reactive power reduces the required power rating of the ALB compared with that of the conventional unity power factor control strategy. [ABSTRACT FROM PUBLISHER]

Neatly represented and properly classified load profiles are fundamental to many control optimization techniques of modern power systems, especially in a distribution area. This paper presents a novel load profile management software framework for boosting the efficiency of power systems operation. The proposed framework encodes and classifies load profiles in real-time. Imperfections as well as time-shifts in the input (measured power consumption levels) are tolerated by the suggested system, thus always providing accurate, fast and reliable output. The framework’s fully component based structure allows easy customizations of the encoding as well as the classification engines. The default encoding engine is based on an artificial neural network, a variant known as a deep learning auto-encoder comprised from stacked sparse auto-encoders. The default classifier engine is based on an implementation of a locality sensitive hashing algorithm. The developed methodology was tested on the real case of a set of anonymous customers supplied by a power distribution company. The paper also contains an elaboration about the experiences gained during the design, implementation and testing phase of this system as well as a detailed engineering use case of the framework’s applicability. [ABSTRACT FROM PUBLISHER]

To respond to volatility and congestion in the power grid, demand response (DR) mechanisms allow for shaping the load compared to a base load profile. When tapping on a large population of heterogeneous appliances as a DR resource, the challenge is in modeling the dimensions available for control. Such models need to strike the right balance between accuracy of the model and tractability. The goal of this paper is to provide a medium-grained stochastic hybrid model to represent a population of appliances that belong to two classes: deferrable or thermostatically controlled loads. We preserve quantized information regarding individual load constraints, while discarding information about the identity of appliance owners. The advantages of our proposed population model are 1) it allows us to model and control load in a scalable fashion, useful for ex-ante planning by an aggregator or for real-time load control; 2) it allows for the preservation of the privacy of end-use customers that own submetered or directly controlled appliances. [ABSTRACT FROM PUBLISHER]

Power Electronic-based Components (PECs) can provide excellent features such as, load regulation, high power factor, and transient performance, especially in the large scale distribution systems. Accordingly, contemporary power distribution systems or Power Electronic-based Distribution Systems (PEDS) are highly penetrated with the Renewable Energy Resources (RERs) as well as innovative PECs such as, Solid State Transformers (SSTs) and inverters. Therefore, they are prone to exhibit negative impedance instability in consequence of high power factor and constant-power nature of the individual components in the system. Thus, small-signal as well as large-signal stability assessments of the PEDS play prominent role in operational (real-time) stage of the systems analyses. In this paper new small-signal stability analysis technique is developed based on d − q impedance measurement and Nyquist criterion that is capable of investigating the systems’ small-signal stability in real-time. Furthermore, small-signal stability of a sample PEDS comprised from a SST connected to the source and variable load is investigated through the proposed method and with utilizing Real-Time Digital Simulator (RTDS) platform. [ABSTRACT FROM AUTHOR]

This Paper deals with the Price Based Load Frequency Control (PBLFC) using optimized gain of integralcontroller with three different system marginal cost cases of single area four generator schemes. Case one having System Marginal Cost (SMC) value more than the nominal Unscheduled Interchange (UI) rate. Case two having system marginal cost value less than the nominal UI rate. Case three illustrates about the peak load condition following sudden loss of large generation to see whether PBLFC can handle such event or not. Particle Swarm Optimization (PSO) technique has been used to optimize gain of integral controllers in case one and two. An attempt has been made to achieve effective system frequency response using optimized gain controllers and also to explore the change in profit earned by Generation Companies (Gencos) in both the cases. For the analysis, UI rate of the year 2012, issued by Central Electricity Regulation Commission (CERC, INDIA) is used. [ABSTRACT FROM AUTHOR]

Distribution network designers use a transformer load-management system to estimate and examine the historical and current loads occurring on transformers and test proposed load situations. Due to a lack of measurements at the feeders and distribution transformers, the confidence on the transformer load-management reports was low in the past. Intelligent equipment and advanced information and communication technology are now being integrated into distribution networks at an unprecedented speed. The technology advancement provides an opportunity to enhance transformer load modeling and management. In this paper, a framework using synchronized measurements obtained from different information systems via a utility's enterprise service bus is proposed to calculate the actual load profiles of distribution transformers and reflect changing system conditions. Network analyses resulting from using improved system models based on distribution state estimation allow the system operators and designers to make informed decisions concerning where new loads can be added and when new transformer capacity must be included. [ABSTRACT FROM PUBLISHER]

A DC-DC buck converter using dual-path-feedback techniques is proposed in this paper. The proposed converter is fabricated with TSMC 0.35 μm DPQM CMOS process. The structure of the proposed buck converter includes the voltage-feedback and current-feedback design to improve load regulation and achieve high efficiency. The experimental results show the maximum power efficiency is about 94 %. The load regulation is 6.22 (ppm/mA) when the load current changes from 0 to 300 mA. With a 3.6 V input power supply, the proposed buck converter provides an adjustable power output with a voltage range is from 1 to 3 V precisely. [ABSTRACT FROM AUTHOR]

This study mainly focuses on the development of intelligent forecasting structures via a similar time method with historical load change rates for the hourly, daily and monthly load forecasting simultaneously based on the basic frameworks of fuzzy neural network (FNN) and particle swarm optimization (PSO). In the regulative aspect of network parameters, conventional back-propagation (BP) and PSO tuning algorithms are used, and varied learning rates are designed in the sense of discrete-time Lyapunov stability theory. The performance comparisons of different intelligent forecasting structures including neural network (NN) structure with BP tuning algorithm (NN-BP), FNN structure with BP tuning algorithm (FNN-BP), FNN structure with BP tuning algorithm and varied learning rates (FNN-BP-V), FNN structure with PSO tuning algorithm (FNN-PSO) and newly-designed adaptive PSO (APSO) structure are verified by numerical simulations. In order to verify the effectiveness of the superior APSO forecasting structure in practical energy-saving load regulation, the load forecasting during every 15 min is also given, and its result is used to manipulate the scheduled unloading control of a real case in Taiwan campus. [ABSTRACT FROM AUTHOR]

DC microgrids are gaining popularity due to high efficiency, high reliability, and easy interconnection of renewable sources as compared to the ac system. Control objectives of dc microgrid are: 1) to ensure equal load sharing (in per unit) among sources; and 2) to maintain low-voltage regulation of the system. Conventional droop controllers are not effective in achieving both the aforementioned objectives simultaneously. Reasons for this are identified to be the error in nominal voltages and load distribution. Though centralized controller achieves these objectives, it requires high-speed communication and offers less reliability due to single point of failure. To address these limitations, this paper proposes a new decentralized controller for dc microgrid. Key advantages are high reliability, low-voltage regulation, and equal load sharing, utilizing low-bandwidth communication. To evaluate the dynamic performance, mathematical model of the scheme is derived. Stability of the system is evaluated by eigenvalue analysis. The effectiveness of the scheme is verified through a detailed simulation study. To confirm the viability of the scheme, experimental studies are carried out on a laboratory prototype developed for this purpose. Controller area network protocol is utilized to achieve communication between the sources. [ABSTRACT FROM AUTHOR]

This paper introduces an approach to dc power delivery that reduces power loss by minimizing redundant energy conversion. Existing power distribution techniques tend to increase the number of cascaded conversion stages, which limits overall efficiency. Differential power processing enables independent load regulation, while processing only a small portion of the total load power. Bulk power conversion occurs once. Load voltage domains are connected in series, and differential converters act as controllable current sources to regulate intermediate nodes. This enables independent, low supply voltages, which can reduce system energy consumption, especially in digital circuits and solid-state lighting. Since differential voltage regulators process a fraction of the load power, decreased size, cost, and conversion losses are attainable. Under balanced load conditions, secondary differential converters do not process any power. This paper analyzes several differential power delivery architectures that can be applied to homogenous and heterogeneous loads at various levels: chip, board, blade, etc. A variety of operating conditions for a test system with four series voltage domains are examined in simulation and verified with experimental hardware. Results in a reference application show a 7–8% decrease in input power and 6–7 percentage points increase in overall conversion efficiency as compared to a conventional cascaded approach. [ABSTRACT FROM AUTHOR]

Low dropout regulators are one of the most important factures of many portable devices. Thus, consider to the complexity of the circuits and increasing request for portable devices, for increasing battery life and minimizing supply noise, regulators with high efficiency, low output noise and small size is required. In this paper, two methods to improve the efficiency of LDO regulators is proposed. First method is increasing gain of the error amplifier by using cascode technique, to improve steady-state specification. Second method is using a simple subtractor circuit between error amplifier and pass transistor of LDO regulator to improve power supply rejection, slew-rate and steady-state specification. In addition, both methods are used to achieve area efficiency replacing MIM capacitors with MOS transistor. These low dropout regulators have been simulated in TSMC 0.18 μm CMOS process. Simulation results show enhancement settling time, good line and load regulation and power supply in compare with others LDO regulators. [ABSTRACT FROM AUTHOR]

A differential-in differential-out error amplifier and a load regulation enhancement mechanism are proposed in the buck converter that aims to improve load regulation and noise immunity. By using the proportional compensator in the proposed converter, there is no need of external compensation components in this design. As a result, a compact-size and high-performance dc-dc buck converter can be guaranteed. Experimental results show that load regulation can be improved from 0.5 to 0.025 mV/mA. The test chip was fabricated by 0.25 μm CMOS process and occupied 1.65 mm active silicon area. [ABSTRACT FROM AUTHOR]

A low-power 0.18 μm CMOS capacitor-less low-dropout voltage regulator for battery-operated portable devices is presented. A highgain telescopic cascode-compensated amplifier is used to attain a stable topology with good static performances, while a very simple dynamic biasing circuit significantly enhances transient performances with no quiescent current penalty. Post-layout results show a 1.8 V output voltage from a 3.6 to 1.9 V battery input voltage, delivering a 50 mA load current over a 100 pF load. The quiescent current is only 7 μA, the line and load regulations are, respectively, 0.039 mV/V and 0.17 mV/mA, and settling times are lower than 3.9 μs at full load transient. [ABSTRACT FROM AUTHOR]

Non-Intrusive Load Monitoring (NILM) provides a way to acquire detailed energy consumption and appliance operation status through a single sensor, which has been proven to save energy. Further, besides load disaggregation, advanced applications (e.g., demand response) need to recognize on/off events of appliances instantly. In order to shorten the time delay for users to acquire the event information, it is necessary to analyze extremely short period electrical signals. However, the features of those signals are easily submerged in complex background loads, especially in cross-user scenarios. Through experiments and observations, it can be found that the feature of background loads is almost stationary in a short time. On the basis of this result, this paper provides a novel model called the concatenate convolutional neural network to separate the feature of the target load from the load mixed with the background. For the cross-user test on the UK Domestic Appliance-Level Electricity dataset (UK-DALE), it turns out that the proposed model remarkably improves accuracy, robustness, and generalization of load recognition. In addition, it also provides significant improvements in energy disaggregation compared with the state-of-the-art. [ABSTRACT FROM AUTHOR]

Robust operation of load management control for a building is important to account for the uncertainty in demand as well as any distributed sources connected to the building. This paper discussed an online load management control solution using distributed energy storage (DES) while considering uncertainties in demand as well as DES to reduce peak demand for economic benefit. In recent years' demand-side management (DSM) solutions using DES such as stationary energy management system (BESS) and plugged-in electric vehicles (PEV) have been popularised. Most of these solutions resort to deterministic load forecast for the day ahead energy scheduling and do not consider the uncertainties in demand and DES making these solutions vulnerable to uncertainties. This study presents an online density demand forecast, k-means clustering of PEV groups and stochastic optimisation for robust operation of BESS and PEV for a building. The proposed method accounts for uncertainties in demand and uncertainties due to mobile energy storage as presented by PEVs. For a case study, we used data obtained from an industrial site in South Korea. The verified results as compared to other methods with a deterministic approach prove the solution is efficient and robust. [ABSTRACT FROM AUTHOR]