With the development of power market demand response capability, load aggregators play a more important role in the coordination between power grid and users. They have a wealth of user side business data resources related to user demand, load management and equipment operation. By building a business model of business data resource utilization and innovating the content and mode of intelligent power service, it can guide the friendly interaction between power supply, power grid and load, effectively improve the flexibility of power grid regulation, speed up demand response and refine load management. In view of the current situation of insufficient utilization of business resources, low user participation and imperfect business model, this paper analyzes the process of home appliance enterprises participating in peak shaving and valley filling (PSVF) as load aggregators, and expounds the relationship between the participants in the power market; a business service model of smart home appliance participating in PSVF based on cloud platform is put forward; the market value created by home appliance business resources for each participant under the joint action of market-oriented means, information technology and power consumption technology is discussed, and typical business scenarios are listed; taking Haier business resource analysis as an example, the feasibility of the proposed business model in innovating the content and value realization of intelligent power consumption services is proved.

Distributed power delivery is blooming in SoC power system because the fine-grained power management needs separate power sources to adjust each voltage island dynamically. In addition, dedicated power sources for critical circuit blocks can achieve better signal integrity. To extensively utilize the power modules when they are redundant and idle, this work applies the cooperation concept in SoC power management. The key controller is a mixed-signal estimator that executes the intelligent procedures, like real-time swap the power module depending on its loading and healthy condition, automatically configure the power system with phase interleaving, and support all the peripheral functions. To demonstrate the proposed concept, a prototype chip for voltage down-conversion is implemented. This chip contains four switched-inductor converter modules to emulate the cooperative power network. Each module is small therefore the power efficiency is not optimal for the heavy load. With the cooperation between power modules, the power efficiency is 88% for 300mA load, that is 8.5% higher than the single module operation.

Analysis of security governed by dynamics of power systems, which we refer to as dynamic security analysis, is a primary but challenging task because of its hybrid nature, that is, nonlinear continuous-time dynamics integrated with discrete switchings. In this paper, we formulate this analysis problem as checking the reachability of a mathematical model representing dynamic performances of a target power system. We then propose a computational approach to the analysis based on the so-called RRT (Rapidly-exploring Random Tree) algorithm. This algorithm searches for a feasible trajectory connecting an initial state possibly at a lower security level and a target set with a desirable higher security level. One advantage of the proposed approach is that it derives a concrete control strategy to guarantee the desirable security level if the feasible trajectory is found. The performance and effectiveness of the proposed approach are demonstrated by applying it to two running examples on power system studies: single machine-infinite system and two-area system for frequency control problem.

Most research projects with respect to energy saving are trying to improve power efficiency and are using software to manage the power systems in the power on mode; but in our design, we modify the original Suspend to RAM mode-S3 state, which is the 3rd system state as defined by the ACPI specification, in order to reduce power consumption. We've redesigned the control circuit to save power while a PC is in the standby mode. First, we re-examine the entire circuit in the standby mode, and clarify which chip is used both to wake up the system and to turn off all unnecessary standby power previously used by the chips. Secondly, we redesign the power sequence and use an additional chip to control the system power supply, to allow a PC's normal system's operation to turn off the unnecessary power control chips. Third, in order to save power supply in the standby mode, we have simplified the multiple remote wake-up mechanism to control the remote boot device. The improvement shows that our design reduced power consumption to 0.21W from the original 0.56W while all the remote wake-up functions are disabled; and consumes 0.42W when using multiple remote wake-up functions. We implement the above modification from the legacy S3 state, and obtain lower power consumption. In order to distinguish the standby states, we name the modified S3 state as Deep S3 state.

This paper proposes the physical architecture of an electric power system with multiple homes. The notion of home is a unit of small-scale power system that includes local energy source, energy storage, load, power conversion circuits, and control systems. An entire power system consists of multiple homes that are interconnected via a distribution network and that are connected to the commercial power grid. The interconnection is autonomously achieved with a recently developed technology of grid-connected inverters. A mathematical model of slow dynamics of the power system is also developed in this paper. The developed model enables the evaluation of steady and transient characteristics of power systems.

In this letter, a design of inverse discrete cosine transform for energy-efficient watermarking mechanism based on DS-CDMA with significant energy and area reduction is presented. Taking advantage of converged input data value set as a precomputation concept, the proposed one-dimensional IDCT is a multiplierless hardware which differs from Loeffler architecture and has benefits of low complexity and low power consumption. The experimental results show that our design can reduce 85.2% energy consumption and 58.6% area. Various spectrum and spatial attacks are also tested to corroborate the robustness.

This letter presents an experiment for estimating accurate state in distributed power systems. This letter employs a technique that combines a projected Jacobi method with a parallel dual-type method to solve the distributed state estimation with constraints problems. Via numerous tests, this letter demonstrates the efficiency of the proposed method on the IEEE 118-bus with four subsystems in a PC network.

Analysis of cascading outages in power systems is important for understanding why large blackouts emerge and how to prevent them. Cascading outages are complex dynamics of power systems, and one cause of them is the interaction between swing dynamics of synchronous machines and protection operation of relays and circuit breakers. This paper uses hybrid dynamical systems as a mathematical model for cascading outages caused by the interaction. Hybrid dynamical systems can combine families of flows describing swing dynamics with switching rules that are based on protection operation. This paper refers to data on a cascading outage in the September 2003 blackout in Italy and shows a hybrid dynamical system by which propagation of outages reproduced is consistent with the data. This result suggests that hybrid dynamical systems can provide an effective model for the analysis of cascading outages in power systems.

This paper presents a study to estimate the composition of an electric load, i.e. to determine the amount of each load class by the direct measurements of the total electric current waveform from instrument reading. Kalman filter algorithm is applied to estimate the electric load composition on a consumer side of a distributed power system. The electric load supplied from the different voltage level by using a non-ideal delta-wye transformer is also studied with consideration of the practical environment for a distributed power system.

Synchronization has gained attention in science recently. In electrical engineering, a power network requires generators and loads to be in synchronization. The increase in distributed dc power sources without sophisticated controls has made synchronization more difficult. This paper proposes a synchronous inverter designed for linking distributed power sources within a power network. The linkage inverters should have high confidential characteristics to keep the network stable. The frequency and phase synchronization between synchronous generators in power network has been acheived through power transmission systems. The synchronous inverters contribute in the development of the sophisticated power networks by providing distributed power sources that maintain synchronous operation.

This paper is to investigate the application of fuzzy c-means clustering to the direct identification of coherent synchronous generators in power systems. Because of the conceptual appropriateness and computational simplicity, this approach is essentially a fast and flexible method. At first, the coherency measures are derived from the time-domain responses of generators in order to reveal the relations between any pair of generators. And then they are used as initial element values of the membership matrix in the clustering procedures. An application of the proposed method to the Taiwan power (Taipower) system is demonstrated in an attempt to show the effectiveness of this clustering approach. The effects of short circuit fault locations, operating conditions, data sampling interval, and power system stabilizers are also investigated, as well. The results are compared with those obtained from the similarity relation method. And thus it is found that the presented approach needs less computation time and can directly initialize a clustering process for any number of clusters.

The output limits of the power system stabilizer (PSS) can improve the system damping performance immediately following a large disturbance. Due to non-smooth nonlinearities from the saturation limits, these values cannot be determined by the conventional tuning methods based on linear analysis. Only ad hoc tuning procedures have been used. A nonlinear least squares method, which is the Gauss-Newton optimization algorithm, is used in this paper. The gradient required in the Gauss-Newton method can be computed by applying trajectory sensitivities from the hybrid system model with the differential-algebraic-impulsive-switched (DAIS) structure. The optimal output limits of the PSS tuned by the proposed method are evaluated by time-domain simulation in a multi-machine power system (MMPS).

In this paper, the interpolation line search (ILS) algorithm to find the desirable step length in a numerical optimization method is investigated to determine the optimal saturation limits with non-smooth nonlinearities. The simple steepest descent algorithm is used to illustrate that the ILS algorithm can provide adequate reductions in an objective function at minimal cost with fast convergence. The power system stabilizer (PSS) with output limits is used as an example for a nonlinear controller to be tuned. The efficient computation to implement the ILS algorithm in the steepest descent method is available by using the hybrid system model with the differential-algebraic-impulsive-switched (DAIS) structure. The simulation results are given to show the performance improved by the ILS algorithm.

Multi-swing trajectories, which refer to those trajectories which oscillate several cycles and then become unbounded, has been a nuisance in general simulation programs for power system stability study since the corresponding transient stability is very difficult to access accurately. In this letter, two possible models are developed to explain possible scenarios of such multi-swing behaviors. Theoretical investigation has strongly indicated a close relationship between multi-swing instability problems and chaotic behaviors of the power system.

Public telephone network have been dramatically changing to IP (Internet Protocol) based network. This paper starts with an overview of the present status of the telecommunications network and the rapid evolution of iDCs (internet Data Centers) now underway. Next, we focus on the existing configurations and the characteristics of power systems for IP equipment and iDCs, and then clarify the cutting-edge technologies for highly reliable powering systems and the advantages of DC power systems. Finally, the paper demonstrates energy-saving activities, and the prospected issues to be solved in the field of power systems for the coming full-fledged IT Age.

This paper discusses stability boundaries in an electric power system with dc transmission based on a differential-algebraic equation (DAE) system. The DAE system is derived to analyze transient stability of the ac/dc power system: the differential equation represents the dynamics of the generator and the dc transmission, and the algebraic equation the active and reactive power relationship between the ac system and the dc transmission. In this paper complete characterization of stability boundaries of stable equilibrium points in the DAE system is derived based on an energy function for the associated singularly perturbed (SP) system. The obtained result completely describes global structures of the stability boundaries in solution space of the DAE system. In addition the characterization is confirmed via several numerical results with a stability boundary.

Stand-alone photovoltaic (PV) power systems are potential power sources for telecommunications equipment especially equipment installed outdoors. To be practical, they must have a high conversion efficiency and a long lifetime. We have proposed a stand-alone photovoltaic power system that uses electric double-layer capacitors (EDLCs) and lead acid batteries as power storage devices. This system smooths out the fluctuations in power generated by the PV array by using the EDLC's charge-and-discharge power; this reduces the number of battery charge-and-discharge cycles. We simulated the system's operating characteristics and evaluated the photovoltaic array mismatching loss, system conversion loss, battery contribution factor, averaged battery state-of-charging, and maximum depth-of-discharging. The results show that the system is effective at reducing the mismatching loss and battery contribution factor, so the system efficiency is expected to be improved by using high conversion efficiency DC-DC converters. Moreover the system can maintain the averaged battery state-of-charging during operation. This indicates that smaller batteries can be used. The maximum depth-of-discharging can be kept lower than in the conventional system. Consequently, the proposed system should have a longer battery lifetime.

C1 class smooth interpolation by a fuzzy reasoning for a small data set is proposed. The drafting technique of a human expert is implemented by using a set of fuzzy rules. The effectiveness of the present method is verified by computer simulations and by applications to the practical interpolation problem in a power system.

The power distribance appeared at a typical electric power system, which can be modeled by a simplified distributed circuit, is discussed. The electric power and the point where its power is injected are then estimated to suppress the power distrbance.