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The inertia constant of an electric power system determines the frequency behavior immediately after a disturbance. The increasing penetration of renewable energy sources is leading to a smaller and more variable inertia, thereby compromising the frequency stability of modern grids. Therefore, a real-time estimation of the inertia would be beneficial for grid operators, as they would become more aware of the frequency stability of their grids. This paper focuses on an estimation method based on the extended Kalman filter. To be started, such method requires the knowledge of the time of disturbance, which, in turn, needs to be estimated. The purpose of this paper is to evaluate the sensitivity of the extended Kalman filter based inertia estimation method to the assumed time of disturbance.

This paper presents an integrated circuit solution for multi-channel neuromuscular electrical stimulation (NMES). The stimulation waveform is digitally controlled and supports monophasic pulses, and both symmetric and asymmetric biphasic pulses. In addition, the current intensity is programmable, ranging from 0 mA to 31 mA with 5-bit resolution. The integrated circuit occupies an area of 1 mm2and it is designed and simulated in a 180 nm high-voltage CMOS technology. The circuits are powered using standard 1.8 V and 3.3 V power supplies for the digital control and digital-to-analog converter, and a single 40 V power supply for the output drivers. The simulation results show that the design achieves a voltage compliance of up to 35 V, meeting the requirements for NMES applications while offering a very compact and scalable solution. Part of proceedings: ISBN 978-1-7281-7204-0QC 20220912

This paper analyzes improvement criteria for the service continuity, the design, construction and verification of electrical systems in road tunnels. Fire prevention in road tunnels must satisfy the primary safety objectives relating to the people safeguarding and the assets protection against fire risks, complying with the sustainability criterion. At this aim, design parameters are identified as the temperature exposure levels (TEL) and the necessary equipment qualification categories (EQC) that characterize their thermal resilience and adequacy to severe environments. Primary objective is to guarantee the service continuity of electrical systems in ordinary operation and in emergency during and after a fire. Effective measures are to apply the zoning and layering criteria of roadway tunnels that suggest specific system topologies as the special “brush” distribution as confirmed by tests of fire simulations. The knowledge of these results help to limit the feeling of uncontrolled panic in people who are in the tunnel during a fire event. A detailed analysis of the results can assist the operators of the intervention services in the decision making of rescue and extinguishing operations.

A workshop on power system harmonics was organized in Stockholm in January 2014. On the agenda was among others a discussion on what are the main issues on harmonics at the moment and in the near future. The results of this discussion are summarized in this paper and some of the issues are discussed in more detail in this paper and in its companion paper. This paper discusses emission from wind and solar power as well as advantages and disadvantages of active and passive filters.

A workshop on power system harmonics was organized in Stockholm in January 2014. On the agenda was among others a discussion on what are the main issues on harmonics at the moment and in the near future. Some of the issues discussed at that workshop are presented in this paper and its companion paper. In this paper the following issues will be addressed: the appearance of emission at higher frequencies (supraharmonics); the need for new and improved standards; measurement issues and data analysis.

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Renewable energies has shown to be a promising solution to improve the energy injected to the electrical network. However, the lack of inertia in such systems have proven to affect the grid stability, as those technologies operate as current controlled sources they not provide grid support functionalities. This issue has fostered the implementation of new control strategies to enable power plants to provide a coordinated action to support some inertia and damping into the system. Synchronous controllers have proven to be an excellent option for distributed renewable generation, which allows to emulate the inertia of a synchronous generators, having a better interaction between the power converter and the electrical grid. However, the implementation of such control strategies require power converter to be smarter and include advanced control algorithms. In this paper, a new control strategy to control different distributed generation units to have a coordinated action in front of the electrical grid is presented, reducing the cost of the power converter by extracting the synchronous control from the internal controller and replacing in by a central synchronous controller.

In the paper the probabilistic evaluation of wind farm transient stability is discussed and an on-line statistical inference approach for this evaluation is proposed. More specifically, the paper deals with the transient stability aspect of wind generation integration into power system, starting from the observation that the impact of distributed generation is able to affect the overall dynamic behavior; in this framework, the paper is devoted to the definition and evaluation of the transient stability probability (TSP). TSP is defined and evaluated by taking into account the random nature of both the prime mover power and the fault clearing time. Once that the probabilistic definition and assessment are illustrated, the paper aim is to establish a proper methodology for an investigation of the transient stability probability and its statistical estimation based upon the fact that the parameters involved are not known, but have to be estimated. Without loss of generality, as motivated by physical and mathematical reasons in the paper, the lognormal distribution assumption is adopted for both fault clearing time (FCT) and the critical clearing time (CCT), which allows a suitable way to handle the stochastic nature of the various parameters and to assess the TSP, once that the statistical parameters (typically, the means and variances of FCT and CCT). Some considerations are effected in order to justify this assumption with respect to the various technologies for wind farm. Hence, point and interval estimations of the TSP can be derived, based upon a suitable Beta probability distribution. In the final part of the paper, a numerical application is provided in order to show the easy feasibility of the proposed methodology.

Hybrid electric vehicles (HEVs) are equipped with multiple power sources for improving the efficiency and performance of their power supply system. An energy management (EM) strategy is needed to optimize the internal power flows and satisfy the driver's power demand. To achieve maximum fuel profits from EM, many solution methods have been presented. Optimal solution methods are typically not feasible in an online application due to their computational demand and their need to have a priori knowledge about future vehicle power demand. In this paper, an online EM strategy is presented with the ability to mimic the optimal solution but without using a priori road information. Rather than solving a mathematical optimization problem, the methodology concentrates on a physical explanation about when to produce, consume, and store electric power. This immediately reveals the vehicle characteristics that are important for EM. It is shown that this concept applies to many existing HEVs as well as possible future vehicle configurations. Since the method only focuses on typical vehicle characteristics, the underlying algorithm requires minor computational effort and can be executed in real time. Clear directions for online implementation are given in this paper. A parallel HEV with a 5-kW integrated starter/generator (ISG) is selected to demonstrate the performance of the EM strategy. Simulation results indicate that the proposed EM strategy exhibits similar behavior as an optimal solution obtained from dynamic programming. Profits in fuel economy primarily arise from engine stop/start and energy obtained during regenerative braking. This latter energy is preferably used for pure electric propulsion where the internal combustion engine is switched off. © 2008 IEEE.

This paper presents a nonlinear control strategy to integrate Battery Energy Storage Systems (BESS) in electrical power systems connected through Voltage Source Converters (VSCs). Exact feedback linearization control technique based on the dynamical model of the system is employed as control strategy. Two VSCs topologies are proposed to control the generated/consumed current by the BESS. The proposed controller allows the charge/discharge of the BESS with either constant current or constant power. The VSC is employed to independently compensate for the active and reactive power from/to the grid to/from the BESS. A radial distribution network modeled in MATLAB/SIMULINK is implemented as a test system to validate the functionality of the controller under two scenarios. © 2018 IEEE.

In this paper the electrical safety of DC urban traction systems is analysed, with particular focus on fault current detection and on dangerous voltages which could arise in case of fault. For the discussion the tram network of Turin, Italy, is used as a case study. Firstly the structure of the DC traction power supply is described; then the safety of the system is analysed, examining possible types of fault. In particular, ground faults inside the substation and along the line are analysed in detail. Fault currents and dangerous voltages are calculated thanks to a simplified circuital model of the traction system. Finally, the consequent risks for the people are examined and some conclusions are presented.

The paper presents a feasible model of architecture for the technical building systems (TBS) particularly suitable for Nearly Zero Energy Buildings (NZEBs). NZEBs are buildings where the energetic consumption are optimized by means of solutions that drastically reduce both electric and thermal demand, while residual required energy has to be provided by local renewable generation. The suggested model aggregates the users around an electric node in a common microgrid in order to reach up the threshold value of electric power and to get a more virtuous and flexible cumulative load profile. The building (or a group of buildings) represents the natural limit of the aggregation of the electric systems, like in the heating systems. Present proposal is a full electric smart micro grid with heating and domestic hot water generated by a centralized electric heat pump system. The renewable energy is provided by a photovoltaic field. The authors suggest to control the whole electric demand of the building by exploiting its thermal inertia as an energy storage by forcing both local and central set points of heating and air conditioning systems and time shifting opportunities of smart appliances. A case study is presented.

Yıldız, Merih (Dogus Author) -- Minaei, Shahram (Dogus Author) In this paper an NMOS based sinusoidal oscillator is presented. The circuit is constructed with voltage-mode (VM) NMOS-based analog adder and subtractor circuits which respectively perform V1+V2 and V1-V2 operations on the input voltages. The most important feature of the proposed circuits is their extremely simple structures containing only twelve NMOS transistors (six for the adder, six for the subtractor). Another significant advantage of the proposed circuits is that no external passive components are being used. The post-layout simulations of the proposed oscillator circuit have been executed using TSMC 0.25 μm process parameters with ±1.25 V power supply voltage.

A topic of interest within the microgrid (MG) community is to achieve accurate sharing of active and reactive power among voltage source inverters (VSI) working in parallel while keeping the voltage frequency and amplitude stable, and close to a given reference. This problem has been mainly solved by the so-called frequency and voltage droop controllers that are local control loops implemented in each VSI. However, since they introduce a frequency and amplitude deviation, a secondary integral-like control loop using a communication system is usually deployed to enable each VSI to cancel the deviations. This paper evaluates two secondary control implementations of the frequency restoration with respect to properties of the communication system. Networked control applications are subject to known problems that are inherent to the use of a communication system such as message losses or varying sampling/transmission intervals, to name a few. The performance analysis reveals that control policies should be designed accounting also for the properties of the communication system. Otherwise, unexpected results violating the control specifications may appear.

This paper investigates the maximum throughput for a rechargeable secondary user (SU) sharing the spectrum with a primary user (PU) plugged to a reliable power supply. The SU maintains a finite energy queue and harvests energy from natural resources, e.g., solar, wind and acoustic noise. We propose a probabilistic access strategy by the SU based on the number of packets at its energy queue. We investigate the effect of the energy arrival rate, the amount of energy per energy packet, and the capacity of the energy queue on the SU throughput under fading channels. Results reveal that the proposed access strategy can enhance the performance of the SU., arXiv admin note: text overlap with arXiv:1407.7267

The More Electric Aircraft power system is characterized by variable supply frequency, in general between 360Hz and 900Hz. All equipment on board the aircraft have to operate delivering high performance under this variable frequency condition. In particular, power electronic converters need accurate control algorithms able to track the fundamental phase and frequency in real time, both in normal and unusual conditions. Phase Locked Loop (PLL) based algorithms are commonly used in traditional single and three phase power systems to provide phase and frequency estimations of the supply. Despite the simplicity of those algorithms, large estimation errors can arise when power supply voltage has variable frequency or amplitude, presents unbalances or is polluted with harmonics. To improve the quality of the phase and frequency real-time estimations, a robust PLL algorithm, based on a prediction-correction filter, is presented in this paper and compared with a Discrete Fourier Transform (DFT) based procedure. The performances of the two algorithms, implemented in a floating-point DSP, have been compared through an experimental validation obtained on a laboratory power converter prototype.

Multi-terminal VSC-HVDC transmission is a promising solution to transport energy from the generating plants to the distribution stations, and the number and size of the corresponding power grids is expected to increase in the next years. Such a system presents challenging control problems that, so far, have been approached with classical control techniques. However, large scale systems of interconnected nodes fall within the framework of the emerging field of complex networks. This paper analyzes the stability of multi-terminal VSC-HVDC systems from a complex dynamical network perspective, and provides sufficient conditions to ensure bounded synchronization of its trajectories. The obtained results are validated via numerical simulations.

This paper proposes a method to utilize distributed energy resources (DERs) to provide reactive power support for voltage control in electric power systems. Rather than controlling each of these resources directly, a distributed control algorithm is developed in which a leader node sends a request for reactive power to a few DERs that it can directly communicate with. Then through an iterative algorithm, the initial request is distributed among all DERs so that they collectively fulfill the leader node's request. A case study illustrating this method is presented. © 2011 IEEE.

The increasing penetration of generation power plants based on renewable energies in the electrical networks has boosted the number of systems connected to the grid. In this scenario the microgrid, providing advanced functionalities to improve the stability and operation of the network, have become very popular. In this paper a control strategy for the microgrid management is presented. The proposed system improves the performance of microgrids and its interaction with the main network, or another microgrid, under grid voltage transients. This technique gives rise to a simple and robust control scheme to ensure the appropriate microgrid disconnection from the main grid. In the following the control algorithm for the intelligent connection agent will be shown, and the grid synchronization system, as well as the voltage and current control loops will be detailed. Finally simulation results obtained using the MATLAB/Simulink & Psim platform will be presented and discussed.

Unmanned Aerial System (UAS) are becoming viable aerial platforms for civil oriented monitoring applications. However, in most cases the selected UAS platforms are ad-hoc vehicles which include highly heterogeneous avionics. Avionics on-board may be COSTS modules that have highly different non-standard power requirements. Additionally, the available power sources in these UAS may be fairly limited or even restricted to battery units. This paper introduces the ELectrical Manager Service (ELMS), an on-board system in charge of offering a flexible power supply architecture that supports minimal reconfiguration overhead for a wide variety of UAS missions. The ELMS Service is designed to offer a continuous monitoring of the state of the power network, and a coherent and controlled response in front of power supply contingencies. The ELMS will monitor the batteries and generator status, the power consumption of the avionics and other systems, manage the connection/disconnections of systems, and provide power availability estimations. The ELMS Service is part of an architecture designed to facilitate the execution of UAS civil missions, the USAL. The USAL is built as a set of cooperating services in a purely distributed and scalable architecture with a middleware that manages inter-service communications.

In this paper, we propose an on-line monitoring scheme to detect lost lines and bus load changes on an embeded power system. The proposed monitoring scheme does not rely on classical estimation schemes used in power systems; instead, it monitors, a carefully selected state dependant signal, using an on-line observer. A special emphasis is placed on distinguishability between the two considered events. Numerical simulations validate the developed theory around the monitoring scheme. © 2006 IEEE. 3 1922 1927

Standard sparsity-based algorithms used in power system applications need to be restructured for efficient vectorization due to the extremely short vectors processed. Further, intrinsic architectural features of vector computers such as chaining and sectioning should also be exploited for utmost performance. This paper presents novel data storage schemes and vectorization algorithms that resolve the recurrence problem, exploit chaining and minimize the number of indirect element selections in the repeated solution of sparse linear system of equations widely encountered in various power system problems. The proposed schemes are also applied and experimented for the vectorization of power mismatch calculations arising in the solution phase of fast decoupled load flow which involves typical repeated sparse power network computations. The relative performances of the proposed and existing vectorization schemes are evaluated, both theoretically and experimentally on an IBM 3090/VF computer. >

Date of Conference: 12-14 April 1994 Conference Name: 7th Mediterranean Electrotechnical Conference, MELECON 1994 Vector processors have promised an enormous increase in computing speed for computationally intensive and time-critical power system problems which require the repeated solution of sparse linear equations. Due to short vectors processed in these applications, standard sparsity-based algorithms need to be restructured for efficient vectorization. This paper presents a novel data storage scheme and an efficient vectorization algorithm that exploits the intrinsic architectural features of vector computers such as sectioning and chaining. As the benchmark, the solution phase of the Fast Decoupled Load Flow algorithm is used in simulations. The relative performances of the proposed and existing vectorization schemes are evaluated, both theoretically and experimentally, on IBM 3090/VF.

Synergies between multiple energy vectors can support decarbonization of local energy islands and, at the same time, relieve stress from the electricity grid. Multi-vector energy systems offer flexibility to integrate variable and economic local energy generation. However, the implementation and operation of multi-vector energy systems face technical, societal and business-related challenges. This paper identifies these challenges and proposes different tools to tackle them. These tools are to be developed in the E-LAND project funded by European Union under the H2020 scheme. Special focus of the paper is on developing a method for optimal planning and operation of multi-vector grid considering robustness. Another novelty of technical tool lies in making scheduling decisions on long-term and short-term storage considering demand response as flexibility resource. By combining technological, societal and business tools, the project expects to create multi-vector energy systems accepted by citizens and with viable business model E-LAND project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 824388

This paper develops a numerical technique for solving the problem of periodic ferroresonant overvoltages in a power system. The system is modeled as a set of nonlinear ordinary differential equations, whose periodical solutions are found by a numerical algorithm based on Galerkin's method. It is shown that this approach takes into account the various aspects of ferroresonance phenomena, i. e. harmonic as well as even or odd order subharmonic oscillations. Results computed by this technique are presented and discussed.