Lossy Power Research Articles

Impasse Surface of Differential–Algebraic Power System Models: An Interpretation Based on Admittance Matrices

The impasse surface is an important concept in the differential-algebraic equation (DAE) model of power systems, which is associated with short-term voltage collapse. This paper establishes a necessary condition for a system trajectory hitting the impasse surface. The condition is in terms of admittance matrices regarding the power network, generators and loads, which specifies the pattern of interaction between those system components that can induce voltage collapse. It applies to generic DAE models featuring high-order synchronous generators, static loads, induction motor loads and lossy power networks. We also identify a class of static load parameters that prevent power systems from hitting the impasse surface; this proves a conjecture made by Hiskens that has been unsolved for decades. Moreover, the obtained results lead to an early indicator of voltage collapse and a novel viewpoint that inductive compensation to the power network has a positive effect on preventing short-term voltage collapse, which are verified via numerical simulations.

An analytical approach for the stability analysis of power networks through Kuramoto oscillators model

In recent years, ensuring stability in power networks has posed a significant challenge for network control engineers, primarily due to the substantial growth in power demand and the complexities involved in integrating renewable energy sources. This study endeavours to augment the existing research by presenting theoretical findings in a practical manner through the introduction of a novel Lyapunov function and the application of LaSalle’s invariance principle to establish an unequivocal and accurate synchronization condition in power networks. The study’s salient contributions include (I) the Fresh approach of utilizing a second-order configuration of asymmetrically networked, dissimilar oscillators; (II) the incorporation of lossy power networks, culminating in non-identical phase delays in the analytical model of the oscillating network; and (III) the introduction of an entirely original Lyapunov function to provide a precise and unambiguous estimation for the region of attraction in power networks. Analytical findings substantiate that network synchronization is assured by the algebraic connectivity of the network graph exceeding a particular threshold value. The study’s transient stability conditions have been authenticated via numerical simulations of the IEEE 39-bus system.

A four‐element 132–140 GHz PA array with 29.7 dBm EIRP in 0.13‐µm SiGe technology

AbstractThis paper presents a 132–140 GHz power amplifier (PA) array in 0.13‐µm SiGe BiCMOS technology. The four dielectric‐loaded end‐fire antennas are integrated with the PA array on chip. With the absence of the lossy power combining networks at the output, the presented PA array achieves a measured maximal effective isotropic radiated power of 29.7 dBm. The array size is only 6.14 × 2.49 mm2 and consumes 5.16 W from a single 4 V DC supply.

Multistability and anomalies in oscillator models of lossy power grids

The analysis of dissipatively coupled oscillators is challenging and highly relevant in power grids. Standard mathematical methods are not applicable, due to the lack of network symmetry induced by dissipative couplings. Here we demonstrate a close correspondence between stable synchronous states in dissipatively coupled oscillators, and the winding partition of their state space, a geometric notion induced by the network topology. Leveraging this winding partition, we accompany this article with an algorithms to compute all synchronous solutions of complex networks of dissipatively coupled oscillators. These geometric and computational tools allow us to identify anomalous behaviors of lossy networked systems. Counterintuitively, we show that loop flows and dissipation can increase the system’s transfer capacity, and that dissipation can promote multistability. We apply our geometric framework to compute power flows on the IEEE RTS-96 test system, where we identify two high voltage solutions with distinct loop flows.

Study on FeSiAl magnetic powder core coated with nano-Y2O3 and its influence on magnetic properties

The microstructure and magnetic properties of the FeSiAl /phosphoric acid/nano-Y2O3/kaolin soft magnetic composites were investigated in this article. The morphology and structure were characterized by SEM, EDS, XRD, DSC, and XPS. The surface of FeSiAl powder particles was densely and uniformly coated with a phosphoric acid/nano-Y2O3/kaolin insulating coating. It was discovered that nano-Y2O3 played a dominant role in the coating process. Using a precision magnetic analyzer and lossy power tester, the effective permeability, quality factor, DC bias performance, and the core loss of the FeSiAl/phosphoric acid/nano-Y2O3/kaolin SMCs after pressing and annealing were computed and examined. The results show that nano-Y2O3 can improve the quality factor and DC bias performance of the powder core, but leads to a reduction in magnetic permeability and the core loss is also a little high. This behavior may be caused by the competition mechanism: nano-Y2O3 lowers the magnetic coupling between FeSiAl particles, resulting in a decrease in permeability and an increase in the core loss. When the content of nano-Y2O3 is 5 wt%, the comprehensive magnetoelectric performance is good (ue=21.04, at f =100 kHz; Pcv = 1555.13 mW/cm3, at f = 50 kHz; Q = 150.25, at f = 70 kHz; at Bm = 1000 Gs). The effects of nano-Y2O3 coating on the permeability and the loss of FeSiAl SMCs will be a major focus of future research and development.

Some Notes on Two Tests for Stability in Lossy Power Systems

Analysis of the small-signal stability of power system is commonly based on the swing equation model. Due to the special structure of the power grid swing equations, an equilibrium set corresponding to a so-called frequency equilibrium has to be analyzed. We present two new and short proofs for two tests by Skar concerning both the nonuniformly and the uniformly damped system. Based on the latter we derive a simple stability test for uniformly damped systems, which does not rely on eigenvalue computations. The nonhyperbolicity of the equilibria in original coordinates is tackled by the concept of normally hyperbolic invariant manifolds. The derivations are completely based on the theory of quadratic pencils.

Performance Evaluation for the Authenticity Verification Method of Evidence Images using Lossy Compression Characteristics and Power Spectrum Density

Performance Evaluation for the Authenticity Verification Method of Evidence Images using Lossy Compression Characteristics and Power Spectrum Density

Multistability in lossy power grids and oscillator networks.

Networks of phase oscillators are studied in various contexts, in particular, in the modeling of the electric power grid. A functional grid corresponds to a stable steady state such that any bifurcation can have catastrophic consequences up to a blackout. Also, the existence of multiple steady states is undesirable as it can lead to transitions or circulatory flows. Despite the high practical importance there is still no general theory of the existence and uniqueness of steady states in such systems. Analytic results are mostly limited to grids without Ohmic losses. In this article, we introduce a method to systematically construct the solutions of the real power load-flow equations in the presence of Ohmic losses and explicitly compute them for tree and ring networks. We investigate different mechanisms leading to multistability and discuss the impact of Ohmic losses on the existence of solutions.

A Deployable LPWAN Platform for Low-Cost and Energy-Constrained IoT Applications.

Many commercial platforms for fast prototyping have gained support for lpwan technologies. However, these solutions do not meet the low-cost and low-power requirements for a large-scale distribution of battery-powered sensor nodes. This paper presents the design, realization and validation of an open-source lpwan versatile platform. Energy and cost are considered key constraints for this hardware design. A power-efficient LoRa radio interface is implemented by hosting MAC functionality on the application microcontroller, eliminating the need for a modem. In the system architecture, power and cost savings are obtained by omitting and controlling lossy power circuitry. The resulting platform allows entry-level prototyping, while featuring an ultra-low sleep power of . This makes lpwan sensor applications accessible in domains that would otherwise require custom hardware development. The proposed design is validated by an illustrative but functional example of sensor nodes deployed in the field.

Transient stability assessment of large lossy power systems

Stability assessment of a lossy power system during a transient is challenging because of the stringent time limit for a conclusion to reliably support protection functions. A coverage-based stability assessment is pursued with focus on resolving computation and scalability issues. This approach involves online tracking of each generator's electromechanical state using a local quasi-steady-state sinusoidal measurement model, and determining whether the state is enclosed in an offline-computed post-fault region of attraction (RoA) at the time the RoA is established by a protection action. The RoA is numerically estimated offline with a scalable ellipsoidal expansion algorithm, and the need for the expansion is delineated. The approach to transient stability assessment is tested on a lossy 68-bus system subject to transmission faults. The study concludes that the coverage-based stability assessment can offer significant advantages in both reliability and swiftness over the existing assessment methods.

Synchronization of Open Systems: Application to the Lossy Power Grid

The transient stability assessment of multi-machine power systems has been a deeply explored research area in the power system community. The nonlinear nature of the evolving dynamics warrants distinctive control approaches, of which, the time domain simulations and Lyapunov based methods have been majorly applied for assessment and estimating the regions of attraction. However, these methods find limitations when applied to the lossy power grid and demand different modeling procedures. Treating the lossy grid as an open system aids in addressing the challenging problems of assessing their stability and achieving control. In this context, this paper explores the synchronization of open systems through the first order non-uniform Kuramoto model, which renders equivalence between rotor angle stability and phase synchronization of coupled oscillators. This paper investigates the distributed and decentralized control architectures for lossy networks and highlights the contexts under which they are applicable. The mean field Kuramoto model is central to the application of distributed control, whereas a generic framework for developing potential functions using notions of passivity to exercise decentralized control is also discussed.

Stability of synchrony against local intermittent fluctuations in tree-like power grids.

90% of all Renewable Energy Power in Germany is installed in tree-like distribution grids. Intermittent power fluctuations from such sources introduce new dynamics into the lower grid layers. At the same time, distributed resources will have to contribute to stabilize the grid against these fluctuations in the future. In this paper, we model a system of distributed resources as oscillators on a tree-like, lossy power grid and its ability to withstand desynchronization from localized intermittent renewable infeed. We find a remarkable interplay of the network structure and the position of the node at which the fluctuations are fed in. An important precondition for our findings is the presence of losses in distribution grids. Then, the most network central node splits the network into branches with different influence on network stability. Troublemakers, i.e., nodes at which fluctuations are especially exciting the grid, tend to be downstream branches with high net power outflow. For low coupling strength, we also find branches of nodes vulnerable to fluctuations anywhere in the network. These network regions can be predicted at high confidence using an eigenvector based network measure taking the turbulent nature of perturbations into account. While we focus here on tree-like networks, the observed effects also appear, albeit less pronounced, for weakly meshed grids. On the other hand, the observed effects disappear for lossless power grids often studied in the complex system literature.

Wireless charging for weighted energy balance in populations of mobile peers

Wireless energy transfer is an emerging technology that is used in networks of battery-powered devices in order to deliver energy and keep the network functional. Existing state-of-the-art studies have mainly focused on applying this technology on networks of relatively strong computational and communicational capabilities (wireless sensor networks, ad-hoc networks); also they assume energy transfer from special chargers to regular network nodes. Different from these works, we study how to efficiently transfer energy wirelessly in populations of battery-limited devices, towards prolonging their lifetime. In contrast to the state-of-the-art, we assume a much weaker population of distributed devices which are exchanging energy in a “peer to peer” manner with each other, without any special charger nodes. We address a quite general case of diverse energy levels and priorities in the network and study the problem of how the system can efficiently reach a weighted energy balance state distributively, under both loss-less and lossy power transfer assumptions. Three protocols are designed, analyzed and evaluated, achieving different performance trade-offs between energy balance quality, convergence time and energy efficiency.

6–18 GHz, 26 W GaN HEMT compact power‐combined non‐uniform distributed amplifier

A 6-18 GHz gallium nitride (GaN) non-uniform distributed amplifier (NDA) monolithic microwave integrated circuit with high power density is implemented with compact four-way combined power. The drain lines and gate lines are shared among the combined NDAs. Sharing drain (or gate) lines reduces the drain (or gate) line length by half, while keeping the same characteristic impedances and eliminates bulky and lossy power combiners, such as Wilkinson combiners. The proposed four-way NDA was fabricated using a commercial 0.25 μm GaN high electron mobility transistor (HEMT) process. It shows average continuous wave output power of 20.8 W and average associated gain of 10.7 dB from 6 to 18 GHz under 33 V drain bias. When pulsed input power and pulsed DC bias are simultaneously supplied to the NDA, the output power increases to 26 W, on average. To the best of the authors' knowledge, the highest RF power and power density among the reported GaN power amplifiers with an octave bandwidth higher than the Ku-band is represented in this work.

Effects of Deposition Process on Poly-Si Microscale Energy Harvesting Systems: A Simulation Study

In this paper, the feasibility of a low-temperature polysilicon (LTPS) microscale energy harvester for a wireless sensor node is investigated. For that purpose, two device-level models for the LTPS solar cell and thin-film transistors are proposed and employed in system-level evaluation of an energy harvesting system. The results of our analysis indicate that: 1) the maximum power operating point for the solar cell is different when connected to a lossy power converter; 2) increasing the average grain size of the LTPS film can reduce the circuit area by 20 times, while increasing the output power by 6%; and 3) the proposed bottom–up approach enables the designers to identify system bottlenecks and improve the performance accordingly.

Amorphous Silicon Solar Vivaldi Antenna

An ultrawideband solar Vivaldi antenna is proposed. Cut from amorphous silicon cells, it maintains a peak power at 4.25 V, which overcomes a need for lossy power management components. The wireless communications device can yield solar energy or function as a rectenna for dual-source energy harvesting. The solar Vivaldi performs with 0.5-2.8 dBi gain from 0.95-2.45 GHz , and in rectenna mode, it covers three bands for wireless energy scavenging.

Millimetre‐wave broadband waveguide‐based power combiner using lossy planar lines

A lossy waveguide-based power combiner is proposed for broadband low-loss symmetrically combining with good port matching and isolation at millimetre-wave frequencies. In the combiner, lossy planar transmission lines are used to provide attenuation to even-mode excitations and to achieve broadband low-loss power combining with good port matching and isolation. The experimental results show that the lossy waveguide-based power combiner has a loss of about 0.14 dB and a reflection coefficient and isolation of about –15 dB in 26.5–40 GHz, respectively. The lossy waveguide-based power combiner can be used in a multi-way power amplifying–combining system to obtain millimetre-wave broadband high solid-state power with high efficiency and good stability.

Mathematical Model for the Determination of Voltage and Current on Lossy Power Transmission Lines

Energy is a basic necessity for the economic development of a nation. There are different forms of energy, but the most important form is the electrical energy. A modern and civilized society is so much dependent on the use of electrical energy. Electrical energy is transmitted by means of transmission lines which deliver bulk power from generating stations to load centers. The industrial development of any nation depends majorly upon the reliability of its interconnected electric power system. Availability of electric energy has been the most powerful vehicle for facilitating economic, industrial and social developments of any nation. When an electric power is generated in sufficient quantities, it needs to be transmitted in bulk to load centers and then distributed to individual consumers in proper form and quality at the lowest possible ecological and economic price. This electric power is transmitted by means of transmission lines. In this paper, we developed mathematical models for the determination of voltage and current on lossy electric power transmission lines. We derived relations which the voltage and current must satisfy on a uniform transmission line. The models contain the primary constants or parameters of the transmission line which include the series resistance (R), the shunt conductance (G), the inductance (L) and the capacitance (C). Values of these constants are specified per unit length.

A Security-constrained Economic Power Dispatch Technique Using Modified Subgradient Algorithm Based on Feasible Values and Pseudo Scaling Factor for a Power System Area Including Limited Energy Supply Thermal Units

A security-constrained power dispatch problem with non-convex cost function for a lossy electric power system area including limited energy supply thermal units fueled under a take-or-pay agreement is formulated. Then, an iterative solution method based on a modified subgradient algorithm based on feasible values and common pseudo scaling factor for limited energy supply thermal units is proposed and used to solve the problem. In the iterative proposed solution method, a modified subgradient algorithm based on feasible values is used to solve the dispatch problem in each subinterval, while the common pseudo scaling factor for limited energy supply thermal units is employed to adjust the amount of fuel consumed by the limited energy supply units during the considered operation period. Since all equality and inequality constraints in the non-linear optimization model of a subinterval are functions of bus voltage magnitudes and phase angles (the off-nominal tap settings), they are taken as independent variables except for those belonging to the reference bus. Load flow equations are added to the model as equality constraints. The unit generation constraints, transmission line capacity constraints, bus voltage magnitude constraints, and off-nominal tap setting constraints are added into the optimization problem as inequality constraints. Since the modified subgradient algorithm based on feasible values requires that all inequality constraints should be expressed in equality constraint form, all inequality constraints are converted into equality constraints by the method given in this article before application of the modified subgradient algorithm based on feasible values to the optimization model. The proposed technique is tested on an IEEE 30-bus test system with a non-convex total cost rate curve. A portion of the dispatch problem considered in this article, where only a loading of the system in a subinterval is considered, was also solved by some other recently reported dispatch techniques. First, minimum total fuel cost rates and solution times obtained from the modified subgradient algorithm based on feasible values versus other techniques are compared, and the outperformance of the modified subgradient algorithm based on feasible values in terms of both total cost rate and solution time is demonstrated. After that, the optimal total fuel cost value and solution time of the system for the operation period for the cases where the fuel constraint is ignored and not ignored are presented, and it is shown that adding the fuel constraint into the dispatch problem further decreases the optimal total fuel cost for the considered dispatch problem. Finally, the modified subgradient algorithm based on feasible values was applied to the fuel constrained dispatch problem directly. It is demonstrated that the proposed solution method, where the modified subgradient algorithm based on feasible values is employed to solve an interval's dispatch problem, gives a solution time that is smaller than that obtained from the direct application of the modified subgradient algorithm based on feasible values to the dispatch problem.

An Operator‐Difference Method for Telegraph Equations Arising in Transmission Lines

A second‐order linear hyperbolic equation with time‐derivative term subject to appropriate initial and Dirichlet boundary conditions is considered. Second‐order unconditionally absolutely stable difference scheme in (Ashyralyev et al. 2011) generated by integer powers of space operator is modified for the equation. This difference scheme is unconditionally absolutely stable. Stability estimates for the solution of the difference scheme are presented. Various numerical examples are tested for showing the usefulness of the difference scheme. Numerical solutions of the examples are provided using modified unconditionally absolutely stable second‐order operator‐difference scheme. Finally, the obtained results are discussed by comparing with other existing numerical solutions. The modified difference scheme is applied to analyze a real engineering problem related with a lossy power transmission line.