Pole Locations Research Articles

Optimization of recloser methods on medium voltage distribution networks

Reassessing methods within a business is important as it can prove certain concepts could indeed work, improve current methods and reinforces knowledge to the assessors. The utility’s (Eskom) recloser placement methodology mainly focuses on improving their performance figures and reaching their performance targets and does not focus on the financial aspect of their methods. The purpose of this paper is to present a method that will optimize the placement of reclosers on medium voltage distribution networks. Eskom can by focusing on the financial aspects of the recloser placements, benefit by improving performance as well as saving money at the same time, especially during fault conditions. A cost-benefit analyses methodology is applied where data is derived from a medium voltage distribution network in the Free State that serves more than 2000 customers. The number of reclosers and the placement of them will be determined by using matrix tables and formulas. Data was extracted from the utility record systems. The findings suggested that a recloser can pay itself back within one year using this method. In order to make an informed decision as to the placing of a recloser on a medium voltage distribution network, it is recommended to use the proposed method. The proposed method will assist in the decision as to the viability of placing a recloser on a specific pole location. Future studies may be done by combining recloser placement methods with other protection sensing equipment like fault path indicators and current-voltage monitoring systems to isolate and find faults.

Design and Fabrication of a Lowpass Filter Using a New Butterfly-Shaped Defected Ground Structure

In this paper, a new Defected Ground Structure (DGS) is introduced and analyzed. The effect of the structure’s dimensions on the location of the attenuation pole and the cutoff frequency to study the frequency characteristics is investigated. In the following, a lowpass filter with 3 dB cutoff frequency at 3 GHz is designed and optimized using the proposed defected ground structure, and its frequency characteristic is reported. The designed lowpass filter is fabricated to verify the simulation process. Also, simulation results, the equivalent circuit, and the measured results with the Network Analyzer are compared.

Tree/link method for transfer function and stability analysis of switched‐capacitor circuits

SummaryThe wide spread application of switched‐capacitor circuits has resulted in complex structures wherein the derivation of transfer function in discrete form is not quite straight forward. A computer‐aided tool for direct transfer function analysis of switched‐capacitor circuits using state formulation method is proposed in this paper. The state equation matrices are directly constructed from the circuit topology using tree/link analysis. The entire topology is formulated only using cutset equations to obtain the state matrices without any modifications. The discretized topological state matrices are used to generate the transfer function in z form by forward substitution of state equation in successive clock phase. Lyapunov criteria‐based matrix equation constructed using the same state matrix is used to investigate the circuit stability. The formulation is also suitable in addressing the effect of non‐idealities like switch resistance and finite gain of operational amplifiers, on the location of poles and zeros. Various numerical examples have been presented to demonstrate the performance of the simulator.

Thermomagnetic renormalons in a scalar self-interactingλϕ4theory

In this article we extend a previous discussion about the influence of an external magnetic field on renormalons in a self interacting scalar theory by including now temperature effects, in the imaginary formalism, together with an external weak external magnetic field. We show that the location of poles in the Borel plane does not change, getting their residues, however, a dependence on temperature and on the magnetic field.The effects of temperature and the magnetic field strength on the residues turn out to be opposite. We present a detailed discussion about the evolution of these residues, showing technical details involved in the calculation.

Gastric cancer – histopathological correlations between tumor and non-tumor gastric mucosa changes

Gastric cancer is a widely geographically distributed malignancy with high prevalence, therefore being a serious health problem that needs standardized methods for early diagnosis and treatment. The aim of the study was to evaluate the correlation of some epidemiological and clinical data with the histological features. The study group was made up of 66 patients that underwent surgical removal of the gastric neoplasm, and the pathological exam showed the morphological features of the tumor, as well as the ones of the unaffected mucosal tissue. Topographically, the highest incidence of the tumor was registered in the gastric antrum, but in recent years, an increased incidence of the superior gastric pole localization was recorded. The macroscopic aspects reveal that the ulcerated type 2 Borrmann is the most frequent, and alongside type 3 Borrmann, the ulcer-infiltrative type represents most of the gastric antrum cancers. The analysis of the tumor invasion showed that most carcinomas underwent surgery when the tumor invaded the serosa (pT3) or even the perigastric tissues (pT4). In our research, we chose Goseki’s microscopic classification because of its best coverage of the histological heterogeneity of the gastric carcinomas, providing information about the percentage of the cellular and secretory differentiation with direct impact on the invasion of the tumor. In more than 70% of the cases, the patients showed lesions of severe chronic atrophic gastritis of the non-tumor mucosa. Lately, the incidence of Helicobacter pylori has been 5.5%, lower than indicated by mainstream literature. We observed that the incidence of type 3 incomplete intestinal metaplasia, as the most commonly involved factor in the etiopathogenesis of gastric neoplasms, was encountered in 36.3% of the cases, this percentage rising proportionally with age and being frequently associated with antrum tumors. In conclusion, the permanent analysis of the relation between epidemiological data and some histological features might be relevant for the characterization of the tumoral process or the non-tumor gastric mucosa, leading to an evaluation of the prognosis.

Power-Law Compensator Design for Plants with Uncertainties: Experimental Verification

A power-law compensator scheme for achieving robust frequency compensation in control systems including plants with an uncertain pole, is introduced in this work. This is achieved through an appropriate selection of the compensator parameters, which guarantee that the Nyquist diagram of the open-loop system compensator-plant crosses a fixed point independent of the plant pole variations. The implementation of the fractional-order compensator is performed through the utilization of a curve-fitting-based technique and the derived rational integer-order transfer function is realized on a Field-Programmable Analog Array device. The experimental results confirm that the the phase margin is well preserved, even for ±40% variation in the pole location of the plant.

A novel optimal PIλDND2N2 controller using coyote optimization algorithm for an AVR system

In this paper, a novel PIλDND2N2 controller is designed for an Automatic Voltage Regulator (AVR) in a power system and is studied in this paper. AVR is responsible for keeping the terminal voltage of a synchronous generator at a specified interval. The proposed control design is achieved by deploying for the first-time the coyote optimization algorithm (COA) in an AVR system by optimizing a novel objective function. A comparison is made among the proposed controller and FOPID, PID, PIDA and PIDD2 controllers optimized by others metaheuristic algorithms in the literature. The comparison is deducted in terms of transient response and disturbance rejection. From the simulations it is concluded that the proposed method outperforms other methods in the literature. Furthermore, the stability of the proposed design is examined via the location of the closed-loop poles and frequency response. Moreover, the robustness of the controller is tested under model uncertainties. In both tests the proposed method displays an outstanding performance.

Line of sight visibility analysis for foreign object debris detection system

It is challenging to monitor busy airports’ runway through visual inspection to precisely detect foreign object debris. Currently, many technologies for the detection of foreign object debris are available. It has been investigated that millimeter-wave radar technology’s detection capability can be one of the most effective techniques for detecting foreign object debris as it is weather-resilient. However, the positioning and height of a millimeter-wave radar pole covering the runway area, considering the existing runway infrastructure, are challenging. The task involves finding the appropriate placement and optimum height. This paper presents a novel method of line of sight visibility for placement and height of radar pole using human factor research to ensure that each point on the runway is visible from various heights of the millimeter-wave radar pole to the runway locations. Kuala Lumpur International Airport, Malaysia runway 32L/14R, has used a case study to test the visibility analysis. The visual analytic test’s successful results for different millimeter-wave radar pole locations and viewing heights under a visible and invisible line of sight conditions on the runway have been verified in the field experiment.

Pole Location and Input Constrained Robust Fuzzy Control for T-S Fuzzy Models Subject to Passivity and Variance Requirements

In this paper, a robust fuzzy controller for stochastic nonlinear systems subject to multiple performance constraints is discussed. To solve the problem of stochastic behaviors in nonlinear systems, the covariance control theory and passive control theory are applied based on the concept of energy. Additionally, the pole placement method is considered for the better transient behaviors of the system responses. However, it is known that the control inputs and maximum overshoot of the system responses may become bigger at the same time when the settling time or converge rate of the system is required to be faster. Due to this reason, the input constraint is also considered in the fuzzy controller design method to limit the value of the control gain. Moreover, an effective robust control method is applied to deal with the perturbation of the nonlinear systems. Based on the above performance constraints, the sufficient conditions can be obtained to achieve the stability in the sense of mean square and the multi-performance requirements. Finally, simulation results of the nonlinear synchronous generator system are presented to verify the feasibility and efficiency of the proposed control method.

INCREASE IN THE ELECTROMAGNETIC MOMENT OF A SUPERMINIATURE ELECTRIC MOTOR EXCITED BY RARE EARTH PERMANENT MAGNETS

The article is devoted to improving the energy and performance characteristics of superminiature electric motors, which are widely used in modern devices of robotics and mechanotronics. With the development of digital and Autonomous robotic systems, the tasks of improving the efficiency of Executive micromechanisms that affect the functionality and duration of work in offline mode have become particularly relevant. Traditional design and technological solutions used in higher-power electric machines are not scalable to the field of superminiature electric machines. Domestic and foreign developers offer various design options and manufacturing technologies. The key design feature of the electric motor under consideration is a glass stator made by polycapillary fiber technology and an excitation system from rare-earth permanent magnets. In the wall of the glass case, holes are evenly distributed around the circumference, in which the control winding is laid. The motor excitation system is a two-pole permanent magnet located on the rotating rotor shaft. The purpose of the research is to determine the effect of changing the design of the excitation system by changing the location of the magnetic poles. The research uses software that simulates the electromagnetic field using the finite element method. In the course of research, it was found that a decrease in the body of a permanent magnet leads to a decrease in the electromagnetic moment, which is not compensated by a decrease in edge effects at the boundary of the poles of the magnet. However, an increase in the value of the maximum magnetic induction in the air gap allows us to conclude that edge effects at the pole boundary have a significant effect on reducing the energy characteristics of superminiature micromachines. Thus, the solutions proposed in this paper are not sufficient to increase the efficiency of the engine, but the data obtained indicate the need to reduce the edge effects of permanent magnets.

Power and energy system oscillation damping using multi-verse optimization

Power system oscillations are the primary threat to the stability of a modern power system which is interconnected and operates near to their transient and steady-state stability limits. Power system stabilizer (PSS) is the traditional controller to damp such oscillations, and flexible AC transmission system (FACTS) devices are advised for the improved damping performance. This paper suggests a technique for controller parameters tuning of PSS and a shunt connected FACTS device to be operated in coordination. A static synchronous compensator (STATCOM) connected in a two-machine system is considered as a test power system for the system studies. A recent meta-heuristic algorithm, Multi-Verse optimizer (MVO) has been suggested and compared with the other state-of-the-art algorithms. Improvement in system damping has been achieved by minimizing the oscillating nature of the system states by framing the objective function as a function of damping ratio and location of poles of the system. The Phillips-Heffron model of the test system has been designed by considering the system dynamics. The coordinated system behavior under the perturbation in system parameters has been observed satisfactory with the tuned controller parameters obtained from the suggested algorithm.

Stability assessment of a stand-alone wind-photovoltaic-battery system via Floquet Theory

This paper presents a methodology, based on both Floquet theory and the participation matrix concepts, aimed at characterization of a time-periodic system in terms of its poles location in the complex plane. The participation matrix allows to find which poles are the most influenced by certain state-variables. The proposed methodology can be utilized as an auxiliary tool for parameter design, stability assessment, and for post-event analysis of time-periodic systems. The proposed methodology is readily applicable to distributed generation systems. A case study involving a stand-alone wind-photovoltaic-battery system is presented to support this statement.

The Location of the Earth's Magnetic Poles From Circum‐Terrestrial Observations

AbstractThe magnetic poles or dip poles are the points on the Earth's surface and circum‐terrestrial area where the magnetic field is vertical, so the horizontal component vanishes. They are not coincident with geomagnetic poles, which are the points where the dipole axis, obtained by analytic models, intersects the Earth's surface, and their instrumental sampling determination from ad hoc ground surveys is difficult due to the harsh environmental conditions and remoteness of the areas where they are located. In this work, we use magnetic field measurements from ESA's Swarm satellites covering 5 years (2015–2019), and determine the position of the magnetic poles by modeling the yearly average horizontal magnetic field component through analytic two‐dimensional Taylor polynomial fit and finding the locations where this component is minimum. The yearly dip poles positions at average satellites geocentric altitudes are also projected at ground level based on WGS84 geodetic reference system. Reliability of our method is evaluated by an optimized Monte Carlo test applied to combined International Geomagnetic Reference Field (IGRF) model and Swarm data. The availability of several years of data allows us to investigate the long term variation and dynamics of the magnetic poles, also in comparison with the results provided by IGRF model (both IGRF12 and IGRF13). Our results agree with the model, in better accordance in the north hemisphere with IGRF13, indicating that both magnetic poles move in the north‐west direction, with a speed of ∼37–72 km/y (lower in year 2016) for the north dip pole and of ∼5–9 km/y for the south one.

Discrete Fundamental AC Voltage Controller for Three-Phase Standalone Converters

Voltage control of standalone converters with LC filter is usually based on proportional-resonant or proportional-integral controllers, which often require further active damping methods to achieve stability. These solutions place design constraints in the selection of the closed-loop pole locations which limit the achievable bandwidth and increase the design complexity. In contrast, in state-space based controllers, the closed-loop poles can be placed freely through state feedback, which makes them particularly suitable for high order plants and/or low sampling frequencies. Among the modern control methods, direct pole placement is a simple technique that enables the establishment of a straightforward relationship between outcome and design, as opposed to more advanced approaches. This paper presents a discrete state-space voltage controller for standalone converters with LC output filter. The proposed method combines the direct pole placement technique with a virtual disturbance observer in order to compensate the effects produced by the load and model mismatches. The design process takes into account both the filter parameters and the sampling frequency, rendering the performance of the obtained controller independent of both. The result is a streamlined design procedure that leads to consistent outcomes for a wide range of plant parameter variations, requiring only one input: the desired closed-loop bandwidth.

Investigation on microstructure and properties of dissimilar joint between TRIP800 and QP980 fabricated by laser welding

Dissimilar weld joints of QP980 and TRIP800 were fabricated by a fibre laser. The microstructure and mechanical properties of dissimilar weld joints were studied. The tensile properties of weld joints were not influenced by the narrow softening zone with a less reduction in hardness of ∼25 HV from the QP980, which contributed to fracture in TRIP800. The DIC images showed that the location of maximum strain was changed from the QP980 side to TRIP800 side during the tensile test of QP980 (1.2 mm)–TRIP800 (1.4 mm) joints. The dissimilar weld joints were characterised by the limited dome height test (LDH). The LDH values were varied with the punch pole location, as a result of the softening zone and non-uniform microstructure on the heat-affected zone of joints.

Development of Non-cooperative Distributed Adaptive MPC Schemes based on ARX Models parameterized using Orthonormal Basis Filters

Abstract Adaptive model predictive control (AMPC) schemes can prove beneficial in the control of non-linear time varying systems due to their ability to maintain closed-loop performance in the face of large transitions in operating conditions. In this work, two non-cooperative distributed adaptive MPC (dAMPC) schemes are proposed that are based on ARX models parameterized using generalized orthonormal basis filters (GOBF). Poles of the GOBF models estimated through offline estimation are kept fixed and only the Fourier coefficients are updated recursively online thereby avoiding drift in the pole locations. The system under consideration is decomposed into a number of subsystems coupled through the inputs. A separate local AMPC controller is implemented for each subsystem. Each local controller optimizes its input trajectories assuming the input trajectories of its neighbors fixed to the last computed values, and then shares the computed inputs with the neighbors. We consider both sequential and iterative distributed control strategies for the dAMPC development. The efficacy of the proposed dAMPC schemes is demonstrated using simulation studies on an octuple tank process. When the system is subjected to large transitions in operating points, the proposed dAMPC schemes generate closed loop performances comparable to a centralized adaptive MPC scheme while significantly reducing the average computation time.

New Evidence of Prehistoric Civilizations in the Holy Land and Surrounding Regions of the Levant

An analysis of more than 375 ancient locations in the Levant was performed to assess the alignment of sites and structures relative to the current and former locations of the geographic pole. A small fraction of the sites had clear rectilinear features/structures suitable for aerial analysis. Of those about a third of the sites are oriented either along cardinal directions or in directions of solstices or lunar standstills. The remainder (almost twice as many) appear to be aligned relative to the directions of former poles in Hudson Bay, the Norwegian Sea, northern Greenland, and the Bering Sea, which according to Charles Hapgood’s theory of earth crustal displacement, suggests the possibility that these sites may have been first established 12,000 to 130,000 years ago.

A Deadbeat PI Controller With Modified Feedforward for PMSM Under Low Carrier Ratio

When the permanent magnet synchronous motor (PMSM) operates at low carrier ratio, the decoupling capability and dynamic performance of the proportional-integral (PI) controller are limited by the digitization delay. In this paper, a deadbeat PI controller is proposed by modified the feedforward. With the modified feedforward, the open-loop transfer function can eliminate imaginary components. Thereby the full decoupling of $d$ and $q$ is realized. At the same time, the controller also has full control over the location of the closed-loop poles, indicating that it can have a deadbeat response for the command tracking. For the disturbance rejection, the controller allows us to select the speed with which the controller can cancel the effect of a disturbance. Further considering that the motor parameters are inaccurate, by designing the controller coefficients with the maximum value of the closed-loop poles, the current-loop can ensure the dynamic performance and harmonic suppression ability. Finally, the effectiveness of the proposed controller is verified by the simulations and experiments.

Robust Speed Control of Electrical Drives with Reduced Ripple Using Adaptive Switching High-order Extended State Observer

Active disturbance rejection control using extended state observer (ESO) is less dependent on the knowledge of the system. It has proved to be an excellent scheme for speed control of electrical drives. However, for time-varying disturbance, the observation precision of conventional ESO is undesired, which limits the speed tracking accuracy. Accordingly, this article proposes an enhanced speed controller for electrical drives based on adaptive switching high-order ESO (ASHESO). First, the critical parameters affecting the steady-state performance of ASHESO are determined according to frequency analytical results. Then, optimized observer gain is obtained by modifying a part of pole locations, which weakens the influence of noise on estimated state. Finally, an adaptive switching gain mechanism is proposed according to the closed-loop tracking error and the swiftness of dynamic response is maintained. The proposed speed controller has achieved high estimation accuracy for disturbance and strong immunity to measurement noise. The feasibility and effectiveness of the strategy is verified on a laboratory permanent magnet synchronous motor (PMSM) drive system.

Direct Adaptive Pole-Placement Controller using Deep Reinforcement Learning: Application to AUV Control

Abstract In this paper we investigate a direct adaptive learning-based tuning strategy for the control of an underwater vehicle under unknown disturbances. This process can be seen as a double integrator without delay and is usually regulated using a PD/PID type controller. A trade-off between performance and robustness may be found when tuning their parameters because a single optimal controller for multiple operating condition does not exist. Therefore, we use a re-parametrization of the PID controller gains in a space of poles where controller stability is guaranteed. We propose to use the maximum entropy deep reinforcement learning algorithm called SAC to explore this space. The adaptation procedure is able to capture a great variety of desired pole locations in order to adapt to process variations without measuring them. Simulation outcomes show the advantages of this approach.