Differential positive sequence power angle-based microgrid feeder protection

Integration of distribution generation (DG) makes the growth of the microgrid protection scheme very challenging issues. Researchers from all over the world continuously are doing hard work for developing the microgrid protection schemes. A differential positive sequence power angle (DPSPA) based microgrid protection scheme is proposed in this paper using positive sequence (PS) components of voltages and currents. The DPSPA for the feeder is calculated considering both ends of voltage and current signal information, when it is more than threshold, internal fault is reported otherwise, it is an external fault. Taking into consideration the varying operational modes of the microgrid, variations in DG penetration, and variations in fault variables namely fault types, and fault locations, the proposed protection scheme is verified on a modified IEEE-13 bus feeder. Moreover, to test the robustness and efficacy of the suggested scheme, various non-faulty events including induction motor starting, non-linear loading, load switching, capacitor switching, and section cutoff have been conducted. The proposed scheme is also verified for external faults and it is found that it continues to be stable for the external faults. The findings exhibit this proposed scheme, which is based on DPSPA, can successfully protect the microgrid under changing operating conditions.

THE MANAGEMENT OF CHARACTERISTICS OF THE NEW TWO-LAYER RUBBER MATRIX SEALS

Rubber seals for closing devices operating in cold climates degrade quickly in aggressive environments at very low temperatures. As a result, leaks and failures occur in the closure devices. Therefore, there is a great need to develop a new model of rubber seals and develop their scientific basis. The article is devoted to increasing the sealing effect of rubber seals of machines and equipment, including closures, by introducing the anisotropy of the rubber matrix into its structure with control of the characteristics of hard closures obtained from rubber. For this purpose, new models of the gate valve design were obtained and new models of two-layer panel seals based on a modified rubber elastomer matrix are applied to these structures. For this, a test program is carried out in the form of an analytical trajectory of large, medium and small constant curves in two closed forms based on characteristic deformations to study the anisotropy of matrix deformations. It is found that the eigenvector of the deformation anisotropy of the matrix is not in the load trajectory before it collapses, it arises with a delay. This delay slows down the rate of destruction. This property of deceleration of the main eigenvector of the deformation anisotropy of the matrix is subjected to a very complex loading of the initial fields, in the latter sections it is also observed in samples No. 2, No. 3, tested along the trajectory of linear loading. This delay slows down the destruction rate. Thus, the direction of the deceleration property of the main eigenvector can be considered quite common. This leads to an increase in its resistance to wear in a highly aggressive environment

Investigation on deformation behavior of magnesium alloy sheet AZ31B in pulsating hydroforming

Magnesium alloys have been known as the next generation material for lightweight body structures. Pulsating hydroforming is an effective method to improve magnesium alloy sheet forming performance, and the formed parts are characterized by lightweight, high-specific strength and stiffness. The deformation performance of magnesium alloy sheet AZ31B with a thickness of 0.6 mm under pulsating hydroforming has been investigated by means of experimental study, numerical simulation and theoretical analysis. The results show that under the same maximum hydraulic pressure, compared with simple linear loading, the magnesium alloy forming parts with pulsating hydraulic loading not only have better wall thickness uniformity and larger bulging height but also can delay the occurrence of fracture, improve the forming performance and ultimate the forming ability of magnesium alloy sheet. A new evaluation index is proposed to simplify the comprehensive forming performance of magnesium alloy parts with different amplitudes and frequencies more accurately, which can also be applied to determine the optimal forming parameters of magnesium alloy sheet AZ31B in the pulsating loading condition.

The Relationship Between Vertical Ground Reaction Force, Loading Rate, and Sound Characteristics During a Single-Leg Landing

Context: Landing kinetic outcomes are associated with injury risk and may be persistently altered after anterior cruciate ligament injury or reconstruction. However, it is challenging to assess kinetics clinically. The relationship between sound characteristics and kinetics during a limited number of functional tasks has been supported as a potential clinical alternative. Objective: To assess the relationship between kinetics and sound characteristics during a single-leg landing task. Design: Observational Setting: Laboratory. Participants: There was total of 26 healthy participants (15 males/11 females, age = 24.8 [3.6] y, height = 176.0 [9.1] cm, mass = 74.9 [14.4] kg, Tegner Activity Scale = 6.1 [1.1]). Intervention: Participants completed single-leg landings onto a force plate while audio characteristics were recorded. Main Outcome Measures: Peak vertical ground reaction force, linear loading rate, instantaneous loading rate, peak sound magnitude, sound frequency were measured. Means and SDs were calculated for each participant’s individual limbs. Spearman rho correlations were used to assess the relationships between audio characteristics and kinetic outcomes. Results: Peak sound magnitude was positively correlated with normalized peak vertical ground reaction force (ρ = .486, P = .001); linear loading rate (ρ = .491, P = .001); and instantaneous loading rate (ρ = .298, P = .03). Sound frequency was negatively correlated with instantaneous loading rate (ρ = −.444, P = .001). Conclusions: Peak sound magnitude may be more helpful in providing feedback about an individual’s normalized vertical ground reaction force and linear loading rate, and sound frequency may be more helpful in providing feedback about instantaneous loading rate. Further refinement in sound measurement techniques may be required before these findings can be applied in a clinical population.

Multi-Level Inverter Topologies Based UPQC Applied to Distribution Systems for Power Quality Improvement

At distribution side most type of loads connected are non-linear types. These loads adversely affect the power quality of the system. If not rectified at times they may distort the sine wave at source side. This paper presents a power quality conditioner which is designed using multi-level inverter (MLI). The advantage that the proposed MLI has over conventional one is that it requires less number of components as compared to the conventional. Also it improves the utility profile by improving harmonic content at output side. The proposed MLI based Unified power Quality Conditioner (UPQC) improves the grid profile at non-linear loading by prohibiting the propagation of high content harmonic load current at source side. The proposed topology has inherent active filtering capability by virtue of which there has been seen a good mitigation of power quality issues at point of common coupling. Comparative analysis of the proposed topology with the conventional MLI is also presented. The comparison of results is also presented in terms of linear and non-linear loading in a UPQC compensated distribution system.

Effect of load current harmonics on vibration of three-phase generator

Almost all today electrical loads are considered non-linear such as switch mode power supply (SMPS) for powering computer and mobile phone or variable speed drive (VSD) for driving home and industrial electric motors. These loads generate ac non-sinusoidal current containing a lot of harmonics as indicated by its high total harmonics distortion (THD) figure. Current harmonics bring negative effects into all electrical power system components, including three-phase generator. This paper provides analysis of load current harmonics effects on vibration of three-phase generator. Three different laboratory experiments have been conducted i.e. three-phase linear resistive loading, non-linear loading with a three-phase ac/dc converter and non-linear loading with three single-phase capacitor filtered ac/dc converters. Results show that the higher load current harmonics content the higher is vibration of the three-phase generator. Non-linear loading with a three-phase ac/dc converter that generate about 24.7% THD gives an increase of 4.3% and 5.5% in average of vertical and horizontal vibrations of the three-phase generator respectively. Further, non-linear loading with three single-phase capacitor filtered ac/dc converters that generate THD as high as 74.9% gives significant increase of 28.1% and 23.6% in average of vertical and horizontal vibrations respectively.

Research on Control Algorithm of Electric Linear Loading System

This paper mainly focused on the problems of low loading accuracy in electric linear loading system, Firstly, the mathematical model is done on loading motor, loading motor driver and ball screw in the system. Then, the current loop proportional control is introduced, which improves the response speed of the load motor; In order to improve the loading accuracy and restrain excess force, a parallel algorithm based on fuzzy PID and repetitive control is designed in the force loop. The fuzzy controller improves the dynamic performance and anti-interference ability of the system. The repetitive controller periodically adjusts the deviation, which reduces the steady-state error of the system. Combination of the two controller results in good dynamic and static characteristics. The simulation results show that the proposed control algorithm is feasible, which has a certain engineering reference value.