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A standalone microgrid (MG) is able to use local renewable resources and reduce the loss in long distance transmission. But the single-phase device in a standalone MG can cause the voltage unbalance condition and additional power loss that reduces the cycle life of battery. This paper proposes an energy management strategy for the battery/supercapacitor (SC) hybrid energy storage system (HESS) to improve the transient performance of bus voltage under unbalanced load condition in a standalone AC microgrid (MG).

The SC has high power density and much more cycling times than battery and thus to be controlled to absorb the transient and unbalanced active power as well as the reactive power under unbalanced condition. Under the proposed energy management design, the battery only needs to generate balanced power to balance the steady state power demand. The energy management strategy for battery/SC HESS in a standalone AC MG is validated in simulation study using PSCAD/EMTDC.

The results show that the energy management strategy of HESS maintains the bus voltage and eliminates the unbalance condition under single-phase load. In addition, with the SC to absorb the reactive power and unbalanced active power, the unnecessary power loss in battery is reduced with shown less accumulate depth of discharge and higher average efficiency.

With this technology, the service life of the HESS can be extended and the total cost can be reduced.

This paper aims to evaluate the effect of optimal use of rooftop photovoltaic (PV) systems on improving the loss of life (LOL) of distribution transformers, reducing power losses as well as the unbalance rate of the 69-bus distribution network.

The problem is studied in three scenarios, considering different objective functions as multi-objective optimization in balanced and unbalanced operations. Meta-heuristic golden ratio optimization method (GROM) is used to determine the optimal size of the rooftop PV in the network.

The simulation results show that in all scenarios, the GROM by optimally installing the rooftop PV is significantly capable to reduce the transformer distribution loss of loss, unbalance rate and power loss as well as reduce the temperature of the oil and transformer winding. Also, the lowest %LOL, power loss and unbalance rate occurred in the second scenario for the balanced network and first scenario, respectively. In addition, the results showed that the unbalance of the network results in increased power losses and LOL of the distribution transformer.

The better capability of GROM is proved compared with the grey wolf optimization algorithm with better objective function and by achieving better values of LOL, unbalance rate and power loss. The results also showed that the %LOL, unbalance and power losses are weakened compared to without considering the PV cost but the achieved results are realistic and cost-effective.

THE balancing of rotating parts can be effected either on a balancing machine, or by means of vibration measurements carried out on the completed assembly.

One of the major problems faced by industry is vibrations in rotating parts. Vibration is a to-and-fro movement of rotating mechanical parts and has many detrimental effects on machinery. It is obvious that no movement can be achieved without consumption of energy. All the energy consumed in vibration of mechanical parts is useless. Unbalance is one of the most common reasons for vibrations. This paper aims to experimentally evaluate the effect of unbalance in a shaft–rotor system on power consumption. An experimental setup consisting of a shaft and a rotor mounted on antifriction bearing was built-up. The shaft was driven through a flexible coupling, by a variable speed DC motor. The shaft–rotor system was rotated at different speeds and electrical power consumed by the system was measured at specific speeds varying from 1,200 to 2400 rpm. The rotor was balanced to grade G6.3 at 1,200 rpm. The power consumption by shaft in balanced condition was taken as baseline data for the further work. The rotor was then made unbalanced by adding different masses at 60 mm radius, and power consumption was recorded again at the same speeds. It was observed that average power loss due to unbalance is of 0.11watt/gm.mm unbalance. This can amount to 2.75 kw if there is unbalance of 50 gm at a radius of 500 mm. This work is meant to emphasis on the fact that the power consumption can be reduced if the vibrations can be kept under control.

The experimental setup consisting of a rotor–shaft system was fabricated. The shaft was supported on two anti-friction bearings. The shaft is driven by a 0.25 HP DC motor. The speed of the motor can be varied by a speed controlling device. A digital ammeter and voltmeter are connected to measure the input current and voltage to the system. The rotor was rotated at different speeds after two-plane balancing and the parameters like voltage, current drawn, rms velocity (average of drive and non-drive side bearing) and displacement at 1× frequency were recorded. The base line data for the balanced shaft–rotor system were recorded for further use.

Power consumption increases with increase in unbalance at each of the speeds. Total power consumed at resonant frequency is high. The average power consumed “W/gm.mm” increases at higher speed due to increased damping force of lubricant in bearings combined with the effect of resonance. Average power consumed due to unbalance is about 0.11 W/gm.mm unbalance. It is important to reduce the vibration to save power which can be effectively achieved by balancing the rotating parts in the machinery.

The experimentation is done on a small rotor. When the same work is done on real situations where the rotors are heavy, we may expect some differences in the actual effect of unbalance on the power consumption.

The experimental work have a huge application in industry in condition monitoring. The power may tend to increase not only because of the unbalance but also due to other reasons of vibrations like misalignment, loose foundation, poor bearing conditions, etc. The power loss may increase due to any other reasons mentioned above. The degree of power saving due to steps taken for reducing vibration will depend on the existing vibration levels.

The work highlights the effect of power loss due to vibrations. Even (1 per cent) small amount of power saved can save millions of dollars in industry, as there are many rotating parts which run 24 × 7. The emphasis is on condition-based monitoring which will help in power saving beyond the conventional advantages of condition monitoring.

The experimentation clearly quantifies power loss in absolute form that is the power loss is expressed per gm.mm of unbalance and not as the percentage of electrical or mechanical power, input or output. The percentage values may be misleading some times, as SMALL percentage of large values is also LARGE and hence should be taken into consideration.

In this paper the influence of the neutral in the thermal performance of a three‐phase squirrel cage induction motor fed by asymmetrical supply voltages is studied and analysed. A 2D finite element formulation was used to solve the steady‐state heat transfer problem. The eddy currents in the rotor bars were evaluated using a combined 3D finite element approach with analytical expressions. The numerical solutions are compared with measured experimental results obtained in laboratory tests for two load conditions and two unbalanced power supply situations with and without the neutral wire connected.

The purpose of this paper is to consider both sides of a back‐to‐back AC‐DC‐AC interface.

The paper presents a mathematical analysis, simulation, laboratory test in scaled model.

The two main findings comprised concept of control methods for grid AC‐DC‐AC converter applied in renewable energy sources with variable speed operation under distorted grid. Active filtering functionality in case of non‐linear current of a parallel load. Second, a control algorithm dedicated for two‐level AC‐DC converter applied in industrial networks with high‐order harmonics compensation working under hard conditions – balanced and unbalanced voltage dips.

The paper shows preliminary results for AC‐DC‐AC converter and active filter (AF) during voltage dips and for harmonics compensation. Control methods and/or topology should be improved and tested in scale and after at high‐power system.

Power quality supplied/received to/from the grid can be increased. In case of low‐cost system only AF can be applied to existing non‐linear receivers. Moreover, in case of full AC‐DC‐AC converter energy saving and production is possible.

Presented control methods give satisfactory results. Paper presents laboratory results for grid and machine side two different power circuits during steady states and transients. Moreover, active filtering operation during voltage dips is presented.

A cascaded observer-based transfer delay frequency locked loop (CODFLL) algorithm is developed to control the distribution static compensator (DSTATCOM) to address various power quality (PQ) issues arise because of distorted grid and load conditions. Moreover, frequency locked loop is included along with the observer to take care of the frequency drift from nominal value and to improve its performance during steady state and transient conditions. During daylight, the proposed system works as photovoltaic (PV) DSTATCOM and performs multiple functions for improving PQ whilst transferring power to grid and load. The system under consideration acts as DSTATCOM during night and bad weather condition to nullify the PQ issues.

CODFLL control algorithm generates reference signal for hysteresis controller. This reference signal is compared with an actual grid signal and a gate pulse is produced for a voltage source converter. The system is made frequency adaptive by transfer delay adaptive frequency locked loop (FLL). Peak power is extracted from a PV source using the perturb and observe technique irrespective of disturbances encountered in the system.

The PV system’s performance with the proposed controller is studied and compared with conventional control algorithms such as least mean fourth (LMF), improved second-order generalized integrator frequency locked loop (ISOGI-FLL), synchronous reference frame phased lock loop (SRF-PLL) and frequency adaptive disturbance observer (DOB) for different cases, for example, steady-state condition, dynamic condition, variable insolation, voltage sag and swell and frequency wandering in the supply side. It is found that the proposed method tracks the frequency variation faster as compared to ISOGI-FLL without any oscillations. During unbalanced loading conditions, CODFLL exhibits zero oscillations. Harmonics in system parameters are reduced to the level of IEEE standard; unity power factor is maintained at the grid side; hassle-free power flow takes place from the source to the grid and load; and consistent voltage profile is maintained at the coupling point.

CODFLL control algorithm is developed for PV-DSTATCOM systems to generate a reference grid current.

Electric motors are present in most industries today, being the main source of power. Thus, detection of faults is very important to rise reliability, reduce the production cost, improving uptime and safety. Vibration analysis for condition-based maintenance is a mature technique in view of these objectives.

This paper shows a methodology to analyze the vibration signal of electric rotating motors and diagnosis the health of the motor using time and frequency domain responses. The analysis lies in the fact that all rotating motor has a stable vibration pattern on health conditions. If the motor becomes faulty, the vibration pattern gets changed.

Results showed that through the vibration analysis using the frequency domain response it is possible to detect and classify the motors in several induced operation conditions: healthy, unbalanced, mechanical looseness, misalignment, bent shaft, broken bar and bearing fault condition.

The proposed methodology is verified through a real experimental setup.

Balance Theory has accumulated an impressive record of empirical confirmation at both the micro- and macro-levels. Yet, it is unclear why humans consistently prefer balanced relations when imbalance offers the opportunity to reap material rewards. We argue that balance is preferred because it functions as a “compression heuristic,” allowing networks to be more easily encoded in, and recalled from, memory.

We present the results of a novel randomized laboratory experiment using nearly 300 subjects. We evaluate the independent and joint effects of degree of balance/imbalance and presence/absence of kin compression heuristics on network recall.

We find that memory for relationship valence is more accurate for balanced, rather than imbalanced, networks and that relationship existence and relationship valence are separable cognitive elements. We also use comparisons between kin and non-kin networks to suggest that humans are implicitly aware of the conditions under which imbalanced networks will be most durable.

We show that the tension/strain postulated to generate mental and behavioral responses to increase balance likely stems from cognitive limitations. More broadly, this connects balance theory to models of human cognition and evolution and suggests that human general processing ability may have evolved in response to social, rather than physical, challenges.

This paper aims to propose a new configuration of a shunt active power filter (SAPF) connected with a photovoltaic (PV) system through a Z-source inverter (ZSI) topology. This topology ensures a single-stage operation and overcomes the limitations of the conventional two-stage operation topologies based on the DC–DC boost converter. The proposed system is designed for the purpose of reducing the total harmonic distortion of the source current by eliminating the current harmonics and exploiting the solar irradiation.

First, all the main parts of the proposed shunt active power filter are fully described in this paper, and then a PV system based on a Z-source inverter with a maximum power point tracking controller is used to exploit the solar irradiance and solve the problem of discharging of the direct current (DC) capacitor during the filtering process.

From the extensive simulation tests carried out using MATLAB/Simulink, the obtained results prove that the proposed shunt active power filter performs well despite several operation scenarios, including different load types and under abrupt irradiance.

A new shunt active power filter configuration has been proposed. This configuration benefits from the solar irradiation and overcomes the drawbacks of the conventional configurations by using the Z-source inverter instead of the voltage source inverter and DC–DC boost converter.