Search

As the second part of the investigation on vibration characteristics of ± 800 kV converter transformers, this part focuses on load conditions. A full-load thermal stability test is carried out on 12 YY and YD converter transformers in a converter station. Vibration, voltage, current, and other important information are collected by online monitoring devices. Vibration amplitude, vibration spectrum, dominant frequency, vibration power ratio of frequency band, vibration power entropy, and odd–even harmonic ratio under different load conditions are calculated and studied to evaluate the vibration state. Theoretical analyses of winding electromagnetic force and vibration acceleration are carried out and results show that the harmonic currents make the dominant frequency shift to 300 Hz or 400 Hz. Most vibration characteristics are sensitive to load rate changes. The odd–even harmonic ratio is sensitive to filter disconnection and reconnection. The results of this study reveal the vibration regularity and corresponding mechanism and can contribute to further study on vibration assessment of ± 800 kV converter transformers under load conditions.

• Propose an algorithm to determine travel time between two adjacent nodes. • Account for planning time with varying acceleration and deceleration. • Develop an algorithm to sequence arrival times as a vehicle approaches a node. In previous studies, the behaviour of each vehicle is assumed to be constant in all situations. However, this assumption is unreasonable, as physical factors—such as load conditions or turn times—are not considered in the trajectory planning process, even though they significantly affect vehicle operation. Therefore, an algorithm for determining travel time between two adjacent nodes (A2D2T-A2AN) is proposed to resolve collisions caused by discrepancies between planned time and actual time, which make these collisions unpredictable. Additionally, vehicles can be controlled with varying accelerations depending on load conditions. Furthermore, an algorithm to adjust arrival times when a vehicle approaches a node (A2CAT-VT2N) is developed. To verify the efficiency and feasibility of these algorithms, several experiments were conducted using a chessboard map simulation under different conditions. The results demonstrate that our method is both suitable and effective for real-world applications. [Display omitted] [ABSTRACT FROM AUTHOR]

In a cross-country skiing competition, the time difference between the winner and the skier coming in at second place is typically very small. Since the skier spends much of the energy on overcoming resistive forces, a relatively small reduction in these forces can have a significant impact on the results. The resistive forces come partly from the friction, at the tribological interface between the ski and the snow, and as with many tribological processes, the characterisation of its origin plays an important role in determining the frictional properties. Furthermore, in cross-country ski friction, there are several scales impacting the frictional performance, with the major contributors being the ski-camber profile and ski-base structure. Macro-scale measurements of the ski-camber profile under loading are often used to determine how adequate the ski is for use under specific conditions. The characteristic properties usually assessed are the force required to collapse the ski in order to obtain a certain camber height, the topography of the kick-wax zone, and the length (determined by simple means) of the frictional interfaces associated with the rear- and front glide zones, i.e., the apparent contact length. These measurements are, however, commonly performed by loading the ski against a much stiffer counter surface than snow and this affects the quantification of the characteristic properties. To date, some mathematical models have been proposed, but there is no reliable approach for determining the macro-scale properties of the contact between a cross-country ski and a counter surface using simulations. In the present paper, an Artificial Neural Network (ANN) has been trained to predict the ski-camber profile for various loads applied at different positions. A well-established deterministic approach has been employed to simulate the contact between the ANN-predicted ski-camber profile and a linearly elastic body with a flat upper surface, representing the snow. Our findings indicate that this method is feasible for the determination of relevant macro-scale contact characteristics of different skis with snow. Moreover, we show that the apparent contact area does not linearly depend on the load and that the material properties of the counter surface also exert a large impact when quantifying the apparent contact area and the average apparent contact pressure. [ABSTRACT FROM AUTHOR]

• Numerical modeling and parameter estimation are performed to explain the 300 Hz or 400 Hz dominant frequency under full-load conditions. • The vibration characteristics of converter transformers show specific regularities and typical distributions under different load rates. • Fitting functions and typical values of vibration characteristics provide a valuable reference for vibration state assessment. As the second part of the investigation on vibration characteristics of ± 800 kV converter transformers, this part focuses on load conditions. A full-load thermal stability test is carried out on 12 YY and YD converter transformers in a converter station. Vibration, voltage, current, and other important information are collected by online monitoring devices. Vibration amplitude, vibration spectrum, dominant frequency, vibration power ratio of frequency band, vibration power entropy, and odd–even harmonic ratio under different load conditions are calculated and studied to evaluate the vibration state. Theoretical analyses of winding electromagnetic force and vibration acceleration are carried out and results show that the harmonic currents make the dominant frequency shift to 300 Hz or 400 Hz. Most vibration characteristics are sensitive to load rate changes. The odd–even harmonic ratio is sensitive to filter disconnection and reconnection. The results of this study reveal the vibration regularity and corresponding mechanism and can contribute to further study on vibration assessment of ± 800 kV converter transformers under load conditions. [ABSTRACT FROM AUTHOR]

The purpose of this work is to compare, with the same digging diagrams, the velocity, accelerations and dynamic performances of two excavators with different arm configurations. In particular, constructive solutions involving the use of two and three mobile arms will be examined. For excavators the different construction geometry (2-3 arms) is mainly dictated by reasons of use, in fact the 3 arms solution is normally used in areas that allow poor mobility of vehicle and present obstacles during the excavation phase. The dynamic comparison between the two solutions is performed on real working conditions to which they can be subjected during the exercise. The elaborations are performed both analytically and numerically. Essentially the analysis shows that in the condition of leveling and lifting at minimum distance from the rotation axis the dynamic performances are similar, there are significant differences in the lifting condition at the maximum distance. The diversity also implies significant variations in the forces of the hydraulic cylinders used to move both the load and the arms, an aspect which finds greater emphasis even in the case in which the arms are made by adopting unconventional materials for their realization as aluminum and composites.

In a cross-country skiing competition, the time difference between the winner and the skier coming in at second place is typically very small. Since the skier spends much of the energy on overcoming resistive forces, a relatively small reduction in these forces can have a significant impact on the results. The resistive forces come partly from the friction, at the tribological interface between the ski and the snow, and as with many tribological processes, the characterisation of its origin plays an important role in determining the frictional properties. Furthermore, in cross-country ski friction, there are several scales impacting the frictional performance, with the major contributors being the ski-camber profile and ski-base structure. Macro-scale measurements of the ski-camber profile under loading are often used to determine how adequate the ski is for use under specific conditions. The characteristic properties usually assessed are the force required to collapse the ski in order to obtain a certain camber height, the topography of the kick-wax zone, and the length (determined by simple means) of the frictional interfaces associated with the rear- and front glide zones, i.e., the apparent contact length. These measurements are, however, commonly performed by loading the ski against a much stiffer counter surface than snow and this affects the quantification of the characteristic properties. To date, some mathematical models have been proposed, but there is no reliable approach for determining the macro-scale properties of the contact between a cross-country ski and a counter surface using simulations. In the present paper, an Artificial Neural Network (ANN) has been trained to predict the ski-camber profile for various loads applied at different positions. A well-established deterministic approach has been employed to simulate the contact between the ANN-predicted ski-camber profile and a linearly elastic body with a flat upper surface, representing the snow. Our findings indicate that this method is feasible for the determination of relevant macro-scale contact characteristics of different skis with snow. Moreover, we show that the apparent contact area does not linearly depend on the load and that the material properties of the counter surface also exert a large impact when quantifying the apparent contact area and the average apparent contact pressure.

Fixed beam structures are widely used in engineering, and a common problem is determining the load conditions of these structures resulting from impact loads. In this study, a method for accurately identifying the location and magnitude of the load causing plastic deformation of a fixed beam using a backpropagation artificial neural network (BP-ANN). First, a load of known location and magnitude is applied to the finite element model of a fixed beam to create plastic deformation, and a polynomial expression is used to fit the resulting deformed shape. A basic data set was established through this method for a series of calculations, and it consists of the location and magnitude of the applied load and polynomial coefficients. Then, a BP-ANN model for expanding the sample data is established and the sample set is expanded to solve the common problem of insufficient samples. Finally, using the extended sample set as training data, the coefficients of the polynomial function describing the plastic deformation of the fixed beam are used as input data, the position and magnitude of the load are used as output data, a BP-ANN prediction model is established. The prediction results are compared with the results of finite element analysis to verify the effectiveness of the method. [ABSTRACT FROM AUTHOR]

The active clamp flyback (ACF) converter utilising gallium nitride (GaN) devices with high‐switching frequency and high efficiency is impressive in system miniaturisation for AC–DC adapters. Owing to poor reverse conduction of GaN devices, the improper dead time between two switches can cause large power consumption in high frequency. This study proposes a dynamic dead time optimisation technique for GaNs ideal zero‐voltage switching (ZVS) to address the issue. It adjusts the clamp switch on time to avoid large reverse conduction voltage stress on the main switch in different loads conditions. In addition, a new control scheme for clamp switch is introduced for enhancing efficiency in light to medium load. These techniques are experimentally verified on a 45 W (20 V/2.25 A) prototype of an ACF converter with a field‐programmable gate array. The controller enables the system to operate at 1 MHz and dynamically modulates the dead‐time under universal input and full load. With the light load ZVS control scheme, the system can achieve a maximum efficiency of 94.12 and 80.23% in the worst case. The prototyped converter can achieve power density (exclude case and controller) of 18 W/in3. [ABSTRACT FROM AUTHOR]

In the unfolding‐type interleaved two‐switch flyback inverter (ILTFI) operating in discontinuous conduction mode (DCM), the hybrid control strategy combining the one‐phase DCM and the two‐phase DCM has a significant impact on improving the efficiency under all load conditions. In the situation where the marginal power of this control strategy is increased, the converter may enter CCM. Consequently, the converter cannot track the reference current and the output current quality is notably decreased. To tackle this issue, a novel hybrid control method is proposed which varies the switching frequency based on the output power. The proposed approach is immune to the loss analysis and power losses of the components. Hence, it is independent of components selection and their characteristics. In this case, the smooth transition between the one‐phase and the two‐phase operation modes is guaranteed without affecting the output power quality and the stability of the converter in DCM. The control complexity of the proposed scheme is low and the converter can be easily controlled in DCM. The performance of the flyback microinverter with the proposed hybrid control scheme is verified by the simulation and the experimental results together with the loss analysis. [ABSTRACT FROM AUTHOR]

High efficiency, high power density and wide output voltage are required for on‐board charger (OBC) applications. LLC resonant converter has the advantage of achieving zero‐voltage switching for variable frequency and different load conditions. Compared with conventional fundamental harmonic approximation method, operation‐mode analysis based on the time domain model provides an accurate description of resonant current, voltage and DC gain. In this study, the efficiency‐oriented modified method is proposed based on the operation‐mode analysis. The converter inductance ratio, characteristic impedance and transformer turns ratio are optimised and both‐side soft switching can be achieved in the high output voltage region. Conduction loss can be minimised by optimising resonant parameters. Finally, a high‐efficiency design method is proposed and validated through experiments on a 3.3kW prototype applied in OBC. The prototype of the LLC resonant converter has been tested for dynamic charging voltage (230–430V) with a peak efficiency value of 98.5%. [ABSTRACT FROM AUTHOR]

Two‐stage power conversion system (PCS) for energy storage systems has been considered in islanded operation mode. A three‐level T‐type three‐leg three‐phase four‐wire topology (3LT2 3L3P4W) is employed as AC/DC part and a three‐level buck/boost converter is used as DC/DC interface. This study is mainly focused on balancing the neutral‐point potential (NPP) of the PCS with asymmetrical load connection. An NPP low‐frequency ripple model of 3LT2 3L3P4 inverter is proposed considering various load conditions firstly, which includes detailed expression of low‐frequency ripple components at fundamental frequency and fundamental frequency multipliers. Then, a novel NPP balancing method based on front‐end three‐level buck/boost converter under proportional resonant control is presented, in which the resonance points are set at fundamental frequency and triple fundamental frequency to suppress the dominant components of NPP ripple. Furthermore, a small‐signal model of three‐level buck/boost NPP control system is established and stability analysis is carried out. Simulation and experimental results have been provided to verify the accuracy of the NPP low‐frequency ripple model and the effectiveness of the NPP balancing method. [ABSTRACT FROM AUTHOR]

A novel converter with a three‐winding coupled inductor, called switched‐coupled‐inductor Z‐source inverter (SCI‐ZSI), is developed based on the switched‐and‐coupled inductor technology in this study. Compared with the conventional switched‐inductor Z‐source inverter and trans‐Z‐source inverter, the novel inverter had a higher voltage‐boosting capability. In addition, the improved topology shared a common ground point between the DC source and the inverter bridge. Under the same modulation index and load conditions, the input diode and capacitor voltage stress of the proposed inverter were lower than those of the other topologies. The operating principles, impedance‐network design, voltage and current stress are presented. The theoretical findings were verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

The linear permanent‐magnet synchronous generator (LPMSG) for direct‐drive wave energy conversion (WEC) suffers from many drawbacks that have not yet been overcome, such as a low power density and a bulky system volume. Therefore, a magnetic field‐modulated linear permanent‐magnet generator (FMLPMG) with a simple structure has been designed and manufactured. First, the operating principle of the FMLPMG is demonstrated by the equivalent magnetic circuit method, which explains the high power density of the FMLPMG. Second, at a constant speed and a sinusoidal speed, the electromagnetic characteristics of the FMLPMG under the no‐load and load conditions are analysed by the finite‐element method. Finally, a direct‐drive WEC test platform is built to simulate the process of wave action on the FMLPMG. No‐load and load experiments of the FMLPMG are conducted on the test platform, and the results are compared with those of an LPMSG with the same volume and operating conditions. The results show that the FMLPMG with a high power density converts wave energy effectively and solves the problem of low power density faced by the LPMSG in direct‐drive WEC. [ABSTRACT FROM AUTHOR]

This study is the first research to present a detailed assessment of core loss, copper loss and magnetic flux density of the interior permanent magnet synchronous motor (IPMSM) with pulse‐amplitude modulation (PAM) inverter under different excitation angles in both no‐load and load conditions. The PAM method automatically controls the amplitude of changeable DC‐link voltage, and the excitation angle for switches in the inverter is varied from 120° to 180° according to a 12‐step switching pattern designed particularly for the PAM‐based inverter of IPMSM. For reference purpose, the pulse‐width modulation excitation with a very high voltage modulation index is performed. Various conditions with changes in speed and torque are examined. Experimental results show that harmonic components produced by the PAM inverter in the IPMSM current, voltage and magnetic flux density have large effects on the motor core and copper losses; physics‐based explanations and insights are also presented. The PAM under 135° excitation angle has an excellent performance in reducing IPMSM core and copper losses since it can significantly decrease the harmonic components in motor current, voltage and magnetic flux density. Furthermore, simulations using the finite element method are conducted to validate the experimental results of IPMSM core loss with the PAM excitations. [ABSTRACT FROM AUTHOR]

A three-phase interleaved (LC)(L)-type dc–dc series-resonant converter with a capacitive output filter using fixed frequency control is proposed. The converter operations for different modes during different intervals have been presented using the operating waveforms. The converter is analysed using the approximate analysis approach, and the design procedure is illustrated with a design example. PSIM simulation results for the designed converter are given for load and input voltage variations. It is shown that the converter operates in zero-voltage switching (ZVS) at the minimum input voltage and for different load conditions. On the other hand, at the maximum input voltage from full load to light load, leading switches operate with ZVS, whereas lagging switches operate with zero-current switching (ZCS).

This paper develops a new field weakening method for an integrated permanent magnet synchronous machine vehicle drive. This method adopts both the DC-link and the rotor speed as a feedback signals to generate the demagnetising current reference. This eliminates the effect of the rotor speed on the FW controller dynamics and ensures stable operation across the whole range of speeds. Mathematical analysis of the system is used to design the controller gains to achieve the desired dynamic response. A maximum torque per ampere (MTPA) strategy is included in the control design, with a linearised function to reduce the computational demand. Experimental results show stable and satisfactory operation at different speeds and load conditions. They also illustrate smooth transition between the MTPA operation and the FW operation when the rotor speed crosses base speed.

In this study, by using the electromagnetic field analysis, the design of brushless DC generator with a novel construction and controller, appropriate for variable speed applications, is proposed. In the proposed machine, unlike the conventional structure, an assisted DC field coil is employed instead of permanent magnet excitation to provide a regulated voltage. Results of the electromagnetic field analysis show that including the DC field coil increases the controllability of the flux in different machine parts which provide a regulated terminal voltage in a wide speed range appropriate for variable speed applications. Moreover, the maximum power point tracking is achieved by controlling the DC field current along with producing optimal turn‐on and turn‐off angles for stator winding using the electromagnetic analysis based on optimal finite element analysis. Also, an appropriate controller is designed to control the DC field coil current. To verify the actual performance of the proposed configuration, a 1.5 Kw machine is manufactured and tested followed by the discussion on results. The obtained experimental results are in good agreement with the results of the electromagnetic analysis which confirm the maximum power trackability and robust output voltage regulation of the proposed conversion system under different shaft speeds and load conditions. [ABSTRACT FROM AUTHOR]

A three-phase interleaved (LC)(L)-type dc–dc series-resonant converter with a capacitive output filter using fixed frequency control is proposed. The converter operations for different modes during different intervals have been presented using the operating waveforms. The converter is analysed using the approximate analysis approach, and the design procedure is illustrated with a design example. PSIM simulation results for the designed converter are given for load and input voltage variations. It is shown that the converter operates in zero-voltage switching (ZVS) at the minimum input voltage and for different load conditions. On the other hand, at the maximum input voltage from full load to light load, leading switches operate with ZVS, whereas lagging switches operate with zero-current switching (ZCS). [ABSTRACT FROM AUTHOR]

This paper develops a new field weakening method for an integrated permanent magnet synchronous machine vehicle drive. This method adopts both the DC-link and the rotor speed as a feedback signals to generate the demagnetising current reference. This eliminates the effect of the rotor speed on the FW controller dynamics and ensures stable operation across the whole range of speeds. Mathematical analysis of the system is used to design the controller gains to achieve the desired dynamic response. A maximum torque per ampere (MTPA) strategy is included in the control design, with a linearised function to reduce the computational demand. Experimental results show stable and satisfactory operation at different speeds and load conditions. They also illustrate smooth transition between the MTPA operation and the FW operation when the rotor speed crosses base speed. [ABSTRACT FROM AUTHOR]

Emerging technologies in the field of integrated circuits demand wider conversion ratios with a substantial reduction in size and weight. Quadratic buck converter is a popular choice for such an application which is investigated under voltage‐mode pulse train control operating in discontinuous conduction mode. The combination of high‐power control pulse PH and low‐power control pulse PL in a control pulse repetition cycle which has a significant effect on the control performance of the system is studied. For a reliable design, a complete assessment of its dynamics under all possible operating conditions is essential for its safe operating horizons. Computer simulations are performed to capture the periodic transformation undergone due to border collision bifurcation. However, the stable periodic operation is examined with the supporting evidence of movement of eigenvalues from 2D discrete‐time model and maximal Lyapunov exponent obtained using QR factorisation method for the variation in the input voltage and the load conditions. An experimental setup is also built to verify the system dynamics which are observed in simulations and analytical results. [ABSTRACT FROM AUTHOR]

This paper proposes a simplified sequential Monte Carlo simulation to enhance the efficiency of bulk power system reliability evaluation. The basic idea is to construct chronological system state sequence by using the chronological probability model of load supplying capability which reflects the joint chronological variation pattern of system state intrinsic properties including load supplying capability (C), system state average duration ( D), and splitting percentage (P). The chronological probability model can simplify sequential simulation procedure no matter how system load pattern changes, and avoid the time-consuming optimal load curtailment model calculations by using the above-mentioned system state intrinsic properties. Thus, the proposed method can considerably accelerate simulation, especially when evaluating system reliability for different system load conditions. Besides, as the proposed method retains the chronological property of system state transition, it can not only obtain the probability distribution of reliability indices but also incorporate time-dependent renewable generations. RBTS, RTS79, and modified RTS79 with wind farm are utilized to verify the effectiveness of the proposed method. [ABSTRACT FROM PUBLISHER]

Perfect power system voltage stability is not possible in practice. Generally, the power grid is continually exposed to changes in its load and operating conditions. Therefore, dynamic stability analysis is one the most important and effective elements for greater security, stability and reliability of planning, design, operation and economic aspects of electric power networks. This study investigates and reports on the dynamic stability of the power system with a large‐scale photovoltaic system (L‐S PV). Two different scenarios with centralised PV power plants are considered in the medium voltage level without voltage regulation capabilities. Simulation results with these scenarios will show how the voltage instability decreases with the L‐S PV based on the bus status, disturbance location, and disturbance duration. In addition, the study discusses network terminal voltage, generator's rotor angle, generator's terminal current, generator's reactive power and electrical power output. This study is an extension of the earlier published conference paper. [ABSTRACT FROM AUTHOR]

This study investigates the effect of moving the binding and adjusting the normal load on friction for a modern cross-country ski. The binding was moved 10 cm forward and backward from the normal position. The results showed that moving the binding backward on the ski reduced the friction at cold (−10 °C) and warm air temperatures (+5 °C). At intermediate temperatures (−2 °C), neither changes to the binding position nor the total load affected the friction coefficient. Measurement of pressure zone profiles revealed that moving the binding backward reduced the apparent contact area, increased the average contact pressure, increased the peak pressure in the rear zone and increased the spacing between the front and rear contact zones of the ski. • The friction reduced when the binding was moved backward for the coldest and warmest temperatures. • The friction coefficient was load dependent only for warm and wet snow conditions. • Ski contact properties changed with load and load application point. • A non-linear correlation between the applied normal load and the apparent contact area was found. [ABSTRACT FROM AUTHOR]

Condition monitoring and predictive maintenance play a key role in the maintenance of an electrical machine. In this study, to monitor the condition of the induction machine, torque is predicted from the acquired acoustic signals. The acoustic signals collected from different locations of an induction motor are analysed using dyadic wavelet transform for various load conditions. The predicted torque is computed using multiple regression method by extracting the root mean square and mean statistical features of the processed acoustic signal. The percentage error is approximately 5–10% at different location validating the feasibility of using acoustic signals for condition monitoring of machines. In addition, the harmonics induced in the healthy machine due to various acoustic sources is verified using acoustic spectrum. Also, using Pseudo spectrum MUltiple SIgnal Classification algorithm, the pattern and peak decibel for the acquired acoustic signal at different locations are analysed. For any number of samples, the patterns are unique for each location at different speeds. The results obtained validate that pattern analysis method can also be used for condition monitoring and predictive maintenance in electric machines. [ABSTRACT FROM AUTHOR]

This study proposes a novel method for the parameter determination of permanent magnet (PM) synchronous machines under different load conditions. It can identify the total dq‐axis flux linkages and also the PM flux linkage separately by the addition of a pair of negative and positive position offsets. It is also noteworthy that the influence of uncertain inverter non‐linearity and winding resistance is cancelled during the modelling process, and the experimental results on two different PM synchronous machines show a good agreement with the finite‐element prediction results. More importantly, it shows good performance in online tracking the variation of PM flux linkage, which is an important feature for aiding the condition monitoring of PMs, for example, monitoring the temperature of PMs. [ABSTRACT FROM AUTHOR]

Accurate transmission line parameters are important for many applications that ensure reliable operation of a power system. The traditional theoretical calculations and offline measurements are widely used approaches obtaining line parameters, but they do not allow tracking of the parameters that change with the environmental factors and load conditions. Synchrophasor‐based real‐time transmission line parameter monitoring algorithms can track the changing parameters. In this study, two novel line parameter estimation algorithms: a lump parameter model and a distributed parameter model are proposed. The performance of the new algorithms are evaluated under various operating conditions using a real‐time digital simulator, and compared with six existing algorithms in terms of both accuracy and computational efficiency. The algorithms were also tested and compared using synchrophasor data obtained from a hardware experimental setup. Furthermore, application of the algorithms to an actual 230 kV transmission line is demonstrated. Finally, the sensitivity of the estimated parameters to bias errors in the measurements is analysed. [ABSTRACT FROM AUTHOR]

A fast method to calculate the iron loss of switched reluctance motor (SRM) is proposed. The key of the method is that the flux density waveforms in different parts of the motor can be obtained quickly. First, the static flux density data varying with phase current and rotor position in various parts of SRM are obtained by finite element method (FEM). Then, the static flux density data are stored in 2D look‐up tables in Matlab/Simulink to get the flux density waveforms by look‐up table method, and the obtained flux density waveforms are verified by FEM results. Since the flux waveforms are non‐sinusoidal and non‐linear, an accurate and fast model for the iron loss prediction is presented, and different modified factors are applied to calculate the hysteresis loss according to the classification of flux density waveforms. Based on that, the calculation model is established in Matlab/Simulink, and iron losses of a three‐phase 6/4 structure SRM under different turn‐on and turn‐off angles and load conditions are calculated and analysed. Finally, measured results are presented to verify the precision of the calculation model. [ABSTRACT FROM AUTHOR]

This paper outlines the use of a finite element model to simulate the behaviour for a standard steel bicycle frames under a range of measured load cases. These load cases include those measured both in the laboratory setting and also in the field, and include loads transmitted at key areas such as the dropouts and hub, the bottom bracket and drive, the headset and handlebars, and the seat post and saddle. The load cases analysed include static representations of dynamic bump situations which occur sporadically and also those which occur constantly or regularly such as those generated at the drive and handlebars during climbing or cruising. The resulting stresses within the bicycle are analysed in the context of frame performance relating to static and fatigue strengths and are also compared to similar load cases presented in the literature. Further research is required to understand the influence of tube profiles on frame strength, and to analyse the modes of failure for various bicycle designs and materials used under typical and extreme usage in order to understand the implications of design on safety. [ABSTRACT FROM AUTHOR]

The paper analyses and examines the efficiency of non-linear reactive power compensation when use the active power filter controlled by an algorithm based on the theory of CPC. The developed physical model of 3-phase active filter has been presented and results of its performance in the system so the linear load and nonlinear RL type are discussed. Particular attention was put on its operation in transient conditions. Based on both simulation and investigation results appropriate practical conclusions are formulated. [ABSTRACT FROM AUTHOR]

This paper proposes a voltage balancing method for flying capacitor multilevel converters based on phase-disposition pulse width modulation (PD-PWM) using optimal transitions between converter switching states. The optimal transitions between converter switching states are possible due to the converter states' redundancy and are decided with the continuous evaluation and minimization of a cost function. Simulation and experimental results verify the robustness of the proposed voltage balancing method against different load conditions. A significant reduction of the average switching frequency is achieved, when compared to the use of the optimal state voltage balancing method, where the optimal states are decided independently for each voltage level ignoring how transitions impact on the converter switching frequency. Moreover, the line-to-line output voltages are compared with the ones obtained with other modulation techniques in terms of total harmonic distortion values, and PD-PWM with the proposed voltage balancing method produces the best results. [ABSTRACT FROM AUTHOR]

In the case of operating in a weak grid system, when wind power becomes a significant portion of the power system or even the sole energy source, the wind power generators and converters are expected to help maintain the grid voltage. The grid‐side converter needs to work as a voltage source to help regulate the terminal (grid) voltage amplitude and frequency by adjusting the reactive power and active power flow, respectively. For a direct‐drive permanent magnet synchronous generator with a full power converter, the active power must be provided by the captured wind power. The active power flow between the source (captured wind power) and the grid (load) must be balanced by actively controlling the generator speed and wind turbine pitch angle. In the study, the coordinated control of generator speed and blade pitch angle is proposed together with a dc‐link voltage controller. A model of the grid‐side converter operating as a voltage source has been built and the strategy regarding voltage and frequency regulation is presented. Simulation is carried out with different wind and load profile. The results show the wind energy can help support the weak grid and power the local grid in stand‐alone mode as well. [ABSTRACT FROM AUTHOR]

Current literature does not provide any generalised method for specific permeance – magneto‐motive force‐based approach to predict all possible harmonic components in the air‐gap flux and line current of an eccentric salient‐pole machine. This study provides an elegant solution to express specific permeance of an eccentric reluctance synchronous machine as a summation of constant coefficient co‐sinusoidal terms. Binomial series expansion has been used to achieve this. The analysis has been validated by matching the presence of the predicted harmonic components in the stator line current by coupled magnetic circuit simulation based on modified winding function approach and experimental results. It is also shown that the effect of sensor errors, machine asymmetry, supply harmonics etc. can be minimised by residual estimation to vastly improve detection sensitivity under all load conditions. Thereafter, a procedure to identify fault type and severity has been presented. [ABSTRACT FROM AUTHOR]

Back-EMF-based sensorless control of permanent magnet synchronous machines (PMSMs) is preferred in many industrial applications due to its control simplicity and high machine efficiency. Position estimation based on the back-EMF is most reliable in the medium-to high-speed range. For applications where low-speed operation is not required, a simple-structure back-EMF-based sensorless controller coupled with a simple startup procedure offers an attractive low-cost solution. This paper proposes a new startup procedure based on closed-loop current regulation. Compared to the existing methods, the new starting method can work under different load conditions and allows smooth transition from the startup procedure to the back-EMF-based sensorless control mode. In order to determine the successful use of the proposed method in various applications, it stability under different load conditions is discussed in detail. The proposed method is robust when it comes to the motor parameter variation and can be used for both surface-mounted PMSMs (SPMSMs) and interior PMSMs. The method presented in this paper is validated using the experimental results on an SPMSM. A general design guideline is also given. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, dynamic behavior and performance of a fuel cell power plant (FCPP) which operates in parallel with a battery bank is tested under classified load conditions, such as mostly resistive, mostly inductive, resistive-inductive and non-linear loads. Thereafter, voltage stability analysis is performed using the dynamic response of the FCPP for stand-alone residential applications. Simulation results are obtained using the MATLAB® and Simulink® software packages, based on the mathematical and dynamic electrical models of the system. Using the experimental results, a validated model has been realized and voltage stability analysis is performed through this model. [Copyright &y& Elsevier]

The analysis and design of electrical machines often require analytical-models for performance assessment and system simulation. Inductances are important parameters of these models. The principles and drawbacks of the existing inductance calculation methods for electrical machines based on generalized electrical machine theory and the finite-element (FE) method are reviewed in this paper. To help alleviate some of the problems associated with these existing methods, the author has developed an improved FE inductance calculation method, and used it to evaluate inductances of equivalent circuit models. The new technique utilizes the same finite-element field solutions of electrical machines under actual multiphase excitations as are used for torque calculations. This eliminates the need for specially designed FE solutions, or for multiple solutions under current perturbations such as are required by existing FE methods. The new method has been verified by test results using a 30 hp permanent magnet synchronous machine under different load conditions. [ABSTRACT FROM PUBLISHER]