Dynamic Load Variations Research Articles

Modeling and Execution the Control Strategy for the Three-Level Rectifier Based on Voltage Oriented Control

In the recent years, three-level rectifier becomes an attractive rectifier replaced the two-level rectifiers. This rectifier provides many advantages, such as sinusoidal input current which contains low harmonics, unity power factor, bi-directional power flow, low voltage and switching loss for each switch. This paper presents a modelling and execution of the three-level rectifier for improvement of power quality under different loading based on voltage oriented control. The mathematical model and the control design were presented in this paper for the current inner loop and voltage outer loop, respectively. In order to evaluate the operation of the three-level rectifier under different conditions, the model was simulated by using MATLAB/Simulink. The experiment has been used to confirm the operation of the rectifier and its controller. The simulation and experimental results show that the excellent performance under steady-state and dynamic load variations was achieved; the unity power factor and pure sinusoidal in the grid side has also been accomplished.

Экспериментальные исследования систем перекрестных балок из деревянных элементов на квадратном плане при изменении динамических и статических нагрузок

Экспериментальные исследования систем перекрестных балок из деревянных элементов на квадратном плане при изменении динамических и статических нагрузок

Real‐time control of hybrid active power filter using conservative power theory in industrial power system

Industrial power system consists of several linear and non-linear loads. The proliferation of non-linear loads in power system causes the power system harmonics. Passive filters (PFs) are one of the ancient solutions to mitigate the harmonics. Some of the industrial power systems use PFs for harmonic compensation. Owing to dynamic load variation, the PFs are not the appropriate solution for harmonic compensation. To improve the system performance with existing PFs, this study presents the conservative power theory (CPT)-based hybrid active power filter (HAPF) with Type-II current controller for compensation of harmonics, reactive power and also the unbalance caused by different linear and non-linear loads of an industrial power system. In this system, the CPT is used as a harmonic reference generator and Type-II controller is designed for current control operation. The proposed HAPF overcomes the drawbacks of PFs and performs the compensation tasks effectively. The industrial power system with the proposed HAPF is modelled in MATLAB/Simulink environment and implemented in the real-time (RT) using OPAL-RT-based RT simulator. The RT results are in compliance with IEEE 519-2014 standard.

Advanced thermal management of automotive fuel cells using a model reference adaptive control algorithm

Temperature control is a critical issue to ensuring the reliable performance of fuel cell systems. However, nominal feedback controllers currently used to regulate system temperature have limitations, due to the high inherent nonlinearity in the systems, and uncertainty in the parameters of the models, especially in the presence of dynamic load variations. In this study, a feedback controller was designed including Model Reference Adaptive Control (MRAC) to address uncertainties and robustly control the stack and the coolant inlet temperature in a proton exchange membrane fuel cell (PEMFC). The proposed controller was then evaluated by comparison with a nominal feedback controller. It was shown that if the parameters vary in the system the MRAC algorithm yields improved transient performances in terms of recovery speed and deviation in comparison to the nominal feedback control algorithm. The MRAC provides enhanced robustness.

맥놀이하중을 받는 공간구조물의 동적좌굴과 임계하중

In this study, the dynamic unstable phenomenon and critical load variation of the spatial truss under the beating-wave load were researched. For this purpose, a non-linear governing equation of a shallow spatial truss was derived. In addition, a dynamic analysis and a characteristic analysis of the buckling phenomenon were conducted using the numerical method. The analysis model was selected considering the number of free nodes and the rise-span ratio, and the response to the periodic parameter that determines the period of the beating function was analyzed. To compare the results, a analysis for the step load and sinusoidal-wave load were also conducted. Resonance was observed in the analysis results for both the sinusoidal-wave load and the beating-wave load. The patterns of critical load level were similar in the area lower than the natural frequency, but they were different in the area above it. Furthermore, the critical level of the beating-wave load changed more sensitively than the sinusoidal-wave load did and was much lower than the step load.

Cascaded Bidirectional Converter Topology for 700 W Transformerless High Frequency Inverter

Home inverter is an important system which provides uninterrupted power supply for domestic requirements. Most of the existing systems use line frequency transformers to generate the desired sinusoidal voltage and exhibit poor load regulation and efficiency. Under spurious conditions, reliable and stable operation of the inverter is a primary requirement. In this paper, 3-stage bidirectional (boost and buck) cascaded converter topology is proposed to boost an input battery voltage from 12 to 375 V and vice-versa. DC link is connected to H-bridge converter to obtain a desired sinusoidal output voltage. In the topology, first and third stages are non-isolated boost converters and second stage is a buck derived push–pull converter. Push–pull configuration of the 2nd stage provides electrical isolation to source from high voltage DC bus. Cascaded DC–DC converter outputs are regulated by designing an average current mode control and instantaneous voltage control is designed for H-bridge inverter. Hardware is designed and developed using digital signal controllers to supply 700 W domestic load. Experiments are conducted for different linear, nonlinear and dynamic load variations.

Neuro-Fuzzy Based Interline Power Flow Controller for Real Time Power Flow Control in Multiline Power System

This article investigates the power quality enhancement in power system using one of the most famous series converter based FACTS controller like IPFC (Interline Power Flow Controller) in Power Injection Model (PIM). The parameters of PIM are derived with help of the Newton-Raphson power flow algorithm. In general, a sample test power system without FACTs devices has generated more reactive power, decreased real power, more harmonics, small power factor and poor dynamic performance under line and load variations. In order to improve the real power, compensating the reactive power, proficient power factor and excellent load voltage regulation in the sample test power system, an IPFC is designed. The D-Q technique is utilized here to derive the reference current of the converter and its D.C link capacitor voltage is regulated. Also, the reference voltage of the inverter is arrived by park transformation technique and its load voltage is controlled. Here, a sample 230 KV test power system is taken for study. Further as the conventional PI controllers are designed at one nominal operating point they are not competent to respond satisfactorily in dynamic operating conditions. This can be circumvented by a Fuzzy and Neural network based IPFC and its detailed Simulink model is developed using MATLAB and the overall performance analysis is carried out under different operating state of affairs.

A Stand Alone Robust PV-FC-Electrolyzer Utilization Scheme

A stand-alone efficient robust photovoltaic (PV)- Electrolyzer Scheme using a PV-Array, a DC-DC buck-boost converter, an Electrolyzer, a hydrogen tank, and an additional Fuel Cell (FC) stack feeding an standalone autonomous load is investigated and validated for efficient energy utilization, voltage stabilization and maximum power point tracking (MPPT) of the PV array under different insolation and temperature variations. The DC-DC Converter by controlled to ensure stable regulated operation. The PV generated power is used to electrolyze water to Hydrogen H2 and Oxygen O2, where hydrogen is stored in a suitably sized tank to be used later for the PEM-Proton Exchange membrane fuel cell (PEMFC). The PEMFC also acts as supplementary energy storage and load balancer to supply dynamic variable load whose value can vary from a minimum of 300W to a maximum of 1Kw. The Hydrogen H2 flow to the FC depends on the dynamic load variations. The controller is fully regulated for efficient energy utilization as well as voltage regulation. The validated scheme components are modeled using Matlab/Simulink and fully integrated, to assess the unified system dynamic performance under varying conditions. Keywords— PV, Buck-Boost converter, Electrolyzer, and PEMFC.

Plumpness Analysis of Indicator Diagram for Vehicle Damper

According to the indicator diagram of damper, the indicator diagram plumpness was proposed as a quantitative index, and its mathematical relationships with the sprung mass acceleration, suspension dynamic travel and tire dynamic load were built. Moreover, the influence of the total area on suspension characteristics was analyzed in time domain and frequency domain. The results show that, the increase of the indicator diagram plumpness can effectively restrain the variation of suspension dynamic travel and tire dynamic load, meanwhile, the body acceleration will be enlarged. Excessive indicator diagram plumpness also affects the dynamic tire load distribution in frequency domain, and it will decrease the driving security. Therefore, it should be reasonably selected from the performance indicators, which is based on the requirement of vehicle demand in the design process.

Synchronous-Reference-Frame-Based Control of Switched Boost Inverter for Standalone DC Nanogrid Applications

Switched boost inverter (SBI) is a single-stage power converter derived from Inverse Watkins Johnson topology. Unlike the traditional buck-type voltage source inverter (VSI), the SBI can produce an ac output voltage that is either greater or less than the available dc input voltage. Also, the SBI exhibits better electromagnetic interference noise immunity when compared to the VSI, which enables compact design of the power converter. Another advantage of SBI is that it can supply both dc and ac loads simultaneously from a single dc input. These features make the SBI suitable for dc nanogrid applications. In this paper, the SBI is proposed as a power electronic interface in dc nanogrid. The structure and advantages of the proposed SBI-based nanogrid are discussed in detail. This paper also presents a dq synchronous-reference-frame-based controller for SBI, which regulates both dc and ac bus voltages of the nanogrid to their respective reference values under steady state as well as under dynamic load variation in the nanogrid. The control system of SBI has been experimentally validated using a 0.5-kW laboratory prototype of the SBI supplying both dc and ac loads simultaneously, and the relevant experimental results are given in this paper. The low cross regulation and the dynamic performance of the control system have also been verified experimentally for a 20% step change in either dc or ac load of SBI. These experimental results confirm the suitability of the SBI and its closed-loop control strategy for dc nanogrid applications.

Penetration impact of wind farms equipped with frequency variations ride through algorithm on power system frequency response

Focus of power system engineers is currently directed to the impact of wind power on system frequency. Research efforts concentrate on the ability of wind farms to contribute in the frequency droop events by injecting active power to the grid. This paper presents a detailed analysis for the effect of wind farm connection to a certain power system on the system frequency response. Most of wind farm parameters were considered, namely, the actual wind speeds, wake effects inside the wind farm, the different arrangements of wind turbines inside the wind farm and pitch control mechanism. Moreover, the major data of a h power system were included; different conventional generation technologies and their suitable speed governors. In addition, instant dynamic load variations were implemented. Five case studies were conducted through this system to test the system frequency attitude during normal operation and in case of sudden and large load changes. Three basic values are used to estimate the mentioned impact; the time needed to reach the safe margin after a certain droop, the RMS value of frequency deviation after the fault initiation by a given fixed time span and the maximum frequency drop for each event. All the previously stated studies are performed using MATLAB and Simulink simulations depending on real wind speeds data.

고속 전차선로 드로퍼에 대한 기계적 하중에 관한 연구

드로퍼는 전차선로에서 여러형태의 클램프로 취부되어 전차선이 수평으로 유지하도록 지지하고, 판토그라프가 통과할 때 굽힘에 대한 기계적 응력에 영향을 받는다. 고속선용 드로퍼의 파단 원인을 조사하기 위해, 이론적 분석 및 시험을 실행하였다. 본 논문에서 사전이도에 의한 드로퍼의 정적 하중을 계산하였고, 시험에서 측정된 값과 유사하였다. 드로퍼 와이어의 파단원인을 분석하기 위해 현장에서 파단된 시료는 SEM 분석을 하였고, 새 시료도 일부 병행하며 시행하였다. 마지막으로, 고속열차가 300km/h로 통과할 때 드로퍼에 대한 동적 하중의 변화를 측정하였다. 기계적 하중이 반복적으로 발생될 때, 드로퍼 와이어는 피로에 의해 파단될 것이다. 이 결과는 고속전차선로 유지보수의 특별 관리와 드로퍼의 수명평가를 하는데 활용될 수 있을 것이다. The dropper supports the contact wire and is attached using various types of dropper clips on the catenary. Droppers are subject to mechanical stress from buckling during the passage of pantographs. In order to investigate failure causes for the high speed line dropper, theoretical analyses and experiments have been carried out. In this paper, mathematical formulas are derived for the pre-sag of the dropper static load. The measured values in the experiment were similar to the theoretical predictions. To analyze the cause on fracture of dropper wire, we have conducted analysis such as SEM(Scanning Electron Microscope) of fractured specimens in the field and new specimens. Finally, we performed measurement for the variation of dynamic load on the dropper when a pantograph moved at 300km/h under the Korean high speed overhead line. If such mechanical load occur repeatedly with every passing pantograph, it is possible that the dropper wire will break due to fatigue. This results will be used for special management of high speed catenary system maintenance and life estimation of dropper.

Dynamic eccentricity fault diagnosis in round rotor synchronous motors

In this paper, a novel approach is presented to detect dynamic eccentricity in round rotor synchronous motors. For this, an efficient index is introduced based on processing developed torque using time series data mining (TSDM) method. This index can be utilized to diagnose eccentricity fault and its degree. The capability of this index to predict dynamic eccentricity is illustrated by investigation of load variation impacts on the nominated index. Stator current spectrum of the faulty synchronous motor under different loads and dynamic eccentricity degrees are computed. Effects of the dynamic eccentricity and load variation simultaneously are scrutinized on the magnitude of 17th and 19th harmonic components as traditional indices for eccentricity fault diagnosis in synchronous motors. Necessity signals and parameters for processing and feature extraction are evaluated by winding function method which is employed to model healthy and faulty synchronous motors.

Load-Following Strategies for Evolution of Solid Oxide Fuel Cells Into Model Citizens of the Grid

Proper converter design can allow solid oxide fuel cells operated as distributed generators to mutually benefit both the load and the electric utility during steady-state conditions, but dynamic load variations still present challenges. Unlike standard synchronous generators, fuel cells lack rotating inertia and their output power ramp rate is limited by design. Two strategies are herein investigated to mitigate the impact of a large load perturbation on the electric utility grid: 1) external use of ultracapacitor electrical storage connected through a DC-DC converter and 2) internal reduction of steady-state fuel utilization in the fuel cell to enable faster response to output power perturbations. Both strategies successfully eliminate the impact of a load perturbation on the utility grid. The external ultracapacitor strategy requires more capital investment while the internal fuel utilization strategy requires higher fuel use. This success implies that there is substantial flexibility for designing load-following fuel cell systems that are model citizens.

Star-hexagon transformer and non-isolated three-leg VSC based three-phase four-wire DSTATCOM

A new three-phase four-wire DSTATCOM (distribution static compensator) is proposed for power quality improvement in the distribution system. The DSTATCOM is based on a star/hexagon transformer and three-leg VSC (voltage source converter). It compensates harmonic current, reactive power and balances the load along with neutral current compensation. Each of the three single phase transformers has three windings and the secondary windings are connected in star/hexagon configuration for interfacing to a three-phase four-wire power distribution system. The IGBT (insulated gate bipolar transistor) based VSC is a capacitor supported and it is controlled for the required compensation of load currents. The DC bus voltage of the VSC is regulated even during dynamic load variations. The DSTATCOM is tested for power factor correction and voltage regulation along with neutral current compensation, harmonic elimination and load balancing under linear loads as well as non-linear loads. The performance of the three-phase four-wire DSTATCOM is validated using MATLAB software with its Simulink and SimPower System (SPS) tool boxes.

Evaluation of dynamic vehicle load on bridge decks

Developed herein is a spectral approach for evaluating the dynamic vehicle load due to the passage of a vehicle moving at constant speed along a rough bridge surface. Based on the approach, a simple closed‐form solution for predicting the variation of dynamic vehicle load on a bridge deck is derived. Numerical examples of the application of the solution to a simply‐supported bridge are presented. Four different classes of pavement roughness (including: very good, good, average, and poor pavements) and three different vehicle speeds (speeds of 60, 100, and 140 km/h) are used in numerical analysis. The Dynamic Load Coefficient (DLC), a parameter used to characterize the magnitude of dynamic vehicle load, is estimated. The effects of vehicle speed and pavement roughness on the variation of dynamic vehicle load are investigated. It is concluded that if the effect of engine motion on vehicle vibration is disregarded, both the DLC and standard deviation of dynamic vehicle load are proportional to the square root of the pavement roughness coefficient S(n 0) for a specified vehicle speed.

Evaluation of an Artificial Neural Network Technique Applied to Multiple-Sensor Weigh-in-Motion Systems

Weigh-in-motion (WIM) accuracy in measuring static axle loads is affected by vehicle dynamics and noise. Neural networks can identify underlying relationships, such as the spatial repeatability in axle dynamics, and can efficiently remove noise. Furthermore, they can adapt to changing circumstances (e.g., traffic characteristics, road profile, or sensor failure), unlike conventional WIM calibration algorithms. The paper performance of a multilayer feed-forward artificial neural network algorithm applied to a multiple-sensor WIM is analyzed. Numerical simulations of the axle forces applied on a smooth road profile are used to train, validate, and test the artificial neural network algorithm. This dynamic axle load variation is predicted with the vehicle simulation model VESYM. The mechanical parameters of the truck models and their speeds are randomly varied over a range established from real traffic measurements. Once the theoretical WIM data are obtained at the sensor locations, the measurements are artificially corrupted with noise up to the typical level of WIM accuracy. Details are given on the process of the neural network design, the size of the training sample, and the length of the training period. The artificial neural networks approach resulted in higher accuracy than the traditional average-based calibration method, especially at high noise levels. As a result, it shows promise for estimating static axle loads from multiple WIM measurements.

Structural design and analysis for a sensor-integrated ball bearing

The structural design issues associated with the development of a sensor-integrated ball bearing were investigated. A finite element model was established to analyze the structural integrity of a ball bearing whose outer ring was modified to accommodate a miniaturized load sensor module. The sensor module was designed to monitor dynamic load variations within the bearing, which is an important indicator of a bearings safe operation. This structural integration of “intelligence” is significant in that it bring's automated, on-line, self-diagnosis capability to a dynamic system for which reliable, safe operation is of critical importance. A design tool was developed to evaluate the effect of outer ring modification on the dynamic load-carrying capability of the bearing. The tool also provided quantitative guidelines for the design of load and other types of sensor modules that will be structurally embedded into the outer ring of a conventional bearing for industrial applications.

Vibration Analysis of a Sensor-Integrated Ball Bearing

This paper presents an analysis of the vibrational behavior of a deep groove ball bearing with a structurally integrated force sensor. The miniaturized force sensor, accommodated within a slot on the bearing’s outer ring, provides on-line condition monitoring capability to the bearing. Analytical and finite element models were developed to predict the sensor output due to bearing dynamic load and rotational speed variations. Experimental studies were conducted on a ball bearing to validate the analytical and numerical solutions. Good agreement was found between the model-predicted sensor outputs and the experimental results. The findings validated the approach of integrated-sensing for on-line bearing condition monitoring. [S0739-3717(00)00203-8]

Enhanced reserved polling multiaccess technique for multimedia personal communication systems

This article describes a multiaccess technique which allows the transport of multimedia information across global personal communication systems (PCS). Impressive growth in the application of wireless technologies to telecommunications has sparked active research on a new generation of mobile radio networks projected to handle heterogeneous traffic types. One of the key requirements of these advanced systems is the multiaccess protocol which must guarantee quality of service and provide efficient access to multirate broadband applications that combine voice, video and data communications. In addition, the protocol is required to operate with the demanding constraints imposed by moving users, dynamic traffic load variations and highly sensitive wireless links. To this end, a multiaccess scheme called “enhanced reserved polling” is proposed. The scheme is designed to execute many PCS-related functions including radio resource assignment, connection control and mobility management. It accommodates a diverse mixture of delay classes/message priorities and can also enhance the bandwidth sharing among different cells in the network.