Analysis Of Transient Characteristics Research Articles

Design and Optimization of Ultradeep Submicron CMOS Inverter Using a Unified All Regional MOSFET Model

Complementary Metal Oxide Semiconductor (CMOS) has always remained the dominant integrated circuit technology specifically for designing digital circuits. This paper examines the modelling (utilizing $\alpha$-power based MOSFET model), simulation (utilizing HSPICE simulation) and optimization (utilizing Particle Swarm Optimization (PSO) and Artificial Bee Colony (ABC) techniques) of ultradeep submicron CMOS based digital inverter, performs insightful analysis and extracts formulas for the optimal transistor sizing. Additionally, the study serves as an implementation forum for the thermal analysis of transient characteristics of CMOS inverters at the ultradeep submicron technology node (at 300K and 400K). The results lie within the acceptable range of 1-10\%.

Transient Response Characteristics Analysis of High-Power Piezoelectric Transducers.

Highlights What are the main findings? Derive the characteristics of transient equations under different excitations, and conclude the time constant is the key to the stability of the transducers.Applying a vector reduction method to analyze a series RLC transient matching scheme, which can change the electromechanical damping and improve the transient response time of the system. What is the implication of the main finding? A matching scheme combined with full-bridge inverter, transformer and series LC, is adopted to improve the transient response characteristic, which can provide suitable electrical damping without causing energy losses. To improve suitability in applications with high dynamic performance requirements, the transient response characteristics of high-power piezoelectric transducers should be studied quantitatively. This paper proposes the vector reduction method to solve the complex transient equations and obtains a transient matching scheme clarifying the mechanism of electrical matching resistance on electromechanical damping. A matching scheme with a combination of full-bridge inverter, transformer and series LC circuit is designed and validated, which can provide suitable electrical damping without causing energy losses. Consequently, the experiment verifies the transient properties of the proposed scheme. For a typical piezoelectric cutting transducer with 100.8 ms response time, our scheme is verified to have high dynamic performance within frequency response time of 5.5 ms and vibration response time of 15.0 ms.

Investigation of PEM Fuel Cell Characteristics in Steady and Dynamic Operation Modes

The article is devoted to the problem of proton-exchange membrane fuel cells (PEMFCs) integration into power supply systems. A hybrid energy complex (HEC) based on PEMFCs and lithium iron phosphate batteries can be used as a reliable energy source. It is necessary to properly determine the PEMFC characteristics in order to develop a PEMFC-based HEC prototype and its control algorithms. This paper presents a 1 kW PEMFC’s test results in steady and dynamic modes. The dependences of the average hydrogen consumption per 1 min, the volume of hydrogen for the generation of 1 kWh, the PEMFC efficiency on the load current were obtained and an analysis of these dependences for steady operation modes was performed. A range of load changes beyond which the efficiency of the PEMFC significantly decreased and it was recommended to switch to the joint operation of the PEMFCs and batteries (or only batteries) was established. Diagrams of the PEMFC output voltage during the dynamic changes in loads are presented and an analysis of transient response characteristics was carried out. The air supply fans were found to affect the performance of PEMFCs.

Transient Characteristic Analysis of Variable Frequency Speed Regulation of Axial Flow Pump

In order to explore the influence of different rotational acceleration on the transient internal and external flow characteristics of the axial flow pump and improve the performance of the pump, numerical simulations and experiments were used to analyze the variable frequency speed regulation characteristics of the axial flow pump. Taking three-dimensional turbulent numerical simulation as the main research method and CFX as the calculation platform, three variable frequency speed regulation methods were used to conduct transient numerical simulation; keep the acceleration constant, increased and decreased; and obtain the real-time pump performance curve and pressure characteristic curve. Uniform acceleration and deceleration with constant acceleration maintained the stable change and good stability of head and shaft power, and the pressure change was the most stable in the process. The acceleration and deceleration with decreasing acceleration ran most smoothly at high speed, and the frequency conversion effect was the best. At the same time, the transition to steady-state operation was also the most stable. The research in this paper can provide reference for the stable operation of variable frequency speed regulation of the axial flow pump.

Analysis of Electromagnetic Transient Characteristics on the Winding of UHVDC Converter Transformers Based on an Improved Broadband Model

This work proposes an improved broadband equivalent circuit model of the winding system of an ultrahigh-voltage direct current (UHVDC) converter transformer and the validation experiment of the model conducted on a tapped transformer. The matrices of the inductance, capacitance, and resistance parameters in the improved model were all obtained by the finite element method according to the winding system structure of a UHVDC transformer. Then, the potential distributions along the windings under impulse voltages with different waveforms were studied in detail. Finally, the relationship between the potential gradient and waveforms was obtained. This work provides a convenient method to acquire the broadband electromagnetic transient characteristics of the winding systems within UHVDC converter transformers.

Study of transient characteristics of BAW filters under high power levels

The improvement of power capacity would benefit greatly from the analysis of transient characteristics of bulk acoustic wave (BAW) devices. For this purpose, a measurement system was established, which could capture the temperatures and the insertion loss (IL) of the BAW devices simultaneously. Based on the obtained testing data of four different commercial BAW filters, we clarified the time dependence of device temperature and IL. The results showed that the BAW filters would exhibit higher power capacity with higher threshold frequency and a lower slope of the characteristic curves. This prompts us to propose an evaluation method for BAW filters under high power levels, which could improve the efficiency of device selection and performance prediction.

Analysis of Transient Characteristics of Submersible Tubular Pump During Runaway Transition

In order to study the transient characteristics of the submersible tubular pump in the process of power failure, the 6DOF model was used to carry out three unsteady numerical values for the whole flow channel of the pump. The results show that the calculation results of the 6DOF model based on the fourth-order multi-point Adams–Moulton formula are in better agreement with the experimental results than the first-order format to predict the impeller motion. When the unit is powered off, the speed and flow of the pump device decrease rapidly with time. At the maximum head 3.41 m, when the unit enters the runaway condition, the speed is about −1.88 times the initial speed and the flow rate is about −1.98 times the initial flow. The axial force and radial force of the impeller increase alternately, and compared with the normal operating condition, the radial force is significantly increased. In the process of the pump device changing from forward flow to reverse flow, the internal flow state of the pump device is relatively chaotic, and there are a large number of vortices in the flow channel, which is easy to cause structural vibration. Before reaching the runaway state, a large number of vortices also appear inside the impeller and guide vane, causing flow blockage, especially when the flow rate is zero. At the same time, the reverse flow impact causes the local pressure on the blade surface to increase, which threatens the stability of the blade structure. The pressure at the impeller inlet, impeller outlet, and guide vane outlet monitoring points is the largest near zero flow, and the smallest during runaway. The main frequency of the pressure pulsation in the pump device is the blade pass frequency (fBRF) and its harmonics (2fBRF, 3fBRF, 5fBRF, etc.), and the pressure pulsation intensity increases with the increase of the impeller speed. The results of this study provide a theoretical reference for the operation of the submersible tubular pump to ensure the safety and stability of the pumping station.

Analysis of high frequency and transient characteristics of the flow past a circular cylinder

Analysis of high frequency and transient characteristics of the flow past a circular cylinder

Collaborative optimization of bushing installation angle and bushing stiffness of torsion beam suspension to improve the handing stability of the whole vehicle

Both the bushing installation angle and bushing stiffness of torsion beam suspension have important and complex effects on suspension characteristics and vehicle handling stability. For improving the vehicle handling stability by optimizing the two, this paper systematically analyzes the influence mechanism of the bushing installation angle and bushing stiffness of the torsion beam suspension on the suspension C characteristic. The nonlinear relationship between the bushing installation angle and the steady-state characteristics index in the local design space is discussed. The influence mechanism of the bushing installation angle and bushing stiffness on the frequency response characteristics is deeply analyzed, the variation relationship of the frequency characteristic index at the low frequency of 0.5 Hz under different bushing installation angles and bushing stiffnesses is obtained. Finally, the bushing stiffness, which has a great influence on the frequency characteristics, and the bushing installation angle are taken as the optimization variables, and the frequency characteristic index is taken as the optimization goal, and the multi-objective collaborative optimization of the frequency characteristic is carried out with the help of genetic algorithm. From the comparative analysis of transient and steady-state characteristics before and after optimization, it can be seen the vehicle handling stability has been improved.

Analysis of transient flow field characteristics during the closing process of water distributor valve core

The integrated water distributor (IWD) is the adjustment terminal during the interval injection process. Its quality and performance are directly related to the effect of layered water injection. The IWD’s flow field is considered the research object, and the transient simulation is developed with Fluent dynamic grid and Fluid-Structure Interaction technology. The internal flow of the IWD during closing is simulated, and the mechanical behavior of the valve core is analyzed. The results show that: as the valve opening decreases, the high-speed areas appear at the throat of the valve core and the upper wall of the valve outlet; the throat of the valve presents a higher pressure gradient; the most serious deformation point appears on the lower side of the valve core, and the deformation increases as the valve core move down; the maximum equivalent strain occurs at the root of the valve core and increases as the valve core moves down.

Transient characteristic analysis for large-scale power system with MMC-MTDC

Modular multi-level converter (MMC)-based multi-terminal dc (MTDC) grid (abbreviated as MMC-MTDC) is promising in the integration and transmission of bulk renewable energy. This paper analyzes the transient characteristic of large-scale power systems with the MMC-MTDC. First, the transient stability-electromagnetic transient (TS-EMT) model of the system is established. The corresponding simulation flowchart is also presented, where the MMC-MTDC grid dynamics are calculated by EMT simulation and the ac grid is simulated by the TS program. Second, based on the mathematical model of the MMC-MTDC grid, the transient characteristics during various faults are analyzed. Third, it analyzes the influences of the controller parameters on the transient characteristics. Test results on the North-China power system with Zhangbei MTDC verifies the correctness of the transient characteristic analyses.

Analysis and optimization of vehicle transient characteristics under sine-swept steering input with considering steering system stiffness and damping

This study focuses on the influence of steering system stiffness and damping on the vehicle transient characteristics at two different types of handling frequencies, and optimizes the vehicle transient characteristics with steering system stiffness and damping as optimization variables at both handling frequencies. The kinematic relationship between wheel angle and steering wheel angle is derived as well as a detailed analysis of the forces on the steering linkage. The differential equations of vehicle dynamics are developed to explain the influence of steering system stiffness and damping on the vehicle transient characteristics theoretically. The stiffness and damping, which have a significant influence on the vehicle transient characteristics, are selected by sensitivity analysis and used as variables for simulation verification. Simulation results show that the influence of steering system stiffness and damping on vehicle transient characteristics is different at high handling frequencies and low handling frequencies. The stiffness and damping are used as optimization variables and the objective evaluation indexes of vehicle transient characteristics at high handling frequencies and low handling frequencies are used as optimization targets for multi-objective optimization by the NSGA-II optimization algorithm. The optimization results show that: The yaw rate gain relative to steering wheel angle and the delay time of lateral acceleration relative to steering wheel angle are improved at both low and high frequencies.

Comparative analysis of transient valve-induced flow characteristics between opening and closing processes

Transient control of process valves, including opening and closing processes, is consistently encountered in many fluid transportation and control industries. During opening and closing processes, valve-induced transient flow presents different unstable flow characteristics. This transient valve-induced unstable flow that develops along the pipeline can cause violent pressure and velocity fluctuations that considerably influence accurate flow measurement downstream. In this paper, gate valve-induced flow characteristics during opening and closing processes were comparatively studied. An experimental system was developed to monitor the downstream pressure along the pipeline, and corresponding transient numerical simulations were performed on opening and closing processes using a user-defined function and dynamic grid technology. The pressure distributions along the pipeline's downstream area during valve opening and closing processes were investigated to verify the accuracy of the numerical simulation. The mechanism of transient flow difference under the same valve opening during opening and closing processes was determined to be a hysteresis effect. The jet flow intensity under a small valve opening in the opening process was greater than that in the closing process, and the difference in flow field under the 50% valve opening was the largest. Moreover, the velocity and turbulent kinetic energy distributions in different downstream cross-sections during valve opening and closing processes were comparatively analyzed. The change rate of the maximum turbulent kinetic energy was introduced to further analyze the different effects of opening and closing processes on the transient flow stability downstream of the valve. Results showed that the flow stability between 40% and 50% valve opening was the worst irrespective of the adjustment process, that is, a large pipeline distance was required to stabilize this transient flow. This study helps in understanding transient valve-induced flow characteristics in fluid transportation pipelines and provides guidance for accurate flow metering industrial applications.

Modelling and simulation analysis of MMC‐HVDC system based on transient energy flow

In the high voltage direct current (HVDC) transmission system composed of modular multilevel converters (MMC), considering the distribution of transient energy flow (TEF) contributes to the transient modelling and fault characteristic analysis when dc short-circuit fault occurs. For single MMC, based on transient energy conservation, the capacitors of half bridge sub-modular (HBSM) can be equivalent to time-varying capacitor. And the MMC transient model is established, in which dynamic switching of HBSM and ac import are considered. By solving state equations of the model, the fault and TEF characteristics of MMC are obtained. For MMC-HVDC grid, a TEF analysis method based on electromagnetic transient simulation results is proposed, which can not only reveal the evolution of dc fault, but also realize quantitative analysis of fault current through recursive calculation. Based on characteristics of TEF, an energy limitation strategy considering the fluctuation range of capacitor voltage in HBSM is proposed, which can delay the blocking time effectively. According to the simulation results in PSCAD, the correctness of the transient model and the energy limitation strategy is verified, meanwhile, the TEF analysis method is applied to the four-terminal MMC-HVDC grid to obtain its fault characteristics.

Simulation analysis of transient output characteristics of inverter with asynchronous motor load based on second-order filtering link

Based on the voltage and current oscillation characteristics of the second-order filtering link, an LC boundary condition analysis method for the steady-state and transient minimum output power of the inverter power supply for asynchronous motor drive based on the concept of dynamic capacitive and inductive coefficients is proposed. For three typical motor topologies below 100 kW class, a dynamic equivalent resistive model based on turndown rate - input frequency is established and its starting transient and speed steady-state resistive characteristics are analyzed. On this basis, the dynamic capacitance coefficient-current amplification curve and dynamic inductance coefficient-voltage amplification curve are introduced, and the optimal (C,L) combination solution is extracted by data screening and 3D fitting to control the inverter output current inrush while improving the voltage utilization efficiency. The optimal (C,L) combination solution is extracted by data filtering and 3D fitting to control the inverter output current inrush while improving the voltage utilization efficiency. The image2data tool is used to compare and analyze the characteristics of second-order filtering parameters selection under two common strategies of specific harmonic cancellation pulse-width modulation (SHEPWM) and triangular carrier pulse-width modulation (TCPWM) for motor drives, and introduce the device voltage distortion model to improve the system accuracy. It is found that the output power of SHEPWM is about 0.03% higher than that of TCPWM under the same loading condition, and the obtained boundary LC parameters can simultaneously meet the transient starting power requirement of the motor and optimize the output efficiency of the inverter at steady state speed.

Analysis of Transient Operating Characteristics of the 10 Kv Tri-Axial HTS Cable Under Fault Current

The Tri-axial high temperature superconducting (HTS) cable usually subjects to the impact of the fault currents in the power system. During the fault, a large amount of the Joule heat is generated, which may be damage cable. In this paper, an analysis model of electromagnetic thermal transient characteristics of the 10 kV/1 kA cable is built. The transient characteristics of the HTS cable are analyzed under a fault current of 15 kA rms lasting 0.14 s, and the current, resistance and temperature of the HTS cable are obtained. The maximum temperature of the HTS cable is 153.1 K under fault current. Meanwhile, the safe operating range of the HTS cable under the fault current of 15 kA to 25 kA is obtained. the analysis results will provide the theoretical basis for the quench protection and relay protection strategy of the tri-axial HTS cable in the Grid.

RECIRCULATION PUMP SCALAR CONTROL SYSTEM ELECTRICAL DRIVE MODEL S DEVELOPMENT AND RESEARCH

On the basis of the analysis of the used models of the electric motor at synthesis of the asynchronous electric drive with frequency control mathematical and simulation models are received. The structural scheme of the three-circuit scalar control system of the electric drive of the recirculation pump in the form of the simulation model for which the parameters of the scalar control system were calculated is offered and realized. The calculation of parameters and coefficients of the mathematical model of the solar control system of the electric drive is given. The calculations of the pressure of the recirculation pump are presented. The scheme of the simulation model of the subsystem of the unit for calculating the performance and pressure of the recirculation pump is given. Calculations and simulation model of PI current regulator are presented. Calculations and simulation model of PID-speed controller subsystem are given. Calculations andsimulation model of PI-pressure regulator subsystem are presented. Calculations of scalar control system parameters in the form of MathCad scripts are presented. On the received model processes of work of the electric drive of the pump in normal and emergency operating modes were considered. Calculations and simulation model of voltage and frequency converter subsystem are given. Calculations of parameters and coefficients of the scalar control system are given. The simulation model of the sensor unit subsystem is given. The calculations of the frequency converter and the voltage converter are given. The transfer functions of the voltage and frequency converter of the scalar control system of the asynchronous electric drive of the recirculation pump are presented. The simulation model of the fan load subsystem of the scalar control system of the boiler's recirculation pump is presented. The table presents an analysis of the transient characteristics of a two-phase mathematical model of an induction motor. The analysis of transient characteristics of the scalar control system of the recirculation pump is presented.

Measurement and Analysis of Transient Information Characteristics of IOT Equipment Using Graphical Programming

The switching on and switching off operation of some IOT devices is a complex physical, chemical and mechanical nonlinear transient process, which contains a lot of information. The information has distinction, stability and clear physical meaning. Due to the short time of transient process and the rapid change of waveform and characteristic parameters from time to time, it is difficult for traditional test instruments to capture the characteristics of voltage, current and power consumption in the transient process. Therefore, this paper develops a set of transient characteristic test system of IOT equipment by using the graphical programming software LabVIEW, which realizes the accurate measurement, automatic analysis and display of transient process waveform and characteristic parameters. Taking the operating coil of an electronic product as the test object, the transient characteristics in the whole process of on-off, closing process and breaking process are tested and verified by using the test system, which improves the efficiency of detection and analysis of the performance of IOT equipment.

Modeling and Analysis of Transient Reactive Power Characteristics of DFIG Considering Crowbar Circuit under Ultra HVDC Commutation Failure

Ultra high voltage direct current (UHVDC) transmission is an effective means of long-distance transmission of renewable power generation, which has obtained a lot of research and practical applications. The commutation failure is a common DC transmission fault, which will cause the voltage amplitude of the sending ac grid in UHVDC system to first decrease then increase. The existing transient mathematical models of the wind power generation system (WPGS) are difficult to apply to scenarios where the grid voltage changes continuously. A mathematical model suitable for commutation failure is established to analyze the transient reactive power characteristics of the doubly fed induction generator (DFIG)-based WPGS with the consideration of the crowbar circuit trigger. The correctness of the mathematical model is validated by an experiment based on the control hardware-in-loop (CHIL) platform. Based on the proposed mathematical model, the influence of the crowbar parameters on the reactive power output of the DFIG is analyzed, and the selection of crowbar parameters to suppress the overvoltage of the sending ac grid is investigated. A simulation model is built based on Matlab/Simulink to verify the overvoltage suppression effect of the proposed selection scheme.

Analysis of power system transient stability characteristics with the application of massive transient stability simulation data

A large number of simulation results will be generated during the calculation of the power system digital simulation. Manual analysis of massive numerical results is inefficient and error-prone. Besides, some imperceptible operating rules of power system operating mode may be ignored. In order to solve these problems, a transient stability assessment method based on deep learning is proposed in this paper. By analyzing simulation data, the relationship between power grid stability characteristics and the set operation mode is constructed. According to these research results, the calculation and analysis of power system transient stability will be effectively supported.