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The paper presents the designed system to measurements of gas sensor transient characteristics. Electrochemical oxygen sensor SK-25F was selected for measurements from point of view application in health care and ensuring human safety in industrial production facilities and laboratories. The aim of this work is to design an automatic system for measuring the transient function G(s) of electrochemical sensors and to identify the mathematic model from a sample of sensors. The automatic measurement system based on a microcontroller for the measurements of dynamical characteristics of gas sensors was designed and developed. The result is transfer function with fit to estimation data higher as 99.48 %. The bandwidth of gas sensors was calculated on average at 0.0285763 Hz with a maximum deviation of 0.34 %. Finally, an algorithm for detecting the exceeding of the frequency range of an electrochemical gas sensor is proposed. Its application is in speed control UAV with the aim of accurate measurements of gases in the air by electrochemical sensors.

In this study, a hybrid steady-state compressor model is proposed that can be used in the real-time performance monitoring, control and optimization of the vapor compression cycle. In the proposed model, first, a detailed analysis of the mass flow rate is presented, which is based on the volumetric efficiency concept and the assumption of a polytropic compression process. Then, discharge temperature of the refrigerant and power consumption of the compressor are also investigated. Three semiempirical models are constructed respectively. Further, to tune the unknown empirical parameters of the models, a social learning particle swarm optimization (SLPSO) algorithm is developed by using the real-time experimental data. An experimental apparatus of a refrigerant system is tested to validate the proposed models. The experimental results demonstrate that the proposed models accurately predict the performance of real-time operating compressors. Meanwhile, the models identified by the SLPSO algorithm are more accurate than those identified by the traditional least-squares method.

The scattered resistive elements residing in a dual-active-bridge (DAB) dc/dc converter can adversely affect its transient performance especially when the load change is large. Conventional phase-shift methods do not take the resistive impact into account in their modeling and analysis. In this paper, a comprehensive analysis of the detrimental influence on the transient performance of a DAB converter due to resistive elements is presented, based on which a modified phase-shift scheme is proposed to further optimize the transient response of the converter. A DAB prototype is designed to verify the resistive impact discussed and validate the proposed phase-shift scheme. The experimental results confirm that better transient response can be effectively achieved with the proposal.

The main spiral blades of helicopter and other non fixed wing aircraft are in the asymmetric and unsteady aerodynamic environment for a long time, which will make the body produce large-scale multi-directional low-frequency vibration, which will become the main vibration source of the body. The linear actuator can only produce single direction driving force, which is difficult to meet the high-precision vibration reduction requirements. Based on this, a direct drive vibration control system based on the space-time coupling method of rotating coordinate system is proposed. Firstly, the mathematical model of the output force of the single side of the electric actuator is deduced, and the space-time coupling method of the rotating coordinate system is proposed to derive the mathematical expression of the two-dimensional vibration suppression output force. Secondly, the two-dimensional output force control strategy based on the cross coupling control of multiple motors is proposed. The controller parameters are designed by state space method and the method of characteristic value of the feedback matrix to ensure the stability of the control system. The controller parameters are optimized according to the sensitivity H∞ control theory to improve the anti-interference of the closed-loop system. Finally, a 14kg prototype is designed by the proposed control strategy, which completes the synchronous verification experiment of position and speed, steady state and dynamic verification experiment of output force. The experimental results show that the coordinated control strategy of multi motors proposed in this paper makes the actuator output force meet the performance requirements of the system vibration reduction and has a good stability.

This paper presents an adaptive funnel control combined with multi-dimensional Taylor Network (MTN) for the prescribed tracking performance of a class of nonlinear systems. In order to make the tracking error satisfies the prescribed performance regarding the transient and steady state responses, a funnel variable is introduced and merged into the controller design. MTNs are employed to handle the nonlinear functions of systems, and an adaptive controller is constructively designed by the backstepping technique. It is proved that all the signals of the closed-loop system are bounded as well as the tracking error converges to a small neighborhood of the origin. Two examples are provided to illustrate the effectiveness of the control scheme proposed in this paper.

Continuous increase of wind power penetration brings high randomness to power system, and also leads to serious shortage of primary frequency regulation (PFR) reserve for power system whose reserve capacity is typically provided by conventional units. Considering large-scale wind power participating in PFR, this paper proposes a unit commitment optimization model with respect to coordination of steady state and transient state. In addition to traditional operation costs, losses of wind farm de-loaded operation, environmental benefits and transient frequency safety costs in high-risk stochastic scenarios are also considered in the model. Besides, the model makes full use of interruptible loads on demand side as one of the PFR reserve sources. A selection method for high-risk scenarios is also proposed to improve the calculation efficiency. Finally, this paper proposes an inner-outer iterative optimization method for the model solution. The method is validated by the New England 10-machine system, and the results show that the optimization model can guarantee both the safety of transient frequency and the economy of system operation.

This article addresses the problem of approximation-free prescribed performance control (PPC) for a class of non-triangular pure-feedback nonlinear dynamics whose nonaffine function of each subsystem is relaxed to rely on the whole state vector. The assumption made in this work is far more relaxed than all the available works in the sense that some commonly used Lipschitz condition or setting bounding function are never involved and only the continuity of nonlinearities are required. Furthermore, the proposed low-complexity PPC is simplified because neither approximators (neural networks and fuzzy logic systems) nor adaptation technique are embeded in the control design. By utilizing the barrier functions, some transient and steady state performances can be also preserved, while guaranteeing the closed-loop stability. Simulation results of hypersonic flight vehicles (HFVs) dynamics eventually validate the effectiveness of the proposed methodology.

The transient of the DFIG engages a lot of non-smooth elements such as switches of controllers and saturation of limiters, thus, the simplified non-smooth model of DFIG for electromechanical transient analysis is needed. This paper proposes a non-smooth simplified model of DFIG for electromechanical transient analysis, with the viewpoint of the transient response and energy accumulation. First, the general non-smooth dynamic behavior of DFIG during fault-on and post-fault periods are presented and the model is divided into four smooth stages. Then, the detailed model for the transient stage, according to without/with the trigger of the crowbar is presented. Furthermore, the simplified model of DFIG in the steady state is introduced according to without/with the trigger of the crowbar and saturation of limiters, determined by the stator voltage. Moreover, the transient model with/without the crowbar protection are simplified according to the principle of constant energy accumulation. Thus, the overall non-smooth simplified models of DFIG is obtained. Finally, the effectiveness of the proposed non-smooth simplified model is verified with the simulations.

© 2013 IEEE. The conventional model-predictive-based direct power control (MPDPC) of the three-phase full-bridge AC/DC converters chooses the best single voltage vector for the following control period, which results in variable switching frequency and power distortion, and thus a relatively higher sampling frequency is needed to achieve acceptable results. This paper proposes a simplified dual-vector-based predictive direct duty-cycle-control (SPDDC) with an additional zero vector implemented in contrast to the MPDPC. With the same best vector selection method, the proposed strategy has retained the control simplicity with just one more step added and much better control performance as well as a fixed switching frequency in comparison to the MPDPC. On the other hand, the duty-cycle optimization procedure is eliminated while the negative duration issue is essentially resolved compared with the conventional dual-vector-based model predictive duty-cycle-control (MPDCC). Comprehensive comparisons of various control methods by numerical simulation and experimental testing show that the SPDDC can achieve better steady state and dynamic performance than the MPDPC and simpler algorithms than the MPDCC.

The five coupled rate equations used to describe laterally-coupled pairs of lasers with weak coupling and unequal pumping are reduced to a new system of three equations. This enables approximate closed-form steady-state solutions and explicit expressions for the boundaries between regions of stable and unstable dynamics to be found. The results of applying these approximations to specific cases of coupled laser pairs are shown to be in good agreement with results obtained from numerical solutions of the original set of five equations as well as earlier results from the literature. In addition the approximations based on the reduced set of equations allow a systematic investigation of the effects of material, device and operating conditions on trends and novel features in the dynamics of laterally-coupled laser pairs. The algebraic results give insight into trends with parameters without the need for extensive numerical computation and should therefore be of use in modelling two-element VCSEL arrays for numerous potential applications.

In this paper, we consider the age of information (AoI) of a discrete time status updating system, focusing on finding the stationary AoI distribution assuming that the Ber/G/1/1 queue is used. Following the standard queueing theory, we show that by invoking a two-dimensional state vector which tracks the AoI and packet age in system simultaneously, the stationary AoI distribution can be derived by analyzing the steady state of the constituted two-dimensional stochastic process. We give the general formula of the AoI distribution and calculate the explicit expression when the service time is also geometrically distributed. The discrete and continuous AoI are compared, we depict the mean of discrete AoI and that of continuous time AoI for system with M/M/1/1 queue. Although the stationary AoI distribution of some continuous time single-server system has been determined before, in this paper, we shall prove that the standard queueing theory is still appliable to analyze the discrete AoI, which is even stronger than the proposed methods handling the continuous AoI., 9 pages, 3 figures, Accepted for presentation in ITW 2021

With the continuous development of domestic power grid construction, coupled with the serious air pollution in some areas, the transmission line has been put into operation for a long time, resulting in the increasing phenomenon of abnormal heating of the tension clamp of the transmission line, which not only affects the safe operation and reliability of the power grid, but also restricts the improvement of the carrying capacity of the transmission line. Therefore, this paper studies the abnormal heating state of strain clamp in transmission line, and proposes an abnormal heating alarm technology of strain clamp based on online monitoring technology and thermal stability principle.

Electrical bearing currents, e.g. in inverted-fed electrical machines, may disturb the performance of the bearings. In this paper the steady-state temperature of the bearing surface at the electrical contact point between the balls and the raceway is derived in the mixed lubrication state. The thermal analysis is presented based on the Holm‘s electric contact model, namely the a-spot. The contact model of Andreason is presented as well for comparison. The results are extended to predict the instantaneous contact surface temperature in an axial bearing (type 51208) at 500 rpm with 1 A average bearing current and with an axial bearing force of 800 N. Moreover the average of the contact surface temperature is obtained for the same bearing in a range of operating points, i.e. a rotating speed from 0 rpm to 3000 rpm, a bearing average current from 0.25 A to 3 A, at an axial bearing force 800 N. The results can be utilized to predict the contact temperature on the bearing surface for any given bearing from the measured bearing voltage.

The development of new technologies in the field of power electronics implies higher switching frequencies. Such frequencies are associated with higher transient voltages. Higher voltages mean stress on the insulation material. As result of this increased load, partial discharge (PD) probability can be increased, which may push the insulation material to its limits. Therefore, it is of high importance to recognize PDs. It is already known that PDs occur not only on the rising edge, but also in the steady state of a voltage pulse. However, double PDs may occur, too. Using a special test arrangement, it is possible to detect also weak PD activity, to localize the time instant and to determine changes in voltage and current. These changes are characterized e.g. by a sudden drop in pulse voltage.

Extended range fuel cell vehicles are developing towards full power fuel cell vehicles, which require fuel cells to undertake most of the vehicle's power demand. Thus, fuel cell output power will change dynamically in a wide range, which may result in local gas shortage. It is necessary to design the control algorithm of fuel cell air supply system to ensure the sufficient reaction gas of fuel cell. This paper focuses on the dynamic characteristics and control method of fuel cell engine air supply system. The model of fuel cell system is built. And a new double-input and double-output control algorithm for air supply system is designed. The simulation results verified that the control algorithm performs well. The actual flow can track the target flow accurately whether the current step is up or down. The rising time of cathode inlet pressure is 0.1s and the overshoot is 1.8% when the load is rising. The falling time of cathode inlet pressure is 0.1s and the overshoot is 1.3% when the load is falling.

The full-size converter fed synchronous machine (CFSM) for variable speed operation of a pumped storage power plant exhibits multiple advantages over the state-of-the-art Doubly Fed Induction Machine (DFIM) technology. The CFSM technology is emerging as the most preferred system for pumped storage plants for efficient operation in wide range of water flow which is not the case in existing power plants. This paper presents the steady state control strategies to execute the variable speed operation of the pumped storage power plants in both turbine and pump mode using full-size back-to-back converter. Also, how the power plant can be started in pump and turbine mode from standstill have been proposed. In addition, the seamless transition of operating modes from turbine to pump mode and vice versa are presented, which is not the case in today’s pumped storage power plants. The proposed control strategies are experimentally verified with a 100 kVA machine and converter setup with emulated reversible pump turbine (RPT).

Discontinuous conduction mode (DCM) for inverters requires a small size of inductor, and can realize soft switching for switches. However, the current stress under the DCM for two-level (2L) circuit is relatively high and there are still no linear models for the control. In this paper, T-type three-level (3L) circuit is used to construct the LCL-type grid-connected inverter (GCI). And the inverter-side inductor works under mixed conduction mode (MCM) combined by DCM when the load current is small and under trapezium conduction mode (TPCM) when it is high, so as to realize the soft switching in all switching cycles and reduce the current stress. In order to realize effective closed-loop control for the GCI under MCM, a linear charge quantity model (CQM) which takes the charge quantity output of the bridge as the control variable is proposed in this paper. Based on the proposed model, a direct charge control (DCC) method with a PID regulator working at fixed switching frequency is further proposed. Finally, the great steady-state and dynamic performance of the proposed model and control method is verified by the simulations and experiments.

CFRP (Carbon Fibre Reinforced Plastic) composites are increasingly used in a variety of applications. N on-destructive testing methods are used for evaluating their condition both as a finished product and during their use. Damage that may occur in these types of composites includes air bubbles, nonuniform arrangement of fibres, regions of fibres not saturated with resin, delamination, and micro-cracks. Various methods of non-destructive testing are used to detect defects in such structures among the most effective of which are infrared thermography methods, the most common being optical heating with various types of lamps and the method of optical lock-in. Pulsed thermography is one of active IR techniques in which a surface of tested material is stimulated by a short heat pulse and the thermal response of the material is analysed. Flash thermography are used when the specimen is stimulated using a short energy pulse. The response contains information about subsurface material defects. After the heat pulse the temperature decrease rate is different on surface over defect in comparison to that over the sound material. In lock-in thermography, an amplitude modulated heat wave is applied to the inspected specimen in steady state. This paper seeks to compare the results obtained from pulsed and flash thermography with results from using optical lock-in thermography. The paper presents selected results of defect detection in a multilayer CFRP composite structure. The tests were carried out on a sample consisting of three plates made of CFRP connected with resin, in which the inner middle layer is made of four non-adherent elements.

In this paper, the Transport Coefficient of SO 2 gas are calculated from swarm model design using BOLSIG+ which is user-friendly open-source computer program based on numerical solution of Boltzman equation (BE) up to two-term approximations. To ensure close agreement of calculated transport coefficients for SO 2 gas with impending experimental works, first we calculate these coefficients for SF 6 , and CO 2 compared the results with reported values. Reasonable agreement is found between calculated and report transport coefficients. For realistic acceptance of SO2 gas as SF6 alternative in long-term for high voltage applications, we discussed the utilization of these coefficients in study of various electrical breakdown related phenomenon to understand its dielectric and electrical insulating behavior during electrostatic discharge. We also predict numerical values of insulating properties in uniform electric field under steady state conditions such as electric strength, breakdown voltage and ionization constant for SO 2 gas using transport coefficients. For SO 2 gas, some of these properties and values are being calculated for first time.

The application of DFIG (Doubly Fed Induction Generator) in wind driven electric power generation has been increasing lately. In general, DFIG-based wind turbine has the capability to operate at two different control modes (i.e. power factor control mode and voltage control mode). However, the voltage control mode of operation has the advantage that the DFIG can be arranged to operate at a specified voltage magnitude and improve the system voltage profile. Load flow analysis is the most fundamental analysis in power system studies. Load flow analysis is usually carried out to assess the steady performances of a power system. The crucial and important step in conducting load flow analysis is modeling of the power system components. The present paper discusses a simple steady state load flow model of DFIG-based wind turbine in voltage control mode. The proposed model can be used for load flow studies of modern electric power system embedded with DFIG-based wind turbine.

To extract the maximum power from available solar energy, the Maximum Power Point Tracking (MPPT) technique is used in solar photovoltaic system. Due to its simplicity and ease of implementation, the Perturb and Observe (P and O) technique is a commonly used approach to track the maximum power point (MPP). However, P and O algorithm oscillates near MPP point and give slow dynamic response. This paper presents a modified P and O method with a variable step size. This modified method is an effort towards overcoming the two major limitations of the conventional P and O method, first is oscillations near MPP and the second is loss of a tracking of MPP point during sudden change in irradiance. Here, the change in the step size is different according to the region of voltage, which will be decided by the difference between a voltage of the current operating point and MPP at desired irradiance. The proposed P and O gives good tracking accuracy in dynamic conditions and very less oscillations near the MPP as accepted. Detailed simulation analysis is done considering various steady-state and dynamic irradiance conditions for both the conventional and modified P and O methods and detail comparative result analysis is presented to validate the effectiveness of proposed algorithm. Proposed method improves the power quality and increase the efficiency of power conversion. Real time implementation is also easy.

This paper proposes an affine projection (AP) algorithm based on maximum correntropy criterion (MCC) to mitigate the disturbances in grid parameters of a photovoltaic (PV) based distribution system. Variable step size is introduced in the algorithm to improve the convergence rate and to reduce the steady-state (SS) error during transient conditions. To alleviate the effects of grid disturbances on system performances dual enhanced generalized integrator (DESOGI) is used. Reference dc voltage for voltage control loop is obtained by using P&O maximum power point (MPP) technique. Smooth power flow between the source and grid is accomplished during daytime and during bad weather or night condition, the whole system acts as DSTATCOM to improve the power quality as per IEEE-519 standard.

A nonlinear electromagnetic actuator (EMA) system that consists of a mechanical motion and electromagnetic circuit is considered in this paper. The dynamics of the electrical and mechanical parts of the system were modeled. Steady-state conditions, in which the actuator position, actuator velocity, and coil current were assumed constants, were used as reference approaches for closed-loop scenarios. A sliding mode control method was applied to design the closed-loop coil voltage such that the nonlinear system slides along a certain sliding surface. The reliability of the presented control law was approved under a wide range of steady-state actuator position dispersions and coil voltage disturbances using Monte-Carlo simulation method. Numerical results with 1000 simulations were obtained to test the presented control law. The simulated results ensured the ability of the EMA to reach the steady-state conditions with fast response, excellent overshoot, and outstanding performance despite the wide range of system uncertainties.

This paper presents a comparative electromagnetic performance analysis of different topologies of Brushless DC (BLDC) Permanent Magnet (PM) machines. In particular, five distinct motor configurations with different rotor structures (i.e., axial flux machine with disk rotor, radial flux machine with inner rotor, and radial flux machine with outer rotor), stator structure (i.e., slotted and slot-less) and winding arrangements (i.e., concentrated winding and distributed winding) are presented, their steady-state electromagnetic performances are compared and conclusions are made on their key differences. The analysis is carried out using field and circuit models. In addition, the impact of the magnets remanence on the motor performance is highlighted.

A solution of the optimal control problem has been found in the work. It involves two artificial neural networks for the identification and control of a dynamical system. In order to train them, two different methods were applied: gradient-based and gradient-free. The former is for identification; the latter is for the solution of the optimal control problem. In order to obtain the weights and biases of neurocontroller, the initial problem has been reduced to the unconstrained optimization problem. A modification of particle swarm optimization (gradient-free) method has been applied to train a neurocontroller. Its high performance has been validated by carrying out an experimental study.

This paper presents a new approach for generating the state-space averaged model of dc-dc converters in the basis of relative variables using the Lagrange theorems. Averaged mathematical models of boost, buck and buck-boost converters have been developed, allowing the analysis of steady-state processes in continuous conduction mode (CCM) and discontinuous conduction mode (DCM). It is shown that a new approach to obtaining averaged models makes it possible to calculate not only the constant components of the process, but also their pulsation components, as well as the duration of the time intervals of the steady-state process, which is an advantage over traditional averaging methods. Using the obtained models, the dependences of the current ripple of the storage choke relative to the load current and the voltage transfer coefficient of the converters were calculated in the entire range of regulation of the switching duration.

The steady state drift-diffusion model (DDM) of organic solar cells that considers the surface recombination processes for majority and minority carriers, as well as their thermionic emission on both electrodes, is presented in this paper. When the full Robin boundary conditions (BCs) and the popular finite difference method with Schaffeter-Gummel discretization (FDSG) were applied, significant instabilities were observed when surface recombination velocities (SRVs) for majority carriers on one or both electrodes were reduced. To analyze this problem and perceive the independent impacts of electron and hole contact processes, the model was simplified by assuming a constant electric field in the device and by solving the electron and hole continuity equations separately. The stability of numerical DDM solutions obtained by the FDSG and Discontinuous Galerkin (DG) methods for three different types of BCs (Dirichlet and two mixed BCs) was examined. The DG method showed a better stability when majority carriers SRVs were reduced. The current density versus voltage (J-V) characteristic calculated by the DDM with Dirichlet BCs using the DG method was compared to the measured ITO/PEDOT:PSS/P3HT:PCBM/Al solar cell J-V curve for the model validation.

Currently, there is a lack of publicly available design specifications for Crossed-Field Amplifiers (CFAs), which severely impedes CFA research in the public domain. The L3-Harris CFA, L-4953, was commonly used for the Air Route Surveillance Radar (ARSR-1/2) since the 1970’s. This is a high power $\left( {P_{out}^{peak} \approx 5\;{\text{MW}},P_{out}^{avg} \approx 3.2\;{\text{kW}}} \right)$ , moderate gain (G=11.2 dB), pulsed ( t pulse = 1.8 µs), L-band (f = 1.28 to 1.35 GHz), reentrant, backward wave, thermionic cathode amplifier. Our group has been developing a particle-in-cell (PIC) model of the CFA to study power saturation and the effects of electron injection. Here, VSim is used to validate the model against CFA operation specifications, such as gain, bandwidth, and dispersion. Preliminary, non-optimized simulation results show as table 9 dB gain at in only 10 ns with a relatively coarse grid of 101×101×60 cells. The short time required to reach steady state and the low number of grid cells allows for short simulation times on the order of only a few hours for common multi-core processors. This makes this CFA design an ideal standard for simulation studies. Additional simulation studies are planned using ICEPIC. We will report the results of the simulations, comparison between the two different PIC codes, assessment with operating specifications, and studies of the electron injection models.

The solution of the dynamic problem of the acoustic-emission field displacements in an elastic half-space generated by steady-state displacements of the surfaces of a circular cracks system is obtained. The solutions are obtained by the boundary integral equations (BIEs) method. For the case of mode III cracks, the dependences of elastic displacements on the surface of the half-space on the wave number, the number of defects and the depths of their location are analyzed.