Ripple Coefficient Research Articles

Analysis on axial force characteristics of variable valve and variable speed adjustment of centrifugal pump

In order to study the evolution mechanism of axial force characteristics of centrifugal pump in the transient process of variable working conditions, the IS80-65-160 centrifugal pump is taken as the research object, and four flow operating points of centrifugal pump 1.0Qr, 0.8Qr, 0.6Qr, and 0.4Qr are selected. Non-constant numerical simulation is carried out, and on the basis that the numerical calculation results of the external characteristics are basically consistent with the experimental results, the changes of the axial force of the impeller during the flow reduction process of the variable valve adjustment and the variable speed adjustment of the centrifugal pump are studied, respectively. The results show that as the flow rate decreases, the force of the variable valve regulating impeller cover plate increases, and the force of the variable speed regulating cover plate decreases. Under the two adjustment methods, the axial force on the pressure surface of the blade becomes smaller, the axial force on the suction surface of the blade is basically unchanged, and the pulsation coefficient of the impeller axial force increases first and then decreases. The axial force pulsation coefficient reaches the maximum value in the variable valve adjustment condition of 0.8Qr and the variable speed adjustment condition of 0.6Qr, respectively, and the axial force on the outer wall of impeller cover plate has the greatest influence on the main frequency axial force ripple coefficient; the axial force acting on the outer wall surface of the front cover plate of the impeller and the inner wall surface of the front and rear cover plates increases with the increase in the radius, The axial force acting on the outer wall surface of the rear cover plate of the impeller has axisymmetrical properties. This study revealed the evolution mechanism of the axial force characteristics of the centrifugal pump impeller during the transient process of variable working conditions, and the research results can provide a reference for improving the stable operation of the centrifugal pump.

Optimization of chaotic light output in semiconductor laser systems based on multi-objective optimization algorithm.

Aiming at the weak performance of chaotic light output in semiconductor laser systems, the study designed a power control algorithm for semiconductor laser drive systems based on linear self-disturbance rejection control. Then the optimization parameters and scope were determined, and multi-objective optimization and direction preference algorithms were introduced. A chaotic optical performance optimization model based on improved multi-objective genetic algorithm was constructed using adaptive functions as evaluation indicators. These results confirmed that the larger the bandwidth of the controller, the faster the response speed of the resonant converter, but the stability was poor. When the input voltage underwent a sudden change, the current ripple coefficient of the PID algorithm was 0.55%. The linear active disturbance rejection control algorithm could ensure that the voltage and current maintained at the set values, and the output current of the algorithm was more stable when the load underwent sudden changes. The directional preference algorithm could further provide more valuable solutions on the basis of adaptive genetic algorithms. When the peak value of the autocorrelation function was equal to 0.2, the delay characteristics of chaotic light were effectively suppressed, having strong signal bandwidth and complexity. In summary, the constructed model has good application effects in optimizing chaotic optical performance and has certain positive significance for communication security.

Increasing the Energy Efficiency of Traction Electric Drives of Direct Current

Purpose. The work is aimed at improving the energy efficiency of direct current traction electric drives of electric transport by introducing transistor pulse width converters (PWC) with an optimal switching frequency to minimize total electrical losses in the electric drive. The electrical losses of traction electric drives consist of electrical losses in the armature winding and in the PWC transistors. Methodology. To study the dependence on the switching frequency of transistors, the electrical losses in the armature winding and PWC transistors are divided into two parts: static losses from the direct current component of the current and dynamic losses, i.e., losses in the armature winding from harmonic current components and losses in the transistors from transient switching currents. Since the dynamic electrical losses in transistors increase with increasing frequency and decrease in the armature winding, it is necessary to find the optimal PWC co-mutation frequency at which the total dynamic losses in the traction electric drive will be minimal. The goal of increasing energy efficiency in a traction electric drive is achieved by determining the dependence of dynamic electrical losses in the armature winding on the switching frequency of the PWC and computer modeling of the transistor electric drive. Findings. It is found that the relative dynamic electrical losses in the armature winding in the case of polyharmonic power supply are equal to the square of the armature current ripple coefficient. An algorithm for determining the optimal switching frequency of the PWC is developed: 1) the dependence of dynamic electrical losses on the switching frequency of transistors is determined experimentally on computer models of the motor and PWC; 2) the graph of the dependence of total dynamic electrical losses of the transistor electric drive on the time-tothe point of minimum losses, which corresponds to the optimal frequency value, is determined. Originality. For the first time, the authors obtained an analytical expression for the relative dynamic electrical losses in the armature windings, which are equal to the square of the armature current ripple factor. Practical value. Establishing the optimal switching frequency of the PWC according to the developed methodology reduces electrical losses in traction electric drives, i.e., increases their energy efficiency.

Experimental investigation on the open cathode air-cooled proton exchange membrane fuel cells: Optimum operating parameters and control strategies

Operating parameters and control strategies are crucial for the performance of open cathode air-cooled proton exchange membrane fuel cells. In present study, effects of hydrogen pressure, anode purging ratio and stack temperature on an open cathode air-cooled PEMFC with 40 single cells are experimentally explored. Comprehensive evaluations of operating parameters and control strategies are adopted from multiple aspects including output performance, stability, hydrogen consumption, and system efficiency. The results show that an anode pressure of 60–70 kPa and a 4% purging ratio can achieve not exceeding 5% ripple coefficient and not less than 35% system efficiency, and the optimum stack temperature is proved to be 54–60 °C. Adaptive purging strategies and temperature control strategies that vary with current are summarized which can be used for programming applications. Finally, these control strategies are executed under simulated loads to observe stack’s dynamic response and confirmed to maintain stable operation of the stack.

РОЗРАХУНОК ПРОЦЕСІВ У ПЕРЕТВОРЮВАЧІ ЗА ТОПОЛОГІЄЮ LUO З ВИКОРИСТАННЯМ МЕТОДА УСЕРЕДНЕННЯ НА ОСНОВІ ТЕОРЕМ ЛАГРАНЖА

The electromagnetic processes in elementary dc converter according to the Luo topology with inverting output in modes of continuous and discontinuous conduction were studied. Using the method of averaging in the state space based on Lagrange theorems, mathematical models of converter for mentioned modes of operation have been devel-oped. The use of developed models made it possible to obtain analytical expressions for calculating the average and pulsation values of currents and voltages in the reactive elements of the converter, as well as their ripple coefficients. Graphical dependences of the mentioned parameters were calculated in the entire commutation range of converter, taking into account the conduction modes. It is shown that, in comparison with traditional topology of buck-boost con-verter, the output filter in elementary Luo converter with inverting output significantly reduces the ripple coefficient of output voltage. It was determined that the amount of voltage ripple reduction is proportional to the product of the in-ductance and filter capacity values, as well as the square of the switching frequency and does not depend on the con-ductivity mode of the converter. Ref. 13, fig. 5, table. Key words: dc voltage converters, Luo converter, averaging method in state space, Lagrange theorems.

РОЗРАХУНОК ПЕРЕТВОРЮВАЧІВ ПОСТІЙНОЇ НАПРУГИ В РЕЖИМАХ ПЕРЕРИВЧАСТОЇ ПРОВІДНОСТІ З ВИКОРИСТАННЯМ МЕТОДА УСЕРЕДНЕННЯ НА ОСНОВІ ТЕОРЕМ ЛАГРАНЖА

The features of calculation of output voltage ripple in dc converters with discontinuous conduction modes are considered. It is shown that the use of behaviors of charge-discharge processes of the output capacitor makes it possible to determine the parameters of voltage pulsation on it, using a mathematical model of the converter with variables averaged using Lagrange's theorems. The specified approach contributes to the significant simplification of calculations and reduction of their labor intensity. Analytical and graphical dependences of the ripple value and the ripple coefficient of output voltage of main circuits of the converters in the mode of discontinuous conduction - buck, boost and buck-boost types - were obtained. The developed analytical dependencies make it possible to effectively calculate the parameters of the converters and investigate their properties at the stage of their design, using available methods of mathematical analysis. The reliability of the obtained analytical ratios and calculation results was confirmed by simulation of converters using the PSim package. References 14, figures 4, tables 3.

Electromagnetic force ripple suppression strategy of the micro permanent magnet linear motor

In order to make the micro permanent magnet linear motor in this paper have an excellent position response in MEMS application scenarios, an electromagnetic force ripple suppression strategy based on harmonic current injection is proposed. Because of the simulation phenomenon of large force ripple under standard sinusoidal current driving, combined with the non-sinusoidal distribution model of the air-gap magnetic field, it is theoretically verified that the odd harmonic current injection can effectively suppress the force ripple. The electromagnetic force under the fundamental + 3rd/7th harmonic currents and only the fundamental current is compared by simulation. The force ripple coefficient is reduced from 31% to 1.3%, and the position response speed is increased by about 11% in the 4 mm position closed-loop response simulation. The experimental results show that under a current with 200 Hz frequency, the motor can achieve a displacement of 5 mm within 0.11 s, providing a peak velocity of 40 mm/s, which verifies the correctness of the design concept and control strategy of the micro linear permanent magnet motor.

Voltage Divider based on Switched Capacitors for MEM Generators

Simulation results of the operation of voltage dividers based on switched capacitors with diode and transistor-diode switching for microelectromechanical (MEM) generators are presented. It has been established that for a divider with diode-switched capacitors, the voltage division factor doesn't remain when the load resistance changes, and for higher load resistances, the value of the load voltage asymptotically approaches to V0, but not to V0/N. At the same time, a divider with transistor-diode switching of capacitors at higher load resistances makes it possible to obtain an output voltage Vl, which is N times lower than the voltage of the primary power source V0. Analytical expressions have been obtained for estimating the parameters of dividers with diode switching, which allow calculating the characteristics of the divider at the stage of preliminary design of MEM generators with diode-capacitor voltage dividers. It is shown that the simulation of the operation of a diode-capacitor voltage divider must be carried out taking into account the dynamic current-voltage characteristic of diodes. It is established that when using a bipolar transistor as a charging switch, the ripple coefficient of the output voltage is less than when using a reed relay

Triboelectric‐Electromagnetic Hybrid Generator with Single Timer Under Monostable Operation for Wind Energy Harvesting

As a renewable clean energy with good application prospects, wind energy has attracted more and more attention. Harvesting energy from the ambient environment with triboelectric nanogenerators (TENGs), for use in electronic devices has become a feasible method. Nevertheless, the alternating‐current signal generated by TENGs needs to be converted into direct‐current signal to be effective in applications. Therefore, this article presents a power management circuit with a self‐triggering triboelectric‐electromagnetic hybrid generator (ST‐TEHG). The switch module of the power management circuit is composed of an electromagnetic (EMG), 555 single timer, and an N‐type metal–oxide–semiconductor, the module converts the AC signal output by EMG into a square wave signal under monostable state. The self‐triggering switching function is realized when in monostable operation. Systematic experiments demonstrate that the 555 single timer function can output waveforms of monostable operation. The back‐end of the circuit can output DC signals stably, the ripple voltage is 0.03 V, and the ripple coefficient is 0.52%. ST‐TEHG provides a new way of thinking for the power supply of microelectronic components.

РЕАЛИЗАЦИЯ ЦИФРОВОГО ДВОЙНИКА В СРЕДЕ МОДЕЛИРОВАНИЯ МАРС

The article considers a technique for constructing a digital twin to simulate the aging processes of electrical circuit components and associated gradual equipment failures. This twin is created by means of I/O boards connected to the STM 32 microcontroller. This allows you to transfer some analog signal from the object and digitize it in the microcontroller, which is then transferred to a computer running the MARS simulation environment on it. The other channel implements the same signals, but from the computer model of the object and further, the signals from the computer model and from the real object are compared using a comparator, and then visualized using a virtual oscilloscope. The hardware-software implementation of the digital twin is given. Goal: implement a digital twin of a rectifier with a filter in the MARS simulation environment. Methods. To implement a digital twin, it is necessary to assemble an electrical circuit of a real object, as well as assemble a virtual circuit based on the components of the MARS simulation environment. Then it is necessary to simulate the degradation of the parameters of a real object by lowering the capacitance of the capacitor. Comparison of voltage signals obtained from a real object and a virtual model is carried out by comparing the ripple coefficients. By the difference in ripple coefficients, determine whether the deviation of the voltage on the capacitor of the real object from the voltage on the capacitor of the virtual object is within the specified allowable range. Results. An electrical circuit of a rectifier with a filter has been assembled. A virtual circuit of a rectifier with a filter has been implemented in the MARS simulation environment. An experiment simulating the degradation of the parameters of a real object was carried out. The results obtained are visualized using a virtual oscilloscope. The pulsation coefficients and their difference are calculated. Conclusion. The experiment showed that the digital twin copes with its task, namely, the detection of a strong deviation of the given parameters from the norm.

A COMPREHENSIVE STUDY OF THE INFLUENCE OF DAMAGES OF THE STATOR WINDING OF ASYNCHRONOUS MOTORS DURING OPERATION OF VEHICLES

The efficiency of providing transportation is related to increasing the reliability of the transportation infrastructure. To ensure reliable and economical operation, it is necessary to develop systems of functional diagnostics of the main elements of vehicles, which provide continuous control of the technical condition of its main elements. Monitoring the state of asynchronous electric motors as part of electric drives of vehicles is an important modern issue, the solution of which depends on the reliability of the entire transport infrastructure. The most common type of damage in motors during operation is an inter-turn short circuit in the stator winding phase. Turn-to-turn closures are difficult to detect, but if they are present, the engine continues to operate with a change in its operating and electrodynamic indicators and characteristics. However, depending on the degree of turn-to-turn closures (the number of closed turns) in the winding phase, the probability and time of an emergency stop of the electric drive increase. In this paper, the influence of turn-to-turn closures of varying degrees on mechanical, electrical and energy parameters and engine characteristics under various operating modes has been studied. In the course of the research, a mathematical model of an induction motor was used with the established adequacy of the simulation results and the possibility of creating an asymmetric rotating stator field. The adopted simulation model of an induction motor with a squirrel-cage rotor is written in retarded coordinates. Also, studies were carried out on the effect of turn-to-turn closures on the ripple coefficient of the electromagnetic torque and the unbalance coefficient of the stator phase currents. Based on the data obtained, recommendations are given on choosing the most effective method of electric current for diagnosing interturn faults in assessing the technical condition and predicting the failure-free operation of an asynchronous electric motor for use as part of an electric motor under construction. - in diagnostic systems of cars.

Millivolt‐Level Stable Voltage Output of Triboelectric Nanogenerator Under Random Excitation by Double Limiting

Against the backdrop of a world energy crisis, triboelectric nanogenerator (TENG) is considered to be a practical solution that could harvest and use different types of mechanical energy. This study fabricates a variable rotor TENG combined with double limiting Zener aspectant diodes (ZAD) for the harvesting of impact energy and stable voltage output. And double limits are used at both ends of the load. The system has two independent rotor generating units. In a small impact, one generating unit is easy to start up; in a strong impact, two generating units operate to output more energy. This article presents a power management circuit design, which mainly comprises a rectifying part and voltage stabilizing part. In the operation of one generating unit, the voltage is stabilized at 3.35 V when using a single Zener diode, and at 3.95 V when using the ZAD circuit. In the simultaneous operation of two generating units, the voltage is stabilized at 4.45 V, ripple coefficient of 1.8%, and ripple voltage is 80 mV at millivolt‐level when using the ZAD circuit. This article presents the prospects of stabilizing the output voltage of the TENG under random excitation in the harvesting of impact energy.

A Series-Connected 40-Pulse Rectifier With DC Link Passive Harmonic Reduction Circuit

This article is focused on power quality improvement of the series-connected multipulse rectifiers (MPRs). For the dc side passive harmonic reduction method, the optimum design of the harmonic injection transformer is the key point to achieve the optimal harmonic elimination effect. First, a novel method for determining the optimum turns ratio of the harmonic injection transformer is proposed. Then, in combination with a five-phase bridge-rectifier-based MPR, the correctness of the general calculation formula is verified. In the verification processes, the operation principle and harmonic reduction mechanism are clearly analyzed before and after using the harmonic reduction circuit (HRC). The optimum turns ratio of the harmonic injection transformer obtained from the view point of minimizing the input voltage total harmonic distortion (THD) value is consistent with that calculated from general formula. Under the optimum design, the kVA rating of the HRC is only 0.87% of the load power. In experimental, the THD values of the input voltages in the 20-pulse rectifier and 40-pulse rectifier are 3.32% and 2.07%, respectively. The proposed method greatly reduces the complexity of the design processes and helpful for the development of the super-MPR. The proposed 40-pulse rectifier has high reliability, easy realization, considerable harmonic reduction ability, and quite a low load voltage ripple coefficient.

Analytical solution for output voltage ripple coefficient of BOOST converter

Analytical solution for output voltage ripple coefficient of BOOST converter

Design of a Low-Ripple Double-Modular-Stator Switched Reluctance Machine for Electric Vehicle Applications

To overcome the disadvantages of traditional switched reluctance machine (SRM) with moderate power/torque density and high torque ripple, this article proposes a novel double-stator SRM (DSSRM) with the inner and outer stators both adopting U-shaped segmental stator structure. By optimizing the polarity distribution of the inner and outer stator magnetic fields, the inner and outer stator magnetic fields are decoupled. Then, the relationships of torque ripple coefficient with the mechanical offset angles of the inner and outer rotor teeth are investigated. To optimize the mechanical offset angle and reduce the torque ripple of the motor, the initial design method is proposed, and five main parameters of the machine are optimized by the finite-element analysis. Then, the static magnetic characteristics and dynamic performance of this novel machine are simulated and analyzed. Finally, a 16/18/18/16 DSSRM is prototyped to validate the above simulation and theoretical analysis.

Hybrid Modified Whale Optimisation Algorithm Simulated Annealing Technique for Control of SRM

The evolutionary multiobjective optimization is an identified field for researchers. The goal of evolutionary multiobjective optimization is to optimize several objectives simultaneously. The problem of multiobjective optimisation is more important when the objective function exhibits conflicting characteristics. In this work, metaheuristic techniques such as modified hybrid whale optimization algorithm with simulated annealing (hybrid mWOASA) is proposed for speed control along with minimization of ripple in torque of a 75 KW, 4-phase, 8/6 switched reluctance motor. The proposed method is used for the combined objective of control of speed with minimization of ripple in the output torque of switched reluctance motor (SRM) considering the armature current as constraint. It is noticed that torque ripple coefficient, integral square error of speed (ISE(speed)), and integral square error of current (ISE(current)) reduced significantly by proposed mWOASA technique as compared to hybrid WOASA, WOA.

Theoretical justification and practical aspects of implementation of Human Centric Lighting Program in production conditions

The relevance of the introduction of HCL systems in production conditions, in which the dynamics of changes in the characteristics of light flux can be synchronized with the circadian biorhythms of the human body. This is determined by the fact that the unsatisfactory characteristics of industrial lighting increase the risk of injury and occupational morbidity. It is shown that providing only normative quantitative characteristics of illumination is not enough, since its qualitative characteristics – ripple coefficient, spectral composition cause non-visual effect of light. They can affect the psychophysiological state of a person, his\her performance, fatigue by affecting the circadian biorhythms of the body. The comparison of standard values of the level of artificial lighting of jobs in different countries with natural ones. Based on the analysis, recommendations were developed aimed at improving artificial lighting. The analysis of the results of the study of non-visual effect of the pulsation of the light flux on the psychophysiology of a person was carried out. Its main negative consequences are given, the necessary tasks for the implementation of the HCL program in a production environment in this aspect are identified. The results of analysis of studies of the influence of the color temperature of the light flux on the psychophysiological state of a person are also presented. Recommendations on the regulation of this parameter for various types of production activities have been developed.
 
 Keywords: industrial lighting; NIF-effect; occupational injuries.

Commutating Current Modulation Method of Brushless Direct Current Motor under Non-ideal Back Electromotive Force

A phase current modulation method that suppresses commutating torque pulsation of brushless direct current motor under non-ideal back EMF was proposed to solve commutating toque ripple problem. This method calculates the duty cycle and commutation time by acquiring the line voltage in real time, and controls the modulation of different duty cycles of the power device to ensure that the on-phase and off-phase current changes at the same rate during commutation, and finally suppresses non-commutation phase current pulsates. It assures the consistent change rate of conducting-phase and shut-off phase currents at commutation, and thereby suppresses non-commutation torque ripple. Moreover, the proposed method realized indirect observation of non-ideal back EMF through real-time acquisition of line voltage, which prevents the difficulty and poor accuracy of observation of back EMF. Comparing with phase current modulation method considering armature resistance, the proposed method can control non-commutation current control at the commutation moment more accurately. The experimental results show that the phase current ripple coefficient is only 11.1% at 1000r/min and 13.9% at 2000 r/min, while the phase current ripple coefficient under contrast method control is 15.3% at 1000r/min and 19.4% at 2000r/min. The ripple of non-commutation current and commutation torque is smaller at the commutation moment.

Development and Performance Analysis of Segmented-Double-Stator Switched Reluctance Machine

This article investigates the design methods and performance optimization of segmented-double-stator switched reluctance machine (SDS-SRM). First, two segmented U-shaped single-stator SRMs are introduced, including inner-rotor and outer-rotor constructions. In order to enhance the torque and power density, these two kinds of single-stator SRMs are combined together to constitute an SDS-SRM. Then, the relationships of torque ripple coefficient with the mechanical offset angles of the inner and outer rotor teeth are investigated to obtain the optimal rotor structure, and the corresponding conduction phase sequences for double-stator excitation mode are also analyzed. Furthermore, the flux distributions of the inner and outer stators with different coil magnetic polarities configurations are researched, and it reveals that the phase windings both on inner and outer stators with NSSNNSSN polarities have better magnetic field decoupling characteristics. To evaluate the final topology of the proposed SDS-SRM, the static magnetic characteristics and dynamic performances are presented. Finally, the SDS-SRM prototype is manufactured and tested to validate the theory and simulation analyses.

Modular electric vehicle battery charger with bidirectional power flow

Prospects for the use of rechargeable battery electric vehicles as regulators of the network or backup power supplies in accordance with the concepts of V2G (Vehicle to Grid) and G2V (Grid to Vehicle) are described. The requirements for bidirectional power converters are defined: a wide range of input voltage parameters, correction of the input current power factor, maximum power take-off from renewable energy sources, high energy efficiency. The chosen topology of the bidirectional dual active bridge converter, which supports soft switching of transistors at zero voltage and the proposed modular approach to the construction of converters, has a number of advantages: provide any voltage or current, reduce ripple, high efficiency, high reliability, due to the ability to include backup modules that can be replaced by the main in case of failure, reduction of the size of reactive elements and the ability to operate each cell on other frequencies. The most effective type of cell combination for the main task is developed - input parallel and output parallel connection are allows sharing input and output current between the modules. The dependence of the ripple coefficient on each cell is defined. The calculation of one cell of converters, namely the calculation of high-frequency transformer, transistors, and smoothing LC-filter is presented and the comparative analysis of technical indicators in one-cell and multi-cell converters is carried out. Modeling in Matlab Simulink software environment, evaluation of the effect of using a modular converter when working with DC and AC sources, comparison of ripple coefficients in converters with a different number of a cell at a constant value of the parameters of the LC-filter, and selected filter parameters at which one coefficient of pulsations is applied. The simulation results showed that the coefficients of the ripple are decreasing depending on the number of cells of the transducer in accordance with the dependence obtained by analytical calculations. Thus, the results are confirming the correctness of the calculations and prove the efficiency of the use of modular transformation topology.