Two-phase Circuit Research Articles

Расчетно-экспериментальное исследование закрученного кольцевого потока

In the course of work on the energy perfection of thermal control systems for spacecraft with a twophase circuit, the issue of partial regeneration of thermal energy into electrical energy in a low-speed turbogenerator is considered, part of the design work requires computational modeling during the transport of swirling flows in the axial direction from the external input to the input plane into the impeller, which determines the need for theoretical and experimental elaboration of the problem. The paper considers transformations of equations for changing the amount of fluid motion in boundary conditions of an axial annular channel with fixed cylindrical surfaces. Assuming the symmetry axis of the flows using the integral form of writing the continuity equation, the relations are obtained in the form of two differential equations with expressed derivatives along the channel axis for the total pressure p* and the circumferential velocity constant Cu = UR (const — at the integration step). The equation forms the basis of the algorithm of integration in finite differences supplemented by a system of service equations describing the friction stress, thermodynamic parameters, etc. Test calculations are carried out using real parameters, the results are analyzed.

PROTECTION COORDINATION OF PHOTOVOLTAIC POWER PLANT IN THE TIME DOMAIN

The safety of workers and equipment in the power grid requires the shutdown of power plants in case of maintenance or malfunction. The shutdown relies on protective devices that must be properly coordinated to isolate only the part of the grid affected by the malfunction. Using the DIgSILENT PowerFactory software, an analysis was conducted on a model of an accurate real grid integrating a photovoltaic power plant with a capacity of 390 kW. Protection coordination testing was carried out for three-phase, two-phase, and single-phase short circuit currents at arbitrarily selected locations at medium and low voltage levels. Protection in the time domain is coordinated on lines and busbars to determine the speed and selectivity of protective devices. The analysis results indicate that adequately adjusting the three-phase short circuit at the main transformer output 110/10 kV with an impedance of 0 Ω and an allowed protection operation time of up to two seconds can be correctly addressed within 36.7 ms.

Experimental studies of using the digital control system in power conversion equipment of high-voltage power supply systems in spacecrafts with a hydrogen energy accumulator

Solar-hydrogen energy for spacecraft, space interplanetary stations, space bases on the planets of the solar system must reliably provide energy: spacecraft during peak periods (repairs at a space facility, energy-consuming experiments, cleaning of facilities, regeneration of waste to extract oxygen and hydrogen, etc. .d.) and bases on planets, especially where the night lasts for a long time.The onboard hydrogen module of the solar-hydrogen plant includes: a container with water; distiller; deionizer; water lines with adjustable shut-off valves; electrolyzer; cryogenic side tanks with hydrogen and oxygen; fuel cell, hydrogen safety sensor systems based on leakage and concentration sensors; level gauges; cryogenic and gas pipelines of hydrogen and oxygen; onboard cryo-refrigerator; automatic control system for the hydrogen module. The article presents the results of experimental studies of static, dynamic and mass-dimensional characteristics of power conversion equipment (hereinafter - PCE) in the power supply system (hereinafter - PSS) of the spacecraft (hereinafter - spacecraft) with a digital control system. The purpose of experimental research is to verify the theoretical results obtained earlier in the design of digital PCE control systems of high-voltage PSS spacecraft, including the study of static and dynamic characteristics. We developed and manufactured an experimental PCE sample with an output power of 2500W in this research. It includes: four voltage stabilization modules and the 100V load supply output bus filter. Each voltage stabilization module includes a battery energy conversion channel, a solar battery energy conversion channel and a digital control system unit. The power conversion channel of the accumulator battery is designed and made on the basis of a bridge volt-booster inverter-transformer circuit. Voltage control in energy converter of accumulator battery is based on phase shift in control pulses of transistors in adjustable inverter rack related to unregulated one. The power conversion channel of the solar battery is designed and made on the basis of a two-phase circuit of a direct voltage converter of an increasing type with switching throttles. The digital control system of the voltage stabilization module is designed on the basis of analogues in the modern electronic component base in the Space class and consists of four identical channels. Each channel of the control system controls its own voltage stabilization module. We obtained the following results during our experimental studies: some pulsations of the output voltage of the energy conversion equipment during operation on an active load, transient processes of the output voltage of the energy conversion equipment during pulsations of the load current without changing the mode of operation, transient processes of the output voltage of the energy conversion equipment when changing the modes of its operation and weight and size characteristics for different values of the output power. The obtained results of experimental studies confirm the previously obtained theoretical results, and also showed that the use of a distributed digital control system will increase the specific energy characteristics of the newly developed PSS spacecraft while ensuring the given static and dynamic characteristics of output voltage quality. The results of the work are designed to create a new on-board power conversion equipment for power supply systems of promising spacecraft. The area of application of the project results is space instrumentation.

Encoderless Five-phase PMa-SynRM Drive System Based on Robust Torque-speed Estimator with Super-twisting Sliding Mode Control

In this paper, a robust torque speed estimator (RTSE) for linear parameter changing (LPC) system is proposed and designed for an encoderless five-phase permanent magnet assisted synchronous reluctance motor (5-phase PMa-SynRM). This estimator is utilized for estimating the rotor speed and the load torque as well as can solve the speed sensor fault problem, as the feedback speed information is obtained directly from the virtual sensor. In addition, this technique is able to enhance the 5-phase PMa-SynRM performance by estimating the load torque for the real time compensation. The stability analysis of the proposed estimator is performed via Schur complement along with Lyapunov analysis. Furthermore, for improving the 5-phase PMa-SynRM performance, five super-twisting sliding mode controllers (ST-SMCs) are employed with providing a robust response without the impacts of high chattering problem. A super-twisting sliding mode speed controller (ST-SMSC) is employed for controlling the PMa-SynRM rotor speed, and four super-twisting sliding mode current controllers (ST-SMCCs) are employed for controlling the 5-phase PMa-SynRM currents. The stability analysis and the experimental results indicate the effectiveness along with feasibility of the proposed RTSE and the ST-SMSC with ST-SMCCs approach for a 750-W 5-phase PMa-SynRM under load disturbance, parameters variations, single open-phase fault, and adjacent two-phase open circuit fault conditions.

Тепловая математическая модель двухфазного контура с механическим насосом и тепловым гидроаккумулятором

Growing heat release in spacecraft accompanied by simultaneous increase in its amount set the task of developing thermal control systems using the two-phase boiling coolant. It accumulates heat in the form of latent vaporization heat making it possible to transfer much larger amount of heat per the coolant unit mass flow rate than at using a single-phase coolant. In addition, introduction of heat transfer at boiling allows maintaining the object temperature in almost the entire circuit close to the boiling temperature of the selected coolant. All heat transfer processes that occur, when the substance aggregation state changes, are much more intensive than with the conventional convective heat transfer; therefore, the mass of heat exchangers, fittings and control elements of the two-phase circuit would be significantly lower than their mass in a single-phase coolant circuit. Capillary or mechanical pumps should pump the coolant in two-phase systems to ensure the thermal regime. At high power, it is more advantageous to use the two-phase boiling coolant with a mechanical pump. Creation of thermal control systems based on the two-phase circuit should be preceded by elaboration of an adequate mathematical model of the two-phase boiling coolant. Mathematical model is proposed that could be used to analyze operation of the two-phase boiling coolant and calculate hydrodynamic, heat and mass transfer processes.

Design of a thermal control system with a two-phase coolant for a spacecraft with a capacity of 7 kW

This article presents a methodological approach to designing a spacecraft thermal control system with coolant pumping with a cooling capacity of up to 7.0 kW. Two design options are considered. There is no airtight instrument container in the spacecraft layout scheme, and all heat-generating equipment is located directly on the power structure panels, so excess heat is removed from the spacecraft directly from the outside of the instrument panels. With all the attractiveness of a two-phase circuit with a heat pipe circuit, its use in automatic spacecraft is complicated by the need to supply concentrated heat to the capillary evaporator of the circuit. To do this, it is necessary to collect heat from a large surface of the structure, on which a large number of heat sources are installed. A schematic solution of the thermal control system is considered, in which the thermal power of the payload module is distributed between the panel of the service systems module and deployable radiators. At the same time, in the first version, the heat pipes of the payload module are connected to the heat pipes of the service systems module along the profile shelves, the contour heat pipes of the deployable radiator are connected only to the heat pipes of the service systems module. Ums, the heat load of the payload module is transferred to the heat pipes of the service systems module and then to the loop heat pipes. The second option differs from the first one in that to equalize the temperatures of the panels of the payload module, each heat pipe of the North panel is connected to the heat pipes of the South panel. From the results of a comparative analysis of the mass budget and energy efficiency, the conclusion follows: the DFC with capillary pumping is the most preferable option 2. which, with the same other characteristics, has a smaller mass. The specific mass-energy: characteristic of such a system is ~22.9 kg/kW.

Research on Open Circuit Fault Modeling and Fault Tolerant Control Strategy of Five-Phase Induction Motor

Five-phase induction motors have the advantages of high reliability and strong fault-tolerant performance, so it’s open circuit fault model and fault-tolerant control strategy are widely studied. Based on the normal operation of the five-phase induction motor, the mathematical model of the five-phase induction motor under the conditions of single-phase open circuits, adjacent two-phase open circuits, and non-adjacent two-phase open circuits are established by using the reduced order decoupling transformation. Based on the principle of constant magnetic potential, the relationship between magnetic potential and each phase current is analyzed by using the symmetrical component method (MSC). The fault-tolerant control strategy of a five-phase induction motor with the above three open-circuit faults is designed. Through simulation and prototype experiments, the phase current and speed conversion under three open-circuit faults are analyzed. The results show that after the open-circuit fault of a five-phase motor, the residual phase current is no longer balanced, the motor speed is decreased, and the vibration is increased significantly. After fault-tolerant control, the residual phase current is balanced, the rated speed can be reached, and the vibration of the motor is reduced. Thus, the validity and correctness of the fault-tolerant control strategy for a five-phase induction motor are verified.

ПРОЕКТИРОВАНИЕ СИСТЕМЫ ТЕРМОРЕГУЛИРОВАНИЯ С ДВУХФАЗНЫМ КОНТУРОМ ДЛЯ КОСМИЧЕСКОГО АППАРАТА ПРОИЗВОДИТЕЛЬНОСТЬЮ ДО 15 кВт

This paper presents a methodological approach to the design of a spacecraft thermal control system with coolant pumping with a cooling capacity of up to 15 kW. Two variants of constructions are considered. A thermal and mass-energy analysis of the thermal control system for an automatic spacecraft with active coolant pumping using the heat of the phase transition is carried out. Structurally, the thermal control system consists of a two-phase circuit and axial heat pipes. Sequential laying of a circuit for heat collection is impractical, as it leads to excessively large diameters of steam paths. It is required to consider either a scheme with parallel laying of steam mains, or a variant with a central two-phase bus and autonomous circuits for heat collection / removal. The proposed layout of the thermal control system with two-phase circuit and active pumping of the coolant with a capacity of up to 15 kW provides for the necessary area of the radiation panels. Two variants are considered: with a central heat bus and with a parallel connection of the evaporation line. The results of the analysis show a mass acceptance of the two-phase thermal control system with a central reserved bus. The reliability parameter for the first option is also higher, since it has full redundancy of the central heat bus. In the second option, it is difficult to reserve the contour. The advantage of the second option is a lower thermal resistance during heat transfer from the equipment, therefore, large estimated reserves for the temperature of the equipment seats.

Thermal-hydraulic model of a two-phase circuit with a compensation cavity

Thermal-hydraulic model of a two-phase circuit with a compensation cavity

Design of a Short-Beam Linear Traveling-Wave Piezoelectric Motor.

A straight short-beam linear piezoelectric motor constructed with two sets of ceramic actuators separated with the 1/4 wavelength interval is designed in this article. The piezoelectric ceramic actuators are fabricated in the whole body, which is driven by a two-phase circuit with the same amplitude but a phase difference of π /4. Traveling wave (TW) is formed by superimposing standing waves generated by each set of ceramic actuators. At the ends of the short beam, a wave-reduction mechanism with larger cross-sectional area is designed so that wave reflection is effectively diminished to preserve the TW. The currently developed short-beam linear piezoelectric motor is estimated, which can produce an ideal output speed of 169 mm/s while applying voltage of Vpp = 300 V at 45.49 kHz. Instead of operating as a stator to drive a carriage for example, the short-beam linear piezoelectric motor is implemented on a guide slider, and therefore, a linear piezoelectric motor stage is built. While driving the linear stage employed with a preload 300 GW and a friction coefficient of about 0.15, the propulsion force is measured about 4.8 N, the speed is about 56 mm/s, and the position resolution can achieve in the submicrometer scale.

Analysis of the FACTS devices impact on the transmission line protection operation

The effect of the static synchronous compensator (STATCOM) on distance protection of a high-voltage transmission line is studied in this article. To carry out the research stated in the topic of the paper, an experimental scheme was developed, equipment was selected, the operation settings of the 3 stages of distance protection were calculated and quad characteristics were built on their basis. All listed above, as well as further experiments, were carried out by the real time digital simulator. The STATCOM model was integrated in the scheme and set next. A series of experiments was carried out: two-phase and three-phase short circuits in various nodes of the scheme with and without the compensator and in various connection nodes. After all the experiments were carried out, appropriate conclusions were made about the impact of FACTS devices on the operation of distance protection. Possible ways to solve detected problems were also proposed.

PWM Investigation of a Field-Oriented Controlled Five-Phase PMSM Under Two-Phase Open Faults

The decoupled model of Five-Phase Permanent Magnet Synchronous Motors (5Ph PMSMs) under a two-phase open circuit has been developed recently, yet the corresponding PWM has not been fully exploited. The Pulse Width Modulation (PWM), which is straightforward for a balanced system, can be problematic to fit a 5Ph PMSM under faulty conditions. During the open faults, the neutral voltage is drifting over the mid-point of DC bus, thus, the PWM typically designed for a balanced system always fails. In this article, an affine transformation is first presented to offset the drifting neutral effect, and only then PWMs can be effective. A quasi-sinusoidal PWM, a Space Vector PWM, and a min-max Carrier-based PWM are presented and compared experimentally. Each method has its own merits and demerits, and their effectiveness or rather the proposed affine transformation is validated by the experimental results.

A Calibration-Free 14-b 0.7-mW 100-MS/s Pipelined-SAR ADC Using a Weighted- Averaging Correlated Level Shifting Technique

This article presents a 14-b 100-MS/s single-channel pipelined-successive-approximation register (SAR) ADC using a weighted-averaging correlated level shifting (WACLS) technique. For a closed-loop residue amplification, the error voltage due to the finite operational amplifier (opamp) gain can be ideally removed by the proposed WACLS technique with a low-gain opamp. In addition, the opamp bandwidth degradation, by an extra level-shift capacitor (CLS) in two-phase amplification CLS-based circuits, can be relaxed and minimized in WACLS. Furthermore, a speed-enhancement scheme is provided to alleviate the speed degradation owing to one extra amplification phase and long bit-cycling time from two-phase amplification and SAR circuits, respectively. A modified reference swapping (RS) technique is applied to diminish the capacitor mismatch error without any calibration. A quick startup ring amplifier design is introduced for duty-cycled control power saving. The chip is implemented in the 28-nm CMOS technology and occupies an active area of 0.018 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . At 100 MS/s and Nyquist-rate input, the measured SNDR is 71.7 dB with 0.7-mW power consumption only. The calibration-free ADC achieves Walden and Schreier figure-of-merit of 2.2 fJ/conversion-step and 180.2 dB, respectively. Compared with the prior-art ADCs with sampling frequency 100 MS/s and SNDR 65 dB, this work advances the state-of-the-art by 3× and 5.3 dB, respectively.

Modeling of an efficient high power wind energy conversion system using self-excited multi-phase machines

Self-Excited Multi-phase Induction Generators (SEMPIG) producing power from wind turbines infar-flung fields are receiving the interest of recent researchers. Small and medium energy wind generators involve 3-phase induction generators. SEMPIG with significant reliability, better fault tolerance, reduced harmonics, and high power-handling capability using reduced current per phase and maintaining the same per phase voltage makes it the promising contender in high-power WECS. This investigation analyzes the proficiency of energy efficient stand-alone self-excited seven-phase induction generator (SE7PIG) in wind energy schemes. This paper develops a cogent model from the two-phase equivalent circuit of SE7PIG using Matlab/Simulink. The study examines the modeling aspects of the SE7PIG with incorporated significant 7-rectifier and 7-phase inverter. The machine operational parameters speed, torque, voltage and current are presented. The 2MW WECS with 7-phase induction generator is analyzed with and without DC link converter. The results are compared with the 3-phase counterpart to illustrate the efficacy of SE7PIG for megawatt wind-power generation. The paper confirms the competence of SE7PIG with better fault tolerance and significant energy output with a decrease in phase current.

Reduced-Order Model of Rotor Cage in Multiphase Induction Machines: Application on the Prediction of Torque Pulsations

For three-phase induction machines supplied by sinusoidal current, it is usual to model the n-bar squirrel-cage by an equivalent two-phase circuit. For a multiphase induction machine which can be supplied with different harmonics of current, the reduced-order model of the rotor must be more carefully chosen in order to predict the pulsations of torque. The proposed analysis allows to avoid a wrong design with non-sinusoidal magnetomotive forces. An analytical approach is proposed and confirmed by Finite-Element modelling at first for a three-phase induction machine and secondly for a five-phase induction machine.

A Evaluation of the Dynamic Strength of the Shaft Line with Welded Rotors of Low Pressure Cylinders of the K-220-44-1 Turbine

To assess the danger of resonance vibrations, the calculations data of the critical rotational speeds and strength in case of a sudden short circuit in the generator of the shaft line of the upgraded K-220-44-1 turbine unit have been presented. The turbine unit comprising a high-pressure cylinder and two low-pressure cylinders has been in operation at nuclear power plants since the early 1970s. The shaft-line consists of a high-pressure all-forged rotor, two low-pressure welded rotors, an intermediate part and a generator rotor. For the rotors of the turbine unit constituting the shafting, rod models with concentrated masses and elastic-damping support were used. Recommendations on the choice of vertical compliance of supports for computational studies are given. Estimates of the critical speeds of the shafting are obtained without taking into account the lubricant layer of the support bearings. The dynamic state of the shafting is considered for two-phase and three-phase short circuits in the generator. The maximum twisting moments in the rotors' necks under the support bearings are estimated, and the safety factors for the limiting table torque in the plasticity state are determined. The calculations were performed using software packages developed in the A. Podgorny Institute of Mechanical Engineering Problems of NASU, Joint Stock Corporation "Turboatom". The calculation data show that no dangerous resonance vibrations of the shaft-line of the upgraded K-220-44-1 turbine unit are detected and the strength of the shaft-line in case of a sudden short circuit in the generator is in conformity with the requirements of regulatory and technical documents.

Two-phase flow void fraction estimation based on bubble image segmentation using Randomized Hough Transform with Neural Network (RHTN)

The International Atomic Energy Agency (IAEA) has been encouraging the use of passive cooling systems in new designs of nuclear power plants. Next nuclear reactor generations are intended to have simpler and robust safety resources. Natural Circulation based systems hold an undoubtedly prominent position among these. The study of limiting conditions of these systems has led to instability behavior analysis where many different two-phase flow patterns are present. Void fraction is a key parameter in thermal transfer analysis of these flow instability conditions. This work presents a new method to estimate void fraction from images captured of an experimental two-phase flow circuit. The method integrates a set of Artificial Neural Networks with a modified Randomized Hough Transform to make multiple scans over acquired images, using crescent-sized masks. This method was called Randomized Hough Transform with Neural Network (RHTN). Each different mask size is chosen according with bubble sizes, which are the main ‘objects of interest’ in this image analysis. Images are segmented using fuzzy inference with different parameters adjusted based on acquisition focus. Void fraction calculation considers the volume of the imaged geometrical section of flow inside cylindrical glass tubes considering the acquisition depth-of-field used. The bubble volume is estimated based on geometrical parameters inferred for each detected bubble. The image database is obtained from experiments performed on a vertical two-phase flow circuit made of cylindrical glass where flow-patterns visualization is possible. The results have shown that the estimation method had good agreement with increasing void fraction experimental values. RHTN has been very efficient as bubble detector with very low ‘false-positive’ cases (<0.004%) due robustness obtained through integration between Artificial Neural Networks with Randomized Hough Transforms.

NSGAII optimization for single phase passive filter allocation in distribution systems

This work presents a methodology for passive filter allocation within an electrical distribution system aiming to minimize the number of nodes that exceed harmonic distortion limits and investment costs. Harmonic distortions are usually mitigated by filters, but their allocation in the system requires attention. Depending on the filters location, harmonic distortion could increase at other nodes. The methodology of this study is based on harmonic flow simulation in the Alternative Transient Program (ATP/EMTP) as well as the NSGA II optimization algorithm simulated on Matrix Laboratory (MATLAB). The filters are located using single-phase units, in order to obtain solutions for unbalanced distribution systems with single-phase and two-phase circuits, while also attending features of single-phase inverter connected Distributed Generation (DG). Different scenarios are generated by MATLAB and simulated on ATP. The optimization problem is non-linear and multi-objective. One objective is to minimize the number of nodes exceeding distortion limits and the other is to minimize filter costs. The results show that the optimal installation of single-phase filters gives better results than the installation of three-phase filters at the critical nodes. The proposed methodology allows the user to choose the best option between the number of nodes exceeding limits and the investment cost.

Investigation of an Induction Wound Rotor Motor to Work as a Synchronous Generator

This paper aims at investigating the use of an induction wound rotor motor to generate voltage instead of the old diesel engines that are still used in many factories, like old cement factories, in Jordan. In this investigation, a simulation model of induction wound rotor motor was implemented using Matlab/Simulink. The excitation dc current was connected to a two-phase rotor circuit, and the voltage-current performance characteristics were investigated and evaluated under different load types. The simulation results confirmed the possibility of using the induction wound rotor motor as a synchronous generator.

New Fault-Tolerant Control Strategy of Five-Phase Induction Motor with Four-Phase and Three-Phase Modes of Operation

The developed torque with minimum oscillations is one of the difficulties faced when designing drive systems. High ripple torque contents result in fluctuations and acoustic noise that impact the life of a drive system. A multiphase machine can offer a better alternative to a conventional three-phase machine in faulty situations by reducing the number of interruptions in industrial operation. This paper proposes a unique fault-tolerant control strategy for a five-phase induction motor. The paper considers a variable-voltage, variable-frequency control five-phase induction motor in one- and two-phase open circuit faults. The four-phase and three-phase operation modes for these faults are utilized with a modified voltage reference signal. The suggested remedial strategy is the method for compensating a faulty open phase of the machine through a modified reference signal. A modified voltage reference signal can be efficiently executed by a carrier-based pulse width modulation (PWM) system. A test bench for the execution of the fault-tolerant control strategy of the motor drive system is presented in detail along with the experimental results.