Frequency Converter System Research Articles

Reducing reactive energy consumption by optimizing operating modes of irrigation pumping stations

The article develops energy and resource efficiency modes of the technological process that meet the requirements of the “frequency converter - asynchronous motor - pump - pressure pipeline” system as a control object. Methods for regulating water pressure and water flow produced by pumping units are considered in order to ensure a schedule for water supply to irrigation pumping stations. The active, reactive and total electrical energies received by an asynchronous motor to change water flow by changing the position of the pressure valve in the pressure pipeline are calculated. In order to optimize water flow and water pressure by changing the speed of rotation of the pump impeller, the frequency converter system of an asynchronous motor with a squirrel-cage rotor was calculated and compared with the method of changing water flow using a push valve, by calculating active, reactive and total electrical energy from the network.

Circulating current suppression for ground tied variable frequency to constant frequency converter system in aircraft

This paper presents a solution to the circulating current fault of aircraft power supply. The DC-link type Variable Frequency to Constant Frequency (VFCF) converter system is the preferred scheme to feed the constant 400 Hz load in an aircraft with a variable frequency power supply. Due to the requirement of aircraft standards, both grounds of the rectification and inversion stage are tied to the metal frame of the aircraft. With such a tied ground, the DC bus voltage rises greatly, and a large circulating current appears in the casing as the ground, which leads to equipment failure and potential safety hazards. According to the existing methods of circulating current fault suppression, this paper analyzes the causes of the above faults and the harmonic components of circulating current and points out the limitations of the existing methods. Therefore, a Common-Mode (CM) choke-based method is proposed to provide a high impedance in the path of the CM circulating current. By doing so, the circulating current can be suppressed without the additional burden of the hardware and control algorithm, which is quite friendly for quality control of mass-production aircraft. Moreover, a simplified mathematic model of the VFCF converter system is derived to calculate the minimum inductance value reference of the CM choke, which saves the weight of passive devices to the greatest extent. Finally, simulation and experimental results are studied to verify the effectiveness of the proposed method.

X-nuclear MRS and MRI on a standard clinical proton-only MRI scanner

In light of the growing interest in-vivo deuterium metabolic imaging, hyperpolarized 13C, 15N, 3He, and 129Xe imaging, as well as 31P spectroscopy and imaging in large animals on clinical MR scanners, we demonstrate the use of a (radio)frequency converter system to allow X-nuclear MR spectroscopy (MRS) and MR imaging (MRI) on standard clinical MRI scanners without multinuclear capability. This is not only an economical alternative to the multinuclear system (MNS) provided by the scanner vendors, but also overcomes the frequency bandwidth problem of some vendor-provided MNSs that prohibit users from applications with X-nuclei of low magnetogyric ratio, such as deuterium (6.536 MHz/Tesla) and 15N (-4.316 MHz/Tesla). Here we illustrate the design of the frequency converter system and demonstrate its feasibility for 31P (17.235 MHz/Tesla), 13C (10.708 MHz/Tesla), and 15N MRS and MRI on a clinical MRI scanner without vendor-provided multinuclear hardware.

First study on harvesting electromagnetic noise energy generated by the frequency converters

This paper proposes a novel environmental energy harvesting process. The source of energy consists of the electromagnetic (EM) noise emitted by the frequency converter system (inverter) and the harvester is composed by a monopole antenna and a full rectifier circuit. The operation of the frequency converter using MOSFET and IGBT switchers produces parasite currents in high frequency (100 KHz to 30 MHz) which are the principal cause of radiated EM noise. We have demonstrated that we can convert this EM noise into useful electrical energy to power wireless sensor nodes (WSNs) and other electronic devices. Experimentally, the EM noise is produced when the system “frequency converter + charge” is in operation mode. Moreover, the harvester has produced an uninterrupted power of 40 mW measured in accredited ISO/IEC 17025 laboratory. Furthermore, we have presented the output power of our device stored in 1 µF capacitor with demonstration examples of loading charges. These results offer opportunities for self-powered WSNs and electronic devices on a very large area of industrial applications with less use of conventional batteries.

Performance Enhancement of Doubly-Fed Induction Generator-Based-Wind Energy System

Nowadays, the challenging errand is enhancing the wind energy system (WES) performance to be more competitive and economically viable. Most researchers believe that one of the best ways to enhance the performance of the doubly-fed induction generator (DFIG)-based-WES is the optimization of the proportional-integral (PI) controllers for the variable frequency converter system. Many objectives with different optimization techniques have been used in literature to achieve optimal performance. Each choice has its advantages and disadvantages; thus, the research area is still open for getting optimal performance. This paper presents a new design approach for better performance of PI controllers and, hence DFIG over a wide range of operating conditions through two main themes. The first is by introducing a new multi-objective formulation, while the second is utilizing recent optimization techniques like Grey Wolf Optimizer and Whale Optimization Algorithm. The proposed approach is applied to get the best parameters of the related PI controllers for rotor and grid side converters of the simulation model of a 6 MW wind farm located in Jabal Alzayt along the Red Sea Coast in Egypt and directly connected to the grid. The results confirmed the effectiveness of the proposed approach to help the DFIG-based-WES to agree with the Egyptian Grid Code during disturbances compared with the traditional objective formulation.

Control signal algorithm of the accelerator pedal providing an effective energy consumption by an electrobus traction gear

BACKGROUND: At the present moment there become more electrobuses in big towns, and the problem of the increasing the their energy efficiency is actual in intertown traffic (that assumes stops and time limitation among stops) because of the limitated on-board capacitors.
 AIMS: Development of the control signal algorithm of the accelerator pedal providing an effective energy consumption by an electrobus traction gear.
 METHODS: The new method for control signal formation of the accelerator pedal is proposed. It has a feature that provides the system operation traction gear frequency converter in zone of the increased efficiency factor and limits the velocity of control signal level growing when a driver tromps gas.
 RESULTS: Analysis of the electrobus operation results in intertown traffic shows, that the aggregate average electric capacity, consumed at electrobus operating equipped with the energy saving systems, is less by 8,2% than at electrobus operating without energy-saving systems at the same conditions. The average efficiency factor of the traction gear frequency converter system of an electrobus equipped with energy-saving systems has been increased by 4.5%. The time of driving on the route of an electrobus equipped with energy saving systems increased by 27 seconds that is an acceptable result. Energy saving in linehaul operation was provided only by an antislip system operation. During the total time driving of the electrobus energy saving was 2.6%.
 CONCLUSIONS: A new method for generating a control signal from the side of the accelerator pedal is proposed, which differs in that it ensures the operation of the traction motor frequency converter system in the zone of increased efficiency and limits the rate of increase in the level of the control action when the driver abruptly presses the accelerator pedal.

Algorithm for improving energy efficient wheel motor for electric vehicles

In accordance with the tendency to reduce the number of mechanical assemblies in electric driven machines and mechanisms, attempts are made to bring the electric motor and the actuator of the mechanism into a single whole. Thereby increasing the quality and productivity of the machines. A motor-wheel is a kind of a driving wheel, an actuator of a traction electric drive system of a pneumatic-wheeled transport vehicle. The work is devoted to the modernization of urban electric transport by equipping it with high-energy efficiency motor wheels, based on the frequency converter system - asynchronous motor. This paper describes the improvement algorithm and technological features.

Structural and emission properties of Tb3+-doped nitrogen-rich silicon oxynitride films

Terbium doped silicon oxynitride host matrix is suitable for various applications such as light emitters compatible with CMOS technology or frequency converter systems for photovoltaic cells. In this study, amorphous Tb3+ ion doped nitrogen-rich silicon oxynitride (NRSON) thin films were fabricated using a reactive magnetron co-sputtering method, with various N2 flows and annealing conditions, in order to study their structural and emission properties. Rutherford backscattering (RBS) measurements and refractive index values confirmed the silicon oxynitride nature of the films. An electron microscopy analysis conducted for different annealing temperatures (TA) was also performed up to 1200 °C. Transmission electron microscopy (TEM) images revealed two different sublayers. The top layer showed porosities coming from a degassing of oxygen during deposition and annealing, while in the region close to the substrate, a multilayer-like structure of SiO2 and Si3N4 phases appeared, involving a spinodal decomposition. Upon a 1200 °C annealing treatment, a significant density of Tb clusters was detected, indicating a higher thermal threshold of rare earth (RE) clusterization in comparison to the silicon oxide matrix. With an opposite variation of the N2 flow during the deposition, the nitrogen excess parameter (Nex) estimated by RBS measurements was introduced to investigate the Fourier transform infrared (FTIR) spectrum behavior and emission properties. Different vibration modes of the Si–N and Si–O bonds have been carefully identified from the FTIR spectra characterizing such host matrices, especially the ‘out-of-phase’ stretching vibration mode of the Si–O bond. The highest Tb3+ photoluminescence (PL) intensity was obtained by optimizing the N incorporation and the annealing conditions. In addition, according to these conditions, the integrated PL intensity variation confirmed that the silicon nitride-based host matrix had a higher thermal threshold of rare earth clusterization than its silicon oxide counterpart. Analysis of time-resolved PL intensity versus TA showed the impact of Tb clustering on decay times, in agreement with the TEM observations. Finally, PL and PL excitation (PLE) experiments and comparison of the related spectra between undoped and Tb-doped samples were carried out to investigate the impact of the band tails on the excitation mechanism of Tb3+ ions.

Energy Saving Potential on Centrifugal Water Chillers with Frequency Converter System: A Case Study in China

In order to evaluate the energy saving potential during centrifugal water chillers’ operation, centrifugal water chillers from an industrial enterprise in China are investigated. Based on the actual operation data gained from 3 different water chillers, their working performances and the energy consumption situations are reported and researched in this paper. Meanwhile, the energy saving potential and economic performance of the chillers are also reported and analyzed, when the appropriate variable frequency systems are introduced.

Using Complex Conjugated Magnitudes- and Orthogonal Park/Clarke Transformation Methods of DC/AC/AC Frequency Converter

The paper deals with mathematical modeling of two-stage frequency converter system with induction motor. There are used two special methods of investigation: method of complex conjugated amplitudes, and the orthogonal Park/Clarke transformation method. The first one is used for steady-state investigation; the second one is suitable for investigation of three-phase electric circuits. The combination of both methods is very useful for analysis of three-phase electric motors in steady-state condition: constant angular speed, and when operator d/dt in its dynamical model is substituted by operator j, ν, ω, t. Then the effect of individual harmonic components on motor properties can be investigated. Ill. 9, bibl. 10 (in English; summaries in English, Russian and Lithuanian).

Modelling and ride‐through capability of variable speed wind turbines with permanent magnet generators

AbstractA model for a variable speed wind turbine with a permanent magnet, multipole, synchronous generator is developed and implemented in the simulation tool PSS/E as a user‐written model. The model contains representations of the permanent magnet generator, the frequency converter system with control, the aerodynamic rotor and a lumped mass representation of the shaft system. This model complexity is needed for investigations of the short‐term voltage stability and ride‐through capability of such wind turbines. Ride‐through capability is a major issue and, for the given concept, can be achieved by applying blocking and restart sequences to the frequency converter at the voltage drop in the power grid. Copyright © 2005 John Wiley & Sons, Ltd.

Generation of external laser field harmonics by an electron beam in a multicomponent undulator with an axial field

An analysis is made of a frequency converter system for coherent radiation using an electron beam propagating through a two-component undulator. It is shown that in many cases, the introduction (in addition to the fields of two helical undulators) of a strong axial magnetic field can substantially improve the gain and intensity of the generated wave. The gain is calculated allowing for the energy scatter of the beam electrons.

Starting of Large Synchronous Motor Using Static Frequency Converter

This paper deals with the synchronous starting of a large synchronous motor, using a static thyristor frequency converter system. This method, in the following called, Converter Starting, is described. Special inverter questions are treated and the results of analytical and computer studies of the system and of a field test are presented. Potential applications of the method are dewatered starting in the pumping mode of reversible pumped-storage generator/motors and the starting of large synchronous condensers. The same equipment can also be used for braking the machines.

Solid state VHF frequency converter

This paper describes the design of a transistor frequency converter suitable for use in mobile communication receiver equipment. Two-port network theory is used to design a 250-Mc RF amplifier, a 250- to 60-Mc mixer, a 310-Mc local oscillator and a two-stage 60-Mc IF amplifier. Performance of silicon planar transistors are first predicted from calculations based on y parameters of these transistors and then compared with experimentally determined performance. The mathematical techniques used in the design of this circuitry are discussed in some detail. Basic design philosophy using terminal, rather than internal, parameters is introduced. Power gain and stability are described in terms of terminal admittance parameters and high frequency performance curves of a popular high frequency silicon transistor are presented. Finally, a transistor frequency converter system suitable for mobile communications equipment is discussed. In particular, the sensitivity, noise figure, selectivity and stability are developed. The over-all converter performance values are: Conversion Gain 65 db Bandwidth 4 Mc Noise Figure 6 db Image Rejection 25 db Temperature sensitivity data indicated that the local oscillator was most sensitive to temperature change and caused the over-all gain to vary from 62.5 db @ 5°C to 65 db at 25°C to 60 db @ 50°C. Center frequency changes (in the same order) were 57 Mc, 60 Mc and 65 Mc.