Transformer Rectifier Research Articles

Analisis Pemasangan Filter Pasif Untuk Mengurangi Harmonisa Pada Transformator Rectifier Di PT. Indah Kiat Pulp And Paper Perawang

The chlor-alkali process is an electrolysis process which plays an important role in the chemical industry such as the pulp industry. The process produces a product in the form of H2 gas, CL2 gas and NaOH (where the source of chloride ion used is NaCl). This electrolysis process requires a dirrect current with a large current and a low voltage. In this electrolysis process a three phase controlled 12 pulse rectifiers are used which a connected with multi-winding transformers. In the rectifiers process there will be harmonic distortion on the source side of the transformer which can reduce the power quality of the system. To overcome the harmonic problems that occur in the system, an installation analysis of the equipment in the form of a passive single tuned filter is aimed at reducing harmonic distortion of current and voltage and increasing the power factor (cos φ). From the result of harmonic analysis using ETAP software, after the installation of harmonic filters orde 11, 13 and 23, the harmonic current value (THDI) and harmonic voltage (THDV) has decreased, namely, before the filter installation, THDI value is 6,5% whereas after installation of filters, THDI value becomes 0,98%, thus there is a THDI decrease of 5,52%. Furthermore, for the voltage harmonic value (THDV) before filter installation is 1,48% while after filtering, THDV value becomes 0,26%, thus there is a THDV decrease of 1,22%. From the results of the simulation of the flow of power (load flow analysis), after installation of filters there is an increase in the value of the power factor (cos φ). Namely, before the filter installation, the value of power factor (cos φ) is 0,8 while after the filter installation the value of the power factor (cos φ) to 0,96, thus an increase in the power factor (cos φ) of 16%.
 
 Keywords : harmonic filter, single tuned filter, power factor, transformer rectifier

A Wireless Rectifier for Inductively Energizing High Direct-Current High-Temperature Superconducting Magnets

High-temperature superconducting (HTS) magnets have been widely used in various applications due to their excellent performance. One long-lasting problem, however, is that they have to be powered by electronic power supplies via a pair of thick current leads, which go through room temperature environment into a cryogenic environment. The considerable heat load generated by these resistive current leads at a cryogenic temperature substantially limits the operating current and the energy density of the magnet. In this article, we report a novel mechanism of inductively energizing closed-loop HTS dc magnets. This exploits a newly discovered effect, which appears within a superconducting loop when a global screening current interacts with local screening current. This results in a dc voltage across the superconductor, which enables an alternating superconducting current to be rectified in order to energize a superconducting magnet. Based on this principle, a superconducting transformer–rectifier prototype is realized and demonstrated. Test results show that the prototype can output a dc voltage of up to 25 mV and a maximum direct current over 500 A. It is envisaged that this work will enable future HTS dc magnets to be operated in a closed cryogenic environment, eliminating the need for electronic power supplies and bulky current leads. This would greatly reduce the footprint and power demand of HTS magnet systems and unlock many new opportunities for the applications of this technology.

Optimisation of power electronics for regulated transformer rectifier units

This study presents a comprehensive approach for the design optimisation of passive components and heatsinks in power electronic converters. The design and selection of passive components are posed as a multi-objective optimisation problem, which can be simplified to a single-objective optimisation based on preferences and weights assigned by the designer. The mathematical equations describing the efficiency, volume, and reliability are laid out to describe the feasible space for optimisation in this study. In addition to the proposed optimisation, a substantial amount of passive component comparison data has been consolidated and presented in this study. The results from the optimisation are demonstrated on the target power electronic circuit of a regulated transformer rectifier unit for more-electric aircrafts. The optimisation framework is developed in a generic manner that would lend itself to the optimisation of any choice of converter topology, circuit components, or objective functions.

TECHNICAL AND ENERGY INDICATORS OF MEAN POWER AUTONOMOUS SYNCHRONOUS GENERATOR

The energy performance improving of the exciter by switching on the zero diodes and capacitors leads to asignificant change in the harmonic composition of the excitation voltage. The study investigates the harmoniccomposition of the excitation voltage of synchronous generators with asymmetrical bridge exciters using the unitsof forced capacitive switching. To determine the harmonic composition of the excitation voltage, we decompose theexperimental curve into a Fourier series and expressions for calculating the harmonic components. The results ofthe spectral analysis indicate that the excitation voltage at the rated mode of the generator contains a significant thirdharmonic, which is 66 percent of the amplitude of the first harmonic. The significant value of the third harmonic isdue to the large angles of control of the exciter thyristor in the nominal mode of operation of the synchronousgenerator. Due to the significant third harmonic, the secondary winding of the rectifier transformer must beconnected to a triangle. The presence of even harmonics is caused by the voltage asymmetry with respect to theabscissa.A non-symmetrical bridge exciter with a forced capacitance switching unit for a synchronous generator hasbeen developed, which provides improved energy performance during its nominal operation. The scheme of controlof the bridge asymmetrical exciter of the synchronous generator with the node of forced capacitive switching for therated mode of operation, as well as in the mode of the field suppression at short circuits of the stator windings hasbeen described.The comparative estimation of the suppression modes of the field at a short circuit of the windings of thegenerator stator with the possible mode of inverting the exciter and using the node of forced capacitive switchinghas been carried out. Experimental studies have confirmed the calculated dependences of the modes of the magneticfield suppression. The analysis of experimental dependencies shows that the units of forced capacitive switchingprovide a higher speed of the field suppression modes, regardless of the presence and magnitude of the supply ofvoltage the exciter.

Study of a 18-Pulse Transformer–Rectifier Unit with an Amorphous Steel Magnetic Core

This article discusses a study of transformer–rectifier units with a magnetic core made of amorphous steel. Transformers with various types of amorphous alloys have been analyzed, and the optimum amorphous alloy for transformers was determined. Thermal processes in transformers with magnetic core of amorphous steel have been simulated, and the maximum temperature under normal operating conditions has been determined. The simulation has demonstrated that no special transformer cooling system is required. An experimental transformer–rectifier unit has been designed and manufactured with a magnetic core of amorphous steel installed on an 18-pulse rectifier with a capacity of 10.5 kV A operating with a frequency of 400–800 Hz and voltage of 115/27 V. To verify the obtained data, experimental studies have been performed that confirmed the validity of the selected design procedure of a transformer engineering flowchart. It has been demonstrated that the thermal loads detected in the transformer during testing are in the range of allowable values.

Multi-Objective Optimization Design of a Notch Filter Based on Improved NSGA-II for Conducted Emissions

This paper develops an improved non dominated sorting genetic algorithm II (NSGA-II) based on objective importance vector γ, abbreviated as γ-NSGA-II. Different importance levels for the multiple objectives are incorporated in the objective importance vector, which is applied to determine the individual selection of sorting individuals in the critical layer. And such an individual selection strategy is developed to the NSGA-II algorithm in order to obtain the optimized solution for a task which has multiple objectives with different importance. The differences between the γ-NSGA-II algorithm and the traditional NSGA-II algorithm are discussed in detail. A notch filter is designed for the conducted emission suppression of a transformer rectifier unit (TRU) used in C919 flight testing, and then the parameters optimization design of a notch filter is discussed and conducted based on the γ-NSGA-II algorithm. The non-linear relationship between the filter's parameters and the suppression effect of the conducted emission is also discussed with the help of an electromagnetic compatibility (EMC) evaluation model based on a back propagation (BP) neural network. The experimental results show that the optimized design of the notch filter is effective and the improved γ-NSGA-II algorithm be more specific.

Analysis of 6-Pulse and 12-Pulse in Conversion of the 115VAC/400Hz to 270 VDC for Application on Fighter

The development of aircraft secondary power technology is moving from mechanical power, pneumatic power and hydraulic power to electric power. The trend toward electric power is known as More Electric Aircraft (MEA). Modern military aircraft are designed using 270VDC for electric power system. Today, some military aircraft still use 115VAC/400Hz for their electrical power system. If this type of aircraft need provides 270VDC electrical power, then they require Multi-Pulse Transformer Rectifier Unit (TRU). The development of this type TRU has not been aimed to comply with aircraft military standards. This research investigates the variation of the number of pulses (p) and firing angle (α) to the amplitude ripple voltage, output voltage, and distortion factor in order to comply with the MIL-STD-704F standards. The multi-pulse transformer rectifier unit being analyzed consists of 6-Pulse and 12-Pulse. The research shows that the amplitude ripple voltage and distortion factor of the 6-Pulse TRU do not comply MIL-STD-704F. The amplitude ripple voltage and distortion factor of 12-Pulse comply MIL-STD-704F with firing angle (α) ≤4°.Keywords: Transformer Rectifier Unit, thyristor, ripple voltage, distortion factor, firing angle

Design Algorithm of an Aircraft Power Generation System

The paper deals with the design and testing of a power generation system for the future and existing aircrafts. A new design algorithm of the power generation components is presented. The proposed design algorithm was tested on a prototype: a full-size starter-generator and transformer–rectifier unit prototype was created with a transformer magnetic core made up of an amorphous magnetic material. Its stand tests were carried out both for each element and for the entire system. The proposed algorithm can be used to create power supply systems for aircraft with different voltage levels, including 270 Vdc and 200 Vac. The developed power generation system turned out to be 25–40% better than serial solutions by mass and efficiency.

Robustness and reliability review of Si and SiC FET devices for more-electric-aircraft applications

Increased electrification of traditionally hydraulic and pneumatic functions on aircrafts has put power electronics at the heart of modern aviation. Aircraft electrical power systems have traditionally operated at 115 V AC and 28 V DC with a constant speed generator and transformer rectifier units converting jet engine power into electrical power. However, due to the increasing trend towards the More Electric Aircraft (MEA), 270 V DC systems are likely in the future. This calls into question, the power semiconductor device technology that enables the on-board power converters needed for electro-mechanical actuation as well as solid-state circuit breakers for system protection. Silicon IGBTs have been the work-horse of power electronics, but as switching speeds increase due to the need for high frequency operation, the bipolar nature of IGBT tail currents become a limiting factor for improved energy conversion efficiency. A number of unipolar FET technologies, including SiC trench MOSFETs, SiC planar MOSFETs, silicon super-junction MOSFETs and SiC JFETs in cascode with a low voltage Si MOSFET, have become commercialized at around 650 V. However, reliability and robustness, especially against single event burn-out and/or single event gate rupture is critical. This paper experimentally investigates the performance of the listed FET devices under Unclamped Inductive Switching and Bias Temperature Instability/gate oxide stress tests.

Magnetic-Integrated Multipulse Rectifier Transformer With a Tight Impedance Equalizing Strategy for Power Quality Improvement of DC Traction Power Supply System

To improve the power quality of dc traction power supply system (DC-TPSS), a magnetic-integrated multipulse rectifier transformer (MI-MPRT) with a tight impedance equalizing strategy is proposed in this article. The configuration and winding-arrangement of MI-MPRT are introduced, and by integrating multiple windings on a same iron core, the volume and cost of the proposed transformer can be decreased significantly. Cooperated with the staggered winding-arrangement, a tight impedance equalizing strategy is proposed to optimize the winding thickness and insulation distance comprehensively, and MI-MPRT would be designed in a minimum axial dimension, with equalizing short-circuit impedance of each winding. A high-power prototype is manufactured, and the efficiency of prototype is verified by the transformer standard test. In addition, the DC-TPSS based MI-MPRT is implemented, and the experiment results validate that the power quality of new system can be improved significantly by harmonic elimination, circulation-currents suppression, and dc-voltage ripple restraint. Both the theoretical and experimental results indicate that the proposed MI-MPRT is suitable for power quality improvement and industrial application in DC-TPSS.

A kilo-ampere level HTS flux pump

This paper reports a newly developed high current transformer–rectifier high-Tc superconducting (HTS) flux pump switched by dynamic resistance. A quasi-persistent current of over 1.1 kA has been achieved at 77 K using the device, which is the highest reported operating current by any HTS flux pumps to date. The size of the device is much smaller than traditional current leads and power supplies at the same current level. Parallel YBCO coated conductors are used in the transformer secondary winding as well as in the superconducting load coil to achieve high current. The output current is limited by the critical current of the load rather than the flux pump itself. Moreover, at over 1 kA current level, the device can maintain high flux injection accuracy, and the overall flux ripple is less than 0.2 milli-Weber. The work has shown the potential of using the device to operate high field HTS magnets in ultra-high quasi-persistent current mode, thus substantially reducing the inductance, size, weight, and cost of high field magnets, making them more accessible. It also indicates that the device is promising for powering HTS NMR/MRI magnets, in which the requirement for magnetic field stability is demanding.

Design and Implementation of 12 Pulse AC to DC Converter in Aircraft for Aerospace Applications

Aircraft applications like landing gears, flaps, rudder systems and etc. use actuator systems which includes combination of motor, actuators and auto transformer rectifier units (ATRU). These systems work at a frequency of 400Hz. These are AC to DC converters used in aircraft's system to supply constant DC power to the motors which in turn operates actuators. These converters varies with the pulses like 12 pulse, 24 pulse etc. For the systems like this harmonics too play a major role. Less the harmonics more efficient and reliable the system will be. In this paper, a 12 pulse AC to DC converter was designed for 400Hz and 50Hz and the actual model was built for 50Hz of 1KW power. The design of 400Hz and 50Hz was done in MATLAB/Simulink and the prototype was built for 50Hz. Total harmonic distortion (THD) was obtained and compared for the two systems. All the results the simulation and the prototype are shown in this paper.

Single-Phase AC–DC Converter With Dual-Output Rectifier, Dual-Input DC Transformer, and Voltage-Split/Sigma Principle

A single-phase ac–dc converter with dual-output rectifier (DOR) and dual-input dc transformer (DI-DCX) is proposed in this paper. A voltage-split/sigma principle is adopted, that is, the grid voltage is split into two variable dc bus voltages first by the front-stage DOR, and then the two bus voltages are combined into an adjustable output voltage by the downstream DI-DCX. DC output voltage is directly regulated by the front-end rectifier. Therefore, no voltage regulation is required for the dc–dc stage, and a DI-DCX with optimized operation condition is employed to improve the overall efficiency of the ac–dc converter. Moreover, since the DOR has two different output voltages, three-level characteristic is achieved naturally to reduce switching losses of the converter. Zero voltage switching of all the active switches in the DI-DCX is realized as well. Detailed operation principles, control and modulation strategies, and characteristics of the proposed ac–dc converter are analyzed in detail. Experimental results of a 1.5-kW prototype are provided to verify the effectiveness of the proposed converter.

Examination of Multi-Pulse Rectifiers of PES Systems Used on Airplanes Compliant with the Concept of Electrified Aircraft

This article focuses on power electronic multi-pulse 12-, 24- and 36-impulse rectifiers based on multi-winding rectifier transformers. The effectiveness of voltage processing with different variants of supply voltage sources is discussed and arguments are formulated for limiting oneself to 24-pulse processing, which is used in the latest technological solutions of modern aviation technology. The main purpose of this article is to conduct a study (analysis, mathematical models, simulations) of selected multi-pulse rectifiers in the context of testing their properties in relation to the impact on the electrified power supply network. The secondary objective of the article is to assess the possibility of using Matlab/Simulink to analyze the work of rectifier circuits implemented in aircraft networks compliant with the more/all electric aircraft (MEA/AEA) concept. The simulation tests included designing a typical auto-transformer rectifier unit (ATRU) system in the Simulink program and generating output voltage waveforms in this program in the absence of damage to the rectifier elements. In the final part of this work, based on a critical analysis of the literature on the subject of the study, simulations were made of exemplary rectifiers in the Matlab/Simulink programming environment along with their brief analysis. Practical conclusions resulting from the implementation of the MEA/AEA concept in modern aviation were formulated.

The Application of Ant Colony Algorithms to Improving the Operation of Traction Rectifier Transformers

In this paper, we discuss a technical issue occurring in electric traction. Tram traction may use DC voltage; this is obtained by rectifying AC voltage supplied by the power grid. In the simplest design— one which is commonly used—only diode uncontrolled rectifiers are used. The rectified voltage is not smooth; it always contains a pulsating (AC) component. The amount of pulsation varies. It depends, among other factors, on the design of the transformer-rectifier set. In the 12-pulse system, we use a three-winding transformer, consisting of one primary winding and two secondary windings: one is delta-connected and the other is star-connected. The unbalance of secondary windings is an extra factor increasing the pulsation of DC voltage. To equalize secondary side voltages, a tap changer may be used. The setting of the tap changer is the question resolved in this paper; it is optimized by application of the ACO (ant colony optimization algorithm). We have analyzed different supply voltage variants, and in particular, distorted voltage containing 5th and 7th harmonics. The results of ant colony optimization application are described in this paper.

On‐site partial discharge test technology of converter transformer

The rectifier transformer is the power transformer of the rectifier equipment. The characteristic of the rectifier device is the AC input, DC output by rectifying the original. Converter transformer and voltage regulation transformer connect through oil and gas casing of Shanxi medium aluminium Huarun Co., Ltd. In order to solve the problems such as high test current caused by 200 kW no-load loss, insufficient capacity of single frequency conversion power supply, complicated field environment, and the great interference, a complete test plan is presented according to the conditions of the field, and the whole process of the successful test is described in detail. The key problems about the selection of test power, the selection of test frequency, and the choice of pressure mode are emphasised. The on-the-spot partial discharge test of the converter transformer has been successfully completed, which provides valuable experience for the test of large capacity transformer in the future.

A New 24-pulse Rectifier Transformer with Delta-extended Connection

The low-voltage distribution system is influenced by ever-increasing harmonics caused by nonlinear loads. A simple and reliable 24-pulse rectifier transformer for high-current and low-voltage is proposed in this paper. The proposed 24-pulse rectifier transformer consists of four secondary windings in which an original delta-extended connection is adopted. First, the existing 24-pulse rectifier system is analyzed. Second, the topology, the phase-shifting principle, the input current and the output voltage of 24-pulse transformer are described. Finally, the simulation results validate the theoretical analysis and the advantages of the new 24-pulse rectifier transformer in multi-pulse rectifier areas.

Research of Large-Capacity Low-Cost DC Deicer With Reactive Power Compensation

DC ice melting is an effective technical method against ice disaster on transmission lines. To satisfy the demand for simultaneous de-icing and reactive power compensation for substations, this paper proposed a large-capacity low-cost DC deicer with reactive power compensation, which is mainly composed of rectifier transformer, Static Var Generator (SVG) and diode rectifier. In the proposed topology, SVG and diode rectifier share the rectifier transformer, but rectifier transformer capacity is not increased compared with a single deicer. This paper firstly presents the proposed topology and analyzes its advantages. Then, the rectifier transformer design is introduced, and the SVG control strategy is presented. Simulation results for the proposed device are presented, and an engineering devices with a capacity of 21.8 MVA developed for the 220 kV Fuchong substation is described. The simulation and application results indicate that the proposed devices work well.

Modeling methodology for a HTS flux pump using a 2D H-formulation

Flux pumps are devices that can magnetize closed superconducting magnets in a gradual manner. High-Tc superconducting (HTS) flux pumps are particularly promising for high-field applications, due to the fact that lossless HTS coils are unavailable. The physics of these devices is also attractive. In this paper, we propose a modeling methodology for a transformer–rectifier HTS flux pump switched by dynamic resistance. A finite element model is built in Comsol and solved by a 2D H-formulation. The simulation result is verified by experimental data. The simulation will give a clear picture of how flux pumping occurs in a superconductor. It will show flux motion across a superconductor by shifting the electric central line, which is a unique feature of type-II superconductors. This work may be interesting in the understanding of magnetization of high-Tc superconductors.

Magnetizing high-Tc superconducting coated conductor stacks using a transformer–rectifier flux pumping method

High-Tc superconducting (HTS) coated conductor stacks have been demonstrated as very promising superconducting permanent magnets (PMs), to be used in applications like rotary motors and levitation devices. In this paper, we present a novel magnetization method to address a key problem in the application of HTS stacks, which is effective magnetization with compact, light and efficient setups. The proposed method, transformer–rectifier flux pumping, uses the mechanism developed for HTS coils to magnetize the modified HTS stacks. The accumulation of flux with time is achieved in the HTS stacks. The results show that the flux pump can effectively magnetize long HTS stacks with a magnetic field applied to a much smaller area. Operational characteristics of the flux pump are experimentally studied and some explanations are proposed for the distinct behaviors observed in the experiments. This study heralds a new direction in the magnetization of superconducting PMs and has the potential to be a practical method for industrial applications.