Design and Implementation of Bi-Directional DC-DC Converter for Wind Energy System

This paper proposes a design and implementation of the bi-directional DC-DC converter for Wind Energy Conversion System. The proposed project consists of boost DC/DC converter, bi-directional DC/DC converter (BDC), permanent magnet DC generator and batteries. A DC-DC boost converter is interface with proposed wind system to step up the initial generator voltage and maintain constant output voltage. The fluctuation nature of wind makes them unsuitable for standalone operation. To overcome the drawbacks an energy storage device is used in the proposed system to compensate the fluctuations and to maintain a smooth and continuous power flow in all operating modes to load. Bi-directional DC-DC converter (BDC) is capable of transforming energy between two DC buses. It can operate as a boost converter which supplies energy to the load when the wind generator output power is greater than the required load power. It also operates in buck mode which charges from DC bus when output power is less than the required load power. The proposed converter reduces the component losses and increases the performance of the overall system. The complete system is implemented in MATLAB/SIMULINK and verified with hardware.

Study of the Parameters of a Magnetic DC Plasma Jet

A Magnetic DC plasma torch has been developed. Magnetic field distributions of solenoid coils have been calculated electrodynamically. For Ar +H2 plasma, the effects of an akial magnetic field and gas flow rate on the characttristics of the plasma jet were studied. Electron temperature, density and plasma velocity at 80 mm from the nozzle have been measured using a floating double probe and a Mach probe. The values of the heat fluxes to substrate were derived from experimental data.

Properties of Brushless DC Machine Induced by Permanent Magnets Applied to a Traction Drive

The paper presents a mathematical model ofbrushless DC machine induced by permanent magnets. Its construction uses the classical model of permanent magnet synchronous machine and induced model of power inverter using the serraphil form. The results of the computer simulation were presented for such states： startup, work under active constant load and the behavior of the machine in terms of exponential and stepping change of the power inverter＇s control angle.

Morphology and distribution of Al_3Fe phase in hypereutectic Al-Fe alloy solidified under magnetic field

In this study, the (low) DC and AC magnetic fields and the high magnetic field were applied separately during the solidification process of Al-2.89%Fe alloy. The influences of these magnetic fields on the morphology and distribution of Al3Fe phase in Al-2.89%Fe alloy were investigated. The microstructure and macrostructure of the samples were observed using an optical microscope. The results show that the majority of the primary Al3Fe phase particles in the hypereutectic Al-2.89%Fe alloy is gathered at the bottom of the sample under DC and AC magnetic fields or without magnetic field. The primary Al3Fe phase becomes coarse when the alloy solidifies under DC magnetic field, while it are refined and accumulated towards the center of the sample under the AC magnetic field. When the high magnetic field of 12 T is applied, the primary Al3Fe phase distributes throughout the sample homogeneously because the magnetic force acting on the primary Al3Fe phase balances with the gravity force; and the long axis of the Al3Fe phase aligns perpendicularly to the magnetic field direction. Also, the mechanism of the effect of magnetic fields is discussed.

A Novel Asymmetrical Single-Phase Multilevel Inverter Suitable for Hybrid Renewable Energy Sources

This paper introduces a novel single-phase asymmetrical multilevel inverter suitable for hybrid renewable energy sources. The proposed inverter consists of two isolated DC sources and six power semiconductor controlled switches. The suggested inverter is capable of generating seven-level output when the input DC voltage is taken in the ratio of 1:2. The higher magnitude DC source is fed from Photo Voltaic (PV) panels, whereas the lower magnitude DC source is fed from Wind Turbine (WT) driven Permanent Magnet DC (PMDC) generator. Both the renewable energy sources are connected to the inverter via two DC-DC boost converters connected in cascade (i.e. one for maximum power point tracking and another for DC-link voltage control). The proposed hybrid renewable energy source inverter is connected to single-phase grid via proper control systems. The complete system is simulated using MATLAB/SIMULINK and the results are presented in detail.

Study on TRV of circuit breaker in two substation operational ways and its countermeasure

To verify a vacuum breaker's feasibility,when a transformer substation chooses a vacuum circuit breaker,it takes two different actual operational ways to cut off a transformer.This paper,using the power system computer aided design/electro magnetic transient in DC system(PSCAD/EMTDC)software,simulates the substation system and studies transient recovery voltage(TRV)caused by the two different ways which can cut off a with load transformer or a no-load transformer.Simulation and calculation results show that TRV indexes of the first way are much higher than that of the second one,and their TRV indexes are both in a permissible range.The breaker is proved to be available.Besides,this paper proves that paralleling resistance has a good effect when the indexes exceed the standard.The resistance value depends on specific circumstances.

Pole-wrapped Negative Equivalent Magnetic Reluctance Structure-based Transformer for Line-frequency Isolation-dependent Applications

Isolation-dependent applications require a transformer with high efficiency,low magnetizing current,and anti-DC bias capability.The kilohertz planar negative magnetic reluctance structure is used to achieve this target with its magnetic-frequency variation property,which reduces the magnetic reluctance of the fundamental component.However,this design cannot be applied to low-frequency transformers owing to the high loss caused by its limited self-inductance and quality factor.To solve this problem,a pole-wrapped negative equivalent magnetic reluctance(PNEMR)structure is presented.The proposed design employed a copper-based PNEMR structure wrapped around the magnetic poles to enhance the fundamental flux and suppress the DC component of flux.Accordingly,the magnetizing current is reduced,and the isolation transformer is less susceptible to the DC bias.The proposed design can simultaneously improve the anti-DC magnetic bias capability,efficiency,and power factor of the transformers.To verify the effectiveness of the proposed design,a 10 kW C-core PNEMR structure-based transformer for isolation-dependent applications was constructed and compared to the generalized structures and transformers with planar negative magnetic reluctance structures.Results indicate that the PNEMR-based transformer can enhance the efficiency and power factor from 96.1%and 0.87 to 96.6%and 0.93,respectively,under full load conditions.

Design of the magnets for the HEPS injector

Purpose The high energy photon source(HEPS)is a diffraction-limited storage ring light source being built in Beijing,China.The HEPS accelerators consist of the storage ring and its injector which includes the linac,booster and beam transport lines.The magnet system is one of the most important systems for the accelerators.In this paper,the field design,mechanical design and some special issues of the main magnets for the injector are presented.Methods The magnets for the linac and transport lines work at DC mode,whereas the magnets for the booster work at dynamic mode.So the module of OPERA/TOSCA is used to design the DC magnetic field and the module of OPERA/ELLEKTRA is used to design the dynamic magnetic field.The CAD programs are used to design the mechanical structures of the magnets.Results The magnetic field simulation results of all the magnets for the injector can meet the physical requirements,the mechanical designs of all magnets are reasonable,and engineering drawings of the magnets for production are finished.Conclusions Both the magnetic field design and mechanical design of all magnets are satisfied with the physical requirements of the HEPS injector;the production of all magnets has been started up.