大型铝电解电容器在变频器中的应用

本文介绍了大型铝电解电容器在变频器中的应用,着重讨论了变频器中滤波电容器的选择和使用注意事项。

A Radial Stub Test Circuit for Microwave Power Devices

With the principles of microwave circuits and semiconductor device physics, two microwave power device test circuits combined with a test fixture are designed and simulated, whose properties are evaluated by a parameter network analyzer within the frequency range from 3 to 8GHz. The simulation and experimental results verify that the test circuit with a radial stub is better than that without. As an example, a C-band AlGaN/GaN HEMT microwave power device is tested with the designed circuit and fixture. With a 5.4GHz microwave input signal,the maximum gain is 8.75dB,and the maximum output power is 33.2dBm.

Tests on the First 500 kV Compact Transmission Line in China

The paper deals with the tests on the first 500 kV compact transmission line. The transmission line stretches from Fangshan Substation to Changping Substation nearby Beijing with a length of 83 km. In order to investigate the characteristics of the transmission line, many tests were performed on the line before and after its operation. The results indicate that all electrical parameters are perfectly identical to the design.

A Novel SPIC with a Simple APFC Circuit

A novel SPIC(smart power IC) with a simple APFC(active power factor correction) circuit on one chip is proposed.The V _ bus (bus voltage) with high power factor falls from 600V to 400V by using a delay circuit in which a long channel length NMOS is used to substitute a large biasing resistance to save chip area.The lower V _ bus results in a smaller R _ on (on-resistance) of power switcher,which reduces the power loss of the power devices,improves the efficiency of the circuit,and reduces the cost of circuits.An integrated high voltage over voltage protect circuit is also designed in the circuits.Theory and simulations both prove the correctness and availability of the design.

Nonlinear Auto-Companding Method for Behavioral Modeling of Switched-Current Circuits

A wavelet collocation method with nonlinear auto companding is proposed for behavioral modeling of switched current circuits.The companding function is automatically constructed according to the initial error distribution obtained through approximating the input output function of the SI circuit by conventional wavelet collocation method.In practical applications,the proposed method is a general purpose approach,by which both the small signal effect and the large signal effect are modeled in a unified formulation to ease the process of modeling and simulation.Compared with the published modeling approaches,the proposed nonlinear auto companding method works more efficiently not only in controlling the error distribution but also in reducing the modeling errors.To demonstrate the promising features of the proposed method,several SI circuits are employed as examples to be modeled and simulated.

Resistivity Instability in Polysilicon Resistors Under Metal Interco-nnects and Its Suppression by Compensating Ion Implantation

The resistivity instability of the boron-doped polysilicon resistors being a line resistance element of ICs is within the range of several kΩ's,especially when our running the underneath metal interconnects.Polysilicon resistors have been fabricated under various processing conditions as well as some electrical and crystallographic characteristics have been obtained.It is shown the resistivity instability mainly results from the variational carrier mobility.By analyzing the Seto's model,the barrier height and trapped charge density are observed reducing under the Al over layer.Therefore,the resistance instability is also caused by both the charge trapping/detrapping occurring at polysilicon grain boundaries and the resultant variation in the potential barrier height.The formation of high-stability polysilicon resistors in the range of several kΩ's has been decided by compensating the ion implantation,which makes the charge trapping/detrapping at the grain boundary less susceptible to the hydrogen annealing.

特殊地段张力放线的施工方法

阐述在大高差,连续上、下山地段,且张力场距离塔位很近的情况下,进行张力放线时,所应采取的施工方法及措施。并通过对牵张力值的计算及对工器具强度校核,为施工提供技术依据。

Modeling of electrode system for three-phase electric arc furnace

To simulate the process of electrode operation, a dynamic model describing the electrode system of three-phase electric arc furnace was developed. This new model can be divided into three submodels in terms of the practical situation. They are the power supply system model the electric arc model and the hydraulic actuator system model. According to the basic circuit theory, the power supply system model where the high voltage transmission circuit and mutual inductances were considered, was set up. The electric arc model, which was novel for the electrode control, served as the electrical load and was connected to the power supply system model. The hydraulic actuator system model consists of the proportional valve part that is modeled to capture the dead-zone nonlinear characteristics and the hydraulic cylinder part where the impact of the load force is taken into account. By comparing simulation data and actual data, the results show that the electrode system model is proved to be accurate.

Analysis and design of high linearity current reference for current mode circuits

A complementary metal-oxide-semiconductor transistor （CMOS） voltage-to-current（VTC）converter with high linearity for current-mode analog and digital integrated circuits is described. A high gain operational amplifier （OPA） is utilized to form negative feedback. A proportional to absolute temperature （PTAT） current reference with transistors operated in a weak inversion is used as the bias circuit. The resistor and the OPA nonlinearity behavior are analyzed in detail. By optimizing parameters in OPA and adopting a small voltage coefficient polysilicon resistor as a linear device, a high linearity is achieved. The circuit is implemented in a standard 0. 6 μm CMOS technology. The low frequency gain of the OPA exceeds 90 dB. The test results indicate that the total harmonic distortion （THD）is 0. 000 2%. The common-mode input linearity range is 0 to 2. 6 V. Correspondingly, the output current range is 50 to 426μA. The sensitivity of the PTAT current reference to Vdd is approximately 0. 021 7. The chip consumes a power of less than 1.3 mW for a 5 V supply, and occupies an area of 0. 112 mm^2.

A power divider based on a new kind of composite right/left-handed transmission line (CRLH TL) unit

A new power divider, composed of a novel composite right/left-handed (CRLH) transmission line (TL) unit, is proposed. The properties of the power divider based on four CRLH TL unit cells are investigated theoretically. By adjusting the parameters of the capacitors and the inductors, the power divider shows perfectly symmetric power division at 5.13 GHz, return loss up to ?24 dB, with the transmitted power being close to ?3.1 dB. The phenomena are demonstrated by simulation results. Being compact in size and low-cost, the proposed power divider is very suitable for microwave and millimeter wave integrated circuits.

Applications of IoT in Smart Grid

In this paper,the basic requirements of the smart grid in China are studied.By applying Internet of Things(IoT) technologies,various intelligent services can be created.The development of the smart grid would rely heavily on the application of IoT.The three-layer architecture of IoT for the smart grid in China is introduced.Various information and communication technologies of IoT applied to smart grid are discussed.Particularly,several typical IoT application solutions such as power transmission line monitoring,smart patrol,smart home and electric vehicle management,are provided.

Power swing and voltage collapse identification schemes for correct distance relay operation in power system

The new techniques were presented for preventing undesirable distance relay maloperation during voltage collapse and power swings in transmission grids. Initially, the work focused on the development of a fast detection of voltage collapse and a three-phase fault at transmission lines by using under impedance fault detector (UIFD) and support vector machine (SVM). Likewise, an intelligent approach was developed to discriminate a fault, stable swing and unstable swing, for correct distance relay operation by using the S-transform and the probabilistic neural network (PNN). To illustrate the effectiveness of the proposed techniques, simulations were carried out on the IEEE 39-bus test system using the PSS/E and MATLAB software.

Inter-Circuit Fault Location Algorithm for Two-Parallel Transmission Line

A novel numerical algorithm of fault location estimation for four-line fault without ground connection involving phases from each of the parallel lines is presented in this paper. It is based on one-terminal voltage and current data. The loop and nodal equations comparing faulted phase to non-faulted phase of two-parallel lines are introduced in the fault location estimation model, in which the source impedance of a remote end is not involved. The effects of load flow and fault resistance on the accuracy of fault location are effectively eliminated, therefore a precise algorithm of locating fault is derived. The algorithm is demonstrated by digital computer simulations.

Fault location for parallel transmission lines using one-terminal current traveling waves

With proper phase module transformation,parallel lines can be decomposed to the same directional net and the reverse directional net. The propagation characteristics of traveling waves in the reverse directional net were analyzed,and the refraction coefficient at the fault point for a single phase fault was derived. In addition,the module selection was discussed. Simulation results show that satisfying accuracy can be achieved with the proposed method. Moreover,it is immune to fault types,fault resistances,and outside system parameters.

Performance-driven Routing Tree Construction with Buffer Insertion and Wire Sizing

A new approach was proposed to construct a performance-driven rectilinear Steiner tree with simultaneous buffer insertion and wiresizing optimization (PDRST/BW) under a higher order resistance-inductance-capacitance (RLC) delay model. This approach is based on the concept of sharing-buffer insertion and dynamic programming approach combined with a bottom-up rectilinear Steiner tree construction. The performances include the timing delay and the quality of signal waveform. The experimental results show that our proposed approach is scalable and obtains better performance than SP-tree and graph-RTBW approaches for the test signal nets.

Quantum Effect in a Diode Included Nonlinear Inductance-Capacitance Mesoscopic Circuit

The mesoscopic nonlinear inductance-capacitance circuit is a typical anharmonie oscillator, due to diodes included in the circuit. In this paper, using the advanced quantum theory of mesoseopie circuits, which based on the fundamental fact that the electric charge takes discrete value, the diode included mesoscopic circuit is firstly studied. Schrodinger equation of the system is a four-order difference equation in p rep asentation. Using the extended perturbative method, the detail energy spectrum and wave functions axe obtained and verified, as an application of the results, the current quantum fluctuation in the ground state is calculated. Diode is a basis component in a circuit, its quantization would popularize the quantum theory of mesoscopie circuits. The methods to solve the high order difference equation are helpful to the application of mesoscopic quantum theory.

Examples of the Teaching of the Health Questions of Electric and Magnetic Fields at Tampere University of Technology in Finland

The objective of the article is to present the examples of the teaching of the health questions of electric and magnetic fields at TUT （Tampere university of technology） in Finland. At TUT, the education of the health questions of electric and magnetic fields has been integrated into part of four courses, which also include other environmental issues. TUT also products two times per year situation report bulletins on medical-oriented studies related to electric and magnetic fields so that graduates and people working in transmission line projects can follow new studies of the area. It is important to develop more education of EMF health questions, so people can more easily understand how new devices and technologies work.

An Outlook on Northwest Power Grid Development

In this paper the basic situation of the Northwest Region in China is introduced, the necessity for the Northwest Power Grid to develop 750 kV transmission line is analyzed, and the target for the power grid construction till 2010 as well as the planning for sending power from west to east and interconnection with adjacent grids are described.

Novel Algorithm for Estimating the Distance of Open-Conductor Faults in HV Transmission Lines

This paper presents an ANN （artificial neural networks）-based technique for improving the performance of distance relays against open-circuit faults in transmission networks. The technique utilizes the small capacitive current measured in the open-phase plus the currents in the two healthy phases in calculating the open-circuit fault distance. The results obtained show that a distance relay with the proposed scheme will not only be able to detect the open-conductor condition in HVTL （high voltage transmission line） but also to locate the place of this fault regardless the value of the pre-fault current loading. There is no need for especial communication schemes since the existing media could work properly for the needs of the proposed technique.

Complete Localization of HVDC Back-to-Back Project Realized

The first completely localized DC back-to-back project for asynchronous interconnection between Northwest and Central China plays an important role in realizing national power grid interconnection, spurring indigenous manufacturing industries and promoting DC transmission equipment. Insisting on the principle of autonomous innovation, this project was based on domestic forces in every aspect, from engineering organization, system design, equipment completion, engineering design, equipment manufacturing and procurement to construction and debugging. By passing through strict quality control, intermediate supervision and acceptance test and assessment, the project has been proved up to world advanced level.