A Novel Crowbar Impulse Current Circuit for Testing the Switch-Type SPD

A crowbar impulse current circuit for testing the switch-type surge protective device （SPD） is presented. The crowbar circuit consists of a computer control circuit, a trigger voltage pulse generator, a main discharging switch, and a crowbar pseudospark switch. The active trigger technology was studied in the crowbar impulse current circuit. The circuit monitors the main discharging current and generates a trigger signal at a proper time for the crowbar pseudospark switch operation. The trigger characteristics of the main discharge switch and the crowbar pseu- dospark switch were investigated. By monitoring the preset applied capacitor voltage, the gap distance of the main discharging switch could be adjusted to ensure a discharging delay time less than 2 μs. Equipped with a surface ttashover trigger device made of high relative perimittivity dielectric material BaTiO3 （εr = 3460）, the discharge delay time of the crowbar pseudospark switch is less than 85 ns, and the minimum operating voltage is less than 1% of its self-breakdown voltage. With a storage capacitor of 9 μF , an inductor of 18 μH and a crowbar pseudospark switch, a load of 30 mΩ and an applied capacitor voltage of 40 kV, an impulse current waveform of maximum 25 kA was generated with a rise time and time to half peak value of 17.2 μs and 336μs respectively.

Direct Current Circuit Breaker in EAST

This paper introduces the configuration and the operation principles of a high power direct current circuit breaker （DCCB）. The commutating current principle of the breaker is described in details with its theory and simulation analysis. The test results presented show that the DCCB meets the requirements for quenching protection. It will be used as the main breaker for quench protection in EAST.

An Adaptive Slope Compensation Circuit for Peak Current Mode of Boost Switching Power Supply

Based on the analysis of the basic principle of slope compensation, a high-precision adaptive slope compensation circuit for peak current mode boost DC/DC converter is designed. The circuit dynamically detects the input and output voltage of the boost circuit to realize automatic adjustment of the compensation amount with the change of duty ratio, which makes the ramp compensation slope optimized. The design uses a high-precision subtracter to improve the accuracy of slope compensation. While eliminating sub-slope oscillation and improving the stability of boost circuit, the negative impact of compensation on boost circuit is minimized, and the load capacity and transient response speed of boost circuit are guaranteed. The circuit is designed based on SMIC 0.18um CMOS technology, with simple structure, high reliability and easy engineering implementation. Spectre circuit simulator 17.1.0.124 64b simulation results show that the circuit has high compensation accuracy and wide input and output voltage range. When the working voltage is 3.3 V, the compensation slope can be adjusted adaptively under different duty cycles, and the minimum error between the compensation slope and the theoretical optimal compensation slope is only 0.42%.

CURRENT MODE CIRCUIT SYMBOLIC ANALYSIS WITH MATH-EMATICA

提出了用Ｍａｔｈｅｍａｔｉｃａ对电流模式电路进行符号分析的方法．利用Ｍａｔｈｅｍａｔｉｃａ强大的符号分析功能，可以极大地简化电流模式电路的符号分析．有源器件的理想模型用零泛器表示．给出了对ＣＣＩ构成的电流模式滤波器电路的分析实例．

Influence of optical interference and carrier lifetime on the short circuit current density of organic bulk heterojunction solar cells

Based on simple analytical equations, short circuit current density （Jsc） of the organic bulk heterojunction solar cells has been calculated. It is found that the optical interference effect plays a very important role in the determination of Jsc; and obvious oscillatory behaviour of Jsc was observed as a function of thickness. At the same time, the influence of the carrier lifetime on Jsc also cannot be neglected. When the carrier lifetime is relatively short, Jsc only increases at the initial stage and then decreases rapidly with the increase of active layer thickness. However, for a relatively long carrier lifetime, the exciton dissociation probability must be considered, and Jsc behaves wave-like with the increase of active layer thickness. The validity of this model is confirmed by the experimental results.

Analysis of each branch current of serial solar cells by using an equivalent circuit model

In this paper, based on the equivalent single diode circuit model of the solar cell, an equivalent circuit diagram for two serial solar cells is drawn. Its equations of current and voltage are derived from Kirchhoff＇s current and voltage law. First, parameters are obtained from the I-V （current-voltage） curves for typical monocrystalline silicon solar cells （125 mmx 125 mm）. Then, by regarding photo-generated current, shunt resistance, serial resistance of the first solar cell, and resistance load as the variables. The properties of shunt currents （Ishl and Ish2）, diode currents （/D1 and/]：）2）, and load current （IL） for the whole two serial solar cells are numerically analyzed in these four cases for the first time, and the corresponding physical explanations are made. We find that these parameters have different influences on the internal currents of solar cells. Our results will provide a reference for developing higher efficiency solar cell module and contribute to the better understanding of the reason of efficiency loss of solar cell module.

DESIGN OF TERNARY CURRENT-MODE CMOS CIRCUITS BASED ON SWITCH-SIGNAL THEORY

By applying switch-signal theory, the interaction between MOS transmission switch-ing transistor and current signal in current-mode CMOS circuits is analyzed, and the theory oftransmission current-switches which is suitable to current-mode CMOS circuits is proposed. Thecircuits, such as ternary full-adder etc., designed by using this theory have simpler circuit struc-tures and correct logic functions. It is confirmed that this theory is efficient in guiding the logicdesign of current-mode CMOS circuits at switch level.

Vacuum Dielectric Recovery Characteristics of a Novel Current Limiting Circuit Breaker Base on Artificial Current Zero

为了保证新型强迫换流型真空直流限流断路器关断短路电流的可靠性，对该型断路器分断过程的真空介质恢复特性进行研究。设计了与断路器关断过程等效的介质恢复试验方案，通过等效试验结果和理论推演公式的拟合，得到了新型强迫换流型限流断路器真空灭弧室触头打开过程的动态介质强度恢复规律。研究结果表明：减小燃弧能量、提高触头运动速度可提高真空灭弧室介质的临界击穿电压；综合考虑燃弧时间与燃弧能量及触头开距的关系，随着燃弧时间的增加，真空灭弧室临界击穿电压先减小后增大。所得介质恢复规律可以作为新型断路器优化设计的参考依据。

A Fault Current Limiting Hybrid DC Circuit Breaker

Due to the low impedance characteristic of the high voltage direct current(HVDC)grid,the fault current rises extremely fast after a DC-side fault occurs,and this phenomenon seriously endangers the safety of the HVDC grid.In order to suppress the rising speed of the fault current and reduce the current interruption requirements of the main breaker(MB),a fault current limiting hybrid DC circuit breaker(FCL-HCB)has been proposed in this paper,and it has the capability of bidirectional fault current limiting and fault current interruption.After the occurrence of the overcurrent in the HVDC grid,the current limiting circuit(CLC)of FCL-HCB is put into operation immediately,and whether the protected line is cut off or resumed to normal operation is decided according to the fault detection result.Compared with the traditional hybrid DC circuit breaker(HCB),the required number of semiconductor switches and the peak value of fault current after fault occurs are greatly reduced by adopting the proposed device.Extensive simulations also verify the effectiveness of the proposed FCL-HCB.

Analysis of Short-circuit Characteristics and Calculation of Steady-state Short-circuit Current for DFIG Wind Turbine

Large-scale doubly-fed induction generator(DFIG)wind turbines are connected to the grid and required to remain grid-connection during faults,the short-circuit current contributed by the generation has become a significant issue.However,the traditional calculation methods aiming at synchronous generators cannot be directly applied to the DFIG wind turbines.A new method is needed to calculate the short-circuit current required by the planning,protection and control of the power grid.The short-circuit transition of DFIG under symmetrical and asymmetric short-circuit conditions are mathematically deduced,and the short-circuit characteristics of DFIG are analyzed.A new method is proposed to calculate the steady-state short-circuit current of DFIG based on the derived expressions.The time-domain simulations are conducted to verify the accuracy of the proposed method.

Effects of current waveform parameters during droplet transfer on spatter in high speed waveform controlled Short-circuiting GMAW

Aim at improving the stability of the Short-circuiting Gas Metal Arc Welding （GMAW-S） process for the enhanced speed usage, effects of current waveform parameters during short-term on the welding stability have been investigated by experimental method. The welding power source used for the research is an inverter with a special current waveform control. It is shown that the spatter decreases at first then increases with each increase of the low current period, current increase rate and the maximum current limit. The test results are provided for welding of 1 mm and 3 mm mild steel at speed of 1.2 m/min. The stable GMA W-S process under high speed welding condition has been achieved by optimizing the parameters.

A Simple Method of Obtaining the z-Domain Transfer Functions of Switched-Current Circuits

Switched-current (SI) is a new analogue sampled data signal processing technique thatfollows the development of switched-capacitor (SC) circuit technique.Recently, this tech-nique has received wide attention. The interest is motivated by the facts that SI

Design and applicability analysis of independent double acquisition circuit of all-fiber optical current transformer

The advantages of the all-fiber optical current transformer include but are not limited to being small in size,having no magnetic saturation,exhibiting high measurement accuracy,and boasting strong electromagnetic interference resistance.However,the high cost of the all-fiber optical transformer limits its promotion and application in engineering.This paper proposes a design scheme of an independent double acquisition loop for the all-fiber optical current transformer based on the single optical path.Firstly,based on the closed-loop control mode and open-loop control mode,the twochannel sampling signal demand for relay protection,and the independent dual-acquisition loop design scheme of the all-fiber optical current transformer are proposed.Secondly,the reliability and economic feasibility of the scheme are demonstrated by an analysis of system failure and cost.The results show that the scheme can actualize the acquisition function of two independent all-fiber optical current transformer products on a single all-fiber current transformer in an integrated manner,which greatly reduces the cost of the all-fiber optical current transformer in engineering applications.

20 MHz Switched-Current Sample-and-Hold Circuit with Low Charge Injection

A switched-current sample-and-hold circuit with low charge injection was proposed. To obtain low noise and charge injection, the zero-voltage switching was used to remove the signal-dependent charge injection, and the signal-independent charge injection was reduced by removing the feed-through voltage from the input port of the memory transistor directly. This current sample-and-hold circuit was implemented using CMOS 180 nm 1.8 V technology. For a 0.8 MHz sinusoidal signal input, the simulated signal-to-noise and distortion ratio and total harmonic distortion were improved from 53.74 dB and -51.24 dB to 56.53 dB and -54.36 dB at the sampling rate of 20 MHz respectively, with accuracy of 9.01 bit and power consumption of 0.44 mW.

A SYNTHESIS METHODOLOGY FOR ECL CIRCUITS BASED ON MIXED VOLTAGE-CURRENT REPRESENTATION

This paper presents a synthesis methodology for ECL circuits based on a mixed voltage-current signal representation and operation defined on the voltage and current signals. The ideas presented in this paper are then demonstrated on the design of an BCL 1-bit full adder. The paper concludes by presenting an algebraic system which is suitable for current signal representation and operation on currents.

Research on Parameter Collaborative Configuration of DC Circuit Breaker and DC Fault Current Limiter

Fault current suppression is the key technology to ensure the safe operation of the DC power distribution system. In order to realize the parameter collabora-tive configuration of the DC circuit breaker and the DC current limiter and improve the fault current suppression capability, the fault current suppression mechanism of the DC power distribution system is revealed based on the circuit model. Then, based on the mathematical model of the DC breaker, the characteristic parameters of DC breaking are extracted, and then the influence of different characteristic parameters on the breaking characteristics of fault current is studied. Finally, the mathematical model of the collaborative process between DC circuit breaker and DC current limiter is established. The charac-teristic parameters of fault current collaborative suppression are extracted. The coupling effects of different characteristic parameters on the fault current col-laborative suppression are studied. The principle of collaborative configuration of DC circuit breaker and DC current limiter is proposed, and the collaborative suppression ability of DC circuit breaker and DC current limiter to fault current is fully exploited to ensure the safe and reliable operation of the DC power distribution system.

DESIGN OF SYMMETRIC TERNARY CURRENT-MODE CMOS CIRCUITS

By applying switch-signal theory, the theory of transmission current-switches based on symmetric ternary logic is proposed, this theory is suitable to design symmetric ternary current-mode CMOS circuits. The symmetric ternary current-mode CMOS circuits designed by using this theory not only have simpler circuit structures and correct logic functions, but also can process bidirectional signals.

Short-circuit Current Characteristics of Wind Generators

To study the effects of wind generators on distribution system protection,the short-circuit current(SCC) characteristics of wind generators is important.Although there are many researches on the issue,a clear agreement has not been reached so far.The SCC characteristics for different wind generators are studied.PSCAD simulation is performed in the same system integrated with different kinds of wind generators,and their results are compared with those reported in IEEE papers.The detection possibility by overcurrent relay(OCR)is discussed based on the simulation results.

Study on Effect of UHV Power Grid Construction Schemes on Short Circuit Current

The commissioning of Southern Hami-Zhengzhou ±800 kV UHVDC transmission project has important significance to heighten operation reliability, transfer capability and supply electric ability of Henan power grid. However, short circuit currents of 500 kV buses in the Center of Henan are almost close to the operation upper limitation. In order to decrease the short circuit currents effectively, it’s necessary to strengthen the network structure of Center of Henan power grid and calculate short circuit currents. Two schemes of strengthening the network structure of Center of Henan power grid are studied. The calculated values of short circuit currents of some important 500 kV buses in the two schemes are still bigger than excepted. According to the latest Plan of State Grid, Yubei UHV substation and Zhumadian UHV substation located in Henan power grid. The calculated values of short circuit currents of some important 500 kV buses with the commissioning of Yubei UHV and Zhumadian UHV are qualified. So, reasonable network structure with UHV is suitable to heighten transfer capability and supply electric ability of Henan power grid.