Wind energy resource assessment is a key step of wind farm planning and design. A hybrid neural network (HNN) based wind energy resource assessment method is proposed to improve the assessment accuracy, and the method allows the use of regional information. Firstly, the HNN based correlate model is developed according to the concurrent wind speeds of the reference weather stations and the candidate wind farm. In order to obtain wider learning capability and avoid being trapped in a local minimum, the different training algorithm and the adaptive particle swarm optimization (APSO) are used in the HNN. Then, the whole long-term wind speed and direction data are applied to the model, thus the long-term wind characteristics of the candidate wind farm are obtained. The wind energy resource assessment parameters are subsequently computed on the basis of the knowledge of these wind speeds. The simulation results show that the proposed method has relatively high accuracy.

积分环节是影响Rogowski线圈电子式电流互感器精度的关键因素.论述了模拟积分器的设计与实现,分析了模拟积分器的频率特性,理论分析和试验结果表明低频信号和温度对其精度有较大的影响.为进一步优化积分环节,设计了基于ARM的数字积分器,分别论述了其硬件结构和梯形积分算法,并且仿真了梯形积分算法对稳态电流和暂态电流的响应.仿真和试验结果表明,梯形积分算法能够很好的还原一次电流,同模拟积分器相比,数字积分器具有更高的精度和稳定性.

The temperature stability of an electronic voltage transformer(EVT)based on current was analyzed.It was presented that the high voltage capacitor and the integral circuit in the primary-side signal processing unit were two main influencing factors. The temperature compensation scheme that employing a number of capacitors with positive temperature coefficient and with the same value negative temperature coefficient in serial connection to comprise the high voltage capacitor was designed,which can improve the temperature stability of the high voltage sensor.The method of using the thermal resistor to compensate the temperature characteristic of the integral capacitor was proposed,reducing the error introduced by the temperature change.According to IEC60044-7,the accuracy versus temperature test on the developed 110 kV EVT prototype was carried out.The results show that the designed compensation schemes are effective and the EVT is compliant with the 0.2 measurement precision class over the temperature range from 40℃to+70℃.

Integral circuit is the key element to restore the signal in the current-based electronic voltage transformer(EVT) , and its performance directly affects the steady and the transient characteristics of the EVT .An integral circuit with DC-isolating con-trol used in the current-based EVT was proposed .It can effectively block the DC component of the input signal ,resulting in the im-provement of the transient performance of the EVT .And its frequency width can assure below 40th harmonic voltage measurement . The method of using the thermal resistor to compensate the temperature characteristic of the integral circuit was also proposed ,which can improve the stability of the EVT .An EVT prototype based on the designed integral circuit was developed and then tested .The analysis and then experimental results demonstrated the practicability and the validity of the proposed integral circuit .

介绍了电流型电子式电压互感器(EVT)的结构,并设计了一种应用于电流型EVT的SF6同轴圆筒形电容传感头.研究了传感头的组成原理,并对其电场分布和屏蔽性能进行了仿真分析,结果表明该传感头的绝缘性能满足要求,且具有抗外电场干扰能力强的优点.分析了影响传感头性能的主要因素,其中SF6压力变化造成传感头电容量改变,应通过监测气体压力信号实现误差校正；环境温度变化影响传感器的电极尺寸和电容量的稳定性,应采用低膨胀材料或进行温度补偿；高、低压电极不同轴会产生电容量误差以及影响传感头的绝缘性能,应对其进行严格控制.所作的分析为传感头的制作和应用提供了重要的理论依据.

This paper analyses the reasons of self-excited oscillation of wire rope of mine hoist,and considers that the main reasons of self-excited oscillation are the variation of friction coefficient and relative sliding.Especially,when the wire rope started to run or finished running the friction coefficient would vary obviously,leading to relative sliding between friction wheel and wire rope.Then the sliding energy exchanges with friction energy and finally oscillation occurs.A real example analysis is presented and perfectly verifies the results descried above.

An improved electronic voltage transformer (EVT) based on direct detecting capacitor current is designed in this paper. The EVT offers a variety of advantages, such as: small size, simple structure, no ferroresonance, high insulating strength, high anti-interference capability, good temperature characteristics, and the transient performance is not influenced by the retained charge of the high voltage capacitors, etc. The working principles are analyzed in detail, and the solution of the EVT is designed. The temperature compensation method that employing a number of capacitors half with positive temperature coefficient while the other half with negative temperature coefficient in serial connection to comprise the high voltage capacitor is proposed, which can improve the stability over temperature. The theory and simulation analysis on the frequency characteristic, transient performance, and anti-interference capability of the EVT were carried out. Subsequently a 10kV electronic voltage transformer has been developed. And the accuracy test, power-frequency withstand voltage test, and temperature test were conducted. The simulation and the tests show that the proposed EVT is fully compliant with IEC 60044—7 standard, assuring 0.2 measurement precision class and 3P protective class.

The absolute stability of an aircraft’s yaw-angle control system was studied based on the Lyapunov direct method.The configuration and dynamic equations of the control system were given.The Lyapunov function and its derivatives were derived by superposition method.The absolute stability condition was also obtained.Using Popov harmonic linearization,the maximum value of nonlinear part was determined.Then Popov stability criterion was introduced to simulate the absolute stability with various parameter settings of the system.Simulation results indicate that the absolute stability condition can be applied to judge the stability of the system effectively.

Integrator is the key element of electronic current transducer based on Rogowski coil.The temperature characteristics of analog integrator are analyzed.Both theoretic analysis and experimental data indicate the temperature is its most influencing factor.Digital integrator has better accuracy and higher stability than analog integrator.Trapezoidal formula is applied in digital integral algorithm and its responses to steady and transient currents are analyzed and simulated.Measures to deal with the drift and initialization of digital integrator are proposed.A digital integrator based on STM32F103 is designed and tested with the new-style PCB planar Rogowski coil current transducer.Its validity is proved by experimental data.

A new current transformer based on planar air core coil was presented in this article. The secondary coil of sensor was implemented on printed circuit boards and each PCB contains two coils in opposite directions to eliminate the impacts of outside magnetic field by the greatest degree. Moreover, multilayer boards were connected to improve mutual inductance. The PCBs were embedded in the primary coil which was designed into special shape. The coil's coefficient of mutual inductance was derived, the influence of external magnetic field was analyzed through ANSYS. The result shows that the special shaped primary coil can produce intensive magnetic field to produce large electrical potential signal and the influence of other two phases can be ignored. Simulation components were influenced easily by temperature, to solve the problem, digital integral was applied in processing circuit .Experimental model was designed, and the linearity and accuracy test results show that the transformer model has high accuracy and strong anti-electromagnetic interference ability.

A new principle and method to measure high voltage by detecting current of high-voltage capacitor were proposed, a new type of high-voltage electronic voltage transformer(EVT) based on this method was designed. The steady-error of the EVT was analyzed considering the effects of capacitor temperature and the power frequency. For the temperature effect, thermistor temperature sensor was used to establish temperature compensation and introduce the error correction, so as to reduce the ratio error of EVT. The equivalent circuit of EVT had established, based on this and the signal processing circuit, the relation between primary and secondary voltage was deduced. The possibility of adjusting the frequency characteristic by changing the EVT's parameters was proved by the MATLAB simulation. Finally, building the steady-error experimental system, the result of high-voltage test shows that these measurements are feasible.

In order to further improve the measurement accuracy of planar Rogowski coil current transformer based on PCB(Printed Circuit Board),the PCB coil equivalent circuit is set up and the rela-tionship between its induced secondary voltage and measured primary current is derived.Its error characteristics are analyzed in the aspects of power frequency and temperature.It is pointed out that,theresistance of sampling resistor(input resistor of integrator) is an important factor affecting the frequency and temperature characteristics of coil.Appropriate increase of the resistance may improve the frequency characteristics of coil.The formula for selecting the resistance to completely eliminate the temperature error is derived.The low accuracy of small current measurement is analyzed and a differentiator is addedto the low frequency band of original integrator to reduce its low frequency band magnification for low frequency interference suppression.Simulation and experiments verify the effectiveness of the design.

Nonlinear elements of speed control systems always lead to self-oscillations. The method of E. П. Попов harmonic linearization has been well-known to provide frequency criterion for stability of such oscillations. It had the contribution of correcting the values of elements after parameters of certain oscillation had been set formerly for better performance. However, the un-sufficient attention was paid in use under practical conditions of this method in modern control systems because it was quite difficult to calculate the necessary and precise values of the method especially when high-dimensioned matrix was employed in discussion. In the present paper Matlab and Mathematica are introduced as new expressions to construct Е.П.Попов models and obtain simulation results in DC double closed-loop control system. Thyristors and speed controller are respectively researched as nonlinear elements leading to self-oscillation. The Fourier series-based models of two elements are constructed. The analysis of stability and correcting of self-oscillation are accomplished. The simulation shows that the proposed combination of advanced mathematical tools and Е. П. Попов methods can lead to a novice way of controlling self-oscillations.

The traditional analysis methods of power angle stability depend on mandatory decoupling of system state values, or rely on system accurate model and parameters, which are easily invalidated with the state changes in the non-linear power system. Profits from the physical concept of static stability in kinetics space, the whole power system was mapped to the elastic mechanics space for intuitive understanding of the relations between partial stability and the entire system stability in multi-generator power system. Based on this mapping, the static angle stability was analysed depend upon generators and the system decoupling. The practical stability criterion and indicator of stability margin were provided by real-time node status messages using wide-area measurement system. The research provides a new mentality for wide-area measurement technology applied to power system security monitoring. © 2010 Chin. Soc. for Elec. Eng.

As for a variety of voltage transformer technical problems emerging in recent years,a new electronic voltage transformer method was presented by detecting micro-current in coupling capacitor.The new type EVT used the current transformer to detect the coupling capacitor's current,and then secondary low current of the current transformer was led into processing equipment in a control room by transmission lines.The secondary voltage signal,which followed proportionally the primary high voltage,was converted from the secondary low current by the processing equipment.The new type high-voltage EVT's principle and structure were analyzed in detail.Based on this,general voltage transformers were compared with it.Then high voltage tests on the high-voltage EVT were conducted.Theoretical research and experiment results show that the EVT is light and small with simple structure,without oil-tank,good at electric insulation,with high measurement accuracy,stable and reliable working ability,and strong anti-electromagnetic interference ability,which has great prospects for the popularization and application.

The structure and principle of printed circuit board (PCB) planar-type of air core coil are analyzed;simulation analysis and experimental investigation of frequency characteristic,steady-state characteristic and transient characteristic of PCB electronic current transformer are carried out;then the structure of digital current transformer is given.Simulation and experimental results show that PCB electronic current transformer possesses such features as wide measuring range,wide working frequency band,fast transient response,good steady-state performance and good linearity,so it is suitable for the measurement of small current lower than 100 A.

This paper presents a sensorless algorithm for the vector control of doubly-fed induction machine(DFIM) using rotor current based model reference adaptive system(MRAS) observer.The stator flux oriented vector control is employed to achieve variable-speed drive and decoupled active/reactive power control.In the proposed MRAS observer,the reference model is the measured rotor current,in comparison with the estimated rotor current obtained from the stator voltages and currents.A proportional-integral(PI) control adjusts the rotational rotor speed,driving the error between the measured and estimated currents to zero.A 50 kW DFIM prototype system is built to verify the theoretical analysis.Using estimated rotational speed and rotor position,both no-load variable speed tracking and decoupled active/reactive power control are achieved in experimental testing.The simulation and laboratory experimental results show the effectiveness of the proposed sensorless control scheme.

The substation simulation system based on the software is too abstract,and the physics-based system is too expensive.Aimed at this condition,this paper proposes the digital-physics mixed simulation training system for integrated substation automation.Structure,principle and function of the physical simulated parts and the digital parts are introluced.Among them,the primary signals of the equipments are generated by the power flow and short-circuit calculation software,and through networking microcomputer-based protective relay test device the secondary signals generating system generates synchronously the current and voltage signals of the measurement and control points,which are provided to the real control and protection devices.The experiments and training results indicate that the simulation system with low price has the comprehensive functions,good simulation effects,and could be applied to train the substation workers.

Presently,most of electronic voltage transformer applies theory of voltage dividing to supply secondary voltage signals and there is not enough electric isolation between the primary and secondary circuit.For this reason,a new type of electronic voltage transformer based on spiral air-core coil current sensor is proposed.In series with the capacitor,the current sensor can detect the current in it to reflect the primary high voltage.As current sensor,the spiral air-core coil has good linearity,big bandwidth without magnetic saturation problem.To meet different requirements of measurement accuracy ratings,two signal processing circuits are provided to supply with related voltage signals.Power amplifiers are adopted in the signal processing circuit to guarantee against losing capability of sustaining secondary load.The experiment data indicate that the electronic voltage transformer has fast dynamic response,a big bandwidth and high linearity.