Development of data acquisition and over-current protection systems for a suppressor-grid current with a neutral-beam ion source

Neutral beam injection is one of the effective auxiliary heating methods in magnetic-confinementfusion experiments. In order to acquire the suppressor-grid current signal and avoid the grid being damaged by overheating, a data acquisition and over-current protection system based on the PXI（PCI e Xtensions for Instrumentation） platform has been developed. The system consists of a current sensor, data acquisition module and over-current protection module. In the data acquisition module,the acquired data of one shot will be transferred in isolation and saved in a data-storage server in a txt file. It can also be recalled using NBWave for future analysis. The over-current protection module contains two modes： remote and local. This gives it the function of setting a threshold voltage remotely and locally, and the forbidden time of over-current protection also can be set by a host PC in remote mode. Experimental results demonstrate that the data acquisition and overcurrent protection system has the advantages of setting forbidden time and isolation transmission.

A Finite Volume Method with Unstructured Triangular Grids for Numerical Modeling of Tidal Current

The finite volume method （FVM） has many advantages in 2-D shallow water numerical simulation. In this study, the finite volume method is used with unstructured triangular grids to simulate the tidal currents. The Roe scheme is applied in the calculation of the intercell numerical flux, and the MUSCL method is introduced to improve its accuracy. The time integral is a two-step scheme of forecast and revision. For the verification of the present method, the Stoker＇s problem is calculated and the result is compared with the mathematically analytic solutions. The comparison indicates that the method is feasible. A sea area of a port is used as an example to test the method established here. The result shows that the present computational method is satisfactory, and it could be applied to the engineering fields.

Numerical Tidal Current Modeling Using Fine Boundary-Fitted Grids for Tidal Flats

Fine grids with small spacing in boundary-fitted coordinates are normally used to treat the computation of fluid dynamics for estuarine areas and tidal flats. However, the adoption of Cartesian components of velocity vectors in this kind of non-orthogonal coordinates will definitely result in a difficulty in solving implicitly the transformed momentum equations, and also complicate the wet-dry point judgement used for flood areas. To solve this problem, equations in terms of generalized contravariant velocity vectors in curvilinear coordinates are derived in the present study, by virtue of which, an Alternative-Direction-Implicit numerical scheme in non-orthogonal grids would then be easily obtained, and wet-dry point judgement would as well be largely simplified. A comparison is made between the explicit scheme and implicit scheme, showing that the present model is accurate and numerically stable for computations of fluid dynamics for estuarine areas and tidal flats.

H6 Non-isolated Full Bridge Grid-connected PV Inverters With Low Leakage Currents

为满足非隔离光伏并网发电系统对共模漏电流的限制，提出一种六开关逆变器拓朴（H6拓扑）。所提出的H6拓扑在功率传输模态时，进网电流半个工频周期流过3支开关管，而另半个工频周期流过2支开关管，故相对于H5拓扑，降低了通态损耗，有利于热应力均衡，且仍满足续流阶段光伏电池输出端与电网脱离的要求。详细分析拓扑的工作原理，并推论给出H6非隔离光伏并网逆变器的其它3种拓扑结构；比较分析了H5拓扑、Heric拓扑和H6拓扑的损耗和成本。通过1kW通用样机平台对比验证了上述3种拓扑的效率和共模特性。实验结果表明，H6拓扑的变换效率高于H5拓扑、但略低于Heric拓扑，共模特性优于Heric拓扑、但略劣于H5拓扑。

Practice and Thinking on Current Planning Environmental Impact Assessment of Transmission and Transformation Power Grid in Jiangsu Province

The planning environmental impact assessment （EIA） of transmission and transformation power grid at levels of 500 and 220 kV had been finished completely in the 13 municipalities of Jiangsu Province by the end of 2012, which played important roles in guiding and planning the following transmission and transformation projects in environmental protection. In this paper, through the detail analysis on the objective and significance of the planning EIA of transmission and transformation power grid, legal basis and planning EIA practices, some suggestions and thinking about the planning EIA of transmission and transformation power grid were put forward.

Topology for current-source grid-connected inverter with improved effciency and pulse width modulation control strategy

A novel topology of the current-source grid-connected inverter is proposed based on the immittance converter theory. A control strategy of sine-sine pulse width modulation （PWM） is studied. Compared with the traditional current-source inverter, the power frequency inductors and power frequency transformer are replaced with high frequency inductors and a high frequency transformer. Thus, the proposed inverter has advantages of small volume, low cost, low total harmonic distortion （THD）, low power losses, high power factor （PF） and simple control. Furthermore, grid voltage cannot influence output current of the grid-connected inverter and the current-source inverter with a high PF that approaches one has been realized. Finally, validity of the theory analysis and feasibility of the control scheme are shown by simulation and experimental results.

GRID探测器的SiPM质子辐照研究

使用100 MeV质子对SensL MicroFJ-60035-TSV SiPM进行地面辐照实验,得到了SiPM漏电流增长与质子注量的关系,漏电流增长率为每片SiPM 3.98×10^(-7)μA·cm^(-2),并与其他文章的地面辐照实验结果进行对比,验证了结果一致性;实验结果与GRID-02载荷在轨漏电流增长进行对比,在量级上一致,增长斜率低约40%,进一步定量分析需要详细讨论空间在轨辐射环境的粒子能谱与类型。此外,实验中还设置了开偏压与关偏压两种测试条件,探究了工作电压对SiPM辐照损伤可能的影响。

Numerical Simulation of the Three-Dimensional Wave-Induced Currents on Unstructured Grid

By coupling the three-dimensional hydrodynamic model with the wave model, numerical simulations of the three- dimensional wave-induced current are carried out in this study. The wave model is based on the numerical solution of the modified wave action equation and eikonal equation, which can describe the wave refraction and diffraction. The hydrodynamic model is driven by the wave-induced radiation stresses and affected by the wave turbulence. The numerical implementation of the module has used the finite-volume schemes on unstructured grid, which provides great flexibility for modeling the waves and currents in the complex actual nearshore, and ensures the conservation of energy propagation. The applicability of the proposed model is evaluated in calculating the cases of wave set-up, longshore currents, undertow on a sloping beach, rip currents and meandering longshore currents on a tri-cuspate beach. The results indicate that it is necessary to introduce the depth-dependent radiation stresses into the numerical simulation of wave-induced currents, and comparisons show that the present model makes better prediction on the wave procedure as well as both horizontal and vertical structures in the wave-induced current field.

Development of A Depth-Integrated Longshore Current Model with Unstructured Grids

A depth-integrated model for simulating wave-induced longshore current was developed with unstructured grids. Effects of surface roller and horizontal mixing under combined waves and currents were incorporated in the numerical model. Recommended values of model coefficients were also proposed based on sensitivity analysis. Field observations and three series of laboratory measurements including two cases conducted on the plane beach and one implemented on the ideal inlet were employed to examine the predictive capability of this model. For the field case and laboratory cases conducted on the plane beach, numerical results were compared favorably with the measured data. For the case with an ideal inlet, simulated circulation pattern is supposed to be reasonable although some deviations between numerical results and measured data still can be detected.

基于动态相量的并联逆变器并网系统超高次谐波零序环流特性分析

为研究共交直流侧母线的并联逆变器并网系统中超高次谐波零序环流特征分量及边带分量的特性,通过分析各逆变器的开关状态研究系统中零序环流的流通路径,并建立零序环流等效电路;利用动态相量法建立计及逆变器间载波相位差的超高次谐波零序环流分析模型;以该模型为基础,分析并联逆变器并网系统的超高次谐波零序环流特征分量特性和边带分量特性。最后,通过仿真验证了理论分析的正确性。

功率同步型构网变流器并网系统暂态同步稳定性研究综述

高比例可再生能源接入电力系统使系统呈现低惯量、弱支撑特点。功率同步型构网变流器通过模拟同步发电机运行特性,可提供频率和电压主动支撑能力。但不同于同步发电机,变流器中电力电子器件过流和过热耐受能力有限,由限流控制引发的功率同步型构网变流器多控制环交互作用显著,其引发的暂态同步失稳与闩锁问题严重影响了功率同步型构网变流器并网系统的安全稳定运行和主动支撑能力的发挥。而功率同步型构网变流器同步环呈现出的高度非线性特性使其并网系统暂态同步稳定性难以分析与量化,给暂态同步稳定性的优化控制带来了新的挑战。针对功率同步型构网变流器并网系统在不考虑故障限流时的暂态失稳问题,以及考虑故障限流作用下的暂态失稳与闩锁问题,对系统建模、分析与稳定边界量化方法进行了总结与归纳。基于暂态失稳与闩锁问题的分析与归纳结果,对功率同步型构网变流器并网系统的暂态同步稳定控制方法进行了综述。最后,对未来功率同步型构网变流器并网系统的暂态同步稳定分析与控制研究方向进行了展望。

考虑电流限幅的构网型变流器暂态稳定分析与自适应限幅方法

电流限幅环节的引入深刻改变了构网型变流器的暂态同步机制与动态特性。为研究大扰动故障下电流限幅环节对构网型变流器暂态同步稳定性的影响,基于功角特性曲线分析了传统d轴优先限幅策略在故障条件下的动态特性。在电网电压暂降且未及时切除故障的工况下,变流器将会“锁死”在限幅控制模式。针对这一问题,提出一种自适应限幅方法,引入自适应系数调整限幅状态下构网型变流器的功角特性曲线。首先,确定自适应系数的取值范围,以保证变流器在各工况下均能恢复正常运行状态。然后,采用等面积法则选取自适应系数最优取值,使变流器获得最大极限切除角和极限切除时间。最后,通过PSCAD/EMTDC仿真验证了理论分析的正确性以及自适应限幅控制策略的有效性。

基于混合同步控制的构网型变流器不对称故障下暂态稳定分析

构网型变流器具有良好的主动支撑特性和弱电网适应能力,已成为目前关注的热点。然而,构网型控制(GFMC)在电网故障下的暂态稳定性能是制约其运行的关键问题,现有成果主要关注对称故障下GFMC策略的暂态同步稳定问题,对于不对称交流故障下的暂态同步稳定特性鲜有深入研究。针对最新的混合同步型构网控制方法,首先,结合正负序解耦模块与混合同步控制结构,使混合同步控制能够应用于不对称故障。其次,建立了不对称故障下系统的详细动态模型,基于此模型,定性分析了正负序电流对暂态稳定的影响规律,并进一步基于相图模型定量解析正负序电流与暂态失稳边界的数学关系。最后,基于电磁暂态数值仿真和硬件在环实验,验证了所提控制策略的有效性和不对称故障下暂态同步稳定性分析的准确性。

Reactive Current Allocation and Control Strategies Improvement of Low Voltage Ride Though for Doubly Fed Induction Wind Turbine Generation System

为满足风电机组低电压穿越（low voltage ride through,LVRT）的测试要求及其电气模型一致性评估需要,提出考虑向电网注入无功电流的双馈风电机组LVRT的控制策略。在阐述风电机组LVRT测试要求及控制原理的基础上,推导双馈发电机（doubly fed induction generator,DFIG）定子侧及网侧变流器输出无功电流极限表达式,研究电网电压跌落深度和发电机总输出有功功率对其无功电流极限值的影响规律,进而提出DFIG在LVRT期间的无功电流分配算法和改进的有功、无功功率控制策略。最后,以某实际2 MW双馈风电机组为例,分别对风速为5和12 m/s、电网电压对称跌落至20%和50%工况下的LVRT运行性能进行仿真比较和样机测试。与传统LVRT控制方法的对比表明,所提改进控制策略能更好地满足风电机组LVRT的测试要求。样机测试结果进一步证明了改进控制策略和仿真模型的有效性。

A Review of Novel Leakage Current Suppression Techniques for Transformerless Photovoltaic Inverters

漏电流抑制是无变压器型光伏并网系统需要解决的关键问题之一。VDE-0126-1-1标准规定,漏电流高于300 mA时光伏并网系统必须在0.3 s内从电网中切除。为了解释漏电流的根源,建立系统共模电压数学模型,在此基础上分析漏电流产生的原因,探讨不同调制策略对漏电流的影响,然后介绍几种典型的、能够有效抑制漏电流的电路拓扑结构,并分析各种拓扑的工作原理和特点。最后对漏电流抑制技术方面的发展趋势做了展望。

Integrated Equipment with Functions of Current Flow Control and Fault Isolation for Multiterminal DC Grids

The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow controller(CFC)are demanded to ensure the multiterminal DC grid to operates reliably and flexibly.However,since the CFC and the DCCB are all based on fully controlled semiconductor switches(e.g.,insulated gate bipolar transistor,integrated gate commutated thyristor,etc.),their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses.To solve these problems,integrated equipment with both current flow control and fault isolation abilities is proposed,which shares the expensive and duplicated components of CFCs and DCCBs among adjacent lines.In addition,the complicated coordination control of CFCs and DCCBs can be avoided by adopting the integrated equipment in themultiterminal DC grid.In order to examine the current flow control and fault isolation abilities of the integrated equipment,the simulation model of a specific meshed four-terminal DC grid is constructed in the PSCAD/EMTDC software.Finally,the comparison between the integrated equipment and the separate solution is presented a specific result or conclusion needs to be added to the abstract.

2-D Current Field Numerical Simulation Integrating Yangtze Estuary with Hangzhou Bay

In this paper, integrating the Yangtze Estuary with the Hangzhou Bay, a 2-D velocity field model is established. In the model, fine self-adaptive grids are employed to adapt to the complicated coastal shape. The hydrodynamic equations satisfied by two contravariant components of velocity vector and surface elevation in non-orthogonal curvilinear coordinates are used. In each momentum equation the coefficients before the two partial derivatives of surface elevation with respect to variables of alternative direction coordinates have different orders of magnitude, i. e., the derivative with the larger coefficient may play a more important role than that with the smaller one. With this advantage, the ADI scheme can be easily employed. The hydrodynamic factors include tidal current, river runoff and wind-induced current. In terms of tidal current, seven main constituents in the area are considered in the open boundaries. The verifications of surface elevation process and current velocity process in the spring tide and in the neap tide show that the model can preferably reflect current fields in the area. Through the simulation of Lagrangian residual current fields in summer and in winter, the paths of the exchange of water and sediment between the Yangtze Estuary and the Hangzhou Bay are elementarily discussed.

基于风光相位特性的新能源电网短路电流计算方法

针对传统短路电流计算方法在新能源电网中的局限性,提出了基于风光相位特性的新能源电网短路电流计算方法。构建了风光互补模型,以确定风力发电和光伏发电之间的相位差。通过对直流电网等效模型中的动态元件进行离散化处理,使用梯形积分法进行数值计算。采用改进节点法建立网络方程,并通过迭代计算求解故障支路在不同时刻下的短路电流值。实验结果表明,设计方法误差最高仅为1.4%,说明设计方法在新能源电网短路电流计算方面具有更高的准确性和实用性。

An extended variable-grid global ocean circulation model and its preliminary results of the equatorial Pacific circulation

To investigate the interaction between the tropical Pacific and China seas a variable-grid global ocean circulation model with fine grid covering the area from 20°S to 50°N and from 99° to 150°E is developed. Numerical computation of the annually cyclic circulation fields is performed. The results of the annual mean zonal currents and deep to abyssal western boundary currents in the equatorial Pacific Ocean are reported. The North Equatorial Current,the North Equatorial Countercurrent, the South Equatorial Current and the Equatorial Undercurrent are fairly well simulated. The model well reproduces the northward flowing abyssal western boundary current.From the model results a lower deep western boundary current east of the Bismarck-Solomon-New Hebrides Island chain at depths around 2 000 m has been found. The model results also show that the currents in the equatorial Pacific Ocean have multi-layer structures both in zonal currents and western boundary currents, indicating that the global ocean overturning thermohaline circulation appears of multi-layer pattern.

基于改进遗传算法的交直流混联电网的无功优化方法

随着中国经济的持续增长,对能源的需求也在不断上升。然而,由于一次能源与负荷中心的逆向分布,采用新能源进行大规模远距离输电已成为行业内的迫切需求。在众多输电技术中,基于换相换流器的高压直流输电技术(line commutated converter high voltage direct current,LCC-HVDC)具有无功消耗特性,可能加剧电网的电压波动与无功平衡的问题。针对这一挑战,重点研究交直流混联电网,并构建了一个旨在优化无功功率的数学模型。为克服遗传算法在初始种群选取困难和易早熟的问题,对传统遗传算法进行了创新性改进。在改进后的IEEE 14节点系统和IEEE 39节点系统上进行系列实验验证,所提改进遗传算法展现出显著的实用性和有效性。该算法能够有效优化电网的无功功率,显著提升电网运行的稳定性和效率,为电网无功优化提供了一种新的解决方案。