Design and Analysis of the Poloidal Field Grid Power Supply System for the HT-7 Tokamak

This paper reports a new project - the poloidal field （PF） grid power supply system to replace the ac flywheel generator power supply system on the basis of the present running parameters of the HT-7 poloidal field and the short-circuit capacity of our transformer substation. The designed parameters of the PF grid power supply system have been verified to meet the requirements of the heating field （HF） and the vertical field （VF）. In the meantime, in order to reduce the disturbance to the local power grid, the device of reactive power and harmonic current compensation has been added. Experimental results have confirmed the feasibility of the PF grid power supply system. Compared with the ac flywheel generator, the PF grid power supply system has the advantages of lower noise, precise control, convenient maintenance, simple operation and cost savings.

Assessing Micro-generation＇s and Non-linear Loads＇ Impact in the Power Quality of Low Voltage Distribution Networks

Distribution networks face an increasing penetration of solar PV （photovoltaic） and small WTG （wind turbine generator） as well as other forms of micro-generation. To this scenario, one must add the dissemination of non-linear loads such as EV （electric vehicles）. There is something in common between those loads and sources： the extensive use of power electronic converters with commutated switches. These devices may be a source of medium-to-high frequency harmonic distortion and their impact on the local distribution grid must be carefully assessed in order to evaluate their negative impacts on the network, on the existing conventional loads and also on other active devices. In this paper, methodologies to characterize effects such as： harmonics, network unbalances, damaging power line resonance conditions, and over/under voltages are described and applied to a real local grid configuration.

A Liability Division Method for Harmonic Pollution Based on Line-Transferred Power Components

The existing liability division methods for harmonic pollution are either inexplicit or incomplete in physical meaning. To compensate these defects, two new methods are proposed based on line-transferred power components in this paper. At first, all harmonic sources are represented by ideal equivalent current source, line current components and bus voltage components of a source are determined by stimulation of this source with all other sources disabled. Then, the line-trans- ferred power component owing to a source under all sources action together is determined by the theory of line-transferred power components, and called source’s line-transferred power component. At last, the liability of a source for line-end harmonic pollution is divided by two methods: the ration of the source’s line-transferred active power component to the total line-transferred power, and the ration of projection of the source’s line-transferred complex power component to absolute value of the total line-transferred complex power. These two methods are taken into account not only harmonic voltage but also harmonic current in the liability division. Simulation results show that the proposed liability division method based on active power component is the most effective and ideal one.

Harmonic Resonance Analysis of Shale Gas Distribution Network with Phased Load

Based on the background of achieving carbon peaking and carbon neutrality, the development and application of new high-power compressors, electric grid drilling RIGS and electric fracturing pump system provide new equipment support for the electric, green and intelligent development of shale gas fields in China. However, the harmonic pollution of shale gas grid becomes more serious due to the converter and frequency conversion device in the system, which easily causes harmonic resonance problem. Therefore, the harmonic resonance of shale gas grid is comprehensively analyzed and treated. Firstly, the working mechanism of compressor, electric drilling RIGS of the harmonic impedance model of electric fracturing pump system is established. Secondly, the main research methods of harmonic resonance analysis are introduced, and the basic principle of modal analysis is explained. Modal analysis method was used to analyze. Finally, harmonic resonance is suppressed. The results show that there may be multiple resonant frequency points in the distribution network changes, but these changes are relatively clear;if the original resonant frequency point of the resonant loop does not exist, the resonant frequency point disappears. The optimal configuration strategy of passive filter can effectively suppress harmonic resonance of distribution network in shale gas field.

Implementation of Dynamic Line Rating in a Sub-Transmission System for Wind Power Integration

Based on conventional static line rating method, the actual current carrying capability of overhead conductors cannot be judged. Due to continuous increment in electricity demand and the difficulties associated with new line constructions, the overhead lines are therefore required to be rated based on a method that should establish their real-time capability in terms of electricity transmission. The method used to determine the real-time ampacity of overhead conductors not only can enhance their transmission capacity but can also help in allowing excessive renewable generation in the electricity network. In this research work, the issues related to analyzing an impact of wind power on periodical loading of overhead line as well as finding its static and dynamic ampacities with line current are investigated in detail. Moreover, the investigation related to finding a suitable location for the construction of a 60 MW wind farm is taken on board. Thereafter, the wind park is integrated with a regional grid, owned by Fortum Distribution AB. In addition to that, the electricity generated from the wind park is also calculated in this project. Later on, the work is devoted to finding the static and dynamic line ratings for “VL3” overhead conductor by using IEEE-738-2006 standard. Furthermore, the project also deals with finding the line current and making its comparison with maximum capacity of overhead conductor (VL3) for loading it in such a way that no any violation of safe ground clearance requirements is observed at all. Besides, the line current, knowing the conductor temperature when it transmits the required electricity in the presence of wind power generation is also an important factor to be taken into consideration. Therefore, based on real-time ambient conditions with actual line loading and with the help of IEEE-738-2006 standard, the conductor temperature is also calculated in this project. At the end, an economic analysis is performed to evaluate the financial advantages related to applying the dynamic line ratings approach in place of traditional static line ratings technique across an overhead conductor (VL3) and to know how much beneficial it is to temporarily postpone the rebuilding and/or construction of a new transmission line. Furthermore, an economic analysis related to wind power system is taken into consideration as well to get familiar with the costs related to building and connecting a 60 MW wind farm with the regional grid.

Load Management Scheme Using Air Conditioning Electric Power Consumption and Photovoltaic Power System Generation

In the last few decades, in the world and also in the European Union, considerable resources had been invested in the rapid development of renewable energy sources and distributed generation in general. At the same time, power consumption is continuously increasing, and consumers are becoming more complex, which ultimately requires new investments in the distribution network. Concept of smart grids is generally accepted as a possible solution. Smart grid is a concept with many elements, where monitoring and control of every element in the chain of production, transmission, distribution and final consumption enable much more efficient delivery and use of electricity. One of the elements of smart grid efficiency is the ability of real-time demand-supply balancing. This balancing is carried out by monitoring of consumption and redistribution of electricity among individual end users, according to their needs. The aim of this paper is creating algorithm for real-time load management using power measurements. Algorithm for real-time load management at the ETFOS （Faculty of Electrical Engineering in Osijek）, Croatia is created based on measurements of photovoltaic power plant production, the power consumption of air conditioning system and the faculty building total electricity consumption. Expected result of real-time re-dispatching of air conditioners consumption, depending on the level of electricity production in photovoltaic power plant is decreasing peak demand of the faculty.

Power Quality Consideration for Off-Grid Renewable Energy Systems

Necessity of electricity access in remote area is the main reason for expanding decentralized energy system such as stand-alone power systems. The best electrical power supply must provide a constant magnitude and frequency voltage. Therefore, good power quality is an important factor for the reliable operation of electrical loads in a power system. However, the current drawn by most of electronic devices and non-linear loads are non-sinusoidal, which can result in a poor power quality, especially in off-grid power systems. Poor power quality is characterized by electrical disturbances such as transients, sags, swells, harmonics and even interruptions in the power supply. Off-grid power systems worldwide often struggle with system failures and equipment damage due to poor power quality. In this paper, MAT- LAB/Simulink is used to model and analyses power quality in an off-grid renewable energy system. The results show high voltage transient when the inductive loads were switched OFF. The voltage and current harmonics are also determined and compared for various types of loads.

Proposal of New PCCS Method for PCS in a PV Generation System

This paper proposes a new peak current control switching(PCCS)method for single-phase inverter in photovoltaic(PV)generation system.This method minimizes the difference between a peak current and the current command with a constant switching frequency.In this paper,the principle and the simulation results of the proposed method are described.In this paper,the principle and the simulated transient characteristics of this PCCS method are described.From the results,it is clarified that the proposed switching method is effective.

光伏多功能并网逆变器不同出力状态下无功和谐波优化方法

利用光伏多功能并网逆变器所具有的电能质量治理、谐波谐振抑制的主动优势,结合逆变器在不同出力状态下光伏发电系统的输出特性,构建光伏多功能并网逆变器不同出力状态下的无功和谐波优化方法。在所提3层优化策略中,上层优化策略以光伏并网有功功率最大化为目标函数,中层优化策略以电压谐波总畸变率和电压偏差达到相应电能质量规定指标为目标函数,下层优化策略以电压谐波总畸变率和电压偏差最小为目标函数,并采用自适应蚁群算法进行求解。基于IEEE 33节点系统进行算例分析,结果表明:基于逆变器不同出力状态的优化方法可以有效改善电网的电能质量,较好地提升电网运行的经济性;在系统稳定运行的基础上,光伏多功能并网逆变器在不同出力状态下分阶段、分主次地治理谐波和调整电压偏差,治理效果更佳。

弱电网下光伏并网系统锁相环参数自适应控制

针对弱电网下PLL(phase-looked loop,PLL)会使并网逆变器的稳定性下降问题,提出一种锁相环带宽自适应控制策略来实现锁相环参数依据电网实时阻抗值来获得最优的控制参数,保证系统最佳控制性能和稳定运行,从而提升跟网型逆变器在弱电网下的对电网阻抗的适应能力。利用PSCAD/EMTDC进行仿真验证,仿真结果证明自适应控制策略正确、有效。

面向电网调峰的盘管式冰蓄冷空调技术研究

储能是助力实现碳达峰碳中和战略目标的关键技术。当前电力供需关系的矛盾随着可再生能源高比例接入和电力需求快速增长日益尖锐,该问题在夏季用电高峰期间尤为突出。冰蓄冷空调系统在夜间利用谷电制冰储存冷量,在白天用电高峰时融冰供冷,有助于电网调峰和改善用能经济性。该文总结分析盘管式冰蓄冷空调关键技术的研究现状和发展方向。系统控制层面:对比分析冰蓄冷空调系统的各种优化控制策略;蓄冰融冰方式层面:详细阐述内融冰、外融冰和内外融冰结合3种方式特点,并对能量模型进行归纳;结构层面:分析典型强化传热方式对传热性能的影响关系。最后,归纳不同材质盘管的研究结果与应用前景。

海上风电中频汇集不控整流系统谐波抑制

目前,深远海上风电换流站采用不控整流器的直流送出方案极大地提高了送出系统的可靠性和经济性。然而,不控整流器会产生大量谐波进而降低风电汇集系统输电能力。针对上述问题,这里提出一种改进电压控制策略,即在风机网侧变换器传统控制策略基础上增加抑制谐波电流的附加控制环,实现对谐波电流的主动抑制。此外,这里分析了谐波电流对变压器和换流器的功率损耗,通过抑制谐波电流进而减小功率损耗,提高输电能力。最后,通过仿真计算和实验验证,证实了改进电压控制策略的正确性和有效性。

复杂大电网非预设性运行工况下的继电保护动作适应性仿真分析

非预设性运行工况下的突发事件多,导致继电保护逻辑的适应性较差,不合理区域较多,为此,进行复杂大电网非预设性运行工况下继电保护动作适应性仿真分析。分析历史常规故障,标记故障点最常发生位置,构建零序、负序方向元件模型、距离元件模型、纵联电流差动元件模型,观察复杂大电网非预设性运行工况下的电网参数变化情况,第一时间掌握电网的耦合性,不断选择电网所需的继电保护动作逻辑,确认继电保护动作适应性。仿真实验表明,将故障点设置在保护区域内和区域外,继电保护动作能够根据故障选择不同保护模型进行故障母线切除或者保护不动作,适应性好。

基于LADRC和准PR控制的风电并网逆变器控制策略

为了稳定风电并网逆变器直流母线电压的波动,提高其动态响应速度并减少并网电流中的谐波含量,本文提出了LADRC+准PR双环控制策略.首先根据两电平风电并网逆变器的拓扑结构建立其数学模型;然后,根据数学模型设计电压外环二阶LADRC控制器和电流内环准PR控制器代替传统的PI控制器,同时对两种控制器的参数进行了设计并整定;最后,在Matlab软件中构建仿真模型,进行了仿真分析和波形对比.结果表明:相较于传统的双闭环PI控制策略,新型控制策略不仅能够快速地稳定直流母线电压,而且交流侧电流的总谐波失真小;并且在电网电压发生扰动的工况下,仍有较好的控制性能.综上所述,基于LADRC和准PR控制的风电并网逆变器控制策略具有较好的抗扰性和优越的鲁棒性.

基于自适应移频滤波的电力系统谐波分析方法

随着非线性负荷和冲击性负荷的不断增加以及新能源的大规模并网,电网环境日趋复杂,各类电能质量问题日益凸显。其中,谐波问题尤为突出,准确估计谐波参数不仅是谐波治理的关键,也是电力企业和用户评价电能质量的重要依据。为此,该文提出一种基于自适应移频滤波的电力系统谐波分析方法。首先,对电网谐波信号进行初次移频滤波操作,以获得信号实际基波频率;然后,根据信号实测基波频率,对信号进行二次移频滤波处理,进而准确获取各次谐波的幅值和相角;最后,仿真实验表明,该文所提算法能够有效地克服非同步采样和噪声的影响,并且具有测量精度高、实时性好和适应性强等特点。此外,通过实际构建的硬件测试平台,进一步验证了所提算法的准确性和可靠性。

基于历史天气的区域电网负荷预测

随着社会经济的迅速发展,人们对电能的需要日益增加,但是在电网运行中,常常会出现电力产能过剩或者不足的情况,为保证电力系统安全稳定、经济运行,就必须掌握各种区域电网负荷的变化规律和发展趋势。论文对重庆市区供电分公司供电区域电网中长期负荷进行预测,提出一种预测区域电网中长期负荷的方法,即一种基于前12个月历史天气条件和区域电网负荷关联关系的多元非线性拟合的特征参数因子曲线的中长期负荷预测方法,建立基于不同算法的多种预测模型,通过归一化处理,得到的区域电网中长期负荷预测的精度高,与实际区域电网负荷之间的误差小,对于区域电网中长期负荷预测分析具有重要参考利用价值。

新型电能通信传输检测设备

目前微电网端口电能质量分析设备较少,加之非线性、不平衡等电气负荷设备的接入,电能质量的检测与分析的问题日益严重,正常情况下电压的波动与间谐波和超高次谐波等问题难以解决。该文通过在MCU的基础上加入基于FFT的分析算法以及控制模块,针对当前问题,提出了一种能够实时检测并传输谐波分量的显示装置,通过SIM900A传输模块,传输到用户侧的电能质量检测装置,方便实时对电网侧电路进行检测。可在电路中接入整流器从而减少谐波分量,实时抑制电网谐波分量的输出,保护输出电压的稳定性。

弱电网下计及背景谐波的多并网逆变器阻抗重塑谐振抑制方法

弱电网下多逆变器并网系统的谐振问题一直广受关注,当计及背景谐波时,逆变器的电网电压前馈环节引入正反馈通路,将进一步恶化系统的电能质量。鉴于此,提出了一种弱电网下计及背景谐波的多并网逆变器阻抗重塑谐振抑制方法。通过对逆变器的控制环节进行导纳划分,建立基于三分解导纳的多逆变器并网等效模型,并利用模态分析法得到逆变器数量和电网侧阻抗变化时系统的谐振特性。计及电网电压前馈和电容电流反馈环节,对加权电流控制进行改进,并通过公共耦合点并联虚拟导纳对逆变器进行阻抗重塑,以实现对弱电网下系统谐振的抑制。仿真结果表明,所提方法既能极大地减小背景谐波对逆变器输出电流的影响,又能有效地抑制弱电网下多逆变器并网系统的谐振。

适应频率偏移及动态变化场景的动态谐波相量在线测量方法

电力电子装置接入加剧了新能源电网谐波污染,动态谐波相量高精度在线测量是谐波监测、溯源、抑制的关键前提。泰勒傅里叶变换方法虽然能够高精度测量动态谐波相量,但在频率偏移和频率动态变化场景下繁重的计算负担与内存开销使其难以应用于资源有限的嵌入式测量单元,是工程应用的主要障碍。针对该问题,该文理论分析谐波频率偏离滤波通带中心情况下的测量误差,阐明频率偏差测量值与真实值的非线性关系,提出基于频率偏差牛顿迭代修正的动态谐波相量快速测量方法,解决频率偏移及动态变化场景下基于泰勒傅里叶变换的动态谐波相量高精度在线测量难题。仿真结果表明,所提方法在频率偏移、频率斜坡、频率振荡、幅值斜坡、幅值振荡等多种场景下能够实现动态谐波相量高精度测量,且执行过程内存需求小、计算复杂度低。最后,将所提方法应用于嵌入式测量单元,通过实时测量电网实际动态场景的含谐波电磁重构波形回放信号,进一步验证了所提方法测量精度与测量速度,展示了该方法在新能源电网动态谐波相量高精度在线测量方面的应用潜力。

单相统一电能质量调节器二次纹波补偿及抑制策略

在单相半桥非隔离统一电能质量调节器(UPQC)中,交、直流间瞬时功率不平衡导致直流侧出现二次电压纹波,影响电能质量的补偿效果。该文分别在UPQC并网、离网两种模式下提出二次纹波的补偿及抑制策略。首先,分析UPQC在并网运行条件下直流二次纹波的产生机理及其对电能质量补偿的影响,并提出分别在并、串联侧变换器加入陷波器及特征次谐波控制,以降低网侧电流及串联侧电压谐波。其次,在UPQC离网运行时,为有效抑制直流电压二次纹波,提出一种利用UPQC闲置的串联侧变换器与复用的直流分裂电容构建半桥有源功率解耦电路的方法,控制难度低且无需额外增加解耦电路元件。最后,通过仿真和实验验证了所提方法的可行性。在并网模式中,所提策略减少了74%的电流谐波及42%的电压谐波;在离网模式中,所提策略减少了66.7%直流电压二次纹波。同时,该文所提出的二次纹波的补偿及抑制策略,可优化直流电容参数设计,并进一步减小UPQC体积。