高压直流断路器研究

本文在梳理直流断路器重要功能需求的基础上,对直流断路器绝缘性能、环境耐受性能和电流转换性能等进行深入梳理,进一步总结了在高压直流断路器状态下的直流故障处理方案,旨在为我国高压直流断路器研究水平的逐步提高和应用范围的不断扩大打下坚实的技术基础.     

直流故障引发直流外送系统新能源脱网问题研究

含高比例新能源的直流外送系统由于送端发电设备支撑能力薄弱,在直流故障发生后新能源发电设备面临着过电压脱网风险。为了防止新能源脱网事故的发生,首先建立新能源直流外送系统仿真模型分析新能源机端暂态过电压形成机理,其次根据无功传输规律分析常规机组、调相机、电气距离等因素对新能源脱网的影响,定量分析常规机组的电压调节灵敏度,在此基础上利用新能源短路比指标对新能源脱网情况进行量化分析,最后根据分析结果提出了提高短路容量、提高风机高压穿越能力等预防直流故障后新能源脱网的策略,采用某规划的直流外送系统BPA仿真算例验证策略的有效性。     

基于模块化多电平换流器的高压直流系统直流侧故障限流技术研究

基于模块化多电平换流器的高压直流输电技术迅速发展,直流侧短路故障电流的限制与开断困难等问题已然成为研究热点.故障限流技术能够快速限制短路电流的峰值与上升率,为直流断路器的快速隔离提供有利条件.在现有混合式直流断路器基础上,提出2种快速限流的技术方案:新型直流故障限制器与直流断路器配合方案、结合限流电路的混合直流断路器方...     

一种高压直流断路器的电路构成及其试验方法

介绍了交流断路器断口并接辅助振荡回路的方法,基于电流叠加产生过零的原理使交流断路器断口实现分断直流电流的功能,描述了高压直流断路器的结构、特点及电路关键参数的计算方法,并探讨了考核、验证高压直流断路器的直流电流开断能力的试验电路形式,提出了实现等效试验基于电容、电感储能形式的模拟直流电源的方案,分别给出了试验时序、仿真...     

适用于大规模风、光直流送出系统的改进型MMC子模块拓扑

高压直流输电系统中多采用模块化多点平换流器,但传统半桥型子模块不具备直流故障自清除能力;逆阻型半桥子模块在换流器闭锁时,下管IGBT两端会出现过电压现象;部分新型直流故障自清除能力的子模块拓扑在闭锁后,故障阻断能力不强。文章将改进型子模块与半桥型子模块相结合,提出一种新型MMC桥臂设计方案,分析了其子模块的拓扑结构、各种运行工况和故障阻断机理,从耐压性与经济性两个方面,与其他经典的子模块作比较分析。最后,在PSCAD/EMTDC中搭建双端21电平MMC直流系统模型进行验证,仿真结果表明,文章所提改进子模块拓扑能够快速有效阻断直流侧故障电流,且子模块下管IGBT两端不会出现过电压,兼具故障自清除与低损耗的特点。     

西北电网外送暨宁东—山东±660kV高压直流联网示范工程浅议

分析了西北与华北电网宁东-山东±660 kV高压直流输电工程中的近10项"世界第一"技术创新特点,从系统联网角度阐述了该工程建设的经济和社会效益.根据国家"西电东送"战略要求.通过国家电网的统一规划、建设和调配,西北750 kV骨干电网作为"三华"送端电网的格局已经形成,该直流联网示范工程将西北黄河上游水电、宁东火电打捆外送,对于西北地区煤电、水电、风电等能源大规模外送具有显著的示范作用,将实现更大范围的能源资源优化配置与利用.     

西北电网外送暨宁东—山东±660 kV高压直流联网示范工程浅议

分析了西北与华北电网宁东-山东±660kV高压直流输电工程中的近10项“世界第一”技术创新特点．从系统联网角度阐述了该工程建设的经济和社会效益。根据国家“西电东送”战略要求,通过国家电网的统一规划、建设和调配,西北750kV骨干电网作为“三华”送端电网的格局已经形成,该直流联网示范工程将西北黄河上游水电、宁东火电打捆外送,对于西北地区煤电、水电、风电等能源大规模外送具有显著的示范作用,将实现更大范围的能源资源优化配置与利用。     

大规模风电送端电网风、火电耦合外送多目标优化模型及算法

针对大规模风电送端电网风、火电共用输电通道解耦外送情况下,风电送出功率受阻、输电通道利用率不高等问题,在比较分析风、火电解耦/耦合外送运行特性基础上,以风电外送功率最大、输电通道利用率最高和火电机组运行成本最低为目标;以风电、火电机组日前调度出力为优化变量,构建了风、火电耦合外送多目标优化模型,并提出一种改进多目标差分进化模型的求解算法,最终得出一组风电、火电日前优化调度出力计划,为运行人员制定调度决策提供了科学依据。文章以某地电网为例,验证了所建模型的合理性及算法的有效性。     

基于高压断路器的状态检修实施技术的研究

介绍了开展状态检修的四大支持技术,阐述了这四种技术在高压断路器状态检修系统中的实现方式、功能和发展趋势,分析它们在状态检修系统中的关系,并指出实施高压断路器状态检修需要解决的关键问题。     

IPOS型光伏直流升压外送系统控制策略研究

当光伏直流升压外送系统启动时升压侧和逆变侧均存在过电流问题,同时有源钳位Boost全桥升压变换器(BFBIC)模块开关频率高,使系统损耗严重及工作可靠性降低.针对上述问题,该文提出一种输入并联输出串联(IPOS)型光伏直流升压外送系统,通过分析系统启动过电流原理,提出该系统的软启动控制策略.同时对有源钳位BFBIC开关...     

Multi-infeed HVDC中混合高压直流输电对传统高压直流输电的影响

为分析Multi-infeed HVDC中两种结构的H-HVDC系统对LCC-HVDC系统的影响,引入换相失败免疫因子(CFII)指标定量评估了两种结构的H-HVDC系统对LCC-HVDC系统抵御换相失败能力的影响,基于PSCAD/EMTDC仿真软件建立了两种混合多馈入子系统,研究了两种混合系统在单相、三相接地故障状态下H-HVDC系统对LCC-HVDC系统暂态运行特性的影响。结果表明,VSC-LCC HVDC系统提高了LCC-HVDC系统抵御换相失败的能力;VSC-LCC HVDC系统有效地降低了LCC-HVDC系统的暂态过电压,对故障恢复时间也有一定的改善,提高了LCC-HVDC系统的暂态运行特性。     

Energy storage-based power buffering control for photovoltaic power generation system

光伏发电系统输出的最大功率随外界环境变化而波动,无法满足负荷的供电需求,针对该问题,建立了基于储能系统的光伏发电系统结构,介绍了光伏发电系统运行原理,分析了系统功率与直流母线电压的关系,设计了无源式储能系统和有源式储能系统对功率进行缓冲以满足控制目标.仿真结果表明,有源式储能系统较无源式储能系统有更好的功率调节作用,通过双向DC-DC变换器的储放能量自动切换控制,使得光伏发电系统输出的功率与负荷需求功率良好匹配,直流电压稳定.     

Supercapacitors for power control in a grid-connected photovoltaic system

并网光伏发电系统输出功率的波动性和随机性给并网后系统稳定性,光伏发电消纳以及光伏电站电能质量等方面带来了负面影响,制约了光伏发电的发展.针对这一问题,将超级电容器作为功率调节装置,控制光伏并网系统按指定值平滑,准确地输出功率,使光伏发电具有可调度性.在分析了超级电容特性,系统构成和双向DC/DC变换器状态空间平均小信号模型的基础上,提出功率,电流双闭环反馈滞环电流控制策略,控制超级电容器吸收或补充输出功率的波动成分.在PSCAD/EMTDC 电力系统仿真软件中构建仿真模型,对提出的系统和控制策略进行了仿真分析,良好的仿真结果验证了方法的可行性.     

Possibilities for biomass-based power plant and wind system integration

In this paper, the integration of a biomass-based diesel–wind system is investigated. The system consists of a pitch controlled wind turbine, which is equipped with an induction generator. The induction generator is connected to an ac bus-bar in parallel with a diesel-generator set consisting of a diesel engine driving a synchronous generator. A power plant can generate electric power using biomass from the olive tree in Spain. A gasifier is capable of converting tons of wood chips per day into a gaseous fuel that is fed into a diesel engine. While there are significant systems whose models may be exactly obtained from physical laws and whose states are measured, it is much less realistic to assume that all the parameters, such as the higher heating value of the biogas or wind speed, are exactly known. It is then natural to investigate what happens to control systems involving unknown, or not precisely known, parameters. In this paper, the derived model of biomass-based wind–diesel systems is quite valid for robust control studies.     

风光互补发电系统中光伏方阵最佳倾角的计算方法

介绍一种计算风光互补发电系统中光伏方阵的最佳倾角的方法。用最小二乘法确定光伏方阵的最佳倾角:先计算出倾角β下各月倾斜面上的太阳能方阵发电量与风机发电量之和,然后减去各月负载耗电量的差,再求出一年内上述差值的平方和,能使得此平方和取得最小值的倾角即为方阵最佳倾角β。根据此方法确定出的最佳倾角可以使太阳能和风机发电量相对不足的月份的发电量尽量接近负载需求量,同时又可以解决有的月份风光发电量远大于负载需求,造成极大浪费的问题。     

基于改进遗传算法的风/光互补发电系统恒压控制

针对带有约束条件的风/光互补发电系统恒压控制这个多极值非线性组合优化问题,采用一种改进遗传算法,以系统发电成本最低为目标,根据拧制规则对一风/光互补发电系统的电压进行了优化.仿真结果表明.该算法能显著地提高收敛速度和计算精度,有效地提高了风/光互补发电系统的电压稳定性.     

Intelligent hybrid power generation system using new hybrid fuzzy-neural for photovoltaic system and RBFNSM for wind turbine in the grid connected mode

Photovoltaic (PV) generation is growing increasingly fast as a renewable energy source. Nevertheless, the drawback of the PV system is intermittent because of depending on weather conditions. Therefore, the wind power can be considered to assist for a stable and reliable output from the PV generation system for loads and improve the dynamic performance of the whole generation system in the grid connected mode. In this paper, a novel topology of an intelligent hybrid generation system with PV and wind turbine is presented. In order to capture the maximum power, a hybrid fuzzy-neural maximum power point tracking (MPPT) method is applied in the PV system. The average tracking efficiency of the hybrid fuzzy-neural is incremented by approximately two percentage points in comparison with the conventional methods. The pitch angle of the wind turbine is controlled by radial basis function network-sliding mode (RBFNSM). Different conditions are represented in simulation results that compare the real power values with those of the presented methods. The obtained results verify the effectiveness and superiority of the proposed method which has the advantages of robustness, fast response and good performance. Detailed mathematical model and a control approach of a three-phase grid-connected intelligent hybrid system have been proposed using Matlab/Simulink.     

A framework to determine optimal offshore grid structures for wind power integration and power exchange

This paper presents a framework to find optimal offshore grid expansions using a transportation model of the power grid. The method extends the standard mixed‐integer linear programming approach to the solution of the transmission expansion planning problem to account for fluctuations in wind power generation and load; this makes the method especially suited to identify optimal transnational offshore high‐voltage direct current grid structures for the integration of large amounts of offshore wind power. The applicability of the method is demonstrated by a case study of the North Sea region. Copyright © 2011 John Wiley & Sons, Ltd.     

Probabilistic small signal stability analysis of power system with wind power and photovoltaic power based on probability collocation method

Recently, with increasing improvements in the penetration of wind power and photovoltaic power in the world, probabilistic small signal stability analysis (PSSSA) of a power system consisting of multiple types of renewable energy has become a key problem. To address this problem, this study proposes a probabilistic collocation method (PCM)-based PSSSA for a power system consisting of wind farms and photovoltaic farms. Compared with the conventional Monte Carlo method, the proposed method meets the accuracy and precision requirements and greatly reduces the computation; therefore, it is suitable for the PSSSA of this power system. Case studies are conducted based on a 4-machine 2-area and New England systems, respectively. The simulation results show that, by reducing synchronous generator output to improve the penetration of renewable energy, the probabilistic small signal stability (PSSS) of the system is enhanced. Conversely, by removing part of the synchronous generators to improve the penetration of renewable energy, the PSSS of the system may be either enhanced or deteriorated.     

Economic evaluation for wind power generation–hybrid energy storage system based on game theory

The installation of energy storage system to smooth the fluctuations of wind power output connected to the grid can effectively improve the electric quality and increase economic benefits of wind‐generated electricity. Aiming at the overall profit maximization of wind power generation and storage system (WPGSS), taking the smoothing effect of active power output, the cost of hybrid energy storage system, and the earnings of wind power connected to the grid into consideration, this paper brings forward a game theory‐based coordination and optimization control methodology for WPGSS adopting two low‐pass filters to smooth the fluctuation of wind power output. The smoothing control to the active power of wind power and the power distribution of the hybrid energy storage system is respectively achieved by regulating the time constants of the two filters. With the combinations of wind power–batteries and wind power–super‐capacitors as game's participants and the maximization of the WPGSS's overall profit as game's goal constraint conditions, game theory is introduced to realize the coordination and optimization between the time constants of the two filters. For comparative analysis, the model's optimal solution is respectively worked out by genetic algorithm and particle swarm optimization. The simulation results verify the effectiveness of the proposed method and provide a theoretical basis for the economic evaluation of the WPGSS. Copyright © 2016 John Wiley & Sons, Ltd.