Renewable energy power generation projects started construction in Tibet

On March 19, the construction of a 10-MW photovoltaic power plant and a 1 000-kW new type geothermal power generation project were started by Guodian Longyuan Group in Yanbajing Town, Dangxiong County of Tibet.

Optimal allocation method of energy storage for integrated renewable generation plants based on power market simulation

This study designs and proposes a method for evaluating the configuration of energy storage for integrated re-newable generation plants in the power spot market,which adopts a two-level optimization model of“system simulation+plant optimization”.The first step is“system simulation”which is using the power market simu-lation model to obtain the initial nodal marginal price and curtailment of the integrated renewable generation plant.The second step is“plant optimization”which is using the operation optimization model of the integrated renewable generation plant to optimize the charge-discharge operation of energy storage.In the third step,“sys-tem simulation”is conducted again,and the combined power of renewable and energy storage inside the plant is brought into the system model and simulated again for 8,760 h of power market year-round to quantify and compare the power generation and revenue of the integrated renewable generation plant after applying energy storage.In the case analysis of the provincial power spot market,an empirical analysis of a 1 GW wind-solar-storage integrated generation plant was conducted.The results show that the economic benefit of energy storage is approximately proportional to its capacity and that there is a slowdown in the growth of economic benefits when the capacity is too large.In the case that the investment benefit of energy storage only considers the in-come of electric energy-related incomes and does not consider the income of capacity mechanism and auxiliary services,the income of energy storage cannot fulfill the economic requirements of energy storage investment.

Current status of national integrated gasification fuel cell projects in China

Coal has been the main energy source in China for a long period.Therefore,the energy industry must improve coal power generation efficiency and achieve near-zero CO_(2) emissions.Integrated gasification fuel cell(IGFC)systems that combine coal gasification and high-temperature fuel cells,such as solid oxide fuel cells or molten carbonate fuel cells(MCFCs),are proving to be promising for efficient and clean power generation,compared with traditional coal-fired power plants.In 2017,with the support of National Key R&D Program of China,a consortium led by the China Energy Group and including 12 institutions was formed to develop the advanced IGFC technology with near-zero CO_(2) emissions.The objectives of this project include understanding the performance of an IGFC power generation system under different operating conditions,designing master system principles for engineering optimization,developing key technologies and intellectual property portfolios,setting up supply chains for key materials and equipment,and operating the first megawatt IGFC demonstration system with near-zero CO_(2) emission,in early 2022.In this paper,the main developments and projections pertaining to the IGFC project are highlighted.

Hydro and Wind Power Integration: A Case Study of Dargai Station in Pakistan

Pakistan is facing acute energy crises since last few years. Due to shortage of fuel oil and its sky touching prices, it seems very uneconomical to generate electricity from fuel oil. In order to generate cheap electricity we have to rely on renewable energy resources. To address these challenges, wind power generation is among the popular options in the world which is now being considered in Pakistan as well. However unremitting change in wind speed from calm to stormy introduces real challenges. Storing wind energy in batteries during the periods of low demand seems an expensive option, especially when dealing with large scale power generation. Due to incessantly varying nature of wind speed, it is not feasible to rely only on wind power for cheap power production. Also, it is not thriftily possible to construct separate transmission line. However if we integrate wind power with hydro power, we can utilize the maximum possible transmission capacity. Existing hydro power station operating in that area or pumped storage scheme can be used. This paper is an attempt to analyze coordination of wind generation with hydro power in those areas of Pakistan where both wind and hydro power sources exist. In this paper, different issues have been analyzed taking case study of Dargai. This paper is first attempt in Pakistan about integration of wind and hydro power to draw some general conclusions and to point out some areas in which further research can be done.

Overview of Wind Power Integration in China

With the rapid development of wind power in China, the grid integration of wind energy systems has imposed lots of influences on the security and operation of power grids. This paper provides an overview of the characteristics of the wind power development in terms of distribution area, wind farm scale, integration voltage level and performance of wind turbines. The paper also presents an analysis of the problems and reasons emerging from the wind power integration in China and ends with putting forward some measures and suggestions about the wind power integration and operation for reference.

Investigation and Mitigation of Transformer Inrush Current during Black Start of an Independent Power Producer Plant

The energizing of large power transformers has long been considered a critical event in the operation of an electric power system. When a transformer is energized by the utility, a typical inrush current could be as high as ten times its rated current. This could cause many problems from mechanical stress on transformer windings to harmonics injection, and system protection malfunction. There have been numerous researches focusing on calculation and mitigation of the transformer inrush current. With the development of smart grid, distributed generation from independent power producers (IPPs) is growing rapidly. This paper investigates the inrush current due to black start of an IPP system with several parallel transformers, through a simulation model in DIgSILENT Power Factory software. The study demonstrates that a single genset is capable of energizing a group of transformers since the overall inrush current is slightly above the inrush of the transformer directly connected to the generator. In addition, a simple method is proposed to mitigate the inrush current of the transformers using an auxiliary transformer.

考虑抑制励磁涌流的风储一体化系统黑启动技术研究

风储一体化系统即配备储能的风力发电,具有黑启动能力,对其加以控制可将该系统作为黑启动电源。基于此,在单台风机的基础上,制定了风储一体化系统的黑启动方案。首先,通过构网型控制的储能装置进行启动,为避免变压器投入过程中的励磁涌流或谐振产生的自励磁,在原有的电压环控制基础上,加入了惯性环节来实现软启动策略;然后,储能系统建立交流频率和电压后,实现风电机组及负荷的恢复;在风储一体化系统稳定启动后,经过主变压器和输电线路将电能输送到35 kV母线,完成黑启动过程。最后,在PSCAD/EMTDC软件平台建立风储一体化仿真模型,验证了采用软启动策略的黑启动方案,验证过程电压保持稳定,功率平衡,系统完成启动,同时有效地抑制了励磁涌流。

移动式固体氧化物燃料电池系统集成技术研究现状与进展

固体氧化物燃料电池(Solid Oxide Fuel Cell,SOFC)是一种能量转换装置,可以通过电化学反应将燃料中的化学能直接转换为电能。目前,SOFC大多被视为固定式发电技术,然而因其具有燃料灵活性、高效率和高能量密度等特点,在移动式发电领域如辅助动力、无人机动力、远程电源等也具有广阔应用前景。与固定式SOFC应用相比,移动式SOFC研究进展起步相对较晚,技术较不完善。移动式SOFC系统通常包括电堆、重整器、供气装置、尾燃器、换热器和储能组件等核心组件。开发SOFC移动系统需要考虑系统的鲁棒性、易用性以及发电能力等,而移动式SOFC系统部件相对较复杂,这些部件的耦合匹配特性又会显著影响系统的紧凑性、启动特性及体积/质量功率密度。从热特性、启动策略及高功率密度混合动力系统集成等方面对国内外移动式SOFC系统集成技术的研究进展进行综述。最后,基于对现有研究成果的总结提出了未来移动式SOFC系统集成中存在的挑战,及在材料与工艺的改进、新型启动策略和混合系统设计与优化等方面的发展方向。

起动/发电技术在柴油发电机中的应用研究

舰船或陆用柴油发电机通常采用压缩空气、电起动和液压等专门的起动装置进行机组起动,起动成功后,这些装置停止运行,致使起动装置存在占用空间大、使用率低、效益不高等问题;鉴于无刷同步起动/发电一体化技术在国外航空发动机中的成功运用,本文在对多级无刷发电机电动模式和发电模式运行机理分析的基础上,通过梳理、对比当前国内外提出的单相交流励磁、两相交流励磁、三相交流励磁三种技术方案的优缺点,并对其在柴油发电机中的应用进行了可行性研究,得出了各方案所适用的领域,为后续研究提供借鉴。

Research on solar aided coal-fired power generation system and performance analysis

Integrating solar power utilization systems with coal-fired power units, the solar aided coal-fired power generation (SACPG) shows a significant prospect for the large-scale utilization of solar energy and energy saving of thermal power units. The methods and mechanism of system integration were studied. The parabolic trough solar collectors were used to collect solar energy and the integration scheme of SACPG system was determined considering the matching of working fluid flows and energy flows. The thermodynamic characteristics of solar thermal power generation and their effects on the performance of thermal power units were studied, and based on this the integration and optimization model of system structure and parameters were built up. The integration rules and coupling mecha- nism of SACPG systems were summarized in accordance with simulation results. The economic analysis of this SACPG system showed that the solar LEC of a typical SACPG system, considering CO2 avoidance, is 0.098 $/kW·h, lower than that of SEGS, 0.14 $/kW·h.

Distributed continuation power flow method for integrated transmission and active distribution network

As the integration of distributed generations(DGs)transforms the traditional distribution network into the active distribution network,voltage stability assessments(VSA)of transmission grid and distribution grid are not suitable to be studied separately.This paper presents a distributed continuation power flow method for VSA of global transmission and distribution grid.Two different parameterization schemes are adopted to guarantee the coherence of load growth in transmission and distribution grids.In the correction step,the boundary bus voltage,load parameter and equivalent power are communicated between the transmission and distribution control centers to realize the distributed computation of load margin.The optimal multiplier technique is used to improve the convergence of the proposed method.The three-phase unbalanced characteristic of distribution networks and the reactive capability limits of DGs are considered.Simulation results on two integrated transmission and distribution test systems show that the proposed method is effective.

A maximum power point tracking strategy applied to building integrated photovoltaics

To solve the problem of permanent-shadow shading of photovoltaic buildings,a maximum power point tracking(MPPT)strategy to determine the search range by pre-delimiting area is proposed to improve MPPT efficiency.The single correspondence between the solar-cell current-voltage(I-V)curve and the illumination conditions was proved by using the single-diode model of photovoltaic cells,thus proving that a change in the illumination conditions corresponds to a unique maximum power point(MPP)search area.According to the approximate relationship between MPP voltage,current and open-circuit voltage and short-circuit current of a photovoltaic module,the voltage region where the MPP is located is determined and the global maximum power point is determined using the power operating triangle strategy in this region.Simulation carried out in MATLAB proves the correctness and feasibility of the theoretical research.Simulation results show that the MPPT strategy proposed in this paper can improve the average efficiency by 1.125%when applied in series as building integrated photovoltaics.

基于条件风险方法的风电黑启动价值评估及其应用

高比例可再生能源电力系统具有大停电的风险,让风电适时、适量地参与黑启动能加快系统恢复进程。为充分发挥风电的黑启动价值,首先基于风电对系统恢复的正、负面影响,定义风电的黑启动价值函数,以表征风电接入系统后,在某研究时段内对系统黑启动的价值;然后计及风电预测误差,得到基于条件风险方法的风电黑启动价值评估方法,并将其应用于确定风电接入时机和求解最佳风电接入容量;最后,在含风电的IEEE 39节点系统和河北南部某地区电网中验证了所提模型和方法的有效性。

考虑风电参与的黑启动方案

风电具有启动功率小、启动速度快的特点,安全、稳定地利用风电将有效加快电力系统恢复进程。考虑系统调频能力和机组爬坡能力约束,提出基于机会约束规划模型的风电参与黑启动最佳接入量评估方法,并对风电接入时机进行评估。为了有效发挥风电的作用,提出考虑风电参与黑启动方案的优化方法,对风电接入和负荷恢复进行分时步协调优化,制定出风电参与的最优黑启动方案。以含风电的IEEE 39节点系统为算例验证所提方法的可行性和有效性。

混合动力汽车发动机快速起动瞬态燃烧和碳氢排放

介绍了用于混合动力汽车动力系统的发动机快速起动模拟试验台架系统和相关试验。针对一台进气道喷射式汽油机,模拟起动/发电一体化电机,研究在不同拖动转速下快速起动过程的瞬态特性和排放特性。试验结果表明:发动机在快速起动情况下,瞬态特性突出;随着拖动转速升高,进气歧管压力降低,对应的喷油策略也应随之调整;在发动机起动后的第2到第9循环,容易发生不完全燃烧和失火,并随着拖动转速升高,不完全燃烧程度增加,导致碳氢排放过高。在不同拖动转速下,三效催化剂都不能高效转化碳氢排放,但转化效率存在差异。随着拖动转速升高,催化剂的转化效率先降低后又升高。从优化排放角度来看,在本文试验条件下,快速拖动至1000 r/min起动时,使用催化剂后排放最低。

有源电力滤波器直流侧电压专家PI控制研究

针对有源电力滤波器(APF)投入电网启动时存在冲击电流和冲击电压的问题,在直流侧电容电压比例积分(PI)控制方法的基础上,设计了一种专家PI控制器来控制APF直流侧电容电压的启动过程。从受控对象和基于经验知识的专家控制理论出发,结合PI控制建立整个电路模型。在Matlab/Simulink中进行了仿真验证,并将该方法在60 kVA实验样机上进行了测试。通过与常规PI控制对比证明该方法具有超调量小、动态性能好、稳态误差小的优点,并且在工程上有良好的应用价值。

VSC-HVDC直接虚拟功率控制策略

提出一种基于空间矢量调制直接功率控制(direct power control with space vector modulation,DPC-SVM)的直接虚拟功率控制算法。此控制算法扩展了现有DPC的适用范围,在电压源换流器(voltage source converter,VSC)交流侧开路及交流测电流为零时,通过虚拟功率保持DPC控制模块的反馈回路,使DPC能够在VSC换流器并网前控制交流侧输出电压幅值和频率稳定并与电网接入点保持一致。此算法计算过程简单,使用大部分原有DPC-SVM控制模块,并且与DPC-SVM结构保持一致,从而使VSC换流器并网前后控制算法切换平滑。该文分别利用PSCAD/EMTDC软件平台和实验室硬件实验电路进行仿真和电路实验,验证提出的控制算法的正确性和有效性。

适用于风电并网的模块化多电平柔性直流启动控制技术

详细讨论了适用于风电并网的模块化多电平柔性直流输电系统启动控制策略。启动控制的核心在于子模块电容充电,可分为不控整流和高频整流两个阶段。针对不控整流阶段,基于其数学模型给出了限流电阻选型依据以抑制风电场侧换流器在启动及控制系统解锁瞬间的冲击电流。针对高频整流阶段,提出了基于直流电压斜率控制的充电策略以避免系统侧换流器输出过流。所设计的两个换流器启动顺序控制流程在仿真平台得到了验证。

异步电机软起动与谐波抑制一体化控制

针对三相异步电机直接起动的超大电流(额定电流的5-8倍)和谐波对电网,电机设备危害较大的问题。提出了一种新型的具有滤波功能软起动的方法。将有源电力滤波器与软起动器相结合,构成具有谐波补偿的新型一体化软起动器。经过仿真和实验验证,结果表明这种软起动一体化控制方法在解决异步电机的起动电流过大起动不平滑问题的同时又降低了电网侧谐波成分,改善了电能质量。将该技术应用到工业当中,可以解决由软启而引起的谐波问题,以及由于软启和滤波器的分散而造成的成本过高的问题。

基于直觉模糊集Choquet积分算子的黑启动群体决策方法

电力系统黑启动策略优化对大停电事故发生后的电力系统快速恢复具有重要意义。现有的黑启动决策方法多数是以假定黑启动指标或权值相互独立为前提的,且在群体决策方面缺乏研究报道,而群体决策结果一般比个体决策结果更加可靠。在此背景下,通过在黑启动决策问题中引入直觉模糊集概念和直觉模糊Cho-quet积分算子,发展了相应的黑启动群体决策方法。与现有方法相比,所提出的方法不仅能处理指标和权值之间可能存在的关联关系,而且还能够弥补现有算法的一些不足,如基于Vague集的决策方法中所采用的Sugeno积分有可能丢失重要决策信息。最后,用算例说明了所提出的黑启动决策方法的基本特征。