Power allocation in cooperative MIMO systems under individual power constraints

allocation （PA） plays an important role in capacity improvement for cooperative multiple-input multipleoutput （Co-MIMO） systems. Many contributions consider a total power constraint （TPC） on the sum of transmit power from all nodes in addressing PA problem. However, in practical implementations, each transmit node is equipped with its own power amplifier and is limited by individual power constraint （IPC）. Hence these PA methods under TPC are not realizable in practical systems. Meanwhile, the PA problem under IPC is essential, but it has not been studied. This paper extends the traditional non-cooperative water-filling PA algorithm to IPC-based Co-MIMO systems. Moreover, the PA matrix is derived based on the compound channel matrix from all the cooperative nodes to the user. Therefore, the cooperative gain of the IPC-based Co-MIMO systems is fully exploited, and further the maximal instantaneous capacity is achieved. Numerical simulations validate that, under the same IPC conditions, the proposed PA scheme considerably outperforms the non-cooperative water-filling PA and uniform PA design in terms of ergodic capacity.

Fuel-optimal trajectory design using solar electric propulsion under power constraints and performance degradation

The fuel-optimal transfer trajectories using solar electric propulsion are designed considering the power constraints and solar array performance degradation.Three different performance degradation models including linear,positive and negative exponential degradations are used in the analysis of three typical rendezvous missions including Apophis,Venus and Ceres,respectively.The optimal control problem is formulated using the calculus of variations and Pontryagin’s maximum principle,which leads to a bang-bang control that is solved by indirect method combined with a homotopic technique.In demonstrating the effects of the power constraints and solar array performance degradation on the power budget and fuel consumption,the time histories of the power profile and the fuel consumptions are compared for the three missions.This study indicates that it is necessary to consider the power constraints and solar array performance degradation for the SEP-based low-thrust trajectory design,espacially for long-duration outbound flights.

Joint Power Control and Spectrum Allocation for Cognitive Radio with QoS Constraint

Spectrum sharing with quality of service (QoS) requirement and power constraint on cognitive users is studied. The objective is to maximize the system throughput. This problem is modeled as a mixed integer nonlinear programming problem and then transformed to a continuous nonlinear programming problem through eliminating integer variables. We propose the joint power control and spectrum allocation algorithm based on particle swarm optimization to obtain the global optimal solution. Simulation results show that the proposed method can achieve higher system throughput and spectrum utilization under the constraints of transmit power and QoS requirement.

OPTIMAL POWER ALLOCATION FOR COGNITIVE RADIO UNDER INTERFERENCE OUTAGE CONSTRAINT

Cognitive radio is able to share the spectrum with primary licensed user,which greatly improves the spectrum efficiency.We study the optimal power allocation for cognitive radio to maximize its ergodic capacity under interference outage constraint.An optimal power allocation scheme for the secondary user with complete channel state information is proposed and its approxi-mation is presented in closed form in Rayleigh fading channels.When the complete channel state in-formation is not available,a more practical transmitter-side joint access ratio and transmit power constraint is proposed.The new constraint guarantees the same impact on interference outage prob-ability at primary user receiver.Both the optimal power allocation and transmit rate under the new constraint are presented in closed form.Simulation results evaluate the performance of proposed power allocation schemes and verify our analysis.

Taking into Account of Functional Constraints in Optimization of Modes of Power Systems by Genetic Algorithms

The development of the capabilities of computational tools has created up new possibilities for the effective use of a number of classical mathematical methods and algorithms for solving many important problems in the power engineering. In particular, a set of algorithms are developed to optimize the modes of electric power systems based on genetic algorithms. At the same time, the issues of taking into account functional constraints in solving such problems by genetic algorithms need to be improved. In accordance with it in this article the problems of taking into account of different constraints in optimization of modes of power systems using genetic algorithms are considered. The algorithm of optimization by genetic algorithm taking into account of functional constraints in forms of equality and inequality by penalty functions is proposed. The results of research of proposed algorithm’s efficiency in example of optimization of mode of power system with 8 buses, 4 thermal power plants and 3 transmission lines with controlled power flow are presented.

马克思廉价政府思想的理论考察与当代价值

廉政建设是推进全面从严治党、党的自我革命的有力保障。马克思在《法兰西内战》中总结了廉价政府的一系列思想,阐释了廉政机制保障,提出了约束贪腐的罢免制度,明确了揭露腐败的监督机制,揭示了规范权力运行的法律制度等。马克思廉价政府思想在本质上要求廉政建设必须具有自我革命的实践性、整合重构的系统性、管党治党的权威性。当代中国廉政建设实践对马克思廉价政府思想的创新发展取得突出成效,以建设党内法规体系保证党对廉政建设的坚强领导,以改革纪检监察体制保证党的执政地位长期巩固,以健全党和国家监督体系保证党的自我革命不断深化。马克思廉价政府思想的当代价值要求我们必须持续加强党对廉政建设的坚强领导和自我革命的政治使命,持续强化廉政建设的科学性和时代变迁的适应性,持续探索增强廉政建设执行力的内在动因和运行规律,持续提升中国特色社会主义廉政建设成果和治理效能。

水电富集区域电量送出能力提升的源储协同优化运行方法

针对可再生能源出力的强波动性、间歇性导致电力外送断面出现短时间尺度重过载、清洁能源送出消纳困难等问题,提出了水电富集区域电量送出能力提升的源储协同优化运行方法,该方法定义了衡量断面外送电量的量化指标,以系统发电成本最小、断面输出电量最大、储能消耗电量最小为目标,建立多目标优化模型,通过求解帕累托前沿,结合熵权双基点法,得到折中最优点。对我国某省级电网算例的仿真结果表明,该方法可有效通过水电、火电和储能的协同优化运行提升断面外送可再生能源的发电量,在保证系统安全稳定运行的前提下提升了可再生能源的消纳率。

基于绿电和自愿减排量交易的园区低碳电力运营优化

为保证园区电力运营经济性,提高清洁电能的使用比例,文章提出了一种基于绿电和自愿减排量交易的园区低碳电力运营优化模型。该模型综合考虑了绿电和火电的购电成本、光伏发电成本及自愿减排量收益,以总运营成本最小为目标函数,结合随机概率约束,分中长期、日前和实时三阶段对绿电、火电电量以及光伏发电量进行优化。以南京市某企业园区的数据为基础,在自愿减排量价格合理的前提下,该优化模型可小幅降低园区总运营成本,并且显著提高了清洁电能的使用比例和园区应对扰动的能力。另外,就自愿减排量价格以及置信度取值对优化结果的影响进行了分析。

基于功率重构和时序特性约束的长预见期光伏集群功率预测

光伏装机容量的逐渐增大为大规模的光伏并网带来了巨大挑战,突破更长预见期的光伏功率预测有助于电力系统的安全稳定运行。现有研究及应用最长预见期为7 d,为将预见期延长至8~15 d,提出了一种基于功率重构和时序特性约束的长预见期光伏集群功率预测方法。首先,采用近似积分计算日电量和辐照能;其次,基于麻雀搜索算法优化变分模态分解以分解电量及辐照能序列,并采用多元线性回归模型对不同频率的分量进行预测叠加得到电量预测结果;然后,根据出力特性建立约束过程,将电量预测结果重构为光伏功率;最后,将所提方法应用于中国甘肃省某光伏集群,模型在不同季节典型月功率预测的均方根误差平均降低2.55%,验证了方法的有效性。

储能虚拟惯量主动支撑与调频状态转移控制

释放储能装置的频率支撑潜力,将是提升风、光高占比系统并网稳定性的关键。该文首先对比分析常规发电机组的固有惯量、风电机组的虚拟惯量及储能的惯性支撑特性。其次,根据系统中的储能容量配置,约束量化储能的虚拟惯量,为系统惯量需求提供评估依据,以保障频率安全。在此基础上,利用储能独特的功率支撑特性,提出恒频控制与调频状态转移控制结合的储能并网频率主动支撑控制策略,突破虚拟惯量及一次调频的传统控制模式。最后,搭建风电高渗透电网仿真系统,验证储能装置在所提控制策略下能够显著提升系统的频率稳定性,改善其对电网的主动支撑性能。

基于双重约束的光伏逆变器无功调控策略

针对光伏并网逆变器在应用中存在无功调节范围小、动态响应速度慢,导致逆变器效率低的问题,结合光伏逆变器的结构特点,提出了一种基于最大功率点追踪(MPPT)与并网点电压双重约束的逆变器无功调控策略。该策略在d-q解耦控制的基础上,通过分析光伏逆变器不同工作状态下的无功调节能力,推导出光伏逆变器最大输出无功约束条件,最大限度将逆变器冗余容量作为备用无功功率输送到配电网进行无功补偿,提高了光伏逆变器无功调节范围和光照强度不足时的利用率。最后搭建Simulink仿真模型和实验平台进行验证。结果表明,在无功功率约束条件下,光伏逆变器可以大范围调节输出无功,验证了所提策略的可行性。

基于全纯嵌入潮流计算的可靠节点类型转换研究

针对潮流计算中节点类型转换可能导致的非可运行解问题,提出了一种基于全纯嵌入的可靠节点类型转换方法。首先,构建了考虑发电机节点无功功率和电压约束的潮流方程,并分析了目前常用的节点类型转换方法可能导致的非可运行解问题。然后基于复分析理论和全纯嵌入方法设计了潮流方程的全纯嵌入形式,并推导求解电压及发电机无功功率幂级数的递推方程。基于发电机无功功率幂级数判断发电机无功功率越限顺序,并设计了节点类型转换框架。最后,采取IEEE标准算例进行测试,表明了该方法能够较可靠地得到潮流方程的可运行解。

基于Power图求解容量限制P-中值问题

针对稠密需求下连续域上的容量P-中值问题,提出基于质心的容量限制Power图(CCCPD)理论,对连续P-中值问题进行近似建模,并加快计算过程。扩展Balzer试位法构造Power图,施加质心限制满足P-中值要求,施加容量限制满足需求密度下的容量要求。实验结果表明所提算法可快速得到近似可行解,同Alper Murata方法相比,计算效率高;同质心容量限制Voronoi图(CCCVT)相比,具有容量限制精确度高等优点,并能适应各种复杂需求密度函数。

容量限制Power图快速计算算法（英文）

与Voronoi图不同,Power图有着精确限容的特性,可应用于众多领域.在普通Power图上,通过给每个站点增加权重来添加容量限制约束,即得到容量限制Power图.现有容量限制Power图的生成算法时间复杂度高,速度较慢.本文首先对Power图权值对于容量的单调性进行理论证明,然后提出了一种Power图权值的快速计算方法,相比于现有的试位法,能大幅提升容量限制Power图的生成性能.实验结果表明,文中算法具有速度快,精确度高,便于计算,密度适应性强等优点.

考虑动态频率约束的多能源电力系统日前-日内优化调度

提出考虑系统动态频率约束的含风电-电池储能-抽蓄电力系统协调优化调度策略。首先,建立含风电机组、电池储能和抽水蓄能的电力系统频率响应模型,并对系统调频响应过程进行分段线性化处理,降低计算的复杂度。然后,根据各机组的爬坡速度、启停约束、功率跟踪能力等因素的差异,建立日前-日内协调的多时间尺度优化调度模型。日前阶段制定考虑动态频率约束的火电机组和抽水蓄能的机组启停和出力计划;日内阶段优化电池储能的充放电状态计划,并调整火电和抽蓄的出力计划,促进风电消纳。最后,在含风电、变速抽蓄和电池储能的改进IEEE-39节点系统中进行算例分析,结果证明所提方法能提高系统频率稳定性,减少弃风量,兼顾电力系统经济调度和频率稳定目标。

具有功率调节和容错能力的风力机自适应控制

水平轴风力机面对高风速变化工况时,极易出现转子灾难性失控超速运行,此时风能转换效率低于预期值,同时恶劣的环境也对桨距角控制提出了容错要求。针对这些问题,提出一种具有功率调节和容错能力的风力机自适应约束控制方案,通过自适应约束的桨距角控制实现安全可靠的功率调节,并集成容错能力以补偿可能的故障影响。介绍水平轴风力机的数学模型和运行要求,分析基准的非线性自适应约束控制方案的设计过程,并在此基础上讨论具有未知控制增益、任意初始条件和存在故障影响下的设计方案,最后搭建MATLAB仿真模型对所提出的方案进行验证。仿真实验结果表明:所提方案可以提高风力机的功率调节效率,同时在不同工况和不同故障条件下均能将转子速度和发电功率控制在安全范围内。

含复杂电源结构省级电力系统电力电量平衡方法

随着风电、光伏大规模接入电力系统,为计及其出力的不确定性,需要以年为尺度、小时为颗粒度进行电力电量平衡分析。以含复杂电源结构、内部断面限制、外部交直流受电的省级电力系统为对象,提出了一种新的电力电量平衡分析方法。该方法以日周期进行滚动平衡分析,针对特定日:通过对各分区同类电源进行聚合以简化问题、降低求解规模;通过构建火电开机优化模型以在考虑断面限制下以均衡开机为原则确定各分区火电开机容量;通过合理设计优化调度模型以在满足不同分区同类电源均衡调度、同一分区不同种类电源顺序调用原则下实现电力平衡计算。算例以实际省级电力系统数据为基础,验证了该方法的有效性、合理性、快速性。

风电富集地区电网动态等值建模

为了满足大规模风电并网下对地区电网进行详细仿真的需求,提出了一种适用于风电并网的地区电网等值方法。与聚焦于主网的传统动态等值不同,风电富集地区电网等值不仅要考察风电在地区电网中密集接入的特点,圈定各个风电场站影响范围,而且还要在边界节点上综合考虑外网的源、荷特性约束。所提方法可在保持稳态、暂态特性一致的前提下对外网进行大规模化简,实现地区电网的等值建模。首先,突破在风电场站接入点仅以短路比等电气强度指标来等效电网的传统方案,提出以节点残压来界定待研究区域与待等值外部区域;其次,考虑地区电网的拓扑约束对地区电网进行进一步化简;再次,考虑在边界节点上以等值同步发电机与复合负荷的组合形式构建外部系统的等值模型;最后,利用所提方法对实际风电富集地区电网进行了验证。仿真结果表明了所提等值方法的有效性。