Load Profile Synthesis and Wind-Power-Generation Prediction for an Isolated Power System

This paper investigates the power load composition of an isolated power system using a load survey study and estimates wind power generation with a probabilistic network. The typical load pattern of various customer classes is derived, which are then used to derive the total power consumption of all customers within each class. A probabilistic neural network is used to solve the wind power generation based on the wind speed for an offshore island in Taiwan. With the hourly wind speed and load composition, the power generation of diesel generators was obtained. Results of this paper demonstrate that wind power generation can economically and effectively replace the power generation of the island's diesel power plant and provide partial power-supply capability for the net peak load requirement.     

Adequacy assessment of power system generation using a modified simple genetic algorithm

This paper presents a new method for the assessment of generation system reliability. The proposed method is based on a modified version of the simple genetic algorithm. In this method, a genetic algorithm is used, not for its traditional objective of optimization, but as a search tool to truncate the probability state space and to track the most probable failure states. The genetic algorithm stores system states, in which there is generation deficiency to supply system maximum load, in a state array. The given load pattern is then convoluted with the state array to obtain adequacy indices. A state array is also used to obtain useful information about the contribution of different states and generation unit combinations to the probability of system failure.     

Frequency-duration analysis of composite distribution system using a non-sequential Monte Carlo simulation

This paper presents a methodology for composite distribution system well being analysis based on non-sequential Monte Carlo simulation technique accounting uncertainties in capacity of distribution substation and distributed generation (DG). The method is based on a system state transition sampling approach which is used to calculate frequency and duration indices along with probabilities in healthy state, marginal state and risky state for a composite distribution system. Capacity of distribution substation and distributed generations are considered as normally distributed i.e. continuous capacity. The effectiveness of the method for evaluation of annual well being indices is demonstrated for a sample test system with DG capacity variation considering a seven step load model based on annual load duration curve. A comparative study is carried out which illustrates the effect of distributed generation capacity on well being indices of a distribution system.     

基于SSTLF与AGC的机组出力调度系统设计

从浙江电网实际负荷特点及浙江AGC的应用现状出发,提出了基于超短期负荷预测的机组出力调度系统的构想。该系统通过调度员的参与能够实现全网机组出力的实时合理调节,从而达到提高浙江电网守口水平的目标。文章进一步介绍了该出力调度系统的总体结构和设计方案,并介绍了目前成功应用于浙江电网的几种超短期负荷预测方法。文章认为该出力调节系统具有较强的实用性,在国内电网中具有普遍的通用性。     

Firefly Optimization Algorithm for the Reactive Power Control of an Isolated Wind-Diesel System

This paper investigates the application of firefly optimization algorithm to design an optimal control for voltage stability of a stand-alone hybrid renewable generation unit based on reactive power control. The studied renewable generation unit mainly consists of a permanent magnet induction generator driven by wind turbine and a synchronous generator driven by diesel engine. A STATCOM is used to stabilize the terminal load bus voltage via compensating of reactive power. The main control objective aims to stabilize the terminal load voltage against any disturbances in load reactive power and/or input wind power by adjusting the total system reactive power. This is accomplished by controlling STATCOM phase angle and hence to control the load bus voltage and also by controlling the excitation voltage of the synchronous generator. The proposed renewable energy power system based on the proposed optimal controller has been tested through step change in input wind power and load reactive power. The system performance based on the proposed control is compared with model predictive control, a robust H_∞ control, and a classical PI control.     

利用日最小负荷置信区间的光伏发电准入容量确定

为解决传统基于节点最小负荷估算值计算光伏发电准入容量可能存在的偏保守或偏乐观的问题,提出了一种利用日最小负荷置信区间的任意一个节点光伏发电准入容量确定方法。首先对系统各节点年度历史负荷数据进行处理,提取各节点的日最小负荷并求其置信区间;然后将各节点负荷置信区间上、下限分别代入目标配电系统进行系统简化;最后利用简化解析式法得到光伏发电准入容量的置信区间。案例分析在一个IEEE 69节点系统中展开,对比所提方法和DIgSILENT商业软件的计算结果,表明了该方法的有效性。     

面向综合负荷的并网光伏发电系统等效建模

基于MATLAB/Simulink和光伏电池自身的物理机理搭建了并网光伏发电的仿真系统,研究了其对配电网综合负荷特性的影响因素,分析比较了已有光伏发电系统等效模型的优劣。在此基础上构建了光伏发电系统传递函数等效模型,该模型具有结构简单、参数少、能有效描述光伏发电系统的出力极限等优点,同时易于在电力系统仿真软件中实现。采用所提出的等效模型与传统综合负荷模型并联,构建广义综合负荷模型,对含光伏发电系统的综合负荷进行建模,仿真实践表明此广义综合负荷模型具有良好的泛化能力,辨识参数稳定,能够满足工程仿真的需要。     

Disturbance detection in grid-connected distributed generation system using wavelet and S-transform

In this paper, wavelet transform and S-transform based approach is proposed for islanding detection and disturbance due to load rejection in distributed generation (DG) based hybrid system. The two types of distributed generation technology: inverter based and rotating machine based, that consists of photovoltaic, fuel cell and wind systems are considered in hybrid system configuration. The negative sequence voltage signal is analyzed through wavelet transform and S-transform for islanding detection of these resources from the grid. The above two approaches are also used in study of voltage profile at point of common coupling (PCC) with a non-linear load connected. The study for different scenarios in operation of DG system is presented in the form of time-frequency analysis. The energy content and standard deviation (STD) of S-transform contour and wavelet transform signal is also reported for both islanding detection and disturbance due to load rejection.     

基于进化捕食策略法的风-水-火电短期负荷分配优化

考虑负荷与风电的不确定性,建立了基于机会约束规划的风-水-火电短期负荷分配优化模型。为了更好地权衡局部搜索与全局搜索性能,应用进化捕食策略法求解水-火电短期优化调度与风-水-火电短期负荷分配问题。算例结果表明,与其他算法相比,进化捕食策略法在水-火电短期优化调度中能够搜索到更优的解,同时基于机会约束规划的优化方法为系统旋转备用容量的合理设置提供了依据。     

输电断面潮流的N-1静态安全约束

就电网运行中广泛采用的N-1原则,建立了输电断面潮流静态安全约束的非线性优化数学模型并给出了迭代求解算法。针对复杂大规模互联电网建立了基于直流潮流的简化模型。考虑了运行方式变化对断面潮流传送能力的影响,提出将运行方式划分为发电模式和负荷模式分别进行分析。运用典型模式方法分析负荷变化对潮流约束的影响,解决了负荷变化规律难以模拟的问题．而发电模式的变化应依据实际系统电源的最大、最小方式确定。算例表明,所提出的方法简捷可靠,能够满足实际电网运行需要。     

A minimum cost assessment method for composite generation andtransmission system expansion planning

Composite generation and transmission system expansion analysis should take into account both economic considerations and adequacy requirements. An optimum expansion plan should achieve the minimum total investment, operation and damage cost. A minimum cost assessment method for composite system expansion planning, which can be used to consider generation expansion and transmission expansion simultaneously, is presented. The minimization model proposed to incorporate both operating and outage costs can recognize different customer damage functions at different load buses and includes the duration of the simulated contingency system states . A computer program based on the presented method has been developed to provide a set of line, load bus, generator bus and system indices which can be used to select optimal expansion plans at different load growth levels. Case studies in which the method is applied to the IEEE Modified Reliability Test System indicate its effectiveness     

经柔直电网互联的含抽蓄的联合发电系统最大供电量计算

为充分利用风光发电能量,合理调度抽水蓄能电站,针对经柔直电网互联的风光蓄联合发电系统向远方负荷中心供电这一工程实际需求,提出基于日供电量最大的抽水蓄能发电优化调度模型及方法。采用最优潮流法计算受电区(负荷中心)全天的消纳极限。并以此极限为约束,同时考虑抽蓄电站库容与运行工况等限制,建立了抽蓄电站功率优化调度模型。提出的分段法与等效面积法显著提升了优化模型的计算速度。在某地风光蓄发电系统与柔直输电网架结构的基础上,用IEEE30节点系统模拟受端电网,建立仿真算例。比较了几种最大供电量计算方法的结果,验证了所提方法与模型的有效性。     

基于分段竞价的售电侧需求响应策略

需求响应可以有效改善负荷曲线,提高系统可靠性。在分段竞价模式基础上,提出了用户可平移负荷参与需求响应的方式。根据发电成本随连续生产时间的增加而有所降低的特性,建立了负荷段组合优化模型,提出售电公司将用户不同的可平移负荷组合为长负荷段参与市场交易,以获得较低的发电成本。在此基础上以购电费用最小为原则建立了市场出清模型,计算出清价格。采用合作博弈双边Shapley值方法,解决用户合作后的购电费用合理分配问题。基于某地区实际负荷数据的算例计算表明,通过售电公司对用户可平移负荷资源的优化组合,可有效降低机组发电成本,减少用户购电费用,实现发电企业和用户的共赢。     

Protection against loss of utility grid supply for a dispersedstorage and generation unit

The requirements of an islanding, or `loss of grid', protection for a dispersed storage and generation unit are examined, and the principal methods used for this type of relaying are outlined. A new protection algorithm is introduced which is based on the rate of change of power as measured at the generator's terminals. The responses of the different measurands are examined for a selection of power system operating conditions in order to demonstrate the operation of this type of protection. The new protection algorithm is shown to trip for loss of grid and for load fluctuations while the dispersed storage and generation unit is operating independently of the utility supply following a loss of grid, and for an out-of-synchronism reconnection of the utility supply to the dispersed storage and generation unit. It is also shown to remain stable for major load fluctuations while the utility supply remains connected to the dispersed generator system     

Optimal load-shedding using local information

This paper describes an optimal load-shedding policy based on quadratic programming using only some power system state variables after severe generation outages. When generation outage is severe, the imbalance between supply and demand causes a declining frequency. Utilities generators cannot be operated excessively at frequencies above normal. Some of the load must be shed to prevent system damage. Optimal load-shedding policies have been studied using all state variables of the power system. However, in real power system operations, it is difficult to obtain remote information in that fraction of a second following generation outages. An optimal load-shedding method is constructed in this research using quadratic programming (QP) under the assumption that all power system state variables can be available. However, these state variables cannot be easily accessible (as already mentioned). A suboptimal load-shedding scheme based on the local state variables is then studied. The proposed load-shedding method is based on the aforementioned optimal one. The change in line-power flows and the amount of generation power outage are used as accessible data at each load point. Incorporating this local information into the optimal loadshedding method based on the QP method, the proposed load-shedding method is established here. The effectiveness of this proposed method is illustrated by two examples and simulation results on a model power system show that the method is encouraging.     

Reliability assessment of restructured power systems using reliability network equivalent and pseudo-sequential simulation techniques

This paper presents a technique to evaluate reliability of a restructured power system with a bilateral market. The proposed technique is based on the combination of the reliability network equivalent and pseudo-sequential simulation approaches. The reliability network equivalent techniques have been implemented in the Monte Carlo simulation procedure to reduce the computational burden of the analysis. Pseudo-sequential simulation has been used to increase the computational efficiency of the non-sequential simulation method and to model the chronological aspects of market trading and system operation. Multi-state Markov models for generation and transmission systems are proposed and implemented in the simulation. A new load shedding scheme is proposed during generation inadequacy and network congestion to minimize the load curtailment. The IEEE reliability test system (RTS) is used to illustrate the technique.     

Dynamic stability study of an isolated wind-diesel hybrid power system with wind power generation using IG,PMIG and PMSG: A comparison

This paper presents a comparative study of reactive power control for isolated wind-diesel hybrid power system in three different cases with wind power generation by induction generator (IG), permanent-magnet induction generator (PMIG) and permanent-magnet synchronous generator. The synchronous generator (SG) is used with diesel engine set. A mathematical model of the system based on small signal analysis, is developed considering reactive power flow balance equations. The variable reactive power needed by the system is provided by a static synchronous compensator (STATCOM) when wind power generation is done by IG and PMIG. When permanent-magnet synchronous generator (PMSG) is used for wind power generation, the variable reactive power demand is fulfilled by a voltage source converter (VSC) which is on the load side. A new mathematical approximation model for VSC connected with PMSG is proposed such that the voltage source converter fulfills the increased reactive power requirement of load and also increases its active power equal to the increased input wind power. Proportional and integral (PI) gains of the STATCOM and VSC controllers are optimized using integral square error criterion (ISE). The dynamic responses of the system for small (1%) step increase in load reactive power with and without 1% step increase in input wind power are shown. The paper also shows the dynamic responses of the system for random step change in load reactive power plus random step change in input wind power. The MATLAB/SIMULINK environment is used for simulation.     

风电并网后电网调峰措施的经济性分析

为接纳大量风电并网运行,电网需采取各种调峰措施并评价措施的经济性。给出了确定用于平衡风电出力波动的电网可调峰容量的方法,阐述了接纳风电所采取的调峰措施,并对各种调峰手段进行经济效益分析。基于系统的安全运行要求、调峰措施、调峰容量、各种发电形式上网电价和化石燃料的消耗量提出了衡量以及评价调峰措施经济性的方法。以区域电网为研究对象,制定了调峰策略,为电网的节能经济调度提供参考依据,并对风电的持续健康发展提出了建议。     

A Monte Carlo method for multi-area generation system reliabilityassessment

The authors present a method for multiarea generation system reliability assessment. It is based on direct sampling of generating unit states, the clustering technique, and the correlative normal distribution sampling technique of the load states. A linear programming model was used to minimize the total load curtailment. Area load uncertainty, correlation between area loads, and generating unit derated state were considered. Incorporation of these factors does not create a significant increase in computing time. Sensitivity indices of both system and each area to area generation and tie line capacities can be calculated. These indices provide information regarding which tie line or which area generating capacity should be reinforced from the overall system and each area point of view. Calculation results of a four-area system are given to demonstrate the effectiveness of the method     

基于自适应模型预测控制的柔性互联配电网优化调度

针对柔性互联配电网中源荷不确定性问题,提出了一种基于改进模型预测控制的优化调度方法。建立基于模型预测控制的柔性互联配电网日内优化调度模型,采用自适应动态权重方法处理包含综合供电成本和电压偏差的多目标优化问题,在预测模型部分采用动态场景生成及K-means聚类场景削减方法对源荷预测误差进行处理,针对经典模型预测控制滚动优化部分域参数恒定问题,提出一种域参数自适应调整的滚动优化方法。通过四馈线互联的33节点系统仿真算例验证了所提优化调度方法的有效性。