Hierarchical optimization for power system control

This paper presents a practical feedback control strategy for the transient stability problem. The control configuration is hierarchical and is proposed to be installed in addition to existing machine excitation and turbine governor controls. The design proceeds in two steps. First, the local controllers associated with the subsystems are independently designed by fixing the interconnections. Then a higher hierarchical level is designed from the interconnection variables and nonlinear terms. The resulting parameter optimization problem is solved by a decentralized computational structure. The scheme is based on multilevel optimization techniques with multiple objectives given by relevant system disturbances, aggregated by means of a weighted sum. The usefulness of the proposed technique is demonstrated by its application to a power system optimization problem with practical soft constraints on the control variables.     

Improved combined cycle power plant operation design using optimization method

Combined cycle power plant takes advantage of the efficiency, fast startup, and small environmental impact. The operation design of this plant is required to make best use of this plant advantage. A large-scale nonlinear mathematical model of this plant was developed to check the plant condition. This simulation model was combined with the optimization using Rosenbrock method. The operation design is optimized in two steps; [Step 1]: Some points of plant condition can be checked roughly; [Step 2]: This plant operation is optimized to design using Rosenbrock method. This optimization is applied to design the combined cycle power plant operation. It is confirmed that this method is effective for the design of plant operation. From this study, plant operation can be designed with this optimization to make best use of this plant advantage. Then operation design point is decided using the optimization method on some evaluation instead of heuristic method.     

An optimization approach for wind turbine commitment and dispatch in a wind park

This paper describes an operational optimization strategy to be adopted at the wind park control level, that enables defining the commitment of wind turbines and their active and reactive power outputs following requests from Wind Park Dispatch Centers, assuming that individual wind turbines short-term wind speed forecasts are known and are expressed as power availability. This operational strategy was also developed with a concern on the minimization of the connection/disconnection changes of the individual wind generators, for a given time horizon. When identifying the active/reactive dispatching policies, wind generators loading capabilities are also taken in account. This optimization tool is especially suited to manage large wind parks.     

基于遗传算法的PID参数优化技术

本文提出了一种基于遗传算法实现ＰＩＤ参数优化的方法，文中给出了ＰＩＤ参数遗传进化的寻优步骤。通过仿真研究，表明该种优化算法的有效性。     

An ordinal optimization based method for power distribution system control

This work presents an Ordinal Optimization Theory based method for power distribution system control. The solution procedure bases on an evolutionary search scheme. The method aims at minimizing the total power losses on network feeders while keeping the node voltages at near rated values against changing loading conditions. By relaxing the definition of optimality and softening the goal of optimization, ordinal optimization makes the problem easier as well as the solution process faster. A solution can be defined as good enough in performance value if it is one of the best m-percent solutions on the search space with probability P%. A solution can be defined as good enough also if its performance value approximates to the optimal value to a pre-defined extent. This work estimates the performance value, the total power loss, of the optimum state of power distribution network at a given loading condition. Then, with the two relaxed definitions for optimality, it finds the optimal settings of on-load tap changers and capacitors in a 24-h time frame. Results verify our method is proper for on-line and off-line operation.     

结合优化设计滤除非周期分量的新方法

提出一种在短数据窗傅氏算法中滤除衰减非周期分量的新方法，即在滤波方程中增加针对非周期分量的方程，通过优化设计法达到设计目标，新滤波算法的数据窗短，对衰减时间常数在设计整定值附近的非周期分量有较好的滤除效果。     

IMS-GL系列伺服控制器在连铸机调宽中的应用

介绍伺服控制器的工作原理以及在结晶器调宽中的作用。结果表明：使用伺服控制器能快速调整结晶器宽度、锥度及精确度,提高板坯连铸机的作业率。     

An optimization planning technique for Suez Canal Network in Egypt

This paper introduces a proposed optimization technique POT for predicting the peak load demand and planning of transmission line systems. Many of traditional methods have been presented for long-term load forecasting of electrical power systems. But, the results of these methods are approximated. Therefore, the artificial neural network (ANN) technique for long-term peak load forecasting is modified and discussed as a modern technique in long-term load forecasting. The modified technique is applied on the Egyptian electrical network dependent on its historical data to predict the electrical peak load demand forecasting up to year 2017. This technique is compared with extrapolation of trend curves as a traditional method. The POT is applied also to obtain the optimal planning of transmission lines for the 220 kV of Suez Canal Network (SCN) using the ANN technique. The minimization of the transmission network costs are considered as an objective function, while the transmission lines (TL) planning constraints are satisfied. Zafarana site on the Red Sea coast is considered as an optimal site for installing big wind farm (WF) units in Egypt. So, the POT is applied to plan both the peak load and the electrical transmission of SCN with and without considering WF to develop the impact of WF units on the electrical transmission system of Egypt, considering the reliability constraints which were taken as a separate model in the previous techniques. The application on SCN shows the capability and the efficiently of the proposed techniques to obtain the predicting peak load demand and the optimal planning of transmission lines of SCN up to year 2017.     

基于组合优化方法的螺线管型超导磁体的建模和电磁优化

本文针对目前超导应用系统中广泛采用的螺线管型超导磁体的设计问题,提出了综合考虑磁体储能、漏磁和体积的优化问题.以单螺线管磁场计算为基础,用矢量叠加的方法计算多螺线管磁体的漏磁和最大磁场,从而建立了用于优化的螺线管型超导磁体的电磁模型.借助多学科优化设计软件Isight,采用全局搜索和传统数学规划相结合的优化方法,对所建立的电磁模型进行了优化计算.结果表明应用这种组合方法进行螺线管型超导磁体电磁优化,能取得满意的结果.     

汽轮机变压运行全局寻优试验方法

结合某660 MW机组在不同运行方式下主要变量的变化趋势和相互耦合,通过小步幅连续变化主蒸汽压力,实现机组热耗在同一负荷可行滑压区间内的全局动态寻优.试验结果表明,该试验方法可精确地搜索到相应负荷下的最优工况点,且具备良好的试验规律,一定程度上克服了以往寻优试验准确度受仪表精度和边界条件制约的局限；所选用的全局寻优定量计算模型,在全局寻优过程中可直观地反映出机组效率的变化趋势,满足常规寻优试验的热力计算要求.     

Accurate Tracking Control of a Limited Angle Torque Motor

This paper presents a novel control scheme that was developed and implemented to provide accurate tracking control of a limited angle torque motor following a 50 Hz sawtooth reference waveform. The approach could be extended to other limited motion actuators which require high tracking accuracy, but are subject to a single dominant nonlinear element, such as magnetic stiffness, which may be defined experimentally. One example is the variable reluctance linear actuator, used in the aerospace industry for control of aerodynamic surfaces. Despite the significant nonlinearities inherent in the torque motor, a complex nonlinear controller can be designed using simple linear design techniques, and it is demonstrated that the motor is then able to track the reference signal with a very high accuracy. The hybrid scheme uses a multicompensator, multiloop linear controller to reshape substantially the motor response characteristics, which have both inherent time-lag and oscillatory dynamics and an additional nonlinear gain-scheduled controller which effectively compensates for the nonlinear variations of the motor parameters. The system stability is ensured by the linear controller.     

Global optimization for the OPF problem via two‐degree SDP method

This letter proposes a two‐degree semidefinite programming (SDP) method for achieving the global optimum of the optimal power flow (OPF) problem. The method extends the variables to four degrees, and formulates an SDP problem with a two‐degree extended matrix. It satisfies the rank‐1 condition. Experimental results show that this method is more reliable for reaching the OPF's global optimum than existing SDP methods. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于WARD等值的电网限流运行方式优化方法

控制短路电流水平,保证断路器安全是电网运行方式安排的重要任务。线路开断及母线分裂以增大变电站母线与电源之间的电气距离是限制电网短路电流水平的有效措施,但同时也可能引起电网运行可靠性水平的降低。首先根据对网络拓扑结构的分析及线路开断前后超标站点的短路电流变化确定可开断支路集;然后添加功率平衡方程约束、支路潮流约束以及N-1安全约束;以开断线路数最少为目标,提出了控制短路电流水平的电网运行方式优化模型,并借助WARD等值缩小模型规模,提高了模型的求解效率。所提模型为混合整数线性规划模型,可以采用线性规划单纯形法及分支定界法迅速求解。使用C++编写了仿真程序,通过对IEEE39节点系统和某实际电网的仿真分析验证了所提模型的正确性和算法的有效性。     

异步电机多变量矢量控制系统

文章以异步电机矢量控制系统双输入双输出状态空间模型为基础,应用多变量线性控制系统调节器设计方法,设计异步电机多变量矢量控制系统.此方法更好地体现了原矢量控制系统多输入多输出的特点,使矢量控制系统的控制特性得到提高.     

New method for controlling large fan of thermal power plant boiler using inverter in abnormal state

This paper presents a new air flow controller for a thermal power plant. When an inverter power source is used for a forced draft fan (FDF) in order to save power, the conventional countermeasures do not cover all abnormal states. The proposed controller is evaluated by performing a simulation. The power source is shown to change from the inverter to a commercial power source within 0.5 second in the abnormal state. The changing time is determined to be 0.55 second based on the mechanical tolerance of the design. Testing was performed in an actual plant using the proposed control method, and the transient response was compared with the simulated and measured data. The errors were less than 3.4%. The FDF changed over smoothly and the plant conditions remained the same as the normal state in the actual plant testing. This paper deals with the safe operation of a thermal power plant that employs the proposed air flow controller. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 180(4): 47–56, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21202     

基于双层优化的微电网系统规划设计方法

规划设计是微电网系统核心技术体系之一。从分布式电源的综合优化(组合优化、容量优化)和分布式电源间的调度优化两个方面对其展开研究。根据分布式电源特性,提出了适用于并网型微电网系统和独立型微电网系统的双层优化规划设计模型。上层优化采用基于NSGA-II的多目标遗传算法计算系统最优配置;下层优化采用混合整数线性规划算法(MILP)计算系统最优运行方案。运用所建立模型,分别针对并网型和独立型微电网系统作了案例计算,验证了所提方法的正确性。     

考虑多风能预测场景的虚拟电厂日内滚动柔性优化调度方法

随着分布式可再生能源接入电网的比例日益提高,其出力间歇性和随机性给电力系统的安全稳定和经济运行带来了一系列的负面影响,虚拟电厂为分布式可再生能源可靠并网提供了新的途径。针对虚拟电厂中风电机组出力的不确定性及预测误差,考虑了由多个风能预测服务商基于不同预测方法提供多个风电出力预测场景,以期望运行成本最小为目标,制定虚拟电厂每个场景对应的最优调度计划。为应对风力状况的随机波动,虚拟电厂当前时段考虑下一时段所有风电出力场景下的计划调整成本。并以期望运行总成本最小为目标,构建基于多风能预测结果的虚拟电厂柔性优化调度模型,并设计了日内虚拟电厂出力计划的滚动调度策略。通过数值仿真,对比分析了不同预测场景下虚拟电厂的运行成本,验证了所提模型的可行性和有效性。     

零相位跟踪控制的交流位置伺服系统研究

本文针对位置伺服系统中存在的跟踪误差,研究了零相位跟踪控制的交流位置伺服系统,提出了一种简便易行的设计零相位跟踪控制器的方法—扩展频带零相位跟踪控制。仿真和实验结果表明,采用零相位跟踪控制器来减小位置伺服系统的跟踪误差是十分有效的。     

基于PSO-LSSVM的离心泵状态预测方法

油田系统中离心泵因长期在恶劣环境下运行,受现场工况、介质腐蚀等因素影响,故障信号多表征出明显的非线性和时变非平稳性,数据量大,运行状态难以实时准确预测,本文提出了一种基于PSO（Particle Swarm Optimization,粒子群算法）优化LS-SVM（Least Squares Support Vector Machines,最小二乘支持向量机）的离心泵状态预测方法。首先利用粒子群算法的全局搜索特性,对最小二乘支持向量机的核参数g和惩罚因子C进行快速自动寻优,其次确定了平均绝对误差、平均相对误差和均方根误差为预测精度评估指标,最后通过实时采集的数据对本文的预测方法进行验证。结果表明：与LS-SVM预测模型相比,PSO优化LS-SVM模型降低了计算的复杂性,具有泛化能力强,预测精度高的优点,平均绝对误差、平均相对误差和均方根误差较LS-SVM模型分别减少了52%、56%和44%。该方法可为预测性维修提供理论依据,在工程实践方面具有良好的应用前景。     

Improved algorithm for optimum reactive power allocation

An improvised algorithm is presented for optimal VAr allocation in a large power system using a linear programming technique. The proposed method requires less computer memory than those algorithms currently available.