Passivity-based control design for a grid-connected hybrid generation system integrated with the energy management strategy

Hybrid generation systems produce electric energy from a wide variety of energy sources, including renewable sources. A hybrid system based on renewable sources usually consists of two or more renewable energy sources with the possibility of including storage units so as to enhance the reliability of the system. The hybrid system requires an energy strategy that determines the operation point of each element of the system depending on multiple variables and subjected to the constraints inherent in this kind of systems. In addition, the system needs controllers to command each of these elements in order to reach the operation point established by the energy strategy. Here, we propose a control design via passivity-based control integrated with an energy management strategy for a hybrid generation system based on solar energy and coupled with the grid. The performance of the control methodology is extensively assessed through computer simulation using a comprehensive nonlinear model of the plant. The results show that the controlled system accomplishes the control tasks with good responses, working under very different atmospheric conditions and required load power.     

Decentralized voltage control of distributed generation using a distribution system structural MIMO model

The voltage control problem in Low Voltage (LV) distribution systems is becoming increasingly important due to the presence of Distributed Generation (DG). Recently, DG units have been proposed to contribute to voltage control according to a Volt/Var law which does not realize regulation. Moreover, since the existing LV systems are operated in a decentralized way without communication links, the simultaneous response of the controllers of the DG units may result into operational conflicts and instability. To overcome these problems, the present paper illustrates a design methodology for decentralized voltage controllers that act on DG reactive power injections. The controllers are suitable for the LV systems since they ensure voltage regulation and stability by using only local measurements and without information exchanges. The design is based on a proposed structural MIMO model of the distribution system. Robust stability is also analyzed: changes in the operating conditions of the distribution system are modeled as unstructured additive uncertainties affecting the MIMO model. A case study gives evidence of the applicability of the proposed design; the performance of the controllers in terms of both stability and regulation of the nodal voltages of three DG units connected to a LV distribution feeder is tested by numerical simulations; finally, a comparison with a Volt/Var technique is performed.     

基于模糊PID控制的微型燃气轮机发电系统研究

根据微型燃气轮发电机系统的动态特性,将微型燃气轮机及其电气部分当作一个整体,建立了微型燃气轮机发电系统完整的数学模型,并在转速环加入模糊PID控制器,分析了微型燃气轮机系统孤网带负荷时的动态特性。仿真结果验证了基于模糊PID控制的微型燃气轮机发电系统具有良好的稳定性和灵活性。     

基于AGC的光伏电站一次调频控制

逆变器调节速度快,且利用光伏电站的调频能力可降低常规调频备用容量,光伏电站深入参与电网一次调频将是一种很好的选择。基于此,本文在光伏电站自动发电控制（AGC）系统基础上增加光伏电站有功-频率下垂控制特性,使光伏电站在无需额外硬件增加或改造基础上实现AGC和一次调频功能一体化集成;其次,增加一次调频和AGC配合策略,实现二者无缝配合;最后,针对有功功率跟踪能力的不足对有功分配策略进行改进,提高了有功功率控制精度,提升了调频贡献能力。经过西北电网组织的新能源电站快速调频试验的验证,基于光伏电站自动发电控制系统的光伏电站一次调频控制具备较好的响应速度和调频贡献能力,能够为电网频率稳定提供支撑作用。     

The Catalog Management Strategy of Distributed Data Base Systems

In this paper the catalog management strategy of the successfully integrating and running DDBMS C-POREL is summarized.The new catalog management strategy and its implementation scheme are based on the analysis of the catalog management methods of the pioneer DDBMS.The goal of the new strategy is to improve the system efficiency.Analysis and practice show that this strategy is successful.     

可再生能源分布式发电能量管理的复杂性研究

本文主要研究可再生能源分布式发电系统能量的优化与协调问题.基于系统能量管理中优化与协调控制问题的复杂性,提出采用基于Agent的建模与仿真方法进行研究.针对系统要求,以分散式发电系统的实体节点的映射封装Agent,提出了智能混合控制Agent的概念,建立了3层混合Agent的内部结构模型;并建立了以个体层、组织层和社会层构成的3层动态层级MAS体系结构,进一步辅以主导Agent和移动Agent辅助系统优化与决策,最终建立了一种新的面向再生能源的分散式发电系统能量管理的MAS宏观模型.最后应用有色Petri网对系统的优化与协调过程进行了动态模拟,验证了所提出的结构的正确性、合理性和有效性.     

Islanding detection of distributed generation by using multi-gene genetic programming based classifier

This paper proposed a new method for detecting islanding of distributed generation (DG), using Multi-gene Genetic Programming (MGP). Islanding has been a serious concern among power distribution utilities and distributed generation owners, because it poses risks to the safety of utilities’ workers and consumers, and can cause damage to power distribution systems’ equipment. Therefore, a DG must be disconnected as soon as an islanding is detected. In addition, an islanding detection method must have high degree of dependability to correctly discriminate islanding from other events, such as load switching, in order to avoid unnecessary disconnection of the distributed generator. In this context, the novelty of the proposed method is that the MGP is capable of obtaining a set of mathematical and logic functions employed to detect and classify islanding correctly. This is a new approach among the computational intelligent methods proposed for DG islanding detection. The main idea was to use local voltage measurements as input of the method, eliminating the need of complex and expensive communication infrastructure. The method has been trained with several islanding and non-islanding cases, by using a power distribution system comprising five concentrated loads, a synchronous distributed generator and a wind power plant. The results showed that the proposed method was successful in differentiating the islanding events from other disturbances, revealing its great potential to be applied in anti-islanding protection schemes for distributed generation.     

Dynamic switching based fuzzy control strategy for a class of distributed parameter system

In this work, a dynamic switching based fuzzy controller combined with spectral method is proposed to control a class of nonlinear distributed parameter systems (DPSs). Spectral method can transform infinite-dimensional DPS into finite ordinary differential equations (ODEs). A dynamic switching based fuzzy controller is constructed to track reference values for the multi-inputs multi-outputs (MIMO) ODEs. Only a traditional fuzzy logic system (FLS) and a rule base are used in the controller, and membership functions (MFs) for different ODEs are adjusted by scaling factors. Analytical models of the dynamic switching based fuzzy controller are deduced to design the scaling factors and analyze stability of the control system. In order to obtain a good control performance, particle swarm optimization (PSO) is adopted to design the scaling factors. Moreover, stability of fuzzy control system is analyzed by using the analytical models, definition of the stability and Lyapunov stability theory. Finally, a nonlinear rod catalytic reaction process is used as an illustrated example for demonstration. The simulation results show that performance of proposed dynamic switching based fuzzy control strategy is better than a multi-variable fuzzy logic controller.     

A two-level emergency control scheme against power system voltage instability

A two-level adaptive control scheme against power system voltage instability is proposed, to deal with emergency conditions by acting on distribution transformers and/or by curtailing some loads. The lower level includes distributed controllers, each acting once the voltage at a monitored transmission bus settles below a threshold value. The upper level benefits from wide-area monitoring and adjusts in real-time the voltage thresholds of the local controllers. Emergency detection is based on the sign of sensitivities. The proposed scheme is robust with respect to communication failures. Its performance is illustrated through detailed simulations of a small but realistic 74-bus test system.     

基于紧急功率支援的直流输电系统研究

VSC-HVDC通过利用全控期间的电压源型换流器,在一定程度上,克服了传统直流输电的不足之处,同时实现了有功功率和无功功率的独立控制。本文通过在仿真软件PSCAD/EMTDC中搭建了基于电压源型换流器的三端直流输电系统,并设计采用了改进型PID控制算法与功率支援模块用以快速改变直流线路传输功率,通过动态电流限幅环节抑制交流侧故障过电流,针对逆变器交流侧的几种常见故障和直流线路故障时系统的运行状况进行了仿真分析,并对不同的故障设计了不同的运行方案,仿真结果表明该系统在多种故障情况下均能够有效的保持系统频率与电压的稳定。     

A distributed parallel alarm management strategy for alarm reduction in chemical plants

A distributed parallel alarm management strategy based on massive historical alarms and distributed clustering algorithm is proposed to reduce the number of alarms presented to operators in modern chemical plants. Due to the large and growing scale of historical alarms as the basis of analysis, it is difficult for traditional alarm management strategy to store and analyze all alarms efficiently. In this paper, by designing the row key and storage structure in a distributed extensible NoSQL database, the strategy spreads alarm data in a group of commercial machines, which ensures the capacity and scalability of the whole system. Meanwhile, Distributed Parallel Query Model (DPQM) proposed as a unified query model provides efficient query and better integration of distributed platform. Based on the characteristics of alarms and time-delay correlation of alarm occurrence, alarm similarity criteria are proposed to effectively identify repetitive and homologous alarms. In order to group massive alarm data, a new distributed clustering algorithm is designed to work concurrently in MapReduce frameworks. The test results using alarm data from real chemical plants show that the strategy is better than traditional method based on MySQL at system performance, and provides excellent redundant alarm suppression in both normal situation and alarm flooding situation.     

Design patterns for real-time distributed control system benchmarking

In this paper, we describe the design and development of a simulation–agent interface for real-time distributed control system benchmarking. This work is motivated by the need to test the feasibility of extending agent-based systems to the physical device level in manufacturing and other industrial automation systems. Our work focuses on the development of hybrid physical/simulation environment that can be used to perform tests at both the physical device level, as well as the planning and scheduling level of control. As part of this work, we have extended the proxy design pattern for this application. This paper focuses on the resulting software design pattern for distributed control system benchmarking and provides examples of its use in our hybrid physical/simulation environment.     

Distributed measurement and control system based on microcontrollers with automatic program generation

The paper describes an open architecture microcontroller based distributed measurement and control system with automatic generation of application program. Interpretation of functions and generation of program for control of the newly added distributed unit or distributed unit of a new type connected to the system performs automatically, without user assistance. The elements of the system are interconnected by means of a serial common bus according to the reduced OSI protocol. The proposed concept was tested in a system developed by using 8-bit Atmel microcontrollers of 89S and 89C series. Apart from the central unit, intelligent distributed units were developed for the control of a stepper motor, programmable linear movement, control of halogen lamps, acquisition and generation of analogue, digital and timing pulses and a real time clock (RTC).     

变速恒频双馈风力发电系统网侧变流器控制策略研究

变速恒频双馈风力发电系统通常采用磁链定向、转子磁链定向和气隙磁场定向进行控制,这些控制系统的结构设计复杂,控制精度不高。为了进一步提高风力发电系统的控制效果,论文对变速恒频双馈风力发电系统的双P W M变流器进行了详细的分析,针对网侧变流器建立了数学模型,对网侧变流器的控制策略进行了研究,并采用电压、电流双闭环控制策略对系统中的网侧变流器进行控制。仿真结果显示,双闭环控制策略系统经过短暂的振荡之后能够快速实现状态的转变,达到预期效果。     

基于PMAC的航空结构件柔性工装分布式控制系统设计

航空结构件是航空飞行器中的重要组成部分,航空结构件的自动化柔性工装质量直接影响航空飞行器的飞行安全水平。为降低系统位置和姿态控制误差,减小航空结构件的磨损面积,设计了基于PMAC的航空结构件柔性工装分布式控制系统。采用PMAC运动控制器,接收电子部件的反馈信号,控制步进电机、直流电机和交流电机。结合工控机、定位器、伺服电机和分布式通信网络,完成硬件系统的设计。根据航空结构件柔性工装操作设备的组成结构和工作原理,构建相应模型。确定航空结构件在目标曲面上的柔性工装位置,从移动位置和装配力两个方面,计算柔性工装控制量。在PMAC控制器的作用下,通过位姿的调整实现系统的航空结构件柔性工装分布式控制功能。系统测试结果表明,设计分布式控制系统的位置和姿态控制误差分别降低了13cm和0.32°,且设计系统控制下航空结构件的磨损面积较小。     

A reactive control strategy for networked hydrographical system management

A reactive control strategy is proposed to improve the water asset management of complex hydrographical systems. This strategy requires the definition of rules to achieve a generic resource allocation and setpoint assignment. A modelling method of the complex hydrographical network based on a weighted digraph of instrumented points is also presented. The simulation results of the strategy applied to a hydrographical system composed of one confluent and two diffluents show its efficiency and its effectiveness.     

基于分布参数控制理论的可变质产品最优经营策略

应用分布参数控制理论,研究了零售企业对于可变质产品的最优经营管理问题.通过建立可变质产品的最优经营管理的分布参数控制系统模型,得出了零售企业每个瞬间每种可变质产品的最优经营管理策略,并对空间伴随函数和控制变量给出了明确的经济学解释.该模型更合理地描述了可变质产品的实际经营特性,具有一定的现实意义和实用价值.     

Impact of wind farms on disturbance detection and classification in distributed generation using modified Adaline network and an adaptive neuro-fuzzy information system

A new disturbance detection and classification technique based on modified Adaline and adaptive neuro-fuzzy information system (ANFIS) is proposed for a distributed generation system comprising a wind power generating system (DFIG) and a photovoltaic array. The proposed technique is based on a fast Gauss–Newton parameter updating rule rather than the conventional Widrow–Hoff delta rule for the Adaline network. The voltage and current signals near the target distributed generation (DG), particularly the DFIG, whose speed varies from minimum to the maximum cut-off speed, are processed through the modified Adaline network to yield the features like the negative sequence power, harmonic amplification factor (HAF), total harmonic distortion (THD), etc. These features are then used as training sets for the ANFIS, which employs a gradient descent algorithm to update its parameters. The proposed technique distinguishes the islanding condition of the distributed generation system with some other disturbances, such as switching faults, capacitor bank switching, voltage swell, voltage sag, distorted grid voltage, unbalanced load switching, etc. which are referred to as non-islanding cases in this paper.     

Hardware-in-the-loop validation of a power management strategy for hybrid powertrains

Previously, a hybrid powertrain management strategy was developed that controls the power sources based on frequency content, mitigating aggressive engine transients. This article presents a hardware-in-the-loop validation of this strategy, with a real engine and battery integrated into a diesel hybrid electric vehicle simulation, thereby allowing for a realistic evaluation of fuel economy, soot emissions, and battery life. Considering an aggressive drive cycle and a state-of-charge regulation strategy as a benchmark, the frequency-based strategy yields 5.9% increase in fuel economy, 62.7% decrease in soot emissions, and 23% reduction in effective Amp-hours processed, which should yield an increase in battery life.