【作者】 胡斌；

【导师】 周念成；

【作者基本信息】 重庆大学 ， 电气工程， 2011， 硕士

【摘要】 本论文受重庆市自然科学基金(CSTC2009BB6190)和输配电装备及系统安全与新技术国家重点实验室自主研究项目(2007DA10512709208)的资助。微网是由分布式电源(Distributed Generation, DG)、本地负荷和储能装置组成的独立可控系统。微网中的DG按输出功率调节特性可分为间歇性电源和连续性电源两类,间歇性电源的输出功率受天气等自然条件的影响较大,出力具有明显的波动性和间歇性,连续性电源具有相对可靠的一次能源供给和连续的出力调节能力,为满足本地用户的不同用电需求和微网运行状态的无缝平滑转换,须在微网中配置适当的储能装置。当微网的网络结构发生变化时,如何对微网中的DG、储能装置、本地负荷、开关进行有效的协调控制,以保证微网在不同运行状态下都尽可能满足本地用户的要求,是微网安全稳定和可靠运行的关键。因此研究多种能源混合微网的协调控制策略对于微网应用和研究具有重要意义。本文针对包含多种连续性和间歇性DG、敏感负荷以及储能装置的分层控制结构的微网,提出了一种基于状态转换的协调控制策略。①根据微网中微源的功率调节特性将微源分为间歇性电源、连续性电源、储能装置,建立各类微源的仿真模型并研究了微源的动态响应特性。为保证可再生能源的最大利用率,间歇性电源采用最大功率跟踪控制方式(Maximum Power Point Tracking, MPPT),不参与微网系统的有功功率调节。连续性电源是微网的主要能源形式,具有充足的一次能源和有功调节能力,但微型燃气轮机和燃料电池等连续性电源有功调节速度较慢,不能响应快速的负荷变化,须配合储能装置以保证微网在各种运行状态的可靠供电。②研究了两级分层控制结构微网的中央控制器(MicroGrid Central Controller, MGCC)和本地控制器,其上层为MGCC利用所采集的负荷信息、DG和储能装置燃料情况、运行状态以及外部电力市场信息,为连续性DG提供有功和无功出力设定值,以达到最优功率分配目的,同时还实现微网运行状态转换;底层包括微源控制器(Microsource Controller, MC)和负荷控制器(Load Controller, LC)为执行MGCC具体操作指令的本地控制单元。分析了微网中电力电子接口微源本地控制器的三种控制方式,包括恒功率控制(PQ control)、下垂控制(Droop control)和恒压恒频控制(V/f control);阐述了中央控制器的结构和功能,研究了中央控制器的功率管理单元、同步并网单元和运行状态管理单元。③提出一种基于状态转换的微网协调控制策略。根据本地负荷的用电需求对微网可能出现的运行状态进行简化组合,得到微网中允许出现的有效运行状态。通过将微网当前运行状态和触发事件作为中央控制器的输入变量,各可控元件的控制方式作为输出变量,制定微网运行状态转换方案。为保证敏感负荷的不间断供电,同时考虑微网所有运行状态下系统频率无差调节和储能装置的容量限制,提出了本文定义运行状态下各元件相应的控制方式和触发事件。④利用PSCAD/EMTDC软件仿真分析了典型状态转换过程中的动态响应特性,验证了所设计的微网协调控制策略的可行性。针对本文提出的微网状态转换控制策略,对微网从连续性连状态转换到连续性支持状态、综合支持状态转换到综合连接状态和综合稳定状态转换到间歇性稳定状态等三种典型状态转换过程进行仿真分析。仿真结果表明所提出的协调控制策略能够实现微网状态平滑转换和频率无差调节,保证了敏感负荷的不间断供电和供电质量。同时,也尽可能得延长了储能装置的使用时间。更多还原

【Abstract】 This thesis was supported by Natural Science Foundation of Chongqing (CSTC 2009BB6190) and independent research project of State Key Laboratory of Power Transmission Equipment & System Security and New Technology(2007DA1051270 9208).As an independent controllable unit, microgrid comprises Distributed generation (DG), local loads and energy storage device. There are two categories of DGs in microgrid according to their power characteristics, intermittent DGs and continuous DGs. Since the output power of the former is greatly affected by physical conditions such as weather, their fluctuation and intermittence are distinct. On the other hand, the continuous DGs are capable of outputting comparative secure power and are with better power control ability. In order to satisfy the local customers’diversified demands and to realize the seamless operation mode switches, a proper Distributed Storage (DS) device is required in microgrid. For a microgrid contains several DGs, the key of a secure and stable operation is how to control the DG, DS, local loads and switches coordinately and effectively so as to meet the local customers’demands as much as possible when the microgrid structure changes. Furthermore, the coordinated control is also a necessary for an economical operation of microgrid. So the study of coordinated control strategy of a microgrid with multi-energy generation systems is significant for applications and research of microgrid. This paper designs a coordinated control strategy of microgrid based on state transition, which targets the hierarchical microgrid containing DGs, local loads and energy storage devices.①According to their power characteristics, DGs in microgrid are divided into three categories, intermittent DGs, continuous DGs and DSs. Simulation models are established to study the dynamic response characteristics of the DGs. Maximum Power Point Tracking (MPPT) is implemented in intermittent DGs, which, in turn, does not participate in the active power regulation, in order to obtain the maximum utilization rate of renewable energy. As a primary energy source in microgrid, continuous DGs are adept at energy and active power regulation, but some continuous DGs, namely micro turbine and fuel cell, are with relatively slow regulation rate. Consequently, they are unable to response promptly to rapid changes in loads unless it cooperates with a proper DS device. ②Microgrid central controller (MGCC) and local controller of a two-stage hierarchical control microgrid is studied. The upper structure, MGCC, aims to determine set value of active and reactive power through collected load information, fuel data of DG and DS, operation state and external electricity market information in order to achieve optimal power allocation as well as microgrid mode switches. The infrastructure includes microsource controller (MC) and load controller (LC), which are local controller units to carry out the operational command from MGCC. Three control methods used in local controllers of power-electronics interfaced DG are analyzed, including PQ control, Droop control and V/f control. And then the power management unit and synchronization unit of MGCC are studied after the expatiation of structure and functions of MGCC.③This paper proposed a coordinated control strategy of microgrid based on state transition. An allowable effective operation state is obtained through simplified combination of the possible operation modes in accordance with local power demands. By taking current operation state and trigger events as input variables of MGCC and the control methods of components as outputs, a real-time adjustment scheme of microgrid operation state is achieved. For the uninterruptible power supply of sensitive loads and with the consideration of no-deviation regulation for frequency under all operation states and the capacity limitation of energy storage devices, the corresponding control methods and trigger events of all components are proposed under the defined operation states in this paper.④Simulation model is established in PSCAD/EMTDC to analyze dynamic response in the process of typical state transition. The feasibility of the proposed coordination control strategy is verified. According to the proposed control strategy, three typical state transition progresses are simulated and analyzed in detail, namely from continuity connection state to continuity support state, from comprehensive support state to comprehensive connection state and from comprehensive standby state to intermittent standby state. The simulation results show that the coordinated control strategy is able to achieve smooth state transition and no-deviation regulation for frequency, to ensure a uninterruptible power supply and good power quality of sensitive loads and to extend the life of energy storage devices as much as possible.更多还原