【作者】 王鹤；

【导师】 李国庆；

【作者基本信息】 华北电力大学 ， 电力系统及其自动化， 2014， 博士

【摘要】 微电网具有先进灵活的运行控制方式,并且整合了高比重的分布式清洁能源,是未来智能电网中配电网的重要组成部分。与传统配电网相比,微电网中大量的分布式电源不仅会改变潮流的方向,而且风力发电、太阳能光伏发电等新能源的随机性也会给微电网运行带来深刻的影响。在多种分布式电源接入条件下,采用先进可靠的运行控制方法实现微电网的安全稳定运行是一项十分重要而又面临很多亟待解决问题的研究课题。本文紧紧围绕这一中心课题,从微电网中各种分布式电源的接入控制入手,对微电网的运行控制策略、运行方式转换以及电能质量管理进行了深入的研究。首先,分析微电网运行控制的基本理论,研究微电网的结构组成、分布式电源接口逆变器的控制方法以及微电网的基本控制策略。在此基础上,对微电网中多种分布式电源的接入和控制方法进行研究。建立微型燃气轮机和燃料电池发电的动态数学模型,并设计相应的电力电子设备接口将其稳定地接入微电网。仿真分析微型燃气轮机和燃料电池发电对变化负荷的跟踪能力,并针对微电网并网及孤岛的不同运行方式给出相应的分布式电源接口逆变器控制方法,满足不同情况下的负荷需求。此外,本文还研究了永磁直驱风力发电、太阳能光伏发电等多种分布式电源接入微电网的控制方法,为微电网中多种分布式电源在不同自然条件下的灵活组合奠定基础。双馈感应风力机组(DFIG)是目前风力发电的主流机型。为了满足DFIG的分布式应用发展需求,本文针对微电网的并网及孤岛运行方式分别提出相应的DFIG控制方法。微电网并网运行时DFIG捕获最大风能,并在此基础上针对微电网线路中电阻参数较大的情况,采用灵敏度分析方法调整DFIG输出的无功功率以抵消有功功率变化引起的电压波动；微电网孤岛运行时,DFIG通过桨距角控制和储能装置的配合,以输出电压频率和幅值可控的方式运行,并且模仿下垂特性直接与微电网中其他采取下垂控制的逆变型分布式电源配合。仿真分析结果表明本文提出的DFIG控制方法能够调节微电网的有功功率平衡并维持系统的电压稳定,在并网及孤岛运行方式下都能够保持微电网的平稳运行。在实现多种分布式电源稳定接入微电网的基础上,研究微电网的运行控制策略和运行方式转换。针对主从结构、对等结构和分层结构的微电网分别提出了相应的运行控制策略。在分层结构微电网中,选择主调频电源对孤岛运行微电网的频率进行二次调节,为微电网重新并网创造条件,同时提高电能质量,避免稳定的频率偏差对储能装置和用户的影响。微电网由并网向孤岛运行方式的转换需要连续进行孤岛检测,一旦发现微电网实际进入孤岛运行状态,立即调整分布式电源的控制方法,以维持稳定的孤岛运行。针对微电网由孤岛向并网运行方式的转换,考虑两种不同的情况：对于规模较小的主从结构的微电网,提出一种有效的微电网运行方式自动转换方法。该方法通过连续检测大电网侧和微电网侧电压的幅值和相角,判断微电网的实际运行状态,并且结合正序电压提取、锁相环和低通滤波等环节监控微电网的运行,在满足并网条件时实现微电网由孤岛向并网运行方式的平稳过渡。对于规模较大的分层结构的微电网,通过连续检测微电网侧和大电网侧的频率以及电压幅值和相角,判断微电网的实际运行状态,并采用电压灵敏度分析方法调节微电网并网接口处电压使其满足并网条件,实现微电网孤岛向并网运行方式的平稳转换。作为智能电网的重要组成部分,微电网的一个重要的目标是向用户提供优质的电能。本文最后研究微电网的电能质量,利用微电网中具有一定调节能力的分布式电源对电能质量进行管理。首先分析微电网中谐波源不在分布式电源接入点情况下进行谐波补偿时补偿效果的影响因素,并在此基础上提出一种微电网中基于逆变型分布式电源控制的重要节点电能质量管理方法。该方法选择逆变电源附近重要程度最高的节点并以其为目标管理微电网的电能质量,提取逆变器连接支路电流和目标节点电压中的谐波和不平衡分量,通过搜索的方法确定各个分量的最优补偿系数,并形成最终的补偿电流。该方法能够充分利用微电网中现有设备提高整体的电能质量,而且本文提出的方法还能够根据用户实际需要灵活的选择补偿目标节点和补偿水平,对提高微电网的管理水平,向用户提供可选择的优质电能具有重要的实际意义。更多还原

【Abstract】 Microgrid is the significant part of the distribution network in the future smart grid, which has advanced and flexible operation and control pattern, and integrates distributed clean energy in high proportion. Compared with triditional distribution network, distributed sources in the microgrid can change the direction of the power flow, and the new energy such as the wind and solar photovoltaic can also bring profound effects to microgricd operation for their randomness. In the condition of various distributed generations, it is a very important and more wrong-headed subject that we complete the safe and stable operation for the microgrid using advanced and stable control method. In this paper, we begin with the access control for various distributed sources, and do deeply research on the issue of running control strategy, operation mode conversion and power quality management.Firstly, we analysis the basic theory on operation control for the microgrid. We also do some research on structure composition of the microgrid, control methods of interface inverter for distributed sources and the basic control strategy of the microgrid. On this basis, we do other researches on the access and control methods for various distributed sources. In addition, we establish the dynamic mathematical model for the microturbine and the fuel cell generation. Further more, we design the power electronical interface equipment correspondingly, which can be accessed to the microgrid. In order to meet different load demands, we analyze the tracking ability to loads for the microturbine and the fuel cell generation using simulations, and show the control methods of interface inverter for distributed sources according to different operation modes for the grid connected and islanding. At last, we do some researches on control methods for various distributed sources accessing the microgrid such as direct driven permanent magnet wind power generation and solar photovoltaic. The work will lay the foundations for flexible combination of various distributed sources in different natural conditions. The work will also provide some references for widespread use of the microgrid.Doubly fed induction generation (DFIG) is the main type of engine for wind power generation. In order to meet the distributed applying and developing demands, we respectively suggest the corresponding control methods to the operation mode of the grid connected and islanding. At the time of grid connected operation, DFIG can capture the most wind energy. According to the condition of bigger resistance parameter, we adopt sensitivity analysis method to adjust reactive power from DFIG, which can offset voltage fluctuation from active power changing, At the time of islanding operation, DFIG, which combined with the control of pitch angle and energy storage device, acted as voltage frequency and amplitude controllable. Thus, DFIG can cooperate with other droop control inverter-based distributed sources by simulate droop characteristic. The simulation results show that the new control method from this paper could adjust the active power balance in the microgrid and keep system voltage stability. This new method can also keep the microgrid running stable in the condition of grid connected and islanding operation.Based on the foundation that various distributed sources access to the microgrid, we do the research on the microgrid operation strategy and operation mode conversion. According to different microgrid structures, such as master slave structure, peer to peer structure and hierarchical structure, we put forward the corresponding operation strategy respectively. For the hierarchical structure microgrid, we complete the secondary frequency regulation for the islanding operation by choosing the principle frequency regulation source. This can improve the power quality and avoid the influence of energy storage devices and users caused by stable frequency offset. This can also create conditions for the reconnection of microgrid. Conversion from the grid connected operation to the islanding operation need continuous islanding detection. Once found the actual islanding state of microgrid, we adjust the control method of distributed source to maintain the stability of the islanding operation immediately. For the conversion form the islanding operation to the grid connected operation, we consider two cases:For the small scale master-slave structure, we propose an effective auto-switch operation mode for the microgrid, which can determine the operation states by contimuously detecting the voltage phase angle and amplitude in the large grid side and the microgrid side. And the new method can monitor the microgrid operation combining with extracting the positive sequence voltage, phase-locked loop and low-pass filter. Moreover, the method can also realize the smooth transition of grid connected and islanding operation. For the large scale hierarchical structure, the new method can determine the operation states by contimuously detecting the voltage frequency, amplitude and phase angle in the large grid side and the microgrid side. And it can also realize the smooth transition of grid connected and islanding operation by adjusting the interface voltage using voltage sensitivity analysis method.Microgrid is a significant part of the smart grid, an important target of whose is to supply electricity to customers of high quality. The last work of this paper is to study the power quality in the microgrid, and manage the power quality using distributed sources with regulating ability. Firstly, we analyze the influencing factors of harmonic compensation effects in the condition that the harmonic source is not in the access point of the distributed sources. Then a kind of power quality management method for important nodes is proposed, which is based on the inverter interfaced distributed sources controlling. For this method, the most important nodes near the inverter interfaced sources are chosen as the target to manage the power quality in the microgrid. In order to get the final compensation currents, the harmonic and the unbalanced component in the branch current of inverter and the target node voltage are extracted, and optimal compensation coefficients of every components are determined by searching. This new method can sufficiently use the existing equipment in the microgrid to improve the power quality entirely. In addition, the new methods in this paper can also flexiblely choose the target nodes and the level for compensation. It is of practical significance to improve management level in the microgrid and supply optional and top quality electricity to the customers.更多还原