微电网分层控制与优化运行研究

发布时间：2018-04-03 02:31

本文选题：分布式发电　切入点：微电网　出处：《华北电力大学》2014年博士论文

【摘要】：随着能源危机加剧、环境日益恶化,加之传统的集中供电方式暴露出诸多弊端,分布式发电技术逐渐受到关注。该技术有助于推动可再生能源的利用,并在一定程度上为传统电力系统提供了有效补充。然而在诸多优势的背后,其出力的随机性和惯性较小的问题限制了其应用范围,大规模接入更是会对电网安全稳定带来负面影响。因此微电网应运而生,成为分布式电源(DG)“友好”接入电网的途径。与以同步发电机为主的传统电力系统不同,微电网包含多种类型的DG,它们的特性和控制方式差距较大,难以标准化。当微电网进行分层控制后,二级控制和三级控制可以依据微电网中的各种测量值进行系统级调节。只需要借助微电网内部的通信,一些难以在DG本地侧实现的功能可由更高级的控制执行。这将有效的简化本地控制结构,有利于实现微电网控制的标准化。本文在国家重点基础计划项目(“973”计划)的资助下完成,研究内容涉及以下四个方面：DG的初级控制、改善无功分布的二级控制、抑制功率脉动的二级控制以及微电网的经济运行,本文的具体内容如下： (1)从微电网的架构和多种DG的数学模型出发,提出了一种微电网初级控制策略,协调了不同调频性质DG的控制,实现了储能、柴油发电机、风力发电以及光伏发电在微电网内共同运行。根据平均值建模方法,对微电网内部可控的电力电子器件以受控电压源和受控电流源形式进行建模,加快了多DG微电网仿真的速度。仿真结果验证了所提控制策略在光伏出力波动、负荷突变、孤岛与并网模式切换等情况下的可行性。 (2)针对传统下垂控制无功分配不均的问题,从下垂增益、负荷侧电压以及微电网传输线路阻抗特性等方面分析了经典电压/无功下垂控制无功负荷分配的机理。在此基础上,通过上传至微电网中央控制器(MGCC)的DG功率信息,建立了基于二级控制的微电网无功控制策略。该策略利用无功出力分配关系和空载输出电压的偏离程度构造势函数。MGCC根据势函数对各DG的空载输出电压进行集中调整,达到改善无功出力分配的目的。该控制方法不需要对经典的下垂控制进行改动,只需借助于MGCC与DG间的通信。另外,在仿真的研究中利用正则环流无功概念量化了环流的程度,并在不同负荷下考察了环流的特点和抑制效果。 (3)微电网内会包含一定比例的单相DG和负荷,这会导致微电网公共连接点(PCC)电压的不对称。在不对称电压下PQ控制的DG会产生有功和无功功率的二倍工频波动。通过对有功和无功脉动的机理分析,首次推导了有功和无功功率脉动的解析关系,并进一步揭示了正负序电气量对功率脉动的根本性影响。在此基础上,提出一种抑制功率脉动的二级控制策略。该方案根据最优化理论,以功率脉动幅值为优化目标,以功率脉动率和PQ控制的功率给定值为约束建立优化模型。利用优化结果,二级控制能够在无功脉动较大时实现对有功和无功脉动的同时抑制,达到功率脉动幅值和脉动率指标的深度优化。 (4)经济运行控制根据优化结果调整各DG的功率输出给定值,可视为微电网的顶层控制策略。由于微电网包含较大比例的间歇性能源,其出力波动对制定微电网发电计划带来较大困难。因此提出了基于机会约束规划的微电网经济运行模型,该模型考虑了储能充放电、备用容量配置以及功率平衡方面的约束。另外,光伏发电采用了一种考虑云量和地理因素的概率模型,该模型能够更真实地反映光伏出力的波动变化。在求解机会约束过程中,利用概率序列理论对光伏和风力发电的概率模型进行了离散化处理,将机会约束转化成了确定性的约束形式,使之可以通过TOMLAB等商业优化软件求解。仿真结果表明,与随机模拟求解相比,该方法具有计算速度快且结果稳定的优势。此外,为了考察概率性序列的合理性,还讨论了不同离散化步长对计算结果的影响,并进一步验证了所提出方法的有效性。
[Abstract]:With the aggravation of energy crisis, the deteriorating environment, coupled with the traditional centralized power supply mode exposed many shortcomings, distributed generation technology has attracted increasing attention. This technology helps to promote the use of renewable energy, and to a certain extent, the traditional power system provides an effective supplement. However in many advantages behind the randomness of the the problem of small inertia and the limitation of its application, large-scale access is will have a negative impact on the security and stability of power grid. So the micro grid came into being, become the distributed power supply (DG) "friendly" access to the grid.
Different from the traditional power system for synchronous generator based, micro grid contains many types of DG, characteristics and control methods of gap is large, difficult to standardize. When the micro grid hierarchical control, two control and three level control can be based on various measured values in the micro grid system only needs the regulation. Micro grid communication inside, some difficult to achieve in the DG local side function can be executed by more advanced control. This will simplify the local control structure, conducive to the realization of microgrid control standard. The project of the national key basic ("973") supported by, the research involves the following four aspects: primary control of DG, improved two level control the distribution of reactive power, two level control and suppression of power fluctuation of the micro grid economic operation, the specific contents are as follows:
(1) starting from the mathematical model of the micro grid architecture and a variety of DG, this paper presents a micro grid primary control strategy, coordinated control of different frequency properties of DG, the energy storage, diesel generator, wind power and photovoltaic power generation in micro grid in joint operation. According to the modeling method of the average value, the power electronic devices the micro grid interior controllable modeling with controlled voltage and current source form, accelerate the DG micro grid simulation speed. The simulation results show that the proposed control strategy in photovoltaic output fluctuation, load mutation, feasibility of island mode and grid connected mode switching condition.
(2) the traditional droop control without the problem of uneven distribution of work, from the load side voltage droop gains, and the power grid transmission line impedance characteristics of classic voltage / reactive power droop control mechanism of reactive load distribution. On this basis, through the micro grid uploaded to the central controller (MGCC) DG the power of information, establish a reactive power control strategy for microgrid based on two level control. The distribution of reactive power output and no-load output voltage deviation from the.MGCC potential function is constructed for centralized adjustment based on the potential function of each DG no-load output voltage by using the strategies to improve the reactive power allocation. The control methods. Need to change the classic droop control, only by means of communication between DG and MGCC. In addition, in the simulation study using the regular circulation of reactive power concept to quantify the degree of circulation, and studied under different load. The circulation characteristics and the effect.
(3) the microgrid will contain a certain proportion of the single-phase DG and load, which will lead to the micro grid point of common coupling (PCC) voltage asymmetry. PQ control under asymmetrical voltage DG will produce two times the frequency fluctuation of active power and reactive power. The mechanism of the active and reactive power fluctuation on the analysis. For the first time in the analysis of the relationship between active power and reactive power fluctuation are derived, and further reveals the fundamental influence on positive and negative electrical power pulsation. On this basis, put forward a kind of restraining power pulsation two level control strategy. Based on the optimization theory, the power pulse amplitude as the optimization goal, given power to power fluctuating rate and control of PQ value optimization model is established for the constraint. By using the optimization results, two level control can suppress the reactive power ripple when reactive power fluctuation on power and at the same time, achieve the power pulsation amplitude and pulse rate and depth Optimization.
(4) the power output of a given economic operation control to adjust the DG value according to the optimization results, can be regarded as the top control strategy of micro grid. The micro grid contains a larger percentage of the output fluctuation of intermittent energy, making the micro grid generation program to bring greater difficulties. Therefore proposed the chance constrained programming model based on the economic operation of the micro grid. The model takes into account the charge and discharge, spare capacity allocation and power balance constraints. In addition, the photovoltaic power generation using a probabilistic model of cloud cover and geographical considerations, this model can reflect the variation of the PV output. In the process of solving chance constraint, using the probabilistic sequence theory of probability model of photovoltaic and the wind power generation is discretized into a chance constraint constraint form of uncertainty, so that it can be through the TOMLAB commercial optimization software solution. The simulation results show that compared with the stochastic simulation solution, this method has fast calculation speed and steady advantage. In addition, in order to investigate the rationality of probability sequence, different discretization step on the calculation result is also discussed, and further verify the effectiveness of the proposed method.

【学位授予单位】：华北电力大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM732

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