【作者】 谭兴国；

【导师】 李庆民；

【作者基本信息】 山东大学 ， 电力电子与电力传动， 2014， 博士

【摘要】 近年来,因面临化石能源日渐短缺与枯竭以及全球气候变化等严峻现实问题,作为分布式可再生能源的有效组织形式,微电网技术在国内外得到前所未有的关注。储能作为微电网的重要组成部分,在微电网稳定控制、平抑可再生能源波动、电能质量补偿、削峰填谷、应急供电等领域可为微电网提供关键技术支撑。然而,受限于储能技术水平发展的掣肘,单一储能往往难以满足微电网内多种不同需求,发展复合储能技术,是目前在经济、技术上较为可行的解决方案。研究微电网复合储能关键技术,具有重要的现实意义和应用价值。本文着眼于微电网对储能技术的多种典型需求,针对微电网中复合储能的柔性控制与容量配置开展探索和创新研究,重点解决复合储能的多端口接入、储能变换器可靠容错运行、储能对微电网的关键支撑作用等基础性问题,在此基础上探讨微电网复合储能容量的多目标优化配置技术。以多绕组高频变压器为基础,构建了复合储能的多端口统一接入拓扑,揭示了端口间的功率传输规律及影响机制；基于超级电容和蓄电池相融合的三端口全桥复合储能等效电路,推导出三端口复合储能的平均电流小信号分析模型,并藉此获得三端口复合储能定功率传输策略；针对超级电容端口电压随储能容量波动较大的特点,研究得到一种异步占空比移相PWM算法,实现多端口变换器在功率传输过程中端口电压的匹配,可有效改善传输效率。上述研究为复合储能整体接入微电网所需的底层功率传输控制提供了技术基础。微电网储能装置的可靠性很大程度上取决于储能变换环节。在兼顾经济成本和控制性能的前提下,针对潜在的储能变换故障,研究三相四开关储能容错拓扑,并给出容错切换的临界条件和切换准则。准确快速地获取储能变换器的故障信息是实现故障容错的前提,针对建模中的故障信息丢失问题,引入电路状态逻辑构建了储能变换器混杂系统动态(HSD)模型,藉此获得一种基于电流状态残差演变特征的储能变换器故障诊断方法,可显著提高故障诊断的快速性。针对四开关变换器的内在缺陷,基于等效阻抗理论揭示了输出阻抗、逆变频率和辅助电容差异对输出不平衡的内在作用机制,根据调制信号与空间电压矢量作用时间的关联规律,推导出一种实现直流中点电位偏差前馈补偿的等效SVPWM控制方法,显著提高了四开关储能变换器容错运行的平衡度。可对微电网电能质量进行补偿的电力有源滤波器(APE),存在功能单一、造价较高等问题,而四开关储能变换器因减少了功率器件和辅助装置,在低成本功率变换领域的应用前景较好。为此,本文开展了低成本三相四开关储能型APF应用技术研究。推导出一种基于电源电流跟踪的微电网谐波和无功直接补偿策略,因无需检测谐波,可有效降低四开关APF的实现难度。进一步研究了电压跌落引起的微电网不平衡对四开关APF的影响机制,推导出基于线电压矢量合成的四开关APE电流参考值生成策略,以适应微电网中的特殊不对称情况。四开关储能型APF可对微电网提供多种柔性支撑。针对四开关储能型APF工作模式的自适应切换,借助坐标变换推导出不同模式下的指令电流算式,并给出切换控制的边界条件；针对四开关APF的物理实现,给出了APF关键控制参数的取值准则及定量计算方法,并得到一种基于周期积分的单相软件锁相方法,实现了对电源电流的精确滞环跟踪补偿。微电网复合储能容量的配置多依赖于工程经验,缺乏理论指导和定量评估标准,为此,本文深入研究了微电网复合储能容量的多目标优化配置技术。构建了以投资成本最低、功率平衡最优、可再生能源发电功率波动最小为目标的复合储能容量配置多目标优化数学模型,从滤波系数、功率限幅、储能充放电管理等角度阐明了影响复合储能优化效果的关键因素；提出一种基于目标函数适应度离差均值排序的子目标函数权重确定方法,用以重组目标函数,可有效降低粒子群优化求解算法的实施难度；为评估多目标最优解的有效性,定义了可再生能源波动系数和供求平衡匹配系数,可实现优化效果的定量评估。针对超级电容和蓄电池构成的典型复合储能,就容量的多目标优化配置开展算例分析,给出了典型目标函数的建立方法以及优化算法实现流程,量化比较了复合储能和单一储能的容量多目标优化配置效果,表明复合储能容量优化配置的合理性。基于构建的微电网实验平台,进一步开展了复合储能柔性控制实验研究。研制了三端口复合储能全桥变换器、三相四开关储能容错装置、储能型四开关APF等实验样机,给出了关键参数的优化结果和软硬件实现方法,重点开展了复合储能定功率控制、容错判断及切换、直接电流滞环跟踪、电能质量统一补偿、锁相跟踪等实验研究,验证了本文理论与方法的有效性。本文研究结果可为微电网复合储能装置的拓扑设计和工程应用提供理论基础和技术依据。更多还原

【Abstract】 As an effective way of integrating distributed renewable energy, micro-grid technology has received widely attention in recent years due to the depletion of fossil energy and the threat of global climate change. Energy storage is an indispensable component in micro-grid, and it could provide critical support for micro-grid, such as stability support, renewable energy power fluctuations smoothing, power quality compensation, load shifting, emergency power, etc. However, due to the limitations of energy storage technologies, it is difficult for a single form of energy storage to meet all the requirements perfectly in micro-grid. Since hybrid energy storage technology is becoming feasible and economical for micro-grid application, it is very important and of great value to study hybrid energy technology in micro-grid.In order to meet various requirements of micro-grid, hybrid energy storage flexible control and storage capacity configuration techniques are mainly discussed in the dissertation, which focus on hybrid energy storage multi-port access technology, energy storage converter fault-tolerant technology, and micro-grid critical support based on hybrid energy storage technology. Based on the above discussion, hybrid energy storage capacity allocation multi-objective optimization techniques are intensively studied.In order to make up feasible hybrid energy storage, the common multi-port topology for hybrid energy storage is presented based on multi windings high frequency transformer. Power transfer principle and affecting factors are revealed. For hybrid energy storage system constituted by batteries and ultra-capacitor, the average current small-signal analysis model of three-port hybrid energy storage topology is derived based on its equivalent circuit of three-port full-bridge converter; Moreover, the given power control strategy for three-port hybrid energy storage is proposed. In view of ultra-capacitor voltage verified with its capacity, an asynchronous duty cycle regulated phase shift PWM based on given power control strategy is introduced to match voltages in different ports, which helps to improve power transmission efficiency. This study provides theoretical support for hybrid energy storage bottom layer power transmission control in micro-grid application.The reliability of the energy storage device largely depends on its DC-AC converter. A three-phase four-switch fault-tolerant topology for energy storage application is proposed to balance cost and reliability performance. The fault tolerant critical condition and switching rules are also created. Accurate and rapid accessing to the fault information of hybrid energy storage converter is the premise of the fault tolerant control. To deal with missed fault information problem, circuit state logic is used to build hybrid system dynamic model of hybrid energy storage converter; an open circuit fault diagnosis method based on residual current vector character is introduced, which can effectively increase the speed of the fault detection technology; To overcome the inner shortcoming of three-phase four-switch fault-tolerant converter, the inherent mechanism of output impedance, inverted frequency and capacitor leading to the unbalanced output are revealed. Based on the relation of modulating signal and space vector action time, an equivalent SVPWM control method with DC bus midpoint compensation is proposed, which can significantly improve symmetry of the three-phase four-switch fault-tolerant converter.Due to the reduction of power components and auxiliary devices, four-switch three-phase converter shows good application prospect in low-cost converter. Furthermore, as an effective way of compensating power quality, active power filter (APF) costs much but its function is limited. Hence, a low cost four-switch shunt APF is put forward. For APF power quality control without load harmonic detection, a direct compensation method based on the supply-side current tracking is proposed, which can be used easily. Given the potential influences of power supply voltage imbalance in micro-grid, four-switch APF current reference generation strategy based on synthetic line voltage vector is proposed.Four-switch energy storage APF could provide various flexible supports for micro-grid. The unified modes self-adaptive switching method for four-switch energy storage APF is presented, based on coordinate transformation, current references calculation method in different modes and switching critical conditions is given. To build up four-switch APF, the criteria to obtain the control parameter and calculation method are given, and a single phase software phase locking method is used to fulfill exact power current hysteresis tracking.Due to the lack of theoretical guidance and quantitative assessment criteria, hybrid energy storage capacity configurations in micro-grid mostly depend on engineering experience, so hybrid energy storage multi-objective capacity configuration optimization techniques are deeply discussed. For typical applications in micro-grid, hybrid energy storage capacity configuration multi-objective optimization model is established, which includes objects such as lowest cost, best power balance level, and best smoothing effect on renewable energy; by analyzing filtering coefficient, output power limit and charging constraints, factors affecting optimization results are given. To determine weights of each objective function and rebuild multi-objective optimization function, an average fitness deviation ranking method is presented, which can be easily solved by particle swarm optimization (PSO) algorithm. To evaluate the impact of energy storage application on micro-grid, quantitative assessment indices of energy storage multi-objective optimization are provided, which include renewable energy fluctuation index and power balance index.Hybrid energy storage (made up of ultra-capacitor and battery) capacity multi-objective optimization example is given, typical object function setting up method and PSO optimization algorithm fulfilled by MATLABare given. Based on the proposed quantitative assessment indices, single battery and hybrid energy storage multi-objective compensation effects are compared with each other. Results show that hybrid energy storage is more feasible in micro-grid application.Based on micro-grid platform, hybrid energy storage related experimental researches are carried out. Experiment devices including three-port full-bridge hybrid energy storage converter, four-switch fault-tolerant converter and four-switch APF are designed; critical parameter, software and hardware design method are also given. Hybrid energy storage given power control, fault-tolerance judge and control, direct current tracking, unified power quality compensation experiments are mainly carried out, which further show the validity of the theory.The research achievements in the dissertation have further developed the fundamental theory, analysis method and innovation techniques of hybrid energy storage in micro-grid, which will provide important reference value for hybrid energy storage design and engineering application in micro-grid.更多还原