【作者】 姜世公；

【导师】 王卫；

【作者基本信息】 哈尔滨工业大学 ， 电力电子与电力传动， 2013， 博士

【摘要】 微网（Microgrid）也称微电网，是一种由分布式电源、储能装置、能量变换装置、负荷、监控和保护装置等组成的能够实现自我控制、管理和保护的小型发配电系统，既可以与大电网联网运行，也可以孤岛运行。本论文在国家自然科学基金项目“光伏并网发电系统与电网间阻抗匹配关系及系统稳定性研究”的支持下，以阻抗匹配和混杂系统相关理论为基础，以孤岛运行模式下的微网为研究对象，针对发电单元与负荷间阻抗失配、能量管理过程中的多目标优化等问题，从分布式发电单元接口逆变器建模及运行特性、恒功率负载影响、多逆变器并联稳定性、微网混杂特性、能量管理策略及其优化控制等方面展开理论和实验研究。研究成果对微网结构及控制系统规范化设计，优化不同工况下能量管理策略具有一定的理论指导意义和实际应用价值。深入分析光伏发电单元、储能单元的拓扑结构和控制方式，建立各单元小信号模型，并根据系统运行过程中各单元不同工作特点设计相应的控制策略。针对光伏发电单元，提出基于功率前馈的控制方法，该方法通过将光伏阵列输出功率信息直接引入到交流电流控制环节，提高光伏发电单元对输入功率波动的响应速度；针对储能单元，在对比以往不同蓄电池充电方式的基础上，设计恒压限流充电控制策略，通过合理配置电压外环输出限幅来减小原有两阶段充电过程中的电压、电流冲击。上述研究也为后续基于阻抗匹配关系的系统稳定性分析和能量管理策略的优化设计奠定理论基础。以阻抗稳定性分析方法为基础，建立光伏发电单元孤岛运行模式下的逆变器输出阻抗模型，分析滤波参数对系统输出阻抗及稳定性的影响，并通过时域分析方法证明分析结果的正确性，从理论上阐明阻抗分析方法的合理性和可行性。详细阐述恒功率负载（CPL）的负阻特性特点及其影响系统稳定性的原因，提出一种虚拟电感控制方法，通过在原有控制结构中增加电感电流正反馈支路的方式降低逆变器输出阻抗，提高系统的稳定性，同时该方法对于系统的动态响应速度和谐波问题也有一定改善作用。另外，考虑到实际微网中多逆变器并联的特点，本文提出单个逆变单元的导纳域稳定性分析方法，并给出相应幅值和相角稳定条件及设计准则，降低微网设计的复杂性。在详细分析微网系统混杂特性基础上，借助混杂系统相关理论建立可完整描述其运行状态的混合逻辑动态（MLD）模型。该模型以光伏单元直流母线能量作为状态变量，给出包括连续状态变量、控制输入、逻辑变量和辅助变量的系统方程及相关约束条件。针对所建立的模型以最优控制和模型预测控制理论为基础，以减少储能装置的充放电切换次数为目标，建立其二次型目标函数并借助混合整数二次规划（MIQP）手段，采用分支界定法求解其最优输入控制序列。通过该方法可以有效减少分布式电源出力和负荷波动情况下储能装置的充/放电次数，提高微网系统的经济性和可靠性。基于混杂理论研究成果，为保证微网孤岛模式下的能量供需平衡，本文以减少微网运行中蓄电池充放电次数为目标，提出主从控制和对等控制相结合的综合控制策略。采用两组光伏发电单元通过下垂控制方式组成主功率单元，为系统运行提供电压和频率支撑；储能单元采用PQ控制作为从功率单元维持系统功率平衡，以提高系统的可靠性和冗余性。在此基础上，针对分布式电源和负荷的随机性特点，提出基于协同控制的能量管理策略，以光伏发电单元直流母线电压为标量，通过调整蓄电池充电电流和交流输出电流参考的方式保证系统能量供需平衡。该方法在保证光伏发电单元直流母线电压稳定的同时，可以快速应对分布式电源和负荷的功率波动。上述所提理论和控制方法通过Matlab/Simulink数字仿真和相关实验等手段进行可行性和有效性的验证。更多还原

【Abstract】 As a self-control, self-management and self-protection power generation anddistribution system, Microgrid is a cluster of interconnected distributed generationsystems, energy storage systems, power conversion devices, loads, monitoring andprotective equipments, which can operate on grid-connected or autonomous mode.Based on the impedance matching and hybrid system theory, the Microgridoperating on autonomous mode is studied in the dissertation, and theoretical studyand practical experiment of modeling to inverters, operating property analysis,restraining to adverse effect of constant power loads, stability analysis of paralleledinverters, hybrid property of Microgrid, power management and its optimal controlare carried out to resolve the unstability caused by mis-matching between thedistributed generation units and loads, and multi-target optimization of the powermanagement strategies. The research results show certain theoretical significanceand practical value for the interpretation of Microgrid structure, normalized controlsystem design and the performance optimization of power management strategy ondifferent operating modes.The topologies and control methods of photovoltaic power generation unitsand energy storage unit are analyzed and revealed in details. With their small-signalmodels, the control strategies are designed. For achieving better dynamicperformance of PV units, input power feed-forward control method is proposed, andthe output power messages of PV arraies are involved into inner current-loop toimprove response speed of output current when the input power is fluctuating. Forbattery energy storage unit, based on relative analysis of different charge methods, aconstant-voltage current-limiting control method is designed to decrease the surgeof current or voltage in traditional methods by regulating the limitation of outervoltage-loop output. The above mentioned property analysises lay a foundation forstability analyzed by impedance matching condition and optimization of powermanagement strategy.Based on the impedance matching theory, the output impedance model of PVunit is set up, filter parameters impact to the output impedance and system stabilityare certified by time-domain anslysis approach, the rationality and feasibility of theimpedance specification approach are clarified theoratically. The negativeincremental impedance property and degeneration of system stability of ACconstant power load (CPL) is studied by impedance specification approach. Avirtual inductor control method, which adopts an inductor current feedback closedloop, is proposed in order to damp the inverter equivalent output impedance and improve system stability. The system dynamic response is enhanced and harmoniccomponent at switching frequency is effectively suppressed. An admittancespecification is proposed to simplify the design process of Microgrid with numbersof distribution generations (DGs) operating in parallel. And the stable quantizedrelation between inverter output and load input admittance is indicated.By analyzing the hybrid property of Microgrid detailedly, a mixed logicaldynamical (MLD) model is set up with Hybrid theory. Choosing the energy in DCbus capacitor as state variable, the system function and constraint condition withcontinuous state variable, input control variable, logical variable and auxiliaryvariable are presented. Based on the MLD model, optimum control and modelpredictive control (MPC) theory, the quadric form objective function is designedand the optimal input control variable sequence is achieved by mixed integerquadratic programming theory and Branch&Bound method to reduce the batteriesswitching times between charge and discharge. Proposed method can improve theeconomy and reliability of Microgrid, and reduce the the batteries switching timesbetween charge and discharge when distributed generation output and loadsfluctuate especially the difference is small.Based on the MPC research results of Microgrid and aimed to reduce thebatteries switching times between charge and discharge, a combination controlstrategy is designed to improve the system reliability and redundancy. Two PV unitsare selected as master units by Droop control and provide voltage and frequencyreference, energy storage unit with PQ control acting as a slave unit to ensurepower balance for the whole system. Based on the random characteristics of PVgeneration and loads, cooperative control strategy of energy storage unit and PVunits is proposed. The DC bus voltage of PV units is considered for identificationsof energy storage unit switching function, and the system power balance is ensuredby adjusting the charge current reference of batteries and output current referenceof the inverter. With proposed method, both the stable of DC bus voltage and fastresponse to PV generation and loads fluctuation can be achieved. Finally, the digitalsimulations based on Matlab/Simulink and experiment platform are carried out, andconsequently the feasibility and validity of the proposed basic theory and keytechnique are verified.更多还原