【作者】 杨波；

【导师】 汤文成；

【作者基本信息】 东南大学 ， 机械电子工程（专业学位）， 2023， 博士

【摘要】 H桥级联型电化学储能系统(Cascaded H-Bridge Battery Energy Storage System,CHBBESS),以下简称为直挂式储能系统,作为一种级联式变流技术与储能技术结合的新型储能技术形态,无需变压器直连中高电压等级电网,有效地提升了储能系统电能转换效率及支撑电网能力。同时,由于系统采用了模块化级联结构,并辅以相应的优化控制策略,将电能均匀地分散至每个功率模块中,可提升系统的有效容量及其利用率,降低系统输出谐波,提升电能品质。CHB-BESS在大规模新能源消纳、支撑电网稳定运行、区域电网黑启动等领域展现了较强的技术优势,具有广阔的应用前景,本文正是以CHB-BESS为研究对象,针对其关键技术展开研究。(1)针对CHB-BESS较为复杂的电气拓扑结构,建立了其连续域等效开关数学模型,推导了其电网侧外部变量(网侧电压、电流等)与内部状态变量(功率模块电容电压、电池簇电压、电池SOC等)关系式;以系统接入电压等级、电能转换速率、二倍频波动抑制等需求为设计目标,提出一种关键参数联合设计方法,降低运行目标期望值与工程设计参数间的偏差,为后续研究奠定理论基础。(2)在CHB-BESS系统中采用传统的矢量控制方法,存在多控制目标无法兼顾以及多控制环嵌套的问题,针对这个问题提出了适用于CHB-BESS的基于安全约束快速电压预测控制方法,可有效提升系统动态响应能力,同时可实现多目标的并行优化控制;提出一种适用于直挂式储能系统的电网频率主动支撑控制方法,在兼顾SOC末段充放电安全性约束前提下实现其对电网的快速主动支撑;提出一种基于模型预测的冗余控制策略,实现冗余模块的快速投切,有效提升了系统的故障穿越能力。(3)针对CHB-BESS电池分散及能量均衡问题,能量均衡环节分设三个控制层级,提出一种基于零序电压注入的变系数直挂式储能系统相间均衡控制策略,在保证系统交流侧输出品质前提下实现三相间的能量均衡;提出一种基于偏置电压分量的相内电池簇SOC均衡控制方法,实现各电池簇的独立控制;提出一种适用于CHB-BESS的电芯SOC动态修正方法,提升电池系统荷电状态估算精度。(4)基于上述研究内容,建成电压等级10kV、额定功率2MW、额定容量1MWh直挂式储能系统示范工程。对系统内功率单元及电池组进行通用型模块化设计;设计冗余功率模块,具备在线投切、带电运维功能;采用集装箱预置的集成方式,在系统绝缘耐压、温度控制等方面均进行了10kV电压等级的针对性设计;并在示范工程中对本文所提关键技术进行应用验证。更多还原

【Abstract】 Cascaded H-Bridge Battery Energy Storage System(CHB-BESS),as a new form of energy storage technology combined with cascade converter technology and electrochemical energy storage technology,is directly connected to medium-high voltage power grid without transformer,effectively improving the energy conversion efficiency and supporting power grid capacity of the energy storage system.Due to the modular cascade structure of the system and the corresponding optimization control strategy,the electric energy is evenly distributed into each power module,which can improve the effective capacity and utilization rate of the system,reduce the system output harmonics,and improve the power quality.CHB-BESS has shown strong technical advantages and broad application prospects in the fields of large-scale new energy consumption,supporting stable operation of power grids,and black start of regional power grids.This paper is taking CHB-BESS as the research object to carry out research on its key technologies.(1)In view of the relatively complex electrical topology of CHB-BESS,the mathematical model of its continuous domain equivalent switch is established,and the relationship between its external variables(grid voltage,current,etc.)and its internal state variables(power module capacitance voltage,battery voltage,battery SOC,etc.)is derived.Aiming at the requirements of system access voltage level,power conversion rate,second harmonic wave suppression and other requirements,a joint design method of key parameters is proposed to reduce the deviation between the expected value of operation objectives and engineering design parameters,laying a theoretical foundation for subsequent research.(2)The traditional vector control method used in CHB-BESS system has the problems that multiple control objectives cannot be considered and multiple control loops are nested.In this paper,a fast voltage predictive control method based on security constraints for CHB-BESS is proposed,which can effectively improve the dynamic response of the system and realize multiobjective parallel optimal control.An active support control method of power grid frequency for direct-mounted energy storage system is proposed,which can realize its fast and active support to the power grid under the premise of taking into account the security constraints of SOC terminal charging and discharging.A redundant control strategy based on model prediction is proposed to realize the fast switching of redundant modules and effectively improve the fault traversal capability of the system.(3)In order to solve the problem of CHB-BESS battery dispersion and energy balance,this paper sets the energy balance control system into three control levels.In this paper,a phaseto-phase balance control strategy of variable coefficient direct-mounted energy storage system based on zero-sequence voltage injection is proposed to achieve the energy balance between three phases under the premise of ensuring the output quality of the AC side of the system.A SOC equalization control method based on the bias voltage component is proposed to achieve independent control of each battery cluster.This paper proposes a dynamic correction method for the SOC of the cell for CHB-BESS to improve the estimation accuracy of the state of charge of the battery system.(4)Based on the above research contents,a demonstration project of direct-mounted energy storage system with voltage level of 10 kV,rated power of 2 MW and rated capacity of 1 MWh was built.The modular design of power unit and battery pack in the system is carried out.Redundant power module is designed,which has online switching and online maintenance functions.The system adopts the integrated mode of container preset,and has carried out targeted design of 10 kV voltage level in terms of system insulation and voltage resistance,temperature control,etc.The key technologies mentioned in this paper are applied and verified in the demonstration project.更多还原