【作者】 李斐；

【导师】 黎灿兵；

【作者基本信息】 湖南大学 ， 电气工程， 2018， 硕士

【摘要】 储能系统是保证微电网稳定运行的重要环节,应根据微电源发电特性、负荷特性、和天气条件的不同,满足微电网不同运行状态下对不同时间尺度功率和能量的需求。为此,微电网中的储能系统必须兼具较好的功率输出特性和一定的储能容量。在单一储能形式难以同时满足功率和能量需求的情况下,将具有不同优势的储能装置组成混合储能系统,是一种较好的解决方案。针对混合储能系统内部的功率分配问题,提出了自适应荷电状态(SOC)功率分配方法。该方法由一次分配和二次分配两步完成,一次分配以储能系统的运行成本最低为优化目标,生成调度周期内所有储能元件的一次功率指令值,保证微电网长时间尺度下的能量平衡;二次分配以实时调整为目的,将等效负荷的实际功率需求与一次分配的差额作为指令值,由功率型储能元件来承担,保证微电网短时间尺度下的功率平衡。并通过将一次分配中功率型储能的SOC约束条件改进为自动调整的动态范围,来优化储能系统内部的一次分配指令。通过算例分析验证了该方法的有效性。针对混合储能系统的容量配置优化问题,考虑到微电网运行目标对储能系统成本的间接影响,建立了兼顾储能生命周期成本和微电网运行经济性的容量配置优化模型。首先设计了滑动时间窗口方法来计算供电可靠性要求下的储能容量配置,然后以该方法计算下的储能容量作为优化模型的起始值,通过遗传算法和简化迭代算法求解出最佳容量配置和此时微电网的能量调度方式。通过算例分析验证了该方法的有效性。针对直流侧DC/DC变换器在传统PI控制下暂态响应速度慢、动态周期长的固有缺陷,将新兴的MPC控制方法加以反馈调节后应用于储能DC/DC变换器中,在实现其对直流母线电压支撑的作用基础上,改善其动态响应性能,实现对功率指令变化的快速追踪。而针对交流侧DC/AC变换器(即逆变器),重新设计了下垂控制器中电压环的构成,使其集成了APF功能,能够有效降低并网电流中的谐波含量,避免大电网遭受谐波污染。通过仿真分析验证了所提方法的有效性。综上,本文面向混合储能系统在微电网中的应用技术需求,详细设计了不同类型储能装置之间的功率分配方法,以及混合储能系统的容量配置优化方法;并根据储能系统不同的控制目标,提出了储能变换器的相应控制策略,改善了储能系统的动态性能和微电网的集成工作效率。更多还原

【Abstract】 Hybrid energy storage system(HESS)takes an important part in micro-grid in several aspects,such as peak shaving,load leveling and uninterrupted power supply.In a micro-grid consisting of renewable energy sources and loads with different characteristics,the energy storage system has to respond to power and energy demands of different time scales,so that both better power performance and adequate capacity may be required.The requirements can be achieved by taking the advantage of different types of energy storage device.In this case,an optimal energy management for hybrid energy storage system must be considered.Focus on the hybrid energy storage system in micro grid,the power distribution method and the capacity allocation optimization method of the hybrid energy storage system are researched.And according to the different control objectives of the energy storage converter,the current control methods are improved.Firstly,in order to keep energy balance for all storage devices on different time scales,the adaptive SOC power distribution method is proposed,which is composed of two steps of power distribution.The first step is to optimize all the power orders of energy storage devices,taking operating cost of the energy storage system as objective function,to assure the energy balance in long time scales.To further optimize the power distribution result of first step,adjust the SOC constraint condition of the power-type storage device from a fixed range to a dynamic rang.The second step is real-time adjustment to compensate the unscheduled power fluctuation undertook by the energy-type storage device,ensuring the power balance in short time scales.The validity of this method is verified by case studies.Secondly,considering the indirect impacts of micro-grid operation target on the life cycle cost of HESS,a two-layer composite model balancing the life cycle cost of HESS and the operating cost of micro-grid is established.To solve this model,a simplified alternate iteration method combining genetic algorithm and traversing method is used,and a sliding time window method is designed to calculate the initial value,which is also the capacity configuration result of HESS under a certain reliability requirement.The validity of this method is verified by case studies.Finally,aiming at overcoming the inherent defect of pure PI controller in slow dynamic response and poor robustness,a new MPC control strategy with feedback adjustment is proposed and it replaces PI controller using in the DC/DC converter.As for the DC/AC converter(inverter),to prevent the nonlinear loads "inject" the harmonic current into the power systems,an improved droop control strategy is proposed.Through redesigning the voltage loop,the harmonic voltage of AC-bus is compensated and the new controller possesses the function of APF,which can effectively reduce the total harmonic distortion(THD)of the grid-connected current.The effectiveness of these proposed methods are verified by simulation analysis.更多还原