储能系统并离网切换特性研究

发布时间：2018-09-08 07:41

【摘要】：随着能源和环境问题的日益严重,新能源发电受到了世界各国的广泛关注,但是风力发电等间歇性电源的接入也对电网的电能质量造成了影响。为了提高可再生能源发电的稳定性,改善电网的电能质量,电池储能系统得到了广泛应用。储能系统的核心是逆变器,研究储能系统逆变器的控制机理和在不同工况下储能系统的各种控制策略具有深远的理论和现实意义。中国电科院项目《储能系统并离网特性及检测技术》进行储能系统的并离网特性检测平台的建设,基于该项目,本论文对储能系统并离网切换特性展开研究。首先,建立了电压型逆变器在不同坐标系下的数学模型,研究储能逆变器双闭环控制策略,并分析了储能系统并网及离网运行时的不同控制策略。其次,根据储能系统在三相电压平衡时的并网和离网运行特性,分析了储能系统并离网切换时的控制原理,设计了基于PI双闭环控制的平滑切换控制策略,通过仿真,分析了储能系统并离网切换特性。再次,针对电网三相电压不平衡的工况,设计了在电网电压不平衡下储能系统并离网切换控制策略,并网转离网时,在切换前以抑制有功功率二次波动为控制目标,切换时采用系统正负序电压协作调节的控制方法;准同期并网时正负序电压外环共同调节,使逆变器输出电压与电网电压同步,从而实现电网电压不平衡下储能系统并离网切换的平滑过渡,并通过仿真验证算法的可行性。最后,在电流内环控制的基础上,提出了一种新型的电压漂移孤岛检测方法。通过在电流内环中添加反馈电压增益模块来提高检测效率,并利用古尔维茨判据对模块中的增益系数进行分析来研究孤岛检测成功边界条件;为防止逆变器输出功率与负荷功率完全相等而无法检测出孤岛的问题,提出在并网运行时逆变器输出功率时刻存在较小波动的方法,通过仿真验证了其有效性。
[Abstract]:With the increasingly serious energy and environmental problems, new energy generation has received extensive attention in the world. However, the access of intermittent power sources such as wind power also has an impact on the power quality of the power grid. In order to improve the stability of renewable energy generation and improve the power quality of power grid, battery energy storage system has been widely used. The inverter is the core of the energy storage system. It is of great theoretical and practical significance to study the control mechanism of the inverter and the various control strategies of the energy storage system under different operating conditions. Based on the project of "Energy storage system and off-grid characteristics and detection technology", a platform for detecting energy storage system's off-grid characteristics is constructed. Based on this project, this paper studies the characteristics of energy storage system and off-grid switching. Firstly, the mathematical models of the voltage source inverter in different coordinate systems are established, and the dual closed loop control strategies of the energy storage inverter are studied, and the different control strategies of the energy storage system when connected to and off the grid are analyzed. Secondly, according to the characteristics of grid-connected and off-grid operation of energy storage system under three-phase voltage balance, the control principle of energy storage system and off-grid switching is analyzed, and a smooth switching control strategy based on PI double closed-loop control is designed. The switching characteristics of energy storage system and off-grid are analyzed. Thirdly, aiming at the condition of unbalanced three-phase voltage, the control strategy of energy storage system and off-grid switching is designed under the condition of unbalanced grid voltage. Before switching, the control target is to restrain the secondary fluctuation of active power. When switching, the control method of positive and negative sequence voltage cooperative regulation is adopted, and the positive and negative sequence voltage outer loop is jointly adjusted in quasi-synchronous grid-connection to synchronize the output voltage of the inverter with the grid voltage. Thus, the smooth transition of energy storage system and off-grid switching is realized under unbalanced grid voltage, and the feasibility of the algorithm is verified by simulation. Finally, on the basis of current inner loop control, a new detection method of voltage drift island is proposed. In order to improve the detection efficiency, the feedback voltage gain module is added to the inner loop of current to improve the detection efficiency, and the Gourwitz criterion is used to analyze the gain coefficient in the module to study the boundary conditions for the successful detection of isolated islands. In order to avoid the problem that the output power of the inverter is equal to the load power and the isolated island can not be detected, a method of small fluctuation of the output power of the inverter in grid-connected operation is proposed, and the effectiveness of the method is verified by simulation.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464;TM614

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