光伏并网发电系统的低电压穿越控制技术研究

发布时间：2018-11-25 15:57

【摘要】：随着传统石化能源储量的匮乏和环境问题的日益严重,光伏并网发电行业在全世界范围内得到迅猛地发展。大容量光伏并网是新能源发展的主流。随着大容量光伏发电系统广泛投入运行,一些问题接踵而至,其中低电压穿越问题被认为是光伏并网设备设计制造控制技术上的最大挑战之一,直接关系到光伏发电的大规模应用。本文主要围绕光伏并网逆变器在电网对称故障、不对称故障时的低电压穿越控制策略展开研究。首先,得出并网逆变器在三相ABC静止坐标系下的数学模型,并通过PARK变换得到两相dq旋转坐标系下的数学模型。其次,当电网发生三相对称跌落时,提出了基于电压定向矢量控制的低电压穿越控制策略,结合直流卸荷电路,保证在电网发生故障时光伏并网发电系统的稳定运行。最后,对光伏并网逆变器在电网电压不对称跌落时的运行特性进行了研究,提出了基于预测电流控制的低电压穿越控制策略,针对该策略中的正、负序分量的分离与检测提出了双二阶广义积分的控制方法,从而保证光伏并网发电系统在电网故障时继续并网运行,实现低电压穿越。本文采用仿真软件PSCAD/EMTDC搭建了额定功率为3MW的光伏并网发电系统模型,来验证提出的LVRT控制策略。仿真结果证明所提控制策略的有效性,当电网故障时,直流侧电压波动得以抑制,光伏发电系统根据电压跌落深度补偿一定的无功功率以恢复电压,系统保持稳定运行。
[Abstract]:With the shortage of traditional petrochemical energy reserves and the increasingly serious environmental problems, photovoltaic grid-connected power generation industry has been rapidly developed in the world. Large-capacity photovoltaic grid-connected is the mainstream of new energy development. With the wide operation of large capacity photovoltaic power generation system, some problems have arisen. Among them, the low-voltage traversing problem is considered as one of the biggest challenges in the design and manufacturing control technology of photovoltaic grid-connected equipment. It is directly related to the large-scale application of photovoltaic power generation. This paper focuses on the low voltage traversing control strategy of photovoltaic grid-connected inverter when the grid is symmetrical fault or asymmetric fault. Firstly, the mathematical model of grid-connected inverter in three-phase ABC stationary coordinate system is obtained, and the mathematical model of two-phase dq rotating coordinate system is obtained by PARK transformation. Secondly, when the three-phase symmetrical drop occurs, a low-voltage traversing control strategy based on voltage oriented vector control is proposed, which combines DC unloading circuit to ensure the stable operation of photovoltaic grid-connected generation system in the event of power grid failure. Finally, the operating characteristics of photovoltaic grid-connected inverter under asymmetric drop of grid voltage are studied, and a low-voltage traversing control strategy based on predictive current control is proposed. A control method based on double second order generalized integral is proposed for the separation and detection of negative sequence components, which ensures that photovoltaic grid-connected generation system continues to run grid-connected when the power network fails, and realizes low voltage traversing. In this paper, a photovoltaic grid-connected power generation system model with rated power of 3MW is built by using the simulation software PSCAD/EMTDC to verify the proposed LVRT control strategy. The simulation results show that the proposed control strategy is effective. When the power network fails, the DC side voltage fluctuation can be restrained, and the photovoltaic power generation system compensates a certain reactive power according to the voltage drop depth to recover the voltage, and the system runs stably.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM615

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