LCL型光伏并网逆变器控制策略研究
本文选题:光伏并网 + 逆变器 ; 参考:《南京理工大学》2017年硕士论文
【摘要】:LCL型三相并网逆变器现有控制策略中PI控制器、PR控制器应用最为广泛,但其参数设计均是基于标况下,且依赖于系统建模的精确度,参数设计较为复杂。针对这一现状,本文针对不同电网状况下的并网逆变器控制策略展开研究。本文首先搭建了 500kW光伏并网模型,包括光伏阵列、DC/DC变换器、DC/AC逆变器三个部分。其中DC/DC部分选择BOOST电路来实现光伏阵列的MPPT控制,逆变器控制策略选用传统电压外环电流内环的双环控制策略。然后,本文提出一种基于RBF网络的自适应控制策略,并给出电流内环相关参数的设计方法。同时,为解决LCL滤波器产生的谐振问题,采用电容电流反馈有源阻尼控制,给出一种基于系统幅相特性的电容电流反馈有源阻尼系数设计方法。通过改变相关参数,对光伏并网系统进行仿真测试,证明所提控制策略的可行性和正确性。其次,考虑到电网实际存在的不平衡因素,在所提自适应控制策略中,分别对正负序分量的提取、正负序电流指令的计算、电流指令跟踪控制进行改进,使光伏系统注入电网的并网电流不出现畸变、谐波含量过大等现象,保证并网点电能质量良好。并通过仿真测试,验证了在电网电压不平衡下,所提控制策略具有有效性。最后,对5MW光伏电站接入配电网模型进行案例分析,分别对理想电网、电网电压不平衡两种情况下的光伏电站并网电流、并网点相关电能质量进行测试、分析。此案例证明了本文提出的基于RBF网络的自适应控制策略的可行性,可以提高并网点电能质量,为光伏电站并网运行提供理论依据。
[Abstract]:Pi controller / PR controller is the most widely used control strategy in LCL three-phase grid-connected inverter, but its parameter design is based on the standard condition and depends on the precision of system modeling, so the parameter design is more complex. In view of this situation, the control strategy of grid-connected inverter under different grid conditions is studied in this paper. In this paper, a 500kW photovoltaic grid-connected model is first built, which consists of three parts: photovoltaic array DC / DC converter and DC / AC inverter. The DC / DC part chooses boost circuit to realize the MPPT control of photovoltaic array, and the inverter control strategy adopts the traditional double loop control strategy of the voltage outer loop current inner loop. Then, an adaptive control strategy based on RBF network is proposed, and the design method of the relative parameters of current inner loop is given. At the same time, in order to solve the resonance problem of LCL filter, a design method of capacitive current feedback active damping coefficient based on the amplitude and phase characteristics of the system is presented by using capacitive current feedback active damping control. The feasibility and correctness of the proposed control strategy are proved by changing the relevant parameters and simulating the photovoltaic grid-connected system. Secondly, considering the unbalanced factors in the power network, in the proposed adaptive control strategy, the extraction of the positive and negative sequence components, the calculation of the positive and negative sequence current instructions, and the tracking control of the current instructions are improved, respectively. The grid-connected current injected into the grid of photovoltaic system is not distorted, the harmonic content is too large, and the power quality of the grid is good. The simulation results show that the proposed control strategy is effective when the voltage is unbalanced. Finally, a case study of 5MW photovoltaic power station connected to distribution network model is carried out. The grid-connected current of photovoltaic power station under the condition of ideal grid and unbalanced grid voltage is tested and analyzed. This case proves the feasibility of the adaptive control strategy based on RBF neural network, which can improve the power quality and provide a theoretical basis for the grid-connected operation of photovoltaic power plants.
【学位授予单位】:南京理工大学
【学位级别】:硕士
【学位授予年份】:2017
【分类号】:TM464;TM615
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