LCL型三相并网变流器系统智能优化设计

发布时间：2018-12-14 07:59

【摘要】：大功率并网变流器广泛应用于光伏并网、风机发电、燃料电池、储能电站等智能电网系统中,是一类重要的电力电子变流装置。对系统主电路的参数优化设计和电流环控制性能优化的研究具有重要的理论和实际工程意义,本文针对LCL滤波的三相并网变流器,对上述问题进行探讨与研究。文章中首先建立了LCL型三相变流器的数学模型,提出一种新型复矢量算子表示方法,推导出系统在旋转坐标系下完全解耦的状态空间表达式,采用复矢量PI电流控制器可以完全消除由于坐标变换而引入的电压耦合问题。为了改善由于LCL滤波器谐振峰而导致系统稳定性恶化的问题,本文利用数字控制中引入的延时效应来改变开环离散传递函数的相频特性曲线,选取合适的开关频率与谐振频率之比可以保证系统的具有一定的相角与幅值裕度。根据频域稳定性判据可以得到电流内环系统稳定条件下优化的谐振频率取值范围,再结合LCL的参数设计准则,合理设计出LCL滤波器的参数。为了改善变流器系统的动态响应性能,提高系统的参数鲁棒性,利用神经网络算法的无限逼近非线性系统的能力,设计了神经网络PI电流调节器,传统PI控制器对电流闭环系统闭环控制,BP神经网络算法根据系统变化在线优化调节器的控制参数,提高系统在不同运行状况下的动态响应性能。基于Saber仿真平台搭建LCL型三相并网变流器仿真模型,通过半物理实物模型仿真验证了系统无阻尼稳定理论分析的正确性、滤波器参数设计的合理性以及神经网络算法的可行性。
[Abstract]:High-power grid-connected converters are widely used in smart grid systems such as photovoltaic grid-connected fan power generation fuel cell energy storage power station and so on. It is of great theoretical and practical significance to study the parameter optimization design of the main circuit and the performance optimization of the current loop control. In this paper, the above problems are discussed and studied for the three-phase grid-connected converter with LCL filter. In this paper, the mathematical model of LCL type three-phase converter is established, a new representation method of complex vector operator is proposed, and the state space expression of complete decoupling of the system in rotating coordinate system is derived. The voltage coupling problem caused by coordinate transformation can be completely eliminated by using complex vector PI current controller. In order to improve the deterioration of system stability due to the resonance peak of LCL filter, the phase frequency characteristic curve of open loop discrete transfer function is changed by using the delay effect introduced in digital control. Selecting the appropriate ratio of switching frequency to resonant frequency can ensure the system has a certain phase angle and amplitude margin. According to the stability criterion in frequency domain, the optimal range of resonance frequency can be obtained under the condition of stability of the current inner loop system, and the parameters of LCL filter can be reasonably designed by combining with the parameter design criterion of LCL. In order to improve the dynamic response performance of the converter system and improve the parameter robustness of the system, a neural network PI current regulator is designed based on the ability of the neural network algorithm to approach the nonlinear system. The traditional PI controller controls the closed loop of the current closed-loop system. The BP neural network algorithm optimizes the control parameters of the regulator on-line according to the system changes, and improves the dynamic response performance of the system under different operating conditions. The simulation model of LCL type three-phase grid-connected converter is built based on Saber simulation platform. The correctness of the theoretical analysis of undamped stability, the rationality of filter parameter design and the feasibility of neural network algorithm are verified by the simulation of semi-physical model.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM46

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