微网虚拟同步发电机下的自适应滑模控制策略研究

发布时间：2019-01-24 08:44

【摘要】：与逐渐减少的化石能源相比,分布式能源因其可再生性以及环境友好性日益受到人们的重视,以分布式能源为主的微电网也应运而生。虽然微电网有诸多优点,但是相对传统的大电网,微电网系统缺少惯性,更易受到外界干扰。借鉴同步发电机的运行特性,虚拟同步发电机(virtual synchronous generator,VSG)通常用作微网逆变器中各种分布式电源的接口,以便使系统具有更大的惯性。本文针对微网VSG下的控制策略进行了研究。首先,本文对同步发电机的模型进行了详细介绍,借鉴同步发电机的模型设计了VSG的本体算法,包括转子运动方程和定子电压方程。同时,借鉴同步发电机的功频调节原理设计了VSG的功频调节器;借鉴同步发电机的励磁原理设计了VSG的励磁调节器,并利用有功功率微分负反馈对系统的二阶功频控制部分进行了改进优化,改善了系统的动态响应特性。其次,分析微网并入大电网的条件,根据微网端电压和电网电压的相位自同步跟踪原理,设计了VSG的预同步控制器。分析了VSG的静态稳定性,讨论了VSG算法中部分关键参数对系统稳定性的影响,为参数的选取提供了一定依据。同时在MATLAB中搭建仿真模型,验证了转动惯量,阻尼系数等关键参数对系统输出的影响,同时也验证了预同步并网的可行性,以及并网时VSG的功率跟踪能力。最后,本文研究了 VSG的底层电压控制策略。由于负荷中的不平衡和非线性负载会对逆变器输出电压造成影响。为此,本文设计了一种电压自适应滑模控制器。以VSG作为基础控制器,然后根据系统在αβ坐标系下的方程,针对系统的负载扰动和参数摄动问题,设计了自适应补偿控制,使系统能在保持稳定的条件下,减少输出电压的抖振。最后,对所提的控制策略与PI双环解耦控制和常规滑模控制进行了对比仿真试验,结果显示了本文提出控制策略在抑制电压不平衡与谐波方面的有效性与鲁棒性,提高了微网逆变器输出电压的电能质量,有效地减少了并联逆变器之间的环流。
[Abstract]:Compared with the decreasing fossil energy, distributed energy has been paid more and more attention because of its renewable and environmental friendliness, and microgrid, which is mainly distributed energy, has emerged as the times require. Although microgrid has many advantages, compared with traditional large power grid, microgrid system lacks inertia and is more susceptible to external interference. Based on the operating characteristics of synchronous generator, virtual synchronous generator (virtual synchronous generator,VSG) is usually used as the interface of distributed power supply in microgrid inverter, so as to make the system have greater inertia. In this paper, the control strategy of microgrid VSG is studied. Firstly, the model of synchronous generator is introduced in detail, and the ontology algorithm of VSG is designed based on the model of synchronous generator, including rotor motion equation and stator voltage equation. At the same time, the power and frequency regulator of VSG is designed based on the principle of power and frequency regulation of synchronous generator. Based on the excitation principle of synchronous generator, the excitation regulator of VSG is designed, and the second order power-frequency control part of the system is improved and optimized by differential and negative feedback of active power, which improves the dynamic response of the system. Secondly, based on the principle of phase self-synchronous tracking of microgrid terminal voltage and grid voltage, the pre-synchronization controller of VSG is designed. The static stability of VSG is analyzed, and the influence of some key parameters in the VSG algorithm on the stability of the system is discussed, which provides a basis for the selection of the parameters. At the same time, the simulation model is built in MATLAB to verify the influence of the key parameters such as moment of inertia and damping coefficient on the output of the system. The feasibility of pre-synchronous grid-connected system and the power tracking ability of VSG in grid-connected system are also verified. Finally, the bottom voltage control strategy of VSG is studied. Because of the unbalanced load and nonlinear load, the output voltage of the inverter will be affected. Therefore, a voltage adaptive sliding mode controller is designed. Taking VSG as the basic controller, according to the equation of the system in 伪尾 coordinate system, the adaptive compensation control is designed for the load disturbance and parameter perturbation of the system. Reduce buffeting of output voltage. Finally, the proposed control strategy is compared with the PI double loop decoupling control and the conventional sliding mode control. The results show that the proposed control strategy is effective and robust in suppressing voltage imbalance and harmonics. The power quality of the output voltage of the microgrid inverter is improved, and the circulation between the parallel inverters is reduced effectively.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM727

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