具有虚拟同步机特性的电压源型变流器控制策略研究

发布时间：2018-05-27 03:36

本文选题：虚拟同步发电机 + 并网逆变器　；参考：《华北电力大学》2017年硕士论文

【摘要】：分布式发电因具有过程简单,无噪声、无污染等众多优点而得到越来越多的关注,其在电力系统的渗透率也不断提升。然而,常规的分布式并网发电控制较多采用电力电子并网逆变器模式,该模式响应速度快,转动惯量小,且缺乏必要的阻尼作用,使其无法参与电网调节,不能保证电力系统电压和频率的稳定。这无疑制约了分布式电源并网发电的大规模发展。针对以上问题,本文提出了一种基于虚拟同步发电机(Virtual Synchronous Generator,VSG)思想的并网发电系统结构,研究逆变器与同步发电机机电模型的对应关系,并从调速调频、励磁电压调节、转动惯量来设计虚拟同步机特性的电压源型变流器的控制策略,使得分布式电源体现出大电网中同步发电机类似的特性,自动自治的参与调节。而后,因虚拟同步发电机并网逆变器在同步旋转坐标系下dq轴电流分量存在耦合,采用一种基于自抗扰控制技术的电流解耦控制策略,该方法将dq轴间的电流耦合和电感参数变化引起的误差看成是系统的扰动,通过扩张状态观测器将该扰动估计出来,利用自抗扰控制器的前馈补偿消除误差,从而实现dq轴电流真正意义上的解耦控制。最后,针对虚拟同步发电机处于孤岛运行时,由于其容量低、并网惯性小,使其稳定性比大电网差很多,负荷的变化会对虚拟同步发电机产生较大的影响这一问题,在传统下垂控制策略的基础上,引入自抗扰控制技术,设计了一种基于自抗扰技术的虚拟机无差调频控制策略,在PSCAD/EMTDC仿真平台,通过与传统PI控制效果进行对比,验证了所提控制策略的正确性与有效性。
[Abstract]:Distributed generation has attracted more and more attention because of its simple process, no noise, no pollution and so on. The permeability of distributed generation in power system is also increasing. However, the conventional distributed grid-connected generation control mostly adopts the power electronic grid-connected inverter mode, which has the advantages of fast response speed, small moment of inertia and lack of necessary damping, which makes it unable to participate in the regulation of the power network. Power system voltage and frequency stability can not be guaranteed. This undoubtedly restricts the large-scale development of distributed power generation. In view of the above problems, this paper presents a grid-connected generation system structure based on the idea of virtual Synchronous generator VSGs, studies the corresponding relationship between inverter and electromechanical model of synchronous generator, and adjusts the frequency modulation and excitation voltage. The control strategy of voltage source converter with virtual synchronous machine characteristics is designed by rotating inertia, which makes the distributed power supply reflect the similar characteristics of synchronous generator in large power network, and automatically participate in the regulation. Then, because of the coupling of DC axis current component in synchronous rotating coordinate system, a current decoupling control strategy based on active disturbance rejection control (ADRC) is proposed. In this method, the error caused by the current coupling between dq axes and the variation of inductance parameters is regarded as the disturbance of the system. The disturbance is estimated by an extended state observer, and the error is eliminated by feedforward compensation of the ADRC. Thus the decoupling control of dq axis current is realized in real sense. Finally, when the virtual synchronous generator is running on an isolated island, the stability of the virtual synchronous generator is much worse than that of the large power grid because of its low capacity and low grid inertia. The change of load will have a great impact on the virtual synchronous generator. Based on the traditional droop control strategy, this paper introduces the active disturbance rejection control technology, designs a virtual machine no-difference frequency modulation control strategy based on the auto disturbance rejection technology, and compares it with the traditional Pi control effect on the PSCAD/EMTDC simulation platform. The correctness and effectiveness of the proposed control strategy are verified.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM61;TM46

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