基于虚拟同步发电机的微网逆变器控制策略研究

发布时间：2018-11-12 20:22

【摘要】：微电网作为整合各种分布式电源的有效途径,已经成为了分布式发电领域的研究重点和热点。然而,以电力电子逆变器为接口的微源响应速度快,外特性较硬,导致系统容易产生振荡,稳定性不高。虚拟同步发电机(Virtual Synchronous Generator,VSG)控制技术作为一种模拟同步发电机特性的方法,可为微电网系统带来如同步发电机固有的旋转惯性特性,对解决微网系统惯性缺失的问题,提高微网系统的稳定性具有重要意义。本文在归纳总结了目前微网逆变器的控制策略的基础上,围绕微源逆变器VSG控制问题。首先详细分析了微源逆变器电压控制的结构,给出了逆变器SVPWM电压控制的基本原理,设计了电压电流双环解耦控制器和滤波器。其次,在分析同步发电机控制结构的基础上,给出了虚拟同步发电机控制系统结构;通过对同步发电机调速器单元调频原理的分析,设计了VSG控制的功频控制器;通过对励磁控制系统调压原理的分析,设计了VSG控制的励磁控制器。最后,针对VSG暂态响应过程中频率调节问题,深入地分析了虚拟惯量与虚拟转子角频率变化率之间的关系,利用虚拟同步发电机虚拟惯量灵活可变的特点,提出了一种自适应虚拟惯量的虚拟同步发电机控制策略,实现虚拟惯量随转子角频率变化率不同而自适应调整,还分析了自适应参数在不同转子角频率下对虚拟惯量的影响,并且重新设计了虚拟同步发电机的功频控制器。在MATLAB/Simulink中搭建了VSG控制策略的仿真模型和自适应虚拟惯量控制策略的仿真模型,通过VSG控制策略与传统下垂控制策略仿真结果的比较,表明了所设计的VSG不仅模拟了同步发电机的下垂外特性,还模拟了同步发电机的旋转惯性特性。通过自适应虚拟惯量的VSG控制与传统固定惯量的VSG控制进行比较,仿真结果验证了所提自适应虚拟惯量的VSG控制策略实现了虚拟惯量实时根据转子角频率变化率变化而调整,解决了VSG暂态响应过程中频率恢复过慢的问题。
[Abstract]:As an effective way to integrate all kinds of distributed generation, microgrid has become the research focus and hotspot in the field of distributed generation. However, the micro-source with power electronic inverter as the interface has a fast response speed and a hard external characteristic, which leads to the system oscillation easily and the stability is not high. Virtual synchronous generator (Virtual Synchronous Generator,VSG) control technology, as a method to simulate the characteristics of synchronous generator, can bring rotating inertia characteristics such as synchronous generator to micro-grid system, and solve the problem of inertia deficiency in micro-grid system. It is important to improve the stability of microgrid system. On the basis of summing up the current control strategy of microgrid inverter, this paper focuses on the VSG control problem of microsource inverter. Firstly, the structure of microsource inverter voltage control is analyzed in detail, the basic principle of inverter SVPWM voltage control is given, and the voltage and current double loop decoupling controller and filter are designed. Secondly, on the basis of analyzing the control structure of synchronous generator, the control system structure of virtual synchronous generator is given, and the power frequency controller controlled by VSG is designed by analyzing the frequency modulation principle of governor unit of synchronous generator. The excitation controller controlled by VSG is designed by analyzing the voltage regulation principle of excitation control system. Finally, aiming at the problem of frequency regulation in the transient response of VSG, the relationship between the virtual inertia and the angular frequency change rate of the virtual rotor is deeply analyzed. The virtual inertia of the virtual synchronous generator is flexible and variable. A virtual synchronous generator control strategy with adaptive virtual inertia is proposed, which can adjust the virtual inertia adaptively with the change rate of rotor angular frequency. The influence of adaptive parameters on virtual inertia is also analyzed. The power and frequency controller of virtual synchronous generator is redesigned. The simulation model of VSG control strategy and adaptive virtual inertia control strategy are built in MATLAB/Simulink. The simulation results of VSG control strategy and traditional droop control strategy are compared. It is shown that the designed VSG not only simulates the droop characteristics of the synchronous generator, but also simulates the rotational inertia characteristics of the synchronous generator. By comparing the adaptive virtual inertia VSG control with the traditional fixed inertia VSG control, the simulation results show that the proposed VSG control strategy of the adaptive virtual inertia can adjust the virtual inertia according to the rotor angular frequency change in real time. The problem of slow frequency recovery in the transient response of VSG is solved.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2018
【分类号】：TM341;TM464

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