微网中接口变换器的多时间尺度分层协同控制策略研究

发布时间：2019-06-27 10:45

【摘要】：微网是以电力电子变换器为主体,配合以储能和负荷单元,以控制策略为支撑,可实现多发电单元联合供能、多控制策略协同工作、多层架构灵活配合。本文主要工作是针对微网变换器间的协调控制及微网控制展开研究,主要分为以下几个部分。首先,分析了 VSG控制与下垂控制之间的关系,推导了不同容量的多台VSG之间的有功和无功功率的均分公式,对孤岛模式下包含多台VSG的微网进行分层控制,在第一层控制输出特性稳定的前提下,采用集中式控制,在第二层控制器中引入了对微网交流母线的频率和电压的二次补偿控制。其次,分析了转子运动方程中的转动惯量对有功功率和频率输出特性的影响,在转动惯量自适应控制的基础上,基于分层理念,研究了隶属于二层控制的改进型转动惯量自适应控制。从VSG并联稳定性分析的角度给出了 VSG参数的大致取值范围,并设计了频率跟踪系数的取值原则。仿真和实验验证了此种改进型转动惯量自适应控制可在时间尺度上通过自适应地调节转动惯量达到不同工况下的良好控制效果。再次,电网电压不对称情况下,依据具有调节系数的连续性电流给定算法,推导了有功和无功功率振荡幅值以及电流峰值表达式,通过调节权重系数可实现特定的控制目标。针对不能同时抑制有功和无功功率振荡,且电流峰值变大的问题,采取折中控制方式:有功功率在微网允许小幅范围内振荡的前提下,通过多目标优化算法使无功功率振荡幅值和电流峰值最小,间接实现三种控制目标。最后,电网电压不对称情况下,针对含多台变换器的交流微网的输出有功功率的振荡会引发前级直流微网中直流母线电压的波动以及并网电流的电能质量问题,以两台变换器并联为例,研究了一种抑制有功功率振荡的控制策略,通过实验结果可知,所得权重系数可使保证微网总的有功功率在稳态过程中以及在限制电流峰值的两级调节过程中不振荡,且总的无功功率振荡幅值保持不变。
[Abstract]:Microgrid is based on power electronic converter, combined with energy storage and load unit, supported by control strategy, which can realize the joint energy supply of multiple power generation units, the cooperative work of multiple control strategies, and the flexible cooperation of multi-layer architecture. The main work of this paper is to study the coordinated control and microgrid control between microgrid converters, which is mainly divided into the following parts. Firstly, the relationship between VSG control and drooping control is analyzed, and the equal distribution formula of active power and reactive power between multiple VSG with different capacity is derived. the microgrid containing multiple VSG in isolated island mode is controlled layered. Under the premise that the output characteristics of the first layer control are stable, the centralized control is adopted, and the secondary compensation control of the frequency and voltage of the AC bus of the microgrid is introduced into the second layer controller. Secondly, the influence of moment of inertia on active power and frequency output characteristics in rotor motion equation is analyzed. on the basis of adaptive control of moment of inertia and hierarchical concept, the improved adaptive control of moment of inertia belonging to two-layer control is studied. From the point of view of VSG parallel stability analysis, the approximate range of VSG parameters is given, and the principle of frequency tracking coefficient is designed. The simulation and experimental results show that the improved adaptive control of moment of inertia can achieve good control effect under different working conditions by adaptively adjusting the moment of inertia on the time scale. Thirdly, under the condition of asymmetrical voltage of power grid, according to the continuous current given algorithm with regulation coefficient, the expressions of active and reactive power oscillation amplitude and current peak value are derived, and the specific control objectives can be achieved by adjusting the weight coefficient. In order to solve the problem that both active power and reactive power oscillations can not be suppressed at the same time, and the peak current becomes larger, a compromise control method is adopted: under the premise that active power oscillates in a small range allowed by microgrid, the amplitude and current peaks of reactive power oscillations are minimized by multi-objective optimization algorithm, and three control objectives are realized indirectly. Finally, under the condition of asymmetrical voltage of power grid, the fluctuation of DC bus voltage and the power quality of grid-connected current in the front DC microgrid will be caused by the output active power oscillation of AC microgrid with multiple converters. Taking the parallel connection of the two converters as an example, a control strategy to suppress the active power oscillation is studied. The obtained weight coefficient can ensure that the total active power of the microgrid does not oscillate in the steady state process and in the two-stage adjustment process of limiting the peak current, and the amplitude of the total reactive power oscillation remains unchanged.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM46

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