面向系统电压动力学演化过程分析的电力电子并网设备内电势幅值运动机制研究

Motion Mechanism of Internal Voltage Amplitude of Power Electronic Equipment for System Voltage Dynamical Evolution Analysis

系统电压和频率演化机制认识一直是开展电力系统稳定、控制和保护等研究的重要基础。针对系统频率演化问题,已有研究以转子运动方程所刻画的内电势频率运动机制为核心形成了频率同步过程的直观认识。而针对系统电压演化问题,由于不明确驱使内电势幅值运动的激励力和支撑内电势幅值运动的物质特性,没有形成与内电势频率运动机制相对应的内电势幅值运动机制认识,更未能结合网络特性开展物理概念明确的电压动力学演化过程研究。随着电力电子设备持续大规模并网,电压问题愈加凸显,亟需更加深入地认识系统电压演化过程。因此,文中首先从设备调节内电势幅值/频率的基本原理出发,明确无功不平衡是驱使内电势幅值运动的主要激励力,并以双馈风机(doubly-fedinduction generator-based wind turbine,DFIG-based WT)为例构建无功/端电压不同控制目标下内电势幅值/频率响应模型。然后,基于三相系统动态过程中无功功率的物理内涵,建立支撑内电势幅值运动的无功不平衡存储特性的直观认识,从而通过类比频率运动机制,指出内电势幅值是反映无功不平衡存储水平的状态。最后,在含DFIG-basedWT单机系统中分析考虑不同控制目标时的电压动力学演化过程,并初步探讨多机系统电压动力学演化过程的研究思路。

The recognition of mechanisms of system voltage and frequency dynamics has always been the basis for the research on stability,control and protection of power systems.For the frequency issue,an intuitive understanding of frequency synchronization process has been formed based on the motion mechanism of internal voltage frequency characterized by the rotor motion equation.But for the voltage issue,the motion mechanism of internal voltage amplitude is not as accessible as that of frequency due to the lack of a clear understanding of the exciting force and characteristics that decide the motion of internal voltage amplitude.This makes that the existing studies fail to study the system voltage dynamical evolution intuitively in combination with network characteristics.As the system voltage issue becomes more and more severe with the increasing integration of power electronic equipment,it is urgent to carry out more in-depth researches on the system voltage dynamical evolution.Therefore,based on the basic principle of controlling internal voltage amplitude/frequency,the main exciting force driving the motion of internal voltage amplitude is identified as reactive power imbalance.And the internal voltage amplitude/frequency response models of the doubly-fed induction generator-based(DFIG-based)wind turbine(WT)are proposed considering different control objectives.Then,based on the physical connotation of reactive power during three-phase system dynamics,the intuitive understanding of the reactive power imbalance storage characteristics that resist the motion of internal voltage amplitude is established.By analogy with the motion mechanism of frequency,the internal voltage amplitude is pointed out to be the state reflecting the level of reactive power imbalance storage.Finally,the voltage dynamical evolution is analyzed in a single-machine infinite-bus system with DFIG-based WT considering different control objectives.The research ideas of voltage dynamical evolution in multi-machine systems are explored.