不平衡工况下链式STATCOM无功补偿的研究

发布时间：2018-11-26 19:31

【摘要】：静止同步补偿器(static synchronous compensator,STATCOM)是一种并联接入电网的补偿装置,既可用于输电网,也可用于配电网。链式结构的STATCOM以其快速的动态响应速度,良好的谐波性能,结构紧凑,经济效益显著等优点,在不平衡负载补偿中得到了广泛应用。链式STATCOM装置的结构有两种接线形式,一种是星形接线,另一种是三角形接线。三角形链式STATCOM由于其含有零序电流流通通道,可以通过注入零序电流很容易实现各相换流链的功率平衡,因此更适合应用于不平衡负载的补偿中。本文所做的工作如下:首先,介绍STATCOM工作的基本原理及主电路结构,然后建立级联H桥STATCOM装置的数学模型,最后为了更好的设计STATCOM装置的控制器,选择采用坐标变换的方法得到其装置的分序数学模型。为了对STATCOM装置进行分序控制,需提前将正序数学模型和负序数学模型完成前馈解耦控制。针对H桥级联STATCOM的调制策略,重点分析了单极倍频SPWM调制方法和双极性SPWM调制方法,通过比较两种方法的输出电平数和输出电压谐波分量后,选择单极倍频CPS-SPWM调制方法。其次,无功电流的准确检测是STATCOM装置完成无功补偿的前提。先介绍了两种传统的基于瞬时无功功率理论的无功电流检测方法:dq无功电流检测方法和p qi-i无功电流检测方法。这两种方法均能在特定的场合下实现对无功电流的精确检测。最后提出了一种适应于补偿不平衡工况下的无功电流的检测方法,搭建相关仿真模型验证所述方法的准确性。最后,通过分析造成级联H桥STATCOM装置直流侧电容电压不平衡的原理后,提出了一种控制其直流侧电容电压平衡的分级控制方法。该控制方法是由分序控制的思想而来的:为了控制其直流侧整体的电压保持平衡,选择通过控制装置的正序电流来实现,同理可得,为了控制其相间直流侧的电压保持平衡,选择通过注入零序电流的方法去实现。对于控制使得装置相内电容电压保持平衡的方法,选择通过控制各个单元模块的输出电压幅值和相位的大小实现。最后,在Matlab/Simulink仿真环境下准确建立3kV/5MVA的模型,仿真验证了所用方法的准确性。
[Abstract]:Static synchronous compensator (static synchronous compensator,STATCOM) is a compensation device connected in parallel to the power network, which can be used in both transmission and distribution networks. STATCOM with chain structure has been widely used in unbalanced load compensation because of its fast dynamic response speed, good harmonic performance, compact structure and remarkable economic benefits. There are two types of connection in chain STATCOM device, one is star connection, the other is triangle connection. Because triangular chain STATCOM contains zero sequence current flow channel, it is easy to realize power balance of each phase commutation chain by injecting zero sequence current, so it is more suitable for unbalanced load compensation. The work of this paper is as follows: firstly, the basic principle and main circuit structure of STATCOM are introduced, then the mathematical model of cascaded H-bridge STATCOM device is established. Finally, in order to design the controller of STATCOM device better, The ordinal mathematical model of the device is obtained by using coordinate transformation method. In order to carry out sequential control of STATCOM device, feedforward decoupling control should be completed by using both positive and negative sequence mathematical models in advance. Aiming at the modulation strategy of H-bridge cascaded STATCOM, the unipolar frequency doubling SPWM modulation method and the bipolar SPWM modulation method are emphatically analyzed. After comparing the output level number and the output voltage harmonic component of the two methods, the unipole frequency doubling CPS-SPWM modulation method is selected. Secondly, the accurate detection of reactive current is the premise of STATCOM device to complete reactive power compensation. This paper introduces two traditional reactive current detection methods based on instantaneous reactive power theory: dq reactive current detection method and p qi-i reactive current detection method. Both methods can accurately detect reactive current in a specific situation. Finally, a reactive current detection method suitable for compensating unbalanced conditions is proposed, and the accuracy of the proposed method is verified by building relevant simulation models. Finally, after analyzing the principle of voltage imbalance in the DC side of cascaded H bridge STATCOM, a hierarchical control method is proposed to control the voltage balance of the capacitor at the DC side of the cascaded H bridge. This control method is based on the idea of sequential control: in order to control the voltage balance of its DC side as a whole, it is chosen to be realized by controlling the positive sequence current of the device. In the same way, in order to control the voltage balance of the DC side between phases, The method of zero sequence current injection is selected to achieve this. To control the balance of capacitance voltage in the device, the output voltage amplitude and phase of each unit module are controlled. Finally, the model of 3kV/5MVA is built accurately in Matlab/Simulink simulation environment, and the accuracy of the method is verified by simulation.
【学位授予单位】：太原科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM761.12

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