固态变压器在智能电网中的应用研究

发布时间：2018-01-22 06:27

本文关键词： 固态变压器智能电网控制策略 FREEDM 电能质量　出处：《山东大学》2014年硕士论文　论文类型：学位论文

【摘要】：固态变压器(SST)是一种新型智能电能变换设备,与传统电力变压器相比,固态变压器融合了电力电子变换技术,采用高频隔离的中间直流环节,可实现原边和副边的灵活控制。其突出的特点在于输入电流、输出电压可调,功率因数可控。由于具备以上优点,将固态变压器用于电力系统可提高系统可控性,并可改善电能质量,便于新能源发电并网,将推动智能电网建设和发展。本文首先介绍了固态变压器发展过程中的几种典型拓扑结构及其控制方式,对其各自的优缺点进行了比较。然后分析了一种具备直流环节的级联式三级结构,即拥有输入级、隔离级和输出级的固态变压器。以此为基础展开研究,针对其核心环节(VSC)进行了建模和分析,并结合各环节的控制目标制定了相应的控制策略。输入级采用电压外环、电流内环的双环解耦控制策略,隔离级采用开环控制,输出级采用具备电压前馈补偿的电压电流双环控制。针对不同的控制要求,可选择灵活的控制方法和调制手段,文中主要采用基于电机学中Park变换理念和空间矢量调制(SVPWM)调制方法对固态变压器的变流器环节进行控制。随后基于固态变压器的优良特性,对其在新能源微网中的应用进行了探索,介绍了FREEDM智能微网的概念和系统构成,并阐述了SST在网络中的配置模式。针对光伏和风电两个典型新能源发电领域,分析了固态变压器的优势和应用价值。利用Matlab/Simulink中的电力系统仿真工具箱对SST各个环节按照设计的参数和给定的控制策略搭建仿真模型,并对控制器的设计进行了参数优化选择,通过仿真结果验证了各环节控制策略的合理性,显示固态变压器具备一定的无功补偿功能,输入级的控制保证了网侧电压电流在负载变动时具备良好的跟随特性,并可实现输入单位功率因数,直流侧输出电压恒定；隔离级在变比一定的情况下,开环控制即可满足输出电压稳定的要求；输出级的控制则保证了在负载变动时,输出三相电压恒定且对称。在电力系统出现非正常运行状态时,具备直流环节的级联式固态变压器可有效改善供电状况,既能实现负载波动下的输入侧电流波形正弦要求和保持输出电压稳定,又能有效隔离原边电源变动对副边负载电压的影响。最后本文在理论分析和软件仿真的基础上,搭建了基于数字信号处理器(DSP)和绝缘栅极双极型晶体管(IGBT)的SST试验系统平台。硬件系统包括主电路、信号采集调理电路和驱动电路,软件基于TMS320F2812的DSP开发平台编写了主程序和中断服务程序,实现了基于双环解耦控制算法(?)口SVPWM调制算法的SST控制,并进行物理实验,验证了SST的优越性能。
[Abstract]:Solid-state transformer (SST) is a new type of intelligent power conversion equipment. Compared with traditional power transformer, solid-state transformer combines power electronic transformation technology and uses high-frequency isolation of the intermediate DC link. The flexible control of the primary and secondary edges can be realized. Its outstanding features are that the input current, the output voltage can be adjusted, and the power factor can be controlled. The application of solid-state transformer in power system can improve the controllability of the system, improve the power quality, facilitate the grid connection of new energy generation, and promote the construction and development of smart grid. In this paper, several typical topology structures and their control methods in the development of solid-state transformer are introduced, and their advantages and disadvantages are compared. Then, a cascade three-stage structure with DC link is analyzed. That is, solid-state transformer with input stage, isolation stage and output stage. Combined with the control objectives of each link, the corresponding control strategy is worked out. The input stage adopts the voltage outer loop, the current inner loop is decoupled, and the isolation stage adopts the open loop control. The output stage adopts voltage and current double loop control with voltage feedforward compensation. According to different control requirements, flexible control methods and modulation methods can be selected. In this paper, the converter link of solid-state transformer is controlled based on the idea of Park transform and space vector modulation (SVPWM) modulation, and then based on the excellent characteristics of solid-state transformer. Its application in new energy microgrid is explored, and the concept and system structure of FREEDM intelligent microgrid are introduced. The configuration mode of SST in the network is expounded, and the advantages and application value of solid-state transformer are analyzed in the field of photovoltaic and wind power generation. The power system simulation toolbox in Matlab/Simulink is used to build the simulation model of each link of SST according to the design parameters and the given control strategy. The optimal design parameters of the controller are selected. The simulation results verify the rationality of each link control strategy and show that the solid-state transformer has a certain reactive power compensation function. The control of the input stage ensures that the voltage and current of the grid side have good following characteristics when the load changes, and the input unit power factor and the output voltage of the DC side are constant. The open loop control can meet the requirement of output voltage stability under the condition of variable ratio of isolation stage. The output stage control ensures that the output three-phase voltage is constant and symmetrical when the load changes. When the power system appears abnormal operation condition, the cascaded solid-state transformer with DC link can effectively improve the power supply condition. It can not only realize the sinusoidal requirement of input side current waveform under load fluctuation and keep the output voltage stable, but also effectively isolate the influence of the change of the primary side power supply on the secondary load voltage. Finally, this paper is based on theoretical analysis and software simulation. The SST test system platform based on DSP (Digital signal processor) and IGBT (Insulated Gate Bipolar Transistor) is built. The hardware system includes main circuit, signal acquisition and conditioning circuit and drive circuit. The main program and interrupt service program are programmed on the DSP development platform based on TMS320F2812, and the dual loop decoupling control algorithm is realized. The SST control of the port SVPWM modulation algorithm and the physical experiment are carried out to verify the superior performance of SST.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM76;TM41

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