模块化多电平变换器控制系统设计及实验研究

发布时间：2019-07-03 19:44

【摘要】：从可持续发展战略的角度出发,以太阳能、风能等可再生能源为主的新能源发电技术成为研究的热点。随着现有技术的发展,基于电压型模块化多电平变换器的柔性直流输电技术成为解决分布式电源并网的必然选择。而控制系统又是整个柔性直流输电系统的大脑和神经,因此本文以模块化多电平变换器(MMC)的控制系统为研究核心,并结合实验研究其控制策略。本文结合现有的MMC柔性直流输电实例,分析了MMC控制系统的研究现状,总结出了现有MMC控制技术的典型控制系统结构,柔性直流输电的控制系统主要包括系统级控制、换流站级控制及换流阀级控制。并且针对典型的半桥子模块型MMC拓扑,分析了背靠背MMC及其子模块的工作原理,以及四象限运行情况,建立了其简化等效模型以及MMC上桥臂小信号模型,方便后续控制策略的设计。在现有研究技术层次化子模块电容电压平衡控制方法的基础上,本文提出了一种基于桥臂电流直接控制的MMC综合控制策略,并将其应用于由整流侧和逆变侧组成的背靠背MMC系统,整流侧负责直流母线电压稳定控制,逆变侧负责并网控制。并以电流内环的控制框图以及调节器设计为例,详细介绍了MMC控制系统的设计过程；针对整流侧MMC本文还提出了一种有功电流前馈方案,增加了有功电流的动态响应速度,提高了系统的快速性和稳定性。为了进行MMC实验的研究,本文研制了一套四个子模块的三相背靠背MMC实验平台。控制系统由主控制器、辅助控制器和子模块控制器三级控制组成,其中主控制器采用TI最新的集ARM和DSP的双核芯片F28M35。其中包含M3核和C28核,M3核主要用于实现与上位机的通信,将MMC的工作状态信息及时的发送到上位机进行显示,同时接收上位机的指令；C28核主要用于实现核心控制算法以及与FPGA的通信。FPGA作为辅助控制器主要实现载波移相以及数据转换,产生各个子模块的PWM信号,串行接收子模块控制器的电容电压反馈值,转换成16位的数据供DSP调用。在实验平台的调试过程中,本文首先利用PSIM仿真验证了MMC综合控制策略的有效性；然后利用此控制策略进行了半实物仿真系统的调试,利用已经调试成功的半实物仿真系统进行控制系统的调试；最后利用已经调试成功的控制系统进行强电主回路的调试,至此整个实验平台调试成功。就可以利用整个实验平台进一步进行模块化多电平变换器的一系列实验研究,为控制策略的研究提供了很好的实验平台。实验结果证明了此实验平台的实用性以及所述MMC综合控制策略的有效性。
[Abstract]:From the point of view of sustainable development strategy, the new energy power generation technology, which is dominated by solar energy, wind energy and other renewable energy, has become a hot research topic. With the development of existing technology, flexible DC transmission technology based on voltage source modular multilevel converter has become an inevitable choice to solve the problem of distributed power supply connected to the grid. The control system is the brain and nerve of the whole flexible HVDC system, so this paper takes the control system of modular multilevel converter (MMC) as the research core, and studies its control strategy with experiments. Based on the existing examples of MMC flexible HVDC, this paper analyzes the research status of MMC control system, and summarizes the typical control system structure of MMC control technology. the control system of flexible HVDC mainly includes system level control, converter station level control and converter valve level control. Aiming at the typical half-bridge submodule MMC topology, the working principle of back-to-back MMC and its sub-modules, as well as the operation of four quadrants are analyzed, and its simplified equivalent model and MMC upper bridge arm small signal model are established to facilitate the design of subsequent control strategy. On the basis of the existing research on the capacitance voltage balance control method of the sub-module, this paper proposes a MMC comprehensive control strategy based on the bridge arm current direct control, and applies it to the back-to-back MMC system composed of rectifier side and inverter side. The rectifier side is responsible for DC bus voltage stability control, and the inverter side is responsible for grid-connected control. Taking the control block diagram of the current inner loop and the design of the regulator as an example, the design process of the MMC control system is introduced in detail, and a feedforward scheme of the active current is also proposed for the rectifier MMC, which increases the dynamic response speed of the active current and improves the rapidity and stability of the system. In order to carry out the research of MMC experiment, a set of three-phase back-to-back MMC experimental platform with four sub-modules is developed in this paper. The control system is composed of three levels of control: main controller, auxiliary controller and sub-module controller. The main controller adopts TI's latest dual-core chip F28M35, which integrates ARM and DSP. The M3 core is mainly used to realize the communication with the upper computer, and the working state information of MMC is sent to the upper computer for display in time, and the instructions of the upper computer are received at the same time. The C28 core is mainly used to realize the core control algorithm and communication with FPGA. FPGA, as an auxiliary controller, mainly realizes carrier phase shift and data conversion, generates the PWM signal of each sub-module, serially receives the capacitance voltage feedback value of the sub-module controller, and converts it into 16 bits of data for DSP call. In the debugging process of the experimental platform, this paper first uses PSIM simulation to verify the effectiveness of the MMC integrated control strategy; then uses this control strategy to debug the hardware-in-the-loop simulation system, and uses the hardware-in-the-loop simulation system that has been debugged to debug the control system; finally, the debugged control system is used to debug the strong electric main circuit, so that the whole experimental platform is debugged successfully. A series of experimental studies of modular multilevel converters can be carried out by using the whole experimental platform, which provides a good experimental platform for the research of control strategy. The experimental results show the practicability of the experimental platform and the effectiveness of the MMC integrated control strategy.
【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】：TM46

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