交直流混合配电系统建模与控制研究

发布时间：2018-02-25 22:25

本文关键词： 交直流混合系统电压源换流器配网控制　出处：《沈阳工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：世界经济发展的大趋势是向低碳绿色经济转型,随着中低压配网中新能源应用的迅速增加,新能源种类和应用形式越来越复杂。各类新能源分散接入和应用的需要已经超过了传统配电网的接纳能力,配网中急需能够实现多源多荷“即插即用”的交直流混合配电系统,用来大量接纳分布式电源的同时向交直流负荷供电。这对于新能源大量接入的情况下,提高中低压配电网的运行水平,具有重要意义。本文提出一种基于柔性直流背靠背模式的交直流混合配电系统,用于实现配电网中直流负荷的承接与风、光、储等新能源的接入。设计了控制策略控制交直流混合配电系统实现功率平衡和电压稳定。建立系统的的仿真模型对其运行特性进行动态仿真分析,并对其功能及有效性进行了仿真验证。首先,阐述了电压源换流器的基本工作原理,基于Park变换建立了其在旋转坐标系下的数学模型;分析了直流微电网中光伏发电、直驱永磁风机、蓄电池等分布式电源的基本原理、等效模型和接口控制模型。其次,设计了一个基于保持直流母线电压的稳定和功率平衡的的控制策略。其中一端电压源换流器采用定直流电压控制,即控制直流母线电压和交流侧无功功率;另一端电压源换流器采用定功率控制,即控制有功功率和无功功率。为了提高控制的精确度,采用基于d-q坐标变换的双闭环控制、内环采用有功和无功解耦控制的策略。在光伏发电和风力发电系统接入直流母线之前,设置Buck降压斩波电路,使光伏和风力发电系统在输出功率之时也能承担维持母线电压稳定的任务。通过这种控制策略实现直流母线间的能量变换、各种分布式电源的接入。最后,在PSCAD软件中搭建了交直流混合配电系统的仿真模型,将控制策略应用在模型中进行动态仿真运行。对于系统在微源无功率输出、光伏和负荷功率变化、风机突然接入系统三种状况下分别进行仿真分析。仿真结果表明在复杂的源荷接入条件下,系统运行平稳,直流母线电压是稳定的,实现了母线间灵活的能量变换。
[Abstract]:The major trend of world economic development is the transition to a low carbon green economy. With the rapid increase of new energy applications in medium and low pressure distribution networks, The types and application forms of new energy are becoming more and more complicated. The need for decentralized access and application of all kinds of new energy sources has exceeded the acceptance capacity of traditional distribution networks. In distribution networks, there is an urgent need to realize a multi-source and multi-load "plug and play" AC / DC hybrid distribution system. It is used to accept distributed power and supply AC / DC load at the same time. This can improve the operation level of medium and low voltage distribution network when new energy is heavily connected. This paper presents a hybrid AC / DC distribution system based on flexible DC back-to-back mode, which is used to carry out DC load and wind and light in distribution network. The control strategy is designed to control the AC / DC hybrid distribution system to achieve power balance and voltage stability. The function and effectiveness of the converter are verified by simulation. Firstly, the basic working principle of the voltage source converter is described, the mathematical model of the converter is established based on Park transform, and the photovoltaic generation in DC microgrid is analyzed. The basic principle, equivalent model and interface control model of direct-drive permanent magnet fan, battery and other distributed power supply. Secondly, A control strategy based on maintaining the stability and power balance of DC bus voltage is designed, in which one end voltage source converter is controlled by constant DC voltage, that is, the DC bus voltage and AC side reactive power are controlled. The other end of the voltage source converter uses constant power control, that is, the active power and reactive power. In order to improve the accuracy of the control, double closed loop control based on d-q coordinate transformation is used. The inner loop adopts the active and reactive power decoupling control strategy. Before the PV and wind power systems are connected to the DC bus, the Buck step-down chopping circuit is set up. So that photovoltaic and wind power generation systems can also take the task of maintaining bus voltage stability when output power. Through this control strategy, the energy conversion between DC bus lines and the access of various distributed power sources can be realized. Finally, The simulation model of AC / DC hybrid distribution system is built in PSCAD software, and the control strategy is applied to the dynamic simulation. The simulation results show that the system runs smoothly and the DC bus voltage is stable under the complicated source load access condition, which realizes the flexible energy transformation between the busbar.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM721.3

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