基于电力电子变压器并网装置的微网控制研究

发布时间：2018-05-02 02:02

本文选题：微电网 + 电力电子变压器　；参考：《杭州电子科技大学》2014年硕士论文

【摘要】：在传统化石能源日趋紧张以及节能减排的全球大背景下，，分布式发电技术飞速发展，整合了分布式发电、电力电子、电力系统控制技术的微型电网技术受到人们越来越多的重视。为实现微网与大电网之间的有效互补，微网并网技术值得深入探究。传统微网并网方式存在并网速度慢、冲击大、供电可靠性低、潮流无法控制等问题，另外由于两个电网之间不存在有效的隔离措施，任何一侧电网发生故障电流、谐波污染等问题都将对另一侧电网产生影响，电能质量得不到有效保证。所以有必要采用一种新的微网并网方式，来提高微网与大电网并网的可靠性和灵活性。本文对微电网并网方式、关键控制技术进行深入剖析的基础上，设计了一种基于电力电子变压器的新型微网并网装置结构。该装置由电力电子变压器及储能系统两部分组成，取代了传统并网所需的常规电力变压器和断路器，不仅能够快速、准确地变换电压，实现电路的接通与开断，还可实现微网与配电网的异步运行。在分析并网装置结构的基础上，提出了微网DG与并网装置的协调控制策略：并网装置中PET输出级VSC作为主控单元采用V/f控制，微网DG作为从控制单元，采用PQ控制或者定直流电压控制；利用PSCAD/EMTDC仿真工具对基于电力电子变压器并网装置的微网模型在联网模式、孤岛模式以及联网与孤岛模式切换下进行了仿真分析，仿真结果表明并网装置在联网和孤岛运行时均能保持微网电压和频率稳定，同时具有无功补偿作用；在联网与孤岛运行模式切换时无需对电力电子变压器输出级及微网内其他DG的控制策略进行改变，且变换速度快，冲击小。讨论了微网接入对配电网在潮流、网损、电能质量、市场模式等方面的影响，明确了电网友好型微网的定义，认为电网友好型微网的核心问题是尽可能地维持微网与大电网之间功率交换的恒定。在此基础上，提出了基于并网装置的电网友好型微网的控制策略：并网装置中电力电子变压器输出级采用PQ控制策略，功率不易调整的微源采用PQ控制或定直流电压控制策略，功率易于调整的微源及可控负荷均采用下垂控制策略。利用PSCAD/EMTDC仿真工具对电网友好模式下的微网进行仿真分析，仿真结果表明当微网内不可控负荷或者微源突变时，微网内部功率易于调整的微源及可控负荷均能对突变的功率进行合理分配，保证微网内功率平衡，维持并网点功率交换的恒定；当并网点功率交换发生突变时，功率易于调整的微源及可控负荷同样能够合理分配功率，维持微网内部功率平衡，实现微网的稳定运行。
[Abstract]:Under the background of the increasing tension of traditional fossil energy and the global background of energy saving and emission reduction, distributed power generation technology has developed rapidly, integrating distributed generation, power electronics, People pay more and more attention to the microgrid technology of power system control technology. In order to realize the effective complementation between microgrid and large power grid, microgrid grid-connected technology is worth exploring deeply. There are some problems in the traditional micro-grid connection, such as slow speed, big impact, low reliability of power supply, uncontrollable power flow, etc. In addition, because there is no effective isolation between the two power grids, fault currents occur on either side of the grid. Harmonic pollution and other problems will have an impact on the other side of the grid, power quality can not be effectively guaranteed. So it is necessary to adopt a new mode of microgrid connection to improve the reliability and flexibility of microgrid and large power grid. Based on the deep analysis of microgrid grid-connected mode and key control technology, a new type of micro-grid grid-connected device based on power electronic transformer is designed in this paper. The device consists of two parts, power electronic transformer and energy storage system. It replaces the conventional power transformer and circuit breaker needed for traditional grid-connection. It can not only quickly and accurately change the voltage, but also realize the circuit switching on and off. The asynchronous operation of microgrid and distribution network can also be realized. On the basis of analyzing the structure of the grid-connected device, the coordinated control strategy between the microgrid DG and the grid-connected device is put forward. In the grid-connected device, the PET output stage VSC is used as the main control unit, and the microgrid DG is used as the slave control unit. Using PQ control or constant DC voltage control, the microgrid model based on power electronic transformer grid-connected device is simulated and analyzed under the network mode, islanding mode, and switching between networked and islanding modes by using PSCAD/EMTDC simulation tool. The simulation results show that the grid-connected device can keep the voltage and frequency of the microgrid stable and has the function of reactive power compensation. There is no need to change the control strategy of the power electronic transformer output stage and other DG in the microgrid when switching the operation mode between the interconnection and the isolated island, and the conversion speed is fast and the impact is small. The influence of microgrid access on power flow, network loss, power quality, market mode and so on is discussed, and the definition of grid-friendly microgrid is defined. It is considered that the core problem of grid-friendly microgrid is to keep the power exchange between microgrid and large grid as constant as possible. On this basis, the control strategy of grid-friendly microgrid based on grid-connected device is put forward. In grid-connected device, PQ control strategy is used for output stage of power electronic transformer, and PQ control strategy or constant DC voltage control strategy is used for micro-source which power is not easy to adjust. The droop control strategy is used for microsource and controllable load which can be adjusted easily. The simulation analysis of microgrid in grid-friendly mode is carried out by using PSCAD/EMTDC simulation tool. The simulation results show that when the load in the microgrid is uncontrollable or the microsource changes, The microsource and controllable load, which are easy to adjust the power inside the microgrid, can distribute the power of the mutation reasonably, ensure the power balance in the microgrid, and maintain the constant power exchange of the parallel network. The microsource and the controllable load, which are easy to adjust the power, can distribute the power reasonably, maintain the balance of the power inside the microgrid, and realize the steady operation of the microgrid.
【学位授予单位】：杭州电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM41

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