【作者】 王聪颖；

【导师】 张东来；

【作者基本信息】 哈尔滨工业大学 ， 电气工程， 2011， 硕士

【摘要】 基于新能源和可再生能源的分布式发电迎来了新的发展机遇,微电网是整合了部分小型分布式发电和本地负荷的微型电网,在降低大量分布式发电并网对大电网的影响、减少长距离输电线路的损耗以及提高供电可靠性方面具有显著的优势。微电网的运行控制成为近几年研究的热点。本文采用PSCAD/EMTDC仿真软件,建立了光伏发电模型和微型燃气轮机发电模型,并以此作为微源,组建了微电网系统。分析了两种微源的不同特性,确定了各自的并网方案,光伏发电以电流源形式并网,输出最大功率,微型燃气轮机以具有下垂特性的电压源形式并网。其次,分别研究了微源以电压源形式并网和电流源形式并网的控制方法。电压源并网采用基于瞬时值反馈的电压电流双环控制方法,内环采用电容电流反馈闭环,提高了系统的动态特性,并用极点配置方法对控制器的参数进行优化设计。电流源形式并网利用d-q分解对有功无功进行单独控制,实现并网功率的单位因数为1,引入电压前馈控制抑制电网背景谐波对电流源谐波含量的影响,并分析了电流源谐波分量对并联点电压的影响。再次,研究了离网运行时并联电压型微源之间的功率分配关系,对比分析了采用频率下垂控制有功较相位下垂控制有功的优点,研究了线路参数以及下垂系数对无功功率分配的影响。并且,在同时计及线路电阻和电感时,分析了有功无功之间的耦合关系以及该情况下如何确保功率准确分配的方法。最后对微电网运行的稳定性进行研究,建立了系统完整的小信号模型,通过特征值分析,得到逆变器控制参数、线路参数以及负荷参数对稳定性的影响,仿真结果验证了分析的正确性,对实际系统有一定的指导意义。更多还原

【Abstract】 Under the background of emphasis on environment protection and fuel saving, distributed generations (DG), based on new energy and renewable energy, become most promising. Microgrid is an aggregation of some DG and some load, which can be regarded as a mini power system. The appearance of Microgrid can reduce the impact on the grid when lots of small-sized DG connecting to the grid, lower the loss of long distance transmission and improve the power supply reliability. So, the study of Microgrid control is hot in recent years.This paper established photovoltaic generation (PV), micro turbine generation (MT) model, and then the Microgrid system based on PSCAD simulation. After analysis of the characteristics of different DG, the scheme of grid connection is decided. PV is connected to the grid as a current source with MPPT, and MT as a voltage source with droop characteristic.The control methods of grid connetion as voltage source and current source are studied respectively. Voltage source control employs voltage as external loop and current as inner loop with instantaneous value as feedback. Inner control loop uses capacitor current as feedback to improve the dynamic characteristic. The paper studies the PI optimization considering the pole set method. Current source control employs the classic d-q current compenet to adjust the active power and reactive power outputs, obtaining power facter as 1. Employing the voltage forward feedback can reduce the haimonic current and the impact of the homonic current from CSI on voltage is studied.Then, power sharing between the parallel DGs is discussed. The paper analyses the advantage of frequency droop control in comparison with angle droop control in terms of active power sharing. The accuracy of reactive power sharing with voltage droop control is influenced by the line parameter, combined with droop coefficient. Considering both the line resistance and inductance, active power flow and reactive power would be coupling. In this condition, the method to insure the accuracy of power sharing is given.At last, the whole small-signal dynamic model, including the VSI, the line parameter and load parameter, is proposed, which can be used in stability analysis. Based on this model, eignvalue locus plots as a function of all kinds of parameters can be gained and so the relationship between system parameter and stability can be obtained, too. Simulation results prove that the conclusion is rational.更多还原