【作者】 李亮；

【导师】 王安娜；

【作者基本信息】 东北大学 ， 电力系统及其自动化， 2018， 硕士

【摘要】 随着经济的发展,能源短缺与环境污染问题日益突出,对包括风能、太阳能等在内的清洁能源的开发利用受到人们的重视。其中,微电网作为目前能够最有效利用分布式能源的一种方式已成为科研人员的研究热点。然而由于分布式能源的间歇性特点,给微电网系统的安全运行带来了极大的挑战,为了保证达到用户对电能质量的要求,提高微电网运行的可靠性和经济性,需要合适的控制方式。逆变器作为微电网系统的核心部分,有效的逆变器控制技术是保证微电网安全可靠运行的关键所在,特别是在微电网离网模式下运行时,除了需要各个并联逆变器稳定输出保证系统电压和频率稳定之外,还要求各逆变器按照自身容量进行负荷功率分配,因此,对于微电网逆变器来说,合理有效的控制策略显得尤为重要。本文首先在研究传统下垂控制的基础之上,分析不同阻抗的传输线路对下垂控制的影响。结合各种逆变器的特点选取电压型三相逆变器作为电路主拓扑结构,并建立逆变器数学模型。设计逆变器电压电流双环控制器,通过仿真验证逆变器双环控制器的动态响应特性。对采用下垂控制算法的逆变器进行稳定性分析,结果表明,相比于传统的准静态模型分析方法,动态相量模型可以得到更加精确的稳定裕度。其次通过研究微电网逆变器的控制方法,在分析逆变器主要控制技术的基础之上,对传统的下垂控制进行改进,传统下垂控制下垂系数为固定值,本文提出了随功率自适应改变的下垂系数,在下垂系数中分别引入有功功率和无功功率。当负荷功率发生变化时,根据逆变器实际输出的功率动态调整下垂系数。在实现各逆变器按照自身容量比进行功率分配的前提下,减小逆变器输出电压以及系统频率的偏差。通过分析线路阻抗和虚拟阻抗引起的电压降落,提出基于下垂控制的母线电压补偿策略。该策略依据逆变器输出的有功功率和无功功率对母线电压偏差进行计算,并以电压偏差作为比例控制器的输入量,进而得到输出电压补偿量。通过不断调整参考电压,所提出的补偿策略可有效改善系统电压因线路阻抗和虚拟阻抗而引起的电压降落问题。最后,本文在Matlab/Simulink环境下搭建逆变器仿真模型,并对所提改进下垂控制策略和母线电压补偿策略进行仿真验证。仿真结果显示,逆变器在所提控制策略下能够更加安全、可靠地工作。更多还原

【Abstract】 With the development of the economy,the problems of energy shortage and environmental pollution have become increasingly seriously,the utilization of clean energy which including wind energy and solar energy has received much attention.Among them,microgrid as the most effective way to make use of distributed energy has gradually become a research hotspot for researchers.However,due to the intermittent nature of distributed energy,which brings a great challenge to the safe operation of the microgrid system.In order to ensure the people’s requirement for power quality and improve the reliability and economy of microgrid operation,proper control strategy is needed.Inverter as the core part of the microgrid system,the effective control technology of the inverter is the key to ensure the microgrid which runs safety and reliability,especially when the microgrid running in the off-grid mode,in addition to keep each parallel output a stable voltage and current,also need the inverter performs load power distribution according to its own capacity In addition to ensuring the stability of the voltage and frequency of the system,each inverter is required to carry out load power distribution according to its own capacity.Therefore,for the inverter of microgrid,a reasonable and effective control strategy is particularly important.In this paper,analyzed and discussed the traditional droop control strategy,studied the effects of different impedance transmission lines on droop control strategy.Combined with the characteristics of various inverters,and select a voltage type three phase inverter as the main topology of the circuit,and a mathematical model of the inverter is established.The inverter voltage and current double loop controller is designed.Verify the dynamic characteristics of the inverter double loop controller through simulation.Compared with the traditional quasi-static model analysis method,when analyses the droop control strategy which used in inverter,the dynamic phasor model can get a more accurate stability margin.Secondly,by studying the control method of the microgrid inverter,and analysis the main control technology of the inverter,the traditional droop control is improved.In this paper,the droop coefficient which is adaptively changed with power is proposed,and the active power and reactive power are respectively introduced in the droop coefficient.When the load power changes,the droop coefficient is dynamically adjusted according to the actual output power of the inverter.Under the premise of realizing the power distribution of each inverter according to its own capacity ratio,the inverter output voltage and the deviation of the system frequency are reduced.By analyzing the voltage drop caused by line impedance and virtual impedance,a bus voltage compensation strategy based on droop control is proposed.The strategy calculates the bus voltage deviation by the active power and reactive power of the inverter,and the voltage deviation is used as the input signal to pass through the P controller,the output obtains the voltage compensation amount.By constantly adjusting the reference voltage.the proposed compensation strategy can effectively improve the voltage drop caused by the line impedance and the virtual impedance of the system voltage.Finally,the inverter simulation model is built in Matlab/Simulink environment,and the improved droop control strategy and bus voltage compensation strategy are simulated and verified.The experimental results show that the improved strategy achieves the expected results.更多还原