微电网分布式单元并联运行控制和稳定性研究

发布时间：2018-05-21 06:11

本文选题：微电网 + 并联逆变器　；参考：《燕山大学》2015年硕士论文

【摘要】：由可再生能源、储能设备和电力电子装置等组成的微电网逐渐成为满足负荷增长需求的有效方式。随着大量分布式发电单元接入,孤岛微电网中存在多逆变器并联运行状态,受线路阻抗不匹配以及本地负载等影响易引起功率分配和环流问题,影响系统稳定运行。针对并联系统功率分配和环流问题,本文考虑线路阻抗和本地负载影响,辨析系统在功率按容量均分和零环流运行状态下的联系和区别,并对比两种状态下线路损耗。考虑系统效率,本文提出一种基于平均功率的改进下垂控制方案。该方案无需分别考虑线路阻抗和本地负荷等因素对功率分配的影响,利用功率差产生的电压偏移量对电压幅值进行补偿以实现功率分配,减小环流,并在相同容量和不同容量并联系统中均能达到较好的负荷分配。为合理设计下垂系数,常忽略电压电流环等影响,并通过建立下垂环节的小信号模型分析系统稳定性。但孤岛系统中各分布式发电单元之间存在谐波交互作用,为此,本文考虑逆变器电压电流闭环作用,通过推导孤岛系统中公共耦合点电压与参考电压和输出电流的关系式,建立多机下垂系统的等效戴维南模型,利用基于阻抗的Nyquist稳定判据判断系统稳定性。理论分析和仿真结果证明了线路阻抗和逆变器并联数量对系统谐波稳定性的重要影响。最后,本文基于TMS320F2812的DSP搭建三相逆变器并联实验平台进行实验验证,实验结果证明控制策略的有效性。
[Abstract]:Microgrid composed of renewable energy, energy storage equipment and power electronic devices has gradually become an effective way to meet the demand of load growth. With the access of a large number of distributed generating units, there is a parallel operation state of multi-inverter in isolated island microgrid. The power distribution and circulation problems are easily caused by the mismatch of line impedance and local load, and the stable operation of the system is affected. Considering the influence of line impedance and local load on the power distribution and circulation of parallel systems, this paper distinguishes the connection and difference of the system under the condition of capacity distribution and zero circulation operation, and compares the line losses in the two states. Considering system efficiency, an improved droop control scheme based on average power is proposed. This scheme does not need to consider the influence of line impedance and local load on power distribution separately. The voltage offset produced by power difference is used to compensate the voltage amplitude to realize power distribution and reduce the circulation. And in the same capacity and different capacity parallel system can achieve better load distribution. In order to design the sag coefficient reasonably, the influence of voltage and current loop is often ignored, and the stability of the system is analyzed by establishing a small signal model of droop link. However, there is harmonic interaction among the distributed generation units in the isolated island system. In this paper, considering the closed-loop effect of inverter voltage and current, the relationship between the common coupling point voltage and the reference voltage and the output current in the isolated island system is derived. The equivalent Thevenin model of multi-machine droop system is established, and the stability of the system is judged by Nyquist stability criterion based on impedance. The theoretical analysis and simulation results show that the line impedance and the number of parallel inverters have important effects on the harmonic stability of the system. Finally, the parallel experiment platform of three-phase inverter based on DSP of TMS320F2812 is built and the experimental results show that the control strategy is effective.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM732;TM712

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