减小三相级联型PET中间直流侧电容的方法研究

发布时间：2018-03-24 20:42

本文选题：电力电子变压器　切入点：正弦功率传输　出处：《东北电力大学》2017年硕士论文

【摘要】：由于分布式电源的不断增多,同时用户用电需求的多样化,传统的城市交流配电网面临越来越多的技术挑战。未来城市配电网必然要以传统城市交流配电网络为支撑,从现有交流配电网变为一个能够实现交流配电网、直流配电网以及交直流混合配电网的不同电压等级互联的新型配电网。电力电子变压器是实现新型交直流混合配电网柔性变换的关键技术,由于它的模块化和可扩展性而得到广泛应用,而且能够将不同额定电压等级、不同性质的两个彼此独立的交直流电网互联起来,达到功率互相传输、稳定协调控制的功能。然而电力电子变压器也存在很多问题亟待解决,如三相级联型电力电子变压器的固有功率波动影响,导致其中间直流侧电容体积过大,传输功率密度较小的问题。因此,如何简单有效地解决这些问题成为本文研究分析的主要内容。本文提出了一种基于LLC谐振变换器的三相级联型电力电子变压器正弦功率传输概念,减小其中间直流侧电容,将交流侧二倍频率的功率波动传递到公共直流侧,并保证了恒定的直流电源,来解决电力电子变压器固有功率波动问题。同时,当LLC谐振变换器工作在近似谐振模式下,可以简单有效地实现正弦功率传输概念,并简化电力电子变压器控制结构实现单级控制,使得三相级联型电力电子变压器的正弦功率传输可以得到更广泛的应用。虽然PET的正弦传输概念只有较小的功率因数调节的能力,但是它对于单向功率传输的PET而言可以有效的减小电容和制造成本。本文根据三相电力电子变压器拓扑结构和正弦功率传输概念,对三相电力电子变压器的工作特性进行了分析。最后,搭建并测试了基于LLC谐振变换器的三相电力电子变压器试验系统,充分验证了正弦功率传输概念的可行性和有效性。
[Abstract]:With the increasing of distributed generation and the diversification of users' demand, the traditional urban AC distribution network faces more and more technical challenges. In the future, the urban distribution network must be supported by the traditional urban AC distribution network. From an existing AC distribution network to an AC distribution network, The power electronic transformer is the key technology to realize the flexible transformation of the new AC / DC hybrid distribution network, which is a new type of distribution network interconnected with different voltage levels of the AC / DC hybrid distribution network. Because of its modularization and extensibility, it is widely used, and it can connect two independent AC / DC power grids with different rated voltage levels and different properties to transmit power to each other. However, there are many problems to be solved urgently, such as the influence of inherent power fluctuation of three-phase cascaded power electronic transformer, which leads to the excessive volume of capacitance in the middle DC side of power electronic transformer. The problem of low transmission power density. How to solve these problems simply and effectively becomes the main content of this paper. In this paper, a concept of sinusoidal power transmission of three-phase cascaded power electronic transformer based on LLC resonant converter is proposed to reduce the middle DC side capacitance. The power fluctuation of the double frequency of AC side is transferred to the common DC side, and a constant DC power supply is guaranteed to solve the inherent power fluctuation problem of power electronic transformer. At the same time, when the LLC resonant converter works in the approximate resonant mode, The concept of sinusoidal power transmission can be realized simply and effectively, and the control structure of power electronic transformer can be simplified to realize single-stage control. This makes the sinusoidal power transmission of three-phase cascaded power electronic transformers more widely used. Although PET's sinusoidal transmission concept has only a small power factor adjustment ability, However, it can effectively reduce the capacitance and manufacturing cost for unidirectional power transmission PET. In this paper, according to the topology of three-phase power electronic transformer and the concept of sinusoidal power transmission, The operating characteristics of three-phase power electronic transformer are analyzed. Finally, a three-phase power electronic transformer test system based on LLC resonant converter is built and tested, which fully verifies the feasibility and validity of the concept of sinusoidal power transmission.
【学位授予单位】：东北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM46;TM41

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