交直流混合微电网中双向功率变换器控制策略及其应用研究

发布时间：2018-08-09 14:04

【摘要】：随着分布式能源的与日俱增,交直流混合微电网作为高效利用分布式能源的有效手段越来越受到关注,双向功率变换器是交直流混合微电网中能量控制的核心,得到了广泛的研究和利用。目前双向功率变换器的控制策略通常采用变流器的传统控制方法,如双闭环、恒功率、V/F等,未考虑交直流混合微电网的特点。本文提出一种针对交直流混合微电网“源-源”特点的自治运行控制策略,能够实现微电网的区域自治及双向功率变换器的模块化并联,具有无需通信、即插即用等优点。本文对基于低压微电网下垂特性的自治运行控制策略、零序环流抑制方法及工程化关键技术进行了较为深入的研究和探讨。主要内容包括:(1)研究了双向功率变换器模型及双闭环控制方法。建立了双向功率变换器在不同坐标系下的数学模型,利用该模型,针对交直流混合微电网特性,设计了双向功率变换器双闭环控制策略,并研究了该策略中控制器参数选取的理论依据,最后Matlab/Simulink中搭建仿真模型对所提控制方法进行验证。该策略可以实现直流母线电压稳定,交、直流两侧的能量双向流动,并对交流侧功率因数进行控制。(2)提出一种双向功率变换器的自治运行控制策略,解决了低压交直流混合微电网区域自治的问题。通过分析低压微电网功率传输特性,建立了功率平衡与母线电压、频率的关系,据此设计了自治运行功率外环,通过理论推导分析,建立了自治运行功率外与电流内环的联系,完成了单模块自治运行控制系统的设计,最后在Matlab/Simulink中搭建仿真,对子网微源出力变化、负荷变化的潮流控制效果进行验证。该策略能够控制交、直流子网母线电压始终在允许范围内运行,在保留交直流混合微电网配置灵活性的同时提高了微电网的运行可靠性(3)研究了多个双向功率变换器并联运行时的零序环流抑制方法及模块化自治运行控制方案。通过分析多双向功率变换器模块直接并联时的零序环流平均等效模型,提出一种零序环流抑制方法,解决了多变换器并联时零序环流过大导致的电流波形畸变问题。并基于平均等效模型,分析了零序电流与功率控制的关系,结合自治运行策略,提出了模块化的自治运行控制方案。最后在Matlab/Simulink中搭建仿真,对零序环流抑制效果及模块化自治运行控制方案的可行性进行验证。该方案能够有效抑制零序环流,减少电流波形畸变,实现双向功率变换器的模块化扩展。(4)研制了采用自治运行策略的双向功率变换器工程样机。详细设计了硬件主电路、控制电路及软件控制系统并研究及设计了DSP程序详细的运行流程。在样机的基础上搭建了低压交直流混合微电网实验平台,对文中所提出的控制策略进行了实验验证。
[Abstract]:With the increasing of distributed energy sources, the AC / DC hybrid microgrid, as an effective means of efficient utilization of distributed energy, has been paid more and more attention. Bidirectional power converter is the core of energy control in AC / DC hybrid microgrid. Has been widely studied and used. At present, the conventional control methods of bidirectional power converters, such as double closed loop, constant power V / F and so on, are usually used in converter control, and the characteristics of AC / DC hybrid microgrid are not taken into account. This paper presents an autonomous operation control strategy for AC / DC hybrid microgrid, which can realize the regional autonomy of microgrid and the modularized parallel connection of bi-directional power converters. It has the advantages of no communication, plug and play, etc. In this paper, the autonomous operation control strategy based on the droop characteristics of low-voltage microgrid, the zero-sequence circulation suppression method and the key engineering techniques are deeply studied and discussed. The main contents are as follows: (1) Bidirectional power converter model and double closed loop control method are studied. The mathematical model of bidirectional power converter in different coordinate systems is established. According to the characteristics of AC / DC hybrid microgrid, a dual closed loop control strategy for bidirectional power converter is designed. The theoretical basis for the selection of controller parameters in the strategy is also studied. Finally, the simulation model in Matlab/Simulink is built to verify the proposed control method. This strategy can realize the stability of DC bus voltage, the bidirectional flow of energy on both sides of AC and DC, and the control of AC side power factor. (2) an autonomous operation control strategy of bi-directional power converter is proposed. The problem of regional autonomy of low voltage AC / DC hybrid microgrid is solved. By analyzing the power transmission characteristics of low-voltage microgrid, the relationship between power balance and bus voltage and frequency is established. Based on this, an autonomous operating power outer loop is designed. The design of the single module autonomous operation control system is completed. Finally, the simulation is built in Matlab/Simulink to verify the power flow control effect of the change of the subnet micro-source force and load. This strategy can control AC, DC subnet bus voltage is always within the allowable range, While preserving the flexibility of AC / DC hybrid microgrid configuration, the operational reliability of microgrid is improved. (3) the zero-sequence circulation suppression method and modular autonomous operation control scheme for parallel operation of several bi-directional power converters are studied. By analyzing the average equivalent model of zero-sequence circulation in direct parallel connection of multi-bidirectional power converters, a zero-sequence circulation suppression method is proposed, which solves the problem of current waveform distortion caused by excessive zero-sequence circulation in parallel. Based on the average equivalent model, the relationship between zero-sequence current and power control is analyzed, and a modular autonomous operation control scheme is proposed in combination with autonomous operation strategy. Finally, the simulation is built in Matlab/Simulink to verify the effect of zero sequence circulation suppression and the feasibility of modular autonomous operation control scheme. This scheme can effectively suppress the zero-sequence circulation, reduce the distortion of the current waveform, and realize the modularization expansion of the bi-directional power converter. (4) the engineering prototype of the bi-directional power converter with autonomous operation strategy is developed. The hardware main circuit, control circuit and software control system are designed in detail, and the detailed running flow of DSP program is studied and designed. Based on the prototype, a low voltage AC / DC hybrid microgrid experimental platform is built, and the proposed control strategy is verified experimentally.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM46;TM727

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