论文总字数：34286字

摘 要

环境污染已经成为了世界各国广泛关注的问题，随着中低压配电网中新能源应用的增加，在目前配电网中，交流配电网仍然为主流形式，各类新能源分散接入已经超过了传统配电网的接纳能力。配网中需要能实现多源多荷“即插即用”的交直流混合配电系统，用来大量接纳分布式电源的同时向交直流负荷供电。  

本文提出一种以柔性直流背靠背模式为基础的交直流混合配电系统，可以用来实现配网中直流负荷的承接与风、光、储等新能源的接入。设计了通过引入对换流器的控制策略控制交直流混合配电系统实现功率平衡和直流母线电压稳定。建立系统的仿真模型对其运行特性进行动态仿真分析，并对其功能及有效性进行了仿真校验。

首先，本文介绍了电压源换流器的组成及其原理，建立基于Park变换的在旋转坐标系下的数学模型：分析了直流微电网中光、风、储等分布式电源的工作原理、等效模型和接口控制模型。

其次，本文基于保持直流母线电压的稳定和功率平衡，设计了一个控制策略。控制策略大致如下：一端的电压源换流器采用定直流电压控制；另一端则采用定功率控制。一端控制直流母线电压和交流测无功功率，另一端控制有功功率和无功功率。为了提高控制的精度，采用基于d-p坐标变换的双环控制、内环采用有功无功解耦控制策略。为了使光伏和风力发电在输出功率时维持母线电压的稳定，在光伏发电和风力发电系统接入直流母线前，加设Buck降压斩波电路。以这种控制策略来直流母线之间的能量变换以及各种分布式电源的接入。

最后，搭建交直流混合配电系统的仿真模型，在模型中应用控制策略并进行动态仿真。仿真研究了两端有源网络的功率传输和向无源网络供电的工程状况。结果表明:设计的系统可以对有功与无功功率进行准确、独立控制且两个换流站之间不需要通信。电网电压跌落过大时VSC阀的过电流保护能控制换流站传输功率降额运行，直流电压斜率控制器可以抑制故障下电压波动。在交直流混合网络中，对电力系统稳定器进行了参数优化，并利用VSC的无功补偿能力提高混合系统稳定性。结果表明:参数优化后发电机的转速与功角能迅速稳定，同时联络线上的功率摇摆对直流输电线路没有影响，VSC能稳定控制直流传输的功率，若利用柔性直流异步互联可以根除系统的低频振荡。

关键词：交直流混合系统，电压源换流器，配电网，控制策略

Abstract

Environmental pollution has become a widespread concern in countries around the world.With the increase in the use of new energy in low-voltage distribution networks, AC distribution networks are still the mainstream in the current distribution network, and various types of new energy sources have been widely used.Exceeded the acceptance capacity of traditional distribution networks.In the distribution network,an AC-DC hybrid power distribution system capable of realizing "plug and play" of multiple sources and multiple loads is required to receive a large amount of distributed power while supplying power to AC and DC loads.

This paper proposes an AC/DC hybrid power distribution system based on a flexible DC back-to-back model, which can be used to achieve the acceptance of DC loads in distribution networks and the access of new energy such as wind, light and storage.The AC/DC hybrid power distribution system is designed to achieve power balance and DC bus voltage stability by introducing the control strategy for the converter. The system"s simulation model was established to perform dynamic simulation analysis of its operating characteristics, and its function and effectiveness were verified by simulation.

Firstly, this paper introduces the composition and principle of the voltage source converter and establishes a mathematical model based on the Park transformation in a rotating coordinate system. It analyzes the working principles of distributed power sources such as light, wind and storage in a DC micro-grid, etc. Effect model and interface control model.

Secondly, this paper designs a control strategy based on keeping the DC bus voltage stability and power balance. The control strategy is roughly as follows: One end of the voltage source converter adopts constant DC voltage control; the other end adopts constant power control. One end controls the DC bus voltage and AC measurement reactive power, and the other end controls active power and reactive power. In order to improve the precision of control, double loop control based on d-p coordinate transformation and active loop reactive reactive decoupling control strategy are adopted. In order to maintain the stability of the bus voltage during the output of photo voltaic and wind power generation, the energy conversion between DC buses and the access of various distributed power sources are performed.

Finally, using MATLAB software to build a simulation model of AC-DC hybrid power distribution system,applying control strategy and dynamic simulation in the model.For the system in the micro-source no power output, photo voltaic and load power changes, the fan suddenly access the system, these three conditions were simulated. The simulation results show that under the condition that the complicated source load suddenly enters, the system operates stably, the DC voltage is stable, and a flexible energy conversion between buses is realized.

Key words: AC-DC hybrid system ;voltage source converter; distribution network; control strategy

目 录

摘要..............................................................................................................................................................I

Abstract........................................................................................................................................................II

第一章 绪论...............................................................................................................................................1

1.1课题研究的背景和意义...................................................................................................................1

1. 2国内外研究动态.......................................................................................................... ...................2

1.2.1柔性直流输电技术的研究动态............................................................................................2

1.2.2直流微电网的研究动态....................................................................................................... 3

1. 3本文研究的主要内容及结构安排..................................................................................................3

第二章 电气元件的工作原理和数学建模...............................................................................................5

2. 1多端直流换流装置的工作原理......................................................................................................5

2. 2直驱永磁风机的数学建模..............................................................................................................7

2.2.1直驱永磁风力发电机原理........................................................................................................7

2.2.2风力发电系统控制方法............................................................................................................8

2. 3光伏发电.........................................................................................................................................10

2.3.1光伏电池数学模型及输出特性...............................................................................................10

2.3.2光伏电池最大功率跟踪...........................................................................................................12

2. 4储能蓄电池.....................................................................................................................................13

2.4.1蓄电池数学模型.......................................................................................................................13

2.4.2蓄电池控制策略.......................................................................................................................16

2. 5本章小结.................................................................................................................... ....................16

第三章 交直流混合配电系统控制策略................................................................................................. 17

3.1电压源换流器的基本控制策略..................................................................................................... 17

3.2交直流混合配电系统的结构和特点............................................................................................. 19

3.3交直流混合配电系统控制策略..................................................................................................... 21

3.4本章小结......................................................................................................................................... 21

第四章 交直流混合配电系统运行特性分析......................................................................................... 25

4.1仿真软件简介..................................................................................................................................25

4.2交直流混合配电系统仿真模型......................................................................................................25

4.3交直流混合配电系统运行特性分析..............................................................................................28

4.4本章小结......................................................................................................................................... 42

第五章 结论与展望................................................................................................................................. 43

致谢........................................................................................................................................................... 44

参考文献................................................................................................................................................... 45

1. 绪论

1.1研究的背景和意义

社会和国民经济的发展导致了城市化的加速。电力系统不仅发展迅速，而且随着速度的提高，供电质量和电力可靠性也越来越高。今天使用的分发网络是通信的形式。交流电源有其优点，即电压易变，且有成熟的技术，是配电网的主要类型。

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