基于改进的RMC-小型风电场仿真研究

发布时间：2018-03-31 20:58

本文选题：永磁直驱风力发电机　切入点：PWM整流器　出处：《新疆大学》2017年硕士论文

【摘要】：目前,风力发电一般采取交流式并入电网,但当大规模风力发电并网时,由于风电的随机性和波动性,将对电网电压、功率以及频率造成较大影响,并注入大量谐波。为此,相继提出了不同类型的HVDC(high voltage direct current)直流输电结构。HVDC系统涵盖了风力发电和功率传输两个方向,此系统不但有利于远距离输电过程中,降低损耗,而且还降低了风电随机性、波动性和谐波对电网的影响。其中提出的VSC-HVDC和MMC-HVDC,适用于大规模风力发电,即风力发电机通过变压器升压汇总到交流母线上,再到换流站进行整流,之后进行较远的直流传输,到网侧换流站进行逆变,并入交流电网,其优点是功率的损耗较小,传输距离较远。针对于分散式或者台数较少的风电场,提出了新型的直流输电结构RMC-HVDC,RMC换流器是将单台风力发电机输出的三相交流电变换成高压直流电,不仅能够减少建设换流站所需的投资成本和占地面积,又有效降低了因转换环节多而带来的功率损耗。本文根据RMC(reduced matrix converter)结构特点,针对小型风力发电场,提出了一种改进的RMC结构。其特点为:永磁直驱风力发电机之间进行直流并联,母线电压经过含高频变压器的DC-DC结构进行升压;采用直流并联,减少了风力发电随机性和波动性对电网电压、频率的影响;而DC-DC升压结构代替换流站,较适用于分散式小型风力场;为有效实现发电机的切、并网,设计了对发电机输出电压瞬时采样来判断发电机整流器侧是否连接到直流母线的断路器模型。本文对此系统开展了以下几方面研究:首先,概述了永磁直驱风力发电机、PWM整流器、断路器、含高频变压器的DC-DC以及网侧逆变器的基本结构以及其基本原理,建立了数学模型,并于Matlab/Simulink搭建了仿真模型。第二,对仿真模型进行了控制策略,及参数正确设置。并比较了不同PI值下,单机切、并网对母线、DC-DC以及网侧逆变器电压、电流的波动影响,找出更加优化的PI值。第三,在基于Matlab/Simulink仿真平台上进行了1或2台发电机,在母线已并有2、5或8台发电机的情况下,切、并直流母线与升压的仿真分析。结果表明:随着已并网发电机台数的增多,PI调节环节个数增多,稳压、稳流作用增大,再有风力发电机切、并网时,其引起的电压波动逐渐减少,且1台引起的电压波动小于2台引起的电压波动;当电网已并网5或8台风力发电机的情况时,单机切、并网引起母线电压DC-DC电压、电流波动对比变化较小,而2台发电机在切网情况下,波动对比,略微有区别;随着并网发电机台数的增多,母线和DC-DC在稳定情况下波动增加,同时考虑到电力电子器件所能承受的容量问题,建议每组电机群以7台较为合适。
[Abstract]:At present, wind power generation is usually integrated into the grid by AC mode, but when large-scale wind power is connected to the grid, due to the randomness and volatility of wind power, it will have a great impact on the voltage, power and frequency of the grid, and inject a large number of harmonics. In this paper, different types of HVDC(high voltage direct current. HVDC systems are proposed, which cover both wind power generation and power transmission. This system not only helps to reduce the loss but also reduces the randomness of wind power during long distance transmission. The effects of volatility and harmonics on the power grid. The proposed VSC-HVDC and MMC-HVDC are suitable for large-scale wind power generation, that is, wind generators are aggregated through transformers to the AC busbar, then rectified to converter stations, and then transmitted further to direct current. The advantages of inverting to the network side converter station and merging with the AC network are that the power loss is lower and the transmission distance is longer. It is aimed at a decentralized wind farm or a wind farm with fewer stations. A new direct current transmission structure RMC-HVDC / RMC converter is proposed to convert the three-phase AC output from a single wind turbine to high-voltage direct current, which can not only reduce the investment cost and occupation area required for the construction of converter station. In this paper, according to the structural characteristics of RMC(reduced matrix converters, the power loss caused by many conversion links is effectively reduced. An improved RMC structure is proposed, which is characterized by DC parallel connection between permanent magnet direct drive wind generators, bus voltage boost through DC-DC structure with high frequency transformer, DC parallel connection, The effect of randomness and fluctuation of wind power generation on the voltage and frequency of the grid is reduced, and the DC-DC boost structure replaces the converter station, which is more suitable for the decentralized small wind field. A circuit breaker model is designed to determine whether the generator rectifier side is connected to DC busbar by instantaneous sampling of generator output voltage. In this paper, the following aspects of the system are studied: firstly, In this paper, the basic structure and principle of permanent magnet direct drive wind generator rectifier, circuit breaker, DC-DC with high frequency transformer and grid-side inverter are summarized. The mathematical model is established, and the simulation model is built in Matlab/Simulink. The control strategy of the simulation model and the correct setting of the parameters are given. The effects of single machine cut and grid connection on the voltage and current fluctuation of the bus bus DC-DC and the grid-side inverter are compared under different Pi values, and the more optimized Pi value is found. One or two generators are carried out on the Matlab/Simulink simulation platform, and when the bus bar has 2 or 8 generators, cut, The simulation analysis of DC busbar and boost voltage shows that: with the increase of the number of connected generators and Pi regulating links, voltage stabilization, steady current effect is increased, and when wind turbine is cut and connected to the grid, The voltage fluctuation caused by it decreases gradually, and the voltage fluctuation caused by one unit is less than that caused by two wind turbines. When the grid has been connected to 5 or 8 wind turbines, the single machine is cut off and the bus voltage DC-DC voltage is connected to the grid. The variation of current fluctuation contrast is small, while the fluctuation contrast of two generators is slightly different when the grid is cut. With the increase of the number of grid-connected generators, the bus and DC-DC fluctuate under stable conditions. At the same time, considering the capacity of power electronic devices, it is suggested that 7 motors are suitable for each group.
【学位授予单位】：新疆大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM614;TM743

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