光伏发电系统多功能逆变器控制策略研究

发布时间：2018-03-26 07:12

本文选题：逆变器　切入点：多功能　出处：《河北工程大学》2017年硕士论文

【摘要】：我国光照资源丰富,为替代消耗的传统化石能源,国家制定政策鼓励开发太阳能。目前,国家大力发展光伏电站的建设,但光伏组件中电池单元却面临在光照、温度等外界条件不佳状态下难以突破发电的局限性,同时,光伏发电系统中功率器件的使用、电力网用户侧非线性负载比例的增加等都加重了公共电网谐波污染和无功消耗问题。应用在光伏发电系统的逆变器和有源滤波器两种设备在功能、结构、控制方法等方面相似,所以为提高光伏发电系统输出功率,降低分布式电源设备对公共电网的谐波污染,提高电网运行稳定性,可利用该特点,发挥逆变器的一机两用的功能,光照充足时进行并网发电,当发电条件不佳时逆变器发挥抑制电网谐波和补偿无功作用。而改变逆变器的功能需要通过控制策略实现。因此,在逆变器功能的拓展及其控制策略方面展开研究。首先本文通过分析光伏并网发电系统中的多功能逆变器及并联型有源滤波器的异同点,确定选择三相电压源型拓扑结构的逆变器为研究对象。然后为高效控制整个光伏并网发电系统,采用了两级式的主电路拓扑结构,并对逆变器前级升压电路选择及逆变器交流侧输出滤波电感、电容参数设置原则进行说明。从而为搭建的光伏发电系统模型设置仿真参数提供依据。阐述了多功能逆变器的工作模式的选择方法,在系统控制电路中设置了信号控制开关,通过控制合成指令电流中成分不同来实现对逆变器工作模式的设置。为了提高光伏并网发电系统功率传输效率,改进了光伏阵列输出特性曲线上的最大功率点跟踪算法,在自适应变步长电导增量法基础上,增加功率预测环节,抑制光照突变造成的最大功率点跟踪振荡。本文对逆变器采用直接电流控制策略,控制电路中主要包括谐波及无功电流检测模块、指令电流合成模块等,为实现各模块功能比较并选择合适算法,并设计了指令电流的跟踪控制器。提出了将模糊控制和变环宽滞环控制相结合,对逆变器的电流内环控制进行优化设计,达到提高电流跟踪控制效果的目的,降低功率器件开关频率。最后,运用MATLAB软件对多功能逆变器的不同工作模式进行仿真。仿真结果表明,本文提出的变环宽滞环电流控制方法能较准确的跟踪光伏并网发电系统在复合工作模式下的指令电流,既提高了并网发电电流跟踪控制的动态性,又实现了对电网的谐波抑制和无功补偿功能,提高逆变设备的性价比,验证了所提控制策略的正确性。
[Abstract]:Our country is rich in light resources. In order to replace the traditional fossil energy consumed, the government has made policies to encourage the development of solar energy. At present, the country has vigorously developed the construction of photovoltaic power plants, but the cell units in photovoltaic modules are facing the illumination. It is difficult to break through the limitation of power generation under poor external conditions such as temperature. At the same time, the use of power devices in photovoltaic power generation system, The problem of harmonic pollution and reactive power consumption is aggravated by the increase of nonlinear load ratio on the user side of power grid. The inverter and active filter used in photovoltaic power system are similar in function, structure, control method and so on. It is considered that by increasing the output power of photovoltaic power generation system, reducing the harmonic pollution caused by the distributed generation equipment to the public grid, and improving the stability of the power grid, we can make use of this characteristic and give full play to the dual-purpose function of the inverter. When light is sufficient, grid-connected power generation is carried out. When the generation conditions are not good, the inverter plays a role of restraining power grid harmonics and compensating reactive power, and changing the function of inverter needs to be realized through control strategy. Firstly, this paper analyzes the similarities and differences of multifunctional inverter and shunt active power filter in photovoltaic grid-connected generation system. The inverter with three-phase voltage source topology is selected as the research object. Then, in order to control the whole photovoltaic grid-connected generation system efficiently, the two-stage main circuit topology is adopted. At the same time, the selection of the front stage boost circuit of the inverter and the output filter inductance of the AC side of the inverter are given. The principle of capacitive parameter setting is explained, which provides the basis for setting up simulation parameters of photovoltaic power system model. The method of selecting the working mode of multifunctional inverter is expounded, and the signal control switch is set up in the control circuit of the system. In order to improve the power transmission efficiency of photovoltaic grid-connected generation system, the maximum power point tracking algorithm on the output characteristic curve of photovoltaic array is improved. On the basis of adaptive variable step length conductance increment method, power prediction is added to suppress the maximum power point tracking oscillation caused by sudden illumination. In this paper, direct current control strategy is adopted for inverter. The control circuit mainly includes harmonic and reactive current detection module, instruction current synthesis module and so on. In order to achieve the functional comparison of each module and select the appropriate algorithm, A tracking controller of instruction current is designed, and the combination of fuzzy control and variable loop width hysteresis control is proposed to optimize the current internal loop control of the inverter, so as to improve the effect of current tracking control. Finally, the MATLAB software is used to simulate the different operation modes of the multifunctional inverter. The simulation results show that, The variable loop wide hysteresis current control method proposed in this paper can accurately track the command current of grid-connected photovoltaic power generation system in composite mode, which improves the dynamic characteristics of grid-connected generation current tracking control. The harmonic suppression and reactive power compensation are realized, and the performance to price ratio of inverter equipment is improved. The correctness of the proposed control strategy is verified.
【学位授予单位】：河北工程大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM615;TM464

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