LCL型并网逆变器控制算法研究

发布时间：2019-05-08 01:13

【摘要】：新能源发电技术的规模日益扩大,并网发电系统中并网逆变器的控制性能直接影响到并入电网的电能质量,在并网发电系统中有极为重要的作用。为了降低并网电流谐波的含量,并网逆变器需要串接输出滤波器。LCL型滤波器具有高频滤波特性,同时LCL型并网逆变器有系统电感量小和系统成本低等优点,并网逆变器采用LCL滤波器成为并网逆变系统交流输出滤波环节发展的必然趋势。但是由于LCL型滤波器存在固有的缺点,LCL型并网逆变器的控制算法的研究是十分必要的。本文以三相LCL型并网逆变器为研究对象,对其控制算法进行了深入理论研究和分析,为LCL型并网逆变器的并网控制算法提供了理论基础和设计依据,具有理论和工程实际意义。本文的研究工作具体如下：首先,对并网逆变系统的基本结构进行了简单介绍,分析了LCL型并网逆变器在三相静止坐标系、两相静止坐标系和同步旋转坐标系下的数学模型,并对LCL滤波器的工作特性和参数的选取准则进行分析,介绍了一种LCL滤波器参数设计方法。其次,针对LCL型并网逆变器,理论研究了并网电流单闭环控制算法和电容电流反馈控制算法,分析了各自的优缺点,在此基础上,给出了一种并网电流反馈及电网电压前馈的控制算法,在保证系统稳定性的情况下,同时克服了电容电流反馈控制算法电流传感器数量较多的问题,通过仿真验证了该算法的有效性。再次,针对电网电压存在谐波下的LCL型并网逆变器,分析了并网逆变系统中电网电压谐波导致并网电流谐波的产生机理,而当并网逆变器采用LCL型滤波器时,并网电流的质量受其影响较为严重。为了抑制电网电压谐波的影响,分析了基于比例谐振控制的控制算法,其本质是提高了并网逆变器的输出阻抗的模值,因此在推导出其输出阻抗模型的基础上,分析了逆变器输出阻抗与抗扰性能之间的关系,并引入了并联虚拟阻抗技术对逆变器输出阻抗进行校正以抑制电网电压谐波的影响,比例谐振控制和虚拟阻抗技术的仿真结果表明控制算法是有效和正确的。最后,在RT-LAB实时仿真器和TMS320F2812控制器的半实物仿真平台上,针对上述LCL型并网逆变器的控制算法进行了相关的半实物仿真验证,半实物仿真结果进一步验证了本文中控制算法的正确性和有效性。
[Abstract]:The scale of new energy generation technology is increasing day by day. The control performance of grid-connected inverter in grid-connected power generation system directly affects the power quality of grid-connected power generation system and plays an important role in grid-connected power generation system. In order to reduce the harmonic content of grid-connected current, the grid-connected inverter needs serial output filter. LCL-type inverter has the characteristics of high-frequency filtering. At the same time, the LCL-type grid-connected inverter has the advantages of small system inductance and low system cost. The application of LCL filter in grid-connected inverter becomes the inevitable trend of AC output filter in grid-connected inverter system. However, due to the inherent shortcomings of LCL filter, it is necessary to study the control algorithm of LCL grid-connected inverter. In this paper, the control algorithm of three-phase LCL grid-connected inverter is studied and analyzed deeply, which provides the theoretical basis and design basis for the grid-connected control algorithm of LCL-type grid-connected inverter. It is of theoretical and practical significance. The research work in this paper is as follows: firstly, the basic structure of grid-connected inverter system is briefly introduced, and the mathematical models of LCL-type grid-connected inverter in three-phase static coordinate system, two-phase static coordinate system and synchronous rotating coordinate system are analyzed. The working characteristic and parameter selection criterion of LCL filter are analyzed, and a parameter design method of LCL filter is introduced. Secondly, for LCL type grid-connected inverter, the single closed-loop control algorithm and capacitor current feedback control algorithm are studied theoretically, and their advantages and disadvantages are analyzed. A control algorithm of grid-connected current feedback and grid voltage feedforward is presented. Under the condition of ensuring the stability of the system, the problem of the large number of current sensors in the capacitive current feedback control algorithm is overcome at the same time. The validity of the algorithm is verified by simulation. Thirdly, the generation mechanism of grid-connected current harmonic caused by grid voltage harmonic in grid-connected inverter is analyzed, and the LCL filter is used when grid-connected inverter adopts LCL filter. The quality of grid-connected current is affected seriously. In order to restrain the influence of voltage harmonic in power network, the control algorithm based on proportional resonance control is analyzed. The essence of the algorithm is to improve the output impedance of grid-connected inverter, so the output impedance model of grid-connected inverter is derived on the basis of its output impedance model. The relationship between the output impedance and the anti-disturbance performance of the inverter is analyzed, and the parallel virtual impedance technique is introduced to correct the output impedance of the inverter in order to restrain the harmonic effect of the power network voltage. The simulation results of proportional resonance control and virtual impedance technique show that the control algorithm is effective and correct. Finally, on the hardware-in-the-loop simulation platform of RT-LAB real-time simulator and TMS320F2812 controller, the relevant hardware-in-the-loop simulation verification is carried out for the control algorithm of the above LCL grid-connected inverter. The hardware-in-the-loop simulation results further verify the correctness and effectiveness of the control algorithm in this paper.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM464

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