基于有源阻尼的LCL并网逆变器控制策略研究

发布时间：2018-07-17 16:40

【摘要】：随着新能源技术的不断发展和应用,发展高性能和低成本的并网逆变设备已成为研究热点。由于L滤波器必须增大电感值来取得较好的滤波效果,这样就会增加系统的体积和损耗,而LCL滤波器凭借着低成本、低损耗和杰出的高频谐波抑制能力逐渐取代了L滤波器在并网逆变器中的应用地位。但是LCL滤波器为三阶系统,会产生一个谐振峰,使得系统极其不稳定,那么LCL滤波器存在的谐振问题就不容忽略。本文针对抑制LCL滤波器谐振峰问题的有源阻尼法进行了探索研究,文章主要包括:首先对LCL并网逆变器的数学模型进行搭建,然后针对本文所选用的并网逆变器的控制策略进行分析,也就是对空间矢量调制方法(SVPWM)和电网电压定向的原理进行了介绍,并且对有源阻尼法和无源阻尼法的区别进行了说明,对LCL滤波器的滤波特性进行了分析。其次是阐述了LCL滤波器的参数设计的约束条件,在参数设计条件约束内优化其参数设计,使得设计的参数不仅能够消除在谐振频率处系统延迟所带来的影响而且能够使系统在开关频率处的衰减最小。并且根据所选的控制方法对阻尼电阻和电流控制器的参数进行选定。另外,在并网逆变器的控制策略基础上对抑制LCL滤波器的谐振峰的有源阻尼算法进行探索研究。在对单侧的电流反馈分析,采用逆变器侧电流反馈影响并网功率因数,而采用网侧电流反馈不能达到很好的稳定效果。故本文分别在传统的电容电流反馈和网侧电流反馈的双环电流控制、电容电压反馈和网侧电流反的双环控制馈基础上加入了谐振积分器进行比较分析。当谐振积分器与基于电容电流反馈的有源阻尼法相结合时,经过改善的谐振积分器,能够有效的提取出谐振频率处及其附近的电流,经过负反馈,以达到有效抑制谐振峰的效果。当谐振积分器与基于电容电压反馈的有源阻尼法结合时,将谐振积分器作另一种改变,使得输出为电容电流的高频分量,经过负反馈后能达到比电容电流反馈更好的效果。并且经过分析,将谐振积分器与电容电压反馈相结合时能够在有效的抑制谐振峰的同时有着更好的稳定性。最后,在理论分析的基础上,在Matlab/simulink平台上搭建仿真模型,对所提出的控制策略进行仿真验证,并且搭建了以TMS320F2812为主控芯片的实验平台。实验与仿真结果均验证改进控制策略的可行性,达到了预期效果。
[Abstract]:With the development and application of new energy technology, the development of high performance and low cost grid-connected inverter equipment has become a research hotspot. Because the L filter must increase the inductance value to obtain the better filtering effect, thus will increase the system volume and the loss, but the LCL filter depends on the low cost, Low loss and excellent high frequency harmonic suppression have gradually replaced the application of L filter in grid-connected inverter. However, the LCL filter is a third-order system, which will produce a resonant peak, which makes the system extremely unstable, so the resonance problem of the LCL filter can not be ignored. In this paper, the active damping method for suppressing the resonance peak of LCL filter is studied. The main contents are as follows: firstly, the mathematical model of LCL grid-connected inverter is built. Then the control strategy of grid-connected inverter selected in this paper is analyzed, that is, the principle of space vector modulation (SVPWM) and grid voltage orientation are introduced, and the difference between active damping method and passive damping method is explained. The filter characteristics of LCL filter are analyzed. Secondly, the constraints of the parameter design of LCL filter are expounded, and the parameter design is optimized within the constraints of the parameter design conditions. The designed parameters can not only eliminate the influence of system delay at the resonant frequency but also minimize the attenuation of the system at the switching frequency. The parameters of damping resistance and current controller are selected according to the selected control method. In addition, based on the control strategy of grid-connected inverter, the active damping algorithm for suppressing the resonant peak of LCL filter is studied. In the analysis of single-side current feedback, the inverter side current feedback is used to influence the grid-connected power factor, but the grid-side current feedback can not achieve a good stability. Therefore, a resonant integrator is added to the conventional double-loop current control, capacitive voltage feedback and double-loop feedback. When the resonant integrator is combined with the active damping method based on capacitive current feedback, the improved resonant integrator can effectively extract the current at and around the resonant frequency and pass through the negative feedback. In order to achieve an effective suppression of the resonance peak effect. When the resonant integrator is combined with the active damping method based on capacitive voltage feedback, the resonant integrator is changed to a high frequency component of the capacitance current, and the negative feedback can achieve a better effect than the capacitive current feedback. After analysis, the resonance integrator and capacitor voltage feedback can effectively suppress the resonance peak and have better stability. Finally, on the basis of theoretical analysis, the simulation model is built on Matlab / Simulink platform, the proposed control strategy is simulated and verified, and the experimental platform with TMS320F2812 as the main control chip is built. Both experimental and simulation results verify the feasibility of the improved control strategy and achieve the desired results.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464

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