LCL型并网逆变器数字电流控制技术研究

发布时间：2018-03-25 02:01

本文选题：并网逆变器　切入点：延时补偿　出处：《湘潭大学》2017年硕士论文

【摘要】：为了使新能源系统发出的电能稳定、高效地并入电网,性能效果优良的高阶滤波器已广泛地应用于新能源系统与电网之间的并网逆变器,但高阶的LCL滤波器存在自身谐振问题影响并网逆变器接口设备的性能,传统的并网逆变器谐振抑制问题多数在模拟域进行研究与分析,但随着数字信号处理技术和数字芯片的飞速发展,全数字控制逐渐取代模拟控制,数字控制中延时环节对系统稳定性的影响已不可忽略,因此本文从考虑延时环节的并网逆变器离散数学建模、数字电流单环、双环有源阻尼谐振抑制控制进行了系统的分析和讨论。采用直接数字法,分析并搭建了考虑数字延时环节的LCL型并网逆变器离散数学模型。在连续域和离散域下,对网侧电流单环控制稳定性进行对比分析,说明数字延时环节改变了系统稳定性,基于此在网侧电流单环反馈控制中设置数字延时为滞后一拍,主要分析滞后一拍情况下采样频率和谐振频率之比对稳定性的影响,并确定其稳定范围,同时对控制器参数进行了设计。在较低谐振频率和采样频率的比值下,网侧电流数字单环控制难以保持稳定,造成网侧电流数字单环鲁棒性不足,因此本文进一步研究数字电容电流反馈有源阻尼方法增强阻尼,分析了数字电容电流反馈带来的内环数字延时对有源阻尼方法的影响,并针对其影响提出一种预测占空比结合零极点补偿控制延时的方法,通过预测控制算法得到占空比和增加零极点,有效地补偿了系统内环数字延时,使系统在有源阻尼方法下能有效地起到增强阻尼的作用,设计简单,稳定性加强,仿真验证了其可行性和有效性。同时本文搭建了并网逆变系统实验平台,针对本文讨论的问题进行了实验验证,增强其说服力。
[Abstract]:In order to make the electric energy produced by the new energy system stable and efficiently integrated into the power grid, high-order filters with good performance have been widely used in grid-connected inverters between the new energy system and the power grid. But the high order LCL filter has its own resonance problem which affects the performance of grid-connected inverter interface equipment. The traditional grid-connected inverter resonance suppression problem is mostly studied and analyzed in analog domain. However, with the rapid development of digital signal processing technology and digital chip, digital control is gradually replacing analog control, and the effect of delay on system stability can not be ignored. In this paper, the discrete mathematical model of grid-connected inverter with time delay, digital current single loop and double loop active damping resonance suppression control are systematically analyzed and discussed. The discrete mathematical model of LCL grid-connected inverter considering digital delay link is analyzed and built. In continuous domain and discrete domain, the stability of grid-side current single-loop control is compared and analyzed, which shows that the digital delay link changes the stability of the system. Based on this, the digital delay is set as one beat lag in the feedback control of single loop of current on the grid side. The influence of the ratio of sampling frequency to resonant frequency on the stability of sampling frequency and resonance frequency is analyzed, and the stability range is determined. At the same time, the controller parameters are designed. Under the condition of low resonant frequency and sampling frequency, it is difficult to keep the stability of grid-side current digital single-loop control, which leads to the lack of robustness of grid-side current digital single-loop. Therefore, this paper further studies the digital capacitive current feedback active damping method to enhance the damping, and analyzes the influence of the digital delay of the inner loop caused by the digital capacitor current feedback on the active damping method. According to its influence, a method of predictive duty cycle and zero pole compensation control delay is put forward. Through predictive control algorithm, the duty cycle is obtained and zero pole is added, which effectively compensates the digital delay in the inner loop of the system. Under the active damping method, the system can effectively enhance the damping. The design is simple, the stability is enhanced, and the simulation proves its feasibility and effectiveness. At the same time, the experiment platform of grid-connected inverter system is built in this paper. Experiments are carried out on the problems discussed in this paper to enhance its persuasiveness.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464

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