三相光伏并网逆变器与控制技术的研究

发布时间：2018-02-15 09:13

本文关键词： 并网逆变器最大功率点跟踪双闭环电流前馈 PI控制　出处：《辽宁工业大学》2014年硕士论文　论文类型：学位论文

【摘要】：光伏并网逆变器是光伏并网发电系统的核心组成部分。本文以三相双级式并网逆变器为研究对象，对光伏并网逆变器的两大核心问题——最大功率点跟踪（MPPT）和逆变器并网双闭环PI控制问题进行深入研究，解决最大功率点跟踪速度与稳态振荡的矛盾，实现逆变器并网电流无误差地跟踪网侧电压。针对最大功率点跟踪速度慢与稳态振荡等问题，本文深入比较分析了电导增量法等典型MPPT算法，，提出一种改进的变步长电导增量最大功率点跟踪速算法。该算法结合了定电压法与变步长电导增量法的优点，仿真结果表明改进的变步长电导增量法能够快速地跟踪到当前最大功率点处，且进入稳态后无振荡现象。为实现逆变器并网电流无误差地跟踪网侧电压问题，本文以三相双级式并网逆变器为研究对象，并确定并网逆变器主电路拓扑结构。分析了三相SPWM与SVPWM技术应用于逆变器调制的优缺点，建立三相逆变器模型，仿真结果表明采用SVPWM调制的逆变器输出电压及电流的谐波性能好，直流电压利用率最高。同时仿真分析了死区时间对逆变器输出的影响以及L与LCL滤波器的设计方法与性能。光伏并网逆变器系统的仿真研究。搭建具有电流前馈功能的电流内环、电压外环的双闭环PI并网控制策略的系统仿真模型。仿真结果表明相对于一般的双闭环并网控制策略，带电流前馈功能的双闭环控制策略可以更好的实现逆变器的并网控制。逆变器电流能够无差地跟踪网侧电压频率，正弦度好，谐波小；在光照强度发生变化时，逆变器可快速调整功率输出，在过渡过程中无振荡。
[Abstract]:Photovoltaic grid-connected inverter is the core part of photovoltaic grid-connected power generation system. In this paper, two core problems of photovoltaic grid-connected inverter, maximum power point tracking (MPPTT) and grid-connected double closed loop Pi control, are studied in order to solve the contradiction between maximum power point tracking speed and steady state oscillation. The inverter grid-connected current can track the voltage of grid-side without error. Aiming at the problems of slow tracking speed and steady state oscillation of the maximum power point, the typical MPPT algorithms such as conductance increment method are compared and analyzed in this paper. An improved variable step length maximum power point tracking algorithm is proposed, which combines the advantages of the constant voltage method and the variable step length conductance increment method. The simulation results show that the improved variable step length conductance increment method can quickly track the current maximum power point, and there is no oscillation after entering the steady state. In order to track the voltage of grid-connected inverter without error, this paper takes the three-phase double-stage grid-connected inverter as the research object. The topology of the main circuit of grid-connected inverter is determined. The advantages and disadvantages of three-phase SPWM and SVPWM in inverter modulation are analyzed, and the model of three-phase inverter is established. The simulation results show that the inverter with SVPWM modulation has good harmonic performance of output voltage and current, and the highest utilization rate of DC voltage. At the same time, the effect of dead-time on the output of inverter and the design method and performance of L and LCL filter are simulated and analyzed. Simulation study of photovoltaic grid-connected inverter system. The system simulation model of double-closed-loop Pi grid-connected control strategy with current feedforward function and voltage outer loop is built. The simulation results show that compared with the conventional double-closed-loop grid-connected control strategy, the simulation results show that, Double closed loop control strategy with current feedforward function can better realize grid-connected control of inverter. Inverter current can track voltage frequency of grid-side without difference, sinusoidal degree is good, harmonic is small, and when illumination intensity changes, The inverter can adjust the power output quickly and has no oscillation during the transition.
【学位授予单位】：辽宁工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM464

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