三电平光伏并网逆变器断续脉宽调制的研究与实现

发布时间：2018-03-29 19:08

本文选题：效率　切入点：光伏并网逆变器　出处：《北京交通大学》2017年硕士论文

【摘要】：随着全球能源危机的不断加剧,作为新能源产业之一的光伏发电技术受到广泛关注和快速发展。光伏并网逆变器作为光伏发电系统的核心装置,其并网效率和并网电能质量是衡量一个系统优劣的关键,而PWM调制技术是影响这两者的重要因素。因此,对在不同逆变器应用场合下PWM调制策略的优化性能进行深入分析具有重要的意义。本文以一种结构更优化、系统效率更高、更有利于系统稳定运行的非隔离型光伏并网逆变器为研究对象,以成本低、损耗小的三电平T-NPC拓扑作为主电路结构,围绕逆变器的损耗、并网电能质量、滤波器设计等问题展开深入研究。(1)三电平断续脉宽调制(DPWM)策略的研究。从空间矢量角度对DPWM的原理进行了详细说明,并根据开关管空间箝位模式的变化,将DPWM分为6类。以一种简单可行的零序电压注入方式,给出了各类DPWM的实现方法及零序电压叠加规律,并分析对比了 SVPWM、DPWM的谐波特性。接着,针对三电平拓扑的中点电位不平衡问题,给出了一种通过注入零序电压实现中点电位平衡,同时降低器件损耗的混合调制策略,并通过仿真验证了其控制中点平衡的良好性能。(2)光伏并网逆变器的网侧滤波器优化设计。在非隔离型光伏并网逆变器中,光伏池板对地产生的共模电流会产生干扰,增大并网电流谐波,影响逆变器正常运行,甚至还会危害人身安全。通过对共模回路的分析,建立了光伏并网逆变器的共模等效模型。针对共模电流和通用型LCL滤波器的共模谐振问题,采用了一种简单、实用的共模差模解耦型的LCL滤波器设计方案,给出了 DPWM下滤波器各个参数的设计方法,仿真验证了该设计的理论正确性和实际可行性。(3)不同功率因数情况下DPWM的器件损耗分析。为保证不同功率因数情况下器件始终有最小损耗,在对各类DPWM下功率器件的损耗进行详细分析的基础上,给出了一种随功率因数角的变化,实时切换DPWM的最小损耗实现方法,并通过仿真验证了其可行性。(4)对上述提出的DPWM策略和滤波器设计等进行相关实验验证。搭建了20kW的三电平T-NPC光伏并网逆变器实验平台,对SVPWM和DPWM下逆变器的并网电流THD、效率进行了实验对比,并验证了中点平衡控制策略的抑制效果。对本文采用的改进型滤波器设计、DPWM的切换方法进行实验效果分析,证明了两者的可行性。
[Abstract]:With the aggravation of the global energy crisis, photovoltaic power generation technology, as one of the new energy industries, has been widely concerned and developed rapidly. Photovoltaic grid-connected inverter is the core device of photovoltaic power generation system. The efficiency of grid-connected and the quality of grid-connected power are the key factors to evaluate a system, and PWM modulation technology is an important factor affecting both of them. It is of great significance to analyze the optimal performance of PWM modulation strategy in different inverter applications. The non-isolated photovoltaic grid-connected inverter, which is more conducive to the stable operation of the system, is studied. The three-level T-NPC topology with low cost and low loss is taken as the main circuit structure, which revolves around the loss of the inverter and the grid-connected power quality. The design of filter is studied in detail. The principle of DPWM is explained in detail from the angle of space vector, and according to the change of switching tube spatial clamping mode, the principle of DPWM is discussed in detail. The DPWM is divided into six categories. By a simple and feasible zero-sequence voltage injection method, the realization method and the zero-sequence voltage superposition rule of all kinds of DPWM are given, and the harmonic characteristics of the DPWM are analyzed and compared. In order to solve the problem of neutral point potential imbalance in three-level topology, a hybrid modulation strategy is proposed to realize neutral point potential balance by injecting zero-sequence voltage and to reduce device loss at the same time. The optimal design of grid-side filter for grid-connected photovoltaic inverter is verified by simulation. In non-isolated photovoltaic grid-connected inverter, the common-mode current generated by photovoltaic cell panel will interfere with the ground. Increasing the harmonics of grid-connected current, affecting the normal operation of the inverter, and even endangering personal safety. Through the analysis of the common-mode loop, The common-mode equivalent model of grid-connected photovoltaic inverter is established. Aiming at the common mode resonance of common-mode current and universal LCL filter, a simple and practical design scheme of common-mode differential mode decoupled LCL filter is adopted. The design method of filter parameters under DPWM is given. The simulation results show that the design is correct in theory and feasible in practice. (3) the loss analysis of DPWM devices under different power factors is carried out. In order to ensure that the devices always have the minimum loss under different power factors, Based on the detailed analysis of the loss of various power devices under DPWM, a method of realizing the minimum loss of real-time switching DPWM with the change of power factor angle is presented. The feasibility of the proposed DPWM strategy and filter design are verified by simulation. The three-level T-NPC photovoltaic grid-connected inverter experimental platform of 20kW is built. The efficiency and efficiency of grid-connected current THD of inverter under SVPWM and DPWM are compared experimentally, and the suppression effect of midpoint balance control strategy is verified. The feasibility of both is proved.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464;TM615

【参考文献】