基于中性点电容的三相光伏逆变器漏电流抑制

针对三相非隔离光伏发电并网系统的漏电流问题,提出了一种基于中性点电容的三相三电平逆变器漏电流抑制方法。建立三相三电平光伏逆变器共模模型,分析了漏电流的产生机理和抑制机理。为了抑制寄生电容上共模电压产生的漏电流,用电容将交流侧中性点和直流侧中性点连接起来,形成漏电流的共模LC滤波电路。该滤波电路可有效滤除共模电压的高频分量,且对差模回路不产生影响。最后通过仿真和实验,验证了所提方法的有效性。     

单相无变压器型光伏并网逆变器的拓扑结构及共模电流分析

针对单相无变压器型光伏并网逆变器拓扑结构存在共模电流的问题,介绍了几种能有效抑制共模电流的拓扑结构,即双极性调制的单相全桥式拓扑结构、带交流旁路的全桥式拓扑结构、H5拓扑结构及NPC拓扑结构;详细分析了这几种拓扑结构抑制共模电流的原理,并从开关损耗及系统效率两个方面对这几种拓扑结构进行了比较,指出H5拓扑结构性能最优。     

三相无变压器型光伏并网逆变器共模电压的分析

详细分析了三相无变压器型光伏并网逆变器共模电压的产生机理,构建了共模电压模型,得出了抑制共模电流的一般规律。利用该规律,对三相全桥拓扑结构的共模电流进行了详细分析,提出了新型控制方法,通过仿真试验对该方法进行了验证。     

Active Power Injection Control for Power Converters Connected to the Grid Through an L Filter

This paper presents the design, implementation, and evaluation of a model-based controller for a general scheme of transformerless power converters connected to the grid through an L filter. The proposed controller is aimed at active power injection, and consists of a damping term over the current error in addition to a filter parameter estimation scheme. The latter provides estimates of the filter internal resistance and inductance values. It involves the fundamental and quadrature components of the grid voltage to asymptotically compensate for current harmonic peturbations. As a result, the closed-loop system fulfills the active power injection objective. The proposed controller is tested in an experimental setup and its performance is compared to that of the Proportional-Resonant controller. Experimental results are presented for a single-phase H-bridge inverter; however, the control scheme can be used in several other H-bridge based inverter topologies such as H5 and HERIC.     

一种新型高效单相非隔离光伏并网逆变器

研究了一种新型高效、高可靠性的单相非隔离光伏并网逆变器,利用相互独立的2只耦合电感隔离并网输出电压的正负半波,逆变桥拓扑为H6对称结构,使网侧电压与光伏组件安全隔离,能彻底去除高频分量,有效抑制共模电流。新型逆变器每只开关管串联一只隔离二极管,解决了传统电压型全桥逆变器存在桥臂直通的短路问题,不需设置"死区"切换时间,改善了交流侧输出波形质量,提高了逆变器效率。经对3 kW实验样机测试和比对分析,验证了逆变器的性能优于传统H4隔离式全桥拓扑。     

新型无变压器的串联混合有源电力滤波器拓扑

本文提出了一种新型无变压器的串联混合有源电力滤波器（TL--SHAPF）的拓扑。有源滤波器和电容是串联关系，然后和电感并联，这样一种总体的结构不通过变压器而是直接串联到线路上。在该拓扑结构中，在串联谐振和并联谐振概念基础上采用了电流分离的方法。源电流被提供了两个通路：一个是谐波电流通路，另一个是基波电流通路。在固定参考坐标系中得到了从低通到带通变换的控制方法。控制器对系统性能的影响用状态空间法来描述。文章也给出了所建模型及仿真结果。     

Analysis,modeling, and implementation of a new transformerless semi-quadratic Buck–boost DC/DC converter

This paper presents a novel transformerless semi-quadratic buck-boost converter (SQBuBoC). In the proposed SQBuBoC, two power switches with simultaneous operation are used and a higher step-up/step-down voltage conversion ratio is achieved compared with the traditional buck-boost, Cuk, single-ended primary-inductor converter, and Zeta converters. The positive polarity of the output voltage, along with low ripple continuous input current and common ground between the source and the output voltages, are some features that make the suggested topology more suitable for many applications with wide range of output voltage such as photovoltaic systems. Moreover, the total voltage stress across the power switches in this converter is lower than the cascade boost, and the traditional buck-boost converters led to power MOSFETs selection with lower drain-source ON resistance (R_ds) and efficiency improvement. All the steady-state analysis and comparisons in continuous conduction mode (CCM) are discussed in details. In addition, to study the low frequency behavior of the SQBuBoC by means of the state-space averaging technique, the small and large signal models of this converter in CCM are presented. Finally, the SQBuBoC analysis is justified using experimental results of a 50 W step-up 25 V to 120 V and a 28 W step-down 25 V to 14 V laboratory prototypes.     

一种不隔离三电平双Buck光伏并网逆变器

为提高变换效率,无变压器式光伏并网逆变器是近年来的研究热点。针对无变压器拓扑的漏电流问题,提出一种三电平双Buck光伏并网逆变器,是在独立型双Buck三电平逆变器基础上,简化其电路结构得到。对地寄生电容电压被输入电容钳位在母线电压的一半,消除了漏电流。该拓扑续流回路经过的器件较传统拓扑数量少,且不经过性能较差的体二极管,有利于获得更高效率。还提出和分析包括均压控制在内的多环控制策略。仿真和实验验证了该结构及控制方案的正确性和可行性。     

无变压器非隔离型光伏并网逆变器漏电流抑制技术

漏电流抑制是无变压器型光伏并网系统需要解决的关键问题之一。VDE-0126-1-1标准规定,漏电流高于300 mA时光伏并网系统必须在0.3 s内从电网中切除。为了解释漏电流的根源,建立系统共模电压数学模型,在此基础上分析漏电流产生的原因,探讨不同调制策略对漏电流的影响,然后介绍几种典型的、能够有效抑制漏电流的电路拓扑结构,并分析各种拓扑的工作原理和特点。最后对漏电流抑制技术方面的发展趋势做了展望。     

一种无变压器有源电压质量调节器的直流侧电压控制

无变压器串联电压质量调节器是一种用来解决多种电压质量问题的新型装置。针对目前大多数类似装置的整流单元都采用不可控整流的情况,本文提出了采用可控整流来控制直流侧电压与系统缺损电压相适应的思想,以提高装置的效率。论文详细介绍了该思想的原理与实现方法,并把两种情况下装置的损耗和效率情况进行了对比。通过仿真和实验可以看出本文提出的直流侧电压可控的无变压器电压质量调节器可以有效解决多种电压质量问题;对于一种电网条件,在相同工况下,效率从直流侧电压不可控时的89.1%提高到96.1%