一种无漏电流非隔离光伏并网逆变器研究

由于效率高、体积小、重量轻和成本低,非隔离逆变器一直是国内外学者研究的重点,但非隔离逆变器易产生漏电流,从而带来安全问题。为此将常规两级式光伏并网逆变器后级全桥逆变中的一个桥臂替换为双向BuckＧ Boost电路,使光伏电池负极与交流侧中性点直接相连,光伏电池对地寄生电容被完全短路,以消除逆变器漏电流。文章对该改进型两级式光伏并网逆变器的工作原理进行了分析,提出了一种通过控制双向 BuckＧBoost电路的支路电 流消除直流母线电容工频纹波的方法。最后通过仿真分析验证了该改进型光伏并网逆变器的可行性。     

风能并网系统中双Boost变换器的研究

对直驱式风力发电系统中交错并联控制器的研究和控制进行了较为深入的分析,得出了单Boost电路下的小信号模型下的传递函数,并据此设计了PI参数。对并联的Boost电路的均流控制和控制时的电流采样时间进行分析。对此,在3.5 kVA的并网逆变器上进行了实验验证,实验结果验证了设计的正确性和价值。     

三电平双降压式半桥逆变器

该逆变器保留了两电平双降压式半桥逆变器无桥臂直通和高频高效率运行的优点.同时,相对于两电平的结构,其开关管的电压应力得到了降低,桥臂输出电压波形的谐波也得到了改善.分析了三电平双降压式半桥逆变器的电路工作原理,提出了一种实现三态运行的电流滞环控制策略,该控制策略实现了电路的半周期运行模式.最后对1 kVA的原理样机进行实验,实验结果验证了该三电平双降压式半桥逆变器具有优良的性能.     

半桥结构的两级功率因数校正器研究

在两级功率因数校正器中,Boost PFC＋半桥DC/DC拓扑结构虽然表现良好,但依然存在着后级功率器件电压应力过大、输出电流纹波不够理想等缺点。将输入串联、输出并联半桥拓扑能使单个模块的输入电压和输出电流减小这一特性运用于两级PFC之中,同时引进了交错控制技术。对采用新结构的两级PFC变换器进行了工作模态分析。仿真结果表明,后级功率器件电压应力以及输出电流纹波明显减小,证明了该半桥组合式拓扑结构及其相应控制方法的正确性。     

基于DSP的非隔离型光伏并网逆变器设计

基于TMS320F28035芯片,设计了一种两级式非隔离型单相光伏并网逆变器.前级采用Boost型DC/DC电路,后级采用改进的DC/AC逆变桥电路.给出了主电路拓扑,详细分析了改进的DC/AC电路.在扰动观察法的基础上,提出了变步长扰动观察法,使最大功率跟踪（MPPT）的快速性及稳定性得到增强.运用无差拍电流控制策略,实现了网侧电流正弦化且功率因数为l.仿真分析及试验结果表明了设计的正确性与可行性.     

并串联交错式三端口半桥变换器

利用半桥变换器原边电路寄生的双向Buck/Boost电路,将两路半桥变换器原边并联、变压器副边绕组串联并共用输出整流滤波支路,提出一种新型并串联交错式三端口半桥变换器拓扑。通过调节变换器原边桥臂开关管的占空比,实现原边输入源和蓄电池电压/功率的调节;通过原边两桥臂的移相控制,实现副边负载侧功率控制,并使得所有开关管都具备软开关的能力。详细分析变换器的工作原理,给出设计要点。通过实验验证所提出拓扑和理论分析的正确性。     

小型永磁直驱风力发电并网变流器的控制方法

小型永磁直驱风力发电系统的并网部分由一个不控整流桥、两路并联Boost变换器和一个单相并网逆变器组成。分析了系统的并网电流控制方法：两路并联Boost变换器采用PI算法实现均流控制;并网逆变器采用无差拍控制实现电流的并网;分析了前后两级控制之间的关系。试制了3．5kW的并网发电逆变器样机,实验结果表明该方法具有良好的动...     

交错并联Boost PFC变换器设计

Boost PFC变换器引入交错并联技术后有效地降低了器件的电流应力、输入电流纹波和磁性元件的体积。介绍交错并联技术的原理,分析应用该技术的Boost PFC电路的具体工作模态,理论上推导了电感值的设计原则,通过详细地损耗分析给出了器件优化的方法。实验结果表明,采用该方案的PFC电路控制简单、功率因数高、效率高。     

交错Boost PFC电路移相驱动信号的实现方法

以双重并联交错Boost电路中移相驱动脉冲的产生为例,提出了一种基于单稳态触发器和D触发器的简单易行的实现方法.移相电路将控制电路产生的一路驱动脉冲延时一定时间后,控制另一路开关,以实现双重并联Boost电路的交错运行.这里详尽给出了该方法的具体实现步骤,通过实验验证了其在交错并联Boost PFC电路中的可行性和有效性.     

两级式电流滞环控制逆变器的研究与优化设计

分析研究了一种两级式电流滞环控制逆变器的电路结构及其工作原理,该电路由前级交错并联双管正激直流变换器与后级电流滞环控制逆变器级联而成.讨论了前级部分的控制方式对变换器效率的影响,给出了滞环宽度和输出滤波电感等关键电路参数的选取与设计方法,优化设计并研制了一台原理样机.实验表明,两级式电流滞环控制逆变器具有控制简单、动态...     

A New PV Converter for Grid Connection Through a High‐Leg Delta Transformer Using Cooperative Control of Boost Converters and Inverters

This paper proposes a new high‐efficiency photovoltaic (PV) converter for grid connection through a high‐leg delta transformer, which is composed of a symmetrically connected boost converter and three half‐bridge inverters. One of the three half‐bridge inverters is connected to the boost converter, and the others are directly connected to the PV terminals. This circuit configuration enables to reduce the power losses in both boost converter and inverter. This paper also proposes a new cooperative control method between the symmetrically connected boost converter and inverter. The control method can reduce the average switching frequency to 75% of that in a conventional one, resulting in a great reduction in switching power loss. Experimental results show that the proposed circuit improves its European efficiency from 91.6% to 94.5%.     

一种新型光伏并网逆变器控制策略

分析了导抗变换器的特性，详细推导了整个系统各点电压、电流，提出一种新颖的三角波-三角波调制方法，该控制策略克服了采用传统正弦波-三角波调制方法带来的并网电流谐波含量高、功率因数低的弊端。将导抗变换器和光伏并网逆变系统有机结合在一起，利用导抗变换器的电压源-电流源变换特性，将光伏电池阵列的直流电压变换为正弦包络线的高频电流，经过高频变压器隔离和电流等级变换，得到的高频电流再经过高频整流桥及工频逆变器逆变后并入电网，实现了电流源并网。相对传统的电流源型并网发电系统，采用该方法不仅省去了串联电感，而且用高频变压器取代了工频变压器，有利于实现装置小型化和降低成本。另外，利用电网电压过零信号控制工频逆变器，保证了并网电流和电网电压同步，进一步提高系统功率因数，实现正弦电流并网。通过实验证明了该控制策略的可行性，该方法非常适合分散式家用光伏并网发电系统。     

Performance Verification of High‐Efficiency PV Power Conditioner Integrated with SiC MOSFETs and Cooperative Control Method

A high conversion efficiency is always required for photovoltaic power conditioners to utilize PV‐generated DC power with minimal loss. The cooperative control method has been developed as one of the control methods that improves the conversion efficiency, which is applicable to nonisolated power conditioners consisting of a boost converter and an inverter. In the cooperative control method, the boost converter creates part of the AC voltage waveform, and either the boost converter or inverter performs switching only during a required period. Therefore, it has the advantage of reducing switching losses. In this paper, we present a study of a cooperative‐control‐type power conditioner assuming its use in grid‐connected operation and the results of a performance verification of prototype power conditioner. A microcontroller is used for cooperative control. The experimental results show that the prototype power conditioner integrated with SiC MOSFETs and the cooperative control method achieves an efficiency of 97.4% at an output of 5.5 kW.     

基于GaN器件的双Buck逆变器共模与损耗

目前市场上的光伏并网逆变器结构按隔离方式来分,可分为隔离型和非隔离型,而抑制或消除共模电流是非隔离型光伏并网系统必须要解决的问题。出于在非隔离型光伏并网逆变器中抑制共模电流的目的,研制一种基于GaN器件的双Buck逆变器,该逆变器较传统全桥电路,共模电流小、效率高、控制简单。针对共模特性进行分析研究,分别对其在正常工况与死区状态的共模电流进行理论分析,并进行仿真与实验验证,得出该逆变器能够很好地抑制共模电流的结论。通过引入GaN器件来提高开关频率解决拓扑自身电感较大这一问题,并基于GaN器件对电路进行损耗分析与实验验证,实验结果与理论分析基本吻合,验证了损耗分析的正确性。该逆变器的实测最高效率高达98.63%。     

Wavelet technique based islanding detection and improved repetitive current control for reliable operation of grid-connected PV systems

Recent years have witnessed a thrust towards the use of solar energy as the major renewable energy source for distributed power generation. The proposed system requires reliable detection technique and suitable current control strategy for proper operation. This paper focuses on plug-in repetitive current (RC) control strategy for grid connected inverter system and wavelet technique for electrical grid status identification. The performance of proposed current control technique employed for grid connected inverter system under distorted and unbalanced grid voltage is compared with the existing conventional methods like PI and PR controller. This controller uses the feedback control system for attenuating periodic disturbances, improving high quality sinusoidal output current and high power factor. The proposed scheme employs fourth order infinite impulse response (IIR) filter for maintaining its resonance frequency, output frequency matching with grid fundamental frequency and reduction of harmonics. The DC-DC boost converter implements incremental conductance based (INC) maximum power point tracker (MPPT) algorithm. The effects of LCL filter for improving disturbance rejection capability and dynamic performance of the proposed system is also demonstrated. Grid connected PV inverter employs wavelet technique for an islanding detection functionality in order to determine the status of the electrical grid. In order to show the effectiveness of the proposed algorithm, modeling and simulation for grid connected PV system is performed using MATLAB/SIMULINK and its PowerSim toolbox.     

一种用于LED路灯照明的单级交直流变换器

提出一种单级用于高亮发光二极管路灯照明系统的交直流变换器.通过共用半桥的上下桥臂,形成两路工作于断续模式的boost电路,由于两路boost电路工作在交错并联模式下,其母线电压只略高于输入,所以即使在高输入电压情况下,系统仍然具有较低电压以及电流应力.半桥负载采用LLC谐振负载,其原边开关管工作在零电压开通状态,副边整流二极管工作在零电流关断状态,减小了系统开关损耗,提高了系统效率.经仿真分析,所提交直流变换器能够实现功率因数校正的作用,并且其可工作在软开关状态下.实验中制作了一个100W样机,经测试,在40%～100%负载范围内,其功率因数大于0.96,总谐波含量小于10%,在满载时效率高达91.1%.     

光伏发电系统最大功率点跟踪控制及拓扑结构研究的新进展

本文针对光伏器件的特点提出两种新的最大功率点跟踪控制方法：短路电流结合扰动观察法及用非对称模糊控制的扰动观察法。前一种方法在短路电流控制方法的基础上引入了优化扰动步长的扰动观察法，它可有效消除光伏器件输出功率在最大功率点的振荡现象。第二种方法把非对称模糊控制引入传统的扰动观察法，它在光伏器件最大功率点两侧的特性采取不同的扰动步长，可有效消除传统方法在最大功率点处的功率振荡。仿真和实验研究证明：上述两种方法可以快速跟踪外部环境变化，并消除系统在最大功率点的振荡现象。同时本文提出一种新型的用于小功率光伏发电的高频逆变电路，它由buck－boost变换器和电流源高频链逆变器构成。由它来实现光伏模块的最大功率点跟踪，得到与电网同步的电压。该电路结构简单、效率高，光伏模块的最大功率点不受负载变化的影响。该方案通过实验验证。     

Grid integration improvement for single-phase inverters of small wind turbines under distorted voltage conditions

In this work, an enhanced control method for the grid-tied single-phase inverter in small wind turbines based on PMSG (permanent-magnet synchronous generator) under grid voltage distortion is introduced. Composite observers are designed for decomposing harmonic and fundamental components of the grid current and voltage accurately, which facilitate current control action and synchronize the inverter with the grid. Grid voltage phase angle is detected by an advanced PLL (phase-locked loop) scheme based on the grid voltage fundamental component. The inverter current is adjusted by multi-PR (proportional-resonant) controllers, where its harmonic components are regulated to zero resulting in a sinusoidal grid current. In this scheme, the DC-link voltage is maintained at constant by a DC boost converter, while generator output power is controlled by the grid-tied inverter. An MPPT (maximum power-point tracking) operation of wind turbine is obtained, with which generator speed is estimated from the input voltage and current of the DC boost converter, thus avoiding the use of an expensive and complex mechanical sensor. The presented method is proved through experimental investigation, where experimental results show that the THD (total harmonic distortion) of grid current is about 3% under 12.25% THD of the grid voltage.