基于空间矢量的三相光伏并网逆变器解耦控制研究

提出一种基于电网线电压空间矢量的三相光伏并网逆变器解耦方法,将复平面分为6个扇区,在每个扇区内实现两相开关解耦,分别控制相应的输出线电流,实现电流跟踪,改善并网电流波形。最后,利用MATLAB建立三相光伏并网逆变器双环系统仿真模型,仿真结果证明了该方法的有效性。     

两级式光伏并网逆变器无差拍控制研究

针对两级式三相光伏并网逆变器的特点,文章采用瞬时功率外环和无差拍控制电流内环的双环控制策略。推导了三相光伏并网逆变器的离散数学模型,外环采取瞬时功率控制方法,省略了传统无差拍电流控制方法中的电流预测环节,简化了逆变器的控制系统。仿真结果表明,在光照导致光伏电池输出功率波动的情况下,该控制策略依然能保证光伏并网逆变器最大限度地输出功率,且并网逆变器的输出电流能够准确、快速地跟踪电网电压,实现了功率因数接近1。     

新型铁路电力光伏三相并网逆变器

针对传统的逆变器技术谐波大、电能质量不稳定等问题,基于单周期控制原理对铁路电力光伏三相并网逆变器进行了研究。介绍了单周期控制的基本原理,分析了单周期控制下的三相逆变器工作原理,推导了三相逆变器的开关数学模型和等效控制方程,建立了用于铁路电力的三相光伏并网逆变器及其控制系统,并通过Matlab/Simulink对三相光伏逆变器建模仿真。结果表明,该三相光伏并网逆变技术可快速有效地消除谐波和校正功率因数,具有良好的性能。     

多支路型光伏并网逆变器

阐述了多支路型光伏并网逆变器的基本原理和研制的关键技术.通过对光伏并网逆变器最大功率点跟踪、并网控制技术和孤岛效应等问题的分析,提出了相应的解决方案:采取最大功率跟踪方法,系统能在光强变化时,迅速、准确地跟踪太阳能电池阵列的最大功率点;以多输入支路的独立最大功率跟踪策略,解决了由于太阳能电池阵列参数不一致造成的输出功率降低的问题;在并网逆变技术上采用电流超前跟踪,简单实现了输出功率因数为1,有效地提高了输出电能质量.     

基于阻抗分析的LCL型并网逆变器相角补偿控制

弱电网条件下,电网阻抗的存在会增加并网电流的谐波含量,甚至造成光伏并网逆变器不稳定。该文以三相LCL型逆变器为研究对象,以阻抗模为出发点,使用阻抗稳定判据分析弱电网在常规电流控制方式下的系统稳定性降低机理,提出在电容电流前馈支路上附加超前校正网络的相角补偿控制策略,通过提高系统输出阻抗的相角提高并网逆变器稳定性。仿真结果表明,该方法可有效解决较高电网阻抗带来的失稳现象,并具有良好的稳态性能和动态响应能力。     

基于有限控制集模型预测的逆变器控制算法

有限控制集模型预测控制是一种变流器优化控制算法,具有动态响应快、无须解耦运算和安装PWM调制器等优点,被广泛应用于光伏并网逆变器。该算法在一个控制周期内须对逆变器多个开关状态的电流、电压预测值和优化目标函数进行计算,导致处理时间较长。文章提出一种简化的基于有限控制集模型预测的光伏逆变器控制算法,将优化目标函数的电流矢量等效替换为电压矢量。由于目标函数电压矢量的测量和计算比电流矢量更方便,该简化的控制算法可有效提高系统的响应速度。仿真及实验结果表明,该简化的控制算法能有效改善光伏逆变器的动态性能。     

一个多种跟踪方式的并网光伏电站

以我国第一座跟踪式并网光伏示范电站为例,介绍了跟踪式并网光伏电站的基本配置;在深入研究太阳自动跟踪机理的基础上,提出了适合无人值守荒漠电站自动跟踪控制策略;给出了高效支路式光伏并网逆变器的设计方案.该并网光伏电站的运行结果表明,跟踪系统可以较大幅度地提高发电效率.     

三相光伏并网逆变器准比例谐振控制器设计

近年来,光伏并网逆变器的电流控制技术成为研究热点,文章针对传统电流控制技术的不足之处,将准比例谐振控制引入到光伏并网逆变器的电流控制中,利用其在谐振频率处增益无穷大和较大带宽的特点,消除稳态误差,提高抗干扰能力。仿真结果表明,设计的准比例谐振控制器能实现三相光伏并网逆变器的电流无误差跟踪,具备抗电网干扰能力,具有较好的动、稳态性能。     

30KVA光伏并网逆变器的设计及控制研究

该文介绍了30kW光伏并网用三相逆变器主电路设计和并网系统的控制方案.系统采用恒电压跟踪技术,使太阳电池输出功率达到最大,采用软件锁相使输出电流同步跟踪电网电压相位,并具有电网掉电识别、过流、欠压和监控等功能,保证了光伏并网发电的安全运行.     

基于DSPIC30F6010A双闭环控制的并网逆变器的研究与实践

光伏并网发电是光伏发电应用发展的趋势.并网逆变器是光伏并网发电系统核心部件之一,基于DSPIC30F6010A芯片控制的并网系统,利用DSP丰富的外围电路和强大的功能实现并网系统的所有工作、控制和相应的保护功能等.针对输出电流谐波含量大的特点,提出了基于同步PI内环控制和直流电压前馈外环控制的双闭环电流控制思路,并网逆变器采用前级DC/DC的boost升压结构电路,减少系统体积和重量;后级DC/AC逆变器采用全桥逆变电路;且具有最大功率跟踪和反孤岛效应等功能.仿真和实验证明:利用提出的算法,可有效减少并网电流的谐波,光伏并网系统具有可靠性强,工作效率高,稳定性好等优点.     

High-efficiency grid-connected photovoltaic module integrated converter system with high-speed communication interfaces for small-scale distribution power generation

This paper presents a high-efficiency grid-connected photovoltaic (PV) module integrated converter (MIC) system with reduced PV current variation. The proposed PV MIC system consists of a high-efficiency step-up DC-DC converter and a single-phase full-bridge DC-AC inverter. An active-clamping flyback converter with a voltage-doubler rectifier is proposed for the step-up DC-DC converter. The proposed step-up DC-DC converter reduces the switching losses by eliminating the reverse-recovery current of the output rectifying diodes. To reduce the PV current variation introduced by the grid-connected inverter, a PV current variation reduction method is also suggested. The suggested PV current variation reduction method reduces the PV current variation without any additional components. Moreover, for centralized power control of distributed PV MIC systems, a PV power control scheme with both a central control level and a local control level is presented. The central PV power control level controls the whole power production by sending out reference power signals to each individual PV MIC system. The proposed step-up DC-DC converter achieves a high-efficiency of 97.5% at 260 W output power to generate the DC-link voltage of 350 V from the PV voltage of 36.1 V. The PV MIC system including the DC-DC converter and the DC-AC inverter achieves a high-efficiency of 95% with the PV current ripple less than 3% variation of the rated PV current.     

A grid-connected photovoltaic power conversion system with single-phase multilevel inverter

This paper presents a grid-connected photovoltaic (PV) power conversion system based on a single-phase multilevel inverter. The proposed system fundamentally consists of PV arrays and a single-phase multilevel inverter structure. First, configuration and structural parts of the PV assisted inverter system are introduced in detail. To produce reference output voltage waves, a simple switching strategy based on calculating switching angles is improved. By calculated switching angles, the reference signal is produced as a multilevel shaped output voltage wave. The control algorithm and operational principles of the proposed system are explained. Operating PV arrays in the same load condition is a considerable point; therefore a simulation study is performed to arrange the PV arrays. After determining the number and connection types of the PV arrays, the system is configured through the arrangement of the PV arrays. The validity of the proposed system is verified through simulations and experimental study. The results demonstrate that the system can achieve lower total harmonic distortion (THD) on the output voltage and load current, and it is capable of operating synchronous and transferring power values having different characteristic to the grid. Hence, it is suitable to use the proposed configuration as a PV power conversion system in various applications.     

A Single-Stage Three-Phase Grid-Connected Photovoltaic System With Modified MPPT Method and Reactive Power Compensation

Single-stage grid-connected photovoltaic (PV) systems have advantages such as simple topology, high efficiency, etc. However, since all the control objectives such as the maximum power point tracking (MPPT), synchronization with the utility voltage, and harmonics reduction for output current need to be considered simultaneously, the complexity of the control scheme is much increased. This paper presents the implementation of a single-stage three-phase grid-connected PV system. In addition to realize the aforementioned control objectives, the proposed control can also remarkably improve the stability of the MPPT method with a modified incremental conductance MPPT method. The reactive power compensation for local load is also realized, so as to alleviate grid burden. A DSP is employed to implement the proposed MPPT controller and reactive power compensation unit. Simulation and experimental results show the high stability and high efficiency of this single-stage three-phase grid-connected PV system.     

基于Matlab/Simulink的两级式光伏并网系统仿真分析

研究一种单相光伏并网发电控制仿真系统。利用Matlab2008b/Simulink,采用boost电路和逆变电路两级式结构,其中采用电导增量法的最大功率跟踪功能在boost电路中实现,并网控制通过采集电网电压参数和逆变输出电流电压参数在逆变电路中通过PI调节实现。通过光伏阵列通用模型验证最大功率跟踪模块的正确性,通过并网实验验证并网跟踪性能。基本实现了光伏阵列最大功率点的快速、准确跟踪功能和逆变输出电流电压与电网电压的同频同相,保证了输出电流为正弦波形且纹波较少,能够快速跟踪电网电压的变化。证明此系统在实际中是可行的。     

并网中小型风电系统最大功率跟踪控制

针对目前中小型风力发电系统发电效率低,提出了一种新型拓扑结构,即机侧采用三相PWM整流器,网侧采用单相PWM逆变器。在对永磁同步发电机数学模型和风力机最佳输出功率进行分析的基础上,采用转子磁链定向控制技术,实现对发电机输出的有功功率的控制,进而实现对风力发电机最大功率的跟踪控制;同时,在单相系统中引入"虚拟电路",使网侧单相变流电路参数可以转化到旋转坐标系下,实现无静差控制。通过仿真试验验证了控制策略的可行性。     

Fuzzy logic-based MPPT controllers for three-phase grid-connected inverters

In photovoltaic (PV) applications, a maximum power point tracking (MPPT) module is necessary to extract the whole energy that the PV module can generate depending on the instantaneous conditions of the PV system. A PV module is obtained by connecting a number of solar cells in series and parallel, which causes voltage and current to increase at module terminations. The present work is based on a three-phase grid-connected inverter designed for a 100 kW PV power plant that uses an MPPT scheme based on fuzzy logic controllers. The whole system presented is simulated in MATLAB. The fuzzy logic-based MPPT controllers show accurate and fast responses and are integrated into the inverter, so that the there is no requirement for a dc–dc converter. The inverter allows full control of reactive power.     

SMC-DPC based active and reactive power control of grid-tied three phase inverter for PV systems

In this paper, sliding mode control (SMC) – direct power controller (DPC) based active and reactive power controller for three-phase grid-tied photovoltaic (PV) system is proposed. The proposed system consists of two main controllers: the DC/DC boost converter to track the possible maximum power from the PV panels and the grid-tied three-phase inverter. The Perturb and Observe (P&O) algorithm is used to transfer the maximum power from the PV panels. Control of the active and reactive powers is performed using the SMC-DPC strategy without any rotating coordinate transformations or phase angle tracking of the grid voltage. In addition, extra current control cycles are not used to simplify the system design and to increase transient performance. The fixed switching frequency is obtained by using space vector modulation (SVM). The proposed system provides very good results both in transient and steady states with the simple algorithms of P&O and SMC-DPC methods. Moreover, the results are evaluated by comparing the SMC-DPC method developed for MPPT and the traditional PI control method. The proposed controller method is achieved with TMS320F28335 DSP processor and the system is experimentally tested for 12 kW PV generation systems.     

Accurate power sharing among multi-DG resources in a microgrid

In this paper, a sliding mode (SM)-based direct active and reactive power control for the distributed generations (DGs) in microgrid is presented. The grid-connected microgrid contains two three-phase DGs that are photovoltaic (PV) units, and three single-phase DGs consisting of fuel cell (FC), PV, and battery. In the proposed strategy, controlling of the active and reactive powers is carried out for the single-phase and three-phase DGs without any phase angle tracking of the network voltage or synchronization transformations. The proposed robust control strategy improves power sharing and regulates power components injected by the DGs, and it is tested under balanced and unbalanced loads.