带缓冲单元的多输入直流变换器电路拓扑

在采用两个甚至多个输入源的新能源联合供电系统中,用单个多输入直流变换器(Multiple-Input Converter, MIC)代替原有的多个单输入直流变换器,可以简化电路结构,降低系统成本。MIC可分为无缓冲单元和带缓冲单元的两类。本文将讨论无缓冲单元的MIC的生成方法。首先给出构成无缓冲单元的MIC电路拓扑的基本单元,提出生成MIC时单元之间的组合级联规则,由此推导出一系列无缓冲单元的MIC电路拓扑,最后将生成的结构较复杂的隔离型的MIC电路拓扑进一步简化,并给出简化原则。     

无缓冲单元的多输入直流变换器电路拓扑

在采用两个甚至多个输入源的新能源联合供电系统中,用单个多输入直流变换器MIC代替原有的多个单输入直流变换器,可以简化电路结构,降低系统成本.MIC可分为无缓冲单元和带缓冲单元的两类,文中讨论了无缓冲单元的MIC电路拓扑的生成方法.首先给出构成无缓冲单元的MIC电路拓扑的基本单元,提出生成MIC时基本单元之间的组合级联规则,由此推导出一系列无缓冲单元的MIC电路拓扑.     

带缓冲单元的多输入直流变换器电路拓扑

在采用两个甚至多个输入源的新能源联合供电系统中,用单个多输入直流变换器(MIC)代替原有的多个单输入直流变换器,可以简化电路结构、降低系统成本。MIC可分为无缓冲单元和带缓冲单元两类。带缓冲单元的MIC是由脉冲电源单元、缓冲单元和输出滤波器构成。文中详细介绍带缓冲单元MIC电路拓扑的生成方法,首先介绍缓冲单元的概念以及具体电路结构;给出脉冲电源单元与缓冲单元的级联规则;最后,推导出一系列带缓冲单元的MIC电路拓扑。     

Maximum power point tracking without current sensor for photovoltaic module integrated converter using Zigbee wireless network

In this paper, a simple maximum power point tracking method for series-connected DC–DC converter module of photovoltaic power conditioning systems is proposed. This approach enables maximum power point tracking control with the converter’s output voltage information instead of calculating solar array power, which significantly simplifies the sensor network by removing any current sensor. Furthermore, there is no multiplication process of power calculation for perturbation-and-observation algorithm to track the maximum power point because the power calculation is replaced by simple output voltage sensing. This simple tracker realization can reduce the cost and size, and can be utilized with a low performance/low cost controller. For the implementation of the proposed control strategy, Zigbee (Xbee-pro) wireless communications and DSP’s Series Communications Interface are utilized. Then, a couple of series-connected hardware prototype of photovoltaic modules was built and tested for the performance evaluation.     

A high performance maximum power point tracker for PV systems

The solar cell characteristics are non-linear and largely influenced by solar radiation, temperature and load condition. The power output of a PV array changes with varying temperature and irradiation. A maximum power point algorithm is investigated to obtain maximum power from a PV array on varying operating conditions. So far various methods have been proposed to achieve the maximum power from PV module. The incremental conductance (INC) and perturb and observe (P&O) algorithm are more noteworthy. In this paper two high performance and simple maximum power point tracker (MPPT) are proposed. These algorithms are modified P&O and INC algorithms. These modified algorithms are capable to track maximum power under rapidly changing atmospheric conditions with higher accuracy than their conventional methods. They increase the harvested power from PV array and thus improve the efficiency of MPPT algorithm. The algorithms using a high step-up-DC/DC converter are implemented on MATLAB/SIMULINK tool. The results demonstrate a good performance and accurate tracking under rapidly changing atmospheric conditions.     

采用交变脉冲电源单元的隔离型多输入直流变换器

多输入直流变换器(MIC)实现多种能源输入,可同时或分时向负载提供能量,具有优先利用能源、简化系统结构及降低系统成本等优点,因此适用于新能源联合供电系统。本文针对输入输出隔离场合,提出采用交变脉冲电源单元构建隔离型MIC的方法:根据交变脉冲电源单元组合规则推导出基本隔离型MIC,利用最大功率传输原则确定MIC的控制策略,通过分析开关管的开关时序对基本隔离型MIC进行简化,进而得到多种不同类型的简化隔离型MIC拓扑。本文将详细给出通过交变脉冲电源单元构建隔离型MIC的方法,并以将半桥三电平单元与全桥单元组合而成的双输入变换器为例,采用有效的能量管理策略实现两输入源的功率分配,最后通过一个1kW的原理样机验证理论分析的正确性。     

光伏系统最大功率点跟踪控制算法

最大功率点跟踪技术(MPPT)在太阳能光伏发电系统中占有重要地位.针对现有MPPT方法动态性能和稳态性能难以兼顾的不足,提出了一种具有良好动态性能和稳态性能的MPPT方法,该方法通过Boost电路的开路电压的测量及最大功率点电压的非线性计算对最大功率点进行跟踪控制.仿真结果表明,该方法快速跟踪到最大功率点,消弱了最大功...     

Investigation of the double input power converter with N stages of voltage multiplier using PSO-based MPPT technique for the thermoelectric energy harvesting system

This research work presents a thermoelectric energy harvesting system comprises of a double input DC-DC converter with maximum power point tracking (MPPT) technique under varying temperature conditions (VTCs). The converter has two inputs with N stages of diode-capacitor to boost the output voltage. It has the advantages of higher voltage gain and flexibility of power-sharing by both the independent sources. The perturb and observe (P&O)-based MPPT algorithm is an efficient and simple method to track the maximum power. However, the power-current (P-I) characteristics of the thermoelectric modules exhibit multiple peaks at VTCs; it fails to identify the global peak point (GPP) and gets track the local peak point. To overcome the drawback of the P&O technique, a particle swarm optimization (PSO)-based MPPT technique is implemented to track the GPP. A comparison is performed between the P&O and PSO technique in terms of MPPT tracking efficiency and oscillation around the maximum power point. From the acquired results of simulation and experiment, it is recommended that the PSO-based MPPT technique has furnished better overall performance.     

Study on maximum power point tracking of photovoltaic array in irregular shadow

Traditional maximum power point tracking (MPPT) methods can hardly find global maximum power point (MPP) because output characteristics curve of photovoltaic (PV) array may have multi local maximum power points in irregular shadow, and thus easily fall into the local maximum power point. To address this drawback, Considering that sliding mode variable structure (SMVS) control strategy have such advantages as simple structure, fast response and strong robustness, and P&O method have the advantages of simple principle and convenient implementation, so a new algorithm combining SMVS control method and P&O method is proposed, besides, PI controller is applied to reduce system chattering caused by switching sliding surface. It is applied to MPPT control of PV array in irregular shadow to solve the problem of multi-peak optimization in partial shadow. In order to verity the rationality of the proposed algorithm, the experimental circuit is built, which achieves MPPT control by means of the proposed algorithm and P&O method. The experimental results show that compared with the traditional P&O algorithm, the proposed algorithm can fast track the global MPP, tracking speed increases by 60% and the relative error decreased by 20%. Moreover, the system becomes more stable near the MPP, the fluctuations of output power is greatly reduced, and thus make full use of solar energy.     

电流扰动双轨迹最大功率跟踪技术研究

提出了一种基于电流扰动的双轨迹最大功率跟踪控制方法。该方法采用 P‐V 、I‐V 相结合进行光伏最大功率点跟踪,跟踪分为3个区域,电流源和电压源区采用短路电流法将光伏阵列工作点电流调整到最大功率点附近,电流扰动工作区采用电流扰动观察法进一步精确跟踪光伏最大功率点。采用短路电流法确定不同光照强度下的上、下边界阈值函数,建立带有线性化光伏电池等效电路模型,对其进行了幅频、相频特性分析,得到了稳定的闭环参数。将该方法用于某115 V／400 Hz独立光伏发电系统,并进行了一系列的仿真和实验研究,结果表明,系统运行稳定、状态良好,验证了方法的可行性和正确性。     

Maximum power point tracking of PVsystem under partial shading conditionsthrough flower pollination algorithm

For maximum utilization of solar energy, photovoltaic (PV) power systems should be operated at the maximum power point (MPP) which can be achieved using maximum power point tracking (MPPT) methods. However, the occurrence of multi-peak on P-V curve of a PV array due to the changing environmental conditions such as being partially shaded increases the complexity of the tracking process. The global MPP cannot always be achieved by the conventional MPPT methods. Therefore a novel MPPT method for PV systems using flower pollination (FP) algorithm is proposed in this paper and the Levy flight is used to improve the convergence of FP algorithm. MPPT model of the PV system is established in MATLAB to verify the effectiveness of the proposed method, and the proposed method is compared with two well established MPPT methods. The simulation results indicate that the proposed MPPT method can quickly track the changes in external environment and effectively handle the partially shaded condition.     

Kalmen estimator as a robust solution for output power maximization of wave energy converter

In this paper, the application of linear quadratic Gaussian (LQG) control for a buoy‐type point absorber of a wave energy converter (PA‐WEC) system is investigated. The proposed wave energy conversion is considered as a two‐body system, which is taut‐anchored to the sea floor using three cables. The main goal of this study is to extract the maximum available power from the ocean wave. This is accomplished via determining the optimal value of the force exerted on the power take‐off (PTO) system taking in account the physical constraints on the position and velocity. First, the reduced nonlinear dynamical model of the WEC system is obtained. The nonlinearity in the mooring force is replaced by a linear law to yield the state space linear model of the system. Then, the standard Kalman filter technique is employed to estimate the full states of the system. Based on the LQG control approach, the optimal PTO force is computed at which the maximum output power can be easily harvested. The computational burden is minimized to a great extent by computing the optimal state feedback gains and the Kalman state space model offline. The feasibility of the proposed control approach in extracting the optimal power of the ocean wave is validated via the simulation example even under different values of the mooring constant and without violating the system limitation. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于柔性工作点追踪的光伏低电压穿越控制策略

为解决现有光伏并网发电系统低电压穿越控制存在的母线过电压问题,提升并网系统故障恢复能力,本文结合柔性工作点追踪控制原理,提出一种经济有效的基于柔性工作点追踪的低电压穿越控制策略。首先,通过图形近似法快速估算出减载点工作电压,推导出故障期间光伏参考工作点位置,提出光伏输出功率快速减载策略;其次,利用拟合出的光伏电流-电压曲线估算光伏短路电流,通过Lambert-W函数计算出最大功率点电压,进一步提出故障快速恢复策略;最后,本文分别通过Matlab仿真和硬件在环测试平台进行仿真和实验分析。分析结果验证了所提控制策略有较好的故障穿越能力和故障恢复效果,且经济性较好,有助于光伏并网发电技术的推广应用。     

基于非线性内点理论的交直流系统无功优化新模型

在交流侧有载调压变压器(Load tap changing transformer,LTC)支路中引进虚拟节点,并通过虚拟节点的电压来表示有载可调变压器支路功率方程;对于直流系统,在换流变压器的理想变压器和换流阻抗之间引进一个虚拟节点,虚拟节点电压幅值等一些变量被用来表示换流器支路方程;耦合方程把不同坐标系下的方程耦合到一起,由此建立了交直流混合系统无功优化问题的二阶新模型。预测-校正原对偶内点法被用来实现这个无功优化问题,该模型的海森矩阵在优化过程中是恒常矩阵,只需要计算一次,这样缩短了内点法的计算总时间。通过测试系统对新模型与传统模型进行仿真计算比较,结果验证了所建模型有较好的收敛特性。     

Annual performance analysis of differentmaximum power point tracking techniquesused in photovoltaic systems

This paper presents an annual performance evaluation of three maximum power point tracking (MPPT) methods. The used MPPT techniques (Perturb and Observe, Incremental Inductance and Sliding mode) are evaluated under an annual data of atmospheric conditions of the target site. The main contribution of this work is to consider real fluctuation conditions of solar irradiations, ambient temperatures and wind velocities. It was found that the Sliding mode provides higher energy yields independently of the period. Compared to the basic P&O and the IC techniques, sliding mode has the potential of generating up to 8.18% more electrical energy than other techniques.     

基于周期性最大功率点检测的风电机组功率备用控制方法

风电机组通常运行于最大功率输出模式,无法为受扰电网提供紧急功率支撑。稳态时预留部分出力可提高风电机组主动电网支撑能力,为此提出一种基于周期性最大功率点(MPP)检测的风电机组功率备用控制(PRC)方法。通过周期性执行最大功率点跟踪程序检测风电机组实时MPP,一旦检测到MPP即可确定PRC模式参考值并切换为直接功率控制。设置伪单调转速-机械功率曲线使风电机组稳定运行在超速功率备用点,并通过储能装置平抑MPP检测产生的峰值功率波动。仿真结果表明提出的控制方法在定风速和变风速情况下均可以准确控制检测风电机组MPP并实现PRC,并且使得风电机组一次调频效果优于传统PRC。     

Materials, structures and power interfaces for efficient piezoelectric energy harvesting

The possibility of recycling ambient energies with miniature electrical generators instead of using batteries with limited lifespan has stimulated important research efforts over the past years. Integration of such miniature generators is mainly envisioned into low power autonomous systems, for various industrial or domestic applications. This paper focuses on the use of piezoelectric materials for generating electrical energy from ambient mechanical vibrations. A review of the piezoelectric materials and the electromechanical structures which have been proposed in this field is first presented. Electrical circuits with one-stage, two-stage and three-stage interfaces which have been developed for optimizing the electrical power flow from piezoelectric devices to energy storage elements are then compared to a novel technique for controlling the energy converted by piezoelectric materials. This novel approach is derived from Ericsson thermodynamic cycle. A solution for practical implementation is proposed, theoretical predictions and experimental results are compared and discussed.     

基于纵横交叉算法的波浪发电装置最大功率跟踪控制

针对波浪能最大功率点跟踪控制中,浮子水动力模型的非线性,使传统群智能算法存在局部最优问题,提出纵横交叉算法(CSO)控制方案。CSO的纵向交叉算子,在纵向交叉概率判定下进行个体维变量间的算术交叉,保证种群能够脱离局部最优状态; CSO的横向交叉算子完成个体间的随机配对与算术交叉,并将解空间全体分割成若干个子空间,每个子空间以配对个体为对角顶点,搜索子空间内部及邻域,实现精细的局部搜索能力。通过纵、横交叉算子的交替作用,任何有益于实现全局最优的信息,都将被迅速地分发到种群的各变量中,用以改变搜索路径。仿真表明,在波浪周期发生变化时,纵横交叉算法能够实现最大功率点跟踪,并提高收敛速度。     

局部阴影下光伏电池最大功率点跟踪方法

随着能源和环境问题的日益严重,太阳能作为一种绿色可再生能源得到大力发展。光伏发电是太阳能利用最常见的形式,最大功率点跟踪（MPPT）是提高光伏发电效率的有效途径之一。由于光伏发电系统所处环境复杂,部分组件被遮挡的问题难以避免,传统的跟踪算法可能出现误判。针对此问题,本文以局部阴影下最大功率点跟踪控制为主线展开研究,分析光伏发电原理,搭建了4串2并结构的光伏阵列。通过仿真和编程探究了阵列在局部阴影下的输出特性并总结规律。在此基础上,对最大功率点跟踪进行了理论分析,并基于粒子群算法设计出了有效的控制方法,实现了局部阴影下最大功率点跟踪,利用Simulink进行仿真,验证了算法的可行性。     

一种优化的光伏全局最大功率点追踪方法

当前的光伏最大功率点追踪技术存在以下不足：在局部阴影工况下,易陷入局部功率峰值;在负载波动时,系统容易出现振荡甚至失稳。针对上述问题,提出一种自适应的光伏全局最大功率点追踪设计方案。该方案将光伏输出端电压-功率扫描电路与Zeta斩波电路有机结合,通过单开关管的简单电路拓扑,既可实现光伏输出端电压?功率特性快速扫描,定位全局最大功率点位置,又能根据后级电路需要,实现升降压斩波直流调节。在光照等输入或负载发生突变后,所述系统均能进行开关管占空比自适应调整,确保稳定工作在全局最大功率点附近,避免出现大幅振荡与失稳。经过PSCAD-EMTCD仿真与样机实验验证,结果表明该方案能在包括局部阴影等各种复杂工况下自适应地快速追踪与锁定当前光伏全局最大功率点。