Power quality improvement of solar power plants in grid connected system using novel Resilient Direct Unbalanced Control (RDUC) technique

Distributed Generation systems (DGs) using solar power is one of the new trends in power generation. These distributed generating units are integrated to form a micro grid to serve the loads among the locality, which is in connection with the utility grid for power transmission. The elimination of the harmonics in the grid and the usage of solar energy resources in the power electronics applications become famous worldwide. In this work, a Resilient Direct Unbalanced Control (RDUC) algorithm is used to improve the performance of the controller by achieving optimal numerical parameters for photovoltaic power generation - Unified Power Quality Conditioner (PV-UPQC). Then the voltage sag, swell and elimination of current harmonics are used to study the effects of proposed RDUC algorithm for photovoltaic feed UPQC system. According to the evaluations, the proposed unified power quality conditioner eliminates both the supply current distortion caused by a non-linear load and the load voltage distortion introduced after adding fifth and seventh harmonics to the Alternating Current (AC) mains voltage. To validate the simulation results of Resilient Direct Unbalanced Control scheme, tests are performed under various operating conditions. Test results show the satisfactory behavior under steady state, and dynamic conditions such as load unbalance, insolation variation, voltage sag and swell. Finally, Total Harmonic Distortions (THDs) of proposed optimization-based grid current and grid voltages found within limits of the IEEE standard.     

FPGA based substantial power evolution controlling strategy for solar and wind forecasting grid connected system

The solar and wind are both the most promising renewable and clean energy sources, the solar stable energy progress and environmental protection have been increasingly noticeable. In this regard, an accurate solar and wind energy prediction is extremely important to avoid large voltage changes to the power grid and to provide a mechanism for the system to optimally manage the generated energy. Wind energy forecasting is widely practiced among modest power systems for high levels of windmills. This paper aims to develop a new hybrid system for wind and solar energy prediction. The proposed hybrid (wind & solar) energy prediction model is based on a Substantial Power Evolution Strategy (SPES) dedicated to short-term forecasting. The proposed forecasting system SPES is implemented using MATLAB. This paper implements the short-term and hybrid power forecasting using Substantial Power Evolution Strategy based on Prediction Intervals (PIs). This feature is one of the major innovations in the proposed hybrid renewable energy forecasting system. The accuracy of the proposed system will be revealed by comparing the results of the corresponding values of the independent forecasting models called persistence models. The designed device presents a real-time application of predicting daily total solar and wind power using any geographic location and environmental conditions using FPGA. Finally, fully developed system packages can be commercialized and/or utilized for further research projects, and researchers can analyze, validate and visualize their models for related fields.     

Direct power control of grid connected voltage source inverters using port-controlled Hamiltonian system

This paper presents a new direct active and reactive power control (DPC) scheme for a three-phase grid connected voltage source inverter (VSI) based on the passivity viewpoint using the port-controlled Hamiltonian (PCH) system. The proposed controller consists of feedforward and feedback parts. The feedforward part (the reference inputs) is generated through the flatness of the dynamics of the VSI model, which makes the error dynamics in the form of PCH system. The nonlinear feedback part is designed to enhance the damping of the error dynamics by using its Lyapunov function. The proposed control method has an ability of the finite time reaching condition similar to sliding mode control (SMC). Moreover, the exponential stability and uniform performance are guaranteed over all operating points without need for reaching a certain manifold. The proposed method is validated by using an experiment through hardware-in-the-loop system with a digital signal processor. The experimental results for the proposed method are compared with those using SMC-DPC method. The proposed method significantly reduces the total harmonic distortion in the output current without deteriorating the transient response of the active and reactive powers. In addition, it provides robust performance against the line impedance variations and the grid voltage sag.     

具有谐波抑制与无功补偿功能的光伏并网系统

介绍了一种新型的光伏并网发电系统模型,在并网发电的同时实现了对电网中的无功和谐波的补偿与抑制。基于光伏阵列的等效电路模型,在Matlab仿真环境下,建立光伏阵列的通用仿真模型。利用该模型,设计新型的光伏并网发电系统。该系统将光伏并网系统的发电控制和无功补偿、有源滤波相结合,使得光伏并网发电系统不仅可以并网发电还具有谐波抑制与无功补偿的功能,进而提高电网的供电质量和能力。最后对该系统进行仿真实验验证,仿真结果验证了系统模型的正确性和有效性。     

An improved power conditioning system for grid integration of solar power using ANFIS based FOPID controller

Power loss become common while integrating with common grid and in specific when power produced through Solar. This is the very lacking area which this proposal implements an Adaptive Neuro Fuzzy Inference System (ANFIS) based controller of Fractional Order Proportional Integral Derivative (FOPID) used for Tracking of Maximum PP of Grid Integrated Solar Power Conditioning System. The proposed work advances with different ambient light conditions for maximum power point traction. In this work a clear-cut Photo Voltaic (PV Cell) model has been developed and an intensive and operative training data have been extracted from the developed controller. This produced dataset have been the feeder input for the ANFIS structure in turn to locate the Tracking of Maximum PP (MPPT). Traction of MPPT is done, the FOPID controller is enforced by matching the voltage from the array of Photo Voltaic cell with attained or reference voltage produced by the ANFIS structure. In the meantime driving this PV array, DC to DC converter's duty cycle is controlled for producing maximum power from the structure. The duty cycle in FOPID controller is generated through calculating the error within the reference voltage and PV voltage. Those values are then simulated through Math Lab and the Simulation results show that this proposed work efficiency is better than the regularly employed controllers in the solar power production and conditioning system     

基于SVG的风电场接入局域电网的电压稳定性分析

研究了用静止无功发生器(SVG)改善基于双馈感应发电机组的风电场的暂态电压稳定性。在DIgSILENT/PowerFactory中建立了双馈感应发电机组及SVG控制模型,通过包含风电场的电力系统仿真,验证了SVG对风电场暂态电压稳定性的作用。仿真结果表明,SVG能够有效地帮助风电场在电网发生故障后迅速恢复电压,提高风电场的故障穿越能力,确保风电机组连续运行及电网安全稳定。     

Power control of a doubly fed induction generator connected to the power grid

In this paper, the regulation control problem of the active and reactive power at the common connection point between a doubly fed induction generator and the grid is approached. The proposed controller is developed exploiting the passivity properties of the considered model for the control system. It is considered the existence of a wind turbine that delivers a time-varying torque to the generation unit which exhibits a highly nonlinear structure due to the variations of the wind speed. From a theoretical perspective, the main feature of the contribution lies in the fact that it is formally proved that the equilibrium point of the closed-loop system that corresponds to the desired power exhibits practical global asymptotic stability properties. This characteristic is obtained applying well-known theory from the perturbed nonlinear dynamical systems theory. However, in the numerical evaluation of the proposed controller, it is illustrated how these properties are indeed stronger since asymptotic stability is achieved.     

一种改进的孤岛检测策略在光伏系统中的应用

在现代电力系统中,可能产生的孤岛效应一定程度上限制了光伏并网发电系统(photovoltaic grid connected power system,PV)的应用和发展,孤岛检测是光伏系统必须具备的功能。传统的滑模频率偏移法有检测效率较低、对系统发电质量影响较大等缺点,提出了一种将传统滑模频率偏移法和电压正反馈机制相结合的孤岛检测策略。分析了改进方法的工作原理,基于d q变换实现了有功电压、无功电压以及有功电流、无功电流的分离,通过与参考量做差作为反馈量,达到破坏功率平衡从而检测出孤岛的目的。仿真实验结果验证了该方法的可行性和有效性,对工程应用有一定的参考价值。     

农村电网电能质量监测系统的设计与实现

随着电力系统中大量非线性负荷的出现,电能质量不断恶化.本文在研究电力系统电能质量指标的基础上,针对农村电网的特点,设计了一种能够监测和管理电能质量指标的新型的电能质量监测系统,并详细介绍了系统总体设计、监测终端设计与实现的方法.     

Power system model validation for power quality assessment applications using genetic algorithm

This paper presents an intelligent system for power quality assessment application. This system is used for power system model validation. A genetic algorithm (GA) based system for validating the power system model in capacitor switching studies has been developed. The problem formulation and the proposed solution are illustrated. The feasibility of the developed system for practical applications is demonstrated by evaluation studies.     

Power system model validation for power quality assessment applications using genetic algorithm

This paper presents an intelligent system for power quality assessment application. This system is used for power system model validation. A genetic algorithm (GA) based system for validating the power system model in capacitor switching studies has been developed. The problem formulation and the proposed solution are illustrated. The feasibility of the developed system for practical applications is demonstrated by evaluation studies.     

光伏并网接入配电网的太阳能发电系统设计

对配电网发电系统进行设计,可以减少电网输电时产生的故障,提高配电网运行效率。当前方法利用一次性能源,例如石油、煤炭以及天然气等化石能源实现发电系统的设计。由于化石能源在本质上,是数万年以来由太阳能辐射至地球的一部分能源,该能源消耗快,导致发电系统运行不稳定。为此,提出光伏并网接入配电网的太阳能发电系统设计方法。该方法对光伏并网接入配电网进行研究,利用图解的方式详细介绍并网点及接入点,系统的硬件部分通过光伏阵列以及一体化框架、逆变单元VSR、交流配电单元以及放电模块和系统电源电路,组建太阳能光伏并网接入配电网发电系统构造。采用三相桥结构对太阳能发电系统电路进行设计,太阳能发电系统的温度采样模块设计中,利用的是温度传感器AD590,根据TLP250驱动Power MOSFET完成放电控制模块的组建,依据光伏阵列、利用80C196MC等可逆变流控制组建光伏并网逆变模块。系统的软件部分利用构建光伏并网接入配电网的太阳能发电数学模型实现。实验证明,所提方法有效利用可再生资源与绿色能源,实现发电系统的稳定设计。     

Power flow Petri Net modelling for building integrated multi-source power system with smart grid interaction

This paper presents an energy management modelling of a multi-source power system composed of photovoltaic (PV) array, storage and power grid connection, and taking into account messages from smart grid. The designed system can supply a tertiary building at the same time as PV may produce energy. The control strategy aims to manage the power flow through the load with respect to its power demand and public grid constraints. The proposed energy management modelling is based on interpreted Petri Nets formalism. The system is tested using a simulation Stateflow model and responds within certain limits. The results show that this approach is valid and can be a solution for the future smart grid communication between buildings and public grid and may contribute to a better balance between production and consumption and future energy management.     

Power quality improvement using controllable inductive power filtering method for industrial DC supply system

This paper proposes a novel controllable inductive power filtering (CIPF) method to solve the power quality issues existed in the industrial DC power supply system. This method is based on the theory of magnetic potential balance and combined with the hybrid active filtering technology. First, the system topology and wiring scheme are presented, and the equivalent circuit and mathematical models of the filtering system are established. Then, to achieve a better filtering performance, a modified control strategy is designed. The technical features, such as harmonic suppression nearby the nonlinear load and resonance damping, are revealed by means of mechanism analysis. Furthermore, the system stability is discussed based on the Nyquist stability criterion. Finally, both the simulation model and the laboratory platform of the filtering system are established. The research results validate the theoretical analysis, and indicate that the proposed CIPF method with a suitable control coefficient can effectively eliminate the harmonics flowing through the transformer, and improve the operational efficiency of the rectifier system.     

电流型并网逆变器的模糊滞环控制

为改善滞环控制应用在并网逆变器中会出现系统开关频率不固定的问题,提出一种将模糊控制器与滞环比较器相结合的控制方法。通过对并网逆变器的建模和滞环电流控制原理的分析,可知开关频率与滞环环宽之间的关系。以电网电压及指令电流的偏微分为输入变量建立模糊控制规则,经过一定的模糊运算输出滞环环宽,从而动态地控制环宽达到稳定频率的目的。该方法能有效地降低开关频率,减小电流谐波。仿真和实验结果证明了该方法对稳定滞环开关频率是有效的,尤其是在过零点与顶点处,同时能够改善谐波特性。     

Performance of three phase AI controller based UPQC to enhance power quality of hybrid RES

Microsystem Technologies - Day-by-day to reduce the greenhouse effects and increase the power generating capacity the dependency of renewable energy systems are increasing. Due to its uncertainty...     

Optimum placement of active power conditioner in distribution systems using improved discrete firefly algorithm for power quality enhancement

This paper presents an improved solution for optimal placement and sizing of active power conditioner (APC) to enhance power quality in distribution systems using the improved discrete firefly algorithm (IDFA). A multi-objective optimization problem is formulated to improve voltage profile, minimize voltage total harmonic distortion and minimize total investment cost. The performance of the proposed algorithm is validated on the IEEE 16- and 69-bus test systems using the Matlab software. The obtained results are compared with the conventional discrete firefly algorithm, genetic algorithm and discrete particle swarm optimization. The comparison of results showed that the proposed IDFA is the most effective method among others in determining optimum location and size of APC in distribution systems.     

Performance analysis of a grid connected microgrid system under fault condition

Microsystem Technologies - The energy demand in the modern power system is increasing day by day. Thus integration of microgrid with the conventional grid can fulfill the high power demand but it...     

Image enhancement using deep-learning fully connected neural network mean filter

Improving the quality of a noisy image is important for image applications. Many novel schemes pay great efforts in the removal of impulse noise. Most of them restore noisy pixels only by using the neighboring noise-free pixels, but the relationship between a noisy image and its noise-free one, which denotes the clean image not corrupted by noise, is ignored. So the reconstruction quality cannot be further improved. In this study, we employ a deep-learning fully connected neural network (FCNN) to select top N candidates of neighboring un-corrupted pixels for the restoration of a center noisy pixel in an analysis window. Hence, the mean value of the gray levels of these top N pixels is computed and employed to replace the noisy pixel, yielding the noisy pixel being restored. The experimental results reveal that the proposed deep-learning FCNN mean filter can remove impulse noise effectively in corrupted images with different noise densities.