Difference between grid connections of large-scale wind power and conventional synchronous generation

In China, regions with abundant wind energy resources are generally located at the end of power grids. The power grid architecture in these regions is typically not sufficiently strong, and the energy structure is relatively simple. Thus, connecting large-capacity wind power units complicates the peak load regulation and stable operation of the power grids in these regions. Most wind turbines use power electronic converter technology, which affects the safety and stability of the power grid differently compared with conventional synchronous generators. Furthermore, fluctuations in wind power cause fluctuations in the output of wind farms, making it difficult to create and implement suitable power generation plans for wind farms. The generation technology and grid connection scheme for wind power and conventional thermal power generation differ considerably. Moreover, the active and reactive power control abilities of wind turbines are weaker than those of thermal power units, necessitating additional equipment to control wind turbines. Hence, to address the aforementioned issues with large-scale wind power generation, this study analyzes the differences between the grid connection and collection strategies for wind power bases and thermal power plants. Based on this analysis, the differences in the power control modes of wind power and thermal power are further investigated. Finally, the stability of different control modes is analyzed through simulation. The findings can be beneficial for the planning and development of large-scale wind power generation farms.

Grid-connected inverter for wind power generation system

In wind power generation system the grid-connected inverter is an important section for energy conversion and transmission, of which the performance has a direct influence on the entire wind power generation system. The mathematical model of the grid-connected inverter is deduced firstly. Then, the space vector pulse width modulation （SVPWM） is analyzed. The power factor can be controlled close to unity, leading or lagging, which is realized based on H-type current controller and grid voltage vector-oriented control. The control strategy is verified by the simulation and experimental results with a good sinusoidal current, a small harmonic component and a fast dynamic response.

Comparison of Experimental and Theoretical Output Power of Grid Connected Photovoltaic System in Super Mega Factory

In this paper, the performance of grid connected PV system that is installed in Super Mega Factory is presented. The output parameters of 4 kW PV is collected and analyzed. Then, according to the results the weak points of the system were found and the theoretical output power was compared. After that we try to get the maximum output power making the correction of collector angle and place suitable panel position.

Forecast of Power Generation for Grid-Connected Photo-voltaic System Based on Grey Theory and Verification Model

Being photovoltaic power generation affected by radiation strength, wind speed, clouds cover and environment temperature, the generating in each moment is fluctuating. The operational characteristics of grid-connected PV systems are coincided with gray theory application conditions. A gray theory model has been applied in short-term forecast of grid-connected photovoltaic system. The verification model of the probability of small error will help to check the accuracy of the gray forecast results. The calculated result shows that the ?model accuracy has been greatly enhanced.

Influence of Control Modes of Grid-Connected Solar Photovoltaic Generation on Grid Power Flow

Integration of Solar Photovoltaic (PV) generation into an existing distribution system has many impacts on the system, with the power flow being one of the major issues. This impact is not generic for any network, but it may manifest itself either positively or negatively, depending on the grid configuration, interface control modes, operation mode, and load profile. Grid-connected PV systems have three control options of the local voltage controller of the interface DC-AC converter. These control modes are Power Factor control, voltage control, and Droop Voltage control. This paper aims at evaluating and comparing the impacts of those control modes on the grid power flow. A set of evaluation criteria and indices is defined and mathematically formulated. Based on the requirements of the used program (Power Factory Dig Silent V14.1.3), a computation plan (algorithm) has been proposed. The algorithm has been applied to a typical weak network and a wide range of simulations has been carried out. Simulation results have been thoroughly discussed and important findings have been concluded.

Steady-State Analysis of Grid-Connected New Energy Power Plants

In order to ease the fossil energy crunch,new energy sources need to be fully utilized.Clean energy sources such as wind,light,and nuclear energy are important tools to solve environmental and energy problems.However,in the process of researching new energy farms,there are some problems when they are integrated into the power system.In order to ensure the stability of new energy power plants,it is necessary to conduct an in-depth analysis of the grid connection technology of new energy farms.In the study,it is necessary to learn about the specific problems of the stability of the grid connection of new energy power plants,and to clarify the specific application of the grid connection technology of new energy power plants from the application principle and advantages of the grid connection technology of new energy power plants.Through simulation experiments,the positive effect of grid connection technology of new energy power plants in improving the stability of power systems was determined.

Regional power connectivity in Southeast Asia: the role of regional cooperation

ASEAN is an interesting case study of regional power connectivity in Asia and the Pacific due to its geographic location and ongoing power connectivity within and beyond ASEAN.This paper reviews ASEAN’s power connectivity within ASEAN and between ASEAN and its neighbours(hereafter ASEAN connectivity).Through literature survey,it identifies challenges to the ASEAN connectivity from political,legal,economic and technical perspectives.Based on these analyses,it then explores what,how and when regional cooperation may be able to facilitate ASEAN power connectivity.

A Control Strategy for Grid-connected Inverters With LCL Filters

把LCL滤波器作为电压源型并网逆变器与电网的接口已受到广泛关注。与单电感L滤波器相比，利用电感值较小的LCL滤波器对入网电流的高次谐波具有显著的衰减效果，特别是在低开关频率的大功率并网逆变系统应用中更具明显优势，但是仅采用直接入网电流控制时，LCL滤波器接口的并网逆变器系统存在稳定性问题。该文采用电网侧电感电流和逆变侧电感电流双闭环控制策略对并网电流进行直接控制，电网侧电感电流作为外环更容易抑制并网电流的谐波因素，且可以直接控制入网电流的单位功率因数，采用逆变器侧电感电流作为内环可以增加系统阻尼，从而可抑制系统振荡，增加系统稳定性。对该方案进行系统建模，并深入分析了滤波器参数、控制器参数及系统稳定性之间的精确量化关系。仿真和实验结果表明，该控制策略既可有效抑制入网电流谐振和实现进网电流的高功率因数运行，同时又具有良好的稳态和动态性能。

Regulating cost for renewable energy integration in power grids

To address the issue of climate change caused by the use of polluting, non-renewable energy sources, the use of renewable energy has gained momentum worldwide. Consequently, the increased integration of renewable energy sources into power grids has necessitated the inclusion of flexible capacities in the power systems to solve problems of intermittent and fluctuating characteristics associated with renewable generation outputs. In this work, we study the regulating cost of a power system with high renewable penetration using an improved time-series system production simulation analysis method. The operational cost of the system is considered as the objective function. Three different methods to increase regulating capacities, including using interconnection lines, building additional flexible power capacities, and retrofitting existing thermal power plants, are adopted and simulated to compare the costs of accommodating renewable energy in the system in these cases. Our results indicate that increasing the flexibility of thermal power plants and developing crossregional connection lines are cost-effective methods of increasing renewable energy consumption.

Low Voltage Ride through Control Capability of a Large Grid Connected PV System Combining DC Chopper and Current Limiting Techniques

This paper presents the development and performance capability of a comprehensive Low voltage ride through (LVRT) control scheme that makes use of both the DC chopper and the current limiting based on the required reactive power during fault time. The study is conducted on an 8.5 MW single stage PV power plant (PVPP) connected to the Rwandan grid. In the event of fault disturbance, this control scheme helps to overcome the problems of excessive DC-link voltage by fast activation of the DC chopper operation. At the same instance, AC current is limited to the maximum rating of the inverter as a function of the injected reactive current. This helps overcome AC-over- current that may possibly lead to damage or disconnection of the inverter. The control scheme also ensures voltage support and power balance through the injection of reactive current as per grid code requirements. Selected simulations using MATLAB are carried out in the events of different kinds of fault caused voltage dips. Results demonstrate the effectiveness of the proposed LVRT control scheme.

Control Strategy of DC Link Voltage Flywheel Energy Storage for Non Grid Connected Wind Turbines Based on Fuzzy Control

The large-scale development of wind power is an important means to reduce greenhouse gas emissions, alleviate environmental pollution and improve the utilization rate of renewable energy. At the same time, large-scale non grid connected wind power generation theory avoids the technical difficulties of wind power integration [1]. However, due to the randomness and uncontrollability of wind energy, the output power of the wind power generation system will fluctuate accordingly [2]. Therefore, the corresponding energy storage devices are arranged in the non-grid-connected wind power generation system to ensure the power quality, and it has become the key to full utilization of renewable energy. In the case of wind speed fluctuation, the DC bus control strategy of the wind turbine is proposed in this paper. It can reduce the impact on the unit converter and the power load;this ensures safe and stable operation of non-grid connected wind turbines.

Extended Quality Characterization of Grid Connected PV Inverters

The overall performance of photovoltaic （PV） inverter imphes many different technical issues.One of the key criterias is based on the measurement of the conversion and the maximum power point tracking （MPPT） efficiency and its applicable evaluation in practice.Intense work has been done in the last few years to formulate applicable standards for measuring static and dynamic efficiencies worldwide.Besides that,this work is presenting on novel methods of analysis on non-trivial system characteristics impacting the final evaluation on the overall performance of the PV inverter.The elaborated testing procedures for complex system behavior under highly nonlinear conditions （unintentional partial shading, mismatching of DC strings） are explained and characterized.With the help of experimental results, the exclusive impact on the overall efficiency is illustrated and helpful statements are given on the resulting technical characteristics of MPP strategies.

Renewable Energy Based Grid Connected Battery Projects around the World—An Overview

The environmental pollution,as well as gradual depletion of mineral resources has encouraged the world to move into renewable energy sources for generation of electricity.At present,the cost of using renewable energy sources,such as sunshine and wind in electricity generation has significantly reduced.This has led to higher penetration of renewable energy into the grid.However,both wind and solar energy photovoltaics are unpredictable energies which reduce the reliability and resiliency of the grid.The integration of battery energy storage system in the grid is one of the proficient solutions to the problem.There are numerous grid connected renewable energy based battery projects that have been deployed in different countries around the world for research,development and commercial application.This review paper will discuss some of the projects based on the battery connected wind and solar energy power generation systems that can operate both in grid connected and grid independent modes.The projects discussed in this paper are selected based on the availability of information.The battery energy storage system(BESS)incorporated in each of the project is found to increase the stability and performance of the grid by addressing the mismatch between power generation and the load of the grid created due to intermittent nature of renewable energy sources.

Research and Design of Inverter Applied in Solar PV Systems Connected to Distribution Grid

This paper presents the results of research on the application of inverter in the grid connected solar photovoltaics (PV) system. The main content of the article is to control the three-phase grid connected inverter to meet the requirement of controlling the reactive power to zero at a node of the distribution network while maximizing the active power transmitted to the grid. The control circuits are synthesized on the dq coordinate system and verified on the simulation model by Matlab/Simulink. Both simulation and experimental prototype on 5 kW inverter, being connected to low voltage grid, have been built to show the good results and the practical readiness for implementation.

Simulation of grid tracking control of power system connection and maximum power brushless doubly-fed generator in point wind

In this paper, based on the analysis of the mathematical model in a common synchronous reference frame of the brushless doubly-fed generator （BDFG）, the grid connection strategy and maximum energy extraction control were both analyzed. Besides, the transient simula- tion of no-load model and generation model of the BDFG have been developed on the MATLAB/Simulink platform. The test results during cutting-in grid confirmed the good dynamic performance of grid synchronization and effective power control approach for the BDFG-based variable speed wind turbines.

PSS/E与PowerWorld风电机组模型对比

单一的电力系统仿真软件无法满足含大规模风电并网系统的所有仿真需求,需根据需求选择恰当的仿真工具,因此对常用的PSS/E和PowerWorld软件的风电机组模型进行对比。首先介绍了当前主流软件PSS/E、PSLF、BPA程序、PowerWorld中风电机组模型的结构和功能,并针对PSS/E和PowerWorld,比较了发电机-换流器模块、有功功率控制模块、机械-调速模块的工作机理。然后以国际大电网会议推荐的标准风电并网系统CIGRE B4-39网络为例,进行了基于PSS/E与PowerWorld的风电并网仿真分析。仿真结果表明:PSS/E风电机组模型的锁相环在电压畸变的情况下能够快速锁定相位,抑制高次谐波;PowerWorld的风电机组模型在控制有功功率的过程中,能有效抑制风电场无功功率波动对有功出力的影响。最后,指出PowerWorld、PSS/E和BPA程序的适用场合。

Large-Scale Distributed Photovoltaic Power Dispatching and Operation Management Review

Distributed photovoltaic power (PV) is the main development model of distributed generation. It is necessary to research on dispatching and operation management with large-scale distributed PV connected. This paper analyzes development status, technical requirement and dispatching and operation management situation of distributed PV in Germany and China. Then introduce the preparation of distributed PV dispatching and operation management criterion. Through summarizing the experiences and lessons of large-scale distributed PV development in Germany, it gives advice to the development of distributed PV dispatching and operation management in China.

Analysis of the Performance Indicators of the PV Power System

The energy assessment of the PV power systems is carried out by using different types of performance indicators that benchmark the output of these systems against the PV panel maximum output at hypothetical operation conditions. In this paper, a comparative analysis of six types of performance indicators is conducted and a new performance indicator which considers PV panel slope and orientation is proposed. The proposed indicator is benchmarking the PV system actual output against the maximum output of the same system if it would operate in two axis tracking mode. The proposed performance indicator is used to develop a friendly user calculator of PV system output that can be used by, energy providers and PV system installers to evaluate the output of the PV grid connect network. The advantage of the developed calculator is high-lighted by a case study that estimates energy capacity of different residential rooftop PV systems installed in a residential suburb in Sydney.

Impact of Reactive Power in Power Evacuation from Wind Turbines

Application of Distributed Generation (DG) to supply the demands of a diverse customer base plays a vital role in the renewable energy environment. Various DG technologies are being integrated into power systems to provide alterna-tives to energy sources and to improve reliability of the system. Power Evacuation from these remotely located DG’s remains a major concern for the power utilities these days. The main cause of concern regarding evacuation is con-sumption of reactive power for excitation by Induction Generators (IG) used in wind power production which affects the power system in variety of ways. This paper deals with the issues related to reactive power consumption by Induc-tion generators during power evacuation. Induction generator based wind turbine model using MATLAB/SIMULINK is simulated and its impact on the grid is observed. The simulated results are analyzed and validated with the real time results for the system considered. A wind farm is also modeled and simulations are carried out to study the various im-pacts it has on the grid &nearby wind turbines during Islanding and system event especially on 3-Phase to ground fault.