Grid-connected Capacity Research Articles

Two-layer operation optimization of concentrated solar power with thermal energy storage system and soft open point

In order to improve the dispatching and grid-connected capacity of new energy, enhance the comprehensive economic benefits, and reduce the voltage offset and fluctuation of the distribution network, this paper proposes a two-layer operational optimization model of concentrated solar power (CSP) with thermal energy storage system (TESS) and soft open point (SOP). Firstly, according to the demand of load, the upper-layer distribution network formulates the optimal scheduling strategy of photovoltaic (PV), wind power (WP), CSP, energy storage system (ESS) and power purchase through the schedulability of CSP with TESS. Secondly, the upper-layer scheduling results are connected to the lower-layer distribution network, and coordinated control is carried out through SOP, on-load tap changer (OLTC) and capacitor bank (CB). Then, the lower model is converted into a linear model, a quadratic cone model and a rotated quadratic cone model, followed by absolute value removal, so as to rapidly and accurately produce the solution of the model. Finally, the model is analyzed on the improved IEEE33 node system. The results show that the proposed model in this paper not only ensures the economy of the power grid but also improves the stability of the voltage.

Hydroelectric operation for hybridization with a floating photovoltaic plant: A case of study

Hybrid renewable systems increase electricity production by reducing the randomness of sources without greenhouse gas emissions. Literature indicates that further research is still required for large systems connected to the grid. The energy storage capability of hydroelectric plants provides an opportunity to develop new renewable energy generation.This work presents the results of a hybrid preliminary design between an existing hydropower plant (HPP) in Brazil, Santa Branca, and a simulated floating photovoltaic plant (FPV), occupying only 2.8% of reservoir's surface. The study analyzed 20 years of HPP historical data, the methodology proposed the injection of the FPV full power into the system during daytime and the HPP adjusting the production. As this process changed the HPP generation profile, operational limits such as reservoir level needed to be verified.In the period, while HPP generated about 4 TWh, the FPV could add 2 TWh without significantly changing the daily generation of HPP. This increase of 50% in production was possible since there was space available in the reservoir to store water during the day and use it during the night, working as a free virtual battery for the FPV. A 50% increase of the grid connection capacity factor was also observed.

“We could have been leaders”: The rise and fall of offshore wind energy on the political agenda in Ireland

Many countries have ambitious plans for increasing the generation of electricity from offshore wind energy in the coming decades. Realising these ambitions requires concerted, often innovative, political action across several policy domains. To understand the unique political challenges facing offshore wind deployment, this article presents a case study of the Republic of Ireland, where decades of sporadic political ambition to support offshore wind energy has not yet translated into commercial deployment. We use the Multiple Streams Framework to guide data collection, 29 elite interviews and extensive documentary analysis, and offer an historical explanation for why political actors did not meet long-standing market ambition. We analyse the battle of ideas between alternative policy approaches that emerge through distinct policy networks and institutions spanning marine planning, grid development, and energy price support. In Ireland, two key drivers restrained political support for offshore wind for over a decade: competition with onshore wind for limited grid connection capacity and resilience, and calibration of policy instruments to attain decadal renewable energy target at least cost. The study shows the value of a deviant case to demonstrate the political complexities of developing and adopting technology-specific policy instruments to support offshore wind energy in the context of long-term climate change targets, grid development, and grid system services plans.

Research on Combined Frequency Regulation Control Method of Wind Storage with Storage System Optimized Intervals Considered

To solve the insufficient frequency regulation capacity and inertia of the power system caused by the increase of grid-connected wind capacity, a combined wind-storage frequency regulation control strategy considering the optimized intervals of the energy storage system is proposed. This article selects the joint frequency regulation of wind turbine overspeed control and energy storage virtual synchronous control, and virtual synchronous control is used as the upper-level control of the entire wind-storage system. In the process of frequency modulation, the output power of wind turbine and energy storage is reasonably distributed through the upper control. On this basis, to ensure the long-term and stable operation of energy storage, the state of charge (SOC) partition principle of energy storage is set up, which is divided into different areas according to the size of the SOC, and the output of the energy storage device is adjusted according to the divided regions. The results of simulation analysis and verification show that the proposed strategy provides additional frequency regulation capacity and inertia during the frequency variation and greatly improves the frequency stability. Besides, the SOC zoning principle ensures the stable operation of the energy storage.

Improving the Grid-Connected Capacity of Offshore Wind Farms: A Case Study of the Taiwan Power System

Improving the Grid-Connected Capacity of Offshore Wind Farms: A Case Study of the Taiwan Power System

Application of the Supercapacitor for Energy Storage in China: Role and Strategy

Supercapacitors are widely used in China due to their high energy storage efficiency, long cycle life, high power density and low maintenance cost. This review compares the differences of different types of supercapacitors and the developing trend of electrochemical hybrid energy storage technology. It gives an overview of the application status of supercapacitors in China’s smart grid and Energy Internet in detail. Some strategies and constructive suggestions are put forward to solve the existing problems. With the improvement of the grid-connected capacity of new energy power generation during the 14th Five-year Period of China, the supercapacitor market in China will usher in a good development opportunity. The role of the supercapacitor in achieving carbon peak carbon neutralization is prospected.

Research on Optimization of Power System Regulation Capacity Based on New Energy Installed Capacity

As the proportion of new energy continues to increase, the safty and stability of the power system faces severe challenges. Many a flexible resource should be established to ensure that the regulating ability of the power system is enough, so as to cope with the load fluctuations caused by the gird-connected new energy. This article analyses the technical characteristics of various flexible resources, and which aspect that each flexible resource can contribute to the regulating ability of the power system. On this basis, this paper proposes a quantitative analysis method of the improvement of power system regulating ability based on the consumption model of new energy, using the addition of new energy grid-connected capacity as a quantitative indicator to evaluate the improvement of system regulating ability contributed by each type of flexible resource. Combined with calculation examples, a quantitative analysis of usual flexibility resources is carried out.

Impedance-Based Stability Analysis of Grid-Tied Photovoltaic System With Superconducting Magnetic Energy Storage System

As the deployment of superconducting magnetic energy storage (SMES), the characteristic of grid-tied photovoltaic system becomes more complicated. However, existing research of the grid-tied photovoltaic system takes no account of the effects of SMES system. Hence, an investigation is made on the effects of digital control delay of SMES converter on the stability of system in this paper. The modelling of grid-tied photovoltaic system is proposed based on impedance modelling method, where the digital control delay of SMES converter system is considered. It is shown that the digital control delay of SMES converter deteriorates system stability and even leads to instability. Meanwhile, the stable grid-connected capacity of photovoltaic system is also reduced due to the weaken of system stability. The simulations are performed to validate that SMES's digital control delay has a significant impact on system.

Assessing electricity generation potential and identifying possible locations for siting hybrid concentrated solar biomass (HCSB) plants in New South Wales (NSW), Australia

This study aims to assess the deployment potential of hybrid concentrated solar biomass (HCSB) plants for dispatchable renewable electricity generation in New South Wales (NSW), Australia. We present an approach for identifying the most suitable locations for siting new plants. HCSB plants generate steam using a biomass boiler and a concentrated solar power (CSP) system and utilise a shared steam turbine for power generation. The total power generation opportunity was estimated based on available resources. This was achieved by mapping solid biomass (bagasse, stubble and forestry residues) and solar resources (direct normal irradiation) in proximity to zone substations with new grid connection capacity. The total installed capacity of HCSB plants at suitable grid connection locations was calculated to be 874 MWe at a cost of about AU$ 6.3 billion. We also estimated the CO2-e emission abatement potential to be about 6 billion kg of CO2-e per year. The Riverina region was identified to be the most prospective region for HCSB plants in NSW owing to excellent biomass and solar resources and 25 suitable grid connection points. These findings underline NSW’s excellent deployment potential for HCSB plants, a technology that can utilize the vast and currently under-exploited biomass residues and solar resources for dispatchable renewable electricity generation.

An integrated flexibility optimizer for economic gains of local energy communities — A case study for a University campus

With a capacity-based network tariff structure, consumers are encouraged to reduce their connection capacity to avoid higher costs. However, overloading beyond the administrative grid connection capacity limit would result in an increased connection capacity, thus prosumers have to pay the increased electricity bill for the rest of the year. Therefore, it is important to optimize the energy generation and consumption profiles of local energy communities (LECs) considering the comfort level of occupants. This work aims to reduce the overloading of the grid connection and increase the utilization of local renewable energy resources (RES) thus avoids being penalized throughout the year due to casual intermittent overloading in peak hours, even once in a year. The present work proposes a novel data-driven flexibility optimizer model for day-ahead scheduling of energy profiles for LECs, considering photovoltaic (PV) generation, heat pump (HPs), and cooling loads. The proposed methodology has been developed to explore the flexibility potentials from a university campus network which includes both electrical and heating/cooling systems in an integrated way. A two-layer optimization strategy is developed, to guard the occupant’s comfort level. Simulation has been performed for complete two months, considering winter and summer scenarios. A peak demand reduction of 16% has been observed with negligible energy usage differences between the proposed and the baseline case. Two types of flexibility indicators are estimated to give a deeper insight into the performance. Economical gains of 9 % and 16 % are estimated depending on the type and voltage level of the connection.

Research on optimal allocation of pumped storage and wind and photovoltaic hybrid power system

In recent years, Zhejiang Province has a great development of wind farm and photovoltaic station, and which has gradually embossed the safety operation margin of the grid. This paper builds a evaluation model of pumped storage and wind and photovoltaic hybrid power system, and optimize configuration research process simulation of pumped storage and wind and photovoltaic hybrid power system. Two methods with increment model and pure model of pumped storage and wind and photovoltaic hybrid power system are adopted to propose a reasonable grid-connected capacity rate and the reasonable proportion and coordinated optimized configuration ratio of pumped storage and wind and photovoltaic hybrid power system. The results show that the method effectively evaluate the influence and benefit of optimal allocation of pumped storage and wind and photovoltaic hybrid power system to Zhejiang power grid.

Grid and user-optimized planning of charging processes of an electric vehicle fleet using a quantitative optimization model

The promotion of electric mobility is considered a counterreaction to climate change and is therefore subsidized by various countries. The possibility of charging individual electric vehicles at employer’s premises enables the use of an electric vehicle for a large part of the population. In addition, solar radiation peaks during common working hours, resulting in economic and ecological advantages of locally installed photovoltaic systems at the workplace. As business-as-usual charging management is based on rudimentary rules, this power is not optimally used. Furthermore, high charging utilization may lead to high loads and thereby exceed the limitations of the respective building’s grid connection capacity. Hence, an optimization approach for improved charging management is required. A non-linear optimization model for coordinated charging of electric vehicles within a local energy system, which consists of a building, a photovoltaic system and a variety of different electric vehicles, is developed in this work. Respective charging profiles take the maximum charging power as a function of the state of charge into account. The objective is to minimize the costs of the charging station operator, incorporating customer satisfaction via penalty costs. The optimization model results in increased consumption of locally provided photovoltaic power and lower electricity costs in most cases. For companies with limited grid connection, the implementation also allows for more vehicles to be charged simultaneously without extending the grid connection capacity. The developed charging management is therefore suitable for real-time charging scheduling.

Generalized Additive Modeling of Building Inertia Thermal Energy Storage for Integration Into Smart Grid Control

The structural mass of a building provides inherent thermal storage capability. Through sector coupling, the building mass can provide additional flexibility to the electric power system, using, for instance, combined heat and power plants or power-to-heat. In this work, a mathematical model of building inertia thermal energy storage (BITES) for integration into optimized smart grid control is introduced. It is shown how necessary model parameters can be obtained using generalized additive modeling (GAM) based on measurable building data. For this purpose, it is demonstrated that the ceiling surface temperature can serve as a proxy for the current state of energy. This allows for real-world implementation using only temperature sensors as additionally required hardware. Compared with linear modeling, GAM enable improved modeling of the nonlinear characteristics and interactions of external factors influencing the storage operation. Two case studies demonstrate the potential of using building storage as part of a virtual power plant (VPP) for optimized smart grid control. In the first case study, BITES is compared with conventionally used hot water tanks, revealing economic benefits for both the VPP and building operator. The second case study investigates the potential for savings in CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> emission and grid connection capacity. It shows similar benefits when using BITES compared to using battery storage, without the need for hardware investment. Given the ubiquity of buildings and the recent advances in building control systems, BITES offers great potential as an additional source of flexibility to the low-carbon energy systems of the future.

Adaptive Voltage Control of Distribution Network with High Proportion PV

With the increase of grid-connected PV capacity, voltage regulation at point of common coupling by controlling the reactive power injected into the grid is available. This paper presents an adaptive voltage control strategy for distribution network with high proportion PV system. The PI gain of the voltage controller is automatically adjusted by the extremum seeking algorithm to dynamically respond to the changes of the network. The PI gains are updated online through the minimization of a cost function, which represents the voltage controller performance. Finally, a distribution network model of 5 MW photovoltaic power generation system is built in MATLAB / Simulink to verify the effectiveness of the proposed control strategy.

Research on frequency Control Strategy of micro grid including wind power and hybrid energy storage system

In view of the frequency fluctuation of the micro-grid system containing wind power, hybrid energy storage system composed of batteries and supercapacitors is adopted to coordinate the output, so as to maintain the frequency stability of the micro-grid and provide the possibility for the micro-grid to further absorb wind power and other clean energy. Firstly, by analyzing the characteristics of wind power output, the power deviation signal of the system is decomposed into low-frequency and high-frequency parts through wavelet packet decomposition, so as to maximize the consumption of wind power output power on the premise of meeting the stability of the system. Then, the high frequency part of the power gap is further divided to determine the initial FM power distribution scheme of the energy storage system. Finally, the energy storage output is modified by the Logistic regression function to take into account both the energy storage adaptive frequency modulation and the energy storage charged state self-recovery. Example analysis shows that the proposed control strategy can realize the optimal distribution of wind power, ensure the full utilization of wind farm output, improve wind power grid connection capacity, and increase efficiency and economy.

New energy grid-connected power quality management system based on internet of things

As a clean and renewable energy source, solar energy has the advantages of inexhaustible, pure and pollution-free. Photovoltaic power generation is different from traditional thermal power generation in that it is more susceptible to external environmental factors. In addition, there are a large number of power electronic devices in the entire system. These various factors will bring a significant shock to the grid power quality after grid connection. The research of grid-connected power quality system is becoming more and more important. A series of researches are carried out around a complete three-phase photovoltaic grid-connected system, which are modeled separately, connected to the distribution network for simulation analysis, and analyzed the power quality impact on the distribution network. Based on the traditional disturbance observation method, this paper proposes a new MPPT algorithm that combines the constant-voltage tracking method with the three-point comparison method (an algorithm derived from the traditional disturbance observation method). This complete three-phase photovoltaic grid-connected system was connected to an IEEE 14-node distribution network, and the impact of grid-connected capacity and grid location on the power quality of different nodes in the distribution network was analyzed. An improved power management scheme is proposed. Finally, the paper analyzes the improvement of power quality by connecting a group of hybrid reactive power compensation device which is composed of static reactive power compensator and shunt capacitor. The results show that the voltage deviation is reduced and the harmonic content is reduced. It can be considered that this measure has achieved the purpose of power quality control to a certain extent.

Correlation analysis between forced oscillation modes caused by wind power

With the increase of the grid-connected capacity of wind power, the influence of power system forced oscillation caused by wind power is becoming bigger and bigger, so it is necessary to understand its production mechanism and general characteristics. In this paper, the nonlinear and non-stationary signal generated by the unstable wind speed is analyzed to speculate the characteristics of wind-induced oscillation. Secondly, the bispectrum analysis and the bicoherence analysis are introduced. The obtained bispectrum and bicoherence coefficients are used to analyze the oscillation caused by wind power and the quadratic phase coupling relationship between oscillation modes. Finally, the simulation is operated considering small wind farm connected to a 4-generator-2-area (4G2A) system. The simulation results verify the correctness of the proposed speculation and the effectiveness of the proposed method.

Short-term wind power prediction based on EMD-LSTM combined model

In recent years, China is actively developing wind power generation. Wind energy is a natural factor with volatility, variability and uncontrollability, which will cause fluctuations in wind farm output. The accurate prediction of wind power is conducive to grid dispatchers deploying scheduling plans or doing ahead of schedule Adjustments to reduce losses to a certain extent are also conducive to improving wind power grid-connected capacity. In this paper, using the advantages of empirical mode decomposition EMD algorithm in nonlinear and non-stationary data processing, a wind farm power prediction model based on EMD-LSTM is established. First, the relevant data is preprocessed to obtain the ideal input sequence, and the LSTM network model is used. The NWP wind speed is corrected first, and the revised forecasted NWP wind speed sequence is closer to the actual wind speed. Then use EMD to decompose the wind power data sequence into data components of different scales, and then use the LSTM long and short-term memory network to model the decomposed IMF components and residual RES respectively, and sum the prediction results of each component and residual As the final prediction result. The research results show that the method described in this paper effectively improves the prediction.

Impact of Wind Power and Photovoltaic Grid Connection on Subsynchronous Oscillation of Thermal Power

Wind power, photovoltaic and thermal power bundling are the main forms of large-scale new energy grid connection and power transmission. Based on the IEEE’s first standard model, this paper incorporates direct-drive fans and photovoltaic systems. The transform method analyzes the effect of direct-drive wind turbines and photovoltaic grid-connected power on sub-synchronous oscillation of thermal power. Simulation results show that appropriately increasing the photovoltaic grid-connected capacity can increase the electrical damping of thermal power in the wind, solar and fire delivery system.

Research on Coordinated Control Technology Among Inverters in Distributed Voltage Regulation Control Mode of Photovoltaic Power Station

Photovoltaic and other renewable energy power generation systems are connected to the grid through power electronic converters. Normally, they do not participate in grid voltage regulation when they are running in the mode of tracking the maximum power point. However, when their grid-connected capacity exceeds a certain scale, photovoltaic needs to participate in grid voltage regulation.