Connected Power Plant Research Articles

Early degradation factors of solar 33 kV grid connected power plant, a comparative study

This paper identifies and analyses early degradation mechanisms observed in photovoltaic (PV) modules of power plants over 7 years of operation on the coast power grid in Mauritania. Performance degradation takes place due to several reasons such as material degradation following dust accumulation, high temperature, and humidity. Also, mismatch of electric power parameters such as increasing loads above projected values of the plant. Therefore, this paper analyses and studies the degradation in four phases. First, the visual inspection detects the degradation of materials and defects such as the presence of dust, cracks, browning (discoloration), and connection corrosion. The second phase proposes a mathematical model to calculate the early degradation rate (DR) of different components, such as short circuit current (Isc), open circuit voltage (VOC), the maximum yield power (Pmax), and the fill factor (FF) of the PV module. The third phase is a MATLAB modeling of the measured real-time data of the operating PV system to test Power versus voltage curves (with and without degradation) to examine the presence of failure of PV modules. Finally, compare the evolution of real-time production data for three measured years (2015, 2016, and 2017) with the simulation curves of this study.

Using a flywheel associated to PV power plant in order to increase the integration of PV into island electrical grid

In a context where renewable energies from both wind and solar energy have low predictability, low controllability and strong variability, their massive integration into power systems may cause instabilities for these grids. The use of storage energy system is a promising solution. In the present article, we propose to focus on a detailed photovoltaic model in order to test flywheel energy storage system (FESS) models. FESS is used to smooth photovoltaic energy for power quality. A 17-kW photovoltaic grid connected power plant is modelled with Matlab/Simulink/SimPowerSystems.

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.

Analiza kvaliteta električne energije na satnom nivou kod priključenja elektrana na obnovljive izvore energije

Analyses necessary for the new power plant connection contain the following power quality analyses carriedout using the simulation model: Estimation of the emission level of the voltage waveform asymmetry at the point of connection, estimation of the high harmonic components at the connection point and estimation of the emission level of long-term and shortterm flicker. Limits for the previously mentioned parameters have been defined in the National Grid Code (at the national level) or in the international standards. According to the international standards, the limit is considered violated if the duration of the parameter value violation exceeds 5% of the monitored period. Conventional approach of power quality analysis through software tool assumes only analysis for the most critical regime: when the short-circuit power at the point of connection is the lowest and the new power plant produces maximum active power. Based on this approach mitigation measures for improving power quality supply are sometimes suggested to the plant investor. In should be noted that Renewable Energy Sources (RES) do not have maximum output power during the whole year, and consequently, power quality deterioration is much less than in the critical regime observed in the simulations. For power quality simulation purposes, technical sheets of the equipment contain high harmonic levels for the full operation range are used from which usually the worst (highest) harmonic injections are considered for modelling RES as a harmonic source. In this paper, the results of power quality analyses for the RES connection using hourly resolution data for the one-year period based on DPL (DIgSILENT Programming Language) in DIgSILENT PowerFactory software package will be presented. This approach gives the duration of the limit violation, and consequently, more reliable results in comparison with the results of the conventional approach.

Photovoltaic power prediction based on multi-layer fusion model

Accurate forecasting of photovoltaic power output can provide technical guidance for smooth grid connection of photovoltaic power plants and avoid grid energy quality problems caused by large fluctuations in photovoltaic power. Therefore, it is very important to obtain more accurate photovoltaic energy forecast data. The traditional photovoltaic power forecasting model has the problems of low forecast accuracy and hysteresis.to further improve the prediction accuracy of pv power, this paper proposes a multi-layer fusion PV power prediction model based on dynamic modification of the weight parameters of each model. The model's benchmark algorithms include XGBoost, LigthGBM and ConvLSTM. In the case study, real photovoltaic station data were used to verify the simulation,The forecast results show that the model proposed in this paper has a better effect than any single model and has strong practicability.

DEVELOPMENT OF PRİORİTİES AND PROSPECTS OF RENEWABLE ENERGY SOURCES IN AZERBAIJAN

DEVELOPMENT OF PRİORİTİES AND PROSPECTS OF RENEWABLE ENERGY SOURCES IN AZERBAIJAN

Impact of the Wind Power Plant Connection to the Kosovo Power System

The integration of renewable energy sources into power system is not straightforward, but very challenging bearing in mind the impact they have on voltages, short circuit currents, power losses, etc. This paper addresses all potential issues caused by connection of wind power plant with installed capacity of 45.6 MW to the Kosova Transmission System. The analysis is performed by using of both on-site measurement results and simulations conducted in ETAP software. Some of the conclusions point to improving of voltage profiles, reduction of active and reactive power losses, as well as short circuit current after wind plant integration.

Application of hybrid model based on CEEMDAN, SVD, PSO to wind energy prediction.

In recent years, a series of environmental problems have come one after another under the use of traditional fossil energy, such as greenhouse effect, acid rain, haze and so on. In order to solve the environmental problems and achieve sustainable development, seeking alternative resources has become the direction of joint efforts of China and the world. As an important part of new energy, wind energy needs strong wind speed prediction support in terms of providing stable electric power. As a result, it is very important to improve the accuracy of wind speed prediction. In view of this, this paper proposes a signal processing method based on complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) combined with singular value decomposition (SVD), and uses Elman neural network optimized by particle swarm optimization algorithm (PSO) and autoregressive integrated moving average model (ARIMA) to predict the intrinsic mode functions (IMFs). Firstly, CEEMDAN combined with SVD is used to decompose and denoise the data, and the weights and thresholds of Elman are optimized by PSO. Finally, the optimized Elman and ARIMA are used to respectively predict the processed wind speed data components, and then the final prediction results are obtained. The final prediction results show that the proposed model can improve the effect of wind speed prediction, reduce the prediction error, and provide strong support for the stable operation of wind farms and the grid connection of power plants.

GRID INTEGRATION OF RENEWABLE ENERGY POWER PLANTS ACCORDING TO THE PORTUGUESE REGULATION

The increasing growth of renewable energies in the power system brings new challenges for both the transmission and distribution system operators regarding planning and operation. In 2016 the European Commission issued a network code aiming to establish new network requirements for grid connection of generators, which is being followed by the European countries in adapting their national regulations accordingly. In Portugal, the performance of wind and solar Power Plants is evaluated according to the European Network Code requirements. Simulation studies are conducted to pre-evaluate the Power Plant's performance. EDP Labelec is responsible for the Performance validation of several Renewable Energy – solar and wind – Power Plants before its integration on the Portuguese network, and has developed and perfected the corresponding methodologies. This paper presents the developed methodology, based on dynamic digital simulation, for assessing the fulfilment of the requirements for grid connection of new Renewable Energy Power Plants. A case study with the application of the methodology is presented.

ENSURING PERMISSIBLE VOLTAGE LEVELS IN LOW-VOLTAGE NETWORKS IN THE DESIGN OF SOLAR POWER PLANTS FOR PRIVATE HOUSEHOLDS

One way to stimulate the development of renewable energy is preferential electricity tariffs for businesses, electricity consumers, including energy cooperatives and private households, whose generators produce electricity from alternative energy sources. Such a state policy exists both in Ukraine (the "green tariff") and in other countries (Feed-in tariffs). The simplified connection mechanism of generating power of private households and the fast payback period of solar power plants have led to a rapid increase in the number of such facilities. The peculiarity of network photovoltaic installations of private households is that the investment is proportional, and sometimes even less than the cost of additional reconstruction, for example, to increase the capacity of the electrical network, so, as a rule, their connection to low voltage networks is carried out without any additional changes of intersections of power lines. At the same time, according to the Law of Ukraine on the Electricity Market, the connection of generating installations to consumers, including private households, should not lead to deterioration of regulatory parameters of electricity quality. Another feature of these objects is the almost complete lack of information about the parameters of the electrical network. In the absence of reliable information, it becomes necessary to develop approximate methods for estimating the allowable capacity of solar power plants of private households depending on the place of connection, the parameters of the modern low-quality distribution network and modes of its operation. The article proposes the use of the distribution network model in the form of a line with evenly distributed load from the solar power plants in the form of a concentrated load at the corresponding point of the line. The voltage distribution along the line is simulated when the power of the solar power plant and the place of its connection change. Analytical relations are obtained for the calculation of the solar power plants power limit values to ensure the admissibility of the mode parameters according to the voltage level when varying the solar power plant connection point. A method is proposed to maintain the allowable minimum voltage levels at the terminals of consumers in short-term congested sections of the network.

Uncertainty Modeling of Fatigue Crack Growth and Probabilistic Life Prediction for Welded Joints of Nuclear Stainless Steel.

Welded joints are widely used in the pipeline connection of nuclear power plants. Defects in these joints are an important factor leading to the failure of welded joints. It is critical to study the fatigue crack growth and life prediction methods for the welded joints with defects, to reduce their likelihood. In this paper, we present our study of the uncertainty of fatigue crack propagation and probabilistic life prediction for welded joints of nuclear stainless steel. The standard compact tension (CT) specimens were fabricated according to the American Society for Testing and Materials (ASTM) standard. Fatigue crack propagation tests with different stress ratios were performed on CT specimens, using the Mei Te Si (MTS) fatigue test system. A fatigue crack propagation rate model considering the uncertainty of material parameters, and based on the Paris formula and crack propagation experimental data, was established. A probabilistic life prediction method based on Monte Carlo simulation was developed. The fatigue crack propagation prediction result of a CT specimen was compared with the actual tested result, to verify the effectiveness of the proposed method. Finally, the method was applied to an embedded elliptical crack in welded joints of nuclear stainless steel, to predict the fatigue crack growth life and evaluate the reliability.

MMC as nonlinear vector current source for grid connection of wave energy generation

Modular multilevel converter (MMC) is a type of electronic converter currently used as voltage source in real HVDC transmission systems. This paper presents, as an alternative, a control system designed to operate an MMC as a nonlinear vector current source (NLVCS). From the design point of view, it features advantages such as constant switching frequency, robustness against grid parameters changes and that the algorithm is entirely designed from space vectors. From the application point of view, the main advantages are its fast dynamic response combined with its capability to handle large amounts of electric power. Together, these two features allow the MMC to deal with highly variable renewable energies.To show the advantages of the proposed control system, it has been chosen a very demanding application: wave energy. In this type of applications, the random nature of the sea produces large and fast variations of the generated power, that enters the DC link and that the grid side converter has to handle very fast, injecting it into the grid in order to maintain the DC voltage constant.The capability of the NLVCS for MMC to handle the energy generated has been tested in two different wave energy applications. Firstly, on a single wave energy converter (WEC), a point absorber. This case is characterized by smaller and faster power changes. Secondly, on a wave farm made up of 200 WECs connected to the grid through an MMC. This case is characterized by much larger but smoother power changes.Wave farms, WECs and MMC are large and sophisticated facilities or devices that are almost impossible to gather in the same laboratory. Consequently, the features of the new control system for MMC and the advantages that provide in the connection of wave energy power plants and point absorbers to the grid has been simulated using detailed models.The results demonstrated the capability of the MMC operating as NLVCS to deal with the fast and random power changes present in renewable energy sources.

Low-voltage ride-through for a three-phase four-leg photovoltaic system using SRFPI control strategy

With the innovative progresses in power electronics in recent years, photovoltaic (PV) systems emerged as one of the promising sources for electricity generation at the distribution network. Nonetheless, connection of PV power plants to the utility grid under abnormal conditions has become a significant issue and novel grid codes should be recommend. The low-voltage ride-through (LVRT) capability is one of the challenges faced by the integration of PV power stations into electrical grid under abnormal conditions. This work firstly provides a discussion on recent control schemes for PV power plants to enhance the LVRT capabilities. Next, a control scheme for a three-phase four-leg grid-connected PV inverter under unbalanced grid fault conditions using synchronous reference frame proportional integral (SRFPI) controller is proposed. Simulation studies are performed to investigate the influence of the control strategy on the PV inverter.

Influence of Cables on Power Transmission Network Frequency Response

Harmonic resonance is an important factor to be considered in a power transmission networks during connection of remote generation units with high-voltage cables (e.g. wind or solar power plants etc.). It is known that cable characteristics differs from characteristics of conventional overhead lines. Cable capacitance is far higher than capacitance of an equivalent overhead line, what can potentially lead to the low resonant frequencies which may be triggered by various switching events, such as transformer or shunt reactor energization etc. In this paper, possible consequences of power plant connection to transmission network with long HVAC cable are analyzed, with regard to harmonic resonance and frequency response of the network. The research has been conducted on developed model of the power transmission network in the software for calculation of electromagnetic transients EMTP-RV.

Wind Speed Prediction Research Considering Wind Speed Ramp and Residual Distribution

The random fluctuation of wind leads to the instability of wind power, particularly wind power intermittency is a critical event in case of grid connected power plants, leading to severe consequences like low system reliability, high reserve capacity and high operational costs. This paper proposes a novel wind speed prediction model based on wind speed ramp (WSR) and residual distribution. Firstly, the variational mode decomposition (VMD) is used to decompose original wind speed series to extract different fluctuation characteristics, and several sub-sequences are obtained. Then, we use 3 different neural networks to predict the main part of decomposition result and use auto-regressive moving average (ARMA) model to predict the rest fluctuation part of decomposition results. Next, WSR optimized by particle swarm optimization (PSO) is used to modify the prediction results of LSTM neural network to decrease the prediction errors caused by one-step lag, the kernel density estimation (KDE) is used to fit the distribution of VMD residuals and sample randomly from the distribution to get residual series. Finally, the final prediction results of V-PSOR-LSTM-KDE are obtained by adding prediction results of WSR modified LSTM, ARMA and random sampling based on KDE. This study decomposes wind speed into the main trend part, fluctuation part and residual part, analyzing each part and makes predictions with different models according to their characteristics, which provides a new thought for wind speed prediction and contributes to the construction of smart grid.

Impact of large scale power plant connection on congestion in the algerian electricity transmission system

In the context of the electrical system, the implementation of a new power plant must be submitted for review so that the economical and technical aspects of the electrical system would not be altered, so far as possible, by this implementation. The conditions set by Directives relating to the electricity company for connecting to the power grid, should also be considered. In addition, the results of the study, made by the network manager, must include feasible solutions for integrating the new generation. This paper gets in sight of the constraints that may occur on the power system after integrating new installation. For this purpose, the Algerian power system was chosen as example to examin the impact of large scale power plant connection on network congestion. The congestion costs associated with this connection are assessed using buy back model. Tow scenarios are considered in order to assess the impact of such power plant on network congestion. These scenarios correspond to the maximum and the minimum of a typical daily demand. The results show that this connection highlights a transmission congestion at the maximum demand level. In order to relieve this congestion, it is recommended to reinforce the concerned transmission line.

Evaluation of Protective Relaying Reliability in Renewable Energy Environment

<p>The decrement in supply of fossil fuel led to the exploration of new energy sources, which varies from wind energy to solar energy, which are known as Renewable Energy. The main problem with these power sources are the inconsistency of their energy that depends very much on the environmental factors. The embedment of these power sources onto conventional power transmission network would affect the sensitivity and reliability of protective relaying. Two different types of solar power plant connection to power system network are presented in this paper, namely Bus Connection and T-Off Connection. Computer Aided Protection Engineering (CAPE) software is used to model the networks being protected by distance protection, and simulate short circuit scenario. This paper specifically focuses on evaluating the impact of the in-feed current being contributed by both network configurations to the reliability of distance protection.</p>

Risks of determining the optimal technical solution of power plant connection to distribution network

Risks of determining the optimal technical solution of power plant connection to distribution network

Design and tuning of wind power plant voltage controller with embedded application of wind turbines and STATCOMs

This study addresses a detailed design and tuning of a wind power plant voltage control with reactive power contribution of wind turbines and static synchronous compensators (STATCOMs). First, small-signal models of a single wind turbine and STATCOM are derived by using the state-space approach. A complete phasor model of the entire wind power plant is constructed, being appropriate for voltage control assessment. An exemplary wind power plant located in the United Kingdom and the corresponding grid code requirements are used as a base case. The final design and tuning process of the voltage controller results in a guidance, proposed for this particular control architecture. It provides qualitative outcomes regarding the parametrisation of each individual control loop and how to adjust the voltage controller depending on different grid stiffnesses of the wind power plant connection. The performance of the voltage controller is analysed by means of a real-time digital simulation system. The impact of discretising the controller being initially developed in continuous-time domain is shown by various study cases.

Logging the Internet of Things - Connected power plants demand a new paradigm

Logging the Internet of Things - Connected power plants demand a new paradigm