Large Wind Power Research Articles

A new design methodology to predict wind farm energy production by means of a spiking neural network–based system

AbstractIn this paper, a spiking neural network–based architecture for the prediction of wind farm energy production is proposed. The model is also able to evaluate the wake effects due to interactions between the elements of a wind farm on the energy production of the whole farm. This method has been applied to a large wind power plant, composed of 28 turbines and 3 anemometric towers, located in the rural area of Vizzini's municipality in province of Catania, Italy, that is characterised by a complex orography and an extension of 30 km2. For the implementation of this architecture it was used the “NeuCube” simulator. The results show that the presented method can be successfully applied for predictions of wind energy generation in real wind farm also in presence of faults.

Identification of vulnerable lines in power grids with wind power integration based on a weighted entropy analysis method

Vulnerable overhead electricity lines are a cause of serious risk to power distribution grids as damage can be the cause of large scale blackouts and cascading failures. With the integration of large scale wind power into generating capacity, both the topology structure and the distribution characteristics of power flow in distribution grid have undergone various changes that have increased line vulnerability. A novel approach to identify vulnerable lines based on the weighted entropy analysis method is proposed in this paper. In this approach, an assessment index, named the incremental power flow entropy, is first developed, which is used to describe influences caused by variation of the lines' capability of carrying power flow transfers on the vulnerability of the lines themselves at the same aggregation level. A second assessment index, named structural importance, describes the structural changes of a power grid that are caused by the integration of wind-generated electric power. The two assessment indices then are merged into one index by using the entropy weight analysis method, which can assess the vulnerability of the lines from the two aspects of power flow transmission and structural links. Vulnerability analysis under different situations, such as with and without the integration of the wind farm, and sharp fluctuations in wind speed at the wind farm, were carried out on an IEEE 39-bus system integrated with a 75 MW wind farm. Simulation results verified that the proposed assessment index not only can identify the vulnerable lines in a power grid with wind farm integration but also accurately reflected the vulnerability of the internal lines of the wind farm itself.

Resonance damping in array cable systems by wind turbine active filtering in large offshore wind power plants

The application of active filtering in large offshore wind power plants (WPPs) is presented in this study. The harmonic challenges such as sources of harmonic emission and resonances are identified and briefly explained. Also modern remedial harmonic mitigation methods as of active filtering are described and their application in real-life WPP systems demonstrated. It is underlined that WPP components such as widespread medium-voltage cable system and offshore grid transformers can introduce significant low-frequency parallel resonances which can cause a significant harmonic voltage distortion at the point of common coupling. Active filtering in modern grid-side converters used in wind turbines is applied simultaneously keeping sufficient harmonic/noise rejection. Extensive harmonic stability studies are also shown to prove the overall system robustness.

English

English

The Problems and Key Technologies of Large Scale Wind Power Into the Power Grid

This paper summarizes a series of problems brought by the large-scale wind power connecting to the grid: effects on power quality, off-grid accidents, bring great difficulties to the power dispatching and the huge increase to the cost. Based on the problems above and the latest researches, this paper enumerates some key technologies of large-scale wind power into the grid, including the LVRT technology, on-line monitoring, evaluation of operation state, climbing control ability and energy storage technology etc.

Power system stability analysis under increasing penetration of photovoltaic power plants with synchronous power controllers

The utilisation of renewable sources brings many benefits to electric power systems, but also some challenges such as the impact that renewable power plants employing power electronics have on the grid, which is gaining importance as the penetration of this type of generating stations increases, driven by the construction of large wind or solar photovoltaic (PV) power plants. This study analyses the impact of large-scale PV power plants on a transmission grid for different penetration levels. The analysis considers power plants formed by a number of power converters employing synchronous power controllers (SPCs), that allow them to have a harmonious interaction with the grid, and compares their performance with that of conventional power converter controllers, assuming in both cases that the power plants participate in frequency and voltage regulation. The study addresses both the small-signal stability of the system and its response to large disturbances that alter the active power balance and frequency stability. The results of the analysis show that PV power plants using SPCs are able to limit frequency deviations, improve the oscillation damping, and reduce the stress of other generating units, thus having a beneficial impact on the power system.

Two-stage voltage control of subtransmission networks with high penetration of wind power

Voltage issues are the main factors that limit the penetration level of wind power in subtransmission systems. In this paper, based on different control characteristics, we propose a two-stage coordinated control framework to deal with the negative voltage impacts caused by wind power fluctuations. In the first control stage, on-load tap changers (OLTCs) are used to deal with the voltage variations caused by large wind power fluctuations. In the second control stage, virtual power plants (VPPs) in the subtransmission network are used to handle the remaining slight voltage variations by controlling their reactive power. The second control stage only takes actions to support voltage regulations when control actions of the first control stage cannot meet the control requirements. Control actions of OLTCs and VPPs are obtained through multi-objective optimization based model predictive control and a fully distributed optimal dispatch scheme, respectively. The effectiveness of the proposed control method is tested through case studies based on the IEEE 14-bus test system and IEEE 30-bus test system with wind farms. In addition, through comparison with the traditional control method, our control scheme can reduce the control costs significantly and achieve the control targets at the same time.

Novel Cost Model for Balancing Wind Power Forecasting Uncertainty

The intermittency of wind generation creates nonlinear uncertainties in wind power forecasting (WPF). Thus, additional operating costs can be incurred for balancing these forecasting deviations. Normally, large wind power penetration requires accurate quantification of the uncertainty-induced costs. This paper defines this type of costs as wind power uncertainty incremental cost (WPUIC) and wind power uncertainty dispatch cost (WPUDC), and it then formulates a general methodology for deriving them based on probabilistic forecasting of wind power. WPUIC quantifies the incremental cost induced from balancing the uncertainties of wind power generation. WPUDC is a balancing cost function with a quadratic form considering diverse external conditions. Besides, the risk probability (RP) of not meeting the scheduled obligation is also modelled. Above models are established based on a newly developed probabilistic forecasting model, varying variance relevance vector machine (VVRVM). Demonstration results show that the VVRVM and RP provide accurate representation of WPF uncertainties and corresponding risk, and thus they can better support and validate the modelling of WPUDC and WPUIC. The proposed cost models have the potential to easily extend traditional dispatches to a new low-carbon system with a high penetration of renewables.

Characterisation of interaction in an offshore AC grid with large WPPs and VSC‐HVDCs

To exploit the full and flexible capability of offshore voltage-sourced converter high-voltage DC (VSC-HVDC) lines, interaction studies in the offshore AC grid are required but are not well understood or reported. This study examines the interaction dynamics of an offshore AC grid for interconnecting large wind power plants (WPPs). The conventional eigenvalue analysis method has limitations which make the interaction analysis of such systems difficult. Hence, in this study, an impedance-based analytical approach is employed to investigate the interaction phenomena. The impedance model of a VSC-HVDC converter for both direct and vector control with outer and droop controls are derived along with the impedance model of the full-converter wind generator. The interaction dynamics of the offshore grid is predicted through the well-established Nyquist criteria and is validated using time-domain simulations. The analysis shows that the system stability is decidedly influenced by the control configurations and tuning of the VSC-HVDC lines.

Wind power plant integration in voltage source converter HVdc grids with voltage droop control

This paper introduces the use of a diode-based HVdc rectifier for the integration of a large off-shore wind power plant into an existing HVdc voltage source converter-based grid. The proposed control system allows for the wind power plant to energize the complete HVdc grid, in order to contribute to service restoration in the case of a black-out. The system exhibits good response to wind power plant black-start operation, rectifier breaker trip and reclosure, and short-circuit ride through at the on-shore ac-grid. The technical feasibility of the proposed topology has been validated by means of detailed PSCAD simulations using frequency dependent parameters for cable modeling.

大規模風力発電電力利用水電解水素とCO<sub>2</sub>のメタネーションで製造した燃料の変換・輸送モデルの概算評価

大規模風力発電電力利用水電解水素とCO<sub>2</sub>のメタネーションで製造した燃料の変換・輸送モデルの概算評価

Research on VSC–HVDC control strategy based on large offshore wind power system

Research on VSC–HVDC control strategy based on large offshore wind power system

大規模風力発電電力利用水電解水素と二酸化炭素のメタネーションで製造した燃料の変換・輸送モデルの実装可能性評価

大規模風力発電電力利用水電解水素と二酸化炭素のメタネーションで製造した燃料の変換・輸送モデルの実装可能性評価

LFC enhancement concerning large wind power integration using new optimised PID controller and RFBs

To improve the frequency stability in an interconnected power system including renewable energy sources, the control actions need to be more robust and efficient. For this reason, this study proposes a new optimised proportional–integral–derivative (PID) controller coordinated with redox flow batteries (RFBs) for the enhancement of load frequency control (LFC) of power system concerning large penetration of wind power generation. The PID controller parameters were obtained using a recently developed meta-heuristic optimisation algorithm named Grey Wolf optimiser. To show the effectiveness of the proposed control strategy, the interconnected two-area IEE Japan East 107-bus-30-machine power system was investigated for the simulation. The system dynamic responses were obtained considering load change in area-1 and large wind farm integration in area-2. A comparative study of performance of the proposed strategy with some well-known optimisation techniques was performed. Furthermore, the sensitivity analysis of the proposed controller was also examined by varying the penetration range of the integrated wind farm. Dynamic responses obtained from the simulation satisfy the LFC requirements. In addition, the results reveal that the frequency control concept-based optimised PID controller coordinated with the RFB will enhance the frequency stability in terms of settling time, peak undershoot, and peak overshoot.

Contributions to the analysis of “Integrating large scale wind power into the electricity grid in the Northeast of Brazil” [Energy 100 (2016) 401–415

This paper contributes to the analysis made by an article recently published in this journal [1]. The purpose of this manuscript is to bring new contributions to this complex subject, namely the limits to the penetration of variable renewable energy (VRE) into national grids. A detailed and advanced model has been used in this work in order to add further contributions to De Jong et al. [1] findings. For example, by applying an optimization model, we were able to show that the high wind penetration (65%) almost without curtailment found by [1] might not happen, mainly due to inflexibility constraints in Brazilian power plants and also to transmission limits.

Simulation of Operating Conditions of a Home Energy System Composed by Home Appliances and Integrated PV Powerplant with Storage

Electricity produced exploiting renewable energy sources has been continuously growing during the last years. It is mainly generated by converting solar radiation and wind, both characterised by well-known aleatory uncertainties. In Italy in 2014 (source GSE) photovoltaic (PV) installed power was 18.6 GW with an energy production of 22.3 TWh, while wind turbines installed power was 8.7 GW with an energy production of 15.2 TWh, both covering an important share of the Italian energy demand.A significant number of powerplants with aleatory uncertainty of electricity production has an important impact on the distribution grid management, where more and more resources have to be allocated to guarantee the due reserve margin to the dispatching market [1]. So, it becomes necessary to reduce the aleatory uncertainty of produced energy to mitigate the negative effects without limiting the market penetration of “zero emission” renewable sources. Large wind and PV power production plants can take advantage of forecasting models and storage systems. In the case of home integrated PV energy production plants, the impact mitigation on the grid can also be achieved through an appropriate design of the whole onsite energy system composed by both electricity using appliances, and PV powerplant (with storage). The objective of this new integrated design is the limitation of electricity exchange with the grid.That need has been partially taken into consideration by the Italian legislation on SEU (User's efficient system) introduced by the Law 115/08: SEU's self-consumption of electricity is not charged with transmission, distribution, dispatching and general costs.

A Novel Method of Equivalencing DFIG based Wind Farm for Stability Studies

Objectives: Analyzing the stability of large scale wind power plant (WPP) is very cumbersome and simulation time required performing the analysis is long-drawn-out. Thus a single equivalent model of WPP is developed. Methods/Statistical analysis: Kron’s based network reduction is proposed for the WPP. Two network reduction methodologies are adopted and wind turbine mechanical and electrical parameters are rescaled which is discussed in detail in the paper. Transient stability analysis is performed to validate the equivalence method. Study system consists of 23 buses with 20 DFIG wind turbine generating units connected to the main grid of utility system. Findings: Transient stability analysis is conducted for the study system. Dynamic response of detailed WPP and proposed equivalent system matches accurately for the three phases to ground fault disturbance at point of common coupling (PCC). At PCC the Voltage, Real power and Reactive power values are very close to proposed equivalent system when compared to detailed WPP. In addition, the percentage error computed is least for the proposed system. Time taken to simulate the equivalent system is very less compared to the detailed WPP and existing literature work. All the simulations are carried out in DIgSILENT Power Factory TM software. Application/Improvements: Remarkable simulation time reduction and accuracy is achieved for the proposed method. Thus, the equivalent method is applied for quick assessment of transient stability of large scale WPP.

Optimal generation scheduling of interconnected wind‐coal intensive power systems

Large scale wind power generation complicated with restrictions on the tie line plans may lead to significant wind power curtailment and deep cycling of coal units during the valley load periods. This study proposes a dispatch strategy for interconnected wind-coal intensive power systems (WCISs). Wind power curtailment and cycling of coal units are included in the economic dispatch analysis of regional systems. Based on the day-ahead dispatch results, a tie line power plan adjustment strategy is implemented in the event of wind power curtailment or deep cycling occurring in the economic dispatch model, with the objective of reducing such effects. The dispatch strategy is designed based on the distinctive operation characteristics of interconnected WCISs, and dispatch results for regional systems in China show that the proposed strategy is feasible and can improve the overall system operation performance.

Statistical wind direction modeling for the analysis of large scale wind power generation

AbstractUnderstanding the effects of large‐scale wind power generation on the electric power system is growing in importance as the amount of installed generation increases. In addition to wind speed, the direction of the wind is important when considering wind farms, as the aggregate generation of the farm depends on the direction of the wind. This paper introduces the wrapped Gaussian vector autoregressive process for the statistical modeling of wind directions in multiple locations. The model is estimated using measured wind direction data from Finland. The presented methodology can be used to model new locations without wind direction measurements. This capability is tested with two locations that were left out of the estimation procedure. Through long‐term Monte Carlo simulations, the methodology is used to analyze two large‐scale wind power scenarios with different geographical distributions of installed generation. Wind generation data are simulated for each wind farm using wind direction and wind speed simulations and technical wind farm information. It is shown that, compared with only using wind speed data in simulations, the inclusion of simulated wind directions enables a more detailed analysis of the aggregate wind generation probability distribution. Copyright © 2016 John Wiley & Sons, Ltd.

Stochastic analysis of wind energy uncertainty impact on ISO risk-taking in joint energy and reserve markets using conditional value at risk

Uncertainty management of the large scale wind power resources is mainly known as one of the most challenging aspects in future electricity market operations, where network operation may put at risk due to the wind power forecasting errors. Therefore, it is necessary to evaluate the impact of the wind power uncertainty on the operator risk-taking by using validated tools. This paper proposes a new mixed integer linear programming model for joint energy and reserve market clearing taking into account the co-optimization of the market clearing and operation cost of the thermal units. Also, wind power uncertainty is handled by means of two-stage stochastic programming and risk concept is introduced and formulated via a well-known measure to account for operator risk taking level. The proposed model is formulated as a two-stage stochastic programming where it clears the joint energy and reserve markets considering different penetration and forecasting accuracy levels of the wind power. Furthermore, supplementary terms are added to the objective function and constraints of the problem in order to measure the risk related to the wind power uncertainty.