High Penetration Of Wind Generation Research Articles

Frequency Dynamics of Power Systems with Inertial Response Support from Wind Generation

Inertial response support from wind turbine generators has become a priority requirement in most grid codes to improve the frequency response and frequency stability margins of power systems. However, the interaction between MPPT and inertial controllers may significantly degrade the power system dynamics. Therefore, there is a need to comprehensively understand the electromechanical dynamics of power systems with high penetration of wind generation. In this context, this work proposes a simplified dynamic model to assess the electromechanical dynamics of modern power systems with inertial response support from wind generation. The proposed simplified model allows simple analyses of the intrinsic and extrinsic aspects of wind generation that directly affect the system frequency dynamics and the dynamics of wind turbine generators. As a secondary contribution, this work also provides a comprehensive assessment of intrinsic and extrinsic aspects of wind generation that significantly affect the electromechanical dynamics of power systems with inertial response support from wind generation.

Dynamical Model for Power Grid Frequency Fluctuations: Application to Islands With High Penetration of Wind Generation

We study the effects of a high share of wind generation on the frequency fluctuations of power grids on islands. We propose a dynamical model that includes conventional and variable renewable generation, as well as demand variations. Our model can assimilate load and generation data and reproduce frequency fluctuations with the current power mix with a high degree of accuracy, and it allows to simulate the frequency dynamics for different scenarios with a very high penetration of renewable energy. As a case study, we analyze the power grid of Gran Canaria island. We characterize the frequency fluctuations and propose a method to estimate the control needed to keep frequency deviations within reasonable limits.

Low-carbon economic planning of integrated electricity-gas energy systems

The energy system carbon reduction is an inevitable trend to deal with the global warming problem. The power industry, being a vital part of energy system, faces severe challenges. To decarbonize the power sectors, the implementation of low-carbon technologies and integration of high penetrated renewable power generation would be an effective solution. Therefore, given the existence of multi-type low-carbon technologies including the flexibility reformation of coal-fired units, construction of gas-fired units and installation of energy storage systems, a low-carbon economic planning model of integrated electricity-gas systems with high penetration of wind generation is proposed. The carbon tax and carbon capture technology are integrated to accelerate carbon reductions. In particular, the strategic planning cases contributed by different scenarios are formulated. The simulation results on an electricity-gas test system demonstrate the feasibility and effectiveness of the proposed model in carbon reduction as well as wind curtailment decrease. Compared with the initial state, the implementations of the proposed three planning strategies can reduce carbon emissions by 9.8%, 32.5% and 9.3%, respectively. Meanwhile, the wind power curtailment ratio is decreased by 63.2%, 38.9%, and 63.7%, respectively. Moreover, a sensitivity analysis of carbon tax price and wind power penetration level are performed to investigate the low-carbon transition of the integrated electricity-gas systems.

Security-Constrained Unit Commitment for Hybrid VSC-MTDC/AC Power Systems With High Penetration of Wind Generation

This paper presents the solution to the security-constrained unit commitment (SCUC) problem for hybrid voltage source converter (VSC) based multi-terminal DC/AC (VSC-MTDC/AC) power systems with high penetration of wind generation. The formulated SCUC model presents a detailed representation of the VSCs with two different VSC control strategies considered, constant DC voltage control (master-slave control) and DC voltage droop control. In addition, Grid Code for wind farm connection is considered. Benders decomposition is used to solve the formulated SCUC problem by decomposing it into a master problem for solving unit commitment (UC) and hourly transmission security check subproblems. The final SCUC solution provides an economic and secure operation and control strategy for the meshed MTDC/AC system. Numerical tests illustrated the efficiency of the proposed SCUC model.

Wind Power Prediction Based on Multi-class Autoregressive Moving Average Model with Logistic Function

The seasonality and randomness of wind present a significant challenge to the operation of modern power systems with high penetration of wind generation. An effective short-term wind power prediction model is indispensable to address this challenge. In this paper, we propose a combined model, i.e., a wind power prediction model based on multi-class autoregressive moving average (ARMA). It has a two-layer structure: the first layer classifies the wind power data into multiple classes with the logistic function based classification method; the second layer trains the prediction algorithm in each class. This two-layer structure helps effectively tackle the seasonality and randomness of wind power while at the same time maintaining high training efficiency with moderate model parameters. We interpret the training of the proposed model as a solvable optimization problem. We then adopt an iterative algorithm with a semi-closed-form solution to efficiently solve it. Data samples from open-source projects demonstrate the effectiveness of the proposed model. Through a series of comparisons with other state-of-the-art models, the experimental results confirm that the proposed model improves not only the prediction accuracy, but also the parameter estimation efficiency.

Negative Sequence Current and Reactive Power Comprehensive Compensation for Freight Railway Considering the Impact of DFIGs

To solve the power quality problems caused by freight railways in weak grids with high penetration of wind generation, this paper proposes a comprehensive control method for negative sequence current (NSC) suppression and reactive power compensation. Firstly, a co-phase traction power supply system (CTPSS) is introduced, and its compensation principle is analyzed. Secondly, to bring a doubly fed induction generator (DFIG) into full play in suppressing voltage unbalance (VU) in the grid, a VU compensation model of stator is developed. Moreover, a comprehensive compensation method is presented to achieve the dynamic compensation of VU and reactive power. Finally, the effectiveness of the proposed approach is demonstrated using a simulation, which can fully solve the power quality issues and effectively reduce the capacity of the CTPSS.

Stochastic hydrothermal unit commitment models via stabilized benders decomposition

The high penetration of wind generation has prompted the development of stochastic hydrothermal unit commitment (SHTUC) models, which are more difficult to be solved than their thermal-based counterparts due to hydro generation constraints and inflow uncertainties. For handling the uncertainty, the problem is usually formulated as a two-stage stochastic model (2S-SHTUC), although multistage (MS-SHTUC) formulations have gained increasing attention due to their more realistic assumptions about on–off decisions over the planning horizon. Benders decomposition (BD) is one of the most common methodologies used for solving 2S-SHTUC and MS-SHTUC problems. To overcome the well-known slow convergence of the classical BD when applied to large problems, most authors use accelerating techniques. In this paper, we implement state-of-the-art stabilization methods tailored for speeding up the convergence of the classical BD: local branching and the level regularization. Our experiments are conducted in a real-life SHTUC problem with 11 thermal units, 16 hydro plants, 46 buses and 95 lines. The results show that 2S and MS-SHTUC can benefit from stabilization. The savings in computing times range from 69 to 95% for the 2S-SHTUC model and from 77 to 89% for the MS-SHTUC.

WPP Model in Power System Security Assessment

The integration of wind power plants at large scale has an impact on the reliability, the stability and the security of power systems. Recent events such as the blackout of Australia in 2016, a power system with large participation of wind generation, have demonstrated the need for appropriate tools to simulate and assess the impacts of wind energy on the security of power systems. Therefore, this paper proposes the inclusion of wind power plants in the simulation and the analysis of cascading phenomena in the power system, to assess the impact of the high penetration of wind generation in the security assessment of the power system based on the well-known Manchester model. This paper proposes a model of wind power plants based on the scheme of connection to the transmission system in order to determine the response of a wind farm when a disturbance occurs in the power system and to obtain a behavior that resembles a situation real. The proposed methodology is tested in the IEEE RTS-system of 24 nodes, in which the impact on security is evaluated by increasing the participation of wind generation, and it is demonstrated that the security of the energy system is reduced by increasing the participation of this type of technology in the generation dispatch.

Variable Speed Pump Storage for the Mitigation of SSR in Power System with Wind Generation

Subsynchronous resonance (SSR) can bring significant negative effects on the grid system like stability, security, and even generator shaft damage. This work presents a new method of using a doubly-fed induction machine (DFIM) based system of variable speed pumped storage plant (VSPS) to mitigate SSR in the power system with high penetration of wind generation. The mitigation is reached based on the principle of balanced shaft mechanical input power and electromagnetic power. The fundamental concepts and phenomena of SSR with wind farm are discussed in brief in this work. For the sake of analysis and verification of performance of the proposed system, the network model including wind farm, VSPS, HVDC, and synchronous machine is built based on Ningxia grid for the SSR study using PSCAD platform. The result shows that VSPS brings significant effect to dampen the SSR in the power system with high penetration of wind generation.

Compressed Air Energy Storage System Modeling for Power System Studies

In this paper, a detailed mathematical model of the diabatic compressed air energy storage (CAES) system and a simplified version are proposed, considering independent generators/motors as interfaces with the grid. The models can be used for power system steady-state and dynamic analyses. The models include those of the compressor, synchronous motor, cavern, turbine, synchronous generator, and associated controls. The configuration and parameters of the proposed models are based on the existing bulk CAES facilities of Huntorf, Germany. The models and performance of the CAES system are first evaluated with step responses, and then examined when providing frequency regulation in a test power system with high penetration of wind generation, comparing them with existing models of CAES systems. The simulation results confirm that the dynamic responses of the detailed and simplified CAES models are similar, and demonstrate that the simultaneous charging and discharging can significantly contribute to reduce the frequency deviation of the system from the variability of the wind farm power.

Stochastic scheduling of battery energy storage system for large‐scale wind power penetration

High penetrations of wind generation have intermittency and volatility issues in deregulated power system. With increasing penetration of wind power, independent system operator (ISO) faces an enormous challenge in secure operation with intermittency and uncertainty of renewable energy resources. To handle these issues, battery energy storage system (BESS) is a probable solution for enhancing the wind penetration in the electric grid. In this regard, this article proposes a stochastic security constrained unit commitment (SCUC) with BESS considering wind uncertainty. The proposed approach is formulated and solved by Benders decomposition (BD) method which reduces computational time. The goal is to detect the optimal amount of SCUC, locational marginal price (LMP), wind curtailment, and line contingency by performing DC optimal power flow (DCOPF). Numerical case studies are investigated in detail using IEEE Reliability test system (RTS) 24-bus network and simulation results are found to be inspiring.

Understanding the Benefits of Dynamic Line Rating Under Multiple Sources of Uncertainty

This paper analyzes the benefits of dynamic line rating (DLR) in the system with high penetration of wind generation. A probabilistic forecasting model for the line ratings is incorporated into a two-stage stochastic optimization model. The scheduling model, for the first time, considers the uncertainty associated with wind generation, line ratings, and line outages to co-optimize the energy production and reserve holding levels in the scheduling stage as well as the redispatch actions in the real-time operation stage. Therefore, the benefits of higher utilization of line capacity can be explicitly balanced against the costs of increased holding and utilization of reserve services due to the forecasting error. The computational burden driven by the modeling of multiple sources of uncertainty is tackled by applying an efficient filtering approach. The case studies demonstrate the benefits of the DLR in supporting cost-effective integration of high penetration of wind generation into the existing network. We also highlight the importance of simultaneously considering the multiple sources of uncertainty in understanding the benefits of DLR. Furthermore, this paper analyzes the impact of different operational strategies, the coordination among multiple flexible technologies, and the installed capacity of wind generation on the benefits of DLR.

Reliability of Power System with High Wind Penetration Under Frequency Stability Constraint

This paper presents a new method to evaluate the reliability of a power system with high penetration of wind generation, considering the impact of not only the intermittence but also the low inertia characteristic of wind power. As wind generation gradually replaces conventional generation, the system stability and the reliability are negatively affected. Some of the measures employed to deal with the challenges resulting from increasing wind penetration include operating wind generators at lower levels than their available output and providing inertia so that wind generation is able to contribute to system frequency regulation. Apart from these measures, another factor that limits the amount of wind power that can be absorbed into the grid is the imposition of the frequency standard and this also affects the reliability of the system in the presence of wind penetration. The reliability evaluation approach proposed in this paper is developed using discrete convolution and implemented on an IEEE RTS-79 system with a suitable modification. Power system reliability with and without considering the impacts of wind intermittence and low inertia are compared to show the effectiveness of the proposed method.

Controlling active power of wind farms to participate in load frequency control of power systems

The high penetration of wind generation into power system may jeopardise the operation of the power system without proper frequency control methodologies. This study proposed a coordinated control strategy to control active power of wind farms to participate in the load frequency control of power systems. In the system level, a coordinated control system is designed to enable the wind farm to participate in the load frequency control of the multi-area interconnected power systems. The designed control system is proved to be asymptotically stable under parameter uncertainties and load changes. In the component level, the coordinated deloading strategy is applied for each wind generator to track the active power command that is distributed by the system level control. The proposed coordination control strategy can achieve fast response under operating changes while avoiding frequent regulation of pitch angles of wind generators and simulation studies verify its effectiveness.

On the Road to Wind Power: China's Experience at Managing Disturbances with High Penetrations of Wind Generation

Today, electric power generated from renewable energy sources accounts for a large share of the Chinese power system. By the end of 2015, the total wind power installed capacity had reached 129 GW , ranking wind as the second largest power source following thermal power in some regions of China.

Short-run impact of electricity storage on CO2 emissions in power systems with high penetrations of wind power: A case-study of Ireland

This article studies the impact on CO2 emissions of electrical storage systems in power systems with high penetrations of wind generation. Using the Irish All-Island power system as a case-study, data on the observed dispatch of each large generator for the years 2008 to 2012 was used to estimate a marginal emissions factor of 0.547 kgCO2/kWh. Selected storage operation scenarios were used to estimate storage emissions factors – the carbon emissions impact associated with each unit of storage energy used. The results show that carbon emissions increase in the short-run for all storage technologies when consistently operated in ‘peak shaving and trough filling’ modes, and indicate that this should also be true for the GB and US power systems. Carbon emissions increase when storage is operated in ‘wind balancing’ mode, but reduce when storage is operated to reduce wind power curtailment, as in this case wind power operates on the margin. For power systems where wind is curtailed to maintain system stability, the results show that energy storage technologies that provide synthetic inertia achieve considerably greater carbon reductions. The results highlight a tension for policy makers and investors in storage, as scenarios based on the operation of storage for economic gains increase emissions, while those that decrease emissions are unlikely to be economically favourable. While some scenarios indicate storage increases emissions in the short-run, these should be considered alongside long-run assessments, which indicate that energy storage is essential to the secure operation of a fossil fuel-free grid.

Sizing a Hybrid Energy Storage System for Maintaining Power Balance of an Isolated System With High Penetration of Wind Generation

A frequency-based approach is proposed in this paper to size a battery-supercapacitor energy storage system for maintaining power balance of an isolated system with high penetration of wind generation, thus to maintain the grid frequency stability with the stochastic wind power fluctuations being considered. The sizing method proposed makes full use of the combined technical merits of two types of energy storage systems, battery and supercapacitor, as their specific power/energy densities and the corresponding expected life cycle cost/year are different. The power imbalance between hourly dispatched wind power and the corresponding actual real-time wind power output is decomposed into different time-varying periodic components by use of the Fourier transformation. Then two different types of energy storage systems are applied to balance the low-frequency and intermediate-frequency component respectively. A computational procedure is developed in the paper for choosing the optimal cut-off frequencies in determining the range of low and intermediate frequency for sizing the hybrid energy storage system. Comparative studies of a real isolated system in China are presented in the paper to demonstrate the effectiveness of the proposed method.

Probabilistic Analysis of Small Signal Stability for Power Systems With High Penetration of Wind Generation

Wind generation is growing fast worldwide. The stochastic variation of large-scale wind generation may impact the power systems in almost every aspect. Probabilistic analysis method is an effective tool to study power systems with random factors. In this paper, a systematic nonlinear analytical probabilistic method is proposed to evaluate the possible effect of random wind power generation on power system small signal stability. A second-order polynomial is proposed to approximate the nonlinear relationship between the wind generation and the damping of a particular dynamic mode, such as the dominant mode. Gaussian mixture model formulates wind uncertainty in a uniform way. Spectral theorem is adopted to reshape the second-order polynomial into a form without cross-product terms. Cholesky decomposition is used to eliminate correlations among outputs of different wind farms. Thereafter the cumulative distribution function (CDF) of the damping ratio with respect to random wind power is consequently constructed. Numerical simulations are carried out in the IEEE standard test system. The proposed method is verified with higher accuracy than the traditional linearized method. Meanwhile, it is much more time-saving in calculation than Monte Carlo simulation.

Assessment of the Role and Value of Frequency Response Support From Wind Plants

High penetration of wind generation causes concerns over frequency stability, as currently wind plants do not provide frequency response support. Extensive research has been conducted to investigate alternative designs of controllers to facilitate the provision of synthetic inertia and primary frequency response from wind plants. However, frequency response support from wind plants differs from that provided by conventional plants and its impact on the system's economic performance is not yet fully understood. In this context, this paper develops a novel methodology to incorporate the frequency response support from wind plants into generation scheduling, thus enabling the benefits of alternative control strategies to be quantified. Studies are carried out on the future Great Britain power system with different wind energy penetration levels and frequency response requirements. The impact of the uncertainty associated with the quantity of wind plants being online and the energy recovery effect are also analyzed. The results demonstrate that the benefits of frequency response support from wind plants may be significant, although these are system specific. The proposed model could also inform the development of grid codes, market mechanisms, and business cases associated with the frequency response support from wind plants.

Stochastic Scheduling With Inertia-Dependent Fast Frequency Response Requirements

High penetration of wind generation will increase the requirement for fast frequency response services as currently wind plants do not provide inertial response. Although the importance of inertia reduction has been widely recognized, its impact on the system scheduling has not been fully investigated. In this context, this paper proposes a novel mixed integer linear programming (MILP) formulation for stochastic unit commitment that optimizes system operation by simultaneously scheduling energy production, standing/spinning reserves and inertia-dependent fast frequency response in light of uncertainties associated with wind production and generation outages. Post-fault dynamic frequency requirements, 1) rate of change of frequency, 2) frequency nadir and 3) quasi-steady-state frequency are formulated as MILP constraints by using the simplified model of system dynamics. Moreover the proposed methodology enables the impact of wind uncertainty on system inertia to be considered. Case studies are carried out on the 2030 Great Britain system to demonstrate the importance of incorporating inertia-dependent fast frequency response in the stochastic scheduling and to indicate the potential for the proposed model to inform reviews of grid codes associated with fast frequency response and future development of inertia-related market.