High Wind Penetration Research Articles

Robust Transmission Expansion Planning Based on Adaptive Uncertainty Set Optimization Under High-Penetration Wind Power Generation

Previous robust transmission expansion planning (RTEP) studies have rarely considered the important question of how large the uncertainty set should be, and hence, how the uncertainty budget can be determined objectively. This study addresses this issue by proposing a novel adaptive optimization method that optimizes the value of the uncertainty budget to minimize the size of the uncertainty set while considering the underlying risk for wind power generation (WPG) fluctuations residing outside of the proposed uncertainty set. As such, the proposed method ensures a good tradeoff between the robustness and costs of RTEP solutions. In addition, the proposed method optimizes investment strategies under forecasted WPG scenarios, while providing a security guarantee under extreme WPG scenarios. The variable-limit integral terms introduced by the proposed method are addressed in the solution process by applying the piecewise linearization approximation method combined with the quadratic Newton-Gregory interpolating polynomial technique, which allows the solution process to be cast as a mixed integer linear programming problem. The good performance and effectiveness of the proposed adaptive uncertainty set optimization method are verified by numerical results.

Innovative system services for facilitating the integration of high levels of renewable generation in Ireland and Northern Ireland

Variable renewable generation technologies such as wind and solar photovoltaic have introduced new challenges in power system management. Grid operators have traditionally used ancillary services such as reserve and reactive power to help to maintain a secure and reliable power system. In addition, conventional synchronous generators have inherent characteristics such as inertial response, which help the power system to recover after an event. In Ireland and Northern Ireland, a weakly-interconnected island system with a high penetration of wind, new ancillary or ‘system’ services have been devised to address the technical scarcities arising from the displacement of synchronous generation. Twelve system services addressing the frequency and voltage control needs have been procured to date, allowing the power system to be operated with up to 65% instantaneous non-synchronous renewable power on the system. This study outlines the implementation of the innovative system services framework. It includes an overview of the services procured and examples of the changed behaviour of existing units in response to financial incentives. It also examines how new technologies have responded to the signals provided, questions how aspects of the arrangements may be further improved and details the challenges of integrating the use of these innovative services into operational policy.

Getting to 100% renewables: operating experiences with very high penetrations of variable energy resources

This study examines experiences of grid operators to successfully integrate very high penetrations of wind and solar photovoltaic (PV) resources. The variability of these resources creates challenges in balancing the system generation and demand, and ensuring resource adequacy and essential reliability services. The inverter-based nature of wind and solar PV leads to challenges in frequency, transient, and small-signal stability. In this study, seven system operators demonstrate the ability to manage these challenges in a variety of power systems, from stand-alone island systems to larger island systems that are interconnected to neighbours, to balancing authorities that are strongly interconnected within very large synchronous systems. They operate within a variety of market constructs, from full regional transmission operators to vertically-integrated utilities. All are experiencing increases in the penetration of inverter-based, variable energy resources and finding creative solutions to these challenges.

Optimal energy management strategy for a renewable‐based microgrid considering sizing of battery energy storage with control policies

SummaryMicrogrids (MGs) are known as suitable options to accommodatethe high penetration of renewable energies, like solar and wind. MGs have provided the requirements of controlling and adjusting these sources. In addition, batteries are becoming indispensable components of MGs because of their capabilities in addressing the renewable energies' power output intermittency. In MGs, the problem of smart energymanagement along with battery sizing has been introduced as the necessity to ensure the efficient use of renewable sources and decrease traditional fossil‐fuel‐based generation technology penetration level in power systems. Accordingly, a novel method is presented in this paper to effectively address the above‐mentioned requirements, utilizing the modified shuffled frog leaping algorithm (MSFLA), applied to different case studies. The results, obtained from the numerical simulation, are compared to several well‐established optimization approaches to verify the performance of MSFLA. In terms of computational efficiency and quality of the obtained solution, the MSFLA has demonstrated promising outcomes, together with superior performance in comparison with other algorithms. The results show that the presented framework, including the battery sizing, would be very beneficial to minimize the operating cost of MGs.

Probabilistic Approaches to the Security Analysis of Smart Grid with High Wind Penetration: The Case of Jeju Island’s Power Grids

As the importance of renewable generating resources has grown around the world, South Korea is also trying to expand the proportion of renewable generating resources in the power generation sector. Among the various renewable energy sources, wind generating resources are emerging as a key alternative to conventional power generations in the electricity sector in Korea accounted for 17.7 GW of total capacity by 2030. As wind generating resources are gradually replacing traditional generating resources, the system security and reliability are negatively affected because of the variability, due to intermittent outputs. Therefore, existing power grids will need to be correctly re-measured to cover the large scale of renewable energy, including wind generation. To expand the grid, we must understand the characteristics of renewable energy and the impact of its adoption in the grid. In this paper, we analyze various characteristics of wind power generation, and then we propose a probabilistic power output modeling method to consider the uncertainty of wind power generation. For the probabilistic approach, Monte-Carlo simulation is used in the modeling method. The modeled wind power outputs can help planning for the reinforcement and expansion of power systems to expand the capacity for large-scale renewable energy in the future. To verify the proposed method, some case studies were performed using empirical data, and probabilistic power flow calculation was performed by integrating large-scale wind power generation to the Jeju Island power system. The probabilistic method proposed in this paper can efficiently plan power system expansion and play a key strategy of evaluating the security of the power system through the results of stochastic power flow calculation.

Coordinated operation of electricity and natural gas systems from day-ahead to real-time markets

Power systems worldwide are becoming more reliant on energy from natural gas, wind, and solar, posing potential reliability and coordination challenges from the tighter coupling of these infrastructure systems. This paper proposes a framework for the market-based coordination of electricity and natural gas system operations. The proposed framework includes a power system model that accounts for flexibility in the commitment of power plants with short start-up and shut-down times, coupled with a dynamic gas model that simulates when gas cannot be delivered to generators. The capabilities of the framework are illustrated using real-world electric power and gas systems, including scenarios around wind and solar penetrations and the analysis of time-variant, “shaped flow” gas nominations. Our results indicate that coordination between power and gas systems improves total gas delivery and reduces out-of-merit order dispatch in the electricity system, and that shaped flows may reduce unserved gas in systems with high penetrations of wind and solar energy sources. Coordination can have mixed effects on carbon-dioxide emissions, with emissions increasing with coordination for current systems during high load weeks but decreasing for systems with high renewable penetrations, particularly during periods of high variability.

Voltage stability improvement with coordinated ULTC–STATCOM controller and VSC-HVDC in high wind penetration cases

In recent years, implementing renewable energy systems such as wind power systems into interconnected grids play a vital role in energy management and production. Besides the good aspects of this energy policy, there may be some undesirable cases if not controlled. Increasing penetration of wind generation into the electricity grid negatively affects the power system stability and the required reactive power that might cause serious voltage stability problems. In order to overcome this problem, especially in the weakest areas of the system with respect to voltage stability, it is necessary to support the reactive power reserve. In this study, a coordinated ULTC–STATCOM controller has been designed to improve the reactive power reserve and enhance voltage stability by the penetration of wind power through the VSC-HVDC wind farm system into weak area of the AC system. The novelty of the proposed coordination control than the classical coordination approaches is changing the tap position of the ULTC especially at high penetration levels and thus to maintain the reactive power reserve of STATCOM. The proposed approach is tested in a two-bus sample system and adapted to the weakest area of the IEEE 10-machine 39-bus test system that simulations are conducted in DIgSILENT PowerFactory 15.0 software. Comparative simulation results show that the proposed approach has enhanced both reactive power reserve and voltage stability margin of the test systems.

Mitigation of Over-Frequency through Optimal Allocation of BESS in a Low-Inertia Power System

The primary objective of this paper is to alleviate the over-frequency problem in low-inertia power systems through optimal allocation of a Battery Energy Storage System (BESS). With prolific integration of wind power, conventional fossil-fuel driven synchronous generators are being replaced in the generation fleet. Variable speed wind machines are connected to the grid via power electronics converters. As such, these machines usually do not participate in frequency regulation. During high wind penetration, a generation-rich zone of an interconnected power system may face significant over-frequency following the loss of interconnection. If the frequency goes above a certain threshold, an Over-Frequency Generator Shedding (OFGS) scheme is activated. This may cause considerable amount of generation cut in a low-inertia power system. To address this challenge, this paper develops a siting and sizing methodology of frequency-responsive BESS to simultaneously maintain frequency and voltage stabilities. As such, BESS is placed at the most voltage-sensitive bus, determined by an index called reactive power margin. Furthermore, an optimization model is formulated to determine the BESS size to avoid generation shedding. The proposed technique is applied to a low-inertia power system, which resembles the equivalent high-voltage transmission network of South Australia. The simulation results reveal that the developed methodology successfully mitigates the over-frequency phenomenon. In addition, the proposed technique is found to be more effective than its counterpart (i.e., without BESS) to enhance the frequency resilience of a low-inertia grid.

Scenario-based probabilistic multi-stage optimization for transmission expansion planning incorporating wind generation integration

Integrated transmission expansion planning (TEP) and generation expansion planning (GEP) with Wind Farms (WFs) is addressed in this paper. The optimal number of expanded lines, the optimal capacity of WFs installed capacity, and the optimal capacity of wind farms lines (WFLs) are determined through a new TEP optimization model. Furthermore, the optimum capacity additions including conventional generating units is obtained in the proposed model. The Benders decomposition approach is used for solving the optimization problem, including a master problem and two sub-problems with internal scenario analysis. In order to reduce the computational burden of the multi-year and multi-objective expansion planning problem, a multi-stage framework is presented in this paper. The uncertainties of wind speed and system demand along with contingency scenarios lead to a probabilistic optimization problem. Moreover, in the proposed model, the planning time horizon is divided into three predefined stages. This multi-stage approach is used to increase the proposed model accuracy in a power system with a high level of wind power penetration. Hence, in this paper a scenario-based probabilistic multi-stage model for transmission expansion planning is proposed, incorporating optimal WFs integration. It is recognized that high wind penetration increases the transmission expansion investment cost, but based on the reduction of the investment cost of conventional units, the total system cost will be smaller. This result emphasizes the main advantage of wind generating system over the conventional generating system. This planning methodology is applied to the modified IEEE 24-bus test system and simplified Iran 400-kV real system to show the feasibility of the proposed algorithm.

Wind can reduce storage-induced emissions at grid scales

Energy storage provides many benefits that can improve electric grid performance but has been shown to increase overall system emissions. Yet, how energy storage might interreact with renewables in existing grids and how these interactions affect overall emissions remain unclear. Here, we estimate emissions induced by battery energy storage in two regions of the United States with very different levels of wind penetration using high-resolution, both spatially and temporally, locational marginal prices and hourly marginal emission factors. We find that the emission intensity of carbon dioxide, sulfur dioxide, nitrogen oxides, and mercury is 4264% lower in the high wind penetration grid (28%) than in the low wind penetration grid (<5%). This is due in part to a significant share of wind dispatched as marginal fuel in baseload hours when battery storage charges from the grid, reducing storage-induced emissions. Our study suggests that more wind generation can favorably pair with storage and reduce the air pollution burdens otherwise caused by storage.

Pumped-storage units to address spinning reserve concerns in the grids with high wind penetration

Abstract The low predictability of hourly available power of wind turbines and their volatile output, cause multiple hardships in the power system which are supposed to be handled by means of keeping a higher amount of contingency and regulation reserve. The intensified reserve requirement along with operational constraints may enforce wind-farms to operate below their maximum available power. It's shown that Pumped-Storage systems, not merely as storage capacity, but also as a high-quality reserve providers make the power system capable to lessen wind power curtailment. It is investigated how increasing the reserve requirement may restrict the overall renewable production and how Pumped-Storage can relieve this restriction. The Pumped-Storage system is precisely modeled based on Siahbisheh, a 1000 MW Pumped-Storage system in northern part of Iran. The soundness of the obtained results is fortified by using actual technical data based on Manjil wind-farm, and other active generating units in Iranian power system, as well as actual prices from the historical records of Iran Wholesale Electricity Market. As well as IEEE 24-Bus test system, the performance of Pumped-Storage system is analyzed on the actual network of Gilan Province in Iran.

Procurement of electrical energy and operating reserve ancillary services in wind incorporated deregulated system considering demand response

This study presents the procurement of electrical energy and operating reserve ancillary services (ORASs) by the simultaneous clearing of the wind integrated power market under the pool-based deregulated environment. This investigation is important due to the intermittent output of wind generators, which is a serious concern for medium and high wind penetration and requirement of high operating reserves for maintaining the security of such systems. The market model is presented for the clearing of energy and ORAS market, where both thermal generators and demand response offers supply the reserves. This model is analysed for energy and spinning reserve (ESR) cost minimisation, emission minimisation, and co-optimisation of ESR cost and emission. The non-dominated sorting multi-objective gravitational search algorithm is employed to obtain Pareto optimal solutions. The efficacy of the presented method is investigated on IEEE 30-bus, IEEE 118-bus, and IEEE 300-bus test systems for different levels of wind uncertainty. The results are compared with multi-objective particle swarm optimisation.

Security constrained optimal power flow in a power system based on energy storage system with high wind penetration

This study is focused on assessing the effect of energy storage system (ESS) presence on security improvement of power systems hosting remarkable renewable energy resources. To this end, ESS presence is suitably included in security-constrained optimal power flow (SCOPF) model; the required technical amendments are hence considered. To launch a realistic model, ramping constraints of thermal units are also taken into account which limit the generators from completely responding to power shortfalls. Considering a high penetration level of renewable generations, different scenarios of outages in transmission lines and generators are simulated to measure the line outage distribution factor (LODF) and power transfer distribution factor (PTDF). also, in order to illustrate the economic impact of wind power generation curtailment and load shedding, two penalty parameters VWC and VOLL are considered in the model. Two test systems, including a PJM 5-bus system and an IEEE 24-bus RTS, are put under numerical studies to assess the possible impact of ESS on security improvement of the investigated systems. The obtained results are discussed in depth.

Performance of wholesale electricity markets with high wind penetration

Abstract This paper examines the impact of progressively deeper levels of wind generation and/or abatement on the performance of a wholesale market and its incumbent thermal generators with non-convex unit commitment constraints. Comparison is made to the result that marginal cost pricing should induce investors to build the least-cost capacity mix, since it is not clear that this will hold in renewable-rich systems. It is first found that unit commitment and forecast uncertainty do not cause significant departure from this result when the generator fleet is optimal. ‘Optimality' in this sense is determined in a capacity expansion problem that does not feature unit commitment, and which allows thermal generators to be built or retired as greater renewable generation or abatement is mandated. In contrast, the wholesale market with no retirement of thermal generation experiences progressively greater disparity between total system prices and costs, and lower returns to generators, simply due to over-capacity rather than any form of variability-related market failure. A carbon price is observed to be far superior to a renewable portfolio standard when the existing set of thermal generators do not retire, but this difference is less stark when the generation mix is optimal. The implications of these results for market design and system planning are then discussed.

High-Resolution Electricity Spot Price Forecast for the Danish Power Market

Energy markets with a high penetration of renewables are more likely to be challenged by price variations or volatility, which is partly due to the stochastic nature of renewable energy. The Danish electricity market (DK1) is a great example of such a market, as 49% of the power production in DK1 is based on wind power, conclusively challenging the electricity spot price forecast for the Danish power market. The energy industry and academia have tried to find the best practices for spot price forecasting in Denmark, by introducing everything from linear models to sophisticated machine-learning approaches. This paper presents a linear model for price forecasting—based on electricity consumption, thermal power production, wind production and previous electricity prices—to estimate long-term electricity prices in electricity markets with a high wind penetration levels, to help utilities and asset owners to develop risk management strategies and for asset valuation.

Genetic Algorithm-Based Analysis of the Effects of an Additional Damping Controller for a Doubly Fed Induction Generator

In view of the problem that large-scale and high-penetration wind power access may weaken the stability of small interference in the power grid, this study proposes a novel additional damping controllers for the doubly-fed induction generator (DFIG) based on the genetic algorithm. A DFIG model and its control system is built, and the parameters of the controller are tuned using the genetic algorithm to optimize the control effect. Based on Western System Coordinating Council (WSCC) 3-machine 9-node system, multi-scenario simulation results verifies that the additional damping controller proposed in this study performs better to suppress the low-frequency oscillation than the power system stabilizer (PSS) installed on the synchronous generators which are farther to the disturbance point. Meanwhile, the proposed strategy is compared with the reactive power modulation control, which can provide a reference for engineering applications of an added DFIG damping controller.

A clustering-based scenario generation framework for power market simulation with wind integration

A critical step in stochastic optimization models of power system analysis is to select a set of appropriate scenarios and significant numbers of scenario generation methods exist in the literature. This paper develops a clustering based scenario generation method, which aims to improve the performance of existing scenario generation techniques by grouping a set of correlated wind sites into clusters according to their cross-correlations. Copula based models are utilized to model spatiotemporal correlations and the Gibbs sampling is then used to generate scenarios for day-ahead markets. Our results show that the generated scenarios based on clustered wind sites outperform existing approaches in terms of reliability and sharpness and can reduce the total computational time for scenario generation and reduction significantly. The clustering-based framework can therefore provide a better support for real-world market simulations with high wind penetration.

Load-Frequency Control Strategy of Power Grid with High Penetration Wind Power Based on Active Disturbance Rejection Control

After large-scale wind power is integrated to the grid, the randomness and uncertainty of wind power will cause problems of active power imbalance and frequency fluctuations, which puts forward higher requirements for load-frequency control of power grids with wind power integrated. Based on the analysis of the load-frequency control system of power grids with wind power integrated, a novel load-frequency control model based on active disturbance rejection control considering random fluctuating wind energy is proposed. The simulation results show that not only the proposed model can effectively maintain the system frequency, but also the control effect is significantly better than the conventional PI load-frequency controller.

Efficient uncertainty quantification in economic re-dispatch under high wind penetration considering interruptible load

Due to the high variability and intermittency of wind power generation, operators tend to have a corrective stage to adjust their predictive dispatch schedules for re-balancing the system following a contingency in the real-time market. This paper presents a new probabilistic real-time re-dispatch model integrating interruptible load (IL) programs with the aim to minimize the total operational cost. The problem is formulated in a probabilistic optimal power flow (P-OPF) framework, accounting for uncertainties on both IL response and wind power forecasts. To address this problem, we develop a probabilistic collocation method (PCM) combining techniques of sparse grids and correlation control, which enables efficient and accurate propagation of correlated uncertain variables with relatively low computational cost. The effectiveness of the proposed model and computational strategy are demonstrated on the modified IEEE RTS 24-bus test case and a simplified regional Jiangsu power grid, where the impacts of IL pricing and capacity on the re-dispatch results are further explored.

Effect of Parameter Variation on Frequency Response of VSG Controlled PMSG System

High penetration of both Wind and Solar energy sources weaken the system in terms of inertia. The inertia of generating system directly affects the dynamic stability. In order to provide inertial support, different options are suggested by researchers among which the Virtual Synchronous Generator (VSG) is proved to be most effective. However, the performance of VSG depends solely on the selection of VSG parameter. This paper takes the case of PMSG based system controlled through a VSG controller and investigates the effect of VSG parameter over system frequency nadir and peak overshoot. The MATLAB/SIMULINK model of VSG based PMSG system is used to simulate the effect. The result shows the advantage of the VSG system over a conventional one and helps the researcher to select the proper parameter for optimal system performance.