Penetration Level Of Wind Generation Research Articles

Adaptive MPPT control applied to virtual synchronous generator to extend the inertial response of type-4 wind turbine generators

The increasing penetration level of wind generation in power systems has resulted in the degradation of the system frequency response and stability issues, where the decrease of the system equivalent inertia is one of the main causes of these problems. In this context, this work proposes an operational and control approach to provide emulated inertial response to wind turbine generators based on fully rated converter that operate at the maximum power point. The inertial response of the wind turbine generator is extended by a control strategy that combines an adaptive MPPT control with an adaptive inertia control based on virtual synchronous generator. The proposed approach mitigates the antagonistic interaction between the traditional MPPT control and inertia control. The impact of the MPPT control and inertia control on the dynamics of the wind turbine and system frequency is comprehensively addressed. The results have shown that the proposed strategy is effective in extending the inertial response of the wind turbine generator and mitigating the amplitude of the second frequency dip and electromechanical oscillations caused by the conventional MPPT control. The adaptive inertia control also prevents the violation of the minimum speed limit of the wind turbine

Operating point optimization of wind turbine generators for provision of inertial response and frequency control

Inertial and frequency control approaches for wind turbine generators have proven to be effective in mitigating the frequency control and stability problems inherent to power systems and microgrids with high penetration levels of wind generation. This paper proposes an optimization formulation to determine the operating point of de-loaded wind turbines in order to improve the mechanical dynamics of the wind turbine-generator set. Such operating point optimization reduces the speed deviation magnitude and settling time of the wind turbine caused by the action of inertial and frequency control. The optimization approach is integrated into a combined inertial and frequency control approach for type-4 wind turbine generators. The optimized control approach, based on the concept of virtual synchronous generator, may extend the inertial response and frequency control capabilities of type-4 wind turbine generators, thus improving the transient and steady-state frequency performance of high wind penetrated power systems.

Allocation of FACTS Devices Using a Probabilistic Multi-Objective Approach Incorporating Various Sources of Uncertainty and Dynamic Line Rating

Flexible AC transmission system (FACTS) controller play an essential role in increasing the penetration level of renewable energy resources owing to their ability in continuously controlling the active and reactive power flow in the network. This paper presents a probabilistic multi-objective optimization approach to obtain the optimal sizes and locations of static var compensators (SVCs) and thyristor-controlled series capacitors (TCSCs) in a power transmission network with high penetration level of wind generation. The objective of the problem is to maximize the system loadability while minimizing the network power losses and the installation cost of the FACTS controllers. In this study, the uncertainties associated with wind power generation and the correlated load demand are considered. The uncertainties are handled in this work using the points estimation method. Moreover, the dynamic line ratings (DLRs) of the transmission lines are considered in this work. In this case, the maximum transmission capacity of transmission lines is estimated dynamically according to the weather conditions. Considering the DLRs or transmission lines is expected to avoid unrealistic congestion in the network, and hence, improve its loadability. The optimization problem is solved using the multi-objective teaching-learning based optimization (MO-TLBO) algorithm to find the best locations and ratings for the FACTS controllers. Additionally, a technique based on the fuzzy decision-making approach is employed to extract one of the Pareto optimal solutions as the best compromise. The proposed approach is applied on the modified IEEE 30-bus system. The numerical results demonstrate the effectiveness of the proposed approach and show that the maximum loadability limit of the study system increases when considering the DLR. This limit can be enhanced to 123.0% without FACTS controller and 137.0 %,130 % and 132.0% by SVC, TCSC and (SVC-TCSC) respectively.

Towards Optimal System Scheduling With Synthetic Inertia Provision From Wind Turbines

The undergoing transition from conventional to converter-interfaced renewable generation leads to significant challenges in maintaining frequency stability due to declining system inertia. In this paper, a novel control framework for Synthetic Inertia (SI) provision from Wind Turbines (WTs) is proposed, which eliminates the secondary frequency dip and allows the dynamics of SI from WTs to be analytically integrated into the system frequency dynamics. Furthermore, analytical system frequency constraints with SI provision from WTs are developed and incorporated into a stochastic system scheduling model, which enables the provision of SI from WTs to be dynamically optimized on a system level. Several case studies are carried out on a Great Britain 2030 power system with different penetration levels of wind generation and inclusion of frequency response requirements in order to assess the performance of the proposed model and analyze the influence of the improved SI control scheme on the potential secondary frequency dip. The results demonstrate that the inclusion of SI provision from WTs into Unit Commitment (UC) can drastically impact the overall system costs.

Decentralized wind uncertainty management: Alternating direction method of multipliers based distributionally-robust chance constrained optimal power flow

How to manage wind power uncertainty in system operation is an urgent and important issue, especially under substantially increasing penetration levels of wind generation in electric power systems. With increasing numbers of wind power plants (WPPs) integrated into power systems, their variability and uncertain power outputs become a challenge to maintaining system reliability. Traditional stochastic optimization-based models face the curse of dimensionality when the number of WPPs increases. This paper proposes a novel decentralized wind power uncertainty management model. In this model, conventional generators optimize their power capacity output and their participation to mitigate wind power uncertainty locally with only limited information exchange with the system operators. First, a distributionally-robust chance-constrained optimal power flow (DRCC-OPF) model is deployed to schedule the generation and reserve considering the wind power forecast uncertainty. Then, the alternating direction method of multipliers (ADMM) is used to reformulate the DRCC-OPF model into the distributed optimization model for each conventional generator and WPP. The tests on a small PJM 5-bus system and the IEEE 118-bus system demonstrate that the proposed decentralized model can increase the operation reliability without sacrificing system operating cost, especially when the wind power penetration levels are high. Using the proposed model, the optimal solutions can be obtained within one minute, for all studied cases, which verifies the computation efficiency of the proposed decentralized model. Furthermore, considering a large number of WPPs integrated into the system, the proposed decentralized method obtains a lower operating cost within one minute which demonstrates its efficiency to deal with high dimension of uncertainties.

A Two-stage Stochastic Programming Model for Optimal Reactive Power Dispatch with High Penetration Level of Wind Generation

The increasing of wind power penetration level presents challenges in classical optimal reactive power dispatch (ORPD) which is usually formulated as a deterministic optimization problem. This paper proposes a two-stage stochastic programming model for ORPD by considering the uncertainties of wind speed and load in a specified time interval. To avoid the excessive operation, the schedule of compensators will be determined in the first-stage while accounting for the costs of adjusting the compensators (CACs). Under uncertainty effects, on-load tap changer (OLTC) and generator in the second-stage will compensate the mismatch caused by the first-stage decision. The objective of the proposed model is to minimize the sum of CACs and the expected energy loss. The stochastic behavior is formulated by three-point estimate method (TPEM) to convert the stochastic programming into equivalent deterministic problem. A hybrid Genetic Algorithm-Interior Point Method is utilized to solve this large-scale mixed-integer nonlinear stochastic problem. Two case studies on IEEE 14-bus and IEEE 118-bus system are provided to illustrate the effectiveness of the proposed method.

Long-Term Voltage Stability Analysis of Variable Speed Wind Generators

This paper presents the impacts caused by the integration of variable speed wind turbines on long-term voltage stability. The technologies used are fully rated converter (FRC) and doubly fed induction generator (DFIG) with two control strategies: grid-side converter (GSC) at unity power factor, which is usually adopted, and GSC controlling reactive power. Also, this paper considers wind turbines capability curves and its variable limits, since they are subject to several limitations that changes with the operating point and wind speed. This study also considers the dynamic models of over excitation limiter (OEL) and on-load tap changers (OLTC) combined with static and dynamic loads using time domain simulations. Different penetration levels of wind generation are analyzed. The results show that long-term voltage stability can be improved when GSC of DFIG is controlling reactive power. Moreover, the capability curve plays an important role in this analysis since reactive power is a key requirement to maintain voltage stability.

Review on Developments in Wind Energy Generation and its Integration to Utility Grid

Efficient conversion of wind power to electricity and its integration to the grid has been a topic of intense research in recent times, to improve the contribution of energy from renewable sources. When the penetration level of wind generation increases in grid, dynamic and transient behaviour of the system get affected. To maintain the reliability of the system, well defined grid codes are to be formed that has to be followed by independent power producers to avoid wind energy curtailment and ensure quality of power available in grid. Given the intermittent nature of wind, the subject of various storage mechanisms becomes critical to avail energy scheduling from a wind farm. This paper undertakes an exhaustive study of various wind electric generators and grid integration technologies along with the grid codes. The review highlights that direct driven generators dominate in recent installations due to their superior performance compared with other generator configurations. Consequently, a permanent magnet synchronous generator based gearless wind electric system along with battery energy storage is modeled and its performance is evaluated. The grid codes that are to be followed are also incorporated in the model.

Impact on Transient Angle Stability with DFIG-Based Wind Generation Connected to Power System

This paper investigates the impact of wind generation consisting of doubly-fed induction generators (DFIG) on the system angle stability. 3 different factors are considered: the penetration level of wind generation, the connection location of wind generation and the reactive power control strategy that the DFIG utilizes. A modified IEEE-3 machine and 10 bus system has been used as the test network and a number of simulations have been conducted. It shows that the higher the penetration level of the DFIG-based wind generation, the better the system angle stability. Compared with unity power factor control strategy, the system stability is better when the DFIG utilizes constant voltage control strategy. Beside, different connection locations of wind generation also have effects on system stability.

Maximum penetration level of wind generation considering power system security limits

In this study, a method is proposed for determining the maximum penetration level of wind farms (WF) based on permanent magnet synchronous generators and doubly-fed induction generators into the power system; it takes power system transient stability as well as frequency security criteria into consideration. Considering the probabilistic nature of wind speed, probabilistic transient stability analysis is introduced and applied to determine the maximum penetration level of WFs. The effect of overall system reduced inertia because of increasing capacity of WFs is investigated. A fast approach for deriving system frequency drop after a sudden disturbance is employed, which is suitable for online frequency stability constrained unit commitment incorporating WFs. The feasibility and effectiveness of the proposed method is evaluated using the IEEE 9-bus test system.

Value of Wind Power at Different Locations in the Grid

Availability of wind energy which differs across locations primarily determines the appropriate location for installing windfarms. However, the grid location of windfarms must always be considered in an attempt to accurately quantify the benefits which can be achieved from windfarms during their lifetime operation to the supply network. The value of wind power is significantly affected by their penetration and concentration, and is further affected by their location within a network. This is because the location and penetration level of wind generation will result in a significant impact on power-flow distribution across the network. The objective of this paper is to measure the impact of grid location of windfarms on economic and operational parameters of a power system in the lifetime of a windfarm project. This paper first develops an assessment tool to quantify the economic and operational impact of wind power in the grid. This is followed by developing different scenarios in which different penetrations of wind power are installed at different locations in the grid, and it shows how the value of wind power is affected by location and network constraints.

Combining the Wind Power Generation System With Energy Storage Equipment

With the advancements in wind turbine technologies, the cost of wind energy has become competitive with other fuel-based generation resources. Due to the price hike of fossil fuel and the concern of global warming, the development of wind power has rapidly progressed over the last decade. The annual growth rate has exceeded 26% since the 1990s. Many countries have set a goal for high penetration levels of wind generation. Recently, several large-scale wind generation projects have been implemented all over the world. It is economically beneficial to integrate very large amounts of wind capacity in power systems. Unlike other traditional generation facilities, using wind turbines presents technical challenges in producing continuous and controllable electric power. A distinct feature of wind energy is its nature of being ldquointermittent.rdquo Since it is difficult to predict and control the output of wind generation, its potential impacts on the electric grid are different from the traditional energy sources. At a high penetration level, an extrafast response reserve capacity is needed to cover the shortfall of generation when a sudden deficit of wind takes place. To enable a proper management of the uncertainty, this paper presents an approach to make wind power become a more reliable source on both energy and capacity by using energy storage devices. Combining the wind power generation system with energy storage will reduce fluctuation of wind power. Since it requires capital investment for the storage system, it is important to estimate the reasonable storage capacities for the desired applications. In addition, an energy storage application for reducing the output variation during the gust wind is also studied.