Wind Penetration Levels Research Articles

Robust fractional-order load frequency control for hybrid power system concerning high wind penetration

Hybrid power systems concerning wind farms have witnessed significant dynamic characteristic changes due to unpredicted generation output and integration mode conversion between frequency-sensitive wind plants and non-scheduled ones. This work presents a robust fractional-order load frequency control (LFC) method for a multi-area hybrid power system in the presence of wind penetration uncertainties. To characterize the injection effect of wind farms, the power system is described by a model with an uncertain wind penetration factor in a pre-estimated range. Then, an enhancement of Levy’s identification method is developed to convert this model into a fractional-order reduced structure to design the load frequency controller, which is in a form of fractional-order PID with a filter for ease of engineering implementation. The closed-loop stability is analyzed by the stability boundary locus (SBL) method under different wind penetration levels. It is shown that superior frequency response performance and system robustness can be obtained if the controller is designed in terms of the model with the worse-case wind penetration. Illustrative examples including a three-area hybrid power system under a variety of wind penetration variations are given to show the effectiveness of the proposed method.

Resilience to extreme storm conditions: A comparative study of two power systems with varying dependencies on offshore wind

In the next decades, the dependencies on power production from renewable energy sources are expected to increase dramatically. A transition towards large-scale offshore wind farms together with an increased electrification of the industry and transportation sectors introduces new vulnerabilities to society. Further, extreme weather events are expected to increase in intensity and frequency, driven by climate change. However, there are significant knowledge gaps concerning the impacts of severe weather conditions on the resilience of power systems with large dependencies on offshore wind. In the present study, a comparison between two different power systems’ resilience to historical extreme storm conditions has been conducted. The power systems are the IEEE39-bus New England model and the Great Britain model. The results show significant differences between the two power systems, which underlying reasons are analysed and explained. With an offshore wind penetration level of 30 %, the New England model stays intact in terms of connected load. When increasing the penetration level to 40 %, about 10 % of the total connected load gets disconnected, whereas about 33 % of the load gets disconnected with a penetration level of 50 %. The Great Britain model stays intact in terms of connected load with a penetration level of at least 49 %.

A fast multi-objective pelican optimizer for optimal coordination of DGs and DSTATCOM considering risk penetration level of wind

In this study, a new variant, the fast pelican optimizer (FPO), is proposed to improve the performance of the radial distribution network (RDEN). The proposed variant is characterized by creating a dynamic interaction between two phases, exploration and exploitation, during the search process. The modifications introduced within the standard algorithm allow the proposed new variant, namely FPO, to be fast and adaptive to efficiently solve various complex optimization problems. In the first stage, the proposed FPO is newly adapted and applied to solve the optimal locations of various types of distributed generation based renewable sources and multi shunt compensators, namely the DSTATCOM devices based FACTS technology, and in the second stage, the proposed FPO is applied to optimize the active power of DG units in coordination with the reactive power of multi DSTATCOM. Three objective functions, such as the total power losses, the total voltage deviation, and the margin stability, are optimized individually and in coordination to enhance the performances of the practical radial distribution network (RDEN) 33-bus. A deep comparative study in terms of solution quality and convergence accuracy based statistical analysis is elaborated to demonstrate the competitive aspect of the proposed FPO.

Dynamic vulnerability assessment of hybrid system considering wind power uncertainty

The stochastic volatility of wind power introduces numerous uncertainties to the security and stability of the hybrid system, which in turn affects the overall vulnerability level of the system. In this study, a wind power output model incorporating the effects of wind abandonment and uncertainty factors is established. Additionally, a hybrid optimal power flow (OPF) method considering economic dispatch, stochastic trip, and islanding strategies is developed to simulate the power flow dispatch during cascading failures. Furthermore, a set of indexes describing the global dynamic vulnerability of the hybrid system is proposed to reveal the effects of changes in wind power uncertainty and penetration levels on the hybrid system in the short term. Simulations were conducted on an adapted IEEE118 system, and the results demonstrate that an increase in wind power uncertainty and penetration will exacerbate the system’s vulnerability. This severity is particularly pronounced during peak and valley load periods, making the hybrid system more susceptible to large-scale outages. When the wind power uncertainty level grows to 4, the overall vulnerability level of the hybrid system increases by 102.3% compared to the initial uncertainty case. When the wind penetration level reaches 46%, the overall vulnerability level rises by 75.9% compared to the initial system. These findings emphasize the sensitivity of the hybrid system to different levels of wind power uncertainties and penetrations, providing evidence-based support for the prevention of system cascade failures.

Research on distributionally robust energy storage capacity allocation for output fluctuations in high permeability wind and solar distribution networks.

This paper presents a novel approach to addressing the challenges associated with energy storage capacity allocation in high-permeability wind and solar distribution networks. The proposed method is a two-phase distributed robust energy storage capacity allocation method, which aims to regulate the stochasticity and volatility of net energy output. Firstly, an energy storage capacity allocation model is established, which considers energy storage's investment and operation costs to minimize the total cost. Then, a two-stage distributed robust energy storage capacity allocation model is established with the confidence set of uncertainty probability distribution constrained by 1-norm and ∞-norm. Finally, a Column and Constraint Generation (C&CG) algorithm is used to solve the problem. The validity of the proposed energy storage capacity allocation model is confirmed by examining different wind and solar penetration levels. Furthermore, the model's superiority is demonstrated by comparing it with deterministic and robust models.

A consecutive power dispatch in wind farms to mitigate secondary frequency dips

With the rapid increase of wind energy integrated into power systems, wind turbine generators (WTGs) are required to provide frequency support to maintain the system frequency stability. However, the frequency regulation is achieved by employing temporary energy reserves from WTGs at the initial stage of a disturbance. Therefore, a second frequency dip (SFD) may occur, if no other energy reserve is available to compensate the power deficiency as WTGs have to recover their operating points and rotor speeds back to the initial operating points. To deal with this problem, this paper proposes a consecutive power dispatch scheme to reduce the SFD and prevent WTGs from over-deceleration. All WTGs are divided into two groups with in a wind farm: Group 1 (G1) WTGs operating at maximum power point tracking (MPPT), Group 2 (G2) WTGs operating at deloading power. If a frequency contingency occurs, the proposed scheme aims to release an amount of kinetic energy (KE) stored in the rotating masses of G1 WTGs to improve the frequency nadir (FN). Following this, energy reserves are released from G2 WTGs to compensate the power shortage during the period when G1 WTGs rotor speeds have to be recovered. The simulation results show that the scheme causes a small SFD while improving the first FN and preventing the rotor from over-decelerations in various wind conditions, contingency sizes, and wind penetration levels.

Look-Ahead Rolling Economic Dispatch Approach for Wind-Thermal-Bundled Power System Considering Dynamic Ramping and Flexible Load Transfer Strategy

With a wind-thermal-bundled power system (WTBPS) under high wind penetration levels, the sharp power fluctuations of tie-lines for interconnected grids trigger a significant challenge of security-constrained power system operation. Smoothing power fluctuations with economic dispatch is widely concerned against this challenge. In this paper, an appropriate look-ahead economic dispatch framework for WTBPS considering the variable ramp rate of retrofitted coal-fired units and the flexible load transfer strategy (LTS) in high voltage distribution networks (HVDNs) is proposed. To cope with this issue, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> ) we derive a new family of tightened ramping constraints of retrofitted coal-fired units in the linear and second-order conic (SOC) forms, respectively. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ii</i> ) Using graph characterization of typical HVDNs, the simplified voltage-constrained LTS via topological structures can be developed. This proposed look-ahead economic dispatch model is cast as a mixed-integer second-order cone programming (MISOCP) problem, which can be reformulated by Multi-cut Generalized Benders Decomposition (MGBD). This MGBD enables multiple sub-problems can be solved in parallel and accelerates the solving process. Finally, simulation results of a large-scale practical system validate the computational accuracy and efficiency of the proposed approach.

Closed-Loop Synthetic Inertia Control for Wind Turbine Generators in Association With Slightly Over-Speeded Deloading Operation

Following a frequency event in a power system, synthetic inertia control (SIC) of a wind turbine generator (WTG) can improve the frequency nadir by instantly releasing the stored kinetic energy in the rotating masses. However, SIC might lower the settling frequency below the maximum steady-state frequency deviation, thereby disabling automatic generation control (AGC). This delays frequency recovery to the nominal value. This paper proposes a closed-loop SIC scheme for a WTG in association with slightly over-speeded deloading operation (SODO) that can improve both the frequency nadir and settling frequency. To achieve this, prior to an event, the proposed SIC scheme performs SODO, which can store more releasable energy into the rotating masses of a WTG while minimizing the energy loss. The proposed scheme can improve the frequency nadir by releasing more energy, improve the settling frequency, which enables AGC, and avoid over-deceleration of the rotor speed of a WTG in the low wind speed region. Simulation results clearly demonstrate that the proposed SIC scheme can improve both the frequency nadir and settling frequency under various wind conditions, event sizes, and penetration levels, thereby supporting the frequency stability in a power system that has a high penetration of wind power.

Resilience to storm conditions of power systems with large dependencies on offshore wind

The ongoing transition towards large installations of offshore wind and the electrification of the transport sector and other critical infrastructures introduce new vulnerabilities to the society. Large dependencies of power production from offshore wind are expected in the next decades, but there are large knowledge gaps regarding the power production reliability under severe weather conditions. Simultaneously, weather extremes may increase in frequency and intensity, driven by climate change. In this paper we investigate the resilience of a power system subject to a hurricane event. The power system is based on the IEEE39-bus New England system but with different scenarios for increasing penetration of offshore wind. We find that an offshore wind penetration level of 30% or less results in a power system resilient to hurricane events, with no need for load disconnection. However, when increased to 40% offshore wind penetration, 650 MW corresponding to 10% of the total load demand gets disconnected during the storm peak. With a penetration of 50% offshore wind, the disconnected load ranges from 2.2 GW of load corresponding to 1/3 of the total load demand, to a total power system blackout.

Enhancing transient stability and dynamic response of wind-penetrated power systems through PSS and STATCOM cooperation

The large-scale integration of doubly-fed induction generator (DFIG) based wind power plants poses stability challenges for power system operation. This study investigates the transient stability and dynamic performance of a modified 3-machine, 9-bus Western System Coordinating Council (WSCC) system. The investigation was conducted by connecting the DFIG wind farm to the sixth bus via a low-impedance transmission line and installing power system stabilizers (PSSs) on all automatic voltage regulators (AVRs). A three-phase fault simulation was carried out to test the system, with and without power system stabilizers and a static synchronous compensator (STATCOM) device. Time-domain simulations demonstrate improved transient response with PSS-STATCOM control. A 50% reduction in settling time and 70% decrease in power angle undershoots at the slack bus are achieved following disturbances, even at minimum wind penetration levels. Load flow analysis shows the coordinated controllers maintain voltages within 0.5% of nominal at 60% wind penetration, while voltages at load buses can deviate up to 15% without control. Eigenvalue analysis indicates the PSS-STATCOM boosts damping ratios of critical oscillatory modes from nearly 0% to over 30% under high wind injection. Together, the present findings provide significant evidence that PSS and STATCOM cooperation enhances dynamic voltage regulation, angle stability, and damping across operating ranges, thereby maintaining secure operation in systems with high renewable integration.

Participation of battery energy storage system for frequency control in wind dominated power systems: An analytical approach

The frequency performance of a power grid is effectively maintained through the utilization of inertia and power reserve provided by synchronous generators. The growing concerns surrounding global warming and the greenhouse effect have led to a significant increase in the integration of wind energy into the grid. But the system may face frequency instability following a contingency due to lack of sufficient inertia and headroom of wind generators. Therefore, the grid operator may require shedding some loads to prevent the system from severe frequency excursion. In this paper, we have estimated proper amount of load shedding through the formulation of analytical expression that will keep a highly wind penetrated & Battery Energy Storage System (BESS) integrated system stable. For this purpose, the maximum amount of wind power penetration level (WPPL) is first calculated using a fast analytical approach which utilizes two frequency response performance metrics, frequency nadir and Rate of Change of Frequency (ROCOF). In scenarios where the wind penetration level exceeds the calculated allowable threshold, it becomes necessary to implement load shedding measures following a contingency event. After installation of BESS, grid frequency response is much enhanced, hence, the required load shedding amount is also different. Therefore, we have derived an analytical expression for a quick measurement of frequency response enhancement attained by BESS. Finally, a frequency nadir-based load shedding scheme, being the goal of this paper, is proposed for a heavily wind penetrated grid with BESS, using the previously derived expression, to retain the grid at its nominal operating condition following a severe contingency. Our proposed scheme incorporates an analytical method to prevent over load shed. We have used DIgSILENT PowerFactory to validate our proposed analytical approaches through dynamic simulation. Results obtained from the proposed approaches nearly resemble the simulated one. Hence, this paper can help generating simplified yet effective models to conduct analysis on a wind integrated grid. This paper can also be regarded as a guide to ensure a wind penetrated resilient grid in view of frequency stability.

Merchant and regulated storage investment in energy and reserve markets: A Stackelberg game

AbstractWith large‐scale integration of renewable generation, energy storage is expected to play an important role in providing flexibility to energy systems. In this paper, the authors construct a trilevel Stackelberg game model to study the co‐investment of merchant and regulated storage in energy and reserve markets. The upper‐level problem is a profit‐maximizing storage investment problem with a desired rate‐of‐return solved by a merchant investor. In the middle‐level problem, the system operator (SO) makes regulated storage investment decisions to minimize system cost. In the lower‐level problem, the SO clears energy and reserve markets. The proposed model captures interactions of regulated and merchant storage investment. Also, it clarifies how different ownership structures of storage influence merchant storage profitability and system cost structures in different capital cost of storage investment and wind penetration level scenarios. The numerical results conducted on a 6‐bus illustrative example and the IEEE 24‐bus Reliability test case validate the proposed model. The results show that both regulated and merchant storage can increase social welfare, and social welfare remains almost the same under different ownership structures of storage.

The role of electricity market design for energy storage in cost-efficient decarbonization

The role of electricity market design for energy storage in cost-efficient decarbonization

Optimal scheduling in demand-side management based grid-connected microgrid system by hybrid optimization approach considering diverse wind profiles

Demand side management (DSM) is one of the trending economic strategies which shifts the elastic demand to the off-peak hours from the peak hours so as to reduce the overall generation cost of the system. The work done in this paper can be categorized in three phases. In the first phase, various wind speed to power conversion mathematical models available in literature are analysed to find out the one with maximum level of wind penetration. For second phase, an economic DSM strategy is implemented to restructure the forecasted load demand model for various participation levels. In the final phase the cost-effective optimization of two microgrid distribution systems are percolated. As an optimization tool, novel hybrid CSAJAYA has been used to carry on the study. Different types of grid participating and pricing strategies along with valve point loading effect and wind energy uncertainty are considered to amplify the complexity and practicality of the study. The generation costs reduced from 3 to 5% when the forecasted demand was reformed with 20% DSM participation for both the test systems. A detailed comparison with the results from various optimization tools studied confirms the effectiveness of the proposed hybrid approach. The hybrid optimization tool presented in this paper performs better in terms of central tendencies, nonparametric statistical analysis, and algorithm execution time.

Stochastic optimisation and economic analysis of combined high temperature superconducting magnet and hydrogen energy storage system for smart grid applications

High Temperature Superconducting (HTS) Magnetic Energy Storage (SMES) devices are promising high-power storage devices, although their widespread use is limited by their high capital and operating costs. This work investigates their inclusion in smart grids when used in tandem with hydrogen fuel cells and other energy storage devices using a novel two-stage model. The first stage presents a stochastic allocation algorithm to optimally size the smart grid assets with the maximum expected profit. The next stage models the time system evolution with these optimal capacities using a dynamic Monte Carlo model to investigate the system reliability, capacity credit and loss of load expectation. A novel energy management algorithm is also presented that maximises the time with which a fleet of energy storage devices can fulfil a stochastically unknown power request. The analysis shows that from a purely economic standpoint, HTS SMES and hydrogen energy do not achieve high penetration levels (up to 10 %) due to their high costs, although the penetration levels can be improved with higher power imbalance penalties in day ahead markets. The novel capacity credit and reliability investigation shows that they can improve the reliability and capacity credit of wind turbines by approximately 30 %, thereby improving potential wind penetration levels. The optimal energy management algorithm improves the fleet lifespan and reliability by up to 9 % depending on the connected capacity.

Designing of robust frequency stabilization using optimized MPC-(1+PIDN) controller for high order interconnected renewable energy based power systems

The challenge of controlling frequency becomes greater as the complexity of a power network increases. The stability of a power system is highly dependent upon the robustness of the controller. This paper presents automatic generation control (AGC) of a four-area interconnected power system along with integrated renewable energy sources of PV and wind energy. The designed model is a challenge given the increased penetration levels of PV and wind along with a thermal-hydropower system. The addition of a hydropower system as a fourth type results in the pole of the open loop system of the hydropower system being located at the right half side of the s-plan. This demands a robust control. A novel MPC-(1 + PIDN) is designed for high-order interconnected areas (HOIA) to stabilize the frequency in a robust way. The salp swarm algorithm is adopted to optimize the parameters of the PIDN controller. The performance of the proposed controller under HOIA is tested in a unbalanced load environment with uncertainty in the power system. The proposed controller can effectively handle the frequency disruption by stabilizing it in 0.86 s for Area-1, 1.08 s for Area-2, 0.81 s for Area-3, and 0.84 s for Area-4 with an average time of 0.89 s for all the areas, whereas the average time for GWO: PI-PD, MPC/PI and GA-PI is 3.48 s, 10.36 s and 18.47 s, respectively. The results demonstrate the effectiveness of the controller when compared to other controllers.

Intraday markets, wind integration and uplift payments in a regional U.S. power system

U.S. electricity markets adopt a two-settlement structure with day-ahead and real-time markets. Wind power integration poses a challenge for this market structure because day-ahead wind production forecasts are uncertain and significant rescheduling costs may occur in real time, increasing the need for out-of-market uplift payments. We investigate whether a multi-settlement structure with four intraday stages taking place 18 to 3 h before electricity generation reduces uplift payments and system costs, relative to a two-settlement structure. We develop unit commitment and dispatch models that account for intertemporal constraints and solve them on a 36-node test system using historical wind forecasts provided by a Regional Transmission Organization, as well as synthetic wind forecasts reproducing the observed correlation in the historical data. Combining historical and simulated forecasts allows us to account for wind uncertainty and draw more robust conclusions about the relative merits of each market structure. Finally, we compare the performance of market designs under varying levels of wind penetration. Under any level of wind penetration, the proposed multi-settlement market design is more likely to yield higher uplift than the two-settlement market design. Wind forecast accuracy and structural differences between the U.S. and European electricity markets are key drivers of our results.

Investigation of distance relay settings under normal and stressed conditions in a wind farm environment

This paper presents an adaptive methodology for setting distance relays connected to a network integrated with a wind farm system. The proposed trip boundary setting is capable of automatic adjustment with varying system conditions making the relay more reliable, faster and more accurate. A wind farm system delivers power according to the wind speed and penetration level at that instant. Distance relays having fixed trip boundary setting may underperform in such conditions as trip boundaries need to be varied according to the wind speed, penetration level, voltage ratio, power angle, system impedance and frequency. These variations in ideal trip boundaries, due to changing conditions, have been investigated. Furthermore, a smart coordination scheme is proposed for the improvement of backup protection (Zone 3) provided by distance relays. Inaccurate sensing of fault in Zone 3 due to load encroachment results in false tripping and makes the relay unreliable. The new scheme enables discrimination between fault inception and false tripping. A typical 400 kV system has been considered for simulation and testing in Matlab®/Simulink™ environment.

Dynamic economic dispatch using hybrid CSAJAYA algorithm considering ramp rates and diverse wind profiles

• Dynamic economic dispatch performed for 10 and 15 units system. • Ramp rate and valve point effect considered for the study. • Penetration level was compared between three different wind profiles. • Novel hybrid CSAJAYA considered as optimization tool. • Results compared with those available in literature. • Statistical analysis performed for proposed hybrid algorithm. Optimal scheduling of the conventional generating units for two different dynamic test systems are percolated in this paper. This paper compares and contrasts among three types of wind profile formulations, namely linear, quadratic, and cubic, which were used to calculate wind power from hourly wind speed to find the profile with the greatest penetration of wind power. Thereafter, the wind profiles were coupled with the test system to execute dynamic economic dispatch. The optimization tool used for the study was a unique hybrid algorithm modelled by combining the properties of the recently developed crow search algorithm (CSA) and JAYA. Involvement of ramp-rate limits and the valve point effects magnified the practicality of the work thereby assessing the proposed hybrid algorithm in solving complex non-linear functions. Results infer that maximum level of wind penetration was attained by linear wind profile and a fuel cost reduction of 2.92% was realized upon incorporation of the same. Numerical results also claims that proposed hybrid CSAJAYA approach consistently yielded better quality solutions within minimum execution time without being affected by the dimension of the problem, thereby outperforming a long list of algorithms implemented for the study.

The error induced by using representative periods in capacity expansion models: system cost, total capacity mix and regional capacity mix

Capacity Expansion Models (CEMs) are optimization models used for long-term energy planning on national to continental scale. They are typically computationally demanding, thus in need of simplification, where one such simplification is to reduce the temporal representation. This paper investigates how using representative periods to reduce the temporal representation in CEMs distorts results compared to a benchmark model of a full chronological year. The test model is a generic CEM applied to Europe. We test the performance of reduced models at penetration levels of wind and solar of 90%. Three measures for accuracy are used: (i) system cost, (ii) total capacity mix and (iii) regional capacity. We find that: (i) the system cost is well represented (~ 5% deviation from benchmark) with as few as ten representative days, (ii) the capacity mix is in general fairly well (~ 20% deviation) represented with 50 or more representative days, and (iii) the regional capacity mix displays large deviations (> 50%) from benchmark for as many as 250 representative days. We conclude that modelers should be aware of the error margins when presenting results on these three aspects.