Maximum Penetration Level Research Articles

재생에너지 확대에 따른 국내 계통관성 별 적정 예비력 평가

As the penetration level of renewable energy sources (RESs) increases, the decrease in the system inertia and spinning reserves will be one of the major challenges for the secure operation of power systems. Recently, in order to secure power system frequency within the limit defined in the grid code, accurate analysis on the frequency responsive reserves is getting important. In this study, method of evaluating the minimum level of inertia along with the required reserves to secure system frequency is developed. Furthermore, maximum allowable penetration level of RESs is analyzed in order to secure frequency after a sudden loss of a single generator unit. And with the evaluated minimum inertia for the secure frequency, this study shows the amount of the increased generation and the system frequency response in the time frame after a single generator or two generator units are tripped off. In the developed method, increase in RES penetration is illustrated as a negative load while considering the merit order of conventional generators. A case study is conducted on the future Korean power system of 2024.

Low Voltage Distribution Networks Modeling and Unbalanced (Optimal) Power Flow: A Comprehensive Review

The rapid increase of distributed energy resources (DERs) installation at residential and commercial levels can pose significant technical issues on the voltage levels and capacity of the network assets in distribution networks. Most of these issues occur in low-voltage distribution networks (LVDNs) or near customer premises. A lack of understanding of the networks and advanced planning approaches by distribution network providers (DNSPs) has led to rough estimations for maximum DERs penetration levels that LVDNs can accommodate. These issues might under- or over-estimate the actual hosting capacity of the LVDNs. Limited available data on LVDNs’ capacity to host DERs makes planning, installing, and connecting new DERs problematic and complex. In addition, the lack of transparency in LVDN data and information leads to model simplifications, such as ignoring the phase imbalance. This can lead to grossly inaccurate results. The main aim of this paper is to enable the understanding of the true extent of local voltage excursions to allow more targeted investment, improve the network’s reliability, enhance solar performance distribution, and increase photovoltaic (PV) penetration levels in LVDNs. Therefore, this paper reviews the state-of-the-art best practices in modeling unbalanced LVDNs as accurately as possible to avoid under- or over-estimation of the network’s hosting capacity. In addition, several PV system modeling variations are reviewed, showing their limitations and merits as a trade-off between accuracy, computational burden, and data availability. Moreover, the unbalanced power flow representations, solving algorithms, and available tools are explained extensively by providing a comparative study between these tools and the ones most commonly used in Australia. This paper also presents an overview of unbalanced optimal power flow representations with their related objectives, solving algorithms, and tools.

Simultaneous Distributed Generation and Electric Vehicles Hosting Capacity Assessment in Electric Distribution Systems

This work presents a strategy, from the perspective of the distribution system operator (DSO), that aims at simultaneously estimating the maximum penetration levels of renewable-based distributed generation (DG) and electric vehicles (EVs) that can be accommodated into an electric distribution system (EDS). To estimate such capacity, operational resources such as generation curtailment and controllable features of EVs can be managed to ensure the safe operation of the EDS and avoid infeasible operational conditions. Through a multi-period representation, the proposed strategy models the variability in demand consumption and DG power production. In addition, driving patterns of EV owners and energy requirements of EVs, obtained through probability density functions, are incorporated in this representation. Inherently, the problem is represented as an optimization model, and to determine its solution, an algorithm based on the metaheuristics greedy randomized adaptive search and tabu search (GRASP-TS) is developed. The applicability of the planning strategy is assessed on a 33-bus EDS under different test conditions and the numerical results show that higher penetrations of EVs and renewable-based DG can be accommodated without impacting the safe operation of the EDS. The results also demonstrate that by controlling the power draw by EV aggregators, an increase of 9% can be obtained in the DG installed capacity compared to the case of uncontrolled charging of EVs. In addition, the scalability of the proposed approach is studied using two distribution systems, the 83-bus system and the 135-bus system, where the results show that the convergence of the algorithm is achieved in a few iterations.

Analysis on the Penetration Level of Wind Farm Considering Transient Stability Constraint and Uncertainty of Wind Power

Background: The penetration level of a wind farm with transient stability constraint and static security constraint has been a key problem in wind power applications. Objective: The study explores maximum penetration level problem of wind considering transient stability constraint and uncertainty of wind power out, based on credibility theory and corrected energy function method. Methods: According to the corrected energy function, the transient stability constraint of the power grid is transferred to the penetration level problem of a wind farm. Wind speed forecast error is handled as a fuzzy variable to express the uncertainty of wind farm output. Then this paper builds a fuzzy chance-constrained model to calculate wind farm penetration level. To avoid inefficient fuzzy simulation, the model is simplified to a mixed integer linear programming model. Results: The results validate the proposed model and investigate the influence of grid-connection node, wind turbine characteristic, fuzzy reliability index, and transient stability index on wind farm penetration level. Conclusion: The result shows that the model proposed in this study can consider the uncertainty of wind power out and establish a quantitative transient stability constraint to determine the wind farm penetration level with a certain fuzzy confidence level.

Impact of Electric Vehicle Charging on Low Voltage Network Stability

The global shift of vehicular transportation from conventional cars to electric vehicles present yet another challenge for the power utilities in meeting the growing demand for Electric Vehicles (EV). Large penetration of electric vehicles can have numerous impacts on the electric grid if left unaddressed. This paper presents the assessment of the impact of EV charging on the electricity distribution network at different penetration levels. A model of an existing electricity distribution network of Thimphu, the capital city of Bhutan was developed in DIgSILENT power factory simulation software. The impact of EV charging on the existing electricity distribution network was analysed based on three hypothetical assumptions, current status-quo, low uptake level, and high uptake level. The impacts were evaluated on two key parameters, the voltage stability, and the transformer loading. The load flow simulation indicated that a low voltage violation was triggered even at a low penetration level of 0.28% and the maximum penetration level is attained at 37.68% where the whole system is likely to breakdown due to severe voltage collapse on the distribution system. Based on the simulation results, a mitigation technique for voltage correction has been discussed.

Load pattern‐based voltage stability analysis in unbalanced distribution networks considering maximum penetration level of distributed generation

Stability analysis in the power system is becoming more important than ever as more distributed energy resources penetrate in the system. This study presents a novel load pattern voltage stability index (LPVSI) applicable to transmission and distribution systems. By considering the nominal value of voltages, the power network is converted into a two-bus equivalent system. Then, LPVSI is derived by only the real-time measurement of the voltage and deviation of active and reactive power loads. Also, the assessment of distributed generation's penetration level on unbalanced systems, with maximum loadability and power loss reduction constraints, is performed with regard to daily load variations. The accuracy and efficiency of the proposed indicator are tested on an unbalanced 34-node radial distribution system. Obtained results in comparison with some other papers in the literature demonstrate that the proposed voltage stability index is fast and effective in identifying non-trivial instabilities in the power system networks.

Assessing the ancillary service potential of electric vehicles to support renewable energy integration in touristic islands: A case study from Balearic island of Menorca

The potential of e-mobility to participate in intermittency flattening ancillary services (AS) to support solar photo-voltaic (PV) grid integration is analysed in this paper. First, the capability of Plug-in Electric Vehicles (PEVs) to act as Energy Storage Systems (ESS) based on daily energy storage potential (ESP) with and without vehicle-to-grid (V2G) services is studied. Mobility behaviour and penetration levels of various categories of vehicles-cars, vans, trucks, buses and motorcycles in the island are modeled using traffic data from Menorca island. Next, ancillary service (AS) potential of 1000 PEVs to support solar PV grid integration is analysed. A crucial parameter of PEVs to offer uni-V2G services under aggregator to participate in hour-ahead AS market, termed achievable power capacity (APC), is explored. Results showed that, for bidirectional V2G services in summer, ESP can reach up to 100 MWh for minimum (P1) and 375 MWh for maximum (P6) penetration levels considered. The regulation potential for every 1000 private PEVs aggregated to a maximum of 4.6 MW and reserve potential to a maximum of 5.25 MW under coordinated charging. This reveals the great potential of PEVs in offering AS in small touristic islands.

Parallel Computing and Multicore Platform to Assess Electric Vehicle Hosting Capacity

The impact generated by the massive connection of electric vehicles (EVs) in the distribution networks needs to be evaluated through methodologies that consider the stochastic behavior of the EV connections. These methodologies must allow obtaining representative results of annual simulations, considering different charging scenarios, with high resolution of time steps. This kind of analysis implies a combinatorial explosion of case studies with a high computational cost. This article presents a methodology aimed at reducing the simulation time required to determine the EV hosting capacity (HC), understood as the maximum EV penetration level that a distribution network could host before affecting its operating limits, through the co-simulation of hardware and software. Monte Carlo methods and quasi-static time series simulation concepts are used to model the connection features of EVs. The simulation and implementation are developed using parallel computing, and MATLAB and OpenDSS software. The methodology is tested on the IEEE 123 nodes system which shows the dependence of the HC indicator with the location and type EV chargers. Finally, the benefits of parallel computing in the proposed methodology are exposed to get a significant reduction in the execution time to evaluate the HC in the IEEE 123 nodes system.

A reliability-constrained demand response-based method to increase the hosting capacity of power systems to electric vehicles

This paper proposes a reliability-constrained demand response-based method to maximise the permissible penetration level of electric vehicles (EVs) at electric power system buses. The continuous increase of EVs will deteriorate the reliability of power systems if no countermeasures are taken. Implementation of demand response (DR) programs can be an effective solution to reduce or even avoid load curtailments. Also, the mobility of EV loads causes a dynamic change in load curtailments. This dynamic change can be captured through building load profiles for EVs considering drivers’ behaviour and preferences to charge EVs. The proposed method is developed based on a DR program and load profiles of EVs. In the proposed method, existing load profiles are combined with load profiles for initial numbers of EVs at corresponding buses. The initial numbers are calculated based on total interruptible/curtailable (I/C) loads at system buses and peak load of EVs. Drivers’ behaviour and preferences in terms of charging times, periods, and locations are modelled in developing load profiles for EVs. Then, I/C loads-based DR is implemented to restructure load profiles of system buses. Both incentives and penalties are considered to develop the DR program. Finally, the maximum permissible penetration level is calculated by increasing the number of EVs until systems’ prior (without EVs) reliability level is achieved. The proposed method is demonstrated on the Roy Billinton Test System, IEEE Reliability Test System, and IEEE-33 Bus Distribution System. Monte Carlo simulation is performed to evaluate the well-known reliability indices of power systems. The results show that the permissible penetration level of EVs in power systems can be increased significantly using the proposed method.

Pile-soil-structure interaction effect on structural response of piled jacket-supported offshore platform through in-place analysis

In-place analysis for offshore platforms is essentially required to make proper design for new structures and true assessment for existing structures, in addition to the structural integrity of platforms components under the maximum and minimum operating loads when subjected to the environmental conditions. In-place analysis have been executed to check that the structural member with all appurtenance&#180s robustness have the capability to support the applied loads in either storm or operating conditions. A nonlinear finite element analysis is adopted for the platform structure above the seabed and pile-soil interaction to estimate the in-place behavior of a typical fixed offshore platform. The SACS software is utilized to calculate the dynamic characteristics of the platform model and the response of platform joints then the stresses at selected members, as well as their nodal displacements. The directions of environmental loads and water depth variations have significant effects in the results of the in-place analysis behavior. The most of bending moment responses of the piles are in the first fourth of pile penetration depth from pile head level. The axial deformations of piles in all load combinations cases of all piles are inversely proportional with penetration depth. The largest values of axial soil reaction are shown at the pile tips levels (the maximum penetration level). The most of lateral soil reactions resultant are in the first third of pile penetration depth from pile head level and approximately vanished after that penetration. The influence of the soil-structure interaction on the response of the jacket foundation predicts that the flexible foundation model is necessary to estimate the force responses demands of the offshore platform with a piled jacket-support structure well.

Steady State and Transient Analysis of FSIG and DFIG Integration to Grid for Different Penetration Levels using VSC-HVDC

Among all the Renewable Energy Sources Wind energy is the fastest growing energy source over the last decade mainly due to crucial developments of technology in wind energy. Nowadays, the penetration of wind energy is increasing in many countries in the world including India. The power system stability with large penetration of wind power is a concern for many electrical utilities. The common technical issues with increased penetration of wind energy are voltage and reactive power control, frequency control and Low Voltage Ride Through (LVRT) capability. The VSC-HVDC system with its benefit of independent control of active and reactive power promises to enhance the system stability at high penetration levels. The maximum wind penetration levels in to the grid is analysed for Fixed Speed Induction Generator (FSIG) & Doubly Fed Induction Generator (DFIG). The penetration levels are further enhanced by considering the evacuation of wind power with VSC-HVDC system without losing system stability. Different controllers for VSC-HVDC system are used to improve the stability and LVRT capability. Standard Benchmark System is considered, and the simulations are performed by using power system simulation software SIMPOW. Results shows that wind power evacuated through VSC-HVDC system has better stability and LVRT Capability compared to AC system at high wind penetration levels.

Optimal Distributed Generation Allocation and Sizing Using Genetic and Ant Colony Algorithms

Distributed generators (DG) which installed into distribution network to face the increasing of load demand. DG can used to enhance power generation systems and improve distribution network efficiency. However, the distributed generators units’ implementation at not convenient position and sizing can lead to negative impacts such as a growing in power losses and invasion of system constraints. Because the rising of demand in energy. The appropriate placement and sizing of DG’s units is a credible solution to much problems in distribution system, for example power loss reduction and voltage regulation. The allocation of distributed generators into the distribution network can significantly impact in the transmission and distribution systems. Therefore, a method, which can identify an optimum DG location and size, is necessary. In this paper, Genetic Algorithm (GA) and Ant colony Algorithm (ACO) optimization techniques are proposed to find optimal sizing and location for distributed generation in electrical networks. The objective function of the work relies upon a linearized model to compute the active power losses as a function of power supplied from the generators. This strategy based on a strong coupling between active power and power flow taking into consideration the voltage angles. With the end goal to exhibit the adequacy of the proposed method, the proposed strategy is applied on IEEE 57-bus standard systems. Different maximum penetration level capacity of DG units and various possible places of DG units among several types of DG (active, reactive or active and reactive power) are considered. Results show that the optimization tools employing GA and ACO are effective in reducing active power losses by finding the optimal placement and sizing of DG units

Protection Coordination of Distribution Network with Optimally Placed Distribution Generation

In this study, optimal distribution network protection coordination scheme with directional over current relays is developed. In addition, impact of optimally placed Distribution Generation (DG) on the protection coordination scheme is subsequently evaluated using relay Coordination Time Interval (CTI). As such, the study is carried out in two stages. In the first stage, optimal relays settings (time dial settings and pickup current) are determined. While in the second stage, the maximum DG penetration level with changes in the protection coordination is evaluated. Particle Swarm Optimization (PSO) algorithm, due to its faster convergence speed, is applied in both stages. The technique is implemented on the distribution section of the IEEE 14-bus and IEEE 30-bus systems and simulated in MATLAB. The simulation results obtained are compared with that obtained using hybrid Genetic Algorithm (GS) – Nonlinear Programming (NP) approach using relays pickup current and operating times as performance metrics. For the IEEE 14 bus system, the developed PSO-based relay coordination has reduced the relays pickup current and operating times by roughly 28% and 32% respectively compared with the hybrid GA-NLP technique. The optimal locations of the DGs are found to be bus 5, 8 and 12 which result in CTI of 0.233sec. While in the IEEE 30 bus system, the developed relay coordination has reduced the relays pickup current and operating times by roughly 31% and 34% respectively compared with the hybrid GA-NLP technique. Similarly, the optimal locations and sizes of the DGs are found to be bus 19, 26 and 30, which result in CTI of 0.462sec.

Probabilistic Approach to Determine Penetration of Hybrid Renewable DGs in Distribution Network Based on Voltage Stability Index

An increase in the applications of renewable-based energy resources in the radial distribution network has led to many uncertainties in the existing system which affects the stable operation of the power systems. The issues regarding the generation uncertainty associated with wind energy and photovoltaic (PV) systems along with load demand uncertainties are considered in this research for the evaluation of the maximum penetration level of renewable energy resources. The nodes which are less voltage stable are considered as the most suitable locations for distributed generations (DGs) placement from voltage stability viewpoint. For identification of DGs locations, a voltage stability index–continuous power flow-based algorithm has been proposed. To analyze the effect of large penetration level of wind and PV on voltage profile, power losses and system voltage stability of the radial distribution network, a probabilistic-based approach has been adopted. It is observed from simulation results that the penetration level limit depends upon the type of DGs connected to the radial distribution network. Usually the integration of DGs reduces the power losses in the network; however, as penetration level increases, the power losses begin to increase. The detailed mathematical model of wind and PV sources has been utilized. The Hong’s 2m + 1 point estimation method combined with Cornish–Fisher expansion has been adopted in this paper for probabilistic studies. The effectiveness of the proposed method has been validated through IEEE 33 and 69 node radial distribution test network for various scenarios. The results obtained are verified and compared with benchmark Monte Carlo simulation technique.

OPTIMAL DISTRIBUTED GENERATION PLACEMENT AND SIZING TO REDUCE ACTIVE POWER LOSS USING GA AND ACO ALGORITHM

In this paper, Genetic Algorithm (GA) and Ant colony Algorithm (ACO) optimization techniquesare proposed to find optimal sizing and location for distributed generation in electrical networks.The objective function of the work relies upon a linearized model to compute the active powerlosses as a function of power generators. This strategy based on a strong coupling between activepower and power flow taking into consideration the voltage angles. With the end goal to exhibitthe adequacy of the proposed method, the proposed strategy is applied on IEEE 30-bus standardsystems. Different maximum penetration level capacity of DG units with three ranges such as,10%, 20% and 30% of maximum power load and various possible places of DG units amongseveral types of DG (active, reactive or active and reactive power) are considered. Results showthat the optimization tools employing GA and ACO are effective in reducing active power lossesand cost loss by finding the optimal placement and sizing of DG units.

Maximum Penetration Level Evaluation of Hybrid Renewable DGs of Radial Distribution Networks Considering Voltage Stability

The issues regarding generation uncertainties associated with wind energy and solar photovoltaic (PV) systems along with load demand uncertainties are considered in this paper to evaluate the maximum penetration of renewable energy resources. The nodes which are less voltage stable are considered as the most suitable locations for distributed generations (DGs) placement. For identification of these critical nodes, a voltage stability index (VSI) has been utilized. To analyze the voltage profile, power losses and system voltage stability with large penetration of the wind energy and solar PV into the distribution networks, a probabilistic-based approach has been adopted. The penetration limit depends upon the type of DG that is connected to the distribution network. Usually, the integration of DGs reduces the power losses in the network, however as penetration level increases, the power losses begins to increase. The detailed mathematical models of wind and solar PV-based renewable resources are used. The Hong’s $$2m+1$$ point estimation method combined with Cornish–Fisher expansion is adopted in this paper to conduct the probabilistic studies. The effectiveness of the method is validated through IEEE 33-node radial distribution test network for four different scenarios. The results obtained have been verified and compared with Monte Carlo simulation technique.

A two-layer control strategy for voltage regulation of active unbalanced LV distribution networks

In this paper, a coordinated control strategy is proposed to effectively address the voltage regulation issue in active unbalanced low-voltage (LV) distribution networks. The proposed control scheme is based on a two-layer centralized approach, consisting of the local and the overlaying control layers. The former is embedded at the hardware level of the distributed renewable energy sources (DRESs). Therefore, it is continuously active, aiming to prevent network overvoltages and to mitigate voltage unbalances based explicitly on local measurements. The overlaying control strategy is implemented at a central controller, at the distribution system operator (DSO) level, acting supplementary to the local control scheme to increase the total injected green energy and to implement DSO policies for the reallocation of the active power curtailment. The validity of the proposed two-layer control strategy is demonstrated on a real Slovenian LV network by means of time-series simulations. Additionally, the impact of the proposed control on the maximum DRESs penetration level is thoroughly evaluated, while its performance is compared against other conventional control strategies, revealing its superiority in terms of voltage regulation, voltage unbalance mitigation and increased green energy production.

Fast method to estimate Maximum penetration level of wind power considering frequency cumulative effect

Reductions in system inertia due to increasing penetration levels of wind power may result in frequency stability issues. Thus, it is necessary to provide a comprehensive method to estimate the maximum level of wind power that can maintain a system's frequency within allowable security limits following a major disturbance. Here, a fast method to estimate maximum wind power penetration level (WPPL) that considers frequency cumulative effect is proposed. The method first establishes an average system frequency response (ASFR) model of integrated wind power and then calculates the corresponding frequency response trajectory characteristics. Subsequently, a new transient frequency security index (TFSI) based on the frequency cumulative effect is expressed. The physical basis for the TFSI is that it can objectively reflect the dynamic security state of the system frequency. The quantitative functional relationship between the WPPL and the TFSI can be obtained by combining the frequency response characteristics and the TFSI definition. A numerical expression for the maximum WPPL integrated into the grid can be obtained, and the maximum WPPL of the integrated wind power system can be instantaneously and quantitatively estimated. Finally, the feasibility and effectiveness of the proposed analytical method is demonstrated on a 10-machine 39-bus system.

Investigation of harmonic distortions in photovoltaic integrated industrial microgrid

Due to the abundance of power electronic appliances, harmonic distortion has become one of the growing power quality concerns in recent years. Harmonic distortion is also caused by the nonlinearity of other power equipment such as transformers and rotating machines. Power systems, rich in harmonics, offer poor power factor and hence low efficiency operation. Due to the large concentration of nonlinear loads such as motor drives, investigation of harmonic distortion in industrial systems is getting special attention. Widespread integration of solar Photovoltaic (PV) systems into distribution systems brings additional challenges to the existing power quality scenario. Inclusion of solar PV systems in an industrial microgrid equipped with a large share of motor drives results in a significant increase in existing Total Harmonic Distortion (THD). To better understand the above issues, a methodology is proposed in this paper to identify the most suitable PV placement topology between the two schemes (namely, centralized and distributed) in terms of THD performance. Also, a technique is developed to estimate the maximum PV penetration level by maintaining the THD within the given acceptable limit. The proposed methodologies are applied to an industrial distribution system under various operating conditions.

Economic dynamics and technology diffusion in indian power sector

There is a growing concern among policy makers about how electricity is generated and consumed in the context of energy security and global climate change. In such a scenario, renewable energy sources, especially solar and wind energy, are likely to play a significant role in providing reliable and sustainable electricity to consumers as they are locally available and their carbon foot print is small. The future share of power by renewables will greatly depend on the expected generation cost and the government's support to investments in the sector. Using levelised cost approach, capital cost, operating and fuel costs of major electricity generation technologies are compared. Then, a forecast is made for electricity generation in India, using non-linear Bass diffusion model over 15-year horizon, until 2030, for all major energy technologies, viz., coal, natural gas, hydro, solar, wind, and biomass. The results show how present trends and future forecasts of electricity-generating technologies change the electricity generation mix, and how solar and wind power may increase their share in the total generation. However, fossil fuels will continue to remain competitive relative to renewables due to their cost advantage. The main issue considered here is whether each energy technology has reached its maximum penetration level. This helps set out a path for renewable energy technology diffusion in the Indian power sector