Grid Development Plan Research Articles

Low voltage grid resilience: Evaluating electric vehicle charging strategies in the context of the grid development plan Germany

The ongoing transition to decentralized renewable energy sources and sector-coupled consumers is reshaping the energy system. Changes at lower grid levels can stress lines and transformers. Crucial for a successful local energy transition are grid relief measures. Battery electric vehicles contribute to higher loads on grid equipment but also offer flexibility. This paper assesses the influence of four different charging strategies for battery electric vehicles across five representative low-voltage grids based on the grid development plan in Germany for the years 2021, 2037, and 2045. Results indicate that grid stress, specifically capacity stress, will emerge by 2037 and 2045. Decentralized photovoltaic systems are the primary contributors to this stress due to high simultaneous generation. Up to nearly 20% of photovoltaic power may need to be curtailed in 2045, especially in rural grids during the summer, to prevent overloads.Charging strategies linked to wholesale power market prices can inadvertently lead to higher consumption-induced grid overloads, necessitating the consideration of local grid restrictions. Implementing grid-friendly charging strategies, such as reduced charging power or alignment with local photovoltaic production, can mitigate those grid overloads from almost 8% down to 0.11%. However, these charging strategies have limited impact on photovoltaic-induced overloads due to the low number of connected battery electric vehicles during the day.In summary, appropriate charging strategies can ease low-voltage grid stress and are suitable measures to manage the challenges of decentralized energy transition and battery-electric vehicle adoption.

Voltage Sag Source Location based on the Random Forest

As one of the most prominent power quality problems in the power system, voltage transients threaten the use of many electrical and electronic devices. The rapid and accurate location of voltage drop sources can better define the responsibility between the power supply and the customer. It can also provide a reliable basis for future grid development planning. In this paper, a random forest model is set up to extract data from several electrical characteristics of voltage transients according to the classical voltage transient location method, which is used as training and test samples to input into the random forest model to achieve the upstream and downstream location of voltage transient sources. The random forest model is more accurate than the single decision tree model and the traditional upstream and downstream voltage drop location method. It is possible to determine which of the traditional judgments is more important under this model.

State-Space Load Flow Calculation of an Energy System with Sector-Coupling Technologies

This paper addresses the sector-coupling principle, highlights each associated sector’s technologies and showcases their future development, according to the German grid development plan. Furthermore, the research project ESM-Regio, and its goals in terms of simulatively analyzing the sector-coupling approach for a specific model region and future scenarios, is introduced. In this context, the key methods for modeling the electricity sector’s loading behavior are showcased. Most importantly, the state-space load flow calculation, load modeling (including the integration of the power demands of the sector-coupling technologies) and an assessment of grid operating equipment, based on thermal aging models, are described.

Multi-method combination site selection of pumped storage power station considering power structure optimization

Energy internet (EI) is the framework foundation for tackling climate change and environmental issues and achieving “carbon peak and carbon neutral”. In this paper, considering the important function of pumped-storage power station (PPS) in promoting the “source-grid-load-storage” synergy and complement in the construction of EI, a novel evaluation index system and evaluation model for the site selection of PPS is proposed to provide decision support for the orderly construction of EI. Firstly, compatible with traditional engineering construction factors and multi-energy complementary needs, a systematic evaluation index system of PPS site selection is established from hydrological conditions, topographical and geological conditions, construction conditions, power grid development planning and economic and environmental benefits. Secondly, considering the inconsistency of conclusions of a single evaluation method, the cycle elimination mechanism based on Kendall’s concordance coefficient (KCC) is introduced into the combination evaluation model of PPS site selection, and the validity measurement method of the model is defined. Finally, a case study on the site selection of PPS in Hebei province of China is carried out to verify the effectiveness of the combination evaluation model, and the sensitivity analysis is carried out. The research shows that it is highly feasible to use the index and model constructed in this paper for the site selection of PPS. The combination evaluation model based on cycle elimination solves the inconsistency of the evaluation conclusions and greatly improves the effectiveness of the combination evaluation model.

How does the vulnerability of an evolving power grid change?

Topological robustness and fault tolerance of the power system are amongst the most studied topics when it comes to the assessment of grid vulnerability. The use of adequate methods and performance metric can greatly contribute to a number of actions, including operation planning, grid development and other specific measures. A shortcoming of several studies is that they fail to take the aspects of network evolution into consideration. In this paper the seven-decade historical dataset (1949–2019) of the Hungarian power system is used to perform vulnerability assessment applying a complex network approach. Damage tolerance of the network is examined against node and edge removals. The results show that the evolving grid has increased its tolerance against large disturbances very early, but vulnerability values show little variance from 1979, despite that the size of the network has increased significantly. It is also found that more efficient and more robust topologies impose slightly conflicting conditions for grid development planning.

Flexibility Reserve of Self-Consumption Optimized Energy Systems in the Household Sector

Energy generation and consumption in the power grid must be balanced at every single moment. Within the synchronous area of continental Europe, flexible generators and loads can provide Frequency Containment Reserve and Frequency Restoration Reserve marketed through the balancing markets. The Transmission System Operators use these flexibilities to maintain or restore the grid frequency when there are deviations. This paper shows the future flexibility potential of Germany’s household sector, in particular for single-family and twin homes in 2025 and 2030 with the assumption that households primarily optimize their self-consumption. The primary focus is directed to the flexibility potential of Electric Vehicles, Heat Pumps, Photovoltaics and Battery Storage Systems. A total of 10 different household system configurations were considered and combined in a weighted average based on the scenario framework of the German Grid Development Plan. The household generation, consumption and storage units were simulated in a mixed-integer linear programming model to create the time series for the self-consumption optimized households. This solved the unit commitment problem for each of the decentralized households in their individual configurations. Finally, the individual household flexibilities were evaluated and then aggregated to a Germany-wide flexibility profile for single-family and twin homes. The results indicate that the household sector can contribute significantly to system stabilization with an average potential of 30 GW negative and 3 GW positive flexibility in 2025. In 2030, the corresponding flexibilities potentially increase to 90 GW and 30 GW, respectively. This underlines that considerable flexibility reserves could be provided by single-family and twin homes in the future.

Research to develop the next generation of electric power capacity expansion tools: What would address the needs of planners?

Close coordination between generation and transmission operations and planning is critical to cost effective and reliable energy production and delivery; such coordination, in the presence of ownership diversity, is indeed a primary and challenging goal of regional transmission organizations in the US and similar organizations worldwide. Optimizing these sectors separately overlooks potential synergies that may allow for more effective design and operation of power systems. Coordinated expansion planning (CEP), where both generation and transmission decisions are coordinated, has become especially relevant to present day planning and operations. There are various reasons for this, some of which include the desire to obtain the most environmental and economic benefit from deeper penetration of renewable energy sources, the need for effective deployment of emerging storage technologies, opportunities to capture and harness the electrification of the transport sector, increased interdependencies with other sectors (e.g., gas), and accommodating increased shares of distributed energy resources in distribution grids. These changes result in increased short-term and long-term uncertainties, as well as an increased need for improved representation of multiscale temporal and spatial dynamics (e.g., representing hourly or sub-hourly intertemporal couplings in multi-decadal expansion models). The purpose of this work is to characterize the state-of-the-art in CEP models and identify technical challenges of grid development planning and research and development (R&D) needs for the new generation of these CEP models.

Principal Component Analysis of Short-term Electric Load Forecast Data Based on Grey Forecast

With the large-scale development of the power industry, new requirements are put forward for the stable operation of the power system. Power system load forecasting refers to the use of historical load data to predict the future load value, which is an important part of energy management system. The short-term load forecasting process is often combined with the basic mechanism of power grid dispatching to achieve the balance of power grid supply and demand, reflecting the highly nonlinear computing ability. Power load forecasting is the premise of power grid real-time control, operation planning and development planning. At present, the grey model model used for power system load forecasting generally has the problems of large calculation amount, no mature theoretical basis for selecting structures and parameters, etc. This paper discusses the application of grey model in short-term power load forecasting, and puts forward a principal component analysis method suitable for ordinary daily power load forecasting data, which improves the accuracy of short-term power load forecasting.

Optimal Sizing and Spatial Allocation of Storage Units in a High-Resolution Power System Model

The paradigm shift of large power systems to renewable and decentralized generation raises the question of future transmission and flexibility requirements. In this work, the German power system is brought to focus through a power transmission grid model in a high spatial resolution considering the high voltage (110 kV) level. The fundamental questions of location, type, and size of future storage units are addressed through a linear optimal power flow using today’s power grid capacities and a generation portfolio allowing a 66% generation share of renewable energy. The results of the optimization indicate that for reaching a renewable energy generation share of 53% with this set-up, a few central storage units with a relatively low overall additional storage capacity of around 1.6 GW are required. By adding a constraint of achieving a renewable generation share of at least 66%, storage capacities increase to almost eight times the original capacity. A comparison with the German grid development plan, which provided the basis for the power generation data, showed that despite the non-consideration of transmission grid extension, moderate additional storage capacities lead to a feasible power system. However, the achievement of a comparable renewable generation share provokes a significant investment in additional storage capacities.

Long-Term Electricity Load Forecasting Considering Volatility Using Multiplicative Error Model

Long-term electricity load forecasting plays a vital role for utilities and planners in terms of grid development and expansion planning. An overestimate of long-term electricity load will result in substantial wasted investment on the construction of excess power facilities, while an underestimate of the future load will result in insufficient generation and inadequate demand. As a first of its kind, this research proposes the use of a multiplicative error model (MEM) in forecasting electricity load for the long-term horizon. MEM originates from the structure of autoregressive conditional heteroscedasticity (ARCH) model where conditional variance is dynamically parameterized and it multiplicatively interacts with an innovation term of time-series. Historical load data, as accessed from a United States (U.S.) regional transmission operator, and recession data, accessed from the National Bureau of Economic Research, are used in this study. The superiority of considering volatility is proven by out-of-sample forecast results as well as directional accuracy during the great economic recession of 2008. Historical volatility is used to account for implied volatility. To incorporate future volatility, backtesting of MEM is performed. Two performance indicators used to assess the proposed model are: (i) loss functions in terms of mean absolute percentage error and mean squared error (for both in-sample model fit and out-of-sample forecasts) and (ii) directional accuracy.

The Influence of New Environment on the Development of Northeast Electric Power Industry

Electricity is the foundation of the national economy, and the influence on the social and economic development is self-evident. At the same time, the power industry is also deeply affected by the economy and society. Firstly, this paper introduces the new environment faced by Northeast power industry from four aspects: power system reform, bilateral stochastic system, technological innovation and related policies; then It deeply analyzed the impact of the new environment on the development of the Northeast Power Industry from the above four angle; finally, the opportunities and challenges of the new environment for the future development of the Northeast power industry are summarized. To pave the way for the formulation of Northeast power grid development planning, and it is also helpful to improve and scientificity and accuracy of the Northeast Power Grid Planning.

Transient Fault Analysis in 63/20 KV Substation

Objectives: An important field of study concerning power grids is the analysis of different incidents that are taking place in the grid. There are various reasons for such incidents. Realizing the cause of failures and finding solutions to prevent their recurrence can be of great help in grid development planning and also for reducing damages caused by such failures. Methods/Analysis: This paper addresses an incident that took place in a 63/20 KV substation. First we overview the substation and its installed equipment in order to have a comprehensive investigation on the failure and its cause. In the following, simulation process based on available data is described. Findings: We address the failure and how it happened, focusing on the factors intensifying it. Novelty/Improvement: A method is proposed to prevent the recurrence of such failures.

Value of power plant flexibility in power systems with high shares of variable renewables: A scenario outlook for Germany 2035

As part of the German transition towards a low-carbon economy, renewable energies are set to account for more than half of the gross electricity consumption by 2035, resulting in a rising flexibility demand. Flexibility is required to balance fluctuations in the residual load. In addition, uncertainties in the wind and solar power generation cause an increased demand for control reserve. A unit commitment model of the German power system is used to analyze the value of power plant flexibility in systems with high shares of variable renewables. To investigate the value of power plant flexibility, the additional revenue that can be generated by flexibility improvements is calculated. The results indicate, that power plant flexibility has a small positive impact on the power plant's contribution margin in 2014. A future power system configuration according to the German Grid Development Plan would provide sufficient flexibility to integrate high shares of renewables without power plant flexibility being very valuable. However, integrating variable renewables into a system relying on coal-fired and nuclear power stations results in power plants being able to significantly increase their revenue with improved flexibility. Under these circumstances, power plant flexibility has a considerable value.

Research of “Foreign Electricity to Enter Jiangxi” Ensure Electricity Supply

In this article, it describes the energy supply and demand situation in Jiangxi Province. To forecast the electricity demand in Jiangxi Province, in-depth analysis the significance of implements the strategy of “Foreign electricity to enter Jiangxi”. In accordance with the national UHV power grid development plan, Combined with characteristics of Jiangxi 500 kV main grid architecture, formulate overall objectives and specific programs of “Foreign electricity to enter Jiangxi”, put forward “Foreign electricity to enter Jiangxi” strategy safeguards.

Barriers and solutions for expansion of electricity grids—the German experience

There is a lack of synchronization in the expansion of renewable energies and the modernization of the electricity grid infrastructure. Main barriers to grid development are the insufficient regulatory framework, an inefficient allocation of planning and authorization competences and a lack of public acceptance of new grids. As response to these barriers, Germany has implemented a fundamental reform of the planning and authorization of high voltage power lines. We analyze the new regime as to what extent it is able to eliminate existing barriers to grid expansion and thus can serve as model for other countries. We find that the establishment of a single authority competent for planning, authorization and regulation may abolish existing lack of coordination. Also, the implementation of early participation on basis of various consultations phases has been proved to be very successful in the establishment of the first grid development plan. Stricter administrative time-limits and sanctions are likely to have an accelerating effect. And an increased openness to new technologies on basis of pilot project gives grid operators more flexibility in grid development. Recently, the European Commission adopted the German approach in its policy guidelines for other EU members.

Impact of Investments in Generating Units and Transmission and Distribution Power Grids by 2025 on Voltage Stability and Branches Load in ENERGA SA Operational Territory – Main Findings of Research Project

The article summarizes a research project which was conducted in order to ensure what will be the influence of future investments and changes in the Polish Power System on the stability and functionality of the ENERGA SA distribution grid system. Development of the ENERGA SA distribution grid system was also included. Only stable states were tested for various cases of system load and generation in power plants (the Nuclear Power Plant in Żarnowiec was taken into account) and also in wind farms. The system was also tested in N-1 and N-2 states. The result of this study is an overall evaluation of the ENERGA SA distribution grid condition, as well as the identification of potential weak points inside this structure. DOI: 10.12736/issn.2300-3022.2013101 1. Project objective and scope The objective of the project was to investigate how the investments made by 2025 will affect the operation of the 110 kV distribution grid owned by ENERGA SA. The study considered the transmission system’s extension by PSE according to [1, 2], the distribution system’s extension in accordance with ENERGAOPERATOR SA’s grid development plan for the next few years, and information about newly-built, planned and connected generation sources. The main focus is on the problem of power output from a large number of wind farms connected in northern Poland, and the planned location of a nuclear power plant in Żarnowiec area. The potentially weakest 110 kV nodes and lines owned by ENERGA SA were identified. The study focused on analysis of the system’s global stability and on analysis of N-1 and N-2 for different variants of the system operation (different system loads and different scenarios for power generation in the system). Additionally, the project continues the master’s thesis [3], which examined the impact of Żarnowiec nuclear power plant’s connection on the operation of the national power system. 2. Research methodology description Power flows were calculated using the PlansLAB software, in which a voltage stability analysing script developed by these authors was implemented. Voltage stability is construed here as the possibility to load down the NPS with an apparent power in a way that triggers neither sharp voltage drops nor a voltage collapse. This is related to the limited potential of reactive power generation in the NPS, which affects voltage levels in substations. The algorithm had enabled monitoring the node voltages and line currents while the power system was loaded down. The loading (here also called simulation) was done by gradually increasing the power supplied to all receivers in the system, and balancing power in the system by some power plants, mainly centrally dispatched generating units (JWCD). The study focused on the steady-states, and neglected dynamic states. The basic variants of the NPS operating states were the following models: summer day (LD), summer night (LN), winter day (ZD) and winter peak (ZS). For comparison of how the system operation conditions will change over the years, calculations were carried out for the years 2012 and 2025. For the line current carrying capacity analysis the ZS model was mainly used, which had the highest currents due to peak of power consumption. • The 2025 models were extended versions of the 2012 models. They include: The change in the electricity generation structure in line with the PSE assumptions [2] for 2025, including the connection in the OSD ENERGA-OPERATOR SA area of wind farms with aggregate output over 5 GW, and of nuclear power plant in Żarnowiec with one 1600 MW unit. Decommissioning of some generation units, according to the PSE plans, was also taken into account. D. Falkowski, M. Zarzycki | Acta Energetica 1/14 (2013) | 4–11

Integrated Electricity Generation Expansion and Transmission Capacity Planning: An Application to the Central European Region

This article presents an integrated electricity dispatch and load flow model with endogenous electricity generation capacity expansion. The target is to quantify generation capacity requirements for 2030 and where within Central Europe it shall be ideally placed when taking into account the projected grid structure. We explicitly model the interdependence between grid operation and power plant placing as we investigate the contribution of centralized power plant placement on reducing the need for grid expansion. The application focuses on Germany and its neighbors and reference is made to recently published plans on grid expansion (TSO 2012). We adopt the perspective of a welfare maximizing system planner and thus determine capacity expansion levels as first-best benchmark. Results show that optimal capacity expansion levels are much lower than previous studies indicate (e.g. dena (2008); EC (2011); EWI et al. (2010); Maurer et al. (2012)). We also show that the need for grid expansion can be reduced by the appropriate placing of just a few Combined Cycle Gas Turbine (CCGT) power plants as well as the use of storage and Demand-Side-Management. The presence of intra-national HVDC lines as proposed in the Grid Development Plan of 2012 (TSO 2012) is found to significantly reduce overall congestion and the need for back-up power plants. However, the contribution of the proposed HVDC lines varies greatly from project to project, calling for a prioritization of plans.