Transmission System Operators Research Articles

Grid Impact Aware TSO-DSO Market Models for Flexibility Procurement: Coordination, Pricing Efficiency, and Information Sharing

This paper proposes five market models for the procurement of flexibility by transmission (TSO) and distribution system operators (DSOs), based on several TSO-DSO coordination schemes, including a disjoint distribution, disjoint transmission, common, fragmented, and multi-level market. The properties of these models are then analyzed. In particular, the common market is first proven to be more efficient than the other market models. Then, different methods are proposed to adequately price TSO/DSO interface flows, when procuring cross-grid flexibility. It is then shown that, when interface flows are optimally priced, the fragmented and multi-level market solutions converge to those of the common market, reaching optimal efficiency. To prevent the need for any network information sharing among system operators in the different coordination schemes, decomposition methods based on bi-level programming and the alternating direction method of multipliers (ADMM) are proposed. A developed case study, considering an interconnected transmission-distribution system, corroborates the mathematical findings by highlighting the greater efficiency of the common market, the effect of adequate interface pricing on reducing procurement costs, and the capability of the decomposition methods to reach optimal market solutions with limited information exchange.

Transmission and Distribution Equipment: Providing Intelligent Maintenance

One of the cornerstones of a reliable transmission and distribution (T&D) grid operation is fully functional components that can operate robustly and with a low outage rate under all specified operating conditions. Dependable maintenance strategies are thus indispensable and are applied by grid operators around the world. One of the present key challenges in many countries with a widely developed T&D grid system is aging components that reach their anticipated end of life. Asset management faces the question of whether the lifetime of components could be prolonged and the replacement could be delayed. For this, the health of the components needs to be assessed and is ideally continuously monitored. In addition to this, the currently ongoing transition of the entire energy system leads to a change and increase of stress on the T&D equipment. The integration of new renewable energy sources on all voltage levels leads to bidirectional power flows and increased variability. The higher demand for electric power not only increases power-flow levels on average, but also in particular, peak flows. The result of this changed and increased stress on the equipment is an accelerated aging component and the need for maintenance strategies to be adopted for this new situation.

An analytical framework for low-power underwater backscatter communications

Acoustic underwater backscatter enables ultra-low-power communication with applications in ocean exploration, monitoring, navigation, and aquaculture. Unlike traditional communication systems, acoustic backscatter does not require active signal generation. Instead, it communicates data by modulating existing acoustic signals, requiring few microwatts of power for operation. Backscatter communication enables ultra-low power sensors by switching between absorbing and reflecting acoustic waves transmitted from a central station. The energy burden is shifted to the transmitting station, and the acoustic power supplied by the station can power the sensor, allowing for battery-free operation. Initial demonstrations of underwater backscatter communication were encouraging; however, the theoretical and practical limits are still unknown. In this work, we develop a multiphysics analytical framework for the communication and power link budget of underwater backscatter. The framework calculates practical communication and power-up range, transmitter power budget, and signal-to-noise ratio, accounting for transducers’ characteristics and the underwater communication channel. The analytical predictions are validated for practical transducers using high-fidelity piezo-acoustic finite element simulations and experimental measurements. The framework will guide future backscatter systems design, identifying practical operation ranges and optimal frequencies for data transmission and batteryless operation.

OSER—A Planning Tool for Power Systems Operation Simulation and for Impacts Evaluation of the Distributed Energy Resources on the Transmission System

The rapid expansion of distributed energy resources and variable renewable energy is occurring in most utilities around the world, pertaining to the clean energy transition. These technologies have brought new challenges and opportunities to transmission grid planners. In this context, the planning process cannot continue to focus solely on the instant of the peak demand to make decisions regarding the evolution of the grid. The OSER simulator (Outil de simulation de l’exploitation du réseau) presented in this paper allows the planning engineers to consider operational and transversal aspects (transmission and distribution view) of the system. OSER is composed of several modules, each of which is related to different parts of the utility. The load, interconnection, and production modules prepare profiles for each substation, interconnection, and generating unit, respectively. The virtual operator module models the actions and mitigation means of the grid operators. These include the generation load balance, voltage, reactive power control, and interconnection management. Thereby, OSER can simulate the reaction of the transmission system for all relevant scenarios by using the guidance of the transmission system operator. The results obtained by simulation validate the performance of the OSER simulator by comparing them with historical data. This tool enables transmission grid planners to include non-wire alternatives in their planning process. Further work will be conducted to extend the simulation modes towards year-long and stochastic simulations for better planning robustness.

Large Scale, Mid Term Wind Farms Power Generation Prediction

Renewable energy sources, such as wind turbines, have become much more prevalent in recent years, and thus a popular form of energy generation. This is in part due to the ‘Fit for 55’ EU initiative, and in part, to rising fossil fuel prices, as well as the perceived requirement for nations to have power independence, and due to the influence of renewable energy sources we can see a marked increase in large wind farms in particular. However, wind farms by their very nature are highly inconsistent regarding power generation and are weather-dependent, thus presenting several challenges for transmission system operators. One of the options to overcome these issues is a system being able to forecast the generated power in a wide-ranging period—ranging from 15 min up to 36 h, and with an adequate resolution. Such a system would better help manage the power grid and allow for greater utilization of the green energy produced. In this document, we present a process of development for such a system, along with a comparison of the various steps of the process, including data preparation, feature importance analysis, and the impact of various data sources on the forecast horizon. Lastly, we also compare multiple machine learning models and their influence on the system quality and execution time. Additionally, we propose an ensemble that concatenates predictions over the forecast horizon. The conducted experiments have been evaluated on seven wind farms located in Central Europe. Out of the experiments conducted, the most efficient solution with the lowest error rate and required computational resources has been obtained for random forest regression, and two independent models; one for the short-term horizon, and the other, for the mid- to long-term horizon, which was combined into one forecasting system.

Natural gas supply from Russia derived from daily pipeline flow data and potential solutions for filling a shortage of Russian supply in the European Union (EU)

Abstract. Russia is the largest natural gas supplier to the European Union (EU). The invasion of Ukraine was followed by a cutoff of gas supplies from Russia to many EU countries, and the EU is planning to ban or drastically reduce its dependence on Russia. We provide a dataset of daily gas consumption in five sectors (household and public building heating, power, industry, and other sectors) with supply source shares in the EU27 (27 EU member countries) and UK from 2016 to 2022. The datasets are available at Zenodo platform: https://doi.org/10.5281/zenodo.7549233 (Zhou et al., 2022). The dataset separates the contributions of Russian imports, liquefied natural gas (LNG) imports, and other supply sources to both direct supply and storage supply for gas consumption estimations. The dataset was developed with a gas network flow simulation model based on mass flow balance by combining data from multiple datasets including daily ENTSOG (European Network of Transmission System Operators for Gas) pipeline gas transport and storage, ENTSOE (European Network of Transmission System Operators for Electricity) daily power production from gas, and Eurostat monthly gas consumption statistics per sector. The annual consumption data were validated against the BP Statistical Review of World Energy and Eurostat datasets. We secondly analyzed the share of gas supplied by Russia in each country to quantify the “gap” that would result from a cessation of all Russian exports to Europe. Thirdly, we collected multiple data sources to assess how national gaps could be alleviated by (1) reducing the demand for heating in a plausible way using the lower envelope of gas empirical consumption – temperature functions, (2) increasing power generation from sources other than gas, (3) transferring gas savings from countries with surplus to those with deficits, and (4) increasing imports from other countries like Norway, the USA, Australia, and northern African countries from either pipelines or LNG imports, accounting for existing capacities. Our results indicate that it should be theoretically possible for the EU to collectively make up for a sudden shortfall of Russian gas by combining the four solutions together, provided a perfect collaboration between EU countries and the UK to redistribute gas from countries with surplus to those with deficits. Further analyses are required to investigate the implications with respect to the costs, including social, economic, and institutional dimensions; political barriers; and negative impacts on climate policies, with inevitable increases in CO2 emissions if the use of coal is ramped up in the power sector.

Advanced Dispatching of a Wind Farm Based on Doubly Fed Induction Generators for the Improvement of LVRT Capability by the ADRC Approach

This paper aims to explore a viable monitoring and management of active and reactive powers for a large-scale wind farm based on Doubly-Fed Induction Generators (DFIG) considering the voltage Fault-Ride-Through capability (FRT), especially Low-Voltage-Ride-Through (LVRT) capability by using a new control strategy, known as Active Disturbance Rejection Control. This strategy uses real-time estimation and compensation of the generalized "total" disturbance before it affects the system. The wind farm supervisory unit is used to coordinate the control of the powers production by the entire wind farm, which must take into account the couplings between each wind generator while producing the individual power commands. The turbine control units (local supervisory units) send the appropriate power references depending on the situation. This can be to produce the maximum power, to manage the active and reactive power given by the Transmission System Operator (TSO) or to meet the requirements of the grid code (LVRT capacity). However, to ensure the dispatching of the references of the active and reactive powers over the all wind generators of the wind farm and to satisfy the security of the power grid, we utilized mean of the proportional distribution algorithm. The effectiveness of the proposed supervisory approach and control strategies are tested and validated through a multiples scenarios of simulations that are made under the MATLAB/Simulink Environment. The results obtained have demonstrated the efficiency and robustness of the control methods, and also the fact that they guarantee good performance and safety of the integration of wind farms into the grid while complying with the requirements of the grid code during power system faults.

Voltage Control Market Integration: Technical and Regulatory Challenges for the Greek Electricity Market

Stochastic power generation is the new reality in power system management. Voltage Control mechanisms based on physical assets of the power system are deemed inadequate and are not guaranteed to lead the energy transformation in a way that ensures system security as well as cost-effective operation. Many countries that recently attained deregulated Balancing Market environments are in need of regulatory provisions and rigorous extension of electricity market mechanisms. On 1 November 2020, the Greek Electricity Market commenced operations conforming to the European Target Model. Apart from the innate difficulties a transformation such as this contains, more challenges occur as Greece is bound by European law to design market-based incentive mechanisms to remunerate Ancillary Services provided to the power system. This paper aims to examine some of the technical and regulatory aspects linked with—future—Transmission System Operator (TSO) and Distribution System Operator (DSO) cooperation in overcoming local transmission system problems concerning Voltage regulation. The interaction between localized Voltage Control Market (VCM) and the Balancing Market, the incorporation and competition of Distributed Energy Resources (DER) and Transmission Energy Resources (TER) within the VCM along with the TSO - DSO procedures and products standardization are the focus points of the present research paper.

Power aware air quality sensing system with efficient data storage capability


 
 
 
 Introduction: This paper presents a portable device of Air QualityMonitoring System (AQMS) based on a sensor platform. The purpose of the study is to power awareness, warning indication, and minimal data storage capability.
 Materials and methods: AQMS is developed by embedded design methodology. The software part is based on the C programming language. AQMS device is made up of “transmitter” and “receiver” sections through the Zigbee wireless network. The objective is to collect concentrations of CO, NO2, CO2, humidity, and temperature to check air pollution for health awareness. A power-saving strategy is adopted in the "transmitter" of AQMS through a Demultiplexer circuit. To minimize the space complexity of storage and availability of long-term data, data encoding techniques are implemented.
 Results: By implementing switching activity on the sensors in AQMS, the active mode of sensing operations are controlled and a power saving of 18.41% is achieved. Extending the duration of transmission operation increases data storage in the “receiver” unit. Hence, two encoding techniques are developed where real-time data are encoded in binary form: 2-bit encoding and 3-bit encoding. According to the results, 2-bit encoding saves 50% of storage space and 3-bit encoding saves 25%, compared to not utilizing any encoding strategy, sacrificing data accuracy by less than 5%.
 Conclusion: AQMS design is created with the implementations of low power consumption and low storage. Additionally, an alarming condition is set in AQMS for indicating the level of pollutants in the air to determine the risk level of exposure which is dangerous for human health.
 
 
 

Open-Circuit Fault-Tolerant Control of a Six-Phase Asymmetric Permanent Magnet Synchronous Motor Drive System

One innovative composite fault-tolerant control tactic is presented for the reliable operation of a power transmission system, which consists of both an asymmetric six-phase permanent magnet synchronous motor (PMSM) and a T-type mid-point clamp type (T-NPC) three-level inverter. First, in order to inherit the better harmonic property of simplified space vector modulation (SVM) and the rapid dynamic capability of direct torque control (DTC), the SVM-DTC control scheme was determined, and the harmonic electric current suppression unit was added to the basic control scheme to obtain good harmonic electric current suppression. In addition, a strategy for open-circuit fault-tolerant control under the SVM-DTC scheme was designed by analyzing the mutual influence between the stator flux linkage and the stator voltage of each phase under an open-circuit fault. Finally, the PMSM drive system principle prototype was tested. By comparing the waveforms of output torque and current of each phase before and after fault tolerance, it shows that the large torque fluctuation (±5%) before fault tolerance was suppressed to ±2% and smoothed out, verifying the effectiveness of fault tolerance control.

An improved rigid rod method for wind-induced swing response prediction of heavily iced transmission lines

Wind-induced swing of overhead transmission lines may cause flashover and line tripping, which will greatly jeopardize the normal operation of power transmission system and give rise to great economy loss. This paper analyzed a swing flashover accident on a practical high-voltage (HV) transmission line and calculated the swing angle of the suspension insulator string using the rigid rod method recommended by the Chinese standard. The aerodynamic coefficients of the iced HV transmission lines were obtained through high frequency force balance wind tunnel tests. An improved rigid rod method was then developed for predicting wind-induced swing response of heavily iced transmission lines in mountainous terrain under severe icy weather conditions. Finally, the improved rigid rod method was also extended to deal with general transmission lines with light ice accretion or regular ice shapes.

USE OF FLEXIBILITY IN DISTRIBUTION NETWORKS

The Electricity Market Act stipulates that the distribution system operator is encouraged to use flexibility, including participation in congestion management in distribution network in coordination with transmission system operator, to increase efficiency, develop the distribution system and promote energy efficiency measures. DSO can access flexibility in one or more of the following ways: market-based procurement of flexibility services, distribution network tariffs, flexible (non-firm) connection agreements, rules based (regulated) approach, in combination or separately. The categories are not necessarily mutually exclusive and the inherent regulatory incentives and implemented measures may overlap. Member States and national regulatory authorities should, therefore, carefully evaluate the interactions when implementing new forms of access to flexibilities or when enhancing existing ones. The paper reviews the mentioned possibilities of using flexibility in the distribution network.

Value-Driven System Design of Utility-Scale Airborne Wind Energy

In the current auction-based electricity market, the design of utility-scale renewable energy systems has traditionally been driven by the levelised cost of energy (LCoE). However, the market is gradually moving towards a subsidy-free era, which will expose the power plant owners to the fluctuating prices of electricity. This paper presents a computational approach to account for the influence of time-varying electricity prices on the design of airborne wind energy (AWE) systems. The framework combines an analytical performance model, providing the power curve of the system, with a wind resource characterisation based on ERA5 reanalysis data. The resulting annual energy production (AEP) model is coupled with a parametric cost model based on reference prototype data from Ampyx Power B.V. extended by scaling laws. Ultimately, an energy price model using real-life data from the ENTSO-E platform maintained by the association of EU transmission system operators was used to estimate the revenue profile. This framework was then used to compare the performance of systems based on multiple economic metrics within a chosen design space. The simulation results confirmed the expected behaviour that the electricity produced at lower wind speeds has a higher value than that produced at higher wind speeds. To account for this electricity price dependency on wind speeds in the design process, we propose an economic metric defined as the levelised profit of energy (LPoE). This approach determines the trade-offs between designing a system that minimises cost and designing a system that maximises value.

Multivariate time series imputation for energy data using neural networks

Multivariate time series with missing values are common in a wide range of applications, including energy data. Existing imputation methods often fail to focus on the temporal dynamics and the cross-dimensional correlation simultaneously. In this paper we propose a two-step method based on an attention model to impute missing values in multivariate energy time series. First, the underlying distribution of the missing values in the data is learned. This information is then further used to train an attention based imputation model. By learning the distribution prior to the imputation process, the model can respond flexibly to the specific characteristics of the underlying data. The developed model is applied to European energy data, obtained from the European Network of Transmission System Operators for Electricity. Using different evaluation metrics and benchmarks, the conducted experiments show that the proposed model is preferable to the benchmarks and is able to accurately impute missing values.

Optimization-Based Methodology to Design the MMC's Sub-Module Capacitors

This paper proposes an optimization-based size reduction methodology for Modular Multilevel Converters (MMC), focusing on minimizing the converter's sub-module capacitor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C_{SM}$</tex-math></inline-formula> . The analysis is performed considering both the converter's current and voltage limitations and the Transmission System Operator (TSO) Fault Ride Through (FRT) requirements. By means of a steady-state analysis, the time-domain expressions of the converter's arms energies are obtained and their behavior throughout the MMC's operating range is shown. Based on these expressions, the optimization-based problem to reduce the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$C_{SM}$</tex-math></inline-formula> size is developed and its constraints are imposed to ensure that the converter's voltage and current levels are within its design limitations. The suggested method is compared with different approaches for distinct active and reactive power set-points, where it is shown that the SM capacitor size can be reduced up to 24% in comparison with the method with worst performance and up to 7% regarding the best method used for comparison purposes. Furthermore, time-domain simulations of the MMC considering several AC voltage sags are performed in order to demonstrate that the dynamics of the SM capacitor and the arm applied voltages are within acceptable margins during the different operations.

Research on Power-Frequency Overvoltages of 220 kV Offshore Cable Transmission System in Liaoning Province

Since power-frequency overvoltages can influence the safe operation of the submarine cable transmission system greatly, it is indispensable to calculate the overvoltages that may occur during actual situations. In this study, the power-frequency overvoltages of the offshore oil-gas field group’s submarine cable transmission system are calculated through PSCAD/EMTDC. Among the different conditions considered, the maximum power-frequency overvoltage is 1.134p.u., which occurs in the case of single-phase fault earthing at the cable joint in L4. The result fulfills the limit of relevant regulations for the 220 kV transmission system, indicating that the submarine cable transmission system can operate safely and effectively, which can provide important guiding significance for the construction and operation of the system.

Polarization and Wavelength Performance Improvement in Large-Scale Silicon Photonics Switches

We review our recent results in multi-port strictly non-blocking optical switches based on silicon photonics. Silicon photonics switches are one of the most important devices to realize future datacenters capable of processing a large amount of data with high efficiency. This is because silicon photonics enables fast (ns - μs) switching, dense integration with high uniformity, low power consumption, and mass production leading to low cost. Thus far, we demonstrated switching, all-paths transmission, and fully-loaded operation of up to 32 input ports × 32 output ports silicon photonics switches. The remaining challenges for practical applications are polarization insensitivity and broadband operation. Regarding the polarization-insensitivity, we presented the non-duplicated polarization-diversity 32 × 32 switch with SiN over path waveguides and demonstrated polarization-insensitive operation in limited paths. Regarding the broadband operation, we achieved ∼90 nm bandwidth for −30 dB crosstalk with polarization-insensitivity in the 8 × 8 switch. We review these, and then discuss how to achieve a large port count (>32 × 32), polarization-insensitivity, and broadband operation simultaneously. Moreover, to broaden the range of applications, integration with wavelength filters and expanding operating wavelengths are important. We demonstrated hybrid integration with the silica platform that is suitable for wavelength filters and the 8 × 8 switch operating in the O-band.

Gear Shift Quality Enhancement Parameters in Light Commercial Vehicles

In the present scenario enhancements of human ergonomics in Light commercial vehicles are imperative to implement customer comfort in vehicle level. Thus the gear shift mechanism plays an important role in the interface between the driver and vehicle. An exact and smooth running gear shift feel typically depends on the combination of both internal and external shifting elements of the gearbox and Change shift operation(CSO) system. The objective of this paper is to explain the parameters that impacts the gear shift quality and how it is improved by taking multiple design iterations in Light commercial vehicle platform through both objective and subjective evaluations. These iterations are given better results on gear shift feel in dynamic as well as static condition. This lead us to facilitate better shift comfort to end users. The content of the paper is limited to the scope of gear shift quality improvements at manual transmission and change shift operation components.&#x0D;

Online fault classification in Connected Autonomous Vehicles using output-only measurements

Different health-monitoring techniques were considered in the literature to enhance the safety and stability of Connected Autonomous Vehicle (CAV) platoons. Mitigating these faults is faster and more reliable if the fault structure is known. In this paper, we propose using transmissibility operators, which are relationships that relate a set of velocities with another in the platoon, to classify the faults. Transmissibility operators were shown to be exceptional in signal estimation. However, it is also shown to be noncausal and thus can only be used offline. To this end, we propose using Data Aggregation (DAgger), an extension to imitation learning, to transfer the classification experience from transmissibility operators to a novice machine learning agent to be used online. The integration of transmissibility-DAgger gives the ability to adapt to new fault classes without the need to re-train the diagnosis model from the beginning. A heterogeneous CAV platoon was modeled with three different faults separately. These faults are actuator disturbances, false data injection attacks, and communication time delays. The classification scheme depends on estimating the faulty signal in the case of each fault class. Next, the measured faulty signal is compared with the three estimations, and the closer fault estimation to the measured one is considered the actual fault on the platoon. The proposed algorithm is then tested on the platoon model and then applied to an experimental setup that consists of three autonomous robots. The proposed results are compared with six different machine learning classification models. The overall classification accuracy achieved was 95.8% for the experiment using the proposed approach.

A bi-level approach for participation of hybrid transmission operating companies in the day-ahead market, considering energy storage systems

This paper presents a new approach for participation strategy of Hybrid Transmission Operating Companies (HTOCs) in the day-ahead energy market. In this paper HTOC refers to private companies that have won physical transmission rights (PTR) and also own energy storage facilities. In the introduced hybrid structure, the HTOC can make profit in two different ways; first, through the flow of transmission lines (the MW-Mile transmission pricing method is used here); and second, through an optimum scheduling of its energy storage system. The optimum charge/discharge pattern of energy storage systems, evaluated in this paper, would also increase the MW-Mile profit of the company. The proposed method is a bi-level optimization model. In the upper level the profit of the HTOC is maximized and in the lower level the market clearing process of the independent system operator (ISO) has been modeled. The uncertain behavior of rival units is modeled using robust optimization (RO) method. The Karush-Kuhn-Tucker (KKT) optimality conditions are implemented to convert the proposed bi-level problem into its equivalent single-level problem. The Big-M method and the strong duality theorem (SDT) are used to linearize the proposed method. To demonstrate the performance of the introduced structure for HTOC, the proposed strategy has been implemented on a standard IEEE 9-bus and 57-bus test systems. The results show that HTOC can achieve a maximum guaranteed profit using storage resource (SR). It is also concluded that the presence of SR has not only increased HTOC's profit but also helped to make the structure more flexible against the uncertain parameters. In addition, the RO as a calculation risk method has been perfectly matched with the implementation of SR as a source of hedging uncertainties in managing the risk.