Medium Voltage Distribution Network Research Articles

A multi-task learning based line parameter identification method for medium-voltage distribution network

Accurate line parameters are critical for and dispatch in distribution systems. External operating condition variations affect line parameters, reducing the accuracy of state estimation and power flow calculations. While many methods have been proposed and obtained results rather acceptable, there is room for improvement as they don’t fully consider line connections in known topologies. Furthermore, inaccuracies in measurement devices and data acquisition systems can introduce noise and outliers, impacting the reliability of parameter identification. To address these challenges, we propose a line parameter identification method based on Graph Attention Networks and Multi-gate Mixture-of-Experts. The topological structure of the power grid and the capabilities of modern data acquisition equipment are utilized to capture. We also introduce a multi-task learning framework to enable joint training of parameter identification across different branches, thereby enhancing computational efficiency and accuracy. Experiments show that the GAT-MMoE model outperforms traditional methods, with notable improvements in both accuracy and robustness.

Convolutional neural network approach for fault detection and characterization in medium voltage distribution networks

Power outages significantly impact the power industry by disrupting social welfare and economic stability. Still, existing methods for fault detection face challenges due to load and network topology, conditions, and installed equipment. However, recent advances in artificial intelligence (AI) are enabling researchers to create alternative approaches for fault detection and location strategies. Therefore, this paper introduces a novel method for detecting, classifying, and locating faults in power systems through voltage waveform analysis using a convolutional neural network (CNN) integrated with the Piecewise Function Put Together (PFPT) algorithm for fault detection and fault zone localization in a power distribution network. Utilizing Park's transformation, noise reduction PFPT sine fitting, and CNNs, the proposed method distinguishes between 'healthy' and 'faulty' conditions. Simulation results reveal that while the voltage Park's vector time behavior of a healthy system remains stable, it exhibits circular or mixed patterns under faulty conditions. These patterns enable the identification of four types of short circuit faults—single-line-to-ground (LG), line-to-line (LL), line-to-line-to-ground (LLG), and three-line (3L) faults—by analyzing 3D voltage Park's waveforms at network buses. The study validates fault type identification through the observation of rotating Park vectors from sine fitting of time-based voltage waveforms. By converting 3D voltage waveforms into high-resolution images, the method utilizes a CNN for fault recognition, achieving an accuracy of 93.1%. This innovative approach underscores the robustness and precision of combining traditional electrical engineering techniques with modern AI.

Fault Line Selection of Small Current Grounding System Research Based on Zero Sequence Circuit Current Phase

Abstract This paper investigates fault line selection in small current grounding systems, focusing on the zero sequence current phase characteristics. Small current grounding systems, prevalent in medium voltage distribution networks, face challenges in fault detection due to minimal fault currents during single status phase grounding faults. Traditional methods relying on manual line switching and zero sequence voltage monitoring are inefficient and can induce overvoltage. This study categorizes fault line selection techniques into three approaches: steady-state fault information, transient information, and modern signal processing technology. The analysis of zero sequence currents in non-grounded systems reveals that fault line zero sequence currents equal the sum of system capacitive currents, flowing opposite to those in non-fault lines. Additionally, transient signal analysis shows that these signals provide more robust information for fault detection. MATLAB simulations validate the theoretical models, demonstrating that zero sequence current direction and amplitude effectively identify fault lines. The results confirm the efficacy of combining steady-state and transient signal analyses for accurate fault line selection, contributing to enhanced safety and reliability in power distribution networks. This research offers practical insights and tools for engineers, improving fault management and reducing potential economic losses in small current grounding systems.

A low voltage load balancing distribution method considering street information and V2G technology application

The low-voltage distribution network (LVDN) is the final stage in delivering electric energy from power plants to consumers, and its operational condition greatly impacts many power users. While medium-voltage and high-voltage distribution networks can be managed through intelligent digital systems, load imbalance issues in LVDNs often rely on planners’ experience, leading to significant limitations. With advancements in electric vehicle (EV) charging technology and vehicle-to-grid (V2G) technology, where EVs act as distributed energy storage units, bidirectional energy exchange between vehicles and the grid can now contribute to LVDN operation. This paper proposes a low-voltage load distribution planning method that integrates street information and V2G technology. A two-stage stochastic programming mixed-integer model is developed to tackle load imbalance in LVDNs, with the planning scheme derived from solving this model. A case study is presented to verify the effectiveness of the method, demonstrating that incorporating V2G technology enhances load distribution accuracy and reduces reliance on manual planning, improving network stability and operational efficiency.

Probabilistic Assessment of the Impact of Electric Vehicle Fast Charging Stations Integration into MV Distribution Networks Considering Annual and Seasonal Time-Series Data

Electric vehicle (EV) fast charging stations (FCSs) are essential for achieving net-zero carbon emissions. However, their high power demands pose technical hurdles for medium-voltage (MV) distribution networks, resulting in energy losses, equipment performance issues, overheating, and unexpected tripping. Integrating FCSs into the grid requires considering annual and seasonal variations in EV fast-charging energy consumption. Neglecting these variations can lead to either underestimating or overestimating the impacts of FCSs on the networks. This paper introduces a probabilistic method to assess voltage profile violations, overload capacity, and increased power losses due to FCSs. By incorporating annual and seasonal time-series data, the method accounts for uncertainties related to EV fast charging. Applied to an MV feeder in Brazil, our evaluations highlight the impact of annual power consumption seasonality on EV-grid integration studies. Considering seasonal dependency is crucial for precise impact assessments of MV distribution networks. The proposed method aids utility engineers and planners in quantifying and mitigating the effects of EV fast charging, contributing to more reliable MV grid integration strategies.

A security-aware dynamic hosting capacity approach to enhance the integration of renewable generation in distribution networks

Hosting capacity (HC) describes the electricity network’s ability to accommodate distributed generation (DG) without deteriorating electrical performance indicators. Distribution system operators typically express their networks’ HC as a single threshold, called static hosting capacity (SHC). SHC is determined via conservative regulatory criteria, increasing connection costs and time. This paper explores the potential for additional energy injection into the network via dynamic hosting capacity (DHC). A network node’s DHC is derived from the hourly operation of the network, accounting for the time variability of existing distributed generation (DG) output and demand. The methodology considers the network assets’ N-1 contingencies and their probabilities, defining the security-aware DHC (SDHC). The SDHC definition is technologically neutral. Through a case study of a radial medium voltage distribution network, the paper highlights the significant limitations of SHC due to conservative calculation criteria mandated by regulators. Annual injectable energy is increased by 62% to 76% when comparing DHC to SHC. Variations between average DHC and SDHC are below 0.01% due to low N-1 probabilities. This finding points out the potential of dynamic hosting capacity definitions, allowing more efficient use of the existing network and facilitating the integration of new DG capacity with reduced connection costs and time.

Optimal planning of photovoltaic and distribution static compensators in medium-voltage networks via the GNDO approach

This research employs the generalized normal distribution optimizer (GNDO) to address the simultaneous integration of solar photovoltaic (PV) sources and distribution static compensators (D-STATCOMs) in medium-voltage distribution networks. Through a discrete-continuous codification process, the GNDO method determines the optimal locations (nodes) and capacities (sizes) of PV systems and D-STATCOMs. A power flow approach based on the successive approximations method is used to solve the power flow equations and assess the solution's technical characteristics, including voltage profiles and power injections. Using a master-slave optimization strategy, the GNDO and the power flow method are used to address the studied problem. Numerical results in the 33- and 69-bus grids demonstrate the effectiveness of the proposed approach, showing superior performance compared to the vortex search algorithm (VSA) and the sine-cosine algorithm (SCA). The results indicate reductions of approximately 35.5554% and 35.6839% when using the GNDO in both test feeders. Additionally, the GNDO reduces the computational efforts required to find solutions in both test feeders, in comparison with the VSA and the SCA. All numerical validations were performed using MATLAB 2024a.

A method for measuring capacitive current in distribution networks based on injection signal method

Abstract In view of the problems that exist in the current distribution network, such as the narrow range of measurement capacitance to the ground and the difficulty of selecting the appropriate signal frequency. Based on the phasor method, this paper proposes a method for measuring capacitance current in a distribution network based on injected signal and analyzes and calculates the error of the method. The measurement technique involves inputting two constant-amplitude signals—one high-frequency and one low-frequency—into a zero-sequence PT (Potential Transformer) configured with an open delta connection. Based on the equivalent circuit models for both high and low-frequency signals, the high-frequency signal’s increased frequency allows the magnitude to be disregarded, simplifying the calculations. Using a simplified equation for the low-frequency signal component, this method enables rapid calculation of the capacitor current in the distribution network. Based on MATLAB software, the simulation calculation model is established, and the simulation results show that the measurement method is simple to calculate and has high accuracy, which can be used to measure the large-capacity grounding capacitance current test, so as to improve the measurement accuracy of the capacitance current of medium and low voltage distribution network.

Coordination of medium-voltage distribution networks and microgrids based on an aggregate flexibility region approach

The large-scale integration of distributed energy resources (DERs) presents operational challenges for medium-voltage distribution networks (MVDNs) and microgrids (MGs) because the conventional centralized scheduling framework lacks of an effective information exchange mechanism for coordinating the scheduling between MVDNs and MGs while supporting privacy concerns. The present work addresses these issues by leveraging a convex hull-based aggregate flexibility region (AFR) associated with the scheduling capability of massive DERs to coordinate the scheduling between an MVDN and MGs efficiently with very limited information exchange. Specifically, the AFR associated with the DERs in an MG is constructed based on the convex hull fitting method, and coordinated scheduling is facilitated by introducing safety operation constraints for the MVDN based on the AFRs of the MGs. Moreover, the coordination model is transformed into a readily solvable quadratically constrained quadratic programming problem by applying second-order cone transformations. The results of numerical computations applied to an IEEE 33-bus test system demonstrate that the obtained AFRs effectively characterize the flexible scheduling capability of DERs, and the proposed coordinated scheduling mechanism between the MVDN and MGs reduces the network losses and voltage deviations of the MVDN, while preserving information privacy.

Low and medium voltage distribution network planning with distributed energy resources: a survey

Abstract The penetration of distributed energy resources (DERs) such as photovoltaic systems, energy storage systems, and electric vehicles is increasing in the distribution system. The distinct characteristics of these resources, e.g., volatility and intermittency, introduce complexity in operation and planning of the distribution system. This paper first summarized the physical characteristics and morphological evaluation of the current and future distribution networks. Then, the impact of these changes on system operation and planning is outlined. Next, the tools, methods, and techniques for energy forecasting, optimal planning, and distribution system state estimation are reviewed and discussed, along with the challenges. As the main contributions, this research systematically organized the published works and assessed the relevant milestones regarding distribution system planning with DERs and emerging technologies. Finally, the key research directions in this domain are outlined. Graphical abstract

Cascade model predictive control strategy for medium voltage flexible interconnected systems with arc suppression capability under single phase grounding fault

The distribution network faces problems such as diversified electricity demand and difficulty in ensuring power quality. At the same time, complex working environments often lead to brief single-phase ground faults, resulting in zero sequence currents in the distribution network. The flexible interconnection system of medium voltage distribution network plays an important role in balancing loads and providing electrical reliability. This article uses a three-phase four-wire converter as a flexible interconnection device, injecting zero sequence current into the neutral point through the fourth bridge arm. Simultaneously, a novel control strategy for medium voltage flexible interconnected systems based on cascaded model predictive control is proposed. The simulation and experimental results demonstrate the effectiveness of the proposed control strategy, which comprehensively achieves power mutual benefit, neutral point displacement voltage suppression, and active arc suppression during single-phase grounding faults in flexible interconnected systems.

Architecture Research on Differentiated Lightning Protection of Distribution Network Considering Plateau Microtopography

Abstract Lightning is the main and severe threat to 10kV and 35kV medium-voltage distribution networks. It will cause equipment failures or damage, tripping and even power outages. With the construction of modern distribution networks, the requirements for power supply reliability are getting higher and higher. Therefore, lightning protection of distribution networks has received great attention. The key point is to find a cost-effective way to protect against lightning. This paper proposed an architecture for differentiated lightning protection of distribution networks considering plateau micro-topography. The main idea is to take multiple measures to obtain rich data, including a lightning positioning system, 3D laser scanning and digital elevation model. Differences in lightning parameters, line and tower parameters, topographic parameters are thought to bring different lightning tripping rates for each tower. Then tripping rate of each area element is obtained through meshing and discrete calculation. Total tripping rate is finally obtained by summation of all elements. The proposed architecture plans to provide a clue for differentiated lightning protection for the distribution network.

Evaluation of maximum power supply carrying capacity of medium-voltage distribution network considering feeder segment transfer

Evaluation of maximum power supply carrying capacity of medium-voltage distribution network considering feeder segment transfer

A Fuzzy OLTC Controller: Applicability in the Transition Stage of the Energy System Transformation

This paper introduces a Fuzzy Logic Controller designed for an on-load tap changer within medium voltage distribution systems with bulk penetration of Distributed Energy Resources. As the on-load tap changer remains one of the most essential forms of voltage regulation in medium voltage distribution networks, improving its operation is a cost-effective response to the emerging voltage violations caused by intermittent generation during the early stages of the energy system transformation. Software-in-the-loop simulations were conducted to validate the effectiveness of the proposed algorithm compared to the conventional methods. A modified CIGRE Medium Voltage Distribution Network Benchmark in European Configuration was modelled while the controller code developed in Python 3.12 was running on a PC, both coupled in a real-time closed-loop environment. The analyses showed that the proposed algorithm managed to reduce overvoltage from 7.02% to 4.85% in the benchmark network, thus demonstrating that the algorithm is efficient and ready for on-field implementation.

New control scheme for a dynamic voltage restorer based on selective harmonic injection technique with repetitive controller

Repetitive controller and selective harmonic injection technique (SHI) in medium and low voltage distribution networks improve dynamic voltage restorer (DVR) DC bus voltages as well as nullify power quality (PQ) problems. DVRs use sinusoidal pulse width modulation (SPWM) firing control, but DC bus use seems to be limited, affecting density, cost, and power packaging. By adding 1/6th of the 3rd harmonic waveform to the basic waveform, SPWM yields the developed model. According to the findings, 15% of DC bus usage improves and produces high voltage AC. Nevertheless, just control systems perturb PQ. The proposed controller uses feed forward and feedback to enhance transient response and justify stable zero error. 3rd third harmonic injection pulse width modulation (THIPWM) improves total harmonic distortion (THD) in the proposed scheme. Power system computer aided design (PSCAD) simulation produced high accuracy for THIPWM and repetitive controllers.

Ground Fault Routing Method for Flexible Grounding System Based on Transient Zero Sequence Current Comparison

Abstract As a new development direction of the domestic medium voltage distribution network, the flexible grounding method has a rapid expansion trend, and accordingly, the ground fault protection scheme needs to follow up quickly. This paper calculates and analyzes the distribution characteristics of transient electric quantities in the system under different fault conditions by establishing the transient equivalent model of shunt small resistor casting and cutting in the flexible grounding system. It is found that if transition resistance is small, the application of parallel small resistors will cause the transient zero sequence current amplitude of the faulty line to be maximum and have opposite polarity to the healthy line. When transition resistance is high, distribution characteristics of the transient zero sequence current projection component are also the same. Based on the above features, a flexible grounding system ground fault routing method is proposed, which can cope with a variety of ground fault situations in engineering practice with high reliability, and the correctness of the method is verified through simulation.

An Active Voltage-Type Grounding Fault Protection Method for Medium-Voltage Distribution Networks With Neutral Point Voltage Flexible Regulation

An Active Voltage-Type Grounding Fault Protection Method for Medium-Voltage Distribution Networks With Neutral Point Voltage Flexible Regulation

Faulty feeder detection based on the fluctuation characteristics of inflection point dense area for DC distribution network

A flexible direct current (DC) distribution network based on modular multilevel converter (MMC), with the advantages of no phase change failure and fewer current conversion links. It has gradually become the development trend of future medium voltage distribution networks. However, when a single-pole ground fault occurs in the feeder, the converter's low inertia and weak damping characteristics lead to a fast-rising fault current with a high peak value, which is harmful to the system. In this paper, for the difficulty of accurately selecting the faulty feeder when a single-pole ground fault occurs in a radial DC distribution network, a detection method based on the zero-mode current within the inflection point dense area (IPDA) for the fluctuation characteristics of concave and convexity (FCCC) is proposed. Firstly, the zero-mode current of each feeder is processed using a low-pass filter to select the eigen-components; Then, taking second order derivatives of the eigen-components, and the IPDA is established, to find a period in micro measurement to achieve accurate direction correspondence with opposite directions; Again, the data within IPDA is normalized; the criterion is constructed by determining each feeder's FCCC. Finally, the simulation model is built by Power Systems Computer Aided Design to verify that the method can identify the faulty feeder in various situations. Compared with existing methods, the fault detection method proposed in this paper has good stability and can withstand large grounding resistances.

Benders Decomposition-based Coordinated Optimization Method for Medium and Low Voltage Distribution Network with Photovoltaics Access

aims: From the perspective of improving the economic benefit of the distribution network and ensuring the safe operation of the distribution network, the medium and low voltage optimization model with the goal of reducing the operation cost is established. background: Double carbon background and new energy power system policy, a large number of distributed photovoltaic access distribution network caused a great influence, not only on the low voltage distribution network user side power quality impact, photovoltaic full hair also can happen when tide back phenomenon, for the stable operation of the medium voltage distribution network and scheduling, therefore, this paper puts forward a scheduling of the voltage distribution network and low voltage distribution network optimization method, to solve the problems of large-scale distributed photovoltaic access. objective: Reducing operating costs and ensuring the stable and safe operation of the distributed network. method: The optimization problem of medium and low voltage distribution network is decomposed into the main optimization problems of medium voltage distribution network and the sub-problems of optimizing the low-voltage distribution network. An optimal solution is obtained by coordinating the boundary coupling variables between the two problems and solving them iteratively. Finally, the effectiveness of the coordination algorithm is verified by simulating the medium and low voltage distribution network. result: A coordinated optimization method for medium and low voltage distribution network with photovoltaics access. conclusion: It reduces the operation cost, ensures the stable and safe operation of the power grid, thus improving the economic benefits. other: None

Power Supply Unit Planning of Distribution Network Including Energy Storage based on N-1 Criterion

In order to realize effective load transfer in medium voltage distribution network when N-1 fault occurs, a method of power supply unit division is proposed. Firstly, according to the content and characteristics of grid planning of distribution network, the principle of power supply unit division is proposed. Then, based on the grid planning of distribution network, the method of power supply unit division is established. Finally, the calculation results show that the division of power supply units based on the power supply grid and energy storage planning improves the line connection rate, meets the N-1 safety check, and improves the safety and reliability of the medium-voltage distribution network.