Medium Voltage Distribution Network Research Articles

Adaptive OCR coordination in distribution system with distributed energy resources contribution

<abstract> <p>More and more distributed energy resources (DERs) are being added to the medium-voltage (MV) or low-voltage (LV) radial distribution networks (RDNs). These distributed power sources will cause the redistribution of power flow and fault current, bringing new challenges to the coordination of power system protection. An adaptive protection coordination strategy is proposed in this paper. It will trace the connectivity of the system structure to determine the set of relay numbers as a tracking path. According to the topology of the system structure, the tracking path can be divided into two categories: the main feeder path and the branch path. The time multiplier setting (TMS) of each relay can be used to evaluate the operation time of the over-current relay (OCR), and the operation time of the relay can be used to evaluate the fitness of the TMS setting combination. Furthermore, the relay protection coordination problem can be modeled to minimize the accumulated summation of all primary and backup relay operation time (OT) subject to the coordination time interval (CTI) limitation. A modified particle swarm optimization (MPSO) algorithm with adaptive self-cognition and society operation scheme (ASSOS) was proposed and utilized to determine TMS for each relay on the tracking path. A 16-bus test MV system with distributed generators (DGs) will be applied to test the adaptive protection coordination approach proposed in this paper. The results show that the proposed MPSO algorithm reduces the overall OT and relieves the impact on protection coordination settings after DG joins the system. The paper also tests and compares the proposed MPSO with other metaheuristic intelligence-based random search algorithms to prove that MPSO possesses with increased efficiency and performance.</p> </abstract>

Reliability modeling of multi-terminal DC circuit breaker and its impact on multi-terminal DC distribution network

In the medium-voltage distribution network, the multi-terminal DC circuit breaker (MTCB) is one of the key pieces of equipment for the connection of multi-terminal converter stations and rapid fault isolation in the future. The reliability level of the multi-terminal DC distribution network is directly impacted by reliability of MTCB. In this paper, the main topological structure and basic working principle of MTCB are systematically analyzed. Then, taking the three-terminal hybrid DC circuit breaker which has been applied in the Zhuhai Tangjiawan “Internet plus” Demonstration Project of China Southern Power Grid (hereafter referred to as Zhuhai Demonstration Project) as an example, the reliability evaluation model of the MTCB is established based on the engineering reliability principle and considering the redundancy level of device. By calculating multi-dimensional reliability index, the reliability of MTCB under different design modes and redundancy levels is analyzed, and the influence of MTCB on the reliability of multi-terminal DC distribution network is further studied based on the minimum cut set method. The influence of the MTCB on the reliability of multi-terminal DC distribution network of Zhuhai Demonstration Project is then studied. Finally, an example of the three-terminal DC distribution network structure of Zhuhai Demonstration Project is analyzed to confirm the accuracy and effectiveness of the proposed model.

Nodal Monitoring in Medium Voltage Distribution Grid using Smart Sensored Cable Termination

Tata Power-DDL worked in collaboration with 3M on a pilot project for making the medium voltage distribution network smart and efficient. This project aimed at enabling real-time monitoring of electrical parameters such as voltage, current and reactive-power-flow. While enabling these features, it was vital to make the solution compact and retrofit-to-existinginfrastructure for saving cost in terms of reduced equipment’s footprint. In this pilot project, electrical parameters and direction of power flow were accurately captured using sensor-based technology. Captured parameters and corresponding benefits are analyzed in detail in this paper. Further, the availability of real-time captured data can be potentially used through analytical tools for enabling many features such as predictive maintenance and identifying faulted-segments in underground cabling networks. Power-flow-direction can potentially be used for advanced protection coordination in the looped distribution network. Thus, enabling reliable integration of existing grid with distributed energy generation source.

A new method for online evaluation of the effects of PV panels and comparison with MVDI in electrical power distribution networks

With the increasing penetration of PV, LV distribution networks experience the condition of reverse power flow and also voltage increase in a part of the network. As a result, the capacity of the installed feeders is approximately within the range of the nominal value defined for them. Therefore, the proper assessment of the impact of PV in distribution networks seems necessary. In this paper, we have investigated the effect of PV systems in low-voltage and medium-voltage (MV) distribution system, and suitable online strategies were presented to alleviate these problems. In this regard, comprehensive modeling and analysis for LV and MV distribution networks have been performed. Therefore; this will allow the proper allocation of PV systems in the network. Using the approach as mentioned above, PV networks can be modeled for medium-voltage three-wire systems and low-voltage four-wire systems, which include Y-Δ transformers and ground impedance. PV systems modeling based on temperature , and ambient radiation data, inverter efficiency, PV panel parameters and V-I feature will be done. By using the above approach, it will be possible to optimally allocate PV systems in LV and MV distribution networks. In addition, a suitable method for carrying out load flow in distribution systems along with PV systems is provided, and in this regard, a suitable design will be proposed to analyze the effect of PV systems in distribution networks. Based on this plan, which was based on stabilizing the voltage of the network feeders at a nominal value, it was shown that the changes in the working conditions for PV systems in the presented algorithm and structure cannot have a negative impact on the network performance.

Aging aware adaptive control of Li-ion battery energy storage system for flexibility services provision

Battery energy storage systems (BESSs) play a major role as flexible energy resource (FER) in active network management (ANM) schemes by bridging gaps between non-concurrent renewable energy sources (RES)-based power generation and demand in the medium-voltage (MV) and low-voltage (LV) electricity distribution networks. However, Lithium-ion battery energy storage systems (Li-ion BESS) are prone to aging resulting in decreasing performance, particularly its reduced peak power output and capacity. BESS controllers when employed for providing technical ancillary i.e. flexibility services to distribution (e.g. through ANM) or transmission networks must be aware of changing battery characteristics due to aging. Particularly of importance is BESSs' peak power changes aiding in protection of the Li-ion BESS by restricting its operation limits of it for safety reasons and improving its lifetime in the long run. In this paper, firstly an architecture for ANM scheme is designed considering Li-ion BESSs as one of the FERs in an existing smart grid pilot (Sundom Smart Grid, SSG) in Vaasa, Finland. Further, Li-ion BESS controllers are designed to be adaptive in nature to include its aging characteristics, i.e. tracking the changing peak power as the aging parameter, when utilised for ANM operation in the power grid. Peak power capability of the Li-ion nickel‑manganese‑cobalt (NMC) chemistry-based battery cell has been calculated with the experimental data gathered from accelerated aging tests performed in the laboratory. Impact of such aging aware and adaptive Li-ion BESS controllers on the flexibility services provision for power system operators needs will be analysed by means of real-time simulation studies in an existing SSG pilot.

A Deep Learning Technique for Detecting High Impedance Faults in Medium Voltage Distribution Networks

Utility companies always struggle with the High Impedance Fault (HIF) in the electrical distribution systems. In this article, the current signal is seen in situations involving 10,400 different samples, with and without HIF, like linear, non-linear load, and capacitance switching. A better method that processes signals very fast and with low sample rates, requiring less memory and computational labor, is demonstrated by Mathematical Morphology (MM). For HIF identification, Deep Convolution Neural Networks (DCNNs) are being developed. This paper presents a novel method for signal processing with low sample rates, high signal processing speed, and low computational and memory requirements. The suggested six-layer DCNN is compared with other models, such as the four-layer and eight-layer DCNN models and the results are discussed.

Research on Line Selection Technology for Two-point Same-phase Ground Faults in Medium-voltage Distribution Networks

At present, the problematic line selection method for single phase grounding faults of the small current grounding system has been mature, but line selection method for two-point same-phase ground faults is rarely studied. For the problem that the accuracy of line selection equipment is low for two-point same-phase ground faults, a fault model is established and the fault signatures are analyzed theoretically. As the faulty line zero-sequence current is affected by more factors, it is not possible to select the line with the common line selection technology for single-phase grounding faults. By further theoretical derivation, a new method for successive judgment of faulty lines is proposed, and the correctness of problematic characteristics and the feasibility of line selection technology are verified to many different cases by simulation using the ATP simulation experimental platform.

Intelligent Detection Algorithm of Medium and Low Voltage Switch Performance Based on the Improved K-means Clustering

The performance of medium and low voltage switches will directly affect the reliability of medium and low voltage distribution networks. The medium and low voltage switch algorithm’s failure form is mainly mechanical. In order to realize its intelligent detection, a medium and low voltage switch detection algorithm based on the improved K-means clustering algorithm is proposed. Optimizing the algorithm’s clustering center selection establishes a model of the switch working state under different vibration signals and an intelligent detection algorithm for medium and low voltage switches with intelligent judgment, adaptive adjustment, and remote fault diagnosis. Experiments show that: the detection algorithm of the medium and low voltage switch controller based on the improved K-means algorithm can more accurately identify the fault of the switch algorithm according to the vibration signals, which provides a new idea for the fault identification and monitoring of the medium and low voltage switch.

Implementation of Unbalanced Thermoelectric Equivalent Circuit for Power Flow and Thermal Rating of Underground LV and MV Cables

This manuscript proposes a time-series temperature-dependent power flow method for unbalanced distribution networks consisting of underground cables. A thermal circuit model for unbalanced three-phase multi-core cables is developed to estimate the conductor temperature and resistance of Medium (MV) and Low Voltage (LV) distribution networks. More specifically, a novel approach is proposed to model and estimate the parameters of the three-phase thermal circuit of 3- or 4-core cables, using the results of Finite Element Method and Particle Swarm Optimization. The proposed approach is generic and can be accurately applied to any kind of 3- or 4-core cables buried in homogeneous or non-homogeneous soil. Furthermore, it is applicable in cases where one or more adjacent cables exist. Using the proposed approach, the conductor temperature of each core can be individually and precisely calculated even under unbalanced loading conditions. The proposed approach is expected to be an important tool for simulating unbalanced distribution networks and estimating the conductor temperatures. The proposed thermal circuit is validated using two 4-core LV and one 3-core MV cables buried in different depths in homogeneous or non-homogeneous soil. Time-series power flow for a whole year is performed in a 25-bus unbalanced LV network consisting of multicore underground cables.

Mapping of Electrical Distribution Networks at Jampit Distribution Substations Using ArcGIS

In the Ijen sub-district, care must be taken to avoid overlapping uses of PTPN XII-owned plantations, resident fields, and the medium-voltage power distribution network. To lessen the interference factor in the distribution of electricity, the proper power distribution path must be chosen. The contact between trees and lightning is one of the variables that disturbs the distribution pathway. It is well known that the Jampit distribution substation in the Ijen district is situated in a region with plantations and private fields, making it susceptible to lightning and contact with trees. The position of distribution substations, medium-voltage overhead lines, and the location of energy users are among the issues examined in this study. In order to create a map of the electricity distribution network at Jampit distribution substations that pass through agricultural land and plantation areas, ArcGIS is used to help process spatial data including regional administration data, type of conductor, power capacity, distribution substation poles and electricity users.

A Two-Layer Control Strategy for Soft Open Points Considering the Economical Operation Area of Transformers in Active Distribution Networks

A soft open point (SOP) can improve the flexibility of power control and thus further enhance the reliability and economy of distribution networks. However, existing SOP regulation strategies have mainly focused on feeder imbalance regulation and line loss optimization in medium-voltage distribution networks, and the loss of SOPs and distribution transformers are often ignored, which has poor applicability in low-voltage distribution network (LDN). Therefore, a novel two-layer control strategy is proposed for SOPs working in LDN, which can improve economy and reliability of the system simultaneously. In terms of the system layer, the proposed load regulation strategy considering the economical operation area of the transformers can improve the system economy while realizing load imbalance regulation. In terms of the equipment layer, the proposed peer-to-peer control of each port in the SOP can effectively suppress the voltage fluctuation on the DC side. Thus, the system layer commands can be quickly tracked and well conducted. Finally, the feasibility and effectiveness of the proposed two-layer control strategy are verified by simulation and experimental results.

A Study of Lightning Performance to Multi-grounded System of KEPCO MV and LV Distribution Network

This paper presents the indirect lightning performance evaluation of Korea Electric Power Company (KEPCO) medium voltage (MV) and low voltage (LV) lines. The main topic of this paper is to analyze an effect of the grounding systems on the indirect lightning performance of MV and LV distribution lines. To this end, we define the models of the MV and LV distribution systems for the analysis of distribution line surge overvoltage due to lightning. With reference to the data typically adopted by KEPCO, the research describes and motivates the use of the most suitable models of distribution lines, transformers, and surge arresters (SAs) to be implemented in EMTP like simulation environments. The sensitivity of the lightning performance of the distribution lines to different configuration of MV and LV grounding systems, distance between SAs, as well as presence of overhead ground wires is also analyzed. Regarding overvoltage, both the temporary overvoltage and the surge overvoltage are considered. The presence of SAs at the MV terminals of distribution transformers is also considered.

Simultaneous Planning of the Medium and Low Voltage Distribution Networks under Uncertainty: A Bi-Level Optimization Approach

Distribution network expansion planning (DNEP) is one of the important matters in the field of planning and operation of electrical power systems. Since many costs and losses have occurred in the distribution networks, it has increased attention towards this network. The electrical energy distribution network is divided into two parts: the medium voltage (MV) network and the low voltage (LV) network. The main problem in this field is that planning is done either only on the MV network or only on the LV network. While planning in each of these networks has a significant effect on the other networks, this important case has not been considered in most research studies. Therefore, this study has tried to do integrated planning in the form of a bi-level model in the presence of different types of distributed generations (DGs) and consider the uncertainties of renewable sources and load demand in both MV and LV networks so that the planning and operation costs are minimized. In the proposed bi-level model, the upper-level section aims to minimize the investment and the operation cost of the MV network, and the lower-level problem minimizes the investment and the operation cost of the LV network considering the DGs and pollution emission. The obtained results show the effectiveness of the proposed model.

Two‐phase BESS optimization methodology to enhance the distribution network power quality and mitigate violations

AbstractThis paper proposes a two‐phase optimization methodology to optimally dispatch the active/reactive power of battery energy storage systems (BESS) installed on the medium voltage distribution network to manage the violations and enhance the power quality and security. The first phase is look‐ahead scheduling that aims to flatten the grid power curve and optimize the network power factor over the scheduling horizon using forecasted demand and generation. The second phase is a real‐time model predictive control (MPC) introduced to adjust the BESS real power setpoints against network violations due to high uncertainties associated with the renewable generation and low carbon technologies as well as other unexpected events. Simulations were carried out for an actual 11 kV, 53‐node distribution network located in Northern Ireland for two case studies representing the winter and summer. The results demonstrate the effectiveness of the proposed methodology in enhancing the network operation through optimizing the power factor, reducing line losses, and mitigating stresses. Sudden over/under voltage events were solved through the real‐time phase efficiently without affecting the power factor or the line losses in a fast manner with a computation time of 0.52 s/time‐point which makes it suitable for real‐time control implementation.

Distribution Network Grid Planning and Automatic Routing Based on Cluster Analysis Algorithm

In order to improve the efficiency of power grid enterprises under the background of new power reform, the author proposes a set of planning ideas and methods for medium-voltage distribution networks based on the optimal division of power supply grids. First, the layout of the main channel in the planning area should be determined to ensure the reservation of land resources. Then, on the basis of clarifying the purpose and principle of grid division, based on the selection of the nearest load backup substation and the load clustering method, the optimal division of the power supply grid should be realized on a global scale. Finally, in each power supply grid, the wiring mode and the primary and secondary construction and renovation standards are selected based on the classification of the supply area, and the main line wiring planning is carried out. For the grid frame in the transition year, in order to avoid repeated reconstruction and facilitate construction, the principle of piece-by-piece construction and reconstruction is proposed. The results show that by the target year, each power supply grid in the planning area will use two substations as power points, the power supply range of the main lines of each grid is limited to this grid, the lines between grids will not be connected, and the line connection rate will reach 100% and all meet the N-1 check. The proposed method follows the basic planning concept of “technically feasible and economically optimal” on the basis of overall planning and transforms the complex global planning of distribution network into local planning within each optimized grid, and it enables different planners to obtain a basically consistent grid optimization scheme, strengthens the scientificity and certainty of planning, and provides a reference for the revision and refinement of relevant guidelines, which has been practically applied.

Comprehensive Economic Benefits Evaluation Model of Greenhouse Photovoltaic

Abstract: Photovoltaic integrated greenhouse has become an important form of deep coupling between new energy power generation and facility agriculture. Greenhouse photovoltaic power generation will affect the light environment, thermal environment, and water environment of facility agriculture. The precise coupling modeling method of greenhouse photovoltaics and loads is to carry out the basis for the calculation of comprehensive economic benefits of greenhouse photovoltaics. This paper studies the deep coupling modeling method of greenhouse photovoltaic and greenhouse load, and accurately calculates the changes in the light environment, thermal environment, and water environment regulation load of facility agriculture caused by the laying of greenhouse photovoltaics. Firstly, the greenhouse photovoltaic power generation model and the environmental regulation load model of facility agriculture are established; secondly, the coupling relationship between greenhouse photovoltaic power generation and facility agricultural load is described, and on this basis, the comprehensive economic benefits evaluation model of photovoltaic power generation is proposed. The 10kV medium-voltage distribution network and facility agricultural greenhouse that exist in the northern region are used as the research objects. It verifies the validity of the photovoltaic comprehensive economic benefits evaluation model proposed in this paper.

Research on Data-Driven Distribution Network Planning Method

With the development of the intelligent and interactive power system, the elements of distribution network planning continue to increase. The distribution network connects the transmission system and individuals, directly affects the individual’s power consumption experience, and is a key link in the power system. A reasonable planning scheme can not only improve the power supply capacity and reliability of the distribution network but also fully apply the data of each system in the distribution network to realize the optimal planning of the medium-voltage distribution network driven by data. Firstly, this paper constructs the CIM model and the distribution network topology model and establishes the wiring pattern recognition feature library. The network reconstruction and planning method research was carried out for the target line, and a typical operation scenario of the distribution network was generated. At the same time, based on the time period network loss index, the distribution network reconfiguration optimization model and distribution network expansion planning model are established, and the solution method of the distribution network reconstruction and expansion planning model is expounded. A reconstruction optimization scheme with the best overall network loss performance is in the network operation scenario. The experimental results of the final example show that based on the proposed time period network loss index, the overall operation loss of the distribution network in a period can be calculated more accurately, and the optimized planning scheme is more suitable for the load power consumption characteristics of the region, and the method has certain feasibility.

Modified unified power flow controller for medium voltage distribution networks

Modified unified power flow controller for medium voltage distribution networks

Deep learning technology of Internet of Things Blockchain in distribution network faults

AbstractNowadays, the development of human society and daily life are inseparable from the power supply. Therefore, people also put forward higher requirements for the reliability of distribution network, but power companies can only passively deal with distribution network failures, which is a bottleneck for the improvement of distribution network reliability. The Internet of Things (IoT) is the best solution for online equipment status monitoring and basic data sharing for large, widely distributed, relatively fixed, and large numbers of equipment. The construction of the IoT for power distribution equipment faces many important problems, including the selection of networking, equipment selection, and interaction standards. When researching the implementation plan, research on the distribution of IoT market was carried out. Based on the grid, the idea of optimizing the investment selection plan of the power distribution using IoT was discussed, and a result verification model was established. After the completion of the theoretical part, a case study of medium-voltage distribution grid equipment management and medium-voltage distribution network equipment management based on the grid was carried out by taking a real enterprise application situation as an example. Realizing fault diagnosis of distribution network will not only provide decision support for operation and maintenance of distribution network for power companies, but also have great economic and social benefits. Aiming at the shortcomings of single data mining method in distribution network fault diagnosis, hybrid data mining method is proposed. First, rough set theory is used to reduce the original fault data and form a simplified rule set. Because of the non-linearity of distribution network fault and the strong learning ability, adaptability, and robustness of Bayesian network, Bayesian network can be used to classify distribution network faults. Therefore, a simplified fault diagnosis system is established in this paper, and its correctness is confirmed. Then, the learning and training are carried out by using Bayesian network to call the simplest rule set, which has the characteristics of short learning and training time and high diagnostic accuracy.

Voltage regulation of a remote microgrid bus with a modular multilevel STATCOM

This paper presents a strategy to control the voltage at a remote bus of a distribution network by using a modular multilevel static synchronous compensator. The mathematical models presented in this paper are based on the transfer impedance of the nodal admittance matrix of the system. They allow building a voltage control loop in the dq-reference frame to regulate the voltage of a remote bus of the power system. As the mains’ impedance may vary during the system operation, the ac voltage control loop is designed considering the worst case to ensure the correct operation of the voltage control loop. It is also shown how the variation of the mains’ inductance impacts the voltage control of the remote bus. Moreover, it is shown that the use of a PI controller provides a better margin phase for the remote bus voltage control loop. A static synchronous compensator based on the modular multilevel converter, with 28 submodules per leg, is modelled in an electromagnetic transient program and connected to a medium-voltage distribution network based on the IEEE 14 bus system. Lastly, an heuristic algorithm is used to regulate the reference signal of the ac voltage control loop so that the PCC voltage does not exceed its voltage limit. It is shown that this algorithm can reconcile the regulation of the remote bus voltage and the PCC voltage limit.