Substation Capacity Research Articles

An integrated approach to improving the ability of power systems to accept distributed PV

At this stage, the main way to develop solar resources is to use the photovoltaic effect as a basis for solar power generation. The article first outlines the problems faced by the power system in accepting distributed photovoltaics, then discusses the “measures to strengthen the power system’s ability to accept distributed photovoltaics”, and proposes measures from the source-load side, the grid side, and the interaction between the two sides. Satisfying the interval number constraint, line transmission capacity constraint, substation capacity constraint, and total investment constraint of the grid-connected line, the optimal access method can give full play to the acceptance capacity of the current grid, and finally, the weak link analysis of the acceptance capacity of the distribution grid is carried out with a regional distribution grid as an example. It is hoped that the discussion in this paper will inspire people in some way and contribute to the effective integration of the power system and distributed PV.

Data-driven assessment for the supervision of District Heating Networks

There is an ongoing trend towards temperature reduction in District Heating Networks, allowing for the reduction of distribution heat loss and enabling the integration of low exergy heat production systems. There is a clear scientific consensus on the improved sustainability of such systems. However, there is not sufficient knowledge on how to deliver a successful transition to a low temperature District Heating system, while ensuring the operational levels of the existing system. This paper presents the experience on the progressive temperature reduction of a district heating subnetwork over the 2018–2021 period in Tartu, Estonia. Data from heat meters is extensively used to assess the capacity of substations and network branches to deliver the required heat and quality levels. Faulty substations are identified for targeted assessment and improvement works. Several substations have been identified as missing some of the performance criteria. This has led to further analysis, closer supervision and interventions in the operational conditions of the network. This is an ongoing process, expected to remain in the established procedures of the DH network operator. At the end of the process, a temperature reduction of 7 ºC has shown an improvement of 4.8% in network heat loss.

The Optimal Sizing of Substation Capacity in a Distribution Network, Considering a Dynamic Time-of-Use Pricing Mechanism.

Application of sensors in the smart grid has promoted the development of demand side management (DSM). However, the incentives of DSM such as peak–valley time-of-use (TOU) price will change the load pattern in the future; the substation capacity sizing will be further influenced accordingly. This paper proposes a substation capacity sizing method in distribution network considering DSM and establishes a peak-valley TOU pricing method based on the cost–benefit analysis of each participant in the TOU price. Compared with the conventional fixed peak–valley ratio, a dynamic division method is proposed to calculate the optimal pull-off ratio for the TOU pricing. By considering the proposed TOU pricing method, a substation capacity sizing model for the distribution network is further proposed. Finally, the economic benefits of the two substation capacity sizing schemes are compared and evaluated according to the selected economic indicators. The results of the case study demonstrate that under the premise of reasonable pricing, considering the impact of TOU on substation capacity sizing, the construction investment and the user cost of power supply companies can be saved while meeting the power demand. The economy and rationality of the planning scheme have been significantly improved.

Optimization for Transformer District Operation Considering Carbon Emission and Differentiated Demand Response

With the promotion of the “dual carbon” goal, a large number of distributed photovoltaic power are connected to the distribution network. Since the current operation optimization of the low-voltage transformer district is based on single objectives such as the economy and power reliability, the model is relatively simple and difficult to adapt to the large-scale access of photovoltaics. Therefore, this article comprehensively considers carbon emissions, different load characteristics, and differentiated demand response of the district. An optimization method for low-voltage transformer district operation under the dual-carbon background is proposed. First, the typical structure of a low-voltage transformer district is introduced. Second, the load types and characteristics of the low-voltage transformer district are analyzed, and differentiated demand response models are established for different types of loads. Finally, taking the minimum economic cost and carbon emission as the objective, the low-voltage transformer district operation optimization model considering carbon emission and differentiated demand response is established by considering the voltage overrun of the photovoltaic access point, substation capacity constraint, and carbon emission constraint. The simulation results show that the model can effectively reduce the economic cost and carbon emissions of the low-voltage transformer district, achieve more than 95% reasonable utilization rate of new energy in the low-voltage transformer district, improve the lateral time distribution of load in the low-voltage transformer district, and provide an effective means for low-carbon scheduling of distribution networks.

EV Senseless Orderly Charging Technology for High User Participation Rate in Residential Area

Private cars are the most active and important incremental factor in the electric vehicle market and are expected to account for 80% of the new energy vehicle sales market by 2030. As the most common charging scenario for private cars, orderly charging in the community can optimize the distribution load curve by dynamically adjusting charging time and power of electric vehicles, so as to achieve peak-load shaving and turn electric vehicles into a friendly load to the distribution grid. However, after the traditional orderly charging strategy was released, the complexity of the operation on the user’s side was a heavy strike to the user’s willingness to participate in orderly charging, resulting in the quite low participation rate and insufficient demonstration of the characteristics of EV’s elastic power demand. To solve this issue, the paper proposes a senseless orderly charging strategy with user charging demand prediction and substation capacity constraint considered to minimize user charging fee or maximize service provider revenue. After a five-month practical application, the proposed strategy was found to effectively improve the user participation rate in orderly charging and to regulate electric vehicles as an elastic load to meet the grid demand.

Optimal location for EV supercharging stations directly connected to primary substations - the E-REDES/CME use case

The presented work explores a deployment strategy for supercharging infrastructure inside urban areas near distribution grid primary substations that facilitate the large-scale introduction of EVs, supported by an optimised economic impact from grid investment and social welfare perspectives. Thinking of Electrical Vehicles (EV) supercharging facilities with power levels of 200kW or higher expected to be widely adopted and knowing that low voltage distribution grid will be insufficient to provide supercharging for multiple simultaneous charge events, a direct connection to primary substations presents as a simple and viable solution to the upcoming challenge. The proposed results support on-grid topology analysis, primary substation capacity availability, asset investment cost, and site topography viability. A multiperiod power flow is performed for each selected node to ensure that supercharging facilities connected to the same busbar with simultaneous charging sequences don't violate voltage and current profiles. Different scenarios were explored supported on the charging infrastructure (level 3 supercharges, level 2 fast charges, and combinations of other models to maximise the grid availability). Also, an optimal amount of charging capacity is being computed to cover the demographics of each area. Results are presented with a matrix that defines the required available capacity, geographical area, and grid investment to build an EV supercharging station. Analysis of the benefits and drawbacks for EV users of centralised supercharging hubs versus decentralised charging stations is also considered in this study.

Electrical power supply system planning for a modern catenary-free rapid charging

Electric power supply system planning is practically an important function of the modern light rail transit system with catenary free operation and rapid charging. Installing a modern dynamic load of the traction power supply system with the local electric distribution network needs to consider its capacity and feeder to support enough and efficiently. In this paper, the design of the electrical power supply system of the pilot project of Nakhon Ratchasima Green Line light rail system with 11.6-km line length and 21 passenger stations operated with catenary-free and powered with an on-board energy storage device has been proposed and planned to replace the old local transportation. The traction power supply of the light rail system drawn power from the MV distribution feeder practically consist of receiving power substation, MV power feeding system power feeder substation, charging power supply and service power supply have been designed provided the configuration circuit. A rapid charge system to delivery high power to fulfill the on-board energy storage is considered to recharge at passenger stations with an overhead conductor or wireless power transfer during a short dwell time. A number of charging station is determined accordingly the capacity of the power substation and its positions. The traction power drawn by a train service round-trip that related to the capacity of the power substation as a charging station has been calculated by the simulation of the train movement. The regenerative braking energy during train operated in braking mode is also considered as a partial charging energy the on-board energy storage device. From the proposed design, the motive energy consumption of each scenario charging formations obtains the maximum charging energy drawn by the train between charging points, the capacity of on-board energy storage devices, maximum charging power and the total charging points.

CHARACTERISTICS OF ELECTRIC COMPANIES BY THE NUMBER AND LENGTH OF TRANSMISSION LINES AND SUBSTATION CAPACITY

The article presents statistical data on the number and length of power transmission lines, the number and capacity of substations of different voltage classes in the branches of the Public Joint Stock Company «Rosseti Center and Volga Region». A review of the literature shows that there is no information about the specific values of the length of the power transmission line, substation capacity and transformer capacity per square kilometer and per inhabitant of the regions where the branches of the Public Joint Stock Company «Rosseti Center and Volga Region» are located. (Research purpose) The research purpose is analyzing the structure of electrical companies on the example of the electric company PJSC Rosseti Center and Volga Region. (Materials and methods) In the research was used literary sources, statistical data on the structure of electrical equipment of the Public Joint Stock Company «Rosseti Center and Volga Region» by area and number of residents in the regions where the branches are located. (Results and discussion) Calculations of average and specific values of the number and length of power transmission lines, the number and capacity of substations by branches of the Public Joint Stock Company «Rosseti Center and Volga Region» were performed. The branches were compared according to the specified values, the largest and smallest values of the considered characteristics. (Conclusions) The characteristics of electric companies providing electricity to rural consumers were given on the example of branches of the Public Joint Stock Company Rosseti Center and Volga Region in terms of the number and length of power transmission lines, the number and capacity of substations of different voltage classes, including their specific values. The described characteristics, when further compared with the values of population density, agricultural production indicators and other indicators of the regions, make it possible to analyze the dependence of the development of regions on the characteristics of electric networks and vice versa. The data obtained for January 2022 make it possible to assess the dynamics of the development of grid complexes of branches of the Public Joint Stock Company Rosseti Center and Volga Region.

Distributed Reactive Power Compensation Method in DC Traction Power Systems With Reversible Substations

This paper proposes a potential distributed reactive power compensation method in dc traction power systems with reversible substations. It utilizes the entire capacity of reversible substations during night hours and the reminding capacity except for regenerative braking energy feedback during day hours. A unified dispatch scheme is developed to allocate reactive power compensation capacity for each reversible substation. During night hours the entire capacity is used to accomplish the optimal power flow objective. During day hours the excess capacity after active power production is used to improve the system reactive power factor dynamically. The different objectives throughout the day are implemented in a unified formula which avoids manually change. In addition the outage of reversible substations and the low dc voltage conditions are considered and an over-modulation suppression strategy is included in the unified dispatch scheme to adjust the reactive power allocation among reversible substations. This novel utilization method of reversible substations is able to provide significant improvements in the power factor of dc traction power systems which would otherwise require expensive additional equipment such as static synchronous compensator. Finally the effectiveness of the proposed method is verified with MATLAB/SIMULINK.

Cabin Temperature Regulation-based Charging Strategy for Electric Vehicles Under 5G

As massive EVs are introduced rapidly, large-scale disordered charging loads appear in the power grid, which may lead to "peak plus peak" and overload for local substations. With the rapid development of 5G, the data transmission of large-scale EVs is suggested to help optimizing the orderly charging strategy under cabin temperature control and load control in EVs in this paper. The charging time, charging cost and substation capacity are considered as constraints, so as to optimize the charging period of EVs. It seems that the temperature control dispatching can effectively reduce the disordered charging load of EVs, smooth the overall load curve of the power grid and result "peak shifting and valley filling" of the power grid.

Experimental Validation of a Reduced-Scale Rail Power Conditioner Based on Modular Multilevel Converter for AC Railway Power Grids

Rail power conditioner (RPC) has the ability to improve the power quality in AC railway power grids. This power conditioner can increase the loading capacity of traction substations, balance the active power between the feeder load sections, and compensate for reactive power and current harmonics. At present, there is increasing use of multilevel converter topologies, which provide scalability and robust performance under different conditions. In this framework, modular multilevel converter (MMC) is emerging as a prominent solution for medium-voltage applications. Serving that purpose, this paper focuses on the implementation, testing, and validation of a reduced-scale laboratory prototype of a proposed RPC based on an MMC. The developed laboratory prototype, designed to be compact, reliable, and adaptable to multipurpose applications, is presented, highlighting the main control and power circuit boards of the MMC. In addition, MMC parameter design of the filter inductor and submodule capacitor is also explained. Experimental analysis and validation of a reduced-scale prototype RPC based on MMC topology, are provided to verify the power quality improvement in electrified railway power grids. Thus, two experimental case studies are presented: (1) when both of the load sections are unequally loaded; (2) when only one load section is loaded. Experimental results confirm the RPC based on MMC is effective in reducing the harmonic contents, solving the problem of three-phase current imbalance and compensating reactive power.

Smart grid planning method based on multi-objective particle swarm optimisation algorithm

Smart grid refers to a modern electric energy supply system to tackle a lot of problems in grid management, such as, resource shortage, environment pollution and so on. In this paper, we propose a novel smart grid planning method using multi-objective particle swarm optimisation algorithm. The goal of smart grid plan is to calculate the minimum investment and annual operating costs, when we obtain the planning level of load distribution, substation capacity and power supply area to satisfy the load requirement and optimised substation location. Afterwards, we propose a multi-objective particle swarm optimisation algorithm which integrates the estimation of distribution algorithm. Furthermore, the propose approach divides the particle population into a lot of sub-populations and then build probability models for each population. Finally, experimental results demonstrate that the proposed method can effectively arrange new substation, which is able to make up for deficiencies of current existing substations.

Research on Multi-Scenario Distributed Wind and Photovoltaic Power Accommodation Capacity of Distribution Network Based on Time Series Production Simulation

With the large-scale access of distributed new energy into the distribution network, the evaluation on the accommodation capacity of distributed new energy in the distribution network has important guiding significance for the scientific planning of distributed generation and grid connection. Considering the parked and regionalized development trend of distributed power generation mode, this paper proposes a method for evaluating the distributed wind and photovoltaic power accommodation capacity of regional distribution networks based on time series production simulation from the perspective of practical applications. Based on the timing difference and complementarity of the load characteristics of substations on the distribution network side, we conducted an evaluation on the distributed wind and photovoltaic power accommodation capacity of the regional distribution network, and through taking the flexible operation mode of the distribution network side into consideration, realized the mutual assistance from time domain and space dimension of distributed new energy consumption and carrying capacity of various substations. Through establishing a mathematical model for the consumption and carrying capacity analysis in the multi-scenario modes such as local node consumption, local station consumption and allowing certain percentage of abandoned electricity, we came out the scale of the maximum consumption of distributed new energy in different scenarios as well as the overall grid connection layout scheme. In the end, we used such evaluation method to conduct an empirical analysis on the distribution network in certain region, verified the correctness and effectiveness of the model, and provided theoretical supports for guiding the regional distributed new energy overall planning and scientific grid connection.

Topologies and Operation Modes of Rail Power Conditioners in AC Traction Grids: Review and Comprehensive Comparison

Electric locomotives in AC traction power systems represent a huge single-phase non-linear load and, detrimentally, affect the power quality and the efficiency of the three-phase power grid. Nevertheless, along the last decades, power electronics are being used to mitigate power quality problems in the three-phase power grid. In particular, Rail Power Conditioner (RPC) helps to increase the loading capacity of traction substations and improve the power quality of three-phase power grids. As the main characteristics, an RPC can supply reactive power, suppress current harmonics and overcome currents imbalance of the three-phase power grid. On the other hand, the traction substations may be constituted by different types of power transformers. For instance, single-phase power transformers and open-delta (V/V) power transformers are widely used, while Scott power transformers are less frequently used, since they are more complex and expensive. In this framework, this work presents a review study of RPC topologies, including their operation modes, and a comprehensive comparison between the characteristics of the RPC topologies when using different types of AC traction substations and power transformers. This helps to ensure the correct selection of the RPC topology for a specific application, according to the main structure of the traction substation. Consequently, and based on the established review, it is possible to sort and allocate each RPC topology for limited or wider applications.

대피선을 통한 도시철도 급행화시 전력 부하량 및 변전소 용량 분석

도시·광역철도를 급행화하기 위해서는 전력인프라의 검토가 필요하다. 이 논문에서는 대피선 설치를 통한 급행화 운행 시 전력소비량과 변전소의 급전 용량의 변화를 실계통 데이터를 기반으로 분석하였다. 인천1호선을 대상으로 모의를 진행하였으며, 열차주행 시뮬레이션과 전력 시뮬레이션 두 단계를 통하여 전력조류해석을 시행하였다. 공급하는 전력량을 분석한 결과, 급행화 시 노선의 중간에 위치한 변전소들은 공급하는 전력량이 줄어드는 경향을 보였으며, 연장급전 시에도 비슷한 경향을 보였다. 변전소의 공급용량 변화량도 검토하였으며, 연장급전까지 고려하여 결정된 변전소의 공급용량이었기 때문에 급행화가 이루어져도 공급용량이 부족하지 않았다.

Increasing the parameters of electrical distribution networks of town districts with low load density

This article presents the results of research on the parameters of electrical networks with a voltage of 6 (10) and 0.38 kV in relation to capital investments. The analysis of existing methods of estimation of parameters before designing for power supply networks in a small town with low load density is carried out. In modern conditions, in the distribution of electrical networks is of paramount importance the introduction of energy-saving schemes and parameters of power supply systems. One of the main ways to implement them is to increase the efficiency of 6-10 / 0.38 kV networks. In the actual design of electrical networks, economic proportionality can not always be maintained for various reasons: the impact of technical constraints, the discreteness of the rated power of transformers and cable crossing scales, a significant deviation of individual capacities of consumers from the average value. In that case there is an increase in the reduced costs. A methodology for determining the optimal power of transformer substations and optimal sections of 0.38 kV power transmission lines is proposed, taking into account the probable nature of the applied load. When assembling the power supply circuit for the optimal form of parameters, voltage, principles of voltage regulation and reactive power compensation. Decisions of this kind are substantiated by technical and economic comparisons of a series of technically acceptable variants of power supply networks. An important measure that facilitates the selection of the most economical option is the assessment of the proposed project, which relates to the selection of the optimal capacity of transformer substation (TS) networks using calculation formulas. The aim of the research was to improve the existing methods on the basis of separate accounting of the reliability coefficient of 0.38 kV and 6-10 kV network. Key words - electric power supply network, network parameters, transformer substation, load density, line wire section, specific load, unit costs, optimum parameter, distribution networks, electric energy.

Vehicle Air Conditioner Temperature Regulation-based Orderly Charging Strategy for Electric Vehicles

Due to high power load peaks and long durations in extreme weather conditions, as well as large-scale unscheduled electric vehicles charging, it may cause “peak plus peak” loading in local areas of the power grid, moreover, lead to transformer substations overload operation in local areas, which is not good for distribution safe and stable operation of the power grid. Considering the driver’s willingness, this study proposes an orderly charging strategy based on the temperature control of electric vehicle on-board air conditioner. The proposed strategy first constructs the temperature control model for electric vehicle cabins with considering the temperature of entire electric vehicle and the special characteristics of urban roads. Then, multi-objective function is formed with minimum user charging cost and variance of grid load fluctuations. Finally, electric vehicles orderly charging period is optimized by combining with electric vehicle travel chains, charge constraints, time-of-use electricity prices, and substation capacity constraints. The results show that temperature-controlled dispatching can effectively reduce the electric vehicles disorderly charging load. It can serve the power grid “cut peaks and fill valleys” and smooth the overall grid load curve using an improved Lagrange relaxation algorithm to optimize electric vehicles charging period.

Optimal land use and distributed generation technology selection via geographic-based multicriteria decision analysis and mixed-integer programming

In the smart grid environment, optimal placement and sizing of microgrids have attracted a great deal of attention. Here, we propose a multi-scale optimization model for determining microgrid configuration, capacity, and geographical location, and we apply it to a municipality in Southwestern Ontario. The proposed approach accounts for the net present value of the project, power balance of the grid, maximum capacity of the current substations, and the geographic availability for the installation of a microgrid. The problem is tackled in two stages. First, a geographic information system/multicriteria decision analysis (GIS/MCDA) is performed to determine the suitable locations for the installation of distributed energy resources (DERs). Then, a mixed integer optimization model is used to determine the capacities and final installation locations of the DERs based on the results obtained in the GIS/MCDA. Finally, three different scenarios are evaluated to elucidate the influence that retail price, microgrids’ minimum contribution to the demand, and available land have over the final architecture, cost, and allocation of a renewable energy project.

A Study on Sizing of Substation for PV With Optimized Operation of BESS

Recent development and cost down of PV(Photovoltaic) technology drive change of power system structure. The participation of PV generation is increasing, and the size of each PV farm is getting larger. In order to integrate large PV farms into the main grid, substation for interconnection needs to be sized properly. Unlike substations for load and conventional generators, PV farm substation has an uneven utilization ratio due to characteristics of solar radiation. With proper sizing method for the capacity of the substation can reduce the building cost of facilities. A combination of an energy storage system can further reduce the capacity of the substation. Battery energy storage system (BESS) can shift the peak production of PV during the daytime to midnight. According to market circumstances, BESS can reduce further construction costs by producing profit based on time difference of electric cost. For proper sizing of substation capacity, several factors must be considered including environmental factors, market structure and BESS in the system. In this article, a series of assessment methodology is introduced to calculate the optimized capacity of substation and BESS for PV farm interconnection. The long-term solar radiation data is analyzed for a given site of the PV farm. Based on market structure, the operation of BESS is optimized to make maximum profit during operation. The iterative calculation of each step results in the calculation of the optimized capacity of BESS and substation for given PV farm size.

Electrical properties of medium voltage electricity distribution networks

An increasing amount of low carbon technologies (LCT) such as solar photovoltaic, wind turbines and electric vehicles are being connected at medium and low voltage levels to electric power networks. To support high-level decision-making processes, the impacts of the LCTs on large numbers of different types (e.g., rural, suburban, urban) of distribution networks need to be fully understood and quantified. However, detailed modeling of large numbers of real-world networks is challenging for two reasons. First, access to real-world network data is limited, and second, cleaning the data requires a significant amount of time, even before modeling of the networks. This paper offers a novel systematic methodology aimed at identifying and quantifying the key electrical properties of medium-voltage level distribution networks. The methodology allows for characterizing different types (e.g., suburban, urban) of distribution networks and obtaining 'depth' dependent electrical properties of the models of the networks. Two key sets of (electrical) data were used for the study. The first set was installed capacities of distribution substations; and the second set was the conductor cross sections of the distribution lines. In the graph models of real-world networks, 'nodes' represent the distribution sub­stations, switchgears, busbars and consumers locations of the network. 'Links/edges' stand for the connections between the nodes through distribution lines. The results of the investigation of the real-world networks showed that, the substation capacities and the conductor cross sections could characterize the electrical properties of suburban and urban type distribution networks. The resulted probability density functions (PDF) of the electrical properties of suburban and urban type distribution networks have the potential to be directly used in generating realistic distribution network models.