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Under the background of achieving the carbon peaking and carbon neutrality goals on time in China, this study constructs a new power system evaluation index system with new energy as the main body from four aspects of “source, network, load, and storage.” This study attempts to use appropriate subjective and objective weighting methods to reasonably distribute index weights and construct an effective, reasonable, scientific, systematic, and comprehensively covered key new power system characteristic index model. From 2017 to 2020, the relevant data for the four dimensions of “source, network, load, and storage” of the power system of three provinces are selected for empirical analysis. The results show that, in the past five years, the performance of the power supply side and network side of the power system in the three provinces was the best and the performance of the load side and energy storage side was slightly insufficient. Specifically, the system outage duration, the number of intelligent sensing terminals, etc., still need to be further optimized and improved.

Currently, DC breakers are commonly used in mainstream protection schemes for DC grids to eliminate faults. However, the cost of high voltage DC (HVDC) breakers is high, and equipping each DC line with DC breakers is expensive. In order to minimize the number of DC breakers while ensuring the reliability of the power supply, a zonal protection strategy suitable for multi-voltage level DC grids is proposed. Subsequently, the qualitative impact of partial power interruption caused by fault DC areas is analyzed in the system. The basic zonal principle of the multi-voltage level DC grid is formulated, taking into account unbalanced power, the mode of system-level control, and the type of converters. Additionally, a time sequence coordination strategy is derived in detail based on the characteristics of DC breakers, AC/DC converters, DC/DC converters, AC breakers, high-speed switches, and other fault removal components. Finally, a seven-terminal DC grid is modeled in the PSCAD/EMTDC simulation platform. According to the simulation analysis, the DC grid can adopt the converter with fault clearing ability or an AC circuit breaker to cooperate with the fast disconnector (FD) to complete fault clearing in the DC fault area under the proposed zonal protection coordination strategy.

The carbon market and electricity market play a decisive role in the optimal allocation of market resources, bringing challenges to the operation and development of power generation companies (especially thermal power). Based on the operation mechanism of the national carbon market, this paper constructs a cost assessment model for thermal power generation units in the context of carbon trading, with the aim of studying the impact of the carbon prices on the cost of thermal power generation both in the near and long term. The calculation results of the model show that the carbon price will have a small impact on the cost of electricity for thermal power companies and the electricity market in the near term. However, in the long term, as the carbon quota is tightened and the carbon price is raised, the carbon market will affect the quotation strategies of market players and market clearing price.

Exploring the power consumption characteristics of user load is an urgent demand for the development of the internet of things technology in power system. This paper presents a high-performance machine learning approach in enabling large-scale load analysis considering class imbalance and frequency domain characteristics, which aims at serving the classification task for the large-scale class imbalanced load data. In order to handle the time series load data, this paper firstly employs Long Short-Term Memory (LSTM) neural network as the basic classification algorithm. Secondly, frequency domain decomposition is incorporated into the classification model to highlight the features of the input data. Thirdly, in order to solve the potential class imbalance issue which may significantly impact the network training, boundary-based data synthesis algorithm (Borderline-SMOTE) is adopted to preprocess the training data. At last, ensemble learning is employed to implement the parallelization of the presented approach using Spark to improve the efficiency of processing large-scale load data. The experimental results indicate the effectiveness of the approach in terms of classification accuracy and efficiency.

The limited regulation capacity in the integrated energy community is a key factor restricting the development of the community-based integrated (distributed) energy system. Based on this, a model for optimal sharing of day-ahead energy in multi-communities considering the matching degree of source-load curves between communities is proposed. Firstly, the relationship between energy supply and multi-energy flow is analysed concretely in a single community. A mathematical model that includes electric vehicles and multiple energy conversion equipment is built, then, an objective function minimizing the cost of energy purchase, equipment operation and maintenance, and EV battery loss is established. Secondly, the comprehensive Spearman constant and Euclidean distance matching index based on photovoltaic and load data among the communities are considered to optimize the multi-community operation efficiency with the goal of minimizing the energy interaction cost. Finally, in a 3-community simulation system simulation, results show that the multi-energy sharing mode can effectively improve the overall economy of the system and the photovoltaic consumption capacity. The introduction of matching index also improves the energy transmission efficiency, verifying the rationality of the proposed model.

With the wide application of multi-energy storage technology in the regional integrated energy system, the configuration of multi-energy storage devices is expected to enhance the economic benefits of regional integrated energy systems. To start with, in this paper, the basic framework of the regional integrated energy system is constructed, and a mathematical model of micro-gas turbine, gas boiler, distributed wind power and multi-energy storage device is established. Then, the multi-energy storage and double-layer planning configuration model with multi-energy complementation is established. The upper level of the model aims to minimize the comprehensive investment cost of multi-energy storage, while the lower level of the model aims to minimize the comprehensive systematic operating cost, in which the net losses cost is also included and the required multi-energy storage capacity from the upper level is set as its constraint. During the programming and problem solving, the second-order conic relaxation technology is introduced to realize the convex relaxation for power flow constraint. At the same time, the piecewise linearization method is adopted to deal with the natural gas pipeline flow constraint, which can convert the original model into a mixed integer programming problem. In the end, the example analysis is carried out in the IEEE 33-bus system and the improved 6-node natural gas system. The results show that the multi-energy storage technology can improve the economics of the regionally integrated energy system to a certain extent, and have verified the validity of the model.

In this paper, the power grid construction project was taken as the research object, and the matching between the project investment progress, construction progress, and cost accounting progress was analyzed. The main reasons for the mismatch between the three progresses were summarized in the aspects of external environment, planning, project construction, and costs accounting management. On this basis, a project whole progress evaluation model based on the matching degree of investment, construction, and costs accounting progresses was constructed, and the overall implementation progresses of some typical power grid construction projects were evaluated. The research results laid a solid foundation for strengthening the monitoring capabilities of the whole process management of power grid construction projects.

In this paper, the complicated arc phenomena in air dc circuit breakers that are widely used in rail transit and vessels are investigated with both experimental and numerical approaches. Initially, the basic arc motion characteristics in the switch are presented by the recorded waveforms and images in the carefully designed breaking experiments. Phenomena of arc stagnation and back commutation are revealed and the influence of arc chamber width on the arc stagnation is preliminarily discussed according to the experimental results. Then, to make the nature of arc motion clear and to determine the influence details of the arc chamber width on arc motion characteristics, a simplified model based on magnetohydrodynamics theory is built and four cases with the arc chambers of different widths are calculated. The simulated arc behavior is presented by the temperature distribution sequences. In addition, the formation process of back commutation is described in detail by the variation of arc column. The influence mechanism of arc chamber width on arc motion is analyzed according to the differences of pressure propagation and temperature distribution in the arc chamber. Furthermore, the calculated arc displacement curves show that the arc stagnation time could be shortened and the risk of back commutation could be reduced by decreasing the arc chamber width within the reasonable extent.

This article proposes a new structure of contact system to improve short-time withstand capacity of direct current circuit breaker. With this new contact system, the electrodynamic repulsion force is compensated. The principle of compensation is illustrated at the beginning. Then the electrodynamic force of the contact system is quantified by analyzing the Lorentz force in conductive loop and the Holm force between contacts. The factors and their influences on electrodynamic force are also investigated. Subsequently, based on multibody dynamics, the movement characteristic model is established. The opening and closing characteristics of breaker and the dynamic stress distribution of closing putters are investigated. The results are verified by experiments. It is indicated that this contact system can improve the short-time withstand capacity. The research could provide theoretical references to large-capacity medium-voltage air direct current circuit breaker development.

This paper focuses on the numerical investigation of arc plasma behavior in a certain type molded circuit breaker. A 3-D simulation model based on the magneto-hydrodynamics theory is built and calculated. The basic arc parameters are described by the coupled equations of gas dynamics and electromagnetic field. By adopting a thin layer of nonlinear resistance elements to represent the voltage drop of plasma sheath, the arc splitting process is included. The detailed arc behaviors are presented and preliminarily discussed according to the calculated temperature and arc current distributions. Moreover, experiments are carried out to validate the simulation results. The arc voltage acquired by the numerical and experimental approaches shows good agreement.

Within this paper, the arc characteristics in a typical air DC circuit breaker (DCCB) are studied through experimental approach. A specially designed experimental setup is employed to observe the dynamic process of arc evolution. The phenomena of arc commutation and arc stagnation under fault currents are revealed according to the high-speed photography and arc voltage curves. The influence of arc currents on the detailed arc behaviors is preliminary discussed. It is found that the arc would burn continuously between the contacts when the arc current decreases to a relatively small value. Assisting measures should be employed to help the switch interrupt the small arc current. Finally, a simple magnetic system is designed to increases the magnetic driving force of arc motion. And the interruption characteristics of the switch with the external magnetic field are investigated.

This paper focuses on the numerical investigation of arc plasma behaviour in arc chamber of direct current (DC) circuit breaker. A 3-D simulation model of arc chamber including ferromagnetic splitter plates is built and calculated, which is based on magneto-hydrodynamics theory. Coupled electromagnetic and gas dynamic interactions are considered as usual, and a thin layer of nonlinear electrical resistance elements is used to represent the voltage drop of plasma sheath and the formation of new arc roots. Therefore, the arc-splitting process with ferromagnetic plates can be included. To reduce the time consuming, the arc simulation results of arc commutation process from contact to arc runner is taken as the calculation initial condition in the model. Arc motion is described in detail by the temperature distribution. Moreover, the simulation result is compared with experimental result, which shows good agreement.

This paper is devoted to the modeling of air arc plasma in a simplified low-voltage arc chamber considering the turbulence effect. The numerical model is built based on the magnetohydrodynamics, and the turbulent flow field is described by the standard k-e model. The calculated arc behavior is presented by the temperature distribution sequence and shows good agreement with the experimental results. Compared with the simulation results under laminar assumption, the simulated arc characteristics taking turbulence effect into consideration are closer to the real situation.

A 3-D simulation model of air arc plasma in a low-voltage circuit breaker, considering the production of iron vapor from splitter-plate erosion, is developed. The distributions of temperature and mass fraction of iron vapor are calculated. The simulation results indicate that the arc splitting process is strongly influenced by the presence of iron vapor from the splitter plate. Images of arc simulation results are presented.

Arc behavior is very important to the performance of a low-voltage circuit breaker. A 3-D arc model for a certain type of miniature circuit breaker is built and calculated in this paper. The arc evolution is described in detail according to the temperature distribution images from the simulation results.