With the advancement of the mode of improving quality and efficiency in power development, the utilization efficiency evaluation of the power distribution system with rapidly growing is of vital importance. The research on the utilization efficiency of power distribution system is in the exploratory stage from shallow to deep while the existing research foundation is not deep and the future research direction is not clear. For this reason, this paper summarizes the research progress and looks forward to the adaptive evaluation ideas for the utilization efficiency evaluation of power distribution system. Firstly, considering that there is no unified definition of utilization efficiency at present, three types of connotations of utilization efficiency of power distribution system are defined. Then, the research progress is summarized at the equipment level and system level, and the consistency between the two research levels are sorted out. On this basis, this paper looks forward to the future research direction of power distribution system utilization efficiency evaluation. Focusing on future adaptability evaluation methods, relevant ideas are discussed such as utilization efficiency evaluation index system of power distribution system based on three dimensions, evaluation model of the interaction between individual equipment and the whole system. It also points out the research ideas for future development of utilization efficiency evaluation.

It is difficult to use the “N-1” criterion to reasonably measure the optimal load capacity of the line under different load structures, and failed to fully consider the economics of line operation under different load structures. A method for evaluating the optimal operational efficiency of medium-voltage distribution lines considering reliability and economy is proposed. Firstly, combining the safety and economy, the operational efficiency of the medium voltage distribution line is defined. Secondly, based on the analysis of the relationship between the reliability index and the line load rate, the reliability evaluation process of the medium voltage distribution line with different load structures is proposed. Thirdly, a model for the optimal load capacity of medium-voltage distribution lines is constructed with the goal of optimal economy. Finally, an example is analyzed to verify the effectiveness and practicability of the proposed method.

In view of the insufficient consideration of voltage quality in the current operation efficiency evaluation process, a method for evaluating the operation efficiency of distribution system considering the temporal and spatial characteristics of the load is proposed. First, on the basis of clarifying the definition of the operation efficiency of the distribution system, the evaluation index system for the operation efficiency of the distribution system is constructed from the perspective of equipment utilization; Secondly, the influence mechanism of factors such as power supply quality, network structure and load temporal and spatial characteristics on the reasonable load rate of power distribution equipment is explored; Finally, based on the analysis of various influencing factors, a reasonable load rate calculation method for power distribution equipment is proposed. The research results can evaluate the current status of the distribution system and provide a reference for the key directions of future distribution system investment planning.

Since the "Thirteenth Five-Year Plan", with the increasingly severe business situation of power grid companies, how to make scientific and reasonable decision-making on power grid investment and improve the accuracy of project arrangements are critical to the sustainable development of enterprises. According to the characteristics of power grid infrastructure reserve projects, this paper studies the contribution of power grid infrastructure reserve projects to the development of power grid from the aspects of economy, safety and coordination, and establishes a scientific and reasonable reserve project evaluation index system. Then, a calculation method for the comprehensive contribution of the reserve project to the overall power grid is proposed by analyzing the improvement of each indicator on the performance evaluation index of the entire power grid. A dynamic optimization ranking model for grid reserve projects is constructed based on the comprehensive contribution of unit investment and the impact of power grid construction timing. Finally, based on a 10 kV distribution network in a certain area, the 10 kV-level reserve projects in a certain area will be evaluated and optimized in 2020, and the scientific and rationality of the proposed power grid reserve project evaluation and prioritization method will be verified in this paper.

A spatial decomposition model and solution of reliability index based on investment optimization are proposed. Associate the reliability indicators of the entire network with the four specific business indicators related to power supply reliability in each region. Realize the spatial decomposition of the reliability index, so as to construct the objective function and list the constraint equations. Calculate the cost of each regional business index for each corresponding reduction in the number of households, and determine the investment sequence in the order of low to high cost-efficiency ratio of each index in each region within the entire network to solve the model. The comparative analysis through calculation examples shows that the space decomposition model and its solution of reliability index based on investment optimization proposed in this paper is effective, it can reduce redundant investment, overcome the blindness when determining the reliability improvement target of each region, and is conducive to reliability refined management and precise investment.

Emergency power supply plays an important and irreplaceable role in the restoration of power supply after a disaster in a resilient distribution network. Mobile energy storage systems (MESSs) can be used as emergency power sources to restore power to important loads. Among them, how to configure MESS reasonably is of great significance in order to recover power supply of important load nodes quickly after disasters. This paper proposes an optimized configuration method of MESS in a resilient distribution network considering efficiency improvement. First of all, considering the risk of power outages of each node in the distribution network and the shortest time limit allowed for the area, the number and location of the most optimal site points in the area are given; secondly, according to the shortest moving distance and shortest moving time of MESS, the priority is established. The optimal configuration model of MESS with hierarchical load recovery, and the objective function minimize the comprehensive cost after the disaster are established. The model proposed in this paper realizes the priority restoration of power supply for important loads by dividing the importance levels of loads, which improves the utilization efficiency of MESS. Finally, a numerical example is used to verify the correctness and effectiveness of the proposed configuration model.

The grid-connected island microgrid is interconnected with the main grid through a tie line. How to reasonably use the energy storage system and tie line is the key to the optimal interaction between the island microgrid and the main grid. This paper proposes an optimal operation strategy of an island microgrid that comprehensively considers tie-line asset utilization and energy storage life characteristics. Random chance constraints are used to describe the uncertainty of natural resources and loads, and battery throughput life models are used to describe charging and discharging and the impact of the state of charge on the life of the battery. In the case of avoiding frequent charging and discharging of energy storage, improving the transmission power of the tie line, and reducing the volatility of the transmission power, the tie line asset utilization is expected to be improved. In order to comprehensively consider the energy storage life and tie-line asset utilization index, this paper adopts the target membership function and uses the maximization satisfaction index method to transform the multi-objective problem into a single objective for optimal solution. Finally, a numerical example is analyzed based on the Nanji Island micro-grid to verify the correctness and validity of the proposed scheme.

In view of the current fact that under the background of the deepening of the coupling degree of various energy sources, the research on the evaluation method of asset utilization efficiency of integrated energy system needs to be carried out urgently, and the analysis of the operation status of integrated energy systems does not take into account the faulty operation status, etc., this paper proposes an integrated energy system asset utilization efficiency analysis method considering the load uncertainty and operation reliability. Firstly, a mathematical model that characterizing the uncertainty of the terminal load is constructed; Secondly, the system asset utilization efficiency and system operational reliability are used as indicators to evaluate the normal operation and fault operation status of the system, and the evaluation method is studied, and the indicators of different dimensions are combined by the membership function; Finally, through actual case simulation, the operation status of the integrated energy system throughout the year and typical days are specifically analyzed, and the uncertainty of load on the system asset utilization efficiency and operation reliability are analyzed. Thus the effectiveness and applicability of the theoretical methods mentioned in this article are verified.

At present, the peaking market of Northwest Power Grid is carried out offline based on the abandoned wind power and solar predicted day-ahead, which has the problems of poor real-time matching and confusion of market compensation benchmarks at all levels. The key to combine the problem is to achieve the coupling operation of peak shaving market and electricity energy market, and to explore the specific implementation methods: the boundary between peak shaving and electricity energy market is defined by calculating the benchmark output of thermal power units online, and the actual peaking contribution is defined by calculating the integral adjustment in real time. The demand transmission and orderly connection are realized by clarifying the boundary of markets at all levels within and between provinces, and the behavioral improvement is realized by direct feedback of power generation subjects through the solidification of price compensation standards. Finally, an example is used to verify the advantages of coupling operation in improving the power grid regulation efficiency and reflecting market value.

Modular multilevel converter (MMC) has the characteristics of multi-frequency coupling, and there is a risk of multi-frequency instability in the power system. Different from the existing modeling method, linear time-periodic (LTP) time-domain analysis method does not ignore the multi-frequency components in the modeling process, nor does it make complex multi-frequency components expansion, which is suitable for stability analysis of MMC. In this paper, the fundamental frequency current controller and time delay of controller are considered, and LTP time domain model of the MMC grid-connected system is established to study the influence of the controller parameters on the system stability when the MMC is connected to the strong and weak grids. The simulation model is built by MATLAB/Simulink to verify the correctness of the analysis results.

Reliable and accurate fault location technology is very important for the stable operation of MMC-HVDC transmission system. Aiming at the difficulty of locating high-resistance ground faults, this paper proposes a method for locating single-pole ground faults of transmission lines based on wavelet packet energy entropy (WPEE) and deep belief network (DBN). By analyzing the fault information contained in the fault waveform under different conditions, the wavelet packet energy entropy is used to extract the deep fault features in the double-ended fault voltage waveform and construct a new feature matrix. Based on the new feature matrix, a DBN model is constructed by particle swarm optimization (PSO) algorithm on the matrix’s model parameters, and finally the DBN regression mechanism is used to achieve accurate fault location. In this paper, the electromagnetic transient simulation software PSCAD/EMTDC is used to build a ± 250 kV double-ended MMC-HVDC system model and simulate single-pole ground faults with different positions and different transition resistances on the line. In order to test the localization performance of the proposed model, the proposed method will be compared with the fault localization method based on support vector machine (SVM). Experimental results show that this method can accurately and reliably locate the DC-side single-pole ground faults with a resistance of up to 4 000 Ω at a low sampling frequency of 20 kHz.

For the thin film capacitance used in voltage source converter based HVDC (VSC-HVDC) projects, the capacitance attenuation is the major criteria of capacitor aging and health. By overviewing the typical capacitance estimation method, two main errors of measurement data in practical engineering are analyzed focusing on the modular-multi-level (MMC) HVDC valve: the AD noise of capacitor voltage and arm current feedback, and the synchronization error between arm current and power cell status. Based on the measurement error analysis, a new online capacitance estimation method is presented using least square method, which takes into account the switching states of Nearest Level Modulation. The average capacitor voltage is calculated when the power cell is switched out, and the arm current is integrated when the power cell is switched in, so that the impacts of AD noise and synchronization error are minimized. The results of simulation comparison with the other two methods verify its accuracy and low sensitivity to measurement error, and it is suitable for industrial projects due to its simplicity and low computational efforts.

The accurate simulation calculation of overvoltage of arrester for AC filter is the basis of its insulation design and stable operation. In this paper, the modeling and simulation calculation under the condition of filter input and AC bus grounding fault are carried out by using the modeling method of gradually refining model. The effects of stray parameters of AC filter, π-type equivalent circuit of lines inside and outside the AC filter field and protection strategy of AC filter on the overvoltage simulation results of lightning arrester used in AC filter are analyzed. The simulation results show that under the above operating conditions, after considering the three parameters, the overvoltage of the arrester changes -4%~25%, the current decreases 36.2%~62%, and the absorbed energy increases 16%~214%. Therefore, if the above factors are not considered in the insulation design, the voltage and current design value of the lightning arrester will have a large deviation, and the energy design value will be small, which will affect the normal operation of the AC filter.

The safe and reliable operation of high voltage direct current transmission project is threatened by the problem of deposition on grading electrodes in the inner valve cooling water system. In this paper, the calculation models of single, double and triple grading electrode systems are established in order to analyze the aggregation stage and deposition stage of the discharged particles in inner cooling water. By means of finite element method, the distributing characteristics of the charged particles around the grading electrodes are calculated. Furthermore, the deposition process on the surface of grading electrodes is revealed through simulation calculation according to the electrophoretic deposition principle. The results show that a threshold value of electric current exists on the grading electrodes when capturing the charged particles. In the engineering condition, the capturing rate of the charged particles by single, double triple electrode system is 12.6%, 33.3% and 33.9%, respectively. The morphology and growth characteristics of the deposition by simulation of electrophoretic deposition are in high consistency with the deposition in the engineering practice.

With the rapid development of distributed energy, DC load, variable frequency load and voltage sensitive load, DC microgrid will be widely used in future power grid. At present, there is no unified standard for grounding design of DC microgrid, and the grounding methods used in various demonstration projects in China are also different. In this paper, the advantages and disadvantages of various grounding methods for the DC microgrid are analyzed based on two-level voltage source converter (VSC) from the perspective of AC and DC side harmonics. It is recommended to adopt the filter capacitor neutral point grounding method of converter LCL filter on the AC side and DC capacitance neutral point grounding method on the DC side. The selection of grounding method in practical engineering needs to consider many factors, so the conclusion of this paper can not be used as the evaluation standard of DC micro-grid grounding design, but they can provide reference for designers.

In view of the frequent damage of circuit breaker caused by lightning in the air insulated switchgear(AIS) substation in recent years, the actual 500 kV AC substation-transmission line model considering the power frequency voltage and induced voltage is established in the electromagnetic transient program EMTP, then the overvoltage level of circuit breaker under different conditions is simulated, and the reason which causes the damage of circuit breaker is analyzed. Then a comparison of lightning protective effects between two different schemes is made. The results show that, the overvoltage caused by the lightning when circuit breaker is open is the main reason that leading to the insulation breakdown and damage of the circuit breaker. For lines with voltage levels of 500 kV or above, the intrusive overvoltage of circuit breaker is from shielding failure more serious than that from the back striking. The effective protective method of the circuit breaker under lightning is installing arrester without-gap at the circuit side of circuit breaker, and the method in relavent regulation should not be directly applied to determine the installation location of substation arrester, which could be determined after simulation. The results proposed in the paper can be used as reference to the actual engineering.