Distribution Network In China Research Articles

Voltage quality improvement method based on adaptive power control of photovoltaic inverter

Abstract With the increasing penetration rate of distributed photovoltaics in the distribution network in China, the energy pressure has been effectively alleviated. However, the voltage over-limit problem of its parallel outlets cannot be ignored. Therefore, this paper put forward a power control method with photovoltaic inverters which is adaptive. First, the principle of photovoltaic voltage overstepping the limit is analyzed, and second, an adaptive control tactic is brought up for the disturbance of the volatile load of photovoltaic output. Finally, combined with the analysis and verification of simulation examples, the results show that the proposed strategy can effectively improve the voltage quality of the grid and prove the effectiveness of the proposed strategy.

A comprehensive resilience evaluation method for power distribution systems based on weighted Page-Rank algorithm

Resilience evaluation plays a critical role in the decarbonized development of modern power distribution systems since it objectively assesses how the distribution system performs in the face of stochastic renewable generation, increasing load demand, and promising to cut carbon emissions. This study proposed a comprehensive resilience evaluation method for regional distribution systems. The proposed resilience evaluation system comprises three sub-groups: performance, economy, and connections. To improve the objectivity of the proposed evaluation method, the weighting factors are calculated based on the Analytic Hierarchy Process (AHP) and weighted Page-ranking algorithm, respectively. Specifically, AHP is adopted to calculate the weighting factors for different metrics. At the same time, the original Page-ranking algorithm is improved according to the importance of the buses and then used to calculate the weighting factors for different buses within the same metric. The proposed method is applied to a real-world distribution network in China. Numerical results show that the proposed method can objectively evaluate the overall resilience level of the distribution network, including the source side, the network, and the load side. The evaluation results can help the decision-makers to make resilience enhancement in an economical and targeted way.

Research on Leak Location Method of Water Supply Pipeline Based on MVMD

At present, the leakage rate of the water distribution network in China is still high, and the waste of water resources caused by water distribution network leakage is quite serious every year. Therefore, the location of pipeline leakage is of great significance for saving water resources and reducing economic losses. Acoustic emission technology is the most widely used pipeline leak location technology. The traditional non-stationary random signal de-noising method mainly relies on the estimation of noise parameters, ignoring periodic noise and components unrelated to pipeline leakage. Aiming at the above problems, this paper proposes a leak location method for water supply pipelines based on a multivariate variational mode decomposition algorithm. This method combines the two parameters of the energy loss coefficient and the correlation coefficient between adjacent modes, and adaptively determines the decomposition mode number K according to the characteristics of the signal itself. According to the correlation coefficient, the effective component is selected to reconstruct the signal and the cross-correlation time delay is estimated to determine the location of the pipeline leakage point. The experimental results show that this method has higher accuracy than the cross-correlation method based on VMD and the cross-correlation method based on EMD, and the average relative positioning error is less than 2.2%.

Exploring Factors that Cause Rt Mart's High Rate of Employee Turnover from the Perspective of Organizational Behavior

The competition in the retailing industry in China is fierce. Retail players compete for the limited market share based on cheaper but higher quality goods and services. Rt-Mart is a leading retailer in China, with wide distribution networks based on its online and offline networks. Depending on its extensive distribution networks in China, Rt-Mart can achieve an effect of scale in reducing suppliers' bargaining power and cost in inbound and outbound logistics. Just the economy of scale is not enough for Rt-Mart. Rt-Mart also tries to minimize the labor cost, although it has benefited from the pandemic purchase during the COVID-19 in China. The decrease in labor cost meant a low wage and an opportunity of no pay for overtime work or overloads. As a result, a high employee turnover rate is ordinary throughout China's retailing industry. This article then identifies the factors that cause the high employee turnover rate from the organizational behavior perspective. Three factors are founded in this article, namely: the organizational culture, the leadership style, and the motivation at Rt-Mart. Rt-Mart's organizational culture is authoritarian, which is harmful to smooth and open communication between the management and employees. Its leadership style is transactional, which emphasizes results rather than the actual needs of followers. Furthermore, Maslow's Need Hierarchy theory poorly motivates employees in the lower levels. Therefore, to reduce the high employee turnover rate, this article recommends that Rt-Mart consider the following three tips: self-management team, developing transformational leadership, and cultivating an organization that embraces teamwork, respect, fairness, and recognition.

Hierarchical multi-objective optimal planning model of active distribution network considering distributed generation and demand-side response

Power grid planning is the basis of power system development, the structure of distribution network in China has changed from single source unidirectional network to multi-source multidirectional complex power network, which further increases the uncertainty and complexity of distribution network operation and planning. From the perspective of distributed energy grid connection, this paper constructs a hierarchical optimization model of distribution network planning under active management mode. The relationship among balanced network loss, line investment, power purchase cost, carbon emission cost and policy subsidies are comprehensively considered. To improve the convergence and effectiveness of the algorithm, NSGA-TS hybrid algorithm is applied for example analysis, which has better global search and local search ability. From the calculation and analysis results of an example, it can be seen that the model is effective in practical analysis, and expands the analysis idea of distribution network planning.

Evaluation of Acceptance Capacity of Distributed Generation in Distribution Network Considering Carbon Emission

Under the background of renewable-dominated electric power system construction, the penetration rate of low-carbon and renewable distributed generation (DG) in distribution network is increasing, which has changed the form and operation mode of the distribution network. To deal with the output fluctuation of high penetration DG in the distribution network operations, it is necessary to evaluate the acceptance capacity of DG. The correct evaluation can realize the secure, economic and low-carbon configuration of DG. In this paper, an evaluation method of acceptance capacity of DG in the distribution network considering the carbon emission is proposed. Firstly, a multi-objective evaluation model of acceptance capacity of DG is constructed with the objectives of minimizing carbon emission in the full life cycle, minimizing node voltage deviation and maximizing line capacity margin. Secondly, the improved non-dominated sorting genetic algorithm II (NSGA-II) is employed to solve the model to determine the Pareto optimal solutions of DG configuration. Then, the comprehensive index of acceptance capacity evaluation is obtained based on entropy weight method to decide the optimal compromise solution. Finally, an actual 55-bus distribution network in China is used to verify the effectiveness of the proposed method. The simulation results show that the proposed evaluation method can comprehensively obtain the optimal compromise solution considering the reliability, economy and carbon emission benefits of distribution network operation, which guides the DG configuration in the distribution network.

Damage prediction of 10 kV power towers in distribution network under typhoon disaster based on data-driven model

This paper presents a data-driven tower damage prediction model to predict the damage spatial arrangement of 10 kV towers under typhoon disaster. The 10 kV tower belongs to distribution network in China. Compared with high voltage level in transmission network, the 10 kV power towers are more vulnerable to typhoon disasters due to their lower design criterion and large amount. The data-driven model proposed in this paper can effectively predict the tower damage situation. It takes meteorological, power grid and geographic information into account and can be divided into two steps. The first step is to predict the damage probability of each tower by using data-driven method such as AdaBoost, Gradient Boosting Regression, K Nearest Neighbor Regressor, Random Forest and Support Vector Regression algorithms. In this step, the data space is constructed by data processing and variable correlation analysis. Then, we use the processed meteorological, power grid and geographic information as input and the damage probability as output for model comparison. The second step is to select the optimal model based on comprehensive index weighting. Through a comprehensive comparison of the efficiency and accuracy of the five models in various actual scenarios, the optimal model is Gradient Boosting Regression, which outperforms the other adverse algorithms and produces the prediction damage consistent with actual data.© 2017 Elsevier Inc. All rights reserved.

Multi-Source Data Processing and Fusion Method for Power Distribution Internet of Things Based on Edge Intelligence

With the rapid advancement of the Energy Internet strategy, the number of sensors within the Power Distribution Internet of Things (PD-IoT) has increased dramatically. In this study, an edge intelligence-based PD-IoT multi-source data processing and fusion method is proposed to solve the problems of confusing storage and insufficient fusion computing performance of multi-source heterogeneous distribution data. First, a PD-IoT multi-source data processing and fusion architecture based on edge smart terminals is designed. Second, the multi-source sensor data in the distribution network is unified in dimension and magnitude. By introducing the Box–Cox transform to improve the data offset problem in the Z-score normalization process, a multi-source heterogeneous data processing method for distribution networks based on the Box–Cox transform Z-score is proposed. Then, the conflicting phenomena of DS inference methods in data source fusion are optimally handled based on the PCA algorithm. A multi-source data fusion model based on DS inference with conflict optimization is constructed to ensure the effective fusion of distribution data sources from different domains. Finally, the effectiveness of the proposed method is verified by an experimental analysis of an IEEE39 node system in a regional distribution network in China.

Adaptive Dynamic State Estimation of Distribution Network Based on Interacting Multiple Model

With the large-scale access of all kinds of distributed generations (DGs), the operation mode of the distribution network is increasingly diverse and changeable. To monitor the operation of an active distribution network, an adaptive dynamic estimation method is proposed to address the new generation of power system. Considering the features of different types of operation scenario change of distribution network and DGs, the proposed method uses the state deviation index to identify the current operation mode before state estimation. In the adaptive estimation stage, two typical estimators are improved to cope with the typical operation mode and embedded in the interactive multiple model (IMM) algorithm framework. IMM uses the identification results of operation mode to give higher weight to the corresponding estimator and finally outputs the joint estimation results. The proposed estimation method is investigated in an improved IEEE 33-bus system and an actual distribution network in China, which results indicate the proposed method converges more quickly and maintains better accuracy while facing the complex distribution network.

Analysis of Fault Characteristics of Distribution Network with PST Loop Closing Device under Small Current Grounding System

With the rapid development of cities and the increasing complexity of distribution network systems, the cableization of transmission lines and the diversification of power users have brought new challenges to the supply reliability of distribution networks. Short-time outages caused by power outages and maintenance are one of the factors that affect the reliability of the power supply in the distribution network. The non-stop load transfer through a phase-shifting transformer (PST) operation can effectively improve the reliability of power supply to complex distribution systems. Considering the operation mode and structure form and fault type of the urban distribution network in China, comparing and analyzing the applicable scenarios of different neutral grounding methods, and based on the structure and zero sequence path characteristics of PST, an improved PST-based phase shifting and grounding transformer loop closing device with low power consumption is proposed. The fault characteristics of the PST-based loop closing device under the small current grounding system are also analyzed by the sequence component method, and, finally, the effectiveness of the phase-shifting and grounding transformer device is verified by simulation under PSCAD/EMTDC for fault routing and protection configuration of the urban distribution network in China.

Research and Application of a Clear Diamond-Shaped Distribution Network Structure

Aiming at the problems of low power supply reliability, poor transfer capacity between stations, and low line utilization in the current distribution network, this paper proposes a diamond-shaped distribution network structure with a clear structure. First, we investigated the typical wiring patterns of medium-voltage distribution networks in Tokyo, Japan, Paris, France, and China’s developed cities, and summarized experience and shortcomings. Secondly, combining the typical wiring patterns of distribution networks in China and abroad, construct a diamond-shaped distribution network structure, and study its adaptability, safety and flexibility, power supply reliability, and economy. Finally, take the transformation of the wiring mode of a regional distribution network in a certain city as an example, compare the use of the diamond-shaped distribution network structure in this article with the use of cable double-ring network wiring, cable “double petal” wiring, and Shanghai diamond-type wiring distribution network grid reconstruction The effect verifies the superiority of the diamond-shaped distribution network structure in this paper.

Wavelet Analysis-Based Simulation Study Of Small-Current Ground Fault System Routing

Small-current grounding is commonly used in medium-voltage distribution networks in China, including ungrounded neutral points, grounding via arc extinguishing coil and resistance grounding. In this paper, the power system modeling simulation of the grounding system via arc extinguishing coil and the transient characteristics when single-phase grounding occurs are studied. The principles and methods for selecting the wavelet basis function in transient component line selection are given. Wavelet analysis of the line current is carried out. It is verified by simulation that the wavelet analysis method in the small current ground fault selection can compare the difference of different lines.

Power flow matching-based topology identification of medium-voltage distribution networks via AMI measurements

Topologies of medium-voltage distribution networks change frequently during normal operation to reduce line losses, handle outages, and accept more intermittent distribution generators. However, topologies generated by telecommunicating information are not credible enough for various reasons. This paper proposes a power flow matching-based topology identification methodology for radial medium-voltage distribution networks that are structurally loopy but operationally radial using only measurements from the advanced metering infrastructure. In the first stage, a mixed-integer quadratic programming model is formulated to obtain an initial radial network topology. Then in the second stage, using this initial topology as the reference tree, a spanning tree generation algorithm is adopted to locally search its neighboring spanning trees, on each of which power flow is executed using power injection measurements as loads. The spanning tree with the best matching performance between estimated and measured voltage magnitudes is selected as the final network topology. During the local search process, spanning trees are ranked according to their matching indices and those that show a bad matching performance are pruned to reduce computation costs. The effectiveness of the proposed methodology is tested using the 33-bus distribution network and an 80-bus realistic distribution network in China with promising results.

Quantitative study on benefits of distribution network investment

The development of distribution network in China lags behind the transmission network seriously, which is difficult to meet the development needs of high proportion of renewable energy power system in the future. Facing the huge investment demand of distribution network, it is urgent to improve the existing extensive experience based investment decision-making method and avoid the subjectivity of qualitative index evaluation method. In this paper, the life cycle theory and input-output method are used to study the quantification of distribution network investment benefit. The quantitative models of economic benefit and social benefit of distribution network investment are established to provide support for the comparison and decision-making of distribution network projects. Finally, an empirical analysis of the investment benefit model of a high-voltage distribution network project is carried out to verify the feasibility of the research results.

Dynamic Monitoring of Low Voltage Distribution Network Leakage Detection Device Based on Internet of Things Technology

The existing dynamic monitoring methods of low-voltage distribution network leakage detection device have been unable to meet the needs of the distribution network in China. Therefore, a dynamic monitoring method of low-voltage distribution network leakage detection device based on Internet of Things technology is proposed. Based on the introduction of the Internet of Things technology sensor sensing technology, the sensor is installed on the leakage detection device to obtain the operation data of the leakage detection device and preprocess it with noise reduction and normalization. At the same time, the statistical analysis of partial discharge signal is carried out to extract the characteristics of fast waveform signal (energy parameters, sample entropy and modal components). Based on the operation data features of the leakage detection device extracted above, the state diagnosis framework of the leakage detection device is built to diagnose the state of the leakage detection device, and the dynamic monitoring of the leakage detection device in low-voltage distribution network is realized. The experimental results show that: compared with the existing methods, the proposed method has stronger anti-interference ability and smaller monitoring error, which fully proves that the proposed method has better application effect.

Field experiment using transient energy method to locate a single-phase to ground fault

Distribution networks in China and several other countries are predominantly neutral inefficiently grounding systems (NIGSs), and more than 80% of the faults in distribution networks are single-phase-to-ground (SPG) faults. Because of the weak fault current and imperfect monitoring equipment configurations, methods used to determine the faulty line sections with SPG faults in NIGSs are ineffective. The development and application of distribution-level phasor measurement units (PMUs) provide further comprehensive fault information for fault diagnosis in a distribution network. When an SPG fault occurs, the transient energy of the faulted line section tends to be higher than the sum of the transient energies of other line sections. In this regard, transient energy-based fault location algorithms appear to be a promising resolution. In this study, a field test plan was designed and implemented for a 10 kV distribution network. The test results demonstrate the effectiveness of the transient energy-based SPG location method in practical distribution networks.

Modelling and analysis of radial distribution network with high penetration of renewable energy considering the time series characteristics

Power distribution networks are in a transformation active distribution networks with distributed energy resources. However, the widely adopted distribution test networks were established many years ago, which are untimely and cannot reflect the characteristics of high penetration renewable energy. Therefore, in this study, a distribution network with high penetration renewable energy is established based on the real data of a renewable-energy-rich radial rural distribution network in China. The proposed radial distribution network includes three types of loads and two types of renewable energy distributed generations. The evaluation indexes are designed to assess the proposed system and compare with the existing distribution networks. In addition, the topical high/low voltage problem of distribution network caused by high penetration of renewables is discussed. Furthermore, based on the measured time series characteristics of load and renewable resources, the effectiveness of the proposed system is validated by power flow analysis and dynamic characteristic criterion.

Enhancing the distribution grid resilience using cyber‐physical oriented islanding strategy

The increasing penetration of distributed generations enables an innovative operation paradigm that allows islanded operation to enhance the resilience of the distribution grid. In this study, a cyber-physical oriented islanding strategy is proposed by coordinating centralised and distributed control to achieve seamless islanding transition and operational flexibility in emergency conditions. A cyber-physical control structure is developed to mitigate various disturbances (e.g. emergencies or fluctuations) according to different operation conditions. Specifically, the distributed fault isolation and seamless islanding transition are coordinated to mitigate the outage caused by unplanned islanding, while a secondary control is proposed to support primary control by reducing the power fluctuations during islanded operation. With a rapid response speed, the local cyber-physical devices are coordinated to accomplish islanding separation by selecting a feasible islanded area even under an unplanned islanding situation. A field test was conducted on a practical distribution network in China, and the results demonstrated the effectiveness and feasibility of the proposed islanding strategy.

Multi-objective Optimization of Accommodation Capacity for Distributed Generation Based on Mixed Strategy Nash Equilibrium, Considering Distribution Network Flexibility

The increasing penetration of distributed generation (DG) brings about great fluctuation and uncertainty in distribution networks. In order to improve the ability of distribution networks to cope with disturbances caused by uncertainties and to evaluate the maximum accommodation capacity of DG, a multi-objective programming method for evaluation of the accommodation capacity of distribution networks for DG is proposed, considering the flexibility of distribution networks in this paper. Firstly, a multi-objective optimization model for determining the maximum accommodation of DG by considering the flexibility of distribution networks is constructed, aiming at maximizing the daily energy consumption, minimizing the voltage amplitude deviation, and maximizing the line capacity margin. Secondly, the comprehensive learning particle swarm optimization (CLPSO) algorithm is used to solve the multi-objective optimization model. Then, the mixed strategy Nash equilibrium is introduced to obtain the frontier solution with the optimal joint equilibrium value in the Pareto solution set. Finally, the effectiveness of the proposed method is demonstrated with an actual distribution network in China. The simulation results show that the proposed planning method can effectively find the Pareto optimal solution set by considering multiple objectives, and can obtain the optimal equilibrium solution for DG accommodation capacity and distribution network flexibility.

An optimal expansion planning of electric distribution network incorporating health index and non-network solutions

The health status of distribution equipment and networks is not considered directly in existing distribution network planning methods. In order to effectively consider the health status and deal with the risk associated with load and renewable generation uncertainties, this paper presents a new optimal expansion planning approach for distribution network (EPADN) incorporating equipment's health index (HI) and non-network solutions (NNSs). HI and relevant risk are used to help develop the optimal equipment replacement strategy and temporary NNSs are considered as promising options for handling the uncertainties of load growth, reliability requirements of power supply and output of distributed energy resources (DERs) at a lower cost than network alternatives. An EPADN model using network solutions (NSs) and NNSs is proposed. The planning objectives of the proposed model are safety, reliability, economy, and `greenness' that are also the meaning of distribution network HI. A method integrating an improved niche genetic algorithm (INGA) and a spanning tree algorithm (STA) is fitted to solve the model presented here for real sized networks with a manageable computational cost. Simulation results of an actual 22-node distribution network in China, illustrate the effectiveness of the proposed approach.