Study on reliability assessment of distribution networks containing distributed power supplies

At present, distributed power sources represented by photovoltaics are being widely connected to the distribution network gradually with their clean and flexible power generation methods. The output of the distributed photovoltaic is easily affected by environmental factors, and this uncertainty will have a huge impact on the economics and reliability of the distribution network. Aiming at the problem of voltage exceeding limits caused by distributed photovoltaic access to active distribution network, this paper introduces the influence on the reliability of distribution network when distributed photovoltaic grid-connected, details the change of distribution network voltage after distributed photovoltaic grid-connected, and analyzes the control strategy of photovoltaic inverter. Also, the simulation model of photovoltaic power supply into distribution network system is established, explores the voltage variation of different line length, voltage load and conductor cross-sectional area after distributed photovoltaic access. The simulation results show that the problem of the voltage exceeding limits of the active distribution network caused by photovoltaic grid connection can be solved by photovoltaic inverter control effectively.

With the development of the economy and the improvement of people’s living standards, energy has become an increasingly indispensable substance. The large-scale development and utilization of fossil energy has caused problems of energy crisis and environmental pollution. In order to solve these two problems, it is necessary to develop and utilize renewable energy sources, and access distributed power sources in the distribution network to form an active distribution network. The active distribution network contains a large number of distributed power sources, energy storage units and reactive power compensation equipment. Although it provides more convenience for voltage and reactive power regulation of the distribution network, the intermittent and volatility of renewable energy sources will also be Its voltage has a big impact. In order to solve the voltage dip and overvoltage problem of active distribution network, a new active distribution network voltage control strategy is proposed by using model prediction control technology. Inaccurate system modeling is reduced by establishing active distribution bus voltages, distributed power supplies, and energy storage device prediction models. With the minimum adjustment cost as the control target, the second-order cone relaxation method is used to optimize the action behavior of each control device. Finally, the IEEE33 node simulation example is built on the matlab simulation platform. The results show that the proposed voltage control strategy has good control effect and robustness.

An evaluation method of distributed generation credible capacity based on island partition

In active distribution network, power supply and load are the key elements to determine the operation of power network, at the same time, the randomness and uncertainty of power supply and load also bring challenges to the safe and economic operation of distribution network. How to explore the regularity of power supply operation, how to analyze the distribution load characteristics, adjustability and interaction with the power grid in depth is the key to realize the cooperative dispatching of active distribution network. In this paper, based on the existing and planned load of power grid, aiming at the new energy such as wind and light, the dispatching strategy of distribution network is studied, and the construction method of load data information is studied. Based on the data mining technology, the mathematical model of accurately predicting load output is established, and the typical load characteristics of the area are studied, and the response potential of all kinds of loads is studied, through which the mathematical model is studied. According to this order, the power grid dispatching center orders each generator set to arrange the power generation plan according to the dispatching plan, so as to realize the basic balance between the active power emitted by the power supply and the load in each period.

In order to meet the high permeability and the access of large scale distributed generation, at present and in the future, active distribution network becomes the trend of smart grid research. This paper introduces the influence of distribution network voltage distribution and stability of distributed energy access based on active distribution network; The reactive power and voltage optimization control method of active power distribution network is summarized from the aspects of optimal voltage regulation measure, voltage regulation measure of power network equipment, reactive power optimal dispatch of power system, and so on. Analysis of the current status of the research, and summarized the existing active distribution network with a distributed power pickup distribution network reactive power and voltage control of the existence of some problems and the insufficiency still some problems that must be solved in the study of reactive power and voltage optimization control of active distribution network are pointed out.

According to the characteristics of uncertainty in distribution network reliability assessment, a short-term reliability assessment model based on interval numbers is proposed. Firstly, the reason that interval numbers are applied to distribution network reliability assessment is analyzed. And then interval numbers of component reliability indices in unit of month are defined according to the weather factors. On this basis, system reliability indices are expressed by interval numbers respectively. And because of system reliability indices existing interval extension in interval arithmetic, an interval perturbation method is applied to effectively control interval extension. Finally, distribution network short-term reliability assessment based on interval numbers verified by BUS 2 of IEEE-RBTS is reasonable. The results showed the method can extend to practical distribution network reliability assessment.

Distributing distributed generators to form microgrids can restore isolated loads in active distribution networks during faults. However, the complex dynamic characteristics and cascading effects within the system during faults make it challenging for existing fault restoration models to accurately analyze these factors and enhance fault restoration capability, highlighting the need for a method that accounts for cascading effects. This paper proposes an optimization model for fault restoration strategies that comprehensively consider fault probabilities, load restoration capacities, and fault durations. Considering the dynamic characteristics and cascading effects, a fault restoration evaluation model is developed to simulate the cascading impacts within microgrids during faults. Then, an optimization-based solution method is established for fault restoration strategy formulation. Finally, simulation cases based on a modified IEEE 33-bus system are presented. The results demonstrate that the proposed method effectively formulates more efficient and reliable fault restoration strategies, significantly enhancing distribution network resilience and power supply reliability.

The power supply and distribution network of prosumer group is equipped with contact switch and section switch. After feeder fault occurs, the topological structure of distribution network can be adjusted by changing the switch state of each switch in the system, so as to realize the reconstruction after the fault, so as to restore the power supply in the fault free area. The optimal configuration of different types of switchgear in the appropriate position of the distribution network can reduce the time of fault location and isolation, and further realize the reconfiguration of the distribution network after the fault occurs, which greatly improves the reliability of the power supply and distribution network for prosumer group. This paper introduces a series of Boolean expressions to describe the existence of switches in distribution network, and then determines the corresponding load interruption time according to different fault types. On this basis, a distribution network fault reconfiguration model is established. By minimizing the investment cost and network loss, a multi-objective optimization model with power supply reliability as the index is established. Finally, the proposed model is tested through the RBIs bus 4 network. The test results show that the solution can effectively reduce the investment cost, improve the reliability of the distribution network, and maximize the investment income.

With the extensive grid connection of distributed generation (DG), due to the safe and stable operation restrictions of the distribution network, the abandoning of wind and solar energy become more serious. As a new type of power distribution device, soft open point (SOP) is reliable and efficient in power control, which not only effectively solve a series of problems caused by distributed power supply access, but also greatly increase the flexibility and economy of active distribution network(ADN). This paper considers the distributed power supply characteristics and demand response (DR), and establishes the planning model of SOP in the active distribution network combining planning and operation. The network layer uses the minimum integrated cost of the power distribution company as the objective function to perform SOP location and capacity. The load layer adjusts the load with the minimum cost of participating DR users. The operation optimization layer determines the power at both ends of the SOP with the minimum cost of the distribution network in each scenario as the objective function. In order to account for the timing characteristics and uncertainties of distributed power output and load, this paper analyzes the distributed power output and load curve in typical scenarios. The time-of-use electricity price mechanism is introduced to reflect the demand side characteristics of the active distribution network. In this paper, an improved multi-objective particle swarm optimization (IMOPSO) is used to solve the above model. Finally, the IEEE-33 node power distribution system is selected as an example to simulate. Through comparative analysis, it is found that the planning model of this paper can maximize economic benefits and has higher feasibility.

Inverter reliability-constrained Volt/Var optimization control of distribution network with high-level PV-storage generation

The location and capacity optimization configuration of distributed power supplies ensures that they. Make better technical and economic use. When the distributed power supply is connected to the distribution network, it will cause the trend size and direction of each branch to change, so that the system loss is not only related to the load size, but also related to the location and capacity of DG. Therefore, it is important to study the rational planning of DG in depth. In order to improve the system network loss effectively, a distributed power distribution power distribution network reactive optimization model with the minimum active loss of the system is established, and an improved multi-target firefly algorithm is proposed for the problem that the traditional firefly algorithm will oscillate repeatedly near the extreme point later in the iteration. In view of the shortcomings of the traditional firefly algorithm, which is easy to precocious and over-dependent on control parameters, the chaotic search strategy and global idea are integrated into the firefly algorithm, and an improved firefly algorithm is proposed, which is applied to solve the planning problem of distributed power supply. The example shows that the proposed algorithm has good practicability and adaptability, and also verifies the practical significance of the proposed model[1].

This study aims to investigate the topology characteristic indices which have a close relationship with reliability of distribution networks via mathematical tools. First, a practical network is extracted into a topology and presented by weighted adjacency matrix associated with a failure degree matrix, which contains more significant information than that of original adjacency matrix. Second, singular value sequence and vertex/edge sharing are proposed as two similarity indices. Finally, similarity functions are applied on two cases to establish the relationship with reliability by curve fitting and clustering. optimisation strategy based on modified contingency‐load‐loss index is elaborated to improve the reliability and guide to distribution network planning.

Marketing and Distribution Integrated System is based on GIS systems, and a unified information model of power grid equipment, basic data and topology-based systems, the use of high-tech information technology, application management and distribution line losses quarter field of network construction planning, customer outage management and other integrated information platform. Energy management system implementation ultimate goal is to achieve through intelligent system integration of existing systems be saving energy consumption and improved. In automation technology and IT based on the establishment of energy management systems, based on objective data, metallurgical, chemical, thermal, power plants and other energy consuming enterprises, energy saving most fundamental way to implement. The foundation and core of this system is that the data distribution network GIS platform, integrated measurement automation, distribution network of production, distribution network planning, distribution network automation, distribution network engineering, marketing and other systems supporting the management and reliability of power supply and distribution network planning decisions Camp with information query formulated meter reading routes and other services.

With increasing connection of distributed generations (DGs), the power flow in electric distribution network is no longer unidirectional and the network has become active distribution network. Thus, the connection of DGs in electric distribution networks has created a challenge for distribution network operators due to bidirectional power flow. One of the main technical challenges of an active distribution network is to maintain an acceptable voltage level in the system. This has initiated efforts in using various voltage control strategies to regulate the network voltage profile so that the voltage is maintained at its allowable voltage limits. A number of voltage control methods have been applied to solve voltage control problems associated with the connection of DGs in a distribution system. These voltage control strategies may be classified as decentralized or distributed and centralized or coordinated voltage control. From the literature, a number of coordinated voltage control strategies have been implemented to provide better and faster control to the system. This chapter presents an improved coordinated voltage control method in active electric distribution network by coordinating the three voltage control methods, namely, power factor control, on load tap changer control and generation curtailment control. These voltage control methods are coordinated using fuzzy logic by considering the load bus voltages and DG power as inputs and the voltage control actions as the outputs. The fuzzy logic if-then control rules which are generated to build the fuzzy logic control system are based on the simulations results as well as from the previous works. Results obtained using the fuzzy logic based coordinated voltage control has shown that the voltages are able to be kept within its permissible limits.

In the context of increasing energy shortage, the application of various renewable and dispersed energy sources for power generation and energy supply will become increasingly widespread. As a small local power grid containing multiple distributed power sources connected to the distribution network, micro grid (MG) can be linked to the distribution network to operate, or can be disconnected from the distribution network to operate when the grid fails or when is needed. Due to the randomness of distributed power and load operation in MG, the direction of power transmission between MG and the distribution network is also uncertain. When the distributed power generation capacity of MG is small and the load level is high, MG must absorb electrical energy from the distribution network to meet the demand of the internal load of itself, which is equivalent to operating in the load state; and when the amount of power generated by the distributed power supply is large, the excess power will be sent back to the distribution network, which is equivalent to the power supply state, and this case will have a great impact on the original protection of the distribution network. In this paper, through the establishment of MG and distribution network grid structure simulation, the impact of MG to distribution network protection in power supply state and load state is analyzed respectively and a variety of improvement measures are proposed based on the actual situation.