Planning model for rural distribution networks with integrated energy stations via robust optimization method

The article presents calculations the additional electric loss in the case of three-phase voltage system unbalance in the real rural electrical distribution networks (0.38 kV). Measurements were carried out at substations that receive power from distribution substation “Petropavlovsk”. Measurements were carried out using a certified device “Resource-UF2M”. Also presented are graphs of changes in currents/voltages of the negative-sequence and zero-sequence, electric loss and other parameters. The results of the economic assessment of electricity losses are presented. As a result, the proposed method for reducing the power loss factor, that can reduce the losses of electricity.

Distribution network operators typically produce a report of network performance for all networks as a whole, by not segregating it in a different area; urban and rural networks. Although the report is sufficient, it does not represent the actual performance of each urban and rural networks. Therefore, this paper presents the configurations, parameters, and component rating for medium voltage urban and rural distribution networks. Both networks are assessed with analytical and Monte-Carlo simulation techniques. Each assessment was correlated with Energy Regulator requirements for accurate results. Urban area has better network performance due to sophisticated network automation and network configuration with n-1 or n-2 security compared to the rural area.

Due to the strong coupling relationship between active power and reactive power in distribution network, the traditional method of optimizing the active and reactive power cannot make the distribution network operate in the optimal state of economical operation. And the uncertainties of load demand and power of distributed generation bring great challenges to the operation of distribution network. Based on this, a two-stage robust economical operation optimization method for distribution network considering multiple adjustment measures, including on-load tap changer, capacitor banks, static var compensator, electrical storage system and switch reconfiguration, is proposed on the basis of the branch power flow model. And the non-linear power flow constraint is relaxed by second order cone so that the economical operation optimization model is transformed into the mixed integer second order conic programming model to solve effectively. To solve the uncertainties of load demand and power of distributed generation, two-stage robust optimization method is adopted, and the optimal robust operation strategy of each adjustment measure is obtained through the column and constraint generation algorithm. Finally, the validity of the proposed model is verified by IEEE 33 bus system.

Georeferenced rural distribution network model considering scalable growth of users in rural areas

In recent years, extreme cold disasters have occurred frequently worldwide. The security of rural distribution network is threatened. The current research on enhancing the resilience of distribution network fails to consider the changes in the operating characteristics and efficiency of equipment under extreme cold disasters. To address this, this paper uses hydrogen‐integrated energy systems (HIES) to enhance the resilience of rural distribution network under extreme cold disasters. The method considers ensuring the power supply of rural lifeline load. A power support capability evaluation model of HIES is established. The model takes into account the impacts of low‐temperature conditions on the operational characteristics and efficiency of hydrogen energy equipment and photovoltaic equipment. An energy demand model considering livelihood security lifeline load, public service lifeline load and cultivation‐breeding lifeline load under extreme cold disasters is established. A rural distribution network resilience enhancement model is developed. Its goal is to maximise the restored energy demand of lifeline load. The example shows that the lifeline load recovery rate is increased by 38.98% and the primary load recovery rate is increased by 5.44% using the method proposed in this paper.

In rural distribution networks with widely dispersed loads, characterized by the utilization of long overhead lines, voltage profiles with big variations appear along the line due to the significant variations of the load between peak hours and valley hours. This paper describes the problems that the integration of distributed generation based on renewable resources could generate in that scenario, and presents solutions that are commonly used to mitigate these problems and proposes new solutions to solve them. The integration of distributed generation (DG) based on renewable resources in these networks increases the variability of the voltage, and in some cases the power flow of the network also can be bidirectional. Usually this integration of distributed generation is limited by the network operator limiting the maximum voltage variation produced by the distributed generation in the point of common coupling (PCC). In this paper different traditional methods for voltage control are described and analyzed for a widely dispersed rural network scenario. The impact of the DG in these methods of voltage control and the advantages of power electronics in this new scenario are exposed. Power Electronic devices applied to these distribution networks allow more efficient management of the network increasing the integration of distributed generation maintaining the security levels.

In recent years, the voltage quality in rural areas has aroused strong concern from the Stat Grid Corporation of China. This paper firstly analyze the over-voltage issues in the rural distribution networks from HUNAN province, and then proposes an output voltage control scheme of the Electric Spring (ES) to alleviate severe over-voltage problem in rural areas. The control objective of the ES is to regulate its output voltage where the load is directly integrated with, it maintains the voltage equals to its nominal value for every incorporated load. An operation mode selector is proposed for the ES control loop to automatically select inductive mode, capacitive mode or terminate the operation depending on the load voltage condition and load type. The control scheme is tested in a rural distribution network based on realistic data using Matlab/Simulink simulation. The effectiveness of voltage regulation is compared with the ES using input voltage control scheme. Simulation results show that under the common voltage condition in rural distribution networks from China, the ES with output voltage control scheme provides better voltage regulation for every customers along the distribution line, and it also reduced the voltage deviation between the distribution transformer and the end user due to the over length power supply distance.

The purpose of this paper is to establish algorithms in the design of rural low-voltage (LV) distribution networks. Planning of rural LV distribution networks involves the optimal design of radial configuration and location of MV/LV substations considering cost functions. In this work both goals are considered by taking into account different conductors, voltage drop constraints, power losses in lines and deterministic loads. The algorithms developed in this paper are based on dynamic programming; and were implemented on large-scale rural LV distribution networks, but they could also be used for other network optimization.

With continuous improvement of the retention rate of household electrical appliances, the peak valley difference of power distribution network, especially the rural distribution network is expanding. A reasonable management method of the demand side is needed to realize load shifting and economic operation of distribution network. At present, the cost of energy storage(ES) equipment is decreasing, which provides a new idea for the optimization of distribution network operation. This paper studied the charge/discharge model and strategy of ES, and constructed a multi-period optimal operation strategy model of distribution network with ES. Sparse coding automatic differentiation technology was applied to reduce coding workload, and constraint reduction of ES was proposed to reduce differential calculation, which enhanced the feasibility and efficiency of the model solving. Finally, the simulation results of an actual distribution network with ES demonstrated the accuracy of the proposed model, the efficiency of the proposed algorithm and the feasibility of the proposed solving method.

The replacement of wooden crossarm as insulation and structural part in rural distribution networks structures has been tackled by several power utilities around the world. UFMG has conducted a research work, supported by CEMIG-D (a major power utility in Brazil), on this issue evaluating alternatives to the present standard which is based on wooden crossarms. Several alternatives were considered and tested in laboratory. Those adequate to rural distribution networks, according to CEMIG-D needs, were installed and monitored in a test network. The paper presents the reasoning on replacing wooden crossarms, the results regarding the laboratory tests, the characteristics of the installed experimental network and the field survey of its performance.

One of the main challenges in microgrid system energy management is dealing with uncertainties such as the power output from renewable energy sources. The classic two-stage robust optimization (C-TSRO) method was proposed to cope with these uncertainties. However, this method is oriented to the worst-case scenario and is therefore somewhat conservative. In this study, focusing on the energy management of a typical islanded microgrid and considering uncertainties such as the power output of renewable energy sources and the power demand of loads, an expected-scenario-oriented two-stage robust optimization (E-TSRO) method is proposed to alleviate the conservative tendency of the C-TSRO method because the E-TSRO method chooses to optimize the system cost according to the expected scenario instead, while ensuring the feasibility of the first-stage variables for all possible scenarios, including the worst case. According to the structural characteristics of the proposed model based on the E-TSRO method, a column-and-constraint generation (C & CG) algorithm is utilized to solve the proposed model. Finally, the effectiveness of the E-TSRO model and the solution algorithm are analysed and validated through a series of experiments, thus obtaining some important conclusions, i.e., the economic efficiency of system operation can be improved at about 6.7% in comparison with the C-TSRO results.

The rapid development of photovoltaics (PVs) and load caused a significant increase in peak loads and peak‐valley differences in rural distribution networks, which require load peak shifting and line upgrading. Large peak‐valley differences also bring challenges on the safe operation of the utility power grid. Considering the integration of a high proportion of PVs, this study establishes a bilevel comprehensive configuration model for energy storage allocation and line upgrading in distribution networks, which can reduce peak loads and peak‐valley differences. In the upper level, a minimum annual planning cost is obtained by developing the installation capacity of centralised energy storage in transformer stations, the installation location and capacity of decentralised energy storage on lines and a scheme of line upgrading. In the lower level, the minimum total annual operation cost of the distribution network is obtained by developing an optimal scheduling for the centralised energy storage in transformer stations and decentralised energy storage on lines. Simulation results show that compared with the conventional energy storage planning strategy, the configuration investment can be reduced by 467.66 million yuan at least with the proposed strategy.

Usually, rural areas can be electrified via three-phase distribution transformers with relatively large capacities. In such areas, low voltage lines are used for long distances, which cause power losses and voltage drop for different types of consumers. Reducing losses and improving voltage profiles in rural distribution networks are significant challenges for electricity distribution companies. However different solutions were proposed in the literature to overcome these challenges, most of them face difficulties when applied in the conventional distribution network. To address the above issues, an applicable solution is proposed in this paper by installing a number of small-capacity distribution transformers instead of every single large-capacity transformer in rural areas. The proposed approach is implemented in the branch network of Al-Hoqool village, which belongs to the Nineveh distribution network. The network has been inspected on-site, drawn, and analyzed using the electrical systems analysis program (ETAP). The analysis showed that using the single-phase pole-mounted transformers can improve the voltage in the network’s end by 29% and enhance the voltage profile for all consumers. The analysis has also demonstrated that the modification can reduce the total power losses by 78% compared to the existing network. Concerning the economic aspect, the payback period for the proposed network is assigned to be 20 months.

With the rapid growth and high-penetration of renewable energy in the distribution network, microgrid cluster appears as an effective way to consume these resources. To deal with the uncertainty of sources and loads and achieve multi-agent game with incomplete information, this paper proposes a bi-level energy management strategy based on reinforcement learning (RL) and robust optimization. For the upper level, a RL-based game method is designed for agents including distribution network, energy supplier and microgrid cluster. By the designed RL searching process, multi-agent equilibrium can be achieved under incomplete information. For the lower level, the robust optimization method is developed based on the column and constraint generation algorithm, which can restrain the influence of the source-load uncertainty. Case study results verify that the proposed strategy can calculate the Nash equilibrium solution under difference operation modes, where both reduced operating cost and increased benefit can be achieved even under the worst scenario.

Against the backdrop of imbalanced urban–rural spatial structures and energy resource allocation, along with the continuous increase in distributed photovoltaic (PV) penetration rate, achieving orderly PV expansion and optimal energy storage (ES) configuration has become an urgent requirement for urban–rural distribution network planning. Existing research generally overlooks regional differences between urban and rural areas, making multiregional collaborative optimization difficult to achieve. Therefore, this paper proposes a distributed collaborative planning model for PV and ES (PV–ES) in multiregional urban–rural distribution networks based on the analytical target cascading (ATC) algorithm. By establishing a collaborative planning model that accounts for urban–rural differences, system decoupling is achieved through decomposition modeling and distributed parallel solution is accomplished using the ATC algorithm. Case validation demonstrates that the proposed model can coordinately optimize PV–ES configuration across multiple urban–rural regions, simultaneously enhancing system economics and significantly reducing impact on the upper‐level grid.The study further proposes a three‐level planning implementation pathway of “municipal–county–township” transmission, providing systematic technical methods and planning support for promoting the integration of urban–rural energy infrastructure.