Hybrid Distribution System Research Articles

Voltage Profile Improvement in a Renewable Energy Based Hybrid Distribution System

The technique of designing and analyzing the mixing of high photovoltaic (PV) and wind penetration into the Distribution device is a critical undertaking that calls for careful consideration and assessment. This integration has been meticulously accomplished on a 33kv machine and a 14-bus node take a look at inside the distribution feeder. The objective of this observe is to illustrate the weight flow assessment and the impact of together with Distributed Generation (DG) in the medium voltage distribution community using ETAP software program. It is important to understand that renewable energy resources preserve big capability in assembly the escalating strength demands on a worldwide scale. Particularly on the distribution facet, there is a great absorption of reactive energy, necessitating the equalization by renewable strength assets to enhance the voltage stage in the distribution community. Moreover, an in-depth exam of the grid performance below those situations is important for ensuring the robustness and reliability of the machine. Within the ETAP software program surroundings, the Adaptive Newton-Raphson approach has been employed in the distribution community to facilitate accurate and efficient evaluation of the gadget conduct.

Fault-Tolerant Multiport Converter for Hybrid Distribution Systems: Configuration, Control Principles and Fault Analysis

Multiport converters (MCs) are widely adopted in many applications, from renewable energy sources and storage integration to automotive applications and distribution systems. They are used in order to interface different energy sources, storage devices and loads with one single, simple converter topology in contrast to the traditional approach, which can require different solutions made by two-port converters. MCs allow for a reduction in the number of components and cascaded conversion stages with respect to an equivalent system of two-port converters, resulting in reduced complexity, dimensions and costs, as well as in improved reliability and enhanced efficiency. Nevertheless, some aspects related to the design of MCs are still worth further discussion when MCs are applied to hybrid AC/DC distribution systems. First, most converters are developed for one specific application and are not modular in structure. Furthermore, many of the proposed solutions are not equally suitable for AC and DC applications and they can introduce significant issues in hybrid distribution systems, with earthing management being particularly critical. Even though most available solutions offer satisfying steady-state and dynamic performances, fault behavior is often not considered and the possibility of maintaining controllability during faults is overlooked. Building on these three aspects, in this paper, a new MC for hybrid distribution systems is presented. An innovative circuit topology integrating three-phase AC ports and three-wire DC ports and characterized by a unique connection between the AC neutral wire and the DC midpoint neutral wire is presented. Its control principles and properties during external faults are highlighted, and extensive numerical simulations support the presented discussion.

Dynamic Regionalization for Unbalanced AC-DC Hybrid Distribution Systems with a Distributionally Robust Guarantee against DG Uncertainty

Dynamic Regionalization for Unbalanced AC-DC Hybrid Distribution Systems with a Distributionally Robust Guarantee against DG Uncertainty

Hierarchical and distributed energy management framework for AC/DC hybrid distribution systems with massive dispatchable resources

Hierarchical and distributed energy management framework for AC/DC hybrid distribution systems with massive dispatchable resources

A spatial analysis of techno-economic feasibility of solar cities of India using Electricity System Sustainability Index

Numerous schemes with solar incentives are introduced by the Government of India to promote the adoption of solar energy technologies in Indian cities. However, the success rate of this program in the selected pilot cities needs to be explored and analyzed. Therefore, this study identifies the resources which may facilitate or obstruct the performance of the solar cities of India. This study was conducted to add a new index value to the literature to assess the regional demand analysis of the nation's future electricity scenario with the help of a hybrid power generation and distribution system. Here, the solar hotspots of India are mapped, not only focusing on the geographical aspects of the region but also with respect to the existing solar energy policies, technology, electricity system, and the economic capacity of the cities. Additionally, a sustainability index of the electricity supply system for each city was formulated to benchmark cities based on their sustainable power generation and distribution system. Finally, TOPSIS approach was used to determine the solar cities with the highest technical and economic potential to fulfil the targets of the solar city mission successfully. The assessment of the technical and economic potential analysis from the dataset indicates that the cities situated in the north, the central and western parts of India have better opportunities to harness solar energy than cities of the north-east, east and southern India. Cities like Leh, Amritsar, Gandhinagar, Indore, Aurangabad, Bhopal, Nagpur, and Raipur, situated along the north-west-central India are highly desirable to attract investors to disseminate solar energy technologies in these cities, thereby highlighting the possible directions of future investments in the solar cities of India. The Electricity System Sustainability Index (ESSI) gives an overview of the extent of sustainability achieved in terms of number of new connections, cost variability, economic productivity, energy losses, power availability during peak hours, and the renewable energy generation capacity of the system. It was observed that cities with better economic performance and environmentally sustainable have performed better in ESSI and are more inclined towards adopting hybrid mode of electricity generation.

Dynamics of supply chain distribution systems in the apparel industry

Expansion into new markets creates new opportunities and dynamics which could enhance a company’s growth prospects. It thus calls for scalable supply chain distribution systems in competitive marketplaces. The retail supply chain requires sustainable distribution systems to enhance cost efficiency. This study examined the influence of centralised, decentralised, or hybrid distribution systems on agile service delivery, productive human capacity and the supply chain process and technology. First, the study aimed to establish whether a centralised or decentralised supply chain distribution system supports expansion to the African marketplace. Secondly, this study assessed the challenges of inventory positioning and availability on the existing outbound and inbound product flow systems across the African continent. Thirdly, the study examined the interrelated strategic distribution centre performance level to develop the supply chain distribution value proposition model. A descriptive research design was employed using univariate and multivariate methods and data were gathered from 100 staff in an apparel company. The study found that a sound distribution centre requires efficient supply chain systems and a strong workforce. This calls for training and development of employees to improve the organisation’s productivity and efficiency. The managerial implications include the need to ensure that distribution centres support sustainable product availability.

Bidirectional Virtual Inertia Control Strategy for Hybrid Distributed Generations Integrated Distribution Systems

The bidirectional ac/dc converter between the ac and dc subgrids plays a crucial role in enhancing the inertia support ability and ensuring the stable operation of the hybrid ac/dc distribution systems. In this paper, the bidirectional virtual inertia control strategy of hybrid distributed generations (DGs) integrated distribution systems is proposed for desired inertia support ability of both ac frequency and dc voltage. Firstly, the active power droop characteristics of the bidirectional ac/dc converter are analyzed, which reveals the steady power-sharing relationship between the ac and dc subgrids. Then, based on the dynamic power balance of the bidirectional ac/dc converter, the bidirectional virtual inertia control is proposed by introducing the virtual capacitor and moment of inertia, which can enhance the interactive inertia support ability of the hybrid distribution system. Finally, the effectiveness of the proposed control scheme is verified with a hybrid DGs integrated distribution simulation system in the PSCAD platform.

Vibration Performance of a Power Electronic Transformer Under Different Phase-Shift Modulation Methods

Power electronic transformers (PETs) have attracted extensive attention in the fields of renewable energy and energy storage, and ac/dc hybrid distribution systems. This article analyzes the vibration generation and conduction of the high-frequency transformer, which is a key component of the PET. An experimental study is presented on the vibration characteristics of a ferrite transformer under different switching frequencies and phase-shift modulation methods. What is more, based on the three vibration sources of the transformer, a quantitative mathematical description between the core vibration acceleration and the excitation voltage and current is obtained under different phase-shifting modulation modes. The errors between the numerical calculated values and the experimental data are basically within 10%, which verifies the validity of the research and prediction of PETs vibration characteristics under different modulation modes.

Two-Stage Research on AC/DC Hybrid High-Voltage Distribution Network Based on Network Reconfiguration and SOP Coordinated Control

DC power grid has the advantages of large power supply capacity, easy access to clean energy, low loss, and easy power control. With the increasing penetration rate of distributed generation and DC load in low-voltage transmission network, the traditional radial AC distribution form develops into AC-DC hybrid form. Large-scale distributed energy access is an important feature of future distribution system. Aiming at the AC-DC hybrid distribution system with soft tie-in switch and voltage source converter, considering the network congestion caused by large-scale access of distributed energy, a two-stage congestion management mechanism is proposed. This strategy solves the congestion problem of AC/DC hybrid transmission network with the help of the power flow control ability of AC/DC transmission network’s own optimization control means and congestion management services provided by distributed energy sources. According to the experiment, the total distributed generation power of DC link is 15 MW, and the load power is 10 MW, that is, the remaining power of DC link is 5 MW, the total distributed generation power of AC link is 8 MW, and the load power is 15 MW, that is, the power shortage of AC link is 7 MW. In the first stage, the tie-in switch, SOP and VSC are coordinated and optimized, and in the second stage, the flexible adjustment ability provided by distributed energy makes up for the deficiency of the adjustment ability of direct control means in some periods of severe congestion and meets the requirements of congestion management of AC-DC hybrid transmission network under high-permeability distributed generation.

Dynamic performance analysis of low-voltage AC/DC hybrid power distribution system under multiple uncertainties

The low-voltage AC/DC hybrid power distribution system is becoming one of the important forms of the future power grid. The system is exposed to multiple uncertainties due to high proportion of power electronics and renewable energy resources. In this paper, a dynamic performance analysis method of low-voltage AC/DC hybrid power distribution system under multiple uncertainties is proposed based on reachability analysis, which depicts the time-varying trajectory and boundary of the system state variables. Firstly, the typical structure of low-voltage AC/DC hybrid distribution system is analyzed. The corresponding differential–algebraic equations (DAEs) are established. Then, the basic theoretical method of reachability analysis is described. Then method is further applied for low-voltage AC/DC hybrid power distribution systems. Finally, scenarios such as fluctuation of bus load and renewable energy resources are tested on the MATLAB/Simulink platform. The comparative analysis is conducted between reachability analysis and time-domain simulation, which verifies the validation of the proposed dynamic performance analysis method. The dynamic performance analysis would provide a technical support for low-voltage AC/DC hybrid power distribution system with growing numbers of uncertainties.

Heat distribution concepts for small solar district heating systems – Techno-economic study for low line heat densities

• Two novel distribution concepts are compared to conventional district heating. • A novel distribution system with central domestic hot-water heating is presented. • Hybrid distribution outperforms a conventional steel pipe system. • A complete low-temperature system outperforms hybrid distribution. • Reduction in line heat density favours a low-temperature GRUDIS system. The high operating temperatures in today’s district heating networks combined with the low energy demand of new buildings lead to high relative network heat losses. New networks featuring lower operating temperatures have reduced relative heat losses while enabling an increase in the use of solar heat. The primary aim of this study was to determine if a particular district heating system can be made more effective with respect to heat losses and useful solar energy, by considering different distribution concepts and load densities. A small solar assisted district heating system with a novel hybrid distribution system has been modelled based on a real case study. This model serves as a basis for two other models where the distribution system and heating network operating temperature is changed. A secondary aim of the study was to determine the economic implications of making these changes, by using costs estimates to calculate the contribution of essential system components to total system cost. Results indicate that a novel distribution concept with lower network temperatures and central domestic hot water preparation is most energy efficient in a sparse network with a heat density of 0.2 MWh/m∙a and a performance ratio of 66%, while a conventional district heating system performs worst and has a performance ratio of less than 58% at the same heat density. In an extremely sparse network with heat density of 0.05 MWh/m∙a, the performance ratio is 41% and 30% for these systems, respectively. A simple economic analysis indicates that the novel distribution concept is also best from an economic point of view, reducing the initial investment cost by 1/3 compared to the conventional concept, which is the most costly. However, more detailed calculations are needed to conclude on this.

Optimal double Q AC-DC hybrid distribution system planning with explicit topology-variable-based reliability assessment

AC-DC hybrid structure offers a promising solution to accommodate AC/DC loads and distributed generators (DGs) in future smart grid. However, due to the complexity brought by reliability assessment and hybrid power flow, almost existing planning models of AC/DC hybrid distribution systems (ADHDS) are solved by heuristic algorithms, which cannot guarantee the optimality of solution. A novel ADHDS planning model that achieves two objectives: economy and reliability (double Q planning technique) is established in this paper. This novel planning model incorporates reliability indices, i.e., SAIDI, SAIFI, and EENS explicitly, which established the relationship between reliability and planning topology with an explicit method. Moreover, a linearized hybrid power flow for ADHDS planning is utilized in this paper. Finally, ADHDS planning model can be established as MILP and solved efficiently. Further, a globally Pareto-optimal set for reliability and economy is constructed based on adaptive ε-constraint method, enabling planners to make better trade-offs. Case studies demonstrate that ADHDS outperform than pure AC or DC solution for systems with high proportion of DC elements, effectively reducing distribution system cost with low-level reliability sacrifice. Besides, the effect of DG penetration, DC proportion, and failure rate of voltage source converter (VSC) on optimal double Q planning solution are revealed.

Security-constrained AC–DC hybrid distribution system expansion planning with high penetration of renewable energy

With the increasing penetration of renewables into the AC–DC hybrid distribution system, it is necessary to develop a security-constrained planning approach to address the uncertainty brought by renewables. Motivated by the urgent need to accommodate high penetration of renewable energy resources in weak grids, this paper presents a novel planning approach for AC–DC hybrid distribution systems considering the N-1 security criterion. Network reconfiguration is incorporated as a method to improve the flexibility of the system under normal and post-contingency conditions. To alleviate the burden of computing all possible N-1 contingencies, a novel solving strategy with a nested loop structure is proposed. In the inner loop, a novel contingency screening method is designed for the fast identification of high-risk contingencies under a given planning solution. In the outer loop, the obtained high-risk contingency set is adopted to refine and filter the security constraints, so that the planning solution can be improved iteratively. The superiority and effectiveness of the proposed planning model and solving strategy are tested on a real-world distribution network in Zhejiang Province, China. Numerical results verify that the proposed planning approach is able to deal with the installation of large-scale renewable energy while ensuring the security of the system.

Power Electronics Converters for the Internet of Energy: A Review

This paper presents a comprehensive review of multi-port power electronics converters used for application in AC, DC, or hybrid distribution systems in an Internet of Energy scenario. In particular, multi-port solid-state transformer (SST) topologies have been addressed and classified according to their isolation capabilities and their conversion stages configurations. Non-conventional configurations have been considered. A comparison of the most relevant features and design specifications between popular topologies has been provided through a comprehensive and effective table. Potential benefits of SSTs in distribution applications have been highlighted even with reference to a network active nodes usage. This review also highlights standards and technical regulations in force for connecting SSTs to the electrical distribution system. Finally, two case studies of multi-port topologies have been presented and discussed. The first one is an isolated multi-port bidirectional dual active bridge DC-DC converter useful in fast-charging applications. The second case of study deals with a three-port AC-AC multi-level power converter in H-Bridge configuration able to replicate a network active node and capable of routing and controlling energy under different operating conditions.

Enhancement of energy efficient distribution generation integrated with solid state transformer using improved rider optimization algorithm

ABSTRACT Nowadays, the usage of the latest technologies and pure energies like photovoltaic energy, wind energy, and electrical vehicles are increasing in demand to minimise environmental pollution. Hence, to hold this kind of technologies, the distribution systems in the future have to be converted to AC–DC hybrid for considering all kinds of DGs and (DC and AC) of loads. This paper attempts to develop an integration of DG with AC–DC hybrid distribution systems connected with solid state transformer (SST). The main intention of this paper is to make an energy-efficient system, by enhancing the voltage profile, reducing greenhouse gas emissions and reducing real and reactive power losses, when DG with SST is connected to a hybrid distribution system. With these constraints, a multi-objective function is formulated, which is solved by a new improved meta-heuristic algorithm in optimal location and sizing of DG. The new algorithm adopted in this paper is the improved Rider Optimisation Algorithm (ROA) termed as Fitness Rate-based ROA (FR-ROA). The experimental analysis on single and multi-objective functions proves the efficacy of SST in providing an energy-efficient system model.

LVDC Bipolar Balance Control of I-M2C in Urban AC/DC Hybrid Distribution System

With the high proportional renewable energy integration and rapid increase in the DC loads, such as the electric vehicle and distributed energy storage, the DC distribution system becomes a prospective solution for the urban power grid enhancement for its high-efficiency and eco-friendly nature. In most DC distribution systems, power interfaces are applied to connect low-voltage DC (LVDC) distribution systems with multiple medium-voltage (MV) systems in order to improve the operating reliability and economy. Compared to other types of multiports power interfaces, the three-port-isolated modular multilevel converter (I-M2C) has shown many advantages, including low cost, high power density, and low control complexity. However, the I-M2C cannot handle the power imbalance at the bipolar LVDC port like the other MMC-based three-port power interfaces, which limits the operating range and decreases the stability of the I-M2C in bipolar LVDC application. In order to solve the bipolar imbalance problems, a novel balance control method is proposed in this article. The proposed balance control method is based on symmetrical decomposition. By decoupling the MV power control and the LV bipolar power compensation control, the proposed method can eliminate the bipolar voltage deviation under different working conditions. The simulation results prove the validity and good control performance of the proposed method.

PSCAD/EMTDC를 이용한 ±35kV급 MVDC 하이브리드 배전망의 사고해석에 관한 연구

Based on ±35kV-scale MVDC hybrid distribution system to demonstrate MVDC distribution technology, this paper presents scenarios of contingency fault analysis and modeling for impact evaluation on MVDC hybrid distribution system in order to examine the operation characteristics of MVDC facilities and customers. And also, this paper proposes a modeling of the ±35kV-scale MVDC hybrid distribution system using PSCAD/EMTDC, which is composed of distribution substation, MVDC distribution feeder, converter station and PV system. From the simulation results of fault analysis in MVDC distribution system based on the modeling for impact evaluation on distribution system with the fault scenarios, it is confirmed that tremendous fault current can be momentarily occurred due to discharging of DC link capacitor in converter station regardless of fault type. Furthermore, it is found that the faults in MVDC feeder can cause the phenomenon of under-voltage at customers in other feeder of the main transformer. In addition, it is clear that the malfunction of recloser in other feeder can be prevented due to ungrounded system of MVDC system, and also the voltages of AC 22.9kV bus and MVDC feeder are maintained in a stable manner even if ground fault is occurred in AC 22.9kV feeder.

An advanced real-time dispatching strategy for a distributed energy system based on the reinforcement learning algorithm

A desirable dispatching strategy is essentially important for securely and economically operating of wind-thermal hybrid distribution systems. Existing dispatch strategies usually assume that wind power has priority of injection. For real-time control, such strategies are simple and easy to realize, but they lack flexibility and incur higher operation and maintenance (O&M) costs. This study analyzed the power dispatching process as a dynamic sequential control problem and established a Markov decision process model to explore the optimal coordinated dispatch strategy for coping with wind and demand disturbance. As a salient feature, the improved dispatch strategy minimizes the long-run expected operation and maintenance costs. To evaluate the model efficiently, a Monte Carlo method and the Q-learning algorithm were employed to the growing computational cost over the state space. Through a specified numerical case, we demonstrated the properties of the coordinated dispatch strategy and used it to address a 24-h real-time dispatching problem. The proposed algorithm shows high efficiency in solving real-time dispatching problems.

Multi-time Scale Dispatch Approach for an AC/DC Hybrid Distribution System Considering the Response Uncertainty of Flexible Loads

This paper examines the response uncertainty of flexible loads in the multi-time scale operation of an AC/DC hybrid distribution system. The price-based demand response (PBDR) model is established based on the principle of consumer psychology and the law of actual response uncertainty. The incentive mechanism of the incentive-based demand response (IBDR) model is designed considering the error of actual response capacity. Then, fuzzy chance-constrained programming is adopted to handle the response uncertainty of flexible loads. A multi-time scale dispatch model considering the response uncertainty of flexible loads for an AC/DC hybrid distribution system is proposed, which involves a day-ahead, intra-day, and real-time dispatch scheme. Mixed integer second-order cone programming (MISOCP) is utilized to solve the established multi-time scale dispatch model. Case studies illustrate the effectiveness of the proposed model, by considering the response uncertainty of flexible loads and the coordinated optimization on multiple time scales, peak shaving and valley filling can be realized and the dispatching cost of network can be reduced.

Study on Optimal Operation of AC-DC Hybrid Distribution Network

With the increase of power load and the access of distributed generation, AC/DC hybrid distribution network will become the development trend of urban distribution network in the future. The core of AC/DC distribution and distributed generation are voltage source converters based on full control switches. This paper simply analyzes the operation principle and control mode of voltage source converters, a power flow calculation method of AC/DC hybrid distribution system is proposed, and the optimization model of AC/DC hybrid distribution network with minimum network loss and minimum voltage deviation of DC network is established. The particle swarm swarm (PSO) algorithm is used to solve the calculation. Considering the load disturbance, the droop control is set for each VSC, at the same time this paper compares the advantages and disadvantages of the whole time optimal power calculation and droop control combined with the optimal power calculation method. Then the control mode of the distribution network is proposed. Finally, an example of PG&E 69-node distribution network in the United States is given to verify the correctness of the proposed model and algorithm.