To improve system reliability for radial distribution systems with distributed generation (DG) under fault conditions, switch placement schemes are proposed to form self-supported areas after fault isolation. Customer priority is also considered in this problem. The switch placement problem is formulated as a nondifferentiable, multiobjective optimization problem. Graph-based algorithms, which incorporate direct load control, are developed to locate switches. Their results enable DG to support customers continuously in the event of fault. The proposed algorithms can be applied to unbalanced distribution networks with single or multiple distributed generators. Simulation results on a 394-bus distribution system, including priority customers, and single or multiple distributed generators, were also provided.

Switch placement to improve system reliability for radial distribution systems with distributed generation

To get the distribution network to operate at its optimum performance in an automated distribution system reconfiguration was been proposed and researched. Considering, however, that optimum performance implies minimum loss, no overloading of transformers and cables, correct voltage profile, and absence of phase voltage and current imbalances, network reconfiguration alone is insufficient. It has to be complemented with techniques for phase rearrangement between the distribution transformer banks and the specific primary feeder with a radial structure and dynamic phase and load balancing along a feeder with a radial structure. This paper contributes such a technique at the low-voltage and medium-voltage levels of a distribution network simultaneously with reconfiguration at both levels. While the neural network is adopted for the network reconfiguration problem, this paper introduces a heuristic method for the phase balancing/loss minimization problem. A comparison of the heuristic algorithm with that of the neural network shows the former to be more robust. The approach proposed here, therefore for the combined problem, uses the neural network in conjunction with a heuristic method which enables different reconfiguration switches to be turned on/off and connected consumers to be switched between different phases to keep the phases balanced. An application example of the proposed method using real data is presented.

Reconfiguration and Load Balancing in the LV and MV Distribution Networks for Optimal Performance

This work presents a new formulation for the power flow problem, with explicit representation of the neutral conductor and grounding. This methodology has been named the four-conductor current injection method (FCIM). The Newton-Raphson method is applied to solve the set of nonlinear current injection equations that are derived using phase coordinates, and the complex variables are written in rectangular form. The proposed algorithm can be used to analyze both balanced and unbalanced systems, meshed or radial, with controls and distributed generation, and is shown to be very efficient and robust for large scale systems.

Three-Phase Power Flow Based on Four-Conductor Current Injection Method for Unbalanced Distribution Networks

This paper develops and presents a unified and generic three-phase, steady-state, fundamental-frequency, sequence-frame-based model of the voltage-sourced converter (VSC) for power-flow analysis of VSC-interfaced Distributed Energy Resource (DER) units. The model is unified since it represents: 1) three-wire and four-wire VSC configurations; 2) balanced and unbalanced power-flow scenarios; 3) various VSC control strategies and options; and 4) operating limits and constraints of the VSC and its host DER unit. Based on the developed model, a new power-flow algorithm in the sequence-component frame is also developed. To achieve numerical and computational efficiency, the interface-VSC operating limits are accommodated in the power-flow algorithm as an interleaved step. The accuracy of the developed model and the computational efficiency of the power-flow algorithm are demonstrated based on several case studies, and where applicable, the results are validated based on comparison with the exact time-domain solution, using the PSCAD/EMTDC software tool.

A Unified Three-Phase Power-Flow Analysis Model For Electronically Coupled Distributed Energy Resources

Comparisons between the three-phase current injection method and the forward/backward sweep method

A multiphase, radial power flow experiment has been developed at Drexel University to provide students with hands-on learning experience in the operation and analysis of unbalanced power distribution systems. The experiment is set up within the Reconfigurable Distribution Automation and Control laboratory (RDAC). A Distribution Energy Management System (DMS) was developed with a graphical user interface for the experiment. The DMS provides students with real-time data from RDAC's distribution system, incorporates computer automated control and network reconfiguration capabilities, and performs calculations of power flows. In this paper, we will present: i) the hardware design and setup and ii) the software design of the multiphase power flow experiment.

Reconfigurable distribution automation and control laboratory: multiphase, radial power flow experiment

This paper presents a power converter model intended for both balanced and unbalanced radial power flow studies. A three-phase steady state model of a power converter (ac/dc-dc/ac) composed of a diode rectifier, a loss-less dc link, and a pulse-width-modulated inverter is presented. Both the three-phase rectifier and the three-phase inverter are modeled as three equivalent Y-connected single-phase rectifiers and single-phase inverters, respectively. The model is implemented within a three-phase power flow solver with phase representation. Simulation results on a balanced and an unbalanced 15-bus system are presented.

https://www.researchgate.net/profile/Dagmar_Niebur/publication/3213988_Three-Phase_Converter_Models_for_Unbalanced_Radial_Power_Flow_Studies/links/0fcfd50ba3992d2043000000.pdf

Three-phase converter models for unbalanced radial power-flow studies

At Drexel University, two power laboratories have been developed: the transmission oriented interconnected power system laboratory (IPSL) and, more recently, the distribution oriented reconfigurable distribution automation and control laboratory (RDAC). The laboratories provide students with hands-on experience on the analysis, operation, and planning of both transmission and distribution systems. This paper discusses power and measurement hardware in both laboratories as well as an energy management system (EMS) for IPSL and a distribution management system (DMS) for RDAC. It also addresses the successful implementation of the laboratories to undergraduate and graduate curricula at Drexel.

Xiaoguang Yang

Papers

Reconfigurable distribution automation and control laboratory: multiphase, radial power flow experiment

Three-phase converter models for unbalanced radial power-flow studies

Power transmission and distribution system laboratories at Drexel University

Correction to "Reconfigurable Distribution Automation and Control Laboratory: Multiphase, Radial Power Flow Experiment"