Xuzhu Dong

A Multi-Stage Restoration Method for Medium-Voltage Distribution System With DGs

A fast and effective service restoration method is proposed for medium-voltage distribution system with distributed generators by combining intentional islanding of distributed generators with network reconfiguration to maximize restoration of out-of-service loads. The whole process is divided into four stages: 1) matching islanding schemes; 2) restoration of network connectivity and distributed generators; 3) network reconfiguration; and 4) optimization of load shedding. Whether the last three stages are executed or not depends on violations of operational constraints. In accordance with the topological feature of distribution system, a new concept of fundamental loop matrix is presented and applied in detecting out-of-service areas, restoration of network connectivity, and network reconfiguration. Simulation studies on the PG&E 69-bus system shows the effectiveness of the proposed approach.

Security analysis and access protection of power distribution wireless private TD-LTE network

This paper investigates into the security challenges of power distribution wireless private TD-LTE network (PDWPN) and proposes a systematic security protection architecture with a secure access scheme. The security challenges are discussed from link/entity/terminal perspectives, based on which a “triple-domain, triple-layer, triple-plane” security protection architecture for PDWPN is proposed. A security access scheme consisting of three procedures, i.e., terminal registration, authentication and key negotiation, security activation at access and non-access layers, is further analyzed to achieve the secure access of PDWPN and ensure the safe operation of PDWPN and power distribution network.

Analysis on the impacts of distribution systems with large-scale grid-connected photovoltaic based on DIgSILENT

When photovoltaic (PV) systems are connected to the traditional distribution system, the distribution of power flow and characteristics of the systems are changed. The integration of large-scale PV systems even affects the normal operation of distribution systems, thus the analysis of the characteristics of the distribution networks with large-scale grid-connected PVs is therefore essential. This paper analyzes the impacts of large-scale PV systems on the voltage, grid losses and short-circuit current of distribution networks based on the simulation tool DIgSILENT/PowerFactory, and an actual distribution network is utilized as the test case. According to the results, some improvement measures are suggested to lay the foundation for the planning and operation of distribution systems.

A hybrid optimization algorithm for distribution network coordinated operation with SNOP based on simulated annealing and conic programming

Soft normally open point (SNOP) is a novel power electronic device installed in place of normally-open point. The application of SNOP will greatly promote the flexibility and controllability of distribution network. Considering the high investment of SNOP, both tie switch and SNOP should be taken into account in the coordinated operation problem of distribution network. Firstly, the optimization model for distribution network coordinated operation with SNOP and tie switch is proposed. Then, combining the simulated annealing method with conic programming, this paper proposes a hybrid optimization algorithm, involving simulated annealing method to obtain the switch states and conic programming to optimize the transmitted power of SNOP. This hybrid algorithm can solve the above large-scale mixed-integer nonlinear problem accurately and rapidly, while satisfying the demand of distribution network coordinated operation. Finally, the IEEE 69-node system is used to demonstrate the effectiveness of the proposed hybrid algorithm.

Research and application on operation and control technologies of smart distribution network

Smart distribution network (SDN) is a comprehensive system integrating a large number of distributed generation (DG), energy storage equipment, electric vehicles and so on. This paper focuses on the key technologies of SDN operation and control, including situation awareness, operation optimization and self-healing control. They provide a theoretical and technical basis for the reliable operation and control of SDN. These technologies have been applied in a pilot project, which significantly improve the energy efficiency and power supply reliability of local distribution network.

Application of conic programming for optimal distributed generation allocation in distribution network

The widely application of distributed generation (DG) technologies poses new challenges to the operation and planning of the distribution network. Firstly, based on the basic DG allocation problem, a conic transformation model is proposed through variable substitution to realize the required format conversion, and then the conic programming(CP) algorithm is employed to acquire the optimal solution accurately, which also realizes the solving of power flow simultaneously. Finally, the optimal DG capacity obtained under different penetration levels and power factors are analyzed on the IEEE 33-node test feeder. Meanwhile, the validity of conic model as well as the CP algorithm is also verified.

A transmission delay compensation method considering circuit latency for power distribution EPON communication

This paper proposes a transmission delay compensation method for EPON system in power distribution communication to overcome the uplink transmission conflicts caused by the inaccurate delay synchronization, which would result in the bit errors and loss of synchronization. EPON system architecture and transmission delay compensation are introduced and the reason of the inaccurate delay synchronization is analyzed. Then, a transmission delay compensation and ranging method considering the circuit latency which is ignored conventionally is proposed. An evaluation platform is also developed to evaluate the effectiveness of the proposed method.

Phased preventive control of smart distribution system under non-fault conditions

Online security early warning and preventive control are important parts of self-healing for smart distribution system. The structure of security early warning and preventive control are presented in this paper. Preventive control is equivalent to a multi-stages decision problem, which is divided into three stages: regulation of output for distributed generators and reactive power compensation device, network reconfiguration of exchanging the status between sectionalizing switches and tie switches, and load shedding. Whether the stage is executed or not based on the value of state function. Order of distributed generators and capacitor rank are determined by the value of sensitivity about injecting reactive power nodes with the over limit of voltage amplitude node, basic-loop matrix is presented to avoid infeasible solutions which do not satisfy topological constraints in the network reconfiguration. The effectiveness of the propose approach is demonstrated by simulations on IEEE 33-nodes system.

Control strategy and its dynamic simulation of energy storage system in microgrid

For a micro-grid, the voltage and frequency may fluctuate due to the switch on and off of heavy power loads. In order to relieve the potential fluctuations, the characteristics of the micro-grid are analyzed and a droop control based power control strategy of the energy storage system (ESS) in the micro-grid is proposed in this paper. By adjusting the active and reactive power injection of the ESS, the voltage and frequency can be regulated within acceptable ranges. The proposed scheme is then tested on a dynamic test micro-grid. The simulation result shows that the power control strategy can achieve the objective of stabilizing both voltage and frequency of the micro-grid.