Chengxue Zhang

Design of Robust Controller of Interconnected Power System Considering Signals Transmission Delay

Wide-area measurement system can retrieve the real time dynamic and static information of the large scale power system under the same time reference, helping to resolve the problems of the dynamic analysis and control for an interconnected power system, especially the low-frequency oscillation. However, communication delay is a non-ignorable factor for the stability of wide-area control. In this thesis, the dynamic model for interconnected power system considering the time delay was established, Simulation of large and small disturbance to a typical four-generator two-area testing system indicates that wide-area damping controller has a strong capability of damping area oscillation and good robustness even at the long wide-area signal time delay.

Studies of an Algorithm of High Speed Travelling Wave Differential Protection for EHV/UHV Transmission Line

With the EHV/UHV power system development, the ultra high speed protection has been developed. Traveling wave differential protection has ultra-high speed, high sensitivity and selectivity. It does not be affected by the distributed capacitive current, busbar structure, fault resistance, current transformer saturation, etc. A new algorithm of travelling wave differential protection proposed for the EHV/UHV transmission line. It throws off noises with morphological gradient filter, and takes out the head of traveling wave, as well as the time of the head arriving. The algorithm is structured by the integraphs of traveling wave and a method of distinguishing lightning wave. Analysis and simulation results show that the new method has high speed and reliability, and can be employed as the primary protection of EHV/UHV transmission line.

HGPSO Based Reactive Power Optimization of Distribution Network with Photovoltaic Generation

With large centralized photovoltaic (PV) power stations connected to the grid, its effects on the distribution networks cannot be ignored. The mathematical model of a photovoltaic power station was built and the power outputs of this model with the changes of illumination were simulated. One photovoltaic power station and one reactive power compensation capacitor were accessed to IEEE 30-node network. The voltages of generators, location and capacity of the PV power station and reactive power compensation capacitor are regarded as controllable variables. A hybrid intelligent algorithm (HGPSO) combining GA and PSO was applied to optimize the reactive power and voltage of the IEEE 30-node network and an optimal power flow distribution and the minimum network losses are realized.

VSC-HVDC Control Based on Rectangular Coordinate Utilizing Negative Sequence Component

The paper models VSC-HVDC (voltage source converter based HVDC) on rectangular coordinate, on which presents control strategy and designs corresponding regulators. In addition, transformation of symmetric component is used to getting negative sequence components aiming at unsymmetrical instantaneous faults at AC side. On PSCAD/EMTDC, whole control system, including VSC-HVDC, AC system and control parts, is established and runs. The simulating results indicate that controlling goals are achieved and adopted control strategy and regulators take effect. Toward various instantaneous faults concerning symmetric and unsymmetrical, the AC-DC power system responds quickly and possess strong stability.

A fast restoration method for distribution network

A new distribution network restoration method is proposed in this paper. A concept called “tail capacity” is introduced to illustrate the distribution networks load-bearing ability. With this concept, large amounting of iteration is unnecessary. Since the method does not optimize the networks economical efficiency, the times of power flow calculation is decreased remarkably. Therefore, the method can restore the loads fast. The simulation results of IEEE33 system validate the proposed methods effectiveness.

Fault Isolation and Reconfiguration of Multi-Voltage Level Distribution Network Based on PSO Algorithm

Fault isolation and reconfiguration are very important aspects of distribution network automation. When there is a fault in the distribution system, the loads connected with the fault zone should be separated and the operation pattern can be found by changing the status of the section switches or contact switches. A method of using different fault isolation and reconfiguration measures to deal with different zone faults is proposed. Different coding methods for different zone faults are introduced. Particle Swarm Optimization (PSO) algorithm is used to find the optimal result of the switch status. A distribution network in Dezhou grid in Shandong province is simulated with MATLAB and simulation results verify the effectiveness of the proposed method.

Design of damping controller of interconnected power system via LMI approach

Wide-area Measurement System can retrieval the real time dynamic and static information of the large scale power system under the same time reference, helping to resolve the problems of the dynamic analysis and control for an interconnected power system, especially the low-frequency oscillation. However, communication delay is a non-ignorable factor for the stability of wide-area control. In this thesis, the dynamic model for interconnected power system considering the time delay was established, Simulation of large and small disturbance to a typical four-generator two-area testing system indicates that wide-area damping controller has a strong capability of damping area oscillation and good robustness even at the long wide-area signal time delay.

Robust Control of Interconnected Power System Based on WAMS Considering Signals Transmission Delay

Wide-area measurement system can retrieval the real time dynamic and static information of the large scale power system under the same time reference, helping to resolve the problems of the dynamic analysis and control for an interconnected power system, especially the low-frequency oscillation. However, communication delay is a non-ignorable factor for the stability of wide-area control. In this thesis, the dynamic model for interconnected power system considering the time delay was established; it also optimized the controller parameters based on particle swarm optimization. Simulation of large and small disturbance to a typical four-generator two-area testing system indicates that wide-area robust controller has a strong capability of damping area oscillation and good robustness even at the long wide-area signal time delay.