Zhijian Hu

Optimal placement of PMUs in power systems based on improved PSO algorithm

Taking the full network observability of power system operation states and the least number of phasor measurement units (PMUs) as an objective function, an improved optimal PMU placement algorithm is proposed. In this algorithm, genetic algorithm (GA) is effectively combined with the particle swarm optimization (PSO) algorithm to ensure that the optimal solution can be obtained. The cross and aberrance operations in GA are used in the PMUs placement scheme to decrease the searching scope of the PSO method and improve the quality of initial PMU placement, thus the solving process is accelerated. In addition, a speedy observability analysis method which is called the pseudo measurement is put forward. The effectiveness of proposed algorithm is verified by the numerical simulation results of IEEE 14-bus and New England 39-bus system respectively.

H ∞ control of inter-area oscillations based on WAMs considering signals transmission delay

The paper proposes an adaptive supervisory controller (ASC) to enhance the damping of inter-area oscillations using wide area measurement (WAM) and accounting for signals transmission delays. The damping controller based on the mixed-sensitivity linear matrix inequality (LMI) approach with pole-placement restriction is designed. In the controller design, the signal transmission delays are regarded as structured uncertainty with linear fractional transformation (LFT) approach. The design of the ASC is explained in detail and its performance validated for a range of operating conditions by frequency and time domain simulations on a 4-machine 2-area test system.

Differential GPS-Based Transmission Conductor Wave and Wind Galloping Real-Time Measurement

Based on differential GPS (DGPS) technology, a realtime direct measurement method of transmission conductor wave and wind galloping is proposed. The hardware structure of the DGPS-based real-time measurement system is described. The design method, DGPS data acquisition and processing are introduced. Artificial neural network (ANN) is used to improve the accuracy of the DGPS measurement system. Virtual reality modeling language (VRML) drawing program is used to draw the tracks of the conductor wave and wind galloping. The experimental results prove that the DGPS-based transmission conductor wave and wind galloping real-time measurement is feasible.

Short-Term Prediction of Wind Farm Power Based on PSO-SVM

In order to improve the precision of wind power prediction, an improved particle swarm optimization (PSO) is used to get the global optimal solution for the three parameters which affect the regression performance of Support Vector Machine (SVM). The SVM regression model with optimized parameters was used to predict the short-term (12 hours) wind power of a wind farm in North China. For comparative analysis, a traditional SVM prediction model is used as well. Compared with the traditional SVM, the forecast results show that the PSO-SVM method applied in this paper has effectively improved the prediction accuracy and reduced the forecast error.

Distribution network reconfiguration based on ant colony system algorithm

In this paper, a novel algorithm based on ant colony system algorithm (ACSA) is presented which is used for the reconfiguration of distribution network in order to reduce the power energy losses under normal operation conditions. Combined with the features of distribution network, it applies the ant colony algorithm (ACA) to solve the problem of distribution network reconfiguration. The corresponding mathematical models are established and corresponding algorithms are given. An example of network reconfiguration is given which adopts the network reconfiguration mathematical mode of ACSA for power loss reduction. The main drawbacks of the basic ACA are the slow convergence and stagnation behavior, so some new measures to overcome these shortcomings are proposed in this paper.

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.

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.

Live Line Measuring the Zero Sequence Impedance Parameters of T-Connection Transmission Line

Based on GPS technology and integral equation, a new method of live line measuring the impedance parameters of T-connection transmission line is proposed. The mathematical model of the new method is explained in detail and the independent measuring cases for live line measurement are introduced. The hardware structure of the measurement system and the digital simulation results are given. The digital simulation results prove that the new method can meet the needs of live line measurement of the impedance parameters of T-connection transmission line.

WAMs based Robust Stability Control of Multi-Machine Systems Via LMI Approach

An adaptive supervisory controller (ASC) to enhance the damping of inter-area oscillations based on Wide Area Measurement (WAM) is proposed. The damping controller using the mixed-sensitivity linear matrix inequality (LMI) approach with pole-placement restriction is designed. One particular feature of this controller is that the number of input frequency signals to the ASC can be adjusted according to the type and severity of faults. The design of the ASC is explained in detail and its performance is validated for a range of operating conditions on a 4-machine 2-area test system.