Hu Zhijian

A live-line measurement method to parameters of high voltage cable lines with mutual inductance based on GPS

The theoretical calculation method with formulae and the conventional measurement method of zero-sequence self-and mutual-impedance of high voltage cable lines are reviewed. Then the principles and mathematical models of zero-sequence parameter live-line measurement method of cable lines with mutual inductance based on GPS (Global Positioning System) technology are presented together with key techniques, hardware structure and software algorithm of the measurement system. Finally, field measurement results with the three different methods are given. Theoretical analysis and field measurement results prove that this new live-line method proposed in the paper is correct, effective and efficient.

New live line measurement methods of transmission lines' inductance parameters based on GPS

This paper firstly reviews the incremental method of live line measurement of parameters of transmission lines with mutual inductance. Then, based on GPS technology and differential equations, new live line measurement methods are proposed. The principles and mathematical models of the new methods are explained in detail. Data processing method using least square method is introduced. RTDS simulation results are provided. Finally, an example of live line measuring two 330 kV transmission lines with mutual inductance in Northwest China power network is given. The wiring diagram, measurement methods and measuring results are shown. Results of incremental method and differential equations method are compared. The field measurement results prove that the new methods can meet the need of live line measurement of parameters of transmission lines.

New methods and realization of live line measurement of zero sequence parameters of transmission lines with mutual inductance

Based on GPS technology and differential equations, two new methods of live line measurement of the parameters of transmission lines with mutual inductance are proposed. The principles and mathematical models of the steady differential method and the transient differential method are explained in details. Data processing algorithm by least square method is introduced in the measurement. The hardware structure of the measuring system and digital simulation results are given. Finally, an example of live line measuring 500 kV transmission lines with mutual inductances in Northeast China power network is given. Comparison of results among the steady differential method, the transient differential equation method and the conventional method is also shown. The field measurement results prove that the new methods can meet the needs of live line parameter measurement of transmission lines

The effects of flexible AC transmission systems device on protective relay

The paper introduces the basic structure and equivalent circuit model of unified power flow controller (UPFC) and then analyzes its effects on the transmission line distance relay in two cases. Different location of the UPFC, fault resistance, parameters of UPFC, the location of the fault and system operation conditions all affect the measured apparent impedance to some degree. The presence of UPFC will make the relay under-reach or over-reach. In order to eliminate the effects of a UPFC device on protective relay, two methods are given in this paper. One is to equip protective relay devices in which the UPFC device is equipped. In this way the UPFC device is always beyond the fault loop. The other is to use an artificial neural network to eliminate the effects of UPFC device.

Realization of high speed digital carrier communication module using COFDM

In this paper, realization of high speed carrier communication module using new coded orthogonal frequency division multiplexing (COFDM) is discussed. OFDM theory and its coding technology are simply introduced .The advantage of using COFDM modulating technology in power carrier wave communication is analyzed, and data transfer flow of the corresponding COFDM wave-carrier system is presented. The module design based on DSP is put forward, channel coding simulation and hardware composition and realization are also presented in this paper.

Harmonic real time estimation by artificial neural network based on network and GPS technology

A new harmonic real time identification approach by adaptive neural network based on GPS technology and distributed Ethernet network was proposed in this paper. The method uses an adaptive neural network to estimate the amplitudes and angles of the distorted current in power system. In this method, only half cycle harmonic current signal was used as the input of the neural network. In order to improve the accuracy of harmonic source identification, GPS (global positioning system) is used as the synchronized signal for the embedded measurement system based on digital signal processor (DSP). The samples selecting and training methods of artificial neural network are explained and the hardware structure of the embedded harmonic identification system is given. RTDS (real-time digital simulator) simulation results illustrate the effectiveness of the proposed approach

A novel coordination control method in the power system containing doubly fed wind farm

A wide-area damping control strategy comprehensively considering synchronous generators and doubly fed induction generators is proposed which is based on the inter-area low frequency oscillation problem caused by large area interconnected power grid and massive grid connected doubly fed wind farms. Also, a new optimization algorithm called Mean-Variance Mapping Optimization algorithm with the advantage of fewer iterations and not easy to fall into local optimal solution is adopted to coordinate the configuration of controller parameters. And the superiority of this new method is proved by contrast with the traditional intelligent algorithms. At last, inter-area low frequency oscillation problem in interconnected power systems with massive grid connected doubly fed wind farms can be effectively solved by the proposed method, which is validated by the simulation results a four-machine and two-area test system with a doubly fed wind farm.

A novel power system stabilizer based on neural network inverse system

A novel power system stabilizer (PSS) based on the neural network /spl alpha/-th order inverse system (called NNIPSS) is proposed in this paper. The reversibility of an excitation system with PSS in power systems is proved firstly. Then with the power angle of the generators as the output variable, the structure of the NNIPSS is given. The designing and training methods of the neural network inverse system are described in detail. In order to improve the dynamic performance and robustness of the neural network inverse system, a fuzzy-PID controller is employed. Simulations of one machine infinite bus system show that the proposed NNIPSS can provide better performances and robustness compared with a conventional PSS (CPSS).

The hardware configuration and field experiment of GPS-based for online parameter tester for transmission lines with mutual inductance

A GPS-based power transmission line tester, in which the time tag of GPS is used as the synchronization signal, is developed practically to realize the online measurement of power system parameters. The principles of the new measurement scheme are reviewed in the first part of the paper. The hardware and numerical algorithms are then presented in details, followed by experimental results.