Research On The Phasor Measurement Approach In Wide Area Measurement System

Power systems operation security includes power-angle stabilization, voltagestabilization, and frequency stabilization. To get safe operation of interconnectednetworks, it's very important to avoid the damage to power systems operation security.Abundant and objective data of systems operation are the base of system stabilityanalysis. Since bus phasor is an important parameter characterizing the system'srunning states, people have researched the on-line phasor measurement for a longtime. However, limited by the technical condition of the time, the on-line phasormeasurement and its application have not made any substantive progress all the while.Along with the development of Global Positioning System, Digital SignalProcessor, and Ethernet communication technology, the on-line phasor measurementin power system is growing mature. And it has helped to settle a firm base forprogress of electric networks towards real-time monitor and control in large acreage.As concerning the calculation, recursive DFT or non-recursive DFT is employedpresently to calculate the synchronized phasor.Besides power fundamental wave, the voltage and current of power systeminclude integer harmonics, inter-harmonics and sub-harmonics. In the face of theproblems such as frequency shift, harmonic, oscillating movement and so on, amethod based on quasi-synchronous sampling and DFT algorithm is proposed in thispaper to track frequency and measure phase, by analyzing various approaches for thephasor measurement which are based on synchronized sampling or quasi-synchronoussampling. In the process of calculating frequency, the DFT which can eliminatedecaying DC component and linear interpolation method are used to calculate theestimated phasor at anytime, and the iteration method is used to find out the twoestimated phasors whose interval is one period. Then, the sampling sequence issynchronized and the phase of the signal is calculated. The simulation results showthat the proposed method has some characteristics such as anti-jamming ability, highprecision, high calculating speed. The proposed method can be used in all kinds ofphasor measurement units or frequency measurement equipments.