The Study Of Online Surveillance Equipment For Power Quality Based On DSP

With the wide application of non-linear load and time-variant load in power system, waveform of electrical current and voltage is significantly distorted. It not only increases the cost of power network, but also can threaten the security of power system.A surveillance equipment for power quality based on DSP(Digital Signal Processor) is designed in this paper. In order to make sampling and data analyzing work simultaneously, on one hand choose the TMS3205509 DSP which's clock rate is up to 144MHz, on the other hand choose CPLD to finish the logical control; in order to transfer the analyzed result of the surveillance to the center of control analyze, adopted the CAN bus communication which is widely use in industrial control.In the detection of flicker, a approach of voltage flicker detection based on synchronous wave detection and multiresolution analysis is proposed in this paper. After the original signal is decomposed using one level multiresolution analysis, synchronization signal and demodulation signal of the approximation component are obtained by means of searching zero-crossing. To extract envelope of the original signal, the demodulation signal is decomposed to the level where the up limit frequency of the approximation component is less than double frequency of power network, and only the approximation component is employed in the process of reconstructing. Meantime, in order that the device can deal with detected signal continuously, appropriate sampling frequency and subsection length are selected. Besides, the boundary effects of subsection is solved by extending data..