Study On The Dynamic Measurement And Control System Of Power Quality

Electric power is very important for all kinds of industries and it plays a primordial role in building of our national economy. With the development of power electronics, nonlinear loads are widely used in power system, which take the advantages of all the recent advances and improvements of power electronics; suffer from the problem of drawing non-sinusoidal current and reactive power from the source. Their contributions to the waveform distortion are of growing interest, and are responsible for different power quality problems. So how to improve power quality and reduce harmonics pollution has been a focus of attention of the specialists and scholars all over the world.At present, most applied systems of harmonic control use the technology of passive filter, but passive filter has many disadvantages. For example, it is easily affected by system parameters and it can only remove some harmonics with given frequencies. Therefore, much research turns to the active power filter (APF) these years for its prior function of compensating harmonics and reactive power dynamically. But in our country, the research on APF stays in an early stage of development for the moment and cannot meet the requirement of application in capacity, cost and stability. So it is of great significance to emphasize the research on APF and accelerate its application.The content of this paper is as follows:(1) The principle and structure of APF is studied and an APF scheme for dynamic compensation of harmonics and reactive power is proposed. The control unit of the proposed scheme is based on DSP (digital signal processor).(2) Some common methods of harmonic measurement are studied and the advantages and disadvantages of each method are analyzed. A method based on UPF (unity power factor) is employed in this paper and its principle is studied in detail. Simulation research of this method is done.(3) A system is designed to verify the proposed APF scheme and harmonic measurement method. The results of simulation and test show that the proposed APF scheme is practical and can compensateharmonics and reactive power effectively. So the research of this paper has much theoretical and practical value for the control of power quality and the reduction of harmonics in power system.