Study On The Active Power Filter For Synthetic Compensation Of Harmonics And Reactive Power

Due to the ever increasing development of power electronic technology and the growing use of non-linear loads, the problem of harmonic distortion becomes ever more important. Harmonics has provoked that voltage and current waveforms in the electrical distribution systems are not sinusoidal. So the importance of harmonic analysis and mitigation has been well recognized by power system planning and electric engineers.At the moment, 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, these years much research turns to the active power filter (APF) for its prior function of compensating harmonics dynamically. But in our country, it doesn't reach the applied stage for the moment.The aim of this paper is to design an applied system of APF based on a new control algorithm to compensate harmonics and reactive power.The content of this paper as follows:1. This paper introduces some APF system types, their characteristics and fundamental operation.2. The reference current calculation circuit in the APF system has been analyzed with the detection of harmonic and reactive currents in chapter 3. Instantaneous reactive power theory is used by APF to detect harmonic and reactive currents resultsin errors of the compensation current. This paper proposes a new control algorithm for shunt APF to compensate harmonics and reactive power required by non-linear loads, which can also isolate the contributions to waveform distortion from customer side and the supply side. The approach will be useful in arriving at equitable ways of setting customer complaints, sharing the cost of waveform distortion through rate structure, penalties, etc. The source current after compensation can have the same waveform as that of the supply voltage, thereby attributing the responsibility of utility and customer at the point of common coupling (PPC). Due to similar shape of the source voltage and currents, reactive power is compensated completely. In order to reduce the delay time effect of DFT and quicken the dynamic response speed evidently, the harmonic voltage is predicted a sampling period ahead in the synchronously rotating reference frame.3. The control algorithm is simple and easy to be realized with excellent operation speed and strong control ability of digital signal processor (DSP) chip.4. Various simulation results are presented with three-phase and single-phase systems. The validity of the control algorithm has been verified by simulation results.The study of harmonic source is the basic problem in the area of harmonic analysis. Moreover, harmonic compensation and mitigation is the central problem and the main purpose of this research area. The studies carried out in this paper are of great importance to the theory and engineering practice of power system harmonic mitigation.