Power Quality Analysis And Study On Harmonic Compensation Method Based On Instantaneous Reactive Power

Power quality has a great significance for grid security, economic operation and the normal work of user equipment. Adopting three-phase voltage and three-phase current of the nonlinear load system as data sources, we mainly studied the calculation methods and standards of power quality indices in this paper. The design and development of the power quality analysis system is realized by using Visual Basic. The developed software platform can calculate various power quality indices in different cycles, including phase voltage, line voltage, phase current, line current, voltage deviation, voltage imbalance degree, distortion rate, harmonic, frequency deviation, power, etc. The status of power quality can be evaluated by comparing the calculated value with national standard index. Meanwhile, the validity of this software is verified by using the simulation data and the field test data.From the VB interface, the calculation results of harmonic are inconformity with national standard. Harmonic compensation is required to improve power quality. Therefore, harmonic detection occupies an important branch in the harmonic problems. And selecting an effective harmonic detection method becomes an important task. In view of this, the harmonic method and reactive current detection method are analyzed theoretically on the basis of the instantaneous reactive power theory. Results show that the accuracy of p-q computation method and the ip-iq computation method are exactly the same when grid voltage distortion doesn’t occur. On the contrary, both of the two methods can detect the harmonic from the load current when grid voltage distortion occurs, in which case the only difference is that the accuracy of ip-iq computation method is higher than p-q computation method, and the ip-iq computation method is unaffected by the distortion of the power grid.Active power filter is adopted in this paper to control harmonic by comparing the advantages and disadvantages of the filter. The instruction current operation circuit and control strategy of the active power filter are also discussed. The main circuit structure, working principle, parameter calculation and the dc side voltage control are analyzed theoretically, which provides theoretical basis for subsequent circuit design and simulation.Finally, in this paper simulation comparisons are made by using the methods of the harmonic detection which are based on the instantaneous reactive power theory by Matlab/Simulink. Results show that the detection accuracy of p-q computation method is significantly higher than ip-iq computation method. The method based on ip-iq is chosen. In the end, modules for the whole system are set up, and simulation results are also analyzed. Results show that the utilization of active power filter is an effective solution to make compensation for the harmonic.