COMPARATIVE ACTIVE CURRENT CALCULATION BY p-q AND CPC THEORIES

− This paper studies the possibilities of decomposition of the current in three-phase, three-wire systems based on the classic p-q theory proposed by Akagi and further developed and, respectively, on the Czarnecki’s theory. In the case of distorted current absorbed by a nonlinear load, the resulted components can be used to generate the reference compensating current in three-phase active power filters. As the major compensation goal of both current harmonics and reactive power involves a current drawn from the network which has the same phase and shape as the grid voltage, the attention in current decomposition is especially directed to the active component. Two case studies were analyzed by simulation in Matlab/Simulink environment, under both sinusoidal and nonsinusoidal voltage conditions. Linear and nonlinear loads were taken into consideration. For each case, the current components had been calculated according to Akagi’s original decomposition, the second interpretation of the p-q theory, and Czarnecki’s expressions based on Current Physical Components theory. It is shown that only the Current Physical Components – based decomposition is able to provide a correct active component of the load current as defined by Fryze for single-phase circuits, irrespective of voltage shape and load nonlinearity. Some additional modifications should be made in p-q based current decomposition in order to obtain an active current which preserves the voltage waveform under nonsinusoidal voltage conditions.