Harmonic Power Detection Based on the pq Theory and its Applications.

Harmonic interference problems generated by bulk semiconductor power converters become more serious in power systems as they are widely used in industrial applications. Shunt passive filters consisting of LC tuned filters or shunt active filters using PWM inverters have been used to suppress harmonic currents in distribution systems. In order to install the passive or active filters, it is necessary to exactly find a dominant harmonic source in distribution feeders. A harmonic power on each phase and order at a receiving terminal has been investigated by using a digital power meter including an FFT analyzer. However, the conventional detection method has such a problem that it is difficult to exactly discuss harmonic power flow because the detected harmonic power is much smaller compared with a fundamental active power at the receiving terminal. In this paper, the harmonic power in three phases, which can be detected on real time, is defined by applying the pq theory. Next, it is verified by a digital simulation that the proposed method can discuss harmonic flows more easily than the conventional method. As a result, it is more simple and precise to find the harmonic source. Moreover, measurement errors of the harmonic power is revealed quantitatively, and the validity of the proposed method is demonstrated by digital simulation.