Suppression of harmonic voltage distortion by neural network controlled active filter

Abstract

47 Umezu-Takase-cho, Ukyo-ku, Kyoto 615, JAPAN d b s f r a c f -This paper presents a newly developed control algorithm using a neural network theory for active AC harmonic filter system to reduce the harmonic voltage distortion in the electrical power system. The authors have already proposed an active filter to cancel the harmonic current generated from the specific nonlinear load. Our new control philosophy is dedicated to the reduction of the harmonic voltage distortion caused by many distributed harmonic generating loads. Recent harmonic disturbance problems, the neural network control algorithm of the active filter and test results on a small-scale power system simulator are presented.Rec t i f i e r I ,

Control techniques for active power filters

“…An early application of a neural network to an APF was arranged to learn the characteristics of the local grid system such that a suitable correction current could be set to achieve a target level of voltage distortion in the grid [41]. It was anticipated that several distorting loads exist and that measurement of load current was not feasible.…”

Operation of One-Cycle Controlled Three-Phase Active Power Filter With Unbalanced Source and Load

“…4. The discussion in the previous section indicates that (5) was derived under the assumption-0. However due to the presence of the zero-sequence components the vector sum of three unbalanced line voltages is not zero any more, i.e.…”

“…Moreover, combining (11) and (12) yields (13) Substituting (13) and (11) into (10) results in (14) Simplifying above equations yields (15) Furthermore, in the time domain, (15) can be simplified into (16) where , , and are the zero-sum components. Finally, (16) can be combined with (8) to yield the relationship between the duty ratios , , , the phase voltages , , , and the dc-bus voltage as follows: (17) Compared to (5), the three-phase voltages , , in (5) is replaced by its zero-sum components , , in (16), which indicates that for a three-phase VSI duty ratios , , only depend on the dc-bus voltage and the zero-sum voltage components , , and . By using original OCC controller, the control key equation in (3) and the control circuit in Fig.…”

“…Based on this fact, the relationship between phase voltages , , , and output voltage for the three-phase VSI working at CCM condition has been derived in [10]. For convenience, it is rewritten as follows: (5) Since the matrix in (5) is singular, it has infinite numbers of solutions. In light of this observation, OCC can be optimized for different applications.…”

“…2. In each region the duty ratio of the switches in the arm with dominant voltage (maximum or minimum) is set to zero or one, while the duty ratios of other two arms are governed by (5). For example, in the 0 60 region, the duty ratio of is set to 1, therefore is kept on in the entire region.…”