Improving the Accuracy of Voltage Regulation on the Active Filter Capacitor

Abstract

The control scheme of the active filter on the basis of the dq-theory with the block of automatic stabilization of voltage on the condenser containing the system of adaptive control of a delay in time and the filter of low frequencies is considered. The introduction of the delay can be implemented using a microcontroller that will automatically calculate the required delay factor and the output scale factor. The low-pass filter is tuned to the seventh harmonic, which allows you to adjust the delay in the range that provides the minimum value of the allowable error of voltage deviation. A study of the quality of voltage maintenance on the capacitor was also carried out using a set of measures. To improve the compensating capacity of the active filter, the sliding current averaging unit was set to the sixth harmonic in the case of a symmetrical load. The time response of the automatic voltage stabilization unit on the DC capacitor provides a stable charge / discharge process of the capacitor and a high level of compensation of higher harmonics without significant additional generation of active power in the network. It is shown that increasing the accuracy of voltage regulation on the capacitor of the power active filter allows to ensure the achievement of the minimum values of harmonic distortion and stable operation of the system. The transient reaction of the power active filter is determined by the control circuit of the output current of the filter. Therefore, its time response is chosen fast enough to track the current shape of the sinusoidal current. On the other hand, the speed of the control circuit of the capacitor voltage should not be too fast, and it is selected at least 10 times slower than the control circuit of the current filter current. Thus, these two control systems can be divided and designed as two independent systems and adjust each to individual characteristics.