Analysis and Specification of Switching Frequency in Parallel Active Power Filter Regarding Compensation Characteristics of Generators

The choice of switching frequency is a very important issue for the development of Parallel Active Power Filter (PAPF), but so far is lack of discussion in a quantitative manner from previous publications. In this paper, an extensive analysis on the switching frequency to the performance of PAPF is carried out, and a specification of the switching frequency values with different compensation results is presented. First, the approximate models are presented. The PAPF are considered as a first-order inertia element and a second-order oscillation element respectively. The magnitude and phase of each order harmonic current are obtained at different switching frequency. The relationship between the output current and the reference current is shown. Second, with different types of system loads which are rectifier with resistance and inductance load and rectifier with resistance, inductance and capacitance load, the total output current is carried out with different switching frequencies, and the THD is proposed, that is, the compensation characteristic is analyzed. Third, the influence of source impedance and load impedance on the compensation characteristic is discussed when the switching frequency is different. Based on these analyses, the specification of compensation characteristics with different switching frequencies is quite straight forward. Both simulation investigations and hardware experimental results are finally provided to verify the analysis and specification.