Input impedance modeling of multipulse rectifiers by double-fourier series method

Rectifier input impedance models are required for stability analysis of ac power systems with significant amount of rectification loads. Such stability analysis is particularly important for mobile and autonomous systems, such as aircraft and ship power systems, where high-power, multipulse rectifiers often dominates the loads. Averaging techniques can be applied to develop input impedance models for PWM rectifiers. To model the input impedance of line-frequency rectifiers, a direct linearization technique was developed recently and has been applied to model direct multipulse rectifiers without using inter-phase transformers. This paper extends the previous work and uses double-Fourier series method to develop describing (mapping) functions for the rectifier bridge. The double-Fourier method overcomes the limitations of conventional Fourier analysis which requires the perturbation frequency to be commensurable with the line fundamental frequency. The method is also applied to model the input impedance of multipulse rectifiers with interphase transformers. Analytical input impedance models are presented and validated by numerical simulation and experimental results.