A Novel Control Scheme for T-Type Three-Level SSG Converters Using Adaptive PR Controller with a Variable Frequency Resonant PLL

Abstract

In this paper, a novel quasi-direct power control (Q-DPC) scheme based on a resonant frequency adaptive proportional-resonant (PR) current controller with a variable frequency resonant phase locked loop (RPLL) is proposed, which can achieve a fast power response with a unity power factor. It can also adapt to variations of the generator frequency in T-type Three-level shaft synchronous generator (SSG) converters. The PR controller under the static α-β frame is designed to track ac signals and to avert the strong cross coupling under the rotating d-q frame. The fundamental frequency can be precisely acquired by a RPLL from the generator terminal voltage which is distorted by harmonics. Thus, the resonant frequency of the PR controller can be confirmed exactly with optimized performance. Based on an instantaneous power balance, the load power feed-forward is added to the power command to improve the anti-disturbance performance of the dc-link. Simulations based on MATLAB/Simulink and experimental results obtained from a 75kW prototype validate the correctness and effectiveness of the proposed control scheme.

Experimental Evaluation of a CPT-Based Four-Leg Active Power Compensator for Distributed Generation

“…As discussed in [26] this discretisation method has important advantages, in terms of preserving the resonant frequency accuracy particularly when high order harmonics have to be compensated. To the best of the author's knowledge, self-tuning adaptive algorithms for the bilinear transform with frequency prewarping have not been discussed in the literature where most of the reported applications are based on the conventional bilinear transform [27].…”